Crystal structure of tris-[4-(di-methyl-amino)-pyridinium] tris-(oxalato-κ(2) O,O')chromate(III) tetra-hydrate.

In the title hybrid salt, (C7H11N2)3[Cr(C2O4)3]·4H2O, the central Cr(III) ion of the complex anion (point group symmetry 2) is coordinated by six O atoms from three chelating oxalate(2-) ligands in a slightly distorted octa-hedral coordination sphere. The Cr-O bond lengths vary from 1.9577 (11) to 1.9804 (11) Å, while the chelate O-Cr-O angles range from 82.11 (6) to 93.41 (5)°. The 4-(di-methyl-amino)-pyridinium cations (one situated in a general position and one on a twofold rotation axis) are protonated at the pyridine N atoms. In the crystal, N-H⋯O and O-H⋯O hydrogen bonds link the cations and anions into a three-dimensional network. π-π inter-actions between the pyridine rings of adjacent cations provide additional stabilization of the crystal packing, with the closest centroid-to-centroid distances being 3.541 (1) and 3.575 (1) Å.

Chemical context

The coordination chemistry of oxalate (C2O4 2−) continues to receive considerable attention because of the ability of this ion to act as a remarkably flexible ligand system in complexations with a wide range of metal ions (Martin et al., 2007 ▸). Over the last decade, Bélombé and coworkers (Bélombé et al., 2003 ▸) prepared a novel barium-oxalatochromate(III), {Ba6(H2O)17[Cr(ox)3]4}·7H2O, and demonstrated the use of this complex as a suitable precursor for the synthesis of multi-functional crystalline materials (Bélombé et al., 2009 ▸; Mbiangué et al., 2012 ▸). Moreover, this complex has received much attention in the field of materials science for its use as a convenient route for the preparation of technologically important metallic composite oxides (Neo et al., 2006 ▸). As part of our ongoing research program, we have now combined this versatile barium-oxalatochromate(III) complex with 4-(di­methyl­amino)­pyridinium oxalate to isolate the organic–inorganic hybrid salt, (C7H11N2)3[Cr(C2O4)3]·4H2O.

Structural commentary

The mol­ecular components of the title compound are shown in Fig. 1 ▸. The asymmetric unit contains one and a half 4-(di­methyl­amino)­pyridinium cations, one half of the tris(oxalato)chromate(III) complex anion and two lattice water mol­ecules. The entities are completed by application of twofold rotation symmetry. The central CrIII ion of the complex anion is coordinated by six O atoms from three chelating oxalato(2−) ligands in a slightly distorted (2 + 2 + 2) octa­hedral coordination sphere. The chelate O—Cr—O angles range from 82.11 (6) to 93.41 (5)°. The Cr—O bond lengths vary from 1.9577 (11) to 1.9804 (11) Å and are similar to those found in the guanidinium tris­(oxalato)chromate(III) salt (Golič & Bulc, 1988 ▸). Bond lengths and angles in the organic cations, [C7H11N2]+, are in agreement with those found in salts with the same cationic entity (Nenwa et al., 2010 ▸; Ghouili et al., 2010 ▸; Benslimane et al., 2012 ▸; Ben Nasr et al., 2015 ▸).

Figure 1

The mol­ecular components of the title compound. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen bonds are shown as dashed lines. [Symmetry codes: (i) 1 − x, y,  − z; (ii) − + x,  − y, − + z; (iii)  − x,  − y, 1 − z; (iv)  − x, − + y,  − z; (v) − + x, − + y, z.]

Supra­molecular features

In the title compound, the crystal packing is stabilized by a network of inter­molecular N—H⋯O and O—H⋯O hydrogen bonds linking the coordination octa­hedra, 4-(di­methyl­amino)­pyridinium cations and lattice water mol­ecules (Table 1 ▸, Fig. 2 ▸). In addition, π–π stacking inter­actions [centroid-to-centroid distances of 3.541 (1) and 3.575 (1) Å] between the pyridine rings contribute to the stabilization of the three-dimensional network (Fig. 3 ▸).

