OXIDATION OF COBALT(II) MACROCYCLES BY TRIS(BIPYRIDYL)RUTHENIUM(III) IONS

The kinetics of the electron-transfer reactions between Ru(bpy)33+ and selected Co(II) complexes were evaluated by laser flash photolysis. The cobalt(II) complexes investigated were (H2O)2Co(N4mac)2+, with N4mac = [14]aneN4, C-meso-Me6[14]aneN4, tim ([14]tetraeneN4), [15]aneN4, and tmc (1,4,8,11-tetramethylcyclam). The respective second-order rate constants at 25 °C, μ = 0.10 M, are 3.2 × 107, 7.8 × 106, 2.1 × 107, 1.7 × 107, and 6 × 105 M−1 s−1. The results have been evaluated for their agreement with the Marcus theory. The complex Co(tmc)2+ also reacts with Ru(phen)33+ (k = 1.0 × 106 M−1 s−1) and with Ru(4,7-Me2phen)33+ (k = 3.2 × 104 M−1 s−1). These cobalt(II) complexes also quench the emission of the excited-state complex *Cr(bpy)33+. Quenching occurs by electron transfer, except for Co(tmc)2+, which appears to react by energy transfer. © 1990, American Chemical Society. All rights reserved.