NMR-Relaxometric Investigation of Mn(II)-Doped Polyoxometalates in Aqueous Solutions.

Solution behavior of K;5[(Mn(H2O))PW11O39]·7H2O (1), Na3.66(NH4)4.74H3.1[(MnII(H2O))2.75(WO(H2O))0.25(α-B-SbW9O33)2]·27H2O (2), and Na4.6H3.4[(MnII(H2O)3)2(WO2)2(ß-B-TeW9O33)2]·19H2O (3) was studied with NMR-relaxometry and HPLC-ICP-AES (High Performance Liquid Chromatography coupled with Inductively Coupled Plasma Atomic Emission Spectroscopy). According to the data, the [(Mn(H2O))PW11O39]5- Keggin-type anion is the most stable in water among the tested complexes, even in the presence of ethylenediaminetetraacetic acid (EDTA) or diethylenetriaminepentaacetic acid (DTPA). Aqueous solutions of 2 and 3 anions are less stable and contain other species resulting from dissociation of Mn2+. Quantum chemical calculations show the change in Mn2+ electronic state between [Mn(H2O)6]2+ and [(Mn(H2O))PW11O39]5-.

Proton Affinity in the Chemistry of Beta-Octamolybdate: HPLC-ICP-AES, NMR and Structural Studies.

The affinity of [ß-Mo8O26]4- toward different proton sources has been studied in various conditions. The proposed sites for proton coordination were highlighted with single crystal X-ray diffraction (SCXRD) analysis of (Bu4N)3[ß-{Ag(py-NH2)Mo8O26]}] (1) and from analysis of reported structures. Structural rearrangement of [ß-Mo8O26]4- as a direct response to protonation was studied in solution with 95Mo NMR and HPLC-ICP-AES techniques. A new type of proton transfer reaction between (Bu4N)4[ß-Mo8O26] and (Bu4N)4H2[V10O28] in DMSO results in both polyoxometalates transformation into [V2Mo4O19]4-, which was confirmed by the 95Mo, 51V NMR and HPLC-ICP-AES techniques. The same type of reaction with [H4SiW12O40] in DMSO leads to metal redistribution with formation of [W2Mo4O19]2-.

Coordination of Pt(IV) by {P8W48} Macrocyclic Inorganic Cavitand: Structural, Solution, and Electrochemical Studies.

Hydrothermal reaction of a macrocyclic inorganic POM cavitand Li17(NH4)21H2[P8W48O184] with [Pt(H2O)2(OH)4] results in coordination of up to six {Pt(H2O)x(OH)4-x} fragments to the internal surface of the polyoxoanion. The product was isolated as K22(NH4)9H3[{Pt(OH)3(H2O)}6P8W48O184]·79H2O (1) and characterized by multiple techniques in the solid state (SCXRD, XRPD, XPS, FTIR, and TGA) and in solution (NMR, ESI-MS, and HPLC-ICP-AES). Electrochemical properties were studied both in solution and as components of the paste electrode. The complex shows electrocatalytic activity in water oxidation.

Heterostructures Based on Cobalt Phthalocyanine Films Decorated with Gold Nanoparticles for the Detection of Low Concentrations of Ammonia and Nitric Oxide.

This work is aimed at the development of new heterostructures based on cobalt phthalocyanines (CoPc) and gold nanoparticles (AuNPs), and the evaluation of the prospects of their use to determine low concentrations of ammonia and nitric oxide. For this purpose, CoPc films were decorated with AuNPs by gas-phase methods (MOCVD and PVD) and drop-casting (DC), and their chemiresistive sensor response to low concentrations of NO (10-50 ppb) and NH3 (1-10 ppm) was investigated. A comparative analysis of the characteristics of heterostructures depending on the preparation methods was carried out. The composition, structure, and morphology of the resulting hybrid films were studied by X-ray photoelectron spectroscopy (XPS) and inductively coupled plasma atomic emission (ICP-AES) spectroscopy, as well as electron microscopy methods to discuss the effect of these parameters on the sensor response of hybrid films to ammonia and nitric oxide. It was shown that regardless of the fabrication method, the response of Au/CoPc heterostructures to NH3 and NO gases increased with an increase in the concentration of gold. The sensor response of Au/CoPc heterostructures to NH3 increased 2-3.3 times compared to CoPc film, whereas in the case of NO it increased up to 16 times. The detection limits of the Au/CoPc heterostructure with a gold content of ca. 2.1 µg/cm2 for NH3 and NO were 0.1 ppm and 4 ppb, respectively. It was shown that Au/CoPc heterostructures can be used for the detection of NH3 in a gas mixture simulating exhaled air (N2-74%, O2-16%, H2O-6%, CO2-4%).

Rh(III) hydroxocomplexes speciation using HPLC-ESI-MS.

A mixture of rhodium(iii) hydroxocomplexes formed during the polycondensation process in alkaline media has been fully characterized by the hyphenated high performance liquid chromatography with electrospray ionization mass spectrometry (HPLC-ESI-MS). The baseline separation was achieved using reverse phase ion-pair chromatography (RP-IP-HPLC) in gradient elution mode. When using SDS as the ion pair, the formation of all types of its associates with the molecules of acetonitrile, as well as oligomers of rhodium aquahydroxocomplexes, etc. was taken into consideration. As a result, it was shown that the test mixture is presented by [Rh(H2O)6]3+, [Rh2(µ-OH)2(H2O)8]4+, [Rh3(µ-OH)4(H2O)10]5+, [Rh4(µ-OH)6(H2O)12]6+.

