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A second monoclinic polymorph of 4,4′-[butane-1,4-diylbis(nitrilo­methyl­­idyne)]dibenzo­nitrile

aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia, and bDepartment of Chemistry, School of Science, Payame Noor University (PNU), Ardakan, Yazd, Iran
*Correspondence e-mail: hkfun@usm.my

(Received 6 November 2008; accepted 12 November 2008; online 20 November 2008)

The asymmetric unit of the title Schiff base compound, C20H18N4, contains one half-mol­ecule, lying across a crystallographic inversion centre and adopting an E configuration with respect to the C=N bonds. The imino group is coplanar with the benzene ring with a maximun deviation of 0.096 (1) Å for the N atom. Within the molecule, the planar units are parallel but extend in opposite directions from the methylene bridge. In the crystal structure, neighbouring mol­ecules are linked together by weak inter­molecular C—H⋯N hydrogen bonds involving the cyano N atoms, forming R22(10) ring motifs.

Related literature

For general background, see: Casellato & Vigato (1977[Casellato, U. & Vigato, P. A. (1977). Coord. Chem. Rev. 23, 31-50.]); Calligaris & Randaccio (1987[Calligaris, M. & Randaccio, L. (1987). Comprehensive Coordination Chemistry, Vol. 2, edited by G. Wilkinson, pp. 715-738. London: Pergamon.]). For related structures, see: Fun et al. (2008[Fun, H.-K., Kargar, H. & Kia, R. (2008). Acta Cryst. E64, o1308.]); Fun, Kia & Kargar (2008a[Fun, H.-K., Kia, R. & Kargar, H. (2008a). Acta Cryst. E64, o1335.],b[Fun, H.-K., Kia, R. & Kargar, H. (2008b). Acta Cryst. E64, o1855.]); Fun & Kia (2008a[Fun, H.-K. & Kia, R. (2008a). Acta Cryst. E64, m1081-m1082.],b[Fun, H.-K. & Kia, R. (2008b). Acta Cryst. E64, m1116-m1117.]). For bond-length data, see: Allen et al. (1987[Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1-19.]). For hydrogen-bond motifs, see: Bernstein et al. (1995[Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555-1573.]).

[Scheme 1]

Experimental

Crystal data
  • C20H18N4

  • Mr = 314.38

  • Monoclinic, P 21 /n

  • a = 4.9958 (1) Å

  • b = 14.8164 (2) Å

  • c = 11.6633 (2) Å

  • β = 97.310 (1)°

  • V = 856.30 (3) Å3

  • Z = 2

  • Mo Kα radiation

  • μ = 0.07 mm−1

  • T = 100.0 (1) K

  • 0.39 × 0.29 × 0.28 mm

Data collection
  • Bruker SMART APEXII CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2005[Bruker (2005). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.891, Tmax = 0.979

  • 18411 measured reflections

  • 4473 independent reflections

  • 3659 reflections with I > 2σ(I)

  • Rint = 0.026

Refinement
  • R[F2 > 2σ(F2)] = 0.044

  • wR(F2) = 0.135

  • S = 1.04

  • 4473 reflections

  • 109 parameters

  • H-atom parameters constrained

  • Δρmax = 0.55 e Å−3

  • Δρmin = −0.26 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C2—H2A⋯N2i 0.93 2.52 3.4037 (11) 158
Symmetry code: (i) -x+2, -y, -z.

Data collection: APEX2 (Bruker, 2005[Bruker (2005). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2005[Bruker (2005). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2003[Spek, A. L. (2003). J. Appl. Cryst. 36, 7-13.]).

Supporting information


Comment top

The condensation of primary amines with carbonyl compounds yields Schiff base compounds (Casellato & Vigato, 1977); these are still one of the most prevalent mixed-donor ligands in coordination chemistry. In the past two decades, the syntheses, structures and properties of Schiff base complexes have stimulated much interest due to their noteworthy contributions in single molecule-based magnetism, materials science and the catalysis of many reactions such as carbonylation, hydroformylation, reduction, oxidation, epoxidation and hydrolysis (Casellato & Vigato 1977). In comparison to the Schiff base metal complexes, only a relatively small number of free Schiff base ligands have been characterized structurally (Calligaris & Randaccio, 1987). 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, we reported herein the crystal structure of the title compound.

The asymmetric unit of the title compound contains one-half molecule (Fig. 1), lying across a crystallographic inversion centre and adopting E configurations with respect to the CN bonds. The bond lengths (Allen et al., 1987) and angles are within normal ranges and are comparable with the related structure (Fun et al., 2008). The imino group is coplanar with the benzene ring, and the planar units are parallel but extend in opposite directions from the methylene bridge.

In the crystal structure, neighbouring molecules are linked together by weak intermolecular C-H···N hydrogen bonds (Table 1) involving the cyano N atoms, forming ten-membered rings with R22(10) ring motifs (Bernstein et al., 1995).

Related literature top

For general background, see: Casellato & Vigato (1977); Calligaris & Randaccio (1987). For related structures, 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-bond motifs, see: Bernstein et al. (1995).

