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Journal logoSTRUCTURAL
CHEMISTRY
ISSN: 2053-2296

Two tautomeric polymorphs of 2,6-di­chloro­purine

aDepartamento de Química Farmacéutica y Orgánica, Facultad de Farmacia, Universidad de Granada, Campus de Cartuja s/n, 18071 Granada, Spain, and bLaboratorio de Estudios Cristalográficos, IACT, CSIC-Universidad de Granada, Avenida de las Palmeras 4, 18100 Armilla, Granada, Spain
*Correspondence e-mail: jmcampos@ugr.es

(Received 19 September 2011; accepted 20 October 2011; online 5 November 2011)

Two polymorphs of 2,6-dichloro­purine, C5H2Cl2N4, have been crystallized and identified as the 9H- and 7H-tautomers. Despite differences in the space group and number of symmetry-independent mol­ecules, they exhibit similar hydrogen-bonding motifs. Both crystal structures are stabilized by inter­molecular N—H⋯N inter­actions that link adjacent mol­ecules into linear chains, and by some nonbonding contacts of the C—Cl⋯π type and by ππ stacking inter­actions, giving rise to a crossed two-dimensional herringbone packing motif. The main structural difference between the two polymorphs is the different role of the mol­ecules in the ππ stacking inter­actions.

Comment

2,6-Dichloro­purine is an important pharmaceutical inter­mediate (Schaefer et al., 1978[Schaefer, H. J., Beauchamp, L., de Miranda, P., Elion, G. B., Bauer, D. J. & Collins, P. (1978). Nature (London), 272, 583-585.]) used in the preparation of purine nucleosides and nucleotides, and other purine derivatives of great importance owing to their biological properties (Nair & Pal, 1998[Nair, V. & Pal, S. (1998). Int. Patent WO 9817781.]; Rao Kode & Phadtare, 2011[Rao Kode, N. & Phadtare, S. (2011). Molecules, 16, 5840-5860.]).

[Scheme 1]

Polymorphism, the ability of a given mol­ecule to crystallize in different crystal structures, is a phenomenon often observed for organics (Bernstein, 2011[Bernstein, J. (2011). Cryst. Growth Des. 11, 632-650.]; Brittain, 2011[Brittain, H. G. (2011). J. Pharm. Sci. 100, 1260-1279.]). The term `tautomeric polymorphs' refers to those tautomers of a given compound that crystallize in different crystal structures and they are very rarely observed (Cruz Cabeza et al., 2011[Cruz Cabeza, A. J. & Groom, C. (2011). CrystEngComm, 13, 93-98.]). We present here the crystal structure of the 9H-, (I)[link], and 7H-, (II)[link], tautomers of 2,6-dichloro­purine.

The mol­ecular geometric parameters in the two presented polymorphs are similar, but the structures differ in the finer details of their crystal packing. As shown in Fig. 1[link], polymorph (I)[link] crystallizes with two independent mol­ecules in the asymmetric unit (A and B, top and middle) as the 9H-tautomer, while polymorph (II)[link] crystallizes with one symmetry-independent mol­ecule (bottom) as the 7H-tautomer.

The effect of the different –N(H) position in the tautomeric forms (N9 or N7) gives rise to subtle differences between the relevant bond lengths and angles in both structures in the imidazole ring. In (I)[link], the N=Csp2 bond corresponds to N7—C8 [1.310 (5) Å] and N17—C18 [1.307 (5) Å] for mol­ecules A and B, respectively, while in (II)[link] it is N9—C8 [1.327 (3) Å]. These N=Csp2 bond lengths are comparable with those in related structures with 9H- (Mahapatra et al., 2008[Mahapatra, S., Nayak, S. K., Prathapa, S. J. & Guru Row, T. N. (2008). Cryst. Growth Des. 8, 1223-1225.]; Trávníček & Rosenker, 2006[Trávníček, Z. & Rosenker, C. J. (2006). Acta Cryst. E62, o3393-o3395.]; Soriano-Garcia & Parthasarathy, 1977[Soriano-Garcia, M. & Parthasarathy, R. (1977). Acta Cryst. B33, 2674-2677.]) and 7H-tautomers (Bo et al., 2006[Bo, Y., Cheng, K., Bi, S. & Zhang, S.-S. (2006). Acta Cryst. E62, o4174-o4175.]; Ikonen et al., 2009[Ikonen, S., Valkonen, A. & Kolehmainen, E. (2009). J. Mol. Struct. 930, 147-156.]; Watson et al., 1965[Watson, D. G., Sweet, R. M. & Marsh, R. E. (1965). Acta Cryst. 19, 573-580.]). The –N(H) tautomeric position is also evident from the greater ring angle at the site where the H atom is attached, namely N9 [C4—N9—C8 = 105.9 (3)°] and N19 [C14—N19—C18 = 105.6 (3)°] for (I)[link], and N7 [C5—N7—C8 = 105.9 (2)°] for (II)[link], compared with the ring angle involving the –N=C– bond [for (I)[link], C5—N7—C8 = 103.6 (3)° and C15—N17—C18 = 103.8 (3)°; for (II)[link], C4—N9—C8 = 103.6 (2)°]. In both polymorphs, the 2,6-dichloro­purine mol­ecules form linear chains along the b axis through inter­molecular N—H⋯N inter­actions forming C(4) motifs (Bernstein et al., 1995[Bernstein, J., Davis, R. E., Shimoni, L. & Chang, N.-L. (1995). Angew. Chem. Int. Ed. Engl. 34, 1555-1573.]).

