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Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Azoarene isomerization lies at the heart of numerous applications, from catalysis or energy storage to photopharmacology. While efficient switching between their E and Z isomers predominantly relies on UV light, a recent study by Klajn and co‐workers introduced visible light sensitization of E azoarenes and their subsequent isomerization as a tool coined disequilibration by sensitization under confinement (DESC) to obtain high yields of the Z isomer. This host–guest approach is, however, still constrained to minimally substituted azoarenes with limited applicability in advanced molecular systems. Herein, we expand DESC for the assembly of surfactants at the air–water interface. Leveraging our expertise with photoswitchable amphiphiles, we induce substantial alterations of the water surface tension through reversible arylazopyrazole isomerization. After studying the binding of charged surfactants to the host, we find that the surface activity differences upon visible light switching for both isomers are comparable to those obtained by UV light excitation. The method is demonstrated on a large concentration range and can be activated using green or red light, depending on the sensitizer chosen. The straightforward implementation of photoswitch sensitization in a complex molecular network showcases how DESC enables the improvement of existing systems and the development of novel applications driven by visible light. [ABSTRACT FROM AUTHOR]

This study investigates unexpected competitive host–guest interactions of β‐cyclodextrin (β‐CD), which can occur with polymers in aqueous solution, using the examples of the two polymers poly(oligo(ethylene glycol) methyl ether methacrylate) and poly(glycerol mono methacrylate). Systematic structural modifications of the polymer provide insight into the host–guest interaction with β‐CD and the competition between side chains and end groups such as hydrophobic end groups remaining from reversible addition fragmentation chain transfer polymerization or intentionally implemented molecular recognition units such as arylazopyrazole photoswitches. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Inspired by nature, self‐regulation can be introduced in synthetic hydrogels by incorporating chemo‐mechanical signals or coupled chemical reactions to maintain or adapt the material's physico‐chemical properties when exposed to external triggers. In this work, we present redox and light dual stimuli responsive hydrogels capable of rapidly adapting the polymer crosslinking network while maintaining hydrogel stability. Upon irradiation with UV light, polymer hydrogels containing redox responsive disulfide crosslinks and light responsive ortho‐nitrobenzyl moieties show a release of payload accompanied by adaptation of the hydrogel network towards higher stiffness due to in situ crosslinking by S‐nitrosylation. Whereas the hydrogel design allows the network to either become softer in presence of reducing agent glutathione or stiffer upon UV irradiation, simultaneous application of both stimuli induces network self‐regulation resulting in a pulsatile form of payload release from the hydrogel. Finally, adaptive stiffness was used to make tunable hydrogels as substrates for different cell lines. [ABSTRACT FROM AUTHOR]

The design of responsive liquid crystals enables a diversity of technological applications. Especially photochromic liquid crystals gained a lot of interest in recent years due to the excellent spatiotemporal control of their phase transitions. In this work we present calamitic light responsive mesogens based on a library of arylazopyrazole photoswitches. These compounds show liquid‐crystalline behavior as shown by differential scanning calorimetry, grazing incidence X‐ray diffraction and polarized optical microscopy. UV‐vis spectroscopy and NMR analysis confirmed the excellent photophysical properties in solution and thin film. Additionally, polarized optical microscopy studies of the pristine compounds show reversible phase transition upon irradiation with light. Moreover, as a dopant in the commercially available liquid crystal 4‐cyano‐4′‐pentylbiphenyl (5CB), the temperature range was reduced to ambient temperatures while preserving the photophysical properties. Remarkably, this co‐assembled system shows reversible liquid‐crystalline to isotropic phase transition upon irradiation with light of different wavelengths. The spatiotemporal control of the phase transition of the liquid crystals offers opportunities in the development of optical devices. [ABSTRACT FROM AUTHOR]

