Four Different Crystals Derived from a Novel Yellow Pyrazolyl Azo Pigment

Four different crystals are presented in the present article that are derived from a novel yellow pyrazolyl azo pigment used for ink jet inks. This compound exhibits a good pigmentary performance in light and heat stability but rather poor in solvent fastness. X-ray structure analysis has been carried out in order to improve the present drawback from the structural point of view. The authors have unexpectedly isolated two kinds of five-coordinate bisazo Na complexes of the cis form (space group: P-1) as well as one Na-free monoazo compound (space group: C2/c). The formation of the Na complex is found to be caused by NaNO2 used for the preparation of diazo components. Then, the authors tried to eliminate the sodium atom from the Na complex using hydrochloric acid in an attempt to develop a better pigment that assumes a trans configuration. The present Na-free compound in the trans form is found to crystallize in space group P-1 and is characterized by good solvent fastness in addition to the light and heat stability of the original title compound. (C) 2011 Society for Imaging Science and Technology. [DOI: 10.2352/J.ImagingSci.Technol.2011.55.2.020504]