Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270108011530/gd3203sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270108011530/gd3203Isup2.hkl |
CCDC reference: 692660
For related literature, see: Bernstein et al. (1995); Coppens & Schimdt (1965a, 1965b); Denne & Small (1971); Dzhelomanova et al. (1956); Etter (1990); Etter & MacDonald (1990); Hamilton (1965); Jeffrey et al. (1980); Johnstone et al. (2008); Kulkarni et al. (1998); Ottersen (1975); Senti & Harker (1940); Wójcik & Mossakowska (2006).
4-Nitrophenol and acetamide were used as provided (Aldrich and Acros). 4-Nitrophenol (5 g, 35.9 mmol) and acetamide (2.1 g, 35.9 mmol) were weighed into a conical flask. The flask was heated at 373 K until both reagents had melted. The yellow liquid was allowed to cool to room temperature and the resulting yellow solid was recrystalized as plates from toluene [m.p. 371.9– 372.9 K; literature 369 K (Dzhelomanova et al., 1956)].
All H atoms were treated as riding atoms, with C—H = 0.95 or 0.98°, N—H = 0.88Å and O—H = 0.84Å, and with Uiso(H) = kUeq(carrier), where k = 1.2 or 1.5.
Data collection: SMART (Bruker, 1988); cell refinement: SMART (Bruker, 1988); data reduction: SMART (Bruker, 1988); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Bruker, 1988); software used to prepare material for publication: SHELXTL (Bruker, 1988).
C6H5NO3·C2H5NO | F(000) = 832 |
Mr = 198.18 | Dx = 1.437 Mg m−3 |
Monoclinic, P21/c | Melting point: 373 K |
Hall symbol: -P 2ybc | Mo Kα radiation, λ = 0.71073 Å |
a = 20.370 (3) Å | Cell parameters from 11096 reflections |
b = 3.7506 (6) Å | θ = 0.8–28.2° |
c = 24.070 (3) Å | µ = 0.12 mm−1 |
β = 94.873 (3)° | T = 100 K |
V = 1832.3 (5) Å3 | Plate, yellow |
Z = 8 | 0.5 × 0.4 × 0.1 mm |
Bruker SMART APEX diffractometer | 2683 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.142 |
Graphite monochromator | θmax = 25.0°, θmin = 1.0° |
ϕ and ω scans | h = −24→13 |
8627 measured reflections | k = −4→4 |
3239 independent reflections | l = −27→28 |
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)] = 0.070 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.185 | H-atom parameters constrained |
S = 1.08 | w = 1/[σ2(Fo2) + (0.0863P)2 + 1.0261P] where P = (Fo2 + 2Fc2)/3 |
3239 reflections | (Δ/σ)max < 0.001 |
257 parameters | Δρmax = 0.40 e Å−3 |
0 restraints | Δρmin = −0.28 e Å−3 |
C6H5NO3·C2H5NO | V = 1832.3 (5) Å3 |
Mr = 198.18 | Z = 8 |
Monoclinic, P21/c | Mo Kα radiation |
a = 20.370 (3) Å | µ = 0.12 mm−1 |
b = 3.7506 (6) Å | T = 100 K |
c = 24.070 (3) Å | 0.5 × 0.4 × 0.1 mm |
β = 94.873 (3)° |
Bruker SMART APEX diffractometer | 2683 reflections with I > 2σ(I) |
8627 measured reflections | Rint = 0.142 |
3239 independent reflections |
R[F2 > 2σ(F2)] = 0.070 | 0 restraints |
wR(F2) = 0.185 | H-atom parameters constrained |
S = 1.08 | Δρmax = 0.40 e Å−3 |
3239 reflections | Δρmin = −0.28 e Å−3 |
257 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 | ||
C1 | 0.40866 (13) | 0.4034 (7) | 0.36499 (12) | 0.0196 (6) | |
C2 | 0.34544 (13) | 0.5146 (7) | 0.34218 (12) | 0.0177 (6) | |
