Azo Schiff Base Research Articles

Chiral Recognition of Azo-Schiff Base Ligands, Their Cu(II) Complexes, and Their Docking to Laccase as Mediators

Chiral crystals were discovered due to spontaneous resolution when enantiomers of 4-phenyldiazenyl-2-[(R or S)-(1-phenylethyl)-iminomethyl]phenol and its racemic mixture were prepared. Using two ligands per molecule, optically active R,R and S,S enantiomers and meso R,S diastereomer of Cu(II) complexes were prepared. Strong chiral recognition was expected for them. Laccase has attracted attention as a catalyst that reduces oxygen to water in a cathode of biofuel cells, which can be effectively mediated by metal complexes. Furthermore, azobenzene can align perpendicularly to the polarization direction of irradiating linearly polarized ultraviolet light (Weigert effect) as well as to the conventional cis-trans photoisomerization accompanying the shift of redox potential. Thus, we also studied the photo-induced control of cis-trans forms and the alignment of these Cu(II) complexes as a mediator to fit laccase appropriately. We discuss photo-induced control on not only electronically but also sterically-favored redox conditions. The meso(R,S)-form of the Cu(II) complex in cis-form was found to be the best at increasing the current of cyclic voltammetry (CV) among the three R,R and S,S enantiomers and the R,S diastereomer of the Cu(II) complexes.

Water-soluble polymeric probe with dual recognition sites for the sequential colorimetric detection of cyanide and Fe (III) ions

A water-soluble polymeric probe derived from an azo-Schiff base was developed for the consecutive colorimetric sensing of CN− and Fe3+ ions in water. Herein, the synthesis of a random copolymer of N,N-dimethylacrylamide (DMA) and 3-vinylbenzaldehyde (VBA) via reversible addition-fragmentation chain transfer polymerization, [p(DMA-co-VBA, P1] is described. A post-polymerization modification reaction between the aldehyde groups of P1 and (E)-2-amino-4-((4-nitrophenyl)diazenyl)phenol in ethanol led to the target polymer, P2, with azo-Schiff base moieties. The colorimetric detection of CN− ions occurred because of the abstraction of phenolic proton of P2 by the CN− ions to form hydrazone, which was accompanied by the color change from brick-red to purple. The selective colorimetric detection of Fe3+ ions with P2 over other cations in water was also observed via the formation of a coordination complex between Fe3+ ions and azo-Schiff base ligands of P2. After the individual detection of CN− and Fe3+ was carried out, consecutive sensing studies were performed. Although Fe3+ was sequentially observed after the presence of CN− ions was noted, detection using a reverse sequence from Fe3+ to CN− was not possible because of the intense color of the resulting P2Fe3+ complexes, which suppressed any observable color changes typically caused by the formation of hydrazone.

Synthesis of novel azo linkage-based Schiff bases including anthranilic acid andhexanoic acid moieties: investigation of azo-hydrazone and phenol-ketotautomerism, solvatochromism, and ionochromism

