2-Amino­anilinium 6-carb­oxy­picolinate monohydrate

Wang, Y.-T.; Gao, D.-J.

doi:10.1107/S1600536811025050

organic compounds

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ISSN: 2056-9890

Volume 67| Part 8| August 2011| Page o1893

doi:10.1107/S1600536811025050

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2-Aminoanilinium 6-carboxypicolinate monohydrate

Yu-Tang Wang ^a ^* and De-Jiang Gao ^b

^aCollege of Food Science and Engineering, Northwest A & F University, Yang Ling 712100, People's Republic of China, and ^bCollege of Chemistry, Jilin University, Changchun 130012, People's Republic of China
^*Correspondence e-mail: wyt991023@gmail.com

(Received 25 June 2011; accepted 25 June 2011; online 2 July 2011)

In the title compound, C₆H₉N₂⁺·C₇H₄NO₄⁻·H₂O, one amino group of diaminobenzene is protonated while one carboxy group of pyridine-2,6-dicarboxylic acid is deprotonated. In the anion, the CO₂ and CO₂H groups make dihedral angles of 4.0 (5) and 8.7 (4)° with the pyridine ring. In the crystal, extensive N—H⋯O, N—H⋯N and O—H⋯O hydrogen bonds occur between anions, cations and water molecules.

Related literature

For related compounds, see: Andre et al. (2011 ); Blagden et al. (2008 ); Smith et al. (2000 ); Kapildev et al. (2011 ).

Experimental

Crystal data

C₆H₉N₂⁺·C₇H₄NO₄⁻·H₂O
M_r = 293.28
Monoclinic, C c
a = 12.408 (3) Å
b = 13.932 (3) Å
c = 8.0951 (16) Å
β = 102.41 (3)°
V = 1366.6 (5) Å³
Z = 4
Mo Kα radiation
μ = 0.11 mm⁻¹
T = 298 K
0.30 × 0.25 × 0.15 mm

Data collection

Rigaku Mercury2 diffractometer
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005 ) T_min = 0.910, T_max = 1.000
7343 measured reflections
1555 independent reflections
1393 reflections with I > 2σ(I)
R_int = 0.041

Refinement

R[F² > 2σ(F²)] = 0.040
wR(F²) = 0.117
S = 1.12
1555 reflections
191 parameters
2 restraints
H-atom parameters constrained
Δρ_max = 0.19 e Å⁻³
Δρ_min = −0.22 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N1—H1A⋯O1Wⁱ	0.89	2.13	3.004 (4)	166
N1—H1B⋯O3ⁱⁱ	0.89	1.98	2.862 (3)	170
N1—H1C⋯N3	0.89	2.12	3.003 (4)	171
N2—H2A⋯O1Wⁱⁱⁱ	0.90	2.41	3.303 (4)	172
N2—H2B⋯O1	0.90	2.14	3.029 (4)	168
O1W—H1WA⋯O2^iv	0.82	2.27	3.034 (3)	155
O1W—H1WB⋯O2	0.82	2.04	2.831 (3)	161
O4—H4⋯O1ⁱ	0.82	1.71	2.532 (3)	179
Symmetry codes: (i) $[x-{\script{1\over 2}}, -y+{\script{1\over 2}}, z-{\script{1\over 2}}]$ ; (ii) $[x+{\script{1\over 2}}, -y+{\script{1\over 2}}, z+{\script{1\over 2}}]$ ; (iii) x, y, z-1; (iv) $[x, -y, z+{\script{1\over 2}}]$ .

Data collection: CrystalClear (Rigaku, 2005); cell refinement: CrystalClear data reduction: CrystalClear; 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.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811025050/xu5250sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811025050/xu5250Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811025050/xu5250Isup3.cml

checkCIF report

Comment top

Cocrystals are most commonly thought of as structural homogeneous crystalline materials that contain two or more organic building blocks that are present in definite stoichiometric amounts. Within the development of pharmaceutical industry, molecular cocrystals are becoming increasingly important as a new drug with higher biomedical activity than the initial components. (Kapildev et al. 2011). Physicochemical properties such as the melting point, stability and solubility of an active pharmaceutical ingredient can be tuned through cocrystal formulation (Andre, et al. 2011; Blagden, et al. 2008; Smith, et al. 2000). These cocrystal forms often relie on the acid-amide H-bonds interactions. Herein, we report the crystal structure of the title compound, 2-aminoanilinium 6-carboxypicolinate monohydrate.

