Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270103016676/de1217sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270103016676/de1217IIIsup2.hkl |
CCDC reference: 221084
Compound (III) was prepared using the method described by Avasthi et al. (1995), by stirring a mixture of 4,6-diisopropylthio- 1H-pyrazolo[3,4-d]pyrimidine and 1,3-dibromopropane in dimethylformamide in the presence of anhydrous potassium carbonate. Diffraction quality crystals were prepared from a solution of methanol and butanol by slow evaporation at room temperature.
Data collection: XSCANS (Siemens, 1996); cell refinement: XSCANS; data reduction: XSCANS; program(s) used to solve structure: SHELXTL (Bruker, 1997); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.
C25H36N8S4 | F(000) = 1224 |
Mr = 576.90 | Dx = 1.235 Mg m−3 |
Monoclinic, C2/c | Melting point: 358 K |
Hall symbol: -C 2yc | Mo Kα radiation, λ = 0.71073 Å |
a = 21.044 (2) Å | Cell parameters from 44 reflections |
b = 8.814 (1) Å | θ = 3.9–12.5° |
c = 18.953 (2) Å | µ = 0.34 mm−1 |
β = 118.07 (1)° | T = 293 K |
V = 3101.9 (6) Å3 | Rectangular, colourless |
Z = 4 | 0.30 × 0.28 × 0.20 mm |
Bruker P4 diffractometer | Rint = 0.020 |
Radiation source: fine-focus sealed tube | θmax = 25.0°, θmin = 2.2° |
Graphite monochromator | h = −24→1 |
θ–2θ scans | k = −1→10 |
3403 measured reflections | l = −20→22 |
2738 independent reflections | 3 standard reflections every 97 reflections |
2352 reflections with I > 2σ(I) | intensity decay: none |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.035 | H-atom parameters constrained |
wR(F2) = 0.094 | w = 1/[σ2(Fo2) + (0.0402P)2 + 1.8299P] where P = (Fo2 + 2Fc2)/3 |
S = 1.03 | (Δ/σ)max = 0.001 |
2738 reflections | Δρmax = 0.22 e Å−3 |
173 parameters | Δρmin = −0.21 e Å−3 |
0 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0045 (3) |
C25H36N8S4 | V = 3101.9 (6) Å3 |
Mr = 576.90 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 21.044 (2) Å | µ = 0.34 mm−1 |
b = 8.814 (1) Å | T = 293 K |
c = 18.953 (2) Å | 0.30 × 0.28 × 0.20 mm |
β = 118.07 (1)° |
Bruker P4 diffractometer | Rint = 0.020 |
3403 measured reflections | 3 standard reflections every 97 reflections |
2738 independent reflections | intensity decay: none |
2352 reflections with I > 2σ(I) |
R[F2 > 2σ(F2)] = 0.035 | 0 restraints |
wR(F2) = 0.094 | H-atom parameters constrained |
S = 1.03 | Δρmax = 0.22 e Å−3 |
2738 reflections | Δρmin = −0.21 e Å−3 |
173 parameters |
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. |
x | y | z | Uiso*/Ueq | Occ. (<1) | |
S1 | 0.72652 (3) | 0.09840 (6) | 0.38944 (3) | 0.06254 (18) | |
