Triboluminescence and crystal structure of the complex [Eu(MBA)3 Dipy]2 (HMBA).

The atomic structure of the crystals [Eu(MBA)3 Dipy]2 (HMBA) (MBA-аnion toluic acid, Dipy-2,2'-dipyridyl, HMBA-toluic acid), displaying intensive luminescence and triboluminescence was determined using single crystal X-ray diffraction analysis. The triclinic centrosymmetric crystals have the following parameters: a = 10.620(2), b = 11.849(2), c = 14.9868(2) Å, α = 68.297(1), ß = 76.172(1), γ = 80.378(1)°, sp.gr. P - 1, Z = 1, ρcalc. = 1.537 g/cm3 . The structure belongs to the insular type and is presented as the isolated complex Eu2 -dimeric formations and outer-sphere HMBA. The structural aspects of the observed luminescence and triboluminescence properties of the compound were discussed, and the cleavage plane role in the process of the crystal destruction was revealed.

Europium(III) tris-dibenzoylmethanate as an efficient chemosensor for detection of ammonia.

The effect of ammonia vapor on luminescence of Eu(III) tris-dibenzoylmethanate immobilized in various matrices has been investigated. It has been revealed that interaction of Eu(III) tris-dibenzoylmethanate with analyte vapor results in increase of the intensity of Eu(III) luminescence. The mechanism of the effect of ammonia vapors on intensification of the Eu(III) luminescence has been suggested using the data of IR spectroscopy, X-ray diffraction analysis and quantum chemistry calculations. The mechanism of luminescence sensitization consists in bonding of an analyte molecule with a water molecule into the coordination sphere of Eu(III). As a result, the bond of a water molecule with the luminescence centre weakens and the blockage of the quenching of luminescence on OH-vibrations takes place.