<Superscript>103</Superscript>Rh and <Superscript>17</Superscript>O NMR study of oligomer rhodium(III) sulfates in aqueous solutions

By virtue of ¹⁰³Rh-, ¹⁷O-NMR, electrophoresis in agarose gel, and pH-metry, we report on the formation of rhodium(III) sulfate complexes in aqueous solutions. At higher concentrations of sulfuric acid (above 3 M), more than 90% of metal was found to stay in the state of symmetric polynuclear complexes containing magnetically equivalent rhodium atoms. We also labeled the ¹⁰³Rh-NMR chemical shifts for the complexes with 3, 4 and 6 metal atoms in the spectra.     

The first (<Superscript>31</Superscript>P, <Superscript>17</Superscript>O,and <Superscript>103</Superscript>Rh) NMR observation complex formation of rhodium(III) with phosphoric acid

³¹P, ¹⁷O, and ¹⁰³Rh NMR spectroscopy shows that rhodium(III) reacts with phosphoric acid to generate polynuclear aquaphosphate complexes in which phosphate ions mostly have a bridging function. Assignment of ¹⁰³Rh NMR signals in dominant rhodium complexes is suggested.     

<Superscript>103</Superscript>Rh, <Superscript>17</Superscript>O,and <Superscript>31</Superscript>P NMR study of Rh(III) complex formation in acidic sulfate-phosphate media

Rhodium(III) complex formation with phosphoric acid in strong acidic solutions has been studied by ¹⁰³Rh, ¹⁷O, and ³¹P NMR. Phosphoric acid is mainly coordinated to rhodium as a monodentate terminal HPO₄²⁻ ion, while the coordinated phosphate ion accounts for no more than 7%.     

<Superscript>103</Superscript>Ru/<Superscript>103m</Superscript>Rh generator

^103mRh is a very promising radionuclide for Auger electron therapy due to its very low photon/electron ratio. The goal of the present work was the elaboration a method for production of large quantities of ^103mRh for generator system. It was found that the combination of solvent extraction with evaporation of ¹⁰³RuO₄ followed by decomposition of H₅IO₆ makes it possible to produce ^103mRh of high radionuclidic and chemical purity.     

X-ray study of rhodium(III) sulfates

Compounds with compositions [Rh(H₂O)₆]₂(SO₄)₃·4H₂O (I), (H₃O)[Rh(H₂O)₆](SO₄)₂ (II), [Rh(H₂O)₅OH](SO₄)·0.5H₂O (III), and [Rh(H₂O)₆]₂(SO₄)·(H₂SO₄) _x ·5H₂O (IV) have been studied. The crystal structures of II, III, and IV were determined. All compounds crystallized in the monoclinic crystal system. Crystal data for II: a = 7.279(2) Å, b = 10.512(7) Å, c = 15.806(3) Å, β = 96.71(3)°, space group P2₁/n, Z = 2, d _calc = 2.334 g/cm³; III: a = 20.433(4) Å, b = 7.820(2) c = 11.215(2) Å, β = 114.14(1)°, space group C2/c, Z = 8, d _calc = 2.559 g/cm³; IV: a = 6.2250(4 Å), b = 27.0270(12) Å, c = 7.2674(5) Å, β = 97.04(3)°, space group P2₁/c, Z = 4, d _calc = 2.143 g/cm³. The compounds were studied by IR spectroscopy and powder X-ray diffraction. All of the isolated crystalline phases are sparingly soluble in ethanol and well soluble in water.     

14N, 17O, 103Rh NMR Studies of Rh(III) State in Diluted Nitric Acid Solutions

The state of rhodium(III) in nitric acid solutions diluted with 3M HNO₃ or water was studied by ¹⁴N, ¹⁷O, and ¹⁰³Rh NMR methods. The ¹⁰³Rh NMR chemical shifts significantly depend on the ionic background of the solution. Concentrated nitric acid solutions (c _Rh = 0.5–1 mol/l) diluted 100 to 200 times retain the polynuclear Rh(III) forms with double (-NO₃, -OH) bridges. The predominant form in the diluted solutions is a dimer.     

A study of solid-state rhodium(III) sulfates

Solid-state rhodium(III) sulfates and their aqueous solutions were examined by IR and electronic absorption spectroscopy, thermogravimetry, X-ray powder diffraction analysis, and ¹⁰³Rh and ¹⁷O NMR spectroscopy. A study of the spontaneous aquation of freshly prepared solutions showed that this process results in an equilibrium between the subsystems of monomeric and oligomeric complexes. It was found that solid-state rhodium(III) sulfates vary in phase composition, basically consisting of dimeric and trimeric complexes.     

Nitration of rhodium(III) sulfates

Nitration of sulfate complexes of rhodium has been investigated by NMR ¹⁰³Rh, ¹⁴N, ¹⁵N, and ¹⁷O NMR. At high pH, [Rh(NO₂)₆]^3?, dimer [Rh₂(μ-OH)₂(NO₂)₈]^4?, and trimer [Rh₃(μ-OH)₄(OH)(NO₂)₉]^5? are the dominant species in solutions.     

