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Photoresponsive materials (PRMs) have long been a hot topic and photo-modulated smart surface is very appealing. Particularly, liquid crystalline PRMs are able to amplify and stabilize photoinduced orientation thanks to their self-assembling and ordering characteristics. Herein, the first pillararene-based azobenzene liquid crystalline PRM with well-defined structure is presented, which can avoid the usually ill-defined composition drawback of polymer PRMs and prevent the severe H-aggregation from suppressing or even completely blocking photoresponse in simple azobenzene derivatives. The pillar[5]arene-based macrocyclic azobenzenes with variant length spacers show wide temperature range smectic liquid crystalline mesophases and excellent film-formation property. The tubular pillar[5]arene macrocyclic framework provides sufficient free volume for azobenzene moieties to achieve reversible photoisomerization and photoalignment; thus, their thin films demonstrate excellent light-triggered modulation of surface free energy, wettability, and even photoalignment-mediated orientation of an upper layer discotic liquid crystal columnar mesophase. Such pillararene-based azobenzene liquid crystals represent novel and promising PRMs with extensive fascinating applications. [ABSTRACT FROM AUTHOR]

Bilayer photomechanical films are fabricated by depositing one layer of molecular azobenzene chromophores onto flexible low-density polyethylene substrates. The photoinduced bending and unbending behavior of five azobenzene derivatives including azobenzene, 4-hydroxy-azobenzene, 4-((4-hydroxyphenyl)diazenyl)bezoitrile, 4-((4-methoxyph-enyl)diazenyl)phenol, and 4-(phenyldiazenyl)phenol is systematically studied by considering the incident light intensity and the thickness of the coated chromophore layers. Precise control of photoinduced curling of the bilayer film is successfully achieved upon irradiation with two beams of UV light, and the curled films can be recovered by thermal relaxation in the dark. The easily fabricated bilayer films show fast photomechanical response, strong photoinduced stress, and stability similar to crosslinked polymeric films. [ABSTRACT FROM AUTHOR]

Photoswitches are traditional pharmacologic agonists, antagonists, or channel blockers that are covalently modified with an azobenzene derivative. Azobenzene undergoes wavelength-dependent isomerization between cis and trans conformation. For some photoswitches, only one of these configurations is biologically active, resulting in light-dependent activation or inhibition of function. Photoswitches that feature a quaternary ammonium coupled to the azobenzene moiety cause light-dependent neuronal depolarization due to blockage of voltage-gated potassium channels. Two photoswitch strategies have been pursued. In the one-component strategy, the photoswitch is applied to native receptors; in the two-component strategy, the photoswitch is combined with virally-mediated expression of a genetically modified receptor, to which the photoswitch may covalently bind. The former approach is simpler but the latter allows precise anatomic targeting of photoswitch activity. Acrylamide-azobenzene-quaternary ammonium (AAQ) is the prototypical first-generation one-component photoswitch. When applied to retinas with outer retinal degeneration, ganglion cell firing occurs in response to blue light, and is abrogated by green light. In vivo , AAQ restored pupillary light responses and behavioral light responses in blind animals. DENAQ is a prototypical second generation one-component photoswitch. It features spontaneous thermal relaxation so cell firing ceases in dark, and features a red-shifted activation spectrum. Interestingly, DENAQ only photoswitches in retinas with outer retinal degeneration. MAG is a photoswitched glutamate analog which covalently binds to a modified ionotropic glutamate receptor, LiGluR. When applied together, MAG and LiGluR also rescue physiologic and behavioral light responses in blind mice. Together, photoswitch compounds offer a potentially useful approach to restoration of vision in outer retinal degeneration. [ABSTRACT FROM AUTHOR]

Recently we found while we were synthesising a cationic surfactant that a synthetic intermediate, 4,4′-bis{1-[2-( N, N-dimethylamino)]ethoxy}azobenzene, produced gold-coloured crystals [Matsumoto et al., J. Oleo Sci., 59, (2010) 151]. Here we describe how an azobenzene derivative, bis[4-(ethoxycarbonylmethoxy)phenyl]diazene, also forms gold-coloured crystals after recrystallisation from a mixture of acetone and water. The profile of the specular reflectance as a function of wavelength for the crystals is very similar to that for metallic gold plate, indicating that the crystals have a golden colour. The maximum specular reflectance of the crystals is 16%. Atomic force microscopy observation shows that the crystals have flat surfaces. X-ray diffraction measurements demonstrate the presence of a periodic structure in the crystals, which indicates that monolayers (lamellar structure) consisting of azobenzene molecules with a thickness of 1.42 nm are stacked in the crystals. The gold-coloured crystals are tolerant of ultraviolet light irradiation. The gold-coloured crystals may be useful as a substitute for conventional metallic pigments in specific coating applications. [ABSTRACT FROM AUTHOR]

Linear supramolecular polymer with photo-responsive morphology was constructed by host-guest molecular recognition between bis- p -sulfonatocalix[4]arenes and monomer containing axially 1,1′-binaphthyl and photoresponsive azobenzene moieties in water. The successful supramolecular polymerization by non-covalent host-guest molecular recognition was confirmed. Scanning electron microscopy, cryogenic transmission electron microscopy and atomic force microscopy measurements were used to investigate its light driven behavior and line morphology change from straight to bent. Its noteworthy light driven morphology change from straight to bent make it possible to envision its' usage as molecular machine based display material in the same way as bent-core liquid crystal material used in technology. [ABSTRACT FROM AUTHOR]

