A number of new complexones – ethylenediaminetetra(O-alkyl)methylenephosphonic acids, the structurally related organophosphorus analogs of ethylenediaminetetraacetic acid – were synthesized. The acid-base and complexing properties of the obtained substances with alkaline-earth and transition metal ions were studied by the methods of potentiometric titration and mathematical simulation. The following parameters were calculated: the ionization constants of the ligands, the stability and deprotonation constants of their 1:1 complexes with metal ions, and the distribution of the complex forms. The calculated stability constants for H4L-Alk ligands and d-elements follow the Irving–Williams series.

Acid-base properties of 2,2′-{[(diisopropoxyphosphoryl)methyl]azanediyl}diacetic acid and its complexing ability towards alkaline-earth and transition metals have been studied by means of potentiometric titration. Comparative analysis of the determined stability constants and these of iminodiacetic and nitrilotriacetic acids has been performed. In comparison with iminodiacetic acid, the studied ligand has formed stronger complexes with alkaline earth metal ions and weaker complexes with transition metal ions; its complexes with the investigated cations have been weaker than these of nitrilotriacetic acid.

Systems based on 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP), iron(iii)—HEDP and manganese(ii)—iron(iii)—HEDP, were studied by pH-potentiometry combined with mathematical modeling and NMR. Diverse and highly stable heteronuclear iron manganese complexes were found to exist in the heteronuclear system. The formation of the MnH3L23–, FeMnH3L20, Fe2MnHL33–, and MnL2– complexes was established. The relaxation efficiency coefficient REC2 (relaxivity) of these complexes was evaluated at ~2000 mol–1 s–1 L. Therefore, these systems hold promise as MRI contrast agents.

pH-Potentiometric method in combination with mathematical modeling was used to study the system manganese(ii)—gadolinium(iii)—1-hydroxyethylidenediphosphonic acid (HEDP, H4L). When both cations simultaneously are present in the solution, the accumulation of heteronuclear forms with the ratio of Gd: Mn: HEDP equal to 1: 1: 1, 1: 1: 2, and 1: 1: 3 was observed already in the strongly acidic pH region, while from homonuclear forms only five complexes were detected in the solution, namely, MnL26–, GdH4L2–, GdH2L+, KGd2HL2↓, and K3Gd2L2(OH)↓. It was concluded that heteronuclear complexes are much stronger and replace homonuclear forms in solution.

Based on pH-potentiometric titration, it was found that the system Mn2+ - HEDP accumulates mono-and binuclear complexes of 1 : 1 and 2 : 2 composition, as well as mononuclear biscomplexes. Equilibrium and stability constants were obtained. Fractional distribution of the forms was studied. The high coefficient of relaxation efficiency (CRE2) of the complexes in the spin-spin relaxation time (T-2) and their considerable stability makes it possible to regard them as potential MRI-contrast reagents. In the test system at pH approximate to 7.4 (the pH of the blood), the following complex forms can be identified: MnHL25-, MnH2L24-, and MnL2-. When modeling the injection of such complexes in the human body, which is accompanied by about 1000-fold dilution, it was found that MnL2- is the most stable of them. Other complexes under these conditions are absent, and the concentration of "free" manganese(II) in the blood does not exceed the maximum concentration limit for drinking water.

The solvation state of D-sorbitol has been determined in water-dimethylformamide (DMF) system (from 0 to 10 m.p.) using the method of polarimetry. The composition and formation constants of D-sorbitol - water - DMF heterosolvates have been obtained. The molar parts of D-sorbitol in heterosolvates have been found. It has been revealed that DMF acts as a selective solvent when its content is minimum (not higher than 0.7 m.p.), which is consistent with its higher nucleophilicity compared to water. If DMF concentration is higher than 0.7 m.p., there is inversion in solvation selectivity with water becoming a selective solvent. Under the experimental conditions, 12 water molecules in hydration shells were substituted with 6 DMF molecules. The substitution sequence of water molecules has been suggested.

Erbium(III)-HEDP and erbium(III)-calcium(II)-HEDP systems (HEDP is 1-hydroxyethylidene-1,1-diphosphonic acid) have been studied using potentiometry method in association with mathematical modelling. In the erbium(III)-HEDP system the formation of compexes having various degree of deprotonation of a ligand, 1 : 1 and 2 : 1 mono- and dinuclear complexes, as well as mononuclear bis-complexes has been shown. It was found, that heteronuclear complexes generated in erbium(III)-calcium(II)-HEDP system, do not coincide neither with calcium nor with erbium forms in composition

The complex formation constant have been determined for the reactions of 1-hydroxyethylidenediphosphonic acid (H4L) with Ca(II) and Gd(III). The solubility constant has been estimated for the products differing in the ligand deprotonation state. In the cases of both cations, four complex types are common: Me(H2L)2, MeH3L2, Me2L, and Me2(HL)2. The Gd(H2L)2 and GdH3L2 complexes are much more stable than the respective calcium complexes. It has been demonstrated that, on the contrary to the commonly accepted practice, gadolinium ion cannot model the behavior of calcium ions.

