Dinuclear Gold Complexes Research Articles

Dinuclear Gold Complexes of Two Simple but Underutilized Dicarbanionic Ligand Types

Both mono- and bisylide zwitterionic complexes of gold(I), [(C6F5){PhCH(PPh3)}Au] (4), [(C6F5)2(C6H4-p){CH(PPh3)}2Au5] (5) and [(C6F5)2(C6H4-m){CH(PPh3)}2Au2] (6) were prepared by THT substitution in [C6F5(THT)Au] (THT = tetrahydrothiophene) using deprotonated mono- and bis-phosphonium salts. Lithiation of 4,4'-dibromo-2,3,5,6,2',3',5',6'-octafluoro-1,1_- biphenyl and transmetallation with [Cl(Ph3P)Au] produced a dinuclear gold complex of octafluorosubstituted biphenyl [[(PPh3)2(C6F4-C6F4)2Au2]] (8)

Synthesis and photophysical properties of luminescent mononuclear and dinuclear gold(I) complexes with ethynyl-substituted phenanthrolines

A novel asymmetric dinuclear gold(I) complex with 3,6-diethynylphenanthroline, 3,6-bis{(PPh3)–Au–C≡C}2-phen, has been synthesized from Au(PPh3)Cl (PPh3 = triphenylphosphine) and 3,6-diethynyl-1,10-phenanthroline. The asymmetrical dinuclear gold(I) complex, 3,6-bis{(PPh3)–Au–C≡C}2-phen, demonstrated a weak phosphorescence assignable to the metal-perturbed 3 π–π* transition in the long wavelength region compared to an intense emission of the symmetrical dinuclear complex with 3,8-diethynylphenanthroline, 3,8-bis{(PPh3)–Au–C≡C}2-phen. A similar tendency of phosphorescent bands for the mononuclear gold(I) complexes with 5-ethynylphenanthroline, 5-{(PPh3)–Au–C≡C}-phen, and 3-ethynylphenanthroline, 3-{(PPh3)–Au–C≡C}-phen was observed. The absorption bands assignable to the π–π*(C≡Cphen) transition and phosphorescent emission assignable to the metal-perturbed 3 π–π* transition for these four gold(I) complexes were reasonably consistent with the results calculated by DFT and TD-DFT.

A tetranuclear molecular rectangle from four gold(I) atoms linked by dicarbene and diphosphine ligands

A tetranuclear molecular rectangle consisting of two bridging dicarbene ligands and two bridging diphosphine ligands was prepared by connection of two dinuclear gold(I) complexes with 1,2-bis(diphenylphosphino)ethane.

Dinuclear gold(i) and gold(iii) complexes of bridging functionalized bis(N-heterocyclic carbene) ligands: synthesis, structural, spectroscopic and electrochemical characterizations

We report the synthesis of Au(I) and Au(III) complexes, involving alcohol functionalized bis(N-heterocyclic carbene) ligands. Two short reaction pathways lead to the diimidazolium precursors, namely 1,1'-(2,6-pyridinediyl)bis[3-(2-hydroxyethyl)-1H-imidazol-3-ium]diiodide (), 3,3'(methanediyl)bis[1-(2-hydroxy-2-methylpropyl)-1H-imidazol-3-ium]dibromide () and 3,3'-(1,3-propanediyl)bis[1-(2-hydroxy-2-methylpropyl)-1H-imidazol-3-ium]bis(4-methylbenzenesulfonate) (), in which the two azolium rings are bridged by a rigid pyridine unit or an aliphatic chain (C1 or C3). The Au(I) complexes [AuI(Lpy)]2(2+)[PF6-]2 () and [AuI(LC1)]2(2+)[PF6-]2 () were obtained by direct metallation of the salts and , respectively, in the presence of sodium acetate with Au(SMe(2))Cl, followed by an anionic metathesis in the presence of KPF6. The trimethylene compound [AuI(LC3)]2(2+)[PF6-]2 () was prepared by transmetallation between the related precursor [AgI(LC3)]2(2+)[PF6-]2 () and Au(SMe2)Cl. The Au(III) complexes, [AuIII(Lpy)Br2]2(2+)[PF6-]2 (), [AuIII(LC1)Br2]2(2+)[PF6-]2 () and [AuIII(LC3)Br2]2(2+)[PF6-]2 () were generated by oxidation of the corresponding Au(I) species with an excess of elemental bromine. Complexes , [AuI(LC1)]2(2+)[Br-]2 () and have been characterized by single-crystal X-ray diffraction analyses. The electrochemical and luminescence properties of the Au(I) and Au(III) compounds have been studied.