We observed unique thermal cis – trans isomerization properties of water-soluble azobenzene derivatives in which a phosphate group was substituted at ortho position of an azobenzene via an amide linkage. Here, we report the effect of the structure of the phosphate groups (the length and the position), pH, and metal ions on thermal cis – trans isomerization. We revealed that the water-soluble azobenzene derivatives, in which di- or tri-phosphate group was substituted at ortho position of the azobenzene via the amide linkage, showed the fast thermal isomerization in low pH condition. In addition, we showed that the effects of the metal ions on the thermal isomerization rate. [ABSTRACT FROM AUTHOR]

Transition-metal complexes containing stimuli-responsive systems are attractive for applications in optical devices, photonic memory, photosensing, as well as luminescence imaging. Amongst them, photochromic metal complexes offer the possibility of combining the specific properties of the metal centre and the optical response of the photochromic group. The synthesis, the electrochemical properties and the photophysical characterisation of a series of donor-acceptor azobenzene derivatives that possess bipyridine groups connected to a 4-dialkylaminoazobenzene moiety through various linkers are presented. DFT and TD-DFT calculations were performed to complement the experimental findings and contribute to their interpretation. The position and nature of the linker (ethynyl, triazolyl, none) were engineered and shown to induce different electronic coupling between donor and acceptor in ligands and complexes. This in turn led to strong modulations in terms of photoisomerisation of the ligands and complexes. [ABSTRACT FROM AUTHOR]

We present the characterization of new binary mixtures made of two rod-like molecules: a photosensitive azobenzene derivative (calledJ7) and a smectogen (calledM11). The interest in these two specific compounds is related to their use as basic constituents of photo-active liquid crystalline elastomers and their opto-mechanic applications. Differential scanning calorimetry and polarized optical microscopy were used to characterize the phase diagram of the binary systemJ7-M11.2H NMR spectroscopy of the2H-selectively labelledM11, either alone or as a probe in binary mixtures containing different ratiosJ7/M11, was applied to study the orientational ordering properties. [ABSTRACT FROM PUBLISHER]

The UV-light-stimulated self-assemblybehavior of a surface activeionic liquid (SAIL), 1-hexadecyl-3-methylimidazolium bromide (C16mimBr), with an azobenzene derivative, sodium azobenzene4-carboxylate (AzoCOONa), was investigated in aqueous solution. Theproperties and structures of the aggregates, formed at a concentrationratio equal to 2:1 ([C16mimBr]:[AzoCOONa]), were comprehensivelycharacterized by rheometer and cryogenic transmission electron microscopy.Initially, viscoelastic wormlike micelles with a viscosity of 0.65Pa·s were constructed in the C16mimBr/AzoCOONa system.Upon irradiation by UV light (365 nm), particularly fascinating isthat the wormlike micelles become much longer and more entangled,exhibiting a high viscosity of 6.9 Pa·s. This can be attributedto photoisomerization of the AzoCOONa molecule from trans to cis form. It is the first timethat, with exposure to UV or visible light, the aggregate type ofthe photoresponsive system has remained unchanged, with only a changeof internal property parameters. The cation−π interactionprevailing over the hydrophobic interaction and electrostatic interactionbetween C16mimBr and AzoCOONa molecules is supposed tobe responsible for this peculiar phase behavior. The wormlike micellesconstructed with the SAIL and photosensitive additive exhibit controllableviscoelastic behavior in the photoresponsive process. In addition,the average contour length of wormlike micelles was found to slightlydecrease with the increase of temperature. We expect this system willreceive particular attention due to its unique properties and potentialapplications in drug delivery, biochemistry, and materials science,etc. [ABSTRACT FROM AUTHOR]

Three azobenzene derivatives ( 2 R, 2 OR, and 2 NR) that differed in their terminal substituent (alkyl, alkyloxy, and dialkylamino, respectively) have been synthesized and investigated as molecular brakes, in which the rigid H-shaped pentiptycene group functioned as a rotor and the dinitrophenyl group as a 'brake pad'. The E and Z isomers of these compounds corresponded to the 'brake-off' and 'brake-on' states, respectively. The rotation rate of the rotor was evaluated by VT NMR spectroscopy for the brake-on state and by DFT calculations for the brake-off state. The difference between the rotation rates for the rotor in the two states was as large as eight orders of magnitude at ambient temperature. Photochemical switching of the azobenzene moieties afforded efficiencies of 55-67 %. A combination of photochemical E→ Z and thermal Z→ E isomerization promoted the switching efficiency up to 78 %. The terminal substituent affected both the photochemical and thermal switching efficiencies. Solvent polarity also played an important role in the lifetimes of the Z isomers. These azobenzene systems displayed similar braking powers but superior switching efficiencies to the stilbene analogue ( 1O R; ca. 60 % vs 20 %). [ABSTRACT FROM AUTHOR]

Herein, a series of novel hydrogen-bonded complexes derived from 4-[[(dodecyloxy)benz-4-yl]azo]benzoic acid (DBA) and melamine are reported. The morphology and surface wettability of the resulting self-assembled supramolecular architectures can be easily modulated not only by varying the molar ratios of DBA and melamine, but also by external UV irradiation. Based on the results of atomic force microscope, X-ray diffractometer and contact angle measurements, orientation of the coassembled units with different molar ratios of DBA and melamine could be clearly confirmed. Moreover, the effect of photo-isomerisation of the azobenzene units on the wettability of the assemblies has been investigated in detail. As we know, the films derived from thecis-azobenzene derivative usually exhibit a more hydrophilic property than that from thetrans-azobenzene derivative. However, the opposite results were obtained for the samples derived from thecisisomers of DBA–melamine (3:1) complexes or DBA. An explanation, based on the surfaces topography, has been proposed. [ABSTRACT FROM AUTHOR]

