Six arylazoxy compounds and one arylazo derivative, including calvatic acid were studied by cyclic voltammetry, in protic (aqueous/ethanolic phosphate buffer, pH 6.9) and aprotic (DMF + TBAP) media and submitted to molluscicidal bioassays. In protic medium, all the arylazoxycyanides behaved similarly. A 4e(-)/4H(+) unique reduction wave generating the hydrazo derivative is evident, as well as its counterpart for oxidation, in the reverse scan, to the azo derivative, which suffers further reduction, in a successive scan. The intermediacy of the azo compound in the reduction process of calvatic acid was recognised, by voltammetric comparison with its chemically reduced azo derivative, which presented a bielectronic reversible wave. Some differences in the electrochemical features are evident for the sulfonyl and carbamoyl azoxyderivatives. In aprotic medium, the electrochemical behaviour of the arylazoxycyanides and the sulfonyl compound was similar, represented by two main waves, the first one reversible, corresponding to the uptake of one electron and a second one, much more intense and irreversible. A stable anion-radical is produced at the first negative potential, followed by a series of electron transfers and kinetically-dependent protonation steps leading, depending on the structure and/or scan rate, to the azo or hydrazo derivatives. For calvatic acid, a more complex feature was evident due to the participation of the acidic proton. For the carbamoyl derivative, the voltammetric behaviour, at low scan rates, showed. an irreversible wave, indicative of an unstable anion-radical, prone to suffer a coupled chemical reaction. All the azoxycyanides showed significant activities against the mollusk Biomphalaria glabrata, while the sulfonyl and carbamoyl derivatives were inactive as molluscicides. These activities are reported for the first time, extending the range of biological activities of the arylazoxy group. Despite the small number of compounds studied, a relationship between Epic (mainly in aprotic medium) and molluscicidal activities was observed, suggesting a trend: the more electrophilic compounds are the more active. (C) 2003 Elsevier Science B.V. All rights reserved.