Synthetic Doping of Acenaphthylene through BN/CC Isosterism and a Direct Comparison with BN-Acenaphthene

Boron/nitrogen-doped acenaphthylenes, a new class of
BN-doped cyclopenta-fused
polycyclic aromatic hydrocarbons, were synthesized via indole-directed
C–H borylation. The reference molecule BN-acenaphthene was
also synthesized in a similar manner. Both BN-acenaphthylene and BN-acenaphthene
were unequivocally characterized by single-crystal X-ray analysis.
The aromaticities of each ring in BN-acenaphthylenes were quantified
by experimental and theoretical methods. Moreover, doping the BN unit
into acenaphthylene can increase the LUMO level and decrease the HOMO
level, resulting in wider HOMO–LUMO energy gaps. Furthermore,
regioselective bromination of BN-acenaphthylene (B-Mes) afforded monobrominated
BN-acenaphthylene in good yield. Subsequently, cross-coupling of brominated
BN-acenaphthylene gave a series of BN-acenaphthylene derivatives.
In addition, the photophysical properties of these BN-acenaphthylene
derivatives can be fine-tuned by the substituents on the BN-acenaphthylene
scaffold.