Two new azo-Schiff base receptors (L$_{{1}}$ and L$_{{2}})$ containing azo and azomethine groups with a conjugated group (benzyl ring of anthranilic acid, in L$_{{1}})$ and electron-donating group (alkyl chain of hexanoic acid, in L$_{{2}})$ were synthesized and characterized. Azo-hydrazone/phenol-keto tautomerism and solvatochromism were investigated. Studying their sensing ability towards cations (Co$^{2+}$, Cu$^{2+}$, Zn$^{2+}$, Ni$^{2+}$, Pb$^{2+}$, Cd$^{2+}$, Mn$^{2+}$, Fe$^{3+}$, Cr$^{3+}$, and Al$^{3+})$, high sensitivity and selectivity were recorded for Fe$^{3+}$ by naked eye and UV-Vis spectra in DMF-aqueous HEPES buffer (v:v, 1:1, pH 6.8). The color of L$_{{1}}$ and L$_{{2}})$ solutions instantly changed from yellow to deep orange and pale orange. L$_{{2}})$ sensed Cu$^{2+}$ and Al$^{3+}$ ions selectively by UV-Vis spectra. The interactions of receptors with F$^{-}$, Cl$^{-}$, CH$_{3}$COO$^{-}$, C$_{2}$O$_{4}^{2-}$, H$_{2}$PO$_{4}^{-}$, and OH$^{-}$ anions were also investigated in DMF-HEPES 1:1 and 4:1 solvent mixtures. L$_{{1}})$ sensitively responded to anions according the order of OH$^{-}$ > C$_{2}$O$_{4}^{2-}$ > F$^{-}$ in the 1:1 mixture and OH$^{-}$ > F$^{-}$ > CH$_{3}$COO$^{-}$ > C$_{2}$O$_{4}^{2-}$ in the 4:1 mixture in UV-Vis spectra with color changing from pale yellow to dark yellow. However, L$_{{2}})$ showed weak spectral changes in the UV-Vis spectra, so its sensitivity was poorer than L$_{{1}})$, attributed to the effect of alkyl chains.

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.

Impact of ligand rotation: Synthesis, crystal structures and third-order nonlinear optical properties of Mn(II), Cu(II) and Ni(II) complexes with 5‑diethylamino‑2‑((4‑(phenyldiazenyl) phenylimino) methyl) phenol

Three new coordination compounds containing 5‑diethylamino‑2‑((4‑(phenyldiazenyl) phenylimino) methyl) phenol ligand have been synthesized and fully characterized. Single crystal structure showed that the ligand shows multiple coordination mode and the phenyl group next to azo group could rotate during the coordination process. In Mn(HDAPPP)2Cl2·CH3CN (1), the HDAPPP behaved as a mono ligand because of the N of the imine group is protonated in the keto form and does not participate in coordination. While the Cu(DAPPP)2 (2) and Ni(DAPPP)2 (3) are classic complexes containing azo-Schiff base ligand. The fluorescence emission peaks of compounds indicated that the fluorescence of the compounds are mainly derived from the π-π* charge transition of the ligand and affected by the rotation of ligand. The UV–Vis data revealed that the compound 1–3 with the maximum absorption peak at 425 nm, 440 nm and 338 nm, respectively. This clearly confirmed that the compound 1 is mainly based on the keto configuration while the compound 3 is mainly based on the enol configuration. Z-scan experiments showed that all compounds exhibited reverse saturable absorption effect and self-defocusing effect for nonlinear optical materials. The nonlinear absorption coefficients (β) of compound 1–3 are evaluated to be 6 × 10−11 m·W−1, 4.4 × 10−11 m·W−1, and 1.7 × 10−11 m·W−1 respectively, and the nonlinear refraction coefficients (n2) are −1.4 × 10−17 m2·W−1, −1.6 × 10−17 m2·W−1, −7.0 × 10−18 m2·W−1 respectively. The nonlinear optical property of compound 1 and 2 are better than compound 3, which are influenced by ligand rotation after coordination.

Azo Schiff Base as Antiscaling Agent for Mild Steel in Hydrochloric Acid: Electrochemical, Non-electrochemical, and DFT Studies

Anticorrosive behavior of Azo Schiff base ligand comprising 4-[5-((4-chlorophenyl) diazenyl)-2-hydroxybenzylideneamino]-1,5-dimethyl-2-phenyl-1H-pyrazole-3-(2H)-one (CDHBAP) on mild steel in 1 M HCl was investigated by Gravimetric method, AC Impedance measurements, and Tafel polarization techniques. The corrosion rate of mild steel in 1 M HCl solutions increased with increasing temperature (308–328 K). When increasing the concentration of CDHBAP (15–100 ppm), the corrosion rate of mild steel in 1 M HCl solutions decreases and inhibition efficiency is increased. Nyquist plot shows that charge resistance value increased with increasing concentration of CDHBAP. Polarization studies confirm that CDHBAP acts as mixed type inhibitor with predominant anodic effect. The Fourier transform-infrared spectroscopy (FT-IR) and UV–visible (UV–Vis) studies confirm the existence of an absorbed film on mild steel surface. Thermodynamic and adsorption studies reveal that adsorption of CDHBAP abide Langmuir adsorption isotherm. Quantum chemical calculations are further employed to enumerate the relation between quantum chemical parameters (EHOMO, ELUMO, ΔN) and corrosion inhibition efficiency.

