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.     

Synthesis and X-ray structures of dinuclear and trinuclear gold(I) and dinuclear gold(II) amidinate complexes

The structures of the trinuclear gold(I), [Au(3)(2,6-Me(2)-form)(2)-(THT)Cl], the dinuclear [Au(2)(2,6-Me(2)-form)(2)], and the oxidative-addition product [Au(2)(2,6-Me(2)-form)(2)Cl(2)] formamidinate complexes are reported. The trinuclear complex is stable with gold-gold distances 3.01 and 3.55 A. The gold-gold distance in the dinuclear complex decreases upon oxidative-addition with halogens from 2.7 to 2.5 A, similar to observations made with the dithiolates and ylides.     

Syntheses,crystal structures and properties of dinuclear copper(I) complexes

Two dinuclear molecule-bridged Cu(I) complexes, (μ-bpym)[Cu(PPh₃)Cl]₂ (1), [(μ-bpym)(CuL)₂](ClO₄)₂·(CH₃CN)₂(H₂O) (2) (bpym = 2,2′-bipyrimidine, L = (R)-(+)-2,2′-bis(diphenylphospho)-1,1′-dinaphthalene) have been synthesized and characterized. The molecular structures of the two new dinuclear compounds exhibit bridging of two copper(I) centers by the symmetrically bis-chelating bpym ligand. Intriguingly, compound 1 features a remarkable “intramolecular organic sandwich” configuration where the central 2,2′-bipyrimidine bridging ligand interacts in π/π/π fashion with two phenyl rings from the coligands above and below the central plane, while chiral compound 2 exhibits second-order nonlinear optical effect and temperature-dependent luminescence. Upon decreasing the temperature from 298 to 10 K, compound 2 shows a red light emission.     

Syntheses and crystal structures of three structurally similar dinuclear silver(I) complexes

Three terephthalato-bridged dinuclear silver(I) complexes with the formulae Ag₂(5map)₄(tphth), [Ag₂(6map)₄(tphth)] · 2H₂O, and [Ag₂(4map)₄(tphth)] · 2H₂O (5map = 5-methyl-2-aminopyridine, 6map = 6-methyl-2-aminopyridine, 4map = 4-methyl-2-aminopyridine, tphth = terephthalate), have been synthesized and characterized by elemental analysis and single crystal X-ray diffraction. The Ag atom in each of the complexes is three-coordinate in a trigonal geometry with one carboxylate O atom and two pyridine N atoms. The characteristic difference among the complexes is the positions for the methyl groups of the aminopyridine ligands. The crystals of the complexes are stabilized by intermolecular N–H···O and O–H···O hydrogen bonds. Electronic supplementary material  The online version of this article () contains supplementary material, which is available to authorized users.     

Mixed ligand gold(I) complexes with phosphines and selenourea

A series of mixed ligand Au^I complexes with selenourea (Seu) and various phosphines, [R₃PAuSeu]Cl, have been prepared and characterized by elemental analysis, i.r. and n.m.r. methods. A decrease in the i.r. frequency of the C=Se mode of Seu upon complexation is indicative of Au^I binding via a selenone group. An upfield shift in the ¹³C-n.m.r. for the C=Se resonance of Seu, and downfield shifts in ³¹P-n.m.r., for the R₃P moiety are consistent with selenium coordination to Au^I.     

Syntheses and characterization of two dioxygen-reactive dinuclear macrocyclic schiff-base copper(I) complexes

The dinuclear copper(I) complex [Cu(2)L(1)(CH(3)CN)(2)](ClO(4))(2) (1, L(1) = 3,6,9,17,20,23-hexaazatricyclo[23.3.1.1]triaconta-1(29),2,9,11(30),12(13),14,16,23,25,27-decaene) has been structurally characterized. As previously described, intramolecular ligand hydroxylation (at the aromatic ring) was observed when 1 was reacted with dioxygen. A stopped-flow analysis of the reaction of 1 with dioxygen under different conditions did not allow a "dioxygen intermediate" to be spectroscopically detected. Detailed NMR and electrochemical data on 1 are also presented and evaluated for the first time. No copper(II) complexes of L(1) could be characterized due to hydrolysis of the compounds. In contrast, complex 2-differing from 1 only in an increase in the size of the chelate rings-did not undergo intramolecular hydroxylation when it was oxidized. The crystal structure of 2 is also described.     

