Metal-ligand Complexes Research Articles

A triradical-containing trinuclear Pd(II) complex: spin-polarized electronic transmission, analog resistive switching and neuromorphic advancements.

Neuromorphic computation has emerged as a potential alternative to subvert the von Neumann bottleneck issue in conventional computing. In this context, the development of resistive switching-based memristor devices mimicking various synaptic functionalities has engendered paramount attention. Here, we report a triradical-containing trinuclear Pd(II) cluster with a cyclohexane-like framework constituted by the Pd-Se coordination motif displaying facile memristor property with neuromorphic functionality as a thin-film device. The metal-ligand complex (complex 1) possessed an St = 1/2 ground state by experiencing a spin-frustrated-type magnetic coupling phenomenon amongst the three ligand-based organic radicals (SR = 1/2), coordinated to the Pd(II) ions. Three reversible one-electron reduction waves countered with a one-electron and one two-electron reversible oxidation waves were noticed in the cyclic voltammogram of the complex, confirming electrons accepting and releasing capacity of the complex at low potentials, i.e., within +0.2 V to -1.1 V. Employing the radical-containing complex 1 as the active thin-film sandwiched between two orthogonal electrodes, resistive switching based memristor property with biological synaptic actions were successfully emulated. Intriguingly, the artificial neural network (ANN) simulated efficient pattern recognition demonstrated using the recorded potentiation and depression curves from the device, which is a step ahead for the hardware realization of neuromorphic computing. The performance of the ANN on MNIST data with reduced image resolution has further been evaluated. Density functional theory (DFT)-based theoretical calculation predicted that the spin-polarized electronic transmission substantiated the memristive property in the neutral complex 1.

Unveiling the ion sensing capabailities of 'click' derived chalcone-tailored 1,2,3-triazolic isomers for Pb(ii) and Cu(ii) ions: DFT analysis.

In this study, two novel chalcone-derived 1,2,3-triazole-appended positional isomers (probe 6 and probe 9) were synthesized via the 'CuAAC' (Cu(i) - catalysed alkyne azide cycloaddition) methodology for the purpose of metal ion detection. The synthesized probes underwent characterization utilizing standard spectroscopic methodologies including FTIR, NMR (1H and 13C), and mass spectrometry. Subsequently, the sensing capabilities of these probes were explored using UV-Vis and fluorescence spectroscopy, wherein their selective recognition potential was established for Pb(ii) and Cu(ii), both of which can pose serious health hazards when prevalent in the environment above permissible limits. Both the probes exhibited fairly low limits of detection (LoD), determined as 5.69 μM and 6.55 μM in the case of probe 6 for Pb(ii) and Cu(ii) respectively; whereas the probe 9 exhibited an LoD of 5.06 μM and 7.52 μM for Pb(ii) and Cu(ii), respectively. The job's plot for the probe demonstrates the formation of a 1 : 1 complex between the metal and ligand. Furthermore, the interaction of the free probes with the metal ions in the metal-ligand complex was elucidated through 1H NMR analysis and validated theoretically using Density Functional Theory (DFT) simulations with the B3LYP/6-311G++(d,p) and B3LYP/LANL2DZ basis sets for geometry optimization of the probes and their corresponding metal complexes. These findings offer a reliable approach to Cu(ii) and Pb(ii) ion detection and can be further used for the potential applications in environmental monitoring and analytical chemistry.

Reversible C-C bond formation in group 4 metal complexes: nitrile extrusion via β-aryl elimination.

Pyridylamides of zirconium and hafnium with [C,N,N]-ligands reversibly insert nitriles into M-CAr bonds leading to an observable equilibrium between the starting [C,N,N]-complexes and newly formed [N,N,N]-complexes with a ketimide moiety in a 7-membered metallacycle. The discovered reversible insertion of nitriles into M-CAr bonds represents an unprecedented example of β-aryl elimination from a ketimide ligand in early transition metal complexes. Experimental and computational studies suggest thermodynamic and electronic reasons for this reactivity. Weak orbital overlap between the ketimide nitrogen and the metal, and an unfavorable 7-membered metallacycle destabilize the product of insertion into the M-CAr bond, while the pyridylamide moiety acts as a directing group making the reverse process viable. The influence of non-chelate spectator ligands on the metal center and substituents in nitrile on the thermodynamic stability of the [N,N,N]-complexes was also studied. Exploiting β-carbon elimination in complexes of early transition metals may extend the range of catalysts that are accessible for C-C activation processes in the future.

