A. Luque, J. Sertucha, Ó. Castillo
Jan 15, 2002
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Influential Citations
35
Citations
Journal
Polyhedron
Abstract
Abstract Three n-ethylpyridinium salts of the tetrabromocuprate(II) anion [n=2 (1), 3 (2) and 4 (3)] were prepared by air evaporation of an ethanolic solution of the aromatic amine base, HBr and CuBr2 in a molar ratio 2:2:1. The compounds were characterized by elemental analysis, IR, UV–Vis and ESR spectroscopies, thermal analysis and variable-temperature magnetic susceptibility measurements. The crystal structures of 2 and 3 were determined by means of single-crystal X-ray diffraction methods. The [CuBr4]2− anion (with C2 symmetry for 2) is connected to two organic cations through N–H⋯Br hydrogen bonds to form cation–anion–cation motifs which are held together by means of offset face-to-face interactions between the aromatic rings to give zig–zag one-dimensional chains in 2 and a dimeric entity in 3. The dimeric units of 3 are joined by means of weak Br⋯Br contacts to give one-dimensional chains as well. The X-band ESR spectra show quasi-axial signals which are clearly resolved operating at Q-band, with g∣∣≫g⊥>2.0, characteristic of a flattened [CuBr4]2− tetrahedral complex. The magnetic susceptibility measurements of powdered samples show that compounds behave as low-dimensional magnetic systems with weak antiferromagnetic exchange interactions. Thermal decomposition of the compounds yield copper(II) oxide and metallic Cu as stable final residues in synthetic air and dinitrogen atmospheres, respectively.