A study of pseudo 1-D copper(I) halide systems exhibiting anomalous copper(II) character: Physical characterization of (paraquat)Cu2X4 (X = Cl, Br, I)

Brian Scott, Roger Willett, Andrea Saccani, Franco Sandrolini, B. L. Ramakrishna

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Abstract

The salts (paraquat)Cu2X4 (X = Cl, Br, I) have been synthesized and their crystal structures determined. The chloride salt is tetragonal, space group P42/n, a = 16.352(2), c = 5.911(2) Å, V = 1580.7(6) Å3, Dx = 1.87 g cm-3, Z = 4 and R = 0.0546. The bromide analog is monoclinic, space group P21/n, a = 8.715(6), b = 11.103(6), c = 13.386(7) Å, β = 98.02(4)°, V = 1666(1) Å3, Dx = 2.52 g cm-3, Z = 4 and R = 0.0680. The iodide salt is tetragonal, space group P42212, a = 12.416(2), c = 6.544(3) Å, V = 1008.8(5) Å3, Dx = 2.70 g cm-3, Z = 2 and R = 0.0995. Infinite chains of distorted, edge sharing, Cu(I)X4 3- tetrahedra are common to all three structures. The bond distances and angles about the copper centers are consistent with known Cu(I)X4 3- species. The paraquat cations form stacks parallel to the chain axis, and all three structures show weak N⋯X and C⋯X contacts. The chloride and iodide salts are nearly isostructural, and differential scanning calorimetry shows a phase transition in the chloride salt at 188 °C. The iodide salt is a pure copper(I) system. A temperature dependent magnetic susceptibility experiment shows the bromide salt to contain a 2% Cu2Br6 2- impurity. Two chloride compounds showing the same structure have been synthesized. One of these salts has 1% copper(II) character, while the other has 10% copper(II) character. EPR shows the 1% character to be a CuCl2 · 2H2O impurity. Magnetic susceptibility, EPR, powder diffraction and electrical conductivity results show that the 10% copper(II) character is incorporated into the [CuCl2] chain structure, with an accompanying vacancy. Preliminary conductivity measurements show that the Cl and I salts are insulators, but hint at enhanced conductivity for the bromide analog.

Original languageEnglish (US)
Pages (from-to)73-80
Number of pages8
JournalInorganica Chimica Acta
Volume248
Issue number1
DOIs
Publication statusPublished - Jul 1 1996

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Keywords

  • Copper complexes
  • Crystal structures
  • Halide complexes
  • Paraquat complexes

ASJC Scopus subject areas

  • Biochemistry
  • Inorganic Chemistry
  • Physical and Theoretical Chemistry
  • Materials Chemistry

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