Azobenzene Research Articles

Bioremediation of Textile Dye Procion Red Yellow by Using Pseudomonas fluorescens

Dyes primarily present in effluents from textile industries are recalcitrant organic molecules with a complex aromatic structure, which are considered difficult to eliminate, degrade and detoxify biologically. In the current study, Pseudomonas fluorescens was used to degrade Procion Red Yellow. The bacterium P. fluorescens NCIM 2100 was procured from National Chemical Laboratory (NCL), Pune, India, that was well adapted to grow and survive in broth supplemented with dyes. The dye was exposed to bacterium followed by the identification of its degradation products by a combination of UV, 1H NMR and IR spectrophotometry. After exposure, the dye was firstly broken down into an intermediate compound lacking azo benzene group. This compound further changed into another intermediate compound that may contain either OH or NH group. This intermediate finally changed into 3, 5-diamino-1, 4, 6, 8-tetrahydroxy-2,7-naphthyldisulfonic acid sodium salt or 1, 3, 4, 5, 6-hexa-hydroxy-2, 7-naphthyldisulfonic acid sodium salt in broth. These breakdown or transformation products were innoxious in nature. Thus P. fluorescens can be used as a promising candidate for the bioremediation of the textile effluents containing Procion Red Yellow to offer promise for environmental decontamination and even greater development for green chemistry in the near future.

Design, Synthesis, Investigation, and Application of a Macromolecule Photoswitch.

Azobenzene (AZO) has attracted increasing interest due to its reversible structural change upon a light stimulus. However, poor fatigue durability and the photobleaching phenomenon restricts its further application. Herein, the AZO domain as a pendent group, was incorporated into copolymers, which was synthesized by radical copolymerization in the research. Structure-properties of synthesized copolymer can be adjusted by monomer ratios. Emphatically, responsive properties of copolymer in different solutions were investigated. In the DMSO solution, copolymer exhibited effective structural change, stable rapid responsive time (1 min) upon UV light at room temperature, stable relative acceptable recovery time (100 min) upon white light at room temperature, and good fatigue resistance property. In an aqueous solution, even more controllable responsive properties and fatigue resistance properties for copolymer were verified by results. More pervasively, the recovery process could be controlled by light density and temperature. In order to clarify reasons for the difference between the AZO molecule and the AZO domain of copolymer, energy barrier or interactions between single atoms or even structural units was calculated using the density functional theory (DFT). Furthermore, the status of copolymer was characterized by dynamic light scattering (DLS) and transmission electron microscope (TEM). Finally, copolymer was further functionalized with bioactive protein (concanavalin, ConA) to reduce the cytotoxicity of the AZO molecule.

Electron Propagator Theory Approach to the Electron Binding Energies of a Prototypical Photo-Switch Molecular System: Azobenzene.

The electron binding energies for the trans and cis conformers of azobenzene (AB), a prototypical photoswitch, were investigated by electron propagator theory (EPT). The EPT results are compared with data from photoelectron and electron transmission spectroscopies and complemented by the calculation of the differences between vertical and adiabatic ionization energies and electron affinities of the AB conformers. These differences are discussed in terms of the geometry changes associated with the processes of ionization and electron attachment. The results pointed out a major difference between these processes when we compare trans-AB and cis-AB. For trans-AB, electron attachment leads to a small geometry change, whereas for cis-AB, it is the ionized structure that keeps some similarity with the neutral species. We emphasize the interest of the present results for a better understanding of recent experiments on the dark cis-trans isomerization in different environments, specifically for azobenzenes in interaction with gold nanoparticles, where the proposed cis-trans isomerization mechanism relies on electron transfer induced isomerization.

Photo-responsive dye-doped liquid crystals for smart windows.

An electric field drives most dye-doped liquid crystal devices. Here, we demonstrate a new photo-responsive dye-doped self-organized cholesteric liquid crystal device. Upon UV or blue light exposure, the helical twisting power of the chiral azobenzene changes because of the trans-cis isomerization. As a result, the initially vertically aligned liquid crystal directors and dye molecules will change from transparent state to dark state. Such a polarizer-free photo-activated dimmer can be used for wide range of applications, such as diffractive photonic devices, portable information system, vehicular head-up displays, and as a smart window for energy-saving buildings.

