Acid Sensors Based on Luminochromism of Solid‐State Excimer Emission of Pyrene‐Modified Polyhedral Oligomeric Silsesquioxane

Abstract

To obtain solid‐state fluorescence sensors, it is essential to simultaneously obtain solid‐state emission and stimuli‐responsiveness. In this research, the modified polyhedral oligomeric silsesquioxane (POSS) tethered with pyrenes was synthesized and we confirmed that both demands for developing solid‐state fluorescence sensors can be satisfied. The POSS derivative exhibited strong emission even in the solid state. In particular, we found that exposure of the POSS films to trifluoroacetic acid vapor resulted in a significant red‐shift of the peak wavelength of the emission band. Excitation spectroscopy and comparison with model compounds suggest that this significant red‐shift should be attributable to the formation of static excimer, meaning a preformed dimer in the ground state induced by protonation of the secondary amino groups. These results indicate that POSS is a promising scaffold for a solid‐state fluorescence sensor.