Optical neural networks (ONNs) hold great potential for faster and more energy‐efficient information processing in coherent photonic circuits. To realize ONNs, linear combinations and nonlinear activation functions have to be implemented in an optical fashion. Optical nonlinearities are, however, still difficult to achieve, and existing designs are usually too inflexible to offer different activation functions as used in artificial neural networks. Herein, the nonlinear properties of the large and highly adaptive class of photoswitchable chemical compounds is made accessible as activation functions in ONNs by employing photo‐induced isomerization in azobenzenes to steer activation behavior through nonlinear modulation of an information‐carrying optical signal. The strength of the nonlinearity can be controlled by the chemical concentration while a physically motivated model describes the experimental data for systematically varied photoswitching parameters, resulting in a tunable yet interpretable activation function. Employing such an activation function in a neural network then allows to gauge its strength and perform established classification tasks. The work combines recent advances with photoswitchable chemical compounds and optical neural networks to enable control over the design of nonlinear activation functions, thus opening exciting perspectives for explaining the emergence of intelligent behavior in neural networks. [ABSTRACT FROM AUTHOR]

Azoheteroarenes are emerging as powerful alternatives to azobenzene molecular photoswitches. In this study, water‐soluble arylazoisoxazole photoswitches are introduced. UV/vis and NMR spectroscopy revealed moderate to very good photostationary states and reversible photoisomerization between the E‐ and Z‐isomers over multiple cycles with minimal photobleaching. Several arylazoisoxazoles form host–guest complexes with β‐ and γ‐cyclodextrin with significant differences in binding constants for each photoisomer as shown by isothermal titration calorimetry and NMR experiments, indicating their potential for photoresponsive host–guest chemistry in water. One carboxylic acid functionalized arylazoisoxazole can act as a hydrogelator, allowing gel properties to be manipulated reversibly with light. The hydrogel was characterized by rheological experiments, atom force microscopy and transmission electron microscopy. These results demonstrate that arylazoisoxazoles can find applications as molecular photoswitches in aqueous media. [ABSTRACT FROM AUTHOR]

Light‐responsive surfaces are attracting increasing interest, not least because their physicochemical properties can be selectively and temporally controlled by a non‐invasive stimulus. Most existing immobilization strategies involve the chemical attachment of light‐responsive moieties to the surface, although this approach often suffers from a low surface concentration of active species or a high inhomogeneity of applied coatings. Herein, electropolymerization of carbazoles as a facile and rapid approach for preparing light‐responsive azo‐based surface coatings is presented. The electrochemical oxidative polymerization of bis‐carbazole containing azo‐monomers yields stable films, in which the photochemical properties and specific pH sensitivity of azo molecular switches are retained. Moreover, the molecular design enables electrocatalytic control over Z→E azo double bond isomerization facilitated by the conductive polycarbazole backbone. Ultimately, the high degree of control over macromolecular properties yields conductive surface coatings responsive to a range of stimuli, showing great promise as a strategy for versatile application in organic electronics. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aromatic units tethered with an azo (−N=N−) functionality comprise a unique class of compounds, known as molecular photoswitches, exhibiting a reversible transformation between their E‐ and Z‐isomers in response to photo‐irradiation. Photoswitches have been explored extensively in the recent past to prepare dynamic self‐assembled materials, optoelectronic devices, responsive biomaterials, and more. Most of such materials involve azobenzenes as the molecular photoswitch and to date, SciFinder lists more than 7000 articles and 1000 patents. Subsequently, a great deal of effort has been invested to improve the photo‐isomerization efficiency and related mesoscopic properties of azobenzenes. Recently, azoheteroarenes and cyclic azobenzenes, such as arylazopyrazoles, arylazoisoxazoles, arylazopyridines, and diazocines, have emerged as second generation molecular photoswitches beyond conventional azobenzenes. These photoswitches offer distinct photoswitching behavior and responsive properties which make them highly promising candidates for multifaceted applications ranging from photoresponsive materials to photopharmacophores. In this minireview, we introduce the structural refinement and photoresponsive properties of azoheteroarenes and diazocines and summarize the state‐of‐the‐art on utilizing these photoswitches as responsive building blocks in supramolecular assembly, material science and photopharmacology, highlighting their versatile photochemical behavior, enhanced functionality, and latest applications. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The development of redox‐triggerable peptide hydrogels poses fundamental challenges, since the highly specific peptide architectures required inevitably limit the versatility of such materials. A powerful, yet rarely applied approach to bypass those barriers is the application of a mediating redox reaction to gradually decrease the pH during hydrogel formation. We report a versatile strategy to trigger the formation of peptide hydrogels from readily accessible acid‐triggerable gelators by generating protons by oxidation of thioethers with triiodide. Adding thiodiglycol as a readily available thioether auxiliary to the basic precursor solution of a peptide gelator efficiently yielded hydrogels after mixing with triiodide, as studied in detail for Nap‐FF and demonstrated for other peptides. Furthermore, incorporation of the thioether moiety in the gelator backbone via the amino acid methionine, as shown for the tailormade Nap‐FMDM peptide, reduces the number of required additives. [ABSTRACT FROM AUTHOR]

