Synthesis, characterization, spectral and electrical properties of peripherally tetratriazole-substituted phthalocyanines and its metal complexes

Abstract

The substituted [1,2,4]triazole 3 was obtained from the reaction between compound 1 and compound 2. Novel substituted phthalonitrile 5 was prepared by the substitution of the nitro group of 4-nitrophthalonitrile 4 with triazole moiety 3. The synthesis of metal-free, zinc, nickel, cobalt and copper phthalocyanines with four substituted [1,2,4]triazole groups on peripheral position were performed from cyclotetramerization of novel substituted dinitrile compound 5. Metal-free phthalocyanine 6 and its Zn-, Ni-, Co- and Cu- complexes 7-10 were prepared in DMAE at reflux temperature. All new compounds were characterized by a combination of elemental analyses, IR, 1H/ 13C NMR, MS and UV-vis spectroscopy. Aggregation behaviors of NiPc 8 and CuPc 10 were also investigated. While NiPc 8 was aggregated in acetone, DMF, DMSO, THF, ethylacetate and toluene and non-aggregated in dichloromethane and pyridine at 10 × 10 -6 mol dm -3 concentration, CuPc 10 showed monomeric behavior in dichloromethane, DMSO, DMF, pyridine, THF and showed aggregation in acetone, ethylacetate and toluene at 14 × 10 -6 mol dm -3 concentration. On the other hand, substituted NiPc 8 and CuPc 10 did not show aggregation behavior between 4 × 10 -6-14 × 10 -6 mol dm -3 concentration range in chloroform. Dc and ac conductivity and Impedance Spectroscopy (IS) studies were also done on thin films of compounds 6, 7, 8, 9 and 10 as a function of temperature (295-523 K) and frequency (40-10 5 Hz) under vacuum (?2 × 10 -3 mbar) in dark. The compounds 7, 8, 9 and 10 showed nearly same dc conductivity values in the measured temperature range. Variation of dc conductivity of 6, 7, 8, 9 and 10 with temperature exhibited the semiconducting behavior. Variation of ac conductivity of the films with frequency represented by the function ? ac = A? s. The results indicated that charge transport mechanism of the films can be explained by hopping and small polaron tunneling model for 6, 7, 8, 9 and 10 depending on temperature and frequency region. Results of the impedance spectra measurements showed that, at high temperatures, depressed semicircles with different radius indicate deviation from Debye dispersion relation. © 2012 Elsevier B.V. All rights reserved.