Isomerisation of an intramolecular hydrogen-bonded photoswitch:Protonated azobis(2-imidazole)

Bull, James N. ORCID:, Scholz, Michael S., Coughlan, Neville J.A. and Bieske, Evan J. (2017) Isomerisation of an intramolecular hydrogen-bonded photoswitch:Protonated azobis(2-imidazole). Physical Chemistry Chemical Physics, 19 (20). pp. 12776-12783. ISSN 1463-9076

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Photoisomerisation of protonated azobis(2-imidazole), an intramolecular hydrogen-bonded azoheteroarene photoswitch molecule, is investigated in the gas phase using tandem ion mobility mass spectrometry. The E and Z isomers exhibit distinct spectral responses, with E-Z photoisomerisation occurring over the 360-520 nm range (peak at 460 nm), and Z-E photoisomerisation taking place over the 320-420 nm range (peak at 390 nm). A minor photodissociation channel involving loss of N2 is observed for the E-isomer with a maximum efficiency at 390 nm, blue-shifted by ≈70 nm relative to the wavelength for maximum photoisomerisation response. Loss of N2 is also the predominant collision-induced dissociation channel. Electronic structure calculations suggest that E-isomer photoisomerisation involves S1(ππ∗) excitation, whereas the Z-isomer photoisomerisation involves S2(ππ∗) excitation. Conversion between the E and Z isomers through collisional excitation, which is calculated to occur through both inversion and torsion pathways, is investigated experimentally by colliding the molecular ions with nitrogen buffer gas over a range of electric fields. This study demonstrates the versatility of tandem ion mobility mass spectrometry for exploring the isomerisation of molecular photoswitches initiated by either light or collisions.

Item Type: Article
Uncontrolled Keywords: physics and astronomy(all),physical and theoretical chemistry ,/dk/atira/pure/subjectarea/asjc/3100
Faculty \ School: Faculty of Science > School of Chemistry
UEA Research Groups: Faculty of Science > Research Groups > Chemistry of Light and Energy
Faculty of Science > Research Groups > Centre for Photonics and Quantum Science
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Depositing User: LivePure Connector
Date Deposited: 04 Feb 2019 14:30
Last Modified: 09 Feb 2023 13:46
DOI: 10.1039/c7cp01733b


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