title: Direct visualization of molecule deprotonation on an insulating surface.
abstract: Elucidating molecular-scale details of basic reaction steps on surfaces is decisive for a fundamental understanding of molecular reactivity within many fields, including catalysis and on-surface synthesis. Here, the deprotonation of 2,5-dihydroxybenzoic acid (DHBA) deposited onto calcite (101;4) held at room temperature is followed in situ by noncontact atomic force microscopy. After deposition, the molecules form two coexisting phases, a transient striped phase and a stable dense phase. A detailed analysis of high-resolution noncontact atomic force microscopy images indicates the transient striped phase being a bulk-like phase, which requires hydrogen bonds between the carboxylic acid moieties to be formed. With time, the striped phase transforms into the dense phase, which is explained by the deprotonation of the molecules. In the deprotonated state, the molecules can no longer form hydrogen bonds, but anchor to the surface calcium cations with their negatively charged carboxylate group. The deprotonation step is directly confirmed by Kelvin probe force microscopy images that unravel the change in the molecular charge.
authors: Institut für Physikalische Chemie, Johannes Gutenberg-Universität Mainz, Duesbergweg 10-14, 55099 Mainz, Germany.
authors: Markus
authors: M
authors: Kittelmann
authors: Philipp
authors: P
authors: Rahe
authors: André
authors: A
authors: Gourdon
authors: Angelika
authors: A
authors: Kühnle
mesh_terms: D002119:Calcium Carbonate / Q000737:chemistry*; D002396:Catechols / Q000737:chemistry*; D004553:Electric Conductivity; D062385:Hydroxybenzoates; D008422:Materials Testing; D018625:Microscopy, Atomic Force / Q000379:methods*; D057054:Molecular Imaging / Q000379:methods*; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure*; D010316:Particle Size; D011522:Protons
chemical_list: D002396:Catechols; D062385:Hydroxybenzoates; D011522:Protons; C009135:2,3-dihydroxybenzoic acid; D002119:Calcium Carbonate