Structure and stability of thioureate anions with water, DFT calculations

Structure and stability of thioureate anion with the water clusters CSNH2NH−-(H2O)n = 1-7, are studied, using density functional theory. Molecular structures and the stability of the clusters are discussed based on the calculation results of the stable conformers and their relative energies. All the clusters are stable thermodynamically in gas phase with respect to separate monomers. The clusters are stabilized progressively with an increasing number of water molecules, as indicated by the increasing of the binding energies. The binding energies of CSNH2NH− and a water molecule are 14.34 and 16.36 kcal/mol for cis CSNH2NH− and trans CSNH2NH−, respectively. As the reaction in aqueous solution progresses, the CS bond distance increases monotonically, indicating that the CS bond of the thioureate anion unit in the clusters is de-stabilized with an increasing number of water molecules.