organic compounds
2-[(2,4-Dimethylphenyl)iminomethyl]-3,5-dimethoxyphenol
aDepartment of Physics, Faculty of Arts & Science, Ondokuz Mayıs University, TR-55139 Kurupelit–Samsun, Turkey, and bDepartment of Chemistry, Faculty of Arts & Science, Ondokuz Mayıs University, 55139 Samsun, Turkey
*Correspondence e-mail: htanak@omu.edu.tr
X-ray analysis reveals that the title Schiff base compound, C17H19NO3, possesses both OH and NH tautomeric character in its molecular structure. The occupancies of the enol and keto tautomers are 0.62 (3) and 0.38 (3), respectively. The presence of the minor keto form could not be confirmed from the IR spectrum. The molecule is approximately planar, the dihedral angle between the planes of the two aromatic rings being 6.97 (8)°. The molecular structure of the major component is stabilized by an intramolecular O—H⋯N hydrogen bond, which generates an S(6) ring motif (N—H⋯O hydrogen bond in the minor component).
Related literature
For tautomeric forms of et al. (1987); Seliger et al. (1990); Sugawara et al. (1999); Tezer & Karakus (2009). For bond-length data, see: Allen et al. (1987); Ogawa & Harada (2003).
see: BeckerExperimental
Crystal data
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Refinement
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Data collection: X-AREA (Stoe & Cie, 2002); cell X-AREA; data reduction: X-RED32; 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).
Supporting information
10.1107/S1600536809021278/ci2808sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536809021278/ci2808Isup2.hkl
A solution of 2-hydroxy-4,6-dimethoxy-benzaldehyde (0.0389 g, 0.21 mmol) in ethanol (20 ml) was added to a solution of 2,4-dimethylaniline (0.0263 g, 0.21 mmol) in ethanol (20 ml). The reaction mixture was stirred for 1 h under reflux. Single crystals suitable for X-ray analysis were obtained from ethyl alcohol by slow evaporation (yield 59%; m.p.386–388 K).
C-bound H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93-0.96 Å and Uiso(H) = 1.2-1.5Ueq(C). The C15-methyl group was refined as idealized disordered one with two positions rotated from each other by 60°. At this stage, the hydroxyl H atom, H1A, was located in a difference map and attempts to refine it freely resulted in a very long O-H distance of 1.22 (3) Å. When the O-bound H atom was positioned geometrically a new peak at 0.97 Å from N1 was observed, indicating a disorder in the H atom i.e the presence of both OH and NH tautomers. At this stage both O and N-bound H atoms, H1A and H1B, were positioned geometrically and their occupancies were refined to 0.62 (3) and 0.38 (3), respectively. The
shows the enol form is the major component. The IR spectrum of the compound confirms only the presence of enol form and we are unable to confirm the minor keto form from the IR spectrum.Data collection: X-AREA (Stoe & Cie, 2002); cell