Metal centers and aromatic moieties in Schiff base complexes: impact on G-quadruplex stabilization and oncogene downregulation

We present the synthesis and characterization of novel square planar transition metal complexes of Schiff base ligands, which act as guanine quadruplex binders and stabilizers.

Manganese(II) and Zinc(II) metal complexes of novel bidentate formamide-based Schiff base ligand: synthesis, structural characterization, antioxidant, antibacterial, and in-silico molecular docking study.

A new bidentate Schiff base ligand (C16H16Cl2N4), condensation product of ethylene diamine and 4-chloro N-phenyl formamide, and its metal complexes [M(C16H16Cl2N4)2(OAc)2] (where M = Mn(II) and Zn(II)) were synthesized and characterized using various analytical and spectral techniques, including high-resolution mass spectrometry (HRMS), elemental analysis, ultraviolet-visible (UV-vis), Fourier-transform infrared (FTIR) spectroscopy, AAS, molar conductance, 1H NMR, and powder XRD. All the compounds were non-electrolytes and nanocrystalline. The synthesized compounds were assessed for antioxidant potential by DPPH radical scavenging and FRAP assay, with BHT serving as the positive control. Inhibitory concentration at 50% inhibition (IC50) values were calculated and used for comparative analysis. Furthermore, the prepared compounds were screened for antibacterial activity against two Gram-negative bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram-positive bacteria (Escherichia coli and Salmonella typhi) using disk-diffusion methods, with amikacin employed as the standard reference. The comparison of inhibition zones revealed that the complexes showed better antibacterial activity than the ligand. To gain insights into the molecular interactions underlying the antibacterial activity, the ligand and complexes were analyzed for their binding affinity with S. aureus tyrosyl-tRNA synthetase (PDB ID: 1JIL) and S. typhi cell membrane protein OmpF complex (PDB ID: 4KR4). These analyses revealed robust interactions, validating the observed antibacterial effects against the tested bacterial strains.

PKaH values and θH angles of phosphanes to predict their electronic and steric parameters.

Phosphanes play an important role in various applications, serving as a class of organic bases with basicities spanning more than 30 orders of magnitude. Accessing comprehensive basicity data for phosphanes has been challenging due to scattered information across multiple sources and notable gaps in the existing data. In this report, we present basicities (pKaH values) of a diverse set of phosphanes, both newly measured or calculated and collected from the literature. We demonstrate that pKaH values can serve as an alternative to Tolman electronic parameters (TEP values) in evaluating the electronic properties of phosphanes. Additionally, we suggest parameters for assessing the steric properties of phosphanes without the need for preparation or calculation of metal-ligand complexes.

Rapid nucleation and optimal surface-ligand interaction stabilize wurtzite MnSe.

Non-native structures (NNS) differ in discrete translational symmetry from the bulk ground state native structure (NS). To explore the extent of deconvolution of various factors relevant to the stabilization of the wurtzite/NNS of MnSe via a heat-up method, we performed experiments using various ligands (oleic acid, oleylamine, octadecylamine, stearic acid, and octadecene), solvents (tetraethylene glycol and octadecene), and precursor salts (manganese chloride and manganese acetate). Experiments suggest that oleic acid in the presence of tetraethylene glycol and oleylamine in the presence of octadecene stabilize wurtzite/NNS. Further, density functional theory (DFT) computations explore the interaction between the functional groups in ligands and the most exposed surfaces of wurtzite/NNS and rocksalt/NS polymorphs. Computations suggest that the interactions between relevant surface facets with carboxylic acid and the double bond functional groups suppress the phase transformation from NNS to NS. In addition, the ionizability of the precursor salt also determines the rate of formation of the metal-ligand complex and the rate of nucleation. Consequently, the formation rate of the Mn-ligand complex is expected to be greater in the case of chloride salt than acetate salt because the chloride salt has higher ionizability in ethylene glycol. From the above, we conclude that the kinetics of the wurtzite/NNS to rocksalt/NS phase transformation depends mainly on two factors: (1) nucleation/growth kinetics which is controlled by the ionizability of the precursor salt, solvent, and stability of the metal-ligand complex, and (2) the activation energy barrier of the NNS to NS conversion which is controlled by surface energy minimization with the ligand.