Assignment of the π → π* and n → π* Transitions to the Spectral Bands of Azobenzene and Dimethylaminoazobenzene

A critical analysis of the UV–Vis absorption spectra of azobenzene (AB) and dimethylaminoazobenzene (DAB) used as an optical probe was performed based on the key empirical regularities of the n → π* transitions of nitrogen- and carbonyl-containing compounds. The spectrum of DAB has an n → π* band located in the same range ν = 28 000–33 000 cm–1 (λ = 350–300 nm) as the n → π* band of protonated azobenzene AB+H, but differs in the presence of a vibronic structure. It was also shown that the low-frequency n → π* band belonging to AB lies in the range where the π → π* band of AB is located with a maximum at a wavelength λmax ≈ 320–340 nm (νmax = 30 300–29 400 cm–1), in contrast to the conventional assignment of this band to the Vis band at 440 nm. This n → π * band is not found in the spectra of AB solutions in polar media, but appears in the nonpolar medium due to the presence of a vibronic structure.

Rational construction of self-assembly azobenzene derivative monolayers with photoswitchable surface properties

Photo-responsive azobenzene (ABZ) derivatives with different end groups (R) as photoswitchable molecules were employed to construct self-assembled monolayers (SAMs) on silicon substrate by using 3-glycidoxypropyltrimethoxysilane (GPTS) as the bridging molecules. The assembly process was optimized by changing various parameters, including the type and concentration of ABZ derivatives, reaction time, etc. The obtained SAMs were fully characterized and evaluated using UV spectroscopy, atomic force microscope (AFM), elllipsometer, static contact angle and X-ray photoelectron spectroscopy (XPS). It is found that the end group property of azobenzene derivatives is critical to the obtained SAMs’ photoresponsive properties. Compared with hydrophobic compounds (4-(4′-aminophenylazo) benzoic acid, ABZ-CF3), the hydrophilic compounds (4-(4′-aminophenylazo) benzoic acid, ABZ-COOH) show excellent reversible photoswitching performance with a large contact angle change of 35° under optimized process, and the SAMs are removable by thermal treatment at 240°C in air for only 5min.

Development of New Photoswitchable Azobenzene Based γ-Aminobutyric Acid (GABA) Uptake Inhibitors with Distinctly Enhanced Potency upon Photoactivation.

A series of nipecotic acid derivatives with new azo benzene based photoswitchable N-substituents was synthesized and characterized in their ( E)- and ( Z)-form for their functional inhibitory activity at γ-aminobutyric acid transporters subtype 1 (GAT1), the most common γ-aminobutyric acid (GABA) transporter subtype in the central nervous system (CNS). This led to the identification of the first photoswitchable ligands exhibiting a moderate uptake inhibition of GABA in their ( E)- but distinctive higher inhibitory potency in their ( Z)-form resulting from photoirradiation. For the most efficient photoactivatable nipecotic acid derivative displaying an N-but-3-yn-1-yl linker with a terminal diphenyldiazene unit, an inhibitory potency of 4.65 ± 0.05 (pIC50) was found for its ( E)-form. which increased by almost two log units up to 6.38 ± 0.04 when irradiated. The effect of this photoswitchable mGAT1 inhibitor has also been evaluated and confirmed in patch-clamp recordings in acute hippocampal slices from mice.

Controlling Self-Assembly of Switchable Azobenzene Derivatives on Highly Oriented Pyrolytic Graphite at Ambient Conditions

Ultrathin films prepared at the solid/air interface of azobenzene (AB), 4-(phenylazo) benzoic acid (PABA), 3,4′-azodibenzoic acid (meta-ADB), and 4,4′-azodibenzoic acid (para-ADB) have been studied on highly oriented pyrolytic graphite using scanning tunneling microscopy (STM) and atomic force microscopy (AFM). While AB molecules form compact herringbone pattern stabilized via van der Waals interaction, AB derivatives with carboxyl groups show patterns formed through strong dimeric hydrogen bonds. Depending on the numbers and the positions of carboxyl group(s), we show that the assembly can be controlled at a global level. Due to the right balance of weak and strong intermolecular interactions, PABA molecules show a unique growth at global levels. meta/para-ADB molecules form chains stabilized through carboxyl groups; however, possible adsorption-induced isomers influence the growth behavior and restrict it to limited size on the surface.

