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 EuIII ion can be described as square antiprismatic, with coordination by the six O atoms of the three chelating β-diketonate ligands and the two N atoms of the neutral bipyridyl ligand.