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Dendrímeros de espín cruzado: cooperatividad dependiente del número de generación para la transición de espín térmico
Tsuyohiko Fujigaya1, Dong-Lin Jiang, Takuzo Aida
1Department of Chemistry and Biotechnology, School of Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan.
Journal of the American Chemical Society
|April 14, 2005
Resumen
Los polímeros de coordinación dendríticos con unidades de triazol exhiben transiciones de espín térmico. El aumento del número de generación de dendronas reduce la polimerización y la temperatura de transición, pero la abruptinidad de la transición de espín varía, con G1trzFe mostrando el cambio más agudo.
Área de la Ciencia:
- Coordinación de la química de los polímeros de la coordinación.
- Ciencia de los materiales ciencia de los materiales.
- Se trata de una química supramolecular.
Sus antecedentes:
- Se sintetizaron dendrones poli (etero bencilo) con unidades focales de triazol.
- Los complejos de hierro (II) con estos dendrones forman polímeros de coordinación dendríticos.
- Estos polímeros exhiben transiciones de espín térmico.
Objetivo del estudio:
- Para investigar el efecto del número de generación de dendronas en las propiedades de transición de espín de los polímeros de coordinación dendrítica.
- Caracterizar la estructura y el comportamiento térmico de estos nuevos materiales.
Principales métodos:
- Síntesis de dendrones de poli (etero bencilo) con unidades de triazol (Gntrz, n=0-2).
- Reacción con (MeSO3) 2Fe para formar polímeros de coordinación dendríticos ([Fe(Gntrz) 3) y MeSO3) 2.2H2O).
- Análisis de la transición de espín térmico utilizando calorimetría y difracción de rayos X.
Principales resultados:
- La temperatura de cruce de espín (Tc) disminuyó con el aumento de la generación de dendros (n = 0: 335 K, n = 1: 315 K, n = 2: 300 K).
- El grado promedio de polimerización disminuyó con el aumento de la generación (n = 0: 20, n = 1: 10, n = 2: 3).
- La abruptidad de la transición de giro varió: G1trzFe mostró una anchura estrecha (10 K), mientras que G0trzFe (30 K) y G2trzFe (50 K) tuvieron transiciones más amplias.
- La difracción de rayos X y la calorimetría revelaron un ensamblaje de núcleo-concha discoteca columnar.
Conclusiones:
- El número de generación de unidades dendríticas influye en la temperatura de transición de espín y el grado de polimerización en los polímeros de coordinación.
- La brusquedad de la transición de giro no depende únicamente del número de generación.
- Los polímeros de coordinación dendrítica forman estructuras supramoleculares ordenadas con aplicaciones potenciales en la ciencia de los materiales.
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