Syntheses,crystal structures and solvatochromic properties of dinuclear oxalato-bridged copper(II) complexes

Three dinuclear copper(II) complexes, [Cu₂(L¹)₂(μ-ox)](ClO₄)₂?2(CH₃CN), [Cu₂(L²)₂(μ-ox)](ClO₄)₂?H₂O, and [Cu₂(L³)₂(μ-ox)](ClO₄)₂ where ox = oxalato; L = N,N-dimethyl,N′-benzylethane-1,2-diamine, L¹, N,N-diethyl,N′-benzylethane-1,2-diamine, L², N,N-diisoprophyl,N′-benzylethane-1,2-diamine, L³, were prepared and characterized by elemental analyses, spectral (IR, UV–Vis) data and molar conductance measurements. The crystal structures of [Cu₂(L¹)₂(μ-ox)](ClO₄)₂?2(CH₃CN) and [Cu₂(L³)₂(μ-ox)](ClO₄)₂ have been determined by single-crystal X-ray analysis. Solvatochromic behaviors were investigated in various solvents, showing positive solvatochromism. The effect of steric hindrance around the copper ion imposed by N-alkyl groups of the diamine chelates on the solvatochromism property of the complexes is discussed. Solvatochromism was also studied with different solvent parameter models using stepwise multiple linear regression method.     

Syntheses,crystal structures,and physical properties of dinuclear copper(I) and tetranuclear mixed-valence copper(I,II) complexes with hydroxylated bipyridyl-like ligands

Four copper complexes with hydroxylated bipyridyl-like ligands, namely [Cu(2)(ophen)(2)] (1), [Cu(4)(ophen)(4)(tp)] (2), [Cu(4)(obpy)(4)(tp)] (3), and [Cu(4)(obpy)(4)(dpdc)].2H(2)O (4), (Hophen=2-hydroxy-1,10-phenanthroline, Hobpy=6-hydroxy-2,2'-bipyridine, tp=terephthalate, dpdc=diphenyl-4,4'-dicarboxylate) have been synthesized hydrothermally. X-ray single-crystal structural analyses of these complexes reveal that 1,10-phenanthroline (phen) or 2,2'-bipyridine (bpy) ligands are hydroxylated into ophen or obpy during the reaction, which provides structural evidence for the long-time argued Gillard mechanism. The dinuclear copper(I) complex 1 has three supramolecular isomers in the solid state, in which short copper-copper distances (2.66-2.68 A) indicate weak metal-metal bonding interactions. Each of the mixed-valence copper(i,ii) complexes 2-4 consists of a pair of [Cu(2)(ophen)(2)](+) or [Cu(2)(obpy)(2)](+) fragments bridged by a dicarboxylate ligand into a neutral tetranuclear dumbbell structure. Dinuclear 1 is an intermediate in the formation of 2 and can be converted into 2 in the presence of additional copper(II) salt and tp ligands under hydrothermal conditions. In addition to the ophen-centered pi-->pi* excited-state emission, 1 shows strong emissions at ambient temperature, which may be tentatively assigned as an admixture of copper-centered d-->s,p and MLCT excited states.     

