Two three-dimensional networks in the binary mol­ecular adducts 4-methyl­imidazolium hydrogen terephthalate and bis­(4-methyl­imidazolium) terephthalate

Both the 1:1 and 2:1 mol­ecular adducts of 4-methyl­imidazole (4-MeIm) and terephthalic acid (H₂TPA) are organic salts, viz. C₄H₇N₂⁺·C₈H₅O₄^-, (I), and 2C₄H₇N₂⁺·C₈H₄O₄^2-, (II), respectively. The component ions in (I) are linked by N-H...O and O-H...O hydrogen bonds into continuous two-dimensional layers built from R₆⁴(32) hydrogen-bond motifs running parallel to the (100) plane. These adjacent two-dimensional layers are in turn linked by a combination of C-H...O, C-H...[pi] and [pi]-[pi] inter­actions into a three-dimensional network. In the crystal structure of (II), with the anion located on an inversion centre, only N-H...O hydrogen bonds result in two-dimensional layers built from R₈⁸(42) hydrogen-bond motifs running parallel to the (102) plane. Being similar to those in (I), these layers are also linked by means of C-H...O, C-H...[pi] and [pi]-[pi] inter­actions, forming a three-dimensional network. This study indicates that, on occasion, a change of the reactant concentration can exert a pivotal influence on the construction of supra­molecular structures based on hydrogen bonds.

S1. Comment

Terephthalic acid (H₂TPA), a rod-like aromatic diacid, has often been used in the synthesis of metal–organic frameworks as a linker molecule (Serre et al., 2007; Mukherjee et al., 2004; Sun et al., 2000; Zakaria et al., 2001; Karanović et al., 2002; Damgaard Poulsen et al., 2006; Li et al., 1998). Recently, with the increase in interest in controlling the crystalline structures of organic-based solid-state materials, H₂TPA is more and more employed in constructing supramolecular structures (Mei et al., 2007; Dale et al., 2004; Zhang & Chen, 2004; Lynch & Jones, 2004; Spencer et al., 2004; Devi & Muthiah, 2007). However, the experimental conditions employed (such as the solvent, temperature, crystallization method and counterions) can all have an important impact on the structure of the final assembly (She et al., 2008; Meng et al., 2007, 2008; Childs et al., 2007; Díaz et al., 2006). In this paper, we chose 4-methylimidazole (4-MeIm) acting as a proton-accepting candidate to study further the influence of its concentration on cocrystals and/or organic salt structures containing H₂TPA. We obtained the title 1:1 and 2:1 binary molecular adducts, (I) and (II), respectively, and report their crystal structures here.

Compounds (I) and (II) crystallize in space groups P1 and P2₁/c, respectively. In (I), the H atom of one carboxylic acid group O atom is transferred to the imidazole N atom, while the other remains as the acid. The carboxylic acid and carboxylate groups are distinctly twisted away from the benzene ring, with dihedral angles of 21.9 (1) and 5.7 (1)°, respectively [Please check amended text - are angles in the right order?]. However, the imidazole ring makes a much larger dihedral angle of 60.6 (1)° with the benzene ring. The 4-MeIm⁺ and HTPA^- component ions are joined together by two intermolecular N—H···O hydrogen bonds (Fig. 2, Table 1).

In contrast with (I), there is an inversion centre lying across the centre of the benzene ring of (II). Both carboxylic acid groups are deprotonated, with a carboxylate–benzene ring dihedral angle of 3.3 (1)° and an imidazole–benzene ring dihedral angle of 30.7 (1)°, roughly half of the corresponding values in (I). The component ions in (II) are linked together mainly by N—H···O hydrogen bonds (Fig. 3, Table 1).