We developed the synthesis of a multicomponent molecular machine by employing the inclusion complex of an azobenzene-containing pyridinium salt (G1) with α-cyclodextrin (α-CD) and tetrasulfonated 1,5-dinaphtho-32-crown-8 (DNC) in water. The interconversion of the heterowheel trans-G1·DNC·α-CD [3]pseudorotaxane into cis-G1·DNC [2]pseudorotaxane was modulated by the photoinduced isomerization of the azobenzene moiety accompanied by the release of α-CD from the molecular axle. In control experiments, the azobenzene center of the bis(pyridinium)-modified azobenzene (G2) could not be isomerized in the presence of DNC and α-CD. Only polymeric aggregates were obtained with the G2·DNC·α-CD system, which indicates that the inclusion complex with α-CD and the electrostatic attraction with DNC are crucial to govern the reversible photoswitchable process. This work may provide a method to induce conformational changes of supramolecular assemblies that have multiple macrocyclic receptors. [ABSTRACT FROM AUTHOR]

• Composites with rubber-like mechanical properties and simultaneous shape memory properties are prepared. • Elastic shape memory process is demonstrated. • Spatially tailorable multi-shape memory effect is demonstrated. Shape memory polymers (SMPs) are crosslinked networks with molecular switches to control network mobility and thus macroscopic deformation. The network crosslinking and the molecular switches make most SMPs behave like hard plastics, with very few exceptions whose extensibilities are comparable to rubbers and elastomers. Here we report a class of composites that comprise polystyrene-b-ethylene-co-butylene-b-styrene (SEBS) as elastic matrices and azobenzene derivatives (ADs) as molecular switches. The incorporation of the ADs does not impair the extensibility of the SEBS substrates, and the tensile strains of the prepared composites can exceed 900% even when the content of the ADs reaches 30 wt%. The thermal- and photo-responsive solid–liquid transitions of the ADs are responsible for the shape memory effects of the composites. The photo-responsive shape recovery process can be completed within 2 s, and 2D-to-3D shape transformations are realized on the samples fixed with tensile strains by spatiotemporal control of UV irradiation. On another aspect, the chemical structures of the ADs can be tailored to regulate their melting points and thus the thermal responsive shape memory properties of the composites. Furthermore, different pieces of composites can be combined by hot-pressing to exhibit spatially tailorable thermal responsive shape recovery behaviors. The facile preparation and interesting shape memory properties of the rubber-like composites can inspire the design of soft SMPs with more promising applications. [ABSTRACT FROM AUTHOR]

A series of symmetric and asymmetric charge-transfer azobenzene complexes are synthesized by Sonogashira coupling reaction, and olefin-alkyne click chemistry without by-products. The click products with adjustable energy levels of the frontier orbitals are tested by NMR, IR, and MS, which have good solubility and are easy to synthesize through the introduction of TCNE, TCNQ, F4-TCNQ. Both UV-VIS-NIR spectroscopy and electrochemical studies are carried out and the cyclic voltammogram has a good correlation with spectroscopy. As a side group, the click part has a positive impact on the material. The nonlinear phenomenon of azobenzene derivatives is experimentally represented by Z-scan technology on 532 nm, and each compound exhibits the expected nonlinear optical properties. • The synthesis route is simple, without side reactions, the reaction is efficient and fast, and the economy is reasonable. • By adjusting the type and number of click reagents, the position of the maximum UV absorption peak of the material can be adjusted to cause a red shift, with different click reagents resulting in different degrees of red shift, thus achieving broad-wave absorption over a wide wavelength band. • The introduction of click reagents makes the materials undergo interconversion between saturable absorption to anti-saturable absorption, which makes it easier to regulate the material properties. [ABSTRACT FROM AUTHOR]

Neoadjuvant chemotherapy has become an indispensable weapon against high-risk resectable cancers, which benefits from tumor downstaging. However, the utility of chemotherapeutics alone as a neoadjuvant agent is incapable of generating durable therapeutic benefits to prevent postsurgical tumor metastasis and recurrence. Herein, a tactical nanomissile (TALE), equipped with a guidance system (PD-L1 monoclonal antibody), ammunition (mitoxantrone, Mit), and projectile bodies (tertiary amines modified azobenzene derivatives), is designed as a neoadjuvant chemo-immunotherapy setting, which aims at targeting tumor cells, and fast-releasing Mit owing to the intracellular azoreductase, thereby inducing immunogenic tumor cells death, and forming an in situ tumor vaccine containing damage-associated molecular patterns and multiple tumor antigen epitopes to mobilize the immune system. The formed in situ tumor vaccine can recruit and activate antigen-presenting cells, and ultimately increase the infiltration of CD8 + T cells while reversing the immunosuppression microenvironment. Moreover, this approach provokes a robust systemic immune response and immunological memory, as evidenced by preventing 83.3% of mice from postsurgical metastasis or recurrence in the B16-F10 tumor mouse model. Collectively, our results highlight the potential of TALE as a neoadjuvant chemo-immunotherapy paradigm that can not only debulk tumors but generate a long-term immunosurveillance to maximize the durable benefits of neoadjuvant chemotherapy., Competing Interests: The authors report no conflicts of interest., (© 2022 Chinese Pharmaceutical Association and Institute of Materia Medica, Chinese Academy of Medical Sciences. Production and hosting by Elsevier B.V.)

