Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270109035069/gd3303sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270109035069/gd3303Isup2.hkl | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270109035069/gd3303IIsup3.hkl |
CCDC references: 720263; 720264
All chemicals were purchased from Sigma–Aldrich and were used without further purification. Crystals of (I) and (II) were obtained by mixing equimolar amounts of 0.1 M methanol solutions of 2M6NA with 2-imidazolidinethione and benzenesulfonic acid hydrate, respectively. The mixtures were then left to evaporate slowly at room temperature. Solution crystallizations of 2M6NA were also prepared with methanol, ethanol, propan-2-ol, butan-1-ol, acetone, acetonitrile and dimethylformamide, and left to evaporate slowly at room temperature. These all yielded form (I).
H atoms were located in difference maps. Those bonded to C atoms were treated as riding atoms in geometrically idealized positions, with C—H = 0.95 (aromatic) or 0.98 Å (methyl), and with Uiso(H) = kUeq(C), where k = 1.5 for the methyl groups, which were permitted to rotate but not to tilt, and 1.2 for the remainder. The coordinates of the H atoms bonded to N atoms were refined subject to an N—H distance restraint of 0.89 (2) Å. For (I), Uiso(H) was set at 1.4Ueq(N), while Uiso(H) values were refined in (II).
Data collection: COLLECT (Nonius, 1998) for (I); COLLECT (Hooft & Nonius 1998) for (II). Cell refinement: DENZO (Otwinowski & Minor, 1997) and COLLECT (Nonius, 1998) for (I); DENZO (Otwinowski & Minor, 1997) & COLLECT (Hooft & Nonius 1998) for (II). Data reduction: DENZO (Otwinowski & Minor, 1997) and COLLECT (Nonius, 1998) for (I); DENZO (Otwinowski & Minor, 1997) & COLLECT (Hooft & Nonius 1998) for (II). For both compounds, program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008). Molecular graphics: Mercury (Macrae et al., 2006) for (I); Mercury CSD 2.2 (CCDC 2008) for (II). Software used to prepare material for publication: publCIF (Westrip, 2009) for (I); publCIF 1.9.3_c (Westrip, 2009) for (II).
C7H8N2O2 | F(000) = 640 |
Mr = 152.15 | Dx = 1.426 Mg m−3 |
Monoclinic, P21/c | Melting point = 364–366 K |
Hall symbol: -P 2ybc | Mo Kα radiation, λ = 0.71073 Å |
a = 8.9267 (5) Å | Cell parameters from 3359 reflections |
b = 11.1863 (6) Å | θ = 2.9–27.5° |
c = 14.6796 (4) Å | µ = 0.11 mm−1 |
β = 104.788 (3)° | T = 120 K |
V = 1417.30 (12) Å3 | Block, orange |
Z = 8 | 0.10 × 0.08 × 0.04 mm |
Bruker Nonius 95mm CCD camera on κ-goniostat diffractometer | 3252 independent reflections |
Radiation source: Bruker Nonius FR591 rotating anode | 2369 reflections with I > 2σ(I) |
10cm confocal mirrors monochromator | Rint = 0.065 |
Detector resolution: 9.091 pixels mm-1 | θmax = 27.5°, θmin = 3.0° |
ϕ and ω scans | h = −11→11 |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | k = −14→14 |
Tmin = 0.989, Tmax = 0.996 | l = −19→17 |
18662 measured reflections |
Refinement on F2 | 4 restraints |
Least-squares matrix: full | 0 constraints |
R[F2 > 2σ(F2)] = 0.049 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.117 | w = 1/[σ2(Fo2) + (0.0445P)2 + 0.5714P] where P = (Fo2 + 2Fc2)/3 |
S = 1.05 | (Δ/σ)max < 0.001 |
3252 reflections | Δρmax = 0.21 e Å−3 |
213 parameters | Δρmin = −0.28 e Å−3 |
C7H8N2O2 | V = 1417.30 (12) Å3 |
