Oxidation of benzyl alcohol by novel peripherally and non-peripherally modular C2-symmetric diol substituted cobalt (II) phthalocyanines

In this study, a modular ligand structure was designed by altering the binding position of the phenyl group at backbone of hydrobenzoin. A series of regio isomeric substituted phthalonitriles derived from this modular C₂-symmetric ligand was synthesized and characterized. Then, eight cobalt (II) phthalocyanines (CoPc) were obtained from the reaction of phthalonitrile derivatives with cobalt (II) chloride. The catalytic activities of synthesized cobalt (II) phthalocyanines were tested for benzyl alcohol oxidation in acetonitrile using tert-butylhydroperoxide as the oxygen source and in the presence of N-bromosuccinimide as an additive at 80 °C for 5 hr of the reaction. In this sense, the effect of substrate to catalyst ratio and oxidant to catalyst ratio have been studied in detail for getting the highest benzaldehyde selectivity (up to 83%). The effect of structural design of substituents at peripheral or non-peripheral positions of phthalocyanine skeleton on the catalytic activity performance of cobalt (II) phthalocyanines in benzyl alcohol oxidation was also clarified. All newly synthesized compounds are characterized by FT-IR, ¹H NMR, IR, UV–Vis and MALDI-TOF MS spectral data.