metal-organic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 64| Part 9| September 2008| Pages m1159-m1160

Di­aqua­bis­(8-chloro-1,3-di­methyl-2,6-dioxo-1,2,3,6-tetra­hydro-7H-purinato-κN7)copper(II) dihydrate

aCollege of Chemistry and Bio-engineering, Yichun University, Yichun, Jiangxi 336000, People's Republic of China
*Correspondence e-mail: djhycu_2006@yahoo.com.cn, guomengping65@163.com

(Received 31 July 2008; accepted 7 August 2008; online 13 August 2008)

The title mononuclear copper(II) complex, [Cu(C7H6ClN4O2)2(H2O)2]·2H2O, based on 8-chloro­theophylline (HCt), has the Cu atom at a center of symmetry in a slightly distorted trans square-planar geometry coordinated by two N atoms of two deprotonated HCt ligands and two O atoms of water mol­ecules. The crystal packing is stabilized by hydrogen bonds involving deprotonated HCt ligands, coordinated water mol­ecules and uncoordinated solvent water mol­ecules.

Related literature

For related literature, see: Halpert et al. (2002[Halpert, A. G., Olmstead, M. C. & Beninger, R. J. (2002). Neurosci. Biobehav. Rev. 26, 61-67.]); Antholine et al. (1985[Antholine, W. E., Kalyanaraman, B. & Petering, D. H. (1985). Environ. Health Perspect. 64, 19-22.]); García-Tojal et al. (1996[García-Tojal, J., García-Jaca, J., Cortés, R., Rojo, T., Urtiaga, M. K. & Arriortua, M. I. (1996). Inorg. Chim. Acta, 249, 25-32.]); Okabe et al. (1993[Okabe, N., Nakamura, T. & Fukuda, H. (1993). Acta Cryst. C49, 1761-1762.]); Saryan et al. (1979[Saryan, L. A., Ankel, E., Krishnamurti, C. & Petering, D. H. (1979). J. Med. Chem. 22, 1218-1221.]); Serafin (1996[Serafin, W. E. (1996). The Pharmacological Basis of the Rapeutics, pp. 659-682. New York: McGraw-Hill.]); Spealman (1988[Spealman, R. D. (1988). Psychopharmacology, 95, 19-24.]); West et al. (1993[West, D. X., Liberta, A. E., Padhye, S. B., Chikate, R. C., Sonawane, P. B., Kumbhar, A. S. & Yerande, R. G. (1993). Coord. Chem. Rev. 123, 49-55.]); Zhao et al. (2003[Zhao, J. S., Zhang, R. L., He, S. Y., Xue, G. L., Dou, J. M. & Wang, D. Q. (2003). Chin. J. Struct. Chem. 22, 477-480.]).

[Scheme 1]

Experimental

Crystal data
  • [Cu(C7H6ClN4O2)2(H2O)2]·2H2O

  • Mr = 562.82

  • Triclinic, [P \overline 1]

  • a = 8.377 (5) Å

  • b = 8.533 (8) Å

  • c = 8.830 (3) Å

  • α = 67.999 (2)°

  • β = 64.180 (7)°

  • γ = 78.388 (6)°

  • V = 526.2 (6) Å3

  • Z = 1

  • Mo Kα radiation

  • μ = 1.35 mm−1

  • T = 293 (2) K

  • 0.36 × 0.24 × 0.16 mm

Data collection
  • Bruker SMART CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 1996[Sheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.]) Tmin = 0.685, Tmax = 0.802

  • 3811 measured reflections

  • 1834 independent reflections

  • 936 reflections with I > 2σ(I)

  • Rint = 0.099

Refinement
  • R[F2 > 2σ(F2)] = 0.058

  • wR(F2) = 0.102

  • S = 0.99

  • 1834 reflections

  • 153 parameters

  • 19 restraints

  • H-atom parameters constrained

  • Δρmax = 0.54 e Å−3

  • Δρmin = −0.66 e Å−3

Table 1
Selected geometric parameters (Å, °)

Cu1—O3 1.934 (5)
Cu1—N1 1.986 (6)
O3i—Cu1—O3 180
O3—Cu1—N1 89.5 (2)
O3—Cu1—N1i 90.5 (2)
N1—Cu1—N1i 180
Symmetry code: (i) -x+1, -y, -z+2.

