Crystal structures and cytotoxicity of isopropylamine Pt(II) complexes: a trinuclear squarato-bridged [Pt3(mu2-C4O4)3(H2NPri)6].3H2O and a mononuclear cis-[Pt(NO3)2(H2NPri)2

Crystals of a novel platinum(II) complex with squarato ligand, [Pt(3)(mu(2)-C(4)O(4))(3)(H(2)NPr(i))(6)].3H(2)O (1) (H(2)NPr(i)=ipa), have been isolated from the aqueous solution of cis-[Pt(H(2)O)(2)(H(2)NPr(i))(2)]SO(4) and barium squarate. Slow evaporation of methanol solution of cis-[Pt(NO(3))(2)(H(2)NPr(i))(2)] (2) resulted in crystallization of nitrato complex. The single crystal X-ray diffraction method was used to determine structures of 1 and 2. Complex 1 crystallizes in a triclinic space group P1 with a=11.17380(10)A, b=14.4535(2)A, c=14.8010(2)A, alpha=86.0901(10) degrees , beta=78.4343(11) degrees , gamma=69.1915(5) degrees , and complex 2 in a monoclinic space group P2(1)/n, with a=10.1161(2)A, b=9.9188(2)A, c=13.3766(2)A, beta=102.7360(7) degrees . The X-ray structure analysis revealed that three platinum atoms in 1 are connected with three squarates which adopt bis(unidentate) binding modes. The squarato ligands span relatively long intramolecular Ptcdots, three dots, centeredPt distances (4.8842(3)-5.2699(3)A). A pair of cis positioned isopropylamine ligands completes a square planar coordination sphere of each Pt(II) ion. The square-planar coordination of complex 2 consists of two cis positioned isopropylamine ligands and two nitrato ligands. The results of cytotoxicity assay of trimer 1, monomer 2 and cis-diamminedichloroplatinum(II) (cisplatin) performed on human bladder tumor cell line T24 provide evidence that complex 2 is less cytotoxic compared to cisplatin and that the survival of tumor cells after exposure to 1 was minimally reduced.     

Unusual dimeric Zn(II)-cytosine complexes: new models of the interaction of Zn(II) with DNA and RNA

Synthesis and crystal structure of two Zn(II) dimer complexes with 1-methylcytosine (1-MeC) are reported. In complex [Zn(2)Cl(4)(mu-1-MeC-O2,N3)(2)] (1), two 1-MeC ligands are bridging two ZnCl(2) moieties. In [Zn(2)(1-MeC-N3)(4)(mu-SO(4))(2)].2H(2)O (2), the sulfates act as bridging ligands and 1-MeC are linked via N3 to Zn(II) as terminal ligands. Both complexes represent the first examples of Zn(II)-pyrimidine dimers. The potential biological significance of 1 and 2 is discussed.     

Antimicrobial and mutagenic activity of some carbono- and thiocarbonohydrazone ligands and their copper(II), iron(II) and zinc(II) complexes.

Several mono- and bis- carbono- and thiocarbonohydrazone ligands have been synthesised and characterised; the X-ray diffraction analysis of bis(phenyl 2-pyridyl ketone) thiocarbonohydrazone is reported. The coordinating properties of the ligands have been studied towards Cu(II), Fe(II), and Zn(II) salts. The ligands and the metal complexes were tested in vitro against Gram positive and Gram negative bacteria, yeasts and moulds. In general, the bisthiocarbonohydrazones possess the best antimicrobial properties and Gram positive bacteria are the most sensitive microorganisms. Bis(ethyl 2-pyridyl ketone) thiocarbonohydrazone, bis(butyl 2-pyridyl ketone)thiocarbonohydrazone and Cu(H2nft)Cl2 (H2nft, bis(5-nitrofuraldehyde)thiocarbonohydrazone) reveal a strong activity with minimum inhibitory concentrations of 0.7 microgram ml-1 against Bacillus subtilis and of 3 micrograms ml-1 against Staphylococcus aureus. Cu(II) complexes are more effective than Fe(II) and Zn(II) ones. All bisthiocarbono- and carbonohydrazones are devoid of mutagenic properties, with the exception of the compounds derived from 5-nitrofuraldehyde. On the contrary a weak mutagenicity, that disappears in the copper complexes, is exhibited by monosubstituted thiocarbonohydrazones.     

