3,3′-Di­bromo-1,1′-[ethyl­ene­dioxy­bis­(nitrilo­methyl­­idyne)]di­benzene

In the centrosymmetric title compound, C₁₆H₁₄Br₂N₂O₂, the intra­molecular interplanar distance between the parallel benzene rings is 1.305 (3) Å, while the inter­molecular interplanar distance (between neighbouring mol­ecules) is 3.463 (3) Å, exhibiting obvious strong inter­molecular π–π stacking inter­actions.

Related literature

For related literature, see: Akine et al. (2006); Atwood & Harvey (2001); Dong & Duan (2008); Dong et al. (2007); Dong, Duan et al. (2008); Dong, Shi et al. (2008); Katsuki (1995); Sun et al. (2004).

Experimental

Crystal data

• C₁₆H₁₄Br₂N₂O₂

• M_r = 426.11

• Monoclinic, P 2₁ /n

• a = 4.5072 (7) Å

• b = 7.615 (2) Å

• c = 23.180 (3) Å

• β = 93.523 (2)°

• V = 794.1 (3) ų

• Z = 2

• Mo Kα radiation

• μ = 5.11 mm⁻¹

• T = 298 (2) K

• 0.42 × 0.27 × 0.15 mm

Data collection

• Siemens SMART 1000 CCD area-detector diffractometer

• Absorption correction: multi-scan (SADABS; Sheldrick, 1996) T_min = 0.223, T_max = 0.514 (expected range = 0.201–0.464)

• 3840 measured reflections

• 1400 independent reflections

• 1168 reflections with I > 2σ(I)

• R_int = 0.043

Refinement

• R[F² > 2σ(F²)] = 0.037

• wR(F²) = 0.097

• S = 1.04

• 1400 reflections

• 100 parameters

• H-atom parameters constrained

• Δρ_max = 0.28 e Å⁻³

• Δρ_min = −0.49 e Å⁻³

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); 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.

Supporting information

S1. Comment

Schiff base compounds have played an important role in the development of coordination chemistry as they can readily form stable complexes with most metal ions (Dong & Duan, 2008; Dong, Duan et al., 2008; Dong, Shi et al., 2008; Atwood & Harvey, 2001). These complexes are very interesting in many fields, such as catalysis and enzymatic reactions (Akine et al., 2006), magnetism and molecular architectures (Sun et al., 2004; Katsuki, 1995). However, to the best of our knowledge, the complexes derived from the Schiff base 3,3'-dibromo-1,1'-[ethylenedioxybis(nitriloethylidyne)]dibenzene have never been reported so far. Information on the structure of the Schiff base compound will help us understand the interactions in the molecule so as to further design and synthesize complexes derived from this ligand. As a further investigation on such compounds, we report herein the synthesis and crystal structure of the Schiff base bisoxime compound 3,3'-dibromo-1,1'-[ethylenedioxybis(nitriloethylidyne)]dibenzene, shown in Fig. 1.

The X-ray crystallography reveals the title compound crystallizes in the monoclinic system, space group P2(1)/n with a = 4.5072 (7) Å, b = 7.615 (2) Å, c = 23.180 (3) Å, β = 93.523 (2) ° and Z= 2. The structure of the title compound consists of discrete C₁₆H₁₄Br₂N₂O₂ molecules in which all bond lengths are in normal ranges.

The molecule is disposed about a crystallographic centre of symmetry at the mid-point of the (CH₂—CH₂) linkage adopting an anti-symmetrized conformation in which two benzaldoxime moieties adopt an extended form. Both intra- and inter-molecular hydrogen bonds are not observed in the title compound. The intramolecular plane-to-plane distance of the benzene rings was found to be 1.305 Å, while that of the intermolecular plane-to-plane distance (between neighbouring molecules) was found to be 3.463 (3) Å, exhibiting obvious strong intermolecular π-π stacking interactions.

Related literature

For related literature, see: Akine et al. (2006); Atwood & Harvey (2001); Dong & Duan (2008); Dong et al. (2007); Dong, Duan et al. ( 2008); Dong, Shi et al. (2008); Katsuki (1995); Sun et al. (2004).