Table 2
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
O3—H3A⋯O2ii 0.82 1.98 2.729 (7) 154
O3—H3B⋯O4iii 0.84 1.81 2.612 (8) 159
O4—H4A⋯O1iv 0.82 2.07 2.897 (9) 176
O4—H4B⋯N4 0.82 2.03 2.839 (8) 170
Symmetry codes: (ii) -x+1, -y+1, -z+1; (iii) x, y, z+1; (iv) x+1, y, z-1.

Data collection: SMART (Bruker, 2004[Bruker (2004). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2004[Bruker (2004). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); software used to prepare material for publication: SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]).

Supporting information


Comment top

8-Chlorotheophylline (Ct) is a methylxathine drug related to caffeine and theophylline (Halpert et al., 2002). It produces a number of effects, including nervousness, restlessness, insomnia, convulsions, anxiety, headaches and nausea (Serafin, 1996). The behavioural effects of this agent are attributed primarily to its ability to block adenosine receptors (Spealman, 1988). In recent years, many copper(II) complexes have draw attention due to the fact that they exhibit a greater biological activity, (antitumour, antibacterial, etc.) than the corresponding free ligand because of their chelating ability and positive redox potential (García-Tojal et al., 1996; West et al., 1993; Antholine et al., 1985; Saryan et al., 1979). Here, we report the structure of the title compound, {[Cu(Ct)2(H2O)2](H2O)2} (I), to our knowledge the first reported metal complex with 8-chlorotheophylline..

The stucture of (I) is shown in Fig. 1. It is composed of a mononuclear entity [Cu(Ct)2(H2O)2], together with two crystal water molecules; the copperII atom, lying in a center of symmetry, is bonded to the nitrogen atoms of two individual 8-Ct molecules and oxygen atoms from two water molecules (Table 1), forming a trans square-planar arrangement. It should be noted that the ligand is in its anionic form (8-Ct-) in order to achieve charge balance.

Selected bond distances and bond angles are given in Table 1. The Cu—N and Cu—O bond lengths and bond angles at Cu1 are similar to those reported in some tetra-coordinated copper complexs (Zhao et al., 2003; Okabe et al., 1993). The 8-Ct molecule deviates slightly from planarity and the dihedral angle created by the least squares planes between the pyrimidine and imidazole ring is 1.2 (1) °.

The structure presents O–H···O, O–H···N intermolecular hydrogen bonds (Table 2). between 8-Cts and water molecules. The coordinated water molecule is a donor towards the pyrimidine O2 and the uncoordinated water O4, thus linking the complex units into a 2-dimentional structure along the b axis. Besides, the lattice water molecules acts as a donor towards the pyrimidine O1 and imidazole N4. These two hydrogen bonds serve to link the 2-D structures into a 3-D array along the c axis.

Related literature top

For related literature, see: Halpert et al. (2002); Antholine et al. (1985); García-Tojal et al. (1996); Okabe et al. (1993); Saryan et al. (1979); Serafin (1996); Spealman (1988); West et al. (1993); Zhao et al. (2003).

Experimental top

A solution of Cu(OAc)2.H2O (0.5 mmol) in water (5 ml) was slowly added to a solution of the ligand (1 mmol) in ethanol (14 ml) under stirring at room temperature. The mixture was sealed in a 25 ml Teflon-lined stainless steel vessel and heated under autogenous pressure at 383 K for 6 days, and then slowly cooled to room temperature. The green crystals obtained were recovered by filtration, washed with ethanol and dried in air. Yield: 52% (based on Cu).

Refinement top

Hydrogen atoms attached to carbon atoms were positioned geometrically and treated as riding, with C—H = 0.96 Å and Uiso(H) = 1.2Ueq(C). The water H atoms were located in a difference Fourier map, and were refined with a distance restraint of O—H = 0.82—0.84 Å and Uiso(H) = 1.5Ueq(O). The crystals are unstable outside the parental solution, for what the quality of the diffraction data was poor. This led to unrealistic displacement parameters for four C and one O atoms, which were accordingly restrained to be nearly isotropic.

