Acta Cryst. (2009). E65, o682-o683 [ doi:10.1107/S1600536809007284 ]
The molecule of the title Schiff base compound, C18H14N4, 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 with a maximum deviation of 0.1574 (12) Å for the N atom. Within the molecule, the planar units are parallel, but extend in opposite directions from the dimethylene bridge. In the crystal structure, pairs of intermolecular C-H
N hydrogen bonds link neighbouring molecules into centrosymmetric dimers with R22(10) ring motifs. An interesting feature of the crystal structure is the short intermolecular CC interaction with a distance of 3.3821 (13) Å, which is shorter than the sum of the van der Waals radius of a carbon atom.
The synthetic method has been described earlier (Fun, Kargar, & Kia, 2008). 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 = 0.95 or 0.97 Å and refined in riding mode with Uiso (H) = 1.2 Ueq (C).
Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (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, 2009).
![[Figure 1]](./at2733fig1thm.gif)
| Fig. 1. The molecular structure of (I) with atom labels and 50% probability ellipsoids for non-H atoms. The suffix A corresponds to symmetry code [-x + 1, -y, -z]. |
![[Figure 2]](./at2733fig2thm.gif)
| Fig. 2. The crystal packing of (I), viewed approximately down the a-axis, showing dimer formation by R22(10) ring motif. Intermolecular interactions are shown as dashed lines. |
| C18H14N4 | Z = 1 |
| Mr = 286.33 | F(000) = 150 |
| Triclinic, P1 | Dx = 1.328 Mg m−3 |
| Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
| a = 4.6843 (2) Å | Cell parameters from 3276 reflections |
| b = 6.9872 (3) Å | θ = 3.1–36.3° |
| c = 11.6208 (5) Å | µ = 0.08 mm−1 |
| α = 78.147 (3)° | T = 100 K |
| β = 87.462 (3)° | Plate, colourless |
| γ = 74.081 (2)° | 0.45 × 0.29 × 0.06 mm |
| V = 357.94 (3) Å3 |
| Bruker SMART APEXII CCD area-detector diffractometer | 2551 independent reflections |
| Radiation source: fine-focus sealed tube | 2034 reflections with I > 2σ(I) |
| graphite | Rint = 0.023 |
| φ and ω scans | θmax = 32.5°, θmin = 3.1° |
| Absorption correction: multi-scan (SADABS; Bruker, 2005) | h = −6→7 |
| Tmin = 0.964, Tmax = 0.995 | k = −10→10 |
| 7927 measured reflections | l = −17→17 |
| 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)] = 0.047 | Hydrogen site location: inferred from neighbouring sites |
| wR(F2) = 0.146 | H-atom parameters constrained |
| S = 1.08 | w = 1/[σ2(Fo2) + (0.0885P)2 + 0.0252P] where P = (Fo2 + 2Fc2)/3 |
| 2551 reflections | (Δ/σ)max < 0.001 |
| 100 parameters | Δρmax = 0.44 e Å−3 |
| 0 restraints | Δρmin = −0.25 e Å−3 |
| C18H14N4 | γ = 74.081 (2)° |
| Mr = 286.33 | V = 357.94 (3) Å3 |
| Triclinic, P1 | Z = 1 |
| a = 4.6843 (2) Å | Mo Kα radiation |
| b = 6.9872 (3) Å | µ = 0.08 mm−1 |
| c = 11.6208 (5) Å | T = 100 K |
| α = 78.147 (3)° | 0.45 × 0.29 × 0.06 mm |
| β = 87.462 (3)° |
| Bruker SMART APEXII CCD area-detector diffractometer | 2551 independent reflections |
| Absorption correction: multi-scan (SADABS; Bruker, 2005) | 2034 reflections with I > 2σ(I) |
| Tmin = 0.964, Tmax = 0.995 | Rint = 0.023 |
| 7927 measured reflections | θmax = 32.5° |
| R[F2 > 2σ(F2)] = 0.047 | H-atom parameters constrained |
| wR(F2) = 0.146 | Δρmax = 0.44 e Å−3 |
