Poly[(μ3-5-bromo­nicotinato)(5-bromo­nicotinato)copper(II)]

Jun Yang; Hong-Ji Chen

doi:10.1107/S1600536809038331

. 2009 Sep 30;65(Pt 10):m1262–m1263. doi: 10.1107/S1600536809038331

Poly[(μ₃-5-bromonicotinato)(5-bromonicotinato)copper(II)]

Jun Yang ^a, Hong-Ji Chen ^a,^*

PMCID: PMC2970337 PMID: 21577774

Abstract

The title coordination polymer, [Cu(C₆H₃BrNO₂)₂]_n, is composed of two structurally similar two-dimensional coordination polymers (twin layers). Both of them have the same chemical composition but they display different bond lengths and angles. In each layer, two N atoms and four carboxylate O atoms from the bridging 5-bromonicotinate ligands and four carboxylate O atoms from the terminal 5-bromonicotinate ligands bind to two Cu^II atoms to form a dinuclear paddle-wheel-like pattern. Adjacent paddle wheels are further linked by bridging 5-bromonicotinate groups to generate a two-dimensional coordination polymer; neighboring twin-like layers are finally stacked through π–π stacking interactions between adjacent pyridine rings [perpendicular distance of 3.626 (2) Å] in a ‘sandwich’ manner, thus generating a three-dimensional supramolecular structure.

Related literature

For related literature on paddle-wheel secondary building units, see: Chen et al. (2006 ▶); Xue et al. (2007 ▶); Striegler & Dittel (2003 ▶); Ma & Moulton (2007 ▶); Banerjee et al. (2008 ▶); Saravanakumar et al. (2004 ▶). For similar structures, see: Yakovenko et al. (2009 ▶); Xue et al. (2007 ▶). For τ distortions of coordination polyhedra, see: Addison & Rao (1984 ▶).

Experimental

Crystal data

[Cu(C₆H₃BrNO₂)₂]
M _r = 465.55
Monoclinic,
a = 21.542 (4) Å
b = 11.746 (2) Å
c = 12.271 (2) Å
β = 104.31 (3)°
V = 3008.6 (9) Å³
Z = 8
Mo Kα radiation
μ = 6.78 mm⁻¹
T = 173 K
0.33 × 0.31 × 0.23 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2004 ▶) T _min = 0.213, T _max = 0.305
15126 measured reflections
6502 independent reflections
4904 reflections with I > 2σ(I)
R _int = 0.031

Refinement

R[F ² > 2σ(F ²)] = 0.034
wR(F ²) = 0.085
S = 1.03
6502 reflections
379 parameters
H-atom parameters constrained
Δρ_max = 1.40 e Å⁻³
Δρ_min = −1.34 e Å⁻³

Data collection: SMART (Bruker, 1998 ▶); cell refinement: SAINT (Bruker, 1998 ▶); data reduction: SAINT (Bruker, 1998 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 2005 ▶); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809038331/bg2298sup1.cif

e-65-m1262-sup1.cif^{(21.5KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809038331/bg2298Isup2.hkl

e-65-m1262-Isup2.hkl^{(318.2KB, hkl)}

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

Acknowledgments

This work was supported by the Natural Science Foundation of Guangdong Province (grant No. 0430064), People’s Republic of China.

supplementary crystallographic information

Comment

Paddle-wheel secondary building units (SBUs) M₂(RCOO)₄ are useful building blocks for constructing complexes and 1D to 3D coordination polymers through bifunctional ligands. Research interest in these compounds with copper(II) paddle-wheel SBUs come from their structural diversity (Chen, et al., 2006; Xue et al., 2007) and potential applications in supramolecular medicinal chemistry (Ma & Moulton 2007), sugar discrimination (Striegler & Dittel 2003), molecular magnets (Banerjee et al., 2008; Saravanakumar et al., 2004; Yakovenko, et al., 2009), respectively. However, most reported Cu(II) complexes with paddle-whell secondary building units are constructed by mixed-ligands, either two kinds of organic ligands or one organic ligand and water molecules (Ma & Moulton 2007). 5-Bromonicotinic acid is a bifunctional ligand with two carboxylic oxygen atoms and one pyridyl nitrogen atom, and it can be coordinated to a metal centre in a variety of ways to create structural diversity. Here, we report a new two-dimentional coordination polymer with Cu(II) paddle-wheel SBUs formed from the organic ligand 5-Bromonicotinic acid and Cu(II) ions.

The title coordination polymer, twin-poly[copper(II) (η-N,O,O-5-bromonicotinato)(η-O,O-5-bromonicotinato)] (I), contains two similar, independent groups in the asymmetric unit consisting of two copper atoms (Cu1 and Cu2) and four 5-bromonicotinato ligands each. The coordination enviroments of the two copper atoms present a nearly perfect [CuO₄N] square pyramid geometry, characterized by τ factors (indicative of the distortion degree of such a coordination sphere, Addison & Rao, 1984), of 0.01 for Cu1 and 0.003 for Cu2. The bond lengths and angles around Cu1 and Cu2 are standard for a Jahn-Teller active square pyramidal Cu²⁺ ion, with basal Cu—O bond lengths ranging from 1.957 (3) Å to 1.979 (3) Å (1.952 (3)–1.976 (3) Å ) and a longer axial bond distance to the the ligand nitrogen atom of 2.150 (3) Å (2.164 (3) Å) for Cu1 (Cu2), respectively (Fig. 1).

As previously stated, each copper atom (Cu1 or Cu2) is located in a penta-coordinated geometry and is bonded by four oxygen atoms from carboxylate anions and one nitrogen atom from the axial ligand, which can also be considered as a molecular square when viewed along the axial direction. When four carboxylate groups of the ligands bridge to two asymmetric copper atoms in a syn-syn manner, a dinuclear paddle-wheel pattern is formed, with Cu—Cu distances of 2.6355 (10) Å for Cu1 and 2.6423 (10) Å for Cu2. These values are similar to those in the paddle-wheel copper(II) complex reported in Yakovenko, et al. 2009, but shorter than the corresponding ones in Xue et al. 2007.

When adjacent Cu1 paddle-wheels are bridged by the η-N,O,O-5-bromonicotinato groups, a layer motif (hereafter "A", [Cu1(η-N,O,O-5-bromonicotinato)(η-O,O-5-bromonicotinato)]_{n )}, is formed along (100). Similarly, those resulting from Cu2 generate another layer motif ( "B", [Cu2(η-N,O,O-5-bromonicotinato)(η-O,O-5-bromonicotinato)]_n) which lies parallel to the former (Fig. 2). Finally, both A and B layers contact along the c axial direction generating a new, twin-like coordination polymer (Fig. 3). Neighboring twin-like layers are further stacked via van der Waals interactions in a sandwich way extending the packing into a three-dimensional supramolecular structure. No significant hydrogen bonds were found in the crystal structure.

Experimental

Copper nitrate trihydrate (0.4 mmol, 0.0966 g) in 10 ml water and 5-Bromonicotinic acid (0.4 mmol, 0.0808 g) were sealed in a Teflon-line autoclave and heated to 433 K for 72 h, after which the mixture was cooled down to room temperatureat at a rate of 5 K per hour. Blue single crystals suitable for x-ray crystallography analysis were obtained with a yield of 46 percent. IR (cm^-1, KBr): 3447m, 3057w, 1639vs, 1557 s, 1443vs, 1393vs, 1292 s, 1238w, 1178w, 1143m, 1024m, 904w, 877m, 781 s, 747vs, 685m, 497 s.