Investigations on photophysical properties and binding strength for the supramolecular complexes of newly designed diporphyrins with fullerenes

Three Zn2-diporphyrins, in which two monoporphyrin units are connected through desired spacers like phenyl (1), carbazole (2) and fluorine (3), have been synthesized. UV–vis and steady-state fluorescence measurements suggest appreciable interaction of the diporphyrins with C60 and C70 in toluene. Selectivity in binding constant (K) values of the diporphyrin complexes of C70 over C60 follows the trend: 1 < 2 < 3. Time-resolved fluorescence experiment reveals considerable increase in the life-time of the designed diporphyrins upon complexation with fullerenes. Estimation of the heat of formation values for the fullerene–diporphyrin complexes corroborates fairly well with the trend in the K values.