The crystal structure of LSbOF

LSbOF is orthorhombic, space group Pnma, with a = 8.873, b = 4.099 and c = 5.483 Å. Four anions are bonded to Sb³⁺, all to one side, and such polyhedra form chains by edge sharing along c. Evidence is given for an ordered arrangement of fluorine and oxygen anions. The lone pair of electrons is described as taking a certain volume, the centre of which is derived. Relationships with other structures are discussed.     

Phosphate buffers in capillary electrophoresis/mass spectrometry using atmospheric pressure photoionization and electrospray ionization

Capillary electrophoresis (CE) has been combined with atmospheric pressure photoionization (APPI) and electrospray ionization (ESI) for mass spectrometric (MS) detection. Separation conditions using potassium phosphate buffer and ammonium formate buffer have been compared for analysis of eleven pharmaceutical bases. The results showed improvements in separation efficiency and peak symmetry when phosphate buffer was used. The low flow in CE may enable utilization of these advances with MS detection. Compared with ESI, the APPI technique provided a cluster-free background. The enhanced signal-to-noise ratio in the total ion current (TIC) and the reduced spectral background indicated that the APPI process is less affected by non-volatile salts in the CE buffers. This results in a wider range of choice of CE buffers in CE/MS analysis when APPI is the ionization method.     

AB initio MO LCAO UHF calculations of magnetic hyperfine interactions in π-radicals. Isotropic and anisotropic couplings of ·CH3, ·NH3+, ·C2H5 and ·N2H4+

A series of π-electron radicals have been investigated with ab initio methods, using the unrestricted Hartree-Fock approximation. The geometries have been partially optimized, and magnetic hyperfine coupling constants have been evaluated. For the dipolar hyperfine couplings, the results obtained are in fair agreement with experiment, whereas the isotropic coupling constants show greater deviations. These values are also shown to be sensitive to annihilation of the quartet contamination of the wavefunction.     

Calculation of chlorine Kα1,2 X-ray emission shifts in molecules

Shifts of the chlorine Kα_1,2 X-ray emission line in gaseous molecules and in crystalline NaCl are correlated with effective atomic charges from CNDO/2 molecular orbital calculations made (i) for the neutral atomic ground states. and (ii) within the equivalent core approximation. For the latter case CNDO/2 parameters are derived for argon. The best agreement with experimental chemical shifts is obtained with the equivalent cores approximation. The results for NaCl depend strongly upon the CNDO/2 treatment of sodium.     

Ab initio MO LCAO UHF calculations of magnetic hyperfine interactions in σ radicals. Isotropic and anisotropic couplings of NO2 and CO2−

The magnetic hyperfine coupling constants in NO₂ and CO₂^? have been computed by an initio methods. Spin annihilation is found to be essential in order to obtain useful results for the dipolar couplings, but has much less influence on the isotropic couplings. The electric quadrupole coupling constants have also been evaluated, and are in good agreement with available experimental data.