Tertiary Hierarchical Complexity in Assemblies of Sulfur-Bridged Metal Chiral Clusters

Abstract

Self-assembly of three-dimensional structures with order across multiple length scaleshierarchical assemblyis of great importance for biomolecules for the functions of life. Creation of similar complex architectures from inorganic building blocks has been pursued toward artificial biomaterials and advanced functional materials. Current research, however, primarily employs only large, nonreactive building blocks such as Au colloids. By contrast, sulfur-bridged transition metal clusters (<2 nm) are able to offer more functionality in catalytic and biochemical reactions. Hierarchical assembly of these systems has not been well researched because of the difficulty in obtaining single-phase clusters and the lack of suitable ligands to direct structure construction. To overcome these challenges, we employ a rigid planar ligand with an aromatic ring and bifunctional bond sites. We demonstrate the synthesis and assembly of 1.2 nm sulfur-bridged copper (SB-Cu) clusters with tertiary hierarchical complexity. The primary structure is clockwise/counterclockwise chiral cap and core molecules. They combine to form clusters, and due to the cap–core interaction (C–H···π), only two enantiomeric isomers are formed (secondary structure). A tertiary hierarchical architecture is achieved through the self-assembly of alternating enantiomers with hydrogen bonds as the intermolecular driving force. The SB-Cu clusters are air stable and have a distribution of oxidation states ranging from Cu(0) to Cu­(I), making them interesting for redox and catalytic activities. This study shows that structural complexity at different length scales, mimicking biomolecules, can occur in active-metal clusters and provides a new platform for investigation of those systems and for the design of advanced functional materials.

Alkynyl-Stabilized Superatomic Silver Clusters Showing Circularly Polarized Luminescence

“…Chirality is a ubiquitous type of geometric symmetry in which an object and its mirror-image counterpart cannot be superimposed. − Ligand-protected atomically precise superatomic metal clusters are among the most promising nanoscale materials that are modeled to investigate their precise structure–property relationships. − Since the chiral Au 38 cluster was first characterized in 2010, the synthesis and separation of enantiomers of metal clusters have gained increasing interest. − Single-crystal X-ray crystallography enables us to see the absolute chiral conformation of metal clusters, and electronic circular dichroism (ECD) signals verify the ground-state chiroptical activity of nanoclusters. − However, CPL that stems from chiral excited states of luminescent materials is very scarce among well-defined superatomic metal clusters because integrating the three basic requirements, namely, perfect single crystals, high-efficiency luminescence, and pure enantiomers, into one superatomic metal cluster remains a considerable challenge. , In particular, the near-infrared (NIR) emission energies of superatomic nanoclusters commonly show a very low quantum efficiency (QY < 0.001). − …”

Janus Cluster: Asymmetric Coverage of a Ag43 Cluster on the Symmetric Preyssler P5W30 Polyoxometalate

“…The linear correlation of the peak current of the anode (I pa ) vs the square root of the scan rate (ν 1/2 ) (Figure 4b inset) indicated that the electrochemical process is diffusion-controlled. 66,67 This has a similar electrochemical evolution trend to P 5 W 30 (Figure S10). Remarkably, the SD/Ag43a carbon paste electrode is stable.…”

Tertiary Chiral Nanostructures from C−H⋅⋅⋅F Directed Assembly of Chiroptical Superatoms

“…[8] Furthermore,t he work reported by Jin and Robinson for the observation of hierarchical complexity in thiolatestabilized metal NCs and their assemblages nicely demonstrated their similarity to natural living systems. [9] It should be noted, however, that although chiral arrangement was observed in hierarchical nanostructures reported by Jin and Robinson, they were racemic in nature.H ere,w e report the synthesis and structure of tertiary chiral nanostructures with 100 %o ptical purity.I nt his work, novel trimetallic chiral clusters,n amely,[ Au 7 Ag 6 Cu 2 (R-o rS-BINAP) 3 (SCH 2 Ph) 6 ] + ,a st he SbF 6…”