A Zn(II) Coordination Polymer for Fluorescent Turn-Off Selective Sensing of Heavy Metal Cation and Toxic Inorganic Anions

A novel coordination polymer [Zn(atyha)2]n (1) (Hatyha = 2-(2-aminothiazole-4-yl)-2- hydroxyiminoacetic acid) was constructed by hydrothermal reaction of Zn2+ with Hatyha ligand. CP 1 exhibits a 2D (4,4)-connected topological framework with Schläfli symbol of {44·62}, where atyha- anions serve as tridentate ligands, bridging with Zn2+ through carboxylate, thiazole and oxime groups. CP 1 displays a strong ligand-based photoluminescence at 390 nm in the solid state, and remains significantly structurally stable in water. Interestingly, it can be utilized as a fluorescent probe for selective and sensitive sensing of Fe3+, Cr2O72- and MnO4- through the fluorescent turn-off effect with limit of detection (LOD) of 3.66 × 10-6, 2.38 × 10-5 and 2.94 × 10-6 M, respectively. Moreover, the efficient recyclability for detection of Fe3+ and Cr2O72- is better than that for MnO4-. The mechanisms of fluorescent quenching involve reversible overlap of UV-Vis absorption bands of the analytes (Fe3+, Cr2O72- and MnO4-) with fluorescence excitation and emission bands for CP 1, respectively.

Fast, Selective and Sensitive Fluorescence Detection of Levofloxacin, Fe3+ and Cu2+ Ions in 100% Aqueous Solution Via Their Reciprocal Recognition

The fluorescence detection of ions and pharmaceutical effluents by using organic chemosensors is a valuable surrogate to the currently existing expensive analytical methods. In this regard, the design of multi-functional chemosensors to recognize desirable guests is of utmost importance. In this study, we first show that levofloxacin (LVO) is able to use as a fluorescent chemosensor for the detection of biologically important Cu2+ (turn-off) and Fe3+ (turn-on) ions via independent signal outputs in 100% aqueous buffer solutions. Next, using the reciprocal recognition of LVO and Fe3+ provides a unique emission pattern for the detection of LVO. This approach exhibited a high specificity to LVO among various pharmaceutical samples, namely acetaminophen (AC), azithromycin (AZ), gemifloxacin (GEM) and ciprofloxacin (CIP) and also showed great anti-interference property in urine. The attractive features of this sensing system are availability, easy-to-use, high sensitivity (limit of detection = 18 nM for Cu2+, 22 nM for Fe3+ and 0.12 nM for LVO), rapid response (5 s) with an excellent selectivity.

Supramolecular Mn(III) Coordination Polymer with Treatment Activity on Diabetic Retinopathy

A new Mn(III) coordination polymer formulated as [Mn2(L)2Cl2(DMF)2]n (1, H2L is 2,2′-bipyridyl-6,6′-dicarboxylic acid; DMF is N,N′-dimethylformamide) was solvothermally prepared using Mn(ClO4)2 · 6H2O, H2L, and (CH3)4NCl as raw materials. The assay of SCXRD for 1 suggests that it features a 0D isolated dinuclear [Mn2(L)2Cl2(DMF)2] structure that exists in P-1 with triclinic system, and the cell parameters are a = 8.4593(2), b = 9.4675(5), c = 11.0147(6) Å, α = 86.023(3), β = 74.892(6), γ = 78.055(4)°, V = 833.11(7) Å3, and Z = 1. These isolated 0D dinuclear [Mn2(L)2Cl2(DMF)2] motifs were extended into a 1D supramolecular chain via the connection of intermolecular C–H…Cl together with the C–H…O H bond. Furthermore, the novel CP’s treatment activity against the diabetic retinopathy was investigated, and the associated mechanism of the new compound was discussed.

Fluorescent Eu3+/Tb3+ Metal-Organic Frameworks for Ratiometric Temperature Sensing Regulated by Ligand Energy

This work presents three series of Eu/Tb metal-organic frameworks (MOFs) containing benzophenone-4,4'-dicarboxylic acid (H₂BPNDC), 4,4'-dicarboxydiphenyl ether (H₂OBA), and terephthalic acid (H₂BDC) as the ligands. Eu/Tb MOFs have the same structural features in that their 3D frameworks are simplified as 2,3,10-connected {4².6}₂{4⁶.6¹⁸.8¹⁹.10²}{4}₂ topological networks. The solid-state fluorescence spectra of three Eu/Tb MOF series are attributed to the combined emissions of ⁵D₀ → ⁷F_J (J = 1-4) transitions in Eu³⁺ and ⁵D₄ → ⁷F_J (J = 6-5) transitions in Tb³⁺. The n_Eu:n_Tb of Eu/Tb MOFs is optimized as 1:69 based on the relationships between I_Tb(545)/I_Eu(614) and n_Eu:n_Tb; that is, Eu_0.0143Tb_0.9857-L (L = BPNDC^2-, OBA^2-, and BDC^2-) were selected to carry out the following temperature (T)-sensing tests. The fluorescence mechanism of Eu_0.0143Tb_0.9857-L can be explained by a ligand-to-metal charge transfer combined with an intermetallic Tb³⁺ → Eu³⁺ energy transfer. The T-dependent fluorescence indicates linear relationships with sensitivities of 1.85% K^-1 for Eu_0.0143Tb_0.9857-BPNDC, 6.49% K^-1 for Eu_0.0143Tb_0.9857-OBA, and 0.28% K^-1 for Eu_0.0143Tb_0.9857-BDC. The influence of T on the lowest excited triplet energy levels (T1 values) of the ligands reveals that the ligand energy regulation impacts their fluorescence properties, including the sensitivity, fluorescence quenching rate, quantum yield, and fluorescence lifetime. This shows that Eu_0.0143Tb_0.9857-BPNDC is sufficiently sensitive to T, making it applicable in noncontact T measurements.