Synthesis and photophysical characterization of highly luminescent silica films doped with substituted 2-hydroxyphthalamide (IAM) terbium complexes

Abstract

Innovative Tb³⁺ antenna complexes employing two different substituted 2-hydroxyphthalamide ligands (HxOH-IAM and bis-HxOH-IAM) acting simultaneously as coordinating sites and light collector units have been synthesized and successively anchored in silica layers by the sol–gel technique. The complexes show remarkable photoluminescence (PL) quantum yields in methanol solution, as high as 0.30 and 0.40 for (HxOH-IAM)₄⊂Tb³⁺ and (bis-HxOH-IAM)₂⊂Tb³⁺, respectively. The grafting of the Tb³⁺ complexes in silica single layers accomplished by exploiting the terminal hydroxyl groups of the IAM chains results in highly transparent and homogeneous films displaying bright green emission and PL efficiencies of up to 0.40. The silica layers containing the (bis-HxOH-IAM)₂⊂Tb³⁺ show remarkable photostability even under prolonged and continuous irradiation (up to 3.5 h). The nature of the IAM ligands allows the photoexcitation of the complexes at wavelengths even longer than 350 nm, which is a spectral window suitable to develop luminescent lanthanide probes dedicated to bioanalyses and bioimaging applications.