p-Methyl­tetrahomodioxacalix­[4]­arene

The title compound, 7,13,21,27-tetramethyl-3,17-dioxapenta­cyclo­[23.3.1.1^5,9.1^11,15.1^9,23]ditriaconta-1(29),5,7,­9(30),­11(31),-12,­14,19(32),20,22,25,27-dodecaene-29,30,31,32-tetraol, C₃₄H₃₆O₆, assumes in the solid state a very distorted cone-like conformation stabilized by intramolecular simple and bifurcated hydrogen bonds involving both phenolic and ether O atoms. One part of the mol­ecule, comprising an ether link, is included in the cavity of an adjacent calixarene related by a screw axis, giving rise to a one-dimensional self-inclusion polymer.

S1. Comment

We have recently reported the first crystal structures of p-tert-butyl-tetrahomodioxacalix[4]arene as well as of its uranyl ion complex (Thuéry, Nierlich, Vicens, Masci & Takemura et al., 2001; Thuéry, Nierlich, Vicens & Masci et al., 2001). Three forms of the uncomplexed ligand have been described, all of them with included solvent molecules (acetonitrile, pyridine, chloroform/tetrahydrofuran) and presenting slightly different conformations and intramolecular hydrogen-bonding pattern. We report herein a closely related new compound, (I), with a methyl substituent in the para position, which crystallizes without any included solvent molecule. \sch

The asymmetric unit in (I) is composed of one calixarene molecule. The conformation of the macrocycle is that of a very distorted cone. It can be characterized by the dihedral angles between the planes of the four phenolic rings and the reference plane defined by the four phenolic O atoms [highest deviation from mean plane 0.026 (3) Å], which are 158.3 (1), 169.6 (1), 109.8 (1) and 118.6 (1)°. These dihedral angles span a range wider than that observed in the three previous compounds, the presence of the ether links allowing for some flexibility while not disrupting the hydrogen bonding pattern. In conformation terms, two kinds of ether links can be distinguished in this family of compounds, which can be characterized by their torsion angles. In the present case, both torsion angles for each bridge correspond to anti geometries: C3—C8—O2—C9 177.0 (3), C8—O2—C9—C10 - 162.9 (3), C20—C25—O5—C26 179.4 (3) and C25—O5—C26—C27 165.9 (3)°. In the previous cases, both ether bridges or at least one of them had one anti and one approximately gauche (values in the range 58.4–86.0°) angle. The first case (two anti angles) gives rise to a quasi-planar 'w' shape for the three atoms of the bridge and the two aromatic C atoms to which they are linked, and the second (one anti and one gauche angles) to a succession of four planar atoms only. In (I), the plane defined by atoms C3, C8, O2, C9 and C10 [highest deviation 0.164 (4) Å] makes a dihedral angle of 52.2 (2)° with the reference O₄ plane, whereas the plane defined by C20, C25, O5, C26 and C27 [highest deviation 0.112 (4) Å] is nearly parallel to it, with a dihedral angle of 8.4 (2)°. O2 is displaced by 0.089 (3) Å on one side of the reference O₄ plane, while O5 is displaced by 2.241 (3) Å on the opposite side. The macrocycle conformation can be described as a distorted cone in the sense that all four oxygen atoms are roughly pointing in the same direction with respect to the mean plane of the molecule. However, it is strongly distorted towards a 1,2-alternate conformation (Masci, Finelli & Varrone, 1998; Masci, 2001). If one considers the units comprising two aromatic rings and a central ether link, i.e. the units separated by the methylenic C atoms C17 and C34, one of them has its concave side directed downwards, and the other one upwards. This confirms that the conformation analysis of homooxacalix[4]arenes is much more complicated than that of calix[4]arenes (Masci, Finelli & Varrone, 1998), both in solution and in the solid state. The hydrogen-bonding pattern is composed of two simple and two bifurcated hydrogen bonds, the latter involving the ether O atoms, as previously observed in tert-butyl derivatives.

