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Acta Cryst. (2008). E64, o1065    [ doi:10.1107/S1600536808013160 ]

(E)-4-Methyl-2-[(R)-1-phenylethyliminomethyl]phenol

F.-F. Dang

Abstract top

In the title Schiff base, C16H17NO, the dihedral angle between the two aromatic rings is 63.59 (2)°. A strong intramolecular O-H...N hydrogen bond is observed between the hydroxyl group and the imine N atom.

Comment top

Compounds presenting photochromism, a reversible colour change brought about in at least one direction, by the action of electromagnetic radiation, attract considerable attention from various fields of chemistry, physics and materials science as potential candidates for practical applications. For a long time, the Schiff bases of salicylaldehyde with aromatic amines (anils or N-salicylideneaniline derivatives) are recognized as such compounds, which undergo enol-keto tautomerism and present common features in their structures and reaction mechanisms. The Schiff base compounds show photochromism and thermochromism in the solid state by proton transfer from the hydroxyl O atom to the imine N atom (Cohen et al., 1964). The tautomerism involves proton transfer from the hydroxylic oxygen to the imino nitrogen atom that occurs intramolecularly via a six-membered ring, with the keto species showing bathochromically shifted spectra. Continuing our studies on the relation between the Schiff base geometry in the crystalline state and photochromism and/or thermochromism, we report presently on the crystal structure of the title compound.

The structure of the title molecule is illustrated in Fig. 1. It is a typical salicylaldehyde Schiff base with normal geometric parameters. The C8?N1 bond show the expected double-bond character. The molecule is not planar. The dihedral angle between the two aromatic rings is 63.59 (2)°. A strong intramolecular O—H···N hydrogen bond is observed between the hydroxyl group and the imine N atom (Table 1).

Related literature top

For photochromism and thermochromism of Schiff bases, see: Cohen et al. (1964).

Experimental top

(R)-1-Phenylethanamine (0.02 mol, 2.42 g) and 2-hydroxy-5-methylbenzaldehyde (0.02 mol, 2.72 g) were dissolved in ethanol and the solution was refluxed for 3 h. After evaporation, a crude product was obtained which was recrystallized twice from ethanol to give a pure yellow product (yield 82.5%). Calculated for C16H17NO: C 80.30, H 7.16, N 5.85%; found: C 80.18, H 7.42, N 5.54%.

Refinement top

H atoms were placed in geometrically idealized positions (C—H = 0.93–0.98%A and O—H = 0.82 Å) and constrained to ride on their parent atoms, with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(Cmethyl, O). In the absence of significant anomalous scattering, Friedel pairs were merged prior to the final refinement.

