Study on synthesis and properties of novel luminescent hole transporting materials based on N,N′-di(p-tolyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine core

Four novel blue luminescent hole transporting materials with N,N′-di(p-tolyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine as the core, containing triphenylamine units and olefinic linkers were synthesized and characterized by FT-IR, 1H NMR and HRMS. Their optical, electrochemical and thermal properties were investigated. Quantum-chemical calculations were performed to obtain their optimized structures and the electron distribution of the molecular orbital energy levels, and the experimental findings suggest that monosubstituted compounds have a similar energy gap to the bisubstituted compounds. The UV–Vis and photoluminescence spectra indicate that these compounds are blue luminescent materials. Cyclic voltammetry measurements show that the four compounds embody suitable highest occupied molecular orbital levels (in a range of −5.08 ∼ −5.14 eV) for hole injection. All of the compounds have excellent thermal stability, with decomposition temperatures above 400 °C and glass transition temperatures above 100 °C, which is of benefit to form stable amorphous glassy states.

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► Four novel blue luminescent hole transporting materials containing triphenylamine units and olefinic linkers were synthesized and characterized.
► The synthesized compounds exhibit blue emissions, good solubility, the appropriate highest occupied molecular orbital energy level and high thermal stability.
► Quantum chemical calculations suggest that the energy gap can be effectively reduced by enlarge any part of conjugated structure.
► The new compounds offer potential for application in organic light-emitting devices.