Stabilization Of Pancake Bonding In (Tcnq)(2)(Center Dot-) Dimers In The Radical-Anionic Salt (N-Ch3-2-Nh2-5cl-Py)(Tcnq)(Ch3cn) Solvate And Antiferromagnetism Induction

We report a new antiferromagnetic radical-anion salt (RAS) formed from 7,7,8,8-tetracyanquinonedimethane (TCNQ) anion and 2-amino-5-chloro-pyridine cation with the composition of (N-CH3-2-NH2-5Cl-Py)(TCNQ)(CH3CN). The crystallographic data indicates the formation of (TCNQ)(2)(center dot-) radical-anion pi-dimers in the synthesized RAS. Unrestricted density functional theory calculations show that the formed pi-dimers characterize with strong pi-stacking "pancake" interactions, resulting in high electronic coupling, enabling efficient charge transfer properties, but pi-dimers cannot be stable in the isolated conditions as a result of strong Coulomb repulsions. In a crystal, where (TCNQ)(2)(.-) pi-dimers bound in the endless chainlets via supramolecular bonds with (N-CH3-2-NH2-5-Cl-Py)(+) cations, the repulsion forces are screened, allowing for specific parallel pi-stacking interactions and stable radical-anion dimers formation. Measurements of magnetic susceptibility and magnetization confirm antiferromagnetic properties of RAS, what is in line with the higher stability of ground singlet state of the radical-anion pair, calculated by means of the DFT. Therefore, the reported radical-anion (N-CH3-2-NH2-5Cl-Py)(TCNQ)(CH3CN) solvate has promising applications in novel magnetics with supramolecular structures.