Photo-induced 6π-electrocyclisation and cycloreversion of isolated dithienylethene anions

Jack Buntine, Eduardo Carrascosa, James N. Bull, Giel Muller, Ugo Jacovella, Christopher R. Glasson, George Vamvounis, Evan J. Bieske

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Abstract

The diarylethene chromophore is commonly used in light-triggered molecular switches. The chromophore undergoes reversible 6π-electrocyclisation (ring closing) and cycloreversion (ring opening) reactions upon exposure to UV and visible light, respectively, providing bidirectional photoswitching. Here, we investigate the gas-phase photoisomerisation of meta- (m) and para- (p) substituted dithienylethene carboxylate anions (DTE ) using tandem ion mobility mass spectrometry coupled with laser excitation. The ring-closed forms of p-DTE and m-DTE are found to undergo cycloreversion in the gas phase with maximum responses associated with bands in the visible (λ max ≈ 600 nm) and the ultraviolet (λ max ≈ 360 nm). The ring-open p-DTE isomer undergoes 6π-electrocyclisation in the ultraviolet region at wavelengths shorter than 350 nm, whereas no evidence is found for the corresponding electrocyclisation of ring-open m-DTE , a situation attributed to the fact that the antiparallel geometry required for electrocyclisation of m-DTE is energetically disfavoured. This highlights the influence of the carboxylate substitution position on the photochemical properties of DTE molecules. We find no evidence for the formation in the gas phase of the undesirable cyclic byproduct, which causes fatigue of DTE photoswitches in solution.

Original languageEnglish
Pages (from-to)16628-16636
Number of pages9
JournalPhysical Chemistry Chemical Physics
Volume24
Issue number27
Early online date23 Jun 2022
DOIs
Publication statusPublished - 21 Jul 2022

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