cyclo-Tetra­kis{μ-2,2′-dimethyl-1,1′-[2,2-bis­(bromo­meth­yl)propane-1,3-di­yl]di(1H-benzimidazole)-κ2 N 3:N 3′}tetra­kis­[bromidocopper(I)]

Xing Wang; Chun-Bo Liu; Yong-Sheng Yan; Shen-Tang Wang; Ling Liu

doi:10.1107/S160053681200102X

. 2012 Jan 14;68(Pt 2):m153. doi: 10.1107/S160053681200102X

cyclo-Tetrakis{μ-2,2′-dimethyl-1,1′-[2,2-bis(bromomethyl)propane-1,3-diyl]di(1H-benzimidazole)-κ² N ³:N ^3′}tetrakis[bromidocopper(I)]

Xing Wang ^a, Chun-Bo Liu ^a,^*, Yong-Sheng Yan ^a, Shen-Tang Wang ^a, Ling Liu ^a

PMCID: PMC3274886 PMID: 22346833

Abstract

The title compound, [Cu₄Br₄(C₂₁H₂₂Br₂N₄)₄], features a macrocyclic Cu₄ L ₄ ring system in which each Cu^I atom is coordinated by one bromide ion and two N atoms from two 2,2′-dimethyl-1,1′-[2,2-bis(bromomethyl)propane-1,3-diyl]di(1H-benzimidazole) (L) ligands in a distorted trigonal–planar geometry. The L ligands adopt either a cis or trans configuration. The asymmetric unit contains one half-molecule with the center of the macrocycle located on a crystallographic center of inversion. Each bromide ion binds to a Cu^I atom in a terminal mode and is oriented outside the ring. The macrocycles are interconnected into a two-dimensional network by π–π interactions between benzimidazole groups from different rings [centroid–centroid distance = 3.803 (5) Å.

Related literature

For the synthesis of the organic ligand, see: Bai et al. (2010 ▶). For related structures, see: Zhu et al. (2005 ▶); Qi et al. (2008 ▶); Li & Du (2006 ▶); Peng et al. (2010 ▶).

Experimental

Crystal data

[Cu₄Br₄(C₂₁H₂₂Br₂N₄)₄]
M _r = 2534.78
Triclinic,
a = 11.585 (2) Å
b = 12.597 (3) Å
c = 15.273 (3) Å
α = 77.75 (3)°
β = 84.88 (3)°
γ = 89.54 (3)°
V = 2169.4 (8) Å³
Z = 1
Mo Kα radiation
μ = 6.55 mm⁻¹
T = 293 K
0.12 × 0.11 × 0.10 mm

Data collection

Rigaku Mercury CCD area-detector diffractometer
Absorption correction: multi-scan (CrystalClear; Rigaku, 2007 ▶) T _min = 0.458, T _max = 0.535
15281 measured reflections
7799 independent reflections
5648 reflections with I > 2σ(I)
R _int = 0.041

Refinement

R[F ² > 2σ(F ²)] = 0.079
wR(F ²) = 0.177
S = 1.12
7799 reflections
523 parameters
H-atom parameters constrained
Δρ_max = 1.60 e Å⁻³
Δρ_min = −3.27 e Å⁻³

Data collection: CrystalClear (Rigaku, 2007 ▶); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: CrystalClear (Rigaku, 2007 ▶) and DIAMOND (Brandenburg, 1998 ▶); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▶).

Supplementary Material

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S160053681200102X/im2344sup1.cif

e-68-0m153-sup1.cif^{(47.2KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S160053681200102X/im2344Isup2.hkl

e-68-0m153-Isup2.hkl^{(373.8KB, hkl)}

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

Acknowledgments

The authors are indebted to Jiangsu University for supporting this work.

supplementary crystallographic information

Comment

Due to the charming structure topologies and applications in various areas, metal-organic frameworks have been widely developed (Zhu et al. 2005). A successful stategy for the construction of metal-organic frameworks is related to the coordination sites of linker and metal ion geometry. The flexible bis(imidazole) ligands are good candidates for constructing metal-organic networks, because of their numerous possible conformations, mainly cis- and trans-geometry (Qi et al. 2008). Copper (I) shows a variety of different coordination numbers such as two, three and four, and the interconversion between copper (I) and copper (II) makes their crystal structures even more versatile (Li et al. 2006; Peng et al. 2010). Here, we have used the flexible bis(benzimidazole) ligand, 1,1'-(2,2-bis(bromomethyl)propane-1,3-diyl) bis(2-methyl-1H- benzimidazol (L), and copper (II) bromide to obtain the title compound in which copper (II) was reduced to copper (I) under hydrothermal conditions.

In the crystal structure of the title compound, each copper (I) atom is coordinated by one bromide ion, and two N atoms from two ligands L, resulting in a trigonal planar geometry. The Cu—N distances range from 1.932 (8) to 2.003 (8) Å, while the distances of Cu1—Br3 and Cu2—Br6 are 2.381 (2) and 2.316 (3) Å, respectively. Two Cu1 atoms and two Cu2 atoms are linked by eight N atoms from four organic ligands L in an alternative cis-/trans-configuration, resulting in a centrosymmetric Cu₄L₄ ring. Only one half of the molecule is observed in the asymmetric unit, and there is a crystallographic center of inversion in the center of the macrocyclic molecule. Each bromide ion connects a copper (I) atom in a monodentate mode, oriented outside the ring (Fig. 2). The pitches of Cu1—Cu2 and Cu1—Cu2A are 12.738 (4) and 9.939 (4) Å, respectively. The rings are further interconnected to a two-dimensional network by π–π interactions. Around the ring, benzimidazol groups connected to N3 and N4, and benzimidazol groups based on N1 and N2, are stacked with a distance of 3.803 (5) Å (red dashed) and 3.613 (4) Å (black dashed), respectively (Fig. 2).

Experimental

The organic ligand (L) was synthesized according to a previously reported procedure (Bai et al. 2010). A mixture of CuBr₂ (22.365 mg, 0.1 mmol), and L (49.023 mg, 0.1 mmol) was dissolved in 10 mL of water of pH = 6. The resulting mixture was then transferred to a 25 mL Teflon–lined stainless steel reactor, and heated to 438 K for three days. After the reactor was slowly cooled to the room temperature yellow block-shaped crystals were obtained with a yield of 53 %.