Photophysical investigations on determination of molecular structure and binding strength of supramolecular complexation between fulleropyrrolidine and a designed bisporphyrin in solution

The present article reports, for the first time, the photophysical aspects of non-covalent interaction of a fullerene derivative, namely, C60 pyrrolidine tris-acid ethyl ester (PyC60) with a designed bisporphyrin (1) (having carbazole spacer unit) in toluene. Absorption spectrophotometric studies reveal that decrease in the absorption intensity of the Soret absorption band of 1 takes in presence of PyC60 in the solvent studied. Steady state fluorescence studies reveal efficient quenching of fluorescence intensity of 1 in presence of PyC60. Static quenching model explores a binding constant (KS) value of 2,910 dm3 mol−1 in toluene. Time resolved emission study establishes static quenching mechanism for the investigated supramolecule in non-polar solvent. Molecular mechanics calculations in vacuo evoke the single projection structure of the PyC60-1 complex and interpret the geometrical arrangement of both PyC60 and 1 during non-covalent complexation.

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► First time report on PyC60-bisporphyrin (1) complexation in solution.
► Fluorescence study elicits efficient quenching of 1 in presence of PyC60.
► Time-resolved emission study reveals static quenching mechanism.
► MMMF calculations explore geometric alignment of PyC60-1 entity.