Research (English)

The construction of organic materials with entirely new frameworks by utilizing the electronic or structural characteristics of various elements, is anticipated to provide a possibility to develop new functions. We aim to create next-generation functional organic materials by controlling the properties and functions of organic materials through innovative molecular design. For example, tricoordinate boron has an empty p orbital, and p-π interactions with adjacent π orbitals can greatly enhance the electron-accepting ability. Additionally, its structural rigidity offers an opportunity to control the conformation when it forms a cyclic structure, enabling the develop new stimuli-responsive chromic materials. Similarly, the spatially expanded σ* orbitals of group 14 heavy atoms, including silicon and germanium, can be utilized to control the electronic states of the π-conjugated system. The heavy atom effect of group 15 bismuth that is the heaviest stable element in the periodic table can improve phosphorescence efficiency. With this element-based strategy, we are developing new types of functional dyes that can be used in organic photoelectron devices and other applications.

Polysilsesquioxanes have a structure in which one organic group is introduced onto each silicon atom of the inorganic material silica, and have been extensively studied as a typical example of organic-inorganic hybrid materials. We are conducting research and development on robust water separation membranes, carbon dioxide separation membranes, anti-fogging materials, and heat insulating materials by utilizing the characteristics of polysilsesquioxanes, which have the processability and flexibility, and the robustness, based on the organic substituent and inorganic framework, respectively.

Heat insulators are key materials for efficient energy use and reduction of CO₂ emissions. Recently, we examined cross-linked polymethylsilsesquioxane (MSQ) for use as the basic structure of heat-resistant insulation materials. In this study, we prepared MSQs with different cross-linking units and examined the effects of their structures on the heat resistance and heat insulation properties.

Group 14 metalloles have attracted much attention as core structures of conjugated functional materials. In this work, we prepared dithieno[3,2-b:4,5-c’]germole as a new unsymmetrically condensed dithienogermole. Conjugated donor–acceptor compounds with the unsymmetrical dithienogermole exhibiting red fluorescence were also prepared.

Germoles and siloles unsymmetrically condensed with heteroaromatic units are attracting much interest. In this study, compounds containing a triazologermole core unit condensed with a benzene or thiophene ring were prepared. Triphenylamine-substituted thienotriazolegermole was also prepared, with an effective extension of conjugation. Triphenylamine-substituted thienotriazolegermole showed clear solvatochromic properties in photoluminescence measurements, suggesting photo-induced intramolecular charge transfer.

New polysilsesquioxane (PSQ)-based CO₂ separation membranes with succinic anhydride and monoalkylurea units as thermally degradable CO₂-philic units were prepared. The succinic anhydride and monoalkylurea units underwent thermal degradation to form ester and dialkylurea units. The effects of thermal degradation on the performance of the obtained membranes were investigated, indicating that the controlled thermal degradation of the organic units provides a new methodology for possible tuning of the CO₂ separation performance of PSQ membranes.