Poly[[dibromomercury(II)]-di-mu-pyrazine-kappa N-4 : N ']

The crystal structure of [HgBr2(Pyp)(2)](n) (Pyp = pyrazine, C4H4N2) consists of almost linear HgBr2 molecules which are linked by pyrazine molecules to form double strands of a coordination polymer in the [010] direction. The Hg and Br atoms lie on mirror planes.

The Films of Joseph H. Lewis

Chlorometallate(III) ionic liquids as Lewis acidic catalysts - a quantitative study of acceptor properties

The Gutmann Acceptor Number (AN), which is a quantitative measure of Lewis acidity, has been estimated using the P-31 NMR chemical shift of a probe molecule, triethylphosphine oxide, for a range of chlorometallate(III) ionic liquids, based on Group 13 metals (aluminium(III), gallium(III) and indium(III)) and the 1-octyl-3-methylimidazolium cation, at different compositions. The results were interpreted in terms of extant speciation studies of chlorometallate(III) ionic liquids, and compared with a range of standard molecular solvents and acids. The value of these data were illustrated in terms of the selection of appropriate ionic liquids for specific applications.

Chlorostannate(II) Ionic Liquids: Speciation, Lewis Acidity, and Oxidative Stability

The anionic speciation of chlorostannate(II) ionic liquids, prepared by mixing 1-alkyl-3-methylimidazolium chloride and tin(II) chloride in various molar ratios, chi(SnCl2), was investigated in both solid and liquid states. The room temperature ionic liquids were investigated by Sn-119 NMR spectroscopy, X-ray photoelectron spectroscopy, and viscometry. Crystalline samples were studied using Raman spectroscopy, single-crystal X-ray crystallography, and differential scanning calorimetry. Both liquid and solid systems (crystallized from the melt) contained [SnCl3](-) in equilibrium with Cl- when chi(SnCl2) < 0.50, [SnCl3](-) in equilibrium with [Sn2Cl5](-) when chi(SnCl2) > 0.50, and only [SnCl3](-) when chi(SnCl2) = 0.50. Tin(II) chloride was found to precipitate when chi(SnCl2) > 0.63. No evidence was detected for the existence of [SnCl4](-) across the entire range of chi(SnCl2) although such anions have been reported in the literature for chlorostannate(II) organic salts crystallized from organic solvents. Furthermore, the Lewis acidity of the chlorostannate(II)-based systems, expressed by their Gutmann acceptor number, has been determined as a function of the composition, chi(SnCl2), to reveal Lewis acidity for chi(SnCl2) > 0.50 samples comparable to the analogous systems based on zinc(II). A change of the Lewis basicity of the anion was estimated using H-1 NMR spectroscopy, by comparison of the measured chemical shifts of the C-2 hydrogen in the imidazolium ring. Finally, compositions containing free chloride anions (chi(SnCl2) < 0.50) were found to oxidize slowly in air to form a chlorostannate(IV) ionic liquid containing the [SnCl6](2-) anion.

Lewis phenotype, secretor status, and coeliac disease

Patients who cannot secrete ABO and Lewis blood group antigens into body fluids, an ability controlled by a single gene on chromosome 19, are known to be at increased risk of certain autoimmune diseases associated with human leucocyte antigen (HLA) markers. This study investigated the possibility of an association with coeliac disease using red cell Lewis (Le) blood group phenotype to infer secretor status. Among 73 patients with coeliac disease who had Le a or b antigen, 48% were non-secretors (Le a + b-) compared with 27% of 137 blood donors (p = 0.004: odds ratio 2.49, 95% confidence intervals 1.37 to 4.51) and 26% of 62 medical and nursing staff controls (p = 0.014: odds ratio 2.65, 95% confidence intervals 1.27 to 5.50). Clinical characteristics did not differ between secretors and non-secretors with coeliac disease. Thus, the non-secretor state is significantly associated with coeliac disease, suggesting that genes on chromosome 19 may directly or indirectly participate in conferring susceptibility.