S2 | 0.49839 (3) | 0.06907 (5) | 0.10838 (3) | 0.05883 (17) | |
N1 | 0.58349 (8) | 0.55675 (16) | 0.26696 (8) | 0.0488 (4) | |
N2 | 0.63817 (8) | 0.59195 (18) | 0.34150 (9) | 0.0598 (4) | |
C3 | 0.67177 (10) | 0.4644 (2) | 0.37210 (11) | 0.0581 (5) | |
H3 | 0.7115 | 0.4557 | 0.4225 | 0.070* | |
C3' | 0.64020 (9) | 0.34162 (19) | 0.31913 (10) | 0.0455 (4) | |
C4 | 0.65180 (9) | 0.18612 (19) | 0.31228 (10) | 0.0463 (4) | |
N5 | 0.60762 (8) | 0.11002 (16) | 0.24719 (8) | 0.0492 (3) | |
C6 | 0.55244 (9) | 0.18830 (19) | 0.18806 (10) | 0.0455 (4) | |
N7 | 0.53710 (7) | 0.33438 (15) | 0.18501 (8) | 0.0451 (3) | |
C7' | 0.58319 (9) | 0.40652 (18) | 0.25234 (10) | 0.0428 (4) | |
C8 | 0.53726 (10) | 0.67407 (19) | 0.21351 (10) | 0.0515 (4) | |
H8A | 0.5012 | 0.6269 | 0.1649 | 0.062* | |
H8B | 0.5660 | 0.7408 | 0.1991 | 0.062* | |
C9 | 0.5000 | 0.7674 (3) | 0.2500 | 0.0518 (6) | |
H9A | 0.4647 | 0.8323 | 0.2090 | 0.062* | 0.50 |
H9B | 0.5353 | 0.8323 | 0.2910 | 0.062* | 0.50 |
C10 | 0.73466 (11) | −0.0806 (2) | 0.34705 (13) | 0.0635 (5) | |
H10 | 0.6883 | −0.1336 | 0.3245 | 0.076* | |
C11 | 0.75587 (17) | −0.0575 (4) | 0.28210 (18) | 0.1069 (10) | |
H11A | 0.8025 | −0.0108 | 0.3044 | 0.160* | |
H11B | 0.7212 | 0.0068 | 0.2413 | 0.160* | |
H11C | 0.7574 | −0.1538 | 0.2593 | 0.160* | |
C12 | 0.79013 (14) | −0.1723 (3) | 0.41677 (17) | 0.0990 (9) | |
H12A | 0.7956 | −0.2702 | 0.3981 | 0.149* | |
H12B | 0.7743 | −0.1847 | 0.4564 | 0.149* | |
H12C | 0.8355 | −0.1200 | 0.4399 | 0.149* | |
C13 | 0.43175 (10) | 0.1936 (2) | 0.03455 (11) | 0.0566 (5) | |
H13 | 0.4108 | 0.2573 | 0.0607 | 0.068* | |
C14 | 0.37376 (12) | 0.0888 (3) | −0.02454 (14) | 0.0809 (7) | |
H14A | 0.3358 | 0.1483 | −0.0648 | 0.121* | |
H14B | 0.3547 | 0.0280 | 0.0032 | 0.121* | |
H14C | 0.3942 | 0.0240 | −0.0493 | 0.121* | |
C15 | 0.46332 (14) | 0.2940 (3) | −0.00501 (12) | 0.0800 (7) | |
H15A | 0.4835 | 0.2324 | −0.0313 | 0.120* | |
H15B | 0.5004 | 0.3562 | 0.0346 | 0.120* | |
H15C | 0.4263 | 0.3576 | −0.0437 | 0.120* |
U11 | U22 | U33 | U12 | U13 | U23 | |
S1 | 0.0607 (3) | 0.0567 (3) | 0.0556 (3) | 0.0120 (2) | 0.0153 (2) | 0.0014 (2) |
S2 | 0.0729 (3) | 0.0385 (3) | 0.0514 (3) | −0.0020 (2) | 0.0178 (2) | −0.00528 (19) |
N1 | 0.0520 (8) | 0.0393 (7) | 0.0509 (8) | 0.0004 (6) | 0.0207 (7) | −0.0064 (6) |
N2 | 0.0563 (9) | 0.0511 (9) | 0.0588 (9) | −0.0033 (7) | 0.0161 (7) | −0.0131 (7) |
C3 | 0.0498 (10) | 0.0570 (11) | 0.0550 (10) | 0.0009 (9) | 0.0143 (8) | −0.0099 (9) |
C3' | 0.0435 (9) | 0.0466 (9) | 0.0473 (9) | 0.0011 (7) | 0.0221 (7) | −0.0032 (7) |
C4 | 0.0483 (9) | 0.0455 (9) | 0.0480 (9) | 0.0027 (7) | 0.0252 (8) | 0.0026 (7) |
