Applications of Luminescent Cyclometalated Metal Complexes as Sensors and Switches

Abstract Cyclometalated complexes, including those with pincer ligands and other chelating frameworks, such as porphyrin rings and polyenes, have garnered significant attention due to their diverse applications in ion and analyte detection across synthetic chemistry, environmental monitoring, medicine, and electronics. These complexes exhibit fascinating chromic behaviors, including mechanochromism, chemochromism, and vapochromism, which are particularly useful in sensing applications. Of particular interest are their photophysical properties, especially in complexes involving lanthanides, which offer unique luminescent and optical characteristics. Metals such as nickel (Ni), palladium (Pd), ruthenium (Ru), gold (Au), and rhodium (Rh) have been extensively studied in order to understand their photochemical activity and to explore their potential applications in light-emitting devices, photo-induced electron transfer, and sensing technologies. Their vapochromic and mechanochromic properties make them highly attractive for environmental sensing, while their photoluminescent capabilities enhance their utility in optoelectronic devices and practical electronics. This review provides a comprehensive overview of their applications, including gas, cation, and anion sensing. The discussion also highlights the need to incorporate specific examples that demonstrate the unique properties and suitability of these complexes for targeted sensing tasks, further emphasizing their promise in advancing sensor and device technologies. 1 Introduction 2 Strategies 3 Applications 4 Other Miscellaneous Examples 5 Drawbacks and Limitations 6 Conclusion and Perspectives 7 List of Abbreviations and Definitions