Adsorption of 4-cyanopyridine on Au(111): ab initio calculations and SFG measurements

Abstract

The adsorption of 4-cyanopyridine (4-CP) on a gold single crystal electrode in sodium perchlorate supporting electrolyte has been investigated by voltammetry, sum frequency generation (SFG) and ab initio calculations. Combination of in situ vibrational SFG spectra and DFT, MP2 and MP2 + SQM calculations allows us to obtain fundamental information on the behavior of adsorbed 4-CP as a function of the electrode potential. The configuration of the adsorbed 4-CP is dependent on the electrode potential. 4-CP is adsorbed perpendicular to the electrode surface through the pyridine nitrogen at negative potential, and through the nitrile nitrogen at positive potential. In the intermediate potential range, the molecule is adsorbed parallel to the electrode surface, through the π electrons of the aromatic ring.