trans-Diaqua­bis[5-carb­oxy-2-(3-pyridyl)-1H-imidazole-4-carboxyl­ato-κ2N3,O4]manganese(II)

Chen, L.-Z.

doi:10.1107/S1600536808029073

metal-organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 64| Part 10| October 2008| Page m1286

doi:10.1107/S1600536808029073

Open

access

trans-Diaquabis[5-carboxy-2-(3-pyridyl)-1H-imidazole-4-carboxylato-κ²N³,O⁴]manganese(II)

Li-Zhuang Chen ^a ^*

^aOrdered Matter Science Research Center, College of Chemistry and Chemical Engineering, Southeast University, Nanjing 210096, People's Republic of China
^*Correspondence e-mail: clz1977@sina.com

(Received 5 September 2008; accepted 10 September 2008; online 20 September 2008)

In the title compound, [Mn(C₁₀H₆N₃O₄)₂(H₂O)₂], synthesized by hydrothermal reaction, the Mn^II ion lies on an inversion centre and displays a distorted octahedral coordination geometry defined by the two imidazole N atoms and two carboxylate O atoms of the two trans-standing chelate ligands, and two O atoms of the water molecules. A two-dimensional supramolecular architecture is formed via N—H⋯O, O—H⋯N and O—H⋯O hydrogen-bonding interactions.

Related literature

For the chemistry of imidazoles, see: Xiao et al. (2004 ); Zhang et al. (2004 ); Lu et al. (2006 ).

Experimental

Crystal data

[Mn(C₁₀H₆N₃O₄)₂(H₂O)₂]
M_r = 555.33
Triclinic, $[P \overline 1]$
a = 6.9574 (7) Å
b = 8.5636 (7) Å
c = 9.4409 (16) Å
α = 81.90 (3)°
β = 83.42 (4)°
γ = 72.10 (2)°
V = 528.41 (11) Å³
Z = 1
Mo Kα radiation
μ = 0.70 mm⁻¹
T = 298 (2) K
0.25 × 0.20 × 0.20 mm

Data collection

Rigaku Mercury2 diffractometer
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005 ) T_min = 0.845, T_max = 0.869
5416 measured reflections
2378 independent reflections
1871 reflections with I > 2σ(I)
R_int = 0.029

Refinement

R[F² > 2σ(F²)] = 0.047
wR(F²) = 0.165
S = 1.11
2378 reflections
175 parameters
2 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.54 e Å⁻³
Δρ_min = −0.44 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
N2—H2A⋯O4ⁱ	0.86	2.00	2.840 (3)	164
O5—H5⋯N3ⁱⁱ	0.82	1.97	2.779 (3)	171
O5—H5B⋯O3ⁱⁱⁱ	0.839 (17)	2.074 (18)	2.908 (3)	173 (3)
O3—H3⋯O2	0.82	1.69	2.456 (3)	155
Symmetry codes: (i) -x, -y+2, -z+1; (ii) -x+1, -y+1, -z+1; (iii) x+1, y-1, z.

Data collection: CrystalClear (Rigaku, 2005); 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: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536808029073/bx2177sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536808029073/bx2177Isup2.hkl

checkCIF report

Comment top

N-Heterocyclic carboxylic acids, such as imidazole-4,5-dicarboxylic acid, are recognized as efficient N,O-donors, exhibiting diverse modes of coordination (Zhang et al., 2004; Xiao et al., 2004; Lu et al., 2006). In this work, we have chosen 2-Pyridin-3-yl-1H-imidazole-4,5-dicarboxylic acid as the building block to obtain the title compound, and we present its crystal structure here. Mn^II ion lies on an inversion centre and displaying distorted octahedral coordination geometry defined by the two imidazole N atoms, two O toms of the carboxylate groups and two O atoms of the water molecules. The pyridine ring and imidazole rings are twisted from each other by a dihedral angle of 20.78 (2)° (Fig. 1). The crystal structure is stabilized by intermolecular O—H···N, O—H···O and N—H···O, hydrogen bonds. A two-dimensional supramolecular architecture is formed via hydrogen-bond interactions (Table 1 and Fig. 2).

Related literature top

For the chemistry of imidazoles, see: Xiao et al. (2004); Zhang et al. (2004); Lu et al. (2006).

Experimental top

A mixture of 2-Pyridin-3-yl-1H-imidazole-4,5-dicarboxylic acid (0.1 mmol, 23 mg) and MnCl₂ (20 mg, 0.1 mmol) and water (1 ml) sealed in a glass tube was maintained at 100°C for 3 d then cooled to room temperature to obtain suitable single crystals for X-ray analysis.

