Blue-red emitting materials based on a pyrido[2,3-b]pyrazine backbone: design and tuning of the photophysical, aggregation-induced emission, electrochemical and theoretical properties.

Pyrido[2,3-b]pyrazine-based donor-acceptor-donor (D-A-D) molecules were designed by altering donor amines and synthesized using the Buchwald-Hartwig C-N coupling reaction. Further, the tunable opto-electrochemical properties of the dyes were studied in detail. The dye possesses intramolecular charge transfer (ICT) transition (412-485 nm), which marked the D-A architecture and induces a broad range of emissions from blue to red (486-624 nm) in the solution and solid state. Some of the dyes show aggregation-induced emission (AIE) features and formation of nanoparticles in the THF/H2O mixture, as confirmed by DLS and FEG-SEM (of 7) analysis. The AIE characteristics indicate its solid/aggregate-state application in organic electronics. The molecules exhibit high thermal stability, low band gap (1.67-2.36 eV) and comparable HOMO (-5.34 to -5.97 eV) and LUMO (-3.61 to -3.70 eV) energy levels with those of reported ambipolar materials. The relationship between the geometrical structure and optoelectronic properties of the dyes, as well as their twisted molecular conformation and small singlet and triplet excitation energy difference (ΔE ST = 0.01-0.23 eV) were analyzed using the DFT/TDDFT method. Thus, potential applications of the dyes are proposed for optoelectronic devices.

A highly effective cobalt catalyst for olefin aziridination with azides: hydrogen bonding guided catalyst design.

[Co(P1)], which was designed on the basis of potential hydrogen-bonding interactions in the metal-nitrene intermediate, is a highly active aziridination catalyst with azides. [Co(P1)] can effectively aziridinate various aromatic olefins with arylsulfonyl azides under mild conditions, forming sulfonylated aziridines in excellent yields. The Co-based system enjoys several attributes associated with the relatively low cost of cobalt and the wide accessibility of arylsulfonyl azides. Furthermore, it generates stable dinitrogen as the only byproduct.

Cobalt-catalyzed intramolecular C-H amination with arylsulfonyl azides.

Cobalt complexes of porphyrins are effective catalysts for intramolecular C-H amination with arylsulfonyl azides. The cobalt-catalyzed process can proceed efficiently under mild and neutral conditions in low catalyst loading without the need of other reagents or additives, generating nitrogen gas as the only byproduct. The catalytic system can be applied to primary, secondary, and tertiary C-H bonds and is suitable for a broad range of arylsulfonyl azides, leading to high-yielding syntheses of various benzosultams.