4,4′-Dimethyl-1,1′-[ethyl­enedioxy­bis(nitrilo­methyl­idyne)]dibenzene

Abstract

The Schiff base, C₁₈H₂₀N₂O₂, which lies about an inversion centre, adopts a linear conformation. The mol­ecules are packed by C—H⋯π inter­actions, forming a two-dimensional supra­molecular network.

Related literature

For background literature on Schiff base oximes, see: Akine et al. (2005 ▶); Dong et al. (2008, 2009a ▶,b ▶); Yamada (1999 ▶). For a related structure, see: Dong et al. (2008 ▶).

Experimental

Crystal data

• C₁₈H₂₀N₂O₂

• M _r = 296.36

• Monoclinic,

• a = 13.6946 (12) Å

• b = 4.8196 (9) Å

• c = 12.1644 (11) Å

• β = 104.936 (1)°

• V = 775.75 (17) ų

• Z = 2

• Mo Kα radiation

• μ = 0.08 mm⁻¹

• T = 298 K

• 0.43 × 0.20 × 0.10 mm

Data collection

• Siemens SMART 1000 CCD area-detector diffractometer

• Absorption correction: none

• 3790 measured reflections

• 1370 independent reflections

• 1012 reflections with I > 2σ(I)

• R _int = 0.043

Refinement

• R[F ² > 2σ(F ²)] = 0.051

• wR(F ²) = 0.158

• S = 1.03

• 1370 reflections

• 100 parameters

• H-atom parameters constrained

• Δρ_max = 0.23 e Å⁻³

• Δρ_min = −0.21 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.

Supplementary Material

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
C9—H9A⋯Cg1	0.96	2.66	3.578 (2)	160

Cg1 is the centroid of the C3–C8 ring.

supplementary crystallographic information

Comment

Schiff bases and their bis-oxime analogues are a significant class of compounds which can be used in a variety of studies such as organic synthesis, catalyst, drug design and life science and so on (Yamada, 1999; Akine et al., 2005; Dong et al., 2009a). In order to extend our work (Dong et al., 2008) on structural characterization of bisoxime compounds, we report the synthesis and the X-ray structure of 4,4'-dimethyl-1,1'-[ethylenedioxybis(nitrilomethylidyne)]dibenzene in this paper (Fig. 1).

The molecule of the title compound is disposed about a crystallographic inversion centre (Symmetry codes: -x, -y,-z) and twofold screw axis (symmetry code: -x, 1/2 + y, 1/2 - z). The oxime, methyl groups and benzene rings have anti-conformation. The two benzene rings of the molecule are parallel, and the methyl and oxime (–CH₂—O—N=C–) functional groups are coplanar with the benzene ring in each half of the molecule.

The molecule adopts a linear-shaped configuration with respect to the oxime C=N bonds, which is different from our previous reported bisoxime of 3,3'-dibromo-1,1'-[ethylenedioxybis(nitrilomethylidyne)]dibenzene in which the molecule assumes an E configuration (Dong et al., 2008). The packing of the molecule is controlled by C—H···π(Ph) interactions linking molecules into infinite supramolecular structure along b axis (Fig. 2).

Experimental

4,4'-Dimethyl-1,1'-[ethylenedioxybis(nitrilomethylidyne)]dibenzene was synthesized according to an analogous method reported earlier (Dong et al., 2009b). To an ethanol solution (4 ml) of 4-methyl-2-hydroxybenzaldehyde (125.8 mg, 1.05 mmol) was added an ethanol solution (3 ml) of 1,2-bis(aminooxy)ethane (47.7 mg, 0.518 mmol). The reaction mixture was stirred at 328–333 K for 8 h. After cool to room temperature, no precipitate was formed, which was concentrated to about 1 ml under reduced pressure. The precipitate formed was separated by filtration, and washed several times with n-hexane. The product was dried under vacuum to yield 90.0 mg of the title compound. Yield, 58.6%. mp. 359–360 K. Anal. Calcd. for C₁₈H₂₀N₂O₂: C, 72.95; H, 6.80; N, 9.45. Found: C, 72.66; H, 6.87; N, 9.32.