Extending the scope of amantadine drug by incorporation of phenolic azo Schiff bases as potent selective inhibitors of carbonic anhydrase II, drug-likeness and binding analysis.

A series of Amantadine-based azo Schiff base dyes 6a-6e have been synthesized and characterized by 1 H NMR and 13 C NMR and evaluated for their in vitro carbonic anhydrase II inhibition activity and antioxidant activity. All of the synthesized showed excellent carbonic inhibition. Compound 6b was found to be the most potent derivative in the series, and the IC50 of 6b was found to be 0.0849±0.00245μm (standard Acetazolamide IC50 =0.9975±0.049μm). The binding interactions of the most active analogs were confirmed through molecular docking studies. Docking studies showed 6b is interacting by making two hydrogen bonds w at His93 and Ser1 residues, respectively. All compounds showed a good drug score and followed Lipinski's rule. In summary, our studies have shown that these amantadine-derived phenolic azo Schiff base derivatives are a new class of carbonic anhydrase II inhibitors.

Inhibition of corrosion of aluminum in alkaline solution by a novel azo-schiff base: Experiment and theory

The inhibition effect of a Schiff base with several functional groups on the corrosion of aluminum in alkaline solution is studied by experimental techniques and density function theory (DFT) calculations. The Schiff base are characterized by 1HNMR, 13CNMR, FT-IR, and CHN elemental analysis. In addition, different electrochemical and corrosion techniques such as weight loss, tafel polarization, electrochemical impedance spectroscopy (EIS) and optical microscopy images are performed to analyze the inhibiting performances. In the Tafel measurements the cathodic Tafel slopes values incurred small changes with increasing the inhibitor concentration, which revealed that the inhibitor was adsorbed on the aluminum surface. The inhibition efficiencies are calculated from weight loss measurement and electrochemical tests. The adsorption of the inhibitor onto the aluminum surface follows the Langmuir adsorption isotherm with the free adsorption energy of −8.66 kJ mol−1. The calculated adsorption energies and the amount of charge transfer obtained by DFT calculation revealed that corrosion inhibition effectively occurs with chemisorption, where new NAl bonds are formed between of N atoms in azo (–NN–) group and Al surface atoms, which is confirmed from ab initio molecular dynamics (AIMD) simulation.

Syntheses, crystal structures, DNA binding, DNA cleavage, molecular docking and DFT study of Cu(ii) complexes involving N2O4donor azo Schiff base ligands

DNA binding and cleavage properties of three novel copper(ii) complexes involving azo Schiff base ligands have been studied.

Multi-properties of a new azo-Schiff base and its binuclear copper(II) chelate: Preparation, spectral characterization, electrochemical, potentiometric and modeling studies

In this study, NN– chromophore group containing a new Schiff base ligand 2-{(E)-[(3-hydroxy-4-methoxyphenyl)imino]methyl}-4-[(E)-phenyldiazenyl]phenol H2L.3/2H2O, formed by the 1:1 M condensation of 5-amino-2-methoxyphenol with 2-hydroxy-5-[(E)-phenyldiazenyl]benzaldehyde and the binuclear copper(II) chelate of this ligand have been prepared. The structures of the ligand and its Cu(II) chelate have been elucidated on the basis of elemental analyses, conductivity measurements, spectral (FT-IR, 1H and 13C NMR and UV.–Vis.), electrochemical studies and theoretical calculations. Cu(II) ion coordinates with the ligand through the oxygen of the phenolic and nitrogen of azomethine group. The redox behaviors of the ligand and its binuclear Cu(II) chelate were investigated in DMSO solution containing 0.1 M tetrabutylammoniumtetrafluoroborate (TBATFB) as supporting electrolyte by cyclic voltammetry (CV). Five dissociation constants were determined for the prepared azo-Schiff base ligand as 3.25 (pKa1), 5.51 (pKa2), 7.18 (pKa3), 9.60 (pKa4) and 11.10 (pKa5). Also, the stability constants of the Cu(II) chelate have been calculated by SUPERQUAD computer program and general mechanisms have been proposed with regard to the formation of the complex.