1D copper(II) and zinc(II) coordination polymers containing an unusual twisted oxalate bridge

Two new copper(II) complexes, Cu(L1)(ClO₄)₂ (1), {[(μ-oxalate)Cu(L1)] · 5H₂O}_n (2), and a zinc(II) complex, {[(μ-oxalate)Zn(L2)] · 3H₂O · 0.5DMF}_n (3) (L = 3,14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane), have been synthesized and characterized by X-ray crystallography. In 1, the ligand conformation is planar, and the octahedral coordination about the copper(II) ion is completed by weakly interacting ions. In 2 and 3, bridging oxalate ligands coordinate to copper(II) or zinc(II) ions in an unusually twisted bis-monodentate (trans-1,1′-bicoordination) mode.

The rigidity and steric hindrance of macrocycles L1 and L2 by the introduction of two cyclohexane rings and methyl groups on a cyclam (1,4,8,11-tetraazacyclotetradecane) skeleton cause the bridging oxalate ligands to adopt such unusual geometries in 2 and 3.     

Sequential binding of cobalt(II) to metallo-beta-lactamase CcrA

In an effort to probe Co(II) binding to metallo-beta-lactamase CcrA, EPR, EXAFS, and (1)H NMR studies were conducted on CcrA containing 1 equiv (1-Co(II)-CcrA) and 2 equiv (Co(II)Co(II)-CcrA) of Co(II). The EPR spectra of 1-Co(II)-CcrA and Co(II)Co(II)-CcrA are distinct and indicate 5/6-coordinate Co(II) ions. The EPR spectra also reveal the absence of significant spin-exchange coupling between the Co(II) ions in Co(II)Co(II)-CcrA. EXAFS spectra of 1-Co(II)-CcrA suggest 5/6-coordinate Co(II) with two or more histidine ligands. EXAFS spectra of Co(II)Co(II)-CcrA also indicate 5/6 ligands at a similar average distance to 1-Co(II)-CcrA, including an average of about two histidines per Co(II). (1)H NMR spectra for 1-Co(II)-CcrA revealed seven paramagnetically shifted resonances, three of which were solvent-exchangeable, while the NMR spectra for Co(II)Co(II)-CcrA showed at least 16 shifted resonances, including an additional solvent-exchangeable resonance and a resonance at 208 ppm. The data indicate sequential binding of Co(II) to CcrA and that the first Co(II) binds to the consensus Zn(1) site in the enzyme.     

Preparation, physicochemical properties and biological activity of copper(II) complexes with 6-(2-chlorobenzylamino)purine (HL1) or 6-(3-chlorobenzylamino)purine (HL2). The single-crystal X-ray structure of

Copper(II) complexes of 6-(2-chlorobenzylamino)purine (HL1) and 6-(3-chlorobenzylamino)purine (HL2), respectively, were prepared. Depending on the pH of the medium and the molar ratio of reactants the following mononuclear (trigonal-bipyramidal) and dinuclear (octahedral, trigonal-bipyramidal or tetrahedral) complexes were isolated: [Cu2(mu-HL1)2(mu-Cl2)2(HL1)2Cl2] (1a,b), [Cu2(mu-Cl)2(mu-L1)2(H2O)2] (2a), [Cu2(mu-Cl)2(mu-L2)2(H2O)2] (2b), [Cu(H+L2)2Cl3]Cl.H2O (3a,b), [Cu2(mu-Cl)2(HL1)2Cl2] (4a), and [Cu2(mu-Cl)2(HL2)2Cl2] (4b). The compounds were characterized by elemental analyses, electronic, infrared and mass (FAB+, ES+) spectral data, magnetic susceptibility temperature dependence measurements and molar conductivity data. An X-ray single-crystal structural analysis of [Cu(H+L2)2Cl3]Cl.2H2O (3b) showed that the Cu2+ ion is penta-coordinated by three chloride ions and by two H+L2 ligands. Thus, the Cu2+ ion adopts a distorted trigonal bipyramidal coordination geometry with the protonated H+L2 ligands coordinated in trans apical positions, while the three chloride ions are situated in an equatorial plane. The cytotoxic activity of the complexes was determined by a calcein AM assay. Mouse melanoma cell line B16-FO, human malignant melanoma cell line G361, human osteogenic sarcoma cell line HOS and human breast adenocarcinoma cell line MCF7 were used. IC50 values, the drug concentrations lethal to 50% of the tumor cells, were estimated. One of the important mechanisms responsible for the cytotoxicity of cytokinin-derived compounds, the inhibition of cyclin-dependent kinases by the studied complexes, was also determined.     

