2-[(4-Hydroxyphenyl)iminomethyl]­thiophene

The molecular structure of the title compound, C₁₁H₉NOS, has three planar moieties, two of which are rings, namely the hydroxy­phenyl and the thio­phene, with an angle of 20.76 (10)° between them. The crystal structure is stabilized by an O—H...N hydrogen bond and by C—H...O intermolecular interactions. The C...O intermolecular contact distance is 3.443 (2) Å.

S1. Comment

Most Schiff bases possess antibacterial, anticancer, antiinflammatory and antitoxic activities (Williams, 1972) and the sulfur-containing Schiff bases are particularly effective. Schiff bases have been extensively used as ligands in the field of coordination chemistry (Calligaris et al., 1972). Schiff-base compounds can be classified by their photochromic and thermochromic characteristics (Cohen et al., 1964; Moustakali et al., 1978). The intramolecular hydrogen bond between the O and N atoms plays an important role in the formation of metal complexes and Schiff-base compounds in the solid state via proton transfer from the hydroxy O atom to the imine N atom (Hadjoudis et al., 1987; Xu et al., 1994). The charge transport occurs through overlapping intramolecular π orbitals with proton transfer (Xu et al., 1994). In this paper we report the structure of 2-[(4-hydroxyphenyl)iminomethyl]thiophene, (III). \sch

An ORTEPIII (Burnett & Johnson, 1996) plot of compound (III) is shown in Fig.1. The C7=N1 bond length of 1.282 (2) Å is typical of a double bond, which is similar to the corresponding bond lengths in N-(2,4-dinitrophenyl)-N-methylhydrazone [1.279 (2) Å; Aygün et al., 1998], 2-salicylideneamino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carbonitrile [1.281 (2) Å; Elerman & Elmal/'i, 1998] and 4-ethyl-2-(2-hydroxynapthylmethylidene)amino-5-methyl-3-thiophene carbonitrile [1.293 (3) Å; Elerman et al., 1997].

The O1—C4 and N1—C1 bond distances are 1.358 (2) and 1.422 (2) Å, respectively, which are similar to the corresponding bond lengths in 4-ethyl-2-(2-hydroxynapthylmethylidene)amino-5-methyl-3-thiophene carbonitrile [1.357 (3) and 1.379 (4) Å, respectively; Elerman et al., 1997], N-(5-bromosalicylidene)-2-aminopyridine [1.348 (6) and 1.414 (6) Å, respectively; Moustakali et al., 1978] and 2,2'-azinodimethyldiphenol [1.364 (8) and 1.386 (9) Å, respectively; Xu et al., 1994]. The increase in the electron density of the aromatic ring due to the –OH electron donor side group has made the N1—C1 bond distance in (III) longer than the values given by Elerman et al. (1997) and Xu et al. (1994). Other relevant bond lengths and angles are listed in Table 1.

The molecule of (III) is not planar. The dihedral angle between the planes of the hydroxyphenyl and thiophene rings is 20.76 (10)°, and these two planes make angles of 26.4 (2) and 5.8 (2)°, respectively, with the plane of the central moiety (C1—N1—C7—C8). The hydroxy-O atom deviates by 0.016 (1) Å from the plane of the phenyl ring.

The crystal structure of (III) is stabilized by an O—H···N hydrogen bond and by C—H···O intermolecular interactions. The O1···N1ⁱ, N1ⁱ···H1 and O1—H1 bond distances are 2.770 (2), 1.89 (3) and 0.89 (3) Å, respectively, and the O1—H1···N1ⁱ angle is 169 (3)°. The C6···O1ⁱⁱ, O1ⁱⁱ···H6 and C6—H6 bond distances are 3.443 (2), 2.50 (2) and 0.96 (2) Å, respectively, and the C6—H6···O1ⁱⁱ angle is 166 (2)° [symmetry codes: (i) x + 1/2, 3/2 − y, z + 1/2; (ii) x + 1/2, 3/2 − y, z − 1/2]. The S···N distance is 3.135 (2) Å, which is shorter than the sum of the Van der Waals radii (3.35 Å; Bondi, 1964).

S2. Experimental

Compound (III) was prepared via the reaction of 2-thiophenecarbaldehyde, (I), with 4-aminophenol, (II), by modifying the methods of Kamonuah (1992) and Rao et al. (1985). The Schiff bases crystallized out on cooling from the hot reaction mixture and were recrystallized from ethanol several times for purification. Crystals of (III) suitable for X-ray diffraction were obtained by slow cooling of a saturated solution in hot tetrahydrofuran-chloroform (2:1) to room temperature.

