organic compounds
1-(2-Oxo-3,4-dihydro-2H-1,3-benzoxazin-4-yl)urea monohydrate
aBaku State University, Z. Khalilov Street 23, Baku, AZ-1148, Azerbaijan
*Correspondence e-mail: mkurbanova72@mail.ru
The organic molecule in the title hydrate, C9H9N3O3·H2O, was obtained by the condenstation of salicylic aldehyde with urea in acetonitrile. The oxazine ring adopts a slightly distorted sofa conformation, with the N atom deviating from the plane passing through the other atoms of the ring by 0.267 (2) Å. The displays intermolecular N—H⋯O and O—H⋯O hydrogen bonding.
Related literature
For details of the condensation of salicyl aldehyde with urea, see: Pandey et al. (2008); El-Hamouly et al. (2007); Bobowski & Shavel (1967).
Experimental
Crystal data
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Refinement
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Data collection: APEX2 (Bruker, 2005); cell SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.
Supporting information
https://doi.org/10.1107/S1600536810032411/rk2226sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810032411/rk2226Isup2.hkl
The solution of salicylic aldehyde (0.02 mol), urea (0.03 mol), 1 ml trichloroacetic acid, 3 ml AcOH in 15 ml acetonitril was mixed for 3-4 h (Fig. 3). Of a reaction course observed using thin layer ν/cm-1: 1456-1541 (C═C), 1646 (NH–C(O)–NH2), 1710 (C(O)–O), 3349 (NH(lactam), associated), 3346 (C(O)–NH2). m/z: 230 [M+Na]+. 1H NMR ((CD3)2SO, 293 K): 8.5 (S, 1H, NH), 7.3(m, 2H, H6, H7), 7.15 (m, 2H, H3, H5),7.05 (d, 1H, H8, 3J = 7.2), 6.2 (d, 1H, H4, 3J = 7.5), 5.65 (S, 2H, NH2). 13C NMR ((CD3)2SO, 293 K): δ = 164 (S, NH–C(O)–NH2), 158 (S, C(O)–O), 150 (S, C9), 130 (S, C8), 127 (S, C5), 124.5 (S, C7), 121 (S, C10), 116 (S, C6), 58 (S, C4).
(TLC) method. After cooling the product was filtered and washed out by ethanol. The target product was obtained by re-crystallization of a water solution of ethanol (1:3) as white crystals. M.p. = 498-500 K. IR,The amino-H atoms as well as H-atoms of the water solvate molecule were localized in the difference Fourier map and included in the
with fixed positional and isotropic displacement parameters [Uiso(H) = 1.2Ueq(N) and Uiso(H) = 1.5Ueq(O)]. The other hydrogen atoms were placed in calculated positions with C–H = 0.93-0.98Å and refined in the riding model with fixed isotropic displacement parameters [Uiso(H) = 1.2Ueq(C)].3,4-Dihydro-3-alkyl-2H-1,3-benzoxazin-2-ones, 4,4'-oxobis(3,4-dihydro-3-alkyl-2H-benzoxazin-2-ones), and 1-(3,4-dihydro-3-alkyl-2-oxo-2H-1,3-benzoxazin-4-yl-1,3-dialkylureas were obtained by the condensation of o-hydroxyaromatic
with alkylisocyanates (Bobowski & Shavel, 1967). The formation 1,1'-[(2-hydroxyphenyl)methylene]diurea by the condensation of salicyl aldehyde with two molecules of carbamide is well known from the literature (El-Hamouly et al., 2007; Pandey et al., 2008).The title molecule contains a fused bicycle system containing two six-membered rings (benzene and oxazin) (Fig. 1). The oxazin cycle adopts a slightly distorted sofa conformation, with the nitrogen N1 atom deviating from plane passed through the other atoms of the cycle by 0.267 (2)Å. Such disposion of the nitrogen atom is defined by the intermolecular N1–H1···O2i hydrogen bonding (Table 1). Symmetry code: (i) -x+1, -y+2, -z+1. The nitrogen N1 atom has a pyramidalized configuration (sum of bond angles at the nitrogen N1 atom is 352.7°, the C2–N1–O1–C1 torsion angle is 22.4 (2)°). The carbamide substituent of the oxazin cycle is in axial position (the C9–N2–C2–N1 torsion angle is -64.31 (15)°).
Compound I possesses one asymmetric center at the C2, but the crystal of I is racemate.
