Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Seiji Ogo Last modified date:2024.02.02

Professor / Biofunctional Chemistry / Department of Applied Chemistry / Faculty of Engineering


Papers
1. Hung, Nguyen Khac; Minato, Takuo; Moniruzzaman, Mohammad; Kiyasu, Yu; Ogo, Seiji; Yoon, Ki-Seok.*, Selective formate production from H2 and CO2 using encapsulated whole-cells under mild reaction conditions. , 10.1016/j.jbiosc.2023.06.002, 136, 182-189, 2023.07.
2. Ogo, Seiji; Yatabe, Takeshi; Tome, Tamon; Takenaka, Riko; Shiota, Yoshihito; Kato, Kenji. , Safe, One-Pot, Homogeneous Direct Synthesis of H2O2., J. Am. Chem. Soc. , 10.1039/an9921701781, 2023.02.
3. Ogo, Seiji; Yatabe, Takeshi; Nakai, Hidetaka, Insights from Hydrogenase Model Studies on C–C Bond Forming Reactions., Coordination Chemistry Reviews, 10.1016/j.ccr.2022.214697, 2022.07.
4. Yamada, Kaho; Yatabe, Takeshi; Yoon, Ki-Seok;* Ogo Seiji.*, Cp*Ir Complex with Mesobiliverdin Ligand Isolated from Thermoleptolyngbya sp. O-77., J. Organomet. Chem., 964, 122302, 2022.04.
5. Nakano, Tatsuya; Abe, Tsukasa; Matsumoto, Takahiro;* Kimura, Kento; Nakamura, Genta; Hayami, Shinya; Shiota, Yoshihito;* Yoshizawa, Kazunari;* Ogo, Seiji.*, Light-Driven Oxidation of CH4 to C1 Chemicals Catalysed by an Organometallic Ru Complex with O2., RSC Adv., 12, 20, 12253-12257, 2022.04.
6. Chapman, Andrew; Ertekin, Elif; Kubota, Masanobu; Nagao, Akihide; Bertsch, Kaila; Macadre, Arnaud; Tsuchiyama, Toshihiro; Masamura, Takuro; Takaki, Setsuo; Komoda, Ryosuke; Dadfarnia, Mohsen; Somerday, Brian; Staykov, Alexander Tsekov; Sugimura, Joichi; Sawae, Yoshinori; Morita, Takehiro; Tanaka, Hiroyoshi; Yagi, Kazuyuki; Niste, Vlad; Saravanan, Prabakaran; Onitsuka, Shugo; Yoon, Ki-Seok; Ogo, Seiji; Matsushima, Toshinori; Tumen-Ulzii, Ganbaatar; Klotz, Dino; Nguyen, Dinh Hoa; Harrington, George; Adachi, Chihaya; Matsumoto, Hiroshige; Kwati, Leonard; Takahashi, Yukina; Kosem, Nuttavut; Ishihara, Tatsumi; Yamauchi, Miho; Saha, Bidyut Baran; Islam, Md. Amirul; Miyawaki, Jin; Sivasankaran, Harish; Kohno, Masamichi; Fujikawa, Shigenori; Selyanchyn, Roman; Tsuji, Takeshi; Higashi, Yukihiro; Kirchheim, Reiner; Sofronis, Petros.*, Achieving a Carbon Neutral Future through Advanced Functional Materials and Technologies., Bull. Chem. Soc. Jpn., 95, 1, 73-103, 2022.02.
7. Yatabe, Takeshi; Futakuchi, Sayaka; Miyazawa, Keishi; Shimauchi, Daiki; Takahashi, Yukina; Yoon, Ki-Seok; Nakai, Hidetaka; Ogo, Seiji.*, Reductive C(sp3)–C(sp3) Homo-Coupling of Benzyl or Allyl Halides with H2 using a Water-Soluble Electron Storage Catalyst., RSC Adv., 11, 62, 39450-39454, 2021.12.
8. Isegawa, Miho;* Matsumoto, Takahiro; Ogo, Seiji., Hydrogen Evolution, Electron-transfer, Hydride-Transfer Reactions in a Nickel-Iron Hydrogenase Model Complex: A Theoretical Study of the Distinctive Reactivities for the Conformational Isomers of Nickel-Iron Hydride., Dalton Trans., 51, 1, 312-323, 2021.12.
9. Yatabe, Takeshi; Tome, Tamon; Takahashi, Yukina; Matsumoto, Takahiro; Yoon, Ki-Seok; Nakai, Hidetaka; Ogo, Seiji.*, C–H Arylation of Benzene with Aryl Halides using H2 and a Water-Soluble Rh-Based Electron Storage Catalyst., Chem. Eur. J., 27, 69, 17326-17330, 2021.10.
10. Minato, Takuo; Teramoto, Takamasa; Adachi, Naruhiko; Hung, Nguyen Khac; Yamada, Kaho; Kawasaki, Masato; Akutsu, Masato; Moriya, Toshio; Senda, Toshiya; Ogo, Seiji; Kakuta, Yoshimitsu;* Yoon, Ki-Seok.*, Non-conventional Octameric Structure of C-phycocyanin., Commun. Biol., 4, 1238, 2021.10.
11. Isegawa, Miho;* Matsumoto, Takahiro; Ogo, Seiji., H2 Activation by Hydrogenase-Inspired NiFe Catalyst Using Frustrated Lewis Pair: Effect of Buffer and Halide Ion in the Heterolytic H–H Bond Cleavage., RSC Adv., 11, 45, 28420-28432, 2021.08.
12. Yatabe, Takeshi; Kamitakahara, Kazuki; Higashijima, Kaede; Ando, Tatsuya; Matsumoto, Takahiro; Yoon, Ki-Seok; Enomoto, Takao; Ogo, Seiji., Synthesis of acetic acid from CO2, CH3I and H2 using a Water-Soluble Electron Storage Catalyst., Chem. Commun. , 10.1039/d1cc01611c, 57, 39, 4772 -4774 , 2021.05.
13. Ogo, Seiji; Ando, Tatsuya; Thi Minh, Le Tu; Mori, Yuki; Matsumoto, Takahiro; Yatabe, Takeshi; Yoon, Ki-Seok; Sato, Yukio; Hibino, Takashi; Kaneko, Kenji. , A NiRhS fuel cell catalyst - lessons from hydrogenase, Chem. Commun. , 10.1039/d0cc04789a, 56, 79, 11787-11790, 2020.10, 本研究では、水素活性化酵素であるニッケル・鉄ヒドロゲナーゼの活性中心構造とその機能を範とする新規均一系ニッケル・ロジウム錯体を合成し、このモデル錯体を乾留(熱分解)することで、新規不均一系触媒の開発を行なった。この不均一系触媒は、ニッケル・ロジウム・硫黄を含み、水素の酸化と酸素の還元を触媒することから、水素燃料電池の電極触媒に応用した。その水素燃料電池は、白金を電極触媒とした水素燃料電池の5-28%の出力である。本研究では、ニッケル・鉄ヒドロゲナーゼのモデル錯体として酵素の反応性を再現した均一系触媒を合成し、その均一系触媒を乾留(熱分解)することで、性能と耐久性が向上した不均一系触媒の開発に成功した。.
14. Ogo, Seiji; Thi Minh, Le Tu; Kikunaga, Takahiro; Ando, Tatsuya; Matsumoto, Takahiro; Yatabe, Takeshi; Kato, Kenji. , Direct Synthesis of Hydrogen Peroxide in Water by Means of a Rh-Based Catalyst. , Organometallics, 10.1021/acs.organomet.0c00565, 39, 20, 3731-3741, 2020.10.
15. Takuo Minato, Takamasa Teramoto, Yoshimitsu Kakuta, Seiji Ogo, Ki Seok Yoon, Biochemical and structural characterization of a thermostable Dps protein with His-type ferroxidase centers and outer metal-binding sites, FEBS Open Bio, 10.1002/2211-5463.12837, 10, 7, 1219-1229, 2020.07, The DNA-binding protein from starved cells (Dps) is found in a wide range of microorganisms, and it has been well characterized. However, little is known about Dps proteins from nonheterocystous filamentous cyanobacteria. In this study, a Dps protein from the thermophilic nonheterocystous filamentous cyanobacterium Thermoleptolyngbya sp. O-77 (TlDps1) was purified and characterized. PAGE and CD analyses of TlDps1 demonstrated that it had higher thermostability than previously reported Dps proteins. X-ray crystallographic analysis revealed that TlDps1 possessed His-type ferroxidase centers within the cavity and unique metal-binding sites located on the surface of the protein, which presumably contributed to its exceedingly high thermostability..
16. Ogo, Seiji; Kishima, Takahiro; Yatabe, Takeshi; Miyazawa, Keishi; Yamasaki, Ryunosuke; Matsumoto, Takahiro; Ando, Tatsuya; Kikkawa, Mitsuhiro; Isegawa, Miho; Yoon, Ki-Seok; Hayami, Shinya., [NiFe], [FeFe], and [Fe] Hydrogenase Models from Isomers., Sci. Adv., 10.1126/sciadv.aaz8181, 6, 24, eaaz8181-eaaz8181, 2020.03, 水素の合成や分解を担う3種類の天然ヒドロゲナーゼ酵素の構造をヒントに1つの新しい触媒を開発した。今回開発した触媒は、同じ分子式で構造だけが異なる3種類の異性体によって、3種類のヒドロゲナーゼ酵素のように(1)燃料電池の水素電極の触媒(2)水素製造の触媒(3)化学工業の水素化の触媒として働くことを発見した。本研究成果は、これまで不明であったヒドロゲナーゼ酵素の触媒反応と触媒の分子構造との関係を解き明かすことで、次世代のエネルギー源である水素を効率よく利用する道を開いた。
本研究成果は.
17. Miho Isegawa, Takahiro Matsumoto, Seiji Ogo, Selective Oxidation of H2 and CO by NiIr Catalyst in Aqueous Solution
A DFT Mechanistic Study, Inorganic chemistry, 10.1021/acs.inorgchem.9b02400, 59, 2, 1014-1028, 2020.01, One of the challenges in utilizing hydrogen gas (H2) as a sustainable fossil fuel alternative is the inhibition of H2 oxidation by carbon monoxide (CO), which is involved in the industrial production of H2 sources. To solve this problem, a catalyst that selectively oxidizes either CO or H2 or one that co-oxidizes H2 and CO is needed. Recently, a NiIr catalyst [NiIICl(X)IrIIICl(Ε5-C5Me5)], (X = N,N′-dimethyl-3,7-diazanonane-1,9-dithiolate), which efficiently and selectively oxidizes either H2 or CO depending on the pH, has been developed (Angew. Chem. Int. Ed. 2017, 56, 9723-9726). In the present work, density functional theory (DFT) calculations are employed to elucidate the pH-dependent reaction mechanisms of H2 and CO oxidation catalyzed by this NiIr catalyst. During H2 oxidation, our calculations suggest that dihydrogen binds to the Ir center and generates an Ir(III)-dihydrogen complex, followed by subsequent isomerization to an Ir(V)-dihydride species. Then, a proton is abstracted by a buffer base, CH3COO-, resulting in the formation of a hydride complex. The catalytic cycle completes with electron transfer from the hydride complex to a protonated 2,6-dichlorobenzeneindophenol (DCIP) and a proton transfer from the oxidized hydride complex to a buffer base. The CO oxidation mechanism involves three distinct steps, i.e., (1) formation of a metal carbonyl complex, (2) formation of a metallocarboxylic acid, and (3) conversion of the metallocarboxylic acid to a hydride complex. The formation of the metallocarboxylic acid involves nucleophilic attack of OH- to the carbonyl-C followed by a large structural change with concomitant cleavage of the Ir-S bond and rotation of the COOH group along the NiIr axis. During the conversion of the metallocarboxylic acid to the hydride complex, intramolecular proton transfer followed by removal of CO2 leads to the formation of the hydride complexes. In addition, the barrier heights for the binding of small molecules (H2, OH-, H2O, and CO) to Ir were calculated, and the results indicated that dissociation from Ir is a faster process than the binding of H2O and H2. These calculations indicate that H2 oxidation is inhibited by CO and OH- and thus prefers acidic conditions. In contrast, the CO oxidation reactions occur more favorably under basic conditions, as the formation of the metallocarboxylic acid involves OH- attack to a carbonyl-C and the binding of OH- to Ni largely stabilizes the triplet spin state of the complex. Taken together, these calculations provide a rationale for the experimentally observed pH-dependent, selective oxidations of H2 and CO..
18. Kei Ikeda, Yuta Hori, Muhammad Haris Mahyuddin, Yoshihito Shiota, Aleksandar Tsekov Staykov, Takahiro Matsumoto, Kazunari Yoshizawa, Seiji Ogo, Dual Catalytic Cycle of H2 and H2O Oxidations by a Half-Sandwich Iridium Complex
A Theoretical Study, Inorganic Chemistry, 10.1021/acs.inorgchem.9b00307, 58, 11, 7274-7284, 2019.06, While hydrogenase and photosystem II enzymes are known to oxidize H2 and H2O, respectively, a recently reported iridium aqua complex [IrIII5-C5Me5){bpy(COOH)2}(H2O)]2+ is able to oxidize both of the molecules and generate energies as in the fuel and solar cells (Ogo et al. ChemCatChem 2017, 9, 4024-4028). To understand the mechanism behind such an interesting bifunctional catalyst, in the present study, we perform density functional theory (DFT) calculations on the dual catalytic cycle of H2 and H2O oxidations by the iridium aqua complex. In the H2 oxidation, we found that the H-H bond is easily cleaved in a heterolytic fashion, and the resultant iridium hydride complex is significantly stabilized by the presence of H2O molecules, due to dihydrogen bond. The rate-determining step of this reaction is found to be the H2O → H2 ligand substitution with an activation energy of 10.7 kcal/mol. In the H2O oxidation, an iridium oxo complex originating from an oxidation of the iridium aqua complex forms a hydroperoxide complex, where an O-O bond is formed with an activation energy of 21.0 kcal/mol. Such a relatively low activation barrier is possible only when at least two H2O molecules are present in the reaction, allowing the water nucleophilic attack (WNA) mechanism to take place. The present study suggests and discusses in detail six reaction steps required for the dual catalytic cycle to complete..
19. Kohsei Tsuji, Ki Suk Yoon, Seiji Ogo, Glyceraldehyde-3-phosphate dehydrogenase from Citrobacter sp. S-77 is post-translationally modified by CoA (protein CoAlation) under oxidative stress, FEBS Open Bio, 10.1002/2211-5463.12542, 9, 1, 53-73, 2019.01, Protein CoAlation (S-thiolation by coenzyme A) has recently emerged as an alternative redox-regulated post-translational modification by which protein thiols are covalently modified with coenzyme A (CoA). However, little is known about the role and mechanism of this post-translational modification. In the present study, we investigated CoAlation of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from a facultative anaerobic Gram-negative bacterium Citrobacter sp. S-77 (CbGAPDH). GAPDH is a key glycolytic enzyme whose activity relies on the thiol-based redox-regulated post-translational modifications of active-site cysteine. LC-MS/MS analysis revealed that CoAlation of CbGAPDH occurred in vivo under sodium hypochlorite (NaOCl) stress. The purified CbGAPDH was highly sensitive to overoxidation by H 2 O 2 and NaOCl, which resulted in irreversible enzyme inactivation. By contrast, treatment with coenzyme A disulphide (CoASSCoA) or H 2 O 2 /NaOCl in the presence of CoA led to CoAlation and inactivation of the enzyme; activity could be recovered after incubation with dithiothreitol, glutathione and CoA. CoAlation of the enzyme in vitro was confirmed by mass spectrometry. The presence of a substrate, glyceraldehyde-3-phosphate, fully protected CbGAPDH from inactivation by CoAlation, suggesting that the inactivation is due to the formation of mixed disulphides between CoA and the active-site cysteine Cys149. A molecular docking study also supported the formation of mixed disulphide without steric constraints. These observations suggest that CoAlation is an alternative mechanism to protect the redox-sensitive thiol (Cys149) of CbGAPDH against irreversible oxidation, thereby regulating enzyme activity under oxidative stress..
20. Takuo Minato, Takahiro Matsumoto, Seiji Ogo, Homogeneous catalytic reduction of polyoxometalate by hydrogen gas with a hydrogenase model complex, RSC Advances, 10.1039/c9ra04396a, 9, 34, 19518-19522, 2019.01, The homogeneous catalytic reduction of a polyoxometalate (POM) by hydrogen gas in aqueous media was investigated for the first time by using a [NiRu] hydrogenase model complex (I) under very mild conditions. By bubbling hydrogen gas into the buffer solution containing I and the Dawson-type POM (IIox), the color of the solution turned from pale yellow to dark blue, suggesting the reduction of IIox. The catalytic and kinetic studies revealed that I acted as an efficient catalyst to yield one-electron-reduced Dawson-type POM (IIred) with a low energy barrier for activating dihydrogen and reducing IIoxvia a hydride complex of I. The process for the one-electron reduction of IIox was confirmed by UV-vis spectroscopy, controlled potential electrolysis, and X-ray photoelectron spectroscopy. POM IIred could stably store protons and electrons and release them by addition of oxidants, demonstrating that POMs acted as redox active mediators for transporting protons and electrons from hydrogen gas to acceptors. The recycle study showed that IIox and IIred could be reduced and oxidized by hydrogen and oxygen gases, respectively, at least five times with >99% yield of reduced species, showing a durable system for extracting protons and electrons from hydrogen gas..
21. Kei Ikeda, Muhammad Haris Mahyuddin, Yoshihito Shiota, Aleksandar Staykov, Takahiro Matsumoto, Seiji Ogo, Kazunari Yoshizawa, Computational Study on the Light-Induced Oxidation of Iridium-Aqua Complex to Iridium-Oxo Complex over WO3(001) Surface, Inorganic chemistry, 10.1021/acs.inorgchem.9b02704, 2019.01, An iridium aqua complex [IrIII(Ε5-C5Me5){bpy(COOH)2}(H2O)]2+ under visible light irradiation has been experimentally reported to form an iridium-oxo (Ir-oxo) complex [IrV(Ε5-C5Me5){bpy(COOH)2}(O)]2+, which oxidizes H2O to O2. However, the mechanism for the formation of this Ir-oxo complex remains unclear, due to the difficulties in observing the unstable Ir-oxo complex and computing light-induced systems having different numbers of electrons. In this study, we perform density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations to investigate more in detail our previously proposed deprotonation and light-induced oxidation reactions composing the formation of the Ir-oxo complex. In particular, we discuss effects of light irradiation and WO3 support on the formation of the Ir-oxo complex. We suggest two distinct mechanisms, that is, direct and indirect for the light-induced oxidation. In the direct mechanism electrons are directly transferred from the occupied Ï€∗ orbitals of IrIII-OH or IrIV=O• to the conduction band of the WO3 surface, whereas in the indirect mechanism electrons are first excited from the valence band to the conduction band of the WO3 surface due to the UV light, and then the resultant electron hole oxidizes the Ir complex. In the direct mechanism, in particular, we found that the lowest energy of the anode's conduction band determines the adsorption wavelength of the light irradiation, enabling us to predict alternative semiconductor anodes for more efficient formation of the Ir-oxo complex..
22. Miho Isegawa, Akhilesh K. Sharma, Seiji Ogo, Keiji Morokuma, Electron and Hydride Transfer in a Redox-Active NiFe Hydride Complex
A DFT Study, ACS Catalysis, 10.1021/acscatal.8b02368, 8, 11, 10419-10429, 2018.11, We present mechanistic details of the formation of a NiFe hydride complex and provide information on its electron- and hydride-transfer processes on the basis of density functional theory calculations and artificial-force-induced-reaction studies. The NiFe hydride complex conducts three transfer reactions: namely, electron transfer, hydride transfer, and proton transfer. In a NiFe hydride complex, the hydride binds to Fe, which is different from the Ni-R state in hydrogenase where the hydride is located between Ni and Fe. According to our calculations, in reaction with the ferrocenium ion, electron transfer occurs from the NiFe hydride complex to the ferrocenium ion, followed by a hydrogen atom transfer (HAT) to the second ferrocenium ion. The oxidation state of Fe varies during the redox process, different from the case of NiFe hydrogenase, where the oxidation state of Ni varies. A single-step hydride transfer occurs in the presence of a 10-methylacridinium ion (AcrH+), which is more kinetically feasible than the HAT process. In contrast to the HAT and hydride-transfer process, the proton transfer occurs through a low barrier from a protonated diethyl ether. The revealed reaction mechanism guides the interpretation of the catalytic cycle of NiFe hydrogenase and leads to the development of efficient biomimetic catalysts for H2 generation and an electron/hydride transfer..
23. Yuki Mori, Tatsuya Ando, Takahiro Matsumoto, Takeshi Yatabe, Mitsuhiro Kikkawa, Ki Suk Yoon, Seiji Ogo, Multifunctional Catalysts for H2O2-Resistant Hydrogen Fuel Cells, Angewandte Chemie - International Edition, 10.1002/anie.201810270, 57, 48, 15792-15796, 2018.11, The development of hydrogen fuel cells is greatly hindered by the unwanted generation of H2O2 at the cathode. A non-Pt cathode catalyst is now shown to be capable of simultaneously reducing both O2 and H2O2, thus rendering H2O2 a useful part of the feed stream. The applicability of this unique catalyst is demonstrated by employing it in a fuel cell running on H2/CO and O2/H2O2..
24. Makoto Takenaka, Mitsuhiro Kikkawa, Takahiro Matsumoto, Takeshi Yatabe, Tatsuya Ando, Ki Suk Yoon, Seiji Ogo, Oxidation of Guanosine Monophosphate with O
2
via a Ru-peroxo Complex in Water, Chemistry - An Asian Journal, 10.1002/asia.201801267, 13, 21, 3180-3184, 2018.11, Oxidative damage of DNA by reactive oxygen species (ROS) is responsible for aging and cancer. Although many studies of DNA damage by ROS have been conducted, there have been no reports of the oxidation of RNA components, such as guanosine monophosphate, by metal-based species in water. Here, we report the first case of oxidation of guanosine monophosphate to 8-oxoguanosine monophosphate by a metal-based oxygen bound species, derived from O
2
and in water..
25. Miho Isegawa, Akhilesh K. Sharma, Seiji Ogo, Keiji Morokuma, DFT Study on Fe(IV)-Peroxo Formation and H Atom Transfer Triggered O2 Activation by NiFe Complex, Organometallics, 10.1021/acs.organomet.8b00098, 37, 10, 1534-1545, 2018.05, The mechanism for dioxygen activation using the biomimetic model complex of [NiFe]-hydrogenase, [NiLFe(η5-C5Me5)]+ [L = N,N′-diethyl-3,7-diazanonane-1,9-dithiolato] was established using density functional theory (DFT) and artificial force-induced reaction (AFIR) methods. Our computational results suggest that O2 binds to the FeII center in an end-on fashion and forms a high-valent iron complex, NiFe-peroxo (NiIIFeIV2-O2)), which has been experimentally observed. The O-O bond cleavage occurs in the presence of borohydride (BH4-) through hydrogen atom transfer (HAT). Once the HAT occurs, the generated BH3 radical anion (BH3•-) binds to the terminal oxygen of NiFe-OOH, giving rise to BH3OH- and NiIIFeIV O. The second HAT from BH4- to the oxygen of NiIIFeIV O leads to BH3OH- and Fe-reduced NiIIFeII complex. Importantly, the dioxygen activation is triggered by HAT, not by proton transfer or hydride transfer. The O2 is activated by the Fe center, and the oxidation state of Fe varies during the process, while the oxidation state of Ni is conserved. These mechanistic insights into O2 activation are essential in understanding the formation of the inactive state and reactivation process in hydrogenase..
