Synthetic dyes with the general formula
is a small number) in which the nitrogen and part of the conjugated chain usually
form part of a heterocyclic system, such as imidazole, pyridine, pyrrole, quinoline
and thiazole, e.g.
PAC, 1995, 67, 1307
(Glossary of class names of organic compounds and reactivity intermediates based on
structure (IUPAC Recommendations 1995))
on page 1329