Formation of oxo-centered trinuclear chromium carboxylate complexes and hydrolysis of Cr3 as established by paramagnetic 2H NMR spectroscopy

•Paramagnetic 2H NMR is used to follow reactions of chromium carboxylate assemblies.•Formation of [Cr3O(O2CCD3)6(H2O)3]+ involves mononuclear & dinuclear intermediates.•Cr3 hydrolysis reaches an equilibrium in water, blood plasma, & cell culture media.•Cr3 degradation is more rapid in muscle homogenate.

Paramagnetic 2H NMR techniques have been utilized to study the mechanism of formation of the oxo-bridged trinuclear Cr(III) carboxylate assembly [Cr3O(O2CCD3)6(H2O)3]+ from [Cr(H2O)6]3 + and d4-acetic acid. These studies reveal a complex mechanism dominated by the involvement of dinuclear intermediates. The oxo-bridged trinuclear Cr(III) carboxylate assembly [Cr3O(O2CCH2CH3)6(H2O)3]+ has been suggested for use as a chromium nutritional supplement and therapeutic agent as it is readily absorbed and has been proposed to enter cells intact. The paramagnetic 2 H NMR technique has been utilized to follow the stability of this Cr(III) carboxylate assembly in biologically relevant media; its stability is consistent with the assembly being able to enter cells intact.

Graphical abstractParamagnetic 2H NMR is a viable technique to study the formation and degradation of trinuclear basic Cr(III) carboxylate assemblies in a variety of solvents. The stability of the nutritional supplement Cr3 in biologically relevant media is consistent with the complex being able to enter cells intact from the bloodstream.Figure optionsDownload full-size imageDownload as PowerPoint slide