Synthesis of Silver(I) and Gold(I) Complexes with Cyclic Tetra‐ and Hexacarbene Ligands

Cyclic polyimidazolium salts have been investigated with respect to their function as anion receptors and cyclophanelike tetraimidazolium tetracations have been shown to bind anions inside the ring cavity. Cyclic polyimidazolium cations can also serve as precursors for N-heterocyclic carbenes (NHCs) and their complexes. Complexes of cyclic di-NHC ligands have been generated from bisazolium cyclophanes like A. However, such dicarbene ligands coordinate in a cisfashion to the metal center. They act as classical bidentate ligands rather than encapsulating the metal in a manner typical for macrocyclic ligands. Only one cyclic tetradentate dicarbene ligand is known to form a saddle-shaped macrocyclic complex B with nickel(II). We have described the first complex with a macrocyclic tetracarbene ligand C. The rhenium complex of a tridentate, facially coordinated [11]ane-P2C NHC macrocycle has also been reported. Since the preparation of complex C in a metal-template controlled domino-reaction is cumbersome we became interested in the preparation of complexes with macrocyclic poly-NHC ligands from cyclic polyimidazolium cations. This approach has previously been applied successfully for the preparation of some mono (Pd) and dinuclear (Cu, Ag) carbene complexes from the cyclic tetraimidazolium salt D. We became particularly interested in the lutidine-bridged tetraimidazolium salt H4-1 ACHTUNGTRENNUNG(Br4)[8] which upon C deprotonation would yield a potentially hexadentate ligand possessing two C-N-C pincer-type binding sites. Here we describe the mono and dinuclear silver(I) complexes with the carbene ligands derived from H4-1(Br)4 and the transfer of the carbene ligand to yield the mono and dinuclear gold(I) complexes (Scheme 1). A slight modification in the synthesis protocol employed for the preparation of H4-1(Br)4 yields the cyclic hexaimidazolium salt H6-6Br ACHTUNGTRENNUNG(BPh4)5 (Scheme 2). The preparation and molecular structure of the hexanuclear silver(I)-NHC complex derived from this ligand is also ACHTUNGTRENNUNGdescribed. The tetraimidazolium salt H4-1(Br)4 is soluble in water. [8]

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.

Syntheses, Structures, and Photophysical Properties of Mono- and Dinuclear Sulfur-Rich Gold(I) Complexes

The dinuclear gold complexes [{Au(PPh 3)} 2(mu- dmid)] ( 1) ( dmid = 1,3-dithiole-2-one-4,5-dithiolate) and [{Au(PPh 3)} 2(mu- dddt)] ( 2) ( dddt = 5,6-dihydro-1,4-dithiine-2,3-dithiolate) were synthesized and characterized by X-ray crystallography. Both complexes exhibit intramolecular aurophilic interactions with Au...Au distances of 3.1984(10) A for 1 and 3.1295(11) A for 2. A self-assembly reaction between 4,5-bis(2-hydroxyethylthio)-1,3-dithiole-2-thione ( (HOCH 2 CH 2 ) 2 dmit) and [AuCl(tht)] affords the complex [AuCl{ (HOCH 2 CH 2 ) 2 dmit}] 2 ( 4), which possesses an antiparallel dimeric arrangement resulting from a short aurophilic contact of 3.078(6) A. This motif is extended into two dimensions due to intra- and intermolecular hydrogen bonds via the hydroxyethyl groups, giving rise to a supramolecular network. Three compounds were investigated for their rich photophysical properties at 298 and 77 K in 2-MeTHF and in the solid state; [Au 2(mu- dmid)(PPh 3) 2] ( 1), [Au 2(mu- dddt)(PPh 3) 2] ( 2), and [AuCl{( HOCH 2 CH 2 ) 2 dmit}] ( 4). 1 exhibits relatively long-lived LMCT (ligand-to-metal charge transfer) emissions at 298 K in solution (370 nm; tau e approximately 17 ns, where M is a single gold not interacting with the other gold atom; i.e., the fluxional C-SAuPPh 3 units are away from each other) and in the solid state (410 nm; tau e approximately 70 mus). At 77 K, a new emission band is observed at 685 nm (tau e = 132 mus) and assigned to a LMCT emission where M is representative for two gold atoms interacting together consistent with the presence of Au...Au contacts as found in the crystal structure. In solution at 77 K, the LMCT emission is also red-shifted to 550 nm (tau e approximately 139 mus). It is believed to be associated to a given rotamer. 2 also exhibits LMCT emissions at 380 nm at 298 K in solution and at 470 nm in the solid state. 4 exhibits X/MLCT emission (halide/metal to ligand charge transfer) where M is a dimer in the solid state with obvious Au...Au interactions, resulting in red-shifted emission band, and is a monomer in solution in the 10 (-5) M concentration (i.e., no Au...Au interactions) resulting in blue-shifted luminescence. Both fluorescence and phosphorescence are observed for 4.

