Synthesis and Unusual Supramolecular Self‐Assembly Behavior of Benzoperylene Imides and Thioimides

ABSTRACT

We report the synthesis of two new thionated benzoperylene imide‐based large rigid π‐systems with tunable optical properties. UV‐Vis absorption and fluorescence spectroscopy studies indicate that thionation significantly improves the absorption in longer wavelengths and quenches fluorescence. Interestingly, these molecules show unusual supramolecular self‐assembly behavior in water‐dioxane solvent mixtures. In dioxane, benzoperylene imides and thioimides exist as monomers and self‐assemble when the water volume percentage is more than 40%. Surprisingly, with less vol% of poor solvent (water) in good solvent, long and crystalline supramolecular self‐assemblies are formed, whereas shorter and amorphous supramolecular self‐assemblies are obtained at higher vol% of water in dioxane. Our investigations reveal the involvement of the nucleation‐elongation mechanism during self‐assembly of benzoperylene imides. Using various spectroscopy and microscopy methods, we found that variations in the kinetics of the nucleation elongation process due to changes in the solvent composition are the major reasons for this unusual behavior.