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6-Methoxypurine crystallizes from
N,
N-methylformamide as the hemihydrate, C
6H
6N
4O·0.5H
2O, and from water as the trihydrate, C
6H
6N
4O·3H
2O. Both forms crystallize in the triclinic crystal system. Upon heating the trihydrate, molecules of water are liberated successively; the hemihydrate is formed at 383 K. In the hemihydrate, the H atom on the imidazole N atom is disordered between the two N atoms. The water molecule in the hemihydrate and the H atoms of a water molecule in the trihydrate are also disordered. In the hemihydrate, the organic moieties are connected by N—H
N hydrogen bonds, while they are connected
via water molecules in the trihydrate.
Supporting information
CCDC references: 231066; 231067
6-Methoxypurine was obtained from a commercial source (Aldrich) and was used without futher purification. Needle-shaped crystals of (I) were grown from N,N-methylformamide, and plate-like crystals of (II) were obtained from water.
Both structures are disordered and therefore the refinement did not converge very satisfactorily. The most difficult part is the refinement of the disordered water molecules. In (I), the water molecules equally occupy two sites and the O atoms refined satisfactorily. One of the H atoms of each water molecule occupies the same site, and therefore it has a full occupancy and refines well. However, only one of the other two H atoms, with an occupancy of 1/2, could be detected and refined. In (II), there are two water molecules that are rotationally disordered, in which one of the H atoms has a full ocupancy. while the second is disordered between two sites.
Data collection: Collect (Nonius, 2001) for (II). For both compounds, cell refinement: DENZO SMN (Otwinowski & Minor 1997); data reduction: DENZO SMN; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997).
(I) 6-Methoxypurine hemihydrate
top
Crystal data top
C6H6N4O·0.5H2O | Z = 4 |
Mr = 158.91 | F(000) = 331 |
Triclinic, P1 | Dx = 1.455 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 3.898 (1) Å | Cell parameters from 2579 reflections |
b = 11.966 (2) Å | θ = 1.3–25.1° |
c = 15.945 (3) Å | µ = 0.11 mm−1 |
α = 79.08 (2)° | T = 293 K |
β = 83.54 (2)° | Needle, colorless |
γ = 87.09 (2)° | 0.30 × 0.12 × 0.09 mm |
V = 725.3 (3) Å3 | |
Data collection top
KappaCCD diffractometer | 1877 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.000 |
Graphite monochromator | θmax = 25.1°, θmin = 1.3° |
Detector resolution: 95 pixels mm-1 | h = −4→0 |
phi scan | k = −14→14 |
2579 measured reflections | l = −18→18 |
2574 independent reflections | |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.050 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.125 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0663P)2 + 0.0856P] where P = (Fo2 + 2Fc2)/3 |
2574 reflections | (Δ/σ)max < 0.001 |
227 parameters | Δρmax = 0.15 e Å−3 |
0 restraints | Δρmin = −0.18 e Å−3 |
Crystal data top
C6H6N4O·0.5H2O | γ = 87.09 (2)° |
Mr = 158.91 | V = 725.3 (3) Å3 |
Triclinic, P1 | Z = 4 |
a = 3.898 (1) Å | Mo Kα radiation |
b = 11.966 (2) Å | µ = 0.11 mm−1 |
c = 15.945 (3) Å | T = 293 K |
α = 79.08 (2)° | 0.30 × 0.12 × 0.09 mm |
β = 83.54 (2)° | |
Data collection top
KappaCCD diffractometer | 1877 reflections with I > 2σ(I) |
