ONO Donor Research Articles

Preparation, characterizations and biological evaluations of new copper(II) complexes containing ONO pincer type ligands

A new heterocyclic Schiff bases, 6‐methyl/8methyl‐2‐oxo‐1,2‐dihydroquinoline‐3‐carboxaldehyde semicarbazones (H2‐6MOQsc‐H) (H2L1) and (H2‐8MOQsc‐H) (H2L2) and their corresponding copper(II) complexes [CuCl2(H2‐6MOQsc‐H)].3H2O (1), [CuCl2(H2‐8MOQsc‐H)].3H2O (2), [CuNO3(H2‐6MOQsc‐H)(H2O)].NO3 (3) and [CuNO3(H2‐8MOQsc‐H)(H2O)].NO3 (4) have been synthesized and characterized by various physicochemical techniques. The single crystal X‐ray diffraction and spectral data revealed that all of the complexes (1‐4), the ligands coordinated to the Cu(II) ion in a neutral manner via ONO donor atoms and all the complexes exhibited distorted squarepyramidal geometry. The consequence of electronegativity and ring size of nitrogen heterocyclic moiety of ONO donor type of copper(II) chelates on nucleic acid interaction and albumin binding was investigated by in vitro experiments. The interaction of compounds with calf‐thymus DNA (CT‐DNA) has been explored by absorption and emission titration, which exposed those ligands/complexes, could bind with CT‐DNA through electrostatic interaction. The results of gel electrophoresis proved the ability of complexes (1‐4) to cleave the pBR322 plasmid DNA. The interaction of serum albumin (BSA) was investigated by UV‐Vis, fluorescence, synchronous and three dimensional fluorescence spectra. In addition, radical scavenging activity, antifungal activity and cytotoxicity of the newly synthesized compounds were also evaluated. From the results of in vitro studies, it is seen that complex 3 has more potential as compared with other complexes and ligands.

New cationic and neutral copper(II) complexes containing 7-hydroxy-4-oxo-4[H]-chromene derived ONO pincer ligands: Synthesis, characterization and in vitro biological evaluations

New Schiff base ligands are prepared by the condensation of 7-hydroxy-3-formylchromone with semicarbazone and phenyl semicarbazone. The complexation of these ligands with Cu(II) ion is proposed in the light of spectral studies (IR, UV–Vis, 1H NMR, 13C NMR, Mass and ESR). In the complexes 1 and 2, the ligands coordinate to the Cu(II) ion in a neutral fashion via ONO donor atoms. The single crystal XRD studies reveal a slightly distorted square-pyramidal geometry for cationic complex (1) and an octahedral geometry for neutral complex (2). Preliminary biological studies such as DNA and Protein binding are carried out by using absorption and emission titration methods. Observation of intercalative mode of binding with Calf Thymus DNA (CT-DNA) is confirmed by means of viscosity measurements. The micro-environmental changes occurring in Bovine Serum Albumin (BSA) and Human Serum Albumin (HSA) are monitored via three dimensional (3D) fluorescence studies. The compounds ability in inhibiting microbial growth is tested against different pathogens. MCF-7 (human breast cancer) and A549 (human lung carcinoma) cell lines are utilized to check the anticancer potential of the synthesized compounds by using MTT, LDH and NO assays. The results show that complexes 1 and 2 exhibited potent cytotoxic activity over standard drug cisplatin.

Bis-diorganotin(IV) complexes with binucleating hydrazones derived from a methylene-bis-aromatic aldehyde as linker: Synthesis, spectral and structural characterization, antibacterial activity and DNA cleavage studies