Computing details top

Data collection: CrystalClear (Rigaku, 2005); cell refinement: CrystalClear (Rigaku, 2005); data reduction: CrystalClear (Rigaku, 2005); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Figures top

	Fig. 1. A view of the title compound with the atomic numbering scheme. Displacement ellipsoids were drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii. Unlabelled atoms are related to labelled atoms by the symmetry code ( -x+1, -y+1, -z).
	Fig. 2. The crystal packing of the title compound viewed along the b axis and all hydrogen atoms not involved in hydrogen bonding (dashed lines) were omitted for clarity.

trans-Diaquabis[5-carboxy-2-(3-pyridyl)-1H-imidazole-4- carboxylato-κ²N³,O⁴]manganese(II) top

Crystal data top

[Mn(C₁₀H₆N₃O₄)₂(H₂O)₂]	Z = 1
M_r = 555.33	F(000) = 283
Triclinic, P1	D_x = 1.745 Mg m⁻³
Hall symbol: -P 1	Mo Kα radiation, λ = 0.71073 Å
a = 6.9574 (7) Å	Cell parameters from 1463 reflections
b = 8.5636 (7) Å	θ = 3.1–27.5°
c = 9.4409 (16) Å	µ = 0.70 mm⁻¹
α = 81.90 (3)°	T = 298 K
β = 83.42 (4)°	Block, colourless
γ = 72.10 (2)°	0.25 × 0.20 × 0.20 mm
V = 528.41 (11) Å³

Data collection top

Rigaku Mercury2 diffractometer	2378 independent reflections
Radiation source: fine-focus sealed tube	1871 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.029
Detector resolution: 13.6612 pixels mm^-1	θ_max = 27.5°, θ_min = 2.5°
ω scans	h = −8→8
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005)	k = −11→11
T_min = 0.845, T_max = 0.869	l = −12→12
5416 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)] = 0.047	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.165	H atoms treated by a mixture of independent and constrained refinement
S = 1.11	w = 1/[σ²(F_o²) + (0.1003P)² + 0.0122P] where P = (F_o² + 2F_c²)/3
2378 reflections	(Δ/σ)_max < 0.001
175 parameters	Δρ_max = 0.54 e Å⁻³
2 restraints	Δρ_min = −0.44 e Å⁻³

Crystal data top

[Mn(C₁₀H₆N₃O₄)₂(H₂O)₂]	γ = 72.10 (2)°
M_r = 555.33	V = 528.41 (11) Å³
Triclinic, P1	Z = 1
a = 6.9574 (7) Å	Mo Kα radiation
b = 8.5636 (7) Å	µ = 0.70 mm⁻¹
c = 9.4409 (16) Å	T = 298 K
α = 81.90 (3)°	0.25 × 0.20 × 0.20 mm
β = 83.42 (4)°

