Ultraviolet Photodissociation of the N-Methylpyridinium Ion: Action Spectroscopy and Product Characterization

Hansen, C. S., Kirk, B. B., Blanksby, S. J., & Trevitt, A. J. (2013) Ultraviolet Photodissociation of the N-Methylpyridinium Ion: Action Spectroscopy and Product Characterization. Journal of Physical Chemistry A, 117(42), pp. 10839-10846.

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The ultraviolet photodissociation of gas-phase N-methylpyridinium ions is studied at room temperature using laser photodissociation mass spectrometry and structurally diagnostic ion-molecule reaction kinetics. The C5H5N-CH3+ (m/z 94), C5H5N-CD3+ (m/z 97), and C5D5N-CH3+(m/z 99) isotopologues are investigated, and it is shown that the N-methylpyridinium ion photodissociates by the loss of methane in the 36 000 - 43 000 cm(-1) (280 - 230 nm) region. The dissociation likely occurs on the ground state surface following internal conversion from the SI state. For each isotopologue, by monitoring the photofragmentation yield as a function of photon wavenumber, a broad vibronically featured band is recorded with origin (0-0) transitions assigned at 38 130, 38 140 and 38 320 cm(-1) for C5H5N-CH3+ C5H5N-CD3+ and C5D5N-CH3+, respectively. With the aid of quantum chemical calculations (CASSCF(6,6)/aug-cc-pVDZ), most of the observed vibronic detail is assigned to two in-plane ring deformation modes. Finally, using ion-molecule reactions, the methane coproduct at m/z 78 is confirmed as a 2-pyridinylium ion.

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ID Code: 68881
Item Type: Journal Article
Refereed: Yes
Keywords: sensitized solar-cells, trap mass-spectrometer, set model chemistry, gas-phase, electrochromic mechanism, electronic states, pyridinium ring, vapor-phase, dye, fluorescence
DOI: 10.1021/jp4075515
ISSN: 1089-5639
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000)
Divisions: Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: American Chemical Society
Deposited On: 20 Mar 2014 03:04
Last Modified: 09 Apr 2014 12:21

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