Heteroradical Salts\nBased on Paramagnetic Derivatives\nof Difurazanopyrazine and <i>N</i>‑Alkylpyridinium\nNitronyl Nitroxides

The effective approach to the synthesis of heteroradical\norganic\nsalts based on the paramagnetic difurazanopyrazine derivative and\npyridinium-substituted nitronyl nitroxides has been proposed. It was\ndemonstrated that the use of [NN<sup>p/m</sup>R]I iodides as a cation-radical\nsource in the reaction with NaL(H<sub>2</sub>O)<sub>3</sub> (where\nL is the anion-radical of bis(1,2,5-oxadiazolo)[3,4-b:3′,4′-e]pyrazine)\nresults in reducing L and the formation of solid solutions [NN<sup>p</sup>Me](L)<i><sub>x</sub></i>(HL)<sub>1–<i>x</i></sub>·H<sub>2</sub>O containing both the paramagnetic\nanion L and its reduced form anion HL. It was found that the use of\n[NN<sup>p/m</sup>R]NO<sub>3</sub> nitrates allows to avoid the reduction\nof L, and heteroradical salts [NN<sup>p/m</sup>R]L can be easily obtained.\nA single crystal XRD study showed that the solid phases of [NN<sup>p/m</sup>R]L salts form crystals formed by quartets of anions and\ncations {NN<sup>p/m</sup>R···L···L···NN<sup>p/m</sup>R}. Within the quartets, the distances between the anion-radical\nplanes of L are ∼3.3 Å, which ensures the presence of\nantiferromagnetic exchange interactions between them and determines\nthe magnetic properties, in general. It was found that in the [NN<sup>m</sup>Me]L·H<sub>2</sub>O structure, alternating cationic and\nanionic radicals are ferromagnetically coupled and form magnetic chains,\nwhich are linked into layers by O<sub>H2O</sub>···N<sub>L</sub> hydrogen bonds. The [NN<sup>p/m</sup>R]L heteroradical salts\nrepresent a new type of paramagnet based on organic fragments with\nfixed charge and spin states.