Data collection top

Rigaku Mercury2 diffractometer	2378 independent reflections
Absorption correction: multi-scan (CrystalClear; Rigaku, 2005)	1871 reflections with I > 2σ(I)
T_min = 0.845, T_max = 0.869	R_int = 0.029
5416 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.047	2 restraints
wR(F²) = 0.165	H atoms treated by a mixture of independent and constrained refinement
S = 1.11	Δρ_max = 0.54 e Å⁻³
2378 reflections	Δρ_min = −0.44 e Å⁻³
175 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
Mn1	0.5000	0.5000	0.0000	0.0299 (2)
C1	0.3266 (4)	0.8677 (4)	−0.0160 (3)	0.0290 (6)
C2	0.2634 (4)	0.8148 (3)	0.1332 (3)	0.0253 (6)
C3	0.1577 (4)	0.9082 (3)	0.2405 (3)	0.0260 (6)
C4	0.0487 (5)	1.0861 (4)	0.2425 (3)	0.0308 (6)
C5	0.2472 (4)	0.6428 (3)	0.3206 (3)	0.0229 (5)
C6	0.2698 (4)	0.4926 (3)	0.4203 (3)	0.0253 (6)
C7	0.3049 (5)	0.3401 (4)	0.3713 (3)	0.0336 (7)
H7A	0.3120	0.3314	0.2737	0.040*
C8	0.3291 (5)	0.2013 (4)	0.4703 (3)	0.0369 (7)
H8A	0.3592	0.0972	0.4399	0.044*
C9	0.3080 (5)	0.2195 (4)	0.6156 (3)	0.0345 (7)
H9A	0.3215	0.1261	0.6817	0.041*
N3	0.2692 (4)	0.3661 (3)	0.6640 (3)	0.0332 (6)
C11	0.2491 (5)	0.4986 (4)	0.5688 (3)	0.0300 (6)
H11A	0.2196	0.6010	0.6025	0.036*
N1	0.3172 (3)	0.6504 (3)	0.1834 (2)	0.0255 (5)
N2	0.1531 (4)	0.7971 (3)	0.3573 (2)	0.0269 (5)
H2A	0.0992	0.8207	0.4412	0.032*
O1	0.4330 (4)	0.7595 (3)	−0.0912 (2)	0.0380 (5)
O2	0.2722 (4)	1.0220 (3)	−0.0599 (2)	0.0408 (6)
O3	0.0641 (4)	1.1816 (3)	0.1292 (2)	0.0397 (6)
H3	0.1602	1.1348	0.0764	0.060*
O4	−0.0526 (4)	1.1310 (3)	0.3540 (2)	0.0457 (6)
O5	0.7793 (4)	0.5087 (3)	0.0738 (2)	0.0414 (6)
H5	0.7544	0.5539	0.1476	0.062*
H5B	0.867 (5)	0.416 (3)	0.083 (3)	0.042 (10)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Mn1	0.0369 (4)	0.0247 (4)	0.0204 (3)	0.0026 (3)	0.0007 (3)	−0.0056 (2)
C1	0.0337 (15)	0.0254 (14)	0.0204 (13)	0.0004 (11)	0.0015 (11)	−0.0017 (10)
C2	0.0307 (14)	0.0207 (13)	0.0197 (13)	−0.0006 (10)	−0.0005 (11)	−0.0035 (10)
C3	0.0315 (14)	0.0231 (14)	0.0205 (12)	−0.0040 (11)	0.0015 (11)	−0.0049 (10)
C4	0.0366 (16)	0.0242 (14)	0.0257 (14)	0.0005 (12)	−0.0005 (12)	−0.0061 (11)
C5	0.0233 (13)	0.0235 (13)	0.0184 (12)	−0.0021 (10)	0.0020 (10)	−0.0047 (9)
C6	0.0270 (13)	0.0265 (14)	0.0208 (13)	−0.0063 (11)	0.0028 (11)	−0.0041 (10)
C7	0.0455 (17)	0.0288 (15)	0.0212 (14)	−0.0052 (13)	0.0077 (13)	−0.0064 (11)
C8	0.0493 (19)	0.0225 (14)	0.0336 (16)	−0.0033 (12)	−0.0003 (14)	−0.0048 (11)
C9	0.0404 (17)	0.0279 (15)	0.0303 (16)	−0.0074 (13)	0.0003 (13)	0.0039 (12)
N3	0.0419 (15)	0.0327 (13)	0.0209 (12)	−0.0075 (11)	0.0023 (10)	−0.0012 (9)
C11	0.0388 (16)	0.0271 (14)	0.0226 (14)	−0.0065 (12)	−0.0030 (12)	−0.0041 (11)
N1	0.0310 (12)	0.0214 (11)	0.0200 (11)	−0.0021 (9)	−0.0007 (10)	−0.0028 (9)
N2	0.0334 (12)	0.0246 (12)	0.0185 (11)	−0.0032 (10)	0.0038 (9)	−0.0058 (8)
O1	0.0503 (14)	0.0304 (11)	0.0210 (10)	0.0023 (10)	0.0077 (9)	−0.0028 (8)
O2	0.0578 (14)	0.0251 (11)	0.0257 (11)	0.0011 (10)	0.0082 (10)	0.0035 (8)
O3	0.0508 (14)	0.0229 (11)	0.0330 (12)	0.0038 (9)	0.0059 (10)	−0.0031 (8)
O4	0.0650 (16)	0.0303 (12)	0.0291 (12)	0.0059 (11)	0.0040 (11)	−0.0123 (9)
O5	0.0423 (13)	0.0434 (14)	0.0309 (12)	0.0012 (11)	−0.0015 (10)	−0.0119 (10)