The most original feature of the present structure, with respect to those of the tert-butyl derivative, lies with the crystal packing. The molecules related by the screw axis parallel to b are positioned so that one of the units defined above, comprising the ether link corresponding to O5 and the two adjacent aromatic rings, points towards the cavity of the neighbouring macrocycle, with intermolecular contacts as short as 3.339 (4) Å (between O5 and C25', with ' = -x - 1/2, y - 1/2, 1/2 - z). Such an arrangement, described as giving a self-inclusion polymer, has been described in p-tert-butylcalix[5]arene (Gallagher et al., 1994), in which the molecules are related by a glide plane. In this case, one tert-butyl group is the included moiety. The resulting one-dimensional columnar arrangement has been compared to a molecular 'zipper'. It may be assumed that the replacement of tert-butyl by methyl groups in (I) reduces the affinity of the macrocycle for solvent molecules, the cavity being then available for self-inclusion.

S2. Experimental

p-Methyltetrahomodioxacalix[4]arene was synthesized as reported elsewhere (Masci, manuscript in preparation) and recrystallized from chloroform.

S3. Refinement

Hydroxyl protons were found on the Fourier difference map and introduced as riding atoms with a displacement parameter equal to 1.2 times that of the parent atom. All other H atoms were introduced at calculated positions as riding atoms with a displacement parameter equal to 1.2 (CH, CH₂) or 1.5 (CH₃) times that of the parent atom.

Computing details

Data collection: Kappa-CCD software (Nonius, 1998); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Sheldrick, 1999); software used to prepare material for publication: SHELXTL and PARST97 (Nardelli, 1995).

Figures

	Fig. 1. The title molecule with the atomic numbering scheme. H atoms have been omitted for clarity, except for those involved in hydrogen bonds, which are drawn as small spheres of arbitrary radii. Hydrogen bonds are shown as dashed lines. Displacement ellipsoids are drawn at the 30% probability level.
	Fig. 2. Arrangement of the molecules in the packing. H atoms have been omitted for clarity. Displacement ellipsoids are drawn at the 10% probability level.

(I)

Crystal data

C34H36O6	F(000) = 1152
Mr = 540.63	Dx = 1.309 Mg m^−3
Monoclinic, P21/n	Mo Kα radiation, λ = 0.71073 Å
a = 12.4311 (14) Å	Cell parameters from 20349 reflections
b = 8.4379 (5) Å	θ = 2.9–25.7°
c = 26.5719 (18) Å	µ = 0.09 mm^−1
β = 100.115 (4)°	T = 100 K
V = 2743.9 (4) Å^3	Needle, colourless
Z = 4	0.50 × 0.10 × 0.10 mm

Data collection

Nonius Kappa-CCD diffractometer	2825 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.084
Graphite monochromator	θmax = 25.7°, θmin = 2.9°
Detector resolution: 18 pixels mm^-1	h = 0→15
ϕ scans	k = 0→10
20349 measured reflections	l = −32→31
5116 independent reflections

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.077	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.188	H-atom parameters constrained
S = 0.97	w = 1/[σ^2(Fo^2) + (0.0537P)^2 + 5.702P] where P = (Fo^2 + 2Fc^2)/3
5116 reflections	(Δ/σ)max < 0.001
361 parameters	Δρmax = 0.39 e Å^−3
0 restraints	Δρmin = −0.35 e Å^−3

Special details

Experimental. crystal-to-detector distance 28 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. Structure solved by direct methods expanded subsequent Fourier-difference synthesis. All non-hydrogen atoms have been refined with anisotropic displacement parameters. The hydroxyl protons were found on the Fourier- difference map and introduced as riding atoms with an isotropic displacement parameter equal to 1.2 times that of the parent atom. All other hydrogen atoms were introduced at calculated positions as riding atoms with an isotropic displacement parameter equal to 1.2 (CH, CH2) or 1.5 (CH3) times that of the parent atom. 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 (Ų)

