Creation of low-coordination gold sites on Au(111) surface by 1,4-phenylene diisocyanide adsorption

The adsorption of CO on a saturated overlayer of 1,4-phenylene diisocyanide (PDI) adsorbed on a Au(111) surface at 300 K is studied using scanning tunneling microscopy (STM), density functional theory (DFT) calculations and reflection absorption infrared spectroscopy (RAIRS). The PDI forms closed-packed rows of gold-PDI chains by extracting gold atoms from the Au(111) substrate. They are imaged by STM and the structure calculated by DFT. The adsorption of CO is studied on the low-coordination gold sites formed on the PDI-covered surface where it adsorbs exhibiting a CO stretching frequency of 2004 cm^-1, consistent with adsorption on an atop site. It is found that CO is stable on heating the sample to ~150 K and is only removed from the surface by heating to ~180 K. Since low-coordination gold atoms are suggested to be the active catalytic sites on supported gold nanoclusters, "embossing" the surface to form similar low-coordination sites using PDI might offer a strategy for tailoring the catalytic activity of gold.