Publication: Compuestos de coordinación de níquel con diferente dimensionalidad como materiales híbridos multifuncionales
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2014-12-15
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Universidad Complutense de Madrid
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Abstract
En esta tesis doctoral se describe la síntesis y caracterización de compuestos de coordinación de níquel moleculares, monodimensionales, bidimensionales y tridimensionales. Además, se ha estudiado el comportamiento magnético de todos los compuestos, así como la adsorción de nitrógeno de los materiales porosos.
Se ha utilizado níquel como metal porque según su estado de oxidación y su geometría puede generar especies paramagnéticas. Además, su precio es asequible y su gran versatilidad permite obtener muy diversas estructuras y propiedades. Se han elegido como ligandos aniones carboxilato y aminas aromáticas porque son adecuados para obtener complejos octaédricos de níquel(II) paramagnéticos. Los ligandos carboxilato pueden presentar una gran variedad de modos de coordinación, que hace que se puedan obtener estructuras y propiedades muy variadas. La síntesis ha sido llevada a cabo utilizando métodos convencionales y métodos solvotermales en presencia y en ausencia de radiación microondas. El empleo de diferentes rutas sintéticas ha estado dirigido por los preceptos de la química sostenible. Para la caracterización se han empleado numerosas técnicas entre las que cabe destacar la resolución estructural mediante difracción de rayos X en monocristal y a partir de difractogramas de polvo. También se han utilizado otras técnicas, como la espectroscopia UV-vis e IR, análisis termogravimétrico o incluso se ha empleado la microscopía electrónica de barrido y de transmisión. Algunos de los resultados más destacables son la formación de estructuras monodimensionales con fuertes acoplamientos antiferromagnéticos que se han estudiado por DFT y el método de simetría rota, o la presencia de interacciones ferromagnéticas a través de enlaces de hidrógeno; materiales bidimensionales donde las interacciones antiferromagnéticas y ferromagnéticas pueden ser moduladas por el tamaño de los ligandos, originando compuestos metamagnéticos con dos campos críticos; o la caracterización de vidrios de espín porosos que despejan el camino hacia la preparación de imanes porosos
In this thesis, the synthesis, structural characterization and properties of molecular and polymeric (one-, two-, and three-dimensional) nickel(II) coordination compounds is described. The magnetic behavior of all the complexes is analyzed together with nitrogen sorption properties of the porous materials. Nickel was selected as the metallic centre because its magnetism depends on its geometry and oxidation state. The square planar complexes of Ni(II) are diamagnetic, however, the octahedral and tetrahedral Ni(II) ones are paramagnetic. Furthermore, nickel has an affordable price and, since nickel(II) is a very versatile ion, it is an appropriate centre to obtain very different structures and properties. Aromatic carboxylates and amines were chosen because they are suitable ligands to obtain octahedral Ni(II) paramagnetic complexes. Moreover, the carboxylate ligands were selected owing to their versatility in binding transition metals with different coordination modes: monodentate, chelate, or bridging. The synthetic procedures were designed, whenever possible, following the Green Chemistry principles, minimizing the hazard and waste and maximizing the efficiency of the chemical procedures. Thus, conventional and microwave-assisted solvothermal one-pot syntheses were carried out. The obtained materials were characterized using several techniques: infrared and electronic spectroscopy, mass spectrometry, thermogravimetric analysis, and single crystal and powder X-ray diffraction. Some of the most relevant results are the formation of one-dimensional structures with strong antiferromagnetic behavior, studied by DFT and broken symmetry approximation; the existence of ferromagnetic interactions through hydrogen bonds; the preparation of two-dimensional materials where the anti- and ferromagnetic interactions can be modulated by the size of the ligands; and the characterization of porous materials with spin glass behavior
In this thesis, the synthesis, structural characterization and properties of molecular and polymeric (one-, two-, and three-dimensional) nickel(II) coordination compounds is described. The magnetic behavior of all the complexes is analyzed together with nitrogen sorption properties of the porous materials. Nickel was selected as the metallic centre because its magnetism depends on its geometry and oxidation state. The square planar complexes of Ni(II) are diamagnetic, however, the octahedral and tetrahedral Ni(II) ones are paramagnetic. Furthermore, nickel has an affordable price and, since nickel(II) is a very versatile ion, it is an appropriate centre to obtain very different structures and properties. Aromatic carboxylates and amines were chosen because they are suitable ligands to obtain octahedral Ni(II) paramagnetic complexes. Moreover, the carboxylate ligands were selected owing to their versatility in binding transition metals with different coordination modes: monodentate, chelate, or bridging. The synthetic procedures were designed, whenever possible, following the Green Chemistry principles, minimizing the hazard and waste and maximizing the efficiency of the chemical procedures. Thus, conventional and microwave-assisted solvothermal one-pot syntheses were carried out. The obtained materials were characterized using several techniques: infrared and electronic spectroscopy, mass spectrometry, thermogravimetric analysis, and single crystal and powder X-ray diffraction. Some of the most relevant results are the formation of one-dimensional structures with strong antiferromagnetic behavior, studied by DFT and broken symmetry approximation; the existence of ferromagnetic interactions through hydrogen bonds; the preparation of two-dimensional materials where the anti- and ferromagnetic interactions can be modulated by the size of the ligands; and the characterization of porous materials with spin glass behavior
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Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Químicas, Departamento de Química Inorgánica, leída el 04-04-2014