記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/chem.201603817

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1246/cl.130118

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/ja1027953

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/ja0767579

記述言語：英語   出版者・発行元：Journal of the American Chemical Society  

Light-induced polarization change has attracted significant attention due to its rapid response and nondestructive nature, positioning it as a promising candidate for next-generation molecular storage devices and energy harvesting. However, achieving substantial photoconversion that results in giant polarization changes via a hidden phase under near-infrared light irradiation remains a formidable challenge. In this study, we successfully synthesized a novel [CrCo] complex with an enantiopure ligand. Unlike previously reported Co valence tautomeric (VT) complexes, this complex exhibits light-induced VT (LIVT) with nearly complete photoconversion ratio upon irradiation with a 1340 nm laser. Additionally, the molecules pack in the P2<inf>1</inf> polar space group with an optimized arrangement, leading to a giant NIR-induced polarization change (1.71 μC cm^-2), which surpasses that of other nonferroelectric crystals. Importantly, electric measurements and single-crystal X-ray analysis after irradiation revealed that the induced polarization change is related to not only the directional electron transfer but also the displacement of anions, which render a distinct hidden metastable phase compared to the thermally approachable one. Moreover, pyroelectric measurement was first used to characterize relaxation kinetics after light irradiation.

DOI： 10.1021/jacs.5c02909

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出版者・発行元：Ccs Chemistry  

Macroscopic polarization switching achieved through directional electron transfer or spin crossover (SCO) has attracted considerable attention because of its potential applications in data storage devices, sensors, and energy converters. Here, by substituting the central metal and anion of a reported compound, [Fe(RR-cth)Co(SS-cth)(μ-dhbq)](AsF<inf>6</inf>)<inf>3</inf>, we obtained two dinuclear compounds that crystallize in the polar space group, P2<inf>1</inf>, [Fe(RR-cth)Ga(SS-cth)(μ-dhbq)] (X)<inf>3</inf> (X = AsF<inf>6</inf> and ClO<inf>4</inf>). Among them, complex 1(AsF<inf>6</inf>)<inf>3</inf> exhibited a two-step magnetic transition, including SCO behavior near 50 K and a gradual valence tautomerism (VT) behavior that occurred over a wide temperature range up to at least 250 K. The SCO behavior of complex 1(AsF<inf>6</inf>)<inf>3</inf> can be triggered by changes in temperature or the application of magnetic fields, leading to a polarization change of approximately 0.5 μC cm⁻². The transition entropy of 55.9 J K⁻¹ mol⁻¹ during the SCO process was obtained using the Clausius–Clapeyron equation. Contrarily, complex 1(ClO<inf>4</inf>)<inf>3</inf> only exhibited gradual VT behavior from a low temperature to room temperature. Single-crystal X-ray diffraction, variable-temperature infrared spectroscopy, and pyroelectric measurements confirmed the gradual VT process that occurs over a wide temperature range in both complexes. This study broadens the range of polarization switching molecular systems by replacing the central metal and anion, thereby facilitating the development of multifunctional molecular materials. (Figure Presented)

DOI： 10.31635/ccschem.025.202405245

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記述言語：英語   出版者・発行元：Accounts of Chemical Research  

Conspectus Compounds with polarization switching properties have a wide range of applications including ferroelectric memories, pyroelectric sensors, and piezoelectric actuators. Ferroelectric compounds are primarily focused owing to their ability to switch between two or more symmetry-equivalent polarization states. Besides ferroelectrics, numerous compounds with polar structures exhibit polarization changes in response to external stimuli such as temperature and pressure; however, such effects are normally too small to be considered in practical applications. Recently, we proposed a strategy to achieve polarization switching via electron transfer in polar crystals. The strategy consists of the synthesis of molecules exhibiting intramolecular electron transfer, combined with crystal engineering to align these molecules so that the molecular dipole moments are not canceled at the lattice level. Consequently, vectorial (or directional) electron transfer results in a significant polarization change comparable to what is found for conventional ferroelectrics. Chemically, since the functional motifs are molecules, operational parameters such as the working temperatures and polarization change can be fine-tuned by adjusting the energy levels of the electron donor and acceptor sites and their separation, which enables a more active control of polarization than ferroelectrics. From a physical perspective, the key difference between these systems and ferroelectrics is that the polarization switching occurs between symmetry inequivalent and nondegenerate polar states. As a direct result, they can be switched by various external stimuli other than electric fields, including temperature, magnetic fields, pressure, and light, owing to their different physical properties such as entropy, magnetization, volume, absorption, etc. Moreover, although thermally- and photoinduced ferroelectrics have been reported, they typically form domain structures with different polarization direction due to a symmetry-related degenerate ground state, causing macroscopic polarization to be largely canceled. In contrast, our compounds, which lack accessible symmetry equivalent states, can achieve a perfect polarization alignment without polarization domains upon temperature changes, photoirradiation, or magnetic field. In this Account, we discuss the synthesis of polarization switching compounds, i.e., dinuclear [CoGa], [FeCo], and [CrCo] complexes, via a chirality-assisted method. The thermally induced polarization switching behavior, or pyroelectric effect, is then explained, highlighting the large polarization change (2.9 μC cm^-2) in the [CoGa] complex, which is comparable to the widely used infrared (IR) detector material, triglycine sulfate (TGS). We then discuss the optical polarization memory effect and photoenergy conversion properties, which are a consequence of the photoinduced valence tautomeric behavior with a long-lived photoinduced metastable state. Furthermore, a magnetoelectric effect in the [FeCo] complex is described. The change in polarization is, to the best of our knowledge, the largest one induced by a magnetic field in molecular compounds to date. Notably, the polarization changes induced by temperature variation, photoirradiation, and magnetic field were detected as an electric current without the need of an electric field because polarization domains are not formed, unlike ferroelectric materials.