The asymmetric unit is composed of one 6-carboxypicolinate anion one 2-aminoanilinium cation and one water molecule (Fig.1). The amine N1 atom was protonated. And one of the carboxyl groups was deprotonated. The interplanar angle between the benzene and the pyridine rings equals to 88.89 (10)°. The geometric parameters of the title compound are in the normal range.

The molecular packing is stabilized by strong intermolecular N—H···O, N—H···N and O—H···O hydrogen bonds. The H-bonds link the molecules into a three-dimensional network (Fig. 2 and Tab. 1).

Related literature top

For related compounds, see: Andre et al. (2011); Blagden et al. (2008); Smith et al. (2000); Kapildev et al. (2011).

Experimental top

A mixture of pyridine-2,6-dicarboxylic acid (2.0 mmol), benzene-1,2-diamine (2.0 mmol) and 40 ml water were added into a 100 ml flask and refluxed for 5 h, then cooled and filtrated. The solution was evaporated slowly in the air. Colorless block crystals suitable for X-ray analysis were obtained after one week.

Computing details top

Data collection: CrystalClear (Rigaku, 2005); cell refinement: CrystalClear (Rigaku, 2005); data reduction: CrystalClear (Rigaku, 2005); 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).

Figures top

	Fig. 1. Molecular view of the title compound with the atomic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level.
	Fig. 2. The crystal packing of the title compound viewed along the c axis showing the three-dimensionnal hydrogen bondings network (dashed line). Hydrogen atoms not involved in hydrogen bonding have been omitted for clarity.

2-Aminoanilinium 6-carboxypicolinate monohydrate top

Crystal data top

C₆H₉N₂⁺·C₇H₄NO₄⁻·H₂O	F(000) = 616
M_r = 293.28	D_x = 1.425 Mg m⁻³
Monoclinic, Cc	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: C -2yc	Cell parameters from 1555 reflections
a = 12.408 (3) Å	θ = 2.2–27.4°
b = 13.932 (3) Å	µ = 0.11 mm⁻¹
c = 8.0951 (16) Å	T = 298 K
β = 102.41 (3)°	Block, colorless
V = 1366.6 (5) Å³	0.30 × 0.25 × 0.15 mm
Z = 4

Data collection top

Rigaku Mercury2 diffractometer	1555 independent reflections
Radiation source: fine-focus sealed tube	1393 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.041
Detector resolution: 13.6612 pixels mm^-1	θ_max = 27.4°, θ_min = 2.2°
CCD profile fitting scans	h = −16→15
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005)	k = −18→18
T_min = 0.910, T_max = 1.000	l = −10→10
7343 measured reflections

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) = 0.117	H-atom parameters constrained
S = 1.12	w = 1/[σ²(F_o²) + (0.0734P)²] where P = (F_o² + 2F_c²)/3
1555 reflections	(Δ/σ)_max < 0.001
191 parameters	Δρ_max = 0.19 e Å⁻³
2 restraints	Δρ_min = −0.22 e Å⁻³

Crystal data top

C₆H₉N₂⁺·C₇H₄NO₄⁻·H₂O	V = 1366.6 (5) Å³
M_r = 293.28	Z = 4
Monoclinic, Cc	Mo Kα radiation
a = 12.408 (3) Å	µ = 0.11 mm⁻¹
b = 13.932 (3) Å	T = 298 K
c = 8.0951 (16) Å	0.30 × 0.25 × 0.15 mm
β = 102.41 (3)°

Data collection top

Rigaku Mercury2 diffractometer	1555 independent reflections
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005)	1393 reflections with I > 2σ(I)
T_min = 0.910, T_max = 1.000	R_int = 0.041
7343 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.040	2 restraints
wR(F²) = 0.117	H-atom parameters constrained
S = 1.12	Δρ_max = 0.19 e Å⁻³
1555 reflections	Δρ_min = −0.22 e Å⁻³
191 parameters

Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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
O1W	0.9144 (2)	0.11509 (17)	0.8457 (3)	0.0468 (6)
H1WA	0.9052	0.0737	0.9133	0.070*
H1WB	0.8972	0.0905	0.7516	0.070*
O1	0.75215 (19)	0.17288 (15)	0.4341 (3)	0.0456 (6)
O2	0.80493 (18)	0.02830 (16)	0.5392 (3)	0.0412 (5)
N3	0.56474 (19)	0.10218 (18)	0.2422 (3)	0.0286 (5)
O3	0.30560 (19)	0.10298 (17)	−0.0480 (3)	0.0436 (6)
O4	0.41055 (17)	0.22264 (15)	0.0827 (3)	0.0397 (5)
H4	0.3599	0.2569	0.0337	0.060*
N1	0.61623 (19)	0.31257 (19)	0.2363 (3)	0.0296 (5)
H1A	0.5582	0.3434	0.2587	0.044*
H1B	0.6772	0.3318	0.3080	0.044*
H1C	0.6076	0.2497	0.2476	0.044*
C8	0.6256 (2)	0.33386 (19)	0.0621 (3)	0.0290 (6)
N2	0.7964 (2)	0.2434 (2)	0.1010 (4)	0.0452 (7)
H2A	0.8342	0.2069	0.0413	0.054*
H2B	0.7933	0.2178	0.2020	0.054*
C1	0.7403 (2)	0.0831 (2)	0.4445 (4)	0.0304 (6)
C6	0.4728 (2)	0.0640 (2)	0.1448 (4)	0.0293 (6)
C7	0.3880 (2)	0.1321 (2)	0.0494 (3)	0.0296 (6)
C3	0.6225 (3)	−0.0586 (2)	0.3262 (4)	0.0371 (7)
H3A	0.6748	−0.0990	0.3909	0.044*
C9	0.7137 (2)	0.2968 (2)	0.0015 (4)	0.0336 (6)
C5	0.4515 (3)	−0.0335 (2)	0.1314 (4)	0.0392 (7)
H5A	0.3870	−0.0566	0.0623	0.047*
C13	0.5445 (3)	0.3890 (2)	−0.0392 (4)	0.0378 (7)
H13A	0.4864	0.4131	0.0041	0.045*
C4	0.5287 (3)	−0.0961 (2)	0.2238 (5)	0.0427 (8)
H4A	0.5173	−0.1621	0.2167	0.051*
C10	0.7174 (3)	0.3179 (3)	−0.1655 (5)	0.0471 (8)
H10A	0.7756	0.2946	−0.2097	0.057*
C2	0.6380 (2)	0.0403 (2)	0.3314 (4)	0.0289 (6)
C12	0.5500 (3)	0.4080 (3)	−0.2044 (5)	0.0503 (9)
H12A	0.4953	0.4444	−0.2731	0.060*
C11	0.6366 (4)	0.3728 (3)	−0.2669 (5)	0.0549 (10)
H11A	0.6409	0.3859	−0.3779	0.066*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O1W	0.0461 (14)	0.0470 (14)	0.0444 (13)	−0.0005 (11)	0.0035 (10)	0.0032 (10)
O1	0.0368 (12)	0.0319 (12)	0.0563 (14)	−0.0070 (10)	−0.0164 (10)	0.0073 (11)
O2	0.0311 (11)	0.0399 (12)	0.0452 (12)	0.0016 (9)	−0.0085 (9)	0.0071 (10)
N3	0.0222 (10)	0.0302 (13)	0.0312 (11)	−0.0011 (9)	0.0014 (9)	0.0013 (10)
O3	0.0307 (12)	0.0408 (13)	0.0504 (14)	0.0011 (9)	−0.0108 (10)	−0.0029 (10)
O4	0.0296 (11)	0.0318 (10)	0.0500 (13)	0.0023 (8)	−0.0086 (9)	0.0000 (10)
N1	0.0244 (11)	0.0326 (12)	0.0292 (12)	0.0008 (9)	−0.0003 (9)	−0.0013 (10)
C8	0.0278 (14)	0.0293 (13)	0.0286 (14)	−0.0010 (11)	0.0035 (10)	−0.0011 (11)
N2	0.0343 (14)	0.0463 (16)	0.0553 (18)	0.0115 (12)	0.0103 (13)	−0.0012 (14)
C1	0.0246 (13)	0.0325 (14)	0.0321 (14)	−0.0003 (11)	0.0015 (10)	0.0035 (12)
C6	0.0217 (12)	0.0314 (14)	0.0331 (14)	−0.0010 (11)	0.0020 (10)	−0.0005 (12)
C7	0.0228 (13)	0.0366 (14)	0.0272 (13)	−0.0010 (11)	0.0008 (10)	−0.0015 (12)
C3	0.0298 (16)	0.0312 (15)	0.0480 (18)	0.0007 (12)	0.0033 (13)	0.0080 (13)
C9	0.0298 (14)	0.0314 (15)	0.0395 (16)	−0.0014 (12)	0.0072 (12)	−0.0035 (12)
C5	0.0291 (16)	0.0372 (15)	0.0461 (18)	−0.0059 (13)	−0.0032 (13)	−0.0018 (14)
C13	0.0357 (15)	0.0397 (16)	0.0369 (17)	0.0079 (13)	0.0054 (12)	0.0033 (13)
C4	0.0363 (16)	0.0275 (15)	0.060 (2)	−0.0048 (13)	0.0016 (15)	0.0003 (14)
C10	0.049 (2)	0.053 (2)	0.045 (2)	0.0026 (16)	0.0206 (16)	−0.0055 (16)
C2	0.0228 (13)	0.0303 (14)	0.0320 (13)	−0.0012 (11)	0.0026 (11)	0.0021 (12)
C12	0.057 (2)	0.053 (2)	0.0387 (18)	0.0148 (18)	0.0064 (15)	0.0112 (16)
C11	0.072 (3)	0.061 (2)	0.0357 (19)	0.008 (2)	0.0202 (17)	0.0082 (17)

