Anil Kuwar

A newly designed receptor 2‐((E)‐(6‐(diethylamino)‐2‐methylpyridin‐3‐ylimino) methyl)phenol ( DMP ) behaves as a highly selective ratiometric fluorescent receptor for Fe ³⁺ in acetonitrile solvent. Probe DMP showed a detectable color change from yellow to light pink with a blue‐shift with addition of Fe ³⁺ in the absorption spectra. A decrease in fluorescence at 424 nm and a red‐shift to 457 nm with a substantial fluorescence enhancement in the presence of Fe ³⁺ indicated the formation of DMP.Fe ³⁺ complex. The binding constant ( K _a ) for a 2:1 stoichiometry was found to be 3.33 × 10 ⁴ M ⁻¹ with a detection limit of 7.739 nM. Theoretical calculations were studied to establish the configurations of DMP.Fe ³⁺ complex, which supported the observed fluorescence turn‐on phenomenon. DMP was found to be efficient in detecting Fe ³⁺ in vitro and has high applicability in lung cancer (A549) cell imaging.

The hydrazine derivatives are known to possess several biological activities including anticancer, antibacterial and anti-fungal, anticonvulsant, and antioxidant. This communication presents the synthesis, X-ray crystal structure analysis, DFT calculations, cell cytotoxicity, and antioxidant activity of the Schiff base 4,4′-((1E,1′E)-hydrazine-1,2-diylidenebis(ethan-1-yl-1-ylidene))bis(benzene-1,3-diol) (compound 2). We have also isolated the side product compound 1 and characterized it using single X-ray crystallography. The crystal structure of compound 1 depicts that the ensuing C–H···N hydrogen bonding interaction is presented and discussed herein. In addition, the calculations using density functional theory (DFT) approximation supported by experimental ¹H and ¹³C NMR studies on the key compound 2 are reported. The results of theoretical and experimental ¹H and ¹³C NMR were concordant. The antioxidant activity of compound 2 was determined by using 2,2′-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS^•+) radical cation assays and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical assay. Compound 2 demonstrated excellent antioxidant activity in ABTS assay (IC₅₀ = 4.30 ± 0.21 µM) and DPPH assay (IC₅₀ = 81.06 ± 0.72 µM) with almost no cytotoxicity below 25 µM.

Herein, a Schiff base ligand FHE was synthesized by condensing 5-allyl-2-hydroxy-3-methoxybenzaldehyde, a eugenol derivative, with the derivative furan-2-carbohydrazide. FHE alone showed low fluorescence signals due to intramolecular charge transfer (ICT). FHE showed highly specific FHE–Zn²⁺ complex formation (K_a = 1.1 × 10⁴ M⁻¹) upon titration with Zn²⁺ ions in HEPES buffer (pH = 7.4, 50% ACN, v/v), which resulted in the disruption of ICT followed by a chelation enhanced fluorescence (CHEF) effect. The complexation of FHE with Zn²⁺ demonstrated a large Stokes shift (Δλ = 198 nm, λ_ex = 305 nm, λ_em = 503 nm) with a 20-fold increase in the quantum yield (FHE, Φ = 0.016; FHE–Zn²⁺ complex, Φ = 0.34). Notably, with the LOD of 12.7 nM for detecting Zn²⁺ ions with green fluorescence and no interference from potentially competing cations and anions, FHE showed high biocompatibility. FHE was successfully used for the nanomolar detection of intracellular Zn²⁺ ions, indicating its live-cell-imaging applicability. Furthermore, FHE also showed promising results in the detection of Zn²⁺ in environmental samples. These results validate the potential applicability of FHE for detecting Zn²⁺ in living cells and in environmental samples such as river water and tap water.

Benzimidazole-based compound 2-(p-tolyl)-1H-benzo[d]imidazole (3) and its derivative probe A-B have been synthesized for the highly selective detection and quantification of Cys in human serum. The photophysical properties of A-B and compound 3 were evaluated by UV-vis absorption and fluorescence spectroscopy. A-B showed high selectivity and sensitivity for Cys among tested analytes, including amino acids, anions, and cations. A-B selectively reacts with Cys and results in compound 3 with fluorescence turn-on effect. A-B did not show any interference from the components in the serum matrix for Cys detection in the human serum sample. A-B detects Cys in serum samples with 2.3–5.4-fold better LOD than reported methods. The detection limit of 86 nM and 43 nM in HEPES buffer using UV-visible and fluorescence spectroscopy, respectively, makes A-B an excellent chemosensor for Cys detection.

Correction for ‘The detection of Al³⁺ and Cu²⁺ ions using isonicotinohydrazide-based chemosensors and their application to live-cell imaging’ by In-ho Song et al., Mater. Adv., 2021, DOI: 10.1039/d1ma00564b.

The quick response, easy-synthesis, and high sensitivity make receptor 3 an ideal sensor for detecting Al³⁺ ions in a semi-aqueous medium and living cells.

Hybrid nanoassembly, fluorescent chemosensors, selective response to ketoprofen, and nanomolar detection.

Fluorescence methods have gained enormous attention due to their ease in use, simplicity, selectivity and sensitivity. Fluo-rescent chemosensors respond instantly by converting molecular recognition to fluorescent signals. The consumption of pharmaceutical products by living beings is on great increase. The disposal of such compounds in the environment is a mat-ter of great concern as these compounds enter aquatic environment and are showing accumulation in tissues of aquatic or-ganisms. In the present study, we have utilized naphthalimide based receptors to fabricate organic nanoparticles. These ONPs were used as a platform for the development of hybrid nanoassemblies and the developed nanoassemblies were characterized using TEM and DLS studies. The recognition studies were performed and the hybrid assembly developed using receptor 2 demonstrated turn-on fluorescence emission response on binding with Amitriptyline. The present sensing system acted as promising candidate for determination of Amitriptyline among other competing drug molecules. The established a sensor that can detect amitriptyline up to a detection limit of 48 nM in aqueous medium using photoluminescence method. Electrochemical recognition studies show binding of nanoassenblies of receptor 2 with Amitriptyline with a detection limit of 21 nM.

Fabrication of near infrared (NIR) and ratiometric chemosensors is very challenging task in supramolecular chemistry. For apprehension of such sensor, in the present manuscript, a thiourea derivative of rhodamine 1 is synthesized and characterized using ¹H, ¹³C NMR and mass spectrometry. Further organic nanoparticles (N1) are fabricated from receptor 1 by reprecipitation method. Upon interaction of N1 with K(I) ion, a new peak appeared at 678 nm with concomitant decrease of peak at 555 nm and thus it acted as ratiometric and NIR fluorescent probe; whereas with other metal ions there is no such appearance of peak. The binding of K(I) ion with N1 was confirmed with titrations with lowest detection limit of 36.86 nM. Further the applicability of N1 for K(I) ion was checked on real biological samples.