4,4′-Dimethoxy-2,2′-[1,1′-(propane-1,3-diyldinitrilo)diethylidyne]diphenol

Abstract

In the crystal structure, the title Schiff base compound, C₂₁H₂₆N₂O₄, has twofold rotation symmetry. The imino group is coplanar with the aromatic ring. An intra­molecular O—H⋯N hydrogen bond forms a six- membered ring, producing an S(6) ring motif. The two benzene rings are almost perpendicular to each other, making a dihedral angle of 85.00 (2)°. The meth­oxy group is approximately coplanar with the benzene ring, with a C—O—C—C torsion angle of 2.34 (12)°. Neighbouring mol­ecules are linked together by weak inter­molecular C—H⋯O hydrogen bonds and a C—H⋯π inter­action, forming a sheet parallel to the ab plane. The mol­ecules also adopt a zigzag arrangement along the c axis.

Related literature

For bond-length data, see: Allen et al. (1987 ▶). For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶). For information on Schiff base ligands and complexes, and their applications, see, for example: Fun, Kargar & Kia (2008 ▶); Fun, Kia & Kargar (2008 ▶); Fun, Mirkhani et al. (2008a ▶,b ▶); Calligaris & Randaccio (1987 ▶); Casellato & Vigato (1977 ▶); Kia, Mirkhani, Kalman & Deak (2007 ▶); Kia, Mirkhani, Harkema & van Hummel (2007 ▶); Pal et al. (2005 ▶); Reglinski et al. (2004 ▶); Hou et al. (2001 ▶); Ren et al. (2002 ▶).

Experimental

Crystal data

• C₂₁H₂₆N₂O₄

• M _r = 370.44

• Monoclinic,

• a = 12.8042 (2) Å

• b = 5.0508 (1) Å

• c = 28.6019 (6) Å

• β = 93.109 (2)°

• V = 1847.00 (6) ų

• Z = 4

• Mo Kα radiation

• μ = 0.09 mm⁻¹

• T = 100.0 (1) K

• 0.47 × 0.44 × 0.29 mm

Data collection

• Bruker SMART APEXII CCD area-detector diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.884, T _max = 0.974

• 34801 measured reflections

• 5229 independent reflections

• 4304 reflections with I > 2σ(I)

• R _int = 0.031

Refinement

• R[F ² > 2σ(F ²)] = 0.057

• wR(F ²) = 0.148

• S = 1.11

• 5229 reflections

• 125 parameters

• H-atom parameters constrained

• Δρ_max = 0.45 e Å⁻³

• Δρ_min = −0.28 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, PLATON (Spek, 2003 ▶) and PARST95 (Nardelli, 1995 ▶).

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
O1—H1O1⋯N1	0.97	1.62	2.5241 (10)	153
C11—H11A⋯O1i	0.96	2.53	3.4448 (12)	160
C11—H11B⋯O1ii	0.96	2.53	3.4360 (12)	157
C10—H10C⋯Cg1iii	0.96	2.68	3.5224 (10)	147

Symmetry codes: (i) ; (ii) ; (iii) . Cg1 is the centroid of the C1–C6 benzene ring.

supplementary crystallographic information

Comment

The condensation of primary amines with carbonyl compounds yields Schiff base (Casellato & Vigato, 1977) that are still now regarded as one of the most potential group of chelators for facile preparations of metallo-organic hybrid materials. In the past two decades, the synthesis, structure and properties of Schiff base complexes have stimulated much interest for their noteworthy contributions in single molecule-based magnetism, materials science, catalysis of many reactions like carbonylation, hydroformylation, reduction, oxidation, epoxidation and hydrolysis, etc (Kia, Mirkhani, Kalman & Deak, 2007; Kia, Mirkhani, Harkema & van Hummel, 2007; Pal et al., 2005; Reglinski et al., 2004; Hou et al., 2001; Ren et al., 2002). This is due to the fact that Schiff bases offer opportunities for inducing substrate chirality, tuning the metal-centered electronic factor and enhancing the solubility and stability of either homogeneous or heterogeneous catalysts. Only a relatively small number of free Schiff base ligands have been characterized (Calligaris & Randaccio, 1987). As an extension of our work (Fun, Kargar & Kia, 2008; Fun, Kia & Kargar, 2008; Fun et al., 2008a,b) on the structural characterization of Schiff base compounds, the title compound (I), is reported here.

