Photophysical investigations on supramolecular interaction of a C60 derivative with free-base and metallo-phthalocyanines

The present paper reports the photophysical investigations on non-covalent interaction of a C60-derivative, namely, tert-butyl-(1,2-methanofullerene)-61-carboxylate (1) with H2- (H2-Pc) and Zn-phthalocyanine (Zn-Pc) in toluene medium. Well defined charge transfer (CT) absorption bands have been located in the ground state. Utilizing the CT absorption bands, various consequential physico-chemical parameters like oscillator strength, transition dipole moment, resonance energy, electronic coupling element and solvent reorganization energy, have been estimated for the complexes of 1 with phthalocyanines. The influence of 1 on the spectral characteristics of H2- and Zn-Pc are explained using a theoretical model that takes into account the interaction between electronic subsystems of 1 with the phthalocyanines (Pcs). Steady-state fluorescence experiment reveals large binding constants in the magnitude of 68,775 and 31,750 dm3 mol−1, for the 1:1 complexes of 1 with H2- and Zn-Pc, respectively. Density functional theoretical calculations reveal significant redistribution of charges between 1 and Pcs.