N,N′-Bis(4-bromo-2-fluoro­benzyl­idene)ethane-1,2-diamine

Fun, H.-K.; Kia, R.

doi:10.1107/S1600536808029000

organic compounds

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ISSN: 2056-9890

Volume 64| Part 10| October 2008| Pages o1941-o1942

doi:10.1107/S1600536808029000

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N,N′-Bis(4-bromo-2-fluorobenzylidene)ethane-1,2-diamine

Hoong-Kun Fun ^a ^* and Reza Kia ^a ‡

^aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia
^*Correspondence e-mail: hkfun@usm.my

(Received 9 September 2008; accepted 10 September 2008; online 13 September 2008)

The molecule of the title Schiff base compound, C₁₆H₁₂Br₂F₂N₂, 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. Within the molecule, the planar units are parallel, but extend in opposite directions from the dimethylene bridge. An interesting feature of the crystal structure is the short intermolecular Br⋯F interactions [3.2347 (16) Å, which is shorter than the sum of the van der Waals radii of these atoms]. These interactions link neighbouring molecules along the c axis. The crystal structure is further stabilized by intermolecular C—H⋯N hydrogen bonds.

Related literature

For bond-length data, see: Allen et al. (1987 ). For halogen–halogen interactions, see: Ramasubbu et al. (1986 ); Brammer et al. (2003 ). For related structures, see, for example: Fun & Kia (2008a ,b ,c ): Fun et al. (2008 ). For Schiff base complexes and their applications, see, for example: Pal et al. (2005 ); Calligaris & Randaccio, (1987 ); Hou et al. (2001 ); Ren et al. (2002 ).

Experimental

Crystal data

C₁₆H₁₂Br₂F₂N₂
M_r = 430.10
Monoclinic, P 2₁ /c
a = 4.1981 (1) Å
b = 14.6190 (3) Å
c = 12.8861 (3) Å
β = 104.751 (2)°
V = 764.78 (3) Å³
Z = 2
Mo Kα radiation
μ = 5.32 mm⁻¹
T = 100.0 (1) K
0.51 × 0.07 × 0.05 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ) T_min = 0.172, T_max = 0.769
19361 measured reflections
2631 independent reflections
1907 reflections with I > 2σ(I)
R_int = 0.050

Refinement

R[F² > 2σ(F²)] = 0.040
wR(F²) = 0.100
S = 1.05
2631 reflections
100 parameters
H-atom parameters constrained
Δρ_max = 1.40 e Å⁻³
Δρ_min = −0.85 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
C2—H2A⋯N1ⁱ	0.93	2.53	3.386 (3)	154
Symmetry code: (i) $[x, -y-{\script{1\over 2}}, z+{\script{1\over 2}}]$ .

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

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536808029000/at2629sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808029000/at2629Isup2.hkl

checkCIF report

Comment top

Schiff bases are one of most prevalent mixed-donor ligands in the field of coordination chemistry. There has been growing interest in Schiff base ligands, mainly because of their wide application in the field of 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 been characterized (Calligaris & Randaccio, 1987). As an extension of our work (Fun & Kia 2008a,b,c; Fun et al., 2008) on the structural characterization of Schiff base ligands, and the halogen-halogen interactions in the halogen-subtituated Schiff bases, the title compound (I), is reported here.

The molecule of the title compound, (I), (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 related structures (Fun & Kia 2008a,b,c; Fun et al., 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 Br···F interactions [symmetry code: 1 - x, -1/2 + y, 1/2 - z] with the distance of 3.2347 (16) Å, which is shorter than the sum of the van der Waals radii of these atoms. The directionality of these interactions, C—X···X—C (X = halogens), has been attributed to anisotropic van der Waals radii for terminally bound halogens or ascribed to donor-acceptor interactions involving a lone pair donor orbital on one halogen and a C—X σ^* acceptor orbital on the other (Ramasubbu et al., 1986; Brammer et al., 2003). These interactions link neighbouring molecules along the c-axis (Fig. 2). The crystal structure is further stabilized by intermolecular C—H···N hydrogen bonds (Table 1).

Related literature top

For bond-length data, see: Allen et al. (1987). For halogen–halogen interactions, see: Ramasubbu et al. (1986); Brammer et al. (2003). For related structures, see, for example: Fun & Kia (2008a,b,c): Fun et al. (2008). For Schiff base complexes and their applications, see, for example: Pal et al. (2005); Calligaris & Randaccio, (1987); Hou et al. (2001); Ren et al. (2002).

Experimental top

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

Computing details top

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 top

	Fig. 1. The molecular structure of (I) with atom labels and 50% probability ellipsoids for non-H atoms [symmetry code for A: -x, -y, -z.
	Fig. 2. The crystal packing of (I), viewed down the a-axis, shows linking of molecules by Br···F contacts along the c-axis and the stacking of these molecules down the a-axis. Intermolecular interactions are shown as dashed lines.