Macromolecular supra-amphiphiles refer to a kind of macromolecular amphiphiles whose hydrophlic and hydrophobic parts are connected by noncovalent forces. They have applications in various fields, such as drug delivery, sensor systems, and biomedical materials. Here we report a novel molecular recognition motif between a new thermoresponsive water-soluble pillar[7]-arene (WP7) and an azobenzene derivative. Furthermore, we utilized this recognition motif to construct the first pillararene-based supra-amphiphilic polypseudorotaxane which can self-assemble to form vesicles in water. Due to the dual-responsiveness of the molecular recognition motif (the thermoresponsiveness of WP7 and photo-responsiveness of azobenzene), the reversible transformations between solid nanospheres based on the self-assembly of the polymer backbone and vesicles based on the self-assembly of the supra-amphiphilic polypseudorotaxane were achieved by adjusting the solution temperature or UV-visible light irradiation. These dual-responsive aggregation behaviors were further used in the controlled release of water-soluble dye calcein molecules. [ABSTRACT FROM AUTHOR]

Two novel cyclic azobenzenophanes (SC, RC) with functional handles have been synthesized efficiently by a Glaser coupling reaction. Through a Suzuki coupling reaction, alternating ring/linear polymers with rigid (conjugated)/flexible (unconjugated) bridges were obtained from the resultant cyclic azobenzenophanes. The optical activities of linear, cyclic, and macromolecular binaphethyl-azobenzene derivatives were investigated by UV/Vis and circular dichroism (CD) spectra and the time-dependent (TD)-DFT method. Experimental results and theoretical analyses indicated that the cyclic configurations exhibited better chiroptical features than the others, and the reverse conformation and difference of dextro-/levo-rotation of azobenzenophanes were detected by comparing linear and cyclic structures, which provides an opportunity for the optical-rotation-controlled 'smart' materials systems in future. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations have been used to investigate the structural properties, dipole moments, polarizabilities, Gibbs energies, hardness, electronegativity, HOMO/LUMO energies, and chemical potentials of trans and cis configurations of eight parasubstituted azobenzene derivatives. All properties have been obtained using the B3LYP functional and 6-31++G(d,p) basis set. The planar structures have been obtained for all optimized trans configurations. The energy difference between trans and cis configurations for considered derivatives was found to be between 64.2–73.1 kJ/mole. It has been obtained that the p-aminodiazo-benzene (ADAB) has the difference in the dipole moments between trans and cis forms higher than for trans and cis azobenzene. [ABSTRACT FROM AUTHOR]

A new series of liquid crystals whose molecular structure consists of a U-shaped unit as a central core and two rod-like azobenzenes as the peripheral units are synthesized. The mesomorphic properties were investigated by differential scanning calorimetry, polarizing optical microscopy and X-ray diffraction. The existence of nematic and smectic A phase was confirmed by textures and X-ray diffraction. The trans -form of azo compounds showed a strong band in the UV region at ~ 365 nm for the π–π* transition, and a weak band in the visible region at ~ 450 nm due to the n–π* transition. These molecules exhibit a strong photoisomerization behavior in which trans–cis take 50 and 55 s for compounds L4/5 and L4/6, respectively, whereas cis–trans take place almost 29 and 30 h, respectively. Long thermal back relaxation allows us to realize that optical storage devices with these materials which need longer periods. [ABSTRACT FROM AUTHOR]

Ionic crystals (ICs) of the azobenzene derivatives show photoinduced IC-ionic liquid (IL) phase transition (photoliquefaction) upon UV-irradiation, and the resulting cis-azobenzene ILs are reversibly photocrystallized by illumination with visible light. The photoliquefaction of ICs is accompanied by a significant increase in ionic conductivity at ambient temperature. The photoliquefaction also brings the azobenzene ICs further significance as photon energy storage materials. The cis-IL shows thermally induced crystallization to the trans-IC phase. This transition is accompanied by exothermic peaks with a total ΔH of 97.1 kJmol-1, which is almost double the conformational energy stored in cisazobenzene chromophores. Thus, the integration of photoresponsive ILs and self-assembly pushes the limit of solar thermal batteries. [ABSTRACT FROM AUTHOR]

Various novel types of supramolecular nanostructures formed by nonamphiphilic azobenzene derivatives, G1 or G2 have been successfully fabricated, where G2 is structurally similar with G1 but an extra phenoxy group is connected with the azobenzene motif . Micellar structures can be obtained from the self-assembly of G1, which further transform to large-sized spindle structures; while nanorods can be initially formed by G2, which will gradually aggregate to form layered structures with much larger size. Moreover, it is found that upon addition of WP6, which can form inclusion-complex with G1 or G2, separately, the nonamphiphilic G1 and G2 thus converse to supramolecular amphiphiles WP6⊃ G1 and WP6⊃ G2, respectively. Consequently, both of the above WP6⊃ G1 and WP6⊃ G2 complexes can further assemble to form supramolecular binary vesicles, which will gradually transform to nanotubes ( WP6⊃ G1) or well-ordered nanosheets ( WP6⊃ G2). [ABSTRACT FROM AUTHOR]

