2-Amino-4-methyl­pyridinium 2-carb­oxy­benzoate

Quah, C.K.; Hemamalini, M.; Fun, H.-K.

doi:10.1107/S1600536810025900

organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 66| Part 8| August 2010| Page o1932

https://doi.org/10.1107/S1600536810025900

Open

access

2-Amino-4-methylpyridinium 2-carboxybenzoate

Ching Kheng Quah,^a ‡ Madhukar Hemamalini ^a and Hoong-Kun Fun ^a ^*§

^aX-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia
^*Correspondence e-mail: hkfun@usm.my

(Received 30 June 2010; accepted 1 July 2010; online 7 July 2010)

In the title molecular salt, C₆H₉N₂⁺·C₈H₅O₄⁻, the anion is stabilized by an intramolecular O—H⋯O hydrogen bond, which generates an S(7) ring motif. In the crystal, the cations and anions are linked to form extended chains along [001] by O—H⋯O and N—H⋯O hydrogen bonds. Adjacent chains are crosslinked via C—H⋯O interactions into sheets lying parallel to (100).

Related literature

For substituted pyridines, see: Pozharski et al. (1997 ); Katritzky et al. (1996 ). For details of hydrogen bonding, see: Scheiner (1997 ); Jeffrey & Saenger (1991 ); Jeffrey (1997 ). For hydrogen-bond motifs, see: Bernstein et al. (1995 ). For related structures, see: Quah et al. (2008a ,b ,c ). For reference bond lengths, see: Allen et al. (1987 ). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986 ).

Experimental

Crystal data

C₆H₉N₂⁺·C₈H₅O₄⁻
M_r = 274.27
Monoclinic, P 2₁ /c
a = 13.0558 (15) Å
b = 6.9182 (8) Å
c = 14.2575 (17) Å
β = 90.218 (2)°
V = 1287.8 (3) Å³
Z = 4
Mo Kα radiation
μ = 0.11 mm⁻¹
T = 100 K
0.41 × 0.19 × 0.11 mm

Data collection

Bruker SMART APEXII DUO CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ) T_min = 0.958, T_max = 0.989
26319 measured reflections
3856 independent reflections
3332 reflections with I > 2σ(I)
R_int = 0.046

Refinement

R[F² > 2σ(F²)] = 0.047
wR(F²) = 0.131
S = 1.13
3856 reflections
233 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.41 e Å⁻³
Δρ_min = −0.33 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O2—H1O2⋯O3	0.86	1.57	2.4009 (14)	163
N1—H1N1⋯O4ⁱ	0.94 (2)	1.77 (2)	2.6919 (16)	169 (2)
N2—H1N2⋯O3ⁱ	0.89 (2)	2.11 (2)	2.9881 (16)	166.6 (19)
N2—H2N2⋯O1ⁱⁱ	0.86 (2)	2.06 (2)	2.8888 (16)	164.5 (19)
C5—H5A⋯O2ⁱⁱⁱ	0.953 (19)	2.532 (19)	3.4133 (17)	153.7 (16)
Symmetry codes: (i) x+1, y, z; (ii) -x+1, -y, -z+2; (iii) $[x+1, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ .

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Sheldrick, 2008 ); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ).

Supporting information

Crystal structure: contains datablocks global, I. DOI: https://doi.org/10.1107/S1600536810025900/hb5537sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810025900/hb5537Isup2.hkl

checkCIF report

Comment top

Pyridine and its derivatives play an important role in heterocyclic chemistry (Pozharski et al., 1997; Katritzky et al., 1996). They are often involved in hydrogen-bond interactions (Jeffrey & Saenger, 1991; Jeffrey, 1997; Scheiner, 1997). Since our aim is to study some interesting hydrogen-bonding interactions, the crystal structure of the title compound, (I), is presented here.

