Extending Conjugation of Linear Cyanostilbene Derivatives via a Pyridine Moiety for Multi-Stimuli-Responsive Fluorescence Organogels

In the design of effective gelators with aggregation-induced emission behavior, amide and cholesterol moieties are generally used to provide multiple driving forces for gelation. In this work, a series of linear cyanostilbene gelators with a pyridine moiety and different lengths of the alkoxyl group, i.e., CSpy-Cn, have been synthesized through nucleophilic substitution and Knoevenagel reaction. The direct connection of pyridine extends the conjugation of the cyanostilbene moiety, while the alkoxyl group can regulate the solubility of the compounds so that the compounds can serve as gelators for common solvents such as acetonitrile, dimethyl sulfoxide, and ethanol at ultra-low concentrations. At the same time, the cyanostilbene group makes the compounds undergo photoisomerization and emit fluorescence under UV light, while the pyridine group can serve as an acid-base responsive group due to easy protonation. The gels can respond to temperature, light, and organic acid/base. The fluorescence intensity and color can reversibly change during the gel-sol transitions. Finally, a thin film based on the CSpy-C8 xerogel has been prepared and utilized as a multi-stimuli-responsive fluorescence display for information storage and anti-counterfeiting.

Smart supramolecular photoresponsive gelator with long-alkyl chain azobenzene incorporated sugar derivatives for recycling aromatic solvents and sequestration of cationic dyes

Phase-selective gelation of low molecular-weight photoresponsive organogelator possessing long aliphatic chain azobenzene sugar derivatives and its applications in the recycling of aromatic solvents and also the removal of cationic dyes is reported. Very low critical gelation concentration (CGC) in aromatic solvents implies that it acts as a very good gelator. The photoinduced gel-to-sol transition was attained by irradiation with UV light at 350 nm. These organogels work as a selective adsorbent for efficiently removing cationic dyes from individual aqueous dye solutions and in a mixture of cationic and anionic dye solutions show more than 95% removal within 12 h. These insights indicate that these sugar derivatives could be exploited in implementing smart materials for environmental remediation.

Acylhydrazone-based supramolecular assemblies undergoing a converse sol-to-gel transition on trans → cis photoisomerization

Photoisomeric supramolecular assemblies have drawn enormous attention in recent years. Although it is a general rule that photoisomerization from a less to a more distorted isomer causes the destruction of assemblies, this photoisomerization process inducing a converse transition from irregular aggregates to regular assemblies is still a great challenge. Here, we report a converse sol-to-gel transition derived from the planar to nonplanar photoisomer conversion, which is in sharp contrast to the conventional light-induced gel collapse. A well-designed acylhydrazone-linked monomer is exploited as a photoisomer to realize the above-mentioned phase transition. In the monomer, imine is responsible for trans-cis interconversion and amide generates intermolecular hydrogen bonds enabling the photoisomerization-driven self-assembly. The counterintuitive feature of the sol-to-gel transition is ascribed to the partial trans → cis photoisomerization of acylhydrazone causing changes in stacking mode of monomers. Furthermore, the reversible phase transition is applied in the valves formed in situ in microfluidic devices, providing fascinating potential for miniature materials.

Fluorescent supramolecular polymers of barbiturate dyes with thiophene-cored twisted π-systems

Because supramolecular polymerization of emissive π-conjugated molecules depends strongly on π-π stacking interaction, the formation of well-defined one-dimensional nanostructures often results in a decrease or only a small increase of emission efficiency. This is also true for our barbiturate-based supramolecular polymers wherein hydrogen-bonded rosettes of barbiturates stack quasi-one-dimensionally through π-π stacking interaction. Herein we report supramolecular polymerization-induced emission of two regioisomeric 2,3-diphenylthiophene derivatives functionalized with barbituric acid and tri(dodecyloxy)benzyl wedge units. In CHCl3, both compounds are molecularly dissolved and accordingly poorly emissive due to a torsion-induced non-radiative decay. In methylcyclohexane-rich conditions, these barbiturates self-assemble to form crystalline nanofibers and exhibit strongly enhanced emission through supramolecular polymerization driven by hydrogen-bonding. Our structural analysis suggests that the barbiturates form a tape-like hydrogen-bonding motif, which is rationalized by considering that the twisted geometries of 2,3-diphenylthiophene cores prevend the competing rosettes from stacking into columnar supramolecular polymers. We also found that a small difference in the molecular polarity originating from the substitutional position of the thiophene core influences interchain association of the supramolecular polymers, affording different luminescent soft materials, gel and nanosheet.

