Microwave-assisted synthesis, electrochemistry and spectroelectrochemistry of phthalocyanines bearing tetra terminal-alkynyl functionalities and click approach

Abstract

This work provides a successful, easy and efficient process for the preparation of both symmetrically tetra nonperipheral and peripheral terminal alkynyl substituted zinc and cobalt phthalocyanines (Pcs) and click approach. Two different routes, conventional and microwave-assisted synthesis, have been used by direct cyclotetramerization reactions. While novel cobalt Pcs were synthesized by using only conventional method, a very fast, efficient and novel method of preparation using microwaves has been also described for the synthesis of ZnPc complexes. In order to develop a novel phthalimide conjugated zinc phthalocyanine, [2,9(10),16(17),23(24)-tetrakis((1-(2-(1,3-dioxoisoindoline-2-yl)ethyl)-1H-1,2,3-triazol-4-yl)ethoxy)phthalocyaninato]zinc(II), was also synthesized via the click reaction. The precursors and the target complexes were characterized comprehensively with H-1 NMR, C-13 NMR, FT-IR, UV-Vis spectra together with elemental and mass analyses. Electrochemical properties of peripheral and nonperipheral complexes were examined to determine effect of the position of the substituents. While nonperipheral substitution of the complexes shifted the redox processes toward the negative potentials, peripherally substituted complexes gave more reversible processes. On the other hand, while ZnPc complexes gave Pc ring-based electron transfer reactions and metal-based reduction and oxidation reactions were also recorded with CoPc complex. Moreover phthalimide-triazole substituent on the periphery was also found to affect the electrochemical properties of ZnPc complex. (C) 2016 Elsevier Ltd. All rights reserved.