Electrochemical and electrical properties of novel mono and ball-type phthalocyanines

Abstract

New mononuclear Co(II) phthalocyanine 3 and ball-type homobinuclear Cu(II)-Cu(II) and Zn(II)-Zn(II) phthalocyanines, 4 and 5 respectively, were synthesized using the corresponding metal salts and the 4,4'-(methane-5-methyl-3-(1-methylcyclohexyl)-2,2'-phenoxy)diphthalonitrile ligand 2, which was prepared from the reaction of 4-nitrophthalonitrile with bis[2-hydroxy-5-methyl-3-(1-methylcyclohexyl)phenyl]methane (1). The novel compounds 3-5 have been characterized using their elemental analysis data and UV-Vis, IR, H-1 NMR and MALDI-TOF mass spectra. The redox properties of the complexes were investigated by cyclic voltammetry in a non-aqueous medium. The electrochemical measurements showed that complex 5 forms a mixed-valence reduction species, due to the strong intramolecular interactions between the two phthalocyanine rings. Complex 4 displayed Pc ring-based redox signals with very high peak currents, which were attributed to the adsorption of the complex on the working electrode. Dc and ac electrical properties of films of 3, 4 and 5 were also investigated as a function of temperature (295-523 K) and frequency (40-10(5) Hz). From the dc conductivity measurements, activation energy values of the films were found, being 0.70, 0.66 and 0.68 eV for films of 3, 4 and 5, respectively. From impedance spectroscopy measurements, it was observed that the bulk resistance decreases with increasing temperature, indicating semiconductor properties