The synthesis, photophysical and electrochemical properties of a series of novel 3,8,13-substituted triindole derivatives

The synthesis and properties of a series of new 3,8,13-substituted triindole derivatives 1a-1e are reported. The 3,8,13-substituted triindoles were thermally robust with high decomposition temperatures (≥405°C) and high melt transitions (219°C-373°C). Compound 5e was crystallized in the monoclinic system with the space group P2 ₁/n. These compounds showed UV-Vis absorption (λ _max ^Abs) in the range of 311-345 nm in DCM solution and 371-391 nm in solid state, and fluorescence maxima (λ _max ^Em) in the range of 394-412 nm in DCM solution and 416-461 nm in solid state. The fluorescence quantum yields ranged from 0.27 to 0.58. The estimated electron affinities (LUMO levels) and estimated ionization potential (HOMO levels) of compounds 1a-1e are 3.54-3.71 eV and 5.12-5.48 eV, respectively. Quantum chemical calculations using DFT B3LYP/6-31G showed nearly identical LUMO (-0.72 to -1.10 eV) and HOMO (-4.65 to -4.84 eV) values. These results demonstrated that the new 3,8,13-substituted triindoles are promising thermally stable host materials for organic light-emitting diodes with reasonable hole mobility.