Radial oscillations of neutron stars in strong magnetic fields

The eigen frequencies of radial pulsations of neutron stars are calculated in a strong magnetic field. At low densities we use the magnetic BPS equation of state (EOS) similar to that obtained by Lai and Shapiro while at high densities the EOS obtained from the relativistic nuclear mean field theory is taken and extended to include strong magnetic field. It is found that magnetized neutron stars support higher maximum mass whereas the effect of magnetic field on radial stability for observed neutron star masses is minimal.     

Characterization of [Re2Cl3(μ-dppm)2(NCCH3)2][Cl] and [Re2Cl3(μ-dppm)2(NCC6H5)2][Cl]·2CH2Cl2 by X-ray Crystallographic and Two-Dimensional NMR Spectroscopic Techniques

The complex Re₂Cl₆(P-n-Bu₃)₂ prepared in situ reacts with CH₃CN to form a blue-green solution. Addition of the chelating phosphine bis(diphenylphosphino)methane (dppm) results in the formation of the complex [Re₂Cl₃(-dppm)₂(NCCH₃)₂][Cl] (1) upon heating. The two acetonitrile molecules adopt a trans geometry on the rhenium center with the axially coordinated chlorine. The analogous trans benzonitrile species [Re₂Cl₃(-dppm)₂(NCC₆H₅)₂][Cl]·2CH₂Cl₂ (2) is synthesized under the same reaction conditions. The coupling constants of the AABB ³¹P{¹H} NMR spectra of the compounds were elucidated from ³¹P–³¹P homonuclear J-resolved NMR experiments. Additional characterization methods include ³¹P{¹H} NMR spectroscopy, UV-vis spectroscopy, and X-ray crystallography.     

A Convenient Preparation of a Bicyclo[3.3.3]undecane Derivative Containing Heteroatoms Through a Rearrangement Step

A convenient method for the preparation of a bicyclo[3,3,3]undecane derivative via the Beckmann rearrangement of bicyclo[3,3,2]decane-9-one is described.     

The evaluation of singlet-triplet separations for [W2(μ-H)(μ-Cl)Cl4(μ-dppm)2] and [W2(μ-H)2 (μ-O2CC6H5)2(P(C6H5)3)2] based on P NMR and crystallographic data

The singlet-triplet separations for the edge-sharing bioctahedral (ESBO) complex W₂(μ-H)(μ-Cl)(Cl₄(μ-dppm)₂ · (THF)₃ (II) has been studied by ³¹P NMR spectroscopy. The structural characterization of [W₂(μ-H)₂(μ-O₂CC₆H₅)₂Cl₂(P(C₆H₅)₃)₂] (I) by single-crystal X-ray crystallography has allowed the comparison of the energy of the HOMOLUMO separation determined using the Fenske-Hall method for a series of ESBO complexes with two hydride bridging atoms, two chloride bridging atoms and the mixed case with a chloride and hydride bridging atom. The complex representing the mixed case, [W₂(μ-H)(μ-Cl)Cl₄(μ-dppm)₂ · (THF)₃] (II), has been synthesized and the value of −2J determined from variable-temperature ³¹P NMR spectroscopy.     

The evaluation of singlet-triplet separations for [W2(μ-H)(μ-Cl)Cl4(μ-dppm)2] and [W2(μ-H)2 (μ-O2CC6H5)2(P(C6H5)3)2] based on P NMR and crystallographic data

The singlet-triplet separations for the edge-sharing bioctahedral (ESBO) complex W₂(μ-H)(μ-Cl)(Cl₄(μ-dppm)₂ · (THF)₃ (II) has been studied by ³¹P NMR spectroscopy. The structural characterization of [W₂(μ-H)₂(μ-O₂CC₆H₅)₂Cl₂(P(C₆H₅)₃)₂] (I) by single-crystal X-ray crystallography has allowed the comparison of the energy of the HOMOLUMO separation determined using the Fenske-Hall method for a series of ESBO complexes with two hydride bridging atoms, two chloride bridging atoms and the mixed case with a chloride and hydride bridging atom. The complex representing the mixed case, [W₂(μ-H)(μ-Cl)Cl₄(μ-dppm)₂ · (THF)₃] (II), has been synthesized and the value of −2J determined from variable-temperature ³¹P NMR spectroscopy.     

Heteronuclear NMR Studies of Cobalt Corrinoids. 18. Correlation of Structure and Magnetic Resonance Parameters in Base-On Cobalamins(1)

Recent X-ray crystal structure determinations (including a new X-ray determination of the structure of cyano-13-epicobalamin reported herein) create a series of seven base-on cobalamins structurally characterized by modern crystallographic techniques in which the intramolecular equilibrium constant for coordination of the axial benzimidazole ligand (Bzm) varies from 76.6 to 4.90 x 10(7). For the five normal, unepimerized cobalamins, the free energy change for this equilibrium correlates linearly with the axial Co-N bond length (r(2) = 0.99). Absolute assignment of the (1)H and (13)C NMR spectra of two of these structurally characterized cobalamins (CH(3)Cbl and CN-13-epiCbl) together with literature assignments for the other complexes now provides reliable (13)C NMR assignments and chemical shifts for all seven complexes. The magnetic anisotropies of the central cobalt atom of all seven complexes, estimated by a method described earlier, are well correlated with the axial Co-N bond distance (r(2) = 0.97) and the free energy of coordination of the Bzm ligand (r(2) = 0.95). The (31)P NMR chemical shift of the phosphodiester moiety of the nucleotide loop is excellently correlated to the axial Co-N bond length (r(2) = 0.996) of the unepimerized cobalamins and provides a reliable method of estimating this bond length. The (15)N chemical shifts of the axially coordinated Bzm nitrogen vary strongly with the axial Co-N bond distance and correlate linearly with this structural parameter (r(2) = 0.991) except for the case of H(2)OCbl(+), which deviates substantially. However, there is a good linear correlation (r(2) = 0.98) of this (15)N chemical shift with the free energy of Bzm coordination for the five unepimerized cobalamins. Attempts to correlate (13)C NMR chemical shifts with structural, thermodynamic, and corrin ring conformational parameters are discussed.