The crystal structures of rac- and Λ-[MIII(tn) 3]P3O9·nH2O (M = Co, Cr; tn = 1,3-diaminopropane = trimethylenediamine; P3O9 = cyclotriphosphate(3-)) were determined by single-crystal X-ray analyses. In rac-[Co(tn)3]P3O9·7.3H2O, the [Co(tn)3]3+ cations with the same absolute configuration (Δ or Λ) and the P3O93- anions are alternately arrayed and connected by multiple NH⋯O hydrogen bonds to form a homochiral columnar structure. Adjacent homochiral columns with opposite chirality are connected by intercolumn hydrogen bonds to form a racemic pair of columns. The crystal structure of rac-[Cr(tn)3]P3O 9·7.5H2O is similar to that of the Co complex; however, there exist two types of racemic pairs of columns. In the crystal of Λ-[Co(tn)3]P3O9·2.5H 2O, a pair of columns consisting of alternately stacked Λ-[Co(tn)3]3+ cations and P3O 93- anions are linked by hydrogen bonds. Neighboring column pairs are further linked by hydrogen bonds to form a three-dimensional (3-D) sheet structure. The crystal structure of Λ-[Cr(tn) 3]P3O9·2.5H2O is isomorphous with the Co complex. The circular dichroism (CD) spectra of aqueous solutions of Λ-[M(tn)3]Br3 (M = Co, Cr) change when P 3O93- is added, and the changes were explained by ion pair formation through hydrogen bonds.
ASJC Scopus subject areas
- Materials Chemistry