AIEgens-NLOphores coumarin-triphenylamine chalcone derivatives: Synthesis, photophysical properties and DFT computational study

Three coumarin-triphenylamine chalcone derivatives (5a-c) with push-pull structures of type A-π-D and D-π-A-π-D were synthesized, varying the substituent at position 7 of coumarin. The characterization of the final compounds as for the intermediates was conducted using 1H and 13C NMR, FT-IR, and HRMS. The study of the photophysical properties of 5a-c revealed a strong solvatochromism, mainly in fluorescent emission, due to the formation of a twisted intramolecular charge transfer (TICT) state. Moreover, aggregation-induced emission (AIE) in MeCNH2O mixtures was notably observed, as well as a strong red emission in the solid state. Computational studies by DFT methods allowed to elucidate the molecular geometries of the ground (S0) and excited states (S1), assign vibrational modes and electronic transitions of IR and UV–Vis spectra, respectively, to describe the reactivity and the electronic distribution from the molecular electrostatic potential (MEP) and the HOMO-LUMO orbitals. Computationally calculated first and second-order hyperpolarizabilities show chalcones 5a-c as potential NLO materials.