Aggregation-Induced Emission-Active Gels: Fabrications, Functions, and Applications

Chromophores that exhibit aggregation-induced emission (i.e., aggregation-induced emission luminogens [AIEgens]) emit intense fluorescence in their aggregated states, but show negligible emission as discrete molecular species in solution due to the changes in restriction and freedom of intramolecular motions. As solvent-swollen quasi-solids with both a compact phase and a free space, gels enable manipulation of intramolecular motions. Thus, AIE-active gels have attracted significant interest owing to their various distinctive properties and promising application potential. Herein, a comprehensive overview of AIE-active gels is provided. The fabrication strategies employed are detailed, and the applications of AIEgens are summarized. In addition, the gel functions arising from the AIE moieties are revealed, along with their structure-property relationships. Furthermore, the applications of AIE-active gels in diverse areas are illustrated. Finally, ongoing challenges and potential means to address them are discussed, along with future perspectives on AIE-active gels, with the overall aim of inspiring research on novel materials and ideas.

The transfer and amplification of cyanostilbene molecular function to advanced flexible optical paints through self-crosslinkable side-chain liquid crystal polysiloxanes

A self-crosslinkable side-chain liquid crystal polysiloxane containing cyanostilbene (Si-CSM) was newly synthesized for the development of a new generation of flexible optical paints. The photoisomerization of the cyanostilbene moiety at the molecular level was transferred and amplified to the phase transition of Si-CSM, resulting in changes in the macroscopic optical properties of the Si-CSM thin film. The self-crosslinking reaction between Si-H groups in the Si-CSM polymer backbone caused the self-crosslinked Si-CSM thin film to be very elastic and both thermally and chemically stable. Therefore, the self-crosslinked Si-CSM thin film endured stretching and bending deformations under relatively harsh conditions. In addition, the uniaxially oriented and self-crosslinked Si-CSM thin film generated linearly polarized light emission. Polarization-dependent and photopatternable secret coatings were fabricated via a spontaneous self-crosslinking reaction after coating the Si-CSM paint and irradiating ultraviolet (UV) light through a photomask. This newly developed flexible optical Si-CSM paint can be applied in next-generation optical coatings.

Tunable morphologies and emission of photosensitive supramolecular self-assemblies through positional and trans-cis isomerization

Cyanostilbene units are widely attractive as photoresponsive supramolecular building blocks whose structures and emission can be modulated by trans-cis isomerization. Generally, the change of properties is related to the molecular structure of cyanostilbene, which is still unpredictable and needs to be explored. Herein, two benzene-1,3,5-tricarboxamide (BTA) based cyanostilbene derivatives with different cyano positions have been designed to investigate the emission as well as structural changes during the trans-cis photoisomerization process in monomer and aggregation states, respectively. In the monomer state, the derivative with cyano groups at the outer position, β-BTTPA, exhibits obvious emission enhancement upon UV irradiation, while the other derivative (α-BTTPA) shows emission quenching. In addition, upon the formation of aggregates, β-BTTPA forms nano-level fibers with blue-green emission, but α-BTTPA forms micron-level flat ribbons with blue emission. More importantly, also driven by the trans-cis photoisomerization, the self-assemblies show morphological transitions (ribbons/fibers to spheres) due to the fact that the equilibrium of the system is broken by the photoreactions. Such changes further contribute to emission switching as well as enhanced hydrophobic properties.

Multi-color tunable circularly polarized luminescence in one single AIE system

Circularly polarized luminescence (CPL) materials with a large luminescence dissymmetry factor (g_lum) and multi-color properties are very attractive. While multi-color tunable CPL can be realized by different organic dyes, the challenge of realizing both a higher g_lum and multiple colors using a single component remains. Here, we design an aggregation-induced emission (AIE) fluorophore, which is a pyridine functionalized cyanostilbene attached to a chiral unit, and realize multi-color tunable CPL with a high g_lum. The compound can self-assemble into a nanohelix and form both gel and xerogel films, exhibiting blue CPL with large g_lum values of −3.0 × 10⁻² and −1.7 × 10⁻², respectively. With the assistance of pyridine protonation, the xerogel films exhibit red-shifted CPL signals from 480 nm to 530 nm, covering from blue via green and yellow to orange. Additionally, the g_lum remains constant during the process. This work paves a simple and convenient way to construct multi-color tunable CPL materials using a single molecule.

