Central Au Atom Research Articles

DFT investigation on the application of a thiol-protected gold cluster Au12(SCH3)9+ toward adsorption of temozolomide

The adsorption behavior of a thiol-protected gold cluster Au12(SCH3)9+ to temozolomide (TMZ) has been investigated at the M06-2X-D3/6-311G(d, p)&LanL2dz//B3LYP-D3(BJ)/6-31G(d,p)&LanL2dz. Results show that TMZ prefers to combine with the central Au atom in the Au cluster via its O and N atoms, forming ionic Au–O and Au–N bonds, respectively. The calculated adsorption energies of TMZ on Au12(SCH3)9+ are − 44.43, −12.27, −43.59, and −10.01 kcal·mol−1 in the gas phase, water, acetic acid, and dimethyl sulfoxide, respectively. The interaction strength and mode between the TMZ drug and Au12(SCH3)9+ vary with different solution environments. Therefore, the solvent could influence the interaction of TMZ-Au12(SCH3)9+ complexes. Such a property of TMZ–Au12(SCH3)9+ could be applied to drug-delivery processes, which might contribute to improving the efficiency of this drug and reducing its toxic and side effects. Based on the natural population analysis and QTAIM analysis, noticeable charge transfer from TMZ to the Au cluster was observed, increasing the dipole moments of TMZ–Au12(SCH3)9+ complexes. We believe that this work could extend the applications of small Au-based clusters, especially thiol-protected gold clusters in drug-delivery processes.

Synthesis and crystal structure of [1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](isocyanato-κN)gold(I)

The title complex, [Au(NCO)(C27H36N2)], was synthesized by ligand metathesis from [1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene]gold(I) chloride and sodium cyanate in anhydrous tetrahydrofuran and crystallized from toluene at 233 K in the orthorhombic space group P212121, as a neutral complex with the central Au atom di-coordinated by an N-heterocyclic carbene [Au—C = 1.963 (2) Å] and an isocyanate [Au—N 1.999 (2) Å] ligands, with a linear CAuNCO moiety. The crystal packing is consolidated by C—H...O hydrogen bonds.

Anion···Anion [AuI4]-···[AuI2]- Complex Trapped in the Solid State by Tetramethylammonium Cations.

A discrete π-hole···σ-hole dimer is synthesized and X-ray characterized. It presents a perfect thumbtack geometry where the σ-hole of the linear [AuI2]- anion points to the π-hole located above the central Au-atom of the [AuI4]- anion. Such discrete π-hole···σ-hole dimers are unprecedented in literature, since all mixed-valence gold(I/III) iodide compounds reported to date form infinite ···([AuI4]-···[AuI2]-) n ·· chains in the solid state. If an excess of iodine is used for the synthesis, triiodide [I3]- ions are partially incorporated into the [AuI2]- sites, forming infinite chains. The nature of the anion···anion interaction has been studied considering two possibilities: (i) a π-hole coinage bond or (ii) σ-hole halogen bond using high-level density functional theory calculations, the quantum theory of atoms in molecules, and the noncovalent interaction plot index.

Enhanced Fluorescence with Tunable Color in Doped Diphosphine-Protected Gold Nanoclusters.

Rational control of the luminescent properties of ligand-protected coinage metal clusters has long been pursued but remains challenging. Here we explore the crucial structural and electronic factors governing the fluorescence of a diphosphine-protected [Au13(dppe)5Cl2]3+ cluster by time-dependent density functional theory calculations. By substituting the central Au atom with group 5 to group 11 transition metal atoms, the emission wavelength is adjustable from red to blue, accompanied by enhanced fluorescence intensity compared with the undoped cluster. The evolution of light-emitting behavior upon doping and the corresponding roles of the dopant, Au cage, ligands, and their interplay are interpreted at the electronic structure level. In particular, strong dopant-Au cage interaction associated with large electron-hole overlap on the dopant are is a key factor to endow large emission energy and intensity. These theoretical results provide vital guidance for designing atomically precise nanoclusters with visible fluorescence and high quantum yield for practical uses.

Double σ-Aromaticity in a Planar Zinc-Doped Gold Cluster: Au9Zn.

