Rossana Galassi

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)°; β = 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)°; β = 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; β = 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.

In Vitro Antitumour Activity of Water Soluble Cu(I), Ag(I) and Au(I) Complexes Supported by Hydrophilic Alkyl Phosphine Ligands

Hydrophilic, monocationic [M(L)(4)]PF(6) complexes (M = Cu or Ag; L: thp = tris(hydroxymethyl)phosphine, L: PTA = 1,3,5-triaza-7-phosphaadamantane, L: thpp = tris(hydroxypropyl)phosphine) were synthesized by ligand exchange reaction starting from [Cu(CH(3)CN)(4)]PF(6) or AgPF(6) precursors at room temperature in the presence of an excess of the relevant phosphine. The related [Au(L)(4)]PF(6) complexes (L = thp, PTA or thpp) were synthesized by metathesis reactions starting from [Au(L)(4)]Cl at room temperature in the presence of equimolar quantity of TlPF(6). The three series of complexes [M(L)(4)]PF(6) were tested as cytotoxic agents against a panel of several human tumour cell lines also including a defined cisplatin resistant cell line. These investigations have been carried out in comparison with the clinically used metallodrug cisplatin and preliminary structure-activity relationships are presented. The best results in terms of in vitro antitumour activity were achieved with metal-thp species and, among the coinage metal complexes, copper derivatives were found to be the most efficient drugs. Preliminary studies concerning the mechanism of action of these [M(L)(4)]PF(6) species pointed to thioredoxin reductase as one of the putative cellular targets of gold and silver complexes and provided evidence that copper derivatives mediated their cytotoxic effect through proteasome inhibition.

Dinuclear gold(I) and silver(I) derivatives with bridging phosphines containing an imidazole ring; X-ray crystal structure of (1-benzyl-2-imidazolyl)diphenylphosphinegold(I)chloride.

Abstract (1-Benzyl-2-imidazolyl)diphenylphosphine [(BzIm)Ph 2 P] can act as a monodentate or bidentate ligand to afford mononuclear (BzIm)Ph 2 PAuCl ( I ) or dinuclear [μ-(BzIm)Ph 2 PAu] 2 2+ 2X − (X = PF 6 − , BF 4 − or NO 3 − ) ( IIa,b,c ) derivatives of gold(I). Analogous dinuclear silver(I) derivatives were obtained reacting the ligand [(BzIm)Ph 2 P] with AgX salts (X = NO 3 − , BF 4 − ) ( IIIa,b ). In solution the silver complexes show a fluxional behaviour, and two conformers were observed by 31 P NMR spectroscopy. The structure of compound I was established by X-ray crystallography (monoclinic, space group C2/c, a = 18.068(2), b = 16.576(2), c = 15.391(2) A , β = 117.2(2)°, Z = 8) . The short intermolecular Au⋯Au distance of 3.03(2) A indicates a metal-metal interaction. The 197 Au Mossbauer parameters of compounds I and IIa are consistent with IR, NMR and crystallographic data.

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.

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.

Solid state and solution investigations of derivatives of Group 11 metal ions with 1-benzyl-2-imidazolyldiphenylphosphine (L). Electrochemical behavior of [M2L3]2+ (M=CuI; AgI) and [AuL2]+ complexes

Abstract The molecular crystal structure of (Bzim)Ph2P=L=1-benzyl-2-imidazolyldiphenylphosphine (monoclinic; space group P21/c #14; a=9.054(2), b=9.394(3), c=21.677(8) A; β=94.52(2)°; Z=4) is reported here. This new P,N ligand reacts with CuI or AgI metal ions to give [M2L3]2+ dinuclear complexes where the bihapto ligand always bridges the metal centers. When L was added to [Au2L2]2+ complex the dinuclear gold cycle underwent a cleavage and the mononuclear species [AuL2]+ was obtained. The solution behavior of the complexes was investigated by 1H and 31P NMR at variable temperature, showing neither dissociative nor equilibrium reactions. The strong coordinating ability of the (Bzim)Ph2P ligand was also indicated by cyclic voltammetry investigation and the electrogenerated Ag(0) neutral complex, namely [Ag2(μ-(Bzim)Ph2P)3], was detected as transient compound. The molecular crystal structure of [Cu2(μ-(Bzim)Ph2P)3][BF4]2 is also reported (monoclinic; space group P21/n #14; a=19.413(9), b=19.81(1), c=21.678(7) A; β=115.51(2)°; Z=4).

