On the photo-physical properties of soluble oligomer from anodic oxidation of chlorine-substituted anisole (OPClAn)

This work aims at completing theoretically the oligomerization mechanism, vibrational and optical properties of soluble oligomer obtained from anodic oxidation of p-chloro-anisole (OPClAn) with a view to get some insight into structure–property relationships. The obtained results were compared with those of oligomers from p-fluoro-anisole (OPFAn) and p-phenylene (OPP). Spectroscopic characterization based on infrared absorption, Raman scattering, optical absorption, photoluminescence (PL) and decays of time-resolved photoluminescence (TR-PL) in chloroform solution and in film states of OPClAn was performed. Further investigations on conformational, geometrical parameters, and electronic structures of these compounds were carried out by applying Density Functional Theory (DFT) calculation based on B3LYP with 6-31G(d,p) and 3-21G* as basis sets. The optimized structures, HOMO–LUMO gaps (ΔH–L), in addition to the ionization potentials (IPs) and electron affinities (EAs) were calculated. The ΔH–Ls, Egs, IPs and EAs of the oligomers were obtained by extrapolating those of the oligomers to the inverse chain length for n = 13. From the combined results, we have evoked an oligomerization mechanism consistent with the OPClAn prepared material. Furthermore, we have shown that introducing electron-donating/withdrawing substituents on oligo-phenylene backbone can tune the HOMO and LUMO levels and thereby control the opto-electronic properties of the designed oligomers.