Conducting Coronene Cation Radical Salt Containing Magnetic Metal Ions
Conducting Coronene Cation Radical Salt Containing Magnetic Metal Ions
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含有磁性金属离子的导电晕苯阳离子自由基盐
DOI：
10.1021/acs.inorgchem.9b02080
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发表时间：
2019
影响因子：
4.6
通讯作者：
Kitagawa Hiroshi
中科院分区：
文献类型：
--
作者：
Yoshida Yukihiro;Maesato Mitsuhiko;Saito Gunzi;Kitagawa Hiroshi
晕苯是苯的最小同系物，是6重对称多环芳烃中石墨烯的最小碎片。在本研究中，我们首次用电化学方法合成了含磁性抗衡离子的晕苯阳离子自由基固体。1：1盐中的晕苯一价阳离子（晕苯·+）（FeBr 4-）通过π-π相互作用以堆叠方式组装，这导致相当高的室温电导率（0.6 S cm-1）。该盐具有半导体性质，在T ≥ 220 K和T ≤ 220 K时的激活能分别为0.25 eV和0.18 eV。磁化率遵循居里-韦斯定律，直到大约30 K，居里常数（4.47 emu K mol-1）预计为S = 5/2自旋的铁（III）离子和高韦斯温度（−32.2 K）。进一步冷却后，盐在16.2 K下表现出磁化率扭结，随后由于长程反铁磁有序而损失了很大一部分磁化率。理论计算表明，通过C-H···Br氢键的间接π-d磁交换作用J πd= −3.10 K.虽然其绝对值低于FeBr 4-阴离子之间的直接d-d磁交换相互作用（Jdd= −13.35 K），但很明显π-d相互作用在决定磁性行为方面发挥了一定的作用。考虑到一种同晶盐（coronene·+）（GaBr 4-）包含一个对应的GaBr 4-，表现出单重态-三重态的磁性行为，自旋能隙为1.44 × 103 K，在（coronene）（FeBr 4）中，π π-电子很可能通过π-d相互作用充当d-自旋磁有序的中介体。
Coronene is the smallest homologue of benzene and is the smallest fragment of graphene among 6-fold symmetric polycyclic aromatic hydrocarbons. In this study, we obtained the first coronene cation radical solid containing magnetic counterions by an electrochemical method. Coronene monocations in the 1:1 salt, (coronene•+)(FeBr4–), assemble in a stacking manner via π–π interactions, which lead to a rather high room-temperature conductivity of 0.6 S cm–1. The salt shows semiconducting behavior as expected from the calculated band structure, and activation energies were estimated to be 0.25 eV atT≥ 220 K and 0.18 eV atT≤ 220 K. The magnetic susceptibility follows the Curie–Weiss law down to about 30 K, with a Curie constant (4.47 emu K mol–1) expected forS= 5/2 spins of iron(III) ions and a high Weiss temperature (−32.2 K). Upon further cooling, the salt exhibits a susceptibility kink at 16.2 K followed by the loss of a significant fraction of the susceptibility due to long-range antiferromagnetic ordering. Theoretical calculations predicted that the indirect π–d magnetic exchange interaction through C–H···Br hydrogen bonds is equal toJπd= −3.10 K. Although the absolute value is lower than that of the direct d–d magnetic exchange interaction between the FeBr4–anions (Jdd= −13.35 K), it is evident that the π–d interactions play a certain role in determining the magnetic behavior. Considering that an isomorphous salt, (coronene•+)(GaBr4–) involving a nonmagnetic counterpart GaBr4–, exhibits singlet–triplet magnetic behavior with a spin gap of 1.44 × 103K, it is most likely that in (coronene)(FeBr4) the nonmagnetic π-electrons serve as mediators of the magnetic ordering of d-spins through the π–d interactions.