Fine-Tuning Ligand Fields with Schiff-Base Ligands in Dy₂ 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, [Ln₂(Hhms)₂(NO₃)₄]·MeCN [Ln = Dy (1) and Er (2)] and [Dy₂(Hhms)₂(NO₃)₂(H₂O)₃]·(NO₃)₂·MeCN·(H₂O)₂ (3), have been isolated bearing the asymmetric Schiff-base ligand 1-(2-hydroxy-3-methoxybenzylidene)semicarbazide (H₂hms). 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 µ₂-OH₂ 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 Dy₂ 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.