Crystal structure, magnetic property and DFT analysis for a bis(tetracyanoquinodimethane)zinc(II) complex

A bis(tetracyanoquinodimethane)zinc(II) complex (1) was structurally characterized, in which the Zn²⁺ ion occupies at an inversion centre and is bonded to two tetracyanoquinodimethane radical anions (TCNQ^-), two H₂O and two DMF molecules to form almost perfectly octahedral coordination geometry. The strong H-bonding interactions are observed between H₂O molecules as well as between H₂O molecule and TCNQ^- radical anion of the neighboring complex molecules, additionally, there exist π⋯π stack interactions between TCNQ^- radical anions. The intermolecular H-bonding and π⋯π stack interactions lead to a supramolecular network sheet forming on the crystallographic ac-plane, and the neighboring supramolecular network sheets further extend into three-dimensional supramolecular structure via weak van der Waals forces. Symmetry-broken approach in the theoretical formwork of DFT for magnetic exchange constants analysis disclosed that the ground state of 1 is singlet state, the excited triplet state is much closed to the nonmagnetic ground state with a small energy gap of 1.25 × 10^-5 eV, and there exist AFM interaction in the TCNQ π-stacks, and these predictions are in agreement with magnetic susceptibility measurements.