The carboxylic acid C—O bond lengths in both title compounds [C7—O1 = 1.275 (2), C7—O2 = 1.229 (2), C8—O3 = 1.210 (2) and C8—O4 = 1.310 (2) Å in (I); C4—O1 = 1.255 (2) and C4—O2 = 1.250 (2) Å in (II)] agree well with those tabulated by Allen et al. (1995) for a carboxylic acid group [1.305 (20) and 1.226 (20) Å] and/or for a carboxylate group [1.255 (10) Å] attached to a phenyl ring. The bond distances and angles in the 4-MeIm⁺ cation are also indicative of its protonation by drawing a comparison between (I), (II) and analogous compounds [Cambridge Structural Database, Version? (Allen, 2002; Macrae et al., 2006); refcodes AHIJUW (Gossman et al., 2002), FETDAK (Aakeröy et al., 2005), HISTPA (Mata et al., 2006), JAXMEB (Wang & Wei, 2005) and HILSAX (Tian, 2007)].

Although compounds (I) and (II) are both linked into their final three-dimensional networks by a combination of N—H···O, O—H···O, C—H···O hydrogen bonds and C—H···π and π–π interactions, the structural subunits are apparently different because of the concentration change of 4-MeIm. In (I), the supramolecular structure can be simply analyzed in terms of three substructures. Firstly, the HTPA^- anions result in discrete one-dimensional C(8) (Bernstein et al., 1995) chains via an O4—H4···O1ⁱⁱⁱ hydrogen bond [symmetry code: (iii) x, y, z + 1] running parallel to the [001] direction (Fig.2). Secondly, these adjacent [001] chains are linked together by 4-MeIm⁺ cations, forming two-dimensional layers built from R⁴₆(32) hydrogen-bond motifs which are parallel to the (100) plane (Fig. 2). If these R⁴₆(32) rings are regarded as the nodes of the resulting net, then this is of the (4,4) type (Batten & Robson, 1998). Finally, these neighbouring two-dimensional layers are assembled into a three-dimensional network by means of two C—H···O hydrogen bonds and two C—H···π interactions (Table 1), and π–π interactions. One of the π–π interactions occurs between centrosymmetrically related imidazole rings, with a ring centroid distance of 3.706 (2) Å, an interplanar spacing of 3.452 (2) Å and a ring offset of 1.348 (2) Å. However, the other one is stronger and is formed between strictly parallel benzene rings; the ring centroid separation is 3.569 (2) Å, with an interpanar spacing of 3.476 (2) Å and a ring offset of 0.807 (2) Å.

By comparison, the component ions in (II) are first linked by N1—H1A···O2^viii [symmetry code: (iii) 1 - x,1/2 + y,3/2 - z] and N2—H2A···O1 hydrogen bonds, forming a two-dimensional layer built from centrosymmetric R₈⁸(42) hydrogen-bonded rings running parallel to the (102) plane (Fig. 3). According to the topology classification for nets, this is a (6,3) net, which is apparently larger than that in (I). These adjacent layers in (II) are in turn linked into a three-dimensional network by a combination of one C—H···O hydrogen bond and one C—H···π interaction (Table 1), and π–π interactions. The π–π interactions in (II) only occur between the strictly parallel imidazole rings, with a ring centroid distance of 3.665 (2) Å, an interplanar spacing of 3.302 (2) Å and a ring offset of 1.591 (2) Å.

Both title compounds should be regarded as organic salts according to the definitions of cocrystals and organic salts (Aakeröy & Salmon, 2005). We might find some reasons from the ΔpK_a rule [ΔpK_a = pK_a(base) - pK_a(acid); Childs et al., 2007; Bhogala et al., 2005] why cocrystallization of H₂TPA and 4-MeIm from water yields the organic salt but not a cocrystal. It is generally accepted that reaction of an acid with a base will be expected to form a salt if ΔpK_a is greater than 3 and will exclusively result in cocrystal formation if ΔpK_a is less than 0. The pK_a value of 4-MeIm is equal to 8.5 in aqueous solution at 303 K calculated using Advanced Chemistry Development Software running under Solaris (Advanced Chemistry Development, 2005). For H₂TPA, pK_a1 = 3.51 and pK_a2 = 4.82. Both the ΔpK_a1 (4.99) and ΔpK_a2 (3.68) values are greater than 3, indicating that the 1:1 and 2:1 organic salts are available.

