Effect of electronic structure of energy transfer in bimetallic Ru(ii)/Os(ii) complexes

Abstract

Novel monometallic (μ-LL′)Ru, Ru(μ-LL′), homobimetallic Ru(μ-LL′)Ru, and heterodimetallic Ru(μ-LL′)Os and Os(μ-LL′)Ru complexes based on two asymmetrical ligands LL′ (where LL′ = L¹L^1′, L²L^2′) have been synthesized and characterized. Spectroscopic analysis indicates that all complexes exhibit intense spin-allowed ligand-centered (LC) transitions at 288 nm and Ru-based moderate spin-allowed MLCT absorption between 440–450 nm. The Ru(μ-LL′)Os and Os(μ-LL′)Ru dinuclear complexes show Os-based unit absorption in the range of 565–583 nm. The Ru-based units of the complexes present different emission intensities due to differing steric hindrance at the coordination sites of the two bridging ligands. The Os(μ-LL′)Ru dinuclear complexes present weaker emission intensity than their parent monometallic complexes (μ-LL′)Ru. These results indicate that the emission of Os(μ-LL′)Ru dinuclear complexes is quenched by the Os(II)-based units.