Poly[[hexa­aqua­(μ3-2,2′-bipyridine-4,4′,6,6′-tetra­carboxyl­ato-κ6O4:N,O6,O6′,N′:O4′)dinickel(II)] dihydrate]

Li, J.; Lei, K.-W.; Xia, D.-G.

doi:10.1107/S1600536812043942

metal-organic compounds

CRYSTALLOGRAPHIC
COMMUNICATIONS

ISSN: 2056-9890

Volume 68| Part 11| November 2012| Page m1421

doi:10.1107/S1600536812043942

Open

access

Poly[[hexaaqua(μ₃-2,2′-bipyridine-4,4′,6,6′-tetracarboxylato-κ⁶O⁴:N,O⁶,O^6′,N′:O^4′)dinickel(II)] dihydrate]

Jie Li,^a Ke-Wei Lei ^a ^* and Dong-Guo Xia ^a

^aState Key Lab. Base of Novel Functional Materials and Preparation Science, Institute of Solid Materials Chemistry, Faculty of Materials Science and Chemical Engineering, Ningbo University, Ningbo 315211, People's Republic of China
^*Correspondence e-mail: leikeweipublic@hotmail.com

(Received 11 April 2012; accepted 23 October 2012; online 31 October 2012)

In the title complex, {[Ni₂(C₁₄H₄N₂O₈)(H₂O)₆]·2H₂O}_n, the two Ni^II atoms are located in different special positions (one on a twofold rotation axis and the second on a centre of symmetry) and have different distorted octahedral environments (one by two N atoms from a bipyridine unit, two O atoms from two water molecules and two O atoms from two carboxylate groups, and the second by four O atoms from four water molecules and two O atoms from two carboxylate groups). Thus, the environments of the Ni^II atoms may be denoted as NiN₂O₄ and NiO₆. In the crystal, there exists an extensive network of classical O—H⋯O hydrogen bonds.

Related literature

For the synthesis of title compound, see: Al-Harbi (2011 ).

Experimental

Crystal data

[Ni₂(C₁₄H₄N₂O₈)(H₂O)₆]·2H₂O
M_r = 589.70
Monoclinic, P 2/n
a = 7.3588 (8) Å
b = 11.8463 (13) Å
c = 11.9942 (13) Å
β = 99.184 (1)°
V = 1032.19 (19) Å³
Z = 2
Mo Kα radiation
μ = 1.91 mm⁻¹
T = 296 K
0.28 × 0.24 × 0.19 mm

Data collection

Rigaku R-AXIS RAPID diffractometer
Absorption correction: multi-scan (ABSCOR; Higashi, 1995 ) T_min = 0.591, T_max = 0.695
8794 measured reflections
2365 independent reflections
2248 reflections with I > 2σ(I)
R_int = 0.038

Refinement

R[F² > 2σ(F²)] = 0.023
wR(F²) = 0.062
S = 1.06
2365 reflections
176 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.40 e Å⁻³
Δρ_min = −0.42 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3B⋯O6	0.85 (2)	1.95 (2)	2.7821 (16)	169 (2)
O3—H3A⋯O8ⁱ	0.82	1.90	2.7189 (16)	174
O4—H4A⋯O6ⁱⁱ	0.82	1.95	2.7697 (17)	178
O4—H4B⋯O7ⁱⁱⁱ	0.78 (3)	2.03 (3)	2.7997 (16)	172 (3)
O5—H5A⋯O2^iv	0.82	1.90	2.6891 (16)	162
O5—H5B⋯O7^v	0.78 (3)	1.96 (3)	2.7395 (17)	172 (3)
O6—H6A⋯O2^v	0.79 (3)	2.03 (3)	2.8096 (17)	170 (2)
Symmetry codes: (i) x, y+1, z; (ii) $[x+{\script{1\over 2}}, -y+2, z+{\script{1\over 2}}]$ ; (iii) -x, -y+1, -z+2; (iv) $[x+{\script{1\over 2}}, -y+1, z-{\script{1\over 2}}]$ ; (v) $[-x-{\script{1\over 2}}, y, -z+{\script{3\over 2}}]$ .