Hydrogels have emerged as one of the best studied, widely applied and most versatile classes of soft materials. Hydrogels are important biomimetic nanomaterials comparable to extracellular matrices in terms of water content, porosity, and rigidity. In this regard, self‐assembled hydrogels based on supramolecular host‐guest interactions have enabled unique characteristics like stimuli response, self‐healing, shape memory and self‐regulation. In particular, the use of cyclodextrins and their host‐guest chemistry is a powerful tool for the development of functional hydrogels with unprecedented properties. In this article, recent advances on hydrogels based on supramolecular chemistry of cyclodextrins are reviewed to provide an overview of the manifold design strategies, material properties and areas of application. We contrast the progress on cyclodextrin containing polymer gels to that of their low molecular weight counterparts by highlighting selected publications from each of these subcategories. [ABSTRACT FROM AUTHOR]

The transport of membrane impermeable compounds into cells is a prerequisite for the efficient cellular delivery of hydrophilic and amphiphilic compounds and drugs. Transport into the cell's cytosolic compartment should ideally be controllable and it should involve biologically compatible and degradable vehicles. Addressing these challenges, nanocontainers based on cyclodextrin amphiphiles that are stabilized by a biodegradable peptide shell are developed and their potential to deliver fluorescently labeled cargo into human cells is analyzed. Host–guest mediated self‐assembly of a thiol‐containing short peptide or a cystamine‐cross‐linked polypeptide shell on cyclodextrin vesicles produce short peptide‐shelled (SPSVss) or polypeptide‐shelled vesicles (PPSVss), respectively, with redox‐responsive and biodegradable features. Whereas SPSVss are permeable and less stable, PPSVss effectively encapsulate cargo and show a strictly regulated release of membrane impermeable cargo triggered by either reducing conditions or peptidase treatment. Live cell experiments reveal that the novel PPSVSS are readily internalized by primary human endothelial cells (human umbilical vein endothelial cells) and cervical cancer cells and that the reductive microenvironment of the cells' endosomes trigger release of the hydrophilic cargo into the cytosol. Thus, PPSVSS represent a highly efficient, biodegradable, and tunable system for overcoming the plasma membrane as a natural barrier for membrane‐impermeable cargo. [ABSTRACT FROM AUTHOR]

In Hydrogele eingebrachte chemische Reaktionsnetzwerke können responsive Materialien zu komplexen, selbstregulierenden Materialien transformieren, die eine Rückkopplung auf externe Stimuli generieren können. Diese Arbeit präsentiert Hydrogele aus dem Wirt‐Gast‐Paar β‐Cyclodextrin und Ferrocen als supramolekulare Vernetzer. Ein redoxresponsives Verhalten des Systems wird induziert durch die Treibstoff‐Enzym‐Paare Meerrettich‐Peroxidase/H2O2 und Glucose‐Oxidase (GOx)/d‐Glucose. Das Hydrogel kann durch Variation der Konzentration des Reduktionstreibstoffs d‐Glucose von einem responsiven zu einem selbstregulierenden supramolekularen System umgewandelt werden. Gestartet wird das selbstregulierende Verhalten durch die Bildung eines Oxidationsmittels innerhalb des Gels durch das Cofaktor‐Intermediat GOx[FADH2]. UV/Vis‐Spektroskopie, Rheologie und kinetische Modellierung wurden angewendet, um dieses Nichtgleichgewichtsverhalten und die Programmierbarkeit der Rückkopplung des Hydrogels, unter anderem die Anpassung des Speichermoduls und die mögliche Anwendung als Glucose‐Sensor, zu beleuchten. [ABSTRACT FROM AUTHOR]

