Photoluminescence of Lanthanide-Titanium-Oxo Clusters Eu 9 Ti 2 and Tb 9 Ti 2 Based on a β-Diketone Ligand.

A series of acetylacetone-protected lanthanide-titanium-oxo clusters (LTOCs), formulated as [La 6 Ti(μ 3 -OH) 8 (acac) 12 (CH 3 O) 2 (CH 3 OH) 6 ] ( La 6 Ti ; Hacac = acetylacetone) and [Ln 9 Ti 2 (μ 4 -O)(μ 3 -OH) 14 (acac) 17 (CH 3 O) 2 (CH 3 OH) 3 ] [Ln = Eu ( Eu 9 Ti 2 ) and Tb ( Tb 9 Ti 2 )], were synthesized through the reactions of LnCl 3 ·6H 2 O (Ln = La, Eu, and Tb), Hacac, Ti(O i Pr) 4 , and triethylamine in methanol. Crystal structural analysis shows that La 6 Ti exhibits an hourglass-like structure consisting of two La 3 Ti cubane subunits by sharing one Ti 4+ ion, while Eu 9 Ti 2 can be viewed as a combination of four Eu 3 Ti cubane subunits by sharing three corners and one side. The photoluminescence (PL) measurements show that Tb 9 Ti 2 exhibits excellent PL properties with a high quantum yield (QY) of 34.8%, while Eu 9 Ti 2 only has a QY of 1.4% because of the different photosensitizations of ligands to Eu 3+ and Tb 3+ ions in the photophysical process.