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

Two complexes containing C-70 anions and tetrakis(dimethylamino)ethylene radical cations (TDAE(center dot+))center dot(C-70(-))center dot(C6H4Cl2)center dot(C6H14)(0.5) (1) and (TDAE(center dot+))center dot(C-70(-))center dot(C6H4Cl2)(2) were obtained as single crystals. Both complexes contain singly bonded (C-70(-))(2) dimers and have close composition. However, their crystal structures are different. Complex 1 has a layered structure in which layers from the (C-70(-))(2) dimers alternate with the TDAE(center dot+)-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 (C-70(-))(2) dimers with large vacancies passing along the c axis and containing TDAE(center dot+) and C6H4Cl2 moieties. IR spectra of the (C-70(-))(2) dimers in both complexes show similar features with more than 40 absorption bands additionally to the absorption bands of parent C-70. According to the IR spectra the (C-70(-))(2) dimers are stable in 1 and 2 up to room temperature. Both complexes show narrow EPR signals characteristic of TDAE(center dot+) (g = 2.0032, the linewidth of 0.3-0.4 mT at 77 K).