Bis[2-(pyrrolidin-2-yl)-1H-benzimidazole-κ2 N 2,N 3]copper(II) dinitrate dihydrate

In the title compound, [Cu(C11H13N3)2](NO3)2·2H2O, synthesized by hydrothermal reaction of Cu(NO3)2 and racemic 2-(pyrrolidin-2-yl)-1H-1,3-benzimidazole, the CuII atom lies on an inversion centre. The distorted octahedral CuII environment contains two planar trans-related N,N-chelating 2-(pyrrolidin-2-yl)-1H-1,3-benzimidazole ligands in the equatorial plane and two monodentate nitrate anions, which are in weak interaction with the Cu atom, in the axial positions. The two benzimidazole ligands have opposite configurations (R/S and S/R) and compound is a meso complex. In the crystal, N—H⋯O and O—H⋯O hydrogen bonds generate an infinite three-dimensional network. One methylene group of the pyrrolidine ring is disordered over two position with a 0.56 (3):0.44 (3) occupancy.

In the title compound, [Cu(C 11 H 13 N 3 ) 2 ](NO 3 ) 2 Á2H 2 O, synthesized by hydrothermal reaction of Cu(NO 3 ) 2 and racemic 2-(pyrrolidin-2-yl)-1H-1,3-benzimidazole, the Cu II atom lies on an inversion centre. The distorted octahedral Cu II environment contains two planar trans-related N,N-chelating 2-(pyrrolidin-2-yl)-1H-1,3-benzimidazole ligands in the equatorial plane and two monodentate nitrate anions, which are in weak interaction with the Cu atom, in the axial positions. The two benzimidazole ligands have opposite configurations (R/S and S/R) and compound is a meso complex. In the crystal, N-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds generate an infinite three-dimensional network. One methylene group of the pyrrolidine ring is disordered over two position with a 0.56 (3):0.44 (3) occupancy.

Comment
Amino acid derivatives have found wide range of applications in material science, such as ferroelectric, fluorescence and dielectric behaviors. And there has been an increased interest in the preparation of amino acid coordination compound (Aminabhavi et al., 1986;Dai & Fu 2008a;Fu & Ye 2007;Dai & Fu 2008b;Fu, et al. 2007). We report here the crystal In the title compound, the Cu II atom lies on an inversion centre. The distorted octahedral Cu II environment contains two planar trans-related N,N-chelating 2-(pyrrolidin-2-yl)-1H-1,3-benzimidazole ligands in the equatorial plane and two monodentate nitrate anion ligands which are in weak interaction with the Cu atom in the axial position. The two benzimidazole ligands have opposite configuration R,S and S,R and the complex is meso (Fig. 1).
In the crystal structure, molecules are linked into a three-dimension network by N-H···O and O-H···O hydrogen bonds. (Fig.2, Table 1).

Refinement
All H atoms attached to C and N atoms were fixed geometrically and treated as riding with C-H = 0.93 Å (aromatic), 0.97 Å (methylene) or 0.98 Å (methine) and N-H = 0.91 Å (N3), 0.86 Å (N2) with U iso (H) = 1.2U eq (C,N). H atoms of water molecule located in difference Fouriermaps and in the last stage of refinement they were treated as riding on the O atom with U iso (H) = 1.5U eq (O).
One of the pyrrolidine rings is disordered with the C10 atom statistically distributed over two positions. These disorders were treated using the tools (SAME and PART) available in SHELXL97 (Sheldrick, 2008  Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.