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Hélices dobles basadas en tiofeno: Síntesis, estructuras de rayos X y propiedades quirópticas
Sheng Zhang1, Xinming Liu2, Chunli Li1
1Engineering Research Center for Nanomaterials, Henan University , Kaifeng 475004, China.
Journal of the American Chemical Society
|July 22, 2016
Resumen
Los investigadores sintetizaron de manera eficiente los oligómeros conjugados de doble escalera helicoidal utilizando bloques de construcción de cicloctatetratiofeno. Estas nuevas estructuras exhiben una alta estabilidad y fuertes propiedades quirópticas, superando a las de compuestos similares.
Área de la Ciencia:
- Química orgánica
- Química supramolecular
- Ciencias de los materiales
Sus antecedentes:
- Las moléculas orgánicas conjugadas son cruciales para los materiales avanzados.
- El desarrollo de nuevas estructuras helicoidales con propiedades sintonizables sigue siendo un desafío.
- El ciclooctatetratiofeno (COTh) ofrece un andamio único en forma de silla de montar para el diseño molecular.
Objetivo del estudio:
- Demostrar un método fácil y eficiente para la construcción de oligómeros de doble escalera helicoidal conjugada.
- Sintetizar y caracterizar nuevos oligómeros basados en bloques de construcción de COTh.
- Investigar las propiedades quirópticas y las barreras de racimización de estas estructuras helicoidales.
Principales métodos:
- Deprotonación de tetra[3,4]tienileno (β,β-COTh) con n-BuLi para el acoplamiento selectivo.
- Acoplamiento diastereoselectivo de precursores racémicos para formar oligómeros de doble escalera helicoidal (rac-DH-1, rac-DH-2, rac-DH-3).
- Cristalografía de rayos X para elucidación estructural, cromatografía líquida de alto rendimiento quiral (HPLC) para resolución y mediciones quirópticas (CD, rotación óptica).
Principales resultados:
- Síntesis exitosa de tres oligómeros racémicos de doble escalera helicoidal con un número variable de unidades de COTh.
- La cristalografía de rayos X confirmó la estructura de andamio doble helicoidal entrelazado.
- Los enantiómeros resueltos de DH-1-D exhibieron fuertes propiedades quirópticas (g = -0.039) y una alta barrera de racemicidad (ΔG‡ > 48 kcal mol−1).
Conclusiones:
- Se establece una ruta sintética robusta para los oligómeros conjugados de doble escalera helicoidal a partir de COTh.
- Estos oligómeros poseen una rigidez estructural significativa y una alta estabilidad enantiomérica.
- Las propiedades quirópticas mejoradas sugieren aplicaciones potenciales en materiales quirales y reconocimiento molecular.
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