Aromatic Azo Research Articles

Skeletal Rearrangement of Azo Compounds Enables Low‐Potential, High‐capacity Organic Anodes for Rechargeable Alkaline Batteries

The widespread adoption of rechargeable alkaline batteries is plagued by the performance‐limiting metal anodes, which are prone to (electro)chemical corrosion and raise environmental or economic concerns. Organic redox‐active materials offer a potential solution, but they typically struggle with dissolution‐induced degradation and insufficiently negative reduction potentials. Herein, we introduce benzo[c]cinnoline and its derivatives (collectively referred to as BCCs), a class of aromatic azo compounds with fused‐ring structure, as promising organic anode materials. BCCs exhibit pronounced aromaticity and Brønsted basicity, conferring low reduction potentials and intrinsic insolubility in alkaline solutions. Paired with the industrially established nickel hydroxide cathode, these batteries deliver high capacity (297 mAh g−1anode), output voltage of 1.3 V, and extended cycle life (≈ 16000 cycles). Notably, they also operate efficiently at extremely low temperatures down to −85 °C with an 8 M KOH electrolyte. We further explore the feasibility for all‐organic alkaline batteries by paring BCCs with the dihydro form of 4,4'‐azopyridine, utilizing azo compounds for both anode and cathodes. This chemistry leverages the unique properties of small organic molecules to achieve batteries with high capacity (236 mAh g–1), fast charging (1200 C), and easy recyclability.

Skeletal Rearrangement of Azo Compounds Enables Low‐Potential, High‐capacity Organic Anodes for Rechargeable Alkaline Batteries

The widespread adoption of rechargeable alkaline batteries is plagued by the performance‐limiting metal anodes, which are prone to (electro)chemical corrosion and raise environmental or economic concerns. Organic redox‐active materials offer a potential solution, but they typically struggle with dissolution‐induced degradation and insufficiently negative reduction potentials. Herein, we introduce benzo[c]cinnoline and its derivatives (collectively referred to as BCCs), a class of aromatic azo compounds with fused‐ring structure, as promising organic anode materials. BCCs exhibit pronounced aromaticity and Brønsted basicity, conferring low reduction potentials and intrinsic insolubility in alkaline solutions. Paired with the industrially established nickel hydroxide cathode, these batteries deliver high capacity (297 mAh g−1anode), output voltage of 1.3 V, and extended cycle life (≈ 16000 cycles). Notably, they also operate efficiently at extremely low temperatures down to −85 °C with an 8 M KOH electrolyte. We further explore the feasibility for all‐organic alkaline batteries by paring BCCs with the dihydro form of 4,4'‐azopyridine, utilizing azo compounds for both anode and cathodes. This chemistry leverages the unique properties of small organic molecules to achieve batteries with high capacity (236 mAh g–1), fast charging (1200 C), and easy recyclability.

Single Step Synthesis of Non-symmetric Azoarenes Using Buchwald-Hartwig Amination.

Aromatic azo compounds stand as a highly sought-after class of substances owing to their extensive array of applications across various fields. Despite their significance, their synthesis often presents challenges, requiring either multistep reactions or being restricted to specific substrate types. In this study, we are showing the universality and mechanistic aspects of a one-step approach for synthesis of nonsymmetrical azoarenes via the Buchwald-Hartwig amination reaction of (pseudo)haloaromatics with arylhydrazines, conducted in the presence of atmospheric oxygen. This reaction protocol yields products in up to 85% yield and is compatible with a wide class of substituents, making it highly adaptable. Notably, the inclusion of BINAP as a ligand plays a pivotal role in achieving favorable outcomes. This study not only offers a versatile solution to a long-standing synthetic challenge but also provides experimental and computational insights into the mechanisms driving the reaction.

Cleavable azobenzene linkers for the design of stimuli-responsive materials.

The azo linkage (NN) is one of the very few functional groups in organic chemistry that exhibits sensitivity towards thermal, chemical, photochemical, and biological stimuli. Consequently, this property has given rise to a distinct class of responsive materials. For example, thermal sensitivity has led to generation of free radical initiators useful in curing and polymerization applications. Chemically-induced cleavage has aided the development of self-immolative polymers and reactive scaffolds for proteomics applications. Photo-isomerization capability has given rise to photo-responsive systems. Azobenzene cleavage in biologically reducing environments, such as that of the colon, and under tumor hypoxia conditions has led to diagnostic, therapeutic, and delivery materials. Such conditions have also allowed for control over formation (assembly) and disruption (disassembly) of micellar nanoparticles. The aim of this review article is to look beyond the prevalent photosensitivity aspect of the aromatic azo compounds and draw attention to the azo scission reaction as a trigger of the change in the structure and properties of organic materials. Thus, the main discussion begins with the mechanism of the reductive cleavage. Then, its application in the design of molecules that can be activated as drugs and fluorescent sensors, (nano)materials with potential to release active substances, and polymers with side-chain and main-chain self-immolative capacity is discussed. Finally, the status and future challenges in this field are discussed.