N5 | 0.0555 (8) | 0.0411 (8) | 0.0499 (8) | 0.0026 (6) | 0.0239 (7) | 0.0012 (6) |
C6 | 0.0526 (9) | 0.0407 (9) | 0.0454 (9) | −0.0009 (7) | 0.0247 (8) | −0.0019 (7) |
N7 | 0.0516 (8) | 0.0396 (7) | 0.0439 (7) | −0.0002 (6) | 0.0222 (6) | −0.0037 (6) |
C7' | 0.0463 (9) | 0.0401 (9) | 0.0472 (9) | 0.0001 (7) | 0.0264 (7) | −0.0028 (7) |
C8 | 0.0636 (11) | 0.0397 (9) | 0.0524 (9) | −0.0006 (8) | 0.0284 (9) | 0.0023 (7) |
C9 | 0.0653 (15) | 0.0307 (11) | 0.0596 (14) | 0.000 | 0.0295 (12) | 0.000 |
C10 | 0.0591 (11) | 0.0446 (10) | 0.0789 (13) | 0.0041 (8) | 0.0260 (10) | 0.0026 (9) |
C11 | 0.124 (2) | 0.108 (2) | 0.114 (2) | 0.0314 (18) | 0.077 (2) | −0.0018 (17) |
C12 | 0.0900 (17) | 0.0618 (15) | 0.114 (2) | 0.0219 (13) | 0.0219 (15) | 0.0168 (14) |
C13 | 0.0592 (11) | 0.0537 (11) | 0.0518 (10) | 0.0087 (9) | 0.0219 (9) | −0.0087 (8) |
C14 | 0.0557 (12) | 0.0914 (17) | 0.0770 (14) | 0.0003 (11) | 0.0157 (11) | −0.0204 (13) |
C15 | 0.1148 (18) | 0.0601 (13) | 0.0571 (12) | −0.0002 (13) | 0.0338 (12) | 0.0050 (10) |
S1—C6 | 1.7497 (17) | C13—C14 | 1.520 (3) |
S1—C13 | 1.8117 (19) | C13—H13 | 0.9800 |
S2—C4 | 1.7452 (17) | C9—C8i | 1.509 (2) |
S2—C10 | 1.815 (2) | C9—H9A | 0.9700 |
N5—C4 | 1.325 (2) | C9—H9B | 0.9700 |
N5—C6 | 1.362 (2) | C10—C11 | 1.508 (3) |
N7—C6 | 1.322 (2) | C10—C12 | 1.520 (3) |
N7—C7' | 1.345 (2) | C10—H10 | 0.9800 |
C7'—N1 | 1.352 (2) | C14—H14A | 0.9600 |
C7'—C3' | 1.393 (2) | C14—H14B | 0.9600 |
N1—N2 | 1.373 (2) | C14—H14C | 0.9600 |
N1—C8 | 1.454 (2) | C15—H15A | 0.9600 |
N2—C3 | 1.309 (2) | C15—H15B | 0.9600 |
C4—C3' | 1.409 (2) | C15—H15C | 0.9600 |
C3'—C3 | 1.412 (2) | C12—H12A | 0.9600 |
C8—C9 | 1.509 (2) | C12—H12B | 0.9600 |
C8—H8A | 0.9700 | C12—H12C | 0.9600 |
C8—H8B | 0.9700 | C11—H11A | 0.9600 |
C3—H3 | 0.9300 | C11—H11B | 0.9600 |
C13—C15 | 1.501 (3) | C11—H11C | 0.9600 |
C6—S1—C13 | 104.79 (9) | C8i—C9—H9A | 108.8 |
C4—S2—C10 | 104.48 (9) | C8—C9—H9A | 108.8 |
C4—N5—C6 | 117.56 (15) | C8i—C9—H9B | 108.8 |
C6—N7—C7' | 111.54 (14) | C8—C9—H9B | 108.8 |
N7—C6—N5 | 128.69 (16) | H9A—C9—H9B | 107.7 |
N7—C6—S1 | 120.07 (13) | C11—C10—C12 | 112.3 (2) |
N5—C6—S1 | 111.24 (12) | C11—C10—S2 | 111.65 (16) |
N7—C7'—N1 | 126.11 (15) | C12—C10—S2 | 105.75 (16) |
N7—C7'—C3' | 126.58 (15) | C11—C10—H10 | 109.0 |
N1—C7'—C3' | 107.29 (15) | C12—C10—H10 | 109.0 |
C7'—N1—N2 | 110.66 (14) | S2—C10—H10 | 109.0 |
C7'—N1—C8 | 128.07 (15) | C13—C14—H14A | 109.5 |
N2—N1—C8 | 121.20 (14) | C13—C14—H14B | 109.5 |
C3—N2—N1 | 106.16 (14) | H14A—C14—H14B | 109.5 |
N5—C4—C3' | 120.14 (16) | C13—C14—H14C | 109.5 |
N5—C4—S2 | 121.10 (13) | H14A—C14—H14C | 109.5 |
C3'—C4—S2 | 118.73 (13) | H14B—C14—H14C | 109.5 |