2579 measured reflections | Rint = 0.000 |
2574 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.050 | 0 restraints |
wR(F2) = 0.125 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.03 | Δρmax = 0.15 e Å−3 |
2574 reflections | Δρmin = −0.18 e Å−3 |
227 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 | x | y | z | Uiso*/Ueq | Occ. (<1) |
O1a | 0.6004 (4) | 0.17735 (12) | 0.57623 (9) | 0.0513 (4) | |
N1a | 0.3007 (5) | 0.10988 (16) | 0.70881 (12) | 0.0517 (5) | |
N2a | 0.3002 (5) | −0.09016 (17) | 0.77123 (11) | 0.0551 (5) | |
N3a | 0.6395 (5) | −0.20579 (15) | 0.67980 (11) | 0.0502 (5) | |
H3a | 0.6094 | −0.2731 | 0.7096 | 0.075* | 0.50 |
N4a | 0.8240 (4) | −0.06582 (14) | 0.57258 (11) | 0.0461 (4) | |
H4a | 0.9274 | −0.0312 | 0.5250 | 0.069* | 0.50 |
C1a | 0.5031 (5) | 0.09128 (18) | 0.64025 (13) | 0.0429 (5) | |
C2a | 0.2139 (6) | 0.0187 (2) | 0.76993 (15) | 0.0588 (6) | |
H2a | 0.0741 | 0.0343 | 0.8178 | 0.088* | |
C3a | 0.5068 (5) | −0.10510 (18) | 0.70015 (13) | 0.0437 (5) | |
C4a | 0.6192 (5) | −0.01840 (17) | 0.63365 (12) | 0.0402 (5) | |
C5a | 0.8262 (6) | −0.17696 (18) | 0.60357 (14) | 0.0501 (6) | |
H5a | 0.9466 | −0.2301 | 0.5749 | 0.075* | |
C6a | 0.4507 (6) | 0.28837 (19) | 0.58251 (16) | 0.0599 (6) | |
H61a | 0.5320 | 0.3422 | 0.5325 | 0.090* | |
H62a | 0.5166 | 0.3113 | 0.6328 | 0.090* | |
H63a | 0.2036 | 0.2856 | 0.5864 | 0.078* | |
O1b | 0.3055 (4) | 0.26814 (13) | 0.99590 (9) | 0.0581 (4) | |
N1b | 0.6583 (5) | 0.25610 (16) | 0.87015 (12) | 0.0526 (5) | |
N2b | 0.7657 (5) | 0.41991 (16) | 0.75812 (11) | 0.0511 (5) | |
N3b | 0.4729 (5) | 0.59235 (15) | 0.79422 (11) | 0.0496 (5) | |
H3b | 0.5360 | 0.6421 | 0.7494 | 0.074* | 0.50 |
N4b | 0.2148 (4) | 0.51723 (15) | 0.92284 (11) | 0.0481 (5) | |
H4b | 0.0908 | 0.5116 | 0.9715 | 0.072* | 0.50 |
C1b | 0.4592 (5) | 0.31604 (18) | 0.91809 (13) | 0.0442 (5) | |
C2b | 0.7993 (6) | 0.3108 (2) | 0.79300 (15) | 0.0543 (6) | |
H2b | 0.9377 | 0.2661 | 0.7601 | 0.081* | |
C3b | 0.5617 (5) | 0.47891 (18) | 0.80940 (13) | 0.0425 (5) | |
C4b | 0.4021 (5) | 0.43178 (17) | 0.88953 (12) | 0.0409 (5) | |
C5b | 0.2680 (6) | 0.60951 (19) | 0.86348 (14) | 0.0520 (6) | |
H5b | 0.1705 | 0.6805 | 0.8695 | 0.078* | |
C6b | 0.3549 (7) | 0.1476 (2) | 1.02206 (18) | 0.0779 (8) | |
H61b | 0.2304 | 0.1233 | 1.0775 | 0.117* | |
H62b | 0.5965 | 0.1294 | 1.0251 | 0.117* | |
H63b | 0.2710 | 0.1092 | 0.9811 | 0.117* | |
O1Wa | −0.1399 (19) | 0.5447 (4) | 0.5806 (3) | 0.0863 (14) | 0.50 |
O1Wb | 0.0946 (18) | 0.5416 (4) | 0.5868 (4) | 0.0790 (14) | 0.50 |
H1W | −0.034 (13) | 0.510 (4) | 0.622 (3) | 0.121 (16)* | |
H1Wb | 0.32 (2) | 0.550 (7) | 0.596 (5) | 0.15 (3)* | 0.50 |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1a | 0.0628 (9) | 0.0363 (9) | 0.0505 (9) | −0.0013 (7) | 0.0042 (7) | −0.0029 (7) |
N1a | 0.0564 (11) | 0.0488 (12) | 0.0474 (11) | −0.0009 (8) | 0.0033 (9) | −0.0078 (9) |
N2a | 0.0633 (12) | 0.0532 (13) | 0.0428 (11) | −0.0045 (9) | 0.0071 (9) | −0.0004 (9) |
N3a | 0.0625 (11) | 0.0381 (11) | 0.0450 (11) | −0.0050 (8) | 0.0026 (9) | 0.0010 (8) |
N4a | 0.0572 (10) | 0.0379 (11) | 0.0404 (10) | −0.0033 (8) | 0.0047 (8) | −0.0055 (8) |
C1a | 0.0459 (11) | 0.0412 (13) | 0.0400 (12) | −0.0057 (9) | −0.0047 (9) | −0.0021 (9) |
C2a | 0.0656 (15) | 0.0618 (17) | 0.0444 (13) | −0.0001 (12) | 0.0108 (11) | −0.0080 (12) |
