Study of Mono-fluorinated Derivative of Benzoyltrifluoroacetone

Acid–base, spectral and complexing properties, as well as keto–enol tautomerism of the para-fluorinated derivative of benzoyl-trifluoroacetone have been investigated. Thermodynamic parameters were studied by UV–vis spectroscopy, NMR, and quantum-chemical modeling. Dissociation constants (p K a ) were obtained in the citric-phosphate buffer (pH 2.0–7.0) for various ionic strengths. The protonation constant (p K H ) was determined in concentrated HCl solution by the non-linear Cox–Yeates method. 1 H-, 13 C-, and 19 F-NMR spectra demonstrate the enolization of the studied ligand in a non-polar solvent. Study of aqueous complexation with rare-earth metals (Sc(III), Y(III), La(III), and trivalent lanthanides, except Pm) have been performed in acetate and glycine–HCl buffer media. The formation of mono-complex species and their conditional stability constants were computed through mathematic modeling of spectrophotometric data. Using the obtained acid–base parameters and taking into account the side reactions, sixteen “true” formation constants were determined. The “true” (thermodynamic) stability constants lie in the range of 4.8–12.0 logarithmic units. Thermodynamic and spectral characteristics have been reproduced by DFT simulations using several density functionals.