title: Homochiral column structure of rac- and lambda-tris(ethylenediamine)cobalt(III) cyclotriphosphate dihydrate in crystal structures and cation-anion association in aqueous solution.
abstract: rac- and Lambda-tris(ethylenediamine)cobalt(III) cyclotriphosphate dihydrate with the chemical formulas rac-[Co(en)(3)]P(3)O(9).2H(2)O (1) and Lambda-[Co(en)(3)]P(3)O(9).2H(2)O (2) were synthesized, and their crystal structures were determined by single-crystal X-ray analyses. In 1, the cationic complex molecule [Co(en)(3)](3+) with the Delta or Lambda enantiomer and cyclotriphosphate anion are alternately arrayed and connected by multiple hydrogen bonds to form a homochiral column structure. Adjacent homochiral columns with different chirality for 1 are connected by intercolumn hydrogen bonds through P(3)O(9)(3)(-) anions, as the bridging groups, to form a tetrameric cyclic cylindrical structure, while the adjacent columns with the same chirality are connected for 2 to form the cyclic cylindrical structure. All 6 amino groups per [Co(en)(3)](3+) participate in the formation of 12 hydrogen bonds, in which 8 hydrogen bonds contribute to the construction of a homochiral column and the remaining 4 hydrogen bonds contribute to the intercolumn interactions. The circular dichroism spectrum of the aqueous solution of Lambda-[Co(en)(3)](3+) changes drastically when excess P(3)O(9)(3)(-) is added, and this change is explained by ion-pair formation. The thermodynamic association constant of [Co(en)(3)](3+) with P(3)O(9)(3)(-), calculated from the conductivity data, was log K = 4.26 at 25 degrees C.
authors.affiliation: Department of Chemistry, Faculty of Education and Welfare Science, Oita University, Dan-noharu, Oita 870-1192, Japan.
authors.forename: Toshio
authors.initials: T
authors.lastname: Nakashima
authors.forename: Junichi
authors.initials: J
authors.lastname: Mishiro
authors.forename: Masami
authors.initials: M
authors.lastname: Ito
authors.forename: Genichiro
authors.initials: G
authors.lastname: Kura
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Ikuta
authors.forename: Naohide
authors.initials: N
authors.lastname: Matsumoto
authors.forename: Kiyohiko
authors.initials: K
authors.lastname: Nakajima
authors.forename: Masaaki
authors.initials: M
authors.lastname: Kojima