(E,E)-N 1,N 4-Bis(2,6-difluoro­benzyl­idene)butane-1,4-diamine

Mohammad Khaledi Sardashti; Reza Kia; William Clegg; Ross W Harrington

doi:10.1107/S1600536811044801

. 2011 Oct 29;67(Pt 11):o3108. doi: 10.1107/S1600536811044801

(E,E)-N ¹,N ⁴-Bis(2,6-difluorobenzylidene)butane-1,4-diamine

Mohammad Khaledi Sardashti ^a,^*, Reza Kia ^b, William Clegg ^c, Ross W Harrington ^c

PMCID: PMC3247493 PMID: 22220111

Abstract

The asymmetric unit of the title compound, C₁₈H₁₆F₄N₂, comprises two half crystallographically independent potentially bidentate Schiff base ligands, with an inversion centre located at the mid-point of the central C—C bond. The crystal packing is stabilized by intermolecular C—H⋯F and π–π interactions [centroid–centroid distance = 3.8283 (11) Å].

Related literature

For background to the synthesis and structural variations of Schiff base ligands and their complexes, see: Granovski et al. (1993 ▶); Elmali et al. (2000 ▶).

Experimental

Crystal data

C₁₈H₁₆F₄N₂
M _r = 336.33
Triclinic,
a = 6.4672 (8) Å
b = 8.9296 (12) Å
c = 14.4939 (19) Å
α = 104.956 (2)°
β = 94.474 (2)°
γ = 93.679 (2)°
V = 803.10 (18) Å³
Z = 2
Mo Kα radiation
μ = 0.12 mm⁻¹
T = 150 K
0.34 × 0.30 × 0.20 mm

Data collection

Bruker SMART 1K CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.962, T _max = 0.977
5828 measured reflections
2819 independent reflections
2394 reflections with I > 2σ(I)
R _int = 0.019

Refinement

R[F ² > 2σ(F ²)] = 0.037
wR(F ²) = 0.100
S = 1.11
2819 reflections
218 parameters
H-atom parameters constrained
Δρ_max = 0.25 e Å⁻³
Δρ_min = −0.17 e Å⁻³

Data collection: SMART (Bruker, 2005 ▶); cell refinement: SAINT (Bruker, 2005 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶); software used to prepare material for publication: SHELXTL and PLATON (Spek,2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811044801/su2336sup1.cif

e-67-o3108-sup1.cif^{(19.1KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811044801/su2336Isup2.hkl

e-67-o3108-Isup2.hkl^{(138.4KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811044801/su2336Isup3.cml

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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C3—H3⋯F3ⁱ	0.95	2.43	3.137 (2)	131
C7—H7⋯F1ⁱⁱ	0.95	2.54	3.378 (2)	148
C12—H12⋯F2	0.95	2.42	3.192 (2)	138

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Symmetry codes: (i) Inline graphic ; (ii) .

Acknowledgments

MK thanks the Islamic Azad University, Shahrkord Branch, for the support of this work. WC and RWH thank the EPSRC (UK) for equipment funding.

supplementary crystallographic information

Comment

Schiff base ligands are among the most prevalent ligands in the field of coordination chemistry. Metal derivatives of Schiff bases have been studied extensively, and Ni^II and Cu^II complexes play a major role in both synthetic and structural research (Elmali et al., 2000; Granovski et al., 1993).

The asymmetric unit of the title compound comprises two half crystallographically independent Schiff base molecules; A (including N1) and B (including N2), see Fig. 1. Each molecule lies about an inversion centre, which is located in the middle of the central C—C bond (Fig. 1). In both molecules the aromatic ring and the imine segment (C—N═C) are approximately coplanar [dihedral angle 14.9 (2)° for molecule A and 3.4 (2)° for molecule B]. These two essentially planar units are linked by a step formed by the four CH₂ groups, so that they are strictly parallel by inversion symmetry but not coplanar.

The crystal packing is stabilized by intermolecular C—H···F interactions (Fig. 2 and Table 1), and by ring stacking of the benzene rings of the two independent molecules [centroid···centroid distance 3.8283 (11) Å, dihedral angle 2.33 (8)°].

Experimental

The title compound was synthesized by mixing 2,4-difluorobenzaldehyde (4 mmol) and butylenediamine (2 mmol) in chloroform (20 ml). After stirring for 2 h, the solution was filtered and the resulting yellow solid was crystallized from ethanol, giving single crystals suitable for X-ray diffraction.