A new layered Ca–succinate coordination polymer

A new layered Ca–succinate coordination polymer, poly[μ₃-succinato-calcium(II)], [Ca(C₄H₅O₄)]_n, was synthesized by reaction of CaCl₂·2H₂O and succinic acid in an aqueous medium under hydro­thermal microwave conditions. The structure contains infinite layers of edge-sharing calcium penta­gonal–bipyramidal polyhedra forming six-membered rings connected through succinate ligands. Such an assembly of inorganic building units is unique for calcium metal–organic framework-type structures. Adjacent layers are packed into a final pseudo-three-dimensional structure through weak C—H...O hydrogen bonds.

S1. Comment

The design of new metal–organic framework (MOF) materials with useful structural properties by combining various metal cations with heteropolyfunctional organic linkers such as polycarboxylates, polyphosphonates or polyamines has become a great challenge in the last decade (Yaghi, 2004; Eddaoudi, 2007; Kuppler et al., 2009; Farrusseng et al., 2009). Calcium-based polycarboxylates can be used in bioapplications due to the nontoxic nature and biocompatability of calcium cations. However, the number of known Ca-based polycarboxylate structures is relatively low compared with more frequently investigated MOFs based on transition metal cations. Several structures are known to date with aromatic polycarboxylic ligands (Platers et al., 1997; Groeneman & Atwood, 1999; Zhu et al., 2005; Volkringer et al., 2007; Dale & Elsegood, 2003) and some with alkylpolycarboxylates (De Lill et al., 2005; Mathew & Takagi, 1995; Mathew et al., 1994). We report here the synthesis and structural characterization of a new layered Ca–succinate compound, the title compound, (I).

The crystal structure of (I) is built from infinite layers of edge-sharing calcium polyhedra. Each polyhedron shares three of its edges with neighbouring polyhedra, generating inorganic layers with six-membered rings (Fig. 1). Fig. 2 shows a view of adjacent inorganic layers connected via weak C—H···O hydrogen bonds along the a axis. Ca atoms in the centres of these polyhedra occupy two different crystallographic sites (Ca1 and Ca2) in general positions and both are coordinated to seven different O atoms, all coming from dicarboxylate groups. This sevenfold coordination defines slightly distorted pentagonal–bipyramidal polyhedra with Ca—O distances in the range 2.3027 (13)–2.5162 (12) Å (Table 1), which is similar to the coordination environment in some other known seven-coordinate Ca carboxylates (Williams et al., 2008; Mathew & Takagi, 1995; Mathew et al., 1994). The Ca1 atoms are coordinated by four O atoms in a monodentate bridging mode from three different succinate dianions (O1ⁱⁱ, O3ⁱⁱ, O4 and O6ⁱⁱⁱ) and by atom O2ⁱ in a monodentate manner (symmetry codes are as in Table 1). The remaining two O atoms (O7 and O8) are connected to Ca1 in chelating and bridging modes. The Ca2 atoms have similar O atom coordination modes. Four O atoms from three different succinate dianions are coordinated to Ca2 in a monodentate bridging mode (O1^v, O6, O7ⁱ and O8). Atom O5 coordinates in a monodentate fashion and the remaining two O atoms (O3ⁱⁱ and O4ⁱⁱ) in a chelating mode. Edge-sharing CaO₇ polyhedra forming six-membered rings are further connected to succinate species from both sides of the inorganic layers (Fig. 1). Structures with edge-sharing metal-based polyhedra forming layers of multi-membered rings are already known in manganese and magnesium glutarates (Vaidhyanathan et al., 2003; Hulvey & Cheetham, 2007) and cobalt succinate (Livage et al., 1998). Ca-based polyhedra in MOF-type structures show a low degree of crystal structure flexibility and are usually arranged through common edges or faces into one-dimensional chain-like inorganic units. The assembly of Ca-based polyhedral units into layers forming six-membered rings in the structure of (I) is, to our knowledge, unique and described in this contribution for the first time.

