Polarographic investigation of Cu(II) complexes with π donor ligands

Abstract The polarographic reduction of Cu(II) complex chlorides with biguanides and N ′- amidinoisoureas have been studied in aqueous 0.5 M KCl solution containing 0.01% gelatin. The complexes [except Cu(enH 2 dbg) 2+ ] show two well defined waves whose heights are pH dependent. The first (lower - E 1/2 ) and the second waves have been attributed to mono and bis (ligand)Cu(II) species respectively. Lower rate constant, higher activation energy and more negative E 1/2 values relative to those of a σ bonded Cu(II) chelates have been explained on the basis of chelate ring current and high π-basicity of the ligands. The gradual change of these values with the size of the N -substituents is due to decreased π-basicity of the respective ligands. Ratio of mono and bis biguanide with pH change has been calculated and activation energies for the complexes, calculated polarographically, have been found to be closely related to D q values obtained from absorption band maxima.