organic compounds
8-[(1E)-1-(2-Aminophenyliminio)ethyl]-2-oxo-2H-chromen-7-olate
aDepartment of Chemistry, Girls Section, University of King Abdulaziz, PO Box 6171, Jeddah 21442, Saudi Arabia, bDepartment of Chemistry, Faculty of Science, Alexandria University, Egypt, and cDepartment of Physics, Ondokuz Mayıs University, TR-55139 Samsun, Turkey
*Correspondence e-mail: wayfield8@yahoo.com
The title Schiff base, C17H14N2O3, exists as an NH tautomer with the H atom of the phenol group transferred to the imine N atom. The iminium H atom is involved in a strong intramolecular N+—H⋯O− hydrogen bond to the phenolate O atom, forming an S(6) motif. In the N—H⋯O hydrogen bonds form a C(9) chain parallel to [100] and a C(11) chain parallel to [010], while C—H⋯O hydrogen bonds form a C(11) chain parallel to [010]. The combination of N—H⋯O and C—H⋯O hydrogen bonds generates R43(30) rings parallel to the ab plane
Related literature
For related structures, see: Patil et al. (2010); Aazam et al. (2006); Filarowski (2005); El Husseiny et al. (2008); Aazam et al. (2008); Karabıyık et al. (2008). For the graph-set analysis of hydrogen-bond patterns, see: Bernstein et al. (1995).
Experimental
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 (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).
Supporting information
10.1107/S1600536810023093/gk2282sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536810023093/gk2282Isup2.hkl
A clear solution of o-phenylenediamine (0.26 g, 2.5 mmol) in 10 ml of ethanol was added to a warm solution of 8-acetyl-7-hydroxy coumarin (0.5 g, 2.5 mmol) in the same solvent (30 ml). The resulting mixture was refluxed for 2–3 h. The yellow product was precipitated, filtered off and washed with ethanol followed by diethyl ether, dried in a vacuum desiccator and crystallized from chloroform/ethanol (2:1). Single crystals were obtained by slow evaporation of dichloromethane solution of I at room temperature; Yield (75%), m.p. 480 K. Purity of the ligand was checked using TLC; (methanol: benzene, 1:4).
All H atoms bound to C atoms were refined using a riding model, with C—H = 0.93Å and Uiso(H) = 1.2Ueq(C) for aromatic C atoms and C—H = 0.96Å and Uiso(H) = 1.5Ueq(C) for methyl C atoms. Amino H atoms bound to N atom were located in difference maps and refined freely. Other H atom bound to N atom was located in difference maps and refined subject to a DFIX restraint of N—H = 0.86 (2) Å.
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).C17H14N2O3 | F(000) = 1232 |
Mr = 294.30 | Dx = 1.365 Mg m−3 |
Orthorhombic, Pbca | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ac 2ab | Cell parameters from 25561 reflections |
a = 7.5462 (3) Å | θ = 2.0–26.7° |
