Novel Rhodafluors: Synthesis, Photophysical, pH and TD-DFT Studies

An efficient protocol for the synthesis of new rhodol derivatives has been developed. The synthesis involves condensation of 2-hydroxy benzophenone derivatives with 1, 3-dihydroxy benzene derivatives in solvents such as ionic liquid (N-methyl-2-pyrrolidonium hydrogen sulfate) and methane sulphonic acid. Both ionic liquid and methane sulphonic acid were found to be promising self-catalyzed solvents to bring out the conversion to form desired rhodols in excellent yields. In N-methyl-2-pyrrolidonium hydrogen sulfate reaction proceeds faster compared to methane sulphonic acid. The new fluorophores are investigated for their photophysical properties in various microenvironments and systematically characterized by means of density functional theory and time dependent density functional theory. Photophysical properties of the new rhodafluors found sensitive towards change in the pH of media and thus can be used as efficient pH sensors.