О СУБСТРАТНОЙ СПЕЦИФИЧНОСТИ И НЕКОТОРЫХ СВОЙСТВАХ ВНЕКЛЕТОЧНОЙ ОКСИДАЗЫ ИЗ БАЗИДИОМИЦЕТА NEONOTHOPANUS NAMBI

An extracellular enzyme with oxidase activity was isolated from the mycelium of the higher fungus Neonothopanus nambi by mild treatment of the biomass with β-glucosidase. A substrate specificity and some properties of the isolated extracellular oxidase were studied in the present work. Experiments revealed that the extracellular oxidase exhibited activity with most phenolic compounds chosen as model substrates. It is important to note that the enzyme exhibited a catalytic function in the reactions without the addition of exogenous hydrogen peroxide and other mediators. The highest catalytic activity of the enzyme was observed with veratryl alcohol and dihydric phenols, hydroquinone and guaiacol. The enzyme showed lower activity with aromatic azo compounds (ABTS, DAB, o-dianisidine). In reactions with dihydric phenol resorcinol and monophenol, the enzyme efficiency was extremely low. The kinetic parameters of the enzymatic reactions with actively oxidized substrates were determined. The addition of a divalent metal ion chelator (EDTA) did not affect the activity of the enzyme, while the addition of the SH reagent (DTT) increased the catalytic efficiency of the studied oxidase. The totality of the data obtained indicates that the extracellular oxidase of the N. nambi fungus catalyzes the oxidation of a wide range of aromatic compounds under slightly acidic and neutral conditions without the addition of additional mediators (in particular, hydrogen peroxide). This creates the prerequisites for studying the applicability of the enzyme in biomedical analytics.

Rb‐Promoted Au/CeO2 Nanocatalyst for Remarkably‐Enhanced Aniline Conversion to Azoxybenzene with Ultrahigh Selectivity

Aromatic azo compounds have proven to be a relevant class of building blocks in chemical synthesis. However, uncontrollable selectivity towards azo compounds and low reactant conversion in traditional synthetic methods seriously impede their applications. Herein, Rb‐doped Au/CeO2 nanocatalyst (Rb‐Au/CeO2) was prepared and utilized as a highly efficient supported metal catalyst for the selective oxidation of anilines to azocompounds using hydrogen peroxide as an oxidant, which reached ultrahigh selectivity (92%) towards azoxybenzene and complete aniline conversion (100%). The addition of Rb+ accelerates the electron transformation of Au to produce Au+, which is ready for catalysis. This research presents a promising Rb‐doped strategy for achieving complete aniline conversion and high selectivity towards azoxybenzene, opening up new possibilities for the application of aromatic azo compounds in chemical synthesis.

Voltammetric methods for determination of Allura Red AC in foods and beverages

Allura Red AC, is one of the azo group dyes, finds extensive application in foods and beverages such as fruit juices, baked goods, meat products, and confections. The substantial consumption of Allura Red AC has been associated with potential adverse effects on human health, like food intolerance, allergies, cancer, attention deficit hyperactivity disorder, multiple sclerosis, brain damage, cardiac diseases, nausea, and asthma, largely attributed to the reaction involving aromatic azo compounds. Therefore, controlling amount of the Allura Red AC in food and beverage is very crucial. The voltammetric analysis of Allura Red AC offers numerous benefits, including high sensitivity, selectivity and rapidity. Furthermore, these methods are characterized by their robustness, reproducibility and user-friendliness. This review is gathered to the comparison of voltammetric methods being in the literature for determination of Allura Red AC in foods and beverages.

