On May 23rd, Dr. Chen Kaikai and Prof. Wei Zhanhua’s team from the Institute of Luminescent Materials and Information Displays and the School of Materials Science and Engineering of Huaqiao University (HQU), published a research paper titled “Management of triplet states in modified mononuclear ruthenium (II) complexes for enhanced photocatalysis” in the Angewandte Chemie International Edition, in collaboration with Wu Kaifeng’s team from Dalian Institute of Chemical Physics (DICP) of Chinese Academy of Sciences (CAS).

HQU graduate student Liang Ping and DICP doctoral student Wang Chaolong co-first authored the paper, with Chen Kaikai, Wu Kaifeng, and Wei Zhanhua as the co-corresponding authors.

Controlling the interplay between relaxation and charge/energy transfer processes in the excited states of photocatalysts is crucial for the performance of artificial photosynthesis. Metal-to-ligand charge-transfer triplet states (3MLCT*) of ruthenium (II) complexes are broadly implemented for photocatalysis, but an effective means of managing the triplets for enhanced photocatalysis has been lacking. Herein, this work proposed a strategy to considerably prolong the triplet excited-state lifetime by decorating a ruthenium(II) phosphine complex (RuP-1) with pendent polyaromatic hydrocarbons (PAHs). Systematic studies demonstrate that in RuP-4 decorated with anthracene, sub-picosecond electron transfer from anthracene to 3MLCT* leads to a charge-separated state that can mediate the formation of the intra-ligand triplet state (3IL) of anthracene, resulting in an exceptionally long excited-state up to several milliseconds. This triplet management strategy enables impressive photocatalytic reduction of CO2 to CO with a turnover number (TON) of 404, an optimized quantum yield of 43% and 100% selectivity, which is the highest reported performance for mononuclear photocatalysts without additional photosensitizers. RuP-4 also catalyzes photochemical hydrogen generation under argon. This work opens up an avenue for regulating the excited-state charge/energy flow for the development of long-lived 3IL multi-functional mononuclear photocatalysts to boost artificial photosynthesis.

This research was sponsored by the National Natural Science Foundation of China, the Natural Science Foundation of Xiamen and the Scientific Research Fund of Huaqiao University.

Link to the paper: https://doi.org/10.1002/anie.202407448

(Editor: Wei Linying)