Structure of binuclear platinum(III) acetamidate complexes in solutions as probed by <Superscript>195</Superscript>Pt, <Superscript>13</Superscript>C,and <Superscript>1</Superscript>H NMR spectroscopy

¹⁹⁵Pt, ¹H, and ¹³C NMR spectroscopy was used to study the structure of binuclear platinum(III) acetamidate complexes with 1,10-phenanthroline and 2,2′-bipyridine ligands [Pt₂(phen)₂(acam)₄](NO₃)₂ (1) and [Pt₂(bipy)₂(acam)₄](NO₃)₂ (2) in aqueous solutions. The ¹⁹⁵Pt NMR spectra of solutions of complexes 1 and 2 in D₂O exhibit two signals with satellites due to the ¹⁹⁵Pt–¹⁹⁵Pt spin-spin coupling (¹ J(Pt–Pt) ≈ 6345 Hz), whereas their ¹H and ¹³C NMR spectra contain four sets of signals for the protons and the carbon atoms of the heterocyclic and acetamidate ligands. The signals were assigned using the COSY, NOESY, and HSQC/ HMBC experiments and comparing the coordination shifts of the signals for the protons of heterocycles. These data allowed us to draw a conclusion that binuclear complexes 1 and 2 in solution have a head-to-head structure with nonequivalent platinum(III) atoms (coordination cores PtN₅ and PtN₃O₂), the axial-equatorial coordination of the bidentate heterocyclic molecules, and two bridging and two terminal acetamidate ligands.     

Synthesis of water and molecular oxygen highly enriched in <Superscript>17</Superscript>O and <Superscript>18</Superscript>O isotopes from carbon oxides

The reaction of carbon oxides and hydrogen in the presence of the Raney nickel catalyst has been used for water synthesis. A procedure has been developed for the recovery and collection of the synthesized water with minimal losses and without deteriorating the ¹⁷O or ¹⁸O isotope enrichment as compared to the initial CO₂ and CO. The recovery of oxygen with high concentrations of ¹⁷O and ¹⁸O isotopes is based on the reaction of xenon difluoride with water. The yield based on oxygen achieves 99% without reduction of isotope enrichment, which is confirmed by mass-spectral measurements of oxygen isotope concentrations in the initial reagents and final reaction products.     

Electrodissolution system for rhodium fragmented electroplated targets used for the industrial cyclotron production of <Superscript>103</Superscript>Pd

The present paper discusses the development of a high current density (2 A cm⁻²) electrodissolution system of Rh targets that allows the solubility of rhodium fragments, powder and pieces of foils and wires in the presence of hydrochloric and chlorine gas for the production of ¹⁰³Pd.     

First-principles simulations of the <Superscript>27</Superscript>Al and <Superscript>17</Superscript>O solid-state NMR spectra of the CaAl<Subscript>2</Subscript>Si<Subscript>3</Subscript>O<Subscript>10</Subscript> glass

The local and medium-range structure of the 20CaO·20Al₂O₃·60SiO₂ glass generated by classical molecular dynamics simulations has been compared to NMR experiments by computing the ²⁷Al and ¹⁷O NMR parameters and NMR spectra from first-principles simulations. The calculation of the NMR parameters (chemical shielding and quadrupolar parameters), which are then used to simulate solid-state MAS and 3QMAS NMR spectra, is achieved by the gauge including projector augmented-wave and the projector augmented-wave methods on the DFT-PBE relaxed structure. The NMR spectra calculated with the present approach are found to be in excellent agreement with the experimental data, providing an unambiguous view of the local and medium-range structure of aluminosilicate glasses.     

The state of Al(III) in alcohol solutions of aluminum alkoxide as probed by <Superscript>27</Superscript>Al and <Superscript>13</Superscript>C NMR and small-angle X-ray scattering

Solutions of aluminum alkoxides obtained by interaction of aluminum metal with methyl, ethyl, and isopropyl alcohols were studied by ²⁷Al and ¹³C NMR and small-angle X-ray scattering. Alkoxides with a tetrahedral environment of aluminum prevail in methanol solutions, and those with an octahedral environment of aluminum predominate in ethanol solutions. In isopropyl alcohol at 293 K, polynuclear alkoxides with tetrahedral, octahedral, and pentacoordinated aluminum environments coexist. The structure of polynuclear complexes was refined by comparison of their calculated dimensions with small-angle X-ray scattering data.     

Structural features of acidic fluorophosphatozirconates (hafnates) from the <Superscript>19</Superscript>F, <Superscript>31</Superscript>P, <Superscript>1</Superscript>H NMR data

Fluorophosphatometallates with the composition K₃H₃Zr₃F₃(PO₄)₅, Rb₃H₃Zr₃F₃(PO₄)₅, Rb₃H₃Hf₃F₃(PO₄)₅, CsH₂Hf₂F₂(PO₄)₃?2H₂O are studied by ³¹P, ¹⁹F, and ¹H NMR. It is found that protons enter in the composition of hydrophosphate groups and fluorine atoms occupy the terminal sites in the tetravalent metal environment. Schemes of the crystal structure of fluorophosphatometallates are proposed. It is established that in CsH₂Hf₂F₂(PO₄)₃?2H₂O water molecules are bonded to the phosphate group proton via a strong hydrogen bond and are characterized by a low energy barrier of molecular motions.     