C3a | 0.0482 (11) | 0.0423 (13) | 0.0386 (11) | −0.0036 (9) | −0.0015 (9) | −0.0032 (9) |
C4a | 0.0457 (11) | 0.0379 (12) | 0.0352 (11) | −0.0031 (9) | −0.0010 (9) | −0.0035 (9) |
C5a | 0.0626 (14) | 0.0380 (13) | 0.0472 (13) | −0.0021 (10) | 0.0014 (11) | −0.0052 (10) |
C6a | 0.0661 (15) | 0.0403 (13) | 0.0698 (16) | 0.0020 (11) | −0.0048 (12) | −0.0042 (12) |
O1b | 0.0726 (10) | 0.0471 (9) | 0.0465 (9) | −0.0057 (7) | 0.0025 (7) | 0.0078 (7) |
N1b | 0.0603 (11) | 0.0451 (11) | 0.0504 (11) | 0.0031 (9) | −0.0031 (9) | −0.0065 (9) |
N2b | 0.0553 (11) | 0.0530 (12) | 0.0420 (10) | 0.0005 (8) | 0.0049 (8) | −0.0076 (9) |
N3b | 0.0614 (11) | 0.0407 (11) | 0.0418 (10) | −0.0047 (8) | 0.0048 (8) | −0.0005 (8) |
N4b | 0.0576 (11) | 0.0431 (11) | 0.0399 (10) | −0.0021 (8) | 0.0074 (8) | −0.0056 (8) |
C1b | 0.0492 (12) | 0.0425 (13) | 0.0393 (12) | −0.0054 (9) | −0.0062 (9) | −0.0016 (10) |
C2b | 0.0597 (14) | 0.0512 (15) | 0.0500 (14) | 0.0073 (11) | 0.0002 (11) | −0.0100 (12) |
C3b | 0.0489 (11) | 0.0389 (12) | 0.0382 (11) | −0.0044 (9) | −0.0012 (9) | −0.0041 (9) |
C4b | 0.0459 (11) | 0.0410 (12) | 0.0344 (11) | −0.0030 (9) | −0.0014 (9) | −0.0049 (9) |
C5b | 0.0638 (14) | 0.0401 (13) | 0.0484 (13) | −0.0005 (10) | 0.0031 (11) | −0.0044 (10) |
C6b | 0.0866 (19) | 0.0533 (16) | 0.0791 (19) | −0.0024 (13) | −0.0033 (15) | 0.0221 (14) |
O1Wa | 0.130 (5) | 0.061 (3) | 0.061 (3) | −0.002 (3) | −0.006 (3) | 0.004 (2) |
O1Wb | 0.087 (3) | 0.064 (3) | 0.073 (3) | −0.004 (3) | 0.012 (3) | 0.011 (2) |
Geometric parameters (Å, º) top
O1a—C1a | 1.342 (3) | N1b—C1b | 1.311 (3) |
O1a—C6a | 1.440 (3) | N1b—C2b | 1.350 (3) |
N1a—C1a | 1.322 (3) | N2b—C2b | 1.325 (3) |
N1a—C2a | 1.347 (3) | N2b—C3b | 1.347 (3) |
N2a—C2a | 1.325 (3) | N3b—C5b | 1.331 (3) |
N2a—C3a | 1.350 (3) | N3b—C3b | 1.367 (3) |
N3a—C5a | 1.339 (3) | N3b—H3b | 0.8600 |
N3a—C3a | 1.368 (3) | N4b—C5b | 1.320 (3) |
N3a—H3a | 0.8600 | N4b—C4b | 1.380 (3) |
N4a—C5a | 1.328 (3) | N4b—H4b | 0.8600 |
N4a—C4a | 1.377 (3) | C1b—C4b | 1.388 (3) |
N4a—H4a | 0.8600 | C2b—H2b | 0.9300 |
C1a—C4a | 1.385 (3) | C3b—C4b | 1.386 (3) |
C2a—H2a | 0.9300 | C5b—H5b | 0.9300 |
C3a—C4a | 1.385 (3) | C6b—H61b | 0.9600 |
C5a—H5a | 0.9300 | C6b—H62b | 0.9600 |
C6a—H61a | 0.9600 | C6b—H63b | 0.9600 |
C6a—H62a | 0.9600 | O1Wa—O1Wb | 0.929 (6) |
C6a—H63a | 0.9600 | O1Wa—H1W | 0.85 (4) |
O1b—C1b | 1.351 (3) | O1Wb—H1W | 0.77 (5) |
O1b—C6b | 1.433 (3) | O1Wb—H1Wb | 0.94 (9) |
| | | |
C1a—O1a—C6a | 116.87 (18) | C2b—N2b—C3b | 112.37 (19) |
C1a—N1a—C2a | 117.3 (2) | C5b—N3b—C3b | 105.39 (18) |
C2a—N2a—C3a | 111.70 (19) | C5b—N3b—H3b | 127.3 |
C5a—N3a—C3a | 105.14 (18) | C3b—N3b—H3b | 127.3 |
C5a—N3a—H3a | 127.4 | C5b—N4b—C4b | 104.72 (18) |
C3a—N3a—H3a | 127.4 | C5b—N4b—H4b | 127.6 |
C5a—N4a—C4a | 104.63 (17) | C4b—N4b—H4b | 127.6 |
C5a—N4a—H4a | 127.7 | N1b—C1b—O1b | 121.63 (19) |
C4a—N4a—H4a | 127.7 | N1b—C1b—C4b | 120.17 (19) |
N1a—C1a—O1a | 121.07 (19) | O1b—C1b—C4b | 118.20 (19) |
N1a—C1a—C4a | 120.1 (2) | N2b—C2b—N1b | 128.3 (2) |
O1a—C1a—C4a | 118.86 (19) | N2b—C2b—H2b | 115.8 |
N2a—C2a—N1a | 129.0 (2) | N1b—C2b—H2b | 115.8 |
N2a—C2a—H2a | 115.5 | N2b—C3b—N3b | 128.11 (19) |
N1a—C2a—H2a | 115.5 | N2b—C3b—C4b | 124.4 (2) |
N2a—C3a—N3a | 127.3 (2) | N3b—C3b—C4b | 107.54 (18) |
N2a—C3a—C4a | 124.9 (2) | N4b—C4b—C3b | 108.08 (18) |
