Hexanuclear Gold Research Articles

Tri‐ and Hexanuclear Gold(I) Systems Based on Tribenzotriquinacene

A tridentate trimethylstannyl substituted alkyne based on the tribenzotriquinacene (TBTQ) scaffold has been transformed into several gold(I)phosphane complexes by tin‐gold exchange. While the molecular structures of the gold(I) derivatives with less bulky trimethyl and dimethylphenylphosphane ligands exhibit intermolecular aurophilic interactions, the sterically demanding triphenylphosphane ligands inhibit the occurrence of Au···Au contacts. In addition, a hexanuclear gold(I) system was synthesised by terminal functionalisation of the hexaalkynyl TBTQ. Investigations of the photophysical properties of the gold(I)phosphane TBTQ compounds revealed their luminescent character at room temperature.

Hyperconjugative Aromaticity-Based Circularly Polarized Luminescence Enhancement in Polyaurated Heterocycles.

Hyperconjugative aromaticity (HA) frequently appears in metalla-aromatics, but its effect on photophysical properties remains unexplored to date. Herein, we reveal two different HA scenarios in nearly isostructural triaurated indolium and benzofuranylium compounds. The biased HAs show a discernible effect on the spatial arrangement of metal atoms and thus tailor metal parentage in frontier orbitals and the HOMO-LUMO energy gap. Theoretical calculations and structural analyses demonstrate that HA not only influences the degree of electron delocalization over the trimetalated aromatic rings but also affects π-coordination of Au(I) and intercluster aurophilic interaction. Consequently, the triaurated benzofuranylium complex shows better photoluminescence performance (quantum yield up to 49.7%) over the indolium analogue. Furthermore, four pairs of axially chiral bibenzofuran-centered trinuclear and hexanuclear gold clusters were purposefully synthesized to correlate their HA-involved structures with the chiroptical response. The triaurated benzofuranylium complexes exhibit strong circular dichroism (CD) response in solution but CPL silence even in solid film. In contrast, the hexa-aurated homologues display strong CD and intense CPL signals in both aggregated state and solid film (luminescence anisotropy factor glum up to 10-3). Their amplified chiroptical response is finally ascribed to the dominant intermolecular exciton couplings of large assemblies formed through the HA-tailored aggregation of hexanuclear compounds.

Tetra- and hexanuclear string complexes of the coinage metals.

Reaction of the PNNP ligand system N,N'-bis[(2-diphenylphosphino)phenyl]formamidinate (dpfam) featuring different coordination compartments with [AuCl(tht)], [CuMes]5, [AgMes]4, or [AuC6F5(tht)] (tht = tetrahydrothiophene) resulted in tetranuclear homo- and heterometallic coinage metal complexes, as well as a hexanuclear gold complex. All of them feature a metal string conformation. Photophysical investigation revealed a significant dependence of the photoluminescence properties on the metal composition. Below 100 K, the PL efficiency of three compounds approaches nearly 100%.

Concentration- and Solvation-Induced Reversible Structural Transformation and Assembly of Polynuclear Gold(I) Sulfido Complexes.

A series of polynuclear gold(I) sulfido complexes of bis(diphenylphosphino)amine ligands has been synthesized and characterized. A rather small variation in the conformation of the bis(diphenylphosphino)amine ligands has led to distinct differences in the identity of the polynuclear gold(I) sulfido complexes formed. Unprecedented concentration-dependent and solvation-dependent reversible cluster-to-cluster transformation between a dodecanuclear gold(I) sulfido complex (LMe-Au12) and a hexanuclear gold(I) sulfido complex (LMe-Au6) has been observed. The transformation process has been monitored not only by 1H and 31P{1H} NMR spectroscopy but also by UV-vis absorption spectroscopy and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) in the solution state. This work has provided a simple approach to achieve structure modulation of gold(I) sulfido complexes and an understanding of supramolecular transformations via external stimuli.

