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

Ritwik Modak; Santu Patra; Senjuti Mandal; Yeasin Sikdar; Sanchita Goswami

doi:10.1107/S1600536813016802

. 2013 Jun 26;69(Pt 7):m412–m413. doi: 10.1107/S1600536813016802

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

Ritwik Modak ^a, Santu Patra ^a, Senjuti Mandal ^a, Yeasin Sikdar ^a, Sanchita Goswami ^a,^*

PMCID: PMC3772438 PMID: 24046581

Abstract

In the title compound, [Cu(C₁₂H₁₆NO₂)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).

Related literature

For the participation of the copper ion in the active sites of a large number of metalloproteins involved in important biological electron-transfer reactions, see: Reedijk & Bouwman (1999 ▶); Solomon et al. (2001 ▶); Hatcher & Karlin (2004 ▶); Kaim & Rall (1996 ▶). For references regarding the t₄ value, see: Yang et al. (2007 ▶). For similar Cu—N and Cu—O bond lengths, see: Maeda et al. (2003 ▶); Akimova et al. (2001 ▶); Pawlicki et al. (2007 ▶); Verma et al. (2011 ▶); Khandar & Nejati (2000 ▶); Sundaravel et al. (2009 ▶).

Experimental

Crystal data

[Cu(C₁₂H₁₆NO₂)₂]
M _r = 476.07
Monoclinic,
a = 11.8815 (8) Å
b = 5.2219 (3) Å
c = 18.9588 (12) Å
β = 102.876 (2)°
V = 1146.70 (12) Å³
Z = 2
Mo Kα radiation
μ = 0.99 mm⁻¹
T = 296 K
0.8 × 0.6 × 0.4 mm

Data collection

Bruker APEXII SMART CCD diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 1996 ▶) T _min = 0.497, T _max = 0.674
13343 measured reflections
2549 independent reflections
2174 reflections with I > 2σ(I)
R _int = 0.027

Refinement

R[F ² > 2σ(F ²)] = 0.030
wR(F ²) = 0.096
S = 0.95
2549 reflections
143 parameters
H-atom parameters constrained
Δρ_max = 0.27 e Å⁻³
Δρ_min = −0.30 e Å⁻³

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 (Macrae et al., 2008 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536813016802/bv2221sup1.cif

e-69-0m412-sup1.cif^{(15.8KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536813016802/bv2221Isup2.hkl

e-69-0m412-Isup2.hkl^{(125.2KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯O1ⁱ	0.82	2.07	2.864 (2)	163
C1—H1B⋯O2ⁱⁱ	0.97	2.34	2.771 (2)	106

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

Financial support from the University Grants Commission for a junior research fellowship to SM [Sanction No. UGC/749/Jr. Fellow(Sc.)] and an RFSMS fellowship (Sanction No. UGC/740/RFSMS) to RM is gratefully acknowledged. We thank the DST for a junior research fellowship to YS (Sanction No. SERB/F/1585/2012–13). DST–FIST is acknowledged for providing the X-ray diffraction facility at the Department of Chemistry, University of Calcutta.

supplementary crystallographic information

Comment

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 copper-containing 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 τ₄ 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 CuN₄ 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 CuN₂O₂ monomer (τ₄ = 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 two-dimensional 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 Na₂SO₄, followed by filtration and the solvent was removed under reduced pressure to get the ligand. Now a solution of Cu(OAc)₂.H₂O (1.5 mmol, 299.47 mg) in methanol (20 ml) was added to the solution of the prepared crude ligand (3 mmol, 621.84 mg) in methanol(20 ml) with constant stirring. The resulting mixture was stirred for 3 h at room temperature and then filtered. The resulting dark brown solution on slow evaporation gave a brown amorphous solid which was washed with diethyl ether properly and dried in vacuum desiccator containing anhydrous CaCl₂. X-ray quality single crystals were grown from acetonitrile by the slow evaporation method.