Geometric parameters (Å, º) top

O1W—H1WA	0.8201	C1—C2	1.518 (4)
O1W—H1WB	0.8201	C6—C5	1.384 (4)
O1—C1	1.264 (4)	C6—C7	1.502 (4)
O2—C1	1.245 (4)	C3—C4	1.378 (5)
N3—C2	1.345 (4)	C3—C2	1.391 (4)
N3—C6	1.349 (4)	C3—H3A	0.9300
O3—C7	1.219 (3)	C9—C10	1.394 (5)
O4—C7	1.307 (4)	C5—C4	1.390 (5)
O4—H4	0.8201	C5—H5A	0.9300
N1—C8	1.470 (4)	C13—C12	1.379 (5)
N1—H1A	0.8900	C13—H13A	0.9300
N1—H1B	0.8900	C4—H4A	0.9300
N1—H1C	0.8900	C10—C11	1.382 (6)
C8—C13	1.386 (4)	C10—H10A	0.9300
C8—C9	1.390 (4)	C12—C11	1.373 (6)
N2—C9	1.378 (4)	C12—H12A	0.9300
N2—H2A	0.9002	C11—H11A	0.9300
N2—H2B	0.8998

H1WA—O1W—H1WB	106.3	C2—C3—H3A	120.4
C2—N3—C6	116.7 (2)	N2—C9—C8	122.5 (3)
C7—O4—H4	110.7	N2—C9—C10	120.3 (3)
C8—N1—H1A	109.5	C8—C9—C10	117.1 (3)
C8—N1—H1B	109.5	C6—C5—C4	118.4 (3)
H1A—N1—H1B	109.5	C6—C5—H5A	120.8
C8—N1—H1C	109.5	C4—C5—H5A	120.8
H1A—N1—H1C	109.5	C12—C13—C8	119.9 (3)
H1B—N1—H1C	109.5	C12—C13—H13A	120.0
C13—C8—C9	121.6 (3)	C8—C13—H13A	120.0
C13—C8—N1	118.8 (3)	C3—C4—C5	118.8 (3)
C9—C8—N1	119.6 (2)	C3—C4—H4A	120.6
C9—N2—H2A	113.6	C5—C4—H4A	120.6
C9—N2—H2B	125.0	C11—C10—C9	121.4 (3)
H2A—N2—H2B	113.1	C11—C10—H10A	119.3
O2—C1—O1	125.4 (3)	C9—C10—H10A	119.3
O2—C1—C2	118.4 (3)	N3—C2—C3	123.1 (3)
O1—C1—C2	116.3 (2)	N3—C2—C1	116.9 (2)
N3—C6—C5	123.8 (3)	C3—C2—C1	120.0 (3)
N3—C6—C7	117.6 (2)	C11—C12—C13	119.6 (3)
C5—C6—C7	118.6 (3)	C11—C12—H12A	120.2
O3—C7—O4	124.6 (3)	C13—C12—H12A	120.2
O3—C7—C6	121.3 (3)	C12—C11—C10	120.3 (3)
O4—C7—C6	114.1 (2)	C12—C11—H11A	119.8
C4—C3—C2	119.1 (3)	C10—C11—H11A	119.8
C4—C3—H3A	120.4

