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Acta Cryst. (2009). E65, o718    [ doi:10.1107/S1600536809007958 ]

3,5-Dimethoxy-2-[(4-propylphenyl)iminomethyl]phenol

Z. S. Sahin, A. A. Agar, F. Ersahin and S. Isik

Abstract top

The title compound, C18H21NO3, crystallizes in the phenol-imine tautomeric form, with the H atom attached to oxygen rather than on nitrogen. This H atom is involved in a strong intramolecular O-H...N hydrogen bond. A C-H...[pi] interaction is also present. The dihedral angle between the aromatic rings is 12.23 (7)°.

Comment top

Schiff bases have been extensively used as ligands in the field of coordination chemistry (Calligaris et al., 1972). There are two characteristic properties of Schiff bases, viz. photochromism and thermochromism (Cohen et al., 1964). These properties result from proton transfer from the hydroxyl O atom to the imine N atom (Hadjoudis et al., 1987). Schiff bases display two possible tautomeric forms, namely the phenol-imine (Dey et al., 2001; Karadayı et al., 2003) and keto-amine (Hökelek et al., 2000; Ünver et al., 2002) forms.

In the structure of the title compound the N1—C16 bond length of 1.280 (3)Å is typical of a double bond. The dihedral angle between the C1—C6 and C8—C13 benzene rings is 12.23 (7)°. The C1—C16—N1—C7 torsion angle is 178.7 (2)°. Fig. 1 also shows a strong intramolecular hydrogen bond (O2—H2···N1) which can be described with an S(6) graph set motif (Bernstein et al.,1995). The compound also contains one intermolecular C—H···π interaction. Atom C18 in the molecule at (x, y, z) acts as hydrogen-bond donor to the centroid Cg2 of the ring C7—C12 in the molecule at (1 - x, 1/2 + y, 3/2 - z), thus forming a chain running parallel to the [010] direction. The details of C—H···π interaction are given in Table 1.

Related literature top

Schiff base compounds can be classified by their photochromic and thermochromic characteristics, see: Cohen et al. (1964); Hadjoudis et al. (1987); Calligaris et al. (1972); Hökelek et al. (2000); Dey et al. (2001); Ünver et al. (2002); Karadayı et al. (2003). Bernstein et al. (1995) describe the use of graph-set models for the description of hydrogen bonds. Cg2 is the centroid of the C7–C12 ring.

Experimental top

The compound 3,5-dimethoxy-2-[(4-propylphenylimino)methyl]phenol was prepared by refluxing of a mixture of a solution containing 2-hydroxy-4,6-dimethoxy-benzaldehyde (0.0236 g 0.129 mmol) in 20 ml ethanol and a solution containing 4-propylaniline (0.0175 g 0.129 mmol) in 20 ml ethanol. The reaction mixture was stirred for 1 h under reflux. Recrystallization from ethanol gave the pure product. The crystals of 4,6-dimethoxy-2-[(4-propylphenylimino)methyl]phenol suitable for X-ray analysis were obtained from ethylalcohol by slow evaporation (yield % 67; m.p.346–348 K) (Fig. 2).

Refinement top

The O—H hydrogen bond was placed in a calculated position with an O—H distance of 0.82Å, but was alloed to rotate around the C—O bond at a fixed angle to best fit the experimental electron density. The H was refined Uiso(H) = 1.5Ueq(O). The other H atoms attached to C atoms were refined using a riding model with C—H = 0.93Å and Uiso(H) = 1.2Ueq(C) for aromatic C atoms, C—H = 0.97Å and Uiso(H) = 1.2Ueq(C) for methylene C atoms and C—H = 0.96Å and Uiso(H) = 1.5Ueq(C) for methyl C atoms.

