Synthesis, characterization, in vitro biological evaluation and molecular docking studies of newly synthesized mononuclear lanthanum(III) complexes of N,N’-bis(2-aminoethyl)oxamide and phenanthroline bases

Four lanthanum(III) complexes were newly synthesized using the ligand N,N’-bis(2-
aminoethyl)oxamide (1) and phenanthroline bases [La(oxae)2 (NO3 )2 ](NO3 ) (2) [La(oxae)(bpy)](NO3 )3
(3), [La(oxae)(phen)](NO3 )3 (4) and [La(oxae)2 (dppz)](NO3 )3 (5) and characterized by 1 H-NMR, IR, UV–
Visible spectroscopic analyses, ESI-Mass spectrometric measurements, molar conductivities, and cyclic
voltammetric measurements. Complex 2 was found to be 1:1 electrolyte and complexes 3, 4 and 5 were
1:3 electrolytes. The redox ehavior of the complexes was confirmed by cyclic voltammetry. The interac-
tions of 1 and its complexes (2, 3, 4 and 5) with calf thymus DNA (CT-DNA) were studied by UV–Visible
absorption spectroscopy, cyclic voltammetric studies, viscosity measurements and molecular docking
studies. The studies confirmed the highest binding propensity for complex 5 (Kb = 2.26 × 106 ± 7) in
the reduced state through the intercalation method. Molecular docking studies revealed that complex 5
was found to bind strongly with the DNA molecule due to intercalation with a more negative binding
energy �G = - 8.6 kcal/mol having an association constant (Ka ) = 0.892 μM. The oxidative cleavage of
SC pUC19 DNA by La(III) complexes was confirmed by the Agarose gel electrophoresis method. Of all the
compounds tested, complex 5 exhibited the highest cleavage ability (94%) in the presence of H2 O2 in the
major groove region. The MTT assay revealed the highest antiproliferative activity of complex 5 against
MCF-7 cell lines at IC50 value is 21.86 μM. The complexes have been tested for antibacterial activities
wherein at 50 μg mL−1 , complex 5 inhibits the growth of K. pneumonia and at 100 μg mL−1 , ligand oxae
(1) and its complex 2 were active against E. coli and K. pneumonia; complex 4 inhibited the growth of
E. coli, K. pneumonia and B. subtilis. The antioxidant activities showed that complex 2 had the highest
chelation ability towards Fe2+.