DFT calculations of <Superscript>14</Superscript>N, <Superscript>17</Superscript>O,and <Superscript>2</Superscript>H NQR parameters: Investigation of hydrogen bond interactions in sulfapyridine crystalline structure

DFT calculations of electric field gradient (EFG) tensors at the sites of ¹⁴N, ¹⁷O, and ²H nuclei are carried out to characterize the hydrogen bond (HB) interactions in the sulfapyridine crystal structure. One-molecule (monomer) and hydrogen-bonded hexameric cluster models of sulfapyridine are constructed according to available X-ray coordinates where the proton positions are optimized. Then, EFG tensors are calculated for both monomer and target molecule in the hexameric cluster of sulfapyridine to show the effect of HB interactions on the tensors. The calculated EFG tensors are converted to the experimentally measurable nuclear quadrupole resonance (NQR) parameters: quadrupole coupling constant (C _Q ) and asymmetry parameter (η _Q ). The results reveal different contribution of various nuclei to N-H⋯N and N-H⋯O HB interactions in the cluster where the N2 and O1 have major contributions. The computations are performed with B3LYP and B3PW91 functionals DFT method and 6-311+G* and 6-311++G** standard basis sets using the Gaussian 98 package.     

2-Amino-4-aryl-1-arylideneaminoimidazoles and Acylation Products: A Multinuclear (<Superscript>1</Superscript>H, <Superscript>13</Superscript>C, <Superscript>15</Superscript>N) NMR Study

Summary. The structure of 2-amino-4-aryl-1-arylideneaminoimidazoles in DMSO-d₆ solution was investigated by means of NMR spectroscopic methods (¹H, ¹³C, ¹⁵N). From these data the (E)-configuration at the excocyclic C=N bond and a strong preference for the conformer with the imidazole H-5 and the N=CH proton being spatially close (s-trans regarding the N–N bond) can be concluded. Reaction of the title compounds with acetic anhydride leads to mono and diacylation at the 2-amino group, whereas treatment with pivalic anhydride exclusively affords the corresponding monoacyl product. The mono- and diacylation products exhibit similar configurational and conformational properties as the parent compounds.     

A <Superscript>1</Superscript>H NMR study of Nile Red solvation

In order to evaluate the capabilities of NMR spectroscopy for investigation of the solvatochromic effect in luminophore solutions, the ¹H NMR chemical shifts of Nile Red in mixtures of solvents with different polarities (benzene, toluene, methanol) has been determined. Their dependence upon the solvent mixture composition has been revealed and binding sites for luminophore and solvent component molecules have been determined. The results of the NMR study are consistent with data on the fluorescence of Nile Red solutions in toluene-ethanol mixtures.     

Kinetics of H<Superscript>+</Superscript>/Na<Superscript>+</Superscript> solid-phase ion exchange on iron(III) hydrogen sulfate

The kinetics of solid-phase reaction between iron(III) hydrogen sulfate and sodium chloride was studied by thermal analysis followed by analysis of leaving gases. The exchange kinetics are described by the soft cylinder model. The hydrogen and sodium ion interdiffusion coefficients were determined for various temperatures, as well as the activation energy of interdiffusion. Sodium ion diffusion through the product layer is the rate-controlling stage of the reaction.     

Solid-phase condensation of rhodium(III) aqua sulfates

Solid-phase condensation of rhodium(III) aqua sulfates yielding oligomeric rhodium(III) aqua sulfate complexes was revealed. The isothermal dehydration of rhodium(III) aqua sulfates under thermal diffusion conditions in the temperature range 100–130°C was studied, and effective rate constants and activation energies were determined. The solid phases of dehydration products were studied by X-ray powder diffraction and IR spectroscopy, and solutions of polymeric phases were studied by ¹⁰³Rh and ¹⁷O NMR, electronic absorption spectroscopy, chromatography, and electrophoresis.     

<Superscript>1</Superscript>H and <Superscript>13</Superscript>C NMR spectra of some drimanic sesquiterpenoids

One- and two-dimensional homo- and heteronuclear correlation proton, carbon, proton—proton, and proton—carbon NMR spectra of fifteen drimanic sesquiterpenoids: 11,12-dibromodrima-5,8-dien-7-one, drim-8-en-7-one, 11-hydroxydrim-8-en-7-one, 11,12-dihydroxydrim-8-en-7-one, 11-hydroxy-11,12-epoxydrim-8-en-7-one, 11-hydroxy-11,12-epoxydrim-8-en-7-one, 8,9-epoxydriman-7-one, 8,9-epoxydriman-7-ol, 11,12-diacetoxydrim-8-en-7-ol, drimane-7,8,11-triol, 7,8-isopropylidenedioxydriman-11-al, 9, 11-dihydroxydrim-7-en-6-one, drimane-7,8,9-triol, drimane-7,8,11-triol, and drim-8-ene-7,11,12-triol were studied. The proton and carbon chemical shifts were assigned.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2589–2594, December, 2004.