Computing details top

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

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound, showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability. The dashed line represents the O-H···N hydrogen bond.
[Figure 2] Fig. 2. Synthesis of the title compound.
3,5-Dimethoxy-2-[(4-propylphenyl)iminomethyl]phenol top
Crystal data top
C18H21NO3F(000) = 640
Mr = 299.36Dx = 1.228 Mg m−3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 10898 reflections
a = 15.1143 (15) Åθ = 1.4–28.0°
b = 7.2587 (5) ŵ = 0.08 mm−1
c = 17.737 (2) ÅT = 296 K
β = 123.669 (7)°Prism, yellow
V = 1619.5 (3) Å30.48 × 0.26 × 0.12 mm
Z = 4
Data collection top
Stoe IPDS-II
diffractometer		1337 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.075
graphiteθmax = 26.5°, θmin = 1.6°
Detector resolution: 6.67 pixels mm-1h = −18→18
ω scansk = −8→9
18964 measured reflectionsl = −22→22
3353 independent reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.052Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.145H-atom parameters constrained
S = 0.86 w = 1/[σ2(Fo2) + (0.0666P)2]
where P = (Fo2 + 2Fc2)/3
3353 reflections(Δ/σ)max < 0.001
200 parametersΔρmax = 0.14 e Å−3
0 restraintsΔρmin = −0.21 e Å−3
Crystal data top
C18H21NO3V = 1619.5 (3) Å3
Mr = 299.36Z = 4
Monoclinic, P21/cMo Kα radiation
a = 15.1143 (15) ŵ = 0.08 mm−1
b = 7.2587 (5) ÅT = 296 K
c = 17.737 (2) Å0.48 × 0.26 × 0.12 mm
β = 123.669 (7)°
Data collection top
Stoe IPDS-II
diffractometer		1337 reflections with I > 2σ(I)
18964 measured reflectionsRint = 0.075
3353 independent reflectionsθmax = 26.5°
Refinement top
R[F2 > 2σ(F2)] = 0.052H-atom parameters constrained
wR(F2) = 0.145Δρmax = 0.14 e Å−3
S = 0.86Δρmin = −0.21 e Å−3
3353 reflectionsAbsolute structure: ?
200 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
Special details top

