(E)-4-Meth­oxy-2-(o-tolyl­imino­meth­yl)phenol

Arzu Özek; Orhan Büyükgüngör; Çiğdem Albayrak; Mustafa Odabaşoğlu

doi:10.1107/S1600536809009192

. 2009 Mar 19;65(Pt 4):o791. doi: 10.1107/S1600536809009192

(E)-4-Methoxy-2-(o-tolyliminomethyl)phenol

Arzu Özek ^a, Orhan Büyükgüngör ^a,^*, Çiğdem Albayrak ^b, Mustafa Odabaşoğlu ^c

PMCID: PMC2968945 PMID: 21582515

Abstract

In the molecule of the title compound, C₁₅H₁₅NO₂, the aromatic rings are oriented at a dihedral angle of 15.46 (6)°. An intramolecular O—H⋯N hydrogen bond results in the formation of a nearly planar six-membered ring [maximum deviation of 0.035 (5) Å for the N atom] which is almost coplanar with the adjacent ring, making a dihedral angle of 0.8 (3)°. The title organic molecule is a phenol–imine tautomer, as evidenced by the C—O, C—N and C—C bond lengths. Molecules are linked by intermolecular C—H⋯O hydrogen bonds that generate a C(5) chain. C—H⋯π and π–π interactions exist in the structure. The π–π interaction occurs between the phenol ring and its symmetry equivalent at (1 − x, 1 − y, −z), with a centroid–centroid distance of 3.727 (7) Å and a plane-to-plane separation of 3.383 (5) Å, resulting in an offset angle of 24.82 (1)°.

Related literature

For previous work in our structural study of Schiff bases, see: Özek et al. (2007 ▶); Odabaşoğlu, Arslan et al. (2007 ▶); Odabaşoğlu, Büyükgüngör et al. (2007 ▶). For a related compound, see: Albayrak et al. (2005 ▶).

Experimental

Crystal data

C₁₅H₁₅NO₂
M _r = 241.28
Monoclinic,
a = 13.2889 (6) Å
b = 8.5986 (6) Å
c = 11.6714 (6) Å
β = 113.284 (3)°
V = 1225.03 (12) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 100 K
0.59 × 0.47 × 0.30 mm

Data collection

Stoe IPDS II diffractometer
Absorption correction: integration (X-RED32; Stoe & Cie, 2002 ▶) T _min = 0.954, T _max = 0.975
6569 measured reflections
2537 independent reflections
2108 reflections with I > 2σ(I)
R _int = 0.039

Refinement

R[F ² > 2σ(F ²)] = 0.036
wR(F ²) = 0.092
S = 1.02
2537 reflections
223 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.20 e Å⁻³
Δρ_min = −0.19 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/S1600536809009192/bv2115sup1.cif

e-65-0o791-sup1.cif^{(17.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809009192/bv2115Isup2.hkl

e-65-0o791-Isup2.hkl^{(122.1KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (Å, °).

Cg2 is the centroid of the C9–C14 ring.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯N1	0.958 (19)	1.68 (2)	2.5794 (13)	154.8 (17)
C8—H8⋯O1ⁱ	0.973 (15)	2.444 (15)	3.4129 (14)	173.5 (12)
C7—H7B⋯Cg2ⁱⁱ	1.01 (2)	2.90 (2)	3.6727 (16)	134 (2)

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Symmetry codes: (i) Inline graphic ; (ii) .

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 No. 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., 2007; Odabaşoğlu, Büyükgüngör et al., 2007; Odabaşoğlu, Arslan et al., 2007) and we report here the structure of (E)-4-methoxy-2-[(o-tolylimino)methyl]phenol, (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. The H atom in title compound (I) is located on atom O1, thus the phenol-imine tautomer is favored over the keto-amine form, as indicated by the C2—O1 [1.3579 (2) Å], C8—N1 [1.2865 (2) Å], C1—C8 [1.4519 (2) Å] and C1—C2 [1.4071 (2) Å] bond lengths (Fig. 1). The C2—O1 bond length of 1.357 (2)Å indicates single-bond character, whereas the C8—N1 bond length of 1.286 (2)Å indicates a high degree of double-bond character. Similar results were observed for 2-(3-methoxysalicylideneamino)-1H-benzimidazolemonohydrate [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 photochromic properties in (I) caused by non-planarity of the molecules; the dihedral angle between rings A(C1—C6) and B (C9—C14) is 15.46 (6)°. 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), oriented with respect to rings A and B at dihedral angles of A/C=0.81 (2)° and B/C= 15.04 (3)°. So, it is coplanar with the adjacent ring A and generates an S(6) ring motif. The O1···N1 distance of 2.579 (2)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 results in the formation of C(5) chains along the c axis (Table 1, Fig. 2). In addition to these intermolecular interactions, C—H···π interactions and π···π interactions play roles in the crystal packing (Table 1, Fig. 3). This slipped π···π interaction occurs between Cg1 (the centroid of the C1—C6 ring) and its symmetry equivalent at (1 - x, 1 - y, -z), with a centroid-to-centroid distance of 3.727 (7)Å and a plane-to-plane separation of 3.383 (5) Å, resulting in an offset angle of 24.82 (1)°.

Experimental

The compound (E)-4-methoxy-2-[(o-tolylimino)methyl]phenol was prepared by reflux a mixture of a solution containing 5-methoxysalicylaldehyde (0.5 g 3.3 mmol) in 20 ml ethanol and a solution containing 2-chloraniline (0.420 g 3.3 mmol) in 20 ml ethanol. The reaction mixture was stirred for 1 h under reflux. The crystals of (E)-4-methoxy-2-[(o-tolylimino)methyl]phenol suitable for X-ray analysis were obtained from methanol by slow evaporation (yield % 73; m.p. 343–344 K).