26. Takeshi Yatabe, Taisuke Tokunaga, Takahiro Matsumoto, Mitsuhiro Kikkawa, Ki Suk Yoon, Seiji Ogo, A MnI model for the photoinhibited species of oxygen-evolving complex, Chemistry Letters, 10.1246/cl.170869, 47, 1, 34-36, 2018.01, We report the reactivity of a new MnI(cyclam) complex (cyclam: 1,4,8,11-tetraazacyclotetradecane) toward O2 and H2O as a model for the photoinhibited species of oxygen-evolving complex (OEC). The reactivity varies according to the number of CO ligands. A MnI dicarbonyl complex, [MnI(cyclam)(CO)2]+ reacts with O2, but not with H2O, to form a bis(μ-oxo)Mn2III,IV complex, though a MnI tricarbonyl complex, [MnI(cyclam)(CO)3]+ does not react with either O2 or H2O. Newly synthesized MnI(cyclam) dicarbonyl complex was characterized by ESI mass spectrometry, UVvis absorption spectroscopy, IR spectroscopy, and X-ray analysis..
27. Noor Dina Muhd Noor, Hiroaki Matsuura, Koji Nishikawa, Hulin Tai, Shun Hirota, Jaehyun Kim, Jiyoung Kang, Masaru Tateno, Ki Suk Yoon, Seiji Ogo, Shintaro Kubota, Yasuhito Shomura, Yoshiki Higuchi, Redox-dependent conformational changes of a proximal [4Fe-4S] cluster in Hyb-type [NiFe]-hydrogenase to protect the active site from O
2, Chemical Communications, 10.1039/c8cc06261g, 54, 87, 12385-12388, 2018.01, Citrobacter sp. S-77 [NiFe]-hydrogenase harbors a standard [4Fe-4S] cluster proximal to the Ni-Fe active site. The presence of relocatable water molecules and a flexible aspartate enables the [4Fe-4S] to display redox-dependent conformational changes. These structural features are proposed to be the key aspects that protect the active site from O
2
attack..
28. Taisuke Tokunaga, Takeshi Yatabe, Takahiro Matsumoto, Tatsuya Ando, Ki Suk Yoon, Seiji Ogo, Mechanistic investigation of the formation of H2 from HCOOH with a dinuclear Ru model complex for formate hydrogen lyase, Science and Technology of Advanced Materials, 10.1080/14686996.2017.1379857, 18, 1, 870-876, 2017.12, We report the mechanistic investigation of catalytic H2 evolution from formic acid in water using a formate-bridged dinuclear Ru complex as a formate hydrogen lyase model. The mechanistic study is based on isotope-labeling experiments involving hydrogen isotope exchange reaction..
29. Mitsuhiro Kikkawa, Takeshi Yatabe, Takahiro Matsumoto, Ki Suk Yoon, Kazuharu Suzuki, Takao Enomoto, Kenji Kaneko, Seiji Ogo, A Fusion of Biomimetic Fuel and Solar Cells Based on Hydrogenase, Photosystem II, and Cytochrome c Oxidase, ChemCatChem, 10.1002/cctc.201700995, 9, 21, 4024-4028, 2017.11, 本業績では、燃料電池と太陽電池を融合する同一触媒の開発に成功した。次世代の電池として、燃料電池と太陽電池はこれまで別々に開発されてきた。本研究では、「自然界の水素酵素と光合成の機能を融合した新しい触媒」を開発に成功した。この触媒を用いると、「水素をエネルギー源として燃料電池が、水と光をエネルギー源として太陽電池が駆動する」ことを見出した。本研究成果はエネルギー研究の分野において格段の発展と波及効果をもたらす可能性が期待できる。.
30. Takahiro Matsumoto, Takahiro Kishima, Takeshi Yatabe, Ki Suk Yoon, Seiji Ogo, Mechanistic Insight into Switching between H2- or O2-Activation by Simple Ligand Effects of [NiFe]hydrogenase Models, Organometallics, 10.1021/acs.organomet.7b00471, 36, 20, 3883-3890, 2017.10, We present a mechanistic investigation for the activation of H2 and O2, induced by a simple ligand effect within [NiFe] models for O2-tolerant [NiFe]hydrogenase. Kinetic study reveals Michaelis-Menten type saturation behaviors for both H2 and O2 activation, which is the same behavior as that found in O2-tolerant [NiFe]hydrogenase. Such saturation behavior is caused by H2 complexation followed by heterolytic cleavage of H2 by an outer-sphere base, resulting in the formation of a hydride species showing hydridic character..
31. Y. Shomura, M. Taketa, H. Nakashima, H. Tai, H. Nakagawa, Y. Ikeda, M. Ishii, Y. Igarashi, H. Nishihara, Ki Suk Yoon, Seiji Ogo, S. Hirota, Y. Higuchi, Structural basis of the redox switches in the NAD+-reducing soluble [NiFe]-hydrogenase, Science, 10.1126/science.aan4497, 357, 6354, 928-932, 2017.09, NAD+ (oxidized form of NAD: nicotinamide adenine dinucleotide)-reducing soluble [NiFe]-hydrogenase (SH) is phylogenetically related to NADH (reduced form of NAD+):quinone oxidoreductase (complex I), but the geometrical arrangements of the subunits and Fe-S clusters are unclear. Here, we describe the crystal structures of SH in the oxidized and reduced states. The cluster arrangement is similar to that of complex I, but the subunits orientation is not, which supports the hypothesis that subunits evolved as prebuilt modules. The oxidized active site includes a six-coordinate Ni, which is unprecedented for hydrogenases, whose coordination geometry would prevent O2 from approaching. In the reduced state showing the normal active site structure without a physiological electron acceptor, the flavin mononucleotide cofactor is dissociated, which may be caused by the oxidation state change of nearby Fe-S clusters and may suppress production of reactive oxygen species..
32. Hidetaka Nakai, Masafumi Kuyama, Juncheol Seo, Takahiro Goto, Takahiro Matsumoto, Seiji Ogo, Luminescent Tb(III) and Sm(III) complexes with a 1,4,7-triazacyclononane-based tris-aryloxide ligand for high-performance oxygen sensors, Dalton Transactions, 10.1039/c7dt01388d, 46, 28, 9126-9130, 2017.06, Taking advantage of the outstanding oxygen-sensitive luminescence properties of the previously synthesised Tb(iii) complex [{(MeMeArO)3tacn}LnIII(THF)] (1Tb, Ln = Tb), herein, we have prepared an oxygen sensor based on 1Tb embedded in polystyrene film (1Tb/PS) and found that 1Tb/PS shows the highest sensitivity (I0/I100 = 14.9) and the fastest response (response/recovery time = 1.9 s/2.9 s), among the lanthanide(iii)-based oxygen sensors with f-f emission. Moreover, we have prepared the lanthanide(iii)-based colorimetric luminescent oxygen sensor (1TbSm/PS) with green-yellow-red responses, by using 1Tb and a newly synthesised oxygen-insensitive Sm(iii) complex (1Sm, Ln = Sm; Φ = 0.010 and τ = 12.2 μs)..
33. Seiji Ogo, H2 and O2 activation by [NiFe]hydrogenases – Insights from model complexes, Coordination Chemistry Reviews, 10.1016/j.ccr.2016.07.001, 334, 43-53, 2017.03, H2 is an important compound from both a biological and a chemical industry perspective. Oxidation and reduction enable H2 to be used as a source of energy and as a raw material in the manufacture of a variety of useful substances. In nature, hydrogenases (H2ases) have been entrusted with the task of activating H2, making it responsible for part of the Earth's energy circulation system since the birth of the planet. H2ases have distinctive active centers and their structures and electronic states can be controlled to produce specific functions. This paper provides an overview of the structures and functions of H2ases and their models..
34. Ki Suk Yoon, Nga T. Nguyen, Kien Trung Tran, Kohsei Tsuji, Seiji Ogo, Nitrogen fixation genes and nitrogenase activity of the non-heterocystous cyanobacterium Thermoleptolyngbya sp. O-77, Microbes and Environments, 10.1264/jsme2.ME17015, 32, 4, 324-329, 2017.01, Cyanobacteria are widely distributed in marine, aquatic, and terrestrial ecosystems, and play an important role in the global nitrogen cycle. In the present study, we examined the genome sequence of the thermophilic non-heterocystous N2-fixing cyanobacterium, Thermoleptolyngbya sp. O-77 (formerly known as Leptolyngbya sp. O-77) and characterized its nitrogenase activity. The genome of this cyanobacterial strain O-77 consists of a single chromosome containing a nitrogen fixation gene cluster. A phylogenetic analysis indicated that the NifH amino acid sequence from strain O-77 was clustered with those from a group of mesophilic species: the highest identity was found in Leptolyngbya sp. KIOST-1 (97.9% sequence identity). The nitrogenase activity of O-77 cells was dependent on illumination, whereas a high intensity of light of 40 µmol m-2 s-1 suppressed the effects of illumination..
35. Seiji Ogo, Yuki Mori, Tatsuya Ando, Takahiro Matsumoto, Takeshi Yatabe, Ki Suk Yoon, Hideki Hayashi, Masashi Asano, One Model, Two Enzymes
Activation of Hydrogen and Carbon Monoxide, Angewandte Chemie - International Edition, 10.1002/anie.201704864, 56, 33, 9723-9726, 2017.01, The ability to catalyze the oxidation of both H2 and CO in one reaction pot would be a major boon to hydrogen technology since CO is a consistent contaminant of H2 supplies. Here, we report just such a catalyst, with the ability to catalyze the oxidation of either or both H2 and CO, based on the pH value. This catalyst is based on a NiIr core that mimics the chemical function of [NiFe]hydrogenase in acidic media (pH 4–7) and carbon monoxide dehydrogenase in basic media (pH 7–10). We have applied this catalyst in a demonstration fuel cell using H2, CO, and H2/CO (1/1) feeds as fuels for oxidation at the anode. The power density of the fuel cell depends on the pH value in the media of the fuel cell and shows a similar pH dependence in a flask. We have isolated and characterized all intermediates in our proposed catalytic cycles..
36. Makoto Takenaka, Ki Seok Yoon, Takahiro Matsumoto, Seiji Ogo, Acetyl-CoA production by encapsulated pyruvate ferredoxin oxidoreductase in alginate hydrogels, Bioresource Technology, 10.1016/j.biortech.2016.12.051, 227, 279-285, 2017, Pyruvate ferredoxin oxidoreductase from Citrobacter sp. S-77 (PFORS77) was purified in order to develop a method for acetyl-CoA production. Although the purified PFORS77showed high O2-sensitivity, the activity could be remarkably stabilized in anaerobic conditions. PFORS77was effectively immobilized on ceramic hydroxyapatite (PFORS77-HA) with an efficiency of more than 96%, however, after encapsulation of PFORS77-HA in alginate, the rate of catalytic acetyl-CoA production was highly reduced to 36% when compared to that of the free enzyme. However, the operational stability of the PFORS77-HA in alginate hydrogels was remarkable, retaining over 68% initial activity even after ten repeated cycles. The results suggested that the PFORS77-HA hydrogels have a high potential for biotechnological application..
37. Takeshi Yatabe, Takahiro Kishima, Hideaki Nagano, Takahiro Matsumoto, Mikio Yamasaki, YOON KI SUK, Seiji Ogo, Structure and Reactivity of a Ru-based Peroxide Complex as a Reactive Intermediate of O2-Promoted Activation of a C–H Bond in a Cp* Ligand. , 10.1246/cl.160909, 46, 1, 74-76, 2016.12.
38. Makoto Takenaka, YOON KI SUK, Takahiro Matsumoto, Seiji Ogo, Acetyl-CoA Production by Encapsulated Pyruvate Ferredoxin Oxidoreductase in Alginate Hydrogels., http://doi.org/10.1016/j.biortech.2016.12.051, 227, 279-285, 2016.12.
39. Seiji Ogo, H2 and O2 Activation by [NiFe]Hydrogenases — Insights from Model Complexes., http://dx.doi.org/10.1016/j.ccr.2016.07.001, 2016.07.
40. Hidetaka Nakai, Juncheol Seo, Kazuhiro Kitagawa, Takahiro Goto, Kyoshiro Nonaka, Takahiro Matsumoto, Seiji Ogo, Control of Lanthanide Coordination Environment: Synthesis, Structure, and Oxygen-Sensitive Luminescence Properties of an Eight-Coordinate Tb(III) Complex., 10.1021/acs.inorgchem.6b00800, 55, 13, 6609-6615, 2016.06.
41. Koji Yoshimoto, Takeshi Yatabe, Takahiro Matsumoto, TRAN VIET HA, ROBERTSON ANDREW, Hidetaka Nakai, Koichiro Asazawa, Hirohisa Tanaka, Seiji Ogo, Inorganic Clusters with a [Fe2MoOS3] Core—A Functional Model for Acetylene Reduction by Nitrogenases., 10.1039/C6DT01655C, 45, 37, 14620-14627, 2016.06.
42. Hidetaka Nakai, Juncheol Seo, Kazuhiro Kitagawa, Takahiro Goto, Takahiro Matsumoto, Seiji Ogo, An Oxygen-Sensitive Luminescent Dy(III) Complex., 10.1039/C6DT01057A, 45, 23, 9492-9496, 2016.05.
43. Hidetaka Nakai, Kazuhiro Kitagawa, Juncheol Seo, Takahiro Matsumoto, Seiji Ogo, A Gadolinium(III) Complex That Shows Room-Temperature Phosphorescence in the Crystalline State., 10.1039/C6DT01303A, 45, 29, 11620-11623, 2016.05.
44. Kohsei Tsuji, Ki Seok Yoon, Seiji Ogo, Biochemical characterization of a bifunctional acetaldehyde-alcohol dehydrogenase purified from a facultative anaerobic bacterium Citrobacter sp. S-77, Journal of Bioscience and Bioengineering, 10.1016/j.jbiosc.2015.06.019, 121, 3, 253-258, 2016.03, Acetaldehyde-alcohol dehydrogenase (ADHE) is a bifunctional enzyme consisting of two domains of an N-terminal acetaldehyde dehydrogenase (ALDH) and a C-terminal alcohol dehydrogenase (ADH). The enzyme is known to be important in the cellular alcohol metabolism. However, the role of coenzyme A-acylating ADHE responsible for ethanol production from acetyl-CoA remains uncertain. Here, we present the purification and biochemical characterization of an ADHE from Citrobacter sp. S-77 (ADHES77). Interestingly, the ADHES77 was unable to be solubilized from membrane with detergents either 1% Triton X-100 or 1% Sulfobetaine 3-12. However, the enzyme was easily dissociated from membrane by high-salt buffers containing either 1.0 M NaCl or (NH4)2SO4 without detergents. The molecular weight of a native protein was estimated as approximately 400 kDa, consisting of four identical subunits of 96.3 kDa. Based on the specific activity and kinetic analysis, the ADHES77 tended to have catalytic reaction towards acetaldehyde elimination rather than acetaldehyde formation. Our experimental observation suggests that the ADHES77 may play a pivotal role in modulating intracellular acetaldehyde concentration..
45. Takahiro Kishima, Takahiro Matsumoto, Nakai Hidetaka, Shinya Hayami, Takehiro Ohta, Seiji Ogo, A High-Valent Iron(IV) Peroxo Core Derived from O2., 10.1002/anie.201507022, 55, 2, 724-727, 2016.02, 本研究では、単核の高原子価(4価)の鉄に酸素が結合したペルオキソ化合物の単離に世界で初めて成功した。X線構造解析により、鉄に酸素が結合したサイド−オン型構造であることを明らかにした。この化合物は、酸素耐性ヒドロゲナーゼの「酸素活性化の中間体」のモデルとなる初めての鉄(4価)ペルオキソ化合物である。このペルオキソ化合物は、水素イオンおよび電子と反応して水を生成する。この反応は、燃料電池のカソード反応に対応している。.
46. Keisuke Takashita, Takahiro Matsumoto, Takeshi Yatabe, Nakai Hidetaka, Seiji Ogo, A Non-precious Metal, Ni Molecular Catalyst for a Fuel Cell Cathode., 10.1246/cl.150988, 45, 2, 137-139, 2016.02.
47. Koji Yoshimoto, Takeshi Yatabe, Takahiro Matsumoto, ROBERTSON ANDREW, Nakai Hidetaka, Hiromasa Tanaka, Takashi Kamachi, Yoshihito Shiota, Yoshizawa Kazunari, Koichiro Asazawa, Hirohisa Tanaka, Seiji Ogo, Synthesis and Structure of a Water-soluble μ-η1:η1-N2 Dinuclear RuII Complex with a Polyamine Ligand., 10.1246/cl.151004, 45, 2, 149-151, 2016.02.
48. Takahiro Matsumoto, Koji Yoshimoto, Chunbai Zheng, Yasuhito Shomura, Yoshiki Higuchi, Hidetaka Nakai, Seiji Ogo, Synthesis and Reactivity of a Water-soluble NiRu Monohydride Complex with a Tethered Pyridine Moiety. , 10.1246/cl.151029, 45, 2, 197-199, 2016.02.
49. Hidetaka Nakai, Kengo Matsuba, Masataka Akimoto, Tomonori Nozaki, Takahiro Matsumoto, Kiyoshi Isobe, Masahiro Irie, Seiji Ogo, Photoinduced Bending of Rod-like Millimetre-size Crystals of a Rhodium Dithionite Complex with n-Pentyl Moieties., 10.1039/C6CC00059B, 52, 23, 4349-4352, 2016.02.
50. Keisuke Takashita, Takahiro Matsumoto, Takeshi Yatabe, Nakai Hidetaka, Masatatsu Suzuki, Seiji Ogo, A Water-soluble Ni Dihydrido Complex That Reduces O2 to H2O in Water., 10.1246/cl.150935, 45, 1, 72-74, 2016.01.
51. Noor Muhd, Dina Noor, Koji Nishikawa, YOON KI SUK, Seiji Ogo, Yoshiki Higuchi, Improved Purification, Crystallization and Crystallographic Study of Hyd-2-type [NiFe]-hydrogenase from Citrobacter sp. S-77., 10.1107/S2053230X15024152, F72, 1, 52-58, 2016.01.
52. Hidetaka Nakai, Kazuhiro Kitagawa, Juncheol Seo, Takahiro Matsumoto, Seiji Ogo, A gadolinium(III) complex that shows room-temperature phosphorescence in the crystalline state, Dalton Transactions, 10.1039/c6dt01303a, 45, 29, 11620-11623, 2016.01, This paper presents a gadolinium(iii) complex that shows blue phosphorescence in the crystalline state at room temperature under air atmosphere; color of the crystals can be changed to pale-green from blue by doping of 1-naphthol..
53. Koji Yoshimoto, Takeshi Yatabe, Takahiro Matsumoto, Viet Ha Tran, Andrew Robertson, Hidetaka Nakai, Koichiro Asazawa, Hirohisa Tanaka, Seiji Ogo, Inorganic clusters with a [Fe2MoOS3] core - A functional model for acetylene reduction by nitrogenases, Dalton Transactions, 10.1039/c6dt01655c, 45, 37, 14620-14627, 2016.01, We report the first example of a wholly inorganic mimic of a part of the FeMoco active centre of nitrogenases. We detail the synthesis, characterisation and reactivity of two related, transient hydride-containing inorganic clusters, a dihydride complex and a vinyl monohydride complex, which bear the [Fe2MoOS3] portion of FeMoco. The dihydride complex is capable of reducing acetylene to ethylene via the vinyl monohydride complex. In the reaction cycle, a transient low-valent complex was generated by the reductive elimination of H2 or ethylene from dihydride or vinyl monohydride complexes, respectively..
54. Hidetaka Nakai, Juncheol Seo, Kazuhiro Kitagawa, Takahiro Goto, Takahiro Matsumoto, Seiji Ogo, An oxygen-sensitive luminescent Dy(III) complex, Dalton Transactions, 10.1039/c6dt01057a, 45, 23, 9492-9496, 2016, This paper presents the first dysprosium(iii) complex, [{(MeMeArO)3tacn}DyIII(THF)] (1Dy), that shows oxygen-sensitive luminescence. The synthesis, structure and oxygen-sensitive luminescence properties of 1Dy are reported (Φ = 0.050 and τ = 17.7 μs under N2, Φ = 0.011 and τ = 4.1 μs under O2 and KSV = 305 M-1 in THF; KSV = 0.0077%-1 in polystyrene film). The oxygen sensitive mechanism of 1Dy is discussed based on the photophysical properties of the corresponding gadolinium(iii) complex, [{(MeMeArO)3tacn}GdIII(THF)]..
55. Hidetaka Nakai, Kengo Matsuba, Masataka Akimoto, Tomonori Nozaki, Takahiro Matsumoto, Kiyoshi Isobe, Masahiro Irie, Seiji Ogo, Photoinduced bending of rod-like millimetre-size crystals of a rhodium dithionite complex with n-pentyl moieties, Chemical Communications, 10.1039/c6cc00059b, 52, 23, 4349-4352, 2016, Rod-like millimetre-size crystals of a newly prepared rhodium dithionite complex with n-pentyl moieties bend upon photoirradiation and return to the initial shape upon heating; the roles of the flexible n-pentyl moieties as well as the photoreactive dithionite unit (μ-O2SSO2) are disclosed by single crystal X-ray diffraction..
56. Takahiro Matsumoto, Tatsuya Ando, Yuki Mori, Takeshi Yatabe, Hidetaka Nakai, Seiji Ogo, A (Ni-SIr)I model for [NiFe]hydrogenase, Journal of Organometallic Chemistry, 10.1016/j.jorganchem.2014.09.025, 796, 73-76, 2015.11, We report the synthesis and characterization of a μ-hydroxo NiRu complex as a model for the active site of (Ni-SIr)I of [NiFe]hydrogenase. This is the first example of the (Ni-SIr)I model with a bridging hydroxo ligand between dimetal centers and an available coordination site on Ni center cis to the bridging hydroxo ligand. We have determined the structure of the (Ni-SIr)I model complex by X-ray analysis and reported reversible switching between the catalytically inactive (Ni-SIr)I and a catalytically active (Ni-SIr)II models..