Light-Enhanced Hypoxia-Response of Conjugated Polymer Nanocarrier for Successive Synergistic Photodynamic and Chemo-Therapy.

The tumorhypoxic environment as well as photodynamic therapy (PDT)-induced hypoxia could severely limit the therapeutic efficacy of traditional PDT. Fortunately, the smart integration of hypoxia-responsive drug delivery system with PDT might be a promising strategy to enhance the PDT efficiency that is hindered bythe hypoxic environment. Herein, a novel azobenzene (AZO) containing conjugated polymers (CPs)-based nanocarriers (CPs-CPT-Ce6 NPs) was constructed forthe combination of PDT with chemotherapy, as well as to enhance the hypoxia-responsive drug release by light. The conjugated polymer chains, used as a matrix to prepare the CPs-CPT-Ce6 NPs, were beneficial for loading hydrophobic photosensitizers and chemotherapy drugs, to improve their cellular uptake. Moreover, the AZO group (-N═N-) in CPs, which can be reduced and cleaved by azoreductase (a typical biomarker of hypoxia) under the hypoxic environment of tumor cells, acts as the hypoxia-responsive linker component. Upon laser irradiation, the CPs-CPT-Ce6 NPs could produce ROS for PDT and then facilitate the enhancement of tumor hypoxic condition, which could further promote the dissociation of CPs via reductive cleavage of AZO bridges to subsequently release cargos (chemotherapeutic drug, CPT) and then significantly enhance the killing effects to tumor cells that were resistant to PDT. Both in vitro and in vivo studies confirmed the improvement of synergistic therapeutic effects of our CPs-CPT-Ce6 NPs. This cascade responsive approach provides an excellent complementary mode for PDT and could open new insights for constructing programmable and controllable responsive systems in biomedical applications.

Solid‐State Electrolyte Anchored with a Carboxylated Azo Compound for All‐Solid‐State Lithium Batteries

AbstractOrganic electrode materials are promising for green and sustainable lithium‐ion batteries. However, the high solubility of organic materials in the liquid electrolyte results in the shuttle reaction and fast capacity decay. Herein, azo compounds are firstly applied in all‐solid‐state lithium batteries (ASSLB) to suppress the dissolution challenge. Due to the high compatibility of azobenzene (AB) based compounds to Li3PS4 (LPS) solid electrolyte, the LPS solid electrolyte is used to prevent the dissolution and shuttle reaction of AB. To maintain the low interface resistance during the large volume change upon cycling, a carboxylate group is added into AB to provide 4‐(phenylazo) benzoic acid lithium salt (PBALS), which could bond with LPS solid electrolyte via the ionic bonding between oxygen in PBALS and lithium ion in LPS. The ionic bonding between the active material and solid electrolyte stabilizes the contact interface and enables the stable cycle life of PBALS in ASSLB.

Solid-State Electrolyte Anchored with a Carboxylated Azo Compound for All-Solid-State Lithium Batteries.

Organic electrode materials are promising for green and sustainable lithium-ion batteries. However, the high solubility of organic materials in the liquid electrolyte results in the shuttle reaction and fast capacity decay. Herein, azo compounds are firstly applied in all-solid-state lithium batteries (ASSLB) to suppress the dissolution challenge. Due to the high compatibility of azobenzene (AB) based compounds to Li3 PS4 (LPS) solid electrolyte, the LPS solid electrolyte is used to prevent the dissolution and shuttle reaction of AB. To maintain the low interface resistance during the large volume change upon cycling, a carboxylate group is added into AB to provide 4-(phenylazo) benzoic acid lithium salt (PBALS), which could bond with LPS solid electrolyte via the ionic bonding between oxygen in PBALS and lithium ion in LPS. The ionic bonding between the active material and solid electrolyte stabilizes the contact interface and enables the stable cycle life of PBALS in ASSLB.

