Oligomerization of dibrominated aminophenol on the basis of the chemical and HRP-catalyzed oxidative processes: Characterization and photoluminescence properties

Abstract

Preparation of oligo (aminophenols) was carried out by chemical oxidative and enzymatic oligomerization of 4-amino-2,6-dibromophenol (ADBP). The former method required hydrogen peroxide as catalyst in an aqueous sodium hydroxide solution and the latter method was catalyzed by an enzyme, horseradish peroxidase, in 1,4-dioxane resulting in the formation of (ADBP)-ox and (ADBP)-enz, respectively. For the structural confirmation for both of the synthesized oligomers were fulfilled using FT-IR, UV–vis and 1H NMR and 13C NMR instruments. The chemical oxidation with H2O2 induced monodisperse particles in the sub-micron size. The thermal treatment of the oligomers at 1000 οC showed that the chemical oxidation resulted in (ADBP)-ox with higher residue% compared to enzymatic oxidation. Neutral ADBP underwent facile oxidation, leading to the formation of its corresponding oligomers, which were composed of head-to-tail or ortho-coupled constitutional moieties with lower optical and electrochemical band gaps than those of ADBP using two oligomerization routes. By analyzing the solvent effect on the absorption, lower optical band gaps of the synthesized oligomers were obtained in some selected solvents, pointing out them as semi-conductive material for the production of optoelectronic and electronic materials. By tuning the excitation wavelength, the fluorescence intensity of both of the oligomers was changed. DMF solution of (ADBP)-ox and (ADBP)-enz had a quantum yield of 17.6 % and 1.2 % for green and orange photoluminescence emission, respectively, with excellent photostability.