Data collection: RAPID-AUTO (Rigaku, 1998 ); cell refinement: RAPID-AUTO; data reduction: CrystalStructure (Rigaku/MSC, 2004 ); 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: SHELXL97.

Supporting information

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536812043942/rk2355sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536812043942/rk2355Isup2.hkl

checkCIF report

Comment top

The complex structure is shown in Fig. 1. In the title complex two Ni atoms are placed in two different special positions: Ni1 - on 2–fold axis and Ni2 - in centre of symmetry. These atoms have different environment: Ni1 is coordinated by two N atoms of dipyridine moiety, two O atoms from water molecules and two O atoms from two carboxylate moieties; Ni2 is coordinated only by six O atoms: four O from four water molecules and two O from two carboxylate moieties.

In the crystal structure there is the wide net of classical O—H···O type H–bonds (Table 1, Fig. 2), which stabilize crystal packing.

Related literature top

For the synthesis of title compound, see: Al-Harbi (2011).

Experimental top

A mixture of 6–(4,6–dicarboxypyridin–2–yl)pyridine–2,4–dicarboxylic acid (0.0332 g, 0.1 mmol), Ni(NO₃)₂^.6H₂O (0.0724 g, 0.3 mmol) and water (10 ml) was placed in a teflon–lined stainless steel vessel (25 ml) and heated at 443.15 K for 72 h, and then cooled to room temperature at a rate of 5/h (Al-Harbi, 2011). The resulting green single crystals were isolated by washing with DMF and dried in vacuo. Yield: 62.3%.

Computing details top

Data collection: RAPID-AUTO (Rigaku, 1998); cell refinement: RAPID-AUTO (Rigaku, 1998); data reduction: CrystalStructure (Rigaku/MSC, 2004); 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: SHELXL97 (Sheldrick, 2008).

Figures top

	Fig. 1. The structure of the title complex with the atom–numbering scheme. Displacement ellipsoids are drawn at 30% probability level.
	Fig. 2. The three–dimensional structure of the title complex. The hydrogen bonds are indicated by dashed lines.

Poly[[hexaaqua(µ₃-2,2'-bipyridine-4,4',6,6'-tetracarboxylato- κ⁶O⁴:N,O⁶,O^6',N':O^4') dinickel(II)] dihydrate] top

Crystal data top

[Ni₂(C₁₄H₄N₂O₈)(H₂O)₆]·2H₂O	F(000) = 604
M_r = 589.70	D_x = 1.897 Mg m⁻³
Monoclinic, P2/n	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2yac	Cell parameters from 8794 reflections
a = 7.3588 (8) Å	θ = 1.7–27.5°
b = 11.8463 (13) Å	µ = 1.91 mm⁻¹
c = 11.9942 (13) Å	T = 296 K
β = 99.184 (1)°	Block, green
V = 1032.19 (19) Å³	0.28 × 0.24 × 0.19 mm
Z = 2

Data collection top

Rigaku R-AXIS RAPID diffractometer	2365 independent reflections
Radiation source: fine–focus sealed tube	2248 reflections with I > 2σ(I)
Graphite monochromator	R_int = 0.038
Detector resolution: 0 pixels mm^-1	θ_max = 27.5°, θ_min = 1.7°
ω scans	h = −9→8
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	k = −15→14
T_min = 0.591, T_max = 0.695	l = −15→15
8794 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)] = 0.023	Hydrogen site location: inferred from neighbouring sites
wR(F²) = 0.062	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	w = 1/[σ²(F_o²) + (0.0255P)² + 0.5729P] where P = (F_o² + 2F_c²)/3
2365 reflections	(Δ/σ)_max < 0.001
176 parameters	Δρ_max = 0.40 e Å⁻³
0 restraints	Δρ_min = −0.42 e Å⁻³

