Bis(1,10-phenanthroline-κ2 N,N′)(sulfato-κO)copper(II) ethanol monosolvate

The crystal structure of the title compound, [Cu(SO4)(C12H8N2)2]·C2H5OH, arises from the assembly of the neutral complex [Cu(SO4)(C12H8N2)2] and an ethanol solvent molecule. The CuII ion is five-coordinate, surrounded by two pairs of N atoms from two independent N,N′-chelating 1,10-phenanthroline ligands, and one O atom of monodentate sulfate ligand, in a distorted trigonal-bipyramidal fashion. Spatial orientation of the ligands and the assembly in the solid state are stabilized by the C—H⋯O hydrogen-bonding interactions, established between the O atoms (from the sulfate ligand and the ethanol molecule) and the neighbouring 1,10-phenanthroline molecules. There is also an offset face-to-face π–π stacking between the 1,10-phenanthroline ligands. The ethanol solvent molecule is disordered over two orientations in the ratio 0.663 (10):0.337 (10). The crystal examined was subject to racemic twinning and the refined twin fraction was 0.346 (19).


Comment
The crystal structure of the title complex, [Cu(SO 4 )(C 12 H 8 N 2 ) 2 ]·C 2 H 6 O (I), is isostructural with the propane-1,2-diol and ethane-1,2-diol solvates, Cu(C 12 H 8 N 2 ) 2 (SO 4 )·C 3 H 8 O 2 (Zhong, 2011a) and [CuSO 4 (C 12 H 8 N 2 ) 2 ]·C 2 H 6 O 2 (Zhong, 2011b). The neutral complex [Cu(SO 4 )(C 12 H 8 N 2 ) 2 ] in I is composed of a central Cu II ion, coordinated by a single oxygen atom (O3) of the monodentate sulfato ligand, and two pairs of nitrogen atoms (N1, N2, N3 and N4) of two independent N,N′-chelating o-phen (see Fig. 1). Rather than the square pyramidal geometry described for some related complexes (Zhong, 2011a;Zhong, 2011b), the coordination about the Cu II ion in I is better described as a trigonal bipyramid. In some previous reports, disorder of the sulfato ligand has introduced problems in the refinement. (e.g a Cu-O bond of length 1.4 Å (Zhong, 2011a)) We see no evidence for disorder in the sulfato ligand. The coordinating atoms N1, N4 and O3 are located in the trigonal bipyramidal plane with a summation of the three angles about the metal center close to 360°: O3-Cu1- and Cu-N (1.995 (5)-2.191 (6) Å) bond lengths in complex I are nontheless in good agreement with those reported for the relevant structures (Zhong, 2011a;Zhong, 2011b). The two independent chelating o-phen ligands anchored onto the same metal ion are oriented in a different planes with a slanting angle of 70.8 (1)° between the two molecular planes.
The spatial arrangement of each structural building motifs and the three-dimensional supramolecular assembly in I are regulated by the weak C-H···O hydrogen-bonding interactions (Fig. 2) in synergy with the π-π interactions ( Fig. 3).
Every oxygen atom, including those of the sulfato ligand, and the solvent molecule display C-H···O interactions with the chelating o-phen ligands, calculated by using the program PLATON (Spek, 2009). A close proximity between the sulfato oxygen atoms and the hydroxyl group of the solvent molecule suggests the possibility for the hydrogen bonding interactions between the two: O41···O2 2.8757 (89) Å and O42···O4 2.719 (16) Å. In addition to the hydrogen bonding interactions, the two adjacent o-phens exhibit the offset face-to-face π-π stacking with the inter-plane distance of 3.529 Å, centroid-to-centroid distance of 4.455 Å, and a displacement angle of 32.72°. Refinements in the two possible space group choices were perfomed and these clearly indicated that C2/c was incorrect.
In particular, the wR2 was substantially better in the non-centric case. (wR2 = 0.1595 for all data in Cc and 0.2498 for all data in C2/c.) The C-C bond precision was better in the non-centric case (0.0115 compared with 0.0130 Å). This would not be the case if a strict centre of symmetry was present. Cc was therefore retained as the space group. The comparison to other structure mentioned previously is important. Those similar structures reported in Cc (eg Zhong, 2011b andCai, 2013) have an ordered monodentate sulfate ligand. Those in C2/c (eg Wojciechowska et al., 2011;Zhu et al., 2006, andZhong et al., 2009) have an orderd bidentate sulfate ligand. Here the stable model in Cc has a mondentate sulfate with no ligand disorder, but the model in C2/c displays a disordered monodentate sulfate in contrast to the other reports. The refinement in C2/c is contained within the CIF for completeness but the crystal data and refinements indicate this is not the correct space group.
The crystal examined displayed racemic twinning. The refined twin fraction of the second component was 0.346 (19).
This value is significantly different from 1/2, the value that would be expected if the compound was truly centrosymmetric and incorrectly refined in the space group Cc.
The ethanol solvent molecule is disordered over two positions, related by a rotation of approximately 180° about the C -C bond. The atoms of each orientation were identified in difference Fourier maps. The presence of ethanol is clear from these and the existence of two molecules in different orientations is apparent. Figure 5 shows the relationship between two orientations of the ethanol. Figures 6 and 7 show F obs Fourier maps calculated using all observed data. From these the molecule can clearly be identified as ethanol, precluding any inclusion of dimethylsulfoxide or thiourea from the reaction mixture. The two orientations are present in the ratio 66.3:33.7 (10) %. For the major orientation, O41 forms a hydrogen bond to O2 while for the minor orientation, O42 forms a hydrogen bond to O4.

Experimental
The crystals of [Cu(SO 4 )(C 12 H 8 N 2 ) 2 ]·C 2 H 4 O (I) were unexpectedly obtained as a by-product during an attempt to synthesize copper complexes using mixing ligands of 1,10-phenanthroline (o-phen) and thiourea by a bilayer-diffusion method. In a typical experiment, two immiscible solutions A and B were first prepared. Solution A: CuSO 4 ·5H 2 O (0.0499 g, 0.2 mmol; Fisher Scientific 99.55%) was dissolved in 4.0 ml dimethylsulfoxide (Riedel-de Haën 99.5%) in a small test tube (diameter of ca 13 mm). Solution B: 1,10-phenanthroline (o-phen; 0.0793 g, 0.4 mmol; QRëC 99.5%) and thiourea (0.0305 g, 0.4 mmol; Merck 99.0%) were dissolved in 4.0 ml e thanol (Merck 99.9%). Solution B was then gently added onto the surface of solution A. After 24 h, blue block shaped crystals were crystallized and isolated for single-crystal Xray diffraction experiment.

Figure 3
View of the π-π interactions between the adjacent o-phen molecules.  Normalized structure factor statistics. The inset graph shows the N(Z) distribution.

Figure 5
Arrangement of the two orientations of the disordered ethanol molecule. The major orientation (66%) is O41 C41a C42b.
The minor orientation (34%) is O42 C42b C41b.      where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 1.02 e Å −3 Δρ min = −1.09 e Å −3 Absolute structure: Flack (1983), 2594 Friedel pairs Absolute structure parameter: 0.346 (19) Special details Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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 R-factors(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Occ. (