Mechanistic Insights into the Formation of Dodecanethiolate-Stabilized Magnetic Iridium Nanoparticles: Thiosulfate vs Thiol Ligands

The synthesis of stable and isolable iridium nanopartides with an average core size of similar to 1.2 +/- 0.3 nm was achieved by employing sodium S-dodecylthiosulfate as a ligand precursor during the modified Brust-Schiffrin reaction. Transmission electron microscopy (TEM) of the isolated Ir nanopartides revealed a high degree of monodispersity. Further characterizations with H-1 NMR, FT-IR, UV-vis spectroscopy, thermogravimetric analysis (TGA), and X-ray photoelectron spectroscopy (XPS) confirmed that the synthesized Ir nanopartides are stabilized by dodecanethiolate ligands produced upon the adsorption/cleavage of S-dodecylthiosulfate on the growing Ir nanoparticle surface. By comparison, synthetic attempts employing dodecanethiol as a stabilizing ligand led to the formation of Ir-thiolate species (Ir(SR)(3)) as an intermediate and Ir-hydroxide species at the completion of reaction. Mechanistic investigations of these two reactions using S-dodecylthiosulfate and dodecanethiol provided deeper understandings on the novelty of thiosulfate ligands, which allow the successful formation of stable thiolate-capped Ir nanopartides. Moreover, these Ir nanopartides were shown to have strong magnetic properties.