Coordination Studies of a New Nonsymmetric Ditertiary Phosphane Bearing a Single Phosphaadamantane Cage

AbstractThe new nonsymmetric ditertiary phosphane, Ph2P(CH2)2PAd (1), was prepared in one‐step from Ph2PCH=CH2 andH‐PAd (H‐PAd = 1,3,5,7‐tetramethyl‐2,4,8‐trioxa‐6‐phosphaadamantane) by a hydrophosphination reaction using 2,2′‐azo‐bisisobutyronitrile (AIBN) as free radical initiator. The sterically encumbered phosphaadamantane cage in 1 was found to influence the coordination capabilities of this ligand. The reaction of 1 with [PdCl2(cod)] or [Pt(CH3)2(cod)] (cod = cycloocta‐1,5‐diene) gave the corresponding κ2‐P,P′‐chelate complexes cis‐[PdCl2(1)] (2) and cis‐[Pt(CH3)2(1)] (3), respectively. The dinuclear gold(I) complex [Ph2P(AuCl)(CH2)2PAd(AuCl)] (4) was prepared from 1 and 2 equiv. of [AuCl(tht)] (tht = tetrahydrothiophene). In contrast, the cleavage of the chloro‐bridged dimers {RuCl2(η6‐p‐cymene)}2 or {MCl2(η5‐Cp*)}2 (M = Rh, Ir) with 1 gave the κ1‐P‐monodentate complexes [RuCl2(η6‐p‐cymene)(1)] (5), [RhCl2(η5‐Cp*)(1)] (6) and [IrCl2(η5‐Cp*)(1)] (7), respectively, in which the ‐PAd group is non‐coordinating. Chloride abstraction from 6 (or 7) can be accomplished upon addition of Na[SbF6] to generate the cationic κ2‐P,P′‐chelate complexes 8b (and 9b). Alternatively 8a (or 9a) could be observed, as their chloride salts, by 31P{1H} NMR spectroscopy upon addition of several drops of CH3OH to CDCl3 solutions of 6 (or 7). The reaction of 5–7 with [AuCl(tht)] gave the dinuclear complexes [κ2‐P,P′‐μ‐RuCl2(η6‐p‐cymene){Ph2P(CH2)2PAd(AuCl)}] (10), [κ2‐P,P′‐μ‐RhCl2(η5‐Cp*){Ph2P(CH2)2PAd(AuCl)}] (11) and [κ2‐P,P′‐μ‐IrCl2(η5‐Cp*){Ph2P(CH2)2PAd(AuCl)}] (12). Reaction of two equiv. of 5 with the labile precursors [PdCl2(CH3CN)2] or [PtCl2(PhCN)2] gave instead the novel trinuclear Ru2Pd and Ru2Pt complexes trans‐[{κ2‐P,P′‐μ‐RuCl2(η6‐p‐cymene){Ph2P(CH2)2PAd}}2PdCl2] (13) and trans‐[{κ2‐P,P′‐μ‐RuCl2(η6‐p‐cymene){Ph2P(CH2)2PAd}}2PtCl2] (14), respectively. All new compounds have been fully characterised by spectroscopic and analytical methods. Furthermore the structures of 3·CHCl3, 4, 5, 7·CHCl3, 10·CH2Cl2·0.5C2H10O and 13·2CH2Cl2 have been elucidated by single‐crystal X‐ray crystallography. The X‐ray structures of 10·CH2Cl2·0.5C4H10O and 13·2CH2Cl2 demonstrate how nonsymmetric ditertiary phosphane complexes bearing one pendant phosphaadamantane moiety can be used as metalloligands in the controlled syntheses of novel bi‐ and trimetallic complexes.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

