Bisindolylmaleimide derivatives as non-doped red organic light-emitting materials

A new series of bisindolylmaleimide (BIM) derivatives were synthesized. The absorption and fluorescence properties of these compounds were investigated in solution and solid state. Dramatic difference in solid-state fluorescence emission spectra was observed by changing the substituents on the fluorophores skeleton from methyl to benzyl. We performed X-ray crystallographic analyses to elucidate the effect of the substituents of the non-conjugated linkage on the solid-state fluorescence emission spectra. The relationships between the solid-state photophysical properties and the chemical and crystal structures of 2,3-bis(N-benzyl-2′methyl-3′-indolyl)-N-methylmaleimide (1S) and 2,3-bis(N-benzyl-2′methyl-3′-indolyl)-N-benzylmaleimide (5S) are discussed on the basis of the X-ray crystal data. Bis[2,3-bis(N-ethyl-2′methyl-3′-indolyl)-N-(prop-2-ynyl)maleimide] (1B) and 1S were utilized in non-doping host red EL device. The brightness reaches 393 cd m−2 at 100 mA cm−2 for 1S.