N,N'-Bis(4-bromo-2-fluorobenzylidene)ethane-1,2-diamine top

Crystal data top

C₁₆H₁₂Br₂F₂N₂	F(000) = 420
M_r = 430.10	D_x = 1.868 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 5643 reflections
a = 4.1981 (1) Å	θ = 3.2–30.0°
b = 14.6190 (3) Å	µ = 5.32 mm⁻¹
c = 12.8861 (3) Å	T = 100 K
β = 104.751 (2)°	Needle, colourless
V = 764.78 (3) Å³	0.51 × 0.07 × 0.05 mm
Z = 2

Data collection top

Bruker SMART APEXII CCD area-detector diffractometer	2631 independent reflections
Radiation source: fine-focus sealed tube	1907 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.050
ϕ and ω scans	θ_max = 32.0°, θ_min = 2.2°
Absorption correction: multi-scan (SADABS; Bruker, 2005)	h = −6→6
T_min = 0.172, T_max = 0.770	k = −21→21
19361 measured reflections	l = −19→18

Refinement top

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)] = 0.040	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.100	H-atom parameters constrained
S = 1.05	w = 1/[σ²(F_o²) + (0.0539P)²] where P = (F_o² + 2F_c²)/3
2631 reflections	(Δ/σ)_max < 0.001
100 parameters	Δρ_max = 1.40 e Å⁻³
0 restraints	Δρ_min = −0.86 e Å⁻³

Crystal data top

C₁₆H₁₂Br₂F₂N₂	V = 764.78 (3) Å³
M_r = 430.10	Z = 2
Monoclinic, P2₁/c	Mo Kα radiation
a = 4.1981 (1) Å	µ = 5.32 mm⁻¹
b = 14.6190 (3) Å	T = 100 K
c = 12.8861 (3) Å	0.51 × 0.07 × 0.05 mm
β = 104.751 (2)°

Data collection top

Bruker SMART APEXII CCD area-detector diffractometer	2631 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2005)	1907 reflections with I > 2σ(I)
T_min = 0.172, T_max = 0.770	R_int = 0.050
19361 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.040	0 restraints
wR(F²) = 0.100	H-atom parameters constrained
S = 1.05	Δρ_max = 1.40 e Å⁻³
2631 reflections	Δρ_min = −0.86 e Å⁻³
100 parameters

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq
Br1	−0.74079 (7)	−0.51485 (2)	0.18481 (2)	0.02329 (11)
F1	−0.0347 (4)	−0.22639 (11)	0.31348 (12)	0.0267 (4)
N1	−0.0960 (6)	−0.12204 (15)	0.01873 (19)	0.0192 (5)
C1	−0.2112 (7)	−0.27577 (19)	0.2280 (2)	0.0199 (5)
C2	−0.3675 (7)	−0.35336 (19)	0.2493 (2)	0.0206 (6)
H2A	−0.3576	−0.3716	0.3192	0.025*
C3	−0.5404 (7)	−0.40314 (18)	0.1619 (2)	0.0181 (5)
C4	−0.5632 (7)	−0.37558 (19)	0.0569 (2)	0.0215 (6)
H4A	−0.6819	−0.4099	−0.0009	0.026*
C5	−0.4047 (7)	−0.29567 (19)	0.0405 (2)	0.0208 (6)
H5A	−0.4212	−0.2761	−0.0293	0.025*
C6	−0.2210 (6)	−0.24370 (18)	0.1260 (2)	0.0174 (5)
C7	−0.0381 (6)	−0.16150 (18)	0.1090 (2)	0.0182 (5)
H7A	0.1239	−0.1380	0.1659	0.022*
C8	0.1076 (7)	−0.04254 (19)	0.0114 (2)	0.0208 (5)
H8A	0.2171	−0.0516	−0.0456	0.025*
H8B	0.2750	−0.0349	0.0783	0.025*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Br1	0.02442 (16)	0.01848 (15)	0.02622 (17)	−0.00289 (11)	0.00507 (11)	0.00316 (11)
F1	0.0383 (10)	0.0214 (9)	0.0173 (8)	−0.0032 (7)	0.0014 (7)	−0.0029 (6)
N1	0.0213 (11)	0.0165 (11)	0.0209 (11)	−0.0001 (9)	0.0072 (9)	0.0004 (9)
C1	0.0220 (13)	0.0195 (14)	0.0163 (12)	0.0024 (10)	0.0015 (10)	−0.0035 (10)
C2	0.0261 (14)	0.0187 (13)	0.0168 (13)	0.0035 (10)	0.0051 (11)	0.0018 (10)
C3	0.0191 (12)	0.0153 (12)	0.0209 (13)	−0.0006 (9)	0.0066 (10)	0.0012 (10)
C4	0.0221 (13)	0.0231 (14)	0.0187 (13)	−0.0001 (11)	0.0042 (11)	−0.0006 (11)
C5	0.0231 (13)	0.0197 (13)	0.0185 (13)	0.0003 (10)	0.0034 (11)	0.0022 (10)
C6	0.0192 (13)	0.0142 (12)	0.0196 (13)	0.0031 (9)	0.0064 (10)	0.0015 (10)
C7	0.0182 (12)	0.0151 (12)	0.0210 (13)	0.0016 (9)	0.0042 (10)	−0.0022 (10)
C8	0.0178 (12)	0.0194 (12)	0.0251 (14)	−0.0027 (10)	0.0055 (10)	−0.0026 (11)

