Synthesis, Structure, Luminescent, and Magnetic Properties of Carbonato-Bridged ZnII2LnIII2 Complexes [(渭4-CO3)2{ZnII<

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• 作者：Kiyomi Ehama ; Yusuke Ohmichi ; Soichiro Sakamoto ; Takeshi Fujinami ; Naohide Matsumoto ; Naotaka Mochida ; Takayuki Ishida ; Yukinari Sunatsuki ; Masanobu Tsuchimoto ; Nazzareno Re
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：November 4, 2013
• 年：2013
• 卷：52
• 期：21
• 页码：12828-12841
• 全文大小：675K
• 年卷期：v.52,no.21(November 4, 2013)
• ISSN：1520-510X

文摘

Carbonato-bridged Zn^II₂Ln^III₂ complexes [(渭₄-CO₃)₂{Zn^IILⁿLn^III(NO₃)}₂]路solvent were synthesized through atmospheric CO₂ fixation reaction of [Zn^IILⁿ(H₂O)₂]路xH₂O, Ln^III(NO₃)₃路6H₂O, and triethylamine, where Ln^III = Gd^III, Tb^III, Dy^III; L¹ = N,N鈥?bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato, L² = N,N鈥?bis(3-ethoxy-2-oxybenzylidene)-1,3-propanediaminato. Each Zn^II₂Ln^III₂ structure possessing an inversion center can be described as two di-渭-phenoxo-bridged {Zn^IILⁿLn^III(NO₃)} binuclear units bridged by two carbonato CO₃^{2鈥?/sup> ions. The ZnII ion has square pyramidal coordination geometry with N₂O₂ donor atoms of Ln and one oxygen atom of a bridging carbonato ion at the axial site. LnIII ion is coordinated by nine oxygen atoms consisting of four from the deprotonated Schiff-base Ln, two from a chelating nitrate, and three from two carbonate groups. The temperature-dependent magnetic susceptibilities in the range 1.9鈥?00 K, field-dependent magnetization from 0 to 5 T at 1.9 K, and alternating current magnetic susceptibilities under the direct current bias fields of 0 and 1000 Oe were measured. The magnetic properties of the ZnII₂LnIII₂ complexes are analyzed on the basis of the dicarbonato-bridged binuclear LnIII鈥揕nIII structure, as the ZnII ion with d10 electronic configuration is diamagnetic. ZnGd1 (L1) and ZnGd2 (L2) show a ferromagnetic GdIII鈥揋dIII interaction with J(Gd鈥揋d) = +0.042 and +0.028 cm鈥?, respectively, on the basis of the Hamiltonian H = 鈭?J(Gd鈥揋d)艤_Gd1路艤_Gd2. The magnetic data of the ZnII₂LnIII₂ complexes (LnIII = TbIII, DyIII) were analyzed by a spin Hamiltonian including the crystal field effect on the LnIII ions and the LnIII鈥揕nIII magnetic interaction. The Stark splitting of the ground state was so evaluated, and the energy pattern indicates a strong easy axis (Ising type) anisotropy. Luminescence spectra of ZnII₂TbIII₂ complexes were observed, while those of ZnII₂DyIII₂ were not detected. The fine structure assignable to the 5D₄ 鈫?7F₆ transition of ZnTb1 and ZnTb2 is in good accord with the energy pattern from the magnetic analysis. The ZnII₂LnIII₂ complexes (LnIII = TbIII, DyIII) showed an out-of-phase signal with frequency-dependence in alternating current susceptibility, indicative of single molecule magnet. Under a dc bias field of 1000 Oe, the signals become significantly more intense and the energy barrier, 螖/k_B, for the magnetic relaxation was estimated from the Arrhenius plot to be 39(1) and 42(8) K for ZnTb1 and ZnTb2, and 52(2) and 67(2) K for ZnDy1 and ZnDy2, respectively.}