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

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 69| Part 6| June 2013| Pages m323-m324

Bis{(Z)-[(E)-2-(pyridin-2-yl­methyl­­idene)hydrazin-1-yl­­idene][(pyridin-2-yl)methyl­sulfan­yl]methane­thiol­ato}nickel(II)

aSchool of Pharmacy, University of Nottingham Malaysia Campus, Selangor, Malaysia, bSchool of Chemical Sciences and Food Technology, Universiti Kebangsaan Malaysia, 43600 Bangi, Malaysia, cDepartment of Chemistry, Faculty of Science, Universiti Putra Malaysia, Malaysia, and dChemical Crystallography, Chemistry Research Laboratory, 12 Mansfield Road, Oxford OX1 3TA, England
*Correspondence e-mail: tengjin.khoo@nottingham.edu.my

(Received 30 April 2013; accepted 13 May 2013; online 18 May 2013)

The title compound, [Ni(C13H11N4S2)2], was obtained by the reaction of S-2-picolyldi­thio­carbazate and pyridine-2-carbaldehyde with nickel(II) acetate. The NiII atom is located on a twofold rotation axis and is bonded to four N atoms at distances of 2.037 (8) and 2.109 (9) Å, and to two S atoms at a distance of 2.406 (3) Å, leading to a distorted octa­hedral coordination. The angle between the mean planes of the coordinating moieties of the two symmetry-related tridentate ligands is 83.3 (2)°. In the crystal, complex mol­ecules are linked by weak C—H⋯S hydrogen bonds, ππ inter­actions between the pyridine rings [centroid–centroid distance = 3.775 (9) Å] and C—H⋯π inter­actions. The hydrogen-bonding inter­actions lead to the formation of layers parallel to (010); ππ inter­actions link these layers into a three-dimensional network.

Related literature

For biological applications of Schiff base ligands and complexes derived from di­thio­carbaza­tes, see: Hossain et al. (1996[Hossain, E., Alam, M., Ali, M., Nazimuddin, M., Smith, E. & Hynes, C. (1996). Polyhedron, 15, 973-980.]); Tarafder et al. (2002[Tarafder, M., Khoo, T. J., Crouse, K. A., Ali, M., Yamin, B. & Fun, H.-K. (2002). Polyhedron, 21, 2691-2698.]); Crouse et al. (2004[Crouse, K. A., Chew, -B., Tarafder, M., Kasbollah, A., Ali, M., Yamin, M. & Fun, H. K. (2004). Polyhedron, 23, 161-168.]). For a related structure, see: Omar et al. (2012[Omar, S. A., Ravoof, T. B. S. A., Mohamed Tahir, M. I. & Crouse, K. A. (2012). Acta Cryst. E68, m316-m317.]).

[Scheme 1]

Experimental

Crystal data
  • [Ni(C13H11N4S2)2]

  • Mr = 633.49

  • Monoclinic, C 2/c

  • a = 26.0501 (4) Å

  • b = 8.0057 (1) Å

  • c = 13.0743 (2) Å

  • β = 103.8993 (9)°

  • V = 2646.80 (7) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 1.08 mm−1

  • T = 150 K

  • 0.04 × 0.03 × 0.02 mm

Data collection
  • Nonius Kappa CCD diffractometer

  • Absorption correction: multi-scan (DENZO/SCALEPACK; Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]) Tmin = 0.97, Tmax = 0.98

  • 5912 measured reflections

  • 3030 independent reflections

  • 2066 reflections with I > 3σ(I)

  • Rint = 0.020

Refinement
  • R[F2 > 2σ(F2)] = 0.045

  • wR(F2) = 0.121

  • S = 1.08

  • 2066 reflections

  • 177 parameters

  • H-atom parameters constrained

  • Δρmax = 0.81 e Å−3

  • Δρmin = −0.74 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

Cg is the centroid of the pyridine ring (C9–C13/N4).