In crystal of I, the organic molecules and solvate water molecules are bound into complex two-tier layers parallel to (0 0 1) by the hydrogen bonds (Fig. 2, Table 1).
For details of the condensation of salicyl aldehyde with urea, see: Pandey et al. (2008); El-Hamouly et al. (2007); Bobowski & Shavel (1967).
Data collection: APEX2 (Bruker, 2005); cell
SAINT-Plus (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).Fig. 1. Molecular structure of I with the atom numbering scheme. Displacement ellipsoids are drawn at the 50% proabbility level. H atoms are presented as a small spheres of arbitrary radius. | |
Fig. 2. Crystal packing of the molecules of I viewed down the a axis. Dashed lines show intermolecular hydrogen bonds. | |
Fig. 3. Condensation of salicyl aldehyde with two molecules of urea with reception benzoxazin. |
C9H9N3O3·H2O | F(000) = 472 |
Mr = 225.21 | Dx = 1.508 Mg m−3 |
Monoclinic, P21/n | Melting point: 499 K |
Hall symbol: -P 2yn | Mo Kα radiation, λ = 0.71073 Å |
a = 5.3393 (10) Å | Cell parameters from 3341 reflections |
b = 8.5465 (16) Å | θ = 2.6–28.2° |
c = 21.846 (4) Å | µ = 0.12 mm−1 |
β = 95.472 (4)° | T = 296 K |
V = 992.3 (3) Å3 | Prism, colourless |
Z = 4 | 0.30 × 0.30 × 0.30 mm |
Bruker APEXII CCD diffractometer | 2448 independent reflections |
Radiation source: fine-focus sealed tube | 1942 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.058 |
φ and ω scans | θmax = 28.4°, θmin = 1.9° |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | h = −7→7 |
Tmin = 0.965, Tmax = 0.965 | k = −11→11 |
10468 measured reflections | l = −29→28 |
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: difference Fourier map |
wR(F2) = 0.117 | H-atom parameters constrained |
S = 1.00 | w = 1/[σ2(Fo2) + (0.0598P)2 + 0.12P] where P = (Fo2 + 2Fc2)/3 |
2448 reflections | (Δ/σ)max < 0.001 |
145 parameters | Δρmax = 0.28 e Å−3 |
0 restraints | Δρmin = −0.29 e Å−3 |
C9H9N3O3·H2O | V = 992.3 (3) Å3 |
Mr = 225.21 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 5.3393 (10) Å | µ = 0.12 mm−1 |
b = 8.5465 (16) Å | T = 296 K |
c = 21.846 (4) Å | 0.30 × 0.30 × 0.30 mm |
β = 95.472 (4)° |
Bruker APEXII CCD diffractometer | 2448 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | 1942 reflections with I > 2σ(I) |
Tmin = 0.965, Tmax = 0.965 | Rint = 0.058 |
10468 measured reflections |
R[F2 > 2σ(F2)] = 0.043 | 0 restraints |
wR(F2) = 0.117 | H-atom parameters constrained |
S = 1.00 | Δρmax = 0.28 e Å−3 |
2448 reflections | Δρmin = −0.29 e Å−3 |
145 parameters |
Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 | ||
O1 | 0.72114 (16) | 0.97940 (12) | 0.35888 (4) | 0.0372 (2) | |
O2 | 0.7419 (2) | 1.05038 (14) | 0.45587 (5) | 0.0500 (3) | |
O3 | 0.74592 (16) | 0.64789 (12) | 0.40776 (4) | 0.0377 (3) | |
N1 | 0.3995 (2) | 0.91465 (14) | 0.41776 (5) | 0.0360 (3) | |
H1 | 0.3548 | 0.9179 | 0.4565 | 0.043* | |