Computing details top

Data collection: SMART (Bruker, 2004); cell refinement: SMART (Bruker, 2004); data reduction: SAINT (Bruker, 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: SHELXTL (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The structure of (I), showing 30% probability displacement ellipsoids and the atom-labeling scheme.
[Figure 2] Fig. 2. The crystal packing of (I).
Diaquabis(8-chloro-1,3-dimethyl-2,6-dioxo-1,2,3,6-tetrahydro-7H-purinato- κN7)copper(II) dihydrate top
Crystal data top
[Cu(C7H6ClN4O2)2(H2O)2]·2H2OZ = 1
Mr = 562.82F(000) = 287
Triclinic, P1Dx = 1.776 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 8.377 (5) ÅCell parameters from 822 reflections
b = 8.533 (8) Åθ = 2.6–25.0°
c = 8.830 (3) ŵ = 1.35 mm1
α = 67.999 (2)°T = 293 K
β = 64.180 (7)°Block, green
γ = 78.388 (6)°0.36 × 0.24 × 0.16 mm
V = 526.2 (6) Å3
Data collection top
Bruker SMART CCD area-detector
diffractometer
1834 independent reflections
Radiation source: fine-focus sealed tube936 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.099
ϕ and ω scansθmax = 25.0°, θmin = 2.6°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 99
Tmin = 0.685, Tmax = 0.802k = 810
3811 measured reflectionsl = 1010
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.058Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.102H-atom parameters constrained
S = 0.99 w = 1/[σ2(Fo2)]
1834 reflections(Δ/σ)max = 0.004
153 parametersΔρmax = 0.54 e Å3
19 restraintsΔρmin = 0.66 e Å3
Crystal data top
[Cu(C7H6ClN4O2)2(H2O)2]·2H2Oγ = 78.388 (6)°
Mr = 562.82V = 526.2 (6) Å3
Triclinic, P1Z = 1
a = 8.377 (5) ÅMo Kα radiation
b = 8.533 (8) ŵ = 1.35 mm1
c = 8.830 (3) ÅT = 293 K
α = 67.999 (2)°0.36 × 0.24 × 0.16 mm
β = 64.180 (7)°
Data collection top
Bruker SMART CCD area-detector
diffractometer
1834 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
936 reflections with I > 2σ(I)
Tmin = 0.685, Tmax = 0.802Rint = 0.099
3811 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.05819 restraints
wR(F2) = 0.102H-atom parameters constrained
S = 0.99Δρmax = 0.54 e Å3
1834 reflectionsΔρmin = 0.66 e Å3
153 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
xyzUiso*/Ueq
Cu10.50000.00001.00000.0214 (5)
N10.5200 (8)0.0829 (8)0.7503 (7)0.0214 (17)
N20.1993 (8)0.4308 (7)0.6697 (7)0.0203 (16)
N30.4180 (8)0.3889 (8)0.4053 (7)0.0264 (18)
N40.6338 (8)0.1570 (8)0.4472 (8)0.0245 (18)
O10.1930 (7)0.2659 (6)0.9464 (6)0.0296 (15)
O20.2040 (6)0.6046 (6)0.3965 (6)0.0210 (13)
O30.6720 (6)0.1598 (6)0.9341 (6)0.0340 (15)
H3A0.71540.20290.82560.051*
H3B0.73760.16510.98150.051*
O40.8607 (7)0.0978 (6)0.1220 (6)0.0330 (16)
H4A0.95780.14130.07040.049*
H4B0.78680.12260.20970.049*
Cl10.8042 (3)0.1040 (3)0.6122 (3)0.0308 (6)
C10.4156 (10)0.2195 (9)0.6872 (9)0.0171 (19)
C20.2692 (10)0.2944 (9)0.7842 (10)0.019 (2)
C30.2719 (10)0.4812 (9)0.4827 (9)0.0142 (18)
C40.4889 (11)0.2531 (10)0.5113 (10)0.022 (2)
