The Influence of the 4-Diethylaminophenyl Substituent on the Physicochemical Properties of Phenanthro[9,10-d]imidazole Derivatives in the Context of Electroluminescent Applications

Does position matter? In many respects, it certainly does, but does it also matter in the case of a functional group such as 4-diethylaminophenyl in the structure of phenanthro[9,10-<i>d</i>]imidazole derivatives? We attempt to answer this question in this article by considering selected physicochemical properties of the presented compounds. Therefore, in this work, four phenanthro[9,10-<i>d</i>]imidazole derivatives (<b>AM-0</b>-<b>AM-3</b>) were obtained by Debus-Radziszewski condensation. All derivatives were purified, and their structures were confirmed using NMR spectroscopy. The synthesized compounds were then compared for their thermal, electrochemical, and optical properties. This demonstrated that the derivatives (<b>AM-0</b> and <b>AM-1</b>) containing a 4-diethylaminophenyl substituent at the C2 position exhibit better physicochemical parameters than the other compounds, particularly in terms of thermal stability, energy gap, and even quantum yield. In the case of the latter parameter, derivatives containing 4-diethylaminophenyl at the C2 position show an increase of up to 15-30% (depending on the solvent used) compared to the compound containing the considered substituent at N1. The obtained research results were compared with DFT calculations to gain a deeper understanding of the experiments performed.