N3a—C3a—C4a | 107.78 (19) | N4b—C4b—C1b | 134.77 (19) |
N4a—C4a—C3a | 108.42 (18) | C3b—C4b—C1b | 117.15 (19) |
N4a—C4a—C1a | 134.48 (19) | N4b—C5b—N3b | 114.3 (2) |
C3a—C4a—C1a | 117.08 (19) | N4b—C5b—H5b | 122.9 |
N4a—C5a—N3a | 114.03 (19) | N3b—C5b—H5b | 122.9 |
N4a—C5a—H5a | 123.0 | O1b—C6b—H61b | 109.5 |
N3a—C5a—H5a | 123.0 | O1b—C6b—H62b | 109.5 |
O1a—C6a—H61a | 109.5 | H61b—C6b—H62b | 109.5 |
O1a—C6a—H62a | 109.5 | O1b—C6b—H63b | 109.5 |
H61a—C6a—H62a | 109.5 | H61b—C6b—H63b | 109.5 |
O1a—C6a—H63a | 109.5 | H62b—C6b—H63b | 109.5 |
H61a—C6a—H63a | 109.5 | O1Wb—O1Wa—H1W | 51 (3) |
H62a—C6a—H63a | 109.5 | O1Wa—O1Wb—H1W | 59 (4) |
C1b—O1b—C6b | 117.08 (19) | O1Wa—O1Wb—H1Wb | 170 (5) |
C1b—N1b—C2b | 117.65 (19) | H1W—O1Wb—H1Wb | 121 (6) |
| | | |
C2A—N1A—C1A—O1A | 179.69 (18) | C2B—N1B—C1B—O1B | 179.50 (18) |
C2A—N1A—C1A—C4A | −0.5 (3) | C2B—N1B—C1B—C4B | −0.7 (3) |
C6A—O1A—C1A—N1A | −5.2 (3) | C6B—O1B—C1B—N1B | −3.1 (3) |
C6A—O1A—C1A—C4A | 174.96 (18) | C6B—O1B—C1B—C4B | 177.03 (19) |
C3A—N2A—C2A—N1A | 0.9 (3) | C3B—N2B—C2B—N1B | −0.1 (3) |
C1A—N1A—C2A—N2A | −0.9 (4) | C1B—N1B—C2B—N2B | 0.5 (3) |
C2A—N2A—C3A—N3A | −178.9 (2) | C2B—N2B—C3B—N3B | 179.7 (2) |
C2A—N2A—C3A—C4A | 0.4 (3) | C2B—N2B—C3B—C4B | −0.3 (3) |
C5A—N3A—C3A—N2A | 179.9 (2) | C5B—N3B—C3B—N2B | 179.9 (2) |
C5A—N3A—C3A—C4A | 0.5 (2) | C5B—N3B—C3B—C4B | −0.2 (2) |
C5A—N4A—C4A—C3A | 0.3 (2) | C5B—N4B—C4B—C3B | −0.2 (2) |
C5A—N4A—C4A—C1A | −177.7 (2) | C5B—N4B—C4B—C1B | 179.8 (2) |
N2A—C3A—C4A—N4A | −179.92 (18) | N2B—C3B—C4B—N4B | −179.87 (18) |
N3A—C3A—C4A—N4A | −0.5 (2) | N3B—C3B—C4B—N4B | 0.2 (2) |
N2A—C3A—C4A—C1A | −1.6 (3) | N2B—C3B—C4B—C1B | 0.1 (3) |
N3A—C3A—C4A—C1A | 177.87 (17) | N3B—C3B—C4B—C1B | −179.79 (17) |
N1A—C1A—C4A—N4A | 179.4 (2) | N1B—C1B—C4B—N4B | −179.6 (2) |
O1A—C1A—C4A—N4A | −0.8 (3) | O1B—C1B—C4B—N4B | 0.2 (3) |
N1A—C1A—C4A—C3A | 1.5 (3) | N1B—C1B—C4B—C3B | 0.4 (3) |
O1A—C1A—C4A—C3A | −178.60 (17) | O1B—C1B—C4B—C3B | −179.80 (17) |
C4A—N4A—C5A—N3A | 0.0 (2) | C4B—N4B—C5B—N3B | 0.1 (2) |
C3A—N3A—C5A—N4A | −0.3 (2) | C3B—N3B—C5B—N4B | 0.1 (2) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N4a—H4a···N4ai | 0.86 | 1.95 | 2.801 (3) | 171 |
N3a—H3a···N3bii | 0.86 | 1.95 | 2.794 (3) | 167 |
N4b—H4b···N4biii | 0.86 | 1.94 | 2.791 (3) | 173 |
N3b—H3b···N3aiv | 0.86 | 1.98 | 2.794 (3) | 158 |
O1Wb—H1Wa···N2bv | 0.77 | 2.30 | 3.021 (3) | 157 |
Symmetry codes: (i) −x+2, −y, −z+1; (ii) x, y−1, z; (iii) −x, −y+1, −z+2; (iv) x, y+1, z; (v) x−1, y, z. |
(II) 6-Methoxypurine trihydrate
top
Crystal data top
C6H6N4O·3H2O | Z = 2 |
Mr = 204.20 | F(000) = 216 |
Triclinic, P1 | Dx = 1.361 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 6.837 (1) Å | Cell parameters from 3048 reflections |
b = 7.819 (2) Å | θ = 2.2–25.0° |
c = 10.281 (2) Å | µ = 0.11 mm−1 |
α = 70.13 (2)° | T = 293 K |
β = 75.49 (2)° | Prism, colorless |
γ = 80.29 (2)° | 0.40 × 0.30 × 0.30 mm |
V = 498.29 (18) Å3 | |
Data collection top
KappaCCD diffractometer | 1244 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.022 |
Graphite monochromator | θmax = 25.0°, θmin = 2.2° |
Detector resolution: 95 pixels mm-1 | h = −8→7 |
phi scan | k = −9→8 |
3048 measured reflections | l = −12→11 |
1765 independent reflections | |
Refinement top
