Azo-azomethine Dyes Research Articles

Synthesis and characterization of enhanced azo-azomethine doped PANI/HCl conducting polymers for electrochemical applications

In this study, conducting polymers composed of polyaniline hydrochloric acid (PANI/HCl) with varying concentrations of a newly synthesized azo-azomethine dye (4-(((Z)-2-hydroxy-5-((Z)-(4-hydroxyphenyl)diazenyl)-3-methoxybenzylidene)amino)benzoic acid) were synthesized using a chemical oxidative polymerization technique. The synthesized azo-azomethine was characterized by FTIR, 1H-NMR, 13C-NMR, and HRMS. The effects of varying the concentration of the dopant azo-azomethine in PANI/HCl on its optical, structural, thermal, and electrical properties were examined using FTIR, UV–Vis, XRD, FESEM, TEM, cyclic voltammetry, and electrical impedance spectra. The results indicate that the optical, direct, and indirect band gaps of the doped polymers decreased from 4.48 and 3.96 eV to 3.91 and 2.49 eV, respectively. The crystalline structure and phase transitions in the doped polymers were examined using X-ray diffraction. Cyclic voltammetry demonstrated that the doped polymers exhibited higher electrochemical conductivity compared to the pure polymer, with the specific capacitance increasing from 161.17 to 816.9 F/g. The electrical impedance spectra revealed the bulk resistance and conductivity of the material. Among all the doped polymers, PANI/HCl with an azo-azomethine concentration of 5 × 10−5 M exhibited lower bulk resistance (10 Ω) and higher electrical conductivity (σ = 50.09 × 10−3 S cm−1).

Cloud Point Extraction Coupled to Flame Atomic Absorbance Spectroscopy for Cobalt (II) determination with Azo-Azomethine Dye

The azo-azomethine dye 6,6'-((1E,1'E)-((4-methyl-1,2-phenylene)bis(azanylylidene))bismethanylylidene))bis(2-methoxy-3-(o-tolyldiazenyl) phenol) (L3) were synthesized and characterized by UV-visible, FT-IR, 1H-NMR and Mass spectroscopy. The effect of the several factors on the CPE pre-concentration of Cobalt (II) with L3 was optimized. Extensive thermodynamic study has been presented to understand the mechanism of extraction and solubilization of studied complex in Triton X-100 micelles. Under the optimized conditions, enrichment factor of 54 is achieved leading to limit of detection and limit of quantitation of 11.5 and 38.4 ngmL-1 respectively. Under the optimal conditions the calibration plot is linear in the range of 0.025-3 μg mL-1, the precision (RSD%; n=8) of the proposed method is of 0.823% at 0.05 μg mL-1 of Co (II). This method is applied to the determination of Co (II) in various environmental samples.

Complex Activity and Sensor Potential toward Metal Ions in Environmental Water Samples of N-Phthalimide Azo-Azomethine Dyes.

Herein, the spectral and electrochemical characterizations of three different substituted N-phthalimide azo-azomethine (NAA) dyes (L) containing an o-hydroxy group and their NAA-M(II) chelates [M(II): Cu, Ni, Co, Pb] were reported by using UV–Vis and fluorescence spectroscopy and potentiometric and voltamperometric techniques. The pK value of the dyes as well as the stoichiometry and stability of the NAA-metal chelates were studied, and the stoichiometry was found to be mostly 1:2 (ML2) with high complex stability constant values. The sensor activity of N-phthalimide azo-azomethine derivatives toward pH and metal ions has been also investigated and tested for indicator application in acid–base analysis and detection of Cu(II) ions in real samples of surface river water using voltamperometric detection. The results showed that one of the ligands possesses the highest electrochemical response upon binding to copper ions and could be successfully used in the analysis of copper in water at a concentration range of the analyte from 3.7 × 10−7 to 5.0 × 10−6 mol L−1, with analytical characteristics of the method being Sr = 1.5%, LOD = 3.58 µg L−1 and LOQ =11.9 µg L−1

Solvent enhancement and isomeric effects on the NLO properties of a photoinduced cis-trans azomethine chromophore: A sequential MC/QM study

