An infrared spectroscopic study of trifluoromethoxybenzene⋯methanol complexes formed in superfluid helium nanodroplets.

We have studied the intermolecular complex formation between trifluoromethoxybenzene and methanol (CD3OD) in superfluid helium droplets by infrared spectroscopy in the spectral range of 2630-2730 cm-1, covering the O-D stretches of methanol-d4 (CD3OD). The cluster size associated with the observed bands is deduced from the variation of infrared intensity of a particular band with the partial pressures of trifluoromethoxybenzene and methanol. Quantum chemical calculations are performed at the MP2/6-311++G(d,p) level of theory to complement the experimental results. As a result, we have identified six different conformers of the trifluoromethoxybenzene⋯methanol intermolecular complex: three bound via O-H⋯O hydrogen bonds and the other three via O-H⋯π hydrogen bonds. Furthermore, to access the effect of fluorination on the methyl unit of anisole molecules, we compare the IR spectrum of trifluoromethoxybenzene (C6H5OCF3)⋯methanol with our earlier reported spectrum of anisole (C6H5OCH3)⋯methanol.