Dimerization of C60˙− in multi-component ionic complexes with bis(ethylenedithio)tetrathiafulvalene: (cation+)2·ET·(C60˙−)2

Abstract

Two multi-component ionic complexes (cation⁺)₂·ET·(C₆₀˙⁻)₂ comprising C₆₀˙⁻ radical anions, neutral bis(ethylenedithio)tetrathiafulvalene (ET) molecules and N-methyldiazabicyclooctane (1) or N,N-dimethylpyrrolidine (2) cations were obtained. At room temperature 1 involves monomeric nearly freely rotating C₆₀˙⁻ radical anions arranged in zigzag double chains passing along the a axis and separated by ET molecules and cations. Dimerization is observed in 1 at 280–250 K within C₆₀˙⁻ pairs with 9.922 Å center-to-center interfullerene distances. It was shown that dimerization temperatures are dependent on the initial distance between the C₆₀˙⁻ anions in the monomeric phase, and the shortest center-to-center interfullerene distance in 1 provides the highest dimerization temperature among ionic C₆₀ complexes studied so far. The crystal structure of the dimeric phase was determined at 100 K. The (C₆₀⁻)₂ dimers are bound by one single bond of 1.589(2) Å length with an interfullerene center-to-center distance of 9.288 Å. The room temperature unit cell parameters of 2 are similar to those of 1 and dimerization is realized in this complex at 280–250 K. Dimerization is reversible in both complexes and results in the transition of the complexes from a paramagnetic to a diamagnetic state.