Large magnetic anisotropy of chromium(III) ions in a bis(ethylenedithio)tetrathiafulvalenium salt of chromium bis(dicarbollide), (ET)<Subscript>2</Subscript>[3,3′-Cr(1,2-C<Subscript>2</Subscript>B<Subscript>9</Subscript>H<Subscript>11</Subscript>)<Subscript>2</Subscript>]

The synthesis of a radical-cation salt based on a derivative of tetrathiafulvalene, (ET)₂[3,3′-Cr(1,2-C₂B₉H₁₁)₂] (ET?=?bis(ethylenedithio)tetrathiafulvalenium), was accomplished by electrochemical anodic oxidation of ET in the presence of (Me₄N)[3,3´-Cr(1,2-C₂B₉H₁₁)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-C₂B₉H₁₁)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-C₂B₉H₁₁)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.