Pyrimidin-2-amine–1-phenyl­cyclo­pentane-1-carb­oxy­lic acid (1/1)

He, G.; Aitipamula, S.; Chow, P.S.; Tan, R.B.H.

doi:10.1107/S1600536811003667

organic compounds

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ISSN: 2056-9890

Volume 67| Part 3| March 2011| Pages o552-o553

doi:10.1107/S1600536811003667

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Pyrimidin-2-amine–1-phenylcyclopentane-1-carboxylic acid (1/1)

Guangwen He,^a ^* Srinivasulu Aitipamula,^a Pui Shan Chow ^a and Reginald B. H. Tan ^a,^b ^*

^aInstitute of Chemical and Engineering Sciences, A*STAR (Agency for Science, Technology and Research), 1 Pesek Road, Jurong Island, Singapore 627833, and ^bDepartment of Chemical & Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, Singapore 117576
^*Correspondence e-mail: he_guangwen@ices.a-star.edu.sg, reginald_tan@ices.a-star.edu.sg

(Received 6 January 2011; accepted 28 January 2011; online 2 February 2011)

In the crystal structure of the title co-crystal, C₄H₅N₃·C₁₂H₁₄O₂, the components are linked by N—H⋯O and O—H⋯N hydrogen bonds. Self-assembly of these dimeric units results in a four-component supramolecular unit featuring a homosynthon between two molecules of the pyrimidin-2-amine involving two N—H⋯O hydrogen bonds, and two heterosynthons between each one molecule of pyrimidin-2-amine and 1-phenylcyclopentane-1-carboxylic acid involving N—H⋯O and O—H⋯N hydrogen bonds.

Related literature

For the structure of pyrimidin-2-amine, see: Scheinbeim & Schempp (1976 ) and for the structure of 1-phenylcyclopentane-1-carboxylic acid, see: Margulis (1975 ). For molecular co-crystals of pyrimidin-2-amine, see: Serafin & Wheeler (2007 ); Shan et al. (2002 ); Goswami et al. (1999a ,b , 2000 ); Chinnakali et al. (1999 ); Lynch et al. (1997 ). For a salt of 2-aminopyridine and 1-phenyl-1-cyclopropanecarboxylic acid, see: He et al. (2010 ). For a recent screening study for co-crystal and salt formation using pulse-gradient spin–echo nuclear magnetic resonance, see: He et al. (2009 ).

Experimental

Crystal data

C₄H₅N₃·C₁₂H₁₄O₂
M_r = 285.34
Monoclinic, P 2₁ /n
a = 9.1461 (18) Å
b = 10.490 (2) Å
c = 15.474 (3) Å
β = 98.14 (3)°
V = 1469.7 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 110 K
0.44 × 0.44 × 0.22 mm

Data collection

Rigaku Saturn 70 CCD area-detector diffractometer
Absorption correction: multi-scan (Blessing, 1995 ) T_min = 0.963, T_max = 0.981
20335 measured reflections
3641 independent reflections
3516 reflections with I > 2σ(I)
R_int = 0.036

Refinement

R[F² > 2σ(F²)] = 0.068
wR(F²) = 0.178
S = 1.21
3641 reflections
202 parameters
1 restraint
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.28 e Å⁻³
Δρ_min = −0.27 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H6⋯N1	0.87 (2)	1.79 (2)	2.653 (2)	173 (3)
N3—H5⋯O1	0.90 (3)	2.08 (3)	2.966 (2)	168 (2)
N3—H1⋯N2ⁱ	0.88 (3)	2.13 (3)	3.006 (2)	173 (2)
Symmetry code: (i) -x+1, -y+1, -z+1.

