Co-crystallization of hemimellitic acid with 4,4′-bipyridine forming a pillar-layered hydrogen-bonded network

Co-crystallization of hemimellitic acid (benzene-1,2,3-tricarboxylic acid) dihydrate (H₃HMA·2H₂O) with 4,4′-bipyridine (4,4′-bpy) affords the 1:1 co-crystal benzene-1,2,3-tricarboxylic acid–4,4′-bipyridine (1/1), H₃HMA·4,4′-bpy or C₉H₆O₆·C₁₀H₈N₂. Strong O—H...O hydrogen bonds connect the acid mol­ecules to form a one-dimensional zigzag chain, around which the 4,4′-bpy components are fixed as arms via O—H...N inter­actions, resulting in a ladder motif. Through weak C—H...O non-covalent forces, the resulting acid layers are extended into a three-dimensional pillar-layered architecture supported by rod-like 4,4′-bpy components. The influence on hydrogen-bonding models is also discussed, with the discovery of an unexpected inter­action motif that does not follow the routine hydrogen-bonded hierarchical rule in the construction of an acid–base co-crystal.

S1. Comment

One of the most important targets in crystal engineering is the rational design and preparation of molecular architectures with desired topologies and functions (Brammer, 2004; Steiner, 2002). The aromatic carboxylic acid family is widely used as versatile building blocks in either coordination polymer synthesis (Yaghi et al., 2003) or the generation of hydrogen-bonding arrays of organic cocrystals (Bowers et al., 2005). Surprisingly, hemimellitic acid (H₃HMA, benzene-1,2,3-tricarboxylic acid) has received little attention from supramolecular scientists (Dale et al., 2004) compared with its well known isomer H₃TMA (benzene-1,3,5-tricarboxylic acid). To the best of our knowledge, there is no example of H₃HMA being introduced to bimolecular cocrystal formation.

In contrast, 4,4'-bipyridine (hereafter 4,4'-bpy) has been investigated in all branches of crystal engineering, from coordination polymers (Hagraman et al., 1999) to non-covalent hydrogen-bonding adducts (Ruiz-Perez et al., 2004). Whenever 4,4'-bpy takes part in the formation of cocrystals with organic molecules containing carboxyl groups, O—H···N hydrogen bonds are conventionally formed (Du et al., 2005). We have used H₃HMA, which contains robust hydrogen-bonding sites, to cocrystallize with the rigid base 4,4'-bpy, affording a binary compound, [(H₃HMA).(4,4'-bpy)], (I), which adopts a pillar-layered hydrogen-bonding architecture.

The structure analysis of (I) reveals a 1:1 stiochiometry, which is not consistent with the ratio of hydrogen-bonding donor and acceptor sites; the asymmetric unit of (I), which contains one formula unit, is depicted in Fig. 1. Bond lengths and angles agree with accepted values. Within each 4,4'-bpy subunit, the dihedral angle between the rings is 31.1 (1)°. For the H₃HMA component, the 2-carboxyl group (O3—C18—O4) presents an anti-planar conformation (Leiserowitz, 1976), in which the H atom is located in an anti orientation with respect to the –COO group; the 1- and 3-carboxyl groups (O1—C17—O2 and O5—C19—O6) adopt a trans arrangement in relation to the central phenyl ring. The 2-carboxyl group lies approximately perpendicular to the phenyl plane, making a dihedral angle of 100.3 (2)°, which is comparable to that in the structures of H₃HMA dihydrate (Mo & Adman, 1975), its 2-methyl ester (Dale & Elsegood, 2003) and its dimethylformamide solvate (Dale & Elsegood, 2004).

