Uracilato and 5-halouracilato complexes of Cu(II), Zn(II) and Ni(II). X-ray structures of [Cu(uracilato-N(1))(2)(NH(3))(2)].2(H(2)O), [Cu(5-chlorouracilato-N(1))(2)(NH(3))(2)](H(2)O)(2), [Ni(5-chlorouracilato-N(1))(2)(en)(2)].2H(2)O and [Zn(5-chlorouracilato-N(1))(NH(3))(3)].(5-chlorouracilato-N(1)).(H(2)O)

Four new complexes of uracilato and 5-halouracilato with the divalent metal ions Cu(II), Zn(II) and Ni(II) were obtained and structurally characterized. [Cu(uracilato- N(1))(2)(NH(3))(2)].2(H(2)O) (1) and [Cu(5-chlorouracilato-N(1))(2)(NH(3))(2)](H(2)O)(2) (2) complexes present distorted square planar co-ordination geometry around the metal ion. Although an additional axial water molecule is present [Cu(II)-OH(2)=2.89 A (for 1) and 2.52 A (for 2)] in both cases, only in the complex 2 would be considered in the limit of a bond distance. The Zn(II) in [Zn(5-chlorouracilato-N(1))(NH(3))(3)].(5-chlorouracilato-N(1)).(H(2)O) presents a tetrahedral co-ordination with three ammonia molecules and the N(1) of the corresponding uracilato moiety. A non-coordinated uracilato molecule is present as a counterion and a recognition between co-ordinated and free ligands, by means a tandem of H-bonds, should be mentioned. Finally, the complex [Ni(5-chlorouracilato-N(1))(2)(en)(2)] (H(2)O)(2) (where en is ethylenediamine) presents a typical octahedral trans co-ordination with additional hydrogen bonds between 5-chlorouracilato and the NH(2) groups of ethylenediamine units.     

Theoretical study of structure, bonding, and electronic behavior of novel sandwich compounds M3(C6R6)2 (M = Ni, Pd, Pt; R = H, F)

The correlations between the structural and electronic properties of the monolayer clusters M(3) (where M = Ni, Pd, Pt) and the sandwich complexes M(3)(C(6)R(6))(2) (where M = Ni, Pd, Pt; R = H, F) were studied by performing quantum-chemical calculations. All of the sandwich complexes are strongly donating and backdonating metal-ligand bonding structures. The influence of the ligand as well as significant variations in the M-C, M-M, and C-C bond lengths and binding energies were examined to obtain a qualitative and quantitative picture of the intramolecular interactions in C(6)R(6)-M(3). Our theoretical investigations show that the binding energies of these sandwich complexes gradually decrease from Ni to Pt as well as from H to F, which can be explained via the frontier orbitals of the clusters M(3) and C(6)R(6).     

Reaction of a model siderophore with Ni(II), Co(II) and Zn(II) in aqueous solution: kinetics and spectroscopy

A spectroscopic study was performed showing that the [Fe(III)(L(2-))(2)](1-) (L(2-)=dopacatecholate) complex reacts with Ni(II), Co(II) and Zn(II) in an aqueous solution containing S(2)O(3)(2-) resulting in the soluble [M(L(1-))(3)](1-) (L(1-)=dopasemiquinone; M=Ni(II), Co(II) or Zn(II) complex species. The Raman and IR spectra of the [CTA][M(L(1-))(3)] complexes, CTA=hexadecyltrimethylammonium cation, in the solid state were obtained. The kinetic constants for the metal substitution reactions were determined at four different temperatures, providing values for DeltaH(not equal), DeltaS(not equal) and DeltaG(not equal). The reactions were slow (k=10(-11) Ms(-1)) and endothermic. The system investigated can be considered as a simplified model to explain some aspects of siderophore chemistry.     

