Role of Redox Metals in Color Formation in a Hair Colorant.

The objective of this work was to identify if low levels of redox metals such as copper would accelerate color formation on hair and to understand the consequent impact on initial color formation and color fade. Kinetics of color formation with oxidative dyes in solution in the presence of varying concentrations of copper ions were assessed imaging and color measurements. Color uptake on hair and color fade were measured with a spectrophotometer, and copper levels in hair were measured with inductively coupled plasma atomic spectroscopy after hair digestion.

High-resolution visualization of cosmetic active compounds in hair using nanoscale secondary ion mass spectrometry.

A wide range of small molecules are used in our daily hair products to improve the appearance of hair and to protect it from damage from the environment. In order to better design formulations of these products, an understanding of the partitioning and distributions of these small molecules in hair is critical. In this study, we used preferential extraction methods to measure the partitioning of active compounds commonly found in hair cosmetic products on the hair surface and inside hair, and investigated the use of stable isotope labelling, cryo-sample preparation and nanoscale secondary ion mass spectrometry (NanoSIMS) for high-resolution visualization of distributions of these compounds.

Metal complexes with varying intramolecular hydrogen bonding networks.

Alfred Werner described the attributes of the primary and secondary coordination spheres in his development of coordination chemistry. To examine the effects of the secondary coordination sphere on coordination chemistry, a series of tripodal ligands containing differing numbers of hydrogen bond (H-bond) donors were used to examine the effects of H-bonds on Fe(II), Mn(II)-acetato, and Mn(III)-OH complexes. The ligands containing varying numbers of urea and amidate donors allowed for systematic changes in the secondary coordination spheres of the complexes.

Synthesis, structure, and physical properties for a series of monomeric iron(III) hydroxo complexes with varying hydrogen-bond networks.

Mononuclear iron(III) complexes with terminal hydroxo ligands are proposed to be important species in several metalloproteins, but they have been difficult to isolate in synthetic systems. Using a series of amidate/ureido tripodal ligands, we have prepared and characterized monomeric Fe (III)OH complexes with similar trigonal-bipyramidal primary coordination spheres. Three anionic nitrogen donors define the trigonal plane, and the hydroxo oxygen atom is trans to an apical amine nitrogen atom.

Comparison of a tartaric acid derived polymeric MRI contrast agent to a small molecule model chelate.

Contrast agents with high relaxivity are needed to increase the sensitivity of magnetic resonance imaging (MRI) for novel clinical and research applications. For this reason, polymeric structures containing multiple Gd(III) chelates are of current interest. Described in this communication are the syntheses and characterization of a glycopolymer derived from L-tartaric acid, Gd 4(H2O), as well as a low molecular weight compound, Gd 10(H2O), that models the Gd(III) chelate structure in the repeat unit of polymer Gd 4(H2O).

A modular approach toward regulating the secondary coordination sphere of metal ions: differential dioxygen activation assisted by intramolecular hydrogen bonds.

Metal ion function depends on the regulation of properties within the primary and second coordination spheres. An approach toward studying the structure-function relationships within the secondary coordination sphere is to construct a series of synthetic complexes having constant primary spheres but structurally tunable secondary spheres. This was accomplished through the development of hybrid urea-carboxamide ligands that provide varying intramolecular hydrogen bond (H-bond) networks proximal to a metal center.

Preparation of iron amido complexes via putative Fe(IV) imido intermediates.

The isolation and characterization of monomeric Fe(III) amido complexes with hybrid ureate/amidate ligands is described. An aryl azide serves as the source of the amido ligand in preparing the complexes from trigonal monopyramidal Fe(II) precursors. Aryl azides more commonly react with transition metal complexes by a two-electron oxidation process to yield imido complexes, suggesting that the Fe(III) amido complexes may be formed from high valent species by hydrogen atom abstraction from an external species.