title: Structural polarity induced by cooperative hydrogen bonding and lone-pair alignment in the molecular uranyl iodate Na2[UO2(IO3)4(H2O)].
abstract: Na2[UO2(IO3)4(H2O)] has been synthesized under mild hydrothermal conditions. Its structure consists of Na+ cations and [UO2(IO3)4(H2O)](2-) anions. The [UO2(IO3)4(H2O)](2-) anions are formed from the coordination of a nearly linear uranyl, UO2(2+), cation by four monodentate IO(3-) anions and a coordinating water molecule to yield a pentagonal bipyramidal environment around the uranium center. The water molecules form intermolecular hydrogen bonds with the terminal oxo atoms of neighboring [UO2(IO3)4(H2O)](2-) anions to yield one-dimensional chains that extend down the b axis. There are two crystallographically unique iodate anions in the structure of Na2[UO2(IO3)4(H2O)]. One of these anions is aligned so that the lone-pair of electrons is also directed along the b axis. The overall structure is therefore polar, owing to the cooperative alignment of both the hydrogen bonds and the lone-pair of electrons on iodate. The polarity of the monoclinic space group C2 (a = 11.3810(12) A, b = 8.0547(8) A, c = 7.6515(8) A, beta = 90.102(2) degrees , Z = 2, T = 193 K) found for this compound is consistent with the structure. Second-harmonic generation of 532 nm light from a 1064 nm laser source yields a response of approximately 16x alpha-SiO2.
authors.affiliation: Department of Chemistry and Biochemistry, and E. C. Leach Nuclear Science Center, Auburn University, Auburn, Alabama 36849, USA.
authors.forename: Travis H
authors.initials: TH
authors.lastname: Bray
authors.forename: James V
authors.initials: JV
authors.lastname: Beitz
authors.forename: Amanda C
authors.initials: AC
authors.lastname: Bean
authors.forename: Yaqin
authors.initials: Y
authors.lastname: Yu
authors.forename: Thomas E
authors.initials: TE
authors.lastname: Albrecht-Schmitt