Synthesis and optical properties of 6,10-dihydrofluoreno[2,3-d:6,7-d′]diimidazole derivatives

A series of 10,10-dioctyl-3,6-dihydrofluoreno[2,3-d:6,7-d′]diimidazole derivatives were conveniently synthesized by condensation of the key intermediate 2,3,6,7-tetraamino-9,9-dioctylfluorene (TADOF) with aldehydes under very mild conditions. All of the target compounds were characterized using 1H NMR, 13C NMR, and elemental analysis. The crystal structure of 3,6-dibenzyl-10,10-dioctyl-2,7-diphenyl-6,10-dihydro-3H-fluoreno[2,3-d:6,7-d′]diimidazole was determined as triclinic, space group P-1 type, using single X-ray crystallography. For seventeen samples, UV–visible absorption maximum wavelength (λmax), fluorescence excitation wavelength (λex), fluorescence emission wavelength (λem) and fluorescence quantum yield (φFL) were measured in dilute dichloromethane solution and in the solid state. These compounds possess a medium strong blue fluorescence-emitting ability with φFL values in the region of 0.30–0.89 and structure-optical behavior characteristics were discussed.

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► 2,3,6,7-Tetraamino-9,9-dioctylfluorene (TADOF) was efficiently synthesized.
► 6,10-Dihydrofluoreno[2,3-d:6,7-d′]diimidazole derivatives were synthesized.
► The UV-visible absorption and fluorescence properties were studied.
► These compounds possess a medium strong blue fluorescence-emitting ability.
► The structure-optical behavior characteristics were discussed.