Electronic structure and reactivity of a biradical cluster: Sc3O6−

Abstract

The Sc₃O₆⁻ cluster anions were produced by laser ablation and studied by reaction with n-butane in a fast flow reactor and by photoelectron spectroscopy. The reactivity experiments indicated that one Sc₃O₆⁻ cluster can activate two n-butane molecules consecutively with rate constants on the order of 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹ under near room-temperature conditions, suggesting that the even-electron system Sc₃O₆⁻ has a highly reactive electronic structure. The photoelectron spectroscopy determined a high vertical detachment energy (VDE) of 5.63 ± 0.08 eV for the Sc₃O₆⁻ cluster. Density functional computations indicated that the lowest energy isomer of Sc₃O₆⁻ is an oxygen-centered biradical with a high VDE and is highly reactive toward n-butane, which is in good agreement with the experiments. The Sc₃O₆⁻ cluster may serve as an ideal model system to provide insight into the real-life chemistry involved with the coupled O⁻˙⋯O⁻˙ dimers over the surfaces of metal oxide catalysts.