Ab initio MP2 and FTIR matrix isolation studies on tert-butanethiol complexes with water

摘要

The complexes between tert-butanethiol (BSH) and water have been studied using the MP2 method with 6-31 1++G(2d,2p) basis set and matrix isolation FTIR spectroscopy. The calculations resulted in two stationary points (D1 and D2) for 1: 1 complex and three minima (T1, T2 and T3) for 1:2 complex. DI involves the O-H center dot center dot center dot S type of interaction with H2O acting as a proton donor to the S-atom of the thiol molecule. In the less stable D2 the S-H group acts as a proton donor to the O-atom of H2O. T1 and T2 are the six-membered cyclic structures while T3 has a chain arrangement. The topological analysis of the charge density (AIM) confirmed the existence of the O-H center dot center dot center dot S, S-H center dot center dot center dot O and/or O-H center dot center dot center dot O hydrogen bonds as well as weak C-H center dot center dot center dot O interactions in the studied species. The calculated BSSE corrected interaction energy equals to -4.45 and -1.52 kcal/mol for D1 and D2, respectively, while is between -11.40 and -8.32 kcal/mol for the ternary complexes. An attractive cooperative effect has been found for the cyclic T1 and T2 of ca. -1.6 kcal/mol, while the least stable chain structure T3 is characterized by a small repulsive three-body interaction energy. The comparison of the experimental frequencies with the calculated ones allowed to identify the D1 complex in the argon matrices. The experimental spectra evidenced that both cyclic T1 and T2 structures may also be present. (c) 2007 Elsevier B.V. All rights reserved.