In order to develop an express procedure for the synthesis of the Eu(III)-containing heteropoly compound Na9[Eu(W5O18)2]·35H2O, a study of the interaction in an aqueous solution of the Na2WO4 – HNO3 – Eu(NO3)3 – H2O system acidified to an acidity of Z = ν(H+)/ν(WO42–) = 0.80 was carried. A procedure for obtaining a single-phase sample of Na9[Eu(W5O18)2]·35H2O is proposed, which is performed by a simple technique in a short time, which does not exceed 5 days from the addition of reactants to obtaining the target product with a yield of more than 90%. It was established that during salting out, the addition of an organic solvent (propan-2-one) results in the crystallization of Na9[Eu(W5O18)2]·35H2O normal salt with plate-like surface micromorphology. The set of oscillations characteristic for the heteropoly tungstate anion with the Peacock–Weakley type of structure, [Eu(W5O18)2]9–, was established by the methods of FT-IR spectroscopy and FT-Raman spectroscopy. By the method of FT-IR spectroscopy the absence of organic solvent molecules (propan-2-one) in the composition of the crystalline product was established. The revealed set of vibrations in the FT-IR and Raman spectra of the isolated salt (the most intense valence vibrations at 710, 797, 849, and 935 cm-1 in the FT-IR spectrum; intense bands in the region of 930–980 cm-1 in the Raman spectrum) is characteristic of the site group of the heteropoly anion [Ln(W5O18)2]9– (Ln = La–Lu) and is identical to the FT-IR and Raman spectra of salts, the crystal structure of which has been reliably established by single crystal X-ray diffraction analysis. By the method of scanning electron microscopy, it was shown that the grain size of Na9[Eu(W5O18)2]·35H2O powder is up to 500 nm. The single phase of the salt was confirmed by the uniform surface contrast in the backscattered electron imaging (BEI) mode and by the uniform distribution of Eu, Na, W, and O during the scanning of the surface in the characteristic X-ray radiation.

The interactions of the Ca2+–WO42––H+–H2O system initially acidified to the molar ratio (acidity) Z=(H+)/(WO42–)=1.00 were studied by the methods of pH-potentiometry, mathematical modeling and conductometry in the interval Z=0.60–2.00 at 2980.1 K with NaNO3 (I=0.05–0.30 moll–1) as the supporting electrolyte. The logarithms of the equilibrium concentration constants were calculated by the Newton's method, and previously unknown logarithms of the thermodynamic constants and Gibbs energy of the reactions of the formation of ion associates Ca2+,[W4O14(OH)2]4–; Ca2+,[W6O20(OH)2]6–; Ca2+,[W12O40(OH)2]10–; Ca2+,H[W12O40(OH)2]9–; Ca2+,H2[W12O40(OH)2]8–; Ca2+,H3[W12O40(OH)2]7–; [W12O38(OH)2]6–; and H[W12O38(OH)2]5– were calculated using the Pitzer method. The formation of particles with a ratio of Сa2+:[W12O40(OH)2]10–=1:1 and Сa2+:[W6O20(OH)2]6–=1:1 in the solutions was shown by the conductometric titration method. The crystals of calcium paratungstate B Ca5[W12O40(OH)2]30H2O were synthesized from Na2WO4 solution acidified to acidity Z = 1.00. By using ATR-FTIR and Raman spectroscopies, it was shown that the isopolyanion in the composition of the salt belongs to the structural type of paratungstate B. The structure of Ca5[W12O40(OH)2]30H2O was determined by single crystal X-ray diffraction: monoclinic, P21/n, a=15.3619(4) Å, b=11.7537(3) Å, c=18.1471(5) Å, =109.2950(10)0, V=3092.58(14) Å3, R1=0.0298, wR(F2)=0.1387.

