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Volume 67 
Part 7 
Pages o235-o240  
July 2011  

Received 25 March 2011
Accepted 6 June 2011
Online 17 June 2011

Planarity of heteroaryldithiocarbazic acid derivatives showing tuberculostatic activity. III. Mono- and diesters of 3-(pyrazin-2-ylcarbonyl)dithiocarbazic acid1

aInstitute of General and Ecological Chemistry, Technical University of Lódz, Poland, and bDepartment of Organic Chemistry, Medical University of Gdansk, Poland
Correspondence e-mail: marekglo@p.lodz.pl

Methyl 2-(pyrazin-2-ylcarbonyl)hydrazinecarbodithioate, C7H8N4OS2, (E1), N'-[bis(methylsulfanyl)methylidene]pyrazine-2-carbohydrazide, C8H10N4OS2, (F1), N'-[bis(methylsulfanyl)methylidene]-6-methoxypyrazine-2-carbohydrazide, C9H12N4O2S2, (F2), and methyl 1-methyl-2-(pyrazin-2-ylcarbonyl)hydrazinecarbodithioate, C8H10N4OS2, (G1), can be considered as derivatives of classical (thio)amide-type tuberculostatics, and all are moderately active against Mycobacterium tuberculosis. This study was undertaken in a search for relationships between activity and specific intramolecular interactions, especially conjugations and hydrogen-bond contacts, and the molecular structures were compared with respective amine analogues, also active against the pathogen. Despite the differences between the amine and carbonyl groups with opposite functions in the hydrogen bond, the two types of structure show a surprisingly similar planar geometry, mostly due to the conjugations aided by the bifurcated intramolecular hydrogen-bond contact between the N-H group of the central hydrazide group as donor and a pyrazine N atom and an S atom of the dithio function as acceptors. Planarity was suggested to be crucial for the tuberculostatic activity of these compounds. The N-methylated derivative (G1) showed a significant twist at the N-N bond [torsion angle = -121.9 (3)°] due to the methyl substitution, which precludes an intramolecular N-H...S contact and the planarity of the whole molecule. Nonetheless, the compound shows moderate tuberculostatic activity.

Comment

For many years, tuberculosis was considered a disease of the past, limited mainly to poor countries which could not afford expensive treatment, and this led to decreased interest in searching for more effective drugs. However, a more recent rise in mortality rates and the spread of the disease in developed countries, attributed to the emergence of multi-drug-resistant strains, have changed this attitude. The search for new lead compounds was continued by several groups, including that of Foks (Foks et al., 2000[Foks, H., Mieczkowska, J. & Sitarz, M. (2000). Phosphorus Sulfur Silicon Relat. Elem. 158, 107-116.]; Gobis, Foks, Zwolska & Augustynowicz-Kopec, 2006[Gobis, K., Foks, H., Zwolska, Z. & Augustynowicz-Kopec, E. (2006). Phosphorus Sulfur Silicon Relat. Elem. 181, 965-975.]; Gobis, Foks, Zuralska & Kedzia, 2006[Gobis, K., Foks, H., Zuralska, A. & Kedzia, A. (2006). Heterocycles, 68, 2615-2626.]), who synthesized several chemical classes of potential tuberculostatic agents, in particular those containing either pyrazin-2-yl-carbonimidoyldithiocarbazic acid esters, heteroaroylcarbonimidoyldithiocarbazate or heteroaroyldithiocarbazate systems. The compounds comprise molecular features present in the classical amide-type tuberculostatics, in particular heteroaroyl, amide and thioacid functions, such as in pyrazinamid, isoniazid and ethionamid (see Scheme 1[link]), which act through the formation of a covalent adduct with nicotinamide adenine dinucleotide (Wang et al., 2007[Wang, F., Langley, R., Gulten, G., Dover, L. G., Besra, G. S., Jacobs, W. R. Jr & Sacchettini, J. C. (2007). J. Exp. Med. 204, 73-78.]).