DOI： 10.1021/acs.accounts.5c00069

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出版者・発行元：Inorganic Chemistry Frontiers  

Materials that exhibit polarization switching induced by directional charge transfer under external stimuli have garnered significant interest due to their high switching rates and potential applications. Nonetheless, most of these crystals contain solvents or counter ions, and their effects during measurement or calculations are far from trivial. Therefore, synthesizing a solvent-free and neutral complex exhibiting polarization switching is highly desirable. Herein, we successfully observed directional charge transfer-induced electronic pyroelectricity in a solvent-free neutral cobalt complex, namely, Co(teeda)(3,6-dbq)<inf>2</inf> (teeda = N,N,N′,N′-tetraethylethane-1,2-diamine and 3,6-dbq = 3,6-di-tert-butylcatecholate or 3,6-di-tert-butylsemiquinonate). The charge transfer property was confirmed by magnetometry, infrared and UV-vis-NIR spectroscopy, and single-crystal X-ray diffraction (SCXRD) measurements. Furthermore, pyroelectric current was observed during the valence tautomerism (VT) process. Theoretical calculations demonstrated that polarization switching mainly originates from the charge transfer. These results indicate that Co(teeda)(3,6-dbq)<inf>2</inf> is a promising candidate for exploring new VT compounds that exhibit polarization switching.

DOI： 10.1039/d4qi01389a

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記述言語：英語   出版者・発行元：Dalton Transactions  

The design of molecular functional materials with multi-step magnetic transitions has attracted considerable attention. However, the development of such materials is still infrequent and challenging. Here, a cyano-bridged square Prussian blue complex that exhibits a thermally induced four-step electron transfer coupled spin transition (ETCST) is reported. The magnetic and spectroscopic analyses confirm this multi-step transition. Variable-temperature infrared spectrum suggested the electronic structures in each phase and a four-step transition model is proposed.

DOI： 10.1039/d4dt01581a

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出版者・発行元：Inorganic Chemistry Frontiers  

Macroscopic polarization switching via directional electron transfer has attracted great attention owing to its potential application in data storage devices, sensors, and energy conversion. However, the acquisition of the desired polar crystals is still a huge challenge to realize polarization switching. Here, a heterometallic [CrCo] complex with an enantiopure ligand was successfully obtained by a stepwise synthetic route, which effectively avoids the contamination caused by the lack of recognition of chiral ligands. Both compound 1·sol and its desolvated form, 1, are packed in the polar P2<inf>1</inf> space group. These forms exhibit valence tautomerism to varying degrees and interconversion to each other through single-crystal-to-single-crystal transformation, which enables solvent-dependent polarization-switching behavior. Moreover, both forms show trapping of the photoinduced electron-transferred states upon light irradiation. These findings highlight the effectiveness of using enantiopure ligands in constructing polar crystals with versatile polarization-switching behavior.

DOI： 10.1039/d4qi00836g

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Dalton Transactions  

Light-induced polarization switchable molecular materials have attracted attention for decades owing to their potential remote manipulation and ultrafast responsiveness. Here we report a valence tautomeric (VT) complex with an enantiopure chiral ligand. By a suitable choice of counter anions, a significant improvement in photoconversion has been demonstrated, leading to novel photo-responsive polarization switching materials.

DOI： 10.1039/d3dt03915c

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the American Chemical Society  

Light, a nondestructive and remotely controllable external stimulus, effectively triggers a variety of electron-transfer phenomena in metal complexes. One prime example includes using light in molecular cyanide-bridged [FeCo] bimetallic Prussian blue analogues, where it switches the system between the electron-transferred metastable state and the system’s ground state. If this process is coupled to a ferroelectric-type phase transition, the generation and disappearance of macroscopic polarization, entirely under light control, become possible. In this research, we successfully executed a nonpolar-to-polar phase transition in a trinuclear cyanide-bridged [Fe<inf>2</inf>Co] complex crystal via directional electron transfer. Intriguingly, by exposing the crystal to the wavelength of light─785 nm─without any electric field─we can drive this ferroelectric phase transition to completely depolarize the crystal, during which a measurable electric current response can be detected. These discoveries signify an important step toward the realization of fully light-controlled ferroelectric memory devices.

