Greig Chisholm

The first red azo lake pigment whose structure is characterized by single crystal diffraction

A model for red azo pigment Ca4B was characterized structurally using synchrotron radiation. This highly anisotropic ladder structure represents a new structural class in azo pigment chemistry. The picture shows that the calcium atoms coordinate in a complex manner to three azo ligands (one terdentate, one bidentate, and one monodentate) and two water molecules simultaneously.

Effects of fluorination on the properties of organic pigments

The solid state properties of two fluorinated pigments are compared with their unfluorinated analogues and the influence of fluoro substitution upon the solid state properties is discussed. The effect of fluorination was examined by a range of techniques including UV/visible spectroscopy, solid state NMR spectroscopy and powder X-ray diffraction. Fluorination modified the crystal packing of the molecules and subsequently altered the pigmentary performance of the compounds. In both cases fluorination gave rise to compounds with poorer fastness properties.