| S = 1.08 | Δρmin = −0.25 e Å−3 |
| 2551 reflections | Absolute structure: ? |
| 100 parameters | Flack parameter: ? |
| 0 restraints | Rogers parameter: ? |
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. |
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 | ||
| N1 | 0.59056 (17) | 0.17735 (11) | 0.08275 (6) | 0.01615 (18) | |
| N2 | 1.42099 (19) | 0.74379 (12) | 0.37951 (7) | 0.0216 (2) | |
| C1 | 0.8714 (2) | 0.45474 (13) | 0.15338 (7) | 0.01522 (19) | |
| H1A | 0.7912 | 0.4927 | 0.0776 | 0.018* | |
| C2 | 1.0275 (2) | 0.57187 (13) | 0.19178 (8) | 0.01621 (19) | |
| H2A | 1.0552 | 0.6873 | 0.1416 | 0.019* | |
| C3 | 1.14366 (19) | 0.51580 (13) | 0.30666 (7) | 0.01489 (19) | |
| C4 | 1.1063 (2) | 0.34172 (13) | 0.38257 (7) | 0.01654 (19) | |
| H4A | 1.1845 | 0.3047 | 0.4586 | 0.020* | |
| C5 | 0.9504 (2) | 0.22467 (13) | 0.34268 (8) | 0.01632 (19) | |
| H5A | 0.9235 | 0.1088 | 0.3927 | 0.020* | |
| C6 | 0.83369 (19) | 0.27878 (13) | 0.22843 (7) | 0.01374 (18) | |
| C7 | 0.67371 (19) | 0.14854 (13) | 0.18937 (7) | 0.01451 (18) | |
| H7A | 0.6322 | 0.0424 | 0.2440 | 0.017* | |
| C8 | 0.4324 (2) | 0.03967 (13) | 0.05429 (7) | 0.01563 (19) | |
| H8A | 0.2243 | 0.1108 | 0.0394 | 0.019* | |
| H8B | 0.4460 | −0.0732 | 0.1202 | 0.019* | |
| C9 | 1.2999 (2) | 0.64058 (13) | 0.34745 (7) | 0.01641 (19) |
| U11 | U22 | U33 | U12 | U13 | U23 | |
| N1 | 0.0164 (4) | 0.0181 (3) | 0.0170 (3) | −0.0075 (3) | −0.0010 (3) | −0.0063 (3) |
| N2 | 0.0229 (4) | 0.0232 (4) | 0.0216 (4) | −0.0100 (3) | −0.0030 (3) | −0.0054 (3) |
| C1 | 0.0149 (4) | 0.0185 (4) | 0.0139 (4) | −0.0058 (3) | −0.0021 (3) | −0.0047 (3) |
| C2 | 0.0167 (4) | 0.0168 (4) | 0.0169 (4) | −0.0068 (3) | −0.0011 (3) | −0.0040 (3) |
| C3 | 0.0127 (4) | 0.0173 (4) | 0.0168 (4) | −0.0051 (3) | −0.0004 (3) | −0.0067 (3) |
| C4 | 0.0169 (4) | 0.0191 (4) | 0.0151 (4) | −0.0059 (3) | −0.0028 (3) | −0.0047 (3) |
| C5 | 0.0175 (4) | 0.0166 (4) | 0.0159 (4) | −0.0063 (3) | −0.0015 (3) | −0.0029 (3) |
| C6 | 0.0120 (4) | 0.0157 (4) | 0.0149 (4) | −0.0040 (3) | −0.0001 (3) | −0.0056 (3) |
| C7 | 0.0142 (4) | 0.0159 (4) | 0.0153 (4) | −0.0059 (3) | 0.0003 (3) | −0.0050 (3) |
| C8 | 0.0159 (4) | 0.0183 (4) | 0.0162 (4) | −0.0085 (3) | −0.0008 (3) | −0.0058 (3) |
| C9 | 0.0158 (4) | 0.0182 (4) | 0.0159 (4) | −0.0047 (3) | −0.0012 (3) | −0.0046 (3) |
| N1—C7 | 1.2745 (11) | C4—C5 | 1.3893 (12) |
| N1—C8 | 1.4585 (11) | C4—H4A | 0.9300 |
| N2—C9 | 1.1551 (11) | C5—C6 | 1.3962 (12) |
| C1—C2 | 1.3821 (11) | C5—H5A | 0.9300 |
| C1—C6 | 1.4031 (12) | C6—C7 | 1.4730 (11) |
| C1—H1A | 0.9300 | C7—H7A | 0.9300 |
| C2—C3 | 1.4017 (12) | C8—C8i | 1.5246 (16) |
| C2—H2A | 0.9300 | C8—H8A | 0.9700 |
| C3—C4 | 1.3966 (12) | C8—H8B | 0.9700 |
| C3—C9 | 1.4389 (11) | ||
| C7—N1—C8 | 117.00 (7) | C6—C5—H5A | 119.6 |
| C2—C1—C6 | 120.14 (8) | C5—C6—C1 | 119.61 (8) |
| C2—C1—H1A | 119.9 | C5—C6—C7 | 118.94 (7) |
| C6—C1—H1A | 119.9 | C1—C6—C7 | 121.45 (8) |
| C1—C2—C3 | 119.68 (8) | N1—C7—C6 | 121.78 (8) |
| C1—C2—H2A | 120.2 | N1—C7—H7A | 119.1 |
| C3—C2—H2A | 120.2 | C6—C7—H7A | 119.1 |
| C4—C3—C2 | 120.80 (8) | N1—C8—C8i | 109.60 (9) |
| C4—C3—C9 | 119.58 (8) | N1—C8—H8A | 109.8 |
| C2—C3—C9 | 119.61 (7) | C8i—C8—H8A | 109.8 |
| C5—C4—C3 | 118.95 (8) | N1—C8—H8B | 109.8 |
| C5—C4—H4A | 120.5 | C8i—C8—H8B | 109.8 |
