Quantum Chemical Study of the Neutral and Ionised DyX, DyX2 and DyX3 Species, X=F,Cl,Br,I, and the Implications for Mass Spectra of DyX3(g)

The mass spectrum pattern of DyF3(g) and the appearance potentials for identified ions were measured and compared with the respective data obtained previously for DyCl3, DyBr3, and DyI3. The structural parameters, total energies, and vibrational frequencies of DyX3, DyX2, and DyX (X = F, Cl, Br, I) neutral and single ionized species were determined by quantum-chemical studies. The theoretical appearance potentials of different ions, calculated from energies of gaseous species, are in the good agreement with the experimental data. Fragmentation energies of the DyXn+ ion, where n = 1, 2, 3, were computed and compared with the mass spectra patterns of the respective vapour species. A theoretical electron population analysis indicates the involvement of the s and f valence electrons of Dy in the bond formation as well as in the ionization processes. The sigma-back donation from halogen atoms to the dysprosium center partially compensates the electron density loss. The ionization strengthens the bonding in the DyX and DyX2 molecules. The ionization of DyX3 destroys the C-3nu symmetrical structure due to the Jahn-Teller effect. Contrary to the other studied systems, the open shell character of DyX3+ arises not only from unpaired electrons of dysprosium but also from electron density on halogen atoms. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004