A triboluminescent europium(III) complex

The crystal structure of (4,4'-dimethyl-2,2'-bipyridyl)tris[3,3,3-trifluoro-1-(2-thenoyl)propan-2-onato]europium(III), or more commonly (4,4'-dimethyl-2,2'-bipyridyl)tris(2-thenoyltrifluoroacetonato)europium(III), [Eu(C8H4F3O2S)(3) (C12H12N2)], has been determined. Crystals of the complex emit vivid red light when scratched or fractured. This triboluminescent activity seems to correlate with the non-centrosymmetric crystal structure and disorder of the thienyl rings and CF3 groups which is present here and in similar compounds. While modeling the thienyl-ring disorder, it was noted that the bond angle at the C atom replaced by S is a sensitive sign of even small rotational ring disorder. The coordination geometry of the Eu III ion can be described as square antiprismatic, with coordination by the six O atoms of the three chelating beta-diketonate ligands and the two N atoms of the neutral bipyridyl ligand.