Deep-blue Fluorophores Based on Phenanthroimidazole Integrated with Benzo[d]thiazole: Experimental and Theoretical Investigation

Three deep-blue emissive donor-acceptor (D-A) fluorophores, 2-(4 '-(1-(4-(tert-butyl)phenyl)-1H-phenanthro[9,10-d]imidazol-2-yl)-[1,1 '-biphenyl]-4-yl)benzo[d]thiazole (PTPISN), 2-(4 '-(1-(3-(trifluoromethyl)phenyl)-1H-phenanthro[9,10-d]imidazol-2-yl)-[1,1 '-biphenyl]-4-yl)benzo[d]thiazole (m-CFPISN) and 3-(2-(4 '-(benzo[d]thiazol-2-yl)-[1,1 '-biphenyl]-4-yl)-1H-phenanthro[9,10-d]imidazol-1-yl)benzonitrile (m-CNPISN) based on benzothiazole with varying substituents at N1-position to tune the properties of the materials were designed and synthesized. The synthesized fluorophores were structurally confirmed by spectroscopic techniques. All the fluorophores exhibited good thermal properties with high thermal degradation temperatures. An optical study reveals that the fluorophores are capable of emitting in the blue spectral region in solution and solid. The quantum chemical investigations were also performed with the aim to understand the electronic structures of the fluorophores. Further, solution-processed OLED device was fabricated by using PTPISN as an emissive dopant and found that bright deep-blue electroluminescence with CIEy of (similar to 0.08). These results suggest that the introduction of benzothiazole moiety is a promising design strategy for obtaining new deep-blue emitters.

Automated summary

Three deep-blue emissive compounds were designed and synthesized by introducing different substituents at the N1 position of benzothiazole. The compounds exhibited good thermal and optical properties, emitting blue fluorescence in both solution and solid states. The introduction of the benzothiazole moiety proved to be a promising design strategy for obtaining new deep-blue emitters.