2-Amino-5-chloro­pyridinium 4-hydroxy­benzoate

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

doi:10.1107/S1600536810004265

organic compounds

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ISSN: 2056-9890

Volume 66| Part 3| March 2010| Page o557

doi:10.1107/S1600536810004265

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2-Amino-5-chloropyridinium 4-hydroxybenzoate

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 1 February 2010; accepted 3 February 2010; online 6 February 2010)

In the title salt, C₅H₆ClN₂⁺·C₇H₅O₃⁻, the carboxylate mean plane of the 4-hydroxybenzoate anion is twisted by 7.16 (9)° from the attached ring. In the crystal structure, the cations and anions are linked via O—H⋯O and N—H⋯O hydrogen bonds, as well as C—H⋯O contacts, forming a three-dimensional network. In addition, weak π–π interactions involving the benzene and pyridinium rings, with centroid-to-centroid distances of 3.8941 (9) Å, are observed.

Related literature

For background to the chemistry of substituted pyridines, see: Pozharski et al. (1997 ); Katritzky et al. (1996 ). For related structures, see: Pourayoubi et al. (2007 ); Akriche & Rzaigui (2005 ); Janczak & Perpétuo (2009 ). For details of hydrogen bonding, see: Jeffrey & Saenger (1991 ); Jeffrey (1997 ); Scheiner (1997 ). For hydrogen-bond motifs, see: Bernstein et al. (1995 ). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 ).

Experimental

Crystal data

C₅H₆ClN₂⁺·C₇H₅O₃⁻
M_r = 266.68
Monoclinic, P 2₁ /c
a = 10.0893 (3) Å
b = 11.7612 (4) Å
c = 11.6634 (3) Å
β = 116.113 (2)°
V = 1242.74 (6) Å³
Z = 4
Mo Kα radiation
μ = 0.31 mm⁻¹
T = 100 K
0.69 × 0.20 × 0.14 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2009 ) T_min = 0.814, T_max = 0.958
12446 measured reflections
3630 independent reflections
2663 reflections with I > 2σ(I)
R_int = 0.020

Refinement

R[F² > 2σ(F²)] = 0.040
wR(F²) = 0.110
S = 1.04
3630 reflections
207 parameters
All H-atom parameters refined
Δρ_max = 0.22 e Å⁻³
Δρ_min = −0.26 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1O1⋯O3ⁱ	0.84 (2)	1.91 (2)	2.7132 (15)	160 (2)
N1—H1N1⋯O2ⁱⁱ	0.99 (2)	1.66 (2)	2.6320 (18)	169.2 (18)
N2—H1N2⋯O2ⁱⁱⁱ	0.857 (19)	2.051 (19)	2.8972 (18)	169 (2)
N2—H2N2⋯O3ⁱⁱ	0.92 (2)	1.93 (2)	2.825 (2)	167 (2)
C3—H3A⋯O3	0.95 (2)	2.488 (19)	3.181 (2)	129.5 (14)
Symmetry codes: (i) $[-x, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (ii) $[-x+1, y-{\script{1\over 2}}, -z+{\script{1\over 2}}]$ ; (iii) -x+1, -y+2, -z+1.

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: 10.1107/S1600536810004265/tk2625sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536810004265/tk2625Isup2.hkl

checkCIF report

Comment top

Pyridine and its derivatives play an important role in heterocyclic chemistry (Pozharski et al., 1997; Katritzky et al., 1996). Pyridine and its substituted derivatives are often involved in hydrogen-bond interactions (Jeffrey & Saenger, 1991; Jeffrey, 1997; Scheiner, 1997). The crystal structures of 2-amino-5-chloropyridine (Pourayoubi et al., 2007), 2-amino-5-chloropyridinium trichloroacetate (Janczak & Perpétuo, 2009) and bis (2-amino-5-chloropyridinium) dihydrogendiphosphate (Akriche & Rzaigui, 2005) have been reported. Since our aim is to study some interesting hydrogen-bonding interactions, the crystal structure of the title salt is presented here.

