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ISSN: 2056-9890

3-Chloro-1-methyl-4-[2-(3-phenyl­allyl­­idene)hydrazinyl­­idene]-3,4-di­hydro-1H-2λ6,1-benzo­thia­zine-2,2-dione

aDepartment of Chemistry, Government College University, Faisalabad 38000, Pakistan, bDepartment of Physics, University of Sargodha, Sargodha, Pakistan, cDepartment of Chemistry, University of Aberdeen, Mston Walk, Aberdeen AB24 3UE, Scotland, and dMaterials Chemistry Laboratory, Department of Chemistry, Government College University, Lahore, Pakistan
*Correspondence e-mail: hafizshafique@hotmail.com

(Received 19 December 2012; accepted 20 December 2012; online 4 January 2013)

In the title compound, C18H16ClN3O2S, the dihedral angle between the aromatic rings is 4.81 (2)° and the alkyl chain takes on an extended conformation [N—C—C—C = 179.2 (4)°]. The conformation of the thia­zine ring is an envelope, with the S atom displaced by −0.805 (3) Å from the mean plane of the other five atoms (r.m.s. deviation = 0.046 Å). The Cl atom is an axial conformation and is displaced by 1.761 (4) Å from the thia­zine ring plane. In the crystal, inversion dimers linked by pairs of C—H⋯O inter­actions generate R22(20) loops and further C—H⋯O hydrogen bonds link the dimers into (001) sheets. Weak aromatic ππ stacking inter­actions [centroid–centroid separations = 3.870 (3) and 3.883 (3) Å] are also observed.

Related literature

For the synthesis and biological activity of the title compound and related materials, see: Shafiq et al. (2011a[Shafiq, M., Zia-Ur-Rehman, M., Khan, I. U., Arshad, M. N. & Khan, S. A. (2011a). JJ. Chil. Chem. Soc. 56, 527-531.]). For further synthetic details, see: Shafiq et al. (2011b[Shafiq, M., Khan, I. U., Arshad, M. N. & Siddiqui, W. A. (2011b). Asian J. Chem. 23, 2101-2106.]).

[Scheme 1]

Experimental

Crystal data
  • C18H16ClN3O2S

  • Mr = 373.85

  • Monoclinic, P 21 /c

  • a = 7.2262 (5) Å

  • b = 13.5823 (9) Å

  • c = 17.9818 (12) Å

  • β = 97.023 (4)°

  • V = 1751.6 (2) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.35 mm−1

  • T = 296 K

  • 0.32 × 0.20 × 0.18 mm

Data collection
  • Bruker APEXII CCD diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2007[Bruker (2007). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.895, Tmax = 0.939

  • 8051 measured reflections

  • 3107 independent reflections

  • 1808 reflections with I > 2σ(I)

  • Rint = 0.043

Refinement
  • R[F2 > 2σ(F2)] = 0.067

  • wR(F2) = 0.201

  • S = 1.03

  • 3107 reflections

  • 227 parameters

  • H-atom parameters constrained

  • Δρmax = 0.97 e Å−3

  • Δρmin = −0.36 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A DA D—H⋯A
C12—H12⋯O2i 0.93 2.51 3.345 (6) 150
C15—H15⋯O2ii 0.93 2.57 3.464 (6) 161
Symmetry codes: (i) -x, -y+1, -z+1; (ii) [-x, y+{\script{1\over 2}}, -z+{\script{1\over 2}}].

Data collection: APEX2 (Bruker, 2007[Bruker (2007). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2007[Bruker (2007). APEX2, SAINT and SADABS. 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: ORTEP-3 (Farrugia, 2012[Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849-854.]); software used to prepare material for publication: SHELXL97.

Supporting information


Comment top

As part of our ongoing studies of benzothiazine derivatives with potential biactivity (Shafiq et al., 2011a,b), we now describe the synthesis and structure of the title compound, (I).

The dihedral angle between the C1–C6 and C13–C18 aromatic rings is 4.81 (2)° and the C9=N2—N3=C10 torsion angle is -178.1 (4)°. The linking alkyl chain takes on an extended conformation [N3—C10—C11—C12 = 179.2 (4)°]. The conformation of the C1/C6/C8/C9/N1/S1 thiazine ring is an envelope, with the S atom displaced by -0.805 (3) Å from the mean plane of the other five atoms (r.m.s. deviation = 0.046 Å). Atom C16 is displaced from the mean plane by 0.343 (6) Å and Cl1, in an axial site, is displaced by 1.761 (4) Å. Atom C8 is a stereogenic centre (R configuration in the arbitrarily-chosen asymmetric unit), but crystal symmetry generates a racemic mixture.

