CRYSTALLOGRAPHY

Author: GONZALEZ MENDEZ LUIS MARÍA.
Year: 2002.
University: EXTREMADURA [www.unex.es].
Place of defense: CENTRO UNIVERSITARIO DE MERIDA.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: This paper emphasizes the capabilities of the difractometria of policistal for solving structures complejas.Se analyzes the scope and limitations of various methods and strategies resolution on a series of compounds simpler (YBaCuO, YAG and oxalatosídico), and finally addressing the structure of an organic compound of great interest biológico.En relation to the methodology note that direct methods commonly used cough of monocristal, remains the best option when the number of data is sufficiently sobredimanibrado. Otherwise, it becomes the apparent rise of the so-called "method of real space."

Author: GONZALEZ MENDEZ LUIS MARÍA.
Year: 2002.
University: EXTREMADURA [www.unex.es].
Place of defense: CENTRO UNIVERSITARIO DE MERIDA.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: This paper emphasizes the capabilities of the difractometria of policistal for solving structures complejas.Se analyzes the scope and limitations of various methods and strategies resolution on a series of compounds simpler (YBaCuO, YAG and oxalatosídico), and finally addressing the structure of an organic compound of great interest biológico.En relation to the methodology note that direct methods commonly used cough of monocristal, remains the best option when the number of data is sufficiently sobredimanibrado. Otherwise, it becomes the apparent rise of the so-called "method of real space."

Author: CAPILLAS LÓPEZ CÉSAR.
Year: 2005.
University: PAÍS VASCO [www.ehu.es].
Place of defense: FACULTAD DE CIENCIA Y TECNOLOGÍA.
Place of preparation: FACULTAD DE CIENCIA Y TECNOLOGÍA.

Summary: The main objective of the work presented in the report is the development of a tool kit cristalográficas to carry out various studies related cristalográfia, química-física solid state and phase transitions. The set of applications implemented part of Bilbao Crystallographic Server (http://www.cryst.ehu.es), a web server with databases and software cristalográficos that provides a working environment for the analysis of problems related to the symmetry the structures. The necessary first step to the widespread program procedures server has been the construction of databases with information from the Vols. A and E of the International Tables crystallography (ITA). Under this theory, have been added databases of groups and subgroups maximal subperiódicos (layer and rod), the series of subgroups maximal isomorfos of space groups and unconventional settings of the groups triclínicos, and ortorrómbicos of monoclinical groups space in ITA. Among the tools cristalográficas include HERMANN, which calculates the different subgroups and distributes classes subgroups combined for a couple grupo-subgrupo and given index, EQUIVSTRU which derives all structures cristalográficamente equivalent of a structure described in the standard setting and Sam, which calculates modes suited to the center of symmetry in the area and classified through their properties and processing activity IR and Raman. Programs devoted to the study of phase transitions in dealing structural problems like the search for pseudosimetría, DOPE and BLOT, the calculation of the modes of primary and secondary symmetry in a transition phase, SYMMODES, and the identification of possible avenues of transition in transitions Phase unrelated grupo-subgrupo, TRANPATH. Once developed programs, the last part has been to their application in specific studies of structural phase transitions. On the one hand, have carried out a systematic study of search pseudosimetría not in polar compounds with symmetry Pna2 1, the Inorganic Crystal Structure Database. The study used two methods for the quantitative estimate of pseudosimetría. Apart from a comparison of the characteristics of the methods, it has obtained a list of candidates for ferroeléctricos with symmetry Pna2 1. It has demonstrated the efficiency of the programs developed in the study of concrete examples: the calculation of IR and Raman active modes for compounds Aurivillius family, and primary and secondary modes in the transition ferro-paraeléctrica a compound family, SrBi2Ta2O9. Lastly, the study of transitions reconstructive, has identified a series of roads transition for three transformations very discussed in the literature: the transformation between the types wurzita and NaCl, zincblenda and NaCl and CsCl and NaCl. The mechanisms include the paths obtained transitional known in the literature. It also suggests new avenues of potential transition on the basis of a set of structural conditions.

Author: CHUNG SEU U-CHAN.
Year: 2005.
University: PAÍS VASCO [www.ehu.es].
Place of defense: FACULTAD DE CIENCIA Y TECNOLOGÍA.
Place of preparation: FACULTAD DE CIENCIA Y TECNOLOGÍA.

