NMR Studies into the Potential Interactions of FullereneC60with Tetraphenylporphyrin and Some of Its Derivatives

摘要

1H NMR relaxation studies were employed to investigate potential interactions between C60and tetraphenylporphyrin, H2[TPP], and parasubstituted tetraphenylporphyrins, H2[(p-X)4TPP], where X = CN and OCH3in solution. The substituted porphyrins provided a means by which to investigate the role that electronic effects play in the interaction process. A comparison of the relaxation rates, R1, and correlation times,τC, of the pyrrole and phenyl hydrogens in these complexes, without and with the presence of C60, revealed that the introduction of C60into solution did not have a noticeable effect on R1andτCof these protons in H2[TPP], indicating the absence of long-term intermolecular interaction at either of these two sites. A similar analysis of the two protons in the other two substituted tetraphenylporphyrin analogs revealed slower molecular dynamics indicating the presence of intermolecular interactions. Stronger interactions were observed in H2[(p-OCH3)4TPP] indicating that the electron-donating abilities of the -OCH3group promote the interaction process. Our results indicate that it is very likely that enhanced selectivity in the chemical purifications of fullerenes and metallofullerenes can be achieved by employing tetraphenylporphyrin-silica stationary phases which have been modified with electron-donating groups.