Modelling ligand exchange in metal complexes with machine learning potentials.

Metal ions are irreplaceable in many areas of chemistry, including (bio)catalysis, self-assembly and charge transfer processes. Yet, modelling their structural and dynamic properties in diverse chemical environments remains challenging for both force fields and ab initio methods. Here, we introduce a strategy to train machine learning potentials (MLPs) using MACE, an equivariant message-passing neural network, for metal-ligand complexes in explicit solvents. We explore the structure and ligand exchange dynamics of Mg2+ in water and Pd2+ in acetonitrile as two illustrative model systems. The trained potentials accurately reproduce equilibrium structures of the complexes in solution, including different coordination numbers and geometries. Furthermore, the MLPs can model structural changes between metal ions and ligands in the first coordination shell, and reproduce the free energy barriers for the corresponding ligand exchange. The strategy presented here provides a computationally efficient approach to model metal ions in solution, paving the way for modelling larger and more diverse metal complexes relevant to biomolecules and supramolecular assemblies.

A new family of macrocyclic antibiotics based-on Pillar[5]arene concluding multi quinoline moieties

Due to the many negative effects of increasing resistance to traditional antibiotics on living organisms, the development of new antibiotic classes has become imperative and macrocyclic compounds come to the fore for the solution of this problem. In this paper, the Pillar [5]arenes including ten and five quinoline units were synthesized and characterized by some procedures such as magnetic susceptibility, FT-IR, elemental analyses, 1H NMR, 13C NMR, melting point. Moreover, zinc(II) and copper (II) complexes were prepared to compare the antimicrobial effects with macrocyclic ligands. In the complex compounds, the metal:ligand ratios were determined with Job method as 1:2 and 1:1 for deca and penta units, respectively. The magnetic properties of the copper (II) complexes are 1.83 BM and 1.87 BM while zinc complexes have a diamagnetic character. The target macrocyclic ligands (Compound 7 and 8) and their metal complexes (Cu(II) and Zn(II)) were screened for the antimicrobial properties against the bacterial strains of Escherichia coli ATCC 25922, Staphylococcus aureus (MRSA) ATCC 43300, Klebsiella pneumoniae. ATCC 70603, Salmonella enteritidis ATTC 13076, Pseudomonas aeruginosa ATCC 27853, Bacillus cereus ATTC 11778, Sarcina lutea ATCC 9341, and yeast Candida albicans NRRL Y-417 by using broth microdilution method. Compound 7 has the optimum MIC values for S. aureus (MRSA), B. cereus, C. albicans and P. aeruginosa microorganisms that they were determined as 23.43, 46.87, 93.75 and 187 μg/mL, respectively. Moreover, Compound 8-Cu(II) complex was defined as an excellent antimicrobial agent against MRSA, B. cereus and C. albicans strains that the MIC values were determined as 3.9 μg/mL for both bacteria. The metal complexes of the target macrocyclic ligands have a more antimicrobial effect than the reactants and the target macrorings. Moreover, they have more successful results for Gram positive derivatives rather than Gram negative microorganisms.

Role of aurone ligands in microwave enhanced Mn (II) and Co (II) catalyzed dehydrogenative coupling reaction: An efficient ligand for the synthesis of quinoline, pyridine, and pyrrole

AbstractThe role of new series of phosphine‐free aurone ligands have been investigated in microwave‐enhanced Mn (II) and Co (II) dehydrogenative coupling reactions. Various heterocyclic compounds such as Quinoline, pyridine, and pyrrole have been synthesized and characterized by NMR spectroscopy. The synthesized ligands (L1–L4) with Mn(II) and Co (II) salt showed excellent catalytic activity and proved to be very effective for the dehydrogenative coupling reaction. This synthetic method involves the in‐situ formation of a metal ligand complex that was analyzed by mass spectrometry. A broad range of substrates including aliphatic ketone, heterocycles, and sterically hindered Ketone coupling partners are well tolerated in the developed protocol.