S2. Experimental

3,3'-Dibromo-1,1'-[ethylenedioxybis(nitriloethylidyne)]dibenzene was synthesized according to our previous work (Dong et al., 2007). To an ethanol solution (3 ml) of 3-bromo-benzaldehyde (398.7 mg, 2.15 mmol) was added dropwise an ethanol solution (2 ml) of 1,2-bis(aminooxy)ethane (96.2 mg, 1.04 mmol). The mixture solution was stirred at 328 K for 4 h. After cooling to room temperature, the precipitate was filtered off, and washed successively with ethanol and ethanol-hexane mixture (1:4), respectively. The product was dried in vacuo to yield 366.0 mg (Yield, 82.3%) of colorless microcrystals; m.p. 363.5 - 365.5 K. Anal. Calcd. for C₁₆H₁₄Br₂N₂O₂: C, 45.10; H, 3.31; N, 6.57. Found: C, 45.01; H, 3.20; N, 6.43%.

Single crystals were obtained by slow evaporation from a ethanol-acetone mixed solution of the title compound at room temperature.

S3. Refinement

Non-H atoms were refined anisotropically. H atoms were treated as riding atoms with distances C—H = 0.97 (CH₂), 0.93 Å (CH), and U_iso(H) = 1.2 U_eq(C).

Computing details

Data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT (Siemens, 1996); 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 (Sheldrick, 2008).

Figures

Fig. 1. The molecular structure of the title compound with atom numbering scheme [Symmetry codes: -x - 1,-y,-z]. Displacement ellipsoids for non-hydrogen atoms are drawn at the 30% probability level.

3,3'-Dibromo-1,1'-[ethylenedioxybis(nitrilomethylidyne)]dibenzene

Crystal data

C16H14Br2N2O2	F(000) = 420
Mr = 426.11	Dx = 1.782 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yn	Cell parameters from 2000 reflections
a = 4.5072 (7) Å	θ = 2.6–26.7°
b = 7.615 (2) Å	µ = 5.11 mm^−1
c = 23.180 (3) Å	T = 298 K
β = 93.523 (2)°	Needle-shaped, colorless
V = 794.1 (3) Å^3	0.42 × 0.27 × 0.15 mm
Z = 2

Data collection

Siemens SMART 1000 CCD area-detector diffractometer	1400 independent reflections
Radiation source: fine-focus sealed tube	1168 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.043
ω and ϕ scans	θmax = 25.0°, θmin = 1.8°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −5→5
Tmin = 0.223, Tmax = 0.514	k = −8→9
3840 measured reflections	l = −19→27

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)] = 0.037	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.097	H-atom parameters constrained
S = 1.04	w = 1/[σ^2(Fo^2) + (0.0535P)^2 + 0.3108P] where P = (Fo^2 + 2Fc^2)/3
1400 reflections	(Δ/σ)max < 0.001
100 parameters	Δρmax = 0.28 e Å^−3
0 restraints	Δρmin = −0.49 e Å^−3

