Synthesis and metal complexation of dual-functionalized silsesquioxane nanoparticles by sequential thiol-epoxy click and esterification reactions

Here, we demonstrate a convenient and robust method for fabricating a series of dual-functionalized silsesquioxane nanoparticles (SQ-NPs) using a thiol-epoxy click reaction and subsequent esterification. Epoxy-functionalized SQ-NP was initially prepared from commercially available (3-glycidyloxypropyl)triethoxysilane. A thiol compound, 2-mercaptopyridine, was used in the thiol-epoxy click reaction, and sulfur-containing acid chloride derivatives were used for subsequent functionalization via esterification. The resulting SQ-NPs have two chemically different groups on a single arm, which affords a high density of peripheral functional groups. The dual-functionalized SQ-NPs with the pyridine and thioether units led to the complexation with copper species, affording a stable Cu complex. This convenient synthetic approach provided dual-functionalized SQ-NPs with narrow size distributions (average particle diameter < 3 nm), reasonable molecular weights (Mn = 3300-4200, Mw/Mn = 1.32-1.45), good solubility, relatively high refractive indices, and the ability to form characteristic metal complexes.