J-Aggregates of Indoheptamethine Cyanine Dye

Abstract

The effect of doubly charged inorganic and organic cations on the aggregation of anionic indoheptamethine cyanine dyes has been studied in aqueous solutions. It is shown that the effective formation of J-aggregates with narrow exciton absorption bands in the IR region of the spectrum with λ_max = 920 nm is characteristic only of a dye with SO₃^- groups in the 6,6′-positions of the benzoindolenine ring. It is found that bis-quaternary salt based on α-picolinium is particularly effective as a J-aggregating agent and causes J-aggregation at a concentration close to the dye concentration. It follows that the introduction of sulfogroups at the 6,6′-positions of the benzoindolenine ring creates optimal conditions for packing the molecules of the indolenine dye into a highly organized structure of a “brickwork” type under the action of multiply charged cations. It is shown that the J-aggregates of the indoheptamethine cyanine dye are photoelectric converters for the IR region of the spectrum.