N2 | 0.32112 (19) | 0.63842 (14) | 0.40155 (5) | 0.0348 (3) | |
H2A | 0.1839 | 0.5802 | 0.4065 | 0.042* | |
N3 | 0.5568 (2) | 0.42106 (15) | 0.43002 (6) | 0.0420 (3) | |
H3A | 0.7098 | 0.3794 | 0.4466 | 0.050* | |
H3B | 0.4077 | 0.3652 | 0.4378 | 0.050* | |
C1 | 0.6227 (2) | 0.98097 (16) | 0.41376 (6) | 0.0337 (3) | |
C2 | 0.2868 (2) | 0.79512 (16) | 0.37637 (6) | 0.0322 (3) | |
H2 | 0.1054 | 0.8154 | 0.3709 | 0.039* | |
C3 | 0.3850 (2) | 0.81370 (15) | 0.31454 (6) | 0.0316 (3) | |
C4 | 0.2696 (3) | 0.74090 (18) | 0.26224 (7) | 0.0418 (3) | |
H4 | 0.1274 | 0.6796 | 0.2652 | 0.050* | |
C5 | 0.3641 (3) | 0.7586 (2) | 0.20596 (7) | 0.0495 (4) | |
H5 | 0.2852 | 0.7098 | 0.1713 | 0.059* | |
C6 | 0.5756 (3) | 0.8489 (2) | 0.20131 (7) | 0.0483 (4) | |
H6 | 0.6398 | 0.8600 | 0.1634 | 0.058* | |
C7 | 0.6926 (3) | 0.92281 (19) | 0.25240 (7) | 0.0418 (3) | |
H7 | 0.8347 | 0.9842 | 0.2493 | 0.050* | |
C8 | 0.5943 (2) | 0.90387 (16) | 0.30837 (6) | 0.0316 (3) | |
C9 | 0.5510 (2) | 0.57119 (16) | 0.41307 (5) | 0.0306 (3) | |
O4 | 0.08489 (19) | 0.29496 (14) | 0.46692 (5) | 0.0499 (3) | |
H4A | 0.0070 | 0.1995 | 0.4555 | 0.075* | |
H4B | 0.1116 | 0.2988 | 0.5099 | 0.075* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0276 (4) | 0.0451 (6) | 0.0392 (5) | −0.0083 (4) | 0.0049 (4) | 0.0007 (4) |
O2 | 0.0477 (6) | 0.0588 (7) | 0.0432 (6) | −0.0203 (5) | 0.0027 (5) | −0.0081 (5) |
O3 | 0.0229 (4) | 0.0452 (6) | 0.0455 (5) | −0.0048 (4) | 0.0059 (4) | 0.0060 (4) |
N1 | 0.0293 (5) | 0.0432 (7) | 0.0368 (6) | −0.0030 (5) | 0.0093 (4) | −0.0067 (5) |
N2 | 0.0218 (5) | 0.0415 (6) | 0.0419 (6) | −0.0091 (4) | 0.0066 (4) | 0.0025 (5) |
N3 | 0.0385 (6) | 0.0410 (7) | 0.0477 (7) | −0.0032 (5) | 0.0101 (5) | 0.0076 (5) |
C1 | 0.0295 (6) | 0.0344 (7) | 0.0371 (7) | −0.0026 (5) | 0.0024 (5) | 0.0001 (5) |
C2 | 0.0177 (5) | 0.0416 (7) | 0.0375 (7) | −0.0009 (5) | 0.0041 (5) | −0.0021 (5) |
C3 | 0.0240 (5) | 0.0363 (7) | 0.0343 (6) | 0.0033 (5) | 0.0019 (5) | 0.0020 (5) |
C4 | 0.0352 (7) | 0.0466 (8) | 0.0423 (8) | −0.0025 (6) | −0.0023 (6) | −0.0008 (6) |
C5 | 0.0556 (9) | 0.0565 (10) | 0.0349 (7) | 0.0027 (7) | −0.0032 (6) | −0.0035 (7) |
C6 | 0.0578 (9) | 0.0539 (9) | 0.0346 (7) | 0.0087 (7) | 0.0121 (6) | 0.0041 (7) |
C7 | 0.0385 (7) | 0.0448 (8) | 0.0437 (8) | 0.0023 (6) | 0.0125 (6) | 0.0086 (6) |
C8 | 0.0248 (5) | 0.0350 (7) | 0.0350 (6) | 0.0040 (5) | 0.0025 (5) | 0.0023 (5) |
C9 | 0.0269 (6) | 0.0396 (7) | 0.0260 (6) | −0.0056 (5) | 0.0062 (4) | −0.0013 (5) |
O4 | 0.0416 (6) | 0.0568 (7) | 0.0506 (6) | −0.0155 (5) | 0.0009 (5) | 0.0044 (5) |
O1—C1 | 1.3541 (16) | C2—H2 | 0.9800 |
O1—C8 | 1.3965 (16) | C3—C8 | 1.3746 (18) |
O2—C1 | 1.2213 (17) | C3—C4 | 1.3919 (19) |
O3—C9 | 1.2449 (15) | C4—C5 | 1.381 (2) |
N1—C1 | 1.3300 (16) | C4—H4 | 0.9300 |
N1—C2 | 1.4558 (17) | C5—C6 | 1.380 (2) |
N1—H1 | 0.9026 | C5—H5 | 0.9300 |
N2—C9 | 1.3567 (17) | C6—C7 | 1.379 (2) |
