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Luminescent Zn(II) coordination polymers as efficient fluorescent sensors for highly sensitive detection of explosive nitroaromatics

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Abstract

The hydro(solvo)thermal reactions of Zn(NO3)2·6H2O, N-(pyridin-3-yl)-4-(pyridin-4-yl)-1,8-naphthalimide (NI-bpy-34) and aromatic polycarboxylic acids afforded the corresponding zinc coordination polymers (CPs) [Zn2(1,4-bdc)(1,4-Hbdc)2(NI-bpy-34)2] (1, 1,4-H2bdc = benzene-1,4-dicarboxylic acid), [Zn2(2,6-ndc)(2,6-Hndc)2(NI-bpy-34)2]·H2O (2, 2,6-H2ndc = naphthalene-2,6-dicarboxylic acid), and [Zn(Hbtc)(NI-bpy-34)(H2O)]·H2O (3, H3btc = benzene-1,3,5-tricarboxylic acid). CP 1 features a 1D ladder structure with lateral arms which expands into a two-fold interweaved supramolecular 2D + 2D → 2D network through H-bonds. CP 2 adopts a complicated 2D thick-layer structure which expands into a 3D H-bonded (4,6)-connected net with a (4462)(44611) topology with three-fold interpenetration. CP 3 adopts a 2D grid-like (4,4)-layer structure. The three CPs all emit strong blue fluorescence in toluene suspension which is effectively turned off in the presence of a variety of electron-deficient aromatic nitro compounds. The quenching efficiencies and the Stern–Volmer quenching constants (Ksv) both indicate that 1,4-dinitrobenzene (79% quenching, Ksv = 2.11 × 103 M−1), 3-nitrophenol (95% quenching, Ksv = 1.61 × 104 M−1), and nitrobenzene (87% quenching, Ksv = 3.91 × 103 M−1) represent the highest quenching responses for CPs 1–3, respectively, for which the limits of detection were calculated to be 8.45 (1.42), 2.47 (0.34), and 5.14 (0.63) μM (ppm), respectively. Thus, CPs 1–3 can be used as promising fluorescence sensors for the highly selective and sensitive detection of aromatic nitro compounds. The mechanism of the quenching sensing of aromatic nitro compounds can mainly be explained by a photoinduced electron transfer process. On the other hand, through metal-ion exchange, the framework Zn2+ ions in CP 3 were partially substituted by Cu2+ ions by about 45% via single-crystal to single-crystal (SCSC) transformations. The resulting Cu2+-exchanged material 3-(Cu : Zn) displays decreased fluorescence emission due to paramagnetic fluorescence quenching caused by d9 configuration Cu2+ ions. Further, the exchange kinetics have been studied.

Graphical abstract: Luminescent Zn(ii) coordination polymers as efficient fluorescent sensors for highly sensitive detection of explosive nitroaromatics

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Publication details

The article was received on 14 Aug 2018, accepted on 24 Sep 2018 and first published on 24 Sep 2018


Article type: Paper
DOI: 10.1039/C8CE01371C
Citation: CrystEngComm, 2018, Advance Article
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    Luminescent Zn(II) coordination polymers as efficient fluorescent sensors for highly sensitive detection of explosive nitroaromatics

    M. Tsai, C. Li and J. Wu, CrystEngComm, 2018, Advance Article , DOI: 10.1039/C8CE01371C

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