Molecular structure, bioavailability and bioactivity of [Cu(o-phen)2(cnge)](NO3)2.2H2O and [Cu(o-phen)(cnge)(H2O)(NO3)2] complexes

Two Cu(II) complexes with cyanoguanidine (cnge) and o-phenanthroline, [Cu(o-phen)(2)(cnge)](NO(3))(2).2H(2)O (1) and [Cu(o-phen)(cnge)(H(2)O)(NO(3))(2)] (2), have been synthesized using different experimental techniques and characterized by elemental analyses, FTIR, diffuse and UV-vis spectra and EPR and magnetic moment measurements techniques. The crystal structures of both complexes were solved by X-ray diffraction methods. Complex (1) crystallizes in the monoclinic space group C2/c with a=12.621(5), b=31.968(3), c=15.39(1)A, beta=111.68(4) degrees, and Z=8 and complex (2) in the monoclinic space group P2(1)/n with a=10.245(1), b=13.923(2), c=12.391(2)A, beta=98.07(1) degrees, and Z=4. The environments of the copper(II) center are trigonal bipyramidal (TBP) for [Cu(o-phen)(2)(cnge)](2+) and an elongated octahedron for [Cu(o-phen)(cnge)(H(2)O)(NO(3))(2)]. Solution studies have been performed to determine the species distribution. The superoxide dismutase (SOD) activities of both complexes have also been tested in order to determine if these compounds mimic the enzymatic action of the enzyme SOD that protects cells against peroxide radicals.     

Synthesis and electrochemistry of Co(III) and Co(I) complexes having C5Me5 auxiliary

The synthesis and electrochemistry of half-sandwich type of Co(III) complexes [(C(5)Me(5))Co(bidentate)(CH(3)CN)](BF(4))(2) {bidentate=dppe (1,2-bis(diphenylphosphino)ethane), dppp (1,3-bis(diphenylphosphino)propane), bpy (2,2'-bipyridine), en (ethylenediamine)) are reported. Cyclic voltammograms of [(C(5)Me(5))Co(bidentate)(CH(3)CN)](BF(4))(2) in CH(3)CN s showed two redox couples assignable to Co(II)/Co(III) and Co(I)/Co(II). The Co(I) complex having C(5)Me(5) and dppe was also prepared. Two redox couples of this Co(I) complex, (C(5)Me(5))Co(dppe), in CH(3)CN coincided with those of [(C(5)Me(5))Co(dppe)(CH(3)CN)](BF(4))(2) in spite of the structural change around the metal center.     

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.     

New Ni(II)-sulfonamide complexes: synthesis, structural characterization and antibacterial properties. X-ray diffraction of [Ni(sulfisoxazole)2(H2O)4].2H2O and [Ni(sulfapyridine)2

The synthesis, structural characterization, voltammetric experiments and antibacterial activity of [Ni(sulfisoxazole)(2)(H(2)O)(4)].2H(2)O and [Ni(sulfapyridine)(2)] were studied and compared with similar previously reported copper complexes. [Ni(sulfisoxazole)(2)(H(2)O)(4)].2H(2)O crystallized in a monoclinic system, space group C2/c where the nickel ion was in a slightly distorted octahedral environment, coordinated with two sulfisoxazole molecules through the heterocyclic nitrogen and four water molecules. [Ni(sulfapyridine)(2)] crystallized in a orthorhombic crystal system, space group Pnab. The nickel ion was in a distorted octahedral environment, coordinated by two aryl amine N from two sulfonamides acting as monodentate ligands and four N atoms (two sulfonamidic N and two heterocyclic N) from two different sulfonamide molecules acting as bidentate ligands. Differential pulse voltammograms were recorded showing irreversible peaks at 1040 and 1070 mV, respectively, attributed to Ni(II)/Ni(III) process. [Ni(sulfisoxazole)(2)(H(2)O)(4)].2H(2)O and [Ni(sulfapyridine)(2)] presented different antibacterial behavior against Staphylococcus aureus and Escherichia coli from the similar copper complexes and they were inactive against Mycobacterium tuberculosis.     

