Phenanthroline derivative based europium(III) covalently bonded silica hybrid material for high-selectivity sensing of anion and small organic molecule

A new polysilsesquioxane bridge (Phen–OH–Si) was synthesized here using 2-(2-hydroxyphenyl)-imidazo[4,5-f]-1,10-phenanthroline (Phen–OH) and 3-(triethoxysilyl)propyl isocyanate respectively as a ligand of Eu³⁺ ion and a siloxane network precursor. Then, an organic–inorganic hybrid material covalently grafted with an Eu³⁺ complex (denoted as Eu(Phen–OH–Si)₂Phen) was synthesized by coordination of an Eu³⁺ ion with a multifunctional precursor Phen–OH–Si and a second ligand Phen in a sol–gel process. This hybrid material was found to exhibit intensive red luminescence under UV light triggered by the ligand antenna effect. Further luminescent studies indicate that Eu(Phen–OH–Si)₂Phen not only displays high sensitivity sensing targeted at fluoride ions, but also exhibits distinct solvent-dependent luminescent spectra with emission intensities that are significantly quenched by N,N-dimethylformamide.