Rearrangement of Cyclotriveratrylene (CTV) Diketone: 9,10-Diarylanthracenes with OLED Applications

Electroluminescent 9,10-diaryl anthracenes have been
shown to be
promising host and hole-transporting materials in organic electroluminescence
due to their high thermal stability, electrochemical reversibility,
and wide band gap useful for organic light-emitting diodes (OLEDs),
especially blue OLEDs. Oxidation of cyclotriveratrylene (CTV) to the
corresponding diketone and subsequent bromination resulted in an unexpected
rearrangement to a highly functionalized 9-aryl-10-bromoanthracene
derivative, which was employed in Suzuki couplings to synthesize a
series of 9,10-diaryl compounds that are structural analogues of anthracene
derivatives used in the preparation of OLEDs but are more highly functionalized,
including electron-donating methoxy groups in addition to substitution
by a carboxylic acid moiety. The UV/fluorescence solution spectra
show strong emissions at 446, 438, and 479 nm, respectively, for the
anthracene 10-phenyl, 10-naphthyl, and 10-pyrenyl adducts containing
a benzoic acid functional group, whereas the analogues bearing the
hydroxymethylene moiety from reduction of the benzoic acid to the
corresponding alcohols gave much shorter emission wavelengths of 408,
417, and 476 nm, respectively, and had somewhat higher quantum yields,
suggesting they are better candidates for OLED applications.