Low-dimensional compounds containing bioactive ligands. Part XVII: Synthesis, structural, spectral and biological properties of hybrid organic-inorganic complexes based on [PdCl4]2- with derivatives of 8-hydroxyquinolinium.

In this study, four hybrid organic-inorganic compounds (8-H2Q)2[PdCl4] (1), (H2ClQ)2[PdCl4] (2), (H2NQ)2[PdCl4] (3) and (H2MeQ)2[PdCl4]·2H2O (4) (where 8-H2Q = 8-hydroxyquinolinium, H2ClQ = 5-chloro-8-hydroxyquinolinium, H2NQ = 5-nitro-8-hydroxyquinolinium and H2MeQ = 2-methyl-8-hydroxyquinolinium) were synthesized through organic cation modulation. Single-crystal X-ray structure analysis of compounds 1 and 3 indicates that their structures are planar and consist of [PdCl4]2- anions and 8-H2Q or H2NQ cations, respectively. Both ionic components are held together through ionic interactions and hydrogen bonds forming infinite chains linked through π-π interactions to form 2D structures. Furthermore, NMR spectroscopy, UV-Vis spectroscopy, elemental analysis, and FT-IR spectroscopy were used to explore the synthesized compounds. The DNA interaction, antimicrobial activity, antiproliferative activity, and radical scavenging effect of the compounds were evaluated. The hybrid compounds and their free ligands can interact with the calf thymus DNA via an intercalation mode involving the insertion of the aromatic chromophore between the base pairs of DNA; compound 1 has the highest binding affinity. Moreover, they have high antimicrobial efficacy against the tested 14 strains of microorganisms with minimum inhibitory concentration values ranging from <1.95 to 250 µg/mL. The antiproliferative activity of the compounds was investigated against three different cancer cell lines, and their selectivity was verified on mesenchymal stem cells. Compounds 1 and 2 displayed selective and high cytotoxicity against human lung and breast cancer cells and showed moderate cytotoxicity against colon cancer cells. Accordingly, they might be auspicious candidates for future pharmacological investigations in lung and breast cancer research.

Synthesis, characterization, DNA interactions and biological activity of new palladium(II) complexes with some derivatives of 2-aminothiazoles.

Newly palladium(II) complexes (C1, C2) with derivatives of 2-aminothiazoles (L1 = 2-amino-6-methylbenzothiazole, L2 = 2-amino-6-chlorobenzothiazole), general formula [PdL2Cl2] were synthesized and characterized by elemental microanalyses, IR, NMR spectroscopy and X-ray spectroscopy in case of [Pd(L2)2Cl2]. The kinetic of the substitution reactions of complexes and the nucleophiles, such as guanosine-5'-monophosphate (5'-GMP), tripeptide glutathione (GSH) and amino acid L-methionine (L-Met), were studied by stopped-flow technique. The complex C2 was always more reactive, while the order of the reactivity of the nucleophiles, due to the associative mode of the reaction, was L-Met > GSH > 5'-GMP. In order to determine the type of interactions between palladium(II) complexes and calf thymus DNA (CT-DNA), we used electronic absorption spectroscopy, viscosity measurements, and fluorescence spectroscopic studies, while interactions with bovine serum albumin (BSA) were determined only with fluorescence spectroscopic studies. The observed results confirmed that both complexes bound to DNA by groove binding. The significantly strong interaction with BSA, especially for complex C2, was also observed. In vitro cytotoxic activity was evaluated against four tumor cell lines, 4 T1, CT26, MDA-MB-468, HCT116 and mesenchymal stem cells (mMSC). C1 complex showed higher cytotoxic activity against CT26 cell line. Flow cytometry analysis showed that C1 stimulated apoptosis of tumor cells via inhibition of expression of antiapoptotic Bcl-2 molecule and decelerated proliferation by decreasing Cyclin-D and increasing expression of P21. In vitro antimicrobial activity for ligands and corresponding palladium(II) complexes was investigated by microdilution method and minimum inhibitory concentration (MIC) and minimum microbicidal concentration (MMC) were determined. Tested compounds exhibited selective and moderate activity.