Aggregation-Induced Emission of Contorted Polycondensed Aromatic Hydrocarbons Made by Edge Extension Using a Palladium-Catalyzed Cyclopentannulation Reaction.

Contorted polycyclic aromatic hydrocarbons (PAHs), CPA1-2 and CPB1-2 , bearing peripheral five-membered rings were synthesized employing a palladium-catalyzed cyclopentannulation reaction using specially designed diaryl acetylene synthons TPE and TPEN with commercially available dibromo- anthracene DBA and bianthracene DBBA derivatives. The resulting target compounds CPA1-2 and CPB1-2 were isolated in excellent yield and found to be highly soluble in common organic solvents, which allowed for their structural characterization and investigation of the photophysical properties, disclosing their aggregation-induced emission (AIE) properties in THF at selective concentration ranges of water fractions in the solvent mixture. Examination of the contorted PAH structures by means of density functional theory (DFT) revealed higher electronic conjugation in the more rigid and planar anthracene-containing CPA1-2 derivatives when compared to the twisted bianthracene-bearing moieties CBPA1-2 with HOMO-LUMO bandgaps (Δ E ) of ∼2.32 eV for the former PAHs and ∼2.78 eV for the latter ones.