metal-organic compounds
Hexaaquacobalt(II) tetraaquabis(2-aminopyrazine-κN4)cobalt(II) disulfate dihydrate
aCollege of Chemistry and Materials Science, Heilongjiang University, Harbin 150080, People's Republic of China, and bDepartment of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia
*Correspondence e-mail: seikweng@um.edu.my
The reaction of cobalt(II) sulfate and 2-aminopyrazine affords the title salt, [Co(H2O)6][Co(C4H5N3)2(H2O)4](SO4)2·2H2O. The metal atoms in the tetraaqua-coordinated and hexaaqua-coordinated complex cations lie on centers of inversion in slightly distorted octahedral geometries. The cations, anions and solvent water molecules are linked by O—H⋯O, O—H⋯N and N—H⋯O hydrogen bonds into a three-dimensional network.
Related literature
The reaction of cobalt(II) chloride and 3-aminopyrazine yields tetrakis(3-aminopyrazine)dichloridocobalt(II); see: Csöregh et al. (2000); Kang et al. (2009).
Experimental
Crystal data
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Refinement
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Data collection: RAPID-AUTO (Rigaku, 1998); cell RAPID-AUTO; data reduction: CrystalClear (Rigaku/MSC, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: publCIF (Westrip, 2009).
Supporting information
10.1107/S1600536809045310/xu2657sup1.cif
contains datablocks global, I. DOI:Structure factors: contains datablock I. DOI: 10.1107/S1600536809045310/xu2657Isup2.hkl
To an aqueous solution of 3-aminopyrazine (0.19 g, 2 mmol) was added cobalt(II) sulfate heptahydrate (0.56 g, 2 mmol). Red crystals of the salt separated from the solution after a few days. CH&N elemental analysis. Calc. for C8H34N6O20S2Co2: C 13.41, H 4.78, N 11.73%; found: C 13.39, H 4.72, N 11.76%.
Carbon-bound H-atoms were placed in calculated positions (C—H 0.93 Å) and were included in the
in the riding model approximation, with U(H) set to 1.2U(C). The amino and water H-atoms were located in a difference Fourier map, and were refined with a distance restraint of N–H = O–H = 0.85±0.01 Å; their temperature factors were refined.Data collection: RAPID-AUTO (Rigaku, 1998); cell
RAPID-AUTO (Rigaku, 1998); data reduction: CrystalClear (Rigaku/MSC, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: X-SEED (Barbour, 2001); software used to prepare material for publication: publCIF (Westrip, 2009).Fig. 1. Thermal ellipsoid plot (Barbour, 2001) of [Co(H2O)6] [Co(H2O)4(C4H5N3)2] 2[SO4].2H2O at the 50% probability level; hydrogen atoms are drawn as spheres of arbitrary radius. |
