EFFECTS OF CONFORMATIONAL TRANSITION ON ELECTRON-TRANSFER REACTION BETWEEN POLY(METHACRYLIC ACID-CO-STYRENESULFONIC ACID)-BOUND CO(III) COMPLEXES AND FE(EDTA)(2-) IN AQUEOUS-SOLUTION

Three Co(III) complex-containing poly(methacrylic acid-co-styrenesulfo nic acid)s (CoPMASs) with different copolymerization ratios were synth esized, and the effects of conformational transition on electron-trans fer reaction between CoPMAS and Fe(edta)(2-) (edta=ethylenediamine-N,N ,N',N'-tetraacetic acid) were investigated, The conformation of CoPMAS varied with the ratio of residues having negative charge as carboxyla te and styrenesulfonate on one polymer chain (alpha'). The alpha'-indu ced conformational transition of CoPMAS was similar to that of PMAS as the parent polymer. In electon-transfer reactions, the degree of redu ction of Co(III) complex by Fe(edta)(2-) depended on alpha'. This depe ndence is explained by the decrease of shield effect: the Co(III) comp lex surrounded in polymer backbone was exposed to the aqueous phase by the alpha'-induced conformational transition. The rates for the elect ron-transfer reactions of CoPMASs with Fe(edta)(2-) increased with inc reasing alpha'. The increase was attributed to a lowering of negative charge density around the Co(III) complex by the alpha'-conformational transition.