Fe (III), Co(II), Ni(II), Cu(II) and Zn(II) complexes of schiff bases based-on glycine and phenylalanine: Synthesis, magnetic/thermal properties and antimicrobial activity

Antifungal activity of Fe3O4@SiO2/Schiff-base/Cu(II) magnetic nanoparticles against pathogenic Candida species

The antifungal efficacy and cytotoxicity of a novel nano-antifungal agent, the Fe3O4@SiO2/Schiff-base complex of Cu(II) magnetic nanoparticles (MNPs), have been assessed for targeting drug-resistant Candida species. Due to the rising issue of fungal infections, especially candidiasis, and resistance to traditional antifungals, there is an urgent need for new therapeutic strategies. Utilizing Schiff-base ligands known for their broad-spectrum antimicrobial activity, the Fe3O4@SiO2/Schiff-base/Cu(II) MNPs have been synthesized. The Fe3O4@SiO2/Schiff-base/Cu(II) MNPs was characterized by Fourier Transform-Infrared Spectroscopy (FT-IR), X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM), Dynamic Light Scattering (DLS), Energy-dispersive X-ray (EDX), Vibrating Sample Magnetometer (VSM), and Thermogravimetric analysis (TGA), demonstrating successful synthesis. The antifungal potential was evaluated against six Candida species (C. dubliniensis, C. krusei, C. tropicalis, C. parapsilosis, C. glabrata, and C. albicans) using the broth microdilution method. The results indicated strong antifungal activity in the range of 8-64 μg/mL with the lowest MIC (8 μg/mL) observed against C. parapsilosis. The result showed the MIC of 32 μg/mL against C. albicans as the most common infection source. The antifungal mechanism is likely due to the disruption of the fungal cell wall and membrane, along with increased reactive oxygen species (ROS) generation leading to cell death. The MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay for cytotoxicity on mouse L929 fibroblastic cells suggested low toxicity and even enhanced cell proliferation at certain concentrations. This study demonstrates the promise of Fe3O4@SiO2/Schiff-base/Cu(II) MNPs as a potent antifungal agent with potential applications in the treatment of life-threatening fungal infections, healthcare-associated infections, and beyond.

Schiff bases complexed with iron and their relation with the life cycle and infection by Schistosoma mansoni

Introduction

The trematode Schistosoma mansoni causes schistosomiasis, and this parasite's life cycle depends on the mollusk Biomphalaria glabrata. The most effective treatment for infected people is administering a single dose of Praziquantel. However, there are naturally resistant to treatment. This work has developed, considering this parasite's complex life cycle.

Methods

The synthetics compound were evaluated: i) during the infection of B. glabrata, ii) during the infection of BALB/c mice, and iii) during the treatment of mice infected with S. mansoni.

Results and Discussion

For the first objective, snails infected with miracidia treated with compounds C1 and C3 at concentrations of 25% IC50 and 50% IC50, after 80 days of infection, released fewer cercariae than the infected group without treatment. For the second objective, compounds C1 and C3 did not show significant results in the infected group without treatment. For the third objective, the mice treated with C3 and C1 reduced the global and differential cell count. The results suggest that although the evaluated compounds do not present schistosomicidal properties when placed in cercariae suspension, they can stimulate an immune reaction in snails and decrease mice's inflammatory response. In general, we can conclude that compound C1 and C3 has an anti-schistosomicidal effect both in the larval phase (miracidia) and in the adult form of the parasite.

Coordination complexes constructed from pyrazole-acetamide and pyrazole-quinoxaline: effect of hydrogen bonding on the self-assembly process and antibacterial activity

