Gas-phase reactivity of hexanuclear molybdenum [Mo6I14]2- and its photo-fragments towards O2 and CO2: combined mass spectrometry (MSn) and quantum chemical simulations

Abstract

The optical properties, photo-decomposition and photo-reactivity of [Mo₆I₁₄]^2- clusters and associated photo-products are examined in the gas phase. The UV-visible optical spectrum of the electron-rich [Mo₆I₁₄]^2- cluster is measured and the wavelength dependence of the principal fragments is interpreted on the basis of the quantum chemistry (QC) simulated spectrum and detailed transitions. A special focus is made on the photo-generated [Mo₆I₁₄]^1- and photo-specific radical [Mo₆I₁₃]^2-• as well as on halogen-depleted clusters [Mo₆I_n]^1- with n<14. The fragmentation and reaction energetics of all species are examined with a combination of mass spectrometry experiments, ion-molecule reactions with O₂ and CO₂ under irradiation and QC simulations. Reactions with O₂ are shown to be very exergonic with up to 5 eV release when O₂ is dissociated on the cluster. Experimental evidences for the photo-decomposition of CO₂ into CO and O on [Mo₆I_n]^1- ions are provided together with detailed QC energetics.