Photophysical, Electrochemical, and Theoretical Studies of Pyrido[2,3‐ b ]Quinoxaline‐Amines: Structure‐Driven Divergence Between AIE and ACQ Behaviors

ABSTRACT

Donor–acceptor (D−A) structured pyrido[2,3‐ b ]quinoxaline‐amines were synthesized using the Buchwald‐Hartwig coupling amination reaction. Characterization of dyes was done via spectroscopic methods. Intramolecular charge transfer (ICT) at (460−535 nm) in the absorption spectra of dyes validates the D−A framework in it and exhibits green–red emission (518–650 nm) in solution and solid state. Positive solvatochromism was observed, indicating that the dyes are sensitive to the environment and solvent polarity changes. The donor amine substitution on the core of the pyrido[2,3‐ b ]quinoxaline also causes variation in the emission behavior in the aggregated state, as only dye 5 can give aggregation‐induced emission (AIE) compared to the other dyes giving aggregation‐caused quenching (ACQ). Aggregate formation in the aqueous media was ascertained by a dynamic light scattering (DLS) study. The combination of AIE/ACQ behavior, positive solvatochromism, large Stokes shifts, good thermal stability, and highest occupied and lowest unoccupied molecular orbital (HOMO–LUMO) energies, which are like those of ambipolar materials, demonstrates its possible applications in optoelectronics. Also, theoretical studies have been carried out using a program known as Gaussian 03 to validate experimental photophysical and electrochemical observations, which are in close agreement with the theoretical values obtained.