Endohedral 1H NMR Chemical Shifts of H2‐, H2O‐ and NH3‐Encapsulated Fullerene Compounds: Accurate Calculation and Prediction

Abstract

AbstractThe endohedral 1H NMR chemical shifts of various known H2‐ H2O‐ and NH3‐encapsulated fullerene compounds have been calculated at the GIAO‐B3LYP/3‐21G and GIAO‐HF/3‐21G levels of theory with AM1‐ and PM3‐optimized structures. The corrected 1H NMR chemical shifts were calculated from the correlation equation derived from linear regression fitting between calculated and experimental 1H NMR chemical shifts in each case. Comparisons of the regression coefficients, standard deviations, and maximum and mean errors of the corrected chemical shifts obtained by the four methods employed showed that the GIAO‐B3LYP/3‐21G//PM3 method is the best for calculating the endohedral 1H NMR chemical shifts of endofullerenes. The endohedral 1H NMR chemical shifts of any H2‐, H2O‐ or NH3‐encapsulated fullerene compound can be predicted by the correlation equation derived by using the GIAO‐B3LYP/3‐21G//PM3 method. The shift tendency of endohedral 1H NMR chemical shifts are discussed and compared with that of endohedral 3He NMR chemical shifts. The encapsulated H2, H2O or NH3 molecule can be employed as a sensitive NMR probe to investigate the ring currents of fullerene cages and to follow the chemical reactions of endofullerenes at the exterior of the fullerene cage.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)