Triarylboranes bearing a benzimidazole or quinoline ring attached to the boron atom: Synthesis, π-conjugation, and fluorescence

Abstract

2-Aryl-6-(dimesitylboryl)-5,7-dimethylbenzimidazoles (1), 2-aryl-5-(dimesitylboryl)-1,4,6-trimethylbenzimidazoles (2), and 2-aryl-6-(dimesitylboryl)-3,5,7-trimethylquinolines (3) were synthesized by imine formation from 4-(dimesitylboryl)-3,5-dimethylaniline (4) and a subsequent intramolecular cyclization reaction affording benzimidazole or quinoline rings. The degree of π-conjugation and fluorescence properties of the obtained triarylboranes were evaluated to develop easily synthesizable fluorescent triarylboranes using imine formation. Compounds 1–3 exhibited blue fluorescence (λem, 389–425 nm) with moderate fluorescence quantum yields (ΦF, 8%–49%) in chloroform.

Keywords

• Triarylborane
• Fluorescence
• Benzimidazole
• Quinoline