Although the force field (FF)-based molecular dynamics (MD) simulation has been widely applied to rationalise the experimental observations and measurements in chemistry, physics, materials and life science for years, traditional FF suffers from the incapability for describing chemical reactions, which are crucial in many important transformation processes. In order to simulate the collective switching process in azobenzene-based self-assemble monolayers on Au(111) surface, reactive MD simulations with alternative FF were implemented. The classic torsion function has been modified to depict the diabatic potential energy curves forcisandtransisomers, respectively. A switching function is further introduced to connect two N = N rotation functions, and the surface hopping between thecisandtranscurves is allowed. By using the reactive rotation potential and switching function, the collective effect of numerous reaction centres and the influence of environment on the quantum yield in the complex system were explored at mesoscopic dimension and timescales. The reactive FF may be also applicable for other complicated systems containing stilbene derivatives. Limitation and perspective for further developments for the other complicated reactions are also addressed. [ABSTRACT FROM AUTHOR]

Resonance Raman spectra of azobenzene derivatives were examined in the presence of lipid membranes to find a probe that can distinguish different membrane phases. The NO 2 symmetric stretching band of 4-(4-nitrophenylazo)aniline, also known as Disperse Orange 3 (DO3), is downshifted by about 4 cm −1 on the phase transition of phosphatidylcholine membranes from the liquid crystalline to the gel phase. A comparable downshift also occurs when DO3 is bound to cholesterol-containing membranes in the liquid-ordered phase. Our results demonstrate that Raman spectrum of DO3 is a unique tool for measuring the molecular order of lipids in membranes. [ABSTRACT FROM AUTHOR]

A new azobenzene-based chromophore was synthesized to create one-dimensional (1D) nanofibers with aggregation-induced emission enhancement characteristics. The enhanced red fluorescence of the fibrous structures can be switched off via mechanical pressure, friction, or heat by pressing, rubbing, or annealing. [ABSTRACT FROM AUTHOR]

Improving the photochemical properties of molecular photoswitches is crucial for the development of light-responsive systems in materials and life sciences. ortho-Fluoroazobenzenes are a new class of rationally designed photochromic azo compounds with optimized properties, such as the ability to isomerize with visible light only, high photoconversions, and unprecedented robust bistable character. Introducing σ-electron-withdrawing F atoms ortho to the NN unit leads to both an effective separation of the n→π* bands of the E and Z isomers, thus offering the possibility of using these two transitions for selectively inducing E/ Z isomerizations, and greatly enhanced thermal stability of the Z isomers. Additional para-electron-withdrawing groups (EWGs) work in concert with ortho-F atoms, giving rise to enhanced separation of the n→π* transitions. A comprehensive study of the effect of substitution on the key photochemical properties of ortho-fluoroazobenzenes is reported herein. In particular, the position, number, and nature of the EWGs have been varied, and the visible light photoconversions, quantum yields of isomerization, and thermal stabilities have been measured and rationalized by DFT calculations. [ABSTRACT FROM AUTHOR]

Azobenzene has been widely used as a photoregulator due to its reversible photoisomerization, large structural change between E and Z isomers, high photoisomerization yield, and high chemical stability. On the other hand, some azobenzene derivatives can be used as universal quenchers for many fluorophores. Nucleic acid is a good candidate to be modified because it is not only the template of gene expression but also widely used for building well-organized nanostructures and nanodevices. Because the size and polarity distribution of the azobenzene molecule is similar to a nucleobase pair, the introduction of azobenzene into nucleic acids has been shown to be an ingenious molecular design for constructing light-switching biosystems or light-driven nanomachines. Here we review recent advances in azobenzene-modified nucleic acids and their applications for artificial regulation of gene expression and enzymatic reactions, construction of photoresponsive nanostructures and nanodevices, molecular beacons, as well as obtaining structural information using the introduced azobenzene as an internal probe. In particular, nucleic acids bearing multiple azobenzenes can be used as a novel artificial nanomaterial with merits of high sequence specificity, regular duplex structure, and high photoregulation efficiency. The combination of functional groups with biomolecules may further advance the development of chemical biotechnology and biomolecular engineering. [ABSTRACT FROM AUTHOR]

New N-p-chloro-, N-p-bromo-, and N-p-nitrophenylazobenzylchitosan derivatives, as well as the corresponding azophenyl and azophenyl-p-sulfonic acids, were synthesized by coupling N-benzylvchitosan with aryl diazonium salts. The synthesized molecules were analyzed by UV-Vis, FT-IR, 1H-NMR and 15N-NMR spectroscopy. The capacity of copper chelation by these materials was studied by AAS. Chitosan and the derivatives were subjected to hydrolysis and the products were analyzed by ESI(+)-MS and GC-MS, confirming the formation of N-benzyl chitosan. Furthermore, the MS results indicate that a nucleophilic aromatic substitution (SnAr) reaction occurs under hydrolysis conditions, yielding chloroaniline from N-p-bromo-, and N-p-nitrophenylazo-benzylchitosan as well as bromoaniline from N-p-chloro-, and N-p-nitrophenylazobenzyl-chitosan. [ABSTRACT FROM AUTHOR]

The direct and reversible transformationof matter between thesolid and liquid phases by light at constant temperature is of greatinterest because of its potential applications in various manufacturingsettings. We report a simple molecular design strategy for the phasetransitions: azobenzenes having para-dialkoxy groupswith a methyl group at the meta-position. The photolithography processeswere demonstrated using the azobenzene as a photoresist in a singleprocess combining development and etching of a copper substrate. [ABSTRACT FROM AUTHOR]