Antibacterial evaluation of Some Synthesis Complexes of Azo-dye Ligands.

In present work, two ligands, azo Schiff-base (AZD1 and AZD2), were synthesized by twosteps. Firstly, Schiff-bases were prepared by condensation of Salicyldehyde with anthranilic acid, followed by diazotization of aromatic amines and their subsequent coupling reaction with Schiff-bases. Consequently, 8 complexes of the type [M(AZD1)Cl2] and [M(AZD2)Cl2], where M = Cu(II), Ni(II), Co(II), Mn(II); were synthesized and characterized with the help of molarconductance, magnetic susceptibility measurements, FT-IR, micro elemental analysis , H1 NMR,and Uv–visible spectroscopy. The spectral data revealed that the ligands act as bidentate ligand,the hydroxyl of carboxylic group and the azo group in AZD1 and hydroxyl of phenyl group andthe azomethin group in AZD2 ligand are co-ordination to the central metal atoms. Lastly, all thecompounds were screened for their antibacterial activity, using well-diffusion method. Inconclusion, the ligands and some of the complexes exhibited appreciable antibacterial activityagainst Escherichia coli Klebsiella pneumonia and Staphylococcus haemolyticus andStaphylococcus aurous.

Nuclearity versus oxidation state in the catalytic efficiency of MnII/IIIazo Schiff base complexes: computational study on supramolecular interactions and phenoxazinone synthase-like activity

Supramolecular interactions of a mononuclear Mn(iii) and a tetranuclear Zn(ii)–Mn(ii) complexes and their comparative bio mimetic catalytic activity have been reported.

Synthesis and Characterization of Some New Heavy Metal Complexes with Azo-Schiff Base Ligands.

Synthesis and Characterization of Some New Heavy Metal Complexes with Azo-Schiff Base Ligands.

A Novel Azo-Schiff Base Ligand and Its Cobalt, Copper, Nickel Complexes: Synthesis, Characterization, Antimicrobial, Catalytic and Electrochemical Features.

A new azo containing Schiff base were synthesized using 3-amino-3-azabicyclo[3.3.0]octane hydrochloride, salicylaldehyde and aniline. The synthesized ligand were reacted with acetate salts of Cobalt (II), Copper (II) and Nickel (II). Synthesized compounds were characterized using spectral techniques. Metal coordination compounds gave good/moderate results as catalysts in the oxidation reactions of styrene and cyclohexene. Antimicrobial activities of the synthesized compounds showed good suppressor effects on a number of Gram (-) and Gram (+) bacteria. Electronic features of all the compounds were also reported.

Synthesis, characterization, thermal and catalytic properties of a novel carbazole derived Azo ligand and its metal complexes

This work explains the synthesis of a new azo-Schiff base compound, derived from condensation between N-ethylcarbazole-3-carbaldehyde and 1,3-diaminopropane, followed by azo coupling reaction with the diazonium salt of 2-amino-4-methyl phenol. The newly synthesized azo-Schiff base was further reacted with the acetate salts of Copper, Cobalt and Nickel to give three coordination compounds. All synthesized compounds have been characterized through spectral analysis. The coordination compounds have been examined for their thermal and catalytic features. Good and moderate yields were obtained for the oxidation of styrene and cyclohexene. Thermal features of the ligand and its complexes have been explained and the results obtained have supported the proposed structures.

