Unveiling the Reversibility of Crystalline–Amorphous Nanostructures via Sonication-Induced Protonation

Self-assembled π-conjugated molecules exhibit switching between crystalline–amorphous nanostructures, attracting significant interest in the field of organic electronics, particularly memory devices. Herein, we report ferrocene-appended tetratolylporphyrin, H2TTP-Fc, which undergoes protonation in 1,2-dichloroethane via sonication and reverses to the original state by deprotonation with time, as confirmed by optical and electrochemical properties. Absorption spectra reveal the selectivity of reversible and irreversible protonation of H2TTP-Fc in halogenated solvents and mineral acids. Microscopic analysis suggested that H2TTP-Fc aggregates exhibit a crystalline flower-like morphology from the joining of 2D microsheets, whereas H4TTP-Fc forms nanospheres with an average diameter of 150–200 nm upon methanol vapor diffusion (MVD). Electrochemical properties of H4TTP-Fc films reveal the ease of oxidation when compared to that in the solution state as a result of high current generation at less work function. ...