Special details

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	0.56056 (10)	0.86904 (5)	0.160074 (19)	0.0576 (2)
N1	−0.2668 (6)	0.2442 (4)	0.05861 (13)	0.0381 (7)
O1	−0.4716 (6)	0.2385 (3)	0.00969 (11)	0.0422 (6)
C1	−0.6114 (8)	0.0710 (5)	0.00676 (17)	0.0396 (8)
H1A	−0.7723	0.0722	−0.0230	0.048*
H1B	−0.6952	0.0452	0.0434	0.048*
C2	−0.1591 (8)	0.3960 (4)	0.06447 (16)	0.0373 (8)
H2	−0.2198	0.4837	0.0384	0.045*
C3	0.0595 (7)	0.4362 (4)	0.11157 (15)	0.0324 (8)
C4	0.1868 (8)	0.6001 (4)	0.11401 (15)	0.0350 (8)
H4	0.1337	0.6827	0.0857	0.042*
C5	0.3929 (8)	0.6427 (4)	0.15821 (16)	0.0369 (8)
C6	0.4796 (9)	0.5227 (5)	0.19990 (16)	0.0449 (9)
H6	0.6198	0.5523	0.2294	0.054*
C7	0.3545 (9)	0.3565 (5)	0.19728 (18)	0.0485 (10)
H7	0.4098	0.2741	0.2256	0.058*
C8	0.1504 (9)	0.3121 (5)	0.15356 (16)	0.0412 (9)
H8	0.0719	0.1992	0.1517	0.049*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0701 (4)	0.0416 (3)	0.0597 (3)	−0.0158 (2)	−0.0076 (2)	−0.00700 (18)
N1	0.0374 (16)	0.0381 (17)	0.0381 (18)	−0.0031 (13)	−0.0038 (13)	−0.0018 (13)
O1	0.0438 (14)	0.0346 (13)	0.0468 (15)	−0.0078 (11)	−0.0083 (12)	0.0016 (11)
C1	0.037 (2)	0.0389 (19)	0.043 (2)	−0.0032 (16)	−0.0004 (16)	−0.0033 (16)
C2	0.0387 (19)	0.0329 (19)	0.040 (2)	0.0004 (15)	0.0022 (16)	0.0032 (15)
C3	0.0310 (18)	0.0343 (18)	0.0323 (19)	0.0008 (14)	0.0061 (14)	−0.0021 (14)
C4	0.039 (2)	0.0322 (18)	0.0337 (19)	0.0024 (15)	0.0026 (15)	−0.0001 (14)
C5	0.038 (2)	0.0344 (19)	0.038 (2)	−0.0041 (15)	0.0036 (16)	−0.0037 (15)
C6	0.047 (2)	0.049 (2)	0.037 (2)	0.0008 (18)	−0.0054 (18)	−0.0027 (17)
C7	0.052 (2)	0.046 (2)	0.047 (2)	0.0059 (19)	−0.0024 (19)	0.0120 (18)
C8	0.048 (2)	0.0334 (19)	0.043 (2)	−0.0055 (17)	0.0102 (18)	0.0027 (16)

Geometric parameters (Å, º)

Br1—C5	1.881 (3)	C3—C8	1.399 (5)
N1—C2	1.258 (4)	C4—C5	1.379 (5)
N1—O1	1.418 (4)	C4—H4	0.9300
O1—C1	1.423 (4)	C5—C6	1.369 (5)
C1—C1^i	1.521 (7)	C6—C7	1.386 (5)
C1—H1A	0.9700	C6—H6	0.9300
C1—H1B	0.9700	C7—C8	1.368 (5)
C2—C3	1.457 (5)	C7—H7	0.9300
C2—H2	0.9300	C8—H8	0.9300
C3—C4	1.373 (5)
C2—N1—O1	110.0 (3)	C3—C4—H4	119.8
N1—O1—C1	109.3 (3)	C5—C4—H4	119.8
O1—C1—C1^i	110.5 (4)	C6—C5—C4	121.1 (3)
O1—C1—H1A	109.5	C6—C5—Br1	119.9 (3)
C1^i—C1—H1A	109.5	C4—C5—Br1	119.0 (3)
O1—C1—H1B	109.5	C5—C6—C7	118.8 (3)
C1^i—C1—H1B	109.5	C5—C6—H6	120.6
H1A—C1—H1B	108.1	C7—C6—H6	120.6
N1—C2—C3	120.8 (3)	C8—C7—C6	120.7 (4)
N1—C2—H2	119.6	C8—C7—H7	119.6
C3—C2—H2	119.6	C6—C7—H7	119.6
C4—C3—C8	118.7 (3)	C7—C8—C3	120.2 (4)
C4—C3—C2	118.9 (3)	C7—C8—H8	119.9
C8—C3—C2	122.3 (3)	C3—C8—H8	119.9
C3—C4—C5	120.4 (3)
C2—N1—O1—C1	−174.7 (3)	C3—C4—C5—Br1	−179.8 (3)
N1—O1—C1—C1^i	−67.7 (5)	C4—C5—C6—C7	−0.5 (6)
O1—N1—C2—C3	−179.6 (3)	Br1—C5—C6—C7	−179.5 (3)
N1—C2—C3—C4	175.5 (3)	C5—C6—C7—C8	0.7 (6)
N1—C2—C3—C8	−2.8 (5)	C6—C7—C8—C3	−1.6 (6)
C8—C3—C4—C5	−2.1 (5)	C4—C3—C8—C7	2.3 (6)
C2—C3—C4—C5	179.6 (3)	C2—C3—C8—C7	−179.4 (4)
C3—C4—C5—C6	1.2 (5)

Symmetry code: (i) −x−1, −y, −z.