The asymmetric unit (Fig. 1) contains a 2-amino-5-chloropyridinium cation and a 4-hydroxybenzoate anion. The proton transfer from the carboxylic acid to atom N1 of 2-amino-5-chloropyridine resulted in the widening of C1—N1—C5 angle of the pyridinium ring to 122.24 (12)°, compared to the corresponding angle of 118.1 (12)° in neutral 2-amino-5-chloropyridine (Pourayoubi et al., 2007). The 2-amino-5-chloropyridinium cation is essentially planar, with a maximum deviation of 0.012 (2) Å for atom C1. In the 4-hydroxybenzoate anion, the carboxylate group is twisted slightly from the attached ring; the dihedral angle between the C6–C11 and O2/O3/C11/C12 planes is 7.16 (9) °.

In the crystal packing (Fig. 2), the protonated N1 atom and the N2-amino group is hydrogen-bonded to the carboxylate oxygen atoms (O2 and O3) via a pair of N—H···O hydrogen bonds forming a R₂²(8) ring motif (Bernstein et al., 1995). The hydroxyl hydrogen atom is also hydrogen-bonded to the carboxylate oxygen atom through an O—H···O hydrogen bond. The packing is further stabilized by weak C—H···O contacts, Table 1, and π···π interactions involving the benzene (centroid Cg1) and pyridinium (centroid Cg2) rings, with Cg1–Cg2 = 3.8941 (9) Å [symmetry code: x, 3/2 - y, 1/2 + z].

Related literature top

For background to the chemistry of substituted pyridines, see: Pozharski et al. (1997); Katritzky et al. (1996). For related structures, see: Pourayoubi et al. (2007); Akriche & Rzaigui (2005); Janczak & Perpétuo (2009). For details of hydrogen bonding, see: Jeffrey & Saenger (1991); Jeffrey (1997); Scheiner (1997). For hydrogen-bond motifs, see: Bernstein et al. (1995). For the stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986).

Experimental top

A hot methanol solution (20 ml) of 2-amino-5-chloropyridine (65 mg, Aldrich) and 4-hydroxybenzoic acid (69 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 crystals of the title compound appeared after a few days.

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 asymmetric unit of the title compound. Displacement ellipsoids are drawn at the 50% probability level.
	Fig. 2. The crystal packing of the title compound, showing hydrogen-bonded (dashed lines) networks.

2-Amino-5-chloropyridinium 4-hydroxybenzoate top

Crystal data top

C₅H₆ClN₂⁺·C₇H₅O₃⁻	F(000) = 552
M_r = 266.68	D_x = 1.425 Mg m⁻³
Monoclinic, P2₁/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 4875 reflections
a = 10.0893 (3) Å	θ = 2.3–29.9°
b = 11.7612 (4) Å	µ = 0.31 mm⁻¹
c = 11.6634 (3) Å	T = 100 K
β = 116.113 (2)°	Block, colourless
V = 1242.74 (6) Å³	0.69 × 0.20 × 0.14 mm
Z = 4

Data collection top

Bruker SMART APEXII CCD area-detector diffractometer	3630 independent reflections
Radiation source: fine-focus sealed tube	2663 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.020
ϕ and ω scans	θ_max = 30.1°, θ_min = 2.3°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −13→14
T_min = 0.814, T_max = 0.958	k = −16→16
12446 measured reflections	l = −16→16

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)] = 0.040	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.110	All H-atom parameters refined
S = 1.04	w = 1/[σ²(F_o²) + (0.0478P)² + 0.2067P] where P = (F_o² + 2F_c²)/3
3630 reflections	(Δ/σ)_max < 0.001
207 parameters	Δρ_max = 0.22 e Å⁻³
0 restraints	Δρ_min = −0.26 e Å⁻³

Crystal data top

C₅H₆ClN₂⁺·C₇H₅O₃⁻	V = 1242.74 (6) Å³
M_r = 266.68	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 10.0893 (3) Å	µ = 0.31 mm⁻¹
b = 11.7612 (4) Å	T = 100 K
c = 11.6634 (3) Å	0.69 × 0.20 × 0.14 mm
β = 116.113 (2)°

Data collection top

Bruker SMART APEXII CCD area-detector diffractometer	3630 independent reflections
Absorption correction: multi-scan (SADABS; Bruker, 2009)	2663 reflections with I > 2σ(I)
T_min = 0.814, T_max = 0.958	R_int = 0.020
12446 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.040	0 restraints
wR(F²) = 0.110	All H-atom parameters refined
S = 1.04	Δρ_max = 0.22 e Å⁻³
3630 reflections	Δρ_min = −0.26 e Å⁻³
207 parameters