Chemical reaction networks (CRN) embedded in hydrogels can transform responsive materials into complex self‐regulating materials that generate feedback to counter the effect of external stimuli. This study presents hydrogels containing the β‐cyclodextrin (CD) and ferrocene (Fc) host–guest pair as supramolecular crosslinks where redox‐responsive behavior is driven by the enzyme–fuel couples horse radish peroxidase (HRP)–H2O2 and glucose oxidase (GOx)–d‐glucose. The hydrogel can be tuned from a responsive to a self‐regulating supramolecular system by varying the concentration of added reduction fuel d‐glucose. The onset of self‐regulating behavior is due to formation of oxidation fuel in the hydrogel by a cofactor intermediate GOx[FADH2]. UV/Vis spectroscopy, rheology, and kinetic modeling were employed to understand the emergence of out‐of‐equilibrium behavior and reveal the programmable negative feedback response of the hydrogel, including the adaptation of its elastic modulus and its potential as a glucose sensor. [ABSTRACT FROM AUTHOR]

Supramolecular nanogels are an emerging class of polymer nanocarriers for intracellular delivery, due to their straightforward preparation, biocompatibility, and capability to spontaneously encapsulate biologically active components such as DNA. A completely biodegradable three‐component cationic supramolecular nanogel was designed exploiting the multivalent host‐guest interaction of cyclodextrin and adamantane attached to a polypeptide backbone. While cyclodextrin was conjugated to linear poly‐L‐lysine, adamantane was grafted to linear as well as star shaped poly‐L‐lysine. Size control of nanogels was obtained with the increase in the length of the host and guest polymer. Moreover, smaller nanogels were obtained using the star shaped polymers because of the compact nature of star polymers compared to linear polymers. Nanogels were loaded with anionic model cargoes, pyranine and carboxyfluorescein, and their enzyme responsive release was studied using protease trypsin. Confocal microscopy revealed successful transfection of mammalian HeLa cells and intracellular release of pyranine and plasmid DNA, as quantified using a luciferase assay, showing that supramolecular polypeptide nanogels have significant potential in gene therapy applications. [ABSTRACT FROM AUTHOR]

Host‐guest interactions are an attractive approach to design redox electrolytes, enabling to precisely tune the key properties for redox flow batteries such as half‐cell redox potential, solubility, and stability. Herein we report a host‐guest complex of highly water soluble (2‐hydroxypropyl)‐β‐cyclodextrin with 1‐decyl‐1′‐ethyl‐4,4′‐bipyridinium dibromide as anolyte in a new aqueous organic redox flow battery (AORFB). The supramolecular anolyte ensured the total RFB voltage increase of ≈9 % up to 0.97 V and provided a stable capacity delivery for more than 500 cycles with a capacity fade rate of 0.037 %/cycle (2.84 %/day) at high Coulombic (>99.5 %) and energy (>62 %) efficiencies. The results highlight host‐guest interactions as promising strategy towards more effective storage of renewable energy within AORFBs. [ABSTRACT FROM AUTHOR]