D—H⋯A D—H H⋯A DA D—H⋯A
C8—H7⋯S2i 0.94 2.72 3.644 (9) 166
C4—H4⋯S2i 0.95 2.92 3.862 (11) 175
C6—H6⋯Cgii 0.98 2.98 3.750 (12) 136
Symmetry codes: (i) [x, -y, z+{\script{1\over 2}}]; (ii) -x+1, -y, -z+2.

Data collection: COLLECT (Nonius, 2001[Nonius (2001). COLLECT. Nonius BV, Delft, The Netherlands.]); cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997[Otwinowski, Z. & Minor, W. (1997). Methods in Enzymology, Vol. 276, Macromolecular Crystallography, Part A, edited by C. W. Carter Jr & R. M. Sweet, pp. 307-326. New York: Academic Press.]); data reduction: DENZO/SCALEPACK; program(s) used to solve structure: SIR92 (Altomare et al., 1994[Altomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994). J. Appl. Cryst. 27, 435.]); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003[Betteridge, P. W., Carruthers, J. R., Cooper, R. I., Prout, K. & Watkin, D. J. (2003). J. Appl. Cryst. 36, 1487.]); molecular graphics: Mercury (Macrae et al., 2006[Macrae, C. F., Edgington, P. R., McCabe, P., Pidcock, E., Shields, G. P., Taylor, R., Towler, M. & van de Streek, J. (2006). J. Appl. Cryst. 39, 453-457.]); software used to prepare material for publication: publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information


Comment top

In the last few decades an increasing interest in the potential benefits of dithiocarbazates has arisen which has led to the synthesis of several Schiff base ligands and complexes that can be derived from dithiocarbazates (Tarafder et al., 2002; Hossain et al., 1996). S-2-picolyl dithiocarbazate (S2PDTC) is one type of a dithiocarbazate compound that has been synthesized recently, and its Schiff bases and complexes have proven to possess antimicrobial and anticancer activities (Crouse et al., 2004). Due to these potential medicinal properties of S2PDTC-derived Schiff bases and complexes, the title compound was synthesized and structurally analyzed.

The NiII atom is situated on a twofold rotation axis and is bonded to four nitrogen atoms [Ni—N3 = 2.037 (8) Å; Ni—N4 = 2.109 (9) Å] and two sulfur atoms [Ni—S2 = 2.406 (3) Å] in a distorted octahedral coordination environment as exemplified by the angle N4—Ni1—S2 = 158.4 (2)° (Fig. 1). The bond length of C7—S2 is 1.723 (10) Å, similar to that of C7—S1 of 1.746 (10) Å, which indicates that the ligand bonds to the NiII ion in its thiol tautomer via the deprotonated S atoms.

The angle between the mean plane defined by (Ni1—S2—C7—N2—N3—N4—C8) and that of the symmetry-related ligand is 83.3 (2)° which shows that the two ligands are nearly orthogonal to each other. The Ni—N bond lengths of the title complex are very similar to that of a previously reported related structure (Omar et al., 2012) [2.013 (2) Å for Ni—N, 2.179 (2) Å for Ni—N where this N atom belongs to the pyridine ring; 2.426 (7) Å for Ni—S] which might indicate that the values of such bond lengths are typical of nickel(II) complexes derived from dithiocarbazates. The pyridine ring (C1—C2—C3—C4—C5—N1) is nearly perpendicular to the rest of the molecule with a torsion angle of C5—C6—S1—C7 = 84.0 (8)°.

The molecules in the crystal are stabilized by weak intermolecular C—H···S hydrogen bonding interactions (Table 1; Fig. 2). Moreover, the pyridine rings (C1—C2—C3—C4—C5—N1) at (x, y, z) and (3/2 - x, 1/2 - y, 2 - z) are stacked parallel to each other and form π···π interactions (Fig. 3) with a centroid-centroid separation of 3.775 (9) Å and a shift distance of 1.878 (17) Å while the distance between the planes of the rings is 3.275 (12) Å. There are also C—H···π interactions (Table 1; Fig. 4).

Related literature top

For biological applications of Schiff base ligands and complexes derived from dithiocarbazates, see: Hossain et al. (1996); Tarafder et al. (2002); Crouse et al. (2004). For a related structure, see: Omar et al. (2012).

