Dual-Emissive Monoruthenium Complexes of N(CH<sub>3</sub>)-Bridged Ligand: Synthesis, Characterization, and Substituent Effect

oleh: Si-Hai Wu, Zhe Zhang, Ren-Hui Zheng, Rong Yang, Lianhui Wang, Jiang-Yang Shao, Zhong-Liang Gong, Yu-Wu Zhong

Format: Article
Diterbitkan: MDPI AG 2023-10-01

Deskripsi

Three monoruthenium complexes <b>1</b>(PF<sub>6</sub>)<sub>2</sub>–<b>3</b>(PF<sub>6</sub>)<sub>2</sub> bearing an N(CH<sub>3</sub>)-bridged ligand have been synthesized and characterized. These complexes have a general formula of [Ru(bpy)<sub>2</sub>(<b>L</b>)](PF<sub>6</sub>)<sub>2</sub>, where <b>L</b> is a 2,5-di(<i>N</i>-methyl-<i>N</i>’-(pyrid-2-yl)amino)pyrazine (dapz) derivative with various substituents, and bpy is 2,2′-bipyridine. The photophysical and electrochemical properties of these compounds have been examined. The solid-state structure of complex <b>3</b>(PF<sub>6</sub>)<sub>2</sub> is studied by single-crystal X-ray analysis. These complexes show two well-separated emission bands centered at 451 and 646 nm (Δ<i>λ</i><sub>max</sub> = 195 nm) for <b>1</b>(PF<sub>6</sub>)<sub>2</sub>, 465 and 627 nm (Δ<i>λ</i><sub>max</sub> = 162 nm) for <b>2</b>(PF<sub>6</sub>)<sub>2</sub>, and 455 and 608 nm (Δ<i>λ</i><sub>max</sub> = 153 nm) for <b>3</b>(PF<sub>6</sub>)<sub>2</sub> in dilute acetonitrile solution, respectively. The emission maxima of the higher-energy emission bands of these complexes are similar, while the lower-energy emission bands are dependent on the electronic nature of substituents. These complexes display two consecutive redox couples owing to the stepwise oxidation of the N(CH<sub>3</sub>)-bridged ligand and ruthenium component. Moreover, these experimental observations are analyzed by computational investigation.