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.037 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.094 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.92 | w = 1/[σ2(Fo2) + (0.0599P)2] where P = (Fo2 + 2Fc2)/3 |
1765 reflections | (Δ/σ)max = 0.024 |
160 parameters | Δρmax = 0.18 e Å−3 |
0 restraints | Δρmin = −0.17 e Å−3 |
Crystal data top
C6H6N4O·3H2O | γ = 80.29 (2)° |
Mr = 204.20 | V = 498.29 (18) Å3 |
Triclinic, P1 | Z = 2 |
a = 6.837 (1) Å | Mo Kα radiation |
b = 7.819 (2) Å | µ = 0.11 mm−1 |
c = 10.281 (2) Å | T = 293 K |
α = 70.13 (2)° | 0.40 × 0.30 × 0.30 mm |
β = 75.49 (2)° | |
Data collection top
KappaCCD diffractometer | 1244 reflections with I > 2σ(I) |
3048 measured reflections | Rint = 0.022 |
1765 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.037 | 0 restraints |
wR(F2) = 0.094 | H atoms treated by a mixture of independent and constrained refinement |
S = 0.92 | Δρmax = 0.18 e Å−3 |
1765 reflections | Δρmin = −0.17 e Å−3 |
160 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 | x | y | z | Uiso*/Ueq | Occ. (<1) |
O1 | 0.19668 (16) | 0.30631 (14) | 0.74931 (11) | 0.0533 (3) | |
N1 | 0.25371 (17) | 0.29417 (17) | 0.52070 (13) | 0.0446 (3) | |
N2 | 0.29658 (17) | 0.56566 (17) | 0.31939 (12) | 0.0447 (3) | |
N3 | 0.26624 (17) | 0.83905 (17) | 0.38841 (13) | 0.0462 (4) | |
H3N | 0.2840 | 0.9223 | 0.3074 | 0.069* | |
N4 | 0.20967 (18) | 0.71038 (17) | 0.62353 (13) | 0.0458 (4) | |
C1 | 0.2274 (2) | 0.3883 (2) | 0.60997 (15) | 0.0406 (4) | |
C2 | 0.2869 (2) | 0.3871 (2) | 0.38155 (16) | 0.0481 (4) | |
H2 | 0.3053 | 0.3174 | 0.3212 | 0.072* | |
C3 | 0.26780 (19) | 0.65585 (19) | 0.41363 (15) | 0.0377 (4) | |
C4 | 0.23320 (18) | 0.57715 (19) | 0.55911 (14) | 0.0386 (4) | |
C5 | 0.2312 (2) | 0.8630 (2) | 0.51637 (16) | 0.0497 (4) | |
H5 | 0.2230 | 0.9770 | 0.5281 | 0.075* | |
C6 | 0.1843 (3) | 0.1112 (2) | 0.80051 (19) | 0.0668 (5) | |
H6a | 0.0612 | 0.0846 | 0.7856 | 0.100* | |
H6b | 0.1850 | 0.0664 | 0.8997 | 0.100* | |
H6c | 0.2986 | 0.0530 | 0.7503 | 0.100* | |
O1W | 0.06376 (19) | 0.67067 (18) | 0.91286 (14) | 0.0568 (4) | |
O2W | 0.60220 (19) | 0.3358 (2) | 0.98014 (14) | 0.0608 (4) | |
O3W | 0.2944 (2) | 0.1132 (2) | 0.13579 (15) | 0.0769 (5) | |
H1Wa | 0.117 (4) | 0.674 (3) | 0.819 (3) | 0.131 (9)* | |
H1Wb | 0.191 (6) | 0.683 (5) | 0.956 (4) | 0.066 (10)* | 0.50 |
H1Wc | 0.029 (6) | 0.565 (5) | 0.961 (4) | 0.071 (14)* | 0.50 |
H2Wa | 0.644 (3) | 0.352 (3) | 0.887 (3) | 0.105 (8)* | |
H2Wb | 0.574 (11) | 0.471 (13) | 0.995 (9) | 0.20 (3)* | 0.50 |
H2Wc | 0.683 (16) | 0.242 (16) | 1.003 (11) | 0.32 (6)* | 0.50 |
H3Wa | 0.180 (5) | 0.178 (4) | 0.120 (3) | 0.163 (13)* | |
H3Wb | 0.395 (4) | 0.175 (3) | 0.082 (2) | 0.095 (7)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0736 (7) | 0.0421 (7) | 0.0385 (6) | −0.0142 (5) | −0.0107 (5) | −0.0018 (5) |
N1 | 0.0521 (7) | 0.0379 (8) | 0.0443 (8) | −0.0073 (6) | −0.0086 (5) | −0.0130 (6) |
N2 | 0.0486 (7) | 0.0465 (9) | 0.0369 (7) | −0.0052 (5) | −0.0078 (5) | −0.0107 (6) |
N3 | 0.0531 (8) | 0.0379 (8) | 0.0401 (7) | −0.0059 (5) | −0.0095 (5) | −0.0022 (6) |
N4 | 0.0578 (8) | 0.0379 (8) | 0.0398 (7) | −0.0053 (6) | −0.0064 (5) | −0.0119 (6) |
C1 | 0.0395 (8) | 0.0397 (10) | 0.0380 (8) | −0.0063 (6) | −0.0076 (6) | −0.0052 (7) |
C2 | 0.0551 (9) | 0.0467 (10) | 0.0447 (9) | −0.0056 (7) | −0.0091 (7) | −0.0174 (8) |
