Novel carbazole dendrimers having a metal coordination site as a unique hole-transport material

We have synthesized novel carbazole dendrimers via the cyclotrimerization of aminophenylketones in the presence of titanium tetrachloride. These dendrimers have the ability to assemble metal ions such as Sn²⁺ and Eu³⁺ with no significant difference in their generation, suggesting the dendrimer with an interior with a small density up to the third generation. We show the dendrimers with higher generations have the higher HOMO values. The most electron rich molecule, the G3 dendrimer, has the highest HOMO value of −5.2 eV. However, for the HOMO energy levels of the carbazole dendrimer complex with Eu(OTf)₃, the energy levels of the carbazoles did not change based on almost the same redox potentials as those of the dendrimers, themselves. Using the carbazole dendrimers and their europium complex, a homogeneous film was produced, which enhanced the performance of the electroluminescence device in comparison with only the dendrimer as the hole-transporting layer. This approach was managed by a solution process, i.e., the spin-coating method, without using the coevaporation technique based on the large equilibrium constants of the coordination of metal ions on the imine sites (K = 10⁵ M⁻¹).