Synthesis and photophysical properties of a series of thermally stable terphenyl-bridged bisbenzimidazoles

Nine novel terphenyl-bridged bisbenzimidazoles were synthesized in high yield by the condensation of o-phenylenediamines and terphenyl dinitriles in the presence of polyphosphoric acid. The bisbenzimidazoles are thermally robust with high decomposition temperatures (>346 °C) and high melting transitions and emit blue light at ∼410 nm with fluorescence quantum yield >0.4 in solution. Electrochemical studies indicate that the novel bisbenzimidazoles have a formal reduction potential in the range of −1.44 to −1.55 V and estimated electron affinities (lowest unoccupied molecular orbital levels) of 3.09–3.24 eV. The results indicate their potential use as blue-emitting materials in organic light-emitting diodes.