Thioether-Functionalized Ferrocenyl-bis(phosphonite), Fe{(C5H4)P(−OC10H6(μ-S)C10H6O−)}2: Synthesis, Coordination Behavior, and Application in Suzuki-Miyaura Cross-Coupling Reactions

The thioether-functionalized metalloligand ferrocenyl-bis(phosphonite), Fe(C5H4PR)2 (4, R=-OC10H6(micro-S)C10H6O-) is synthesized in three steps starting from ferrocene, and its coordination behavior toward various transition-metal derivatives is described. The reactions of 4 with [Rh(CO)2Cl]2 or M(COD)Cl2 afforded the chelate complexes, cis-[Rh(CO)Cl{Fe(C5H4PR)2-kappaP,kappaP}] (5) or cis-[MCl2{Fe(C5H4PR)2-kappaP,kappaP}] (6, M=PdII; 7, M=PtII), respectively. However, treatment of 4 with CuX (X=Cl, Br, and I) produces binuclear complexes, [Cu2(micro-X)2(MeCN){Fe(C5H4PR)2-kappaP,kappaP}] (8, X=Cl; 9, X=Br; 10, X=I) where the sulfur atom on one side of the ligand is involved in a weak interaction with the copper center. Reaction of 4 with 1 equiv of Ag(PPh3)OTf gives the mononuclear chelate complex [Ag(OTf)PPh3{Fe(C5H4PR)2-kappaP,kappaP}] (11), whereas treatment with 2 equiv of AuCl(SMe2) produces the dinuclear gold complex [Au(Cl){Fe(C5H4PR)2-kappaP,kappaP}Au(Cl)] (12). The crystal structures of 10 and 12 are reported, where a strong metallophilic interaction is observed between the closed-shell metal centers. The palladium complex 6 catalyzes the Suzuki cross-coupling reactions of aryl bromides with phenylboronic acid with excellent turnover numbers (TON up to 1.36x10(5)).

Bidentate amino- and iminophosphine ligands in mono- and dinuclear gold(I) complexes: Synthesis, structures and AuCl displacement by AuC6F5

Bidentate imino- and aminophosphine ligands were prepared by firstly a Schiff-base condensation reaction between 2-(diphenylphosphino)benzaldehyde and the corresponding primary amines to afford the imino derivatives and secondly reduction of the imines with NaBH4 to the aminophosphine ligands in satisfactory yields. The ligands readily reacted with chlorogold(I) compounds to produce new mononuclear iminophosphine- and dinuclear aminophosphine chlorogold(I) complexes. Further, reaction of the dinuclear chlorogold complex with C6F5Au(tht) (tht=tetrahydrothiophene) led to the displacement of one AuCl moiety by AuC6F5 forming a digold(I) mixed halogen/organometallic complex. Both digold(I) complexes displayed intramolecular Au⋯Au interactions, whilst the di(chlorogold) complex also showed an intermolecular Au⋯ Au interaction, as determined by X-ray crystallography. The displacement of only one of the two AuCl groups presumably relates to the strength of the Au–P bond (inert) vs. the weakness of the Au–N bond (labile), the latter being more easily broken.