A multi-color tunable circularly polarized luminescence (CPL) xerogel film with a large luminescence dissymmetry factor (g_lum) is achieved using a single compound upon protonation.

Selective Cu(ii) sensing by a versatile AIE cyanostilbene-based gel system

Cyanostilbene-based derivatives 1-3 were designed, synthesized and fully characterized. By screening their gelating abilities, we observed that the subtle difference in the position of the pyridine nitrogen greatly affected the resulting fluorescence and gelation properties. Notably, 1 was found to be a versatile ambidextrous gelator capable of forming organo-, hydro-, and Cu(ii) specific metallogels. Furthermore, a rare organogel-to-metallogel transformation at room temperature was also observed upon exposure of the 1-DMSO/H₂O gel to aqueous Cu(ii). This process, accompanied by colour and fluorescence changes, provides an effective strategy for the preparation of novel sensing soft materials.

Multi-stimuli responsive supramolecular gels based on a D-π-A structural cyanostilbene derivative with aggregation induced emission properties

Developing multi-stimuli responsive fluorescent gel materials in a single system remains challenging. Gelator molecules with classical fluorophores suffer from the aggregation-caused quenching (ACQ) effect, limiting their applications further. Herein, a novel V-shaped cyanostilbene-based molecule (BAPBIA) with aggregation induced emission (AIE) characteristics and great gelation ability was synthesized and was found to exhibit multi-stimuli responsive behaviors. Reversible gel-sol phase transitions together with emission quenching are realized in response to external stimuli including heat, light and fluoride ions. Especially, the introduction of a dimethylaniline group (donor) and a cyano group (acceptor) generates a D-π-A structure, further leading to an intramolecular charge transfer (ICT) effect, which enlarges the emission contrast with the variation of the distribution of charge. Thus, upon trifluoroacetic acid (TFA) triggered protonation of the dimethylaniline group, not only a gel-sol transition but also emission color switching (yellow-to-blue) is achieved due to the loss of the ICT effect. This work paves an easy way to construct fully reversible multi-stimuli responsive fluorescence modulation smart materials.

Perfluoroarene induces a pentapeptidic hydrotrope into a pH-tolerant hydrogel allowing naked eye sensing of Ca2+ ions

Self-assembly of a novel thermoresponsive, pyrene-appended oligopeptide sequence VPGKP (PyP) leads to the formation of spherical aggregates in water. The sizes of the globular aggregates of the peptide, PyP, strongly depend on the temperature of its suspension in water and decrease with the decrease in temperature showing a lower critical solution temperature (LCST) phenomenon. Furthermore, a pyrene-octafluoronaphthalene (OFN) 'pair' has been used as a supramolecular synthon to induce hydrogelation of PyP in the presence of an equimolar amount of OFN via complementary quadrupole-quadrupole interactions. The gel shows excellent pH tolerance and thixotropic behavior. Detailed studies suggest the existence of lamellar packing of the gelators in a right-handed helical fashion which yields globular aggregates. The globular aggregates are sticky in nature and form a gel via inter-globular interactions. Addition of Ca2+ ions reinforces the mechanical strength and also reduces the critical gelator concentration of the native gel through coordination with the free -COO- group of the gelator. Therefore, the present hydrogel system could further be used as a naked eye sensor of Ca2+ ions.

Insights into a novel class of azobenzenes incorporating 4,6-O-protected sugars as photo-responsive organogelators

A novel class of 4,6-O-butylidene/ethylidene/benzylidene β-d-glucopyranose gelator functionalized with photo-responsive azobenzene moieties were designed and synthesized and also characterized using different spectral techniques. These azobenzene-based organogelators can gel even at lower concentrations (critical gelation concentration – 0.5% and 1%). A morphological study of the gels shows one-dimensional aggregated bundles and helical fibres. The main driving force for the self-assembly is through cooperative interactions exhibited by the different groups viz., sugar hydroxyl (hydrogen bonding interaction), azobenzene (aromatic π–π interaction) and alkyl chain of the protecting group (van der Waals interaction).