The asymmetric unit of the title compound contains one 2-amino-4-methylpyridinium cation and one 2-carboxybenzoate anion. A proton transfer from the carboxyl group of 2-carboxybenzoice acid to atom N1 of 2-amino-4-methylpyridinium resulted in the formation of ions. The bond lengths (Allen et al., 1987) and angles in the title compound (Fig. 1) are within normal ranges and comparable with the related structures (Quah et al., 2008a,b,c). The 2-amino-4-methylpyridinium cation is essentially planar, with the maximum deviation of 0.024 (1) Å for atom C2 and makes a dihedral angle of 19.56 (6)° with benzene (C7—C12) ring in 2-carboxybenzoate anion. The molecular structure is stabilized by an intramolecular O2—H1O2···O3 hydrogen bond which generates an S(7) ring motif (Bernstein et al., 1995).

In the solid state, the cations and anions are linked to form extended chains along [0 0 1] by O–H···O and N–H···O hydrogen bonds (Table 1). The adjacent chains are cross-linked via C5–H5A···O2 interactions into two-dimensional networks (Fig. 2) parallel to the (1 0 0).

Related literature top

For substituted pyridines, see: Pozharski et al. (1997); Katritzky et al. (1996). For details of hydrogen bonding, see: Scheiner (1997); Jeffrey & Saenger (1991); Jeffrey (1997). For hydrogen-bond motifs, see: Bernstein et al. (1995). For related structures, see: Quah et al. (2008a,b, c). For reference bond lengths, see: Allen et al. (1987). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986).

Experimental top

A hot methanol solution (20 ml) of 2-amino-4-methylpyridine (27 mg, Aldrich) and phthalic acid (41 mg, Merck) were mixed and warmed over a heating magnetic stirrer for a few minutes. The resulting solution was allowed to cool slowly at room temperature and colourless blocks of (I) appeared after a few days.

Structure description top

For substituted pyridines, see: Pozharski et al. (1997); Katritzky et al. (1996). For details of hydrogen bonding, see: Scheiner (1997); Jeffrey & Saenger (1991); Jeffrey (1997). For hydrogen-bond motifs, see: Bernstein et al. (1995). For related structures, see: Quah et al. (2008a,b, c). For reference bond lengths, see: Allen et al. (1987). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986).

Computing details top

Data collection: APEX2 (Bruker, 2009); cell refinement: SAINT (Bruker, 2009); data reduction: SAINT (Bruker, 2009); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top

	Fig. 1. The molecular structure of (I), showing 50% probability displacement ellipsoids for non-H atoms. The intramolecular hydrogen bond is shown in dashed line.
	Fig. 2. The crystal structure of (I) viewed along the b axis. H atoms not involved in intermolecular interactions (dashed lines) have been omitted for clarity.

2-Amino-4-methylpyridinium 2-carboxybenzoate top

Crystal data top

C₆H₉N₂⁺·C₈H₅O₄⁻	F(000) = 576
M_r = 274.27	D_x = 1.415 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 6320 reflections
a = 13.0558 (15) Å	θ = 2.9–30.3°
b = 6.9182 (8) Å	µ = 0.11 mm⁻¹
c = 14.2575 (17) Å	T = 100 K
β = 90.218 (2)°	Block, colourless
V = 1287.8 (3) Å³	0.41 × 0.19 × 0.11 mm
Z = 4

Data collection top

Bruker SMART APEXII DUO CCD diffractometer	3856 independent reflections
Radiation source: fine-focus sealed tube	3332 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.046
φ and ω scans	θ_max = 30.3°, θ_min = 2.9°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −18→18
T_min = 0.958, T_max = 0.989	k = −9→9
26319 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)] = 0.047	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.131	H atoms treated by a mixture of independent and constrained refinement
S = 1.13	w = 1/[σ²(F_o²) + (0.0537P)² + 0.7248P] where P = (F_o² + 2F_c²)/3
3856 reflections	(Δ/σ)_max = 0.001
233 parameters	Δρ_max = 0.41 e Å⁻³
0 restraints	Δρ_min = −0.33 e Å⁻³

Crystal data top

C₆H₉N₂⁺·C₈H₅O₄⁻	V = 1287.8 (3) Å³
M_r = 274.27	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 13.0558 (15) Å	µ = 0.11 mm⁻¹
b = 6.9182 (8) Å	T = 100 K
c = 14.2575 (17) Å	0.41 × 0.19 × 0.11 mm
β = 90.218 (2)°

Data collection top

Bruker SMART APEXII DUO CCD diffractometer	3856 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2009)	3332 reflections with I > 2σ(I)
T_min = 0.958, T_max = 0.989	R_int = 0.046
26319 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.047	0 restraints
wR(F²) = 0.131	H atoms treated by a mixture of independent and constrained refinement
S = 1.13	Δρ_max = 0.41 e Å⁻³
3856 reflections	Δρ_min = −0.33 e Å⁻³
233 parameters

Special details top

Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.