There are two symmetry-independent succinate ligands which are fully deprotonated, with C—O distances in the range 1.246 (2)–1.271 (2) Å. C—C bonds in the succinate chain are within the range of 1.518 (3)–1.524 (3) Å typical for distances between C atoms in aliphatic chains (Livage et al., 1998; Hulvey & Cheetham, 2007). The succinate ligands connect to the inorganic layers from both sides. Selected bond lengths and angles are shown in Table 1. Two dicarboxylate groups from two different succinate ligands chelate one Ca²⁺ centre and also bridge a second Ca²⁺ centre. The remaining two dicarboxylate anions bridge three Ca²⁺ centres in a monodentate manner with one O atom and in a bidentate manner with the second O atom. The coordination geometries of the Ca²⁺ centres and succinate ligands are shown in Fig. 3.

There are no classical hydrogen-bond donors (O—H···O) in (I) and consequently no such hydrogen bonds in the structure. However, two potential weak C—H···O contacts (C2—H21···O2 and C2—H21···O6) between metal-coordinated carboxylate O atoms from one layer and C-chain-bonded H atoms from a neighbouring layer connect the Ca–succinate units into a hydrogen-bonded network. Despite the relatively long C—H···O contacts between these layers [C2···O2 = 3.432 (2) Å and C2···O6 = 3.584 (2) Å], the C—H···O angles tend towards linearity [144 (2) and 140 (2)°], which indicates the existence of weak hydrogen-bonding interactions between neighbouring layers (Desiraju, 1991). There are also two weak intra-layer C—H···O interactions between coordinated O atoms and the H atoms bonded to atoms C3 and C7 (Table 2).

Related literature

For related literature, see: Dale & Elsegood (2003); De Lill, Bozzuto & Cahill (2005); Desiraju (1991); Eddaoudi (2007); Farrusseng et al. (2009); Groeneman & Atwood (1999); Hulvey & Cheetham (2007); Kuppler et al. (2009); Livage et al. (1998); Mathew & Takagi (1995); Mathew et al. (1994); Platers et al. (1997); Vaidhyanathan et al. (2003); Volkringer et al. (2007); Williams et al. (2008); Yaghi (2004); Zhu et al. (2005).

S2. Experimental

CaCl₂.2H₂O (0.68 g, 4.6 mmol) and succinic acid (0.82 g, 6.9 mmol) were dissolved in demineralized water (10 ml) prior to the addition of KOH (1.04 g, 18.5 mmol). The reaction mixture was placed in a Teflon-lined autoclave and hydrothermally treated by microwave heating [Power?] at 453 K for 3 h. The colourless X-ray quality crystals obtained were filtered off and washed repeatedly with distilled water. Elemental composition obtained by energy-dispersive X-ray analysis (EDAX) was found to be 25.3 wt.% Ca, 31.5 wt.% C and 43.2 wt.% O, which correspond to the theoretical values for Ca[O₂C(CH₂)₂CO₂] (25.7 wt% Ca, 30.8 wt.% C and 41.0 wt.% O).

S3. Refinement

All H atoms were located from a difference Fourier map and refined isotropically.

Computing details

Data collection: COLLECT (Bruker Nonius, 2000); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN (Otwinowski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2010); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures

	Fig. 1. A layer of edge-shared Ca pentagonal–bipyramidal polyhedra forming six-membered rings, viewed along the c axis, with succinate ligands shown in ball-and-stick representation.
	Fig. 2. A view of the Ca–succinate structure along the a axis, with the cell edges, showing two adjacent layers of edge-sharing calcium polyhedra connected through succinate anions. Adjacent layers are connected through C—H···O hydrogen bonds (dotted lines). Generic atom labels are shown. (In the electronic version of the paper, purple dots are Ca atoms, red dots are O atoms and black dots are C atoms.)
	Fig. 3. The coordination of the Ca^2+ ions in (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level. Dotted lines represent possible intra-layer C—H···O interactions. [Symmetry codes: (i) -x+1, y-1/2, -z+1/2; (ii) -x, y-1/2, -z+1/2; (iii) -x+1, y+1/2, -z+1/2; (iv) x-1, y, z; (v) x, y-1, z; (viii) x+1, y, z; (x) -x+2, y+1/2, -z+1/2.]