Data collection: CrystalClear (Rigaku, 2007 ); cell refinement: CrystalClear; data reduction: CrystalClear; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001 ); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811003667/ng5101sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811003667/ng5101Isup2.hkl

checkCIF report

Comment top

An analysis of the crystal structure of pyrimidin-2-amine reveals that it forms a homosynthon (I) involving two N–H···N hydrogen bonds (Scheinbeim and Schempp, 1976). However, when it is cocrystallized with the molecules possessing at least one carboxylic acid group in the structure, it forms a pyrimidin-2-amine–carboxylic acid supramolecular heterosynthon (II) (Fig. 1) involving two hydrogen bonds, namely N–H···O and O–H···N. These strong hydrogen bonds are preferred over potential alternative arrangements and play a significant role in structure-directing (Shan et al., 2002). We have chosen pyrimidin-2-amine and 1-phenylcyclopentane-1-carboxylic acid for cocrystallization experiment as an extension work to our previous study on screening for molecular cocrystals and salts (He et al., 2009).

The crystal structure of the title cocrystal contains one molecule of pyrimidin-2-amine and one molecule of 1-phenylcyclopentane-1-carboxylic acid in the crystallographic asymmetric unit (Fig. 2). The identity of the cocrystal was confirmed by Fourier Transform Infrared (FT—IR) spectrum which showed carboxylic acid O—H stretching band at 3167 cm^-1 and carbonyl stretching band at 1685 cm^-1 (Fig. 3). Two pyrimidin-2-amine molecules that are related by an inversion center form the synthon I involving N–H···O (N···O = 3.006 (2) Å) hydrogen bonds. Two 1-phenylcyclopentane-1-carboxylic acid molecules hydrogen bond to either side of the dimeric motif involving synthon II which is sustained by N–H···O (N···O = 2.966 (2) Å) and O–H···O (O···O = 2.653 (2) Å) hydrogen bonds and forms a four-component supramolecular unit (Fig. 4). These four-component supramolecular units self assemble in the crystal structure via several weak C–H···O interactions (Fig. 5).

Related literature top

For the structure of pyrimidin-2-amine, see: Scheinbeim & Schempp (1976) and for the structure of 1-phenylcyclopentane-1-carboxylic acid, see: Margulis (1975). For recent molecular co-crystals of pyrimidin-2-amine, see: Serafin & Wheeler (2007); Shan et al. (2002); Goswami et al. (1999a,b, 2000); Chinnakali et al. (1999); Lynch et al. (1997). For a salt of 2-aminopyridine and 1-phenyl-1-cyclopropanecarboxylic acid, see: He et al. (2010). For a recent screening study for co-crystal and salt formation using pulse-gradient spin–echo nuclear magnetic resonance, see: He et al. (2009).

Experimental top

0.0957 g (1 mmol) of pyrimidin-2-amine (Alfa Aesar, 99%) and 0.1909 g (1 mmol) of 1-phenylcyclopentane-1-carboxylic acid (Alfa Aesar, 98%) and were dissolved into 7.6 ml of ethyl acetate (Fisher Scientific, HPLC). Solution was then filtered through a 0.22µm PTFE filter. Filtered solution was finally sealed with Parafilm and small holes were made to allow solvent to slowly evaporate. The block-shaped crystal (0.44 × 0.44 × 0.22 mm) suitable for single-crystal X-ray diffraction (Rigaku Saturn 70 CCD area detector with Mo K_α radiation = 0.71073 Å at 50 kV and 40 mA) was collected after one day. Fourier Transform Infrared (FT—IR) experiments were performed using Bio-Rad spectrometer (FTS3000MX) to confirm whether the resulting molecular complex is a cocrystal or a salt.

