Pyridine-cored V-shaped π-conjugated oligomers: synthesis and optical properties

Tetrakispyrazolylethene: Protonation-Induced Emission

Tetrakispyrazolylethene (1) was synthesized from pyrazole and hexachloroethane through a one-step substitution reaction. The increase of emission was detected both in solid and aqueous THF solution, compared with that in anhydrous THF. While the former originates from the crystal packing, the latter is attributed to the protonation-induced emission, independent of aggregation, based on the optical measurement under varying concentrations and particle-size distribution analysis.

Four-Winged Propeller-Shaped Indole-Modified and Indole-Substituted Tetraphenylethylenes: Greenish-Blue Emitters with Aggregation-Induced Emission Features for Conventional Organic Light-Emitting Diodes

Aggregation-induced emission (AIE) is an extraordinary photochemical phenomenon described by Tang's group in 2001, where the aggregation of some organic molecules enhances their light emission by limiting intramolecular activity in the aggregate state. This phenomenon offers new opportunities for researchers due to its potential applications in optoelectronics, energy, and biophysics. Tetraphenylethylenes (TPEs) are reliable AIE luminogens with a wide range of successful applications in material chemistry. To expand the library of AIE-active TPEs, both a series of TPE analogues, in which the phenyl rotor has been replaced by the indole ring, and indole-substituted TPE derivatives were designed and synthesized through vinyl-aryl and aryl-aryl bond formations using the Suzuki coupling reaction. Efficient synthetic routes that delivered indole-modified and indole-substituted TPEs have been developed, and almost all heterocyclic TPE analogues have demonstrated AIE behavior. Furthermore, to test whether the indole ring can be diversified, two title compounds were converted to a series of bis(indolyl)methane (BIM), and these BIM-TPE materials showed typical AIE properties. Interestingly, two compounds indicated a solvent vapor fuming reversible switch between bright blue emission and greenish-yellow emission. Upon fuming with dichloromethane, their fluorescence spectra showed 8 and 32 nm red-shift and could return to the original state after fuming with hexane. Furthermore, we have explored the effects of replacing the phenyl ring in TPE with indole together with the substitution of TPE with indole ring(s) on the performance of organic light-emitting diode (OLED) device applications. In addition, density functional theory calculations; the optical, electrochemical, light emission, electroluminescence characteristics; and admittance spectroscopic analysis of OLED devices of four representative TPEs have been investigated in detail. As a result, the indole-TPEs are potential blue emitters with AIE features for conventional OLEDs, which is a significant color in displays and lighting.

Isolation and structural characterization of a titanacyclopropane as key intermediate in the double aryl Grignard addition to 2-(arylethynyl)pyridine derivatives

A titanacyclopropane species, which is a key reaction intermediate in the Ti(OiPr)₄-mediated double aryl Grignard addition to 1,2-di(pyridin-2-yl)ethyne and related alkynes, was isolated and fully characterized.

A selective fluorescent sensor for Zn(2+) based on aggregation-induced emission (AIE) activity and metal chelating ability of bis(2-pyridyl)diphenylethylene

Polypyridyl ethylenes have been prepared as heterocyclic analogues of tetraphenylethylene. In addition to conventional AIE effects, a derivative possessing a 1,1-bis(2-pyridyl)ethylene fragment displays Zn(2+)-selective enhanced fluorescence in aqueous solution, in contrast to the behavior of isomeric bis(3- and 4-pyridyl)ethylenes. The Zn(2+)-sensing capability of this material is attributed to formation of chelated Zn(2+)-bis(pyridyl) complexes and is supported by the X-ray crystal structure of a bis(2-pyridyl)ethylene-Zn(OAc)2 complex.

Alphabet-Inspired Design of (Hetero)Aromatic Push-Pull Chromophores

Push-pull molecules represent a unique and fascinating class of organic π-conjugated materials. Herein, we provide a summary of their recent extraordinary design inspired by letters of the alphabet, especially focusing on H-, L-, T-, V-, X-, and Y-shaped molecules. Representative structures from each class were presented and their fundamental properties and prospective applications were discussed. In particular, emphasis is given to molecules recently prepared in our laboratory with T-, X-, and Y-shaped arrangements based on indan-1,3-dione, benzene, pyridine, pyrazine, imidazole, and triphenylamine. These push-pull molecules turned out to be very efficient charge-transfer chromophores with tunable properties suitable for second-order nonlinear optics, two-photon absorption, reversible pH-induced and photochromic switching, photocatalysis, and intercalation.

Fluorosolvatochromism of furanyl- and thiophenyl-substituted acetophenones

Fluorosolvatochromism of four furanyl- or thiophenyl-substituted acetophenone derivatives is suitable to measure environmental effects.

Planar–rotor architecture based pyrene–vinyl–tetraphenylethylene conjugated systems: photophysical properties and aggregation behavior

Pyrene–tetraphenylethylene based monomers and tetramers were synthesized. Photophysical and electrochemical properties were investigated. Spacer, architecture and substituent dependent aggregation behavior were reported.

Synthesis and aggregation-induced emission properties of pyridine and pyridinium analogues of tetraphenylethylene

Tetraphenylethylenes in which one or two of the core phenyl rings have been replaced with pyridine or pyridinium groups have been prepared and evaluated as aggregation-induced emission fluorophores.