Two polymorphs of anhydrous 4-pyridone at 100 K

Two polymorphs of the title compound, C₅H₅NO, (I), have been obtained from ethanol. One polymorph crystallizes in the monoclinic space group C2/c [henceforth (I)-M], while the other crystallizes in the ortho­rhom­bic space group Pbca [henceforth (I)-O]. In the two forms, the lattice parameters, cell volume and packing motifs are very similar. There are also two independent mol­ecules of 4-pyridone in each asymmetric unit. The mol­ecules are linked by N—H...O hydrogen bonds into one-dimensional zigzag chains extending along the b axis in the (I)-M polymorph and along the a axis in the (I)-O polymorph, with the graph set C₂²(12). The structures are stabilized by weak C—H...O hydrogen bonds linking adjacent chains, thus forming a ring with the graph set R₆⁵(28). The significance of this study lies in the analysis of the hydrogen-bond inter­actions occurring in these structures. Analyses of the crystal structures of the two polymorphs of 4-pyridone are helpful in elucidating the mechanism of the generation of spectroscopic effects observed in the IR spectra of these polymorphs in the frequency range of the N—H stretching vibration band.

S1. Comment

In the literature, one can find many papers concerning the powerful biological activities of 4-pyridone derivatives. Some of them are known to have a potential antitumor effects, e.g. 2-methyl-3-acetoxy-4-pyridone (Hwang et al.,1980). It has also been proved that some 4-pyridone derivatives exhibit a strong antibacterial effect, for instance against Staphylococcus aureus (Takahata et al., 2007). A series of 4-pyridone derivatives have been identified, which show antimicrobial properties in the case of Staphylococcus aureus, a group of bacteria that is resistant to triclosan. Other investigators have shown that diaryl ether-substituted 4-pyridones inhibit mitochondrial electron transport in Plasmodium falciparum and Plasmodium yoelii, meaning that they have a potential antimalarial effect (Yeates et al., 2008). In the past few years, 4-pyridone has also been used as a bifunctional ligand, which is capable of binding to metal centres, e.g. to cobalt (Gao et al., 2004), lanthanum (Deng et al., 2005) or cadmium (Englert & Schiffers, 2006).

The above-mentioned compounds were investigated not only in terms of their chemical activity but also to determine their crystal structures. In the Cambridge Structural Database (CSD; Version 5.29; Allen, 2002) there are 57 records concerning derivatives of 4-pyridone, including 17 for organometallic compounds. Surprisingly, many structures of 4-pyridone derivatives have been described, but the simple compound was only known to exist in the keto form as 4-pyridone (Smith, 1979).

Jones (2001) obtained colourless crystals of 4-pyridone 6/5-hydrate by evaporating anhydrous 4-pyridone from waterless acetone. He concluded that the hydrate is formed by the influence of adventitious water.

Our interest in defining the crystal structure of anhydrous 4-pyridone was the result of investigations of the IR spectra of hydrogen bonding in various compounds, such as pyridine-4-thione (Flakus et al., 2002), imidazole (Flakus & Michta, 2004) and pyridine-2-thione (Flakus & Tyl, 2008). Hence, the study of the IR spectra of 4-pyridone was a natural continuation of this work. The IR spectra of 4-pyridone were measured in KBr pellets and in single crystals. The spectra showed that the compound was totally anhydrous. Moreover, the spectra showed the existence of two anhydrous forms of 4-pyridone, a monoclinic form, (I)-M, and an orthorhombic form, (I)-O. To allow the correct interpretation of the temperature, isotopic substitution of deuterium and linear dichroism effects in IR crystalline spectra of the described compound, we have determined the crystal structures of these two polymorphs.

In the asymmetric units of (I)-M and (I)-O, there are two geometrically similar independent molecules (Figs. 1 and 2). The interplanar angles between molecules A and B are 47.71 (6) and 47.82 (3)° in forms (I)-M and (I)-O, respectively. The molecules are linked by N—H···O hydrogen bonds in the sequence A···B···A···B···. The bond lengths and angles in the 4-pyridone rings of the two polymorphs are similar and correspond well to the molecular dimensions of the pyridine rings in the hydrated form, in the sulfur analogue (Flakus et al., 2002; Muthu & Vittal, 2004) and in the 4-pyridone derivatives reported in the CSD.

