| Popis: |
Cyclic voltammetry in water-free N,N-dimethylformamide (DMF) containing 0.1 M tetraethylammonium hexafluorophosphate (TEAH) at −54°C showed a complete set of six one-electron reversible reduction wave for each mixed-ligand ruthenium(II) 2,2′-bipyridine (bpy) complex [Ru(bpy)3-nLn]2+ (L=2-(2′-pyridyl)quinoline (pq), 2,2′-bipyrazine (bpz), 4,4′-diphenyl-2,2′-bipyridine (4-dbpy); n=0,1, 2, and 3), and extra waves for [Ru(bpy)3-n(4-dbpy)n]2+ (n=3, 2, and 1). It is demonstrated that the first three reduction waves are independent of an ion-association effect with tetraethylammonium cation, while their next three are affected. Cyclic voltammetric and spectroscopic data in acetonitrile and theoretical considerations lead to linear relations with unit slope between absorption (and emission) energy and the oxidation-reduction half-wave potential difference for these mixed-ligand Ru(II) bpy complexes. It is suggested that these relations can be an energy criterion for assignment of charge-transfer transitions (absorption and emission) for transition metal bpy complexes. |
