The coordination structures of the Cu ions in the mixed solvent system of HCONH2-HCOONH4 at room temperature and 100 °C have been investigated using the EXAFS (extended X-ray absorption fine structure) method for the Cu K-edge, together with visible absorption spectrum analyses and ion-exchange experiments. The Cu ions, which are divalent, CuII, at room temperature, are reduced to univalence, CuI, by heating with HCOO- ions, ca. 80% of CuII ions are transformed into CuI, ions at 100 °C. In the mixed solvent system, it was found that CuII ions form neutral [Cu(HCOO)2(HCONH2)4] octahedra, distorted by the Jahn-Teller effect, with four short Cu-O bond lengths of ca. 1.97 Å and two long Cu-O bond lengths of ca. 2.82 Å at room temperature, and CuI ions form cationic [Cu(HCONH2)3]+ plane triangles with three Cu-O bond lengths of ca. 1.90 Å at 100 °C. The transition of the coordination structures occurs reversibly in the mixed solvent system as a function of the temperature.
|Number of pages||7|
|Journal||Journal of the Chemical Society, Faraday Transactions 2: Molecular and Chemical Physics|
|Publication status||Published - 1989|
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Physical and Theoretical Chemistry