Novel Near-Infrared Luminescent Hybrid Materials Covalently Linking with Lanthanide [Nd(III), Er(III), Yb(III), and Sm(III)] Complexes via a Primary β-Diketone Ligand: Synthesis and Photophysical Studies

A series of novel, colorless, and transparent sol−gel derived hybrid materials Ln-DBM-Si covalently grafted with Ln(DBM−OH) 3 ·2H 2 O (where DBM−OH = o -hydroxydibenzoylmethane, Ln = Nd, Er, Yb, and Sm) were prepared through the primary β-diketone ligand DBM−OH. The structures and optical properties of Ln-DBM-Si were studied in detail. The investigation results revealed that the lanthanide complexes were successfully in situ grafted into the corresponding hybrids Ln-DBM-Si. Upon excitation at the maximum absorption of ligands, the resultant materials displayed excellent near-infrared luminescence. Meanwhile, a model for the indirect excitation mechanism was introduced to discuss the ligands-to-Ln 3+ intramolecular energy transfer. Furthermore, the radiative properties of the Nd 3+ ion and the Er 3+ ion in Ln-DBM-Si are evaluated by applying the Judd-Ofelt analysis.