	x	y	z	Uiso*/Ueq
O1	−0.0900 (2)	0.2546 (3)	0.14626 (11)	0.0275 (7)
H1	−0.0966	0.3599	0.1448	0.033*
O2	0.0522 (2)	0.0106 (3)	0.18730 (11)	0.0257 (7)
O3	0.0590 (2)	0.2863 (3)	0.23849 (11)	0.0248 (7)
H3	0.0338	0.2144	0.2071	0.030*
O4	−0.0192 (2)	0.5967 (3)	0.24272 (11)	0.0281 (7)
H4	0.0055	0.5018	0.2298	0.034*
O5	−0.2582 (2)	0.5876 (3)	0.22940 (11)	0.0272 (7)
O6	−0.1673 (2)	0.5599 (3)	0.14428 (12)	0.0288 (7)
H6	−0.1577	0.5950	0.1769	0.035*
C1	−0.1523 (3)	0.2319 (5)	0.05425 (16)	0.0252 (9)
C2	−0.1049 (3)	0.1681 (5)	0.10160 (17)	0.0263 (10)
C3	−0.0764 (3)	0.0063 (5)	0.10672 (17)	0.0257 (10)
C4	−0.0911 (3)	−0.0868 (5)	0.06300 (17)	0.0312 (11)
H4B	−0.0716	−0.1932	0.0660	0.037*
C5	−0.1338 (3)	−0.0268 (5)	0.01502 (17)	0.0277 (10)
C6	−0.1646 (3)	0.1317 (5)	0.01158 (17)	0.0292 (10)
H6B	−0.1945	0.1728	−0.0203	0.035*
C7	−0.1478 (4)	−0.1313 (5)	−0.03199 (18)	0.0386 (12)
H7A	−0.1222	−0.2363	−0.0224	0.058*
H7B	−0.1064	−0.0885	−0.0561	0.058*
H7C	−0.2237	−0.1356	−0.0473	0.058*
C8	−0.0422 (4)	−0.0657 (5)	0.15819 (17)	0.0296 (10)
H8A	−0.1023	−0.0589	0.1770	0.035*
H8B	−0.0260	−0.1770	0.1542	0.035*
C9	0.0782 (3)	−0.0577 (5)	0.23744 (16)	0.0259 (10)
H9A	0.1131	−0.1597	0.2353	0.031*
H9B	0.0112	−0.0752	0.2507	0.031*
C10	0.1523 (3)	0.0472 (5)	0.27325 (17)	0.0268 (10)
C11	0.1362 (3)	0.2102 (5)	0.27419 (16)	0.0256 (10)
C12	0.1956 (3)	0.3050 (5)	0.31310 (17)	0.0262 (10)
C13	0.2738 (3)	0.2327 (5)	0.34948 (17)	0.0296 (10)
H13A	0.3132	0.2942	0.3754	0.036*
C14	0.2954 (3)	0.0703 (5)	0.34838 (17)	0.0283 (10)
C15	0.2327 (3)	−0.0199 (5)	0.31035 (17)	0.0279 (10)
H15A	0.2447	−0.1286	0.3096	0.033*
C16	0.3838 (4)	−0.0041 (6)	0.38782 (18)	0.0379 (12)
H16A	0.3871	−0.1158	0.3815	0.057*
H16B	0.3672	0.0129	0.4214	0.057*
H16C	0.4529	0.0435	0.3857	0.057*
C17	0.1682 (3)	0.4788 (5)	0.31557 (17)	0.0277 (10)
H17A	0.1719	0.5278	0.2829	0.033*
H17B	0.2221	0.5298	0.3413	0.033*
C18	0.0557 (3)	0.5053 (5)	0.32832 (17)	0.0270 (10)
C19	−0.0297 (4)	0.5698 (5)	0.29315 (16)	0.0263 (10)
C20	−0.1301 (3)	0.6102 (5)	0.30712 (17)	0.0265 (10)
C21	−0.1457 (3)	0.5698 (5)	0.35592 (16)	0.0269 (10)
