Azo Nitrogen Research Articles

Nano‐synthesis, solid‐state structural characterization, and antimicrobial and anticancer assessment of new sulfafurazole azo dye‐based metal complexes for further pharmacological applications

AbstractA new azo dye ligand (abbreviated as H3L) derived from coupling of sulfafurazole diazonium salt with 2,4‐dihydroxybenzaldehyde was prepared and characterized applying different spectroscopic and analytical techniques. The novel nanosized trivalent Cr and Fe alongside with divalent Mn, Co, Ni, and Cd complexes with H3L have been synthesized for further promising pharmaceutical uses. All complexes were totally characterized by investigating various analytical and spectral tools such as microanalysis, FT‐IR, 1H NMR, UV‐Vis, powder XRD, and TEM spectra as well as magnetic moment and molar conductance measurements. Microanalysis, TGA, and conductance studies confirmed the formation of all metal complexes in 1:1 (L: M) molar ratio with covalent mode. The FT‐IR and 1H NMR investigation asserted the chelation of H3L to different metal ions through azo nitrogen and phenolic deprotonated hydroxy oxygen in the o‐position. UV‐Vis, ESR, and magnetic moment studies revealed octahedral geometry around Cr and Fe ions, whereas Mn, Co, Ni, and Cd complexes displayed tetrahedral configurations. XRD patterns and TEM images proved homogeneous distribution over the chelates surfaces and nanometric size of complexes particles. Molecular modeling was used to optimize the complexes' geometric structure showing good harmonity with the experimental results. The antifungal and antibacterial efficiencies were strongly enhanced upon complex formation. Cr(III) and Ni(II) complexes showed the strongest and promising anticancer activities (IC50 = 7.64 and 6.99 μg/ml) among the tested compounds, whereas Cd(II) complex showed moderate anticancer efficiency (IC50 = 12.10 μg/ml), compared with the 5‐fluorouracil (applied standard drug) with IC50 = 6.44 μg/ ml.

Metal complexes of azo mesalamine drug: Synthesis, characterization, and their application as an inhibitor of pathogenic fungi

A novel azo dye ligand, formed by the coupling of 5‐aminosalycalic acid (mesalamine drug) with 2‐amino pyrimidine (H2L) and its Co2+, Ni2+, and Cu2+ complexes, was synthesized. The structures of ligand and its complexes have been described by elemental analysis, inductively coupled plasma (ICP), thermogravimetric analysis (TGA), magnetic moment measurements, molar conductance, ultraviolet–visible (UV–Vis), X‐ray powder diffraction, infrared (IR), 1H‐nuclear magnetic resonance (NMR), 13C NMR, and electron impact (EI) mass spectral studies. The obtained data detected that the H2L ligand acts as monobasic tridentate via C=N, azo nitrogen, and deprotonated OH groups. The data supported the formation of 1:2 (M:L) for Co2+ complex, while Ni2+ and Cu2+ gave 1:1 (M:L) complexes mononuclear formulation. The Co2+ and Ni2+ complexes have octahedral structures, while Cu2+ complex has tetrahedral geometry. The ligand and its Co2+, Ni2+, and Cu2+ complexes were applied as an antifungal against a set of root rot‐associated soil‐born phytopathogenic fungi and compared with the effect of Hatric (recommended fungicide). Our findings revealed that the metal complexes exhibited greater antifungal activity than the parent ligand. The Cu2+ complex was found to be the most effective compound. The effect of Hatric and Cu2+ complex on structural alterations of Fusarium semitectum was studied by scanning electron microscopy (SEM).

Ru(III) complexes of triazole based Schiff base and azo dye ligands: An insight into the molecular structure and catalytic role in oxidative dimerization of 2-aminophenol

