Structural analysis of 1-chlorosilacyclopentane by means of vibrational spectroscopy

The structure of the newly synthesised compound, 1-chlorosilacyclopentane (1-ClSiCP), was investigated using vibrational spectroscopy and theoretical calculations. ATR FT-IR and Raman spectroscopy were used to analyse the liquid sample. Matrix isolation FT-IR spectroscopy was used for the analysis of closely located infrared spectral bands of 1-ClSiCP. Spectroscopic data analysis was performed using theoretical methods such as density functional theory (DTF) and ab initio calculations. FT-IR spectra of 1-ClSiCP isolated in Ne and N2 matrices were collected before and after annealing. During the theoretical structural analysis, the envelope (1E) and twisted (2T3) ring shapes, with the chlorine atom in axial and equatorial positions, were investigated utilising the aug-cc-pVTZ basis set included in the MP2 and DFT calculations. Potential energy surface scans were performed to trace the energy changes and the structure of transition states during the ring conversion. Depending on the method applied, the theoretical results indicate the presence of different conformers, including twisted and envelope ring shapes. The experimental results confirm the existence of only one conformer in the twisted ring configuration. Good agreement between the experimental matrix isolation spectra and in the anharmonic approximation calculated IR absorption spectrum of the 2T3 conformer is observed. The difference between the calculated and experimental frequencies of the normal modes does not exceed 2%.