Ionic fullerene complex (DMI+)3·(C60˙−)·(I−)2 with 2H-hexagonal fullerene packing and 3-D DMI+-I− network

Abstract

A new ionic complex of fullerene (DMI⁺)₃·(C₆₀˙⁻)·(I⁻)₂ (1) (DMI⁺ is the N,N`-dimethylimidazolium cation) was obtained as single crystals. The complex has a unique structure with a three-dimensional (3D) DMI⁺–I ⁻ network which arranges C₆₀˙⁻radical anions. The network consists of the (DMI⁺)₃·(I⁻) units and is held together by the hydrogen H(DMI⁺)–(I⁻) bonds. The C₆₀˙⁻radical anions are located in the center of a trihedral prism from fullerenes with a center-to-center distance of 11.05 Å, providing the 2H-hexagonal 3D packing. The relatively large distances between C₆₀˙⁻ prevent their dimerization but allow the manifestation of a magnetic interaction between them. The Weiss temperature of −9.6 K in the 40–300 K range indicates antiferromagnetic coupling of spins. This coupling can be accompanied by the spin frustration due to the triangular arrangement of C₆₀˙⁻. The complex demonstrates an unusually broad EPR signal (21.5–23.1 mT) in the 82–297 K range attributed to C₆₀˙⁻ which has a g-factor value of 2.0035 at 297 K. The signal abruptly narrows below 82 K, probably due to the freezing of C₆₀˙⁻ rotation.