A compound of the Formula (1) and salts thereof: wherein: D is the residue of a mono-azo chromophore; Z is an optionally substituted nitrogen containing heterocyclic group; R1 is H or optionally substituted alkyl; the dyes of Formula (1) being free from fibre reactive groups; provided that the compound of Formula (1) is other than the compound of Formula (A): Also claimed are compositions and inks containing a compound of Formula (1), a process for ink jet printing using the inks and to an ink jet printer cartridge containing the ink.