[Co(H2O)6][Co(C4H5N3)2(H2O)4](SO4)2·2H2O | Z = 1 |
Mr = 716.40 | F(000) = 370 |
Triclinic, P1 | Dx = 1.750 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 6.5722 (3) Å | Cell parameters from 6326 reflections |
b = 8.3264 (4) Å | θ = 3.2–27.5° |
c = 13.2337 (7) Å | µ = 1.47 mm−1 |
α = 75.732 (2)° | T = 293 K |
β = 78.571 (1)° | Prism, red |
γ = 78.795 (1)° | 0.30 × 0.20 × 0.20 mm |
V = 679.81 (6) Å3 |
Rigaku RAXIS-RAPID IP diffractometer | 3071 independent reflections |
Radiation source: fine-focus sealed tube | 2762 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.027 |
ω scans | θmax = 27.4°, θmin = 3.2° |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | h = −7→8 |
Tmin = 0.668, Tmax = 0.758 | k = −10→10 |
6692 measured reflections | l = −17→17 |
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)] = 0.031 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.085 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | w = 1/[σ2(Fo2) + (0.0511P)2 + 0.1887P] where P = (Fo2 + 2Fc2)/3 |
3071 reflections | (Δ/σ)max = 0.001 |
231 parameters | Δρmax = 0.47 e Å−3 |
14 restraints | Δρmin = −0.33 e Å−3 |
[Co(H2O)6][Co(C4H5N3)2(H2O)4](SO4)2·2H2O | γ = 78.795 (1)° |
Mr = 716.40 | V = 679.81 (6) Å3 |
Triclinic, P1 | Z = 1 |
a = 6.5722 (3) Å | Mo Kα radiation |
b = 8.3264 (4) Å | µ = 1.47 mm−1 |
c = 13.2337 (7) Å | T = 293 K |
α = 75.732 (2)° | 0.30 × 0.20 × 0.20 mm |
β = 78.571 (1)° |
Rigaku RAXIS-RAPID IP diffractometer | 3071 independent reflections |
Absorption correction: multi-scan (ABSCOR; Higashi, 1995) | 2762 reflections with I > 2σ(I) |
Tmin = 0.668, Tmax = 0.758 | Rint = 0.027 |
6692 measured reflections |
R[F2 > 2σ(F2)] = 0.031 | 14 restraints |
wR(F2) = 0.085 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | Δρmax = 0.47 e Å−3 |
3071 reflections | Δρmin = −0.33 e Å−3 |
231 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
Co1 | 1.0000 | 1.0000 | 0.5000 | 0.02058 (10) | |
Co2 | 0.0000 | 0.5000 | 1.0000 | 0.02713 (11) | |
S1 | 0.48109 (7) | 0.88842 (5) | 0.80066 (3) | 0.02386 (12) | |
O1 | 0.4133 (2) | 0.98162 (18) | 0.70001 (10) | 0.0309 (3) | |
O2 | 0.5369 (3) | 0.70948 (18) | 0.79992 (14) | 0.0439 (4) | |
O3 | 0.6685 (2) | 0.95119 (18) | 0.81446 (11) | 0.0317 (3) | |
O4 | 0.3094 (2) | 0.9161 (2) | 0.88747 (12) | 0.0410 (4) | |