[Scheme 1]

Our earlier crystallographic studies of selected representatives of 3-[amino(pyrazin-2-yl)methylidene]thiocarbazic acid esters (see Scheme 2[link], formula A) showed that all of them maintained planarity of the whole molecule, except for the terminal aliphatic substituents (Glówka et al., 2005[Glówka, M. L., Martynowski, D., Olczak, A., Orlewska, C., Foks, H., Bojarska, J., Szczesio, M. & Golka, J. (2005). J. Chem. Crystallogr. 35, 477-480.]; Olczak et al., 2007[Olczak, A., Glówka, M. L., Golka, J., Szczesio, M., Bojarska, J., Kozlowska, K., Foks, H. & Orlewska, C. (2007). J. Mol. Struct. 830, 171-175.]; Orlewska et al., 2001[Orlewska, C., Foks, H., Sowinski, P., Martynowski, D., Olczak, A. & Glówka, M. L. (2001). Pol. J. Chem. 75, 1237-1245.]). The planarity observed in these structures was caused by extensive conjugation aided by a bifurcated intramolecular hydrogen-bond contact between the protonated atom N3 as a donor and two acceptors. One acceptor was a negatively charged S atom and the other was an ortho-positioned N atom of a pyrazine or pyridine ring on the other side of the donor (Scheme 2[link], formula A). The analysis of these data resulted in a working hypothesis that planarity of the molecules is a prerequisite for their tuberculostatic activity (Orlewska et al., 2001[Orlewska, C., Foks, H., Sowinski, P., Martynowski, D., Olczak, A. & Glówka, M. L. (2001). Pol. J. Chem. 75, 1237-1245.]).

Next, we showed that similar planarity was maintained in compounds lacking an H atom at N3, such as the dithioesters (formula B in Scheme 2[link]), due to conjugation, and, except in thioesters (formula A), an intramolecular N-H...N contact was maintained between the same ortho N atom of the reversed pyridine (or pyrazine) ring as acceptor and the N5 amine group as donor. The overall planarity was lost only in the case of N2 substitution in an appropriate monoester (formula C in Scheme 2[link]) (Olczak et al., 2011[Olczak, A., Szczesio, M., Golka, J., Orlewska, C., Gobis, K., Foks, H. & Glówka, M. L. (2011). Acta Cryst. C67, o37-o42.]).

[Scheme 2]

The compounds described here represent both S-monothioesters [(E1)[link] and (G1)[link]] and S,S'-dithioesters [(F1)[link] and (F2)[link]] of heteroaroyldithiocarbazic acids (see Scheme 3[link] and Figs. 1[link]-4[link][link][link]), in which an aryl-C(NH2)=N- function present in the former study (Olczak et al., 2011[Olczak, A., Szczesio, M., Golka, J., Orlewska, C., Gobis, K., Foks, H. & Glówka, M. L. (2011). Acta Cryst. C67, o37-o42.]) has been replaced by a 2-pyrazine-C(O)-NH- function. Thus, the compounds may be considered derivatives of the well known tuberculostatic pyrazinamid (Scheme 1[link]). Despite the significant differences between these compounds and their amine analogues A, B and C (Scheme 2[link]), we supposed that, due to the presence of an H atom at N3 in compounds (E1)[link], (F1)[link] and (F2)[link], an analogous intramolecular hydrogen-bond contact will be formed as in the N-H heteroarylcarbamidoyl hydrazinium cation (compound A in Scheme 2[link]). As a result, the molecules should be planar and the compounds may show similar antibacterial activity.

[Scheme 3]

In addition, we included in this study compound (G1)[link] (with a methyl substituent at atom N2), which was unable to maintain planarity of the whole molecule due to spatial repulsion between this methyl group and the carbonyl group (see Scheme 2[link]). As the compound showed some tuberculostatic activity, it was important to examine changes in its molecular structure. The question concerning planarity could not be answered by simple inspection of the Cambridge Structural Database (CSD, Version 5.32; Allen, 2002[Allen, F. H. (2002). Acta Cryst. B58, 380-388.]), as among about 20 structures comprising esters of heteroaroyldithiocarbazic acid, N2-substituted derivatives are not present. Structures in which the N atom is incorporated into the pyrazine or pyridine ring at the ortho position, thus playing an important role of acceptor in an N3-H...N(aryl) intramolecular hydrogen-bond contact, are similarly absent.

As we expected, the molecules of compounds (E1)[link], (F1)[link] and (F2)[link] are planar except for the terminal ester group, while the molecule of (G1)[link] shows a twist at the N-N bond (Fig. 4[link]) caused by spatial repulsion introduced by the methyl group at N2. Thus, we suppose that the main factor responsible for planarity is conjugation from the aryl ring to the thio group. Conjugation along the C1=N2-N3-C4-C41 chain in (F1)[link] and (F2)[link], or along the S=C1-N2-N3-C4-C41 chain in (E1)[link], is confirmed by both the values of the respective torsion angles in these fragments, all being close to 180°, and the shortening of the formally single bonds N3-C4 and C4-C41 (Table 5[link]).

