Carbonato-Bridged NiII2LnIII2 (LnIII = GdIII, TbIII, DyIII) Complexes Generated by Atmospheric CO2 Fi

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• 作者：Soichiro Sakamoto ; Takeshi Fujinami ; Koshiro Nishi ; Naohide Matsumoto ; Naotaka Mochida ; Takayuki Ishida ; Yukinari Sunatsuki ; Nazzareno Re
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：June 17, 2013
• 年：2013
• 卷：52
• 期：12
• 页码：7218-7229
• 全文大小：693K
• 年卷期：v.52,no.12(June 17, 2013)
• ISSN：1520-510X

文摘

Atmospheric CO₂ fixation of [Ni^II(3-MeOsaltn)(H₂O)₂]路2.5H₂O [3-MeOsaltn = N,N鈥?bis(3-methoxy-2-oxybenzylidene)-1,3-propanediaminato], Ln^III(NO₃)₃路6H₂O, and triethylamine occurred in methanol/acetone, giving a first series of carbonato-bridged Ni^II₂Ln^III₂ complexes [(渭₄-CO₃)₂{Ni^II(3-MeOsaltn)(MeOH)Ln^III(NO₃)}₂] (1Gd, 1Tb, and 1Dy). When the reaction was carried out in acetonitrile/water, it gave a second series of complexes [(渭₄-CO₃)₂{Ni^II(3-MeOsaltn)(H₂O)Ln^III(NO₃)}₂]路2CH₃CN路2H₂O (2Gd, 2Tb, and 2Dy). For both series, each Ni^II₂Ln^III₂ structure can be described as two di-渭-phenoxo-bridged Ni^IILn^III binuclear units bridged by two carbonato CO₃^{2鈥?/sup> units to form a carbonato-bridged (渭₄-CO₃)₂{NiII₂LnIII₂} structure. The high-spin NiII ion has octahedral coordination geometry, and the LnIII ion is coordinated by O₉ donor atoms from NiII(3-MeOsaltn), bidentate NO₃鈥?/sup>, and one and two oxygen atoms of two CO₃2鈥?/sup> ions. The NO₃鈥?/sup> ion for the first series roughly lie on Ln鈥揙(methoxy) bonds and are tilted toward the outside, while for the second series, the two oxygen atoms roughly lie on one of the Ln鈥揙(phenoxy) bonds due to the intramolecular hydrogen bond. The temperature-dependent magnetic susceptibilities indicated a ferromagnetic interaction between the NiII and LnIII ions (LnIII = GdIII, TbIII, DyIII) for all of the complexes, with a distinctly different magnetic behavior between the two series in the lowest-temperature region due to the LnIII鈥揕nIII magnetic interaction and/or different magnetic anisotropies of the TbIII or DyIII ion. Alternating-current susceptibility measurements under the 0 and 1000 Oe direct-current (dc) bias fields showed no magnetic relaxation for the NiII₂GdIII₂ complexes but exhibited an out-of-phase signal for NiII₂TbIII₂ and NiII₂DyIII₂, indicative of slow relaxation of magnetization. The energy barriers, 螖/k_B, for the spin flipping were estimated from the Arrhenius plot to be 12.2(7) and 6.1(3) K for 1Tb and 2Tb, respectively, and 18.1(6) and 14.5(4) K for 1Dy and 2Dy, respectively, under a dc bias field of 1000 Oe. Compound 1Dy showed relatively slow relaxation of magnetization reorientation even at zero dc applied field with 螖/k_B = 6.6(4) K.}