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

Journal logoCRYSTALLOGRAPHIC
COMMUNICATIONS
ISSN: 2056-9890
Volume 67| Part 11| November 2011| Page o2851
doi:10.1107/S1600536811040232

Monoclinic polymorph of 3,7-di­methyl-1-(5-oxohex­yl)-3,7-di­hydro-1H-purine-2,6-dione

Dmitrijs Stepanovsa and Anatoly Mishneva*

aLatvian Institute of Organic Synthesis, 21 Aizkraukles Street, Riga, LV-1006, Latvia
*Correspondence e-mail: mishnevs@osi.lv

(Received 21 September 2011; accepted 29 September 2011; online 5 October 2011)

The structure of the title compound, pentoxifylline, C13H18N4O3, has been previously characterized as a triclinic polymorph [Pavelčík et al. (1989[Pavelčík, F., Sivý, J., Havránek, E., Sivý, P., Komanová, E. & Nevýdal, J. (1989). Acta Cryst. C45, 836-837.]). Acta Cryst. C45, 836–837]. We have discovered the monoclinic form. There are no strong hydrogen bonds in the crystal structure, rather, moderate C—H⋯O hydrogen bonds are present, which serve to stabilize the three-dimensional architecture.

Related literature

For general background to pentoxifylline, see Dettelbach & Aviado (1985[Dettelbach, H. R. & Aviado, D. M. (1985). J. Clin. Pharmacol. 25, 8-26.]). For the structure and the nature of the hydrogen bonding in the triclinic polymorph, see: Pavelčík et al. (1989[Pavelčík, F., Sivý, J., Havránek, E., Sivý, P., Komanová, E. & Nevýdal, J. (1989). Acta Cryst. C45, 836-837.]); Gilli (2002[Gilli, G. (2002). Fundamentals of Crystallography, edited by C. Giacovazzo, pp. 585-666. Oxford University Press.]).

[Scheme 1]

Experimental

Crystal data

  • C13H18N4O3

  • Mr = 278.31

  • Monoclinic, P 21 /c

  • a = 9.743 (6) Å

  • b = 17.410 (8) Å

  • c = 7.956 (3) Å

  • β = 90.89 (2)°

  • V = 1349.4 (12) Å3

  • Z = 4

  • Mo Kα radiation

  • μ = 0.10 mm−1

  • T = 190 K

  • 0.40 × 0.30 × 0.05 mm
Data collection

  • Nonius KappaCCD diffractometer

  • 5073 measured reflections

  • 3103 independent reflections

  • 1817 reflections with I > 2σ(I)

  • Rint = 0.053
Refinement

  • R[F2 > 2σ(F2)] = 0.066

  • wR(F2) = 0.163

  • S = 1.01

  • 3065 reflections

  • 184 parameters

  • H-atom parameters constrained

  • Δρmax = 0.24 e Å−3

  • Δρmin = −0.20 e Å−3

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A D—H H⋯A D⋯A D—H⋯A
C2—H2⋯O18i 0.93 2.39 3.206 (4) 147
C15—H15B⋯O19ii 0.96 2.60 3.439 (4) 147
C16—H16A⋯O18i 0.96 2.55 3.395 (4) 148
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{1\over 2}}].

Data collection: KappaCCD Server Software (Nonius, 1997[Nonius (1997). KappaCCD Server Software. Nonius BV, Delft, The Netherlands.]); cell refinement: HKL SCALEPACK (Otwinovski & Minor, 1997[Otwinovski, 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: HKL DENZO (Otwinovski & Minor, 1997[Otwinovski, 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.]) and SCALEPACK; 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, 1997[Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.]); software used to prepare material for publication: SHELXL97.

