Synthesis,characterization and antimicrobial activities of novel silver(I) complexes with coumarin substituted N-heterocyclic carbene ligands

Eight new coumarin substituted silver(I) N-heterocyclic carbene (NHC) complexes were synthesized by the interaction of the corresponding imidazolium or benzimidazolium chlorides and Ag₂O in dichloromethane at room temperature. Structures of these complexes were established on the basis of elemental analysis, ¹H NMR, ¹³C NMR, IR and mass spectroscopic techniques. The antimicrobial activities of carbene precursors and silver NHC complexes were tested against standard strains: Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and the fungi Candida albicans and Candida tropicalis. Results showed that all the compounds inhibited the growth of the all bacteria and fungi strains and some complexes performed good activities against different microorganisms. Among all the compounds, the most lipophilic complex bis[1-(4-methylene-6,8-dimethyl-2H-chromen-2-one)-3-(naphthalene-2-ylmethyl)benzimidazol-2-ylidene]silver(I) dichloro argentate (5e) was found out as the most active one.     

Synthesis,structural characterization and antimicrobial activities of 12 zinc(II) complexes with four thiosemicarbazone and two semicarbazone ligands

Twelve zinc(II) complexes with thiosemicarbazone and semicarbazone ligands were prepared and characterized by elemental analysis, thermogravimetric and differential thermal analysis (TG/DTA), FT-IR and 1H and 13C NMR spectroscopy. Seven three-dimensional structures of zinc(II) complexes were determined by single-crystal X-ray analysis. Their antimicrobial activities were evaluated by MIC against four bacteria (B. subtilis, S. aureus, E. coli and P. aeruginosa), two yeasts (C. albicans and S. cerevisiae) and two molds (A. niger and P. citrinum). The 5- and 6-coordinate zinc(II) complexes with a tridentate thiosemicarbazone ligand (Hatsc), ([Zn(atsc)(OAc)](n) 1, [Zn(Hatsc)(2)](NO(3))(2).0.3H(2)O 2, [ZnCl(2)(Hatsc)] 3 and [Zn(SO(4))(Hatsc)(H(2)O)].H(2)O 4 [Hatsc=2-acetylpyridine(thiosemicarbazone)]), showed antimicrobial activities against test organisms, which were different from those of free ligands or the starting zinc(II) compounds. Especially, complex 2 showed effective activities against P. aeruginosa, C. albicans and moderate activities against S. cerevisiae and two molds. These facts are in contrast to the results that the 5- or 6-coordinate zinc(II) complexes with a tridentate 2-acetylpyridine-4N-morpholinethiosemicarbazone, ([Zn(mtsc)(2)].0.2EtOH 5, the previously reported catena-poly [Zn(mtsc)-mu-(OAc-O,O')](n) and [Zn(NO(3))(2)(Hmtsc)] [Hmtsc=2-acetylpyridine (4N-morpholyl thiosemicarbazone)]), showed no activities against the test microorganisms. The 5- and 6-coordinate zinc(II) complexes with a tridentate 2-acetylpyridinesemicarbazone, ([Zn(OAc)(2)(Hasc)] 6 and [Zn(Hasc)(2)](NO(3))(2) 7 [Hasc=2-acetylpyridine(semicarbazone)]), showed no antimicrobial activities against bacteria, yeasts and molds. Complex [ZnCl(2)(Hasc)] 8, which was isostructural to complex 3, showed modest activity against Gram-positive bacterium, B. subtilis. The 1:1 complexes of zinc(II) with pentadentate thiosemicarbazone ligands, ([Zn(dmtsc)](n) 9 and [Zn(datsc)](n) 10 [H(2)dmtsc=2,6-diacetylpyridine bis(4N-morpholyl thiosemicarbazone) and H(2)datsc=2,6-diacetylpyridine bis(thiosemicarbazone)]), did not inhibit the growth of the test organisms. On the contrary, 7-coordinate zinc(II) complexes with one pentadentate semicarbazone ligand and two water molecules, ([Zn(H(2)dasc)(H(2)O)(2)](OAc)(2).5.3H(2)O 11 and [Zn(H(2)dasc)(H(2)O)(2)](NO(3))(2).H(2)O 12 [H(2)dasc=2,6-diacetylpyridine bis(semicarbazone)]), showed modest to moderate activities against bacteria. Based on the X-ray structures, the structure-activity correlation for the antimicrobial activities was elucidated. The zinc(II) complexes with 4N-substituted ligands showed no antimicrobial activities. In contrast to the previously reported nickel(II) complexes, properties of the ligands such as the ability to form hydrogen bonding with a counter anion or hydrated water molecules or the less bulkiness of the 4N moiety would be a more important factor for antimicrobial activities than the coordination number of the metal ion for the zinc(II) complexes.     

