Solid-state photoluminescence of biaryls: Relationship between photophysical feature and crystal structure

Thanks to recent developments in spectrophotometric apparatuses, fluorescence quantum yields (Φ_f) and lifetimes (τ_f) of emissive compounds can be readily determined not only in solution but also in the solid state. In this work, we found that solid-state photoluminescence of biaryls consisting of naphthyl, phenanthryl and pyrenyl moieties emerged in the visible wavelength region at room temperature. The Φ_f and τ_f values of the studied biaryls were determined in the solid state as well as in solution. The biaryls showed fluorescence in the wavelength regions longer than that of the corresponding parent chromophores, i.e., naphthalene, phenanthrene and pyrene, and the Φ_f values in solution were greater than those of the parent ones. Some biaryls showed the solid-state emission spectra in the wavelength region longer than those in solution. Based on the crystallographic analysis results, relationship between the crystal packing and the emission features in the solid state was discussed.