Novel donor- π- acceptor dye: synthesis, solvatochromism and DFT calculations

A novel D–π–A system having indole moiety 5 was synthesized in four steps، which exhibit interesting solvatochromism ranging from yellow in CHCl3 to red in DMF، violet in acetone، deep purple in DMSO and green in CH3CN. Also the studies on the fluorescence properties of 5 in different solvents revealed that the emission peaks are dependent on the polarity of solvents. The quantum–chemical calculations of 5 was performed using the Gaussian 03 program at the B3LYP/6-31G* level، which revealed that the HOMO is localized on the 3-hydroxy indole donor moiety، while LUMO is localized on the methylidene dimalononitrile acceptor moieties.