title: Self-Assembled Monolayers of Oligophenylenecarboxylic Acids on Silver Formed at the Liquid-Solid Interface.
abstract: A series of para-oligophenylene mono- and dicarboxylic acids (R-(C6H4)nCOOH, n = 1-3, R = H,COOH) was studied. Adsorbed on Au(111)/mica modified by an underpotential deposited bilayer of Ag, the self-assembled monolayers (SAMs) were analyzed by near-edge X-ray absorption fine structure spectroscopy, X-ray photoelectron spectroscopy, and scanning tunneling microscopy. In all cases SAMs are formed with molecules adopting an upright orientation and anchored to the substrate by a carboxylate. Except benzoic acid, all SAMs could be imaged at molecular resolution, which revealed highly crystalline layers with a dense molecular packing. The structures of the SAMs are described by a rectangular (5 × √3) unit cell for the prevailing phase of the monocarboxylic acids and an oblique ([Formula: see text]) unit cell for the dicarboxylic acids, thus evidencing a pronounced influence of the second COOH moiety on the SAM structure. Density functional theory calculations suggest that hydrogen bonding between the SAM-terminating COOH moieties accounts for the difference. Contrasting other classes of SAMs, the systems studied here are determined by intermolecular interactions whereas molecule-substrate interactions play a secondary role. Thus, eliminating problems arising from the mismatch between the molecular and the substrate lattices, coordinatively bonded carboxylic acids on silver should provide considerable flexibility in the design of SAM structures.
authors: EaStCHEM School of Chemistry, University of St. Andrews , North Haugh, St. Andrews KY16 9ST, United Kingdom.
authors: Hannah
authors: H
authors: Aitchison
authors: Angewandte Physikalische Chemie, Universität Heidelberg , Im Neuenheimer Feld 253, 69120 Heidelberg, Germany.
authors: Hao
authors: H
authors: Lu
authors: EaStCHEM School of Chemistry, University of St. Andrews , North Haugh, St. Andrews KY16 9ST, United Kingdom.
authors: Simon W L
authors: SW
authors: Hogan
authors: EaStCHEM School of Chemistry, University of St. Andrews , North Haugh, St. Andrews KY16 9ST, United Kingdom.
authors: Herbert
authors: H
authors: Früchtl
authors: EaStCHEM School of Chemistry, University of St. Andrews , North Haugh, St. Andrews KY16 9ST, United Kingdom.
authors: Izabela
authors: I
authors: Cebula
authors: Angewandte Physikalische Chemie, Universität Heidelberg , Im Neuenheimer Feld 253, 69120 Heidelberg, Germany.
authors: Michael
authors: M
authors: Zharnikov
authors: EaStCHEM School of Chemistry, University of St. Andrews , North Haugh, St. Andrews KY16 9ST, United Kingdom.
authors: Manfred
authors: M
authors: Buck