X-ray and computational structural study of (E)-2-(4-chloro­phenyl­imino­meth­yl)-4-methoxy­phenol

In the mol­ecule of the title compound, C₁₄H₁₂ClNO₂, the two aromatic rings are oriented at a dihedral angle of 5.92 (7)°. An intra­molecular O—H...N hydrogen bond results in the formation of a nearly planar six-membered ring, which is oriented at dihedral angles of 1.55 (4) and 5.95 (4)° with respect to the phenol and chlorophenyl rings, respectively. In the crystal structure, weak inter­molecular C—H...O hydrogen bonds link the mol­ecules into a three-dimensional network.

Key indicators

• Single-crystal X-ray study
• T = 296 K
• Mean [sigma](C-C) = 0.002 Å
• R factor = 0.038
• wR factor = 0.099
• Data-to-parameter ratio = 14.2

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PLAT063_ALERT_4_C Crystal Probably too Large for Beam Size .......       0.68 mm

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S1. Comment

The present work is part of a structural study of Schiff bases Özek et al., 2007; Odabaşoğlu, Büyükgüngör et al., 2007; Odabaşoğlu, Arslan et al., 2007). We report herein the crystal structure of the title compound, (I).

In general, O-hydroxy Schiff bases exhibit two possible tautomeric forms, the phenol-imine (or benzenoid) and keto-amine (or quinoid) forms. Depending on the tautomers, two types of intramolecular hydrogen bonds are possible: O-H···N in benzenoid and N-H···O in quinoid tautomers. The H atom in (I) is located on atom O1, thus the phenol-imine tautomer is favored over the keto-amine form, as indicated by the C2-O1, C8-N1, C1-C8 and C1-C2 bonds (Fig. 1 and Table 2). The O1-C2 bond has single-bond character, whereas the N1-C8 bond has a high degree of double-bond character as in 2-(3-methoxysalicylideneamino)-1H-benzimidazole- monohydrate, (II) [where the corresponding values are C-O = 1.357 (2) Å, C-N = 1.285 (2) Å, Albayrak et al., 2005]. It is known that Schiff bases may exhibit thermochromism or photochromism, depending on the planarity or non-planarity of the molecule, respectively. Therefore, one can expect thermochromic properties in (I) caused by the planarity of the molecule; the dihedral angle between rings A (C1-C6) and B (C9-C14) is 5.92 (7)°. The intramolecular O-H···N hydrogen bond (Table 1) results in the formation of a nearly planar six-membered ring C (O1/H1/N1/C1/C2/C8), in which it is oriented with respect to rings A and B at dihedral angles of A/C = 1.55 (4)° and B/C = 5.95 (4)°. So, it is coplanar with the adjacent ring A. It generates an S(6) ring motif. The O1···N1 [2.621 (2) Å] distance is comparable to those observed for analogous ones in N-(2-hydroxyphenyl)salicylaldimine, (III) [2.675 (7) Å; Elerman et al., 1995] and in three(E)-2-[(bromophenyl)iminomethyl]-4-methoxyphenols, (IV) [2.603 (2), 2.638 (7) and 2.577 (4) Å;Özek et al., 2007].

In the crystal structure, weak intermolecular C-H···O hydrogen bonds (Table 1) link the molecules into a three-dimensional network (Fig. 2), in which they may be effective in the stabilization of the structure.

Ab-initio Hartree-Fock (HF), density-functional theory (DFT) and semi-empirical (AM1 and PM3) calculations and full-geometry optimizations were performed by means of GAUSSIAN 03 W package (Frisch et al., 2004). The selected bond lengths and angles together with the torsion angles are compared with the obtained ones from semi-empirical, ab-initio HF and DFT/B3LYP methods (Table 2). We observe an acceptable general agreement between them. Although the DFT molecular orbital theory was considered as the most accurate method for geometry optimization for free and complex ligands (Friesner, 2005; Liu et al., 2004), the HF method led to better results in regard to the bond lengths and angles.

Related literature

For related literature, see: Özek et al. (2007); Odabaşoğlu, Büyükgüngör et al. (2007); Odabaşoğlu, Arslan et al. (2007); Albayrak et al. (2005); Elerman et al. (1995). For general background, see: Friesner (2005); Liu et al. (2004).

