Microwave spectrum and non-covalent interactions of the 1, 2, 3, 4-tetrafluorobenzene-water complex.

The 1, 2, 3, 4-tetrafluorobenzene-water complex was investigated by pulsed-jet Fourier transform microwave spectroscopy. One isomer was detected in the jet expansion. calculations and non-covalent interaction (NCI) analysis were performed to characterize the intermolecular NCIs. In the observed isomer, the water molecule lies almost in the plane of the benzene ring acting as a proton donor to one of the fluorine atoms and as an acceptor to one of the hydrogen atoms forming a six-membered ring structure. The CH⋯O and H⋯FC bonding distances are determined to be 2.385(1) Å and 2.429(1) Å, respectively. The interaction energy is calculated to be -18.0 kJ mol at the SAPT2+(3)/aug-cc-pVDZ level of theory. The observed transitions exhibit splitting in the order of tens to hundreds of kHz due to the internal rotation of water moiety. The possible tunneling paths of water were investigated by calculations resulting in a barrier for an internal rotation of about 201 cm.