Dinuclear Gold(I) Isocyanide Complexes with Luminescent Properties, and Displaying Thermotropic Liquid Crystalline Behavior

Dinuclear gold(I) complexes [mu-(4,4'-CN-R-NC){Au(C6F4OC4H9)}2] [R = 1,4-phenylene, n = 8; R = 4,4'-biphenylene, 2,2'-dichloro-4,4'-biphenylene, 2,2'-dimethyl-4,4'-biphenylene, n = 4,6,8,10] have been prepared and their liquid crystal behavior and optical properties studied. Although the free ligands are not mesomorphic, all the gold(I) derivatives described, except the phenylisonitrilegold(I) derivative [mu-(1,4-CN-C6H4-NC){Au(C6F4OC8H17)}2], display liquid crystal behavior, giving rise to a nematic mesophase. The transition temperatures decrease in the order 4-4'-biphenylene > 2,2'-dichloro-4-4'-biphenylene > 2,2'dimethyl-4-4'-biphenylene. All compounds show photoluminescence in the solid state and in solution. The single-crystal X-ray diffraction structures of [mu-(4,4'-CN-R-NC){Au(C6F4OCnH2n+1)}2] (R = 4-4'-biphenylene and 2,2'-dichloro-4-4'-biphenylene) have been determined confirming the rodlike structure of the molecule, with a linear coordination around the gold atoms. There are Au...Au interactions in the 2,2'-dichlorobiphenyl derivative but not in the 4-4'-biphenyl compound.

Reactions of Potassium Bis(phosphinimino)methanide with Group 11 Compounds

Transmetalation of the potassium methanide complex, K{CH(PPh2NSiMe3)2}, with [(Ph3P)2CuI] afforded the corresponding copper complex [{CH(PPh2NSiMe3)2}CuPPh3] (1), whereas the reaction of K{CH(PPh2NSiMe3)2} with [Ph3PAuCl] resulted in the dinuclear gold complex [(Ph3PAu)2{C(PPh2NSiMe3)2}] (2). The solid-state structure of 1 shows the formation of a six-membered metallacycle (N1-P1-C1-P2-N2-Cu) that has a twist boat conformation. In contrast, compound 2 is an alpha,alpha-diaurated species, in which the two gold atoms are coordinated in a linear fashion onto the ligand backbone. Photoluminescence measurements show that the latter compound has a strong violet emission.

{μ-2-[1-(N,N-Dimethylamino)ethyl]ferrocene-1,1′-diylbis(diphenylphosphine)-κ2 P:P′}bis[thiocyanatogold(I)

The title compound, [Au2Fe(C38H37NP2)(SCN)2], is a dinuclear gold(I) complex containing an unsymmetrical bidentate ferrocenyl–phosphine ligand. Selected geometrical parameters for the compound are Au—P = 2.265 (2) and 2.260 (3) Å, Au—S = 2.327 (3) and 2.313 (3) Å, and P—Au—S = 175.61 (9) and 176.86 (9)°.

Isomeric dinuclear gold(i) complexes with highly functionalised ditertiary phosphines: Self-assembly of dimers, rings and 1-D polymeric chains

An isomeric series of six linear, dinuclear, gold(I) complexes (AuCl)2{P,P-C6H4N(CH2PPh2)2(CO2H)(OH)} 6a–6f have been synthesised in high yields (>90%) from AuCl(tht) (tht = tetrahydrothiophene) and the appropriate building blocks C6H4N(CH2PPh2)2(CO2H)(OH) 3a–3f in CH2Cl2. The diphosphine ligands C6H4N(CH2PPh2)21, 4-CO2HC6H4N(CH2PPh2)22 and their corresponding digold(I) complexes 4 and 5 have also been prepared. Solution NMR (31P{1H}, 1H), FT-IR and microanalytical data are in full agreement with the proposed structures. Single crystal X-ray studies confirm that in each case, compounds 4, 5, 6a–6e are linear, with typical Au–P [2.227(4)–2.2349(17) A]/Au–Cl [2.271(2)–2.325(4) A] bond lengths and P–Au–Cl [169.37(1)–179.05(4)°] bond angles. Furthermore these studies demonstrate the relationship between regioselectivity, with respect to the –N(CH2PPh2)2, –CO2H and –OH functionalities around the benzene core, and solid state structures of the gold(I) complexes 6a–6e. In 6a, molecules are associated into pairs through classical intermolecular O–H⋯O hydrogen bonding, whilst in 6b and 6c, dimer pairs are formed using intermolecular O–H⋯Cl hydrogen bonds. 1-D chains of alternate 20-/22- or 8-/18-membered hydrogen bonded rings are propagated using O–H⋯Cl and/or O–H⋯O hydrogen bonds in compounds 6d and 6e. The Au⋯Au separation decreases from 6.179(3) A (for 6a) to 3.0722(9) A (for 6e) suggesting that aurophilicity increases within this series. The X-ray structure of a representative diphosphine 3a is also presented.