57. Kohsei Tsuji, YOON KI SUK, Seiji Ogo, Biochemical Characterization of a Bifunctional Acetaldehyde-Alcohol Dehydrogenase Purified from a Facultative Anaerobic Bacterium Citrobacter sp. S-77. , J. Biosci. Bioeng. , 10.1016/j.jbiosc.2015.06.019. , 2015.10.
58. Takeshi Yatabe, Mitsuhiro Kikkawa, Takahiro Matsumoto, Keishi Urabe, ANDREW ROBERTSON, Nakai Hidetaka, Seiji Ogo, An Fe-based Model for Metabolism Linking between O2-reduction and H2O-oxidation. , Chem. Lett. , 10.1246/cl.150468, 44, 9, 1263-1265, 2015.09.
59. Viet Ha Tran, Takeshi Yatabe, Takahiro Matsumoto, Hidetaka Nakai, Kazuharu Suzuki, Takao Enomoto, Takashi Hibino, Kenji Kaneko, Seiji Ogo, An IrSi oxide film as a highly active water-oxidation catalyst in acidic media, Chemical Communications, 10.1039/c5cc04286k, 51, 63, 12589-12592, 2015.08, We report an acid-stable Si oxide-doped Ir oxide film (IrSi oxide film), made by metal organic chemical vapour deposition (MOCVD) of an IrV complex for electrochemical water-oxidation. This is a successful improvement of catalytic ability and stability depending upon the pH of Ir oxide by doping of Si oxide. The turnover frequency (TOF) of the electrochemical water-oxidation by the IrSi oxide film is the highest of any Si oxide-doped Ir oxide materials and higher even than that of Ir oxide in acidic media..
60. Tran Viet-Ha, Takeshi Yatabe, Takahiro Matsumoto, Nakai Hidetaka, Kazuharu Suzuki, Takao Enomoto, Hibino Takeshi, Kenji Kaneko, Seiji Ogo, An IrSi Oxide Film as a Highly Active Water-Oxidation Catalyst in Acidic Media. , Chem. Commun., 10.1039/C5CC04286K, 51, 63, 12589-12592, 2015.07.
61. Tran Viet-Ha, Takeshi Yatabe, Takahiro Matsumoto, Nakai Hidetaka, Kazuharu Suzuki, Takao Enomoto, Seiji Ogo, An N2-Compatible Ni0 MOCVD Precursor. , Chem. Lett. , org/10.1246/cl.150155, 44, 6, 794-796, 2015.06.
62. Hidetaka Nakai, Kyoshiro Nonaka, Takahiro Goto, Juncheol Seo, Takahiro Matsumoto, Seiji Ogo, A macrocyclic tetraamine bearing four phenol groups
a new class of heptadentate ligands to provide an oxygen-sensitive luminescent Tb(iii) complex with an extendable phenol pendant arm, Dalton Transactions, 10.1039/c5dt00816f, 44, 24, 10923-10927, 2015.06, This paper presents a 1,4,7,10-teraazacyclododecane-based tetrakis-phenol as a protonated ligand precursor and its oxygen-sensitive luminescent terbium(iii) complex with an extendable phenol pendant arm (Φ = 0.91 under N2, Φ = 0.031 under air), in which the potentially N4O4-octadentate ligand unprecedentedly coordinates to the Tb3+ ion in a N4O3-heptadentate fashion..
63. Nakai Hidetaka, Nonaka Kyoshiro, Goto Takahiro, Seo Juncheol, Takahiro Matsumoto, Seiji Ogo, A Macrocyclic Tetraamine bearing Four Phenol Groups: A New Class of Heptadentate Ligands To Provide an Oxygen-Sensitive Luminescent Tb(III) Complex with an Extendable Phenol Pendant Arm., Dalton Trans., 10.1039/C5DT00816F, 2015.05.
64. Viet Ha Tran, Takeshi Yatabe, Takahiro Matsumoto, Hidetaka Nakai, Kazuharu Suzuki, Takao Enomoto, Seiji Ogo, An N2-compatible Ni0 metal-organic chemical vapor deposition (MOCVD) precursor, Chemistry Letters, 10.1246/cl.150155, 44, 6, 794-796, 2015.01, We report the first example of a Ni0 precursor that provides a contamination-free (2 as the carrier gas. The structure and physical properties of the Ni0 precursor and subsequent film are described..
65. Taketa Midori, Hanae Nakagawa, Habukawa Mao, Osuka Hisao, Kihira Kiyohito, Komori Hirofumi, Shibata Naoki, Ishii Masaharu, Igarashi Yasuo, Nishihara Hirofumi, YOON KI SUK, Seiji Ogo, Shomura Yasuhito, Higuchi, Yoshiki, Crystallization and Preliminary X-ray Analysis of the NAD+-Reducing [NiFe] Hydrogenase from Hydrogenophilus Thermoluteolus TH-1. , Acta Crystallogr. Sect. F Struct. Biol. Commun. , 10.1107/S2053230X14026521, F71, 1, 96-99, 2014.12.
66. Nga T. Nguyen, Yuki Mori, Takahiro Matsumoto, Takeshi Yatabe, Ryota Kabe, Hidetaka Nakai, Ki Seok Yoon, Seiji Ogo, A [NiFe]hydrogenase model that catalyses the release of hydrogen from formic acid, Chemical Communications, 10.1039/c4cc05911e, 50, 87, 13385-13387, 2014.11, We report the decomposition of formic acid to hydrogen and carbon dioxide, catalysed by a NiRu complex originally developed as a [NiFe]hydrogenase model. This is the first example of H2 evolution, catalysed by a [NiFe]hydrogenase model, which does not require additional energy..
67. Hidetaka Nakai, Takahiro Goto, Kazuhiro Kitagawa, Kyoshiro Nonaka, Takahiro Matsumoto, Seiji Ogo, A highly luminescent and highly oxygen-sensitive Tb(III) complex with a tris-aryloxide functionalised 1,4,7-triazacyclononane ligand, Chemical Communications, 10.1039/c4cc07717b, 50, 99, 15737-15739, 2014.11, This communication presents a new terbium(III) complex that shows the highest luminescence quantum yield among the oxygen-sensitive lanthanide complexes (Φ = 0.91 under N2, Φ = 0.054 under air)..
68. Nakai Hidetaka, Goto Takahiro, Kitagawa Kazuhiro, Nonaka Kyoshiro, Takahiro Matsumoto, Seiji Ogo, A Highly Luminescent and Highly Oxygen-Sensitive Tb(III) Complex with a Tris-Aryloxide Functionalised 1,4,7-Triazacyclononane Ligand. , Chem. Commun. , 10.1039/C4CC07717B, 50, 99, 15737-15739, 2014.10.
69. Tatsuhiko Yagi, Seiji Ogo, Yoshiki Higuchi, Catalytic cycle of cytochrome-c3 hydrogenase, a [NiFe]-enzyme, deduced from the structures of the enzyme and the enzyme mimic, International Journal of Hydrogen Energy, 10.1016/j.ijhydene.2013.12.174, 39, 32, 18543-18550, 2014.10, Hydrogenases catalyze uptake and production of H2. Heterolytic cleavage of H2 bound on [NiFe]-hydrogenase (E) produces two unequal H species to form E:HaHb, where Ha and Hb behave differently. The structures of various states of the enzyme established by crystallography and spectroscopy were used to construct a catalytic cycle of the enzyme. The Ni-Fe center of the active enzyme has the Ni-Fe bridging site vacant. The enzyme is suggested to bind H2 either at Ni or Fe atom. In E:HaHb, Ha is considered to be a protein-bound hydron (proton or deuteron) at the entrance to the hydrophobic gas tunnel. The structure of a synthetic hydrogenase-mimic suggests Hb to be the 6th ligand to Fe. Two successive one-electron processes from E:HaHb complete the catalytic cycle of H2 uptake. The reverse of the cycle operates in the H2 production. The proposed catalytic cycle is consistent with the kinetic, crystallographic and spectroscopic studies..
70. Nga T. Nguyen, Takeshi Yatabe, Ki Seok Yoon, Seiji Ogo, Molybdenum-containing membrane-bound formate dehydrogenase isolated from Citrobacter sp. S-77 having high stability against oxygen, pH, and temperature, Journal of Bioscience and Bioengineering, 10.1016/j.jbiosc.2014.03.011, 118, 4, 386-391, 2014.10, Membrane-bound formate dehydrogenase (FDH) was purified to homogeneity from a facultative anaerobic bacterium Citrobacter sp. S-77. The FDH from Citrobacter sp. S-77 (FDHS77) was a monomer with molecular mass of approximately 150kDa. On SDS-PAGE, the purified FDHS77 showed as three different protein bands with molecular mass of approximately 95, 87, and 32kDa, respectively. Based on the N-terminal amino acid sequence analysis, the sequence alignments observed for the 87kDa protein band were identical to that of the large subunit of 95kDa, indicating that the purified FDHS77 consisted of two subunits; a 95kDa large subunit and a 32kDa small subunit. The purified FDHS77 in this purification did not contain a heme b subunit, but the FDHS77 showed significant activity for formate oxidation, determined by the Vmax of 30.4U/mg using benzyl viologen as an electron acceptor. The EPR and ICP-MS spectra indicate that the FDHS77 is a molybdenum-containing enzyme, displaying a remarkable O2-stability along with thermostability and pH resistance. This is the first report of the purification and characterization of a FDH from Citrobacter species..
71. Harutaka Nakamori, Takahiro Matsumoto, Takeshi Yatabe, Ki Seok Yoon, Hidetaka Nakai, Seiji Ogo, Synthesis and crystal structure of a dinuclear, monomeric MnIIp-semiquinonato complex, Chemical Communications, 10.1039/c4cc06055e, 50, 86, 13059-13061, 2014.10, Herein, we report the first crystal structure of a monomeric p-semiquinonato d-block complex and its reactivity toward dioxygen, closely associated with a biological system of an oxygen evolving centre of photosystem II..
72. Harutaka Nakamori, Takahiro Matsumoto, Takeshi Yatabe, YOON KI SUK, Nakai Hidetaka, Seiji Ogo, Synthesis and Crystal Structure of a Dinuclear, Monomeric MnII p-Semiquinonato Complex. , Chem. Commun., 50, 86, 13059-13061, 2014.09.
73. Nguyen, Nga T., Yuki Mori, Takahiro Matsumoto, Takeshi Yatabe, 嘉部 量太, Nakai Hidetaka, YOON KI SUK, Seiji Ogo, A [NiFe]hydrogenase Model That Catalyses the Release of Hydrogen from Formic Acid. , Chem. Commun., 50, 87, 13385-13387, 2014.09.
74. Takahiro Matsumoto, Tatsuya Ando, Yuki Mori, Takeshi Yatabe, Nakai Hidetaka, Seiji Ogo, A (Ni-SIr)I Model for [NiFe]hydrogenase. , J. Organomet. Chem., 2014.09.
75. Hidetaka Nakai, Kihun Jeong, Takahiro Matsumoto, Seiji Ogo, Catalytic C-F bond hydrogenolysis of fluoroaromatics by [(η5-C5Me5)RhI(2,2′-bipyridine)], Organometallics, 10.1021/om500647h, 33, 17, 4349-4352, 2014.09, A new class of efficient catalyst, the Rh(I) complex [(η5-C5Me5)RhI(bpy)] (1; bpy = 2,2′-bipyridine), for the C-F bond hydrogenolysis of fluoroaromatics (C6F5CF3, C6F6, C6F5H, and C6F5CH3) is presented. The best turnover number of 380 for C6F6 is afforded by using 0.1 mol % of 1, 0.8 MPa of H2, and 2 equiv of Et2NH in CH3CN at 25 °C. The successful isolation of the C-F bond cleavage product [(η5-C5Me5)RhIII(bpy)(C6F5)](F) as a plausible intermediate of the catalytic hydrogenolysis of C6F6 by 1 is also described..
76. Takeshi Yatabe, Takahiro Kikunaga, Takahiro Matsumoto, Nakai Hidetaka, YOON KI SUK, Seiji Ogo, Synthesis of Aqueous-stable and Water-soluble Mononuclear Nonheme MnV–oxo Complexes Using H2O2 as an Oxidant., Chem. Lett. , 43, 8, 1380-1382, 2014.08.
77. Nakai Hidetaka, Kihun Jeong, Takahiro Matsumoto, Seiji Ogo, Catalytic C−F Bond Hydrogenolysis of Fluoroaromatics by [(η5‑C5Me5)RhI(2,2′-bipyridine)]. , Organometallics, 33, 17, 4349-4352, 2014.08.
78. Takahiro Matsumoto, Shigenobu Eguchi, Hidetaka Nakai, Takashi Hibino, Ki Suk Yoon, Seiji Ogo, Hydrogenase from citrobacter sp. S-77 surpasses platinum as an electrode for H2 oxidation reaction, Angewandte Chemie - International Edition, 10.1002/anie.201404701, 53, 34, 8895-8898, 2014.08, Reported herein is an electrode for dihydrogen (H2) oxidation, and it is based on [NiFe]Hydrogenase from Citrobacter sp. S-77 ([NiFe] S77). It has a 637 times higher mass activity than Pt (calculated based on 1 mg of [NiFe]S77 or Pt) at 50 mV in a hydrogen half-cell. The [NiFe]S77 electrode is also stable in air and, unlike Pt, can be recovered 100% after poisoning by carbon monoxide. Following characterization of the [NiFe]S77 electrode, a fuel cell comprising a [NiFe] S77 anode and Pt cathode was constructed and shown to have a a higher power density than that achievable by Pt..
79. Harutaka Nakamori, Takeshi Yatabe, Ki Seok Yoon, Seiji Ogo, Purification and characterization of an oxygen-evolving photosystem II from Leptolyngbya sp. strain O-77, Journal of Bioscience and Bioengineering, 10.1016/j.jbiosc.2014.01.009, 118, 2, 119-124, 2014.08, A new cyanobacterium of strain O-77 was isolated from a hot spring at Aso-Kuju National Park, Kumamoto, Japan. According to the phylogenetic analysis determined by 16S rRNA gene sequence, the strain O-77 belongs to the genus Leptolyngbya, classifying into filamentous non-heterocystous cyanobacteria. The strain O-77 showed the thermophilic behavior with optimal growth temperature of 55°C. Moreover, we have purified and characterized the oxygen-evolving photosystem II (PSII) from the strain O-77. The O2-evolving activity of the purified PSII from strain O-77 (PSIIO77) was 1275±255μmol O2 (mg Chl a)-1h-1. Based on the results of MALDI-TOF mass spectrometry and urea-SDS-PAGE analysis, the purified PSIIO77 was composite of the typical PSII components of CP47, CP43, PsbO, D2, D1, PsbV, PsbQ, PsbU, and several low molecular mass subunits. Visible absorption and 77K fluorescence spectra of the purified PSIIO77 were almost identical to those of other purified PSIIs from cyanobacteria. This report provides the successful example for the purification and characterization of an active PSII from thermophilic, filamentous non-heterocystous cyanobacteria..
80. Takahiro Matsumoto, Shigenobu Eguchi, Nakai Hidetaka, Takashi Hibino, YOON KI SUK, Seiji Ogo, [NiFe]Hydrogenase from Citrobacter sp. S-77 Surpasses Platinum as an Electrode for H2 Oxidation Reaction. , Angew. Chem. Int. Ed, , 53, 34, 8895-8898, 2014.06, 水素と酸素から電気を作る燃料電池は、排出物として水しか生成しないクリーンな発電装置である。燃料電池はその構造によって数種類に分類され、なかでも低温作動や小型軽量化が可能な固体高分子形燃料電池(polymer electrolyte fuel cell、PEFC)は、家庭用、携帯用、自動車用電源に適している。しかし、PEFCの電極触媒は枯渇資源で高価な白金触媒であり、その代替触媒の開発が行われてきたが、未だに白金に代わる実用触媒の開発には至っていない。本研究では、水素極(水素から電子を取り出す電極)の脱白金触媒として水素酸化酵素であるヒドロゲナーゼを用いたPEFCを初めて作製し、それらの発電実験に成功した。本研究で使用したヒドロゲナーゼS–77(当研究室で新規に探索・精製・単離)は、これまでのヒドロゲナーゼよりも高活性かつ頑丈であり、PEFCの作動条件でも十分にその機能を発揮できる。ヒドロゲナーゼS–77の単位重量あたりの水素酸化活性は、白金触媒に対して637倍であることを明らかにした。.
81. Seiji Ogo, H2 and O2 activation - A remarkable insight into hydrogenase, Chemical Record, 10.1002/tcr.201402010, 14, 3, 397-409, 2014.06, This article summarizes the development of a range of organometallic, biomimetic analogues of [NiFe]hydrogenases and their employment in a new generation of H2-O2 fuel cells. It begins with a summary of O2-sensitive and O2-tolerant enzyme chemistry before detailing the properties and functionality of our biomimetic complexes, including: the first ever fully functional model, selective H2 and O2 activation, and the first catalyst using only common metals. These systems are centered on Ni-Fe, Ni-Ru, Ir-Ir, and Rh-Rh cores and use a range of ligands that all follow a set of design principles described herein. The development of a range of organometallic, biomimetic analogues of [NiFe]hydrogenases and their employment in a new generation of H 2-O2 fuel cells are described. This account begins with a summary of O2-sensitive and O2-tolerant enzyme chemistry before detailing the properties and functionality of our biomimetic complexes, including: the first ever fully functional model, selective H2 and O2 activation, and the first catalyst using only common metals..
82. Seiji Ogo, H2 and O2 Activation—A Remarkable Insight into Hydrogenase. , Chem. Rec. , 14, 3, 397-409, 2014.05.
83. David P. Smith, Hong Chen, Seiji Ogo, Ana I. Elduque, Miriam Eisenstein, Marilyn M. Olmstead, Richard H. Fish, Bioorganometallic chemistry. 27. Synthetic, x-ray crystallographic, and competitive binding studies in the reactions of nucleobases, nucleosides, and nucleotides with [Cp*Rh(H2O)3](OTf)2, as a function of pH, and the utilization of several Cp*Rh-DNA base complexes in host-guest chemistry, Organometallics, 10.1021/om500106r, 33, 10, 2389-2404, 2014.05, The reactions of the air- and water-stable tris(aqua) complex [Cp*Rh(H2O)3](OTf)2 (1; OTf = trifluoromethanesulfonate) with nucleobases and nucleosides that included 9-methyladenine (9-MA), 9-ethylguanine (9-EG), 9-methylhypoxanthine (9-MH), 9-ethylhypoxanthine (9-EH), 1-methylcytosine (1-MC), 1-methylthymine (1-MT), adenosine (Ado), and guanosine (Guo) provided new bonding modes, all as a function of pH. The 9-MA nucleobase provided a novel cyclic trimer, at pH 6, characteristic for all Ado complexes: [Cp*Rh(μ2- η1(N1): η2(N6,N7)-9-MA/Ado)]3(OTf) 3. The Cp*Rh(9-EG) and Cp*Rh(Guo) complexes showed N7 and 6-C-O binding modes in water, [Cp*Rh((η2(N7,O6)-9-EG/Guo) (OH)](OTf), and no cyclic trimer products, due to a pronounced steric effect of the 2-amino group. This was shown convincingly by the results with 9-MH and 9-EH, which did form cyclic trimers at pH 6.1, [Cp*Rh(μ2- η1(N1):η2(N7,O6)-9-MH/9-EH)]3(OTf) 3, with a structure similar to that of 9-EG, but with no 2-amino group available. At pH 10.2, the pKa of the 9-MH's NH1 hydrogen dictated the structure, providing a μ-hydroxy dimer, trans- [Cp*Rh(η1(N1)-9-MH)(μ-OH)]2(OTf) 2, while in methanol the same reaction provided a mononuclear complex, [Cp*Rh(η1(N7)-9-MH)(MeOH)2](OTf) 2. The reaction of 1 and 1-MC, at pH 5.4, provided another μ-hydroxy dimer with intramolecular H bonding of the O and H atoms of the μ-OH groups (H-acceptor and H-donor, respectively), trans- [Cp*Rh(η1(N3)-1-MC)(μ-OH)]2(OTf) 2, while in acetone, the product was a monomeric complex, [(η5-Cp*Rh)(η1(N3)-1-MC)( η2(O2,N3)-1-MC)](OTf)2. The reaction of 1 and 1-MT at pH 10 showed the initial complex 1 being converted to its equilibrium complex, [(Cp*Rh)2(μ-OH)3]+, and this led to two components being formed. The anionic component was a linear [(η1(N3)-MT)-RhI-(η1(N3)-MT)] - (12e RhI center) assembly, formed via a presumed reductive elimination of Cp*OH, and included an orthogonal array of two thymine planes. The cationic component was [(Cp*Rh)2(μ-OH) 3]+, with its Cp* moiety being π-π stacked with thymine rings, as well as the π-π interactions of two thymine rings: {[RhI1(N3)-1-MT)2]2[(Cp* Rh)2(μ-OH)3]3}OH. The competitive order of nucleoside reactivity was Ado ≫ Guo, while for the nucleotides it was GMP > AMP ≫ CMP ≈ TMP. Finally, we also discuss several examples of the utilization of these unique Cp*Rh-DNA base complexes, as aqueous hosts for molecular recognition of aromatic amino acids and as NMR shift reagents for many organic compounds..
84. Nguyen, Nga T., Takeshi Yatabe, YOON KI SUK, Seiji Ogo, Molybdenum-Containing Membrane-Bound Formate Dehydrogenase Isolated from Citrobacter sp. S-77 Having High Stability against Oxygen, pH, and Temperature. , J. Biosci. Bioeng. , 118, 4, 386-391, 2014.04.
85. Smith, David P., Chen, Hong, Seiji Ogo, Elduque, Ana I., Eisenstein, Miriam, Olmstead, Marilyn M., Fish, Richard H., Bioorganometallic Chemistry. 27. Synthetic, X-ray Crystallographic, and Competitive Binding Studies in the Reactions of Nucleobases, Nucleosides, and Nucleotides with [Cp*Rh(H2O)3](OTf)2, as a Function of pH, and the Utilization of Several Cp*Rh–DNA Base Complexes in Host–Guest Chemistry. , Organometallics , 33, 10, 2389-2404, 2014.04.
86. Kyoshiro Nonaka, YOON KI SUK, Seiji Ogo, Biochemical Characterization of Psychrophilic Mn-Superoxide Dismutase from Newly Isolated Exiguobacterium sp. OS-77. , Extremophiles 2014, 18 , 2, 363–373, 2014.03.
87. Takeshi Yatabe, Mitsuhiro Kikkawa, Takahiro Matsumoto, Nakai Hidetaka, Kenji Kaneko, Seiji Ogo, A model for the water-oxidation and recovery systems of the oxygen-evolving complex., Dalton Trans., 43, 8, 3063–3071, 2014.02.
88. Harutaka Nakamori, Takeshi Yatabe, YOON KI SUK, Seiji Ogo, Purification and Characterization of an Oxygen-Evolving Photosystem II from Leptolyngbya sp. strain O-77. , J. Biosci. Bioeng., 118, 2, 119–124, 2014.02.