DOI： 10.1021/jacs.3c07545

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemical Science  

Ferroelectric, pyroelectric, and piezoelectric compounds whose electric polarization properties can be controlled by external stimuli such as electric field, temperature, and pressure have various applications, including ferroelectric memory materials, sensors, and thermal energy-conversion devices. Numerous polarization switching compounds, particularly molecular ferroelectrics and pyroelectrics, have been developed. In these materials, the polarization switching usually proceeds via ion displacement and reorientation of polar molecules, which are responsible for the change in ionic polarization and orientational polarization, respectively. Recently, the development of electronic ferroelectrics, in which the mechanism of polarization change is charge ordering and electron transfer, has attracted great attention. In this article, representative examples of electronic ferroelectrics are summarized, including (TMTTF)<inf>2</inf>X (TMTTF = tetramethyl-tetrathiafulvalene, X = anion), α-(BEDT-TTF)<inf>2</inf>I<inf>3</inf> (BEDT-TTF = bis(ethylenedithio)-tetrathiafulvalene), TTF-CA (TTF = tetrathiafulvalene, CA = p-chloranil), and [(n-C<inf>3</inf>H<inf>7</inf>)<inf>4</inf>N][Fe^IIIFe^II(dto)<inf>3</inf>] (dto = 1,2-dithiooxalate = C<inf>2</inf>O<inf>2</inf>S<inf>2</inf>). Furthermore, polarization switching materials using directional electron transfer in nonferroelectrics, the so-called electronic pyroelectrics, such as [(Cr(SS-cth))(Co(RR-cth))(μ-dhbq)](PF<inf>6</inf>)<inf>3</inf> (dhbq = deprotonated 2,5-dihydroxy-1,4-benzoquinone, cth = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraaza-cyclotetradecane), are introduced. Future prospects are also discussed, particularly the development of new properties in polarization switching through the manipulation of electronic polarization in electronic ferroelectrics and electronic pyroelectrics by taking advantage of the inherent properties of electrons.

DOI： 10.1039/d3sc03432a

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the American Chemical Society  

Molecular-based magnetoelectric materials are among the most promising materials for next-generation magnetoelectric memory devices. However, practical application of existing molecular systems has proven difficult largely because the polarization change is far lower than the practical threshold of the ME memory devices. Herein, we successfully obtained an [FeCo] dinuclear complex that exhibits a magnetic field-induced spin crossover process, resulting in a significant polarization change of 0.45 μC cm^-2. Mössbauer spectroscopy and theoretical calculations suggest that the asymmetric structural change, coupled with electron redistribution, leads to the observed polarization change. Our approach provides a new strategy toward rationally enhancing the polarization change.

DOI： 10.1021/jacs.3c02977

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemistry A European Journal  

The crystallization of a complex having electron transfer properties in a polar space group can induce the polarization switching of a crystal in a specific direction, which is attractive for the development of sensors, memory devices, and capacitors. Unfortunately, the probability of crystallization in a polar space group is usually low. Noticing that enantiopure compounds crystallize in Sohncke space groups, this paper reports a strategy for the molecular design of non-ferroelectric polarization switching crystals based on the use of intramolecular electron transfer and chirality. In addition, this paper describes the synthesis of a mononuclear valence tautomeric (VT) cobalt complex bearing an enantiopure ligand. The introduction of enantiomer enables the crystallization of the complex in the polar space group (P2<inf>1</inf>). The polarization of the crystals along the b-axis direction is not canceled out and the VT transition is accompanied by a change in the macroscopic polarization of the polar crystal. Polarization switching via electron transfer is realized at around room temperature.

DOI： 10.1002/chem.202202161

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Angewandte Chemie International Edition  

Using light as a local heat source to induce a temporary pyroelectric current is widely recognized as an effective way to control the polarization of crystalline materials. In contrast, harnessing light directly to modulate the polarization of a crystal via excitation of the electronic bands remains less explored. In this study, we report an Fe^II spin crossover crystal that exhibits photoinduced macroscopic polarization change upon excitation by green light. When the excited crystal relaxes to the ground state, the corresponding pyroelectric current can be detected. An analysis of the structures, magnetic properties and the Mössbauer and infrared spectra of the complex, supported by calculations, revealed that the polarization change is dictated by the directional relative movement of ions during the spin transition process. The spin transition and polarization change occur simultaneously in response to light stimulus, which demonstrates the enormous potential of polar spin crossover systems in the field of optoelectronic materials.

DOI： 10.1002/anie.202208771

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

Capability to control macroscopic molecular properties with external stimuli offers the possibility to exploit molecules as switching devices of various types. However, application of such molecular-level switching has often been limited by its speed and thus efficiency. Herein, we demonstrate ultrafast, photoinduced polarization switching in the crystal of a [CrCo] dinuclear complex by ultrafast pump–probe spectroscopy in the visible and mid-infrared regions. The photoinduced polarization switching was found to have a time constant of 280 fs, which makes the [CrCo] complex crystal the fastest polarization-switching material realized using the metastable state. Moreover, the pump–probe data in the visible region reveal the pronounced appearance of coherent nuclear wavepacket motion with a frequency as low as 22 cm⁻¹, which we attribute to a lattice vibrational mode. The pronounced non-Condon effect for its resonance Raman enhancement implies that this mode couples the relevant electronic states, thereby facilitating the ultrafast polarization switching.

