Crystal packing of TCNQ anion π-radicals governed by intermolecular covalent π–π bonding: DFT calculations and statistical analysis of crystal structures

摘要: On the basis of a thorough Cambridge Structural Database survey, we present statistical analysis packing TCNQ anion π-radicals in charge transfer salts, which reveals three motifs between neighboring TCNQs: one with zero longitudinal offset and an approximate 1 A transversal offset, another 2 third relatively long σ-bond length r = 1.6–1.7 connecting two fragments. Along crystal structures, also density functional theory calculations total energy, covalent π–π bonding interaction Coulombic repulsion energy for [TCNQ]22−π-dimers various geometries. We find that interactions include contributions from intermolecular local dipole repulsions, addition to repulsion, van der Waals attractive electrostatic forces counter-cations anions pointed out recently by other groups TCNE radicals. describe formula Eint Ecoul + Ebond EvdW, systems vacuum, while solid state is compensated anions. conclude molecules their salts predominantly determined term, Ebond.