Syntheses, crystal structures and antimicrobial activities of 6-coordinate antimony(III) complexes with tridentate 2-acetylpyridine thiosemicarbazone, bis(thiosemicarbazone) and semicarbazone ligands

Five novel antimony(III) complexes with the mono- and bis(thiosemicarbazone) ligands of 2N1S or 4N2S donor atoms, N'-[1-(2-pyridyl)ethylidene]morpholine-4-carbothiohydrazide (Hmtsc, L1) and bis[N'-[1-(2-pyridyl)ethylidene]]-1,4-piperazinedicarbothiohydrazide (H(2)ptsc, L7), and the tridentate semicarbazone ligand of 2N1O donor atoms, 2-acetylpyridine semicarbazone (Hasc, L2b), were prepared by reactions of SbCl(3) or SbBr(3), and characterized by elemental analysis, TG/DTA, FT-IR and (1)H NMR spectroscopy. The crystal and molecular structures of five antimony(III) complexes were determined by single-crystal X-ray structure analysis. The neutral, 6-coordinate antimony(III) complexes ([Sb(mtsc)Cl(2)] 1, [Sb(mtsc)Br(2)] 2, [Sb(asc)Cl(2)] 3 and [Sb(asc)Br(2)] 4) are depicted with one electron pair (5s(2)) of the antimony(III) atom, deprotonated forms of multidentate thiosemicarbazone or semicarbazone ligands, and two monodentate halogen ligands, respectively. In the dimer complex 5 ([Sb(2)(ptsc)Cl(4)]) with the ligand in which two tridentate thiosemicarbazone moieties are connected by the piperazine moiety, each antimony(III) was also described as a neutral 6-coordinate structure. These antimony(III) complexes were thermally stable around 200 degrees C. Water-soluble antimony(III) complexes 1 and 2 showed moderate antimicrobial activities against Gram-positive (Bacillus subtilis and Staphylococcus aureus) and -negative bacteria (Escherichia coli and Pseudomonas aeruginosa), yeasts (Candida albicans and Saccharomyces cerevisiae) and molds (Aspergillus niger and Penicillium citrinum). Complex 5 showed moderate antimicrobial activities against four bacteria, and two molds, while the ligand itself showed only modest antimicrobial activities against selected bacteria (B. subtilis, E. coli and S. aureus). The molecular structures and antimicrobial activities of antimony(III) complexes were compared with those of bismuth(III) complexes in the same 15 group in the periodic table.     

A pyridine bridged dicarbene ligand and its silver(I) and palladium(II) complexes: synthesis, structures, and catalytic applications

The potentially tridentate ligand 2,6-bis[(3-methylimidazolium-1-yl)methyl]pyridine dibromide reacts readily with silver(I) oxide in dichloromethane or dimethylsulfoxide to give a dinuclear silver(I)-carbene complex that was isolated as the tetrafluoroborate salt. Single crystal X-ray crystallography shows that each silver(I) ion is bridged by two ligands bonding through the carbene donors. Treatment of the silver(I) complex with suitable palladium(II) precursors gave the complexes PdCl[(CNC)]BF₄ and [PdMe(CNC)]BF₄ (CNC=2,6-bis[(3-methylimidazolin-2-yliden-1-yl)methyl]pyridine), in which the pyridyl and both carbene moieties are coordinated to a single palladium(II). The palladium(II) complexes have been fully characterised, including X-ray crystallography, and exhibit good activities in the Heck coupling reaction of 4-bromoacetophenone and n-butyl acrylate.     

