Some new nano-sized Cr(III), Fe(II), Co(II), and Ni(II) complexes incorporating 2-((E)-(pyridine-2-ylimino)methyl)napthalen-1-ol ligand: Structural characterization, electrochemical, antioxidant, antimicrobial, antiviral assessment and DNA interaction

Syntheses and characterization of novel antimony (III) and bismuth (III) derivatives containing β-enamino ester along with antimicrobial evaluation, DFT calculation, and cytotoxic study

Four novel antimony (III) and bismuth(III) complexes of the kind Cl-Sb-O-C(OR)-CH(CH3 )C-NH-(CH2 )2 -NH-C(CH3 )CH:C(OR)-O [where R = -CH3 , M = Sb (1a); R = -C2 H5 , M = Sb (1b); R = -CH3, M = Bi (1c); R = -C2 H5 , M = Bi (1d)] were successfully prepared by reacting antimony(III)chloride and bismuth(III)chloride with sodium salt of β-enamino esters in 1:1 stoichiometry, which were further structurally characterized by physicochemical and IR, 1 H, 13 C NMR spectral and mass spectrometry. Structural analysis revealed that all four derivatives of both antimony and bismuth display octahedarl geometry which has been optimized through computational studies. These derivatives along with their parent ligands were subsequently assayed in vitro for antibacterial (Bacillus subtilis, Pseudomonas aeruginosa) and antifungal (Aspergillus niger and Candida albicans) activities. Synthesized complexes were more efficacious in terms of biological activities as compared to parent ligands Further synthesized compounds were evaluated for their in vitro cytotoxic activity against lung cancer cell line A549 using MTT method. IC50 value for all four complexes was determined and all of them are found active. Computational studies of the representative complexes have been done using B3LYP/631-G* basis sets to provide optimized geometry.

Novel Schiff Base Derived from Amino Pyrene: Synthesis, Characterization, Crystal Structure Determination, and Anticancer Applications of the Ligand and Its Metal Complexes

In this study, we report the cytotoxicity of a newly synthesized Schiff base HL ((E)-2-ethoxy-6((pyren-1-ylimino)methyl)phenol) and its derived metal complexes (Zn(II), Cu(II), Co(II), Cr(III), and Fe(III)) along with their structural characterizations by means of elemental analysis, magnetic moment, molar conductance, IR, UV-Vis, ESR, and mass spectrometry. The single X-ray diffraction of the HL shows that it exists in the phenol-imine form in its solid state. The NMR and IR data indicate that the bidentate binding of the Schiff base ligand with the metal center occurs during complexation through the azomethine nitrogen atom and the hydroxyl group oxygen atom of the 3-ethoxy salicylaldehyde. The electronic spectra and magnetic measurements indicate that the Co(II) complex has a tetrahedral geometry and that the Cr(III) and Fe(III) complexes have a distorted octahedral geometry. The ESR and electronic spectra suggest that the Cu(II) complex has a distorted tetrahedral geometry. The cytotoxic effects of the HL and all of the metal complexes were studied using human breast cancer (MCF-7) cells. The Cu(II) and Zn(II) complexes exhibited the highest activity against the tested cell line, with IC50 values of 5.66 and 12.74 μg/mL, respectively, and their activity was higher than that of the fluorouracil cancer drug against the MCF-7 cells (18.05 μg/mL).

Antimicrobial Agents Based on Metal Complexes: Present Situation and Future Prospects

The rise in antimicrobial resistance is a cause of serious concern since the ages. Therefore, a dire need to explore new antimicrobial entities that can combat against the increasing threat of antibiotic resistance is realized. Studies have shown that the activity of the strongest antibiotics has reduced drastically against many microbes such as microfungi and bacteria (Gram-positive and Gram-negative). A ray of hope, however, was witnessed in early 1940s with the development of new drug discovery and use of metal complexes as antibiotics. Many new metal-based drugs were developed from the metal complexes which are potentially active against a number of ailments such as cancer, malaria, and neurodegenerative diseases. Therefore, this review is an attempt to describe the present scenario and future development of metal complexes as antibiotics against wide array of microbes.

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.

Inhibitory effect and mechanism of gelatin stabilized ferrous sulfide nanoparticles on porcine reproductive and respiratory syndrome virus

Background

The infection and spread of porcine reproductive and respiratory syndrome virus (PRRSV) pose a serious threat to the global pig industry, and inhibiting the viral infection process is a promising treatment strategy. Nanomaterials can interact with viruses and have attracted much attention due to their large specific surface area and unique physicochemical properties. Ferrous sulfide nanoparticles (FeS NPs) with the characteristics of high reactivity, large specific surface area, and low cost are widely applied to environmental remediation, catalysis, energy storage and medicine. However, there is no report on the application of FeS NPs in the antiviral field. In this study, gelatin stabilized FeS nanoparticles (Gel-FeS NPs) were large-scale synthesized rapidly by the one-pot method of co-precipitation of Fe²⁺ and S^2‒.

Results

The prepared Gel-FeS NPs exhibited good stability and dispersibility with an average diameter of 47.3 nm. Additionally, they were characterized with good biocompatibility and high antiviral activity against PRRSV proliferation in the stages of adsorption, invasion, and replication.

Conclusions

We reported for the first time the virucidal and antiviral activity of Gel-FeS NPs. The synthesized Gel-FeS NPs exhibited good dispersibility and biocompatibility as well as effective inhibition on PRRSV proliferation. Moreover, the Fe²⁺ released from degraded Gel-FeS NPs still displayed an antiviral effect, demonstrating the advantage of Gel-FeS NPs as an antiviral nanomaterial compared to other nanomaterials. This work highlighted the antiviral effect of Gel-FeS NPs and provided a new strategy for ferrous-based nanoparticles against PRRSV.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01281-4.

Temperature and salt effects of the kinetic reactions of substituted 2-pyridylmethylene-8-quinolyl iron (II) complexes as antimicrobial, anti-cancer, and antioxidant agents with cyanide ions

Kinetics of substitution reaction of three high-spin pyridylmethylene-8-quinolyl iron (II) complexes by CN– ions were studied spectrophotometrically in various ratios of aqueous–methanol binary mixtures at 298 ± 0.2 K. Kinetics of the substitution reaction follow the rate law (k2[CN−][complex]) on applying of the conditions of the pseudo first order reaction. Reactivity of the reaction was investigated in terms of ligand moiety and solvent effects. The rate of the reaction increased as the co-solvent methanol ratio increased. This reactivity trend is predominantly due to increases in the activity coefficient of those hydrophobic complexes in the organic methanol co-solvent, depending upon the hydrophobicity of the substituent groups (R) in the coordinated ligand in the complexes. Reactivity trends of the prepared complexes in the presence of the inserted hydrophobic salts such as tetrabutylammonium bromide (TBAB), tetraethylammonium bromide (TEAB), and tetramethylammonium bromide (TMAB) or hydrophilic salt potassium bromide (KBr) were studied. The observed decrease in the rate constants with increasing salt concentration was due to the cationic character of the reacting complexes. In addition, the synthesized compounds were tested for antimicrobial activity against selected strains of microbes. The results showed that the order of reactivity of the investigated complexes against the selected microbes were as follows: ppaqFe > paaqFe > pmaqFe. In addition, the investigated ligands and their Fe(II) complexes were screened for anticancer activities against several cell lines of cancer. The ppaqFe complex showed the best cytotoxic efficiency against the selected cancer lines (IC50 = 8.75–21.50 µg/µl), whereas the pmaq ligand showed the lowest cytotoxic efficiency (IC50 = 58.25– 72.40). Furthermore, the antioxidant potential of the presented compounds was studied by applying DPPH assays and showed a potential activity compared with standard vitamin C. The excellent antimicrobial and anticancer activities of the investigated Fe(II) chelates compared with literature values are promising and deserve further study.

Structural elucidation, theoretical investigation, biological screening and molecular docking studies of metal(II) complexes of NN donor ligand derived from 4-(2-aminopyridin-3-methylene)aminobenzoic acid

Complexes of 4-(((2-aminopyridin-3-yl)methylene)amino)benzoic acid ligand with cobalt(II) (1), nickel(II) (2), copper(II) (3), zinc(II) (4) and palladium(II) (5) are synthesized and characterized by using different spectroscopic methods like, UV-Visible, infrared, ¹H, ¹³C NMR, molar conductance, ESR and elemental analysis. Quantum chemical computations were made using DFT (density functional theory), B3LYP functional and 6-31+ +G(d,p)/SDD basis set in order to determine optimized structure parameters, frontier molecular orbital parameters and NLO properties. Based on DFT and experimental evidence, the complexes ensured that the octahedral geometry have been proposed for complexes 1, 2 and 4, square planar for complexes 3 and 5. All the complexes showed only residual molar conductance values and hence they were considered as non-electrolytes in DMF. In addition, the anti-proliferative activity of the compounds was evaluated against different human cancer cell lines (IMR-32, MCF-7, COLO205, A549, HeLa and HEK 293) and cisplatin is used as a reference drug. Compounds 1 and 4 showed remarkable cytotoxicity in five cancer cell lines tested except MCF-7. Also, the compounds were examined for their in vitro antimicrobial and scavenging activities. The molecular docking results are well corroborated with the experimental anticancer activity results.