In polymorph (I)[link], chains built by mol­ecules of type A are linked by inter­molecular face-to-face ππ stacking inter­actions involving the N1/C2/N3/C4–C6 ring and a symmetry-related counterpart at (−x + 1, −y + 1, −z + 1), with a centroid–centroid distance of 3.493 (3) Å. Mol­ecules of type B are not involved in ππ stacking inter­actions. There are also C—Cl⋯π inter­actions involving atom Cl16 and ring N1/C2/N3/C4–C6 (Cg1I), with a Cl⋯centroid distance of 3.468 (2) Å and a C16—Cl16⋯Cg1Ii angle of 113.46 (17)° [symmetry code: (i) x, −y + [{1\over 2}], z + [{1\over 2}]], and atom Cl6 and ring N11/C12/N13/C14–C16 (Cg2I), with a Cl⋯centroid distance of 3.664 (2) Å and a C6—Cl6⋯Cg2I angle of 94.54 (13)°, resulting in a structure containing a two-dimensional herringbone-like motif of constituent mol­ecules.

The crystal structure of polymorph (II)[link] is similar to that of polymorph (I)[link]. Despite the fact that ππ stacking inter­actions are not observed in (II)[link], the supra­molecular structure features a similar herringbone motif to that in (I)[link], due to the presence of C—Cl⋯π inter­actions between atom Cl6 and ring N1/C2/N3/C4–C6 (Cg1II), with a Cl⋯centroid distance of 3.3471 (15) Å and a C6—Cl6⋯Cg1IIii angle of 108.45 (10)° [symmetry code: (ii) x − [{1\over 2}], −y + [{3\over 2}], −z + 1]. As a consequence of the absence of stacking inter­actions in (II)[link], the width of the herringbone motif (12.352 Å) is greater than that of (I)[link] (11.797 Å) (Fig. 2[link]) [the width of the motifs was calculated as the distance between the two planes containing the furthermost atoms in the herringbone motif, corresponding to the Cl atoms of 2,6-dichloropurine; 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.])].

[Figure 1]
Figure 1
The contents of the asymmetric units of polymorph (I)[link] (top and middle) and polymorph (II)[link] (bottom), showing the atom-numbering schemes. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 2]
Figure 2
A view of the crystal packing, showing the herringbone arrangement of 2,6-dichloro­purine mol­ecules in polymorph (I)[link] (left) and polymorph (II)[link] (right).

Experimental

Polymorph (I)[link] (m.p. 466.05–466.75 K) was obtained unintentionally in an attempted synthesis of (RS)-2,6-dichloro-9-(2,3-dihydro-1,4-benzoxathiin-3-ylmeth­yl)-9H-purine (Díaz-Gavilán et al., 2008[Díaz-Gavilán, M., Conejo-García, A., Cruz-López, O., Núñez, M. C., Choquesillo-Lazarte, D., González-Pérez, J. M., Rodríguez-Serrano, F., Marchal, J. A., Aránega, A., Gallo, M. A., Espinosa, A. & Campos, J. M. (2008). ChemMedChem, 3, 127-135.]). Unreacted 2,6-dichloro­purine was recovered using ethyl acetate as eluent. After concentrating the solvent under reduced pressure, suitable crystals of 2,6-dichloro­purine were obtained after dissolving the compound in CH2Cl2. A vial with a screw top allowed slow evaporation of the solvent at room temperature to produce colourless crystals. Crystals of polymorph (II)[link] (m.p. 467.95–468.85 K) were obtained by solvent evaporation with commercially available 2,6-di­chloro­purine using ethanol as solvent. The remarkable similarity of the crystal structures of the reported polymorphs yields minimal differences in the shape and position of the peaks in the FT–IR spectra (polycrystalline samples in KBr disks). Hence, the stretching mode ν(N—H) (a weak peak at 3210 cm−1) and the in-plane deformation mode δ(N—H) (1513 cm−1) appear at the same site in (I)[link] and (II)[link].

