Starodub Tetiana N, Čižmár Erik, Kliuikov Andrii, Starodub Vladimir A, Feher Alexander, Kozlowska Mariana
Institute of Chemistry Jan Kochanowski University 25-405 Kielce Poland.
Institute of Physics, Faculty of Science P. J. Šafárik University Park Angelinum 9 041 54 Košice Slovakia.
ChemistryOpen. 2019 Jul 18;8(7):984-988. doi: 10.1002/open.201900179. eCollection 2019 Jul.
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-CH-2-NH-5Cl-Py)(TCNQ)(CHCN). The crystallographic data indicates the formation of (TCNQ) radical-anion π-dimers in the synthesized RAS. Unrestricted density functional theory calculations show that the formed π-dimers characterize with strong π-stacking "pancake" interactions, resulting in high electronic coupling, enabling efficient charge transfer properties, but π-dimers cannot be stable in the isolated conditions as a result of strong Coulomb repulsions. In a crystal, where (TCNQ) π-dimers bound in the endless chainlets via supramolecular bonds with (N-CH-2-NH-5-Cl-Py) cations, the repulsion forces are screened, allowing for specific parallel π-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-CH-2-NH-5Cl-Py)(TCNQ)(CHCN) solvate has promising applications in novel magnetics with supramolecular structures.
我们报道了一种由7,7,8,8-四氰基对苯二醌二甲烷（TCNQ）阴离子和2-氨基-5-氯吡啶阳离子形成的新型反铁磁自由基阴离子盐（RAS），其组成为（N-CH₂-NH-5Cl-Py）（TCNQ）（CHCN）。晶体学数据表明在合成的RAS中形成了（TCNQ）自由基阴离子π-二聚体。无限制密度泛函理论计算表明，形成的π-二聚体具有强烈的π-堆积“薄饼”相互作用，导致高电子耦合，具有高效的电荷转移特性，但由于强烈的库仑排斥作用，π-二聚体在孤立条件下不能稳定存在。在晶体中，（TCNQ）π-二聚体通过与（N-CH₂-NH-5-Cl-Py）阳离子的超分子键结合在无尽的链节中，排斥力被屏蔽，允许特定的平行π-堆积相互作用和稳定的自由基阴离子二聚体形成。磁化率和磁化强度的测量证实了RAS的反铁磁性质，这与通过DFT计算得到的自由基阴离子对基态单重态的较高稳定性一致。因此，报道的自由基阴离子（N-CH₂-NH-5Cl-Py）（TCNQ）（CHCN）溶剂化物在具有超分子结构的新型磁性材料中有广阔的应用前景。
