Photophysical insights into supramolecular interaction of a designed bisporphyrin with fullerenes C60 and C70

The present paper reports the photophysical investigations of a designed bisporphyrin (1), and its supramolecular complexes with C60 and C70 in toluene medium. UV–vis studies reveal appreciable ground state interaction between fullerenes and 1. The stoichiometry of the fullerene complexes of 1 is found to be 1:1. Steady state fluorescence studies elicit quenching of fluorescence of 1 in the presence of fullerenes. The binding constants of the C60/1 and C70/1 complexes are estimated to be 3760 and 31,222.5 dm3 mol−1, respectively. Time resolved emission studies establish relatively long-lived charge separated state for the C70/1 complex. Molecular mechanics calculations in vacuo evoke the stereoscopic structures of the fullerene/1 complexes and interpret the stability difference between C60 and C70 complexes of 1 in terms of heat of formation values.