Design and Functionality of Near-Infrared Organic Materials with Intermediate Open-Shell Character

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K05215
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 35030:Organic functional materials-related
• Research Institution: Osaka Metropolitan University (2022-2023); Osaka Prefecture University (2021)
• Principal Investigator: Maeda Takeshi 大阪公立大学, 大学院工学研究科, 准教授 (90507956)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 近赤外 / 機能性色素 / 中間ジラジカル性 / 二光子吸収 / 反強磁性相互作用

Outline of Final Research Achievements

Robust near-infrared absorbing organic materials are essential for advancing technologies that utilize near-infrared light. In this study, we focused on polymethine dyes composed of an oxocarbon skeleton and chalcogenopyrylium, investigating their electronic structures and physical properties to enhance their functionality. Our findings indicate that these dyes exhibit intermediate diradical properties due to the presence of an open-shell singlet state, where two unpaired electrons have a singlet electron configuration. Additionally, we observed that the contribution of the open-shell singlet state increases with the atomic number of the chalcogen element. These dyes also display paramagnetic properties due to the unpaired electrons and demonstrate excellent light absorption capabilities beyond 1000 nm.

Free Research Field

有機材料化学

Academic Significance and Societal Importance of the Research Achievements

これまでに多様な近赤外線吸収有機色素が報告されているが，それらは閉殻構造の分子と認識されてきた．本研究では，近赤外線吸収有機色素の一種であるポリメチン色素が中間ジラジカル性を持つことを初めて明らかにした．中間ジラジカル性という概念は多環芳香族化合物などの特定の分子に適用されきたが，本研究は，その概念を有機色素にまで拡張しており，学術的に意義深い．また，近赤外線吸収有機色素の正確な電子状態を明示できたことは，近赤外吸収有機材料の設計新機軸の確立に貢献するものと考えられ，情報通信，生体深部の可視化，非侵襲性治療に利活用される近赤外吸収有機材料の創製につながると期待でき，社会的に意義深い．