Highly Fluorescent Red-Light Emitting Bis(boranils) Based on Naphthalene Backbone

Ten bis­(boranils) differently substituted at the boron atom and iminophenyl groups were synthesized from 1,5-dihydroxynaphthalene-2,6-dicarboxaldehyde using a simple one-pot protocol. Their photophysical properties can be easily tuned in a wide range by the variation of substituents. Their absorption and emission spectral bands are significantly red-shifted (λmax = 495–590 nm, λem = 533–683 nm) when compared with simple boranils, whereas fluorescence quantum yields are strongly improved to reach 83%. The attachment of pendant NO2 and NEt2 groups at the opposite positions of the π-conjugated bis­(boranil) scaffold resulted in the formation of an unprecedented system featuring push–pull architecture.