Effect of Ligand Substitution around the DyIII on the SMM Properties of Dual-Luminescent Zn–Dy and Zn–Dy–Zn Complexes with Large Anisotropy Energy Barriers: A Combined Theoretical and Experimental Magnetostructural Study

详细信息    查看全文

• 作者：Jean Pierre Costes ; Silvia Titos-Padilla ; Itziar Oyarzabal ; Tulika Gupta ; Carine Duhayon ; Gopalan Rajaraman ; Enrique Colacio
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：May 2, 2016
• 年：2016
• 卷：55
• 期：9
• 页码：4428-4440
• 全文大小：764K
• 年卷期：0
• ISSN：1520-510X

文摘

The new dinuclear Zn^II–Dy^III and trinuclear Zn^II–Dy^III-Zn^II complexes of formula [(LZnBrDy(ovan) (NO₃)(H₂O)](H₂O)·0.5(MeOH) (1) and [(L¹ZnBr)₂Dy(MeOH)₂](ClO₄) (3) (L and L¹ are the dideprotonated forms of the N,N′-2,2-dimethylpropylenedi(3-methoxysalicylideneiminato and 2-{(E)-[(3-{[(2E,3E)-3-(hydroxyimino)butan-2-ylidene ]amino}-2,2-dimethylpropyl)imino]methyl}-6-methoxyphenol Schiff base compartmental ligands, respectively) have been prepared and magnetostructurally characterized. The X-ray structure of 1 indicates that the Dy^III ion exhibits a DyO₉ coordination sphere, which is made from four O atoms coming from the compartmental ligand (two methoxy terminal groups and two phenoxido bridging groups connecting Zn^II and Dy^III ions), other four atoms belonging to the chelating nitrato and ovanillin ligands, and the last one coming to the coordinated water molecule. The structure of 3 shows the central Dy^III ion surrounded by two L¹Zn units, so that the Dy^III and Zn^II ions are linked by phenoxido/oximato bridging groups. The Dy ion is eight-coordinated by the six O atoms afforded by two L¹ ligands and two O atoms coming from two methanol molecules. Alternating current (AC) dynamic magnetic measurements of 1, 3, and the previously reported dinuclear [LZnClDy(thd)₂] (2) complex (where thd = 2,2,6,6-tetramethyl-3,5-heptanedionato ligand) indicate single molecule magnet (SMM) behavior for all these complexes with large thermal energy barriers for the reversal of the magnetization and butterfly-shaped hysteresis loops at 2 K. Ab initio calculations on 1–3 show a pure Ising ground state for all of them, which induces almost completely suppressed quantum tunnelling magnetization (QTM), and thermally assisted quantum tunnelling magnetization (TA-QTM) relaxations via the first excited Kramers doublet, leading to large energy barriers, thus supporting the observation of SMM behavior. The comparison between the experimental and theoretical magnetostructural data for 1–3 has allowed us to draw some conclusions about the influence of ligand substitution around the Dy^III on the SMM properties. Finally, these SMMs exhibit metal- and ligand-centered dual emissions in the visible region, and, therefore, they can be considered as magnetoluminescent bifunctional molecular materials.