Two La(III) complexes (C1) and (C2) were designed through a one-pot reaction between pyridine-2,6- dicarboxylic acid, 2-aminobenzimidazole and/or 2-aminopyridine with lanthanum(III) nitrate hexahydrate. The structure of compounds was confirmed by single-crystal X-ray diffraction and distorted tricapped triangular prism geometry was suggested for them. The inhibitory potent of the compounds was tested in vitro against four cell lines including HL60 (a human lymphocyte), HepG2 (a human liver hepatocellular carcinoma), HT29 (a human colon adenocarcinoma), and HFF (a human foreskin fibroblast). The most prominent antiproliferative effect was indicated for both C1 (IC50 = 0.69 μM, MAE = 85.34 %) and C2 (IC50 = 62.50 μM, MAE = 61.71 %) against the HL60 cell line. The assay of the reactive oxygen species (ROS) and mitochondrial membrane potential (MMP) confirmed that apoptosis through a mitochondria pathway may be the main mechanism for the death of HL60 cells treated with the complexes
