SOLVATION AND CATALYST-SUBSTRATE SUPERSTRUCTURE OF A TUNGSTEN TRIS(DITHIOLENE) COMPLEX DISSOLVED IN WATER-ACETONE - A MOLECULAR-DYNAMICS MODEL CALCULATION

The intermolecular interactions of the catalyst tris(1,2-ethylenedithi olate-S,S')tungsten, W(S2C2H2)(3), with the molecules of a 25 : 75 wat er-acetone mixed solvent, are examined by statistical mechanical metho ds, and specifically by a molecular dynamics (MD) technique, using cha rge distributions obtained by extended Huckel calculations. The result s are presented in the form of pair correlation functions (PCF), and s how that an average of up to three water molecules come close to the s ites of the catalyst, whereas the acetone molecules form an open cage at a somewhat longer distance. The supramolecular structure around the catalyst is asymmetric, and is examined in the two characteristic geo metries corresponding to the D-3h and C-2v symmetries which the 'tris( dithiolene)' molecule transiently assumes during its fluxional metamor phoses in solution. At large distance (large values of the correlation parameter r) the system is homogeneous. Yet, at nanometer distances t he symmetry breaks down, and the system becomes highly asymmetric with differentiation (selectivity) in space. The mobility of the water and acetone molecules, close to the catalyst, was also studied by estimat ing the translational self-diffusion coefficients D-wat and D-acet fro m the center of mass linear velocity correlation functions. The result s show that the water molecules are more mobile than the acetone molec ules, which is the opposite of what happens without the catalyst.