Potential-Energy Surfaces for Ring-Puckering Motions of Flexible Cyclic Molecules through Cremer-Pople Coordinates: Computation, Analysis, and Fitting.

Ring-puckering motion in 12 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 D5 h or C2 v. The issue of PES fitting and that of solving the nuclear dynamics using ring-puckering coordinates are also addressed. Analytical formulations of the computed PESs using suitable functional forms with a limited set of parameters are provided.