Acta Cryst. (2008). E64, o1941-o1942 [ doi:10.1107/S1600536808029000 ]
The molecule of the title Schiff base compound, C16H12Br2F2N2, lies across a crystallographic inversion centre and adopts an E configuration with respect to the azomethine C=N bonds. The imino groups are coplanar with the aromatic rings. Within the molecule, the planar units are parallel, but extend in opposite directions from the dimethylene bridge. An interesting feature of the crystal structure is the short intermolecular Br
F interactions [3.2347 (16) Å, which is shorter than the sum of the van der Waals radii of these atoms]. These interactions link neighbouring molecules along the c axis. The crystal structure is further stabilized by intermolecular C-HN hydrogen bonds.
The synthetic method has been described earlier (Fun & Kia 2008a). Single crystals suitable for X-ray diffraction were obtained by evaporation of an ethanol solution at room temperature.
All of the hydrogen atoms were positioned geometrically with C—H = 0.93 or 0.97 Å and refined in riding model with Uiso (H) = 1.2 Ueq (C). The highest peak is located 1.73 Å from Br1 and the deepest hole is located 0.7 Å from Br1.
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]](./at2629fig1thm.gif)
| Fig. 1. The molecular structure of (I) with atom labels and 50% probability ellipsoids for non-H atoms [symmetry code for A: -x, -y, -z. |
![[Figure 2]](./at2629fig2thm.gif)
| Fig. 2. The crystal packing of (I), viewed down the a-axis, shows linking of molecules by Br···F contacts along the c-axis and the stacking of these molecules down the a-axis. Intermolecular interactions are shown as dashed lines. |
| C16H12Br2F2N2 | F(000) = 420 |
| Mr = 430.10 | Dx = 1.868 Mg m−3 |
| Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
| Hall symbol: -P 2ybc | Cell parameters from 5643 reflections |
| a = 4.1981 (1) Å | θ = 3.2–30.0° |
| b = 14.6190 (3) Å | µ = 5.32 mm−1 |
| c = 12.8861 (3) Å | T = 100 K |
| β = 104.751 (2)° | Needle, colourless |
| V = 764.78 (3) Å3 | 0.51 × 0.07 × 0.05 mm |
| Z = 2 |
| Bruker SMART APEXII CCD area-detector diffractometer | 2631 independent reflections |
| Radiation source: fine-focus sealed tube | 1907 reflections with I > 2σ(I) |
| graphite | Rint = 0.050 |
| φ and ω scans | θmax = 32.0°, θmin = 2.2° |
| Absorption correction: multi-scan (SADABS; Bruker, 2005) | h = −6→6 |
| Tmin = 0.172, Tmax = 0.770 | k = −21→21 |
| 19361 measured reflections | l = −19→18 |
| 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)] = 0.040 | Hydrogen site location: inferred from neighbouring sites |
| wR(F2) = 0.100 | H-atom parameters constrained |
| S = 1.05 | w = 1/[σ2(Fo2) + (0.0539P)2] where P = (Fo2 + 2Fc2)/3 |
| 2631 reflections | (Δ/σ)max < 0.001 |
| 100 parameters | Δρmax = 1.40 e Å−3 |
| 0 restraints | Δρmin = −0.86 e Å−3 |
| C16H12Br2F2N2 | V = 764.78 (3) Å3 |
| Mr = 430.10 | Z = 2 |
| Monoclinic, P21/c | Mo Kα radiation |
| a = 4.1981 (1) Å | µ = 5.32 mm−1 |
| b = 14.6190 (3) Å | T = 100 K |
| c = 12.8861 (3) Å | 0.51 × 0.07 × 0.05 mm |
| β = 104.751 (2)° |
| Bruker SMART APEXII CCD area-detector diffractometer | 2631 independent reflections |