Designing Metal Complexes for Redox Flow Batteries By High-Throughput Synthesis

Redox flow batteries (RFBs) are an attractive device for high-capacity energy storage systems. Due to the disadvantages of vanadium RFBs such as high cost and limited temperature operability [1], researchers have been developing new redox couples to replace vanadium. The use of relatively inexpensive transition metals (Fe, Cr, Co, etc.) in combination with ligands to form metal-ligand complexes has received considerable attention [2]. The redox potential of a metal ion of a metal-ligand complex can be tuned by forming a complex with a ligand, and the metal-ligand complex form helps alleviate the crossover problem [3].A major challenge in the discovery and development of functional materials is to find and select the most optimized candidates from millions of possible materials [4]. High-throughput Synthesis (HTSy) enables simultaneous screening, synthesis and characterization of a large number of different material classes, providing unprecedented throughput and reproducibility. Therefore, HTSy can save energy, time, and cost for more efficient discovery of advanced functional materials [5]. In this study, based on HTSy methods, we used an automatic synthesis device (OT-2 liquid pipetting robot) to mix and heat metals (Ni, Cr, Cu, etc.) and ligand liquids to automatically design metal complexes. At the same time, a robot platform is developed to perform high-throughput electrochemical tests to quickly select suitable metal complexes for RFBs, and then conduct further related RFBs performance tests.

A critical review of the quantification, analysis and detection of radionuclides in the environment using diffusive gradients in thin films (DGT): advances and perspectives

Abstract This critical review explores the quantification, analysis, and detection of radionuclides in the environment using the diffusive gradients in thin films (DGT) technique. Radionuclides, unstable isotopes emitting ionising radiation, are present in the environment due to natural and anthropogenic sources for which concerns are raised about their impact on human health and ecosystems. DGT offers a unique passive sampling approach for understanding the behaviour of radionuclides and other trace elements. This review provides insights into method development, real case scenarios, advantages, limitations, and future perspectives of DGT in radionuclide analysis. In terms of method development, various isotopes have been analysed with varying significance based on origin, concentration, risks, and persistence. Notably, U, Th, Pu, Am, Cm, 99Tc, 226Ra, 137Cs, 134Cs, 232U, 237Np, and 152Eu have been measured, revealing their diverse roles in environmental radioactivity. Real case scenarios illustrate applications in uranium mining, water quality monitoring, and metal speciation studies, shedding light on mobility, bioavailability, and ecological impacts. DGT’s advantages include in-situ monitoring, time-averaged mean concentrations, and comprehensive speciation insights. Challenges include potential influences from biofouling, temperature changes and specifically the possible degradation of the binding and diffuse layer due to ionising radiation in long term exposures. In addition, the distinction between fully labile free metal ions and partially labile metal-ligand complexes introduces a potential limitation in the DGT technique, hence being an opportunity for future studies. Looking forward, DGT is expected to contribute to radiation dose modelling, environmental risk assessment, and water quality monitoring, with ongoing developments enhancing its utility and accuracy.

Design and synthesis of acyclic bis-triazole ligands: Complexation with metal ions, DFT calculations, and biological activity

Triazole-derived heterocyclic compounds have significant biological activities and pharmaceutical stability. A new series of acyclic bis-triazole ligands 16–20 with ester end groups were designed. The synthesized ligands were evaluated for their complexation ability with transition metals (Cu2+, Hg2+, Pb2+, and Zn2+). The molar conductivity of bis-1,2,3-triazole ligand-metal complexes was measured in acetonitrile at a temperature range 288.15–308.15 K. Furthermore, the thermodynamic quantities (∆H°, ∆S°, and ∆G°) were determined using the van't Hoff equation and the computational stability constants of the resulting 1:1 complexes were determined based on 1:1 stoichiometry. Meanwhile, the optimized geometry of ligands and ligand-metal complexes was computationally calculated using density fraction theory (DFT). Moreover, the antioxidant potential, in DPPH and ABTS assays, as well as the antibacterial activity of the bis-1,2,3-triazole ligands were evaluated. Ligands 16, 19, and 20 complexed with Hg2+ as well as ligand 17 with Cu2+, Hg2+, and Pb2+ showed a continuous decrease in molar conductivity on complexation, however, ligand 18 complexed with Cu2+, Hg2+, Pb2+, and Zn2+ begins to level off at a mole ratio of 1:1 (ligand:metal) indicating the formation of stable complexes. Noteworthy, ligand 17 formed a 1:2 and 2:1 ligand-to-metal ratio with Hg2+ and Pb+2 cations, respectively. The formation reactions of all ligand-metal complexes were exothermic and spontaneous indicating a strong triazole-metal interaction based on ∆H° and ∆G° values. Bis-triazole ligands 16–20 revealed antioxidant activity with IC50 values ranging from 89.0 to 156.1 µg/ml in DPPH and 91.3–167.2 µg/ml in ABTS assays. Ligands 16–19 exhibited antibacterial activity against the Gram-positive Bacillus cereus with MICs ranging from 150 to 250 µg/ml. The synthesized bis-triazole ligands have a potential application in the pharmaceutical and food industries. Moreover, the selectivity of ligands 16, 19, and 20 to Hg2+ could be useful for removing such a metal from industrial wastewater containing a variety of toxic heavy metals and ISE construct.

