Azo Derivatives Research Articles

Enhanced Rates of Photoinduced Molecular Orientation in a Series of Molecular Glassy Thin Films.

Photoinduced orientation in a series of molecular glasses made of small push-pull azo derivatives is dynamically investigated for the first time. Birefringence measurements at 632.8 nm are conducted with a temporal resolution of 100 ms to probe the fast rate of the azo orientation induced under polarized light and its temporal stability over several consecutive cycles. To better evaluate the influence of the azo chemical substituents and their electronic properties on the orientation of the whole molecule, a series of push-pull azo derivatives involving a triphenylaminoazo core substituted with distinct electron-withdrawing moieties is studied. All resulting thin films are probed using polarization modulation infrared spectroscopy that yields dynamical linear dichroism measurements during a cycle of orientation followed by relaxation. We show here in particular that the orientation rates of small molecule-based azo materials are systematically increased up to 7-fold compared to those of a reference polymer counterpart. For specific compounds, the percentage of remnant orientation is also higher, which makes these materials of great interest and promising alternatives to azobenzene-containing polymers for a variety of applications requiring a fast response and absolute control over the molecular weight.

Synthesis and cytotoxicity of azo nano-materials as new biosensors for L-Arginine determination.

Inspired from biological counterparts, chemical modification of azo derivatives with function groups may provide a highly efficient method to detect amino acid. Herein, we have designed and prepared a series of azo nano-materials involving -NO2, -COOH, -SO3H and naphthyl group, which showed high response for Arginine (Arg) among normal twenty kinds of (Alanine, Valine, Leucine, Isoleucine, Methionine, Aspartic acid, Glutamic acid, Arginine, Glycine, Serine, Threonine, Asparagine, Phenylalanine, Histidine, Tryptophan, Proline, Lysine, Glutamine, Tyrosine and Cysteine). Furthermore, theoretical investigation further illustrated the possible binding mode in the host-guest interaction and the roles of molecular frontier orbitals in molecular interplay. In addition, nano-material 3 exhibited high binding ability for Arg and low cytotoxicity to KYSE450 cells over a concentration range of 5-50μmol·L(-1) which may be used a biosensor for the Arg detection in vivo.

Design, synthesis and pharmacological assay of novel azo derivatives of dihydropyrimidinones

AbstractThe present work deals with the synthesis of some novel azo derivatives of dihydropyrimidinones. The structures of newly synthesized compounds were established on the basis of their FTIR, 1H NMR, Mass spectrometry and elemental analysis data results. The synthesized agents were assessed for their in vivo anti-inflammatory activity on the Wistar albino rats. The compounds were also screened for their anthelmintic activity on Indian earthworms and anti-bacterial activity against some Gram-positive and Gram-negative strains of bacteria. This pharmacological activity appraisal unveils that among all the compounds screened, compounds 4b, 4c and 4g were found to have potential anti-inflammatory activity. Furthermore, compounds 4b and 4c exhibited appreciable anthelmintic properties while compounds 4b and 4d showed leading anti-bacterial activity against the selected pathogenic strains of bacteria.

Supramolecular structure of azodye rhodanine compounds and their complexes: a review

