Boron/nitrogen-doped fluoranthenes, a new class of BN-doped cyclopenta-fused polycyclic aromatic hydrocarbons, were synthesized via pyrrolic-type nitrogen directed C−H borylation. Regioselective bromination of BN-fluoranthene (3a) gave mono-and dibrominated BN-fluoranthenes. The halogenated BN-fluoranthene (3b) can undergo various of further crosscoupling reactions to deliver a series of BN-fluoranthenes. Moreover, incorporating BN unit in to fluoranthene resulted in a wider HOMO−LUMO energy gaps. The aromaticities of the BN-fluoranthene (3a) were quantified by experimental and computational studies.
Two types of "parental" BN-dibenzo[f,k]tetraphenes (BNDBT-1 and BNDBT-2) have been synthesized via a transition-metal-catalyzed tandem cross-coupling reaction as key steps. Both BNDBT-1 and BNDBT-2 are fully characterized; one of them is unambiguously confirmed by a single Xray crystal structure. Compared to its all-carbon analogue DBT, BNDBT-1 and BNDBT-2 exhibit a higher highest occupied molecular orbital (HOMO) and lower lowest unoccupied molecular orbital (LUMO) energy, while the BN doping position slightly influences the HOMO and LUMO energies of BNDBT-1 and BNDBT-2. Both BNDBT-1 and BNDBT-2 exhibit red-shifted absorption and emission spectra and higher emission efficiencies, as compared to their carbonaceous analogue DBT. Moreover, organic light emitting diodes were fabricated using BNDBT-1 and BNDBT-2 as emitters, demonstrating their potential applications.
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.
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