Preparation of Fe3O4-Cys-Cu magnetic nanocatalyst for expedient synthesis of tripodal C3 symmetric chromofluorogenic receptor for sensing of fluoride ion selectively: An experimental and computational slant

Abstract

In this paper, an ecofriendly nanocatalyst (Fe3O4-Cys-Cu) was synthesized by the coordinating copper ions to the l-cysteine functionalized magnetic nanoparticles. The prepared nanocatalyst was characterized by XRD, HRTEM, EDS-SEM, FT-IR, TGA, and DTA techniques. Afterward, the catalytic activity of this magnetic nanocatalyst was explored for the one-pot synthesis of a series of tripodal triazoles (7a-d) as an important class of sensors in the field of sensing and biosensing. This magnetically nanocatalytic methodology is advantageous in terms of high yield of the products, use of non-conventional microwaves, green solvent, reduction of reaction time, low catalyst dosage, and recyclability of catalyst up to six cycles. Further, synthesized triazole 7b was then evaluated as a selective chromofluorogenic receptor for the recognition of duplicitous fluoride ions in DMSO. Receptor upon addition of F− ion shows colorimetric response by displaying naked-eye color change from pale yellow to shiny green with a redshift in the UV–vis spectra and fluorescent green under UV lamp. The 1:3 binding stoichiometry of receptor-fluoride ion was determined by Job's plot and further verified by ESI-HRMS data. 1H NMR and 19F NMR validate the binding of the receptor with F− ion by hydrogen bonding with subsequent deprotonation, and further, theoretical calculations using density functional theory confirm the presence of the same.