catechol ligand in a very rapid step followed by a slow replacement of water molecule through a dissociative path way in which attachment of donor oxygen atom of catechol takes the position vacated by leaving water molecule which increases the electron density on cobalt (III) centre and as a result the second water molecule is labilised leading to rapid chelation.
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formula unit. Each component is completed by crystal- lographic twofold symmetry: in the cation, one C and the N atom lie on the rotation axis; in the anion, the Cr III ion lies on the axis; in the solvent molecule, the C and the O atom lie on the axis. The aqua ligands are in a trans disposition in the resulting CrO 6 octahedron. In the crystal, the components are
acid). Each Cr III atom is hexacoordinated by four O and two N atoms from two (hypydc) 2 fragments, which act as tridentate ligands, in a distorted octahedral geometry. The O—Cr—O— C torsion angles between the two planes of the (hypydc) 2 fragments [ 99.81 (17) and 97.77 (17) ] indicate that these two units are almost perpendicular to one another. In the crystal structure, extensive O—H O, N—H O and C— H O hydrogen bonds with D A distances ranging from 2.560 (2) to 3.279 (3) A ˚ , ion pairing, C—O [O = 3.166 (2) A ˚ ] and – stacking interactions between (hypydc) 2 and (pydaH) + rings [with a centroid–centroid distance of 3.3353 (14) A ˚ ] contribute to the formation of a three-dimensional supramolecular structure.
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The iminodiacetate dianion (IDA) and its alkyl-substituted derivatives with an alkyl substituent on the N atom form several stable 2:1 metal complexes, in which each tridentate IDA ligand forms two ®ve-membered chelate rings with the central metal ion (Nesterova et al., 1979; Mootz & Wunderlich, 1980; Suh et al., 1997). The title compound, (I), has been obtained recently in this laboratory.
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corresponding methylquinolinium ion), whereas unsubstituted quinoline forms a binary (1:1) crystalline salt (Warnke et al., 2003). Unexpectedly, during the synthesis of the analogous compound with 2-methylquinoline, we obtained the title compound, (I), which is a mixed salt of molar ratio 1:1 consisting of 2-methylquinolinium chloride and 2-methyl- quinolinium tetrachloroferrate(III). This composition is the same as that of bis(8-hydroxyquinolinium) tetrachloro- ferrate(III) chloride (Bottomley et al., 1984).
The present study is a continuation of our investigations on the synthesis, characterization and stereochemistry of metallophthalocyaninate complexes, which have been obtained through oxidation by iodine vapour (Janczak & Idemori, 2001; Janczak, 2003). The title compound, (I), is an example of a complex containing the same metal ion in both parts of the complex, the cation and the anion, i.e. [SbPc] + and [Sb 4 I 14 ]
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and an aquapentachloridoindate anion. The In III ion is in a slightly distorted octahedral coordination geometry. In the crystal, alternating layers of cations and anions are arranged along  and are linked via intermolecular N—H O, O— H Cl and N—H Cl hydrogen bonds, forming sheets parallel to (001). Additional stabilization within these sheeets is provided by weak intermolecular C—H O interactions.
ion is coordinated in a slightly distorted octahedral environ- ment by four O atoms from two oxalate ligands in the equatorial plane and by two water O atoms in the axial sites. The 2-aminopyridinium cation is disordered over two sets of sites in a 0.800 (7):0.200 (7) ratio. In the crystal, N—H O and O—H O hydrogen bonds connect the components into a three-dimensional network. The crystal studied was an inversion twin with components in a ratio 0.75 (2):0.25 (2).
onate complex, a study was performed on female Wistar rats exposed through a diet supplement, and the comet assay was used to evaluate DNA damage in peripheral blood lympho- cytes (PBLs). High doses (equivalent to 100 mg Cr/kg body mass/day for 4 weeks) of supplementary Cr(III) did not affect body mass, feeding-efficiency ratio, or internal organ mass. Treatment of rats with the Cr(III)–propionate complex did not significantly affect the comet-assay results in lymphocytes, which suggests that the compound does not exert genotoxic effects in rats. Most in vivo experiments have demonstrated that Cr(VI) is carcinogenic, but the carcinogenicity of Cr(III) in animals is uncertain.
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A putative chromate ion binding site was identi- fied proximal to a rigidly bound FMN from elec- tron densities in the crystal structure of the quinone reductase from Gluconacetobacter han- senii (Gh-ChrR) (3s2y.pdb). To clarify the loca- tion of the chromate binding site, and to under- stand the role of FMN in the NADPH-dependent reduction of chromate, we have expressed and purified four mutant enzymes involving the site- specific substitution of individual side chains within the FMN binding pocket that form non- covalent bonds with the ribityl phosphate (i.e., S15A and R17A in loop 1 between β1 sheet and α1 helix) or the isoalloxanzine ring (E83A or Y84A in loop 4 between the β3 sheet and α4 he- lix). Mutations that selectively disrupt hydrogen bonds between either the N3 nitrogen on the isoalloxanzine ring (i.e., E83) or the ribitylphos- phoate (i.e., S15) respectively result in 50% or 70% reductions in catalytic rates of chromate re- duction. In comparison, mutations that disrupt π-π ring stacking interactions with the isoal- loxanzine ring (i.e., Y84) or a salt bridge with the ribityl phosphate result in 87% and 97% inhibit- tion. In all cases there are minimal alterations in chromate binding affinities. Collectively, these results support the hypothesis that chromate binds proximal to FMN, and implicate a struc- tural role for FMN positioning for optimal chro- mate reduction rates. As side chains proximal to the β3/α4 FMN binding loop 4 contribute to both
µmoles/liter. This transport mechanism is highly specific for chromate; other divalent tetrahedral anions only slightly inhibit influx at concentrations up to 10 times that of chromate. Metavanadate, however, competitively inhibits chromate influx at equimolar concentrations. Exposure of cells to unlabeled chromate leads to inhibition of subsequent influx of 51-chromate. It is suggested that this is due to a primary inhibitory effect of
with the monoprotonated 2-methyl-2-propanamine molecule, has been synthesized. The structure of the compound consists of discrete chromate ions stacked in layers perpendicular to the (010) plane, separated by organic layers containing [(CH 3 ) 3 CNH 3 ] + groups. The cohesion and stability of the
All the complexes were screened in-vitro for their antimicrobial activity against bacteria and fungi. Iron (III) complexes analyzed for antifungal and antibacterial activities in vitro conditions. All the complexes inhibit the growth of bacteria and fungi. For this study, we used lactobacillus bacteria in curd and A. Niger, Mucer on pickle. To check the
tion with organic amines in organic synthesis is one reason for the continued interest in this ®eld. The base-promoted cation exchange reactions developed by us for the synthesis of the sul®de complexes of Mo and W mentioned above can also be used for the synthesis of oxochromates. Thus the title complex, (I), was obtained in good yields by reacting the cyclic diamine piperazine with ammonium chromate.
