Crystal structure and triboluminescence of centrosymmetric complex [Eu(NO3)3(HMPA)3]

By single crystal X-ray analysis, the atomic structure of the crystals of [Eu(NO3)3(HMPA)3] complex (HMPA is hexamethylphosphorotriamide) possessing intense triboluminescence is determined. Symmetry of centrosymmetrical crystals is monoclinic: a = 13.785(1) Å, b = 19.746(2) Å, c = 14.723(1) Å, β= 102.143(2)°, P21/n space group, Z = 4, dx = 1.484 g/cm3. The crystal structure is represented by separate C18H54EuN12O12P3 complexes linked by van der Waals interactions with pronounced cleavage planes. The coordination polyhedron of Eu(III) atom reflects the state of distorted square antiprism. The possible causes of spectral differences in the Stark structure of photo- and triboluminescence are discussed.