Synthesis And Properties Of Polyarylimidazole π-conjugated Materials

Organic small molecule luminescent materials have attracted much attention due to their strong chemical modification and high fluorescence quantum efficiency,as well as their unique optical and electrochemical properties.Multi-aryl imidazoles with the rigid conjugated structure are favored for efficient injection and transport of charge,and have high thermal stability,so these compounds are expected to become organic light-emitting host materials.In this paper,three kinds of multi-aryl imidazole derivatives with fluorescent properties were designed by DFT theory,and then the target compounds were synthesized through cyclization reaction and coupling reaction,etc.The structures of the target compounds were confirmed by IR,NMR and HRSM.The thermal stabilities,photophysical and electrochemical properties of the target compounds were tested by TGA,UV,PL and CV.4-Bromobenzaldehyde as the starting material,seven multi-aryl substituted bis-imidazole derivatives were synthesized through Suzuki coupling reaction with different arylboronic acids and cyclization with 2,3,5,6-tetraaminopyridine hydrochloride,then following by alkylation.The experimental results indicated that these compounds exhibited good thermal stability due to the introduction of the bis-imidazole heterocyclic molecular structure,while the introduction of the alkyl chain also improved the solubility of the products,thus improving the device processing performance of these compounds.The compounds exhibited good PL characteristics and the emission peaks were located in the deep blue region(424-478 nm),therefore these compounds could be used as the deep blue light emitting materials.1,2-Diphenyl ethanedione and aniline as starting materials,seven mono-aryl substituted mono-imidazole derivatives were synthesized through the cyclization and Suzuki coupling reaction.Due to their good conjugated structure and dissolution properties,the compounds showed stable blue light emission in both solution and solid state,and could be used as potential blue light emitting materials.The deeper HOMO energy levels of these compounds(5.33-5.68 eV)were lower than the work function of ITO(4.7 eV),which could effectively reduce the energy barrier of the hole injection emission layer and improve the device efficiency.1,2-Diphenyl ethanedione and 4-bromoaniline as starting materials,five bis-aryl substituted mono-imidazole derivatives were synthesized through the cyclization and Suzuki coupling reaction.Since the molecules contained two side-arm substituted 1,4,5-triphenylimidazole conjugated structures,these compounds showed relatively separated molecular orbital energy levels of HOMO and LUMO.This characteristic could facilitate the preparation of thermally activated delayed fluorescent materials.