Water‐soluble pH‐sensitive 2,6‐bis(substituted ethylidene)‐cyclohexanone/hydroxy cyanine dyes that absorb in the visible/near‐infrared regions

Abstract
Three methods were used to synthesize a series of the title compounds. The ketones absorb in the visible region, and upon protonation (pH700 nm). The conversion is reversible and depends solely on pH conditions.