The strong relativistic effects result in many interesting chemical and physical properties for gold and gold compounds. One of the most surprising findings has been that small gold clusters prefer planar structures. Dopants can be used to tune the electronic and structural properties of gold nanoclusters. Here we report an experimental and theoretical investigation of a Zn-doped gold cluster, Au9Zn-. Photoelectron spectroscopy reveals that Au9Zn- is a highly stable electronic system with an electron binding energy of 4.27 eV. Quantum chemical studies show that the global minimum of Au9Zn- has a D3h structure with a closed-shell electron configuration (1A1'), which can be viewed as replacing the central Au atom by Zn in the open-shell parent Au10- cluster. The high electronic stability of Au9Zn- is corroborated by its extremely large HOMO-LUMO gap of 3.3 eV. Chemical bonding analyses revealed that the D3h Au9Zn- are bonded by two sets of delocalized σ bonds, giving rise to double σ aromaticity and its remarkable stability. Two planar low-lying isomers are also observed, corresponding to a similar triangular structure with the Zn atom on the edge and another one with one of the corner Au atoms moved to the edge of the triangle.

Bright NIR-II Photoluminescence in Rod-Shaped Icosahedral Gold Nanoclusters.

Fluorophores with high quantum yields, extended maximum emission wavelengths, and long photoluminescence (PL) lifetimes are still lacking for sensing and imaging applications in the second near-infrared window (NIR-II). In this work, a series of rod-shaped icosahedral nanoclusters with bright NIR-II PL, quantum yields up to ≈8%, and a peak emission wavelength of 1520nm are reported. It is found that the bright NIR-II emission arises from a previously ignored state with near-zero oscillator strength in the ground-state geometry and the central Au atom in the nanoclusters suppresses the non-radiative transitions and enhances the overall PL efficiency. In addition, a framework is developed to analyze and relate the underlying transitions for the absorptions and the NIR-II emissions in the Au nanoclusters based on the experimentally defined absorption coefficient. Overall, this work not only shows good performance of the rod-shaped icosahedral series of Au nanoclusters as NIR-II fluorophores, but also unravels the fundamental electronic transitions and atomic-level structure-property relations for the enhancement of the NIR-II PL in gold nanoclusters. The framework developed here also provides a simple method to analyze the underlying electronic transitions in metal nanoclusters.

Aggregation induced emission of a new naphthyridine-ethynyl-gold(i) complex as a potential tool for sensing guanosine nucleotides in aqueous media.

A new organometallic alkynyl-gold(i) complex capable of exhibiting aggregation induced emission was designed and synthesized. The linear complex structure possesses a central Au(i) atom, bearing two axial ligands: (1) 1,3,5-triaza-7-phosphaadamantane and (2) 2-acetamido-7-ethynyl-1,8-naphthyridine. While the former accounts for its partial solubility in an aqueous environment, the latter acts as a receptor unit for binding guanosine nucleotides and derivatives via multiple hydrogen bonding interactions. At high concentrations, aggregation of the complex was observed by the formation of new absorption (λmax∼ 400 nm) and emission bands (550-700 nm). Formation of aggregates of ca. 60 nm diameter was confirmed by Small Angle X-ray Scattering (SAXS). Disruption of the aggregates in the presence of guanosine derivatives resulted in a ratiometric signal with apparent association constants in the order of 105 M-1 and high sensitivity (around 63% signal change) which are, to the best of our knowledge, in line with the highest values recorded for nucleotide sensors based on hydrogen bonding and capable of working in water. Computational studies indicate the presence of additional hydrogen bonding interactions that account for the strong binding of the Au(i) complex to phosphorylated guanosine nucleotides.

A Correlated Series of Au/Ag Nanoclusters Revealing the Evolutionary Patterns of Asymmetric Ag Doping.

Doping of metal nanoclusters is an effective strategy for tailoring their functionalities for specific applications. To gain fundamental insight into the doping mechanism, it is of critical importance to have access to a series of correlated bimetal nanoclusters with different doping levels and further reveal the successive transformations. Herein, we report asymmetric doping of Ag into an Au21 nanocluster to form a series of new Au/Ag bimetal nanoclusters and the effects of doping on the evolution of size, structure, and properties based upon X-ray crystallography and optical spectroscopy analyses. The asymmetric doping discovered in the series reveals two important rules. First, the heteroatom doping-induced kernel transformation mechanism is revealed, explaining the successive conversions from Au21(S-Adm)15 with an incomplete cuboctahedral kernel to Au20Ag1(S-Adm)15 with a complete cuboctahedral Au12Ag1 kernel and then to Au19Ag4(S-Adm)15 with an icosahedral Au10Ag3 kernel. The electron density accumulated on the central Au atom(s) is rationalized to force an expansion of radial metal-metal bond angles, which triggers the cuboctahedral-to-icosahedral kernel conversion. This mechanism is generalized by elucidating several other cases. Second, through comparison of a series of seven nanoclusters (all protected by adamantanethiolate), we find that the unit cell symmetry of their crystals is correlated with the symmetry of the cluster's kernel. Specifically, we observe a sequential change from triclinic to monoclinic to trigonal unit cell in the series with increasing kernel symmetry. The kernel structure-dependent optical properties are also discussed.

