Microwave spectroscopy of 2-(trifluoromethyl)pyridine⋯water complex: Molecular structure and hydrogen bond

In order to explore the -CF₃ substitution effect on the complexation of pyridine, we investigated the 2-(trifluoromethyl)pyridine⋯water complex by using pulsed jet Fourier transform microwave spectroscopy complemented with quantum chemical calculations. Experimental assignment and ab initio calculations confirmed that the observed complex is stabilized through N⋯H-O and O⋯H-C hydrogen bonds forming a five-membered ring structure. The bonding distance in N⋯H-O is determined to be 2.027(2) Å, whilst that in O⋯H-C interaction is 2.728(2) Å. The quantum theory of atoms in molecules analysis indicates that the interaction energy of N⋯H-O hydrogen bond is ∼22 kJ mol^-1 and that for O⋯H-C hydrogen bond is ∼5 kJ mol^-1. The water molecule lies almost in the plane of the aromatic ring in the complex. The -CF₃ substitution to pyridine quenches the tunneling splitting path of the internal motion of water molecule.