The optical absorption properties of 5-(4′-derivatives phenylazo)-2-thioxothiazolidin-4-one (HLn) (where X = H) thin films have been studied. It was found that the values of the energy band gap, Eg, for derivatives were in the range of 1.77–2.29 eV depending on the nature of the substituent. The optical values of the energy band gap (Eg) for all derivatives near the absorption edge were found to be direct allowed transition. The synthesized ligands (HLn) (where X = H) were screened as antibacterial and antifungal agents. The proton–ligand dissociation constant of the rhodanine azo derivatives (HLn) (where X = H and X = P-OCH3Ph) and metal–ligand stability constants of their complexes with metal ions (Mn2+, Co2+, Ni2+, Cu2+ and Zn2+) have been determined potentiometrically in 0.1 M KCl. The stoichiometries of copper(II) and cadmium(II) complexes of HLn (where X = Ph) were determined conductometrically and indicated the formation of 1:1 and 1:2 (metal:ligand) complexes. The molar ratio of ligand (HLn) (where X = H) and Ru(III) complexes is (1:2)/(1:3)(M:Ln), respectively. The study revealed octahedral geometry around Ru(III) complexes. A series of heterocyclic mixed ligands of oxovanadium(IV) complexes have been synthesized by the reaction of vanadium(IV) sulfate with rhodanine azo (HLn) (where X = H) in the presence of β-diketone (LH). Palladium(II) complexes of the general formula [Pd(Ln)L] (where LH = diketone = acetylacetone, HLn = azorhodanine) have been synthesized. In these complexes, the azo ligand acts as a monobasic bidentate ligand and is coordinated to the metal ion through the azo-nitrogen, enolic oxygen atoms forming stable six-membered heterocyclic rings. The D.C. electrical conductivity of HLn (where X = Ph) and their complexes were measured. The bond lengths and the force constants have been calculated for uranyl complexes (26–30) of HLn (where X = Ph). The plotting of r1, r2 and r3 (bond distance, rU–O) versus ν3 give a straight line with increasing the value of ν3 and decreasing rU–O.

Synthesis of 5,7-dihydroxy-4,8-dimethylchromen-2-one and its azo derivatives

5,7-Dihydroxy-4,8-dimethylchromen-2-one was synthesized based on methyl phloroglucinol and its spectral and physicochemical characteristics were obtained. Reactions of the newly synthesized coumarin with different diazonium salts were studied, conditions allowing selective obtaining the corresponding monoor bisazo compounds were found. The synthesized azo compounds dye nylon in the yellow-brown colors under standard coloration conditions, providing high stability of obtained colors upon exposure to physicochemical conditions.

A mild CuBr–NMO oxidative system for the coupling of anilines leading to aromatic azo compounds

An efficient methodology was developed for the synthesis of aromatic azo derivatives under mild reaction conditions utilizing CuBr with N-methylmorpholine N-oxide as an oxidant.

Geometrical structure and potentiometric studies of 5-chloro-2,3-dihydroxy pyridine azo derivatives and their metal complexes

5-Chloro-3-hydroxy-4-(phenylediazenyl)pyridine-2(1H)-one and its derivatives (HLn) were synthesized and characterized using different spectroscopic techniques. The geometrical structures of the ligands are carried out by HF method with 3-21G basis set. The proton–ligand dissociation constant of the ligands (HLn) and their metal–ligand stability constants with (Mn2+, Co2+, Ni2+ and Cd2+) have been determined potentiometrically. The potentiometric studies were carried out in 0.1M (KCl) and 10% (by volume) DMF–water mixture. The effect of temperature was studied at (298, 308 and 318K) and the corresponding thermodynamic parameters (ΔG, ΔH and ΔS) were derived and discussed. The dissociation process is non-spontaneous, endothermic and entropically unfavorable. The formation of the metal complexes has been found to be spontaneous, endothermic and entropically favorable.

Multiresponsive hydrogel coassembled from phenylalanine and azobenzene derivatives as 3D scaffolds for photoguiding cell adhesion and release.

A multiresponsive hydrogel system coassembled from phenylalanine derivative gelator (LPF2) and azobenzene (Azo) derivative (PPI) is constructed, which can respond to temperature, pH, host-guest interaction, and photoirradiation. A set of techniques including circular dichroism, Fourier transform infrared spectroscopy, (1)H NMR, and X-ray powder diffraction confirm that the hydrogel is formed through hydrogen bonds between amide moieties/pyridine and carbonyl groups, enduing the coassembled hydrogel with multiresponsive properties that make it possible to control cell encapsulation and release in three-dimensional environments under multistimulus, for example, UV irradiation. This study brings a novel approach to develop multistimuli-responsive hydrogels by coassembly of various responsive components for biomedical interest, for example, the controlled delivery of various therapeutic biological agents.