Preparation and cell growth inhibitory activity of [PtR(2)L(2)] (R=polyfluorophenyl,L(2)=diene,cyclohexane-1,2-diamine (chxn) or cis-(dimethyl sulfoxide)(2)) and the X-ray crystal structure of [Pt(C(6)F(5))(2)(cis-chxn)

A range of [PtR(2)(chxn)] (R=C(6)F(5), o-HC(6)F(4), p-HC(6)F(4), p-MeOC(6)F(4) or 3,5-H(2)C(6)F(3); chxn=cyclohexane-1,2-diamine) and cis-[PtR(2)(dmso)(2)] (R=C(6)F(5), p-HC(6)F(4) or p-MeOC(6)F(4); dmso=dimethyl sulfoxide) complexes have been prepared from the corresponding [PtR(2)(diene)] (diene=cis,cis-cycloocta-1,5-diene (cod), hexa-1,5-diene (hex), norbornadiene (nbd) or dicyclopentadiene (dcy)) derivatives and have been spectroscopically characterized. A representative crystal structure of [Pt(C(6)F(5))(2)(cis-chxn)] was determined and shows a slightly distorted square planar geometry for platinum with chxn virtually perpendicular to the coordination plane. The biological activity against L1210 and L1210/DDP cell lines of these compounds together with the behaviour of other organoplatinum complexes, [PtR(2)L(2)] (L(2)=ethane-1,2-diamine (en) or cis-(NH(3))(2)) have been determined. Despite the use of relatively inert fluorocarbon anions as leaving groups, moderate-high cell growth inhibitory activity is observed. None of the fluorocarbon complexes displayed any cross resistance with cisplatin.     

DNA interactions of new mixed-ligand complexes of cobalt(III) and nickel(II) that incorporate modified phenanthroline ligands

Four new mixed-ligand complexes, namely [Co(phen)(2)(qdppz)](3+), [Ni(phen)(2)(qdppz)](2+), [Co(phen)(2)(dicnq)](3+) and [Ni(phen)(2)(dicnq)](2+) (phen=1,10-phenanthroline, qdppz=naptho[2,3-a]dipyrido[3,2-H:2',3'-f]phenazine-5,18-dione and dicnq=dicyanodipyrido quinoxaline), were synthesized and characterized by FAB-MS, UV/Vis, IR, 1H NMR, cyclic voltammetry and magnetic susceptibility methods. Absorption and viscometric titration as well as thermal denaturation studies revealed that each of these octahedral complexes is an avid binder of calf-thymus DNA. The apparent binding constants for the dicnq- and qdppz-bearing complexes are in the order of 10(4) and >10(6) M(-1), respectively. Based on the data obtained, an intercalative mode of DNA binding is suggested for these complexes. While both the investigated cobalt(III) complexes and also [Ni(phen)(2)(qdppz)](2+) affected the photocleavage of DNA (supercoiled pBR 322) upon irradiation by 360 nm light, the corresponding dicnq complex of nickel(II) was found to be ineffective under a similar set of experimental conditions. The physico-chemical properties as well as salient features involved in the DNA interactions of the cobalt(III) and nickel(II) complexes investigated here were compared with each other and also with the corresponding properties of the previously reported ruthenium(II) analogues.     

Three new Cu(II) and Cd(II) complexes with 3-(2-pyridyl)pyrazole-based ligand: syntheses, crystal structures, and evaluations for bioactivities

Three new complexes [Cu(L)(2)(NO(3))](NO(3))(H(2)O)(1/2)(CH(3)OH)(1/2) (1), [Cd(L)(2)(NO(3))(2)](H(2)O)(3) (2) and [Cd(L)(2)(ClO(4))(CH(3)OH)](ClO(4))(H(2)O)(1/4)(CH(3)OH) (3) (L=1-[3-(2-pyridyl)pyrazol-1-ylmethyl]naphthalene) were synthesized and characterized by elemental analyses, IR and X-ray diffraction analysis. Among them, the Cu(II) and Cd(II) ions were both coordinated by four N donors from two distinct L ligands via N,N-bidentate chelating coordination mode. Additional weak interactions, such as the face-to-face pi-pi stacking and C-Hcdots, three dots, centeredO H-bonding interactions, linked the mononuclear unit into 1D chain and further into 2D network. Complexes 1-3 were subjected to biological assays in vitro against six different cancer cell lines. All of them exhibited cytotoxic specificity and notable cancer cell inhibitory rate. The interactions of 1-3 with calf thymus DNA were investigated by thermal denaturation, viscosity measurements, spectrophotometric and electrophoresis methods. The results indicate that these complexes bound to DNA by intercalation mode via the ligand L and had different nuclease activities, which were in good agreement with their DNA-binding strength. Moreover, the central metal ions of 1-3 played a vital role in DNA-binding behaviors, DNA-cleavage activities and cytotoxicities, whereas the contribution of the different counter anions to their bioactivities also should not be ignored.     