Two bis-hydrazone, H4La and H4Lb, have been synthesized from reaction of 5,5′-methylene-bis-salicylaldehyde with benzhydrazide and furan-2-carbohydrazide, respectively. New organotin(IV) complexes, (R2Sn)2L [L = La: R = Me (1), Ph (2); L = Lb: R = Me (3), Ph (4)] have been synthesized by reaction of dihydrazone ligands with R2SnCl2 (R = Me or Ph). The synthesized compounds have been investigated by elemental analysis and IR, 1H NMR, and 119Sn NMR spectroscopy. The structures of 1 and 2 have been also confirmed by X-ray crystallography. The results show that the dihydrazone acts as a tetrabasic ligand in the enolic form and is coordinated to two SnR2 moieties via ONO donor domains by the imine nitrogen and phenolic and enolic oxygen atoms. All complexes are binuclear and the coordination number of both tin is five. The in vitro antibacterial activity of ligands and complexes has been evaluated against Gram-positive (Bacillus subtilis and Staphylococcus aureus) and Gram-negative (Escherichia coli and Pseudomonas aeruginosa) bacteria and compared with standard drugs. The synthesized compounds also have been investigated for the chromosomal and plasmid DNA cleavage activity. The complexes significantly inhibited bacterial growth, while none of compounds showed DNA cleavage activity.

Pi-pi interaction and hydrogen bonding in crystal structure of vanadium(V) complex containing mono hydrazone ligand: Synthesis and protein binding studies

Dioxidovanadium(V) complex containing hydrazone ligand has been synthesized in good yield, the complexes was characterized by elemental analysis, IR, UV–Visible and 1H NMR spectroscopy. The structure of the complex has been established by Single Crystal X-ray diffraction technique. Complex crystallized with monoclinic P21/n space group with cell parameters a/Å=11.9791(7), b/Å=19.7898(10), c/Å=16.4661(9), α/°=90, β/°=106.059(6), and γ/°=90, respectively. The ligand bonded to metal ion in tridentate fashion through ONO donor atoms forming a distorted square pyramidal geometry around vanadium and sodium ion with their geometrical index τ=0.33 and τ=0.12. The binding interaction of the synthesized complex with protein (BSA) was also studied and KBSA was found to be 2.712×107M−1.

Synthesis, Characterization, Antimicrobial Evaluation and DFT Calculations of Fe(III), Ni(II) and Cu(II) Complexes of Tridentate ONO Donor Ligand

Synthesis, Characterization, Antimicrobial Evaluation and DFT Calculations of Fe(III), Ni(II) and Cu(II) Complexes of Tridentate ONO Donor Ligand

New approach for the quantification of metallic species in healthcare products based on optical switching of a Schiff base possessing ONO donor set

A new method is reported for the quantification of some metallic components of healthcare products utilizing a Schiff base chelator derived from 2-hydroxyacetophenone and ethanolamine. The Schiff base chelator recognizes some metallic species such as iron, copper and zinc (important components of some healthcare products), and cadmium (common contaminant in healthcare products) giving colorimetric/fluorimetric response. It coordinates with Fe2+/Fe3+ and Cu2+ ions via ONO donor set and switches the colour to bright red, green and orange, respectively. Similarly, it switches ‘ON’ a fluorometric response when coordinates with Zn2+ and Cd2+ ions. In the present approach, detailed studies on the colorimetric and fluorimetric response of ONO Schiff base is investigated in detail. The Job plot for the complexation of ONO switch with various metal ions suggested formation of 1:1 (metal-chelator) complex with Fe2+, Fe3+, and Cu2+ while 1:2 (metal-chelator) for Zn2+ and Cd2+ ions. The limit of detection, limit of quantification are 6.73, 18.0, 25.0, 0.65, 1.10μM and 27.0, 72.0, 100.0, 2.60 and 4.40μM for Fe2+, Fe3+, Cu2+, Zn2+ and Cd2+ ions, respectively. Under the optimized conditions, chelator was used for the quantification of important metals present in healthcare products via direct dissolution and furnace treatment during sample preparation. The results were found precise and accurate for both sample preparation techniques using the developed method.

Synthesis, spectroscopic characterization and antimicrobial activity evaluation of new tridentate Schiff bases and their Co(II) complexes

A series of Schiff base tridentate ligands and their respective Co(II) complexes have been synthesized and characterized by elemental analysis, magnetic susceptibility, IR, NMR and UV–Visible spectra, thermal studies. The IR spectral data suggested that all the ligands acted as monobasic tridentate towards central Co(II) ion with an ONO donor atoms sequentially. Analytical data and magnetic susceptibility revealed 1:2 metal to ligand stoichiometry and octahedral geometry for all Co(II) complexes. All the prepared compounds were also screened for antimicrobial activity against 5 ESBL (Extended Spectrum β-lactamase) and 5 MBL (Metallo β-lactamase) producing uropathogens and for antitubercular activity against Mycobacterium tuberculosis (H37Rv strain).

