Cupriphication of gold to sensitize d10-d10 metal-metal bonds and near-unity phosphorescence quantum yields.

Outer-shell s0/p0 orbital mixing with d10 orbitals and symmetry reduction upon cupriphication of cyclic trinuclear trigonal-planar gold(I) complexes are found to sensitize ground-state Cu(I)-Au(I) covalent bonds and near-unity phosphorescence quantum yields. Heterobimetallic Au4Cu2 {[Au4(µ-C2,N3-EtIm)4Cu2(µ-3,5-(CF3)2Pz)2], (4a)}, Au2Cu {[Au2(µ-C2,N3-BzIm)2Cu(µ-3,5-(CF3)2Pz)], (1) and [Au2(µ-C2,N3-MeIm)2Cu(µ-3,5-(CF3)2Pz)], (3a)}, AuCu2 {[Au(µ-C2,N3-MeIm)Cu2(µ-3,5-(CF3)2Pz)2], (3b) and [Au(µ-C2,N3-EtIm)Cu2(µ-3,5-(CF3)2Pz)2], (4b)} and stacked Au3/Cu3 {[Au(µ-C2,N3-BzIm)]3[Cu(µ-3,5-(CF3)2Pz)]3, (2)} form upon reacting Au3 {[Au(µ-C2,N3-(N-R)Im)]3 ((N-R)Im = imidazolate; R = benzyl/methyl/ethyl = BzIm/MeIm/EtIm)} with Cu3 {[Cu(µ-3,5-(CF3)2Pz)]3 (3,5-(CF3)2Pz = 3,5-bis(trifluoromethyl)pyrazolate)}. The crystal structures of 1 and 3a reveal stair-step infinite chains whereby adjacent dimer-of-trimer units are noncovalently packed via two Au(I)⋯Cu(I) metallophilic interactions, whereas 4a exhibits a hexanuclear cluster structure wherein two monomer-of-trimer units are linked by a genuine d10-d10 polar-covalent bond with ligand-unassisted Cu(I)-Au(I) distances of 2.8750(8) Å each-the shortest such an intermolecular distance ever reported between any two d10 centers so as to deem it a "metal-metal bond" vis-à-vis "metallophilic interaction." Density-functional calculations estimate 35-43 kcal/mol binding energy, akin to typical M-M single-bond energies. Congruently, FTIR spectra of 4a show multiple far-IR bands within 65-200 cm-1, assignable to vCu-Au as validated by both the Harvey-Gray method of crystallographic-distance-to-force-constant correlation and dispersive density functional theory computations. Notably, the heterobimetallic complexes herein exhibit photophysical properties that are favorable to those for their homometallic congeners, due to threefold-to-twofold symmetry reduction, resulting in cuprophilic sensitization in extinction coefficient and solid-state photoluminescence quantum yields approaching unity (ΦPL = 0.90-0.97 vs. 0-0.83 for Au3 and Cu3 precursors), which bodes well for potential future utilization in inorganic and/or organic LED applications.

Solventless supramolecular chemistry via vapor diffusion of volatile small molecules upon a new trinuclear silver(I)-nitrated pyrazolate macrometallocyclic solid: an experimental/theoretical investigation of the dipole/quadrupole chemisorption phenomena.

