DESIGN, SYNTHESIS, AND PHYSICOCHEMICAL CHARACTERISTICS OF STABLE NITRONYL-NITROXIDE DIRADICALS AND THEIR COMPLEXES WITH Cu(II) BASED ON FUNCTIONAL DERIVATIVES OF ISOPHTHALALDEHYDE

Stable high-spin organic radicals (S ≥ 1) are attractive objects for organic materials with potential applications in fields such as organic magnets, spintronics, spin filters, and memory devices [1]. However, the synthesis of thermally stable di- and polyradicals is a challenging task, especially when ferromagnetic exchange interactions between multiple paramagnetic centers are desired. The report discusses methods for obtaining promising synthetic blocks for the synthesis of functionally substituted di-nitronyl nitroxyl radicals and their complexes with Cu(hfac)2 based on m-xylene. Using the strategy of Pd-catalyzed cross-coupling reactions of active aryl halides based on 4,6-dibromoiso-phthalaldehyde, an approach to obtaining a new type of polyhetero-radicals is proposed. The structural features of the obtained paramagnets and their EPR spectra are considered. Recently, the bifunctional substituted nitronyl nitroxide (NNR) diradical which was synthesized by cross coupling reaction such as 1 which was successfully used as a working body in a molecular heat engine in the study of spin phase transitions between superconducting electrodes [2].

In this presentation and graphical abstract , various synthetic approaches to previously unknown types
of functionally substituted (X, Y = Br, NO2, COOR) diradicals 2, 3 with meta-positioning of the NHR fragments will be discussed. Special attention will be paid to methods of introducing reactive groups into the diradical molecule by using cross coupling reaction and the possibility of obtaining various complexes with copper salts.

References:
[1] E. V. Tretyakov, I. A. Zayakin, A. A. Dmitriev, M. V. Fedin et al. Chem. Eur. J. 2024, 30, e202303456.
[2] S. Volosheniuk, D. Bouwmeester, D. Vogel, H.S.J. van der Zant et al. Nat. Commun., 2025, 16, 3279.