Large magnetic anisotropy of chromium(III) ions in a bis(ethylenedithio)tetrathiafulvalenium salt of chromium bis(dicarbollide), (ET)2[3,3′-Cr(1,2-C2B9H11)2]

• Published in: Transition metal chemistry (Weinheim) Vol. 43; no. 7; pp. 647 - 655
• Main Authors: Čižmár, Erik, Šoltésová, Daniela, Kazheva, Olga N., Alexandrov, Grigorii G., Kravchenko, Andrey V., Chekulaeva, Lyubov A., Kosenko, Irina D., Sivaev, Igor B., Bregadze, Vladimir I., Fedorchenko, Alexey V., Starodub, Vladimir A., Buravov, Lev I., Dyachenko, Oleg A., Feher, Alexander
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 01.10.2018
• Subjects: Catalysis; Chemistry; Chemistry and Materials Science; Inorganic Chemistry; Organometallic Chemistry; Physical Chemistry
• ISSN: 0340-4285; 1572-901X
• DOI: 10.1007/s11243-018-0253-1

The synthesis of a radical-cation salt based on a derivative of tetrathiafulvalene, (ET) 2 [3,3′-Cr(1,2-C 2 B 9 H 11 ) 2 ] (ET = bis(ethylenedithio)tetrathiafulvalenium), was accomplished by electrochemical anodic oxidation of ET in the presence of (Me 4 N)[3,3´-Cr(1,2-C 2 B 9 H 11 ) 2 ] in the galvanostatic regime. An electric conductivity σ (293 K) = 7 × 10 −3 Ohm −1  cm −1 with semiconductor activation energy E a  ≅ 0.1 eV in the range of 127–300 K was observed. The crystal structure of (ET) 2 [3,3′-Cr(1,2-C 2 B 9 H 11 ) 2 ] was determined by X-ray diffraction at 173 K, revealing the presence of structural tetramers in radical-cation stacks. The magnetic properties of the complex were investigated in the temperature range 1.8–300 K using magnetometry and EPR, showing that the magnetic structure of (ET) 2 [3,3′-Cr(1,2-C 2 B 9 H 11 ) 2 ] consists of two independent magnetic subsystems. Cation radicals form a rectangular magnetic lattice in the ab -plane with significant antiferromagnetic exchange interactions. The chromium bis(dicarbollide) anions are characterized by unusually strong positive zero-field splitting of the Cr(III) ions, which was confirmed by ab initio calculations.