記述言語：英語   掲載種別：研究論文（学術雑誌）  

The development of magnetic molecules with long spin reversal/decoherence times highly depends on the understanding of relaxation behavior under different external conditions. Herein, a magnetic study on a Ru-III complex (1) is presented. Detailed analysis of the relaxation time and the magneto-heat capacity data suggests that the resonant phonon trapping process dominates the magnetic relaxation in the crystalline sample of 1, slowing down the spin relaxation rate, as further confirmed by the measurements on a ground sample and frozen solution. Thus, it provides a rare example showing that 4d metal-centered mononuclear compounds without second-order anisotropy can display slow magnetic relaxation.

DOI： 10.1002/chem.201702047

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Atypically anisotropic and large changes in magnetic susceptibility, along with a change in crystalline shape, were observed in a Co-II complex at near room temperature. This was achieved by combining oxalate molecules, acting as rotor, and a Co-II ion with unquenched orbital angular momentum. A thermally controlled 908 rotation of the oxalate counter anion triggered a symmetry-breaking ferroelastic phase transition, accompanied by contraction-expansion behavior (ca. 4.5%) along the long axis of a rod-like single crystal. The molecular rotation induced a minute variation in the coordination geometry around the Co-II ion, resulting in an abrupt decrease and a remarkable increase in magnetic susceptibility along the direction perpendicular and parallel to the long axis of the crystal, respectively. Theoretical calculations suggested that such an unusual anisotropic change in magnetic susceptibility was due to a substantial reorientation of magnetic anisotropy induced by slight disruption in the ideal D-3 coordination environment of the complex cation.

DOI： 10.1002/anie.201606165

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/jacs.4c02882

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this study, we investigated reversible intermolecular proton shifting (IPS) coupled with spin transition (ST) in a novel FeII complex. The host FeII complex and the guest carboxylic acid anion were connected by intermolecular hydrogen bonds (IHBs). We extended the intramolecular proton transfer coupled ST phenomenon to the intermolecular system. The dynamic phenomenon was confirmed by variable-temperature single-crystal X-ray diffraction, neutron crystallography, and infrared spectroscopy. The mechanism of IPS was further validated using density functional theory calculations. The discovery of IPS-coupled ST in crystalline molecular materials provides good insights into fundamental processes and promotes the design of novel multifunctional materials with tunable properties for various applications, such as optoelectronics, information storage, and molecular devices.

DOI： 10.1002/anie.202404843

記述言語：英語   掲載種別：研究論文（学術雑誌）  

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 [Fe2Co] 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

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Molecular-basedmagnetoelectric materials are among themost promisingmaterials for next-generation magnetoelectric memory devices. However,practical application of existing molecular systems has proven difficultlargely because the polarization change is far lower than the practicalthreshold of the ME memory devices. Herein, we successfully obtainedan [FeCo] dinuclear complex that exhibits a magnetic field-inducedspin crossover process, resulting in a significant polarization changeof 0.45 & mu;C cm(-2). Mo''ssbauer spectroscopyand theoretical calculations suggest that the asymmetric structuralchange, coupled with electron redistribution, leads to the observedpolarization change. Our approach provides a new strategy toward rationallyenhancing the polarization change.

DOI： 10.1021/jacs.3c02977

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Abstract

To alleviate the energy and environmental crisis, in the last decades, energy harvesting by utilizing optical control has emerged as a promising solution. Here we report a polar crystal that exhibits photoenergy conversion and energy storage upon light irradiation. The polar crystal consists of dinuclear [CoGa] molecules, which are oriented in a uniform direction inside the crystal lattice. Irradiation with green light induces a directional intramolecular electron transfer from the ligand to a low-spin Co^III centre, and the resultant light-induced high-spin Co^II excited state is trapped at low temperature, realizing energy storage. Additionally, electric current release is observed during relaxation from the trapped light-induced metastable state to the ground state, because the intramolecular electron transfer in the relaxation process is accompanied with macroscopic polarization switching at the single-crystal level. It demonstrates that energy storage and conversion to electrical energy is realized in the [CoGa] crystals, which is different from typical polar pyroelectric compounds that exhibit the conversion of thermal energy into electricity.

DOI： 10.1038/s41467-023-39127-8

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.cclet.2022.05.006

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/chem.202202161

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s11426-022-1294-8

記述言語：英語   掲載種別：研究論文（学術雑誌）  

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 FeII 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

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Spin-crossover (SCO) complexes have been extensively studied in the past few decades owing to their bistable nature which find application in a myriad of areas. In order to enhance and optimize the SCO behavior, considerable attention is being paid towards the synthesis of discrete multinuclear spin-crossover complex systems. Here, two mixed-valence (Fe2FeII)-Fe-III trinuclear complexes of the formula {[Fe-II(TPMA)][Fe-III(Tp(R))(CN)(3)](2)}center dot MeOH center dot 2H(2)O (1) and {[Fe-II(TPMA)][Fe-III(Tp(R))(CN)(3)](2)}center dot H2O (2) [where TPMA = tris(2-pyridylmethyl)amine, Tp = tris(pyrazol-1-yl)borate, R = 3,5-dimethyl for 1 and H for 2] were synthesized and characterized. Magnetic measurements confirmed that complex 1 undergoes SCO at a high temperature (T-1/2 = 410 K for the fresh sample and T-1/2 = 406 K for the dried sample), while complex 2 displays near room temperature SCO (T-1/2 = 283 K for the fresh sample and T-1/2(up arrow) = 283 K and T-1/2(down arrow) = 257 K for the dried sample). To the best of our knowledge, complex 1 has the highest transition temperature reported among trinuclear SCO complexes so far, which is a remarkable feature of multinuclear materials. Slight structural modifications tend to upend the SCO behavior which paves the way for fine tuning SCO.

DOI： 10.1039/d1qi01086g

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.31635/ccschem.020.202000489

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Pyroelectricity plays a crucial role in modern sensors and energy conversion devices. However, obtaining materials with large and nearly constant pyroelectric coefficients over a wide temperature range for practical uses remains a formidable challenge. Attempting to discover a solution to this obstacle, we combined molecular design of labile electronic structure with the crystal engineering of the molecular orientation in lattice. This combination results in electronic pyroelectricity of purely molecular origin. Here, we report a polar crystal of an [FeCo] dinuclear complex exhibiting a peculiar pyroelectric behavior (a substantial sharp pyroelectric current peak and an unusual continuous pyroelectric current at higher temperatures) which is caused by a combination of Fe spin crossover (SCO) and electron transfer between the high-spin Fe ion and redox-active ligand, namely valence tautomerism (VT). As a result, temperature dependence of the pyroelectric behavior reported here is opposite from conventional ferroelectrics and originates from a transition between three distinct electronic structures. The obtained pyroelectric coefficient is comparable to that of polyvinylidene difluoride at room temperature.

DOI： 10.1038/s41467-021-25041-4

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Many crystalline molecular rotors have been developed in the past decades. However, manipulating the rotational gesture that intrinsically controls the physical performance of materials remains a challenge. Herein, we report a series of crystalline rotors whose rotational gestures can be modulated by modifying the structures of molecular stators. In these dynamic crystals, the ox(2-) (ox(2-) = oxalate anion) behave as molecular rotators performing axial-free rotation in cavities composed of five complex cations, [M-II(en)(3)](2+) (en = ethylenediamine). The structure of [M-II(en)(3)](2+) that serves as a molecular stator can be tuned by varying the metal center with different ionic radii, consequently altering the chemical environment around the molecular rotator. Owing to the quasi-transverse isotropy of ox(2-) and multiple hydrogen-bond interactions around it, the molecular rotator exhibits unusual motional malleability, i.e., it can rotate either longitudinally in the compound of Zn-II, or with a tilt angle of 42 degrees in the compound of Fe-II, or even laterally in the compound of Cd-II. The atypical dynamic behavior demonstrated here provides a new chance for the development of exquisite crystalline molecular rotors with advanced tunable functionalities.

DOI： 10.1021/acs.inorgchem.1c00558

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.1038/s41467-021-23057-4

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Water reorientation is essential in a wide range of chemical and biological processes. However, the effects of such reorientation through rotation around the metal-oxygen bond on the chemical and physical properties of the resulting complex are usually ignored. Most studies focus on the donor property of water as a recognized σ donor-type ligand rather than a participant in the π interaction. Although a theoretical approach to study water-rotation effects on the functionality of a complex has recently been conducted, it has not been experimentally demonstrated. In this study, we determine that the magnetic anisotropy of a Co(II) complex can be effectively controlled by the slight rotation of coordinating water ligands, which is achieved by a two-step structural phase transition. When the water molecule is rotated by 21.2 ± 0.2° around the Co-O bond, the directional magnetic susceptibility of the single crystal changes by approximately 30% along the a-axis due to the rotation of the magnetic anisotropy axis through the modification of the π interaction between cobalt(II) and the water ligand. The theoretical calculations further support the hypothesis that the reorientation of water molecules is a key factor contributing to the magnetic anisotropy transition of this complex.

DOI： 10.1038/s41467-021-23057-4

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A proton-electron coupling system, exhibiting unique bistability or multistability of the protonated state, is an attractive target for developing new switchable materials based on proton dynamics. Herein, we present an iron(II) hydrazone crystalline compound, which displays the stepwise transition and bistability of proton transfer at the crystal level. These phenomena are realized through the coupling with spin transition. Although the multi-step transition with hysteresis has been observed in various systems, the corresponding behavior of proton transfer has not been reported in crystalline systems; thus, the described iron(II) complex is the first example. Furthermore, because proton transfer occurs only in one of the two ligands and yr electrons redistribute in it, the dipole moment of the iron(II) complexes changes with the proton transfer, wherein the total dipole moment in the crystal was canceled out owing to the antiferroelectric-like arrangement.

DOI： 10.1002/anie.202006763

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Manipulating the collective molecular movements to implement macroscopic mechanical response of bulk material is attractive and challenging. Here, an organic-inorganic hybrid single crystal is synthesized, which exhibits a giant macroscopic shape transformation with a remarkable thermal hysteretic feature. The colossal anisotropic shape change, which manifests as an abrupt elongation of ca. 9 % along the crystallographic c-axis and a concomitant contraction of ca. 9 % in a perpendicular direction, is induced by a significant reorientation of imidazolium, accompanied with a substantial configurational variation in CuBr42- complex anions. The synergistic motions of both the molecular cations and anions engender a remarkable large thermal hysteresis (>30 K) in the shape transformation of the single crystal, implying that this material may play a role in alternating memory media. Furthermore, due to the stable crystal lattice, a single crystal that demonstrates naked-eye detectable large shape transformation was used as a thermal actuator to spontaneously control an electric circuit by temperature variation.

DOI： 10.1002/chem.202000845

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A rational approach to modulating easy-axis magnetic anisotropy by varying the axial donor ligand in heptacoordinated Fe-II complexes has been explored. In this series of complexes with formulae of [Fe(H4L)(NCS)(2)].3 DMF.0.5 H2O (1), [Fe(H4L)(NCSe)(2)].3 DMF.0.5 H2O (2), and [Fe(H4L)(NCNCN)(2)].DMF.H2O (3) [H4L=2,2 '-{pyridine-2,6-diylbis(ethan-1-yl-1-ylidene)}bis(N-phenylhydrazinecarboxamide)], the axial positions are successively occupied by different nitrogen-based pi-donor ligands. Detailed dc and ac magnetic susceptibility measurements reveal the existence of easy-axis magnetic anisotropy for all of the complexes, with 1 [U-eff=21 K, tau(0)=1.72x10(-6) s] and 2 [U-eff=25 K, tau(0)=2.25x10(-6) s] showing field-induced slow magnetic relaxation behavior. However, both experimental studies and theoretical calculations indicate the magnitude of the D value of complex 3 to be larger than those of complexes 1 and 2 due to the axial bond angle being smaller than that for an ideal geometry. Detailed analysis of the field and temperature dependences of relaxation time for 1 and 2 has revealed that multiple relaxation processes (quantum tunneling of magnetization, direct, and Raman) are involved in slow magnetic relaxation for both of these complexes. Magnetic dilution experiments support the role of intermolecular short contacts.

DOI： 10.1002/chem.201905166

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Polarization change induced by directional electron transfer attracts wide attention for its fast switching rate and potential light control. Here, electronic pyroelectricity was investigated in the crystal of a mononuclear complex, [Co(phendiox)(rac-cth)](ClO4)·0.5EtOH (1·0.5EtOH, H2phendiox = 9, 10-dihydroxyphenanthrene, rac-cth = racemic 5, 5, 7, 12, 12, 14-hexamethyl-1, 4, 8, 11-tetraazacyclotetradecane), which undergoes a two-step valence tautomerism (VT). Correspondingly, pyroelectric current exhibited double peaks in the same temperature domain with the polarization change consistent with the change in dipole moments during the VT process. The time-resolved IR spectroscopy showed that the photo-induced metastable state can be generated within 150 ps at 190 K. Such state can be trapped for tens of minutes at 7 K, revealing that photo-induced polarization change could be realized in this system. These results directly demonstrate that the change in the molecular dipole moments induced by intramolecular electron transfer can introduce a macroscopic polarization change in VT compounds.

