Sytnhesis of some unsymmetric diketopyrrolopyrrole pigments and investigation of their properties

In this study, six series of unsymmetrical diaryl substituted diketopyrrolopyrrole (DPP) pigments were synthesized. The unsymmetrical DPPs have been synthesized by base catalyzed condensation of the corresponding aromatic nitriles and pyrolinone esters. The compounds have been characterized by spectrophotometric methods and mass spectroscopy. Absorption and fluoresence spectra of the compounds were investigated in solvents of different polarity. The compounds showed small solvatochromism of absorption and a moderate positive solvatochromism of fluoresence in general. The diketopyrrolopyrrole derivative containing pyrazine and thienyl rings exhibited the largest positive solvatochromism. Absorption and fluoresence spectral data indicate that the substituents on the phenyl ring has small effect on the systems regardless of the electron donating or electron withdrawing characteristics of the substituents. The effect of base on the absorption spectra of the compounds were also investigated. It has been seen that the N-heterocyclic ring containing compounds have been more sensitive towards base.