Supporting information

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536811040232/tk2793sup1.cif

Structure factors: contains datablock I. DOI: 10.1107/S1600536811040232/tk2793Isup2.hkl

Supporting information file. DOI: 10.1107/S1600536811040232/tk2793Isup3.cml

checkCIF report


Comment top

The background to pentoxifylline has been summarized (Dettelbach & Aviado, 1985). The polymorph structure II differs from the known form I Pavelčík et al., 1989; Gilli, 2002) in their molecular conformation and the packing of the molecules in the lattice. The bond lengths of forms I and II are close to their standard values, but torsion angle N7—C10—C11—C12 (75.6 (3)° for I and 175.8 (2)° for II) and some bond angles significantly differ: N7—C10—C11 (114.2 (2)° for I and 111.9 (2)° for II), C10—C11—C12 (115.4 (2)° for I and 115.4 (2)° for II), C11—C12—C13 (111.0 (2)° for I and 114.1 (2)° for II). In the crystal structure of II, the molecules are connected by means of C—H···O hydrogen bonds, Table 1.

Related literature top

For general background to pentoxifylline, see Dettelbach & Aviado (1985). For the structure and the nature of the hydrogen bonding in the triclinic polymorph, see: Pavelčík et al. (1989); Gilli (2002).

Experimental top

Title compound was obtained by recrystallization of Trental tablets, produced by Sanofi-Aventis Deutschland GmbH. Crystals were grown by slow evaporation from dichloromethane at temperature range 308–315 K.

Refinement top

All hydrogen atoms were positioned geometrically with C—H distances ranging from 0.93 to 0.97 Å and refined as riding on their parent atoms with Uiso (H) = 1.5Ueq (C) for methyl groups and Uiso (H) = 1.2Ueq (C) for others.

Computing details top

Data collection: KappaCCD Server Software (Nonius, 1997); cell refinement: HKL SCALEPACK (Otwinovski & Minor, 1997); data reduction: HKL DENZO and SCALEPACK (Otwinovski & Minor, 1997); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: SHELXL97 (Sheldrick, 2008).