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).C17H19NO3 | F(000) = 608 |
Mr = 285.33 | Dx = 1.276 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71069 Å |
Hall symbol: -P 2ybc | Cell parameters from 10962 reflections |
a = 4.7070 (2) Å | θ = 1.5–26.2° |
b = 11.283 (5) Å | µ = 0.09 mm−1 |
c = 28.216 (5) Å | T = 296 K |
β = 97.542 (11)° | Prism, yellow |
V = 1485.6 (7) Å3 | 0.67 × 0.31 × 0.09 mm |
Z = 4 |
Stoe IPDS II diffractometer | 2797 independent reflections |
Radiation source: fine-focus sealed tube | 1808 reflections with I > 2σ(I) |
Plane graphite monochromator | Rint = 0.043 |
Detector resolution: 6.67 pixels mm-1 | θmax = 25.6°, θmin = 1.5° |
rotation method scans | h = −5→5 |
Absorption correction: integration (X-RED32; Stoe & Cie, 2002) | k = −13→13 |
Tmin = 0.977, Tmax = 0.994 | l = −34→34 |
13316 measured reflections |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.043 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.111 | H-atom parameters constrained |
S = 0.98 | w = 1/[σ2(Fo2) + (0.0599P)2] where P = (Fo2 + 2Fc2)/3 |
2797 reflections | (Δ/σ)max = 0.001 |
195 parameters | Δρmax = 0.09 e Å−3 |
0 restraints | Δρmin = −0.14 e Å−3 |
C17H19NO3 | V = 1485.6 (7) Å3 |
Mr = 285.33 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 4.7070 (2) Å | µ = 0.09 mm−1 |
b = 11.283 (5) Å | T = 296 K |
c = 28.216 (5) Å | 0.67 × 0.31 × 0.09 mm |
β = 97.542 (11)° |
Stoe IPDS II diffractometer | 2797 independent reflections |
Absorption correction: integration (X-RED32; Stoe & Cie, 2002) | 1808 reflections with I > 2σ(I) |
Tmin = 0.977, Tmax = 0.994 | Rint = 0.043 |
13316 measured reflections |
R[F2 > 2σ(F2)] = 0.043 | 0 restraints |
wR(F2) = 0.111 | H-atom parameters constrained |
S = 0.98 | Δρmax = 0.09 e Å−3 |
2797 reflections | Δρmin = −0.14 e Å−3 |
195 parameters |
Experimental. 240 frames, detector distance = 130 mm |
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. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
O1 | −0.1970 (3) | 0.07461 (10) | 0.06735 (5) | 0.0759 (4) | |
H1A | −0.0686 | 0.0847 | 0.0896 | 0.114* | 0.62 (3) |
O2 | −0.3588 (3) | 0.47471 (10) | 0.10480 (4) | 0.0735 (4) | |
O3 | −0.9431 (3) | 0.29177 (10) | −0.02381 (4) | 0.0721 (4) | |
N1 | 0.1167 (3) | 0.18286 (12) | 0.13482 (5) | 0.0584 (4) | |
H1B | 0.0796 | 0.1207 | 0.1175 | 0.070* | 0.38 (3) |
C1 | −0.2694 (3) | 0.27691 (13) | 0.08638 (6) | 0.0534 (4) | |
C2 | −0.3428 (4) | 0.17509 (14) | 0.05865 (6) | 0.0580 (4) | |
C3 | −0.5703 (4) | 0.17634 (14) | 0.02150 (6) | 0.0610 (5) | |
H3 | −0.6186 | 0.1085 | 0.0035 | 0.073* | |
C4 | −0.7208 (3) | 0.27934 (14) | 0.01202 (6) | 0.0569 (4) | |
C5 | −0.6564 (4) | 0.38249 (14) | 0.03878 (6) | 0.0593 (4) | |