Assembly of transition metal ion on cellulose surface anchored with azo-Schiff base and its catalytic activity for H2O2 decomposition

To form polymer-supported catalysts, to eliminate excess H2O2 during wastewater treatment, the assembly of metal ion on cellulose was investigated. Cellulose was covalently grafted with reactive azo-Schiff base containing azo-conjugated system, 3,5-bis {2-hydroxyphenyl-5-[(2-sulfate-4-sulfatoethylsulphonyl-azobenzol) methylene amino]} benzoic acid. Metal ions, Co2+, Mn2+, and Cu2+, were anchored to the modified cellulose by controlling assembly. The cellulose-supported complexes were characterized and the catalytic activity for H2O2 was investigated. Elemental analyses of the cellulose supported complexes, MC–Co, MC–Mn, were well agreed with the proposed composition. Three cellulose-supported complexes had strong catalytic activities for H2O2. H2O2 decomposition rates in 10 min were 84.54% for MC–Co, 94.87%, for MC–Mn, and 77.21% for MC–Cu, respectively. The manganese complex had the strongest catalytic activity among them. The cellulose-supported complexes have potential application in wastewater treatment and biotechnology.

NEW AZO-SCHIFF BASE DERIVED WITH Ni(II), Co(II), Cu(II), Pd(II) AND Pt(II) COMPLEXES: PREPARATION, SPECTROSCOPIC INVESTIGATION, STRUCTURAL STUDIES AND BIOLOGICAL ACTIVITY

ABSTRACT The coordination ability of the azo-Schiff base 2-[1,5-Dimethyl-3-[2-(5-methyl-1H-indol-3-yl)-ethyl imino]-2-phenyl-2,3-dihydro-1H-pyrazol-4-ylazo]-5-hydroxy-benzoic acid has been proven in complexation reactions with Co(II), Ni(II), Cu(II), Pd(II) and Pt(II) ions. The free ligand (LH) and its complexes were characterized using elemental analysis, determination of metal concentration, magnetic susceptibility, molar conductivity, FTIR, Uv-Vis, (1H, 13C) NMR spectra, mass spectra and thermal analysis (TGA). The results confirmed the coordination of the ligand through the nitrogen of the azomethine, Azo group (Azo) and the carboxylate ion with the metal ions. The activation thermodynamic parameters, such as ΔE*, ΔH * , ΔS, ΔG * and K are calculated from the TGA curves using Coats–Redfern method. Hyper Chem-8 program has been used to predict structural geometries of compounds in the gas phase. The synthesized ligands and their metal complexes were screened for their biological activity against bacterial species, two Gram positive bacteria (Bacillus subtillis and Staphylococcus aureus) and two Gram negative bacteria (Escherichia coli and Pseudomonas aereuguinosa).

Synthesis of novel Schiff base metal complexes with reactive groups and their catalytic property for hydrogen peroxide decomposition

A novel water soluble azo Schiff base ligand containing crosslinking reactive groups (A), 3,5-bis [(2-hydroxy-4′-sodiumsulphatoethylsulphonyl) azobenzene- methyneimino]-benzoic acid (BHSABA), and its complexes with Mn2+, Cu2+, Co2+, were synthesized and characterized by elemental analysis, Fourier transform infrared (FT-IR) and proton nuclear magnetic resonance (1HNMR) spectroscopy. The Schiff base ligand and its complexes had excellent water solubility. Two reactive groups, p-[(2′-sulphatoethyl) sulphonyl groups, were able to form covalent bonds with biomass, such as cellulose, chitosan and so on, to obtain functional material. Ultraviolet–visible (UV-vis) electronic absorbance and fluorescence spectra of the ligand having azo conjugated system and of the metal complexes were measured. The catalytic activity of the ligand and the complexes for H2O2 decomposition were also investigated. The results show that the fluorescence spectra of the complexes, Co2A and Mn2A, had increased fluorescence phenomena. They had strong catalytic activity for H2O2 decomposition. When the concentration of manganese complex, Mn2A, was 5 mg/l, H2O2 decomposition nearly finished in 40 min at 40℃. The order of catalytic activity of three complexes for H2O2 decomposition was Mn2A > Co2A > Cu2A. The ligand itself had no noticeable catalytic activity for H2O2 decomposition. These novel water soluble Schiff base metal complexes with reactive groups have potential application in the H2O2 decomposition of water treatment fields.

