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The isomerization of azobenzo-13-crown ether can be expected to be hindered due to the polyoxyethylene linkage connecting the 2,2′-positions of azobenzene. The mixed reference spin-flip time-dependent density functional theory results reveal that the planar and rotational minima of the first photo-excited singlet state (S1) of the trans-isomer pass through a barrier (2.5–5.0 kcal/mol) as it goes toward the torsional conical intersection (S0/S1) geometry (

This paper proposes a molecular model of covalent grafting of azobenzene derivatives with graphite-like carbon nitride based on hydrogen bond regulation to improve the azobenzene photothermal energy storage density. The enthalpy of isomerization (Δ H) of azobenzene molecular cis - trans isomers is calculated using density functional theory, and the magnitude of Δ H is used to evaluate the photothermal storage performance of the azobenzene graphite-like carbon nitride model. The results showed that the molecular Δ H value increased by 0.105–0.243 eV after the azobenzene derivatives were covalently grafted to the graphitic carbon nitride template. In addition, when the donator group replaced the active benzene ring ortho-site of azobenzene, its value was 0.069–0.295 eV higher than that of the electron-withdrawing groups. Moreover, intramolecular hydrogen bonds can stabilize cis - trans isomers and increase the energy of azobenzene. Compared with unsubstituted azobenzene, the energy of azobenzene Δ H containing one intramolecular hydrogen bond increased by 0.295 eV, while the energy of azobenzene Δ H containing multiple intramolecular hydrogen bonds increased by 0.775 eV. [Display omitted] • A molecular model for covalent grafting of azobenzene onto g-C 3 N 4 with hydrogen bond was developed. • The energy conversion density of azobenzene synthetic was determined using density functional theory. • The grafting effect was evaluated by considering intramolecular hydrogen bond, substitution location, and electron group. [ABSTRACT FROM AUTHOR]

A problem of systemic pharmacotherapy is off‐target activity, which causes adverse effects. Outstanding examples include neuroinhibitory medications like antiseizure drugs, which are used against epilepsy and neuropathic pain but cause systemic side effects. There is a need of drugs that inhibit nerve signals locally and on‐demand without affecting other regions of the body. Photopharmacology aims to address this problem with light‐activated drugs and localized illumination in the target organ. Here, we have developed photoswitchable derivatives of the widely prescribed antiseizure drug carbamazepine. For that purpose, we expanded our method of ortho azologization of tricyclic drugs to meta/para and to N‐bridged diazocine. Our results validate the concept of ortho cryptoazologs (uniquely exemplified by Carbazopine‐1) and bring to light Carbadiazocine (8), which can be photoswitched between 400–590 nm light (using violet LEDs and halogen lamps) and shows good drug‐likeness and predicted safety. Both compounds display photoswitchable activity in vitro and in translucent zebrafish larvae. Carbadiazocine (8) also offers in vivo analgesic efficacy (mechanical and thermal stimuli) in a rat model of neuropathic pain and a simple and compelling treatment demonstration with non‐invasive illumination. [ABSTRACT FROM AUTHOR]

A supramolecular low molecular weight organogelator (CNAZO) containing azobenzene and cholesterol units was synthesized, and its applications have been studied. The CNAZO gelator displays excellent gelation ability in six kinds of organic solvents with satisfactory transparency and lower critical gelation concentrations. Meanwhile, the chirality can be transferred from the cholesterol unit to the azobenzene group, which can be reversibly modulated through 365 nm UV light irradiation and heating‐cooling treatment. Compared with D‐limonene, CNAZO can form a stable organogel and exhibits obvious CD signals in the mixed solvent that containing L‐limonene, which can be used for chiral recognition of limonene. Owing to the phase‐selective ability and porous network structure, CNAZO can also be chosen for the separation and recovery of petrol from water and be utilized for rhodamine B (RhB) adsorption with removal efficiency (Re) of 99 %. These interesting insights indicated that the CNAZO gelator could be selected in the design of sensors and in environmental remediation fields. [ABSTRACT FROM AUTHOR]

Molecular photoswitches provide interesting tools to reversibly control various biological functions with light. Thanks to its small size and easy introduction into the biomolecules, azobenzene derivatives have been widely employed in the field of photopharmacology. All visible‐light switchable azobenzenes with controllable thermostability are highly demanded. Based on the reported tetra‐o‐chloroazobenzenes, we synthesized push‐pull systems, by introducing dialkyl amine and nitro groups as strong electron‐donating and electron‐withdrawing groups on the para‐positions, and then transformed to push‐push systems by a simple reduction step. The developed push‐pull and push‐push tetra‐o‐chloroazobenzene derivatives displayed excellent photoswitching properties, as previously reported. The half‐life of the Z‐isomers can be tuned from milliseconds for the push‐pull system to several hours for the push‐push system. The n‐π* and π‐π* transitions have better resolution in the push‐push molecules, and excitation at different wavelengths can tune the E/Z ratio at the photostationary state. For one push‐pull molecule, structure and absorption spectra obtained from theoretical calculations are compared with experimental data, along with data on the push‐push counterpart. [ABSTRACT FROM AUTHOR]

Carbohydrate-based macrocyclic compounds are of particular interest because of their multifunctionality, their unique structural and physicochemical properties as well as their potential applications in chemistry, biology, and drug discovery. Introducing a molecular photoswitch into the skeleton of glycomacrocycles makes possible the reversible control of properties of the resulting photoswitchable glycomacrocycles by light illumination. Therefore, development of stereoselective synthesis of this class of glycomacrocycles is of great interest. Two new azobenzene-based glycomacrocycles have been synthesized through an intramolecular glycosylation approach. Excellent 1,2- cis stereoselectivity has been achieved for the mannosylation. [ABSTRACT FROM AUTHOR]

Many polypeptides form stable, helical secondary structures enabling the formation of lyotropic liquid crystalline (LLC) phases. Contrary to the well‐studied polyglutamate, their counterparts based on polyaspartates exhibit a much lower helix inversion barrier. Therefore, the helix sense is not solely dictated by the chirality of the amino acid used, but additionally by the nature and conformation of the polymer sidechain. In this work, polymers responsive to irradiation with visible light are designed achieving conformational transitions from helix‐to‐coil and helix‐to‐helix. The synthesis and the application as LLC mesogens of several (co‐)polyaspartates bearing ortho‐fluorinated azobenzene (FAB) as a photochromic group are presented. Many of the obtained polymers undergo changes in their secondary structure upon E‐Z‐isomerization of the FAB‐containing sidechain. Of special interest are copolymers that exhibit photo‐responsive helix inversion without loss of their helical secondary structure. These copolymers form stable LLC phases in helicogenic solvents, where the effect of photo‐switching on the macroscopic behavior is studied by NMR spectroscopy. Especially, the irradiation of the different LLC phases of the helix inversion polymers displays a change in the LLC order experienced by the solvent. These peculiar properties are promising for future applications as photo‐responsive alignment media for structure elucidation in NMR. [ABSTRACT FROM AUTHOR]