Due to the overall planarity of the molecules of (E1)[link], (F1)[link] and (F2)[link], there are two short intramolecular hydrogen-bond contacts, both with the N3-H group as the donor (see Scheme 2[link] and Tables 1[link]-4[link][link][link]). The first contact, N3-H...N(pyrazine), is observed in all compounds studied here having an N3-H group, including (G1)[link]. The H...N distances and N-H...N angles are in the ranges 2.21-2.28 Å and 107-110°, respectively (Table 6[link]). Similar contacts are observed in N-substituted picolinamides found in the CSD, i.e. 2.15-2.32 Å and 100-116°. The other intramolecular contact is that of N3-H...S, with H...S distances between 2.42 and 2.55 Å and N-H...S angles between 108 and 113° (Table 6[link]). The values agree well with those found in similar molecules in the CSD (2.37-2.61 Å and 107-113°). The exception is structure (G1)[link], in which substitution at atom N2 twists the molecule (see Scheme 2[link]) and makes an intramolecular N3-H...S contact impossible.

There are some doubts concerning the structural significance of these contacts (Table 6[link]), mostly due to the commonly accepted view that hydrogen bonds with D-H...A angles below 120° do not contribute substantially to the stabilization energy of the structure (Wood et al., 2009[Wood, P. A., Allen, F. H. & Pidcock, E. (2009). CrystEngComm, 11, 1563-1571.]). However, the value of 120° refers to intermolecular hydrogen bonds, while in this study we are concerned with intramolecular systems. In the crystallographic literature, arrangements similar to that formed by the N3-H...N contact (i.e. five-membered ring motifs) were discussed by Bilton et al. (2000[Bilton, C., Allen, F. H., Shields, G. P. & Howard, J. A. K. (2000). Acta Cryst. B56, 849-856.]) and Galek et al. (2010[Galek, P. T. A., Fábián, L. & Allen, F. H. (2010). Acta Cryst. B66, 237-252.]), who found for them a probability of formation of over 70% and an average hydrogen-bond angle of only 109°. Less is known about N-H...S arrangements similar to those present in the structures described in this study. However, it seems from our data (Table 6[link]), and from a couple of examples comprising a five-membered intramolecular N-H...S motif which were found in the CSD, that N3-H...S contacts are geometrically less stressed than N3-H...N ones. Consequently, we believe that both the N3-H...N and N3-H...S close contacts observed in this study may be considered intramolecular resonance-assisted hydrogen bonds of some structural significance. The bonds aid conjugation along the main molecular chain to maintain planarity of the whole molecule, except for the terminal substituents of the ester group.

The molecular packing in (E1)[link], (F1)[link] and (F2)[link] is determined mainly by their planarity (Fig. 1[link] and Figs. 5[link]-6[link]) and relatively weak intermolecular hydrogen bonds. In the diesters (F1)[link] and (F2)[link], there is only one weak C-H...O interaction in each structure. In (F1)[link], C44-H...O5(x - 1, y, z) hydrogen bonds join the molecules into infinite C(7) chains parallel to the [100] direction, while in (F2)[link] the molecules form dimers - R22(10) rings according to the graph-set definition of Bernstein et al. (1995[Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555-1573.]) - through C46-H...O5(-x + 1, y, [{3\over 2}] - z) hydrogen bonds. In ester (E1)[link], which comprises one hydrogen-bond donor group, N2-H, in each of the three independent molecules, the intermolecular interactions are more complicated. Molecules B and C are connected by N2B-H...O5C and N2C-H...O5B hydrogen bonds (Table 1[link]), joining molecules into approximately coplanar dimers in which R22(10) rings are present. Molecules A and B are connected into asymmetric dimers (Fig. 1[link]) by C44B-H...O5A and N2A-H...N45B hydrogen bonds, forming R22(8) rings. In the N'-methylated ester (G1)[link], one weak intermolecular C43-H...O5(x - 1, y - 1, z) hydrogen bond is observed (Table 4[link]). The bonds join the molecules into infinite C(6) chains running parallel to the [110] direction. In addition, an intermolecular N3-H3...S1(x - 1, y, z) short contact may be considered a weak hydrogen bond (Fig. 7[link]).

