organic compounds
(E)-2-[(2,4-Dihydroxybenzylidene)azaniumyl]-3-(1H-indol-3-yl)propanoate monohydrate
aSchool of Chemical Sciences, Universiti Sains Malaysia, Minden, Penang, Malaysia, bDepartment of Chemistry, International University of Africa, Sudan, and cChemistry Department, Faculty of Science, University of Malaya, Malaysia
*Correspondence e-mail: sgteoh@usm.my
In the zwitterionic title compound, C18H16N2O4·H2O, the dihedral angle between the planes of the benzene and indole rings is 39.20 (8)°. An intramolecular N—H⋯O hydrogen bond generates an S(6) ring motif. In the crystal, intermolecular hydroxy and water O—H⋯O(carboxylate) and N+—H⋯O(carboxylate) and indole N—H⋯O(water) hydrogen bonds give a three-dimensional structure.
Related literature
For related structures, see: Grant et al. (1999); Emge et al. (2000). For the anticancer activity of see: Dao et al. (2000), for their anti-HIV activity, see: Sriram et al. (2006) and for their antibacterial and antifungal activity, see: Karthikeyan et al. (2006). For analytical applications, see: Eltayeb & Ahmed (2005a,b). For standard bond lengths, see: Allen et al. (1987).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2008); cell SAINT (Bruker, 2008); data reduction: SAINT; 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: publCIF (Westrip, 2010).
Supporting information
10.1107/S1600536811028200/zs2121sup1.cif
contains datablocks I, global. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536811028200/zs2121Isup2.hkl
Supporting information file. DOI: 10.1107/S1600536811028200/zs2121Isup3.cml
To a stirred solution of 2 mmol of tryptophan (0.416 g) in 20 ml of (3:1) methanol-water solvent was added 2 mmol of 2,4-dihydroxybenzaldehyde (0.282 g), giving a light pink clear solution. The mixture was refluxed with stirring for seven hours, after which it was filtered and left to cool to room temperature. After 12 h, brown-yellow crystals of the titls compound began to form and were removed by filtration after two days.
Hydrogen atoms attached to N and water H atoms were located from a difference map and their positional and isotropic displacenent parameters were refined. For the water molecule, there is no possible acceptor for the one of the hydrogen atom (H5A). Other H atoms were placed geometrically and were allowed to ride on the parent atom, with C—H = 0.93 Å and O—H = 0.84 Å and with Uiso(H) set to 1.2–1.5 times Ueq(C, O). The uncertainty of the
[-0.02 (8) for 1677 Friedel pairs] did not allow the the to be definitively assigned (S for C10).Data collection: APEX2 (Bruker, 2008); cell
SAINT (Bruker, 2008); data reduction: SAINT (Bruker, 2008); 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: publCIF (Westrip, 2010).Fig. 1. The molecular structure of the title compound, with atom labels and 50% probability ellipsoids for non-H atoms. | |
Fig. 2. The crystal packing of title compound, viewed down a axis. |
