Marriott Katie E R, Bhaskaran Lakshmi, Wilson Claire, Medarde Marisa, Ochsenbein Stefan T, Hill Stephen, Murrie Mark
WestCHEM , School of Chemistry , University of Glasgow , Glasgow , G12 8QQ , UK . Email:
Department of Physics and NHMFL , Florida State University , Tallahassee , FL 32310 , USA . Email:
Chem Sci. 2015 Dec 1;6(12):6823-6828. doi: 10.1039/c5sc02854j. Epub 2015 Sep 8.
Monometallic complexes based on 3d transition metal ions in certain axial coordination environments can exhibit appreciably enhanced magnetic anisotropy, important for memory applications, due to stabilisation of an unquenched orbital moment. For high-spin trigonal bipyramidal Ni(ii), if competing structural distortions can be minimised, this may result in an axial anisotropy that is at least an order of magnitude stronger than found for orbitally non-degenerate octahedral complexes. Broadband, high-field EPR studies of [Ni(MDABCO)Cl]ClO () confirm an unprecedented axial magnetic anisotropy, which pushes the limits of the familiar spin-only description. Crucially, compared to complexes with multidentate ligands that encapsulate the metal ion, we see only a very small degree of axial symmetry breaking. displays field-induced slow magnetic relaxation, which is rare for monometallic Ni(ii) complexes due to efficient spin-lattice and quantum tunnelling relaxation pathways.
在某些轴向配位环境中，基于3d过渡金属离子的单金属配合物可表现出明显增强的磁各向异性，这对存储应用很重要，因为未猝灭的轨道矩得以稳定。对于高自旋三角双锥Ni(ii)，如果能将竞争性结构畸变降至最低，这可能会导致轴向各向异性比轨道非简并八面体配合物的轴向各向异性至少强一个数量级。对[Ni(MDABCO)Cl]ClO ()的宽带高场电子顺磁共振研究证实了前所未有的轴向磁各向异性，这突破了常见的仅考虑自旋的描述的极限。至关重要的是，与具有包裹金属离子的多齿配体的配合物相比，我们仅观察到非常小程度的轴向对称性破坏。 表现出场诱导的慢磁弛豫，这对于单金属Ni(ii)配合物来说很罕见，因为存在高效的自旋-晶格弛豫和量子隧穿弛豫途径。
