Nitroimidazole and glucosamine conjugated heteroscorpionate ligands and related copper(II) complexes. Syntheses, biological activity and XAS studies.

New nitroimidazole and glucosamine conjugated heteroscorpionate ligands, namely 2,2-bis(3,5-dimethyl-1H-pyrazol-1-yl)-N-(2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl)acetamide (L(MN)) and 1,3,4,6-tetra-O-acetyl-2-{[bis(3,5-dimethyl-1H-pyrazol-1-yl)acetyl]amino}-2-deoxy-ß-D-glucopyranose (L(DAC)), respectively, were synthesized by direct coupling of preformed side chain acid and amine components. The related copper(II) complexes {[(L(MN))(2)Cu]Cl(2)}, and {[(L(DAC))(2)Cu]Cl(2)} have been prepared from the reaction of CuCl(2)*2H(2)O with L(MN) or L(DAC) ligand in methanol solution. Single crystal structural characterization was undertaken for the L(MN) ligand. In the absence of a coordinated metal core, the overall arrangement of the ligand is determined by some loose intra- and inter-molecular nonbonding contacts. X-Ray Absorption Spectroscopy (XAS) has been used to probe the local structure of the two copper(II) complexes, {[(L(MN))(2)Cu]Cl(2)} and {[(L(DAC))(2)Cu]Cl(2)}. The EXAFS analysis has permitted the identification of the local environment of the copper site. Copper interacts with 2 units of ligand in both complexes, and it is found to be 6-fold coordinated. Its local structure is described by four Cu-N and two Cu-O interactions to form a pseudo-octahedron core, with a 0.14 Å lengthening of the Cu-O bond length in the case of L(DAC) complex with respect to the L(MN) one, likely due to the higher steric hindrance of the glucosamine moiety. The XANES analysis agrees with these results, also confirming the Cu(II) formal copper oxidation state for both complexes. The new copper(II) complexes {[(L(MN))(2)Cu]Cl(2)} and {[(L(DAC))(2)Cu]Cl(2)} as well as the corresponding uncoordinated ligands were evaluated for their cytotoxic activity towards a panel of several human tumour cell lines. The results reported here indicate that both copper(II) complexes show similar spectra of cytotoxicity and very low resistance factors (RF < 2) against C13* ovarian cancer cells which have acquired resistance to cisplatin.

A study on the coordinative versatility of new N,S-donor macrocyclic ligands: XAFS, and Cu2+ complexation thermodynamics in solution.

We investigated, both in the solid state and in aqueous solution, the coordination environment and stability behavior of four macrocyclic ligands (three N(2)S(2) and one N(3)S(2)) and of the corresponding Cu(II) complexes. The structural characterization in the solid state of the copper derivatives was performed by X-Ray Absorption Spectroscopy. Copper is found to be 4-fold coordinated with a CuN(2)S(2) environment with different Cu-S distances depending on the size of the macrocyclic ring. The EXAFS technique has indicated that nitrogen and sulfur atoms are more preferable to oxygen atoms as donor systems, without the evidence of coordination of the carboxylic moieties to copper in the first shell. The joint EXAFS and XANES study of the copper(II) complex with the N(3)S(2) ligand confirms the 4-fold coordination with an additional, long Cu-N interaction. The Cu(2+) complexation constants for one ligand were determined in aqueous solution. The results indicate that the species [CuL], although isolated in the solid state, is not the most abundant at the pH of blood serum. Instead, at pH 7.4 the protonated [Cu(HL)](+) species was found to be the most relevant. The behaviour of the copper complexes in the presence of the strong copper chelating bioagent human serum albumin was also examined in order to gain information on the stability of these compounds in biological fluids.

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.

Scorpionates bearing nitro substituents: mono-, bis- and tris-(3-nitro-pyrazol-1-yl)borate ligands and their copper(I) complexes.

