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Estructura del complejo Pi de los cationes gaseosos benceno-NO analizados por espectroscopia de disociación de

Barbara Chiavarino¹, Maria Elisa Crestoni, Simonetta Fornarini

¹Dipartimento di Studi di Chimica e Tecnologia delle Sostanze Biologicamente Attive, Università di Roma La Sapienza, I-00185 Roma, Italy.

Journal of the American Chemical Society

|September 21, 2006

Resumen

La espectroscopia de disociación múltiple de fotones infrarrojos en fase gaseosa (IRMPD, por sus siglas en inglés) distinguió dos isómeros del ion [C(6) H(6) NO](+). Esta técnica diferenció con éxito entre un complejo pi de benceno-NO (((+) y nitrosobenceno protonado, crucial para la comprensión de las reacciones de nitrosado aromático.

Área de la Ciencia:

Química Física es la química física.
La espectroscopia es una técnica de espectroscopia.
La ionización química es la ionización química.

Sus antecedentes:

Las reacciones de nitrozación aromática involucran intermediarios clave como los iones [C(6) H(6) NO](+).
La distinción entre las formas isoméricas de estos intermediarios es crucial para comprender los mecanismos de reacción.
Los métodos anteriores como la disociación inducida por colisión tienen limitaciones en la discriminación de isómeros.

Objetivo del estudio:

Para producir y analizar la fase gaseosa [C6H6NO]+) iones en dos formas isoméricas.
Para utilizar la espectroscopia de disociación múltiple de fotones infrarrojos (IRMPD) para el esclarecimiento estructural.
Para comparar los espectros IRMPD con los espectros de absorción IR calculados para la identificación de isómeros.

Principales métodos:

Generación de iones [C6H6NO]+ utilizando un láser de electrones libres (FEL) acoplado a trampas de iones (FT-ICR y trampa de iones Paul).
Análisis de iones a través de la espectroscopia de disociación múltiple de fotones IR (IRMPD) en el rango de 800-2200 cm.
Comparación de espectros IRMPD experimentales con espectros de absorción IR calculados por la teoría funcional de la densidad (DFT).

Principales resultados:

Se produjeron y analizaron dos formas isoméricas distintas de [C(6) H(6) NO](+).
La espectroscopia del IRMPD identificó un isómero como un complejo pi [benceno,NO]{+}, caracterizado por una banda prominente a 1963 cm{-1}.
El segundo isómero, formado por ionización por electrospray del nitrosobenzeno, fue identificado como nitrosobenzeno protonado, el isómero más estable desde el punto de vista computacional.

Conclusiones:

La espectroscopia IRMPD es una técnica poderosa para discriminar entre las especies isoméricas [C(6) H(6) NO](+).
El complejo pi [benceno,NO](+) representa un adducto iónico no covalente entre el benceno y el NO(+).
Este estudio proporciona conocimientos estructurales críticos sobre los intermediarios de las reacciones de nitrosión aromática.

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