title: Does the 4f electron configuration affect molecular geometries? A joint computational, vibrational spectroscopic, and electron diffraction study of dysprosium tribromide.
abstract: The molecular geometry and vibrational frequencies of monomeric and dimeric dysprosium tribromide, DyBr(3) and Dy(2)Br(6), together with the electronic structure of their ground and first few excited-state molecules were determined by high-level computations, electron diffraction, gas-phase infrared, and matrix isolation infrared and Raman spectroscopy. The effect of partially filled 4f orbitals and spin-orbit coupling on their structure was studied by computations. While the geometry of the monomer does not depend on the 4f orbital occupation, the bond angles of the dimer are noticeably influenced by it. The monomer is found to be planar from all methods; the suggested equilibrium bond length of the molecule (r(e)) is 2.591(8) A, while the thermal average distance (r(g)) is 2.606(8) A. Although the gas-phase DyBr(3) molecule is planar, it forms a complex with the matrix molecules in the matrix-isolation spectroscopic experiments, leading to the pyramidalization of the DyBr(3) unit. Our model calculations in this regard also explain the often conflicting results of computations and different experiments about the shape of lanthanide trihalides.
authors.affiliation: Materials Structure and Modeling Research Group of the Hungarian Academy of Sciences, Budapest University of Technology and Economics, P.O. Box 91, 1521 Budapest, Hungary.
authors.forename: Cornelis Petrus
authors.initials: CP
authors.lastname: Groen
authors.forename: Zoltán
authors.initials: Z
authors.lastname: Varga
authors.forename: Mária
authors.initials: M
authors.lastname: Kolonits
authors.forename: Kirk A
authors.initials: KA
authors.lastname: Peterson
authors.forename: Magdolna
authors.initials: M
authors.lastname: Hargittai