2-[(2-Hydro­xy-4-nitro­phenyl)­amino­methyl­ene]­cyclo­hexa-3,5-dien-1(2H)-one

The title compound, C₁₃H₁₀N₂O₄, adopts the keto–amine tautomeric form and displays an intramolecular N—H...O [N...O = 2.579 (2) Å] and three intermolecular O—H...O [O...O = 2.561 (2) Å] and C—H...O [C...O = 3.274 (2) and 3.318 (2) Å] hydrogen bonds. The keto–amine structure is favoured by through-mol­ecule conjugation between the hydroxy O atom and imine N atom. The dihedral angle between the planes of the two aromatic rings is 10.79 (4)°.

S1. Comment

The extensive application of Schiff bases in industry and in analytical determinations has attracted attention for decades. N-substituted ortho-hydroxylimines have been reported to display thermochromism and photochromism in the solid state by H-atom transfer from the hydroxy O atom to the N atom (Hadjoudis et al., 1987; Xu et al., 1994). The overall behaviour of these compounds has been ascribed to a proton-transfer reaction between a phenolimine and a ketoamine tautomer. In solution, the existence of this tautomerism, depending on the formation of intramolecular hydrogen bonding, is offered (Filarowski & Koll, 1998; Yıldız et al., 1998; Nazır et al., 2000; Deziembowska et al., 2001; Ünver et al., 2001). It is claimed that phenolimine tautomerism is dominant in salicylaldimine, while ketoamine is in naphthaldimine Schiff bases, depending on the solvent polarities. However, in the solid state, it is specified that ketoamine tautomerism is present in naphthaldimine, while the phenolimine form exists in salicylaldimine Schiff bases (Kaitner & Pavlovic, 1996; Yıldız et al., 1998). Our X-ray investigation of the title compound, (I), has indicated that the ketoamine tautomer is favored over the phenolimine tautomer.

An ORTEP-III (Farrugia, 1997) view of the molecule of (I) and a packing diagram are shown in Figs. 1 and 2, respectively. The crystal and molecular structure of (I) reveals some interesting features. There is a strong intramolecular N—H···O hydrogen bond, with the H atom transferred from the O to the N atom. The intramolecular hydrogen bond is shorter than the sum of the van der Waals radii of O and N (3.07 Å; Bondi, 1964). Other intermolecular O—H···O hydrogen bonds are characterized by relatively short O1···O2 distances [shorter than the sum of van der Waals radii of O atoms (3.04 Å; Pizzala et al., 2000)]. The strong O···O hydrogen bond facilitates the H-atom transfer from the O to the N atom. Each molecule of (I) also participates in weak C3—H3···O3 and C2—H2···O4 hydrogen bonds, details of which can be found in Table 2.

The salicylidene ring in (I) is significantly deformed from a regular hexagonal geometry, and this deformation can be explained by a possible through-resonance effect between the electron-donating O atom and two-electron-accepting imino N atom. This also causes the elongation of the C1—C2 and C1—C6 bonds and a carbonyl group and exocyclic double bond on the salicylidene ring. The C1—O1 and N1—C7 bond lengths are 1.298 (2) and 1.308 (2) Å, respectively. These values correspond to those expected for a ketoamine structure (Pizzala et al., 2000; Hökelek et al., 2000) and are consistent with the typical length of a C═O double bond; the C═O bond length is 1.289–1.304 Å in 3-hydroxysalicylaldehyde derivatives (Pizzala et al., 2000), 1.274 Å in 1-[N-(2-pyridyl)aminomethylidene]-2-(1H)-naphthalenone (Hökelek et al., 2000) and 1.263 Å in N-(2-pyridyl)-2-oxo-1- naphthylidenemethylamine (Nazır et al., 2000). Similarly, the N1—C7 distance of 1.308 (2) Å is also consistent with an N—C single bond. Furthermore, this form is supported by the C1—C2 and C1—C6 bonds. X-ray structure determination reveals that the ketoamine tautomer is favoured over the phenolimine tautomer. Similar form is observed in 4-[(3-chlorophenyl)diazenyl]-2-{[tris-(hydroxymethyl)methyl] aminomethylene}cyclohexa-3,5-dien-1(2H)-one (Odabaşoǧlu et al., 2003).

