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Acylhydrazone Subunits as a Proton Cargo Delivery System in 7‐Hydroxyquinoline
Author(s) -
Nakashima Kosuke,
Petek Anton,
Hori Yutaro,
Georgiev Anton,
Hirashima Shinichi,
Matsushima Yasuyuki,
Yordanov Dancho,
Miura Tsuyoshi,
Antonov Liudmil
Publication year - 2021
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.202101650
Subject(s) - quinoline , tautomer , chemistry , protonation , imine , covalent bond , hydrogen bond , proton , isomerization , photochemistry , steric effects , stereochemistry , crystallography , organic chemistry , molecule , catalysis , ion , physics , quantum mechanics
The reimagined concept of long‐range tautomeric proton transfer using crane subunits is shown by designing and synthesising two new acylhydrazones containing a 7‐hydroxyquinoline (7‐OHQ) platform. The acylhydrazone subunits attached to the 7‐OHQ at the 8th position act as crane arms for delivering proton cargo to the quinoline nitrogen. Light‐induced tautomerization to their keto forms leads to Z / E isomerization of the C=C axle bond, followed by proton delivery to the quinoline nitrogen by the formation of covalent or hydrogen bonds. The axle‘s being either an imine or ketimine bond is the structural difference between the studied compounds. The −CH 3 group in the latter provides steric strain, resulting in different proton transport pathways. Both compounds show long thermal stability in the switched state, which creates a tuneable action of bidirectional proton cargo transport by using different wavelengths of irradiation. Upon the addition of acid, the quinoline nitrogen is protonated; this results in E / Z configuration switching of the acylhydrazone subunits. This was proven by single‐crystal X‐ray structure analysis and NMR spectroscopy.