The photocatalyzed uphill isomerization of drugs using Ru(bpy3)2 is reported by Nicolas Winssinger et al. in their Research Article (e202203390). This chemistry was shown to locally convert inactive ...drugs into active ones that alter the tubulin dynamics in cells (green structures in the background of the picture).
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•The selective reflection of light in the oblique helicoidal structure is tunable by the electric field.•Cholesteric mixtures were doped with rod-like, chiral, and bent-shaped ...azobenzene compounds.•Cholesterics with newly designed photosensitive molecules can be tuned by the electric field and UV light.•The tuning mechanism, reflection coefficient, and response time are related to the structure of azobenzene compounds.
The oblique helicoidal structure is formed in right-angle cholesterics under the applied electric field. The electric field changes the pitch and cone angle but preserves the single-harmonic modulation of the refractive index. As a result, in such a supramolecular system, we can tune the selective reflection of light in a broad range. Here, we report that structural colors can be tuned by simultaneously illuminating the structure with UV light and the action of an electric field. The cholesterics with the oblique helicoidal structure were doped with newly designed rod-like, chiral, and bent-shaped azo-photosensitive materials characterized by a very low rate of thermal back cis (Z) – trans (E) isomerization. The E-Z isomerization of the photo-active compounds under UV light causes the red shift of the selective light reflection in the cholesteric mixtures. We found that the molecular structure of the photosensitive materials used affects the reflection coefficient, bandwidth, response time to UV irradiation, and tuning range. The effect was explained by considering the effect of molecular matching, cis–trans isomerization, and electric field action. We investigated the dynamics of molecular changes in the oblique helicoidal structure under the influence of external factors. The designed supramolecular system has the potential application in soft matter UV detectors.
Chirality control of the title compound by photoracemization is depicted, inspired by “Jack and the Beanstalk”. The spiraling trees reaching skyward symbolize molecular changes induced by sunlight, ...specifically photoirradiation. This image vividly portrays the N−N bond cleavage within the dihydropyridazine (DHP) ring, rotational motions around a C−C bond, and the subsequent recombination of N−N bonds. These transformations serve as a visual representation of the concept of T‐type photochromism of new‐type helicene molecules. More information can be found in the Research Article by K. Usui, Y. Kobori, S. Karasawa and co‐workers (DOI: 10.1002/chem.202302413).
Known as a bright and photostable fluorophore, widely employed in chemistry, biology and physics, the DCM molecule and its photophysical properties remain mysterious. Its multiple isomers and ...conformers, especially the light‐induced E–Z isomerization, have a great influence on the DCM behavior. A complete investigation, involving structure characterization, HPLC separation, steady‐state and time‐resolved spectroscopy and DFT calculations, deciphers the role of the solvent and irradiation wavelength on the fluorescence photoswitching capability of the DCM molecule. More information can be found in the Full Paper by J. Xie, R. Métivier, et al. on page 14341.
In article number 2300844, Kwang‐Un Jeong and co‐workers present smart anti‐counterfeiting inks using a cyanostilbene‐based liquid crystal monomer. The phase and luminescence polarization of the inks ...are controlled and fixed by a continuous process of shear coating, UV irradiation, and subsequent blue light irradiation, which leads to anti‐counterfeiting effects.
We design a cyanostilbene-glutamide-based amphiphile L-GC bearing a long alkyl chain. It can form gels in methanol and exhibit circular dichroism (CD) signals. Upon ultraviolet-light irradiation, the ...CD signals are inverted and the morphology transforms from fibers to spheres. Chirality and energy transfer can be achieved when L-GC co-assembles with the energy acceptor DBTOC18. Moreover, the energy-transfer efficiency of the co-assembly can be modulated via photoirradiation-induced isomerization.
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•UV irradiation triggers the transformation of CD spectra and nanostructure.•Both chirality and energy transfer can be realized in the co-gel.•Chirality and energy transfer efficiency can be modulated simultaneously.
Manipulating chirality and energy transfer simultaneously in a single self-assembly system is important but remains challenging. In this study, we design a cyanostilbene-glutamide-based amphiphile L-GC bearing a long alkyl chain. It can form gels in methanol and exhibit circular dichroism (CD) signals. Upon ultraviolet-light irradiation, the CD signals are inverted and the morphology transforms from fibers to spheres. Chirality and energy transfer can be achieved when L-GC co-assembles with the energy acceptor DBTOC18, which is conjugated to a long alkyl chain. Moreover, the energy-transfer efficiency of the co-assembly can be modulated via photoirradiation-induced isomerization. Molecular dynamics simulation was conducted to elucidate the photomodulated assembly behavior. This study realizes the dual modulation of chirality and energy and presents some perspectives for information exchange in chiroptical materials.
Control over molecular motion represents an important objective in modern chemistry. Aromatic azobenzenes are excellent candidates as molecular switches since they can exist in two forms, namely the ...cis (Z) and trans (E) isomers, which can interconvert both photochemically and thermally. This transformation induces a molecular movement and a significant geometric change, therefore the azobenzene unit is an excellent candidate to build dynamic molecular devices. We describe selected examples of systems containing an azobenzene moiety and their motions and geometrical changes caused by external stimuli.
A simple, radially arranged, highly anthracene congested 1,2,3‐tri(9‐anthryl)benzene has been synthesized in a Negishi coupling reaction with a PdI catalyst. This beautiful three‐anthracene clustered ...structure shows unique behavior in both the solid and excited states, but work is still in progress. There are three more anthracenes on the wooden desk for construction of the final target: hexa(9‐anthryl)benzene. More information can be found in the Research Article by T. Nishiuchi, H. Sotome, K. Shimizu, H. Miyasaka, and T. Kubo (DOI: 10.1002/chem.202104245).
The kinetics of photoisomerization and thermal back reaction of mercury(II) and zinc(II) dithizonates, M(HDz)2, were analyzed by photolysis assays in fluid solution and in poly(methyl methacrylate), ...PMMA, films. In fluid solution, the photo- and thermoisomerization of both complexes can be described by a single exponential function. The Zn(II) dithizonate exhibits rate constants three orders of magnitude greater than that for Hg(II) complex, which is attributed to the higher charge density of the Zn(II) cation. In PMMA films, the thermal back reaction of both complexes can only be described by bi-exponential functions. On this more rigid medium the rate constants are about one order of magnitude slower than the respective ones in fluid solution and the bi-exponential behavior is related to regions in the polymeric matrix with distinct free volumes. The rate constants for both photo- and thermoisomerization of Zn(HDz)2 in PMMA are reported for the first time and are compared with the well-studied Hg(II) analog. The experimental data provides insights on the role of the metal cation on the photocromic behavior in rigid media, which can lately contribute for technological applications.
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