Molecular Aggregation to and from Disaggregation of an Organic Emitter for Strategic Emission Modulation

“Aggregation-caused fluorescence quenching” is a well-established phenomenon by now. The procedure from aggregation to disaggregation usually causes a revival of emission signals, and thus affords an interesting new path to design “turn-on” optical probes. For this purpose, the photophysics, energetics and dynamics of supra-molecular encapsulation induced disaggregation of a self-assembled bis-indole derivative, 3,3’-bisindolyl(phenyl)methane (BIPM), and its further reaggregation are reported herein. Compared to disaggregation strategies, its reverse process, reaggregation, has received much less attention so far. The gamma-cyclodextrin (γ-CD) molecules were found to be effective in disaggregating the BIPM associations and emission enhancement, whereas, the incorporation of guanidine hydrochloride (Gnd-HCl) into the aqueous solution of disaggregated BIPM monomers in γ-CD environment resulted in probe reaggregation leading to quenching of the restored emission. Here, γ-CD and Gnd-HCl can be considered as the molecular modulators of BIPM fluorescence based on the disaggregation–reaggregation mechanisms. The spectroscopic and thermodynamic findings associated with the disaggregation-reaggregation processes might be insightful in reversible controlling of molecular aggregation and the associated optical properties for diverse applications.