[Figure 1]
Figure 1
The molecular structure of (E1)[link], showing the atom-numbering scheme. Intermolecular hydrogen bonds determining the packing of the molecules in the crystal structure are indicated as dashed lines. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 2]
Figure 2
The molecular structure of (F1)[link], showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 3]
Figure 3
The molecular structure of (F2)[link], showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 4]
Figure 4
The molecular structure of (G1)[link], showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 5]
Figure 5
The intermolecular hydrogen-bond contact (dotted line) of (F1)[link] determining the packing of the molecules in the crystal structure. [Symmetry code: (i) x - 1, y, z.]
[Figure 6]
Figure 6
The intermolecular hydrogen-bond contacts (dotted lines) of (F2)[link] determining the packing of the molecules in the crystal structure. [Symmetry code: (i) -x + 1, y, -z + [{3\over 2}].]
[Figure 7]
Figure 7
The intermolecular hydrogen-bond contacts (dotted lines) of (G1)[link] determining the packing of the molecules in the crystal structure. [Symmetry codes: (i) x - 1, y, z; (ii) x - 1, y - 1, z.]

Experimental

The syntheses of the title compounds were described by Foks et al. (2000[Foks, H., Mieczkowska, J. & Sitarz, M. (2000). Phosphorus Sulfur Silicon Relat. Elem. 158, 107-116.]) for (E1)[link] and (F1)[link], by Gobis, Foks, Zwolska & Augustynowicz-Kopec (2006[Gobis, K., Foks, H., Zwolska, Z. & Augustynowicz-Kopec, E. (2006). Phosphorus Sulfur Silicon Relat. Elem. 181, 965-975.]) for (G1)[link], and by Gobis, Foks, Zuralska & Kedzia (2006[Gobis, K., Foks, H., Zuralska, A. & Kedzia, A. (2006). Heterocycles, 68, 2615-2626.]) for (F2)[link]. Single crystals of compounds (E1)[link], (F1)[link], (F2)[link] and (G1)[link] suitable for X-ray diffraction were obtained from chloroform-ethanol (1:1 v/v), dioxane, ethanol and ethanol solutions, respectively, by slow evaporation of the solvents at room temperature.

Compound (E1)[link]

Crystal data
  • C7H8N4OS2

  • Mr = 228.29

  • Triclinic, [P \overline 1]

  • a = 7.2326 (3) Å

  • b = 12.7207 (4) Å

  • c = 17.7516 (5) Å

  • [alpha] = 77.877 (3)°

  • [beta] = 79.096 (3)°

  • [gamma] = 73.968 (4)°

  • V = 1519.67 (9) Å3

  • Z = 6

  • Mo K[alpha] radiation

  • [mu] = 0.50 mm-1

  • T = 295 K

  • 0.3 × 0.2 × 0.05 mm

Data collection
  • Kuma KM-4 CCD area-detector diffractometer

  • Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2010[Oxford Diffraction (2010). CrysAlis PRO. Version 1.171.33.66. Oxford Diffraction Ltd, Yarnton, Oxfordshire, England.]) Tmin = 0.876, Tmax = 1.000

  • 18215 measured reflections

  • 6187 independent reflections

  • 4162 reflections with I > 2[sigma](I)

  • Rint = 0.021

Refinement
  • R[F2 > 2[sigma](F2)] = 0.035

  • wR(F2) = 0.094

  • S = 1.00

  • 6187 reflections

  • 382 parameters

  • H-atom parameters constrained

  • [Delta][rho]max = 0.23 e Å-3

  • [Delta][rho]min = -0.20 e Å-3

Table 1
Hydrogen-bond geometry (Å, °) for (E1)[link]

D-H...A D-H H...A D...A D-H...A
N2A-H2A...N45B 0.86 2.13 2.987 (2) 174
C44B-H44B...O5A 0.93 2.36 3.061 (2) 132
N2B-H2B...O5C 0.86 1.94 2.790 (2) 172
N2C-H2C...O5B 0.86 2.00 2.850 (2) 170

Compound (F1)[link]

