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Un pentaceno con un giro de 144 grados
Jun Lu1, Douglas M Ho, Nancy J Vogelaar
1Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
Journal of the American Chemical Society
|September 10, 2004
Resumen
Los investigadores sintetizaron un hidrocarburo aromático policíclico altamente retorcido, el 9,10,11,20,21,22-hexafeniltetrabenzo[a,c,l,n]pentaceno. Su estructura única exhibe una torsión significativa, y sus enantiómeros muestran una alta rotación óptica, pero se someten a una lenta racemización.
Área de la Ciencia:
- Química orgánica es la química orgánica.
- Ciencia de los materiales Ciencia de los materiales.
- Química supramolecular de las moléculas.
Sus antecedentes:
- Los hidrocarburos aromáticos policíclicos (HAP) son cruciales en la ciencia de los materiales.
- Comprender la torsión molecular es clave para diseñar nuevos materiales funcionales.
- Los HAP altamente retorcidos presentan propiedades estructurales y electrónicas únicas.
Objetivo del estudio:
- Para sintetizar y caracterizar un nuevo, altamente retorcido hidrocarburo aromático policíclico.
- Para investigar las propiedades estructurales y quirópticas del compuesto sintetizado.
- Para explorar la dinámica de racemización de la molécula quiral.
Principales métodos:
- Síntesis a través de la reacción de 1,3-diphenylphenanthro [9,10-c]furan con un equivalente de bisarina.
- Desoxigenación del doble adducto utilizando titanio de baja valencia.
- Cristalografía de rayos X para la determinación estructural.
- Cromatografía quiral para la separación enantiomérica.
- Polarimetría para medir las rotaciones específicas.
- Estudios de racemicidad a temperatura ambiente.
Principales resultados:
- Se ha logrado la síntesis del 9,10,11,20,21,22-hexafeniltetrabenzo[a,c,l,n]pentaceno (1).
- La estructura de rayos X revela el compuesto 1 como el hidrocarburo aromático policíclico más altamente retorcido conocido (143,6 grados de torsión de extremo a extremo).
- Los enantiómeros puros del compuesto 1 exhiben altas rotaciones específicas (>7000 grados).
- El compuesto 1 se somete a una lenta racemización a 25°C con una vida media de 9,3 horas.
Conclusiones:
- 9,10,11,20,21,22-Hexaphenyltetrabenzo[a,c,l,n]pentaceno representa un nuevo punto de referencia en la torsión molecular para los HAP.
- La quiralidad y la dinámica de racemización de la molécula ofrecen información sobre la estereocímica en sistemas tensos.
- Este estudio amplía el alcance de la síntesis y caracterización compleja de HAP.
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