Water activation and splitting by single anionic iridium atoms

Mass spectrometric analysis of anionic products that result from interacting Ir− with H2O shows the efficient generation of [Ir(H₂O)]⁻ complexes and IrO⁻ molecular anions. Anion photoelectron spectra of [Ir(H₂O)]⁻, formed under various source conditions, exhibit spectral features that are due to three different forms of the complex: the solvated anion–molecule complex, Ir⁻(H₂O), as well as the intermediates, [H–Ir–OH]⁻ and [H₂–Ir–O]⁻, where one and two O–H bonds have been broken, respectively. The measured and calculated vertical detachment energy values are in good agreement and, thus, support identification of all three types of isomers. The calculated reaction pathway shows that the overall reaction Ir⁻ + H₂O → IrO⁻ + H₂ is exothermic. Two minimum energy crossing points were found, which shuttle intermediates and products between singlet and triplet potential surfaces. This study presents the first example of water activation and splitting by single Ir⁻ anions.