|Masatoshi Ishida||Last modified date：2019.06.18|
Assistant Professor / Organic Chemistry of Functional Molecules / Department of Applied Chemistry / Faculty of Engineering
|Masatoshi Ishida||Last modified date：2019.06.18|
|1.||Shota Ooi, Takayuki Tanaka, Takahisa Ikeue, Kazuhisa Yamasumi, Kento Ueta, Daiki Shimizu, Masatoshi Ishida, Hiroyuki Furuta, Atsuhiro Osuka, Bis-copper(II) Complex of Triply-linked Corrole Dimer and Its Dication, Chemistry - An Asian Journal, 10.1002/asia.201801467, 14, 10, 1771-1776, 2019.05, Copper complexes of corroles have recently been a subject of keen interest due to their ligand non-innocent character and unique redox properties. Here we investigated bis-copper complex of a triply-linked corrole dimer that serves as a pair of divalent metal ligands but can be reduced to a pair of trivalent metal ligands. Reaction of triply-linked corrole dimer 2 with Cu(acac) 2 (acac=acetylacetonate) gave bis-copper(II) complex 2Cu as a highly planar molecule with a mean-plane deviation value of 0.020 Å, where the two copper ions were revealed to be divalent by ESR, SQUID, and XPS methods. Oxidation of 2Cu with two equivalents of AgBF 4 gave complex 3Cu, which was characterized as a bis-copper(II) complex of a dicationic triply-linked corrole dimer not as the corresponding bis-copper(III) complex. In accord with this assignment, the structural parameters around the copper ions were revealed to be quite similar for 2Cu and 3Cu. Importantly, the magnetic spin–spin interaction differs depending on the redox-state of the ligand, being weak ferromagnetic in 2Cu and antiferromagnetic in 3Cu..|
|2.||Poornenth Pushpanandan, Dong Hoon Won, Shigeki Mori, Yuhsuke Yasutake, Susumu Fukatsu, Masatoshi Ishida, Hiroyuki Furuta, Doubly N-Confused Calixphyrin Bis-Organopalladium Complexes
Photostable Triplet Sensitizers for Singlet Oxygen Generation, Chemistry - An Asian Journal, 10.1002/asia.201801671, 14, 10, 1729-1736, 2019.05, Triplet photosensitizers that generate singlet oxygen efficiently are attractive for applications such as photodynamic therapy (PDT). Extending the absorption band to a near-infrared (NIR) region (700 nm≈) with reasonable photostability is one of the major demands in the rational design of such sensitizers. We herein prepared a series of mono- and bis-palladium complexes (1-Pd-H 2 , 2-Pd-H 2 , 1-Pd-Pd, and 2-Pd-Pd) based on modified calixphyrins as photosensitizers for singlet oxygen generation. These palladium complexes showed intense absorption profiles in the visible-to-NIR region (500–750 nm) depending on the number of central metals. Upon photoirradiation in the presence of 1,5-dihydroxynaphthalene (DHN) as a substrate for reactive oxygen species, the bis-palladium complexes generated singlet oxygen with high efficiency and excellent photostability. Singlet oxygen generation was confirmed from the characteristic spectral feature of the spin trapped complex in the EPR spectrum and the intact 1 O 2 emission at 1270 nm..
|3.||Yufeng Yang, Masatoshi Ishida, Yuhsuke Yasutake, Susumu Fukatsu, Chihoko Fukakusa, Masa-Aki Morikawa, Teppei Yamada, Nobuo Kimizuka, Hiroyuki Furuta, Hierarchical Hybrid Metal-Organic Frameworks
Tuning the Visible/Near-Infrared Optical Properties by a Combination of Porphyrin and Its Isomer Units, Inorganic Chemistry, 10.1021/acs.inorgchem.9b00251, 58, 7, 4647-4656, 2019.04, Hybrid metal-organic frameworks (MOFs) with core/shell-like hierarchical structure comprised of zirconium metal and porphyrin (e.g., TPP) and its isomer, N-confused porphyrin (NCP), were synthesized through a seed-mediated reaction. The hierarchical structures of hybrid MOFs were characterized by the microscopic image analyses (e.g., scanning electron microscope (SEM), energy dispersive X-ray (EDX) spectrometry, and confocal laser scanning microscope (CLSM)). Taking advantage of the intrinsic light-harvesting properties of the porphyrin dye and the N-confused isomer, changing the core/shell layer structures of hybrid MOFs allows for tuning of the visible-to-near-infrared (NIR) absorption/emission characters, excited-state energy migrations, and photosensitization capabilities. The Förster energy transfer event occurring in the bulk MOF samples by photoexcitation enabled us to control the photoinduced singlet oxygen generation through the comprehensive light-harvesting ability of these hybrid porphyrinic MOFs. Therefore, implementation of a precisely designed porphyrin "substitute" into the MOF-based materials indeed provides a new mimic of the photosynthetic pigment system and should be potentially applicable for solar-light-driven devices..
|4.||Qizhao Li, Chengjie Li, Jinseok Kim, Masatoshi Ishida, Xin Li, Tingting Gu, Xu Liang, Weihua Zhu, Ågren Hans, Dongho Kim, Hiroyuki Furuta, Yongshu Xie, Regioselectively Halogenated Expanded Porphyrinoids as Building Blocks for Constructing Porphyrin-Porphyrinoid Heterodyads with Tunable Energy Transfer, Journal of the American Chemical Society, 10.1021/jacs.8b13148, 141, 13, 5294-5302, 2019.04, Expanded porphyrins have been attracting increasing attention owing to their unique optical and electrochemical properties as well as switchable aromaticity. Toward material applications, regioselective functionalization of the expanded porphyrins at their periphery is indeed challenging due to the presence of multiple reactive sites. Herein, a set of regioselective halogenated isomers (L5-Br-A/B/C) of neo-confused isosmaragdyrin (L5) are synthesized by a combination of the halogenation reaction of L5 and sequential macrocycle-to-macrocycle transformation reactions of its halogenated isomers. On this basis, the regioselectively functionalized isosmaragdyrins are utilized as building blocks for constructing multichromophoric porphyrinoids, specifically, heterodyads L5-ZnP-A/B/C, in which a common zinc porphyrin is linked at three different pyrrolic positions of isosmaragdyrins, respectively, by Sonogashira coupling reactions. The highly efficient energy cascade from porphyrin to isosmaragdyrin is elucidated using steady-state/time-resolved spectroscopies and theoretical calculations. Notably, the energy transfer processes from the porphyrin to the isosmaragdyrin moieties as well as the excitation energy transfer rates in L5-ZnP-A/B/C are highly dependent on the linking sites by through-bond and Förster-type resonance energy transfer mechanisms. The site-selective functionalization and subsequent construction of a set of heterodyads of the expanded porphyrinoid would provide opportunities for developing new materials for optoelectronic applications..|
|5.||Qizhao Li, Masatoshi Ishida, Hiroto Kai, Tingting Gu, Chengjie Li, Xin Li, Glib Baryshnikov, Xu Liang, Weihua Zhu, Ågren Hans, Hiroyuki Furuta, Yongshu Xie, Skeletal Rearrangement of Twisted Thia-Norhexaphyrin
Multiply Annulated Polypyrrolic Aromatic Macrocycles, Angewandte Chemie - International Edition, 10.1002/anie.201900010, 2019.03, A hybrid thia-norhexaphyrin comprising a directly linked N-confused pyrrole and thiophene unit (1) revealed unique macrocycle transformations to afford multiply inner-annulated aromatic macrocycles. Oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone triggered a cleavage of the C-S bond of the thiophene unit, accompanied with skeletal rearrangement to afford unique π-conjugated products: a thiopyrrolo-pentaphyrin embedded with a pyrrolo[1,2]isothiazole (2), a sulfur-free pentaphyrin incorporating an indolizine moiety (3), and a thiopyranyltriphyrinoid containing a 2H-thiopyran unit (4). Furthermore, 2 underwent desulfurization reactions to afford a fused pentaphyrin containing a pyrrolizine moiety (5) under mild conditions. Using expanded porphyrin scaffolds, oxidative thiophene cleavage and desulfurization of the hitherto unknown N-confused core-modified macrocycles would be a practical approach for developing unique polypyrrolic aromatic macrocycles..
|6.||Neha Manav, Praseetha E Kesavan, Masatoshi Ishida, Shigeki Mori, Yuhsuke Yasutake, Susumu Fukatsu, Hiroyuki Furuta, Iti Gupta, Phosphorescent rhenium-dipyrrinates
efficient photosensitizers for singlet oxygen generation, Dalton Transactions, 10.1039/c8dt04540b, 48, 7, 2467-2478, 2019.02, A series of rhenium(i) dipyrrinato complexes (Re1-Re8) have been prepared and characterized; their crystal structures, phosphorescence and singlet oxygen generation studies are reported. The aromatic substituents, such as thienyl, p-bromophenyl, p-fluorophenyl, m-fluorophenyl, pentaflurophenyl, N-butylcarbazole, N-phenylcarbazole, and N-butylphenothiazine, are linked to the C5 position of Re-dipyrrinates. Varying the electronic nature of the substituents from electron donating (e.g., carbazole) to electron withdrawing (e.g., pentaflurophenyl) allowed the change in the structural, electrochemical, and spectroscopic properties of these complexes. In particular, the rhenium dipyrrinates showed phosphorescence in the near IR region with sufficiently longer triplet state lifetimes (τT = 9-29 μs). Also, a large Stokes shift (Δν = 5682-6957 cm-1) was witnessed for all the rhenium dipyrrinates. Triplet emission was reflected in the efficient singlet oxygen generation yields (ΦΔ ∼ 0.75-0.98) along with the distinct photo-stability. Density functional theory (DFT) calculations revealed that the electron density is spread over the dipyrrin unit in most complexes. Rhenium dipyrrinate having a phenothiazine substituent exhibited the smallest HOMO-LUMO band gap (2.820 eV) among all Re-complexes..
|7.||Jayaprakash Ajay, Sriram Shirisha, Masatoshi Ishida, Kosuke Ito, Shigeki Mori, Hiroyuki Furuta, Sabapathi Gokulnath, Planar Antiaromatic Core-Modified 24π Hexaphyrin(184.108.40.206.1.0) and 32π Octaphyrin(220.127.116.11.18.104.22.168) Bearing Alternate Hybrid Diheterole Units, Chemistry - A European Journal, 10.1002/chem.201805861, 25, 11, 2859-2867, 2019.02, The Lewis acid catalyzed self-condensation of hybrid diheterole (furan-pyrrole and thiophene-pyrrole) precursors has afforded novel Hückel antiaromatic 24π hexaphyrin(22.214.171.124.1.0) and 32π octaphyrin(126.96.36.199.188.8.131.52) structures without β-annulated bridges. Single-crystal X-ray diffraction analysis of the hybrid porphyrinoids (S
-ox and O
-ox) revealed a nearly planar conformation and the
H NMR spectra suggest the presence of paratropic ring currents. These antiaromatic macrocycles show characteristic optical features and underwent reversible two-electron reduction to Hückel aromatic 26π- and 34π-electron species, respectively, as is evident from the results of spectroscopic and theoretical studies (nucleus-independent chemical shift (NICS) and anisotropy of the current-induced density (ACID) calculations). The incorporation of hybrid diheteroles alternately into expanded porphyrin skeletons provides a novel approach to the fine-tuning of the electronic structures of planar antiaromatic macrocycles..