Syntheses, structures and antimicrobial activities of various metal complexes of hinokitiol

Metal-oxygen bonding complexes (M = Mg^II, Mn^II, Ni^II, Mo^VI, W^VI, Pd^II, Sb^III, Bi^III, Fe^III, Ti^IV, K^I, Ba^II, Zr^IV and Hf^IV) with a hinokitiol (Hhino; 2-hydroxy-4-isopropylcyclohepta-2,4,6-trienone or β-thujaplicin) ligand, which has two unequivalent oxygen donor atoms, were synthesized and characterized by elemental analysis, TG/DTA, FT-IR and solution (¹H and ¹³C) NMR spectroscopy. Single-crystal X-ray structure analysis revealed various molecular structures for the complexes, which were classified into several families of family, i.e. type A [M^II(hino)₂(L)]₂ (M = Mg^II, Mn^II, Ni^II; L = EtOH or MeOH), with a dimeric structure consisting of one bridging hino⁻ anion, one chelating hino⁻ anion and one alcohol or water molecule, type B, with the octahedral, cis-dioxo, bis-chelate complexes cis-[M^VIO₂(hino)₂] (M = Mo^VI, W^VI), type C, with square planar complex [M^II(hino)₂] (M = Pd^II), type D, with tris-chelate, 7-coordinate complexes with one inert electron pair [M^III(hino)₃] (M = Sb^III, Bi^III), type D′, with the bis-chelate, pseudo-6-coordinate complexes with one inert electron pair [M^III(hino)₂X] (M = Sb^III, X = Br), type E, with tris-chelate, 6-coordinate complexes with Δ and Λ isomers [M^III(hino)₃] (M = Fe^III), type E′ of bis-chelate, 6-coordinate complex [M^IV(hino)₂X₂] (M = Ti^IV, X = Cl), type F, with water-soluble alkali metal salts [M^I(hino)] (M = K^I), and type H, with tetrakis-chelate, 8-coordinate complexes [M^IV(hino)₄](M = Zr^IV, Hf^IV). These structural features were compared with those of metal complexes with a related ligand, tropolone (Htrop). The antimicrobial activities of these complexes, evaluated in terms of minimum inhibitory concentration (MIC; μg mL⁻¹) in two systems, were compared to elucidate the relationship between structure and antimicrobial activity.     

Synthesis, crystal structure and antimicrobial activities of two isomeric gold(I) complexes with nitrogen-containing heterocycle and triphenylphosphine ligands, [Au(L)(PPh3)] (HL = pyrazole and imidazole)

Two isomeric gold(I)-triphenylphosphine complexes with nitrogen-containing heterocycles, [Au(L)(PPh3) (HL = pyrazole (1), imidazole (2)) were isolated as colorless cubic crystals for 1 and colorless plate crystals for 2, respectively. The crystal structures of 1 and 2 were determined by single-crystal X-ray diffraction. These complexes were also fully characterized by complete elemental analyses, thermogravimetric/differential thermal analyses (TG/DTA) and FT-IR in the solid state and by solution NMR (31P, 1H and 13C) spectroscopy and molecular weight measurements in acetone solution. These complexes consisted of a monomeric 2-coordinate AuNP core both in the solid state and in solution. The molecular structures of 1 and 2 were compared with those of related gold(I) complexes, [Au(1,2,3-triz)(PPh3)] (3, Htriz = triazole), [Au(1,2,4-triz)(PPh3)]2 (4) as a dimer through a gold(I)-gold(I) bond in the solid state, and [Au(tetz)(PPh3)] (5, Htetz = tetrazole). Selective and effective antimicrobial activities against two gram-positive bacteria (B. subtilis, S. aureus) and modest activities against one yeast (C. albicans) found in these gold(I) complexes 1-4 are noteworthy, in contrast to poor activities observed in the corresponding silver(I) complexes.     

Synthesis, structural characterization and biological study of new organotin(IV), silver(I) and antimony(III) complexes with thioamides