The only significant differences between all the independent molecules in the two structures are in the torsion angles. The 4-pyridone rings are approximately planar, but the N—H bonds lie out of the plane of the pyridone rings (Tables 1 and 3). This fact is consistent with the presence of π-electron delocalization extending from the N atom through the π system of the ring to the carbonyl group. The keto–enol tautomerism of 4-pyridone derivatives can be easily monitored by consideration of the geometry. In the hydroxy tautomer, the C═O bond distance is about 1.35 Å, the endocyclic angle at the N atom is significantly lower than 120°, the pyridone ring is planar and the form is more stable than the keto form (Kettmann et al., 2001).

The lattice parameters and volumes of the (I)-M and (I)-O phases are surprisingly similar, with abc in (I)-M corresponding to cab in the (I)-O form. The cell volume of (I)-M is only about 10 ų larger than that of (I)-O at 100 K. The real difference between these two phases is connected with their symmetry. Views of the crystal packing (Figs. 3 and 4) show the similarities and differences in the packing arrangements of the molecules, which result in the symmetries characteristic of the observed space groups.

The intermolecular hydrogen bonds observed in (I)-O and (I)-M form C₂²(12) graph-set chains (Etter et al., 1990; Bernstein et al., 1995) with second-level patterns via the path O1—C3—C2—C1—N1—H1N···O2—C8—C7—C6—N2—H2N···O1ⁱ, involving two symmetry-independent N—H···O hydrogen bonds. This chain runs along the [010] direction [symmetry code: (i) x, y + 1, z] in (I)-M (Fig. 5) and along the [100] direction [symmetry code: (i) x + 1, y, z] in (I)-O (Fig. 6). Additionally, in both forms, atom C6 of the heterocyclic ring of molecule B acts as a donor in a weak intermolecular hydrogen bond with atom O2 of molecule B from an adjacent chain. This interaction links the molecules into a C—H···O hydrogen-bonded chain via glide planes along the c- and b-axis directions in (I)-M and (I)-O, respectively. The graph-set motif of C(5) is formed by the following path: O2—C8—C7—C6—H6···O2ⁱⁱ (see Tables 2 and 4 for geometric parameters and symmetry codes). The infinite C—H···O-bonded chain has only one type of hydrogen bond.

The chains of N—H···O hydrogen-bonded molecules in the hydrated form of 4-pyridone (Jones, 2001) also show a tendency to weak interaction. In contrast to the anhydrous forms, in hydrated 4-pyridone there are several C—H···O interactions linking pyridone and water molecules, but no such bonds appear between the pyridone molecules.

The packing motifs are common to the two forms of 4-pyridone described here. All graph sets characterizing hydrogen bonds are presented in Table 5. There are four types of noncyclic dimer, two with the motifs for the first-level and two with the motifs for the second-level patterns. There are also two infinite chains, described above, and one R₆⁵(28) ring containing three different types of hydrogen bond (Figs. 5 and 6). The assignment of graph-set descriptors was performed using RPluto as described by Motherwell et al. (1999).

Although there are seven different graph-set motifs, only one of them is important for the interpretation of the IR spectra. In hydrogen-bond spectroscopy, the way in which hydrogen-bonded molecules aggregate plays an important role. In the case of monoclinic and orthorhombic 4-pyridone, the crucial information received from the graph-set analysis is that the molecules are linked by N—H···O hydrogen bonds, forming an infinite chain along the b axis and along the a axis, respectively. The predominance of the N—H···O over the C—H···O hydrogen bonds follows from their energy. All the geometric parameters of the N—H···O interactions observed in both forms of the anhydrous 4-pyridone (Tables 2 and 4) are within the limits for strong hydrogen bonds defined by Desiraju & Steiner (1999). Judging from the bond distances, the N—H···O hydrogen bonds between two 4-pyridone molecules in the (I)-M and (I)-O polymorphs appear to be slightly stronger than those in hydrated 4-pyridone. In the latter compound, there are four different N—H···O hydrogen bonds excluding those between 4-pyridone and water molecules. The difference between the averages of the N···O bond distances in the hydrated and anhydrous 4-pyridone is significant at the 3σ confidence limit, while the difference between the N—H···O angles in both forms of 4-pyridone is not significant. The average of these angles in hydrated 4-pyridone is 165°.

