title: Inclusion of a nitronyl nitroxyl radical and its hydrochloride in cucurbit[8]uril.
abstract: 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=-2JS(1)S(2)) and a triplet ground spin state for the inclusion complex.
authors.affiliation: Institution Nikolaev Institute of Inorganic Chemistry SB RAS, 3 Lavrentiev avenue, Novosibirsk 630090, Russia.
authors.forename: Eugenia V
authors.initials: EV
authors.lastname: Peresypkina
authors.forename: Vladimir P
authors.initials: VP
authors.lastname: Fedin
authors.forename: Vincent
authors.initials: V
authors.lastname: Maurel
authors.forename: André
authors.initials: A
authors.lastname: Grand
authors.forename: Paul
authors.initials: P
authors.lastname: Rey
authors.forename: Kira E
authors.initials: KE
authors.lastname: Vostrikova