have been prepared by introduction of various substituents into the pyrazoline and phenyl rings. The fluoro-substituted derivative (R¹ = R² = R³ = F; R⁴ = CF₃) is shown to be a state-of-the-art substance in terms of luminescent efficiency and photostability. (Y. Matsubara, Z. Yoshida, et al., September 3, Adv. Mater. 2002, 14, 1211-1213)