Development of fluorescence sensors for quantifying anions based on polyhedral oligomeric silsesquioxane that contains flexible side chains with urea structures

Since anions play a significant role in various biological phenomena, developing fluorescence anion sensors is important. Previously, we focused on polyhedral oligomeric silsesquioxane (POSS) as a three-dimensional (3D) scaffold to design an anion receptor. In this study, we evaluated the anion binding properties of an POSS derivative with eight urea groups and applied the derivative to an anion fluorescence sensor utilizing its 3D structure. 1 H NMR measurements revealed that the POSS derivative with urea groups can bind to sulfate ions. Compared to the model compound, the POSS derivative exhibits a greater binding ability due to the cooperative effects of multiple urea groups. Through the introduction of naphthyl urea groups, the POSS derivative can be used as a fluorescence sensor for quantifying sulfate ions.