C3 | 0.0357 (7) | 0.0354 (9) | 0.0389 (8) | −0.0030 (6) | −0.0072 (6) | −0.0080 (7) |
C4 | 0.0392 (8) | 0.0376 (9) | 0.0373 (8) | −0.0044 (6) | −0.0072 (6) | −0.0096 (7) |
C5 | 0.0589 (10) | 0.0380 (10) | 0.0507 (10) | −0.0028 (7) | −0.0098 (7) | −0.0139 (8) |
C6 | 0.0895 (13) | 0.0430 (11) | 0.0562 (11) | −0.0200 (9) | −0.0162 (9) | 0.0067 (8) |
O1W | 0.0659 (8) | 0.0577 (9) | 0.0424 (7) | −0.0096 (6) | −0.0084 (6) | −0.0103 (6) |
O2W | 0.0698 (8) | 0.0679 (10) | 0.0415 (7) | −0.0143 (7) | −0.0068 (5) | −0.0125 (6) |
O3W | 0.0655 (9) | 0.0673 (9) | 0.0683 (9) | −0.0104 (7) | −0.0094 (7) | 0.0153 (7) |
Geometric parameters (Å, º) top
O1—C1 | 1.3333 (17) | C3—C4 | 1.385 (2) |
O1—C6 | 1.444 (2) | C5—H5 | 0.9300 |
N1—C1 | 1.3220 (19) | C6—H6a | 0.9600 |
N1—C2 | 1.3463 (19) | C6—H6b | 0.9600 |
N2—C2 | 1.3287 (19) | C6—H6c | 0.9600 |
N2—C3 | 1.3405 (18) | O1W—H1Wa | 0.93 (3) |
N3—C5 | 1.348 (2) | O1W—H1Wb | 1.11 (4) |
N3—C3 | 1.3649 (19) | O1W—H1Wc | 0.84 (3) |
N3—H3N | 0.8600 | O2W—H2Wa | 0.90 (3) |
N4—C5 | 1.3207 (19) | O2W—H2Wb | 1.10 (10) |
N4—C4 | 1.3816 (19) | O2W—H2Wc | 0.85 (10) |
C1—C4 | 1.393 (2) | O3W—H3Wa | 0.87 (3) |
C2—H2 | 0.9300 | O3W—H3Wb | 0.87 (2) |
| | | |
C1—O1—C6 | 117.77 (13) | C3—C4—C1 | 116.39 (14) |
C1—N1—C2 | 117.71 (13) | N4—C5—N3 | 114.07 (14) |
C2—N2—C3 | 112.03 (12) | N4—C5—H5 | 123.0 |
C5—N3—C3 | 106.02 (12) | N3—C5—H5 | 123.0 |
C5—N3—H3N | 127.0 | O1—C6—H6a | 109.5 |
C3—N3—H3N | 127.0 | O1—C6—H6b | 109.5 |
C5—N4—C4 | 103.67 (12) | H6A—C6—H6b | 109.5 |
N1—C1—O1 | 121.46 (13) | O1—C6—H6c | 109.5 |
N1—C1—C4 | 120.06 (13) | H6A—C6—H6c | 109.5 |
O1—C1—C4 | 118.49 (14) | H6B—C6—H6c | 109.5 |
N2—C2—N1 | 128.29 (15) | H1Wa—O1W—H1Wb | 107 (2) |
N2—C2—H2 | 115.9 | H1Wa—O1W—H1Wc | 109 (3) |
N1—C2—H2 | 115.9 | H1Wb—O1W—H1Wc | 103 (3) |
N2—C3—N3 | 128.22 (13) | H2Wa—O2W—H2Wb | 108 (5) |
N2—C3—C4 | 125.53 (13) | H2Wa—O2W—H2Wc | 94 (7) |
N3—C3—C4 | 106.26 (13) | H2Wb—O2W—H2Wc | 136 (9) |
N4—C4—C3 | 109.99 (13) | H3Wa—O3W—H3Wb | 109 (2) |
N4—C4—C1 | 133.62 (13) | | |
| | | |
C2—N1—C1—O1 | −179.04 (12) | C5—N4—C4—C1 | −179.61 (14) |
C2—N1—C1—C4 | 0.41 (19) | N2—C3—C4—N4 | −179.81 (12) |
C6—O1—C1—N1 | −2.6 (2) | N3—C3—C4—N4 | 0.22 (15) |
C6—O1—C1—C4 | 177.97 (12) | N2—C3—C4—C1 | −0.30 (19) |
C3—N2—C2—N1 | −0.2 (2) | N3—C3—C4—C1 | 179.73 (11) |
C1—N1—C2—N2 | −0.2 (2) | N1—C1—C4—N4 | 179.19 (14) |
C2—N2—C3—N3 | −179.56 (13) | O1—C1—C4—N4 | −1.3 (2) |
C2—N2—C3—C4 | 0.47 (19) | N1—C1—C4—C3 | −0.17 (19) |
C5—N3—C3—N2 | 179.90 (13) | O1—C1—C4—C3 | 179.29 (12) |
C5—N3—C3—C4 | −0.12 (14) | C4—N4—C5—N3 | 0.14 (16) |
C5—N4—C4—C3 | −0.22 (15) | C3—N3—C5—N4 | −0.01 (16) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N3—H3N···O3Wi | 0.86 | 1.88 | 2.735 (2) | 174 |
O1W—H1Wa···N4 | 0.94 (3) | 1.89 (3) | 2.816 (2) | 173 (2) |
O1W—H1Wb···O2Wii | 1.11 | 1.66 | 2.759 (2) | 170 |
O1W—H1Wc···O1Wiii | 0.84 | 1.96 | 2.801 (2) | 174 |
O2W—H2Wa···N2iv | 0.90 (3) | 1.95 (3) | 2.838 (2) | 169 |
O2W—H2Wb···O2Wii | 1.10 | 1.81 | 2.815 (2) | 150 |
O3W—H3Wb···O2Wv | 0.87 (3) | 1.91 (3) | 2.770 (2) | 172 |
O3W—H3Wa···O1Wvi | 0.88 (3) | 1.91 (3) | 2.783 (2) | 177 |
Symmetry codes: (i) x, y+1, z; (ii) −x+1, −y+1, −z+2; (iii) −x, −y+1, −z+2; (iv) −x+1, −y+1, −z+1; (v) x, y, z−1; (vi) −x, −y+1, −z+1. |
Experimental details
| (I) | (II) |
Crystal data |