Computing details top

Data collection: CrystalClear (Rigaku, 2007); cell refinement: CrystalClear (Rigaku, 2007); data reduction: CrystalClear (Rigaku, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top

	Fig. 1. pyrimidin-2-amine–pyrimidin-2-amine supramolecular homosynthon (I) and pyrimidin-2-amine–carboxylic acid supramolecular heterosynthon (II).
	Fig. 2. The molecular structures of pyrimidin-2-amine and 1-phenyl-1-cyclopropentanecarboxylic acid, with atom labels and 50% probability displacement ellipsoids for non-H atoms.
	Fig. 3. F T—IR spectra for pyrimidin-2-amine, 1-phenylcyclopentane-1-carboxylic acid and the 1/1 cocrystal of them, respectively.
	Fig. 4. A four-component supramolecular unit that features N–H···O and O–H···N heterosynthon interactions, and O–H···O homosynthon interaction in the crystal structure of the title cocrystal.
	Fig. 5. Part of the crystal structure of the title cocrystal, showing the arrangement of the four-component supramolecular units.

Pyrimidin-2-amine–1-phenylcyclopentane-1-carboxylic acid (1/1) top

Crystal data top

C₄H₅N₃·C₁₂H₁₄O₂	F(000) = 608
M_r = 285.34	D_x = 1.290 Mg m⁻³
Monoclinic, P2₁/n	Mo Kα radiation, λ = 0.71073 Å
a = 9.1461 (18) Å	Cell parameters from 4896 reflections
b = 10.490 (2) Å	θ = 1.9–31.1°
c = 15.474 (3) Å	µ = 0.09 mm⁻¹
β = 98.14 (3)°	T = 110 K
V = 1469.7 (5) Å³	Block, colorless
Z = 4	0.44 × 0.44 × 0.22 mm

Data collection top

Rigaku Saturn 70 CCD area-detector diffractometer	3641 independent reflections
Radiation source: fine-focus sealed tube	3516 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.036
ω scans	θ_max = 28.3°, θ_min = 2.4°
Absorption correction: multi-scan (Blessing, 1995)	h = −12→12
T_min = 0.963, T_max = 0.981	k = −13→13
20335 measured reflections	l = −20→20

Refinement top

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)] = 0.068	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.178	H atoms treated by a mixture of independent and constrained refinement
S = 1.21	w = 1/[σ²(F_o²) + (0.0804P)² + 0.5855P] where P = (F_o² + 2F_c²)/3
3641 reflections	(Δ/σ)_max < 0.001
202 parameters	Δρ_max = 0.28 e Å⁻³
1 restraint	Δρ_min = −0.27 e Å⁻³

Crystal data top

C₄H₅N₃·C₁₂H₁₄O₂	V = 1469.7 (5) Å³
M_r = 285.34	Z = 4
Monoclinic, P2₁/n	Mo Kα radiation
a = 9.1461 (18) Å	µ = 0.09 mm⁻¹
b = 10.490 (2) Å	T = 110 K
c = 15.474 (3) Å	0.44 × 0.44 × 0.22 mm
β = 98.14 (3)°

Data collection top

Rigaku Saturn 70 CCD area-detector diffractometer	3641 independent reflections
Absorption correction: multi-scan (Blessing, 1995)	3516 reflections with I > 2σ(I)
T_min = 0.963, T_max = 0.981	R_int = 0.036
20335 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.068	1 restraint
wR(F²) = 0.178	H atoms treated by a mixture of independent and constrained refinement
S = 1.21	Δρ_max = 0.28 e Å⁻³
3641 reflections	Δρ_min = −0.27 e Å⁻³
202 parameters