In conclusion, H₂TPA is a good participant in hydrogen-bonding networks for the formation of acid–base molecular adducts. With the aim of gaining more insight into crystal engineering based on hydrogen bonds, further organic salts and/or cocrystals containing H₂TPA are expected to obtained by means of the ΔpK_a rule.

S2. Experimental

All reagents and solvents were used as obtained without further purification. Crystals of (I) were obtained by mixing equivalent molar quantities of 4-methylimidazole (0.2 mmol, 16.4 mg) and terephthalic acid (0.2 mmol, 33.2 mg) dissolved in water (10 ml). The mixture was stirred for 10 min at ambient temperature and then filtered. The resulting colourless solution was kept in air for one week. Colourless plate crystals of (I) suitable for single-crystal X-ray diffraction analysis were grown by slow evaporation of the solution at the bottom of the vessel. The crystals were filtered carefully, washed with distilled water and dried in air (yield 30%, 15.0 mg, based on the 1:1 organic salt).

Crystals of (II) were obtained by mixing 2:1 molar quantities of 4-methylimidazole (0.4 mmol, 32.8 mg) and terephthalic acid (0.2 mmol, 33.2 mg) in water (20 ml). The mixture was stirred for 30 min at ambient temperature and then filtered. The resulting colourless solution was kept in air for three weeks. Block colourless crystals of (II) suitable for single-crystal X-ray diffraction analysis were grown by slow evaporation of the solution at the bottom of the vessel. The crystals were filtered carefully, washed with distilled water and dried in air (yield 50%, 33.0 mg, based on the 2:1 organic salt).

S3. Refinement

For both compounds, H atoms bonded to C atoms were positioned geometrically, with C—H = 0.93 (aromatic) or 0.96 Å (methyl), and refined in riding mode, with U_iso(H) = 1.2U_eq(aromatic C) or 1.5U_eq(methyl C). H atoms bonded to N and O atoms were found in difference maps. N—H and O—H distances were refined freely (refined distances are given in Table 1), with U_iso(H) = 1.2U_eq(N) or 1.5U_eq(O).

Computing details

For both compounds, data collection: SMART (Bruker, 2001); cell refinement: SMART (Bruker, 2001); data reduction: SAINT-Plus (Bruker, 2001); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2003); software used to prepare material for publication: PLATON (Spek, 2003).

Figures

	Fig. 1. The molecular structures of (a) (I) and (b) (II), showing the atom-numbering schemes. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Hydrogen bonds are shown as dashed lines. [Symmetry code: (i) -x, -y, 2 - z.]
	Fig. 2. Part of the crystal structure of (I), showing the formation of the two-dimensional layer running parallel to the (100) plane. Hydrogen bonds are shown as dashed lines. For the sake of clarity, 4-MeIm^+ cations and H atoms not involved in the motif have been omitted. [Symmetry codes: (ii) x, y - 1, z; (iii) x, y, z + 1.]
	Fig. 3. Part of the crystal structure of (II), showing the formation of the two-dimensional layer built from N—H···O hydrogen bonds. For the sake of clarity, H atoms not involved in the motif have been omitted. [Symmetry code: (viii) -x + 1, y + 1/2, -z + 3/2.]