A comparative study on the tendency of a new trinuclear silver(I) pyrazolate, namely, [N,N-(3,5-dinitropyrazolate)Ag]3 (1), and a similar compound known previously, [N,N-[3,5-bis(trifluoromethyl)pyrazolate]Ag]3 (2), to adsorb small volatile molecules was performed. It was found that 1 has a remarkable tendency to form adducts, at room temperature and atmospheric pressure, with acetone, acetylacetone, ammonia, pyridine, acetonitrile, triethylamine, dimethyl sulfide, and tetrahydrothiophene, while carbon monoxide, tetrahydrofuran, alcohols, and diethyl ether were not adsorbed. On the contrary, 2 did not undergo adsorption of any of the aforementioned volatile molecules. Adducts of 1 were characterized by elemental analysis, IR, thermogravimetric analysis (TGA), Brunauer-Emmett-Teller (BET) surface area, and diffusion NMR measurements. The crystal structures of 1·2CH3CN and compound 3, derived from an attempt to crystallize the adduct of 1 with ammonia, were determined by single-crystal X-ray diffractometric studies. The former shows a sandwich structure with a 1:2 stoichiometric [Ag3]/[CH3CN] ratio in which one acetonitrile molecule points above and the other below the centroid of the Ag3N6 metallocycle. Compound 3 formed via rearrangement of the ammonia adduct to yield an anionic trinuclear silver(I) derivative with an additional bridging 3,5-dinitropyrazolate and having [Ag(NH3)2](+) as the counterion, [Ag(NH3)2][N,N-(3,5-dinitropyrazolate)4Ag3]. Irreversible sorption and/or decomposition upon vapor exposure are desirable advantages toward toxic gas filtration applications, including ammonia inhalation. TGA confirms the analytical data for all of the samples, showing weight loss for each adsorbed molecule at temperatures significantly higher than the corresponding boiling temperature, which suggests a chemical-bonding nature for adsorption as opposed to physisorption. BET surface measurements of the "naked" compound 1 excluded physical adsorption in its porous cavities. Density functional theory simulation results are also consistent with the chemisorption model, explain the experimental adsorption selectivity for 1, and attribute the lack of similar adsorption by 2 to significantly less polarizable electrostatic potential and also to strong argentophilic bonding whose energy is even higher than the quadrupole-dipole adduct bond energy upon proper selection of the density functional.

Halide and nitrite recognizing hexanuclear metallacycle copper(II) pyrazolates.

Halide-centered hexanuclear, anionic copper(II) pyrazolate complexes [trans-Cu(6)((3,5-CF(3))(2)pz)(6)(OH)(6)X](-), X = Cl, Br, I are isolated in a good yield from the redox reaction of the trinuclear copper(I) pyrazolate complex [µ-Cu(3)((3,5-CF(3))(2)pz)(3)] with a halide source such as PPh(3)AuCl or [Bu(4)N]X, X = Cl, Br, or I, in air. X-ray structures of the anion-centered hexanuclear complexes show that the six copper atoms are bridged by bis(3,5-trifluoromethyl)pyrazolate and hydroxyl ligands above and below the six copper atom plane. The anions are located at the center of the cavity and weakly bound to the six copper atoms in a µ(6)-arrangement, Cu-X = ~3.1 Å. A nitrite-centered hexanuclear copper(II) pyrazolate complex [trans-Cu(6)((3,5-CF(3))(2)pz)(6)(OH)(6)(NO(2))](-) was obtained when a solution of [PPN]NO(2) in CH(3)CN was added dropwise to the trinuclear copper(I) pyrazolate complex [µ-Cu(3)((3,5-CF(3))(2)pz)(3)] dissolved in CH(3)CN, in air. Blue crystals are produced by slow evaporation of the acetonitrile solvent. The X-ray structure of [PPN][trans-Cu(6)((3,5-CF(3))(2)pz)(6)(OH)(6)(NO(2))] complex shows the nitrite anion sits in the hexanuclear cavity and is perpendicular to the copper plane with a O-N-O angle of 118.3(7)°. The (19)F and (1)H NMR of the pyrazolate ring atoms are sensitive to the anion present in the ring. Anion exchange of the NO(2)(-) by Cl(-) can be observed easily by (1)H NMR.

Mono and tetranuclear gold(I) complexes of tris(1-benzylimidazole-2-yl)phosphine.