C50.6432 (10)0.0543 (9)0.6041 (10)0.019 (2)
C60.0408 (9)0.5307 (9)0.7496 (9)0.021 (2)
H6A0.07590.63600.73890.032*
H6B0.02030.46860.87310.032*
H6C0.03670.55270.68900.032*
C70.4918 (9)0.4281 (9)0.2102 (8)0.020 (2)
H7A0.39800.47040.16850.030*
H7B0.54650.32730.18090.030*
H7C0.57880.51220.15440.030*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cu10.0267 (10)0.0224 (10)0.0140 (9)0.0032 (8)0.0113 (8)0.0001 (7)
N10.019 (4)0.027 (4)0.017 (4)0.011 (3)0.010 (3)0.001 (3)
N20.027 (4)0.021 (4)0.009 (3)0.004 (3)0.004 (3)0.003 (3)
N30.030 (5)0.036 (5)0.011 (4)0.006 (4)0.004 (3)0.008 (3)
N40.022 (4)0.033 (4)0.012 (4)0.006 (3)0.002 (3)0.003 (3)
O10.036 (4)0.033 (4)0.014 (3)0.006 (3)0.007 (3)0.003 (3)
O20.0205 (16)0.0215 (16)0.0201 (15)0.0010 (9)0.0110 (10)0.0035 (10)
O30.052 (4)0.038 (4)0.013 (3)0.031 (3)0.015 (3)0.008 (3)
O40.027 (4)0.050 (4)0.018 (3)0.005 (3)0.010 (3)0.004 (3)
Cl10.0279 (15)0.0291 (15)0.0273 (13)0.0002 (11)0.0096 (11)0.0031 (11)
C10.027 (5)0.014 (5)0.009 (4)0.002 (4)0.010 (4)0.002 (3)
C20.019 (2)0.019 (2)0.019 (2)0.0004 (10)0.0083 (12)0.0056 (11)
C30.014 (2)0.014 (2)0.014 (2)0.0005 (10)0.0066 (12)0.0031 (11)
C40.022 (2)0.022 (2)0.022 (2)0.0005 (10)0.0092 (12)0.0064 (12)
C50.011 (5)0.019 (5)0.028 (5)0.002 (4)0.002 (4)0.014 (4)
C60.021 (2)0.021 (2)0.020 (2)0.0002 (10)0.0092 (12)0.0055 (11)
C70.020 (2)0.020 (2)0.019 (2)0.0004 (10)0.0088 (12)0.0048 (11)
Geometric parameters (Å, º) top
Cu1—O3i1.934 (5)O2—C31.244 (7)
Cu1—O31.934 (5)O3—H3A0.8200
Cu1—N11.986 (6)O3—H3B0.8388
Cu1—N1i1.986 (6)O4—H4A0.8242
N1—C51.329 (8)O4—H4B0.8243
N1—C11.401 (8)Cl1—C51.711 (7)
N2—C31.407 (8)C1—C41.333 (9)
N2—C21.442 (8)C1—C21.351 (9)
N2—C61.472 (8)C6—H6A0.9600
N3—C31.369 (8)C6—H6B0.9600
N3—C41.402 (8)C6—H6C0.9600
N3—C71.479 (7)C7—H7A0.9600
N4—C51.361 (8)C7—H7B0.9600
N4—C41.347 (9)C7—H7C0.9600
O1—C21.234 (8)
O3i—Cu1—O3180.0 (3)O1—C2—N2118.4 (7)
O3i—Cu1—N190.5 (2)C1—C2—N2110.6 (7)
O3—Cu1—N189.5 (2)O2—C3—N3123.4 (6)
O3i—Cu1—N1i89.5 (2)O2—C3—N2120.1 (7)
O3—Cu1—N1i90.5 (2)N3—C3—N2116.5 (6)
N1—Cu1—N1i180.000 (1)C1—C4—N4116.5 (7)
C5—N1—C1104.1 (6)C1—C4—N3119.0 (7)
C5—N1—Cu1131.8 (5)N4—C4—N3124.4 (7)
C1—N1—Cu1122.9 (5)N1—C5—N4116.4 (7)
C3—N2—C2125.4 (6)N1—C5—Cl1122.0 (6)
C3—N2—C6115.4 (6)N4—C5—Cl1121.6 (6)
C2—N2—C6119.2 (6)N2—C6—H6A109.5
C3—N3—C4120.1 (6)N2—C6—H6B109.5
C3—N3—C7118.8 (6)H6A—C6—H6B109.5
C4—N3—C7121.0 (6)N2—C6—H6C109.5
C5—N4—C498.7 (6)H6A—C6—H6C109.5
Cu1—O3—H3A109.4H6B—C6—H6C109.5
Cu1—O3—H3B132.7N3—C7—H7A109.5
H3A—O3—H3B112.4N3—C7—H7B109.5
H4A—O4—H4B118.2H7A—C7—H7B109.5
C4—C1—C2128.2 (7)N3—C7—H7C109.5
C4—C1—N1104.3 (7)H7A—C7—H7C109.5
C2—C1—N1127.5 (7)H7B—C7—H7C109.5
O1—C2—C1131.0 (7)
Symmetry code: (i) x+1, y, z+2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O3—H3A···O2ii0.821.982.729 (7)154
O3—H3B···O4iii0.841.812.612 (8)159
O4—H4A···O1iv0.822.072.897 (9)176
O4—H4B···N40.822.032.839 (8)170
Symmetry codes: (ii) x+1, y+1, z+1; (iii) x, y, z+1; (iv) x+1, y, z1.

