A new Tellurium-bearing substituted β-diketone: Synthesis and properties

Abstract

The synthesis of a new derivative of hexafluoroacetylacetonate containing a tellurophene ring was developed and described. A new ligand (tellurophene-trifluoroacetone, Te-CF3) was obtained by a multistep synthesis, starting with metallic tellurium and finishing with Claisen-type condensation by ethyl ester of trifluoroacetic acid. The structure and purity of the obtained compound were estimated by NMR (1H, 13C, 19F, 125Te) and EI-MS. Acid-base, keto-enol, and complexation properties have been studied in aqueous solutions using spectrophotometric technique. Thermodynamic and spectral parameters of ML complexes (M3+= Sc3+, Y3+, La3+, Ce3+, Pr3+, Nd3+, Sm3+, Eu3+, Gd3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Yb3+, and Lu3+) were determined using the molar series method and non-linear regression analysis. The studied ligand demonstrates a typical (for perfluorinated diketones) acid-base behavior in water, but differs significantly in chelation capacity. Rare-earth complexes of Te-CF3 have less thermodynamic stability than complexes with its analogs. Model systems based on eight-coordinated rare earth complexes was simulated by DFT and TD-DFT calculations to gain insights into the features of metal–ligand bonding in studied complexes.