O1W | 0.7178 (2) | 0.91396 (17) | 0.53377 (11) | 0.0295 (3) | |
O2W | 1.0213 (2) | 0.96509 (18) | 0.66021 (11) | 0.0305 (3) | |
O3W | 0.2836 (2) | 0.4730 (2) | 0.90039 (14) | 0.0435 (4) | |
O4W | −0.1433 (3) | 0.4747 (2) | 0.87641 (13) | 0.0399 (4) | |
O5W | 0.0399 (2) | 0.23895 (19) | 1.05544 (14) | 0.0421 (4) | |
O6W | 0.6169 (3) | 0.2195 (2) | 0.91230 (13) | 0.0397 (3) | |
N1 | 0.8413 (2) | 1.25974 (19) | 0.49825 (13) | 0.0257 (3) | |
N2 | 0.7121 (3) | 1.6016 (2) | 0.49242 (14) | 0.0302 (3) | |
N3 | 0.7876 (3) | 1.6554 (2) | 0.30956 (16) | 0.0423 (4) | |
C1 | 0.8491 (3) | 1.3722 (2) | 0.40789 (15) | 0.0289 (4) | |
H1 | 0.9012 | 1.3361 | 0.3452 | 0.035* | |
C2 | 0.7812 (3) | 1.5450 (2) | 0.40335 (16) | 0.0283 (4) | |
C3 | 0.7021 (3) | 1.4852 (3) | 0.58309 (16) | 0.0317 (4) | |
H3 | 0.6516 | 1.5207 | 0.6461 | 0.038* | |
C4 | 0.7624 (3) | 1.3170 (2) | 0.58746 (15) | 0.0306 (4) | |
H4 | 0.7489 | 1.2415 | 0.6523 | 0.037* | |
H1W1 | 0.615 (3) | 0.941 (3) | 0.5778 (16) | 0.039 (7)* | |
H1W2 | 0.708 (4) | 0.822 (2) | 0.521 (2) | 0.043 (7)* | |
H2W1 | 0.924 (3) | 0.961 (3) | 0.7118 (14) | 0.038 (7)* | |
H2W2 | 1.136 (3) | 0.983 (4) | 0.671 (2) | 0.058 (9)* | |
H3W1 | 0.348 (5) | 0.556 (3) | 0.872 (3) | 0.072 (10)* | |
H3W2 | 0.376 (3) | 0.387 (2) | 0.906 (2) | 0.050 (8)* | |
H4W1 | −0.199 (5) | 0.387 (3) | 0.886 (3) | 0.068 (10)* | |
H4W2 | −0.234 (3) | 0.558 (2) | 0.856 (2) | 0.043 (7)* | |
H5W1 | 0.135 (3) | 0.176 (3) | 1.0881 (19) | 0.046 (8)* | |
H5W2 | −0.062 (4) | 0.185 (4) | 1.076 (2) | 0.066 (9)* | |
H6W1 | 0.637 (6) | 0.145 (4) | 0.876 (3) | 0.094 (13)* | |
H6W2 | 0.625 (5) | 0.164 (4) | 0.9747 (12) | 0.065 (10)* | |
H3N1 | 0.830 (5) | 1.618 (4) | 0.2538 (15) | 0.062 (9)* | |
H3N2 | 0.751 (5) | 1.7602 (15) | 0.307 (3) | 0.064 (9)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Co1 | 0.02009 (17) | 0.01865 (17) | 0.02239 (18) | −0.00235 (12) | −0.00307 (13) | −0.00400 (12) |
Co2 | 0.02194 (19) | 0.02479 (19) | 0.0323 (2) | −0.00440 (14) | −0.00566 (14) | 0.00002 (14) |
S1 | 0.0220 (2) | 0.0245 (2) | 0.0240 (2) | −0.00519 (17) | −0.00492 (16) | −0.00072 (16) |
O1 | 0.0285 (7) | 0.0353 (7) | 0.0270 (7) | −0.0006 (6) | −0.0095 (5) | −0.0022 (5) |
O2 | 0.0429 (9) | 0.0237 (7) | 0.0623 (10) | −0.0039 (6) | −0.0138 (8) | −0.0005 (7) |
O3 | 0.0241 (6) | 0.0394 (8) | 0.0336 (7) | −0.0094 (6) | −0.0057 (5) | −0.0074 (6) |