Special details top

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 (Å²) top

	x	y	z	U_iso*/U_eq
O2	0.04632 (14)	0.55094 (13)	0.70052 (8)	0.0344 (3)
O1	0.22224 (15)	0.40633 (14)	0.73866 (9)	0.0397 (3)
C16	0.12059 (18)	0.47154 (16)	0.75641 (11)	0.0281 (3)
C6	−0.09084 (18)	0.42117 (16)	0.83708 (10)	0.0273 (3)
C5	0.06701 (18)	0.47220 (17)	0.84621 (11)	0.0289 (4)
C8	−0.35533 (19)	0.45531 (18)	0.80273 (12)	0.0337 (4)
H8	−0.4356	0.5110	0.7842	0.040*
C12	0.17880 (19)	0.3999 (2)	0.91211 (12)	0.0396 (4)
H12A	0.2180	0.3247	0.8843	0.047*
H12B	0.1319	0.3709	0.9625	0.047*
C7	−0.21065 (18)	0.50062 (17)	0.81043 (11)	0.0305 (4)
H7	−0.1936	0.5873	0.7972	0.037*
C10	−0.2643 (2)	0.24866 (18)	0.84809 (12)	0.0362 (4)
H10	−0.2821	0.1620	0.8610	0.043*
C11	−0.1195 (2)	0.29396 (17)	0.85543 (12)	0.0332 (4)
H11	−0.0395	0.2376	0.8731	0.040*
C15	0.0807 (2)	0.6105 (2)	0.88196 (13)	0.0380 (4)
H15A	0.0410	0.6727	0.8365	0.046*
H15B	0.0279	0.6204	0.9332	0.046*
C9	−0.3820 (2)	0.32934 (19)	0.82208 (12)	0.0354 (4)
H9	−0.4805	0.2985	0.8175	0.042*
C13	0.3039 (2)	0.4964 (3)	0.94177 (14)	0.0523 (6)
H13A	0.3269	0.4975	1.0062	0.063*
H13B	0.3945	0.4731	0.9172	0.063*
C14	0.2473 (2)	0.6273 (2)	0.90771 (16)	0.0517 (6)
H14A	0.2684	0.6930	0.9537	0.062*
H14B	0.2944	0.6530	0.8566	0.062*
H6	0.082 (3)	0.557 (3)	0.6516 (13)	0.066 (8)*
C2	0.24306 (19)	0.66091 (17)	0.39920 (12)	0.0318 (4)
H2	0.2760	0.6860	0.3462	0.038*
N3	0.36606 (18)	0.47957 (17)	0.58582 (11)	0.0391 (4)
N1	0.14713 (15)	0.58831 (14)	0.54997 (9)	0.0299 (3)
N2	0.33123 (16)	0.58740 (14)	0.45437 (10)	0.0314 (3)
C3	0.1056 (2)	0.70251 (18)	0.41554 (12)	0.0345 (4)
H3	0.0445	0.7554	0.3757	0.041*
C4	0.06304 (19)	0.66250 (18)	0.49318 (12)	0.0346 (4)
H4	−0.0304	0.6890	0.5068	0.041*
H5	0.331 (3)	0.447 (2)	0.6325 (17)	0.051 (7)*
C1	0.27973 (18)	0.55295 (16)	0.52886 (11)	0.0285 (3)
H1	0.451 (3)	0.454 (2)	0.5716 (16)	0.051 (7)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O2	0.0317 (6)	0.0434 (7)	0.0300 (6)	0.0106 (5)	0.0113 (5)	0.0085 (5)
O1	0.0385 (7)	0.0472 (8)	0.0361 (7)	0.0150 (6)	0.0146 (6)	0.0093 (6)
C16	0.0247 (7)	0.0303 (8)	0.0297 (8)	−0.0005 (6)	0.0056 (6)	0.0009 (6)
C6	0.0259 (7)	0.0322 (8)	0.0249 (8)	−0.0013 (6)	0.0071 (6)	−0.0011 (6)
C5	0.0226 (7)	0.0380 (9)	0.0268 (8)	−0.0023 (6)	0.0055 (6)	−0.0003 (6)
C8	0.0249 (8)	0.0410 (9)	0.0361 (9)	0.0003 (7)	0.0070 (7)	−0.0050 (7)
C12	0.0264 (8)	0.0626 (13)	0.0297 (9)	0.0001 (8)	0.0039 (7)	0.0093 (8)
C7	0.0279 (8)	0.0307 (8)	0.0336 (9)	−0.0016 (6)	0.0074 (6)	−0.0031 (7)
C10	0.0408 (10)	0.0329 (9)	0.0364 (9)	−0.0097 (7)	0.0102 (7)	−0.0021 (7)
C11	0.0331 (9)	0.0333 (9)	0.0336 (9)	0.0005 (7)	0.0058 (7)	0.0018 (7)
C15	0.0305 (9)	0.0449 (10)	0.0402 (10)	−0.0110 (7)	0.0106 (7)	−0.0113 (8)
C9	0.0303 (8)	0.0436 (10)	0.0339 (9)	−0.0108 (7)	0.0104 (7)	−0.0084 (7)
C13	0.0274 (9)	0.0954 (18)	0.0335 (10)	−0.0092 (10)	0.0018 (8)	−0.0042 (11)
C14	0.0357 (10)	0.0700 (15)	0.0500 (12)	−0.0211 (10)	0.0082 (9)	−0.0156 (11)
C2	0.0328 (8)	0.0344 (9)	0.0292 (8)	0.0018 (7)	0.0077 (6)	0.0018 (7)
N3	0.0306 (8)	0.0513 (10)	0.0383 (9)	0.0149 (7)	0.0150 (7)	0.0168 (7)
N1	0.0238 (6)	0.0371 (8)	0.0294 (7)	0.0027 (5)	0.0065 (5)	0.0024 (6)
N2	0.0294 (7)	0.0340 (7)	0.0320 (8)	0.0035 (6)	0.0087 (6)	0.0040 (6)
C3	0.0304 (8)	0.0403 (10)	0.0326 (9)	0.0052 (7)	0.0045 (7)	0.0057 (7)
C4	0.0257 (8)	0.0437 (10)	0.0348 (9)	0.0070 (7)	0.0060 (6)	0.0041 (7)
C1	0.0256 (8)	0.0291 (8)	0.0316 (8)	0.0016 (6)	0.0066 (6)	0.0010 (6)

