Investigation of the Spectroscopic, Electrochemical, and Spectroelectrochemical Properties of Osmium(II) Complexes Incorporating Polyazine Bridging Ligands: Formation of the Os/Os and Os/Ru Mixed-Valence Complexes
A series of homobimetallic Os(II) complexes have been prepared of general formula [[(bpy)2Os]2(BL)]4+ (where BL = bridging ligand and bpy = 2,2′-bipyridine). The bridging ligands used were 2,3-bis(2-pyridyl)pyrazine (dpp), 2,3-bis(2-pyridyl)quinoxaline (dpq), and 2,3-bis(2-pyridyl)benzoquinoxaline (dpb). The compounds' electrochemical, spectroscopic, and spectroelectrochemical properties have been studied and comparisons have been made with previously prepared Os/Ru heterobimetallic and Ru/Ru homobimetallic complexes incorporating the same bridging ligands. The lowest energy electronic transitions in these homometallic systems have been assigned as Os(dπ) BL(π*) 1MLCT transitions. On the basis of spectroelectrochemical experiments, assignments for the electronic absorption spectra have been made. The Os(II)/Os(III) and Os(III)/Ru(II) mixed-valence complexes of this series of ligands have been prepared. These mixed-valence systems display rich near-infrared spectra. Values for the extent of electron delocalization between the metal centers, α2, range from 2.7 × 10−3 to 1.0 × 10−2, which indicates that these systems are much more weakly coupled Robin and Day class II systems than has been previously implied through electrochemical analysis.
Richter, Mark M., and Karen J. Brewer. "Investigation of the spectroscopic, electrochemical, and spectroelectrochemical properties of osmium (II) complexes incorporating polyazine bridging ligands: formation of the Os/Os and Os/Ru mixed-valence complexes." Inorganic Chemistry 32, no. 13 (1993): 2827-2834.