b = 18.9324 (11) Å | µ = 0.10 mm−1 |
c = 20.0445 (9) Å | T = 296 K |
V = 2863.7 (2) Å3 | Prism, yellow |
Z = 8 | 0.44 × 0.29 × 0.20 mm |
Stoe IPDS 2 diffractometer | 2868 independent reflections |
Radiation source: fine-focus sealed tube | 1972 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.039 |
rotation method scans | θmax = 26.2°, θmin = 2.0° |
Absorption correction: integration (X-RED32; Stoe & Cie, 2002) | h = −9→9 |
Tmin = 0.962, Tmax = 0.984 | k = −23→23 |
25561 measured reflections | l = −24→24 |
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)] = 0.038 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.095 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.00 | w = 1/[σ2(Fo2) + (0.0515P)2 + ] where P = (Fo2 + 2Fc2)/3 |
2868 reflections | (Δ/σ)max < 0.001 |
212 parameters | Δρmax = 0.11 e Å−3 |
1 restraint | Δρmin = −0.15 e Å−3 |
C17H14N2O3 | V = 2863.7 (2) Å3 |
Mr = 294.30 | Z = 8 |
Orthorhombic, Pbca | Mo Kα radiation |
a = 7.5462 (3) Å | µ = 0.10 mm−1 |
b = 18.9324 (11) Å | T = 296 K |
c = 20.0445 (9) Å | 0.44 × 0.29 × 0.20 mm |
Stoe IPDS 2 diffractometer | 2868 independent reflections |
Absorption correction: integration (X-RED32; Stoe & Cie, 2002) | 1972 reflections with I > 2σ(I) |
Tmin = 0.962, Tmax = 0.984 | Rint = 0.039 |
25561 measured reflections |
R[F2 > 2σ(F2)] = 0.038 | 1 restraint |
wR(F2) = 0.095 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.00 | Δρmax = 0.11 e Å−3 |
2868 reflections | Δρmin = −0.15 e Å−3 |
212 parameters |
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 | ||
C1 | 0.3733 (2) | 0.81253 (7) | 0.38471 (7) | 0.0462 (4) | |
C2 | 0.5193 (2) | 0.83854 (7) | 0.41971 (8) | 0.0487 (4) | |
C3 | 0.4876 (2) | 0.89106 (8) | 0.46724 (8) | 0.0584 (4) | |
H3 | 0.5822 | 0.9095 | 0.4914 | 0.070* | |
C4 | 0.3197 (3) | 0.91605 (8) | 0.47909 (9) | 0.0632 (5) | |
H4 | 0.3019 | 0.9507 | 0.5113 | 0.076* | |
C5 | 0.1777 (3) | 0.89021 (9) | 0.44379 (9) | 0.0646 (5) | |
H5 | 0.0642 | 0.9073 | 0.4519 | 0.077* | |
C6 | 0.2051 (2) | 0.83870 (8) | 0.39613 (9) | 0.0581 (4) | |
H6 | 0.1098 | 0.8215 | 0.3716 | 0.070* | |
C7 | 0.44310 (18) | 0.69702 (7) | 0.33766 (7) | 0.0446 (3) | |
C8 | 0.4588 (2) | 0.66606 (8) | 0.40572 (8) | 0.0602 (4) | |
H8A | 0.4121 | 0.6987 | 0.4379 | 0.072* | |
H8B | 0.5813 | 0.6569 | 0.4154 | 0.072* | |
H8C | 0.3932 | 0.6227 | 0.4077 | 0.072* | |
C9 | 0.47034 (19) | 0.65822 (7) | 0.27529 (7) | 0.0442 (3) | |
C10 | 0.4368 (2) | 0.69219 (7) | 0.21251 (8) | 0.0491 (4) | |
C11 | 0.4623 (2) | 0.65452 (8) | 0.15220 (8) | 0.0584 (4) | |
H11 | 0.4402 | 0.6767 | 0.1117 | 0.070* | |
C12 | 0.5186 (2) | 0.58675 (8) | 0.15284 (9) | 0.0587 (4) | |
H12 | 0.5332 | 0.5630 | 0.1126 | 0.070* | |