C2—N3—C6—C5	−0.6 (4)	C6—C5—C4—C3	0.7 (5)
C2—N3—C6—C7	177.7 (3)	N2—C9—C10—C11	−178.8 (4)
N3—C6—C7—O3	176.1 (3)	C8—C9—C10—C11	−0.5 (5)
C5—C6—C7—O3	−5.4 (4)	C6—N3—C2—C3	0.1 (4)
N3—C6—C7—O4	−4.8 (4)	C6—N3—C2—C1	−178.6 (3)
C5—C6—C7—O4	173.7 (3)	C4—C3—C2—N3	0.8 (5)
C13—C8—C9—N2	178.7 (3)	C4—C3—C2—C1	179.4 (3)
N1—C8—C9—N2	−2.8 (4)	O2—C1—C2—N3	174.0 (3)
C13—C8—C9—C10	0.4 (4)	O1—C1—C2—N3	−5.8 (4)
N1—C8—C9—C10	178.9 (3)	O2—C1—C2—C3	−4.7 (4)
N3—C6—C5—C4	0.2 (5)	O1—C1—C2—C3	175.5 (3)
C7—C6—C5—C4	−178.1 (3)	C8—C13—C12—C11	−0.6 (6)
C9—C8—C13—C12	0.2 (5)	C13—C12—C11—C10	0.6 (6)
N1—C8—C13—C12	−178.4 (3)	C9—C10—C11—C12	0.0 (7)
C2—C3—C4—C5	−1.2 (5)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O1Wⁱ	0.89	2.13	3.004 (4)	166
N1—H1B···O3ⁱⁱ	0.89	1.98	2.862 (3)	170
N1—H1C···N3	0.89	2.12	3.003 (4)	171
N2—H2A···O1Wⁱⁱⁱ	0.90	2.41	3.303 (4)	172
N2—H2B···O1	0.90	2.14	3.029 (4)	168
O1W—H1WA···O2^iv	0.82	2.27	3.034 (3)	155
O1W—H1WB···O2	0.82	2.04	2.831 (3)	161
O4—H4···O1ⁱ	0.82	1.71	2.532 (3)	179

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

Experimental details

Crystal data
Chemical formula	C₆H₉N₂⁺·C₇H₄NO₄⁻·H₂O
M_r	293.28
Crystal system, space group	Monoclinic, Cc
Temperature (K)	298
a, b, c (Å)	12.408 (3), 13.932 (3), 8.0951 (16)
β (°)	102.41 (3)
V (Å³)	1366.6 (5)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.11
Crystal size (mm)	0.30 × 0.25 × 0.15

Data collection
Diffractometer	Rigaku Mercury2 diffractometer
Absorption correction	Multi-scan (CrystalClear; Rigaku, 2005)
T_min, T_max	0.910, 1.000
No. of measured, independent and observed [I > 2σ(I)] reflections	7343, 1555, 1393
R_int	0.041
(sin θ/λ)_max (Å⁻¹)	0.648

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.040, 0.117, 1.12
No. of reflections	1555
No. of parameters	191
No. of restraints	2
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.19, −0.22

Computer programs: CrystalClear (Rigaku, 2005), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···O1Wⁱ	0.89	2.13	3.004 (4)	166
N1—H1B···O3ⁱⁱ	0.89	1.98	2.862 (3)	170
N1—H1C···N3	0.89	2.12	3.003 (4)	171
N2—H2A···O1Wⁱⁱⁱ	0.90	2.41	3.303 (4)	172
N2—H2B···O1	0.90	2.14	3.029 (4)	168
O1W—H1WA···O2^iv	0.82	2.27	3.034 (3)	155
O1W—H1WB···O2	0.82	2.04	2.831 (3)	161
O4—H4···O1ⁱ	0.82	1.71	2.532 (3)	179

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

Acknowledgements

This work was supported by the start-up fund of Northwest A & F University, China.

References

Andre, V., Fernandes, A., Santos, P. P. & Duarte, M. T. (2011). Cryst. Growth Des. 11, 2325–2334. CAS Google Scholar
Blagden, N., Berry, D. J., Parkin, A., Javed, H., Ibrahim, A., Gavan, P. T., De Matos, L. L. & Seaton, C. C. (2008). New J. Chem. 32, 1659–1672. Web of Science CSD CrossRef CAS Google Scholar
Kapildev, K. A., Nitin, G. T. & Raj, S. (2011). Mol. Pharm. 8, 982–989. Web of Science PubMed Google Scholar
Rigaku (2005). CrystalClear. Rigaku Corporation, Tokyo, Japan. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS IUCr Journals Google Scholar
Smith, G., Bott, R. C. & Lynch, D. E. (2000). Acta Cryst. C56, 1155–1156. Web of Science CSD CrossRef CAS IUCr Journals Google Scholar