The influence of water molecule coordination to a metal ion on water hydrogen bonds

The geometry of hydrogen bonds in the crystal structures from the Cambridge Structural Database and calculated data show that water coordination to a metal ion has a remarkable influence on hydrogen bonds. The calculated energies of hydrogen bonds of coordinated water are much stronger, even if the aqua complex is neutral.     

Borane and Borohydride Complexes of the Rare‐Earth Elements: Synthesis,Structures, and Butadiene Polymerization Catalysis

The reaction of potassium 2,5‐bis[N‐(2,6‐diisopropylphenyl)iminomethyl]pyrrolyl [(dip₂‐pyr)K] with the borohydrides of the larger rare‐earth metals, [Ln(BH₄)₃(thf)₃] (Ln=La, Nd), afforded the expected products [Ln(BH₄)₂(dip₂‐pyr)(thf)₂]. As usual, the trisborohydrides reacted like pseudohalide compounds forming KBH₄ as a by‐product. To compare the reactivity with the analogous halides, the dimeric neodymium complex [NdCl₂(dip₂‐pyr)(thf)]₂ was prepared by reaction of [(dip₂‐pyr)K] with anhydrous NdCl₃. Reaction of [(dip₂‐pyr)K] with the borohydrides of the smaller rare‐earth metals, [Sc(BH₄)₃(thf)₂] and [Lu(BH₄)₃(thf)₃], resulted in a redox reaction of the BH₄^? group with one of the Schiff base functions of the ligand. In the resulting products, [Ln(BH₄){(dip)(dip‐BH₃)‐pyr}(thf)₂] (Ln=Sc, Lu), a dinegatively charged ligand with a new amido function, a Schiff base, and the pyrrolyl function is bound to the metal atom. The by‐product of the reaction of the BH₄^? anion with the Schiff base function (a BH₃ molecule) is trapped in a unique reaction mode in the coordination sphere of the metal complex. The BH₃ molecule coordinates in an η² fashion to the metal atom. The rare‐earth‐metal atoms are surrounded by the η²‐coordinated BH₃ molecule, the η³‐coordinated BH₄^? anion, two THF molecules, and the nitrogen atoms from the Schiff base and the pyrrolyl function. All new compounds were characterized by single‐crystal X‐ray diffraction. Low‐temperature X‐ray diffraction data at 6 K were collected to locate the hydrogen atoms of [Lu(BH₄){(dip)(dip‐BH₃)‐pyr}(thf)₂]. The (DIP₂‐pyr)^? borohydride and chloride complexes of neodymium, [Nd(BH₄)₂(dip₂‐pyr)(thf)₂] and [NdCl₂(dip₂‐pyr)(thf)]₂, were also used as Ziegler–Natta catalysts for the polymerization of 1,3‐butadiene to yield poly(cis‐1,4‐butadiene). Very high activities and good cis selectivities were observed by using each of these complexes as a catalyst in the presence of various cocatalyst mixtures.     

Complete asymptotic analysis of positive solutions of odd-order nonlinear differential equation

We study the asymptotic behavior of solutions of the odd-order differential equation of Emden–Fowler type $$ {x^{{\left( {2n+1} \right)}}}(t)=q(t){{\left| {x(t)} \right|}^{\gamma }}\operatorname{sgn}x(t) $$ in the framework of regular variation under the assumptions that 0 < γ < 1 and q(t) : [a, ∞) → (0, ∞) is regularly varying function. We show that complete and accurate information can be acquired about the existence of all possible positive solutions and their asymptotic behavior at infinity.     

Comparison of Numerical Simulation Models for Open Loop Flight Simulations in the Human Centrifuge

To achieve predefined Gz load profile in high G training in human centrifuge, it is necessary to determine angular velocity and acceleration of a planetary axis (centrifuge arm). Initial value problem that can not be solved in closed form was obtained. Several discretization methods for calculating angular velocity of centrifuge arm driven by DC servo motor are presented. Simulations are performed for different positive and negative values of Gz onset. (© 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ionization energies of LinX (n = 2, 3; X = Cl, Br, I) molecules

Molecules of Li(n)X (n = 2, 3; X = Cl, Br, I) were examined with a magnetic sector mass spectrometer by surface ionization using a triple rhenium filament impregnated with fullerene (C60). The ionization energies obtained for Li(2)Cl, Li(2)Br and Li(2)I molecules are 3.8 +/- 0.1, 3.9 +/- 0.1 and 4.0 +/- 0.1 eV, respectively. The first ionization energy of Li(2)Cl is documented, while there are no literature data for the ionization energies of Li(2)Br and Li(2)I. The molecules of Li(3)Cl, Li(3)Br and Li(3)I were detected experimentally for the first time with ionization energies of 4.0 +/- 0.1, 4.1 +/- 0.1 and 4.1 +/- 0.1 eV, respectively. The ionization energies of Li(n)X (n = 2, 3; X = Cl, Br, I) are in correlation with the theoretical prediction of their hyperlithiated configurations.     