C13 | 0.5555 (2) | 0.55134 (7) | 0.21273 (8) | 0.0525 (4) | |
C14 | 0.53174 (19) | 0.58766 (7) | 0.27212 (8) | 0.0455 (4) | |
C15 | 0.6172 (2) | 0.48034 (8) | 0.21610 (10) | 0.0641 (5) | |
H15 | 0.6307 | 0.4548 | 0.1768 | 0.077* | |
C16 | 0.6561 (2) | 0.44943 (8) | 0.27412 (10) | 0.0671 (5) | |
H16 | 0.6943 | 0.4027 | 0.2746 | 0.081* | |
C17 | 0.6397 (2) | 0.48719 (7) | 0.33552 (10) | 0.0588 (4) | |
N1 | 0.39971 (17) | 0.76316 (6) | 0.33146 (7) | 0.0488 (3) | |
N2 | 0.68956 (19) | 0.81302 (8) | 0.41013 (8) | 0.0631 (4) | |
O1 | 0.38245 (16) | 0.75749 (5) | 0.20935 (6) | 0.0603 (3) | |
O2 | 0.67878 (17) | 0.46798 (5) | 0.39135 (7) | 0.0735 (4) | |
O3 | 0.57044 (14) | 0.55503 (5) | 0.33133 (5) | 0.0541 (3) | |
H1 | 0.390 (3) | 0.7742 (10) | 0.2853 (8) | 0.087 (6)* | |
H2A | 0.715 (2) | 0.7907 (9) | 0.3703 (10) | 0.071 (5)* | |
H2B | 0.772 (3) | 0.8469 (11) | 0.4178 (11) | 0.099 (7)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0615 (9) | 0.0363 (7) | 0.0409 (9) | −0.0009 (6) | 0.0025 (7) | 0.0007 (6) |
C2 | 0.0586 (9) | 0.0435 (7) | 0.0439 (9) | −0.0018 (7) | 0.0053 (7) | −0.0002 (6) |
C3 | 0.0700 (11) | 0.0557 (8) | 0.0494 (10) | −0.0061 (8) | 0.0042 (8) | −0.0116 (7) |
C4 | 0.0844 (13) | 0.0537 (9) | 0.0515 (10) | 0.0048 (8) | 0.0143 (9) | −0.0090 (7) |
C5 | 0.0651 (10) | 0.0662 (10) | 0.0623 (12) | 0.0133 (8) | 0.0086 (9) | −0.0029 (9) |
C6 | 0.0586 (10) | 0.0577 (9) | 0.0579 (11) | 0.0039 (7) | −0.0008 (8) | −0.0007 (8) |
C7 | 0.0490 (8) | 0.0393 (7) | 0.0454 (9) | −0.0045 (6) | −0.0014 (7) | 0.0024 (6) |
C8 | 0.0889 (12) | 0.0459 (8) | 0.0459 (10) | 0.0056 (8) | 0.0010 (9) | 0.0037 (7) |
C9 | 0.0483 (8) | 0.0397 (7) | 0.0446 (9) | −0.0056 (6) | −0.0026 (6) | −0.0011 (6) |
C10 | 0.0563 (9) | 0.0455 (7) | 0.0454 (9) | −0.0067 (6) | −0.0048 (7) | 0.0001 (6) |
C11 | 0.0734 (11) | 0.0588 (9) | 0.0431 (10) | −0.0053 (8) | −0.0043 (8) | −0.0011 (7) |
C12 | 0.0681 (10) | 0.0594 (9) | 0.0486 (11) | −0.0077 (8) | 0.0003 (8) | −0.0134 (7) |
C13 | 0.0544 (9) | 0.0465 (8) | 0.0565 (11) | −0.0054 (6) | −0.0008 (7) | −0.0097 (7) |
C14 | 0.0474 (8) | 0.0411 (7) | 0.0480 (10) | −0.0076 (6) | −0.0040 (7) | 0.0001 (6) |
C15 | 0.0686 (11) | 0.0489 (8) | 0.0749 (13) | −0.0011 (8) | −0.0002 (10) | −0.0181 (8) |
C16 | 0.0724 (11) | 0.0416 (8) | 0.0874 (15) | 0.0047 (7) | −0.0082 (10) | −0.0091 (9) |
C17 | 0.0586 (10) | 0.0384 (7) | 0.0795 (14) | −0.0011 (7) | −0.0101 (9) | 0.0018 (8) |
N1 | 0.0667 (8) | 0.0393 (6) | 0.0403 (8) | 0.0007 (5) | −0.0026 (6) | −0.0012 (5) |
N2 | 0.0562 (8) | 0.0674 (9) | 0.0659 (10) | −0.0034 (7) | 0.0055 (8) | −0.0179 (8) |
O1 | 0.0862 (8) | 0.0476 (6) | 0.0472 (7) | 0.0064 (5) | −0.0074 (6) | 0.0060 (5) |
O2 | 0.0904 (9) | 0.0482 (6) | 0.0820 (10) | 0.0054 (6) | −0.0181 (8) | 0.0106 (6) |