(I) 4-methylimidazolium hydrogen terephthalate

Crystal data

C4H7N2^+·C8H5O4^−	Z = 2
Mr = 248.24	F(000) = 260
Triclinic, P1	Dx = 1.432 Mg m^−3
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 7.2649 (5) Å	Cell parameters from 2409 reflections
b = 8.9459 (7) Å	θ = 2.3–27.9°
c = 9.6844 (7) Å	µ = 0.11 mm^−1
α = 75.406 (1)°	T = 298 K
β = 72.731 (1)°	Plate, colourless
γ = 77.966 (2)°	0.30 × 0.10 × 0.04 mm
V = 575.52 (7) Å^3

Data collection

Bruker SMART APEX CCD area-detector diffractometer	2204 independent reflections
Radiation source: fine focus sealed Siemens Mo tube	1820 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.021
0.3° wide ω exposures scans	θmax = 26.0°, θmin = 2.3°
Absorption correction: multi-scan (SADABS; Sheldrick, 1997)	h = −8→8
Tmin = 0.956, Tmax = 0.996	k = −11→11
5915 measured reflections	l = −10→11

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)] = 0.049	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.156	H atoms treated by a mixture of independent and constrained refinement
S = 1.07	w = 1/[σ^2(Fo^2) + (0.1121P)^2] where P = (Fo^2 + 2Fc^2)/3
2204 reflections	(Δ/σ)max < 0.001
173 parameters	Δρmax = 0.25 e Å^−3
0 restraints	Δρmin = −0.29 e Å^−3

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
C1	0.1846 (2)	0.60860 (16)	0.24746 (17)	0.0301 (4)
C2	0.0813 (2)	0.74895 (17)	0.28407 (17)	0.0321 (4)
H2	0.0221	0.8210	0.2167	0.039*
C3	0.0654 (2)	0.78263 (17)	0.41915 (17)	0.0326 (4)
H3	−0.0031	0.8771	0.4421	0.039*
C4	0.1525 (2)	0.67416 (17)	0.52099 (18)	0.0301 (4)
C5	0.2507 (2)	0.53242 (18)	0.48622 (18)	0.0332 (4)
H5	0.3063	0.4587	0.5547	0.040*
C6	0.2667 (2)	0.49982 (17)	0.35039 (18)	0.0340 (4)
H6	0.3328	0.4045	0.3282	0.041*
C7	0.2108 (2)	0.57179 (17)	0.09894 (18)	0.0323 (4)
C8	0.1396 (2)	0.71605 (18)	0.66356 (17)	0.0337 (4)
C9	0.2188 (3)	0.09526 (18)	0.00584 (19)	0.0399 (4)
H9	0.1271	0.0885	0.0968	0.048*
C10	0.4236 (2)	0.03340 (18)	−0.19768 (19)	0.0357 (4)
C11	0.4271 (2)	0.18388 (19)	−0.1976 (2)	0.0398 (4)