Figures top
[Figure 1] Fig. 1. The molecular structure of the title compound, II, showing 50% probability ellipsoids and hydrogen atoms are shown as small spheres of arbitrary radii.
3,7-Dimethyl-1-(5-oxohexyl)-3,7-dihydro-1H-purine-2,6-dione top
Crystal data top
C13H18N4O3Dx = 1.370 Mg m−3
Mr = 278.31Melting point: 365 K
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 9.743 (6) ÅCell parameters from 6273 reflections
b = 17.410 (8) Åθ = 1.0–27.5°
c = 7.956 (3) ŵ = 0.10 mm−1
β = 90.89 (2)°T = 190 K
V = 1349.4 (12) Å3Plate, colourless
Z = 40.4 × 0.3 × 0.05 mm
F(000) = 592
Data collection top
Nonius KappaCCD
diffractometer		1817 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.053
Graphite monochromatorθmax = 27.5°, θmin = 2.4°
CCD scansh = −12→12
5073 measured reflectionsk = −22→19
3065 independent reflectionsl = −10→10
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)] = 0.066Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.150H-atom parameters constrained
S = 1.02 w = 1/[σ2(Fo2) + (0.0525P)2 + 0.5672P]
where P = (Fo2 + 2Fc2)/3
3065 reflections(Δ/σ)max = 0.004
184 parametersΔρmax = 0.24 e Å−3
0 restraintsΔρmin = −0.20 e Å−3
Crystal data top
C13H18N4O3V = 1349.4 (12) Å3
Mr = 278.31Z = 4
Monoclinic, P21/cMo Kα radiation
a = 9.743 (6) ŵ = 0.10 mm−1
b = 17.410 (8) ÅT = 190 K
c = 7.956 (3) Å0.4 × 0.3 × 0.05 mm
β = 90.89 (2)°
Data collection top
Nonius KappaCCD
diffractometer		1817 reflections with I > 2σ(I)
5073 measured reflectionsRint = 0.053
3065 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0660 restraints
wR(F2) = 0.150H-atom parameters constrained
S = 1.02Δρmax = 0.24 e Å−3
3065 reflectionsΔρmin = −0.20 e Å−3
184 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
O19−0.79244 (18)0.03718 (9)−0.4841 (2)0.0407 (5)
O18−0.54702 (19)−0.15692 (9)−0.2345 (2)0.0431 (5)
N7−0.6688 (2)−0.05902 (10)−0.3550 (2)0.0314 (5)
O20−1.1444 (2)−0.31616 (11)−0.4130 (3)0.0550 (6)
N1−0.5641 (2)0.14522 (11)−0.3470 (2)0.0337 (5)
N5−0.4583 (2)−0.03670 (11)−0.2089 (2)0.0350 (5)
C9−0.5831 (2)0.06649 (13)−0.3380 (3)0.0304 (5)
N3−0.3878 (2)0.09676 (12)−0.1963 (3)0.0380 (5)
C4−0.4742 (2)0.04006 (13)−0.2463 (3)0.0319 (6)
C10−0.7740 (3)−0.11505 (13)−0.4085 (3)0.0351 (6)
H10A−0.7303−0.1639−0.43170.042*
H10B−0.8180−0.0973−0.51160.042*
C6−0.5568 (3)−0.08839 (14)−0.2631 (3)0.0331 (6)
C13−0.9288 (3)−0.26965 (13)−0.3170 (3)0.0323 (6)
H13A−0.8532−0.2731−0.39460.039*
H13B−0.8920−0.2790−0.20490.039*
C14−1.0310 (3)−0.33177 (14)−0.3593 (3)0.0326 (6)
C12−0.9861 (2)−0.18878 (13)−0.3236 (3)0.0361 (6)
H12A−1.0633−0.1856−0.24840.043*
H12B−1.0203−0.1787−0.43660.043*
C15−0.9876 (3)−0.41325 (14)−0.3319 (3)0.0412 (6)
H15A−1.0331−0.4457−0.41280.062*
H15B−1.0117−0.4290−0.22060.062*
H15C−0.8900−0.4173−0.34460.062*
C17−0.3361 (3)−0.06489 (15)−0.1159 (3)0.0427 (6)
H17A−0.2675−0.0805−0.19420.064*
H17B−0.3612−0.1079−0.04740.064*
H17C−0.3002−0.0246−0.04560.064*
C8−0.6905 (3)0.01842 (13)−0.4012 (3)0.0324 (6)
C11−0.8821 (3)−0.12644 (14)−0.2754 (3)0.0388 (6)
H11A−0.9303−0.0784−0.25830.047*
H11B−0.8373−0.1403−0.17000.047*
C16−0.6522 (3)0.20142 (14)−0.4321 (3)0.0420 (6)
H16A−0.60970.2511−0.42680.063*
H16B−0.73940.2034−0.37780.063*
H16C−0.66530.1867−0.54750.063*
C2−0.4478 (3)0.15899 (15)−0.2608 (3)0.0386 (6)
H2−0.41180.2081−0.24690.046*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O190.0381 (11)0.0348 (10)0.0490 (10)−0.0019 (8)−0.0061 (8)0.0061 (8)
O180.0530 (12)0.0232 (9)0.0530 (11)0.0008 (8)−0.0011 (8)0.0021 (8)
N70.0359 (12)0.0224 (10)0.0358 (11)−0.0046 (9)0.0003 (8)−0.0003 (8)
O200.0438 (13)0.0385 (11)0.0818 (14)−0.0051 (9)−0.0226 (10)−0.0014 (10)
N10.0327 (12)0.0231 (10)0.0452 (12)0.0017 (9)0.0017 (9)0.0010 (8)
N50.0334 (12)0.0288 (11)0.0428 (12)0.0007 (9)−0.0018 (9)0.0033 (9)
C90.0322 (13)0.0217 (11)0.0374 (13)−0.0010 (10)0.0039 (10)0.0004 (10)
N30.0362 (12)0.0304 (11)0.0473 (12)−0.0030 (10)−0.0003 (9)−0.0037 (9)