A Gold Quartet Framework with Reversible Anisotropic Structural Transformation Accompanied by Luminescence Response

Summary Hierarchy and chirality are the fundamental characteristics of biomolecules. Chemistry on hierarchical self-assembly and spontaneous symmetry breaking helps to uncover the mechanism of living activities and the origin of chirality in nature. Herein, we describe a chiral gold quartet framework (GQF) with C4-symmetric structure hierarchically aggregated from an achiral anionic [Au10(dpptrz)4S4]2− (dpptrz-Au10), which was acquired via click-reaction-induced and Au(I)⋅⋅⋅Au(I)-interaction-directed cluster-to-cluster transformation (CCT) from the rationally designed [(dppa)6Au18S8]2+ (dppa-Au18). Inter-cluster hydrogen bonding and alkali ion coordination were observed to assist the hierarchical self-assembly and chiral self-organization of the GQF. Upon exposing the crystal to vacuum, the bottom-up constructed GQF showed an anisotropic structural transformation accompanied by a visual luminescence change in a single-crystal-to-single-crystal (SCSC) manner that became reversible upon removal of vacuum. This research largely advances the potential of polynuclear gold(I)-sulfido clusters in hierarchical self-assembly and luminescent materials.

Synthesis, structural characterization, and photophysical studies of hexanuclear gold(I) chalcogenido complexes

AbstractA hexanuclear gold(I) selenido cluster and its sulfido counterpart, [Au6{μ‐Ph2PN(CH2‐o‐Py)PPh2}3(μ3‐E)2](ClO4)2 (E = S, Se), with bridging bis(diphenylphosphino)amine ligands were synthesized and characterized. The X‐ray crystal structure of the selenido cluster was determined, with the gold core possessing a distorted heterocubane structure. Intramolecular aurophilic interactions with short Au(I)⋯Au(I) contacts of around 3.09–3.13 Å were observed. The complexes were found to emit strongly in the solid state with orange to red emission colors. Their electronic absorption and emission properties were also investigated.

Dual Emission of a Cyclic Hexanuclear Gold(I) Complex. Interplay between Au3 and Au2 Ligand-Supported Luminophores

Finding diverse and tunable molecular structures is relevant toward the design of functional nanostructures. The photoluminescence of complex [Au2Cl(μ-P-C-κP,κC,κN)]3 (1), featuring a ligand-suppor...

Synthesis of Silver(I) and Gold(I) Complexes Containing Enantiopure Pybox Ligands. First Assays on the Silver(I)-Catalyzed Asymmetric Addition of Alkynes to Imines.

Dinuclear complexes [Ag2(CF3SO3){(S,S)-(i)Pr-pybox}2][CF3SO3] (1), [Ag2(R-pybox)2][X]2 [R-pybox = 2,6-bis[4-(S)-isopropyloxazolin-2-yl]pyridine (S,S)-(i)Pr-pybox and X = PF6 (2) and BF4 (3); R-pybox = 2,6-bis[(3aS,8aR)-8,8a-dihydro-3aH-indeno[1,2-d]oxazol-2-yl]pyridine (3aS,3a'S,8aR,8a'R)-indane-pybox and X = CF3SO3 (4)], [Ag2{(S,S)-(i)Pr-pybox}{(3aS,3a'S,8aR,8a'R)-indane-pybox}][CF3SO3]2 (5), and [Ag2(R-pybox)3][X]2 [R-pybox = (3aS,3a'S,8aR,8a'R)-indane-pybox and X = CF3SO3 (10), SF6 (11), and PF6 (12)] as well as mononuclear complexes [Ag(R-pybox)2][X] [R-pybox = (S,S)-(i)Pr-pybox and X = SbF6 (6), PF6 (7), and BF4 (8); R-pybox = (3aS,3a'S,8aR,8a'R)-indane-pybox) and X = BF4 (9)] have been prepared by the reaction of the corresponding silver salts and pybox ligands using the appropriate molar ratio conditions. The first gold(I)/pybox complex [Au6Cl4{(S,S)-(i)Pr-pybox}4][AuCl2]2 (13) has been synthesized by the reaction of [AuCl{S(CH3)2}] and (S,S)-(i)Pr-pybox (1:1 molar ratio) in acetonitrile. The structures of the dinuclear (1, 4, 5, 10, and 11) and mononuclear (6 and 9) silver complexes and the hexanuclear gold complex 13 have been determined by single-crystal X-ray diffraction analysis. These studies have been complemented with a solution-state study by NMR spectroscopy, which included structure elucidation, variable-temperature measurements, and diffusion studies using diffusion-ordered spectroscopy (DOSY; for complexes 1, 4, 10, and 12). Complexes 1, 2, 4, and 10 have been assayed as catalysts in the asymmetric addition of phenylacetylene to N-benzylideneaniline.

