Department of Chemistry, University of California, Berkeley, California 94720, USA.
J Am Chem Soc. 2010 Mar 24;132(11):3980-8. doi: 10.1021/ja910963x.
An S = 3/2, high-anisotropy building unit, trans-ReCl(4)(CN)(2), representing the first paramagnetic complex with a mixture of just cyanide and halide ligands, has been synthesized through the reaction of (Bu(4)N)CN with ReCl(4)(THF)(2). This species is characterized in detail and employed in directing the formation of a series of one-dimensional coordination solids of formula (DMF)(4)MReCl(4)(CN)(2) (M = Mn (2), Fe (3), Co (4), Ni (5)). Variable-temperature dc magnetic susceptibility measurements demonstrate the presence of intrachain antiferromagnetic (2) and ferromagnetic (3-5) exchange coupling within these solids. In addition, probing the ac magnetic susceptibility as a function of both temperature and frequency reveals that all of the chain compounds exhibit slow relaxation of the magnetization. The relaxation time is shown to be thermally activated, with energy barriers to relaxation of Delta(tau) = 31, 56, 17, and 20 cm(-1) for 2-5, respectively. Notably, the field-dependent magnetization of the iron congener exhibits a significant hysteresis effect at low temperature, with a coercive field of H(C) = 1.0 T, thus demonstrating magnetlike behavior in this one-dimensional system. Finally, the magnetization dynamics of all solids occur within the finite-size regime, where the magnetic domain growth is limited due to physical defects along the chains within the crystals.
一个 S = 3/2、高各向异性的建筑单元，trans-ReCl(4)(CN)(2)，代表了第一个具有氰化物和卤化物配体混合物的顺磁性配合物，是通过（Bu(4)N)CN 与 ReCl(4)(THF)(2)反应合成的。该物种被详细地进行了表征，并用于指导一系列一维配位固体的形成，其化学式为（DMF)(4)MReCl(4)(CN)(2)（M = Mn(2)、Fe(3)、Co(4)、Ni(5)）。变温直流磁导率测量表明，这些固体中存在链内反铁磁（2）和铁磁（3-5）交换耦合。此外，通过温度和频率的交流磁导率探测表明，所有链状化合物都表现出磁化的缓慢弛豫。弛豫时间被证明是热激活的，对于 2-5，弛豫能垒分别为 Delta(tau) = 31、56、17 和 20 cm(-1)。值得注意的是，铁同系物的场依赖磁化在低温下表现出显著的磁滞效应，具有 1.0 T 的矫顽场 H(C)，因此在这个一维体系中表现出类似磁铁的行为。最后，所有固体的磁化动力学都发生在有限尺寸范围内，由于晶体中链内的物理缺陷，磁畴的生长受到限制。
