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 C-60 and C-70. Fluorescence spectroscopic measurements showed that emission of TP, AP and DP in toluene was quenched in the presence of C-60 or C-70. Large binding constants (K) in the magnitude of similar to 1.5 x 10(4) dm(3) mol(-1) have been obtained for the 1:1 complexes of C-70 with TP, AP and DP. However, the C-60 complexes have exhibited similar to 8.5 times smaller K compared to C-70 complexes. Ab initio, theoretical calculations give a good support in favor of strong complexation between C-70 and porphyrins. (c) 2006 Elsevier B.V. All rights reserved.