Geometric parameters (Å, º) top

O2—C16	1.318 (2)	C15—H15A	0.9900
O2—H6	0.869 (17)	C15—H15B	0.9900
O1—C16	1.217 (2)	C9—H9	0.9500
C16—C5	1.537 (2)	C13—C14	1.535 (4)
C6—C7	1.392 (2)	C13—H13A	0.9900
C6—C11	1.397 (2)	C13—H13B	0.9900
C6—C5	1.527 (2)	C14—H14A	0.9900
C5—C12	1.538 (2)	C14—H14B	0.9900
C5—C15	1.551 (3)	C2—N2	1.334 (2)
C8—C9	1.384 (3)	C2—C3	1.387 (2)
C8—C7	1.395 (2)	C2—H2	0.9500
C8—H8	0.9500	N3—C1	1.340 (2)
C12—C13	1.548 (3)	N3—H5	0.90 (3)
C12—H12A	0.9900	N3—H1	0.88 (3)
C12—H12B	0.9900	N1—C4	1.334 (2)
C7—H7	0.9500	N1—C1	1.352 (2)
C10—C9	1.384 (3)	N2—C1	1.355 (2)
C10—C11	1.397 (2)	C3—C4	1.380 (3)
C10—H10	0.9500	C3—H3	0.9500
C11—H11	0.9500	C4—H4	0.9500
C15—C14	1.530 (3)