Table 1

Hydrogen-bond geometry (, )

DHA	DH	HA	D A	DHA
N1H1O8W i	0.91(2)	1.84(2)	2.702(2)	157.8(19)
N3H3O6ii	0.92(4)	2.12(3)	2.879(3)	139(1)
N3H3O6iii	0.92(4)	2.12(3)	2.879(3)	139(1)
O7WH7WAO4iv	0.83(1)	1.99(1)	2.819(2)	178(3)
O7WH7WBO1v	0.82(1)	2.12(1)	2.9079(19)	161(3)
O8WH8WAO7W	0.81(1)	1.95(1)	2.7578(19)	172(3)
O8WH8WBO6vi	0.82(1)	1.99(1)	2.8007(19)	175(3)

Symmetry codes: (i) ; (ii) ; (iii) ; (iv) ; (v) ; (vi) .

Figure 2

Projection on the ab plane of the crystal structure of the title compound. Hydrogen bonds are shown as dashed lines.

Figure 3

π–π stacking inter­actions (dashed lines) between adjacent organic cations in the title compound.

Synthesis and crystallization

The title compound was obtained by reaction of an aqueous solution of the freshly prepared barium-oxalatochromate(III) salt {Ba6(H2O)17[Cr(C2O4)3]4}·7H2O (1 mmol, 2.536 g), with an aqueous solution of 4-(di­methyl­amino)­pyridine (12 mmol, 1.464 g) and oxalic acid (6 mmol, 0.756 g). The mixture was stirred at 333 K for about 30 minutes and then cooled to room temperature and filtered. The title compound crystallized by slow evaporation of the solvent at room temperature in form of light-violet crystals with dimensions up to 3 mm within a few weeks.

Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2 ▸. H atoms bonded to C atoms were positioned geometrically and allowed to ride on their parent atoms with C—H = 0.93 Å and U iso(H) = 1.2U eq(C) for aromatic and 0.96 Å and U iso(H) = 1.5U eq(C) for methyl H atoms. H atoms of water mol­ecules as well as those bonded to N atoms were located from a difference Fourier map. Water H atoms were refined with soft restraints on O—H and H⋯H distances [O—H = 0.82 (1) Å and H⋯H = 1.30 (2) Å] and U iso(H) = 1.5U eq(O) whereas H atoms bonded to N atoms were refined freely.

Table 2

Experimental details

Crystal data
Chemical formula	(C7H11N2)3[Cr(C3O4)3]4H2O
M r	757.66
Crystal system, space group	Monoclinic, C2/c
Temperature (K)	296
a, b, c ()	19.1141(5), 16.7537(4), 11.0053(2)
()	98.803(1)
V (3)	3482.73(14)
Z	4
Radiation type	Mo K
(mm1)	0.41
Crystal size (mm)	0.58 0.21 0.14
Data collection
Diffractometer	Bruker APEXII CCD
Absorption correction	Multi-scan (SADABS; Krause et al., 2015 ▸)
T min, T max	0.708, 0.746
No. of measured, independent and observed [I > 2(I)] reflections	56955, 5322, 3757
R int	0.038
(sin /)max (1)	0.714
Refinement
R[F 2 > 2(F 2)], wR(F 2), S	0.038, 0.120, 1.03
No. of reflections	5322
No. of parameters	249
No. of restraints	6
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
max, min (e 3)	0.23, 0.42

Computer programs: SAINT and APEX2 (Bruker, 2014 ▸), SHELXS97 (Sheldrick, 2008 ▸), SHELXL2014 (Sheldrick, 2015 ▸), OLEX2 (Dolomanov et al., 2009 ▸), publCIF (Westrip, 2010 ▸) and PLATON (Spek, 2009 ▸).

