Positional effects of fluorine substitution on room temperature phosphorescence in hexaphenylmelamine derivatives†

Three hexaphenylmelamine phosphors substituted with fluorine at meta, ortho, and para positions were synthesized and characterized, showing increasing phosphorescence lifetimes and quantum yields. Crystal analysis and theoretical calculations suggest that the superior RTP of HPM-p-F is attributed to its higher oscillator strength, increased molecular binding energy, and favorable spin–orbit coupling.