Synthesis, structure and in vitro anticancer activity of Pd(II) complexes of mono- and bis-pyrazolyl-s-triazine ligands

Abstract

The square planar complexes [Pd(MPT)Cl2] (1) and [Pd(BPT)Cl]ClO4 (2) were synthesized by the reaction of the 4,4′-(6-(3,5-dimethyl-1H-pyrazol-1-yl)-1,3,5-triazine-2,4-diyl)dimorpholine (MPT) and N-methyl-N-phenyl-4,6-di(1H-pyrazol-1-yl)-1,3,5-triazin-2-amine (BPT) ligands with PdCl2 (1:1) in acetone under thermal conditions, respectively. In complex 1, the Pd(II) ion is coordinated with the MPT ligand as a bidentate NN-chelate, augmented with two chloride ligands in cis positions. In complex 2, the Pd(II) ion is coordinated with the BPT ligand as a tridentate N-chelate in a pincer fashion, together with one chloride ligand. Hirshfeld analysis indicated that complex 1 is packed with a significant quantity of Cl…H (20.2%), O…H (6.8–8.1%) and N…H (10.8–11,7%) hydrogen bonds, as well as some C[sbnd]H…π (8.1–9.0%) interactions and C…O contacts (1.1–2.0%). On the other hand, O…H (13.8%), C[sbnd]H…π (16.5%) and anion-π stacking (C…O: 1.2%) are the most important interactions in 2. The atoms in molecules topological parameters correlate well with the Pd-N distances. In vitro anticancer experiments showed that both complexes have higher activity than their free ligands against MDA-MB-231 and MCF-7 cell lines. Complex 2 showed the highest cytotoxic activity with IC50 = 13.5 and 18.6 µg/mL against MDA-MB-231 and MCF-7, respectively, compared to 30.5 µg/mL for complex 1.