The paper of NIOCh's researchers (Evgeny V. Tretyakov, Svetlana I. Zhivetyeva, Irina Yu. Bagryanskaya, Maxim S. Kazantsev, Inna K. Shundrina, Elena V. Zaytseva, Elena G. Bagryanskaya) is published on the site of the journal Angewandte Chemie Int. Ed. (IF=12.959)
Ferromagnetically Coupled S = 1 Chains in Crystals of Verdazyl‐Nitronyl Nitroxide Diradicals
Angewandte Chemie International Edition
Publication Date:July 27, 2020
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 the corresponding iodoverdazyls with a nitronyl nitroxide‐2‐ide gold(I) complex with high yields (up to 82%). The synthesized diradicals exhibit high stability and do not decompose in an inert atmosphere up to 180 °C. The magnetic properties of prepared phenylene‐coupled diradicals were investigated and magneto‐structural correlations were established. For the studied diradicals, both substantial antiferromagnetic (D E ST » ‐64 cm –1 ) and ferromagnetic (D E ST ³ 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.