Microwave spectrum and structure of C₆H₅CCH…H₂S complex

Abstract

Rotational spectra of C₆H₅CCH…H₂S, C₆H₅CCH…H₂³⁴S, C₆H₅CCH…HDS, C₆H₅CCH…D₂S and C₆H₅CCD…H₂S complexes have been observed using a pulsed nozzle Fourier transform microwave spectrometer. The observed spectrum is consistent with a structure in which hydrogen sulphide is located over the phenyl ring p cloud and the distance between the centers of masses of the two monomers is 3.74±0.01 Å. In the complex, the H₂S unit is shifted from the phenyl ring center towards the acetylene group. The vibrationally averaged structure has an effective Cs symmetry. Ab initio calculations were performed at MP2/aug-cc-pVDZ level of theory to locate the possible geometries of the complex. The calculations reveal the experimentally observed structure to be more stable than a coplanar arrangement of the monomers, which was observed for the C₆H₅CCH…H₂O complex. Atoms in molecule theoretical analysis shows the presence of S-H…π hydrogen bond. For the parent isotopologue, each transition frequency was found to split into two resulting from an interchange of the equivalent hydrogens of H₂S unit in the complex.