Experimental and theoretical studies of Mn(II) and Co(II) metal complexes of a tridentate Schiff's base ligand and their biological activities

Synthesis, structure, theoretical calculation and antibacterial property of two novel Zn(II)/Ni(II) compounds based on 3, 5-dichlorosalicylaldehyde thiocarbamide ligand

Two new compounds namely [Zn(L1)phen]31 and Ni(L1)phen(MeOH) 2 (L1 = 3, 5-dichlorosalicylaldehyde thiosemicarbazone) were synthesized by the slow evaporation method at room temperature. The structure of ligand L1 was determined using 1H NMR and 13C NMR spectra. X-ray single crystal diffraction analysis revealed that compounds 1-2 can form 3D supramolecular network structures through π···π stacking and hydrogen bonding interactions. The DFT calculation shows that the coordination of ligand and metal is in good agreement with the experimental results. Hirshfeld surface analysis revealed that H…H and Cl…H interactions were the predominant interactions in compounds 1-2. Energy framework analysis indicated that dispersion energy played a dominant role in the energy composition of compounds 1-2. The inhibitory effects of compounds 1-2 against Escherichia coli (E. coli) and Methicillin-resistant Staphylococcus aureus (MRSA) were tested using the paper disk diffusion method (1: E. coli: 18 mm, MRSA: 17 mm, 2: E. coli: 15 mm, MRSA: 16 mm). Ion releasing experiments were conducted to assess the ion release capacity of compounds 1-2 (Zn2+, 4 days, 38.33 µg/mL; Ni2+, 4 days, 29.12 µg/mL). Molecular docking demonstrated the interaction modes of compounds 1-2 with UDP-N-acetylenolpyruvoylglucosamine reductase (MurB) and dihydrofolate reductase (DHFR) in bacteria, involving hydrophobic, stacking, hydrogen bonding and halogen bonding interactions. The generation of reactive oxygen species (ROS) in bacteria under the presence of compounds 1-2 were evaluated using a fluorescent dye known as dichlorodihydrofluorescein diacetate (DCFH-DA). Potential antibacterial mechanisms of compounds 1-2 were proposed.

Pincer Complexes Derived from Tridentate Schiff Bases for Their Use as Antimicrobial Metallopharmaceuticals

Within the current challenges in medicinal chemistry, the development of new and better therapeutic agents effective against infectious diseases produced by bacteria, fungi, viruses, and parasites stands out. With chemotherapy as one of the main strategies against these diseases focusing on the administration of organic and inorganic drugs, the latter is generally based on the synergistic effect produced by the formation of metal complexes with biologically active organic compounds. In this sense, Schiff bases (SBs) represent and ideal ligand scaffold since they have demonstrated a broad spectrum of antitumor, antiviral, antimicrobial, and anti-inflammatory activities, among others. In addition, SBs are synthesized in an easy manner from one-step condensation reactions, being thus suitable for facile structural modifications, having the imine group as a coordination point found in most of their metal complexes, and promoting chelation when other donor atoms are three, four, or five bonds apart. However, despite the wide variety of metal complexes found in the literature using this type of ligands, only a handful of them include on their structures tridentate SBs ligands and their biological evaluation has been explored. Hence, this review summarizes the most important antimicrobial activity results reported this far for pincer-type complexes (main group and d-block) derived from SBs tridentate ligands.

Synthesis, characterization, antiproliferative of pyrimidine based ligand and its Ni(II) and Pd(II) complexes and effectiveness of electroporation

In the study, a new Schiff base (ligand) was obtained using 4-aminopyrimidine-2(1H)-one, the starting material, and 2,3,4-trimethoxy benzaldehyde. Ni(II) and Pd(II) complexes were obtained from the reaction of the ligand and NiCl₂·6H₂O, PdCl₂(CH₃CN)₂ (1:1 ratio). These compounds were characterized using the elemental and mass analysis, ¹H, ¹³C-NMR, FT-IR, UV-Vis, magnetic susceptibility, thermal analysis, and the X-ray diffraction analyses. The antiproliferative activities of the synthesized ligand, Ni(II) and Pd(II) complexes were identified on the HepG2 (human liver cancer cells) cell line and their biocompatibility was tested on the L-929 (fibroblast cells) cell line by the MTT analysis method. Furthermore, the effects of electroporation (EP) on the cytotoxic activities of synthesized compounds were investigated in HepG2 cancer cells. According to the MTT findings of the study, the ligand did not exhibit an antiproliferative activity while its Ni(II) and Pd(II) complexes exhibited an antiproliferative activity. Moreover, it was observed that the antiproliferative activity of the Pd(II) complex was stronger than that of the Ni(II) complex. The combined application of EP + compounds is much more effective than the usage of the compounds alone in the treatment of HepG2 cancer cells. The EP increased the cytotoxicity of the Ni(II) and Pd(II) complexes by 1.66, and 2.54 times, respectively. It was concluded that Ni(II) and Pd(II) complexes may contribute as potential anti-cancer agents for the treatment of hepatocellular carcinoma and yield promising results in the case of being used in ECT.Communicated by Ramaswamy H. Sarma.