C40.0313 (14)0.0261 (12)0.0384 (13)0.0001 (11)0.0032 (10)−0.0009 (10)
C100.0425 (15)0.0245 (12)0.0383 (13)−0.0080 (11)0.0011 (11)−0.0020 (10)
C60.0370 (14)0.0279 (13)0.0346 (13)0.0003 (11)0.0044 (10)−0.0021 (10)
C130.0356 (14)0.0267 (12)0.0345 (12)−0.0052 (10)−0.0001 (10)0.0001 (10)
C140.0366 (15)0.0322 (13)0.0290 (12)−0.0029 (11)−0.0008 (10)−0.0002 (10)
C120.0335 (14)0.0284 (13)0.0465 (14)−0.0009 (11)0.0060 (11)−0.0015 (11)
C150.0443 (16)0.0282 (13)0.0510 (15)−0.0050 (12)−0.0026 (12)0.0002 (11)
C170.0404 (16)0.0372 (14)0.0503 (16)0.0079 (12)−0.0051 (12)0.0051 (12)
C80.0332 (14)0.0294 (13)0.0347 (13)0.0002 (11)0.0061 (11)0.0011 (10)
C110.0453 (16)0.0253 (12)0.0459 (15)−0.0048 (11)0.0095 (11)−0.0065 (11)
C160.0392 (15)0.0289 (14)0.0578 (16)0.0077 (11)−0.0040 (12)0.0066 (11)
C20.0322 (15)0.0328 (14)0.0509 (15)−0.0039 (11)−0.0013 (11)−0.0039 (12)
Geometric parameters (Å, º) top
O19—C81.228 (3)C13—C121.515 (3)
O18—C61.218 (3)C13—H13A0.9700
N7—C61.401 (3)C13—H13B0.9700
N7—C81.413 (3)C14—C151.495 (3)
N7—C101.473 (3)C12—C111.530 (3)
O20—C141.209 (3)C12—H12A0.9700
N1—C21.337 (3)C12—H12B0.9700
N1—C91.385 (3)C15—H15A0.9600
N1—C161.461 (3)C15—H15B0.9600
N5—C41.377 (3)C15—H15C0.9600
N5—C61.380 (3)C17—H17A0.9600
N5—C171.476 (3)C17—H17B0.9600
C9—C41.359 (3)C17—H17C0.9600
C9—C81.426 (3)C11—H11A0.9700
N3—C21.330 (3)C11—H11B0.9700
N3—C41.353 (3)C16—H16A0.9600
C10—C111.518 (3)C16—H16B0.9600
C10—H10A0.9700C16—H16C0.9600
C10—H10B0.9700C2—H20.9300
C13—C141.505 (3)
C6—N7—C8126.6 (2)C13—C12—H12A108.7
C6—N7—C10116.24 (19)C11—C12—H12A108.7
C8—N7—C10117.1 (2)C13—C12—H12B108.7
C2—N1—C9105.3 (2)C11—C12—H12B108.7
C2—N1—C16127.2 (2)H12A—C12—H12B107.6
C9—N1—C16127.5 (2)C14—C15—H15A109.5
C4—N5—C6119.3 (2)C14—C15—H15B109.5
C4—N5—C17121.2 (2)H15A—C15—H15B109.5
C6—N5—C17119.4 (2)C14—C15—H15C109.5
C4—C9—N1105.0 (2)H15A—C15—H15C109.5
C4—C9—C8123.6 (2)H15B—C15—H15C109.5
N1—C9—C8131.4 (2)N5—C17—H17A109.5
C2—N3—C4102.3 (2)N5—C17—H17B109.5
N3—C4—C9112.8 (2)H17A—C17—H17B109.5
N3—C4—N5125.2 (2)N5—C17—H17C109.5
C9—C4—N5121.9 (2)H17A—C17—H17C109.5
N7—C10—C11111.85 (19)H17B—C17—H17C109.5
N7—C10—H10A109.2O19—C8—N7120.7 (2)
C11—C10—H10A109.2O19—C8—C9128.1 (2)
N7—C10—H10B109.2N7—C8—C9111.2 (2)
C11—C10—H10B109.2C10—C11—C12112.4 (2)
H10A—C10—H10B107.9C10—C11—H11A109.1
O18—C6—N5121.9 (2)C12—C11—H11A109.1
O18—C6—N7120.9 (2)C10—C11—H11B109.1
N5—C6—N7117.2 (2)C12—C11—H11B109.1
C14—C13—C12114.7 (2)H11A—C11—H11B107.8
C14—C13—H13A108.6N1—C16—H16A109.5
C12—C13—H13A108.6N1—C16—H16B109.5
C14—C13—H13B108.6H16A—C16—H16B109.5
C12—C13—H13B108.6N1—C16—H16C109.5
H13A—C13—H13B107.6H16A—C16—H16C109.5
O20—C14—C15121.3 (2)H16B—C16—H16C109.5
O20—C14—C13121.0 (2)N3—C2—N1114.6 (2)
C15—C14—C13117.6 (2)N3—C2—H2122.7
C13—C12—C11114.1 (2)N1—C2—H2122.7
C2—N1—C9—C4−0.3 (2)C8—N7—C6—O18−177.9 (2)
C16—N1—C9—C4179.9 (2)C10—N7—C6—O182.0 (3)
C2—N1—C9—C8177.9 (2)C8—N7—C6—N51.3 (3)
C16—N1—C9—C8−2.0 (4)C10—N7—C6—N5−178.80 (19)
C2—N3—C4—C90.1 (3)C12—C13—C14—O208.2 (3)
C2—N3—C4—N5−179.1 (2)C12—C13—C14—C15−171.5 (2)
N1—C9—C4—N30.1 (3)C14—C13—C12—C11178.31 (19)
C8—C9—C4—N3−178.2 (2)C6—N7—C8—O19179.1 (2)
N1—C9—C4—N5179.3 (2)C10—N7—C8—O19−0.8 (3)
C8—C9—C4—N51.0 (4)C6—N7—C8—C9−1.5 (3)
C6—N5—C4—N3177.8 (2)C10—N7—C8—C9178.54 (19)
C17—N5—C4—N3−3.8 (4)C4—C9—C8—O19179.7 (2)
C6—N5—C4—C9−1.3 (3)N1—C9—C8—O191.8 (4)
C17—N5—C4—C9177.1 (2)C4—C9—C8—N70.4 (3)
C6—N7—C10—C1187.7 (2)N1—C9—C8—N7−177.5 (2)
C8—N7—C10—C11−92.3 (2)N7—C10—C11—C12−175.8 (2)
C4—N5—C6—O18179.4 (2)C13—C12—C11—C1071.4 (3)
C17—N5—C6—O181.0 (3)C4—N3—C2—N1−0.3 (3)
C4—N5—C6—N70.2 (3)C9—N1—C2—N30.3 (3)
C17—N5—C6—N7−178.2 (2)C16—N1—C2—N3−179.8 (2)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2···O18i0.932.393.206 (4)147
C15—H15B···O19ii0.962.603.439 (4)147
C16—H16A···O18i0.962.553.395 (4)148
Symmetry codes: (i) −x−1, y+1/2, −z−1/2; (ii) −x−2, y−1/2, −z−1/2.

