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Control de la reactividad y la regioselectividad para la formación de enlaces arilo-arilo deshidrogenados en la

Nemanja Kocić¹, Xunshan Liu², Songjie Chen²

¹Institute of Experimental and Applied Physics, University of Regensburg , 93053 Regensburg, Germany.

Journal of the American Chemical Society

|April 10, 2016

Resumen

En las superficies metálicas, la regioselectividad en la síntesis química se demuestra mediante microscopía de fuerza atómica (AFM) y microscopía de túnel de barrido (STM). Los investigadores lograron el acoplamiento selectivo arilo-arilo de pirazino [2,3-f] [4,7] fenantrolina (pap) en el oro, revelando la activación preferencial de C-H en los anillos de pirazina.

Área de la Ciencia:

Química de las superficies
Síntesis orgánica
Nanotecnología

Sus antecedentes:

La regioselectividad es crucial en la síntesis química, pero su transferencia a las reacciones de superficie es un desafío.
Las superficies metálicas alteran los estados electrónicos reactivos, y los métodos tradicionales de caracterización química de la solución no son aplicables.
Los avances en la microscopía de sonda de barrido permiten el estudio de las reacciones en la superficie a nivel atómico.

Objetivo del estudio:

Para investigar la activación regioselectiva de C-H y las reacciones de acoplamiento en una superficie metálica.
Caracterizar la formación de arquitecturas moleculares complejas a partir de un precursor heteroaromático.
Para aclarar los sitios de activación preferenciales y el papel del sustrato metálico.

Principales métodos:

Utilizando una técnica combinada de microscopía de túnel de barrido (STM) y microscopía de fuerza atómica (AFM).
Realización de recocido térmico de las moléculas de pirazino tetraciclicas [2,3-f] [4,7]fenantrolina (pap) en una superficie Au{11} bajo vacío ultraalto (UHV).
Análisis de los productos de reacción para distinguir entre las fracciones de pirazina y piridina con detalle atomístico.

Principales resultados:

Se ha demostrado el acoplamiento selectivo intermolecular arilo-arilo a través de la activación C-H deshidrogenativa en Au.
Se identificó la activación preferente de los átomos de ortohidrógeno en los anillos de pirazina sobre los anillos de piridina.
Proporcionó información atómica sobre la formación de enlaces C-C covalentes y enlaces de coordinación metal-orgánico que involucran átomos de sustrato.

Conclusiones:

Se puede lograr la regioselectividad en la superficie, reflejando y extendiendo los principios de la fase de solución.
La técnica combinada STM/AFM es poderosa para caracterizar reacciones complejas en la superficie.
El estudio revela patrones específicos de reactividad y mecanismos de unión en la síntesis orgánica con plantilla metálica.

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