Although vat dyes are widely used on cellulosic fibres on which they exhibit characteristically excellent light and wet fastness properties, this dye class is not routinely used on polyamide fibres (with the exception of their minor usage on nylon/cotton blends) wing to their low substantivity and the generally pale shades that
accrue from their limited extent of diffusion within the substrate [1]. The dyes contain at least two conjugated carbonyl groups which