Magnetic properties of fullerene salts containing d- and f-metal cations (Co2+, Ni2+, Fe2+, Mn2+, Eu2+, Cd2+). Specific features of the interaction between C60 ·− and the metal cations

Abstract

The interaction between the radical anions C60·− and divalent d- and f-metal (Co, Fe, Ni, Mn, Eu, Cd) cations in DMF and acetonitrile-benzonitrile (AN-BN) mixture was studied. Black solid polycrystalline salts (C60·−)2{(M2+)(DMF)x} (x = 2.4–4, 1–6) containing the radical anions C60·− and metal(ii) cations solvated by DMF were prepared for the first time and their optical and magnetic properties were studied. The salts containing Co2+, Fe2+, and Ni2+ are characterized by antiferromagnetic interactions between the radical anions C60·−, which result in unusually large broadening of the EPR signal of C60·− upon lowering the temperature (from 5.55–12.6 mT at room temperature to 35–40 mT at 6 K for Co2+ and Ni2+). The salts containing Mn2+ and Eu2+ form diamagnetic dimers (C60−)2, which causes a jumpwise decrease in the magnetic moment of the complexes and disappearance of the EPR signal of C60·− in the temperature range 210–130 K. A feature of salt 6 is magnetic isolation of the radical anions C60·− due to the presence of diamagnetic cation Cd2+. The salts prepared are unstable in air and decompose in o-dichlorobenzene or AN. Reactions of C60·− with metal(ii) cations in AN-BN mixture result in decomposition products of the salts that contain neutral fullerene dimers and metals solvated by BN.