Two scorpionates sodium trihydro(3-nitro-pyrazol-1-yl)borate (Na[H(3)B(3-(NO(2))pz)]) and sodium hydrotris(3-nitro-pyrazol-1-yl)borate (Na[HB(3-(NO(2))pz)(3)]), featuring electron withdrawing substituents, have been synthesized in high yield starting from 3(5)-nitropyrazole and sodium borohydride. The treatment of CuX (X = (CH(3)CN)(4)PF(6), Cl or I) with Na[H(3)B(3-(NO(2))pz)], Na[HB(3-(NO(2))pz)(3)] or the related bis(pyrazolyl)borate Na[H(2)B(3-(NO(2))pz)(2)] in the presence of triphenylphosphine or tert-butyl isocyanide afforded the corresponding (azolyl)borate supported copper(I) triphenylphosphine or tert-butyl isocyanide adducts. These compounds have been characterized by elemental analyses, FT-IR, ESI-MS and multinuclear NMR spectroscopy. X-Ray crystal structures of [H(3)B(3-(NO(2))pz)]Cu[P(C(6)H(5))(3)](2), [H(2)B(3-(NO(2))pz)]Cu(CNt-Bu)(2), and [HB(3-(NO(2))pz)(3)]Cu[P(C(6)H(5))(3)], as well as that of the {[HB(3-(NO(2))pz)(3)]Na}(4) are also reported. The latter displays a particularly interesting tetrameric structure with each tris(pyrazolyl)borate adopting an unusual inverted configuration and serves as a bridging ligand for three different sodium ions.

The relationship between the electrospray ionization behaviour and biological activity of some phosphino Cu(I) complexes.

Electrospray ionization mass spectrometry was usefully employed for the characterization of three phosphino copper(I) complexes of medicinal interest. This technique revealed that the original [CuL(4)](+) pro-drugs (L = hydrophilic tertiary phosphine) underwent dissociation with production of coordinative unsaturated [CuL(3)](+) and [CuL(2)](+) species, which represented key intermediates for the activation of potential biological properties. The more favoured was the displacement of the ligands from the [CuL(4)](+) parent complex, the more favoured was in turn the possibility for the metal ion to directly interact with biological substrates, including pharmacological targets related to cancer proliferation. An inverse correlation between the stability and the cytotoxic activity of the three copper(I) complexes investigated has been clearly established.

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.

Trinuclear copper(I) complexes with triscarbene ligands: catalysis of C-N and C-C coupling reactions.

Novel synthetic routes for the preparation of trinuclear copper(I) complexes with triscarbene ligands are presented, which yield higher purity products than the one previously described. The first crystal structure of one of these complexes is reported and confirms the expected structure. The trinuclear complexes proved to be efficient catalysts of Ullmann-type reactions as well as of the Sonogashira reaction.

Synthesis and characterization of the copper(II) complexes of new N2S2-donor macrocyclic ligands: synthesis and in vivo evaluation of the (64)Cu complexes.

The aim of this work was to prepare a novel class of (64)Cu(II) labeled complexes with the new macrocyclic ligands 1,10-dithia-4,7-diazacyclododecane-3,8-dicarboxylic acid (NEC-SE, 1), 1,10-dithia-4,7-diazacyclotridecane-3,8-dicarboxylic acid (NEC-SP, 2) and 1,10-dithia-4,7-diazacyclotetradecane-3,8-dicarboxylic acid, (NEC-SB, 3 ) to evaluate the usefulness of these macrocycles for potential utility as (64)Cu(II) chelators. The corresponding non-radioactive complexes [Cu(NEC-SE)] x 3H(2)O (4), [Cu(NEC-SP)] x 3H(2)O (5) and [Cu(NEC-SB)] (6) were prepared and their (64)Cu-analogs, [(64)Cu(NEC-SE)] (7) and [(64)Cu(NEC-SP)] (8) and [(64)Cu(NEC-SB)] (9) were produced in >98% radiochemical purity. Rats were injected with complex 7, 8 or 9 and were euthanized at 1, 4 and 24 h. All three complexes are cleared from the blood over the first hour following injection but there is poor clearance of this activity over 24 h. A similar pattern of retention was noted in the liver where the levels of activity in this tissue at 1 h are not statistically different from those at 24 h. Molecular mechanics and DFT studies were performed on the complexes in order to gain insight into the lower stability.

In vitro antitumor activity of the water soluble copper(I) complexes bearing the tris(hydroxymethyl)phosphine ligand.

