Mechanistic Insight into the Thermal "Blueing" of Cyanine Dyes.

ABSTRACT: In recent work to develop cyanine dyes with especially large Stokes shifts, we encountered a "blueing" reaction, in which the heptamethine cyanine dye Cy7 (IUPAC: 1,3,3-trimethyl-2-((1E,3E,5E)-7-((E)-1,3,3-trimethylindolin-2-ylidene)hepta-1,3,5-trien-1-yl)-3H-indol-1-ium) undergoes shortening in two-carbon steps to form the pentamethine (Cy5) and trimethine (Cy3) analogs. Each step blue-shifts the resulting absorbance wavelength by ca. 100 nm. Though photochemical and oxidative chain-shortening reactions had been noted previously, it is simple heating alone or with amine bases that effects this unexpected net C₂H₂ excision. Explicit acetylene loss would be too endothermic to merit consideration. Our mechanistic s

SUBMITTER: Vahdani A 

PROVIDER: S-EPMC11273608 | biostudies-literature | 2024 Jul

REPOSITORIES: biostudies-literature