Some Relationships Between Structure and Chemiluminescence in Triphenylimidazoles*

Lophine (2, 4, 5‐triphenylimidazole) and sixteen of its derivatives bearing substituents in the 2‐phenyl group have been synthesized and characterized. The fluorescence excitation and emission spectra in neutral and basic solution in 70% dimethylsulfoxide‐30 % water have been determined. The chemiluminescent intensities in 70% DMSO‐30% water, 0.33 N in NaOH have been measured. The maximum chemiluminescent emission wavelength was found to fall at 530 mμ for all compounds except the nitro derivatives whose intensities were too low to measure. The compounds bearing substituents in the meta and/or para positions of the 2‐phenyl group give linear Hammett plots. The value of p is —1.96 + 0.06. The constant emission wavelength and linear Hammett relation is interpreted in terms of the same mechanism and emitting species for all the compounds studied.