Synthesis, DNA binding, antibacterial and anticancer properties of two novel water-soluble copper(II) complexes containing gluconate

In this paper, two new Cu(II) complexes, [Cu(Gluc)(HPB)(H₂O)]Gluc (CuG1) and [Cu(Gluc)(HPBC)(H₂O)]Gluc (CuG2) (where HPB = 2-(2'-pyridyl)benzimidazole, HPBC = 5-chloro-2-(2'-pyridyl)benzimidazole, Gluc = d-Gluconic acid), with good water solubility were synthesized and characterized. These complexes exhibited a five-coordinated tetragonal pyramidal geometry. The DNA binding and cleavage properties of the complexes were investigated using multi-spectroscopy, viscosity measurement, molecular docking and gel electrophoresis analysis methods. The results showed that the complexes could interact with DNA by insertion and groove binding, and cleave CT-DNA through a singlet oxygen-dependent pathway in the presence of ascorbic acid. The studies on antibacterial and anticancer activities in vitro demonstrated that both complexes had good inhibitory activity against three Gram-positive bacteria (Staphylococcus aureus, Bacillus subtilis, Listeria monocytogenes) and one Gram-negative bacterium (Escherichia coli) and good cytotoxic activity toward the tested cancer cells (A549, HeLa and SGC-7901). CuG2 showed higher antimicrobial and cytotoxic activities than CuG1, which was consistent with their binding strength and cleavage ability to DNA, indicating that their antimicrobial and cytotoxic activities may be related to the DNA interaction. Moreover, the cell-based mechanism studies have indicated that CuG1 and CuG2 could arrest the cell cycle at G2/M phase, elevate the levels of intracellular reactive oxygen species (ROS) and decrease the mitochondrial membrane potential (MMP). The results showed that the complexes could induce apoptosis through DNA-damaged and ROS-mediated mitochondrial dysfunction pathways. Finally, the in vivo antitumor study revealed that CuG2 inhibited tumor growth by 50.44%, which is better than that of cisplatin (40.94%).

The use of complex formation manner for spectrophotometric analysis of gatifloxacin drug based on Co(II), Ni(II) and La(III) ions

Herein, a simple and accurate spectrophotometric method was developed to detect gatifloxacin (HGAT) in a pure and ophthalmic formulation. The method depends on complexation of HGAT with Co (II), Ni (II) and La(III) ions in ethanol medium at room temperature. The experimental conditions have been investigated to reach optimum conditions for HGAT-metal ions interaction, including detection of a suitable wavelength, medium pH, reaction time and reactants concentration. Moreover, the composition of these complexes in addition to their stability constants were also investigated and the result indicated that the molar ratio of HGAT: Metal ion is 1:1 for Ni (II) and La(III) ions and 1:2 for Co (II) ion. Beer's law plots were obeyed in the concentration ranges 18.77-150.16, 18.77-131.39 and 18.77-112.62 (μg mL-1) for Co(II), Ni(II) and La(III) ions interaction, respectively. The apparent molar absorptivity, Sandell's sensitivity, standard deviation, detection and quantification limits were calculated. The proposed method was successfully applied for the determination of HGAT in the bulk and ophthalmic formulation. The obtained results were compared statistically with other published methods and the results were in good agreement with those obtained by reported methods.