poly[µ₃-succinato-calcium(II)]

Crystal data

[Ca(C4H4O4)]	F(000) = 640
Mr = 156.15	Dx = 1.851 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 2705 reflections
a = 5.8860 (1) Å	θ = 1.0–27.5°
b = 11.2117 (3) Å	µ = 1.05 mm^−1
c = 17.0754 (4) Å	T = 293 K
β = 95.9450 (15)°	Plate-like, colourless
V = 1120.78 (4) Å^3	0.30 × 0.30 × 0.02 mm
Z = 8

Data collection

Nonius KappaCCD area-detector diffractometer	2567 independent reflections
Radiation source: fine-focus sealed tube	2096 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.014
ϕ and ω scans	θmax = 27.5°, θmin = 3.0°
Absorption correction: multi-scan (DENZO-SMN; Otwinowski & Minor, 1997)	h = −7→7
Tmin = 0.744, Tmax = 0.979	k = −14→14
4997 measured reflections	l = −22→22

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)] = 0.035	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.109	All H-atom parameters refined
S = 0.99	w = 1/[σ^2(Fo^2) + (0.0808P)^2 + 0.1895P] where P = (Fo^2 + 2Fc^2)/3
2567 reflections	(Δ/σ)max < 0.001
195 parameters	Δρmax = 0.95 e Å^−3
0 restraints	Δρmin = −0.56 e Å^−3

