Solution-Based Alkyne-Azide Coupling on Functionalized Si(001) Prepared under UHV Conditions

Synthesis of organic bilayers on silicon was realized by a combination of surface functionalization under ultrahigh vacuum (UHV) conditions and solution-based click chemistry. The silicon (001) surface was prepared with a high degree of perfection in UHV and functionalized via chemoselective adsorption of ethynyl cyclopropyl cyclooctyne from the gas phase. A second organic layer was then coupled in acetonitrile via the copper-catalyzed alkyne-azide click reaction. The samples were directly transferred from UHV via the vapor phase of the solvent into the solution of reactants and back to UHV without contact to ambient conditions. Each reaction step was monitored by means of X-ray photoelectron spectroscopy in UHV; the N 1s spectra clearly indicated the click reaction of the azide group in the two test molecules employed, i.e., methyl-substituted benzyl azide and azide-substituted pyrene. In both cases, up to 50-60% of the ethynyl cyclopropyl cyclooctyne molecules on the surface were reacted.

Automated summary

The synthesis of organic bilayers on silicon was achieved through a combination of surface functionalization under ultrahigh vacuum conditions and solution-based click chemistry; each reaction step was monitored in UHV, with up to 50-60% of the ethynyl cyclopropyl cyclooctyne molecules on the surface reacting with the azide groups.