We also note that the mono-substituted product from the reaction of 1,4-dibromonaphthalene and phenoxazine, 1-bromo-4-phenoxylnaphthalene, could not be isolated, regardless of the stoichiometry of phenoxazine used. The synthesised emitters were fully characterised by 1 H and C nuclear magnetic resonance (NMR) spectroscopy, gas-chromatography/mass-spectrometry (GCMS), highpressure liquid chromatography (HPLC), melting point analysis, and structure elucidation by singlecrystal X-ray diffraction. Full synthetic details are available in the supporting information. The structures of each of the three emitters were determined by single crystal X-ray crystallography.