special position on an inversion centre. The Bi–Cl bond lengths vary from 2.6817 (8) to 2.7209 (8) Å with an average bond lengths of 2.7014 (8) Å. These values are much shorter than the sum of the van der Waal radii of Bi and Cl (4.7 Å) according to Pauling (Pauling, 1960). In addition to the bond length differences, the Cl—Bi—Cl angles for the Cl atoms in cis position with respect to each other fall in the range of 85.80 (3)-94.20 (3)°. It should be mentioned that the Cl—Bi —Cl bond angles deviate substantially from 90° by 4.2° for Bi(1) and 3.1° for Bi(2). By taking into account the sixth-fold coordination of bismuth atoms, we have proceeded to calculate the bond-valence sum (BVS) of this metal using the parameters given by Brown (Brown et al., 1985). The BVS calculation of the Bi1 and Bi2 ions gave respectively values of 3.23 and 3.38 valence units. These results confirm the presumed oxidation state of Bi(III). The distortion of the [BiCl 6 ] 3- octahedral are correlated primary to the deformations resulting from the stereochemical activity of the Bi lone
ion of the complex anion (point group symmetry 2) is coordinated by six O atoms from three chelating oxalate(2) ligands in a slightly distorted octahedral coordina- tion sphere. The Cr—O bond lengths vary from 1.9577 (11) to 1.9804 (11) A ˚ , while the chelate O—Cr—O angles range from 82.11 (6) to 93.41 (5) . The 4-
cell; when it is mutated (X) the transport of chromate diminishes. (B) Extracellular reduction of Cr(VI) to Cr(III) which does not cross the membrane. (C) Intracellular Cr(VI) to Cr(III) reduction may generate oxidative stress, as well as protein and DNA damage. (D) Detoxifying enzymes are involved in protection against oxidative stress, minimizing the toxic effects of chromate. (E) Plasmid-encoded transporters may efflux chromate from the cytoplasm. (F) DNA repair systems participate in the protection from the damage generated by chromium derivatives (Ramírez-Díaz et al., 2008). 3.2 Diagrammatic representation of QIAprep spin
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in aqueous solution (molar ratio 1:2:2). The cation is a protonated creatinine (creatH + ) while the anion is a bis- pydc 2 Cr III complex. The Cr III is coordinated by four oxygen and two nitrogen atoms of two (pydc) 2– groups and has a disorted octahedral coordination environment. The structure also contains a neutral molecule of pydcH 2 that is hydrogen
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The title compound, (I), was isolated as part of a wider study (Barker et al., 1996) of the potential use of amidine compounds of group 13 elements as potential precursors in synthesis. The paucity of structural data, particularly for the amidinates of the heavier group 13 elements, is illustrated by the fact that the structures of only three indium complexes have been previously reported; these are the structures of chlorobis(N,N 0 -dicyclohexylneopentamidinato)indium(III)
Extensive use of hexavalent chromium, (Cr(VI)) in various industrial applications is a threat to human health, living resources and ecological system due to its high solubility, toxicity and carcinogenic effects. Previously, one locally isolated Cr(VI) reducing-resistant bacteria, Acinetobacter haemolyticus was used in the ChromeBac™ system, to remove toxic Cr(VI) from industrial wastewater. However, this process required long retention time which was primarily due to the toxicity of Cr(VI) towards immobilized whole cells used. The use of enzymes can be a suitable option for the effective Cr(VI) reduction as compared to whole cells. In view of this, this study was conducted to assess in vitro characterization of the enzymatic chromate reductase activity in cell free-extract (CFE) for maximum activity of Cr(VI) reduction. Cr(VI) resistance and reduction of A. haemolyticus was evaluated in Luria-Bertani (LB) medium supplemented with various Cr(VI) concentrations. From the results, A. haemolyticus can resist up to 200 mg/L Cr(VI) in LB broth compared to 100 mg/L Cr(VI) in LB agar. The FTIR and FESEM-EDX analysis suggested Cr deposition onto the bacterial cells surface via complex formation between Cr species and either carboxyl, hydroxyl or amide groups. TEM analysis showed that Cr(III) is also distributed in membrane and cytosolic fractions of bacteria. ESR analysis revealed that chromium accumulated on bacterial surface and mostly as Cr(III). The enzyme activity was optimal at 30°C and pH 7 in the presence of 1 mM Co 2+ . The Michaelis-Menten constants, K m and maximum reaction
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