Due to the intrinsic porosity and photo‐regulated pore environment, azobenzene (Azo) functionalized covalent organic frameworks (COFs) show great potential for contaminant removal. However, the stability and degree of functionality of the COFs greatly affect the porosity and subsequent adsorption capacity and selectivity. Herein, a highly stable thiazole‐linked COF containing phenolic hydroxyl groups (OH‐COF) is constructed by using 4,4′,4′‐(1,3,5‐triazine‐2,4,6‐triyl)trianiline and 2,5‐dihydroxyterephthalaldehyde in the presence of sulfur, which shows high crystallinity and specific surface. Azo‐functionalized COFs ((Azo)x‐COFs) are prepared by grafting different amounts azobenzene groups onto OH‐COF through post‐modification, whose aperture is conveniently tuned by the grafted azobenzene amount. The pore size of (Azo)x‐COFs also can be reversibly adjusted under UV and visible light irradiation without affecting the crystallinity. Appropriate amount of Azo‐grafted (Azo)0.1‐COF possessed a high adsorption capacity (1216.93 mg g−1) to Congo red (CR). While the adsorption capacity of (Azo)1.0‐COF to CR significantly increased 2.9 times to reach 1489.96 mg g−1 after UV irradiation. (Azo)1.0‐COF also can selectively separate dye molecules with different sizes based on photo‐regulated pore size, showing excellent reversibility and reusability. As such, the ability to photo‐regulate the adsorption and interception of (Azo)x‐COFs highlights their significance in functioning as smart porous nanomaterials for pollutant removal and water purification. [ABSTRACT FROM AUTHOR]

Photo‐responsive liquid crystal polymers (LCPs) have potential application value in flexible robots, artificial muscles, and microfluidic control. In recent years, significant progress has been made in the development of LCPs. However, the preparation of LCPs with continuous and controllable stepwise deformation capabilities remains a challenge. In this study, visible photo‐responsive cyanostilbene monomer, UV photo‐responsive azobenzene monomer, and multiple hydrogen bond crosslinker are used to prepare photo‐responsive LCPs capable of achieving continuously and controllable stepwise deformation. The comprehensive investigation of the multiple light response ability and photo‐induced deformation properties of these copolymers is conducted. The results reveal that in the first stage of photo‐induced deformation under 470 nm blue light irradiation, the deformation angle decreases with a reduction in cyanostilbene content in the copolymer component, ranging from 40° in AZ0‐CS4 to 0° in AZ4‐CS0. In the second stage of photo‐induced deformation under 365 nm UV irradiation, the deformation angle increases with the increase of azobenzene content, ranging from 0° of AZ0‐CS4 to 89.4° of AZ4‐CS0. Importantly, the deformation between these two stages occurs as a continuous process, allowing for a direct transition from the first‐stage to the second‐stage deformation by switching the light source from 470 to 365 nm. [ABSTRACT FROM AUTHOR]

The template wetting method is a common method used for preparing one‐dimensional polymer nanostructures, which can be widely applied in many fields. Although the template wetting method has generality in controlling the morphology of nanomaterials, it still poses challenges in generating patterned polymer nanoarrays. Here, we present the fabrication of patterned and anti‐patterned azopolymer (PAzo) nanoarrays via the light‐induced nanowetting method. By shining UV lights, the trans‐PAzo converts to cis‐PAzo, causing a reduction of the glass transition temperature (Tg) of the PAzo below room temperature. Consequently, the PAzo polymers can undergo reversible solid–liquid transitions by shining UV and visible lights. When PAzo films are covered with photomasks and anodic aluminum oxide (AAO) templates, followed by shining UV lights, patterned PAzo nanoarrays can be generated. We further apply the concept that cis‐PAzo films can be selectively removed by solvents to generate anti‐patterned PAzo nanoarrays. By covering PAzo films with photomasks and illuminating UV lights, the unmasked areas can be converted to cis‐form, which can then be selectively removed by selected solvents. The patterned PAzo films are then covered with AAO templates, followed by shining UV lights, forming hierarchical anti‐patterned PAzo nanoarrays. [ABSTRACT FROM AUTHOR]

This study reports the reversible solubility switching of a polymer triggered by non‐phototoxic visible light. A photochromic polymerizable azobenzene monomer with four methoxy groups at the ortho‐position (mAzoA) was synthesized, exhibiting reversible photoisomerization between trans‐ and cis‐states using green (546 nm) and blue light (436 nm). Free radical copolymerization of hydrophilic dimethylacrylamide (DMAAm) with mAzoA produced a light‐responsive random copolymer (P(mAzoA‐r‐DMAAm)) that shows a reversible photochromic reaction to visible light. Optimizing mAzoA content resulted in P(mAzoA10.7‐r‐DMAAm)3.0 kDa exhibiting LCST‐type phase separation in PBS (pH 7.4) with trans‐ and cis‐states at 39.2 °C and 32.9 °C, respectively. The bistable temperature range of 6.3 °C covers 37 °C, suitable for mammalian cell culture. Reversible solubility changes were demonstrated under alternating green and blue light at 37 °C. 1H NMR indicated significant retardation of thermal relaxation from cis‐ to trans‐states, preventing undesired thermal mechanical degradation. Madin Darby Canine Kidney (MDCK) cells adhered to the P(mAzoA‐r‐DMAAm) hydrogel, confirming its non‐cytotoxicity and potential for biocompatible interfaces. This principle is useful for developing hydrogels that can reversibly stimulate cells mechanically or chemically in response to visible light. [ABSTRACT FROM AUTHOR]

Manipulable lenses with tunable focal length have garnered great attention due to their unique advantages including strong adjustability, low power consumption, fast response times, and ease of integration. However, in the context of advancing intellectualization, weight reduction, and miniaturization of imaging systems, mere focal length adjustment is no longer sufficient. Herein, an innovative method is introduced for creating a dynamic light manipulable (DLM) lens with surface reshaping. This breakthrough is accomplished through the collaborative integration of a medium lens with an actuator based on photo‐active liquid crystal polymer (LCP) film, where the deformation of the photo‐active LCP film can be arbitrarily controlled by meticulously designing the orientation distributions of liquid crystal (LC) mesogens within the film. The lens with three distinct surfaces, including quasi‐cone, paraboloid, and 3 × 3 paraboloid array, are demonstrated with infrared stability, robust fatigue resistance, long natural recovery time, outstanding thermal stability, and excellent solvent resistance, further confirming the feasibility of the lens application in tunable display, imaging, infrared optics, and other systems. This work holds the promise of paving the way for a new generation of imaging systems. [ABSTRACT FROM AUTHOR]

