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合成并表征了一种新的离子对化合物[4-NH2-Py][TCNQ](其中4-NH2-Py+是4-氨基吡啶阳离子,TCNQ-为7,7,8,8-四氰基对苯二醌二甲烷自由基阴离子)。在该离子对化合物晶体中,2个TCNQ-离子形成了面对面堆积的二聚体;阴离子中的氰基分别和阳离子上的氨基、吡啶质子化氮原子之间存在非常强的分子间氢键。通过氢键作用,相邻的TCNQ-二聚体被阳离子连成三维氢键网络。变温磁化率测量表明,在2～400 K温度范围内,该离子对化合物表现为抗磁性。在密度泛函理论框架下,用对称性破损方法计算了化合物晶体中π二聚体内以及通过氢键连接的相邻的TCNQ-离子之间的磁交换常数,发现π二聚体内存在非常强的反铁磁交换作用,与之相比,通过氢键连接的TCNQ-离子之间的磁交换作用可以忽略。π二聚体内强反铁磁交换作用(J/kB≈1805 K)导致了该化合物基本表现为抗磁性。
A novel ion pair compound [4-NH2-Py] [TCNQ] was synthesized and characterized (where 4-NH2-Py + is a 4-aminopyridinium cation and TCNQ- is 7,7,8,8- Diphenoquinodimethane free radical anion). In the ion-pairing compound crystal, two TCNQ- ions formed face-to-face stacking dimers. There was a very strong intermolecular hydrogen bond between the cyano groups in the anion and the amino groups on the cation and the protonated pyridine nitrogen atom, respectively. By hydrogen bonding, adjacent TCNQ-dimers are catenated into three-dimensional hydrogen-bonding networks. The temperature-dependent magnetic susceptibility measurements show that the compounds exhibit diamagnetism over the temperature range of 2 to 400 K. In the framework of density functional theory, the symmetry damage method was used to calculate the magnetic exchange constants between π-dimers and adjacent TCNQ- ions connected by hydrogen bonds in the crystal of the compound. It was found that the π-dimer had a very strong In contrast to the antiferromagnetic exchange, the magnetic exchange between TCNQ- ions linked by hydrogen bonds is negligible. Strong anti-ferromagnetic exchange within the π-dimer (J / kB≈1805 K) resulted in the compound exhibiting essentially diamagnetism.