DOI： 10.1002/anie.202004583

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Orbital angular momentum plays a vital role in various applications, especially magnetic and spintronic properties. Therefore, controlling orbital angular momentum is of paramount importance to both fundamental science and new technological applications. Many attempts have been made to modulate the ligand-field-induced quenching effects of orbital angular momentum to manipulate magnetic properties. However, to date, reported changes in the magnitude of orbital angular momentum are small in both molecular and solid-state magnetic materials. Moreover, no effective methods currently exist to modulate orbital angular momentum. Here we report a dynamic bond approach to realize a large change in orbital angular momentum. We have developed a Co(II) complex that exhibits coordination number switching between six and seven. This cooperative dynamic bond switching induces considerable modulation of the ligand field, thereby leading to substantial quenching and restoration of the orbital angular momentum. This switching mechanism is entirely different from those of spin-crossover and valence tautomeric compounds, which exhibit switching in spin multiplicity.

DOI： 10.1021/jacs.0c02257

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Some cyanide-bridged complexes are known for exhibiting slow magnetic relaxation behavior in a light-induced metastable state. Herein, an unexpected reverse effect is observed for the first time in the S= (Formula presented.) {Fe^II _LS-Co^III _LS-Fe^III _LS} (HS=high spin, LS=low spin) ground state of a novel V-shaped trinuclear cyanide-bridged {Fe₂Co} complex. In this complex, light-switchable iron-cobalt charge transfer with repeatable off/on switching of slow magnetic relaxation is discovered upon alternating laser irradiation at 785 and 560 nm. An important characteristic of the present compound is that the S= (Formula presented.) ground state exhibits slow magnetic relaxation before irradiation, whereas this is accelerated after irradiation. This is different from the typical behavior, where the light-induced metastable state exhibits slow magnetic relaxation.

DOI： 10.1002/chem.202000154

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The study of transition metal clusters exhibiting fast electron hopping or delocalization remains challenging, because intermetallic communications mediated through bridging ligands are normally weak. Herein, we report the synthesis of a nanosized complex, [Fe(Tp)(CN)₃]₈[Fe(H₂O)(DMSO)]₆ (abbreviated as [Fe₁₄], Tp⁻, hydrotris(pyrazolyl)borate; DMSO, dimethyl sulfoxide), which has a fluctuating valence due to two mobile d-electrons in its atomic layer shell. The rate of electron transfer of [Fe₁₄] complex demonstrates the Arrhenius-type temperature dependence in the nanosized spheric surface, wherein high-spin centers are ferromagnetically coupled, producing an S = 14 ground state. The electron-hopping rate at room temperature is faster than the time scale of Mössbauer measurements (<~10⁻⁸ s). Partial reduction of N-terminal high spin Fe^III sites and electron mediation ability of CN ligands lead to the observation of both an extensive electron transfer and magnetic coupling properties in a precisely atomic layered shell structure of a nanosized [Fe₁₄] complex.

DOI： 10.1038/s41467-019-13279-y

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1246/bcsj.20190219

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Intermediate amide complexes of NHC-ligated monovalent nickel in Buchwald-Hartwig amination of aryl halides were isolated and structurally characterized. The amide complexes reacted with aryl bromide to form a cross-coupling product. Lowerature observation of the oxidative addition product of the Ni(i) amide complex with aryl bromide indicated the presence of a Ni(iii) intermediate. The results showed that a well-defined mononuclear NHC-Ni(i) complex can act as a key intermediate in homogeneous catalysis.

DOI： 10.1039/c8cy02427h

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/anie.201606165

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/anie.201607886

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A series of three-coordinate monovalent nickel halide complexes bearing N-heterocyclic carbene (NHC) ligands, i.e., NiCl(IPr)(L) [L = pyridine, P(OPh)₃, bis(diphenylphosphino)butane (dppb), IPr = 1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene], NiX(IMes)(PPh₃) (X = Cl and Br, IMes = 1,3-bis(mesityl)imidazol-2-ylidene), were prepared. The complexes were identified using NMR spectroscopy, superconducting quantum interference device (SQUID), and X-ray crystallography. Additionally, ESR spectra of NiCl(IPr)(pyridine) were taken in toluene. These complexes had three-coordinate Y-shaped geometries in both the solid and solution states. The compounds containing IPr showed equilibrium between the monomeric and dimeric forms, with liberation of ligands. Addition of 1,2-bis(diphenylphosphino)ethane and 1,3-bis(diphenylphosphino)propane to the dinickel(I) IPr complex instead of dppb resulted in heterolytic cleavage to nickel(0) and nickel(II) species. Catalysis of Suzuki cross-coupling and Buchwald-Hartwig amination of aryl bromide using the complexes was investigated. The efficiencies in the amination of aryl bromide depended strongly on the additional donor ligands.

DOI： 10.1021/acs.organomet.6b00419

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

Heterometallic Prussian blue analogues are known to exhibit thermally induced charge transfer, resulting in switching of optical and magnetic properties. However, charge-transfer phase transitions have not been reported for the simplest FeFe cyanide-bridged systems. A mixed-valence Fe-II/Fe-III cyanide-bridged coordination polymer, {[Fe(Tp)(CN)(3)](2)Fe(bpe)5H(2)O}(n), which demonstrates a thermally induced charge-transfer phase transition, is described. As a result of the charge transfer during this phase transition, the high-spin state of the whole system does not change to a low-spin state. This result is in contrast to FeCo cyanide-bridged systems that exhibit charge-transfer-induced spin transitions.
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DOI： 10.1002/anie.201601526

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

Flexible porous materials generally switch their structures in response to guest removal or incorporation. However, the design of porous materials with empty shape-switchable pores remains a formidable challenge. Here, we demonstrate that the structural transition between an empty orthorhombic phase and an empty tetragonal phase in a flexible porous dodecatuple intercatenated supramolecular organic framework can be controlled cooperatively through guest incorporation and thermal treatment, thus inducing empty shape-memory nanopores. Moreover, the empty orthorhombic phase was observed to exhibit superior thermoelasticity, and the molecular-scale structural mobility could be transmitted to a macroscopic crystal shape change. The driving force of the shape-memory behaviour was elucidated in terms of potential energy. These two interconvertible empty phases with different pore shapes, that is, the orthorhombic phase with rectangular pores and the tetragonal phase with square pores, completely reject or weakly adsorb N-2 at 77 K, respectively.