H5 | −0.7616 | 0.4515 | 0.0317 | 0.071* | |
C6 | −0.4362 (3) | 0.38028 (13) | 0.07557 (6) | 0.0553 (4) | |
C7 | −0.0392 (3) | 0.27603 (14) | 0.12467 (6) | 0.0565 (4) | |
H7 | −0.0002 | 0.3443 | 0.1428 | 0.068* | |
C8 | 0.3450 (3) | 0.17699 (14) | 0.17280 (6) | 0.0555 (4) | |
C9 | 0.4693 (3) | 0.06605 (15) | 0.18298 (6) | 0.0590 (4) | |
C10 | 0.6896 (4) | 0.05720 (16) | 0.22082 (6) | 0.0657 (5) | |
H10 | 0.7713 | −0.0168 | 0.2279 | 0.079* | |
C11 | 0.7925 (4) | 0.15256 (17) | 0.24829 (6) | 0.0655 (5) | |
C12 | 0.6723 (4) | 0.26180 (17) | 0.23629 (7) | 0.0694 (5) | |
H12 | 0.7412 | 0.3283 | 0.2536 | 0.083* | |
C13 | 0.4512 (4) | 0.27460 (16) | 0.19910 (6) | 0.0661 (5) | |
H13 | 0.3736 | 0.3492 | 0.1918 | 0.079* | |
C14 | 0.3707 (4) | −0.04062 (15) | 0.15315 (7) | 0.0758 (6) | |
H14A | 0.4782 | −0.1089 | 0.1653 | 0.114* | |
H14B | 0.4005 | −0.0269 | 0.1206 | 0.114* | |
H14C | 0.1706 | −0.0540 | 0.1546 | 0.114* | |
C15 | 1.0290 (4) | 0.1388 (2) | 0.28958 (7) | 0.0865 (6) | |
H15A | 0.9977 | 0.1930 | 0.3146 | 0.130* | 0.50 |
H15B | 1.2103 | 0.1555 | 0.2789 | 0.130* | 0.50 |
H15C | 1.0293 | 0.0590 | 0.3015 | 0.130* | 0.50 |
H15D | 1.1605 | 0.0787 | 0.2821 | 0.130* | 0.50 |
H15E | 0.9479 | 0.1162 | 0.3177 | 0.130* | 0.50 |
H15F | 1.1289 | 0.2127 | 0.2952 | 0.130* | 0.50 |
C16 | −0.5298 (4) | 0.57876 (15) | 0.09754 (7) | 0.0788 (6) | |
H16A | −0.4572 | 0.6380 | 0.1204 | 0.118* | |
H16B | −0.7242 | 0.5602 | 0.1015 | 0.118* | |
H16C | −0.5232 | 0.6082 | 0.0658 | 0.118* | |
C17 | −1.0150 (5) | 0.19050 (17) | −0.05323 (8) | 0.0852 (7) | |
H17A | −1.1735 | 0.2093 | −0.0770 | 0.128* | |
H17B | −1.0670 | 0.1261 | −0.0339 | 0.128* | |
H17C | −0.8529 | 0.1679 | −0.0686 | 0.128* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0732 (8) | 0.0612 (7) | 0.0852 (9) | 0.0155 (6) | −0.0198 (7) | −0.0036 (7) |
O2 | 0.0791 (9) | 0.0578 (7) | 0.0746 (8) | 0.0127 (6) | −0.0235 (7) | −0.0093 (6) |
O3 | 0.0703 (8) | 0.0676 (7) | 0.0697 (8) | 0.0140 (6) | −0.0237 (6) | −0.0097 (6) |
N1 | 0.0537 (8) | 0.0624 (8) | 0.0559 (8) | 0.0062 (6) | −0.0046 (7) | 0.0033 (6) |
C1 | 0.0488 (9) | 0.0570 (9) | 0.0529 (9) | 0.0024 (7) | 0.0002 (7) | 0.0055 (7) |
C2 | 0.0541 (10) | 0.0562 (9) | 0.0613 (10) | 0.0076 (7) | −0.0010 (8) | 0.0058 (8) |
C3 | 0.0585 (10) | 0.0574 (9) | 0.0635 (10) | 0.0047 (8) | −0.0058 (8) | −0.0043 (8) |
C4 | 0.0513 (9) | 0.0615 (9) | 0.0548 (10) | 0.0041 (7) | −0.0048 (8) | 0.0020 (8) |
C5 | 0.0575 (10) | 0.0553 (9) | 0.0616 (10) | 0.0094 (7) | −0.0054 (8) | 0.0037 (8) |
C6 | 0.0555 (10) | 0.0538 (8) | 0.0545 (9) | 0.0004 (7) | −0.0009 (8) | 0.0006 (7) |
C7 | 0.0534 (9) | 0.0598 (9) | 0.0549 (10) | 0.0010 (8) | 0.0009 (8) | 0.0021 (7) |
C8 | 0.0476 (9) | 0.0671 (10) | 0.0499 (9) | 0.0022 (7) | −0.0013 (7) | 0.0033 (8) |