DNA interaction, antioxidant and in vitro cytotoxic activities of some mononuclear metal(II) complexes of a bishydrazone ligand

A tridentate ONO donor bishydrazone ligand, 3-(((3-oxoindolin-2-ylidene)hydrazono) methyl)quinoxalin-2(1H)-one (L) was synthesized. Using the ligand, mononuclear metal complexes of the type [M(L)(OAc)] (M=Co(II), Ni(II), Cu(II) and Zn(II), OAc=–OCOCH3) were synthesized. The newly synthesized compounds were thoroughly characterized by various analytical and spectral techniques. Tetrahedral geometry was proposed for Co(II), Ni(II) and Zn(II) complexes, while square planar geometry has been assigned to the Cu(II) complex. The in vitro antibacterial, antifungal and antioxidant studies reveal that the Cu(II) complex of the bishydrazone ligand possess higher activities. DNA binding studies suggest that the present compounds interact with CT DNA through intercalation. This was further supported by molecular docking. Gel electrophoresis studies substantiated the involvement of free radicals in the cleavage of pUC18 DNA. In vitro cytotoxicity of the compounds against MCF-7 cell line was also examined. The molecular modeling studies reveal that the compounds strongly interact with VEGFR-2 kinase receptor through hydrogen bonding, π-π, π-cation and sigma-π interactions. The bioavailability and bioactivity determination of the compounds suggest that the present compounds may be utilized as drug candidates.

Synthesis, characterization and antibacterial activity evaluation of trinuclear Ni(II) complexes with N-substituted salicylhydrazide ligands

Three novel trinuclear Ni(II) complexes, [Ni3(L1)2(py)4] (1), [Ni3(L2)2(H2O)2(DMA)2] (2) and [Ni3(L3)2(py)4] (3), with trianionic pentadentate ligands derived from salicylhydrazide with N-acyl substituents [H3L1=N2-crotonoylsalicylhydrazide, H3L2=N2-(3,3-dimethylacryloyl)salicylhydrazide, H3L3=N2-cinnamoylsalicylhydrazide] were synthesized and characterized by elemental analysis, spectroscopic techniques, like UV–Vis, FT-IR and NMR, molar conductivity and magnetic susceptibility measurements, and single crystal X-ray diffraction. The solid state structures of the complexes reveal the binding modes of the different ligands via ONO donor atoms. Complex 1 crystallises in the triclinic system while complexes 2 and 3 crystallise in the monoclinic system with space groups P1¯ (1) and P21/c (2 and 3). Computational studies were performed using Density Functional Theory (DFT) to obtain physical properties of all three complexes. The ligands and their metal complexes were screened for antibacterial activity to assess their inhibition potential against two Gram positive bacteria; Staphylococcus aureus and Bacillus subtilis and two Gram negative bacteria; Escherichia coli and Pseudomonas aeruginosa by the well diffusion method using gentamicin as a positive control. Antibacterial screening data reveals that the trinuclear Ni(II) complexes have significantly enhanced inhibitory activities compared to the ligands.

New polymeric, dimeric and mononuclear dioxidomolybdenum(vi) complexes with an ONO donor ligand: crystal structures, DFT calculations, catalytic performance and protein binding study of the ligand

Catalytic activity and BSA binding is reported.

