Substituted pyridil-imidazole derivatives as red-green-blue (RGB) as well as white-light emitters

A series of 2-(2-pyridyl)imidazole-based compounds were synthesized via condensation of 2,2'-pyridil with p-substituted benzaldehydes and thoroughly characterized by standard analytical tools and spectroscopic techniques, including the single-crystal X-ray structure of a representative compound. Both electron-withdrawing and electron-releasing groups have been incorporated to fine-tune their spectral characteristics. The absorption and emission spectral properties of all the compounds have been thoroughly investigated in a wide range of solvents. The compounds are able to display a broad range of fluorescent colors across the entire visible region (red, green and blue), depending upon the electronic nature of the substituents as well as the type of solvent. Interestingly, the nitro derivative is able to display white-light emission in a chloroform-methanol (9 : 1 v/v) mixture. In addition to experimental demonstration, theoretical calculations employing density functional theory (DFT) and time-dependent density functional theory (TD-DFT) have been implemented to visualize the electronic structures of the compounds as well as for accurate assignment of the spectral bands.