Synthesis, electrochemical and complexation studies of Zn(II) aryloxyporphyrins with fullerene C60

A new series of aryloxyporphyrins bearing benzyl and naphthyl substituents viz., ZnTBPP (1), ZnTNPP (2) and ZnONPP (3) has been synthesized and characterized by UV-vis, fluorescence and 1 H NMR spectroscopic techniques and mass spectrometry. 1–3 have been utilized as donors to interact with fullerene (C60) acceptor to form 1:1 complex in toluene at 298 K. The subsequent investigation into quenching measurements with concomitant increase in fullerene concentration revealed effective quenching constants. The calculated association constants were in the order of 103 M-1. However, ZnTNPP (2) exhibited higher binding constant as compared to other analogs due to effective p–p interactions. ZnONPP (3) exhibited 3.4 times lower association constant than ZnTNPP (2) due to steric hindrance offered by meso-(3,5-dinapthyloxyphenyl) groups. The geometric and electronic structure of Zn(II) porphyrin-fullerene dyad was probed by DFT calculations which suggested the possibility of charge transfer from meso-aryloxyporphyrin core to fullerene C60.