|8.||Takaaki Miyazaki, Kazuki Fukuyama, Shunichi Mashita, Yuya Deguchi, Takaaki Yamamoto, Masatoshi Ishida, Shigeki Mori, Hiroyuki Furuta, Ruthenium N-Confused Porphyrins
Selective Reactivity for Ambident 2-Heteroatom-Substituted Pyridines Serving as Axial Ligands, ChemPlusChem, 10.1002/cplu.201800630, 2019.01, Three types of ruthenium(II) N-confused porphyrin (NCP) complexes bearing an axial 2-thiopyridine, 2-pyridone, and 2-iminopyridine moiety at the inner carbon atom, respectively, were synthesized. The unique reactivity of the 2-substituted pyridine derivatives (2-X-pyridine; X=SH, OH, NH
) toward the inner carbon atom of the NCP allows the formation of two types of coordinated products (i. e., pyridine donor versus 2-heteroatom donors), as inferred from single-crystal X-ray structures. The selective reactivity was investigated by using density functional theory (DFT) calculations. Finally, the catalytic activity of these ruthenium complexes was demonstrated through the styrene oxidation reactions. As a result, the ruthenium(II) NCP complex bearing a 2-thiopyridine moiety, together with aqueous H
as an oxidant showed the highest selectivity for benzaldehyde (benzaldehyde/styrene oxide=20 : 1)..
|9.||Yogesh Kumar Maurya, Katsuya Noda, Kazuhisa Yamasumi, Shigeki Mori, Tomoki Uchiyama, Kazutaka Kamitani, Tomoyasu Hirai, Kakeru Ninomiya, Maiko Nishibori, Yuta Hori, Yoshihito Shiota, Kazunari Yoshizawa, Masatoshi Ishida, Hiroyuki Furuta, Ground-State Copper(III) Stabilized by N-Confused/N-Linked Corroles
Synthesis, Characterization, and Redox Reactivity, Journal of the American Chemical Society, 10.1021/jacs.8b01876, 140, 22, 6883-6892, 2018.06, Stable square planar organocopper(III) complexes (CuNCC2, CuNCC4, and CuBN) supported by carbacorrole-based tetradentate macrocyclic ligands with NNNC coordination cores were synthesized, and their structures were elucidated by spectroscopic means including X-ray crystallographic analysis. On the basis of their distinct planar structures, X-ray absorption/photoelectron spectroscopic features, and temperature-independent diamagnetic nature, these organocopper complexes can be preferably considered as novel organocopper(III) species. The remarkable stability of the high-valent Cu(III) states of the complexes stems from the closed-shell electronic structure derived from the peculiar NNNC coordination of the corrole-modified frameworks, which contrasts with the redox-noninnocent radical nature of regular corrole copper(II) complexes with an NNNN core. The proposed structure was supported by DFT (B3LYP) calculations. Furthermore, a π-laminated dimer architecture linked through the inner carbons was obtained from the one-electron oxidation of CuNCC4. We envisage that the precise manipulation of the molecular orbital energies and redox profiles of these organometallic corrole complexes could eventually lead to the isolation of yet unexplored high-valent metal species and the development of their organometallic reactions..
|10.||Yutaka Hisamune, Taeyeon Kim, Keiichi Nishimura, Masatoshi Ishida, Motoki Toganoh, Shigeki Mori, Dongho Kim, Hiroyuki Furuta, Switch-ON Near IR Fluorescent Dye Upon Protonation
Helically Twisted Bis(Boron Difluoride) Complex of π-Extended Corrorin, Chemistry - A European Journal, 10.1002/chem.201705516, 24, 18, 4628-4634, 2018.03, A novel helically twisted π-extended corrorin derivative having two boron dipyrrin (BODIPY) moieties at the periphery, a BODIPY DYEmer (6-BF2) cross-bridged with π-conjugated dipyrrinylidene unit, was synthesized and characterized. The neutral 6-BF2 is nonfluorescent due to the internal photoinduced charge transfer (CT) character in the excited state as inferred from the femtosecond transient absorption spectroscopy. However, upon protonation, the CT process is suppressed and the species H6-BF2 + becomes near infrared (IR) emissive. With the aid of rigid helical conformations in 6-BF2, the helical isomers (P- and M-forms) were resolved and their chiroptical property was investigated. The distinct circular dichroism (CD) spectral changes of the enantiomers were observed in the presence of acids, which demonstrates that 6-BF2 can be utilized for potential acid-responsive chiroptical materials..
|11.||Takaaki Miyazaki, Takaaki Yamamoto, Shunichi Mashita, Yuya Deguchi, Kazuki Fukuyama, Masatoshi Ishida, Shigeki Mori, Hiroyuki Furuta, N-Confused Porphyrin Metal Complexes with an Axial Pyridine Directly Tethered from an Inner Carbon
A Bioinspired Ligand as a Versatile Platform for Catalysis, European Journal of Inorganic Chemistry, 10.1002/ejic.201701494, 2018, 2, 203-207, 2018.01, Bioinspired pentadentate ligand N-confused porphyrin (NCP) bearing a 2-mercaptopyridine group and its RuII and CoIII complexes were synthesized. Their structures were revealed by single-crystal X-ray crystallographic analysis. Installation of an axial thiopyridine ligand shifts the redox potentials negatively and enhances the catalytic activity largely, which was demonstrated in the cyclopropanation reaction using the Co complex..
|12.||Takaaki Yamamoto, Koki Mitsuno, Shigeki Mori, Shuhei Itoyama, Yoshihito Shiota, Kazunari Yoshizawa, Masatoshi Ishida, Hiroyuki Furuta, Two Discrete RuCp* (Cp*=Pentamethylcyclopentadienyl) Binding Modes of N-Confused Porphyrins
Peripheral π Complex and Sitting Atop Ruthenocenophane Complex by Skeletal Transformation, Chemistry - A European Journal, 10.1002/chem.201801237, 2018.01, Complexation of a RuCp* cation with N-confused tetraarylporphyrins (NCPs) forms directly bound ruthenium(II) pentamethylcyclopentadienyl (Cp*) π-complex on a specific meso-aryl group (e.g., phenyl) neighboring peripheral imino nitrogen of NCPs in high yields. In contrast, in the case of NCPs bearing bulky meso-substituents (e.g., 3,5-di-tert-butylphenyl), new ruthenocenophane-like complex embedded on an N-confused calixphyrin was formed through multiple C-H bond activation of methyl groups of Cp* ligand. The mechanistic insight into the formation of the ruthenocenophane was derived from DFT calculations..
|13.||Kazuhisa Yamasumi, Keiichi Nishimura, Yutaka Hisamune, Yusuke Nagae, Tomoki Uchiyama, Kazutaka Kamitani, Tomoyasu Hirai, Maiko Nishibori, Shigeki Mori, Satoru Karasawa, Tatsuhisa Kato, Ko Furukawa, Masatoshi Ishida, Hiroyuki Furuta, Bis-Copper(II)/π-Radical Multi-Heterospin System with Non-innocent Doubly N-Confused Dioxohexaphyrin(184.108.40.206.1.0) Ligand, Chemistry - A European Journal, 10.1002/chem.201704321, 23, 61, 15322-15326, 2017.11, A contracted doubly N-confused dioxohexaphyrin(220.127.116.11.1.0) complex consisting of two paramagnetic copper metals and open-shell π-radical ligand was synthesized as a new multi-heterospin motif. X-ray spectroscopy supported the divalent character of the inner copper centers, and electron paramagnetic resonance and magnetometric studies suggested the presence of unpaired d electrons strongly antiferromagnetically coupled with π-radicals delocalized on the macrocycle. The 25 π non-innocent dioxohexaphyrin ligand allowed the facile interconversion between antiaromatic 24 π and aromatic 26 π species, respectively, upon redox reactions..|
|14.||Koki Mitsuno, Takafumi Yoshino, Iti Gupta, Shigeki Mori, Satoru Karasawa, Masatoshi Ishida, Hiroyuki Furuta, Doubly N-Confused Octaphyrin(18.104.22.168.22.214.171.124)
Isomerization, Bis-Metal Coordination, and Topological Chirality, Angewandte Chemie - International Edition, 10.1002/anie.201708253, 56, 45, 14252-14256, 2017.11, A novel octaphyrin analogue embedding two N-confused pyrrole units demonstrated unique prototropy-coupled isomerization between the Figure-of-eight and dumbbell conformers. Upon bis-metal coordination, fixation of fully π-conjugated Figure-of-eight structures was achieved as referred from the X-ray crystal structure. Chirogenesis of the helical enantiomers was proved by intense circular dichroism (CD) response in the near infrared (NIR) region..
|15.||Hideaki Matsuo, Motoki Toganoh, Masatoshi Ishida, Shigeki Mori, Hiroyuki Furuta, Stereoretentive Ligand Exchange Reactions of N-Fused Porphyrin Ruthenium(II) Complexes, Inorganic Chemistry, 10.1021/acs.inorgchem.7b01972, 56, 22, 13842-13851, 2017.11, The ligand exchange reactions of the ruthenium(II) complex of N-fused tetraphenylporphyrin, Ru(NFp)(CO)2Cl (2), with various anions were investigated. The chloride ligand of the isomers 2a-c was stereoretentively exchanged with bromide (Br-), iodide (I-), and acetate (AcO-) anions in toluene at 100 °C, structures of which were confirmed by 1H NMR as well as single crystal X-ray diffraction analysis. The silver (AgOAc, AgOTf) and boron (NaBPh4) reagents also afforded the corresponding stereoretentive products. On the other hand, the reaction with NaBH4 afforded the hydride complex Ru(NFp)(CO)2H (7) with low stereospecificity, showing a higher reactivity of 2c than other isomers. The ligand dissociation mechanism was proposed with the help of theoretical calculations on the plausible five-coordinated intermediates..|
|16.||Poornenth Pushpanandan, Yogesh Kumar Maurya, Toshihiro Omagari, Ryuji Hirosawa, Masatoshi Ishida, Shigeki Mori, Yuhsuke Yasutake, Susumu Fukatsu, John Mack, Tebello Nyokong, Hiroyuki Furuta, Singly and Doubly N-Confused Calixphyrin Organoplatinum(II) Complexes as Near-IR Triplet Sensitizers, Inorganic Chemistry, 10.1021/acs.inorgchem.7b02047, 56, 20, 12572-12580, 2017.10, Organoplatinum(II) complexes of calixphyrin analogues, singly N-confused calixphyrin (Pt-2), and doubly N-confused calixphyrin (Pt-3), were synthesized and characterized. The explicit structures of these organoplatinum(II) complexes were elucidated by single-crystal X-ray diffraction and spectroscopic studies. The introduction of N-confused pyrrole rings to the parent calixphyrin scaffold was found to have profound effects on the photophysical properties, such as the bathochromic shifts of both the absorption and phosphorescence maxima. The triplet excited state properties of these platinum complexes were analyzed by DFT calculations at the B3LYP level. The organoplatinum(II) complexes derived from the deformed scaffolds can serve as potent triplet sensitizers for singlet oxygen generation under aerobic conditions..|
|17.||Jiaying Yan, Yufeng Yang, Masatoshi Ishida, Shigeki Mori, Bao Zhang, Yaqing Feng, Hiroyuki Furuta, Organometallic Group 11 (CuIII, AgIII, AuIII) Complexes of a trans-Doubly N-Confused Porphyrin
An “Expanded Imidazole” Structural Motif, Chemistry - A European Journal, 10.1002/chem.201701958, 23, 47, 11375-11384, 2017.08, Complexation of group 11 metal cations with an α-bis(phenylthio)-substituted trans-doubly N-confused porphyrin (trans-N2CPSPh: 4) afforded a series of square-planar trivalent organometallic complexes (i.e., Cu-H4, Ag-H4, and Au-H4). The X-ray crystal structures of the complexes revealed highly planar core geometries along with the presence of peripheral amine and imine nitrogen sites of the pyrrolic moieties. NMR, UV/Vis absorption, and magnetic circular dichroism (MCD) spectroscopies suggested the 18 π-electron aromaticity of the complexes. The aromaticity was also fully analyzed by various theoretical methodologies such as nucleus-independent chemical shift (NICS) and anisotropic induced current density (ACID) calculations. The central metal affects the amphiprotic character of the complexes possessing both pyrrolic amino nitrogen and imino nitrogen atoms at the periphery, which was examined by the photometric titration with trifluoroacetic acid (TFA) and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), respectively. The inherent acidity of the complexes was followed in the order; Cu-H4>Au-H4>Ag-H4 and that of basicity was Au-H4>Ag-H4>Cu-H4. The complexes could be considered as an “expanded imidazole” structural motif..
