Blue organic light-emitting diodes based on fluorene-bridged quinazoline and quinoxaline derivatives

Synthesis of a fluorene and quinoxaline-based co-polymer for organic electronics

Quinoxaline has recently gained interest as monomer in conjugated copolymers because of its easy synthetic accessibility and successful use in highly efficient organic solar cells. In this contribution, we introduce a quinoxaline–fluorene-co-polymer, PFQ10, synthesized by copolymerization of 5,8-dibromo-6,7-difluoro-2-[(2-hexyldecyl)oxy]quinoxaline and 9,9-dioctyl-9H-9-fluorene-2,7-bis(boronic acid pinacol ester) using the Suzuki–Miyaura reaction. By optimization of the reaction conditions, polymers with molecular weights up to 17.2 kDa and a low dispersity of 1.3 were obtained. PFQ10 showed blue photoluminescence with an emission maximum at 459 nm and a relative fluorescence quantum yield of 0.37. As proof of principle, PFQ10 was employed in organic light-emitting diodes and showed a blue–green electroluminescence.

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Synthesis of cinnamils and quinoxalines and their biological evaluation as anticancer agents

We synthesized multiple cinnamils and quinoxalines to evaluate their anticancer activity. Cinnamils were used as precursors for quinoxalines via condensation with 1,2-diaminobenzene. Among the 26 synthesized compounds reported in this article, we found that cinnamil 3l exhibited its inhibitory effect with an IC50 value of 1.45 ± 0.98 μM, significantly higher than doxorubicin (8.5 ± 0.85 μM) against pancreatic cancer cells (PANC-1). Additionally, cinnamil 3l (IC50 10.98 ± 3.63 μM) showed less cytotoxicity than doxorubicin to Hs68 cells (0.92 ± 1.11 μM). The colony formation assay demonstrated that 3l obviously decreased the PANC-1 cell viability, and Western blot assays confirmed that 3l markedly induced apoptosis of PANC-1 cells through Bax, Bcl-2, and caspase 3 signaling cascades. These results demonstrate that cinnamil 3l has great potential to be further developed as a promising chemotherapeutic agent for pancreatic cancer.

Synthesis and Photophysical Properties of Quinoxaline-Based Blue Aggregation-Induced Emission Molecules

A series of quinoxaline-based compounds 1–4 have been synthesized by Palladium-Catalyzed cross-coupling reaction and their photophysical properties have been extensively studied. Compounds 1–4 show deep blue light emission both in solution (λem ≤ 425 nm, CIEy≤0.03) and in solid-state. Moreover, compounds 1–3 show a non-typical aggregation-induced enhanced emission (AIEE), which would be effective deep blue light-emitting materials. The DFT calculation indicated that the HOMO energy levels of compounds 1–3 are distributed throughout the molecule, and the LUMO energy levels are mainly concentrated on the quinoxaline group. while the HOMO of compound 4 is mainly on the benzene ring at 2,3-position, and the LUMO is distributed both of the quinoxaline and the benzaldehyde group at the 6,7-position.

Synthesis and Structure-Photophysics Evaluation of 2-N-Amino-quinazolines: Small Molecule Fluorophores for Solution and Solid State

2-N-aminoquinazolines were prepared by consecutive S_N Ar functionalization. X-ray structures display the nitrogen lone pair of the 2-N-morpholino group in conjugation with the electron deficient quinazoline core and thus representing electronic push-pull systems. 2-N-aminoquinazolines show a positive solvatochromism and are fluorescent in solution and in solid state with quantum yields up to 0.73. Increase in electron donor strength of the 2-amino substituent causes a red-shift of the intramolecular charge transfer (ICT) band (300-400 nm); whereas the photoluminescence emission maxima (350-450 nm) is also red-shifted significantly along with an enhancement in photoluminescence efficiency. HOMO-LUMO energies were estimated by a combination of electrochemical and photophysical methods and correlate well to those obtained by computational methods. ICT properties are theoretically attributed to an excitation to Rydberg-MO in SAC-CI method, which can be interpreted as n-π* excitation. 7-Amino-2-N-morpholino-4-methoxyquinazoline responds to acidic conditions with significant increases in photoluminescence intensity revealing a new turn-on/off fluorescence probe.