Microcalorimetric studies on the interactions of lanthanide ions with bovine serum albumin

The interactions of lanthanide ions (Ln³⁺) with bovine serum albumin (BSA) under mimetic physiological conditions (310.15 K, pH 6.7, 0.1MNaCl) were studied by microcalorimetry. For the first time, based on Two Sets of Independent Sites Model, molar enthalpies (Δ_r H _m1, Δ_r H _m2) and coordination number (n ₁, n ₂) of the two sets of binding sites with different affinity were obtained directly from the microcalorimetric results. It was shown that the interactions are endothermic and entropy-driving processes. By combining with fluorescence spectroscopy, other thermodynamic parameters (Δ_r G _m1, Δ_r S _m1) were determined for high-affinity specific sites.     

New synthesis of mullite. Structural evolution study by 17O, 27Al and 29Si MAS NMR spectroscopy

Mullite has been prepared from a new combination of precursors. An aluminum alkoxide, aluminium isopropoxide, and silicon tetrachloride, are hydrolysed in tetrahydrofuran solution by ¹⁷O enriched water. The resulting powder is chemically homogeneous, crystallizing into mullite at 980°C. The structural evolution has been studied by DTA, TGA, XRD and ¹⁷O, ²⁷Al and ²⁹Si MAS NMR spectroscopy.     

Boron coordination compounds derived from 2-phenyl-benzimidazole and 2-phenyl-benzotriazole bidentate ligands

The syntheses and structural analyses of a series of boron heterocycles derived from 2-(1H-benzimidazol-2-yl)-phenylamine (1), 2-(1H-benzimidazol-2-yl)-phenol (2), 2-(1H-benzimidazol-2-yl)-benzenedisulfide (3), 2-[3-(1,1,1,3,-tetramethyl-butyl)-phenyl]-2H-benzotriazole (4), 2-[3,5-bis-(1-methyl-1-phenylethyl)-phenyl]-2H-benzotriazole (5) and (C₆H₅)₂BOH or BF₃·OEt₂ are reported. The new boron compounds: diphenyl-[2-(1H-benzimidazol-2-yl-κN)-phenylamide-κN]-boron (6), diphenyl-[2-(1H-benzimidazol-2-yl-κN)-phenolate-κO]-boron (7), diphenyl-[2-(1H-benzimidazol-2-yl-κN)-benzenethiolate-κS]-boron (8), diphenyl-[2-(2H-benzotriazol-2-yl-κN)-4-(1,1,3,3-tetramethyl-butyl)-phenolate-κO]-boron (9), diphenyl-[2-(2H-benzotriazol-2-yl-κN)-4,6-(1-methyl-1-phenylethyl)-phenolate-κO]-boron (10), difluoro-[2-(1H-benzimidazol-2-yl-κN)-phenolate-κO]-boron (11), difluoro-[2-(2H-benzotriazol-2-yl-κN)-4-(1,1,3,3-tetramethylbutyl)-phenolate-κO]-boron (12) and difluoro-[2-(2H-benzotriazol-2-yl-κN)-4,6-(1-methyl-1-phenylethyl)-phenolate-κO]-boron (13) have four fused rings, with boron included in a six-membered ring and bound to N, O or S atoms and strongly coordinated by a nitrogen atom from the imidazole or triazole rings. Their structures are zwitterionic, with a negative charge on the boron and a delocalized positive charge on the ligand. Compounds 6-12 were studied by NMR, IR, mass spectrometry, and 6-10 and 12 by X-ray diffraction analyses.     

Application of139La NMR spectroscopy to the coordination chemistry of lanthanum. Ligand exchange in cyclopentadienyl and metal carbonyl complexes of lanthanum

The ligand-exchange equilibria in cyclopentadienyl and metal carbonyl complexes of lanthanum have been qualitatively studied by¹³⁹La NMR spectroscopy: 2X¹X²X³La X¹X² ₂ La + X¹X³, La, where X¹=X²=Cp, X³=I; X¹=X² = 1, 3-(Me₃Si)₂C₅H₃, X³=Cl; X¹=Ru(CO)₂Cp; X²=Cp, X³=I. Similar equilibria are typical of the coordination chemistry of light lanthanides.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 578–581, March, 1993.     