|18.||Ryuichi Sakashita, Yasutaka Oka, Hisanori Akimaru, Praseetha E. Kesavan, Masatoshi Ishida, Motoki Toganoh, Tomoya Ishizuka, Shigeki Mori, Hiroyuki Furuta, Tautomerism-Induced Cis-Trans Isomerization of Pyridylethenyl N-Confused Porphyrin, Journal of Organic Chemistry, 10.1021/acs.joc.7b01770, 82, 16, 8686-8696, 2017.08, Pyridylethenyl-substituted N-confused porphyrins (NCPs) were synthesized, and their cis-trans isomerization was studied. Among four possible isomers, trans-3H and cis-2H types of structures, of which aromaticity and absorption/emission properties differ largely, were isolated. The cis-isomer was largely stabilized by the intramolecular hydrogen bonding between the pyrrolic-NH and the pyridinic-N in the vicinity. The thermal cis-trans isomerization proceeded even at 30 °C, which was significantly accelerated by the pyridine added to the system. The kinetic studies revealed that the isomerization reaction was second-order and the activation energy of the thermal isomerization from cis to trans isomer was ΔG0 ‡ cis→trans = 35.7 kcal/mol at 298 K, which is significantly smaller than that of Ni complex (42.3 kcal/mol). An intermolecular proton transfer induced cis-trans isomerization mechanism was proposed..|
|19.||Sudipta Das, Haamid R. Bhat, Naresh Balsukuri, Prakash C. Jha, Yutaka Hisamune, Masatoshi Ishida, Hiroyuki Furuta, Shigeki Mori, Iti Gupta, Donor-acceptor type A2B2 porphyrins
Synthesis, energy transfer, computational and electrochemical studies, Inorganic Chemistry Frontiers, 10.1039/c6qi00558f, 4, 4, 618-638, 2017.04, A series of donor-acceptor type trans-A2B2 porphyrins and their Zn(ii) and Pd(ii) complexes 5-13 have been synthesized and characterized by various spectroscopic techniques. The effect of the donor moieties (e.g., N-butylcarbazole, N-butylphenothiazine, and triphenylamine) on the spectroscopic properties of the porphyrins has been studied. The structural changes indeed affected the optical and electrochemical properties of these porphyrins. Higher energy shifts of the Soret bands were observed for porphyrins upon varying the donor moieties. The electrochemical studies of all the derivatives indicated increased interactions between the donor groups and the porphyrin core, which in turn are reflected in the anodic shifts in their reduction potentials. Both steady-state and time-resolved fluorescence studies revealed effective energy transfer (EET; up to 87%) from donor groups to the porphyrin core in the porphyrins, 5-10. The palladium(ii) porphyrin complexes, 11-13, showed characteristic phosphorescence in the near IR region. Density functional theory (DFT) studies support the presence of donor-acceptor interaction between the porphyrin core and the meso-substituents in the dyads. Density functional theory (DFT) and time dependent-density functional theory (TD-DFT) studies showed that in 5, 8 and 11, the transitions are of π → π∗ type; whereas in the other molecules viz.6, 7, 9, 10, 12 and 13 intramolecular charge transfer (ICT) is involved in all the respective highest intensity absorption transitions..
|20.||Yufeng Yang, Ryuichi Sakashita, Kazuhisa Yamasumi, Masatoshi Ishida, Teppei Yamada, Hiroyuki Furuta, Zirconium-based metal-organic frameworks with N-confused porphyrins
Synthesis, structures, and optical properties, Chemistry Letters, 10.1246/cl.170461, 46, 8, 1230-1232, 2017.04, Metalorganic frameworks (MOFs) composed of zirconium (Zr6) and N-confused porphyrins (NCPs) were synthesized. The cubic structures with ftw topology were determined by powder X-ray diffraction and microscopic analyses. These complexes represent high chemical stability toward various pH ranges and NIR absorption/emission derived from the NCP moieties..
|21.||Masatoshi Ishida, Taniyuki Furuyama, Jong Min Lim, Sangsu Lee, Zhan Zhang, Sudip K. Ghosh, Vincent M. Lynch, Chang Hee Lee, Nagao Kobayashi, Dongho Kim, Jonathan L. Sessler, Structural, Photophysical, and Magnetic Circular Dichroism Studies of Three Rigidified meso-Pentafluorophenyl-Substituted Hexaphyrin Analogues, Chemistry - A European Journal, 10.1002/chem.201700759, 23, 27, 6682-6692, 2017.01, Detailed electronic, structural, photophysical, and redox studies of a series of meso-pentafluorophenyl-substituted hexaphyrins, namely amethyrin (1), rosarin (2), and rubyrin (3), are described. In prior work, it was found that the electronic states of the antiaromatic hexapyrrolic macrocycle, rosarin 2, could be modified by exposure to several Brønsted acids (e.g., HCl, HBr and HI) to produce either one- and two-electron reduced species, or both. In an effort to gain further insights into the reactivity of hexaphyrins possessing different π-conjugation pathways, the β-dodecamethyl-substituted amethyrin 1 was prepared and its electronic structure was analyzed along with that of the o-phenylene-bridged rubyrin 3 and rosarin 2 The [4n] and [4n+2] π-conjugated formulations of 2 and 3, respectively, were inferred from steady-state, fs-transient absorption and two photon absorption measurements. Similar photophysical analyses lead to the conclusion that 1 is best considered as nonaromatic or weakly antiaromatic. Magnetic circular dichroism (MCD) spectroscopic analyses of hexaphyrins 1 and 3, as well as comparisons to 2, and theoretical perimeter MO diagram analyses provided support for the electronic assignments. In contrast to what was found for 2, simple protonation of 1 and 3 by halohydric acids did not induce an evident, redox-based change in the electronic structure of the macrocycle..|
|22.||Masatoshi Ishida, Hiroyuki Fujimoto, Tatsuki Morimoto, Shigeki Mori, Motoki Toganoh, Soji Shimizu, Hiroyuki Furuta, Supramolecular dimeric structures of pyrazole-containing meso-oxo carbaphlorin analogues, Supramolecular Chemistry, 10.1080/10610278.2016.1158408, 29, 1, 8-16, 2017.01, Synthesis and properties of a novel meso-oxo carbaphlorin analogue embedded with an N-free pyrazole moiety are described. The N-benzyl precursor was prepared by a [3 + 1]-MacDonald condensation of N-benzyl pyrazole dialdehyde and β-alkyl-substituted tripyrrane dicarboxylic acid and subsequent oxidation by ferric chloride. Upon deprotection of the benzyl group, the resulting N-free oxophlorin analogue formed a unique supramolecular dimer through mutual hydrogen bonding interactions between the pyrazole NH and meso-carbonyl group. The assembled behaviour was characterised by various spectroscopies, X-ray crystallographic analysis and vapour pressure osmometry. Under the similar reaction conditions, the condensation of meso-phenyl-substituted tripyrrane derivative afforded an unprecedented tetrapyrrolic macrocycle fused with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone unit at their α-pyrrolic positions. The X-ray crystallographic analysis of the macrocycle revealed a twisted core structure, and nonaromatic nature was elucidated..|
|23.||Masatoshi Ishida, Toshihiro Omagari, Ryuji Hirosawa, Keisuke Jono, Young Mo Sung, Yuhsuke Yasutake, Hidemitsu Uno, Motoki Toganoh, Hajime Nakanotani, Susumu Fukatsu, Dongho Kim, Hiroyuki Furuta, Boron Difluoride Complexes of Expanded N-Confused Calix[n]phyrins That Demonstrate Unique Luminescent and Lasing Properties, Angewandte Chemie - International Edition, 10.1002/anie.201606246, 55, 39, 12045-12049, 2016.09, Complexation of novel multiply N-confused expanded calix[n]phyrins with boron difluoride afforded a new class of cyclic BODIPY (boron-dipyrromethene) arrays. The structures of circularly arranged BODIPY subunits linked in an N-confused fashion give rise to such photophysical properties unique to the macrocycles as redshifted emission wavelengths along with apparent large Stokes shifts, long emission lifetimes, and solid-state lasing. The DFT calculations support the size-dependent excited-state dynamics of the macrocycles..|
|24.||Soumyajit Das, Tun Seng Herng, José L. Zafra, Paula Mayorga Burrezo, Masaaki Kitano, Masatoshi Ishida, Tullimilli Y. Gopalakrishna, Pan Hu, Atsuhiro Osuka, Juan Casado, Jun Ding, David Casanova, Jishan Wu, Fully Fused Quinoidal/Aromatic Carbazole Macrocycles with Poly-radical Characters, Journal of the American Chemical Society, 10.1021/jacs.6b04539, 138, 24, 7782-7790, 2016.06, While the chemistry of open-shell singlet diradicaloids has been successfully developed in recent years, the synthesis of π-conjugated systems with poly-radical characters (i.e., beyond diradical) in the singlet ground state has been mostly unsuccessful. In this study, we report the synthesis and isolation of two fully fused macrocycles containing four (4MC) and six (6MC) alternatingly arranged quinoidal/aromatic carbazole units. Ab initio electronic structure calculations and various experimental measurements indicate that both 4MC and 6MC have an open-shell singlet ground state with moderate tetraradical and hexaradical characters, respectively. Both compounds can be thermally populated to high-spin excited states, resulting in weak magnetization at room temperature. Our study represents the first demonstration of singlet π-conjugated molecules with poly-radical characters and also gives some insights into molecular magnetism in neutral π-conjugated polycyclic heteroarenes..|
|25.||Yogesh Kumar Maurya, Takahiro Ishikawa, Yasunori Kawabe, Masatoshi Ishida, Motoki Toganoh, Shigeki Mori, Yuhsuke Yasutake, Susumu Fukatsu, Hiroyuki Furuta, Near-Infrared Phosphorescent Iridium(III) Benzonorrole Complexes Possessing Pyridine-based Axial Ligands, Inorganic Chemistry, 10.1021/acs.inorgchem.6b00853, 55, 12, 6223-6230, 2016.06, Novel near-infrared phosphorescent iridium(III) complexes based on benzo-Annulated N-linked corrole analogue (termed as benzonorrole) were synthesized. The structures of the complexes revealed octahedral coordination geometries involving an organometallic iridium-carbon bond with two external axial ligands. Interestingly, the iridium(III) complex exhibits near-infrared phosphorescence at room temperature at wavelengths beyond 900 nm. The significant redshift of the emission, as compared to the corrole congener, is originated from the ligand-centered triplet character. The fine-Tuning of the photophysical properties of the complexes was achieved by introducing electron-donating and electron-withdrawing substituents on the axial pyridine ligands..|
|26.||Jung Ho Hong, Adil S. Aslam, Masatoshi Ishida, Shigeki Mori, Hiroyuki Furuta, Dong Gyu Cho, 2-(Naphthalen-1-yl)thiophene as a New Motif for Porphyrinoids
Meso-Fused Carbaporphyrin, Journal of the American Chemical Society, 10.1021/jacs.6b01063, 138, 15, 4992-4995, 2016.05, The first synthesis of meso-fused carbaporphyrin via a premodification method was accomplished by substituting two pyrrole moieties and one meso-carbon with 2-(naphthalen-1-yl)thiophene. The obtained global π-conjugation pathway of the macrocycle noticeably disturbs the 10π local aromaticity of naphthalene, and its aromatic nature was supported by NMR spectroscopy together with nucleus-independent chemical shift, anisotropy of the induced current density, and harmonic oscillator stabilization energy calculations. In addition, the meso-fused carbaporphyrin also allowed the formation of a square planar PdII complex..
