Interaction of Isophorone with Pd 111 A Combination of Infrared Reflection Absorption Spectroscopy, Near Edge X ray Absorption Fine Structure, and Density Functional Theory Studies

摘要

Atomistic level understanding of interaction of amp; 945;, amp; 946; unsaturated carbonyls with late transition metals is a key prerequisite for rational design of new catalytic materials with the desired selectivity toward C C or C O bond hydrogenation. The interaction of this class of compounds with transition metals was investigated on amp; 945;, amp; 946; unsaturated ketone isophorone on Pd 111 as a prototypical system. In this study, infrared reflection absorption spectroscopy IRAS , near edge X ray absorption fine structure NEXAFS experiments, and density functional theory calculations including van der Waals interactions DFT vdW were combined to obtain detailed information on the binding of isophorone to palladium at different coverages and on the effect of preadsorbed hydrogen on the binding and adsorption geometry. According to these experimental observations and the results of theoretical calculations, isophorone adsorbs on Pd 111 in a flatlying geometry at low coverages. With increasing coverage, both C C and C O bonds of isophorone tilt with respect to the surface plane. The tilting is considerably more pronounced for the C C bond on the pristine Pd 111 surface, indicating a prominent perturbation and structural distortion of the conjugated amp; 960; system upon interaction with Pd. Preadsorbed hydrogen leads to higher tilting angles of both amp; 960; bonds, which points to much weaker interaction of isophorone with hydrogen precovered Pd and suggests the conservation of the in plane geometry of the conjugated amp; 960; system. The results of the DFT vdW calculations provide further insights into the perturbation of the molecular structure of isophorone on Pd 111