This work uses a sequential Monte Carlo/Quantum Mechanics procedure to discuss how specific solute-solvent interactions and the photoinduced cis-trans isomerization affect the nonlinear optical (NLO) response of a recently synthesized azo-azomethine dye. The results show that the trans geometry increases the number of solvent molecules around the solute concerning the cis structure. Consequently, the trans isomer performed the major number of hydrogen-bonded structures with the solvent molecules. Considering the solvent contribution to the quantum mechanical properties, the results show that the solute polarization affects drastically all electronic properties drastically. For instance, concerning the vacuum conditions, the molecular dipole moment increases ca. 25% insolvent. Moreover, from vacuum to solvent, Density Functional Theory methods coupled to 6-311++G(d,p) basis set to show that the first and second-hyperpolarizability (β and γ) increase ca. 12% for the trans structure, indicating a high-power generation of second and third harmonic, which can be 580 times greater than that reported for urea (β=0.34×10-30 esu), which is a common NLO chromophore. Finally, the photo-induced cis-trans isomerization tunes the NLO response of the material from βcis=53.31×10-30 esu to βtrans=197×10-30 esu, which means an improvement of 270%.

Three Indole Derived Azo-Azomethine Dyes as Effective Chemosensors for F− Ion and Trace Water Detection

Abstract Three new dyes 1–3 derived from indol-carbohydrazide and azo-azomethine for the optical detection of F− ion have been developed. Dye 1 was found to be an effective colorimetric sensor for F− ion response with over 250 nm red-shift. Moreover, the resultant dye⋯HF2− complex (dye-F) could be successfully used as a secondary sensor for analyzing trace water in aprotic organic solvents especially in acetonitrile with a low limit of detection. In addition to detection of low-level water content in solution, test paper incorporated with 1-F complex or 2-F complex was well developed for naked-eye detection of water content in four organic solvents as mentioned above. Importantly, the test paper prepared by introducing 1-F complex or 2-F complex could be developed to prepare an ink-free rewritable paper by using water as the sole trigger. Furthermore, the same test paper could still work for many cycles without obvious loss in color quality.

Media polarity and substituent effects on the photo-physical properties of some nickel complexes with azo-azomethine dyes

Nickel complexes as one of the most applicable elements are widely involved in the various physical, chemical and biological phenomena. The finding of effective factors that can modify their behaviors in various systems is an important scientific work. In this paper, substituents and molecular surrounding media induced effects on the photo-physical properties of some groups of nickel (II) complexes with azo-azomethine dyes were investigated. In order to determine the various molecular interactions contributions on the photo-physical characteristics of various forms of nickel complexes, Kamlet- Abboud-Taft and Catalan models were used. Furthermore, the solvatochromic method was considered for measuring ground and excited state dipole moments. The calculated solvent accessible surfaces also indicate that nickel complexes with both methyl and methoxy groups indicate high solvent accessible surfaces. Therefore, these experimental results can give important information about how these metal complexes can operate in various phenomena in similar environments.

Triazole derived azo-azomethine dye as a new colorimetric anion chemosensor.

In the pursue of developing anion sensors, an efficient triazole derived azo-azomethine dye chemosensor (S) that differentially senses F‾ and AcO‾ ions has been reported. The ions recognition ability of S was investigated by colorimetric and UV-visible spectroscopic methods. Interestingly, this chemosensor molecule is virtually inactive in presence of other anions such as Cl‾, Br‾ and I‾ and HSO4‾. We have further presented a ratiometric approach to differentiate F‾ and AcO‾ ions. The reversibility of F‾ ion binding with S was established by the addition of Ca(NO3)2 to the fluoride bound S, which led to the regeneration of S. The quantum chemical calculation of energies of unbound and bound S has been employed using Density Functional Theory (DFT) to understand the interaction between chemosensor and anions. Evidence in support of fluoride-induced deprotonation of a O-H bond during the detection of F⁻ ion has been demonstrated by employing 1H NMR titration experiments.

Synthesis and photochromic properties of some N-phthalimide azo-azomethine dyes. A DFT quantum mechanical calculations on imine-enamine tautomerism and trans-cis photoisomerization.