The hydrogen-bond geometries and symmetry codes are listed in Table 2. The three carboxyl groups in each H₃HMA molecule display different hydrogen-bonding modes. The terminal carboxyl group at atom C13 forms intermolecular interactions with the 4,4'-bpy molecule via strong O6—H6···N2ⁱ hydrogen bonds, while the carboxyl moiety at atom C11 (or C12) forms a unique `double hydrogen-bonded bridge' [referring to the linkage of two related carboxyl groups by a pair of O—H···O hydrogen bonds, denoted as R₂²(4); see Fig. 2] via a pair of O1—H1···O1ⁱⁱ (or O4—H4···O4ⁱⁱⁱ) interactions, instead of engendering O—H···N bonds to N1 of the base subunit. Thus, the acid molecules are linked to afford a one-dimensional zigzag chain parallel to [001], and the 4,4'-bpy building blocks are located around this chain to produce a ladder-shaped motif (see Fig. 2). With respect to the acid molecules only, the C15—H15···O2^iv interactions connects the adjacent zigzag acid chains into a two-dimensional corrugated layer. By a combination of the O—H···N bonds and additional weak C—H···O interactions, including C3—H3···O3^v, C8—H8···O2, C8—H8···O1ⁱⁱ and C9—H8···O3^vi, between the base pillar and neighboring acid layer, a three-dimensional pillar-layered hydrogen-bonded architecture is generated (Fig. 3). Examination of this structure with PLATON (Spek, 2003) showed that there were no solvent-accessible voids in the crystal structure.

Heteromeric intermolecular interactions are powerful synthetic tools for the formation of acid/base binary cocrystals. The hydrogen-bonding motifs in these compounds are always consistent with Etter's analysis (Etter, 1990) of hierarchical rules, that is, the best hydrogen-bond donor and the best hydrogen-bond acceptor will preferentially form stable hydrogen bonds. The most common case occurs between a pyridyl N atom and a carboxyl group (Du et al., 2005). However, in (I), pyridyl atom N1 does not form such a heteromeric bond with any carboxyl groups, nor is there even a possible C—H···N weak interaction. Instead, unusual `double hydrogen-bonded bridges' as described above are observed between the carboxyl groups. A CSD search (Cambridge Structural Database; Version 5.26 of November 2004, plus two updates) was carried out using CONQUEST Version 1.7 (Allen, 2002) to investigate the general robustness of such double hydrogen-bonded bridges. 40 related examples were identified (those structures with R1 > 0.1, as well as organometallic entries, were discarded). More details for the target O—H···O interactions are as follows: (i) H···O distances are found to range between 1.55 and 1.98 Å, while the mean value is ca 1.77 Å; (ii) the O···O distances lie between 2.44 and 2.76 Å, and the mean value is ca 2.56 Å; (c) most of the O—H···O angles (37 cases among the 40 search results) lie in the range 154–178°, with a mean value of 168°. All related values in this structure are comparable to the above analysis.

S2. Experimental

An aqueous solution (10 ml) containing 4,4'-bpy (0.1 mmol, 15.6 mg) and H₃HMA·2H₂O (0.1 mmol, 24.6 mg) was placed in a Teflon-lined stainless steel vessel (20 ml) under autogenous pressure; the vessel was heated to 413 K for 72 h and then cooled to room temperature at a rate of 5 K h⁻¹. The reaction mixture was filtered, and colorless block-shaped crystals were collected by slow evaporation of the solvent (yield 37%). Analysis calculated for C₁₉H₁₄N₂O₆: C 62.30, H 3.85, N 7.65%; found: C 63.36, H 4.41, N 7.19%. IR (KBr pellet, cm⁻¹): 3589 (w), 3286 (w), 3064 (w), 2303 (m), 2233 (w), 2168 (vs), 1639 (w), 1612 (w), 1574 (s), 1536 (vs), 1484 (m), 1417 (w), 1364 (s), 1219 (w), 1159 (w), 1059 (w), 1014 (w), 849 (w), 720 (w), 697 (m), 602 (w), 517 (w).

S3. Refinement

All H atoms were visible in difference maps. C-bound H atoms were placed at calculated positions, with C—H distances of 0.93 Å, and refined as riding atoms. O-bound H atoms were refined as rigid groups, allowed to rotate but not tip. Isotropic displacement parameters were derived from the parent atoms [U_iso(H) = 1.2U_eq(C) and 1.5U_eq(O)].

Computing details

Data collection: Apex II (Bruker, 2003); cell refinement: Apex II and SAINT (Bruker, 2001); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2001) and Diamond (Brandenburg & Berndt, 1999); software used to prepare material for publication: SHELXTL.