Photorefractive effect in an azobenzene chromophore side groups polymer

We have analyzed the photorefractive (PR) effect of a polymer composite was reported which combines a novel bi-functional poly(N-vinyl)-3-[p-nitrophenylazo]carbazolyl (PVNPAK) and 2,4,7-trinitro-9-fluorenone (TNF). PVNPAK was synthesized by a post-azo-coupling reaction, with an azo derivative as the electrooptic chromophore and carbazolyl as photoconductive moiety. The asymmetric two-beam coupling gain of 13.9 cm−1 and diffraction efficiency of 1.2% for poled polymer film fabricated using a corona poling are obtained at the wavelength of 647.1 nm, confirming photorefractivity. We interpreted this result as the orientational enhancement, in which the spatial charge field may enhance the modulated orientation of the azobenzen chromophore. It is unexpected that the photorefractive gain of 9.5 cm−1 for the unpoled polymer film also was observed without external field in two-beam coupling (TBC) experiment. This phenomenon is attributed to a light-induced orientational grating when the azobenzene groups are illuminated by polarized light.

Photoisomerization of Azophenylcarbazole Self-assembled Monolayer on GaN Studied by Kelvin Probe

Self assembled monolayers of two fabricated azophenylcarbazoles on GaN epitaxial layers were obtained. Isomerization of the azo derivatives has been accomplished by illumination with wavelength of 440 nm, which coincides with their absorption maxima. The process has been observed in situ by Kelvin probe. A few parameters for azophenylcarbazoles (V-650 and V-728) of trans-cis switching such as difference between work function in trans and cis state and time constant for trans-cis and cis-trans isomerizations have been determined.

Catalytic Reactions on the Surface of Ag Nanoparticles: A Photochemical Effect and/or Molecule Property?

Using time-dependent surface-enhanced Raman scattering (TDSERS), we demonstrate the surface-catalyzed oxidation of 3-hydroxy anthranilic acid (HAA) to its azo derivatives. No external source either in the form of laser excitation or heat was required for the surface-catalyzed reaction, which clearly established that thermal energy alone was sufficient. But the possibility of enhanced reaction rate due to the surface plasmon resonance could not be ignored. To mimic in vivo conditions that prevail in healthy and unhealthy cells, SERS measurements were recorded under different environmental conditions. It is shown that the surface-catalyzed azo formation and its isomerization were strongly dependent on the external conditions, namely, temperature, pH, and environment. A plausible mechanism based on electron transfer to the adsorbed O2 is proposed for the trans–cis isomerization. This study can lead toward a new strategy of surface-catalyzed reactions not only for the synthesis of azo dyes but also to disting...

Phototunable Liquid‐Crystalline Phases Made of Nanoparticles

AbstractThe properties of liquid‐crystalline (LC) hybrid systems made of inorganic nanoparticles grafted with photosensitive azo compounds are presented. For materials with a large density of azo ligands at the surface, the LC structure can be reversibly melted by UV light, and the return to the LC state does not require the absorption of visible light. For systems with a lower density of azo ligands, UV light causes shortening of the distance between metal sublayers in the lamellar phase. Interestingly, the azo derivatives attached to the nanoparticle surface show very different kinetics of cis/trans conformational change as compared to the free molecules. The cis form of free ligands in solution is stable for days, whereas the isomerization of molecules attached to the nanoparticle surface to the trans form takes only a few minutes. Apparently, owing to the crowded environment, azo ligands immobilized at a metal surface behave as they would in the condensed state.

Phototunable liquid-crystalline phases made of nanoparticles.

