title: O-H...O interactions involving doubly charged anions: charge compression in carbonate-bicarbonate crystals.
abstract: The O-H...O interaction formed by the anions HCO(3)(-) and CO(3)(2-) has been investigated on the basis of data retrieved from the Inorganic Crystal Structure Database (ICSD) and by means of ab initio computations. It has been shown that the O-H...O separations associated with HCO(3)(-)...(3)(2-) interactions are shorter than those found in crystals containing hydrogen carbonate monoanions such as HCO(3)(-)...HCO(3)(-). Ab initio MP2/6-311G++(2d,2p) computations on the crystal Na(3)(HCO(3))(CO(3)).2H(2)O have shown that the interaction between the monoanion donor and the dianion acceptor, for example HCO(3)(-)...CO(3)(2-), is more repulsive than that between singly charged ions, for example HCO(3)(-)...HCO(3)(-), but is largely overcompensated for by anion-cation electrostatic attractions. The shortening of the (-)O-H...O(2-) interaction relative to the (-)O-H...O(-) interaction has been explained as a consequence of the increased charge compression, that is of the stronger cation-anion interactions established by the CO(3)(2-) dianions with respect to those established by monoanions, and does not reflect an increase in the strength of the (-)O-H ...O(-) interaction. To expand the structural sample in the crystal packing analysis, the structure of the novel mixed salt K(2)Na(HCO(3))(CO(3)).2H(2)O has been determined by single-crystal X-ray diffraction and compared with the structure of the salt Na(3)(HCO(3))(CO(3)).2H(2)O used in the computations.
authors.affiliation: Department of Chemistry G. Ciamician, University of Bologna, 40126 Bologna, Italy. dbraga@ciam.unibo.it
authors.forename: Dario
authors.initials: D
authors.lastname: Braga
authors.forename: Emiliana
authors.initials: E
authors.lastname: D'Oria
authors.forename: Fabrizia
authors.initials: F
authors.lastname: Grepioni
authors.forename: Fernando
authors.initials: F
authors.lastname: Mota
authors.forename: Juan J
authors.initials: JJ
authors.lastname: Novoa
authors.forename: Concepció
authors.initials: C
authors.lastname: Rovira