Characterisation of H2S••••CuCl and H2S•••AgCl isolated in the gas phase: A rigidly pyramidal geometry at sulphur revealed by rotational spectroscopy and ab initio calculations

Pure rotational spectra of the ground vibrational states of eight isotopologues of H2S center dot center dot center dot CuCl and twelve isotopologues of H2S center dot center dot center dot AgCl have been analysed allowing rotational constants and hyper-fine coupling constants to be determined. The molecular structures have been determined from the measured rotational constants and are presented alongside the results of calculations at the CCSD(T) level. Both molecules have C-s symmetry at equilibrium and are pyramidal at the sulphur atom. The chlorine, metal, and sulphur atoms are collinear while the local C-2 axis of the hydrogen sulphide molecule intersects the axis defined by the heavy atoms at an angle, phi = 74.46(2)degrees for Cu and phi = 78.052(6)degrees for Ag. The molecular geometries are rationalised using simple rules that invoke the electrostatic interactions within the complexes. Centrifugal distortion constants, Delta(J), and nuclear quadrupole coupling constants, chi(aa)(Cu) and chi(aa)(Cl) for H2S center dot center dot center dot CuCl are presented for the first time. The geometry of H2S center dot center dot center dot AgCl is determined with fewer assumptions and greater precision than previously. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3598927]