Along with similarities in packing motifs between the monoclinic and orthorhombic 4-pyridone polymorphs there is one difference. The N—H···O hydrogen-bonded chains running in the same direction are closer in the monoclinic polymorph than in the orthorhombic one. The distance between the centres of the hydrogen bonds from the adjacent chains is ca 3.56 Å in (I)-M and ca 3.69 Å in (I)-O. The shortest contact between the centres of the hydrogen bonds from two adjacent chains running in opposite directions is ca 4 Å in both polymorphs. This increase of the distance between the neighbouring hydrogen bonds in orthorhombic 4-pyridone is probably the cause of the observed differences between the IR spectra of the two polymorphs of anhydrous 4-pyridone.

Related literature

For related literature, see: Allen (2002); Bernstein et al. (1995); Deng et al. (2005); Desiraju & Steiner (1999); Englert & Schiffers (2006); Etter et al. (1990); Flakus & Michta (2004); Flakus & Tyl (2008); Flakus et al. (2002); Gao et al. (2004); Hwang et al. (1980); Jones (2001); Kettmann et al. (2001); Motherwell et al. (1999); Muthu & Vittal (2004); Smith (1979); Takahata et al. (2007); Yeates (2008).

S2. Experimental

Single crystals for X-ray analysis were obtained by dissolving anhydrous 4-pyridone (from Sigma–Aldrich) in anhydrous ethanol. The solvent was allowed to evaporate slowly in a dry air-tight glass container over a period of three weeks at room temperature. Crystals suitable for X-ray diffraction were selected directly from the sample, where crystals from both phases appeared simultaneously.

S3. Refinement

H atoms that take part in hydrogen bonding were located in a difference Fourier map and their positional parameters were refined freely (refined bond lengths are given in Tables 2 and 4). The remaining aromatic H atoms were treated as riding on their parent C atoms (C—H = 0.95 Å). All H atoms were assigned U_iso values equal to 1.2U_eq of the parent C or N atom, except for atoms H2N in (I)-M and H1N in (I)-O, for which the U_iso(H) values were refined. [Please check highlighted changes made in accordance with data in CIF.]

Computing details

For both compounds, data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis RED (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2003) and Mercury (Macrae et al., 2006); software used to prepare material for publication: publCIF (Westrip, 2008).

Figures

	Fig. 1. A view of the two independent molecules of (I)-M, showing the atom and molecule numbering schemes. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. A view of the two independent molecules of (I)-O, showing the atom and molecule numbering schemes. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 3. The packing of (I)-M viewed along the b axis. Molecules have been coloured by symmetry equivalence.
	Fig. 4. The packing of (I)-O viewed along the a axis. Molecules have been coloured by symmetry equivalence.
	Fig. 5. Part of the crystal structure of (I)-M, viewed along the a axis, showing the C2^2(12) chains and the R6^5(28) ring formed via three types of hydrogen bonds. [Symmetry codes: (i) x, y + 1, z; (ii) x, -y + 1, z - 1/2.]
	Fig. 6. Part of the crystal structure of (I)-O, viewed along the c axis, showing the C2^2(12) chains and the R6^5(28) ring formed via three types of hydrogen bonds. [Symmetry codes: (i) x + 1, y, z; (ii) -x + 3/2, y - 1/2, z.]

(IM) 4-pyridone

Crystal data

C5H5NO	F(000) = 800
Mr = 95.10	Dx = 1.356 Mg m^−3
Monoclinic, C2/c	Melting point: 423 K
Hall symbol: -C 2yc	Mo Kα radiation, λ = 0.71073 Å
a = 15.137 (6) Å	Cell parameters from 7267 reflections
b = 11.966 (2) Å	θ = 2.8–34.4°
c = 11.168 (2) Å	µ = 0.10 mm^−1
β = 112.90 (2)°	T = 100 K
V = 1863.4 (9) Å^3	Polyhedron, colourless
Z = 16	0.4 × 0.27 × 0.26 mm