Structurally Precise Dichalcogenolate-Protected Copper and Silver Superatomic Nanoclusters and Their Alloys.

The chalcogenolato silver and copper superatoms are currently a topic of cutting edge research besides the extensively studied Au n(SR) m clusters. Crystal structure analysis is an indispensable tool to gain deep insights into the anatomy of these sub-nanometer clusters. The metal framework and spatial arrangement of the chalcogenolates around the metal core assist in unravelling the structure-property relationships and fundamental mechanisms involved in their fabrication. In this Account, we discuss our contribution toward the development of dichalcogenolato Ag and Cu cluster chemistry covering their fabrication and precise molecular structures. Briefly introducing the significance of the single crystal structures of the atomically precise clusters, the novel dichalcogenolated two-electron superatomic copper and its alloy systems are presented first. The [Cu13{S2CNR}6{C≡CR'}4]+ is so far the first unique copper cluster having Cu13 centered cuboctahedra, which is a miniature of bulk fcc structure. The galvanic exchange of the central Cu with Ag or Au results in a similar anatomy of formed bimetallic [Au/Ag@Cu12(S2CN nBu2)6(C≡CPh)4][CuCl2] species. This is unique in the sense that other contemporary M13 cores in group 11 superatomic chemistry are compact icosahedra. The central doping of Ag or Au significantly affects the physiochemical properties of the bimetallic Cu-rich clusters. It is manifested in the dramatic quantum yield enhancement of the doped species [Au@Cu12(S2CN nBu2)6(C≡CPh)4]+ with a value of 0.59 at 77 K in 2-MeTHF. In the second part, the novel eight-electron dithiophosphate- and diselenophosphate-protected silver systems are presented. A completely different type of architecture was revealed for the first time from the successful structural determination of [Ag21{S2P(O iPr)2}12]+, [Ag20{S2P(O iPr)2}12] and [Au@Ag19{S2P(OPr)2}12]. They exhibit a nonhollow M13 (Ag or AuAg12) icosahedron, capped by 8 and 7 Ag atoms in the former and latter two species, respectively. The overall metal core units are protected by 12 dithiophosphate ligands and the metal-ligand interface structure was found to be quite different from that of Au n(SR) m. Notably, the [Ag20{S2P(O iPr)}12] cluster provides the first structural evidence of a silver superatom with a chiral metallic core. This chirality arises through the simple removal of one of capping Ag+ cations of [Ag21{S2P(O iPr)2}12]+ present on its C3 axis. Further, the effects of the ligand exchange on the structures of [Ag20{Se2P(O iPr)2}12], [Ag21{Se2P(OEt)2}12]+, and [AuAg20{Se2P(OEt)2}12]+ are studied extensively. The structure of the former species is similar to its dithiophosphate counterpart ( C3 symmetry). The latter two ( T symmetry) differ in the arrangement of 8 capping Ag atoms, as they form a cube engraving the Ag13 (AuAg12) icosahedron. The blue shifts in absorption spectra and photoluminescence further indicate the strong influence of the central Au atom in the doped clusters. Finally, the first paradigm of unusual heteroatom doping induced size-structure transformations is discussed by presenting the case of formation of [Au3Ag18{Se2P(O iPr)2}12]+ upon Au doping into [Ag20{Se2P(O iPr)2}12]0. Finally, before concluding this Account, we discuss the possibility of many unique structural isomers with different physical properties for the aforementioned Ag superatoms which need to be explored extensively in the future.

Suppressing Isomerization of Phosphine-Protected Au9 Cluster by Bond Stiffening Induced by a Single Pd Atom Substitution.

