Spectroscopic and theoretical investigations on effective and selective complexation between porphyrins and fullerenes

We have tailored some interesting mono- and diporphyrins, viz., 5, 10, 15, 20-tetrakis(octadecyloxyphenyl)-21H,23H-porphyrin (TP), 5, 15-bis(3, 5-dioctylphenyl)-2, 8, 12, 18-tetramethyl-3, 7, 13, 17-tetradodecyl-21H,23H-porphyrin (AP) and 1, 3-bis(10′,20′-diundecyl-21′H,23′H-porphyrin-5′-yl)benzene (DP) as host molecules to study their complexation behavior with C60 and C70. Fluorescence spectroscopic measurements showed that emission of TP, AP and DP in toluene was quenched in the presence of C60 or C70. Large binding constants (K) in the magnitude of ∼1.5 × 104 dm3 mol−1 have been obtained for the 1:1 complexes of C70 with TP, AP and DP. However, the C60 complexes have exhibited ∼8.5 times smaller K compared to C70 complexes. Ab initio theoretical calculations give a good support in favor of strong complexation between C70 and porphyrins.