Polymorph (I)[link]

Crystal data
  • C5H2Cl2N4

  • Mr = 189.01

  • Monoclinic, P 21 /c

  • a = 14.0867 (12) Å

  • b = 9.4898 (7) Å

  • c = 12.2656 (9) Å

  • β = 115.381 (4)°

  • V = 1481.4 (2) Å3

  • Z = 8

  • Cu Kα radiation

  • μ = 7.36 mm−1

  • T = 296 K

  • 0.12 × 0.10 × 0.06 mm

Data collection
  • Bruker X8 Proteum diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2001[Bruker (2001). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.377, Tmax = 0.753

  • 18199 measured reflections

  • 2547 independent reflections

  • 1713 reflections with I > 2σ(I)

  • Rint = 0.085

Refinement
  • R[F2 > 2σ(F2)] = 0.051

  • wR(F2) = 0.154

  • S = 1.10

  • 2547 reflections

  • 199 parameters

  • H-atom parameters constrained

  • Δρmax = 0.27 e Å−3

  • Δρmin = −0.29 e Å−3

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

D—H⋯A D—H H⋯A DA D—H⋯A
N9—H9⋯N7i 0.86 1.96 2.785 (4) 161
N19—H19⋯N17ii 0.86 1.94 2.768 (5) 160
Symmetry codes: (i) [-x+1, y+{\script{1\over 2}}, -z+{\script{1\over 2}}]; (ii) [-x+2, y+{\script{1\over 2}}, -z+{\script{3\over 2}}].

Polymorph (II)[link]

Crystal data
  • C5H2Cl2N4

  • Mr = 189.01

  • Orthorhombic, P 21 21 21

  • a = 5.5716 (9) Å

  • b = 9.5820 (16) Å

  • c = 13.159 (2) Å

  • V = 702.5 (2) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.85 mm−1

  • T = 120 K

  • 0.12 × 0.10 × 0.08 mm

Data collection
  • Bruker SMART APEX diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2001[Bruker (2001). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.905, Tmax = 0.935

  • 6847 measured reflections

  • 1243 independent reflections

  • 1156 reflections with I > 2σ(I)

  • Rint = 0.041

Refinement
  • R[F2 > 2σ(F2)] = 0.033

  • wR(F2) = 0.071

  • S = 1.38

  • 1243 reflections

  • 100 parameters

  • H-atom parameters constrained

  • Δρmax = 0.33 e Å−3

  • Δρmin = −0.22 e Å−3

  • Absolute structure: Flack (1983[Flack, H. D. (1983). Acta Cryst. A39, 876-881.]), with 489 Friedel pairs

  • Flack parameter: 0.03 (10)

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

D—H⋯A D—H H⋯A DA D—H⋯A
N7—H7⋯N9i 0.94 1.88 2.774 (3) 158
Symmetry code: (i) [-x+1, y+{\script{1\over 2}}, -z+{\script{3\over 2}}].

H atoms on N atoms were located in difference maps and refined as riding, with N—H = 0.86 [in (I)] and 0.94 Å [in (II)], and Uiso(H) = 1.2Ueq(N). Other H atoms were positioned geometrically and treated as riding, with C—H = 0.93–0.95 Å and Uiso(H) = 1.2Ueq(C).

For both compounds, data collection: APEX2 (Bruker, 2010[Bruker (2010). APEX2 and SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2010[Bruker (2010). APEX2 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: PLATON (Spek, 2009[Spek, A. L. (2009). Acta Cryst. D65, 148-155.]); software used to prepare material for publication: publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information


Comment top

2,6-Dichloropurine is an important pharmaceutical intermediate (Schaefer et al., 1978) used in the preparation of purine nucleosides and nucleotides, as well as other purine derivatives of great importance, owing to their biological properties (Nair & Pal, 1998; Rao Kode & Phadtare, 2011).

Polymorphism, the ability of a given molecule to crystallize in different crystal structures, is a phenomenon often observed for organics (Bernstein, 2011; Brittain, 2011). The term `tautomeric polymorphs' refers to those tautomers of a given compound that crystallize in different crystal structures and are very rarely observed (Cruz Cabeza et al., 2011). We present here the crystal structure of the 9H-, (I), and 7H-, (II), tautomers of 2,6-dichloropurine.

The molecular geometric parameters in the two presented polymorphs are similar, but the structures differ in the finer details of their crystal packing. As shown in Fig. 1, polymorph (I) crystallizes with two independent molecules in the asymmetric unit (A and B, top and middle) as the 9H- tautomer, while polymorph (II) crystallizes with one symmetry-independent molecule (bottom) as the 7H- tautomer.