Four New ruthenium(III) complexes encompassing triazole based Schiff base or azo dye ligands (HL1-HL4) have been prepared. The structural composition of the isolated compounds has been fully identified following alternative spectral and analytical methods of investigation. Among the applied tools is the measurement of the molar conductivity of the complexes solutions which demonstrated that all of them are non-electrolytes. 1:2 (M:L) stoichiometry has been concluded for all the isolated complexes with an octahedral geometrical architectures. IR spectral results of the isolated chelates assured the chelation of the ligand to the Ru center via azo or azomethine nitrogen and deprotonated hydroxyl oxygen affording the monobasic bidentate fashion of the ligands. The four synthesized complexes have been investigated for mimicking phenoxazinone synthase using o-aminophenol (OAP) as the substrate in acetonitrile/dimethyl formamide, ACN/DMF (80/20% ratio) mixed solvent by evaluating the catalytic performance of the compounds for oxidative coupling of 2-aminophenol (OAP) to 2-aminophenoxazine-3-one (APX). The obtained results showed that the complexes have TOF numbers in the range 46.92–12.12 h−1 increasing in the order Ru-(L2)2 < Ru-(L3)2 < Ru-(L4)2 < Ru-(L1)2.

Synthesis and Identification and Biological Studies of New Azo Dyes Derived from Imidazole and their Chelate Complexes

Anew azo ligand (E)-2-((4- fluoro phenyl)diazenyl)-4,5-bis(4-methoxy phenyl)-1H-imidazolehas beensynthesized from coupling 4,5-bis(4-methoxyphenyl)imidazole with para-chloro-anline. The structures ofthe new ligand and their transition metal complexes ware investigated and characterized using differentphysicochemical studies as elemental analysis, IR spectra, 1HNMR,, UV-Vis spectra, mass spectra, Molarconductance ,and magnetic susceptibility .The complexes were found to have the general formula [ML2Cl2].H2O where M = Co(II), Ni(II), Cu(II) ,Mn(II),and Fe(II), [MLCl2].H2Owhere M=Zn(II),Cd(II),Hg(II), andPd(II). The IR results demonstrate that the co-ordination sites are the azomethine nitrogen of the imidazolering and azo nitrogen atom of the azo ligand. The electronic spectral and magnetic measurement dataindicate that the complexes exhibit octahedral geometry,except the Zn(II),Cd(II),andHg(II) complexessuggest tetrahedral and Pd(II) a square planar geometry.The cytotoxicity of Pd(II) complex on human LungCancer (SCLC) and normal cells.

Nano-Azo Ligand and Its Superhydrophobic Complexes: Synthesis, Characterization, DFT, Contact Angle, Molecular Docking, and Antimicrobial Studies

Metal complexes of the 2,2'-(1,3-phenylenebis(diazene-2,1-diyl))bis(4-aminobenzoic acid) diazo ligand (H2L) derived from m-phenylenediamine and p-aminobenzoic acid were synthesized and characterized by different spectral, thermal, and analytical tools. The H2L ligand reacted with the metal ions Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) as 1 : 1 stoichiometry. All complexes displayed an octahedral geometry according to the electronic and magnetic moment measurements. The IR spectra revealed the binding of the azo ligand to the metal ions via two azo nitrogen atoms and protonated carboxylate O in a neutral tetradentate manner. Both IR and 1H NMR spectra documented the involvement of the carboxylate group without proton displacement. The thermal studies pointed out that the complexes had higher thermal stability comparable with that of the free ligand. SEM images revealed the presence of the diazo ligand and its Cd(II) complex in a nanostructure form. The contact angle measurements proved that the Cd(II) complex can be considered as a superhydrophobic material. The molecular and electronic structure of H2L and [Cd(H2L)Cl2].H2O were optimized theoretically, and the quantum chemical parameters were calculated. The biological activities of the ligand, as well as its metal complexes, have been tested in vitro against some bacteria and fungi species. The results showed that all the tested compounds have significant biological activities with different sensitivity levels. The binding between H2L and its Cd(II) complex with receptors of the crystal structure of S. aureus (PDB ID: 3Q8U), crystal structure of protein phosphatase (PPZ1) of Candida albicans (PDB ID: 5JPE), receptors of breast cancer mutant oxidoreductase (PDB ID: 3HB5), and crystal structure of Escherichia coli (PDB ID: 3T88) was predicted and given in detail using molecular docking.

