Ferromagnetically Coupled <i>S</i> =1 Chains in Crystals of Verdazyl‐Nitronyl Nitroxide Diradicals
E.V. Tretyakov, S.I. Zhivetyeva, Pavel V. Petunin, Dmitry E. Gorbunov, Nina P. Gritsan, Irina Yu. Bagryanskaya, A.S. Bogomyakov, Павел С. Постников, Maxim S. Kazantsev, Marina E. Trusova, Inna K. Shundrina, Elena Zaytseva, Dmitriy A. Parkhomenko, Elena G. Bagryanskaya, В.И. Овчаренко
Abstract
Abstract Thermally stable organic diradicals with a triplet ground state along with large singlet‐triplet energy gap have significant potential for advanced technological applications. A series of phenylene‐bridged diradicals with oxoverdazyl and nitronyl nitroxide units were synthesized via a palladium‐catalyzed cross‐coupling reaction of iodoverdazyls with a nitronyl nitroxide‐2‐ide gold(I) complex with high yields. The diradicals exhibit high stability and do not decompose in an inert atmosphere up to 180 °C. For the diradicals, both substantial AF (Δ E ST ≈−64 cm −1 ) and FM (Δ E ST ≥25 and 100 cm −1 ) 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 oxoverdazyl block (C‐linked or N‐linked). Upon crystallization, diradicals with the triplet ground state form unique one‐dimensional exchange‐coupled chains with strong intra‐ and weak inter‐diradical ferromagnetic coupling.