C18H16N2O4·H2O | F(000) = 720 |
Mr = 342.34 | Dx = 1.334 Mg m−3 |
Orthorhombic, P212121 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2ac 2ab | Cell parameters from 6129 reflections |
a = 8.4214 (3) Å | θ = 2.7–28.3° |
b = 10.6787 (4) Å | µ = 0.10 mm−1 |
c = 18.9554 (8) Å | T = 100 K |
V = 1704.65 (11) Å3 | Block, brown-yellow |
Z = 4 | 0.20 × 0.10 × 0.10 mm |
Bruker SMART APEXII CCD area-detector diffractometer | 3904 independent reflections |
Radiation source: fine-focus sealed tube | 3587 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.035 |
ϕ and ω scans | θmax = 27.5°, θmin = 2.2° |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | h = −10→10 |
Tmin = 0.618, Tmax = 0.746 | k = −13→13 |
15797 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)] = 0.034 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.085 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0474P)2 + 0.2857P] where P = (Fo2 + 2Fc2)/3 |
3904 reflections | (Δ/σ)max < 0.001 |
244 parameters | Δρmax = 0.25 e Å−3 |
0 restraints | Δρmin = −0.16 e Å−3 |
C18H16N2O4·H2O | V = 1704.65 (11) Å3 |
Mr = 342.34 | Z = 4 |
Orthorhombic, P212121 | Mo Kα radiation |
a = 8.4214 (3) Å | µ = 0.10 mm−1 |
b = 10.6787 (4) Å | T = 100 K |
c = 18.9554 (8) Å | 0.20 × 0.10 × 0.10 mm |
Bruker SMART APEXII CCD area-detector diffractometer | 3904 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 1996) | 3587 reflections with I > 2σ(I) |
Tmin = 0.618, Tmax = 0.746 | Rint = 0.035 |
15797 measured reflections |
R[F2 > 2σ(F2)] = 0.034 | 0 restraints |
wR(F2) = 0.085 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.03 | Δρmax = 0.25 e Å−3 |
3904 reflections | Δρmin = −0.16 e Å−3 |
244 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 | ||
O4 | 0.45139 (13) | 0.65534 (9) | 0.31898 (6) | 0.0204 (2) | |
H4 | 0.3667 | 0.6867 | 0.3036 | 0.031* | |
O2 | 0.19336 (12) | −0.24604 (9) | 0.26862 (6) | 0.0211 (2) | |
O3 | 0.17010 (12) | 0.27877 (9) | 0.26869 (6) | 0.0235 (2) | |
H3 | 0.0984 | 0.3300 | 0.2579 | 0.035* | |
N2 | 0.29712 (15) | 0.06525 (11) | 0.31452 (6) | 0.0170 (2) | |
C16 | 0.43988 (17) | 0.53039 (13) | 0.31846 (7) | 0.0172 (3) | |
O1 | 0.04987 (13) | −0.07062 (10) | 0.26999 (7) | 0.0294 (3) | |
C18 | 0.55615 (17) | 0.33389 (13) | 0.34947 (7) | 0.0169 (3) | |
H18 | 0.6416 | 0.2870 | 0.3689 | 0.020* | |
C17 | 0.56704 (18) | 0.46154 (13) | 0.34693 (7) | 0.0176 (3) | |
H17 | 0.6590 | 0.5031 | 0.3641 | 0.021* | |
C15 | 0.30669 (18) | 0.47039 (13) | 0.29074 (7) | 0.0184 (3) | |
H15 | 0.2236 | 0.5181 | 0.2701 | 0.022* | |
C13 | 0.42086 (17) | 0.26989 (13) | 0.32395 (7) | 0.0162 (3) | |
C12 | 0.41503 (17) | 0.13809 (13) | 0.33109 (7) | 0.0161 (3) | |
H12 | 0.5068 | 0.0987 | 0.3500 | 0.019* | |
C10 | 0.29777 (18) | −0.06908 (12) | 0.32974 (7) | 0.0172 (3) | |
H10 | 0.4045 | −0.1051 | 0.3186 | 0.021* | |
C11 | 0.17062 (18) | −0.13330 (13) | 0.28460 (7) | 0.0192 (3) | |
