One-dimensional electron systems in condensed matter are an important subject in material science, where charge, lattice, and spin are dominant factors for non-linear physical properties. Here, I introduced the fundamental knowledge of the quasi-one-dimensional halogen-bridged metal (MX) complexes and the charge-density-wave-to-Motto-Hubbard (CDW-to-MH) charge transfer phase transition and its mechanism of the Pd complex with alkyl chain. Then, unique CDW-to-MH charge transfer phase transition and CDW-MH phase separation and its mechanism of the Pd complex with weak in-plane ligand field, where the hydrogen bond network induced the perturbation and propagation of the phase transition and separation. In addition, the CDW-MH phase separation was observed in the macro and nano scale by optical and scanning tunneling microscopies.
Thermoelectric properties sensitively reflect the topology of the electronic band structure and hydrostatic pressure is the useful parameter to control the crystal structure and the corresponding electronic state.Measurements of the variation of thermoelectric properties accompanied by the topological change in the band structure could disclose the unique features of the relativistic electrons in condensed matter systems.In this review article, we describe a method for measuring the Seebeck and Nernst effect under pressure and report an actual application in the topological nodal line semimetal PbTaSe2 in which the topological band structure, nodal line (ring) structure, was changed by pressure. 3) In PbTaSe2, application of a relatively low pressure, ~ 0.3 GPa, causes a structural phase transition and annihilates 2/3 nodal rings in the momentum space. Our systematic study of pressure dependence of the Nernst coefficients reveals that magnetic field dependence of the Nernst effect dramatically change through the structural transition. We consider that Berry curvature-induced anomalous Nernst effect reduces with relative to the decrease in the number of nodal line structures. We expect that under-pressure Seebeck/Nernst measurement, which are sensitive probe to the electric structures, greatly contribute to the study of not only topological materials but also various other materials.
Cyclophanes comprise aromatic groups and aliphatic linkers bridging the aromatic moieties. Photoluminescent
cyclophanes have been mainly investigated in solution because formation of inclusion complexes with guest ions or molecules changes the photophysical properties. In contrast, stimuli-responsive luminescent properties of luminescent cyclophane in the crystalline or liquid-crystalline states have not been explored well, though cyclophanes would be promising candidates of thermo- and/or mechanoresponsive luminescent materials. In this contribution, recent research progress concerning luminescent cyclophanes prepared in my group is introduced. A 1,6-bis(phenylethynyl)pyrene-based cyclophane featuring hexaethyleneglycol linkers shows a nematic liquid-crystalline phase showing blue-green emission due to the excimer formation. Rapid cooling from the nematic phase leads to appearance of a supercooled nematic phase and both the blue-green emission and the nematic molecular order are well retained. Subsequent annealing procedure induces a phase transition to a crystalline phase showing blue emission. A 9,10-bis(phenylethynyl)anthracene-based cyclophane having tetraetylene glycol linkers have been found to form two different quasipolymorphs. One crystalline state exhibits two-step mechanochromic luminescence. Another crystal contains chloroform as the guest molecules and mechanical or thermal stimuli induces release of the guest molecules. Differential scanning calorimetry and thermogravimetric analysis clarified the phase transition behavior of the luminescent cyclophanes.
Detail pore size control for silica composite separation membrane was performed. Silica composite membranes were deposited on porous ceramic substrates by chemical vapor deposition. An organic group is introduced into the silica structure by introducing an organic group into the silica precursor used during membrane preparation. A membrane with a pore diameter of 0.37 nm without organic groups was obtained, which selectively permeated hydrogen. The pore diameters increased to 0.40 nm when propyl groups were introduced as an organic group. Furthermore, the hydrogen permeance also increased to 3.7 times. This vapor deposition phenomenon was investigated by investigating the thermal decomposition behavior of organic groups on hydrated silica powder. The decomposition/deposition behavior changes at low, medium, and high temperatures. Decomposition of organic groups by ozone was observed at a low temperature of about 200 °C. On the other hand, at medium temperatures of about 250 °C, the decomposition of the reaction aid, ozone, progressed, and the decomposition of the organic groups is limited. At high temperatures above 400 °C, thermal decomposition of the organic groups is dominant, and the amount of organic groups in the separation layer is decreasing.
Lipid bilayer membranes are the fundamental structure of biological membranes and are responsive to environmental changes such as temperature, pressure and concentrations of other components. Changes in the environment give rise to structural changes in the lipid bilayer membranes called phase transitions. In particular, the effect of membrane-active substances (i.e, ligands) on the phase transitions of lipid bilayer membranes varies significantly depending on the kinds of ligands. This is closely related to the affinities of ligands to the various phases of the bilayer membranes. In this review, the effect of representative ligands, long-chain fatty acids and inhalation anesthetics, on the lipid bilayer membrane under atmospheric and high pressure is described and the differences in ligand affinity to the bilayer membrane are explained thermodynamically.
Fragment molecular orbital (FMO) method has recently been used to analyze interactions between proteins and inhibitors for the purpose of drug discovery research. Unlike methods that use force field such as docking simulations, FMO method considered electrons. Therefore, it is characterized by the ability to analyze interactions involving electron correlation such as dispersion force. Furthermore, if a strong correlation can be obtained between the sum of inter-fragment interaction energy (IFIE-sum) and the enthalpy change between the protein and the inhibitor, we have also devised a method to predict free energy changes only by obtaining fragment interaction energies. As part of this research, we investigated the correlation between IFIE-sum and the enthalpy change in HIV protease inhibitors, and obtained a good correlation by appropriately classifying the target structures.