Special details top

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

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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
Cl1	0.21064 (4)	0.98776 (4)	−0.17272 (4)	0.06226 (15)
N1	0.51321 (13)	0.78671 (10)	0.07645 (11)	0.0444 (3)
N2	0.63089 (16)	0.77385 (14)	0.29586 (13)	0.0574 (3)
C1	0.53134 (15)	0.82441 (12)	0.19187 (13)	0.0439 (3)
C2	0.44186 (16)	0.91497 (14)	0.19530 (14)	0.0510 (4)
C3	0.34358 (17)	0.96337 (14)	0.08507 (15)	0.0512 (4)
C4	0.33162 (14)	0.92372 (13)	−0.03259 (13)	0.0454 (3)
C5	0.41534 (15)	0.83516 (13)	−0.03444 (13)	0.0454 (3)
O1	0.00092 (13)	0.66336 (10)	0.45630 (11)	0.0579 (3)
O2	0.34526 (13)	1.11961 (9)	0.47186 (9)	0.0567 (3)
O3	0.22698 (11)	1.09176 (8)	0.26301 (8)	0.0463 (2)
C6	0.21056 (18)	0.92410 (14)	0.51840 (13)	0.0531 (4)
C7	0.14592 (19)	0.82697 (15)	0.53591 (13)	0.0563 (4)
C8	0.06192 (15)	0.75826 (12)	0.43312 (13)	0.0438 (3)
C9	0.04555 (15)	0.78713 (12)	0.31209 (12)	0.0426 (3)
C10	0.11107 (14)	0.88452 (12)	0.29507 (12)	0.0397 (3)
C11	0.19355 (14)	0.95522 (12)	0.39715 (11)	0.0392 (3)
C12	0.25875 (14)	1.06243 (12)	0.37582 (12)	0.0398 (3)
H2A	0.4538 (17)	0.9382 (14)	0.2769 (16)	0.059 (5)*
H3A	0.283 (2)	1.0251 (15)	0.0866 (17)	0.064 (5)*
H5A	0.4139 (17)	0.8021 (14)	−0.1096 (16)	0.060 (5)*
H6A	0.2676 (19)	0.9721 (15)	0.5889 (17)	0.065 (5)*
H7A	0.1571 (19)	0.8087 (16)	0.6168 (18)	0.068 (5)*
H9A	−0.0099 (17)	0.7369 (13)	0.2417 (15)	0.054 (4)*
H10A	0.1007 (16)	0.9043 (13)	0.2125 (15)	0.048 (4)*
H1O1	−0.053 (2)	0.6331 (17)	0.386 (2)	0.073 (6)*
H1N1	0.575 (2)	0.7250 (16)	0.0689 (18)	0.076 (6)*
H1N2	0.6509 (19)	0.8050 (16)	0.3681 (18)	0.062 (5)*
H2N2	0.689 (2)	0.7177 (19)	0.2877 (19)	0.080 (6)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Cl1	0.0607 (2)	0.0623 (3)	0.0572 (2)	0.00938 (18)	0.01990 (18)	0.00670 (19)
N1	0.0523 (6)	0.0433 (6)	0.0410 (6)	0.0039 (5)	0.0235 (5)	−0.0053 (5)
N2	0.0729 (8)	0.0590 (9)	0.0403 (6)	0.0110 (7)	0.0249 (6)	−0.0023 (6)
C1	0.0515 (7)	0.0438 (7)	0.0425 (6)	−0.0042 (6)	0.0262 (6)	−0.0069 (6)
C2	0.0587 (8)	0.0536 (9)	0.0476 (7)	0.0000 (7)	0.0297 (6)	−0.0132 (7)
C3	0.0528 (7)	0.0479 (9)	0.0585 (8)	0.0037 (7)	0.0297 (7)	−0.0092 (7)
C4	0.0441 (6)	0.0451 (8)	0.0475 (7)	−0.0022 (6)	0.0206 (5)	−0.0043 (6)
C5	0.0504 (7)	0.0467 (8)	0.0416 (7)	0.0000 (6)	0.0226 (6)	−0.0071 (6)
O1	0.0716 (7)	0.0539 (7)	0.0450 (5)	−0.0210 (6)	0.0228 (5)	0.0014 (5)
O2	0.0799 (7)	0.0531 (6)	0.0401 (5)	−0.0245 (5)	0.0291 (5)	−0.0082 (5)
O3	0.0597 (5)	0.0440 (5)	0.0370 (4)	0.0000 (4)	0.0229 (4)	0.0042 (4)
C6	0.0709 (9)	0.0536 (9)	0.0333 (6)	−0.0166 (8)	0.0217 (6)	−0.0052 (6)
C7	0.0763 (10)	0.0591 (10)	0.0347 (6)	−0.0180 (8)	0.0256 (7)	0.0003 (7)
C8	0.0486 (7)	0.0423 (7)	0.0406 (6)	−0.0039 (6)	0.0197 (5)	0.0024 (6)
C9	0.0485 (6)	0.0418 (7)	0.0345 (6)	−0.0032 (6)	0.0155 (5)	−0.0028 (6)
C10	0.0466 (6)	0.0403 (7)	0.0329 (6)	0.0027 (6)	0.0181 (5)	0.0014 (5)
C11	0.0459 (6)	0.0384 (7)	0.0348 (6)	0.0000 (5)	0.0192 (5)	−0.0001 (5)
C12	0.0480 (6)	0.0380 (7)	0.0372 (6)	0.0018 (6)	0.0224 (5)	−0.0011 (5)