The binding of Ni(II) ions to hexahistidine as a model system of the interaction between nickel and His-tagged proteins

The aim of this work is to study the binding of nickel ions to hexahistidine (His(6)) combining potentiometric titrations and spectroscopic (UV-Vis and circular dichroism) determinations in order to establish the species distribution as a function of the pH, their stoichiometry, stability and geometry. For comparative purposes, the same procedure was applied to the Ni-histidine (His) system. His behaves as a tridentate ligand, coordinating the carboxyl group, the imidazole and the amino nitrogen atoms to Ni(II) ions in an octahedral coordination and a bis(histidine) complex is formed at pH higher than 5. For the Ni-His(6) system, the complex formation starts at pH 4 and five different species (Ni(His(6))H, Ni(His(6)), Ni(n)(His(6))(n), Ni(n)(His(6))(n)H(-n/2), Ni(n)(His(6))(n)H(-n)) are formed as a function of the pH. Ni(His(6))H involves the coordination of the imidazole nitrogen and a deprotonated amide nitrogen (N(Im), N(-)) resulting in an octahedral geometry. In Ni(His(6)), an imidazole nitrogen is deprotonated and coordinated (2N(Im), N(-)) to the metal ion with a square planar geometry. The aggregated forms result from the extra Ni-N(Im) coordination, resulting in a 4N square planar geometry that is stabilized by inter/intramolecular hydrogen bonds. This coordination mode is not altered during the deprotonation steps from Ni(n)(His(6))(n).     

Biological activity of complexes derived from thiophene-2-carbaldehyde thiosemicarbazone. Crystal structure of [Ni(C(6)H(6)N(3)S(2))(2)

The crystal structure of [Ni(L(III))(2)] (1), where HL(III)=thiophene-2-carbaldehyde thiosemicarbazone, consists of monomeric entities where the nickel(II) ions exhibit distorted square planar geometry. The two bidentate thiosemicarbazone ligands are centrosymmetric. C...S van der Waals' links and nonbonded intramolecular interactions are present in the structure. The biological activity of 1 is compared to that of the free ligand, and the cobalt(III) (2) and copper(II) (3) derivatives. The observed order of cytotoxicity against melanoma B16F10 and Friend erythroleukemia cells is: 1< or =ligand<2<3. A structure-activity correlation using Extended-Hückel MO calculations is described.     

The interaction of 5-fluoroorotic acid with transition metals: synthesis and characterisation of Ni(II), Cu(II) and Zn(II) complexes

5-Fluoroorotic acid (H(3)FOro) is a potent inhibitor for some metalloproteins such as dihydroorotase and dihydroorotate dehydrogenase and for thymidylate synthase (nonmetalloprotein) in the human malaria parasite Plasmodium falciparum. To study the coordination chemistry of H(3)Foro, the ammonium salt [NH(4)(+)][H(2)FOro(-)].1H(2)O (1) and the first coordination compounds of H(3)FOro with transition metals [Ni(HFOro(2-))(H(2)O)(4)].1H(2)O (2), [Cu(HFOro(2-))(NH(3))(H(2)O)](n) (3) and [Cu(3)(FOro(3-))(2)(NH(3))(6)(H(2)O)(2)] (4) have been synthesised and characterised by single-crystal X-ray diffraction, IR spectroscopy and by thermogravimetry. Three different coordination modes of 5-fluoroorotic acid have been established. In all cases the ligand is chelated to the metal via an amido-nitrogen and a carboxylate-oxygen but for (3), there is also a carboxylate oxygen from another HFOro(2-) ligand resulting in a polymeric structure and for (4), the second amido-nitrogen in the ororotic acid ring coordinates to give a trinuclear complex. The metal coordination polyhedra are octahedral in (2), square-pyramidal in (3) and square-planar and approximately square-pyramidal in (4). An octahedral coordination geometry including a N(1)/O(61)-chelating HFOro(2-) ligand with four aqua ligands is proposed for the Zn complex [Zn(HFOro(2-)) (H(2)O)(4)].0.5H(2)O (5), based on IR and thermogravimetric data. Extensive hydrogen bonded networks and some ring-ring stacking interactions are observed in each of the structures.     