O4 | 0.0292 (7) | 0.0610 (10) | 0.0311 (7) | −0.0127 (7) | 0.0028 (6) | −0.0080 (7) |
O1W | 0.0249 (7) | 0.0264 (7) | 0.0383 (8) | −0.0067 (5) | 0.0030 (6) | −0.0134 (6) |
O2W | 0.0266 (7) | 0.0413 (8) | 0.0242 (7) | −0.0062 (6) | −0.0044 (5) | −0.0069 (6) |
O3W | 0.0280 (8) | 0.0322 (8) | 0.0594 (10) | −0.0041 (6) | 0.0049 (7) | 0.0007 (7) |
O4W | 0.0383 (8) | 0.0344 (8) | 0.0493 (9) | −0.0060 (7) | −0.0199 (7) | −0.0029 (7) |
O5W | 0.0314 (8) | 0.0290 (8) | 0.0618 (10) | −0.0075 (6) | −0.0170 (7) | 0.0077 (7) |
O6W | 0.0501 (9) | 0.0321 (8) | 0.0387 (9) | −0.0050 (7) | −0.0107 (7) | −0.0089 (7) |
N1 | 0.0231 (7) | 0.0206 (7) | 0.0326 (8) | −0.0019 (6) | −0.0050 (6) | −0.0053 (6) |
N2 | 0.0271 (8) | 0.0234 (8) | 0.0425 (9) | −0.0026 (6) | −0.0079 (7) | −0.0104 (7) |
N3 | 0.0564 (12) | 0.0247 (9) | 0.0399 (11) | 0.0015 (8) | −0.0053 (9) | −0.0040 (8) |
C1 | 0.0305 (9) | 0.0241 (9) | 0.0318 (10) | −0.0029 (7) | −0.0039 (8) | −0.0072 (7) |
C2 | 0.0244 (9) | 0.0224 (9) | 0.0378 (10) | −0.0034 (7) | −0.0059 (7) | −0.0052 (7) |
C3 | 0.0290 (9) | 0.0318 (10) | 0.0361 (10) | 0.0005 (8) | −0.0061 (8) | −0.0138 (8) |
C4 | 0.0305 (10) | 0.0296 (10) | 0.0294 (9) | −0.0018 (8) | −0.0040 (8) | −0.0052 (7) |
Co1—O1W | 2.0451 (13) | O3W—H3W1 | 0.846 (10) |
Co1—O1Wi | 2.0451 (13) | O3W—H3W2 | 0.846 (10) |
Co1—O2Wi | 2.0970 (13) | O4W—H4W1 | 0.847 (10) |
Co1—O2W | 2.0970 (13) | O4W—H4W2 | 0.850 (10) |
Co1—N1i | 2.2076 (15) | O5W—H5W1 | 0.849 (10) |
Co1—N1 | 2.2076 (15) | O5W—H5W2 | 0.840 (10) |
Co2—O3W | 2.0670 (16) | O6W—H6W1 | 0.849 (10) |
Co2—O3Wii | 2.0670 (16) | O6W—H6W2 | 0.847 (10) |
Co2—O5W | 2.0977 (15) | N1—C1 | 1.324 (2) |
Co2—O5Wii | 2.0977 (15) | N1—C4 | 1.352 (3) |
Co2—O4W | 2.1128 (16) | N2—C2 | 1.340 (3) |
Co2—O4Wii | 2.1128 (16) | N2—C3 | 1.343 (3) |
S1—O2 | 1.4656 (16) | N3—C2 | 1.349 (3) |
S1—O4 | 1.4703 (15) | N3—H3N1 | 0.849 (10) |
S1—O1 | 1.4717 (13) | N3—H3N2 | 0.852 (10) |
S1—O3 | 1.4866 (14) | C1—C2 | 1.411 (3) |
O1W—H1W1 | 0.836 (10) | C1—H1 | 0.9300 |
O1W—H1W2 | 0.846 (10) | C3—C4 | 1.370 (3) |
O2W—H2W1 | 0.838 (10) | C3—H3 | 0.9300 |
O2W—H2W2 | 0.843 (10) | C4—H4 | 0.9300 |
O1W—Co1—O1Wi | 180.0 | Co1—O1W—H1W1 | 126.4 (17) |
O1W—Co1—O2Wi | 87.43 (6) | Co1—O1W—H1W2 | 120.7 (18) |
O1Wi—Co1—O2Wi | 92.57 (6) | H1W1—O1W—H1W2 | 110 (2) |
O1W—Co1—O2W | 92.57 (6) | Co1—O2W—H2W1 | 128.2 (18) |
O1Wi—Co1—O2W | 87.43 (6) | Co1—O2W—H2W2 | 114 (2) |
O2Wi—Co1—O2W | 180.000 (1) | H2W1—O2W—H2W2 | 116 (3) |