Two mononuclear coordination complexes of N-(2-aminophenyl)-2-(5-methyl-1H-pyrazol-3-yl)acetamide (L₁), namely [Cd(L₁)₂Cl₂] (C₁) and [Cu(L₁)₂(C₂H₅OH)₂](NO₃)₂ (C₂) and one mononuclear complex [Fe(L₂)₂(H₂O)₂](NO₃)₂·2H₂O (C₃), obtained after in situ oxidation of L₁, have been synthesized and characterized spectroscopically. As revealed by single-crystal X-ray diffraction, each coordination sphere made of two heterocycles is completed either by two chloride anions (in C₁), two ethanol molecules (in C₂) or two water molecules (in C₃). The crystal packing analysis of C₁, C₂ and C₃, revealed 1D and 2D supramolecular architectures, respectively, via various hydrogen bonding interactions, which are discussed in detail. Furthermore, evaluation in vitro of the ligands and their metal complexes for their antibacterial activity against Escherichia coli (ATCC 4157), Pseudomonas aeruginosa (ATCC 27853), Staphylococcus aureus (ATCC 25923) and Streptococcus fasciens (ATCC 29212) strains of bacteria, revealed outstanding results compared to chloramphenicol, a well-known antibiotic, with a normalized minimum inhibitory concentration as low as 5 μg mL⁻¹.

Two mononuclear coordination complexes of N-(2-aminophenyl)-2-(5-methyl-1H-pyrazol-3-yl)acetamide (L₁) and one mononuclear complex, obtained after in situ oxidation of L₁, have been synthesized and characterized spectroscopically.

Synthesis, spectral and thermo-kinetics explorations of Schiff-base derived metal complexes

Schiff-base ligand, 2,6-bis(benzimino)-4-phenyl-1,3,5-triazine (L), and its transition metal complexes of Co(ii), Ni(ii), and Cu(ii) were synthesized by refluxing the reaction mixture and its analytical, spectral, and thermogravimetric characteristics were explored by various techniques: AAS, FT-IR, UV-vis, TG-DTG, CHNS/O, and VSM. It was observed that all the metal containing complexes are non-electrolytic, mononuclear, and paramagnetic in nature, confirmed by the molar conductance and magnetic susceptibility measurements. Optical spectral data were used to investigate the geometrical and spectral parameters of [Co(L)(ac)2], [Ni(L)(ac)2], [Cu(L)(ac)2], [Cu(L)(acac)2], and [Cu(L)(fmc)2] complexes. Simultaneous thermal analyses (TG-DTG) in nitrogen atmosphere reveal that the ligand decomposes in one step, [Co(L)(ac)2], [Ni(L)(ac)2], and [Cu(L) (ac)2] complexes are decomposed in three steps, whereas [Cu(L)(acac)2] and [Cu(L) (fmc)2] are decomposed in five and two steps, respectively. In addition, activation energy (Ea) and pre-exponential factor (ln A) were evaluated by TG-DTG decomposition steps of compounds using the Coats–Redfern formula. Enthalpy (∆H), entropy (∆S), and Gibbs free energy (∆G) of the as-prepared metal complexes were also speculated by various thermodynamic equations.

Structures and esterolytic reactivity of novel binuclear copper(ii) complexes with reduced l-serine Schiff bases as mimic carboxylesterases

Three novel binuclear copper(ii) complexes with reduced l-serine Schiff bases were synthesized and their structures were analyzed with single-crystal X-ray diffraction and DFT calculations. The crystal data revealed that all of these binuclear complexes are chiral. Both 5-halogenated (bromo- and chloro-) binuclear complexes exhibit right-handed helix structural character. Interestingly, the 5-methyl-containing analogue has a two-dimensional pore structure. In this paper, the esterolysis reactivity of the as-prepared complexes shows that in the hydrolysis of p-nitrophenyl acetate (PNPA) these three complexes provide 26, 18, 40-fold rate acceleration as compared to the spontaneous hydrolysis of PNPA at pH 7.0, respectively. Under selected conditions, in excess buffered aqueous solution a rate enhancement by three orders of magnitude was observed for the catalytic hydrolysis of another carboxylic ester, p-nitrophenyl picolinate (PNPP). These complexes efficiently promoted PNPP hydrolysis in a micellar solution of cetyltrimethylammonium bromide (CTAB), giving rise to a rate enhancement in excess of four orders of magnitude, which is approximately 2.0-3.2 times higher than that in the buffer.