The preparation of switchable azobenzene derivatives driven by visible light is desirable for applications in biomolecular systems. o -R-substituted 4,4′-diacetamidoazobenzene derivatives (R H, CH 3 , OCH 3 or OH) were investigated by using both density functional theory (DFT) and reactive molecular dynamics simulations. DFT calculations demonstrated that the nonplanar azo trans geometric structure, which caused by bulky groups tetra substituted in the ortho-position, is the key factor to enable the trans → cis transition with visible light. Furthermore, 100 independent reactive MD simulations demonstrated that 71% trans isomers of tetra o -OCH 3 -substituted 4,4′-diacetamidoazobenzene translated to cis , in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

Cis–transisomerizations are among the fundamental processesin photochemistry. In azobenzene or its derivatives this dynamicsis, due to its reversibility, one of the reactions widely used inphotostimulation of molecular motors or in molecular electronics.Though intensively investigated in the optical regime, no detailedstudy exists in the X-ray regime so far. Because the X-ray emissionspectroscopy echoes the electronic structure sensitive to the geometry,this theoretical report based on the density functional theory andits time-dependent version presents different nitrogen K-edge X-rayemission spectra for cis and trans isomers with close interrelationto their electron configuration. Considering the spectrum along theisomerization path, these structural signatures can be utilized toprobe the isomerization dynamics in the excited molecule. The schemecan further be generalized to the element specific photoreactions. [ABSTRACT FROM AUTHOR]

A series of new liquid-crystalline dendrimers is synthesized from hexa(4-hydroxyphenyloxy)­cyclotriphosphazene as the central core and bis(MPA) as a branching agent. The dendrimers are functionalized with azobenzene mesogenic moieties. The monodisperse nature of the dendrimers is confirmed by 1H and 31P{1H} NMR and by matrix assisted laser desorption/ionization (MALDI) mass spectrometry (MS). A study of the thermal properties reveals mesomorphic behavior. All of the materials exhibit a lamellar phase and this is confirmed to be smectic A in nature by X-ray diffraction. A nematic phase is also observed for the dendrimers that contain 4-cyanoazobenzene. A calamitic arrangement in which the mesogenic moieties point both upwards and downwards with respect to the cyclotriphosphazene core is proposed to explain the mesomorphic properties. The introduction of photochromic moieties leads to a photoresponse for these materials. The response to linearly polarized light is studied and an order parameter of about 0.5 is measured for dendrimer G1-Azo-3. [ABSTRACT FROM AUTHOR]

The new, unsymmetrical azobenzene-tagged ligand 4-(4-azobenzene)-3,6-di(2-pyridyl)pyridazine, adpp, forms complexes with platinum(II) and platinum(IV), which exist as a mixture of geometrical isomers. The complexes are characterized primarily by their NMR spectra, while the structures of the ligand and its complexes [PtMe2(adpp)], [PtBrMe2(CH2C6H4-4- t-Bu)(adpp)], and [PtBrMe2(CH2C6H3-3,5- t-Bu2)(adpp)] have been structurally characterized. In solution, the compounds undergo easy photochemical trans− cis switching of the azobenzene group, with subsequent slow thermal isomerization back to the more stable trans-azobenzene isomer. [ABSTRACT FROM AUTHOR]

A new azobenzene derivative, bis[4-(3-methylbutoxy)phenyl]diazene(DC-azo), was synthesized as yellow powder through a three-step reaction.DC-azo was crystallized from a mixture of acetone/water in the formof highly insulating gold-colored crystals with a specular reflectanceof 21% over the wavelength range of 520–800 nm. The CIELABcolor space of the crystals indicated that the crystals were slightlymore reddish and less yellowish than metallic Au. The crystals retainedtheir gold coloration under dry conditions and were stable up to 383K. The X-ray diffraction (XRD) measurements estimated the long-rangeperiodical thickness in the crystal to be 1.12 nm, thereby indicatingthat the DC-azo molecules were oriented such that the azobenzene moietiesshowed a tilt angle of 32.2° against the crystal surface. Thegold-colored crystals of DC-azo could be a potential substitute forthe conventional metallic paints. [ABSTRACT FROM AUTHOR]

An oxidative route to N-substituted sulfonamidic azobenzene derivatives is reported. A mechanism, based on a rationalization of previous findings, is proposed. This simple one-pot method could be adapted to the synthesis of a range of substituted sulfonylazobenzenes with potential applications in the pharmaceutical and industrial fields. [ABSTRACT FROM AUTHOR]

Simulations based on molecular dynamics coupled to excitation energy calculations were used to generate simulated absorption spectra for a family of halide derivatives of azobenzene, a family of photoswitch molecules with a weak absorption band around 400-600 nm and potential uses in living tissue. This is a case where using the conventional approach in theoretical spectroscopy (estimation of absorption maxima based on the vertical transition from the potential energy minimum on the ground electronic state) does not provide valid results that explain how the observed band shape extends towards the low energy region of the spectrum. The method affords a reasonable description of the main features of the low-energy UV-Vis spectra of these compounds. A bathochromic trend was detected linked to the size of the halide atom. Analysis of the excitation reveals a correlation between the energy of the molecular orbital where excitation starts and the energy of the highest occupied atomic orbital of the free halide atom. This was put to the test with a new brominated compound with good results. The energy level of the highest occupied orbital on the free halide was identified as a key factor that strongly affects the energy gap in the photoswitch. This opens the way for the design of bathochromically shifted variants of the photoswitch with possible applications.

