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Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions
Published on: July 17, 2020
Múltiples vías para el paso primario de la reacción fotocrómica de espiropirano: un estudio CASPT2//CASSCF
1Fukui Institute for Fundamental Chemistry, Kyoto University, Kyoto 606-8103, Japan.
Journal of the American Chemical Society
|July 4, 2013
Resumen
Este estudio revela que el fotocromismo de espiropirano implica una escisión de enlaces C-O sin barreras y un nuevo canal de desintegración de hidrógeno fuera del plano, no un mecanismo de intersección cónico. Esto aclara la formación ultrarrápida de merocianina y guía el diseño de dispositivos fotocromáticos.
Área de la Ciencia:
- Química computacional es la química computacional.
- La fotoquímica es la fotoquímica.
- Ciencia de los materiales Ciencia de los materiales.
Sus antecedentes:
- El espiropirano (SP) y la merocianina (MC) son moléculas fotocrómicas clave.
- Comprender su mecanismo de interconversión es crucial para el desarrollo de dispositivos fotocrómicos avanzados.
- Los modelos anteriores proponían mecanismos de intersección cónicos para la apertura del anillo SP.
Objetivo del estudio:
- Para investigar el mecanismo de reacción de la apertura de anillo fotocromático de espiropirano.
- Para explorar las vías de escisión de enlaces C-O y C-N en estado excitado.
- Para identificar los canales de transición no adiabáticos S1-S0 en los espiropiranos.
Principales métodos:
- Utilizó los métodos computacionales de Campo Autoconsistente de Espacio Activo Completo (CASSCF) y CASPT2.
- Puntos de cruce optimizados y vías de reacción en superficies de estado excitado.
- Se analizaron los canales de desintegración no adiabáticos y las brechas de energía.
Principales resultados:
- La escisión del enlace C-O en el espiropirano no procede a través de un mecanismo de intersección cónico; en su lugar, implica cruces evitadas.
- La escisión del enlace C-O en el estado S1 que conduce a los intermediarios de merocianina no tiene barreras, lo que explica la formación ultrarrápida.
- Un inesperado valle de hidrógeno fuera de plano (HOOP) de baja energía actúa como un canal de desintegración no adiabático S1-S0 eficiente.
Conclusiones:
- El estudio aclara el complejo mecanismo de la interconversión espiropyran-merocianina.
- Los hallazgos destacan la importancia de los modos HOOP y los cruces evitados en la desintegración no adiabática.
- Proporciona ideas fundamentales para el diseño de materiales y dispositivos fotocrómicos mejorados basados en espiropirano.
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