Near-infrared heptamethine cyanine dyes. Synthesis, spectroscopic characterization, thermal properties and photostability

Near-infrared heptamethine cyanine dyes were synthesized without substitution to the polyene chain but with various substituents on the indoleninium fragments. To develop indotricarbocyanine dyes with improved photochemical characteristics, we studied the relationship between the structures of these compounds, their spectral properties, their photostability, and thermal stability.

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► Symmetrical and unsymmetrical near-infrared heptamethine cyanine dyes were synthesized.
► The relationship between molecular structure of the cyanine dyes and their photophysical properties was studied.
► The intramolecularly 1,1′-crosslinked heptamethine dyes exhibited enhanced photostability and thermal stability.