EFFECT OF ALPHA-CYCLODEXTRIN AND BETA-CYCLODEXTRIN ON THE ELECTROCHEMISTRY OF METHYLHEPTYLVIOLOGEN AND DIBENZYLVIOLOGEN

The electrochemistry of N-methyl-N'-heptyl-4,4'-bipyridinium (C1C7V2+) and N,N'-dibenzyl-4,4'-bipyridinium (BBV2+) salts with alpha-cyclodextrin and beta-cyclodextrin (CD) was studied. The cyclic voltammetric behavior of both viologens revealed a cyclodextrin-induced conproportionation reaction between the electrogenerated viologen neutral forms and viologen dications with beta-CD, but not with the alpha form. Both alpha-CD and beta-CD suppress dimerization of C1C7V.+, whereas only beta-CD is effective for disruption of the BBV.+ dimer. These results are interpreted in terms of the involvement of the bipyridine ring and benzyl group, depending on the oxidation state of viologen, in the inclusion complexation with beta-CD, but not significantly with alpha-CD.