S2. Experimental

To a solution of salicylaldehyde (2.44 g, 20 mmol) in butane-1-ol (75 ml) was added a solution of 2-hydroxy-4-nitroaniline (3.08 g, 20 mmol) in butane-1-ol (75 ml). The mixture was stirred at reflux temperature, and the occurring water in the reaction was distilled out of the reaction mixture. The resulting red precipitate was filtered off, and well shaped crystals of (I) were obtained by slow evaporation from ethyl alcohol (yield 90%).

S3. Refinement

All H-atom positions were calculated using a riding model [C—H = 0.93 Å and U_iso = 1.2 U_eq(C)], except for that involved in the N—H···O hydrogen bond and the hydroxy H atom, which were found from difference Fourier maps and refined.

Computing details

Data collection: X-AREA (Stoe & Cie, 2002); cell refinement: X-AREA; data reduction: X-RED (Stoe & Cie, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures

	Fig. 1. A view of the molecule of (I), showing the atom-labelling scheme and displacement ellipsoids at the 50% probability level.
	Fig. 2. A packing diagram of (I), showing the hydrogen-bonding scheme.

2-[(2-Hydroxy-4-Nitrophenyl)aminomethylene]cyclohexa-3,5-dien-1(2H)-one

Crystal data

C13H10N2O4	F(000) = 536
Mr = 258.23	Dx = 1.504 Mg m^−3
Monoclinic, P21/c	Melting point: 222-224°C K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 11.9528 (13) Å	Cell parameters from 8569 reflections
b = 8.0910 (5) Å	θ = 3.3–24.2°
c = 12.4205 (14) Å	µ = 0.11 mm^−1
β = 108.268 (9)°	T = 293 K
V = 1140.65 (19) Å^3	Prism, red
Z = 4	0.60 × 0.30 × 0.25 mm

Data collection

STOE IPDS 2 diffractometer	1961 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.036
Plane graphite monochromator	θmax = 27.1°, θmin = 1.8°
rotation method scans	h = −15→13
8738 measured reflections	k = −10→9
2494 independent reflections	l = −15→15

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.038	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.108	w = 1/[σ^2(Fo^2) + (0.0695P)^2 + 0.0297P] where P = (Fo^2 + 2Fc^2)/3
S = 1.04	(Δ/σ)max < 0.001
2494 reflections	Δρmax = 0.15 e Å^−3
181 parameters	Δρmin = −0.15 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.056 (8)