Complexes of Ni(II) and Cu(II) with ofloxacin. Crystal structure of a new Cu(II) ofloxacin complex

Several coordination compounds formed between Ni(II) or Cu(II) with ofloxacin have been synthesised and characterised. According to elemental chemical analysis and FT-IR spectroscopy data, direct reaction of Ni(II) and Cu(II) salts with ofloxacin leads to formation of precipitates for which mass spectrometry demonstrates their polymeric nature. However, crystalline [Cu(oflo)2(H2O)].2H2O is formed if the reaction is carried out in the presence of ammonia. This complex crystallises in the triclinic system, space group P-1 with a=9.2887(12), b=11.2376(14), c=17.874(2) A, alpha=92.12(3), beta=95.39(3), gamma=91.71(3) degrees and Z=2. The local geometry around the Cu(II) ion is a slightly distorted square base pyramid. Electronic spectra, magnetic susceptibility measurements and EPR spectra of the synthesised complexes indicate a tetragonal environment.     

Complexes of Cu(II), Ni(II) and Co(II) with the shiff base: 1H-indole-3-ethylensalicylaldimine as ligand

Complexes of Cu(II), Ni(II) and Co(II) with the Schiff base 1H-indole-3-ethylensalicylaldimine as ligand are studied. The isolated complexes correspond to the general formulae ML₂ (where L= ligand).The complexes were characterized by mass spectra, IR, ¹H NMR, UVVis spectra and magnetic measurements.The results indicated that the ligands coordinate through N and O with the metal ions in different stereochemistries.     

Synthesis and crystal structure of tetrakis(dimethylsulfoxide) platinum(II) bis(triflouromethanesulfonate)

Crystals of Pt(DMSO)₄(TFMS)₂ have been prepared by dissolution of platinum(II) hydroxide in a solution of CF₃SO₃H in DMSO and subsequent evaporation. The structure was determined by use of a CAD-4 diffractometer with monochromatic Mo Kα radiation. The space group is P with Z = 2, a = 8.630(2), b = 9.557(3), c = 16.659(3) Å, α = 73.33(2), β = 77.38(2) and γ = 79.19(3)°. The refinement converged to R = 0.056. The coordination around platinum is distorted square-planar with two S- and two O-bonded DMSO ligands in a cis-arrangement. The four donor atoms and the platinum are coplanar within 0.03 Å. There is a severe steric crowding between the two S-bonded DMSO molecules, which gives rise to a distortion of the bond angles around the platinum. The crowding is minimized as much as possible by a staggered arrangement of oxygen atoms and methyl groups of adjacent ligands. Pt---S bond lengths 2.208(3) and 2.205(4) Å are significantly shorter that those in the corresponding palladium complex, in accordance with a much stronger bond in the case of platinum. Bond length comparisons also indicate that ground state transinfluence of S-bonded DMSO probably is about the same in platinum and palladium complexes.     

Synthesis, characterization, and cytotoxic activity of copper(II) and platinum(II) complexes of 2-benzoylpyrrole and X-ray structure of bis[2-benzoylpyrrolato(N,O)]copper(II)

Copper(II) and platinum(II) complexes of 2-benzoylpyrrole (2-BZPH) were synthesized and characterized with IR, 1H and 13C NMR spectroscopies and coordination geometry with ligands arranged in transoid fashion. The crystal structure of [Cu(II)(2-BZP)2] was determined by X-ray diffraction. Death of complex treated Jurkat cells was measured by flow cytometry. The bis-chelate complexes [Cu(II)(2-BZP)2] and [Pt(II)(2-BZP)2] adopt square-planar coordination geometry with ligands, arranged in transoid fashion. Concentrations of 1-10 microM Platinum(II) complexes reduced cell survival from 100% to 20%, in contrast to the copper(II) complex which caused no cell death at a concentration of 10 microM. While the Pt(II) complexes may have damaged DNA to induce cell death, treatment with the Cu(II) complex did not induce Jurkat cell death.     

