Schiff Base Derived Lanthanide(III) Complexes with Emphasis on Structural and Biological Studies

The macrocyclic octaaza-bis-α-diimine complex was synthesized through the condensation of dione dihydrazone with an acid. Through the reaction of this complex with lanthanide chloride, [Ln(C36H34N10O4)Cl] complexes were formed, where Ln represents La(III), Ce(III), or Yb(III). Thorough spectral characterization was conducted on both the ligand and its respective metal complexes. Infrared spectroscopy, energy-dispersive X-ray spectroscopy (EDS), and elemental analysis were employed to confirm the successful synthesis of the complexes and accurately identify their constituent elements. The stability of the metal-ligand complex was evaluated through thermogravimetric analysis (TGA). Additionally, fractal analysis was performed on the ligand lanthanide (III) complex. The cube counting method revealed that the fractal dimension (Df) value followed the order of La > Ce > Yb, indicating that lanthanum exhibited the highest surface roughness. Consequently, La demonstrated the greatest antibacterial and antifungal properties, attributable to its rough surface. The enhanced biological activity of the La(III) complexes can be attributed to the presence of surface roughness. Furthermore, due to the structural modification of the metal complexes into nanostructures, the antimicrobial activities exhibited by the metal complexes surpassed those of the ligands. Notably, the La(III) nanosized complex displayed excellent antimicrobial activity. The results of these evaluations are presented and discussed in detail within this paper.