Special details

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
C1	0.65660 (10)	0.11285 (14)	0.60076 (9)	0.0387 (3)
C2	0.76399 (11)	0.02430 (17)	0.63365 (10)	0.0488 (3)
H2	0.8029	0.0072	0.7103	0.059*
C3	0.81175 (12)	−0.03669 (17)	0.55544 (12)	0.0507 (3)
H3	0.8829	−0.0935	0.5800	0.061*
C4	0.75612 (12)	−0.01568 (17)	0.43917 (11)	0.0497 (3)
H4	0.7893	−0.0597	0.3870	0.060*
C5	0.65280 (11)	0.06998 (17)	0.40300 (10)	0.0453 (3)
H5	0.6158	0.0845	0.3257	0.054*
C6	0.60099 (10)	0.13719 (14)	0.48134 (9)	0.0382 (3)
C7	0.49632 (10)	0.22855 (15)	0.44146 (9)	0.0395 (3)
H7	0.4610	0.2390	0.3636	0.047*
C8	0.34224 (10)	0.39415 (14)	0.47974 (9)	0.0379 (3)
C9	0.31734 (10)	0.47537 (14)	0.56910 (9)	0.0399 (3)
C10	0.21513 (11)	0.56742 (15)	0.54729 (10)	0.0439 (3)
H10	0.1964	0.6206	0.6058	0.053*
C11	0.14172 (10)	0.57880 (16)	0.43745 (11)	0.0439 (3)
C12	0.16516 (12)	0.50230 (17)	0.34786 (11)	0.0514 (3)
H12	0.1142	0.5138	0.2743	0.062*
C13	0.26595 (12)	0.40833 (17)	0.36991 (10)	0.0495 (3)
H13	0.2830	0.3541	0.3109	0.059*
N1	0.44629 (8)	0.29958 (12)	0.50916 (8)	0.0389 (2)
N2	0.03319 (10)	0.67526 (15)	0.41591 (11)	0.0557 (3)
O1	0.61009 (7)	0.16936 (11)	0.67479 (6)	0.0458 (2)
O2	0.39673 (8)	0.45970 (13)	0.67292 (7)	0.0556 (3)
O3	0.00891 (10)	0.73020 (18)	0.49683 (11)	0.0821 (4)
O4	−0.02877 (10)	0.69607 (16)	0.31818 (10)	0.0836 (4)
H11	0.4902 (14)	0.281 (2)	0.5874 (15)	0.069 (5)*
H21	0.3850 (17)	0.538 (3)	0.7233 (17)	0.089 (6)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0416 (6)	0.0406 (6)	0.0335 (5)	−0.0020 (5)	0.0112 (4)	0.0006 (4)
C2	0.0476 (7)	0.0570 (8)	0.0379 (6)	0.0077 (6)	0.0076 (5)	0.0023 (5)
C3	0.0450 (7)	0.0549 (8)	0.0513 (7)	0.0075 (6)	0.0136 (5)	−0.0003 (6)
C4	0.0510 (7)	0.0576 (8)	0.0446 (7)	0.0043 (6)	0.0210 (5)	−0.0042 (5)
C5	0.0499 (7)	0.0515 (7)	0.0356 (6)	−0.0004 (5)	0.0152 (5)	−0.0007 (5)
C6	0.0410 (6)	0.0404 (6)	0.0327 (5)	−0.0027 (5)	0.0111 (4)	0.0011 (4)
C7	0.0441 (6)	0.0418 (6)	0.0315 (5)	−0.0022 (5)	0.0103 (4)	0.0011 (4)
C8	0.0395 (6)	0.0367 (6)	0.0342 (5)	−0.0001 (4)	0.0068 (4)	0.0014 (4)
C9	0.0406 (6)	0.0430 (6)	0.0330 (5)	−0.0013 (5)	0.0071 (4)	−0.0012 (4)
C10	0.0431 (6)	0.0466 (7)	0.0427 (6)	−0.0004 (5)	0.0144 (5)	−0.0024 (5)
C11	0.0368 (6)	0.0421 (6)	0.0492 (7)	−0.0007 (5)	0.0080 (5)	0.0008 (5)
C12	0.0514 (7)	0.0556 (8)	0.0380 (6)	0.0068 (6)	0.0006 (5)	0.0007 (5)
C13	0.0566 (7)	0.0537 (7)	0.0331 (6)	0.0085 (6)	0.0070 (5)	−0.0027 (5)
N1	0.0420 (5)	0.0410 (5)	0.0314 (5)	0.0021 (4)	0.0080 (4)	0.0009 (4)
N2	0.0411 (6)	0.0543 (7)	0.0663 (7)	0.0028 (5)	0.0090 (5)	−0.0003 (6)
O1	0.0499 (5)	0.0561 (5)	0.0319 (4)	0.0070 (4)	0.0134 (3)	0.0019 (3)
O2	0.0549 (5)	0.0721 (6)	0.0318 (4)	0.0164 (5)	0.0024 (4)	−0.0086 (4)
O3	0.0593 (6)	0.1041 (10)	0.0859 (9)	0.0252 (6)	0.0268 (6)	−0.0060 (7)
O4	0.0609 (7)	0.0919 (9)	0.0752 (8)	0.0244 (6)	−0.0114 (6)	0.0003 (6)

Geometric parameters (Å, º)

