(E)-2-[(4-Ethoxy­phen­yl)imino­meth­yl]-4-methoxy­phenol

Arzu Özek; Çiğdem Albayrak; Orhan Büyükgüngör

doi:10.1107/S1600536809040586

. 2009 Oct 10;65(Pt 11):o2705. doi: 10.1107/S1600536809040586

(E)-2-[(4-Ethoxyphenyl)iminomethyl]-4-methoxyphenol

Arzu Özek ^a, Çiğdem Albayrak ^b, Orhan Büyükgüngör ^a,^*

PMCID: PMC2971308 PMID: 21578305

Abstract

In the molecule of the title compound, C₁₆H₁₇NO₃, the aromatic rings are oriented at a dihedral angle of 29.25 (8)°. An intramolecular O—H⋯N hydrogen bond results in the formation of a nearly planar [maximum deviation 0.034 (13) Å] six-membered ring, which is oriented at dihedral angles of 0.91 (1) and 28.91 (12)° with respect to the aromatic rings. The title molecule is a phenol–imine tautomer, as evidenced by C—O, C—N and C—C bond lengths. In the crystal, molecules are linked by intermolecular C—H⋯O hydrogen bonds that generate C(8) chains.

Related literature

For background to this study, see: Özek et al., 2007 ▶. For related structures, see: Özek et al. (2009 ▶); Özek et al. (2008 ▶).

Experimental

Crystal data

C₁₆H₁₇NO₃
M _r = 271.31
Monoclinic,
a = 14.8558 (7) Å
b = 13.7669 (7) Å
c = 6.9042 (3) Å
β = 90.287 (4)°
V = 1412.02 (11) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 296 K
0.77 × 0.51 × 0.28 mm

Data collection

Stoe IPDS II diffractometer
Absorption correction: integration (X-RED32; Stoe & Cie, 2002 ▶) T _min = 0.943, T _max = 0.973
14704 measured reflections
2938 independent reflections
2014 reflections with I > 2σ(I)
R _int = 0.051

Refinement

R[F ² > 2σ(F ²)] = 0.044
wR(F ²) = 0.123
S = 1.04
2938 reflections
250 parameters
All H-atom parameters refined
Δρ_max = 0.11 e Å⁻³
Δρ_min = −0.12 e Å⁻³

Data collection: X-AREA (Stoe & Cie, 2002 ▶); cell refinement: X-AREA; 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 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536809040586/ez2189sup1.cif

e-65-o2705-sup1.cif^{(18.3KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809040586/ez2189Isup2.hkl

e-65-o2705-Isup2.hkl^{(141.3KB, hkl)}

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—H1⋯N1	0.93 (3)	1.75 (3)	2.5962 (18)	149 (2)
C10—H10⋯O1ⁱ	0.965 (18)	2.571 (18)	3.3801 (19)	141.5 (13)

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Symmetry code: (i) Inline graphic .

Acknowledgments

The authors acknowledge the Faculty of Arts and Sciences, Ondokuz Mayıs University, Turkey, for the use of the Stoe IPDS II diffractometer (purchased under grant F.279 of the University Research Fund).

supplementary crystallographic information

Comment

The present work is part of a structural study of Schiff bases (Özek et al., 2009; Özek et al., 2008; Özek et al., 2007) and we report here the structure of (E)-2-[(4-ethoxyphenylimino)methyl]-4-methoxyphenol, (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 intra-molecular hydrogen bonds are possible: O—H···N in benzenoid and N—H···O in quinoid tautomers. In the title compound the H atom 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 bond lengths (Fig. 1 and Table 2). The O1—C2 bond length of 1.351 (2) Å indicates single-bond character, whereas the N1—C8 bond length of 1.277 (2) Å indicates a high degree of double-bond character. A similar result was observed in the X-ray crystal and computational structural study of (E)-2-[(2-chlorophenyl) iminomethyl]-4-methoxyphenol [C—O=1.357 (17) Å, C—N= 1.278 (17) Å, Özek et al., 2008.

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 photochromic properties in (I) caused by non-planarity of the molecules; the dihedral angle between ring A (C1—C6) and ring B (C9—C14) is 29.25 (8) °. 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= 0.91 (1) ° and B/C= 28.91 (12) °. It is thus coplanar with the adjacent ring A. It generates an S(6) ring motif. The O1···N1 distance of 2.5962 (18) Å is comparable to those observed for analogous hydrogen bonds in three (E)-2-[(bromophenyl)iminomethyl]-4-methoxyphenols [2.603 (2) Å, 2.638 (7) Å, 2.577 (4) Å; Özek et al., 2007]. In the crystal structure, weak intermolecular C—H···O hydrogen bonds (Table 1) result in the formation of C(8) chains along the c axis (Fig. 2), which may play a role in the stabilization of the structure.

Experimental

The compound (E)-2-[(4-ethoxyphenylimino)methyl]-4-methoxyphenol was prepared by refluxing a mixture of a solution containing 5-methoxysalicylaldehyde (0.5 g, 3.3 mmol) in 20 ml ethanol and a solution containing 4-ethoxyaniline (0.45 g, 3.3 mmol) in 20 ml ethanol. The reaction mixture was stirred for 1 h under reflux. Crystals of (E)-2-[(4-ethoxyphenylimino)methyl]-4- methoxyphenol suitable for X-ray analysis were obtained from ethanol by slow evaporation (yield % 75; m.p. 365–367 K).