The effect of the different –N(H) position in the tautomeric forms (N9 or N7) gives rise to subtle differences between the relevant bond lengths and angles in both structures in the imidazole ring. In (I), the NCsp2 bond corresponds to N7—C8 [1.310 (5) Å] and N17—C18 [1.307 (5) Å] for molecules A and B, respectively, while in (II) it involves N9—C8 [1.327 (3) Å]. These NCsp2 bond lengths are comparable with those in related structures with 9H- (Mahapatra et al., 2008; Trávníček & Rosenker, 2006; Soriano-Garcia & Parthasarathy, 1977) and 7H- tautomers (Bo et al., 2006; Ikonen et al., 2009; Watson et al., 1965). The –N(H) tautomeric position is also evident from the greater ring angle at the site where the H atom is attached, namely N9 [C4/N9/C8 105.9 (3)°] and N19 [C14/N19/C18 105.6 (3)°] for (I) and N7 [C5/N7/C8 105.9 (2)°] for (II), compared with the ring angle involving the –NC– bond [for (I), C5—N7—C8 = 103.6 (3)° and C15—N17—C18 = 103.8 (3)°; for (II), C4—N9—C8 = 103.6 (2)°]. In both polymorphs, the 2,6-dichloropurine molecules form linear chains along the b axis through intermolecular N—H···N interactions with C(4) motifs (Bernstein et al., 1995).

In polymorph (I), chains built by molecules of type A are linked by intermolecular face-to-face ππ stacking interactions involving ring N1/C2/N3/C4–C6 and a symmetry-related ring (symmetry code: -x + 1, y + 1, -z + 1), with a centroid-to-centroid distance of 3.493 (3) Å. Molecules of type B are not involved in ππ stacking interactions. There are also C—Cl···π interactions involving atom Cl16 and ring N1/C2/N3/C4–C6 (Cg1I), with a Cl···centroid distance of 3.468 (2) Å and a C16—Cl16···Cg1iI angle of 113.46 (17)° [symmetry code: (i) x, -y + 1/2, z + 1/2], and atom Cl6 and ring N11/C12/N13/C14–C16 (Cg2I), with a Cl···centroid distance of 3.664 (2) Å and a C6—Cl6···Cg2I angle of 94.54 (13)°, resulting in a structure containing a two-dimensional herringbone-like motif of constituent molecules.

The crystal structure of polymorph (II) is similar to that of polymorph (I). Despite the fact that ππ stacking interactions are not observed in (II), the supramolecular structure features a similar herringbone motif to that in (I), due to the presence of C—Cl···π interactions between atom Cl6 and ring N1/C2/N3/C4–C6 (Cg1II), with a Cl···centroid distance of 3.3471 (15) Å and a C6—Cl6···Cg1iiII angle of 108.45 (10)° [symmetry code: (ii) x - 1/2, -y + 3/2, -z + 1]. As a consequence of the absence of stacking interactions in (II), the width of the herringbone motif (12.352 Å) is greater than that of (I) (11.797 Å) (Fig. 2).

Related literature top

For related literature, see: Bernstein (2011); Bernstein et al. (1995); Bo et al. (2006); Brittain (2011); Cruz & Groom (2011); Díaz-Gavilán, Conejo-García, Cruz-López, Núñez, Choquesillo-Lazarte, González-Pérez, Rodríguez-Serrano, Marchal, Aránega, Gallo, Espinosa & Campos (2008); Ikonen et al. (2009); Mahapatra et al. (2008); Nair & Pal (1998); Rao & Phadtare (2011); Schaefer et al. (1978); Soriano-Garcia & Parthasarathy (1977); Trávníček & Rosenker (2006); Watson et al. (1965).

Experimental top

Polymorph (I) (m.p. 466.05–466.75 K) was obtained unintentionally in an attempted synthesis of (RS)-2,6-dichloro-9-(2,3-dihydro-1,4-benzoxathiin-3-ylmethyl)-9H-purine (Díaz-Gavilán et al., 2008). Unreacted 2,6-dichloropurine was recovered using ethyl acetate as eluent. After concentrating the solvent under reduced pressure, suitable crystals of 2,6-dichloropurine were obtained after dissolving the compound in CH2Cl2. A vial with a screw top allowed the slow evaporation of the solvent at room temperature to produce colourless crystals. Crystals of polymorph (II) (m.p. 467.95–468.85 K) were obtained by solvent evaporation with commercially available 2,6-dichloropurine using ethanol as solvent. The remarkable similarity of the crystal structures of the reported polymorphs yields minimal differences in the shape and position of the peaks in the FT–IR spectra (polycrystalline samples in KBr disks). Hence, the stretching mode ν(N—H) (a weak peak at 3210 cm-1) and the in-plane deformation mode δ(N—H) (1513 cm-1) appear at the same site in (I) and (II).

