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 P21/n. These compounds showed UV–Vis absorption (λmaxAbs) in the range of 311–345 nm in DCM solution and 371–391 nm in solid state, and fluorescence maxima (λmaxEm) 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.

► Our work succeeds in synthesizing a series of novel 3,8,13-substituted triindoles.
► These triindoles synthesized by trimerization of derivatives of indolin-2-one.
► Their photophysical and electrochemical properties were investigated.
► They are expected to be promising hole-transport and injection materials for OLEDs.