89. Takeshi Yatabe, Mitsuhiro Kikkawa, Takahiro Matsumoto, Hidetaka Nakai, Kenji Kaneko, Seiji Ogo, A model for the water-oxidation and recovery systems of the oxygen-evolving complex, Dalton Transactions, 10.1039/c3dt52846d, 43, 8, 3063-3071, 2014.02, We propose a model for the water-oxidation and recovery systems of the oxygen-evolving complex (OEC) of the photosystem II (PSII) enzyme. The whole system is constructed from two catalytic cycles, conducted as a tandem reaction: (i) a water-oxidation loop uses cerium(iv) ammonium nitrate as an oxidant to activate a dimanganese complex for water-oxidation and thereby liberate a molecule of O2 and (ii) a recovery loop begins with photoinhibition of the dimanganese complex but then uses O2 to reactivate the manganese centre. The net result is a catalytic water-oxidation catalyst that can use self-generated O2 for recovery..
90. Tatsuhiko Yagi, Seiji Ogo, Yoshiki Higuchi, Catalytic Cycle of Ctochrome-c3 Hydrogenase, a [NiFe]-Enzyme, Deduced from the Structures of the Enzyme and the Enzyme Mimic. , Int. J. Hydrogen Energy , 39, 32, 18543–18550, 2014.01.
91. Kyoshiro Nonaka, Ki Suk Yoon, Seiji Ogo, Biochemical characterization of psychrophilic Mn-superoxide dismutase from newly isolated Exiguobacterium sp. OS-77, Extremophiles, 10.1007/s00792-013-0621-x, 18, 2, 363-373, 2014.01, Many types of superoxide dismutases have been purified and characterized from various bacteria, however, a psychrophilic Mn-superoxide dismutase (MnSOD) has not yet been reported. Here, we describe the purification and the biochemical characterization of the psychrophilic MnSOD from Exiguobacterium sp. strain OS-77 (EgMnSOD). According to 16S rRNA sequence analysis, a newly isolated bacterium strain OS-77 belongs to the genus Exiguobacterium. The optimum growth temperature of the strain OS-77 is 20 °C. The EgMnSOD is a homodimer of 23.5 kDa polypeptides determined by SDS-PAGE and gel filtration analysis. UV-Vis spectrum and ICP-MS analysis clearly indicated that the homogeneously purified enzyme contains only a Mn ion as a metal cofactor. The optimal reaction pH and temperature of the enzyme were pH 9.0 and 5 °C, respectively. Notably, the purified EgMnSOD was thermostable up to 45 °C and retained 50 % activity after 21.2 min at 60 °C. The differential scanning calorimetry also indicated that the EgMnSOD is thermostable, exhibiting two protein denaturation peaks at 65 and 84 °C. The statistical analysis of amino acid sequence and composition of the EgMnSOD suggests that the enzyme retains psychrophilic characteristics..
92. Takeshi Yatabe, Takahiro Kikunaga, Takahiro Matsumoto, Hidetaka Nakai, Ki Seok Yoon, Seiji Ogo, Synthesis of aqueous-stable and water-soluble mononuclear nonheme MnV-Oxo complexes using H2O2as an oxidant, Chemistry Letters, 10.1246/cl.140376, 43, 8, 1380-1382, 2014.01, We report the synthesis of mononuclear nonheme manganese(V)oxo complexes in aqueous acetonitrile solution from the reaction of manganese(III) complexes using hydrogen peroxide as an oxidant for the first time. A crystal structure of chloro derivative of manganese(V)oxo complex and its reactivity toward 3,5-di-tert-butyl-catechol are also reported..
93. Takahiro Kikunaga, Takahiro Matsumoto, Takehiro Ohta, Nakai Hidetaka, Yoshinori Naruta, Kwang-Hyun Ahn, Yoshihito Watanabe, Seiji Ogo, Isolation of a MnIV Acylperoxo Complex and Its Monooxidation Ability., Chem. Commun., 49, 75, 8356-8358, 2013.10.
94. Daisuke Inoki, Takahiro Matsumoto, Hidetaka Nakai, Seiji Ogo, Isolation and crystal structure of the proposed low-valent active species in the H2 activation catalytic cycle, European Journal of Inorganic Chemistry, 10.1002/ejic.201300049, 22-23, 3978-3986, 2013.10, We provide confirmation of our proposed design principles for a H 2 activation catalytic cycle by constructing a new catalyst. We have been able to obtain a crystal structure to confirm our proposition that a reduced, dinuclear species stores electrons from hydrogen molecules in a metal-metal bond..
95. Daisuke Inoki, Takahiro Matsumoto, Nakai Hidetaka, Seiji Ogo, Isolation and Crystal Structure of the Proposed Low-Valent Active Species in the H2 Activation Catalytic Cycle. , Eur. J. Inorg. Chem. , 2013, 22-23, 3978-3986, 2013.08.
96. Nakai Hidetaka, Kazuhiro Kitagawa, Harutaka Nakamori, Taisuke Tokunaga, Takahiro Matsumoto, Koichi Nozaki, Seiji Ogo, Reversible Switching of the Luminescence of a Photoresponsive Gadolinium(III) Complex. , Angew. Chem. Int. Ed. , 52, 33, 8722-8725, 2013.08.
97. Takahiro Kikunaga, Takahiro Matsumoto, Takehiro Ohta, Hidetaka Nakai, Yoshinori Naruta, Kwang Hyun Ahn, Yoshihito Watanabe, Seiji Ogo, Isolation of a MnIV acylperoxo complex and its monooxidation ability, Chemical Communications, 10.1039/c3cc43447h, 49, 75, 8356-8358, 2013.08, The first example of monooxygenation by a high-valent MnIV complex with a peroxide is described. A key MnIV acylperoxo intermediate, which uses m-chloroperoxybenzoic acid as the oxygen donor, is directly observed by electro-spray ionization mass spectrometry and resonance Raman spectroscopy..
98. Hidetaka Nakai, Kazuhiro Kitagawa, Harutaka Nakamori, Taisuke Tokunaga, Takahiro Matsumoto, Koichi Nozaki, Seiji Ogo, Reversible switching of the luminescence of a photoresponsive gadolinium(III) complex, Angewandte Chemie - International Edition, 10.1002/anie.201303137, 52, 33, 8722-8725, 2013.08, From blue to red: The structure and luminescence properties of the gadolinium(III) complex 1 were investigated. Reversible switching of the luminescence of 1 in THF at room temperature by alternating light irradiation and O2 exposure is presented, during which the emission color changes as shown in the picture. Light-induced phosphorescence of 1 plays a key role in this behavior..
99. Takahiro Matsumoto, Kyoungmok Kim, Nakai Hidetaka, Takashi Hibino, Seiji Ogo, Organometallic Catalysts for Use in a Fuel Cell. , ChemCatChem, 5, 6, 1368-1373, 2013.06.
100. Takahiro Matsumoto, Kyoungmok Kim, Hidetaka Nakai, Takashi Hibino, Seiji Ogo, Organometallic Catalysts for Use in a Fuel Cell, ChemCatChem, 10.1002/cctc.201200595, 5, 6, 1368-1373, 2013.06, We report the successful increase in performance of a fuel cell based on organometallic catalysis. An organometallic [NiIIRuIV] peroxo complex functions as cathode catalyst and was designed following mechanistic consideration of the cell. It was confirmed that the organometallic [NiIIRuIV] peroxo catalyst could function in the fuel cell with a 240% increase in power output over our previous systems. This organometallic catalyst can act in both solid and solution phases and allows observation of the mechanism, hence providing us further opportunity for future improvement..
101. Kyoshiro Nonaka, Nguyen, Nga T., Yoon, Ki-Seok, Seiji Ogo, Katsuhiro Kusaka, Takashi Ohhara, Novel “H2-oxidizing” [NiFeSe]hydrogenase from Desulfovibrio vulgaris Miyazaki F., J. Biosci. Bioeng., 115, 4, 366-371, 2013.04.
102. Kyoshiro Nonaka, Nga T. Nguyen, Ki Suk Yoon, Seiji Ogo, Novel H2-oxidizing [NiFeSe]hydrogenase from Desulfovibrio vulgaris Miyazaki F, Journal of Bioscience and Bioengineering, 10.1016/j.jbiosc.2012.10.011, 115, 4, 366-371, 2013.04, [NiFeSe]hydrogenases are promising biocatalysts in H2-based technology due to their high catalytic activity and O2-stability. Here, we report purification and characterization of a new membrane-associated [NiFeSe]hydrogenase from Desulfovibrio vulgaris Miyazaki F ([NiFeSe]DvMF). The [NiFeSe]DvMF was composed of two subunits, corresponding to a large subunit of 58.3 kDa and a small subunit of 29.3 kDa determined by SDS-PAGE. Unlike conventional [NiFeSe]hydrogenases having catalytic bias toward H2-production, the [NiFeSe]DvMF showed 11-fold higher specific activity of H2-oxidation (2444 U/mg) than that of H2-production (217 U/mg). At the optimal reaction temperature of the enzyme (65°C), the specific activity of H2-oxidation could reach up to 21,553 U/mg. Amperometric assays of the [NiFeSe]DvMF clearly indicated that the enzyme had a remarkable O2-stability. According to the amino acid sequence alignment, the conserved cysteine residue at position 281 in medial cluster of other [NiFeSe]hydrogenases was specifically replaced by a serine residue (Ser281) in the [NiFeSe]DvMF. These results indicate that the [NiFeSe]DvMF can play as a new H2-oxidizing and O2-stable biocatalyst, along with providing helpful insights into the structure-function relationship of [NiFeSe]hydrogenases..
103. Seiji Ogo, Koji Ichikawa, Takahiro Kishima, Takahiro Matsumoto, Nakai Hidetaka, Katsuhiro Kusaka, Takashi Ohhara, A Functional [NiFe]Hydrogenase Mimic That Catalyzes Electron and Hydride Transfer from H2. , Science , 339, 6120, 682-684, 2013.02, ニッケル・鉄ヒドロゲナーゼは、常温・常圧という温和な条件下で触媒的に水素を酸化する酵素である。多くの研究グループが、ニッケル・鉄ヒドロゲナーゼの機能モデル錯体の開発を試みてきたが、これまで達成されることはなかった。本研究では、世界で初めて常温・常圧で水素をヘテロリティックに活性化し、水素を酸化できるニッケル・鉄モデル錯体の開発に成功した。その反応中間体であるヒドリド錯体の構造は、X線構造解析をはじめとする種々の分光学的測定によって決定された。.
104. Seiji Ogo, Koji Ichikawa, Takahiro Kishima, Takahiro Matsumoto, Hidetaka Nakai, Katsuhiro Kusaka, Takashi Ohhara, A functional [NiFe]hydrogenase mimic that catalyzes electron and hydride transfer from H2, Science, 10.1126/science.1231345, 339, 6120, 682-684, 2013.02, Chemists have long sought to mimic enzymatic hydrogen activation with structurally simpler compounds. Here, we report a functional [NiFe]-based model of [NiFe]hydrogenase enzymes. This complex heterolytically activates hydrogen to form a hydride complex that is capable of reducing substrates by either hydride ion or electron transfer. Structural investigations were performed by a range of techniques, including x-ray diffraction and neutron scattering, resulting in crystal structures and the finding that the hydrido ligand is predominantly associated with the Fe center. The ligand's hydridic character is manifested in its reactivity with strong acid to liberate H2..
105. Kyoungmok Kim, Takahiro Kishima, Takahiro Matsumoto, Hidetaka Nakai, Seiji Ogo, Selective redox activation of H2 or O2 in a [NiRu] complex by aromatic ligand effects, Organometallics, 10.1021/om300833m, 32, 1, 79-87, 2013.01, We present two closely related series of a [NiFe] hydrogenase analogue. Based on a [NiRu] core, these complexes demonstrate inactivity, H2 activation, or O2 activation depending only on the nature of the Ru-coordinated aromatic ligand. It is demonstrated that even small changes made to this aromatic ligand can modulate the catalytic activity of the complex. Structural, electrochemical, kinetic, and thermodynamic studies reveal that differences in activation and binding modes of the substrates, combined with differences in σ donation and lability of the aromatic ligands, result in abrupt changes in catalytic activity..
106. Kyoungmok Kim, Takahiro Kishima, Takahiro Matsumoto, Nakai Hidetaka, Seiji Ogo, Selective Redox Activation of H2 or O2 in a [NiRu] Complex by Aromatic Ligand Effects. , Organometallics, 32, 1, 79-87, 2012.12.
107. Eguchi, Shigenobu; Yoon, Ki-Seok; Ogo, Seiji.* , O2-stable Membrane-bound [NiFe] hydrogenase from a Newly Isolated Citrobacter sp. S-77, J. Biosci. Bioeng. , 114, 5, 479-484, 2012.11.
108. Shigenobu Eguchi, Ki Seok Yoon, Seiji Ogo, O 2-stable membrane-bound [NiFe]hydrogenase from a newly isolated Citrobacter sp. S-77, Journal of Bioscience and Bioengineering, 10.1016/j.jbiosc.2012.05.018, 114, 5, 479-484, 2012.11, Hydrogenases are of great interest due to their potential use in H 2-based technology. However, most hydrogenases are highly sensitive to O 2, which have been the major bottleneck in hydrogenase studies. Here we report an O 2-stable membrane-bound [NiFe]hydrogenase (MBH) purified from a newly isolated strain, S-77. According to the 16S rRNA gene sequence and phylogenetic analysis of the strain S-77, it belongs to the genus of Citrobacter. In vitro experiments using the cytoplasmic membrane of strain S-77 suggested that a cytochrome b acts as the physiological electron acceptor of the MBH. The purified MBH was composed of a dimer of heterodimers, consisting of two distinct subunits with the molecular weights of 58.5 and 38.5 kDa. The enzyme showed a specific activity for H 2-oxidation of 661U/mg, which is 35-fold greater than that for H 2-production of 18.7U/mg. Notably, the MBH showed a remarkable O 2-stability, maintaining almost 95% of its original activity even after incubation for 30 h in air at 4°C. These results suggest that the O 2-stable MBH may play an important role in the H 2-metabolic pathway under the aerobic conditions of Citrobacter sp. S-77. This is the first report of the purification and biochemical characterization of an O 2-stable MBH from the genus of Citrobacter..
109. Jeong, Kihun; Nakamori, Harutaka; Imai, Shunsuke; Matsumoto, Takahiro; Ogo, Seiji;*Nakai, Hidetaka.* , A Neutral Five-coordinated Organoruthenium(0) Complex: X-ray Structure and Unique Solvatochromism, Chem. Lett., 41, 6, 650-651, 2012.06.
110. Kihun Jeong, Harutaka Nakamori, Shunsuke Imai, Takahiro Matsumoto, Seiji Ogo, Hidetaka Nakai, A neutral five-coordinated organoruthenium(0) complex
X-ray structure and unique solvatochromism, Chemistry Letters, 10.1246/cl.2012.650, 41, 6, 650-651, 2012.06, The structure of a neutral five-coordinated organoruthenium( 0) complex [(η 6-C 6Me 6)Ru 0(bpy)] (1, bpy: 2,2′-bipyridine) was determined by X-ray diffraction analysis. The solvent-induced reversible color change based on the interconversion between the purple Ru 0 complex 1 and a yellow Ru IIhydride complex [(η 6-C 6Me 6)Ru II(bpy)H] + is presented..
111. Kyoungmok Kim, Takahiro Matsumoto, Andrew Robertson, Hidetaka Nakai, Seiji Ogo, Simple ligand effects switch a hydrogenase mimic between H 2 and O 2 activation, Chemistry - An Asian Journal, 10.1002/asia.201101020, 7, 6, 1394-1400, 2012.06, Herein, we report a [NiRu] biomimetic system for O 2-tolerant [NiFe]hydrogenases and demonstrate that electron donation to the [NiRu] center can switch the system between the activation of H 2 and O 2 through simple ligand effects by using hexamethylbenzene and pentamethylcyclopentadienyl ligands, respectively. Furthermore, we present the synthesis and direct observations of a [NiRu]-peroxo species, which was formed by the oxygenation of a Ni-SIa model [NiRu] complex, that we propose as a biomimetic analogue of O 2-bound species (OBS) of O 2-tolerant [NiFe]hydrogenases. The [NiRu]-peroxo complex was fully characterized by X-ray analysis, X-ray photoelectron spectroscopy (XPS), mass spectrometry, and 1H NMR spectroscopy. The OBS analogue was capable of oxidizing p-hydroquinone and sodium borohydride to turn back into the Ni-SIa model complex..
112. Daisuke Inoki, Takahiro Matsumoto, Hideki Hayashi, Keisuke Takashita, Hidetaka Nakai, Seiji Ogo, Establishing the mechanism of Rh-catalysed activation of O 2 by H 2, Dalton Transactions, 10.1039/c1dt11599e, 41, 15, 4328-4334, 2012.04, Reductive activation of O 2 by H 2 with rhodium terpyridine complexes in H 2O and CH 3CN is described and the mechanism is fully elucidated. The rhodium complex extracts electrons from H 2 and reductively activates O 2 to form a peroxo active intermediate. This intermediate is able to oxidise triphenyl phosphine to triphenyl phosphine oxide. A model system constructed in CH 3CN provides isolable analogues of catalytic intermediates in H 2O, allowing a detailed look at each step in the catalytic cycle..
113. Daisuke Inoki, Takahiro Matsumoto, Hidetaka Nakai, Seiji Ogo, Experimental study of reductive elimination of H 2 from rhodium hydride species, Organometallics, 10.1021/om2009759, 31, 8, 2996-3001, 2012.04, A Rh III monohydride terpyridine complex undergoes reductive elimination of H 2 in CH 3CN to form a dinuclear Rh II complex with a metal-metal bond. Kinetic studies have revealed that the conversion from the monohydride species to the dinuclear species with evolution of H 2 obeys first-order kinetics and have determined the kinetic deuterium isotope effect value to be 2.0. We discuss the mechanism for the reductive elimination of H 2 from rhodium hydride species..
114. Kim, Kyoungmok; Matsumoto, Takahiro; Robertson, Andrew; Nakai, Hidetaka; Ogo, Seiji.*, Simple Ligand Effects Switch a Hydrogenase Mimic between H2 and O2 Activation, Chemistry - An Asian Journal, 2012.03.
115. Inoki, Daisuke; Matsumoto, Takahiro; Nakai, Hidetaka; Ogo, Seiji.* , Experimental Study of Reductive Elimination of H2 from Rhodium Hydride Species, Organometallics, 31, 8, 2996-3001, 2012.03.
116. Tatsuya Ando, Naoki Nakata, Kazuharu Suzuki, Takahiro Matsumoto, Seiji Ogo, Ru cyclooctatetraene precursors for MOCVD, Dalton Transactions, 10.1039/c1dt11454a, 41, 6, 1678-1682, 2012.02, A series of Ru 0 cyclooctatetraene complexes are presented with optimal properties for MOCVD (metal organic chemical vapour deposition) applications, including combinations of the two lowest melting points and lowest decomposition temperatures yet reported for such materials. The compounds are easy to handle and lead to highly conformal thin films of Ru on SiO 2 features; even within holes with aspect ratios of 40:1. SEM, AFM and XPS studies confirm the near ideal nature of the resulting conformal thin film..
117. Yatabe, Takeshi; Karasawa, Masaki; Isobe, Kiyoshi; Ogo, Seiji; Nakai, Hidetaka.* , A Naphthyl-substituted Pentamethylcyclopentadienyl Ligand and its Sm(II) Bent-metallocene Complexes with Solvent-induced Structure Change, Dalton Trans., 41, 354-356, 2012.01.
118. Inoki, Daisuke; Matsumoto, Takahiro; Hayashii, Hideki; Takashita, Keisuke; Nakai, Hidetaka; Ogo, Seiji.*, Establishing the Mechanism of Rh-catalysed Activation of O2 by H2, Dalton Trans. , 2012.01.
119. Daisuke Inoki, Takahiro Matsumoto, Hidetaka Nakai, Seiji Ogo, A mer-Triaqua Rh complex with a terpyridine ligand, Chemistry Letters, 10.1246/cl.2012.116, 41, 1, 116-118, 2012.01, We report the synthesis of a mer-triaqua Rh III complex using terpyridine as a meridional tridentate ligand. This is the first example of a structurally characterized six-coordinated mertriaqua complex for any second- or third-row element from the main transition-metal groups (groups 511). This is also the first example of a structurally characterized mer-triaqua complex with terpyridine for any transition metal. Acid dissociation constants, pK a1 and pK a2, of the triaqua complex are determined to be 3.0 and 6.9, respectively..
120. Takeshi Yatabe, Masaki Karasawa, Kiyoshi Isobe, Seiji Ogo, Hidetaka Nakai, A naphthyl-substituted pentamethylcyclopentadienyl ligand and its Sm(ii) bent-metallocene complexes with solvent-induced structure change, Dalton Transactions, 10.1039/c1dt11844g, 41, 2, 354-356, 2012.01, A naphthyl-substituted pentamethylcyclopentadienyl ligand (Cp Naph = η 5-C 5Me 4CH 2C 10H 7) and its Sm(ii) complexes [Sm(Cp Naph) 2(THF) x] (1: x = 2, 2: x = 0) have been prepared and characterised. The solvent-induced reversible conversion between the di-THF solvated purple complex 1 and the un-solvated dark green complex 2 is presented..
121. Inoki, Daisuke; Matsumoto, Takahiro; Nakai, Hidetaka; Ogo, Seiji.* , A mer-Triaqua Rh Complex with a Terpyridine Ligand, Chem. Lett. , 41, 116-118, 2011.12.
122. Takahiro Matsumoto, Kyoungmok Kim, Seiji Ogo, Molecular catalysis in a fuel cell, Angewandte Chemie - International Edition, 10.1002/anie.201104498, 50, 47, 11202-11205, 2011.11, Jack of all trades: A fuel cell based on a single molecular catalyst (see picture) uses a [NiFe]hydrogenase mimic to catalyze the oxidation of H
2
. Crucially, the catalyst is also active for the reduction of O
2
, allowing the construction of a fully functional fuel cell. This molecular catalyst can function both in solid and solution phases, allowing precise observation of the mechanism..
123. Takahiro Matsumoto, Takuma Nagahama, Jaeheung Cho, Takuhiro Hizume, Masatatsu Suzuki, Seiji Ogo, Preparation and reactivity of a nickel dihydride complex, Angewandte Chemie - International Edition, 10.1002/anie.201104918, 50, 45, 10578-10580, 2011.11, A generous donor: A dinuclear octahedral bis(μ-hydrido)dinickel(II) complex (see picture; C gray, H black, N blue, Ni green) acts as an electron donor to reduce electron acceptors such as methyl viologen. The complex is proposed as a functional model for the dihydride intermediate of an NiRu hydrogenase mimic and, by extension, of [NiFe]hydrogenase itself..
124. Ando, Tatsuya; Nakata, Naoki; Suzuki, Kazuharu; Matsumoto, Takahiro; Ogo, Seiji, Ru Cyclooctatetraene Precursors for MOCVD, Dalton Trans., 41, 1678-1682, 2011.10.
