The intramolecular self-healing strategy applied to near infrared fluorescent aminotricarbocyanines

We present the synthesis and photophysical studies of three novel near-infrared (NIR) aminotricarbocyanine derivatives with self-contained antioxidant moieties, gallic acid and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox). The aim of this work is to apply the intramolecular self-healing strategy to water soluble aminotricarbocyanines exploring the effect of the direct attachment of an antioxidant moiety to the fluorophore core. The synthesized dyes also include a functional group (-COOH) in their chemical structure for further (bio)conjugation of the fluorescent probe to biomolecules or surfaces. The photostability of the dyes was investigated spectroscopically in cuvette experiments as well as microscopically in dye embedded PMMA films. The rigid heptamethine modified dyes show enhanced photostability in aqueous and non-aqueous air-saturated environments by means of a self-healing process through redox quenching of reactive intermediates from excited states.