Synthesis of J-Aggregating Dibenz[a,J]anthracene-Based Macrocycles

Several fluorescent macrocycles based on 1,3-butadiyne-bridged dibenz[a,J]anthracene subunits have been synthesized via a multistep route. The synthetic strategy involved the initial construction of a functionalized dibenz[a,J]anthracene building block, subsequent installation of free alkyne groups on one side of the polycyclic aromatic framework, and a final cyclization based on a modified Glaser coupling under high-dilution conditions. Photophysical studies on three conjugated macrocycles revealed the formation of J-aggregates in thin films, as well as in concentrated solid solutions (polyisobutylene matrix), with peak absorption and emission wavelength in the range of lambda = 460-480 nm. The characteristic red-shifting of the J-aggregate features as compared to the monomer spectra, enhancement in absorption intensities, narrowed linewidths, and minimal Stokes shift values, were all observed. We demonstrate that improvements in spectral features can be brought about by annealing the films under a solvent-saturated atmosphere, where for the best films the luminescence quantum efficiency as high as 92% was measured. This class of macrocycles represents a new category of J-aggregates that due to their high peak oscillator strength and high luminescence efficiency have the potential to be utilized in a variety of optoelectronic devices.