Figures

	Fig. 1. The molecular structure of (I), drawn with 30% probability displacement ellipsoids.
	Fig. 2. The one-dimensional ladder structure formed via O—H···O and O—H···N interactions (H atoms not involved in these hydrogen bonds, which are represented by dashed lines here and in Fig. 3, have been omitted).
	Fig. 3. T h e three-dimensional pillar-layered supramolecular network, viewed in the crystallographic [001] direction (4,4'-bpy molecules are simplified to rods, and weak C—H···O interactions between the base pillar and acid layer have been omitted for clarity).

benzene-1,2,3-tricarboxylic acid–4,4'-bipyridine (1/1)

Crystal data

C9H6O6·C10H8N2	F(000) = 1520
Mr = 366.32	Dx = 1.502 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 2052 reflections
a = 26.118 (3) Å	θ = 2.6–23.1°
b = 7.8131 (9) Å	µ = 0.11 mm^−1
c = 19.881 (2) Å	T = 293 K
β = 127.005 (1)°	Block, colorless
V = 3239.8 (6) Å^3	0.42 × 0.26 × 0.20 mm
Z = 8

Data collection

Bruker APEX-II CCD area-detector diffractometer	2845 independent reflections
Radiation source: fine-focus sealed tube	2212 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.024
ϕ and ω scans	θmax = 25.0°, θmin = 2.0°
Absorption correction: multi-scan (SADABS; Sheldrick, 1996)	h = −29→30
Tmin = 0.829, Tmax = 1.000	k = −7→9
8469 measured reflections	l = −23→22

Refinement

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.041	H-atom parameters constrained
wR(F^2) = 0.133	w = 1/[σ^2(Fo^2) + (0.0824P)^2 + 0.8334P] where P = (Fo^2 + 2Fc^2)/3
S = 1.07	(Δ/σ)max < 0.001
2845 reflections	Δρmax = 0.56 e Å^−3
247 parameters	Δρmin = −0.33 e Å^−3
0 restraints	Extinction correction: SHELXL97, Fc^*=kFc[1+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: none