The surface chemistry of colloidal silica has tremendous effects on its properties and applications. Commonly the design of silica particles is based on their de novo synthesis followed by surface functionalization leading to tailormade properties for a specific purpose. Here, the design of robust "precursor" polymer‐decorated silica nano‐ and microparticles is demonstrated, which allows for easy post‐modification by polymer embedded thiolactone chemistry. To obtain this organic‐inorganic hybrid material, silica particles (SiO2P) were functionalized via surface‐initiated atom transfer radical polymerization (SI‐ATRP) with poly(2‐hydroxyethyl acrylate) (PHEA)‐poly(thiolactone acrylamide (PThlAm) co‐polymer brushes. Exploiting the versatility of thiolactone post‐modification, a system was developed that could be used in three exemplary applications: 1) the straightforward molecular post‐functionalization to tune the surface polarity, and therefore the dispersibility in various solvents; 2) the immobilization of metal nanoparticles into the polymer brushes via the in situ formation of free thiols that preserved catalytic activity in a model reaction; 3) the formation of redox‐responsive, permeable polymer capsules by crosslinking the thiolactone moieties with cystamine dihydrochloride (CDH) followed by dissolution of the silica core. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Hydroarylation is an effective strategy to rapidly increase the complexity of organic structures by transforming flat alkene moieties into three‐dimensional frameworks. Many strategies have already been developed to achieve the hydroarylation of styrenes, however most of these reports examine the hydroarylation of unpolar, β‐mono‐ or β‐unsubstituted styrenes, while exploring mainly electron‐rich benzene nucleophiles. Herein, we report a mild and general catalytic system for the selective hydroheteroarylation of multiply substituted styrenes and heteroaromatic styrenes. Mechanistic analysis of the reaction led to the discovery of commercially available 2,2′:5′,2′′‐terthiophene as a key reagent. [ABSTRACT FROM AUTHOR]

Control over the self‐assembly of mixed nanoparticles (NP) is a challenging but versatile concept for the bottom‐up fabrication of novel nanomaterials. Moreover, stimulus‐responsive self‐assembly is fundamental to the development of adaptive and intelligent materials. In this study, we demonstrate the orthogonal self‐assembly of cyclodextrin (CD) decorated noble metal NP. Utilizing the guest selectivity of αCD and γCD, divalent photoresponsive supramolecular crosslinkers were identified and applied in selective NP assembly. By design of specific crosslinkers, narcissistic as well as social self‐sorting of sub 10 nm metal NP was enabled. Irradiation experiments confirmed that the aggregation process is induced by photoresponsive host‐guest chemistry, which allows to form and dissolve the NP aggregates over several cycles and to photo‐initiate the NP aggregation. The molecular recognition as well as the specific response of CD‐functionalized NP show significant potential in the reversible self‐assembly of inorganic‐organic hybrid nanomaterials in aqueous solution. [ABSTRACT FROM AUTHOR]

The synthesis of adamantane‐terminated polypeptides by N‐carboxyanhydride (NCA) polymerization and their use in the template‐based self‐assembly of redox‐responsive nanocontainers is described. Cyclodextrin vesicles (CDV) serve as a supramolecular template to anchor adamantane terminated polypeptides on to the surface of CDV and to form polypeptide shelled vesicles (PPSVss) which are stabilized by crosslinking with cystamin. Polypeptides are characterized by nuclear magnetic resonance, matrix‐assisted laser desorption/ionization (MALDI), and gel permeation chromatography, and nanocontainer formation at each step is confirmed by dynamic light scattering (DLS) and zeta potential measurements. MALDI confirms the presence of the adamantane at the end of the polymers, and isothermal titration calomatry (ITC) of the adamantane‐terminated polypeptides with β‐cyclodextrin proves the capability of adamantane on the polypeptides to form host–guest inclusion complexes even with the longest polypeptides. Encapsulation of a model dye carboxyfluorescein in PPSVss and its redox‐responsive release demonstrates the potential use of this novel type of completely biodegradable and biocompatible nanocontainer for the purpose of intracellullar delivery. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A novel photoresponsive and fully conjugated N‐heterocyclic carbene (NHC) has been synthesized that combines the excellent photophysical properties of arylazopyrazoles (AAPs) with an NHC that acts as a robust surface anchor (AAP‐BIMe). The formation of self‐assembled monolayers (SAMs) on gold was proven by ToF‐SIMS and XPS, and the organic film displayed a very high stability at elevated temperatures. This stability was also reflected in a high desorption energy, which was determined by temperature‐programmed SIMS measurements. E‐/Z‐AAP‐BIMe@Au photoisomerization resulted in reversible alterations of the surface energy (i.e. wettability), the surface potential (i.e. work function), and the conductance (i.e. resistance). The effects could be explained by the difference in the dipole moment of the isomers. Furthermore, sequential application of a dummy ligand by microcontact printing and subsequent backfilling with AAP‐BIMe allowed its patterning on gold. To the best of our knowledge, this is the first example of a photoswitchable NHC on a gold surface. These properties of AAP‐BIMe@Au illustrate its suitability as a molecular switch for electronic devices. [ABSTRACT FROM AUTHOR]