Conditions necessary for the formation of La(III)-containing polyoxotungstates in solutions of the system Na2WO4 – HNO3 – La(NO3)3 – H2O/Solvent (Solvent = acetone, acetonitrile, ethanol; 50/50 vol.% Н2О: Solvent ratio) acidified to acidity Z = ν(H+)/ν(WO42–) = 0.80 were elaborated. It was established that during salting out, the addition of an organic solvent leads to the crystallization of normal salts, Na9[La(W5O18)2]·nH2O (n = 32–35). Using FT-IR spectroscopy, it was shown that the anion [La(W5O18)2]9– in the composition of the isolated salts belongs to the Peacock–Weakley type of structure and the absence of solvent molecules in the composition of the crystalline product was established. Using the method of scanning electron microscopy, the single-phase nature of the synthesized salts was established (according to the uniform contrast of the surface of the samples during scanning in the backscattered electron mode and according to the results of energy dispersive X-ray microanalysis), and the grain sizes were determined (from 140–300 nm for the salt isolated from the H2O: acetone medium, to 300–450 nm for the salt isolated from the H2O: ethanol system). Microphotographs of powders of Na9[La(W5O18)2]·nH2O salts powders in characteristic X-ray emission do not show zones with different surface morphology, and demonstrate uniform distributions of Na, La, W, and O without segregation, which confirms the single–phase nature of the samples isolated from aqueous-organic solutions. The conducted research made it possible to expand the list of organic solvents that can be used for the synthesis of normal salts with a heteropoly anion with a Peacock–Weakley type of structure from aqueous-organic solutions. The use of acetonitrile and ethanol for Na9[La(W5O18)2 ]·nH2O isolating can be extended to the synthesis of salts with other lanthanide heteroatoms.

A new procedure for the preparation of sodium–manganese paratungstate was developed and used to synthesize Na5[Mn2.5(W12O40(OH)2)]36H2O. This procedure implies an acidity ratio represented as Z=С(H+)/С(WO42–)=1.00 and a component ratio of CW:CMn=6:1, which enables the synthesis of compounds to be faster, more cost-effective, and with lower energy consumption. The composition and single-phase nature of the compound was confirmed by elemental analysis and scanning electron microscopy. Furthermore, the nature of the paratungstate anion within its composition was determined by IR spectroscopy. Thermolysis of synthesized Na5[Mn2.5(W12O40(OH)2)]36H2O was studied, revealing that the dehydratation process proceeds in a full accordance with the entry of water molecules into the coordination spheres of cations and anions. The sequence of H2O removal with increasing temperature is as follows: outer sphere; H2O molecules from the Na coordination environment; H2O molecules from the Mn coordination environment; and constitutional H2O molecule from the anion composition.

Novel composite self-disinfecting films of polylactic acid (PLA) filled with nanosized particles of double sodium–copper(II) paratungstate B Na2Cu3(CuOH)2[W12O40(OH)2]·32H2O (POM) were developed. The solvent casting (POM/PLA film) and solvent-free melt extrusion methods (Extr. POM/PLA film) were applied for film preparation. The copper (II) ion release to water from both types of the films after 10 days at different temperatures demonstrated that the PLA matrix acts as a diffusion barrier, and the resulting concentration of released copper in water at room temperature remained low, at 0.79% for POM/PLA film and 0.51% for Extr. POM/PLA film. The POM-containing films reveals a significant inhibitory effect against E. coli ATCC 25922 in the agar diffusion test. The numbers of CFUs in washes of the films after incubation for 24 h were found to be 3.6 log CFU mL–1 (POM/PLA film) and 4.1 log CFU mL–1 (Extr. POM/PLA film). The films combine the antibacterial properties of POM and a bio-based polymer matrix, which makes them a prospective coating material for applications in hospital indoor environments. Excellent thermal stability of POM gives a technological advantage for industrial manufacturing to allow the processing of novel composite material in the solvent free (molten) state.

