Nitrogen atom modulation enables high-sensitive mechanofluorochromism of tetraphenylethylene-based luminescent materials

Mechanofluorochromic (MFC) materials, capable of undergoing color changes in response to external forces, hold vast potential for a wide range of applications. Here, we designed and synthesized four compounds based on the tetraphenylethylene (TPE) unit, denoted as TPE-1, TPE-2, TPE-3, and TPE-4. The TPE moiety serves as the common core among these compounds, while nitrogen atom fine-tuning is employed on the modifying groups of the four compounds to explore its influence on their photophysical properties and MFC performance. These compounds display significant variations in their solid-state photophysical properties and MFC characteristics. Especially, TPE-3 and TPE-4 exhibit excellent MFC properties and different sensitivity to external mechanical stimuli. These research findings not only offer a fresh perspective on the MFC mechanism of TPE-based compounds but also provide valuable insights for the design and development of novel MFC molecules.