Planarized B,N-diarylated dibenzoazaborine compounds for deep blue fluorescence

Abstract

A series of planarized B,N-diarylated dibenzoazaborine compounds (5a–5e) in which various functional groups are introduced into the B-Ph and N-Ph moieties of nonsubstituted dibenzoazaborine compound (I) were prepared. All compounds exhibit strong low-energy absorptions at ca. 410–426 nm with a gradual red-shift depending on the electron-accepting property of the four substituents (4-R = 4-Ph < 4-Pm < 4-CNPh <4-CN) on the B-Ph ring in 5a–5d. Introduction of an electron-donating tBu group into the N-Ph ring further shifts slightly the absorption band toward a lower-energy region (5e). Importantly, all compounds undergo gradual red-shifts in the emission leading to deep blue fluorescence for CN-substituted 5d and 5e. Furthermore, the emissions have narrow full width at half maximum values of ca. 30 nm, high photoluminescence quantum yields (ΦPL ≈ 100%), and small Stokes shifts (11–16 nm). The electrochemical and theoretical studies further support the bandgap control and photophysical properties of compounds.