A facile route to generate Au and Pd nanoparticles (NPs) on zeolite L crystals decorated with photoactive polymer brushes is described. The polymers used in this approach serve a dual role: Upon irradiation with UV light, they release highly reducing ketyl radicals in a Norrish‐Type‐I reaction. These radicals serve as one electron donors to reduce metal salts to the corresponding metal NPs. At the same time the polymer shell stabilizes the in situ generated metal NPs. It is shown that the zeolite‐polymer‐NP composites can be used as recyclable catalysts for the oxidation of benzylic alcohols to aldehydes and the stereoselective semihydrogenation of alkynes to Z‐alkenes. The polymer shell in these hybrid catalysts protects the NPs from aggregation and also alters their catalytic properties. [ABSTRACT FROM AUTHOR]

In polymer science, mechanochemistry is emerging as a powerful tool for materials science and molecular synthesis, offering novel avenues for controlled polymerization and post‐synthetic modification. Building upon the previous research, nitroxide‐mediated polymerization (NMP) is merged with mechanochemistry through the design of nitroxide‐based mechanophore macroinitiators, pioneering the first instance of a sonochemical nitroxide‐mediated‐type polymerization. As NMP usually requires high temperatures, this study demonstrates that a sonochemical NMP‐type process allows polymerization under reduced temperatures down to 55 °C. Moreover, depending on the nature of the employed monomers, gelated networks are obtained, demonstrating the adaptability of the mechanophore system. This study elucidates the potential of mechanochemistry in polymer synthesis, offering insights into manipulating polymerization kinetics and advancing materials science applications. [ABSTRACT FROM AUTHOR]

Carriers for intracellular delivery are required to overcome limitations of therapeutic agents such as low specificity, systemic toxicity, high clearance rate, and low therapeutic index. Nanocontainers comprised of an aqueous core and a polymer shell have received increasing attention because they readily combine stimuli response to improve intracellular payload release and surface modification to enhance selectivity towards the desired region of action. This Minireview summarizes the design and properties of polymer nanocontainers for intracellular delivery, classified according to the polymer architecture. [ABSTRACT FROM AUTHOR]

Trägersysteme für den Transport in das Zellinnere sind notwendig, um Einschränkungen klassischer Therapeutika, wie geringe Spezifität, systemische Toxizität, zu hohe Freisetzungsraten sowie geringe therapeutische Indices, überwinden zu können. Nanocontainer aus einem wassergefüllten Kern und einer Polymerhülle sind dabei von besonderem Interesse, da sie die Möglichkeiten von stimuligesteuerter Frachtfreisetzung und gezielter Oberflächenmodifikation zur Erhöhung der lokalen Selektivität kombinieren. Dieser Kurzaufsatz fasst die Herstellung wie auch die Eigenschaften derartiger Polymernanocontainer für den Transport in das Zellinnere zusammen, klassifiziert nach dem Aufbau der verwendeten Polymere. [ABSTRACT FROM AUTHOR]

Versatile photoresponsive gels based on tripodal low molecular weight gelators (LMWGs) are reported. A cyclohexane‐1,3,5‐tricarboxamide (CTA) core provides face‐to‐face hydrogen bonding and a planar conformation, inducing the self‐assembly of supramolecular polymers. The CTA core was substituted with three arylazopyrazole (AAP) arms. AAP is a molecular photoswitch that isomerizes reversibly under alternating UV and green light irradiation. The E isomer of AAP is planar, favoring the self‐assembly, whereas the Z isomer has a twisted structure, leading to a disassembly of the supramolecular polymers. By using tailor‐made molecular design of the tripodal gelator, light‐responsive organogels and hydrogels were obtained. Additionally, in the case of the hydrogels, AAP was coupled to the core through hydrazones, so that the hydrogelator and, hence, the photoresponsive hydrogel could also be assembled and disassembled by using dynamic covalent chemistry. [ABSTRACT FROM AUTHOR]

