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Photoredox‐Switchable Resorcin[4]arene Cavitands: Radical Control of Molecular Gripping Machinery via Hydrogen Bonding
Author(s) -
Milić Jovana,
Zalibera Michal,
Talaat Darius,
Nomrowski Julia,
Trapp Nils,
Ruhlmann Laurent,
Boudon Corinne,
Wenger Oliver S.,
Savitsky Anton,
Lubitz Wolfgang,
Diederich François
Publication year - 2018
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201704788
Subject(s) - chemistry , photochemistry , hydrogen bond , electron paramagnetic resonance , ultrafast laser spectroscopy , quinone , pyrrole , indole test , electron transfer , imidazole , spectroscopy , molecule , stereochemistry , organic chemistry , physics , nuclear magnetic resonance , quantum mechanics
Semiquinones ( SQ ) are generated in photosynthetic organisms upon photoinduced electron transfer to quinones ( Q ). They are stabilized by hydrogen bonding (HB) with the neighboring residues, which alters the properties of the reaction center. We designed, synthesized, and investigated resorcin[4]arene cavitands inspired by this function of SQ in natural photosynthesis. Cavitands were equipped with alternating quinone and quinoxaline walls bearing hydrogen bond donor groups (HBD). Different HBD were analyzed that mimic natural amino acids, such as imidazole and indole, along with their analogues, pyrrole and pyrazole. Pyrroles were identified as the most promising candidates that enabled the cavitands to remain open in the Q state until strengthening of HB upon reduction to the paramagnetic SQ radical anion provided stabilization of the closed form. The SQ state was generated electrochemically and photochemically, whereas properties were studied by UV/Vis spectroelectrochemistry, transient absorption, and EPR spectroscopy. This study demonstrates a photoredox‐controlled conformational switch towards a new generation of molecular grippers.