125. Matsumoto, Takahiro; Nagahama, Takuma; Cho, Jaeheung; Hizume, Takuhiro; Suzuki, Masatatsu; Ogo, Seiji, Preparation and Reactivity of a Nickel Dihydride Complex, Angew. Chem. Int. Ed., 50, 10578-10580, 2011.10, 水素酸化酵素(ヒドロゲナーゼ)は、水中・常温・常圧という温和な条件下で、触媒的に水素を酸化する魅力的な酵素である。その酵素1分子単位での水素酸化の触媒効率は、人工触媒である白金よりも優れていることが知られている。そのため、ヒドロゲナーゼの水素酸化触媒サイクルの解明は非常に重要である。しかし、触媒反応の鍵となる還元活性種であるジヒドリド錯体は、これまで観測されていなかった。本研究では世界で初めてその還元活性種のモデル錯体の合成とその反応性を明らかにすることに成功した。.
126. Matsumoto, Takahiro; Kim, Kyoungmok; Ogo, Seiji, Molecular Catalysis in a Fuel Cell, Angew. Chem. Int. Ed., 50, 11202-11205, 2011.10, 一般的に燃料電池電極触媒には、枯渇資源で高価な白金触媒が使用されている。そのため、白金代替触媒の開発が実用化に向けての大きな課題である。本論文では、白金の代替分子触媒を開発し、世界初の分子触媒を用いた分子燃料電池を開発し、水素と酸素を用いて発電させることに成功した。.
127. Robertson, Andrew; Matsumoto, Takahiro; Ogo, Seiji, The Development of Aqueous Transfer Hydrogenation Catalysts, Dalton Trans., 40, 10304-10310, 2011.10.
128. Andrew Robertson, Takahiro Matsumoto, Seiji Ogo, The development of aqueous transfer hydrogenation catalysts, Dalton Transactions, 10.1039/c1dt10544b, 40, 40, 10304-10310, 2011.10, This review discusses the development of aqueous phase, homogeneous, transfer hydrogenation catalysis. Transfer hydrogenation catalysts, based on Ru, Ir and Rh, reduce organic substrates in water by assisting the transfer of hydrogen from simple donor species. These catalysts are expected to have significant benefits when compared with organic phase catalysts, including greater activity, greater selectivity and smaller environmental impact. They will therefore be expected to make a significant contribution to homogeneous catalysis and 'green chemistry'. Here, we comprehensively examine these catalysts, paying special attention to structural features..
129. Takahiro Matsumoto, Ryota Kabe, Kyoshiro Nonaka, Tatsuya Ando, Ki Suk Yoon, Hidetaka Nakai, Seiji Ogo, Model study of CO inhibition of [NiFe]hydrogenase, Inorganic Chemistry, 10.1021/ic200965t, 50, 18, 8902-8906, 2011.09, We propose a modified mechanism for the inhibition of [NiFe]hydrogenase ([NiFe]H 2ase) by CO. We present a model study, using a NiRu H 2ase mimic, that demonstrates that (i) CO completely inhibits the catalytic cycle of the model compound, (ii) CO prefers to coordinate to the Ru II center rather than taking an axial position on the Ni II center, and (iii) CO is unable to displace a hydrido ligand from the NiRu center. We combine these studies with a reevaluation of previous studies to propose that, under normal circumstances, CO inhibits [NiFe]H 2ase by complexing to the Fe II center..
130. Matsumoto, Takahiro; Kabe, Ryota; Nonaka, Kyoshiro; Ando, Tatsuya; Yoon, Ki-Seok; Nakai, Hidetaka; Ogo, Seiji, Model Study of CO Inhibition of [NiFe]hydrogenase, Inorg. Chem., 50, 8902-8906, 2011.08.
131. Kanemitsu, Hironobu; Harada, Ryosuke; Ogo, Seiji.*, A Water-soluble Iridium(III) Porphyrin, Chem. Commun., 10.1039/c000263a, 46, 18, 3083, 2010.05, イリジウム錯体は数多く合成されており、触媒として様々な分野で幅広く用いられている。その中の1つとしてポルフィリンを配位子として有するイリジウム錯体も報告されているが、現在までに水溶性イリジウムポルフィリン錯体の報告例は1例もない。水中で触媒反応を行う利点は、pHにより反応を制御できることや環境調和型であることなどがあげられる。本研究では、世界で初めて水溶性ポルフィリン錯体の合成に成功し、その構造をX線構造解析により決定した。X線構造解析の結果、軸位にアクアが配位子していることを明らかにした。1H MNRを用いた滴定実験により、第一pKaを7.26、第二pKaを10.42と決定した。.
132. Ichikawa, Koji; Nonaka, Kyoshiro; Matsumoto, Takahiro; Kure, Bunsho; Yoon, Ki-Seok; Higuchi, Yoshiki; Yagi, Tatsuhiko, Ogo, Seiji.*, Concerto Catalysis — Harmonising [NiFe]hydrogenase and NiRu Model Catalysts, Dalton Trans., 10.1039/b926061g, 39, 12, 2993, 2010.03.
133. Zheng, Chunbai; Kim, Kyoungmok; Matsumoto, Takahiro; Ogo, Seiji.*, The Useful Properties of H2O as a Ligand of a Hydrogenases Mimic, Dalton Trans., 10.1039/b921273f, 39, 9, 2218, 2010.03.
134. Seiji Ogo, Bioinspired catalysis., Dalton Transactions, 10.1039/b926640m, 39, 12, 2963, 2010.03.
135. Seiji Ogo, Editorial
Bioinspired catalysis, Dalton Transactions, 10.1039/b926640m, 39, 12, 2010.03.
136. Kizaki, Tetsuro; Matsumoto, Takahiro; Ogo, Seiji.*, Dissolved N2 Sensing by pH-dependent Ru Complexes, Dalton Trans., 10.1039/b918940h, 39, 5, 1339, 2010.02.
137. Zheng, Chunbai; Inoki, Daisuke; Matsumoto, Takahiro; Ogo, Seiji.*, An Acid-Stable Organoruthenium Complex Suitable as a Bidentate Building Block, Chem. Lett., 10.1246/cl.2010.130, 39, 2, 130, 2010.01.
138. Kizaki, Tetsuro; Abe, Takeru; Matsumoto, Takahiro; Ogo Seiji.*, A pH-Stable Ruthenium(II)-based Sensing System for Dissolved Dinitrogen, Chem. Lett., 10.1246/cl.2010.128, 39, 2, 128, 2010.01, [URL].
139. Ichikawa, Koji; Matsumoto, Takahiro; Ogo, Seiji.* , Critical Aspects of [NiFe]hydrogenase Ligand Composition, Dalton Trans., 4304-4309, 2009.06.
140. Ogo, Seiji.*, Electrons form Hydrogen, Chem. Commun., 10.1039/b900297a, 23, 3317, 2009.06.
141. Koji Ichikawa, Takahiro Matsumoto, Seiji Ogo, Critical aspects of [NiFe]hydrogenase ligand composition, Dalton Transactions, 10.1039/b819395a, 22, 4304-4309, 2009.06, Structural analysis of the resting state of [NiFe]hydrogenase ([NiFe]H 2ase) shows that the active site has a characteristic bis(μ-thiolato)NiFe unit, where the Ni atom and the Fe atom are bridged by an undetermined oxygen-bearing ligand. This ligand probably derives from the aqueous solvent and is therefore most likely to be H2O, OH - or O2-. Here, we compare the reactivities of a NiFe and a NiRu complex when bearing either acetonitrile or aqueous ligands and demonstrate the critical role of an aqueous ligand in hydrogenase and its mimics. We also make observations on the necessity of organometallic metal-carbon bonds to the supporting frameworks..
142. Hironobu Kanemitsu, Keiji Uehara, Shunichi Fukuzumi, Seiji Ogo, Isolation and crystal structures of both enol and keto tautomer intermediates in a hydration of an alkyne-carboxylic acid ester catalyzed by iridium complexes in water, Journal of the American Chemical Society, 10.1021/ja807254d, 130, 50, 17141-17147, 2008.12, Hydration of tetrolic acid ethyl ester as an alkyne-carboxylic acid ester catalyzed by an Ir-aqua complex [IrIIICp*(bpy)(OH 2)]2+ (1, Cp* = η5-C 5Me5, bpy = 2,2′-bipyridine) in water provides ethyl acetoacetate as a β-keto acid ester. We report the successful isolation of both an Ir-enol tautomer intermediate [IrIIICp*(bpy){CH 3C(OH)=CC(O)OC2H5}]+ (2) and an Ir-keto tautomer intermediate [IrIIICp*(bpy){CH 3C(O)-CHC(O)OC2H5}]+ (3) in the catalytic hydration by optimizing the conditions of the isolation, such as pH of the solution, reaction time, and selection of counteranions. The structures of the enol and keto complexes with characteristic Ir-(sp2carbon) bond and Ir-(sp3 carbon) bond, respectively, were unequivocally determined by X-ray analysis, IR, electrospray ionization mass spectrometry (ESI-MS), and NMR studies including 1H, 13C, distortionless enhancement by polarization transfer (DEPT) and correlation spectroscopy (COSY) experiments. It was confirmed that the hydration of tetrolic acid ethyl ester catalyzed by 2 or 3 as initial catalysts provides ethyl acetoacetate. Mechanism of the catalytic hydration of tetrolic acid ethyl ester as an alkyne-carboxylic acid ester is discussed based on isotopic labeling experiments with the Ir-enol and Ir-keto tautomers..
143. Kanemitsu, Hironobu; Uehara, Keiji; Fukuzumi, Shunichi; Ogo, Seiji.*, Isolation and Crystal Structures of Both Enol and Keto Tautomer Intermediates in a Hydration of an Alkyne-Carboxylic Acid Ester Catalyzed by Iridium Complexes in Water. , J. Am. Chem. Soc. , 130, 17141-17147., 2008.11.
144. Takahiro Matsumoto, Bunsho Kure, Seiji Ogo, Extraction of electrons from H2 with a NiIRu I catalyst, Chemistry Letters, 10.1246/cl.2008.970, 37, 9, 970-971, 2008.09, The mechanism of extraction of electrons from H2 catalyzed by hydrogenases has proven challenging to elucidate. Catalytic extraction of electrons from H2 has been achieved by use of a low-valent Ni IRuI complex [NiI(μ-SR)2Ru I6-C6Me6)]{μ-SR) 2 = N,N′-dimethyl-N,N′-bis(2-mercaptoethyl)-1,3- propanediamine) as the active catalyst with evolution of H2 under ambient conditions. The electrons extracted from H2 have been used for a catalytic reduction of Cu2+ to Cu0 with the NiRu complexes..
145. Bunsho Kure, Takahiro Matsumoto, Koji Ichikawa, Shunichi Fukuzumi, Yoshiki Higuchi, Tatsuhiko Yagi, Seiji Ogo, PH-Dependent isotope exchange and hydrogenation catalysed by water-soluble NiRu complexes as functional models for [NiFe]hydrogenases, Dalton Transactions, 10.1039/b807555g, 35, 4747-4755, 2008.09, The pH-dependent hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes and hydrogenation of the carbonyl compounds have been investigated with water-soluble bis(μ-thiolate)(μ-hydride)NiRu complexes, NiII(μ-SR)2(μ-H)RuII {(μ-SR)2 = N,N′-dimethyl-N,N′-bis(2-mercaptoethyl)-1, 3-propanediamine}, as functional models for [NiFe]hydrogenases. In acidic media (at pH 4-6), the μ-H ligand of the NiII(μ-SR) 2(μ-H)RuII complexes has H+ properties, and the complexes catalyse the hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes. A mechanism of the hydrogen isotope exchange reaction between gaseous isotopes and medium isotopes through a low-valent NiI(μ-SR)2RuI complex is proposed. In contrast, in neutral-basic media (at pH 7-10), the μ-H ligand of the Ni II(μ-SR)2(μ-H)RuII complexes acts as H-, and the complexes catalyse the hydrogenation of carbonyl compounds..
146. Matsumoto, Takahiro; Kure, Bunsho; Ogo, Seiji.*, Extraction of Electrons from H2 with a NiIRuI Catalyst., Chem. Lett. , 2008, 37, 970-971., 2008.08.
147. Kure, Bunsho; Matsumoto, Takahiro; Ichikawa, Koji; Fukuzumi, Shunichi; Higuchi, Yoshiki; Yagi, Tatsuhiko; Ogo, Seiji.*, pH-Dependent Isotope Exchange and Hydrogenation Catalysed by Water-soluble NiRu Complexes as Functional Models for [NiFe]hydrogenases. , Dalton Trans., 2008, 4747-4755. , 2008.07.
148. Bunsho Kure, Shunichi Fukuzumi, Seiji Ogo, A new water-soluble and acid-stable dinuclear organoiridium dinitrate complex, Chemistry Letters, 10.1246/cl.2007.1468, 36, 12, 1468-1469, 2007.12, A new water-soluble and acid-stable dinuclear organoiridium(III) dinitrate complex [{Cp*Ir(NO3)}2(μ-Cl)2] (1, Cp* = η5-C5Me5) was synthesized by the reaction of a water-insoluble organoiridium(III) complex [(Cp*IrCl)2(μ-Cl)2] (2) with two equivalents of AgBF4 in aqueous nitric acid (1 M HNO3/H2O) at 23°C for 12h. The structure of 1 with two monodentate NO3 - ligands is discussed in comparison with structure of a mononuclear organoiridium(III) complex with one monodentate and one bidentate NO 3- ligands, [Cp*Ir(NO3)2] (3)..
149. Ogo, Seiji;* Kabe, Ryota; Uehara, Keiji; Kure, Bunsho; Nishimura, Takashi; Menon, Saija C.; Harada, Ryosuke; Fukuzumi, Shunichi; Higuchi, Yoshiki; Ohhara, Takashi; Tamada, Taro; Kuroki, Ryota, A Dinuclear Ni(μ-H)Ru Complex Derived from H2, Science, 316, 585-587, 2007.04.
150. Seiji Ogo, Ryota Kabe, Keiji Uehara, Bunsho Kure, Takashi Nishimura, Saija C. Menon, Ryosuke Harada, Shunichi Fukuzumi, Yoshiki Higuchi, Takashi Ohhara, Taro Tamada, Ryota Kuroki, A dinuclear Ni(μ-H)Ru complex derived from H2, Science, 10.1126/science.1138751, 316, 5824, 585-587, 2007.04, Models of the active site in [NiFe]hydrogenase enzymes have proven challenging to prepare. We isolated a paramagnetic dinuclear nickel-ruthenium complex with a bridging hydrido ligand from the heterolytic cleavage of H 2 by a dinuclear NiRu aqua complex in water under ambient conditions (20°C and 1 atmosphere pressure). The structure of the hexacoordinate Ni(μ-H)Ru complex was unequivocally determined by neutron diffraction analysis, and it comes closest to an effective analog for the core structure of the proposed active form of the enzyme..
151. Kure, Bunsho; Fukuzumi, Shunichi; Ogo, Seiji.* , A New Water-soluble and Acid-stable Dinuclear Organoiridium Dinitrate Complex. , Chem. Lett., 36, 1468-1469, 2007.01.
152. Uehara, Keiji; Fukuzumi, Shunichi;* Ogo, Seiji.*, Synthesis and Crystal Structure of a New Water-Soluble Sulfur-Containing Palladacyclic Diaqua Complex, J. Organomet. Chem., 692, 499-504, 2007.01.
153. Keiji Uehara, Shunichi Fukuzumi, Seiji Ogo, Synthesis and crystal structure of a new water-soluble sulfur-containing palladacyclic diaqua complex, Journal of Organometallic Chemistry, 10.1016/j.jorganchem.2006.08.088, 692, 1-3, 499-504, 2007.01, A new water-soluble sulfur-containing palladacyclic diaqua complex [(SC)PdII(H2O)2]2 (SO4) {[1]2(SO4), SC = C6H4-2-(CH2StBu)} was synthesized from a reaction of Ag2SO4 with a water-insoluble palladacyclic dichloro complex [(SC)PdII(μ-Cl)]2 (2) in water. Water-solubility of [1]2(SO4) at pH 7 at 25 °C is 9.4 mg/mL. NH4PF6 was added to the solution of [1]2(SO4) in water to give [1](PF6). The structures of [1](PF6) and 2 were unequivocally determined by X-ray analysis..
154. Seiji Ogo, Ryota Kabe, Hideki Hayashi, Ryosuke Harada, Shunichi Fukuzumi, Mechanistic investigation of CO2 hydrogenation by Ru(ii) and Ir(iii) aqua complexes under acidic conditions
Two catalytic systems differing in the nature of the rate determining step, Dalton Transactions, 10.1039/b607993h, 39, 4657-4663, 2006.10, Ruthenium aqua complexes [(η6-C6Me 6)RuII(L)(OH2)]2+ {L = bpy (1) and 4,4′-OMe-bpy (2), bpy = 2,2′-bipyridine, 4,4′-OMe-bpy = 4,4′-dimethoxy-2,2′-bipyridine} and iridium aqua complexes [Cp*IrIII(L)(OH2)]2+ {Cp* = η5-C5Me5, L = bpy (5) and 4,4′-OMe-bpy (6)} act as catalysts for hydrogenation of CO2 into HCOOH at pH 3.0 in H2O. The active hydride catalysts cannot be observed in the hydrogenation of CO2 with the ruthenium complexes, whereas the active hydride catalysts, [Cp*IrIII(L)(H)] + {L = bpy (7) and 4,4′-OMe-bpy (8)}, have successfully been isolated after the hydrogenation of CO2 with the iridium complexes. The key to the success of the isolation of the active hydride catalysts is the change in the rate-determining step in the catalytic hydrogenation of CO 2 from the formation of the active hydride catalysts, [(η6-C6Me6)RuII(L)(H)] +, to the reactions of [Cp*IrIII(L)(H)]+ with CO2, as indicated by the kinetic studies..
155. Ogo, Seiji;* Kabe, Ryota; Hayashi, Hideki; Harada, Ryosuke; Fukuzumi, Shunichi.*, Mechanistic investigation of CO2 hydrogenation by Ru(II) and Ir(III) aqua complexes under acidic conditions: two catalytic systems differing in the nature of the rate determining step, Dalton Trans. , 4657-4663, 2006.08.
156. Hironori Kitaguchi, Kei Ohkubo, Seiji Ogo, Shunichi Fukuzumi, Electron-transfer oxidation properties of unsaturated fatty acids and mechanistic insight into lipoxygenases, Journal of Physical Chemistry A, 10.1021/jp054648f, 110, 5, 1718-1725, 2006.02, Rate constants of photoinduced electron-transfer oxidation of unsaturated fatty acids with a series of singlet excited states of oxidants in acetonitrile at 298 K were examined and the resulting electron-transfer rate constants (ket) were evaluated in light of the free energy relationship of electron transfer to determine the one-electron oxidation potentials (E ox) of unsaturated fatty acids and the intrinsic barrier of electron transfer. The ket values of linoleic acid with a series of oxidants are the same as the corresponding ket values of methyl linoleate, linolenic acid, and arachidonic acid, leading to the same Eox value of linoleic acid, methyl linoleate, linolenic acid, and arachidonic acid (1.76 V vs SCE), which is significantly lower than that of oleic acid (2.03 V vs SCE) as indicated by the smaller ket values of oleic acid than those of other unsaturated fatty acids. The radical cation of linoleic acid produced in photoinduced electron transfer from linoleic acid to the singlet excited state of 10-methylacridinium ion as well as that of 9,10-dicyanoanthracene was detected by laser flash photolysis experiments. The apparent rate constant of deprotonation of the radical cation of linoleic acid was determined as 8.1 × 103 s-1. In the presence of oxygen, the addition of oxygen to the deprotonated radical produces the peroxyl radical, which has successfully been detected by ESR. No thermal electron transfer or proton-coupled electron transfer has occurred from linoleic acid to a strong one-electron oxidant, Ru(bpy)33+ (bpy = 2,2′-bipyridine) or Fe(bpy)33+. The present results on the electron-transfer and proton-transfer properties of unsaturated fatty acids provide valuable mechanistic insight into lipoxygenases to clarify the proton-coupled electron-transfer process in the catalytic function..
157. Ogo, Seiji;* Takebe, Yoshitaka; Uehara, Keiji; Yamazaki, Takayuki; Nakai, Hidetaka; Watanabe, Yoshihito; Fukuzumi, Shunichi.*, pH-Dependent C-C Coupling Reactions Catalyzed by Water-Soluble Palladacycle Aqua Catalysts in Water, Organometallics, 25, 331-338, 2006.01.
158. Hironori Kitaguchi, Kei Ohkubo, Seiji Ogo, Shunichi Fukuzumi, Additivity rule holds in the hydrogen transfer reactivity of unsaturated fatty acids with a peroxyl radical
Mechanistic insight into lipoxygenase, Chemical Communications, 10.1039/b515004c, 9, 979-981, 2006.01, A simple additivity rule holds in the hydrogen transfer reactivity of unsaturated fatty acids with cumylperoxyl radical, which is expressed by the additive contributions of the reactivity of active hydrogens from the 1,4-pentadiene subunit and those of the allylic subunit; the kinetic isotope effect on the hydrogen transfer reactions (KIE = 6.1) is significantly smaller than that observed for lipoxygenase (KIE = 81)..
159. Seiji Ogo, Yoshitaka Takebe, Keiji Uehara, Takayuki Yamazaki, Hidetaka Nakai, Yoshihito Watanabe, Shunichi Fukuzumi, PH-dependent C-C coupling reactions catalyzed by water-soluble palladacyclic aqua catalysts in water, Organometallics, 10.1021/om0503592, 25, 2, 331-338, 2006.01, The series of water-soluble palladacyclic aqua complexes [( tBu-SCS)PdII(H2O)]+ ([1] +, tBu-SCS = C6H3-2,6-(CH 2StBu)2), [(iPr-SCS)Pd II(H2O)]+ ([2]+, iPr-SCS = C6H3-2,6-(CH2SiPr)2), [(PCP)PdII(H2O)]+ ([3]+, PCP = C2H3-2,6-(OPiPr2)2), and [(PC)PdII(H2O)2]+ ([4]+, PC = 4-MeC6H3-2-(OPiPr2)) have been synthesized from the reaction of the corresponding palladacyclic chloro complexes with silver salts in water to optimize the catalytic activity for pH-dependent C-C coupling reactions in water by changing the supporting ligands from S-supporting (SCS) to P-supporting (PCP) ligands and also from tridentate (PCP) to bidentate (PC) ligands. It was confirmed that there was no precipitation of palladium black under the present reaction conditions. The PC palladacyclic aqua complex [4]+ exhibits the highest catalytic activity among the water-soluble palladacyclic aqua complexes [1] +-[4]+ for the pH-dependent Suzuki Miyaura, Mizoroki-Heck, and Stille coupling reactions in water. This is one of the highest catalytic activities ever reported for coupling reactions with water-soluble palladium catalysts in water. The catalytic abilily of the palladacyclic aqua catalysts is drastically dependent on the pH of the solution and the structures of supporting ligands. The structures of palladacyclic aqua and chloro complexes were unequivocally determined by X-ray analysis..