Crystal data top

[Ni₂(C₁₄H₄N₂O₈)(H₂O)₆]·2H₂O	V = 1032.19 (19) Å³
M_r = 589.70	Z = 2
Monoclinic, P2/n	Mo Kα radiation
a = 7.3588 (8) Å	µ = 1.91 mm⁻¹
b = 11.8463 (13) Å	T = 296 K
c = 11.9942 (13) Å	0.28 × 0.24 × 0.19 mm
β = 99.184 (1)°

Data collection top

Rigaku R-AXIS RAPID diffractometer	2365 independent reflections
Absorption correction: multi-scan (ABSCOR; Higashi, 1995)	2248 reflections with I > 2σ(I)
T_min = 0.591, T_max = 0.695	R_int = 0.038
8794 measured reflections

Refinement top

R[F² > 2σ(F²)] = 0.023	0 restraints
wR(F²) = 0.062	H atoms treated by a mixture of independent and constrained refinement
S = 1.06	Δρ_max = 0.40 e Å⁻³
2365 reflections	Δρ_min = −0.42 e Å⁻³
176 parameters

Special details top

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 > 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
Ni1	0.2500	0.36726 (2)	0.7500	0.01154 (8)
Ni2	0.0000	1.0000	1.0000	0.01064 (8)
O1	−0.10038 (16)	0.87338 (9)	0.89420 (9)	0.0161 (2)
O3	0.10695 (15)	1.06255 (9)	0.86383 (9)	0.0145 (2)
H3A	0.0846	1.1302	0.8571	0.022*
O2	−0.33996 (15)	0.76758 (9)	0.92552 (9)	0.0162 (2)
O4	0.23852 (15)	0.90408 (10)	1.03816 (9)	0.0162 (2)
H4A	0.3218	0.9436	1.0709	0.024*
O8	0.04444 (15)	0.28697 (9)	0.82901 (9)	0.0152 (2)
C1	0.1670 (2)	0.60269 (12)	0.77858 (12)	0.0118 (3)
N1	0.10800 (18)	0.49784 (10)	0.79747 (10)	0.0110 (2)
C6	−0.1837 (2)	0.78123 (12)	0.89848 (11)	0.0112 (3)
C4	−0.1418 (2)	0.56825 (12)	0.88022 (11)	0.0112 (3)
H4C	−0.2463	0.5552	0.9130	0.013*
C2	0.0741 (2)	0.69601 (13)	0.81220 (12)	0.0123 (3)
H2A	0.1153	0.7688	0.8011	0.015*
C5	−0.0391 (2)	0.47890 (12)	0.84663 (12)	0.0112 (3)
C3	−0.0820 (2)	0.67854 (12)	0.86283 (11)	0.0108 (3)
O7	−0.21194 (15)	0.32298 (9)	0.90173 (9)	0.0157 (2)
O5	0.07941 (17)	0.35897 (11)	0.59723 (10)	0.0201 (2)
H5A	0.1245	0.3169	0.5548	0.030*
C7	−0.0751 (2)	0.35285 (12)	0.86043 (12)	0.0120 (3)
O6	0.02584 (17)	0.96743 (11)	0.64958 (10)	0.0191 (2)
H6A	−0.015 (3)	0.909 (2)	0.6259 (19)	0.031 (6)*
H6B	0.114 (4)	0.976 (2)	0.621 (2)	0.037 (7)*
H5B	−0.025 (4)	0.352 (2)	0.603 (2)	0.043 (7)*
H4B	0.240 (4)	0.842 (2)	1.059 (2)	0.047 (8)*
H3B	0.069 (3)	1.031 (2)	0.801 (2)	0.035 (6)*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
Ni1	0.01010 (14)	0.00796 (14)	0.01721 (14)	0.000	0.00415 (10)	0.000
Ni2	0.01066 (15)	0.00722 (14)	0.01465 (14)	0.00026 (9)	0.00393 (10)	−0.00035 (9)
O1	0.0192 (6)	0.0099 (5)	0.0203 (5)	−0.0022 (4)	0.0067 (4)	−0.0040 (4)
O3	0.0182 (6)	0.0093 (5)	0.0165 (5)	−0.0002 (4)	0.0048 (4)	0.0003 (4)
O2	0.0151 (5)	0.0139 (5)	0.0209 (5)	0.0015 (4)	0.0067 (4)	0.0015 (4)
O4	0.0140 (5)	0.0103 (5)	0.0241 (5)	0.0009 (4)	0.0025 (4)	0.0019 (4)
O8	0.0136 (5)	0.0090 (5)	0.0239 (5)	0.0007 (4)	0.0059 (4)	0.0014 (4)
C1	0.0120 (7)	0.0097 (7)	0.0135 (6)	−0.0012 (5)	0.0020 (5)	0.0007 (5)
N1	0.0108 (6)	0.0092 (6)	0.0131 (6)	−0.0003 (4)	0.0025 (5)	−0.0002 (4)
C6	0.0130 (7)	0.0107 (7)	0.0097 (6)	0.0016 (5)	0.0015 (5)	0.0008 (5)
C4	0.0098 (7)	0.0124 (7)	0.0114 (6)	−0.0002 (5)	0.0018 (5)	0.0010 (5)
C2	0.0138 (7)	0.0092 (7)	0.0140 (6)	−0.0012 (5)	0.0023 (5)	0.0005 (5)
C5	0.0106 (7)	0.0107 (7)	0.0119 (6)	−0.0004 (5)	0.0005 (5)	0.0008 (5)
C3	0.0112 (7)	0.0100 (7)	0.0109 (6)	0.0003 (5)	0.0001 (5)	−0.0010 (5)
O7	0.0127 (5)	0.0124 (5)	0.0227 (5)	−0.0007 (4)	0.0049 (4)	0.0029 (4)
O5	0.0117 (6)	0.0275 (7)	0.0217 (6)	−0.0010 (5)	0.0045 (4)	−0.0089 (5)
C7	0.0111 (7)	0.0103 (7)	0.0139 (6)	0.0001 (5)	−0.0004 (5)	0.0012 (5)
O6	0.0156 (6)	0.0219 (6)	0.0210 (6)	−0.0053 (5)	0.0061 (5)	−0.0033 (5)