Experimental top

The nickel complex was synthesized according to a modified procedure reported by Crouse et al. (2004): 0.02 mole of S-picolyl dithiocarbazate were added to a beaker containing 40 ml of absolute ethanol followed by heating the mixture on a heating plate with constant stirring in order to ensure complete dissolving. Similarly, 0.02 mole of pyridine-2-carbaldehyde were dissolved in a separate beaker containing 40 ml of absolute ethanol followed by heating and stirring of the mixture. The reactants were later mixed and 2–4 drops of concentrated H2SO4 were added to the mixture followed by heating of the mixture for 5 minutes. The mixture was cooled to 273 K in an ice-bath until the precipitation of the Schiff base ligand was achieved, and this was followed by filtration of the precipitated Schiff base ligand via suction filtration, washing it with cold ethanol and drying over silica gel.

0.0076 mole of the synthesized Schiff base ligand were dissolved in 50 ml of absolute ethanol followed by the addition of an equimolar amount of KOH and the mixture was heated over a heating plate and stirred until the compounds had been completely dissolved. The solution was then treated with a stoichiometric amount of nickel(II) acetate (0.0038 moles) dissolved in 50 ml of absolute ethanol followed by heating for 5 minutes and then kept in an ice-salt bath. Finally, the obtained product was isolated via suction filtration, washed with ethanol and dried over silica gel.

Refinement top

The H atoms were all located in a difference map, but those attached to carbon atoms were repositioned geometrically. The H atoms were initially refined with soft restraints on the bond lengths and angles to regularize their geometry (C—H in the range 0.93–98 Å) and isotropic temperature factors (Uiso(H) in the range 1.2–1.5 times Ueq of the parent atom), after which the positions were refined with riding constraints.

