Chirality and Surface Bonding Correlation in Atomically Precise Metal Nanoclusters

Abstract

In chemical science, chirality is indeed one of the most extensively studied phenomena. A chiral molecule possesses a pair of enantiomers and sometimes, only one of the enantiomers is effective as a functional unit or drug. [1,2] The mechanism on how the notorious enantiomers of thalidomide lead to teratogenic newborns has been revealed recently. [3] Chirality in coordination complexes has also been generalized in detail. [4] A classic example of molecules with point chirality is that it contains an asymmetric sp 3 carbon atom which is attached with four different atoms or groups. Such a molecule is not superimposable with its mirror image, and for a simple coordination complex, a metal atom-which is at the centerserves as the role of the chiral carbon (i.e., point chirality). As a result, the relative spatial arrangement of the substituents gives either a clockwise or an anticlockwise order, corresponding to the R and S enantiomers. Of note, the R/S notation of chirality has no fixed relation to the d/l notation (for sugars and amino acids). More generally speaking, chiral object is lack of S n symmetry elements; in other words, if a mirror plane (σ) and inversion (i) are both missing in the object, then it becomes chiral. From this definition, irregular objects are all chiral. Objects of C n (with n-fold axis) or D n (with C 2 axis perpendicular to the n-fold axis) symmetry are much more appealing as long-range order is created. Along with organic chiral molecules, [2] chiral complexes, [4] and chiral supramolecular systems with autonomous self-assembly generated by intermolecular noncovalent interactions have been discussed thoroughly in previous reviews. [5-9] Chiral inorganic nanostructures, with intermediate sizes between molecules of Å and objects of micrometers, are of critical significance owing to their tremendous applications in chiral catalysis, chiroptical metamaterials, enantioseparation, biomolecular and enantiomer sensing, as well as medicine. [10-12] For chiral semiconductor nanoparticles (NPs), commonly called quantum dots (QDs), such as cadmium chalcogenides, the chiral surface ligands are attached onto the QDs through covalent bonds, [13-17] and many applications can be designed. [18] The interactions of chiral moieties attached on graphene NPs lead to their helical assembly, enriching the optical and electronic properties of these chiral nanostructures and facilitating their applications. [19-21] The studies on chiral metal NPs greatly overwhelm those on the semiconductor counterparts. Metal NPs are known to have Chirality is ubiquitous in nature and occurs at all length scales. The development of applications for chiral nanostructures is rising rapidly. With the recent achievements of atomically precise nanochemistry, total structures of ligand-protected Au and other metal nanoclusters (NCs) are successfully obtained, and the origins of chirality are discovered to be associated with different parts of the cluster, including the surface ligands (e.g., swirl patterns), the organic-inorganic in...

Polymerization Isomerism in Co-M (M = Cu, Ag, Au) Carbonyl Clusters: Synthesis, Structures and Computational Investigation

“…These advancements have been possible owing the total structural determination of molecular nanoclusters and atomically precise metal nanoclusters by single-crystal X-ray diffraction (SC-XRD) [ 6 , 7 , 8 , 9 , 10 ]. Enantiomerism is the main type of stereoisomerism found up to now in molecular nanoclusters which, therefore, can be chiral [ 11 , 12 ]. Different types of structural isomerism have been revealed, including core (kernel) isomerism, staple (shell) isomerism and complex isomerism [ 13 ].…”

Chirality communications between inorganic and organic compounds

“…Chiral Au clusters have attracted broad research interests due to their potential in both fundamental science and application. 69,70 The achiral-core@chiral-ligand configuration is just one kind of the chiral clusters, such as Au 246 (SR) 80 , where R is 4-methylbenzenethiol ligands ( Figure 4A). 71 There are two more kinds of chiral clusters: (1) chiral metal kernels, such as Au 20 (SR) 16 72 ( Figure 4B); (2) chiral arrangement of staple motifs on the surface, such as Au 38 (SR) 24 73 ( Figure 4C).…”

“…Schaaff et al 68 report an Au@glutathione structure as early as 1998. Chiral Au clusters have attracted broad research interests due to their potential in both fundamental science and application 69,70 . The achiral‐core@chiral‐ligand configuration is just one kind of the chiral clusters, such as Au 246 (SR) 80 , where R is 4‐methylbenzenethiol ligands (Figure 4A).…”

Luminescent metal nanoclusters: Biosensing strategies and bioimaging applications

“…[5] As a result, MNCs no longer support SPR, but feature a variety of molecule‐like properties, including highest occupied molecular orbital‐lowest occupied molecular orbital transition, luminescence, intrinsic chirality, etc. [6,7]…”