Fluorophore interactions with the surface modes and internal modes of a photonic crystal

The metal-ligand complex tris(2,2′-bipyridine)ruthenium(II) chloride (Ru probe) displays a broad emission spectrum ranging from 540 to 730 nm. The emission spectra of Ru probe were measured when placed on top of a one-dimensional photonic crystal (1DPC), which supports both Bloch surface wave (BSW) and internal modes for wavelengths below 640 nm and only internal modes above 640 nm. The S-polarized emission spectra, with the electric vector parallel to the 1DPC surface, were found to be strongly dependent on the observation angle through the coupling prism. Also, the usual single broad-emission spectrum of Ru probe on glass was converted into two or more narrow-band-spectrum on the 1DPC, with emission band maxima dependent on the observation angle. The two S-polarized emission band peaks for Ru probe were found to be consistent with coupling to the BSW and first internal mode (IM1) of the 1DPC. The same spectral shifts and changes in emission maxima were observed by using Kretschmann and reverse Kretschmann illuminations. As the coupling requires the emitter to be in proximity with the photonic structure, we calculated near- and far-field distributions of a dipole directly located on the 1DPC surface. Finite-Difference Time-Domain (FDTD) simulations were performed to confirm fluorophore coupling to the BSW and internal modes (IMs). Both the measured and simulated results showed that IM coupled emission is significant. Coupling to the IM mode occurred at longer wavelengths where the 1DPC did not support a BSW. These results demonstrate that a simple Bragg grating, without a BSW mode, can be used for detection of surface-bound fluorophores.

Theoretical insights into the extraction behaviors of neptunium(VI) and plutonium(IV) based on the structure of organophosphorus ligands

Organophosphorus ligands such as TBP, TiAP, and DMHMP have exhibited excellent performance in recovering actinides from spent fuel. In this work, the molecular geometries and properties of TBP, TiAP and DMHMP were investigated using density functional theory calculations. Furthermore, the extraction mechanism of ligands for actinides (Np(Ⅵ), Pu(Ⅳ)) was further elucidated by simulating the microstructures and extraction reactions of metal–ligand complexes. The results demonstrate that the complexation ability of the three ligands on actinide cations (NpO22+ and Pu4+) follows the order of DMHMP > TiAP > TBP. The electrostatic potential (ESP) analysis indicates that the nucleophilic ability of DMHMP is stronger than that of the other two ligands. The frontier molecular orbital analysis of the three ligands represents that DMHMP has the highest HOMO energy, suggesting that it has the strongest electron-donating capability and is more likely to bond with metal ions. The values of Wiberg bond indices (WBI) suggest that the MO bonds in DMHMP complexes have more covalency. According to the QTAIM analysis, the interactions between actinide cations and the ligands are predominantly ionic in nature. The molecular orbital analysis of the complexes shows that the M(NO3)n·2DMHMP (MNpO22+ and Pu4+) complexes are more stable, which is supported by thermodynamic energy analysis. This work has clarified the complexing properties of actinide cations with three ligands, shedding light on the extraction mechanisms of organophosphorus ligands for actinide cations. It is anticipated to lay the theoretical foundation for the efficient recovery of critical actinide elements in spent fuel reprocessing, which will also provide innovative approaches for the design and development of related separation processes.

