Combination band studies of some cyclic silanes

Abstract

The vapor-phase mid-infrared spectra of six cyclic molecules were investigated using long path lengths and high vapor pressures. Eight different sum and difference bands resulting from the combination of the ring-puckering vibration with a higher frequency fundamental were observed for these molecules. No combination bands were found for silacyclopent-2-ene of 1,1-difluoro-1-silacyclobutane. For a planar molecule such as silacyclopent-3-ene the analysis of the bands is straightforward. For nonplanar silacyclobutane the spectrum is complex and unexplained doublets and extra bands occur. In general, the ring-puckering energy levels in the excited state of another vibration were found to differ little from those in the ground state for the vibrations studied.