The reversible photoisomerization of azobenzene (Azo) has been utilized to construct supramacromolecular hydrogels (SMHGs) in which the structure can be controlled by light. However, most of these examples have been realized only through grafting Azo functional group onto the macromolecular chains, and low-molecular-weight Azo derivatives are relatively scarce. Here, a novel amphiphilic azobenzene derivative (APA) has been designed and synthesized, which can be used as a low-molecular-weight crosslinker to construct SMHGs via host-guest interactions between Azo and β-cyclodextrin (β-CD). APA, with two hydrophobic ends and a hydrophilic segment, can self-assemble to spherical particles in the mixed solvent of THF and H 2 O, and disassemble upon UV light irradiation. When APA is mixed with the solution of hyaluronic acid modified by β-CD (HA-CD), hydrogels can form at different mass fractions of HA-CD. Moreover, when the molar ratio of APA and β-CD is 0.5, the resultant hydrogel has the highest G ' value. Benefiting from the host-guest interactions between Azo and β-CD, as well as the intermolecular hydrogen bonds of hyaluronic acid, hydrogels undergo both photo- and thermo-responsive sol-gel transition. The release of Rhodamine B from the hydrogel, could be controlled by UV light irradiation or high temperature. The work presented here demonstrates a simple strategy to construct photo-responsive SMHGs by Azo-derived low-molecular-weight crosslinkers. [Display omitted] • A novel amphiphilic azobenzene derivative (APA) has been designed and synthesized. • APA is composed of two hydrophobic ends and a hydrophilic segment. • APA can undergo photo-responsive self-assemble and disassemble behaviors. • APA can be used as ideal low-molecular-weight crosslinkers to construct smart SMHGs. [ABSTRACT FROM AUTHOR]

A reversible and repeatable gel-sol transitioned low molecular weight gel is constructed by controlling the photoisomerization of azobenzene between its trans and cis form. Significantly, by non-covalent loading fluorescence dyes, this photocontrolled gel achieves fluorescence tunable emission, that is, fluoresce strongly in gel but barely emits in sol, which is reversible and repeatable. [Display omitted] • Three azobenzene derivatized gelators were obtained directly. • LMWG underwent reversible and repeatable gel-sol transition with photoirradiation. • The photoswitchable LMWG system was successfully applied for tuning the fluorescent emission intensity of dyes including ACQ and AIE by noncovalent loading. Photoresponsive low-molecular-weight gel, a class of fascinating soft material, draws increasing attention due to their versatile applications. Herein, three azobenzene derivatives (A 1-3) containing urea moiety and various alkyl chains were synthesized directly as organic gelators. They displayed satisfactory gelation capacity in plenty of solvents. Benefitting from the various configurations and/or polarities of trans -/ cis -azobenzene, which may break the balance of the cooperation of various non-covalent interactions, the gel prepared by A 2 in DMSO underwent reversible gel-sol transition with light irradiation at different wavelengths. Moreover, the tunable fluorescence intensity of dyes was achieved by this photoswitchable gel-sol system. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fabrication and characterization of a novel C 3 F 7 -azo+-Nb 3 O 8 composite were performed for the first time. • C 3 F 7 -azo+-Nb 3 O 8 /GCE can detect AA and DA simultaneously, and has a low detection limit. The detection limit of AA and DA are 4.71 μM and 1.81 μM, respectively. • C 3 F 7 -azo+-Nb 3 O 8 /GCE has a long-term stability and amazing anti-interference ability. The polyfluorinated cationic azobenzene derivative, trans-[2-(2,2,3,3,4,4,4-heptafluorobutylamino)ethyl]-{2-[4-(4-hexyphenylazo)-phenoxy]ethyl}-dimethylammonium (abbreviated as C 3 F 7 -azo+Br-) was intercalated into layer semiconductor KNb 3 O 8 by guest–guest exchange method to synthesize a sandwich-structured C 3 F 7 -azo+-Nb 3 O 8 composite, which can be utilized as an electrochemical sensor for simultaneous detection of ascorbic acid (AA) and dopamine (DA). X-ray diffraction (XRD), scanning electron microscope (SEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive spectrometer analysis (EDS) and Fourier transform infrared spectrometer (FTIR) were used to characterize the structure, morphology and composition of C 3 F 7 -azo+-Nb 3 O 8. It is proposed that C 3 F 7 -azo+ ions were intercalated into [Nb 3 O 8 ]- lamellar forming a bi-molecular layer at angle of 47.85°. The results of cyclic voltammetry (CV) and differential pulse voltammetry (DPV) show that the as-prepared C 3 F 7 -azo+-Nb 3 O 8 /GCE can detect AA and DA simultaneously in N 2 -saturated PBS (0.2 M, pH = 5.0), and the detection limits of AA and DA are 4.71 μM and 1.81 μM severally. Moreover, C 3 F 7 -azo+-Nb 3 O 8 /GCE has a long-term stability and good anti-interference capability. [ABSTRACT FROM AUTHOR]

