Hydrogen bond character and proton transfer behavior in water-thiophenol clusters and their cation radicals: Insight into water number size dependence

摘要

The molecular structures and vibrational frequencies of [C,6H5SH-(H2O)(n)](center dot+) (n = 1-4) clusters are studied employing B3LYP density functional theory (DFT) with a 6-311+ + G** basis set. The features related to structures of the SH stretching vibrational spectrum of the thiophenol and of the intermolecular stretching vibration of S. . . H-O are also obtained and discussed in detail. The stable structures show that the hydrogen bonds between the thiophenol cation radical and water molecules are stronger than that between neutral thiophenol and water molecules and become stronger along with the increased water number n. Thus, the possibility of proton transfer depends on the water number; that is, the position of the proton of the thiophenol cation radical lies on the water number n. The theoretically obtained charge distribution and energy indicate simultaneously that (i) the cluster ions with n = 1-2 have the proton-nontransferred form; (ii) the cluster ion with n = 3 settles mainly on the proton-transferred branched form; and (iii) in the case of n = 4 cluster ions, can be a mixture of proton-transferred ringed and branched forms. (c) 2005 Wiley Periodicals, Inc.