Aryl-linked bischalcones: Spectroscopic, photophysical, cyclic voltammetry, and DFT computational studies

Abstract

A series of 1,3- and 1,4-aryl-linked bischalcones was synthesized and characterized by IR, 1H NMR, 13C NMR, and UV–vis spectroscopies. The effects of the type of linking of two chalcone moieties (via the carbonyl or C=C double bond functional groups) to the 1,3- or 1,4-positions of the central aryl ring on the spectral data, fluorescence emission and electrochemical behavior were investigated, and compared with those of the monochalcones. Introduction of the electron-donating para-methoxy group to the wing aryl rings of both chalcone moieties created more effective donor-π-acceptor (D-π-A) systems (p-MeOC6H4-CHdbndCH-CO- or p-MeOC6H4-CO-CHdbndCH-), resulting in a red shift of their UV–vis absorption and fluorescence emission peaks, compared to that of the meta-methoxy group. The HOMO and LUMO energies, their gaps (HLG), and UV–vis spectra were calculated for the optimized geometries of bischalcones using density functional theory by B3LYP/6–311++G(d,p) method. The structures of two representative bischalcones 1a and 1d, in their excited states with the highest UV–vis transition oscillator strengths, were optimized by TD-DFT computation and their electron density distributions were investigated. Cyclic voltammetry data were used to elucidate the dependence of the oxidation behavior of the synthesized bischalcones on the type of linking and substitution. © 2025