The pentamethylene sulfide center dot center dot center dot HCl dimer: a theoretical study

An ab initio study, using MP2/6-31G(d,p) and MP2/cc-pVDZ levels of theory, of the pentamethylene sulfide...HCl potential energy surface gives two chai r-like complexes involving axial and equatorial hydrogen bonds as the most stable structures. Their computed geometrical parameters and rotational con stants are in good agreement with the experimental ones. The basis set supe rposition error is crucial in giving the equatorial conformer as the most s table structure in accord with the experimental observation. Both the high barrier to interconversion between the axial and equatorial conformers and their low energy difference explain why the intensity ratio experimentally observed for them remains unchanged when different carrier gases are employ ed. (C) 2001 Elsevier Science B.V. All rights reserved.