Oligo and polyuronic acids interactions with hypervalent chromium

Selective oxidation of galacturonic residues of oligo and polyuronic acids by CrVI affords CO2/HCO2H, oxidized uronic acid, and CrIII as final redox products. Kinetic studies show that the redox reaction proceeds through a mechanism combining CrVI → CrIV → CrII and CrVI → CrIV → CrIII pathways. The mechanism is supported by the observation of free radicals, CrO22+ and CrV as reaction intermediates. The EPR spectra show that five- and six coordinated oxo-CrV intermediates are formed. Penta-coordinated oxo-CrV species are present at any [H+], whereas hexa-coordinated ones are only observed at pH <1. At low pH CrV predominating species are coordinated by carboxylate groups and Oring (giso = 1.9783/5). At pH 7.5, the predominating ones are those coordinated by alcoholate groups of the ligand (giso = 1.9800). Polygal can reduce CrVI and efficiently trap CrIII. This behaviour represents an interesting model for the study of biomaterials, which possess a high proportion of polygal, in order to remove chromium from polluted waters.Fil: González, Juan Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: García, Silvia Isabel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Bellú, Sebastián Eduardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Atria, Ana María. Universidad de Chile; ChileFil: Salas Pelegrín, Juan Manuel. Universidad de Granada. Facultad de Ciencias; EspañaFil: Rockenbauer, Antal. Hungary Academy of Sciences. Chemical Research Center; HungríaFil: Korecz, Lazlo. Hungary Academy of Sciences. Chemical Research Center; HungríaFil: Signorella, Sandra Rosanna. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; ArgentinaFil: Sala, Luis Federico. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Rosario. Instituto de Química Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquímicas y Farmacéuticas. Instituto de Química Rosario; Argentin

Three isotypic polymeric complexes with rare earth cations, but-2-enoate anions and 4,4'-(ethane-1,2-diyl)dipyridine and 4,4'-(ethene-1,2-diyl)dipyridine bridging ligands

© 2015 International Union of Crystallography.Three isotypic rare earth complexes, catena-poly[[aquabis(but-2-enoato-κ2 O,O')yttrium(III)]-bis(μ-but-2-enoato)-κ3 O,O':O;κ3 O:O,O'-[aquabis(but-2-enoato-κ2 O,O')yttrium(III)]-μ-4,4'-(ethane-1,2-diyl)dipyridine-κ2 N:N'], [Y2(C4H5O2)6(C12H12N2)(H2O)2], the gadolinium(III) analogue, [Gd2(C4H5O2)6(C12H12N2)(H2O)2], and the gadolinium(III) analogue with a 4,4'-(ethene-1,2-diyl)dipyridine bridging ligand, [Gd2(C4H5O2)6(C12H10N2)(H2O)2], are one-dimensional coordination polymers made up of centrosymmetric dinuclear [M(but-2-enoato)3(H2O)]2 units (M = rare earth), further bridged by centrosymmetric 4,4'-(ethane-1,2-diyl)dipyridine or 4,4'-(ethene-1,2-diyl)dipyridine spacers into sets of chains parallel to the [20 ] direction. There are intra-chain and inter-chain hydrogen bonds in the structures, the former providing cohesion of the linear arrays and the latter promoting the formation of broad planes parallel to (010)

Catena(hexa-aqua-cobalt(II) tetra-aqua-(μ2-1,2,4,5-benzenecarboxylato-o, o') -cobalt(II) hydrate): A new symmetry for an old polymorphic phase

The title cobalt complex (C10H38Co2O26) consists of [Co(H2O)4(C10H2O8)]2-n anionic chains, balanced by [(Co(H2O)6]2+ cations and eight solvato water molecules, some of which are disordered. The chains are formed by Co(H2O)4 "beads" threaded by fully deprotonated benzenecarboxylato anions binding in a stretched, trans fashion, and they are linked by H-bonds into a 2D structure. The cationic groups and solvato water molecules form a second kind of 2D arrays, "sanwiched" by the latter ones and linking the lot into a 3D structure through a very complex H-bonding interaction scheme. The structure presents a very conspicuous pseudo symmetry, and it appears to be a slight polymorphic modification of an already published isologue of identical formulation but with the higher symmetry properly attained, in a volume half as large. The slight differences between both structures seems to reside mainly in the (disordered) solvates, as suggested by the overlap of both models

Crystal structure of zwitterionic 4-(ammoniomethyl)benzoate: a simple molecule giving rise to a complex supramolecular structure

The asymmetric unit of the title compound, C8H9NO2·H2O consists of an isolated 4-(ammoniomethyl)benzoate zwitterion derived from 4-aminomethylbenzoic acid through the migration of the acidic proton, together with a water molecule of crystallization that is disordered over three sites with occupancy ratios (0.50:0.35:0.15). In the crystal structure, N—H...O hydrogen bonds together with π–π stacking of the benzene rings [centroid–centroid distance = 3.8602 (18) Å] result in a strongly linked, compact three-dimensional structure

Three isomorphous Ln complexes: {[Ln2(bt)6(bno) (H2O)4]·bno} n (bt is but-2-enoate and bno is 4,4′-bipyridyl N,N′-dioxide), with Ln = Nd, Er and y

The polymeric title compounds, namely catena-poly[[[di - but-2-enoato- 3 O:O,O′;3 O,O′:O′-bis-[diaqua-dibut-2- enoato-O;2 O,O′-neodymium(III)]] - 4,4′-bipyridyl N,N′-dioxide-2 O:O′] 4,4′-bipyridyl N,N′-dioxide solvate] and the erbium(III) and yttrium(III) analogues, {[Ln2(C4H5O2)6(C10H8N2O2)(H2O)4]·C10H8N2O2} n (Ln = Nd, Er and Y), form from [Ln2(bt)6(H2O)4] dimers (bt is but-2-enoate) bridged by 4,4′-bipyridyl dioxide (bno) spacers into sets of parallel chains; these linear arrays are inter-connected by aqua-mediated hydrogen bonds into broad two-dimensional structures, which in turn inter-act with each other though the hydrogen-bonded bridged bno solvent units. Both independent bno units in the structures are bisected by symmetry centres. © International Union of Crystallography 2007

[Cu(2-Me-imidH)(4)Cl]Cl: a conflict between high symmetry and packing efficiency

The crystal and molecular structure of the monomeric title compound, chlorotetrakis(2-methylimidazole)copper(II) chloride, [CuCl(C4H6N2)(4)]Cl, is presented, and compared with those of two other closely related monomeric structures. The monomers are similar, but the supramolecular structures are very different. The influence that steric effects might have in determining crystal properties, such as space group symmetry or packing efficiency, is analysed