Six new palladium(II) mixed ligand complexes of 2-, 3-, 4-monosubstituted derivative of pyridine ring with caffeine moiety: Synthesis, spectroscopic, morphological structures, thermal, antimicrobial and anticancer properties

Abstract

In the present article, new complexes of mononuclear palladium, formed by the interaction of PdCl2 with nicotinamide (nta), picolinic acid (pia), and isonicotinic acid (ina) have been isolated in the solid state with 1:2 M ratio affords the new compounds [Pd(nta)2(Cl)2] (I), [Pd(pia)2] (II), and [Pd(ina)2] (III). The mixed ligand complexes with caffeine (caf) as a secondary ligand have been synthesized and formulated as [Pd(nta)(caf)(Cl)2] (IV), [Pd(pia)(caf)(Cl)] (V), and [Pd(ina)(caf)(Cl)] (VI) with ratio of metal: ligand: ligand is 1:1:1. Structures of these products has been established by elemental analyses, conductivity, FTIR, 1H NMR and thermal analysis data. The shifts of the ν(N–H) amino, ν(CN1) pyridine, ν(CO) carboxylic, and ν(CN9) caffeine stretches have been monitored in order to find out the donor sites of the ligands. According to the experimental data, the six complexes can be characterized in the solid state as mononuclear, with a four-coordinate stereochemistry. SEM, TEM, and XRD analysis determined the characteristics of synthesized nanoparticles. The in vitro antibacterial efficiency of the compounds were evaluated by paper disc diffusion method. Compounds were also screened for their anti-cancer activity against colorectal adenocarcinoma (Caco-2) and breast cancer (Mcf-7) cell lines. This study reveals that [Pd(pia)2] complex has a potent cytotoxic agent against human colorectal adenocarcinoma and breast cancer.