Realization of photochemical oxygen evolution using iridium complexes as photosensitizers

2018 Fiscal Year Final Research Report

• Project/Area Number: 17K14457
• Research Category: Grant-in-Aid for Young Scientists (B)
• Allocation Type: Multi-year Fund
• Research Field: Inorganic chemistry
• 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): 2017-04-01 – 2019-03-31
• Keywords: イリジウム錯体 / 増感剤 / リン光 / 人工光合成 / 水の酸化 / 酸素発生 / ルテニウム錯体

Outline of Final Research Achievements

Highly active and durable molecular water-oxidation catalysts have been extensively pursued due to the increasing demand for artificial photosynthesis. Photochemical oxygen evolution using these catalysts has also been studied in combination with a ruthenium(Ru) tris-bipyridine photosensitizer in order to effectively utilize solar energy. However, this conventional Ru complex is known to be labile during irradiation, and new photosensitizers are required to further promote scientific researches in this field.
In this context, we for the first time tried to develop a photochemical oxygen-evolution system sensitized by bis-cyclometalated iridium (Ir) complexes. Despite several attempts, we were unable to observe oxygen evolution using new Ir(III)-based photosensitizers even though they displayed reasonable oxidation potentials and excited-state lifetimes. Nevertheless, our results provided valuable guidelines for future photosensitizer design.

Free Research Field

錯体化学

Academic Significance and Societal Importance of the Research Achievements

人工光合成は、“地球上に無尽蔵に降り注ぐ太陽光のエネルギーを、人類が利用可能な化学エネルギーに変換する技術”と一般的には理解され、実用化されればエネルギー問題の解決策になりうる。近年、Ir錯体を増感剤とする光触媒的なプロトン還元や二酸化炭素還元が多数報告されているが、鍵となる水の酸化反応(光酸素発生)については皆無である。その観点から本研究は挑戦的であったが、目標が達成できなかったという結果にも重要な意義はある。何故これまで報告例がなかったのかという“問い”に対する“答え”を当該分野に提示することで、今後の研究の効率化や新規増感剤の開発に貢献できるためである。