DOI： 10.1038/ncomms11564

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

Dinuclear iron carbonyl complex 2, which contains an elongated unsupported Fe-Fe bond, was synthesized by the reaction between Fe-2(CO)(9) and phosphinyl radical 1. Thermal Fe-Fe bond homolysis led to the generation of a four-coordinate carbonyl-based iron-centered radical, 3, which is stabilized by pi-donation. Complex 3 exhibited high reactivity toward organic radicals to form diamagnetic five-coordinate Fe(II) complexes.

DOI： 10.1039/c5sc02601f

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The Fe^III anionic complex exhibiting cooperative spin transition with a wide thermal hysteresis near room temperature, K[Fe(5-Brthsa)₂] (5-Brthsa-H₂=5-bromosalicylaldehyde thiosemicarbazone), is reported. The hysteresis shows a one-step transition in heating mode and a two-step transition in cooling mode. X-ray structure analysis shows the coexistence of hydrogen bond and cation-π interactions, along with metal coordination bonds, to give 2D coordination polymer structure.

DOI： 10.1002/chem.201680262

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

The anionic Fe-III complex exhibiting cooperative spin transition with a wide thermal hysteresis near room temperature, K[Fe(5-Brthsa)(2)] (5-Brthsa-H-2=5-bromosalicylaldehyde thiosemicarbazone), is reported. The hysteresis (Delta=69 K in the first cycle) shows a one-step transition in heating mode and a two-step transition in cooling mode. X-ray structure analysis showed that the coexistence of hydrogen bond and cation-pi interactions, as well as alkali metal coordination bonds, to give 2D coordination polymer structure. This result is contrary to previous reports of broad thermal hysteresis induced by coordination bonds of FeII spin crossover coordination polymers (with 1D/3D structures), and by strong intermolecular interactions in the molecular packing through pi-pi stacking or hydrogen-bond networks. As a consequence, the importance, or the very good suitability of alkali metal-based coordination bonds and cation-pi interactions for communicating cooperative interactions in spin-crossover (SCO) compounds must be reconsidered.

DOI： 10.1002/chem.201503392

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

Harnessing molecular motion to reversibly control macroscopic properties, such as shape and size, is a fascinating and challenging subject in materials science. Here we design a crystalline cobalt(II) complex with an n-butyl group on its ligands, which exhibits a reversible crystal deformation at a structural phase transition temperature. In the low-temperature phase, the molecular motion of the n-butyl group freezes. On heating, the n-butyl group rotates ca. 100 degrees around the C-C bond resulting in 6-7% expansion of the crystal size along the molecular packing direction. Importantly, crystal deformation is repeatedly observed without breaking the single-crystal state even though the shape change is considerable. Detailed structural analysis allows us to elucidate the underlying mechanism of this deformation. This work may mark a step towards converting the alkyl rotation to the macroscopic deformation in crystalline solids

DOI： 10.1038/ncomms9810

記述言語：英語  

DOI： 10.1038/ncomms6955

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Many molecular machines with controllable molecular-scale motors have been developed. However, transmitting molecular movement to the macroscopic scale remains a formidable challenge. Here we report a single crystal of a Ni complex whose shape changes abruptly and reversibly in response to thermal changes at around room temperature. Variableerature single-crystal X-ray diffraction studies show that the crystalline shape change is induced by an unusual 90° rotation of uniaxially aligned oxalate molecules. The oxalate dianions behave as molecular-scale rotors, with their movement propagated through the entire crystalline material via intermolecular hydrogen bonding. Consequently, the subnanometre-scale changes in the oxalate molecules are instantly amplified to a micrometre-scale contraction or expansion of the crystal, accompanied by a thermal hysteresis loop. The shape change in the crystal was clearly detected under an optical microscope. The large directional deformation and prompt response suggest a role for this material in microscale or nanoscale thermal actuators.

DOI： 10.1038/nchem.2092

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Both spin-crossover complexes and molecular nanomagnets display bistable magnetic states, potentially behaving as elementary binary units for information storage. It is a challenge to introduce spin-crossover units into molecular nanomagnets to switch the bistable state of the nanomagnets through external stimuli-tuned spin crossover. Here we report an iron(II) spin-crossover unit and paramagnetic iron(III) ions that are incorporated into a well-isolated double-zigzag chain. The chain exhibits thermally induced reversible spin-crossover and light-induced excited spin-state trapping at the iron(II) sites. Single-chain magnet behaviour is actuated accompanying the synergy between light-induced excited spin-state trapping at the iron(II) sites and ferromagnetic interactions between the photoinduced high-spin iron(II) and low-spin iron(III) ions in the chain. The result provides a strategy to switch the bistable state of molecular nanomagnets using external stimuli such as light and heat, with the potential to erase and write information at a molecular level.

