Monoazo (Monohydrazone) pigments based on benzimidazolones

Robert Christie*, Adrian Abel

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


A series of azo pigments containing the benzimidazolone ring were introduced in the mid to late twentieth century as high-performance organic pigments in the yellow, orange, red, and brown shade areas. The structures of the commercial benzimidazolone azo pigments are derived from either the monoazoacetoacetanilide or monoazonaphtharylamide classical azo pigments systems and exist in the ketohydrazone tautomeric forms. The high-performance properties of the pigments have been attributed to a network of intermolecular hydrogen bonds involving the benzimidazolone group, and efficient molecular packing, as demonstrated by X-ray crystal structure determinations. The manufacturing processes leading to the pigments involve traditional diazotization and azo coupling reaction procedures, although they require special conditioning aftertreatments to optimize their performance. Although benzimidazolone azo pigments were initially developed for the coloration of plastics, they have probably had a greater impact on the paint industry. The application properties of the benzimidazolone azo pigments are discussed for individual products.

Original languageEnglish
Pages (from-to)17-30
Number of pages14
JournalPhysical Sciences Reviews
Issue number1
Early online date1 Jul 2021
Publication statusPublished - Jan 2022


  • azo pigments
  • azoacetoacetanilide
  • azonaphtharylamide
  • benzimidazolone azo pigments
  • benzimidazolones
  • CI Pigment Brown 25
  • CI Pigment Orange 36
  • CI Pigment Orange 62
  • CI Pigment Orange 64
  • CI Pigment Red 171
  • CI Pigment Red 175
  • CI Pigment Red 176
  • CI Pigment Red 185
  • CI Pigment Red 208
  • CI Pigment Viloet 32
  • CI Pigment Yellow 120
  • CI Pigment Yellow 151
  • CI Pigment Yellow 154
  • CI Pigment Yellow 175
  • CI Pigment Yellow 180
  • CI Pigment Yellow 181
  • CI Pigment Yellow 194
  • CI Pigment Yellow 213
  • intermolecular hydrogen bonds
  • monohydrazone
  • tetrahydroquinoxalinedione

ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Physics and Astronomy(all)


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