O3 | 0.0671 (7) | 0.0391 (5) | 0.0560 (7) | 0.0035 (5) | −0.0068 (5) | 0.0008 (5) |
C1—C6 | 1.381 (2) | C9—C10 | 1.436 (2) |
C1—C2 | 1.396 (2) | C10—O1 | 1.3040 (17) |
C1—N1 | 1.4327 (18) | C10—C11 | 1.417 (2) |
C2—N2 | 1.386 (2) | C11—C12 | 1.351 (2) |
C2—C3 | 1.398 (2) | C11—H11 | 0.9300 |
C3—C4 | 1.373 (2) | C12—C13 | 1.403 (2) |
C3—H3 | 0.9300 | C12—H12 | 0.9300 |
C4—C5 | 1.374 (3) | C13—C14 | 1.386 (2) |
C4—H4 | 0.9300 | C13—C15 | 1.424 (2) |
C5—C6 | 1.381 (2) | C14—O3 | 1.3695 (17) |
C5—H5 | 0.9300 | C15—C16 | 1.334 (2) |
C6—H6 | 0.9300 | C15—H15 | 0.9300 |
C7—N1 | 1.3004 (17) | C16—C17 | 1.429 (3) |
C7—C9 | 1.464 (2) | C16—H16 | 0.9300 |
C7—C8 | 1.490 (2) | C17—O2 | 1.213 (2) |
C8—H8A | 0.9600 | C17—O3 | 1.3893 (17) |
C8—H8B | 0.9600 | N1—H1 | 0.952 (15) |
C8—H8C | 0.9600 | N2—H2A | 0.92 (2) |
C9—C14 | 1.4153 (19) | N2—H2B | 0.91 (2) |
C6—C1—C2 | 121.01 (14) | O1—C10—C9 | 121.51 (13) |
C6—C1—N1 | 119.04 (14) | C11—C10—C9 | 119.89 (13) |
C2—C1—N1 | 119.65 (13) | C12—C11—C10 | 120.84 (16) |
N2—C2—C1 | 122.62 (14) | C12—C11—H11 | 119.6 |
N2—C2—C3 | 120.05 (15) | C10—C11—H11 | 119.6 |
C1—C2—C3 | 117.31 (14) | C11—C12—C13 | 121.61 (15) |
C4—C3—C2 | 121.38 (16) | C11—C12—H12 | 119.2 |
C4—C3—H3 | 119.3 | C13—C12—H12 | 119.2 |
C2—C3—H3 | 119.3 | C14—C13—C12 | 118.17 (13) |
C3—C4—C5 | 120.51 (15) | C14—C13—C15 | 118.01 (16) |
C3—C4—H4 | 119.7 | C12—C13—C15 | 123.82 (16) |
C5—C4—H4 | 119.7 | O3—C14—C13 | 119.53 (13) |
C4—C5—C6 | 119.43 (16) | O3—C14—C9 | 117.17 (13) |
C4—C5—H5 | 120.3 | C13—C14—C9 | 123.30 (14) |
C6—C5—H5 | 120.3 | C16—C15—C13 | 121.81 (16) |
C5—C6—C1 | 120.36 (16) | C16—C15—H15 | 119.1 |
C5—C6—H6 | 119.8 | C13—C15—H15 | 119.1 |
C1—C6—H6 | 119.8 | C15—C16—C17 | 120.82 (15) |
N1—C7—C9 | 115.89 (13) | C15—C16—H16 | 119.6 |
N1—C7—C8 | 119.11 (13) | C17—C16—H16 | 119.6 |
C9—C7—C8 | 124.99 (12) | O2—C17—O3 | 115.12 (15) |
C7—C8—H8A | 109.5 | O2—C17—C16 | 128.58 (15) |
C7—C8—H8B | 109.5 | O3—C17—C16 | 116.29 (16) |
H8A—C8—H8B | 109.5 | C7—N1—C1 | 126.31 (13) |
C7—C8—H8C | 109.5 | C7—N1—H1 | 108.9 (11) |
H8A—C8—H8C | 109.5 | C1—N1—H1 | 124.8 (11) |
H8B—C8—H8C | 109.5 | C2—N2—H2A | 118.0 (11) |
C14—C9—C10 | 116.18 (13) | C2—N2—H2B | 111.5 (13) |
C14—C9—C7 | 123.89 (13) | H2A—N2—H2B | 109.3 (17) |
C10—C9—C7 | 119.92 (12) | C14—O3—C17 | 123.35 (13) |
O1—C10—C11 | 118.60 (14) | ||
C6—C1—C2—N2 | 179.24 (15) | C11—C12—C13—C15 | −179.15 (16) |
N1—C1—C2—N2 | −7.1 (2) | C12—C13—C14—O3 | −178.55 (13) |
C6—C1—C2—C3 | 1.0 (2) | C15—C13—C14—O3 | 1.0 (2) |
N1—C1—C2—C3 | 174.61 (13) | C12—C13—C14—C9 | 0.8 (2) |
N2—C2—C3—C4 | −178.25 (16) | C15—C13—C14—C9 | −179.68 (14) |
C1—C2—C3—C4 | 0.0 (2) | C10—C9—C14—O3 | 177.82 (12) |