S3. Refinement

The H atoms were located from difference maps and refined isotropically. The C—H bond distances range from 0.90 (3) to 1.01 (3) Å, while U_iso values for the H atoms are in the range 0.051 (5)–0.098 (10) Ų.

Computing details

Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1993); cell refinement: CAD-4 EXPRESS; data reduction: MolEN (Fair, 1990); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEPIII (Burnett & Johnson, 1996); software used to prepare material for publication: SHELXL97.

Figures

Fig. 1. An ORTEPIII (Burnett & Johnson, 1996) drawing of compound (III) showing the atomic numbering scheme. Displacement ellipsoids are shown at the 50% probability level and H atoms are drawn as small spheres of arbitrary size.

2-[(4-Hydroxyphenyl)iminomethyl]thiophene

Crystal data

C11H9NOS	F(000) = 424
Mr = 203.25	Dx = 1.362 Mg m^−3
Monoclinic, P21/n	Cu Kα radiation, λ = 1.54180 Å
Hall symbol: -P 2yn	Cell parameters from 25 reflections
a = 6.4268 (3) Å	θ = 10.6–21.7°
b = 14.3420 (12) Å	µ = 2.60 mm^−1
c = 10.7559 (6) Å	T = 293 K
β = 90.618 (4)°	Prismatic, light brown
V = 991.35 (11) Å^3	0.48 × 0.42 × 0.24 mm
Z = 4

Data collection

Enraf-Nonius CAD4 diffractometer	1883 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.000
Graphite monochromator	θmax = 74.2°, θmin = 5.1°
ω/2θ scans	h = 0→8
Absorption correction: empirical (using intensity measurements) via ψ-scans (north et al., 1968) ?	k = 0→17
Tmin = 0.417, Tmax = 0.536	l = −13→13
2007 measured reflections	3 standard reflections every 120 min
2007 independent reflections	intensity decay: 1.9%

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)] = 0.046	All H-atom parameters refined
wR(F^2) = 0.125	Calculated w = 1/[σ^2(Fo^2) + (0.0615P)^2 + 0.431P] where P = (Fo^2 + 2Fc^2)/3
S = 1.05	(Δ/σ)max = 0.001
2007 reflections	Δρmax = 0.21 e Å^−3
164 parameters	Δρmin = −0.31 e Å^−3
0 restraints	Extinction correction: SHELXL97 (Sheldrick, 1997), Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0159 (13)