The fluxional nature of small gold clusters has been exemplified by reversible isomerization between [Au9(PPh3)8]3+ with a crown motif (Au9(C)) and that with a butterfly motif (Au9(B)) induced by association and dissociation with compact counteranions (NO3-, Cl-). However, structural isomerization was suppressed by substitution of the central Au atom of the Au9 core in [Au9(PPh3)8]3+ with a Pd atom: [PdAu8(PPh3)8]2+ with a crown motif (PdAu8(C)) did not isomerize to that with a butterfly motif (PdAu8(B)) upon association with the counteranions. Density functional theory calculation showed that the energy difference between PdAu8(C) and PdAu8(B) is comparable to that between Au9(C) and Au9(B), indicating that the relative stabilities of the isomers are not a direct cause for the suppression of isomerization. Temperature dependence of Debye-Waller factors obtained by X-ray absorption fine-structure analysis revealed that the intracluster bonds of PdAu8(C) were stiffer than the corresponding bonds in Au9(C). Natural bond orbital analysis suggested that the radial Pd-Au and lateral Au-Au bonds in PdAu8(C) are stiffened due to the increase in the ionic nature and decrease in electrostatic repulsion between the surface Au atoms, respectively. We conclude that the formation of stiffer metal-metal bonds by Pd atom doping inhibits the isomerization from PdAu8(C) to PdAu8(B).

Optical Absorption of Small Palladium‐Doped Gold Clusters

The effect of Pd doping on the structure and optical absorption of small cationic gold clusters is investigated by a combined photodissociation spectroscopy and time‐dependent density functional theory study of Aun+Arp and PdAun‐1+Arp (n = 4,5; p = 0,1). While pure Au clusters are planar, the Pd‐doped clusters are 3D. UV–visible absorption is studied in the 2.0–4.7 eV photon energy range, allowing the observation of previously unreported absorption bands for Au4+ and Au4+Ar. The oscillator strength of the optical transitions is dramatically reduced upon incorporating a Pd atom in Au4+ and Au4+Ar, while this effect is less pronounced for Au5+Ar. Analysis of the electron density transfer shows a different influence of Pd with size. While Pd has a formal negative charge in Au3Pd+, in Au4Pd+ most of the charge is attracted by the highly coordinated central Au atom, leaving Pd positively charged, also affecting the induced structural changes. In addition, orbital analysis of the optical transitions is carried out in order to identify the levels involved in the optical absorption of the pure Au and Pd doped clusters. A reduction of the s density near the Fermi energy, induced by Pd doping, causes a quenching of optical absorption.

Role of the Central Gold Atom in Ligand-Protected Biicosahedral Au24 and Au25 Clusters

The crystal structures of the ligand-protected clusters [Au24(PPh3)10(SC2H4Ph)5Cl2]+ and [Au25(PPh3)10(SC2H4Ph)5Cl2]2+ have been elucidated recently, and they comprise the same biicosahedral structural motif for the Au core. The only difference is the central Au atom joining two icosahedra which is absent in the Au24 cluster. On the basis of density functional simulations, we have evaluated the structural, electronic, optical, and vibrational properties of the clusters in question with a full presentation for the thiolate and phosphine side groups. Our spherical harmonics analysis of the electronic structure shows that the chemical stability of both clusters can be understood based on an 8 + 8 electron superatom model, where each icosahedron represents a closed-shell superatom of its own with a 1S21P6 electronic configuration. Similar optical absorption and circular dichroism spectra are computed for the two cluster sizes. The hollow site in Au24 makes the cluster more rigid as the associated icosahedral strain in the Au core is released. This results in a significant shortening of interplanar Au–Au distances and increases the breathing mode frequencies of the individual Au icosahedra.

Au(CN)n Complexes: Superhalogens with Pseudohalogen as Building Blocks

Electron affinity (EA) is one of the most important factors that govern reactivity of atoms and molecules. Chlorine, with the highest electron affinity (3.6 eV) of all elements in the periodic table, is a classic example of reactive elements. Over past thirty years, much research has been done to expand the scope of molecules with electron affinities even larger than that of Cl. These molecules, called superhalogens, have the general formula MX(n+1) where M is a metal atom, X is a halogen atom, and n is the valency of the metal. In this paper we explore the potential of pseudohalogens such as CN, which mimic the chemistry of halogens, to serve as building blocks of new superhalogens. Using calculations based on density functional theory, we show that when a central Au atom is surrounded by CN moieties, superhalogens can be created with electron detachment energies as high as 8.4 eV. However, there is a stark contrast between the stability of these superhalogens and that of conventional AuF(n) superhalogens. Whereas AuF(n) complexes are stable up to n = 5 for neutrals and n = 6 for anions, Au(CN)(n) complexes (with CN moieties attached individually) are metastable beyond n = 1 for neutrals and n = 3 for anions. We investigate the nature and origin of these differences. In addition, we elucidate important distinctions between electron affinity (EA) and adiabatic detachment energy (ADE), two terms that are often used synonymously in literature.