C7'—C3'—C4 | 115.37 (15) | C13—C15—H15A | 109.5 |
C7'—C3'—C3 | 104.30 (15) | C13—C15—H15B | 109.5 |
C4—C3'—C3 | 140.13 (17) | H15A—C15—H15B | 109.5 |
N1—C8—C9 | 112.99 (13) | C13—C15—H15C | 109.5 |
N1—C8—H8A | 109.0 | H15A—C15—H15C | 109.5 |
C9—C8—H8A | 109.0 | H15B—C15—H15C | 109.5 |
N1—C8—H8B | 109.0 | C10—C12—H12A | 109.5 |
C9—C8—H8B | 109.0 | C10—C12—H12B | 109.5 |
H8A—C8—H8B | 107.8 | H12A—C12—H12B | 109.5 |
N2—C3—C3' | 111.58 (16) | C10—C12—H12C | 109.5 |
N2—C3—H3 | 124.2 | H12A—C12—H12C | 109.5 |
C3'—C3—H3 | 124.2 | H12B—C12—H12C | 109.5 |
C15—C13—C14 | 112.36 (18) | C10—C11—H11A | 109.5 |
C15—C13—S1 | 112.32 (15) | C10—C11—H11B | 109.5 |
C14—C13—S1 | 105.22 (15) | H11A—C11—H11B | 109.5 |
C15—C13—H13 | 108.9 | C10—C11—H11C | 109.5 |
C14—C13—H13 | 108.9 | H11A—C11—H11C | 109.5 |
S1—C13—H13 | 108.9 | H11B—C11—H11C | 109.5 |
C8i—C9—C8 | 113.9 (2) | ||
C7'—N1—N2—C3 | 0.7 (2) | S2—C6—N7—C7' | 178.21 (11) |
C8—N1—N2—C3 | −176.34 (16) | C6—N7—C7'—N1 | 177.79 (16) |
N1—N2—C3—C3' | −0.3 (2) | C6—N7—C7'—C3' | −0.8 (2) |
N2—C3—C3'—C7' | −0.2 (2) | N2—N1—C7'—N7 | −179.63 (15) |
N2—C3—C3'—C4 | 174.1 (2) | C8—N1—C7'—N7 | −2.8 (3) |
C7'—C3'—C4—N5 | −3.4 (2) | N2—N1—C7'—C3' | −0.82 (19) |
C3—C3'—C4—N5 | −177.3 (2) | C8—N1—C7'—C3' | 175.97 (15) |
C7'—C3'—C4—S1 | 174.67 (12) | C4—C3'—C7'—N7 | 3.4 (2) |
C3—C3'—C4—S1 | 0.8 (3) | C3—C3'—C7'—N7 | 179.39 (16) |
C10—S1—C4—N5 | 12.30 (16) | C4—C3'—C7'—N1 | −175.37 (15) |
C10—S1—C4—C3' | −165.77 (14) | C3—C3'—C7'—N1 | 0.59 (18) |
C3'—C4—N5—C6 | 1.0 (2) | C7'—N1—C8—C9 | 126.74 (18) |
S1—C4—N5—C6 | −177.00 (12) | N2—N1—C8—C9 | −56.8 (2) |
C4—N5—C6—N7 | 2.1 (3) | N1—C8—C9—C8i | −49.76 (11) |
C4—N5—C6—S2 | −178.28 (12) | C4—S1—C10—C11 | 67.79 (19) |
C13—S2—C6—N7 | 2.52 (16) | C4—S1—C10—C12 | −169.71 (15) |
C13—S2—C6—N5 | −177.16 (12) | C6—S2—C13—C15 | 71.75 (15) |
N5—C6—N7—C7' | −2.2 (2) | C6—S2—C13—C14 | −165.75 (14) |
Symmetry code: (i) −x+1, y, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C25H36N8S4 |
Mr | 576.90 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 293 |
a, b, c (Å) | 21.044 (2), 8.814 (1), 18.953 (2) |
β (°) | 118.07 (1) |
V (Å3) | 3101.9 (6) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.34 |
Crystal size (mm) | 0.30 × 0.28 × 0.20 |
Data collection | |
Diffractometer | Bruker P4 diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3403, 2738, 2352 |
Rint | 0.020 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.035, 0.094, 1.03 |
No. of reflections | 2738 |
No. of parameters | 173 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.22, −0.21 |
Computer programs: XSCANS (Siemens, 1996), XSCANS, SHELXTL (Bruker, 1997), SHELXTL.
