Fluorescence spectral studies of some imidazole derivatives

The photophysical properties of imidazole derivatives namely 2-(2,4-difluorophenyl)-4,5-dimethyl-1-p-tolyl-1H-imidazole and N,N-dimethyl-4-(4,5-dimethyl-2-phenyl-1H-imidazol-1-yl)benzenamine, synthesized from an unusual four components assembling, were studied in several solvents. Polarization also plays major role in the increase of excited-state dipole moment (μe). From the spectral results, it was found that there is equilibrium between neutral species and monocationic (MC) species in polar aprotic and polar protic solvents. The basicity of the solvent, Cβ or CSB has a negative value, suggesting that the absorption and fluorescence bands shift to lower energies with increasing electron-donating ability of the solvent. Therefore, resonance structures 1b and 2b has the positive charge located at the nitrogen atom stabilized in basic solvents.

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► Photophysical properties of the imidazole derivatives.
► Correlation analysis—physicochemical property is correlated with solvent parameters.
► In alcoholic solvents, bathochromic shifts were observed.
► The polar solvents would stabilize the S0 state more extensively than the S1 state.
► Values of Cβ or CSB shows λabs and λemi bands shift to lower energies.