Experimental top

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

Refinement top

H atoms were positioned geometrically, with C-H = 0.93 and 0.97 Å for aromatic and methylene H, respectively, and constrained to ride on their parent atoms with Uiso(H) = 1.2Ueq(C). The highest peak is located 0.68 Å from C5 atom.

Computing details top

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, 2003).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level [symmetry code: (A) -x, 1 - y, -z].
[Figure 2] Fig. 2. A partial packing diagram viewed down the a axis, showing R22(10) ring motifs. Hydrogen bonds are shown as dashed lines.
4,4'-[butane-1,4-diylbis(nitrilomethylidyne)]dibenzonitrile top
Crystal data top
C20H18N4F(000) = 332
Mr = 314.38Dx = 1.219 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ynCell parameters from 6822 reflections
a = 4.9958 (1) Åθ = 2.2–39.9°
b = 14.8164 (2) ŵ = 0.08 mm1
c = 11.6633 (2) ÅT = 100 K
β = 97.310 (1)°Block, yellow
V = 856.30 (3) Å30.39 × 0.29 × 0.28 mm
Z = 2
Data collection top
Bruker SMART APEXII CCD area-detector
diffractometer
4473 independent reflections
Radiation source: fine-focus sealed tube3659 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.026
ϕ and ω scansθmax = 37.5°, θmin = 2.8°
Absorption correction: multi-scan
(SADABS; Bruker, 2005)
h = 88
Tmin = 0.891, Tmax = 0.979k = 2425
18411 measured reflectionsl = 1918
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.044Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.135H-atom parameters constrained
S = 1.04 w = 1/[σ2(Fo2) + (0.0727P)2 + 0.1307P]
where P = (Fo2 + 2Fc2)/3
4473 reflections(Δ/σ)max < 0.001
109 parametersΔρmax = 0.55 e Å3
0 restraintsΔρmin = 0.26 e Å3
Crystal data top
C20H18N4V = 856.30 (3) Å3
Mr = 314.38Z = 2
Monoclinic, P21/nMo Kα radiation
a = 4.9958 (1) ŵ = 0.08 mm1
b = 14.8164 (2) ÅT = 100 K
c = 11.6633 (2) Å0.39 × 0.29 × 0.28 mm
β = 97.310 (1)°
Data collection top
Bruker SMART APEXII CCD area-detector
diffractometer
4473 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2005)
3659 reflections with I > 2σ(I)
Tmin = 0.891, Tmax = 0.979Rint = 0.026
18411 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0440 restraints
wR(F2) = 0.135H-atom parameters constrained
S = 1.04Δρmax = 0.55 e Å3
4473 reflectionsΔρmin = 0.26 e Å3
109 parameters
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
N10.01080 (11)0.32548 (4)0.04403 (5)0.01925 (11)
N21.09394 (17)0.03532 (5)0.17351 (7)0.03381 (17)
C10.40142 (14)0.18220 (4)0.04338 (6)0.01953 (12)
H1A0.30660.19730.02790.023*
C20.59829 (14)0.11593 (5)0.04968 (6)0.02080 (12)
H2A0.63600.08660.01690.025*
C30.74003 (13)0.09356 (4)0.15748 (6)0.01898 (11)
C40.68642 (13)0.13779 (5)0.25771 (6)0.02032 (12)
H4A0.78270.12310.32880.024*
C50.48772 (13)0.20402 (4)0.25021 (5)0.01888 (11)
H5A0.45030.23350.31680.023*
C60.34401 (12)0.22663 (4)0.14350 (5)0.01610 (11)
C70.13465 (12)0.29707 (4)0.13917 (5)0.01716 (11)
H7A0.09190.32150.20800.021*
C80.19246 (13)0.39541 (4)0.05029 (6)0.02132 (12)
H8A0.19370.41350.13010.026*
H8B0.36940.37150.02210.026*
C90.13397 (12)0.47738 (4)0.02174 (6)0.01933 (12)
H9A0.13140.45870.10130.023*
H9B0.27850.52090.02040.023*
C100.93805 (15)0.02262 (5)0.16554 (6)0.02439 (14)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0200 (2)0.0161 (2)0.0217 (2)0.00380 (17)0.00313 (18)0.00211 (17)
N20.0380 (4)0.0346 (4)0.0290 (3)0.0179 (3)0.0052 (3)0.0058 (3)
C10.0237 (3)0.0179 (2)0.0164 (2)0.0047 (2)0.00064 (19)0.00065 (19)
C20.0249 (3)0.0188 (3)0.0187 (3)0.0055 (2)0.0026 (2)0.0003 (2)
C30.0188 (2)0.0166 (2)0.0215 (3)0.00276 (18)0.00223 (19)0.00326 (19)
C40.0197 (2)0.0220 (3)0.0185 (3)0.0020 (2)0.00060 (19)0.0026 (2)
C50.0199 (2)0.0200 (3)0.0163 (2)0.00113 (19)0.00059 (18)0.00036 (19)
C60.0173 (2)0.0140 (2)0.0168 (2)0.00002 (17)0.00157 (17)0.00093 (17)
C70.0183 (2)0.0148 (2)0.0187 (2)0.00041 (17)0.00331 (18)0.00005 (18)
C80.0179 (2)0.0180 (2)0.0289 (3)0.00373 (19)0.0065 (2)0.0041 (2)
C90.0152 (2)0.0177 (2)0.0252 (3)0.00334 (17)0.00291 (19)0.0039 (2)
C100.0252 (3)0.0242 (3)0.0238 (3)0.0065 (2)0.0032 (2)0.0043 (2)
Geometric parameters (Å, º) top
N1—C71.2714 (8)C4—H4A0.9300
N1—C81.4590 (8)C5—C61.3962 (9)
N2—C101.1548 (9)C5—H5A0.9300
C1—C21.3851 (9)C6—C71.4740 (8)
C1—C61.4015 (9)C7—H7A0.9300
C1—H1A0.9300C8—C91.5260 (9)
C2—C31.4019 (9)C8—H8A0.9700
C2—H2A0.9300C8—H8B0.9700
C3—C41.3955 (10)C9—C9i1.5249 (13)
C3—C101.4382 (9)C9—H9A0.9700
C4—C51.3906 (9)C9—H9B0.9700
C7—N1—C8117.13 (6)C1—C6—C7121.58 (5)
C2—C1—C6120.53 (6)N1—C7—C6121.92 (6)
C2—C1—H1A119.7N1—C7—H7A119.0
C6—C1—H1A119.7C6—C7—H7A119.0
C1—C2—C3119.30 (6)N1—C8—C9110.76 (5)
C1—C2—H2A120.3N1—C8—H8A109.5
C3—C2—H2A120.3C9—C8—H8A109.5
C4—C3—C2120.75 (6)N1—C8—H8B109.5
C4—C3—C10119.48 (6)C9—C8—H8B109.5
C2—C3—C10119.75 (6)H8A—C8—H8B108.1
C5—C4—C3119.36 (6)C9i—C9—C8112.85 (7)
C5—C4—H4A120.3C9i—C9—H9A109.0
C3—C4—H4A120.3C8—C9—H9A109.0
C4—C5—C6120.49 (6)C9i—C9—H9B109.0
C4—C5—H5A119.8C8—C9—H9B109.0
C6—C5—H5A119.8H9A—C9—H9B107.8
C5—C6—C1119.57 (6)N2—C10—C3178.58 (8)
C5—C6—C7118.86 (5)
C6—C1—C2—C30.04 (10)C2—C1—C6—C50.30 (10)
C1—C2—C3—C40.57 (10)C2—C1—C6—C7179.71 (6)
C1—C2—C3—C10177.78 (6)C8—N1—C7—C6179.98 (5)
C2—C3—C4—C50.76 (10)C5—C6—C7—N1174.67 (6)
C10—C3—C4—C5177.60 (6)C1—C6—C7—N15.31 (10)
C3—C4—C5—C60.41 (10)C7—N1—C8—C9124.91 (7)
C4—C5—C6—C10.12 (10)N1—C8—C9—C9i62.65 (9)
C4—C5—C6—C7179.90 (6)
Symmetry code: (i) x, y+1, z.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2A···N2ii0.932.523.4037 (11)158
Symmetry code: (ii) x+2, y, z.