Interactions in the Ba2+–WO42––H+–H2O system, that was acidified to the molar ratio (acidity) Z=(H+)/(WO42–)=1.00, in the range of Z=0.60–2.00 at 2980.1 K with NaNO3 as the background electrolyte (I=0.1–0.3 mol•l–1), were studied by the methods of pH-potentiometry, mathematical modeling and conductometry. Logarithms of concentration constants of equilibrium were calculated by Newton's method. Previously unknown logarithms of thermodynamic constants and Gibbs energies of formation reactions for some ion pairs (BaOH+,[W12O40(OH)2]10–; Ba2+,[W12O40(OH)2]10–; Ba2+,H2[W12O40(OH)2]8–; Ba2+,H3[W12O40(OH)2]5–; Ba2+,[W12O18(OH)2]6–; and Ba2+,H[W12O18(OH)2]5–) were calculated by Pitzer's method. The formation of particles with a Ba2+:[W12O40(OH)2]10–=1:1 ratio in solutions was established by conductometric titration method. A scheme of interconversions between ion pairs in an aqueous solution was proposed. From acidified to different Z values aqueous solutions of Na2WO4, the normal and double barium(II) paratungstates B Ba5[W12O40(OH)2]30H2O (Z=1.17), Na4Ba2[W12O40(ОН)2]28Н2О (Z=1.25), and Na2Ba4[W12O40(ОН)2]25Н2О (Z=1.33) were synthesized. The data of FTIR spectroscopy showed that the isopoly anion in the salts' composition belongs to the paratungstate B structural type.

The conditions required for the formation of double sodium–copper(II) paratungstate B Na 2 Cu 4 [W 12 O 40 (OH) 2 ]·22H 2 O ( 1 ) and mixed copper(II) paratungstate B–hydroxide Cu 5 [W 12 O 40 (OH) 2 ]·2Cu(OH) 2 ·30H 2 O ( 2 ) in Cu(NO 3 ) 2 – Na 2 WO 4 – HNO 3 – H 2 O solution acidified up to Z = ν(H + )/ν(WO 4 2– ) = 1.29 are determined. The synthesized salts 1 and 2 are examined using chemical analysis, X-ray single crystal analysis, and FTIR spectroscopy. The X-ray single crystal data obtained for compound 1 : triclinic, P1̅ , a = 11.155(4) Å, b = 12.448(4) Å, c = 21.979(6) Å, α = 105.30(3)00B0, β = 91.99(3)00B0, γ = 112.51(3)00B0, V = 2687.8(16) Å 3 at T = 293 K, Z = 2, d calc = 4.419 g/cm 3 . The crystal data for 2 : triclinic, P1̅ , a = 10.588(4) Å, b = 12.830(4) Å, c = 12.852(4) Å, α = 95.86(3)00B0, β = 113.65(3)00B0, γ = 91.76(3)00B0, V = 1586.0(10) Å 3 at T = 293 K, Z = 1, d calc = 4.119 g/cm 3 . In structure 1 , Na atoms form distorted octahedra having common vertices with two [W 12 O 40 (OH) 2 ] 10– anions, and there are three types of coordination polyhedra of Cu atoms: distorted tetragonal bipyramids, trigonal bipyramids, and centrosymmetric rhombic bipyramids. In structure 2 , the Cu1, Cu2, and Cu5 atoms are located in the centers of symmetry; their coordination polyhedra are rhombic bipyramids. The anions [W 12 O 40 (OH) 2 ] 10– are connected by pairs of tetragonal pyramids Cu3O 5 and Cu4O 5 having a common edge of their bases, and their vertices are oriented in opposite directions with respect to the base plane, similarly to the structure of Cu(OH) 2 .

The equilibria processes in aqueous solutions of CrO42– – H+ – H2O and Cr2O72– – OH– – H2O systems were studied by pH‑potentiometric titration, mathematical modeling and UV–Vis. spectroscopy. It was established that in the CrO42– – H+ – H2O systems with acidity ZН = ν(H+)/ν(Cr(VI)) = 0–2.5 the processes of dichromate and hydrochromate anion formation and hydrolytic conversion of dichromate to hydrochromate take place, for which the logarithms of the equilibrium concentration constants were calculated by the quasi-Newton method (CLINP 2.1 software; 95 % confidence probability). The calculated values of the logarithms of the concentration equilibrium constants lgKC reliably agree with the literature data. The calculated lgKC were used to build of chromium(VI) anions distribution diagrams depending on ZH, and ZOH in solutions. For the first time, by the Pitzer method the thermodynamic equilibria constants of hydrochromate HCrO4– (lgK10 = 6,94), the dichromate anion Cr2O72– (lgK20 = 15,49) formation processes from the CrO4 2– and H+ ions, and the logarithm of equilibrium constant of the interconversion of the dichromate anion to the hydrochromate anion (lgK30 = –1,61) were calculated. Mathematical modeling and UV–Vis. spectroscopy show that the composition of anions in Cr2O72– – OH– – H2O solutions with alkality ZOH = ν(OH–)/ν(Cr(VI)) = 0–2.5 is identical to CrO42– – H+ – H2O systems. It is established that the experimental dependencies pH = f(Z) for the Cr2O72– – OH– – H2O system can be reliably reproduced by hydrolysis reactions of dichromate anion to hydrochromate anion and by subsequent neutralization to chromate anion with equilibrium constants calculated for processes in CrO42– – H+ – H2O solutions with same ionic strengths. The quantitative composition of chromium(VI) solutions was confirmed qualitatively by UV–Vis. spectroscopy.

