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 t Bu 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 ( Φ PL ≈ 100%), and small Stokes shifts (11–16 nm). The electrochemical and theoretical studies further support the bandgap control and photophysical properties of compounds.