In the crystal, inversion dimers linked by pairs of C—H···O interactions (Table 1) to generate R22(20) loops. Further C—H···O bonds link the dimers into (001) sheets. Weak aromatic π-π stacking interactions between the C1—C6 and C13—C18 benzene rings [centroid-centroid separations = 3.870 (3) and 3.883 (3) Å] are also observed.

Related literature top

For the synthesis and biological activity of the title compound and related materials, see: Shafiq et al. (2011a). For further synthetic details, see: Shafiq et al. (2011b).

Experimental top

The Schiff base derivative of (4Z)-4-hydrazinylidene-1-methyl-3,4-dihydro -1H-2,1-benzothiazine 2,2-dioxide and trans cinnamaldehyde was prepared using the methods reported previously (Shafiq et al., 2011a). The chlorination of the Schiff base was undertaken using N-chloro succinimide and dibenzoylperoxide (Shafiq et al., 2011b). The crude product was recrystallized from ethyl acetate solution to obtain yellow blocks of the title compound.

Refinement top

The H atoms were placed in calculated positions (C—H = 0.93–0.97 Å) and refined as riding. The methyl group was allowed to rotate, but not to tip, to best fit the electron density. The constraint Uiso(H) = 1.2Ueq(C) or 1.5Ueq(methyl C) was applied.