Uji Kualitatif Kandungan Methanyl Yellow Pada Manisan Buah Yang Beredar di Mamuju

Methanyl yellow is a synthetic dye, in the form of a brownish yellow powder, soluble in water, and slightly soluble in acetone which contains aromatic azo chemical compounds which have N=N bonds which can accumulate in the human body and are carcinogenic if consumed in the long term can cause abnormalities in human organs that cause tumors in various tissues of the liver, bladder, digestive tract or skin tissue. This research is a qualitative descriptive study with esting in the laboratory using a test kit to determine whether or not there is methanyl yellow content in candied fruit circulating in Mamuju. The results of this research show that 7 samples of candied fruit circulating in Mamuju have been subjected to organoleptic and chemical tests, so they were declared not to contain methanyl yellow. However, it is still recommended that people be more selective in choosing the food they want to consume. This research can be continued using UV Vis spectrophotometry so that the research is more accurate by knowing the level of methanyl yellow content in certain samples

A Review on Traditional and Modern Methods for the Synthesis of Aromatic Azo Compounds

Abstract: Aromatic azo compounds are “derivatives of diazene/diimide”, wherein the two hydrogens are substituted by phenyl groups. Azo compounds are very important universal scaffolds that show multiple applications in many areas of science, mainly chemical industries, where they are used in the synthesis of organic dyes, pigments, food additives, indicators, etc. They also remarkably exhibit various potential applications in the fields of pharmaceuticals, electronics, optics, etc., because of their fascinating photophysical properties. Moreover, several azo compounds have been strongly utilized as chemosensors, diagnostic probes, radical initiators, nanotubes, and building blocks of various polymers as well as natural products. This interesting and immense importance of the azo compounds has attracted the attention of researchers to establish novel synthetic routes to synthesize these important scaffolds. In organic chemistry, azo compounds can be synthesized by various methods utilizing coupling reactions with the aid of a catalyst or sometimes in the absence of it. The main purpose of writing this review was to provide a summary of the synthesis of both symmetric and asymmetric azobenzenes via various traditional and recently developed oxidative aza-coupling reactions.

Recent Advances in the Synthesis of Aromatic Azo Compounds.

Aromatic azo compounds have -N=N- double bonds as well as a larger π electron conjugation system, which endows aromatic azo compounds with wide applications in the fields of functional materials. The properties of aromatic azo compounds are closely related to the substituents on their aromatic rings. However, traditional synthesis methods, such as the coupling of diazo salts, have a significant limitation with respect to the structural design of aromatic azo compounds. Therefore, many scientists have devoted their efforts to developing new synthetic methods. Moreover, recent advances in the synthesis of aromatic azo compounds have led to improvements in the design and preparation of light-response materials at the molecular level. This review summarizes the important synthetic progress of aromatic azo compounds in recent years, with an emphasis on the pioneering contribution of functional nanomaterials to the field.

Alkaline-thermal hydrolysate of waste activated sludge as a co-metabolic substrate enhances biodegradation of refractory dye reactive black 5

Aromatic azo dyes possess inherent resistance and are known to be carcinogenic, posing a significant threat to human and ecosystems. Enhancing the biodegradation of azo dyes usually requires the presence of co-metabolic substrates to optimize the process. In addressing the issue of excessive waste activated sludge (WAS) generation, this study explored the potential of utilizing alkaline-thermal hydrolysate of WAS as a co-metabolic substrate to boost the degradation of reactive black 5 (RB5) dyes. The acclimated microbial consortium, when supplemented with the WAS hydrolysate obtained at a hydrolysis temperature of 30 °C, achieved an impressive RB5 decolorization efficiency of 90.3% (pH = 7, 35 °C) with a corresponding COD removal efficiency of 45.0%. The addition of WAS hydrolysate as a co-substrate conferred the consortium with a remarkable tolerance to high dye concentration (1500 mg/L RB5) and salinity levels (4–5%), surpassing the performance of conventional co-metabolic sugars in RB5 degradation. 3D-EEM analysis revealed that protein-like substances rich in tyrosine and tryptophan, present in the WAS hydrolysate, played a crucial role in promoting RB5 biodegradation. Furthermore, the microbial consortium community exhibited an enrichment of dye-degrading species, including Acidovorax, Bordetella, Kerstersia, and Brevundimonas, which dominated the community. Notably, functional genes associated with dye degradation and intermediates were also enriched during the RB5 decolorization and biodegradation process. These findings present a practical strategy for the simultaneous treatment of dye-containing wastewater and recycling of WAS.

Sustainable Synthesis of N−N Bond Bearing Organic Frameworks by Advanced Heterogeneous Metal Catalysis

AbstractThe most significant task in synthetic organic chemistry is developing organic reactions from a green and sustainable perspective. In these ways, heterogeneous catalysts are essential in many organic reactions. Thus, this study focuses on the synthesis of N−N bond bearing organic frameworks, particularly aromatic azo compounds and indazoles, using a heterogeneous metal catalyst. Organic molecules containing nitrogen‐nitrogen bonds are greatly sought after in the synthesis of dyes, photochemical switches, food additives, and bioactive chemicals due to industry and human requirements. Finally, this review provides an overview of synthetic routes for the formation of N−N bonds by using various heterogeneous metal catalytic systems.