Определены условия, необходимые для образования двойного паравольфрамата Б натрия-меди(ІІ) Na2Cu4[W12O40(ОН)2]·22Н2О (1) и смешанного паравольфрамата Б—гидро­ксида меди(II) Cu5[W12O40(OH)2]·2Cu(OH)2·30H2O (2) при взаимодействии в системе Cu(NO3)2—Na2WO4—HNO3—H2O при Z = ν(H+) / ν(WO42–) = 1.29. Синтезированные соли 1 и 2 исследованы с использованием химического и рентгеноструктурного анализа монокристаллов и ИК спектроскопии. Расшифровка кристаллической структуры соединения 1 показала: триклинная сингония, пространственная группа P–1, a = 11.155(4) Å, b = 12.448(4) Å, c = 21.979(6) Å, α = 105.30(3)°, β = 91.99(3)°, γ = 112.51(3)°, V = 2687.8(16) Å3 при T = 293 K, Z = 2, dвыч = 4.419 г/см3. Кристаллографические данные соединения 2: триклинная сингония, пространственная группа P–1, a = 10.588(4) Å, b = 12.830(4) Å, c = 12.852(4) Å, α = 95.86(3)°, β = 113.65(3)°, γ = 91.76(3)°, V = 1586.0(10) Å3 при T = 293 K, Z = 1, dвыч = 4.119 г/см3. В структуре 1 атомы Na находятся в искаженных октаэдрах, имеющих общие вершины с двумя анионами [W12O40(ОН)2]10–; наблюдается три типа координационных полиэдров атомов Cu: искаженные тетрагональные и тригональные дипирамиды, центросимметричные ромбические дипирамиды. В структуре 2 атомы Cu1, Cu2 и Cu5 находятся в центрах симметрии, их координационные полиэдры представляют собой ромбические дипирамиды. Анионы [W12O40(ОН)2]10– соединены парами тетрагональных пирамид Cu3O5 и Cu4O5 c общим ребром основания, а их вершины ориентированы в противоположные стороны относительно плоскости основания, как и в структуре Cu(OH)2.

The conditions required for the formation of double sodium–copper(II) paratungstate B Na2Cu4[W12O40(OH)2]·22H2O (1) and mixed copper(II) paratungstate B–hydroxide Cu5[W12O40(OH)2]·2Cu(OH)2·30H2O (2) in Cu(NO3)2 – Na2WO4 – HNO3 – H2O solution acidified up to Z = ν(H+)/ν(WO42–) = 1.29 are determined. The synthesized salts 1 and 2 are examined using chemical analysis, X-ray single crystal analysis, and FTIR spectroscopy. The X-ray single crystal data obtained for compound 1: triclinic, $$P\bar{1}$$ , a = 11.155(4) Å, b = 12.448(4) Å, c = 21.979(6) Å, α = 105.30(3)00B0, β = 91.99(3)00B0, γ = 112.51(3)00B0, V = 2687.8(16) Å3 at T = 293 K, Z = 2, dcalc = 4.419 g/cm3. The crystal data for 2: triclinic, $$P\bar{1}$$ , a = 10.588(4) Å, b = 12.830(4) Å, c = 12.852(4) Å, α = 95.86(3)00B0, β = 113.65(3)00B0, γ = 91.76(3)00B0, V = 1586.0(10) Å3 at T = 293 K, Z = 1, dcalc = 4.119 g/cm3. In structure 1, Na atoms form distorted octahedra having common vertices with two [W12O40(OH)2]10– anions, and there are three types of coordination polyhedra of Cu atoms: distorted tetragonal bipyramids, trigonal bipyramids, and centrosymmetric rhombic bipyramids. In structure 2, the Cu1, Cu2, and Cu5 atoms are located in the centers of symmetry; their coordination polyhedra are rhombic bipyramids. The anions [W12O40(OH)2]10– are connected by pairs of tetragonal pyramids Cu3O5 and Cu4O5 having a common edge of their bases, and their vertices are oriented in opposite directions with respect to the base plane, similarly to the structure of Cu(OH)2.