H11	0.5028	0.2516	−0.2711	0.048*
C12	0.5354 (3)	−0.0689 (2)	−0.3029 (2)	0.0547 (5)
H12A	0.6312	−0.0144	−0.3790	0.082*
H12B	0.4481	−0.0969	−0.3465	0.082*
H12C	0.5991	−0.1617	−0.2512	0.082*
N1	0.2993 (2)	0.21901 (15)	−0.07028 (17)	0.0401 (4)
H1	0.278 (3)	0.308 (2)	−0.032 (2)	0.048*
N2	0.2900 (2)	−0.01884 (16)	−0.06859 (16)	0.0369 (4)
H2A	0.256 (3)	−0.116 (2)	−0.035 (2)	0.044*
O1	0.19191 (18)	0.68756 (12)	−0.00654 (12)	0.0411 (4)
O2	0.2498 (2)	0.43430 (13)	0.08750 (14)	0.0523 (4)
O3	0.0675 (2)	0.84331 (14)	0.69107 (14)	0.0516 (4)
O4	0.2186 (2)	0.60306 (14)	0.75314 (13)	0.0454 (4)
H4	0.203 (3)	0.636 (2)	0.845 (2)	0.054*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0393 (8)	0.0268 (8)	0.0264 (9)	−0.0086 (6)	−0.0086 (7)	−0.0061 (6)
C2	0.0425 (9)	0.0280 (8)	0.0265 (9)	−0.0017 (6)	−0.0135 (7)	−0.0038 (6)
C3	0.0410 (9)	0.0273 (8)	0.0282 (9)	0.0002 (6)	−0.0086 (7)	−0.0079 (6)
C4	0.0371 (8)	0.0301 (8)	0.0241 (8)	−0.0068 (6)	−0.0071 (6)	−0.0063 (6)
C5	0.0447 (9)	0.0277 (8)	0.0284 (9)	−0.0004 (6)	−0.0151 (7)	−0.0049 (6)
C6	0.0477 (9)	0.0248 (8)	0.0305 (9)	−0.0001 (6)	−0.0131 (7)	−0.0082 (6)
C7	0.0447 (9)	0.0281 (8)	0.0276 (9)	−0.0071 (6)	−0.0121 (7)	−0.0068 (6)
C8	0.0447 (9)	0.0314 (8)	0.0250 (9)	−0.0051 (7)	−0.0080 (7)	−0.0071 (7)
C9	0.0510 (10)	0.0384 (9)	0.0320 (10)	−0.0033 (7)	−0.0104 (8)	−0.0132 (7)
C10	0.0418 (9)	0.0339 (8)	0.0341 (10)	−0.0023 (7)	−0.0129 (7)	−0.0105 (7)
C11	0.0451 (9)	0.0349 (9)	0.0402 (11)	−0.0079 (7)	−0.0109 (8)	−0.0077 (7)
C12	0.0625 (12)	0.0532 (11)	0.0498 (13)	−0.0013 (9)	−0.0069 (9)	−0.0279 (10)
N1	0.0529 (9)	0.0292 (7)	0.0442 (9)	−0.0006 (6)	−0.0176 (7)	−0.0162 (6)
N2	0.0514 (8)	0.0277 (7)	0.0332 (8)	−0.0055 (6)	−0.0127 (6)	−0.0074 (6)
O1	0.0689 (8)	0.0317 (6)	0.0267 (7)	−0.0066 (6)	−0.0184 (6)	−0.0064 (5)
O2	0.0983 (11)	0.0284 (6)	0.0379 (8)	−0.0046 (6)	−0.0269 (7)	−0.0128 (6)
O3	0.0871 (10)	0.0350 (7)	0.0330 (8)	0.0064 (6)	−0.0200 (7)	−0.0145 (5)
O4	0.0723 (9)	0.0393 (7)	0.0288 (7)	0.0067 (6)	−0.0249 (6)	−0.0123 (6)

