This paper reports the synthesis of two complexes through one-pot reactions of pyridine-2,6-dicarboxylic acid (pydcH2), phenanthroline, and 2-aminopyridine, with Gd(NO3)3⋅6H2O and Ce (NO3)3⋅6H2O metal salts. The new coordination complexes C1 and C2 were identified by spectroscopic methods. The complexes were characterized by X-ray crystallography. The nature of metal–ligand interactions was studied theoretically using NBO and EDANOCV analyses. The results showed that the contribution of electrostatic interactions in both complexes is considerably larger than that of orbital. However, the contribution of orbital interactions in [CeL3]2 , is more than that in [GdL3]3 (28.8% vs. 21.8%). In following, the cytotoxic effect of synthetic complexes was investigated in vitro using oxaliplatin as a standard against three cancer cell lines including human breast cancer (MCF7), human colon adenocarcinoma (HT29), human lymphocyte (HL60) and also one normal cell, human foreskin fibroblast (HFF). The most significant inhibition activity was observed by both C1 (IC50 = 80.7 μM, Viability inhibition = 83.41%) and C2 (IC50 = 98.3 μM, Viability inhibition = 77.19%) toward the MCF7 cell line.
