Speciation of strontium in human and bovine milk

The speciation of strontium in human and bovine milk has been computed using a chemical equilibrium model and the ECCLES program. The calculations show     

Synthetic metals based on tetramethyltetraselenafulvalene(TMTSF): Varied anisotropy in the low temperature (125K) structures of (TMTSF)2X,X=C104-, PF6-, and AsF6-.

The low temperature (125K) X-ray crystal structures of (TMTSF)₂X, X=C10₄^-, PF₆^-, and AsF₆^- reveal decreases in the intermolecular interand intrastack Se-Se contact distances upon cooling (298K to 125K) which are highly anisotropic and different from one salt to another. The changes in the interstack distances, which are normal to the stacking direction, are approximately twice those involving intrastack Se-Se interactions. These observations establish that the anisotropic structural changes which accompany decreased temperature are common to numerous (TMTSF)₂X radical cation conducting salts.     

Diffusion-limited energy transfer from Tb3+ → Nd3+ and Tb3+ → Ho3+ in DMSO

The energy transfer phenomenon has been studied from Tb³⁺ → Nd³⁺ and Tb³⁺ → Ho³⁺ in DMSO. A diffusion limited dipole-dipole mechanism of energy transfer is suggested for both systems. At high acceptor concentrations, P_da depends linearly on C² consistent with the Fong and Diestler theory of energy transfer. However, at low acceptor concentrations the observations of time evolutions of Tb³⁺ luminescence decay following flash excitation has enabled us to examine diffusion limited energy transfer from Tb³⁺ to Nd³⁺ and Tb³⁺ to Ho³⁺ in DMSO.     

Hall coefficient in solution for a simple dynamical model

A model Liouville equation is proposed for a system composed of an ion moving in a solvent fluid. Using this model, explicit results are obtained for the Ohmic conductivityL and the Hall conductivityh. These results are then used to calculate the Hall coefficientR = ehL^–2, which is a measure of the effect of non-Brownian motion, for several charge carriers of interest. Our results are in agreement with earlier findings based on a stochastic model which predictR > 1 for H⁺(aq). Our results also indicate thatR 1 for charge carriers such as Na⁺, Cl^–, and K⁺ which have a mass greater than that of a solvent molecule (here taken as 18 amu).This research was supported in part by grants from the National Science Foundation and by the Research Foundation of the State University of New York.     

Improved synthesis of arachno-6,9-C2B8H14 and its halogenation under electrophilic conditions

A convenient synthesis of arachno-6,9-C₂B₈H₁₄, based on the reduction of nido-5,6-C₂B₈H₁₂ with sodium tetrahydroborate, is reported. Electrophilic halogenation of the former carborane produced a series of 1-X-6,9-C₂B₈H₁₃ (X = Cl, Br and I) derivatives whose constitution was established on the basis of their ¹H and ¹¹B NMR spectra.     

Studies on yellow and colourless molybdophosphate complexes in the aqueous solution by laser raman spectroscopy

Yellow and colourless complexes of molybdophosphate were investigated by the use of laser Raman spectroscopy. Two kinds of yellow molybdophosphates were identified in the weakly acidic solutions: 12-molybdophosphoric and 11-molybdophosphoric acid which are in equilibrium in solution at pH 1-2. When excess phosphate is present, the colourless molybdophosphate is formed. This complex exists in the solutions of pH 4-1 under the condition of excess phosphate ([P]/[Mo] > 2). This complex was confirmed to be P₂Mo₅O^6?₂₃ and is so stable that the yellow molybdophosphate is converted into the colourless by excess phosphate.     

Spatially resolved,intracavity absorption for inductively coupled plasma diagnostics

Continuous wave intracavity absorption provides a sensitive method for probing the distribution of absorbing species in a plasma flame. There exists considerable potential for plasma mechanistic studies using this method both as a spatial diagnostic for selected species, and as a spectral diagnostic for the detection of low concentration or low oscillator strength species.     

