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Synthesis and Characterisation of a Paramagnetic [2]Rotaxane Based on a Crown Ether‐Like Wheel Incorporating a Nitroxide Motif
Author(s) -
Bleve Valentina,
Franchi Paola,
Konstanteli Evangelia,
Gualandi Lorenzo,
Goldup Stephen M.,
Mezzina Elisabetta,
Lucarini Marco
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.201704969
Subject(s) - rotaxane , electron paramagnetic resonance , crown ether , nitroxide mediated radical polymerization , chemistry , moiety , nitrone , viologen , photochemistry , stereochemistry , polymer chemistry , crystallography , molecule , supramolecular chemistry , polymer , organic chemistry , nuclear magnetic resonance , ion , polymerization , radical polymerization , physics , cycloaddition , catalysis
The synthesis of the new nitroxide crown ether 8 and its use as the wheel in a bistable [2]rotaxane, containing dialkylammonium and 4,4′‐bipyridinium recognition sites, is reported. The synthesis of 8 was achieved by the sequential addition of substituted phenyl groups to a nitrone derivatives leading to the preferential formation of the cis stereoisomer. Due to charge–dipole interactions between the nitroxide unit and the bipyridinium moiety, it was possible to probe the movement of the macrocycle between the two molecular stations of the [2]rotaxane after addition of a base by measuring the nitrogen hyperfine splitting in the corresponding EPR spectra. The equilibrium constant for the complexation of dibenzyl viologen by the macrocycle 8 was also determined by EPR titration.