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 CeIII complex is linked to neighbouring ones by hydrogen bonding. Within the complex, the CeIII 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 CeIII 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.

A new lanthanum(III) complex containing acetyl-acetone and 1H-imidazole.

In the title complex, di-aqua-(1H-imidazole-κN3)(nitrato-κ2O,O')bis-(4-oxo-pent-2-en-2-olato-κ2O,O')lanthanum(III), [La(C5H7O2)2(NO3)(C3H4N2)(H2O)2], the La atom is coordinated by eight O atoms of two acetyl-acetonate (acac) anions acting as bidentate ligands, two water mol-ecule as monodentate ligands, one nitrate anions as a bidentate ligand and one N atom of an imidazolate (ImH) molecule as a monodentate ligand. Thus, the coordination number of the La atom is nine in a monocapped square anti-prismatic polyhedron. There are three types of inter-molecular hydrogen bonds between ligands, the first involving nitrate-water O⋯H-O inter-actions running along the [001] direction, the second involving acac-water O⋯H-O inter-actions along the [010] direction and the third involving an Im-nitrate N-H⋯O inter-action along the [100] direction (five inter-actions of this type). Thus, an overall one-dimensional network structure is generated. The mol-ecular plane of an ImH molecule is almost parallel to that of a nitrate ligand, making an angle of only 6.04 (12)°. Inter-estingly, the ImH plane is nearly perpendicular to the planes of two neighbouring acac ligands.