An overview of our work on the synthesis and biological activity of a series of tin(IV), silver(I) and antimony(III) complexes with thioamides is reported. Organotin(IV) complexes of formulae (n-Bu)2Sn(MBZT)2 (1), Me2Sn(CMBZT)(2) (2), {(Ph3Sn)2(MNA) (Me2CO)} (3), Ph3Sn(MBZT) (4), Ph3Sn(MBZO) (5), Ph3Sn(CMBZT) (6), Ph2Sn(CMBZT)2 (7) and (n-Bu)2Sn(CMBZT)2 (8), Me2Sn(PMT)2 (9), (n-Bu)2Sn(PMT)2 (10), Ph2Sn(PMT)2 (11), Ph3Sn(PMT) (12) {where MBZT=2-mercapto-benzothiazole, CMBZT=5-chloro-2-mercapto-benzothiazole, H2MNA=2-mercapto-nicotinic acid, MBZO=2-mercapto-benzoxazole and PMTH=2-mercapto-pyrimidine} were characterized by spectroscopic (NMR, IR, Mossbauer, etc.) and X-ray diffraction techniques and their influence on the peroxidation of oleic acid was studied. They were found to inhibit strongly the peroxidation of linoleic acid by the enzyme lipoxygenase. In addition, organotin(IV) complexes were found to exhibit stronger cytotoxic activity in vitro, against leiomyosarcoma cells, than cisplatin. The antiproliferative activity of the organotin complexes studied, against leiomyosarcoma cells follow the same order of LOX activity inhibition. This is, 3>12>7>6 approximately 8 approximately 10>5 approximately 4>2>9. Thus, among organotin(IV)-CMBZT complexes, 7 exhibits higher activity than the others and this is explained by a free radical mechanism, as it is revealed by an EPR study. The results are compared with the corresponding ones found for the silver(I) complexes of formulae complexes {[Ag6(mu3-HMNA)4(mu3-MNA)2](2-).[(Et(3)NH)+]2.(DMSO)2.(H2O)} (13), {[Ag4Cl4(mu3-STHPMH2)4]n} (14), {[Ag6(mu2-Br)6(mu2-STHPMH2)4(mu3-STHPMH2)2]n} (15), {[Ag4(mu2STHPMH2)6](NO3)4}(n) (16), {[AgCl(TPTP)]4} (17), [AgX(TPTP)3] with X=Cl (18), Br (19), I (20) (where STHPMH2=2-mercapto-3,4,5,6-tetrahydro-pyrimidine, TPTP=tri(p-toly)phosphine) and those of antimony(III) complexes {[SbCl2(MBZIM)4](+).Cl(-).2H2O.(CH3OH)} (21), {[SbCl2(MBZIM)4]+.Cl(-).3H2O.(CH3CN)} (22), [SbCl3(MBZIM)2] (23), [SbCl3(EMBZIM)2] (24), [SbCl3(MTZD)2] (25), {[SbCl3(THPMT)2]} (26) and {[Sb(PMT)3].0.5(CH3OH)} (27) (where MBZIM is 2-mercapto-benzimidazole, EMBZIM=5-ethoxy-2-mercapto-benzimidazole and MTZD is 2-mercapto-thiazolidine), which they have characterized with similar techniques as in case of organotin(IV) complexes. Silver(I) and antimony(III) complexes were found to be cytotoxic against various cancer cell lines.     

Synthesis, solid-state characterization and antimicrobial activities of three different polymorphs of a copper(II) complex with 4-isopropyltropolone (hinokitiol)

There exist at least three different polymorphs in the copper(II) complex [Cu(hino)₂] with a hinokitiol ligand (Hhino; 4-isopropyltropolone¹). In addition to deep-green plate crystals 1a and deep-green rod crystals 1b, whose crystal structures have been recently reported, novel green needle crystals 1c of [Cu(hino)₂] were found, the crystal structure of which was here determined by single-crystal X-ray analysis. Since only one crystal structure has been reported for the copper(II) complex [Cu(trop)₂] with a tropolone ligand (Htrop), the polymorphism found in the crystals of [Cu(hino)₂] would be due to the presence of the isopropyl group on the tropolone ring. The synthetic conditions giving the three polymorphs in good yields were found and the crystals were characterized with elemental analysis, FT-IR, TG/DTA and X-ray powder diffraction (XPD) measurements, as well as solution molecular weight measurements for 1a. The solid-state magnetic behaviors or the temperature-dependent magnetic susceptibilities were measured with Superconductivity Quantum Interference Devices (SQUID): 1a showed a weak ferromagnetic interaction, 1b showed a paramagnetic nature with S=1/2, while 1c showed a weak antiferromagnetic interaction. The antimicrobial activities for selected bacteria, yeasts and molds were also measured in the water-suspension system: 1a and 1b showed no activity, while 1c showed modest activities, and these activities were compared with those of the neutral Hino and the anionic hino⁻ ligands.     

Copper complexes with heterocyclic sulfonamides: synthesis, spectroscopic characterization, microbiological and SOD-like activities: crystal structure of [Cu(sulfisoxazole)2(H2O)4] . 2H2O

