Determination of Acid–Base and Complexing Parameters of Chlorine-Substituted Trifluorobenzoylacetone in Water Medium

Abstract

In this work, we study the behavior of 1-(4-chlorophenyl)-4,4,4-trifluoro-1,3-butanedione (ClTFBA) using a spectrophotometric technique under various conditions. Acid–base characteristics have been studied in citrate-phosphate buffer and hydrochloric acid solutions. Dissociation constants were determined in the pH range 3.0–8.0 for three ionic strengths (I = 0.1, 0.5, and 1.0 M; NaCl). Protonation equilibria have been investigated in concentrated HCl by the nonlinear Cox–Yeats method. The interaction between ClTFBA and rare-earth metals was examined in glycine and acetate buffers. Stability constants of monocomplexes were obtained for trivalent metals—Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The received formation constants lie from 4.5 to 11.8 logarithmic units. Analysis of the results shows that the thermodynamic stability of complexes increased from Ce(III) to Lu(III) and has a linear correlation with the ionic potential. The relationship described in this work demonstrates the electrostatic nature of the M(III)–ClTFBA bonds. Pronounced ionic character, observed for complexes with Ce, Pr, Nd, Sm, Eu, and Gd, points to high charge carrier mobility for these compounds and iterates the appropriateness to use the studied complexes to generate new organic light-emitting diode materials. Equilibrium and spectral characteristics were reproduced by density functional theory (DFT) and time-dependent DFT calculations performed using different basis sets and exchange–correlation functionals.