Controlling charge transfer to/from the Cu(111) surface through benzene functionalization

Organic molecules adsorbed on a noble metal surface can self-assemble as a result of attractive supramolecular interactions, or repel one another if the amount of charge transferred at the adsorbate-surface interface is large. In order to better understand some of the factors affecting the patterns which are formed upon molecular deposition dispersion-corrected density functional theory (DFT-D3) calculations have been performed on substituted benzenes adsorbed to the Cu(111) surface.

The results indicate that quintessential activating and deactivating groups can be used to control the amount and direction of charge transferred between the organic molecule and the metal surface. A frontier orbital perspective was employed, and through the use of the SFO analysis in ADF intuitive level diagrams could be constructed which led to a better understanding of the surface-adsorbate interaction. The ADF-GUI was used to illustrate how the charge density of the system changed upon molecular adsorption.

Generally, it was found that activating groups increase and deactivating groups decrease or even reverse the direction of charge transferred from the adsorbate to the metal surface.

Charge density of the substituted benzene colored by the electrostatic potential (right), and the redistribution of charge upon molecular adsorption, where red indicates a build-up and blue a depletion of electron density (left).