Mr = 152.15 | Z = 8 |
Monoclinic, P21/c | Mo Kα radiation |
a = 8.9267 (5) Å | µ = 0.11 mm−1 |
b = 11.1863 (6) Å | T = 120 K |
c = 14.6796 (4) Å | 0.10 × 0.08 × 0.04 mm |
β = 104.788 (3)° |
Bruker Nonius 95mm CCD camera on κ-goniostat diffractometer | 3252 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | 2369 reflections with I > 2σ(I) |
Tmin = 0.989, Tmax = 0.996 | Rint = 0.065 |
18662 measured reflections |
R[F2 > 2σ(F2)] = 0.049 | 4 restraints |
wR(F2) = 0.117 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.05 | Δρmax = 0.21 e Å−3 |
3252 reflections | Δρmin = −0.28 e Å−3 |
213 parameters |
Experimental. Single crystal X-ray diffraction analyses of (I) and (II) were performed using a Nonius Kappa CCD area-detector diffractometer mounted at the window of a rotating anode FR591 generator with a molybdenum anode (λ = 0.71073?Å) and equipped with an Oxford Cryosystems cryostream device. Crystals were mounted on the end of glass fibres and data were collected at 120?(2)?K. Melting points were obtained using a hot-stage microscope (Mettler–Toledo FP82HT hot-stage). Packing indices were calculated using PLATON (Spek 2009). |
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 > 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. Data were processed using the Collect (Nonius 1998) package and unit-cell parameters were refined against all data. An empirical absorption correction was carried out using SADABS (Sheldrick, 2003). |
x | y | z | Uiso*/Ueq | ||
C1 | 0.57244 (19) | 0.65953 (15) | 0.41748 (11) | 0.0231 (4) | |
C2 | 0.54684 (19) | 0.66788 (16) | 0.31766 (11) | 0.0237 (4) | |
C3 | 0.6365 (2) | 0.60254 (16) | 0.27280 (12) | 0.0252 (4) | |
H3 | 0.6171 | 0.6079 | 0.2062 | 0.030* | |
C4 | 0.7560 (2) | 0.52804 (16) | 0.32220 (12) | 0.0265 (4) | |
H4 | 0.8176 | 0.4847 | 0.2895 | 0.032* | |
C5 | 0.7830 (2) | 0.51836 (16) | 0.41772 (12) | 0.0252 (4) | |
H5 | 0.8641 | 0.4684 | 0.4519 | 0.030* | |
C6 | 0.6912 (2) | 0.58220 (15) | 0.46524 (11) | 0.0229 (4) | |
C7 | 0.4210 (2) | 0.74894 (18) | 0.26361 (13) | 0.0326 (4) | |
H7A | 0.4168 | 0.7446 | 0.1963 | 0.049* | |
H7B | 0.4430 | 0.8313 | 0.2857 | 0.049* | |
H7C | 0.3212 | 0.7238 | 0.2735 | 0.049* | |
N1 | 0.48139 (19) | 0.72491 (16) | 0.45950 (11) | 0.0338 (4) | |
N6 | 0.72772 (18) | 0.56744 (14) | 0.56571 (10) | 0.0290 (4) | |
O6A | 0.83624 (17) | 0.50241 (13) | 0.60495 (9) | 0.0409 (4) | |
O6B | 0.64891 (16) | 0.62087 (14) | 0.61224 (9) | 0.0395 (4) | |
H1A | 0.502 (2) | 0.722 (2) | 0.5224 (11) | 0.047* | |
H1B | 0.423 (2) | 0.7812 (18) | 0.4274 (15) | 0.047* | |
C21 | 0.82756 (19) | 0.59564 (15) | 0.89978 (11) | 0.0215 (4) | |
C22 | 0.9428 (2) | 0.68037 (15) | 0.89127 (11) | 0.0226 (4) | |
C23 | 1.0325 (2) | 0.73437 (16) | 0.97011 (12) | 0.0259 (4) | |
H23 | 1.1086 | 0.7906 | 0.9631 | 0.031* | |
C24 | 1.0166 (2) | 0.70995 (16) | 1.06081 (12) | 0.0264 (4) | |
H24 | 1.0793 | 0.7501 | 1.1140 | 0.032* | |
C25 | 0.9096 (2) | 0.62762 (15) | 1.07143 (11) | 0.0243 (4) | |
H25 | 0.8987 | 0.6091 | 1.1326 | 0.029* | |
C26 | 0.81596 (19) | 0.57050 (15) | 0.99251 (11) | 0.0210 (4) | |
C27 | 0.9653 (2) | 0.70693 (17) | 0.79535 (12) | 0.0289 (4) | |
H27A | 1.0450 | 0.7686 | 0.8006 | 0.043* | |
H27B | 0.8676 | 0.7354 | 0.7541 | 0.043* | |
H27C | 0.9980 | 0.6340 | 0.7688 | 0.043* | |
