N,N'-Bis(4-bromo-benzyl-idene)butane-1,4-diamine.

The mol-ecule of the title Schiff base compound, C(18)H(18)Br(2)N(2), lies across a crystallographic inversion centre and adopts an E configuration with respect to the C=N bond. In the crystal structure, mol-ecules are linked into chains along [201] through inter-molecular Br⋯Br inter-actions [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 π-π stacking inter-actions [centroid-centroid distance 3.6811 (11) Å].

Related literature

For halogen–halogen inter­actions, see: Ramasubbu et al. (1986 ▶); Brammer et al. (2003 ▶). For the crystal structures of related compounds, 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-bondong motifs, see: Bernstein et al. (1995 ▶). For background, see: Casellato & Vigato (1977 ▶).

Experimental

Crystal data

C18H18Br2N2

M = 422.16

Monoclinic,

a = 11.2612 (5) Å

b = 9.5213 (4) Å

c = 8.2645 (4) Å

β = 100.040 (3)°

V = 872.56 (7) Å3

Z = 2

Mo Kα radiation

μ = 4.64 mm−1

T = 100.0 (1) K

0.52 × 0.23 × 0.08 mm

Data collection

Bruker APEXII CCD area-detector diffractometer

Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T min = 0.192, T max = 0.688

15460 measured reflections

3843 independent reflections

2600 reflections with I > 2σ(I)

R int = 0.037

Refinement

R[F 2 > 2σ(F 2)] = 0.037

wR(F 2) = 0.092

S = 1.02

3843 reflections

136 parameters

All H-atom parameters refined

Δρmax = 0.68 e Å−3

Δρmin = −0.59 e Å−3

Data collection: APEX2 (Bruker, 2005 ▶); cell refinement: SAINT (Bruker, 2005 ▶); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2003 ▶).

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808028122/rz2242sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536808028122/rz2242Isup2.hkl

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

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

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)