Computing details top

Data collection: COLLECT (Nonius, 2001); cell refinement: DENZO/SCALEPACK (Otwinowski & Minor, 1997); data reduction: DENZO/SCALEPACK (Otwinowski & Minor, 1997); program(s) used to solve structure: SIR92 (Altomare et al., 1994); program(s) used to refine structure: CRYSTALS (Betteridge et al., 2003); molecular graphics: Mercury (Macrae et al., 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound showing 50% probability displacement ellipsoids in addition to the atomic numbering scheme. Hydrogen atoms were omitted for clarity. The second ligand is related to the first by symmetry code x, -y, z + 1/2.
[Figure 2] Fig. 2. The molecules in the structure are stabilized by intermolecular C—H···S hydrogen bonding interactions. Probability function as in Fig. 1. [Symmetry code: (ii) x, -y, z + 1/2.]
[Figure 3] Fig. 3. The molecules in the structure are also linked by π···π interactions between pairs of pyridine rings with a centroid···centroid distance of 3.775 (9) Å. Probability function as in Fig. 1. [Symmetry code: 3/2 - x, 1/2 - y, 2 - z.]
[Figure 4] Fig. 4. Diagram showing the C—H···π interaction between the molecules in the structure. Probability function as in Fig. 1. [Symmetry code: 1 - x, - y, 2 - z.]
Bis{(Z)-[(E)-2-(pyridin-2-ylmethylidene)hydrazin-1-ylidene][(pyridin-2-yl)methylsulfanyl]methanethiolato}nickel(II) top
Crystal data top
[Ni(C13H11N4S2)2]F(000) = 1304
Mr = 633.49Dx = 1.590 Mg m3
Monoclinic, C2/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 3175 reflections
a = 26.0501 (4) Åθ = 1–27°
b = 8.0057 (1) ŵ = 1.08 mm1
c = 13.0743 (2) ÅT = 150 K
β = 103.8993 (9)°Plate, dark green
V = 2646.80 (7) Å30.04 × 0.03 × 0.02 mm
Z = 4
Data collection top
Nonius Kappa CCD
diffractometer
2066 reflections with I > 3σ(I)
Graphite monochromatorRint = 0.020
ω scansθmax = 27.5°, θmin = 2.7°
Absorption correction: multi-scan
(DENZO/SCALEPACK; Otwinowski & Minor, 1997)
h = 3333
Tmin = 0.97, Tmax = 0.98k = 1010
5912 measured reflectionsl = 1616
3030 independent reflections
Refinement top
Refinement on FPrimary atom site location: structure-invariant direct methods
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.045H-atom parameters constrained
wR(F2) = 0.121 Method = Quasi-Unit weights W = 1.0 or 1./2F
S = 1.08(Δ/σ)max = 0.000256
2066 reflectionsΔρmax = 0.81 e Å3
177 parametersΔρmin = 0.74 e Å3
0 restraints
Crystal data top
[Ni(C13H11N4S2)2]V = 2646.80 (7) Å3
Mr = 633.49Z = 4
Monoclinic, C2/cMo Kα radiation
a = 26.0501 (4) ŵ = 1.08 mm1
b = 8.0057 (1) ÅT = 150 K
c = 13.0743 (2) Å0.04 × 0.03 × 0.02 mm
β = 103.8993 (9)°
Data collection top
Nonius Kappa CCD
diffractometer
3030 independent reflections
Absorption correction: multi-scan
(DENZO/SCALEPACK; Otwinowski & Minor, 1997)
2066 reflections with I > 3σ(I)
Tmin = 0.97, Tmax = 0.98Rint = 0.020
5912 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0450 restraints
wR(F2) = 0.121H-atom parameters constrained
S = 1.08Δρmax = 0.81 e Å3
2066 reflectionsΔρmin = 0.74 e Å3
177 parameters
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
H10.82340.13141.06740.0390*
H20.80390.34611.17400.0419*
H30.72430.33311.22520.0430*
H40.66480.11151.16740.0380*
H50.69990.26131.08300.0320*
H60.64830.15611.08640.0320*
H70.52880.18491.04170.0250*
H80.45190.38551.05300.0351*
H90.38300.56320.96380.0430*
H100.36380.56940.77680.0412*
H110.41100.40020.68690.0369*
C10.7910 (4)0.1272 (16)1.0890 (8)0.0279
C20.7800 (5)0.2562 (16)1.1526 (9)0.0301
C30.7328 (5)0.2491 (16)1.1824 (9)0.0304
C40.6977 (4)0.1170 (16)1.1487 (8)0.0266
C50.7126 (4)0.0081 (14)1.0863 (7)0.0204
C60.6789 (4)0.1619 (14)1.0548 (8)0.0229
C70.5986 (4)0.0675 (13)0.8762 (8)0.0197
C80.5162 (4)0.1936 (13)0.9682 (7)0.0177
