Abstract
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.
Highlights
The title complex crystallizes in the orthorhombic space group Pcab with eight formula units of [Ce(C5F3H4O2)3(H2O)3]
The central Ce atom is coordinated by nine O atoms of three hfa and three water molecules (Fig. 1)
The Ce—O bond lengths can be classified into two categories; the first is involved in interactions with a bidentate hfa, and the second in interactions with monodentate water molecules
Summary
-diketonate ligands have been used widely in metal–organic complexes involving rare earth elements because of their simple usage as organic bidentate ligands (Binnemans, 2005). The nature of the ligand used is important for a possible enhancement of the luminescence efficiency and intensity; for example, acac is known to have a possible effect on the 4f–4f transition emission of Eu3+ (Kuz’mina et al, 2006). Tb(acac) was first used as an active light-emitting layer material in LEDs based on the emission from the lanthanide complex (Kido et al, 1990). The probability of three types of energy transfer from hfa to Tb3+, from Tb3+ to Eu3+ and from Tb3+ to hfa is temperature dependent. Symmetry codes: (i) Àx þ 1; Ày þ 1; Àz þ 1; (ii) x þ 12; Ày þ 12; z; (iii) x À 12; Ày þ 12; z
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