N21 | 0.73956 (19) | 0.54404 (14) | 0.82128 (10) | 0.0284 (4) | |
N26 | 0.71130 (17) | 0.48160 (13) | 1.00975 (9) | 0.0242 (3) | |
O26A | 0.71380 (15) | 0.45487 (11) | 1.09225 (8) | 0.0299 (3) | |
O26B | 0.62105 (15) | 0.43052 (12) | 0.94227 (8) | 0.0334 (3) | |
H21A | 0.669 (2) | 0.4905 (17) | 0.8273 (15) | 0.040* | |
H21B | 0.744 (2) | 0.5658 (19) | 0.7643 (11) | 0.040* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0219 (9) | 0.0228 (9) | 0.0244 (8) | −0.0023 (7) | 0.0057 (7) | −0.0030 (7) |
C2 | 0.0216 (9) | 0.0242 (9) | 0.0243 (9) | −0.0010 (7) | 0.0042 (7) | −0.0010 (7) |
C3 | 0.0263 (10) | 0.0271 (10) | 0.0220 (8) | −0.0034 (8) | 0.0058 (7) | −0.0044 (7) |
C4 | 0.0260 (9) | 0.0261 (10) | 0.0283 (9) | −0.0001 (8) | 0.0086 (7) | −0.0061 (7) |
C5 | 0.0238 (9) | 0.0222 (9) | 0.0280 (9) | 0.0012 (7) | 0.0036 (7) | −0.0011 (7) |
C6 | 0.0251 (9) | 0.0239 (9) | 0.0187 (8) | −0.0027 (7) | 0.0040 (7) | −0.0006 (6) |
C7 | 0.0309 (10) | 0.0355 (11) | 0.0295 (10) | 0.0062 (9) | 0.0046 (8) | 0.0011 (8) |
N1 | 0.0355 (10) | 0.0407 (10) | 0.0265 (8) | 0.0116 (8) | 0.0100 (7) | −0.0026 (7) |
N6 | 0.0327 (9) | 0.0298 (9) | 0.0233 (8) | −0.0014 (7) | 0.0047 (6) | 0.0002 (6) |
O6A | 0.0478 (9) | 0.0413 (9) | 0.0276 (7) | 0.0116 (7) | −0.0014 (6) | 0.0046 (6) |
O6B | 0.0404 (8) | 0.0563 (10) | 0.0240 (7) | 0.0060 (7) | 0.0121 (6) | −0.0015 (6) |
C21 | 0.0235 (9) | 0.0194 (9) | 0.0208 (8) | 0.0045 (7) | 0.0041 (6) | 0.0019 (6) |
C22 | 0.0252 (9) | 0.0189 (9) | 0.0253 (8) | 0.0045 (7) | 0.0093 (7) | 0.0038 (6) |
C23 | 0.0274 (10) | 0.0197 (9) | 0.0317 (9) | −0.0021 (7) | 0.0097 (7) | −0.0006 (7) |
C24 | 0.0300 (10) | 0.0228 (9) | 0.0248 (9) | −0.0019 (8) | 0.0042 (7) | −0.0043 (7) |
C25 | 0.0291 (10) | 0.0240 (9) | 0.0203 (8) | 0.0037 (7) | 0.0072 (7) | 0.0002 (7) |
C26 | 0.0216 (9) | 0.0211 (9) | 0.0208 (8) | 0.0013 (7) | 0.0067 (6) | 0.0014 (6) |
C27 | 0.0319 (11) | 0.0298 (10) | 0.0276 (9) | 0.0019 (8) | 0.0122 (8) | 0.0033 (7) |
N21 | 0.0332 (9) | 0.0325 (9) | 0.0185 (7) | −0.0062 (7) | 0.0045 (6) | 0.0027 (6) |
N26 | 0.0249 (8) | 0.0268 (8) | 0.0211 (7) | −0.0008 (6) | 0.0062 (6) | 0.0010 (6) |
O26A | 0.0351 (7) | 0.0362 (8) | 0.0209 (6) | −0.0036 (6) | 0.0116 (5) | 0.0034 (5) |
O26B | 0.0332 (8) | 0.0407 (8) | 0.0240 (6) | −0.0131 (6) | 0.0032 (5) | 0.0009 (5) |
C1—N1 | 1.353 (2) | C21—N21 | 1.348 (2) |
C1—C6 | 1.409 (2) | C21—C26 | 1.419 (2) |
C1—C2 | 1.427 (2) | C21—C22 | 1.428 (2) |
C2—C3 | 1.370 (2) | C22—C23 | 1.368 (2) |
C2—C7 | 1.503 (2) | C22—C27 | 1.502 (2) |
C3—C4 | 1.401 (2) | C23—C24 | 1.401 (2) |
C3—H3 | 0.9500 | C23—H23 | 0.9500 |
C4—C5 | 1.365 (2) | C24—C25 | 1.364 (3) |
C4—H4 | 0.9500 | C24—H24 | 0.9500 |
C5—C6 | 1.400 (2) | C25—C26 | 1.398 (2) |
C5—H5 | 0.9500 | C25—H25 | 0.9500 |
C6—N6 | 1.436 (2) | C26—N26 | 1.431 (2) |
C7—H7A | 0.9800 | C27—H27A | 0.9800 |
C7—H7B | 0.9800 | C27—H27B | 0.9800 |
C7—H7C | 0.9800 | C27—H27C | 0.9800 |
N1—H1A | 0.894 (15) | N21—H21A | 0.890 (16) |
N1—H1B | 0.873 (16) | N21—H21B | 0.883 (15) |
N6—O6A | 1.231 (2) | N26—O26A | 1.2421 (18) |
N6—O6B | 1.251 (2) | N26—O26B | 1.2447 (18) |
N1—C1—C6 | 124.64 (16) | N21—C21—C26 | 124.46 (16) |
N1—C1—C2 | 118.37 (16) | N21—C21—C22 | 119.04 (15) |
C6—C1—C2 | 117.00 (15) | C26—C21—C22 | 116.49 (15) |
C3—C2—C1 | 119.90 (16) | C23—C22—C21 | 119.88 (15) |
C3—C2—C7 | 121.17 (15) | C23—C22—C27 | 121.09 (16) |