O1W—Co1—N1i | 88.71 (6) | Co2—O3W—H3W1 | 121 (2) |
O1Wi—Co1—N1i | 91.29 (6) | Co2—O3W—H3W2 | 125.2 (19) |
O2Wi—Co1—N1i | 90.16 (6) | H3W1—O3W—H3W2 | 107 (3) |
O2W—Co1—N1i | 89.84 (6) | Co2—O4W—H4W1 | 117 (2) |
O1W—Co1—N1 | 91.29 (6) | Co2—O4W—H4W2 | 114.2 (18) |
O1Wi—Co1—N1 | 88.71 (6) | H4W1—O4W—H4W2 | 107 (3) |
O2Wi—Co1—N1 | 89.84 (6) | Co2—O5W—H5W1 | 128.5 (19) |
O2W—Co1—N1 | 90.16 (6) | Co2—O5W—H5W2 | 122 (2) |
N1i—Co1—N1 | 180.000 (1) | H5W1—O5W—H5W2 | 103 (3) |
O3W—Co2—O3Wii | 180.0 | H6W1—O6W—H6W2 | 104 (3) |
O3W—Co2—O5W | 88.95 (7) | C1—N1—C4 | 117.08 (16) |
O3Wii—Co2—O5W | 91.05 (7) | C1—N1—Co1 | 119.42 (13) |
O3W—Co2—O5Wii | 91.05 (7) | C4—N1—Co1 | 122.75 (13) |
O3Wii—Co2—O5Wii | 88.95 (7) | C2—N2—C3 | 116.49 (17) |
O5W—Co2—O5Wii | 180.0 | C2—N3—H3N1 | 118 (2) |
O3W—Co2—O4W | 87.20 (7) | C2—N3—H3N2 | 121 (2) |
O3Wii—Co2—O4W | 92.80 (7) | H3N1—N3—H3N2 | 121 (3) |
O5W—Co2—O4W | 89.82 (7) | N1—C1—C2 | 122.25 (18) |
O5Wii—Co2—O4W | 90.18 (7) | N1—C1—H1 | 118.9 |
O3W—Co2—O4Wii | 92.80 (7) | C2—C1—H1 | 118.9 |
O3Wii—Co2—O4Wii | 87.20 (7) | N2—C2—N3 | 119.21 (18) |
O5W—Co2—O4Wii | 90.18 (7) | N2—C2—C1 | 120.28 (18) |
O5Wii—Co2—O4Wii | 89.82 (7) | N3—C2—C1 | 120.50 (19) |
O4W—Co2—O4Wii | 180.0 | N2—C3—C4 | 123.26 (19) |
O2—S1—O4 | 110.72 (10) | N2—C3—H3 | 118.4 |
O2—S1—O1 | 109.81 (9) | C4—C3—H3 | 118.4 |
O4—S1—O1 | 108.83 (9) | N1—C4—C3 | 120.53 (18) |
O2—S1—O3 | 108.89 (9) | N1—C4—H4 | 119.7 |
O4—S1—O3 | 109.26 (9) | C3—C4—H4 | 119.7 |
O1—S1—O3 | 109.31 (8) |
Symmetry codes: (i) −x+2, −y+2, −z+1; (ii) −x, −y+1, −z+2. |
D—H···A | D—H | H···A | D···A | D—H···A |
O1w—H1w1···O1 | 0.84 (1) | 1.93 (1) | 2.755 (2) | 168 (3) |
O1w—H1w2···N2iii | 0.85 (1) | 1.95 (1) | 2.795 (2) | 175 (3) |
O2w—H2w1···O3 | 0.84 (1) | 1.94 (1) | 2.769 (2) | 170 (2) |
O2w—H2w2···O1iv | 0.84 (1) | 1.93 (1) | 2.765 (2) | 170 (3) |
O3w—H3w1···O2 | 0.85 (1) | 1.91 (1) | 2.743 (2) | 169 (3) |
O3w—H3w2···O6w | 0.85 (1) | 1.89 (1) | 2.730 (2) | 170 (3) |
O4w—H4w1···O6wv | 0.85 (1) | 1.95 (1) | 2.781 (2) | 168 (3) |
O4w—H4w2···O2v | 0.85 (1) | 1.91 (1) | 2.745 (2) | 167 (2) |
O5w—H5w1···O3vi | 0.85 (1) | 1.98 (1) | 2.816 (2) | 170 (3) |
O5w—H5w2···O4ii | 0.84 (1) | 1.90 (1) | 2.737 (2) | 174 (3) |
O6w—H6w1···O3iii | 0.85 (1) | 1.94 (1) | 2.782 (2) | 171 (4) |
O6w—H6w2···O4vi | 0.85 (1) | 1.89 (1) | 2.711 (2) | 164 (3) |
N3—H3n2···O1vii | 0.85 (1) | 2.20 (1) | 3.036 (2) | 168 (3) |