The synthesis, characterization and comparative biological study of a series of antibacterial copper complexes with heterocyclic sulfonamides were reported. Two kinds of complexes were obtained with the stoichiometries [Cu(L)2] . H2O and [Cu(L)2(H2O)4] . nH2O. They were characterized by infrared and electronic spectroscopies and the crystal structure of [Cu(sulfisoxazole)2(H2O)4] . 2H2O was determined by single crystal X-ray diffraction. It crystallized in the C2/c with Z = 8 monoclinic space group C2/c with Z = 8. The Cu(II) is in a slightly tetragonal distorted octahedron formed by four oxygen atoms from water molecules and two nitrogen atoms from two isoxazole rings. The antimicrobial activity was evaluated for all the synthesized complexes and ligands using the agar dilution test. The results showed that the complexes with five-membered heterocyclic rings were more active than the free sulfonamides while the pyrimidine, pyridine and pyridazine complexes had similar or less activity than the free ligands. In order to find an explanation for this behavior lipophilicity and superoxide dismutase-like activity were tested, showing that the [Cu(sulfamethoxazol)2(H2O)4] . 3H2O presented the highest antimicrobial potency and a superoxide dismutase-like activity comparable with pharmacological active compounds.     

Synthesis, structural characterization and antimicrobial activities of 4- and 6-coordinate nickel(II) complexes with three thiosemicarbazones and semicarbazone ligands

To investigate the relationship between antimicrobial activities and the molecular structures of nickel(II) complexes with thiosemicarbazone and semicarbazone ligands, nickel(II) complexes with ligands Hmtsc, Hatsc, Hasc and H2dmtsc, were prepared and characterized by elemental analysis, FT-IR, 1H and 13C NMR spectroscopies, magnetic susceptibility measurements, UV-Vis absorption spectra, TG/DTA and single-crystal X-ray analysis. Their antimicrobial activities were evaluated by the MIC against four bacteria (B. subtilis, S. aureus, E. coli and P. aeruginosa), two yeasts (C. albicans and S. cerevisiae) and two molds (A. niger and P. citrinum). The 4-coordinate, diamagnetic nickel(II) complexes showed antimicrobial activities which were different from those of free ligands or the starting nickel(II) compounds; [Ni(mtsc)(OAc)] 1 showed selective and effective antimicrobial activities against two Gram-positive bacteria (B. subtilis and S. aureus) and modest activities against a yeast (S. cerevisiae), [Ni(mtsc)Cl] 3 exhibited moderate activities against a Gram-positive bacterium (S. aureus), and [Ni(atsc)(OAc)] 5 showed modest activities against two Gram-positive bacteria (B. subtilis and S. aureus). On the other hand, the 6-coordinate, paramagnetic nickel(II) complexes with two protonated or deprotonated ligands ([Ni(mtsc)2] 2, [Ni(atsc)(mtsc)] 4, [Ni(atsc)2] 6, [Ni(Hatsc)2](NO3)(2)7, [Ni(Hatsc)2]Cl(2)8 and [Ni(Hasc)2](OAc)(2)9) and the sterically crowded 4-coordinate, diamagnetic nickel(II) complex ([Ni(dmtsc)] 10) did not inhibit the growth of the test organisms. The structure-activity correlation in this series of nickel(II) complexes was discussed based on their ligand-replacement abilities.     

Novel benzimidazol-2-ylidene carbene precursors and their silver(I) complexes: Potential antimicrobial agents

Novel benzimidazolium salts were synthesized as N-heterocyclic carbene (NHC) precursors, these NHC precursors were metallated with Ag₂O in dichloromethane at room temperature to give novel silver(I)–NHC complexes. Structures of these benzimidazolium salts and silver(I)–NHC complexes were characterized on the basis of elemental analysis, ¹H NMR, ¹³C NMR, IR and LC–MS spectroscopic techniques. A series of benzimidazolium salts and silver(I)–NHC complexes were tested against standard bacterial strains: Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and the fungal strains: Candida albicans and Candida tropicalis. The results showed that benzimidazolium salts inhibited the growth of all bacteria and fungi strains and all silver(I)–NHC complexes performed good activities against different microorganisms.     

Ligand-exchangeability of 2-coordinate phosphinegold(I) complexes with AuSP and AuNP cores showing selective antimicrobial activities against Gram-positive bacteria. Crystal structures of [Au(2-Hmpa)(PPh(3))] and [Au(6-Hmna)(PPh(3))] (2-H(2)mpa=2-mercaptopropionic acid, 6-H(2)mna=6-mercaptonicotinic acid)