Special details

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 > 2σ(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
Ca1	0.21306 (5)	0.56909 (3)	0.185162 (19)	0.01560 (14)
Ca2	0.28839 (5)	0.27309 (3)	0.316014 (19)	0.01573 (14)
O1	0.1722 (2)	1.09158 (12)	0.37734 (8)	0.0241 (3)
O2	0.5089 (2)	0.99948 (13)	0.38864 (8)	0.0274 (3)
O3	−0.0738 (2)	0.87384 (12)	0.29840 (8)	0.0282 (3)
O4	0.0504 (2)	0.69623 (11)	0.27102 (7)	0.0205 (3)
O5	1.0192 (2)	0.34454 (13)	0.39387 (8)	0.0294 (3)
O6	0.6808 (2)	0.25373 (12)	0.37624 (7)	0.0225 (3)
O7	0.5521 (2)	0.64704 (11)	0.27198 (7)	0.0199 (3)
O8	0.4234 (2)	0.47090 (12)	0.30160 (8)	0.0276 (3)
C1	0.3024 (3)	1.00470 (15)	0.39902 (10)	0.0177 (4)
C2	0.2035 (3)	0.89929 (16)	0.43968 (10)	0.0201 (4)
C3	0.2142 (4)	0.78654 (17)	0.39078 (12)	0.0239 (4)
C4	0.0550 (3)	0.78576 (15)	0.31555 (10)	0.0173 (4)
C5	0.8109 (3)	0.33934 (15)	0.40094 (10)	0.0173 (3)
C6	0.7070 (3)	0.44431 (16)	0.44085 (10)	0.0193 (4)
C7	0.7159 (3)	0.55767 (16)	0.39201 (11)	0.0209 (4)
C8	0.5549 (3)	0.55807 (15)	0.31726 (10)	0.0174 (4)
H61	0.798 (4)	0.457 (2)	0.4890 (14)	0.029 (6)*
H62	0.553 (4)	0.423 (2)	0.4489 (12)	0.032 (6)*
H71	0.690 (4)	0.629 (2)	0.4236 (14)	0.031 (6)*
H21	0.297 (3)	0.8905 (17)	0.4894 (12)	0.015 (5)*
H31	0.357 (5)	0.771 (3)	0.3772 (16)	0.051 (9)*
H22	0.055 (4)	0.917 (2)	0.4484 (12)	0.026 (5)*
H32	0.173 (4)	0.716 (2)	0.4210 (15)	0.037 (6)*
H72	0.863 (5)	0.573 (2)	0.3799 (14)	0.039 (7)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Ca1	0.0120 (2)	0.0131 (2)	0.0215 (2)	−0.00025 (11)	0.00086 (14)	0.00022 (12)
Ca2	0.0122 (2)	0.0130 (2)	0.0219 (2)	−0.00021 (11)	0.00093 (15)	−0.00055 (12)
O1	0.0212 (7)	0.0174 (6)	0.0324 (7)	−0.0011 (5)	−0.0026 (5)	0.0047 (5)
O2	0.0187 (7)	0.0292 (7)	0.0351 (7)	−0.0021 (5)	0.0070 (6)	0.0049 (6)
O3	0.0287 (7)	0.0195 (7)	0.0335 (7)	0.0091 (5)	−0.0112 (6)	−0.0050 (6)
O4	0.0183 (6)	0.0173 (6)	0.0256 (6)	0.0018 (5)	0.0006 (5)	−0.0041 (5)
O5	0.0192 (7)	0.0285 (7)	0.0416 (8)	0.0006 (5)	0.0087 (6)	−0.0075 (6)
O6	0.0202 (7)	0.0165 (6)	0.0299 (7)	0.0014 (5)	−0.0012 (5)	−0.0039 (5)
O7	0.0178 (6)	0.0168 (6)	0.0248 (6)	−0.0013 (5)	0.0006 (5)	0.0048 (5)
O8	0.0266 (7)	0.0200 (7)	0.0336 (7)	−0.0087 (5)	−0.0092 (6)	0.0044 (5)
C1	0.0178 (9)	0.0180 (8)	0.0169 (8)	−0.0025 (7)	−0.0002 (6)	−0.0020 (7)
C2	0.0234 (9)	0.0192 (9)	0.0173 (8)	−0.0038 (7)	0.0012 (7)	0.0013 (7)
C3	0.0255 (10)	0.0166 (9)	0.0273 (10)	0.0004 (7)	−0.0082 (8)	0.0002 (7)
C4	0.0142 (8)	0.0154 (8)	0.0220 (9)	−0.0007 (6)	0.0010 (7)	0.0013 (6)
C5	0.0164 (8)	0.0158 (8)	0.0194 (8)	0.0029 (6)	0.0004 (6)	−0.0006 (7)
C6	0.0205 (9)	0.0184 (8)	0.0188 (8)	0.0019 (7)	0.0016 (7)	−0.0007 (7)
C7	0.0217 (10)	0.0143 (9)	0.0256 (9)	−0.0013 (7)	−0.0028 (7)	0.0011 (7)
C8	0.0141 (8)	0.0142 (8)	0.0236 (9)	0.0004 (6)	0.0004 (6)	−0.0008 (6)

Geometric parameters (Å, º)