Aurophilicity-triggered assembly of novel cyclic penta- and hexanuclear gold(I) complexes with rigid anionic NHC-type ligands.

The products of the reaction between N,N'-diphosphanylimidazol-2-ylidene (P-C-P) and gold(I) precursors depend on the nature of the anions associated with the latter. In contrast to the reported reaction with [Au(tht)2(OTf)], the use of [AuCl(tht)] led to the new hexanuclear complex 1, which features a Au6(μ3-P-C,κC,κN,κP)3 skeleton. The reaction of lithium imidazolide (P-C-Li) and [AuCl(tht)] also afforded 1, together with an unusual salt of the general formula [Au5Cl(μ3-P-C-κP,κC,κN)3]2[AuCl2]2 (2), which contains [Au5(μ3-P-C-κP,κC,κN)](+) subunits. In the solid state, one of these Au5 cations is associated with an [AuCl2](-) anion, while two other cations interact through their unique dicoordinated N-Au-N center with a [AuCl2](-) anion, with the charge of the resulting monocation being compensated for by another [AuCl2](-) anion to give a Au12 salt. Remarkably, the latter displays seven different bonding types at Au(I): C-Au-C, N-Au-N, P-Au-P, Cl-Au-Cl, C-Au-N, P-Au-Cl, and Au···Au.

Hexanuclear Gold(I) Phosphide Complexes as Platforms for Multiple Redox-Active Ferrocenyl Units

The synthesis, X-ray crystal structures, electrochemical, and spectroscopic studies of a series of hexanuclear gold(I) μ(3)-ferrocenylmethylphosphido complexes stabilized by bridging phosphine ligands, [Au(6)(P-P)(n)(Fc-CH(2)-P)(2)][PF(6)](2) (n=3, P-P=dppm (bis(diphenylphosphino)methane) (1), dppe (1,2-bis(diphenylphosphino)ethane) (2), dppp (1,3-bis(diphenylphosphino)propane) (3), Ph(2)PN(C(3)H(7))-PPh(2) (4), Ph(2)PN(Ph-CH(3)-p)PPh(2) (5), dppf (1,1′-bis(diphenylphosphino)ferrocene) (6); n=2, P-P=dpepp (bis(2-diphenylphosphinoethyl)phenylphosphine) (7)), as platforms for multiple redox-active ferrocenyl units, are reported. The investigation of the structural changes of the clusters has been probed by introducing different bridging phosphine ligands. This class of gold(I) μ(3)-ferrocenylmethylphosphido complexes has been found to exhibit one reversible oxidation couple, suggestive of the absence of electronic communication between the ferrocene units through the Au(6)P(2) cluster core, providing an understanding of the electronic properties of the hexanuclear Au(I) cluster linkage. The present complexes also serve as an ideal system for the design of multi-electron reservoir and molecular battery systems.

A Hexanuclear Gold Cluster Supported by Three‐Center–Two‐Electron Bonds and Aurophilic Interactions

Herz aus Gold: Der erste sechskernige Goldcluster, der ausschließlich aus Gold(I)-Zentren aufgebaut ist (siehe Bild; Au gelb, C schwarz, P lila), katalysiert die Aktivierung von Alkinen unter homogenen Bedingungen.

