| Abstract: | A modified synthetic route for the complexes Cu(II)5,7,12,14-tetramethyldinaphtho b,i]1,4,8,11]tetraaza14]annulene], Cu(II)tmdnTAA], and Cu(II) 5,7,12,14-tetramethyl-6,13-dichloro-dinaphthob,i]1,4,8,11]tetraaza14]annulene], Cu(II)dCltmdnTAA], is presented in this work. The electrochemical characterization of both complexes and their precursors, bis(2,4-pentanedionato)copper(II)], Cu(II)(acac)2] and bis(3-chloro-2,4-pentanedionato)copper(II)], Cu(II)(3-Cl-acac)2], respectively, under nitrogen and carbon dioxide is also presented. The voltammetric response of Cu(II)(acac)2] and Cu(II)(3-Cl-acac)2] are different compared to Cu(II)tmdnTAA] and Cu(II)dCltmdnTAA] under nitrogen. Precursors show the reduction of Cu(I) to Cu(0) and the tetraazadinaphtho14]annulene complexes do not. The chlorine substituted complex has a lower reduction potential than the unsubstituted homologue under nitrogen atmosphere. However, the contrary response is obtained in the presence of carbon dioxide: the unsubstituted complex is more catalytic in terms of potential because the current discharge appears 270?mV shifted to the anodic region. These facts can be explained in terms of electronic and steric effects. The modified electrode obtained by oxidative electropolymerization of Cu(II)tmdnTAA] over glassy carbon electrode presented a suitable amperometric response for the sulfite reduction in acidic medium (pH?=?2.7). A linear correlation was observed for the catalytic current and sulfite concentration between 0.6–6.0?mM range. |