H2 | 0.3157 | 0.6215 | 0.3656 | 0.021* | |
C3 | 0.32704 (12) | 0.4690 (7) | 0.28678 (11) | 0.0173 (6) | |
H3 | 0.2849 | 0.5461 | 0.2716 | 0.021* | |
C4 | 0.37046 (13) | 0.3087 (7) | 0.25257 (12) | 0.0174 (6) | |
C5 | 0.43252 (13) | 0.1909 (7) | 0.27436 (12) | 0.0174 (6) | |
H5 | 0.4614 | 0.0778 | 0.2509 | 0.021* | |
C6 | 0.45111 (13) | 0.2396 (7) | 0.32944 (12) | 0.0189 (6) | |
H6 | 0.4934 | 0.1619 | 0.3442 | 0.023* | |
C7 | 0.09395 (13) | 0.7769 (7) | 0.63608 (11) | 0.0172 (6) | |
C8 | 0.05236 (13) | 0.8974 (7) | 0.67591 (12) | 0.0172 (6) | |
H8 | 0.0117 | 1.0088 | 0.6639 | 0.021* | |
C9 | 0.06969 (12) | 0.8562 (7) | 0.73151 (11) | 0.0160 (6) | |
H9 | 0.0414 | 0.9396 | 0.7582 | 0.019* | |
C10 | 0.12932 (13) | 0.6904 (7) | 0.74897 (11) | 0.0157 (6) | |
C11 | 0.17149 (12) | 0.5698 (7) | 0.71035 (11) | 0.0162 (6) | |
H11 | 0.2119 | 0.4575 | 0.7228 | 0.019* | |
C12 | 0.15471 (12) | 0.6132 (7) | 0.65465 (12) | 0.0169 (6) | |
H12 | 0.1837 | 0.5338 | 0.6283 | 0.020* | |
C13 | 0.34446 (13) | 0.8232 (7) | 0.52092 (11) | 0.0181 (6) | |
C14 | 0.41348 (13) | 0.9358 (8) | 0.54068 (12) | 0.0212 (6) | |
H14A | 0.4404 | 0.7239 | 0.5498 | 0.032* | |
H14B | 0.4124 | 1.0855 | 0.5740 | 0.032* | |
H14C | 0.4325 | 1.0712 | 0.5112 | 0.032* | |
C15 | 0.15396 (13) | 0.4365 (7) | 0.47456 (11) | 0.0180 (6) | |
C16 | 0.08455 (13) | 0.3232 (8) | 0.45599 (11) | 0.0201 (6) | |
H16A | 0.0652 | 0.2025 | 0.4868 | 0.030* | |
H16B | 0.0852 | 0.1599 | 0.4243 | 0.030* | |
H16C | 0.0581 | 0.5338 | 0.4448 | 0.030* | |
N1 | 0.35187 (11) | 0.2638 (6) | 0.19397 (10) | 0.0212 (6) | |
N2 | 0.14565 (11) | 0.6368 (6) | 0.80801 (10) | 0.0185 (5) | |
N3 | 0.29652 (11) | 0.8955 (6) | 0.55246 (10) | 0.0213 (6) | |
H3A | 0.2559 | 0.8311 | 0.5417 | 0.026* | |
H3B | 0.3051 | 1.0081 | 0.5843 | 0.026* | |
N4 | 0.20141 (11) | 0.3526 (6) | 0.44301 (10) | 0.0209 (5) | |
H4A | 0.2422 | 0.4181 | 0.4529 | 0.025* | |
H4B | 0.1923 | 0.2310 | 0.4120 | 0.025* | |
O1 | 0.42965 (9) | 0.4481 (6) | 0.41819 (8) | 0.0245 (5) | |
H1 | 0.3986 | 0.5254 | 0.4357 | 0.037* | |
O2 | 0.29833 (9) | 0.3860 (6) | 0.17403 (8) | 0.0259 (5) | |
O3 | 0.38951 (10) | 0.1050 (6) | 0.16480 (9) | 0.0304 (5) | |
O4 | 0.07502 (9) | 0.8246 (6) | 0.58245 (8) | 0.0230 (5) | |
H4 | 0.1054 | 0.7613 | 0.5631 | 0.035* | |
O5 | 0.19740 (9) | 0.4715 (6) | 0.82298 (8) | 0.0259 (5) | |
O6 | 0.10815 (9) | 0.7470 (6) | 0.84165 (8) | 0.0252 (5) | |
O7 | 0.33360 (9) | 0.6632 (5) | 0.47537 (8) | 0.0227 (5) | |
O8 | 0.16552 (9) | 0.6090 (5) | 0.51875 (8) | 0.0228 (5) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0128 (14) | 0.0144 (13) | 0.0315 (16) | −0.0022 (11) | 0.0017 (11) | 0.0016 (11) |
C2 | 0.0101 (13) | 0.0117 (13) | 0.0319 (15) | 0.0013 (10) | 0.0058 (11) | 0.0015 (11) |
C3 | 0.0075 (13) | 0.0113 (13) | 0.0333 (16) | −0.0016 (10) | 0.0036 (11) | 0.0053 (11) |
C4 | 0.0113 (13) | 0.0097 (12) | 0.0311 (15) | −0.0046 (10) | 0.0013 (11) | 0.0018 (11) |
C5 | 0.0100 (13) | 0.0093 (12) | 0.0339 (16) | −0.0010 (10) | 0.0073 (11) | 0.0008 (11) |
