Ultraviolet Photodissociation Action Spectroscopy Of Protonated Azabenzenes

Hansen, Christopher S.

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https://hdl.handle.net/2142/50954 Copy

Description

Title

Ultraviolet Photodissociation Action Spectroscopy Of Protonated Azabenzenes

Author(s)

Hansen, Christopher S.

Contributor(s)

• Trevitt, Adam J.
• Reimers, Jeffrey R.
• Bieske, Evan
• Blanksby, Stephen J.

Issue Date

2014-06-18

Keyword(s)

Mini-symposium: Beyond the Mass-to-Charge Ratio: Spectroscopic Probes of the Structures of Ions

Abstract

\begin{wrapfigure}{r}{0pt} \includegraphics[scale=0.3]{isms69absfig.eps} \end{wrapfigure} Azabenzenes are derivatives of benzene containing between one and six nitrogen atoms. Protonated azabenzenes are the fundamental building blocks of many biomolecules, charge-transfer dyes, ionic liquids and fluorescent tags. However, despite their ubiquity, there exists limited spectroscopic data that reveals the structure, behaviour and stability of these systems in their excited states. For the case of pyridinium (C$_5$H$_5$N-H$^+$), the simplest azabenzene, the electronic spectroscopy is complicated by short excited state lifetimes, efficient non-radiative deactivation methods and limited fluorescence. Ultraviolet (UV) photodissociation (PD) action spectroscopy\footnote{Hansen, C.S. \emph{et al.}; J. Am. Soc. Mass Spectrom. 24:932-940 (2013) $^b$Hansen, C.S. \emph{et al.}; J. Phys. Chem. A 117:10839-10846 (2013)} provides new insight into the spectroscopic details, excited state behaviour and photodissociation processes of a series of protonated azabenzenes including pyridinium, diazeniums and their substituted derivatives. The room-temperature UV PD action spectra, often exhibiting vibronic detail,$^b$ will be presented alongside PD mass spectra and the kinetic data from structurally-diagnostic ion-molecule reaction kinetics. Analysis of the spectra, with the aid of quantum chemical calculations, reveal that many azabenzenes prefer a non-planar excited state geometry reminiscent of the structures encountered in 'channel 3'-like deactivation of aromatics. The normal modes active in this isomerization contribute largely to the spectroscopy of the \emph{N}-pyridinium ion as they build upon totally-symmetric vibronic transitions leading to repeating sets of closely-spaced spectral features.

Publisher

International Symposium on Molecular Spectroscopy

Type of Resource

text

Language

English

Permalink

http://hdl.handle.net/2142/50954

DOI

https://doi.org/10.15278/isms.2014.WG05

Copyright and License Information

Copyright 2014 by the authors. Licensed under a Creative Commons Attribution 4.0 International License. http://creativecommons.org/licenses/by/4.0/

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