Synthesis, structure and biomimetic properties of Cu(II)-Cu(II) and Cu(II)-Zn(II) binuclear complexes: possible models for the chemistry of Cu-Zn superoxide dismutase

Four imidazolate-bridged binuclear copper(II)-copper(II) and copper(II)-zinc(II) complexes viz., [(Bipy)(2)Cu-Im-Cu(Bipy)(2)](ClO(4))(3).CH(3)OH, [(Phen)(2)Cu-Im-Cu(Phen)(2)](BF(4))(3).2CH(3)OH, [(Bipy)(2)Cu-Im-Zn(Bipy)(2)](BF(4))(3), and [(Phen)(2)Cu-Im-Zn(Phen)(2)](BF(4))(3), (Bipy=2,2'-Bipyridyl, Phen=1-10-Phenanthroline and Im=imidazolate ion) were synthesized as a possible models for superoxide dismutase (SOD). Complex [(Bipy)(2)Cu-Im-Cu(Bipy)(2)](ClO(4))(3).CH(3)OH has been structurally characterized. This complex crystallizes in the triclinic space group P1, with the unit parameters a=8.88(5) A, b=13.79(17) A, c=20.18(18) A, alpha=76.424(8)(o), beta=85.888(6)(o), gamma=82.213(7). The metal-nitrogen bond length from 1.972-2.273 A and the distance Cu-Cu is 5.92 A. The five-coordinate geometry about the copper(II) ion is square pyramidal. Magnetic moment and electron paramagnetic resonance (e.p.r.) spectral measurements of the homobinuclear complexes have shown an antiferromagnetic exchange interaction. From the e.p.r. and UV-Vis spectral measurement studies, these complexes have been found to be stable (pH 8.5-10.5 for 1, 10.5 for 2,3 and 8.5 for 4). These complexes catalyse the dismutation of superoxide radical (O(2)(-)) at biological pH. All the observations indicate that these complexes act as good possible models for superoxide dismutase.     

Study on the amount of binding of anti-tumor metal complexes to different target sites of dGMP using trans-[en(2)Os(eta2-H(2))(CF(3)SO(3))](CF(3)SO(3)) in a competitive mode

In order to investigate the binding sites and the amount of binding of a number of anti-tumor metal complexes (cisplatin, Cp(2)TiCl(2) and (CH(3))(2)SnCl(2)) to target molecule DNA mononucleotides in aqueous solution, a 1H NMR recognition probe, trans-[en(2)Os(eta2-H(2))(CF(3)SO(3))](CF(3)SO(3)), was used in a competitive mode. The minimum percentages of binding of anti-tumor metal complexes to different sites of dGMP were also determined.     

Synthesis, characterization, DNA-binding and cleavage studies of [Ru(bpy)2(actatp)]2+ and [Ru(phen)2(actatp)]2+ (actatp=acenaphthereno[1,2-b]-1,4,8,9-tetraazariphenylence)

New ligand acenaphthereno[1,2-b]-1,4,8,9-tetraazariphenylence (actatp) and its complexes [Ru(bpy)(2)(actatp)](ClO(4))(2).2H(2)O (1) (bpy=2,2'-bipyridine) and [Ru(phen)(2)(actatp)](ClO(4))(2).2H(2)O (2) (phen=1,10-phenanthroline) have been synthesized and characterized by UV-vis, 1H NMR, and mass spectra. The electrochemical behavior of the two complexes was studied by cyclic voltammetry. The interaction of the two complexes with calf thymus DNA has been investigated by spectrophotometric methods and viscosity measurements. The experimental results suggest that both complexes bind to DNA through an intercalative mode. The circular dichroism signals of the dialysates of the racemic complexes against calf thymus DNA are discussed. When irradiated at 302 nm, both complexes have also been found to promote the photocleavage of plasmid pBR 322 DNA.     

