Oxygen Atom Replacement in Coumarins: A Strategy to Tune Spectral Properties

Abstract Coumarins are highly polarized fluorophores with indispensable use in various applications, such as bioimaging, sensing, and optoelectronics, due to their inherent merits of tunable photophysical properties. Despite their established utility, ongoing research aims to further enhance and diversify their emission characteristics. Recent studies have demonstrated that strategic modifications, such as element replacement within the coumarin core, can significantly alter key attributes like absorption, emission, and quantum yields, all while preserving the fundamental benefits of their skeletal framework. This concept article highlights the latest progress in heteroatom substitution, including oxygen‐to‐nitrogen, silicon, sulfur, and carbon replacements, showcasing their impact on spectral tuning and their potential for the design of next‐generation fluorophores.