|27.||Abhijit Mallick, Juwon Oh, Dongho Kim, Masatoshi Ishida, Hiroyuki Furuta, Harapriya Rath, Induced Correspondence of a Local π-Aromatic Sextet in Heteroannulenes
Synthesis and Characterization, Chemistry - A European Journal, 10.1002/chem.201600380, 22, 16, 5504-5508, 2016.04, Acid-catalyzed [3+3] condensation reactions of two hitherto unknown tripyrrane moieties with pentafluorobenzaldehyde has led to the formation of new generation heteroannulene (126.96.36.199) and mutant heteroannulene (188.8.131.52.1.1). Inclusion of local π-aromatic sextets, namely the N-methyl pyrrole rings through β,β-linkages and α,β-linkages, has led to the isolation of first ever heteroannulenes cross-conjugated at four points and two points respectively within the macrocycles..
|28.||Atanu Jana, Luke McKenzie, Ashley B. Wragg, Masatoshi Ishida, Jonathan P. Hill, Julia A. Weinstein, Elizabeth Baggaley, Michael D. Ward, Porphyrin/Platinum(II) C^N^N Acetylide Complexes
Synthesis, Photophysical Properties, and Singlet Oxygen Generation, Chemistry - A European Journal, 10.1002/chem.201504509, 22, 12, 4164-4174, 2016.03, A new class of substituted porphyrins has been developed in which a different number of cyclometalated PtII C^N^N acetylides and polyethylene glycol (PEG) chains are attached to the meso positions of the porphyrin core, which are meant for photophysical, electrochemical, and in vitro light-induced singlet oxygen (1O2) generation studies. All of these ZnII porphyrin-PtII C^N^N acetylide conjugates show moderate to high (ΦΔ=0.55 to 0.63) singlet oxygen generation efficiency. The complexes are soluble in organic solvents but, despite the PEG substituents, slowly aggregate in aqueous solvent systems. These conjugates also exhibit interesting photophysical properties, including near-complete photoinduced energy transfer (PEnT) through the rigid acetylenic bond(s) from the PtII C^N^N antenna units to the ZnII porphyrin core, which shows sensitized luminescence, as shown by quenching of PtII C^N^N-based luminescence. Electrochemical measurements show a set of redox processes that are approximately the sum of what is observed for the PtII C^N^N acetylide and ZnII porphyrin units. UV/Vis spectroscopic properties are supported by DFT calculations. The photophysical, electrochemical, and light-induced singlet oxygen (1O2) generation properties are reported for a series of ZnII porphyrin/PtII C^N^N acetylide compounds. One, two, or three cyclometallated PtII C^N^N luminophores are grafted onto a ZnII porphyrin core (see figure; R=PEG chain)..
|29.||Kai Zhang, Mathew Savage, Xin Li, Yu Jiang, Masatoshi Ishida, Koki Mitsuno, Satoru Karasawa, Tatsuhisa Kato, Weihua Zhu, Sihai Yang, Hiroyuki Furuta, Yongshu Xie, Rational syntheses of helical π-conjugated oligopyrrins with a bipyrrole linkage
Geometry control of bis-copper(II) coordination, Chemical Communications, 10.1039/c6cc00707d, 52, 29, 5148-5151, 2016.03, A rational and effective approach for synthesizing linear π-conjugated hexa-, hepta- and octapyrrins through the regioselective oxidative coupling of monoacylated tripyrrane and bilane is described. Depending upon the numbers of pyrrolic units, the geometry and properties of bis-copper(ii) complexes could be systematically modulated..
|30.||Yong Ni, Sangsu Lee, Minjung Son, Naoki Aratani, Masatoshi Ishida, Animesh Samanta, Hiroko Yamada, Young Tae Chang, Hiroyuki Furuta, Dongho Kim, Jishan Wu, A Diradical Approach towards BODIPY-Based Dyes with Intense Near-Infrared Absorption around λ=1100 nm, Angewandte Chemie - International Edition, 10.1002/anie.201511151, 55, 8, 2815-2819, 2016.02, A diradical approach to obtain stable organic dyes with intense absorption around λ=1100 nm is reported. The para- and meta-quinodimethane-bridged BODIPY dimers BD-1 and BD-2 were synthesized and were found to have a small amount of diradical character. These molecules exhibited very intense absorption at λ=1088 nm (ε=6.65×105 M-1 cm-1) and 1136 nm (ε=6.44×105 M-1 cm-1), respectively, together with large two-photon-absorption cross-sections. Structural isomerization induced little variation in their diradical character but distinctive differences in their physical properties. Moreover, the compounds showed a selective fluorescence turn-on response in the presence of the hydroxyl radical but not with other reactive oxygen species..|
|31.||Miao Li, Pingchun Wei, Masatoshi Ishida, Xin Li, Mathew Savage, Rui Guo, Zhongping Ou, Sihai Yang, Hiroyuki Furuta, Yongshu Xie, Macrocyclic Transformations from Norrole to Isonorrole and an N-Confused Corrole with a Fused Hexacyclic Ring System Triggered by a Pyrrole Substituent, Angewandte Chemie - International Edition, 10.1002/anie.201510879, 55, 9, 3063-3067, 2016.02, Three kinds of fused porphyrinoids, L2-L4, possessing different types of corrole-based frameworks were synthesized from a pyrrole-substituted corrole isomer (norrole L1). Oxidation of L1 afforded a unique N-Cmeso-fused pyrrolyl isonorrole L2, involving the fusion of an auxiliary pyrrolic NH moiety with a meso-sp3-hybridized carbon atom. Subsequently, L2 underwent macrocycle transformations to give singly and doubly N-CAr-fused N-confused corroles, L3 and L4, respectively. L3 and L4 contain fused [184.108.40.206]-tetra- and [220.127.116.11.6.5]-hexacyclic structures, respectively, prepared through lateral annulation. These skeletal transformation reactions from norrole to its isomer isonorrole and finally to N-confused corrole indicate that multiply fused porphyrinoids could be readily synthesized from pyrrole-appended confused porphyrinoids..|
|32.||Kai Zhang, Junda Zhang, Xin Li, Rui Guo, Ågren Hans, Zhongping Ou, Masatoshi Ishida, Hiroyuki Furuta, Yongshu Xie, Synthesis of a Neo-Confused Octaphyrin and the Formation of Its Mononuclear Complexes, Organic Letters, 10.1021/acs.orglett.5b02363, 17, 19, 4806-4809, 2015.10, Novel neo-confused octaphyrin(18.104.22.168.22.214.171.124) (1) was synthesized by oxidative ring closure of an octapyrrane bearing two terminal confused pyrroles. Crystal structures of its Zn(II) and Cu(II) complexes (2 and 3) show a figure-of-eight conformation with unique mononuclear coordination structures. Photophysical data and theoretical calculations suggest that the neo-confused octaphyrin 1 is a 34π electron conjugated species showing nonaromaticity. Coordination of copper and zinc ions results in the further narrowing of the HOMO-LUMO gaps..|
|33.||Masatoshi Ishida, Daesub Hwang, Zhan Zhang, Yung Ji Choi, Juwon Oh, Vincent M. Lynch, Dong Young Kim, Jonanthan L. Sessler, Dongho Kim, β-Functionalized Push-Pull Porphyrin Sensitizers in Dye-Sensitized Solar Cells
Effect of π-Conjugated Spacers, ChemSusChem, 10.1002/cssc.201500085, 8, 17, 2967-2977, 2015.09, A series of new β-functionalized push-pull-structured porphyrin dyes were synthesized so as to investigate the effect of the π-conjugated spacer on the performance of dye-sensitized solar cells (DSSCs). Suzuki- and Heck-type palladium-catalyzed coupling methodologies were used to obtain various β-functionalized porphyrins and β-benzoic acid (ZnPHn) and β-vinylbenzoic acid (ZnPVn) derivatives from β-borylated porphyrin precursors. Photophysical studies of the resulting porphyrins revealed a clear dependence on the nature of the β linker. In particular, it was found that a β-vinylene linkage perturbs the electronic structure of the porphyrin core; this is less true for a β-phenyl linkage. Theoretical analyses provided support for the intrinsic intramolecular charge-transfer character of the β-functionalized, push-pull porphyrins of this study. The extent of charge transfer depends on the nature of the β-conjugated linkage. The photovoltaic performances of the cells sensitized with β-phenylenevinylene ZnPVn exhibited higher power conversion efficiency values than those bearing β-phenyl linkages (ZnPHn). This was ascribed to differences in light-harvesting efficiency. Furthermore, compared to the use of a standard iodine-based electrolyte, the DSSC performance of cells made from the present porphyrins was improved by more than 1% upon using a cobalt(II/III)-based electrolyte. Under standard AM 1.5 illumination, the highest efficiency, 8.2%, was obtained by using cells made from the doubly β-butadiene-linked porphyrin..
|34.||Shunichi Fukuzumi, Kei Ohkubo, Masatoshi Ishida, Christian Preihs, Bo Chen, Weston Thatcher Borden, Dongho Kim, Jonathan L. Sessler, Formation of Ground State Triplet Diradicals from Annulated Rosarin Derivatives by Triprotonation, Journal of the American Chemical Society, 10.1021/jacs.5b05309, 137, 31, 9780-9783, 2015.08, Annulated rosarins, β,β′-bridged hexaphyrin(126.96.36.199.1.0) derivatives 1-3, are formally 24 π-electron antiaromatic species. At low temperature, rosarins 2 and 3 are readily triprotonated in the presence of trifluoroacetic acid in dichloromethane to produce ground state triplet diradicals, as inferred from electron paramagnetic resonance (EPR) spectral studies. From an analysis of the fine structure in the EPR spectrum of triprotonated rosarin H333+, a distance of 3.6 Å between the two unpaired electrons was estimated. The temperature dependence of the singlet-triplet equilibrium was determined by means of an EPR titration. Support for these experimental findings came from calculations carried out at the (U)B3LYP/6-31G∗ level, which served to predict a very low-lying triplet state for the triprotonated form of a simplified model system 1..|
|35.||Yutaka Hisamune, Keiichi Nishimura, Koji Isakari, Masatoshi Ishida, Shigeki Mori, Satoru Karasawa, Tatsuhisa Kato, Sangsu Lee, Dongho Kim, Hiroyuki Furuta, Stable π Radical from a Contracted Doubly N-Confused Hexaphyrin by Double Palladium Metalation, Angewandte Chemie - International Edition, 10.1002/anie.201502285, 54, 25, 7323-7327, 2015.06, A contracted doubly N-confused dioxohexaphyrin derivative served as a dinucleating metal ligand for unsymmetrical coordination. The complexation of two palladium(II) cations led to the formation of π-radical species that were persistent in atmospheric air in the presence of moisture. Effective delocalization of an unpaired electron over the hexaphyrin backbone could contribute to the distinct chemical stability..|
|36.||Ramababu Bolligarla, Masatoshi Ishida, Vijayendra S. Shetti, Kazuhisa Yamasumi, Hiroyuki Furuta, Chang Hee Lee, Intramolecular charge transfer character in tetrathiafulvalene-annulated porphyrinoids
effects of core modification and protonation, Physical Chemistry Chemical Physics, 10.1039/c4cp05385k, 17, 14, 8699-8705, 2015.04, The synthesis, characterization, and photophysical and electrochemical properties of a novel tetrathiafulvalene (TTF)-annulated core-modified porphyrin (1) and its expanded rubyrin analogue (2) are described. The sulfur core modifications in 1 and 2 allow a feasible intramolecular charge transfer from the TTF fragments to the central conjugated core as inferred from comparative spectroscopic and electrochemical measurements. DFT calculations also support the intramolecular charge transfer nature of 1 and 2 upon excitation. Further the electronic perturbation of the TTF-annulated porphyrins was achieved by protonation, giving rise to a drastic change in the optical features with an extremely low energy band in the NIR region. The pronounced electron accepting ability of the macrocyclic core of the dicationic species (H212+ and H222+) resulted in the thermally excited electron transfer occurring at room temperature as elucidated by EPR spectroscopy. This journal is.
