Ternary palladium(II) complexes with N-benzyliminodiacetic acid derivatives and 2,2′-bipyridine: Preparation, thermogravimetric, vibrational spectroscopic, DFT, NMR studies and biological activity in vitro

The reactions of N-benzyliminodiacetic acid (BnidaH₂) and its para-substituted derivatives, namely: N-(p-chlorobenzyl)iminodiacetic acid (p-ClBnidaH₂), N-(p-nitrobenzyl)iminodiacetic acid (p-NO₂BnidaH₂) and N-(p-methoxybenzyl)iminodiacetic acid (p-MeOBnidaH₂) with paladium(II) chloride and 2,2′-bipyridine, were performed in water-acetonitrile solutions. Four new prepared complexes [Pd(Bnida)(bipy)]∙2H₂O (1), [Pd(p-ClBnida)(bipy)]∙4H₂O (2), [Pd(p-NO₂Bnida)(bipy)]∙2H₂O (3) and [Pd(p-MeOBnida)(bipy)]∙3H₂O (4) were identified by means of chemical analysis and mass spectrometry, and characterized by infrared spectroscopy and thermal analysis (TG/DTA). The molecular geometry and infrared spectra of these four complexes were modelled using DFT calculations at the BP86/def2-TZVP (Pd: ECP) level of theory. Extensive NMR studies have shown the presence of two isomers in solution (DMSO). The characterized palladium(II) complexes demonstrate valuable antiproliferative activity against Caco-2, SW620, NCI-H358 and MDCK I reducing cell growth from 71.7% to 79.9% (10⁻⁴ M) (1; 4). PANC-1 display mild sensitivity and slow reduction in cell growth (less than 50%) while BJ present higher viability range and proliferative status. BJ proliferation after exposure to palladium complexes at 10⁻⁴ M concentration ranged from 55.2% to 83.5% (1–4). In descending order, antiproliferative effect of tested palladium complexes is, as follows: 4 > 1 > 2 > 3.