Computing details top

Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 2012); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I), showing displacement ellipsoids at the 50% probability level.
3-Chloro-1-methyl-4-[2-(3-phenylallylidene)hydrazinylidene]- 3,4-dihydro-1H-2λ6,1-benzothiazine-2,2-dione top
Crystal data top
C18H16ClN3O2SF(000) = 776
Mr = 373.85Dx = 1.418 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 305 reflections
a = 7.2262 (5) Åθ = 3.5–24.5°
b = 13.5823 (9) ŵ = 0.35 mm1
c = 17.9818 (12) ÅT = 296 K
β = 97.023 (4)°Rod, yellow
V = 1751.6 (2) Å30.32 × 0.20 × 0.18 mm
Z = 4
Data collection top
Bruker APEXII CCD
diffractometer
3107 independent reflections
Radiation source: fine-focus sealed tube1808 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.043
ω scansθmax = 25.5°, θmin = 2.7°
Absorption correction: multi-scan
(SADABS; Bruker, 2007)
h = 88
Tmin = 0.895, Tmax = 0.939k = 1316
8051 measured reflectionsl = 2118
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)] = 0.067Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.201H-atom parameters constrained
S = 1.03 w = 1/[σ2(Fo2) + (0.1036P)2 + 0.2998P]
where P = (Fo2 + 2Fc2)/3
3107 reflections(Δ/σ)max < 0.001
227 parametersΔρmax = 0.97 e Å3
0 restraintsΔρmin = 0.36 e Å3
Crystal data top
C18H16ClN3O2SV = 1751.6 (2) Å3
Mr = 373.85Z = 4
Monoclinic, P21/cMo Kα radiation
a = 7.2262 (5) ŵ = 0.35 mm1
b = 13.5823 (9) ÅT = 296 K
c = 17.9818 (12) Å0.32 × 0.20 × 0.18 mm
β = 97.023 (4)°
Data collection top
Bruker APEXII CCD
diffractometer
3107 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2007)
1808 reflections with I > 2σ(I)
Tmin = 0.895, Tmax = 0.939Rint = 0.043
8051 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0670 restraints
wR(F2) = 0.201H-atom parameters constrained
S = 1.03Δρmax = 0.97 e Å3
3107 reflectionsΔρmin = 0.36 e Å3
227 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
C10.2953 (5)0.2779 (3)0.6118 (2)0.0406 (11)
C20.3170 (6)0.3399 (4)0.6745 (3)0.0526 (12)
H20.31460.40770.66730.063*
C30.3415 (7)0.3037 (4)0.7460 (3)0.0601 (14)
H30.35490.34650.78670.072*
C40.3463 (7)0.2037 (4)0.7574 (3)0.0622 (14)
H40.36600.17910.80590.075*
C50.3225 (7)0.1399 (4)0.6983 (3)0.0584 (13)
H50.32310.07240.70690.070*
C60.2973 (6)0.1759 (3)0.6248 (2)0.0422 (11)
C70.3297 (8)0.0041 (3)0.5761 (3)0.0762 (17)
H7A0.45200.00030.60360.114*
H7B0.33020.02710.52820.114*
H7C0.24190.02860.60360.114*
C80.2780 (6)0.2531 (3)0.4704 (3)0.0422 (11)
H80.21420.28560.42570.051*
C90.2729 (5)0.3201 (3)0.5368 (2)0.0381 (10)
C100.2243 (6)0.5395 (3)0.4480 (3)0.0507 (12)
H100.22330.57620.49160.061*
C110.2092 (6)0.5897 (3)0.3787 (3)0.0489 (12)
H110.21160.55420.33450.059*
C120.1917 (6)0.6871 (3)0.3759 (3)0.0480 (12)
H120.18930.71810.42190.058*
C130.1756 (6)0.7522 (3)0.3107 (3)0.0450 (11)
C140.1646 (7)0.7194 (4)0.2366 (3)0.0563 (13)
H140.16650.65220.22660.068*
C150.1508 (7)0.7866 (5)0.1777 (3)0.0634 (14)
H150.14340.76390.12870.076*
C160.1482 (7)0.8848 (5)0.1912 (3)0.0683 (15)
H160.14020.92910.15150.082*
C170.1573 (7)0.9191 (4)0.2634 (3)0.0638 (14)
H170.15360.98640.27250.077*
C180.1717 (6)0.8543 (3)0.3220 (3)0.0517 (12)
H180.17910.87860.37060.062*
S10.15957 (18)0.14181 (8)0.48575 (7)0.0514 (4)
O10.1890 (5)0.0698 (2)0.42999 (19)0.0666 (10)
O20.0251 (4)0.1739 (2)0.49385 (18)0.0542 (9)
N10.2763 (5)0.1075 (3)0.5651 (2)0.0518 (10)
N20.2523 (5)0.4134 (3)0.5278 (2)0.0478 (10)
N30.2393 (5)0.4455 (3)0.4536 (2)0.0526 (10)
Cl10.51237 (17)0.22812 (9)0.45547 (8)0.0621 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.043 (2)0.041 (3)0.039 (3)0.0041 (18)0.0078 (19)0.002 (2)
C20.064 (3)0.050 (3)0.044 (3)0.006 (2)0.007 (2)0.006 (3)
C30.071 (3)0.075 (4)0.034 (3)0.009 (3)0.006 (2)0.016 (3)
C40.066 (3)0.082 (4)0.038 (3)0.007 (3)0.007 (2)0.009 (3)
C50.071 (3)0.054 (3)0.049 (3)0.006 (2)0.004 (2)0.013 (3)
C60.049 (3)0.040 (3)0.038 (3)0.0043 (19)0.006 (2)0.004 (2)
C70.116 (5)0.035 (3)0.074 (4)0.008 (3)0.004 (3)0.004 (3)
C80.058 (3)0.032 (2)0.037 (3)0.0042 (18)0.009 (2)0.001 (2)
C90.045 (2)0.028 (2)0.041 (3)0.0045 (17)0.0049 (19)0.003 (2)
