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The crystal structure of the title compound, [ZnCl2(C10H9NO)2], has been determined from laboratory powder diffraction data. Although the powder pattern was initially indexed with tetragonal unit-cell dimensions, the correct solution was found in an orthorhombic space group using a combination of grid-search and simulated-annealing techniques. The subsequent bond-restrained Rietveld refinement gave bond lengths and angles within expected ranges. The molecule has crystallographically imposed twofold symmetry.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102005292/sk1538sup1.cif
Contains datablocks I, global

rtv

Rietveld powder data file (CIF format) https://doi.org/10.1107/S0108270102005292/sk1538Isup2.rtv
Contains datablock I

CCDC reference: 187912

Comment top

Heteroatomic N-oxides, and their complexes and salts demonstrate a broad spectrum of biological activity. Some are used as medical remedies (Albini & Pietra, 1991) or plant growth activators (Ponomarenko, 1999). N-oxidation is one of the detoxification pathways of heterocycles in living things (Murray et al., 1997; Hecht, 1996). The necessity of establishing structure-property relationships for this class of compounds led to the crystal structure determination of the title compound, (I). \sch

In the crystal structure of (I), the Zn atom is situated on a twofold axis (Fig. 1). Selected geometric parameters are given in Table 1. The coordination polyhedron of the Zn atom is a slightly distorted tetrahedron, with edge lengths of Cl1—Cl1i 3.885 (6), O1—O1i 3.20 (2), Cl1—O1 3.41 (1) and Cl1—O1i 3.38 (1) Å [symmetry code: (i) -x, y, 1/2 - z]. Is this the correct symmetry code? The distortions of the Zn tetrahedron in (I) are less than those in dichlorobis(2,6-lutidine N-oxide)zinc(II) (Sager & Watson, 1968) and dichlorobis(pyridine N-oxide-O)zinc(II) (McConnell et al., 1986). The molecules of (I) form bent chains stretching along the a axis. The distance between Zn atoms in the chain is 9.95 Å.

Although the unit-cell dimensions seemed to be tetragonal, the crystal structure solution of (I) from powder data turned out not to be an easy task. The measured powder patterns admitted a long list of possible space groups. Therefore, various space groups (first, tetragonal, such as P42212 (94), P42/m (84), P42 (77) and some others, and then orthorhombic) were tested while also using grid-search (Chernyshev & Schenk, 1998) and simulated annealing (Zhukov et al., 2001) techniques to solve the crystal structure of (I). The solution was found in the orthorhombic space group Pna21 (33) and transformed with the ADDSYM option of PLATON (Spek, 2000) into Pbcn (60).

Experimental top

2-Methylquinoline N-oxide was synthesized according to the procedure of Ochiai (1953). Compound (I) was prepared in polycrystalline form by mixing warm saturated 2-methylquinoline N-oxide and zinc chloride solutions in ethanol in molar ratio, and subsequent washing with ethanol and diethyl ether of the precipitate obtained (yield 60%). IR spectra were measured in KBr using a Specord M-40 spectrometer. The intensities of the N—O bands (1340 and 1272 cm-1) decreased in (I) in comparison with the spectrum of the parent N-oxide. Bands at 1188 cm-1 (induced by connection of zinc chloride to the N—O group) and 328–305 cm-1 (Zn—Cl bonds) (Whyman et al., 1967; Garvey et al., 1968) are also present.

Refinement top

Two X-ray powder diffraction patterns were measured in reflection mode on an XPert PRO X-ray powder diffraction system equipped with a standard PW 3050/60 resolution goniometer and PW 3011/20 proportional point detector. The first pattern, measured in the range 2–40° with the narrowest beam attenuator, was used for indexing, while the second was used for structure solution and refinement. The powder was sprinkled on the sample holder using a small sieve to avoid a preferred orientation. The thickness of the sample was no more than 0.1 mm. During the exposures, the specimen was spun in its plane to improve particle statistics. The unit-cell dimensions were determined with the indexing program TREOR (Werner et al., 1985), and were refined in tetragonal space groups with the program LSPAID (Visser, 1986) to M20 = 47 and F30 = 85 (0.006, 61) using the first 30 peak positions. However, several of the tested tetragonal space groups could not provide an appropriate solution. A correct solution was found in the orthorhombic space group Pna21 (33) in a two-step procedure. First, the rigid ZnCl2O2 fragment was located in the asymmetric part of the unit cell using the grid-search procedure (Chernyshev & Schenk, 1998), using a set of 250 high-angle Xobs values extracted from the pattern by the full pattern decomposition procedure. Second, the orientations of the two 2-methylquinoline N-oxide fragments were found with the simulated annealing technique (Zhukov et al., 2001), using a set of 70 low-angle Xobs values. Preliminary bond-restrained Rietveld refinement showed the presence of local symmetry, axis 2. The crystal structure obtained at this stage was tested with the ADDSYM option of PLATON (Spek, 2000) and transformed into space group Pbcn (60). The final bond-restrained Rietveld refinement was performed in the correct space group, Pbcn. The strength of the restraints was a function of interatomic separation and, for intramolecular bond lengths, corresponds to an r.m.s. deviation of 0.03 Å. An additional restraint was applied to the planarity of the 2-methylquinoline N-oxide fragment. Three isotropic atomic displacement parameters were refined: two for Zn and Cl1, and the overall Uiso parameter for the rest of non-H atoms. H atoms were placed in geometrically calculated positions and allowed to refine using bond restraints, with a common isotropic displacement parameter Uiso(H) fixed to 0.05 Å2. The diffraction profiles and the differences between the measured and calculated profiles are shown on Fig. 2.