Selective and effective antimicrobial activities against Gram-positive bacteria (B. subtilis and/or S. aureus) were found in 2-coordinate gold(I)-PPh(3) complexes with AuSP and AuNP cores, i.e. [Au(L)(PPh(3))] (HL=2-H(2)mna [H(2)mna=mercaptonicotinic acid] 3, D-H(2)pen [H(2)pen=penicillamine] 4, D,L-H(2)pen 5, 4-H(2)mba [H(2)mba=mercaptobenzoic acid] 8, Hpz [Hpz=pyrazole] 9, Him [Him=imidazole] 10, 1,2,3-Htriz [Htriz=triazole] 11, 1,2,4-Htriz 12, Htetz [Htetz=tetrazole] 13), whereas no activity was observed in 2-coordinate AuSP core complexes [Au(2-Hmba)(PPh(3))] 6 and [Au(3-Hmba)(PPh(3))] 7. The two novel AuSP core complexes, [Au(2-Hmpa)(PPh(3))] [H(2)mpa=mercaptopropionic acid] 1 and [Au(6-Hmna)(PPh(3))] 2, were prepared and characterized by elemental analysis, FT-IR, TG/DTA, and ((31)P, 1H and 13C) NMR spectroscopy. The crystal structures of 1 and 2 were determined as a supramolecular arrangement of the 2-coordinate AuSP core. Both 1 and 2 significantly showed antibacterial activities. As a model reaction of phosphinegold (I) complexes with the cysteine residue in the biological ligands, we examined if the ligand exchange reactions of the aromatic anions L(1)(-) in [Au(L(1))(PPh(3))] (HL(1)=6-H(2)mna 2, 2-H(2)mna 3, 2-H(2)mba 6, Hpz 9, Him 10, 1,2,3-Htriz 11, 1,2,4-Htriz 12) with aliphatic thiols HL(2) (HL(2)=2-H(2)mpa, D-H(2)pen) occurred under the mild conditions and, also, if the 'reverse' reactions, namely, the ligand exchange reactions of the thiolate anions in [Au(2-Hmpa)(PPh(3))] 1, [Au(D-Hpen)(PPh(3))] 4 and [Au(2-Hmba)(PPh(3))] 6 with the free ligands HL(1) took place under similar conditions. In this work, a relationship of the ligand-exchangeability among 2-coordinate gold(I) complexes (1-4, 6, 9-12) was revealed. Complex 6 was substitution-inert, whereas complexes 1-4 and 9-12 were substitution-labile. The ligand-exchangeability of Au-S and Au-N bonds in the 2-coordinate phosphinegold(I) complexes with AuSP and AuNP cores to form new AuSP cores, with retention of the Au-P bond, was closely related to the observed activities against Gram-positive bacteria, and the ease of the ligand-exchange reaction was strongly related to the intensity of the activities.     

Secondary ion mass spectrometry of nonvolatile isocyanide complexes of silver(I) and copper(I)

A series of silver and copper coordination complexes has been studied using secondary ion mass spectrometry (SIMS). Results are presented for the monomeric silver(I) complexes [Ag(CNR)₄]X, where R = cyclohexyl for X  ClO₄⁻, and R = methyl or t-butyl for X  PF₆⁻. Likewise, Cu(I) complexes [Cu(CNR)₄]PF₆, where R =methyl, t-butyl, or cyclohexyl, were examined. The presence of AgL₂⁺ (L represents the intact RNC ligand) and the absence of AgL₃⁺ and AgL₄⁺ species attests to the gas phase stability of two-coordinate silver(I). Similar results to these were obtained for the Cu(I) complexes, with the exception of [Cu(CNCH₃)₄]PF₆ whose spectrum contains CuL₄⁺, CuL₃⁺, CuL₂⁺, CuL⁺, and Cu⁺ ions. The latter result reflects the enhanced stability of the tetrahedral Cu(I) geometry compared to Ag(I) in the gas phase. Cross labeling experiments and isotopic labeling studies have provided insights into fragmentation mechanisms. Ligand exchange occurs when mixtures are examined. These exchange reactions provide evidence for extensive molecular mixing which can accompany SIMS even under low primary ion dose conditions. Cluster ion formation as well as the observation of α-cleavage of the NC bonds of RNC ligands have been observed and these results are discussed. Granulated graphite and ammonium chloride were employed to study matrix effects. Granulated graphite enhanced NC cleavage for the silver complexes but had little effect on the relative abundance of silver cluster ions. On the other hand, copper cluster ions were more sensitive to matrix effects.     