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
N1	0.92537 (9)	0.10419 (17)	0.64609 (8)	0.0185 (2)
N2	0.85884 (10)	0.0110 (2)	0.78891 (8)	0.0230 (3)
C1	0.84333 (10)	0.05716 (19)	0.69918 (9)	0.0174 (3)
C2	0.74595 (10)	0.05677 (19)	0.65551 (9)	0.0173 (2)
C3	0.73580 (10)	0.10080 (19)	0.56198 (9)	0.0173 (2)
C4	0.82425 (10)	0.1503 (2)	0.50975 (9)	0.0188 (3)
C5	0.91673 (10)	0.1521 (2)	0.55390 (9)	0.0190 (3)
C6	0.63362 (11)	0.0948 (2)	0.51390 (11)	0.0233 (3)
O1	0.29640 (8)	0.07772 (17)	1.07382 (7)	0.0256 (2)
O2	0.14735 (7)	0.13709 (16)	1.00722 (7)	0.0220 (2)
H1O2	0.1249	0.1484	0.9510	0.033*
O3	0.07013 (7)	0.10883 (16)	0.85474 (7)	0.0232 (2)
O4	0.11341 (8)	0.01778 (17)	0.71187 (7)	0.0255 (2)
C7	0.25074 (10)	0.07219 (19)	0.81743 (9)	0.0169 (2)
C8	0.31459 (11)	0.0630 (2)	0.73921 (10)	0.0252 (3)
C9	0.42058 (12)	0.0674 (3)	0.74708 (11)	0.0343 (4)
C10	0.46574 (12)	0.0806 (3)	0.83501 (11)	0.0307 (4)
C11	0.40349 (10)	0.0909 (2)	0.91336 (10)	0.0212 (3)
C12	0.29652 (10)	0.08811 (18)	0.90749 (9)	0.0158 (2)
C13	0.24430 (10)	0.10053 (19)	1.00235 (9)	0.0178 (3)
C14	0.13713 (10)	0.0649 (2)	0.79293 (10)	0.0186 (3)
H2A	0.6866 (15)	0.030 (3)	0.6899 (13)	0.025 (5)*
H4A	0.8212 (13)	0.180 (3)	0.4489 (13)	0.020 (4)*
H5A	0.9801 (14)	0.181 (3)	0.5240 (13)	0.026 (5)*
H6A	0.6231 (16)	0.198 (3)	0.4689 (15)	0.038 (6)*
H6B	0.6280 (18)	−0.026 (4)	0.4780 (16)	0.044 (6)*
H6C	0.5785 (19)	0.100 (3)	0.5570 (18)	0.050 (7)*
H8A	0.2830 (17)	0.056 (3)	0.6805 (16)	0.038 (6)*
H9A	0.4616 (17)	0.062 (3)	0.6884 (16)	0.039 (6)*
H10A	0.5374 (18)	0.080 (3)	0.8406 (15)	0.037 (6)*
H11A	0.4322 (14)	0.106 (2)	0.9756 (13)	0.018 (4)*
H1N1	0.9896 (18)	0.087 (3)	0.6745 (15)	0.038 (6)*
H1N2	0.9214 (18)	0.022 (3)	0.8138 (15)	0.037 (6)*
H2N2	0.8067 (17)	−0.025 (3)	0.8207 (14)	0.028 (5)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
N1	0.0148 (5)	0.0233 (6)	0.0174 (5)	−0.0020 (4)	−0.0001 (4)	0.0000 (4)
N2	0.0200 (6)	0.0340 (7)	0.0150 (5)	−0.0024 (5)	−0.0008 (4)	0.0032 (5)
C1	0.0176 (6)	0.0188 (6)	0.0159 (6)	−0.0008 (4)	0.0006 (4)	−0.0010 (4)
C2	0.0148 (5)	0.0198 (6)	0.0172 (6)	−0.0013 (4)	0.0019 (4)	−0.0013 (5)
C3	0.0169 (6)	0.0176 (6)	0.0175 (6)	0.0003 (4)	−0.0015 (4)	−0.0015 (4)
C4	0.0204 (6)	0.0204 (6)	0.0156 (6)	−0.0002 (5)	0.0010 (5)	0.0009 (5)
C5	0.0184 (6)	0.0208 (6)	0.0178 (6)	−0.0020 (5)	0.0031 (5)	0.0009 (5)
C6	0.0176 (6)	0.0309 (7)	0.0212 (6)	−0.0006 (5)	−0.0036 (5)	0.0001 (6)
O1	0.0203 (5)	0.0412 (6)	0.0153 (4)	−0.0024 (4)	−0.0015 (4)	−0.0009 (4)
O2	0.0181 (5)	0.0317 (5)	0.0163 (4)	0.0040 (4)	0.0016 (3)	−0.0018 (4)
O3	0.0147 (4)	0.0350 (6)	0.0199 (5)	0.0033 (4)	−0.0001 (4)	0.0006 (4)
O4	0.0199 (5)	0.0366 (6)	0.0201 (5)	0.0000 (4)	−0.0039 (4)	−0.0031 (4)
C7	0.0149 (5)	0.0197 (6)	0.0160 (5)	0.0004 (4)	−0.0009 (4)	0.0009 (4)
C8	0.0204 (6)	0.0397 (8)	0.0156 (6)	0.0001 (6)	0.0003 (5)	−0.0003 (6)
C9	0.0196 (7)	0.0636 (12)	0.0197 (7)	−0.0003 (7)	0.0047 (5)	−0.0031 (7)
C10	0.0152 (6)	0.0530 (10)	0.0239 (7)	0.0010 (6)	0.0017 (5)	−0.0021 (7)
C11	0.0164 (6)	0.0292 (7)	0.0181 (6)	0.0014 (5)	−0.0014 (5)	−0.0003 (5)
C12	0.0155 (5)	0.0170 (6)	0.0150 (5)	0.0004 (4)	0.0003 (4)	0.0006 (4)
C13	0.0172 (6)	0.0199 (6)	0.0163 (6)	−0.0019 (5)	0.0010 (4)	−0.0013 (5)
C14	0.0169 (6)	0.0202 (6)	0.0188 (6)	−0.0004 (5)	−0.0012 (5)	0.0026 (5)