C100.063 (3)0.038 (3)0.051 (3)0.002 (2)0.006 (2)0.000 (2)
C110.065 (3)0.036 (3)0.047 (3)0.001 (2)0.010 (2)0.002 (2)
C120.060 (3)0.038 (3)0.046 (3)0.003 (2)0.010 (2)0.000 (2)
C130.046 (3)0.042 (3)0.046 (3)0.0007 (18)0.003 (2)0.000 (2)
C140.065 (3)0.049 (3)0.055 (4)0.001 (2)0.008 (2)0.009 (3)
C150.061 (3)0.088 (4)0.039 (3)0.009 (3)0.001 (2)0.002 (3)
C160.065 (3)0.080 (4)0.061 (4)0.002 (3)0.010 (3)0.024 (3)
C170.072 (3)0.046 (3)0.073 (4)0.003 (2)0.011 (3)0.016 (3)
C180.065 (3)0.042 (3)0.050 (3)0.003 (2)0.013 (2)0.003 (2)
S10.0683 (9)0.0383 (7)0.0475 (8)0.0027 (5)0.0070 (6)0.0040 (6)
O10.109 (3)0.0401 (19)0.052 (2)0.0042 (17)0.0127 (19)0.0149 (17)
O20.0472 (19)0.060 (2)0.055 (2)0.0051 (14)0.0033 (15)0.0113 (17)
N10.081 (3)0.031 (2)0.042 (3)0.0058 (17)0.0017 (19)0.0016 (19)
N20.066 (3)0.038 (2)0.039 (2)0.0037 (16)0.0049 (18)0.0004 (18)
N30.076 (3)0.035 (2)0.046 (3)0.0026 (18)0.0063 (19)0.0018 (19)
Cl10.0630 (8)0.0605 (8)0.0664 (10)0.0036 (5)0.0223 (6)0.0108 (7)
Geometric parameters (Å, º) top
C1—C21.401 (6)C10—C111.414 (6)
C1—C61.405 (6)C10—H100.9300
C1—C91.455 (6)C11—C121.329 (6)
C2—C31.368 (7)C11—H110.9300
C2—H20.9300C12—C131.462 (6)
C3—C41.373 (7)C12—H120.9300
C3—H30.9300C13—C141.398 (7)
C4—C51.365 (7)C13—C181.402 (6)
C4—H40.9300C14—C151.393 (7)
C5—C61.399 (6)C14—H140.9300
C5—H50.9300C15—C161.357 (7)
C6—N11.415 (6)C15—H150.9300
C7—N11.463 (6)C16—C171.373 (7)
C7—H7A0.9600C16—H160.9300
C7—H7B0.9600C17—C181.366 (6)
C7—H7C0.9600C17—H170.9300
C8—C91.506 (6)C18—H180.9300
C8—S11.775 (4)S1—O21.428 (3)
C8—Cl11.780 (4)S1—O11.435 (3)
C8—H80.9800S1—N11.634 (4)
C9—N21.283 (5)N2—N31.397 (5)
C10—N31.284 (5)
C2—C1—C6117.4 (4)C12—C11—C10120.7 (5)
C2—C1—C9119.8 (4)C12—C11—H11119.7
C6—C1—C9122.8 (4)C10—C11—H11119.7
C3—C2—C1122.0 (5)C11—C12—C13129.1 (5)
C3—C2—H2119.0C11—C12—H12115.4
C1—C2—H2119.0C13—C12—H12115.4
C2—C3—C4119.5 (5)C14—C13—C18117.0 (4)
C2—C3—H3120.2C14—C13—C12124.0 (4)
C4—C3—H3120.2C18—C13—C12119.0 (4)
C5—C4—C3120.9 (5)C15—C14—C13120.4 (5)
C5—C4—H4119.5C15—C14—H14119.8
C3—C4—H4119.5C13—C14—H14119.8
C4—C5—C6120.2 (5)C16—C15—C14120.7 (5)
C4—C5—H5119.9C16—C15—H15119.7
C6—C5—H5119.9C14—C15—H15119.7
C5—C6—C1120.0 (4)C15—C16—C17120.2 (5)
C5—C6—N1118.5 (4)C15—C16—H16119.9
C1—C6—N1121.5 (4)C17—C16—H16119.9
N1—C7—H7A109.5C18—C17—C16120.0 (5)
N1—C7—H7B109.5C18—C17—H17120.0
H7A—C7—H7B109.5C16—C17—H17120.0
N1—C7—H7C109.5C17—C18—C13121.8 (5)
H7A—C7—H7C109.5C17—C18—H18119.1
H7B—C7—H7C109.5C13—C18—H18119.1
C9—C8—S1109.4 (3)O2—S1—O1120.0 (2)
C9—C8—Cl1110.5 (3)O2—S1—N1112.8 (2)
S1—C8—Cl1110.3 (2)O1—S1—N1108.1 (2)
C9—C8—H8108.9O2—S1—C8103.3 (2)
S1—C8—H8108.9O1—S1—C8110.9 (2)
Cl1—C8—H8108.9N1—S1—C899.9 (2)
N2—C9—C1120.3 (4)C6—N1—C7121.7 (4)
N2—C9—C8120.7 (4)C6—N1—S1118.1 (3)
C1—C9—C8119.1 (4)C7—N1—S1119.4 (3)
N3—C10—C11123.1 (5)C9—N2—N3115.0 (4)
N3—C10—H10118.5C10—N3—N2112.4 (4)
C11—C10—H10118.5
C6—C1—C2—C30.8 (6)C14—C15—C16—C170.7 (8)
C9—C1—C2—C3178.9 (4)C15—C16—C17—C180.9 (8)
C1—C2—C3—C40.4 (7)C16—C17—C18—C130.7 (7)
C2—C3—C4—C51.5 (7)C14—C13—C18—C170.2 (7)
C3—C4—C5—C61.5 (7)C12—C13—C18—C17179.9 (4)
C4—C5—C6—C10.4 (7)C9—C8—S1—O260.3 (3)
C4—C5—C6—N1178.9 (4)Cl1—C8—S1—O2178.0 (2)
C2—C1—C6—C50.8 (6)C9—C8—S1—O1170.0 (3)
C9—C1—C6—C5178.9 (4)Cl1—C8—S1—O148.2 (3)
C2—C1—C6—N1180.0 (4)C9—C8—S1—N156.2 (3)
C9—C1—C6—N10.4 (6)Cl1—C8—S1—N165.6 (3)
C2—C1—C9—N27.8 (6)C5—C6—N1—C716.9 (6)
C6—C1—C9—N2172.6 (4)C1—C6—N1—C7162.4 (4)
C2—C1—C9—C8171.1 (4)C5—C6—N1—S1153.4 (3)
C6—C1—C9—C88.5 (6)C1—C6—N1—S127.4 (5)
S1—C8—C9—N2142.1 (3)O2—S1—N1—C656.8 (4)
Cl1—C8—C9—N296.3 (4)O1—S1—N1—C6168.2 (3)
S1—C8—C9—C139.1 (5)C8—S1—N1—C652.3 (4)
Cl1—C8—C9—C182.5 (4)O2—S1—N1—C7113.7 (4)
N3—C10—C11—C12179.2 (4)O1—S1—N1—C721.3 (4)
C10—C11—C12—C13179.5 (4)C8—S1—N1—C7137.2 (4)
C11—C12—C13—C144.2 (7)C1—C9—N2—N3177.7 (3)
C11—C12—C13—C18175.5 (5)C8—C9—N2—N31.2 (5)
C18—C13—C14—C150.1 (7)C11—C10—N3—N2180.0 (4)
C12—C13—C14—C15179.5 (4)C9—N2—N3—C10178.1 (4)
C13—C14—C15—C160.1 (7)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C12—H12···O2i0.932.513.345 (6)150
C15—H15···O2ii0.932.573.464 (6)161
Symmetry codes: (i) x, y+1, z+1; (ii) x, y+1/2, z+1/2.