Evaluation of whole-genome amplification of low-copy-number DNA in chimerism analysis after allogeneic stem cell transplantation using STR marker typing

Whole-genome DNA amplification (WGA) is a promising method that generates large amounts of DNA from samples of limited quantity. We investigated the accuracy of a multiplex PCR approach to WGA over STR loci. The amplification bias within a locus and over all analyzed loci was investigated in relation to the amount of template in the WGA reaction, the specific STR locus, and allele length. We observed reproducible error-free STR profiles with 10 ng down to 1 ng of DNA template. The amplification deviation at a locus and between loci was within the intra-method reproducibility. WGA is the method of choice for amplifying nanogram amounts of genomic DNA for different applications. We detected unbalanced STR amplifications at one locus and between loci, allelic drop-outs, and additional alleles after WGA of low-copy-number DNA. We found that the high number of drop-outs and drop-ins could be eradicated using pooled DNA from separate WGA reactions even with as little as 100 pg of starting template. Nevertheless, the quality of the results was still not sufficient for use in routine chimerism analysis of limited specific cell populations after allogeneic stem cell transplantation.     

Synthesis, characterization and antiproliferative activity of transition metal complexes with 3-(4,5-diphenyl-1,3-oxazol-2-yl)propanoic acid (oxaprozin)

A series of novel Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes with oxaprozin (Hoxa), a non-steroidal anti-inflammatory drug, has been synthesized. The drug and complexes have been characterized by elemental and thermogravimetric (TG) analysis, Fourier transform (FT)-IR, 1H-NMR, 13C-NMR, UV-Vis spectroscopy and magnetic susceptibility measurements. The (pseudo)octahedral geometry has been proposed for all complexes based on electronic spectra and magnetic moments. With exception of the Cu(II) complex, where bridging bidentate mode of COO groups has been found, FT-IR spectra confirmed chelately coordinated COO groups in the other complexes. The general formula of the complexes is [M(H2O)2(oxa)2 ·χH2O, with χ=2 for M=Mn, Co and Ni and χ=1.5 for Zn. The binuclear Cu(II) complex, [Cu2(H2O)2(OH)(oxa)3]·2H2O, has strong Cu-Cu interactions of antiferromagnetic type. The complexes and Hoxa did not exhibit the cytotoxic effect to peritoneal macrophages. For the first time these complexes have been tested for their in vitro antiproliferative activity against human colon and breast cancer cell lines, HCT-116 and MDA-231, respectively. For all investigated compounds significant antiproliferative effects have been observed. Ni(II) complex has been shown to be a promising antiproliferative agent exerting excellent activity against HCT-116 even in nanomolar concentrations.     

Arsenopyrite mineral based electrochemical sensor for acid–base titrations in γ-butyrolactone and propylene carbonate

Abstract  

A novel acid–base sensor based on the natural mineral arsenopyrite for titrations in γ-butyrolactone and propylene carbonate is validated and studied. This sensor, which requires only small sample volumes, was employed for the titrations of some important organic acids (benzoic, anthranilic, and salicylic acid) with potassium hydroxide. A stable stationary potential was attained at the arsenopyrite electrode in γ-butyrolactone and propylene carbonate in less than 5 min. The change in the electrode potential from the acidic to basic region was 379 to −160 mV in γ-butyrolactone and 434 to −67 mV in propylene carbonate. The arsenopyrite electrode showed a relatively fast response time in the investigated solvents (11 s in γ-butyrolactone and 14 s in propylene carbonate). It can be used without any time limit or without considerable divergence in the potential. The investigated electrode showed a linear dynamic response for p-toluenesulfonic acid concentrations in the range 0.1–0.001 M, and a sub-Nernst dependence in γ-butyrolactone as well as in propylene carbonate. Unlike traditional pH titration, an end-point color indicator is unnecessary in this method, and real-time monitoring can be realized. The relative standard deviations for measurements of benzoic, anthranilic, and salicylic acids were 0.10–0.31%, which show that the repeatability and accuracy of measurements taken with the sensor are satisfactory.     

Positive solutions of fourth order Emden-Fowler type differential equations in the framework of regular variation

The fourth order nonlinear differential equations

(A)