C1—C2—C7 | 118.93 (15) | C21—C22—C27 | 119.02 (15) |
C2—C3—C4 | 121.96 (16) | C22—C23—C24 | 122.55 (17) |
C2—C3—H3 | 119.0 | C22—C23—H23 | 118.7 |
C4—C3—H3 | 119.0 | C24—C23—H23 | 118.7 |
C5—C4—C3 | 119.38 (16) | C25—C24—C23 | 118.95 (16) |
C5—C4—H4 | 120.3 | C25—C24—H24 | 120.5 |
C3—C4—H4 | 120.3 | C23—C24—H24 | 120.5 |
C4—C5—C6 | 119.92 (16) | C24—C25—C26 | 120.12 (15) |
C4—C5—H5 | 120.0 | C24—C25—H25 | 119.9 |
C6—C5—H5 | 120.0 | C26—C25—H25 | 119.9 |
C5—C6—C1 | 121.82 (15) | C25—C26—C21 | 121.98 (16) |
C5—C6—N6 | 116.41 (15) | C25—C26—N26 | 116.77 (14) |
C1—C6—N6 | 121.74 (15) | C21—C26—N26 | 121.21 (15) |
C2—C7—H7A | 109.5 | C22—C27—H27A | 109.5 |
C2—C7—H7B | 109.5 | C22—C27—H27B | 109.5 |
H7A—C7—H7B | 109.5 | H27A—C27—H27B | 109.5 |
C2—C7—H7C | 109.5 | C22—C27—H27C | 109.5 |
H7A—C7—H7C | 109.5 | H27A—C27—H27C | 109.5 |
H7B—C7—H7C | 109.5 | H27B—C27—H27C | 109.5 |
C1—N1—H1A | 117.5 (14) | C21—N21—H21A | 118.4 (14) |
C1—N1—H1B | 119.1 (15) | C21—N21—H21B | 122.2 (14) |
H1A—N1—H1B | 121 (2) | H21A—N21—H21B | 119.2 (19) |
O6A—N6—O6B | 120.81 (14) | O26A—N26—O26B | 120.82 (14) |
O6A—N6—C6 | 119.58 (15) | O26A—N26—C26 | 119.33 (14) |
O6B—N6—C6 | 119.61 (15) | O26B—N26—C26 | 119.84 (14) |
N1—C1—C2—C3 | −179.73 (17) | N21—C21—C22—C23 | 179.51 (16) |
C6—C1—C2—C3 | −0.2 (2) | C26—C21—C22—C23 | −1.4 (2) |
N1—C1—C2—C7 | 0.3 (3) | N21—C21—C22—C27 | −1.6 (2) |
C6—C1—C2—C7 | 179.81 (16) | C26—C21—C22—C27 | 177.47 (15) |
C1—C2—C3—C4 | −1.0 (3) | C21—C22—C23—C24 | 0.1 (3) |
C7—C2—C3—C4 | 178.92 (17) | C27—C22—C23—C24 | −178.77 (16) |
C2—C3—C4—C5 | 1.0 (3) | C22—C23—C24—C25 | 1.2 (3) |
C3—C4—C5—C6 | 0.3 (3) | C23—C24—C25—C26 | −1.1 (3) |
C4—C5—C6—C1 | −1.6 (3) | C24—C25—C26—C21 | −0.3 (3) |
C4—C5—C6—N6 | −179.75 (16) | C24—C25—C26—N26 | 177.37 (16) |
N1—C1—C6—C5 | −179.00 (18) | N21—C21—C26—C25 | −179.45 (16) |
C2—C1—C6—C5 | 1.5 (2) | C22—C21—C26—C25 | 1.5 (2) |
N1—C1—C6—N6 | −0.9 (3) | N21—C21—C26—N26 | 3.0 (3) |
C2—C1—C6—N6 | 179.60 (15) | C22—C21—C26—N26 | −176.02 (15) |
C5—C6—N6—O6A | 0.9 (2) | C25—C26—N26—O26A | −3.8 (2) |
C1—C6—N6—O6A | −177.27 (16) | C21—C26—N26—O26A | 173.87 (15) |
C5—C6—N6—O6B | −179.14 (16) | C25—C26—N26—O26B | 177.50 (15) |
C1—C6—N6—O6B | 2.7 (3) | C21—C26—N26—O26B | −4.8 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O6B | 0.89 (2) | 1.97 (2) | 2.628 (2) | 130 (2) |
N1—H1A···O26Bi | 0.89 (2) | 2.68 (2) | 2.980 (2) | 100 (2) |
N1—H1B···O26Ai | 0.87 (2) | 2.28 (2) | 3.091 (2) | 156 (2) |
N1—H1B···O26Bi | 0.87 (2) | 2.65 (2) | 2.980 (2) | 104 (2) |
N21—H21A···O26B | 0.89 (2) | 1.96 (2) | 2.616 (2) | 129 (2) |
N21—H21B···O6B | 0.88 (2) | 2.26 (2) | 3.0891 (19) | 156 (2) |
Symmetry code: (i) −x+1, y+1/2, −z+3/2. |
C7H8N2O2 | F(000) = 320 |
Mr = 152.15 | Dx = 1.404 Mg m−3 |
Monoclinic, P21/c | Melting point = 334–338 K |
Hall symbol: -P 2ybc | Mo Kα radiation, λ = 0.71073 Å |
a = 3.9248 (2) Å | Cell parameters from 1678 reflections |
b = 12.8496 (8) Å | θ = 2.9–27.5° |
c = 14.2746 (9) Å | µ = 0.11 mm−1 |
β = 91.464 (4)° | T = 120 K |
V = 719.66 (7) Å3 | Needle, orange |
Z = 4 | 0.50 × 0.08 × 0.05 mm |
Bruker Nonius 95mm CCD camera on κ-goniostat diffractometer | 1631 independent reflections |
Radiation source: Bruker Nonius FR591 rotating anode | 1089 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.034 |