C9 | 0.0538 (10) | 0.0672 (10) | 0.0542 (10) | 0.0052 (8) | 0.0008 (8) | 0.0053 (8) |
C10 | 0.0570 (10) | 0.0762 (11) | 0.0614 (11) | 0.0099 (8) | −0.0018 (9) | 0.0105 (9) |
C11 | 0.0494 (10) | 0.0920 (13) | 0.0531 (10) | 0.0037 (9) | −0.0002 (8) | 0.0085 (9) |
C12 | 0.0607 (11) | 0.0834 (12) | 0.0613 (11) | −0.0051 (9) | −0.0023 (9) | −0.0070 (9) |
C13 | 0.0595 (11) | 0.0696 (10) | 0.0661 (11) | 0.0056 (8) | −0.0034 (9) | −0.0001 (9) |
C14 | 0.0810 (13) | 0.0660 (11) | 0.0750 (12) | 0.0091 (9) | −0.0097 (10) | 0.0030 (9) |
C15 | 0.0623 (12) | 0.1271 (17) | 0.0645 (12) | −0.0006 (11) | −0.0125 (10) | 0.0102 (12) |
C16 | 0.0879 (14) | 0.0586 (10) | 0.0823 (13) | 0.0180 (9) | −0.0175 (11) | −0.0103 (9) |
C17 | 0.0864 (14) | 0.0770 (12) | 0.0816 (13) | 0.0157 (10) | −0.0293 (11) | −0.0214 (10) |
O1—C2 | 1.3312 (18) | C10—C11 | 1.376 (3) |
O1—H1A | 0.82 | C10—H10 | 0.93 |
O2—C6 | 1.3673 (19) | C11—C12 | 1.380 (3) |
O2—C16 | 1.4229 (19) | C11—C15 | 1.510 (2) |
O3—C4 | 1.3634 (18) | C12—C13 | 1.385 (2) |
O3—C17 | 1.427 (2) | C12—H12 | 0.93 |
N1—C7 | 1.293 (2) | C13—H13 | 0.93 |
N1—C8 | 1.4159 (19) | C14—H14A | 0.96 |
N1—H1B | 0.86 | C14—H14B | 0.96 |
C1—C2 | 1.407 (2) | C14—H14C | 0.96 |
C1—C6 | 1.416 (2) | C15—H15A | 0.96 |
C1—C7 | 1.426 (2) | C15—H15B | 0.96 |
C2—C3 | 1.397 (2) | C15—H15C | 0.96 |
C3—C4 | 1.369 (2) | C15—H15D | 0.96 |
C3—H3 | 0.93 | C15—H15E | 0.96 |
C4—C5 | 1.399 (2) | C15—H15F | 0.96 |
C5—C6 | 1.367 (2) | C16—H16A | 0.96 |
C5—H5 | 0.93 | C16—H16B | 0.96 |
C7—H7 | 0.93 | C16—H16C | 0.96 |
C8—C13 | 1.384 (2) | C17—H17A | 0.96 |
C8—C9 | 1.396 (2) | C17—H17B | 0.96 |
C9—C10 | 1.391 (2) | C17—H17C | 0.96 |
C9—C14 | 1.507 (2) | ||
C2—O1—H1A | 109.5 | C8—C13—C12 | 120.38 (17) |
C6—O2—C16 | 117.08 (12) | C8—C13—H13 | 119.8 |
C4—O3—C17 | 116.70 (13) | C12—C13—H13 | 119.8 |
C7—N1—C8 | 123.93 (15) | C9—C14—H14A | 109.5 |
C7—N1—H1B | 118.0 | C9—C14—H14B | 109.5 |
C8—N1—H1B | 118.0 | H14A—C14—H14B | 109.5 |
C2—C1—C6 | 117.64 (14) | C9—C14—H14C | 109.5 |
C2—C1—C7 | 121.47 (14) | H14A—C14—H14C | 109.5 |
C6—C1—C7 | 120.88 (14) | H14B—C14—H14C | 109.5 |
O1—C2—C3 | 118.22 (14) | C11—C15—H15A | 109.5 |
O1—C2—C1 | 120.65 (14) | C11—C15—H15B | 109.5 |
C3—C2—C1 | 121.13 (14) | H15A—C15—H15B | 109.5 |
C4—C3—C2 | 118.77 (15) | C11—C15—H15C | 109.5 |
C4—C3—H3 | 120.6 | H15A—C15—H15C | 109.5 |
C2—C3—H3 | 120.6 | H15B—C15—H15C | 109.5 |
O3—C4—C3 | 124.01 (14) | C11—C15—H15D | 109.5 |
O3—C4—C5 | 113.93 (13) | H15A—C15—H15D | 141.1 |
C3—C4—C5 | 122.06 (14) | H15B—C15—H15D | 56.3 |
C6—C5—C4 | 118.92 (14) | H15C—C15—H15D | 56.3 |
C6—C5—H5 | 120.5 | C11—C15—H15E | 109.5 |
C4—C5—H5 | 120.5 | H15A—C15—H15E | 56.3 |
O2—C6—C5 | 124.00 (14) | H15B—C15—H15E | 141.1 |
O2—C6—C1 | 114.55 (13) | H15C—C15—H15E | 56.3 |
C5—C6—C1 | 121.46 (15) | H15D—C15—H15E | 109.5 |