A novel class of 4,6-O-butylidene/ethylidene/benzylidene β-d-glucopyranose gelator functionalized with photo-responsive azobenzene moieties were designed and synthesized and also characterized using different spectral techniques.

Branching effect on triphenylamine-CF3 cyanostilbenes: enhanced emission and aggregation in water

Aggregation-induced emission and gelation behavior of symmetric and asymmetric triphenylamines

Hierarchical self-assembly of a fluorescence emission-enhanced organogelator and its multiple stimuli-responsive behaviors

A discrete hexagonal metallacycle 1 decorated with tetraphenylethylene, amide groups and long hydrophobic alkyl chains was constructed via [3 + 3] coordination-driven self-assembly, from which the fluorescence emission-enhanced organogelator with multiple stimuli-responsiveness was successfully prepared via hierarchical self-assembly.

Self-Assembled α-Cyanostilbenes for Advanced Functional Materials

In the specific context of condensed media, the significant and increasing recent interest in the α-cyanostilbene (CS) motif [ArCHC(CN)Ar] is relevant. These compounds have shown remarkable optical features in addition to interesting electrical properties, and hence they are recognized as very suitable and versatile options for the development of functional materials. This progress report is focused on current and future use of CS structures and molecular assemblies with the aim of exploring and developing for the next generations of functional materials. A critical selection of illustrative materials that contain the CS motif, including relevant subfamilies such as the dicyanodistyrylbenzene and 2,3,3-triphenylacrylonitrile shows how, driven by the self-assembly of CS blocks, a variety of properties, effects, and possibilities for practical applications can be offered to the scientific community, through different rational routes for the elaboration of advanced materials. A survey is provided on the research efforts directed toward promoting the self-assembly of the solid state (polycrystalline solids, thin films, and single crystals), liquid crystals, nanostructures, and gels with multistimuli responsiveness, and applications for sensors, organic light-emitting diodes, organic field effect transistors, organic lasers, solar cells, or bioimaging purposes.

Tunable multicolor emissions in a monocomponent gel system by varying the solvent, temperature and fluoride anion

The facile tuning of the fluorescent properties of organogels is highly desirable for optical switches, light-emitting diodes, chemosensors and bioprobes. The design of organic molecules with multiple emission colors but only one molecular platform remains challenging. Herein, a new cholesterol-based organogelator N1 containing D-A pairs (salicylaldehyde and naphthalimide units) was designed. We successfully obtained multiple solvent-tuned emission colors in both the solution and gel states using a unimolecular platform. Moreover, the effects of the solvent on the gel morphology, rheology and anion-responsive properties were studied. Finally, we showed that the gel in benzene displayed reversible thermochromic properties with changes in emission color from yellow-green to red. Several experiments suggested that a short-distance and ordered array of the D-A pairs facilitated the efficient intermolecular electron transfer of the fluorophores.

Photophysical studies of pyrenyl cyanostyrenes: effect of trifluoromethyl substitution on gelation

Efficient organogel formation with CF₃ substituted styrylpyrenes.

A dual response organogel system based on an iridium complex and a Eu(iii) hybrid for volatile acid and organic amine vapors

A thiophene-based hybrid organogel system consisting of complex iridium (Ir) and EuCl₃·6H₂O was designed and synthesized to realize dual responses to volatile acids and organic amine vapors. The photophysical properties and self-assembly of compound 1 and the hybrid organogel were also studied. Compound 1 could gelate some organic solvents and self-assemble into 3D nanofibers in the gels. The stable hybrid organogel 1-Ir-Eu could be obtained after addition of complex Ir and EuCl₃·6H₂O. FTIR spectral results showed that the hydrogen bond still remained even upon addition of complex Ir, EuCl₃·6H₂O, NaOH and CF₃COOH to organogel 1. Interestingly, the emission properties of the hybrid organogel 1-Ir-Eu could undergo interconversion between cyan light and red light via addition of NaOH and CF₃COOH. The emission properties of xerogel film 1-Ir-Eu obtained in the presence of NaOH could also undergo fast and reversible transition in response to volatile acids such as CF₃COOH, formic acid, acetic acid, propionic acid and organic amine vapors such as ammonium hydroxide, Et₃N, tripropylamine, and ethylenediamine. The emission spectral change of Ir-Eu in the organogel or xerogel in the presence of base and acid demonstrated the formation of a new complex between complex Ir and EuCl₃·6H₂O. This dual-response process could be repeated many times. Contact angle experiment results further showed the morphology and internal components of the xerogel film surface in the process of response to gaseous CF₃COOH and Et₃N. This work provides a method for producing multifunctional supramolecular materials for sensing volatile acids and organic amine vapors.