This paper presents synthesis, photophysical characterization and quantum mechanical calculations of some N-phthalimide azo-azomethine dyes. The dyes were synthesized via azo coupling reaction between 2,4-substituted aromatic anilines and salicylic aldehyde followed by condensation reactions between azo dyes and N-aminophtalimide. Quantum chemical calculations to optimise the molecular geometry and to determine the electron densities of the trans (E) imine ⇌ enamine and the cis (Z) imine ⇌ enamine isomers and their vibrational frequencies have been computed by using DFT at B3LYP/6-31 + G(d,p) level of theory in vacuo. The effect of the used DMF solvent on the molecular structure and bond energies has been determined by using the IEFPCM model. Thermodynamic parameters such as total electronic energy E(RB3LYP), enthalpy H298 (sum of electronic and thermal enthalpies), free Gibbs energy G298 (sum of electronic and thermal free Gibbs energies) and dipole moment μ were computed in order to estimate the ΔE, Δμ, ΔH, ΔG and ΔS values. The NBO analysis was performed in order to understand the intramolecular charge transfer and the energy of resonance stabilization. After molecular geometry optimization, the electronic spectra were obtained by TD-DFT calculations at the above mentioned basis set using the IEFPCM model of DMF as a solvent. The solvatochromic effect of the dyes in four solvents with different polarity has been studied by UV-VIS spectroscopy and compared with the theoretically predicted. The coincidence between measured and calculated spectra is satisfactory. The dynamic photoisomerization experiments were performed in DMF under irradiation with UV light at λ = 365 nm (mostly E → Z) and with VIS light at λ = 400-800 nm (mostly Z → E). The spectra were recorded in the spectral region from 300 to 800 nm at identical sample concentrations of the three dyes and illumination times in order to investigate the photodynamical E → Z → E conversion of the NN chromophore group of the dyes as well as the imine ⇌ enamine tautomerization.

Structure-property relationship and photoinduced birefringence of the azo and azo-azomethine dyes thin films in PMMA matrix

Here, we present previously synthesized azo and azo-azomethine dyes as thin films in PMMA matrix in order to investigate their spectral and optical properties. The spectral properties of the vapour deposited 100 nm nanosized films of the dyes have been characterized by UV-VIS and Fluorescence spectroscopy to determine the excitation and emission energies of the electron transitions. Photoinduced birefringence was induced in the films by pump lasers with wavelengths 355 nm and 491 nm in the region of the absorbance band of the chromophores used. The kinetics of recording, relaxation and erasure of birefringence were presented. The photochromic behaviour of the chromophore groups in azo dyes (-N=N-) and azo-azomethine dyes (-N=N- and CH=N-) were evaluated as potential light driven reversible optical storage devices. The presence of two photoactive groups in azo-azomethines makes them appropriate candidates for optical photoswitches.

Half-sandwich Ruthenium(II) arene complexes bearing the azo-azomethine ligands: Electrochemical, computational, antiproliferative and antioxidant properties

Three novel azo-azomethine ligands have been synthesized in an accomplished one-pot synthesis protocol. The mononuclear Ru(II) complexes of these azo-azomethine dyes were prepared and characterized by the combination of elemental analyses, IR, UV–Visible spectroscopy and 1H13C NMR spectra. Solid state structures of 3, 4 and 7 were determined by single crystal X-ray diffraction studies. The electrochemical and photoluminescence properties of the compounds were studied. The 1931 CIE (x,y) chromaticity coordinates of the ligands and their metal complexes were investigated and the x, y values of the compounds were found to be close to the National Television Standard Committee (NTSC) standard. Quantum chemical calculation of related ligands and complexes are performed at B3LYP/6-31G(d,p) and B3LYP/6-31G(d,p) (LANL2DZ) level in vacuum.In addition, the azo-azomethine ligands and their Ru(II) complexes were evaluated for both their in-vitro antibacterial activity by the disc diffusion method and antioxidant properties using ferric reduction power, DPPH free radical, and ABTS cation radical scavenging activities as in vitro. Radical scavenging activities of compounds 5–7 were found higher than BHT, BHA, and Trolox used as positive controls. Compounds 2–4 antioxidant capacities were lower than the positive controls. Finally, the new azo-azomethine dyes and their Ru(II) complexes were investigated for their in vitro antiproliferative activities against non-small cell lung cancer cells (H2126), prostate adenocarcinoma cells (PC3) and breast cancer cells (MCF7) in vitro. Cell proliferation test were performed as dose-dependent assays at 200 μM. The new azo-azomethine ligands and their Ru(II) complexes have shown anticancer activity on the studied cell lines after 24 h exposure to 200 μM compounds. However, the activities of the compounds are much lower than 5-Fu.

