First ab Initio and Density Functional Study on the Structure, Bowl-to-Bowl Inversion Barrier, and Vibrational Spectra of the Elusive C3v-Symmetric Buckybowl: Sumanene, C21H12

Abstract

The synthetically elusive C3v symmetric sumanene (C21H12), a key structural motif of C60, was subjected to a detailed computational study, exploring the structure, bowl-to-bowl inversion dynamics, vibrational spectra, and some other physicochemical properties. Hartree−Fock (HF), pure (BLYP, BP86, and BPW91), and hybrid density functional (B3LYP, B3P86, and B3PW91) calculations were done with an array of basis sets (STO-3G, 3-21G, 6-31G*, 6-31G**, 6-311G*, 6-311G**, 6-311+G*, 6-311++G*, cc-pVDZ, and cc-pVTZ). The effect of a basis set higher than double-ζ quality and the inclusion of dynamic correlation on the geometry and bowl-to-bowl inversion barrier was insignificant. The B3LYP or HF method with the cc-pVDZ or 6-311G* basis set gave satisfactory results. The previously computed modified neglect of diatomic overlap (MNDO) value of 24.2 kcal/mol for the bowl-to-bowl inversion was found to be too high, and a revised value of 16.9 kcal/mol was obtained by the B3LYP/cc-pVTZ//B3LYP/cc-pVDZ method. Consequent...