DOI： 10.1038/ncomms3826

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The mononuclear ferric compound Fe(H-5-Cl-thsa-Me)(5-Cl-thsa-Me) ·H₂O (1) was synthesized and characterized using powder/single-crystal X-ray diffraction, Mössbauer spectroscopy, differential scanning calorimetry (DSC), and magnetic susceptibility measurements. This photo-responsive compound shows reversible, two-step spin-crossover behaviour. Moreover, dielectric anomalies were observed during the spin transitions, demonstrating the multifunctional properties of compound 1.

DOI： 10.1039/c3dt51554k

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/chem.201302272

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/ejic.201300531

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Light-induced valence tautomerism (LIVT) and the relaxation process of a mononuclear complex, [Co(phen)(3,5-DTBSQ)(3,5-DTBCat)] (1) (phen = 1,10-phenanthroline, 3,5-DTBSQ = 3,5-di-tert-butyl-semiquinone, 3,5-DTBCat = 3,5-di-tert-butyl-catechol) were investigated by monitoring the ESR signal of the semiquinonate radical both in powder sample and in the sample diluted in butyronitrile or benzene glass matrix. LIVT phenomena were observed in all samples. The ESR signal decay and the relaxation in the glass matrixes were well analyzed by double exponential fitting, indicating the possibility of two-step mechanism in the LIVT process.

DOI： 10.1016/j.poly.2013.03.039

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/ejic.201201069

記述言語：英語  

This chapter introduces compounds synthesized to develop new spin-crossover conductors, in which spin-crossover phenomena and conductivity coexist or interact. It also introduces spin-crossover magnets, in which spin-crossover phenomena and magnetic interaction coexist or interact. A possible route for the synthesis of multifunctional materials exhibiting spin-crossover and conductivity is the preparation of double salts, by combining spin-crossover cations/anions and conducting molecular anions/cations through electrostatic interactions. Another route is the preparation of a spin-crossover complex with a potentially conducting ligand. The preparation of spin-crossover conductors in which conductivity and light-induced excited spin state trapping (LIESST) exhibit synergistic effects is desired. Multifunctional materials exhibiting both spin-crossover and magnetic interaction are achieved by combining a spin-crossover cation/anion with an anionic/cationic magnetic framework. Another route is the incorporation of spin-crossover sites into magnetic frameworks. This edition first published 2013

DOI： 10.1002/9781118519301.ch11

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1039/c2dt31168b

記述言語：英語   掲載種別：研究論文（学術雑誌）  

N,N-Dipyridilaminoxyl, NOpy ₂, having a stable aminoxyl, was prepared as a new magnetic coupler for heterospin systems. Solutions of NOpy ₂ were mixed with those of bis{1,1,1,5,5,5, hexafluoro-4- (phenylimino)-2-pentanonate}cobalt derivatives, Co(hfpip-X) ₂, at a 1:1 ratio to afford the polymeric cobalt(II) complexes, [Co(hfpip-X) ₂(NOpy ₂)] _n; X = H (1), F (2), F ₃ (3), F ₅ (4), Cl (5), Cl ₃ (6), Br (7), and I (8) as single crystals. In all complexes, the local structures of the cobalt-complex units were compressed octahedra and the pyridine ligands in NOpy ₂ units coordinated to the cobalt ions in trans configuration to form linear chains for 1-4 and in cis configuration to form helical chains for 5-8. In the chains, the aminoxyl in NOpy ₂ ferromagnetically interacted with the cobalt ions to produce the ferromagnetic chains with J _intra/k _B = 9-14 K. In the magnetic susceptibility experiments of aligned sample of 6, the magnetic easy axis was determined to be the a* axis, which was the direction perpendicular to the b axis of the chain axis. The resulting chains, all except 4, interacted antiferromagnetically among each other, and especially in 1, 5, 7, and 8, the magnetic behaviors characteristic to canted two-dimensional (2D) antiferromagnets with T _c = 5.6, 4.0, 4.0, and 6.2 K, respectively, were observed. All complexes showed slow magnetic relaxations affected by the interchain antiferromagnetic interaction. The effective activation barriers, Δ _eff/k _B, for the reorientation of the magnetism for all complexes except 4 were estimated to be 25-39 K in the presence of a direct current (dc) field.

DOI： 10.1021/ic202397m

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Charge-transfer-induced spin transition occurs cooperatively and reversibly in the isolated FeIII2CoII chains of {[Fe(pzTp)(CN)3]2Co(4-styrylpyridine)2}⋅2 H2O ⋅2 CH3OH (1). When 1 is irradiated with 532 nm light, it shows single-chain magnetic behavior with no antiferromagnetic ordering after irradiation (see picture; C gray, N blue, B yellow; LS=low spin, HS=high spin).

DOI： 10.1002/anie.201105987

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A linear cyanido-bridged Fe2Co compound (see picture) exhibits a reversible, thermally induced cooperative charge transfer transition accompanying spin transition and polar–nonpolar transformation in the trinuclear cluster. The change in magnetic properties and polarity could also be induced by irradiation with light.