Monocationic hydrophilic complexes [Cu(thp)4](+) 3 and [Cu(bhpe)2](+) 4 were synthesized by ligand exchange reactions starting from the labile [Cu(CH3CN)4][PF6] precursor in the presence of an excess of the relevant hydrophilic phosphine. Complexes 3 and 4 were tested against a panel of several human tumor cell lines. Complex 3 has been shown to be about 1 order of magnitude more cytotoxic than cisplatin. Chemosensitivity tests performed on cisplatin and multidrug resistance phenotypes suggested that complex 3 acts via a different mechanism of action than the reference drug. Different short-term proliferation assays suggested that lysosomal damage is an early cellular event associated with complex 3 cytotoxicity, probably mediated by an increased production of reactive oxygen species. Cytological stains and flow cytometric analyses indicated that the phosphine copper(I) complex is able to inhibit the growth of tumor cells via G2/M cell cycle arrest and paraptosis accompanied with the loss of mitochondrial transmembrane potential.

Synthesis, in vitro and in vivo characterization of (64)Cu(I) complexes derived from hydrophilic tris(hydroxymethyl)phosphane and 1,3,5-triaza-7-phosphaadamantane ligands.

Four novel (64)Cu complexes ([(64)Cu(thp)(4)](+) (1), [(64)Cu(TPA)(4)](+) (2), [HC(CO(2))(pz(Me2))(2) (64)Cu(thp)(2)] (3) and [HC(CO(2))(tz)(2) (64)Cu(thp)(2)] (4), [where thp is tris(hydroxymethyl)phosphine, TPA is 1,3,5-triaza-7-phosphaadamantane, pz(Me2) is 3,5-dimethylpyrazole and tz is 1,2,4-triazole] were successfully synthesized and characterized. The complexes were produced in high radiochemical purity and yield (more than 98%) without the need for further purification. Their logP values and serum stabilities were measured and in vitro behavior was observed in cultured EMT-6 cells. The logP values (+/- standard deviation) obtained were -2.26 +/- 0.04 (1), 0.01 +/- 0.01 (2), -1.24 +/- 0.03 (3) and -2.06 +/- 0.03 (4). Complex 3 demonstrated the highest serum stability, with approximately 33% of the complex still intact after 1-h incubation. Complex 2 showed a rapid cell-association with EMT-6 cells, with more than 8.5% association at 2 h. This association was significantly higher (P < 0.001) than for the other three compounds after a 2-h incubation (1, 1.21%; 3, 0.63%; 4, 2.75%). Biodistribution and small-animal positron emission tomography/computed tomography was undertaken with 1 in mice bearing EMT-6 tumors. EMT-6 tumor uptake was high at 1 h (7.71 +/- 2.17 %ID/g) and decreased slowly over 24 h (4 h, 4.90 +/- 0.78 %ID/g; 24 h, 3.74 +/- 0.73 %ID/g). The PET/CT images show that the EMT-6 tumors can be visualized at all time points. In this proof-of-concept study, we have successfully synthesized and characterized a novel series of versatile water-soluble Cu(I) complexes containing monophosphine ligands. We also report the use of 1 as a building block for new radiopharmaceuticals, perhaps the first time such a method has been used in the production of copper radiopharmaceuticals.

Silver(I)-organophosphane complexes of electron withdrawing CF3- or NO2-substituted scorpionate ligands.