The synthesis conditions of novel double potassium-cadmium paratungstate BK2 Cd4[W12O40(OH)2]·28H2O from the aqueous solution of potassium tungstate acidified to Z=1.00 with a ratio v(Cd):v(W)=1:6 were elaborated. Using FTIR spectroscopy, it was shown that the anion contained in the isolated salt has the paratungstate B structure. Using Scanning Electron Microscopy, the surface morphology of isopoly compound was studied, and it was found out that the grain size is within the range of 20-45nm. The single-phase condition of the synthesized salt was confirmed by the surface uniform contrast in backscattered electron mode.

We report Peacock–Weakley complexes, Na9[Ln(W5O18)2]∙35H2O, formed with Tm(III), 1, and Yb(III), 2. Their syntheses, physico-chemical characterizations, crystal structures, and magnetic properties are described. Ab initio calculations are also reported. These polyoxometalate (POM) complexes were obtained using original synthetic conditions where acidification was performed with a stoichiometric amount of nitric acid to an acidity of Z = ν(H+)/ν(WO42–) = 8/10 = 0.80. Both the Tm(III) and Yb(III) derivatives were found to exhibit field-induced slow relaxation of their magnetization likely controlled by Raman and Orbach relaxation processes. 1 is a rare example of a Tm(III)-based single-molecule magnet (SMM) and is a consequence of the oblate tetragonal anti-prismatic symmetry of the coordination sphere.

Conditions necessary for the formation of isostructural sodium heteropoly decatungstolanthanidates(III) with Peacock–Weakley type anion Na9[Ln(W5O18)2]·35H2O (Ln = Gd, Er) in Ln(NO3)3–Na2WO4–HNO3–H2O solutions with a ratio ν(Ln): ν(W) = 1:10, acidified up to Z = ν(H+)/ν(WO42−) = 0.80, were established. The synthesized salts were characterized by Single Crystal X-ray analysis, FT-IR spectroscopy, and scanning electron microscopy. The correlation between structural parameters and the charge of Ln-heteroatom nuclei was determined. Comparison of structural parameters for isostructural neutral salts Na9[Ln(W5O18)2]·35H2O (Ln = Eu, Gd, Tb, Dy, Ho, Er) allowed us to establish linear dependences between decreasing lengths of Ln—Ob(W) bonds and interatomic distances O⋯O in Peacock–Weakley type heteropoly anions, and the nuclear charge of Ln–heteroatom. Two isostructural sodium heteropoly decatungstolanthanidates(III) with Peacock–Weakley type anion Na9[Ln(W5O18)2]·35H2O (Ln = Gd, Er) have been synthesized from Ln(NO3)3–Na2WO4–HNO3–H2O solutions, acidified up to Z = ν(H+)/ν(WO42−) = 0.80, and characterized by single-crystal X-ray diffraction, FT-IR spectroscopy, and scanning electron microscopy.

В сучасній хімії більше за половину наукових досліджень виконується з об’єктами, що відносяться до координаційних сполук. Тому проблема викладання курсу «Координаційна хімія» стала актуальною особливо в класичних університетах, де цей курс входить до навчальних програм бакалаврату. Склалася така ситуація, що рекомендовані підручники з хімії комплексних сполук в основному орієнтовані не на дисципліну професійної підготовки, а на спеціальні курси, що викладаються в магістратурі та аспірантурі і включають матеріали фундаментальних дисциплін, ще не засвоєних студентами другого, третього курсу бакалаврату.