Geometric parameters (Å, º) top

Ni1—N1ⁱ	1.9996 (12)	O8—C7	1.2769 (18)
Ni1—N1	1.9996 (12)	C1—N1	1.3468 (18)
Ni1—O5	2.0516 (12)	C1—C2	1.393 (2)
Ni1—O5ⁱ	2.0516 (12)	C1—C1ⁱ	1.493 (3)
Ni1—O8	2.1327 (11)	N1—C5	1.3317 (19)
Ni1—O8ⁱ	2.1327 (11)	C6—C3	1.525 (2)
Ni2—O1	2.0265 (11)	C4—C5	1.397 (2)
Ni2—O1ⁱⁱ	2.0265 (11)	C4—C3	1.405 (2)
Ni2—O3ⁱⁱ	2.0607 (10)	C4—H4C	0.9300
Ni2—O3	2.0607 (10)	C2—C3	1.398 (2)
Ni2—O4ⁱⁱ	2.0796 (11)	C2—H2A	0.9300
Ni2—O4	2.0796 (11)	C5—C7	1.530 (2)
O1—C6	1.2570 (18)	O7—C7	1.2427 (19)
O3—H3A	0.8200	O5—H5A	0.8200
O3—H3B	0.85 (2)	O5—H5B	0.78 (3)
O2—C6	1.2541 (18)	O6—H6A	0.79 (3)
O4—H4A	0.8200	O6—H6B	0.79 (3)
O4—H4B	0.78 (3)