Antibacterial activities and DNA-cleavage properties of novel fluorescent imidazo-phenanthroline derivatives

Design and biological activities of fluorescent imidazo-phenanthroline derivatives; (E)-5-((4-((4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)phenoxy)methyl)benzylidene)amino)- isophthalicacid, 2 and 2-(4-(((5-chloroquinolin-8-yl)oxy)methyl)phenyl)-1H-imidazo[4,5f] [1,10]phenanthroline, 3, have been reported. Their characterizations were performed by spectroscopic techniques. Their promising photophysical behaviours were observed in absorbance and fluorescence studies. The antibacterial activities of the compounds were determined against seven different microorganisms; Bacillus subtilis ATCC 6633(G + ), Pseudomonas aeruginosa ATCC 29853(G-), Escherichia coli ATCC 35,218 (G-), Enterococcus faecalis ATCC 292,112 (G + ), Salmonella typhimurium ST-10 (G-), Streptococcus mutans NCTC 10,449 (G + ), and Staphylococcus aureus ATCC 25923(G + ). MIC values of 3 was determined as 156,25 μM on all tested bacteria. A preliminary study of the structure-activity relationship (SAR) also revealed that the antimicrobial activity depended on the substituents on the phenyl ring. The electron withdrawing Cl-substitued compound 3 most favour for antimicrobial activity even at lowest concentration compared to other compounds. DNA-cleavage activities of the compounds were also investigated. The interactions of the compounds with supercoiled pBR322 plasmid DNA were obtained by agarose gel electrophoresis. All imidazo-phenanthroline derivatives were found to be highly effective on DNA, even at the lowest concentrations because of their planar nature which provides ease of bind to the helix structure of DNA.

Some new nanostructure zinc complex: Synthesis, spectral analyses, crystal structure, Hirshfeld surface analyses, antimicrobial/anticancer, thermal behavior and usage as precursor for ZnO nanostructure

In this work, a new tridentate ligand, its some novel zinc halide/pseudohalide complexes and their antimicrobial and cytotoxic effects of them are described. Characterization data of these compounds have been achieved via several physical and micro analytical techniques. As typical one, X-ray crystal structure analysis of zinc azide complex was run showing zinc center is penta-coordinated by three nitrogen atoms from Schiff base ligand and two terminal azide nitrogen atoms as a distorted square pyramidal geometry. Hirshfeld surfaces analysis clears the important role of interactions related to azide groups (NH⋯N and CH⋯N hydrogen bonds) in the stabilization of its supramolecular structure. According to data obtained from thermal analysis (TG/DTG/DTA), all complexes are decomposed at four or more thermal stages below 1000 °C. Moreover antimicrobial activities of the compounds were screened against some gram positive and gram negative bacteria. Furthermore anticancer activities of the complexes were studied against MDA-MB468 and k562 as two cancer cell lines. In final, three zinc complexes were also synthesized in nano scale by sonochemical method and one of them was utilized as the precursor for preparation of nanostructure ZnO confirmed by XRD pattern and SEM image.

Photochemical reduction of Cr(vi) compounds by amino acid Schiff base copper complexes with a hydroxyl group and titanium oxide composites in aqueous solutions

The photo-driven reduction reaction of Cr(vi) to Cr(iii) by Schiff base Cu(ii) complexes was studied in aqueous and methanol solutions. The Cr(vi) reduction ratio with the CuVDB–TiO₂ system reached 91%.

A selective chemosensor and fluorescence probe for relay recognition of cations and fluoride ions in aqueous media with logic gate function

Cation to anion relay recognition was studied for the first time with sequential specificity (Cu²⁺ → F^- or Co²⁺ → F^-) using a fluorescence "ON-OFF-ON" mechanism. L₁ is a receptor with high selectivity for F^-, Cu²⁺ and Co²⁺ ions in the solution of DMSO/H₂O with a 9:1 vol ratio. Absorption and fluorescence spectra were used to investigate the sensing process. Fluorescent emission intensity of L₁ at 324 is quenched (switch-Off) after the addition of Cu²⁺ and Co²⁺. Surprisingly, complex L₁ + Cu²⁺ or L₁ + Co²⁺ is restored with addition of F^- into the compound (switch-On). Consequently, implication (from emission) and inhibit (from absorption) logic gates are constructed at molecular level. The gates operate in fluorescence and absorption modes when Cu²⁺ and F^- or Co²⁺ and F^- are used as input materials and the fluorescence intensity signal as outputs. Based on reversible and reproducible system, a sequential memory unit with integrated ''Writing-Reading-Erasing-Reading'' behavior, is developed.

