Synthesis, characterization and electrochemical properties of tetra 7-oxy-3-biphenylcoumarin substituted metal-free, zinc(II), cobalt(II) and indium(III) phthalocyanines

Abstract

A novel coumarin, 7-hydroxy-3-biphenylcoumarin 1, was prepared by Perkin reaction of 4-biphenylacetic acid with 2,4-dihydroxybenzaldehyde in the presence of NaOAc/Ac2O. In addition, two respective phthalonitril derivatives, 7-(2,3-dicyanophenoxy)-3-biphenylcoumarin 2/7-(3,4-dicyanophenoxy)-3-biphenylcoumarin 3, were synthesized by nucleophilic aromatic substitution reactions of 3-nitro/4-nitrophthalonitrile with 7-hydroxy-3-biphenylcoumarin 1. The synthesis of corresponding novel zinc(II) phthalocyanines (Pcs) 4 and 8, cobalt(II) Pcs 5 and 9, indium(III)(Cl) Pcs 6 and 10, and metal-free Pcs 7 and 11, carrying 7-oxy-3-biphenylcoumarins in the non-periphery/periphery was performed by cyclotetramerization of compounds 2 or 3. The novel chromogenic coumarin 1, phthalonitriles (2 and 3) and Pcs (4–11) were characterized by elemental and spectroscopic analysis, including 1H NMR, FT–IR, UV–vis spectral and MALDI–TOF mass data. The redox properties of these compounds were also investigated by voltammetry and in situ spectroelectrochemistry on Pt in dimethylsulfoxide/tetrabutylammonium perchlorate. Furthermore, the electrocatalytic performances of the compounds for the oxygen reduction reaction were also studied.