A new pyrene derivative bearing a benzene dicarboxylic acid unit was designed for sensitive self-assembly in solid and solution states. Single-crystal X-ray analysis revealed polymorphism, with non-solvated and solvent incorporated forms showing distinct packing and excimer emission. In the solution state, concentration, hydrogen-bonding, and pH influenced the photophysical behavior, with a bathochromic shift observed in acidic conditions.

Abstract

A new pyrene derivative, 1, containing a benzene dicarboxylic acid moiety at the K-region of pyrene was studied to explore its potential for producing highly sensitive self-assembled structures in both solid and solution states. Single crystal X-ray analysis revealed that 1 shows crystal polymorphism, producing two distinct structures: a non-solvated form (crystal A) and a solvent-incorporated form (crystal B). The effects of the external environment on the self-assembly process, as well as the optical properties of the compound in solid and solution states were investigated. Solid-state emission spectroscopy revealed excimer emission from the pyrene units in both crystals, consistent with the observed packing structures. In the case of the solution, three key factors were identified to affect the photophysical behavior: 1) concentration, 2) hydrogen-bonding, and 3) pH. A clear bathochromic shift was observed under acidic conditions, attributed to changes in protonation states and stacking modes between acidic and basic environments.