DOI： https://doi.org/10.1038/s41467-020-15988-1

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=1/2 {Fe-LS(II)-Co-LS(III)-Fe-LS(III)} (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=1/2 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）  

Two rhodamine 6G-based mononuclear dysprosium complexes, [DY(L-R)(L-A)(2)](ClO4)(3)center dot Et2O center dot 1.5MeOH center dot 0.5H(2)O (1) and [Dy(L-R)-(H2O)(4)(MeCN)](ClO4)(3)center dot 2H(2)O center dot MeCN (2) (L-R = salicylaldehyde rhodamine 6G hydrazone, L-A = 2-pyridylcarboxaldehyde benzoyl hydrazone), are synthesized, aiming at improving the magnetic behavior by modulating their coordination environment. Both complexes own one exclusive short Dy-O-phenoxy coordination bond as the predominant bond and exhibit singlemolecule magnet behavior under zero dc field with the energy barrier (U-eff/k(B)) of 90 K (1) and 320 K (2) and apparent hysteresis at 1.9 K. The ab initio calculations indicate that the short Dy-O-phenoxy bond determines the direction of magnetic anisotropic axis for 1 and 2. The quantum tunneling of magnetization (QTM) between the ground Kramers doublets (KDs) in 1 cannot be neglected, leading to an experimental U-eff/k(B) much lower than the calculated energy of the first excited state (318.2 K). For 2, the stronger magnetic anisotropy and negligible QTM between the ground KDs guarantees that the energy barrier is close to the calculated energy of first KDs (320.8 K). On the other hand, the presence of ring-opened xanthene moiety makes complexes 1 and 2 in the solid state emit red light with emission bands of 645 and 658 nm, respectively.

DOI： 10.1021/acs.inorgchem.9b03105

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 [Fe-14], 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 [Fe-14] 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 electronhopping rate at room temperature is faster than the time scale of Mossbauer measurements (<similar to 10(-8) s). Partial reduction of N-terminal high spin Fern 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 [Fe-14] 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）  

Materials demonstrating unusual large positive and negative thermal expansion are fascinating for their potential applications as high-precision microscale actuators and thermal expansion compensators for normal solids. However, manipulating molecular motion to execute huge thermal expansion of materials remains a formidable challenge. Here, we report a single-crystal Cu(II) complex exhibiting giant thermal expansion actuated by collective reorientation of imidazoliums. The circular molecular cations, which are rotationally disordered at a high temperature and statically ordered at a low temperature, demonstrate significant reorientation in the molecular planes. Such atypical molecular motion, revealed by variable-temperature single crystal X-ray diffraction and solid-state NMR analyses, drives an exceptionally large positive thermal expansion and a negative thermal expansion in a perpendicular direction of the crystal. The consequent large shape change (similar to 10%) of bulk material, with remarkable durability, suggests that this complex is a strong candidate as a microscale thermal actuating material.

DOI： 10.1038/s41467-019-12833-y

記述言語：英語   掲載種別：研究論文（学術雑誌）  

An important technique to realize novel electron- and/or proton-based functionalities is to use a proton-electron coupling mechanism. When either a proton or electron is excited, the other one is modulated, producing synergistic functions. However, although compounds with proton-coupled electron transfer have been synthesized, crystalline molecular compounds that exhibit proton-transfer-coupled spin-transition (PCST) behavior have not been reported. Here, we report the first example of a PCST Fe(II) complex, wherein the proton lies on the N of hydrazone and pyridine moieties in the ligand at high-spin and low-spin Fe(II), respectively. When the Fe(II) complex is irradiated with light, intramolecular proton transfer occurs from pyridine to hydrazone in conjunction with the photoinduced spin transition via the PCST mechanism. Because the light-induced excited high-spin state is trapped at low temperatures in the Fe(II) complex-a phenomenon known as the light-induced excited-spin-state trapping effect-the light-induced proton-transfer state, wherein the proton lies on the N of hydrazone, is also trapped as a metastable state. The proton transfer was accomplished within 50 ps at 190 K. The bistable nature of the proton position, where the position can be switched by light irradiation, is useful for modulating proton-based functionalities in molecular devices.

DOI： 10.1021/jacs.9b07204

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Two new complexes were constructed via the coordination of fluorophores with Fe(II) ions to study the effects of ligand substituents on fluorescent-spin crossover (SCO) materials. Single-crystal structural determination suggests that the central iron(II) of complexes 1-2 adopted an N4O2 coordination configuration, chelated by two ligands L-1 or L-2. The pi center dot center dot center dot pi stacking interaction between the pi-conjugated xanthene groups of the adjacent ligands for complex 1 is apparently stronger than that for complex 2. Magnetic susceptibility measurements show that complex 1 is high spin, while complex 2 is diamagnetic at room temperature. Interestingly, the desolvated form 1-d of complex 1 exhibits SCO behavior (T-c = 175 K) without hysteresis. Significantly, complex 1-d displays the correlation between the spin crossover and the fluorescence.

