N,N′-Bis(3-bromo­benzyl­­idene)ethane-1,2-di­amine

The mol­ecule of the title Schiff base compound, C₁₆H₁₄Br₂N₂, lies across a crystallographic inversion centre. The C=N bond adopts a trans configuration. The imino group is coplanar with the benzene ring. Within the mol­ecule, the planar units are parallel, but extend in opposite directions from the dimethyl­ene bridge. The inter­esting feature of the structure is the weak Br⋯Br inter­action [3.7501 (2) Å] linking the mol­ecules into chains along the c axis. These chains are stacked along the b axis.

Related literature

For bond-length data, see: Allen et al. (1987). For related structures, see, for example: Fun, Kargar & Kia (2008); Fun, Kia & Kargar (2008); Fun, Mirkhani et al. (2008); Calligaris & Randaccio, (1987). For information on Schiff base complexes and their applications, see, for example: Kia, Mirkhani, Harkema & van Hummel (2007); Kia, Mirkhani, Kalman & Deak (2007); Pal et al. (2005); Hou et al. (2001); Ren et al. (2002).

Experimental

Crystal data

• C₁₆H₁₄Br₂N₂

• M_r = 394.11

• Monoclinic, P 2₁ /c

• a = 6.2578 (1) Å

• b = 4.6549 (1) Å

• c = 25.3272 (5) Å

• β = 93.592 (1)°

• V = 736.32 (2) ų

• Z = 2

• Mo Kα radiation

• μ = 5.50 mm⁻¹

• T = 100.0 (1) K

• 0.57 × 0.22 × 0.17 mm

Data collection

• Bruker SMART APEXII CCD area-detector diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2005) T_min = 0.125, T_max = 0.393

• 24876 measured reflections

• 3822 independent reflections

• 2975 reflections with I > 2σ(I)

• R_int = 0.033

Refinement

• R[F² > 2σ(F²)] = 0.028

• wR(F²) = 0.066

• S = 1.07

• 3822 reflections

• 119 parameters

• H atoms treated by a mixture of independent and constrained refinement

• Δρ_max = 0.69 e Å⁻³

• Δρ_min = −0.61 e Å⁻³

Data collection: APEX2 (Bruker, 2005); cell refinement: APEX2; data reduction: SAINT (Bruker, 2005); 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).

Supporting information

S1. Comment

Schiff bases are one of most prevalent mixed-donor ligands in the field of coordination chemistry. Schiff bases have been used widely as ligands in the formation of transition metal complexes. Many such complexes have been structurally characterized, but only a relatively small number of free Schiff base ligands have been characterized (Calligaris & Randaccio, 1987). There has been growing interest in Schiff base ligands, mainly because of their wide application in the field of biochemistry, synthesis, and catalysis (Kia et al., 2007a,b; Pal et al., 2005; Hou et al., 2001; Ren et al., 2002). As an extension of our work (Fun et al., 2008a,b,c) on the structural characterization of Schiff base compounds, the title compound (I), is reported here.

The molecule of the title compound, (I), (Fig. 1), lies across a crystallographic inversion centre. The bond lengths and angles are within normal ranges (Allen et al.,1987). The asymmetric unit is composed of one-half of the molecule. The C═N bond adopts a trans configuration. The imino group is coplanar with the benzene ring. Within the molecule, the planar units are parallel, but extend in opposite directions from the methylene bridge.The interesting feature of the crystal structure is the weak Br···Br [symmetry code: 1 - x,-1/2 + y, 1/2 - z] interactions with distance 3.7501 (2) Å linking the molecules into chains along the c axis. These chains are stacked along the b axis (Fig. 2).

Related literature

For bond-length data, see: Allen et al. (1987). For related structures, see, for example: Fun, Kargar & Kia (2008); Fun, Kia & Kargar (2008); Fun, Mirkhani, Kia & Vartooni (2008); Calligaris & Randaccio, (1987). For information on Schiff base complexes and their applications, see, for example: Kia, Mirkhani, Harkema & van Hummel (2007); Kia, Mirkhani, Kalman & Deak (2007); Pal et al. (2005); Hou et al. (2001); Ren et al. (2002).