Special details

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
O1	0.00470 (8)	0.62634 (18)	0.04046 (8)	0.0471 (4)
H1	−0.0106	0.5398	0.0114	0.071*
O2	0.03844 (8)	0.44554 (17)	0.14488 (9)	0.0487 (4)
O3	0.15311 (6)	0.50974 (18)	0.33856 (8)	0.0389 (4)
O4	0.05817 (6)	0.45596 (16)	0.30515 (7)	0.0325 (3)
H4	0.0216	0.4686	0.2619	0.049*
O5	0.16515 (9)	0.9775 (2)	0.44631 (10)	0.0710 (6)
O6	0.11423 (7)	0.73634 (19)	0.42988 (8)	0.0457 (4)
H6	0.1337	0.7460	0.4809	0.069*
N1	0.36332 (9)	0.1491 (2)	0.52918 (10)	0.0450 (5)
N2	0.17152 (8)	0.2477 (2)	0.09181 (10)	0.0423 (5)
C1	0.35244 (10)	0.2406 (3)	0.40921 (13)	0.0452 (5)
H1A	0.3711	0.2827	0.3849	0.054*
C2	0.38955 (11)	0.2067 (3)	0.49364 (13)	0.0490 (6)
H2	0.4336	0.2243	0.5264	0.059*
C3	0.30044 (12)	0.1255 (3)	0.48483 (13)	0.0492 (6)
H3	0.2832	0.0880	0.5117	0.059*
C4	0.26064 (11)	0.1560 (3)	0.39964 (12)	0.0449 (5)
H4A	0.2167	0.1394	0.3690	0.054*
C5	0.28653 (10)	0.2118 (3)	0.35963 (11)	0.0365 (5)
C6	0.24615 (9)	0.2301 (3)	0.26644 (11)	0.0347 (5)
C7	0.18193 (10)	0.2711 (3)	0.21904 (12)	0.0404 (5)
H7	0.1627	0.2931	0.2451	0.049*
C8	0.14659 (10)	0.2792 (3)	0.13253 (12)	0.0436 (5)
H8	0.1034	0.3080	0.1012	0.052*
C9	0.23335 (11)	0.2080 (3)	0.13773 (13)	0.0488 (6)
H9	0.2514	0.1861	0.1101	0.059*
C10	0.27185 (10)	0.1976 (3)	0.22373 (12)	0.0448 (5)
H10	0.3149	0.1690	0.2533	0.054*
C11	0.04310 (8)	0.7420 (2)	0.17188 (11)	0.0281 (4)
C12	0.07494 (8)	0.7225 (2)	0.25857 (11)	0.0264 (4)
C13	0.09214 (8)	0.8693 (2)	0.30836 (11)	0.0321 (4)
C14	0.07660 (10)	1.0304 (3)	0.27098 (13)	0.0418 (5)
H14	0.0885	1.1276	0.3043	0.050*
C15	0.04401 (10)	1.0477 (3)	0.18589 (13)	0.0438 (5)
H15	0.0330	1.1560	0.1615	0.053*
C16	0.02758 (9)	0.9049 (2)	0.13653 (12)	0.0364 (5)
H16	0.0058	0.9172	0.0788	0.044*
C17	0.02755 (9)	0.5900 (2)	0.11672 (10)	0.0295 (4)
C18	0.09726 (8)	0.5502 (2)	0.30177 (10)	0.0271 (4)
C19	0.12770 (9)	0.8660 (3)	0.40173 (12)	0.0383 (5)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0715 (10)	0.0377 (8)	0.0241 (7)	0.0052 (7)	0.0244 (7)	−0.0003 (6)