|37.||Christina M. Davis, Kei Ohkubo, I. Ting Ho, Zhan Zhang, Masatoshi Ishida, Yuanyuan Fang, Vincent M. Lynch, Karl M. Kadish, Jonathan L. Sessler, Shunichi Fukuzumi, Near-infrared-induced electron transfer of an uranyl macrocyclic complex without energy transfer to dioxygen, Chemical Communications, 10.1039/c5cc00903k, 51, 31, 6757-6760, 2015.04, Photoexcitation of dichloromethane solutions of an uranyl macrocyclic complex with cyclofuranpyridine-pyrrole (1) at the near-infrared (NIR) band (1177 nm) in the presence of electron donors and acceptors resulted in NIR-induced electron transfer without producing singlet oxygen via energy transfer. This journal is.|
|38.||Wangdong Zeng, Sangsu Lee, Minjung Son, Masatoshi Ishida, Ko Furukawa, Pan Hu, Zhe Sun, Dongho Kim, Jishan Wu, Phenalenyl-fused porphyrins with different ground states, Chemical Science, 10.1039/c4sc03866e, 6, 4, 2427-2433, 2015.04, Materials based on biradicals/biradicaloids have potential applications for organic electronics, photonics and spintronics. In this work, we demonstrated that hybridization of porphyrin and polycyclic aromatic hydrocarbon could lead to a new type of stable biradicals/biradicaloids with tunable ground state and physical property. Mono- and bis-phenalenyl fused porphyrins 1 and 2 were synthesized via an intramolecular Friedel-Crafts alkylation-followed-by oxidative dehydrogenation strategy. Our detailed experimental and theoretical studies revealed that 1 has a closed-shell structure with a small biradical character (y = 0.06 by DFT calculation) in the ground state, while 2 exists as a persistent triplet biradical at room temperature under inert atmosphere. Compound 1 underwent hydrogen abstraction from solvent during the crystal growing process while compound 2 was easily oxidized in air to give two dioxo-porphyrin isomers 11a/11b, which can be correlated to their unique biradical character and spin distribution. The physical properties of 1 and 2, their dihydro/tetrahydro-precursors 7/10, and the dioxo-compounds 11a/11b were investigated and compared..|
|39.||Ryuichi Sakashita, Masatoshi Ishida, Hiroyuki Furuta, Spectroscopic and theoretical studies of acid-base behaviors of n-confused porphyrins
Effects of meso -aryl substituents, Journal of Physical Chemistry A, 10.1021/jp512229k, 119, 6, 1013-1022, 2015.02, The acid-base properties of a series of meso-aryl-substituted N-confused porphyrins (NCPs) were examined in aqueous sodium dodecyl sulfate (SDS) micellar solutions by both spectrophotometric methods and theoretical calculations. Reflecting the unsymmetrical structure of NCP having an outward-pointing pyrrolic nitrogen atom, the first and second protonations were distinguishable in the absorption and 1H NMR spectra, unlike for porphyrins, and the pK3 and pK4 values were determined discretely. The individual basicities of the NCPs were directly related to the inductive effect of para substituents on the meso-phenyl groups: A linear relationship between the pK3 (pK4) and Hammett σpara parameters was revealed. In the case of deprotonation, the structure of monoanionic NCP species was similarly characterized by the absorption and 1H NMR spectra. For the second deprotonation, the pK1 value was determined to be 11.39 for the NCP derivative with pentafluorophenyl groups. DFT calculations support the changes in electronic structures and aromaticity of the cationic and anionic species. It is demonstrated that NCPs are easily protonated and deprotonated compared to the corresponding regular congeners..
|40.||Atanu Jana, Habtom B. Gobeze, Masatoshi Ishida, Toshiyuki Mori, Katsuhiko Ariga, Jonathan P. Hill, Francis D'Souza, Breaking aggregation in a tetrathiafulvalene-fused zinc porphyrin by metal-ligand coordination to form a donor-acceptor hybrid for ultrafast charge separation and charge stabilization, Dalton Transactions, 10.1039/c4dt03157a, 44, 1, 359-367, 2015.01, A novel electron rich, tetrathiafulvalene fused zinc porphyrin, (TTF)4PZn, has been newly synthesized and characterized using spectral and electrochemical methods. In spite of the presence of eight t-butyl groups, (TTF)4PZn exhibited appreciable aggregation in solution. Scanning electron microscopic (SEM) imaging of the aggregates revealed their spherical particulate morphology. Attenuation of intermolecular aggregation was possible by metal-ligand coordination of a nitrogenous ligand. Further, using this strategy, a donor-acceptor hybrid was formed by coordinating imidazole functionalized fullerene as an electron acceptor. The occurrence of intrasupramolecular ultrafast photoinduced charge separation has been established using fluorescence and transient absorption spectroscopic techniques. The determined rate of charge separation, kCS, and rate of charge recombination, kCR were found to be 1.4 × 1011 s-1 and 2.5 × 106 s-1, respectively. The lower kCR values indicate charge stabilization in the assembled donor-acceptor conjugate via an electron transfer-hole transfer mechanism..|
|41.||Arghya Basu, Motoki Kitamura, Shigeki Mori, Masatoshi Ishida, Yongshu Xie, Hiroyuki Furuta, Near-infrared luminescent Sn(IV) complexes of N-confused tetraphenylporphyrin
Effect of axial anion coordination, Journal of Porphyrins and Phthalocyanines, 10.1142/S1088424615500212, 19, 1-3, 361-371, 2015.01, Novel tin(IV) halo complexes of an N-confused tetraphenylporphyrin with different axial ligands have been synthesized and characterized by various spectroscopic methods including X-ray crystallographic analysis. The molecular structures of the dichloro and dibromo derivatives possess perfect octahedral geometries, which are nearly comparable to the corresponding regular porphyrin complexes. In contrast, the iodide/triiodide complex obtained by a same reaction manner, demonstrated that the tin(IV) cation is slightly displaced towards axially coordinated iodide anion, giving rise to the different electronic structure due to the tautomeric form of N-confused porphyrin ligand. These structural differences reflected to the distinct photophysical and electrochemical properties. The Sn(IV) complexes are near IR luminescent, however the unsymmetrical axial coordination of iodide and triiodide anions in the tin(IV) N-confused porphyrin complex allows, in particular, the longer emission lifetimes and a smaller singlet-triplet energy gap, which were investigated by steady-state and time-resolved spectroscopies as well as theoretical calculations..
|42.||Jiaying Yan, Makoto Takakusaki, Yufeng Yang, Shigeki Mori, Bao Zhang, Yaqing Feng, Masatoshi Ishida, Hiroyuki Furuta, Doubly N-confused isophlorin
Synthesis, structure and copper coordination, Chemical Communications, 10.1039/c4cc06259k, 50, 93, 14593-14596, 2014.12, A novel doubly N-confused isophlorin (2) was prepared by the nucleophilic ring-opening reaction of N-confused, N-fused porphyrin (1) with benzenethiol. The structure, redox property and copper coordination ability of isophlorin 2 were investigated by various spectroscopic methods and theoretical calculations..
|43.||Dowoo Park, Seung Doo Jeong, Masatoshi Ishida, Chang Hee Lee, Stepwise π-extension of meso-alkylidenyl porphyrins through sequential 1,3-dipolar cycloaddition and redox reactions, Chemical Communications, 10.1039/c4cc04283b, 50, 66, 9277-9280, 2014.08, Several regioselectively π-extended, pyrrole fused porphyrinoids have been synthesized by the 1,3-dipolar cycloaddition of meso-alkylidene-(benzi) porphyrins. Pd(ii) complexes gave oxidation resistant, bis-pyrrole fused adducts. The repeated 1,3-dipolar cycloaddition followed by oxidation-reduction of pentaphyrin analogs afforded π-extended porphyrin analogs..|
|44.||Zhan Zhang, Won Young Cha, Neil J. Williams, Elise L. Rush, Masatoshi Ishida, Vincent M. Lynch, Dongho Kim, Jonathan L. Sessler, Cyclopyridinepyrrole
A dynamic, twisted macrocycle with no meso bridges, Journal of the American Chemical Society, 10.1021/ja503451m, 136, 21, 7591-7594, 2014.05, A large porphyrin analogue, cyclopyridinepyrrole, containing no meso bridging atoms, has been synthesized through Suzuki coupling. In its neutral form, this macrocycle exists as a mixture of two figure-eight conformers that undergo fast exchange in less polar solvents. Upon protonation, the dynamic twist can be transformed into species that adopt a ruffled planar structure or a figure-eight shape depending on the extent of protonation and counteranions. Conversion to a bisboron difluoride complex via deprotonation with NaH and treatment with BF3 acts to lock the macrocycle into a figure-eight conformation. The various forms of cyclopyridinepyrrole are characterized by distinct NMR, X-ray crystallographic, and spectroscopic features..
|45.||Masatoshi Ishida, Kensuke Nakahara, Ryuichi Sakashita, Tomoya Ishizuka, Motonori Watanabe, Hidemitsu Uno, Atsuhiro Osuka, Hiroyuki Furuta, N -confused phlorin
A stable dihydroporphyrin isomer containing a confused pyrrole ring, Journal of Porphyrins and Phthalocyanines, 10.1142/S1088424614500692, 18, 10-11, 909-918, 2014.05, Synthesis of bona fideN-confused phlorin derivatives through simple chemical reduction of N-confused porphyrin precursors using sodium borohydride, p-toluenesulfonyl hydrazide, etc. is described. Spectroscopic, X-ray diffraction analyses and DFT-assisted calculations of these species support the nonaromatic phlorin electronic structure..