Experimental details

Crystal data
Chemical formula[Cu(C7H6ClN4O2)2(H2O)2]·2H2O
Mr562.82
Crystal system, space groupTriclinic, P1
Temperature (K)293
a, b, c (Å)8.377 (5), 8.533 (8), 8.830 (3)
α, β, γ (°)67.999 (2), 64.180 (7), 78.388 (6)
V3)526.2 (6)
Z1
Radiation typeMo Kα
µ (mm1)1.35
Crystal size (mm)0.36 × 0.24 × 0.16
Data collection
DiffractometerBruker SMART CCD area-detector
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.685, 0.802
No. of measured, independent and
observed [I > 2σ(I)] reflections
3811, 1834, 936
Rint0.099
(sin θ/λ)max1)0.595
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.058, 0.102, 0.99
No. of reflections1834
No. of parameters153
No. of restraints19
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.54, 0.66

Computer programs: SMART (Bruker, 2004), SAINT (Bruker, 2004), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Sheldrick, 2008).

Selected geometric parameters (Å, º) top
Cu1—O3i1.934 (5)Cu1—N11.986 (6)
Cu1—O31.934 (5)Cu1—N1i1.986 (6)
O3i—Cu1—O3180.0 (3)O3i—Cu1—N1i89.5 (2)
O3i—Cu1—N190.5 (2)O3—Cu1—N1i90.5 (2)
O3—Cu1—N189.5 (2)N1—Cu1—N1i180.000 (1)
Symmetry code: (i) x+1, y, z+2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O3—H3A···O2ii0.82001.97692.729 (7)154
O3—H3B···O4iii0.83881.81352.612 (8)159
O4—H4A···O1iv0.82422.07002.897 (9)176
O4—H4B···N40.82432.02942.839 (8)170
Symmetry codes: (ii) x+1, y+1, z+1; (iii) x, y, z+1; (iv) x+1, y, z1.
 

Acknowledgements

This work was supported by the 2007 Science Foundation of Yichun University.

References

First citationAntholine, W. E., Kalyanaraman, B. & Petering, D. H. (1985). Environ. Health Perspect. 64, 19–22.  CrossRef CAS PubMed Web of Science Google Scholar
First citationBruker (2004). SMART and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.  Google Scholar
First citationGarcía-Tojal, J., García-Jaca, J., Cortés, R., Rojo, T., Urtiaga, M. K. & Arriortua, M. I. (1996). Inorg. Chim. Acta, 249, 25–32.  CSD CrossRef Web of Science Google Scholar
First citationHalpert, A. G., Olmstead, M. C. & Beninger, R. J. (2002). Neurosci. Biobehav. Rev. 26, 61–67.  Web of Science CrossRef PubMed CAS Google Scholar
First citationOkabe, N., Nakamura, T. & Fukuda, H. (1993). Acta Cryst. C49, 1761–1762.  CSD CrossRef CAS Web of Science IUCr Journals Google Scholar
First citationSaryan, L. A., Ankel, E., Krishnamurti, C. & Petering, D. H. (1979). J. Med. Chem. 22, 1218–1221.  CrossRef CAS PubMed Web of Science Google Scholar
First citationSerafin, W. E. (1996). The Pharmacological Basis of the Rapeutics, pp. 659–682. New York: McGraw–Hill.  Google Scholar
First citationSheldrick, G. M. (1996). SADABS. University of Göttingen, Germany.  Google Scholar
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals Google Scholar
First citationSpealman, R. D. (1988). Psychopharmacology, 95, 19–24.  CrossRef CAS PubMed Google Scholar
First citationWest, D. X., Liberta, A. E., Padhye, S. B., Chikate, R. C., Sonawane, P. B., Kumbhar, A. S. & Yerande, R. G. (1993). Coord. Chem. Rev. 123, 49–55.  CrossRef CAS Web of Science Google Scholar
First citationZhao, J. S., Zhang, R. L., He, S. Y., Xue, G. L., Dou, J. M. & Wang, D. Q. (2003). Chin. J. Struct. Chem. 22, 477–480.  CAS 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.

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 64| Part 9| September 2008| Pages m1159-m1160
Follow Acta Cryst. E
Sign up for e-alerts
Follow Acta Cryst. on Twitter
Follow us on facebook
Sign up for RSS feeds