Highly efficient conversion, long-term storage and controllable release of solar energy is always a significantly scientific issue for humans. Solar thermal fuel (STF) is considered as one kind of promising strategy with close-cycled energy-storage ability resulted from the reversible chemical isomerization of photo-responsive molecular. Azobenzene and its derivatives have been widely investigated as promising candidates for STF due to the unique photo-isomerization. However, STFs based on azobenzene moiety without any pretreatment in the charging process have seldom been reported. Here, a flexible STF device is designed and fabricated by combining photo-liquefiable 1-(4-(isopentyloxy)phenyl)-2-(p -tolyl)diazene (IPDAZ) as a photothermal conversion materials and a commercial fabric cloth as a flexible template. The total energy storage density of our STF device is as high as 288 J g−1 (80 W h kg−1) which is greatly increased by the photoinduced phase transition of the IPDAZ. Besides, the flexible IPDAZ STF film possesses good toughness, solvent stability, energy-storage capacity and recyclability, which has potential application in environment-friendly STF. • A novel solid-state STF is fabricated by green method without any solution. • The ESD of STF is greatly increased by the photo-induced phase change. • The charging speed and storage life are improved due to H-bond. • The flexible STF exhibits good toughness and solution stability. [ABSTRACT FROM AUTHOR]

From the inside out or from the outside in? Two photoswitchable foldamers that incorporate azobenzene moieties as the energy‐acceptor units have been designed. The pathway of helix unfolding can be controlled by localizing these photoinduced triggers (shown in red) either at the core (left) or at the termini (right) of the helix. [ABSTRACT FROM AUTHOR]

ABSTRACT We report the preparation, photoisomerization properties, and three-dimensional (3D) microstructure fabrication with two-photon polymerization of crosslinked azo-polymers. A series of bi-acrylate-substituted azobenzene derivatives were designed and synthesized as the monomers and/or crosslinkers of the crosslinked azo-polymers. The doping concentration of the derivatives in pre-polymer resins was significantly increased due to the introduction of bulky tert-butyl and flexible alkyl chains. The double-exponential dynamics of trans-to- cis photoisomerization of the azo-polymers indicated the coexistence of different processes for the azobenzene moieties in the polymeric crosslinked networks. The crosslinked azo-polymers exhibited ideal 'on-off' switching performance in the highly reversible trans- cis- trans isomerization cycles. Furthermore, we prepared a photoresist containing the azobenzene derivative for 3D microstructure fabrication based on two-photon polymerization. A woodpile photonic crystal with a photonic bandgap at telecommunication wavelength region was successfully fabricated with the azobenzene-containing photoresist, which would open the way for the design and manufacturing of miniature optical communication devices. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2947-2956, 2013 [ABSTRACT FROM AUTHOR]

The reaction of meta- and para-bromomethylene-azobenzenes with 1-methyl-imidazole yields the respective meta-/para-functionalized azobenzenes tagged with an imidazolium group. Similar reactions of ortho- and para-bromo-azobenzene with imidazole and successive quaternation with benzylbromide give the analogues, with an imidazolium group in ortho/para substituted azobenzenes. With the exception of the ortho derivative, all imidazolium salts could be transformed into their respective silver(i) complexes by reaction with Ag2O. Transmetallation of these silver(i) complexes with (Me2S)AuCl gives the azobenzene-containing complexes (NHC)AuCl. Two of these formed crystals suitable for X-ray diffraction, which revealed the typical linear coordination geometry of the NHC–Au–Cl moiety. All gold complexes feature E→Z photo-isomerisation upon irradiation with UV light. The thermal back reaction to the E-isomers is relatively slow and comparable to that of other azobenzene compounds. [ABSTRACT FROM AUTHOR]

Abstract: ATP synthase and protein kinase (PKs) are prime targets for drug discovery in a variety of diseases. It is well known that numerous stilbenes are capable to interact and inhibit ATP synthase and PKs. This work focuses on a series of azobenzene based molecules having high structural similarity with antimicrobial stilbenes. An investigation was carried out analyzing the potential toxicity of a large set of molecules by means of computational analysis. A small selection of potential low toxic molecules have been therefore synthesized, characterized and finally microbiologically tested. The synthesized compounds show potent bactericidal activity against Gram+ and a fungus, and are capable of inhibiting biofilm formation. Finally, the compounds demonstrated a thermal stability that makes them potential candidates for incorporation in polymer matrix for application as biomedical devices and food packaging. [Copyright &y& Elsevier]

Highlights: [•] Pattern of liquid crystal droplets dispersed in isotropic liquid is being formed. [•] Formation of the pattern is reversible and pattern diffracts light into orders. [•] Such grating can be recorded in certain temperature and light intensity range. [•] Photothermal and orientational effects are assumed as responsible for the effect. [ABSTRACT FROM AUTHOR]

Abstract: Nanostructured monolayer of azobenzene derivatives was prepared on carbon materials. The method is based on the electrochemical reduction of a specific silyl-protected aryl diazonium salt followed by a deprotection step and a click chemistry coupling reaction. This procedure leads to a robust modification of the surface where molecular entities are placed in a “frozen” structuration thanks to the covalent nature of the modification. The photo-switchable properties of the surface were examined by electrochemistry using different redox probes. UV–visible light irradiation provides an easy way to reversibly modulate the permeability in a monolayer film grafted onto carbon materials. [Copyright &y& Elsevier]

Highlights: [•] DFT study of the structural, mechanical, and chiroptical properties of n-(phenylazo)-azobenzenes (n =1–10). [•] Photo-switching capability from a “strip”-like conformation (all-trans) to a “spring”-like conformation (all-cis). [•] Good match between the predicted and the experimental geometries. [•] Surprising nexus between the geometrical and elastic parameters and the Golden Ratio. [Copyright &y& Elsevier]