The influence of fluorination on the structure and properties of azo pigments

• Fluorination had a profound influence on the structure of molecules and crystals.
• Fluorination enhanced solvent resistance and decreased fastness to light and heat in both cases.
• Fluorinated pigments exhibited irregular and smaller crystals compared to its analogues.

The synthesis and single crystal X-ray structures of two fluorinated azo pigments and their nonfluorinated analogues derived from N-acetoacetanilide and N,N′-(1,4-phenylene) bis-(acetoacetamide) as coupling components were described. These two kinds of pigments existed in the ketohydrazone and bisketohydrazone tautomeric form with intramolecular hydrogen bondings respectively. Fluorination had a profound influence on the structure of molecules and crystals and consequently altered the morphology and pigmentary performance. The results demonstrated that the solvent resistance was improved upon fluorination due to enhanced intermolecular interactions and efficient π-packing of molecules. However, in both cases fluorination gave rise to pigments with poorer stability to heat and light.

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