Facile synthesis of 2-aza-9,10-diphenylanthracene and the effect of precise nitrogen atom incorporation on OLED emitters performance

Polycyclic aromatic hydrocarbons (PAHs) are important compounds in materials chemistry, particularly for optoelectronic applications. One strategy for tuning PAH properties involves the net exchange of carbon atoms for heteroatoms, such as nitrogen. We report a comparative study of the well-known fluorophore 9,10-diphenylanthracene with an aza analog. The latter compound is accessed using a short sequence involving the use of two strained cyclic alkynes, benzyne and a 3,4-piperidyne, in Diels-Alder cycloaddition sequences. Comparative studies of 9,10-diphenylanthracene and the aza-analog show how the addition of a single nitrogen atom impacts electrochemical and optical properties. Organic light-emitting diode (OLED) devices were prepared using both compounds, which showed that nitrogen substitution leads to an unexpected red shift in electroluminescence, likely due to exciplex formation between the active layer and the 4,4'-N,N'-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB) hole-transport layer. These studies highlight a unique approach to accessing heteroatom-containing PAHs, while underscoring the impact of heteroatoms on OLED device performance.