Affinity Studies of Hemicyanine Derived Water Soluble Colorimetric Probes with Reactive Oxygen/Nitrogen/Sulfur Species

Abstract Peroxynitrite (ONOO ‐ ) is an essential endogenous reactive oxygen species (ROS) generated in mitochondria under various pathological and physiological conditions. An increase in its level in mitochondria is related to numerous diseases. Herein, we report a series of hemicyanine‐derived water‐soluble colorimetric probes ( 1 – 4 ) and the reactivity of which was studied with various reactive oxygen, nitrogen, and sulfur species. Probes 1 – 4 are formed by conjugating 1,2,3,3‐tetramethyl‐3 H ‐indolium iodide and 4‐hydroxybenzaldehyde or its derivatives through an alkene linkage formed by the Knoevenagel reaction. Oxidative cleavage of the electron‐rich double bond of the conjugated hemicyanine dye revealed a discerning affinity of probe 3 towards peroxynitrite among all reactive oxygen species. The rapid change in color of 3 provides a sensitive and selective method for detecting peroxynitrite with a low detection limit of 180 nM. Notably, the water solubility of the probe displays excellent performance for the selective detection of peroxynitrite among ROS and reactive nitrogen (RNS)/sulfur species (RSS). UV‐vis, 1 H NMR, and 13 C NMR spectroscopic data and results from theoretical calculations provide further information on the interaction of peroxynitrite with probe 3 .