Synthesis, electrochemical, in situ spectroelectrochemical and in situ electrocolorimetric characterization of new phthalocyanines peripherally fused to four flexible crown ether moieties

Abstract

Novel Ni(II), Zn(II), Co(II) and Cu(II) phthalocyanines with four peripheral 4-[methyleneoxy(18-crown-6)] groups have been synthesized via the cyclic tetramerization of 4-[{(18-crown-6)-yl}methyleneoxy]phthalonitrile and the corresponding metal salts (NiCl 2, Zn(CH 3COO) 2, CoCl 2 and CuCl 2). The thermal stabilities of the metal-free and metallophthalocyanine compounds were determined by thermogravimetric analysis. The structures of the target compounds were confirmed using elemental analysis, IR, 1H-NMR, 13C-NMR, UV–Vis and MS spectral data. Voltammetric and in situ spectroelectrochemical measurements show that while the cobalt phthalocyanine complex gives both metal-based and ring-based redox processes, the metal-free, nickel, zinc and copper phthalocyanines show only ring-based reduction and oxidation processes. An in situ electrocolorimetric method has been applied to investigate the color of the electro-generated anionic and cationic forms of the complexes.