O2	0.0835 (11)	0.0291 (8)	0.0336 (7)	0.0051 (7)	0.0354 (8)	0.0016 (6)
O3	0.0311 (8)	0.0472 (9)	0.0361 (7)	0.0078 (6)	0.0191 (6)	0.0095 (6)
O4	0.0276 (7)	0.0379 (8)	0.0238 (6)	−0.0004 (6)	0.0111 (6)	0.0069 (5)
O5	0.0925 (14)	0.0635 (11)	0.0363 (9)	−0.0370 (10)	0.0277 (9)	−0.0199 (8)
O6	0.0559 (10)	0.0515 (9)	0.0249 (7)	−0.0131 (7)	0.0218 (7)	−0.0075 (6)
N1	0.0549 (12)	0.0423 (10)	0.0278 (9)	0.0080 (9)	0.0195 (9)	0.0024 (7)
N2	0.0428 (11)	0.0543 (11)	0.0263 (9)	0.0112 (8)	0.0190 (8)	0.0057 (7)
C1	0.0409 (12)	0.0592 (14)	0.0299 (10)	0.0032 (10)	0.0183 (10)	0.0034 (9)
C2	0.0426 (13)	0.0548 (14)	0.0343 (11)	0.0037 (10)	0.0151 (10)	−0.0007 (10)
C3	0.0643 (16)	0.0530 (14)	0.0376 (11)	0.0073 (11)	0.0346 (12)	0.0081 (10)
C4	0.0443 (12)	0.0581 (14)	0.0312 (10)	0.0043 (10)	0.0221 (10)	0.0057 (10)
C5	0.0397 (11)	0.0407 (11)	0.0264 (10)	0.0087 (9)	0.0184 (9)	0.0039 (8)
C6	0.0354 (11)	0.0412 (11)	0.0249 (9)	0.0055 (8)	0.0167 (9)	0.0054 (8)
C7	0.0396 (12)	0.0542 (13)	0.0300 (10)	0.0101 (9)	0.0222 (9)	0.0055 (9)
C8	0.0362 (11)	0.0584 (14)	0.0307 (10)	0.0125 (10)	0.0173 (9)	0.0072 (9)
C9	0.0471 (13)	0.0718 (16)	0.0333 (11)	0.0147 (11)	0.0273 (11)	0.0071 (11)
C10	0.0355 (11)	0.0680 (15)	0.0296 (10)	0.0134 (10)	0.0190 (9)	0.0086 (10)
C11	0.0291 (10)	0.0301 (10)	0.0252 (9)	−0.0004 (7)	0.0163 (8)	0.0000 (7)
C12	0.0254 (9)	0.0296 (10)	0.0260 (9)	−0.0011 (7)	0.0164 (8)	−0.0003 (7)
C13	0.0326 (10)	0.0323 (10)	0.0300 (10)	−0.0026 (8)	0.0180 (9)	−0.0040 (8)
C14	0.0505 (13)	0.0291 (11)	0.0391 (11)	−0.0031 (9)	0.0235 (10)	−0.0069 (9)
C15	0.0542 (13)	0.0272 (11)	0.0432 (12)	0.0026 (9)	0.0258 (11)	0.0061 (9)
C16	0.0425 (12)	0.0331 (11)	0.0288 (10)	0.0019 (8)	0.0189 (9)	0.0053 (8)
C17	0.0329 (10)	0.0337 (11)	0.0220 (9)	0.0022 (8)	0.0166 (8)	0.0023 (8)
C18	0.0283 (10)	0.0334 (10)	0.0195 (8)	−0.0007 (8)	0.0143 (8)	−0.0024 (7)
C19	0.0428 (11)	0.0377 (11)	0.0309 (10)	−0.0045 (9)	0.0202 (9)	−0.0087 (9)

