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

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 H-1 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. (C) 2016 Elsevier Ltd. All rights reserved.