[Ag(L)NO3] Complexes with 2-Benzoylpyridine-Derived Hydrazones: Cytotoxic Activity and Interaction with Biomolecules

Binding profile of a mixed-ligand silver(I) complex with DNA and Topoisomerase I

A new mixed-ligand Ag(I) complex, [Ag(daf)(phen)]NO₃ (daf = 4,5-diazafluoren-9-one and dian = N-(4,5-diazafluoren-9-ylidene)aniline), was synthesized. The elemental analysis, FTIR, ¹HNMR, UV-Vis spectroscopy, cyclic voltammetry, and DFT (Density Functional Theory) geometry optimization method were applied in order to predict the Ag(I) complex structure which concluded to a distorted tetrahedral N4 coordination around the Ag(I) center. A detailed in silico analysis of the bioaffinity of the complex to DNA and human DNA-Topoisomerase I was conducted using molecular docking simulations and ONIOM (Our own N-layered Integrated molecular Orbital and molecular Mechanics) techniques. In this overall scenario, the results suggest the dominance of π-π stacking interactions of the heteroaromatic ligands in the intercalating pocket of DNA and the active site of the enzyme and the rational correlation between being a good intercalator and a potent Topoisomerase I inhibitor. In vitro DNA-binding experiments by spectrophotometric, spectrofluorometric, Voltammetric, and viscometric techniques at physiological pH also confirmed the computational results. The complex inhibited MCF-7 cell growth in a dose-dependent manner while being nontoxic on HUVEC normal cells.

Multifunctional organometallic compounds for the treatment of Chagas disease: Re(I) tricarbonyl compounds with two different bioactive ligands

Chagas' disease (American Trypanosomiasis) is an ancient and endemic illness in Latin America caused by the protozoan parasite Trypanosoma cruzi. Although there is an urgent need for more efficient and less toxic chemotherapeutics, no new drugs to treat this disease have entered the clinic in the last decades. Searching for metal-based prospective antichagasic drugs, in this work, multifunctional Re(I) tricarbonyl compounds bearing two different bioactive ligands were designed: a polypyridyl NN derivative of 1,10-phenanthroline and a monodentate azole (Clotrimazole CTZ or Ketoconazol KTZ). Five fac-[Re(CO)₃(NN)(CTZ)](PF₆) compounds and a fac-[Re(CO)₃(NN)(KTZ)](PF₆) were synthesized and fully characterized. They showed activity against epimastigotes (IC₅₀ 3.48-9.42 μM) and trypomastigotes of T. cruzi (IC₅₀ 0.61-2.79 μM) and moderate to good selectivity towards the parasite compared to the VERO mammalian cell model. In order to unravel the mechanism of action of our compounds, two potential targets were experimentally and theoretically studied, namely DNA and one of the enzymes involved in the parasite ergosterol biosynthetic pathway, CYP51 (lanosterol 14-α-demethylase). As hypothesized, the multifunctional compounds shared in vitro a similar mode of action as that disclosed for the single bioactive moieties included in the new chemical entities. Additionally, two relevant physicochemical properties of biological interest in prospective drug development, namely lipophilicity and stability in solution in different media, were determined. The whole set of results demonstrates the potentiality of these Re(I) tricarbonyls as promising candidates for further antitrypanosomal drug development.

New silver(I) phosphino complexes: Evaluation of their potential as prospective agents against Mycobacterium tuberculosis

Despite being a preventable and curable disease, Tuberculosis (TB) is the world's top infectious killer. Development of new drugs is urgently needed. In this work, the synthesis and characterization of new silver(I) complexes, that include N'-[(E)-(pyridine-2-ylmethylene)pyrazine-2-carbohydrazide, HPCPH, as main ligand and substituted aryl-phosphines as auxiliary ligands, is reported. HPCPH was synthesized from pyrazinoic acid, the active metabolite of the first-line antimycobacterial drug pyrazinamide. Complexes [Ag(HPCPH)(PPh₃)₂]OTf (1), [Ag(HPCPH)((P(p-tolyl)₃)₂]OTf (2) and [Ag(HPCPH)(P(p-anisyl)₃)₂]OTf (3) were characterized in solid state and in solution by elemental analysis and FTIR and NMR spectroscopies (OTftriflate). Crystal structures of (1,2) were determined by XRD. The Ag atom is coordinated to azomethine and pyridine nitrogen atoms of HPCPH ligand and to the phosphorous atom of each aryl-phosphine co-ligand. Although HPCPH did not show activity, the Ag(I) compounds demonstrated activity against Mycobacterium tuberculosis (MTB), H₃₇Rv strain, and multi-drug resistant clinical isolates (MDR-TB). Globally, results showed that the compounds are not only effective against the sensitive strain, but are more potent against MDR-TB than antimycobacterial drugs used in therapy. The compounds showed low to moderate selectivity index values (SI) towards the bacteria, using MRC-5 cells (ATCC CCL-171) as mammalian cell model. Interaction with DNA was explored to get insight into the potential mechanism of action against the pathogen. No significant interaction was detected, allowing to discard this biomolecule as a potential molecular target. Compound 1 was identified as a hit compound (MIC₉₀ 2.23 μM; SI 4.4) to develop further chemical modifications in the search for new drugs.

