Density Functional Theory based study on structural, vibrational and NMR properties of cis - trans fulleropyrrolidine mono-adducts

Since the early nineties, countless publications have been devoted to the study of possible uses of [60] fullerene (C(60)) and its derivatives in the fields of materials and nano-biomedical sciences. However, in spite of the importance of conformers notably from the pharmacological point of view, the cis/trans isomerization of C(60) mono-adducts has been rarely seldom investigated. Here we present the results of DFT calculations of the structural, vibrational and NMR properties of both cis and trans isomers of fulleropyrrolidine mono-adduct obtained by photo-addition of glycine methyl ester to C(60). Taken together, our results have shown that the cis isomer is more stable than the trans one. For the cis conformation, the simulated vibrational spectrum shows a more intense peak at 1298 cm(-1). While (13)C spectra revealed no significant differences between the two isomers as compared to experimental results, the calculated (1)H chemical shifts show a significant difference between the two conformers in both the gas phase and in solution. The trans isomer presents a proton at 5.86 ppm, which is more deshielded than the proton of the cis conformer (5.24 ppm).