Crystal data
  • C8H10N4OS2

  • Mr = 242.32

  • Monoclinic, P 21 /c

  • a = 7.8332 (2) Å

  • b = 21.0883 (4) Å

  • c = 7.3920 (2) Å

  • [beta] = 116.121 (4)°

  • V = 1096.36 (5) Å3

  • Z = 4

  • Mo K[alpha] radiation

  • [mu] = 0.46 mm-1

  • T = 297 K

  • 0.2 × 0.1 × 0.05 mm

Data collection
  • Kuma KM-4 CCD area-detector diffractometer

  • Absorption correction: multi-scan (CrysAlis PRO; Oxford Diffraction, 2010[Oxford Diffraction (2010). CrysAlis PRO. Version 1.171.33.66. Oxford Diffraction Ltd, Yarnton, Oxfordshire, England.]) Tmin = 0.946, Tmax = 1.000

  • 12975 measured reflections

  • 2236 independent reflections

  • 1960 reflections with I > 2[sigma](I)

  • Rint = 0.015

Refinement
  • R[F2 > 2[sigma](F2)] = 0.031

  • wR(F2) = 0.087

  • S = 1.07

  • 2236 reflections

  • 139 parameters

  • H-atom parameters constrained

  • [Delta][rho]max = 0.26 e Å-3

  • [Delta][rho]min = -0.20 e Å-3

Table 2
Hydrogen-bond geometry (Å, °) for (F1)[link]

D-H...A D-H H...A D...A D-H...A
C44-H44...O5i 0.93 2.59 3.219 (2) 125
Symmetry code: (i) x-1, y, z.

Compound (F2)[link]

Crystal data
  • C9H12N4O2S2

  • Mr = 272.35

  • Monoclinic, C 2/c

  • a = 23.111 (2) Å

  • b = 7.5812 (7) Å

  • c = 15.6547 (14) Å

  • [beta] = 115.430 (2)°

  • V = 2477.1 (4) Å3

  • Z = 8

  • Mo K[alpha] radiation

  • [mu] = 0.43 mm-1

  • T = 270 K

  • 0.5 × 0.2 × 0.1 mm

Data collection
  • Bruker SMART APEX CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 2003[Sheldrick, G. M. (2003). SADABS. Version 2.10. University of Göttingen, Germany.]) Tmin = 0.516, Tmax = 1.000

  • 27591 measured reflections

  • 3051 independent reflections

  • 2351 reflections with I > 2[sigma](I)

  • Rint = 0.043

Refinement
  • R[F2 > 2[sigma](F2)] = 0.043

  • wR(F2) = 0.126

  • S = 1.03

  • 3051 reflections

  • 157 parameters

  • H-atom parameters constrained

  • [Delta][rho]max = 0.41 e Å-3

  • [Delta][rho]min = -0.41 e Å-3

Table 3
Hydrogen-bond geometry (Å, °) for (F2)[link]

D-H...A D-H H...A D...A D-H...A
C46-H46...O5i 0.93 2.53 3.385 (3) 153
Symmetry code: (i) [-x+1, y, -z+{\script{3\over 2}}].

Compound (G1)[link]

Crystal data
  • C8H10N4OS2

  • Mr = 242.32

  • Monoclinic, P 21

  • a = 4.0900 (4) Å

  • b = 6.4482 (6) Å

  • c = 20.7828 (19) Å

  • [beta] = 91.151 (2)°

  • V = 548.00 (9) Å3

  • Z = 2

  • Mo K[alpha] radiation

  • [mu] = 0.47 mm-1

  • T = 290 K

  • 0.35 × 0.2 × 0.1 mm

Data collection
  • Bruker SMART APEX CCD area-detector diffractometer

  • Absorption correction: multi-scan (SADABS; Sheldrick, 2003[Sheldrick, G. M. (2003). SADABS. Version 2.10. University of Göttingen, Germany.]) Tmin = 0.716, Tmax = 1.000

  • 12608 measured reflections

  • 2642 independent reflections

  • 2523 reflections with I > 2[sigma](I)

  • Rint = 0.023

Refinement
  • R[F2 > 2[sigma](F2)] = 0.046

  • wR(F2) = 0.123

  • S = 1.10

  • 2642 reflections

  • 138 parameters

  • 1 restraint

  • H-atom parameters constrained

  • [Delta][rho]max = 0.68 e Å-3

  • [Delta][rho]min = -0.21 e Å-3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), with 1175 Friedel pairs

  • Flack parameter: 0.18 (11)

Table 4
Hydrogen-bond geometry (Å, °) for (G1)[link]

D-H...A D-H H...A D...A D-H...A
N3-H3...S1i 0.86 2.85 3.473 (3) 131
C43-H43...O5ii 0.93 2.37 3.297 (4) 179
Symmetry codes: (i) x-1, y, z; (ii) x-1, y-1, z.