Synthesis, characterization and <i>In-silico</i> study of anti-cancer potential of Cu(II) and Ni(II) complexes of (E)-2- benzylidenehydrazinecarboxamide

In this study, (E)-2-benzylidenehydrazinecarboxamide coordination compounds and mixed ligand metal complexes with oxalic acid or 1,2-diaminocyclohexane were synthesized. Their potential cytotoxic effects and interactions with B-DNA evaluated. This was with a view to demonstrate their potential as anticancer agents for breast cancer. (E)-2-Benzylidenehydrazinecarboxamide (benzaldehyde semicarbazone) coordination compounds of Cu(II) and Ni(II) and mixed ligand metal complexes with oxalic acid and 1,2- diaminocyclohexane were synthesized. The resultant complexes were characterized by physicochemical techniques including melting point measurement, percent metal analysis, solubility, and magnetic susceptibility measurements. Electronic and Fourier transform infrared (FTIR) spectroscopy, were performed to further lucidate the structures of the complexes. The synthesized compounds were examined for their cytotoxic effects and DNA interactions with B-DNA. The results obtained showed that all the ligands used were bidentate ligands. They bound to the metal ions through oxygen and nitrogen atoms. All synthesized compounds showed good cytotoxic activity against brine shrimp nauplii except for the (E)-2-benzylidenehydrazinecarboxamide copper(II) complex. All of the metal complexes, with the exception of the (E)-2- enzylidenehydrazinecarboxamide coordination copper complex, bound to DNA with moderate binding energies. They favoured conventional hydrogen bonding and hydrophobic interaction mostly. The copper complex with 1,2-diaminocyclohexane had the most interaction and a good binding effect to the DNA and better than oxaliplatin, the standard used. This therefore indicated the potential of these compounds as probable chemotherapeutic agents against breast cancer cells.

Crystal structure, Hirshfeld surface analysis and energy framework calculations of different metal complexes of a biphenol-based ligand: Role of solvent and transition metal ion

A new Pd(II) complex of the previously reported ligand N,N′-bis[(2,2′-dihydroxybiphen-3-yl)methyl]-N,N′-dimethylethylenediamine (L) was obtained from N,N-dimethylformamide/water. The roles in the solid state assembly of solvent molecules and molecular conformation were studied by comparing six complexes of L containing different metal centers (Ni(II), Cd(II), Cu(II), Pd(II)). Hirshfeld surface analysis, 2D fingerprint plots and energy frameworks calculations were used to investigate the intermolecular interactions within the crystal packings. Pd(II) and Ni(II) complexes arrange to form ribbons, while Cd(II) and Cu(II) complexes form 3D networks. Interactions between complexes and solvent molecules in the previously reported Pd(II) complex are replaced by complex-complex interactions in the new Pd(II) complex, while butanol and methanol are interchangeable in the interactions within the Ni(II) complexes. The present study suggested that the solid state assembly of these systems is mainly driven by the molecular conformation, that depends in turn by the metal ion involved, while the solvent only plays a minor role.

Isolation, Characterization and Reactivity of Key Intermediates Relevant to Reductive (Electro)catalysis with Cp*Rh Complexes Containing Pyridyl-MIC (MIC=Mesoionic Carbene) Ligands.

In recent years, metal complexes of pyridyl-mesoionic carbene (MIC) ligands have been reported as excellent homogeneous and molecular electrocatalysts. In combination with group 9 metals, such ligands form highly active catalysts for hydrogenation/transfer hydrogenation/hydrosilylation catalysis and electrocatalysts for dihydrogen production. Despite such progress, very little is known about the structural/electrochemical/spectroscopic properties of crucial intermediates for such catalytic reactions with these ligands: solvato complexes, reduced complexes and hydridic species. We present here a comprehensive study involving the isolation, crystallographic characterization, electrochemical/spectroelectrochemical/theoretical investigations, and in-situ reactivity studies of all the aforementioned crucial intermediates involving Cp*Rh and pyridyl-MIC ligands. A detailed mechanistic study of the precatalytic activation of [RhCp*] complexes with pyridyl-MIC ligands is presented. Intriguingly, amphiphilicity of the [RhCp*]-hydride complexes was observed, displaying the substrate dependent transfer of H+ , H or H- . To the best of our knowledge, this study is the first of its kind targeting intermediates and reactive species involving metal complexes of pyridyl-MIC ligands and investigating the interconversion amongst them.