|46.||Ken Ichi Sakaguchi, Takuya Kamimura, Hidemitsu Uno, Shigeki Mori, Shuwa Ozako, Hirofumi Nobukuni, Masatoshi Ishida, Fumito Tani, Phenothiazine-bridged cyclic porphyrin dimers as high-affinity hosts for fullerenes and linear array of C60 in self-assembled porphyrin nanotube, Journal of Organic Chemistry, 10.1021/jo500034f, 79, 7, 2980-2992, 2014.04, Free-bases and a nickel(II) complex of phenothiazine-bridged cyclic porphyrin dimers bearing self-assembling 4-pyridyl groups (M2-Ptz- CPDPy(OCn); M = H2 or Ni, OCn = OC6 or OC3) at opposite meso-positions have been prepared as host molecules for fullerenes. The free-base dimer (H4-Ptz- CPDPy(OC6)) includes fullerenes with remarkably high association constants such as 3.9 ± 0.7 × 106 M -1 for C60 and 7.4 ± 0.8 × 107 M-1 for C70 in toluene. This C60 affinity is the highest value ever among reported receptors composed of free-base porphyrins. The nickel dimer (Ni2-Ptz-CPDPy(OC 6)) also shows high affinities for C60 (1.3 ± 0.2 × 106 M-1) and C70 (over 107 M-1). In the crystal structure of the inclusion complex of C 60 within H4-Ptz-CPDpy(OC3), the C60 molecule is located just above the centers of the porphyrins. The two porphyrin planes are almost parallel to each other and the center-to-center distance (12.454 Å) is close to the optimal separation (∼12.5 Å) for C60 inclusion. The cyclic porphyrin dimer forms a nanotube through its self-assembly induced by C-H⋯N hydrogen bonds between porphyrin β-CH groups and pyridyl nitrogens as well as π-π interactions of the pyridyl groups. The C60 molecules are linearly arranged in the inner channel of this nanotube..|
|47.||Sudip Kumar Ghosh, Masatoshi Ishida, Jiazhu Li, Won Young Cha, Vincent M. Lynch, Dongho Kim, Jonathan L. Sessler, Synthesis and anion binding studies of o-phenylenevinylene-bridged tetrapyrrolic macrocycle as an expanded analogue of calixpyrrole, Chemical Communications, 10.1039/c4cc00686k, 50, 28, 3753-3756, 2014.04, An o-phenylenevinylene-bridged tetrapyrrolic macrocycle (2) was synthesized by means of a Horner-Wadsworth-Emmons reaction between benzylbisphosphonate and SEM-protected diformylpyrrole, followed by deprotection of the SEM groups. This conformationally flexible tetrapyrrole can be considered as an expanded calixpyrrole analogue, which acts as a receptor for the chloride and bromide anions in THF-d8, but undergoes deprotonation upon exposure to the fluoride anion. This journal is.|
|48.||I. Ting Ho, Zhan Zhang, Masatoshi Ishida, Vincent M. Lynch, Won Young Cha, Young Mo Sung, Dongho Kim, Jonathan L. Sessler, A hybrid macrocycle with a pyridine subunit displays aromatic character upon uranyl cation complexation, Journal of the American Chemical Society, 10.1021/ja412520g, 136, 11, 4281-4286, 2014.03, Reported here is a new hybrid macrocycle, cyclofuranpyridine pyrrole (1), that bears analogy to the previously reported mixed heterocycle system cyclopyridinepyrrole (2) and cyclopyrrole 3, an all-pyrrole 22 π-electron aromatic expanded porphyrin. The oxidized, dianionic form of 1, [1 - 4H]2-, has been characterized as its uranyl complex. In contrast to 2 and 3 and in spite of the presence of a 2,6-disubstituted pyridine subunit, the uranyl complex of [1 - 4H]2- displays solid-state structural and solution-phase spectroscopic features consistent with contributions to the overall electronic structure that involve a conjugated, (4n + 2) π-electron aromatic periphery..|
|49.||Nathan L. Bill, Masatoshi Ishida, Yuki Kawashima, Kei Ohkubo, Young Mo Sung, Vincent M. Lynch, Jong Min Lim, Dongho Kim, Jonathan L. Sessler, Shunichi Fukuzumi, Long-lived charge-separated states produced in supramolecular complexes between anionic and cationic porphyrins, Chemical Science, 10.1039/c4sc00803k, 5, 10, 3888-3896, 2014.01, A new supramolecular approach to generating a long-lived photoinduced charge separated state is described. It is predicated on the use of tetra-anionic sulfonated porphyrins (1-M4-: M = H2 and Zn) that form 1 : 2 supramolecular complexes with dicationic zinc(ii) porphyrinato tetrathiafulvalenes (2-Zn2+) via strong electrostatic interactions. The X-ray crystal structure of the complex 1-Zn4-/(2-Zn 2+)2 reveals a slipped sandwich-type interaction wherein 1-Zn4- is covered on both its top and bottom faces by two separate 2-Zn2+ porphyrins. Upon photoexcitation of the supramolecular ensemble, efficient photoinduced electron transfer from 1-M4- to the triplet excited state [2-Zn2+]* occurs to afford the triplet charge-separated (CS) states, as revealed by laser flash photolysis and EPR measurements. The CS state was found to decay via intramolecular back electron transfer within the supramolecular complex. This was evidenced by the observation that the CS state decay of this three-component system obeyed first-order kinetics and afforded the same long lifetimes irrespective of the initial concentrations of the CS state (e.g., 83 ms for the 1-H2 4-/(2-Zn2+)2 complex in benzonitrile at 298 K). Such an extremely long CS lifetime is thought to result from the spin-forbidden back electron transfer and the small electron coupling term, as inferred from temperature dependent studies of the CS lifetime. Decay of the CS state via intermolecular back electron transfer between two separate CS species of the type [1-M3-/(2-Zn+)(2-Zn2+)] is not observed, as revealed by the absence of second order decay kinetics. The absence of appreciable bimolecular decay processes and consequently the long-lived nature of the CS state is attributed to the central radical trianionic porphyrin (1-M3-) being protected from close-contact interactions with other species, precluding bimolecular decay processes. This supramolecular effect is thought to be the result of the radical species, 1-M3-, being sandwiched between two cationic porphyrins (2-Zn+ and 2-Zn 2+). These latter cationic entities cover the top and bottom of the anionic species thus providing both a physical and electrostatic barrier to intermolecular deactivation processes. These conclusions are supported by solution state binding studies, as well as solid state single crystal X-ray diffraction analyses..|
|50.||Zebing Zeng, Sangsu Lee, José L. Zafra, Masatoshi Ishida, Nina Bao, Richard D. Webster, Juan T. López Navarrete, Jun Ding, Juan Casado, Dongho Kim, Jishan Wu, Turning on the biradical state of tetracyano-perylene and quaterrylenequinodimethanes by incorporation of additional thiophene rings, Chemical Science, 10.1039/c4sc00659c, 5, 8, 3072-3080, 2014.01, Polycyclic hydrocarbon with a singlet biradical ground state has recently become a hot topic among various studies on π-conjugated systems and it is of importance to understand the fundamental structure-biradical character-physical properties relationship. In this work, we found that after incorporation of two additional thiophene rings into the closed-shell tetracyano-perylene (Per-CN) and quaterrylenequinodimethanes (QR-CN), the obtained new quinoidal compounds QDTP and QDTQ became a singlet biradical in the ground state due to the recovery of aromaticity of the thiophene rings in the biradical form and additional steric repulsion between the thiophene rings and the rylene unit. The ground state geometries and electronic structures of QDTP and QDTQ were systematically studied by variable-temperature nuclear magnetic resonance, electron spin resonance, superconducting quantum interference device measurements and FT Raman spectroscopy, assisted by density functional theory calculations. Both compounds were found to be a singlet biradical in the ground state with a small singlet-triplet energy gap and the biradical character was enlarged by elongation of the π-conjugation length. Strong one-photon absorption and large two-photon absorption cross-sections were observed for both compounds in the near-infrared region. Our studies demonstrated that a slight structural modification could significantly change the ground state and the electronic, optical and magnetic properties of a pro-aromatic π-conjugated system, and finally lead to new materials with unique properties..|
|51.||Wangdong Zeng, Masatoshi Ishida, Sangsu Lee, Young Mo Sung, Zebing Zeng, Yong Ni, Chunyan Chi, Dongho Kim, Jishan Wu, A p-quinodimethane-bridged porphyrin dimer, Chemistry - A European Journal, 10.1002/chem.201302023, 19, 49, 16814-16824, 2013.12, A p-quinodimethane (p-QDM)-bridged porphyrin dimer 1 has been prepared for the first time. An unexpected Michael addition reaction took place when we attempted to synthesize compound 1 by reaction of the cross-conjugated keto-linked porphyrin dimers 8 a and 8 b with alkynyl/aryl Grignard reagents. Alternatively, compound 1 could be successfully prepared by intramolecular Friedel-Crafts alkylation of the diol-linked porphyrin dimer 14 with concomitant oxidation in air. Compound 1 shows intense one-photon absorption (OPA, λmax=955 nm, ε=45400 M-1 cm-1) and a large two-photon absorption (TPA) cross-section (σ(2) max=2080 GM at 1800 nm) in the near-infrared (NIR) region due to its extended π-conjugation and quinoidal character. It also exhibits a short singlet excited-state lifetime of 25 ps. The cyclic voltammogram of 1 displays multiple redox waves with a small electrochemical energy gap of 0.86 eV. The ground-state geometry, electronic structure, and optical properties of 1 have been further studied by density functional theory (DFT) calculations and compared with those of the keto-linked dimer 8 b. This research has revealed that incorporation of a p-QDM unit into the porphyrin framework had a significant impact on its optical and electronic properties, leading to a novel NIR OPA and TPA chromophore..|
|52.||Atanu Jana, Masatoshi Ishida, Kevin Cho, Sudip Kumar Ghosh, Kyuju Kwak, Kei Ohkubo, Young Mo Sung, Christina M. Davis, Vincent M. Lynch, Dongil Lee, Shunichi Fukuzumi, Dongho Kim, Jonathan L. Sessler, Tetrathiafulvalene-annulated hexaphyrin(188.8.131.52.1.1)
A multi-electron donor system subject to conformational control, Chemical Communications, 10.1039/c3cc44934c, 49, 79, 8937-8939, 2013.10, Tetrathiafulvalenes (TTF)-annulated hexaphyrin affords an electron rich flexible π-conjugated system whose limiting conformations can be controlled through choice of solvents. The conformation-dependent intramolecular charge transfer character, as well as electron reserve capability of the hexakis-TTF annulated hexaphyrin, was analyzed..
|53.||Masatoshi Ishida, Deasub Hwang, Young Bean Koo, Jooyoung Sung, Dong Young Kim, Jonathan L. Sessler, Dongho Kim, β-(Ethynylbenzoic acid)-substituted push-pull porphyrins
DSSC dyes prepared by a direct palladium-catalyzed alkynylation reaction, Chemical Communications, 10.1039/c3cc44847a, 49, 80, 9164-9166, 2013.10, The palladium-catalyzed oxidative alkynylation of β-borylated porphyrins allows for concise preparation of push-pull structured ethynylbenzoic acid porphyrin derivatives. The resulting β-singly- and doubly-substituted porphyrin dyes are regarded as isomeric derivatives of the corresponding meso-substituted reference systems, and were found to give rise to nearly equal power conversion efficiencies when analyzed in DSSCs..
|54.||Masatoshi Ishida, Pyosang Kim, Jiyoung Choi, Juyoung Yoon, Dongho Kim, Jonathan L. Sessler, Benzimidazole-embedded N-fused aza-indacenes
Synthesis and deprotonation-assisted optical detection of carbon dioxide, Chemical Communications, 10.1039/c3cc43938k, 49, 62, 6950-6952, 2013.08, N-fused aza-indacene-based fluorophores 1 and 2 were prepared via a three-component condensation involving benzimidazole-carbinol, trifluoroacetic acid, and either pyrrole or indole, respectively. The N-fused aza-indacenes act as optical-based chemosensors for dissolved carbon dioxide gas following fluoride anion-mediated deprotonation..
