A new Fe3+ colorimetric sensor: Nitrophenyl bispyrazole derivative synthesis using Fe3O4@SiO2@Si-Pr-NH-(CH2)2-NH2 and its DFT study

The efficient synthesis of bispyrazole derivatives was reported in the presence of Fe3O4@SiO2@Si-Pr-NH-(CH2)2NH2 as a nanomagnetic catalyst in solvent-free conditions. The UV-Vis spectroscopy study of 4,4'-((3-nitrophenyl)methylene)bis(3-methyl-1H-pyrazol-5-ol) derivative 6a was demonstrated that it could be used as a Fe3+ ion colorimetric chemosensor, which was shown an apparent color change from white to orange with high selectivity toward the addition of Fe3+ ion in CH3CN/H2O (1:9 v/v) as a solvent. The UV-Vis absorption was increased linearly, and its detection limit was calculated 2.19 x 10-6 M. The orientations of hydroxyl groups for 5-membered and 6-membered rings of the most stable configurations of the bispyrazoles cause generation of T-shaped conformations based on Independent Gradient Model (IGM) analysis, conformational stability of the considered complexes can be related to the formation of Sigma-pi molecular interaction heterocyclic rings which confirms with the vibrational stretching modes of hydroxyl groups and the character of the Kohn-Sham HOMO and LUMO orbitals.