Fluorescence determination of Fe(iii) in drinking water using a new fluorescence chemosensor

L-Tryptophan-based pyrene conjugate for intracellular zinc-guided excimer emission and controlled nano-assembly

This article describes intracellular zinc-induced excimer emission and tuning of self-assembly from L-tryptophan-pyrene conjugate (1). The zinc-guided excimer formation is due to the interaction of the pyrene moiety in an excited state. AFM studies show the structural modification in the supramolecular nano-assembly of 1 from dome-shaped to porous surface after complexation with zinc ions. Further, the interaction of 1 with Zn(II) ion is also studied using DFT, Job's plot, NMR titration and HRMS. The results of Zn(II) ion determination in natural water samples and RAW 264.7 cells demonstrate the practical utility of 1.

Development of Fluorescent Chemosensors for Calcium and Lead Detection

In the present work, several coumarin-3-carboxamides with different azacrown ether moieties were designed and tested as potential luminescent sensors for metal ions. The derivative containing a 1-aza-15-crown-5 as a metal chelating group was found to yield the strongest response for Ca2+ and Pb2+, exhibiting an eight- and nine-fold emission increase, respectively, while other cations induced no changes in the optical properties of the chemosensor molecule. Job's plots revealed a 1:1 binding stoichiometry, with association constants of 4.8 × 104 and 8.7 × 104 M-1, and limits of detection of 1.21 and 8.04 µM, for Ca2+ and Pb2+, respectively. Computational studies suggest the existence of a PET quenching mechanism, which is inhibited after complexation with each of these two metals. Proton NMR experiments and X-ray crystallography suggest a contribution from the carbonyl groups in the coumarin-3-carboxamide fluorophore in the coordination sphere of the metal ion.

Synthesis of a novel hydrazone-based compound applied as a fluorescence turn-on chemosensor for iron(iii) and a colorimetric sensor for copper(ii) with antimicrobial, DFT and molecular docking studies

Hydrazone-hydrazide-based linkers perform a crucial role in environmental as well as biological fields. Such linkers are employed to detect exact metal ions at a minute level; hence, numerous probes are available. Even though thiophene-based molecules have a unique position in the medicinal arena, only very few chemosensors are reported based on such a moiety. In this current work, a novel hydrazide-hydrazone-based fluorogenic molecule 5-bromo-2-hydroxy-N'-[(1E)-1-(thiophen-2-yl)ethylidene]benzohydrazide (L) has been successfully designed and synthesized. The sensing studies of L demonstrated a ratio metric as well as turn-on-enhanced fluorescence and colorimetric response toward Fe3+ and Cu2+ ions, respectively and it was observed to be insensitive toward various metal ions. The Job plots revealed that the binding stoichiometry of L and metal ions is 2 : 1. In addition, density functional theory (DFT) results strongly suggested that L can be used as a powerful colorimetric sensor for the detection of Cu2+ ions. In vitro antimicrobial activities of L were evaluated by disk diffusion and results revealed good antibacterial activities against E. coli. Further, molecular docking was executed with DNA gyrase (PDB ID: 1KZN) of E. coli and the calculated interaction energy value was found to be -7.7 kcal mol-1. Finally, molecular docking, fluorescence, colorimetry and the HOMO-LUMO energy gap of the compound can provide new insights into developing drugs and detecting metals in biomolecules.