AQUEOUS ELECTROCHEMISTRY OF MONONUCLEAR AND BINUCLEAR COPPER(II) COMPLEXES WITH POLYAZA[N]PARACYCLOPHANE LIGANDS

The aqueous electrochemistry of the Cu2+ complexes of the azaparacyclo phanes 2,6,9,13-tetraaza[14]paracyclophane (L1), 2,5,8,11-tetraaza[12] paracyclophane (L2) and 2,5,8,11,14-pentaaza[15]paracyclophane (L3) ha s been studied. Copper(II) forms stable mononuclear [CuH,L](2+r)+ spec ies with all three ligands (r = -1 to 1, L1 and L2; -1 to 2, L3) while L2 and L3 also form binuclear [Cu2H(r)L](4+r)+ species (r = -2, L2; 0 to -2, L3) in a pH-dependent stepwise manner. Frozen-solution ESR mea surements show that all the complexes prefer a square-planar co-ordina tion. In neutral and basic media reduction at mercury and glassy carbo n electrodes occurs in two quasi-reversible steps, indicating the form ation of stable Cu+ species. Stabilization of the Cu+ complexes with r espect to disproportionation in the order L3 > L1 > L2 has been found.