Solid state and solution structural studies of silver(I) cyclic complexes bearing the (Bzim)Ph2P ligand

Cyclic silver(I) compounds having a [μ-(Bzim)Ph 2 PAg] 2 2+ unit ((Bzim)Ph 2 P=1-benzyl-2-imidazolyldiphenylphosphine) and NO 3 − ( I ), BF 4 − ( II ), and B[3,5-(CF 3 ) 2 C 6 H 3 ] 4 − ( III ) as counterions were characterized in the solid state by X-ray crystal structure determinations ( I , II ), and in solution by 1 H-, 13 C-, 19 F- and 31 P-NMR spectroscopies. The crystal structure of complex [μ-(Bzim)Ph 2 PAg(NO 3 )] n ( n =2, 4) ( I ) (triclinic, space group P 1 (no. 2), a =15.118(5), b =17.755(3), c =14.123(4) A, α =90.23(2), β =111.67(2), γ =85.92(2)°, Z =2) shows two conformers A and B in the unit cell. The conformer A consists of a tetranuclear species formed by two [μ-(Bzim)Ph 2 PAg] 2 2+ moieties, related by a center of symmetry, bonded together by two bridging nitrate anions. The nitrate anions are coordinated to the silver atoms in an unusual fashion. The conformer B is a dinuclear species where the silver atoms present in the eight-membered ring complete their tetracoordination with two chelate nitrate anions. The crystal structure of complex {[μ-(Bzim)Ph 2 PAg(BF 4 )] 2 } ∞ ( II ) (monoclinic, space group P 2 1 / c (no. 14), a =11.563(3), b =8.353(4), c =26.188(7) A, β =95.88(2)°, Z =2) consists of infinite chains of the dinuclear cyclic silver moieties held together by BF 4 − bridging anions. The low temperature experimental and simulated 31 P-NMR spectra of complexes I – III show complex apparent doublets of multiplets due to the resonance of the spin systems of the three isotopomers of the silver atoms present in the cyclic units. The interionic solution structure of complex II was investigated by 19 F{ 1 H}-HOESY NMR spectroscopy. In methylene chloride solution the BF 4 − anion is not more coordinated to the silver(I) atoms as in the solid state, and it is localized in between the phenyl and benzyl groups of the ligand.

Reactivity of bis(diphenylphosphines)digold(I) dications with azotate neutral heterocycles: X-ray crystal structure of eclipsed [μ-dppmAu2(pzH)2]2+ · 2ClO4− · H2O and staggered [μ-dppeAu2(pzH)2]2+ · 2ClO4− complexes

Dinuclear gold(I) dicationic complexes were prepared reacting [ μ -dpp(CH 2 ) n Au 2 ] 2+ (dpp(CH 2 ) n =bis(diphenylphosphine)alkane; n =1, 2, 3) with azotate neutral heterocycles. Using 3,5-dimethylpyrazole (pzH) as ancillary ligand and ClO 4 − as counterion, insoluble polymeric species were obtained by a kinetic control of the reactions; extractions by hot chloroform yield the corresponding monomeric derivatives [ μ -dpp(CH 2 ) n Au 2 (pzH) 2 ] 2+  · 2ClO 4 − ( I , IIa , III ). In one case using NO 3 − instead of ClO 4 − anion the monomeric specie ( IIb ) was directly obtained. Using as neutral coordinating ligand bis(imidazo-2-yl)methane (BIMH 2 ), ten- and 11-membered heterobridged cyclic derivatives [ μ -dpp(CH 2 ) n Au 2 μ -BIMH 2 ] 2+  · 2ClO 4 − ( IV , V ) were also obtained. 31 P-NMR spectrum of ( IV ) revealed partial and complete opening of the cycle in solution. The X-ray crystal structures of [ μ -dppmAu 2 (pzH) 2 ] 2+  · 2ClO 4 −  · H 2 O ( I ) and [ μ -dppeAu 2 (pzH) 2 ] 2+  · 2ClO 4 − ( IIa ) are reported (( I ): monoclinic, space group P 2 1 / n , a =12.253(4), b =19.417(3), c =19.152(2) A, β =97.90(2)°, Z =4; ( IIa ): monoclinic, space group P 2 1 / n , a =10.997(3), b =13.629(2), c =14.812(2) A, β =104.63(1)°, Z =2). The short intramolecular Au⋯Au distance of 3.133(2) A found in complex ( I ) indicates a metal–metal interaction.