Detector resolution: 9.091 pixels mm-1 | θmax = 27.5°, θmin = 4.3° |
ϕ & ω scans | h = −4→5 |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | k = −15→16 |
Tmin = 0.949, Tmax = 0.995 | l = −18→16 |
8872 measured reflections |
Refinement on F2 | 0 constraints |
Least-squares matrix: full | H atoms treated by a mixture of independent and constrained refinement |
R[F2 > 2σ(F2)] = 0.045 | w = 1/[σ2(Fo2) + (0.0564P)2 + 0.1081P] where P = (Fo2 + 2Fc2)/3 |
wR(F2) = 0.125 | (Δ/σ)max < 0.001 |
S = 1.04 | Δρmax = 0.17 e Å−3 |
1631 reflections | Δρmin = −0.13 e Å−3 |
110 parameters | Extinction correction: SHELXL |
2 restraints | Extinction coefficient: 0.081 (16) |
C7H8N2O2 | V = 719.66 (7) Å3 |
Mr = 152.15 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 3.9248 (2) Å | µ = 0.11 mm−1 |
b = 12.8496 (8) Å | T = 120 K |
c = 14.2746 (9) Å | 0.50 × 0.08 × 0.05 mm |
β = 91.464 (4)° |
Bruker Nonius 95mm CCD camera on κ-goniostat diffractometer | 1631 independent reflections |
Absorption correction: multi-scan (SADABS; Sheldrick, 2003) | 1089 reflections with I > 2σ(I) |
Tmin = 0.949, Tmax = 0.995 | Rint = 0.034 |
8872 measured reflections |
R[F2 > 2σ(F2)] = 0.045 | 2 restraints |
wR(F2) = 0.125 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.04 | Δρmax = 0.17 e Å−3 |
1631 reflections | Δρmin = −0.13 e Å−3 |
110 parameters |
Experimental. Single crystal X-ray diffraction analyses of (I) and (II) were performed using a Nonius Kappa CCD area-detector diffractometer mounted at the window of a rotating anode FR591 generator with a molybdenum anode (λ = 0.71073?Å) and equipped with an Oxford Cryosystems cryostream device. Crystals were mounted on the end of glass fibres and data were collected at 120?(2)?K. |
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 > 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. Data were processed using the Collect (Nonius, 1998) package and unit-cell parameters were refined against all data. An empirical absorption correction was carried out using SADABS (Sheldrick, 2003). |
x | y | z | Uiso*/Ueq | ||
C1 | 0.3383 (3) | 0.84204 (11) | 0.25832 (10) | 0.0447 (4) | |
C2 | 0.1879 (4) | 0.92341 (13) | 0.20402 (11) | 0.0527 (4) | |
C3 | 0.0633 (4) | 1.01012 (13) | 0.24766 (13) | 0.0605 (5) | |
H3 | −0.0398 | 1.0633 | 0.2104 | 0.073* | |
C4 | 0.0821 (4) | 1.02305 (13) | 0.34367 (13) | 0.0641 (5) | |
H4 | −0.0061 | 1.0841 | 0.3717 | 0.077* | |
C5 | 0.2281 (4) | 0.94741 (13) | 0.39741 (12) | 0.0574 (5) | |
H5 | 0.2457 | 0.9559 | 0.4635 | 0.069* | |
C6 | 0.3526 (3) | 0.85709 (11) | 0.35587 (10) | 0.0464 (4) | |
C7 | 0.1676 (6) | 0.91331 (18) | 0.09944 (12) | 0.0820 (6) | |
H7A | 0.0508 | 0.9742 | 0.0726 | 0.123* | |
H7B | 0.0404 | 0.8502 | 0.0824 | 0.123* | |
H7C | 0.3982 | 0.9090 | 0.0750 | 0.123* | |
N1 | 0.4565 (4) | 0.75594 (11) | 0.21480 (11) | 0.0611 (4) | |
N6 | 0.5077 (4) | 0.78146 (11) | 0.41765 (10) | 0.0608 (4) | |
O6A | 0.5386 (4) | 0.80276 (11) | 0.50157 (9) | 0.0909 (5) | |
O6B | 0.6083 (4) | 0.69781 (11) | 0.38718 (10) | 0.0876 (5) | |
H1B | 0.553 (5) | 0.7044 (13) | 0.2494 (14) | 0.078 (6)* | |
H1A | 0.468 (5) | 0.7543 (15) | 0.1541 (11) | 0.077 (6)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0461 (8) | 0.0458 (8) | 0.0422 (8) | −0.0079 (6) | 0.0018 (6) | 0.0009 (6) |