Geometric parameters (Å, º) top

N1—C1	1.3535 (17)	O1—C13	1.2331 (16)
N1—C5	1.3599 (17)	O2—C13	1.2929 (16)
N1—H1N1	0.94 (2)	O2—H1O2	0.8555
N2—C1	1.3332 (17)	O3—C14	1.2807 (17)
N2—H1N2	0.89 (2)	O4—C14	1.2391 (17)
N2—H2N2	0.86 (2)	C7—C8	1.3963 (19)
C1—C2	1.4136 (18)	C7—C12	1.4186 (17)
C2—C3	1.3738 (18)	C7—C14	1.5233 (18)
C2—H2A	0.94 (2)	C8—C9	1.388 (2)
C3—C4	1.4183 (19)	C8—H8A	0.93 (2)
C3—C6	1.4981 (18)	C9—C10	1.386 (2)
C4—C5	1.3596 (19)	C9—H9A	1.00 (2)
C4—H4A	0.892 (18)	C10—C11	1.386 (2)
C5—H5A	0.953 (19)	C10—H10A	0.94 (2)
C6—H6A	0.97 (2)	C11—C12	1.3988 (18)
C6—H6B	0.98 (2)	C11—H11A	0.967 (18)
C6—H6C	0.95 (3)	C12—C13	1.5195 (18)

