The effective electron-transfer distance in dinuclear ruthenium complexes containing the unsymmetrical bridging ligand 3,5-Bis(2-pyridyl)-1,2,4-triazolate

Abstract

Electroabsorption (Stark effect) measurements on the intervalence charge-transfer (IVCT) transitions in the diastereoisomers of [{Ru(bpy)2}2(-bpt-)]4+ [bpy = 2,2-bipyridine, bpt- = 3,5-bis(2-pyridyl)-1,2,4-triazolate] in n-butyronitrile glass at 77 K reveal effective charge-transfer distances of 5.92 ± 0.03 Å for the / form and 5.44 ± 0.04 Å for the / form. These values correspond to approximately 95 and 88 %, respectively, of the geometrical metal-metal distance of 6.185(10) Å, obtained from the X-ray crystal structure of the cation in the related complex ()-[{Ru(Me2bpy)2}2(-bpt-)](PF6)3. The results are consistent with a localized Class II classification for the mixed-valence systems [{Ru(pp)2}2(-bpt-)]4+, where pp = bpy, Me2bpy = 4,4-dimethyl-2,2-bipyridine.