Crystal structure: contains datablock(s) I. DOI: 10.1107/S2056989015020113/wm5230sup1.cif

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989015020113/wm5230Isup2.hkl

CCDC reference: 1400490

Additional supporting information: crystallographic information; 3D view; checkCIF report

(C7H11N2)3[Cr(C3O4)3]·4H2O	F(000) = 1588
Mr = 757.66	Dx = 1.445 Mg m−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 19.1141 (5) Å	Cell parameters from 9987 reflections
b = 16.7537 (4) Å	θ = 2.4–27.8°
c = 11.0053 (2) Å	µ = 0.41 mm−1
β = 98.803 (1)°	T = 296 K
V = 3482.73 (14) Å3	Prism, violet
Z = 4	0.58 × 0.21 × 0.14 mm

Bruker APEXII CCD diffractometer	3757 reflections with I > 2σ(I)
Radiation source: sealed X-ray tube	Rint = 0.038
φ and ω scans	θmax = 30.5°, θmin = 2.6°
Absorption correction: multi-scan (SADABS; Krause et al., 2015)	h = −27→27
Tmin = 0.708, Tmax = 0.746	k = −23→23
56955 measured reflections	l = −15→15
5322 independent reflections

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: mixed
wR(F2) = 0.120	H atoms treated by a mixture of independent and constrained refinement
S = 1.03	w = 1/[σ2(Fo2) + (0.056P)2 + 1.554P] where P = (Fo2 + 2Fc2)/3
5322 reflections	(Δ/σ)max = 0.001
249 parameters	Δρmax = 0.23 e Å−3
6 restraints	Δρmin = −0.42 e Å−3

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.

	x	y	z	Uiso*/Ueq
Cr1	0.5000	0.25122 (2)	0.2500	0.04246 (11)
O2	0.44865 (6)	0.33279 (7)	0.32829 (9)	0.0502 (3)
O1	0.41659 (6)	0.25871 (7)	0.12056 (10)	0.0521 (3)
O5	0.45866 (6)	0.16208 (7)	0.33354 (10)	0.0522 (3)
O7W	0.82663 (8)	0.36686 (8)	0.49953 (15)	0.0698 (4)
O6	0.45686 (8)	0.02935 (8)	0.34038 (13)	0.0695 (4)
O3	0.35256 (8)	0.40942 (8)	0.29279 (12)	0.0714 (4)
N2	0.28924 (8)	0.40160 (8)	0.65828 (12)	0.0507 (3)
O8W	0.87475 (9)	0.52183 (8)	0.53015 (16)	0.0762 (4)
N1	0.33363 (7)	0.16521 (9)	0.60672 (13)	0.0499 (3)
O4	0.31735 (7)	0.32756 (9)	0.06984 (14)	0.0767 (4)
N3	0.5000	0.87873 (15)	0.2500	0.0615 (5)
C6	0.30440 (7)	0.32468 (9)	0.64377 (12)	0.0405 (3)
N4	0.5000	0.63400 (15)	0.2500	0.0730 (7)
C1	0.39125 (9)	0.35760 (9)	0.26335 (14)	0.0475 (3)
C7	0.34073 (8)	0.29953 (10)	0.54716 (12)	0.0442 (3)
H7	0.3556	0.3370	0.4943	0.053*
C2	0.37147 (9)	0.31285 (10)	0.13931 (15)	0.0496 (4)
C5	0.28590 (9)	0.26379 (10)	0.72219 (14)	0.0483 (4)
H5	0.2636	0.2770	0.7888	0.058*
C3	0.47543 (8)	0.09271 (10)	0.30033 (14)	0.0486 (4)
C4	0.30043 (9)	0.18699 (11)	0.70089 (14)	0.0521 (4)
H4	0.2872	0.1478	0.7527	0.063*
C12	0.5000	0.71391 (15)	0.2500	0.0505 (5)
C8	0.35377 (8)	0.22127 (10)	0.53192 (14)	0.0476 (3)
H8	0.3773	0.2057	0.4679	0.057*
C10	0.30788 (12)	0.46256 (11)	0.57456 (17)	0.0626 (5)
H10A	0.3583	0.4633	0.5769	0.094*
H10B	0.2924	0.5138	0.5991	0.094*
H10C	0.2853	0.4508	0.4925	0.094*
C13	0.47586 (10)	0.75888 (12)	0.34435 (16)	0.0563 (4)
H13	0.4593	0.7330	0.4091	0.068*
C14	0.47685 (9)	0.83913 (12)	0.34033 (17)	0.0608 (4)
H14	0.4608	0.8678	0.4030	0.073*
C9	0.25007 (13)	0.42746 (13)	0.75514 (19)	0.0741 (6)
H9A	0.2037	0.4041	0.7419	0.111*
H9B	0.2460	0.4846	0.7537	0.111*
H9C	0.2748	0.4108	0.8336	0.111*
C11	0.47408 (17)	0.58935 (16)	0.3474 (3)	0.1074 (10)
H11A	0.5028	0.6012	0.4247	0.161*
H11B	0.4764	0.5332	0.3310	0.161*
H11C	0.4259	0.6041	0.3509	0.161*
H3	0.5000	0.934 (2)	0.2500	0.091 (11)*
H7WA	0.7843 (7)	0.3544 (19)	0.481 (3)	0.136*
H8WA	0.8595 (16)	0.4767 (9)	0.528 (3)	0.136*
H8WB	0.8988 (14)	0.5268 (17)	0.475 (2)	0.136*
H7WB	0.8432 (14)	0.3280 (13)	0.540 (3)	0.136*
H1	0.3406 (11)	0.1122 (13)	0.5955 (18)	0.068 (6)*