Data collection

Oxford Diffraction KM-4 diffractometer with Sapphire3 CCD detector	1452 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.016
Graphite monochromator	θmax = 25.1°, θmin = 2.9°
ω–scan	h = −17→18
5978 measured reflections	k = −14→7
1633 independent 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)] = 0.065	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.176	H atoms treated by a mixture of independent and constrained refinement
S = 1.00	w = 1/[σ^2(Fo^2) + (0.1512P)^2 + 0.7892P] where P = (Fo^2 + 2Fc^2)/3
1633 reflections	(Δ/σ)max = 0.001
137 parameters	Δρmax = 0.72 e Å^−3
0 restraints	Δρmin = −0.26 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
O1	0.40132 (9)	−0.11095 (9)	0.06803 (11)	0.0211 (4)
N1	0.36797 (10)	0.19648 (12)	0.20224 (14)	0.0192 (4)
C1	0.40723 (12)	0.18618 (13)	0.11241 (16)	0.0197 (5)
H1	0.4281	0.2515	0.0826	0.024*
C2	0.41757 (12)	0.08562 (14)	0.06392 (16)	0.0193 (4)
H2	0.4441	0.0817	−0.0003	0.023*
C3	0.38889 (12)	−0.01500 (13)	0.10852 (16)	0.0165 (4)
C4	0.34675 (12)	0.00021 (13)	0.20234 (16)	0.0159 (4)
H4	0.3242	−0.0628	0.2338	0.019*
C5	0.33884 (11)	0.10428 (14)	0.24675 (16)	0.0187 (4)
H5	0.3122	0.1123	0.3105	0.022*
H1N	0.3700 (15)	0.2660 (18)	0.240 (2)	0.022*
O2	0.38881 (10)	0.38868 (9)	0.32945 (12)	0.0255 (4)
N2	0.37176 (10)	0.69672 (12)	0.16555 (14)	0.0187 (4)
C6	0.33962 (12)	0.60572 (13)	0.08866 (16)	0.0186 (4)
H6	0.3135 (14)	0.6223 (16)	−0.0069 (19)	0.022*
C7	0.34294 (12)	0.50180 (13)	0.13995 (16)	0.0158 (4)
H7	0.3186	0.4398	0.0836	0.019*
C8	0.38264 (12)	0.48475 (13)	0.27772 (17)	0.0174 (4)
C9	0.41531 (12)	0.58457 (13)	0.35407 (16)	0.0183 (4)
H9	0.4412	0.5798	0.4462	0.022*
C10	0.40964 (12)	0.68468 (13)	0.29640 (16)	0.0194 (5)
H10	0.4330	0.7489	0.3493	0.023*
H2N	0.377 (2)	0.768 (2)	0.130 (3)	0.048 (7)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0309 (8)	0.0131 (7)	0.0214 (7)	0.0014 (5)	0.0124 (6)	−0.0005 (4)
N1	0.0225 (8)	0.0142 (8)	0.0209 (9)	0.0012 (5)	0.0083 (6)	−0.0010 (5)
C1	0.0242 (9)	0.0140 (9)	0.0212 (10)	0.0002 (6)	0.0091 (7)	0.0038 (6)
C2	0.0255 (9)	0.0178 (9)	0.0164 (9)	−0.0019 (7)	0.0101 (7)	0.0006 (6)
C3	0.0152 (8)	0.0162 (8)	0.0145 (9)	−0.0010 (6)	0.0018 (7)	−0.0007 (6)
C4	0.0152 (9)	0.0145 (9)	0.0168 (9)	−0.0025 (6)	0.0048 (7)	0.0016 (6)
C5	0.0177 (9)	0.0217 (9)	0.0174 (9)	0.0001 (6)	0.0076 (7)	0.0009 (6)
O2	0.0429 (8)	0.0130 (7)	0.0232 (8)	0.0034 (5)	0.0158 (6)	0.0027 (5)
N2	0.0216 (8)	0.0144 (8)	0.0208 (8)	0.0001 (5)	0.0091 (6)	0.0017 (5)
C6	0.0184 (9)	0.0213 (9)	0.0160 (9)	0.0025 (6)	0.0065 (7)	−0.0008 (6)
C7	0.0156 (9)	0.0128 (8)	0.0183 (9)	−0.0013 (6)	0.0059 (7)	−0.0039 (6)
C8	0.0187 (9)	0.0161 (9)	0.0198 (10)	0.0034 (6)	0.0099 (7)	0.0009 (6)
C9	0.0209 (9)	0.0185 (9)	0.0141 (8)	−0.0006 (6)	0.0051 (7)	−0.0021 (6)
C10	0.0215 (9)	0.0161 (9)	0.0206 (9)	0.0004 (6)	0.0082 (7)	−0.0028 (6)

