Assembly of Imidazolyl-Substituted Nitronyl Nitroxides into Ferromagnetically Coupled Chains

Vasily Romanov,Yulia Vlasenko,Irina Bagryanskaya,Elena Zaytseva,Evgeny Tretyakov,Mehman Yusubov,Nina Gritsan,Dmitry Gorbunov,Dominique Luneau

doi:10.3390/cryst9040219

Abstract

New nitronyl nitroxides, namely, 2-(4,5-dimethylimidazol-2-yl)- and 2-(4,5-dichloroimidazol-2-yl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazol-3-oxide-1-oxyl, were prepared in crystalline form. According to single-crystal X-ray data, intra- and intermolecular hydrogen bonds are formed between NH groups of the imidazole cycles and O atoms of the nitroxide moieties. The intermolecular H-bonds contribute to the alignment of molecules into chains along the a-axis; this alignment causes short intrachain contacts between O and C atoms carrying spin density of opposite signs. Such an arrangement of nitroxides induces ferromagnetic intrachain interactions (J ≈ 10 cm−1) between neighboring radicals.

Highlights

Long-range ferromagnetic ordering has been and is the main target of many scientists looking for organic magnets [1]
Nitronyl nitroxides 1a and 1b were synthesized according to the classical scheme [29] involving the condensation of corresponding aldehydes 2a,b with with 2,3-bis(hydroxyamino)-2,3-dimethylbutane
We describe magneto–structural correlations inherent in the whole family of of imidazolyl-substituted nitronyl nitroxides to show the influence of a substitution of the imidazolyl-substituted nitronyl nitroxides to show the influence of a substitution of the imidazole imidazole ring on the self-arrangement of the nitronyl nitroxide moieties for the purpose of control over the ferromagnetic alignment of the spins in the solid

Summary

Introduction

Long-range ferromagnetic ordering has been and is the main target of many scientists looking for organic magnets [1]. The reason is that the magnetic behavior of monoradicals results from a combination of the magnetic intermolecular interactions generated by the individual contacts, which depends on all the functional groups present in the paramagnetic molecule [2] This fact makes it impossible to perform magneto–structural analysis of all available data on purely organic paramagnets. We believe, to concentrate on a series of compounds having closely related structures tending to form similar first crystalline motifs These motifs are formed due to the strongest intermolecular contacts among which hydrogen bonds are the most predictable, and simultaneously they have an important role in the propagation of ferromagnetic interactions in organic molecular solids [3,4,5,6,7,8,9,10,11,12]. Keeping all this in mind, we performed the synthesis and characterization of new nitroxide radicals 1a,b carrying an imidazole ring substituted

Methods

Results

Conclusion