H21A	−0.2113	0.5974	0.3659	0.032*
C22	−0.0676 (3)	0.4900 (5)	0.39054 (16)	0.0270 (10)
C23	0.0335 (3)	0.4631 (5)	0.37624 (16)	0.0266 (10)
H23A	0.0884	0.4150	0.3996	0.032*
C24	−0.0932 (4)	0.4303 (6)	0.44063 (17)	0.0359 (11)
H24A	−0.1663	0.4605	0.4436	0.054*
H24B	−0.0426	0.4756	0.4684	0.054*
H24C	−0.0870	0.3170	0.4418	0.054*
C25	−0.2168 (3)	0.6936 (5)	0.27060 (17)	0.0283 (10)
H25A	−0.2755	0.7261	0.2880	0.034*
H25B	−0.1866	0.7876	0.2573	0.034*
C26	−0.3427 (3)	0.6604 (5)	0.19319 (17)	0.0302 (10)
H26A	−0.3209	0.7666	0.1852	0.036*
H26B	−0.4093	0.6676	0.2073	0.036*
C27	−0.3616 (3)	0.5605 (5)	0.14559 (16)	0.0264 (10)
C28	−0.2736 (3)	0.5197 (5)	0.12179 (17)	0.0278 (10)
C29	−0.2876 (3)	0.4385 (5)	0.07560 (16)	0.0264 (10)
C30	−0.3926 (3)	0.3908 (5)	0.05462 (16)	0.0264 (10)
H30A	−0.4032	0.3357	0.0238	0.032*
C31	−0.4834 (3)	0.4217 (5)	0.07762 (17)	0.0283 (10)
C32	−0.4659 (4)	0.5090 (5)	0.12311 (17)	0.0308 (10)
H32A	−0.5251	0.5334	0.1388	0.037*
C33	−0.5957 (3)	0.3601 (5)	0.05614 (18)	0.0337 (11)
H33A	−0.5934	0.3034	0.0250	0.050*
H33B	−0.6457	0.4473	0.0492	0.050*
H33C	−0.6196	0.2901	0.0805	0.050*
C34	−0.1916 (3)	0.4026 (5)	0.04872 (17)	0.0287 (10)
H34A	−0.2129	0.4267	0.0126	0.034*
H34B	−0.1313	0.4719	0.0624	0.034*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0321 (17)	0.0211 (15)	0.0294 (18)	0.0000 (12)	0.0060 (14)	−0.0028 (12)
O2	0.0263 (16)	0.0241 (15)	0.0265 (17)	−0.0009 (12)	0.0039 (13)	0.0003 (12)
O3	0.0259 (16)	0.0229 (15)	0.0247 (17)	0.0006 (12)	0.0023 (13)	−0.0008 (12)
O4	0.0320 (17)	0.0261 (15)	0.0271 (17)	0.0012 (13)	0.0080 (14)	−0.0005 (12)
O5	0.0287 (16)	0.0230 (15)	0.0287 (17)	0.0027 (12)	0.0019 (13)	−0.0016 (12)
O6	0.0249 (16)	0.0276 (15)	0.0338 (18)	−0.0024 (12)	0.0046 (13)	−0.0042 (13)
C1	0.025 (2)	0.026 (2)	0.025 (2)	−0.0023 (18)	0.0057 (19)	0.0016 (18)
C2	0.023 (2)	0.030 (2)	0.028 (3)	−0.0022 (18)	0.0096 (19)	−0.0052 (19)
C3	0.021 (2)	0.023 (2)	0.034 (3)	−0.0021 (18)	0.0052 (19)	0.0006 (19)
C4	0.024 (2)	0.030 (2)	0.039 (3)	−0.0039 (19)	0.005 (2)	−0.008 (2)
