Isomer Identification for Fullerene C₈₄ by ¹³C NMR Spectrum:  A Density-Functional Theory Study

Optimized geometries of all 24 isolated pentagon rule (IPR) abiding isomers of fullerene C84 have been calculated using density-functional theory (DFT) at the B3LYP/6-31G* level. 13C NMR chemical shieldings are obtained employing the gauge-independent atomic orbital method. The calculated chemical shifts are in good agreement with experimental values for isomers 4, 22, and 23, all of which have been experimentally assigned without ambiguity. The calculated NMR spectra allow us to confirm earlier assignment and validate the DFT approach. The previously temporarily assigned isomers D2(II), C2, Cs(a), and Cs(b) are isomers 5, 11, 16, and 14, respectively. Discrepancies exist between the experimental and theoretical NMR spectra for isomers 19 and 24. The predicted NMR spectra for other isomers are also presented. The local geometry is determined largely by connectivity. The relationship between the chemical shift and the π-orbital axis vector (POAV) angle is far from linear, although the chemical shift genera...