| C3—C4—H4A | 120.5 | H8A—C8—H8B | 108.2 |
| C4—C5—C6 | 120.81 (8) | N2—C9—C3 | 178.76 (9) |
| C4—C5—H5A | 119.6 | ||
| C6—C1—C2—C3 | −1.03 (13) | C4—C5—C6—C7 | 179.13 (7) |
| C1—C2—C3—C4 | 0.65 (13) | C2—C1—C6—C5 | 1.07 (13) |
| C1—C2—C3—C9 | −178.50 (7) | C2—C1—C6—C7 | −178.76 (7) |
| C2—C3—C4—C5 | −0.28 (13) | C8—N1—C7—C6 | −179.67 (7) |
| C9—C3—C4—C5 | 178.86 (7) | C5—C6—C7—N1 | −172.24 (8) |
| C3—C4—C5—C6 | 0.32 (14) | C1—C6—C7—N1 | 7.59 (14) |
| C4—C5—C6—C1 | −0.71 (14) | C7—N1—C8—C8i | −131.42 (10) |
| Symmetry codes: (i) −x+1, −y, −z. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| C4—H4A···N2ii | 0.93 | 2.60 | 3.4702 (12) | 156 |
| Symmetry codes: (ii) −x+3, −y+1, −z+1. |
| D—H···A | D—H | H···A | D···A | D—H···A |
| C4—H4A···N2i | 0.93 | 2.60 | 3.4702 (12) | 156 |
| Symmetry codes: (i) −x+3, −y+1, −z+1. |
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. HK thanks PNU for financial support. HKF also thanks Universiti Sains Malaysia for the Research University Golden Goose grant No. 1001/PFIZIK/811012.
Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–S19.
Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555–1573.
Bruker (2005). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.
Calligaris, M. & Randaccio, L. (1987). Comprehensive Coordination Chemistry, Vol. 2, edited by G. Wilkinson, pp. 715–738. London: Pergamon.
Cosier, J. & Glazer, A. M. (1986). J. Appl. Cryst. 19, 105–107.
Fun, H.-K., Kargar, H. & Kia, R. (2008). Acta Cryst. E64, o1308.
Fun, H.-K. & Kia, R. (2008). Acta Cryst. E64, o1722–o1723.
Fun, H.-K., Kia, R. & Kargar, H. (2008). Acta Cryst. E64, o1335.
Hou, B., Friedman, N., Ruhman, S., Sheves, M. & Ottolenghi, M. (2001). J. Phys. Chem. B, 105, 7042–7048.
Pal, S., Barik, A. K., Gupta, S., Hazra, A., Kar, S. K., Peng, S.-M., Lee, G.-H., Butcher, R. J., El Fallah, M. S. & Ribas, J. (2005). Inorg. Chem. 44, 3880–3889.
Ren, S., Wang, R., Komatsu, K., Bonaz-Krause, P., Zyrianov, Y., McKenna, C. E., Csipke, C., Tokes, Z. A. & Lien, E. J. (2002). J. Med. Chem. 45, 410–419.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.
Spek, A. L. (2009). Acta Cryst. D65, 148–155.
Schiff bases are among the most prevalent mixed-donor ligands in the field of coordination chemistry in which there has been growing interest, mainly because of their wide application in the areas such as 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 had their X-ray structures reported (Calligaris & Randaccio, 1987). As an extension of our work (Fun, Kargar & Kia 2008; Fun, Kia & Kargar 2008) on the structural characterization of Schiff base ligands, the title compound (I), 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 azomethine (C═N) bond. The bond lengths (Allen et al., 1987) and angles are within normal ranges and are comparable with the values found in related structures (Fun & Kia 2008; Fun, Kargar & Kia 2008; Fun, Kia & Kargar 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 C3···C6 interactions [symmetry code: 1 + x, y, z] with a distance of 3.3821 (13) Å, which is shorter than the sum of the van der Waals radius of carbon atom. In the crystal structure, pairs of intermolecular C—H···N hydrogen bonds link neighbouring molecules into dimer with R22(10) ring motif (Bernstein et al., 1995) (Table 1, Fig. 2).