Selenoyl-Trifluoroacetone: Synthesis, Properties, And Complexation Ability Towards Trivalent Rare-Earth Ions

The selenium-containing analog of thenoyl-trifluoroacetone has been synthesized and first characterized by UV-visible and NMR-spectroscopies. Synthesis of selenoyltrifluoroacetone was performed by a two-step procedure: acetylation of selenophene and interaction of 2-acetylselenophene with ethyl-trifluoroacetate. The structure of the obtained product has been confirmed using NMR, EI-MS, and elemental analysis. Spectral, acid-base, complexing, and keto-enol parameters were studied under various conditions. Received values of dissociation and protonation constants characterize selenoyltrifluroracetone as a stronger acid and stronger base than acetylacetone. The aqueous chelation with sixteen rare-earth metals has been studied in acetate and glycine buffer media at I = 0.5 M (NaCl). Values of logK non-monotonically increase from La(III) to Lu(III) and lay within the range of 4.5-11.5 logarithmic units. Most of the determined formation constants were higher than analogous values for thenoyl- and furoyl-trifluoroacetone rare-earth metal complexes. Thermodynamic and spectral parameters were simulated using both DFT and TD-DFT approaches.