|55.||Zebing Zeng, Sangsu Lee, José L. Zafra, Masatoshi Ishida, Xiaojian Zhu, Zhe Sun, Yong Ni, Richard D. Webster, Run Wei Li, Juan T. López Navarrete, Chunyan Chi, Jun Ding, Juan Casado, Dongho Kim, Jishan Wu, Tetracyanoquaterrylene and tetracyanohexarylenequinodimethanes with tunable ground states and strong near-infrared absorption, Angewandte Chemie - International Edition, 10.1002/anie.201305348, 52, 33, 8561-8565, 2013.08, Biradicaloids based on quinoidal rylenes! Soluble and stable tetracyanoquaterrylenequinodimethane (QR-CN) and tetracyanohexarylenequinodimethane (HR-CN) were synthesized. QR-CN has a closed-shell quinoidal structure in the ground state, whereas HR-CN has a singlet biradical ground state. Both compounds showed very strong one-photon and two-photon absorption in the NIR range..|
|56.||Nathan L. Bill, Masatoshi Ishida, Steffen Bähring, Jong Min Lim, Sangsu Lee, Christina M. Davis, Vincent M. Lynch, Kent A. Nielsen, Jan O. Jeppesen, Kei Ohkubo, Shunichi Fukuzumi, Dongho Kim, Jonathan L. Sessler, Porphyrins fused with strongly electron-donating 1,3-dithiol-2-ylidene moieties
Redox control by metal cation complexation and anion binding, Journal of the American Chemical Society, 10.1021/ja404830y, 135, 29, 10852-10862, 2013.07, A new class of redox-active free base and metalloporphyrins fused with the 1,3-dithiol-2-ylidene subunits present in tetrathiafulvalene, termed MTTFP (M = H2, Cu, Ni, Zn), have been prepared and characterized. The strong electron-donating properties of MTTFP were probed by electrochemical measurement and demonstrated that oxidation potentials can be tuned by metalation of the free base form, H2TTFP. X-ray crystal structures of H 2TTFP, ZnTTFP, and CuTTFP revealed that a severe saddle-shape distortion was observed with the dithiole rings bent out of the plane toward one another in the neutral form. In contrast, the structure of the two-electron oxidized species (CuTFFP2+) is planar, corresponding to a change from a nonaromatic to aromatic structure upon oxidation. A relatively large two-photon absorption (TPA) cross-section value of H2TTFP 2+ (1200 GM) was obtained for the free base compound, a value that is much higher than those typically seen for porphyrins (<100 GM). Augmented TPA values for the metal complexes were also seen. The strong electron-donating ability of ZnTTFP was further enhanced by binding of Cl- and Br - as revealed by thermal electron-transfer between ZnTTFP and Li +-encapsulated C60 (Li+@C60) in benzonitrile, which was "switched on" by the addition of either Cl- or Br- (as the tetrabutylammonium salts). The X-ray crystal structure of Cl--bound ZnTTFP was determined and provided support for the strong binding between the Cl- anion and the Zn 2+ cation present in ZnTTFP..
|57.||Zebing Zeng, Masatoshi Ishida, José L. Zafra, Xiaojian Zhu, Young Mo Sung, Nina Bao, Richard D. Webster, Byung Sun Lee, Run Wei Li, Wangdong Zeng, Yuan Li, Chunyan Chi, Juan T López Navarrete, Jun Ding, Juan Casado, Dongho Kim, Jishan Wu, Pushing extended p-quinodimethanes to the limit
Stable tetracyano-oligo(N-annulated perylene)quinodimethanes with tunable ground states, Journal of the American Chemical Society, 10.1021/ja402467y, 135, 16, 6363-6371, 2013.04, p-Quinodimethane (p-QDM) is a fundamental building block for the design of π-conjugated systems with low band gap and open-shell biradical character. However, synthesis of extended p-QDMs has usually suffered from their intrinsic high reactivity and poor solubility. In this work, benzannulation together with terminal cyano-substitution was demonstrated to be an efficient approach for the synthesis of a series of soluble and stable tetracyano-oligo(N-annulated perylene)quinodimethanes nPer-CN (n = 1-6), with the longest molecule having 12 para-linked benzenoid rings! The geometry and electronic structures of these oligomers were investigated by steady-state and transient absorption spectroscopy, nuclear magnetic resonance, electron spin resonance, superconducting quantum interference device, and FT Raman spectroscopy assisted by density functional theory calculations. They showed tunable ground states, varying from a closed-shell quinoidal structure for monomer, to a singlet biradical for dimer, trimer, and tetramer, and to a triplet biradical for pentamer and hexamer. Large two-photon absorption cross-section values were observed in the near-infrared range, which also exhibited a clear chain-length dependence..
|58.||Atanu Jana, Masatoshi Ishida, Kyuju Kwak, Young Mo Sung, Dong Sub Kim, Vincent M. Lynch, Dongil Lee, Dongho Kim, Jonathan L. Sessler, Comparative electrochemical and photophysical studies of tetrathiafulvalene-annulated porphyrins and their Znii complexes
The effect of metalation and structural variation, Chemistry - A European Journal, 10.1002/chem.201202727, 19, 1, 338-349, 2013.01, A series of tetrathiafulvalene (TTF)-annulated porphyrins, and their corresponding ZnII complexes, have been synthesized. Detailed electrochemical, photophysical, and theoretical studies reveal the effects of intramolecular charge-transfer transitions that originate from the TTF fragments to the macrocyclic core. The incremental synthetic addition of TTF moieties to the porphyrin core makes the species more susceptible to these charge-transfer (CT) effects as evidenced by spectroscopic studies. On the other hand, regular positive shifts in the reduction signals are seen in the square-wave voltammograms as the number of TTF subunits increases. Structural studies that involve the tetrakis-substituted TTF-porphyrin (both free-base and Zn II complex) reveal only modest deviations from planarity. The effect of TTF substitution is thus ascribed to electronic overlap between annulated TTF subunits rather than steric effects. The directly linked thiafulvalene subunits function as both π acceptors as well as σ donors. Whereas σ donation accounts for the substituent-dependent charge-transfer transitions, it is the π-acceptor nature of the appended tetrathiafulvalene groups that dominates the redox chemistry. Interactions between the subunits are also reflected in the square-wave voltammograms. In the case of the free-base derivatives that bear multiple TTF subunits, the neighboring TTF units, as well as the TTF+ generated through one-electron oxidation, can interact with each other; this gives rise to multiple signals in the square-wave voltammograms. On the other hand, after metalation, the electronic communication between the separate TTF moieties becomes restricted and they act as separate redox centers under conditions of oxidation. Thus only two signals, which correspond to TTF.+ and TTF2+, are observed. The reduction potentials are also seen to shift towards more negative values after metalation, a finding that is considered to reflect an increased HOMO-LUMO gap. To probe the excited-state dynamics and internal CT character, transient absorption spectral studies were performed. These analyses revealed that all the TTF-porphyrins of this study display relatively short excited-state lifetimes, which range from 1 to 20 ps. This reflects a very fast decay to the ground state and is consistent with the proposed intramolecular charge-transfer effects inferred from the ground-state studies. Complementary DFT calculations provide a mechanistic rationale for the electron flow within the TTF-porphyrins and support the proposed intramolecular charge-transfer interactions and π-acceptor effects..
|59.||Masatoshi Ishida, Soo Jin Kim, Christian Preihs, Kei Ohkubo, Jong Min Lim, Byung Sun Lee, Jung Su Park, Vincent M. Lynch, Vladimir V. Roznyatovskiy, Tridib Sarma, Pradeepta K. Panda, Chang Hee Lee, Shunichi Fukuzumi, Dongho Kim, Jonathan L. Sessler, Protonation-coupled redox reactions in planar antiaromatic meso-pentafluorophenyl-substituted o-phenylene-bridged annulated rosarins, Nature Chemistry, 10.1038/nchem.1501, 5, 1, 15-20, 2013.01, Proton-coupled electron transfer (PCET) processes are among the most important phenomena that control a variety of chemical and biological transformations. Although extensively studied in a variety of natural systems and discrete metal complexes, PCET mechanisms are less well codified in the case of purely organic compounds. Here we report that a planar β,β′- phenylene-bridged hexaphyrin (184.108.40.206.1.0), a 24 π-electron antiaromatic species termed rosarin, displays unique redox reactivity on protonation. Specifically, treatment with acid (for example, HI) yields a 26 π-electron aromatic triprotonated monocationic species that is produced spontaneously via an intermediate - but stable - 25 π-electron non-aromatic triprotonated monoradical dication. This latter species is also produced on treatment of the original 24 π-electron antiaromatic starting material with HCl or HBr. The stepwise nature of the proton-coupled reduction observed in the planar rosarin stands in marked contrast to that seen for non-annulated rosarins and other ostensibly antiaromatic expanded porphyrinoids..|
|60.||Masatoshi Ishida, Jong Min Lim, Byung Sun Lee, Fumito Tani, Jonathan L. Sessler, Dongho Kim, Yoshinori Naruta, Photophysical analysis of 1,10-phenanthroline-embedded porphyrin analogues and their magnesium(II) complexes, Chemistry - A European Journal, 10.1002/chem.201201793, 18, 45, 14329-14341, 2012.11, The synthesis, characterization, photophysical properties, and theoretical analysis of a series of tetraaza porphyrin analogues (H-Pn: n=1-4) containing a dipyrrin subunit and an embedded 1,10-phenanthroline subunit are described. The meso-phenyl-substituted derivative (H-P1) interacts with a Mg2+ salt (e.g., MgCl2, MgBr2, MgI2, Mg(ClO 4)2, and Mg(OAc)2) in MeCN solution, thereby giving rise to a cation-dependent red-shift in both the absorbance- and emission maxima. In this system, as well as in the other H-Pn porphyrin analogues used in this study, the four nitrogen atoms of the ligand interact with the bound magnesium cation to form Mg2+-dipyrrin-phenanthroline complexes of the general structure MgX-Pn (X=counteranion). Both single-crystal X-ray diffraction analysis of the corresponding zinc-chloride derivative (ZnCl-P1) and fluorescence spectroscopy of the Mg-adducts that are formed from various metal salts provide support for the conclusion that, in complexes such as MgCl-P1, a distorted square-pyramidal geometry persists about the metal cation wherein a chloride anion acts as an axial counteranion. Several analogues (H-Pn) that contain electron-donating and/or electron-withdrawing dipyrrin moieties were prepared in an effort to understand the structure-property relationships and the photophysical attributes of these Mg-dipyrrin complexes. Analysis of various MgX-Pn (X=anion) systems revealed significant substitution effects on their chemical, electrochemical, and photophysical properties, as well as on the Mg2+-cation affinities. The fluorescence properties of MgCl-Pn reflected the effect of donor-excited photoinduced electron transfer (d-PET) processes from the dipyrrin subunit (as a donor site) to the 1,10-phenanthroline acceptor subunit. The proposed d-PET process was analyzed by electron paramagnetic resonance (EPR) spectroscopy and by femtosecond transient absorption (TA) spectroscopy, as well as by theoretical DFT calculations. Taken together, these studies provide support for the suggestion that a radical species is produced as the result of an intramolecular charge-transfer process, following photoexcitation. These photophysical effects, combined with a mixed dipyrrin-phenanthroline structure that is capable of effective Mg 2+-cation complexation, lead us to suggest that porphyrin-inspired systems, such as H-Pn, have a role to play as magnesium-cation sensors. Anything can H-Pn: A new series of tetraaza porphyrin analogues (H-Pn: n=1-4) containing a dipyrrin subunit and an embedded 1,10-phenanthroline subunit have been developed as Mg2+-responsive fluorescent sensors. Upon complexation with Mg2+ ions, a structure-dependent emission enhancement is seen that is partially governed by donor-excited photoinduced electron-transfer (d-PET) events (see figure)..|
|61.||Zebing Zeng, Young Mo Sung, Nina Bao, Davin Tan, Richmond Lee, José L. Zafra, Byung Sun Lee, Masatoshi Ishida, Jun Ding, Juan T. López Navarrete, Yuan Li, Wangdong Zeng, Dongho Kim, Kuo Wei Huang, Richard D. Webster, Juan Casado, Jishan Wu, Stable tetrabenzo-Chichibabin's hydrocarbons
Tunable ground state and unusual transition between their closed-shell and open-shell resonance forms, Journal of the American Chemical Society, 10.1021/ja3050579, 134, 35, 14513-14525, 2012.09, Stable open-shell polycyclic aromatic hydrocarbons (PAHs) are of fundamental interest due to their unique electronic, optical, and magnetic properties and promising applications in materials sciences. Chichibabin's hydrocarbon as a classical open-shell PAH has been investigated for a long time. However, most of the studies are complicated by their inherent high reactivity. In this work, two new stable benzannulated Chichibabin's hydrocarbons 1-CS and 2-OS were prepared, and their electronic structure and geometry in the ground state were studied by various experiments (steady-state and transient absorption spectra, NMR, electron spin resonance (ESR), superconducting quantum interference device (SQUID), FT Raman, X-ray crystallographic etc.) and density function theory (DFT) calculations. 1-CS and 2-OS exhibited tunable ground states, with a closed-shell quinoidal structure for 1-CS and an open-shell biradical form for 2-OS. Their corresponding excited-state forms 1-OS and 2-CS were also chemically approached and showed different decay processes. The biradical 1-OS displayed an unusually slow decay to the ground state (1-CS) due to a large energy barrier (95 ± 2.5 kJ/mol) arising from severe steric hindrance during the transition from an orthogonal biradical form to a butterfly-like quinoidal form. The quick transition from the quinoidal 2-CS (excited state) to the orthogonal biradicaloid 2-OS (ground state) happened during the attempted synthesis of 2-CS. Compounds 1-CS and 2-OS can be oxidized into stable dications by FeCl 3 and/or concentrated H 2SO 4. The open-shell 2-OS also exhibited a large two-photon absorption (TPA) cross section (760 GM at 1200 nm)..
