Department of Chemistry and Biochemistry, The Ohio State University, Columbus, Ohio43210, United States.
J Am Chem Soc. 2022 Nov 9;144(44):20177-20182. doi: 10.1021/jacs.2c07209. Epub 2022 Oct 25.
The excited states of the series [Ru(tpy)(L)(CHCN)] (-) ( = 1, 2) containing bidentate ligands L with varying electron-donating ability were characterized through Arrhenius analysis of the temperature dependence of their excited-state lifetimes. Complexes - undergo photoinduced CHCN dissociation upon 450 nm irradiation with ligand exchange quantum yields that increase with the energy barrier to populating a dissociative triplet ligand field (LF) state from the lowest-energy triplet metal-to-ligand charge transfer (MLCT) excited state. Combined with DFT calculations, the data indicate that ligand photodissociation in - occurs directly from the MLCT state instead of a LF state. This finding is in contrast to the generally accepted mechanism for ligand photodissociation in Ru(II) complexes and indicates that alternative pathways for photoinduced ligand dissociation are available. These results can widely impact design principles for applications that require ligand photodissociation, such as photochemotherapy and photocatalysis, as well as for those where photosubstitution is undesirable, such as solar energy conversion.
该系列[Ru(tpy)(L)(CHCN)] (-)（ = 1, 2）的激发态，其中 L 为具有不同电子给体能力的双齿配体，通过激发态寿命随温度变化的 Arrhenius 分析进行了表征。当用 450nm 光照射时，复合物 - 会发生 CHCN 离解，配体交换量子产率随激发态最低能量三重态金属-配体电荷转移（MLCT）态到离解三重态配体场（LF）态的能垒的增加而增加。结合 DFT 计算，数据表明 - 中的配体光解直接从 MLCT 态发生，而不是 LF 态。这一发现与通常认为的 Ru(II) 配合物中配体光解的机制相反，表明存在可供选择的光诱导配体解离途径。这些结果广泛影响需要配体光解的应用的设计原则，例如光化学疗法和光催化，以及那些不希望发生光取代的应用，如太阳能转换。
