Highly selective luminescent sensing of xylene isomers by a water stable Zn-organic framework

Chlorine Dioxide: Friend or Foe for Cell Biomolecules? A Chemical Approach

This review examines the role of chlorine dioxide (ClO₂) on inorganic compounds and cell biomolecules. As a disinfectant also present in drinking water, ClO₂ helps to destroy bacteria, viruses, and some parasites. The Environmental Protection Agency EPA regulates the maximum concentration of chlorine dioxide in drinking water to be no more than 0.8 ppm. In any case, human consumption must be strictly regulated since, given its highly reactive nature, it can react with and oxidize many of the inorganic compounds found in natural waters. Simultaneously, chlorine dioxide reacts with natural organic matter in water, including humic and fulvic acids, forming oxidized organic compounds such as aldehydes and carboxylic acids, and rapidly oxidizes phenolic compounds, amines, amino acids, peptides, and proteins, as well as the nicotinamide adenine dinucleotide NADH, responsible for electron and proton exchange and energy production in all cells. The influence of ClO₂ on biomolecules is derived from its interference with redox processes, modifying the electrochemical balances in mitochondrial and cell membranes. This discourages its use on an individual basis and without specialized monitoring by health professionals.

Syntheses, crystal structures and Hirshfeld surface analysis of (Z)-3-[(3-acetyl-2-hydroxyphenyl)amino]-2-bromoprop-2-enal and a novel ZnII complex

A novel zero-dimensional dinuclear zinc complex, di-μ-acetato-1:2κ4 O:O′-(μ-2-acetyl-6-{[(Z)-2-bromo-3-oxoprop-1-en-1-yl]azanidyl}phenolato-1κ2 O 1,O 2:2κ3 O 1,N,O 6)(N,N-dimethylacetamide-1κO)dizinc(II), [Zn2(C11H8BrNO3)(CH3COO)2(C4H9NO)] or [Zn2(L)(CH3COO)2(DMA)], 1, was synthesized using (Z)-3-[(3-acetyl-2-hydroxyphenyl)amino]-2-bromoprop-2-enal (H2 L), which was synthesized from 1-(3-amino-2-hydroxyphenyl)ethanone and 2-bromomalonaldehyde. H2 L and 1 were characterized by single-crystal X-ray diffraction, FT–IR spectroscopy and elemental analysis. Theoretical calculations of the bond orders and excited state of H2 L confirmed that there is extensive electron delocalization in the H2 L molecules. Single-crystal X-ray diffraction shows that the two Zn atoms are pentacoordinated in distorted trigonal bipyramidal configurations in the crystals of 1. The thermogravimetric analysis of 1 shows that the main frame of the complex remains stable to about 190 °C. Powder X-ray diffraction (PXRD) analysis shows that 1 possesses high purity and acid and alkali resistance. The intermolecular interactions of H2 L and 1 were analyzed using Hirshfeld surface analysis and the results indicate that the H...H and O...H interactions of H2 L and 1 play a considerable role in stabilizing the self-assembly process.

Efficient chemosensors for toxic pollutants based on photoluminescent Zn(ii) and Cd(ii) metal-organic networks

Optical sensors with high sensitivity and selectivity, as important analytical tools for chemical and environmental research, can be realized by straightforward synthesis of luminescent one-, two- and three-dimensional Zn(ii) and Cd(ii) crystalline coordination arrays (CPs and MOFs). In these materials with emission centers typically based on charge transfer and intraligand emissions, the quantitative detection of specific analytes, as pesticides or anions, is probed by monitoring real-time changes in their photoluminescence and color emission properties. Pesticides/herbicides have extensive uses in agriculture and household applications. Also, a large amount of metal salts of cyanide is widely used in several industrial processes such as mining and plastic manufacturing. Acute or chronic exposure to these compounds can produce high levels of toxicity in humans, animals and plants. Due to environmental concerns associated with the accumulation of these noxious species in food products and water supplies, there is an urgent and growing need to develop direct, fast, accurate and low-cost sensing methodologies. In this critical frontier, we discuss the effective strategies, chemical stability, luminescence properties, sensitivity and selectivity of recently developed hybrid Zn(ii)/Cd(ii)-organic materials with analytical applications in the direct sensing of pesticides, herbicides and cyanide ions in the aqueous phase and organic solvents.

Exploration of reaction rates of chlorine dioxide with tryptophan residue in oligopeptides and proteins

Chlorine dioxide (ClO₂), an alternative disinfectant to chlorine, has a superior ability to inactivate microorganisms, in which protein damage has been considered as the main inactivation mechanism. However, the reactivity of ClO₂ with amino acid residues in oligopeptides and proteins remains poorly investigated. In this research, we studied the reaction rate constants of ClO₂ with tryptophan residues in five heptapeptides and four proteins using stopped-flow or competition kinetic method. Each heptapeptide and protein contain only one tryptophan residue and the reactivity of tryptophan residue with ClO₂ was lower than that of free tryptophan (3.88 × 10⁴ (mol/L)^-1sec^-1 at pH 7.0). The neighboring amino acid residues affected the reaction rates through promoting inter-peptide aggregation, changing electron density, shifting pK_a values or inducing electron transfer via redox reactions. A single amino acid residue difference in oligopeptides can make the reaction rate constants differ by over 60% (e.g. 3.01 × 10⁴ (mol/L)^-1sec^-1 for DDDWNDD and 1.85 × 10⁴ (mol/L)^-1sec^-1 for DDDWDDD at pH 7.0 (D: aspartic acid, W: tryptophan, N: asparagine)). The reaction rates of tryptophan-containing oligopeptides were also highly pH-dependent with higher reactivity for deprotonated tryptophan than the neutral specie. Tryptophan residues in proteins spanned a 4-fold range reactivity toward ClO₂ (i.e. 0.84 × 10⁴ (mol/L)^-1sec^-1 for ribonuclease T1 and 3.21 × 10⁴ (mol/L)^-1sec^-1 for melittin at pH 7.0) with accessibility to the oxidant as the determinating factor. The local environment surrounding the tryptophan residue in proteins can also accelerate the reaction rates by increasing the electron density of the indole ring of tryptophan or inhibit the reaction rates by inducing electron transfer reactions. The results are of significance in advancing understanding of ClO₂ oxidative reactions with proteins and microbial inactivation mechanisms.

Structure of a Luminescent MOF-2 Derivative with a Core of Zn(II)-Terephthalate-Isoquinoline and Its Application in Sensing of Xylenes

A new blue photoluminescent 2D metal–organic framework, 1, with formula {[Zn2(μ2-BDC)2(iQ)2]}∞ has been synthesized in a high yield under solvothermal conditions by reacting Zn(II) ions with 1,4-benzenedicarboxylic acid (H2BDC) and isoquinoline (iQ) in DMF. Compound 1 was thoroughly characterized by single-crystal X-ray diffraction, solid-state cross-polarization magic-angle spinning 13C NMR, X-ray powder diffraction, scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), and thermoanalysis. The crystal structure of 1 showed interpenetrated 2D frameworks consisting of dinuclear paddle-wheel cores Zn2; moreover, this material possessed thermostability up to 310 °C. The CPMAS 13C-NMR spectrum of 1 is consistent with the symmetry of the crystal structure. Luminescence studies showed that 1 strongly enhances its fluorescence emission in the presence of xylene isomers with a pronounced selectivity to p-xylene.

Array-based detection of isomeric and analogous analytes employing synthetically modified fluorophore attached β-cyclodextrin derivatives

Improved selectivity and sensitivity using covalent fluorophore–cyclodextrin analogues resulted in 100% successful classification for five classes of analytes.