Dioxidomolybdenum(VI) complexes of tridentate ONO donor aroylhydrazones: Syntheses, spectral and structural characterization

Four dioxidomolybdenum(VI) complexes, [MoO2(L1)(H2O)] (1), [MoO2(L1)(H2O)]·(4,4′-bipy) (2), [(MoO2(L1))2(4,4′-bipy)]·2H2O (3) and [MoO2(L2)(DMF)] (4), of two tridentate ONO donor aroylhydrazones, H2L1 and H2L2 (where H2L1=3-methoxy-2-hydroxybenzaldehyde-2-furoic acid hydrazone and H2L2=4-benzyloxy-2-hydroxybenzaldehyde-4-nitrobenzoic hydrazone), have been synthesized and characterized by partial elemental analyses, molar conductivity measurements, FT-IR and electronic spectral studies. A distorted octahedral geometry was established for all the complexes using single crystal XRD studies. In all the complexes, the aroylhydrazone coordinates to the MoO22+ core through the phenolate oxygen, azomethine nitrogen and iminolate oxygen atoms, furnishing a vacant coordination site that can be utilized for binding of substrates like solvents or heterocyclic bases. The monomeric complexes [MoO2(L1)(H2O)] (1) and [MoO2(L2)(DMF)] (4) were formed by the stoichiometric reaction of MoO2(acac)2 with the respective aroylhydrazones. The reaction of H2L1 with MoO2(acac)2 and 4,4′-bipyridine in an equimolar ratio yielded the 4,4′-bipyridine adduct [MoO2(L1)(H2O)]·(4,4′-bipy) (2), whereas the binuclear complex [(MoO2(L1))2(4,4′-bipy)]·2H2O (3) was formed, in which 4,4′-bipyridine acts as a bidentate linker between two molybdenum centers, by taking twice the molar concentration of 4,4′-bipyridine.

Cu(II), Ni(II) complexes derived from chiral Schiff-base ligands: Synthesis, characterization, cytotoxicity, protein and DNA–binding properties

A series of novel copper (II) and nickel (II) complexes derived from chiral Schiff-base ligands [(R)/(S)-H2L1=(R)/(S)-2-[(1-Hydroxymethyl-propylimino)-methyl]-5-methoxy-phenol and (R)/(S)-H2L2=(R)/(S)-2-[(1-Hydroxymethyl-2-phenyl-ethylimino)-methyl]-5-methoxy-phenol], were synthesized and characterized by elemental analyses, 1H NMR spectra, FT-IR spectrum. The crystal structures of complexes 1–5 were determined through single crystal X-ray diffraction (SXRD). The structures showed the ligands coordinated to the Cu/Ni (II) ion in a neutral manner via ONO donor atoms, and oxygen atoms of solvent molecules occupy the axial positions in Ni (II) complexes 3 and 4. The complexes interactions with BSA and CT-DNA were investigated by various spectroscopic methods (UV–Visible, circular dichroism spectrum, fluorescence spectroscopic and synchronous fluorescence spectra). Interactions of chiral copper (II) complexes are stronger than nickel (II) complexes. Further, the cytotoxicities of the complexes 1–6 towards three kinds of cancerous cell lines, were human lung adenocarcinoma (A549), human cervical carcinoma cell (HeLa) and human breast cancer cell (MCF-7) respectively, were evaluated by MTT assay. All complexes exhibited good cytotoxic activity. Furthermore, Cu (II) complex 5 derived from (R)-Schiff-base ligand was found to be more effective towards HeLa cancerous cell. The results showed that chirality and metal ion have important influence on their anticancer activities and interactions with DNA/BSA.

Versatile Reactivity and Theoretical Evaluation of Mono- and Dinuclear Oxidovanadium(V) Compounds of Aroylazines: Electrogeneration of Mixed-Valence Divanadium(IV,V) Complexes.