Computing details top

Data collection: APEX2 (Bruker, 2004); cell refinement: SAINT (Bruker, 2004); data reduction: SAINT (Bruker, 2004); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound, showing 30% probability displacement ellipsoids and the atom-numbering scheme.
(E)-4-Methyl-2-[(R)-1-phenylethyliminomethyl]phenol top
Crystal data top
C16H17NOF000 = 512
Mr = 239.31Dx = 1.162 Mg m−3
Monoclinic, C2Mo Kα radiation
λ = 0.71073 Å
Hall symbol: C 2yCell parameters from 1435 reflections
a = 20.342 (8) Åθ = 1.0–27.6º
b = 5.911 (2) ŵ = 0.07 mm−1
c = 14.551 (5) ÅT = 296 (2) K
β = 128.585 (4)ºBlock, yellow
V = 1367.7 (9) Å30.35 × 0.34 × 0.26 mm
Z = 4
Data collection top
Bruker APEXII area-detector
diffractometer		1726 independent reflections
Radiation source: fine-focus sealed tube1609 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.034
T = 296(2) Kθmax = 27.6º
φ and ω scansθmin = 1.8º
Absorption correction: multi-scan
(SADABS; Sheldrick, 1997)		h = −24→26
Tmin = 0.971, Tmax = 0.986k = −7→7
5952 measured reflectionsl = −18→18
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.033H-atom parameters constrained
wR(F2) = 0.100  w = 1/[σ2(Fo2) + (0.0539P)2 + 0.1688P]
where P = (Fo2 + 2Fc2)/3
S = 1.08(Δ/σ)max = 0.001
1726 reflectionsΔρmax = 0.16 e Å−3
166 parametersΔρmin = −0.12 e Å−3
1 restraintExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.023 (3)
Crystal data top
C16H17NOV = 1367.7 (9) Å3
Mr = 239.31Z = 4
Monoclinic, C2Mo Kα
a = 20.342 (8) ŵ = 0.07 mm−1
b = 5.911 (2) ÅT = 296 (2) K
c = 14.551 (5) Å0.35 × 0.34 × 0.26 mm
β = 128.585 (4)º
Data collection top
Bruker APEXII area-detector
diffractometer		1726 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1997)		1609 reflections with I > 2σ(I)
Tmin = 0.971, Tmax = 0.986Rint = 0.034
5952 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.033H-atom parameters constrained
wR(F2) = 0.100Δρmax = 0.16 e Å−3
S = 1.08Δρmin = −0.12 e Å−3
1726 reflectionsAbsolute structure: ?
166 parametersFlack parameter: ?
1 restraintRogers 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
O10.40281 (8)−0.3392 (2)−0.02219 (12)0.0730 (4)
H10.4410−0.26530.03420.110*
N10.47315 (9)0.0034 (2)0.12256 (11)0.0538 (3)
C10.32941 (11)−0.2272 (3)−0.07580 (15)0.0532 (4)
C20.25597 (12)−0.3196 (3)−0.17537 (17)0.0641 (5)
H20.2577−0.4590−0.20350.077*
C30.18064 (12)−0.2067 (4)−0.23274 (16)0.0637 (5)
H30.1323−0.2725−0.29900.076*
C40.17441 (11)0.0028 (3)−0.19481 (15)0.0573 (4)
C50.24764 (10)0.0946 (3)−0.09567 (14)0.0525 (4)
H50.24510.2337−0.06820.063*
C60.32532 (10)−0.0142 (3)−0.03530 (13)0.0475 (3)
C70.09140 (12)0.1267 (4)−0.2595 (2)0.0782 (6)
H7A0.10060.2860−0.25970.117*
H7B0.06740.0999−0.22100.117*
H7C0.05360.0729−0.33910.117*
C80.40074 (10)0.0940 (3)0.06644 (13)0.0509 (4)
H80.39590.23360.09120.061*
C90.54666 (10)0.1249 (3)0.22409 (14)0.0548 (4)
H90.52680.26030.23900.066*
C100.60292 (14)0.1982 (4)0.19397 (19)0.0727 (5)
H10A0.57400.30840.13200.109*
H10B0.61660.06920.16870.109*
H10C0.65370.26330.26220.109*
C110.58971 (10)−0.0289 (3)0.33046 (13)0.0519 (4)
C120.62976 (13)−0.2262 (4)0.33758 (17)0.0664 (5)
H120.6319−0.26230.27720.080*
C130.66655 (14)−0.3697 (4)0.4330 (2)0.0802 (6)
H130.6936−0.50020.43660.096*
C140.66345 (14)−0.3215 (5)0.52172 (19)0.0864 (7)
H140.6876−0.41930.58530.104*
C150.62443 (17)−0.1278 (6)0.51633 (19)0.0894 (8)
H150.6226−0.09390.57710.107*
C160.58746 (13)0.0192 (4)0.42139 (16)0.0696 (5)
H160.56120.15020.41910.083*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0677 (7)0.0529 (7)0.0784 (9)0.0080 (6)0.0357 (7)−0.0145 (7)
N10.0630 (8)0.0471 (7)0.0489 (6)0.0001 (6)0.0337 (6)−0.0041 (6)
C10.0620 (9)0.0425 (8)0.0575 (8)0.0013 (7)0.0385 (7)−0.0019 (7)
C20.0730 (10)0.0470 (9)0.0696 (10)−0.0048 (9)0.0432 (9)−0.0123 (9)
