We have characterized the covalent binding of the CO(2) reduction electrocatalyst ReC0A (Re(CO)(3)Cl(dcbpy) (dcbpy =4,4'-dicarboxy-2,2'-bipyridine)) to the TiO(2) rutile (001) surface. The analysis based on sum frequency generation (SFG) spectroscopy and density functional theory (DFT) calculations indicates that ReC0A binds to TiO(2) through the carboxylate groups in bidentate or tridentate linkage motifs. The adsorbed complex has the dcbpy moiety nearly perpendicular to the TiO(2) surface and the Re exposed to the solution in a configuration suitable for catalysis.
Gas phase C 6H 7 (+) and C 7H 9 (+) ions are studied with infrared photodissociation spectroscopy (IRPD) and the method of rare gas tagging. The ions are produced in a pulsed electric discharge supersonic expansion source from benzene or toluene precursors. We observe exclusively the formation of either the C 2 v benzenium ion (protonated benzene) or the para isomer of the toluenium ion (protonated toluene). The infrared spectral signatures associated with each ion are established between 750 and 3400 cm (-1). Comparing the gas phase spectrum of the benzenium ion to the spectrum obtained in a superacid matrix [ Perkampus, H. H.; Baumgarten, E. Angew. Chem. Int. Ed. 1964, 3, 776 ], we find that the C 2 v structure of the gas phase species is minimally affected by the matrix environment. An intense band near 1610 cm (-1) is observed for both ions and is indicative of the allylic pi-electron density associated with the six membered ring in these systems. This spectral signature, also observed for alkyl substituted benzenium ions and protonated naphthalene, compares favorably with the interstellar, unidentified infrared emission band near 6.2 microm (1613 cm (-1)).
Uranium and uranium dioxide carbonyl cations produced by laser vaporization are studied with mass-selected ion infrared spectroscopy in the C-O stretching region. Dissociation patterns, spectra, and quantum chemical calculations establish that the fully coordinated ions are U(CO)(8)(+) and UO(2)(CO)(5)(+), with D(4d) square antiprism and D(5h) pentagonal bipyramid structures. Back-bonding in U(CO)(8)(+) causes a red-shifted CO stretch, but back-donation is inefficient for UO(2)(CO)(5)(+), producing a blue-shifted CO stretch characteristic of nonclassical carbonyls.
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