C5	0.023 (2)	0.029 (2)	0.032 (3)	−0.0034 (18)	0.009 (2)	−0.0074 (19)
C6	0.021 (2)	0.038 (3)	0.028 (3)	−0.0039 (19)	0.0045 (19)	−0.001 (2)
C7	0.036 (3)	0.040 (3)	0.040 (3)	−0.007 (2)	0.007 (2)	−0.013 (2)
C8	0.029 (2)	0.024 (2)	0.035 (3)	−0.0025 (19)	0.004 (2)	−0.0018 (19)
C9	0.030 (2)	0.024 (2)	0.025 (2)	0.0004 (18)	0.0070 (19)	−0.0008 (18)
C10	0.028 (2)	0.025 (2)	0.031 (3)	0.0019 (18)	0.013 (2)	0.0017 (18)
C11	0.023 (2)	0.028 (2)	0.026 (2)	0.0043 (18)	0.0063 (19)	0.0027 (18)
C12	0.022 (2)	0.027 (2)	0.031 (3)	−0.0010 (18)	0.010 (2)	−0.0004 (18)
C13	0.025 (2)	0.033 (2)	0.030 (3)	−0.0036 (19)	0.005 (2)	−0.001 (2)
C14	0.020 (2)	0.036 (2)	0.031 (3)	0.0049 (18)	0.0087 (19)	0.006 (2)
C15	0.027 (2)	0.027 (2)	0.032 (3)	0.0048 (19)	0.011 (2)	0.0056 (19)
C16	0.036 (3)	0.041 (3)	0.035 (3)	0.006 (2)	0.001 (2)	0.006 (2)
C17	0.025 (2)	0.025 (2)	0.033 (3)	−0.0025 (18)	0.007 (2)	−0.0016 (18)
C18	0.028 (2)	0.020 (2)	0.033 (3)	−0.0011 (18)	0.007 (2)	−0.0013 (18)
C19	0.032 (2)	0.023 (2)	0.026 (2)	−0.0012 (18)	0.010 (2)	−0.0035 (18)
C20	0.025 (2)	0.019 (2)	0.034 (3)	−0.0039 (17)	0.003 (2)	−0.0026 (18)
C21	0.023 (2)	0.028 (2)	0.031 (3)	0.0007 (18)	0.0057 (19)	−0.0059 (19)
C22	0.031 (2)	0.029 (2)	0.022 (2)	−0.0054 (19)	0.008 (2)	−0.0091 (18)
C23	0.026 (2)	0.027 (2)	0.027 (2)	−0.0014 (18)	0.0045 (19)	−0.0032 (18)
C24	0.033 (3)	0.046 (3)	0.028 (3)	0.000 (2)	0.005 (2)	−0.003 (2)
C25	0.029 (2)	0.024 (2)	0.032 (3)	0.0040 (18)	0.005 (2)	−0.0038 (19)
C26	0.026 (2)	0.026 (2)	0.038 (3)	0.0097 (18)	0.006 (2)	0.0013 (19)
C27	0.025 (2)	0.026 (2)	0.028 (2)	0.0041 (18)	0.0046 (19)	0.0044 (18)
C28	0.025 (2)	0.027 (2)	0.031 (3)	0.0023 (18)	0.0053 (19)	0.0052 (19)
C29	0.026 (2)	0.027 (2)	0.026 (2)	0.0034 (18)	0.0037 (19)	0.0062 (18)
C30	0.032 (2)	0.023 (2)	0.024 (2)	0.0019 (18)	0.006 (2)	−0.0006 (18)
C31	0.026 (2)	0.027 (2)	0.030 (3)	0.0011 (18)	0.003 (2)	0.0061 (19)
C32	0.028 (2)	0.032 (2)	0.035 (3)	0.0063 (19)	0.014 (2)	0.008 (2)
C33	0.023 (2)	0.038 (3)	0.039 (3)	−0.001 (2)	0.004 (2)	0.002 (2)
C34	0.026 (2)	0.034 (2)	0.026 (2)	−0.0022 (19)	0.0018 (19)	−0.0005 (19)