Colorless needle-like single crystals suitable for X-ray diffraction studies were obtained after about four days by slow evaporation from an diethyl ether solution of the title compound.

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), C—H = 0.96 (CH₃) Å and U_iso(H) = 1.2 U_eq(C) and 1.5 U_eq(O).

Figures

Fig. 1.

The molecular structure of the title compound with atom numbering scheme [Symmetry codes: -x + 2,-y,-z + 1]. Displacement ellipsoids for non-hydrogen atoms are drawn at the 30% probability level.

Fig. 2.

Part of the supramolecular structure of the title compound. C—H···π(Ph) interactions are shown as dashed lines.

Crystal data

C18H20N2O2	F(000) = 316
Mr = 296.36	Dx = 1.269 Mg m−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 1400 reflections
a = 13.6946 (12) Å	θ = 3.4–27.7°
b = 4.8196 (9) Å	µ = 0.08 mm−1
c = 12.1644 (11) Å	T = 298 K
β = 104.936 (1)°	Column, colorless
V = 775.75 (17) Å3	0.43 × 0.20 × 0.10 mm
Z = 2

Data collection

Siemens SMART 1000 CCD area-detector diffractometer	1012 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.043
graphite	θmax = 25.0°, θmin = 1.5°
φ and ω scans	h = −16→15
3790 measured reflections	k = −5→5
1370 independent reflections	l = −14→13

Refinement

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)] = 0.051	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.158	H-atom parameters constrained
S = 1.03	w = 1/[σ2(Fo2) + (0.1037P)2] where P = (Fo2 + 2Fc2)/3
1370 reflections	(Δ/σ)max = 0.001
100 parameters	Δρmax = 0.23 e Å−3
0 restraints	Δρmin = −0.21 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
N1	0.87170 (11)	0.4357 (3)	0.55939 (12)	0.0389 (4)
O1	0.95570 (9)	0.2523 (3)	0.58336 (10)	0.0424 (4)
C1	0.95420 (13)	0.0920 (4)	0.48465 (15)	0.0381 (5)
H1A	0.9568	0.2120	0.4214	0.046*
H1B	0.8931	−0.0187	0.4631	0.046*
C2	0.86877 (13)	0.5688 (4)	0.64775 (16)	0.0386 (5)
H2	0.9180	0.5342	0.7148	0.046*
C3	0.79062 (13)	0.7762 (4)	0.64868 (15)	0.0366 (5)
C4	0.71621 (13)	0.8512 (4)	0.55207 (15)	0.0417 (5)
H4	0.7148	0.7693	0.4825	0.050*
C5	0.64425 (14)	1.0474 (4)	0.55907 (16)	0.0439 (5)
H5	0.5956	1.0971	0.4934	0.053*
C6	0.64272 (13)	1.1717 (4)	0.66137 (17)	0.0434 (5)
C7	0.71769 (15)	1.0973 (4)	0.75725 (16)	0.0457 (5)
H7	0.7189	1.1784	0.8270	0.055*
C8	0.79055 (14)	0.9047 (4)	0.75058 (15)	0.0424 (5)
H8	0.8406	0.8602	0.8158	0.051*
C9	0.56330 (16)	1.3823 (4)	0.6689 (2)	0.0577 (6)
H9A	0.5911	1.5656	0.6709	0.086*
H9B	0.5417	1.3507	0.7369	0.086*
H9C	0.5065	1.3647	0.6038	0.086*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
N1	0.0315 (8)	0.0384 (9)	0.0465 (9)	0.0052 (7)	0.0093 (6)	0.0011 (7)
O1	0.0343 (8)	0.0455 (8)	0.0446 (8)	0.0100 (6)	0.0052 (6)	−0.0053 (6)
C1	0.0335 (10)	0.0397 (10)	0.0405 (10)	0.0010 (8)	0.0084 (8)	−0.0035 (8)
C2	0.0349 (10)	0.0398 (11)	0.0396 (10)	0.0016 (8)	0.0072 (8)	0.0006 (8)
C3	0.0324 (10)	0.0365 (10)	0.0414 (10)	−0.0013 (7)	0.0104 (8)	0.0016 (8)
C4	0.0393 (10)	0.0446 (11)	0.0415 (10)	−0.0007 (9)	0.0108 (8)	−0.0032 (8)
C5	0.0366 (10)	0.0462 (11)	0.0473 (11)	0.0040 (8)	0.0080 (8)	0.0058 (9)
C6	0.0398 (11)	0.0342 (10)	0.0604 (12)	0.0000 (9)	0.0204 (9)	0.0036 (9)
C7	0.0537 (12)	0.0417 (11)	0.0452 (11)	0.0029 (9)	0.0189 (9)	−0.0056 (9)
C8	0.0452 (11)	0.0419 (11)	0.0388 (10)	0.0018 (9)	0.0085 (8)	0.0006 (8)
C9	0.0510 (12)	0.0461 (12)	0.0816 (17)	0.0075 (10)	0.0276 (11)	0.0031 (12)

