Examinando por Autor "Baumbach, Ryan E."

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    Creation of an unexpected plane of enhanced covalency in cerium(III) and berkelium(III) terpyridyl complexes
    (Nature Research, 2021-12) Gaiser, Alyssa N.; Celis-Barros, Cristian; White, Frankie D.; Beltran-Leiva, Maria J.; Sperling, Joseph M.; Salpage, Sahan R.; Poe, Todd N.; Gomez Martinez, Daniela; Jian, Tian; Wolford, Nikki J.; Jones, Nathaniel J.; Ritz, Amanda J.; Lazenby, Robert A.; Gibson, John K.; Baumbach, Ryan E.; Páez-Hernández, Dayán; Neidig, Michael L.; Albrecht-Schönzart, Thomas E.
    Controlling the properties of heavy element complexes, such as those containing berkelium, is challenging because relativistic effects, spin-orbit and ligand-field splitting, and complex metal-ligand bonding, all dictate the final electronic states of the molecules. While the first two of these are currently beyond experimental control, covalent M‒L interactions could theoretically be boosted through the employment of chelators with large polarizabilities that substantially shift the electron density in the molecules. This theory is tested by ligating BkIII with 4’-(4-nitrophenyl)-2,2’:6’,2”-terpyridine (terpy*), a ligand with a large dipole. The resultant complex, Bk(terpy*)(NO3)3(H2O)·THF, is benchmarked with its closest electro chemical analog, Ce(terpy*)(NO3)3(H2O)·THF. Here, we show that enhanced Bk‒N inter actions with terpy* are observed as predicted. Unexpectedly, induced polarization by terpy* also creates a plane in the molecules wherein the M‒L bonds trans to terpy* are shorter than anticipated. Moreover, these molecules are highly anisotropic and rhombic EPR spectra for the CeIII complex are reported.
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    Electronic Structure and Properties of Berkelium Iodates
    (Journal, 2017-09) Silver, Mark A.; Cary, Samantha K.; Garza, Alejandro J.; Baumbach, Ryan E.; Arico, Alexandra A.; Galmin, Gregory A.; Chen, Kuan-Wen; Johnson, Jason A.; Wang, Jamie C.; Clark, Ronald J.; Chemey, Alexander; Eaton, Teresa M.; Marsh, Matthew L.; Seidler, Kevin; Galley, Shane S.; Van De Burgt, Lambertus; Gray, Ashley L.; Hobart, David E.; Hanson, Kenneth; Van Cleve, Shelley M.; Gendron, Frédéric; Autschbach, Jochen; Scuseria, Gustavo E.; Maron, Laurent; Speldrich, Manfred; Kögerler, Paul; Celis-Barros, Cristian; Páez-Hernández, Dayán; Arratia-Pérez, Ramiro; Ruf, Michael; Albrecht-Schmitt, Thomas E.
    The reaction of 249Bk(OH)4 with iodate under hydrothermal conditions results in the formation of Bk(IO3)3 as the major product with trace amounts of Bk(IO3)4 also crystallizing from the reaction mixture. The structure of Bk(IO3)3 consists of nine-coordinate BkIII cations that are bridged by iodate anions to yield layers that are isomorphous with those found for AmIII, CfIII, and with lanthanides that possess similar ionic radii. Bk(IO3)4 was expected to adopt the same structure as M(IO3)4 (M = Ce, Np, Pu), but instead parallels the structural chemistry of the smaller ZrIV cation. BkIII-O and BkIV-O bond lengths are shorter than anticipated and provide further support for a postcurium break in the actinide series. Photoluminescence and absorption spectra collected from single crystals of Bk(IO3)4 show evidence for doping with BkIII in these crystals. In addition to luminescence from BkIII in the Bk(IO3)4 crystals, a broad-band absorption feature is initially present that is similar to features observed in systems with intervalence charge transfer. However, the high-specific activity of 249Bk (t1/2 = 320 d) causes oxidation of BkIII and only BkIV is present after a few days with concomitant loss of both the BkIII luminescence and the broadband feature. The electronic structure of Bk(IO3)3 and Bk(IO3)4 were examined using a range of computational methods that include density functional theory both on clusters and on periodic structures, relativistic ab initio wave function calculations that incorporate spin-orbit coupling (CASSCF), and by a full-model Hamiltonian with spin-orbit coupling and Slater-Condon parameters (CONDON). Some of these methods provide evidence for an asymmetric ground state present in BkIV that does not strictly adhere to Russel-Saunders coupling and Hund's Rule even though it possesses a half-filled 5f 7 shell. Multiple factors contribute to the asymmetry that include 5f electrons being present in microstates that are not solely spin up, spin-orbit coupling induced mixing of low-lying excited states with the ground state, and covalency in the BkIV-O bonds that distributes the 5f electrons onto the ligands. These factors are absent or diminished in other f7 ions such as GdIII or CmIII. © 2017 American Chemical Society.