DFT/FF study on electronic structure and second-order NLO property of dinuclear gold complex [Au(SeC 2B 10H 11)(PPh 3)] 2

There is a growing interest in the structures and properties of gold complexes because of their especial chemical bonds. The crystal structure of [Au(SeC 2B 10H 11)(PPh 3)] 2 has been determined by X-ray diffraction studies recently. The Au(I)...Au(I) interaction, electronic structures of ligands and nonlinear optical(NLO) properties of systems were discussed by means of DFT and finite field methods in this paper. The calculation results indicate that the second order NLO coefficient of [Au(SeC 2B 10H 11)(PPh 3)] 2 is as high as 10 −29 esu, which is superior to common organic conjugated systems.

Molecular Design of Luminescence Ion Probes for Various Cations Based on Weak Gold(I)···Gold(I) Interactions in Dinuclear Gold(I) Complexes

A series of luminescent dinuclear gold(I) complexes with different crown ether pendants, [Au(2)(PwedgeP)(S-B15C5)(2)] [S-B15C5 = 4'-mercaptobenzo-15-crown-5, P(wedge)P = bis(dicyclohexylphosphino)methane (dcpm) (1), bis(diphenylphosphino)methane (dppm) (2)] and [Au(2)(P(wedge)P)(S-B18C6)(2)] [S-B18C6 = 4'-mercaptobenzo-18-crown-6, P(wedge)P = dcpm (3), dppm (4)], and their related crown-free complexes, [Au(2)(P(wedge)P)(SC(6)H(3)(OMe)(2)-3,4)(2)] [P(wedge)P = dcpm (5), dppm (6)], were synthesized. The low-energy emission of the mercaptocrown ether-containing gold(I) complexes are tentatively assigned as originated from states derived from a S --> Au ligand-to-metal charge transfer (LMCT) transition. The crown ether-containing gold(I) complexes showed specific binding abilities toward various metal cations according to the ring size of the crown pendants. Spectroscopic evidence was provided for the metal-ion-induced switching on of the gold...gold interactions upon the binding of particular metal ions in a sandwich binding mode.

Mitochondrial permeability transition induced by dinuclear gold(I)–carbene complexes: potential new antimitochondrial antitumour agents

Seven dinuclear gold(I) complexes of bidentate N-heterocyclic carbene ligands have been evaluated for their ability to induce mitochondrial membrane permeabilisation (MMP) in isolated rat liver mitochondria. Six of the compounds, at concentrations of 10 μM, induced Ca 2+-sensitive MMP as evidenced by mitochondrial swelling. In the absence of low concentrations of exogenous Ca 2+, the compounds were either inactive or their activity was significantly decreased. The mitochondrial swelling was completely blocked by the addition of cyclosporin A, a well established inhibitor of the mitochondrial permeability transition pore (MPT) that is believed to be responsible for MMP. The rates and levels of uptake of these compounds into mitochondria were estimated by measuring mitochondrial Au levels using inductively coupled plasma optical emission spectroscopy. Significant differences were found in the levels at which the different compounds accumulated in the mitochondria, but these differences did not correlate with the rate at which they induced mitochondrial swelling. These results suggest that the mechanism by which MMP is induced by these lipophilic cationic Au(I)–carbene complexes is not purely a function of the level of compound accumulation. Instead, a more specific mechanism, possibly involving disruption of the function of a particular enzyme, or interaction with a MPT component, appears to be more likely.