Synthesis, spectroscopic and TD-DFT quantum mechanical study of azo-azomethine dyes. A laser induced trans-cis-trans photoisomerization cycle

This paper describes the synthesis, spectroscopic characterization and quantum mechanical calculations of three azo-azomethine dyes. The dyes were synthesized via condensation reaction between 4-(dimethylamino)benzaldehyde and three different 4-aminobenzene azo dyes. Quantum chemical calculations on the optimized molecular geometry and electron densities of the trans (E) and cis (Z) isomers and their vibrational frequencies have been computed by using DFT/B3LYP density-functional theory with 6-311++G(d,p) basis set in vacuo. The thermodynamic parameters such as total electronic energy E (RB3LYP), enthalpy H298 (sum of electronic and thermal enthalpies), free Gibbs energy G298 (sum of electronic and thermal free Gibbs energies) and dipole moment μ were computed for trans (E) and cis (Z) isomers in order to estimate the ΔEtrans→cis, Δμtrans→cis,ΔHtrans→cis, ΔGtrans→cis and ΔStrans→cis values. After molecular geometry optimization the electronic spectra have been obtained by TD-DFT calculations at same basis set and correlated with the spectra of vapour deposited nanosized films of the dyes. The NBO analysis was performed in order to understand the intramolecular charge transfer and energy of resonance stabilization. Solvatochromism was investigated by UV-VIS spectroscopy in five different organic solvents with increasing polarity. The dynamic photoisomerization experiments have been performed in DMF by pump lasers λ=355nm (mostly E→Z) and λ=491nm (mostly Z→E) in spectral region 300nm – 800nm at equal concentrations and times of illumination in order to investigate the photodynamical trans-cis-trans properties of the CHN and NN chromophore groups of the dyes.

In vitro antibacterial, radical scavenging and solvato-chromism properties of some 4-((4-R-phenyldiazenyl-2-(pyridin-2-ylimino)methyl) phenols

The 4-((4-R-phenyldiazenyl-2-(pyridin-2-ylimino) methyl) phenols were synthesized from the reaction of 5-((4-R-phenyl)diazenyl)-2-hydroxybenzaldehyde with aminopyridines in absolute ethanol and characterized by elemental analysis, mass, FT-IR, UV and NMR spectroscopy. The absorption maxima of synthesized compounds show bathochromic shift in various solvents. The nature of substitutions, solvent environment, hydrogen bonds, temperature, pH and dipole moment of the molecules are the key factors in deciding the solvato-chromism of azo–azomethine dyes. Antibacterial activity was studied by disk diffusion and broth microdilution methods. Diphenylpicrylhydrazyl assay was used to determine the radical scavenging properties. Compounds having electron donating groups in the aryl azo component showed significant antibacterial activity against Bacillus cereus, Staphylococcus aureus, Escherichia coli and Klebsiella pneumonia. Derivative 2-((E)-(pyridin-4-ylimino) methyl)-4-((E)-p-tolyldiazenyl) phenol (2h) with excellent antibacterial activity showed the highest scavenging effect, while the minimum antibacterial and scavenging activity was observed by 4-((E)-(4-chlorophenyl)diazenyl)-2-((E)-(pyridin-2-ylimino)methyl) phenol (2f) having electron withdrawing Cl substituent in the aryl azo component. The antibacterial and scavenging activity of synthesized derivatives are affected by the nature and position of the substituent groups and position of the nitrogen atoms in the pyridine ring. The aminopyridine-based azo–azomethine compounds have been synthesized by condensation reaction of 5-((4-R-phenyl)diazenyl)-2-hydroxybenzaldehyde with n-aminopyridine. The spectra indicated positive solvato-chromism in prepared substances which is dependent on the solvent, substitution, pH and temperature. All the synthesized azo Schiff bases except 2f showed significant antibacterial activity.

