Brightening New Horizons: Luminescent Transition Metal Complexes in Optical Imaging and Theranostic Applications

Small-molecule fluorescent probes have revolutionized fluorescence imaging in both biological research and clinical applications, allowing the exploration of intricate cellular processes and aiding disease diagnosis and treatment. Advances in the designs of molecular probes have led to the development of fluorescent theranostics that combine therapeutic and diagnostic modalities in a single platform. These dual-functional agents enable simultaneous disease diagnosis, treatment, and monitoring, representing an innovative approach to precision medicine. Luminescent transition metal complexes have emerged as promising alternatives to traditional organic fluorophores for optical imaging and theranostic applications, and they offer distinctive advantages such as high photostability, long emission lifetimes, and efficient generation of reactive oxygen species. In this Outlook, we highlight emerging trends in the designs and applications of luminescent transition metal complexes as optical imaging and theranostic agents, leveraging their unique photophysical and photochemical properties. We also discuss current challenges to the clinical applications of these complexes and outline potential directions to inspire the development of next-generation theranostics for advancing disease management and improving patient care.