Rotational Spectrum and Internal Dynamics of Tetrahydrofuran–Krypton

The rotational spectrum of the tetrahydrofuran krypton van der Waals complex has been investigated by pulsed jet Fourier transform microwave spectroscopy. The spectra of the 84Kr and 86Kr isotopologues have been assigned. The krypton atom is located nearly over the oxygen atom, almost perpendicularly to the COC plane. Each rotational transition is split into two component lines due, according to the observed Coriolis coupling term between the tunnelling states, to the residual pseudorotational effects of the ring in the complex. The splitting between the two vibrational sublevels has been determined to be 87.462(2) and 87.062(2) MHz for the 84Kr and 86Kr isotopologues, respectively. These splittings have been used to determine the barrier to inversion, B2 = 67 cm-1. The dissociation energy has been estimated to be 3.7 kJ mol-1, from centrifugal distortion effects.