C3 | 0.53472 (19) | −0.05160 (14) | 0.46542 (7) | 0.0207 (3) | |
C14 | 0.29580 (18) | 0.34069 (13) | 0.29342 (7) | 0.0180 (3) | |
C9 | 0.25679 (18) | −0.09299 (14) | 0.40849 (7) | 0.0211 (3) | |
H9A | 0.1471 | −0.0642 | 0.4179 | 0.025* | |
H9B | 0.2614 | −0.1840 | 0.4181 | 0.025* | |
N1 | 0.47368 (18) | 0.12210 (13) | 0.52719 (7) | 0.0263 (3) | |
C1 | 0.33771 (19) | 0.07978 (15) | 0.49523 (8) | 0.0249 (3) | |
H1 | 0.2365 | 0.1185 | 0.4992 | 0.030* | |
C8 | 0.5967 (2) | 0.04331 (15) | 0.50975 (8) | 0.0231 (3) | |
C7 | 0.7571 (2) | 0.04678 (16) | 0.52806 (8) | 0.0273 (4) | |
H7 | 0.7982 | 0.1111 | 0.5575 | 0.033* | |
C4 | 0.6373 (2) | −0.14419 (15) | 0.43870 (8) | 0.0244 (3) | |
H4A | 0.5984 | −0.2079 | 0.4083 | 0.029* | |
C6 | 0.85398 (19) | −0.04657 (16) | 0.50188 (8) | 0.0283 (4) | |
H6 | 0.9633 | −0.0471 | 0.5143 | 0.034* | |
C5 | 0.7951 (2) | −0.14071 (17) | 0.45741 (8) | 0.0279 (3) | |
H5 | 0.8653 | −0.2031 | 0.4399 | 0.033* | |
C2 | 0.36843 (18) | −0.02646 (14) | 0.45657 (8) | 0.0213 (3) | |
O5 | 0.41346 (18) | 0.32658 (13) | 0.62788 (7) | 0.0344 (3) | |
H2A | 0.208 (2) | 0.0933 (17) | 0.2981 (9) | 0.023 (4)* | |
H5B | 0.410 (3) | 0.311 (2) | 0.6689 (16) | 0.055 (8)* | |
H1A | 0.476 (3) | 0.186 (2) | 0.5555 (12) | 0.041 (6)* | |
H5A | 0.387 (4) | 0.394 (3) | 0.6163 (18) | 0.083 (11)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O4 | 0.0223 (5) | 0.0114 (5) | 0.0276 (5) | 0.0001 (4) | −0.0034 (5) | −0.0001 (4) |
O2 | 0.0241 (5) | 0.0119 (5) | 0.0274 (5) | −0.0006 (4) | −0.0056 (4) | −0.0014 (4) |
O3 | 0.0216 (5) | 0.0120 (5) | 0.0369 (6) | 0.0004 (4) | −0.0124 (5) | 0.0013 (4) |
N2 | 0.0185 (6) | 0.0117 (5) | 0.0208 (6) | 0.0010 (5) | −0.0045 (5) | 0.0001 (4) |
C16 | 0.0220 (7) | 0.0119 (6) | 0.0176 (6) | −0.0012 (5) | 0.0018 (6) | −0.0001 (5) |
O1 | 0.0251 (6) | 0.0147 (5) | 0.0484 (7) | 0.0010 (4) | −0.0173 (5) | −0.0028 (5) |
C18 | 0.0151 (7) | 0.0157 (7) | 0.0199 (6) | 0.0019 (6) | −0.0013 (5) | −0.0006 (5) |
C17 | 0.0184 (7) | 0.0149 (7) | 0.0196 (6) | −0.0024 (6) | −0.0010 (5) | −0.0024 (5) |
C15 | 0.0207 (7) | 0.0141 (7) | 0.0204 (6) | 0.0023 (6) | −0.0031 (6) | 0.0020 (5) |
C13 | 0.0188 (7) | 0.0122 (6) | 0.0177 (6) | 0.0001 (5) | 0.0000 (5) | −0.0017 (5) |
C12 | 0.0172 (7) | 0.0145 (7) | 0.0166 (6) | 0.0019 (5) | −0.0003 (5) | −0.0013 (5) |
C10 | 0.0189 (7) | 0.0101 (6) | 0.0226 (7) | 0.0007 (5) | −0.0029 (6) | 0.0005 (5) |
C11 | 0.0216 (7) | 0.0136 (7) | 0.0225 (7) | −0.0024 (6) | −0.0040 (6) | 0.0029 (5) |
C3 | 0.0255 (8) | 0.0201 (7) | 0.0165 (6) | −0.0034 (6) | −0.0016 (6) | 0.0037 (6) |
C14 | 0.0193 (7) | 0.0152 (7) | 0.0194 (6) | 0.0000 (6) | −0.0028 (5) | −0.0009 (5) |
C9 | 0.0217 (7) | 0.0181 (7) | 0.0235 (7) | −0.0021 (6) | −0.0009 (6) | 0.0018 (6) |
N1 | 0.0332 (8) | 0.0243 (7) | 0.0215 (6) | −0.0028 (6) | 0.0001 (6) | −0.0055 (5) |
C1 | 0.0275 (8) | 0.0253 (8) | 0.0218 (7) | −0.0003 (7) | 0.0020 (6) | 0.0003 (6) |
