Tuning the Electronic Coupling in Cyclometalated Diruthenium Complexes through Substituent Effects: A Correlation between the Experimental and Calculated Results |
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| Authors: | Jiang‐Yang Shao Prof. Dr. Yu‐Wu Zhong |
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| Affiliation: | Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190 (P.R. China) |
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| Abstract: | A common bridging ligand, 3,3′,5,5′‐tetrakis(N‐methylbenzimidazol‐2‐yl)biphenyl, and four terpyridine terminal ligands with various substituents (amine, tolyl, nitro, and ester groups) have been used to synthesize ten cyclometalated diruthenium complexes 1 2+– 10 2+. Among them, compounds 1 2+– 6 2+ are redox nonsymmetric, and others are symmetric. These complexes show two RuIII/II processes and an intervalence charge transfer (IVCT) transition in the one‐electron oxidized state. The potential separation (ΔE) of 1 2+– 10 2+ has been correlated to the energy difference ΔG0, the energy of the IVCT band Eop, and the ground‐state delocalization coefficient α2. Time‐dependent (TD)DFT calculations suggest that the absorptions in the visible region of 1 2+– 6 2+ are mainly associated with the metal‐to‐ligand charge‐transfer transitions from both ruthenium ions and to both terminal ligands and the bridging ligand. However, the energies of these transitions vary significantly. DFT calculations have been performed on 1 2+– 6 2+ and 1 3+– 6 3+ to give information on the electronic structures and spin populations of the mixed‐valent compounds. The TDDFT‐predicted IVCT excitations reproduce well the experimental trends in transition energies. In addition, three monoruthenium complexes have been synthesized for a comparison study. |
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| Keywords: | density functional theory electron transfer mixed‐valent compounds ruthenium transition states |
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