Table 5
Selected bond lengths (Å) and torsion angles (°) for the title compounds

Structure N2-N3 N3-C4 C4-C41 C1-N2-N3-C4
(E1)[link] 1.377 (2) 1.338 (2) 1.494 (3) 176.6 (2)
(E1)[link] 1.372 (2) 1.333 (2) 1.493 (2) -178.79 (19)
(E1)[link] 1.382 (2) 1.322 (3) 1.498 (3) 179.6 (2)
(F1)[link] 1.3785 (17) 1.344 (2) 1.502 (2) 177.07 (15)
(F2)[link] 1.3839 (19) 1.342 (2) 1.499 (2) -177.06 (16)
(G1)[link] 1.395 (3) 1.341 (4) 1.497 (4) -121.9 (3)

Table 6
Intramolecular hydrogen-bond contact geometry (Å, °) for the title compounds

N3-H3...N42 H...N N...N N-H...N
(E1)[link] 2.25 2.641 (2) 108
(E1)[link] 2.25 2.648 (2) 109
(E1)[link] 2.27 2.663 (3) 108
(F1)[link] 2.21 2.625 (2) 110
(F2)[link] 2.25 2.652 (2) 108
(G1)[link] 2.28 2.666 (4) 107
       
N3-H3...S H...S N...S N-H...S
(E1)[link] 2.54 2.9228 (18) 108
(E1)[link] 2.50 2.9031 (16) 109
(E1)[link] 2.55 2.9305 (19) 108
(F1)[link] 2.43 2.8775 (14) 113
(F2)[link] 2.42 2.8587 (18) 112

H atoms were located in difference Fourier maps and subsequently geometrically optimized and allowed for as riding atoms, with C-H = 0.95 Å for aromatic CH groups, 0.97 Å for secondary CH2 groups and 0.96 Å for methyl groups, and N-H = 0.86 Å, and with Uiso(H) = 1.2Ueq(C,N). For (G1)[link], the precision of the Flack x parameter [Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]); x = 0.18 (11)], whether calculated by the `hole-in-one' method or using TWIN/BASF in SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]), indicated that the structure was correctly oriented with respect to the polar-axis direction, but was too imprecise to rule out the possibility of partial inversion twinning. However, the value of the Hooft y parameter [Hooft et al. (2008[Hooft, R. W. W., Straver, L. H. & Spek, A. L. (2008). J. Appl. Cryst. 41, 96-103.]); y = 0.20 (2)] certainly suggests that partial inversion twinning is present.

Data collection: CrysAlis CCD (Oxford Diffraction, 2007[Oxford Diffraction (2007). CrysAlis CCD and CrysAlis RED. Versions 1.171. Oxford Diffraction Ltd, Abingdon, Oxfordshire, England.]) for (E1)[link] and (F1)[link]; APEX2 (Bruker, 2002[Bruker (2002). APEX2. Bruker AXS Inc., Madison, Wisconsin, USA.]) for (F2)[link] and (G1)[link]. Cell refinement: CrysAlis RED (Oxford Diffraction, 2007[Oxford Diffraction (2007). CrysAlis CCD and CrysAlis RED. Versions 1.171. Oxford Diffraction Ltd, Abingdon, Oxfordshire, England.]) for (E1)[link] and (F1)[link]; SAINT-Plus (Bruker, 2003[Bruker (2003). SAINT-Plus (Version 6.45) and SMART (Version 5.629). Bruker AXS Inc., Madison, Wisconsin, USA.]) for (F2)[link] and (G1)[link]. Data reduction: CrysAlis RED for (E1)[link] and (F1)[link]; SAINT-Plus for (F2)[link] and (G1)[link]. For all compounds, 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.]) for (E1)[link] and (G1)[link]; SHELXTL (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]) for (F1)[link] and (F2)[link]. For all compounds, molecular graphics: PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]) and Mercury (Macrae et al., 2008[Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P., Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood, P. A. (2008). J. Appl. Cryst. 41, 466-470.]); software used to prepare material for publication: PLATON.


Supplementary data for this paper are available from the IUCr electronic archives (Reference: GD3386 ). Services for accessing these data are described at the back of the journal.


Acknowledgements

This study was supported by the Ministry of Science and Higher Education under project No. N204 111735.

References

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Acta Cryst (2011). C67, o235-o240   [ doi:10.1107/S0108270111021767 ]