Evaluating the electronic structure of formal LnII ions in LnII(C5H4SiMe3)31- using XANES spectroscopy and DFT calculations

Megan E. Fieser, Maryline G. Ferrier, Jing Su, Enrique Batista, Samantha K. Cary, Jonathan W. Engle, William J. Evans, Juan S. Lezama Pacheco, Stosh A. Kozimor, Angela C. Olson, Austin J. Ryan, Benjamin W. Stein, Gregory L. Wagner, David H. Woen, Tonya Vitova, Ping Yang

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The isolation of [K(2.2.2-cryptand)][Ln(C5H4SiMe3)3], formally containing LnII, for all lanthanides (excluding Pm) was surprising given that +2 oxidation states are typically regarded as inaccessible for most 4f-elements. Herein, X-ray absorption near-edge spectroscopy (XANES), ground-state density functional theory (DFT), and transition dipole moment calculations are used to investigate the possibility that Ln(C5H4SiMe3)31- (Ln = Pr, Nd, Sm, Gd, Tb, Dy, Y, Ho, Er, Tm, Yb and Lu) compounds represented molecular LnII complexes. Results from the ground-state DFT calculations were supported by additional calculations that utilized complete-active-space multi-configuration approach with second-order perturbation theoretical correction (CASPT2). Through comparisons with standards, Ln(C5H4SiMe3)31- (Ln = Sm, Tm, Yb, Lu, Y) are determined to contain 4f6 5d0 (SmII), 4f13 5d0 (TmII), 4f14 5d0 (YbII), 4f14 5d1 (LuII), and 4d1 (YII) electronic configurations. Additionally, our results suggest that Ln(C5H4SiMe3)31- (Ln = Pr, Nd, Gd, Tb, Dy, Ho, and Er) also contain LnII ions, but with 4fn 5d1 configurations (not 4fn+1 5d0). In these 4fn 5d1 complexes, the C3h-symmetric ligand environment provides a highly shielded 5d-orbital of a′ symmetry that made the 4fn 5d1 electronic configurations lower in energy than the more typical 4fn+1 5d0 configuration.

Original languageEnglish (US)
Pages (from-to)6076-6091
Number of pages16
JournalChemical Science
Issue number9
StatePublished - 2017

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    Fieser, M. E., Ferrier, M. G., Su, J., Batista, E., Cary, S. K., Engle, J. W., Evans, W. J., Lezama Pacheco, J. S., Kozimor, S. A., Olson, A. C., Ryan, A. J., Stein, B. W., Wagner, G. L., Woen, D. H., Vitova, T., & Yang, P. (2017). Evaluating the electronic structure of formal LnII ions in LnII(C5H4SiMe3)31- using XANES spectroscopy and DFT calculations. Chemical Science, 8(9), 6076-6091. https://doi.org/10.1039/c7sc00825b