Syntheses,crystal structures,and electrochemical studies of dinuclear coordination compounds with the Fe2(CO)6 core

Reaction of 2-C₅H₄ NCOSPh, generated from 2-C₅H₄NCO₂H and PhSH in the presence of DCC, with Fe₃(CO)₁₂ affords (μ-κ²C,N-2-C₅H₄N)(μ-PhS)Fe₂(CO)₆ (1) and (μ-PhS)₂Fe₂(CO)₆ (2). Reaction of (NC)₂C=C(SMe)₂, formed from NCCH₂CN, CS₂, and MeI in the presence of NaOH, with Fe₃(CO)₁₂ provides (μ-κ²C,S-(NC)₂C=CSMe)(μ-MeS)Fe₂(CO)₆ (3) and (μ-MeS)₂Fe₂(CO)₆ (4). All complexes have been fully characterized by EA, IR, ¹H NMR, and ¹³C NMR spectroscopy and structurally determined by X-ray crystallography. In 1 and 3, the group attached to the bridging S is at the equatorial position. In 2, two phenyl groups are at equatorial positions. Two isomers of 4, ae-4 and ee-4, can be separated by thin-layer chromatography. DFT calculations reveal that the Gibbs energy difference between ae-4 and ee-4 is ?2.17 kcal mol^?1 in THF and ?2.29 kcal mol^?1 in benzene, and the isomerization barrier between ae-4 and ee-4 is 14.92 kcal mol^?1 in THF and 16.84 kcal mol^?1 in benzene. All these results suggest that ae-4 is more stable than ee-4 in either THF or benzene, and the two isomers do not interconvert. Electrochemical studies of 1 and 3 demonstrate that using HOAc as a proton source 1 and 3 can catalyze H₂ production.     

Mono- and dinuclear tricarbonyltechnetium(I) complexes with thiosemicarbazones

[NEt4]2[Tc(CO)3Cl3] reacts with thiosemicarbazones derived from 2,2'-dipyridyl ketone (HL3) and 4-acetylpyridine (HL4) to form stable technetium(I) complexes of the compositions [Tc(CO)3Cl(HL3-Npy,Npy)] and [Tc2(CO)6Cl2(micro-HL4-Npy,S)]. Whereas exclusively the pyridine nitrogen atoms are involved in coordination in the monomeric complex, the binuclear compound represents the first technetium complex with a coordinated thiosemicarbazone functionality.     

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.     

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.     

Syntheses,characterization, and crystal structures of two dinuclear nickel(II) and copper(II) complexes with Schiff bases

The phenolic azide bridged dinuclear nickel(II) complex, [Ni₂(L¹)₂(N₃)(H₂O)(μ_1,1-N₃)] · EtOH (I), and the thiocyanate bridged dinuclear copper(II) complex, [Cu₂(L²)₂(μ_1,1-NCS)₂] (II), where L¹ and L² are the deprotonated forms of 2-mothoxy-6-[(2-piperidin-1-ylethylimino)methyl]phenol and 2,4-dichloro-6-[(2-methylaminoethylimino)methyl]phenol, respectively, were synthesized and characterized by elemental analysis, IR spectra, and single-crystal X-ray diffraction. The crystal of I is orthorhombic: space group Pbca, a = 12.172(1), b = 20.953(1), c = 29.779(2) Å, V = 7594.8(9) ų, Z = 8. The crystal of II is monoclinic: space group P2₁/n, a = 8.7615(11), b = 19.672(2), c = 16.568(2) Å, β = 99.449(2)°, V = 2816.9(6) ų, Z = 4. The Ni atoms in I are in octahedral coordinations, and the Cu atoms in II are in square-pyramidal coordinations.     

The first beta-diketiminate-Ag(I) complexes. Macrocyclic dinuclear and tetranuclear Ag(I)-complexes and linear coordination polymer Ag(I)-complex

Reactions of Ag(I) and a series of beta-diketiminate ligands have been investigated to demonstrate that unique macrocyclic dinuclear and tetranuclear Ag(I)-complexes and a linear coordination polymer Ag(I)-complex as well as oxidative C-C coupling dimer products of the ligands were obtained depending on the substituents on the carbon framework of beta-diketiminate ligands.     