Despite that extensive efforts have been dedicated to the search for advanced catalysts to boost the electrocatalytic nitrobenzene reduction reaction (eNBRR), its progress is severely hampered by the limited understanding of the relationship between catalyst structure and its catalytic performance. Herein, this review aims to bridge such a gap by first analyzing the eNBRR pathway to present the main influential factors, such as electrolyte feature, applied potential, and catalyst structure. Then, the recent advancements in catalyst design for eNBRR are comprehensively summarized, particularly about the impacts of chemical composition, morphology, and crystal facets on regulating the local microenvironment, electron and mass transport for boosting catalytic performance. Finally, the future research of eNBRR is also proposed from the perspectives of performance enhancement, expansion of product scope, in‐depth understanding of the reaction mechanism, and acceleration of the industrialization process through the integration of upstream and downstream technologies. [ABSTRACT FROM AUTHOR]

Azobenzene (Azo) liquid‐crystalline polymers are intriguing due to their unique photo‐induced isomerization and supramolecular chirality. However, clarification on multicomponent chiral induction towards Azo polymers remains ambiguous and challenging. Herein, chiral solvents and amines were employed to control the chiroptical activity of achiral Azo polymers. Methyl L‐/D‐lactate was added as the poor solvent and chiral inducer to achieve the first chiral induction in Azo aggregates. Chiral amines were utilized for the second chiral induction based on the acid–base interactions between the carboxyl groups of polymers and amines. The chiral enhancement and inversion of Azo units could be observed through the synergistic or antagonistic effect between solvents and amines. The impacts of solvent, chemical structures, feed ratio, enantiomeric excess, and temperature on supramolecular chirality were systematically studied. Furthermore, this system displayed the chiroptical switching property and chiral recovery under reversible irradiation. [ABSTRACT FROM AUTHOR]

In this report, a new series of mono‐, di‐, tri‐, and tetra‐cationic pyridinium and vinyl pyridinium‐modified [2.2]paracyclophanes as useful molecular tectons for supramolecular systems are described. Regioselective functionalization at specific positions, followed by resolution step and successive transformations through Pd‐catalyzed Suzuki‐Miyaura and Mizoroki‐Heck cross‐coupling chemistry furnish a series of modular PCP scaffolds. In our proof‐of‐concept study, on N‐methylation, the PCPs bearing (cationic) pyridyl functionalities were demonstrated as useful molecular receptors in host‐guest supramolecular assays. The PCPs on grafting with light‐responsive azobenzene (−N=N−) functional core as side‐groups impart photosensitivity that can be remotely transformed on irradiation, offering photo‐controlled smart molecular functions. Furthermore, the symmetrical PCPs bearing bi‐, and tetra‐pyridyl functionalities at the peripheries have enormous potential to serve as ditopic and tetratopic 3D molecular tectons for engineering non‐covalent supramolecular assemblies with new structural and functional attributes. [ABSTRACT FROM AUTHOR]

The structure and absorption properties of a series of azobenzene derivatives are investigated using the density functional theoretical methods. The study showed that π → π* transitions of azobenzene undergo red shift after mono- and di- substitutions at para positions. Considering the fact that o-fluoro and o-methoxy derivatives of azobenzene have long living cis isomers, the effect of ortho substitution on the excitation energies is examined. An investigation on the azo-protonation revealed prominent red shift for n → π* and π → π* transitions bringing both absorptions in visible region. The effect of substitution on the cis to trans thermal relaxation is also analysed. [ABSTRACT FROM AUTHOR]

Heavy atoms can form highly coordinated states, and their optical properties have attracted much attention. Recently, we have demonstrated that a reversible coordination-number shift of hypervalent tin(IV) from five to six can provide predictable hypsochromic shifts in light absorption and emission properties in small molecules and a π-conjugated polymer film. Herein, we show the preparation of seven-coordinated tin and reveal that the binding constant of the seven coordination with ethylenediamine (EDA, K = 2900 M−1) is 200 times higher than that of six coordination with propylamine (PA, K = 14 M−1) owing to the chelate effect. Moreover, reversible vapochromism of the π-conjugated polymer film was observed upon exposure (λabs = 598 nm and λPL = 697 nm) and desorption (λabs = 641 nm and λPL = 702 nm) of EDA vapor. Furthermore, as a unique demonstration, the thermochromic film was prepared by fixing the seven coordination as the initial state using 1,10-phenanthroline. These optical variations are predictable by quantum chemical calculations. Our findings are valuable for the development of designable and controllable stimuli-responsive materials focusing on the inherent properties of the elements. [ABSTRACT FROM AUTHOR]

An efficient palladium‐catalyzed ortho C−H acyloxylation of azobenzenes, allowing the introduction of the difunctionalised substituent, diethylphosphonoacetate, is reported. Thanks to the mild reaction conditions implemented, this regioselective late‐stage ortho‐functionalization tolerates a wide range of functional groups and permits the access of diversely substituted azobenzenes in good to excellent yields. Selective hydrolysis of the diethyl phosphonate group leads to stable water‐soluble azo‐photoswitches with interesting photophysical properties such as an extended Z‐isomer half‐life, opening new opportunities in the design of optochemical tools for the exploration of living organisms. [ABSTRACT FROM AUTHOR]

Although natural dual‐ion exchangers are indispensable for bio‐organic functions, developing their artificial counterparts remains nearly unexplored. Herein, this work proposes a novel light‐controlled K+/Na+‐transport‐exchanger TE12, realizing an unprecedented reversible switch between K+‐ and Na+‐transmembrane transport by changing its transport mechanism (channel and carrier). The conformational transformation of the azobenzene moiety in TE12 essentially induces this. The K+/Na+ selectivity of K+‐channel Trans‐TE12 is as high as 20.3, making it one of the most selective artificial K+‐transporters. Moreover, considering the scarcity of artificial Na+‐transporters, the Na+‐carrier Cis‐TE12 with high Na+/K+ selectivity (9.25) represents a breakthrough. Cis‐TE12 significantly triggers cell apoptosis by igniting fascinating "Na+ sparks" first observed on cancer cells treated with synthetic channels, while K+‐channel Trans‐TE12 exhibits low toxicity. Importantly, TE12 can function as a spatiotemporally controllable ion interference therapy, enabling in situ 365 nm light‐triggered and 450 nm light‐inhibited cell death. This work realizes sophisticated functions in a simplified structure by the "Less is More" design concept. It opens a shortcut toward the future iterative updating of artificial ion transporters to make them better biological analogs and therapeutic agents. [ABSTRACT FROM AUTHOR]

