Vibrational Potential Energy Surfaces of Non-Rigid Molecules in Ground and Excited Electronic States

Abstract

Far-infrared and low-frequency Raman spectroscopy have been used for many years to determine the potential energy surfaces which govern the conformational changes in four-, five-, or six-membered ring molecules. The definition of the coordinates, the calculation of the kinetic energy functions, and the calculation of the energy levels are described. The analysis of the data for.1,3-dioxole, which shows an unusual anomeric effect resulting in a barrier to planarity of 270 cm−1, and of other “pseudo-four-membered rings” is discussed. Two-dimensional potential energy surfaces defining the conformational energy changes for silacyclopentane, 3-phospholene, and cyclohexene are presented.