Ionic hydrogen bonds controlling two-dimensional supramolecular systems at a metal surface.
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.
Payer
Dietmar
D
Max Planck Institut für Festkörperforschung, Heisenbergstrasse 1, 70563 Stuttgart, Germany.
Comisso
Alessio
A
Dmitriev
Alexandre
A
Strunskus
Thomas
T
Lin
Nian
N
Wöll
Christof
C
Devita
Alessandro
A
Barth
Johannes V
JV
Kern
Klaus
K