160. Bunsho Kure, Seiji Ogo, Daisuke Inoki, Hidetaka Nakai, Kiyoshi Isobe, Shunichi Fukuzumi, Synthesis and crystal structure of an open capsule-type octanuclear heterometallic sulfide cluster with a linked incomplete double cubane framework without an intramolecular inversion center, Journal of the American Chemical Society, 10.1021/ja051748q, 127, 41, 14366-14374, 2005.10, An open capsule-type octanuclear heterometallic sulfide cluster without an intramolecular inversion center [Ru(η6-C6Me 6){P(OMe)3}{MoO(μ3-S)3}(Cul) 2]2 (5) has been synthesized for the first time by stepwise connection of three mononuclear building blocks, i.e., (i) [RuCl 26-C6Me6){P(OMe)3}] (1a) as an octahedral terminal building block to control the direction of cluster expansion, (ii) [MoOS3]2- as a tetrahedral polydentate building block owing to the strong coordination ability of the S atoms, and (iii) a Cul building block to form a trigonal planar (μ-S) 2Cul unit or to form a linkage unit of two incomplete cubane-type octanuclear frameworks. The stepwise connection was made in the following order: [RuCl26-C6Me6){P(OMe) 3}] (1a, mononuclear) → [Ru(η6-C 6Me6){P(OMe)3}{MoOS(μ2-S) 2}] (2a, dinuclear) → [Ru(η6-C6Me 6){P(OMe)3}{MoO-(μ2-S)23-S)}Cul] (3a, butterfly-type trinuclear) → [Ru(η 6-C6Me6){P(OMe)3} {MoO(μ3-S)3}(Cul)2]2 (5). When P(OMe)3 was replaced by P(OEt)3, which is more bulky than P(OMe)3, in the starting ruthenium building block [RuCl 26-C6Me6){P(OEt)3}] (1b, mononuclear), only the tetranuclear incomplete single cubane cluster [Ru(η6-C6Me6){P(OEt)3} {MoO(μ3-S)3}(Cul)2] (6) was generated, owing to the steric effect of P(OEt)3..
161. Kure, Bunsho; Ogo, Seiji;* Inoki, Daisuke; Nakai, Hidetaka; Isobe, Kiyoshi; Fukuzumi, Shunichi.*, Synthesis and Crystal Structure of an Open Capsule-Type Octanuclear Heterometallic Sulfide Cluster with a Linked Incomplete Double Cubane Framework without an Intramolecular Inversion Center, J. Am. Chem. Soc. , 127, 14366-14374, 2005.09.
162. Seiji Ogo, Hiromi Nishida, Hideki Hayashi, Yusuke Murata, Shunichi Fukuzumi, Aqueous transformation of a metal diformate to a metal dihydride carbonyl complex accompanied by H2 evolution from the formato ligands, Organometallics, 10.1021/om0504147, 24, 20, 4816-4823, 2005.09, The rhodium diformate complex [RhIII(tacn)(HCOO) 2](OTf) (2, tacn = 1,4,7-triazacy-clononane, OTf- = CF3SO3-) reacts with HCOONa at pH 6-7 at 80°C in water to form a rhodium dihydride CO complex, [Rh III(tacn)(H)2(CO)](OTf) (5), with H2 evolution from the formato ligands of 2. This is the first example of H2 evolution from hydrogen atoms of formato ligands of a metal diformate complex. Complex 2 was synthesized from the reaction of a rhodium aqua complex, [Rh III(tacn)(H2O)3](OTf)3 (1), with HCOONa in water. Recrystallization of 2 with HCOONa in water gave crystals of a rhodium triformate complex, [RhIII-(tacn)(HCOO)3] (3), whose structure was unequivocally determined by X-ray analysis. The key intermediate in the transformation from 2 to 5 is a rhodium hydride formate complex, [RhIII(tacn)H(HCOO)](OTf) (4), which was obtained by heating of an aqueous solution of the rhodium diformate complex 2 with 10 equiv of dimethyl sulfoxide (DMSO) at pH 6-7 in water. Complex 4 was well characterized by isotopic labeling measurements of 1H NMR, electrospray ionization mass spectrometry (ESI-MS), and GC..
163. Yutaka Hitomi, Akira Ando, Hajime Matsui, Tomoyuki Ito, Tsunehiro Tanaka, Seiji Ogo, Takuzo Funabiki, Aerobic catechol oxidation catalyzed by a bis(μ-oxo)dimanganese(III,III) complex via a manganese(II)-semiquinonate complex, Inorganic Chemistry, 10.1021/ic050109d, 44, 10, 3473-3478, 2005.05, A 3,5-di-terf-butyl-1,2-semiquinonato (DTBSQ) adduct of Mn(II) was prepared by a reaction between MnII(TPA)Cl2 (TPA = tris(pyridin-2-ylmethyl)amine) and DTBSQ anion and was isolated as a tetraphenylborate salt. The X-ray crystal structure revealed that the complex is formulated as a manganese(II)-semiquinonate complex [MnII(TPA) (DTBSQ)]+ (1). The electronic spectra in solution also indicated the semiquinonate coordination to Mn. The exposure of 1 in acetonitrile to dioxygen afforded 3,5-di-tert-butyl-1,2-benzoquione and a bis(μ-oxo)dimanganese(III, III) complex [MnIII2(μ-oxo)2(TPA) 2]2+ (2). The reaction of 2 with 3,5-di-terf-butylcatechol (DTBCH2) quantitatively afforded two equivalents of 1 under anaerobic conditions. The highly efficient catalytic oxidation of DTBCH 2 with dioxygen was achieved by combining the above two reactions, that is, by constructing a catalytic cycle involving both manganese complexes 1 and 2. It was revealed that dioxygen is reduced to water but not to hydrogen peroxide in the catalytic cycle..
164. Seiji Ogo, Hideki Hayashi, Keiji Uehara, Shunichi Fukuzumi, Crystal structures of organometallic aqua complexes [Cp*Rh III(bpy)(OH2)]2+ and [Cp*Rh III(6,6′-Me2bpy)(OH2)]2+ used as key catalysts in regioselective reduction of NAD+ analogues, Applied Organometallic Chemistry, 10.1002/aoc.837, 19, 5, 639-643, 2005.05, Crystal structures of organometallic aqua complexes [Cp*Rh III(bpy)(OH2)]2+ (1, Cp* = η 5-C5Me5, bpy = 2,2′-bipyridine) and [Cp*RhIII(6,6′-Me2bpy)(OH2)] 2+ (2, 6,6′-Me2bpy = 6,6′-dimethyl-2,2′-bipyridine) used as key catalysts in regioselective reduction of NAD+ analogues were determined definitely by X-ray analysis. The yellow crystals of 1(PF6) 2 and orange crystals of 2(CF3SO3)2 used in the X-ray analysis were obtained from aqueous solutions of 1(PF 6)2 and 2(CP3SO3)2. The Rh-Oaqua length of 2.194(4) Å obtained for 1(PF 6)2 is significantly different from that of 2.157(3) Å obtained for the previously reported disorder model [Cp*Rh III(bpy)(0.7H2O/0.3CH3H)](CF3SO 3)2̇0.7H2O in which the coordinated water is replaced by a coordinated methanol. The five-membered ring involving the Rh atom and the 6,6′-Me2bpy chelating unit in 2(CF 3SO3)2 is not flat, whereas the five-membered chelate ring in 1(PF6)2 is nearly flat. Such a non-planar structure in 2(CF3SO3)2 is ascribed to the steric repulsion between the 6,6′-Me2bpy ligand and the Cp* ligand..
165. Hironori Kitaguchi, Kei Ohkubo, Seiji Ogo, Shunichi Fukuzumi, Direct ESR detection of pentadienyl radicals and peroxyl radicals in lipid peroxidation
Mechanistic insight into regioselective oxygenation in lipoxygenases, Journal of the American Chemical Society, 10.1021/ja044345j, 127, 18, 6605-6609, 2005.05, Well-resolved ESR spectra of free pentadienyl radicals have been observed under photoirradiation of di-tert-butylperoxide (ButOOBut) and polyunsaturated fatty acids in the absence of O2, allowing us to determine the hfc values. The hfc values of linoleyl radical indicate that the spin density is the largest at the C-11 position. The linoleyl radical is readily trapped by O2 to produce the peroxyl radical (11-HPO ) in which O2 is added mainly at the C-11 position of the pentadienyl radical as indicated by the comparison of the ESR spectra of peroxyl radicals derived from linoleic acid and [11,11-2H 2]linoleic acid. The peroxyl radical (13-HPO), which is initially formed by the hydrogen abstraction from 13-(S)-hydroperoxy-9(Z), 11(E)-octadecadienoic acid (13-HPOD) by ButO, is found to isomerize to 11-HPO via removal of O2 from 13-HPO and addition of O2 to linoleyl radical to produce 11-HPO. This finding supports an idea of O2 entering via a specific protein channel, which determines the stereo- and regiochemistry of the biradical combination between O2 and linoleyl radical in lipoxygenases..
166. Hideki Hayashi, Seiji Ogo, Shunichi Fukuzumi, Aqueous hydrogenation of carbon dioxide catalysed by water-soluble ruthenium aqua complexes under acidic conditions, Chemical Communications, 10.1039/b411633j, 23, 2714-2715, 2004.12, Hydrogenation of carbon dioxide (P(H2/CO2) = 5.5/2.5 MPa) into formic acid (HCOOH) under acidic conditions (pH 2.5-5.0) in water has been achieved by using water-soluble ruthenium aqua catalysts [η6-C6Me6)RuII(L)(OH 2)]SO4 (L = 2,2′-bipyridine or 4,4′-dimethoxy- 2, 2′-bipyridine)..
167. Seiji Ogo, Keiji Uehara, Tsutomu Abura, Yoshihito Watanabe, Shunichi Fukuzumi, pH-selective synthesis and structures of alkynyl, acyl, and ketonyl intermediates in anti-markovnikov and markovnikov hydrations of a terminal alkyne with a water-soluble iridium aqua complex in water, Journal of the American Chemical Society, 10.1021/ja0473541, 126, 50, 16520-16527, 2004.12, Chemoselective synthesis and isolation of alkynyl [Cp*Ir III(bpy)CCPh]+ (2, Cp* = η5-C 5Me5, bpy = 2,2′-bipyridine), acyl [Cp*Ir III(bPy)C(O)CH2Ph]+ (3), and ketonyl [Cp*IrIII(bpy)CH2C(O)Ph]+ (4) intermediates in anti-Markovnikov and Markovnikov hydration of phenylacetylene in water have been achieved by changing the pH of the solution of a water-soluble aqua complex [Cp*IrIII(bpy)(H2O)] 2+ (1) used as the same starting complex. The alkynyl complex [2]2·SO4 was synthesized at pH 8 in the reaction of 1·SO4 with H2O at 25 °C, and was isolated as a yellow powder of 2·X (X = CF3SO3 or PF 6) by exchanging the counteranion at pH 8. The acyl complex [3] 2·SO4 was synthesized by changing the pH of the aqueous solution of [2]2·SO4 from 8 to 1 at 25°C, and was isolated as a red powder of 3·PF6 by exchanging the counteranion at pH 1. The hydration of phenylacetylene with 1·SO4 at pH 4 at 25°C gave a mixture of [4] 2·SO4 and [4]2·SO4. After the counteranion was exchanged from SO42- to CF 3SO3-, the ketonyl complex 4·CF 3SO3 was separated from the mixture of 2·CF 3SO3 and 4·CF3SO3 because of the difference in solubility at pH 4 in water. The structures of 2-4 were established by IR with 13C-labeled phenylacetylene (Ph 12C≡13CH), electrospray ionization mass spectrometry (ESI-MS), and NMR studies including 1H, 13C, distortionless enhancement by polarization transfer (DEPT), and correlation spectroscopy (COSY) experiments. The structures of 2·PF6 and 3·PF6 were unequivocally determined by X-ray analysis. Protonation of 3 and 4 gave an aldehyde (phenylacetaldehyde) and a ketone (acetophenone), respectively. Mechanism of the pH-selective anti-Markovnikov vs Markovnikov hydration has been discussed based on the effect of pH on the formation of 2-4. The origins of the alkynyl, acyl, and ketonyl ligands of 2-4 were determined by isotopic labeling experiments with D2O and H 218O..
168. Seiji Ogo, Bunsho Kure, Hidetaka Nakai, Yoshihito Watanabe, Shunichi Fukuzumi, Why do nitrogenases waste electrons by evolving dihydrogen?, Applied Organometallic Chemistry, 10.1002/aoc.744, 18, 11, 589-594, 2004.11, In nature, nitrogen is commonly fixed as the most reduced form, ammonia (NH3) and as the most oxidized form, i.e. nitrate ion (NO 3-). Nitrogenases catalyze the reduction of N2 into NH3 by using protons and electrons with evolution of H 2. However, the reason why the enzymes waste electrons by evolving H2 has yet to be clarified. We have previously reported (J. Am. Chem. Soc. 2002; 124: 597) pH-dependent heterolytic cleavage of H2 and subsequent reduction of NO3- with evolution of H 2 by iridium complexes in water. We propose herein a catalytic mechanism of nitrogenases, which can account for evolution of H2 in the reduction of N2 to NH3 in relation to a mechanism of the reduction of NO3-..
169. Hideki Hayashi, Hiromi Nishida, Seiji Ogo, Shunichi Fukuzumi, Synthesis and crystal structures of water-soluble rhodium(III) complexes with 1,4,7-triazacyclononane and 2,2-bipyridine supporting ligands, Inorganica Chimica Acta, 10.1016/j.ica.2004.03.001, 357, 10, 2939-2944, 2004.07, New water-soluble rhodium(III) complexes with a tacn (1,4,7- triazacyclononane) and a bpy (2,2-bipyridine) supporting ligands were synthesized. The reaction of [RhIII(tacn)Cl3] (1) with equimolar amount of bpy and two equivalents of AgNO3 in H2O at reflux for 10 h gave a water-soluble chloro complex [Rh III(tacn)(bpy)Cl](NO3)2 {2(NO3) 2}. Complex 2(NO3)2 was treated with equimolar amount of AgNO3 in H2O at reflux for 10 h to give a water-soluble nitrato complex [RhIII(tacn)(bpy)(NO 3)](NO3)2 {3(NO3)2}. Water-solubility of 3 with NO3- ligand (46.5 mg/mL) is high compared with that of 2 with Cl- ligand (14.5 mg/mL) under the same conditions (at pH 7.0 at 25°C). The structures of 2 and 3 were unequivocally determined by X-ray analysis. Their structures in H2O were also examined by 1H NMR, IR, and electrospray ionization mass spectrometry (ESI-MS)..
170. Seiji Ogo, Keiji Uehara, Tsutomu Abura, Yoshihito Watanabe, Shunichi Fukuzumi, Aqueous polymerization of styrene promoted by water-soluble robust ruthenium hydride complexes, Organometallics, 10.1021/om034335b, 23, 12, 3047-3052, 2004.06, Aqueous polymerization of styrene in biphasic media (styrene/water) has been achieved by water-soluble robust mononuclear hydride complexes [(ν6-C6Me6)RuII(bpy)H] n(X) {[1]n(X), where X = SO4 (n = 2) or CF 3SO3 (n = 1), bpy = 2,2′-bipyridine}. The hydride complex [1]2(SO4) was synthesized from the reaction of an aqua complex [(ν6-C6Me6)RuII. (bpy)(H2O)](SO4) {2(SO4)} with a water-soluble hydrogen donor HCOONa in H2O in a pH range of 4-12 at 70-100°C. The structures of [1]2(SO4) and 1(CF3SO 3) were determined by X-ray analysis, 1H and 2H NMR, IR, and electrospray ionization mass spectrometry (ESI-MS). X-ray analysis has revealed that complex 1(CF3SO3) adopts a distorted octahedral geometry with the Ru atom coordinated by one ν6-C 6Me6 ligand, one bidentate bpy ligand, and one terminal hydrido ligand that occupies a bond position. Complex [1]2(SO 4) reacts with excess amounts of styrene in biphasic media to provide polystyrene in a 62% isolated yield for 8 h. The polydispersity (M w/Mn) of the obtained polystyrene is 1.8. The isolated yield of polystyrene shows a maximum around pH 8. The pH-dependence is similar to the pH-dependent formation of 1. Growing polymer intermediates [(C 6Me6)Ru(bpy){(C2H3)-(C 6H5)}nH]+ (n = 1-4) were directly observed by ESI-MS..
171. Seiji Ogo, Keiji Uehara, Tsutomu Abura, Shunichi Fukuzumi, pH-Dependent Chemoselective Synthesis of α-Amino Acids. Reductive Amination of α-Keto Acids with Ammonia Catalyzed by Acid-Stable Iridium Hydride Complexes in Water, Journal of the American Chemical Society, 10.1021/ja031633r, 126, 10, 3020-3021, 2004.03, An acid-stable hydride complex [Cp*IrIII(bpy)H]+ {1, Cp* = η5-C5Me5, bpy = 2,2′-bipyridine} serves as the active catalyst for the highly chemoselective synthesis of α-amino acids by reductive amination of α-keto acids with aqueous NH3 and HCOO- in water at pH 5?8. pH-dependent catalytic 15N- and 2H-double-labeling has also been accomplished by using 15NH3 and DCOONa, which are ideal amine and hydride ion sources, respectively..
172. Shunichi Fukuzumi, Hiroaki Kotani, Kei Ohkubo, Seiji Ogo, Nikolai V. Tkachenko, Helge Lemmetyinen, Electron-Transfer State of 9-Mesityl-10-methylacridinium Ion with a Much Longer Lifetime and Higher Energy Than That of the Natural Photosynthetic Reaction Center, Journal of the American Chemical Society, 10.1021/ja038656q, 126, 6, 1600-1601, 2004.02.
173. Hideki Hayashi, Seiji Ogo, Tsutomu Abura, Shunichi Fukuzumi, Accelerating Effect of a Proton on the Reduction of CO2 Dissolved in Water under Acidic Conditions. Isolation, Crystal Structure, and Reducing Ability of a Water-Soluble Ruthenium Hydride Complex, Journal of the American Chemical Society, 10.1021/ja036117f, 125, 47, 14266-14267, 2003.11, A water-soluble hydride complex [(η6-C6Me6)RuII(bpy)H]+ {1, bpy = 2,2′-bipyridine} serves as a robust reducing agent for the reduction of CO2 in water in a pH range of about 3-5 at ambient temperature under stoichiometric conditions. The structure of 1 was unequivocally determined by X-ray analysis. The mechanism of acid-catalyzed reduction of CO2 promoted by 1 in water under acidic conditions is disclosed..
174. Tomoyoshi Suenobu, Dirk M. Guldi, Seiji Ogo, Shunichi Fukuzumi, Excited-State Deprotonation and H/D Exchange of an Iridium Hydride Complex, Angewandte Chemie - International Edition, 10.1002/anie.200352061, 42, 44, 5492-5495, 2003.11, Visible-light irradiation of the hexafluorophosphate salt of [Cp*lrIII(bpy)H]+ (1, Cp*=η-C 5Me5, bpy=2,2′-bipyridine) results in excited-state deprotonation to form the conjugate base [Cp*lrI(bpy)]. The H/ D exchange reaction of 1 also occurs during photoirradiation of 1 in [D 4]methanol in the steady state (see picture)..
175. Tsutomu Abura, Seiji Ogo, Yoshihito Watanabe, Shunichi Fukuzumi, Isolation and crystal structure of a water-soluble iridium hydride
A robust and highly active catalyst for acid-catalyzed transfer hydrogenations of carbonyl compounds in acidic media, Journal of the American Chemical Society, 10.1021/ja0288237, 125, 14, 4149-4154, 2003.04, This paper reports the isolation and structural determination of a water-soluble hydride complex [Cp*IrIII(bpy)H]+ (1, Cp* = η5-C5Me5, bpy = 2,2′-bipyridine) that serves as a robust and highly active catalyst for acid-catalyzed transfer hydrogenations of carbonyl compounds at pH 2.0-3.0 at 70 °C. The catalyst 1 was synthesized from the reaction of a precatalyst [Cp*IrIII(bpy)(OH2)2]2+ (2) with hydrogen donors HCOOX (X = H or Na) in H2O under controlled conditions (2.0 a value of 2 = 6.6). X-ray analysis shows that complex 1 adopts a distorted octahedral geometry with the Ir atom coordinated by one η5-Cp*, one bidentate bpy, and one terminal hydrido ligand that occupies a bond position. The isolation of 1 allowed us to investigate the robust ability of 1 in acidic media and reducing ability of 1 in the reaction with carbonyl compounds under both stoichiometric and catalytic conditions. The rate of the acid-catalyzed transfer hydrogenation is drastically dependent on pH of the solution, reaction temperature, and concentration of HCOOH. The effect of pH on the rate of the transfer hydrogenation is rationalized by the pH-dependent formation of 1 and activation process of the carbonyl compounds by protons. High turnover frequencies of the acid-catalyzed transfer hydrogenations at pH 2.0-3.0 are ascribed not only to nucleophilicity of 1 toward the carbonyl groups activated by protons but also to a protonic character of the hydrido ligand of 1 that inhibits the protonation of the hydrido ligand..
176. Hideki Furutachi, Mizue Murayama, Amane Shiohara, Satoshi Yamazaki, Shuhei Fujinami, Akira Uehara, Masatatsu Suzuki, Seiji Ogo, Yoshihito Watanabe, Yonezo Maeda, Regioselective hydroxylation of the xylyl linker in a diiron(III) complex having a carboxylate-rich ligand with H2O2, Chemical Communications, 10.1039/b304171a, 3, 15, 1900-1901, 2003, Reaction of a diiron(III) complex having a xylta4− ligand (N, N, N′, N′-m-xylylenediamine tetraacetate) with H2O2 resulted in regioselective hydroxylation of the m-xylyl linker. The reaction mimics the self-hydroxylation of a phenylalanine side chain found for ribonucleotide reductase (R2-W48F/D84E)..
