Engineering high-performance dicyanomethylene-4H-pyran fluorophores for biosensing and phototherapy

Near-infrared (NIR) fluorescence imaging, with its deep tissue penetration, reduced autofluorescence, and improved signal-to-noise ratios, offers immense potential for in vivo applications including biomolecule sensing, cancer research, and drug delivery. The development of high-stable and bright NIR fluorophores is in high demand for precise biosensing and imaging. Dicyanomethylene-4H-pyran (DCM) derivatives, firstly introduced in 1989 as a highly fluorescent dopant for the development of red organic light-emitting diodes, have emerged as versatile fluorophores with excellent properties, including high sensitivity, long emission wavelength to the NIR region, and high fluorescent yield. In this review, we focus on recent advances in engineering DCM-based fluorophores for NIR biosensing and phototherapy. Specifically, we discuss the DCM dyes' structure–property relationship for extending the emission wavelength and enhancing emission intensity in molecular or aggregate state, and strategies for modulating the excited states of DCM chromophores to develop activatable (including off–on activation, ratiometric sensing, and high-fidelity labeling) fluorescent/chemiluminescent probes. We also discuss how to regulate intersystem crossing and excited-state intramolecular motion of DCM chromophores to enhance the efficiency of phototherapy. It is hoped that this review provides deepening of research on DCM chromophores for the development of novel high-performance NIR probes for physiological/pharmacological studies and clinical applications.