Refinement top

H atoms on N atoms were located in difference maps and refined as riding, with N—H = 0.86 Å and Uiso(H) = 1.2Ueq(N). Other H atoms were positioned geometrically and treated as riding, with C—H = 0.92–0.95 Å and Uiso(H) = 1.2Ueq(C).

Computing details top

For both compounds, data collection: APEX2 (Bruker, 2010); cell refinement: SAINT (Bruker, 2010); data reduction: SAINT (Bruker, 2010); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: PLATON (Spek, 2009); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. The asymmetric units of polymorph (I) (top and middle) and polymorph (II) (bottom), with the atom-numbering schemes. Displacement ellipsoids are drawn at the 50% probability level.
[Figure 2] Fig. 2. A view of the crystal packing, showing the herringbone arrangement of 2,6-dichloropurine molecules in polymorph (I) (left) and polymorph (II) (right).
(I) 2,6-dichloro-9H-purine top
Crystal data top
C5H2Cl2N4F(000) = 752
Mr = 189.01Dx = 1.695 Mg m3
Monoclinic, P21/cCu Kα radiation, λ = 1.54178 Å
Hall symbol: -P 2ybcCell parameters from 2440 reflections
a = 14.0867 (12) Åθ = 3.5–65.0°
b = 9.4898 (7) ŵ = 7.36 mm1
c = 12.2656 (9) ÅT = 296 K
β = 115.381 (4)°Cut block, colourless
V = 1481.4 (2) Å30.12 × 0.10 × 0.06 mm
Z = 8
Data collection top
Bruker X8 Proteum
diffractometer
2547 independent reflections
Radiation source: fine-focus rotating anode1713 reflections with I > 2σ(I)
Graded multilayer optics monochromatorRint = 0.085
ϕ and ω scansθmax = 66.0°, θmin = 5.8°
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
h = 1616
Tmin = 0.377, Tmax = 0.753k = 1111
18199 measured reflectionsl = 1413
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)] = 0.051Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.154H-atom parameters constrained
S = 1.10 w = 1/[σ2(Fo2) + (0.0735P)2 + 0.6074P]
where P = (Fo2 + 2Fc2)/3
2547 reflections(Δ/σ)max < 0.001
199 parametersΔρmax = 0.27 e Å3
0 restraintsΔρmin = 0.29 e Å3
Crystal data top
C5H2Cl2N4V = 1481.4 (2) Å3
Mr = 189.01Z = 8
Monoclinic, P21/cCu Kα radiation
a = 14.0867 (12) ŵ = 7.36 mm1
b = 9.4898 (7) ÅT = 296 K
c = 12.2656 (9) Å0.12 × 0.10 × 0.06 mm
β = 115.381 (4)°
Data collection top
Bruker X8 Proteum
diffractometer
2547 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
1713 reflections with I > 2σ(I)
Tmin = 0.377, Tmax = 0.753Rint = 0.085
18199 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0510 restraints
wR(F2) = 0.154H-atom parameters constrained
S = 1.10Δρmax = 0.27 e Å3
2547 reflectionsΔρmin = 0.29 e Å3
199 parameters
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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
N10.6775 (3)0.4986 (3)0.6268 (3)0.0531 (8)
C20.6641 (3)0.6302 (5)0.5827 (4)0.0532 (10)
Cl20.71871 (10)0.76088 (13)0.68964 (11)0.0745 (4)
N30.6148 (3)0.6744 (3)0.4701 (3)0.0485 (8)
C40.5742 (3)0.5666 (4)0.3941 (3)0.0449 (9)
C50.5820 (3)0.4237 (4)0.4254 (3)0.0455 (9)
C60.6369 (3)0.3951 (4)0.5480 (3)0.0501 (10)
Cl60.65201 (10)0.22623 (12)0.60104 (11)0.0710 (4)
N70.5292 (3)0.3429 (3)0.3227 (3)0.0506 (8)
C80.4929 (3)0.4362 (4)0.2358 (4)0.0536 (10)
H80.45390.41140.15550.064*
N90.5165 (3)0.5715 (3)0.2720 (3)0.0514 (8)
H90.49890.64550.22710.062*
N110.8212 (3)0.2753 (4)0.9484 (3)0.0600 (9)
C120.8426 (3)0.4071 (5)0.9271 (4)0.0569 (11)
Cl120.79181 (11)0.53758 (13)0.98390 (12)0.0801 (4)
N130.8973 (3)0.4514 (3)0.8684 (3)0.0560 (9)
C140.9317 (3)0.3431 (4)0.8255 (4)0.0510 (10)
C150.9166 (3)0.2009 (4)0.8412 (4)0.0521 (10)
C160.8593 (3)0.1724 (4)0.9055 (4)0.0564 (10)
Cl160.83484 (10)0.00077 (12)0.93271 (12)0.0798 (4)
N170.9637 (3)0.1194 (4)0.7842 (3)0.0592 (9)
C181.0046 (4)0.2121 (4)0.7380 (4)0.0618 (11)
H181.04190.18660.69410.074*
N190.9884 (3)0.3483 (3)0.7590 (3)0.0590 (9)
H191.00950.42240.73530.071*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.058 (2)0.054 (2)0.0489 (18)0.0015 (17)0.0237 (16)0.0004 (17)
C20.054 (2)0.058 (3)0.056 (2)0.003 (2)0.030 (2)0.006 (2)
Cl20.0826 (8)0.0732 (8)0.0662 (7)0.0190 (6)0.0304 (6)0.0211 (6)
N30.060 (2)0.0436 (18)0.0478 (19)0.0046 (16)0.0283 (16)0.0047 (15)
C40.055 (2)0.040 (2)0.046 (2)0.0004 (17)0.0274 (19)0.0028 (17)
C50.051 (2)0.037 (2)0.053 (2)0.0030 (17)0.0269 (19)0.0018 (17)