New silver(I) complexes have been synthesized from the reaction of AgNO(3), monodentate tertiary phosphanes PR(3) (PR(3) = P(C(6)H(5))(3), P(o-C(6)H(4)CH(3))(3), P(m-C(6)H(4)CH(3))(3), P(p-C(6)H(4)CH(3))(3), PCH(3)(C(6)H(5))(2)) and two novel electron withdrawing ligands: potassium dihydrobis(3-nitropyrazol-1-yl)borate and potassium dihydrobis(3-trifluoromethylpyrazol-1-yl)borate. These compounds have been characterized by elemental analyses, FT-IR, ESI-MS and multinuclear ((1)H, (19)F and (31)P) NMR spectroscopy. Solid state structures of the potassium salts K[H(2)B(3-(NO(2))pz)(2)] and K[H(2)B(3-(CF(3))pz)(2)] have been reported. They form polymeric networks due to intermolecular contacts of various types between the potassium ion and atoms of the neighboring molecules. The silver adducts [H(2)B(3-(NO(2))pz)(2)]Ag[P(C(6)H(5))(3)](2) and [H(2)B(3-(NO(2))pz)(2)]Ag[P(p-C(6)H(4)CH(3))(3)] have pseudo tetrahedral and trigonal planar silver sites, respectively. The bis(pyrazolyl)borate ligand acts as a kappa(2)-N(2) donor. The nitro-substituents are coplanar with the pyrazolyl rings in all these adducts indicating efficient electron delocalization between the two units. The [H(2)B(3-(CF(3))pz)(2)]Ag[P(C(6)H(5))(3)] complex has been obtained from re-crystallization of {[H(2)B(3-(CF(3))pz)(2)]Ag[P(C(6)H(5))(3)](2)} in a dichloromethane-diethyl ether solution; it is a three-coordinate, trigonal planar silver complex.

Small scorpionate ligands: silver(I)-organophosphane complexes of 5-CF(3)-substituted scorpionate ligand combining a B-H...Ag coordination motif.

The first 5-substituted trihydro(azolyl)borate system, the sodium trihydro(5-CF3-pyrazol-1-yl)borate, Na[H3B(5-(CF3)pz)], has been synthesized by the reaction of 3-trifuoromethyl-pyrazole with NaBH4 in high yield. Na[H3B(5-(CF3)pz)] reacts with AgNO3 in the presence of monodentate tertiary phosphanes PR3 (PR3=P(C6H5)3, P(p-C6H4CH3)3, P(m-C6H4CH3)3, P(o-C6H4CH3)3, or PCH3(C6H5)2) to afford silver(I) bis(phosphane) adducts. These compounds have been characterized by elemental analyses, FTIR, ESI-MS, and multinuclear (1H, 19F, and 31P) NMR spectroscopy. Solid-state structures of {[H3B(5-(CF3)pz)]Ag[P(C6H5)3]2} and {[H3B(5-(CF3)pz)]Ag[P(p-C6H4CH3)3]2} are also reported. They feature kappa2-N,H-bonded trihydro(pyrazolyl)borate ligands and pseudo-tetrahedral silver atoms.

Novel rhenium(V) oxo complexes containing bis(pyrazol-1-yl)acetate and bis(pyrazol-1-yl) sulfonate as tripodal N,N,O-heteroscorpionate ligands.

Reactions of [NBu4][Re(O)Cl4] with bis(pyrazol-1-yl)methane (bpzm) and bis(pyrazol-1-yl)acetate (Hbpza) and with the lithium salts lithium [bis(3,5-dimethylpyrazol-1-yl)acetate] (Libdmpza) and lithium [bis(3,5-dimethylpyrazol-1-yl)methanesulfonate] (Libdmpzs) produce a series of new compounds containing either a kappa2-N,N bidentate pyrazolyl ligand [Re(O)(bpzm)Cl3 (1), Re(O)(bpzm)(OMe)Cl2 (2), Re(O)(bpzaOMe)(OMe)Cl2 (4)] or a kappa3-N,N,O heteroscorpionate [Re(O)(bpza)Cl2 (3), Re(O)(bdmpza)Cl2 isomers 5 and 6, Re(O)(bdmpza)(OMe)Cl (7), Re(O)(bdmpza)(OEt)Cl (8), Re(O)(bdmpzs)(OMe)Cl (9), Re(O)(bdmpzs)(OEt)Cl (10)]. X-ray analyses of 1 and 3 show in both cases a distorted octahedral environment around the rhenium atom. The nature and the geometry of the products are strongly determined by the reaction solvent and by the heteroscorpionate ligand itself. When scorpionates bear methylated pyrazolyl rings mixed heterocomplexes Re(O)(bdmpza)(glycol) (11) and Re(O)(bdmpzs)(glycol) (12) are obtained (H2glycol = ethylene glycol). Also 11 shows an octahedral geometry as assessed by X-ray study.