Masayuki Gon

Assistant Professor,Graduate School of Engineering, Kyoto University*Profile is at the time of the award.

2020Inamori Research GrantsScience & Engineering

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Research topics: Development of Fused Conjugated Polymer Complexes for Highly Efficient Near‐Infrared Emission

Keyword

Summary: Azobenzene scaffolds have been used for dyes in the long history and recently, they have been applied to reversible photoswitching materials. Azobenzene scaffolds are the conjugated system including nitrogen-nitrogen double bonds, however, the synthesis of the conjugated polymers using the azobenzene skeletons have been rarely reported. Conjugated polymers have attracted attention as organic-based light and flexible devices such as organic light-emitting diodes (OLEDs) and organic photovoltaics (OPVs). Herein, we newly prepared novel conjugated polymers containing azobenzene moieties in the main chain to obtain the organic materials exhibiting unprecedented performances such as highly efficient near-infrared emissions.

Message

Thank you very much for adopting this theme. Through this research, I hope to create a new trend in materials chemistry by focusing on interesting organic structures.

Outline of Research Achievments

Near-infrared light is used for bioimaging and optical communication because of its high biopermeability, transparency and low attenuation. The demand is increasing more and more with the development of IoT era and medical fields. We have proposed tin-fused azobenzene complexes for a versatile structure showing highly efficient near-infrared emission.

In this research, we synthesized hypervalent tin-fused azobenzene complexes and investigated their optical properties. As a result, it was found that the complexes showed emission in the deep-red region without expanding the π-conjugation length. Furthermore, we have found the emission color is blue-shifted by changing the hypervalent tin complexes from a five-coordinated state to a six-coordinated state. The alteration to the six-coordinated state proceeded easily by exposing the powder to solvent vapor. To the best of my knowledge, it is the first report of discovering vapochromism based on hypervalent bond. We have experimentally and theoretically proved that the three-center four-electron (3c-4e) bond, which is one of the bond modes peculiar to the hypervalent bond, had a great influence on the energy level of the π-conjugated system. It is difficult for a general conjugated system to realize these properties, and it can be said that they are unique to hypervalent complexes. It will be possible to synthesize highly efficient near-infrared-emissive π-conjugated polymers by using the hypervalent tin complex, and it is expected that it will greatly contribute to the development of science and technology in the near future.

Gon M, Tanaka K, Chujo Y (2021) Vapochromic Luminescent pi-Conjugated Systems with Reversible Coordination-Number Control of Hypervalent Tin(IV)-Fused Azobenzene Complexes. Chemistry — A European Journal 27(27):7561-7571. https://doi.org/10.1002/chem.202100571