Synthesis, Spectroscopy, Single-Crystal Structure Analysis and Antibacterial Activity of Two Novel Complexes of Silver(I) with Miconazole Drug

In a previous article, we reported on the higher toxicity of silver(I) complexes of miconazole [Ag(MCZ)₂NO₃ (1)] and [Ag(MCZ)₂ClO₄ (2)] in HepG2 tumor cells compared to the corresponding salts of silver, miconazole and cisplatin. Here, we present the synthesis of two silver(I) complexes of miconazole containing two new counter ions in the form of Ag(MCZ)₂X (MCZ = 1-[2-(2,4-dichlorobenzyloxy)-2-(2,4-dichlorophenyl)ethyl]-1H-imidazole]; X = BF₄⁻ (3), SbF₆⁻ (4)). The novel silver(I) complexes were characterized by elemental analysis, ¹H NMR, ¹³C NMR and infrared (IR) spectroscopy, electrospray ionization (ESI)-MS spectrometry and X-ray-crystallography. In the present study, the antimicrobial activity of all obtained silver(I) complexes of miconazole against six strains of Gram-positive bacteria, five strains of Gram-negative bacteria and yeasts was evaluated. The results were compared with those of a silver sulfadiazine drug, the corresponding silver salts and the free ligand. Silver(I) complexes exhibited significant activity against Gram-positive bacteria, which was much better than that of silver sulfadiazine and silver salts. The highest antimicrobial activity was observed for the complex containing the nitrate counter ion. All Ag(I) complexes of miconazole resulted in much better inhibition of yeast growth than silver sulfadiazine, silver salts and miconazole. Moreover, the synthesized silver(I) complexes showed good or moderate activity against Gram-negative bacteria compared to the free ligand.

Self-Assembly by Tridentate or Bidentate Ligand: Synthesis and Vapor Adsorption Properties of Cu(II), Zn(II), Hg(II) and Cd(II) Complexes Derived from a Bis(pyridylhydrazone) Compound

Four complexes, [Cu₄L₂(OCH₃)₂(CH₃OH)₂]·2H₂O (1), [Zn₂L₂Cl₄]·2H₂O·2CH₃OH (2), [Hg₂L₂Br₄]·4CH₃OH (3), and {[CdL₂Cl₂]·4H₂O·4CH₃OH}_n (4), have been synthesized and characterized from a bis(pyridylhydrazone) ligand (L) with copper(II), zinc(II), mercury(II) or cadmium(II), respectively. Complex 1 exists as a centrosymmetric tetranuclear dimer with L as deprotonated tridentate ligand. Complexes 2 and 3 exist as centrosymmetric metallamacrocycles with L as bidentate ligand. Complex 4 exists as a 1D looped-chain coordination polymer. The thermal stabilities and vapor adsorption properties of the four complexes were investigated as well.

(2-Hydroxyphenyl)(4,2′:4′,4′′-terpyridin-6′-yl)methanone

The title compound, C22H15N3O2, can be described as a ketone with a phenol substituent and a terpyridine ligand coordinated to the carbonyl group. The three six-membered rings of the terpyridine ligand are not coplanar. The dihedral angles between the mean planes of the central ring and the external pyridine ligands are 22.77 (9) and 26.77 (7)°. The central ring of the terpyridine ligand is also not coplanar with the o-hydroxy phenyl ring, the dihedral angle being 39.72 (5)°. An intramolecular O—H...O hydrogen bond occurs. The crystal structure of the title compound is consolidated by C—H...O and C—H...N hydrogen bonding interactions.

