Luminescence and Generation of Reactive Oxygen Species in Solution by TaBr Clusters.

An intrinsic metal cluster NIR-II emission of the {TaBr} aqua/hydroxocomplexes was determined in aqueous solutions under inert atmosphere. The photoluminescence (PL) is enhanced in DO, and the lifetime scale expands from nanoseconds to microseconds. Possible cluster emission transitions have been assigned and analyzed from a computational perspective. In the presence of O, the cluster compound kept its robustness but showed partial quenching of the PL. Stern-Volmer and laser-flash photolysis studies confirmed that quenching is mainly associated with O diffusion. Laser-flash photolysis experiments showed that singlet oxygen (O) was not detected under measurement conditions. Generation of peroxide and superoxide radical species after irradiation in DO was confirmed by using luminol as a probe, whereas no hydroxide radical species were detected as evidenced by the emission of the 3-coumarin carboxylic acid (3-CCA) molecular sensor.