A Hexanuclear Gold Cluster Supported by Three‐Center–Two‐Electron Bonds and Aurophilic Interactions

A heart of gold: The first hexanuclear gold cluster formed exclusively by gold(I) centers (see picture; Au yellow, C black, P purple) has been shown to be catalytically active for the activation of alkynes under homogeneous conditions.

A hexanuclear gold(i) metallatriangle derived from a chiral dithiophosphate: synthesis, structure, luminescence and oxidative bromination reactivity

We report the synthesis, structure, luminescence and reactivity of a 27-membered gold(I) metallatriangle containing three separate dinuclear gold(I) units self-assembled from a chiral tetradentate dianionic dithiophosphate ligand. The hexanuclear complex luminesces in the solid-state (λmax = 488 nm) at 298 K. Additionally, the Au(I) complex forms an unexpected dinuclear Au(III) oxidative addition product upon reaction with Br2.

Reactions of Gold(I) Acetylides with 1,1′-Diisocyanoferrocene: From Orthodox to Unorthodox Behavior

1,1′-Diisocyanoferrocene (1) reacts with the gold(I) acetylides [Au(C≡C-p-C6H4R)]n (2a R = CF3, 2b R = H, 2c R = OMe, 2d R = NMe2) to afford the respective dinuclear gold complexes [{Au(C≡C-p-C6H4R)}2(μ-1)] (3), whose aurophilic aggregation in the solid state depends on the nature of the substituent R. The product of the reaction of 1 with [Au(C≡C-Fc)]n (2e, Fc = ferrocenyl) is the hexanuclear gold cluster [(Fc-C≡C-Au-C≡N-C5H4)Fe{C5H4-N═C(Au)-C≡C-Fc}]3, which is composed of three subunits 4 and exhibits an unusual arrangement of gold atoms. The formation of (4)3 is based on a different specific reaction of the two chemically equivalent functional groups of 1 with 2e, viz., coordination and 1,1-insertion. This “schizoid” behavior apparently is a novel variant of induced reaction asymmetry and constitutes a new phenomenon in chemistry. The reaction of 2e with 1,1′-bis(diphenylphosphanyl)ferrocene (5) affords the expected [(Au-C≡C-Fc)2(μ-5)] (6), which does not exhibit aurophilic interactions.

Mononuclear, Dinuclear, and Hexanuclear Gold(I) Complexes with (aza-15-crown-5)Dithiocarbamate

The reactions of sodium (aza-15-crown-5)dithiocarbamate with [AuClL] precursors lead to mono-, di-, or hexanuclear derivatives depending on L. The homoleptic hexanuclear gold(I) cluster [Au6(S2CNC10H20O4)6] is formed by displacement of the chloride and isocyanide ligands in [AuCl(CN(2,6-Me2C6H3))]. X-ray diffraction studies show a novel geometry in gold cluster chemistry where the six gold atoms display a cyclohexane-like geometry in a chair conformation with Au-Au-Au angles of 117.028(9) degrees, two short gold-gold distances of 2.9289(5) A, and bidentate bridging dithiocarbamate ligands. The molecular structure shows a crown of gold atoms surrounded by crown ethers. This derivative luminesces at 569 nm at room temperature in the solid state. A dinuclear isomer [Au2(S2CNC10H20O4)2] had been reported previously and was obtained by reaction with [AuCl(SMe2)]. The mechanism to obtain the hexanuclear derivative involves a mononuclear intermediate [Au(S2CNC10H20O4)(CNR)] for which the X-ray structure shows a short gold-gold distance of 3.565 A with the two molecules in an anti configuration. Phosphine gold(I) mononuclear derivatives [Au(S2CNC10H20O4)(PR3)] (R = Me, Ph, both characterized by X-ray diffraction) and dinuclear diphosphine derivatives [{Au(S2CNC10H20O4)}2(mu-P-P)] (P-P = dppm, bis(diphenylphosphinomethane); dppp, 1,3-bis(diphenylphosphinopropane); and dppf, 1,1'-bis(diphenylphosphinoferrocene)) are also reported. In the mononuclear complexes, the molecular structure confirms that the dithiocarbamato ligand is mainly acting as monodentate, with a second longer Au-S distance of 3.197 (PMe3), 2.944(4) (PPh3), and 2.968 A (CNR). Three phosphine complexes are emissive at 562 (PMe3), 528 (PPh3), and 605 nm (dppm), at 77 K. X-ray diffraction studies of the dppm derivative show gold-gold intramolecular contacts of 3.0972(9) A (3.2265(10) A for a second independent molecule) and basically monodentate coordination of the dithiocarbamato ligands. All the complexes extract sodium and potassium salts from aqueous solutions. The diphosphine derivatives are noticeably better extractors than the monophosphino derivatives, mainly for potassium salts.