The properties of liquid-crystalline (LC) hybrid systems made of inorganic nanoparticles grafted with photosensitive azo compounds are presented. For materials with a large density of azo ligands at the surface, the LC structure can be reversibly melted by UV light, and the return to the LC state does not require the absorption of visible light. For systems with a lower density of azo ligands, UV light causes shortening of the distance between metal sublayers in the lamellar phase. Interestingly, the azo derivatives attached to the nanoparticle surface show very different kinetics of cis/trans conformational change as compared to the free molecules. The cis form of free ligands in solution is stable for days, whereas the isomerization of molecules attached to the nanoparticle surface to the trans form takes only a few minutes. Apparently, owing to the crowded environment, azo ligands immobilized at a metal surface behave as they would in the condensed state.

Optical and thermal properties of azo derivatives of salicylic acid thin films

N-acryloyl-4-aminosalicylic acid (4-AMSA), monomer (HL) and 5-(4′-alkyl phenylazo)-N-acryloyl-4-aminosalicylic acid (HLn) are synthesized and characterized with various physico-chemical techniques. Thin films of 5-(4′-alkyl phenylazo)-N-acryloyl-4-aminosalicylic acid (HLn) are prepared by spin coating technique. The X-ray diffraction (XRD) patterns of 4-aminosalicylic acid (4-ASA) and its derivatives are investigated in powder and thin film forms. Thermal properties of the compounds are investigated by thermogravemetric analysis (TGA). The optical energy gap and the type of optical transition are investigated in the wavelength range (200–2500nm) for 4-ASA, HL and HLn. The values of fundamental energy gap (Eg) are in the range 3.60–3.69eV for all compounds and the type of optical transition is found to be indirect allowed. The onset energy gap Eg∗ appeared only for azodye compounds is found to be in the range 0.95–1.55eV depending on the substituent function groups. The refractive index, n, shows a normal dispersion in the wavelength range 650–2500nm, while shows anomalous dispersion in the wavelength rang 200–650nm. The dispersion parameters ε∞, εL, Ed, Eo and N/m∗ are calculated. The photoluminescence phenomena (PL) appear for thin films of 4-ASA and its derivatives show three main emission transitions.

Azo compounds with different sized fluorophores and characterization of their photophysical properties based on trans to cis conformational change

We synthesized fluorophores of different sizes attached to azo derivatives, such as thiophene-, naphthalene-, anthracene-, and pyrene-based azo compounds, and studied their photophysical properties. The compounds exhibited strong color and intensity changes in absorption and emission during the structural change from trans to cis, which also resulted in a large Stokes shift and a difference in quantum yield. Depending on their size, the compounds had different rates of transformation from the trans to cis structure: less conjugated (smaller) fluorophore azo compounds showed higher transition rates than more conjugated (larger) ones.

Self-assembled cardanol azo derivatives as antifungal agent with chitin-binding ability

Cardanol is a non-isoprenoic phenolic lipid-mixture of distilled cashew nut shell liquid obtained from Anacardium occidentale. Herein, cardanol is purified from cashew nut shell liquid (CNSL) and synthesized to new compounds with different azo amphiphiles. These synthesized compounds are allowed to self-assembled in hydrophobic environment and checked antifungal activity against Candida albicans. Self-assembled structure of CABA showed higher antifungal activity (16μg/mL) and chitin-binding ability in comparison to CAP and CANB. Furthermore, the self-assembled azo amphiphiles are immobilized with silver ions to prepare hydrogel which showed eight folds enhanced antifungal activity. Toxicity is reduced by several folds of self-assembled or hydrogel structure in comparison to pure compounds. Thus, the self-assembled structure of amphiphiles and their hydrogels have been found to be new macromolecules of interest with potential use as antifungal drugs.

Synthesis and Pharmacological Studies of Novel 3-Substituted Indole Derivatives as Potential Anti-Inflammatory and Analgesic Agents

Facile synthesis of some novel anti-inflammatory and analgesic agents was established by initially treating 3- acetyl indole (1) with the various aromatic aldehydes (2) which afforded the corresponding 3-chalconylindoles 3a-e. These products 3a-e upon treatment with hydrazine hydrate gave the resultant pyrazoline derivatives 4a-e. Also, the diazotized salt of aniline, when reacted with these pyrazoline indoles 4a-e yielded azo derivatives of pyrazoline indoles 5a-e. These newly synthesized compounds were screened for the mentioned activities and were found to possess good potential to act against inflammation and pain. Keywords: Analgesic & indomethacin, anti-inflammatory, azo derivatives, indole, pyrazoline.