Synthesis, structural characterization, antimicrobial activities and theoretical investigations of some 4-(4-aminophenylsulfonyl) phenylimino) methyl)-4-(aryldiazenyl) phenol

The azo-azomethine dyes with a different substitution have been designed from the reaction of 4,4′-diaminodiphenyl sulfone with 2-hydroxy-5-(aryldiazenyl)benzaldehyde. The compounds have been characterized by elemental analysis, Mass, IR, UV–Vis, TGA-DTA and NMR spectroscopy. The solvatochromism behaviors, effects of substitution and pH on the electronic absorption spectra of dyes were evaluated. The in vitro antimicrobial activities were also screened for their potential for antibiotic activities by broth micro dilution method. Also, the optimum molecular geometries, molecular electrostatic potential (MEP), nucleus-independent chemical shift (NICS) and frontier molecular orbitals (FMO), vibrational spectra (IR ) and electronic absorption (UV–Vis) spectra of the title compounds have been investigated with the help of DFT and TDDFT methods with 6-311++G(d,p) basis sets and PCM calculations. The results of the calculations show excellent agreement with the experimental value.

Post-modification of 2-formylthiophene based heterocyclic azo dyes

In order to further adjust the π-conjugated system, solubility and electronic spectrum of 2-amino-3-cyano-4-chloro-5-formylthiophene based blue colored heterocyclic blue azo dyes, a post-modification strategy has been used to extend their terminal aldehyde radical into either an imine, acetal or α,β-unsaturated cyanoacetic ester group. The resultant azo-azomethine dyes exhibit slight bathochromic shifts in their UV–Vis spectra with the increase of the π-conjugated system. In contrast, acetal terminated products display good solubility in organic solvents but hypsochromic shifts in their UV–Vis spectra. It is worth mentioning that the α,β-unsaturated cyanoacetic ester derivatives show significant bathochromic shifts and improvement of solubility simultaneously originating from the presence of increased π-conjugated system as well as the terminal cyano and ester groups. It is believed that the current study could provide a practical post-modification strategy for decorating and improving the dyeing performance of certain dyes with functional end groups.

Molecular logic circuits and a security keypad lock based on a novel colorimetric azo receptor with dual detection ability for copper(II) and fluoride ions

A novel azoimine dye-based colorimetric chemosensor (1) has been designed and synthesised for dual recognition of copper(II) and fluoride ions in aqueous media. Significantly, the outstanding dual-ion recognition properties along with the excellent reversibility prompted us to consider 1 as an ideal candidate for fabrication of multiple logic circuits. According to the response profile of 1 towards Cu2+ and F− inputs, we developed a unique tunable system integrated with one INHIBIT logic gate as well as one OR gate. Also, 1 behaved as a molecular keypad lock with sequential addition of Cu2+ and F− inputs. In accession, a reversible ‘Write–Read–Erase–Read’ function with complementary ‘IMP/INH’ logic gate has been demonstrated through a feedback loop using F− and trifluoroacetic acid as two chemical inputs. To the best of our knowledge, this is the first report where the symmetrical bis azo-azomethine dye has been exploited as a molecular keypad lock.

Synthesis of two new azo-azomethines; spectral characterization, crystal structures, computational and fluorescence studies

This study describes the preparation, characterization and the photoluminescence properties of novel azo-azomethines (2-{(E)-[(4-ethylphenyl)imino]methyl}-4-[(E)-phenyldiazenyl]phenol, HL1 and 2-{(E)-[(3-ethylphenyl)imino]methyl}-4-[(E)-phenyldiazenyl]phenol, HL2 dyes). The dyes were characterized by elemental analysis, spectroscopic studies such as IR, 1H and 13C NMR, mass and fluorescence spectra. Molecular structures of the dyes were examined by X-ray diffraction analysis. The molecular structures are mostly similar, differing mainly in the position of the ethyl group and dihedral angles between aromatic rings. X-ray data revealed that both HL1 and HL2 favor phenol-imine tautomer in the solid state. An intramolecular phenol-imine hydrogen bond (O1⋯N1) were observed in both compounds resulting in a S(6) hydrogen bonding motif. Molecular packing of both compounds are determined by π⋯π interactions. Quantum chemical investigation of mentioned molecules were performed by using DFT hybrid function (B3LYP) with 6-31+G(d) basis set. The compounds HL1 and HL1 gave intense light emissions upon irradiation by Ultra-Violet light. The photoluminescence quantum yields and long excited-state lifetimes of the compounds HL1 and HL2 were measured. The azo-azomethine dyes HL1 and HL2 have photoluminescence quantum yields of 34% and 32% and excited-state lifetimes of 3.21 and 2.98ns, respectively. The photoluminescence intensities and quantum yields of these dyes were dependent on the position of alkyl group on the phenyl ring.