Symmetry codes: (ii) −x, −y+1, −z+2; (iii) x, y−1, z; (iv) x+1, y, z; (v) x−1, y, z; (vi) −x+1, −y+1, −z+2; (vii) −x+1, −y+3, −z+1. |
Experimental details
Crystal data | |
Chemical formula | [Co(H2O)6][Co(C4H5N3)2(H2O)4](SO4)2·2H2O |
Mr | 716.40 |
Crystal system, space group | Triclinic, P1 |
Temperature (K) | 293 |
a, b, c (Å) | 6.5722 (3), 8.3264 (4), 13.2337 (7) |
α, β, γ (°) | 75.732 (2), 78.571 (1), 78.795 (1) |
V (Å3) | 679.81 (6) |
Z | 1 |
Radiation type | Mo Kα |
µ (mm−1) | 1.47 |
Crystal size (mm) | 0.30 × 0.20 × 0.20 |
Data collection | |
Diffractometer | Rigaku RAXIS-RAPID IP diffractometer |
Absorption correction | Multi-scan (ABSCOR; Higashi, 1995) |
Tmin, Tmax | 0.668, 0.758 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6692, 3071, 2762 |
Rint | 0.027 |
(sin θ/λ)max (Å−1) | 0.648 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.031, 0.085, 1.05 |
No. of reflections | 3071 |
No. of parameters | 231 |
No. of restraints | 14 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.47, −0.33 |
Computer programs: RAPID-AUTO (Rigaku, 1998), CrystalClear (Rigaku/MSC, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), X-SEED (Barbour, 2001), publCIF (Westrip, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
O1w—H1w1···O1 | 0.84 (1) | 1.93 (1) | 2.755 (2) | 168 (3) |
O1w—H1w2···N2i | 0.85 (1) | 1.95 (1) | 2.795 (2) | 175 (3) |
O2w—H2w1···O3 | 0.84 (1) | 1.94 (1) | 2.769 (2) | 170 (2) |
O2w—H2w2···O1ii | 0.84 (1) | 1.93 (1) | 2.765 (2) | 170 (3) |
O3w—H3w1···O2 | 0.85 (1) | 1.91 (1) | 2.743 (2) | 169 (3) |
O3w—H3w2···O6w | 0.85 (1) | 1.89 (1) | 2.730 (2) | 170 (3) |
O4w—H4w1···O6wiii | 0.85 (1) | 1.95 (1) | 2.781 (2) | 168 (3) |
O4w—H4w2···O2iii | 0.85 (1) | 1.91 (1) | 2.745 (2) | 167 (2) |
O5w—H5w1···O3iv | 0.85 (1) | 1.98 (1) | 2.816 (2) | 170 (3) |
O5w—H5w2···O4v | 0.84 (1) | 1.90 (1) | 2.737 (2) | 174 (3) |
O6w—H6w1···O3i | 0.85 (1) | 1.94 (1) | 2.782 (2) | 171 (4) |
O6w—H6w2···O4iv | 0.85 (1) | 1.89 (1) | 2.711 (2) | 164 (3) |
N3—H3n2···O1vi | 0.85 (1) | 2.20 (1) | 3.036 (2) | 168 (3) |
Symmetry codes: (i) x, y−1, z; (ii) x+1, y, z; (iii) x−1, y, z; (iv) −x+1, −y+1, −z+2; (v) −x, −y+1, −z+2; (vi) −x+1, −y+3, −z+1. |
Acknowledgements
We thank the Natural Science Foundation of Heilongjiang Province (No. B200501), Heilongjiang University, China, and the University of Malaya for supporting this study.
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