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Cambio de fluorescencia inducido por cizallamiento y UV en cristales pi-diméricos stilbénicos impulsados por

Jong Won Chung¹, Youngmin You, Hyun Sue Huh

¹Center for Supra molecular Optoelectronics Materials and Department of Materials Science and Engineering, ENG445, Seoul National University, San 56-1, Shilim-dong, Kwanak-ku, Seoul 151-744, Korea.

Journal of the American Chemical Society

|May 26, 2009

Resumen

Los nuevos derivados de cianoestilbeno sustituidos por trifluorometil exhiben una conmutación de fluorescencia reversible. La tensión mecánica o la luz UV inducen la fluorescencia, mientras que el recocido restaura el estado no fluorescente, lo que demuestra el control de embalaje molecular en estado sólido.

Área de la Ciencia:

Ciencia de los materiales Ciencia de los materiales.
Química orgánica es la química orgánica.
Química del estado sólido.

Sus antecedentes:

Se exploran derivados asimétricos de cianoestilbeno para sistemas de pi-dimero.
Los sustituyentes de trifluorometil influyen en el empaque y las propiedades moleculares.
La conmutación de fluorescencia reversible es un objetivo clave en la ciencia de los materiales.

Objetivo del estudio:

Diseñar y sintetizar derivados asimétricos de cianoestilbeno con grupos trifluorometilo.
Para investigar su capacidad para formar sistemas de pi-dimeros densamente empacados en cristales.
Para explorar la modulación de fluorescencia reversible impulsada por estímulos externos.

Principales métodos:

Síntesis de (Z) -3- ((3',5'-Bis ((trifluoromethyl) biphenyl-4-yl) -2- ((4'- ((trifluoromethyl) biphenyl-4-yl) acrilonitrilo (CN ((L)) -TrFMBE) y sus derivados.
Análisis cristalográfico para determinar el empaque molecular y las interacciones intermoleculares (C-F...H, C-F...pi).
Estudios espectroscópicos (fluorescencia) y aplicación de estímulos externos (deformación por corte, irradiación UV, recocido térmico).

Principales resultados:

Los derivados CN(L) -TrFMBE forman pilas antiparalelas de pi-dimeros en los cristales.
Los cristales son inicialmente no fluorescentes, pero se convierten en altamente fluorescentes (hasta un 24% de rendimiento cuántico) tras la tensión de corte o la irradiación UV.
La conmutación de fluorescencia se atribuye al desplazamiento lateral inducido por cizallamiento de los pares de dímeros pi, que afecta a la cicloadición.
La conmutación reversible (restauración del estado "apagado") se logra a través del recocido térmico.

Conclusiones:

Desarrolló un raro ejemplo de conmutación de fluorescencia reversible de alto contraste en materiales en estado sólido.
Se demostró que los cambios en el modo de empaque molecular pueden controlar la fluorescencia.
El sistema exhibe respuestas piezocrómicas y fotocrómicas debido a la conmutación de fluorescencia reversible.

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