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Alkaline-Earth Metal Based MOFs with Second Scale Long-Lasting Phosphor Behavior

Abstract

Three novel 3D metal-organic frameworks (MOFs) based on alkaline-earth (AE) metal ions and aromatic carboxylic linkers, i.e. {[Ca3(btb)2(DMF)3]•7DMF}n (1), {[Ca(bdc)(DMF)(H2O)]•2H2O}n (2) and {[Ba(NH2-bdc)(DMF)]}n (3) [where btb = 1,3,5-tris(4-carboxyphenyl)benzene, bdc = 1,4-benzenedicarboxylate and NH2-bdc = 2-amino-1,4-benzenedicarboxylate] have been synthesized under mild solvothermal conditions. All compounds contain three-dimensional frameworks built up from rod-like AE-carboxylate based secondary building units joined by the aromatic carboxylate linkers. Moreover, crystal structures present intriguing physical features such as chirality (1 and 3) or large voids occupied by solvent molecules (1 and 2), in addition to less frequent long-lasting phosphorescence (LLP) originated at ligands triplet states as confirmed DFT calculations. This persistent photoluminescence characterizes for steady-state blue fluorescence that leads to pale blue (compound 2) and green (1 and 3) afterglow, which lasts for seconds. Exhaustive characterization of long-lasting phosphorescence at low temperature by means of time-resolved spectroscopy reveals remarkably long lifetimes (τ) of ca. 835 and 375 ms (for 1 and 3), and as large as to those record breaking τ ≈ 2 seconds for 2, which are remarkably larger than those recorded for free ligands. Interestingly, compound 2 preserves excellent room temperature phosphorescence (RTP) characterized for an emission lifetime of nearly 1 second.

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Publication details

The article was received on 28 Mar 2018, accepted on 05 Jul 2018 and first published on 06 Jul 2018


Article type: Paper
DOI: 10.1039/C8CE00479J
Citation: CrystEngComm, 2018, Accepted Manuscript
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    Alkaline-Earth Metal Based MOFs with Second Scale Long-Lasting Phosphor Behavior

    D. Briones, P. Leo, J. Cepeda, G. Orcajo, G. Calleja, R. Sanz, A. Rodríguez Diéguez and F. Martínez, CrystEngComm, 2018, Accepted Manuscript , DOI: 10.1039/C8CE00479J

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