N,N′-Bis(4-bromo­benzyl­idene)butane-1,4-diamine

Hoong-Kun Fun; Hadi Kargar; Reza Kia

doi:10.1107/S1600536808028122

. 2008 Sep 6;64(Pt 10):o1894. doi: 10.1107/S1600536808028122

N,N′-Bis(4-bromobenzylidene)butane-1,4-diamine

Hoong-Kun Fun ^a,^*, Hadi Kargar ^b,^‡, Reza Kia ^a

PMCID: PMC2959343 PMID: 21201106

Abstract

The molecule of the title Schiff base compound, C₁₈H₁₈Br₂N₂, lies across a crystallographic inversion centre and adopts an E configuration with respect to the C=N bond. In the crystal structure, molecules are linked into chains along [201] through intermolecular Br⋯Br interactions [3.3747 (3) Å], which are significantly shorter than the sum of the van der Waals radii for Br atoms (3.70 Å). The crystal structure is further stabilized by π–π stacking interactions [centroid–centroid distance 3.6811 (11) Å].

Related literature

For halogen–halogen interactions, see: Ramasubbu et al. (1986 ▶); Brammer et al. (2003 ▶). For the crystal structures of related compounds, see: Fun et al. (2008 ▶); Fun, Kia & Kargar (2008a ▶,b ▶); Fun & Kia (2008a ▶,b ▶). For bond-length data, see: Allen et al. (1987 ▶). For hydrogen-bondong motifs, see: Bernstein et al. (1995 ▶). For background, see: Casellato & Vigato (1977 ▶).

Experimental

Crystal data

C₁₈H₁₈Br₂N₂
M _r = 422.16
Monoclinic,
a = 11.2612 (5) Å
b = 9.5213 (4) Å
c = 8.2645 (4) Å
β = 100.040 (3)°
V = 872.56 (7) Å³
Z = 2
Mo Kα radiation
μ = 4.64 mm⁻¹
T = 100.0 (1) K
0.52 × 0.23 × 0.08 mm

Data collection

Bruker APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.192, T _max = 0.688
15460 measured reflections
3843 independent reflections
2600 reflections with I > 2σ(I)
R _int = 0.037

Refinement

R[F ² > 2σ(F ²)] = 0.037
wR(F ²) = 0.092
S = 1.02
3843 reflections
136 parameters
All H-atom parameters refined
Δρ_max = 0.68 e Å⁻³
Δρ_min = −0.59 e Å⁻³

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: SAINT (Bruker, 2005 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2003 ▶).

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808028122/rz2242sup1.cif

e-64-o1894-sup1.cif^{(13.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808028122/rz2242Isup2.hkl

e-64-o1894-Isup2.hkl^{(188.4KB, hkl)}

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

Acknowledgments

HKF and RK thank the Malaysian Government and Universiti Sains Malaysia for the Science Fund (grant No. 305/PFIZIK/613312). RK thanks Universiti Sains Malaysia for the award of a postdoctoral research fellowship. HK thanks PNU for financial support.

supplementary crystallographic information

Comment

The condensation of primary amines with carbonyl compounds yields Schiff bases (Casellato & Vigato, 1977) that are still one of the most prevalent mixed-donor ligand in coordination chemistry. In the past two decades, the synthesis, structure and properties of Schiff base complexes have stimulated much interest for their noteworthy contributions in single molecule-based magnetism, materials science, catalysis of many reactions like carbonylation, hydroformylation, reduction, oxidation, epoxidation and hydrolysis (Casellato & Vigato 1977). As an extension of our work (Fun et al., 2008; Fun, Kia & Kargar 2008a,b; Fun & Kia 2008a,b) on the structural characterization of Schiff base ligands, the title compound is reported here.

The molecule of the title compound (Fig 1), lies across a crystallographic inversion centre and adopts an E configuration with respect to the C═N bond. The bond lengths (Allen et al., 1987) and angles are within normal ranges. The asymmetric unit of the compound is composed of one-half of the molecule. The imino group is coplanar with the benzene ring. Within the molecule, the planar units are parallel but extend in opposite directions from the methylene bridge. An interesting feature of the crystal structure is the short Br···Br [3.3747 (3) Å] interaction (Fig. 2), which is significantly shorter than the sum of the van der Waals radii for two Br atoms (3.70 Å). The directionality of these interactions, C—X···X—C (X = halogens), has been attributed to anisotropic van der Waals radii for terminally bound halogens or ascribed to donor–acceptor interactions involving a lone pair donor orbital on one halogen and a C—X σ^* acceptor orbital on the other (Ramasubbu et al., 1986; Brammer et al., 2003). In the crystal structure, molecules are linked into chains along the [201] direction through the short intermolecular Br···Br interactions (Fig. 2). In addition, the crystal structure is further stabilized by π–π interaction (Fig. 3) with centroid-to-centroid distance of 3.6811 (11) Å, perpendicular interplanar distance of 3.3617 (8) Å, and centroid···centroid offset of 1.4997 (5) Å.

Experimental

The synthetic method has been described earlier (Fun, Kia & Kargar, 2008b). Single crystals suitable for X-ray diffraction were obtained by evaporation of an ethanol solution at room temperature.