C16—O2—H6	113.4 (19)	C5—C15—H15B	111.1
O1—C16—O2	123.13 (16)	H15A—C15—H15B	109.1
O1—C16—C5	123.93 (16)	C10—C9—C8	119.54 (16)
O2—C16—C5	112.93 (14)	C10—C9—H9	120.2
C7—C6—C11	118.03 (15)	C8—C9—H9	120.2
C7—C6—C5	120.77 (15)	C14—C13—C12	106.50 (16)
C11—C6—C5	121.20 (15)	C14—C13—H13A	110.4
C6—C5—C16	109.44 (13)	C12—C13—H13A	110.4
C6—C5—C12	114.81 (15)	C14—C13—H13B	110.4
C16—C5—C12	109.27 (14)	C12—C13—H13B	110.4
C6—C5—C15	112.84 (14)	H13A—C13—H13B	108.6
C16—C5—C15	107.86 (14)	C15—C14—C13	105.13 (18)
C12—C5—C15	102.24 (15)	C15—C14—H14A	110.7
C9—C8—C7	120.06 (17)	C13—C14—H14A	110.7
C9—C8—H8	120.0	C15—C14—H14B	110.7
C7—C8—H8	120.0	C13—C14—H14B	110.7
C5—C12—C13	105.58 (17)	H14A—C14—H14B	108.8
C5—C12—H12A	110.6	N2—C2—C3	123.13 (16)
C13—C12—H12A	110.6	N2—C2—H2	118.4
C5—C12—H12B	110.6	C3—C2—H2	118.4
C13—C12—H12B	110.6	C1—N3—H5	120.2 (16)
H12A—C12—H12B	108.8	C1—N3—H1	118.2 (16)
C6—C7—C8	121.24 (16)	H5—N3—H1	121 (2)
C6—C7—H7	119.4	C4—N1—C1	117.03 (15)
C8—C7—H7	119.4	C2—N2—C1	116.58 (15)
C9—C10—C11	120.36 (17)	C4—C3—C2	115.97 (16)
C9—C10—H10	119.8	C4—C3—H3	122.0
C11—C10—H10	119.8	C2—C3—H3	122.0
C10—C11—C6	120.76 (17)	N1—C4—C3	122.94 (16)
C10—C11—H11	119.6	N1—C4—H4	118.5
C6—C11—H11	119.6	C3—C4—H4	118.5
C14—C15—C5	103.19 (17)	N3—C1—N1	117.64 (16)
C14—C15—H15A	111.1	N3—C1—N2	118.00 (15)
C5—C15—H15A	111.1	N1—C1—N2	124.36 (16)
C14—C15—H15B	111.1

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H6···N1	0.87 (2)	1.79 (2)	2.653 (2)	173 (3)
N3—H5···O1	0.90 (3)	2.08 (3)	2.966 (2)	168 (2)
N3—H1···N2ⁱ	0.88 (3)	2.13 (3)	3.006 (2)	173 (2)

Symmetry code: (i) −x+1, −y+1, −z+1.

Experimental details

Crystal data
Chemical formula	C₄H₅N₃·C₁₂H₁₄O₂
M_r	285.34
Crystal system, space group	Monoclinic, P2₁/n
Temperature (K)	110
a, b, c (Å)	9.1461 (18), 10.490 (2), 15.474 (3)
β (°)	98.14 (3)
V (Å³)	1469.7 (5)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.09
Crystal size (mm)	0.44 × 0.44 × 0.22

Data collection
Diffractometer	Rigaku Saturn 70 CCD area-detector diffractometer
Absorption correction	Multi-scan (Blessing, 1995)
T_min, T_max	0.963, 0.981
No. of measured, independent and observed [I > 2σ(I)] reflections	20335, 3641, 3516
R_int	0.036
(sin θ/λ)_max (Å⁻¹)	0.667

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.068, 0.178, 1.21
No. of reflections	3641
No. of parameters	202
No. of restraints	1
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.28, −0.27

Computer programs: CrystalClear (Rigaku, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), X-SEED (Barbour, 2001).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H6···N1	0.869 (17)	1.788 (18)	2.653 (2)	173 (3)
N3—H5···O1	0.90 (3)	2.08 (3)	2.966 (2)	168 (2)
N3—H1···N2ⁱ	0.88 (3)	2.13 (3)	3.006 (2)	173 (2)

Symmetry code: (i) −x+1, −y+1, −z+1.

Acknowledgements

This work was supported by the Science and Engineering Research Council of A*STAR (Agency for Science, Technology and Research), Singapore.

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