Chemical formula | C6H6N4O·0.5H2O | C6H6N4O·3H2O |
Mr | 158.91 | 204.20 |
Crystal system, space group | Triclinic, P1 | Triclinic, P1 |
Temperature (K) | 293 | 293 |
a, b, c (Å) | 3.898 (1), 11.966 (2), 15.945 (3) | 6.837 (1), 7.819 (2), 10.281 (2) |
α, β, γ (°) | 79.08 (2), 83.54 (2), 87.09 (2) | 70.13 (2), 75.49 (2), 80.29 (2) |
V (Å3) | 725.3 (3) | 498.29 (18) |
Z | 4 | 2 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.11 | 0.11 |
Crystal size (mm) | 0.30 × 0.12 × 0.09 | 0.40 × 0.30 × 0.30 |
|
Data collection |
Diffractometer | KappaCCD diffractometer | KappaCCD diffractometer |
Absorption correction | – | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2579, 2574, 1877 | 3048, 1765, 1244 |
Rint | 0.000 | 0.022 |
(sin θ/λ)max (Å−1) | 0.596 | 0.596 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.050, 0.125, 1.03 | 0.037, 0.094, 0.92 |
No. of reflections | 2574 | 1765 |
No. of parameters | 227 | 160 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.15, −0.18 | 0.18, −0.17 |
Hydrogen-bond geometry (Å, º) for (I) top
D—H···A | D—H | H···A | D···A | D—H···A |
N4a—H4a···N4ai | 0.86 | 1.95 | 2.801 (3) | 171 |
N3a—H3a···N3bii | 0.86 | 1.95 | 2.794 (3) | 167 |
N4b—H4b···N4biii | 0.86 | 1.94 | 2.791 (3) | 173 |
N3b—H3b···N3aiv | 0.86 | 1.98 | 2.794 (3) | 158 |
O1Wb—H1Wa···N2bv | 0.77 | 2.30 | 3.021 (3) | 157 |
Symmetry codes: (i) −x+2, −y, −z+1; (ii) x, y−1, z; (iii) −x, −y+1, −z+2; (iv) x, y+1, z; (v) x−1, y, z. |
Comparison of selected geometric parameters (Å, °) top | Hemihydrate (I) | Hemihydrate (I) | Trihydrate (II) |
| Molecule A | Molecule B | |
O1-C1 | 1.342 (3) | 1.351 (3) | 1.333 (2) |
O1-C6 | 1.440 (3) | 1.433 (3) | 1.444 (2) |
N1-C1 | 1.322 (3) | 1.311 (3) | 1.322 (2) |
N1-C2 | 1.347 (3) | 1.350 (3) | 1.346 (2) |
N2-C2 | 1.325 (3) | 1.325 (3) | 1.329 (2) |
N2-C3 | 1.350 (3) | 1.347 (3) | 1.341 (2) |
N3-C3 | 1.368 (3) | 1.367 (3) | 1.365 (2) |
N4-C5 | 1.329 (3) | 1.320 (3) | 1.321 (2) |
N4-C4 | 1.377 (3) | 1.380 (3) | 1.382 (2) |
C1-C4 | 1.385 (3) | 1.388 (3) | 1.393 (2) |
C3-C4 | 1.385 (3) | 1.386 (3) | 1.385 (2) |
| | | |
C1-O1-C6 | 116.8 (2) | 117.1 (2) | 117.8 (1) |
C1-N1-C2 | 117.3 (2) | 117.7 (2) | 117.7 (1) |
C2-N2-C3 | 111.7 (2) | 112.4 (2) | 112.0 (1) |
C5-N3-C3 | 105.1 (2) | 105.4 (2) | 106.0 (1) |
C5-N4-C4 | 104.6 (2) | 104.7 (2) | 103.7 (1) |
N1-C1-O1 | 121.1 (2) | 121.6 (2) | 121.5 (1) |
N1-C1-C4 | 120.1 (2) | 120.2 (2) | 120.1 (1) |
O1-C1-C4 | 118.9 (2) | 118.2 (2) | 118.5 (1) |
N2-C2-N1 | 129.0 (2) | 128.3 (2) | 128.3 (2) |
N2-C3-N3 | 127.3 (2) | 128.1 (2) | 128.2 (1) |
N2-C3-C4 | 124.9 (2) | 124.4 (2) | 125.5 (1) |
N3-C3-C4 | 107.8 (2) | 107.5 (2) | 106.3 (1) |
N4-C4-C1 | 134.5 (2) | 134.8 (2) | 133.6 (1) |
N4-C4-C3 | 108.4 (2) | 108.1 (2) | 110.0 (1) |
C1-C4-C3 | 117.1 (2) | 117.2 (2) | 116.3 (1) |
N4-C5-N3 | 114.0 (2) | 114.2 (2) | 114.1 (1) |
Hydrogen-bond geometry (Å, º) for (II) top
D—H···A | D—H | H···A | D···A | D—H···A |
N3—H3N···O3Wi | 0.86 | 1.88 | 2.735 (2) | 174 |
O1W—H1Wa···N4 | 0.94 (3) | 1.89 (3) | 2.816 (2) | 173 (2) |
O1W—H1Wb···O2Wii | 1.11 | 1.66 | 2.759 (2) | 170 |
O1W—H1Wc···O1Wiii | 0.84 | 1.96 | 2.801 (2) | 174 |
O2W—H2Wa···N2iv | 0.90 (3) | 1.95 (3) | 2.838 (2) | 169 |
O2W—H2Wb···O2Wii | 1.10 | 1.81 | 2.815 (2) | 150 |
O3W—H3Wb···O2Wv | 0.87 (3) | 1.91 (3) | 2.770 (2) | 172 |
