Infrared Studies of the Symmetry Changes of the 28SiH4 Molecule in Low-Temperature Matrixes. Fundamental, Combination, and Overtone Transitions

Stretching force constants as descriptors of energy and geometry of F···HF hydrogen bonds

In this work applicability of proton donor group stretching vibration force constants k_s and intermolecular stretching force constants k_σ for evaluations of hydrogen bond strength and geometry are discussed. For a set of 30 complexes with F···HF hydrogen bonds in a wide range 0.5-48 kcal/mol by means of quantum chemical calculations equilibrium geometries, complexation energies, vibrational frequencies and corresponding force constants were calculated (MP2/aug-cc-pVTZ). It is shown, that properties of a hydrogen bond are more strictly correlated with the values of force constants than with vibrational frequencies. Easy-to-use equations for estimations of hydrogen bond energy ∆E and geometry (r_FH, r_FF) based on k_s and k_σ values are proposed.

Mid-infrared spectra of silane dispersed in solid neon

We report mid-infrared spectra of silane dispersed in solid neon at relative concentrations 1:1000 and 1:5000, recorded with spectral resolution 0.15 cm^-1. Apart from major lines associated with internal vibrational motions of ²⁸SiH₄, ²⁹SiH₄ and ³⁰SiH₄ in fundamental modes ν₃ and ν₄, several weak accompanying lines in each region become discernible at the resolution of our experimental measurements, and are tentatively associated with librational motions of silane molecules in the solid neon lattice. The wavenumbers associated with a few overtone and combination modes are also presented.