Development of effective iridium(III) photosensitizers based on a novel ion-pairing strategy

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K05525
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 34010:Inorganic/coordination chemistry-related
• Research Institution: The University of Tokyo
• Principal Investigator: Takizawa Shin-ya 東京大学, 大学院総合文化研究科, 助教 (40571055)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: イリジウム錯体 / 増感剤 / りん光 / 励起エネルギー移動 / 人工光合成 / 二酸化炭素還元 / ベシクル / イオン対

Outline of Final Research Achievements

Ir(III) complexes have attracted attention as photosensitizers for various photoreactions including light-chemical energy conversion. However, the development of new Ir(III) photosensitizers is required to impart both strong visible-light absorption and durability. In addition, most of the Ir(III) photosensitizers are not water-soluble preventing their further applications to environmentally benign systems. In this project, we developed a new ion pair comprising cationic and anionic Ir(III) photosensitizers for photocatalytic CO2 reduction at lipid membrane surfaces. While the cationic component offered stability, cyclometalating coumarin-based ligands in the anionic component ensured effective visible-light absorption. The triplet excited state of the cationic Ir(III) complex, which is the key photoredox species in this system, was generated through triplet excitation-energy transfer from the anionic complex.

Free Research Field

錯体化学、光化学

Academic Significance and Societal Importance of the Research Achievements

光-化学エネルギー変換、すなわち太陽光エネルギーによる二酸化炭素の再資源化や水素製造が実用化されれば、人類が直面しているエネルギー問題や気候変動の解決策になりうる。本研究は、光を吸収してそのような反応を誘起するための耐久性に優れた新しい増感剤やそれを活かせる環境調和型反応の開発に資するものである。さらに本研究課題で見出した手法は、希少金属であるイリジウムだけでなく、地球上に豊富に存在する金属に基づく増感剤開発にも今後適用できることが期待される。