Electronic structure of the "molecular light switch" bis(bipyridine)dipyrido[3,2-a:2',3'-c]phenazineruthenium(2+). Cyclic voltammetric, UV/visible and EPR/ENDOR study of multiply reduced complexes and ligands

The chelate ligand dipyrido[3,2-a:2',3'-c]phenazine (dppz), its 11,12-dimethylderivative dmdppz, and corresponding complexes with [Ru(bpy) 2 ] 2+ were studied in multiply reduced states by low-temperature cyclic voltammetry and UV/vis and EPR spectroscopy. The (dm)dppz ligands are reduced in two reversible steps. Higly resolved EPR and 1 H-ENDOR spectra of the intermediate anion radicals were obtained and analyzed.