Fine-Tuning Ligand Fields with Schiff-Base Ligands in Dy<sub>2sub> Compounds
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- 作者：Min Li ; Haipeng Wu ; Sheng Zhang ; Lin Sun ; Hongshan Ke ; Qing Wei ; Gang Xie ; Sanping Chen and Shengli Gao
- 刊名：European Journal of Inorganic Chemistry
- 出版年：2017
- 出版时间：January 26, 2017
- 年：2017
- 卷：2017
- 期：4
- 页码：811-819
- 全文大小：2179K
- ISSN：1099-0682c
文摘
Three dinuclear coordination compounds, [Ln<sub>2sub>(Hhms)<sub>2sub>(NO<sub>3sub>)<sub>4sub>]·MeCN [Ln = Dy (1) and Er (2)] and [Dy<sub>2sub>(Hhms)<sub>2sub>(NO<sub>3sub>)<sub>2sub>(H<sub>2sub>O)<sub>3sub>]·(NO<sub>3sub>)<sub>2sub>·MeCN·(H<sub>2sub>O)<sub>2sub> (3), have been isolated bearing the asymmetric Schiff-base ligand 1-(2-hydroxy-3-methoxybenzylidene)semicarbazide (H<sub>2sub>hms). The potentially tetradentate ONOO-donor ligand shows considerable metal-ion-selective phenoxo bridging in 1–3. Compounds 1 and 2 display a hula-hoop-like coordination geometry, whereas this geometry is broken by an additional µ<sub>2sub>-OH<sub>2sub> bridge in compound 3. The structural discrepancies induced by the different bridging modes in 1 and 3 affect the magnetism. Compound 1 exhibits slow relaxation of the magnetization, which suggests single-molecule magnet (SMM) behavior, whereas no out-of-phase alternating-current signal was observed for 3. Meanwhile, compared with a previously reported Dy<sub>2sub> compound, compound 1 has the same coordination sphere but exhibits different magnetic properties, which has been attributed to differences in the ligand backbone. Fine-tuning of the ligand field is dominated by µ-O bridges and by the extent of conjugation in the backbone of the ligand, which affects the SMM/non-SMM behavior.