Synthesis of Tetraphenylethenes Bearing Two Bis(Pyrrolyl)methene Groups With Strong Aggregation‐Induced Emission Luminescent Intensity and Studies of Halochromic Switch Properties Depending on pH

ABSTRACT In this study, we synthesized a unique luminescent compound, a tetraphenylethene derivative adorned with two pyrromethene groups, showcasing a remarkable aggregation‐induced emission (AIE) effect. This was achieved through a concise four‐step synthesis using commercially available chemicals, and the compound exhibited noteworthy photophysical properties. Notably, 1,1′‐bis( p ‐pyrromethene phenyl)‐2,2′‐diphenylethene demonstrated a robust AIE effect, with an intense fluorescence of 120 000 a.u. At 298 K and an excitation wavelength ( λ ex ) of 360 nm, at a concentration of 10 −5 M. Impressively, its AIE fluorescence was four times greater than its protonated counterpart. Furthermore, the strategic placement of pyrromethene groups at the para‐position of tetraphenylethene resulted in a fivefold increase in AIE fluorescence compared to the meta‐position. This tetraphenylethene derivative, featuring the donor‐pyrromethene group, exhibited superior AIE efficacy compared to its protonated form. Beyond its luminescent properties, the compound holds promise as a pH‐responsive and chelating ligand for transition metals, suggesting applications in diverse scientific domains. The straightforward synthesis using readily available chemicals enhances its accessibility and potential impact across various fields.