Absorption spectrophotometric, fluorescence and theoretical investigations on supramolecular interaction of a designed bisporphyrin with C60 and C70

The present article reports the spectroscopic and theoretical investigations on supramolecular interaction between fullerenes (C60 and C70) and a designed bisporphyrin, namely 1, in toluene. Job's method of continuous variation establishes 1:1 stoichiometry of the fullerene/1 complexes. Both absorption spectrophotometric and steady-state fluorescence studies reveal effective and selective interaction between fullerenes and 1 as average binding constants (K) for the C60/1 and C70/1 complexes are enumerated to be 34,700 and 359,925 dm3 mol−1, respectively. Large selectivity ratio in K  , i.e., KC70/KC60KC70/KC60, indicates that 1 acts as an effective molecular tweezers for C70 in solution. Time-resolved fluorescence study evokes that the quenching of fluorescence of 1 by fullerenes is of static type in nature. Molecular mechanics calculations in vacuo determine the energies and single projection structures of the supramolecular systems, which provide very good support in favor of strong binding between C70 and 1.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► The present paper introduces a newly designed Zn2-bisporphyrin, namely, 1. ► 1 serves as an effective and selective molecular tweezers for C70 in toluene. ► Binding of C60 and C70 in the cleft of 1 is clearly demonstrated by MMMF calculations. ► Steady state and time-resolved fluorescence prove the mechanism of energy transfer from 1 to fullerenes.