Experimental details

Crystal data
Chemical formulaC18H16ClN3O2S
Mr373.85
Crystal system, space groupMonoclinic, P21/c
Temperature (K)296
a, b, c (Å)7.2262 (5), 13.5823 (9), 17.9818 (12)
β (°) 97.023 (4)
V3)1751.6 (2)
Z4
Radiation typeMo Kα
µ (mm1)0.35
Crystal size (mm)0.32 × 0.20 × 0.18
Data collection
DiffractometerBruker APEXII CCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2007)
Tmin, Tmax0.895, 0.939
No. of measured, independent and
observed [I > 2σ(I)] reflections
8051, 3107, 1808
Rint0.043
(sin θ/λ)max1)0.606
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.067, 0.201, 1.03
No. of reflections3107
No. of parameters227
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.97, 0.36

Computer programs: APEX2 (Bruker, 2007), SAINT (Bruker, 2007), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 2012).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C12—H12···O2i0.932.513.345 (6)150
C15—H15···O2ii0.932.573.464 (6)161
Symmetry codes: (i) x, y+1, z+1; (ii) x, y+1/2, z+1/2.
 

Acknowledgements

MS acknowledges the HEC Pakistan for granting a PhD fellowship.

References

First citationBruker (2007). APEX2, SAINT and SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.
First citationFarrugia, L. J. (2012). J. Appl. Cryst. 45, 849–854.  Web of Science CrossRef CAS IUCr Journals
First citationShafiq, M., Khan, I. U., Arshad, M. N. & Siddiqui, W. A. (2011b). Asian J. Chem. 23, 2101–2106.  CAS
First citationShafiq, M., Zia-Ur-Rehman, M., Khan, I. U., Arshad, M. N. & Khan, S. A. (2011a). JJ. Chil. Chem. Soc. 56, 527–531.  CSD CrossRef CAS
First citationSheldrick, G. M. (2008). Acta Cryst. A64, 112–122.  Web of Science CrossRef CAS IUCr Journals

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