Crystal structure and X-ray photoelectron spectroscopy of ciprofloxacinium tetrachloroaurate monohydrate

The complex (CfqH2AuCl4 · H2O ((CfqH2)+ is the ciprofloxacinium cation) was isolated and analyzed by spectral luminescence, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. The central Au(III) atom has no direct interatomic contacts with the 1-cyclopropyl-6-fluoro-4-oxo-(1-piperazinyl)-1,4-dihydro-3-quinolinecarboxylic acid (CfqH) molecule. The structure is formed by the [AuCl4]− anions having a square structure, (CfqH2)+ cations, and water molecules combined by hydrogen bonds. The protonation of CfqH occurs at the terminal nitrogen atom of the piperazinyl group. Core-level X-ray photo-electron spectra of carbon, oxygen, nitrogen, and fluorine were measured. Cleavage of the Su-Cl bond was shown to be the primary step of the photoinduced decomposition of the compound.

Inhibited and enhanced nucleation of gold nanoparticles at the water|1,2-dichloroethane interface

The deposition of gold at the interface between immiscible electrolyte solutions has been investigated using reduction of tetrachloroaurate or tetrabromoaurate in 1,2-dichloroethane, with aqueous phase hexacyanoferrate as reducing agent. In a clean environment without defects present at the interface, the Au(III) complex was reduced to the Au(I) complex, but no solid phase formation could be observed. A deposition process could only be observed through the addition of artificial nucleation sites in the form of palladium nanoparticles at the interface. This process could be associated with the reduction of the Au(I) halide complex to metallic gold, by determining the gold reduction potentials in 1,2-dichloroethane. XANES measurements indicate that tetrachloroaurate ion transfers intact into the organic phase, with the central Au atom retaining its oxidation state of +3 and the overall anion remaining charged at -1.

Vapochromic and Mechanochromic Tetrahedral Gold(I) Complexes Based on the 1,2‐Bis(diphenylphosphino)benzene Ligand

Tetrahedral gold(I) complexes containing the diphosphane ligand (dppb=1,2-bis(diphenylphosphino)benzene), [Au(dppb)(2)]X [X=Cl (1), Br (2), I (3), NO(3) (4), BF(4) (5), PF(6) (6), B(C(6)H(4)F-4)(4) (7)], and the ethanol and methanol adducts of complex 4, 8, and 9, were prepared to analyze their unique photophysical properties. These complexes are classified into two categories on the basis of their crystal structures. In Category I, the complexes (1-5) have relatively-small counter anions and two dppb ligands are symmetrically coordinated to the central Au(I) atom, and display an intense blue phosphorescence. Alternatively, the complexes (6-9) in Category II have large counter anions and two dppb ligands asymmetrically coordinated to Au(I) atom, and display a yellow or yellow orange phosphorescence. The difference in the phosphorescence color of the complexes between the Category I and II is ascribed to the change in the structure of the cationic moiety in the complex. According to DFT calculations, the symmetry reduction caused by the large counter anion of the complex in Category II gives the destabilization of HOMO (σ*) levels, leading to the red-shift of the emission peak. We have demonstrated that the symmetry reductions are responsible for the phosphorescence color alteration caused by external stimuli (volatile organic compounds and mechanical grinding).

(Z)-O-Ethyl-N-propylthiocarbamato-κS](triphenylphosphine-κP)gold(I)

The title compound, [Au(C6H12NOS)(C18H15P)], features a linear S,P-donor set about the central Au atom with a deviation from linearity [S—Au—P = 176.66 (5)°] due to an intra­molecular Au⋯O contact [2.991 (5) Å]. Supra­molecular dimers are formed in the crystal structure mediated by C—H⋯N inter­actions.