Geometric parameters (Å, º)

O1—C3	1.2745 (19)	O2—C8	1.2736 (19)
N1—C5	1.353 (2)	N2—C10	1.354 (2)
N1—C1	1.356 (2)	N2—C6	1.354 (2)
N1—H1N	0.93 (2)	N2—H2N	0.96 (3)
C1—C2	1.353 (2)	C6—C7	1.362 (2)
C1—H1	0.9500	C6—H6	1.003 (19)
C2—C3	1.433 (2)	C7—C8	1.432 (2)
C2—H2	0.9500	C7—H7	0.9500
C3—C4	1.435 (2)	C8—C9	1.439 (2)
C4—C5	1.363 (2)	C9—C10	1.347 (2)
C4—H4	0.9500	C9—H9	0.9500
C5—H5	0.9500	C10—H10	0.9500
C5—N1—C1	119.81 (14)	C10—N2—C6	119.71 (14)
C5—N1—H1N	121.3 (13)	C10—N2—H2N	118.0 (16)
C1—N1—H1N	118.3 (13)	C6—N2—H2N	121.6 (16)
C2—C1—N1	121.95 (15)	N2—C6—C7	121.47 (15)
C2—C1—H1	119.0	N2—C6—H6	114.3 (11)
N1—C1—H1	119.0	C7—C6—H6	124.2 (11)
C1—C2—C3	120.66 (15)	C6—C7—C8	120.89 (14)
C1—C2—H2	119.7	C6—C7—H7	119.6
C3—C2—H2	119.7	C8—C7—H7	119.6
O1—C3—C2	121.79 (15)	O2—C8—C7	122.82 (15)
O1—C3—C4	122.85 (14)	O2—C8—C9	122.21 (15)
C2—C3—C4	115.35 (14)	C7—C8—C9	114.97 (14)
C5—C4—C3	120.58 (14)	C10—C9—C8	120.78 (15)
C5—C4—H4	119.7	C10—C9—H9	119.6
C3—C4—H4	119.7	C8—C9—H9	119.6
N1—C5—C4	121.62 (15)	C9—C10—N2	122.15 (15)
N1—C5—H5	119.2	C9—C10—H10	118.9
C4—C5—H5	119.2	N2—C10—H10	118.9
C5—N1—C1—C2	0.7 (3)	C6—C7—C8—O2	−178.57 (16)
N1—C1—C2—C3	−1.4 (3)	C6—C7—C8—C9	1.4 (2)
C1—C2—C3—O1	−177.24 (16)	O2—C8—C9—C10	178.60 (16)
C1—C2—C3—C4	2.0 (2)	C7—C8—C9—C10	−1.4 (2)
O1—C3—C4—C5	177.12 (16)	C8—C9—C10—N2	1.3 (3)
C2—C3—C4—C5	−2.1 (2)	C6—N2—C10—C9	−1.1 (3)
C1—N1—C5—C4	−0.8 (3)	C4—C5—N1—H1N	−171.8 (15)
C3—C4—C5—N1	1.6 (3)	C2—C1—N1—H1N	172.0 (15)
C10—N2—C6—C7	1.1 (2)	C9—C10—N2—H2N	−172.3 (19)
N2—C6—C7—C8	−1.3 (2)	C7—C6—N2—H2N	172 (2)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N···O2	0.93 (2)	1.73 (2)	2.6567 (19)	172 (2)
N2—H2N···O1^i	0.96 (3)	1.71 (3)	2.6575 (18)	172 (3)
C6—H6···O2^ii	1.003 (19)	2.506 (19)	3.258 (2)	131.6 (14)

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

(IO) 4-pyridone

Crystal data

C5H5NO	Dx = 1.363 Mg m^−3
Mr = 95.10	Melting point: 423 K
Orthorhombic, Pbca	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ac 2ab	Cell parameters from 9088 reflections
a = 11.953 (2) Å	θ = 3.4–34.5°
b = 11.146 (2) Å	µ = 0.10 mm^−1
c = 13.914 (3) Å	T = 100 K
V = 1853.7 (6) Å^3	Polyhedron, colourless
Z = 16	0.50 × 0.34 × 0.16 mm
F(000) = 800