C30.0608 (9)0.0626 (11)0.0617 (10)−0.0105 (9)0.0352 (8)−0.0081 (9)
C40.0601 (9)0.0568 (9)0.0627 (9)0.0030 (8)0.0421 (8)0.0094 (8)
C50.0650 (9)0.0448 (8)0.0604 (9)0.0031 (7)0.0453 (8)0.0026 (7)
C60.0610 (8)0.0407 (7)0.0508 (7)0.0016 (6)0.0398 (7)0.0022 (6)
C70.0649 (10)0.0782 (15)0.0904 (13)0.0100 (11)0.0479 (10)0.0140 (12)
C80.0671 (9)0.0418 (7)0.0516 (8)0.0007 (7)0.0409 (7)−0.0026 (7)
C90.0647 (9)0.0460 (8)0.0528 (8)−0.0027 (7)0.0362 (7)−0.0084 (7)
C100.0849 (12)0.0704 (12)0.0686 (11)−0.0137 (11)0.0507 (10)−0.0019 (10)
C110.0539 (8)0.0520 (9)0.0493 (7)−0.0096 (7)0.0320 (6)−0.0094 (7)
C120.0769 (11)0.0587 (10)0.0629 (10)0.0032 (9)0.0433 (9)−0.0030 (9)
C130.0765 (12)0.0642 (12)0.0738 (12)0.0015 (11)0.0341 (10)0.0061 (11)
C140.0861 (14)0.0835 (16)0.0554 (10)−0.0224 (13)0.0273 (10)0.0057 (11)
C150.1092 (17)0.1044 (19)0.0575 (11)−0.0279 (16)0.0535 (12)−0.0134 (13)
C160.0833 (12)0.0720 (12)0.0616 (9)−0.0097 (10)0.0492 (9)−0.0132 (10)
Geometric parameters (Å, °) top
O1—C11.350 (2)C8—H80.93
O1—H10.82C9—C111.516 (2)
N1—C81.274 (2)C9—C101.522 (3)
N1—C91.476 (2)C9—H90.98
C1—C21.389 (2)C10—H10A0.96
C1—C61.414 (2)C10—H10B0.96
C2—C31.377 (3)C10—H10C0.96
C2—H20.93C11—C161.382 (2)
C3—C41.394 (3)C11—C121.389 (3)
C3—H30.93C12—C131.383 (3)
C4—C51.383 (2)C12—H120.93
C4—C71.514 (3)C13—C141.362 (4)
C5—C61.397 (2)C13—H130.93
C5—H50.93C14—C151.367 (4)
C6—C81.457 (2)C14—H140.93
C7—H7A0.96C15—C161.390 (4)
C7—H7B0.96C15—H150.93
C7—H7C0.96C16—H160.93
C1—O1—H1109.4N1—C9—C10108.95 (14)
C8—N1—C9118.78 (15)C11—C9—C10113.93 (15)
O1—C1—C2119.47 (15)N1—C9—H9108.6
O1—C1—C6121.80 (15)C11—C9—H9108.6
C2—C1—C6118.71 (15)C10—C9—H9108.6
C3—C2—C1120.53 (17)C9—C10—H10A109.5
C3—C2—H2119.7C9—C10—H10B109.5
C1—C2—H2119.7H10A—C10—H10B109.5
C2—C3—C4122.18 (18)C9—C10—H10C109.5
C2—C3—H3118.9H10A—C10—H10C109.5
C4—C3—H3118.9H10B—C10—H10C109.5
C5—C4—C3117.16 (17)C16—C11—C12117.99 (18)
C5—C4—C7121.14 (18)C16—C11—C9120.77 (17)
C3—C4—C7121.69 (18)C12—C11—C9121.20 (15)
C4—C5—C6122.38 (16)C13—C12—C11121.01 (18)
C4—C5—H5118.8C13—C12—H12119.5
C6—C5—H5118.8C11—C12—H12119.5
C5—C6—C1119.04 (15)C14—C13—C12120.5 (2)
C5—C6—C8119.88 (15)C14—C13—H13119.8
C1—C6—C8121.07 (15)C12—C13—H13119.8
C4—C7—H7A109.5C13—C14—C15119.3 (2)
C4—C7—H7B109.5C13—C14—H14120.3
H7A—C7—H7B109.5C15—C14—H14120.3
C4—C7—H7C109.5C14—C15—C16121.0 (2)
H7A—C7—H7C109.5C14—C15—H15119.5
H7B—C7—H7C109.5C16—C15—H15119.5
N1—C8—C6122.04 (15)C11—C16—C15120.2 (2)
N1—C8—H8119.0C11—C16—H16119.9
C6—C8—H8119.0C15—C16—H16119.9
N1—C9—C11108.04 (14)
O1—C1—C2—C3−178.86 (18)C1—C6—C8—N10.4 (2)
C6—C1—C2—C3−0.5 (3)C8—N1—C9—C11123.36 (15)
C1—C2—C3—C40.3 (3)C8—N1—C9—C10−112.39 (18)
C2—C3—C4—C5−0.2 (3)N1—C9—C11—C16−110.20 (17)
C2—C3—C4—C7179.20 (18)C10—C9—C11—C16128.59 (19)
C3—C4—C5—C60.5 (2)N1—C9—C11—C1267.34 (19)
C7—C4—C5—C6−178.95 (15)C10—C9—C11—C12−53.9 (2)
C4—C5—C6—C1−0.8 (2)C16—C11—C12—C13−0.2 (3)
C4—C5—C6—C8178.08 (14)C9—C11—C12—C13−177.84 (18)
O1—C1—C6—C5179.05 (16)C11—C12—C13—C140.7 (3)
C2—C1—C6—C50.8 (2)C12—C13—C14—C15−0.8 (3)
O1—C1—C6—C80.2 (2)C13—C14—C15—C160.5 (4)
C2—C1—C6—C8−178.06 (16)C12—C11—C16—C15−0.1 (3)
C9—N1—C8—C6179.41 (13)C9—C11—C16—C15177.52 (19)
C5—C6—C8—N1−178.41 (14)C14—C15—C16—C110.0 (3)
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O1—H1···N10.821.892.613 (2)147
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
O1—H1···N10.821.892.613 (2)147
Acknowledgements top

This project was supported by the Talent Fund of Xi'an University of Architecture and Technology.

references
References top

Bruker (2004). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.

Cohen, M. D., Schmidt, G. M. J. & Flavian, S. (1964). J. Chem. Soc. 2041–2043.

Sheldrick, G. M. (1997). SADABS. University of Göttingen, Germany.

Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.