Geometric parameters (Å, º)

C1—C6	1.385 (2)	C8—O4	1.310 (2)
C1—C2	1.392 (2)	C9—N1	1.309 (2)
C1—C7	1.505 (2)	C9—N2	1.3260 (19)
C2—C3	1.382 (2)	C9—H9	0.9300
C2—H2	0.9300	C10—C11	1.352 (2)
C3—C4	1.395 (2)	C10—N2	1.378 (2)
C3—H3	0.9300	C10—C12	1.485 (2)
C4—C5	1.388 (2)	C11—N1	1.370 (2)
C4—C8	1.492 (2)	C11—H11	0.9300
C5—C6	1.385 (2)	C12—H12A	0.9600
C5—H5	0.9300	C12—H12B	0.9600
C6—H6	0.9300	C12—H12C	0.9600
C7—O2	1.2288 (18)	N1—H1	0.932 (19)
C7—O1	1.2751 (18)	N2—H2A	0.907 (19)
C8—O3	1.2095 (19)	O4—H4	0.98 (2)
C6—C1—C2	119.12 (14)	N1—C9—N2	108.51 (15)
C6—C1—C7	118.92 (13)	N1—C9—H9	125.7
C2—C1—C7	121.95 (14)	N2—C9—H9	125.7
C3—C2—C1	120.91 (15)	C11—C10—N2	105.41 (14)
C3—C2—H2	119.5	C11—C10—C12	131.97 (16)
C1—C2—H2	119.5	N2—C10—C12	122.58 (15)
C2—C3—C4	119.68 (14)	C10—C11—N1	107.88 (15)
C2—C3—H3	120.2	C10—C11—H11	126.1
C4—C3—H3	120.2	N1—C11—H11	126.1
C5—C4—C3	119.42 (14)	C10—C12—H12A	109.5
C5—C4—C8	122.02 (15)	C10—C12—H12B	109.5
C3—C4—C8	118.55 (14)	H12A—C12—H12B	109.5
C6—C5—C4	120.53 (15)	C10—C12—H12C	109.5
C6—C5—H5	119.7	H12A—C12—H12C	109.5
C4—C5—H5	119.7	H12B—C12—H12C	109.5
C1—C6—C5	120.29 (14)	C9—N1—C11	108.78 (13)
C1—C6—H6	119.9	C9—N1—H1	121.4 (12)
C5—C6—H6	119.9	C11—N1—H1	129.4 (12)
O2—C7—O1	124.92 (14)	C9—N2—C10	109.41 (14)
O2—C7—C1	118.34 (14)	C9—N2—H2A	123.1 (12)
O1—C7—C1	116.73 (13)	C10—N2—H2A	127.4 (12)
O3—C8—O4	123.84 (14)	C7—O2—H1	143.9 (6)
O3—C8—C4	122.88 (15)	C8—O4—H4	109.5 (11)
O4—C8—C4	113.25 (13)
C6—C1—C2—C3	2.1 (2)	C5—C4—C8—O3	174.27 (15)
C7—C1—C2—C3	−177.54 (13)	C3—C4—C8—O3	−4.7 (3)
C1—C2—C3—C4	−0.6 (2)	C5—C4—C8—O4	−4.0 (2)
C2—C3—C4—C5	−1.3 (2)	C3—C4—C8—O4	177.07 (13)
C2—C3—C4—C8	177.66 (13)	N2—C10—C11—N1	0.55 (19)
C3—C4—C5—C6	1.6 (2)	C12—C10—C11—N1	−177.41 (18)
C8—C4—C5—C6	−177.35 (14)	N2—C9—N1—C11	−0.2 (2)
C2—C1—C6—C5	−1.9 (2)	C10—C11—N1—C9	−0.2 (2)
C7—C1—C6—C5	177.83 (14)	N1—C9—N2—C10	0.59 (19)
C4—C5—C6—C1	0.0 (2)	C11—C10—N2—C9	−0.71 (19)
C6—C1—C7—O2	21.7 (2)	C12—C10—N2—C9	177.50 (17)
C2—C1—C7—O2	−158.63 (15)	O1—C7—O2—H1	−8.2 (11)
C6—C1—C7—O1	−157.80 (14)	C1—C7—O2—H1	172.4 (10)
C2—C1—C7—O1	21.9 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1···O2	0.932 (19)	1.749 (19)	2.6536 (17)	162.7 (18)
O4—H4···O1^i	0.98 (2)	1.59 (2)	2.5657 (16)	176.5 (19)
N2—H2A···O1^ii	0.907 (19)	1.84 (2)	2.7383 (17)	168.0 (18)
C3—H3···O3^iii	0.93	2.53	3.2762 (19)	138
C9—H9···O3^iv	0.93	2.27	3.155 (2)	160

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

(II) bis(4-methylimidazolium) terephthalate

Crystal data

2C4H7N2^+·C8H4O4^2^−	F(000) = 348
Mr = 330.34	Dx = 1.341 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 2847 reflections
a = 10.7759 (7) Å	θ = 3.3–28.1°
b = 7.5608 (5) Å	µ = 0.10 mm^−1
c = 10.3254 (7) Å	T = 296 K
β = 103.454 (1)°	Block, colourless
V = 818.17 (9) Å^3	0.36 × 0.30 × 0.10 mm
Z = 2