Summary: The work has been to carry out a multidisciplinary task of gathering and study and structural properties of new phosphites, trying to establish a relationship propiedad-estructural and glimpse a possible technological application. The system has been explored group anionic fosfito (HPO3), "organic cations or alkali metals and transition FeII, FeIII and MnII. Choosing this anionic group has been based on his versatility in the form of new phases both structures open as condensed, due to its pyramidal topology. Phases were obtained by hydrothermal synthesis in soft conditions, and have been previously characterized by X-ray diffraction on shows policristalina, infrared spectroscopy, chemical analysis (ICP-AES, ASA, ICP-MS, elemental analysis) and density measurement using the method of flotation. Subsequently, all of them have studied s structural, thermal, espectroscópica and magnetically. were studied a fosfito manganese, Mn (HPO3), a fosfito of FeII and ethylene diamine, C2H10N2) [Fe3 (HPO3) 4], a fosfitotrihidratado of FeIII and N - (2-Aminoetil) 1, 3-propanodiamina (C5H18N3) [Fe3 (HPO3) 6] .3 H2O and a family of phosphites Fe / Mn in which it has changed its cationic (R) No [M5-x IIFex III (HPO3) 6] (M = Fe, Mn, R = organic cations or alkaline). study by X-ray diffraction on monocrital , revealed the structural characteristics of different phosphites, some of whom presented for certain positions atomic disorder. study its thermal behavior by thermogravimetry termodifractometría, helped establish the limits of thermal stability, as well as the processes which take place between 30 and 810Â ° C. The phases that contain iron cations have been studied by spectroscopy MÃ ¶ ssbauer obtaining information from the states of oxidation environments coordination and relative amounts of the same through and diffuse reflectance, we checked the electronic configuration of metallic cations and convalecía their links. for Luminiscencia showed that the phase Mn (HPO3) presents potential application as a component in the production of red diodes whites. magnetic behavior studied by SPR, susceptibility mangética and, in some cases, specific heat shows the dominance of magnetic interactions in all phases. In all cases, except the (C2H10N2) [Fe3 (HPO3) 4] FM components are observed at low temperatures due to canting of spins and phenomena ferrigmanetismo. phase ( C5H18N3) [Fe3 (HPO3) 6] .3 H2O presents a unique magnetic behavior with a three-dimensional FM order to 30K and a reordering of spins at 16 K. The phases (R) No [M5-x II FexIII (HPO) 3) 6 ] (M = Fe, Mn, R = organic cations or alkaline), given its characteristics químico-estructurales, have interesting properties of ionic conduction, studied by impedance spectroscopy. phenomenon responsible is the ferroelectricidad and is a trend according to what , to sizes smaller species loaded, activation energies greater.

Author: RODRIGUEZ BLANCO JUAN DIEGO.
Year: 2005.
University: OVIEDO [www.uniovi.es].
Place of defense: FACULTAD DE GOEOLOGÍA.
Place of preparation: FACULTAD DE GEOLOGIA.

Summary: This thesis explores the mechanisms of interacciónd the As (V) in aqueous solution with plaster different pH ranges. The study concluded that such interaction leads to a decrease in the initial concentration of arsenic and a number of sorption phenomena. This is the sorption precipitation surface arsenaitos calcic with varying degrees of protonación, depending on the pH of the solution during the experiment. In all cases, the efficiency of these mechanisms is very limited, as the sorption occurs only at concentrations of As (V) very high) 20-100 mM), thereby eliminating less than 50% of the initial concentration of contaminant. During the investigation had preceded the resolution of a new structural composites, Ca2Na (HAsO4) (AsO4) .6 H2O and the study of the relationship epitaxial between plaster and farmacolita (CaHAsO4.2H2O).

Author: Pasán García Jorge.
Year: 2006.
University: LA LAGUNA [www.ull.es].
Place of defense: D.de Física.
Place of preparation: Facultad de Física.