A visible‐light responsive ionic liquid crystalline (LC) system based on gallic ester and tetra‐ortho‐substituted azobenzene is designed and synthesized. All the prepared derivatives exhibit columnar hexagonal mesophases at room temperature either in their pristine form or on cooling from isotropic states. The strategic design of these molecules allows for rapid photoisomerization, which is further aided by the dynamic LC phase. These systems attains photostationary states (PSSs) within 5 min of charging and discharging. The maximum Z conversion on charging in the solid‐state at room‐temperature is ≈80% with a highest temperature rise of 9.1 °C on discharging. This new molecular design enables the efficient working of solar thermal fuels (STFs) even in low sunlight intensity conditions, potentially promoting widespread adoption for mitigating global energy demands. [ABSTRACT FROM AUTHOR]

Stimuli‐responsive surfaces have garnered intensive research attention in addressing the challenges of severe information leakage problems, but they exhibit limitations in terms of intricate preparation and compatibility. Herein, the study reports a time‐dependent wrinkled surface controlled by photo‐induced stress relaxation of azobenzene‐ containing crosslinked polymer network comprised of furan‐containing polymer (PEA‐Fu) and maleimide‐substituted azobenzene (AZO‐2MI) as skin layer. Two kinds of wrinkled surfaces induced by two crosslinked networks (thermal‐ and UV‐induced) can be prepared by Diels‐Alder reaction and UV‐induced radical coupling reaction, exhibiting distinct amplitude decrease rate resulted from different stress relaxation rate induced by photo‐isomerization of azobenzene. By UV preprogramming with photomasks, various time‐dependent wrinkle patterns are obtained and can be identified at specific times under 450 nm irradiation. The time window for information read out can be preset through different UV preprogramming time and boundary conditions to achieve multi‐level information encryption. Furthermore, the written information can be camouflaged as another “false” information by regional‐selective irradiation under 450 nm irradiation, which offers a new method for information protection. Based on distinctive time‐dependent characteristics and excellent stability, this responsive wrinkled surface offers bright prospects in multi‐level information encryption. [ABSTRACT FROM AUTHOR]

Orexinergic neurons are critically involved in regulating arousal, wakefulness, and appetite. Their dysfunction has been associated with sleeping disorders, and non-peptide drugs are currently being developed to treat insomnia and narcolepsy. Yet, no light-regulated agents are available to reversibly control their activity. To meet this need, a photoswitchable peptide analogue of the endogenous neuroexcitatory peptide orexin-B was designed, synthesized, and tested in vitro and in vivo. This compound – photorexin – is the first photo-reversible ligand reported for orexin receptors. It allows dynamic control of activity in vitro (including almost the same efficacy as orexin-B, high nanomolar potency, and subtype selectivity to human OX2 receptors) and in vivo in zebrafish larvae by direct application in water. Photorexin induces dose- and light-dependent changes in locomotion and a reduction in the successive induction reflex that is associated with sleep behavior. Molecular dynamics calculations indicate that trans and cis photorexin adopt similar bent conformations and that the only discriminant between their structures and activities is the positioning of the N-terminus. This, in the case of the more active trans isomer, points towards the OX2 N-terminus and extra-cellular loop 2, a region of the receptor known to be involved in ligand binding and recognition consistent with a "message-address" system. Thus, our approach could be extended to several important families of endogenous peptides, such as endothelins, nociceptin, and dynorphins among others, that bind to their cognate receptors through a similar mechanism: a "message" domain involved in receptor activation and signal transduction, and an "address" sequence for receptor occupation and improved binding affinity. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Photoresponsive liquid‐crystalline elastomers (LCEs) are promising candidates for light‐controlled soft actuators. Photoinduced stress/strain originates from the changes in mechanical properties after light irradiation. However, the correlation between the photoinduced mechanical performance and in‐use conditions such as stress/strain states and polymer network properties (such as effective crosslink density and dangling chain density) remains unexplored for practical applications. Here, isometric photo‐induced stress or isotonic strain is investigated at different operating strains or stresses, respectively, on LCEs with polymer network variations, produced by different amounts of solvent during polymerization. As the solvent volume increases, the moduli and photoinduced stresses decrease. However, the photo‐induced strain, fracture strain, fracture stress, and viscosity increase. The optical response performance initially increases with the operating strain/stress, peaks at a higher actuation strain/stress, and then, decreases depending on the polymer network. The maximum work densities, which also depend on the operating stress, are in the range of ≈200–300 kJm−3. These findings, highlighting the significant variations in the mechanical performance with the operating stress/strain ranges and amount of solvent used in the synthesis, are critical for designing LCE‐based mechanical devices. [ABSTRACT FROM AUTHOR]

With the rapid development of intelligent materials in recent years, intelligent hydrophobic materials have become a new research direction, and hydrophobic surfaces with adjustable wettability have enormous application potential in many fields. Generally speaking, surface wettability is determined by the combined effect of surface chemical composition and surface morphology. Therefore, the photoresponsive wettability of azobenzene-modified surfaces can be achieved by constructing rough surface of micro-nano scale and reducing the surface free energy. In this paper, we synthesized two photo responsive hydrophobic azobenzene derivatives (AAAB-PFDT and UAAB-PFDT), characterized their structure, thermal degradation behavior, and microscopic morphology. The light conversion performance of the two materials in dispersion was also studied using a UV–Vis spectrometer. By depositing the materials on the glass slide, the measurements of the water contact angle (WCA) under different lighting conditions were performed, demonstrating that both materials exhibit excellent photoswitchable hydrophobicity and reversibility. [ABSTRACT FROM AUTHOR]

Herein, we report the design, synthesis, and supramolecular behavior of 30 structurally diverse photoresponsive azobenzene molecular systems. To establish structure–property relationships, azobenzenes appended with N‐picolinyl and/or N‐benzyl groups tethered directly through carboxamides or via triazolylmethyl carboxamide linkages were explored. We have evaluated the photoswitching characteristics and thermal stability of the Z isomers through systematic studies. All the targets were also screened for their aggregation behavior and supramolecular aspects. Among all the derivatives, a few carboxamide‐based systems formed microcrystals upon aggregation, showing light responsiveness. In contrast, the derivatives tethered via triazolylmethyl carboxamide linkage exhibited hydrogel formation with excellent water‐absorbing capacity. All supramolecular aspects of the morphology of the microcrystal and hydrogel states and their stimuli‐responsiveness have been studied using spectroscopy and various microscopic techniques. [ABSTRACT FROM AUTHOR]