The substituted hydrazones H2L(1-4) (L(1-4) = dibasic tridentate ONO(2-) donor ligands) obtained by the condensation of 2-hydroxy-1-naphthaldehyde and 2-aminobenzoylhydrazine (H2hnal-abhz) (H2L(1)) , 2-hydroxy-1-naphthaldehyde and 2-hydroxybenzoylhydrazine (H2hnal-hbhz) (H2L(2)), 2-hydroxy-1-acetonaphthone and benzoylhydrazine (H2han-bhz) (H2L(3)), or 2-hydroxy-1-acetonaphthone and 2-aminobenzoylhydrazine (H2han-abhz) (H2L(4)) are prepared and characterized. Reaction of ammonium vanadate with the appropriate H2L(1-4) results in the formation of oxidoethoxidovanadium(V) [V(V)O(OEt)(L(1-4))] (1-4) complexes. All compounds are characterized in the solid state and in solution by spectroscopic techniques (IR, UV-vis, (1)H, (13)C, and (51)V NMR, and electrospray ionization mass spectrometry). Single-crystal X-ray diffraction analysis of 1, 3, and 4 confirms the coordination of the corresponding ligands in the dianionic (ONO(2-)) enolate tautomeric form. In solution, the structurally characterized [V(V)O(OEt)(L)] compounds transform into the monooxido-bridged divanadium(V,V) [(V(V)OL)2-μ-O] complexes, with the processes being studied by IR and (1)H, (13)C, and (51)V NMR. The density functional theory (DFT) calculated Gibbs free energy of reaction 2[V(V)O(OEt)(L(4))] + H2O ⇆ [(V(V)OL(4))2-μ-O] + 2EtOH is only 2-3 kcal mol(-1), indicating that the dinuclear complexes may form in a significant amount. The electrochemical behavior of the complexes is investigated by cyclic voltammetry, with the V(V)-V(IV) E1/2(red) values being in the range 0.27-0.44 V (vs SCE). Upon controlled potential electrolysis, the corresponding (L)(O)V(IV)-O-V(V)(O)(L) mixed-valence species are obtained upon partial reduction of the [(V(V)OL)2-μ-O] complexes formed in solution, and some spectroscopic characteristics of these dinuclear mixed-valence complexes are investigated using DFT calculations and by electron paramagnetic resonance (EPR), with the formation of V(IV)-O-V(V) species being confirmed by the observation of a 15-line pattern in the EPR spectra at room temperature.

Bio-important antipyrine derived Schiff bases and their transition metal complexes: Synthesis, spectroscopic characterization, antimicrobial, anthelmintic and DNA cleavage investigation

Spectroscopic (IR, NMR, UV–vis, ESR, ESI-mass), magnetic and TGA studies suggests octahedral geometry for all the CoII, NiII and CuII complexes of the Schiff bases, derived from 4-aminoantipyrine and 8-formyl-7-Hydroxy-4-methylcoumarin/5-formyl-6-hydroxycoumarin, coordinated through ONO donor sites. Antibacterial (Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella typhi), antifungal (Aspergillus niger, Aspergillus flavus and Cladosporium) and DNA cleavage properties of the metal complexes are investigated. The results suggested that some of the synthesized compounds are potential antimicrobials. The synthesized compounds tested for their anthelmintic activities and it was found that CoII and NiII complexes exhibited good anthelmintic properties.

Synthesis, Spectroscopic, and Biological Investigations of the Ternary Metal Complexes of Schiff Bases Derived From 2-hydroxy-1-naphthaldehyde and Some Amino Acids

In this work the ternary metal complexes of Cu(II) and UO2(II) with some Schiff bases derived from 2-hydroxy-1-naphthaldehyde and some amino acids as a primary ligand and two different heterocyclic bases as a secondary ligand have been synthesized. FT-IR results disclosed that the Schiff bases are coordinated to the central metal ion as a bivalent tridentate ONO donor. Electronic absorption spectra showed bands that are very distinguishable to copper and UO2(II) ternary complexes. Furthermore, the effect of these complexes on the gram-positive bacteria is more than their effect on the gram-negative bacteria.

Transition metal complexes of a novel quinoxaline‐based tridentate ONO donor ligand: synthesis, spectral characterization, thermal, in vitro pharmacological and molecular modeling studies

