Rotational spectrum, H, 19F spin–spin and D–nuclear quadrupole coupling constants, and molecular geometry of the sulphur dioxide–hydrogen fluoride dimer

The ground state rotational spectra of three isotopic species 32SO2⋅⋅⋅HF, 32SO2⋅⋅⋅DF, and 34SO2⋅⋅⋅HF of a dimer formed between sulphur dioxide and hydrogen fluoride have been detected and measured using a pulsed-nozzle, Fourier-transform microwave spectrometer. An analysis of observed nuclear hyperfine structure leads to the H, 19F nuclear spin–nuclear spin coupling constants DHFaa =−190(2) kHz and (DHFbb−DHFcc) =−57(4) kHz for 32SO2⋅⋅⋅HF, and to the D-nuclear quadrupole coupling constants χaa =227(3) kHz and (χbb−χcc) =68(13) kHz for 32SO2⋅⋅⋅DF. Rotational and centrifugal constants have been determined for all three isotopic species, with the following values for 32SO2⋅⋅⋅HF: A0=16 502.775(4) MHz, B0=2100.308(1) MHz, C0=1853.642(1) MHz, ΔJ =18.31(2) kHz, ΔJK =−521.78(4) kHz, and δJ =4.37(3) kHz. The rotational constants for the three isotopic species are interpreted in terms of a planar geometry in which hydrogen fluoride forms a cis hydrogen bond to one of the oxygen atoms of SO2. Assuming a linear hydrogen bond and unchanged subunit geometries, it is found that r(O⋅⋅⋅F)=2.818(8) Å and θ=215.1° where θ is the S=O⋅⋅⋅H bond angle. The nuclear hyperfine coupling constants are shown to be consistent with this arrangement.