Generation of Catalytically Active Gold Nanocrystals in Water Induced with Ferrocene Carboxylate

Abstract

The fabrication and properties of anisotropic gold nanoparticles (AuNPs) are of great interest from fundamental and application standpoints. Whereas various neutral ferrocene derivatives have been shown to reduce Au III to Au 0 NPs owing to slightly exergonic electron transfer in biphasic systems, the question remained open for water soluble ferrocenes containing electron withdrawing substituents increasing the Fe III /Fe II oxidation potential. Here, it is shown that reaction of sodium ferrocene carboxylate, NaFcCO 2 , alone, does not reduce H[Au III Cl 4 ] to stable AuNPs under ambient conditions in water. On the other hand, reaction between NaFcCO 2 and H[Au III Cl 4 ] in water in the presence of poly (vinyl pyrrolidone) (PVP), citrate or other 1,2,3triazole (trz)-containing stabilizers is shown to produce catalytically active Au nanocrystals with various shapes. EDX results confirm the fixation of the ferrocenyl carboxylate ligand onto the AuNP surface. 4-nitrophenol reduction to 4-aminophenol by Na [BH 4 ] in water proceeds in the presence of the various stabilizers, without induction time in most cases, which confirms the weakness of the ferrocenyl carboxylate ligand bonded to the AuNP surface and the favorable role of ferrocenyl carboxylate ligand for catalysis at the AuNP surface.

Redox Activation of Acyclic (Aryl)(amino)carbene Gold(I) Complexes

“…Importantly, ethoxy carbene 1 and the 4-DMA and 2-furyl amino carbene derivatives 2 and 3 produced a gold mirror on the tube wall during the reaction. This suggests that gold nanoparticles − decorated with amino carbene ligands instead of a homogeneous catalytic active species might be the catalytically active species. On the other hand, no gold mirror or gold precipitate is observed with the ferrocenyl substituted precatalysts 4a and 4b substantiating the formation of a molecular catalytically active species.…”