title: Intermediate-valence tautomerism in decamethylytterbocene complexes of methyl-substituted bipyridines.
abstract: Multiconfigurational, intermediate valent ground states are established in several methyl-substituted bipyridine complexes of bis(pentamethylcyclopentadienyl)ytterbium, Cp2*Yb (Me(x)-bipy). In contrast to Cp2*Yb(bipy) and other substituted-bipy complexes, the nature of both the ground state and the first excited state are altered by changing the position of the methyl or dimethyl substitutions on the bipyridine rings. In particular, certain substitutions result in multiconfigurational, intermediate valent open-shell singlet states in both the ground state and the first excited state. These conclusions are reached after consideration of single-crystal X-ray diffraction (XRD), the temperature dependence of X-ray absorption near-edge structure (XANES), extended X-ray absorption fine-structure (EXAFS), and magnetic susceptibility data, and are supported by CASSCF-MP2 calculations. These results place the various Cp2*Yb(bipy) complexes in a new tautomeric class, that is, intermediate-valence tautomers.
authors.affiliation: Chemical Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA. chbooth@lbl.gov
authors.forename: Corwin H
authors.initials: CH
authors.lastname: Booth
authors.forename: Daniel
authors.initials: D
authors.lastname: Kazhdan
authors.forename: Evan L
authors.initials: EL
authors.lastname: Werkema
authors.forename: Marc D
authors.initials: MD
authors.lastname: Walter
authors.forename: Wayne W
authors.initials: WW
authors.lastname: Lukens
authors.forename: Eric D
authors.initials: ED
authors.lastname: Bauer
authors.forename: Yung-Jin
authors.initials: YJ
authors.lastname: Hu
authors.forename: Laurent
authors.initials: L
authors.lastname: Maron
authors.forename: Odile
authors.initials: O
authors.lastname: Eisenstein
authors.forename: Martin
authors.initials: M
authors.lastname: Head-Gordon
authors.forename: Richard A
authors.initials: RA
authors.lastname: Andersen