Electrostatic versus polarization effects in the adsorption of aromatic molecules of variedpolarity on an insulating hydrophobic surface

Abstract

Ab initio calculations have been used to investigate the electronic and energeticbehaviour accompanying the adsorption of aromatic molecules of different polaritiesonto an insulating hydrophobic surface, as a convenient model for the study ofcharacteristic weak adsorption processes in biochemistry (ligand–receptor interactions)and geochemistry (aromatic pollutants on soil minerals). Four poly-chlorinateddibenzo-p-dioxin molecules of different polarities were chosen as adsorbates; the surface was the (001)surface of pyrophyllite, a chemically inert, weakly polar, covalently bonded surface. Thefairly weak interactions were observed to be dominated by local electrostatics rather thanglobal multipoles or hybridization. The polarization induced on the adsorbate has beenanalysed. A small transfer of electron density was also observed from the molecule to thesurface.