Summary: This thesis has as a key objective the preparation and characterization of structural and magnetic new molecular magnetic materials and is based on the previous work of our investigative team composed of acid malónico with transition metals. The investigation is based on changes in the ligand malonate in order to get a grip on the crystal packing. To that end, one of the hydrogen atoms of methylene group acid malónico has been replaced by different functional groups: a methyl group (acid metilmalónico), a group ethyl acid (etilmalónico) and a phenyl group (acid fenilmalónico). These groups are able to establish interactions weak type pi, hidrófobicas repulsiones estéricas that can change the behavior of structural acid malónico. The influence can exert on the synthesis process will allow us some control over packaging crystalline compound, and thus on their magnetic properties. The preparation of compounds of copper (II) with different coligandos, their characterization by X-ray diffraction magnetic measures is the main objective of this thesis. It produced a total of thirty-nine compounds that exhibit a wide variety of both structural and magnetic behavior. Destacable is the synthesis of compounds with up to three dimensional magnetic order and the observation of other phenomena as metamagnetismo, rail or antiferromagnetismo.

Author: TODOROVA DOBRINOVITCH ISABEL.
Year: 2006.
University: ZARAGOZA [www.unizar.es].
Place of defense: FACULTAD DE CIENCIAS.
Place of preparation: FACULTAD DE CIENCIAS.

Summary: It has been determined the molecular structure of metal complexes of chiral type half-sanwich [(areno) ML (N, N'-pyam)] [SbF6] n (areno) = M (p-cimeno) Ru (p-cimeno) Os (Cp *) Rh, Ir (Cp *), N, N'-pyam = N-2- (piridilmetileno) - (1R, 2S, 4R) -1-bornilamina, N-2-piridilmetileno- (R) -1 - feniletilamina, N-2-piridilmetileno- (R) -1-naftilrtilamina; L = Cl or H2O. In all the complex molecular level presents coordination pseudo-octaédrica, with the group areno occupy three positions in the field of coordination of the metal and ligand bidentado N N'-pyam linked so the cento metal chelate. The structural analysis has identified the absolute configuration of the metal and nitrógéno amínico. The results of the analysis at the molecular level have highlighted the lack of substantial variations in the distances and angles liaison. The analysis conformacional conducted on metalaciclo MN (py) -CCN (am) has allowed the influence of the ligand areno on the molecular structure of the species studied. Although inert from a reactive this ligand are always located in equatorial position in the metalaciclo and seems condition relative stability of different diastereomeros possible. The statistical study of the interactions C / F NH produced from the information contained in the Cambridge Structural Database has highlighted the need for strict two types of corrections normalization prior to the observation of the frequency distributions Ay H distances angles DH A. These corrections, called 'cone' and 'spherical', have been reflected in the method of correction of population density isotropic. The application of this method has enabled display geometrical parameters associated with this type of interactions and characterize the interactions CH F PF6-, SbF6- and NH F PF6-como hydrogen bond Nature weak. There have been distributions of distances and angles for CH F interactions with PF6-, Cl CH and CH Cl-M when groups giving presents carbons with hibridizaciones sp2 and sp3. In all three cases it has been estimated strength of the interaction when the carbon atom presents hybridization type sp2. The elimination of the angular dependence has enabled obtaining diagrams showing the relationship between population and the distance of interaction H F. The least squares adjustment of the experimental data to a function gausiana amended estimating distances has enabled optimum interaction, as well as more likely ranks along with other values that characterize the tight curve and allowing the comparison of numeric distributions. Among the contacts intramoleculares highlights contacts sustituyente bornilo with the rest of the molecule which have slight variations between the complexes studied by highlighting the high structural similarity of the area near this replacement. In the complex containing the replacement fenil- or naftiletilo contacts of this replacement with the rest of the molecule depends on the configuration of nitrogen amínico. The structural analysis has characterized made possible interactions CH / pi intramoleculares confirming the presence of such interactions between the ligand p-cimeno and ring piridínico in derivatives containing sustituyente bornilo. In derivatives containing substituents fenil- or naftiletilo interaction was observed CH / pi between the ligand p-cimeno and the aromatic rings of phenyl groups or naftilo. Interactions intermoleculares dominated in these complexes are mostly links hidógeno weak type F CH, NH Buddha CH Cl. The atoms involved in these interactions show areas of accessibility of these molecules to the formation of inter - interactions.