Fabrication of light-responsively controlled-release herbicide using a nanocomposite

In this work, a light-responsively controlled-release herbicide particle (LCHP) with core–shell structure was developed using a nanocomposite composed of biochar, attapulgite (ATP), glyphosate (Gly), azobenzene (AZO), and amino silicon oil (ASO). Therein, nanonetwork-structured ATP distributed evenly in the pores of biochar to form porous biochar-ATP compound which acts as a carrier to efficiently load plenty of Gly and AZO molecules, obtaining porous biochar-ATP-Gly-AZO granule. Subsequently, the resulting biochar-ATP-Gly-AZO granule was incompletely coated by ASO, forming LCHP with abundant micro pores in the ASO coating. Under UV–Vis light radiation, trans-cis and cis-trans isomer transformation of AZO molecules will occur, acting as light-motivated “stirrers” to promote the release of Gly from LCHP through those nano pores. Thus LCHP displayed an excellent light-responsively controlled release performance, which could be also demonstrated by pot experiments. Importantly, LCHP possessed a good adhesion performance on surface of weeds leaves, which was greatly favorable for improving the control efficacy on weeds. Besides, coexisting ions (CO32−, SO42−, and Cl−) and pH posed little impact on LCHP release in water, proving the high stability of this technology. Therefore, this work provides a promising approach to control the release and enhance utilization efficiency of herbicide, which has a potential application prospect.

Photo‐Induced Programmable Morphological Transition of the Hybrid Coassembles

AbstractMorphology and nanoparticle's distribution are both key factors to the hybrid coassemblies. A fancy method to dynamically control the morphology of hybrid core–shell microspheres (CSMs) with UV light is introduced. The CSMs used here are fabricated with azobenzene (AZO) ended hyperbranched poly(ether amine) in the shell and AZO containing polyhedral oligomer silsesquioxane in the core through coassembly. Upon UV irradiation, the dynamic morphology transition from core–shell microsphere to vesicle is realized by synergistic effects and photothermal effects of AZO, resulting in the size of coassemblies increasing from 1.2 to 2.5 µm. And versatile multivesicular structures can be fixed and captured as mid‐states in taking advantage of the easy control of ON/OFF of UV light. This programmable morphology transition provides a new insight for fabricating light‐controlled hybrid materials with ideal structure in soft nanotechnology which matches with requirements in in situ tunable functions, controlled release, and so on.

Ethylenediamine promoted the hydrogenative coupling of nitroarenes over Ni/C catalyst

Azobenzene and its derivatives are key raw materials and it is an environmentally friendly method for the preparation of azobenzene by hydrogenative coupling of nitrobenzene. The development of nickel based catalyst for organic transformations is of importance because of its relatively low cost and toxicity. In this work, we found that ethylenediamine can enrich the electron state of Ni and make the azobenzene easily desorb from the surface of the catalyst, which inhibits the hydrogenation of azobenzene to aniline. The selectivity of azobenzene is greatly improved. When the ratio of Ni and ethylenediamine is 1:10, the yield of the azobenzene can reach 95.5%.

Computational Treatments of Hybrid Dye Materials of Azobenzene and Chiral Schiff Base Metal Complexes

Molecular orientation of dyes must be one of the important factors for designing dye-sensitized solar cells (DSSC). As model systems, we have prepared new hybrid materials composed of azobenzene (AZ) and chiral Schiff base Cu(II) complexes (pn(S)Cu and pn(R)Cu) in polymethyl methacrylate (PMMA) cast films. In addition to experimental results, in order to understand their behavior due to anisotropic alignment of them by linearly polarized UV light irradiation, the so-called Weigert effect, we treated theoretically and discussed based on computational chemistry and mathematical treatments (MD simulation and Bayesian statistics).

Azobenzene-bridged diradical janus nucleobases with photo-converted magnetic properties between antiferromagnetic and ferromagnetic couplings.