	U11	U22	U33	U12	U13	U23
Cr1	0.04232 (19)	0.0513 (2)	0.03681 (16)	0.000	0.01578 (13)	0.000
O2	0.0557 (6)	0.0565 (7)	0.0411 (5)	0.0033 (5)	0.0164 (5)	−0.0054 (4)
O1	0.0505 (6)	0.0617 (7)	0.0445 (6)	−0.0005 (5)	0.0087 (5)	−0.0094 (5)
O5	0.0572 (7)	0.0538 (6)	0.0530 (6)	−0.0008 (5)	0.0318 (5)	−0.0011 (5)
O7W	0.0775 (9)	0.0497 (7)	0.0849 (10)	−0.0032 (7)	0.0211 (8)	−0.0005 (7)
O6	0.0851 (9)	0.0556 (7)	0.0795 (9)	−0.0022 (7)	0.0499 (8)	0.0054 (6)
O3	0.0916 (10)	0.0639 (8)	0.0653 (8)	0.0297 (7)	0.0330 (7)	0.0100 (6)
N2	0.0646 (8)	0.0478 (7)	0.0431 (6)	−0.0014 (6)	0.0191 (6)	−0.0055 (5)
O8W	0.0914 (11)	0.0531 (8)	0.0954 (11)	−0.0067 (7)	0.0501 (9)	−0.0132 (7)
N1	0.0509 (7)	0.0481 (8)	0.0498 (7)	0.0025 (6)	0.0041 (6)	−0.0044 (6)
O4	0.0598 (8)	0.0853 (10)	0.0794 (9)	0.0068 (7)	−0.0076 (7)	0.0037 (8)
N3	0.0568 (12)	0.0558 (13)	0.0701 (14)	0.000	0.0036 (10)	0.000
C6	0.0399 (7)	0.0492 (8)	0.0323 (6)	−0.0036 (6)	0.0057 (5)	−0.0039 (5)
N4	0.0845 (17)	0.0570 (13)	0.0703 (14)	0.000	−0.0111 (12)	0.000
C1	0.0565 (9)	0.0447 (8)	0.0467 (8)	0.0018 (7)	0.0250 (7)	0.0078 (6)
C7	0.0462 (8)	0.0530 (8)	0.0351 (6)	−0.0040 (6)	0.0123 (6)	−0.0008 (6)
C2	0.0469 (8)	0.0526 (9)	0.0512 (8)	−0.0051 (7)	0.0132 (7)	0.0065 (7)
C5	0.0542 (9)	0.0568 (9)	0.0363 (7)	−0.0040 (7)	0.0150 (6)	−0.0003 (6)
C3	0.0462 (8)	0.0569 (9)	0.0469 (8)	−0.0014 (7)	0.0205 (6)	0.0010 (7)
C4	0.0598 (10)	0.0540 (9)	0.0431 (8)	−0.0056 (7)	0.0098 (7)	0.0052 (7)
C12	0.0461 (12)	0.0573 (14)	0.0448 (11)	0.000	−0.0033 (9)	0.000
C8	0.0435 (8)	0.0603 (9)	0.0401 (7)	0.0017 (7)	0.0097 (6)	−0.0075 (6)
C10	0.0877 (14)	0.0462 (9)	0.0567 (10)	−0.0061 (9)	0.0197 (9)	−0.0016 (7)
C13	0.0509 (9)	0.0763 (13)	0.0430 (8)	−0.0002 (8)	0.0113 (7)	0.0062 (7)
C14	0.0546 (10)	0.0712 (12)	0.0572 (10)	0.0095 (9)	0.0107 (8)	−0.0094 (8)
C9	0.1006 (16)	0.0638 (12)	0.0665 (11)	0.0046 (11)	0.0406 (11)	−0.0154 (9)
C11	0.127 (2)	0.0759 (16)	0.108 (2)	−0.0233 (15)	−0.0179 (17)	0.0327 (14)