Geometric parameters (Å, º) top

Cl1—C4	1.7241 (15)	O1—H1O1	0.83 (2)
N1—C1	1.3511 (17)	O2—C12	1.2682 (15)
N1—C5	1.3595 (18)	O3—C12	1.2577 (15)
N1—H1N1	0.99 (2)	C6—C7	1.375 (2)
N2—C1	1.3271 (19)	C6—C11	1.3963 (18)
N2—H1N2	0.858 (19)	C6—H6A	0.954 (18)
N2—H2N2	0.91 (2)	C7—C8	1.384 (2)
C1—C2	1.408 (2)	C7—H7A	0.925 (19)
C2—C3	1.356 (2)	C8—C9	1.3892 (19)
C2—H2A	0.946 (16)	C9—C10	1.3798 (19)
C3—C4	1.403 (2)	C9—H9A	0.965 (16)
C3—H3A	0.953 (18)	C10—C11	1.3889 (18)
C4—C5	1.347 (2)	C10—H10A	0.950 (15)
C5—H5A	0.953 (17)	C11—C12	1.4929 (19)
O1—C8	1.3581 (17)

C1—N1—C5	122.24 (12)	C7—C6—C11	120.90 (13)
C1—N1—H1N1	121.1 (11)	C7—C6—H6A	120.6 (11)
C5—N1—H1N1	116.5 (11)	C11—C6—H6A	118.5 (11)
C1—N2—H1N2	117.6 (12)	C6—C7—C8	120.42 (13)
C1—N2—H2N2	119.3 (13)	C6—C7—H7A	119.5 (11)
H1N2—N2—H2N2	121.8 (18)	C8—C7—H7A	120.1 (11)
N2—C1—N1	118.66 (13)	O1—C8—C7	117.77 (12)
N2—C1—C2	123.35 (13)	O1—C8—C9	122.79 (12)
N1—C1—C2	117.98 (13)	C7—C8—C9	119.43 (13)
C3—C2—C1	120.07 (13)	C10—C9—C8	119.92 (12)
C3—C2—H2A	123.3 (10)	C10—C9—H9A	121.4 (10)
C1—C2—H2A	116.6 (10)	C8—C9—H9A	118.7 (10)
C2—C3—C4	120.00 (14)	C9—C10—C11	121.19 (12)
C2—C3—H3A	120.6 (11)	C9—C10—H10A	120.2 (9)
C4—C3—H3A	119.4 (11)	C11—C10—H10A	118.7 (9)
C5—C4—C3	119.20 (13)	C10—C11—C6	118.13 (13)
C5—C4—Cl1	120.66 (11)	C10—C11—C12	120.30 (11)
C3—C4—Cl1	120.14 (11)	C6—C11—C12	121.56 (12)
C4—C5—N1	120.45 (13)	O3—C12—O2	122.55 (12)
C4—C5—H5A	125.1 (10)	O3—C12—C11	118.55 (11)
N1—C5—H5A	114.5 (10)	O2—C12—C11	118.89 (11)
C8—O1—H1O1	108.3 (14)