(Z)-O-Ethyl-N-(p-tolyl)thiocarbamato-κS](triphenylphosphine)-κP]gold(I)

The title compound, [Au(C10H12NOS)(C18H15P)], features a linear S,P-donor set about the central Au atom. The thio­carbamate ligand is orientated to place the aryl ring in close proximity to Au [the closest Au⋯C distance is 3.238 (4) Å], which results in a small deviation from the ideal linear P—Au—S geometry.

Partial Oxidation of Propylene to Propylene Oxide over a Neutral Gold Trimer in the Gas Phase: A Density Functional Theory Study

We report a B3LYP study of a novel mechanism for propylene epoxidation using H(2) and O(2) on a neutral Au(3) cluster, including full thermodynamics and pre-exponential factors. A side-on O(2) adsorption on Au(3) is followed by dissociative addition of H(2) across one of the Au-O bonds (DeltaE(act) = 2.2 kcal/mol), forming a hydroperoxy intermediate (OOH) and a lone H atom situated on the Au(3) cluster. The more electrophilic O atom (proximal to the Au) of the Au-OOH group attacks the C=C of an approaching propylene to form propylene oxide (PO) with an activation barrier of 19.6 kcal/mol. We predict the PO desorption energy from the Au(3) cluster with residual OH and H to be 11.5 kcal/mol. The catalytic cycle can be closed in two different ways. In the first subpathway, OH and H, hosted by the same terminal Au atom, combine to form water (DeltaE(act) = 26.5 kcal/mol). We attribute rather a high activation barrier of this step to the breaking of the partial bond between the H atom and the central Au atom in the transition state. Upon water desorption (DeltaE(des) = 9.9 kcal/mol), the Au(3) is regenerated (closure). In the second subpathway, H(2) is added across the Au-OH bond to form water and another Au-H bond (DeltaE(act) = 22.6 kcal/mol). Water spontaneously desorbs to form an obtuse angle Au(3) dihydride, with one H atom on the terminal Au atom and the other bridging the same terminal Au atom and the central Au atom. A slightly activated rearrangement to a symmetric triangular Au(3) intermediate with two equivalent Au-H bonds, addition of O(2) into the Au-H bond, and rotation reforms the hydroperoxy intermediate in the main cycle. On the basis of the DeltaG(act), which contains contribution from both pre-exponetial factor and activation energy, we identify the propylene epoxidation step as the actual rate-determining step (RDS) in both the pathways. The activation barrier of the RDS (epoxidation step: DeltaE(act) = 19.6 kcal/mol) is in the same range as that in the published computationally investigated olefin epoxidation mechanisms involving Ti sites (without Au involved) indicating that isolated Au clusters and possibly Au clusters on non-Ti supports can be active for gas-phase partial oxidation, even though cooperative mechanisms involving Au clusters/Ti-based-supports may be favored.

Synthesis and characterisation of N-coordinated pentafluorophenyl gold(i) thiazole-derived complexes and an unusual self-assembly to form a tetrameric gold(i) complexElectronic supplementary information (ESI) available: Characterisation data for 1. See http://www.rsc.org/suppdata/dt/b3/b303625a/

Treatment of [Au(C6F5)(SC4H8)] (1) (SC4H8 = tetrahydrothiophene or tht) with HCNC(CH3)C(H)S, CH3SCNC(CH3)C(H)S, (I) or piperidine yields the neutral mononuclear imine complexes [Au(C6F5){NC(H)SC(H)CCH3}] (2) and [Au(C6F5){NC(SCH3)SC(H)CCH3}] (3), or the amine complex [Au(C6F5){N(H)CH2(CH2)3CH2}] (4). The reaction of 1 with SCN(H)C(CH3)C(H)S, (II) affords the thione complex [Au(C6F5){SCN(H)C(CH3)C(H)S}] (5), which, in CH2Cl2via spontaneous intermolecular deprotonation of the thione ligand, self-assembles to an unique tetramer of Au(I), [Au{SCNC(CH3)C(H)S}]4 (6) containing a folded rectangle of Au-atoms with aurophlilic interactions [av. Au⋯Au distance, 3.02(4) Å and av. Au–Au–Au angle, 87(2)°]. N-coordination of the imine complexes has been confirmed by 15N NMR and the crystal structure determination of 2 which exhibits the expected linear N-coordination and intermolecular Au⋯Au [3.345(1) Å] contacts. The crystal structure of 5 shows thione S-coordination of II to the central Au atom.