DOI： 10.1002/anie.201201305

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Light-induced valence tautomerism (LIVT) of a dinuclear complex, [{Co(dpqa)}₂(dhbq)](PF₆)₃ (1), was investigated by ESR analysis of dhbq^3-. LIVT phenomena were observed in the sample diluted in the glass matrix as well as that in powder form. The signal decay and the relaxation were analyzed by double exponential fitting; the results suggest a two-step mechanism. Quantum mechanical tunneling was clearly observed in the glass matrix. Light-induced valence tautomerism (LIVT) of a dinuclear complex, [{Co(dpqa)}₂(dhbq)](PF₆)₃ (1), was investigated by ESR analysis of dhbq^3-. LIVT phenomena were observed in the glass matrix as well as in the powder sample. The signal decay and the relaxation, analyzed by double exponential fitting, suggest a two-step mechanism. Quantum tunneling phenomena were clearly observed in the glass matrix.

DOI： 10.1002/ejic.201100467

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A novel two-dimensional mixed-metal coordination polymer, [Fe(bipe)(Au(CN)₂)₂·MeOH], composed of polyrotaxane with Fe₂(bipe)₂ loops and rigid [Au(CN)₂] ^- rods, forms a 2D → 2D parallel interpenetrating structure. The two networks are clipped by gold clusters via aurophilic interaction.

DOI： 10.1039/c0ce00376j

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/anie.201002881

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/ja908670u

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/ja901539y

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/ja808448j

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Three cobalt(II) complexes, [Co(X) ₂(4NOpy) ₄] (X = NCO ^-, NCS ^-, and Br ^-; 4NOpy = 4-(N-tert-butylaminoxyl)-pyridine) were prepared, and their molecular structures were characterized by X-ray structure analysis. The molecular geometry of [Co(X) ₂(4NOpy) ₄] (X = NCO ^- and NCS ^-) is a compressed octahedron, in which the counter ions occupy the apical positions with short bond distances of 2.064-2.098 Å. In the crystalline state, from plots of χ _mol vs T and χ′ _mol vs T, [Co(NCO) ₂(4NOpy) ₄] and [Co(NCS) ₂(4NOpy) ₄] are antiferromagnets with T _N = 4.5 and 15 K, respectively. In frozen solution, on the other hand, both complexes and [Co(Br) ₂(4NOpy) ₄] functioned as single-molecule magnets. The χ″ _mol vs T plot for [Co(Br) ₂(4NOpy) ₄] gave a effective activation barrier (U _eff) of 20 K for the reorientation of the spin. From the field dependence of magnetization at various temperatures below 5 K for [Co(X) ₂(4NOpy) ₄] (X = NCO ^-, NCS ^-, and Br ^-) the values of the zero-field splitting parameters, D/k _B, were estimated to be -14, -9.7, and -4.5 K with S = 5/2, respectively. Theoretical studies based on the ligand-field theory model for [Co(NCO) ₂(4NOpy) ₄] gave an exchange coupling parameter, J/k _B, of 29 K and a thermodynamic activation barrier, U, of 60 K.

DOI： 10.1246/bcsj.79.1372

開催年月日： 2021年3月

記述言語：英語   会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：Online   国名：日本国  

開催年月日： 2020年1月 - 2020年2月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Nagoya University   国名：日本国  

Dinuclear valence tautomeric(VT) complexes [(M1(cth))(M2(cth)) (-dhbq)](PF6)3 [M1 = M2 = Co; 1[1], M1 = Cr, M2 = Co; 2[2], cth = hexamethyl tetraazacyclotetradecane, dhbq = dihydroxybenzoquinone] are very promising candidates for materials exhibiting electronic ferroelectricity and pyroelectricity. The VT complexes have stimuli-responsible intramolecular electron transfers, which result switching in electronic dipoles in a molecules. The pyroelectricities of a centrosymmetric crystal of 1 and a polar crystal of 2 were investigated by temperature sweep method. Both 1 and 2 exhibited VT behaviors with T1/2 = 245 K and 360 K, respectively, in magnetic measurements. However, only 2 showed thermally-induce electric current around VT transition temperature. The contrasting results between 1 and 2 obtained in pyroelectricities are well consistent with crystalline symmetries.

開催年月日： 2019年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：Hokkaido University   国名：日本国  

本講演では，外場応答性原子価互変異性(VT)錯体分子から得られた電子焦電特性を示す結晶についてその構築戦略と具体的な測定結果について発表する．

開催年月日： 2019年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：名古屋大学　東山キャンパス   国名：日本国  

Our chirality-assisted co-crystallization resulted pseudo-racemic solid solution of cobalt and zinc complexes as crystals. Onlythe cobalt complexes in heterometallic co-crystals, CoZn, exhibited a valence tautomerism (VT): intramolecular charge transfer. DFTcalculations revealed that complex 3 shows polarization switching behaviors due to the molecular packing with pseudo-inversion centerfor CoZn crystals.