C2 | 0.0503 (8) | 0.0580 (9) | 0.0495 (9) | −0.0079 (7) | −0.0024 (6) | 0.0097 (7) |
C3 | 0.0548 (9) | 0.0533 (9) | 0.0735 (12) | 0.0005 (7) | 0.0012 (8) | 0.0161 (8) |
C4 | 0.0646 (10) | 0.0513 (10) | 0.0767 (13) | 0.0043 (7) | 0.0123 (8) | −0.0035 (8) |
C5 | 0.0643 (10) | 0.0577 (10) | 0.0505 (9) | −0.0026 (7) | 0.0095 (7) | −0.0059 (7) |
C6 | 0.0513 (8) | 0.0457 (8) | 0.0423 (8) | −0.0030 (6) | 0.0026 (6) | 0.0039 (6) |
C7 | 0.0939 (14) | 0.0990 (15) | 0.0525 (11) | −0.0003 (11) | −0.0108 (9) | 0.0168 (10) |
N1 | 0.0817 (10) | 0.0555 (9) | 0.0461 (8) | 0.0020 (7) | 0.0018 (7) | −0.0066 (7) |
N6 | 0.0764 (10) | 0.0604 (9) | 0.0456 (8) | 0.0018 (7) | 0.0008 (6) | 0.0058 (7) |
O6A | 0.1401 (14) | 0.0898 (11) | 0.0423 (8) | 0.0080 (9) | −0.0095 (7) | 0.0074 (7) |
O6B | 0.1305 (12) | 0.0675 (9) | 0.0646 (9) | 0.0354 (8) | −0.0007 (8) | 0.0074 (7) |
C1—N1 | 1.356 (2) | C5—H5 | 0.9500 |
C1—C6 | 1.406 (2) | C6—N6 | 1.437 (2) |
C1—C2 | 1.421 (2) | C7—H7A | 0.9800 |
C2—C3 | 1.373 (2) | C7—H7B | 0.9800 |
C2—C7 | 1.499 (2) | C7—H7C | 0.9800 |
C3—C4 | 1.381 (2) | N1—H1B | 0.904 (15) |
C3—H3 | 0.9500 | N1—H1A | 0.868 (15) |
C4—C5 | 1.356 (2) | N6—O6A | 1.2318 (19) |
C4—H4 | 0.9500 | N6—O6B | 1.2284 (18) |
C5—C6 | 1.397 (2) | ||
N1—C1—C6 | 124.09 (14) | C5—C6—C1 | 121.95 (14) |
N1—C1—C2 | 119.50 (14) | C5—C6—N6 | 116.65 (13) |
C6—C1—C2 | 116.40 (13) | C1—C6—N6 | 121.37 (13) |
C3—C2—C1 | 119.84 (14) | C2—C7—H7A | 109.5 |
C3—C2—C7 | 120.79 (15) | C2—C7—H7B | 109.5 |
C1—C2—C7 | 119.37 (15) | H7A—C7—H7B | 109.5 |
C2—C3—C4 | 122.52 (15) | C2—C7—H7C | 109.5 |
C2—C3—H3 | 118.7 | H7A—C7—H7C | 109.5 |
C4—C3—H3 | 118.7 | H7B—C7—H7C | 109.5 |
C5—C4—C3 | 119.10 (16) | C1—N1—H1B | 119.4 (13) |
C5—C4—H4 | 120.4 | C1—N1—H1A | 120.2 (13) |
C3—C4—H4 | 120.4 | H1B—N1—H1A | 119.7 (19) |
C4—C5—C6 | 120.17 (15) | O6A—N6—C6 | 118.44 (15) |
C4—C5—H5 | 119.9 | O6B—N6—O6A | 120.94 (15) |
C6—C5—H5 | 119.9 | O6B—N6—C6 | 120.62 (14) |
N1—C1—C2—C3 | 179.06 (14) | C4—C5—C6—N6 | 179.17 (14) |
C6—C1—C2—C3 | −0.7 (2) | N1—C1—C6—C5 | 179.83 (14) |
N1—C1—C2—C7 | −1.0 (2) | C2—C1—C6—C5 | −0.4 (2) |
C6—C1—C2—C7 | 179.29 (14) | N1—C1—C6—N6 | 2.1 (2) |
C1—C2—C3—C4 | 1.0 (2) | C2—C1—C6—N6 | −178.23 (13) |
C7—C2—C3—C4 | −178.95 (16) | C5—C6—N6—O6A | −4.0 (2) |
C2—C3—C4—C5 | −0.2 (2) | C1—C6—N6—O6A | 173.94 (15) |
C3—C4—C5—C6 | −1.0 (2) | C5—C6—N6—O6B | 176.40 (15) |
C4—C5—C6—C1 | 1.3 (2) | C1—C6—N6—O6B | −5.7 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O6Ai | 0.87 (2) | 2.32 (2) | 3.160 (2) | 162 (2) |
N1—H1B···O6B | 0.90 (2) | 1.98 (2) | 2.625 (2) | 128 (2) |
Symmetry code: (i) x, −y+3/2, z−1/2. |
Experimental details
(I) | (II) | |
Crystal data | ||
Chemical formula | C7H8N2O2 | C7H8N2O2 |
Mr | 152.15 | 152.15 |
Crystal system, space group | Monoclinic, P21/c | Monoclinic, P21/c |
Temperature (K) | 120 | 120 |
a, b, c (Å) | 8.9267 (5), 11.1863 (6), 14.6796 (4) | 3.9248 (2), 12.8496 (8), 14.2746 (9) |
β (°) | 104.788 (3) | 91.464 (4) |
V (Å3) | 1417.30 (12) | 719.66 (7) |
Z | 8 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.11 | 0.11 |
Crystal size (mm) | 0.10 × 0.08 × 0.04 | 0.50 × 0.08 × 0.05 |
Data collection | ||
Diffractometer | Bruker Nonius 95mm CCD camera on κ-goniostat diffractometer | Bruker Nonius 95mm CCD camera on κ-goniostat diffractometer |
Absorption correction | Multi-scan (SADABS; Sheldrick, 2003) | Multi-scan (SADABS; Sheldrick, 2003) |