Data collection

Bruker SMART APEX CCD area-detector diffractometer	1860 independent reflections
Radiation source: fine focus sealed Siemens Mo tube	1491 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.029
0.3° wide ω exposures scans	θmax = 27.5°, θmin = 1.9°
Absorption correction: multi-scan (SADABS; Sheldrick, 1997)	h = −11→14
Tmin = 0.945, Tmax = 0.990	k = −9→9
8924 measured reflections	l = −13→13

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)] = 0.048	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.151	H atoms treated by a mixture of independent and constrained refinement
S = 1.08	w = 1/[σ^2(Fo^2) + (0.0899P)^2 + 0.1197P] where P = (Fo^2 + 2Fc^2)/3
1860 reflections	(Δ/σ)max < 0.001
116 parameters	Δρmax = 0.24 e Å^−3
0 restraints	Δρmin = −0.21 e Å^−3

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
C1	0.11809 (13)	0.04803 (19)	0.97667 (14)	0.0322 (3)
C2	0.09761 (15)	0.0555 (2)	1.10452 (15)	0.0423 (4)
H2	0.1627	0.0926	1.1752	0.051*
C3	0.02051 (15)	−0.0074 (3)	0.87335 (15)	0.0433 (4)
H3	0.0337	−0.0129	0.7876	0.052*
C4	0.24642 (14)	0.0995 (2)	0.95080 (15)	0.0341 (4)
C5	0.64073 (16)	0.3094 (2)	1.03102 (16)	0.0442 (4)
H5	0.6706	0.2690	1.1178	0.053*
C6	0.51308 (15)	0.3646 (2)	0.83893 (16)	0.0451 (4)
H6	0.4409	0.3695	0.7691	0.054*
C7	0.70940 (14)	0.3985 (2)	0.95839 (16)	0.0374 (4)
C8	0.84578 (17)	0.4522 (3)	0.9885 (2)	0.0569 (5)
H8A	0.8780	0.4587	1.0833	0.085*
H8B	0.8534	0.5659	0.9498	0.085*
H8C	0.8940	0.3667	0.9521	0.085*
N1	0.62720 (12)	0.43310 (18)	0.83836 (13)	0.0387 (4)
H1A	0.6463 (19)	0.495 (3)	0.780 (2)	0.046*
N2	0.52027 (13)	0.28898 (19)	0.95533 (14)	0.0443 (4)
H2A	0.455 (2)	0.230 (2)	0.9814 (19)	0.053*
O1	0.33403 (11)	0.14222 (19)	1.04883 (11)	0.0516 (4)
O2	0.25708 (11)	0.09877 (17)	0.83280 (11)	0.0480 (4)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.0270 (7)	0.0371 (8)	0.0353 (7)	−0.0042 (5)	0.0128 (6)	−0.0010 (6)
C2	0.0296 (8)	0.0648 (11)	0.0337 (8)	−0.0135 (7)	0.0099 (6)	−0.0078 (7)
C3	0.0342 (8)	0.0686 (11)	0.0307 (7)	−0.0117 (7)	0.0150 (6)	−0.0065 (7)
C4	0.0281 (7)	0.0372 (8)	0.0405 (8)	−0.0035 (6)	0.0149 (6)	−0.0017 (6)
C5	0.0377 (8)	0.0494 (10)	0.0475 (9)	−0.0013 (7)	0.0140 (7)	0.0095 (7)
C6	0.0283 (8)	0.0572 (11)	0.0485 (9)	−0.0011 (7)	0.0064 (6)	−0.0119 (8)
C7	0.0294 (7)	0.0398 (8)	0.0436 (8)	−0.0017 (6)	0.0100 (6)	0.0011 (6)
C8	0.0320 (9)	0.0675 (13)	0.0689 (12)	−0.0090 (8)	0.0075 (8)	0.0051 (9)
N1	0.0333 (7)	0.0490 (8)	0.0365 (7)	−0.0044 (5)	0.0135 (5)	0.0007 (5)
N2	0.0341 (7)	0.0479 (8)	0.0560 (8)	−0.0086 (6)	0.0204 (6)	−0.0003 (6)
O1	0.0311 (6)	0.0797 (9)	0.0459 (7)	−0.0199 (6)	0.0131 (5)	−0.0080 (6)
O2	0.0368 (6)	0.0721 (8)	0.0411 (6)	−0.0052 (5)	0.0210 (5)	−0.0015 (5)

