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

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 1 H NMR, 13 C NMR and elemental analysis. The electrochemical properties of complexes 1-3 were inves-tigated by cyclic voltammetry (CV) and square-wave voltammetry (SWV), and different potential differ-ence 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 Gamma. 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 effec-tively attributed to Ru-C equivalent to C -> Ru IVCT absorption characteristics.(c) 2022 Elsevier B.V. All rights reserved.

Automated summary

Isomeric diruthenium complexes with bis(ethynyl)pyridine as a bridge core were prepared and characterized. The electrochemical properties and absorption spectra of the complexes were investigated, and the results showed that the N atom position and distance between redox metal centers affected their properties.