Alkaline Earth Metal Ion/Dihydroxy鈥揟erephthalate MOFs: Structural Diversity and Unusual Luminescent Properties

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• 作者：Antigoni Douvali ; Giannis S. Papaefstathiou ; Maria Pia Gullo ; Andrea Barbieri ; Athanassios C. Tsipis ; Christos D. Malliakas ; Mercouri G. Kanatzidis ; Ioannis Papadas ; Gerasimos S. Armatas ; Antonios G. Hatzidimitriou ; Theodore Lazarides ; Manolis J. Manos
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：June 15, 2015
• 年：2015
• 卷：54
• 期：12
• 页码：5813-5826
• 全文大小：853K
• ISSN：1520-510X

文摘

Alkaline earth (group 2) metal ion organic frameworks (AEMOFs) represent an important subcategory of MOFs with interesting structures and physical properties. Five MOFs, namely, [Mg₂(H₂dhtp)₂(渭-H₂O)(NMP)₄] (AEMOF-2), [Mg₂(H₂dhtp)_1.5(DMAc)₄]Cl路DMAc (AEMOF-3), [Ca(H₂dhtp)(DMAc)₂] (AEMOF-4), [Sr₃(H₂dhtp)₃(DMAc)₆]路H₂O (AEMOF-5), and [Ba(H₂dhtp)(DMAc)] (AEMOF-6) (H₄dhtp = 2,5-dihydroxy-terepthalic acid; DMAc = N,N-dimethylacetamide; NMP = N-methylpyrrolidone), are presented herein. The reported MOFs display structural variety with diverse topologies and new structural features. Interestingly, AEMOF-6 is the first example of a Ba²⁺鈥揌₂dhtp^{2鈥?/sup> MOF, and AEMOF-5 is only the second known Sr2+鈥揌₂dhtp2鈥?/sup> MOF. Detailed photoluminescence studies revealed alkaline earth metal ion-dependent fluorescence properties of the materials, with the heavier alkaline earth metal ions exhibiting red-shifted emission with respect to the lighter ions at room temperature. A bathochromic shift of the emission was observed for the MOFs (mostly for AEMOF-3 and AEMOF-4) at 77 K as a result of excited state proton transfer (ESIPT), which involves an intramolecular proton transfer from a hydroxyl to an adjacent carboxylic group of the H₂dhtp2鈥?/sup> ligand. Remarkably, AEMOF-6 displays rare yellow fluorescence at room temperature, which is attractive for solid state lighting applications. To probe whether the alkaline earth metal ions are responsible for the unusual luminescence properties of the reported MOFs, the potential energy surfaces (PESs) of the ground, S₀, and lowest energy excited singlet, S₁, states of model complexes along the intramolecular proton transfer coordinate were calculated by DFT and TD-DFT methods.}