C60.053 (2)0.054 (2)0.049 (2)0.0043 (19)0.0267 (19)0.012 (2)
Cl60.0859 (8)0.0571 (7)0.0740 (7)0.0127 (6)0.0379 (7)0.0202 (6)
N70.066 (2)0.0346 (17)0.0542 (19)0.0030 (15)0.0284 (17)0.0011 (15)
C80.073 (3)0.038 (2)0.052 (2)0.0025 (19)0.029 (2)0.0052 (18)
N90.072 (2)0.0366 (17)0.0465 (18)0.0016 (15)0.0267 (17)0.0026 (14)
N110.068 (2)0.054 (2)0.065 (2)0.0005 (18)0.035 (2)0.0045 (18)
C120.056 (3)0.059 (3)0.055 (2)0.007 (2)0.023 (2)0.007 (2)
Cl120.0956 (9)0.0677 (8)0.0907 (9)0.0121 (7)0.0528 (8)0.0122 (6)
N130.062 (2)0.0447 (19)0.063 (2)0.0015 (16)0.0287 (19)0.0038 (16)
C140.051 (2)0.041 (2)0.061 (2)0.0010 (18)0.024 (2)0.0018 (19)
C150.056 (2)0.040 (2)0.057 (2)0.0015 (18)0.021 (2)0.0019 (18)
C160.058 (3)0.052 (2)0.063 (3)0.001 (2)0.030 (2)0.004 (2)
Cl160.0988 (10)0.0541 (7)0.1062 (10)0.0107 (6)0.0627 (8)0.0022 (6)
N170.071 (2)0.0411 (19)0.077 (2)0.0010 (17)0.042 (2)0.0021 (17)
C180.070 (3)0.046 (2)0.077 (3)0.001 (2)0.039 (3)0.005 (2)
N190.069 (2)0.0418 (18)0.078 (2)0.0035 (17)0.044 (2)0.0012 (17)
Geometric parameters (Å, º) top
N1—C61.324 (5)N11—C161.327 (5)
N1—C21.341 (5)N11—C121.339 (5)
C2—N31.320 (5)C12—N131.328 (5)
C2—Cl21.728 (4)C12—Cl121.720 (4)
N3—C41.336 (5)N13—C141.337 (5)
C4—N91.365 (5)C14—N191.367 (5)
C4—C51.401 (5)C14—C151.392 (5)
C5—N71.387 (5)C15—C161.376 (6)
C5—C61.392 (5)C15—N171.387 (5)
C6—Cl61.708 (4)C16—Cl161.726 (4)
N7—C81.310 (5)N17—C181.307 (5)
C8—N91.352 (5)C18—N191.356 (5)
C8—H80.9300C18—H180.9300
N9—H90.8600N19—H190.8600
C6—N1—C2117.0 (3)C16—N11—C12116.5 (4)
N3—C2—N1129.6 (4)N13—C12—N11129.3 (4)
N3—C2—Cl2115.4 (3)N13—C12—Cl12115.5 (3)
N1—C2—Cl2114.9 (3)N11—C12—Cl12115.2 (3)
C2—N3—C4111.3 (3)C12—N13—C14111.2 (3)
N3—C4—N9127.9 (3)N13—C14—N19127.6 (4)
N3—C4—C5126.2 (3)N13—C14—C15126.1 (4)
N9—C4—C5105.9 (3)N19—C14—C15106.3 (3)
N7—C5—C6134.9 (4)C16—C15—N17134.8 (4)
N7—C5—C4109.8 (3)C16—C15—C14115.6 (4)
C6—C5—C4115.3 (3)N17—C15—C14109.7 (4)
N1—C6—C5120.7 (4)N11—C16—C15121.3 (4)
N1—C6—Cl6118.3 (3)N11—C16—Cl16118.0 (3)
C5—C6—Cl6121.0 (3)C15—C16—Cl16120.7 (3)
C8—N7—C5103.6 (3)C18—N17—C15103.8 (3)
N7—C8—N9114.9 (4)N17—C18—N19114.7 (4)
N7—C8—H8122.6N17—C18—H18122.7
N9—C8—H8122.6N19—C18—H18122.7
C8—N9—C4105.9 (3)C18—N19—C14105.6 (3)
C8—N9—H9127.0C18—N19—H19127.2
C4—N9—H9127.0C14—N19—H19127.2
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N9—H9···N7i0.861.962.785 (4)161
N19—H19···N17ii0.861.942.768 (5)160
Symmetry codes: (i) x+1, y+1/2, z+1/2; (ii) x+2, y+1/2, z+3/2.
(II) 2,6-dichloro-7H-purine top
Crystal data top
C5H2Cl2N4F(000) = 376
Mr = 189.01Dx = 1.787 Mg m3
Orthorhombic, P212121Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2ac 2abCell parameters from 4413 reflections
a = 5.5716 (9) Åθ = 2.6–27.4°
b = 9.5820 (16) ŵ = 0.85 mm1
c = 13.159 (2) ÅT = 120 K
V = 702.5 (2) Å3Plate, colourless
Z = 40.12 × 0.10 × 0.08 mm
Data collection top
Bruker SMART APEX
diffractometer
1156 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.041
ϕ and ω scansθmax = 25.0°, θmin = 2.6°
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
h = 66
Tmin = 0.905, Tmax = 0.935k = 1111
6847 measured reflectionsl = 1515
1243 independent reflections
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.033H-atom parameters constrained
wR(F2) = 0.071 w = 1/[σ2(Fo2) + (0.0253P)2]
where P = (Fo2 + 2Fc2)/3
S = 1.38(Δ/σ)max = 0.006
1243 reflectionsΔρmax = 0.33 e Å3
100 parametersΔρmin = 0.22 e Å3
0 restraintsAbsolute structure: Flack (1983), with how many Friedel pairs?
Primary atom site location: structure-invariant direct methodsAbsolute structure parameter: 0.03 (10)
Crystal data top
C5H2Cl2N4V = 702.5 (2) Å3
Mr = 189.01Z = 4
Orthorhombic, P212121Mo Kα radiation
a = 5.5716 (9) ŵ = 0.85 mm1
b = 9.5820 (16) ÅT = 120 K
c = 13.159 (2) Å0.12 × 0.10 × 0.08 mm
Data collection top
Bruker SMART APEX
diffractometer
1243 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2001)
1156 reflections with I > 2σ(I)
Tmin = 0.905, Tmax = 0.935Rint = 0.041
6847 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.033H-atom parameters constrained
wR(F2) = 0.071Δρmax = 0.33 e Å3
S = 1.38Δρmin = 0.22 e Å3
1243 reflectionsAbsolute structure: Flack (1983), with how many Friedel pairs?
100 parametersAbsolute structure parameter: 0.03 (10)
0 restraints
Special details top

Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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
N10.1017 (5)0.6250 (3)0.56651 (17)0.0259 (6)
C20.0199 (6)0.4957 (3)0.5851 (2)0.0264 (7)
Cl20.18790 (15)0.36192 (8)0.53068 (6)0.0325 (2)
N30.1656 (5)0.4541 (3)0.63990 (19)0.0262 (6)
C40.2858 (6)0.5621 (3)0.6803 (2)0.0234 (7)
C50.2224 (6)0.7022 (3)0.6650 (2)0.0237 (7)
C60.0226 (6)0.7281 (3)0.6077 (2)0.0262 (7)
Cl60.08278 (14)0.89604 (7)0.59069 (6)0.0293 (2)
N70.3879 (4)0.7792 (3)0.71888 (17)0.0254 (6)
H70.39360.87750.72330.030*
C80.5365 (6)0.6864 (3)0.7618 (2)0.0251 (7)
H80.66780.71320.80350.030*
N90.4858 (5)0.5539 (2)0.7414 (2)0.0262 (6)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
N10.0277 (14)0.0230 (13)0.0270 (13)0.0014 (12)0.0019 (11)0.0000 (10)
C20.0312 (18)0.0212 (16)0.0266 (16)0.0056 (14)0.0030 (16)0.0006 (14)
Cl20.0378 (5)0.0234 (4)0.0363 (4)0.0044 (4)0.0058 (4)0.0034 (4)
N30.0295 (15)0.0203 (14)0.0289 (14)0.0013 (12)0.0012 (13)0.0002 (11)
C40.0266 (16)0.0208 (17)0.0229 (15)0.0018 (14)0.0037 (14)0.0010 (13)
C50.0285 (18)0.0213 (17)0.0213 (14)0.0035 (14)0.0042 (14)0.0008 (13)
C60.0321 (18)0.0203 (16)0.0261 (17)0.0026 (14)0.0078 (15)0.0041 (14)
Cl60.0328 (4)0.0217 (4)0.0335 (4)0.0030 (3)0.0002 (4)0.0008 (3)
N70.0302 (15)0.0183 (13)0.0277 (13)0.0011 (12)0.0014 (13)0.0017 (11)
C80.0266 (19)0.0273 (17)0.0215 (15)0.0025 (14)0.0004 (14)0.0003 (14)
N90.0337 (16)0.0170 (13)0.0278 (14)0.0002 (12)0.0018 (13)0.0004 (12)
Geometric parameters (Å, º) top
N1—C61.323 (4)C5—C61.367 (4)
N1—C21.342 (4)C5—N71.378 (4)
C2—N31.322 (4)C6—Cl61.728 (3)
C2—Cl21.741 (3)N7—C81.340 (4)
N3—C41.343 (4)N7—H70.9442
C4—N91.376 (4)C8—N91.327 (3)
C4—C51.403 (4)C8—H80.9500
C6—N1—C2115.9 (3)N1—C6—C5121.1 (3)
N3—C2—N1130.0 (3)N1—C6—Cl6117.7 (2)
N3—C2—Cl2115.0 (2)C5—C6—Cl6121.1 (2)
N1—C2—Cl2115.0 (2)C8—N7—C5105.9 (2)
C2—N3—C4112.0 (3)C8—N7—H7128.0
N3—C4—N9126.3 (3)C5—N7—H7126.0
N3—C4—C5123.7 (3)N9—C8—N7114.7 (3)
N9—C4—C5110.0 (3)N9—C8—H8122.6
C6—C5—N7137.0 (3)N7—C8—H8122.6
C6—C5—C4117.2 (3)C8—N9—C4103.6 (2)
N7—C5—C4105.7 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N7—H7···N9i0.941.882.774 (3)158
Symmetry code: (i) x+1, y+1/2, z+3/2.

