Preparation of a simple biocompatible magnetite@citric acid: An efficient reusable solid acid catalyst for the rapid synthesis of antipyrine Schiff’s bases and study of their radical scavenging potential

Antipyrine based Schiff's base as a reversible fluorescence turn "off-on-off" chemosensor for sequential recognition of Al3+ and F- ions: A theoretical and experimental perspective

A Schiff's base probe (L) based on antipyrine has been intended, synthesized and assessed as a turn "off-on-off" probe for successive recognition of Al³⁺ and F^-. The probe L act out as a turn "on" fluorescence probe towards Al³⁺ in methanol at pH 6 which turned "off" by F^- at 433 nm. The 1:1 binding stoichiometry of L + Al³⁺ complex was revealed by Job's plot and approved by ESI-HRMS data. The binding constant and limit of detection of probe L for Al³⁺ were found to be 2.951 × 10⁷ M^-1 and 0.61 × 10^-7 M respectively, which is lesser than the acceptable limit (0.74 × 10^-7 M) in drinking water. The proposed binding sites and the mode of interaction of probe L was studied and validated by ¹H NMR titration and ²⁷Al NMR spectroscopic studies. To get detailed vision into binding mechanism and optimized structure of receptor L and L + Al³⁺, L + Al³⁺ + F^- complex, theoretical calculations using DFT/DND and TDDFT method were performed. Furthermore, probe L can mimic INHIBIT logic function using Al³⁺ and F^- being logic inputs and examining the fluorescence maxima at 433 nm as output.

Robust synthesis of sugar-coumarin based fluorescent 1,4-disubstituted-1,2,3-triazoles using highly efficient recyclable citrate grafted β-cyclodextrin@magnetite nano phase transfer catalyst in aqueous media

Green synthesis of 1,4-disubstituted-1,2,3-triazoles via click reaction using nano magnetic Fe₃O₄ core decorated with cyclodextrin-citric acid (Fe₃O₄@CD-CIT) acting as a phase transfer nanoreactor with low copper loading under ultrasonication at 40 °C, in aqueous media is described. Anchoring the surface of magnetite with cyclodextrin (CD) prevents its agglomeration and at the same time, CD provides a hydrophobic niche for lipophilic reactants while its outer hydrophilic core makes the reaction feasible in water yielding almost quantitative yield of desired products. Magnetic separation using an external magnet, recyclability and reuse (7 times), without appreciably affecting the %yield of the products are its other attractive attributes. Gram scale synthesis was also achieved with 93% yield.