| Absorption correction: multi-scan (SADABS; Bruker, 2005) | 1907 reflections with I > 2σ(I) |
| Tmin = 0.172, Tmax = 0.770 | Rint = 0.050 |
| 19361 measured reflections | θmax = 32.0° |
| R[F2 > 2σ(F2)] = 0.040 | H-atom parameters constrained |
| wR(F2) = 0.100 | Δρmax = 1.40 e Å−3 |
| S = 1.05 | Δρmin = −0.86 e Å−3 |
| 2631 reflections | Absolute structure: ? |
| 100 parameters | Flack parameter: ? |
| 0 restraints | Rogers parameter: ? |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s 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 > σ(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 | −0.74079 (7) | −0.51485 (2) | 0.18481 (2) | 0.02329 (11) | |
| F1 | −0.0347 (4) | −0.22639 (11) | 0.31348 (12) | 0.0267 (4) | |
| N1 | −0.0960 (6) | −0.12204 (15) | 0.01873 (19) | 0.0192 (5) | |
| C1 | −0.2112 (7) | −0.27577 (19) | 0.2280 (2) | 0.0199 (5) | |
| C2 | −0.3675 (7) | −0.35336 (19) | 0.2493 (2) | 0.0206 (6) | |
| H2A | −0.3576 | −0.3716 | 0.3192 | 0.025* | |
| C3 | −0.5404 (7) | −0.40314 (18) | 0.1619 (2) | 0.0181 (5) | |
| C4 | −0.5632 (7) | −0.37558 (19) | 0.0569 (2) | 0.0215 (6) | |
| H4A | −0.6819 | −0.4099 | −0.0009 | 0.026* | |
| C5 | −0.4047 (7) | −0.29567 (19) | 0.0405 (2) | 0.0208 (6) | |
| H5A | −0.4212 | −0.2761 | −0.0293 | 0.025* | |
| C6 | −0.2210 (6) | −0.24370 (18) | 0.1260 (2) | 0.0174 (5) | |
| C7 | −0.0381 (6) | −0.16150 (18) | 0.1090 (2) | 0.0182 (5) | |
| H7A | 0.1239 | −0.1380 | 0.1659 | 0.022* | |
| C8 | 0.1076 (7) | −0.04254 (19) | 0.0114 (2) | 0.0208 (5) | |
| H8A | 0.2171 | −0.0516 | −0.0456 | 0.025* | |
| H8B | 0.2750 | −0.0349 | 0.0783 | 0.025* |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| Br1 | 0.02442 (16) | 0.01848 (15) | 0.02622 (17) | −0.00289 (11) | 0.00507 (11) | 0.00316 (11) |
| F1 | 0.0383 (10) | 0.0214 (9) | 0.0173 (8) | −0.0032 (7) | 0.0014 (7) | −0.0029 (6) |
| N1 | 0.0213 (11) | 0.0165 (11) | 0.0209 (11) | −0.0001 (9) | 0.0072 (9) | 0.0004 (9) |
| C1 | 0.0220 (13) | 0.0195 (14) | 0.0163 (12) | 0.0024 (10) | 0.0015 (10) | −0.0035 (10) |
| C2 | 0.0261 (14) | 0.0187 (13) | 0.0168 (13) | 0.0035 (10) | 0.0051 (11) | 0.0018 (10) |
| C3 | 0.0191 (12) | 0.0153 (12) | 0.0209 (13) | −0.0006 (9) | 0.0066 (10) | 0.0012 (10) |
| C4 | 0.0221 (13) | 0.0231 (14) | 0.0187 (13) | −0.0001 (11) | 0.0042 (11) | −0.0006 (11) |
| C5 | 0.0231 (13) | 0.0197 (13) | 0.0185 (13) | 0.0003 (10) | 0.0034 (11) | 0.0022 (10) |
| C6 | 0.0192 (13) | 0.0142 (12) | 0.0196 (13) | 0.0031 (9) | 0.0064 (10) | 0.0015 (10) |
| C7 | 0.0182 (12) | 0.0151 (12) | 0.0210 (13) | 0.0016 (9) | 0.0042 (10) | −0.0022 (10) |
| C8 | 0.0178 (12) | 0.0194 (12) | 0.0251 (14) | −0.0027 (10) | 0.0055 (10) | −0.0026 (11) |
| Br1—C3 | 1.895 (3) | C4—C5 | 1.387 (4) |
| F1—C1 | 1.366 (3) | C4—H4A | 0.9300 |
| N1—C7 | 1.265 (3) | C5—C6 | 1.398 (4) |
| N1—C8 | 1.460 (4) | C5—H5A | 0.9300 |
| C1—C2 | 1.373 (4) | C6—C7 | 1.472 (4) |
| C1—C6 | 1.387 (4) | C7—H7A | 0.9300 |
| C2—C3 | 1.382 (4) | C8—C8i | 1.521 (6) |
| C2—H2A | 0.9300 | C8—H8A | 0.9700 |
| C3—C4 | 1.391 (4) | C8—H8B | 0.9700 |
| C7—N1—C8 | 116.3 (2) | C4—C5—H5A | 119.1 |
