Electron transfer in the system, tris-(1,10-phenanthroline)-cobalt(II)-tris-(1,10-phenanthroline)-cobalt(III)

Abstract

The rates of electron transfer in the system tris-(1,10-phenanthroline)-cobalt(II)-tris-(1,10-phenanthroline)-cobalt(III) and analogous 2,2′-bipyridine and 2,2′,2″-tripyridine systems have been studied by a tracer technique. The rate laws as well as rate constants depend upon the anion present and the results are discussed in terms of ion-association. The rate is the same in D2O as in water but decreases in acetone-water solutions with increasing acetone concentration. The latter effect is discussed in terms of the barrier tunneling model for electron transfer. The rates and energy of activation are compared to those of other cobalt systems and the results are discussed in terms of the field strength of the ligand, metal ion electron configuration and shielding or conducting nature of the ligand.