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
S1	0.16541 (9)	0.48263 (5)	0.18228 (6)	0.0720 (3)
O1	0.3861 (2)	0.83954 (11)	0.82412 (12)	0.0542 (4)
N1	0.2798 (2)	0.61136 (11)	0.40847 (13)	0.0448 (4)
C7	0.4266 (3)	0.56235 (13)	0.36208 (17)	0.0465 (4)
C5	0.5399 (3)	0.76283 (14)	0.64723 (17)	0.0465 (4)
C1	0.3207 (3)	0.66810 (13)	0.51437 (15)	0.0431 (4)
C4	0.3717 (3)	0.78340 (13)	0.72272 (15)	0.0440 (4)
C2	0.1526 (3)	0.68971 (15)	0.59036 (17)	0.0477 (4)
C6	0.5145 (3)	0.70600 (14)	0.54417 (16)	0.0456 (4)
C3	0.1774 (3)	0.74579 (15)	0.69330 (17)	0.0490 (5)
C8	0.4002 (3)	0.50377 (13)	0.25355 (18)	0.0484 (4)
C9	0.5551 (4)	0.45560 (15)	0.1954 (2)	0.0579 (5)
C10	0.4834 (5)	0.40239 (16)	0.0946 (2)	0.0689 (6)
C11	0.2779 (5)	0.41009 (17)	0.0769 (2)	0.0733 (7)
H6	0.635 (3)	0.6959 (16)	0.4941 (19)	0.055 (6)*
H9	0.688 (4)	0.455 (2)	0.224 (3)	0.081 (8)*
H2	0.018 (4)	0.6644 (16)	0.572 (2)	0.058 (6)*
H5	0.675 (4)	0.7878 (17)	0.667 (2)	0.061 (6)*
H3	0.065 (4)	0.7608 (17)	0.744 (2)	0.065 (7)*
H11	0.188 (4)	0.3812 (19)	0.014 (3)	0.082 (8)*
H10	0.569 (5)	0.362 (2)	0.038 (3)	0.098 (10)*
H7	0.569 (3)	0.5626 (15)	0.403 (2)	0.051 (5)*
H1	0.517 (5)	0.856 (2)	0.841 (3)	0.095 (10)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
S1	0.0591 (4)	0.0767 (4)	0.0800 (5)	−0.0045 (3)	−0.0087 (3)	−0.0239 (3)
O1	0.0447 (7)	0.0722 (9)	0.0457 (7)	−0.0016 (6)	0.0013 (5)	−0.0132 (6)
N1	0.0446 (8)	0.0490 (8)	0.0408 (7)	−0.0013 (6)	−0.0008 (6)	0.0004 (6)
C7	0.0478 (10)	0.0465 (9)	0.0453 (9)	−0.0010 (8)	−0.0005 (7)	0.0035 (7)
C5	0.0383 (9)	0.0565 (10)	0.0446 (9)	−0.0022 (8)	0.0014 (7)	0.0001 (8)
C1	0.0432 (9)	0.0483 (9)	0.0379 (8)	0.0015 (7)	−0.0005 (7)	0.0028 (7)
C4	0.0424 (9)	0.0515 (10)	0.0380 (8)	0.0010 (7)	−0.0005 (7)	0.0009 (7)
C2	0.0377 (9)	0.0599 (11)	0.0454 (9)	−0.0016 (8)	−0.0003 (7)	0.0008 (8)
C6	0.0399 (9)	0.0550 (10)	0.0420 (9)	0.0007 (7)	0.0032 (7)	−0.0005 (8)
C3	0.0391 (9)	0.0644 (12)	0.0437 (9)	0.0017 (8)	0.0032 (7)	−0.0026 (8)
C8	0.0546 (11)	0.0436 (9)	0.0470 (10)	−0.0008 (8)	0.0023 (8)	0.0020 (7)
C9	0.0615 (13)	0.0539 (11)	0.0584 (12)	0.0077 (9)	0.0025 (10)	−0.0017 (9)
C10	0.0922 (18)	0.0533 (12)	0.0614 (13)	0.0068 (12)	0.0079 (12)	−0.0096 (10)
C11	0.0947 (19)	0.0595 (13)	0.0654 (14)	−0.0092 (13)	−0.0098 (13)	−0.0143 (11)

Geometric parameters (Å, º)

S1—C11	1.705 (3)	C8—C9	1.369 (3)
S1—C8	1.712 (2)	C9—C10	1.400 (3)
O1—C4	1.358 (2)	C10—C11	1.336 (4)
N1—C7	1.282 (2)	O1—H1	0.89 (3)
N1—C1	1.422 (2)	C7—H7	1.01 (2)
C7—C8	1.447 (3)	C5—H5	0.96 (2)
C5—C6	1.384 (3)	C2—H2	0.95 (2)
C5—C4	1.391 (2)	C6—H6	0.96 (2)
C1—C6	1.393 (3)	C3—H3	0.93 (2)
C1—C2	1.397 (2)	C9—H9	0.91 (3)
C4—C3	1.393 (3)	C10—H10	1.00 (3)
C2—C3	1.376 (3)	C11—H11	0.98 (3)
C11—S1—C8	91.58 (12)	C10—C11—S1	112.41 (19)
C7—N1—C1	119.69 (16)	C4—O1—H1	112 (2)
N1—C7—C8	123.52 (18)	N1—C7—H7	119.7 (12)
C6—C5—C4	120.43 (17)	C8—C7—H7	116.8 (12)
C6—C1—C2	118.31 (17)	C6—C5—H5	119.5 (14)
C6—C1—N1	124.37 (16)	C4—C5—H5	120.1 (14)
C2—C1—N1	117.28 (16)	C3—C2—H2	118.8 (14)
O1—C4—C5	123.21 (16)	C1—C2—H2	120.0 (14)
O1—C4—C3	117.72 (16)	C5—C6—H6	116.7 (13)
C5—C4—C3	119.07 (17)	C1—C6—H6	122.5 (13)
C3—C2—C1	121.12 (17)	C2—C3—H3	121.5 (15)
C5—C6—C1	120.77 (16)	C4—C3—H3	118.2 (15)
C2—C3—C4	120.30 (17)	C8—C9—H9	122.4 (18)
C9—C8—C7	125.62 (19)	C10—C9—H9	124.2 (18)
C9—C8—S1	110.36 (16)	C11—C10—H10	120.6 (18)
C7—C8—S1	124.00 (15)	C9—C10—H10	127.0 (18)
C8—C9—C10	113.2 (2)	C10—C11—H11	129.9 (17)
C11—C10—C9	112.4 (2)	S1—C11—H11	117.7 (17)