Co(II), Ni(II), Cu(II) and Zn(II) complexes of a novel tridentate heterocyclic ligand, 3‐{[(2‐benzoyl‐4‐chlorophenyl)imino]methyl}quinoxalin‐2(1H)‐one, have been synthesized. The ligand and the metal complexes were characterized using elemental analysis, molar conductance and magnetic susceptibility measurements, and UV–visible, Fourier transform infrared, 1H NMR, 13C NMR, electron spin resonance and DART mass spectral data. The ligand behaves as a tridentate one, coordinating through two oxygen atoms from two keto groups and through the azomethine nitrogen atom. The thermal properties of the newly synthesized compounds were determined using thermogravimetric analysis. The ligand and its metal complexes were subjected to powder X‐ray diffraction analysis by which average crystallite size and unit cell parameters were calculated. The electrochemical behaviour of the compounds was studied using cyclic voltammetry. The ligand and the metal complexes were screened for their in vitro antimicrobial activities against the bacterial strains E. coli, K. pneumoniae, S. pneumoniae and S. aureus and the fungal species A. niger, A. flavus, P. chrysogenum and R. stolonifer. DNA binding, DNA cleavage and antioxidant activities of the compounds were also evaluated. The compounds bind with DNA through groove binding. The Cu(II) and Zn(II) complexes exhibit higher superoxide anion and hydrogen peroxide scavenging activities, respectively. The Cu(II) complex exhibits better anticancer activity against the MCF7 cell line. The compounds were subjected to molecular docking study against B‐DNA dodecamer d(CGCGAATTCGCG)2 and vascular endothelial growth factor receptor kinase to justify the experimental DNA binding and MTT assay. Density functional theory studies were used to optimize the geometry of the compounds and to calculate the nonlinear optical properties. Copyright © 2016 John Wiley & Sons, Ltd.

Synthesis, characterization of new copper (ii) Schiff base and 1,10 phenanthroline complexes and study of their bioproperties

Three mononuclear Cu(II) complexes [Cu(naph-phe)phen] (1), [Cu(naph-tyr)(phen)] (2) and [Cu(naph-trp)(phen)] (3) were synthesized, characterized and their biological properties were studied. Complexes 1, 2, 3 exhibit square pyramidal geometry where Schiff base acts as a binegative tridentate ONO donor ligand and phen acts as NN donor ligand. CT-DNA binding studies revealed that the complexes bind through intercalative mode and show good binding propensity. The hydrolytic DNA cleavage activity of these complexes has been studied using gel electrophoresis. The DNA binding and cleavage affinities decrease in the order of 3>2>1. The in-vitro antimicrobial activities of the complexes were also studied.

Synthesis, characterization, crystal structure, DNA and BSA binding, molecular docking and in vitro anticancer activities of a mononuclear dioxido-uranium(VI) complex derived from a tridentate ONO aroylhydrazone

A mononuclear dioxido-uranium(IV) complex [UO2(L)(DMSO)2], was prepared from the reaction of (2-hydroxy-3-methoxybenzylidene)benzohydrazide [HL] with UO2(OAc)2·2H2O in DMSO. The obtained complex was fully characterized. Single crystal X-ray diffraction analysis of [UO2(L)(DMSO)2] revealed that U(VI) ion has been coordinated by ONO donor atoms of the dianionic ligand (L2−), oxo groups and two DMSO molecules in a pentagonal bipyramid geometry. In addition, interactions of the complex with salmon sperm DNA and bovine serum albumin (BSA) were thoroughly investigated using UV–vis absorption, voltammetry and molecular docking methods. The experimental studies showed an intercalative mode of interaction between the complex and DNA. Experiments on BSA interaction indicated a change in the polarity of the environment surrounded the complex as a result of the interaction between BSA and [UO2(L)(DMSO)2]. Finally, MTT assays indicated that the U(VI) complex had excellent cytotoxicity against human carcinoma cell lines of MCF-7, HPG-2, and HT-29, with IC50 values of 8.4, 10.6 and 10.0μM, respectively.

Geometrical structures, thermal properties and antimicrobial activity studies of azodye complexes

