Acta Cryst. (2008). E64, o1894 [ doi:10.1107/S1600536808028122 ]
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 ![[pi]](/logos/entities/pi_rmgif.gif)
- stacking interactions [centroid-centroid distance 3.6811 (11) Å].
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.
Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2 (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2003).
![[Figure 1]](./rz2242fig1thm.gif)
| Fig. 1. The molecular structure of the title compound with atom labels and 50% probability ellipsoids for non-H atoms. The suffix A corresponds to symmetry code (-x, -y + 1, -z). |
![[Figure 2]](./rz2242fig2thm.gif)
| Fig. 2. The crystal packing of the title compound viewed down the b axis, showing molecules linked into chains along the [201] direction by short intermolecular Br···Br interactions. |
![[Figure 3]](./rz2242fig3thm.gif)
| Fig. 3. The crystal packing of the title compound viewed down the b-axis, showing the π–π stacking arrangement of molecules. |
| C18H18Br2N2 | F(000) = 420 |
| Mr = 422.16 | Dx = 1.607 Mg m−3 |
| Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
| Hall symbol: -P 2ybc | Cell parameters from 5047 reflections |
| a = 11.2612 (5) Å | θ = 2.8–33.0° |
| b = 9.5213 (4) Å | µ = 4.64 mm−1 |
| c = 8.2645 (4) Å | T = 100 K |
| β = 100.040 (3)° | Plate, colourless |
| V = 872.56 (7) Å3 | 0.52 × 0.23 × 0.08 mm |
| Z = 2 |
| Bruker SMART APEXII CCD area-detector diffractometer | 3843 independent reflections |
| Radiation source: fine-focus sealed tube | 2600 reflections with I > 2σ(I) |
| graphite | Rint = 0.037 |
| φ and ω scans | θmax = 35.0°, θmin = 1.8° |
| Absorption correction: multi-scan (SADABS; Bruker, 2005) | h = −10→18 |
| Tmin = 0.192, Tmax = 0.688 | k = −15→15 |
| 15460 measured reflections | l = −13→13 |
| Refinement on F2 | Primary atom site location: structure-invariant direct methods |
| Least-squares matrix: full | Secondary atom site location: difference Fourier map |
| R[F2 > 2σ(F2)] = 0.037 | Hydrogen site location: inferred from neighbouring sites |
| wR(F2) = 0.092 | All H-atom parameters refined |
| S = 1.02 | w = 1/[σ2(Fo2) + (0.0376P)2 + 0.4289P] where P = (Fo2 + 2Fc2)/3 |
| 3843 reflections | (Δ/σ)max = 0.001 |
| 136 parameters | Δρmax = 0.68 e Å−3 |
| 0 restraints | Δρmin = −0.59 e Å−3 |
| C18H18Br2N2 | V = 872.56 (7) Å3 |
| Mr = 422.16 | Z = 2 |
| Monoclinic, P21/c | Mo Kα radiation |
| a = 11.2612 (5) Å | µ = 4.64 mm−1 |
| b = 9.5213 (4) Å | T = 100 K |
| c = 8.2645 (4) Å | 0.52 × 0.23 × 0.08 mm |
| β = 100.040 (3)° |
| Bruker SMART APEXII CCD area-detector diffractometer | 3843 independent reflections |
| Absorption correction: multi-scan (SADABS; Bruker, 2005) | 2600 reflections with I > 2σ(I) |
| Tmin = 0.192, Tmax = 0.688 | Rint = 0.037 |
| 15460 measured reflections | θmax = 35.0° |
| R[F2 > 2σ(F2)] = 0.037 | All H-atom parameters refined |
| wR(F2) = 0.092 | Δρmax = 0.68 e Å−3 |
| S = 1.02 | Δρmin = −0.59 e Å−3 |
| 3843 reflections | Absolute structure: ? |
| 136 parameters | Flack parameter: ? |
| 0 restraints | Rogers parameter: ? |
Experimental. The low-temperature data was collected with the Oxford Cyrosystem Cobra low-temperature attachment. |
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2sigma(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
| x | y | z | Uiso*/Ueq | ||
| Br1 | 0.863352 (18) | 0.42295 (2) | 0.45375 (3) | 0.03180 (8) | |
| N1 | 0.26074 (15) | 0.39137 (18) | 0.1162 (2) | 0.0234 (3) | |
| C1 | 0.50731 (18) | 0.31392 (19) | 0.4478 (2) | 0.0208 (4) | |