Computing details top

Data collection: local program; cell refinement: LSPAID (Visser, 1986); data reduction: local program; program(s) used to solve structure: MRIA (Zlokazov & Chernyshev, 1992); program(s) used to refine structure: MRIA; molecular graphics: PLATON (Spek, 2000); software used to prepare material for publication: MRIA, SHELXL97 (Sheldrick, 1997) and PARST (Nardelli, 1983).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I) with the atomic numbering.
[Figure 2] Fig. 2. The Rietveld plot, showing the observed and difference profiles for (I). The reflection positions are shown above the difference profile.
Dichlorobis(2-methylquinoline N-oxide-κO)zinc(II) top
Crystal data top
[ZnCl2(C10H9NO)2]F(000) = 928
Mr = 454.63Dx = 1.501 Mg m3
Orthorhombic, PbcnMelting point: 493(1) K
Hall symbol: -P 2n 2abCu Kα1 radiation, λ = 1.54056 Å
a = 14.052 (6) ÅT = 293 K
b = 10.192 (5) ÅParticle morphology: no specific habit
c = 14.047 (6) Ålight grey
V = 2011.8 (16) Å3flat_sheet, 20 × 20 mm
Z = 4
Data collection top
XPert PRO X-ray diffraction system
diffractometer
Data collection mode: reflection
Radiation source: PW3373/00, line-focus sealed tubeScan method: step
PW3110/65, four Ge(220) crystals monochromator2θmin = 10°, 2θmax = 70°, 2θstep = 0.01°
Specimen mounting: The powder was sprinkled on the sample holder using a small sieve. The thickness of the layer was no more than 0.1 mm.
Refinement top
Refinement on Inet64 parameters
Least-squares matrix: full with fixed elements per cycle74 restraints
Rp = 0.0831 constraint
Rwp = 0.114H-atom parameters constrained
Rexp = 0.086Weighting scheme based on measured s.u.'s
χ2 = 1.742(Δ/σ)max = 0.01
6001 data pointsBackground function: Chebyshev polynomial up to the 5th order
Profile function: split-type pseudo-Voigt (Toraya, 1986)Preferred orientation correction: none
Crystal data top
[ZnCl2(C10H9NO)2]V = 2011.8 (16) Å3
Mr = 454.63Z = 4
Orthorhombic, PbcnCu Kα1 radiation, λ = 1.54056 Å
a = 14.052 (6) ÅT = 293 K
b = 10.192 (5) Åflat_sheet, 20 × 20 mm
c = 14.047 (6) Å
Data collection top
XPert PRO X-ray diffraction system
diffractometer
Scan method: step
Specimen mounting: The powder was sprinkled on the sample holder using a small sieve. The thickness of the layer was no more than 0.1 mm.2θmin = 10°, 2θmax = 70°, 2θstep = 0.01°
Data collection mode: reflection
Refinement top
Rp = 0.0836001 data points
Rwp = 0.11464 parameters
Rexp = 0.08674 restraints
χ2 = 1.742H-atom parameters constrained
Special details top

