Synthesis and Optical Study of a New Oligophenylene

A new substituted oligophenylene was prepared by the Knoevenagel condensation of 4-methoxybezaldehyde with a functionalized oligophenylene (OMPA). The latter was obtained by (4-methoxy phenyl) acetonitrile electrochemical oxidation. The resulting modified oligomer was characterized by various spectroscopic techniques: NMR, FTIR and UV. The thermal study showed that the modified material exhibited a lower thermal stability compared with OMPA. Finally, the optical study revealed that in solution, the emission was red-shifted when compared with the non-modified oligomer emission and that the optical gap changed from 3.1 eV to 2.75 eV. In thin layer solid state, photoluminescence was again red-shifted by 120 nm, which is probably due to an interaction between the oligomer chains. In addition, a transient photoluminescence study was undertaken for the synthesized materials. It showed that the lifetimes of the photo-generated species were shortened by the conjugation extension in the modified oligomer and by the inter-chain interactions in the solid state.