Emission‐Tunable B←N Lewis Pair‐Functionalized Naphthalenes

Abstract

Herein, we simultaneously synthesized three different double B←N Lewis pair‐functionalized naphthalenes including the asymmetric BNNY and BNNO and the mirror‐symmetric BNNR, via a one‐pot method. The annulation modes of the B←N Lewis pairs and the substituents on the boron atoms efficiently tune the molecular frontier orbitals and emission colors. α‐Position fusion leads to a significant enhancement of the HOMO energy level and a decrease in the HOMO‐LUMO gap, while the electron‐withdrawing groups attached to the boron atom make the LUMO energy level more stable. In particular, the LUMO energy level of BNNO is as low as ‐3.12 eV. BNNY, BNNO, and BNNR emit cyan, green, and red fluorescence at 509, 534, and 620 nm, respectively, with fluorescence quantum yields of 24%, 49%, and 30%, respectively.