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 (Å2) top
xyzUiso*/Ueq
C10.53442 (17)0.1004 (3)0.80353 (15)0.0667 (6)
C20.57933 (17)0.1123 (3)0.75252 (15)0.0672 (6)
C30.68738 (17)0.1079 (3)0.79200 (16)0.0722 (7)
H30.71550.11700.75690.087*
C40.75352 (18)0.0896 (3)0.88549 (17)0.0730 (7)
C50.71280 (19)0.0762 (4)0.93799 (17)0.0825 (8)
H50.75840.06291.00040.099*
C60.60502 (18)0.0825 (3)0.89829 (16)0.0732 (7)
C70.26549 (18)0.0884 (3)0.76044 (16)0.0678 (6)
C80.1924 (2)0.1356 (4)0.67118 (18)0.0873 (8)
H80.21590.17220.63480.105*
C90.0850 (2)0.1289 (4)0.63550 (19)0.0919 (8)
H90.03750.15970.57490.110*
C100.0452 (2)0.0787 (4)0.6858 (2)0.0817 (7)
C110.1189 (2)0.0343 (4)0.7747 (2)0.0931 (9)
H110.09530.00020.81120.112*
C120.2272 (2)0.0384 (4)0.81199 (18)0.0870 (8)
H120.27450.00690.87250.104*
C160.42105 (17)0.1008 (3)0.76044 (16)0.0719 (7)
H160.37750.10810.69760.086*
C180.90908 (19)0.1115 (4)0.8815 (2)0.1004 (9)
H18A0.98500.10250.92190.151*
H18B0.89040.23180.85460.151*
H18C0.88400.02000.83490.151*
C170.5443 (2)0.1229 (5)0.60388 (16)0.0988 (9)
H17A0.48530.13570.54210.148*
H17B0.57920.00740.61130.148*
H17C0.59360.22190.61910.148*
C13−0.0731 (2)0.0740 (5)0.6453 (2)0.1140 (11)
H13A−0.08320.05280.69410.137*
H13B−0.10180.19500.62050.137*
C14−0.1353 (2)−0.0597 (5)0.5758 (2)0.1255 (12)
H14A−0.1062−0.18110.59960.151*
H14B−0.1278−0.03670.52570.151*
C15−0.2534 (2)−0.0615 (5)0.5394 (2)0.1338 (14)
H15A−0.2886−0.15490.49370.201*
H15B−0.28380.05660.51360.201*
H15C−0.2621−0.08720.58800.201*
N10.37759 (14)0.0914 (3)0.80506 (13)0.0738 (6)
O10.86157 (12)0.0821 (3)0.93083 (11)0.0921 (6)
O20.56789 (13)0.0725 (3)0.95188 (11)0.0995 (7)
H20.50270.07580.92050.149*
O30.50721 (11)0.1284 (3)0.66174 (10)0.0869 (6)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0666 (14)0.0706 (17)0.0586 (14)−0.0048 (12)0.0320 (13)−0.0038 (13)
C20.0695 (15)0.0707 (17)0.0538 (14)−0.0022 (12)0.0293 (13)−0.0031 (13)
C30.0699 (15)0.0791 (18)0.0677 (16)−0.0023 (13)0.0382 (13)−0.0020 (15)
C40.0604 (14)0.0728 (18)0.0689 (16)−0.0079 (12)0.0254 (13)−0.0030 (14)
C50.0741 (16)0.106 (2)0.0550 (14)−0.0098 (15)0.0280 (13)−0.0006 (15)
C60.0744 (16)0.0859 (19)0.0553 (15)−0.0108 (13)0.0334 (14)−0.0040 (14)
C70.0701 (15)0.0712 (17)0.0626 (15)0.0008 (13)0.0370 (14)0.0005 (13)
C80.0779 (17)0.100 (2)0.0752 (18)−0.0001 (15)0.0368 (15)0.0181 (16)
C90.0726 (17)0.103 (2)0.0811 (19)0.0046 (15)0.0309 (15)0.0133 (17)
C100.0770 (16)0.0770 (19)0.094 (2)0.0042 (14)0.0491 (17)−0.0086 (16)
C110.092 (2)0.112 (2)0.094 (2)0.0066 (17)0.0632 (19)−0.0021 (19)
C120.0814 (18)0.111 (2)0.0739 (17)0.0118 (15)0.0463 (16)0.0044 (15)
C160.0728 (15)0.0767 (18)0.0590 (14)0.0011 (13)0.0322 (13)−0.0028 (14)
C180.0740 (16)0.115 (2)0.109 (2)−0.0058 (16)0.0486 (17)0.0204 (19)
C170.0904 (17)0.151 (3)0.0602 (16)0.0001 (18)0.0451 (15)−0.0106 (18)
C130.0812 (18)0.124 (3)0.131 (3)0.0047 (18)0.0549 (19)−0.025 (2)
C140.0813 (19)0.153 (3)0.137 (3)−0.007 (2)0.057 (2)−0.023 (3)
C150.0733 (19)0.149 (3)0.162 (3)−0.0030 (19)0.054 (2)0.006 (3)
N10.0709 (12)0.0871 (16)0.0628 (12)−0.0019 (11)0.0367 (11)−0.0005 (11)
O10.0646 (10)0.1177 (16)0.0783 (12)−0.0085 (10)0.0298 (10)0.0050 (11)
O20.0793 (11)0.156 (2)0.0590 (10)−0.0110 (13)0.0359 (9)0.0003 (12)
O30.0715 (10)0.1344 (16)0.0519 (10)0.0047 (10)0.0324 (9)0.0013 (11)
Geometric parameters (Å, °) top
C1—C21.403 (3)C11—H110.9300
