Binuclear ruthenium and osmium mixed-valence complexes containing fused and flexible polypyridyl bridging ligands

{Os(bpy)2}2+ and {Ru(CN)4}2− mononuclear and binuclear complexes with ligands 2,3-di-(2-pyridyl)quinoxaline (dpq) and dipyrido[2,3-a:3′,2′-c]phenazine (ppb) have been prepared. For the binuclear complexes a splitting in oxidation potentials is observed consistent with the formation of mixed-valence species with comproportionation constants (Kcom) ranging from 2.5 × 104 to 1.8 × 106. The electronic absorption spectra of the mixed-valence species reveal IVCT transitions in the near infrared region. The absorption maximum for the IVCT band ranges from 5800 to 9980 cm−1 and the extinction coefficients from 80 to 6300 M−1 cm−1. In general the {Os(bpy)2}2+ complexes show larger Kcom values and more intense IVCT bands than the corresponding {Ru(CN)4}2− complexes.

Graphical abstractHomonuclear binuclear complexes with ligands 2,3-di-(2-pyridyl)quinoxaline and the fused dipyrido[2,3-a:3′,2′-c]phenazine and {Os(bpy)2}2+ and {Ru(CN)4}2− have been prepared. The oxidation potentials are split consistent with the formation of mixed-valence species with comproportionation constants (Kcom) ranging from 2.5 × 104 to 1.8 × 106. The electronic absorption spectra of the mixed-valence species reveal IVCT transitions in the near infrared region. The absorption maximum for the IVCT band ranges from 5800 to 9980 cm−1 and the extinction coefficients from 80 to 6300 M−1 cm−1.Figure optionsDownload full-size imageDownload as PowerPoint slide