Development of novel redox photosensitizer using metal complexes having tridentate ligands

2019 Fiscal Year Final Research Report

• Project/Area Number: 18K14238
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 34010:Inorganic/coordination chemistry-related
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: TAMAKI Yusuke 東京工業大学, 理学院, 助教 (10752389)
• Project Period (FY): 2018-04-01 – 2020-03-31
• Keywords: 光増感剤 / 光触媒 / CO2還元 / 金属錯体

Outline of Final Research Achievements

In order to add new functions, which cannot be achieved using most-frequently used [Ru(NN)3]2+, as a photosensitizer, we used [Ru(NNN)2]2+ complexes.
(1) [Ru(NNN)2]2+ complexes exhibited longer-wavelength absorption by S-T transitions and functioned as a photosensitizer. Under red-light irradiation, it photoctalyzed the reduction of CO2 in combination with the rhenium(I) catalyst. By surveying various substituents on ligands of [Ru(NNN)2]2+ complexes, we achieved both longer-wavelength absorption (< 720 nm) and longer lifetime in the excited state (327 ns).
(2) The hybrid photocatalyst consisting of semiconductor photocatalyst and the supramolecular photocatalyst with [Ru(NNN)2]2+ photosensitizer unit photocatalyzed the reduction of CO2 to HCOOH. In neutral-basic condition, it exhibited better photocatalytic abilities than that having [Ru(NN)3]2+ photosensitizer unit.

Free Research Field

金属錯体の光化学

Academic Significance and Societal Importance of the Research Achievements

三重項励起状態への直接遷移（S-T遷移）を示すルテニウム錯体レドックス光増感剤を初めて開発した。従来の物性変調とは全く異なる方法で、吸収を長波長化することができた。これにより本来は相反する長波長吸収と励起状態の長寿命化を両立できた。またこの光増感部を有する超分子光触媒と半導体光触媒からなる複合系が、中性~塩基性条件で従来の系より優れた光触媒能を示した。三座配位子を有するルテニウム錯体光増感部が、多機能複合系における優れた分子設計であることが示唆された。