Organo-imido alkoxides of tungsten(VI). The crystal and molecular structures of [W(NPh)(μ-OMe)(OMe)3]2 and [W(NPh)(OCMe3)3Cl(NH2CMe3)]

Reaction of phenylimido tungsten tetrachloride with MeOH and t-butylamine gave the dimeric complexes [W(NPh)(μ-OMe)(OMe)₃]₂ and [W(NPh)(μ-OMe)(OMe)₂Cl]₂. With ethanol [W(NPh)(μ-OEt)(OEt)₂Cl]₂ was formed whereas isopropyl and neopentyl alcohols gave the monomeric complexes [W(NPh)(OR)₄(NH₂CMe₃)](R = CHMe₂, CH₂CMe₃); t-butanol gave [W(NPh)(OCMe₃)3Cl(NH₂CMe₃)] which could not be converted to [W(NPh) (OCMe₃)₄]. Further reaction of [W(NPh)(μ-OMe)(OMe)₃]₂ with o-HOC₆H₄CH = NC₆H₃Me₂(salim-H) gave the salicylaldimine complex [W(NPh)(OMC)₃(salim)]. The products were characterised by analytical data, IR, ¹H NMR, ¹³C NMR and mass spectroscopy. The crystal and molecular structures of the title complexes have been determined from single crystal X-ray diffractometer data. Crystals of [W(NPh)(μ-OMe)(OMe)₃]₂are triclinic with a = 8.473(7), b = 10.776(5), c = 7.683(Å, α = 102.26(3), β = 102.68(4), γ = 71.13(6)°, space group P$\text{1}$ Crystals of 3) [W(NPh)(OCMe₃)₃Cl(NH₂CMe₃) are monoclinic with a = 9.341(2), b = 29.608(7), c = 10.257(2) Å, β = 106.28(2)°, space group, P2₁/c. Both structures were solved by Patterson and Fourier methods and refined to R = 0.075 for the 1022 observed data of [W(NPh) (μ-OMe)(OMe)₃]₂ and to R = 0.074. For the 2033 observed data of [W(NPh)(OCMe₃)₃Cl(NH₂CMe₃). The former molecule is shown to be a dimer, the two halves of the molecule being related by a centre of symmetry. Both W atoms adopt a distorted octahedral coordination geometry and they are linked by two methoxy bridges. Trans to one of the bridging donors is the phenyl imido group with a WN bond length of 1.61(4) Å; the remaining coordination sites are filled with methoxy groups. The structure of W(NPh)(OCMe₃)₃ Cl(NH₂CMe₃) is monomeric with the phenylimido group trans to the NH₂CMe₃ ligand in a distorted octahedral coordination geometry. Remaining sites are filled with the chloride and 3 OCMe₃ ligands. The WN (imido) bond length is 1.71(2) Å, whilst WN(amine) is 2.40(2) Å     

Dicarboxylate rhodium complexes with diolefins and carbon monoxide

Dinuclear rhodium complexes of the type [Rh₂(C₂O₄)(diolefin)₂] (diolefin)₂  1,5-cyclooctadiene, 2,5-norbornadiene and tetrafluorobenzobarrelene) with bridging oxalate ligands have been obtained by reaction of [Rh(acac)(diolefin)] with oxalic acid (2: 1 mol ratio). The use of a 1 : 1 molar ratio affords [Rh(HC₂O₄)(COD)], that reacts with [Ir(acac)(COD)] yielding the heterodinuclear [(COD)Rh(C₂O₄)Ir(COD)] complex. Treatment of [Rh₂(C₂O₄)(diolefin)₂] complexes with phenanthroline type ligands leads to ionic complexes of formula [Rh(diolefin) (phen)][Rh(C₂O₄)(diolefin)]. Bubbling of carbon monoxide through solutions of the diolefin complexes leads to the formation of carbonylrhodium species of formula [Rh₂(C₂O₄)(CO)₂L₂] (L = CO, PPh₃t-BuNC) or [Rh(CO)₂(phen)] - [Rh(C₂O₄)(CO)₂]. Other related malonate complexes are also described.     

Structural influences on the lanthanide-actinide selectivity of some aminocarboxylates

Data for the resolution of americium from europium and terbium using 2,2′-diaminodiethylether-N,N,N′,N′-tetraacetate and 1,5-diaminopentane-N,N,N′,N′-tetraacetate are reported along with values of the formation constants of the La-Lu and Y chelates of the latter. It is shown that the minimum single-stage separation factor for Am³⁺ from Ln³⁺ cations, using 2,2′-diaminodiethylether-N,N,N′,-N′-tetraacetate with Dowex 50 resin, exceeds 1.7 for all Am-Ln pairs, and runs as high as 350 in the case of Am³⁺, La³⁺. The minimum of 1.7 occurs at Eu³⁺ in the lanthanon sequence. A novel separation of Am³⁺, Cm³⁺ and heavier actinons from each other and from all the lanthanons and yttrium appears to be feasible.