C2—C3—C4—C5 | −0.5 (3) | C7—C9—C14—O3 | −1.3 (2) |
C3—C4—C5—C6 | 0.0 (3) | C10—C9—C14—C13 | −1.5 (2) |
C4—C5—C6—C1 | 1.0 (3) | C7—C9—C14—C13 | 179.41 (14) |
C2—C1—C6—C5 | −1.5 (2) | C14—C13—C15—C16 | −1.7 (2) |
N1—C1—C6—C5 | −175.19 (14) | C12—C13—C15—C16 | 177.81 (17) |
N1—C7—C9—C14 | 174.71 (14) | C13—C15—C16—C17 | −1.0 (3) |
C8—C7—C9—C14 | −6.3 (2) | C15—C16—C17—O2 | −175.59 (18) |
N1—C7—C9—C10 | −4.4 (2) | C15—C16—C17—O3 | 4.2 (3) |
C8—C7—C9—C10 | 174.68 (14) | C9—C7—N1—C1 | −177.28 (14) |
C14—C9—C10—O1 | −178.93 (14) | C8—C7—N1—C1 | 3.6 (2) |
C7—C9—C10—O1 | 0.2 (2) | C6—C1—N1—C7 | −112.84 (17) |
C14—C9—C10—C11 | 1.2 (2) | C2—C1—N1—C7 | 73.42 (19) |
C7—C9—C10—C11 | −179.71 (14) | C13—C14—O3—C17 | 2.5 (2) |
O1—C10—C11—C12 | 179.96 (15) | C9—C14—O3—C17 | −176.83 (13) |
C9—C10—C11—C12 | −0.1 (2) | O2—C17—O3—C14 | 174.78 (14) |
C10—C11—C12—C13 | −0.7 (3) | C16—C17—O3—C14 | −5.1 (2) |
C11—C12—C13—C14 | 0.4 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O1 | 0.95 (2) | 1.56 (2) | 2.4534 (17) | 155 (2) |
N2—H2A···O1i | 0.92 (2) | 2.13 (2) | 2.9933 (19) | 154.7 (15) |
N2—H2B···O2ii | 0.91 (2) | 2.37 (2) | 3.1203 (19) | 138.7 (17) |
C5—H5···O2iii | 0.93 | 2.48 | 3.242 (2) | 139 |
Symmetry codes: (i) x+1/2, y, −z+1/2; (ii) −x+3/2, y+1/2, z; (iii) −x+1/2, y+1/2, z. |
Experimental details
Crystal data | |
Chemical formula | C17H14N2O3 |
Mr | 294.30 |
Crystal system, space group | Orthorhombic, Pbca |
Temperature (K) | 296 |
a, b, c (Å) | 7.5462 (3), 18.9324 (11), 20.0445 (9) |
V (Å3) | 2863.7 (2) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.44 × 0.29 × 0.20 |
Data collection | |
Diffractometer | Stoe IPDS 2 diffractometer |
Absorption correction | Integration (X-RED32; Stoe & Cie, 2002) |
Tmin, Tmax | 0.962, 0.984 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 25561, 2868, 1972 |
Rint | 0.039 |
(sin θ/λ)max (Å−1) | 0.622 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.038, 0.095, 1.00 |
No. of reflections | 2868 |
No. of parameters | 212 |
No. of restraints | 1 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.11, −0.15 |
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 |
N1—H1···O1 | 0.952 (15) | 1.556 (16) | 2.4534 (17) | 155.4 (17) |
N2—H2A···O1i | 0.92 (2) | 2.13 (2) | 2.9933 (19) | 154.7 (15) |
N2—H2B···O2ii | 0.91 (2) | 2.37 (2) | 3.1203 (19) | 138.7 (17) |
C5—H5···O2iii | 0.93 | 2.48 | 3.242 (2) | 139 |
Symmetry codes: (i) x+1/2, y, −z+1/2; (ii) −x+3/2, y+1/2, z; (iii) −x+1/2, y+1/2, z. |
Acknowledgements
The authors acknowledge King Abdulaziz University for financial support and the Faculty of Arts and Sciences, Ondokuz Mayıs University, Turkey, for the use of the Stoe IPDS 2 diffractometer (purchased under grant F.279 of the University Research Fund).