N2—C2 | 1.4527 (18) | C6—H6 | 0.9300 |
N2—H2A | 0.9010 | C7—C8 | 1.3853 (19) |
N3—C9 | 1.3350 (19) | C7—H7 | 0.9300 |
N3—H3A | 0.9321 | O4—H4A | 0.9390 |
N3—H3B | 0.9572 | O4—H4B | 0.9361 |
C2—C3 | 1.5032 (18) | ||
C1—O1—C8 | 120.28 (10) | C4—C3—C2 | 121.70 (12) |
C1—N1—C2 | 125.32 (11) | C5—C4—C3 | 120.75 (14) |
C1—N1—H1 | 111.6 | C5—C4—H4 | 119.6 |
C2—N1—H1 | 118.3 | C3—C4—H4 | 119.6 |
C9—N2—C2 | 122.67 (10) | C6—C5—C4 | 119.86 (14) |
C9—N2—H2A | 118.4 | C6—C5—H5 | 120.1 |
C2—N2—H2A | 118.7 | C4—C5—H5 | 120.1 |
C9—N3—H3A | 118.1 | C7—C6—C5 | 120.49 (14) |
C9—N3—H3B | 122.1 | C7—C6—H6 | 119.8 |
H3A—N3—H3B | 117.0 | C5—C6—H6 | 119.8 |
O2—C1—N1 | 124.29 (12) | C6—C7—C8 | 118.70 (14) |
O2—C1—O1 | 116.96 (12) | C6—C7—H7 | 120.7 |
N1—C1—O1 | 118.66 (11) | C8—C7—H7 | 120.6 |
N2—C2—N1 | 112.46 (11) | C3—C8—C7 | 122.14 (13) |
N2—C2—C3 | 113.30 (11) | C3—C8—O1 | 121.28 (11) |
N1—C2—C3 | 108.97 (10) | C7—C8—O1 | 116.57 (12) |
N2—C2—H2 | 107.3 | O3—C9—N3 | 122.31 (12) |
N1—C2—H2 | 107.3 | O3—C9—N2 | 120.61 (12) |
C3—C2—H2 | 107.3 | N3—C9—N2 | 117.07 (11) |
C8—C3—C4 | 118.06 (12) | H4A—O4—H4B | 108.6 |
C8—C3—C2 | 120.24 (11) | ||
C2—N1—C1—O2 | −161.10 (14) | C3—C4—C5—C6 | 0.2 (2) |
C2—N1—C1—O1 | 22.4 (2) | C4—C5—C6—C7 | −0.5 (3) |
C8—O1—C1—O2 | −179.29 (12) | C5—C6—C7—C8 | 0.3 (2) |
C8—O1—C1—N1 | −2.56 (18) | C4—C3—C8—C7 | −0.5 (2) |
C9—N2—C2—N1 | −64.31 (15) | C2—C3—C8—C7 | 179.31 (12) |
C9—N2—C2—C3 | 59.82 (15) | C4—C3—C8—O1 | −179.47 (12) |
C1—N1—C2—N2 | 98.81 (15) | C2—C3—C8—O1 | 0.31 (19) |
C1—N1—C2—C3 | −27.67 (17) | C6—C7—C8—C3 | 0.2 (2) |
N2—C2—C3—C8 | −110.70 (13) | C6—C7—C8—O1 | 179.23 (13) |
N1—C2—C3—C8 | 15.31 (16) | C1—O1—C8—C3 | −8.08 (18) |
N2—C2—C3—C4 | 69.07 (15) | C1—O1—C8—C7 | 172.86 (12) |
N1—C2—C3—C4 | −164.92 (12) | C2—N2—C9—O3 | 6.81 (19) |
C8—C3—C4—C5 | 0.3 (2) | C2—N2—C9—N3 | −173.09 (11) |
C2—C3—C4—C5 | −179.52 (14) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O2i | 0.90 | 2.05 | 2.946 (2) | 174 |
N2—H2A···O3ii | 0.90 | 2.41 | 3.088 (2) | 132 |
N3—H3A···O4iii | 0.93 | 2.14 | 3.054 (2) | 169 |
N3—H3B···O4 | 0.96 | 1.99 | 2.923 (2) | 166 |
O4—H4A···O2iv | 0.94 | 1.91 | 2.774 (2) | 153 |
O4—H4B···O3v | 0.94 | 1.94 | 2.842 (2) | 161 |
Symmetry codes: (i) −x+1, −y+2, −z+1; (ii) x−1, y, z; (iii) x+1, y, z; (iv) x−1, y−1, z; (v) −x+1, −y+1, −z+1. |
Experimental details
Crystal data | |
Chemical formula | C9H9N3O3·H2O |
Mr | 225.21 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 296 |
a, b, c (Å) | 5.3393 (10), 8.5465 (16), 21.846 (4) |
β (°) | 95.472 (4) |
V (Å3) | 992.3 (3) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.12 |
Crystal size (mm) | 0.30 × 0.30 × 0.30 |
Data collection | |
Diffractometer | Bruker APEXII CCD |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2003) |
Tmin, Tmax | 0.965, 0.965 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10468, 2448, 1942 |
Rint | 0.058 |
