Different coordination abilities of 1,7- and 4,7-phenanthroline in the reactions with copper(II) salts: Structural characterization and biological evaluation of the reaction products

Copper(ii) and silver(i) complexes with dimethyl 6-(pyrazine-2-yl)pyridine-3,4-dicarboxylate (py-2pz): the influence of the metal ion on the antimicrobial potential of the complex

Dimethyl 6-(pyrazine-2-yl)pyridine-3,4-dicarboxylate (py-2pz) was used as a ligand for the synthesis of new copper(ii) and silver(i) complexes, [CuCl2(py-2pz)]2 (1), [Cu(CF3SO3)(H2O)(py-2pz)2]CF3SO3·2H2O (2), [Ag(py-2pz)2]PF6 (3) and {[Ag(NO3)(py-2pz)]·0.5H2O} n (4). The complexes were characterized by spectroscopic and electrochemical methods, while their structures were determined by single crystal X-ray diffraction analysis. The X-ray analysis revealed the bidentate coordination mode of py-2pz to the corresponding metal ion via its pyridine and pyrazine nitrogen atoms in all complexes, while in polynuclear complex 4, the heterocyclic pyrazine ring of one py-2pz additionally behaves as a bridging ligand between two Ag(i) ions. DFT calculations were performed to elucidate the structures of the investigated complexes in solution. The antimicrobial potential of the complexes 1-4 was evaluated against two bacterial (Pseudomonas aeruginosa and Staphylococcus aureus) and two Candida (C. albicans and C. parapsilosis) species. Silver(i) complexes 3 and 4 have shown good antibacterial and antifungal properties with minimal inhibitory concentration (MIC) values ranging from 4.9 to 39.0 μM (3.9-31.2 μg mL-1). All complexes inhibited the filamentation of C. albicans and hyphae formation, while silver(i) complexes 3 and 4 had also the ability to inhibit the biofilm formation process of this fungus. The binding affinity of the complexes 1-4 with calf thymus DNA (ct-DNA) and bovine serum albumin (BSA) was studied by fluorescence emission spectroscopy to clarify the mode of their antimicrobial activity. Catechol oxidase biomimetic catalytic activity of copper(ii) complexes 1 and 2 was additionally investigated by using 3,5-di-tert-butylcatechol (3,5-DTBC) and o-aminophenol (OAP) as substrates.

Design, synthesis, theoretical study, antioxidant, and anticholinesterase activities of new pyrazolo-fused phenanthrolines

Pyrazole-fused phenanthroline compounds were obtained through several synthetic routes. NMR, HRMS, and IR techniques were used to characterize and confirm the chemical structures. Crystal structures were obtained from compounds 3a, 5b, 5j, 5k, and 5n and analyzed using X-ray diffraction. Compounds were evaluated as acetyl (AChE) and butyrylcholinesterase (BChE) inhibitors, and the results showed a moderate activity. Compound 5c presented the best activity against AChE (IC50 = 53.29 μM) and compound 5l against BChE enzyme (IC50 = 119.3 μM). Furthermore, the ability of the synthetic compounds to scavenge cationic radicals DPPH and ABTS was evaluated. Compound 5e (EC50 = 26.71 μg mL-1) presented the best results in the DPPH assay, and compounds 5e, 5f and 5g (EC50 = 11.51, 3.10 and <3 μg mL-1, respectively) showed better ABTS cationic radical scavenging results. Finally, in silico analyses indicated that 71% of the compounds show good oral availability and are within the ranges established by the Lipinski criteria.

Novel cytotoxic 1,10-phenanthroline–triterpenoid amphiphiles with supramolecular characteristics capable of coordinating 64Cu(ii) labels

Novel 1,10-phenanthroline–triterpenoid amphiphiles formed nano-assemblies in water, coordinated Cu(ii) and 64Cu(ii) salts for potential cancer monitoring and therapy, and displayed cytotoxicity partly dependent on the formation of nano-assemblies.

Tailoring copper(ii) complexes with pyridine-4,5-dicarboxylate esters for anti-Candida activity

Five novel copper(ii) complexes with pyridine-4,5-dicarboxylate esters as ligands, [Cu(NO₃)(py-2tz)(H₂O)₃]NO₃ (1), [Cu(NO₃)₂(py-2metz)(H₂O)] (2), [Cu(NO₃)₂(py-2py)(H₂O)]·H₂O (3), [CuCl₂(py-2tz)]₂ (4) and [CuCl₂(py-2metz)]_n (5) (py-2tz is dimethyl 2-(thiazol-2-yl)pyridine-4,5-dicarboxylate, py-2metz is dimethyl 2-(4-methylthiazol-2-yl)pyridine-4,5-dicarboxylate and py-2py is dimethyl 2,2'-bipyridine-4,5-dicarboxylate), were synthesized and structurally characterized by different spectroscopic and electrochemical methods. The structure of these complexes was determined by single-crystal X-ray diffraction analysis, confirming the bidentate coordination mode of the corresponding pyridine-4,5-dicarboxylate ester to the Cu(ii) ion through the nitrogen atoms. The antimicrobial potential of copper(ii) complexes 1-5 was assessed against two bacterial and two Candida species. These complexes showed better growth inhibiting activity against Candida spp. with respect to the tested bacterial species, also being moderately toxic towards normal human lung fibroblast cells (MRC-5). Complexes 1 and 4 showed the greatest ability to inhibit the filamentation of C. albicans, which is an important process during fungal infection, and these two complexes efficiently inhibited the biofilm formation of C. albicans at subinhibitory concentrations. Complex 4 also successfully prevented the adhesion of C. albicans in an in vitro epithelial cell model. The mechanism of the antifungal activity of copper(ii) complexes 1-5 was studied through their interaction with ct-DNA, as one of the possible target biomolecules, by fluorescence spectroscopy and gel electrophoresis. Finally, the ability of these complexes to bind to bovine serum albumin (BSA) was studied by fluorescence emission spectroscopy.

Zinc(II) complexes with aromatic nitrogen-containing heterocycles as antifungal agents: Synergistic activity with clinically used drug nystatin

Three novel Zn(II) complexes, [ZnCl₂(qz)₂] (1), [ZnCl₂(1,5-naph)]_n (2) and [ZnCl₂(4,7-phen)₂] (3), where qz is quinazoline, 1,5-naph is 1,5-naphthyridine and 4,7-phen is 4,7-phenanthroline, were synthesized by the reactions of ZnCl₂ and the corresponding N-heterocyclic ligand in 1:2 molar ratio in ethanol at ambient temperature. The characterization of these complexes was done by NMR, IR and UV-Vis spectroscopy, and their crystal structures were determined by single-crystal X-ray diffraction analysis. Complexes 1 and 3 are mononuclear species, in which Zn(II) ion is tetrahedrally coordinated by two nitrogen atoms belonging to two qz or 4,7-phen ligands, respectively, and by two chloride anions, while complex 2 is a 1D coordination polymer that contains 1,5-naph as bridging ligand between two metal ions. In agar disc-diffusion assay, complexes 1-3 manifested good inhibitory activity against two investigated Candida strains (C. albicans and C. parapsilosis), while not inducing toxic effects on the healthy human fibroblast cell line (MRC-5). This activity was not fungicidal, as revealed by the broth microdilution assay, however complex 3 showed the ability to modulate Candida hyphae formation, which is an important process during infection and showed significant synergistic effect with clinically used antifungal polyene nystatin.