Solubilization of lanthanide ions by cyclodextrins in basic aqueous solutions

Cyclodextrins form complexes with lanthanide ions in basic aqueous solutions. This complex formation in basic solution dramatically enhances the solubility of lanthanide ions, which are otherwise insoluble due to the formation of hydroxide gels. Solutions of the -cyclodextrin-Ce³⁺ complex effectively hydrolyze 2-deoxyadenosine-5-monophosphate to 2-deoxyadenosine.     

F NMR spectroscopy as useful tool for determining the structure in solution of coordination compounds of MF5 (M = Nb, Ta)

The salts [S(NMe₂)₃][MF₆] (M = Nb, 2a; M = Ta, 2b) and [S(NMe₂)₃][M₂F₁₁] (M = Nb, 2c; M = Ta, 2d) have been prepared by reacting MF₅ (M = Nb, 1a; M = Ta, 1b) with [S(NMe₂)₃][SiMe₃F₂] (TASF reagent) in the appropriate molar ratio. The solid state structure of 2b has been ascertained by X-ray diffraction. The 1:1 molar ratio reactions of 1a with a variety of organic compounds (L) give the neutral adducts NbF₅L [L = Me₂CO, 3a; L = MeCHO, 3b; L = Ph₂CO, 3c; L = tetrahydrofuran (thf), 3d; L = MeOH, 3e; L = EtOH, 3f; L = HOCH₂CH₂OMe, 3g; L = Ph₃PO, 3h; L = NCMe, 3i] in good yields. The complexes MF₅L [M = Nb, L = HCONMe₂, 3j; M = Nb, L = (NMe₂)₂CO, 3k; M = Ta, L = (NMe₂)₂CO, 3l; M = Nb, L = OC(Me)CHCMe₂, 3m] have been detected in solution in admixture with other unidentified products, upon 2:1 molar reaction of 1 with the appropriate reagent L. The ionic complexes [NbF₄(tht)₂][NbF₆], 4a, and [NbF₄(tht)₂][Nb₂F₁₁], 4b, have been obtained by combination of tetrahydrothiophene (tht) and 1a, in 1:1 and 2:3 molar ratios, respectively. The treatment of 1 with a two-fold excess of L leads to the species [MF₄L₄][MF₆] [M = Nb, L = HCONMe₂, 5a; M = Ta, L = HCONMe₂, 5b; M = Nb, L = thf, 5c; M = Ta, L = thf, 5d; M = Nb, L = OEt₂, 5e]. The new complexes have been fully characterised by NMR spectroscopy. Moreover, the revised ¹⁹F NMR features of the known compounds MF₅L [M = Ta, L = Me₂CO, 3n; M = Ta, L = Ph₂CO, 3o; M = Ta, L = MePhCO, 3p; M = Ta, L = thf, 3q; M = Nb, L = CH₃CO₂H, 3r; M = Nb, L = CH₂ClCO₂H, 3s; M = Ta, L = CH₂ClCO₂H, 3t], TaF₄(acac), TaF₄(Me-acac) and [TaF(Me-acac)₃][TaF₆] (Me-acac = methylacetylacetonato anion) are reported.     

17O-NMR-spectroscopy as a tool for stereochemical analysis — Application to a diterpene-derivative

Summary Treatment of abietic acid methylester with Hg(OAc)₂/MeOH produces a dimethoxy derivative. The determination of the configuration at C-7 of this product by means of 1D- and 2D-NMR-spectroscopic methods is described. The results are verified by application of¹⁷O-NMR spectroscopy and comparison with well-established stereochemical dependencies of¹⁷O chemical shifts.

