Photoejection–recapture of the Ca2+ cation studied by time resolved spectroscopy and TDDFT calculations: the case study of an azacrown–iridium(III) complex

In this study, we examined the photophysical properties of an azacrown–iridium(III) complex while focusing on its interactions with calcium ions (Ca2+). We explored the dynamic processes within the complex combining time-dependent density functional theory (TDDFT) calculations and time-resolved spectroscopies. In the presence of Ca2+, the complex exhibits significant shifts in absorption and emission profiles, from 494 nm to 375 nm, aligning with theoretical predictions. Notably, we observed the ultrafast photo-ejection of Ca2+ within 70 femtoseconds, followed by its recapture in 250 nanoseconds, revealing a 10-million-fold timescale difference between the two phenomena. These behaviors confirm the established photophysical properties of polypyridyl iridium(III) complexes and their intrinsic sensitivity to their surrounding environment. Our comprehensive kinetic analysis highlights the azacrown moiety's competitive binding and photo-release capabilities, suggesting its potential for practical sensing applications. The versatile properties of these iridium(III) complexes offer promising prospects for their application as stimuli-responsive materials and in advanced optoelectronic devices, targeted imaging, and biomedical ion sensors and delivery systems.