Rational Development of Near-Infrared Fluorophores with Large Stokes Shifts, Bright One-Photon, and Two-Photon Emissions for Bioimaging and Biosensing Applications.

Fluorophores with near-infrared emissions play a crucial role in numerous bioimaging and biosensing applications, owing to their deep penetration depths, low auto-fluorescence, and minimal tissue damages. Herein, the rational development of a new class of near-infrared fluorophores with bright one-photon and two-photon emissions at ≈740 nm, large Stokes shifts (≈80 nm), significant two-photon action absorption cross-section (≈185 GM at 820 nm), excellent water solubility, outstanding photostability, and low toxicity is reported. Their biological applications in mitochondrial labelling, deep tissue imaging, and H2 S detection in live cells and mice are also demonstrated. In addition, a rational design strategy for enlarging the Stokes shifts and enhancing two-photon emissions of these fluorophores is presented. These fluorophores will serve as a useful platform for developing novel imaging and sensing agents, and the design methodologies will inspire the molecular engineering of abundant high-performance near-infrared fluorophores.