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Inclusion of a Nitronyl Nitroxyl Radical and Its Hydrochloride in Cucurbit[8]uril
Author(s) -
Peresypkina Eugenia V.,
Fedin Vladimir P.,
Maurel Vincent,
Grand André,
Rey Paul,
Vostrikova Kira E.
Publication year - 2010
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.201001194
Subject(s) - crystallography , chemistry , nitroxide mediated radical polymerization , electron paramagnetic resonance , hydrochloride , nitroxyl , ferromagnetism , stereochemistry , polymer chemistry , polymer , nuclear magnetic resonance , organic chemistry , radical polymerization , condensed matter physics , physics , copolymer
The recognition properties of cucurbit[8]uril (CB8) toward nitronyl nitroxide 2‐(2‐benzimidazolyl)‐4,4,5,5‐tetramethylimidazolidinyl‐3‐oxide‐1‐oxy ( 1 ) and its hydrochloride have been investigated. 1⋅ HCl led to 1:1 inclusion complex [ 1⋅ HCl@CB8], which was characterized both in solution and by single‐crystal X‐ray diffraction. In this compound only the tetramethylimidazolidinyl fragment is included in the host. The magnetic behavior of the complex corresponds to a Curie law with a large separation of the spin carriers in the solid. In contrast, an insoluble species exhibiting ferromagnetic behavior is formed when pure 1 reacts with acid‐free CB8. The formula [( 1 ) 2 @(CB8) 3 ], in which two radical guests are arranged in such a way that the phenyl groups of the benzimidazolyl substituents are both stacked into one CB8 and the tetramethyl fragments are each capped by a terminal macrocycle, is proposed, in agreement with microanalysis, spectrophotometric, EPR, and magnetic measurements. According to McConnell’s rules, the alternating spin densities within the stacked aromatic fragments result in a ferromagnetic interaction ( J =+2.3 cm −1 , H =−2 JS 1 S 2 ) and a triplet ground spin state for the inclusion complex.