S2. Experimental

The synthetic method has been described earlier (Fun et al., 2008a,b,c). Single crystals suitable for X-ray diffraction were obtained by evaporation of an ethanol solution at room temperature.

S3. Refinement

All of the H atoms were located from the difference Fourier map and freely refined.

Computing details

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).

Figures

	Fig. 1. The molecular structure of (I) with atom labels and 50% probability ellipsoids for non-H atoms [symmetry code for A: -x, 0.5 + y, 0.5 - z].
	Fig. 2. The crystal packing of (I), viewed down the b axis, showing chains along the c axis and stacking of these chains along the b-axis. The Br···Br contacts are shown as dashed lines.

N,N'-Bis(3-bromobenzylidene)ethane-1,2-diamine

Crystal data

C16H14Br2N2	F(000) = 388
Mr = 394.11	Dx = 1.778 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 8650 reflections
a = 6.2578 (1) Å	θ = 3.2–38.3°
b = 4.6549 (1) Å	µ = 5.50 mm^−1
c = 25.3272 (5) Å	T = 100 K
β = 93.592 (1)°	Block, colourless
V = 736.32 (2) Å^3	0.57 × 0.22 × 0.17 mm
Z = 2

Data collection

Bruker SMART APEXII CCD area-detector diffractometer	3822 independent reflections
Radiation source: fine-focus sealed tube	2975 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.033
ϕ and ω scans	θmax = 37.5°, θmin = 3.2°
Absorption correction: multi-scan (SADABS; Bruker, 2005)	h = −10→10
Tmin = 0.125, Tmax = 0.393	k = −7→7
24876 measured reflections	l = −43→43

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.028	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.066	H atoms treated by a mixture of independent and constrained refinement
S = 1.07	w = 1/[σ^2(Fo^2) + (0.0244P)^2 + 0.509P] where P = (Fo^2 + 2Fc^2)/3
3822 reflections	(Δ/σ)max = 0.001
119 parameters	Δρmax = 0.69 e Å^−3
0 restraints	Δρmin = −0.62 e Å^−3

Special details

Experimental. The low-temperature data was collected with the Oxford Cyrosystem Cobra low-temperature attachment.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
Br1	0.30202 (2)	0.03394 (3)	0.278341 (6)	0.02085 (4)
N1	0.35517 (18)	0.8207 (3)	0.44274 (5)	0.0165 (2)
C1	0.2106 (2)	0.3996 (3)	0.36391 (5)	0.0158 (2)
C2	0.1288 (2)	0.1862 (3)	0.33044 (5)	0.0165 (2)
C3	−0.0766 (2)	0.0762 (3)	0.33433 (6)	0.0188 (3)
C4	−0.2013 (2)	0.1822 (3)	0.37319 (6)	0.0194 (3)
C5	−0.1226 (2)	0.3970 (3)	0.40730 (6)	0.0181 (2)
C6	0.0838 (2)	0.5062 (3)	0.40303 (5)	0.0158 (2)
C7	0.1634 (2)	0.7313 (3)	0.43991 (6)	0.0162 (2)
C8	0.4077 (2)	1.0477 (3)	0.48093 (6)	0.0171 (2)
H1	0.348 (3)	0.476 (4)	0.3617 (9)	0.021 (5)*
H3	−0.128 (3)	−0.067 (5)	0.3113 (9)	0.026 (6)*
H4	−0.344 (3)	0.115 (5)	0.3752 (8)	0.025 (5)*
H5	−0.207 (4)	0.474 (5)	0.4344 (10)	0.030 (6)*
H7	0.064 (3)	0.805 (5)	0.4623 (8)	0.019 (5)*
H8A	0.448 (3)	1.212 (5)	0.4612 (8)	0.024 (5)*
H8B	0.283 (3)	1.109 (4)	0.5004 (7)	0.014 (4)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.02520 (7)	0.02173 (8)	0.01584 (6)	0.00015 (5)	0.00296 (4)	−0.00294 (6)
N1	0.0157 (5)	0.0168 (6)	0.0168 (5)	−0.0003 (4)	0.0000 (4)	−0.0027 (4)
C1	0.0152 (5)	0.0160 (6)	0.0160 (5)	0.0002 (4)	−0.0002 (4)	0.0008 (5)
C2	0.0188 (5)	0.0167 (6)	0.0137 (5)	0.0010 (4)	−0.0007 (4)	−0.0002 (4)
C3	0.0206 (6)	0.0168 (7)	0.0183 (6)	−0.0013 (5)	−0.0037 (4)	−0.0018 (5)
C4	0.0153 (5)	0.0196 (7)	0.0232 (7)	−0.0019 (4)	−0.0014 (5)	−0.0012 (5)
C5	0.0154 (5)	0.0184 (7)	0.0205 (6)	−0.0008 (4)	0.0012 (4)	−0.0019 (5)
C6	0.0151 (5)	0.0147 (6)	0.0173 (5)	0.0000 (4)	−0.0003 (4)	−0.0010 (4)
C7	0.0154 (5)	0.0162 (6)	0.0170 (6)	0.0007 (4)	0.0001 (4)	−0.0015 (5)
C8	0.0160 (5)	0.0170 (6)	0.0179 (6)	0.0001 (4)	−0.0018 (4)	−0.0030 (5)

