Reactivity of Tetraphenoxy-Substituted Phthalocyanines in Acid–Base Reactions with Organic Bases

The interaction of tetra-4-(2-methoxyphenoxy)phthalocyanine and tetra-4-(3-methoxyphenoxy)phthalocyanine with pyridine, 2-methylpyridine, morpholine, piperidine, n-butylamine, tert-butylamine, diethylamine, and triethylamine in benzene has been studied. The acid–base reaction involving n-butylamine and piperidine is an unusually slow process, leading to the formation of kinetically stable proton transfer complexes. The structure of these complexes is proposed. The change in the reactivity of tetraphenoxy-substituted phthalocyanines depending on the proton-acceptor ability and spatial structure of the nitrogen-containing base is considered. Pyridine, 2-methylpyridine, and morpholine do not form proton transfer complexes because of their weak basicity. A similar picture is observed in the case of tert-butylamine, diethylamine, and triethylamine, which have a more sterically screened nitrogen atom than that in n-butylamine and, as a result, do not react with tetraphenoxy-substituted phthalocyanines.