開催年月日： 2019年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：名古屋大学　東山キャンパス   国名：日本国  

Dinuclear valence tautomeric(VT) complexes [(M1(cth))(M2(cth)) (-dhbq)](PF6)3 [M1 = M2 = Co; 1[1], M1 = Cr, M2 = Co; 2[2], M1 = Fe, M2 = Co; 3, cth = hexamethyl　tetraazacyclotetradecane, dhbq = dihydroxybenzoquinone] are very promising candidates for materials exhibiting electronic ferroelectricity and pyroelectricity. The VT complexes have stimuli-responsible intramolecular electron transfers, which result switching in electronic dipoles in a molecules. The pyroelectricities of centrosymmetric crystal of 1 and polar crystals of 2 and 3 were investigated by temperature sweep method. Both 1 and 2 exhibited VT behaviors with T1/2 = 245 K and 360 K, respectively, in magnetic measurements. However, only 2 showed thermally-induce electric current around VT transition temperature. The contrasting results between 1 and 2 obtained in pyroelectricities are well consistent with thier crystalline symmetries.

開催年月日： 2019年3月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：甲南大学　岡本キャンパス   国名：日本国  

開催年月日： 2018年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡国際会議場   国名：日本国  

開催年月日： 2018年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：福岡国際会議場   国名：日本国  

開催年月日： 2017年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：札幌   国名：日本国  

開催年月日： 2017年9月

記述言語：英語  

開催地：Zao, Miyagi   国名：日本国  

開催年月日： 2016年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Sendai   国名：日本国  

開催年月日： 2015年12月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：Honolulu, Hawaii   国名：アメリカ合衆国  

開催年月日： 2015年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：奈良女子大学   国名：日本国  

開催年月日： 2015年3月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：日本大学理工学部船橋キャンパス／薬学部   国名：日本国  

開催年月日： 2014年9月

記述言語：日本語  

開催地：中央大学、東京都   国名：日本国  

開催年月日： 2014年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：中央大学、東京都   国名：日本国  

今回、光学分割したキラル配位子からなる各種遷移金属単核錯体から新規異核複核錯体を合成し、これらの結晶構造及び電子物性について評価した。

開催年月日： 2014年7月

記述言語：英語  

開催地：Saint Petersburg   国名：ロシア連邦  

開催年月日： 2014年6月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

本研究では、カチオン性の導電性分子としてよく知られるTTF(Tetrathiafulvalene)類縁体を用いた新規ハイブリッド分子材料を開発するため、外場感応性部位としてアニオン性SCO錯体に着目し、新規ハイブリッド化合物の合成に成功したのでその結晶構造と物性について報告する。

開催年月日： 2014年3月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：名古屋大学　東山キャンパス   国名：日本国  

開催年月日： 2014年1月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：九州大学　西陣プラザ   国名：日本国  

開催年月日： 2013年12月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：TOKOホテル　東京五反田   国名：日本国  

開催年月日： 2013年11月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：琉球大学   国名：日本国  

開催年月日： 2013年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：愛媛大学   国名：日本国  

Photo-responsive Magnetic Properties of Valence Tautomeric Co Di-nuclear Complexes

開催年月日： 2013年3月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：立命館大学びわこ・くさつキャンパス   国名：日本国  

本研究では、N2 キレート型配位が可能なヴェルダジルラジカルに着目し、新規架橋型配位子(ver-prm)を用いてその金属錯体の構造及び磁気的性質について基礎的な研究を行った。

開催年月日： 2012年10月

記述言語：英語  

開催地：Orlando   国名：アメリカ合衆国  

開催年月日： 2012年9月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：富山大学　五福キャンパス   国名：日本国  

本研究ではテトラオキソレン架橋コバルト複核錯体分子類縁体の合成を行い、これらの磁気的挙動について検討するとともに誘電特性の評価を行った。

開催年月日： 2012年3月

会議種別：口頭発表（一般）  

開催地：神奈川   国名：日本国  

開催年月日： 2012年3月

会議種別：口頭発表（一般）  

開催地：神奈川   国名：日本国  

開催年月日： 2012年3月

会議種別：口頭発表（一般）  

開催地：神奈川   国名：日本国  

開催年月日： 2012年3月

会議種別：口頭発表（一般）  

開催地：神奈川   国名：日本国  

開催年月日： 2012年3月

会議種別：口頭発表（一般）  

開催地：神奈川   国名：日本国  

開催年月日： 2011年11月

会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：名古屋   国名：日本国  

開催年月日： 2011年9月

会議種別：口頭発表（一般）  

開催地：岡山   国名：日本国  

開催年月日： 2011年9月

会議種別：口頭発表（一般）  

開催地：岡山   国名：日本国  

開催年月日： 2011年1月

会議種別：シンポジウム・ワークショップ パネル（公募）  

開催地：札幌   国名：日本国  

開催年月日： 2010年12月

会議種別：口頭発表（一般）  

開催地：京都   国名：日本国  

開催年月日： 2010年9月

会議種別：口頭発表（一般）  

開催地：千葉   国名：日本国  

開催年月日： 2010年3月

会議種別：口頭発表（一般）  

開催地：大阪府東大阪市   国名：日本国  

開催年月日： 2010年3月

会議種別：口頭発表（一般）  

開催地：大阪府東大阪市   国名：日本国  

開催年月日： 2009年9月

会議種別：口頭発表（一般）  

開催地：長崎県長崎市   国名：日本国  

開催年月日： 2009年9月

会議種別：口頭発表（一般）  

開催地：長崎県長崎市   国名：日本国  

種別：大会・シンポジウム等 

種別：大会・シンポジウム等