Characterization of self-dyed silk yarn with Rhodamine B dye for fashion applications

PurposeThe textile industry has consumed large quantities of water and discharged large volumes of wastewater in the dyeing process. The study aims to characterize self-dyed silk with Rhodamine B (RhB) for fashion applications to reduce textile hazards to the environment and increase the added value of silk.Design/methodology/approachBombyx mori was fed with RhB-colored mulberry leaves (1500 ppm). The effects of self-dyeing were investigated via color strength K/S, Fourier-transform infrared spectroscopy (FT-IR), scanning electron microscope, X-ray diffraction, tensile strength, color fastness to washing, rubbing, perspiration and light.FindingsSelf-dyed silk possesses effective coloration and impressive color fastness (4–5/5), higher crystalline index (CrI) (73.26 ± 2.28%), less thermal stability and tenacity, slight change in amino acid composition compared with the pristine and no existence of harmful aromatic azo amines and arylamine salts.Practical implicationsThe application of self-dyed silk with RhB dye has expanded new technology into fashion industry, contributing partly to economic growth and adding value to silk in the global supply chain. Besides, the self-dyeing will yield practical values in the reduction of dyeing discharge in textile industry.Originality/valueSelf-dyed silk was characterized for textile applications in comparison with pristine silk in terms of color strength and fastness as well as determined its polymeric properties relating to crystallinity, morphology, chemical composition, tensile properties and thermal stability which have not been investigated before.

Investigation of Congo Red Toxicity towards Different Living Organisms: A Review

The use of dyes is widespread across almost all industries. Consequently, these dyes are found in various sources of water and food that humans, animals, and plants consume directly or indirectly. Most of these dyes are comprised of complex aromatic structures that have proven harmful. Congo red dye, a complex aromatic azo dye based on benzidine, is most commonly used in these dyes; its metabolites (benzidine and analogs) can be toxic, but Congo red dye itself is not always harmful. The present review summarizes the toxicity of Congo red dye towards different living forms. Herein, the primary emphasis has been given to the mutagenic, teratogenic, and carcinogenic consequences of Congo red and its metabolites. The mechanisms of azo dyes’ carcinogenicity have also been discussed. This review will undoubtedly be beneficial for researchers to understand the harmful effects of Congo red in genotoxic, teratogenic, mutagenic, and carcinogenic factors.

SYNTHETIC PROTOCOLS AND SIGNIFICANCE OF HETEROCYCLIC FLUORESCENT - REINFORCING POLYMERS: A COMPREHENSIVE REVIEW

Fluorescent High-Performance polymers are well known as high performance engineering thermoplastics because of their good thermal stability, chemical resistance and excellent mechanical properties. Polymers having S-triazine ring become a subject of interest because of enhanced toughness and low moisture absorption and commercially available high performance engineering plastic materials. However, the thermal stability of triazine ring makes it an attractive monomer for use in high temperature polymers. Synthesis of polymers containing chromophoric groups which are responsible for fluorescent property have significant applications in fields such as biosensors, clean energy technologies, explosive sensing, pH/temperature sensor, biological imaging, life science, material science, ultrasensitive molecular diagnosis and novel light - emitting nano devices. The aromatic azo group is being more interest because of the existence of cis-trans isomerism and its effect on the photochromic properties of the polymers. Therefore, polymers having azo group have potential use in a variety of applications. Fluorescent polymers can be developed with different methods; generally, there are two methods for preparation of fluorescent polymers. One of them is polymerization of a monomer having a fluorescent chromophore such as fluorescent compounds as initiator, fluorescent compounds as chain transfer agents, chemical bonding between fluorescent groups and polymers. The second way, chemical alteration of commercially available polymers having reactive groups by using fluorescent dyes or organic molecules.

Self-Sustained Three-Dimensional Macroporous TiO2-Graphene Photocatalyst for Sunlight Decolorization of Methyl Orange.

The development of highly efficient sunlight-driven photocatalysts has triggered increased attention due to their merit in effluent treatment through a chemically green approach. To this end, we present herein the synthesis and characterization of the TiO2/3D-GF/Ni hybrid emphasizing the main structural and morphological properties and the photodegradation process of a highly resistant aromatic azo dye, methyl orange, under both UV light and simulated sunlight. Three-dimensional (3D) graphene was grown by the thermal CVD method on the nickel foam and subsequently coated with thin films of anatase employing the sol-gel method. Thereafter, it was gratifyingly demonstrated that the hybrid nanomaterial, TiO2/3D-GF-Ni, was able to bring about more than 90% decolorization of methyl orange dye after 30 min under simulated sunlight irradiance. Moreover, the efficiency of the methyl orange decolorization was 99.5% after three successive cycles. This high-performance photocatalyst which can effectively decolorize methyl orange will most likely make a great contribution to reducing environmental pollution by employing renewable solar energy.