C8 | 0.0306 (8) | 0.0233 (8) | 0.0155 (6) | −0.0035 (6) | 0.0001 (6) | 0.0019 (6) |
C7 | 0.0330 (9) | 0.0309 (9) | 0.0180 (7) | −0.0082 (7) | −0.0047 (6) | −0.0011 (6) |
C4 | 0.0295 (8) | 0.0217 (8) | 0.0221 (7) | −0.0003 (7) | −0.0034 (6) | 0.0000 (6) |
C6 | 0.0234 (8) | 0.0387 (9) | 0.0227 (7) | −0.0054 (7) | −0.0050 (6) | 0.0013 (7) |
C5 | 0.0285 (9) | 0.0294 (8) | 0.0257 (8) | 0.0024 (7) | −0.0012 (6) | −0.0017 (6) |
C2 | 0.0243 (8) | 0.0213 (8) | 0.0184 (7) | −0.0048 (6) | 0.0002 (6) | 0.0031 (6) |
O5 | 0.0503 (8) | 0.0244 (7) | 0.0286 (7) | −0.0047 (6) | 0.0015 (6) | 0.0015 (5) |
O4—C16 | 1.3379 (17) | C10—H10 | 1.0000 |
O4—H4 | 0.8400 | C3—C4 | 1.407 (2) |
O2—C11 | 1.2562 (18) | C3—C8 | 1.416 (2) |
O3—C14 | 1.3333 (17) | C3—C2 | 1.436 (2) |
O3—H3 | 0.8400 | C9—C2 | 1.490 (2) |
N2—C12 | 1.2999 (18) | C9—H9A | 0.9900 |
N2—C10 | 1.4631 (17) | C9—H9B | 0.9900 |
N2—H2A | 0.87 (2) | N1—C1 | 1.372 (2) |
C16—C15 | 1.395 (2) | N1—C8 | 1.375 (2) |
C16—C17 | 1.407 (2) | N1—H1A | 0.87 (2) |
O1—C11 | 1.2485 (18) | C1—C2 | 1.375 (2) |
C18—C17 | 1.367 (2) | C1—H1 | 0.9500 |
C18—C13 | 1.4139 (19) | C8—C7 | 1.395 (2) |
C18—H18 | 0.9500 | C7—C6 | 1.380 (3) |
C17—H17 | 0.9500 | C7—H7 | 0.9500 |
C15—C14 | 1.3890 (19) | C4—C5 | 1.376 (2) |
C15—H15 | 0.9500 | C4—H4A | 0.9500 |
C13—C12 | 1.4148 (19) | C6—C5 | 1.403 (2) |
C13—C14 | 1.420 (2) | C6—H6 | 0.9500 |
C12—H12 | 0.9500 | C5—H5 | 0.9500 |
C10—C11 | 1.5327 (19) | O5—H5B | 0.80 (3) |
C10—C9 | 1.553 (2) | O5—H5A | 0.78 (3) |
C16—O4—H4 | 109.5 | O3—C14—C15 | 122.29 (13) |
C14—O3—H3 | 109.5 | O3—C14—C13 | 117.91 (12) |
C12—N2—C10 | 122.42 (12) | C15—C14—C13 | 119.80 (13) |
C12—N2—H2A | 122.9 (12) | C2—C9—C10 | 111.67 (12) |
C10—N2—H2A | 114.4 (12) | C2—C9—H9A | 109.3 |
O4—C16—C15 | 121.28 (13) | C10—C9—H9A | 109.3 |
O4—C16—C17 | 117.60 (13) | C2—C9—H9B | 109.3 |
C15—C16—C17 | 121.11 (12) | C10—C9—H9B | 109.3 |
C17—C18—C13 | 121.60 (14) | H9A—C9—H9B | 107.9 |
C17—C18—H18 | 119.2 | C1—N1—C8 | 108.72 (13) |
C13—C18—H18 | 119.2 | C1—N1—H1A | 123.3 (15) |
C18—C17—C16 | 118.93 (13) | C8—N1—H1A | 127.9 (15) |
C18—C17—H17 | 120.5 | N1—C1—C2 | 110.49 (14) |
C16—C17—H17 | 120.5 | N1—C1—H1 | 124.8 |
C14—C15—C16 | 119.83 (13) | C2—C1—H1 | 124.8 |
C14—C15—H15 | 120.1 | N1—C8—C7 | 130.80 (15) |
C16—C15—H15 | 120.1 | N1—C8—C3 | 107.65 (14) |
C18—C13—C12 | 118.43 (13) | C7—C8—C3 | 121.55 (15) |
C18—C13—C14 | 118.68 (12) | C6—C7—C8 | 117.62 (15) |
C12—C13—C14 | 122.89 (13) | C6—C7—H7 | 121.2 |
N2—C12—C13 | 126.78 (13) | C8—C7—H7 | 121.2 |
N2—C12—H12 | 116.6 | C5—C4—C3 | 118.77 (15) |
C13—C12—H12 | 116.6 | C5—C4—H4A | 120.6 |
N2—C10—C11 | 109.03 (11) | C3—C4—H4A | 120.6 |
N2—C10—C9 | 110.48 (11) | C7—C6—C5 | 121.64 (15) |
C11—C10—C9 | 107.92 (11) | C7—C6—H6 | 119.2 |
N2—C10—H10 | 109.8 | C5—C6—H6 | 119.2 |
C11—C10—H10 | 109.8 | C4—C5—C6 | 121.05 (16) |
C9—C10—H10 | 109.8 | C4—C5—H5 | 119.5 |
O1—C11—O2 | 125.77 (13) | C6—C5—H5 | 119.5 |
