Luminescence of new hydroxy-2,4,5-triarylimidazoles with an intramolecular hydrogen bond

Abstract

Spectral and luminescent properties of novel derivatives of 2,4,5-triphenylimidazole synthesized in this study have been investigated in different solvents. For solutions of azomethine-substituted hydroxytriphenylimidazole (I) and two structural isomers, hydroxy-meta-bisimidazoles III and IV differing in the position of the OH group, two luminescence bands due to the presence of two ground-state conformers are observed. The equilibrium between the two conformers depends on the structure of the molecule and the solvent. For solutions of III and IV in polar and nonpolar solvents and for I in nonpolar solvents, long-wave-length luminescence dominates from the conformer with possibility of intramolecular proton transfer in the excited state. For I in protic and highly polar solvents, short-wavelength luminescence is the main one; depending on the excitation wavelength, it is possible to detect weak long-wavelength (green) or more intense short-wavelength (blue) luminescence.