Luminescent dinuclear gold complexes of bis(diphenylphosphano)acetylene

We have synthesized a series of dinuclear gold(I) derivatives with the diphosphane bis(diphenylphosphano)acetylene, namely [(AuX) 2(μ-dppa)] (X=Cl, C 6F 5, SC 6F 5, S 2CN(CH 2Ph) 2). X-ray structure determinations for the first three derivatives reveal a linear geometry for the gold centres. There are no intramolecular gold–gold interactions, although for X=Cl intermolecular gold(I)–gold(I) interactions of 3.0694(4) Å lead to an infinite twisted chain; the further presence of C–H⋯Cl contacts leads to a more complex three-dimensional structure. All the derivatives are luminescent in the solid state at low temperature in the range 455–593 nm; most of them are emissive at room temperature in the range 470–598 nm. We have also prepared the dinuclear gold(III) derivative [(Au(C 6F 5) 3) 2(μ-dppa)]. Finally, we have prepared the derivative [(AuCl) 2(μ-dppa) 3], which forms a cage with two tetrahedrically coordinated gold(I) centres at the apical positions bridged by three rigid diphosphane ligands, with a helical twist of 26.2°, and a gold–gold distance of 5.769 Å. The gold(III) and the four-coordinate gold(I) derivatives are not luminescent.

Au 2(μ-G)(μ-dmpe)] · (KBr) 0.75 · 2H 2O, a cyclic dinuclear gold(I) complex with an N3,N9-bridging coordination mode of guanine and aurophilic interactions: synthesis, X-ray crystal structure and luminescence properties (dmpe=1,2-bis(dimethylphosphino)ethane and G=guaninato dianion)

The digold complex [Au 2(μ-G)(μ-dmpe)](KBr) 0.75 · 2H 2O (dmpe=1,2-bis(dimethylphosphino)ethane ( 1)) has been prepared by nucleophilic attack of the guaninate dianion on the gold(I) atoms of [(AuBr) 2(μ-dmpe)] and has been characterised by X-ray crystallography and spectroscopic studies. The structure of 1 consists of dinuclear nine-membered ring molecules, K + cations, Br − anions and water molecules, all of them involved in either weak K⋯O or hydrogen bonding interactions. Within the cyclic dinuclear molecules, gold(I) atoms are bridged on one side by the diphosphine ligand and on the other side by a doubly deprotonated guaninate anion coordinated through neighbouring N3 and N9 nitrogen atoms, with gold(I)⋯gold(I) interactions of 3.030(2) Å. This is the first X-ray example showing an N3,N9-bridging mode for guanine. There are two types of K + cations in the structure, K1 and K2. The former interacts with water molecules to form a unique [K(H 2O) 3(μ-H 2O) 2K(H 2O) 3] 2+ dipotassium unit whereas K2 interact with the O6 atom of the guaninate ligands and oxygen atoms of the dipotassium unit leading to a chain running along the c-axis. Each chain is interdigitated with four neighbouring ones to give rise to an intricate network in which Br1, Br2 and [K(H 2O) 3(μ-H 2O) 2K(H 2O) 3] 2+ fit snugly into cavities defined by digold molecules. Complex 1 luminescence at room temperature and 77 K in the solid state with excitation maxima at 385 nm and emission maxima at 451.8 and 448.7 nm, respectively. The emission spectrum of a saturated solution of 1 in DMSO (dimethyl sulfoxide) shows the maximum at about 440 nm.

Blue Phosphorescence of the Novel Dinuclear Gold(I) Complex Bridged by 1,3-Benzenedithiolate in Solution

Abstract A novel dinuclear benzenedithiolatogold(I) complex was synthesized and characterized spectroscopically. This complex showed intense blue emission [quantum yield at 1.0 × 10−4 mol dm−3: Φ = 0.026(2)] at room temperature in fluid solvents. This emission originates from a metal-perturbed ligand-centered transition. The relatively long life time of the excited state (τ50 = ca. 2 μsec) and the large stokes shift suggest that the emission is phosphorescence. The X-ray single crystal structural determination showed that the complex has a distorted 12-membered macrocyclic structure bridged by two benzenedithiolate ligands, with no gold–gold interactions.