Underwater organisms exhibit sophisticated propulsion mechanisms, enabling them to navigate fluid environments with exceptional dexterity. Recently, substantial efforts have focused on integrating these movements into soft robots using smart shape‐changing materials, particularly by using light for their propulsion and control. Nonetheless, challenges persist, including slow response times and the need of powerful light beams to actuate the robot. This last can result in unintended sample heating and potentially necessitate tracking specific actuation spots on the swimmer. To tackle these challenges, new azobenzene‐containing photopolymerizable inks are introduced, which can be processed by extrusion printing into liquid crystalline elastomer (LCE) elements of precise shape and morphology. These LCEs exhibit rapid and significant photomechanical response underwater, driven by moderate‐intensity ultraviolet (UV) and green light, being the actuation mechanism predominantly photochemical. Inspired by nature, a biomimetic four‐lapped ephyra‐like LCE swimmer is printed. The periodically illumination of the entire swimmer with moderate‐intensity UV and green light, induces synchronous lappet bending toward the light source and swimmer propulsion away from the light. The platform eliminates the need of localized laser beams and tracking systems to monitor the swimmer's motion through the fluid, making it a versatile tool for creating light‐fueled robotic LCE free‐swimmers. [ABSTRACT FROM AUTHOR]

The crystal structures of two inter­mediates, 4-amino-3,5-di­fluoro­benzo­nitrile, C7H4F2N2 (I), and ethyl 4-amino-3,5-difluorobenzoate, C9H9F2NO2 (II), along with a visible-light-responsive azo­benzene derivative, diethyl 4,4′-(diazene-1,2-di­yl)bis­(3,5-difluoro­benzoate), C18H14F4N2O4 (III), obtained by four-step synthetic procedure, were studied using single-crystal X-ray diffraction. The mol­ecules of I and II demonstrate the quinoid character of phenyl rings accompanied by the distortion of bond angles related to the presence of fluorine substituents in the 3 and 5 (ortho) positions. In the crystals of I and II, the molecules are connected by N--H...N, N--H...F and N--H...O hydrogen bonds, C--H...F short contacts, and π-stacking inter­actions. In crystal of III, only stacking inter­actions between the molecules are found. [ABSTRACT FROM AUTHOR]

Sulfamethymidine, a commonly employed sulfonamide, is introduced into the human body through the food chain, posing a threat to human health. Consequently, the development of a rapid and efficient detection technique is imperative. In this investigation, a photoresponsive sulfamethyridiazine‐imprinted polymer was synthesized to etch a silicon core, thereby effectively addressing the limitations encountered with conventional molecularly imprinted polymers including diminished binding capacity, restricted site accessibility and sluggish binding kinetics. The photosensitive monomer utilized in the molecularly imprinted polymers is 5[(4 (methylacryloxy) phenyl) diazene] isophthalic acid, which exhibits a stimulating reaction mechanism. The N=N bond undergoes photoisomerization, transitioning between trans and cis configurations. The adsorption experiment provides additional evidence that the hollow molecularly imprinted polymers exhibit a higher adsorption capacity, achieving a value of 0.192 mmol L−1. The experiments conducted to assess selectivity and repeatability confirm that the photoresponsive molecularly imprinted polymers exhibit a high level of selectivity and favorable repeatability. Following four cycles, the adsorption rate remains consistently at 64.3%. Additionally, the recoveries of the actual samples ranged from 95.6% to 99.7%. This finding presents a novel approach to detecting the concentration of trace pollutants in intricate substrates. © 2024 Society of Industrial Chemistry. [ABSTRACT FROM AUTHOR]

Nanofilms that can fast permeate solvents and accurately sieve molecules are of significant importance for separation. A promising strategy is to align the inner cavities of macrocycles into the channels within nanofilms, and control the channel size by selecting the macrocycles. However, the channels outside the macrocycles are ignored. Here, we prepare nanofilms with hydrophobic channels (cyclodextrin inner cavity) and hydrophilic channels (cyclodextrin outer space) through interfacial polymerization of azobenzene-4,4′-dicarbonyl dichloride and amino-functionalized β-cyclodextrin. By utilizing the significant geometric changes caused by the photoisomerization of azobenzene, nanofilms with adjustable hydrophilic channel sizes were obtained. Our nanofilms have high permeability to polar and non-polar solvents, and can distinguish molecules with almost the same molecular weight but different shapes. This work expands the development of next-generation nanofilms generated through interfacial polymerization by incorporating rational molecular design. [ABSTRACT FROM AUTHOR]

Enzymes have flexible structures and can modulate the multiple catalytic sites efficiently for synergistic catalysis. Inspired by enzymes, various artificial catalysts have been designed, while controllable synergistic effects in artificial catalysts have never been reported. Here, we report the first example of photo‐regulated synergistic catalyst (PRSC) and the synergistic effects between acidic and basic sites can be regulated by light. PRSCs have acidic sites on pore walls and basic sites on pendant azobenzene groups, and photo‐regulation is achieved through azobenzene isomerization. In the cascade reaction of converting benzaldehyde dimethyl acetal (BA) to benzylidenemalononitrile (BM), the PRSC shows a change of up to 33.6% in BM yield. Mechanism exploration indicates that cis azobenzene makes the catalytic system more stable. The promoted adsorption energy of the reactant malononitrile (MN) on basic sites and the activated C atom of MN that connects to methylene groups are responsible for the tunable synergistic effects of PRSCs. [ABSTRACT FROM AUTHOR]

Dynamic, responsive materials can be built using photosurfactants (PS) that self-assemble into ordered nanostructures, such as micelles or liquid crystals. These PS contain photoswitchable groups, such as azobenzene (Azo) or, more recently, arylazopyrazoles (AAPs), which change shape and polarity on photoisomerisation between the E and Z states, thus changing the self-assembled structure. Small-angle X-ray scattering (SAXS) is a powerful technique to probe the morphology of PS and can be used to measure the mechanisms of structural changes using in-situ light irradiation with rapid, time-resolved data collection. However, X-ray irradiation has been shown previously to induce Z-to-E isomerisation of Azo-PS, which can lead to inaccuracies in the measured photostationary state. Here, we investigate the effect of light and X-ray irradiation on micelles formed from two different PS, containing either an Azo or AAP photoswitch using SAXS with in-situ light irradiation. The effect of X-ray irradiation on the Z isomer is shown to depend on the photoswitch, solvent, concentration and morphology. We use this to create guidelines for future X-ray experiments using photoswitchable molecules, which can aid more accurate understanding of these materials for application in solar energy storage, catalysis or controlled drug delivery.

The crystal structures of two intermediates, 4-amino-3,5-difluorobenzonitrile, C7H4F2N2 (I), and ethyl 4-amino-3,5-difluorobenzoate, C9H9F2NO2 (II), along with a visible-light-responsive azobenzene derivative, diethyl 4,4′-(diazene-1,2-diyl)bis(3,5-difluorobenzoate), C18H14F4N2O4 (III), obtained by four-step synthetic procedure, were studied using single-crystal X-ray diffraction. The molecules of I and II demonstrate the quinoid character of phenyl rings accompanied by the distortion of bond angles related to the presence of fluorine substituents in the 3 and 5 (ortho) positions. In the crystals of I and II, the molecules are connected by N—H...N, N—H...F and N—H...O hydrogen bonds, C—H...F short contacts, and π-stacking interactions. In crystal of III, only stacking interactions between the molecules are found.