Synthesis, structural characterization, and antimicrobial efficiency of sulfadiazine azo-azomethine dyes and their bi-homonuclear uranyl complexes for chemotherapeutic use

Two sulfadiazine azo-azomethine dyes containing two active coordination centers and their bi-homonuclear UO 2 (II)-complexes were synthesized for potential chemotherapeutic use. The ligands were prepared, starting from the coupling of sulfadiazine dizonium salt with acetylacetone, followed by condensation with ethylenediamine and 1,6-hexanediamin (HL I and HL II ) using a modied literature procedure. The structures of the ligands and their

Colorimetric detection of anions in aqueous media using N-monosubstituted diaminomaleonitrile-based azo-azomethine receptors: Real-life applications

New N-monosubstituted diaminomaleonitrile-based azo-azomethine dyes have been synthesized in order to develop colorimetric sensors for detection of biologically important anions in aqueous media. Importantly, the reported sensor decorated with strong electron-withdrawing group can detect inorganic fluoride in water even at 0.037ppm level, which is lower than WHO permissible level (below 1ppm). Successfully, the prepared dyes were used for qualitative and quantitative detection of inorganic fluoride in toothpaste and mouthwash. The anion recognition mechanism was also investigated by detailed UV–Vis and 1H NMR experiments. The detailed 1H NMR experiments corroborated that anion recognition is based on the deprotonation phenomenon.

The triazine-based azo-azomethine dyes; synthesis, characterization, spectroscopy, solvatochromism and biological properties of 2,2′-(((6-methoxy-1,3,5-triazine-2,4-diyl)bis(sulfanediyl)bis(2,1-phenylene))bis(azanylylidene)bis(methanylylidene))bis(4-(phenyldiazenyl)phenol)

The macrocyclic azo-azomethine dyes 2,2′-(((6-methoxy-1,3,5-triazine-2,4-diyl)bis(sulfanediyl)bis(2,1-phenylene))bis(azanylylidene)bis(methanylylidene))bis(4-(phenyldiazenyl)phenol) and its derivatives were synthesized and characterized by elemental analysis, mass, FT-IR, UV–vis and NMR spectroscopy. The solvatochromism as well as effects of substitutions on the electronic absorption of these compounds have been studied in the DMSO, DMF, THF, CH3CN, CH3OH and CH3COOH as solvents. Also they positive solvatochromism behaviors are explained on the basis of intramolecular hydrogen bonding, enol–keto tautomeric and dipole moment changes. Compounds having electron donating substituent on the phenyl ring showed good antioxidant activity. However, none of them has a considerable antibacterial activity.

Solar-light induced photodecolorization of water soluble azo-azomethine dye: influence of operational parameters and nanophotocatalysts

Photocatalytic decolorization of a new water soluble azo-azomethine dye, sodium 4-((4-hydroxy-3-((2-(4-(4-(2-hydroxy-5-((4-sulfonatophenyl)diazenyl)benzylide-neamino)butyl)piperazin-1-yl)ethylimino)methyl)phenyl)diazenyl)benzenesulfonate, 2,4-PIP, has been reviewed under solar light and UV irradiation. The effects of experimental parameters such as (i) initial dye concentration, (ii) the nanophotocatalyst dosage, (iii) hydrogen peroxide concentration, (iv) irradiation time, and (v) pH on photodecolorization of the dye have been investigated. The photocatalytic activity of TiO2 and ZnO on rate and efficiency of decolorization was also investigated. The result indicated that TiO2 was a valuable alternative nanocatalyst than ZnO for decolorization of the dye in the presence of solar light and UV irradiation at pH 5–7. Furthermore, maximum decolorization of the dye (more than 95%) was occurred in the presence of TiO2 during 30 min under solar light. The intermediate products of photodecolorization were also identified using gas chromatography–mass spectrometry.