S2. Experimental

The title compound was prepared by refluxing a mixture of a solution containing 5-methoxysalicylaldehyde (0.5 g 3.3 mmol) in ethanol (20 ml) and a solution containing 4-chloraniline (0.420 g 3.3 mmol) in ethanol (20 ml). The reaction mixture was stirred for 1 h under reflux. The crystals suitable for X-ray analysis were obtained from ethanol by slow evaporation (yield; 76%, m.p. 378-379 K).

S3. Refinement

H1 atom (for OH) was located in difference syntheses and refined isotropically [O-H = 0.88 (3) Å and U_iso(H) = 0.112 (9) Ų]. The remaining H atoms were positioned geometrically, with C-H = 0.93 and 0.96 Å for aromatic and methyl H, respectively, and constrained to ride on their parent atoms with U_iso(H) = 1.2U_eq(C).

Computing details

Data collection: X-AREA (Stoe & Cie, 2002); cell refinement: X-AREA (Stoe & Cie, 2002); data reduction: X-RED32 (Stoe & Cie, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999) and GAUSSIAN (Frisch et al.,2004).

Figures

	Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level. Hydrogen bond is shown as dashed line.
	Fig. 2. A partial packing diagram of (I) [symmetry codes: (i) 1 - x, y - 1/2, 3/2 - z; (ii) 1 - x, y + 1/2, 3/2 - z]. Hydrogen bonds are shown as dashed lines. H atoms not involved in hydrogen bonding have been omitted for clarity.

(E)-2-(4-chlorophenyliminomethyl)-4-methoxyphenol

Crystal data

C14H12ClNO2	F(000) = 544
Mr = 261.70	Dx = 1.423 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 10205 reflections
a = 21.2642 (19) Å	θ = 1.7–27.2°
b = 4.7101 (3) Å	µ = 0.31 mm^−1
c = 12.2175 (12) Å	T = 296 K
β = 93.361 (8)°	Prismatic long stick, red
V = 1221.56 (18) Å^3	0.68 × 0.44 × 0.21 mm
Z = 4

Data collection

Stoe IPDSII diffractometer	2364 independent reflections
Radiation source: fine-focus sealed tube	1789 reflections with I > 2σ(I)
Plane graphite monochromator	Rint = 0.080
Detector resolution: 6.67 pixels mm^-1	θmax = 26.0°, θmin = 1.9°
ω scans	h = −26→26
Absorption correction: integration (X-RED32; Stoe & Cie, 2002)	k = −5→5
Tmin = 0.825, Tmax = 0.925	l = −14→14
10205 measured reflections

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) = 0.099	H atoms treated by a mixture of independent and constrained refinement
S = 1.00	w = 1/[σ^2(Fo^2) + (0.0641P)^2] where P = (Fo^2 + 2Fc^2)/3
2364 reflections	(Δ/σ)max < 0.001
167 parameters	Δρmax = 0.20 e Å^−3
0 restraints	Δρmin = −0.20 e Å^−3

