Microwave spectrum and structure of C<SUB>6</SUB>H<SUB>5</SUB>CCH&#8230;H<SUB>2</SUB>S complex

Rotational spectra of C6H5CCH&#8230;H2S, C6H5CCH&#8230;H234S, C6H5CCH&#8230;HDS, C6H5CCH&#8230;D2S and C6H5CCD&#8230;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&#177;0.01 &#197;. 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&#8230;H2O complex. Atoms in molecule theoretical analysis shows the presence of S-H&#8230;&#960; 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