Conformational diversity of the THF molecule in N2 matrix by means of FTIR matrix isolation experiment and Car-Parrinello molecular dynamics simulations.

Abstract

Tetrahydrofuran (THF) is a widely used chemical compound, in particular as a solvent in organic and inorganic synthesis. The THF molecule has also an interesting property, namely, undergoes pseudorotation, similar to the case of the cyclopentane. Low energy difference between the envelope (Cs symmetry) and twisted (C2 symmetry) conformations of the THF molecule leads to the interconversion between the two conformers. We study the influence of the molecular environment (N2) on the Cs-C2 equilibrium of tetrahydrofuran in the THF@N2 system utilizing nitrogen matrix isolation infrared spectroscopy. We observe a different ratio between envelope (Cs) and twisted (C2) conformations with respect to a change of the temperature. FTIR experimental studies are supported by the results of the static density functional theory calculations and Car-Parrinello molecular dynamics simulations. We focus on the dynamics of the pseudorotation process, in particular, the lifetime of the THF conformations and their mutual rearrangements. On the basis of the THF@N2 matrix model, with explicit nitrogen molecules, the anharmonic infrared spectra are generated from the Fourier transformation of the dipole moment autocorrelation function.