José Luis Alcántara-Flores

The triclinic polymorph of di­bromo[(–)-sparteine-κ2N,N′]­zinc(II)

The title compound, [ZnBr 2 (C 15 H 26 N 2 )], when synthesized starting from Zn 0 , is obtained in two polymorphic forms, one belonging to space group P2 1 2 1 2 1 and one to P1. The present contribution deals with the triclinic phase, which is isostructural with the orthorhombic form but presents a larger metal-metal intermolecular separation; the Zn...Zn distance is 7.4715 (6) A for the triclinic polymorph as opposed to 6.534 A for the orthorhombic polymorph.

Determinación del potencial bioquímico de metano (PBM) de residuos de frutas y verduras en hogares

In this work we studied the decomposition of organic matter of food kitchen wastes (substrate) by sewage sludge (inoculum) from a wastewater treatment plant, through theprocess of anaerobic digestion (AD) in order to obtain biogas and to determinethe biochemical methane potential (BMP) at the end of this process. The tests were performed with substrate:inoculum ratios 1:2 and 1:3, in terms of volatile solids (VS). The most important parameters that influence AD were VS, total solids (TS), chemical oxigen demand (COD) and pH. They were measured in the course of the process in mesophilic conditions (35 °C) and retention times of 15 days. The biogas obtained was purified by removing H 2 S and NH 3 with NaOH and H 2 SO 4 traps. For experiments with inoculum and substrate, 1.235 L of biogas with 80.15 % CH 4 were recovered and for tests without substrate, 0.720 L of biogas with 90.47 % of CH 4 were gathered. The quantification of this gas was performed by gas chromatography. The results agree with biogas production and organic load decrease, expressed as COD. For experiments S:I, the BMP values obtained were 124.82 and 127.89 mL CH 4 /g VS, for 1:3 and 103.39 and 116.27 mL CH 4 /g VS for 1:2.

(Benzoato-κO)chlorido[(–)-sparteine-κ2N,N′]zinc(II)

The title complex, [Zn(C7H5O2)Cl(C15H26N2)], used for the magnetic dilution of the analogous CuII complex, was synthesized through a direct synthesis route. The coordination geometry around ZnII is best described as distorted tetrahedral, the largest deviation arising from the (–)-sparteine ligand, as is invariably found in complexes containing this rather rigid molecule. The benzoate anion behaves as a monodentate ligand, with a non-coordinating Zn⋯O separation of 2.969 (5) Å. Molecules are packed in the crystal without significant intermolecular interactions. The shortest Zn⋯Zn separation [6.8186 (7) Å] is observed between molecules related through the 21 screw axis. This is an important feature for the magnetic behaviour of the CuII analogue, which is intended for modeling isolated metal centers in the active site of type 1 blue copper proteins.

Bis{μ-2,2′-[(3-aza­pentane-1,5-di­yl)bis­(nitrilo­methyl­idyne)]diphenolato}dicopper(II) dimethyl sulfoxide disolvate

The title compound, [Cu2(C18H19N3O2)2]·2C2H6OS or [Cu2(SalenN3H)2]·2DMSO, where SalenN3H is the multidentate Schiff base 2,2′-[(3-azapentane-1,5-diyl)bis(nitrilomethylidyne)]diphenolate dianion and DMSO is dimethyl sulfoxide, is a solvated dinuclear CuII complex. The neutral complex is built from two Cu(SalenN3H) units related by an inversion center. All heteroatoms in the Schiff bases coordinate the CuII ions, which display highly distorted trigonal bipyramidal geometries. The solvent molecules are located in the structural voids of the complex and are disordered over two positions with occupancies of 0.642 (15) and 0.358 (15). The previously characterized acetone disolvate of the same complex presents identical molecular and crystal structures, and crystallizes with cell parameters very close to those of the DMSO disolvate reported here.

Crystal structure, spectroscopy and ferromagnetostructural behavior of the complex [CuII(L)(Cl)(L´)]•H2O (L = 2-aminomethylbenzimidazole, L´= L-isoleucinate)

Cu(L)(Cl)(L ́)]·H2O 1 (L = 2-aminomethylbenzimidazole, L ́ = L-isoleucinate) compound crystallizes in the orthorhombic space group P212121. A short Cu—O...Cu contact is observed between neighboring molecules in the crystal structure, with a O...Cu separation of 4.214(3) Ǻ. Molecular structure of 1 shows that L and L ́ act as bidentate ligands, forming the base of the square pyramidal geometry environment of the Cu ion, while the chloro is the fifth apical ligand. UV/VIS spectrum of 1 shows d-d transitions with λmax = 603 nm, characteristic of a low symmetry. Far IR spectrum shows νCu-N at 493, 404 cm, νCu-O at 446 cm, and at 302 cm νCuCl. ESR X-band of polycrystalline 1 at 77, 300 K show axial spectra with the ratio A77/A300 = 4.51, and a linewidth increase by 14.5 % on going from 300 K to 77 K, suggesting a incipient ferromagnetic exchange interaction. ESR axial spectrum of 1 in solution shows abundant hfs and shfc interactions. Susceptibility vs Temperature data measured from 2-300 K range, show that the magnetic ordering may be due to Cu ions linking by oxygen bridges given place to a weak ferromagnetic interaction. The very weak exchange interaction, J = 0.103 cm, is in agreement with the ESR spectra results and with a Cu—O...Cu direct interaction. Issue in Honor of Prof Rosalinda Contreras Theurel ARKIVOC 2008 (v) 31-42 ISSN 1424-6376 Page 32 ARKAT USA, Inc.