The new process of abies ethanol lignin sulfation by a low-toxic mixture of sulfamic acid and urea in 1,4dioxane medium was optimized and the structure of sulfated ethanol lignin was studied. The process of lignin sulfation is described by a first-order equation in the temperature range 70-100˚C. The value of the rate constants are weakly dependent on the ratios of lignin and sulfating complex (SC-sulfamic acid-urea mixture). The activation energy of the sulfation process decreaseses from 95 kJ / mol to 24 kJ / mol with an increase in the content of the sulfating complex. The optimal conditions for sulfation of abies ethanol lignin with a high yield of water-soluble sulfated lignin ((100% of mass) with sulfur content of 7.9%) where found: temperature 95-100°С, L / SC ratio 1: 2,3-1:2,9 and the 2-hour duration of the process. The composition and structure of water-soluble sulfated ethanol lignin were proven by elemental analysis, FTIR spectroscopy, two-dimensional NMR spectroscopy and gel permeation chromatography. It was shown that only alcoholic OH-groups of ethanol lignin react with sulfation complex. Sulfated ethanol lignin has a higher molecular weight and a lower degree of polydispersity compared to the initial ethanol lignin .

In this work, we demonstrate the fundamental relationships between stability constants and periodic, acid–base, and structural parameters for complexes of some 1,3-diketones. The four analogues of hexafluoroacetylacetone2-thenoyltrifluoroacetone, 2-furoyltrifluoroacetone, benzoyltrifluoroacetone, and 2-naphthyltrifluoroacetonehave been studied as chelating ligands for 16 rare-earth metals (Sc, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu) in aqueous solutions. Systems have been investigated spectrophotometrically using a multiwave nonlinear least-squares regression algorithm for data processing. Conditional stability constants were obtained for a wide pH region (2.0–5.4) at constant ionic strength (I = 0.5 M, NaCl). To receive the apparent (“true”) equilibrium parameters, acid–base and keto–enol characteristics of the studied ligands have been described and revised for specific conditions. Dissociation constants were obtained in citrate–phosphate buffer media and protonation parameters were received in concentrated hydrochloric acid by the Cox–Yates method. The apparent formation constants for monocomplex species were obtained as thermodynamic invariants (depend only on the temperature) for each ligand and lie from 4.2 to 12.7 logarithmic units. Although the studied ligands have similar values of pK a, the stabilities of their complexes vary considerably. Systematic analysis of 64 apparent stability constants demonstrates that the force of interaction between the metals and nonsymmetric β-diketones increases as 2-furoyltrifluoroacetone < 2-thenoyltrifluoroacetone < benzoyltrifluoroacetone < 2-naphthyltrifluoroacetone. The studied ligands display varying degrees of the correlation between the periodic parameters and formation constants. Naphthyltrifluoroacetone and its complexes with heavy lanthanides exhibit a clear trend in properties with increasing ionic potential. In general, the received set of data can be described from purely electrostatic grounds within the framework of the periodic law. Spectral, keto–enol, acid–base, and complexing properties were reproduced using density functional theory modeling and explain some of the regularities discovered.

The crystal structure of catena (μ 4 1,3 diethyl 2 thiobarbiturato O,O',S,S)silver(I) [Ag(μ 4 DETBA O,O',S,S] (1), where HDETBA is 1,3 diethyl 2 thiobarbituric acid C 8 H 12 N 2 O 2 S, has been solved by X ray powder diffraction. Crystals of complex 1 are monoclinic, a = 7.8339(2) Å, b = 15.4970(4) Å, c = 8.7502(2) Å, β = 111.916(2)°, V = 985.53(5) Å 3 , space group P2 1 /c, Z = 4. The Ag + ion is coordinated by two oxygen atoms and two sulfur atoms to form a distorted tetrahedron. Tetrahedra share sulfur atom vertices to form infinite chains linked via bridging DETBAions into a three dimensional framework. No hydrogen bonds have been found in the structure, but π-π interaction is observed between DETBAions.

The acid–base properties, protonation activity, and complexing abilities of two substituted β-diketones have been studied. The equilibrium constants of dissociation (pK a) were obtained at constant ionic strength (I = 0.5 M) in the pH 2.0–7.5 region. Protonation processes have been investigated in a strongly acidic solution of HCl for the determination of protonation constants (−pK H). All received acid–base parameters characterize both ligands as more acidic compounds than the­noyl­tri­fluoro­acetone. The study of complexation with 11 lanthanides (Ce, Nd, Pr, Sm, Eu, Gd, Dy, Er, Tm, Yb, and Lu) was carried out in glycine buffer. The determined values of formation constants for monocomplex species lie in the region from 5.5 to 6.9 logarithmic units. Using DFT procedures, the optimal computational protocol for describing the studied equilibria has been found.

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.

The aqueous complexation of some lanthanides(III) and lanthanum(III) ions with quercetin and quercetinsulfanate are reported. The equilibrium stability constants for the formation of 1 : 1 monocomplexes Ln(III)-quercetin/ quercetinsulfanate (Ln(III)=La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III), Gd(III), Tb(III), Dy(III), Er(III), Tm(III), Yb(III)) were determine in an acetic buffered solution. The measurements were conducted by spectrophotometric method at 293 K and I = 1(NaClO 4). Structures of formed complexes were suggested with using DFT simulations.

The coordination mode for interactions between Bi(iii) and 3-mercaptopropionic acid has been established by combined experimental and theoretical investigation.

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