Ca1—O2^i	2.3027 (13)	O4—C4	1.258 (2)
Ca1—O4	2.3215 (12)	O4—Ca2^vi	2.5126 (12)
Ca1—O3^ii	2.3646 (13)	O5—C5	1.245 (2)
Ca1—O1^ii	2.4171 (13)	O5—Ca2^viii	2.3144 (13)
Ca1—O6^iii	2.4312 (13)	O6—C5	1.273 (2)
Ca1—O8	2.4876 (13)	O6—Ca1^i	2.4312 (13)
Ca1—O7	2.5162 (12)	O7—C8	1.261 (2)
Ca1—C8	2.8655 (18)	O7—Ca2^iii	2.3300 (12)
Ca2—O5^iv	2.3144 (13)	O8—C8	1.258 (2)
Ca2—O7^i	2.3300 (12)	C1—C2	1.517 (2)
Ca2—O8	2.3774 (13)	C2—C3	1.520 (3)
Ca2—O1^v	2.4197 (13)	C2—H21	0.97 (2)
Ca2—O6	2.4387 (13)	C2—H22	0.93 (2)
Ca2—O3^ii	2.4855 (13)	C3—C4	1.510 (3)
Ca2—O4^ii	2.5126 (13)	C3—H31	0.92 (3)
Ca2—C4^ii	2.8654 (18)	C3—H32	0.99 (3)
O1—C1	1.271 (2)	C4—Ca2^vi	2.8654 (18)
O1—Ca1^vi	2.4171 (13)	C5—C6	1.520 (2)
O1—Ca2^vii	2.4197 (13)	C6—C7	1.524 (2)
O2—C1	1.248 (2)	C6—H61	0.94 (2)
O2—Ca1^iii	2.3027 (13)	C6—H62	0.96 (2)
O3—C4	1.260 (2)	C7—C8	1.509 (2)
O3—Ca1^vi	2.3646 (13)	C7—H71	0.98 (2)
O3—Ca2^vi	2.4855 (13)	C7—H72	0.93 (3)
O2^i—Ca1—O4	156.46 (5)	C1—O2—Ca1^iii	145.06 (12)
O2^i—Ca1—O3^ii	91.48 (5)	C4—O3—Ca1^vi	154.85 (12)
O4—Ca1—O3^ii	108.83 (5)	C4—O3—Ca2^vi	94.07 (10)
O2^i—Ca1—O1^ii	118.75 (5)	Ca1^vi—O3—Ca2^vi	111.09 (5)
O4—Ca1—O1^ii	77.61 (4)	C4—O4—Ca1	152.55 (11)
O3^ii—Ca1—O1^ii	80.10 (5)	C4—O4—Ca2^vi	92.86 (10)
O2^i—Ca1—O6^iii	79.84 (5)	Ca1—O4—Ca2^vi	101.01 (5)
O4—Ca1—O6^iii	83.73 (4)	C5—O5—Ca2^viii	141.15 (12)
O3^ii—Ca1—O6^iii	161.30 (5)	C5—O6—Ca1^i	127.77 (11)
O1^ii—Ca1—O6^iii	89.54 (5)	C5—O6—Ca2	125.73 (11)
O2^i—Ca1—O8	87.96 (5)	Ca1^i—O6—Ca2	99.69 (5)
O4—Ca1—O8	88.32 (5)	C8—O7—Ca2^iii	153.47 (11)
O3^ii—Ca1—O8	69.24 (4)	C8—O7—Ca1	92.61 (10)
O1^ii—Ca1—O8	139.96 (5)	Ca2^iii—O7—Ca1	100.29 (4)
O6^iii—Ca1—O8	126.34 (4)	C8—O8—Ca2	155.18 (12)
O2^i—Ca1—O7	82.82 (5)	C8—O8—Ca1	94.04 (11)
O4—Ca1—O7	76.61 (4)	Ca2—O8—Ca1	110.58 (5)
O3^ii—Ca1—O7	121.01 (4)	O2—C1—O1	124.18 (16)
O1^ii—Ca1—O7	150.98 (4)	O2—C1—C2	117.01 (16)
O6^iii—Ca1—O7	74.62 (4)	O1—C1—C2	118.81 (15)
O8—Ca1—O7	51.98 (4)	C1—C2—C3	110.89 (15)
O2^i—Ca1—C8	86.30 (5)	C1—C2—H21	105.6 (12)
O4—Ca1—C8	80.28 (5)	C3—C2—H21	110.0 (12)
O3^ii—Ca1—C8	95.19 (5)	C1—C2—H22	108.3 (14)
O1^ii—Ca1—C8	154.43 (5)	C3—C2—H22	111.2 (15)
