4-nitrophenyl Azo Research Articles

Experimental and Computational studies on Intramolecular charge transfer, Terahertz and Two photon absorption of 3-[(4-Nitrophenyl Azo)]-9H-Carbazole-9-Ethanol (NPACE) from their Vibrational spectra for Optical limiting and NLO applications

Non-linear optical (NLO) features of 3-[(4-Nitrophenyl Azo)]-9H-Carbazole-9-Ethanol (NPACE) chromophore were investigated by FT-IR, FT-Raman, and UV–visible spectra aided by Density Functional Theory (DFT) using the B3LYP/6–311++G(d,p) basis set of Gaussian 16 W package. It is observed from the DFT calculation that the slight increase in the endocyclic angle of C13 -C14 -C15 and the reduction in exocyclic angle of N40 –N39 -C14 and C15 -C14 –N39 ascertained by experimental XRD values indicating the intramolecular charge-transfer interaction between the carbazole and nitrophenyl group through the diazo bridge. The vibrational contribution to the linear electro-optic effect is 15% of the total hyperpolarizability being calculated at B3LYP/6–311++G (d, p) for the NPACE molecule. It is also observed that the 8a, 19a, and 19b modes of the carbazole ring and the 8a, 8b, and 19b modes of the phenyl ring are found to be simultaneously and intensely active in IR and Raman spectra explaining the charge transfer interactions throughout the molecule. The low value of the HOMO- LUMO energy gap (2.5843 eV) and the deviation between the measured absorption wavelength (3.36 eV) from the computed (3.87 eV), both these facts substantiate the intramolecular charge transfer. The polarizability and first-order hyperpolarizability were calculated as 6.48 × 10-24 and 3.8 × 10-29 esu, respectively. The second harmonic generation (SHG) measurement experiment of NPACE was carried out using the powder method. The SHG efficiency is measured in comparison with the urea standard. The calculated torsional mode at 20 cm−1 is in excellent quantitative agreement with the experimentally determined terahertz absorption peak. The two-photon absorption coefficient of NPACE was estimated to be 0.9 × 10-11 mW−1, which is mainly due to the D-π-A type of molecular structure, and the optical limiting threshold for NPACE was estimated to be 1.52 × 1013 Wm−2 enabling this material as a potential candidate for optical limiting applications.

Quantum Chemical Computations of an Efficient Push-Pull NLO Chromophore 3-[4-Nitrophenyl Azo]- 9H- Carbazole-9-Ethanol

Electric-optic (EO) materials are being explored for applications ranging from fiber and satellite telecommunications, optical gyroscopes, to photonic detection of radar etc. Dipolar push-pull Organic chromophores that exhibit extended π-conjugation, in particular, show enhanced second order NLO properties. The present investigation reports the quantum chemical computations of the high efficiency push-pull NLO molecule 3-[(4-Nitrophenyl Azo)] - 9H-Carbazole-9-Ethanol (NPACE). The organic push-pull molecule is optimized in gaseous and in various solvent condition using Exchange correlation function (B3LYP/MP2). Molecular electrostatic potential, thermal properties and NBO analysis have also been performed in detail. The effective electron cloud moment in the molecule is mainly governed by the physical process termed intramolecular Charge Transfer (ICT).

Anion sensing properties of electrospun nanofibers incorporating a thiourea-based chromoionophore in methanol.

To sense hydrophilic anions in protic solvents, we fabricated polymethylmethacrylate (PMMA) nanofibers incorporating 4-nitrophenyl azo thiourea polymer as a chromoionophore. When methanol solutions containing anions contacted the PMMA nanofiber, a bathochromic shift from 386 nm was observed in the absorption maximum of the chromoionophore. This spectral change is due to hydrogen bond formation between the urea moiety of the thiourea-based polymer and anions penetrating the nanofiber. This spectral change was not observed in PMMA film incorporating the same anion sensor, and the difference is attributed to the much larger specific surface area of the nanofiber compared to the film. As a result, many anions could react with the anion-sensing polymers in the nanofiber and induce a large spectral response.

Preparation of Photoresponsive Azo Polymers Based on Lignin, a Renewable Biomass Resource

Lignin-based azo polymers are prepared from alkali lignin, a byproduct in spent liquor from the pulping and papermaking industry, and their structures and photochromic effects are characterized by elemental analysis, Fourier transform infrared, 1H nuclear magnetic resonance, and ultraviolet–visible spectroscopy. Results show that only the 2-(4-nitrophenyl azo) phenol lignin-modified polymer (AL-azo-NO2) shows a significant photochromic effect, and its photoresponsive behavior is evidently slower than that of the synthetic polymer with a similar azo chromophore. For the 2-(4-methoxyphenyl azo) phenol lignin-modified polymer, its photoisomerization behavior was expected to be similar to that of azobenzene-type molecules, but its photoresponse is not obvious. The abnormal photochromic effect of AL-azo polymers is related to strong steric hindrance of lignin backbones. With addition of water (poor solvent), AL-azo-NO2 shrinks gradually, which prevents azobenzene groups from isomerizing and results in a lower ...

