Synthesis and Computational Studies of pyrazole-chromeno[2,3-d]pyrimidines: As a novel Hg2+ fluorescent sensor

Abstract

The synthesis of pyrazole-chromeno[2,3-d]pyrimidines through the three-component condensation reaction of salicylaldehyde, pyrazolone derivatives, and barbituric acid has been reported in the presence of Fe3O4@SiO2@Pr-SO3H under reflux conditions. Fe3O4@SiO2@Pr-SO3H as a heterogeneous magnetic catalyst is a green, effective and reusable magnetic nanoparticle, which can readily separate by an external magnet. The sensing ability of 4b was tested by adding various cations by fluorescence emission spectroscopy. It was shown outstanding Hg2+ fluorescence activity among various competing cations with a detection limit of 8.5 × 10−7 M. DFT results indicated two intramolecular O–H⋯O and C–H⋯O hydrogen bonds in the most stable configuration of the pyrazol-chromeno[2,3-d]pyrimidine. Natural bonding orbital analysis, Bader Atom in Molecule theory, and frequency analysis were employed to confirm the proposed intramolecular hydrogen bonds. The pyrazol-chromeno[2,3-d]pyrimidine complex with Hg2+ ion has two different Hg2+ coordination. The strongest interaction between ligand and metal is due to the delocalization of electrons from lone donor pairs of nitrogen and oxygen atoms to the empty LP* of transition metals as an acceptor.