Experimental details

(I)(II)
Crystal data
Chemical formulaC5H2Cl2N4C5H2Cl2N4
Mr189.01189.01
Crystal system, space groupMonoclinic, P21/cOrthorhombic, P212121
Temperature (K)296120
a, b, c (Å)14.0867 (12), 9.4898 (7), 12.2656 (9)5.5716 (9), 9.5820 (16), 13.159 (2)
α, β, γ (°)90, 115.381 (4), 9090, 90, 90
V3)1481.4 (2)702.5 (2)
Z84
Radiation typeCu KαMo Kα
µ (mm1)7.360.85
Crystal size (mm)0.12 × 0.10 × 0.060.12 × 0.10 × 0.08
Data collection
DiffractometerBruker X8 Proteum
diffractometer
Bruker SMART APEX
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2001)
Multi-scan
(SADABS; Bruker, 2001)
Tmin, Tmax0.377, 0.7530.905, 0.935
No. of measured, independent and
observed [I > 2σ(I)] reflections
18199, 2547, 1713 6847, 1243, 1156
Rint0.0850.041
(sin θ/λ)max1)0.5930.594
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.051, 0.154, 1.10 0.033, 0.071, 1.38
No. of reflections25471243
No. of parameters199100
H-atom treatmentH-atom parameters constrainedH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.27, 0.290.33, 0.22
Absolute structure?Flack (1983), with how many Friedel pairs?
Absolute structure parameter?0.03 (10)

Computer programs: APEX2 (Bruker, 2010), SAINT (Bruker, 2010), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), PLATON (Spek, 2009), publCIF (Westrip, 2010).

Hydrogen-bond geometry (Å, º) for (I) top
D—H···AD—HH···AD···AD—H···A
N9—H9···N7i0.861.962.785 (4)160.9
N19—H19···N17ii0.861.942.768 (5)160.4
Symmetry codes: (i) x+1, y+1/2, z+1/2; (ii) x+2, y+1/2, z+3/2.
Hydrogen-bond geometry (Å, º) for (II) top
D—H···AD—HH···AD···AD—H···A
N7—H7···N9i0.941.882.774 (3)157.7
Symmetry code: (i) x+1, y+1/2, z+3/2.
 

Acknowledgements

The project `Factoría de Cristalización, CONSOLIDER INGENIO-2010' provided X-ray structural facilities for this work.

References

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