A generalized ZnCl2 activation method to produce nitrogen-containing nanoporous carbon materials for supercapacitor applications

We demonstrate a generalized but efficient ZnCl2 activation method to produce nitrogen-containing nanoporous carbon materials, using 4-(4-nitrophenylazo)resorcinol, sodium 5-[(4-nitrophenyl)azo]salicylate, and tartrazine as carbon/nitrogen sources. It reveals that the mass ratios between carbon/nitrogen precursors and ZnCl2 activating agent, and activation temperatures have crucial impacts upon carbon structures as well as the resultant capacitive behaviors. The carbon samples produced in this work are amorphous in nature. The carbon sample obtained by the ZnCl2 activation of 4-(4-nitrophenylazo)resorcinol at 900°C, named as carbon-1#, exhibits the largest nitrogen contents of 5.96% and best porosity, including the BET surface area of 891.1m2g−1, and total pore volume of 0.54cm3g−1. As a result, the carbon-1# sample delivers the superior specific capacitances of 431.5Fg−1 at a current density of 1Ag−1, as well as long-term cycling stability of 97.16% even after charging-discharging for 10,000 times. The present ZnCl2 activation method is expected to produce other carbon materials, exhibiting large porosities and superior electrochemical behaviors for supercapacitor applications.

Synthesis and Characterization of Photochromic Copolymer Grafting Azoaromatic Chromospheres on Pullulan

Preparation of photochromic copolymer grafting 4-(4-nitro phenylazo)-1-naphthol units on a pullulan molecular surface has been accomplished. Surface modification was carried out in aqueous solution by an inverse emulsion polymerization method. Polymerization products were characterized by IR, SEM, XRD and TG-DTA. UV-vis spectroscopy has been used to monitor the photoisomerization of azobenzene moieties on a pullulan molecular surface. The results indicated that functional copolymer has a better photochromism property than its corresponding azobenzene moieties, reflecting the macromolecular backbone of pullulan should actively affect the photoisomerization of azoaromatic moieties.

Flame atomic absorption spectrometric determination of μg amounts of Fe (III) ions after solid phase extraction using modified octadecyl silica membrane disks

A simple, rapid and reliable method has been developed to selectively separate and concentrate ultra trace amounts of Fe (III) ions from aqueous samples for the measurement by flame atomic absorption spectrometry (FAAS). By the passage of aqueous samples through an octadecyl silica membrane disk modified by a recently synthesized Schiff base (Bis-(4-nitro phenyl azo) salisilidine-1,3-diamino propane), Fe(III) ions adsorb quantitatively and most of matrix elements will pass through the disk to drain. The retained iron ions are then stripped from the disk by minimal amount of 0.1 mol l − 1 sulfuric acid as eluent. Extraction efficiency and the influence of pH, flow rates, amount of ligand, type and least amount of stripping acid as eluent were evaluated. The recovery of the iron from aqueous solution on the membrane disk modified with 3 mg Schiff's base was quantitative over pH 2–4.5. The linear dynamic range of the proposed method for Fe (III) ions was found in a wide concentration range of 0.20 (± 0.05)–680 (± 2) μg l − 1 . The detection limit and preconcentration factor of this solid phase extraction method were found 20.0 (± 0.7) ng l − 1 and 100 respectively. The reproducibility of the procedure is at the most 1.5%.

New Schiff base modified carbon paste and coated wire PVC membrane electrode for silver ion

A new modified carbon paste electrode (CPE) and a coated wire PVC membrane electrode (CWE) based on a recently synthesized Schiff base of [bis 5-(4-nitrophenyl azo)salisylaldimine] 1,8-diamino, 3,6-dioxo octan (BNSAO) as a suitable carrier for Ag + ion are described. The electrodes exhibit a Nernstian slope of 56.2 ± 0.7 (CWE) and 58.4 ± 0.3 (CPE) mV per decade for Ag + ion over a wide concentration range from 3.1 × 10 −2 to 9.0 × 10 −7 M for CPE and 2.7 × 10 −2 to 1.9 × 10 −6 M Ag + for CWE. The lower detection limits are 4.2 × 10 −7 M Ag + for CPE and 7.8 × 10 −7 M Ag + for CWE electrode. Their electrodes have a fast response time (∼5 s), a satisfactory reproducibility and relatively long life time. The proposed sensors show a fairly good selectivity toward Ag + ion in comparison to other common cations. The potentiometric responses are independent of the pH of the test solution in the pH range 3.5–7.0 for CPE and 2.5–7.0 for CWE. The proposed electrodes were used as indicator electrodes in potentiometric titration of silver ion with standard solution of potassium iodide. The direct determination of silver in spiked wastewater and radiology film gave results that compare favorably with those obtained by the atomic absorption spectrometric method.