The molecule of the title compound, (I), has a crystallographic twofold rotation symmetry (Fig. 1). The bond lengths and angles are within normal ranges (Allen et al.,1987). The asymmetric unit of the compound is composed of one-half of the molecule. An intramolecular O—H···N hydrogen bond forms a six-membered ring, producing an S(6) ring motif (Bernstein et al. 1995). The two benzene rings are almost perpendicular to each other with a dihedral angle of 85.00 (2)°. The methoxy group is coplanar with the benzene ring, with the C10–O2–C4–C3 torsion angle of 2.34 (12)°. In the crystal structure neighbouring molecules are linked together by weak intermolecular C—H···O hydrogen bonds and a C—H···π interaction to form a sheet parallel to the ab plane (Fig. 2). These molecules also adopt a zigzag arrangement along the c axis (Fig. 3).

Experimental

The synthetic method has been described earlier (Reglinski et al., 2004). Single crystals suitable for X-ray diffraction were obtained by evaporation of an ethanol solution at room temperature.

Refinement

H atom bound to O1 was located from a difference Fourier map and refined as riding, with U_iso(H) = 1.5U_eq(O). Other H atoms were positioned geometrically (C—H = 0.93 – 0.96 Å) and refined using a riding model. A rotating-group model was applied for the methyl groups.

Figures

Fig. 1.

The molecular structure of (I) with atom labels and 50% probability ellipsoids for non-H atoms. The suffix A corresponds to symmetry code (-x + 1, y, -z + 1/2).

Fig. 2.

The crystal packing, showing stacking of molecules down the b axis. Intramolecular and intermolecular interactions are shown as dashed lines.

Fig. 3.

The crystal packing, showing zigzag arrangement of molecules along the c axis.

Crystal data

C21H26N2O4	F000 = 792
Mr = 370.44	Dx = 1.332 Mg m−3
Monoclinic, C2/c	Mo Kα radiation λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 9900 reflections
a = 12.8042 (2) Å	θ = 2.9–38.4º
b = 5.0508 (1) Å	µ = 0.09 mm−1
c = 28.6019 (6) Å	T = 100.0 (1) K
β = 93.109 (2)º	Block, yellow
V = 1847.00 (6) Å3	0.47 × 0.44 × 0.29 mm
Z = 4

Data collection

Bruker SMART APEXII CCD area-detector diffractometer	5229 independent reflections
Radiation source: fine-focus sealed tube	4304 reflections with I > 2σ(I)
Monochromator: graphite	Rint = 0.031
T = 100.0(1) K	θmax = 38.8º
φ and ω scans	θmin = 2.9º
Absorption correction: multi-scan(SADABS; Bruker, 2005)	h = −22→18
Tmin = 0.884, Tmax = 0.974	k = −8→8
34801 measured reflections	l = −48→50

Refinement

Refinement on F2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.057	H-atom parameters constrained
wR(F2) = 0.148	w = 1/[σ2(Fo2) + (0.0571P)2 + 1.5152P] where P = (Fo2 + 2Fc2)/3
S = 1.11	(Δ/σ)max < 0.001
5229 reflections	Δρmax = 0.45 e Å−3
125 parameters	Δρmin = −0.28 e Å−3
Primary atom site location: structure-invariant direct methods	Extinction correction: none

