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A novel fluorescent material that can change its emission properties in response to different external stimuli holds significant importance for the development of sensors, information storage, and encryption materials. In this work, we designed and synthesized two zinc(II) coordination compounds, [Zn(HL)I2]·CH3OH (1) and [Zn(HL)Br2]·CH3OH (2), which exhibit remarkable changes in their emission properties under three different external stimuli. The two compounds were prepared using a simple one-pot method by reacting zinc(II) salts with 4-(N,N-diphenylamino)benzaldehyde and 3-amino-2-pyridinone. Under the stimulation of NH3 vapor, both compounds underwent decomposition, leading to a transformation of their fluorescence from yellow to blue, exhibiting a significant blue-shift of more than 170 nm. After exposure to HCl vapor, the fluorescence color of the two original compounds changed from yellow to red, and the color change could be easily distinguished by the naked eye under UV light irradiation. Then after fumigation with NH3 vapor, the color of both samples changed from red to blue. Based on the high-contrast NH3-responsive properties and HCl-responsive properties, we designed and developed test papers capable of detecting HCl vapor and NH3 vapor. Furthermore, due to the transformation from the crystalline state to the amorphous state during grinding, the two compounds also demonstrated high-contrast mechanochromic luminescence properties. After grinding, the color of the two compounds changes significantly from yellow to orange. [ABSTRACT FROM AUTHOR]

Four new Zn(II) metal–organic frameworks (MOFs): {[Zn(L1)(BTEC)0.5]·3.1H2O}n (1), {[Zn(L2)0.5(BTEC)0.5]·1.5H2O}n (2), {[Zn2(L3)(BTEC)(H2O)]·H2O}n (3), and {[Zn2(L4)(BTEC)]·H2O}n (4) were constructed by selecting N-containing linkers with the Zn(II)/H4BTEC system (H4BTEC = 1,2,4,5-benzenetetracarboxylic acid, L1 = 1,4-bis(1-(pyridin-4-ylmethyl)-1H-benzo[d]imidazol-2-yl)cyclohexane, L2 = 1,4-bis(1-(pyridin-4-ylmethyl)-1H-benzo[d]imidazol-2-yl)butane, L3 = 1,5-bis(1-(pyridin-4-ylmethyl)-1H-benzo[d]imidazol-2-yl)pentane, L4 = 1,4-bis(1-(pyridin-4-ylmethyl)-1H-benzo[d]imidazol-2-yl)methyl)benzene). Structural analyses indicate that 1 exhibits a (3,4)-connected 2D 3,4L13 sheet. 2 manifests a rare (4,4,4)-connected 2D 4,4,4L10 layer. 3 displays an unprecedented (3,3,4,4,4)-connected 3D network based on the point symbol {4·82}2{42·6·83}2{42·6}2{42·82·102}{84·122} and 4 presents an unusual 4,4,4,6,6T3 3D network with a 5-node (4,4,4,6,6)-connected network. The structural variety of these Zn(II) MOFs demonstrates that different N-containing ligands can induce the BTEC4− linkers exhibiting various coordination modes, exerting a great influence on the final MOF frameworks. Further, MOFs 1–4 are favorable dual-functional fluorescent sensors for the detection of Fe3+/acetylacetone with high sensitivity and selectivity. To our knowledge, this is the first report of fluorescent MOFs based on L1–L4 ligands for the detection of Fe3+ and acac in the naked eye range. [ABSTRACT FROM AUTHOR]

Three water-stable 2D cadmium(II)-coordination polymers (CPs), namely {[Cd(MIP)](L)·1.35H2O}n (1), [Cd(NTP)(L)]n (2) and [Cd(1,4-NDC)(L)]n (3) (L = 1,3-bis(5,6-dimethylbenzimidazol-1-yl)propane, H2MIP = 5-methylisophthalic acid, H2NTP = 2-nitroterephthalic acid and 1,4-H2NDC = 1,4-naphthalenedicarboxylic acid), were synthesized and characterized. 1 exhibits a 3,4L83 framework, 2 is a 3,5L2 network and 3 exhibits a rare 3,4-connected 3,4L27 network. 1 and 3 are dual-function luminescence sensors for sensing Cr2O72− (pH = 3.0)/CrO42− (pH = 13.0) in aqueous solution with high sensitivity, selectivity and excellent recyclable behaviors. [ABSTRACT FROM AUTHOR]

