Phthalocyanines, porphyrins and related aza[18]annulenes

This chapter describes annulenes, in which chains of methine groups form 18-member ring systems in which all double bonds are conjugated. Most dyes are copper complexes in which the metal ion is bound by the nitrogen atoms of the pyrrole units. The usual sequence of nonionic dyes, anions, and cations is followed. Within each subgroup dyes are listed in order of increasing formula weight, although certain anionic and cationic dyes which are only occasionally used in biology have generic not individual entries. Cuprolinic blue is also used to stain glycosaminoglycans, for instance, to permit quantitation. Such staining can be carried out both on paraffin and water-miscible resin sections. Indeed demonstration of glycosaminoglycans can be achieved with epoxy resin sections, though in this case staining is slow.