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Mesomorfismo, isomerización y dinámica en una nueva serie de cristales líquidos piramidal
Herbert Zimmermann1, Victoria Bader, Raphy Poupko
1Max-Planck-Institut für Medizinische Forschung, Jahnstrasse 29, 69120 Heidelberg, Germany.
Journal of the American Chemical Society
|December 19, 2002
Resumen
Los isómeros nona-alkanoyloxi tribenzociclononeno (CTV-n) existen en formas de corona rígida y silla de montar flexible, exhibiendo distintas propiedades mesomórficas. Se caracterizó su dinámica de isomerización y comportamiento de fase, revelando transformaciones dependientes de la temperatura y dinámica molecular en mesofasas columnares.
Área de la Ciencia:
- Química supramolecular de las moléculas.
- Ciencia de los materiales Ciencia de los materiales.
- Química orgánica es la química orgánica.
Sus antecedentes:
- Los compuestos de nona-alkanoyloxi tribenzociclononeno (CTV-n) exhiben un isomerismo estructural único.
- Comprender la relación entre la estructura molecular, la dinámica y las propiedades mesomórficas es crucial para el diseño de materiales.
Objetivo del estudio:
- Para investigar los equilibrios de isomerización y la dinámica de los isómeros CTV-n en solución.
- Para caracterizar las propiedades mesomórficas y el comportamiento de fase de los compuestos CTV-n en estado puro.
- Para dilucidar la dinámica molecular dentro de las mesofasas columnares tanto de isómeros de corona como de silla de montar.
Principales métodos:
- Espectroscopia de RMN 1H y 13C de alta resolución en solución para estudiar la cinética y la dinámica de la isomerización.
- Difracción de rayos X, microscopía polarizadora óptica y calorimetría de barrido diferencial (DSC) para analizar las propiedades de la mesofase.
- 13C estado sólido MAS RMN para sondear la dinámica molecular en las mesofasas.
Principales resultados:
- Los isómeros CTV-n existen como formas estables de corona y silla de montar con distintos equilibrios de isomerización y cinética.
- Ambos isómeros forman mesofasas columnares hexagonales para cadenas laterales suficientemente largas (n >= 4 o 5).
- Las mesofasas de corona exhiben saltos moleculares dinámicos de 3 veces, mientras que las mesofasas de silla de montar muestran dinámicas y libraciones restringidas.
Conclusiones:
- Los isómeros de la corona y la silla de montar de CTV-n muestran una solución compleja y comportamientos de estado sólido.
- La dinámica molecular en las mesofasas columnares es dependiente de la conformación, lo que influye en las propiedades del material.
- El estudio proporciona información sobre las relaciones estructura-propiedad en los cristales líquidos discoticos.
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