A new class of pyrenyl solid-state emitters: 1-pyrenyl ynones. Synthesis via the Friedel-Crafts route, molecular and electronic structure and photophysical properties

Abstract

Friedel-Crafts acylation of pyrene with alkynoic acids in the presence of trifluoroacetic anhydride and triflic acid constitutes a direct and efficient route to 1-pyrenyl ynones. These compounds in chloroform solution emit fluorescence at longer wavelengths, with higher quantum yields and longer lifetimes than a typical saturated acylpyrene derivative, 1-acetylpyrene. Moreover, in contrast to 1-acetylpyrene, they are moderate solid-state emitters. Comparative DFT studies revealed strong stabilization of the LUMOs of 1-pyrenyl ynones in comparison to the LUMO of 1-acetylpyrene. The single-crystal X-ray structure of 1-(pyren-1-yl)but-2-yn-1-one showed π-interactions of pyrenyl moieties in the crystal lattice. Investigations of the solid-state fluorescence of this compound revealed emission from long-lived excited states, including excimer species. © 2014 the Partner Organisations.