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¹⁷O-NMR-Spectroskopie zur stereochemischen Analyse. Anwendung auf ein Diterpen-Derivat

Zusammenfassung Umsetzung von Abietinsäuremethylester mit Hg(OAc)₂/MeOH führt zu einem Dimethoxyderivat. Die Bestimmung der Konfiguration am Zentrum C-7 erfolgt durch Anwendung von 1D- und 2D-NMR-Methoden. Die Resultate konnten durch¹⁷O-NMR-Spektroskopie aufgrund der bekannten stereochemischen Verschiebungsabhängigkeit bestätigt werden.

     

Solvent effects on 17O nuclear magnetic shielding: N-methylformamide in polar and apolar solutions

The solvent effect on ¹⁷O isotropic shielding was computed by different methods: the polarizable continuum model and a mixed approach, including a few real solvent molecules treated as the solute. The experimental data show that the behavior of protic and aprotic solvents is markedly different: we found that the continuum approach describes well the observed shielding at various dielectric constants for aprotic solvents, while the mixed procedure is needed when hydrogen bonds to the magnetic centre are present.Contribution to the Jacopo Tomasi Honorary Issue     

The structure of the lanthanide aquo ions in solution as studied by 17O NMR spectroscopy and DFT calculations

The (17)O NMR shifts of aqueous samples of lanthanide triflates were measured and analysed. In these systems the triflate anion does not enter the first coordination sphere. The contact contribution to the shifts showed a break at Eu(III), which reflects a change in the number of water molecules in the first coordination sphere of the Ln(III) ion from 9 for La-Sm to 8 for the heavier lanthanides. This change in hydration number is accompanied by a change in the parameters governing the pseudo-contact shifts. Fitting of the data with tricapped trigonal prism and square antiprismatic geometries obtained by DFT (density function theory) calculations showed that the crystal field parameters for these geometries differ by an order of magnitude. The hyperfine coupling constant for both geometries was determined to be A/(Planck's constant)= -4.2 x 10(6) rad s(-1).     

Study of ion exchange selectivity of organic ions by using (31)P NMR spectroscopy

Ion exchange distribution of the phenylphosphoric acid has been studied on various types of chloride form strong base resins as a function of pH at 25 °C, at 0.1 M ionic strength. Equilibrium measurements were supplemented by the study of pH dependence of the ³¹P NMR spectra of the resin-phase phenylphosphate species. Equations were derived to describe the pH dependence of the overall distribution coefficient and the chemical shift of the resin-phase solute species. Experimental data were evaluated by using these model equations and the values of the individual distribution coefficients, ion exchange selectivity coefficients and the resin-phase ³¹P chemical shifts of the mono- and divalent ions have been calculated. Comparison of distribution data of the individual species corroborated the significance of the role of hydrophobic interaction in the selectivity of organic ion exchange processes. A well-defined correlation between the ion exchange selectivity and the resin-phase ³¹P NMR chemical shift data has been pointed out.     

Solvation of ions,part XXX. Thermodynamics of transfer of copper ions from water to solvent mixtures

Free energies and Walden products show that the Cu⁺ and Ag⁺ ions are specifically solvated by acetonitrile (AN), 2-hydroxycyanoethane (HAN), and by pyridine (Py) whereas Na⁺ is specifically solvated by water, in mixtures of these organics with water. The Cu²⁺ ion is specifically solvated by pyridine in pyridine-water mixtures, but by water in acetonitrile-water mixtures. Ion-solvent, coordinated solvent-bulk solvent, and solvent-solvent interactions produce large entropy losses in the order Cu⁺Ag⁺>Na⁺ for transfer of these ions from water to dilute acetonitrile-water. The metallurgically important oxidations of copper, silver, CuS and Cu₂ with CuSO₄ in water are strongly favored in an enthalpic and free energy sense by the addition of acetonitrile, but addition of acetonitrile also produces a large loss of entropy for the reactions.     

