An unsymmetric diazaborepin framework NBNH was synthesized, featuring a fused 6/5/7-ring core. Further π-extension via meta- and para-N-π-N arrangements afforded two bis-diazaborepin-embedded isomers m-dNBNH and p-dNBNH. The two isomers display distinct frontier molecular orbital distributions, and the para isomer p-dNBNH exhibits a photoluminescence quantum yield of 100%. All three compounds exhibit singlet-oxygen sensitization and pronounced antiaromatic character for the diazaborepin units.
Chen et al. (Wed,) studied this question.