jiachunman81

We report a NaOH-mediated NaBH₄ reduction method for the synthesis of mono-, bi-, and tri-thiolate-protected Au₂₅ nanoclusters (NCs) with precise control of both the Au core and thiolate ligand surface. The key strategy is to use NaOH to tune the formation kinetics of Au NCs, i.e., reduce the reduction ability of NaBH₄ and accelerate the etching ability of free thiolate ligands, leading to a well-balanced reversible reaction for rapid formation of thermodynamically favorable Au₂₅ NCs. This protocol is facile, rapid (≤3 h), versatile (applicable for various thiolate ligands), and highly scalable (>1 g Au NCs). In addition, bi- and tri-thiolate-protected Au₂₅ NCs with adjustable ratios of hetero-thiolate ligands were easily obtained. Such ligand precision in molecular ratios, spatial distribution and uniformity resulted in richly diverse surface landscapes on the Au NCs consisting of multiple functional groups such as carboxyl, amine, and hydroxy. Analysis based on NMR spectroscopy revealed that the hetero-ligands on the NCs are well distributed with no ligand segregation. The unprecedented synthesis of multi-thiolate-protected Au₂₅ NCs may further promote the practical applications of functional metal NCs.

One, two … many: A novel NaOH-mediated NaBH₄ reduction method was developed for the synthesis of mono-, bi-, and tri-thiolate-protected Au₂₅ nanoclusters. Both the Au core and thiolate ligand surface can be precisely controlled.

Hydrogenation was only the beginning: Hantzsch esters have now been used to transfer alkyl groups to imines under mild catalytic conditions to provide a variety of amines (see scheme). Benzyl, secondary alkyl, and tertiary alkyl groups containing ether, ester, and hydroxy functionalities were transferred successfully. The use of Hantzsch esters as alkylation reagents offers a practical and complementary alternative to organometallic processes.