C1—C61.411 (3)C12—H120.9300
C1—C161.438 (3)C16—N11.280 (3)
C2—O31.360 (2)C16—H160.9300
C2—C31.375 (3)C18—O11.422 (3)
C3—C41.389 (3)C18—H18A0.9600
C3—H30.9300C18—H18B0.9600
C4—O11.364 (3)C18—H18C0.9600
C4—C51.375 (3)C17—O31.417 (2)
C5—C61.371 (3)C17—H17A0.9600
C5—H50.9300C17—H17B0.9600
C6—O21.347 (3)C17—H17C0.9600
C7—C121.374 (3)C13—C141.435 (4)
C7—C81.380 (3)C13—H13A0.9700
C7—N11.418 (3)C13—H13B0.9700
C8—C91.379 (3)C14—C151.525 (3)
C8—H80.9300C14—H14A0.9700
C9—C101.373 (3)C14—H14B0.9700
C9—H90.9300C15—H15A0.9600
C10—C111.373 (4)C15—H15B0.9600
C10—C131.514 (3)C15—H15C0.9600
C11—C121.385 (3)O2—H20.8200
C2—C1—C6117.2 (2)N1—C16—H16118.7
C2—C1—C16121.1 (2)C1—C16—H16118.7
C6—C1—C16121.6 (2)O1—C18—H18A109.5
O3—C2—C3123.5 (2)O1—C18—H18B109.5
O3—C2—C1114.34 (19)H18A—C18—H18B109.5
C3—C2—C1122.2 (2)O1—C18—H18C109.5
C2—C3—C4118.4 (2)H18A—C18—H18C109.5
C2—C3—H3120.8H18B—C18—H18C109.5
C4—C3—H3120.8O3—C17—H17A109.5
O1—C4—C5115.9 (2)O3—C17—H17B109.5
O1—C4—C3122.8 (2)H17A—C17—H17B109.5
C5—C4—C3121.3 (2)O3—C17—H17C109.5
C6—C5—C4120.0 (2)H17A—C17—H17C109.5
C6—C5—H5120.0H17B—C17—H17C109.5
C4—C5—H5120.0C14—C13—C10117.5 (3)
O2—C6—C5118.5 (2)C14—C13—H13A107.9
O2—C6—C1120.6 (2)C10—C13—H13A107.9
C5—C6—C1120.9 (2)C14—C13—H13B107.9
C12—C7—C8117.7 (2)C10—C13—H13B107.9
C12—C7—N1116.5 (2)H13A—C13—H13B107.2
C8—C7—N1125.8 (2)C13—C14—C15115.1 (3)
C9—C8—C7120.5 (2)C13—C14—H14A108.5
C9—C8—H8119.8C15—C14—H14A108.5
C7—C8—H8119.8C13—C14—H14B108.5
C10—C9—C8122.7 (3)C15—C14—H14B108.5
C10—C9—H9118.7H14A—C14—H14B107.5
C8—C9—H9118.7C14—C15—H15A109.5
C9—C10—C11116.1 (2)C14—C15—H15B109.5
C9—C10—C13121.7 (3)H15A—C15—H15B109.5
C11—C10—C13122.2 (3)C14—C15—H15C109.5
C10—C11—C12122.3 (3)H15A—C15—H15C109.5
C10—C11—H11118.8H15B—C15—H15C109.5
C12—C11—H11118.8C16—N1—C7121.3 (2)
C7—C12—C11120.7 (3)C4—O1—C18118.6 (2)
C7—C12—H12119.7C6—O2—H2109.5
C11—C12—H12119.7C2—O3—C17118.41 (18)
N1—C16—C1122.7 (2)
C6—C1—C2—O3179.7 (2)C8—C9—C10—C11−0.2 (4)
C16—C1—C2—O31.6 (3)C8—C9—C10—C13179.5 (3)
C6—C1—C2—C3−0.3 (4)C9—C10—C11—C12−0.4 (4)
C16—C1—C2—C3−178.5 (2)C13—C10—C11—C12180.0 (3)
O3—C2—C3—C4−179.5 (2)C8—C7—C12—C110.6 (4)
C1—C2—C3—C40.5 (4)N1—C7—C12—C11179.0 (2)
C2—C3—C4—O1179.3 (2)C10—C11—C12—C70.2 (4)
C2—C3—C4—C5−0.1 (4)C2—C1—C16—N1−179.5 (2)
O1—C4—C5—C6180.0 (2)C6—C1—C16—N12.5 (4)
C3—C4—C5—C6−0.6 (4)C9—C10—C13—C1466.0 (4)
C4—C5—C6—O2−178.8 (2)C11—C10—C13—C14−114.4 (4)
C4—C5—C6—C10.8 (4)C10—C13—C14—C15178.4 (3)
C2—C1—C6—O2179.2 (2)C1—C16—N1—C7−178.7 (2)
C16—C1—C6—O2−2.7 (4)C12—C7—N1—C16166.3 (2)
C2—C1—C6—C5−0.3 (4)C8—C7—N1—C16−15.5 (4)
C16—C1—C6—C5177.8 (2)C5—C4—O1—C18−174.5 (2)
C12—C7—C8—C9−1.1 (4)C3—C4—O1—C186.1 (4)
N1—C7—C8—C9−179.3 (2)C3—C2—O3—C176.2 (4)
C7—C8—C9—C100.9 (4)C1—C2—O3—C17−173.8 (2)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O2—H2···N10.821.872.602 (2)148
C18—H18B···Cg2i0.962.803.764 (3)178
Symmetry codes: (i) −x+1, y+1/2, −z+3/2.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O2—H2···N10.821.872.602 (2)148
C18—H18B···Cg2i0.962.803.764 (3)178
Symmetry codes: (i) −x+1, y+1/2, −z+3/2.
Acknowledgements top

The authors acknowledge the Faculty of Arts and Sciences of Ondokuz Mayıs University, Turkey, for the use of the Stoe IPDS-II diffractometer (purchased under grant No. F279 of the University Research Grant of Ondokuz Mayıs University).

references
References top

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