Experimental details

Crystal data
Chemical formulaC13H18N4O3
Mr278.31
Crystal system, space groupMonoclinic, P21/c
Temperature (K)190
a, b, c (Å)9.743 (6), 17.410 (8), 7.956 (3)
β (°) 90.89 (2)
V (Å3)1349.4 (12)
Z4
Radiation typeMo Kα
µ (mm−1)0.10
Crystal size (mm)0.4 × 0.3 × 0.05
Data collection
DiffractometerNonius KappaCCD
diffractometer
Absorption correction–
No. of measured, independent and
observed [I > 2σ(I)] reflections		5073, 3065, 1817
Rint0.053
(sin θ/λ)max (Å−1)0.650
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.066, 0.150, 1.02
No. of reflections3065
No. of parameters184
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å−3)0.24, −0.20

Computer programs: KappaCCD Server Software (Nonius, 1997), HKL SCALEPACK (Otwinovski & Minor, 1997), HKL DENZO and SCALEPACK (Otwinovski & Minor, 1997), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
C2—H2···O18i0.932.393.206 (4)147
C15—H15B···O19ii0.962.603.439 (4)147
C16—H16A···O18i0.962.553.395 (4)148
Symmetry codes: (i) −x−1, y+1/2, −z−1/2; (ii) −x−2, y−1/2, −z−1/2.
 

Acknowledgements

This work was supported by the European Regional Development Fund (No. 2DP/ 2.1.1.1.0/10/APIA/VIAA/066).

References

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ISSN: 2056-9890
Volume 67| Part 11| November 2011| Page o2851
doi:10.1107/S1600536811040232
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