C1—N1—C5	122.43 (12)	H6B—C6—H6C	108 (2)
C1—N1—H1N1	115.9 (14)	C13—O2—H1O2	107.5
C5—N1—H1N1	121.3 (14)	C8—C7—C12	118.39 (12)
C1—N2—H1N2	119.7 (14)	C8—C7—C14	113.53 (12)
C1—N2—H2N2	117.3 (13)	C12—C7—C14	128.08 (12)
H1N2—N2—H2N2	122.9 (19)	C9—C8—C7	122.17 (13)
N2—C1—N1	118.46 (12)	C9—C8—H8A	120.7 (14)
N2—C1—C2	123.73 (13)	C7—C8—H8A	117.1 (14)
N1—C1—C2	117.80 (12)	C10—C9—C8	119.66 (14)
C3—C2—C1	120.69 (12)	C10—C9—H9A	122.3 (13)
C3—C2—H2A	118.3 (12)	C8—C9—H9A	118.0 (13)
C1—C2—H2A	121.0 (12)	C11—C10—C9	118.92 (14)
C2—C3—C4	119.17 (12)	C11—C10—H10A	121.3 (13)
C2—C3—C6	121.37 (12)	C9—C10—H10A	119.8 (13)
C4—C3—C6	119.46 (12)	C10—C11—C12	122.65 (13)
C5—C4—C3	118.86 (12)	C10—C11—H11A	121.2 (11)
C5—C4—H4A	119.0 (11)	C12—C11—H11A	116.1 (11)
C3—C4—H4A	122.2 (11)	C11—C12—C7	118.20 (12)
C4—C5—N1	121.03 (12)	C11—C12—C13	113.40 (11)
C4—C5—H5A	124.5 (11)	C7—C12—C13	128.40 (12)
N1—C5—H5A	114.4 (11)	O1—C13—O2	121.18 (12)
C3—C6—H6A	114.0 (12)	O1—C13—C12	118.71 (12)
C3—C6—H6B	109.1 (14)	O2—C13—C12	120.10 (12)
H6A—C6—H6B	105.8 (19)	O4—C14—O3	122.37 (12)
C3—C6—H6C	112.3 (15)	O4—C14—C7	117.53 (12)
H6A—C6—H6C	107.2 (19)	O3—C14—C7	120.09 (12)

C5—N1—C1—N2	179.65 (13)	C10—C11—C12—C7	0.6 (2)
C5—N1—C1—C2	0.7 (2)	C10—C11—C12—C13	179.86 (15)
N2—C1—C2—C3	−178.20 (13)	C8—C7—C12—C11	−0.9 (2)
N1—C1—C2—C3	0.7 (2)	C14—C7—C12—C11	179.59 (13)
C1—C2—C3—C4	−1.1 (2)	C8—C7—C12—C13	179.96 (13)
C1—C2—C3—C6	178.00 (13)	C14—C7—C12—C13	0.5 (2)
C2—C3—C4—C5	0.2 (2)	C11—C12—C13—O1	−12.47 (18)
C6—C3—C4—C5	−178.95 (13)	C7—C12—C13—O1	166.68 (13)
C3—C4—C5—N1	1.2 (2)	C11—C12—C13—O2	166.57 (13)
C1—N1—C5—C4	−1.6 (2)	C7—C12—C13—O2	−14.3 (2)
C12—C7—C8—C9	0.5 (2)	C8—C7—C14—O4	12.57 (19)
C14—C7—C8—C9	−179.94 (16)	C12—C7—C14—O4	−167.93 (14)
C7—C8—C9—C10	0.3 (3)	C8—C7—C14—O3	−166.62 (14)
C8—C9—C10—C11	−0.6 (3)	C12—C7—C14—O3	12.9 (2)
C9—C10—C11—C12	0.2 (3)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1O2···O3	0.86	1.57	2.4009 (14)	163
N1—H1N1···O4ⁱ	0.94 (2)	1.77 (2)	2.6919 (16)	169 (2)
N2—H1N2···O3ⁱ	0.89 (2)	2.11 (2)	2.9881 (16)	166.6 (19)
N2—H2N2···O1ⁱⁱ	0.86 (2)	2.06 (2)	2.8888 (16)	164.5 (19)
C5—H5A···O2ⁱⁱⁱ	0.953 (19)	2.532 (19)	3.4133 (17)	153.7 (16)