Rhodium, iridium and gold complexes of the short-bite ligand 1-benzyl-2-imidazolyldiphenylphosphine

Abstract Reactions of [{M(μ-Cl)(cod)}2] (M=Rh, Ir) with 1-benzyl-2-imidazolyldiphenylphosphine gave the mononuclear P-bonded compounds [MCl(cod)(Ph2PBzIm)]. They react with [M(cod)(acetone)x]BF4 to give the cationic [{M(cod)}2(μ-Cl)(μ-Ph2PBzIm)]+ complexes, while they react with silver salts to give the homometallic dinuclear complexes HT-[{M(μ-Ph2PBzIm)(cod)}2](BF4)2 (M=Rh, Ir) containing two mutually cis bridging ligands in a HT disposition. Addition of [AuCl(tht)] to [MCl(cod)(Ph2PBzIm)] gave the heterometallic complexes [MCl(cod)(μ-Ph2PBzIm)AuCl] with the gold atom coordinated to the P-end. While the Ir–Au compound remained as such in solution, the Rh–Au complex was found to be in equilibrium with [AuCl(Ph2PBzIm)] and [{Rh(μ-Cl)(cod)}2]. Reaction of trans-[RhCl(CO)(Ph2PBzIm)2] with [{Rh(μ-Cl)(CO)2}2] gave the ‘A-frame’ complex [{RhCl}2(μ-CO)(μ-Ph2PBzIm)2] while the reaction with [PdCl2(NCMe)2] resulted in the formation of three isomers of the metal–metal bonded compound [(CO)Cl2Rh(μ-Ph2PBzIm)2PdCl].

A Single-Strand Helical Motif Induced by Self-Assembly of [Ag(TFP)]+ Moieties with Nitrate Anions − 31P NMR Spectroscopic and X-ray Crystal Structure Characterization of the Complexes Involved in Equilibrium Reactions of Silver Salts and TFP Ligand

The ability of the ligand tris(2-furyl)phosphane (TFP) to coordinate AgI ions has been investigated. The molar ratio and the nature of the counterions used (NO3−; BF4−) affected the reaction. Moreover, equilibrium reactions were observed and the [Ag(TFP)n]+ (n = 1−4) species involved were identified by variable-temperature 31P NMR spectroscopy. The [Ag(TFP)3]BF4 complex turned out to be the more labile species in solution and it disproportionates by means of an SN2 mechanism to yield the complexes [Ag(TFP)2(H2O)]BF4 (3) and [Ag(TFP)4]BF4 (4). Most of the compounds detected in solution were isolated and characterized in the solid state. The molecular structures of the complexes [Ag(TFP)NO3] (1), [Ag(TFP)3NO3] (2), and [Ag(TFP)2(H2O)]BF4 (3) were determined by X-ray crystal structure diffraction confirming the solution characterization data. In these structures the TFP ligand was always only bonded to the metal centre by the phosphorous atom. It is noteworthy to underline that the molecular structure of complex 1 consists of an infinite single-strand helix arising from the ability of the bridging nitrate anions to connect the [Ag(TFP)]+ units. In the structure the nitrate anions are coordinated to the metal centres in unusual modes acting simultaneously as chelating and bridging ligands. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)