Dilution-Triggered SMM Behavior under Zero Field in a Luminescent Zn2Dy2 Tetranuclear Complex Incorporating Carbonato-Bridging Ligands Derived from Atmospheric CO2 Fix

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• 作者：Silvia Titos-Padilla ; Jos茅 Ruiz ; Juan Manuel Herrera ; Euan K. Brechin ; Wolfgang Wersndorfer ; Francesc Lloret ; Enrique Colacio
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：August 19, 2013
• 年：2013
• 卷：52
• 期：16
• 页码：9620-9626
• 全文大小：388K
• 年卷期：v.52,no.16(August 19, 2013)
• ISSN：1520-510X

文摘

The synthesis, structure, magnetic, and luminescence properties of the Zn<sub>2sub>Dy<sub>2sub> tetranuclear complex of formula {(渭<sub>3sub>-CO<sub>3sub>)<sub>2sub>[Zn(渭-L)Dy(NO<sub>3sub>)]<sub>2sub>}路4CH<sub>3sub>OH (1), where H<sub>2sub>L is the compartmental ligand N,N鈥?N鈥?trimethyl-N,N鈥?bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine, are reported. The carbonate anions that bridge two Zn(渭-L)Dy units come from the atmospheric CO<sub>2sub> fixation in a basic medium. Fast quantum tunneling relaxation of the magnetization (QTM) is very effective in this compound, so that single-molecule magnet (SMM) behavior is only observed in the presence of an applied dc field of 1000 Oe, which is able to partly suppress the QTM relaxation process. At variance, a 1:10 Dy:Y magnetic diluted sample, namely, 1鈥?/b>, exhibits SMM behavior at zero applied direct-current (dc) field with about 3 times higher thermal energy barrier than that in 1 (U<sub>effsub> = 68 K), thus demonstrating the important role of intermolecular dipolar interactions in favoring the fast QTM relaxation process. When a dc field of 1000 Oe is applied to 1鈥?/b>, the QTM is almost fully suppressed, the reversal of the magnetization slightly slows, and U<sub>effsub> increases to 78 K. The dilution results combined with micro-SQUID magnetization measurements clearly indicate that the SMM behavior comes from single-ion relaxation of the Dy<sup>3+sup> ions. Analysis of the relaxation data points out that a Raman relaxation process could significantly affect the Orbach relaxation process, reducing the thermal energy barrier U<sub>effsub> for slow relaxation of the magnetization.