Synthesis and characterization of some binuclear metal complexes with a pentadentate azodye ligand: An experimental and theoretical study

A novel series of binuclear complexes with Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) ions derived from a pentadentate azo dye ligand (H3L) was synthesized and structurally investigated by various physicochemical analyses, namely, scanning electron microscopy, transmission electron microscopy, NMR, UV–visible spectroscopy, and Electron‐Spin Resonance (ESR) studies. The infrared spectral data revealed characteristic bands due to ν(N=N) and ν(C=O) at 1606 and 1631 cm−1in the free ligand. However, their positions shifted and appeared at ~1564 and ~1592 cm−1on coordination, suggesting the involvement of carbonyl oxygen and azo nitrogen in complex formation. The spectral data suggested octahedral geometry for the complexes. The kinetic parameters such as order and activation energy were determined from the thermal decomposition values. X‐ray powder diffraction analysis showed the orthorhombic nature of the cadmium complex. Furthermore, Density functional theory (DFT) calculations were also recorded to describe the insight bonding. The synthesized compounds were tested forin vitroantibacterial activity againstK. aerogenes,S. aureus,B. acidoterrestris,E. coli,andV. choleraestrains by the cup‐plate method. In addition, the interactions that occurred in the protein–ligand complexes have been predicted by docking analysis.

Preparation and Characterization of Some Complexes with New (Azo-Schiff base) Ligand and Study of Complex as Anticancer

Anew series of transition metal complexes of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), Au(III) and Pt(II) have been preparation and characterization using anew azo-Schiff base ligand derived from schiff base (N1Z,N2Z)-N1,N2-bis(4-amino-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-ylidene)benzene-1,2-diamine with 5-methyl-imidazole.The structures of the new ligand azo-schiff base and their transition metal complexes are characterized using several techniques,including analysis(C.H.N),molar conductance,magnetic measurements, electronic spectral,IR spectral studies,13CNMR,1HNMR and mass spectra The data show that these complexes have composition of[MLCl2] where M=Co(II),Ni(II), Cu(II),Zn(II),Cd(II) and Hg(II),[ML] Cl3 where M=Au(III) and[ML]Cl2 ,where M=Pt(II).The electronic spectral, and magnetic susceptibility data of the complexes suggest octahedral geometry of all complexes,except the Au(III) and Pt(II) complex suggest a square planar geometry.The IR results demonstrate that the co-ordination sites are the azomethine nitrogen and azo nitrogen atoms of the ligand.The ligand behaves natural tetra dentate manner.The biological screening effect of the Pt(II) complex are tested against human breast cancer cell line MCF-7and normal cells( cell line WRL68).The results show the highest inhibitory effect for complex.

Photocatalytic Degradation Dynamics of Methyl Orange Using Coprecipitation Synthesized Fe3O4 Nanoparticles

This study aims to investigate the photocatalytic degradation performance, mechanism, and dynamics of methyl orange (MO) which is a widely used organic dye in textile industries as well a hazardous wastewater pollutant. The degradation process was catalyzed by employing a synthesized Fe3O4 magnetic nanoparticle (NP) using the coprecipitation method. The structural and morphological properties of the synthesized Fe3O4 NPs were investigated by employing XRD, HR-SEM, and XPS, which proved that acquired Fe3O4 NPs were in a pure phase. Moreover, the crystallite sizes fall in the range of 28–31.8 nm and were estimated by applying the Scherrer equation on the XRD spectrum as well as calculated independently by applying a statistical approach on the SEM micrographs. The UV–Vis maximum in the visible range at 468.8 nm consists of two absorption frequency bands due to the effect of the hydrogen-bond interaction between water and the azo nitrogens in the MO. A non-monotonic spectral dynamic accompanied by peak wavelength shifts, as well as the absolute signal amplitude and signal area of the MO band, suggests that a cleavage of the azo bond is not the only and/or the dominant process in the photocatalytic oxidization of the MO in a protic solvent. The overall absorbance process is a complicated response to a combination of nonspecific and specific solute-solvent interactions, dipole-dipole interactions, hydrogen-bonding networks, and other possible intermolecular interactions such as hydrophobic/hydrophilic interactions. A bi-exponential decay was found to be the best fitting function to model the decay of the time-dependent electrical conductivity of the MO aqueous solution under photocatalytic oxidization. The Fe3O4 NPs exhibited a 98.3% removal of MO within 110 min. Photocatalytic degradation of methyl orange can be modeled to the first-order model with a rate constant k of 0.037 min−1 taking into account the initial concentration of 1175 ppm of MO. The degradation/decolorization efficiency deduced from the low-frequency band of the visible spectra is around 99.4% after 110 min. The real-time degradation/decolorization efficiencies deduced from the overall absorbance maxima and the low-frequency band have a discrepancy of 50.1% at 20 min and 12.3% at 60 min representing the progressive attenuation of the H-bond impact dissociation of MO (degradation/decolorization).