177. Seiji Ogo, Ryo Yamahara, Mark Roach, Tomoyoshi Suenobu, Michihiko Aki, Takashi Ogura, Teizo Kitagawa, Hideki Masuda, Shunichi Fukuzumi, Yoshihito Watanabe, Structural and spectroscopic features of a cis (hydroxo)-FeIII-(carboxylato) configuration as an active site model for lipoxygenases, Inorganic Chemistry, 10.1021/ic0200040, 41, 21, 5513-5520, 2002.10, In our preliminary communication (Ogo, S.; Wada, S.; Watanabe, Y.; Iwase, M.; Wada, A.; Harata, M.; Jitsukawa, K.; Masuda, H.; Einaga, H. Angew. Chem., Int. Ed. 1998, 37, 2102-2104), we reported the first example of X-ray analysis of a mononuclear six-coordinate (hydroxo)iron(III) non-heme complex, [FeIII(tnpa)(OH)(RCO2)]-CIO4 [tnpa = tris(6-neopentylamino-2-pyridylmethyl)amine; for 1, R = C6H5], which has a characteristic cis (hydroxo)-FeIII-(carboxylato) configuration that models the cis (hydroxo)-FeIII-(carboxylato) moiety of the proposed (hydroxo)- iron(III) species of lipoxygenases. In this full account, we report structural and spectroscopic characterization of the cis (hydroxo)-FeIII-(carboxylato) configuration by extending the model complexes from 1 to [FeIII(tnpa)(OH)(RCO2)]-CIO4 (2, R = CH3; 3, R = H) whose cis (hydroxo)-FeIII-(carboxylato) moieties are isotopically labeled by 18OH-, 16OD-, 18OD-, 12CH3
12 C18O2
-, 12CH3
13C16 O2
-, 13CH3
12C16 O2
-, 13CH3
13C16 O2
-, and H13C16O2
-. Complexes 1-3 are characterized by X-ray analysis, IR, EPR, and UV-vis spectroscopy, and electrospray ionization mass spectrometry (ESI-MS)..
178. Seiji Ogo, Tsutomu Abura, Yoshihito Watanabe, pH-dependent transfer hydrogenation of ketones with HCOONa as a hydrogen donor promoted by (η6-C6Me6)Ru complexes, Organometallics, 10.1021/om011059x, 21, 14, 2964-2969, 2002.07, The paper reports on the development of a new class of water-soluble organometallic catalysts for pH-dependent transfer hydrogenation. An organometallic aqua complex [η6-C6Me6)RuII(bpy)(H2 O)]2+ (1, bpy = 2,2′-bipyridine) acts as a catalyst precursor for pH-dependent transfer hydrogenation of water-soluble and -insoluble ketones with HCOONa as a hydrogen donor in water and in biphasic media. Irrespective of the solubility of the ketones toward water, the rate of the transfer hydrogenation shows a sharp maximum around. pH 4.0 (in the case of biphasic media, the pH value of the aqueous phase is adopted). In the absence of the reducible ketones, as a function of pH, complex 1 reacts with HCOONa to provide a formato complex [(η6-C6Me6)RuII(bpy)(HCOO)] + (2) as an intermediate of β-hydrogen elimination and a hydrido complex [(η6-C6Me6)RuII(bpy)H]+ (3) as the catalyst for the transfer hydrogenation. The structures of 1(PF6)2, 2(HCOO)·HCOOH, and [(η6-C6Me6)RuII(H2O) 3]SO4·3H2O {4(SO4)·3H2O}, the starting material for the synthesis of 1, were unequivocally determined by X-ray analysis..
179. Koji Hashimoto, Shigenori Nagatomo, Shuhei Fujinami, Hideki Furutachi, Seiji Ogo, Masatatsu Suzuki, Akira Uehara, Yonezo Maeda, Yoshihito Watanabe, Teizo Kitagawa, A new mononuclear iron(III) complex containing a peroxocarbonate ligand, Angewandte Chemie - International Edition, 10.1002/1521-3773(20020402)41:73.0.CO;2-E, 41, 7, 1202-1205, 2002.04, Stabilization of a peroxocarbonate ligand by formation of a five-membered chelate ring. The mononuclear peroxocarbonate complex 1 was prepared by the reaction of a bis(μ-hydroxo)diiron(III) complex with H2O2 and CO2. Compound 1 is the first crystallographically characterized transition metal complex with a peroxocarbonate ligand. Formation of the peroxocarbonate moiety in 1 proceeds by a nucleophilic addition of a peroxide anion to CO2. Hqn = quinaldic acid..
180. Hidetaka Nakai, Seiji Ogo, Yoshihito Watanabe, pH-dependent cross-coupling reactions of water-soluble organic halides with organoboron compounds catalyzed by the organometallic aqua complex [(SCS)PdII(H2O)]+ (SCS = C6H3-2,6-(CH2SBut)2), Organometallics, 10.1021/om0109298, 21, 8, 1674-1678, 2002.04, This paper reports on the first example of pH-dependent cross-coupling reactions of water-soluble organic halides (3-X(C6H4)CC2H, where X = Cl, Br, I) with organoboron compounds (PhB(OH)2 and Ph4BNa) to form 3-Ph(C6H4)CO2H, catalyzed by the mononuclear organometallic aqua complex [(SCS)PdII(H2O)]2(SO4) ([1]2(SO4), SCS = C6H3-2,6-(CH2SBut)2) in basic media (8 3/NaOH buffers). The structure of 1(PF6) was unequivocally determined by X-ray analysis. The reactions show unique pH selectivity depending upon the organoboron compounds; i.e., the rate of the reactions with PhB(OH)2 shows a sharp maximum around pH 10, though the rate of the reactions with Ph4BNa shows a flat maximum in a pH range of about 8-11. The pH dependence is discussed on the basis of the pKa values of [1]2(SO4) and PhB(OH)2..
181. Ryo Yamahara, Seiji Ogo, Hideki Masuda, Yoshihito Watanabe, (Catecholato)iron(III) complexes
Structural and functional models for the catechol-bound iron(III) form of catechol dioxygenases, Journal of inorganic biochemistry, 10.1016/S0162-0134(01)00353-1, 88, 3-4, 284-294, 2002.03, Catechol dioxygenases are mononuclear non-heme iron enzymes that catalyze the oxygenation of catechols to aliphatic acids via the cleavage of aromatic rings. In the last 20 years, a number of (catecholato)iron(III) complexes have been synthesized and characterized as structural and functional models for the catechol-bound iron(III) form of catechol dioxygenases. This review focuses on the structural and spectroscopic characteristics and oxygenation activity of the title complexes..
182. Akira Wada, Seiji Ogo, Shigenori Nagatomo, Teizo Kitagawa, Yoshihito Watanabe, Koichiro Jitsukawa, Hideki Masuda, Reactivity of hydroperoxide bound to a mononuclear non-heme iron site, Inorganic Chemistry, 10.1021/ic001058h, 41, 4, 616-618, 2002.02, The first isolation and spectroscopic characterization of the mononuclear hydroperoxo-iron(III) complex [Fe(H2bppa)(OOH)]2+ (2) and the stoichiometric oxidation of substrates by the mononuclear iron-oxo intermediate generated by its decomposition have been described. The purple species 2 obtained from reaction of [Fe(H2bppa)(HCOO)](CIO4)2 with H2O2 in acetone at -50 °C gave characteristic UV-vis (λmax = 568 nm, ε = 1200 M-1 cm-1), ESR (g = 7.54, 5.78, and 4.25, S = 5/2), and ESI mass spectra (m/z 288.5 corresponding to the ion, [Fe(bppa)(OOH)]2+), which revealed that 2 is a high-spin mononuclear iron(III) complex with a hydroperoxide in an end-on fashion. The resonance Raman spectrum of 2 in d6-acetone revealed two intense bands at 621 and 830 cm-1, which shifted to 599 and 813 cm-1, respectively, when reacted with 18O-labeled H2O2, Reactions of the isolated (bppa)FeIII-OOH (2) with various substrates (single turnover oxidations) exhibited that the iron-oxo intermediate generated by decomposition of 2 is a nucleophilic species formulated as [(H2bppa)FeIII-O]..
183. Shunichi Fukuzumi, Hironori Kitaguchi, Tomoyoshi Suenobu, Seiji Ogo, Activation of electron transfer reduction of p-benzoquinone derivatives by intermolecular regioselective hydrogen bond formation, Chemical Communications, 10.1039/b205517a, 17, 1984-1985, 2002.01, Electron transfer reduction of p-benzoquinones by cobalt tetraphenylporphyrin is enhanced significantly by the presence of o-bis(phenylcarbamoylmethyl)benzene (o-L) due to the regioselective hydrogen bond formation between the corresponding semiquinone radical anions and o-L, whereas m- and p-isomers (m-L and p-L) have no effect on the electron transfer equilibrium or the rate..
184. Kei Ohkubo, Roger Taylor, Olga V. Boltalina, Seiji Ogo, Shunichi Fukuzumi, Electron transfer reduction of a highly electron-deficient fullerene, C60F18, Chemical Communications, 10.1039/b205642a, 17, 1952-1953, 2002.01, Electron transfer reduction of a highly electron-deficient fullerene, C60F18, to the defluorinated anion, C60F17- occurs efficiently by a relatively weak one-electron reductant, p-chloranil radical anion; the one-electron reduction potential of C60F18 is evaluated as 0.04 V (vs. SCE) by comparison of the rate constant for electron-transfer from 10,10′-dimethyl-9,9′,10,10′-tetrahydro-9,9′- biacridine to C60F18 with those of other one-electron reductants..
185. Seiji Ogo, Hidetaka Nakai, Yoshihito Watanabe, pH-dependent H2-activation cycle coupled to reduction of nitrate ion by Cp*Ir complexes, Journal of the American Chemical Society, 10.1021/ja011846l, 124, 4, 597-601, 2002.01, This paper reports a pH-dependent H2-activation {H2 (pH 1-4) → H+ + H- (pH -1) → 2H+ + 2e-} promoted by Cp*Ir complexes {Cp* = η5-C5(CH3)5}. In a pH range of about 1-4, an aqueous HNO3 solution of [Cp*III(H2O)3]2+ (1) reacts with 3 equiv of H2 to yield a solution of [(Cp*IrIII)2(μ- H)3]+ (2) as a result of heterolytic H2-activation {2[1] + 3H2 (pH 1-4) → [2] + 3H+ + 6H2O}. The hydrido ligands of 2 display protonic behavior and undergo H/D exchange with D+: [M-(H)3-M]+ + 3D+ ⇌ [M-(D)y3-M]+ + 3H+ (where M = Cp*Ir). Complex 2 is insoluble in a pH range of about -0.2 (1.6 M HNO3/H2O) to -0.8 (6.3 M HNO3/H2O). At pH -1 (10 M HNO3/H2O), a powder of 2 drastically reacts with HNO3 to give a solution of [Cp*IrIII(NO3)2] (3) with evolution of H2, NO, and NO2 gases. D-labeling experiments show that the evolved H2 is derived from the hydrido ligands of 2. These results suggest that oxidation of the hydrido ligands of 2 {[2] + 4NO3- (pH -1) → 2[3] + H2 + H+ + 4e-} couples to reduction of NO3- (NO3- → NO2- → NO). To complete the reaction cycle, complex 3 is transformed into 1 by increasing the pH of the solution from.-1 to 1. Therefore, we are able to repeat the reaction cycle using 1, H2, and a pH gradient between 1 and -1. A conceivable mechanism for the H2-activation cycle with reduction of NO3- is proposed..
186. Seiji Ogo, Nobuyuki Makihara, Yuichi Kaneko, Yoshihito Watanabe, pH-dependent transfer hydrogenation, reductive amination, and dehalogenation of water-soluble carbonyl compounds and alkyl halides promoted by Cp*Ir complexes, Organometallics, 10.1021/om010523v, 20, 23, 4903-4910, 2001.11, This paper reports pH-dependent transfer hydrogenation, reductive amination, and dehalogenation of water-soluble substrates with the organometallic aqua complexes [Cp*IrIII(H2O)3]2+ (1, Cp* = η5-pentamethylcyclopentadienyl), [(CpΛpy)IrIII(H2O)2]2+ (2, CpΛpy = η5-(tetramethylcyclopentadienyl)methylpyridine), and [Cp*IrIII(bpy)(H2O)]2+ (3, bpy = 2,2′-bipyridine) as catalyst precursors and the formate ions HCOONa and HCOONH4 as hydrogen donors. Because of the difference in the electron-donating ability of the Cp*, CpΛpy, and bpy ligands, the Lewis acidity of the iridium ions of 1-3 are ordered in strength as follows: 1 > 2 > 3. Complexes 1-3 are reversibly deprotonated to form the catalytically inactive hydroxo complexes [(Cp*IrIII)2(μ-OH)3]+ (5), [{(CpΛpy)IrIII}2(μ-OH)2]2+ (6), and [Cp*IrIII(bpy)(OH)]+ (7) around pH 2.8, 4.5, and 6.6, respectively. The deprotonation behavior of 1-3 indicates that the more Lewis acidic iridium ions would lower the pKa values of the coordinated H2O ligands. As a function of pH, the catalyst precursors 1 and 3 react with the formate ions to form the hydride complexes [(Cp*IrIII)2(μ-H)(μ-OH) (μ-HCOO)]+ (8) and [Cp*IrIII(bpy)(H)]+ (9), respectively, which act as active catalysts in these catalytic reductions. A similar hydride complex would be formed from the reaction of 2 with the formate ions, though we have no definite structural information on the hydride complex. The structures of 3(OTf)2·H2O (OTf = CF3SO3-), [(CpΛpy)IrIIICl2] (4), 6(OTf)2, 7(OTf)·2H2O, and 8(PF6) were unequivocally determined by X-ray analysis..
187. Takeshi Tomita, Seiji Ogo, Tsuyoshi Egawa, Hideo Shimada, Noriaki Okamoto, Yoshio Imai, Yoshihito Watanabe, Yuzuru Ishimura, Teizo Kitagawa, Elucidation of the Differences between the 430- and 455-nm Absorbing Forms of P450-Isocyanide Adducts by Resonance Raman Spectroscopy, Journal of Biological Chemistry, 10.1074/jbc.M104932200, 276, 39, 36261-36267, 2001.09, Alkylisocyanide adducts of microsomal P450 exist in two interconvertible forms, each giving the Soret maximum around 430 or 455 nm. This is demonstrated with a rabbit liver P450 2B4. Resonance Raman spectra of the 430- and 455-nm forms were examined for typical P450s of the two types as well as for P450 2B4 because the 430-nm form of P450 2B4 is liable to change into P420. P450cam and P450nor were selected as a model of the 430- and 455-nm forms, respectively. For the n-butyl isocyanide (CNBu) adduct, the Fe(II)-CNBu stretching band was observed for the first time at 480/467 cm-1 for P450cam and at 471/459 cm-1 for P450nor with their 12CNBu/ 13CNBu derivatives. For P450cam, but not P450nor, other 13C isotope-sensitive bands were observed at 412/402, 844/835, and 940/926 cm-1. The C-N stretching mode was identified by Fourier transform IR spectroscopy at 2116/2080 cm-1 for P450cam and at 2148/ 2108 cm-1 for P450nor for the 12C/13C derivatives. These findings suggest that the binding geometry of isocyanide differs between the two forms-bent and linear structures for P450cam-CNBu and P450nor-CNBu, respectively. In contrast, in the ferric state, the Raman 13C isotopic frequency shifts, and the IR C-N stretching frequencies (2213/2170 and 2215/2172 cm-1) were similar between P450cam and P450nor, suggesting similar bent structures for both..
188. H. Ohtsu, S. Itoh, S. Nagatomo, T. Kitagawa, S. Ogo, Y. Watanabe, S. Fukuzumi, Characterization of imidazolate-bridged dinuclear and mononuclear hydroperoxo complexes, Inorganic chemistry, 10.1021/ic001036v, 40, 13, 3200-3207, 2001.06, Dinucleating ligands having two metal-binding sites bridged by an imidazolate moiety, Hbdpi, HMe2bdpi, and HMe4bdpi (Hbdpi = 4,5-bis(di(2-pyridylmethyl)aminomethyl)imidazole, HMe2bdpi = 4,5-bis((6-methyl-2-pyridylmethyl)(2-pyridylmethyl)aminomethyl)imidazole, HMe4bdpi = 4,5-bis(di(6-methyl-2-pyridylmethyl)-aminomethyl)imidazole), have been designed and synthesized as model ligands for copper-zinc superoxide dismutase (Cu,Zn-SOD). The corresponding mononucleating ligands, MeIm(Py)2, MeIm(Me)1, and MeIm(Me)2 (MeIm(Py)2 = (1-methyl-4-imidazolylmethyl)bis(2-pyridylmethyl)amine, MeIm(Me)1 = (1-methyl-4-imidazolylmethyl)(6-methyl-2-pyridylmethyl) (2-pyridylmethyl)amine, MeIm(Me)2 = (1-methyl-4-imidazolyl-methyl)bis(6-methyl-2-pyridylmethyl)amine), have also been synthesized for comparison. The imidazolate-bridged Cu(II)-Cu(II) homodinuclear complexes represented as [Cu2(bdpi)(CH3CN)2](ClO4) 3·CH3CN·3H2O (1), [Cu2(Me2bdpi)-(CH3CN)2] (ClO4)3 (2), [Cu2(Me4bdpi)(H2O)2] (ClO4)3·4H2O (3), a Cu(II)-Zn(II) heterodinuclear complex of the type of [CuZn(bdpi)(CH3CN)2](ClO4) 3·2CH3CN (4), Cu(II) mononuclear complexes of [Cu(MeIm(Py)2)(CH3-CN)] (ClO4)2·CH3CN (5), [Cu(MeIm(Me)1(CH3CN)](ClO4)2 (6), and [Cu(MeIm(Me)2)(CH3CN)](ClO4)2 (7) have been synthesized and the structures of complexes 5-7 determined by X-ray crystallography. The complexes 1-7 have a pentacoordinate structure at each metal ion with the imidazolate or 1-methylimidazole nitrogen, two pyridine nitrogens, the tertiary amine nitrogen, and a solvent (CH3CN or H2O) which can be readily replaced by a substrate. The reactions between complexes 1-7 and hydrogen peroxide (H2O2) in the presence of a base at -80 °C yield green solutions which exhibit intense bands at 360-380 nm, consistent with the generation of hydroperoxo Cu-(II) species in all cases. The resonance Raman spectra of all hydroperoxo intermediates at -80 °C exhibit a strong resonance-enhanced Raman band at 834-851 cm-1, which shifts to 788-803 cm-1 (Δv = 46 cm-1 when 18O-labeled H2O2 was used, which are assigned to the O-O stretching frequency of a hydroperoxo ion. The resonance Raman spectra of hydroperoxo adducts of complexes 2 and 6 show two Raman bands at 848 (802) and 834 (788), 851 (805), and 835 (789) cm-1 (in the case of H2 18O2, Δv = 46 cm-1) respectively. The ESR spectra of all hydroperoxo complexes are quite close to those of the parent Cu(II) complexes except 6. The spectrum of 6 exhibits a mixture signal of trigonal-bipyramid and square-pyramid which is consistent with the results of resonance Raman spectrum..
189. Nobuyuki Makihara, Seiji Ogo, Yoshihito Watanabe, pH-selective hydrogenation of water-soluble carbonyl compounds and alkenes with [Cp*IrIII(H2O)3]2+ (Cp* = η5-C5Me5) as a catalyst precursor in very acidic media, Organometallics, 10.1021/om0008676, 20, 3, 497-500, 2001.02, The organometallic aqua complex [Cp*IrIII(H2O)3]2+ (1) acts as a catalyst precursor for hydrogenation of water-soluble carbonyl compounds and alkenes in water (5-20 mM of 1, 100 mM of the substrates) in a pH range of about -1 to 4 under H2 at a pressure of 0.1-0.7 MPa at 25°C. The solution pH was adjusted by using 0.1-10 M HClO4/H2O and 0.1 M NaOH/H2O. The aqueous hydrogenation shows unique pH-selectivity to be governed by the following three factors: (i) pH-dependent structural change of the catalyst precursor 1, which is deprotonated to form a catalytically inactive dinuclear complex, [(Cp*IrIII)2(μ-OH)3]+ (2) above pH 4, (ii) stability of a putative iridium hydride active catalyst depending upon pH, and (iii) difference in the proton affinity of the substrates, i.e., Lewis basicity of the carbonyl oxygen atoms of the carbonyl compounds and the C=C moieties of the alkenes. Turnover frequencies of the hydrogenations are also discussed on the basis of Lewis acidity of the carbocations that accept a hydride ion from the active catalyst..
190. Seiji Ogo, Ryo Yamahara, Takuzo Funabiki, Hideki Masuda, Yoshihito Watanabe, Biomimetic intradiol-cleavage of catechols with incorporation of both atoms of O2
The role of the vacant coordination site on the iron center, Chemistry Letters, 10.1246/cl.2001.1062, 10, 1062-1063, 2001.01, This is the first example of model system for the active site of protocatechuate 3,4-dioxygenase to display intradiol-cleavage of catechols with incorporation of two oxygen atoms of O2 promoted by iron complexes..
191. Hideki Ohtsu, Shinobu Itoh, Shigenori Nagatomo, Teizo Kitagawa, Seiji Ogo, Yoshihito Watanabe, Shunichi Fukuzumi, Characterization of imidazolate-bridged Cu(II)-Zn(II) heterodinuclear and Cu(II)-Cu(II) homodinuclear hydroperoxo complexes as reaction intermediate models of Cu,Zn-SOD, Chemical Communications, 10.1039/b002208j, 12, 1051-1052, 2000.06, Imidazolate-bridged Cu(II)-Zn(II) heterodinuclear and Cu(II)-Cu(II) homodinuclear hydroperoxo complexes are generated in the reactions between imidazolate-bridged heterodinuclear and homodinuclear complexes and H2O2 in the presence of triethylamine base and characterized spectroscopically as reaction intermediate models of Cu,Zn-SOD..
192. Ryo Yamahara, Seiji Ogo, Yoshihito Watanabe, Takuzo Funabiki, Koichiro Jitsukawa, Hideki Masuda, Hisahiko Einaga, (Catecholato)iron(III) complexes with tetradentate tripodal ligands containing substituted phenol and pyridine units as structural and functional model complexes for the catechol-bound intermediate of intradiol-cleaving catechol dioxygenases, Inorganica Chimica Acta, 10.1016/S0020-1693(99)00604-0, 300-302, 587-596, 2000.04, This paper reports the synthesis and structures of (catecholato)iron(III) complexes with tetradentate tripodal ligands (L(R',R'') = (2-hydroxy-3-R'-5-R''-phenyl-bis(2-pyridylmethyl)amine)) containing substituted phenol and pyridine units: [Fe(III)(L(R',R''))(DBC)] (1a: R',R'' = H,H; 1b: R',R'' = Me,Me; and 1c: R',R'' = H,Cl, DBC = 3,5-di-tert-butylcatecholato). X-ray structure analysis has revealed that the coordination arrangement around the iron atom of 1a is similar to that proposed for the active site of the catechol-bound intermediate of protocatechuate 3,4-dioxygenase (3,4-PCD). The series of complex 1 derivatives has been synthesized by two different methods: (i) reaction of [Fe(III)(L(R',R''))(acac)]+ (2a: R',R''= H,H; 2b: R',R''= Me,Me; and 2c: R',R'' = H,Cl, acac = acetylacetonato) with 1 equiv. of DBC and 1 equiv. of Et3N in N,N-dimethylformamide (abbreviated as DMF), and (ii) reaction of [Fe(III)L(R',R''))Cl2] (3a: R',R'' = H,H; 3b: R',R'' = Me,Me; and 3c: R',R'' = H,Cl) with 2 equiv. of AgOTf (OTf = O3SCF3-), 1 equiv. of the catechols, and 2 equiv. of Et3N in DMF. The exogenous acac ligand of 2 acts as a Lewis base like the Tyr447 ligand in the active site of 3,4-PCD in the formation of the catechol-bound intermediate. Complexes 1, 2, and 3 have been characterized by X-ray analysis, visible and EPR spectroscopies, and cyclic voltammetry. Oxygenation of the bound DBC on 1 in the presence of O2 has also been investigated and is discussed based on the Lewis basicity of the tripodal ligand containing the substituted phenolato group which is introduced to mimic the Tyr408 ligand of 3,4-PCD. (C) 2000 Elsevier Science S.A..