Synthesis, physico-chemical studies of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes with some p-substituted acetophenone benzoylhydrazones and their antimicrobial activity

Complexes of the type [M(pabh)(H2O)Cl], [M(pcbh)(H2O)Cl] and [M(Hpabh)(H2O)2 (SO4)] where, M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); Hpabh = p-amino acetophenone benzoyl hydrazone and Hpcbh = p-chloro acetophenone benzoyl hydrazone have been synthesized and characterized with the help of elemental analyses, electrical conductance, magnetic susceptibility measurements, electronic, ESR and IR spectra, thermal (TGA & DTA) and X-ray diffraction studies. Co(II), Ni(II) and Cu(II) chloride complexes are square planar, whereas their sulfate complexes have spin-free octahedral geometry. ESR spectra of Cu(II) complexes with Hpabh are axial and suggest d(x(2)-y(2) as the ground state. The ligand is bidentate bonding through > C = N--and deprotonated enolate group in all the chloro complexes, whereas, >C = N and >C = O groups in all the sulfato complexes. Thermal studies (TGA & DTA) on [Cu(Hpabh)(H2O)2(SO4)] indicate a multistep decomposition pattern, which are both exothermic and endothermic in nature. X-ray powder diffraction parameters for [Co(pabh)(H2O)Cl] and [Ni(Hpabh)(H2O)2(SO4)] correspond to tetragonal and orthorhombic crystal lattices, respectively. The ligands as well as their complexes show a significant antifungal and antibacterial activity. The metal complexes are more active than the ligand.     

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.     

Copper(II) complexes of salicylaldehyde hydrazones: synthesis, structure, and DNA interaction

Three hydrazone ligands, H2L1-H2L3, made from salicylaldehyde and ibuprofen- or naproxen-derived hydrazides, were prepared and transformed into the corresponding copper(II) complexes [Cu(II)L1] x H2O, [Cu(II)L2], and [(Cu(II))2(L3)2] x H2O x DMF (Scheme). The X-ray crystal structure of the last-mentioned complex was solved (Fig. 1), showing a square-planar complexation geometry, and the single units were found to form a one-dimensional chain structure (Fig. 2). The interactions of these complexes with CT-DNA were studied by different techniques, indicating that they all bind to DNA by classical and/or non-classical intercalation modes.     

Paramagnetic NMR investigations of Co(II) and Ni(II) amicyanin

 The paramagnetic ¹H NMR spectra of the Co(II) and Ni(II) substituted forms of the type 1 blue copper protein (cupredoxin) amicyanin have been assigned. This is the first such analysis of a cupredoxin, which has a distorted tetrahedral active site with the ligands provided by two histidines, a cysteine and a methionine. The isotropic shifts of the resonances in these spectra are compared with those of Co(II) and Ni(II) azurin. A number of interesting similarities and differences are found. The coordination of the metal by the two equatorial histidine ligands is very similar in both proteins. The interaction between the introduced metal and the thiolate sulfur of the equatorial cysteine ligand is enhanced in the amicyanin derivatives. Resonances belonging to the weak axial methionine ligand exhibit much larger shifts in the amicyanin derivatives, indicative of shorter M(II)-S(Met) distances. The presence of shorter axial M(II)-S(Met) and equatorial M(II)-S(Cys) distances in both Co(II) and Ni(II) amicyanin is ascribed to the absence of a second axially interacting amino acid at the active site of this cupredoxin. Received: 2 February 1999 / Accepted: 19 May 1999     

Complexation of 2-hydroxynicotinic and 3-hydroxypicolinic acids with zinc(II). Solution state study and crystal structure of trans-diaqua-bis-(3-hydroxypicolinato)zinc(II)

The interactions between zinc(II) and the two ligands 2-hydroxynicotinic acid (HNic) and 3-hydroxypicolinic acid (HPic) have been investigated by means of potentiometric titrations in aqueous 0.6 m (Na)Cl at 25 °C. In both cases, only mononuclear complexes are formed. The qualitative and quantitative results obtained have been confirmed in part by UV-Vis spectrophotometry and ¹H NMR spectroscopy. The complex trans-diaqua-bis-(3-hydroxypicolinato)zinc(II) was obtained as a crystal and examined by X-ray crystallography. The thermodynamic results allow drawing some conclusions regarding the extent of Zn(II) interference in a hypothetical chelation therapy treatment of aluminium or iron overload with these two ligands.     

