Fournet Adeline D, Mitchell Kylie J, Wernsdorfer Wolfgang, Abboud Khalil A, Christou George
Department of Chemistry, University of Florida , Gainesville, Florida 32611, United States.
Institut Néel-CNRS and University Grenoble Alpes , F-38000 Grenoble, Cedex 9, France.
Inorg Chem. 2017 Sep 5;56(17):10706-10716. doi: 10.1021/acs.inorgchem.7b01676. Epub 2017 Aug 22.
A new member of the Mn family of single-molecule magnets (SMMs) has been prepared and found to be the first of this family to give a 3-D ferromagnetic network. [MnO(OCCH-p-F)(HO)] (2) was prepared by carboxylate substitution on the acetate derivative with p-F-benzoic acid and crystallizes as 2·8MeCN in space group I4̅2m with extensive formation of intermolecular C-H···F hydrogen-bonding. The latter leads to a combination of ferromagnetic (F) and antiferromagnetic (AF) interactions and an overall F network that gives a χT value at low T that is abnormally high for an S = 10 ground state. 2·8MeCN undergoes solvent loss under vacuum to 2, with a decrease in unit-cell volume of 17%, primarily due to a 13% decrease in the c-axis. The χT vs T plot for 2 indicates a switch to a net AF network. Exposure to air causes hydration to 2·3HO, a concomitant increase in unit cell volume, and a switch back to a F network. The same conversion of 2·8MeCN to 2·3HO can also be accomplished in one step rather than two steps, by leaving crystals of the former exposed to air at ambient temperature and pressure for 10 days, giving the same magnetic plots. Interestingly, the desolvation/solvation processes cause Jahn-Teller isomerism to occur, but the ratio of the faster-relaxing isomer to the normal slowly relaxing one does not change monotonically. Single-crystal micro-SQUID studies on 2·8MeCN show the expected magnetization hysteresis loops for a SMM and a small exchange-bias from the intermolecular interactions that is unexpectedly AF. Since the micro-SQUID study only identifies interactions along the easy-axis (z-axis) of the crystal, this is readily rationalized as due to the J components of the intermolecular interactions in 2·8MeCN being net AF. The combined results offer useful insights into the degree of sensitivity of the magnetic properties to small environmental perturbations.
已制备出单分子磁体（SMM）锰家族的一个新成员，发现它是该家族中首个形成三维铁磁网络的成员。[MnO(OCCH-p-F)(HO)] (2) 通过用对氟苯甲酸对乙酸衍生物进行羧酸盐取代反应制备而成，以2·8MeCN的形式结晶，属于空间群I4̅2m，分子间形成大量C-H···F氢键。后者导致铁磁（F）和反铁磁（AF）相互作用的组合以及一个整体的F网络，在低温下给出的χT值对于S = 10基态来说异常高。2·8MeCN在真空下发生溶剂损失转变为2，晶胞体积减小17%，主要是由于c轴减小了13%。2的χT对T曲线表明转变为净AF网络。暴露在空气中会导致水合形成2·3HO，晶胞体积随之增加，并再次转变为F网络。2·8MeCN到2·3HO的相同转变也可以一步而非两步完成，即将前者的晶体在环境温度和压力下暴露在空气中10天，得到相同的磁性曲线。有趣的是，去溶剂化/溶剂化过程会导致 Jahn-Teller 异构现象发生，但快速弛豫异构体与正常缓慢弛豫异构体的比例并非单调变化。对2·8MeCN进行的单晶微SQUID研究显示了SMM预期的磁化滞后回线以及来自分子间相互作用的小交换偏置，该相互作用出人意料地为AF。由于微SQUID研究仅识别沿晶体易轴（z轴）的相互作用，这很容易解释为2·8MeCN中分子间相互作用的J分量为净AF。综合结果为磁性对小环境扰动的敏感程度提供了有用的见解。