O3W—H3Wa···O1Wvi | 0.88 (3) | 1.91 (3) | 2.783 (2) | 177 |
Symmetry codes: (i) x, y+1, z; (ii) −x+1, −y+1, −z+2; (iii) −x, −y+1, −z+2; (iv) −x+1, −y+1, −z+1; (v) x, y, z−1; (vi) −x, −y+1, −z+1. |
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6-Methoxypurine, (1), has been examined for its ability to undergo methyl rearrangement in the solid or liquid state (Kaftory & Handelsman-Benory, 1994; Handelsman-Benory et al., 2000; Greenberg et al. 2001; Kaftory et al., 2001; Kaftory, 2002). Therefore, the structure and the thermal behavior of the commercially available 6-methoxypurine hemihydrate were investigated. Attempts to crystallize the hemihydrate of (1) from water failed, and a trihydrate form was obtained. Later, it was found that the hemihydrate can be crystallized from N,N-methylformamide. The crystal structures and the thermal behavior of the two hydrates are described below.
The structures of the hemihydrate, (I), and trihydrate, (II), showing the atomic numbering and hydrogen bonding, are given in Figs. 1 and 2, respectively. 6-Methoxypurine was expected to pack in a similar way to aminopurine, (2) (Serra, Dorner & Silver, 1992). Aminopurine forms dimers held by hydrogen bonds, as shown in the scheme. However, 6-methoxypurine crystallizes either with half a molecule or with three molecules of water. 6-Methoxypurine hemihydrate, (I), crystallizes with two symmetry-independent molecules. The water molecule is hydrogen bonded to the organic moiety, while the organic moieties are linked to one another by N—H···N hydrogen bonds (Table 2 and Fig. 1). It should be noted that the water molecule is equally disordered, as well as the amino H atom (H3), which is equally distributed between atoms N3 and N4. The disorder is also expressed by the similar lengths of the N3—C5 and N4—C5 bonds. Formally, one bond should be a single and the other a double bond. However, the experimental distances are 1.339 and 1.328 Å [(in molecule A of (I)], and 1.331 and 1.320 Å (in molecule B), while in 6-methoxypurine trihydrate, (II), those distances are 1.348 and 1.321 Å for the single and double bonds, respectively. In the crystal structure of (II), the water molecules serve as linkers between the organic molecules, via hydrogen bonding. There are nine strong hydrogen bonds, of which six are between the water molecules, and three are between molecules of water and the organic moiety (Table 3 and Fig. 2). One of the water molecules is found to be disordered.
The thermal behavior of (I) is shown by the DSC thermograph given in Fig. 3. The thermograph consists of two single endotherms. The first endothermic peak is assigned to the liberation of molecules of water at 399 K (ΔH = 11.08 kJ mol−1). The second endothermic peak at 466 K (ΔH = 5.27 kJ mol−1) is assigned to the melting, and the last exothermic peak at 470 K (ΔH = −33.06 kJ mol−1) is assigned to the methyl rearrangement in the liquid state. The DSC thermographs of (I) and (II) (Fig. 4) are identical in the temperature range 383–493 K, but that of (II) includes two more endothermic peaks at lower temperatures. The extra two peaks are assigned to the liberation of two crystallographically non-identical molecules of water. One is liberated at 342 K (ΔH1 = 21.84 kJ mol−1) and the second is liberated at 372 K (ΔH2 = 44.71 kJ mol−1).