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
O1	0.59948 (5)	0.57780 (14)	0.14698 (2)	0.01790 (13)
H1O1	0.5565	0.4795	0.1680	0.027*
O2	0.32409 (5)	1.27531 (14)	0.05669 (2)	0.01928 (13)
N1	0.44774 (6)	0.41178 (14)	0.19154 (2)	0.01406 (12)
C1	0.53083 (6)	0.74582 (16)	0.12471 (3)	0.01383 (13)
C2	0.56814 (6)	0.91899 (18)	0.09166 (3)	0.01619 (14)
H2A	0.6385	0.9140	0.0851	0.019*
C3	0.50202 (7)	1.09968 (17)	0.06815 (3)	0.01633 (14)
H3A	0.5281	1.2150	0.0463	0.020*
C4	0.39649 (6)	1.10628 (16)	0.07764 (3)	0.01411 (13)
C5	0.35797 (6)	0.93301 (16)	0.11033 (3)	0.01378 (13)
H5A	0.2873	0.9380	0.1162	0.017*
C6	0.42331 (6)	0.75110 (15)	0.13460 (3)	0.01242 (13)
C7	0.38248 (6)	0.57157 (16)	0.17015 (3)	0.01281 (13)
C8	0.41119 (7)	0.23770 (17)	0.22797 (3)	0.01519 (14)
H8A	0.3572	0.1216	0.2145	0.018*
H8B	0.3807	0.3436	0.2520	0.018*
C9	0.5000	0.0715 (2)	0.2500	0.01590 (19)
H9	0.4651	−0.0665	0.2746	0.019*
C10	0.35993 (8)	1.44822 (19)	0.02170 (3)	0.01964 (16)
H10A	0.3025	1.5528	0.0090	0.029*
H10B	0.3883	1.3457	−0.0029	0.029*
H10C	0.4131	1.5628	0.0353	0.029*
C11	0.26922 (7)	0.57899 (19)	0.18136 (4)	0.01984 (16)
H11A	0.2370	0.4123	0.1733	0.030*
H11B	0.2343	0.7180	0.1638	0.030*
H11C	0.2639	0.6114	0.2142	0.030*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
O1	0.0124 (2)	0.0187 (3)	0.0228 (3)	0.0024 (2)	0.0023 (2)	0.0063 (2)
O2	0.0159 (3)	0.0187 (3)	0.0233 (3)	0.0031 (2)	0.0012 (2)	0.0076 (2)
N1	0.0143 (3)	0.0140 (3)	0.0139 (3)	−0.0006 (2)	0.0013 (2)	0.0014 (2)
C1	0.0119 (3)	0.0142 (3)	0.0155 (3)	0.0007 (2)	0.0015 (2)	0.0006 (2)
C2	0.0130 (3)	0.0177 (3)	0.0181 (3)	0.0002 (3)	0.0032 (2)	0.0024 (3)
C3	0.0160 (3)	0.0162 (3)	0.0170 (3)	−0.0008 (3)	0.0028 (3)	0.0027 (3)
C4	0.0137 (3)	0.0132 (3)	0.0154 (3)	0.0011 (2)	0.0008 (2)	0.0010 (2)
C5	0.0120 (3)	0.0139 (3)	0.0155 (3)	0.0005 (2)	0.0015 (2)	0.0005 (2)
C6	0.0114 (3)	0.0124 (3)	0.0135 (3)	0.0001 (2)	0.0018 (2)	−0.0001 (2)
C7	0.0122 (3)	0.0125 (3)	0.0137 (3)	−0.0008 (2)	0.0013 (2)	−0.0009 (2)
C8	0.0156 (3)	0.0152 (3)	0.0147 (3)	−0.0021 (2)	0.0011 (2)	0.0011 (3)
C9	0.0191 (5)	0.0125 (4)	0.0161 (5)	0.000	0.0000 (4)	0.000
C10	0.0229 (4)	0.0173 (3)	0.0186 (4)	0.0016 (3)	0.0005 (3)	0.0046 (3)
C11	0.0134 (3)	0.0215 (4)	0.0250 (4)	0.0007 (3)	0.0045 (3)	0.0063 (3)

Geometric parameters (Å, °)

