Crystal Structure of a Luminescent Europium(III) Complex: Probing the Active Species in Dissociation-Enhanced Lanthanide Fluoroimmunoassay

Abstract

The highly luminescent complex [ Eu ( fnac )₂( topo )₂(NO₃)], which contains the two component ligands [ fnac, the anion of 4,4,4-trifluoro-1-(2-naphthyl)butane-1,3-dione, and topo, trioctylphosphine oxide] of the luminescent species in the dissociation-enhanced lanthanide fluoroimmunoassay method, has been prepared and defined by an X-ray crystal structure analysis. The complex crystallizes in the Ccmm space group, a 17.064(18), b 30.254(21) and c 16.391(4) Ǻ, Z = 4, and a single-crystal X-ray structure determination refined to R 0.056 for 1772 independent 'observed' reflections. The complex exhibits a dodecahedral EuO₈ structure with bidentate nitrate ion [ Eu -O 2.512(10)Ǻ], two bidentate substituted acetylacetonate ( fnac )[ Eu -O 2.379(9), 2.400(9)Ǻ], and two monodentate long-chain phospine oxide ( topo ) ligands [ Eu -O 2.295(9)Ǻ].