THE TWO-DIMENSIONAL POTENTIAL-ENERGY SURFACE FOR THE RING PUCKERING AND RING TWISTING OF 1-SILACYCLOPENT-3-ENE-DO, 1-D1, AND 1, 1-D2
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abstract
The far-infrared spectra of 1-silacyclopent-3-ene and an isotopic mixture containing both 1-d1 and 1,1-d2 species have been recorded and analyzed. In addition to the main ring-puckering series, a weak side band series, resulting from molecules in the ring-twisting excited state, was observed for the undeuterated molecule. In the 330-520 cm-1 region of the infrared spectrum of the isotopic mixture, combination bands of the puckering with the SiHD or SiD2 rocking were observed. The ring-twisting fundamental was also assigned to the 380.6 cm-1 band in this region. Analysis of the data for all three isotopic species results in the following two-dimensional potential energy surface: V(cm-1)=2. 08105x14-0.00510 5x12+0.547105x 22+1.70105x12x22, where x1 and x2 are the ring-puckering and ring-twisting coordinates (in ), respectively. The potential minimum corresponds to a planar conformation and the positive cross term shows the vibrational interaction to be anticooperative. 1984 American Institute of Physics.