| C2 | 0.63137 (18) | 0.3255 (2) | 0.4915 (3) | 0.0240 (4) | |
| C3 | 0.69332 (18) | 0.40815 (19) | 0.3962 (2) | 0.0222 (4) | |
| C4 | 0.63436 (18) | 0.4810 (2) | 0.2596 (2) | 0.0216 (4) | |
| C5 | 0.50998 (17) | 0.4680 (2) | 0.2182 (2) | 0.0200 (3) | |
| C6 | 0.44549 (16) | 0.38295 (19) | 0.3101 (2) | 0.0184 (3) | |
| C7 | 0.31505 (17) | 0.3638 (2) | 0.2606 (2) | 0.0204 (3) | |
| C8 | 0.13050 (18) | 0.3707 (2) | 0.0806 (3) | 0.0261 (4) | |
| C9 | 0.06720 (18) | 0.5093 (2) | 0.0273 (3) | 0.0245 (4) | |
| H1 | 0.462 (2) | 0.260 (3) | 0.514 (3) | 0.028 (6)* | |
| H2 | 0.679 (2) | 0.273 (3) | 0.586 (3) | 0.028 (6)* | |
| H4 | 0.678 (2) | 0.540 (3) | 0.209 (3) | 0.032 (7)* | |
| H5 | 0.470 (2) | 0.515 (3) | 0.130 (3) | 0.024 (6)* | |
| H7 | 0.276 (2) | 0.330 (2) | 0.341 (3) | 0.018 (5)* | |
| H8A | 0.113 (2) | 0.300 (3) | −0.016 (3) | 0.023 (6)* | |
| H8B | 0.1034 (19) | 0.336 (2) | 0.172 (3) | 0.016 (5)* | |
| H9A | 0.111 (3) | 0.550 (3) | −0.053 (4) | 0.034 (7)* | |
| H9B | 0.092 (3) | 0.576 (3) | 0.111 (3) | 0.033 (7)* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Br1 | 0.01994 (10) | 0.03249 (12) | 0.04155 (14) | −0.00088 (8) | 0.00144 (8) | −0.00353 (9) |
| N1 | 0.0197 (7) | 0.0250 (8) | 0.0255 (8) | 0.0015 (6) | 0.0042 (6) | 0.0006 (6) |
| C1 | 0.0261 (9) | 0.0185 (8) | 0.0185 (8) | −0.0004 (7) | 0.0055 (7) | 0.0000 (7) |
| C2 | 0.0273 (9) | 0.0214 (8) | 0.0220 (9) | 0.0017 (7) | 0.0012 (7) | −0.0003 (7) |
| C3 | 0.0221 (8) | 0.0208 (8) | 0.0237 (9) | 0.0000 (7) | 0.0041 (7) | −0.0045 (7) |
| C4 | 0.0248 (9) | 0.0185 (8) | 0.0230 (9) | −0.0022 (7) | 0.0088 (7) | −0.0014 (7) |
| C5 | 0.0239 (9) | 0.0175 (7) | 0.0194 (9) | 0.0003 (7) | 0.0060 (7) | 0.0009 (7) |
| C6 | 0.0204 (8) | 0.0156 (7) | 0.0196 (8) | 0.0008 (6) | 0.0048 (6) | −0.0013 (6) |
| C7 | 0.0213 (8) | 0.0190 (8) | 0.0224 (9) | −0.0001 (7) | 0.0080 (7) | 0.0014 (7) |
| C8 | 0.0201 (9) | 0.0286 (10) | 0.0301 (11) | −0.0004 (7) | 0.0055 (8) | 0.0020 (8) |
| C9 | 0.0200 (8) | 0.0248 (9) | 0.0285 (10) | −0.0005 (7) | 0.0034 (7) | 0.0018 (8) |
| Br1—C3 | 1.896 (2) | C5—C6 | 1.398 (3) |
| N1—C7 | 1.270 (2) | C5—H5 | 0.91 (2) |
| N1—C8 | 1.458 (3) | C6—C7 | 1.466 (3) |
| C1—C2 | 1.385 (3) | C7—H7 | 0.92 (2) |
| C1—C6 | 1.391 (3) | C8—C9 | 1.527 (3) |
| C1—H1 | 0.95 (3) | C8—H8A | 1.04 (2) |
| C2—C3 | 1.385 (3) | C8—H8B | 0.93 (2) |
| C2—H2 | 1.00 (3) | C9—C9i | 1.512 (4) |
| C3—C4 | 1.391 (3) | C9—H9A | 0.97 (3) |
| C4—C5 | 1.388 (3) | C9—H9B | 0.94 (3) |
| C4—H4 | 0.90 (3) | ||
| C7—N1—C8 | 117.69 (18) | C1—C6—C7 | 120.26 (18) |
| C2—C1—C6 | 120.93 (19) | C5—C6—C7 | 120.70 (17) |
| C2—C1—H1 | 120.3 (15) | N1—C7—C6 | 122.12 (18) |
| C6—C1—H1 | 118.7 (15) | N1—C7—H7 | 123.0 (14) |
| C3—C2—C1 | 118.83 (18) | C6—C7—H7 | 114.8 (14) |
| C3—C2—H2 | 118.2 (15) | N1—C8—C9 | 110.13 (18) |
| C1—C2—H2 | 122.9 (15) | N1—C8—H8A | 107.3 (13) |
| C2—C3—C4 | 121.89 (18) | C9—C8—H8A | 108.9 (13) |
| C2—C3—Br1 | 119.12 (14) | N1—C8—H8B | 110.2 (13) |
| C4—C3—Br1 | 118.99 (15) | C9—C8—H8B | 109.9 (14) |
| C5—C4—C3 | 118.31 (19) | H8A—C8—H8B | 110.3 (19) |
| C5—C4—H4 | 123.6 (17) | C9i—C9—C8 | 112.2 (2) |
| C3—C4—H4 | 117.8 (17) | C9i—C9—H9A | 116.2 (16) |
| C4—C5—C6 | 120.99 (18) | C8—C9—H9A | 106.1 (16) |
| C4—C5—H5 | 119.6 (16) | C9i—C9—H9B | 116.7 (18) |
| C6—C5—H5 | 119.4 (16) | C8—C9—H9B | 107.8 (16) |
| C1—C6—C5 | 119.02 (17) | H9A—C9—H9B | 96 (2) |
| Symmetry codes: (i) −x, −y+1, −z. |
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.
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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.