Review on Applications of 17O in Hydrological Cycle

The triple oxygen isotopes (¹⁶O, ¹⁷O, and ¹⁸O) are very useful in hydrological and climatological studies because of their sensitivity to environmental conditions. This review presents an overview of the published literature on the potential applications of ¹⁷O in hydrological studies. Dual-inlet isotope ratio mass spectrometry and laser absorption spectroscopy have been used to measure ¹⁷O, which provides information on atmospheric conditions at the moisture source and isotopic fractionations during transport and deposition processes. The variations of δ¹⁷O from the developed global meteoric water line, with a slope of 0.528, indicate the importance of regional or local effects on the ¹⁷O distribution. In polar regions, factors such as the supersaturation effect, intrusion of stratospheric vapor, post-depositional processes (local moisture recycling through sublimation), regional circulation patterns, sea ice concentration and local meteorological conditions determine the distribution of ¹⁷O-excess. Numerous studies have used these isotopes to detect the changes in the moisture source, mixing of different water vapor, evaporative loss in dry regions, re-evaporation of rain drops during warm precipitation and convective storms in low and mid-latitude waters. Owing to the large variation of the spatial scale of hydrological processes with their extent (i.e., whether the processes are local or regional), more studies based on isotopic composition of surface and subsurface water, convective precipitation, and water vapor, are required. In particular, in situ measurements are important for accurate simulations of atmospheric hydrological cycles by isotope-enabled general circulation models.     

Hydrolysis of Volatile Ammonium Oxofluorotitanate According to 19F, 17O, and 49Ti NMR Data

Hydrolysis of NH₄TiO_xF_5-2x (x0.4) (I) was investigated by ¹⁹F, ¹⁷O, and ⁴⁹Ti NMR. The interaction of complex I with water is accompanied by the formation of [TiF₆]^2- and multinuclear titanium forms. The composition of the main forms resulting from hydrolysis of I has been established. The bonding of titanium octahedra into dimers and other oligomers occurs by formation of hydroxyl bridges, considerably lowering the pH of the solution. Close analogy has been found between hydrolysis of the title complex and that of titanium tetrafluoride.     

17O NMR Investigation of Chemical Homogeneity in Hybrid Systems

¹⁷O NMR experiments using enriched water were performed to followthe hydrolysis-condensation process of dimethyldiethoxysilanetetraethoxysilane and a 1/1 mixture of dimethyldiethoxysilane andtetraethoxysilane (H₂O/OEt = 0.5; pH = 2). The spectrarecorded over several hours time period were simulated to followquantitatively the variations of residual water, hydroxyl groups(Si–¹⁷ H) and oxo bridges (Si–¹⁷ –Si). Presence of a resonance signal due oxo bridges between di- andtetrafunctional Si units clearly demonstrates that co-condensationreactions occur to a large extent between the two alkoxides, and that thesebonds are stable during the aging period.     

Distortion of the tetrahedral coordination of Fe(III) ions stabilized in ZSM-5 zeolite framework

A simple qualitative method to analyze d-d-electronic transitions in cations of the transition elements in oxide matrices is proposed. In the particular case, all the excited states of interest differ only in the electronic configuration of d-orbitals, and the energies of transitions can be computed via the configuration interaction (CI) method restricted by the active space of five cation d-orbitals. An ordinary cluster model that takes into account the first coordination sphere of transition metal ion consisting of the framework of oxygen ions is sufficient for this purpose. The systematic overestimation error of transition energies can be corrected through the empirical factor calculated to fit experimental UV-VIS spectra. The physical meaning of the scaling factor proposed is the dynamic part of electron correlation that remains unaccounted for in the chosen active CI space. The observed d-d-transitions of Fe³⁺ ions in MFI zeolites are analyzed in detail. It is suggested that the specifics of the observed electronic spectra are caused by the distortion of the tetrahedron of oxygen atoms around Fe³⁺. The latter can be easily taken into account when selecting an appropriate Fe³⁺ cluster model in the framework. It is shown that the occurrence of the weak low-frequency band below 21,000 cm^?1 indicates the distortion of the tetrahedral environment around Fe³⁺.     

