From Au₁₁ to Au₁₃: Tailored Synthesis of Superatomic Di-NHC/PPh₃-Stabilized Molecular Gold Nanoclusters

Abstract

Herein, we report a new method to synthesize molecular gold nanoclusters (AuNCs) stabilized by phosphine (PR3) and di-N-heterocyclic carbene (di-NHC) ligands. The interaction of di-NHC gold(I) complexes, with the general formula [(di-NHC)Au2Cl2] with well-known [Au11(PPh3)8Cl2]Cl clusters provides three new classes of AuNCs through a controllable reaction sequence. The synthesis involves an initial ligand metathesis reaction to produce [Au11(di-NHC)(PPh3)6Cl2]+ (type 1 clusters), followed by a thermally induced rearrangement/metal complex addition with the formation of Au13 clusters [Au13(di-NHC)2(PPh3)4Cl4]+ (type 2 clusters). Finally, an additional metathesis process yields [Au13(di-NHC)3(PPh3)3Cl3]2+ (type 3 clusters). The electronic and steric properties of the employed di-NHC ligand affect the product distribution, leading to the isolation and full characterization of different clusters as the main product. A type 3 cluster has been also structurally characterized and was preliminarily found to be strongly emissive in solution.

Thermal Stability and Electronic Properties of N-Heterocyclic Carbene-Protected Au13 Nanocluster and Phosphine-Protected Analogues

“…Au 13 nanocluster with icosahedral centered structure is one of the hotspots, as first observed in the [Au 13 (PMe 2 Ph) 10 Cl 2 ] 3+ cluster by Mingos and co-workers, and later as a fundamental building block in extended nanocluster research. − According to the superatom model, the I h symmetry Au 13 5+ core is an 8- ce species with an (1S) 2 (1P) 6 closed-shell electronic structure, which exhibits a particularly stable electronic configuration. In recent years, numerous researchers have conducted studies on various ligand-protected Au 13 nanoclusters, − specifically those capped with phosphine. For instance, the Konishi and Li research groups , have synthesized the [Au 13 (dppe) 5 Cl 2 ]­Cl 3 (dppe = 1,2-bis­(diphenylphosphino)­ethane) cluster, exhibiting enhanced optical, near-infrared photoluminescence and chiral capabilities, in comparison with the Au 9 phosphine-protected cluster .…”

Monoarsine-protected icosahedral cluster [Au13(AsPh3)8Cl4]+: comparative studies on ligand effect and surface reactivity with its stibine analogue

“…The exquisite “cluster-to-cluster” synthetic strategy based on ligand exchange has recently become increasingly prevailing. 47,66,67 Taking Au 13 clusters as examples, reactivity studies on Au 13 Sb 8 or its bromo-analogue [Au 13 (SbPh 3 ) 8 Br 4 ] + had shown that they could readily react with glutathione (GSH) or 1-adamantanethiol (S-Adm) to give the achiral Au 25 (SG) 18 or chiral Au 18 (SAdm) 8 (SbPh 3 ) 4 Br 2 , respectively. 39,41 The Wang group also developed a new method of synthesizing thiol-protected Au 25 clusters through reactions of [Au 13 (L′′) 8 Cl 4 ] + (L′′ = P(CH 2 CH 2 CO 2 CH 3 ) 3 ) with appropriate thiols.…”

“…The exquisite "cluster-to-cluster" synthetic strategy based on ligand exchange has recently become increasingly prevailing. 47,66,67 7,68 These preliminary trials conrm the potential use of Au 13 As 8 in the "cluster-to-cluster" syntheses. In comparison, the reactions with Au 13 As 8 proceed more slowly than with Au 13 Sb 8 , indicating that it is more likely for the former to realize more controlled derivatization or functionalization by ligand engineering.…”

“…34,35 More recently, comparative studies on several new types of Au 13 analogues protected by other pnictines ( e.g. , functionalized diphosphine, 36 phosphinous acid, 37 diarsine, 38 and monostibine 39–41 ) or mimics of pnictine ( N -heterocyclic carbenes) 42–47 have also been extensively made both experimentally and theoretically.…”

“…In this context, the past 15 years have rst witnessed a renewed interest in the typical phosphine-protected Au 13 clusters involving development of new synthetic routes (e.g., HCl-induced convergence), 6,7,22,23 exploration of formation mechanisms, 24,25 tuning of electronic properties (e.g., by heterometal doping [26][27][28][29] ), and optical properties (e.g., NIR emission 6,7,30 and chiroptical activity [31][32][33] ), as well as further expansion of their potential applications (e.g., photodynamic catalysis and nano-electronic devices). 34,35 More recently, comparative studies on several new types of Au 13 analogues protected by other pnictines (e.g., functionalized diphosphine, 36 phosphinous acid, 37 diarsine, 38 and monostibine [39][40][41] ) or mimics of pnictine (N-heterocyclic carbenes) [42][43][44][45][46][47] have also been extensively made both experimentally and theoretically.…”