5,12‐Diacetyl‐5,12‐dihydroquinoxalino[2,3‐ b ]quinoxalines: Solid‐State Fluorescence, AIE Properties, and Orbital Switching by Substituent Effect

Quinoxaline-based azamacrocycles: synthesis, AIE behavior and acidochromism

The development of luminescent molecular materials has advanced rapidly in recent decades, primarily driven by the synthesis of novel emissive compounds and a deeper understanding of excited-state mechanisms. Herein, we report a streamlined synthetic approach to light-emitting diazapolyoxa- and polyazamacrocycles N2CnOxQ and NyCnQ (n = 3-10; x = 2, 3; y = 2-5), incorporating a 2,3-diphenylquinoxaline residue (DPQ). This synthetic strategy based on macrocyclization through Pd-catalyzed amination reaction yields the target macrocycles in good or high yields (46-92%), enabling precise control over their structural parameters. A key role of the PhPF-tBu ligand belonging to the JosiPhos series in this macrocyclization was elucidated through DFT computation. This macrocyclization reaction eliminates the need for complex protecting-deprotecting procedures of secondary amine groups, offering a convenient and scalable method for the preparation of target compounds. Moreover, it boasts a potentially broad substrate scope, making it promising for structure-properties studies within photophysics, sensor development, and material synthesis. Photophysical properties of representative macrocycles were investigated, employing spectroscopic techniques and DFT computation. It was demonstrated that DPQ-containing macrocycles display aggregation-induced emission in a DCM-hexane solvent mixture despite the presence of flexible tethers within their structures. Single-crystal X-ray diffraction analysis of a representative compound N2C8O3Q allowed us to gain deeper insight into its molecular structure and AIE behaviour. The emissive aggregates of the N2C10O3Q macrocycle were immobilized on filter paper yielding AIE-exhibiting test strips for measuring acidity in vapors and in aqueous media.

V-shaped fluorophores with a 1-methyl-4,5-bis(arylethynyl)imidazole skeleton displaying solid-state fluorescence, acid responsiveness, and remarkable fluorescence solvatochromism

V-Shaped fluorophores with a 1-methyl-4,5-bis(arylethynyl)imidazole skeleton displayed both solid-state and solution fluorescence, which remarkably changed on exposure to acid vapor.

Synthesis and electrochromic behavior of a multi-electron redox-active N-heteroheptacenequinone

We report a novel N-heteroheptacenequinone derivative (C6OAHCQ) as a large π-conjugated framework. C6OAHCQ shows good electron-accepting behaviour owing to eight electron-deficient imino-N atoms and two carbonyl moieties and excellent solubility in common organic solvents. When a potential between 0 and -2.20 V is applied, C6OAHCQ is able to accept four electrons, which is more than fullerene C60 (three electrons) could accept in this voltage range. Moreover, a solution of C6OAHCQ and nBu4NPF6 in CH2Cl2 exhibits a clearly reversible brown-to-green colour change, suggesting that C6OAHCQ has potential as an electrochromic material.

Effect of scaffold structures on the artificial light-harvesting systems: a case study with an AIEE-active pillar[5]arene dyad

The presence of a supramolecular polymeric scaffold structure enhanced the energy transfer capacity of the artificial light-harvesting nanoparticles.

Preparation, Electronic and Liquid Crystalline Properties of Electron-Accepting Azaacene Derivatives

A series of electron-accepting azaacene-type materials 1-4 with different kinds and degrees of intermolecular interactions were synthesized. Simple modification of the terminal substituents significantly modulated the photophysical and electrochemical properties. The degree of weak intermolecular interaction determined the emergence of a liquid crystalline (LC) phase for each compound. Dipole-dipole interaction, π-π interaction, and van der Waals interaction all contributed to stabilize the LC phase of 1 and 2. The introduction of strong hydrogen bonding interaction enabled the formation of a highly ordered LC phase in 4. Charge-transport properties of 1, 2, and 4 were also investigated.