J. Barrett

Chromium(V) can be generated in the reduction of chromium(VI) by glutathione

Etude de la reaction du glutathion avec le chromate a pH neutre et formation de complexes de Cr(V) en solution aqueuse a temperature ordinaire

Preparation and characterization of some Cr(III) chloro-complexes with nicotinic acid esters

Abstract The preparation and characterisation of the trichlorotris(alkylnicotinate)chromium(III) complexes of general formula CrCl3(py·3COOR)3·nH2O, where R = Me, Et, Pr and Bu are reported, n being 3.5, 1.0, 0 and 0 respectively. It is concluded that the ligation of the three chloride ions and that of the three nitrogen atoms is consistent with a C2u arrangement in each case.

Synthesis and characterization of some chromium(III) complexes with glutathione

The glutathione (H5L) complexes K2[Cr(H3L)(H2L)]·3H2O, K2[Cr(H2L)(A)]·nH2O (A = the dianion of the amino acids L-cysteine, L-glutamic acid, or L-aspartic acid), and K2[Cr(H2L)(gly)(OH)]·2H2O [gly = glycinate(1–)] have been synthesized. All the complexes exhibit an intense u.v. chargetransfer band which is characteristic of a Cr–S bond. The sulphydryl to chromium linkage undergoes an acid-catalysed hydrolysis. The complexes have been characterized by elemental and thermogravimetric analyses, electronic and i.r. spectroscopy, and circular dichroism. Comparison of these properties with those of known chromium(III) complexes leads to the conclusion that glutathione is bound to chromium(III) by the terminal glycine group (N,O) and the deprotonated sulphur of cysteine. The glutamic acid residue of glutathione does not apparently interact with the chromium centre in these complexes.

A kinetic and equilibrium study of the reaction of glycine with chromium(III) in aqueous solution

The formation of tetra-aquaglycinatochromium(III) from glycine and chromium(III) has been studied at pH = 3.0–3.8, 40–54 °C, and I= 0.4 mol dim–3(NaClO4). The equilibrium constant (log10K1) is 7.60 at 44.8 °C. The reaction obeys the rate equation kobs.=k+k′[H+]–1 and under all the conditions studied is zero order in the concentration of glycine. A mechanism involving extensive outer-sphere complexation of hexa-aquachromium(III) and its conjugate base is proposed. The activation parameters are compared to literature values.

Mössbauer and electronic-reflectance spectroscopic studies and resistivity measurements on the systems CsPb1–xSnxBr3, CsPb1–xSnxBr2Cl, MxCs1–xSnBr3, and MxCs1–xSnBr2Cl (M = Na, K, Rb, and NH4)

A series of coloured compounds of general formula CsPb1–xSnxX3(X3= Br3 or Br2Cl) has been prepared. X-Ray and Mossbauer data show that the compounds have highly symmetrical tin–lead environments. Their electronic resistivity and optical-reflectance spectra are interpretable in terms of the partial filling of electronic bands produced by the interaction of orbitals of the bromine atoms. As x increases the band population increases, consistent with the lower ionisation energies of the tin 5s electrons compared to those of the lead 6s electrons. Replacement of Cs+ by Na+, K+, Rb+, or [NH4]+ shows that these singly charged ions have no effect on band formation. Replacement of Br3 by Br2Cl raises the energy of the band due to the inclusion of the higher-energy chlorine orbitals.