Absorption maxima shifted to the near IR region are observed for the cations 1. These cations can be synthesized by the reaction of benzothiazolium iodides and squaric acid in the ratio 3:2 without the addition of a base. The chromophore of 1 is a polymethine chromophore and not a triarylmethane one. R = Bu, Pr, Et.
No takes yet. Share an insight, caveat, or question.
Nakazumi et al. (1994) studied this question.
Synapse has enriched 4 closely related papers on similar clinical questions. Consider them for comparative context: