Abstract
The geometric and electronic structure of the metal–molecule interface in metal/molecule/metal junctions is of great interest since it affects the functionality of such units in possible nanoelectronic devices. We have investigated the interaction between water and a palladium monolayer of a Au(111)/4-mercaptopyridine/Pd junction by means of DFT calculations. A relatively strong bond between water and the palladium monolayer of the Au/Mpy/Pd complex is observed via a one-fold bond between the oxygen atom of the water molecule and a Pd atom. An isolated H2O molecule adsorbs preferentially in a flat-lying geometry on top of a palladium atom that is at the same time also bound to the nitrogen atom of a Mpy molecule of the underlying self-assembled monolayer. The electronic structure of these Pd atoms is considerably modified which is reflected in a reduced local density of states at the Fermi energy. At higher coverages, water can be arranged in a hexagonal ice-like bilayer structure in analogy to water on bulk metal surfaces, but with a much stronger binding which is dominated by O–Pd bonds.
Highlights
An elegant electrochemical method for the metalization of molecular layers assembled on surfaces has been established [1]
In order to elucidate the nature of the NMpy–Pdb–Ow bonding and its effect on the electronic structure of the Au/Mpy/Pd junction we determined the local density of states (LDOS) of the species involved in the complex formation, namely nitrogen, Mpy, oxygen, and palladium
Au/Mpy/Pd junction upon the adsorption of water by first principles electronic structure calculations based on density functional theory
Summary
An elegant electrochemical method for the metalization of molecular layers assembled on surfaces has been established [1]. Ab initio molecular dynamics simulations showed that at room temperature the hexagonal water bilayer structure on bulk metal surfaces becomes disordered [19], but it may persist on the Au/ Mpy/Pd junction because of the higher stability of the H2O layer, which is not governed by intermolecular H-bond interactions.
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