Theoretical investigation into the effect of atomic electronegativity related chalcogen on ESIPT behaviour for the novel biphenyl-modified 2-(2’-hydroxyphenyl)benzothiazole compounds

Inspired by the remarkable photochemical and photophysical properties of novel 2-(2’-hydroxyphenyl)benzothiazole (HBT) derivatives that could be potentially applied across various disciplines, in this work, effects of atomic electronegativity of chalcogen elements on excited state hydrogen bond effects and excited state intramolecular proton transfer (ESIPT) reaction of the biphenyl-modified HBT derivatives (i.e. HBT-HH-O, HBT-HH-S and HBT-HH-Se) are focused. By comparing the structural changes and infrared (IR) vibrational spectra of the HBT-HH fluorophores in toluene solvent, combined with the preliminary detection of hydrogen bond interaction by core-valence bifurcation (CVB) index, we can conclude that the hydrogen bond could be strengthened in S1 state, which is favourable for the occurrence of ESIPT reactions. The charge recombination behaviour of hydrogen bond induced by photoexcitation also further illustrates this point. Via constructing potential energy curves (PECs) based on restrictive optimisation and searching transition state (TS) form, we confirm the variations of atomic electronegativity of chalcogen have the regulatory effect on the ESIPT behaviour for HBT-HH derivatives, that is, the lower the atomic electronegativity is more conducive to the ESIPT reaction.</p

De- and Recoherence of Charge Migration in Ionized Iodoacetylene

During charge migration, electrons flow rapidly from one site of a molecule to another, perhaps inducing subsequent processes (e.g., selective breaking of chemical bonds). The first joint experimental and theoretical preparation and measurement of the initial state and subsequent quantum dynamics simulation of charge migration for fixed nuclei was demonstrated recently for oriented, ionized iodoacetylene. Here, we present new quantum dynamics simulations for the same system with moving nuclei. They reveal the decisive role of the nuclei, i.e. they switch charge migration off (decoherence) and on (recoherence). This is a new finding in attosecond-to-femtosecond chemistry and physics which opens new prospects for laser control over electronic dynamics via nuclear motions

Preparation of the colorful retroreflective film based on the polymer-stabilized cholesteric liquid crystal

A cholesteric liquid crystal (CLC) mixture was prepared using a photoisomerizable chiral dopant and acrylates. With extending the irradiation time of a 365-nm UV light, the Bragg reflection band of the CLC mixture shifted to long wavelength. After photopolymerization, a polymer-stabilized CLC (PSCLC) film was obtained. The colorful PSCLC patterns with glass microspheres on the surface were prepared by controlling the competition between the photoisomerization of the chiral dopant and the photopolymerization of the acrylates. Due to the retroreflective property, the patterned PSCLC films can be applied as the traffic signs and for advertisement.</p

Control of the Handedness of Self-assemblies of Dipeptides by the Chirality of Phenylalanine and Steric Hindrance of Phenylglycine

Eight dipeptides, composed of phenylalanine and phenylglycine, that are able to self-assemble into twisted nanoribbons in deionized water are synthesized. The handedness of the nanoribbons is controlled by the chirality of the phenylalanine and the steric hindrance owing to the phenyl group of the phenylglycine. When the phenylalanine is at the C-terminal, π–π stacking by the phenyl groups, hydrogen bonding by the NH group of the phenylalanine, and hydrophobic associations of the alkyl chains control the stacking of the molecules. When phenylglycine is at the C-terminal, the chiral π–π stacking by the phenyl groups of the phenylalanines is suppressed. The hydrogen bonds formed by the NH groups of the phenylalanines had a greater contribution on forming organic self-assemblies than those formed by the NH groups of the phenylglycines

Interception of Secondary Amide Ylide with Sulfonamides: Catalyst-Controlled Synthesis of <i>N</i>‑Sulfonylamidine Derivatives

A novel, secondary amide activation strategy has been developed through the in situ generation of ylides from amides and diazoacetates. Under the developed reaction conditions, Mn-catalyzed ylide formation and interception reaction by sulfonamide delivered a variety of <i>N</i>-sulfonylamidines. Notably, when highly active Zn­(OTf)₂ was used as the catalyst, further N–H insertion products were obtained. In contrast with traditional methods, our amide activation strategy is distinguished by accessible starting material, inexpensive catalyst, and broad substrate scope

Control of Mesoporous Silica Nanostructures and Pore-Architectures Using a Thickener and a Gelator