Geometric parameters (Å, º)

O1—C2	1.378 (5)	C12—C17	1.510 (6)
O2—C9	1.435 (5)	C13—C14	1.398 (6)
O2—C8	1.439 (5)	C14—C15	1.390 (6)
O3—C11	1.383 (5)	C14—C16	1.515 (6)
O4—C19	1.388 (5)	C17—C18	1.513 (6)
O5—C26	1.432 (5)	C18—C23	1.396 (6)
O5—C25	1.437 (5)	C18—C19	1.395 (6)
O6—C28	1.393 (5)	C19—C20	1.405 (6)
C1—C2	1.400 (6)	C20—C21	1.387 (6)
C1—C6	1.401 (6)	C20—C25	1.493 (6)
C1—C34	1.520 (6)	C21—C22	1.389 (6)
C2—C3	1.411 (6)	C22—C23	1.394 (6)
C3—C4	1.388 (6)	C22—C24	1.508 (6)
C3—C8	1.489 (6)	C26—C27	1.503 (6)
C4—C5	1.388 (6)	C27—C32	1.398 (6)
C5—C6	1.389 (6)	C27—C28	1.400 (6)
C5—C7	1.514 (6)	C28—C29	1.390 (6)
C9—C10	1.493 (6)	C29—C30	1.387 (6)
C10—C11	1.391 (6)	C29—C34	1.524 (6)
C10—C15	1.395 (6)	C30—C31	1.399 (6)
C11—C12	1.409 (6)	C31—C32	1.400 (6)
C12—C13	1.386 (6)	C31—C33	1.505 (6)
C9—O2—C8	110.4 (3)	C12—C17—C18	112.2 (3)
C26—O5—C25	111.6 (3)	C23—C18—C19	117.5 (4)
C2—C1—C6	117.6 (4)	C23—C18—C17	120.3 (4)
C2—C1—C34	121.9 (4)	C19—C18—C17	122.2 (4)
C6—C1—C34	120.4 (4)	O4—C19—C18	121.4 (4)
O1—C2—C1	122.8 (4)	O4—C19—C20	117.0 (4)
O1—C2—C3	115.8 (4)	C18—C19—C20	121.6 (4)
C1—C2—C3	121.2 (4)	C21—C20—C19	117.6 (4)
C4—C3—C2	118.2 (4)	C21—C20—C25	121.3 (4)
C4—C3—C8	120.8 (4)	C19—C20—C25	121.0 (4)
C2—C3—C8	120.7 (4)	C20—C21—C22	122.8 (4)
C5—C4—C3	122.4 (4)	C21—C22—C23	117.2 (4)
C4—C5—C6	117.9 (4)	C21—C22—C24	121.0 (4)
C4—C5—C7	121.0 (4)	C23—C22—C24	121.8 (4)
C6—C5—C7	121.1 (4)	C18—C23—C22	122.6 (4)
C5—C6—C1	122.6 (4)	O5—C25—C20	108.8 (3)
O2—C8—C3	112.7 (3)	O5—C26—C27	108.3 (3)
O2—C9—C10	111.5 (3)	C32—C27—C28	118.0 (4)
C11—C10—C15	118.4 (4)	C32—C27—C26	122.0 (4)
C11—C10—C9	121.6 (4)	C28—C27—C26	119.9 (4)
C15—C10—C9	119.7 (4)	C29—C28—O6	117.5 (4)
O3—C11—C10	122.1 (4)	C29—C28—C27	122.3 (4)
O3—C11—C12	116.8 (3)	O6—C28—C27	120.3 (4)
C10—C11—C12	121.1 (4)	C28—C29—C30	117.4 (4)
C13—C12—C11	118.3 (4)	C28—C29—C34	121.7 (4)
C13—C12—C17	122.2 (4)	C30—C29—C34	120.9 (4)
C11—C12—C17	119.4 (4)	C29—C30—C31	123.1 (4)
C12—C13—C14	122.0 (4)	C30—C31—C32	117.4 (4)
C15—C14—C13	117.8 (4)	C30—C31—C33	122.4 (4)
C15—C14—C16	121.5 (4)	C32—C31—C33	120.2 (4)
C13—C14—C16	120.7 (4)	C31—C32—C27	121.6 (4)
C14—C15—C10	122.2 (4)	C1—C34—C29	114.1 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1···O6	0.89	1.90	2.747 (4)	157
O3—H3···O1	1.03	2.06	2.813 (4)	128
O3—H3···O2	1.03	1.82	2.689 (4)	139
O4—H4···O3	0.94	1.94	2.803 (4)	152
O6—H6···O4	0.90	2.23	2.939 (4)	135
O6—H6···O5	0.90	2.03	2.710 (4)	131