Data collection

Oxford Diffraction KM-4 diffractometer with Sapphire3 CCD detector	1356 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.018
Graphite monochromator	θmax = 25.0°, θmin = 3.4°
ω–scan	h = −14→7
11099 measured reflections	k = −13→13
1626 independent reflections	l = −16→16

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)] = 0.037	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.111	H atoms treated by a mixture of independent and constrained refinement
S = 1.00	w = 1/[σ^2(Fo^2) + (0.0751P)^2 + 0.4363P] where P = (Fo^2 + 2Fc^2)/3
1626 reflections	(Δ/σ)max < 0.001
137 parameters	Δρmax = 0.32 e Å^−3
0 restraints	Δρmin = −0.24 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
O1	0.13937 (7)	−0.01164 (8)	0.34924 (7)	0.0211 (3)
N1	0.44692 (9)	0.13953 (10)	0.38343 (8)	0.0185 (3)
C1	0.35485 (10)	0.19967 (11)	0.41182 (9)	0.0178 (3)
H1	0.3629	0.2778	0.4381	0.021*
C2	0.25087 (10)	0.15155 (11)	0.40381 (8)	0.0165 (3)
H2	0.1879	0.1955	0.4262	0.020*
C3	0.23503 (11)	0.03523 (11)	0.36199 (9)	0.0166 (3)
C4	0.33592 (10)	−0.02483 (11)	0.33384 (9)	0.0188 (3)
H4	0.3320	−0.1033	0.3073	0.023*
C5	0.43665 (11)	0.02877 (11)	0.34459 (9)	0.0197 (3)
H5	0.5021	−0.0125	0.3243	0.024*
H1N	0.5112 (15)	0.1764 (15)	0.3814 (11)	0.029 (4)*
O2	0.63864 (7)	0.25582 (8)	0.36014 (7)	0.0238 (3)
N2	0.94663 (9)	0.10088 (9)	0.37745 (8)	0.0179 (3)
H2N	1.0137 (14)	0.0645 (14)	0.3716 (10)	0.021*
C6	0.85578 (10)	0.04119 (11)	0.40966 (9)	0.0176 (3)
H6	0.8702 (11)	−0.0376 (13)	0.4352 (9)	0.021*
C7	0.75210 (10)	0.09061 (11)	0.40650 (8)	0.0169 (3)
H7	0.6902	0.0469	0.4312	0.020*
C8	0.73447 (10)	0.20740 (11)	0.36662 (9)	0.0165 (3)
C9	0.83359 (10)	0.26629 (11)	0.33298 (9)	0.0181 (3)
H9	0.8284	0.3445	0.3063	0.022*
C10	0.93471 (10)	0.21169 (12)	0.33879 (9)	0.0191 (3)
H10	0.9989	0.2522	0.3151	0.023*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
O1	0.0133 (5)	0.0176 (5)	0.0323 (6)	−0.0010 (4)	−0.0009 (4)	−0.0022 (4)
N1	0.0152 (6)	0.0180 (6)	0.0223 (6)	−0.0021 (4)	−0.0010 (4)	−0.0004 (4)
C1	0.0211 (7)	0.0143 (6)	0.0181 (6)	0.0011 (5)	0.0000 (5)	−0.0008 (5)
C2	0.0159 (7)	0.0151 (6)	0.0184 (6)	0.0019 (5)	0.0027 (5)	0.0004 (5)
C3	0.0167 (6)	0.0163 (6)	0.0169 (6)	0.0002 (5)	0.0000 (5)	0.0035 (5)
C4	0.0187 (7)	0.0137 (7)	0.0242 (7)	0.0026 (5)	0.0002 (5)	−0.0012 (5)
C5	0.0165 (7)	0.0188 (7)	0.0238 (7)	0.0040 (5)	0.0001 (5)	−0.0010 (5)
O2	0.0137 (5)	0.0179 (5)	0.0398 (6)	0.0009 (4)	−0.0014 (4)	0.0002 (4)
N2	0.0141 (6)	0.0172 (6)	0.0223 (6)	0.0020 (4)	−0.0008 (4)	−0.0020 (4)
C6	0.0208 (7)	0.0134 (6)	0.0187 (7)	−0.0015 (5)	−0.0018 (5)	−0.0007 (5)
C7	0.0165 (7)	0.0158 (6)	0.0184 (7)	−0.0039 (5)	0.0013 (5)	−0.0001 (5)
C8	0.0153 (6)	0.0154 (6)	0.0189 (6)	0.0002 (5)	−0.0027 (5)	−0.0036 (5)
C9	0.0193 (7)	0.0134 (6)	0.0215 (7)	−0.0015 (5)	−0.0015 (5)	0.0019 (5)
C10	0.0158 (6)	0.0201 (7)	0.0213 (7)	−0.0049 (5)	0.0002 (5)	−0.0010 (5)