NMR Spectra of Cyclic Nitrones. 7. The Influence of Substituents and a Hydrogen Bond on <Superscript>14</Superscript>N and <Superscript>17</Superscript>O Chemical Shifts in Derivatives of 3-Imidoazoline 3-Oxide

Derivatives of 3-imidazoline 3-oxide have been studied by ¹⁴N and ¹⁷O NMR methods. Regularities of the influence of substituents and of a hydrogen bond on chemical shifts have been made apparent. The range of changes of the chemical shifts of the nitrogen and oxygen nuclei of the nitrone group has been determined. Both in the ¹⁷O and in the ¹⁴N NMR spectra the signals of the amino derivatives are the highest field signals for the nitrone group, and the lowest field signals are the signals of the cyano derivatives in the series of derivatives investigated. Depending on the substituent (from amino to cyano group) the ¹⁷O chemical shifts varied over a range ∼155 ppm, but the interval of change of the ¹⁴N chemical shifts for the same substituents was ∼110 ppm. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1336–1341. September, 2005.     

Invertomers at nitrogen in aziridine carboxylates by mltltinuclear (1H,13C,17O,and15N) NMR study

A confrgurational and conformational study of NH, N-acetyl- and N-sulfonylaziridine carboxylates is performed by¹H ,¹³C,¹⁷O, and¹⁵N NMR spectroscopy. The presence of acetyl and su fonyl groups on the ring nitrogen atom seems to reduce greatly the configurational stability at nitrogen.Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1226–1234, September, 1995.     

四种同构镧系金属有机框架的合成、结构和荧光传感Fe3+和盐酸环丙沙星

采用溶剂热法,以含氮四羧酸3,5-二(3′,5′-二羧苯)-1H-1,2,4-三唑(H₄BDT)为配体,成功合成了4种同构镧系金属有机框架(Ln-MOFs)：{[La₃(BDT)₂(HCOO)(H₂O)₅]·0.5H₂O·3DMF}_n (1)、{[Ce₃(BDT)₂(HCOO)(H₂O)₅]·3DMF}_n (2)、{[Pr₃(BDT)₂(HCOO)(H₂O)₅]·3DMF}_n (3)和{[Nd₃(BDT)₂(HCOO)(H₂O)₅]·3DMF}_n (4),并采用单晶X射线衍射、粉末X射线衍射、元素分析、热重、红外、N₂吸附实验和荧光光谱对其进行表征。结果表明,这些Ln-MOFs均为单斜C2/m空间群晶体,是双核为无机建筑单元的三维介孔结构。其中2可选择性荧光检测Fe³⁺离子和盐酸环丙沙星药物分子,检测限分别为4.59和0.77 μmol·L^-1。     

Nuclear magnetic resonance of donor atoms as a tool for determination of the structure of platinum metal complexes in solutions

Data on the NMR spectroscopy of C, N, O, Si, P, and Sn donor atoms of platinum metal complexes in solutions are surveyed. The chemical shift of a donor atom mainly depends on the ligand in the trans-position (due to the trans-effect). The chemical shift of a donor atom on a particular coordinate of the complex (coordinate shift, CSh) is an attribute of this coordinate and can be used to identify such a coordinate in platinum metal complexes and to determine the structures of complexes. Based on the known data, CSh diagrams were composed for ¹H, ¹³C, ¹⁴N, ¹⁷O, ¹⁹F, ³¹P, and ¹¹⁹Sn. Examples of using the CShs for determining the structures of platinum metal complexes in solutions are presented.     

Calorimetric determination of the heats of formation of lanthanide monosulfate complexes in D2O1

Heats of formation of rate-earth monosulfate complexes have been measured calorimetrically for the ions La³⁺, Sm³⁺, Tb³⁺, and Er³⁺, in D₂O and H₂O solvents. Within the limits of experimental error there is no evidence for a solvent isotope effect on the heat and entropy changes of these complexation reactions.This paper was abstracted from W.D.W.'s Ph.D. dissertation, May 1973.