Geometric parameters (Å, º)

C1—C3	1.378 (2)	C5—H5	0.9300
C1—C2	1.3893 (19)	C6—N2	1.317 (2)
C1—C4	1.5189 (19)	C6—N1	1.336 (2)
C2—C3^i	1.393 (2)	C6—H6	0.9300
C2—H2	0.9300	C7—N1	1.370 (2)
C3—C2^i	1.393 (2)	C7—C8	1.486 (2)
C3—H3	0.9300	C8—H8A	0.9600
C4—O2	1.2501 (18)	C8—H8B	0.9600
C4—O1	1.2552 (19)	C8—H8C	0.9600
C5—C7	1.350 (2)	N1—H1A	0.82 (2)
C5—N2	1.359 (2)	N2—H2A	0.92 (2)
C3—C1—C2	119.14 (13)	N1—C6—H6	125.9
C3—C1—C4	120.26 (13)	C5—C7—N1	105.97 (14)
C2—C1—C4	120.60 (13)	C5—C7—C8	131.54 (16)
C1—C2—C3^i	119.90 (14)	N1—C7—C8	122.47 (15)
C1—C2—H2	120.0	C7—C8—H8A	109.5
C3^i—C2—H2	120.0	C7—C8—H8B	109.5
C1—C3—C2^i	120.96 (13)	H8A—C8—H8B	109.5
C1—C3—H3	119.5	C7—C8—H8C	109.5
C2^i—C3—H3	119.5	H8A—C8—H8C	109.5
O2—C4—O1	124.38 (13)	H8B—C8—H8C	109.5
O2—C4—C1	117.65 (13)	C6—N1—C7	108.91 (13)
O1—C4—C1	117.96 (13)	C6—N1—H1A	127.5 (14)
C7—C5—N2	108.11 (15)	C7—N1—H1A	123.3 (14)
C7—C5—H5	125.9	C6—N2—C5	108.73 (14)
N2—C5—H5	125.9	C6—N2—H2A	125.9 (12)
N2—C6—N1	108.28 (14)	C5—N2—H2A	125.4 (12)
N2—C6—H6	125.9
C3—C1—C2—C3^i	−0.1 (3)	N2—C5—C7—N1	0.79 (19)
C4—C1—C2—C3^i	−179.82 (15)	N2—C5—C7—C8	−177.79 (18)
C2—C1—C3—C2^i	0.1 (3)	N2—C6—N1—C7	0.36 (19)
C4—C1—C3—C2^i	179.83 (16)	C5—C7—N1—C6	−0.71 (18)
C3—C1—C4—O2	3.8 (2)	C8—C7—N1—C6	178.03 (16)
C2—C1—C4—O2	−176.41 (15)	N1—C6—N2—C5	0.1 (2)
C3—C1—C4—O1	−177.13 (16)	C7—C5—N2—C6	−0.6 (2)
C2—C1—C4—O1	2.6 (2)

Symmetry code: (i) −x, −y, −z+2.

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O2^ii	0.82 (2)	1.90 (2)	2.6968 (18)	161.0 (19)
C6—H6···O1^iii	0.93	2.30	3.164 (2)	154
N2—H2A···O1	0.92 (2)	1.74 (2)	2.6632 (17)	171.8 (18)
N2—H2A···O2	0.92 (2)	2.52 (2)	3.1691 (18)	127.3 (15)

Symmetry codes: (ii) −x+1, y+1/2, −z+3/2; (iii) x, −y+1/2, z−1/2.