13C and 15N NMR identification of product compound classes from aqueous and solid phase photodegradation of 2,4,6-trinitrotoluene.

Photolysis is one of the main transformation pathways for 2,4,6-trinitrotoluene (TNT) released into the environment. Upon exposure to sunlight, TNT is known to undergo both oxidation and reduction reactions with release of nitrite, nitrate, and ammonium ions, followed by condensation reactions of the oxidation and reduction products. In this study, compound classes of transformation products from the aqueous and solid phase photodegradation of 2,4,6-trinitrotoluene (TNT) have been identified by liquid and solid state 13C and 15N NMR. Aqueous phase experiments were performed on saturated solutions of T15NT in deionized water, natural pond water (pH = 8.3, DOC = 3.0 mg/L), pH 8.0 buffer solution, and in the presence of Suwannee River Natural Organic Matter (SRNOM; pH = 3.7), using a Pyrex-filtered medium pressure mercury lamp. Natural sunlight irradiations were performed on TNT in the solid phase and dissolved in the pond water. In deionized water, carboxylic acid, aldehyde, aromatic amine, primary amide, azoxy, nitrosophenol, and azo compounds were formed. 15N NMR spectra exhibited major peaks centered at 128 to 138 ppm, which are in the range of phenylhydroxylamine and secondary amide nitrogens. The secondary amides are proposed to represent benzanilides, which would arise from photochemical rearrangement of nitrones formed from the condensation of benzaldehyde and phenylhydroxylamine derivatives of TNT. The same compound classes were formed from sunlight irradiation of TNT in the solid phase. Whereas carboxylic acids, aldehydes, aromatic amines, phenylhydroxylamines, and amides were also formed from irradiation of TNT in pond water and in pH 8 buffer solution, azoxy and azo compound formation was inhibited. Solid state 15N NMR spectra of photolysates from the lamp irradiation of unlabeled 2,6-dinitrotoluene in deionized water also demonstrated the formation of aromatic amine, phenylhydroxylamine/ 2° amide, azoxy, and azo nitrogens.

Synthesis, Spectral Identification and Biological Activity of Chelate Complexes Derived from New Azo Naphthresorcenol.

A new azo compounds is prepared by coupling the diazonium salts of (2- Cyano aniline) with 1,3- dihydroxynaphthalene to form (E)-2-((2,4-dihydroxynaphthalen-1- yl) diazenyl)benzonitrile. The azo ligand was identified by: Mass, 1H-NMR, C13NMR,UV-Vis. and IR spectra, in addition to elemental analysis measurement. The chelate complexes were characterized by elemental analysis, magnetic susceptibility, Molar conductance, UV-Vis. and IR spectra. The geometry of metal complexes were proposed based on analytical and spectral data. Analytical data revealed that all the complexes exhibited 1:2 metal–ligand ratio. On the basis of magnetic susceptibility measurements, suitable geometry was proposed for each complex. IR spectra of complexes show that the ligand is coordinated to the metal ions in bidentate manner with Oxygen and Nitrogen donor sites of hydroxynaphthalene (OH) and azo Nitrogen, which suggest octahedral geometry for all complexes. Also, biological evaluation of all synthesized compound shows moderate to good activity against Candida albicans, as antifungal.

