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Ultrafast Light‐Driven Substrate Expulsion from the Active Site of a Photoswitchable Catalyst
Author(s) -
Pescher Manuel D.,
van Wilderen Luuk J. G. W.,
Grützner Susanne,
Slavov Chavdar,
Wachtveitl Josef,
Hecht Stefan,
Bredenbeck Jens
Publication year - 2017
Publication title -
angewandte chemie
Language(s) - English
Resource type - Journals
eISSN - 1521-3757
pISSN - 0044-8249
DOI - 10.1002/ange.201702861
Subject(s) - azobenzene , photochemistry , catalysis , chemistry , isomerization , moiety , active site , steric effects , hydrogen bond , stereochemistry , organic chemistry , molecule
The photoswitchable piperidine general base catalyst is a prototype structure for light control of catalysis. Its azobenzene moiety moves sterically shielding groups to either protect or expose the active site, thereby changing the basicity and hydrogen‐bonding affinity of the compound. The reversible switching dynamics of the catalyst is probed in the infrared spectral range by monitoring hydrogen bond (HB) formation between its active site and methanol (MeOH) as HB donor. Steady‐state infrared (IR) and ultrafast IR and UV/Vis spectroscopies are used to uncover ultrafast expulsion of MeOH from the active site within a few picoseconds. Thus, the force generated by the azobenzene moiety even in the final phase of its isomerization is sufficient to break a strong HB within 3 ps and to shut down access to the active site.