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Fulvenes, fulvalenes y azuleno: ¿son camaleones aromáticos?
Helene Möllerstedt1, Mari Carmen Piqueras, Raül Crespo
1Department of Chemistry and Bioscience, Kemigården 3, Chalmers University of Technology, SE- 412 96 Göteborg, Sweden.
Journal of the American Chemical Society
|October 28, 2004
Resumen
Los fulvenes, fulvalenos y azulenos exhiben un comportamiento de "camaleón aromático", adaptando su aromaticidad y sus momentos dipolo entre los estados electrónicos. Esta adaptabilidad les permite mantener el carácter aromático tanto en los estados de tierra como en los excitados.
Área de la Ciencia:
- Química teórica es la química teórica.
- Química orgánica es la química orgánica.
- Química cuántica es la química cuántica.
Sus antecedentes:
- La regla de Hückel rige la aromaticidad en los anilenos basándose en el recuento de electrones pi.
- La teoría de Baird predice una inversión de la regla de Hückel en el estado triple más bajo (T1).
Objetivo del estudio:
- Para investigar el concepto de "camaleones aromáticos" en fulvenes, fulvalenes y azuleno.
- Para explorar cómo la aromaticidad y los momentos dipolo cambian entre la base (S0) y los estados electrónicos excitados (T1, Q1).
Principales métodos:
- Aplicación de la teoría de Baird en la inversión de la aromaticidad.
- Cálculos químicos cuánticos que incluyen los métodos OLYP, CASSCF y CASPT2.
- Análisis de los momentos dipolo, las poblaciones pi-orbitales y los niveles de energía.
Principales resultados:
- Los fulvenos, fulvalenos y azulenos demuestran un comportamiento de "camaleón aromático".
- Los momentos dipolo en T1 (para fulvenos) y Q1 (para fulvenos y azuleno) son comparables en magnitud pero opuestos en dirección a los estados S0.
- Estas moléculas pueden alcanzar la aromaticidad tanto en los estados S0 como en los excitados, adaptando las estructuras de resonancia.
Conclusiones:
- Las moléculas estudiadas exhiben una aromaticidad adaptable, comportándose como "camaleones aromáticos".
- Los cálculos químicos cuánticos apoyan la hipótesis del comportamiento del camaleón a través de diferentes estados electrónicos.
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