C90.4708 (4)0.2967 (13)0.9196 (7)0.0178
C100.4431 (4)0.3919 (15)0.9783 (8)0.0243
C110.4023 (4)0.4963 (15)0.9253 (9)0.0281
C120.3908 (4)0.4991 (15)0.8152 (9)0.0284
C130.4192 (4)0.3980 (16)0.7618 (8)0.0253
S10.65548 (10)0.1902 (4)0.9126 (2)0.0223
S20.56873 (11)0.0826 (4)0.7438 (2)0.0273
N10.7591 (3)0.0039 (12)1.0560 (7)0.0250
N20.5828 (3)0.0209 (11)0.9494 (6)0.0185
N30.5379 (3)0.1138 (11)0.9056 (6)0.0168
N40.4582 (3)0.2990 (11)0.8126 (6)0.0196
Ni10.50000.1151 (3)0.75000.0172
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.019 (5)0.037 (7)0.026 (5)0.004 (5)0.002 (4)0.004 (5)
C20.027 (6)0.032 (6)0.028 (6)0.007 (5)0.000 (5)0.001 (5)
C30.025 (6)0.034 (6)0.029 (6)0.004 (5)0.002 (5)0.012 (5)
C40.022 (5)0.034 (6)0.023 (5)0.002 (5)0.005 (4)0.006 (5)
C50.019 (5)0.024 (5)0.015 (4)0.004 (4)0.002 (4)0.005 (4)
C60.022 (5)0.026 (6)0.018 (5)0.001 (4)0.001 (4)0.004 (4)
C70.019 (5)0.017 (5)0.020 (5)0.002 (4)0.000 (4)0.000 (4)
C80.022 (5)0.020 (5)0.010 (4)0.002 (4)0.001 (4)0.002 (4)
C90.019 (5)0.016 (5)0.018 (5)0.000 (4)0.004 (4)0.000 (4)
C100.026 (5)0.025 (6)0.023 (5)0.005 (5)0.007 (4)0.002 (5)
C110.025 (5)0.026 (6)0.035 (6)0.002 (5)0.012 (5)0.005 (5)
C120.021 (5)0.025 (6)0.039 (6)0.003 (5)0.005 (5)0.004 (5)
C130.022 (5)0.031 (6)0.021 (5)0.004 (5)0.002 (4)0.002 (5)
S10.0207 (12)0.0238 (14)0.0197 (12)0.0040 (11)0.0003 (9)0.0014 (11)
S20.0276 (14)0.0357 (17)0.0145 (11)0.0112 (12)0.0026 (10)0.0066 (11)
N10.019 (4)0.032 (5)0.023 (4)0.005 (4)0.003 (3)0.001 (4)
N20.018 (4)0.019 (4)0.016 (4)0.002 (4)0.001 (3)0.001 (3)
N30.017 (4)0.018 (4)0.014 (4)0.001 (4)0.002 (3)0.002 (3)
N40.019 (4)0.023 (5)0.016 (4)0.001 (4)0.003 (3)0.001 (4)
Ni10.0172 (9)0.0210 (10)0.0120 (8)0.00000.0007 (6)0.0000
Geometric parameters (Å, º) top
H1—C10.952C5—N11.361 (13)
H2—C20.948C6—S11.826 (10)
H3—C30.936C7—S11.746 (10)
H4—C40.949C7—S21.723 (10)
H5—C60.986C7—N21.333 (13)
H6—C60.982C8—C91.458 (14)
H7—C80.940C8—N31.272 (13)
H8—C100.949C9—C101.398 (14)
H9—C110.956C9—N41.358 (12)
H10—C120.944C10—C111.399 (16)
H11—C130.951C11—C121.398 (16)
C1—C21.397 (17)C12—C131.392 (16)
C1—N11.345 (15)C13—N41.335 (13)
C2—C31.377 (16)S2—Ni12.406 (3)
C3—C41.398 (17)N2—N31.388 (11)
C4—C51.404 (15)N3—Ni12.037 (8)
C5—C61.512 (15)N4—Ni12.109 (9)
H1—C1—C2118.2H9—C11—C12121.5
H1—C1—N1117.1C10—C11—C12118.0 (10)
C2—C1—N1124.6 (10)C11—C12—H10120.4
H2—C2—C1121.6C11—C12—C13119.9 (10)
H2—C2—C3120.9H10—C12—C13119.7
C1—C2—C3117.5 (11)H11—C13—C12119.4
H3—C3—C2119.8H11—C13—N4118.5
H3—C3—C4120.0C12—C13—N4122.0 (10)
C2—C3—C4120.2 (11)C6—S1—C7105.2 (5)
H4—C4—C3121.2C7—S2—Ni194.6 (4)
H4—C4—C5120.7C5—N1—C1116.8 (9)
C3—C4—C5118.1 (10)C7—N2—N3111.3 (8)
C4—C5—C6121.0 (9)N2—N3—C8117.6 (8)
C4—C5—N1122.8 (10)N2—N3—Ni1124.9 (6)
C6—C5—N1116.1 (9)C8—N3—Ni1117.2 (7)
C5—C6—H5108.8C9—N4—C13119.1 (9)
C5—C6—H6108.9C9—N4—Ni1111.8 (7)
H5—C6—H6108.4C13—N4—Ni1128.7 (7)
C5—C6—S1114.1 (7)N4—Ni1—N4i91.5 (5)
H5—C6—S1107.4N4—Ni1—S2158.4 (2)
H6—C6—S1109.1N4i—Ni1—S289.4 (2)
S1—C7—S2112.5 (6)N4—Ni1—S2i89.4 (2)
S1—C7—N2119.4 (7)N4i—Ni1—S2i158.4 (2)
S2—C7—N2128.0 (8)S2—Ni1—S2i97.72 (17)
H7—C8—C9122.4N4—Ni1—N377.7 (3)
H7—C8—N3121.3N4i—Ni1—N3102.7 (3)
C9—C8—N3116.3 (8)S2—Ni1—N381.0 (2)
C8—C9—C10122.7 (9)S2i—Ni1—N398.6 (2)
C8—C9—N4115.2 (9)N4—Ni1—N3i102.7 (3)
C10—C9—N4122.1 (9)N4i—Ni1—N3i77.7 (3)
H8—C10—C9120.4S2—Ni1—N3i98.6 (2)
H8—C10—C11120.6S2i—Ni1—N3i81.0 (2)
C9—C10—C11119.0 (10)N3—Ni1—N3i179.4 (5)
H9—C11—C10120.5
Symmetry code: (i) x+1, y, z+3/2.
Hydrogen-bond geometry (Å, º) top
Cg is the centroid of the pyridine ring (C9–C13/N4).
D—H···AD—HH···AD···AD—H···A
C8—H7···S2ii0.942.723.644 (9)166
C4—H4···S2ii0.952.923.862 (11)175
C6—H6···Cgiii0.982.983.750 (12)136
Symmetry codes: (ii) x, y, z+1/2; (iii) x+1, y, z+2.