Synthesis, structural characterization, and biological studies of ATBS-M complexes (M(II) = Cu, Co, Ni, and Mn): Access for promising antibiotics and anticancer agents

A new bidentate Schiff base ligand (ATBS [4-bromo-2-(thiazole-2-yliminomethyl)phenol]) was synthesized via the condensation reaction of 2-aminothiazole with 5-bromosalicylaldehyde in ethanol. The reaction of ATBS with transition metal salts of Cu(II), Co(II), Ni(II), and Mn(II) afforded the corresponding ATBS-M complexes. Results from physicochemical and spectral analyses, such as elemental analysis, infrared, UV-Vis spectroscopy, magnetic susceptibility, and molar conductance, revealed a nonelectrolytic nature with octahedral (O_h ) geometry and a metal/ligand ratio of 1:2 for Cu(II), Co(II), and Ni(II), but 1:1 for the Mn(II) complex. The density functional theory (DFT) calculations are correlated very well with the proposed structure and molecular geometry of the complexes as [M(ATBS)₂ ] (M = Cu, Co, and Ni) and [Mn(ATBS)(H₂ O)₂ ]. Significantly, the prepared compounds showed strong inhibition activity for a wide spectrum of bacteria (Escherichia coli, Bacillus subtilis, and Staphylococcus aureus) and fungi (Candida albicans, Aspergillus flavus, and Trichophyton rubrum), with the ATBS-Ni complex being the most promising antibiotic agent. Molecular docking studies of the binding interaction between the title complexes with the bacterial protein receptor CYP51 revealed clear insights about the inhibition nature against the studied microorganisms, with the following order: ATBS-Cu > ATBS-Mn > ATBS-Ni > ATBS-Co for complex stability. Moreover, the cytotoxicity measurements of all prepared metal complexes against the colon carcinoma (HCT-116) and hepatocellular carcinoma (Hep-G2) cell lines showed exceptional anticancer efficacy of the complexes as compared with the free ATBS Schiff base ligand. Significantly, the results attested that ATBS-Cu is the most effective complex against HCT-116 cells, whereas ATBS-Mn has the highest cytotoxic efficiency against Hep-G2 cells. Furthermore, electronic spectra, viscosity measurements, and gel electrophoresis techniques were employed to probe the interaction of all prepared ATBS-metal complexes with calf thymus (CT)-DNA. Results confirmed that all complexes are strongly bound to CT-DNA via intercalation mode, with the ATBS-Co complex having the highest binding ability.

New Coordination Compounds of CuII with Schiff Base Ligands—Crystal Structure, Thermal, and Spectral Investigations

The new mono-, di- and tetranuclear coordination compounds [Cu(HL1)]·H2O (1), [Cu2(L1)(OAc)(MeOH)]·2H2O·MeOH (2), [Cu4(L2)2(OAc)2]·4MeOH (3), and [Cu4(L2)2(OAc)2]·4H2O·4MeOH (4) were synthesized by the direct reaction of 2,2′-{(2-hydroxypropane-1,3-diyl)bis[nitrilomethylidene]}bis(4-bromo-6-methoxyphenol) (H3L1) or 2,2′-{(2-hydroxypropane-1,3-diyl)bis(nitriloeth-1-yl-1-ylidene)}diphenol (H3L2) and the Cu(II) salt. They were characterized by elemental analysis, X-ray fluorescence (XRF), Fourier transform infrared (FTIR) spectroscopy, simultaneous thermal analysis and differential scanning calorimetry (TG/DSC), and thermal analysis coupled with Fourier transform infrared spectroscopy (TG-FTIR) techniques and the single crystal X-ray diffraction study. In the dinuclear complex 2, the copper(II) ions are bridged by an alkoxo- and a carboxylato bridges. The tetranuclear complexes 3 and 4 are formed from dinuclear species linkage through the phenoxo oxygen atoms of the fully deprotonated H3L2. Compounds 1–4 are stable at room temperature. During heating in air, at first, the solvent molecules (water and/or methanol) are lost and after that, the organic part undergoes defragmentation and combustion. The final decomposition solid product is CuO. The main gaseous products resulting from the thermal degradation of 1–4 in a nitrogen atmosphere were: H2O, MeOH, CH3COOH, CH4, C6H5OH, CO2, CO, and NH3.

