Development of Rofecoxib‐Based Fluorophores from ACQ to AIE by Positional Regioisomerization

Abstract

The development of aggregation‐induced emission luminogens (AIEgens) has attracted increasing attention due to their potential applications in various areas in recent years. In this study, a facile conversion from aggregation‐caused quenching (ACQ) to aggregation‐induced emission (AIE) was achieved by an efficient regioisomerization strategy based on the rofecoxib scaffold. Two compounds, named PYR2 and PYR4, were identified as regioisomers of rofecoxib derivatives to show dramatically different fluorescent properties. Compound PYR2 with an ortho‐substituted piperidine group showed typical AIE activity while compound PYR4 with a para‐piperidine group exhibited typical ACQ behavior. Notably, compound PYR2 showed polymorphism with two forms of crystals. It was also endowed with reversible mechanochromic luminescence and acidochromic properties. The different fluorescent properties were elucidated by UV/Vis absorption spectroscopy, powder X‐ray diffraction, differential scanning calorimetry, and thermogravimetric analyses. Its application as a security ink and in lipid droplets imaging have been demonstrated.

One-Step Transformations from ACQ Luminogens to DSEgens via the Boc Protection Process

“…After grinding with a pestle in a mortar, the fluorescence emission was red shifted by 14 nm with dark yellow emissions at 558 nm (Figure A). The ground samples showed a weak red shift as compared with the initial samples because the original ordered structure was transformed into a much tighter packing, which increased the intermolecular conjugation effect and resulted in a red shift of the emission. , In addition, the reversibility of the MFC was investigated. The ground sample could be reversed to its initial state by immersing in acetone, and mechanochromic conversion could be repeated for 4 cycles without fatigue (Figure B).…”