The functionality and efficiency of proteins within a biological membrane are highly dependent on both the membrane lipid composition and the physiochemical properties of the solution. Lipid mesophases are directly influenced by changes in temperature, pH, water content or due to individual properties of single lipids such as photoswitchability. In this work, we were able to induce light- and temperature-driven mesophase transitions in a model membrane system containing a mixture of 1,2-dipalmitoyl-phosphatidylcholine phospholipids and azobenzene amphiphiles. We observed reversible and reproducible transitions between the lamellar and Pn3m cubic phase after illuminating the sample for 5 min with light of 365 and 455 nm wavelengths, respectively, to switch between the cis and trans states of the azobenzene N=N double bond. These light-controlled mesophase transitions were found for mixed complexes with up to 20% content of the photosensitive molecule and at temperatures below the gel-to-liquid crystalline phase transition temperature of 33°C. Our results demonstrate the potential to design bespoke model systems to study the response of membrane lipids and proteins upon changes in mesophase without altering the environment and thus provide a possible basis for drug delivery systems.

Azobenzene is a prototype and a building block of a class of molecules of extreme technological interest as molecular photo-switches. We present a joint experimental and theoretical study of its response to irradiation with light across the UV to x-ray spectrum. The study of valence and inner shell photo-ionization and excitation processes combined with measurement of valence photoelectron-photoion coincidence and mass spectra across the core thresholds provides a detailed insight into the site- and state-selected photo-induced processes. Photo-ionization and excitation measurements are interpreted via the multi-configurational restricted active space self-consistent field method corrected by second order perturbation theory. Using static modeling, we demonstrate that the carbon and nitrogen K edges of azobenzene are suitable candidates for exploring its photoinduced dynamics thanks to the transient signals appearing in background-free regions of the NEXAFS and XPS. [ABSTRACT FROM AUTHOR]

The geometrical re parameters of trans-azobenzene (E-AB) free molecule were refined by gas electron diffraction (GED) method using available experimental data obtained previously by S. Konaka and coworkers. Structural analysis was carried out by various techniques. First of all, these included the widely used molecular orbital constrained gas electron diffraction method and regularization method. The results of the refinements using different models were also compared—a semirigid model, three variants of one-dimensional dynamic models, and a two-dimensional pseudoconformer model. Several descriptions have been used due to the fact that E-AB has a shallow potential energy surface along the rotation coordinates of phenyl groups. Despite this, it turned out that the semirigid model is suitable for use for E-AB and allows good agreement with experimental data to be achieved. According to the results of GED structural analysis, coupled with the results of DLPNO-CCSD(T0) calculations, E-AB has a planar structure. Based only on GED data, it is impossible to unambiguously determine the rotational angle of the phenyl group due to the facts that (i) with rotation over a wide range of angles, the bonded distances in the molecule change insignificantly and (ii) potential function in a structural analysis within a dynamic model is not determined with the necessary accuracy. This work also examines the sensitivity of the GED method to structural changes caused by trans-cis isomerization. The paper also analyzes the applicability of different variants of density functional theory (DFT) calculations in GED structural analysis using E-AB as an example. There are not enough similar methodological works in the literature. This experimental and methodological information is especially important and relevant for planning and implementing GED experiments and corresponding processing of the results for azobenzene derivatives, in which the conformer and isomeric diversity are even more complicated due to the presence of different substituents.

The title copper(II) complex, [Cu(C18H19N3O3)(C3H4N2)], consists of a tridentate ligand synthesized from L-leucine and azobenzene-salicylaldehyde. One imidazole molecule is additionally coordinated to the copper(II) ion in the equatorial plane. The crystal structure features N—H...O hydrogen bonds. A Hirshfeld surface analysis indicates that the most important contributions to the packing are from H...H (52.0%) and C...H/H...C (17.9%) contacts.

Building stimuli-responsive supramolecular systems is a way for chemists to achieve spatio-temporal control over complex systems as well as a promising strategy for applications ranging from sensing to drug-delivery. For its large spectrum of biological and biomedical implications, adenosine 5'-triphosphate (ATP) is a particularly interesting target for such a purpose but photoresponsive ATP-based systems have mainly been relying on covalent modification of ATP. Here, we show that simply mixing ATP with AzoDiGua, an azobenzene-guanidium compound with photodependent nucleotide binding affinity, results in the spontaneous self-assembly of the two non-fluorescent compounds into photoreversible, micrometer-sized and fluorescent aggregates. Obtained in water at room temperature and physiological pH, these supramolecular structures are dynamic and respond to several chemical, physical and biological stimuli. The presence of azobenzene allows a fast and photoreversible control of their assembly. ATP chelating properties to metal dications enable ion-triggered disassembly and fluorescence control with valence-selectivity. Finally, the supramolecular aggregates are disassembled by alkaline phosphatase in a few minutes at room temperature, resulting in enzymatic control of fluorescence. These results highlight the interest of using a photoswitchable nucleotide binding partner as a self-assembly brick to build highly responsive supramolecular entities involving biological targets without the need to covalently modify them. Building stimuli-responsive supramolecular materials enables spatiotemporal control over complex systems, and is a promising strategy for a range of applications. Here, mixing adenosine 5'-triphosphate (ATP) with an azobenzene-guanidium compound possessing photodependent nucleotide binding affinity is shown to result in the spontaneous photo-reversible self-assembly of these compounds into micrometer-sized fluorescent aggregates that display dynamic responses to several chemical, physical and biological stimuli. [ABSTRACT FROM AUTHOR]

Dynamic covalent liquid crystal networks (DCv‐LCNs) with straightforward (re)programmability, reprocessability, and recyclability facilitates the manufacture of sophisticated LCN actuators and intelligent robots. However, the DCv‐LCNs are still limited to heat‐assisted programming and polymer‐to‐polymer reprocessing/recycling, which inevitably lead to deterioration of the LCN structures and the actuation performances after repeated programming/processing treatments, owing to the thermal degradation of the polymer network and/or external agent interference. Here, a totally renewable azobenzene‐based DCv‐LCN with room‐temperature programmability and polymer‐to‐monomers chemical recyclability is reported, which was synthesized by crosslinking the azobenzene‐containing dibenzaldehyde monomer and the triamine monomer via the dynamic and dissociable imine bonds. Thanks to the water‐activated dynamics of the imine bonds, the resultant DCv‐LCN can be simply programmed, upon water‐soaking at room temperature, to yield a UV/Vis light‐driven actuator. Importantly, the reported DCv‐LCN undergoes depolymerization in an acid‐solvent medium at room temperature because of the acid‐catalyzed hydrolysis of the imine bonds, giving rise to easy separation and recovery of both monomers in high purity, even with tolerance to additives. The recovered pure monomers can be used to regenerate totally new DCv‐LCNs and actuators, and their functionalities can be reconfigured by removing old and introducing new additives, by implementing the closed‐loop polymer‐monomers‐polymer recycling. [ABSTRACT FROM AUTHOR]