X-ray structure and magnetic and fluorescence characteristics of new Cu(ii) complexes with Schiff bases derived from 2-(2-aminoethyl)pyridine and 2-hydroxy-1-naphthaldehyde; morphology and fluorescence of their thin films

Cu(ii) complexes with tridentate Schiff bases derived from 2-(2-aminoethyl)pyridine and 2-hydroxy-1-naphthaldehyde and COO-, Cl- and NO3- as ligands were obtained and characterized by crystal and molecular, spectroscopic (UV-Vis, fluorescence, IR, and EPR), magnetic and thermal methods. The X-ray crystal structure analysis revealed a distorted square planar geometry for [Cu(ii)(PEMN)CH3COO]CHCl3, 1, and [Cu(ii)(PEMN)Cl], 2, and a distorted square-pyramidal geometry for [Cu(ii)(PEMN)NO3], 3, corresponding to the values of EPR g-matrix diagonal components. The copper(ii) complexes exhibited fluorescence in solution in the range of 370-410 nm. Thin layers of the studied copper(ii) complexes were deposited on Si(111) by a spin coating method and studied by scanning electron microscopy (SEM/EDS), atomic force microscopy (AFM) and fluorescence spectroscopy. For copper(ii) layers (2/Si), the most intense fluorescence band from an intraligand and a d-d transition between 490 and 550 nm was observed.

Synthesis, Structure, DNA Interaction, and SOD Activity of Three Nickel(II) Complexes Containing L-Phenylalanine Schiff Base and 1,10-Phenanthroline

Three hexacoordinated octahedral nickel(II) complexes, [Ni(sal-L-phe)(phen)(CH₃OH)]·CH₃OH (1), [Ni(naph-L-phe)(phen)(CH₃OH)] (2), and [Ni(o-van-L-phe)(phen)(CH₃OH)]·5CH₃OH (3) (sal-L-phe = a Schiff base derived from salicylaldehyde and L-phenylalanine, naph-L-phe = a Schiff base derived from 2-hydroxy-1-naphthaldehyde and L-phenylalanine, o-van-L-phe = a Schiff base derived from o-vanillin and L-phenylalanine, and phen = 1,10-phenanthroline), have been synthesized and characterized by elemental analysis, IR spectra, and single-crystal X-ray diffraction. The interactions of these complexes with CT-DNA were studied by UV-Vis absorption spectroscopy, fluorescence spectroscopy, circular dichroism spectroscopy, and viscosity measurements. The binding constant (K_b) values of 1.82 × 10⁴ M⁻¹ for 1, 1.96 × 10⁴ M⁻¹ for 2, and 2.02 × 10⁴ M⁻¹ for 3 suggest that each of these complexes could bind with DNA in a moderate intercalative mode. Complex 3 exhibited a stronger interaction with CT-DNA than complexes 1 and 2. In addition, the superoxide scavenging activity of these complexes was investigated by the nitrotetrazolium blue chloride (NBT) light reduction method, and the results showed that they exhibited a significant superoxide scavenging activity with the IC₅₀ values of 4.4 × 10⁻⁵ M for complex 1, 5.6 × 10⁻⁵ M for complex 2, and 3.1 × 10⁻⁵ M for complex 3, respectively.

The first alternating MnII–MnIII 1D chain: structure, magnetic properties and catalytic oxidase activities

A one-dimensional mixed-valence Mn^II/Mn^III chain has been synthesized using N-salicylidene-l-alanine and 2,2′-bipyridine. The complex shows moderate catecholase and phenoxazinone synthase-like activity.