Synthesis and characterization of novel molybdovanadophosphoric acid supported kaolin hybrid catalyst for Chromotrope 2R dye degradation in water

The present study provides a complete perspective of recyclable molybdovanadophosphoric acid immobilized on kaolin (MVPA/Kaolin), a hybrid material for catalytic degradation of the dye, Chromotrope 2R in water under mild reaction conditions. Novel MVPA/Kaolin was synthesized with an advanced impregnation method. The material was characterized with PXRD, FTIR, ICP-OES, SEM–EDX, TEM, TGA, surface area, porosity, and 31P NMR measurements. The material that can be classified as a Keggin type catalyst, could be used for hydrogen peroxide oxidation of aromatic azo (–N=N–) dyes with –OH and –SO3H functional groups. The degradation showed excellent conversion of 99.1% under optimum conditions of normal pressure and 60 °C temperature. Products like malonic acid and oxalic acid have been identified as the final products with GC–MS analysis. The present work has demonstrated the application of a simple and effective catalyst for degradation of azo dyes and the catalyst had the reusability capacity of up to six cycles without loss in performance.

Non-linear disulphide-centred S-shaped oligomers with inner and outer spacers connected by aromatic azo moieties

ABSTRACT The synthesis and characterisation of a series of non-linear S-shaped oligomers [bis-n-(2-(6-(4-{4-acetylphenylazo}phenoxy)hexyloxy)phenoxy)alkyl]disulphide are reported. The length of the two outer spacers for this series are retained at n 1 = 6 while the length of the inner spacer, n 2, is varied from four to nine methylene units. All oligomers exhibit monotropic nematic phase except compound with butyl spacer which is non-mesogenic. The odd-even effect can be verified at the I-N transition temperature wherein the oligomers with odd-numbered inner spacers display higher transition temperature in comparison to its even-membered analogous compounds. The molecules in this series exhibit prominent photoisomerisation behaviour that can be validated by the rate of conversion from trans to cis (1620 s) and vice versa (3120 min).

Palladium-mediated base-free and solvent-free synthesis of aromatic azo compounds from anilines catalyzed by copper acetate

Abstract Herein, we report a new one-step direct synthesis of aromatic azo compounds from anilines under mild conditions. With the catalysis of copper acetate mediated by palladium salt, rapid conversion of anilines to aromatic azo compounds can be observed under the conditions of base-free along with solvent-free. Furthermore, the cross-coupling nitridation reaction based on this strategy was also studied. This research provides not only a new way for the synthesis of symmetrical and asymmetrical aromatic azo compounds but also a strategy and platform for exploring catalytic applications of transition metal compounds.

Plasmon-driven oxidative coupling of aniline-derivative adsorbates: A comparative study of para-ethynylaniline and para-mercaptoaniline.

Plasmon-driven photocatalysis has emerged as a paradigm-shifting approach, based on which the energy of photons can be judiciously harnessed to trigger interfacial molecular transformations on metallic nanostructure surfaces in a regioselective manner with nanoscale precision. Over the past decade, the formation of aromatic azo compounds through plasmon-driven oxidative coupling of thiolated aniline-derivative adsorbates has become a testbed for developing detailed mechanistic understanding of plasmon-mediated photochemistry. Such photocatalytic bimolecular coupling reactions may occur not only between thiolated aniline-derivative adsorbates but also between their nonthiolated analogs. How the nonthiolated adsorbates behave differently from their thiolated counterparts during the plasmon-driven coupling reactions, however, remains largely unexplored. Here, we systematically compare an alkynylated aniline-derivative, para-ethynylaniline, to its thiolated counterpart, para-mercaptoaniline, in terms of their adsorption conformations, structural flexibility, photochemical reactivity, and transforming kinetics on Ag nanophotocatalyst surfaces. We employ surface-enhanced Raman scattering as an in situ spectroscopic tool to track the detailed structural evolution of the transforming molecular adsorbates in real time during the plasmon-driven coupling reactions. Rigorous analysis of the spectroscopic results, further aided by density functional theory calculations, lays an insightful knowledge foundation that enables us to elucidate how the alteration of the chemical nature of metal-adsorbate interactions profoundly influences the transforming behaviors of the molecular adsorbates during plasmon-driven photocatalytic reactions.