Geometric parameters (Å, º)

O1—C3	1.2696 (15)	O2—C8	1.2695 (15)
N1—C1	1.3478 (16)	N2—C6	1.3501 (16)
N1—C5	1.3532 (17)	N2—C10	1.3547 (17)
N1—H1N	0.871 (19)	N2—H2N	0.902 (17)
C1—C2	1.3582 (17)	C6—C7	1.3568 (17)
C1—H1	0.9500	C6—H6	0.963 (14)
C2—C3	1.4337 (18)	C7—C8	1.4307 (18)
C2—H2	0.9500	C7—H7	0.9500
C3—C4	1.4339 (18)	C8—C9	1.4331 (18)
C4—C5	1.3524 (18)	C9—C10	1.3556 (18)
C4—H4	0.9500	C9—H9	0.9500
C5—H5	0.9500	C10—H10	0.9500
C1—N1—C5	119.78 (11)	C6—N2—C10	119.76 (11)
C1—N1—H1N	119.7 (11)	C6—N2—H2N	121.6 (10)
C5—N1—H1N	119.8 (11)	C10—N2—H2N	117.9 (10)
N1—C1—C2	121.79 (11)	N2—C6—C7	121.59 (11)
N1—C1—H1	119.1	N2—C6—H6	115.4 (8)
C2—C1—H1	119.1	C7—C6—H6	123.0 (8)
C1—C2—C3	120.75 (11)	C6—C7—C8	121.10 (11)
C1—C2—H2	119.6	C6—C7—H7	119.5
C3—C2—H2	119.6	C8—C7—H7	119.4
O1—C3—C2	123.22 (11)	O2—C8—C7	123.19 (11)
O1—C3—C4	121.82 (11)	O2—C8—C9	121.87 (11)
C2—C3—C4	114.96 (11)	C7—C8—C9	114.94 (11)
C5—C4—C3	120.82 (12)	C10—C9—C8	120.80 (12)
C5—C4—H4	119.6	C10—C9—H9	119.6
C3—C4—H4	119.6	C8—C9—H9	119.6
C4—C5—N1	121.87 (11)	N2—C10—C9	121.79 (12)
C4—C5—H5	119.1	N2—C10—H10	119.1
N1—C5—H5	119.1	C9—C10—H10	119.1
C5—N1—C1—C2	0.90 (19)	C6—C7—C8—O2	178.27 (12)
N1—C1—C2—C3	−1.76 (19)	C6—C7—C8—C9	−1.04 (17)
C1—C2—C3—O1	−177.01 (12)	O2—C8—C9—C10	−178.57 (12)
C1—C2—C3—C4	2.14 (17)	C7—C8—C9—C10	0.74 (18)
O1—C3—C4—C5	177.34 (12)	C6—N2—C10—C9	1.31 (19)
C2—C3—C4—C5	−1.82 (18)	C8—C9—C10—N2	−0.91 (19)
C3—C4—C5—N1	1.10 (19)	C4—C5—N1—H1N	−170.5 (12)
C1—N1—C5—C4	−0.56 (19)	C2—C1—N1—H1N	170.9 (12)
C10—N2—C6—C7	−1.61 (18)	C9—C10—N2—H2N	171.2 (10)
N2—C6—C7—C8	1.51 (19)	C7—C6—N2—H2N	−171.1 (11)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1N···O2	0.871 (19)	1.787 (19)	2.6526 (14)	172.0 (15)
N2—H2N···O1^i	0.902 (17)	1.754 (17)	2.6523 (14)	174.3 (14)
C6—H6···O2^ii	0.963 (14)	2.530 (14)	3.2552 (16)	132.1 (10)

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