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Results are presented from investigating the structure of maleic acid, processes of gas-phase protonation, and acid–base equilibria with the participation of maleic acid in water–ethanol and water–dimethylsulfoxide solutions. The рK values of maleic acid dissociation in water–ethanol and water–dimethylsulfoxide solvents are determined. It is established that the рK values grow along with the content of the nonaqueous component in a water–organic mixture. Analysis of the solvation contributions from all reagents participating in the acid dissociation of maleic acid in water–ethanol and water–dimethylsulfoxide solvents reveals that the main contribution to the increase in рK1 and рK2 comes from the desolvation of anions.

The effect aqueous ethanol solvents have on the stability of coordination compounds between Cu(II) ions and anions of succinic (Y2–) and maleic (L2–) acids is studied via UV–Vis spectrophotometry. Logarithms of stability constants for succinate and maleate complexes are compared to ones obtained via potentiometric titration. Quantum chemistry calculations are performed for the structures of maleic and succinic acids and complexes of them with Cu(II) ions to explain the difference between the stabilities of succinate and maleate complexes.

Tinh thể hình que có kích thước nano của vật liệu hydroxyapatite khuyết canxi (d-HAp) đã được tổng hợp thành công bằng phương pháp kết tủa trong dung dịch. Các mẫu được đặc trưng bởi phương pháp hiển vi điện tử truyền qua (TEM), hiển vi điện tử quét (SEM), nhiễu xạ bột tia X (XRD), huỳnh quang tia X (XRF), phổ hồng ngoại biến đổi Fourie (FTIR) và phân tích nguyên tố bằng phương pháp tán xạ năng lượng tia X (EDX). Kết quả nghiên cứu chỉ ra rằng, vật liệu hydroxyapatite khuyết canxi tổng hợp được là đơn pha, các hạt có kích thước nano với chiều rộng trong khoảng 20-30nm và chiều dài trong khoảng 200-250nm. Theo kết quả phân tích bằng phương pháp XRD, hydroxyapatite khuyết canxi tổng hợp được có cấu trúc không gian hệ lục phương thuộc nhóm P63/m (số 176), hằng số mạng a=b=9.41Å, c=6.88Å. Vật liệu hydroxyapatite khuyết canxi được khảo sát khả năng xử lý dư lượng kim loại nặng trong đất trồng cây rau muống bị nhiễm Fe(II), Cu(II), Ni(II) and Cr(VI) nhân tạo. Kết quả nghiên cứu cho thấy vật liệu hydroxyapatite khuyết canxi có khả năng xử lý rất tốt dư lượng Fe, Cu: xử lý được 69.7% lượng Cu; 52.2% lượng Fe

The paper provides an overview of own data on complexation of nickel (II), cobalt (II) and cooper (II) ions with succinic acid anion in water-organic mixed solvents. Proper data are compared with data reported in literature for d-metal complexes with anions of maleic and succinic acids. The effect of aqueous ethanol solvent compositions on the stability of coordination compounds of M2+ with succinic acid anion as well as on рК values of stepwise succinic acid dissociation was carried out by a potentiometric titration at ionic strength of 0.1 maintained with sodium perchlorate at 298.15 ± 0.10 K. Mono ligand complexes of Ni2+, Co2+ and Cu2+ ions with succinic acid anion become stronger when ethanol content rises. In aqueous solutions Cu2+ ion forms stronger complexes with succinic and maleic acid anions than Ni2+ and Co2+ ions. In the studied water - ethanol solution this ratio is maintained for complexes with succinic acid anion, but a water-isopropanol solvent exerts leveling effect on the stability of complexes of nickel (II) and cobalt (II). An increase in the stability of complexes of d-metal with anions of maleic and succinic acids is due to the destabilization of the ligand with increasing ethanol concentration. The principal contribution of the changes in the solvation state of ligand is a typical for the stability changes of d-metal complexes with amine, glycinate, and acetate type ligands in water-organic mixed solvents. For citation: Tukumova N.V., Usacheva T.R., Thuan Tran Thi Dieu, Sharnin V.A., Giancola C. Stability of coordination compounds of some d-metal ions with succinic acid anion in aqueous-ethanol solvents. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2018. V. 61. N 9-10. P. 15-22

Stability constants of the coordination compounds of nickel(II) and cobalt(II) ions with succinic acid anion in water–ethanol solvents are determined via potentiometric titration at ionic strength of 0.1 and at T = 298.15 K. It is found that logβ values of monoligand complexes of these ions and succinic acid anions rise along with the content of ethanol in solution (XEtOH = 0–0.7 mole fractions). Based on an analysis of the thermodynamic characteristics of the solvation of the reagents involved in complex formation, it is found that the increased stability of succinate complexes of nickel(II) and cobalt(II) ions in water–ethanol solvents is mainly determined by the weakening of the solvation of succinic acid anion (Y2−).

The Gibbs energies of transferring succinic acid from water to aqueous ethanol and aqueous dimethylsulfoxide solvents are determined according to solubility. An increase in the negative values of the Gibbs energy upon moving from water to aqueous–organic solvents is observed. The effect the composition of solvents has on the acid–base properties of succinic acid is analyzed using the thermodynamic solvation approach. It is shown that the main contribution to the shift of the acid–base equilibria of succinic acid in aqueous ethanol and aqueous dimethylsulfoxide comes from the weakening of the solvation of its deprotonated forms.

The composition and stability of coordination compounds of the anions of maleic (H2L) and succinic (H2Y) acids with copper(II) ions in water-ethanol solutions is studied by means of potentiometric titration at a sodium perchlorate ionic strength of 0.1 and a temperature of 298.15 K. The composition of the water-ethanol solvent was varied from 0 to 0.7 molar parts of ethanol for maleic acid and from 0 to 0.4 molar parts for succinic acid. The stability of monoligand complexes of copper ions with the anions of maleic and succinic acids grows with increase of ethanol concentration from 3.86 to 6.62 for logβCuL and from 2.98 to 6.01 for logβCuY. It is shown that a monotonic rise in stability upon an increase in the content of ethanol in solution is observed, while the values of logβCuL change more sharply. The succinic acid anion forms a stronger complex with copper ions than maleic acid anions do at an ethanol content of 0.4 molar parts. The possibility of the formation of a protonated CuHY+ particle is established.

Composition and stability of coordination compounds of nickel(II) and cobalt(II) ions with maleic acid anion in aqueous isopropanol solutions (H2O-IPA) of composition χIPA = 0–0.5 mole fraction was studied by potentiometric titration at ionic strength of 0.1 maintained with sodium perchlorate at 298.15 K. Monoligand complexes of Ni2+ and Co2+ ions with maleic acid anion become stronger when isopropanol content rises. In the solvent of the studied composition, Co2+ ions form less stable complexes than Ni2+ ions that corresponds to the Irving-Williams series established for aqueous solutions. Variations in complex stability are more expressed at small IPA content and differ within experimental error at χIPA = 0.5 mole fraction. Obtained results were compared with literature data for akin compounds.