The reaction of tris(1-benzylimidazole-2-yl)phosphine, (Bzim)(3)P, 1, with Ph(3)AsAuCl in 1:1 stoichiometric ratio produced (Bzim)(3)PAuCl, 2. The reaction of (Bzim)(3)PAuCl with NaAuCl(4) in 1:1 stoichiometry in dichloromethane gives an orange-yellow crystalline tetranuclear gold(I) cluster [{mu-N,N'-(Bzim)(3)PAuCl}(2)Au(2)][AuCl(2)][AuCl(4)], 3. Complex 4, [{mu-N,N'-(Bzim)(3)PAuCl}(2)Au(2)][AuCl(2)](2) is formed when the reaction stoichiometry of (Bzim)(3)PAuCl and AuCl(4)(-) is 2:1. The crystal structure of 3 shows the formation of a 12-membered macrocycle with Au...Au distances of approximately 3.0 A. The structures of (Bzim)(3)PAuCl and 3 show Au...H-C interactions ranging from 2.57 to 2.95 A. Complex 2 crystallizes in the monoclinic space group P2(1)/n (Z = 4), a = 9.1927(5), b = 13.528(2), c = 22.995(2) A, and beta = 94.537(5)(o). Complex 3 crystallizes in the monoclinic space group P2(1)/c (Z = 4), a = 13.785(4), b = 21.426(6), c = 25.203(8) A, and beta = 96.51(6)degrees.

A study on the inhibition of dihydrofolate reductase (DHFR) from Escherichia coli by gold(i) phosphane compounds. X-ray crystal structures of (4,5-dichloro-1H-imidazolate-1-yl)-triphenylphosphane-gold(i) and (4,5-dicyano-1H-imidazolate-1-yl)-triphenylphosphane-gold(i).

An unprecedented study on the inhibitory activities of a class of phosphane gold(i) complexes on E. coli dihydrofolate reductase (DHFR) is reported. The gold(i) complexes considered in this work consist of azolate or chloride ligands and phosphane as co-ligands. The ligands have been functionalized with polar groups (-COOH, -COO(-), NO2, Cl, CN) to obtain better solubility in polar media. Neutral, anionic and cationic gold(i) complexes have been tested as DHFR inhibitors by means of a continuous direct spectrophotometric method. X-ray structural characterizations were performed on ((triphenylphosphine)-gold(i)-(4,5-dicyanoimidazolyl-1H-1yl) and on the analog (triphenylphosphine)-gold(i)-(4,5-dichloroimidazolyl-1H-1yl). The inhibition constants obtained from the enzyme tests range from 20 µM to 63 nM (auranofin) and are conducive to promoting these compounds as potential DHFR inhibitors.

Luminescent Chains Formed from Neutral, Triangular Gold Complexes Sandwiching TlI and AgI. Structures of {Ag([Au(µ-C2,N3-bzim)]3)2}BF4·CH2Cl2, {Tl([Au(µ-C2,N3-bzim)]3)2}PF6·0.5THF (bzim = 1-Benzylimidazolate), and {Tl([Au(µ-C(OEt)═NC6H4CH3)]3)2}PF6·THF, with MAu6 (M = Ag+, Tl+) Cluster Cores.

It has been found that several trinuclear complexes of AuI interact with silver and thallium salts to intercalate Ag+ and Tl+ cations, thereby forming chains. The resulting sandwich clusters center the cations between the planar trinuclear moieties producing structures in which six AuI atoms interact with each cation in a distorted trigonal prismatic coordination. The resultant (B3AB3B3AB3)∞ pattern of metal atoms also shows short (∼3.0 Å) aurophilic interactions between BAB molecular centers. These compounds display a strong visible luminescence, under UV excitation, which is sensitive to temperature and the metal ion interacting with the gold. X-ray crystal structures are reported for Ag([Au(µ-C2,N3-bzim)]3)2BF4·CH2Cl2 (P [Formula: see text] , Z = 2, a = 14.4505(1)Å; b = 15.098(2)Å; c = 15.957(1)Å; α = 106.189(3)°; ß = 103.551(5)°; γ = 101.310(5)°); Tl([Au(µ-C2,N3-bzim)]3)2PF6·0.5C4H8O (P [Formula: see text] , Z = 2, a = 15.2093(1)Å; b =15.3931(4)Å; c = 16.1599(4)Å; α = 106.018(1)°; ß = 101.585(2)°; γ=102.068(2)°); and Tl([Au(µ-C(OEt)═NC6H4CH3)]3)2PF6·C4H8O (P2(1)/n, Z = 4, a = 16.4136(3)Å; b = 27.6277(4)Å; c = 16.7182(1)Å; ß = 105.644(1)°). Each compound shows that the intercalated cation, Ag+ or Tl+, coordinates to a distorted trigonal prism of six AuI atoms. The counteranions reside well apart from the cations between the cluster chains.