Thiourea derivatives and their nickel(II) and platinum(II) complexes: antifungal activity

We have synthesized two thiourea derivatives of methyl anthranilate (1, 2) and their complexes with nickel (3) and platinum(II) (4). We have also prepared the complexes of nickel(II) with two benzoylthiourea derivatives (5, 6). The obtained compounds were characterized by elemental analysis, spectroscopic methods (FT-IR, UV-vis, NMR), mass spectrometry and thermal analysis. Compound 1, C(20)H(23)N(3)O(2)S, crystallizes in monoclinic space group P21/n, with Z=4, and unit cell parameters, a=8.8042(4) A, b=7.6608(3) A, c=28.834(2) A, alpha=gamma=90 degrees, beta=90.94(1) degrees. Compound 2, C(20)H(21)N(3)O(3)S, crystallizes in monoclinic space group P21/c, with Z=4, and unit cell parameters, a=7.7345(4) A, b=8.6715(4) A, c=29.113(2) A, alpha=gamma=90 degrees, beta=90.67(1) degrees. Compound 5, C(24)H(30)N(4)NiO(2)S(2), crystallizes in monoclinic space group P21/n, with Z=4, and unit cell parameters, a=10.4317(8) A, b=18.517(2) A, c=13.299(1) A, alpha=gamma=90 degrees, beta=104.53(1) degrees. Compound 6, C(25)H(28)Cl(2)N(4)NiO(4)S(2), crystallizes with a molecule of CH(2)Cl(2) in triclinic space group P-1, with Z=2, and unit cell parameters, a=10.362(1) A, b=11.849(2) A, c=12.536(2) A, alpha=90.04(2) degrees, beta=84.73(1) degrees, gamma=113.43(2) degrees. Compounds 1 and 2 show antifungal activity against the major pathogens responsible for important plant diseases (Botrytis cinerea, Colletotrichum fragariae, Fusarium oxysporum and Phoma betae). The antifungal activity is practically the same for morpholine and ethyl derivatives.     

Synthesis, characterization and the first crystal structure of the Zn(II) complex of 4,6-O-ethylidine-N-(2-hydroxybenzylidene)-beta-D-glucopyranosylamine.

4,6-O-Ethylidine-N-(2-hydroxybenzylidene)-beta-D-glucopyranosylamine (H(3)L(1)) and N-(5-bromo-2-hydroxybenzylidene-4,6-O-ethylidine-beta-D-glucopyranosylamine (H(3)L(2)) molecules possessing a single bond C-1 single bond N double bond C(H) single bond moiety for metal-ion binding were synthesized by condensing the 4,6-O-ethylidene-beta-D-glucopyranosylamine with salicylaldehyde or 5-bromosalicylaldehyde. Complexes of these ligands with Zn(II) were isolated and characterized using elemental analysis, FTIR, UV-Vis absorption, NMR spectroscopic and FAB mass spectrometric techniques. The structure of the Zn(II) complex derived from H(3)L(1) was established for the first time by a single-crystal X-ray diffraction study. The anomeric nature of the saccharide moiety was established based on (1)H NMR studies and was confirmed by the crystal structure. Further, the structure and binding aspects of the ligand, and the coordination features of this in its Zn(II) complex were derived from the corresponding crystal structure.     

Interaction of guanylic acid with the Mg(II), Ca(II), Sr(II), and Ba(II) ions in the crystalline solid and aqueous solution: evidence for the ribose C2'-endo/anti and C3'-endo/anti conformational changes.