| F1—C1—C2 | 117.7 (2) | C6—C5—H5A | 119.1 |
| F1—C1—C6 | 117.7 (2) | C1—C6—C5 | 116.2 (2) |
| C2—C1—C6 | 124.6 (3) | C1—C6—C7 | 121.8 (2) |
| C1—C2—C3 | 116.8 (3) | C5—C6—C7 | 122.0 (2) |
| C1—C2—H2A | 121.6 | N1—C7—C6 | 121.6 (2) |
| C3—C2—H2A | 121.6 | N1—C7—H7A | 119.2 |
| C2—C3—C4 | 122.2 (2) | C6—C7—H7A | 119.2 |
| C2—C3—Br1 | 119.2 (2) | N1—C8—C8i | 109.6 (3) |
| C4—C3—Br1 | 118.6 (2) | N1—C8—H8A | 109.8 |
| C5—C4—C3 | 118.4 (3) | C8i—C8—H8A | 109.8 |
| C5—C4—H4A | 120.8 | N1—C8—H8B | 109.8 |
| C3—C4—H4A | 120.8 | C8i—C8—H8B | 109.8 |
| C4—C5—C6 | 121.9 (3) | H8A—C8—H8B | 108.2 |
| F1—C1—C2—C3 | −179.0 (2) | F1—C1—C6—C7 | 2.4 (4) |
| C6—C1—C2—C3 | 1.3 (4) | C2—C1—C6—C7 | −177.9 (3) |
| C1—C2—C3—C4 | −1.5 (4) | C4—C5—C6—C1 | −1.1 (4) |
| C1—C2—C3—Br1 | 176.3 (2) | C4—C5—C6—C7 | 176.7 (3) |
| C2—C3—C4—C5 | 0.4 (4) | C8—N1—C7—C6 | −178.5 (2) |
| Br1—C3—C4—C5 | −177.4 (2) | C1—C6—C7—N1 | −165.9 (3) |
| C3—C4—C5—C6 | 1.0 (4) | C5—C6—C7—N1 | 16.4 (4) |
| F1—C1—C6—C5 | −179.8 (2) | C7—N1—C8—C8i | −115.8 (3) |
| C2—C1—C6—C5 | −0.1 (4) |
| Symmetry codes: (i) −x, −y, −z. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| C2—H2A···N1ii | 0.93 | 2.53 | 3.386 (3) | 154. |
| Symmetry codes: (ii) x, −y−1/2, z+1/2. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| C2—H2A···N1i | 0.93 | 2.53 | 3.386 (3) | 154. |
| Symmetry codes: (i) x, −y−1/2, z+1/2. |
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 post-doctoral research fellowship.
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Schiff bases are one of most prevalent mixed-donor ligands in the field of coordination chemistry. There has been growing interest in Schiff base ligands, mainly because of their wide application in the field of biochemistry, synthesis, and catalysis (Pal et al., 2005; Hou et al., 2001; Ren et al., 2002). Many Schiff base complexes have been structurally characterized, but only a relatively small number of free Schiff bases have been characterized (Calligaris & Randaccio, 1987). As an extension of our work (Fun & Kia 2008a,b,c; Fun et al., 2008) on the structural characterization of Schiff base ligands, and the halogen-halogen interactions in the halogen-subtituated Schiff bases, the title compound (I), is reported here.
The molecule of the title compound, (I), (Fig. 1), lies across a crystallographic inversion centre and adopts an E configuration with respect to the azomethine C═N bond. The bond lengths (Allen et al., 1987) and angles are within normal ranges and are comparable with the related structures (Fun & Kia 2008a,b,c; Fun et al., 2008). The two planar units are parallel but extend in opposite directions from the dimethylene bridge. The interesting feature of the crystal structure is the short intermolecular Br···F interactions [symmetry code: 1 - x, -1/2 + y, 1/2 - z] with the distance of 3.2347 (16) Å, which is shorter than the sum of the van der Waals radii of these atoms. 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). These interactions link neighbouring molecules along the c-axis (Fig. 2). The crystal structure is further stabilized by intermolecular C—H···N hydrogen bonds (Table 1).