Exploration of the Binding Properties of the Azo Dye Pollutants with Nitrogen‐Doped Graphene Oxide by Computational Modeling for Wastewater Treatment Improvement

AbstractSystematic studies were carried out to investigate the binding properties of ten selected azo dye pollutants with nitrogen‐doped graphene oxide. Acid Blue 29, Acid Orange 5, Acid Orange 7, Acid Orange 8, Acid Orange 52, Blue 113, Direct Blue 71, hydrolyzed Reactive Black 5H, hydrolyzed Reactive Orange 16H, and hydrolyzed Reactive Orange 107H were selected to be studied. At the first step, docking studies were done to provide the best binding modes between azo dye and nitrogen–doped graphene oxide. In continue, molecular dynamics simulation method, molecular mechanics/generalized Born and surface area (MM/GBSA) analysis, and energy decomposition analysis were carried out to examine the strength and nature of interactions between azo dye pollutants and nitrogen–doped graphene oxide. Analyzing of interaction during molecular dynamics simulation showed that van der Waals interaction has the most important role on the binding of the azo dyes to the surface of the nitrogen‐doped graphene oxide. Also, the contribution of electrostatic and hydrogen bonding interactions are not ignorable. The –SO3H, –OH, and –NH2 moieties on the azo dyes have a contribution in hydrogen bonding with the epoxide and –OH functional groups and pyridinium–like and pyrrole–like nitrogen‐containing functional groups on the nitrogen‐doped graphene oxide. No contributions from the carboxylic acid moieties and graphite‐like nitrogen‐containing functional groups in the hydrogen bonding were observed. The binding energies related to ADs/NGO systems during the MD simulation process, calculated by MM/GBSA approach. Entry Azo dye Binding energy (kcal mol–1) 1 Acid Blue 29 –42.7 2 Acid Orange 5 –32.6 3 Acid Orange 7 –30.1 4 Acid Orange 8 –32.2 5 Acid Orange 52 –28.3 6 Blue 113 –55.2 7 Direct Blue 71 –67.3 8 Hydrolyzed Reactive Black 5H –30.2 9 Hydrolyzed Reactive Orange 16H –32.6 10 Hydrolyzed Reactive Orange 107H –27.0

Synthesis, structural characterization and DNA binding affinity of new bioactive nano‐sized transition metal complexes with sulfathiazole azo dye for therapeutic applications

The azo dye ligand 4‐(5‐chloro‐2‐hydroxyphenylazo)‐N‐thiazol‐2‐ylbenzenesulfonamide (H2L) formed by the coupling reaction of sulfathiazole and p‐chlorophenol was synthesized and characterized using elemental analysis and Fourier transform infrared (FT‐IR) as well as UV–visible spectra. Nano‐sized divalent Cu, Co, Ni, Mn and Zn complexes of the synthesized azo dye ligand were prepared and investigated using various spectroscopic and analytical techniques. Elemental and thermal analyses indicated the formation of the Cu(II), Ni(II) and Mn(II) complexes in a molar ratio of 1:2 (L:M) while Co(II) and Zn(II) complexes exhibited a 1:1 (M:L) ratio. FT‐IR spectral studies confirmed the coordination of the ligand to the metal ions through the phenolic hydroxyl oxygen, azo nitrogen, sulfonamide oxygen and/or thiazole nitrogen. The geometric arrangements around the central metal ions were investigated applying UV–visible and electron spin resonance spectra, thermogravimetric analysis and molar conductance measurements. X‐ray diffraction patterns revealed crystalline nature of H2L and amorphous nature of all synthesized complexes. Transmission electron microscopy images confirmed nano‐sized particles and their homogeneous distribution over the complex surface. Antibacterial, antifungal and antitumour activities of the investigated complexes were screened compared with familiar standard drugs to confirm their potential therapeutic applications. The Cu(II) complex showed IC50 of 3.47 μg ml−1 (5.53 μM) against hepatocellular carcinoma cells, which means that it is a more potent anticancer drug compared with the standard cisplatin (IC50 = 3.67 μg ml−1 (12.23 μM)). Furthermore, the Co(II), Ni(II), Cu(II) and Zn(II) complexes displayed IC50 greater than that of an applied standard anticancer agent (5‐flurouracil) towards breast carcinoma cells. Hence, these complexes can be considered as promising anticancer drugs. The mode of binding of the complexes with salmon serum DNA was determined through electronic absorption titration and viscosity studies.

C3N5: A Low Bandgap Semiconductor Containing an Azo-Linked Carbon Nitride Framework for Photocatalytic, Photovoltaic and Adsorbent Applications.

