Leveraging Metal Complexes for Microsecond Lifetime-Based Chloride Sensing

Chloride is the most abundant anion in cell physiology and plays many critical roles in maintaining cellular homeostasis. However, current chloride sensors are rare, with inherent sensitivity in their emission properties, such as vulnerability to pH changes or short emission lifetimes. These limitations restrict their application in aqueous media and imaging. In this work, we employed a transition metal complex bearing pyridinium as a recognition unit for chloride and studied the phosphorescence emission properties. Iridium(III) complex 1 was synthesized as an alternative chloride-sensitive luminophore. The conjugable design also allows customization for desired applications. Complex 1 exhibited high sensitivity and selectivity in chloride sensing across different physiological environments, regardless of pH fluctuation and ionic strength. Additionally, complex 1 featured a long microsecond emission lifetime. The chloride sensing ability of complex 1 can be measured through both luminescence intensity and long-lived phosphorescent lifetime simultaneously, providing an alternative potential route for chloride imaging.