N1ⁱ—Ni1—N1	78.65 (7)	H3A—O3—H3B	108.0
N1ⁱ—Ni1—O5	93.20 (5)	Ni2—O4—H4A	109.5
N1—Ni1—O5	91.05 (5)	Ni2—O4—H4B	124 (2)
N1ⁱ—Ni1—O5ⁱ	91.05 (5)	H4A—O4—H4B	114.4
N1—Ni1—O5ⁱ	93.20 (5)	C7—O8—Ni1	115.42 (9)
O5—Ni1—O5ⁱ	174.51 (7)	N1—C1—C2	119.82 (13)
N1ⁱ—Ni1—O8	155.70 (5)	N1—C1—C1ⁱ	112.73 (8)
N1—Ni1—O8	77.21 (5)	C2—C1—C1ⁱ	127.45 (8)
O5—Ni1—O8	89.96 (5)	C5—N1—C1	122.43 (12)
O5ⁱ—Ni1—O8	87.60 (5)	C5—N1—Ni1	119.63 (10)
N1ⁱ—Ni1—O8ⁱ	77.21 (5)	C1—N1—Ni1	117.94 (10)
N1—Ni1—O8ⁱ	155.70 (5)	O2—C6—O1	126.58 (14)
O5—Ni1—O8ⁱ	87.60 (5)	O2—C6—C3	118.75 (13)
O5ⁱ—Ni1—O8ⁱ	89.96 (5)	O1—C6—C3	114.64 (13)
O8—Ni1—O8ⁱ	127.03 (6)	C5—C4—C3	117.70 (13)
O1—Ni2—O1ⁱⁱ	180.00 (4)	C5—C4—H4C	121.1
O1—Ni2—O3ⁱⁱ	94.76 (4)	C3—C4—H4C	121.1
O1ⁱⁱ—Ni2—O3ⁱⁱ	85.24 (4)	C1—C2—C3	118.91 (13)
O1—Ni2—O3	85.24 (4)	C1—C2—H2A	120.5
O1ⁱⁱ—Ni2—O3	94.76 (4)	C3—C2—H2A	120.5
O3ⁱⁱ—Ni2—O3	180.000 (1)	N1—C5—C4	121.05 (13)
O1—Ni2—O4ⁱⁱ	93.22 (5)	N1—C5—C7	112.28 (12)
O1ⁱⁱ—Ni2—O4ⁱⁱ	86.78 (5)	C4—C5—C7	126.67 (13)
O3ⁱⁱ—Ni2—O4ⁱⁱ	87.43 (4)	C2—C3—C4	120.06 (13)
O3—Ni2—O4ⁱⁱ	92.57 (4)	C2—C3—C6	118.55 (13)
O1—Ni2—O4	86.78 (5)	C4—C3—C6	121.39 (13)
O1ⁱⁱ—Ni2—O4	93.22 (5)	Ni1—O5—H5A	109.5
O3ⁱⁱ—Ni2—O4	92.57 (4)	Ni1—O5—H5B	113.3 (19)
O3—Ni2—O4	87.43 (4)	H5A—O5—H5B	119.4
O4ⁱⁱ—Ni2—O4	180.0	O7—C7—O8	125.72 (14)
C6—O1—Ni2	138.47 (10)	O7—C7—C5	119.10 (13)
Ni2—O3—H3A	109.5	O8—C7—C5	115.18 (13)
Ni2—O3—H3B	115.5 (17)	H6A—O6—H6B	105 (2)

Symmetry codes: (i) −x+1/2, y, −z+3/2; (ii) −x, −y+2, −z+2.