Geometric parameters (Å, °)

N1—C2	1.261 (2)	C4—H4	0.9300
N1—O1	1.4203 (18)	C5—C6	1.386 (3)
O1—C1	1.424 (2)	C5—H5	0.9300
C1—C1i	1.503 (3)	C6—C7	1.388 (3)
C1—H1A	0.9700	C6—C9	1.508 (3)
C1—H1B	0.9700	C7—C8	1.380 (3)
C2—C3	1.466 (2)	C7—H7	0.9300
C2—H2	0.9300	C8—H8	0.9300
C3—C8	1.386 (2)	C9—H9A	0.9600
C3—C4	1.390 (3)	C9—H9B	0.9600
C4—C5	1.384 (2)	C9—H9C	0.9600
C2—N1—O1	110.10 (14)	C4—C5—H5	119.1
N1—O1—C1	109.26 (12)	C6—C5—H5	119.1
O1—C1—C1i	106.32 (17)	C5—C6—C7	117.62 (17)
O1—C1—H1A	110.5	C5—C6—C9	121.59 (19)
C1i—C1—H1A	110.5	C7—C6—C9	120.78 (19)
O1—C1—H1B	110.5	C8—C7—C6	120.92 (18)
C1i—C1—H1B	110.5	C8—C7—H7	119.5
H1A—C1—H1B	108.7	C6—C7—H7	119.5
N1—C2—C3	122.47 (17)	C7—C8—C3	121.35 (17)
N1—C2—H2	118.8	C7—C8—H8	119.3
C3—C2—H2	118.8	C3—C8—H8	119.3
C8—C3—C4	118.06 (17)	C6—C9—H9A	109.5
C8—C3—C2	118.70 (17)	C6—C9—H9B	109.5
C4—C3—C2	123.24 (17)	H9A—C9—H9B	109.5
C5—C4—C3	120.27 (17)	C6—C9—H9C	109.5
C5—C4—H4	119.9	H9A—C9—H9C	109.5
C3—C4—H4	119.9	H9B—C9—H9C	109.5
C4—C5—C6	121.76 (17)
C2—N1—O1—C1	176.47 (14)	C4—C5—C6—C7	1.4 (3)
N1—O1—C1—C1i	178.87 (16)	C4—C5—C6—C9	−179.11 (16)
O1—N1—C2—C3	179.41 (14)	C5—C6—C7—C8	−0.5 (3)
N1—C2—C3—C8	177.36 (16)	C9—C6—C7—C8	−179.96 (17)
N1—C2—C3—C4	−2.7 (3)	C6—C7—C8—C3	−0.9 (3)
C8—C3—C4—C5	−0.5 (3)	C4—C3—C8—C7	1.4 (3)
C2—C3—C4—C5	179.58 (16)	C2—C3—C8—C7	−178.65 (16)
C3—C4—C5—C6	−0.9 (3)

Symmetry codes: (i) −x+2, −y, −z+1.

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
C9—H9A···Cg1	0.96	2.66	3.578 (2)	160