catena-Poly[copper(II)-{μ3-4,4′-dibromo-2,2′-[butane-1,4-diylbis(nitrilo­methanyl­yl­idene)]diphenolato-κ4 N,O:N′,O′:O′}]

Hadi Kargar; Reza Kia

doi:10.1107/S1600536811009949

. 2011 Mar 26;67(Pt 4):m499–m500. doi: 10.1107/S1600536811009949

catena-Poly[copper(II)-{μ₃-4,4′-dibromo-2,2′-[butane-1,4-diylbis(nitrilomethanylylidene)]diphenolato-κ⁴ N,O:N′,O′:O′}]

Hadi Kargar ^a,^*, Reza Kia ^b

PMCID: PMC3099995 PMID: 21754007

Abstract

The asymmetric unit of the title coordination polymer, [Cu(C₁₈H₁₆Br₂N₂O₂)]_n, consists of a Schiff base complex in which a crystallographic twofold rotation axis bisects the central C—C bonds of the n-butyl spacers of the designated Schiff base ligands, making symmetry-related dimer units, which are twisted around Cu^II atoms in a bis-bidentate coordination mode. In the crystal, these dimeric units are connected through Cu—O bonds, forming one-dimensional coordination polymers, which propagate along [001]. The Cu^II atom adopts a square-based pyramidal coordination geometry, being coordinated by two N and two O atoms of symmetry-related ligands and by a third O atom of a neighboring complex. Furthermore, intermolecular π–π interactions [centroid–centroid distance = 3.786 (2) Å] and C—H⋯O interactions stabilize the crystal packing.

Related literature

For van der Waals radii, see: Bondi (1964 ▶). For background to coordination polymers, see: Kido & Okamoto (2002 ▶); Li et al. (2006 ▶); Eddaoudi et al. (2001 ▶); Dietzel et al. (2005 ▶). For background to bis-bidentate Schiff base complexes, see: Hannon et al. (1999 ▶); Lavalette et al. (2003 ▶). For the synthesis and structural variations of Schiff base complexes see: Granovski et al. (1993 ▶); Elmali et al. (2000 ▶). For the crystal structure of the chloro derivative, see: Kargar & Kia (2011 ▶).

Experimental

Crystal data

[Cu(C₁₈H₁₆Br₂N₂O₂)]
M _r = 515.69
Monoclinic,
a = 24.0964 (9) Å
b = 10.5885 (3) Å
c = 15.3528 (5) Å
β = 117.354 (3)°
V = 3479.2 (2) Å³
Z = 8
Mo Kα radiation
μ = 5.86 mm⁻¹
T = 100 K
0.41 × 0.32 × 0.17 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2001 ▶) T _min = 0.197, T _max = 0.439
36229 measured reflections
6017 independent reflections
4887 reflections with I > 2σ(I)
R _int = 0.037

Refinement

R[F ² > 2σ(F ²)] = 0.049
wR(F ²) = 0.139
S = 1.19
6017 reflections
226 parameters
H-atom parameters constrained
Δρ_max = 2.19 e Å⁻³
Δρ_min = −0.73 e Å⁻³

Data collection: APEX2 (Bruker, 2007 ▶); cell refinement: SAINT (Bruker, 2007 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536811009949/su2263sup1.cif

e-67-0m499-sup1.cif^{(21.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536811009949/su2263Isup2.hkl

e-67-0m499-Isup2.hkl^{(294.7KB, 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
C9—H9B⋯O2	0.97	2.28	2.973 (5)	128

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Acknowledgments

HK thans PNU for support of this work. RK thanks the Science and Research Branch, Islamic Azad University.

supplementary crystallographic information

Comment

The design and construction of metal-organic coordination polymers (MOCPs) have attracted considerable attention, not only for their novel topologies but also for their potential in the area of magnetic applications and functional materials (Kido & Okamoto, 2002; Li et al., 2006; Eddaoudi et al., 2001; Dietzel et al., 2005). One of the key strategies in the construction of metal-organic coordination polymers is to select suitable bi- or multi-dentate bridging ligands. Among these, bis-bidentate NN- or NO-donor Schiff base ligands with aliphatic and aromatic spacers (Hannon et al., 1999; Lavalette et al., 2003) have attracted much attention because of the flexibility in their coordination modes and the resulting intermolecular interactions. The long chain aliphatic spacers or rigid aromatic spacers with large bite angles in these ligands favour the bis-bidentate coordination mode and allow the ligands to accomodate metal centers in one unit of the ligand. On the other hand, Schiff bases are one of the most prevalent ligands in coordination chemistry and their complexes are some of the most important stereochemical models in transition metal-organic chemistry, with their ease of preparation and structural variations (Granovski et al., 1993; Elmali et al., 2000).

The crystal structure of the chloro derivative, Poly[N,N'-Bis(5-chlorosalicylidene)-1,4-butanediaminato copper(II)], has been descibed in the previous paper (Kargar & Kia, 2011).

The molecular structure of the title complex (Fig. 1) consists of symmetry-related dimers in which the Schiff base ligands are twisted around Cu^II centers in a bis-bidentate coordinⁿation mode, having a crystallographic twofold rotation axis which passes through the central C—C bonds of the n-butyl spacers [C9—C9Aⁱ and C18—C18Aⁱ; symmetry code: (i) -x + 1, y, -z + 1/2].

In the crystal the dimer units are connected through Cu—O bonds, forming one-diensional coordination polymer running along the c axis (Fig. 2), in which the Cu^II atom adopts a square-based pyramidal coordination geometry. The Cu^II atoms are supported by the two nitrogen and oxygen atoms of the symmetry-related ligands and a third oxygen atom of neighboring complexes. The lengths of the intermolecular Cu1—O1ⁱ bonds [2.394 (3) Å Å; symetry code (i) -x, -y + 1, -z] is significantly shorter than the sum of the van der Waals (vdW) radii of these atoms [Cu, 1.43Å and O, 1.52 Å; Bondi, 1964]. There are different non-bonded internuclear Cu···Cu distances. The longer one is separated by the butyl spacers [4.718 Å], and the shorter one is in the centrosymmetric Cu₂O₂ rectangular unit [3.314 Å]. Furthermore, intermolecular π-π interactions stabilize the crystal packings with centroid to centroid distances of 3.786 (2)Å [Cg1 and Cg2 are the centroids of the rings (C1–C6) and (C10–C15)]. There are also C—H···O interactions present (Table 1).

Experimental

The title complex was synthesized by the template method of mixing an ethanolic solution (50 ml) of 5-bromosalicylaldeyde (4 mmol), 1,4-butanediamine (2 mmol), and CuCl₂.4H₂O (2.1 mmol). After stirring at reflux conditions for 2 h, the solution was filtered and the resulting green solid was crystallized from ethanol, giving single crystals suitable for X-ray diffraction.