Synthesis and electrocatalytic properties of octaalkoxycobalt phthalocyanine for the oxidation of 2-mercaptoethanol

We report on the synthesis of cobalt 2,3,9,10,16,17,23,24-octakis(2-ethylhe xyloxy)phthalocyanine. This complex, when pre-adsorbed onto graphite electr odes, is active for the electro-oxidation of 2 mercaptoethanol. Its activit y is higher than that of cobalt phthalocyanine and cobalt tetrasulfonated p hthalocyanine adsorbed on graphite. The voltammetric response of adsorbed c obalt 3,4-octaethylhexyloxyphthalocyanine exhibits both Co(II)/Co(I) and Co (III)/Co(II) reversible processes. However, the Co(III)/Co(II) couple shows a pH dependence that is different from that reported for other cobalt phth alocyanine derivatives. The much higher activity of cobalt 3,4-octaethylhex yloxyphthalocyanine compared with cobalt tetrasulfonated phthalocyanine and cobalt phthalocyanine is attributed to the electron-donating ability of th e ethylhexyloxy substituents on the periphery of the phthalocyanine ligand. Copyright (C) 1999 John Wiley & Sons, Ltd.