Synthesis and Structural Characterizations of New Coordination Polymers Generated by the Interaction Between the Trinuclear Triangular SBU [Cu 3 (μ 3 -OH)(μ-pz) 3 ] 2+ and 4,4′-Bipyridine. 3°

The reactions of 4,4′-bipyridine with selected trinuclear triangular copper(II) complexes, [Cu3(μ3-OH)(μ-pz)3(RCOO)2Lx], [pz = pyrazolate anion, R = CH3(CH2)n (2 ≤ n ≤ 5); L = H2O, MeOH, EtOH] yielded a series of 1D coordination polymers (CPs) based on the repetition of [Cu3(μ3-OH)(μ-pz)3] secondary building units joined by bipyridine. The CPs were characterized by conventional analytical methods (elemental analyses, ESI-MS, IR spectra) and single crystal XRD determinations. An unprecedented 1D CP, generated through the bipyridine bridging hexanuclear copper clusters moieties, two 1D CPs presenting structural analogies, and two monodimensional tapes having almost exactly superimposable structures, were obtained. In one case, the crystal packing makes evident the presence of small, not-connected pores, accounting for ca. 6% of free cell volume.

DmeRF system is required for nickel and cobalt resistance in Rhizobium leguminosarum bv. viciae.

A member of the Cation Diffusion Facilitator (CDF) family with high sequence similarity to DmeF (Divalent metal efflux) from Cupridavirus metallidurans was identified in Rhizobium leguminosarum bv. viciae UPM1137. The R. leguminosarum dmeF mutant strain was highly sensitive to Co2+ and moderately sensitive to Ni2+, but its tolerance to other metals such as Zn2+, Cu2+ or Mn2+ was unaffected. An open reading frame located upstream of R. leguminosarum dmeF, designated dmeR, encodes a protein homologous to the nickel and cobalt regulator RcnR from E.coli. Expression of the dmeRF operon was induced by nickel and cobalt ions in free-living cells, likely by alleviating DmeR-mediated transcriptional repression of the operon.

Expression of endogenous peptide-major histocompatibility complex class II complexes derived from invariant chain-antigen fusion proteins.

CD4+ T cells recognize major histocompatibility complex (MHC) class II-bound peptides that are primarily obtained from extracellular sources. Endogenously synthesized proteins that readily enter the MHC class I presentation pathway are generally excluded from the MHC class II presentation pathway. We show here that endogenously synthesized ovalbumin or hen egg lysozyme can be efficiently presented as peptide-MHC class II complexes when they are expressed as fusion proteins with the invariant chain (Ii). Similar to the wild-type Ii, the Ii-antigen fusion proteins were associated intracellularly with MHC molecules. Most efficient expression of endogenous peptide-MHC complex was obtained with fusion proteins that contained the endosomal targeting signal within the N-terminal cytoplasmic Ii residues but did not require the luminal residues of Ii that are known to bind MHC molecules. These results suggest that signals within the Ii can allow endogenously synthesized proteins to efficiently enter the MHC class II presentation pathway. They also suggest a strategy for identifying unknown antigens presented by MHC class II molecules.

Tables of interplanar spacings computed for the characteristic radiations of copper, molybdenum, iron, chromium and cobalt

"ASTIA document no. AD142344."

Synthesis and characterization of cobalt(III) complexes with sinambic amplector ligands

The synthesis of the hexadentate ligand 5,6-dimethyl-2,2,9,9-tetra(methyleneamine)-4,7-dithiadecane (1,2-Me(2)EtN(4)S(2)amp) is reported. The diastereiosomers were separated as cobalt(III) complexes using cation exchange chromatography. The rac and mesa isomers were characterized by NMR (C-13, H-1, Co-59), ESI-MS, UV-Vis spectroscopy and cyclic voltammetry. Single crystals of [Co(rac-1,2-Me(2)EtN(4)S(2)amp)] Cl-2(ClO4) (.) 2H(2)O were characterized by X-ray diffraction. The low-temperature (11 K) absorption spectra of the complexes have been measured in Nafion films and from the observed positions of both spin-allowed (1)A(1g) --> T-1(1g) and (1)A(1g) --> T-1(2g) and spin forbidden (1)A(1g) --> T-3(2g) bands, octahedral ligand-field parameters (10Dq, B and C) were determined. These results, in conjunction with the Co-59 NMR data, are used to further explore the relationship between the Co-59 magnetogyric ratio (gamma(Co)) and the product of the nephelauxetic ratio and the wavelength of the (1)A(1g) --> T-1(1g) transition (beta(DeltaE)(-1)) for complexes of mixed donor nitrogen-thioether ligands. (C) 2004 Elsevier Ltd. All rights reserved.

Stereocontrol in complexes of cyclam-like macrocycles - influences of chirality

Enforcement of chirality upon a macrocyclic tetramine ligand structure by the introduction of an asymmetric pendent arm which does not significantly modify the macrocycle conformation has no significant effect upon the geometry of the coordination sphere of a bound metal. Where substitution engendering chirality does cause a change in the ligand conformation, in particular for a ligand of restricted stereochemistry, these effects can be much greater. Thus, conversion of 3,7-diazacycloheptane to a macrocycle via attachment of chiral sidearms and ring closure through a template reaction leads to cyclam derivatives with unusual coordination properties. (C) 2004 Elsevier Ltd. All rights reserved.