(sin θ/λ)max (Å−1) | 0.668 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.043, 0.117, 1.00 |
No. of reflections | 2448 |
No. of parameters | 145 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.28, −0.29 |
Computer programs: APEX2 (Bruker, 2005), SAINT-Plus (Bruker, 2001), SHELXTL (Sheldrick, 2008).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O2i | 0.90 | 2.05 | 2.946 (2) | 174 |
N2—H2A···O3ii | 0.90 | 2.41 | 3.088 (2) | 132 |
N3—H3A···O4iii | 0.93 | 2.14 | 3.054 (2) | 169 |
N3—H3B···O4 | 0.96 | 1.99 | 2.923 (2) | 166 |
O4—H4A···O2iv | 0.94 | 1.91 | 2.774 (2) | 153 |
O4—H4B···O3v | 0.94 | 1.94 | 2.842 (2) | 161 |
Symmetry codes: (i) −x+1, −y+2, −z+1; (ii) x−1, y, z; (iii) x+1, y, z; (iv) x−1, y−1, z; (v) −x+1, −y+1, −z+1. |
Acknowledgements
The authors thank Dr Victor N. Khrustalev for fruitful discussions and help with this work.
References
Bobowski, G. & Shavel, J. (1967). J. Org. Chem. 32, 953–959. CrossRef CAS Web of Science Google Scholar
Bruker (2001). SAINT-Plus. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Bruker (2005). APEX2. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
El-Hamouly, W. S., Tawfeek, H. A. & Abbas, M. H. (2007). Egypt. J. Chem. 50, 97–104. CAS Google Scholar
Pandey, V. K., Mukesh, A. K. & Noopur, T. (2008). Indian J. Chem. Sect. B, 47, 1910–1914. Google Scholar
Sheldrick, G. M. (2003). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
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3,4-Dihydro-3-alkyl-2H-1,3-benzoxazin-2-ones, 4,4'-oxobis(3,4-dihydro-3-alkyl-2H-benzoxazin-2-ones), and 1-(3,4-dihydro-3-alkyl-2-oxo-2H-1,3-benzoxazin-4-yl-1,3-dialkylureas were obtained by the condensation of o-hydroxyaromatic aldehydes with alkylisocyanates (Bobowski & Shavel, 1967). The formation 1,1'-[(2-hydroxyphenyl)methylene]diurea by the condensation of salicyl aldehyde with two molecules of carbamide is well known from the literature (El-Hamouly et al., 2007; Pandey et al., 2008).
The title molecule contains a fused bicycle system containing two six-membered rings (benzene and oxazin) (Fig. 1). The oxazin cycle adopts a slightly distorted sofa conformation, with the nitrogen N1 atom deviating from plane passed through the other atoms of the cycle by 0.267 (2)Å. Such disposion of the nitrogen atom is defined by the intermolecular N1–H1···O2i hydrogen bonding (Table 1). Symmetry code: (i) -x+1, -y+2, -z+1. The nitrogen N1 atom has a pyramidalized configuration (sum of bond angles at the nitrogen N1 atom is 352.7°, the C2–N1–O1–C1 torsion angle is 22.4 (2)°). The carbamide substituent of the oxazin cycle is in axial position (the C9–N2–C2–N1 torsion angle is -64.31 (15)°).
Compound I possesses one asymmetric center at the C2, but the crystal of I is racemate.
In crystal of I, the organic molecules and solvate water molecules are bound into complex two-tier layers parallel to (0 0 1) by the hydrogen bonds (Fig. 2, Table 1).