The development and amino acid binding ability of nano-materials based on azo derivatives: Theory and experiment

Two nano-material-containing azo groups have been designed and developed, and the binding ability of nano-materials with various amino acids has been characterized by UV–vis and fluorescence titrations. Results indicated that two nano-materials showed the strongest binding ability for homocysteine among twenty normal kinds of amino acids (alanine, valine, leucine, isoleucine, methionine, aspartic acid, glutamic acid, arginine, glycine, serine, threonine, asparagine, phenylalanine, histidine, tryptophan, proline, lysine, glutamine, tyrosine and homocysteine). The reason for the high sensitivity for homocysteine was that two nano-materials containing an aldehyde group reacted with SH in homocysteine and afforded very stable thiazolidine derivatives. Theoretical investigation further illustrated the possible binding mode in host–guest interaction and the roles of molecular frontier orbitals in molecular interplay. Thus, the two nano-materials can be used as optical sensors for the detection of homocysteine.

Design and Synthesis of azo Derivatives of 5-Fluorouacil for Targeting Colon Cancer

5-Fluorouracil (5-FU) is a drug that belong to the antimetabolite class of antineoplastic agents, with a broad spectrum of activity against solid tumors, the use of oral 5-FU was abandoned decades ago because of its irregular absorption and rapid degradation. A potential strategy to improve the selective properties of 5-FU is the chemical transformation into reversible derivatives (prodrugs) which are converted to the parent drug by virtue of enzymatic or chemical means. In the present study, three derivatives of 5-fluorouracil have been designed to be synthesized as an azo derivatives of 5-fluorouracil in order to selectively deliver 5-fluorouracil into the cancer cells of the colon. The synthesis of the target compounds were accomplished following multistep reaction procedures. The chemical reactions were followed up and purity of the products was checked by TLC. The structure of the final compounds and their intermediates were characterized and identified by their melting points, infrared spectroscopy and elemental microanalysis. Compounds 2 and 3 were subjected to a stability study in phosphate buffer (pH 1.5 and 7.8) for different time intervals (0 – 240 min) at 37°C.

Enhancing the sensitivity of the LC-MS/MS detection of propofol in urine and blood by azo-coupling derivatization

Propofol is a low-polarity, volatile molecule that is difficult for an electrospray ion source (ESI) to ionize in either negative ion mode (NIM) or positive ion mode (PIM), which hampers its detection via liquid chromatography-mass spectrometry. The aim of the present study was to use a new derivatization agent to improve ionization efficiency and to develop an efficient liquid chromatography-multiple mass spectrometry (LC-MS/MS) determination of propofol in urine and blood, taking advantage of an electrophilic aromatic substitution. An azo-coupling reaction with a diazonium salt from aniline was performed to introduce a protonation site into the molecule. The diazonium salt was generated by aniline in water solution by HCl and sodium nitrite; derivatization was achieved by stirring a mixture of the diazonium salt and propofol in sodium hydroxide solution for 30min below 5°C. A liquid-liquid extraction with dichloromethane and ethyl acetate was performed to obtain the azo derivative (molecular composition: C18H22ON2; molecular weight: 282Da) in high yield. The compound provided very high ionization yields in both PIM and NIM ESI, and the protonated or deprotonated molecule gave intense signals. The transitions m/z 283 → 77, 241 and m/z 281 → 176, 161 were chosen for the PIM and NIM, respectively, in order to develop quantitative methods of detecting propofol in urine and blood via triple-quadrupole LC-MS/MS. These methods proved to be highly sensitive, with limits of quantification of 0.4pg/mL and 0.1ng/mL obtained in the NIM when analyzing 1mL of urine and 100μL of blood, respectively.