Syntheses of mixed-ligand tetranuclear gold(I)-nitrogen clusters by ligand exchange reactions with the dinuclear gold(I) formamidinate complex Au(2)(2,6-Me2Ph-form)2

The reaction of the sterically crowded dinuclear gold(I) amidinate complex Au2(2,6-Me2Ph-form)2, 1, with the less bulky bidentate nitrogen ligands results in the formation of tetranuclear gold(I) complexes. When the less bulky amidinate, K(4-MePh-form), A, was reacted with 1 in a 1:1 stoichiometric ratio, crystals containing equal amounts of the tetranuclear and dinuclear gold(I) aryl formamidinates, Au4(4-MePh-form)4 and Au2(2,6-Me2Ph-form)2, where 2,6-Me2Ph-form = B, were found in the same unit cell, 2 x 2THF: space group P, a = 10.794(11) A, b = 14.392(15) A, c = 25.75(3) A, alpha = 82.564(17) degrees, beta = 85.443(18) degrees, gamma = 82.614(19) degrees. The reaction of K(4-MePh-form), A, and 1 in a 1:2 ratio (excess) produced the tetranuclear complex only, 3. The potassium salt of the exchanged bulky ligand, K(2,6-Me2Ph-form), formed as a byproduct. The reaction of the dinuclear gold(I) complex Au2(2,6-Me2Ph-form)2 with the 3,5-diphenylpyrazolate salt, K(3,5-Ph2pz), resulted in the formation of two tetranuclear mixed-ligand complexes, Au4(3,5-Ph2pz)2(2,6-Me2Ph-form)2 x 2THF, 4 x 2THF (space group P21/c, a = 11.5747(19) A, b = 25.497(4) A, c = 21.221(3) A, beta = 96.979(3) degrees) and Au4(3,5-Ph2pz)3(2,6-Me2Ph-form) x THF, 5 x THF (space group P21/c, a = 23.058(5) A, b = 14.314(3) A, c = 18.528(4) A, beta = 90.94(3) degrees. The block crystals from the tetranuclear complex, 4 x 2THF, contain mixed ligands with each pyrazolate ring facing an amidinate ring. The tetranuclear mixed ligand complex, 5 x THF, was isolated as needles with ligands alternating above and below the Au4 plane. The two tetranuclear mixed-ligand complexes emit at 490 and 530 nm, respectively, under UV excitation.     

Synthesis and anti-cancer activities of a pair of enantiomeric gold(I) complexes containing sulfanyl-substituted P-stereogenic phosphines

A pair of enantiomeric gold(I) complexes containing enantiomerically pure 2,3-dimethyl-7-phenyl-5-(phenylsulfanyl)-7-(R/S)-phosphabicyclo[2.2.1]hept-2-ene has been prepared and in vitro cytotoxicity tests showed that both the enantiomers are relatively nontoxic against healthy lymphocytes, but are highly potent against suspension and monolayer human tumor cell lines.     

Quantum chemical simulation of the reaction of methane with gold(I) acetylacetonate and aquaacetylacetonate complexes

The interaction between methane and gold(I) acetylacetonate via electrophilic substitution (reaction (I)) and oxidative addition (reaction (II)) is simulated. In both cases, the formation of the products is thermodynamically favorable: the decrease in energy is 31 kcal/mol for reaction (I) and 26 kcal/mol for reaction (II). The product of reaction (II) is additionally stabilized by Au-H interaction. Both reactions have a low activation barrier and proceed via the formation of structurally different methane complexes reducing the energy of the system by 9.3 kcal/mol for reaction (I) and by 10.9 kcal/mol for reaction (II). The complex [Au(H₂O)(acac)] is also capable of forming methane complexes. These complexes result from a thermally neutral reaction and turn into products after overcoming a low energy barrier. The structure of the complex activating methane in the gold-rutin system is deduced from the data obtained.