Modification of carbon nitride based polymeric 2D materials for tailoring their optical, electronic and chemical properties for various applications has gained significant interest. The present report demonstrates the synthesis of a novel modified carbon nitride framework with a remarkable 3:5 C:N stoichiometry (C3N5) and an electronic bandgap of 1.76 eV, by thermal deammoniation of the melem hydrazine precursor. Characterization revealed that in the C3N5 polymer, two s-heptazine units are bridged together with azo linkage, which constitutes an entirely new and different bonding fashion from g-C3N4 where three heptazine units are linked together with tertiary nitrogen. Extended conjugation due to overlap of azo nitrogens and increased electron density on heptazine nucleus due to the aromatic π network of heptazine units lead to an upward shift of the valence band maximum resulting in bandgap reduction down to 1.76 eV. XRD, He-ion imaging, HR-TEM, EELS, PL, fluorescence lifetime imaging, Raman, FTIR, TGA, KPFM, XPS, NMR and EPR clearly show that the properties of C3N5 are distinct from pristine carbon nitride (g-C3N4). When used as an electron transport layer (ETL) in MAPbBr3 based halide perovskite solar cells, C3N5 outperformed g-C3N4, in particular generating an open circuit photovoltage as high as 1.3 V, while C3N5 blended with MA xFA1- xPb(I0.85Br0.15)3 perovskite active layer achieved a photoconversion efficiency (PCE) up to 16.7%. C3N5 was also shown to be an effective visible light sensitizer for TiO2 photoanodes in photoelectrochemical water splitting. Because of its electron-rich character, the C3N5 material displayed instantaneous adsorption of methylene blue from aqueous solution reaching complete equilibrium within 10 min, which is significantly faster than pristine g-C3N4 and other carbon based materials. C3N5 coupled with plasmonic silver nanocubes promotes plasmon-exciton coinduced surface catalytic reactions reaching completion at much low laser intensity (1.0 mW) than g-C3N4, which showed sluggish performance even at high laser power (10.0 mW). The relatively narrow bandgap and 2D structure of C3N5 make it an interesting air-stable and temperature-resistant semiconductor for optoelectronic applications while its electron-rich character and intrasheet cavity make it an attractive supramolecular adsorbent for environmental applications.

Tetradentate amido azo Schiff base Cu(II), Ni(II) and Pd(II) complexes: Synthesis, characterization, spectral properties, and applications to catalysis in C–C coupling and oxidation reaction

New Schiff base ligands (H2L1 &H2L2) were synthesized by the reaction of salicylaldehyde with (2-((2-aminophenyl)diazenyl)-N-alkylaniline), and were used for the preparation of complexes with Cu(II), Ni(II) and Pd(II) metal ions. The structural features of the synthesized compounds were examined by UV–Vis, IR and 1H NMR spectroscopy. The crystal structures of Schiff base (H2L1) and two metal complexes Cu(L1) and Ni(L2) were determined by single crystal X-ray diffraction. The studies revealed that the synthesized Schiff bases existed as tetradentate (N,N,N,O) ligands and bonded to the metal ions through the donor atoms of the amido nitrogen, azo nitrogen, azomethine nitrogen and phenolic oxygen atoms. The redox property of Cu(L1) and Ni(L1) and emission behavior of ligand H2L1 and complexes Cu(L1) and Ni(L1) were examined. The complex Cu(L1) shows excellent catalytic activity towards oxidation of benzyl alcohol to benzyldehyde (under solvent-free condition) using H2O2 as the oxidant. Complex Pd(L1) acts as highly efficient catalyst in the Suzuki–Miyaura cross-coupling reaction of various aryl halides with phenyl boronic acid to produce the corresponding biaryls with high yields under mild reaction conditions. Both the catalysts Cu(L1) and Pd(L1) were easily recovered by simple chromatographic separation and reused for next catalytic cycle.