Synthesis, Characterization and DNA Interaction Studies of (N,N'-Bis(5-phenylazosalicylaldehyde)-ethylenediamine) Cobalt(II) Complex

In the present study, at first, azo Schiff base ligand of (N,N'-bis(5-phenylazosalicylaldehyde)-ethylenediamine) (H2L) has been synthesized by condensation reaction of 5-phenylazosalicylaldehyde and ethylenediamine in 2:1 molar ratio, respectively. Then, its cobalt complex (CoL) was synthesized by reaction of Co(OAc)2·4H2O with ligand (H2L) in 1:1 molar ratio in ethanol solvent. This ligand and its cobalt complex containing azo functional groups were characterized using elemental analysis, 1 H-NMR, UV-vis and IR spectroscopies. Subsequently, the interaction between native calf thymus deoxyribonucleic acid (ct-DNA) and CoL complex was investigated in 10 mM Tris/HCl buffer solution, pH = 7 using UV-vis absorption, thermal denaturation technique and viscosity measurements. From spectrophotometric titration experiments, the binding constant of CoL complex with ct-DNA was found to be (2.4 ± 0.2) × 10 4 M �1 . The thermodynamic parameters were calculated by van’t Hoff equation.The enthalpy and entropy changes were 5753.94 ± 172.66 kcal/mol and 43.93 ± 1.18 cal/mol·K at 25 °C, respectively. Thermal denaturation experiments represent the increasing of melting temperature of ct-DNA (about 0.93 °C) due to binding of CoL complex. The results indicate that the process is entropy- driven and suggest that hydrophobic interactions are the main driving force for the complex formation.

Preparation, spectral, X-ray powder diffraction and computational studies and genotoxic properties of new azo–azomethine metal chelates

A new tridentate azo–azomethine ligand, N′-[{2-hydroxy-5-[(4-nitrophenyl)diazenyl]phenyl}methylidene]benzohydrazidemonohydrate, (sbH·H2O) (1), is prepared by condensation of benzohydrazide and 2-hydroxy-5-[(4-nitrophenyl)diazenyl]benzaldehyde (a) with treatment of a solution of diazonium salt of p-nitroaniline and 2-hydroxybenzaldehyde in EtOH. The five coordination compounds, [Co(sb)2]·4H2O (2), [Ni(sb)2]·H2O (3), [Cu(sb)2]·4H2O (4), [Zn(sb)2]·H2O (5) and [Cd(sb)2]·H2O (6) are prepared by reacting the Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) ions with the ligand. The structures of the compounds are elucidated from the elemental analyses data and spectroscopic studies. It is found the ligand acts as a tridentate bending through phenolic and carbonyl oxygens and nitrogen atom of the CN group similar to the most of salicylaldimines. Comparison of the infrared spectra of the ligand and its metal complexes confirm that azo-Schiff base behaves as a monobasic tridentate ligand towards the central metal ion with an ONO donor sequence. Upon complexation with the ligand, the Cd(II), and Zn(II) ions form monoclinic structures, while Co(II), Cu(II) and Ni(II) ions form orthorhombic structures. Quantum chemical calculations are performed on tautomers and its metal chelates by using DFT/B3LYP method. Most stable tautomer is determined as tautomer (1a). The geometrical parameters of its metal chelates are obtained as theoretically. The NLO properties of tautomer (1a) and its metal complexes are investigated. Finally, the ligand and its metal complexes are assessed for their genotoxicity.