Synthesis and characterization of azolate gold(I) phosphane complexes as thioredoxin reductase inhibiting antitumor agents.

Following an increasing interest in the gold drug therapy field, nine new neutral azolate gold(I) phosphane compounds have been synthesized and tested as anticancer agents. The azolate ligands used in this study are pyrazolates and imidazolates substituted with deactivating groups such as trifluoromethyl, nitro or chloride moieties, whereas the phosphane co-ligand is the triphenylphosphane or the more hydrophilic TPA (TPA = 1,3,5-triazaphosphaadamantane). The studied gold(I) complexes are: (3,5-bis-trifluoromethyl-1H-pyrazolate-1-yl)-triphenylphosphane-gold(I) (1), (3,5-dinitro-1H-pyrazolate-1-yl)-triphenylphosphane-gold(I) (2), (4-nitro-1H-pyrazolate-1-yl)-triphenylphosphane-gold(I) (5), (4,5-dichloro-1H-imidazolate-1-yl)-triphenylphosphane-gold(I) (7), with the related TPA complexes (3), (4), (6) and (8) and (1-benzyl-4,5-di-chloro-2H-imidazolate-2-yl)-triphenylphosphane-gold(I) (9). The presence of deactivating groups on the azole rings improves the solubility of these complexes in polar media. Compounds 1-8 contain the N-Au-P environment, whilst compound 9 is the only one to contain a C-Au-P environment. Crystal structures for compounds 1 and 2 have been obtained and discussed. Interestingly, the newly synthesized gold(I) compounds were found to possess a pronounced cytotoxic activity on several human cancer cells, some of which were endowed with cis-platin or multidrug resistance. In particular, among azolate gold(I) complexes, 1 and 2 proved to be the most promising derivatives eliciting an antiproliferative effect up to 70 times higher than cis-platin. Mechanistic experiments indicated that the inhibition of thioredoxin reductase (TrxR) might be involved in the pharmacodynamic behavior of these gold species.

Sulfonate- or carboxylate-functionalized N-heterocyclic bis-carbene ligands and related water soluble silver complexes.

New N-heterocyclic carbene ligand precursors {H(2)C(HTz(R))(2)} and {H(2)C(HIm(R))(2)} (HTz = 1,2,4-triazole; HIm = imidazole; R = PrSO(3) or EtCOO) were obtained starting from the compounds bis(1,2,4-triazol-1-yl)methane and bis(imidazol-1-yl)methane. The related silver(i) carbene complexes were prepared in degassed water solution by treatment of the triazolium or imidazolium species with Ag(2)O, resulting in well-characterized and water soluble bimetallic complexes of general formula {Na(2)[H(2)C(Tz(R))(2)](2)Ag(2)} and {Na(2)[H(2)C(Im(R))(2)](2)Ag(2)}. In these metallacycles every silver atom is coordinated to two triazolin- or imidazolin-2-ylidene rings, belonging to two different dicarbene units.

Self-assembly of a high-nuclearity chloride-centered copper(II) cluster. Structure and magnetic properties of [Au(PPh3)2][trans-Cu6(micro-OH)6[micro-(3,5-CF3)2pz]6Cl].

A chloride-centered hexanuclear copper(II) pyrazolate [Au(PPh3)2][trans-Cu6(micro-OH)6[micro-(3,5-CF3)2pz]6Cl] is isolated from the reaction of the trinuclear copper(I) pyrazolate [Cu3[micro-(CF3)2pz]3] with PPh3AuCl and Ph3P in moist air. The six copper atoms are bridged by pyrazolate and hydroxyl ligands, above and below the copper plane. The chloride anion exists at the center of the planar cavity formed by the copper atoms with Cu-Cl distances of 3.02-3.13 A. The magnetic susceptibility measurements show a strong antiferromagnetic coupling between the copper centers with an estimated exchange constant of J approximately 650 cm-1.

