Molecular recognition of anions or neutral molecules in water by artificial probes remains a challenging yet vibrant area in supramolecular chemistry. Herein, we report a novel colorimetric probe based on a phenolphthalein scaffold. This probe exhibits excellent sensitivity toward acetate and various organic solvents in pure water, with a distinct colorimetric response. UV–vis titration experiments revealed a high binding affinity for acetate ( β 2 ≈ 3.3 × 10 6 (mol/L) −2 ) and weaker affinities for solvents (0.1–1159 (mol/L) −2 ). Notably, a correlation between solvent binding strength and lipophilicity (log P) is observed for the first time for solvents with negative log P, the affinity increases as lipophilicity decreases. Mechanistic studies suggest a hydrogen bond-induced proton transfer process, wherein an intramolecular O···H–N hydrogen bond and the tautomeric properties of the phenolphthalein moiety play key roles. This work introduces a new design strategy for artificial probes capable of rapid and selective detection of both charged and neutral species in aqueous media.
The 3, 4, 9, 10-perylene tetracarboxylic acid (PTCA) functionalized MoS2 nanocomposite (PTCA-MoS2) was synthesized via the hydrothermal method, and its structural and catalytic properties were investigated. The results demonstrated that PTCA-MoS2 exhibits enhanced peroxidase-mimicking activity and efficiently catalyzes the reaction of H2O2 oxidizing 3, 3′, 5, 5′- tetramethyl benzidine (TMB). Notably, owing to the synergistic interaction between PTCA and MoS2, the incorporation of PTCA significantly enhances the peroxidase-mimicking activity of MoS2. The experimental conditions were optimized, and the peroxidase-mimicking activity of PTCA-MoS2 followed Michaelis-Menten kinetics. Additionally, fluorescent probe experiments confirmed that hydroxyl radicals (·OH) play a crucial role in the catalytic reaction process. Based on these findings, a facile colorimetric sensing platform was established for the detection of glucose and H2O2, achieving low limits of detection (LODs) of 0.61 μM and 0.47 μM, respectively.
Herein, we demonstrate that chloride, triflate, and tetrafluoroborate salts of an N-methyl benzoselenadiazolium cation catalyze bromination of activated aromatic substrates with N-bromosuccinimide (NBS). Departing from the common strategy of employing the heaviest chalcogen, tellurium, with weakly coordinating counteranions in catalyst design, our chloride-bearing catalyst instead affords better catalytic performance than the other investigated salts. At ambient temperature, a quantitative yield of 4-bromoanisole was obtained within 3 h and >90% conversion of 9,10-dibromoanthracene was achieved within minutes. Crystal structures of the chloride salt obtained from mixing with NBS reveal bromide and polybromide anions, and DFT analysis of the optimized catalyst•NBS adduct suggest that chalcogen bonds mediate NBS carbonyl activation while chloride stabilizes the electrophilic bromine derived from NBS via a halogen-bond Br … Cl − motif. Our results highlight that in chalcogen bond catalysis, the nature of the counteranion can override simple σ-hole strength considerations and must be regarded as an integral contributor to NBS activation rather than a passive spectator.
In this work, new nanocomposites with a Bentonite clay (Bt-Na+) and different amounts of poly (1-naphthylamine) (PNA) were synthesised by in situ chemical polymerisation. The structural characteristics of the obtained materials were analysed utilising characterisation such as XRD, XPS, SEM, UV-Vis, fluorescence, FTIR and TGA, and the results confirmed the creation of nanocomposites. Furthermore, the antimicrobial efficacy of the synthesized nanocomposites was evaluated against (Bacillus subtilis, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans). The observed inhibition values ranged from 0 to 24 mm depending on the polymer and the strain tested. The inhibition zones for all yeast and bacterias increased as the concentrations of PNA. All results demonstrated that PNA@Bt-Na+ nanocomposites show great promise for applications in research and technology related to the development of antimicrobial materials.
A simple, rapid, selective, precise, and accurate spectrophotometric method was developed for the determination of cephalexin in dosage form and pharmaceutical formulations. This analytical technique is based on condensation reaction of amino group of cephalexin with 2,4-dimethylbenzaldehyde using sulfuric acid. Yellow Schiff base complex will be formed in this experiment. The highest absorbance was obtained at 397 nm for the Schiff base complex. The Beer-Lambert Law was obeyed at 5-45 & micro;g mL-1 concentrations, with R2 value being 0.993. Molar absorptivity of the product was estimated to be 3.5 & times; 103 L mol-1 cm-1. Experimental conditions such as reagents concentration, volume, and temperature, which affect the reaction, have been examined and optimized. Limit of detection and limit of quantitation were found to be 1.026 and 3.42 & micro;g mL-1, respectively. The proposed method demonstrated satisfactory reproducibility, with relative standard deviation of 7.46% (n = 5). Potential interference from commonly used excipients present in commercial formulations was evaluated and found to be negligible. The greenness of the proposed method was confirmed using Eco-scale, AGREE, and BAGI metrics, demonstrating its environmental sustainability, and method validation was performed through statistical analysis and recovery studies, and the procedure was successfully applied to the quantification of cephalexin in dosage forms and pharmaceutical preparations. The percentage recoveries ranged from 93.80% to 98.34% for dosage forms and from 97.00% to 106.83% for pharmaceutical formulations.
