Thermally stable organic diradicals with at riplet ground state along with large singlet-triplet energy gap have significant potential for advanced technological applications.A series of phenylene-bridged diradicals with oxoverdazyla nd nitronyl nitroxide units were synthesized via ap alladiumcatalyzedc ross-coupling reaction of iodoverdazyls with an itronyl nitroxide-2-ide gold(I) complex with high yields.T he diradicals exhibit high stability and do not decompose in an inert atmosphere up to 180 8 8C. Fort he diradicals,b oth substantial AF (DE ST %À64 cm À1)a nd FM (DE ST ! 25 and 100 cm À1)intramolecular exchange interactions were observed. The sign of the exchange interaction is determined both by the bridging moiety (para-or meta-phenylene) and by the type of oxoverdazylb lock(C-linked or N-linked). Upon crystallization, diradicals with the triplet ground state form unique onedimensional exchange-coupled chains with strong intra-and weak inter-diradical ferromagnetic coupling.

Thermally resistant air-stable organic triradicals with a quartet ground state and a large energy gap between spin states are still unique compounds. Moreover, stable triradicals with bridging units of the ethylene-1,1-diyl type and ferromagnetic coupling are limited to the family of nitroxides. In this work, for the first time, we designed and prepared the triradical having a quartet ground state based on oxoverdazyl and nitronyl nitroxide radical fragments. The triradical and appropriate triplet diradical precursor were synthesized via a palladium-catalyzed cross-coupling reaction of diiodoverdazyl with nitronyl nitroxide-2-ide gold(I) complex. Both the di-and triradical are air-stable and possess good thermal stability with decomposition onset at ∼160 °C in an inert atmosphere. X-ray diffraction analysis of single crystals confirmed the presence of verdazyl and nitroxide radical centers. In the diradical, the verdazyl and nitronyl nitroxide centers showed fully reversible redox waves. In case of the triradical, the electrochemical processes occur practically at the same redox potentials but become quasi-reversible for the nitroxide moieties. Magnetic properties of the di-and triradical were characterized by a SQUID magnetometry of polycrystalline powders and by EPR spectroscopy in different matrices. Collected data analyzed using of the highlevel quantum chemical calculations confirmed that the di-and triradical have high-spin ground states. Unique high stability of prepared verdazyl-nitronylnitroxyl triradical opens new perspectives for further functionalization and design of high-spin systems with four or more spins.

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The interaction of octafluorotoluene (1a), as well as pentafluorobenzonitrile (1b) with tert-butylamine, followed by the oxidation of thus formed tert-butylanilines (2a,b) with meta-chloroperoxybenzoic acid led to functionalized perfluorinated phenyl tert-butyl nitroxides [namely, 4-(N-tert-butyl(oxyl)amino)heptafluorotoluene (3a) and 4-(N-tert-butyl(oxyl)amino)tetrafluorobenzonitrile (3b)] with nearly quantitative total yields. The molecular and crystal structures of nitroxide 3a were proved by single crystal X-ray diffraction analysis. The radical nature of both nitroxides was confirmed by ESR data. The interaction of Cu(hfac)2 with the obtained nitroxides 3a,b gave corresponding trans-bis(1,1,1,5,5,5-hexafluoropentane-2,4-dionato-κ2O,O′)bis{4-(N-tert-butyl(oxyl)amino)perfluoroarene-κO}copper (II) complexes ([Cu(hfac)2(3a)2] and [Cu(hfac)2(3b)2]). X-ray crystal structure analysis showed square bipyramid coordination of a centrally symmetric Cu polyhedron with the axial positions occupied by oxygen atoms of the nitroxide groups. Magnetic measurements revealed intramolecular ferromagnetic exchange interactions between unpaired electrons of Cu(II) ions and paramagnetic ligands, with exchange interaction parameters JCu–R reaching 53 cm−1.