Tmin, Tmax | 0.989, 0.996 | 0.949, 0.995 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 18662, 3252, 2369 | 8872, 1631, 1089 |
Rint | 0.065 | 0.034 |
(sin θ/λ)max (Å−1) | 0.650 | 0.650 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.049, 0.117, 1.05 | 0.045, 0.125, 1.04 |
No. of reflections | 3252 | 1631 |
No. of parameters | 213 | 110 |
No. of restraints | 4 | 2 |
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) | 0.21, −0.28 | 0.17, −0.13 |
Computer programs: , DENZO (Otwinowski & Minor, 1997) and COLLECT (Nonius, 1998), DENZO (Otwinowski & Minor, 1997) & COLLECT (Hooft & Nonius 1998), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), Mercury (Macrae et al., 2006), Mercury CSD 2.2 (CCDC 2008), publCIF (Westrip, 2009), publCIF 1.9.3_c (Westrip, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O6B | 0.894 (15) | 1.97 (2) | 2.628 (2) | 129.7 (19) |
N1—H1A···O26Bi | 0.894 (15) | 2.68 (2) | 2.980 (2) | 100.4 (15) |
N1—H1B···O26Ai | 0.873 (16) | 2.276 (17) | 3.091 (2) | 156 (2) |
N1—H1B···O26Bi | 0.873 (16) | 2.65 (2) | 2.980 (2) | 104.0 (16) |
N21—H21A···O26B | 0.890 (16) | 1.962 (19) | 2.616 (2) | 129.2 (18) |
N21—H21B···O6B | 0.883 (15) | 2.262 (16) | 3.0891 (19) | 155.9 (18) |
Symmetry code: (i) −x+1, y+1/2, −z+3/2. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1A···O6Ai | 0.868 (15) | 2.322 (16) | 3.160 (2) | 162.4 (17) |
N1—H1B···O6B | 0.904 (15) | 1.98 (2) | 2.625 (2) | 127.5 (17) |
Symmetry code: (i) x, −y+3/2, z−1/2. |
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The formation of polymorphs by solution crystallization is influenced by thermodynamic and kinetic factors which control the processes of nucleation and crystal growth. The mechanisms and rate by which crystallization occurs depend on a number of factors including solubility, supersaturation and impurities. If a solution crystallization is performed, the solvent used can be a major factor in determining the polymorph formed (Buckley, 1951), as can be the concentration and temperature (Threlfall, 2000; Lahav & Leiserowitz, 2001; Rohani et al., 2005). The cooling rate can also affect polymorph selection; for example, flash cooling a melt often produces the metastable form (Kuhnert-Brandstätter, 1971). The presence of additives or impurities can also affect the polymorphic outcome through inhibiting the growth of one form, or accelerating the growth of nuclei of another (Blagden, 2004). As a consequence of these many possible contributions, the investigation of the effects of various crystallization parameters and the role of structure in determining the properties of compounds still depends extensively on experimental screening methods. Temperature and solvent are usually the first factors to be assessed. We are currently engaged in a systematic study of solid forms, including polymorphs, cocrystals and salts, produced by simple organic molecules with weakly interacting functional groups. In this paper, a crystal form of pure 2-methyl-6-nitroaniline, 2M6NA, produced unexpectedly during cocrystal screening, is reported. It should be noted that the other isomers of 2-methylnitroaniline (2-methyl-3-nitroaniline, 2-methyl-4-nitroaniline and 2-methyl-5-nitroaniline) so far only have one characterized crystal form.
