Modeling the Adsorption of Alkanes on an Au(111) Surface

Abstract

The adsorption of alkanes on a gold substrate is simulated by a simple computational scheme that combines the "glue model" for gold, a standard force field for alkanes, and a combination of the charge equilibration model and the Born-Mayer potential for their interaction. The adsorption energies of 10 short chains on the Au(111) surface are reproduced with an average error of less than 1 kcal mol -1 . The results allow extension of the use of the model to investigate the appeareance/disappeareance of ordered deposition on gold of longer alkanes. The unexpected transition to disorder occurs for chains between 18 and 26 carbon atoms and has been ascribed to the mismatch between the Au(111) lattice and the CH2 group periodicity, a feature that here is shown to hinder the formation of short, i.e., docking, C-Au distances.

Quantifying the atomic-level mechanics of single long physisorbed molecular chains

“…As described by Steele, the interaction of each particle with a rigid crystal may be approximated by a truncated Fourier series, with position variables in the plane parallel to the surface. The assumption of an undeformed surface is reasonable in the case of alkanes adsorbed flat on Au(111), because measured adsorption energies are nearly proportional to the number of units (29), with small slopes consistent with physisorption and weak electron transfer (30). This also applies to conjugated arenes on the same surface (31).…”

Electro-catalytic scission of carbon–iodine bonds. Building of SAMs at gold surfaces through long chain primary radical adsorption

“…Additionally, solutions of TBAI and TBAPF 6 were also tested. The supporting salt concentration was in all cases fixed at 0.1 M. It is worth mentioning that procedures given hereafter do not require extremely dry solutions (water content <1000 ppm).…”

“…On the other hand, linear alkanes were reported to adsorb at gold; binding energy is 14-81 kJ mol -1 [6]. Specific adsorption of alkyl chains at Au(111) [7] occurs with parallel orientation of the C-C-C plane to the surface.…”

Gold and gold–graphene used as cathodic interfaces for scission of carbon–halogen bonds. Application to the building of anthraquinone-Au electrodes

“…Solutions of tetra-n-butylammonium and tetramethylammonium tetrafluoroborates (TMABF 4 and TBABF 4 ) in dimethylformamide (DMF) were used. The supporting salt concentration was 0.1 M. It is worth mentioning that the procedures given hereafter did not need extremely dry solutions (water content <1000 ppm).…”

“…However, it appears that an interesting behavior of gold lies in its propensity to undergo strong adsorption of organic molecules. Thus, it is known that linear alkanes adsorb at gold with binding energy of kJ mol -1 [4]. Concerning organic halides, a metastable adsorption of MeI at Au(100) [5] occurs (in first layer) with the C-I bonds parallel to the surface, practically without decomposition.…”