The formation of diamagnetic singly bonded (C70−)2 dimers in ionic complexes of fullerene C70 with tetrakis(dimethylaminoethylene)

Abstract

Two complexes containing C₇₀ anions and tetrakis(dimethylamino)ethylene radical cations (TDAE˙⁺)·(C₇₀⁻)·(C₆H₄Cl₂)·(C₆H₁₄)_0.5 (1) and (TDAE˙⁺)·(C₇₀⁻)·(C₆H₄Cl₂) (2) were obtained as single crystals. Both complexes contain singly bonded (C₇₀⁻)₂ dimers and have close composition. However, their crystal structures are different. Complex 1 has a layered structure in which layers from the (C₇₀⁻)₂ dimers alternate with the TDAE˙⁺-C₆H₄Cl₂ layers. Ionic fullerene layers contain large hexagonal vacancies which are occupied by completely ordered hexane molecules. Complex 2 has a three-dimensional packing of the (C₇₀⁻)₂ dimers with large vacancies passing along the c axis and containing TDAE˙⁺ and C₆H₄Cl₂ moieties. IR spectra of the (C₇₀⁻)₂ dimers in both complexes show similar features with more than 40 absorption bands additionally to the absorption bands of parent C₇₀. According to the IR spectra the (C₇₀⁻)₂ dimers are stable in 1 and 2 up to room temperature. Both complexes show narrow EPR signals characteristic of TDAE˙⁺ (g = 2.0032, the linewidth of 0.3–0.4 mT at 77 K).