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Interactions between aromatic moieties are known to play an important role in chemistry (Desiraju & Steiner, 1999; Hunter et al., 2001; Tsuzuki et al., 2002), stabilization of DNA/RNA structures (Hobza & Sponer, 1999), crystal engineering (Desiraju, 1995) and drug development (Meyer et al. 2003). Use of a polymethylene and especially a trimethylene linker for demonstrating intramolecular stacking was pioneered by Browne et al. (1968) and early work has been reviewed by Leonard (1979). In 1995, we reported the first synthesis (Avasthi et al., 1995) and crystal structure determination (Biswas et al., 1995) of a trimethylene-linker molecule, (I), based on the pyrazolo[3,4-d]pyrimidine core, which is isomeric with the biologically important purine system. The crystal structure exhibits an unusual intramolecular stacking (U-motif) and intermolecular stacking. The robustness of the U-motif in (I) has been further demonstrated by the crystal structure determination of the ethyl analog, (II) (Avasthi, Rawat et al., 2001) and other related propylene-linker compounds (Maulik et al.,1998; Avasthi, Aswal & Maulik, 2001; Avasthi, Tewari et al., 2002). Interestingly, no intramolecular stacking is observed when the trimethylene linker is replaced by an ethylene (Avasthi, Rawat et al., 2001) or tetramethylene linker (Maulik et al., 2000; Avasthi, Farooq et al., 2002). We report here the structure of 1,3-bis(4,6-di-isopropylthio-1H-pyrazolo[3,4-d] pyrimidin-1-yl)propane, (III). The conformation of (III) is shown in Fig. 1. The asymmetric unit contains only half of the molecule, which is related to the other half by the crystallographic symmetry operation (1 − x, y, 0.5 − z). The molecule is folded at the centre of the bridge [C8—C9—C8A = 113.9 (2)°] as a result of intramolecular stacking between the pyrazolo[3,4-d]pyrimidine rings. For comparison, the corresponding angles in (I) and (II) are 114.1 (2) and 113.5 (2)°, respectively. In (III), as in (I) and (II), the two pyrazolo[3,4-d]pyrimidine rings are positioned in such a way that only part of the pyrimidinyl rings overlap (Fig. 1). The overlapping six-membered rings are separated by an average distance (the mean value of the distances of all the atoms in one ring from the least-squares plane through the atoms in the other ring) of 3.555 Å [3.4 and 3.37 Å in (I) and (II), respectively], thus confirming the presence of an intramolecular π–π interaction. The pyrazolo[3,4-d]pyrimidine rings in (III), like those in (I) and (II), are nearly planar [maximum deviation = −0.036 (1) Å] and the angle between the least-squares planes is 21.96 (4)° [13.2 (1)° in (I) and ? in (II)]. It appears that because of the bulkiness of the isopropyl group, compared with the methyl/ethyl groups, the average intramolecular distance (3.555 Å) and angle between the least-squares planes [21.96 (4)°] have increased appreciably. However, the most striking effect of the presence of the isopropyl group instead of the methyl/ethyl groups found in (I) and (II) is seen in the packing diagram of (III) (Fig. 2). Molecule (III) does not exhibit intermolecular stacking due to the π–π interaction, but instead contains an intermolecular C—H···π interaction (Fig. 2) between one methyl group of the isopropyl group and the adjacent C3' atom of the pyrazolo[3,4-d]pyrimidine group [H···C3': 3.14 Å]. In conclusion, the replacement of the methyl or ethyl group in (I) or (II) by a bulky isopropyl group does not seriously affect the robustness of the U-motif formed by intramolecular stacking due to the aromatic π–π interaction. However, the parallel mode of intermolecular stacking seen in (I) and (II) is not present in (III) but is replaced by a C—H···π interaction.