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Los estados electrónicos de la molécula cuasilinear propargileno (HCCCH) de la espectroscopia de iones negativos

David L Osborn¹, Kristen M Vogelhuber, Scott W Wren

¹Combustion Research Facility, Sandia National Laboratories , Livermore, California 94551-0969, United States.

Journal of the American Chemical Society

|July 11, 2014

Resumen

Este estudio utiliza la espectroscopia de fotoelectrones para investigar los estados electrónicos del propargileno carbeno cuasilinear (HCCCH). Los investigadores determinaron su afinidad electrónica y la división singleta-tripleta, revelando información sobre su estructura electrónica y enlaces únicos.

Área de la Ciencia:

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

Sus antecedentes:

El propargileno (HCCCH) es un carbeno cuasilinear con una estructura electrónica única.
Comprender sus estados electrónicos es crucial para la química teórica y experimental.
Estudios anteriores han sido limitados en la caracterización completa de sus estados excitados y propiedades electrónicas.

Objetivo del estudio:

Para caracterizar los estados electrónicos del propargileno (HCCCH) y su isotopólogo (DCCCD) utilizando espectroscopia de fotoelectrones de iones negativos en fase gaseosa.
Para determinar la afinidad de los electrones y la división en singlet-triplet del propargileno.
Para dilucidar la geometría molecular y la configuración electrónica de los estados de base y excitados del propargileno.

Principales métodos:

Se empleó la espectroscopia de fotoelectrones de iones negativos en fase gaseosa.
Se realizaron experimentos de fotodistajamiento con propargileno (HCCCH) y su isotopólogo deuterado (DCCCD).
Se realizó un análisis de las progresiones vibratorias y las distribuciones angulares de los fotoelectrones.

Principales resultados:

El estudio identificó el estado fundamental X̃(3B) y varios estados excitados (ã(1A), b̃ (1B), d̃(1A2 y B̃(3A2)) del propargileno.
La afinidad de electrones de HCCCH se midió como 1.156 ± (0.095) ((0.010) eV.
Se determinó que la división singlet-tripleta era ΔEST = 0.500 ± (0.01)(0.10) eV, con energías térmicas experimentales para estados excitados también reportadas.
El análisis vibratorio reveló cambios geométricos significativos en el fotodetachamiento, particularmente para los estados X̃(3B) y b̃ (1B), e indicó un carácter π sustancial en las orbitales moleculares de frontera.

Conclusiones:

Los resultados experimentales apoyan una estructura cuasi-lineal, no plana, doblemente alílica para el estado fundamental X̃(3B) del propargileno, que exhibe un carácter tanto diradical como carbénico.
Los patrones vibratorios observados y las asignaciones de estados electrónicos proporcionan una comprensión completa del paisaje electrónico del propargylene.
Este trabajo avanza en la comprensión de pequeñas moléculas orgánicas reactivas y sus propiedades electrónicas.

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