Spectral investigations of meso-tetraalkylporphyrin-fullerene host–guest complexes

Abstract

Meso-tetraalkylporphyrins and their Zn(II) complexes were synthesized and characterized by various spectroscopic techniques. Single crystal X-ray structure of meso-tetrapropylporphyrin (3) revealed the orientation of alkyl chains and planar conformation of porphyrin macrocycle. Spectroscopic, photophysical and electrochemical redox properties of self-assembled donor–acceptor dyads formed by meso-tetraalkylporphyrins and fullerene C60 were investigated. These studies revealed 1:1 supramolecular dyad formation between the electron donor porphyrins and the electron acceptor, fullerene entities. The determined association constants (K) follow the order: H2TMeP (1) > H2TEtP (2) > H2TPrP (3) > H2THexP > H2TPP. The effect of alkyl chain length on porphyrin-fullerene complexation was investigated. The redox behavior of self-assembled dyads was investigated in PhCN containing 0.1 M TBAPF6 as supporting electrolyte. The oxidation potentials of dyads are positively shifted (20–100 mV) as compared to corresponding meso-tetraalkylporphyrins indicating the supramolecular interactions between the constituents in the ground state. The geometric and electronic structure of 1:C60 was probed by DFT calculations which suggested the possibility of charge transfer from meso-tetraalkylporphyrin to fullerene C60.