The synthesis, structure, and luminescence of two silver(I)-dppm complexes based on sulfate anion and nitrogen heterocyclic ligands

At ambient temperature, two silver(I) complexes [Ag₄(SO₄)₂(dppm)₄]·5CH₃CH₂OH·1/2H₂O (1) and [Ag₂(SO₄)(dppm)₂(2-ampz)]·CH₃OH·H₂O (2) (dppm = bis(diphenylphosphino)methane, 2-ampz = 2-aminopyrazine) were obtained by the reaction of Ag₂SO₄ with dppm in the presence of pyrazine or 2-aminopyrazine. They are characterized by IR, X-ray crystallography, luminescence and ¹H, ³¹P NMR spectroscopy. Complex 1 is a tetranuclear cluster. In complex 2, the units [Ag₂(SO₄)(dppm)₂] are connected by 2-aminopyrazine to form a 1D linear polymer. Due to the subtle interactions of different nitrogen heterocyclic ligands with silver ions, two SO₄²⁻ anions in 1 adopt μ₃-O, O′, O′ and unique μ₄-O, O, O′, O′ bonding modes respectively, while SO₄²⁻ anion in 2 adopts μ-O, O′ bonding mode.     

Characterization of oxovanadium (IV) complexes of D-gluconic and D-saccharic acids and their bioactivity on osteoblast-like cells in culture

Oxovanadium (IV) complexes of the alpha-hydroxycarboxylic ligands D-gluconic and D-saccharic acids of stoichiometry Na(2)[VO(gluconate)(2)].H(2)O, K(2)[VO(saccharate)(2)].4H(2)O, Na(4)[VO(gluconate)(2)].2H(2)O and K(5)[VO(saccharate)(2)].4H(2)O were obtained in aqueous solutions; the first two in acid, the other two in alkaline media. They were characterized by infrared and UV-Vis spectroscopies, thermoanalytical (thermogravimetric and differential thermal analysis) data and magnetic susceptibility measurements. The complexes were found to be mononuclear, possessing the VO(2+) moiety, and the thorough analysis of the spectral data allowed the determination of the characteristics of the metal-to-ligand interactions. The biological activities of these complexes on the proliferation, differentiation and glucose consumption were tested on osteoblast-like cells in culture. Comparisons of these effects and those of the oxovanadium (IV) cation and the free ligands were performed. Different behaviors could be observed for the complexes obtained at acidic or alkaline pH-values, as well as for the different cellular types. The free ligands did not show any biological effect.     

M-S vibrational study in three-coordinate thiolato compounds (NEt4)2[M(SC6H4-p-X)3] and (NEt4)

By using p-substituted benzenethiolate ligands, the novel three-coordinate copper(I) and silver(I) thiolato complexes (NEt4)2[Cu(SC6H4-p-X)3] (X=Cl (1) and Br (2)), (NEt4)2[Ag(SC6H4-p-X)3] (X=Cl (3) and Br (4)) and novel clusters (NEt4)2[M4(mu-SC6H4-p-Cl)6] (M=Cu (5) and Ag(6)) have been prepared and structurally characterized by single crystal X-ray diffraction. All the complexes have three-coordinate sites having point-group D3h symmetry. The three-coordinate mononuclear silver(I) complexes 3 and 4 are the first examples. The M-S stretching bands were determined by far-IR and FT-Raman spectroscopies; nu(Cu-S) 363-372 cm(-1) and nu(Ag-S) 353-363 cm(-1). These results indicate that M-S stretching vibration energy in the three-coordinate metal(I) site of the mononuclear compounds or clusters is around 340-380 cm(-1), and it is a useful tool for determining their coordination modes.     

Syntheses, crystal structures, spectroscopic, fluorescence and thermal properties of silver(I) 5,5-diethylbarbiturato complexes with some aminopyridines

Three new silver(I) complexes of 5,5-diethlybarbiturate (barb), [Ag(barb)(apy)]·H₂O (1), {[Ag(μ-ampy)][Ag(μ-barb)₂]}_n (2) and [Ag(barb)(dmamhpy)] (3) [apy = 2-aminopyridine, ampy = 2-aminomethylpyridine and dmamhpy = 2-(dimethylaminomethyl)-3-hydroxypyridine] have been synthesized and characterized by elemental analysis and FT-IR. Single crystal X-ray diffraction analyses showed that complexes 1 and 3 are mononuclear. In 1, the silver(I) ion is linearly coordinated by a barb anion and a ampy ligand, while a bidentate dmamhpy ligand together with an N-coordinated barb anion forms a trigonal coordination geometry around silver(I) in 3. Complex 2 is a one-dimensional coordination polymer in which silver(I) ions are bridged by ampy ligands, leading to a cationic chain . The [Ag(barb)₂]⁻ units contains two N-bonded barb ligands, bridging the silver centers in the cationic and anionic units via the carbonyl O atoms. Thus, complex 2 contains two-coordinated and four-coordinated silver ions. All complexes display hydrogen-bonded network structures and exhibit appreciable fluorescence at room temperature. Thermal analysis (TG-DTA) data are in agreement with the structures of the complexes.     

