The Synthesis and Coordination Chemistry of Two Families of Polydentate Ligands - Exploring Their Potential for the Preparation of Molecule-Based Magnets

The synthesis and studies of two classes of poly dentate ligands are presented as two projects. In project 1, four new carboxamide ligands have been synthesised via the condensation of 2,2',6,6'-tetrachloroformyl-4,4'-bipyridine or 2,6-dichloroformyl pyridine together with heterocyclic amines containing pyridine or pyrazole substituents. The coordination chemistry of these ligands has been investigated and studies have shown that with a Cu(II) salt, two carboxamide ligands LJ and L2 afford large clusters with stoichiometries [Cu8(L1)4Cl16].CHCl3.5H2O.7CH3OH (I) and [Cu9(L2)6Cl6].CH3OH.5H2O.(C2H5)3N (II) respectively. [molecular diagram availabel in pdf]. X-ray diffraction studies of cluster (I) reveal that it has approximate S4 symmetry and is comprised of four ligands and eight copper (II) centers. Here, coordination takes place via amide 0 atoms, and pyrazole nitrogens. This complex is the first reported example of an octanuclear copper cluster with a saddle-shaped structure. The second cluster comprises nine copper ions that are arranged in a cyclic array. Each ligand coordinates three copper centers and each copper ion shares two ligands to connect six ligands with nine copper ions. The amide nitrogens are completely deprotonated and both amide Nand 0 atoms coordinate the metal centres. The cluster has three-fold symmetry. There are six chloride ions, three of which are bridging two neighbouring Cu(II) centres. Magnetic studies of (I) and (II) reveal that both clusters display weak antiferromagnetic interactions between neighbouring Cu(II) centers at low temperature. In the second project, three complexes with stoichiometries [Fe[N302](SCN)2]2 (III), R,R-[Fe[N3O2](SCN)2 (IV) and R,R-]Fe[N3O2](CN)2] (V) were prepared and characterized, where [N302] is a pentadentate macrocycle. Complex (III) was prepared via the metal templated Schiff-base condensation of 2,2',6,6'-tetraacetyl-4,4'-bipyridine together with 3,6-dioxaoctane-I,8-diamine and comprises of a dimeric macro cycle where the two Fe(II) centres are in a pentagonal-bipyramidal environment with the [N302] ligands occupying the equatorial plane and two axial NCS ligands. Complexes (IV) and (V) were prepared via the condensation of 2,6-diacetylpyridine together with a chiral diamine in the presence of FeCh. The synthetic strategy for the preparation of the chiral diamine (4R,5R)-4,5-diphenyl-3,6-dioxa-I,8-octane-diamine was elucidated. The chirality of both macrocycles (IV) and (V) was probed by circular dichroism spectroscopy. The crystal structure of (IV) at 200 K contains two independent molecules in the unit cell, both of which contain a hepta-coordinated Fe(II) and axial NCS ligands. Variable temperature magnetic susceptibility and structural studies are consistent with a high spin Fe(II) complex and show no evidence of any spin crossover behaviour. In contrast, the bis cyanide derivative (V) crystallizes with two independent molecules in the unit cell, both of which have different coordination geometries consistent with different spin states for the two Fe(II) centres. At 250 K, the molecular structure of (V) shows the presence of both 7- and a 6-coordinate Fe(II) complexes in the crystal lattice. As the temperature is lowered, the molecules undergo a structural change and at 100 K the structural data is consistent with a 6- and 5-coordinate Fe(II) complex in the unit cell. Magnetic studies confirm that this complex undergoes a gradual, thermal, spin crossover transition in the solid state. Photomagnetic measurements indicate this is the first chiral Fe (II) sea complex to exhibit a LIESST.

Nuevos conductores de ion litio en los sistemas Li2O-AlO3-MO2, M=Si,Ge

Tesis (Maestría en Ciencias con Especialidad en Físicoquímica) UANL

Estudio respirométrico de Lactobacillus casei ATCC 393 en presencia de iones Cu (II) y Zn (II)

Tesis (Maestría en Ciencias con Especialidad en Microbiología Industrial) UANL

Caracterización electroquímica de la inserción de litio en MnNb2O6 (M= Mn, Co, Ni, Cu, Zn, Cd) y en Li3X2NbO6 (X= Mn, Co, Ni)

Tesis (Maestría en Ciencias con Especialidad en Ingeniería Cerámica) UANL

Determinación del ion cloruro en materias relacionadas con el cemento Portland usando el electrodo de ion selectivo [por] Laura Isabel Cepeda González

Tesis (Maestría en Ciencias, con especialidad en Química Analítica) U.A.N.L.

Inserción electroquímica de litio en compuestos de fórmula general MWO4 (M= Co, Cu, Mn, Ni, Zn, y Zn) preparados por dos rutas de síntesis [por] Sagrario Martínez Montemayor

Tesis (Maestría en Ciencias con Especialidad en Ingeniería Cerámica) U.A.N.L.

Estudio de adhesibilidad entre una aleación de aluminio A319.0 y una camisa de aluminio base Al-Si-Cu-MG. para aplicaciones automotrices

Teis ( Maestro en Ciencias de Ingeniería Mecánica con Especialidad en materiales) U.A.N.L.

Películas delgadas de Cu(In,Al)Se?(CIAS) por métodos no tóxicos para aplicación en celdas solares.

Tesis (Maestría en Ciencias de la Ingeniería Mecánica con Especialidad en Materiales) UANL, 2011.

Eliminación fotocatalítica de tricloroetileno empleando como catalizador TiO? dopado con Cu (II).

Tesis (Maestría en Ciencias con Orientación en Procesos Sustentables) UANL, 2013.

Evaluación de la retención de Cu(II), Ni(II), Zn(II), Cd(II) y Pb(II) por extracción sólido-líquido y líquido-líquido del poli(ácido acrílico-co-ácido 2-acrilamidoglicólico).

Tesis (Maestría en Ciencias con Especialidad en Química Analítica Ambiental) UANL, 2011.

Implantation de Metalib : par où commencer? Les principales étapes de l’implantation à l’université de Montréal.

Présentation des étapes d'implantation de Metalib (le répertoire de ressources électroniques Maestro) à l'Université de Montréal, lors de la Journée d’information du 8 septembre 2006 intitulée "La bibliothèque de recherche virtuelle québécoise (BRVQ) : une vision commune d’une réalisation en devenir", organisée par la CREPUQ.

Des arguments en faveur de l'implantation des compteurs d'eau dans la ville de Montréal.

Rapport de recherche