Construction of coumarin-appended calix[4]arene-based fluorescence sensor for the detection of carbofuran in cabbage.

This study presents a novel approach for the detection of carbofuran (CBF) insecticide by systematically exploring a calix[4]arene-derived fluorescence probe, CouC4S, functionalized with two coumarin-labelled cystamine linkages at the narrow edge of the calix[4]arene platform. The proposed method showed a fluorescence "signal - off" effect when CBF binds with CouC4S by quenching the fluorescence intensity of CouC4S. Its limit of detection was as low as 5.55 µM according to the emission study. The working concentration range for this ligand was observed to be up to 5-65 µM. This method could be applied for the on-spot detection of CBF in real samples such as cabbage by spiking CBFvia in situ experiments, which exhibited a limit of detection of 8.823 ppm. For the further confirmation of CouC4S:CBF binding, cyclic voltammetry, differential pulse voltammetry, powder X-ray diffraction, FT-IR spectroscopy, 1H NMR titration, MALDI-TOF and computational investigations were carried out.

Turn on fluorescence strip based sensor for recognition of Sr2+ and CN- via lowerrim substituted calix[4]arene and its computational investigation.

Fluorescence sensor L designed around a calix[4]arene scaffold, bearing two fluorogenic aminoquinoline moities, has been synthesized. It is found to be selective and sensitive towards Sr2+ and CN- over a wide range of cations and anions in a spectrofluorometric study in acetonitrile. The ion-binding property of L was monitored by fluorescence spectroscopy, UV-vis spectroscopy, ESI-MS, 1H NMR, FT-IR investigation and PXRD study. The host L shows a minimum detection limit which is 1.36 nM for Sr2+ and 1.23 nM for CN- having concentration range 5-120 nM and 5-115 nM respectively. The calculated binding constants for L:Sr2+ and L: CN- are respectively 8.859 × 108 M-1 and 8.574 × 108 M-1. Our host L has been utilised in formation of a user-friendly, affordable, and disposable paper-based analytical device (PAD) for rapid chemical screening of Sr2+ and CN- ion via single strip. Moreover, the optimization of probe L has also been done by the MOPAC-2016 software package using NM7 popular method resulting -21.71 kcals/mol heat of formation and also determined the HOMO-LUMO energy band gap for L, L:Sr2+ and L: CN-. Further, molecular docking score has been calculated using HEX software. The applicability of our probe in real samples containing Sr2+ and CN- has also been checked by emission study with 94-99% recovery.

Crystal structure and Hirshfeld surface analysis of methyl 4-[(E)-2-(5-bromo-2-meth-oxy-benzyl-idene)hydrazin-yl]-3-nitro-benzoate.

The title compound, C16H14BrN3O5, is a novel halogen (Br) substituted hydrazine derivative. The hydrazine derivatives were the group of compounds with the general structure, R1R2C=NNH2 (Uppal et al., 2011 ▸), with the central RC=NNH2 moiety bridging two different groups on both sides. An all-trans configuration of the backbone (RC=NNH2) results in an extended mol-ecular conformation. The dihedral angle between the 5-bromo-2-meth-oxy-phenyl ring and the nitrophenyl ring is 4.4 (3)°. Intra-molecular N-H⋯O inter-actions form S(6) graph-set motifs, while C-H⋯O and C-H⋯N inter-actions form S(5) graph-set motifs. Symmetry-related mol-ecules are linked by C-H⋯O inter-molecular inter-actions forming an R21(10) graph-set motif. There are nearly face-to-face directional specific π-π stacking inter-actions between the centroids of the nitrophenyl ring and the benzene ring of the 5-bromo-2-meth-oxy group [centroid-centroid distance = 3.6121 (5) Šand slippage = 1.115 Å], which also contributes to the mol-ecular packing. The Hirshfeld surface analysis was performed in order to visualize, explore and qu-antify the inter-molecular inter-actions in the crystal lattice of the title compound.