Near-Infrared Cyanine Dyes: A New Approach to an Old Problem

The design and synthesis of new heterocyclic end-groups for NM cyanine dyes based on the annelation of the pyrrole and benz[c,d]indole nucleus have been developed. The main principle used was the inclusion of the polymethine chain of the dye into a molecule of the condensed heterocycle thus achieving the deepest absorption of the cyanine dye with the minimum length of polymethine chain and in such a manner to increase the stability of the resulting compound.