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

Experimental details

Crystal data
Chemical formula	C₆H₉N₂⁺·C₈H₅O₄⁻
M_r	274.27
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	13.0558 (15), 6.9182 (8), 14.2575 (17)
β (°)	90.218 (2)
V (Å³)	1287.8 (3)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.11
Crystal size (mm)	0.41 × 0.19 × 0.11

Data collection
Diffractometer	Bruker SMART APEXII DUO CCD
Absorption correction	Multi-scan (SADABS; Bruker, 2009)
T_min, T_max	0.958, 0.989
No. of measured, independent and observed [I > 2σ(I)] reflections	26319, 3856, 3332
R_int	0.046
(sin θ/λ)_max (Å⁻¹)	0.711

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.047, 0.131, 1.13
No. of reflections	3856
No. of parameters	233
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.41, −0.33

Computer programs: APEX2 (Bruker, 2009), SAINT (Bruker, 2009), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O2—H1O2···O3	0.86	1.57	2.4009 (14)	163
N1—H1N1···O4ⁱ	0.94 (2)	1.77 (2)	2.6919 (16)	169 (2)
N2—H1N2···O3ⁱ	0.89 (2)	2.11 (2)	2.9881 (16)	166.6 (19)
N2—H2N2···O1ⁱⁱ	0.86 (2)	2.06 (2)	2.8888 (16)	164.5 (19)
C5—H5A···O2ⁱⁱⁱ	0.953 (19)	2.532 (19)	3.4133 (17)	153.7 (16)

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

Footnotes

‡Thomson Reuters ResearcherID: A-5525-2009.

§Thomson Reuters ResearcherID: A-3561-2009.

Acknowledgements

The authors thank Universiti Sains Malaysia (USM) for the Research University Golden Goose Grant (1001/PFIZIK/811012). CKQ thanks USM for the award of a USM fellowship. MH thanks USM for the award of a postdoctoral fellowship.

References

Allen, F. H., Kennard, O., Watson, D. G., Brammer, L., Orpen, A. G. & Taylor, R. (1987). J. Chem. Soc. Perkin Trans. 2, pp. S1–19. CSD CrossRef Web of Science Google Scholar
Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555–1573. CrossRef CAS Web of Science Google Scholar
Bruker (2009). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA. Google Scholar
Cosier, J. & Glazer, A. M. (1986). J. Appl. Cryst. 19, 105–107. CrossRef CAS Web of Science IUCr Journals Google Scholar
Jeffrey, G. A. (1997). An Introduction to Hydrogen Bonding. Oxford University Press. Google Scholar
Jeffrey, G. A. & Saenger, W. (1991). Hydrogen Bonding in Biological Structures. Berlin: Springer. Google Scholar
Katritzky, A. R., Rees, C. W. & Scriven, E. F. V. (1996). Comprehensive Heterocyclic Chemistry II. Oxford: Pergamon Press. Google Scholar
Pozharski, A. F., Soldatenkov, A. T. & Katritzky, A. R. (1997). Heterocycles in Life and Society. New York: Wiley. Google Scholar
Quah, C. K., Jebas, S. R. & Fun, H.-K. (2008a). Acta Cryst. E64, o1878–o1879. Web of Science CSD CrossRef IUCr Journals Google Scholar
Quah, C. K., Jebas, S. R. & Fun, H.-K. (2008b). Acta Cryst. E64, o2230. Web of Science CSD CrossRef IUCr Journals Google Scholar
Quah, C. K., Jebas, S. R. & Fun, H.-K. (2008c). Acta Cryst. E64, o2333. Web of Science CSD CrossRef IUCr Journals Google Scholar
Scheiner, S. (1997). Hydrogen Bonding: a Theoretical Perspective. Oxford University Press. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Spek, A. L. (2009). Acta Cryst. D65, 148–155. Web of Science CrossRef CAS IUCr Journals Google Scholar