Special details

Experimental. 225 frames, detector distance = 120 mm

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 > 2sigma(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
Cl1	0.03208 (2)	1.40379 (9)	0.66121 (4)	0.06631 (18)
O1	0.26185 (6)	0.2746 (3)	0.35438 (10)	0.0677 (4)
H1	0.2404 (12)	0.393 (5)	0.394 (2)	0.112 (9)*
O2	0.42346 (6)	−0.2199 (3)	0.66813 (10)	0.0676 (4)
N1	0.21631 (6)	0.5615 (3)	0.51562 (10)	0.0455 (3)
C1	0.29911 (7)	0.2216 (3)	0.54240 (12)	0.0428 (3)
C2	0.30182 (7)	0.1541 (3)	0.43144 (12)	0.0480 (4)
C3	0.34597 (8)	−0.0395 (4)	0.39932 (13)	0.0575 (4)
H3	0.3478	−0.0841	0.3254	0.069*
C4	0.38738 (8)	−0.1674 (4)	0.47512 (14)	0.0551 (4)
H4	0.4170	−0.2964	0.4521	0.066*
C5	0.38493 (7)	−0.1042 (3)	0.58541 (13)	0.0493 (4)
C6	0.34078 (7)	0.0873 (3)	0.61831 (13)	0.0484 (3)
H6	0.3387	0.1278	0.6925	0.058*
C7	0.47390 (9)	−0.3918 (4)	0.63688 (19)	0.0753 (6)
H7A	0.5012	−0.2819	0.5936	0.090*
H7B	0.4576	−0.5499	0.5945	0.090*
H7C	0.4971	−0.4604	0.7013	0.090*
C8	0.25442 (7)	0.4252 (3)	0.58089 (12)	0.0461 (3)
H8	0.2534	0.4579	0.6558	0.055*
C9	0.17376 (7)	0.7637 (3)	0.55533 (12)	0.0436 (3)
C10	0.12943 (7)	0.8772 (3)	0.48017 (13)	0.0522 (4)
H10	0.1291	0.8199	0.4073	0.063*
C11	0.08576 (8)	1.0737 (3)	0.51122 (14)	0.0550 (4)
H11	0.0561	1.1474	0.4599	0.066*
C12	0.08649 (7)	1.1592 (3)	0.61875 (14)	0.0496 (4)
C13	0.13070 (8)	1.0524 (4)	0.69489 (14)	0.0557 (4)
H13	0.1312	1.1129	0.7674	0.067*
C14	0.17395 (7)	0.8564 (3)	0.66347 (13)	0.0531 (4)
H14	0.2037	0.7848	0.7151	0.064*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Cl1	0.0617 (3)	0.0529 (2)	0.0864 (3)	0.01245 (18)	0.0222 (2)	0.0027 (2)
O1	0.0789 (8)	0.0846 (9)	0.0392 (6)	0.0278 (7)	−0.0008 (6)	−0.0003 (6)
O2	0.0658 (7)	0.0785 (8)	0.0577 (7)	0.0260 (6)	−0.0028 (6)	0.0012 (6)
N1	0.0478 (7)	0.0442 (6)	0.0448 (7)	0.0018 (5)	0.0049 (5)	−0.0012 (5)
C1	0.0448 (7)	0.0422 (7)	0.0418 (8)	−0.0002 (6)	0.0068 (6)	−0.0005 (6)
C2	0.0521 (8)	0.0535 (9)	0.0387 (8)	0.0048 (6)	0.0045 (7)	0.0015 (6)
C3	0.0654 (10)	0.0667 (10)	0.0414 (8)	0.0101 (8)	0.0104 (7)	−0.0051 (7)
C4	0.0548 (9)	0.0571 (9)	0.0545 (10)	0.0100 (7)	0.0114 (8)	−0.0039 (7)
C5	0.0484 (8)	0.0499 (8)	0.0495 (8)	0.0037 (6)	0.0014 (7)	0.0014 (7)
C6	0.0531 (8)	0.0507 (8)	0.0414 (8)	0.0036 (7)	0.0031 (7)	−0.0039 (7)
C7	0.0683 (11)	0.0716 (12)	0.0849 (14)	0.0251 (10)	−0.0049 (10)	0.0002 (10)
C8	0.0505 (8)	0.0467 (8)	0.0415 (8)	0.0019 (6)	0.0060 (7)	−0.0027 (6)
C9	0.0439 (7)	0.0406 (7)	0.0468 (8)	−0.0016 (6)	0.0061 (6)	−0.0005 (6)
C10	0.0572 (9)	0.0534 (9)	0.0458 (9)	0.0035 (7)	0.0021 (7)	−0.0005 (7)
C11	0.0535 (9)	0.0532 (9)	0.0579 (10)	0.0075 (7)	−0.0002 (7)	0.0058 (7)
C12	0.0464 (8)	0.0404 (7)	0.0632 (10)	−0.0002 (6)	0.0133 (7)	0.0026 (7)
C13	0.0614 (9)	0.0561 (9)	0.0500 (9)	0.0054 (7)	0.0074 (8)	−0.0058 (7)
C14	0.0548 (9)	0.0558 (9)	0.0482 (9)	0.0106 (7)	−0.0002 (7)	−0.0019 (7)

Geometric parameters (Å, º)

