Potential-energy surfaces for ring-puckering motions of flexible cyclic molecules through Cremer-Pople coordinates: computation, analysis and fitting

Ring-puckering motion in twelve flexible cyclic molecules is investigated by calculation and analysis of two-dimensional potential-energy surfaces (PESs) using the so-called ring-puckering coordinates proposed by Cremer and Pople. The PESs are calculated by means of density-functional theory using a B2PLYP-D3BJ exchange- correlation functional with a maug-cc-pVTZ basis set, and results are compared to the available experimental and theoretical data. Special care is devoted to the aspect of symmetry in such two-dimensional PESs, which are here reported for the first time also for molecules whose planar form has symmetry lower than D5h or C2v. The issue of PES fitting and that of solving the nuclear dynamics using ring-puckering coordinates are also addressed. Analytitcal formulations of the computed PESs using suitable functional forms with a limited set of parameters are provided.