Cobalt complexes of dibenzotetraaza[14]annulene (CoTAA), 5,7,12,14-tetramethyldibenzotetraaza[14]annulene (CoTMTAA), and dichlorodibenzotetraaza[14]annulene (CoTAACl2) have been studied by voltammetry in benzonitrile (BN). Their electropolymerization from solutions in BN was performed by oxidation at carbon and platinum electrodes. The Co(II)/Co(I) and Co(III)/Co(II) redox systems are clearly apparent on the voltammograms, as well as the electroactivity of the conducting polymer, when the electrode is in contact with the non-aqueous solvent. More surprising is the fact that the modification of electrode surfaces is also possible from the oxidation of aqueous acidic solutions of CoTAA and CoTAACl2 (2.25 M H2SO4). In contact with an acidic aqueous medium (0.5 M H2SO4), the Co(III)/Co(II) system of poly(CoTAA) is fully reversible. The polymer thus obtained can grow as a remarkably thick, dense and conducting phase. © 2000 Elsevier Science B.V.