Five new CdII-based ternary metal–organic frameworks (MOFs) constructed from structurally related ligands, namely, [Cd(L1)(DCTP)]n (1), [Cd2(L2)2(DCTP)2]n (2), {[Cd2(L3)(DCTP)2]·3.75H2O}n (3), {[Cd(L4)(DCTP)]·0.85H2O}n (4) and [Cd0.5(L5)0.5(DCTP)0.5]n (5) (H2DCTP = 2,5-dichloroterephthalic acid, L1 = 1,4-di(1H-benzo[d]imidazol-2-yl)butane, L2 = 1,5-di(1H-benzo[d]imidazol-2-yl)pentane, L3 = 1,3-bis(1-(pyridin-4-ylmethyl)-1H-benzo[d]imidazol-2-yl)propane, L4 = 1,4-bis(1-(pyridin-4-ylmethyl)-1H-benzo[d]imidazol-2-yl)butane and L5 = 1,6-bis(1-(pyridin-4-ylmethyl)-1H-benzo[d]imidazol-2-yl)hexane), have been hydrothermally synthesized and characterized. While 1 and 5 show the common 2D hcb and 3D sqc6 topologies, respectively, 2 exhibits a rare (4,4)-connected 2-node 2D 4,4L62 network, 3 reveals an unprecedented 3D (3,3,4,5)-connected framework with the point symbol {4·92}2{42·82·92}{42·84·93·10}2{93}2 and 4 presents an unusual (3,5)-connected 3D gra topological framework. The results show that the coordination mode of dicarboxylate ligands and the auxiliary N-containing linkers have a crucial impact on the structural diversities of ternary Cd-MOFs. Further, 2 and 3 are favorable dual-functional fluorescent sensors for the detection of Fe3+/acetylacetone and Cr2O72− (pH = 4)/acetylacetone, respectively, with high sensitivity and selectivity. [ABSTRACT FROM AUTHOR]

Two new Cd2+ coordination polymers (CPs), namely {[Cd(L)(1,4-PDA)]·0.7(C2H5OH)}n (1) and {[Cd(L)0.5(1,8-NDC)·H2O]}n (2) [L = 1,4-bis(5,6-dimethybenzimidazol-1-yl)-2-butene, 1,4-H2PDA = 1.4-phenylenediacetic acid, 1,8-H2NDC = 1,8-naphthalenedicarboxylic acid], were hydrothermally synthesized and characterized. 1 is a (4,4)-layered structure and further extended into a 3D supramolecular network via π–π stacking interactions. 2 features a 2D (3,4)-connected 3,4L83 framework. 1 and 2 can act as luminescence sensors for detecting acetylacetone (acac) and Fe3+ with high sensitivity, selectivity and recyclability. This is the first dual fluorosensors employing CPs for the detection of Fe3+ and acac. The mechanism for the luminescent sensing of acac and Fe3+ was suggested. [ABSTRACT FROM AUTHOR]

The development of stimulus-responsive luminescent materials, especially those based on a single compound exhibiting multicolor and high-contrast (Δλem ≥ 100 nm) chromic properties, is a critical challenge. In this work, we synthesized and characterized a zinc(II) complex (1). As expected, 1 displays aggregation-induced emission enhancement (AIEE) in THF/H2O mixtures, and remarkable multicolor switching under external stimuli in the solid state. Complex 1 shows reversible mechanochromic luminescence behavior with a large wavelength shift (Δλem = 100 nm) during the grinding–fuming cycles, due to the phase transformation between the crystalline and amorphous states. More impressively, 1 exhibits obvious acidochromic properties (Δλem = 130 nm) which originate from the adsorption of vapor and a gas–solid reaction on the crystal surface. Furthermore, 1 exhibits electrochemical oxidation behavior accompanied by quenching of yellow-green emission due to the overlap of an emission band and an absorption band. The above-mentioned color changes under ambient light can also be observed by the naked eye during the mechanical, acid–base vapor and electrical stimulation. Based on the high-contrast and multicolor switching, complex 1 was successfully developed into test papers and films in the field of rapid detection of mechanical stimuli and HCl/NH3 vapors. [ABSTRACT FROM AUTHOR]

Selective detection of antibiotics and MnO4− is crucial for human health improvement and protecting the environment. Two stable Zn(II)-based metal–organic frameworks (MOFs) {[Zn6(L1)2(NDC)5(μ2-OH)2]·0.5H2O}n (1), and {[Zn(L2)(NDC)]·2H2O}n (2) (H2NDC = 1,4-naphthalenedicarboxylic acid, L1 = 1,5-bis(1-(pyridine-4-ylmethyl)-1H-benzo[d]imidazol-2-yl)pentane, L2 = 1,6-bis(1-(pyridine-4-ylmethyl)-1H-benzo[d]imidazol-2-yl)hexane) were successfully synthesized by adopting the mixed ligands approach. 1 is a rare 3D 3,5,6T23 framework based polynuclear complex group. 2 possesses a 2D sql layer. The two MOFs exhibit excellent chemical and thermal stability. The title compounds are promising dual-functional fluorescent sensors for detecting enrofloxacin/MnO4− anions with high selectivity and sensitivity (Ksv values toward enrofloxacin: 4.29 × 106 L mol−1 for 1 and 4.59 × 106 L mol−1 for 2 and toward MnO4−: 1.05 × 104 for 1, 5.48 × 103 L mol−1 for 2, respectively), which are the first observations of fluorescent MOFs for the sensing of enrofloxacin and MnO4− anions. [ABSTRACT FROM AUTHOR]