Estudio de polímeros de coordinación porosos que presenten transición de espín
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2020
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Idioma
es
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Universidad Andrés Bello
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Licencia CC
Licencia CC
Resumen
En el presente trabajo se realizó una investigación exhaustiva en polímeros de coordinación
porosos (PCPs) capaces de expresar un comportamiento multifuncional gracias a las interacciones
anfitrión-huésped, produciendo cambios en las propiedades físicas tales como color,
conductividad, fluorescencia, magnetismo, entre otras. De esta manera, se estudió la posibilidad de
modular propiedades físicas como la transición de espín o SCO (spin crossover) en PCPs frente a
la adsorción/desorción dinámica de analitos.
Los polímeros con transición de espín presentan dos estados de espín intercambiables de
forma reversible, controlable y detectable como respuesta a estímulos externos como temperatura,
irradiación de luz, presión e inclusive por la sorción de moléculas huéspedes. El fenómeno de SCO
conlleva a cambios estructurales en sus propiedades macroscópicas como el magnetismo, el color,
entre otras. Por lo tanto, el estudio y desarrollo de nuevos PCPs que exhiban el fenómeno de SCO
podría ser un método adecuado para la búsqueda de nuevos materiales multifuncionales con
posibles aplicaciones tecnológicas. La correcta elección de los componentes básicos de un PCPs, catión metálico y ligante,
serán cruciales no solo en la topología sino también en las propiedades que tendrá el sistema. Así,
el centro metálico debe ser uno que pueda presentar la transición de espín, como es el caso de los
sistemas basados en cetros de Fe(II) con geometría octaédrica. Por su parte, los ligantes que se
emplean deben generar conectividades adecuadas para otorgar un campo cristalino adecuado en
torno al catión central y así favorecer transiciones de espín. Sumado a esto, el ligante debe servir
como espaciador para generar la porosidad necesaria para albergar moléculas huésped, y así, poder
estudiar el potencial efecto que tendrá la interacción huésped-anfitrión en el fenómeno de transición
de espín En este contexto, los PCPs tipo Hofmann, {Fe(L)[M(CN)n]}⸱nG, corresponden a redes
heterometálicas formadas por Fe(II), un ligante puente L y cianometalatos de cationes de transición.
Se analizaron tres redes de Hoffman {Fe(pz)[Pt(CN)4]}⸱nG, {Fe(4,4’-bipiridina)[Au(CN)2]2}n∙nG
y {Fe(II)(pina)[M(I)(CN)2]2}⸱xMeOH, los cuales fueron obtenidos por tres ligantes diferentes:
pirazina, 4,4’-bipiridina y ligante N-(piridil-4-il)isonicotinamida. Usando estos tres sistemas se
analizará el efecto que tiene la longitud y complejidad de ligante en el fenómeno de transición de espín y como la interacción con moléculas huéspedes puede ser una potencial estrategia para
generar nuevos materiales que respondan a su entorno.
The following work presents a review of porous coordination polymers (PCPs) capable of expressing multifunctional properties due to host-host interactions, producing changes in physical properties such as color, conductivity, fluorescence, magnetism, among others. In this way, the possibility of modulating the physical property of spin crossover (SCO) in PCPs dependent the dynamic sorption of analytes was studied. PCPs with SCO present two interchangeable spin states in a reversible, controllable, and detectable way in response to external stimuli such as temperature, light irradiation, pressure and even by the sorption of host molecules. The SCO phenomenon involves changes in structural and macroscopic properties such as magnetism and color, among others. Therefore, the study and development of new PCPs that exhibit the SCO phenomenon could be a suitable method for the research in new multifunctional materials with possible technological applications. The correct choice of the basic components of a PCPs, metal cation and ligand, will be crucial not only in the topology of the structures but also in the properties that the system will present. Thus, the metallic center must present the spin transition, as is the case of systems based on Fe(II) with octahedral geometry. On the other hand, the used ligands must generate the right connectivity to provide an adequate crystalline field around the central cation and thus favor spin transitions. In addition, the ligand must serve as a spacer to generate the necessary porosity to locate host molecules, and thus produce a material to study the impact of the host-guest interaction into the spin transition phenomenon. In this context, the Hofmann PCPs, {Fe(L)[M(CN)n]}⸱nG, correspond to heterometallic networks formed by Fe(II), an L bridging ligand and cyanometalates of transition cations. Three Hoffman networks were analyzed {Fe(pz)[Pt(CN)4]}⸱nG, {Fe(4,4'-bipyridine)[Au(CN)2]2}n∙nG and {Fe(II)(pine)[M(I)(CN)2]2}⸱xMeOH, which were obtained by three different ligands: pyrazine, 4,4'-bipyridine and N-(pyridyl-4-yl)isonicotinamide. Using these three PCP, the spin transition properties was analyzed showing that host-guest chemistry can be a potential strategy to generate new materials that respond to their environment.
The following work presents a review of porous coordination polymers (PCPs) capable of expressing multifunctional properties due to host-host interactions, producing changes in physical properties such as color, conductivity, fluorescence, magnetism, among others. In this way, the possibility of modulating the physical property of spin crossover (SCO) in PCPs dependent the dynamic sorption of analytes was studied. PCPs with SCO present two interchangeable spin states in a reversible, controllable, and detectable way in response to external stimuli such as temperature, light irradiation, pressure and even by the sorption of host molecules. The SCO phenomenon involves changes in structural and macroscopic properties such as magnetism and color, among others. Therefore, the study and development of new PCPs that exhibit the SCO phenomenon could be a suitable method for the research in new multifunctional materials with possible technological applications. The correct choice of the basic components of a PCPs, metal cation and ligand, will be crucial not only in the topology of the structures but also in the properties that the system will present. Thus, the metallic center must present the spin transition, as is the case of systems based on Fe(II) with octahedral geometry. On the other hand, the used ligands must generate the right connectivity to provide an adequate crystalline field around the central cation and thus favor spin transitions. In addition, the ligand must serve as a spacer to generate the necessary porosity to locate host molecules, and thus produce a material to study the impact of the host-guest interaction into the spin transition phenomenon. In this context, the Hofmann PCPs, {Fe(L)[M(CN)n]}⸱nG, correspond to heterometallic networks formed by Fe(II), an L bridging ligand and cyanometalates of transition cations. Three Hoffman networks were analyzed {Fe(pz)[Pt(CN)4]}⸱nG, {Fe(4,4'-bipyridine)[Au(CN)2]2}n∙nG and {Fe(II)(pine)[M(I)(CN)2]2}⸱xMeOH, which were obtained by three different ligands: pyrazine, 4,4'-bipyridine and N-(pyridyl-4-yl)isonicotinamide. Using these three PCP, the spin transition properties was analyzed showing that host-guest chemistry can be a potential strategy to generate new materials that respond to their environment.
Notas
Unidad de Investigación (Licenciado en Química)
Proyecto FONDECYT 1170887.
Proyecto FONDECYT 1170887.
Palabras clave
Polímeros de Coordinación Porosos, Transición de Espín