References
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Coumarin and its derivatives have been a subject of numerous investigations due to their diverse biological activities, interesting photophysical, photochemical and metal binding properties. Schiff base complexes play an important role in coordination chemistry (Patil et al., 2010). We have recently reported synthesis, single-crystal X-ray diffraction studies, characterization and antibacterial activity of a Schiff-base ligand incorporating coumarin moiety and their metal complexes (Aazam et al., 2006; El Husseiny, et al., 2008; Aazam et al., 2008). In this work, we would like to present an X-ray investigation of a newly synthesized coumarin Schiff base derived from 8-acetyl-7-hydroxycoumarin and o-phenylenediamine. We report here the crystal structure of (I) (Figure 1).
Schiff bases exhibit two well known tautomeric forms viz. OH and NH tautomers. NH tautomers can be regarded as a resonance hybrid of two canonical structures the non-charged quinoid and ionic zwitterionic forms. Our investigations show that compound (I) formula can be given as a combination of two canonical forms: phenolate with negative charge predominantly at the phenolate O atom or as chromen-8-ide with negative charge at the C atom. Compound I is a hyprid of two zwitterionic canonical forms (Fig. 2) having N+—H bond (0.952 Å) longer than standared interatomic separations observed in neutral N—H bonds (0.878 Å)(Karabıyık et al., 2008). Compound (I) crystallizes in the orthorhombic space group Pbca (No. 61) with one molecule per asymmetric unit. The iminium H atom is almost coplanar with the coumarin ring (deviation from the coumarin plane 0.0444 Å) and on the same side of the molecule as the phenolic O atom, allowing the formation of an intramolecular N—H···O hydrogen bond. A summary of bond lengths and angles of the ketoimine system is presented in Table 1.
In order to compare the bond lengths found in (I) with other molecules containing similar functional groups, a comparison with a previous search in the Cambridge Structural Database (CSD) was performed (Filarowski, 2005). The comparison with the mean bond lengths of similar molecules clearly tends to confirm that (I) is cis-ketoimine tauutomer and that the C7—N1 in agreement with double-bond character, the C10—O1 is 1.3040 Å, this bond is not double (keto group) and is one of the longest among similar iminium derivatives, also C7—C9 bond length is not a typical single-bond. Moreover C9—C14 ring is in agreement with the cyclohexadienide bond character. The intramolecular hydrogen bond produces S(6) motif (Bernstein et al., 1995). The amino atom N2 in the molecule at (x, y, z) acts as a hydrogen-bond donor (Table 1) to atom O1i so forming a C(9) chain running parallel to the [100] direction. Amino atom N2 in the molecule at (x, y, z) acts as a hydrogen-bond donor to atom O2ii so forming a C(11) chain running parallel to the [010] direction. Similarly, atom C5 in the molecule at (x, y, z) acts as a hydrogen-bond donor to atom O2iii so forming a C(11) chain running parallel to the [010] direction. The combination of N—H···O and C—H···O hydrogen bonds generates R43(30) rings parallel to the ab plane (Fig. 3).