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Metal-complex Dyes
Metal-complex dyes that are otherwise known as pre-metallized dyes shows great affinity towards protein fibers. Generally it has been seen that metal complex dyes are Chromium or Cobalt complexes. Among the popular metal-complex dyes, a variety known as 1:2 metal-complex dyes finds application for dyeing polyamide fibers. For dyeing wool, metal complex dyes are the most favoured. The following table shows a comparison between 1:1 metal-complex and 1:2 metal complex dye.

Dye Type Levelling Ability Wash Fastness pH Range
1:1 metal-complex Good Good 2
1:2 metal complex Poor Very Good 6-7

Metal-complex dyes generally cannot be said as belonging to a particular application dye class. In fact, Metal-complex dyes belong to numerous application classes of dyes. For example, they are found among direct, acid, and reactive dyes. When applied in the dyeing processes, metal-complex dyes are used in pH conditions that is regulated by user class and the type of fiber type (wool, polyamide, etc). The pH levels for wool typically ranges from:
  • Strongly acidic (ranging from 1.8 - 4 for 1:1 metal-complex dyes)
  • Moderately acidic neutral (ranging from 4 - 7 for 1:2 metal-complex dyes)
Types of Metal Complex Dyes

Chemically speaking, Metal copmplex Dyes can be broadly classified into two classes. 1:1 metal-complexes, where, one dye molecule gets co-ordinated with a single metal atom. In 1:2 metal complexes, one metal atom is co-ordinated with double dye molecules. The dye molecules are typically a monoazo structure which can contain additional groups like hydroxyl, carboxyl or amino groups. They can form strong co-ordination complexes with transition metal ions, like Nickel, Chromium, Cobalt and Copper. One point to note here is that phthalocyanine dyes are not classified as metal-complex dyes.

Metal Complex Dyes
Typical molecular structures of 1.1 metal-complex dyes

Metal Complex Dyes
Typical molecular structures of 1.2 metal-complex dyes

Features of Metal Complex Dyes

  • Excellent, light-fastness.
  • Medium washing fastness.
  • Shows very good level dyeing and penetration characteristics.
  • Can cover up for the irregularities in the substrates.
Application of Metal Complex Dyes

Metal Complex Dyes is using for a variety of applications like wood stains, leather finishing, stationery printing inks, inks, coloring for metals, plastic etc.


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