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(3h) J ((((15) N- ((31) P) Las constantes de acoplamiento de espín-espín a través de los enlaces de hidrógeno

Janet E Del Bene¹, S Ajith Perera, Rodney J Bartlett

¹Department of Chemistry, Youngstown State University, Youngstown, Ohio 44555, USA. fr042008@ysub.ysu.edu

Journal of the American Chemical Society

|May 30, 2002

Resumen

Los cálculos de cúmulos acoplados a ecuaciones de movimiento revelan que las constantes de acoplamiento de tres enlaces de nitrógeno-15 a fósforo-31 a través de enlaces de hidrógeno son medibles y dependen de la distancia para arreglos lineales, lo que permite la determinación estructural.

Área de la Ciencia:

Química computacional es la química computacional.
Química cuántica es la química cuántica.
La espectroscopia es una técnica de espectroscopia.

Sus antecedentes:

La espectroscopia de resonancia magnética nuclear (RMN) proporciona información valiosa sobre la estructura molecular y el enlace.
Las constantes de acoplamiento de tres enlaces (15)N-(31)P ((3h)J(N[enlace]P)) a través de enlaces de hidrógeno son sensitivas sondas de geometría molecular.
Comprender estos acoplamientos puede ayudar a determinar las distancias en sistemas de enlaces de hidrógeno.

Objetivo del estudio:

Para investigar la magnitud y el comportamiento de las constantes de acoplamiento de tres enlaces (15)N-(31)P a través de enlaces de hidrógeno N-H...O-P.
Para explorar la influencia de la geometría molecular (lineal vs. no lineal) en estas constantes de acoplamiento.
Evaluar el potencial de utilizar (3h) J ((N[bond]P) para determinar las distancias N-P y N-O en complejos con enlaces de hidrógeno.

Principales métodos:

Se emplearon cálculos individuales y dobles de racimos acoplados a ecuaciones de movimiento (EOM-CCSD).
Los cálculos se realizaron en modelos de complejos catiónicos y aniónicos con enlaces de hidrógeno N-H...O-P.
Se estudiaron varias estructuras, incluidas las especies P(V) y P(III), y arreglos lineales y no lineales.

Principales resultados:

Las constantes de acoplamiento de tres enlaces (15) N- ((31) P son significativas para P ((V) pero insignificantes para P ((III)).
(3h) J ((N[bond]P) valores son típicamente menos de 1 Hz para las estructuras no lineales (cíclicas o abiertas).
Se observaron valores más grandes (3h) J ((N[bond]P) en arreglos lineales o casi lineales, a pesar de las distancias N-P más largas.

Conclusiones:

El término de contacto de Fermi influye significativamente (3h) J(N[bond]P) en complejos lineales y es dependiente de la distancia.
Las constantes de acoplamiento (15)N-(31)P medidas experimentalmente se pueden utilizar para determinar las distancias N-P y N-O de enlace de hidrógeno en sistemas lineales.
Este enfoque ofrece un método novedoso para la aclaración estructural en sistemas moleculares específicos enlazados por hidrógeno.

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