Diaqua(6-bromopicolinato-κ2 N,O)(nitrato-κ2 O,O)copper(II)

In the monomeric title complex, [Cu(C6H3BrNO2)(NO3)(H2O)2], the CuII ion is coordinated by a bidentate 6-bromopicolinate ion, one nitrate ion and two water molecules in a geometry intermediate between five- and six-coordinate. Conventional O—H⋯O hydrogen bonds link the complex molecules, forming layers parallel to the ab plane.


Related literature
For general background to copper complexes with lowdimensionality synthesized by our group, see: , ; Ramos Silva et al. (2001aSilva et al. ( ,b,c, 2005a. For a magnetic low-dimensional system with picolinic acid, see: Eppley et al. (1997). For a similar compound with magnetic properties, see: Kukovec et al. (2008).

Experimental
Crystal data [Cu(C 6

Comment
The title compound was obtained within a project of synthesizing new molecular magnets Ramos Silva et al., 2001a, 2001b, 2001c, 2005a, 2005b. Molecular based magnets can capitalize on the flexibility inherent in carbon chemistry. Such flexibility allows a rational choice of ligands to control the dimensionality of the system, so that quantum effects can be enhanced. Picolinic and hydroxypicolinic acid have been widely used as ligands in low-dimensional metallic systems (Eppley et al., 1997) but 6-bromopicolinic acid has been scarcely used. A different substituent in the pyridine ring may lead to significant electronic and steric effects enlarging the structural diversity. In fact, Kukovec et al. (2008) synthesized a copper (II) complex with 6-bromopicolinic acid as a bidentate ligand in which the magnetic exchange pathway is connected to the Br···π interaction.
In the title compound, the Cu II ion is coordinated by a bromopicolinate ligand, two water molecules and a nitrate ion ( Fig.   1). One of the Cu-O bonds is rather long [Cu1-O4 2.682 (3) °] so that the coordination about the copper ion is intermediate between five and six-coordination. If the latter bond is to be ignored, the remaining coordination stereochemistry is near a square pyramid. In that case, the copper ion is 0.3149 (5) Å above the least-squares plane of the basal coordinating atoms.
The H-bond network is confined to layers parallel to the ab plane ( Fig. 2, Table 1). The bromine also forms a short contact The magnetic susceptibility was measured using a SQUID magnetometer in function of temperature with an applied magnetic field of 2 T. The inverse susceptibility showed a linear dependence with temperature, excluding any interaction between magnetic centers. Experimental 0.14 mmol of 6-bromo-2-pyridinecarboxaldehyde in dichloromethane (10 ml) was added to 0.12 mmol of Cu(NO3)2.3H2O in water (10 ml). After a few weeks, blue single crystals of the title compound were obtained.

Refinement
H atoms bound to C atoms were placed at calculated positions and were treated as riding on the parent atoms with C-H = 0.93 Å (aromatic) and with U iso (H) = 1.2 U eq (C). H atoms of water molecules O6 an O7 could not be correctly located in a difference Fourier map. They were placed at positions calculated to optimize H-bonds and refined using restraints  Fig. 1. ORTEPII (Johnson, 1976) plot of the title compound. Displacement ellipsoids are drawn at the 50% level.