We computationally design a series of azobenzene (AB)-bridged double radicalized nucleobases, a novel kind of diradical Janus-type nucleobases, and explore their spin coupling characteristics. Calculations prove that such diradical Janus-bases not only normally match with their complementary bases, but also exhibit well-defined diradical character with photo-convertible intramolecular magnetic couplings (antiferromagnetic vs. ferromagnetic). Combination of four radical nucleobases (rG, rA, rC, rT) and photoswitch AB can yield 10 diradical Janus-bases with different magnetic characteristics in which AB functions a bridge to mediate the spin coupling between two radical bases. The trans-form supports mild antiferromagnetic couplings with the spin coupling constants (J) ranging from -153.6 cm-1 to -50.91 cm-1 while the cis-form has weak magnetic couplings with ferromagnetic (0.22-8.50 cm-1 ) for most of them or antiferromagnetic (-0.77, -1.73, -3.30 cm-1 ) properties for only three. Further structural examination and frontier molecular orbital analyses indicate that the extended π conjugation for better spin polarization provides an effective through-π-bond pathway to mediate the spin coupling in the trans conformation while nonplanarity of the cis conformation weakens the through-bond coupling and causes a competitive through-space pathway and as an overall result inhibits the spin coupling between two spin moieties. Meanwhile, we also find that the J values of the cis conformation vary with their angle between the radical base and its linked phenylene. Furthermore, the magnetic properties of the diradical Janus-bases can be significantly increased by interacting with metal ions. They also maintain a good UV absorption characteristics and there is a clear redshift compared with AB. This work provides a promising strategy for the rational design of photo-convertible Janus-base magnets as the magnetism-tunable DNA building blocks. © 2018 Wiley Periodicals, Inc.

Palladium-Catalyzed Direct o-Nitrification of Azobenzenes with Co(NO3)2·6H2O via C-H Activation

Palladium-Catalyzed Direct <i>o</i>-Nitrification of Azobenzenes with Co(NO₃)₂·6H₂O via C<b>-</b>H Activation

Computational design of a molecular triple photoswitch for wavelength-selective control.

A small single molecule with multiple photoswitchable subunits, selectively and independently controllable by light of different wavelengths, is highly attractive for applications in multi-responsive materials and biological sciences. Herein, triple photoswitches are presented consisting of three independent azobenzene (AB) subunits that share a common central phenyl ring: the meta-trisazobenzenes (MTA). It is the unique meta-connectivity pattern leading to decoupling of all azo-subunits although they do overlap spatially. Based on this pattern, we design a triple MTA photoswitch, as proof-of-principle, with three different, electronically independent AB branches on the computer, which can be individually photo-excited to trigger ultra-fast E → Z isomerization at the selected AB branch.

Cis Versus trans-Azobenzene: Precise Determination of NMR Parameters and Analysis of Long-Lived States of 15N Spin Pairs

We provide a detailed evaluation of nuclear magnetic resonance (NMR) parameters of the cis- and trans-isomers of azobenzene (AB). For determining the NMR parameters, such as proton–proton and proton–nitrogen J-couplings and chemical shifts, we compared NMR spectra of three different isotopomers of AB: the doubly 15N labeled azobenzene, 15N,15N′-AB, and two partially deuterated AB isotopomers with a single 15N atom. For the total lineshape analysis of NMR spectra, we used the recently developed ANATOLIA software package. The determined NMR parameters allowed us to optimize experiments for investigating singlet long-lived spin states (LLSs) of 15N spin pairs and to measure LLS lifetimes in cis-AB and trans-AB. Magnetization-to-singlet-to-magnetization conversion has been performed using the SLIC and APSOC techniques, providing a degree of conversion up to 17 and 24% of the initial magnetization, respectively. Our approach is useful for optimizing the performance of experiments with singlet LLSs; such LLSs can be exploited for preserving spin hyperpolarization, for probing slow molecular dynamics, slow chemical processes and also slow transport processes.

Photoswitchable Nanomaterials Based on Hierarchically Organized Siloxane Oligomers

AbstractMaterials with highly ordered molecular arrangements have the capacity to display unique properties derived from their nanoscale structure. Here, the synthesis and characterization of azobenzene (AZO)‐functionalized siloxane oligomers of discrete length that form photoswitchable supramolecular materials are described. Specifically, synergy between phase segregation and azobenzene crystallization leads to the self‐assembly of an exfoliated 2D crystal that becomes isotropic upon photoisomerization with UV light. Consequently, the material undergoes a rapid athermal solid‐to‐liquid transition which can be reversed using blue light due to the unexpectedly fast 2D crystallization that is facilitated by phase segregation. In contrast, enabling telechelic supramolecular polymerization through hydrogen bonding inhibits azobenzene crystallization, and nanostructured pastes with well‐ordered morphologies are obtained based on phase segregation alone, thus demonstrating block copolymer‐like behavior. Therefore, by tailoring the balance of self‐assembly forces in the azobenzene‐functionalized siloxane oligomers, fast and reversible phase‐changing materials can be engineered with various mechanical properties for applications in photolithography or switchable adhesion to lubricant properties.