193. Hideki Hayashi, Shuhei Fujinami, Shigenori Nagatomo, Seiji Ogo, Masatatsu Suzuki, Akira Uehara, Yoshihito Watanabe, Teizo Kitagawa, A bis(μ-oxo)dicopper(III) complex with aromatic nitrogen donors
Structural characterization and reversible conversion between copper(I) and bis(μ-oxo)dicopper(III) species, Journal of the American Chemical Society, 10.1021/ja992680f, 122, 9, 2124-2125, 2000.03.
194. Kazushi Shiren, Seiji Ogo, Shuhei Fujinami, Hideki Hayashi, Masatatsu Suzuki, Akira Uehara, Yoshihito Watanabe, Yoshihiko Moro-oka, Synthesis, structures, and properties of bis(μ-oxo)nickel(III) and bis(μ-superoxo)nickel(II) complexes
An unusual conversion of a Ni(III)2(μ- O)2 core into a Ni(II)2(μ-OO)2 core by H2O2 and oxygenation of ligand, Journal of the American Chemical Society, 10.1021/ja990311d, 122, 2, 254-262, 2000.01, A six-coordinate bis(μ-oxo)nickel(III) complex, [Ni2(μ-O)2(Me3- tpa)2]2+ (1), was synthesized by the reaction of [Ni2(μ-OH)2(Me3- tpa)2]2+ (2) with 1 equiv of hydrogen peroxide in methanol at -90 °C, where Me3-tpa = tris(6-methyl-2-pyridylmethyl)amine. The 6-methyl groups of Me3-tpa have a significant influence on the formation and stabilization of the high-valent bis(μ-oxo)dinickel(III) species. The reaction of 2 with a large excess of hydrogen peroxide (> 10 equiv) afforded a novel bis(μ- superoxo)dinickel(II) complex, [Ni2(μ-O2)2(Me3-tpa)2]2+ (3), thus, the reaction demonstrates a unique conversion of a Ni(III)(μ-O)2Ni(III) core into a Ni(II)(μ-OO)2Ni(II) core upon exposure to hydrogen peroxide. Complexes 1, 2, and 3 have been characterized by X-ray crystallography and various physicochemical techniques. Complex 1 has a Ni(μ-O)2Ni core and the average Ni-O and Ni-N bond distances (1.871 and 2.143 Å, respectively) are significantly shorter than those of 2 (2.018 and 2.185 Å, respectively), suggesting that 1 is a bis(μ-oxo)dinickel(III) complex. Complex 3 consists of a Ni(μ-OO)2Ni core with two μ-1,2-O-O bridges to form a six-membered ring with chair conformation and the O-O bond distance is 1.345(6) Å. The resonance Raman spectrum of a powdered sample of 3 measured at ~110 K showed an isotope-sensitive band at 1096 cm-1 (1044 cm-1 for an 18O-labeled sample), indicating that 3 is a bis(μ-superoxo)dinickel(II) complex. Thermal decomposition of both 1 and 3 in acetone at -20 °C under N2 atmosphere resulted in partial hydroxylation of a methyl group of Me3-tpa in yields of 21-27% for both complexes. For complex 3, a carboxylate complex, [Ni(Me2- tpaCOO)(OH2)]+ (4) where one of the three methyl groups of Me3-tpa is oxidized to carboxylate, was also isolated as a decomposed product under N2 atmosphere. During the decomposition process of 3, dioxygen evolution was simultaneously observed. The electrospray ionization mass spectrometry (ESI- MS) of 3 revealed the formation of 1 during the decomposition process. These results suggest that one possible decomposition pathway of 3 is disproportionation of two coordinated superoxides to dioxygen and peroxide followed by the O-O bond scission of peroxide to regenerate 1, which is responsible for the hydroxylation and the oxidation of the 6-methyl group of Me3-tpa..
195. Seiji Ogo, Nobuyuki Makihara, Yoshihito Watanabe, pH-dependent transfer hydrogenation of water-soluble carbonyl compounds with [Cp*IrIII(H2O)3]2+ (Cp* = η5C5Me5) as a catalyst precursor and HCOONa as a hydrogen donor in water, Organometallics, 10.1021/om9903689, 18, 26, 5470-5474, 1999.12, This paper reports a pH-dependent hydrogenation of water-soluble carbonyl compounds by hydrogen transfer from HCOONa as a hydrogen source (transfer hydrogenation) promoted by [Cp*IrIII(H2O)3]2+ (1, Cp* = η5-C5Me5) as a catalyst precursor in water. Complex 1 has been characterized by X-ray structure analysis, 1H NMR, and potentiometric titration experiments. The active catalyst, a dinuclear μ-hydride complex [(Cp+IrIII)2(μ-H)(μ-OH)(μ-HCOO)]+ (2), has been isolated and characterized by 1H NMR, IR, and electrospray ionization mass spectrometry (ESI-MS). The rate of this transfer hydrogenation shows a sharp maximum at pH 3.2 because the active catalyst 2 is generated from the reaction of 1 with HCOONa at pH 3.2 in the highest yield. The series of the carbonyl compounds consists of a straight chain aldehyde (n-butyraldehyde), a cyclic aldehyde (cyclopropanecarboxaldehyde), a ketone (2-butanone), an aldehyde-acid (glyoxylic acid), and a keto-acid (pyruvic acid). Products were determined by 1H NMR and atmospheric pressure chemical ionization mass spectrometry (APCI-MS). A possible mechanism for this transfer hydrogenation is proposed..
196. Seiji Ogo, Olivier Buriez, John B. Kerr, Richard H. Fish, Bioorganometallic chemistry
Part 12. Reaction of [Cp*Rh(H2O)3](OTf)2 with nicotinamide adenine dinucleotide in water: Synthesis, structure, and a pH-dependent 1H-NMR and voltammetric study of the cyclic trimer product, [Cp*Rh(μ-η1(N1):η 2(N6,N7)-9-(5′-ribose pyrophosphate-5″-ribose-1″-nicotinamide, Journal of Organometallic Chemistry, 10.1016/s0022-328x(99)00303-4, 589, 1, 66-74, 1999.10, The reaction of [Cp*Rh(H2O)3](OTf)2 (1) with nicotine adenine dinucleotide (NAD+, 2), an important co-factor in enzymatic reactions, was studied utilizing 1H-NMR spectroscopy, electrospray ionization mass spectroscopy (ESI/MS), cyclic voltammetry (CV), and isolation techniques, as a function of pH. The product was formulated from the above-mentioned spectroscopic data as the well-known Cp*Rh cyclic trimer structure, [Cp*Rh(μ-η1(N1):η 2(N6,N7)-9-(5′-ribose pyrophosphate-5″-ribose-1″-nicotinamide)adeninato] 3(OTf)3, 3, which forms via a self-assembly mechanism as the pH is increased from 3 to 6 (1H-NMR). We also compared 3 with the putative one reported that formed via reaction with [(Cp*Rh)2(μ-Cl2)Cl2] and was tentatively assigned the formula, [Cp*Rh(NAD)Cl](Cl). In fact, both Cp*Rh synthons provide the same cyclic trimer product at pH 6, while a presumed mixture of [Cp*Rh(NAD)] and Cp*Rh aqua intermediates (at least eight Cp*Rh 1H-NMR signals are evident) were formed at pH 3.0. A full analysis of the CV data reveals that some Cp*Rh aqua complexes are electroactive at potentials around -1.2 V versus Ag AgCl, but probably not the cyclic trimer, complex 3. Unfortunately, we were not able to utilize complex 3 in an intramolecular, regioselective reduction reaction, with sodium formate as the hydride source, to provide the corresponding biologically active 1,4-dihydro derivative..
197. Satoshi Takara, Seiji Ogo, Yoshihito Watanabe, Koji Nishikawa, Isamu Kinoshita, Kiyoshi Isobe, Direct observation by electrospray ionization mass spectrometry of [Cp*RhMo3O8(OMe)5]-, a key intermediate in the formation of the double- bookshelf-type oxide cluster [(Cp*Rh)2Mo6O20(OMe)2]2, Angewandte Chemie - International Edition, 10.1002/(SICI)1521-3773(19991018)38:203.0.CO;2-C, 38, 20, 3051-3053, 1999.10, The use of methanol as solvent is essential for the formation of the double-bookshelf-type oxide cluster [(Cp*Rh)2Mo6O20(OMe)2]2- from [{Cp*Rh(μ-Cl)Cl}2] and four equivalents of [Mo2O7]2. The reaction proceeds via [Cp*RhMo3O8(OMe)5]-. The proposed structure for this key intermediate (shown schematically) is supported by electrospray ionization mass spectrometry and labeling experiments with CD3OD as solvent. Cp* = η5-C5Me5..
198. Akira Wada, Seiji Ogo, Yoshihito Watanabe, Masahiro Mukai, Teizo Kitagawa, Koichiro Jitsukawa, Hideki Masuda, Hisahiko Einaga, Synthesis and characterization of novel alkylperoxo mononuclear iron(III) complexes with a tripodal pyridylamine ligand
A model for peroxo intermediates in reactions catalyzed by non-heme iron enzymes, Inorganic chemistry, 10.1021/ic9900298, 38, 16, 3592-3593, 1999.
199. Seiji Ogo, Shigeyuki Nakamura, Hong Chen, Kiyoshi Isobe, Yoshihito Watanabe, Richard H. Fish, A new, aqueous 1H NMR shift reagent based on host-guest molecular recognition principles for organic compound structural analysis
Non-covalent π-π and hydrophobic interactions using a supramolecular host, [Cp*Rh(2′-deoxyadenosine)]3(OTf)3, Journal of Organic Chemistry, 10.1021/jo972204c, 63, 21, 7151-7156, 1998.10, We have discovered that the supramolecular host [Cp*Rh(2′-deoxyadenosine)]3(OTf)3 (1, Cp* = η5-C5Me5, OTf = CF3SO3-) has utility as a new, aqueous 1H NMR shift reagent, via a host-guest molecular recognition process that occurs by non-covalent π-π and hydrophobic interactions, with a wide variety of H2O-soluble organic substrates. These organic compound guests that we present, to illustrate the utility of host 1 as a novel, aqueous 1H NMR shift reagent, encompass examples such as aromatic carboxylic acids, phenylacetic acid (G1), 1-naphthoic acid (G2), and 2-naphthoic acid (G3), an aliphatic carboxylic acid, cyclohexylacetic acid (G4), as well as biological compounds, a di- and a tetrapeptide containing terminal L-tryptophan (Trp) or L-phenylalanine (Phe) groups, L-Trp-L-Phe (G5) and L-Trp-L-Met-L-Asp-L-Phe amide (G6) in the pH range 5-10. A discussion of the molecular recognition parameters that effect the 1H NMR shifts of the organic guests and a comparison with the water-soluble lanthanide shift reagents (LSRs) will be presented to demonstrate the usefulness of this aqueous molecular receptor as an aid for organic compound structural analysis..
200. Seiji Ogo, Senji Wada, Yoshihito Watanabe, Masakazu Iwase, Akira Wada, Manabu Harata, Koichiro Jitsukawa, Hideki Masuda, Hisahiko Einaga, Synthesis, structure, and spectroscopic properties of [Fe(III)(tnpa)(OH)(PhCOO)ClO4
A model complex for an active form of soybean lipoxygenase-1, Angewandte Chemie - International Edition, 10.1002/(SICI)1521-3773(19980817)37:153.0.CO;2-A, 37, 15, 2102-2104, 1998.08.
201. Ray Bakhtiar, Hong Chen, Seiji Ogo, Richard H. Fish, Gas phase molecular recognition of aromatic amino acid and aromatic carboxylic acid guests with a supramolecular [(η 5-pentamethylcyclopentadienyl)rhodium(2′-deoxyadenosine)] 33+ cyclic trimer host via non-covalent π-π interactions utilizing electrospray ionization mass spectroscopy, Chemical Communications, 10.1039/a703100i, 22, 2135-2136, 1997.01, A novel, gas phase, host-guest molecular recognition process, detected by electrospray ionization mass spectrometry, using guests that encompass aromatic amino acids and aromatic and aliphatic carboxylic acids with a supramolecular, bioorganometallic host, [Cp*Rh(2′-deoxyadenosine)]3[OTf]3 (Cp* = η5-C5Me5), is found to occur predominately via non-covalent π-π interactions; non-covalent hydrophobic forces apparently being weak or non-existent..
202. Hong Chen, Seiji Ogo, Richard H. Fish, Bioorganometallic chemistry. 8. The molecular recognition of aromatic and aliphatic amino acids and substituted aromatic and aliphatic carboxylic acid guests with supramolecular(η5-pentamethylcyclopentadienyl) rhodium-nucleobase,nucleoside,and nucleotide cyclic trimer hosts vianon-covalent π-πand hydrophobic interactions in water:Steric,electronic, Journal of the American Chemical Society, 10.1021/ja954040s, 118, 21, 4993-5001, 1996.05, Molecular recognition, via non-covalent processes such as hydrogen bonding, π-π, and hydrophobic interactions, is an important biological phenomenon for guests, such as drugs, proteins, and other important biological molecules with, for example, host DNA/RNA. We have studied a novel molecular recognition process using guests that encompass aromatic and aliphatic amino acids [L-alanine, L-glutamine (L-Gln), L-histidine, L-isoleucine (L-Ile), L-leucine (L-Leu), L-phenylalanine (L-Phe), L-proline, L-tryptophan (L-Trp), L-valine (L-Val)], substituted aromatic carboxylic acids [o-, m-, p-aminobenzoic acids (G1-3), benzoic acid (G4), phenylacetic acid (G5), p-methoxyphenylacetic acid (G6), o-methyoxybenzoic acid (G9), o-nitrobenzoic acid (G10)], and aliphatic carboxylic acids [cyclohexylacetic acid (G7), 1-adamantanecarboxylic acid (G8)] with supramolecular, bioorganometallic hosts, (η5-pentamethylcyclopentadienyl)rhodium (Cp*Rh)-nucleobase, nucleoside, and nucleotide cyclic trimer complexes, [Cp*Rh(9-methyladenine)]3(OTf)3 (1) (OTf = trifluoromethanesulfonate), [Cp*Rh(adenosine)]3(OTf)3 (2), [Cp*Rh-(2′-deoxyadenosine)]3(OTf)3 (3), [Cp*Rh(2′,3′-dideoxyadenosine)]3(OTf)3 (4), and [Cp*Rh(Me-5′-AMP)]3 (5), in aqueous solution at pH 7, utilizing 1H NMR, NOE, and molecular modeling techniques, and, as well, determining association constants (Ka) and free energies of complexion (ΔG°). The host-guest complexation occurs predominantly via non-covalent π-π, hydrophobic, and possible subtle H-bonding interactions, with steric, electronic, and molecular conformational parameters as important criteria. Moreover, we note that both the π-π and hydrophobic interactions seem to be equally important when competing aromatic and aliphatic carboxylic acid guests, G5 and G7, for host 3. The solvophobic effects in H2O also control the extent of host-guest interaction and will be discussed..
203. Seiji Ogo, Hong Chen, Marilyn M. Olmstead, Richard H. Fish, Aqueous organometallic chemistry. 2. 1H NMR spectroscopic, synthetic, and structural study of the chemo- and diastereoselective reactions of [Cp*Rh-(H2O)3]2+ with nitrogen ligands as a function of pH, Organometallics, 10.1021/om950681k, 15, 8, 2009-2013, 1996.04, The reactions of a new Cp*Rh aqua synthon, [Cp*Rh(H2O)3]2+ (1), at acidic pH values (2-6) with aniline (2), pyridine (3), and L-phenylalanine (4) have provided interesting chemo-and diastereoselectivities as studied by 1H NMR, FAB/MS, and single-crystal X-ray crystallography. The reaction of 2 and aqua complex 1, at pH values from 4 to 6, quantitatively provided [Cp*Rh(η6-aniline)]2+ (5); the structure of 5 was unequivocally determined by a single-crystal X-ray analysis, which also showed an approximate 25% η5 component. Compound 3 reacted with 1, at pH 2-6, to selectively provide [Cp*Rh(η1-pyridine)n(H2O) 3-n]2+ (n = 1-3) complexes 6a-c as a function of pH. Surprisingly, complex 1 reacted with 4, from pH 4 to 6, to provide only one diastereomer of the known cyclic trimer [(Cp*Rh)(μ-η1(OCO):η2-(N,OCO)-L- phenylalanine)]33+ (7; Sc,Sc,Sc,SRh,SRh,S Rh), an example of a one-step, highly diastereoselective reaction in H2O..
204. Hideaki Watanabe, Seiji Ogo, Takeshi Yamamura, Bulky thiols and their coordination compounds. An improvement of the removal method of tetrahydropyranyl group from thiols and its application for ligand syntheses, Chemistry Letters, 10.1246/cl.1996.999, 11, 999-1000, 1996.01, The route for the syntheses of alkanthiols having bulky groups at the neighborhood of sulfur atoms was improved, and applied for the preparation of thiol ligands that mimic the cysteine containing metal binding sites in proteins. The new method developed the deprotection of tetrahydropyranyl group from α,α-diphenylalkyl 2-tetrahydropyranyl sulfides..
205. Seiji Ogo, Takayoshi Suzuki, Yoshiki Ozawa, Kiyoshi Isobe, Structures, Bonding, and Reactivity of M-S-M' (M and M' = Rh, W, and Cu) Groups in Higher-Nuclearity Heterometallic Sulfide Clusters, Inorganic chemistry, 10.1021/ic9601807, 35, 21, 6093-6101, 1996, This paper reports (i) a rational synthesis of heterometallic sulfide clusters with M-S-M' (M and M' = Rh, W, and Cu) groups, (ii) structures and bonding of the M-S-M' groups determined by X-ray crystallographic analysis and IR spectroscopy, and (iii) reactivity of the M-S-M' groups unique to higher-nuclearity heterometallic sulfide clusters toward H2O and H2S. A branched-type octanuclear sulfide cluster [{Cp*RhP(OEt)3(μ-WS4)(CuCl)Cu} 2-(μ-Cl)2] (4, Cp* = η5-C5Me5) was stepwise prepared from the following sequence: [Cp*RhP(OEt)3Cl2] (1, mononuclear) → [Cp*RhP(OEt)3WS4] (2, dinuclear) → [Cp*RhP(OEt)3(μ-WS4)CuCl] (3, linear-type trinuclear) → 4 by a systematic building-block method. A bridging sulfide ligand in the W-S-Cu group of 4 reacts with a water-saturated CH2Cl2 solution to convert the terminal O atom of [{Cp*RhP(OEt)3(μ-WOS3)(CuCl)Cu} 2(μ-Cl)2] (5, linked incomplete cubane-type octanuclear) with a drastic structural change in the cluster framework. The transformation reaction of 4 to 5 includes the first example of the conversion of the bridging S atom in the M-S-M' group into the terminal O atom without releasing the metal atoms, and this reaction is peculiar to the higher-nuclearity heterometallic sulfide cluster 4. Clusters 4, 5, and 6 ([Cp*RhP(OEt)3(μ-WOS3)CuCl], butterfly-type trinuclear) react with H2S in CH2Cl2 giving 3 as a major product. The formation of 3 in these reactions are based on the reactivity of M-S-Cu groups in the sulfide clusters toward H2S: the (μ3-S)-Cu bonds are easily broken by H2S, but not the (μ2-S)-Cu ones. The crystal data for 1, 2, 3, 4, 5, and 6 confirmed by X-ray analysis are as follows. 1: C16H30Cl2O3PRh, orthorhombic, P21cn, a = 8.988(3) Å, b = 28.591(5) Å, c = 8.276(3) Å, 2 = 4. 2: C16H30O3PRhS4W, monoclinic, P21/n, a = 14.633(2) Å, b = 15.191(2) Å, c = 11.490(1) Å, β = 104.97(1)°, Z = 4. 3: C16H30ClCuO3PRhS4W, monoclinic, P21/m, a = 10.221(2) Å, b = 11.943(2) Å, c = 10.809(1) Å, β = 94.40(1)°, Z = 2. 4: C32H60Cl4Cu4O6P 2Rh2S8W2, monoclinic, P21/n, a = 10.170(3) Å, b = 14.495(3) Å, c = 19.411(3) Å, β = 104.42(1)°, Z = 2. 5·2DMF: C38H74Cl4Cu4N2O 10P2Rh2S6W2, monoclinic, P21/c, a = 10.011(3) Å, b = 17.115(3) Å, c = 18.678(3) Å, β = 95.10(2)°, Z = 2. 6: C16H30ClCuO4PRhS3W, orthorhombic, P21nb, a = 14.515(2) Å, b = 17.225(3) Å, c = 10.261(3) Å, Z = 4..
206. Seiji Ogo, Takayoshi Suzuki, Sachiyo Nomura, Kiyotaka Asakura, Kiyoshi Isobe, Synthesis of a linear-type pentanuclear (RhIII-WVI-CuI-WVI-RhIII) sulfide cluster predicted by fast atom bombardment mass spectrometry, Journal of Cluster Science, 10.1007/BF01165471, 6, 3, 421-436, 1995.09, The positive ion FAB mass spectrum of a linear trinuclear sulfide cluster, [Cp*RhP(OEt)3(μ-WS4CuCl] (1; Cp* = η5-C5Me5), shows many ions heavier than the molecular ion. One of the envelopes corresponds to a pentanuclear cationic cluster of [{Cp*RhP(OEt)3(WS4)}2Cu]+. It has been synthesized by a reaction between [Cp*RhP(OEt)3WS4] and Cu+ in a 2:1 molar ratio as the PF6 salt [{Cp*RhP(OEt)3(μ-WS4)}2Cu][PF6] (2 · PF6), which is characterized by a single-crystal X-ray diffraction, EXAFS, and IR measurements..
207. Seiji Ogo, Takayoshi Suzuki, Kiyoshi Isobe, A Unique Three-Step Cyclic Reaction Sequence of Heterotrimetallic Sulfide Clusters. Structures and Properties of [{Cp*RhP(OEt)3(μ-WS4)(CuCl)Cu}2(μ-Cl)2] (Cp* = η5-C5Me5) with a Branched Structure and [{Cp*RhP(OEt)3(μ-WOS3)(CuCl)Cu}2(μ-Cl)2] with a Linked Incomplete Cubane-Type Structure, Inorganic chemistry, 10.1021/ic00110a003, 34, 6, 1304-1305, 1995.03.