N1—C7—C1 | 121.77 (15) | C11—C15—H15F | 109.5 |
N1—C7—H7 | 119.1 | H15A—C15—H15F | 56.3 |
C1—C7—H7 | 119.1 | H15B—C15—H15F | 56.3 |
C13—C8—C9 | 119.42 (15) | H15C—C15—H15F | 141.1 |
C13—C8—N1 | 123.59 (15) | H15D—C15—H15F | 109.5 |
C9—C8—N1 | 116.99 (14) | H15E—C15—H15F | 109.5 |
C10—C9—C8 | 118.20 (16) | O2—C16—H16A | 109.5 |
C10—C9—C14 | 121.02 (15) | O2—C16—H16B | 109.5 |
C8—C9—C14 | 120.76 (14) | H16A—C16—H16B | 109.5 |
C11—C10—C9 | 123.23 (17) | O2—C16—H16C | 109.5 |
C11—C10—H10 | 118.4 | H16A—C16—H16C | 109.5 |
C9—C10—H10 | 118.4 | H16B—C16—H16C | 109.5 |
C10—C11—C12 | 117.21 (16) | O3—C17—H17A | 109.5 |
C10—C11—C15 | 121.56 (18) | O3—C17—H17B | 109.5 |
C12—C11—C15 | 121.23 (18) | H17A—C17—H17B | 109.5 |
C11—C12—C13 | 121.49 (17) | O3—C17—H17C | 109.5 |
C11—C12—H12 | 119.3 | H17A—C17—H17C | 109.5 |
C13—C12—H12 | 119.3 | H17B—C17—H17C | 109.5 |
C6—C1—C2—O1 | −179.15 (16) | C7—C1—C6—C5 | 179.61 (16) |
C7—C1—C2—O1 | −0.4 (3) | C8—N1—C7—C1 | −179.15 (15) |
C6—C1—C2—C3 | 0.6 (3) | C2—C1—C7—N1 | 1.8 (3) |
C7—C1—C2—C3 | 179.39 (17) | C6—C1—C7—N1 | −179.44 (15) |
O1—C2—C3—C4 | −179.62 (16) | C7—N1—C8—C13 | −9.1 (3) |
C1—C2—C3—C4 | 0.6 (3) | C7—N1—C8—C9 | 172.11 (16) |
C17—O3—C4—C3 | −1.3 (3) | C13—C8—C9—C10 | 2.6 (3) |
C17—O3—C4—C5 | 178.46 (17) | N1—C8—C9—C10 | −178.54 (15) |
C2—C3—C4—O3 | 178.77 (17) | C13—C8—C9—C14 | −176.31 (17) |
C2—C3—C4—C5 | −0.9 (3) | N1—C8—C9—C14 | 2.6 (2) |
O3—C4—C5—C6 | −179.76 (16) | C8—C9—C10—C11 | −0.7 (3) |
C3—C4—C5—C6 | 0.0 (3) | C14—C9—C10—C11 | 178.17 (18) |
C16—O2—C6—C5 | 3.4 (3) | C9—C10—C11—C12 | −1.5 (3) |
C16—O2—C6—C1 | −176.22 (17) | C9—C10—C11—C15 | 179.01 (18) |
C4—C5—C6—O2 | −178.32 (16) | C10—C11—C12—C13 | 1.9 (3) |
C4—C5—C6—C1 | 1.3 (3) | C15—C11—C12—C13 | −178.59 (18) |
C2—C1—C6—O2 | 178.09 (15) | C9—C8—C13—C12 | −2.2 (3) |
C7—C1—C6—O2 | −0.7 (2) | N1—C8—C13—C12 | 178.98 (17) |
C2—C1—C6—C5 | −1.6 (3) | C11—C12—C13—C8 | −0.1 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1A···N1 | 0.82 | 1.82 (1) | 2.561 (2) | 149 |
N1—H1B···O1 | 0.86 | 1.86 (1) | 2.561 (2) | 137 (1) |
Experimental details
Crystal data | |
Chemical formula | C17H19NO3 |
Mr | 285.33 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 296 |
a, b, c (Å) | 4.7070 (2), 11.283 (5), 28.216 (5) |
β (°) | 97.542 (11) |
V (Å3) | 1485.6 (7) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.09 |
Crystal size (mm) | 0.67 × 0.31 × 0.09 |
Data collection | |
Diffractometer | Stoe IPDS II diffractometer |
Absorption correction | Integration (X-RED32; Stoe & Cie, 2002) |
Tmin, Tmax | 0.977, 0.994 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 13316, 2797, 1808 |
Rint | 0.043 |
(sin θ/λ)max (Å−1) | 0.609 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.043, 0.111, 0.98 |
No. of reflections | 2797 |
