Intermolecular
complexes between CHF<sub>3</sub> and CO have been
studied by ab initio calculations and IR matrix isolation spectroscopy.
The computations at the MP2 and CCSD(T) levels of theory indicated
five minima on the potential energy surface (PES). The most energetically
favorable structure is the C(CO)–H(CHF<sub>3</sub>) coordinated
complex (<i>C<sub>s</sub></i> symmetry) with the stabilization
energy of 0.84 kcal/mol as computed at the CCSD(T) level (with ZPVE
and BSSE corrections). This is the only structure experimentally found
in argon and krypton matrixes, whereas the weaker non-hydrogen-bonded
complexes predicted by theory were not detected. The vibrational spectrum
of this complex is characterized by a red-shift of the CF<sub>3</sub> asymmetric stretching, splitting of the C–H bending mode,
and blue-shifts of the C–H and C–O stretching vibrations
as compared to the monomer molecules. The observed complexation-induced
shifts of CHF<sub>3</sub> and CO fundamentals are in good agreement
with the computational predictions. It was shown that both MP2 and
CCSD(T) calculations generally provided a reasonable description of
the vibrational properties for the weak intermolecular complexes of
fluoroform