C1—O1	1.298 (2)	C8—C9	1.400 (2)
C1—C2	1.414 (2)	C8—N1	1.407 (2)
C1—C6	1.437 (2)	C9—O2	1.346 (2)
C2—C3	1.365 (2)	C9—C10	1.384 (2)
C2—H2	0.9300	C10—C11	1.375 (2)
C3—C4	1.398 (2)	C10—H10	0.9300
C3—H3	0.9300	C11—C12	1.377 (2)
C4—C5	1.364 (2)	C11—N2	1.465 (2)
C4—H4	0.9300	C12—C13	1.378 (2)
C5—C6	1.416 (2)	C12—H12	0.9300
C5—H5	0.9300	C13—H13	0.9300
C6—C7	1.403 (2)	N1—H11	0.96 (2)
C7—N1	1.308 (2)	N2—O3	1.214 (2)
C7—H7	0.9300	N2—O4	1.219 (2)
C8—C13	1.388 (2)	O2—H21	0.93 (2)
O1—C1—C2	121.7 (2)	C9—C8—N1	116.1 (2)
O1—C1—C6	121.4 (2)	O2—C9—C10	123.5 (2)
C2—C1—C6	116.9 (2)	O2—C9—C8	117.0 (2)
C3—C2—C1	121.5 (2)	C10—C9—C8	119.5 (2)
C3—C2—H2	119.3	C11—C10—C9	118.7 (2)
C1—C2—H2	119.3	C11—C10—H10	120.6
C2—C3—C4	121.5 (2)	C9—C10—H10	120.6
C2—C3—H3	119.3	C10—C11—C12	122.9 (2)
C4—C3—H3	119.3	C10—C11—N2	118.1 (2)
C5—C4—C3	119.4 (2)	C12—C11—N2	119.0 (2)
C5—C4—H4	120.3	C11—C12—C13	118.3 (2)
C3—C4—H4	120.3	C11—C12—H12	120.8
C4—C5—C6	121.0 (2)	C13—C12—H12	120.8
C4—C5—H5	119.5	C12—C13—C8	120.4 (2)
C6—C5—H5	119.5	C12—C13—H13	119.8
C7—C6—C5	119.6 (2)	C8—C13—H13	119.8
C7—C6—C1	120.6 (2)	C7—N1—C8	128.1 (2)
C5—C6—C1	119.8 (2)	C7—N1—H11	111.5 (10)
N1—C7—C6	122.8 (2)	C8—N1—H11	120.4 (10)
N1—C7—H7	118.6	O3—N2—O4	123.0 (2)
C6—C7—H7	118.6	O3—N2—C11	118.1 (2)
C13—C8—C9	120.2 (2)	O4—N2—C11	118.8 (2)
C13—C8—N1	123.7 (2)	C9—O2—H21	111.7 (13)
O1—C1—C2—C3	179.15 (12)	O2—C9—C10—C11	178.20 (12)
C6—C1—C2—C3	−0.71 (19)	C8—C9—C10—C11	−1.17 (18)
C1—C2—C3—C4	−0.6 (2)	C9—C10—C11—C12	0.14 (19)
C2—C3—C4—C5	1.1 (2)	C9—C10—C11—N2	179.35 (11)
C3—C4—C5—C6	−0.3 (2)	C10—C11—C12—C13	1.0 (2)
C4—C5—C6—C7	178.26 (12)	N2—C11—C12—C13	−178.25 (12)
C4—C5—C6—C1	−1.06 (19)	C11—C12—C13—C8	−1.0 (2)
O1—C1—C6—C7	2.34 (18)	C9—C8—C13—C12	0.0 (2)
C2—C1—C6—C7	−177.80 (11)	N1—C8—C13—C12	179.48 (12)
O1—C1—C6—C5	−178.35 (11)	C6—C7—N1—C8	179.82 (11)
C2—C1—C6—C5	1.51 (17)	C13—C8—N1—C7	9.23 (19)
C5—C6—C7—N1	−177.20 (11)	C9—C8—N1—C7	−171.26 (11)
C1—C6—C7—N1	2.11 (18)	C10—C11—N2—O3	−5.37 (19)
C13—C8—C9—O2	−178.30 (12)	C12—C11—N2—O3	173.87 (13)
N1—C8—C9—O2	2.17 (16)	C10—C11—N2—O4	175.00 (12)
C13—C8—C9—C10	1.12 (18)	C12—C11—N2—O4	−5.76 (19)
N1—C8—C9—C10	−178.41 (10)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H11···O1	0.96 (2)	1.76 (2)	2.579 (2)	142.0 (15)
O2—H21···O1^i	0.93 (2)	1.64 (2)	2.561 (2)	169.5 (2)
C3—H3···O3^ii	0.93	2.52	3.274 (2)	138
C2—H2···O4^iii	0.93	2.62	3.318 (2)	132

Symmetry codes: (i) −x+1, y+1/2, −z+3/2; (ii) x+1, y−1, z; (iii) x+1, −y+1/2, z+1/2.