A novel series of metal complexes with 4-(2,3-dimethyl-1-phenylpyrazol-5-one azo)-3-aminophenol ligand (HL) are prepared and characterized by elemental analyses, IR, UV–Visible spectra, 1H NMR spectra, mass spectra, X-ray diffraction analysis, conductivity measurements and magnetic susceptibility measurements as well as thermal analysis. The IR spectrum revealed that the ligand (HL) coordinates as monobasic tridentate manner with ONO donor sites of nitrogen atom of azo group (NN), oxygen atom of the deprotonated phenolic OH group and exocyclic carbonyl oxygen atom forming a five/six-membered chelate structures. The 1H NMR spectra data indicated that the phenolic proton is also displaced during complexation. From the magnetic and spectral studies, it was obvious that the geometrical structures of these complexes are octahedral. The molecular structures of the ligand (HL) and its metal complexes are optimized theoretically and the quantum chemical parameters are calculated. The XRD patterns of the ligand (HL) and complex (3) are a mixture of crystalline and amorphous phases. The activation thermodynamic parameters, such as activation energy (Ea), enthalpy (ΔH⁎), entropy (ΔS⁎), and Gibbs free energy change of the decomposition (ΔG⁎) are calculated using Coats–Redfern and Horowitz–Metzger methods. The ligand (HL) and its metal complexes are screened for their antimicrobial activity against, four bacteria (two Gram positive, i.e. Bacillus subtilis, Streptococcus pneumoniae, and two Gram negative, i.e. Escherichia coli and Pseudomonas aeruginosa) and two fungi species (Aspergillus fumigatus and Candida albicans). The obtained data implies that all the complexes have high antimicrobial activities toward B. subtilis, S. pneumoniae, E. coli and A. fumigatus than the ligand (HL). In addition to that, complexes (1), (3) and (5) showed antifungal effect against C. albicans.

Geometrical structures, thermal stability and antimicrobial activity of Schiff base supramolecular and its metal complexes

The 1:1 condensation of 4-amino-1-phenyl-2,3-dimethylpyrazoline-5-one and 8-hydroxy-7-formylquinoline under template condition to obtain the Schiff base ligand 4-{(8-hydroxyquinoline-7-yl)methyleneamino}-1,2-dihydro-1,5-dimethyl-2-phenylpyra-zol-3-one (HL) with NO2 donor set. Reaction of the ligand with metal salts gives a series of novel complexes. The ligand and its metal complexes were characterized by elemental analyses, IR, 1H and 13C NMR, electronic, ESR, X-ray diffraction and mass spectral, conductivity and magnetic susceptibility measurements as well as thermal analyses. The analytical and spectroscopic tools showed that the complexes can be formulated as: [Cu(L)2] (1), [CuLX] nH2O, where X=OAc, n=2 (2); ONO2, n=3 (3); NCS, n=0 (4), [MHLX] nH2O, where M=Cu(II), X=OSO3, n=5 (5); M=VO(II), X=O2SO2, n=2H2O (6) and [UO2L(ONO2)(OH2)2].2H2O (7). The X-ray diffraction (XRD) patterns of start 1, start 2, Schiff base and complex [Cu(L)2] (1) are investigated in powder forms. The molecular and electronic structures of the ligand (HL) and its complexes have been discussed. It was found that form (A) is more stable than other forms (B and C). The HL ligand acts as a monobasic tridentate ONO donor for complexes (1–4 and 7) and neural tridentate HONO donor for complexes (5 and 6). The molar conductivity shows that the complexes are non-electrolytes nature. Electronic spectra and magnetic moments suggested varieties of geometries around the central metal atoms. The ESR spectra of complexes (2–4) show square planar of axial type symmetry (dx2–y2) with considerable ionic bond character, while complex (1) shows a spectrum of octahedral geometry. The stability of these complexes has also been investigated. The ligand is designed as a building block for larger molecule and supramolecular assemblies. Schiff base of HL and complexes were tested against four local bacterial species; namely two Gram positive bacteria (Staphylococcus aureus and Bacillus cereus) and two Gram negative bacteria (Escherichia coli and Klebsiella pneumoniae) and against four local fungal species (Aspergillus niger, Fusarium oxysporium, Penicillium italicum and Alternaria alternata). 8-Hydroxy-7-formylquinoline and 4-amino-1-phenyl-2,3-dimethylpyrazolin-5-one showed antimicrobial activities against E. coli, K. pneumoniae, P. italicum and A. alternata. The inhibitive action of this Schiff base, against the corrosion of mild steel in 2M HCl solution has been investigated using Tafel polarization and electrochemical impedance spectroscopy (EIS).