Dynamics of Pyrene Excimer in a Cholesteryl-based Supramolecular Host Matrix.

Abstract

Aggregation-caused quenching (ACQ) reduces luminescence and compromises brightness in solid-state displays, necessitating strategies to mitigate its effects for enhanced performance. This study presents cost-effective method to mitigate ACQ of pyrene by co-assembling polycyclic aromatic hydrocarbons within low molecular weight gelator. ​Synthesized from readily available materials-cholesteryl chloroformate and pentaerythritol-in one-step reaction, gelator incorporates four cholesteryl units, reported to promote robust supramolecular gels in various solvents. Encapsulation of pyrene in a supramolecular host has effectively addressed the challenge of ACQ in the solid state. Utilizing steady-state and time-resolved techniques, we probed the excimer formation dynamics across solution, powder, and xerogel phases. Through time-resolved emission spectra (TRES) and time-resolved area-normalized emission spectra (TRANES) methods, we observed the monomer-to-excimer transition under various conditions. In solution, this transition occurs in a single step, characterized by a single isoemissive point (~443 nm) observed in TRANES. In powder, two isoemissive points (~445 nm and ~485 nm) were observed, indicating more complex process with an additional relaxed or trap state. The xerogel phase revealed an intricate excimer formation pathway, involving three isoemissive points (~418 nm, ~442 nm, and ~423 nm). These observations suggest multiple intermediate states in monomer-excimer transition and distinct dynamics in the solid matrix.