Spectroscopic Studies and Thermal Analysis of New Azo Dyes Ligands and their Complexes with some Transition of Metal Ions

New Azo ligands HL1 [2-Hydroxy-3-((5-mercapto-1,3,4-thiadiazol-2-yl)diazenyl)-1-naphth aldehyde] and HL2 [3-((1,5-Dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazol-4-yl)diazenyl)-2-hydroxy-1-naphthaldehyde] have been synthesized from reaction (2-hydroxy-1-naphthaldehyde) and (5-amino-1,3,4-thiadiazole-2-thiol) for HL1 and (4-amino-1,5-dimethyl-2-phenyl-1H-pyrazol-3(2H)-one) for HL2. Then, its metal ions complexes are synthesized with the general formula; [CrHL1Cl3(H2O)], [VOHL1(SO4)] [ML1Cl(H2O)] where M = Mn(II), Co(II), Ni(II) and Cu(II), and general formula; [Cr(L2)2 ]Cl and [M(L2)2] where M = VO(II), Mn(II), Co(II), Ni(II) and Cu(II) are reported. The ligands and their metal complexes are characterized by phisco- chemical spectroscopic techniques (FT.IR, Mass, UV-Vis, 1H and 13C-NMR, TGA, (C.H.N.), molar conductivity, Atomic Absorbance, Chloride containing magnetic susceptibility). The spectral data suggest that the (HL1) behaves as a bidentate ligand in all complexes, whereas (HL2) behaves as a tridentate ligand for all complexes; bidentate ligand in Vanadium complex is coordinated with the metal ions through azo nitrogen and oxygen atoms. Theoretical studies of these ligands and their metal complexes in gas phase using Hyper chem.8. Studies of these compounds are prepared for their bacterial activity

Protonation of a Cobalt Phenylazopyridine Complex at the Ligand Yields a Proton, Hydride, and Hydrogen Atom Transfer Reagent.

Protonation of the Co(I) phenylazopyridine (azpy) complex [CpCo(azpy)] 2 occurs at the azo nitrogen of the 2-phenylazopyridine ligand to generate the cationic Co(I) complex [CpCo(azpyH)]+ 3 with no change in oxidation state at Co. The N-H bond of 3 exhibits diverse hydrogen transfer reactivity, as studies with a variety of organic acceptors demonstrate that 3 can act as a proton, hydrogen atom, and hydride donor. The thermodynamics of all three cleavage modes for the N-H bond (i.e., proton, hydride, and hydrogen atom) were examined both experimentally and computationally. The N-H bond of 3 exhibits a p Ka of 12.1, a hydricity of Δ G°H- = 89 kcal/mol, and a bond dissociation free energy (BDFE) of Δ G°H• = 68 kcal/mol in CD3CN. Hydride transfer from 3 to the trityl cation (Δ G°H- = 99 kcal/mol) is exergonic but takes several hours to reach completion, indicating that 3 is a relatively poor hydride donor, both kinetically and thermodynamically. Hydrogen atom transfer from 3 to 2,6-di- tert-butyl-4-(4'-nitrophenyl)phenoxyl radical (tBu2NPArO·, Δ G°H• = 77.8 kca/mol) occurs rapidly, illustrating the competence of 3 as a hydrogen atom donor.

Color and nitrogen removal from synthetic dye wastewater in an integrated mesophilic hydrolysis/acidification and multiple anoxic/aerobic process

Dye wastewater is one kind of refractory pollutant and it is commonly treated by the integrated anaerobic and aerobic process. A new integrated hydrolysis/acidification and multiple anoxic/aerobic (AO) process was proposed for the removal of color and nitrogen from azo dye wastewater. System performance, the degradation pathway of azo dye and nitrogen metabolic pathway were investigated with quadrupole-time-of-flight and metagenomic analyses. The proposed process removed color and nitrogen efficiently, with the removal percentages of 89.4% and 54.0%, respectively. A colorful intermediate C16H11N3O7S2 during the degradation of azo dye was detected. Controlling a low dissolved oxygen concentration in the multiple AO process could enhance nitrogen removal. The detected bacteria possessing azoreductase for the azo dye degradation included Desulfovibrio aminophilus, Thermoanaerobacter, Lactococcus raffinolactis, Ruminiclostridium and Rhodopirellula. The nitrifying genes of amo and hao were mainly detected in Nitrosomonas, while the denitrifying genes were detected in Thauera, Candidatus Accumulibacter and Rhodothermus marinus.