Experimental details

Crystal data
Chemical formulaC20H18N4
Mr314.38
Crystal system, space groupMonoclinic, P21/n
Temperature (K)100
a, b, c (Å)4.9958 (1), 14.8164 (2), 11.6633 (2)
β (°) 97.310 (1)
V3)856.30 (3)
Z2
Radiation typeMo Kα
µ (mm1)0.08
Crystal size (mm)0.39 × 0.29 × 0.28
Data collection
DiffractometerBruker SMART APEXII CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2005)
Tmin, Tmax0.891, 0.979
No. of measured, independent and
observed [I > 2σ(I)] reflections
18411, 4473, 3659
Rint0.026
(sin θ/λ)max1)0.857
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.044, 0.135, 1.04
No. of reflections4473
No. of parameters109
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.55, 0.26

Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2005), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2003).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2A···N2i0.932.523.4037 (11)158
Symmetry code: (i) x+2, y, z.
 

Acknowledgements

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.

References

First citationAllen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19.  CrossRef Web of Science Google Scholar
First citationBernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555–1573.  CrossRef CAS Web of Science Google Scholar
First citationBruker (2005). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
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First citationFun, H.-K., Kargar, H. & Kia, R. (2008). Acta Cryst. E64, o1308.  Web of Science CSD CrossRef IUCr Journals Google Scholar
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First citationFun, H.-K. & Kia, R. (2008b). Acta Cryst. E64, m1116–m1117.  Web of Science CSD CrossRef CAS IUCr Journals Google Scholar
First citationFun, H.-K., Kia, R. & Kargar, H. (2008a). Acta Cryst. E64, o1335.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationFun, H.-K., Kia, R. & Kargar, H. (2008b). Acta Cryst. E64, o1855.  Web of Science CSD CrossRef IUCr Journals Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSpek, A. L. (2003). J. Appl. Cryst. 36, 7–13.  Web of Science CrossRef CAS IUCr Journals Google Scholar

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