Microwave, infrared, and Raman spectra, structural parameters, vibrational assignments and theoretical calculations of 1,1,3,3-tetrafluoro-1,3-disilacyclopentane

Highlights: • Structural parameters have been determined for the stable twist conformer. • Rotational constants for the six isotopologues for the twist conformer were determined from the microwave spectra. • Vibrational assignments are given for the molecule. • Ab intio and density functional theory calculations have been carried out for all possible conformers. - Abstract: The FT-microwave spectrum of 1,1,3,3-tetrafluoro-1,3-disilacyclopentane (c-C3H6Si2F4) has been recorded and 339 transitions for 6 isotopologues have been assigned for the twist conformation. The ground state rotational constants were determined with values for the normal species: A = 2102.74026(68), B = 751.34319(32), C = 736.51478(31). Adjusted r0 parameters are reported with distances (Å): rCα–Si = 1.859(2), rSi–Cβ = 1.864(2), rSi–F1 = 1.583(3), rSi–F2 = 1.578(3), and rCβ–Cβ = 1.559(3), and angles (°): ∠SiCαSi = 102.8(3), ∠CαSiCβ = 104.3(3), ∠SiCβCβ′ = 106.6(3), τCβSiCαSi = 10.7(3), and τ SiCβCβ′Si = 40.8(3). The conformational stabilities have been predicted from ab initio calculations utilizing several various basis sets. Vibrational assignments have been provided for the observed bands for the twist conformer which are supported by ab initio calculations to predict harmonic force constants, vibrational wavenumbers, infrared intensities, Raman activities and depolarization ratios. The results are discussed and compared to the corresponding properties of some related molecules