Enhanced azo dye decolorization through charge transmission by σ-Sb3+-azo complexes on amorphous Sb2S3 under visible light irradiation

Three types of Sb2S3 with different degrees of crystallinity were synthesized via a hydrothermal procedure by adjusting the concentration of hydrochloric acid. The amorphous Sb2S3 sample (A-Sb2S3) exhibited nearly 13 times higher photocatalytic activity for the decolorization and biodegradability improvement of MO solution compared with both crystalline samples under visible light (λ > 420 nm). It was verified that MO and Congo Red azo dyes were adsorbed onto A-Sb2S3 by displacing hydroxyl groups (OH−) to complex with Sb3+ on A-Sb2S3, which occurred via σ bonding to the lone pairs of azo nitrogen atoms with Sb3+ (σ-Sb-(NN)). Moreover, the decolorization rate of MO was positively related to its adsorption onto A-Sb2S3, and no significant degradation was observed for non-azo intermediates. The predominant photodegradation pathways of MO were reduction and oxidization to sulfanilic acid, NO3− and small-molecule acids. On the basis of photoelectron spectra, ESR (Electron spin resonance) measurements and other experimental information, it was proposed that the complexes (σ-Sb-(NN)) could transmit photogenerated electrons and holes to the azo group, breaking the NN bond, causing azo dye decolorization to improve their biodegradability; while on the surface of bare A-Sb2S3, the strong coordination interaction of OH− with Sb3+ made OH− groups become the recombination centers for photogenerated electrons and holes during the photocatalytic reaction.

Synthesis and Characterization of Tetranuclear Metal Complexes with an Octadentate Azodye Ligand

An octadentate azodye ligand containing phenolic/ketonic oxygen and azo nitrogen donor atoms when complexed with divalent metal ions forms tetranuclear complexes of composition [M4LCl4(H2O)12] and [ $$ M_{4}^{/} $$ LCl4(H2O)4] where, M = CoII,CuII, NiII, MnII and M/ = Zn II,, CdII and LH4 = 4,4/-bis(2,4/-dihydroxy-5/-acylphenylazo)diphenylsulphone (BDHAPADPS). The metal complexes were characterised by analytical, magnetic moment, conductance, I.R., electronic spectra, thermal, ESI–MS, ESR, XRD, SEM and EDX. DFT calculations of the ligand and metal complexes have been made by GAUSSIAN 03 rev. A.01 programme package. The antibacterial study of the ligand and the complexes has been made using Gram positive and Gram negative bacteria.

Halide Control of N,N-Coordination versus N,C-Cyclometalation and Stereospecific Phenyl Ring Deuteration of Osmium(II) p-Cymene Phenylazobenzothiazole Complexes.

We report the synthesis of halido Os(II) p-cymene complexes bearing bidentate chelating phenylazobenzothiazole (AZBTZ) ligands. Unlike the analogous phenylazopyridine (AZPY) complexes, AZBTZ-NMe2 is capable of both N,N-coordination to Os(II) and cyclometalation to form N,C-coordinated species. N,C-Coordination occurs via an azo nitrogen and an ortho carbon on the aniline ring, as identified by 1H NMR and X-ray crystallography of [Os(p-cym)(N,N-AZBTZ-NMe2)Cl]PF6 (1a), [Os(p-cym)(N,N-AZBTZ-NMe2)Br]PF6 (2a), [Os(p-cym)(N,C-AZBTZ-NMe2)Br] (2b), and [Os(p-cym)(N,C-AZBTZ-NMe2)I] (3b). The N,C-coordinated species is more stable and is not readily converted to the N,N-coordinated complex. Analysis of the crystal structures suggests that their formation is influenced by steric interactions between the p-cym and AZBTZ-NMe2 ligands: in particular, larger monodentate halide ligands favor N,C-coordination. The complexes [Os(p-cym)(N,N-Me2-AZBTZ-NH2)Cl]PF6 (4) and [Os(p-cym)(N,N-Me2-AZBTZ-NH2)I]PF6 (5) were synthesized with methyl groups blocking the ortho positions on the aniline ring, forcing an N,N-coordination geometry. 1H NMR NOE experiments confirmed hindered rotation of the arene ligand and steric crowding around the metal center. Complex 2b exhibited unexpected behavior under acidic conditions, involving regiospecific deuteration of the aniline ring at the meta position, as observed by 1H NMR and high-resolution ESI-MS. Deuterium exchange occurs only under acidic conditions, suggesting an associative mechanism. The calculated partial charges on 2b show that the meta carbon is significantly more negatively charged, which may account for the regiospecificity of deuterium exchange.