Ultraviolet Patterned Calixarene-Derived Supramolecular Gels and Films with Spatially Resolved Mechanical and Fluorescent Properties

Supramolecular assemblies have in the past been considered mechanically weak and in most cases unable to withstand their own weight. Calixarene-derived networks can, however, provide robust supramolecular gels. Incorporating a photoreactive stilbene moiety, we show that the aggregation state of the material can be tuned by heating and UV exposure in order to control the mechanical as well as the fluorescent properties. Regulating the extent of heating to control the proportion of H-aggregates and J-aggregates and further cross-linking of H-aggregates by control over UV exposure allows for adjustable photopatterning of the fluorescence as well as the material stiffness in the range from ∼100 to 450 kPa. We expect this straightforward supramolecular system will be suitable for advanced prototyping in applications where modulus and shape are important design criteria.

Simple modification of basic dyes with bulky &symmetric WCAs for improving their solubilities in organic solvents without color change

A simple and easy solubility enhancement of basic dyes was performed with bulky and symmetric weakly coordinating anions (WCAs). The WCAs decreased the ionic character of the dyes by broadening the partial charge distribution and causing a screening effect on the ionic bonding. This new modification with WCAs has advantages in that it has no influence on the optical properties of the dyes. The solubilities of unmodified and modified dyes were tested in several organic solvents. X-ray powder diffraction patterns of the dyes were measured. Color films were prepared with the dyes and their color loci were analyzed to evaluate the optical properties. By the modification with WCAs, commercial basic dyes showed sufficient solubilities for be applied to various applications while preserving their superior optical properties.

Electrothermally Driven Fluorescence Switching by Liquid Crystal Elastomers Based On Dimensional Photonic Crystals

In this article, the fabrication of an active organic-inorganic one-dimensional photonic crystal structure to offer electrothermal fluorescence switching is described. The film is obtained by spin-coating of liquid crystal elastomers (LCEs) and TiO₂ nanoparticles alternatively. By utilizing the property of LCEs that can change their size and shape reversibly under external thermal stimulations, the λ_max of the photonic band gap of these films is tuned by voltage through electrothermal conversion. The shifted photonic band gap further changes the matching degree between the photonic band gap of the film and the emission spectrum of organic dye mounting on the film. With rhodamine B as an example, the enhancement factor of its fluorescence emission is controlled by varying the matching degree. Thus, the fluorescence intensity is actively switched by voltage applied on the system, in a fast, adjustable, and reversible manner. The control chain of using the electrothermal stimulus to adjust fluorescence intensity via controlling the photonic band gap is proved by a scanning electron microscope (SEM) and UV-vis reflectance. This mechanism also corresponded to the results from the finite-difference time-domain (FDTD) simulation. The comprehensive usage of photonic crystals and liquid crystal elastomers opened a new possibility for active optical devices.

Smart Fluorescent Nanoparticles in Water Showing Temperature-Dependent Ratiometric Fluorescence Color Change

We synthesized two different amphiphilic small molecules 1 and 2 by attaching the same oligo(ethylene glycol) (OEG) unit to the same dicyanodistyrylbenzene (DCS) fluorophore but at different positions. These molecules self-assemble into nanoparticles in water and show lower critical solution temperature (LCST) at 26 and 58 °C, respectively. Upon heating, the transition of hydrophilic coils to hydrophobic globules of the OEG unit leads to the change in the stacking structure of the luminescent DCS cores. As a result, it shows significant ratiometric fluorescence color changes from excimeric yellow emission to monomer-dominated green emission. Interestingly, the coassembly of 1 and 2 exhibits single transition temperature between the transition temperatures of the two components. Moreover, it is demonstrated that the transition temperature of the coassembly is delicately tuned over 26-58 °C by varying the molar mixing ratio of them.

