title: Molecular imaging of reductive coupling reactions: interstitial-mediated coupling of benzaldehyde on reduced TiO2(110).
abstract: We report the first visualization of a reactive intermediate formed from coupling two molecules on a surface-a diolate formed from benzaldehyde coupling on TiO(2)(110). The diolate, imaged using scanning tunneling microscopy (STM), is reduced to gaseous stilbene upon heating to ∼400 K, leaving behind two oxygen atoms that react with reduced Ti interstitials that migrate to the surface, contrary to the popular expectation that strong bonds in oxygenated molecules react only with oxygen vacancies at the surface. Our work further provides both experimental and theoretical evidence that Ti interstitials drive the formation of diolate intermediates. Initially mobile monomers migrate together to form paired features, identified as diolates that bond over two adjacent five-coordiante Ti atoms on the surface. Our work is of broad importance because it demonstrates the possibility of imaging the distribution and bonding configurations of reactant species on a molecular scale, which is a critical part of understanding surface reactions and the development of surface morphology during the course of reaction.
authors.affiliation: Department of Chemistry and Biochemistry, University of San Diego, San Diego, California 92110, USA.
authors.forename: Lauren
authors.initials: L
authors.lastname: Benz
authors.forename: Jan
authors.initials: J
authors.lastname: Haubrich
authors.forename: Stephen C
authors.initials: SC
authors.lastname: Jensen
authors.forename: Cynthia M
authors.initials: CM
authors.lastname: Friend
mesh_terms: D000327:Adsorption; D001547:Benzaldehydes / Q000737:chemistry*; D005240:Feasibility Studies; D016252:Microscopy, Scanning Tunneling; D008958:Models, Molecular; D008968:Molecular Conformation; D049329:Nanostructures / Q000737:chemistry; D010084:Oxidation-Reduction; D013499:Surface Properties; D013696:Temperature; D014025:Titanium / Q000737:chemistry*
chemical_list: D001547:Benzaldehydes; C009495:titanium dioxide; D014025:Titanium; C032175:benzaldehyde