Cr1—O2i	1.9577 (11)	C6—C5	1.416 (2)
Cr1—O2	1.9577 (11)	N4—C12	1.339 (3)
Cr1—O1i	1.9728 (12)	N4—C11	1.455 (3)
Cr1—O1	1.9728 (12)	N4—C11i	1.455 (3)
Cr1—O5i	1.9804 (11)	C1—C2	1.553 (2)
Cr1—O5	1.9804 (11)	C7—H7	0.9300
O2—C1	1.2834 (19)	C7—C8	1.350 (2)
O1—C2	1.290 (2)	C5—H5	0.9300
O5—C3	1.274 (2)	C5—C4	1.344 (2)
O7W—H7WA	0.830 (10)	C3—C3i	1.558 (3)
O7W—H7WB	0.822 (10)	C4—H4	0.9300
O6—C3	1.223 (2)	C12—C13i	1.416 (2)
O3—C1	1.2162 (19)	C12—C13	1.416 (2)
N2—C6	1.336 (2)	C8—H8	0.9300
N2—C10	1.456 (2)	C10—H10A	0.9600
N2—C9	1.459 (2)	C10—H10B	0.9600
O8W—H8WA	0.810 (10)	C10—H10C	0.9600
O8W—H8WB	0.818 (10)	C13—H13	0.9300
N1—C4	1.346 (2)	C13—C14	1.345 (3)
N1—C8	1.343 (2)	C14—H14	0.9300
N1—H1	0.91 (2)	C9—H9A	0.9600
O4—C2	1.214 (2)	C9—H9B	0.9600
N3—C14i	1.326 (2)	C9—H9C	0.9600
N3—C14	1.326 (2)	C11—H11A	0.9600
N3—H3	0.92 (4)	C11—H11B	0.9600
C6—C7	1.4200 (19)	C11—H11C	0.9600
O2i—Cr1—O2	91.45 (7)	O4—C2—O1	124.63 (17)
O2—Cr1—O1	82.48 (5)	O4—C2—C1	121.68 (16)
O2—Cr1—O1i	92.41 (5)	C6—C5—H5	119.8
O2i—Cr1—O1	92.41 (5)	C4—C5—C6	120.39 (15)
O2i—Cr1—O1i	82.47 (5)	C4—C5—H5	119.8
O2—Cr1—O5i	173.35 (5)	O5—C3—C3i	114.17 (8)
O2—Cr1—O5	93.41 (5)	O6—C3—O5	126.08 (14)
O2i—Cr1—O5	173.35 (5)	O6—C3—C3i	119.75 (9)
O2i—Cr1—O5i	93.41 (5)	N1—C4—H4	119.1
O1—Cr1—O1i	172.70 (7)	C5—C4—N1	121.88 (15)
O1—Cr1—O5i	92.78 (5)	C5—C4—H4	119.1
O1i—Cr1—O5	92.79 (5)	N4—C12—C13	122.15 (11)
O1—Cr1—O5	92.72 (5)	N4—C12—C13i	122.15 (11)
O1i—Cr1—O5i	92.72 (5)	C13—C12—C13i	115.7 (2)
O5i—Cr1—O5	82.11 (6)	N1—C8—C7	121.82 (14)
C1—O2—Cr1	115.12 (10)	N1—C8—H8	119.1
C2—O1—Cr1	114.55 (10)	C7—C8—H8	119.1
C3—O5—Cr1	114.77 (9)	N2—C10—H10A	109.5
H7WA—O7W—H7WB	102 (2)	N2—C10—H10B	109.5
C6—N2—C10	121.50 (13)	N2—C10—H10C	109.5
C6—N2—C9	121.25 (15)	H10A—C10—H10B	109.5
C10—N2—C9	117.18 (15)	H10A—C10—H10C	109.5
H8WA—O8W—H8WB	108 (2)	H10B—C10—H10C	109.5
C4—N1—H1	117.7 (13)	C12—C13—H13	120.0
