Crotonaldehyde adsorption on Ir(1Â 1Â 1), an interesting trans- and cis-configuration transformation

Trans- and cis-crotonaldehyde (CAL) adsorption behaviors on Ir(1 1 1) were systematically investigated using density functional theory (DFT) method. Our results indicate that the interaction between CC bond of CAL and Ir(1 1 1) is stronger than that between CO and surface; and the configurations with both CO and CC bonds simultaneously adsorbed at Ir(1 1 1) are more stable than those with an individual CO or CC one at surface. It is very interesting to find that the stability of trans- and cis-CAL on Ir(1 1 1) reverses compared with that in gas phase. On the basis of the potential energy surface (PES) of CAL isomerization, CAL mainly exists as trans-structure in gas phase; while trans- and cis-CAL might coexist on Ir(1 1 1). The electronic interactions between CAL and Ir(1 1 1) are well explained by charge density difference. Different coverages of CAL on Ir(1 1 1) indicates that the interactions between CAL and Ir(1 1 1) decrease with coverage. This work provides important information for the further study of the selective hydrogenation mechanism of CAL.