Density functional studies of the electronic and geometric kstructures Of Pt3+, Pt3O+, Pt3O2+ and Pt3CH4+

The lower energy electronic states of Pt-3(+), Pt3O+, Pt3O+ and Pt3CH4+ have been determined with the hybrid density functional B3LYP method. The Pt-3(+) geometries are found to be close to equilateral triangle. The oxygen atom is found to bind preferentially bidentately to two Pt atoms in the Pt-3(+) plane with a binding energy of 72 kcal/mol. There are two less exothermic binding modes: tridentate above the plane and monodentate in the plane. The Pt-3(+)-O-2 binding energy, on the other hand, is calculated to be only 14 kcal/mol, with O-2 bound to a single Pt atom in an end-on manner. The Pt-3(+)-O and Pt-3(+)-O-2 binding energies imply that Pt-3(+) can split the O-O bond. The methane molecule is found to bind Pt-3(+) through two Pt...HC interactions on a single Pt atom with the binding energy of 17 kcal/mol. There are distinct differences in the cluster-complex charge distributions depending on the substrate (O, O-2 and CH4) that could affect their subsequent reactions. (C) 2002 Elsevier Science B.V. All rights reserved.