Revisiting Unsubstituted Ullazine: Concise Synthesis, Single Crystal X-Ray Structure and Photophysical Properties

We have developed an efficient synthetic route of parental ullazine in three steps from commercially available synthons with overall yield of 53%. The single crystal X-ray structure of parental ullazine was studied in detail. Parental ullazine core can be functionalized either by late-stage Vilsmeier-Haack formylation/condensation sequence or by C-N cross-coupling with a pre-installed bromine. Pre-liminary results show that the condensation of CHO-substituted ullazine (U-CHO) gave a novel imidazole substituted ullazine. The brominated ullazine (U-Br) can undergo Buchwald-Hartwig cross-coupling smoothly, resulting a carbazole substituted ullazine. In ad-dition, parental ullazine showed redshifted absorption and emission spectra as compared to its isoelectronic isomer pyrene, and no excimer formation in higher concentration.