Configuration-independent AIE-active supramolecular polymers of cyanostilbene through the photo-stable host–guest interaction of pillar[5]arene

We report a cyanostilbene system with retained AIE activity at Z and E isomeric state through host–guest of pillar[5]arene.

Adjustment of the solid fluorescence of a chalcone derivative through controlling steric hindrance

A chalcone derivative, ANPEO, exhibits weak emission in the solution state but high fluorescence efficiency in the solid state (66%).

Photoresponsive Cyanostilbene Bent-Core Liquid Crystals as New Materials with Light-Driven Modulated Polarization

Two isomeric cyanostilbene photoswitchable bent-core mesogens with polar liquid crystal phases in which macroscopic polarization and luminescence can be light-modulated are introduced. Z/E isomerization or [2+2] cycloaddition photochemical processes occur depending on the chemical structure, which make the compounds very innovative multifunctional advanced materials.

Controlled self-organization of cyanostilbene: emission tuning and photo-responsiveness

Cyanostilbene modified with dimethylaniline (CMD) could self-assemble into vesicles and fibrous morphologies depending on the solvophobic properties. Furthermore, morphology of well-defined nanostructures could be changed with enhanced emission triggered by the photo-isomerization of cyanostilbene. The present system has potential for building luminescent color conversion materials.

First report of charge-transfer induced heat-set hydrogel. Structural insights and remarkable properties

The remarkable ability of a charge-transfer (CT) complex prepared from a pyrene-based donor (Py-D) and a naphthalenediimide-based acceptor (NDI-A) led to the formation of a deep-violet in color, transparent hydrogel at room temperature (RT-gel). Simultaneously, the RT-gel was diluted beyond its critical gelator concentration (CGC) to obtain a transparent sol. Very interestingly, the resultant sol, on heating above 70 °C, transformed into a heat-set gel instantaneously with a hitherto unknown CGC value. Detailed studies revealed the smaller globular aggregates of the RT-gels fuse to form giant globules upon heating, which, in turn, resulted in heat-set gelation through further aggregation. The thermoresponsive property of Py-D alone and 1 : 1 Py-D : NDI-A CT complex was investigated in detail which revealed the hydrophobic collapse of the oxyethylene chains of the CT complex upon heating was mainly responsible for heat-set gelation. Thixotropy, injectability, as well as stimuli responsiveness of the RT-gels were also addressed. In contrast, heat-set gel did not show thixotropic behavior. The X-ray diffraction (XRD) patterns of the xerogel depicted lamellar packing of the CT stacks in the gel phase. Single crystal XRD studies further evidenced the 1 : 1 mixed CT stack formation in the lamellae and also ruled out orthogonal hydrogen bonding possibilities among the hydrazide unit in the CT gel although such interaction was observed in a single crystal of NDI-A alone. In addition, a Ag(+)-ion triggered metallogelation of NDI-A and nematic liquid-crystalline property of Py-D were also observed.

Rationally introduce multi-competitive binding interactions in supramolecular gels: a simple and efficient approach to develop multi-analyte sensor array

A supramolecular-gel-based twenty-two-member sensor array has been created by introducing well-designed multi-competitive binding interactions into a supramolecular gel.

Sensor arrays are a powerful tool for multianalyte sensing and the development of an efficient sensor array has become one of the most intriguing problems. However, sensor arrays often employ lots of receptors which need large amounts of work to synthesise. This study describes an efficient method for the fabrication of a simple sensor array based on the competitive binding in supramolecular gels. By rationally introducing various well-designed competitive binding interactions into the supramolecular gel, which is self-assembled from a naphthylhydrazone-based organogelator, a supramolecular gel-based twenty-two-member sensor array has been created. Interestingly, the sensor array has been shown to accurately identify fourteen kinds of important ions (F^–, Cl^–, I^–, CN^–, HSO₄^–, SCN^–, S^2–, OH^–, Al³⁺, Fe³⁺, Zn²⁺, Hg²⁺, Pb²⁺ and H⁺) in water. It's important to note that this sensor array needs only one synthesized receptor. Moreover, using this method, we also obtained a series of ion response fluorescent supramolecular materials, which could act as security display materials. Therefore, it's a novel and facile way for the design of a simple sensor array as well as ion response fluorescent supramolecular materials.