Nucleobase Derivatives as Building Blocks to Form Ru(II)-Based Complexes with High Cytotoxicity

Two new Ru(II)-based complexes containing 2-thiouracil derivatives, known as 2-thiouracil (2TU) and 6-methyl-2-thiouracil (6m2TU), were synthesized using cis,trans-[RuCl₂(PPh₃)₂(bipy)] as a precursor. The obtained compounds with a general formula trans-[Ru(2TU)(PPh₃)₂(bipy)]PF₆ (1) and trans-[Ru(6m2TU)(PPh₃)₂(bipy)]PF₆ (2) were characterized by analytical techniques such as NMR, UV-vis, and IR spectroscopies, elementary analysis, mass spectrometry, and single-crystal X-ray diffraction. Moreover, the investigation of the complexes-DNA interaction were carried out using spectrophotometric titrations and showed that the complexes present a weak interaction with this biomolecule. The compounds were evaluated against HL-60, K-562, HepG2, and B16-F10 cancer cells and against noncancer cells (PBMCs). The results of the biological assay revealed that complex 2 is more promising than complex 1. Finally, the present study suggests that complexes 1 and 2 causes cell death by apoptosis, significantly increasing the percentage of apoptotic HL-60 cells, in which the compounds altered the cell cycle, reducing the cells in G₁/G₀, G₂/M, and S phases.

Binding interaction of a heteroleptic silver(I) complex with DNA: A joint experimental and computational study

A new heteroleptic Ag(I) complex formulated as [Ag(daf)(phen)]NO₃, where daf and phen stand for 4,5-diazafluoren-9-one and 1,10-phenanthroline, respectively, has been prepared and structurally characterized by elemental analysis, spectroscopic methods (IR, ¹HNMR, and UV-Vis) and cyclic voltammetry. The geometry optimization around Ag(I) at the level of DFT has demonstrated that the Ag(I) center has been nested in a tetrahedral N4 coordination geometry which found to be in close agreement with the experimentally proposed structure. The bond lengths, angles, and the HOMO/LUMO energies have been calculated to substantiate the geometry of the complex. The DNA binding property of the Ag(I) complex has been explored in detail both theoretically (DFT and molecular docking) and experimentally (UV-Vis absorption spectroscopy, circular dichroism spectroscopy, luminescence quenching, competitive binding with ethidium bromide, cyclic voltammetry, and gel electrophoresis), indicating the good affinity of the Ag(I) complex for the intercalation (K_b (binding constant) = 3.45 × 10⁵ M^-1). Providing a fuller picture of Ag(I) complex-DNA interaction, the energy-minimized structure of the complex has been docked to the DNA with a d(AGACGTCT)₂ sequence and the results are in close agreement with experimental achievements and make a deeper insight into the relationship between the structure and biological activity of the complex.

Investigation of the antitrypanosomal effects of 2-formyl-8-hydroxyquinoline-derived hydrazones and their antimony(iii) and bismuth(iii) complexes

2-formyl-8-hydroxyquinoline-4-nitroimidazolhydrazone (H2Q4NO₂Im, H2La, 1) and 2-formyl-8-hydroxyquinoline-4-nitrobenzenehydrazone (H2Q4NO₂Ph, H2Lb, 2) were obtained, as well as their Sb(iii) [Sb(L)Cl₂] (3, 4) and Bi(III) [Bi(L)Cl₂] (5, 6) complexes.

Neutral 4-phenyl-1-[phenyl(pyridin-2-yl)methylidene]semicarbazide and its salt forms with inorganic anions

Semicarbazones can exist in two tautomeric forms. In the solid state, they are found in the keto form. This work presents the synthesis, structures and spectroscopic characterization (IR and NMR spectroscopy) of four such compounds, namely the neutral molecule 4-phenyl-1-[phenyl(pyridin-2-yl)methylidene]semicarbazide, C₁₉H₁₆N₄O, (I), abbreviated as HBzPyS, and three different hydrated salts, namely the chloride dihydrate, C₁₉H₁₇N₄O⁺·Cl^-·2H₂O, (II), the nitrate dihydrate, C₁₉H₁₇N₄O⁺·NO₃^-·2H₂O, (III), and the thiocyanate 2.5-hydrate, C₁₉H₁₇N₄O⁺·SCN^-·2.5H₂O, (IV), of 2-[phenyl({[(phenylcarbamoyl)amino]imino})methyl]pyridinium, abbreviated as [H₂BzPyS]⁺·X^-·nH₂O, with X = Cl^- and n = 2 for (II), X = NO₃^- and n = 2 for (III), and X = SCN^- and n = 2.5 for (IV), showing the influence of the anionic form in the intermolecular interactions. Water molecules and counter-ions (chloride or nitrate) are involved in the formation of a two-dimensional arrangement by the establishment of hydrogen bonds with the N-H groups of the cation, stabilizing the E isomers in the solid state. The neutral HBzPyS molecule crystallized as the E isomer due to the existence of weak π-π interactions between pairs of molecules. The calculated IR spectrum of the hydrated [H₂BzPyS]⁺ cation is in good agreement with the experimental results.