O6^iii—Ca1—C8	100.68 (5)	H21—C2—H22	110.6 (18)
O8—Ca1—C8	25.97 (5)	C4—C3—C2	114.50 (15)
O7—Ca1—C8	26.08 (4)	C4—C3—H31	107.4 (17)
O5^iv—Ca2—O7^i	157.82 (5)	C2—C3—H31	112.5 (18)
O5^iv—Ca2—O8	89.57 (5)	C4—C3—H32	105.8 (15)
O7^i—Ca2—O8	109.74 (5)	C2—C3—H32	110.7 (15)
O5^iv—Ca2—O1^v	78.55 (5)	H31—C3—H32	105 (2)
O7^i—Ca2—O1^v	85.40 (4)	O4—C4—O3	120.67 (16)
O8—Ca2—O1^v	160.39 (5)	O4—C4—C3	119.44 (15)
O5^iv—Ca2—O6	117.61 (5)	O3—C4—C3	119.89 (16)
O7^i—Ca2—O6	77.92 (4)	O4—C4—Ca2^vi	61.14 (9)
O8—Ca2—O6	79.31 (5)	O3—C4—Ca2^vi	59.91 (9)
O1^v—Ca2—O6	92.32 (4)	C3—C4—Ca2^vi	173.06 (13)
O5^iv—Ca2—O3^ii	88.38 (5)	O5—C5—O6	124.61 (16)
O7^i—Ca2—O3^ii	88.55 (5)	O5—C5—C6	116.96 (16)
O8—Ca2—O3^ii	69.07 (4)	O6—C5—C6	118.43 (15)
O1^v—Ca2—O3^ii	125.38 (4)	C5—C6—C7	111.23 (14)
O6—Ca2—O3^ii	138.94 (5)	C5—C6—H61	106.7 (14)
O5^iv—Ca2—O4^ii	84.83 (5)	C7—C6—H61	107.8 (14)
O7^i—Ca2—O4^ii	76.03 (4)	C5—C6—H62	107.8 (14)
O8—Ca2—O4^ii	120.80 (4)	C7—C6—H62	111.6 (14)
O1^v—Ca2—O4^ii	74.04 (4)	H61—C6—H62	111.6 (19)
O6—Ca2—O4^ii	151.38 (4)	C8—C7—C6	114.24 (15)
O3^ii—Ca2—O4^ii	51.92 (4)	C8—C7—H71	109.8 (13)
O5^iv—Ca2—C4^ii	87.94 (5)	C6—C7—H71	111.3 (13)
O7^i—Ca2—C4^ii	79.80 (5)	C8—C7—H72	109.4 (15)
O8—Ca2—C4^ii	95.09 (5)	C6—C7—H72	111.6 (15)
O1^v—Ca2—C4^ii	99.96 (5)	H71—C7—H72	100 (2)
O6—Ca2—C4^ii	153.55 (5)	O8—C8—O7	121.04 (17)
O3^ii—Ca2—C4^ii	26.03 (4)	O8—C8—C7	119.76 (16)
O4^ii—Ca2—C4^ii	26.00 (4)	O7—C8—C7	119.19 (15)
C1—O1—Ca1^vi	123.96 (11)	O8—C8—Ca1	59.99 (9)
C1—O1—Ca2^vii	125.57 (11)	O7—C8—Ca1	61.31 (9)
Ca1^vi—O1—Ca2^vii	101.01 (5)	C7—C8—Ca1	173.89 (13)

Symmetry codes: (i) −x+1, y−1/2, −z+1/2; (ii) −x, y−1/2, −z+1/2; (iii) −x+1, y+1/2, −z+1/2; (iv) x−1, y, z; (v) x, y−1, z; (vi) −x, y+1/2, −z+1/2; (vii) x, y+1, z; (viii) x+1, y, z.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
C3—H31···O7	0.91 (4)	2.63 (3)	3.370 (3)	139 (3)
C2—H21···O2^ix	0.97 (2)	2.59 (2)	3.424 (2)	144 (2)
C2—H21···O6^x	0.97 (2)	2.79 (2)	3.584 (2)	140 (2)
C7—H72···O4^viii	0.92 (3)	2.67 (3)	3.376 (3)	135 (2)

Symmetry codes: (viii) x+1, y, z; (ix) −x+1, −y+2, −z+1; (x) −x+1, −y+1, −z+1.