Synthesis, characterization and biological activity of Mixed ligand Lanthanum (III) complexes, Derived from 1-(2-pyridylazo)-2-naphthol and secondary ligands

Abstract

This study involved the preparation of two lanthanum (III) complexes using 1-(2-pyridylazo)-2-naphthol (PAN) as the primary ligand, combined with the secondary ligands 1,10-phenanthroline (Phen) and 8-hydroxyquinoline (8HQ). The complexes were synthesized by controlling the reaction medium with a buffer solution. The prepared complexes were characterized by spectroscopic analyses, including Fourier-transform infrared spectroscopy (FT-IR), UV-Vis spectroscopy, and proton nuclear magnetic resonance (¹H-NMR), as well as by elemental analysis (CHN) and molar conductivity measurements. In the [La(PAN)₂(NO₃)] complex, the PAN ligand coordinates as a tridentate ligand through the azo nitrogen, the pyridine-ring nitrogen, and the phenolic oxygen atom, while the nitrate group behaves as a bidentate ligand. Thus, the coordination number of the central atom is eight. In the mixed-ligand complexes, the secondary ligand Phen coordinates as a bidentate ligand through its two nitrogen donor atoms (N,N). In the [La(PAN)₂(8HQ)] complex, the 8HQ ligand coordinates as a bidentate ligand via its nitrogen and oxygen donor atoms (N,O). Based on the spectroscopic data, the primary ligand PAN behaves consistently as a tridentate ligand (N,N,O). The biological activity of these complexes was studied using the agar diffusion method. The study revealed that the mixed-ligand complexes exhibited enhanced biological activity, particularly the [La(PAN)₂(8HQ)] complex