New lanthanum (III) complexes containing azaphosphor β-diketon and diimine ligands: Synthesis, crystallography, morphology properties, DNA binding, DNA cleavage, and DFT calculation.

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Two octa-coordinated lanthanum (III) complexes of deprotonated azaphosphor β-diketon and diimine ligands, [LnL3Q] (L = [Cl2CHC(O)NP(O)(NC6H12)2], Q = Phen (C1) and Bipy (C2)), were synthesized and characterized by elemental analysis, IR, and NMR spectra. X-ray crystallography revealed a distorted tetragonal antiprism LaO6N2 coordination geometry around the lanthanum atom in both compounds. Nano-sized complexes (Ć1 and Ć2) were synthesized via a sonochemical process and analyzed using SEM and XRPD. TGA-DTA analysis were performed on complexes in both bulk and nano scales. Redox behavior was also examined by cyclic voltammetry. The interaction between the complexes and calf thymus DNA (ct-DNA) was investigated using UV-Vis spectroscopy, fluorescence titration, viscosity measurements, and gel electrophoresis. C2 and Ć2 likely intercalate between DNA base pairs through van der Waals forces and hydrogen bonding, whereas C1 and Ć1 interact with DNA via groove binding. Further, result indicated the apparent association constant (Kapp) in the range of 4.53 × 104 M-1-26.86 × 104 M-1 with the highest value for nanocomplex Ć2. Fluorescence studies revealed dynamic and static quenching for C1, while the other compounds followed a static quenching process. Hirshfeld surface analysis and the NCI method were employed to demonstrate how non-covalent interactions influence the crystal packing through intermolecular interactions.