Binuclear metal ruthenium complexes bridged by isomeric bis(ethynyl)pyridine: Syntheses, characterization and electronic coupling properties

• Published in: Journal of organometallic chemistry Vol. 980-981; p. 122491
• Main Authors: Ou, Ya-Ping, Yang, Xiaofei, Lin, Zishun, Kong, Lingqiao, Liu, Sheng Hua
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2022
• Subjects: Bis(ethynyl)pyridine; Diruthenium Complex; Mixed-valence systems; Theoretical calculations; UV-vis-NIR spectroelectrochemistry; UV-vis-NIR spectroelectrochemistry; Bis(ethynyl)pyridine; Theoretical calculations; Diruthenium Complex; Mixed-valence systems
• ISSN: 0022-328X; 1872-8561
• DOI: 10.1016/j.jorganchem.2022.122491

•Isomericdiruthenium complexes with bis(ethynyl)pyridine as bridge core 1–3 were synthesized and characterized.•Compared with compounds 1 and 2, compound 3 with linear conjugate structure has higher charge-beneficial capacity.•IVCT band parameters (Hab = 387 cm−1 and Г = 0.08) revealed that 3+ belongs to a weakly coupled class II system. Isomeric diruthenium complexes with bis(ethynyl)pyridine as bridge core [2,6-bis(ethynyl)pyridine (1), 3,5-bis(ethynyl)pyridine (2), 2,5-bis(ethynyl)pyridine (3)] were successfully prepared and characterized by 1H NMR, 13C NMR and elemental analysis. The electrochemical properties of complexes 1–3 were investigated by cyclic voltammetry (CV) and square-wave voltammetry (SWV), and different potential difference values were revealed and affected by N atom position and distance between redox metal centers. Electron absorption spectra showed that the absorption of the linear molecule 3 displayed a red shift relative to that of complexes 1 and 2. The broad near-infrared absorption characteristic of the singly-oxidized complex 3+ revealed the existence of a mixed-valence state, which can be classified as a class II mixed-valence system according to the intervalence charge transfer (IVCT) absorption parameter Hab and Г. These results indicated that 3 has higher conjugation and charge delocalization ability than isomers 1 and 2. Density functional theory (DFT) calculations spin density distribution analysis further confirmed the above results, and time-dependent DFT showed the NIR multi-absorption of complex 3+, and effectively attributed to Ru–CC→Ru IVCT absorption characteristics. [Display omitted]