Spectroscopic and Theoretical Insights on Non-covalent Binding of PyC 60 with a Designed Diporphyrin in Solution

The present paper reports the spectroscopic and theoretical investigations on non-covalent interaction of a functionalized fullerene, namely, C 60 pyrrolidine tris-acid ethyl ester (PyC 60 ) with a designed diporphyrin ( 1 ) in solvents having varying polarity: toluene and benzonitrile. UV–Vis studies reveal that PyC 60 undergoes an appreciable amount of ground state electronic interaction with 1 as the intensity of the Soret absorption band of 1 suffers a considerable decrease in the presence of PyC 60 in both solvents. Steady state fluorescence studies elicit efficient quenching of the fluorescence of 1 in the presence of PyC 60 . The binding constant ( K ) values of the PyC 60 / 1 complex follow the trend: PyC 60 / 1 (in toluene, K = 2,825 dm 3 ·mol −1 ) < PyC 60 / 1 (in benzonitrile, K = 3,540 dm 3 ·mol −1 ). Time resolved emission studies establish a relatively long-lived charge separated state for the PyC 60 / 1 complex in benzonitrile. The magnitude of the quantum yield of the charge separated state for the PyC 60 / 1 complex indicates that, while energy transfer is feasible in toluene, there is strong propensity of electron transfer in benzonitrile.