O1—C1	1.3556 (10)	C5—H5A	0.9300
O1—H1O1	0.9728	C6—C7	1.4787 (11)
O2—C4	1.3736 (10)	C7—C11	1.5025 (11)
O2—C10	1.4230 (11)	C8—C9	1.5221 (11)
N1—C7	1.2917 (11)	C8—H8A	0.9700
N1—C8	1.4597 (11)	C8—H8B	0.9700
C1—C2	1.3915 (12)	C9—C8i	1.5221 (11)
C1—C6	1.4208 (11)	C9—H9	1.1014
C2—C3	1.3928 (12)	C10—H10A	0.9600
C2—H2A	0.9300	C10—H10B	0.9600
C3—C4	1.3929 (12)	C10—H10C	0.9600
C3—H3A	0.9300	C11—H11A	0.9600
C4—C5	1.3906 (12)	C11—H11B	0.9600
C5—C6	1.4010 (11)	C11—H11C	0.9600
C1—O1—H1O1	103.6	C6—C7—C11	120.84 (7)
C4—O2—C10	116.90 (7)	N1—C8—C9	111.49 (6)
C7—N1—C8	119.36 (7)	N1—C8—H8A	109.3
O1—C1—C2	118.35 (7)	C9—C8—H8A	109.3
O1—C1—C6	121.93 (7)	N1—C8—H8B	109.3
C2—C1—C6	119.71 (7)	C9—C8—H8B	109.3
C1—C2—C3	121.18 (8)	H8A—C8—H8B	108.0
C1—C2—H2A	119.4	C8—C9—C8i	113.08 (10)
C3—C2—H2A	119.4	C8—C9—H9	107.1
C2—C3—C4	119.50 (8)	C8i—C9—H9	113.8
C2—C3—H3A	120.3	O2—C10—H10A	109.5
C4—C3—H3A	120.3	O2—C10—H10B	109.5
O2—C4—C5	115.40 (7)	H10A—C10—H10B	109.5
O2—C4—C3	124.67 (7)	O2—C10—H10C	109.5
C5—C4—C3	119.94 (7)	H10A—C10—H10C	109.5
C4—C5—C6	121.46 (7)	H10B—C10—H10C	109.5
C4—C5—H5A	119.3	C7—C11—H11A	109.5
C6—C5—H5A	119.3	C7—C11—H11B	109.5
C5—C6—C1	118.21 (7)	H11A—C11—H11B	109.5
C5—C6—C7	121.26 (7)	C7—C11—H11C	109.5
C1—C6—C7	120.52 (7)	H11A—C11—H11C	109.5
N1—C7—C6	117.71 (7)	H11B—C11—H11C	109.5
N1—C7—C11	121.44 (7)
O1—C1—C2—C3	−178.88 (8)	C2—C1—C6—C5	0.02 (12)
C6—C1—C2—C3	0.44 (13)	O1—C1—C6—C7	0.25 (12)
C1—C2—C3—C4	−0.42 (13)	C2—C1—C6—C7	−179.04 (8)
C10—O2—C4—C5	−177.58 (8)	C8—N1—C7—C6	177.96 (7)
C10—O2—C4—C3	2.34 (13)	C8—N1—C7—C11	−1.07 (12)
C2—C3—C4—O2	−179.99 (8)	C5—C6—C7—N1	−179.06 (8)
C2—C3—C4—C5	−0.07 (13)	C1—C6—C7—N1	−0.02 (11)
O2—C4—C5—C6	−179.53 (7)	C5—C6—C7—C11	−0.02 (12)
C3—C4—C5—C6	0.54 (13)	C1—C6—C7—C11	179.01 (8)
C4—C5—C6—C1	−0.51 (12)	C7—N1—C8—C9	−178.18 (7)
C4—C5—C6—C7	178.54 (7)	N1—C8—C9—C8i	58.96 (5)
O1—C1—C6—C5	179.32 (8)

Symmetry codes: (i) −x+1, y, −z+1/2.

Hydrogen-bond geometry (Å, °)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1O1···N1	0.97	1.62	2.5241 (10)	153
C11—H11A···O1ii	0.96	2.53	3.4448 (12)	160
C11—H11B···O1iii	0.96	2.53	3.4360 (12)	157
C10—H10C···Cg1iv	0.96	2.68	3.5224 (10)	147

Symmetry codes: (ii) x−1/2, y−1/2, z; (iii) x−1/2, y+1/2, z; (iv) x, y+1, z.