title: Ionic hydrogen bonds controlling two-dimensional supramolecular systems at a metal surface.
abstract: Hydrogen-bond formation between ionic adsorbates on an Ag(111) surface under ultrahigh vacuum was studied by scanning tunneling microscopy/spectroscopy (STM/STS), X-ray photoelectron spectroscopy (XPS), near-edge X-ray absorption fine structure (NEXAFS), and molecular dynamics calculations. The adsorbate, 1,3,5-benzenetricarboxylic acid (trimesic acid, TMA), self-assembles at low temperatures (250-300 K) into the known open honeycomb motif through neutral hydrogen bonds formed between carboxyl groups, whereas annealing at 420 K leads to a densely packed quartet structure consisting of flat-lying molecules with one deprotonated carboxyl group per molecule. The resulting charged carboxylate groups form intermolecular ionic hydrogen bonds with enhanced strength compared to the neutral hydrogen bonds; this represents an alternative supramolecular bonding motif in 2D supramolecular organization.
authors.affiliation: Max Planck Institut für Festkörperforschung, Heisenbergstrasse 1, 70563 Stuttgart, Germany.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Payer
authors.forename: Alessio
authors.initials: A
authors.lastname: Comisso
authors.forename: Alexandre
authors.initials: A
authors.lastname: Dmitriev
authors.forename: Thomas
authors.initials: T
authors.lastname: Strunskus
authors.forename: Nian
authors.initials: N
authors.lastname: Lin
authors.forename: Christof
authors.initials: C
authors.lastname: Wöll
authors.forename: Alessandro
authors.initials: A
authors.lastname: Devita
authors.forename: Johannes V
authors.initials: JV
authors.lastname: Barth
authors.forename: Klaus
authors.initials: K
authors.lastname: Kern