Geometric parameters (Å, º) top

Mn1—O5ⁱ	2.163 (2)	C5—N2	1.356 (3)
Mn1—O5	2.163 (2)	C5—C6	1.460 (4)
Mn1—O1ⁱ	2.194 (2)	C6—C7	1.389 (4)
Mn1—O1	2.194 (2)	C6—C11	1.399 (4)
Mn1—N1ⁱ	2.322 (2)	C7—C8	1.383 (4)
Mn1—N1	2.322 (2)	C7—H7A	0.9300
C1—O1	1.246 (3)	C8—C9	1.388 (4)
C1—O2	1.279 (3)	C8—H8A	0.9300
C1—C2	1.477 (4)	C9—N3	1.335 (4)
C2—N1	1.370 (3)	C9—H9A	0.9300
C2—C3	1.380 (4)	N3—C11	1.326 (4)
C3—N2	1.355 (3)	C11—H11A	0.9300
C3—C4	1.480 (4)	N2—H2A	0.8600
C4—O4	1.238 (3)	O3—H3	0.8200
C4—O3	1.267 (4)	O5—H5	0.8200
C5—N1	1.331 (3)	O5—H5B	0.839 (17)

O5ⁱ—Mn1—O5	180.00 (11)	N2—C5—C6	123.9 (2)
O5ⁱ—Mn1—O1ⁱ	90.51 (10)	C7—C6—C11	117.7 (3)
O5—Mn1—O1ⁱ	89.49 (10)	C7—C6—C5	121.3 (2)
O5ⁱ—Mn1—O1	89.49 (10)	C11—C6—C5	121.0 (2)
O5—Mn1—O1	90.51 (10)	C8—C7—C6	118.9 (3)
O1ⁱ—Mn1—O1	180.0	C8—C7—H7A	120.6
O5ⁱ—Mn1—N1ⁱ	90.00 (8)	C6—C7—H7A	120.6
O5—Mn1—N1ⁱ	90.00 (8)	C7—C8—C9	119.2 (3)
O1ⁱ—Mn1—N1ⁱ	74.86 (8)	C7—C8—H8A	120.4
O1—Mn1—N1ⁱ	105.14 (8)	C9—C8—H8A	120.4
O5ⁱ—Mn1—N1	90.00 (8)	N3—C9—C8	122.5 (3)
O5—Mn1—N1	90.00 (8)	N3—C9—H9A	118.8
O1ⁱ—Mn1—N1	105.14 (8)	C8—C9—H9A	118.8
O1—Mn1—N1	74.86 (8)	C11—N3—C9	118.2 (3)
N1ⁱ—Mn1—N1	180.0	N3—C11—C6	123.5 (3)
O1—C1—O2	123.7 (3)	N3—C11—H11A	118.2
O1—C1—C2	118.1 (3)	C6—C11—H11A	118.2
O2—C1—C2	118.2 (3)	C5—N1—C2	105.7 (2)
N1—C2—C3	110.3 (2)	C5—N1—Mn1	145.47 (18)
N1—C2—C1	119.8 (2)	C2—N1—Mn1	108.75 (16)
C3—C2—C1	129.9 (3)	C3—N2—C5	109.1 (2)
N2—C3—C2	104.8 (2)	C3—N2—H2A	125.5
N2—C3—C4	121.9 (2)	C5—N2—H2A	125.5
C2—C3—C4	133.1 (3)	C1—O1—Mn1	118.36 (18)
O4—C4—O3	124.5 (3)	C4—O3—H3	109.5
O4—C4—C3	117.8 (3)	Mn1—O5—H5	109.5
O3—C4—C3	117.7 (2)	Mn1—O5—H5B	113 (2)
N1—C5—N2	110.0 (2)	H5—O5—H5B	112.4
N1—C5—C6	126.0 (2)