Non-Linear Optical Property and Biological Assays of Therapeutic Potentials Under In Vitro Conditions of Pd(II), Ag(I) and Cu(II) Complexes of 5-Diethyl amino-2-({2-[(2-hydroxy-Benzylidene)-amino]-phenylimino}-methyl)-phenol

Herein, we report facile procedures for synthesis of a new Schiff base ligand (H₂L,5-Diethylamino-2-({2-[(2-hydroxy-benzylidene)-amino]-phenylimino}-methyl)-phenol) and its Ag(I), Pd(II) and Cu(II) complexes. The structure of the H₂L ligand as well as its metal complexes was deduced based on wide range of analytical, structural and spectroscopic tools, along with theoretical evidence via density functional theory (DFT) calculations. The obtained results indicated that the Schiff base (H₂L) ligand acts as a tetradentate N₂O₂ donor with two azomethine nitrogen’s (N1, N2) and two deprotonated phenolic oxygens (O1, O2) atoms. A distorted octahedral structure is assigned to [CuL(OH₂)₂]·3/2H₂O complex and square planar structure for PdL and AgL complexes. The electronic structure and non-linear optical (NLO) property of the prepared compounds were discussed theoretically by the B3LYP/GENECP program. Results revealed that all complexes have non-planner geometries as indicated from the dihedral angles. The charge transfer occurs within the synthesized complexes as indicated from the calculated energy gap between HOMO and LUMO energies. The H₂L ligand and its complexes are excellent candidates for NLO materials as implied from their hyperpolarizabilities and polarizabilities values. The biological activities of the prepared complexes against selected microorganisms and cancer cell lines gave good growth inhibitory effect. The biocidal potencies of the ligand and its complexes can be arranged as follows: AgL > CuL > PdL > H₂L, as compared to the used standard drugs. The antiproliferative activity of the studied complexes against different carcinoma cell lines such as liver (Hep-G2), breast (MCF-7) and colon (HCT-116) followed the order H₂L < AgL< PdL < CuL < vinblastine. Probing the binding interactions of prepared complexes with calf thymus (CT)-DNA using electronic absorption, gel electrophoresis and viscosity measurements revealed strong interaction via intercalation modes, as also evidenced by their molecular docking study.

Recent Studies on the Antimicrobial Activity of Transition Metal Complexes of Groups 6–12

Antimicrobial resistance is an increasingly serious threat to global public health that requires innovative solutions to counteract new resistance mechanisms emerging and spreading globally in infectious pathogens. Classic organic antibiotics are rapidly exhausting the structural variations available for an effective antimicrobial drug and new compounds emerging from the industrial pharmaceutical pipeline will likely have a short-term and limited impact before the pathogens can adapt. Inorganic and organometallic complexes offer the opportunity to discover and develop new active antimicrobial agents by exploiting their wide range of three-dimensional geometries and virtually infinite design possibilities that can affect their substitution kinetics, charge, lipophilicity, biological targets and modes of action. This review describes recent studies on the antimicrobial activity of transition metal complexes of groups 6–12. It focuses on the effectiveness of the metal complexes in relation to the rich structural chemical variations of the same. The aim is to provide a short vade mecum for the readers interested in the subject that can complement other reviews.

Synthesis and characterization of new Cr(III), Fe(III) and Cu(II) complexes incorporating multi-substituted aryl imidazole ligand: Structural, DFT, DNA binding, and biological implications

Designing new metal-based molecular antibiotics is an efficient approach to overcome the growing threat of antimicrobial resistance. In this paper, novel Cr(III), Fe(III) and Cu(II) complexes comprising substituted aryl imidazole ligand (MSEB), namely (2-(1-(2-hydroxyethyl)-4,5-diphenyl-1H-imidazole-2-yl)(4-bromophenol)) have been synthesized and characterized using infra-red (IR), ultraviolet-visible (UV-Vis) and ¹H, ¹³C NMR spectroscopic techniques, together with elemental (CHN) and thermogravimetric analyses, molar conductance, and magnetic susceptibility measurements. The combined results along with the DFT calculations revealed a 1:1 (M: L) stoichiometric ratio and the complexes adopted distorted-octahedral geometries to afford [Cr(MSEB)Cl₂(H₂O)₂], [Fe(MSEB)(NO₃)₂(H₂O)₂] and [Cu(MSEB)Cl(H₂O)₃] respectively. Biological studies showed that all complexes exhibited powerful antimicrobial activity against various strains of bacteria and fungi, S. aureus (+ve), E. coli (-ve) and P. aeruginosa (-ve) bacteria and T. Rubrum, C. albicans, and A. flavus fungi. Moreover, the three metal-complexes showed high in vitro cytotoxicity against Colon (HCT-116), Breast (MCF-7), and hepatic cellular (HepG-2) carcinoma cell lines, with MSEBCu complex being the most cytotoxic one. Finally the binding interactions of the complexes with CT-DNA were explored using UV-Vis spectroscopy, viscosity and gel electrophoreses measurements.