The outer-sphere association of p-sulfonatothiacalix[4]arene with some Co(III) complexes: The effect on their redox activity in aqueous solutions

Abstract

The effect of the ion-pairing of Co(III) complexes with p-sulfonatothiacalix[4]arene (STCA) on Fe(II)-Co(III) electron transfer rate was evaluated from the analysis and comparison of kinetic data in double Co(III)-Fe(II) and triple Co(III)-Fe(II)-STCA systems at various concentration conditions. Complexes [Co(en)3]3+(1), [Co(en) 2ox]+(2), [Co(dipy)3]3+ (3), [Co(His)2]+(4) and [Fe(CN)6]4- were chosen as Co(III) and Fe(II) compounds. The effect of STCA was found to correlate with the association mode. The outer-sphere association with STCA was found to exhibit the insignificant effect on Fe(II)-Co(III) electron transfer k et constants for complexes 3 and 4 with bulky and rigid chelate rings, while more sufficient inclusion of flexible ethylendiaminate rings of 1 and 2 into the cavity of STCA results in the unusual increase of k et. © 2007 Springer Science+Business Media, Inc.