O1—C11—C10 | 116.93 (12) | C1—C2—C3 | 105.99 (14) |
O2—C11—C10 | 117.20 (12) | C1—C2—C9 | 126.92 (14) |
C4—C3—C8 | 119.35 (15) | C3—C2—C9 | 126.72 (14) |
C4—C3—C2 | 133.49 (15) | H5B—O5—H5A | 117 (3) |
C8—C3—C2 | 107.15 (14) | ||
C13—C18—C17—C16 | 0.3 (2) | C11—C10—C9—C2 | −176.14 (12) |
O4—C16—C17—C18 | 177.64 (13) | C8—N1—C1—C2 | −0.01 (18) |
C15—C16—C17—C18 | −2.3 (2) | C1—N1—C8—C7 | 179.16 (16) |
O4—C16—C15—C14 | −177.57 (14) | C1—N1—C8—C3 | −0.11 (17) |
C17—C16—C15—C14 | 2.4 (2) | C4—C3—C8—N1 | 178.89 (13) |
C17—C18—C13—C12 | −177.31 (14) | C2—C3—C8—N1 | 0.19 (16) |
C17—C18—C13—C14 | 1.6 (2) | C4—C3—C8—C7 | −0.5 (2) |
C10—N2—C12—C13 | −174.50 (13) | C2—C3—C8—C7 | −179.16 (14) |
C18—C13—C12—N2 | 175.73 (14) | N1—C8—C7—C6 | −179.74 (15) |
C14—C13—C12—N2 | −3.2 (2) | C3—C8—C7—C6 | −0.6 (2) |
C12—N2—C10—C11 | −162.62 (12) | C8—C3—C4—C5 | 0.9 (2) |
C12—N2—C10—C9 | 78.95 (17) | C2—C3—C4—C5 | 179.23 (16) |
N2—C10—C11—O1 | −31.31 (18) | C8—C7—C6—C5 | 1.1 (2) |
C9—C10—C11—O1 | 88.72 (15) | C3—C4—C5—C6 | −0.4 (2) |
N2—C10—C11—O2 | 152.17 (13) | C7—C6—C5—C4 | −0.6 (3) |
C9—C10—C11—O2 | −87.79 (16) | N1—C1—C2—C3 | 0.13 (17) |
C16—C15—C14—O3 | 178.95 (13) | N1—C1—C2—C9 | −173.23 (14) |
C16—C15—C14—C13 | −0.4 (2) | C4—C3—C2—C1 | −178.63 (16) |
C18—C13—C14—O3 | 179.05 (12) | C8—C3—C2—C1 | −0.20 (16) |
C12—C13—C14—O3 | −2.1 (2) | C4—C3—C2—C9 | −5.2 (3) |
C18—C13—C14—C15 | −1.5 (2) | C8—C3—C2—C9 | 173.18 (14) |
C12—C13—C14—C15 | 177.34 (14) | C10—C9—C2—C1 | 105.32 (17) |
N2—C10—C9—C2 | −57.03 (16) | C10—C9—C2—C3 | −66.71 (19) |
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H4···O2i | 0.84 | 1.76 | 2.5966 (15) | 178 |
O3—H3···O1ii | 0.84 | 1.72 | 2.5605 (15) | 176 |
O3—H3···O2ii | 0.84 | 2.64 | 3.1526 (14) | 121 |
N2—H2A···O3 | 0.87 (2) | 2.082 (19) | 2.6642 (15) | 123.9 (16) |
O5—H5B···O2iii | 0.80 (3) | 2.19 (3) | 2.9438 (17) | 157 (2) |
N1—H1A···O5 | 0.87 (2) | 2.10 (2) | 2.9441 (19) | 164 (2) |
Symmetry codes: (i) x, y+1, z; (ii) −x, y+1/2, −z+1/2; (iii) −x+1/2, −y, z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C18H16N2O4·H2O |
Mr | 342.34 |
Crystal system, space group | Orthorhombic, P212121 |
Temperature (K) | 100 |
a, b, c (Å) | 8.4214 (3), 10.6787 (4), 18.9554 (8) |
V (Å3) | 1704.65 (11) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.10 |
Crystal size (mm) | 0.20 × 0.10 × 0.10 |
Data collection | |
Diffractometer | Bruker SMART APEXII CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 1996) |
Tmin, Tmax | 0.618, 0.746 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 15797, 3904, 3587 |
Rint | 0.035 |
(sin θ/λ)max (Å−1) | 0.650 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.034, 0.085, 1.03 |
No. of reflections | 3904 |
No. of parameters | 244 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.25, −0.16 |
Computer programs: APEX2 (Bruker, 2008), SAINT (Bruker, 2008), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008), publCIF (Westrip, 2010).