C5—N1—C1—N2	−178.89 (13)	C6—C7—C8—C9	1.2 (2)
C5—N1—C1—C2	1.8 (2)	O1—C8—C9—C10	−179.65 (13)
N2—C1—C2—C3	179.25 (15)	C7—C8—C9—C10	−0.9 (2)
N1—C1—C2—C3	−1.5 (2)	C8—C9—C10—C11	−0.2 (2)
C1—C2—C3—C4	−0.4 (2)	C9—C10—C11—C6	1.0 (2)
C2—C3—C4—C5	2.1 (2)	C9—C10—C11—C12	−177.69 (12)
C2—C3—C4—Cl1	−178.10 (12)	C7—C6—C11—C10	−0.8 (2)
C3—C4—C5—N1	−1.8 (2)	C7—C6—C11—C12	177.90 (15)
Cl1—C4—C5—N1	178.38 (11)	C10—C11—C12—O3	5.95 (19)
C1—N1—C5—C4	−0.2 (2)	C6—C11—C12—O3	−172.73 (13)
C11—C6—C7—C8	−0.3 (3)	C10—C11—C12—O2	−173.19 (12)
C6—C7—C8—O1	179.94 (15)	C6—C11—C12—O2	8.1 (2)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O1—H1O1···O3ⁱ	0.84 (2)	1.91 (2)	2.7132 (15)	160 (2)
N1—H1N1···O2ⁱⁱ	0.99 (2)	1.66 (2)	2.6320 (18)	169.2 (18)
N2—H1N2···O2ⁱⁱⁱ	0.857 (19)	2.051 (19)	2.8972 (18)	169 (2)
N2—H2N2···O3ⁱⁱ	0.92 (2)	1.93 (2)	2.825 (2)	167 (2)
C3—H3A···O3	0.95 (2)	2.488 (19)	3.181 (2)	129.5 (14)

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

Experimental details

Crystal data
Chemical formula	C₅H₆ClN₂⁺·C₇H₅O₃⁻
M_r	266.68
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	100
a, b, c (Å)	10.0893 (3), 11.7612 (4), 11.6634 (3)
β (°)	116.113 (2)
V (Å³)	1242.74 (6)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.31
Crystal size (mm)	0.69 × 0.20 × 0.14

Data collection
Diffractometer	Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction	Multi-scan (SADABS; Bruker, 2009)
T_min, T_max	0.814, 0.958
No. of measured, independent and observed [I > 2σ(I)] reflections	12446, 3630, 2663
R_int	0.020
(sin θ/λ)_max (Å⁻¹)	0.706

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.040, 0.110, 1.04
No. of reflections	3630
No. of parameters	207
H-atom treatment	All H-atom parameters refined
Δρ_max, Δρ_min (e Å⁻³)	0.22, −0.26

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
O1—H1O1···O3ⁱ	0.84 (2)	1.91 (2)	2.7132 (15)	160 (2)
N1—H1N1···O2ⁱⁱ	0.99 (2)	1.66 (2)	2.6320 (18)	169.2 (18)
N2—H1N2···O2ⁱⁱⁱ	0.857 (19)	2.051 (19)	2.8972 (18)	169 (2)
N2—H2N2···O3ⁱⁱ	0.92 (2)	1.93 (2)	2.825 (2)	167 (2)
C3—H3A···O3	0.95 (2)	2.488 (19)	3.181 (2)	129.5 (14)

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

Footnotes

‡Thomson Reuters ResearcherID: A-3561-2009.

Acknowledgements

MH and HKF thank the Malaysian Government and Universiti Sains Malaysia for the Research University Golden Goose grant No. 1001/PFIZIK/811012. MH also thanks Universiti Sains Malaysia for a post-doctoral research fellowship.

References

Akriche, S. & Rzaigui, M. (2005). Acta Cryst. E61, o2607–o2609. Web of Science CSD CrossRef CAS IUCr Journals 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
Janczak, J. & Perpétuo, G. J. (2009). Acta Cryst. C65, o339–o341. Web of Science CSD CrossRef 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
Pourayoubi, M., Ghadimi, S. & Ebrahimi Valmoozi, A. A. (2007). Acta Cryst. E63, o4631. Web of Science CSD CrossRef IUCr Journals Google Scholar
Pozharski, A. F., Soldatenkov, A. T. & Katritzky, A. R. (1997). Heterocycles in Life and Society. New York: Wiley. Google Scholar
Scheiner, S. (1997). Hydrogen Bonding. A Theoretical Perspective. New York: 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