Configuration and internal dynamics of CH2ClF...krypton

The molecular complex chlorofluoromethane-krypton has been investigated by Fourier transform microwave spectroscopy in a supersonic expansion. The rotational spectra have been assigned for the CH235ClF...84Kr, CH235ClF...86Kr, and CH237ClF...84Kr species, showing that, in the equilibrium configuration, the krypton atom is located out of the ClCF plane, interacting with both F and Cl atoms. All rotational transitions are split in several 35Cl or 37Cl quadrupole components, each of them further split into two lines, due to the tunneling motion of the Kr atom between two equivalent positions, below and above the ClCF plane. The feasible low-energy pathway between these two structurally degenerate conformations is described, in a first approximation, by a circular motion around the C-Cl bond, with a barrier estimated to be about 74 cm(-1).