D—H···A | D—H | H···A | D···A | D—H···A |
O4—H4···O2i | 0.84 | 1.76 | 2.5966 (15) | 177.9 |
O3—H3···O1ii | 0.84 | 1.72 | 2.5605 (15) | 175.8 |
O3—H3···O2ii | 0.84 | 2.64 | 3.1526 (14) | 121.1 |
N2—H2A···O3 | 0.87 (2) | 2.082 (19) | 2.6642 (15) | 123.9 (16) |
O5—H5B···O2iii | 0.80 (3) | 2.19 (3) | 2.9438 (17) | 157 (2) |
N1—H1A···O5 | 0.87 (2) | 2.10 (2) | 2.9441 (19) | 164 (2) |
Symmetry codes: (i) x, y+1, z; (ii) −x, y+1/2, −z+1/2; (iii) −x+1/2, −y, z+1/2. |
Acknowledgements
The authors thank the Malaysian Government and Universiti Sains Malaysia for the RU research grant (1001/PKIMIA/815067). NEE thanks Universiti Sains Malaysia for a post-doctoral fellowship and the International University of Africa (Sudan) for providing study leave. SAB thanks the Ministry of Higher Education and Scientific Research (Yemen) for a scholarship.
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This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
Schiff bases have received much attention because of their potential applications, with some of these compounds exhibiting various pharmacological activities, as noted by their anticancer (Dao et al., 2000), anti-HIV (Sriram et al., 2006), antibacterial and antifungal (Karthikeyan et al., 2006) properties. In addition, some of them may be used as analytical reagents for the determination of trace elements (Eltayeb & Ahmed, 2005a,b). In this paper, we report the crystal structure of the title compound C18H16N2O4.H2O (Fig. 1), obtained by the reaction of tryptophan and 2,4-dihydroxybenzaldehyde.
The asymmetric unit of the title compound (Fig. 1) consists of one zwitterionic E)-2-(2,4-dihydroxybenzylideneammonio)-3-(1H- indol-3-yl)propanoate molecule and one molecule of water. Bond lengths and angles have normal values (Allen et al., 1987). The dihedral angle between the planes of the benzene and the indole rings in the organic molecule is 39.55 (6)°. Intramolecular N—H···O hydrogen bonds generate S(6) ring motifs. The C13 in the six-membered ring and C2 in the nine-membered ring are connected together by a chain of four atoms, C12/N2/C10/C9 which has torsion angle 78.95 (17) °. The torsion angles of the chain N2/C10/C9/C2 and C10/N2/C12/C13 are -57.03 (16) ° and -174.50 (13) °, respectively. In the crystal structure, the molecules are linked by intermolecular hydroxy O—H···Ocarboxylate hydrogen bonds into chains which extend along the b axis and peripherally by N+—H··· Ocarboxylate hydrogen bonds (Table 1 and Fig. 2). The three-dimensional structure is also stabilized by the indole N—H···Owater and water O—H···Ocarboxylate associations.
The absolute configuration could not be determined definitively [Flack parameter -0.02 (8) (Flack, 1983)] but C10 (S) was assumed for the title compound.