Gold(I) and silver(I) mixed-metal trinuclear complexes: dimeric products from the reaction of gold(I) carbeniates or benzylimidazolates with silver(I) 3,5-diphenylpyrazolate.

Trinuclear mixed-metal gold-silver compounds are obtained by the reaction of gold(I) carbeniate [Au(mu-C(OEt)=NC6H4-p-CH3)]3, TR(carb), or gold(I) imidazolate [Au-mu-C,N-1-benzyl-2-imidazolate]3, TR(bzim), with silver(I) pyrazolate [Ag(mu-3,5-Ph2pz)]3. The crystalline products are mixed-ligand, mixed-metal dimeric products [Au(carb)Ag2(mu-3,5-Ph2pz)2], [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2, [Au(bzim)2Ag2(mu-3,5-Ph2pz)], and [Au2(bzim)2Ag(mu-3,5-Ph2pz)]. They have been characterized by elemental analysis and 1H NMR and mass spectrometry. The X-ray structure of [Au(carb)Ag2(mu-3,5-Ph2pz)2] shows it to be a dimer with two Ag...Au contacts between the trinuclear units of 3.083(2) and 3.310(2) A and with average intramolecular Ag...Ag and Au...Ag distances of approximately 3.3 and 3.2 A, respectively. The structure of [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2 is a dimer with one intermolecular Au...Au attraction of 3.3354(10) A and a short Ag...Au distance of approximately 3.42 A and intramolecular Ag...Au and Au...Au contacts of approximately 3.2 and approximately 3.3 A, respectively. Packing diagrams of both complexes show that the dimeric units are independent, similar to their parent molecules. The dimers of trinuclear [Au(carb)Ag2(mu-3,5-Ph2pz)2] and [Au2(carb)2Ag(mu-3,5-Ph2pz)].CH2Cl2 crystallize in the triclinic space group P (Z = 2), a = 9.688(3) A, b = 15.542(4) A, c = 23.689(6) A, alpha = 82.560(5) degrees , beta = 87.887(6) degrees , gamma = 78.060(5) degrees , and the orthorhombic space group Pca2(1) (Z = 4), a = 29.644(4) A, b = 7.4582(10) A, c = 30.473(4) A, respectively. The structure of [Au(bzim)Ag2(mu-3,5-Ph2pz)2] is a dimer with two metallophilic Ag...Au interactions of 3.14 A. The complex crystallizes in the monoclinic space group C2/c (Z = 4), a = 26.368(5) A, b = 15.672(3) A, c = 17.010(3) A, beta = 102.206(3) degrees .

Mixed-metal triangular trinuclear complexes: dimers of gold-silver mixed-metal complexes from gold(I) carbeniates and silver(I) 3,5-diphenylpyrazolates.

Dimers of trinuclear mixed gold-silver compounds are obtained by the reaction of a gold(I) carbeniate, [Au(mu-C(OEt)=NC6H4-p-CH3)]3, with a silver(I) pyrazolate, [Ag(mu-3,5-Ph2pz)]3. The crystalline products are the mixed-metal species Au(carb)Ag2(mu-3,5-Ph2pz)2 and Au2(carb)2Ag(mu-3,5-Ph2pz)CCH2Cl2.

19F, (1)H-HOESY and PGSE NMR studies of neutral trinuclear complexes of Au(I) and Hg(II): evidence for acid-base stacking in solution.

By combining the information from 19F, 1H-HOESY and PGSE NMR methodologies, unprecedented direct evidence has been obtained for the formation of supramolecular assemblies in solution between the trinuclear cyclic AuI basic compounds ([Au(mu-C2,N3-bzim)]3 (bzim = 1-benzylimidazolate), 1, and [Au(mu-C,N-C(OEt)=N-p-C6H4-CH3)]3, 2, on one hand, and the trinuclear cyclic HgII acid complex [Hg(mu-C,C-C6F4)]3, 3, on the other hand. HOESY experiments indicate that a stacking similar to that observed in the solid state occurs. PGSE studies demonstrate the presence of an equilibrium between the free trinuclear entities and adduct A in the case of 2/3 admixtures (see Sketch) while for 1/3 admixtures, adducts A and B are mainly present in solution.