Experimental details

Crystal data
Chemical formula[Ni(C13H11N4S2)2]
Mr633.49
Crystal system, space groupMonoclinic, C2/c
Temperature (K)150
a, b, c (Å)26.0501 (4), 8.0057 (1), 13.0743 (2)
β (°) 103.8993 (9)
V3)2646.80 (7)
Z4
Radiation typeMo Kα
µ (mm1)1.08
Crystal size (mm)0.04 × 0.03 × 0.02
Data collection
DiffractometerNonius Kappa CCD
diffractometer
Absorption correctionMulti-scan
(DENZO/SCALEPACK; Otwinowski & Minor, 1997)
Tmin, Tmax0.97, 0.98
No. of measured, independent and
observed [I > 3σ(I)] reflections
5912, 3030, 2066
Rint0.020
(sin θ/λ)max1)0.649
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.045, 0.121, 1.08
No. of reflections2066
No. of parameters177
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.81, 0.74

Computer programs: COLLECT (Nonius, 2001), DENZO/SCALEPACK (Otwinowski & Minor, 1997), SIR92 (Altomare et al., 1994), CRYSTALS (Betteridge et al., 2003), Mercury (Macrae et al., 2006), publCIF (Westrip, 2010).

Hydrogen-bond geometry (Å, º) top
Cg is the centroid of the pyridine ring (C9–C13/N4).
D—H···AD—HH···AD···AD—H···A
C8—H7···S2i0.942.723.644 (9)166
C4—H4···S2i0.952.923.862 (11)175
C6—H6···Cgii0.982.983.750 (12)136
Symmetry codes: (i) x, y, z+1/2; (ii) x+1, y, z+2.
 

Acknowledgements

The authors thank the Ministry of Higher Education Malaysia (MOHE) under FRGS (F0010.54.02) for providing a grant for this study.

References

First citationAltomare, A., Cascarano, G., Giacovazzo, C., Guagliardi, A., Burla, M. C., Polidori, G. & Camalli, M. (1994). J. Appl. Cryst. 27, 435.  CrossRef Web of Science IUCr Journals Google Scholar
First citationBetteridge, P. W., Carruthers, J. R., Cooper, R. I., Prout, K. & Watkin, D. J. (2003). J. Appl. Cryst. 36, 1487.  Web of Science CrossRef IUCr Journals Google Scholar
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Volume 69| Part 6| June 2013| Pages m323-m324
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