DOI： 10.1039/c9qi00111e

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Network structures based on Star-of-David catenanes with multiple superior functionalities have been so far elusive, although numerous topologically interesting networks are synthesized. Here, a metal-organic framework featuring fused Star-of-David catenanes is reported. Two triangular metallacycles with opposite handedness are triply intertwined forming a Star-of-David catenane. Each catenane fuses with its six neighbors to generate a porous twofold intercatenated gyroid framework. The compound possesses exceptional stability and exhibits multiple functionalities including highly selective CO2 capture, high proton conductivity, and coexistence of slow magnetic relaxation and long-range ordering.

DOI： 10.1002/adma.201703301

記述言語：英語   掲載種別：研究論文（学術雑誌）  

An octacoordinated Fe(II) complex, [Fe-II(dpphen)(2)](BF4)(2)center dot 1.3H(2)O (1; dpphen = 2,9-bis(pyrazol-1-yl)-1,10-phenanthroline), with a pseudo-D-2d-symmetric metal center has been synthesized. Magnetic, high-frequency/-field electron paramagnetic resonance (HF-EPR), and theoretical investigations reveal that 1 is characterized by uniaxial magnetic anisotropy with a negative axial zero-field splitting (ZFS) (D approximate to -6.0 cm(-1)) and a very small rhombic ZFS (E approximate to 0.04 cm(-1)). Under applied dc magnetic fields, complex 1 exhibits slow magnetic relaxation at low temperature. Fitting the relaxation time with the Arrhenius mode combining Orbach and tunneling terms affords a good fit to all the data and yields an effective energy barrier (17.0 cm(-1)) close to the energy gap between the ground state and the first excited state. The origin of the strong uniaxial magnetic anisotropy for 1 has been clearly understood from theoretical calculations. Our study suggests that high-coordinated compounds featuring a D-2d-symmetric metal center are promising candidates for mononuclear single-molecule magnets.

DOI： 10.1021/acs.inorgchem.7b00765

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Two polymorphic structures have been well determined in a valence tautomeric (VT) dinuclear cobalt complex. These polymorphs showed distinct thermal- and photomagnetic behavior, and are thus ideal for studying the pure intermolecular factors to VT transitions. In polymorph 1A, the VT cations are arranged head-to-waist with their neighbors and exhibit weak interactions, resulting in a gradual and incomplete thermal VT transition. In contrast, the cations in polymorph 1B are arranged head-to-tail and exhibit relatively strong interactions, leading to an abrupt and complete thermal VT transition with adjustable hysteresis loop at around room temperature. The VT process for both polymorphs can be induced by light, but the light-excited state of 1B2H(2)O has a higher thermal relaxation temperature than that of 1A3H(2)O.

DOI： 10.1002/chem.201603817

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Proton transport via dynamic molecules is ubiquitous in chemistry and biology. However, its use as a switching mechanism for properties in functional molecular assemblies is far less common. In this study, we demonstrate how an intra-carboxyl proton shuttle can be generated in a molecular assembly akin to a rack-and-pinion cascade via a thermally induced single-crystal-to-single-crystal phase transition. In a triply interpenetrated supramolecular organic framework (SOF), a 4,4'-azopyridine (azpy) molecule connects to two biphenyl-3,3', 5,5'-tetracarboxylic acid (H4BPTC) molecules to form a functional molecular system with switchable mechanical properties. A temperature change reversibly triggers a molecular movement akin to a rack-and-pinion cascade, which mainly involves 1) an intra-carboxyl proton shuttle coupled with tilting of the azo molecules and azo pedal motion and 2) H4BPTC translation. Moreover, both the molecular motions are collective, and being propagated across the entire framework, leading to a macroscopic crystal expansion and contraction.

DOI： 10.1002/anie.201607886

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Structural assembly and reversible transformation between a metallogrid Dy-4 SMM (2) and its fragment Dy-2 (1) were established in the different solvent media. The zero-field magnetization relaxation was slowed for dysprosium metallogrid (2) with relaxation barrier of U-eff = 61.3 K when compared to Dy-2 (1). Both magnetic dilution and application of a moderate magnetic field suppress ground-state quantum tunneling of magnetization and result in an enhanced U-eff of 119.9 and 96.7 K for 2, respectively. Interestingly, the lanthanide metallogrid complex (2) exhibits magnetic hysteresis loop even up to 16 K at a given field sweep rate of 500 Oe/s.

DOI： 10.1021/acs.inorgchem.6b00500

記述言語：英語   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