Synthesis and auration of primary and di-primary heteroaryl-phosphines

Convenient high-yield syntheses of the primary and di-primary heteroaryl-phosphines R-PH2 and H2P-R'-PH2(with R = 2-thienyl, 2-furyl, and R'= 2,5-thiophenediyl, 2,5-furandiyl, respectively) are presented. The products and a set of precursor molecules have been characterized by analytical and spectral data, and the crystal structures of selected molecules have been determined: 2-C4H3O-PCl2, 2,5-(Cl2P)2C4H2O, 2,5-[(Et2N)2P]2C4H2E (with E = O, S). In the crystals, the two molecules with -PCl2 substituents adopt trans conformations, while the other two have the -P(NEt2)2 groups rotated into a twist conformation. The reaction of the thienyl compounds with tris[(tert-phosphine)gold]oxonium tetrafluoroborates gave almost quantitative yields of the tri- and hexanuclear gold complexes, respectively: {2-C4H3S-P[Au(PR3)]3}+BF4- and [2,5-{[(R3P)Au]3P}2C4H2S]2+(BF4(-)2, (R =tBu, Ph). The structures of the compounds with R3P =tBu3P ligands have been determined. In both cases the [2-C4H3/2S-P] units cap triangles of gold atoms in an array that can be described as three [Au(PR3)]+ cations bridged by a phosphido dianion (RP)2-.

A Novel Polynuclear Gold-Sulfur Cube with an Unusually Large Stokes Shift

A 1.87-eV energy gap between the lowest energy excitation maximum and the emission maximum in solution was found for the novel hexanuclear gold(I) sulfido complex 1 (Ar=p-CH3C6H4), which has a heterocubane-type structure. Besides this abnormally large Stokes shift of around 15 000 cm−1, 1 exhibits intense orange luminescence in the solid state.

Benzenehexathiol as a template rim for a golden wheel: synthesis and structure of [{CSAu(PPh3)}6

The reaction of benzenehexathiol, C6(SH)6, with [Au(PPh3)Cl] in the presence of triethylamine gave the hexanuclear gold(I) compound [{CSAu(PPh3)}6] whose structure has been determined; the hexagon of the central benzene carbon atoms is surrounded by a hexagon of sulfur atoms, followed by a hexagon of gold atoms and the wheel-like structure is completed by six peripheral phosphine ligands with interlocked aryl groups.

Mononuclear gold(I) and heteronuclear gold(I)-palladium(II) bibenzimidazolate complexes with new coordination modes of the ligand

Metathetic reactions of gold(I) halide complexes and the potassium salt of 2,2′-bibenzimidazol afford binuclear bibenzimidazolate gold(I) complexes with the general formula {Au 2L 2}(μ-BiBzIm) L = PPh 3, PBu n 3, P(OMe) 3; L 2 = 1,1-bis(diphenylphosphine)-methane (dppm), 1,2-bis(diphenylphosphine)ethane (dppe). These complexes are Lewis bases and can be used as precursors for the synthesis of tri and tetranuclear cationic gold(I) complexes, or trinuclear gold(I) and palladium(II) complexes where the bibenzimidazolate anion is acting as bridging tetranuclear ligand. An hexanuclear gold(I)-palladium(II) complex is also described.