C8—N1—C4	119.70 (15)	C14—C13—C12	119.98 (17)
C8—N1—H1	122.5 (13)	C14—C13—H13	120.0
C14—N3—C14i	120.0 (3)	N3—C14—C13	122.18 (19)
C14i—N3—H3	120.02 (13)	N3—C14—H14	118.9
C14—N3—H3	120.01 (13)	C13—C14—H14	118.9
N2—C6—C7	121.05 (14)	N2—C9—H9A	109.5
N2—C6—C5	122.92 (13)	N2—C9—H9B	109.5
C5—C6—C7	116.04 (14)	N2—C9—H9C	109.5
C12—N4—C11i	120.94 (15)	H9A—C9—H9B	109.5
C12—N4—C11	120.93 (15)	H9A—C9—H9C	109.5
C11i—N4—C11	118.1 (3)	H9B—C9—H9C	109.5
O2—C1—C2	113.93 (13)	N4—C11—H11A	109.5
O3—C1—O2	125.85 (16)	N4—C11—H11B	109.5
O3—C1—C2	120.19 (15)	N4—C11—H11C	109.5
C6—C7—H7	119.9	H11A—C11—H11B	109.5
C8—C7—C6	120.14 (14)	H11A—C11—H11C	109.5
C8—C7—H7	119.9	H11B—C11—H11C	109.5
O1—C2—C1	113.67 (13)
Cr1—O2—C1—O3	−177.75 (14)	C7—C6—C5—C4	−2.3 (2)
Cr1—O2—C1—C2	4.37 (16)	C5—C6—C7—C8	2.0 (2)
Cr1—O1—C2—O4	178.94 (14)	C4—N1—C8—C7	−1.0 (2)
Cr1—O1—C2—C1	−2.76 (16)	C12—C13—C14—N3	−0.1 (3)
Cr1—O5—C3—O6	179.09 (15)	C8—N1—C4—C5	0.7 (2)
Cr1—O5—C3—C3i	−0.6 (2)	C10—N2—C6—C7	1.3 (2)
O2—C1—C2—O1	−1.05 (19)	C10—N2—C6—C5	−178.85 (16)
O2—C1—C2—O4	177.30 (15)	C13i—C12—C13—C14	0.02 (12)
O3—C1—C2—O1	−179.06 (15)	C14i—N3—C14—C13	0.03 (13)
O3—C1—C2—O4	−0.7 (2)	C9—N2—C6—C7	178.16 (16)
N2—C6—C7—C8	−178.10 (14)	C9—N2—C6—C5	−2.0 (3)
N2—C6—C5—C4	177.81 (15)	C11i—N4—C12—C13	−179.27 (16)
C6—C7—C8—N1	−0.4 (2)	C11i—N4—C12—C13i	0.74 (16)
C6—C5—C4—N1	1.0 (3)	C11—N4—C12—C13i	−179.26 (16)
N4—C12—C13—C14	−179.98 (12)	C11—N4—C12—C13	0.74 (16)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O8Wii	0.91 (2)	1.84 (2)	2.702 (2)	157.8 (19)
N3—H3···O6iii	0.92 (4)	2.12 (3)	2.879 (3)	139 (1)
N3—H3···O6iv	0.92 (4)	2.12 (3)	2.879 (3)	139 (1)
O7W—H7WA···O4i	0.83 (1)	1.99 (1)	2.819 (2)	178 (3)
O7W—H7WB···O1v	0.82 (1)	2.12 (1)	2.9079 (19)	161 (3)
O8W—H8WA···O7W	0.81 (1)	1.95 (1)	2.7578 (19)	172 (3)
O8W—H8WB···O6vi	0.82 (1)	1.99 (1)	2.8007 (19)	175 (3)