Fluorinated Trimers for Enhancing the Stability and Solubility of Organic Small Molecules Without Spectral Shifts:...

The development of highly stable organic small molecules for optical applications is of growing interest. Multimerization of monomeric small molecules can enhance stability via increased π-π stacking, but it often reduces solubility and induces undesirable spectral shifts due to π-extension. To overcome this trade-off, we report a trimeric small molecule (F-TPBT) derived from a model monomer (Tinuvin 327) using a 1,3,5-fluorinated phenyl linker. This design markedly improves thermal stability and solubility while minimizing changes in the optical absorption spectrum. F-TPBT shows superior thermal properties (5 wt% decomposition temperature = 427 °C; weight loss after 1 hour at 300 °C = 0.32 wt%) and excellent solubility (5.3 wt% in dichloromethane; 6.4 wt% in N-methylpyrrolidone (NMP)), with an absorption spectrum nearly identical to that of Tinuvin 327. These properties make F-TPBT a promising UV light absorber for transparent polyimide (TPI) films, which require processing above 300 °C and are widely used in flexible displays. Notably, F-TPBT-containing films retain their absorption properties even after 80 hours of accelerated UV irradiation, demonstrating excellent photostability. This study presents a broadly applicable molecular design strategy for enhancing the stability and solubility of organic small molecules while avoiding significant spectral shifts.