Поліоксометалати відносяться до метал-кисневих сполук з унікальним структурним різноманіттям та цікавими фізико-хімічними властивостями, що дозволяє використовувати їх у каталізі, медицині та матеріалознавстві. Враховуючи це, розробка нових методик синтезу, характеристика будови та властивостей цього класу сполук є актуальною задачею і метою проведення досліджень.

New procedure for synthesis of isostructural sodium heteropoly decatungstolanthanidates(III) with Peacock–Weakley type anion Na9[Ln(W5O18)2]·35H2O (Ln = La–Yb) in Ln(NO3)3 – Na2WO4 – HNO3 – H2O solutions with a ratio ν(Ln) : ν(W) = 1:10, acidified up to Z = ν(HNO3)/ν(Na2WO4) = 0.80, were elaborated (Mariichak O.Yu., et al. Patent of Ukraine No. 121322, 2017). The synthesized salts were characterized by Single Crystal X-ray analysis (Fig. 1), FT-IR and FT-Raman spectroscopy, and scanning electron microscopy.

The formation of Ho(III)-containing polyoxotungstates in acidified to different acidity Z = ν(H+)/ν(WO42–) = 0.80, 1.17, 1.29, and 1.50 solutions of the Na2WO4 – HNO3 – Ho(NO3)3 – H2O system was studied. The conditions for the synthesis of Na9[Но(W5O18)2]·23H2O from the aqueous solution of sodium tungstate acidified to Z=0.80 and with acetone admixture were elaborated. The FT–IR spectroscopy was used to determine the belonging of anion [Ho(W5O18)2]9– in the synthesized compound to the Peacock–Weakley type of structure. By the method of scanning electron microscopy salt is proved to be single-phase, and its grain size is in the range 200-400 nm. The technique developed in this work for the preparation of sodium decatungstoholmiate(ІІІ) is new and differs in that it allows one to synthesize a normal salt, which can be used for the synthesis of other normal salts of sodium heteropoly decatungstolanthanidates(ІІІ). As a result of attempts to synthesize salts by the interaction of holmium(III) nitrate with aqueous solutions of sodium tungstate acidified to Z = 1.17 and 1.29, X-ray amorphous solids were obtained, which most likely are mixtures of paratungstate B and holmium heptatungstate. Using the methods of chemical analysis and FTIR spectroscopy, the conditions for the formation of a sodium-holmium double salt with lacunar undecatungstate anion, derived from Keggin structure Na2Ho2[Нo2(H2O)10W22O72(OH)2]·46H2O are established. Procedure for the synthesis of holmium(III) paratungstate B Ho10[W12O40(OH)2]3·54H2O by the exchange reaction of holmium(ІІІ) nitrate with sodium paratungstate B was elaborated, and by the method of scanning electron microscopy it is proved to be single–phase. It was found that the grain size of the sample is in the range 200–450 nm. The absence of sodium(I) ions in the composition of the synthesized salt was proved by atomic absorption spectroscopy and EDX. Microphotographs of the salt powders Na9[Но(W5O18)2]·23H2O and Ho10[W12O40(OH)2]3·54H2O in the characteristic X–ray radiation show no zones with different surface morphologies, and show uniform distribution of Na, Ho, W, O is observed without segregation, which confirms the single–phase nature of the products.

Возросший в последние годы интерес к теме синтеза новых соединений, в частности полиоксосоединений на основе вольфрама (VI), являющихся перспективными в химии металлокомплексного и фото-катализа, требует поиска и создания воспроизводимых методик синтеза и целенаправленных систематических исследований в данной области. Исследование процессов образования и устойчивости полиоксовольфрамат-анионов в водных и водно-органических системах, первоначально базируется на построении математической модели комплексообразования таких частиц в растворах.

Современные методики синтеза новых полиоксовольфраматов невозможно представить без тщательного изучения условий их образования и последующей устойчивости в различных средах.

In present study the procedure for successful synthesis of sodium heteropoly decatungstoterbate(III), Na9[Tb(W5O18)2]·34H2O, from acidified up to Z=ν(H+ )/ν(WO4 2– ) = 0.80 solution of sodium tungstate with a ratio of ν(Tb):ν(W) = 1:10 from aqueous-acetone media was elaborated.