The crystallization of two binary systems each containing 2M6NA resulted in two polymorphs of 2M6NA being formed. One polymorph, (I), produced by crystallization with 2-imidazolidinethione, was found to be the same form as that characterized by Jing et al. (2006). Further studies have found that (I) crystallizes from methanol, ethanol, propan-2-ol, butan-1-ol, acetone, acetonitrile and dimethylformamide. A second polymorph, (II), only formed on crystallization in the presence of benzenesulfonic acid. The crystallographic data for each structure are summarized below.
Although the room-temperature structure of the most common polymorph of 2M6NA, (I), has already been published, a structure description has not been given which is pertinent for the comparison of the two polymorphs. In (I), where Z' = 2, the two independent molecules form a dimer connected by a single and a bifurcated hydrogen bond [N1—H1A···O26B = 2.68 (2), N1—H1B···O26A = 2.30 (2) and N1—H1B···O26B = 2.66 (2) Å] between the amine and nitro groups (Fig. 3a). Although single and bifurcated N—H···O hydrogen bonds between amine and nitro groups are more commonly found separately in the Cambridge Structural Database (CSD, Version?; Allen 2002), this synthon is seen in a number of structures with similar distances between the amine and O atoms. The nitro group of molecule A then forms a single hydrogen bond with the amine group of a different molecule B [N21···O6B = 2.27 (2) Å]. This results in a helical chain arrangement, due to the orientation of the molecules [83.52 (4)° between the planes of the molecules]. The chains then fit together with weak C—H···O hydrogen bonds to the remaining O atom of the nitro group of molecule A that is not involved in any N—H···O hydrogen bonding. This results in molecules B being arranged in pairs in an offset manner where the perpendicular distance between the molecules in a pair is 3.38 Å, which is suggestive of π–π interactions (Fig. 3 b). The nitro groups are nearly coplanar with the aromatic ring, due to an intramolecular hydrogen bond in both molecules between the amine and nitro groups [N···O = 1.96 (2) Å]. The angles between the planes of the ring and the nitro group are 1.8 (1) and 6.0 (3)° for molecules A and B, respectively.
The new form of 2M6NA, (II), consists of chains of N—H···O hydrogen-bonded molecules [N1···O6B = 2.35 (2) Å]. However, the hydrogen bonds do not form rings as seen in (I). The molecules form linear V-shaped chains, with an angle of 127.8 (2)° between the planes of adjacent molecules (Fig. 4). The chains are stacked on top of each other in an offset manner, with a perpendicular distance of 3.51 Å between the molecules. Similarly to (I), the nitro group is approximately coplanar with the aromatic ring [angle between the planes of the ring and nitro group = 5.2 (2)°], due to the intramolecular hydrogen bond between the amine and nitro group [N1···O6A = 1.96 (2) Å].
Although not immediately noticeable by eye, the program XPac (Gelbrich, 2002) identifies a zero-dimensional construct that is common to both structures (Fig. 5). This consists of two molecules arranged about an inversion centre, with O6A···H4 and H5···H5 distances of 3.09 (2) and 2.58 (2) Å, respectively, in (I), and O6B···H4 and H5···H5 distances of 2.94 (2) and 2.52 (2) Å, respectively in (II).
It was noted by Rafilovich & Bernstein (2006) that a number of attempts to prepare cocrystals have led to new polymorphic forms of the intended cocrystal components due to the creation of new `crystallization media'. In the present work, the occurrence of the second polymorph fof 2M6NA may be due to the more acidic conditions instigated by the benzenesulfonic acid in the methanol solution, or the benzenesulfonic acid may have acted as an impurity, thus enabling a different polymorph to form. Both of these scenarios are evidenced in the literature. Of particular note is a study by Towler et al. (2004) concerning the role of pH and additives in the polymorphic selection of γ-glycine. They attribute the appearance of the more stable but less kinetically favourable γ form to an `impurity' effect, where the glycine ions selectively inhibit the nucleation and crystal growth of α-glycine which is kinetically more favourable. Indeed, further work by Poornachary et al. (2008) regarding the glycine polymorphs highlighted the controlling effect of pH over the charged impurities. There are a number of other studies in the literature where impurities or additives that are structurally similar to the target compound have been shown to inhibit the development of one polymorphic form or to stabilize one kinetic form over another (Gu et al., 2002; Lancaster et al., 2007; Davey et al., 1997; Mukuta et al., 2005). Other work involving structurally different impurities affecting polymorph formation attributes the selection to a change in solubility or impeding mass transport (Mohan et al., 2001), or inclusion of the impurity in the fastest growing faces (Blagden et al., 1998). Due to the small molecules used here, the mass transport theory will not be applicable, whereas hydrogen bonding between the crystallization components is a possibility. Review of the literature and the unique occurrence of the second 2M6NA polymorph suggest that benzenesulfonic acid most likely acts as an impurity during the crystallization, but further work is required to substantiate this concept.