Bis{2-[(5-hydroxypentyl)iminomethyl]phenolato-κ2 N,O 1}copper(II)

In the title compound, [Cu(C12H16NO2)2], the CuII ion, located on a center of inversion, is coordinated by two singly deprotonated Schiff base ligands derived from condensation of salicyldehyde and 1-aminopentan-5-ol. The imino N and phenol O atoms from both ligands offer a square-planar arrangement around the metal ion. The Cu—N and Cu—O bond lengths are 2.0146 (15) and 1.8870 (12) Å, respectively. Since the Cu—O and Cu—N bond lengths are different, it can be concluded that the resulting geometry of the complex is distorted. The aliphatic –OH group of the ligand is not coordinated and points away from the metal coordination zone and actively participates in hydrogen bonding connecting two other units and thus stabilizing the crystal lattice. This results in a two-dimensional extended array parallel to (201).

In the title compound, [Cu(C 12 H 16 NO 2 ) 2 ], the Cu II ion, located on a center of inversion, is coordinated by two singly deprotonated Schiff base ligands derived from condensation of salicyldehyde and 1-aminopentan-5-ol. The imino N and phenol O atoms from both ligands offer a square-planar arrangement around the metal ion. The Cu-N and Cu-O bond lengths are 2.0146 (15) and 1.8870 (12) Å , respectively. Since the Cu-O and Cu-N bond lengths are different, it can be concluded that the resulting geometry of the complex is distorted. The aliphatic -OH group of the ligand is not coordinated and points away from the metal coordination zone and actively participates in hydrogen bonding connecting two other units and thus stabilizing the crystal lattice. This results in a two-dimensional extended array parallel to (201).
Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: Mercury  Coordination chemistry of copper complexes of chelating ligands is a subject of continuing importance in connection with their structural, spectral, and redox properties in general and from the standpoint of their relevance to coppercontaining metalloproteins in particular (Solomon et al., 2001;Hatcher & Karlin, 2004;Kaim & Rall, 1996). Copper ions are found in the active sites of a large number of metalloproteins involved in important biological electron-transfer reactions, as well as in redox processes of molecular oxygen (Reedijk & Bouwman, 1999).
Crystallographic analysis reveals that the asymmetric unit of the title mononuclear complex consists of one Cu II ion, which is located on a center of inversion, and two singly deprotonated ligands, HL -, with the phenolic O atom being deprotonated. The phenolic O atoms (O2 and O2_a; symmetry code: (a) 2-x, 1-y, 1-z) and the imine N atoms (N1 and N1_a; symmetry code: (a) 2-x, 1-y, 1-z) from both the ligands coordinate to the same Cu II center in the trans disposition to each other. The aliphatic -OH group remains as a pendant arm and is pointing away from the metal coordination zone.
This uncoordinated oxygen atom, O1, is 8.083 Å away from the Cu II ion. The complex has a τ 4 value of 0 (α = O2 -Cu1 -O2_a = 180.00 and β = N1 -Cu1 -N1_a = 180.00) as a consequence of the Cu lying on a center of inversion thus supporting an assignment of distorted square planar geometry around the central metal ion (Yang et al. 2007). The complex exhibits a Cu1 -N1 bond length of 2.0146 (16) Å. In a perfectly square planar CuN 4 moiety, the average Cu II -N distance lies in the range of 1.980 (9) and 2.018 (9) Å (Maeda et al.,2003, Akimova et al., 2001. The Cu -N bond length value is comparable to the previously reported nearly planar Cu II porphyrins (2.020 Å, 2.065 Å, 1.977 Å) (Pawlicki et al. 2007). It agrees well with the CuN 2 O 2 monomer (τ 4 = 1/5) having average Cu II -N bond length range of 2.071 Å (Verma et al., 2011). The Cu1 -O2 bond distance in the complex is 1.8871 (11) Å. It is well established in the literature that in a nearly square planar geometry, the Cu II -phenolic oxygen bond length lies in the range of 1.84 Å to 1.93 Å (Khandar & Nejati, 2000;Sundaravel et al., 2009). Since the Cu -O and Cu -N bond lengths are different, therefore, it can be concluded that the resultant geometry is a distorted square planar one. The pendant -OH group actively participates in H-bonding and connects two other units stabilizing the crystal lattice. As a result we have a twodimensional extended array parallel to 201 plane with O1 -H1 ---O1 length 2.864 (2) Å.

Experimental
The solution of 5-amino-1-pentanol (3 mmol, 650.8 mg) in methanol (20 mL) was added to the solution of salicylaldehyde (3 mmol, 366.36 mg) in methanol (20 ml) under vigorous stirring condition. The resulting reaction mixture was subsequently refluxed with stirring for 4 h. Completion of the reaction checked by thin layer chromatography (TLC).
After reaction was complete, the solution was dried over Na 2 SO 4 , followed by filtration and the solvent was removed slow evaporation gave a brown amorphous solid which was washed with diethyl ether properly and dried in vacuum desiccator containing anhydrous CaCl 2 . X-ray quality single crystals were grown from acetonitrile by the slow evaporation method.

Refinement
The H atoms were placed in calculated positions and refined as riding atoms, with C-H = 0.93 Å, aliphatic C -H = 0.97 Å and O -H = 0.82 Å.

Figure 1
The structure of (I), showing the atom-labelling scheme. H atoms omitted for clarity. Displacement ellipsoids are drawn at the 50% probability level.

Bis{2-[(5-hydroxypentyl)iminomethyl]phenolato-κ 2 N,O 1 }copper(II)
Crystal data 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.