Geometric parameters (Å, º)

O1—C17	1.283 (2)	C5—C6	1.488 (2)
O1—H1	0.8200	C6—C7	1.379 (3)
O2—C17	1.215 (2)	C6—C10	1.386 (3)
O3—C18	1.216 (2)	C7—C8	1.380 (3)
O4—C18	1.293 (2)	C7—H7	0.9300
O4—H4	0.8200	C8—H8	0.9300
O5—C19	1.207 (2)	C9—C10	1.368 (3)
O6—C19	1.304 (2)	C9—H9	0.9300
O6—H6	0.8200	C10—H10	0.9300
N1—C2	1.324 (3)	C11—C16	1.391 (3)
N1—C3	1.329 (3)	C11—C12	1.400 (2)
N2—C9	1.328 (3)	C11—C17	1.497 (2)
N2—C8	1.332 (3)	C12—C13	1.401 (3)
C1—C2	1.367 (3)	C12—C18	1.513 (2)
C1—C5	1.394 (3)	C13—C14	1.392 (3)
C1—H1A	0.9300	C13—C19	1.494 (3)
C2—H2	0.9300	C14—C15	1.368 (3)
C3—C4	1.373 (3)	C14—H14	0.9300
C3—H3	0.9300	C15—C16	1.373 (3)
C4—C5	1.388 (3)	C15—H15	0.9300
C4—H4A	0.9300	C16—H16	0.9300
C17—O1—H1	109.5	C10—C9—H9	118.4
C18—O4—H4	109.5	C9—C10—C6	119.48 (19)
C19—O6—H6	109.5	C9—C10—H10	120.3
C2—N1—C3	121.52 (17)	C6—C10—H10	120.3
C9—N2—C8	117.55 (16)	C16—C11—C12	119.87 (16)
C2—C1—C5	119.9 (2)	C16—C11—C17	119.18 (15)
C2—C1—H1A	120.1	C12—C11—C17	120.91 (15)
C5—C1—H1A	120.1	C11—C12—C13	118.77 (16)
N1—C2—C1	120.6 (2)	C11—C12—C18	122.43 (15)
N1—C2—H2	119.7	C13—C12—C18	118.52 (15)
C1—C2—H2	119.7	C14—C13—C12	119.77 (16)
N1—C3—C4	120.7 (2)	C14—C13—C19	116.25 (16)
N1—C3—H3	119.7	C12—C13—C19	123.98 (17)
C4—C3—H3	119.7	C15—C14—C13	120.94 (18)
C3—C4—C5	119.5 (2)	C15—C14—H14	119.5
C3—C4—H4A	120.2	C13—C14—H14	119.5
C5—C4—H4A	120.2	C14—C15—C16	119.84 (18)
C4—C5—C1	117.74 (18)	C14—C15—H15	120.1
C4—C5—C6	121.27 (18)	C16—C15—H15	120.1
C1—C5—C6	120.88 (18)	C15—C16—C11	120.78 (17)
C7—C6—C10	117.54 (17)	C15—C16—H16	119.6
C7—C6—C5	122.16 (17)	C11—C16—H16	119.6
C10—C6—C5	120.23 (17)	O2—C17—O1	124.27 (17)
C6—C7—C8	119.23 (18)	O2—C17—C11	120.95 (15)
C6—C7—H7	120.4	O1—C17—C11	114.73 (15)
C8—C7—H7	120.4	O3—C18—O4	121.32 (16)
N2—C8—C7	122.98 (19)	O3—C18—C12	119.05 (16)
N2—C8—H8	118.5	O4—C18—C12	119.34 (15)
C7—C8—H8	118.5	O5—C19—O6	123.64 (18)
N2—C9—C10	123.22 (19)	O5—C19—C13	121.52 (19)
N2—C9—H9	118.4	O6—C19—C13	114.83 (16)
C3—N1—C2—C1	−1.4 (3)	C17—C11—C12—C18	2.1 (3)
C5—C1—C2—N1	−1.0 (3)	C11—C12—C13—C14	0.9 (3)
C2—N1—C3—C4	1.8 (3)	C18—C12—C13—C14	174.98 (17)
N1—C3—C4—C5	0.1 (3)	C11—C12—C13—C19	−178.33 (17)
C3—C4—C5—C1	−2.4 (3)	C18—C12—C13—C19	−4.3 (3)
C3—C4—C5—C6	174.0 (2)	C12—C13—C14—C15	0.8 (3)
C2—C1—C5—C4	2.8 (3)	C19—C13—C14—C15	−179.93 (19)
C2—C1—C5—C6	−173.5 (2)	C13—C14—C15—C16	−1.6 (3)
C4—C5—C6—C7	30.5 (3)	C14—C15—C16—C11	0.7 (3)
C1—C5—C6—C7	−153.3 (2)	C12—C11—C16—C15	1.0 (3)
C4—C5—C6—C10	−146.3 (2)	C17—C11—C16—C15	−176.70 (18)
C1—C5—C6—C10	29.9 (3)	C16—C11—C17—O2	−177.48 (18)
C10—C6—C7—C8	−0.5 (3)	C12—C11—C17—O2	4.8 (3)
C5—C6—C7—C8	−177.3 (2)	C16—C11—C17—O1	4.9 (3)
C9—N2—C8—C7	−0.4 (3)	C12—C11—C17—O1	−172.78 (17)
C6—C7—C8—N2	0.5 (3)	C11—C12—C18—O3	99.1 (2)
C8—N2—C9—C10	0.2 (3)	C13—C12—C18—O3	−74.7 (2)
N2—C9—C10—C6	−0.2 (4)	C11—C12—C18—O4	−86.9 (2)
C7—C6—C10—C9	0.3 (3)	C13—C12—C18—O4	99.23 (19)
C5—C6—C10—C9	177.2 (2)	C14—C13—C19—O5	−32.6 (3)
C16—C11—C12—C13	−1.8 (3)	C12—C13—C19—O5	146.7 (2)
C17—C11—C12—C13	175.89 (16)	C14—C13—C19—O6	146.48 (19)
C16—C11—C12—C18	−175.62 (17)	C12—C13—C19—O6	−34.2 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O6—H6···N2^i	0.82	1.79	2.612 (2)	175
O1—H1···O1^ii	0.82	1.72	2.464 (2)	150
O4—H4···O4^iii	0.82	1.67	2.454 (2)	159
C15—H15···O2^iv	0.93	2.30	3.194 (3)	160
C3—H3···O3^v	0.93	2.50	3.129 (3)	125
C8—H8···O2	0.93	2.56	3.250 (4)	131
C8—H8···O1^ii	0.93	2.57	3.410 (3)	151
C9—H9···O3^vi	0.93	2.47	3.120 (4)	127

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