Tridentate N(2)S ligand from 2,2'-dithiodibenzaldehyde and N,N-dimethylethylenediamine: Synthesis, structure, and characterization of a Ni(II) complex with relevance to Ni Superoxide Dismutase

Nickel Superoxide Dismutase (NiSOD) and the A-cluster of Carbon Monoxide Dehydrogenase/Acetyl Coenzyme A Synthase (CODH/ACS) both feature active sites with Ni coordinated by thiolate and amide donors. It is likely that the particular set of donors is important in tuning the redox potential of the Ni center(s). We report herein an expansion of our efforts involving the use of 2,2′-dithiodibenzaldehyde (DTDB) as a synthon for metal-thiolate complexes to reactions with Ni complexes of N,N-dimethylethylenediamine (dmen). In the presence of coordinating counterions, these reactions result in monomeric square-planar complexes of the tridentate N₂S donor ligand derived from the Schiff-base condensation of dmen and DTDB. In the absence of a coordinating counterion, we have isolated a Ni(II) complex with an asymmetric N₂S₂ donor set involving one amine and one imine N donor in addition to two thiolate donors. This latter complex is discussed with respect to its relevance to the active site of NiSOD.     

Kinetic study of azole-bridged dinuclear platinum(II) complexes reacting with a hairpin-stabilized double-stranded oligonucleotide

The cytotoxic dinuclear platinum(II) complexes [[cis-Pt(NH(3))(2)](2)(mu-OH)(mu-pz)](NO(3))(2) (pz=pyrazolate) (1) and [[cis-Pt(NH(3))(2)](2)(mu-OH)(mu-1,2,3-ta-N1,N2)](NO(3))(2) (1,2,3-ta=1,2,3-triazolate) (2), were allowed to react with the hairpin-stabilized double-stranded oligonucleotide d(TATGGCATT(4)ATGCCATA), to determine the amounts of intrastrand and interstrand DNA adducts. The reaction kinetics was investigated by reversed-phase HPLC, and the resulting products were analyzed using mass spectroscopy combined with enzymatic digestion, and Maxam-Gilbert sequencing. The reaction of 1 results in the formation of the 1,2-intrastrand d(GG) adduct as the major final product. The two most abundant products of 2 were identified as isomeric 1,2-intrastrand d(GG) adducts differing probably in platinum coordination to the triazole ring. No GG-interstrand crosslinks were detected with either compound. d(GGC)-d(GCC) sequences of DNA do thus not appear to represent significant targets for forming interstrand crosslinks with either 1 or 2.     

Ternary complexes metal [Co(II), Ni(II), Cu(II) and Zn(II)]--ortho-iodohippurate (I-hip)--acyclovir. X-ray characterization of isostructural [(Co, Ni or Zn)(I-hip)(2)(ACV)(H(2)O)(3)] with stacking as a recognition factor

Four ternary metal--ortho-iodohippurate (I-hip)--acyclovir (ACV) complexes, [M(I-hip)(2)(ACV)(H(2)O)(3)] where M is Co(II) (1), Ni(II) (2), Cu (3) and Zn(II) have been obtained by reaction between the corresponding binary complexes M(II)(I-hip)(2)xnH(2)O and ACV. Three ternary complexes (M=Co, Ni and Zn) and the corresponding Zn(II)--ortho-iodohippurate binary derivative have been structurally characterized by X-ray diffraction: The studies show these three ternary complexes are isostructural and present, in solid state, an interesting stacking between the nucleobase and the aryl ring of the hippurate moiety, which probably promotes the formation of ternary complexes. Moreover, the two different ligands interact between them by means of ancillary hydrogen bonds with water molecules coordinated to the metal ion. It must be mentioned that these two recognition factors, hydrogen bonds plus stacking, could explain the reason for the isostructurality of these ternary derivatives with so different three metal ions, with diverses trends in coordination numbers and geometries. In solid state, there are two enantiomeric molecules that are related by an inversion center as the crystal-building unit (as a translational motif) for the ternary complexes.     

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.