Chemical photoswitches have become a widely used approach for the remote control of biological functions with spatiotemporal precision. Several molecular scaffolds have been implemented to improve photoswitch characteristics, ranging from the nature of the photoswitch itself (e.g. azobenzenes, dithienylethenes, hemithioindigo) to fine‐tuning of aromatic units and substituents. Herein, we present deuterated azobenzene photoswitches as a general means of enhancing the performance of photopharmacological molecules. Deuteration can improve azobenzene performance in terms of light sensitivity (higher molar extinction coefficient), photoswitch efficiency (higher photoisomerization quantum yield), and photoswitch kinetics (faster macroscopic rate of photoisomerization) with minimal alteration to the underlying structure of the photopharmacological ligand. We report synthesized deuterated azobenzene‐based ligands for the optimized optical control of ion channel and G protein‐coupled receptor (GPCR) function in live cells, setting the stage for the straightforward, widespread adoption of this approach. [ABSTRACT FROM AUTHOR]

Stimuli‐responsive block copolymer nanoparticles (NPs) have received close attention in recent years owing to their tremendous application potential in smart materials. Azobenzene‐containing NPs are widely studied due to the advantages of light as a stimulus and fast reversible trans–cis isomerization of azobenzene chromophores. However, the inefficient preparation process and difficult reversible transformation of morphologies limit their development. Herein it is demonstrated that the light‐triggered reversible swelling behavior of wormlike NPs with high azobenzene content could be realized via confined deformation. These worms are prepared in large quantities via polymerization‐induced self‐assembly based on the copolymerization of 11‐(4‐(4‐butylphenylazo)phenoxy)undecyl methacrylate (MAAz) and N‐(methacryloxy)succinimide (NMAS) monomers. Upon UV/visible light irradiation, the reversible deformation of worms is achieved when the feed molar ratio of NMAS/MAAz is relatively high or via crosslinking using diamines, which leads to the reduction of the photoisomerization efficiency. The diameter variation of the worms is influenced by the amount and types of crosslinkers. Moreover, the scalability of this strategy is further proved by the fabrication of photo‐ and reductant‐responsive crosslinked worms. It is expected that this study not only provides a new route to affording reversible photoresponsive NPs but also offers a unique insight into the reversible photodeformation mechanism of azobenzene‐containing NPs. [ABSTRACT FROM AUTHOR]

Conjugated polymers (CPs) have been developed quickly as an emerging functional material with applications in optical and electronic devices, owing to their highly electron‐delocalized backbones and versatile side groups for facile processibility, high mechanical strength, and environmental stability. CPs exhibit multistimuli responsive behavior and fluorescence quenching properties by incorporating azobenzene functionality into their molecular structures. Over the past few decades, significant progress has been made in developing functional azobenzene‐based conjugated polymers (azo‐CPs), utilizing diverse molecular design strategies and synthetic pathways. This article comprehensively reviews the rapidly evolving research field of azo‐CPs, focusing on the structural characteristics and synthesis methods of general azo‐CPs, as well as the applications of charged azo‐CPs, specifically azobenzene‐based conjugated polyelectrolytes (azo‐CPEs). Based on their molecular structures, azo‐CPs can be broadly categorized into three primary types: linear CPs with azobenzene incorporated into the side chain, linear CPs with azobenzene integrated into the main chain, and branched CPs containing azobenzene moieties. These systems are promising for biomedical applications in biosensing, bioimaging, targeted protein degradation, and cellular apoptosis. [ABSTRACT FROM AUTHOR]

Photoelectrocatalytic (PEC) reduction of nitrobenzene (NB) is an extremely promising technology for renewable energy utilization and conversion. PEC reduction of NB to produce higher‐value azobenzene (AZB) instead of aniline (AN), which is now commonly reported, is not currently achievable. In this work, we fabricated Ag nanoparticles (AgNPs)‐decorated silicon nanocone (SiNC) array photocathodes with which the PEC reduction of NB to azobenzene (AZB) was realized for the first time. The SiNC array structure constructed by cryogenic dry etching greatly improved the light absorption ability of the photoelectrode. Ag was chosen as the cocatalyst because of its larger potential difference for the NB reduction reaction and the competing side reaction hydrogen evolution reaction. The Schottky junction formed by AgNPs with Si facilitates the rapid extraction of photogenerated electrons to participate in the PEC reaction. Under the optimized conditions, the PEC reduction of NB was achieved with a conversion of more than 90 %, with the reduction products being mainly AZB (9 : 1 ratio of AZB to AN) as well as excellent stability. The present work provides a photoelectrode that highly selectively PEC reduction of NB to AZB, and also provides insights into the design and preparation of high‐performance silicon‐based photoelectrodes. [ABSTRACT FROM AUTHOR]

A macrocyclic azobenzene with unique thermal stability, demonstrating potential for use in optical data storage material is presented: The Z‐isomer of this novel photoswitch exhibits unparalleled thermal stability, with a thermal half‐life surpassing 120 years at 25 °C. This stability is attributed to the strategic fluorination at two ortho‐ and both para‐positions. Comparative analyses involving its non‐fluorinated counterpart, ortho‐only‐fluorinated variant, and open‐chain analog are performed. Employing NMR and UV–vis spectroscopy, X‐ray diffraction, alongside Arrhenius, Eyring, and DFT calculations, revealed insights into its extraordinary stability. Furthermore, when incorporated into poly(methylmethacrylate), this material showcase efficient switching with visible light in the solid state, emphasizing its potential for optical data storage applications. [ABSTRACT FROM AUTHOR]

The development of photoresponsive systems with non‐invasive orthogonal control by distinct wavelengths of light is still in its infancy. In particular, the design of photochemically triggered‐orthogonal systems integrated into solid materials that enable multiple dynamic control over their properties remains a longstanding challenge. Here, we report the orthogonal and reversible control of two types of photoswitches in an integrated solid porous framework, that is, visible‐light responsive o‐fluoroazobenzene and nitro‐spiropyran motifs. The properties of the constructed material can be selectively controlled by different wavelengths of light thus generating four distinct states providing a basis for dynamic multifunctional materials. Solid‐state NMR spectroscopy demonstrated the selective transformation of the azobenzene switch in the bulk, which in turn modulates N2 and CO2 adsorption. [ABSTRACT FROM AUTHOR]