O1—H1	0.88 (3)	C7—H7C	0.9600
C1—C6	1.396 (2)	C8—N1	1.2763 (19)
C1—C2	1.397 (2)	C8—H8	0.9300
C1—C8	1.448 (2)	C9—C10	1.384 (2)
C2—O1	1.3554 (18)	C9—C14	1.391 (2)
C2—C3	1.382 (2)	C9—N1	1.4186 (19)
C3—C4	1.379 (2)	C10—C11	1.380 (2)
C3—H3	0.9300	C10—H10	0.9300
C4—C5	1.384 (2)	C11—C12	1.373 (2)
C4—H4	0.9300	C11—H11	0.9300
C5—O2	1.3756 (18)	C12—C13	1.378 (2)
C5—C6	1.379 (2)	C12—Cl1	1.7337 (15)
C6—H6	0.9300	C13—C14	1.374 (2)
C7—O2	1.414 (2)	C13—H13	0.9300
C7—H7A	0.9600	C14—H14	0.9300
C7—H7B	0.9600
C2—O1—H1	102.0 (17)	O2—C7—H7C	109.5
C5—O2—C7	117.19 (14)	H7A—C7—H7C	109.5
C8—N1—C9	121.22 (13)	H7B—C7—H7C	109.5
C6—C1—C2	118.74 (14)	N1—C8—C1	122.35 (14)
C6—C1—C8	119.18 (13)	N1—C8—H8	118.8
C2—C1—C8	122.08 (13)	C1—C8—H8	118.8
O1—C2—C3	119.19 (14)	C10—C9—C14	118.22 (14)
O1—C2—C1	121.27 (14)	C10—C9—N1	117.10 (13)
C3—C2—C1	119.54 (14)	C14—C9—N1	124.68 (13)
C4—C3—C2	121.03 (15)	C11—C10—C9	121.32 (15)
C4—C3—H3	119.5	C11—C10—H10	119.3
C2—C3—H3	119.5	C9—C10—H10	119.3
C3—C4—C5	120.05 (15)	C12—C11—C10	119.31 (14)
C3—C4—H4	120.0	C12—C11—H11	120.3
C5—C4—H4	120.0	C10—C11—H11	120.3
O2—C5—C6	115.56 (14)	C11—C12—C13	120.51 (15)
O2—C5—C4	125.11 (15)	C11—C12—Cl1	120.72 (12)
C6—C5—C4	119.33 (14)	C13—C12—Cl1	118.77 (13)
C5—C6—C1	121.29 (14)	C14—C13—C12	119.87 (15)
C5—C6—H6	119.4	C14—C13—H13	120.1
C1—C6—H6	119.4	C12—C13—H13	120.1
O2—C7—H7A	109.5	C13—C14—C9	120.76 (14)
O2—C7—H7B	109.5	C13—C14—H14	119.6
H7A—C7—H7B	109.5	C9—C14—H14	119.6
C6—C1—C2—O1	178.95 (14)	C14—C9—C10—C11	−1.0 (2)
C8—C1—C2—O1	−0.9 (2)	N1—C9—C10—C11	179.50 (14)
C6—C1—C2—C3	−0.9 (2)	C9—C10—C11—C12	0.3 (2)
C8—C1—C2—C3	179.23 (14)	C10—C11—C12—C13	0.6 (2)
O1—C2—C3—C4	−179.82 (16)	C10—C11—C12—Cl1	−179.55 (12)
C1—C2—C3—C4	0.1 (3)	C11—C12—C13—C14	−0.8 (2)
C2—C3—C4—C5	0.4 (3)	Cl1—C12—C13—C14	179.40 (12)
C3—C4—C5—O2	179.54 (16)	C12—C13—C14—C9	0.0 (2)
C3—C4—C5—C6	0.0 (2)	C10—C9—C14—C13	0.9 (2)
O2—C5—C6—C1	179.51 (14)	N1—C9—C14—C13	−179.70 (14)
C4—C5—C6—C1	−0.9 (2)	C1—C8—N1—C9	−178.85 (13)
C2—C1—C6—C5	1.4 (2)	C10—C9—N1—C8	−172.84 (13)
C8—C1—C6—C5	−178.79 (14)	C14—C9—N1—C8	7.7 (2)
C6—C1—C8—N1	177.90 (14)	C6—C5—O2—C7	−172.96 (15)
C2—C1—C8—N1	−2.3 (2)	C4—C5—O2—C7	7.5 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···N1	0.88 (3)	1.79 (3)	2.6210 (18)	157 (2)
C7—H7C···O2^i	0.96	2.56	3.495 (2)	164

Symmetry code: (i) −x+1, y−1/2, −z+3/2.