O1—C1—C2—N1	−1.9 (4)	C6—C5—N1—C2	−179.2 (3)
O2—C1—C2—N1	179.4 (3)	N2—C5—N1—Mn1	176.6 (2)
O1—C1—C2—C3	175.6 (3)	C6—C5—N1—Mn1	−2.2 (5)
O2—C1—C2—C3	−3.1 (5)	C3—C2—N1—C5	−0.6 (3)
N1—C2—C3—N2	1.4 (3)	C1—C2—N1—C5	177.3 (3)
C1—C2—C3—N2	−176.2 (3)	C3—C2—N1—Mn1	−178.84 (19)
N1—C2—C3—C4	−173.1 (3)	C1—C2—N1—Mn1	−0.9 (3)
C1—C2—C3—C4	9.3 (6)	O5ⁱ—Mn1—N1—C5	95.6 (3)
N2—C3—C4—O4	−1.9 (5)	O5—Mn1—N1—C5	−84.4 (3)
C2—C3—C4—O4	171.9 (3)	O1ⁱ—Mn1—N1—C5	5.0 (4)
N2—C3—C4—O3	178.8 (3)	O1—Mn1—N1—C5	−175.0 (4)
C2—C3—C4—O3	−7.4 (5)	O5ⁱ—Mn1—N1—C2	−87.49 (19)
N1—C5—C6—C7	−22.7 (4)	O5—Mn1—N1—C2	92.51 (19)
N2—C5—C6—C7	158.6 (3)	O1ⁱ—Mn1—N1—C2	−178.01 (18)
N1—C5—C6—C11	159.7 (3)	O1—Mn1—N1—C2	1.99 (18)
N2—C5—C6—C11	−18.9 (4)	C2—C3—N2—C5	−1.7 (3)
C11—C6—C7—C8	−3.7 (4)	C4—C3—N2—C5	173.6 (3)
C5—C6—C7—C8	178.7 (3)	N1—C5—N2—C3	1.4 (3)
C6—C7—C8—C9	3.1 (5)	C6—C5—N2—C3	−179.8 (2)
C7—C8—C9—N3	−1.4 (5)	O2—C1—O1—Mn1	−177.4 (2)
C8—C9—N3—C11	0.4 (5)	C2—C1—O1—Mn1	3.9 (4)
C9—N3—C11—C6	−1.1 (5)	O5ⁱ—Mn1—O1—C1	86.8 (2)
C7—C6—C11—N3	2.8 (4)	O5—Mn1—O1—C1	−93.2 (2)
C5—C6—C11—N3	−179.6 (3)	N1ⁱ—Mn1—O1—C1	176.7 (2)
N2—C5—N1—C2	−0.4 (3)	N1—Mn1—O1—C1	−3.3 (2)

Symmetry code: (i) −x+1, −y+1, −z.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2A···O4ⁱⁱ	0.86	2.00	2.840 (3)	164
O5—H5···N3ⁱⁱⁱ	0.82	1.97	2.779 (3)	171
O5—H5B···O3^iv	0.84 (2)	2.07 (2)	2.908 (3)	173 (3)
O3—H3···O2	0.82	1.69	2.456 (3)	155

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

Experimental details

Crystal data
Chemical formula	[Mn(C₁₀H₆N₃O₄)₂(H₂O)₂]
M_r	555.33
Crystal system, space group	Triclinic, P1
Temperature (K)	298
a, b, c (Å)	6.9574 (7), 8.5636 (7), 9.4409 (16)
α, β, γ (°)	81.90 (3), 83.42 (4), 72.10 (2)
V (Å³)	528.41 (11)
Z	1
Radiation type	Mo Kα
µ (mm⁻¹)	0.70
Crystal size (mm)	0.25 × 0.20 × 0.20

Data collection
Diffractometer	Rigaku Mercury2 diffractometer
Absorption correction	Multi-scan (CrystalClear; Rigaku, 2005)
T_min, T_max	0.845, 0.869
No. of measured, independent and observed [I > 2σ(I)] reflections	5416, 2378, 1871
R_int	0.029
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.047, 0.165, 1.11
No. of reflections	2378
No. of parameters	175
No. of restraints	2
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.54, −0.44

Computer programs: CrystalClear (Rigaku, 2005), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
N2—H2A···O4ⁱ	0.86	2.00	2.840 (3)	164.2
O5—H5···N3ⁱⁱ	0.82	1.97	2.779 (3)	171.0
O5—H5B···O3ⁱⁱⁱ	0.839 (17)	2.074 (18)	2.908 (3)	173 (3)
O3—H3···O2	0.82	1.69	2.456 (3)	154.8

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

Acknowledgements

This work was supported by a start-up grant from Southeast University to Professor Ren-Gen Xiong.

References

Lu, W.-G., Su, C.-Y., Lu, T.-B., Jiang, L. & Chen, J.-M. (2006). J. Am. Chem. Soc. 128, 34–35. Web of Science CSD CrossRef PubMed CAS 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
Xiao, H.-P., Li, X.-H. & Shi, Q. (2004). Acta Cryst. E60, m1519–m1521. Web of Science CSD CrossRef IUCr Journals Google Scholar
Zhang, X.-M., Fang, R.-Q., Wu, H.-S. & Ng, S. W. (2004). Acta Cryst. E60, m12–m13. Web of Science CSD CrossRef IUCr Journals Google Scholar

This is an open-access article distributed under the terms of the Creative Commons Attribution (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.