13907-45-4Relevant articles and documents
Hydrolytic and redox transformations of chromium(III) bis-oxalato complexes with glutaminic acid and glutamine: A kinetic, UV-Vis and EPR, study
Kiersikowska, Emilia,Kita, Ewa,Kita, Przemys?aw,Wrzeszcz, Grzegorz
, p. 435 - 445 (2016/04/19)
The title complexes have been synthesized, chromatographically isolated and characterized by their ligands to metal ratio determinations and spectroscopic analyses. The kinetics of the first aquation stage, i.e., the amino acid chelate ring opening via the Cr-N bond cleavage, has been studied spectrophotometrically in acidic and alkaline media. Hydrogen peroxide oxidizes the complexes in alkaline media to CrO 42- anion and a relatively stable Cr(V) complex. Consecutive biphasic kinetics through two first-order steps were observed for the base hydrolysis and the oxidation process, whereas the acid-catalyzed aquation obeys a simple first-order pattern. Based on the kinetic and spectroscopic data, mechanisms of the coordinated amino acid liberation and chromium(III) oxidation are discussed.
Chromium(V) peptide complexes: Synthesis and spectroscopic characterization
Barnard, Peter J.,Levina, Aviva,Lay, Peter A.
, p. 1044 - 1053 (2008/10/09)
A series of stable Cr(V) model complexes that mimic the binding of Cr(V) to peptide backbones at the C-terminus of proteins have been prepared for N,N-dimethylurea derivatives of the tripeptides Aib3-DMF, AibLAlaAib-DMF, and AibDAlaAib-DMF (Aib = 2-amino-2-methylpropanoic acid, DMF = N,N-dimethylformamide). The Cr(II) precursor complexes were synthesized by the initial deprotonation of the amide and acid groups of the peptide ligands in DMF with potassium tert-butoxide in the presence of CrCl2. The Cr(II) intermediates thus formed were then immediately oxidized to Cr(V) using tert-butyl hydroperoxide. Spectroscopic and mass-spectrometric analyses of the Cr(V) complexes showed that a new metal-directed organic transformation of the ligand had occurred. This involved a DMF solvent molecule becoming covalently bound to the amine group of the peptide ligand, yielding a urea group, and a third coordinated deprotonated urea nitrogen donor. A metal-directed oxidative coupling has been proposed as a possible mechanism for the organic transformation. The Cr(V/IV) reduction potential was determined for the three Cr(V) complexes using cyclic voltammetry, and in all cases it was quasi-reversible. These are the first isolated and fully characterized Cr(V) complexes with non-sulfur-containing peptide ligands.
Biomimetic oxidation of chromium(III): Does the antidiabetic activity of chromium(III) involve carcinogenic chromium(VI)?
Mulyani, Irma,Levina, Aviva,Lay, Peter A.
, p. 4504 - 4507 (2007/10/03)
The insulin-enhancing activities of some CrIII complexes, such as [Cr3O(OCOEt)6-(OH2)3]+ (1), previously attributed to specific interactions of CrIII ions with cellular insulin receptors, are more likely to be caused by the formation of [CrO4]2- (2). Oxidation of 1 to 2 by biologically relevant oxidants, including enzymes (see scheme), and inhibition of an isolated protein tyrosine phosphatase by a CrVI complex are reported.