The equilibria of complex formation between Ni(II) and glycerol in a wide range of PH have been studied by nuclear magnetic relaxation, pH-potentiometry, and mathematical modelling. The self-association of glycerol (H(3)Glr)(2) and the formation of outer-sphere complexes {[Niaq] H(3)Glr}(2)+ and {[Niaq](H(3)Glr)(2)}(2+) as well as mono-and polynuclear glycerates [NiH(2)Glr]+, [NiHGlr], [Ni(2)Glr]+, [Ni(H(2)Glr)(H(3)Glr)]+ and [Ni-4(HGlr) 3(H(2)Glr)] NO3 have been observed. The stoichiometry and equilibrium constants have been calculated.

Ionization constants of a series of aminomethylphosphine oxides and respective amino precursors, as well as their isostructural amino phosphonates in water-2-propanol or water medium were determined. The main regularities of the effect of the phosphoryl group on the protolytic equilibria involving mono- and bisphosphorylated amines and diamines were found. The environment effect on the ionization constants of hydrophilic aminophosphoryl compounds and amines was estimated quantitatively. The relationship between the dissociation constants of aminophosphoryl compounds and related constants of amino precursors in the framework of the principle of linearity of free energies was demonstrated.

Data on the formation constants and the distribution of various forms of 1-hydroxyethylidenediphosphonic acid (H4L, H3L , H2L2, HL3, L-4, H6L22, H5L23, H4L24, H3L25, H2L26) in a solution with different pH and concentration of HEDPA were found. The processes of self-association and complexation with the cations of alkali titrant (KOH) were considered.

The possibility of synthesizing heteronuclear compounds in the systems based on Fe(II), Fe(III), Al(III), SO 4 2− , Cl−-H2O-OH−, and NH3 was studied. A mathematical model based on data on the potentiometric titration was developed. The elemental and phase composition and the structure of the compounds synthesized were determined by the XPA, DTA and NMR methods to optimize the conditions of the synthesis.

A joint study using polarimetry, spectrophotometry, and mathematical modeling revealed the formation of 1: 1, 2: 1, and 4: 4 outer-sphere complexes of nickel(II) ions with neutral D -glucitol (H 6 Glc-ol), viz., {[Ni(H 2 O) n ]•(H 6 Glc-ol)aq} 2 +, {[Ni(H 2 O) n ] 2 •(H 6 Glc-ol)aq} 4+ , and {[Ni(H 2 O) n ] 4 •[(H 6 Glc-ol)aq] 4 } 8+ in a weakly acidic medium. In aqueous solutions, D-glucitol forms tetramers. For each form, the constant of formation and the specific optical rotation was calculated.

α-Aminophosphoryl compounds of the phosphonate, phosphine oxide, and α,ω-bis(phosphine oxide) series and some of their thiophosphoryl analogs were synthesized. Potentiometric measurements of the pKa of the conjugate acids revealed an insignificant effect of variation of substituents on the phosphorus, nitrogen, and α-carbon atoms on the basicity of the phosphorylated amines. The latter are weak bases. Organophosphorus groups decrease the basicity of the amines by almost 5 pKa units. The role of the hydrophobic effect and intramolecular H-bonding in the obtained substances was discussed.

A method was suggested for separation of the Gibbs energy of transfer of atomic, molecularspecies from a solvent Solv1 into a binary solvent (Solv1 + Solv2) into the contribution from solvation of thereaction centers and that from nonspecific interactions, solvent reorganization, and cavity formation. The relationship for calculating the former contribution can be used for thermodynamically adequate comparative estimation of the stability of complex species in solution.

Selective solvation of rare-earth (yttrium subgroup), cobalt(II), nickel(II), and copper(II) ions and proton donors [L-(+)-tartaric acid and its dianion; protonated, zwitterionic, and anionic forms of L-alpha-alanine and L-beta-phenyl-alpha-alanine] in binary water-dipolar aprotic solvent (acetonitrile, dimethyl sulfoxide, dimethylformamide, and hexamethylphosphoramide) mixtures of variable composition is examined. The relationships X-2' = f(X-2(0)), where X-2' and X-2(0) are the mole fractions of the dipolar aprotic solvent (DAS) in the nearest surroundings of the solvated species and in the bulk, respectively, show that, on the background of the preferential solvation by the DAS molecules, there are some cases of inversion of solvation selectivity. This fact is explained in terms of the steric and dipole-dipole intermolecular interactions.

The effect of a substituent inm-,o-, andp-aminobenzoic and isonicotinic acids and 4-amiopyridine on the stability of their complexes with Dy3+ in H2O and H2O-DMSO(DMF) has been studied by pH-metric and magnetoopticrl titration. An increase in the efficiency of the salvation of a ligand decreases the effect of a substituent on the stability of the complex.