Abstract and subjects
The synthesis, electronic structure, and characterization via single-crystal X-ray diffraction, nuclear magnetic resonance (NMR) spectroscopy, and magnetic susceptibility of (Me4N)(2)PuCl6 are reported. NMR measurements were performed to both search for the direct Pu-239 resonance and to obtain local magnetic and electronic information at the Cl site through Cl-35 and Cl-37 spectra. No signature of Pu-239 NMR was observed. The temperature dependence of the Cl spectra was simulated by diagonalizing the Zeeman and quadrupolar Hamiltonians for Cl-35, Cl-37, and N-14 isotopes. Electronic structure calculations predict a magnetic Gamma(5) triplet ground state of Pu(IV) in the crystalline electric field of the undistorted PuCl6 octahedron. A tetragonal distortion would result in a very small splitting (similar to 20 cm(-1)) of the triplet ground state into a nonmagnetic singlet and a doublet state. The Cl shifts have an inflection point at T approximate to 15 K, differing from the bulk susceptibility, indicating a nonmagnetic crystal field ground state. The Cl spin-lattice relaxation time is constant to T = 15 K, below which it rapidly increases, also supporting the nonmagnetic crystal field ground state.