Interplay between Supramolecularity and Substrate Symmetry in the Dehydrogenation of D‑Alaninol on Cu(100) and Cu(110) Surfaces G. Contini,* ,†,‡ P. Gori, †,‡ M. Di Giovannantonio, † N. Zema, † S. Turchini, † D. Catone, † T. Prosperi, † and A. Palma § † Istituto di Struttura della Materia, Consiglio Nazionale delle Ricerche (CNR), Via Fosso del Cavaliere 100, 00133 Roma, Italy ‡ Centro Interdipartimentale Nanoscienze & Nanotecnologie & Strumentazione (NAST), University of Rome “Tor Vergata”, 00133 Roma, Italy § Istituto per lo Studio dei Materiali Nanostrutturati, CNR, Via Salaria Km 29.3, 00015 Monterotondo S. (RM), Italy * S Supporting Information ABSTRACT: The adsorption of organic chiral molecules on metallic substrates is widely studied as a tool to obtain chiral surfaces. The chirality transfer from the molecules to the surface is strongly driven by the availability of hydrogen atoms, which guides a specific chiral self-assembled structure. In this paper we report, by combination of photoelectron spectros- copy, low-energy electron diffraction, and density functional theory calculations, on the adsorption of the D-enantiomer of alaninol on Cu(100) and on Cu(110) with the aim of revealing dehydrogenation in the formation of the molecular chiral superstructure. We show that, on both surfaces, at low coverage alaninol is dehydrogenated at the hydroxyl group, whereas at saturated coverage the substrate symmetry, in combination with intermolecular interactions, induces partial amino group dehydrogenation on Cu(100) or inhibits hydroxyl group dehydrogenation on Cu(110). ■ INTRODUCTION Two-dimensional (2D) chiral surfaces obtained functionalizing metal surfaces with chiral molecules are active in biological processes and biomedicine and are of fundamental importance in enantiomeric compound separation, catalysis, and sen- sors. 1-4 Chirality is transferred from molecules to the surface via the formation of self-assembled monolayers, driven by supramolecular effects such as long-range interactions and hydrogen bond network formation. 5-9 Several molecules have been used to produce chiral surfaces, containing one or more functional groups, carboxylic, alcoholic, or amino, that may be involved in bonding to the metal surface; some of them are chiral and others prochiral, leading to a form of 2D chirality. 10,11 H-bondings involving alcoholic and/or amino groups play a central role, through formation of intermediate clusters and chains, in guiding a specific chiral self-assembled structure; in this respect, the number and positions of the hydrogen atoms are relevant for the degree of surface enantioselectivity, 12 and possible dehydrogenation due to the adsorption should be considered. Dehydrogenation processes of the hydroxyl group on surfaces have been mostly studied in the case of alcohols, both experimentally and theoretically; as an example, oxidation of methanol on Cu(110) starts with its decomposition into methoxy (CH 3 O) and hydrogen, 13,14 in contrast to platinum- based catalysts, on which the O-H and the C-H bond scission pathways have comparable barriers. 15 Preadsorbed oxygen on copper plays an important role in any, partial or total, oxidation of methanol. Dehydrogenation of alcohols has been observed on metal catalysts, and hydrogen-bonded neighbors assist it: hydrogen bonds modulate the alcohol dehydrogenation process, either an intermolecular hydrogen bond with a neighboring molecule or an intramolecular hydrogen bond in a polyol. 16 Primary amines, on the other side, usually adsorb molecularly on metal surfaces at room temperature, as has been observed for, e.g., methylamine on Ni 3 Al(111) and NiAl(110) 17 or on Cu(110). 18 In this paper, we focus our attention on the chemical behavior of D-alaninol, the simplest chiral amino alcohol presenting two reactive groups, when it is adsorbed on Cu(100) and Cu(110) surfaces. D-Alaninol produces a chiral surface when adsorbed on Cu(100) since it gives rise to a long- range-ordered self-assembled monolayer, with a 14° clockwise rotation of the molecular superstructure with respect to the high-symmetry directions of the substrate. 5,19-21 We show here, using a combination of core level and valence band photoelectron spectroscopy, low-energy electron diffraction (LEED) experiments, and density functional theory (DFT) calculations, how alcohol dehydrogenation occurs on the two surfaces with different extents and that, in some cases, Received: February 21, 2013 Revised: April 18, 2013 Published: April 18, 2013 Article pubs.acs.org/JPCC © 2013 American Chemical Society 10545 dx.doi.org/10.1021/jp401822h | J. Phys. Chem. C 2013, 117, 10545-10551