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O3—H3B···O6	0.85 (2)	1.95 (2)	2.7821 (16)	169 (2)
O3—H3A···O8ⁱⁱⁱ	0.82	1.90	2.7189 (16)	174
O4—H4A···O6^iv	0.82	1.95	2.7697 (17)	178
O4—H4B···O7^v	0.78 (3)	2.03 (3)	2.7997 (16)	172 (3)
O5—H5A···O2^vi	0.82	1.90	2.6891 (16)	162
O5—H5B···O7^vii	0.78 (3)	1.96 (3)	2.7395 (17)	172 (3)
O6—H6A···O2^vii	0.79 (3)	2.03 (3)	2.8096 (17)	170 (2)

Symmetry codes: (iii) x, y+1, z; (iv) x+1/2, −y+2, z+1/2; (v) −x, −y+1, −z+2; (vi) x+1/2, −y+1, z−1/2; (vii) −x−1/2, y, −z+3/2.

Experimental details

Crystal data
Chemical formula	[Ni₂(C₁₄H₄N₂O₈)(H₂O)₆]·2H₂O
M_r	589.70
Crystal system, space group	Monoclinic, P2/n
Temperature (K)	296
a, b, c (Å)	7.3588 (8), 11.8463 (13), 11.9942 (13)
β (°)	99.184 (1)
V (Å³)	1032.19 (19)
Z	2
Radiation type	Mo Kα
µ (mm⁻¹)	1.91
Crystal size (mm)	0.28 × 0.24 × 0.19

Data collection
Diffractometer	Rigaku R-AXIS RAPID diffractometer
Absorption correction	Multi-scan (ABSCOR; Higashi, 1995)
T_min, T_max	0.591, 0.695
No. of measured, independent and observed [I > 2σ(I)] reflections	8794, 2365, 2248
R_int	0.038
(sin θ/λ)_max (Å⁻¹)	0.649

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.023, 0.062, 1.06
No. of reflections	2365
No. of parameters	176
H-atom treatment	H atoms treated by a mixture of independent and constrained refinement
Δρ_max, Δρ_min (e Å⁻³)	0.40, −0.42

Computer programs: RAPID-AUTO (Rigaku, 1998), CrystalStructure (Rigaku/MSC, 2004), 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
O3—H3B···O6	0.85 (2)	1.95 (2)	2.7821 (16)	169 (2)
O3—H3A···O8ⁱ	0.82	1.90	2.7189 (16)	174.4
O4—H4A···O6ⁱⁱ	0.82	1.95	2.7697 (17)	177.8
O4—H4B···O7ⁱⁱⁱ	0.78 (3)	2.03 (3)	2.7997 (16)	172 (3)
O5—H5A···O2^iv	0.82	1.90	2.6891 (16)	161.9
O5—H5B···O7^v	0.78 (3)	1.96 (3)	2.7395 (17)	172 (3)
O6—H6A···O2^v	0.79 (3)	2.03 (3)	2.8096 (17)	170 (2)

Symmetry codes: (i) x, y+1, z; (ii) x+1/2, −y+2, z+1/2; (iii) −x, −y+1, −z+2; (iv) x+1/2, −y+1, z−1/2; (v) −x−1/2, y, −z+3/2.

Acknowledgements

This project was sponsored by the K. C. Wong Magna Fund in Ningbo University, the Talent Fund of Ningbo Municipal Natural Science Foundation (No. 2010 A610187) and the Talent Fund of Ningbo University (No. Xkl09070).

References

Al-Harbi, T. (2011). J. Alloys Compd, 509, 387–390. CAS Google Scholar
Higashi, T. (1995). ABSCOR. Rigaku Corporation, Tokyo, Japan. Google Scholar
Rigaku (1998). RAPID-AUTO. Rigaku Corporation, Tokyo, Japan. Google Scholar
Rigaku/MSC (2004). CrystalStructure. Rigaku/MSC Inc., The Woodlands, Texas, USA. Google Scholar
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122. Web of Science CrossRef CAS 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.