Structure of tri-aqua-tris-(1,1,1-tri-fluoro-4-oxo-pentan-2-olato)cerium(III) as a possible fluorescent compound

Luminescence due to the d-f transition of Ce³⁺ is quite rare in metal-organic complexes where concentrate quenching frequently occurs. One of the possible ways to avoid this is to design an architecture with elongated metal-metal distances. In the structure of the title complex, tri-aqua-tris-(1,1,1-tri-fluoro-4-oxo-pentan-2-olato-κ²O,O')cerium(III), [Ce(C₅H₄F₃O₂)₃(H₂O)₃], the Ce^III complex is linked to neighbouring ones by hydrogen bonding. Within the complex, the Ce^III atom is coordinated by nine O atoms from three 1,1,1-tri-fluoro-4-oxo-pentan-2-olate (tfa) anions as bidentate ligands and three water mol-ecules as monodentate ligands. Thus, the coordination number of Ce^III atom is nine in a monocapped square-anti-prismatic polyhedron. The F atoms of all three independent CF₃ groups in tfa are disordered over two positions with occupancy ratios of about 0.8:0.2. The inter-molecular hydrogen bonds between the ligands involve tfa-water inter-actions along the [110] and [1-10] directions, generating an overall two-dimensional layered network structure. The presence of the F atoms in the tfa anion is responsible for an increased inter-molecular metal-metal distance compared to that in the analogous acetyl-acetonate (acac) derivatives. Fluorescence from Ce³⁺ is, however, not observed.