Geometric and Electronic Structures of Multiple-Decker One-End Open Sandwich Clusters:  Eu_n(C₈H₈)_n^- (n = 1−4)

Abstract

We have measured the photoelectron spectra of the multiple-decker 1:1 sandwich clusters of Eu(n)(COT)n- (n = 1-4; COT = 1,3,5,7-cyclooctatetraene), synthesized in the gas phase, and studied theoretically the bonding scheme, charge distribution, valence orbital energies, and photodetachment energies. We calculated the ground electronic state X- and the first excited electronic state A-, both of which have strong ionic bonding and a characteristic charge distribution. Moreover, we found that the valence orbital energies of Eu (6s) and COT (L delta) depend strongly on cluster size and their positions in the clusters. With the calculated vertical detachment energies for these valence orbitals, we assigned the peaks in the experimental photoelectron spectra and analyzed the origin of their interesting behavior by employing simple point charge models. From these analyses, it became clear that the characteristic behavior of the spectra is due to the strong ionic bonding and the charge distribution. In addition, using the point charge models, we estimated the vertical detachment energies of the one-dimensional polymer [Eu(COT)]infinity-.

Controlling the Magnetization Direction in Molecules via Their Oxidation State

“…Our calculations confirm that the structures of the Eu 2 C 8 H 8 3 molecule and its ionic species are sandwiches with the metal atom above the center of gravity of C 8 H 8 ligand molecules [8][9][10] anion for which the energy difference between FM and AFM magnetic states vanishes.…”

“…The charge-difference plots of the molecule against the sum of the separated systems, Eu 2 and C 8 H 8 3 , together with the analysis of the charge transfer in or out of the pseudopotential spheres confirm a strong ionic character of the bonding between Eu and C 8 H 8 ligands [8][9][10]18]. The Eu 6s electrons are transferred to an aromatic type molecular orbital characterized by a high density of states of the C sites; therefore, the Eu atom can formally be seen as a 2 positive ion [10].…”

“…The photoelectron spectra for the Eu n C 8 H 8 ÿ1 n1 n 1-7 sandwiches show a photodetachment contribution of 4f orbitals between 3.0 -4.0 eV [8,10]. More precisely, a value of 3.7 eV corresponds to the photodetachment energy in one-end double sandwich anion Eu 2 C 8 H 8 1ÿ 2 [10]. Here we present the results with the U 3:7 eV, but we have carefully checked the consistency of our results for a set of U values between PRL 100, 117207 (2008) …”

“…In order to take into account the proper orbital dependence of the Coulomb and exchange interaction we employed the LDA U method in treating the Eu 4f states [15], which improves not only the description of the ground state properties such as magnetic moments and interatomic exchange parameters, but also excited states and energy gaps [15,16]. The photoelectron spectra for the Eu n C 8 H 8 ÿ1 n1 n 1-7 sandwiches show a photodetachment contribution of 4f orbitals between 3.0 -4.0 eV [8,10]. More precisely, a value of 3.7 eV corresponds to the photodetachment energy in one-end double sandwich anion Eu 2 C 8 H 8 1ÿ 2 [10].…”

“…The Eu 6s electrons are transferred to an aromatic type molecular orbital characterized by a high density of states of the C sites; therefore, the Eu atom can formally be seen as a 2 positive ion [10].…”