Is It Possible To Prepare a Heterometal Anderson-Evans Type Anion?

Reaction of [SbW9O33]9- with [Pt(H2O)2(OH)4] results in the first example of the mixed addenda Anderson-Evans type PtIV{SbV(OH)2}WVI5O22]7- anion, isolated and characterized as K6Na2[Pt{Sb(OH)2}W5O22](NO3)0.1(OH)0.9̇11H2O (1).

[{AgL}2Mo8O26]n- complexes: a combined experimental and theoretical study.

Self-assembly reactions between AgNO3, L (PPh3, PPh2Py, AsPh3, SbPh3) and [ß-Mo8O26]4- in DMF led to the formation of [ß-{AgL}2Mo8O26]2- anions, which were isolated as Bu4N+ salts (1-4) and characterized by XRD, IR and elemental analysis. In the crystal structures Ag+ can switch the coordination number from 5 (P, As) to 6 (Sb) by uptake of a DMF molecule. High-level QAIM analysis of the coordination sphere around Ag shows critical points even in the case of longer Ag-O distances. Changing the ligand type to a family of substituted pyridines results in novel Ag-L-POM complexes with different environments around Ag+. For 3-X-pyridine ligands (X = Cl, Br, I), complexes with additional DMF molecules [ß-{AgL(DMF)}2Mo8O26]2- (5-7) have been isolated. Halogen bonding of the XO type was detected in the crystal structures of 5-7 and studied by DFT calculations, providing estimated energies from 0.9 to 3.4 kcal mol-1. Variation of substituents at the pyridine ring results in the formation of [ß-{AgL}2Mo8O26]2- in the case of 2-NH2-py (8), 2-CH3-Py (9), 2,4,6-collidine (10) and 2,6-NH2-py (11). Solution behavior of 1-4 in CH3CN was studied by a hyphenated HPLC-ICP-AES technique. According to the results, the [ß-{AgL}2Mo8O26]2- anions are largely dissociated in this medium. An attempt to change the [Mo8O26]4- precursor to [Mo6O19]2- (in the case of AgNO3 and PyPPh2) resulted in the crystallization of [Ag2(PyPPh2)2(DMF)4][Mo6O19] (12).

Reactions of [Ru(NO)Cl5]2- with pseudotrilacunary {XW9O33}9- (X = AsIII, SbIII) anions.

Reactions of [Ru(NO)Cl5]2- with pseudotrivacant B-α-[XW9O33]9- (X = AsIII, SbIII) at 160 °C result in the rearrangement of polyoxometalate backbones into {XM18} structures. In the case of arsenic, oxidation of AsIII to AsV takes place with the formation of a mixture of plenary and monosubstituted Dawson [As2W18O62]6- and [As2W17Ru(NO)O61]7- anions, of which the latter was isolated as Me2NH2+ (DMA-1a and DMA-1b) and Bu4N+ (Bu4N-1) salts and fully characterized. Both α1 and α2 isomers of [As2W17Ru(NO)O61]7- were present in the reaction mixture; pure [α2-As2W17Ru(NO)O61]7- was isolated as the Bu4N+ salt. In the case of antimony, [SbW9O33]9- is converted into a mixture of [SbW18O60]9- and [SbW17{Ru(NO)}O59]10-. The formation of trisubstituted [SbW15{Ru(NO)}3O57]12- as a minor byproduct was detected by HPLC-ICP-AES. The monosubstituted [SbW17{Ru(NO)}O59]10- anion was isolated as DMAH+ (DMA-2) and mixed inorganic cation (CsKNa-2) salts and characterized by XRD, HPLC-ICP-AES, EA and TGA techniques. X-ray analysis shows the presence of the {Ru(NO)}-group in the 6-membered ("equatorial") belt of the Sb-free hemisphere. The experimental findings were confirmed and interpreted by means of quantum chemical calculations.

The study of Rh(iii) hydroxocomplexes using capillary zone electrophoresis with a UV-Vis detector: the development of the method.

The expediency of capillary zone electrophoresis application in the study of a mixture of rhodium(iii) hydroxocomplexes is shown for the species formed during the thermal treatment of [Rh(OH)6]3- at 60 °C in alkaline media. As these compounds are unstable in solution because of polycondensation at pH > 10 and the formation of insoluble rhodium(iii) hydroxides at pH 5-10, their acidic derivatives with terminal aqua ligands acted as the objects of the study. Optimal separation conditions were achieved using sodium perchlorate as a background electrolyte, a voltage of +20 kV and pH 2.6. Rhodium(iii) species with different nuclearities were identified in accordance with their UV spectra and the regularities of electrophoretic migration in the capillary. The presence of a dimer was also verified by the spiking of the mixture under investigation with a previously synthesised complex [Rh2(µ-OH)2(H2O)8](NO3)4, which confirms the correct identification.