Synthesis and characterization of new Cr(III) complex with a tetradentate Schiff base ligand for polymer composite application

Abstract

In this investigation, we successfully synthesized an asymmetrical N, N, N, O tetradentate Schiff base ligand (L) through the condensation reaction between 1-phenylbutane-1,3-dione and 2,6-diaminopyridine. Subsequently, this ligand was used to form a new Cr(III) complex (LMC) by reacting with Cr(NO₃)₃·9H₂O. The synthesis of the ligand and the complex was confirmed using various techniques, including elemental analysis, magnetic susceptibility, molar conductance, FTIR, UV–visible, ¹H-NMR, mass spectrometry, and thermogravimetric analysis. The FTIR spectra indicated that L acted as a dibasic tetradentate ligand, coordinating with the metal ion through multiple binding sites: the oxygen atom of the carbonyl group, the nitrogen atoms of the imine and amine groups, and the pyridine nitrogen atom. The molar conductance values suggested that the LMC possessed electrolytic properties. Analysis of electronic spectra and magnetic moments further supported the assignment of an octahedral geometry to the LMC complex. Furthermore, the complex was integrated into a chitosan (Cs) matrix using an acidic solution method, resulting in the formation of polymer composites denoted as Cs/LMC. These composites exhibit enhanced optical properties. Specifically, the optical bandgap of the composite decreased from 5.2 to 1.85 eV, while the refractive index increased from 1.29 to 1.341. This innovative approach holds promise for enhancing the optical characteristics of chitosan-based materials, rendering them suitable for various applications.

Graphical abstract