Ag9(1,2-BDT)6]3-: How Square-Pyramidal Building Blocks Self-Assemble into the Smallest Silver Nanocluster.

Badriah J Alamer,Megalamane S Bootharaju,Sergey M Kozlov,Luigi Cavallo,Saidkhodzha Nematulloev,Mohamed Eddaoudi,Partha Maity,Zhen Cao,Jean-Marie Basset,Osman M Bakr,Aleksander Shkurenko,Omar F Mohammed

doi:10.1021/acs.inorgchem.1c00334

Abstract

The emerging promise of few-atom metal catalysts has driven the need for developing metal nanoclusters (NCs) with ultrasmall core size. However, the preparation of metal NCs with single-digit metallic atoms and atomic precision is a major challenge for materials chemists, particularly for Ag, where the structure of such NCs remains unknown. In this study, we developed a shape-controlled synthesis strategy based on an isomeric dithiol ligand to yield the smallest crystallized Ag NC to date: [Ag9(1,2-BDT)6]3– (1,2-BDT = 1,2-benzenedithiolate). The NC’s crystal structure reveals the self-assembly of two Ag square pyramids through preferential pyramidal vertex sharing of a single metallic Ag atom, while all other Ag atoms are incorporated in a motif with thiolate ligands, resulting in an elongated body-centered Ag9 skeleton. Steric hindrance and arrangement of the dithiolated ligands on the surface favor the formation of an anisotropic shape. Time-dependent density functional theory based calculations reproduce the experimental optical absorption features and identify the molecular orbitals responsible for the electronic transitions. Our findings will open new avenues for the design of novel single-digit metal NCs with directional self-assembled building blocks.

Highlights

Investigation of the synthesis and chemistry of noble-metal nanoclusters (NCs), such as Au and Ag, is extensively growing[1−4] and has set the scene for establishing these materials as promising candidates for an expansive range of applications, including medical therapy,[5] drug delivery,[6] sensing,[7,8] and catalysis.[9−11] NCs are desirable for catalysis because of their high catalytic activity and/or selectivity.[12,13]
1,2-BDT plays an important role in controlling the size of the NC
The crystal structure shows that the metal core is a combination of two square pyramids that share one vertex capped by six smallfootprint dithiolate ligands

Summary

■ INTRODUCTION

Investigation of the synthesis and chemistry of noble-metal nanoclusters (NCs), such as Au and Ag, is extensively growing[1−4] and has set the scene for establishing these materials as promising candidates for an expansive range of applications, including medical therapy,[5] drug delivery,[6] sensing,[7,8] and catalysis.[9−11] NCs are desirable for catalysis because of their high catalytic activity and/or selectivity.[12,13] The major conceptual driver for NC utilization in catalysis is based on maximization of the per-atom reaction efficiency through control of the metal particle’s size from the nanometer to subnanometer scale and to a few single atoms.[14,15] NCs exhibit a range of unique and often unexpected properties compared to larger nanoparticles and bulk materials. The optical properties are studied in detail using density functional theory (DFT) calculations

■ RESULTS AND DISCUSSION

■ CONCLUSION

■ REFERENCES