This article discusses the creation of a birefringent thin film of liquid crystals using photoswitchable arylazopyrazoles. The liquid crystals exhibit a calamitic structure and undergo a phase transition when exposed to UV and green light. When irradiated with UV light, the liquid crystal becomes isotropic, and when irradiated with green light, it reassembles. The phase transition can be induced locally using an optical fiber. The article provides more detailed information on this research. [Extracted from the article]

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Herein, we present a novel upconversion nanoparticle/photocatalyst system for infrared‐light‐initiated photoredox catalysis. A tailor‐made, metal‐based photoredox catalyst was immobilized by ligand exchange to stabilize NaYF4 upconversion nanoparticles. The absorption properties of the immobilized photoredox catalyst were only negligibly changed and the particles could excite the photoredox catalyst by energy transfer, determined by extensive luminescence spectroscopy and excited‐state lifetime measurements using a 980 nm near‐infrared laser excitation source. The system successfully catalyzed a [Ru(bpy)3]2+ promoted oxidation reaction, normally performed with visible light, by using 980 nm near‐infrared light. Neither the complex nor the particle without immobilized complex was active in this reaction. The presented system enables potential in vivo application of photoredox catalysis, utilizing the biological window of tissues for near‐infrared light by combining the mildness of photoredox catalysis and near‐infrared light. Made to measure: A dual upconversion nanoparticle/photocatalyst system was established for infrared‐light‐initiated photoredox catalysis. The system might be a promising candidate as an effective in vivo photoredox catalyst, utilizing deep‐tissue penetration of low‐energy infrared light as an excitation source. [ABSTRACT FROM AUTHOR]

The preparation of water‐soluble, N‐heterocyclic‐carbene‐stabilized Au–Pd alloy nanoparticles by a straightforward ligand exchange process is presented. Extensive analysis revealed excellent size retention and stability over years in water. The alloy nanoparticles were applied as biomimetic catalysts for aerobic oxidation of d‐glucose, for which monometallic Au and Pd nanoparticles showed no or negligible activity. The alloy nanoparticles were further applied as titania‐supported heterogeneous catalysts for the mild hydrogenation of nitroarenes and the semihydrogenation of 1,2‐diphenylacetylene with a solvent‐dependent selectivity switch between E‐ and Z‐stilbene. It's all about the mix! The preparation of water‐soluble, N‐heterocyclic‐carbene‐stabilized Au–Pd alloy nanoparticles is presented. The particles were stable over years and were used as biomimetic catalysts in water or as heterogeneous catalysts in hydrogenation reactions. [ABSTRACT FROM AUTHOR]

Copyright of Angewandte Chemie is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Patterned monolayers of N‐heterocyclic carbenes (NHCs) on gold surfaces were obtained by microcontact printing of NHC–CO2 adducts and NHC(H)[HCO3] salts. The NHC‐modified areas showed an increased conductivity compared to unmodified gold surface areas. Furthermore, the remaining surface areas could be modified with a second, azide‐functionalized carbene, facilitating further applications and post‐printing modifications. Thorough elucidation by a variety of analytical methods offers comprehensive evidence for the viability of the methodology reported here. The protocol enables facile access to versatile, microstructured NHC‐modified gold surfaces with highly stable patterns, enhanced conductivity, and the option for further modification. [ABSTRACT FROM AUTHOR]

A method for the preparation of mixed AuPd nanoparticles that are used as catalysts for selective alkyne Z‐semihydrogenation is described. It is shown that the corresponding monometallic Pd nanoparticles display a lower activity, documenting the cooperative effect exerted by the two metals. These mixed AuPd nanoalloys are readily prepared by irradiation of the corresponding precursor salts in the presence of photoactive polymers or commercially available photoinitiators as reducing and stabilizing agents. Alkyne semihydrogenation using these catalyst systems with H2 proceeds in high yield (up to 97 % yield of isolated product) and excellent Z‐selectivity (up to 99 %). Hydrogenations work on larger scale and the hybrid catalyst can be recovered and reused by simple centrifugation. [ABSTRACT FROM AUTHOR]

