TY - JOUR

T1 - Vibrational spectroscopic and force field studies of copper(II) chloride and bromide compounds, and crystal structure of KCuBr3

AU - Stepakova, Liubov V.

AU - Skripkin, Mikhail Yu

AU - Chernykh, Lyudmila V.

AU - Starova, Galina L.

AU - Hajba, László

AU - Mink, János

AU - Sandström, Magnus

PY - 2008/1/1

Y1 - 2008/1/1

N2 - Vibrational spectroscopic and force field studies have been performed of 15 related copper(II) chloride and copper(II) bromide compounds, including hydrated salts crystallizing in ternary aqueous systems with alkali and ammonium halides. For halocuprates with distorted octahedral coordination characteristic stretching Raman wavenumbers, corresponding to symmetric stretching Cu II-X modes in the equatorial plane, were found in the ranges 247-288 cm-1 for X = Cl, and 173-189 cm-1 for X = Br, while the low-wavenumber stretching modes for the weaker axial Cu-X interactions varied considerably. The tetrahedral coordination for Cs2CuCl4 and Cs2CuBr4 leads to somewhat lower Cu-X symmetric stretching wavenumbers, 295 and 173 cm-1, respectively. The assignments of the copper-ligand stretching vibrations were performed with the aid of normal coordinate calculations. Correlations between force constants, averaged Cu-X stretching wavenumbers and bond distances have been evaluated considering the following aspects: (1) Jahn-Teller tetragonal distortion (axial elongation) of the octahedral copper(II) coordination environment, (2) differences between terminal and bridging halide ligands (3) effects of coordinated water and the influence of outer-sphere cations. Force constant ratios for terminal and bridging metal-halide bonds reveal characteristic differences between planar and tetrahedrally coordinated M2X 6 species. In the hydrated copper(II) halide complexes, the halide ligands are more strongly bound than coordinated water molecules. The crystal structure of KCuBr3 (K2Cu2Br6), which was determined to provide structural information for the force field analyses, contains stacks of planar dimeric [Cu2Br6] 2- complexes held together by weak axial Cu-Br interactions.

AB - Vibrational spectroscopic and force field studies have been performed of 15 related copper(II) chloride and copper(II) bromide compounds, including hydrated salts crystallizing in ternary aqueous systems with alkali and ammonium halides. For halocuprates with distorted octahedral coordination characteristic stretching Raman wavenumbers, corresponding to symmetric stretching Cu II-X modes in the equatorial plane, were found in the ranges 247-288 cm-1 for X = Cl, and 173-189 cm-1 for X = Br, while the low-wavenumber stretching modes for the weaker axial Cu-X interactions varied considerably. The tetrahedral coordination for Cs2CuCl4 and Cs2CuBr4 leads to somewhat lower Cu-X symmetric stretching wavenumbers, 295 and 173 cm-1, respectively. The assignments of the copper-ligand stretching vibrations were performed with the aid of normal coordinate calculations. Correlations between force constants, averaged Cu-X stretching wavenumbers and bond distances have been evaluated considering the following aspects: (1) Jahn-Teller tetragonal distortion (axial elongation) of the octahedral copper(II) coordination environment, (2) differences between terminal and bridging halide ligands (3) effects of coordinated water and the influence of outer-sphere cations. Force constant ratios for terminal and bridging metal-halide bonds reveal characteristic differences between planar and tetrahedrally coordinated M2X 6 species. In the hydrated copper(II) halide complexes, the halide ligands are more strongly bound than coordinated water molecules. The crystal structure of KCuBr3 (K2Cu2Br6), which was determined to provide structural information for the force field analyses, contains stacks of planar dimeric [Cu2Br6] 2- complexes held together by weak axial Cu-Br interactions.

KW - Copper bromide bonds

KW - Copper chloride bonds

KW - Far-infrared spectra

KW - Force constant correlation

KW - Raman spectra

UR - http://www.scopus.com/inward/record.url?scp=38549170619&partnerID=8YFLogxK

U2 - 10.1002/jrs.1778

DO - 10.1002/jrs.1778

M3 - Article

AN - SCOPUS:38549170619

VL - 39

SP - 16

EP - 31

JO - Journal of Raman Spectroscopy

JF - Journal of Raman Spectroscopy

SN - 0377-0486

IS - 1

ER -