The interaction of guanosine-5'-monophosphoric acid (H2-GMP) with the alkaline earth metal ions has been studied in aqueous solution at neutral pH. The crystalline salts of the type Mg-GMP.5H2O, Ca-GMP.6H2O, Sr-GMP.7H2O, and Ba-GMP.7H2O were isolated and characterized by Fourier transform ir, 1H-nmr and x-ray powder diffraction measurements. Two types of macrochelate complexes have been identified: (a) The direct metalbase and indirect metal-phosphate bindings (inner and outer sphere interaction) for the Mg(II), Ca(II), and Sr(II), ions; and (b) the indirect metal-base and direct metal-phosphate bindings (outer and inner sphere interaction) for the Ba(II) ion. In aqueous solution, an equilibrium exists between the base-metal-H2O...PO3 and base...H2O-M-PO3 interactions. The ribose moiety shows C3'-endo/anti conformation in the free acid; C2'-endo/anti in the Na2-GMP salt; C3'-endo/anti in the Mg(II)-, Ca(II)-, and Sr(II)-GMP salts; and C2'-endo/anti, in the Ba(II)-GMP salt.     

Low-temperature (180 K) crystal structures of tetrakis-mu-(niflumato)di(aqua)dicopper(II) N,N-dimethylformamide and N,N-dimethylacetamide solvates, their EPR properties, and anticonvulsant activities of these and other ternary binuclear copper(II)niflumate complexes

Two pseudopolymorphs, solvates, of [Cu(2)(II)(niflumate)(4)(H(2)O)(2)] of unknown structure were obtained following solution of [Cu(2)(II)(niflumate)(4)(H(2)O)(2)] in N,N-dimethylacetamide (DMA) or N,N-dimethylformamide (DMF). Low-temperature crystal structures obtained for these solvates revealed that they were ternary aqua DMA and DMF solvates: [Cu(2)(II)(niflumate)(4)(H(2)O)(2)].4DMA and [Cu(2)(II)(niflumate)(4)(H(2)O)(2)].4DMF. Intermolecular hydrogen bonding interactions account for the formation of these stable DMA and DMF solvates. These pseudopolymorphs contain a centrosymmetric binuclear center with Cu-Cu bond distances ranging from 2.6439(7) to 2.6452(9) A; the coordination sphere of Cu(II) is characterized by one long Cu-O (water) bond length of 2.128(3)-2.135(3) A and four short Cu-O (carboxylate) bonds of 1.949(3)-1.977(3) A. Crystal parameters for the DMA pseudopolymorph: a=10.372(1), b=19.625(2), c=17.967(2) A, beta=97.40(1) degrees , V=3626.8(6) A(3); monoclinic system; space group: P2(1)/a and for the DMF pseudopolymorph: a=10.125(2), b=18.647(3), c=19.616(4) A, alpha=74.38(2)(o), beta=88.18(2)(o), gamma=79.28(2)(o), V=3504(1) A(3); triclinic system; space group: P1. EPR spectra of these solids are identical and show strong antiferromagnetic coupling between the copper atoms, similar to the spectrum obtained for [Cu(2)(II)(niflumate)(4)(DMSO)(2)]. The [Cu(2)(II)(niflumate)(4)(H(2)O)(2)], [Cu(2)(II)(niflumate)(4)(H(2)O)(2)].4DMA, [Cu(2)(II)(niflumate)(4)(H(2)O)(2)].4DMF, [Cu(2)(II)(niflumate)(4)(DMF)(2)], and[Cu(2)(II)(niflumate)(4)(DMSO)(2)] evidenced protection against maximal electroshock-induced seizures and Psychomotor seizures at various times after treatment, consistent with the well known antiinflammatory activities of Cu chelates, but failed to protect against Metrazol-induced seizures while evidencing some Rotorod Toxicity consistent with a mechanism of action involving sedative activity.     

Mechanism of catalysis of Fe(II) oxidation by ferritin H chains.

Recombinant H chain ferritins bearing site-directed amino acid substitutions at their ferroxidase centres have been used to study the mechanism of catalysis of Fe(II) oxidation by this protein. UV-difference spectra have been obtained at various times after the aerobic addition of Fe(II) to the recombinants. These indicate that the first product of Fe(II) oxidation by wild type H chain apoferritin is an Fe(III) mu-oxo-bridged dimer. This suggests that fast oxidation is achieved by 2-electron transfer from two Fe(II) to dioxygen. Modelling of Fe(III) dimer binding to human H chain apoferritin shows a solvent-accessible site, which resembles that of ribonucleotide reductase in its ligands. Substitution of these ligands by other amino acids usually prevents dimer formation and leads to greatly reduced Fe(II) oxidation rates.