Bis(cyclohexylammonium) tetrabromidocuprate(II)

The structure of the title salt, (C6H14N)2[CuBr4], is built up from cyclohexylammonium cations and tetrabromidocuprate anions, the latter being located on an inversion center. In the crystal, anions and cations are interconnected by N—H⋯Br hydrogen bonds, forming ribbons parallel to [0-11].

The structure of the title salt, (C 6 H 14 N) 2 [CuBr 4 ], is built up from cyclohexylammonium cations and tetrabromidocuprate anions, the latter being located on an inversion center. In the crystal, anions and cations are interconnected by N-HÁ Á ÁBr hydrogen bonds, forming ribbons parallel to [011].

Related literature
For background to the development of ferroelectric pure organic or inorganic compounds, see: Haertling (1999); Homes et al. (2001). For the synthesis of a variety of compounds with potential piezoelectric and ferroelectric properties, see:  ;Hang et al. (2009). For the synthesis of the title compound, see: Willett (2004).
The author is grateful to the starter fund of Southeast University for financial support to buy the X-ray diffractometer.

Meng Ting Han Comment
At present, much attention in ferroelectric material field is focused on developing ferroelectric pure organic or inorganic compounds (Haertling, 1999;Homes et al. 2001). Recently we have reported the synthesis of a variety of compounds Hang et al., 2009), which have potential piezoelectric and ferroelectric properties. In order to find more dielectric ferroelectric materials, we investigated the physical properties of the title compound ( Fig. 1). The dielectric constant of the title compound as a function of temperature indicates that the permittivity is basically temperatureindependent (dielectric constant equaling to 0.42 to 6.6), suggesting that this compound should be not a real ferroelectrics or that no phase transition occurs within the measured temperature range. Similarly, below the melting point (443 K) of the compound, the dielectric constant as a function of temperature also goes smoothly, and there is no dielectric anomaly observed. Herein, we report the synthesis and crystal structure of the title compound.
The structure of the title compound is shown in Fig. 1. There are one half CuBr 4 2anion and one cyclohexylammonium cation in the asymmetric unit. The cyclohexyl ring has the chair conformation. As it can be seen from the packing diagram ( Fig. 2), ions are connected via intermolecular N-H···Br hydrogen bonds to form a one dimensional chain in the crystal. Dipole-dipole and van der Waals interactions are effective in the molecular packing.

Experimental
Crystals of the title compound were grown by evaporation of an aqueous solution containing a 2:1 ratio of cyclohexylammonium bromide and copper(II) bromide. A few drops of hydrobromic acid were added to the solution to avoid hydrolysis of the Cu(II) ion (Willett, 2004).

Figure 2
The crystal packing of the title compound viewed along the b axis showing the hydrogen bonds network. Some of the H atoms have been omitted for clarity.