A chiral cationic thickener l-ValPyBr, which was able to enhance the viscosity of water and form loosely physical gel in mixtures of water and alcohols, was synthesized. Sol−gel polymerization of TEOS was carried out in mixtures of water and alcohols under basic conditions using the self-assemblies of l-ValPyBr as template. The left-handed twisted mesoporous silica nanoribbons, which were constructed by nanotubes in monolayer, were obtained, and they tended to self-assemble into bundle structure. Stirring under the preparation process played an important role in the formation of this bundle structure. The obtained silica nanoribbons were uniform in width, thickness, and helical pitch without combining amorphous particles. The helical pitch and pore size of the mesoporous silica nanoribbons sensitively depended on the volume ratio of alcohols to water in the reaction mixtures. With increasing volume ratio of alcohols to water in the reaction mixture, the morphologies of the obtained silica changed from left-handed twisted ribbon to coiled ribbon, then to tubular structure. A compound l-ValPyPF6, structurally related to thickener l-ValPyBr, was able to form physical gel in ethanol, THF, acetonitrile, and the mixtures of ethanol and water. Left-handed multiple helical mesoporous silica nanofibers were prepared by using the self-assemblies of l-ValPyPF6 as template in mixtures of water and alcohols under basic conditions. By controlling both the volume ratio of ethanol to water and the weight ratio of l-ValPyPF6 to TEOS, two- or three-dimensional pore-architecture constructed by porous chiral nanotubes was obtained

Preparation of Helical Mesoporous Silica and Hybrid Silica Nanofibers Using Hydrogelator

Helical mesoporous silica, methylene−silica, ethane−silica, ethene−silica, octane−silica, and phenylene−silica nanofibers were successfully prepared by sol−gel polymerization using a chiral cationic gelator under a shear flow. These helical nanofibers were constructed by bundles of ultrafine nanofibers that were formed by bundles of nanotubes. The nanotubes of the smallest unit had inner helical channels with uniform inside diameters. The morphologies of the silica nanofibers were sensitive to preparation conditions. In acidic conditions, scanning electron microscopy images showed right-handed helical nanofibers. In basic conditions, rodlike mesoporous nanofibers were formed. The circular dichroism spectrum of the phenylene−silica indicated that the chirality of the gelator was transferred to the arrangement of the phenylene segment of the hybrid silica. The thermostability was so high that the morphologies of the phenylene−silica were maintained even after being calcined at 650 °C for 5 h in air

Liquid crystalline behaviours of some 3-perfluoroalkylbenzoate esters

A series of 3-perfluoroalkylbenzoate esters are synthesised. They tend to exhibit enantiotropic SmA and SmC phases. The clearing points are decreased with increasing the alkoxy chain length and show odd-even effect. With increasing the fluorocarbon chain length, the melting and clearing points increase; however, the SmC phase is suppressed.</p

Rovibrational Dynamics of RbCs on its Lowest ^1,3Σ⁺ Potential Curves Calculated by Coupled Cluster Method with All-Electron Basis Set

Relativistic ab initio potential curves of RbCs lowest ^1,3Σ⁺ states are calculated by diagonalizing the Douglas–Kroll–Hess Hamiltonian as implemented in Gaussian09 suite of programs. The ab initio calculations are performed at the CCSD­(T) level with UGBS1P+ basis set, a huge all-electron basis set. The rovibrational eigenenergies and eigenfunctions on the lowest ^1,3Σ⁺ ab initio potential curves are calculated by direct diagonalization of molecular Hamiltonian in a Fourier grid discrete variable representation. The results agree well with available experimental and theoretical work and the accuracy of theoretical descriptions of RbCs are increased, which is expected to be a good reference for further investigations

Colourful cholesteric liquid crystal polymer network gratings prepared through nanoimprinting

Both the colourful cholesteric liquid crystal polymer network (CLCN) patterns and the gratings have attracted much attention for their applications as optical materials. Herein, the photochromic cholesteric liquid crystal (CLC) mixtures were prepared using a photoisomerizable chiral dopant. The structural colour of the CLC mixtures was tunable by changing the chiral dopant concentration and the intensity of the 365-nm irradiation light. The CLCN gratings with a structural colour were prepared using the UV nanoimprinting lithography method. The structural colours of the CLCN gratings originate from both the cholesteric and the grating structures. Moreover, a patterned CLCN grating was prepared using a photochromic CLC mixture, which could be applied for decoration and anti-counterfeiting.</p