ENHANCEMENT AND QUENCHING OF LUMINESCENCE OF DIVALENT EUROPIUM ION AT INTERACTION OF EuCl<sub>3</sub>∙6H<sub>2</sub>O WITH ALUMINIUM ALKYLS IN TETRAHYDROFURAN
Due to its ability to emit bright luminescence in solid matrices, the divalent europium ion Eu<sup>2+</sup> is widely used in the production of phosphors, displays, light sources, luminescent paints, etc. At the same time, the first report on the chemical generation and emission of Eu<sup>2+</sup>* in solutions appeared only in 2013 by the example of bright blue chemiluminescence (CL), which is clearly visible by the eye in daylight, and which was found at the interaction of EuCl<sub>3</sub>∙6H<sub>2</sub>O crystalline hydrate with <sup>i</sup>Bu<sub>2</sub>AlH in THF in the presence of oxygen. Due to the high brightness of CL and its extraordinary sensitivity to even trace amounts of oxygen, it is promising for creating a chemiluminescent method for determination of ultra-low amounts of oxygen in solutions and gases. In this regard, studies on the effect of a number of experimental conditions on the parameters of this CL are relevant. In this work, the authors applied luminescent methods to study the effect of the nature and concentration of aluminum alkyls R<sub>2</sub>AlR` (R = Me, Et, <sup>i</sup>Bu, R` = H, Me, Et, <sup>i</sup>Bu) on the kinetic and spectral-brightness CL characteristics, as well as on photoluminescence (PL) in the system EuCl<sub>3</sub>∙6H<sub>2</sub>O-R<sub>2</sub>AlR`-THF-O<sub>2</sub>. The spectra and quantum yields of CL and PL in this system were measured. It was found that the reduction of Eu(III) to Eu(II) occurs for all aluminum alkyls. The time of complete dehydration of EuCl<sub>3</sub>∙6H<sub>2</sub>O and reduction of europium strongly depends on the nature of aluminum alkyl and varies from 7 to 60 minutes. In the present work, it was shown for the first time that all commercial aluminum alkyls can be successfully used for the effective one-pot synthesis of soluble complexes of divalent europium from the available crystalline hydrate EuCl<sub>3</sub>∙6H<sub>2</sub>O. It was found that with an increase in the initial concentration of <sup>i</sup>Bu<sub>2</sub>AlH, the CL intensity and light sum increase in direct proportion to a wide concentration range from 0.01 to 0.56 М. However, with a very large excess of <sup>i</sup>Bu<sub>2</sub>AlH (> 1.5 M) with respect to Eu(II), partial quenching of the luminescence of Eu<sup>2+</sup>* occurs.