Two new dysprosium-organic frameworks contaning rigid dicarboxylate ligands: Synthesis and effect of solvents on the luminescent properties

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• 作者：Huijie Zhang ; Ruiqing Fan ; Wei Chen ; Xubin Zheng ; Kai Li ; Ping Wang ; Yulin Yang
• 关键词：Dysprosium coordination polymer ; Fluorescence intensities ; Lifetime ; Energy transfer process
• 刊名：Journal of Luminescence
• 出版年：2013
• 出版时间：November, 2013
• 年：2013
• 卷：143
• 期：Complete
• 页码：611-618
• 全文大小：891 K

文摘

Two new two-dimensional (2D) dysprosium coordination polymers [Dy(2,4¡ä-bpdc)(DMF)₂(NO₃)]_n (1) and {[Dy(2,4¡ä¨Cbpdc)(1,4-BDC)_0.5(DMF)(H₂O)]1.5H₂O}_n (2) (2,4¡ä-H₂bpdc=2,4¡ä¨Cbiphenyldicarboxylic acid, 1,4-H₂BDC=1,4-benzenedicarboxylic acid, DMF=N,N¡ä-dimethylformamide) were synthesized under solvothermal condition and stucturally characterized by means of single-crystal X-ray diffraction, IR spectroscopy, and elemental analysis. Single-crystal X-ray analysis revealed that the two coordination polymers possess two types of 2D layered structures. From the viewpoint of network topology, the structures of 1 and 2 can be simplified as (4,4) network. We discuss the effect of solvents and temperature on luminescence properties. The fluorescence spectra of 1 at room temperature and 77 K in the solid-state are almost the same, except the stronger emission intensities derived from ligand-centered at 77 K. It is because the quenching by O3H oscillators was protected at low temperature. Coordination polymer 2 displays characteristic Dy³⁺ ion yellow-green luminescence under 290 nm excitation in DMSO (dimethyl sulfoxide), CH₃CN, and CH₃OH solvents. The fluorescence intensities of 2 increased in the order of DMSO>CH₃CN>CH₃OH. We also studied the fluorescence lifetimes of 1 and 2, and the results revealed that the lifetime in DMSO solvent at room temperature reached to 9.53 ¦Ìs. Compared with the dysprosium coordination polymers, coordination polymer 2 presents a longer lifetime. Additionally, we calculate the triplet state T₁ datum from the emission spectrum of the Gd³⁺ coordination polymer and discuss the energy transfer mechanisms. The energy transfer process from the lowest triplet state energy level of 2,4¡ä-H₂bpdc ligand to the ⁴F_9/2 state energy level of Dy³⁺ ion is inefficient for both 1 and 2. The energy transfer process is effective after we introducing the chelating ligand 1,4-H₂BDC to the construct of coordination polymer 2, which is ascribe to 1,4-H₂BDC may participate in the process of energy transfer.