Geometric parameters (Å, º)

Br1—C2	1.8967 (14)	C4—C5	1.391 (2)
N1—C7	1.2676 (17)	C4—H4	0.95 (2)
N1—C8	1.4564 (19)	C5—C6	1.3985 (19)
C1—C2	1.383 (2)	C5—H5	0.96 (2)
C1—C6	1.399 (2)	C6—C7	1.470 (2)
C1—H1	0.93 (2)	C7—H7	0.93 (2)
C2—C3	1.393 (2)	C8—C8^i	1.525 (3)
C3—C4	1.385 (2)	C8—H8A	0.96 (2)
C3—H3	0.93 (2)	C8—H8B	0.991 (19)
C7—N1—C8	116.70 (12)	C4—C5—H5	121.6 (14)
C2—C1—C6	118.96 (12)	C6—C5—H5	118.0 (14)
C2—C1—H1	122.9 (13)	C5—C6—C1	119.58 (13)
C6—C1—H1	118.1 (13)	C5—C6—C7	119.22 (13)
C1—C2—C3	121.90 (13)	C1—C6—C7	121.20 (12)
C1—C2—Br1	119.28 (10)	N1—C7—C6	123.50 (13)
C3—C2—Br1	118.81 (11)	N1—C7—H7	120.7 (12)
C4—C3—C2	118.88 (13)	C6—C7—H7	115.8 (12)
C4—C3—H3	121.0 (14)	N1—C8—C8^i	109.87 (15)
C2—C3—H3	120.1 (13)	N1—C8—H8A	106.8 (12)
C3—C4—C5	120.27 (13)	C8^i—C8—H8A	110.5 (12)
C3—C4—H4	119.5 (13)	N1—C8—H8B	112.9 (11)
C5—C4—H4	120.1 (13)	C8^i—C8—H8B	110.9 (11)
C4—C5—C6	120.41 (14)	H8A—C8—H8B	105.7 (17)
C6—C1—C2—C3	0.5 (2)	C4—C5—C6—C7	−179.45 (14)
C6—C1—C2—Br1	−178.55 (10)	C2—C1—C6—C5	−0.4 (2)
C1—C2—C3—C4	−0.6 (2)	C2—C1—C6—C7	179.52 (13)
Br1—C2—C3—C4	178.42 (11)	C8—N1—C7—C6	179.20 (13)
C2—C3—C4—C5	0.7 (2)	C5—C6—C7—N1	172.14 (14)
C3—C4—C5—C6	−0.6 (2)	C1—C6—C7—N1	−7.8 (2)
C4—C5—C6—C1	0.5 (2)	C7—N1—C8—C8^i	123.51 (16)

Symmetry code: (i) −x+1, −y+2, −z+1.

 

Footnotes

‡Additional correspondence author, e-mail: [e-mail].