Effect of changing the charge of an iron(II) chelate on electron transfer to a cobalt(III) complex-containing poly(methacrylic acid-co-styrenesulfonic acid) in aqueous solution

Three different poly(methacrylic acid-co-styrenesulfonic acid)-bound cis-Co-III(en)(2)(OH2)L species (CoPMAS) (en = ethylenediamine, L = methacrylate residue on the polymer) having different degrees of copolymerization and varying amounts of bound Co-III were synthesized. The effect of charge on the iron(II) chelate on the electron transfer between CoPMAS and [Fe(edta)](2-) (H(4)edta = ethylenediamine-N,N,N',N'-tetraacetic acid) or [Fe(hedta)](-) [H(3)hedta = N-(2-hydroxyethyl)ethylenediamine-N, N',N'-triacetic acid) was investigated. The Co-III was reduced via electron transfer from Fe-II to CoPMAS. The degree of reduction of Co-III by both iron(II) chelates, R(Co), and the electron-transfer rate significantly depend on the proportion of functional groups having a negative charge on the polymer chain. The alpha'-dependence of R(Co) for both iron(II) chelates was similar, but their reaction rates differed: the rate for [Fe(hedta)](-) being larger than that for [Fe(edta)](2-). The value of R(Co) was independent of the charge of the iron(II) chelate, but the reaction rate was influenced by the charge.