Synthesis, crystal structures and in vitro anti-fungal activities of two silver(I) coordination polymers with fluconazole

Two new polymeric silver(I)-fluconazole complexes: [Ag(HFlu)(NO₃)]_n (1) and {[Ag(HFlu)₂](ClO₄)}_n (2), have been synthesized and structurally characterized. The crystal structure of 1 consists of infinite 1D single strand helical coordination arrays with alternative …PMPM… arrangements, which are interlinked through hydrogen bonding interactions to generate a 3D network. The shortest intrachain Ag?Ag distance bridged by HFlu ligand is 8.287(1) Å. In 2, each Ag(I) ion is coordinated by four triazole N atoms from four HFlu ligands to form a 2D coordination layer, which has a helical arrangement along the [1 0 0] direction. The results of anti-fungal studies demonstrate that both silver(I) complexes are more active in comparison to the fluconazole drug.     

Molecular design, crystal structure, antimicrobial activity and reactivity of light-stable and water-soluble Ag-O bonding silver(I) complexes, dinuclear silver(I) N-acetylglycinate

The reaction in water of silver oxide with N-acetylglycine (H₂acgly) possessing the partial structure, i.e. the OC-N-C-COOH moiety, afforded light-stable and water-soluble dinuclear silver(I) complex _∞{[Ag(Hacgly)]₂} (complex 1). X-ray crystallography revealed that complex 1 in the solid state formed a ladder polymeric structure based on bis(carboxylato-O,O′)-bridged centrosymmetric Ag₂O₄ core, which was different from the two previously reported structures of silver(I) glycinate. Complex 1 which only comprises labile Ag-O bonding showed a wide range of antimicrobial activities against selected bacteria, yeasts and molds. Complex 1 can also work as an useful silver(I) precursor for novel silver(I) cluster synthesis.     

Di- and polynuclear silver(I) saccharinate complexes of tertiary diphosphane ligands: synthesis, structures, in vitro DNA binding, and antibacterial and anticancer properties

A series of new silver(I) saccharinate (sac) complexes, [Ag₂(sac)₂(μ-dppm)H₂O]·H₂O (1), {[Ag₂(μ-sac)₂(μ-dppe)]·3H₂O·CH₂Cl₂} _n (2), [Ag₂(μ-sac)₂(μ-dppp)] _n (3), and [Ag(sac)(μ-dppb)] _n (4) [dppm is 1,1-bis(diphenylphosphino)methane, dppe is 1,2-bis(diphenylphosphino)ethane, dppp is 1,3-bis(diphenylphosphino)propane, and dppb is 1,4-bis(diphenylphosphino)butane], have been synthesized and characterized by C, H, N elemental analysis, IR spectroscopy, ¹H NMR, ¹³C NMR, and ³¹P NMR spectroscopy, electrospray ionization mass spectrometry, and thermogravimetry–differential thermal analysis. Single-crystal X-ray studies show that the diphosphanes act as bridging ligands to yield a dinuclear complex (1) and one-dimensional coordination polymers (2 and 4), whereas the sac ligand adopts a μ₂-N/O bridging mode in 2, and is N-coordinated in 1 and 4. The interaction of the silver(I) complexes with fish sperm DNA was investigated using UV–vis spectroscopy, fluorescence spectroscopy, and agarose gel electrophoresis. The binding studies indicate that the silver(I) complexes can interact with fish sperm DNA through intercalation, and complexes 1 and 3 have the highest binding affinity. The gel electrophoresis assay further confirms the binding of the complexes with the pBR322 plasmid DNA. The minimum inhibitory concentrations of the complexes indicate that complex 1 exhibits very high antibacterial activity against standard bacterial strains of Escherichia coli, Salmonella typhimurium, and Staphylococcus aureus, being much higher than those of AgNO₃, silver sulfadiazine, ciprofloxacin, and gentamicin. Moreover, complexes 1–3 exhibit very high cytotoxic activity against A549 and MCF-7 cancer cell lines, compared with AgNO₃ and cisplatin. The bacterial and cell growth inhibitions of the silver(I) complexes are closely related to their DNA binding affinities.