The geometrical re parameters of trans-azobenzene (E-AB) free molecule were refined by gas electron diffraction (GED) method using available experimental data obtained previously by S. Konaka and coworkers. Structural analysis was carried out by various techniques. First of all, these included the widely used molecular orbital constrained gas electron diffraction method and regularization method. The results of the refinements using different models were also compared—a semirigid model, three variants of one-dimensional dynamic models, and a two-dimensional pseudoconformer model. Several descriptions have been used due to the fact that E-AB has a shallow potential energy surface along the rotation coordinates of phenyl groups. Despite this, it turned out that the semirigid model is suitable for use for E-AB and allows good agreement with experimental data to be achieved. According to the results of GED structural analysis, coupled with the results of DLPNO-CCSD(T0) calculations, E-AB has a planar structure. Based only on GED data, it is impossible to unambiguously determine the rotational angle of the phenyl group due to the facts that (i) with rotation over a wide range of angles, the bonded distances in the molecule change insignificantly and (ii) potential function in a structural analysis within a dynamic model is not determined with the necessary accuracy. This work also examines the sensitivity of the GED method to structural changes caused by trans-cis isomerization. The paper also analyzes the applicability of different variants of density functional theory (DFT) calculations in GED structural analysis using E-AB as an example. There are not enough similar methodological works in the literature. This experimental and methodological information is especially important and relevant for planning and implementing GED experiments and corresponding processing of the results for azobenzene derivatives, in which the conformer and isomeric diversity are even more complicated due to the presence of different substituents. [ABSTRACT FROM AUTHOR]

Photoresponsiveness of materials is critical to their tunability and efficiency in terminal applications. Photoresponsive metal-organic polyhedra (PMOPs) feature intrinsic pores and remote controllability, but aggregation of PMOPs in solid state hampers their photoresponsiveness seriously. Herein, we report the construction of a new PMOP (Cu24(C16H12N2O4)12(C18H22O5)12, denoted as MOP-PR-LA), where long alkyl (LA) chains act as the intermolecular poles, propping against adjacent PMOP molecules to create individual microenvironment benefiting the isomerization of photoresponsive (PR) moieties. Upon ultraviolet (UV)- and visible-light irradiation, MOP-PR-LA is much easier to isomerize than the counterpart MOP-PR without LA. For propylene adsorption, MOP-PR has a low change of adsorption capacity (9.9%), while that of MOP-PR-LA reaches 58.6%. Density functional theory calculations revealed that PR in the cis state has a negative effect on adsorption, while the trans state of PR favors adsorption. This work might open an avenue for the construction of photoresponsive materials with high responsiveness and controllability. [ABSTRACT FROM AUTHOR]

The novel photoswitchable ligand 3,3'‐Azobenz(metPA)2 (1) is used to prepare a [Cu2(1)2](BF4)2 metallocycle (2), whose photoisomerization was characterized using static and time‐resolved spectroscopic methods. Optical studies demonstrate the highly quantitative and reproducible photoinduced cyclic E/Z switching without decay of the complex. Accordingly and best to our knowledge, [Cu2(1)2](BF4)2 constitutes the first reversibly photoswitchable (3d)‐metallocycle based on azobenzene. The photoinduced multiexponential dynamics in the sub‐picosecond to few picosecond time domain of 1 and 2 have been assessed. These ultrafast dynamics as well as the yield of the respective photostationary state (PSSZ = 65 %) resemble the behavior of archetypical azobenzene. Also, the innovative pump‐probe laser technique of gas phase transient photodissociation (τ‐PD) in a mass spectrometric ion trap was used to determine the intrinsic relaxation dynamics for the isolated complex. These results are consistent with the results from femtosecond UV/Vis transient absorption (fs‐TA) in solution, emphasizing the azobenzene‐like dynamics of 2. This unique combination of fs‐TA and τ‐PD enables valuable insights into the prevailing interplay of dynamics and solvation. Both analyses (in solution and gas phase) and quantum chemical calculations reveal a negligible effect of the metal coordination on the switching mechanism and electronic pathway, which suggests a non‐cooperative isomerization process. [ABSTRACT FROM AUTHOR]

Luminescence in the second near‐infrared (NIR‐II, 1,000–1,700 nm) window is beneficial especially for deep tissue imaging and optical sensors because of intrinsic high permeability through various media. Strong electron‐acceptors with low‐lying lowest unoccupied molecular orbital (LUMO) energy levels are a crucial unit for donor–acceptor (D–A) π‐conjugated polymers (CPs) with the NIR‐II emission property, however, limited kinds of molecular skeletons are still available. Herein, D–A CPs involving fluorinated boron‐fused azobenzene complexes (BAz) with enhanced electron‐accepting properties are reported. Combination of fluorination at the azobenzene ligand and trifluoromethylation at the boron can effectively lower the LUMO energy level down to −4.42 eV, which is much lower than those of conventional strong electron‐acceptors. The synthesized series of CPs showed excellent absorption/fluorescence property in solution over a wide NIR range including NIR‐II. Furthermore, owing to the inherent solid‐state emissive property of the BAz skeleton, obvious NIR‐II fluorescence from the film (up to λFL=1213 nm) and the nanoparticle in water (λFL=1036 nm, brightness=up to 29 cm−1 M−1) were observed, proposing that our materials are applicable for developing next‐generation of NIR‐II luminescent materials. [ABSTRACT FROM AUTHOR]

Molecular photoswitches are widely used in material sciences, physics, chemistry, and biology. As needs grow more complex, materials have to react more than one‐dimensionally. The use of multiple photoswitches at once opens manifold opportunities for further improved and more complicated systems. However, this requires independent addressability, i.e., orthogonality, and reversible processes. Herein, the first study on ultrafast excited state dynamics of two orthogonal photoswitches, a push‐pull azobenzene and a donor‐acceptor Stenhouse adduct is reported. In order to gain detailed insight in their interactions and mutual influences on their photoswitching behavior, they are addressed individually and simultaneously via transient absorption spectroscopy supported by quantum chemical calculations. They show reversible photoswitchability and in addition, can be used in 4D printing to provide easy access to a plethora of functional devices. Furthermore, environmental influences on the excited state dynamics are examined using different solvents and thin films. Both compounds photoisomerize independently when addressed individually or simultaneously and only little impacts on the excited state dynamics are found. Especially the vibrational relaxation is affected by different surroundings changing the energy dissipation while hardly affecting the electronic states involved. The orthogonal and simultaneous addressability is thereby crucial for their usage in 4D printed microactuators. [ABSTRACT FROM AUTHOR]