A twofold interpenetrated two-dimensional zinc(II) coordination polymer for the highly sensitive detection of nitrofurantoin in aqueous medium

A novel ZnII coordination polymer, namely, poly[{μ2-bis[4-(2-methyl-1H-imidazol-1-yl)phenyl]methanone-κ2N3:N3'}(μ2-5-bromobenzene-1,3-dicarboxylato-κ2O1:O3)zinc(II)], [Zn(C8H3BrO4)(C21H18N4O)]n or [Zn(Br-BDC)(MIPMO)]n, (I), has been synthesized by the solvothermal method using 5-bromoisophthalic acid (Br-H2BDC), bis[4-(2-methyl-1H-imidazol-1-yl)phenyl]methanone (MIPMO) and Zn(NO3)2·6H2O. Structure analysis showed that compound (I) displays twofold parallel interwoven sql nets. Fluorescence experiments confirmed that the compound can sensitively and selectively detect nitrofurantoin (NFT) in aqueous medium. In addition, the possible fluorescence quenching mechanisms of compound (I) toward NFT are investigated.

Chiral Sensing of Tryptophan Enantiomers Based on the Enzyme Mimics of β-Cyclodextrin-Modified Sulfur Quantum Dots

Chiral recognition of amino acid plays a significant role in pharmaceutical, medical, and food science. This study describes a chiral sensing system of β-cyclodextrin (β-CD)-coated sulfur quantum dots (CD-SQDs) for the selective fluorescence recognition of tryptophan (Trp) enantiomers. CD-SQDs were prepared by a facile assembly fission method and could selectively recognize L-Trp by the different binding ability between L/D-Trp and β-CD. The inclusion of L-Trp and the stereoselective catalysis of CD-SQDs enzyme mimics cause the increased fluorescence intensity of CD-SQDs, which has a linear response ranging from 10 to 500 nM and the detection limit as 2.3 nM. CD-SQDs also show great selectivity for L-Trp from the commercial compound amino acid injection. The study could provide an effective method for the chiral recognition of amino acid enantiomers based on the catalytic activity of nanoenzymes.

Study on Fluorescence Recognition of Fe(3+), Cr(2)O(7)(2-) and p-Nitrophenol by a Cadmium Complex and Related Mechanism

The effective detection of environmental pollutants is very important to the sustainable development of human health and the environment. A luminescent Cd(II) coordination complex, {[Cd(dbtdb)(1,2,4-H₃btc)]·0.5H₂O}_n (1) (dbtdb = 1-(2,3,5,6-tetramethyl-4-((2-(thiazol-4-yl)-2H-benzo[d]imidazol-3(3aH)-yl)methyl)benzyl)-2,7a-dihydro-2-(thiazol-4-yl)-1H-benzo[d]imidazole, 1,2,4-H₃btc = 1,2,4-benzenetricarboxylic acid), was obtained by hydrothermal reactions. Complex 1 has a chain structure decorated with uncoordinated Lewis basic O and S donors and provides good sensing of Fe³⁺, Cr₂O₇^2-, and p-nitrophenol with fluorescence quenching through an energy transfer process. The calculated binding constants were 3.3 × 10³ mol^-1 for Fe³⁺, 2.36 × 10⁴ mol^-1 for Cr₂O₇^2-, and 9.3 × 10³ mol^-1 for p-nitrophenol, respectively. These results show that 1 is a rare multiresponsive sensory material for efficient detection of Fe³⁺, Cr₂O₇^2-, and p-nitrophenol.

A new two-dimensional cadmium(II) coordination polymer based on Cd6(CHADC)6 clusters (H2CHADC is cyclohexane-1,2-dicarboxylic acid): synthesis, structure and properties

The highly effective recognition and detection of metal ions and anions in water has attracted much attention with respect to environmental safety. Herein, a novel Cd-based coordination polymer, poly[[4,4'-bis(2-methylimidazol-1-yl)biphenyl]bis(cyclohexane-1,2-dicarboxylato)dicadmium(II)], [Cd₂(C₈H₁₀O₄)₂(C₂₀H₁₈N₄)]_n or [Cd(CHADC)(4,4'-BMIBP)_0.5]_n, (I), has been synthesized employing cis-cyclohexane-1,2-dicarboxylic acid (H₂CHADC) and 4,4'-bis(2-methyl-1H-imidazol-1-yl)biphenyl (4,4'-BMIBP). Single-crystal X-ray analysis reveals that (I) presents a 6-connected hxl two-dimensional layer based on Cd₆(CHADC)₆ clusters with the point symbol (3⁶·4⁶·5³). Furthermore, (I) has been characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis and fluorescence spectroscopy, and exhibits good stability and excellent photoluminescence properties. Coordination polymer (I) was chosen as a fluorescent probe to sense different target analytes and shows an obvious selective recognition response to Fe³⁺ cations and Cr₂O₇^2-/CrO₄^2- anions through luminescence-quenching effects in aqueous solution. The sensing mechanism was investigated and showed that the detection mechanism was resonance energy transfer between (I) and the Fe³⁺, Cr₂O₇^2- and CrO₄^2- ions.