Electrochemical Properties of n-Sulfonatothiacalyx[4]arene
Complexes with Fe3+ and [Co(dipy)3]3+ Ions

N. V. Nastapova, A. S. Stepanov, V. V. Yanilkinz, V. A. Burilov, V. V. Skripacheva,
A. R. Mustafina, S. E. Solov’eva, and A. I. Konovalov

Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center,
Russian Academy of Sciences, 8, ul. Arbuzova, Kazan, 420088 Russia

Received May 25, 2008

Abstract—The electrochemical properties of n-sulfonatothiacalyx[4]arene (H4XNa4) complexes with
[Co(dipy)3]3+ and Fe3+ ions were studied by means of cyclic voltammetry in aqueous solution at pH 2.5. The
observed single-electron reduction of [Co(dipy)3]3+ bound extraspherically to the upper rim and Fe3+ ion bound
intraspherically to the lower rim of n-sulfonatothiacalyx[4]arene in binary [Co(dipy)3]3+ · H3X5frame0, H3X5frame1 · Fe3+,
and ternary [Co(dipy)3]3+ · H3X5frame2 · Fe3+ heterometal complexes was more difficult than in the free state. The
reversible single-electron transfer to the metal ion results in lower binding energy ([Co(dipy)3]3+, G0 =
3.9kJ/mol) or in full fast dissociation of the complex (Fe3+). The ternary complex in the solution forms the
aggregates, in which inner encapsulated Fe(III) and Co(III) ions are not reduced on the electrode. Their quan-
titative reduction takes place by the relay mechanism of intra– and intermolecular electron transfer through
electrochemically generated [Co(dipy)3]2+ outer ions.

Key words: n-sulfonatothiacalyx[4]arene, [Co(dipy)3]3+ and Fe3+ ions, complex, electrochemical reduction

DOI: 10.1134/S102319350907012X

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