The pentanuclear Zn(II) and Co(II) complexes of phthalocyanine substituted with four 15-membered tetraazamacrocyles (15M-TAMPc) have been studied in dimethyl sulphoxide solution by cyclic voltammetric methods. The cyclic voltammogram of Zn(II) complex of 15M-TAMPc is characterised with one cathodic wave and two anodic waves. The reduction wave and the second oxidation wave show irreversible behaviour. The first oxidation peak appears as a quasi-reversible one on the anodic scan. These are one-electron oxydo-reduction waves. For the Co(II) analog, two one-electron reduction waves were observed. These waves show a quasi-reversible behaviour at all sweep rates studied. The reaction mechanisms and diffusion coefficients have been investigated in this work.