CO chemisorption on the surfaces of the golden cages.

We report a joint experimental and theoretical study of CO chemisorption on the golden cages. We find that the Au(17)(-) cage is highly robust and retains its cage structure in Au(17)(CO)(-). On the other hand, the Au(16)(-) cage is transformed to a structure similar to Au(17)(-) upon the adsorption of CO. Au(18)(-) is known to consist of two nearly degenerate structures, i.e., a cage and a pyramidal isomer, which coexist in the cluster beam. However, upon CO chemisorption only the cage isomer is observed while the pyramidal isomer no longer exists due to its less favorable interaction with CO, compared to the cage isomer. We find that inclusion of the spin-orbit effects is critical in yielding simulated spectra in quantitative agreement with the experimental data and providing unequivocal structural information and molecular insights into the chemical interactions between CO and the golden cages.