Experimental. specimen was rotated in its plane

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Zn0.00000.2186 (3)0.25000.060 (1)*
Cl10.1368 (3)0.3277 (4)0.2700 (3)0.064 (2)*
O10.0144 (6)0.1043 (8)0.1370 (6)0.049 (1)*
N10.0601 (10)0.1072 (13)0.0775 (8)0.049*
C20.1317 (11)0.0199 (13)0.0905 (11)0.049*
C30.2118 (9)0.0180 (14)0.0273 (11)0.049*
C40.2171 (10)0.0999 (15)0.0489 (10)0.049*
C50.1496 (11)0.2879 (14)0.1372 (12)0.049*
C60.0764 (12)0.3752 (14)0.1497 (9)0.049*
C70.0011 (12)0.3774 (13)0.0885 (10)0.049*
C80.0106 (12)0.2866 (14)0.0164 (8)0.049*
C90.0645 (11)0.1963 (15)0.0012 (9)0.049*
C100.1450 (11)0.1957 (13)0.0622 (10)0.049*
C110.1271 (10)0.0802 (14)0.1690 (10)0.049*
H30.25920.04390.03620.051*
H40.27040.09830.08840.051*
H50.19980.28490.18030.051*
H60.07850.43360.20130.051*
H70.05100.43540.09980.051*
H80.06250.28950.02430.051*
H1110.07410.06380.20760.051*
H1120.12340.16560.13980.051*
H1130.18540.07510.20480.051*
Geometric parameters (Å, º) top
Zn—Cl1i2.238 (5)C5—H50.93
Zn—O1i1.979 (9)C6—C71.39 (2)
Zn—Cl12.238 (5)C6—H60.94
Zn—O11.979 (9)C7—C81.38 (2)
O1—N11.341 (16)C7—H70.93
N1—C91.432 (18)C8—H80.93
C2—N11.35 (2)C9—C81.42 (2)
C2—C111.50 (2)C9—C101.42 (2)
C3—C41.36 (2)C10—C51.41 (2)
C3—C21.43 (2)C10—C41.42 (2)
C3—H30.93C11—H1110.94
C4—H40.93C11—H1120.96
C5—C61.37 (2)C11—H1130.96
O1—Zn—O1i107.9 (6)C3—C4—C10119 (1)
O1—Zn—Cl1i106.2 (3)C3—C4—H4120
O1i—Zn—Cl1i107.8 (3)C10—C4—H4121
O1—Zn—Cl1107.8 (3)C6—C5—C10120 (1)
O1i—Zn—Cl1106.2 (3)C6—C5—H5121
Cl1i—Zn—Cl1120.4 (2)C10—C5—H5120
N1—O1—Zn114.0 (7)C5—C6—C7121 (1)
C4—C3—C2121 (1)C5—C6—H6119
C4—C3—H3119C7—C6—H6120
C2—C3—H3119C8—C7—C6121 (1)
N1—C2—C3121 (1)C8—C7—H7119
N1—C2—C11121 (1)C6—C7—H7120
C3—C2—C11119 (1)C7—C8—C9118 (1)
O1—N1—C2119 (1)C7—C8—H8121
O1—N1—C9122 (1)C9—C8—H8121
C2—N1—C9119 (1)C2—C11—H111110
C8—C9—C10120 (1)C2—C11—H112108
C8—C9—N1120 (1)H111—C11—H112111
C10—C9—N1120 (1)C2—C11—H113108
C5—C10—C9119 (1)H111—C11—H113111
C5—C10—C4122 (1)H112—C11—H113109
C9—C10—C4120 (1)
Cl1—Zn—O1—N1135.0 (8)Zn—O1—N1—C290 (1)
Symmetry code: (i) x, y, z+1/2.

Experimental details

Crystal data
Chemical formula[ZnCl2(C10H9NO)2]
Mr454.63
Crystal system, space groupOrthorhombic, Pbcn
Temperature (K)293
a, b, c (Å)14.052 (6), 10.192 (5), 14.047 (6)
V3)2011.8 (16)
Z4
Radiation typeCu Kα1, λ = 1.54056 Å
Specimen shape, size (mm)Flat_sheet, 20 × 20
Data collection
DiffractometerXPert PRO X-ray diffraction system
diffractometer
Specimen mountingThe powder was sprinkled on the sample holder using a small sieve. The thickness of the layer was no more than 0.1 mm.
Data collection modeReflection
Scan methodStep
2θ values (°)2θmin = 10 2θmax = 70 2θstep = 0.01
Refinement
R factors and goodness of fitRp = 0.083, Rwp = 0.114, Rexp = 0.086, χ2 = 1.742
No. of data points6001
No. of parameters64
No. of restraints74
H-atom treatmentH-atom parameters constrained

Computer programs: local program, LSPAID (Visser, 1986), MRIA (Zlokazov & Chernyshev, 1992), PLATON (Spek, 2000), MRIA, SHELXL97 (Sheldrick, 1997) and PARST (Nardelli, 1983).

Selected geometric parameters (Å, º) top
Zn—Cl12.238 (5)O1—N11.341 (16)
Zn—O11.979 (9)
O1—Zn—O1i107.9 (6)Cl1i—Zn—Cl1120.4 (2)
O1—Zn—Cl1107.8 (3)N1—O1—Zn114.0 (7)
O1i—Zn—Cl1106.2 (3)
Cl1—Zn—O1—N1135.0 (8)Zn—O1—N1—C290 (1)
Symmetry code: (i) x, y, z+1/2.
 

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