REDOX PROPERTIES OF THE DIATOMIC BARE IRON CHALCOGENIDES FEO AND FES IN THE GAS-PHASE

The electron-transfer behavior of the binary iron chalcogenides FeO an d FeS has been examined by means of mass spectrometry and ab initio ca lculations using the averaged coupled-pair functional (ACPF) method. T he experimental and theoretical results are in good agreement with eac h other and also with previous studies, The ionization energies (IE) o f the diatomic species are found to be IE(FeO) = 8.8 +/- 0.2 eV, IE(FE O(+)) = 17.9 +/- 0.4 eV, IE(FeS) = 8.3 +/- 0.3 eV, and IE(FeS+) = 16.3 +/- 0.5 eV. Two new diatomic dications, FeS2+ and FeO2+, are shown to exist as metastable minima on the corresponding potential-energy surf aces, The data enable an evaluation of the intrinsic gas-phase redox p roperties of FeS and FeO, and the comparison demonstrates that iron su lfide is more prone to undergo facile reduction and oxidation than iro n oxide.