Geometric parameters (Å, º) top

Br1—C3	1.895 (3)	C4—C5	1.387 (4)
F1—C1	1.366 (3)	C4—H4A	0.9300
N1—C7	1.265 (3)	C5—C6	1.398 (4)
N1—C8	1.460 (4)	C5—H5A	0.9300
C1—C2	1.373 (4)	C6—C7	1.472 (4)
C1—C6	1.387 (4)	C7—H7A	0.9300
C2—C3	1.382 (4)	C8—C8ⁱ	1.521 (6)
C2—H2A	0.9300	C8—H8A	0.9700
C3—C4	1.391 (4)	C8—H8B	0.9700

C7—N1—C8	116.3 (2)	C4—C5—H5A	119.1
F1—C1—C2	117.7 (2)	C6—C5—H5A	119.1
F1—C1—C6	117.7 (2)	C1—C6—C5	116.2 (2)
C2—C1—C6	124.6 (3)	C1—C6—C7	121.8 (2)
C1—C2—C3	116.8 (3)	C5—C6—C7	122.0 (2)
C1—C2—H2A	121.6	N1—C7—C6	121.6 (2)
C3—C2—H2A	121.6	N1—C7—H7A	119.2
C2—C3—C4	122.2 (2)	C6—C7—H7A	119.2
C2—C3—Br1	119.2 (2)	N1—C8—C8ⁱ	109.6 (3)
C4—C3—Br1	118.6 (2)	N1—C8—H8A	109.8
C5—C4—C3	118.4 (3)	C8ⁱ—C8—H8A	109.8
C5—C4—H4A	120.8	N1—C8—H8B	109.8
C3—C4—H4A	120.8	C8ⁱ—C8—H8B	109.8
C4—C5—C6	121.9 (3)	H8A—C8—H8B	108.2

F1—C1—C2—C3	−179.0 (2)	F1—C1—C6—C7	2.4 (4)
C6—C1—C2—C3	1.3 (4)	C2—C1—C6—C7	−177.9 (3)
C1—C2—C3—C4	−1.5 (4)	C4—C5—C6—C1	−1.1 (4)
C1—C2—C3—Br1	176.3 (2)	C4—C5—C6—C7	176.7 (3)
C2—C3—C4—C5	0.4 (4)	C8—N1—C7—C6	−178.5 (2)
Br1—C3—C4—C5	−177.4 (2)	C1—C6—C7—N1	−165.9 (3)
C3—C4—C5—C6	1.0 (4)	C5—C6—C7—N1	16.4 (4)
F1—C1—C6—C5	−179.8 (2)	C7—N1—C8—C8ⁱ	−115.8 (3)
C2—C1—C6—C5	−0.1 (4)

Symmetry code: (i) −x, −y, −z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2A···N1ⁱⁱ	0.93	2.53	3.386 (3)	154

Symmetry code: (ii) x, −y−1/2, z+1/2.

Experimental details

Crystal data
Chemical formula	C₁₆H₁₂Br₂F₂N₂
M_r	430.10
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	4.1981 (1), 14.6190 (3), 12.8861 (3)
β (°)	104.751 (2)
V (Å³)	764.78 (3)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	5.32
Crystal size (mm)	0.51 × 0.07 × 0.05

Data collection
Diffractometer	Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2005)
T_min, T_max	0.172, 0.770
No. of measured, independent and observed [I > 2σ(I)] reflections	19361, 2631, 1907
R_int	0.050
(sin θ/λ)_max (Å⁻¹)	0.746

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.040, 0.100, 1.05
No. of reflections	2631
No. of parameters	100
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	1.40, −0.86

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

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
C2—H2A···N1ⁱ	0.9300	2.5300	3.386 (3)	154.00

Symmetry code: (i) x, −y−1/2, z+1/2.

Footnotes

‡Additional correspondence author, e-mail: zsrkk@yahoo.com.

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.

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