| Abstract
| - The synthetically elusive C3v symmetric sumanene (C21H12), a key structural motif of C60, was subjected toa 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 hybriddensity 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). Theeffect of a basis set higher than double-ζ quality and the inclusion of dynamic correlation on the geometryand 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 16.9kcal/mol was obtained by the B3LYP/cc-pVTZ//B3LYP/cc-pVDZ method. Consequently, the computed resultsindicate that sumanene (2) is not locked in the bowl geometry and that a definitive bowl-to-bowl inversionshould exist at room temperature. The highest level of theory used in the study (B3LYP/6-311G**) yieldsvalues of 1.14 Å, 2.45 D, and 98.8° for the bowl depth, dipole moment, and π-orbital axis vector angle at thehub carbon for sumanene, respectively. Interesting temperature dependency of inversion dynamics is predictednear room temperature.
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