|62.||Zhan Zhang, Jong Min Lim, Masatoshi Ishida, Vladimir V. Roznyatovskiy, Vincent M. Lynch, Han Yuan Gong, Xiaoping Yang, Dongho Kim, Jonathan L. Sessler, Cyclo[m]pyridine[n]pyrroles
Hybrid macrocycles that display expanded π-conjugation upon protonation, Journal of the American Chemical Society, 10.1021/ja211985k, 134, 9, 4076-4079, 2012.03, Novel hybrid cyclo[m]pyridine[n]pyrroles have been synthesized using Suzuki coupling. Their NMR and optical spectroscopic features and solid state structural parameters provide support for the proposal that these species are best described as locally aromatic compounds devoid of long-range intersubunit conjugation. However, an extension of the π-conjugation in the macrocycles can be realized through protonation, as inferred from optical spectroscopic and X-ray diffraction-based structural studies..
|63.||Masatoshi Ishida, Sun Woo Park, Daesub Hwang, Young Bean Koo, Jonathan L. Sessler, Dong Young Kim, Dongho Kim, Donor-Substituted β-functionalized porphyrin dyes on hierarchically structured mesoporous TiO2 spheres. Highly efficient dye-sensitized solar cells, Journal of Physical Chemistry C, 10.1021/jp202307b, 115, 39, 19343-19354, 2011.10, Novel zinc porphyrin dyes for use in dye-sensitized solar cells (DSSCs) have been synthesized. These dyes are based on a molecular design that relies on donorπ-acceptor interactions, a concept implemented by introducing a bis(4-tert-butylphenyl)amino group at the meso position of the porphyrin opposite to what are 2-propenoic or 2,4-pentadienoic acid anchoring groups at the β-pyrrolic positions. Incorporating an electron-donating group (i.e., the diarylamine) on the porphyrin core serves as the considerable electronic coupling between the donor site and porphyrin core, and hence, the HOMO-LUMO energy gap is decreased. This change is reflected in the remarkable red shift and broadening of the absorption spectra relative to an unfunctionalized parent system. This substitution, in conjunction with functionalization with carboxylic acid moieties on the β-pyrrolic positions, also provides what is an effectively aligned donorπ-acceptor dipolar architecture. This, in turn, gives rise to advantageous charge-transfer properties, including what are significant improvements of the electron injection efficiency on titanium oxide (TiO2) compared to our previous models without a donor substituent. The DSSCs of this study were composed of zero-dimensional hierarchical structured TiO2 spheres with a diameter of 600-800 nm prepared from P-25 and anatase TiO2 nanoparticles, which functioned as the photoelectrodes. With the anatase TiO2-based DSSCs, the power conversion efficiencies (η) as well as the photocurrent action spectra were relatively enhanced, an effect ascribed to the characteristic mesoporous effect and associated electrophysical properties of the anatase TiO2 spheres. Among the dyes prepared in the context of the present study, the doubly functionalized carboxylic acid derivative, tda-2b-bd-Zn, gave rise to the highest power conversion. The η value was 7.47%, and the maximum incident photon-to-current efficiency was 77.3% at the Soret band. The overall η value of tda-2b-bd-Zn is comparable to the performance of typical ruthenium-based dyes, such as N3 (η = 7.68%), under the same conditions..|
|64.||Masatoshi Ishida, Jae Yoon Shin, Jong Min Lim, Byung Sun Lee, Min Chul Yoon, Taro Koide, Jonathan L. Sessler, Atsuhiro Osuka, Dongho Kim, Neutral radical and singlet biradical forms of meso-free, -keto, and -diketo hexaphyrins(220.127.116.11.1.1)
Effects on aromaticity and photophysical properties, Journal of the American Chemical Society, 10.1021/ja204626t, 133, 39, 15533-15544, 2011.10, We have investigated the electronic structures and photophysical properties of 5,10,20,25-tetrakis(pentafluorophenyl)-substituted hexaphyrin(18.104.22.168.1.1) (1) and its meso-keto (2) and meso-diketo derivatives (3) using various spectroscopic measurements. In conjunction with theoretical calculations, these analyses revealed fundamental structure-property relationships within this series, including unusual ground-state electronic structures with neutral, monoradical, and singlet biradical character. The meso-free species 1 is a representative 26 π-electron aromatic compound and shows characteristic spectroscopic features, including a sharp Soret band, well-defined Q-like bands, and a moderately long excited state lifetime (τ = 138 ps). In contrast, the meso-keto derivative 2 displays features characteristic of a neutral monoradical species at the ground state, including the presence of lower energy absorption bands in the NIR spectral region and a relatively short excited-state lifetime (13.9 ps). The meso-diketo 3 exhibits features similar to those of 2, specifically NIR absorptions and a short excited-state lifetime (9.7 ps). Compound 3 is thus assigned as being a ground-state singlet biradicaloid. Two photon absorption (TPA) measurements revealed comparatively large δ(2) values of 600 GM for 2 and 1600 GM for 3 with excitation at λex =1600 nm as compared to that observed for 1 (δ(2): 360 GM). The enhanced nonlinear optical properties of 2 and 3 are rationalized in terms of the open-shell electronic configuration allowing a large, field-induced fluctuation in the electron density (i.e., a large polarization). This interpretation is supported by theoretical evaluations of the static second hyperpolarizabilities (γ) and γ density analyses. Furthermore, nucleus-independent chemical shift (NICS) and harmonic oscillator model of aromaticity (HOMA) values and anisotropy of the induced current density (AICD) plots revealed a clear distinction in terms of the aromatic character of 1-3. Importantly, the open-shell radicaloid 2 and singlet biradicaloid 3 can be formally regarded as 27 π-electron nonaromatic and 26 π-electron aromatic species, respectively, constrained within a dominant 28 π-electron conjugated network. On the basis of the combined experimental and theoretical evidence, it is concluded that the meso-carbonyl groups of 2 and 3 play an important role in perturbing the macrocyclic π-conjugation of the parent hexaphyrin structure 1. In particular, they lead to the imposition of intrinsic radical and biradical character on the molecule as a whole and thus easy-to-discern modifications of the overall electronic effects..
|65.||Masatoshi Ishida, Satoru Karasawa, Hidemitsu Uno, Fumito Tani, Yoshinori Naruta, Protonation-induced formation of a stable singlet biradicaloid derived from a modified sapphyrin analogue, Angewandte Chemie - International Edition, 10.1002/anie.200907350, 49, 34, 5906-5909, 2010.08, (Figure Presented) Acid does the trick: A novel 1,10-phenanthroline- embedded sapphyrin analogue 1 (see scheme; R = COOEt, Ar = p-tolyl) bearing meso alkylidenyl double bonds has been synthesized. Interestingly, the protonated form of! ([1-3 H]3+) exhibits singlet biradicaloid character..|
|66.||Masatoshi Ishida, Yoshinori Naruta, Fumito Tani, Copper(ii) and nickel(ii) hexafluorophosphate complexes derived from a monoanionic porphyrin analogue
Solvato-and thermochromism of the ni complexes by spin-interconversion, Journal of the Chemical Society. Dalton Transactions, 10.1039/b921609j, 39, 10, 2651-2659, 2010.02, Phenanporphodimethene (1) is a porphyrin analogue which has a dipyrromethene unit replaced by a 1,10-phenanthroline moiety. This modification effectively coverts a dianionic porphyrin to a monoanionic porphyrin analogue with a porphyrin-like N4 coordination sphere. The ligand 1 forms copper and nickel hexafluorophosphate complexes, Cu-1 and Ni-1, respectively. X-ray crystallographic analysis of Cu-1 indicates that the Cu(ii) complex istetracoordinated by two pyrrolic nitrogen atoms and two phenanthrolic nitrogen atoms and includes a non-bondingPF6 counter-anion. The Ni-1 complex has similar geometry with a tetracoordinate square-planar structure in non-coordinating solvents such as CHCl3. In coordinating solvents such as MeOH, the coordinationstructure adopts an octahedral geometry. These results indicate that Ni-1 can be converted from a low-spin tohigh-spin configuration by the coordination of two solvent molecules to the nickel center. This solvatochromic conversion of Ni-1 is accompanied by thermochromic behavior resulting from the transformation between square planar and octahedral configurations in THF solution. The redox peak responsible for the nickel-centered redox reactionof Ni-1 is observed at −0.66 V (vs. Fc/Fc+) in CH2Cl2 solution, which indicates generation of low valent Ni(i) species. Thus, Ni-1 may be useful for future investigations as a novel structural model of the active site of cofactor F430 in methyl-coenzyme M reductase..
|67.||Masatoshi Ishida, Yoshinori Naruta, Fumito Tani, A Porphyrin-related macrocycle with an embedded 1,10-phenanthroline moiety
Fluorescent magnesium(ii) ion sensor, Angewandte Chemie - International Edition, 10.1002/anie.200904859, 49, 1, 91-94, 2010.01, (Figure Presented) Room for accommodation: A novel porphyrin-related macrocycle was constructed by replacement of the dipyrromethene unit with a 1,10-phenanthrollne moiety. This macrocycle is capable of complexation and fluorescent detection of Mg2+ with high selectivity over other physiologically relevant metal ions such as Na+, K+, and Ca2+. It functions well as a fluorescent sensor for Mg2+ even In HEPES buffered aqueous DMSO solution (pH 7.4)..