Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University , Beijing 100871, PR China.
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences , 345 Lingling Road, Shanghai 200032, PR China.
J Am Chem Soc. 2017 Jan 11;139(1):373-380. doi: 10.1021/jacs.6b11043. Epub 2016 Dec 21.
The pursuit of single-molecule magnets (SMMs) with better performance urges new molecular design that can endow SMMs larger magnetic anisotropy. Here we report that two-coordinate cobalt imido complexes featuring highly covalent Co═N cores exhibit slow relaxation of magnetization under zero direct-current field with a high effective relaxation barrier up to 413 cm, a new record for transition metal based SMMs. Two theoretical models were carried out to investigate the anisotropy of these complexes: single-ion model and Co-N coupling model. The former indicates that the pseudo linear ligand field helps to preserve the first-order orbital momentum, while the latter suggests that the strong ferromagnetic interaction between Co and N makes the [CoN] fragment a pseudo single paramagnetic ion, and that the excellent performance of these cobalt imido SMMs is attributed to the inherent large magnetic anisotropy of the [CoN] core with |M = ± 7/2⟩ ground Kramers doublet.
我们报道了具有高共价 Co═N 核的二配位钴亚胺配合物在零直流场下表现出缓慢的磁化弛豫，其有效弛豫势垒高达 413 cm，这是过渡金属基 SMMs 的新纪录。我们进行了两个理论模型来研究这些配合物的各向异性：单离子模型和 Co-N 耦合模型。前者表明，拟线性配体场有助于保持一阶轨道动量，而后者表明，Co 和 N 之间的强铁磁相互作用使 [CoN] 片段成为伪单顺磁离子，这些钴亚胺 SMM 的优异性能归因于 [CoN] 核固有的大磁各向异性，具有 |M = ± 7/2 ⟩ 基态 Kramer 双重态。
