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Dímeres de porfirina conjugados: efectos cooperativos y comunicación electrónica en conjuntos supramoleculares con
Luis Moreira1,2, Joaquín Calbo3, Juan Aragó3
1Laboratorie de Chimie des Matériaux Moléculaires, Université de Strasbourg et CNRS (UMR 7509), ECPM , 67087 Strasbourg, Cedex 2, France.
Journal of the American Chemical Society
|September 20, 2016
Resumen
Los nuevos sistemas de éter de porfirina en la corona se unen eficientemente a los huéspedes de fullereno. Estos receptores supramoleculares muestran una fuerte unión pero una cooperatividad negativa, lo que indica interacciones moleculares complejas.
Área de la Ciencia:
- Química supramolecular
- Química orgánica
- Ciencias de los materiales
Sus antecedentes:
- Los sistemas de porfirina conjugada son andamios versátiles para el reconocimiento molecular.
- Los éteres de la corona son conocidos por su capacidad para unirse a cationes y sales de amonio.
- Los derivados del fullereno presentan propiedades electrónicas y estructurales únicas para la química huésped-invitado.
Objetivo del estudio:
- Para sintetizar nuevos receptores basados en porfirina que incorporan éteres de la corona.
- Para investigar la complejación huésped-huésped de un derivado de sal de fullereno-amonio.
- Caracterizar las afinidades de unión y los efectos de cooperación en los conjuntos supramoleculares resultantes.
Principales métodos:
- Síntesis de dimeros conjugados de éter de porfirina y corona (3 y 4).
- Experimentos de titulación con rayos UV en diclorometano a temperatura ambiente para determinar las constantes de asociación.
- Cálculo del factor cooperativo alostérico (α).
- Cálculos teóricos para sondear los cambios de estructura electrónica y los mecanismos de interacción.
Principales resultados:
- Se han sintetizado con éxito dos nuevos sistemas de éter porfirina-corona (dimeros 3 y 4).
- Se han alcanzado altas constantes de asociación (hasta ~5 × 10 M-1) para la sal de fullereno-amonio invitada (1).
- Se observó una cooperatividad alostérica negativa (α < 1) en la formación de complejos supramoleculares [3·12] y [4·12].
- Interacciones clave identificadas: éter de corona de amonio y interacciones π-π entre las porfirinas y C60.
Conclusiones:
- Los receptores de éter de la corona de porfirina diseñados se unen eficazmente a los huéspedes de fullereno-amonio.
- La cooperatividad negativa surge de los efectos electrónicos sobre la unión inicial del invitado, parcialmente compensada por las interacciones C60-C60 en conformaciones específicas.
- Estos hallazgos avanzan en la comprensión de las interacciones supramoleculares complejas en sistemas anfitrión-invitado a medida.
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