Rotational characterization of SF chalcogen bonds in the complex of 2,2,4,4-tetrafluoro-1,3-dithietane and difluoromethane.

Sulfur chalcogen bonds (ChBs) play important roles in fields ranging from protein science to molecular self-assembly and organic conductor materials. Understanding of the intrinsic nature of sulfur ChBs is critical to reveal their functions. In this work, we report the first rotational spectroscopic investigation on the novel SF ChB in a 1 : 1 molecular complex of 2,2,4,4-tetrafluoro-1,3-dithietane (CFS) and difluoromethane (DFM). The rotational spectra measured with Fourier transform microwave spectroscopy on the six isotopologues of the complex allow the determination of the SF distance to be 2.9759(6) Å and the associated angle to be 157.90(3)°. Experimental results and quantum chemical calculations clearly support the formation of SF ChB in the complex. The uncovered structure also shows the existence of two C-HF and two C-FF-C contacts. Further theoretical analyses reveal the electrostatic and dispersion interactions to be dominant in stabilizing the complex, and the dissociation energy of the complex to be 15.2 kJ mol.