Aromatic Ring Fused BOPHYs as Stable Red Fluorescent Dyes

Facile synthetic routes to a new
class of red α-benzo-fused
BOPHYs with 6,5,6,6,5,6-hexacyclic fused rings and β-thiophene-fused
BOPHYs with 5,5,6,6,5,5-hexacyclic fused rings are presented. These
dyes were characterized by NMR spectroscopy, HRMS, X-ray structure
analysis, cyclic voltammetry, and optical measurements. Compared to
parent BOPHY, significant red-shifts in the absorption (up to 600
nm in solution) and emission (up to 648 nm in solution and 717 nm
in solid state), as well as high chemical stability and photostability,
were found for these aromatic-ring-fused BOPHY dyes. As shown in cyclic
voltammetry and DFT calculations, the aromatic ring fusions induced
significantly increased HOMO energy levels, giving effective expansion
of π-conjugation over these BOPHY dyes. These new molecular
skeletons would be promising candidates for various applications in
light of their unique structure and attractive photophysical properties.