No. of parameters | 195 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.09, −0.14 |
Computer programs: X-AREA (Stoe & Cie, 2002), X-RED32 (Stoe & Cie, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1A···N1 | 0.82 | 1.82 (1) | 2.561 (2) | 149 |
N1—H1B···O1 | 0.86 | 1.86 (1) | 2.561 (2) | 136.73 (1) |
Acknowledgements
This study was supported financially by the Research Center of Ondokuz Mayıs University (Project No. F-476). 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).
References
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Proton tautomerism plays an important role in many fields of chemistry and biochemistry (Sugawara et al., 1999). The study of ground state intramolecular proton (hydrogen) transfer (IPT) reactions have received increasing attention in recently aiming at the characterization of a large number of compounds in which rapid hydrogen migration occurs both in solution and in solid state. Salicilidine aniline and its derivatives are among the earliest examples of a chemical system involving IPT. A prototropic tautomeric attitude has been recognized in a number of aromatic Schiff bases (Becker et al., 1987; Seliger et al., 1990; Tezer & Karakus, 2009). O-hydroxy Schiff bases are of interest mainly due to the existence of O—H···N and N—H···O type hydrogen bonds and tautomerism between the enol-imine (OH) and keto-amine (NH) forms.
The X-ray analysis reveals that in the title compound both the enol (OH) and keto (NH) tautomers coexist with occupancies of 0.62 (3) and 0.38 (3), respectively. But we are unable to confirm the presence of minor keto form from the IR spectrum. The major enol (OH) tautomer is shown in Fig. 1. The C2—O1 [1.3312 (18) Å] bond length is intermediate between the C—O single (1.362 Å) and C═O double (1.222 Å) bonds. Similarly, the C7—N1 bond length of 1.293 (2) Å is shorter than C—N and C═N bond lengths (1.339 and 1.279 Å, respectively; Allen et al., 1987). The shortened C2—O1 bond and the slightly longer C7—N1 bond provide structural evidence for the double tautomeric forms of the title compound. Similar result was observed for N-(5-chloro-2-hydroxybenzylidene) -4-hydroxyaniline [C—O = 1.321 (2) and C—N = 1.293 (2) Å; Ogawa & Harada, 2003].
The molecule of the title compound is approximately planar, with the dihedral angle between the two aromatic rings being 6.97 (8)°. The molecular structure is stabilized by an intramolecular O1—H1A···N1 hydrogen bond (Table 1) which generates a six-membered ring, producing a S(6) ring motif. It is known that Schiff bases may exhibit thermochromism or photochromism, depending on the planarity or non-planarity of the molecule, respectively. Therefore, the title compound may exhibit thermochromic properties.
No significant π-π interactions are observed in the crystal structure.