(E)-2-Hydr­oxy-6-[(4-propyl­phenyl)­iminiometh­yl]phenolate

Serap Yazıcı; Çiğdem Albayrak; İsmail Gümrükçüoğlu; İsmet Şenel; Orhan Büyükgüngör

doi:10.1107/S1600536809052246

. 2009 Dec 9;66(Pt 1):o93. doi: 10.1107/S1600536809052246

(E)-2-Hydroxy-6-[(4-propylphenyl)iminiomethyl]phenolate

Serap Yazıcı ^a,^*, Çiğdem Albayrak ^b, İsmail Gümrükçüoğlu ^c, İsmet Şenel ^a, Orhan Büyükgüngör ^a

PMCID: PMC2980080 PMID: 21580188

Abstract

The title compound, C₁₆H₁₇NO₂, crystallizes with three crystallographically independent zwitterionic molecules in the asymmetric unit which differ significantly in the orientations of the propyl side chains. The dihedral angles between the two benzene rings in the three molecules are 6.17 (7), 6.75 (7) and 23.67 (7)°, respectively. In each independent molecule, an intramolecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, each independent molecule exists as part of an O—H⋯O hydrogen-bonded centrosymmetric R ₂ ²(10) dimer.

Related literature

For general background to Schiff base compounds in coordination chemistry, see: Cohen et al. (1964 ▶); Moustakali-Mavridis et al. (1978 ▶); Hadjoudis et al. (1987 ▶); Ogawa & Harada (2003 ▶); Krygowski et al. (1997 ▶). For related structures, see: Petek et al. (2006 ▶); Kılıç et al. (2008 ▶); Gao et al. (2005 ▶); Temel et al. (2006 ▶). For bond-length data, see: Allen et al. (1987 ▶).

Experimental

Crystal data

C₁₆H₁₇NO₂
M _r = 255.31
Triclinic,
a = 11.5743 (4) Å
b = 12.7635 (4) Å
c = 14.1706 (5) Å
α = 90.418 (3)°
β = 103.259 (3)°
γ = 95.540 (3)°
V = 2027.14 (11) Å³
Z = 6
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 150 K
0.56 × 0.42 × 0.28 mm

Data collection

Stoe IPDS II diffractometer
Absorption correction: integration (X-RED32; Stoe & Cie, 2002 ▶) T _min = 0.972, T _max = 0.985
25371 measured reflections
7976 independent reflections
6241 reflections with I > 2σ(I)
R _int = 0.028

Refinement

R[F ² > 2σ(F ²)] = 0.042
wR(F ²) = 0.110
S = 1.04
7976 reflections
538 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.33 e Å⁻³
Δρ_min = −0.26 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/S1600536809052246/ci2970sup1.cif

e-66-00o93-sup1.cif^{(33.7KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809052246/ci2970Isup2.hkl

e-66-00o93-Isup2.hkl^{(382.3KB, 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
N1A—H1A⋯O1A	1.02 (2)	1.63 (2)	2.5444 (16)	147 (2)
N1B—H1B⋯O1B	1.06 (2)	1.57 (2)	2.5229 (16)	146 (2)
N1C—H1C⋯O1C	1.08 (2)	1.57 (2)	2.5502 (17)	149 (2)
O2A—H5A⋯O1Aⁱ	0.90 (2)	1.89 (2)	2.7032 (17)	148 (2)
O2B—H5B⋯O1Bⁱⁱ	0.89 (2)	1.91 (2)	2.7049 (15)	148 (2)
O2C—H5C⋯O1Cⁱⁱⁱ	0.92 (2)	1.84 (2)	2.6659 (15)	148 (2)

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

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. F279 of the University Research Fund).

supplementary crystallographic information

Comment

Schiff bases are of interest because they have long been known to show photochromism and thermochromism in the solid state which may involve reversible proton transfer from the amino N atom to the hydroxyl O atom (Cohen et al., 1964; Moustakali-Mavridis et al., 1978; Hadjoudis et al., 1987). On the basis of some thermochromic and photochromic Schiff base compounds, it was proposed that molecules exhibiting thermochromism are planar, while those exhibiting photochromism are non-planar (Moustakali-Mavridis et al., 1978). In general, there are two types of tautomeric forms in Schiff bases viz. keto-amine (quinoid with N—H···O bond) and phenol-imine (benzenoid with O—H···N bond). Quinoid tautomers can also be found in the zwitterionic form which consist of ionic intramolecular N⁺—H···O^- hydrogen bond (Ogawa & Harada, 2003). The zwitterionic form is rarely seen in the solid state (Krygowski et al., 1997).

The three independent molecules (A, B and C) of the title compound are shown in Fig. 1. The N⁺—H bond lengths in molecules A, B and C are [1.02 (2), 1.06 (2) and 1.08 (3) Å, respectively] as expected in the zwitterionic form of Schiff bases (Petek et al., 2006; Kılıç et al., 2008). These values are longer than the N—H distance of 0.87 Å. The C6—O1 bond lengths in molecules A, B and C are 1.3034 (18), 1.3028 (17), 1.3060 (18) Å, respectively, and are intermediate between C—O single (1.362 Å) and C═O double bond (1.222 Å) lengths (Allen et al., 1987). The C7—N1 bond lengths [1.3034 (19), 1.3068 (19) and 1.3065 (19) Å for A, B and C, respectively] are comparable to those observed in related zwitterions (Gao et al.,2005; Temel et al., 2006). Each molecule displays an E configuration with respect to its C═N bond. The dihedral angle between the two benzene rings in molecules A, B and C are 6.17 (7)°, 6.75 (7)° and 23.67 (7)°, respectively. In each independent molecule, an intramolecular N—H ···O hydrogen bond generates an S(6) ring motif (Table 1).

The crystal packing is stabilized by intermolecular O—H···O hydrogen bonds (Table 1), generating centrosymmetric R₂² (10) dimers (Fig.2).

Experimental

The title compound was prepared by refluxing a mixture of 2,3-dihydroxybenzaldehyde (0.5 g 3.6 mmol) in ethanol (20 ml) and 4-propylaniline (0.49 g 3.6 mmol) in ethanol (20 ml). The reaction mixture was stirred for 1 h under reflux. Single crystals of the title compound suitable for X-ray analysis were obtained by slow evaporation of an ethanol solution (yield 68%, m.p. 371–372 K).