Abstract: The design of multifunctional nanomaterials that respond to external stimuli and mimic the capacity of biological materials to respond and adapt to their environment has become a focus of interest in nanotechnology. In this Concept, we describe the development of supramolecular nanoparticle assemblies constructed by use of host–guest interactions between cyclodextrins and suitable guest molecules. The nanoparticle assembly is reversible and can be directed by applying different stimuli that act either on the guest molecules or the nanoparticles. This strategy can be extended to mesoscale assembly of microparticles. We highlight the newest research work in this field of nanochemistry and point out future perspectives and opportunities. [ABSTRACT FROM AUTHOR]

Abstract: The covalent immobilization of the biomimetic, photo‐organocatalyst (−)‐riboflavin on silica micro‐ and nanoparticles via atom transfer radical polymerization (ATRP) is disclosed. Given the effectiveness of (−)‐riboflavin as a versatile, environmentally benign photocatalyst, an immobilization strategy based on acrylate‐linker modification of the catalyst core and controlled polymerization on initiator pre‐functionalized silica particles has been developed. Validation of this approach is demonstrated in the E→Z isomerization of a benchmark cinnamonitrile (Z/E up to 88:12) with 0.97 mol % catalyst loading. Characterization of the immobilized photocatalyst supports covalent embedding of the catalyst in the polymeric brushes on the silica particle surface. [ABSTRACT FROM AUTHOR]

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Abstract: A glue, based on dynamic covalent chemistry, with a strong adhesion (2.38 kg cm−2), water resistance and carbohydrate responsive reversibility is presented. Using surface initiated atom transfer radical polymerization (SI‐ATRP), glass and silicon surfaces were coated with copolymers functionalized with phenylboronic acids and catechols. In combination with microcontact printing (μCP) these polymer brushes give access to a carbohydrate responsive “supramolecular Velcro”. [ABSTRACT FROM AUTHOR]

A photoswitchable arylazopyrazole (AAP) derivative binds with cucurbit[8]uril (CB[8]) and methylviologen (MV2+) to form a 1:1:1 heteroternary host-guest complex with a binding constant of Ka=2×103m-1. The excellent photoswitching properties of AAP are preserved in the inclusion complex. Irradiation with light of a wavelength of 365 and 520 nm leads to quantitative E- to Z- isomerization and vice versa, respectively. Formation of the Zisomer leads to dissociation of the complex as evidenced using 1H NMR spectroscopy. AAP derivatives are then used to immobilize bioactive molecules and photorelease them on demand. When Arg-Gly-Asp-AAP (AAP-RGD) peptides are attached to surface bound CB[8]/MV2+ complexes, cells adhere and can be released upon irradiation. The heteroternary host-guest system offers highly reversible binding properties due to efficient photoswitching and these properties are attractive for designing smart surfaces. [ABSTRACT FROM AUTHOR]

Abstract: An effective and universal method for delivering structurally diverse biomolecules in vivo would greatly benefit modern drug therapy, but has yet to be discovered. Self‐assembled supramolecular complexes containing vesicles of amphiphilic cyclodextrin and linker molecules with an azobenzene guest unit and a charged functionality have been established as nanoscale carriers for proteins and DNA, making use of multivalent electrostatic attraction. However, light‐induced cargo release is only feasible up to a maximum net charge of the biomacromolecules. Herein, it is shown that it is possible to fine‐tune macromolecular complex stability and size by addition of a competitive guest molecule that acts as a stopper, partly blocking the vesicle surface. The superior performance of arylazopyrazoles in photoisomerization compared to azobenzenes, which enables a lower surface charge density of the vesicles in the photostationary state, is also demonstrated. Both strategies allow reversible supramolecular aggregation of high molecular weight DNA (2 and 4.8 kbp). [ABSTRACT FROM AUTHOR]