SYNTHESIS, CHARACTERIZATION AND XRD ANALYSIS OF COPPER (II) AND IRON (II) COMPLEXES OF BENZOIC ACID HYDRAZIDE.

Schiff bases are an important class of organic compounds, which play an important role in medicinal and pharmaceutical applications. Metal complexes formed by the reactions of keto forms of Benzoic acid hydrazide (BAH) with Cu(II) and Fe(II) sulphate ions were prepared and characterized by X-ray Diffraction analysis (XRD), Fourier Transform Infrared (FTIR) and electronic absorption spectra studies. The results showed that the hydrazides reacted with the metal salts in 1:2 molar ratio in all the complexes and acts as neutral bidentate ligands. The X-ray diffraction (XRD) pattern of the metal complexes provides a detailed comparative account of the behavior of the metal complexes of hydrazide ligand metal complexes. The pattern of BAH complexes shows the main characteristics peak and broad shoulder. In view of the relative half value width (FWHM), it may be concluded that the BAH-Cu is partially crystalline and while the BAH-Fe shows an amorphous nature. The broad characteristic peak indicates the amorphous nature of the polymers. The solubility test on the ligands and its metal (II) complexes revealed their solubility in ethanol and dimethylsulphoxide (DMSO). The infrared spectra of the hydrazide showed that ?(C=O), the carbonyl stretching mode, the coupling between the in-plane bending ?(N-H) and ?(C-N) and the stretching frequency for the amino group ?(NH2) all experienced shifts to lower wave numbers in the complexes suggesting the coordination of the moieties to the metal ions. The electronic absorption spectra of Cu(II) complexes showed absorption band located at 36,496 cm-1 showing a tetrahedral geometry while Fe(II) BAH and BAH ligand show absorption band at a shoulder around 16051 cm-1 with 4A2 ? 4T1 (P) respectively consistent with a four coordinate tetrahedral geometry.

Antibacterial, antifungal, DNA interactions, and antioxidant evaluation of Cu(II) Co(II), Ni(II), Mn(II) and UO2(II) mixed ligand metal complexes: Synthesis, characterization and molecular docking studies

The current work was designed to prepare novel 1:1:1 Metal (M): primary ligand (HL1): co-ligand (HL2) complexes; [Cu(L1)(L2)(OH2)2] (1), [Co(L1)(L2)]H2O (2), [Ni(L1)(L2)(OH2)2] 0·.75H2O (3) and [Mn(L1)(L2)(OH2)2] 4·.5H2O (4) and [UO2(L1)(L2)] (5) from ligands 7-Formyl-8-hydroxyquinoline (oxine) (HL1), 2-aminophenol (HL2) and characterized by analytical and spectroscopic techniques. FTIR, mass spectra, ESR techniques, elemental analysis, and thermal analysis were used to characterize the newly formed complexes. The results of the elemental analysis show the formation of [HL1:M:HL2] complexes. The ligands act as a mononegative bidentate chelating agent coordinating through C = O, NH2 and two OH groups by replacement of a proton from the latter groups. The molecular docking between the protein receptors and the ligand (HL1), ligand (HL2) and its mixed ligand metal complexes (1–5) was studied. The interface between HL2, complexes and calf thymus DNA (CT-DNA) displays hypochromism behavior. The binding value constant (Kb) are calculated and found to be 5.29 × 103, 8.49 × 104, 2.45 × 105, 2.96 × 104 and 1.16 × 104, 3.08 × 104 M−1 for HL2 and its mixed ligand metal complexes (1–5), respectively. Antimicrobial properties of ligands and the synthesized complexes were also screened versus G + ve bacteria (S. aureus and B. cereus), G-ve bacteria (K. pneumoniae, Pseudomonas sp. and E. coli, and fungi (F. oxysporum, A. niger, and C. albicans). The obtained results revealed the strong antimicrobial action of metal complexes with MIC, MBC and MFC values ranging from 5 to 45 µg/ml. HL1 showed higher antimicrobial and antioxidant activities than HL2 and major of the prepared metal complexes. All metal mixed ligand complexes inhibited the multidrug-resistant bacterium; Klebsiella pneumoniae compared to the standard antibiotic, penicillin G. Also, all metal mixed ligand complexes showed potent antifungal activities against both Aspergillus niger and Candida albicans.