The antioxidant potential of modified quercetins and quercetin-metal complexes

Quercetin is a naturally occurring polyphenol compound present in grapes, red wine, tea, apples and some vegetables. Like other flavonoids, it has been found to have antioxidant activity in studies in vitro, although there is still much debate about the bioavailability of flavonoids in the diet and their in vivo antioxidant activity. In general, it is thought that the antioxidant efficiency of polyphenols increases with increasing hydroxylation of the rings, but there have been few studies of other substitutions. We have prepared several derivatives of quercetin, to test the effect of modification on their antioxidant potential. Sodium salts of quercetin-5-sulfonate and quercetin-5,8-sulfonate, and transition metal complexes of quercetin-5-sulfonate were analysed for their total antioxidant potential using the FRAP assay, and compared to unmodified quercetin. It was found that quercetin-5-sulfonate complexes with Zn, Cu(II), Fe(II) and Mg were all significantly better antioxidants than quercetin, quercetin-5-sulfonate was comparable to quercetin, whereas the sodium salt of quercetin-5,8-sulfonate had a decreased total antioxidant potential. Kinetic studies of the FRAP reaction showed no significant differences between quercitin and any of the derivatives. The reaction of all the quercetins in the FRAP assay was found to be slower to reach completion than ascorbate, and appeared to have biphasic characteristics. These results suggest that transition metal ions may facilitate the transfer of electrons from the polyphenol ring system to the oxidant, while substitution with S03 is electron-withdrawing and destabilizes the ring system. This is important both for understanding the antioxidant ability of flavonoids, and for the design of novel antioxidant compounds. Further work is being carried out to assess the ability of the quercetin complexes to protect cultured cells from oxidative stress.

Nanostructured copper oxides and phosphates from a new solid-state route

Nanostructured copper containing materials of CuO, Cu3(PO4)3 and Cu2P2O7 have been prepared by solid-state pyrolysis of molecular CuCl2·NC5H4OH (I), CuCl2·CNCH2C6H4OH (II), oligomeric [Cu(PPh3)Cl]4 (III), N3P3[OC6H4CH2CN·CuCl]6[PF6] (IV), N3P3[OC6H5]5[OC5H4N·Cu][PF6] (V), polymeric chitosan·(CuCl2)n (VI) and polystyrene-co-4-vinylpyridine PS-b-4-PVP·(CuCl2) (VII) precursors. The products strongly depend on the precursor used. The pyrolytic products from phosphorus-containing precursors (III), (IV) and (V) are Cu phosphates or pyrophosphates, while non-phosphorous-containing precursors (VI) and (VII), result in mainly CuO. The use of chitosan as a solid-state template/stabilizer induces the formation of CuO and Cu2O nanoparticles. Copper pyrophosphate (Cu2P2O7) deposited on Si using (IV) as the precursor exhibits single-crystal dots of average diameter 100 nm and heights equivalent to twice the unit cell b-axis (1.5–1.7 nm) and an areal density of 5.1–7.7 Gigadots/in.2. Cu2P2O7 deposited from precursor (VI) exhibits unique labyrinthine high surface area deposits. The morphology of CuO deposited on Si from pyrolysis of (VI) depends on the polymer/Cu meta ratio. Magnetic measurements performed using SQUID on CuO nanoparticle networks suggest superparamagnetic behavior. The results give insights into compositional, shape and morphological control of the as-formed nanostructures through the structure of the precursors.

X-Ray crystal structure of [Cu2OH(O2CCF 3)3(quinoline)2]2, a tetranuclear basic copper(II) carboxylate adduct with significant metal-metal interaction

The basic copper(II) carboxylate adduct, [Cu2-OH(O 2CCF3)3(quinoline)2]2, has been shown by an X-ray structural analysis to have a novel tetranuclear structure; magnetic susceptibility data show that substantial Cu-Cu interaction is present in this compound.

Host-guest chemistry of solid coordination frameworks (SCFs) based on Copper(II)-Pyridine Ligands

283 p.

Aminotriazines as locking fragments in macrocyclic synthesis

The macrocyclic compounds (6-(4',6'-diamino-1',3',5'-triazinyl)-1,4,6,8,11-pentaazacyclotetradecane)copper(II) triperchlorate dihydrate, [Cu(HL2)](ClO4)(3). 2H(2)O, (6-(6'-amino-4'-oxo-1'H-1',3',5'-triazinyl)-1,4,6,8,11-pentaazacyclotetradecane)copper(II) diperchlorate hydrate, [CuL3](ClO4)(2). H2O, and [(6-(4',6'-dioxo-1'H-1',3',5'-triazinyl) 1,4,6,8,11-pentaazacyclotetradecane)copper(II)] diperchlorate, [CuL4](ClO4)(2), have been synthesized. The macrocycles synthesized contain respectively pendant melamine, ammeline,and ammelide rings. The X-ray cyrstallographic analyses of [Cu(HL2)](ClO4)(3). 2H(2)O, triclinic, space group P (1) over bar, a = 9.489(10) Angstrom, b = 12.340(2) Angstrom, c = 24.496(4) Angstrom, alpha = 87.74(10)degrees beta = 85.51(10)degrees gamma = 70.95(10)degrees and Z = 4, and {[CuL3](ClO4)(2). H2O}2, monoclinic, space group C2/c, a = 18.624(8) Angstrom, b = 17.160(2) Angstrom, c = 15.998(6) Angstrom, beta = 117.82(2)degrees, and Z = 4, are reported. The structure of [Cu(HL2)](ClO4)(3). 2H(2)O shows the formation of linear tapes, formed by a combination of hydrogen bonds and pi-pi stacking interactions. The structure of [CuL3](ClO4)(2). H2O displays formation of dimers, formed by a coordinate bond from the oxygen in one molecule to the copper atom of another. The tautomeric forms of the ammeline and ammelide moieties have been determined. The potential of these compounds as subunits for cocrystallization has been investigated.