Light and cucurbit[7]uril complexation dual-responsiveness of a cyanostilbene-based self-assembled system

A cyanostilbene-based amphiphile (CS) was synthesized, which could self-assemble into non-emissive bilayer vesicles and ultra-thin ribbons. Cucurbit[7]uril (CB[7]) could form an inclusion complex with CS with a significant hypochrome effect, giving a strong blue emission from non-emissive species. CS underwent photoisomerization induced by light irradiation, which allowed the membrane contraction into smaller vesicles.

Gel properties of T-shaped tetrathiafulvalene–pyridazine conjugates and F4TCNQ-induced morphological transformation

T-shaped organic π-conjugates and their F₄TCNQ charge-transfer (CT) complexes are developed as LMOGs. The morphological changes of the organogels occur obviously due to the CT interaction.

Excited-state dynamics of Si–rhodamine and its aggregates: versatile fluorophores for NIR absorption

The properties of SiR monomers and aggregates in the excited states are thoroughly characterized for the first time using time-resolved spectroscopy.

Shining light on clay-chromophore hybrids: layered templates for accelerated ring closure photo-oxidation

Templates with specific microenvironments have been long employed to facilitate specialized reactions. From enzymes to metal organic frameworks (MOFs), various systems have exerted their prowess to affect specific chemical reactions. Here we report, for the first time, the acceleration of a ring closure photo-oxidation reaction due to the specific structural constraints provided by layered materials. A stilbene derivative has been used as a prototype reactant and the di-hydrophenanthrene intermediate has been isolated and characterized en route to the complete photo-oxidation. Combining the gathered evidence, a possible mechanism for the chemical transformation has been proposed. Kinetic analysis showed that layered materials help to manipulate the rate of the electrocyclic ring closure and, in turn, accelerate the complete reaction sequence. The structural microenvironment induced by layered materials could be a unique platform to probe and stabilize a plethora of photo-oxidative reactions and intermediates.

Flexible self-supporting nanofibers thin films showing reversible photochromic fluorescence

Highly sensitive stimuli-responsive fluorescent films play an important role in smart sensors and readable optical devices. However, systems involving light-driven fluorescence changes are still limited compared with photochromic materials that simply change color upon photostimulation. Herein, by incorporation of stilbene-based molecules into a poly(vinyl alcohol) host, we have developed new flexible self-supporting nanofiber films that exhibited fast and obvious photochromic fluorescence (PCF). The reversible transfer between two fluorescent states can be easily recycled. Fluorescence microscopy and atomic force microscopy images supplied in situ evidence of changes in fluorescence and surface morphology, respectively. Density functional theoretical calculations showed that the PCF can be attributed to photoisomerization of the stilbene-based molecules. Therefore, based on the combination of experimental and theoretical studies, this work not only supplies new stilbene-based systems with light-induced fluorescence change, but also gives detailed understanding on the photoisomerization and PCF processes of the nanofibers systems. We anticipate that these PCF films can be applied in erasable memory devices and antiforgery materials, and that our strategy may be extended to other systems to fabricate multistimuli-responsive fluorescent materials.

A novel supramolecular metallogel-based high-resolution anion sensor array

A novel anion sensor array based on supramolecular metallogels has been developed. The sensor array could accurately identify CN⁻, SCN⁻, S²⁻ and I⁻ in water. Interestingly, the metallogel-based sensor array needs only one synthesized gelator G1.

Bent-core liquid crystalline cyanostilbenes: fluorescence switching and thermochromism

Incorporation of the cyanostilbene unit in a bent-core liquid crystal-type structure gives rise to fluorescent systems whose emission is very sensitive to different environments.

Cholesterol-tethered AIEE fluorogens: formation of self-assembled nanostructures

Design and synthesis of cholesterol conjugated chromophores exhibiting intramolecular charge transfer (ICT) and Aggregation Induced Enhanced Emission (AIEE) and their self-assembling behavior is described.