C6 | 0.0072 (12) | 0.0154 (13) | 0.0342 (16) | −0.0004 (10) | 0.0017 (11) | 0.0040 (12) |
C7 | 0.0132 (14) | 0.0108 (13) | 0.0271 (15) | −0.0051 (10) | −0.0010 (11) | 0.0003 (11) |
C8 | 0.0081 (13) | 0.0119 (13) | 0.0316 (15) | −0.0003 (10) | 0.0011 (11) | 0.0010 (11) |
C9 | 0.0077 (13) | 0.0106 (12) | 0.0310 (15) | −0.0013 (10) | 0.0090 (11) | −0.0038 (11) |
C10 | 0.0117 (13) | 0.0081 (12) | 0.0274 (14) | −0.0039 (10) | 0.0013 (11) | −0.0002 (10) |
C11 | 0.0069 (13) | 0.0092 (12) | 0.0325 (15) | −0.0025 (10) | 0.0010 (11) | 0.0026 (11) |
C12 | 0.0071 (12) | 0.0114 (13) | 0.0328 (15) | −0.0007 (10) | 0.0041 (11) | −0.0030 (11) |
C13 | 0.0169 (14) | 0.0161 (13) | 0.0207 (14) | −0.0008 (11) | −0.0027 (11) | 0.0045 (11) |
C14 | 0.0139 (15) | 0.0183 (14) | 0.0308 (15) | −0.0021 (11) | −0.0017 (12) | 0.0014 (12) |
C15 | 0.0124 (14) | 0.0187 (13) | 0.0224 (14) | −0.0027 (11) | −0.0014 (11) | 0.0042 (11) |
C16 | 0.0147 (14) | 0.0208 (14) | 0.0247 (14) | −0.0027 (11) | 0.0014 (11) | 0.0006 (11) |
N1 | 0.0148 (12) | 0.0183 (12) | 0.0311 (14) | −0.0018 (10) | 0.0058 (10) | 0.0024 (10) |
N2 | 0.0109 (12) | 0.0152 (12) | 0.0299 (13) | −0.0043 (9) | 0.0039 (10) | 0.0005 (10) |
N3 | 0.0156 (12) | 0.0242 (13) | 0.0239 (12) | −0.0021 (10) | 0.0016 (10) | −0.0046 (10) |
N4 | 0.0157 (12) | 0.0223 (13) | 0.0247 (12) | −0.0041 (10) | 0.0010 (10) | −0.0037 (10) |
O1 | 0.0156 (10) | 0.0311 (12) | 0.0268 (11) | 0.0041 (9) | 0.0020 (8) | −0.0014 (9) |
O2 | 0.0154 (11) | 0.0324 (12) | 0.0295 (11) | 0.0009 (9) | −0.0008 (8) | 0.0053 (9) |
O3 | 0.0221 (12) | 0.0396 (13) | 0.0305 (12) | 0.0006 (10) | 0.0091 (9) | −0.0072 (10) |
O4 | 0.0136 (10) | 0.0297 (11) | 0.0258 (11) | 0.0033 (8) | 0.0021 (8) | −0.0006 (9) |
O5 | 0.0161 (11) | 0.0293 (11) | 0.0321 (12) | 0.0078 (9) | 0.0001 (9) | 0.0064 (9) |
O6 | 0.0152 (10) | 0.0346 (12) | 0.0273 (11) | −0.0010 (9) | 0.0098 (8) | −0.0030 (9) |
O7 | 0.0135 (10) | 0.0289 (11) | 0.0257 (11) | −0.0016 (8) | 0.0021 (8) | −0.0049 (9) |
O8 | 0.0157 (10) | 0.0283 (11) | 0.0244 (11) | −0.0019 (8) | 0.0023 (8) | −0.0044 (8) |
C1—O1 | 1.326 (3) | C12—H12 | 0.9500 |
C1—C6 | 1.408 (4) | C13—O7 | 1.253 (3) |
C1—C2 | 1.419 (4) | C13—N3 | 1.315 (4) |
C2—C3 | 1.365 (4) | C13—C14 | 1.506 (4) |
C2—H2 | 0.9500 | C14—H14A | 0.9800 |
C3—C4 | 1.395 (4) | C14—H14B | 0.9800 |
C3—H3 | 0.9500 | C14—H14C | 0.9800 |
C4—C5 | 1.398 (4) | C15—O8 | 1.250 (3) |
C4—N1 | 1.439 (4) | C15—N4 | 1.317 (4) |
C5—C6 | 1.360 (4) | C15—C16 | 1.507 (4) |
C5—H5 | 0.9500 | C16—H16A | 0.9800 |
C6—H6 | 0.9500 | C16—H16B | 0.9800 |
C7—O4 | 1.328 (3) | C16—H16C | 0.9800 |
C7—C8 | 1.407 (4) | N1—O3 | 1.236 (3) |
C7—C12 | 1.419 (4) | N1—O2 | 1.241 (3) |
C8—C9 | 1.364 (4) | N2—O6 | 1.231 (3) |
C8—H8 | 0.9500 | N2—O5 | 1.249 (3) |
C9—C10 | 1.397 (4) | N3—H3A | 0.8800 |
C9—H9 | 0.9500 | N3—H3B | 0.8800 |
C10—C11 | 1.394 (4) | N4—H4A | 0.8800 |
C10—N2 | 1.446 (4) | N4—H4B | 0.8800 |
C11—C12 | 1.365 (4) | O1—H1 | 0.8400 |
C11—H11 | 0.9500 | O4—H4 | 0.8400 |
O1—C1—C6 | 118.5 (2) | C11—C12—H12 | 120.0 |
O1—C1—C2 | 123.0 (3) | C7—C12—H12 | 120.0 |
C6—C1—C2 | 118.5 (3) | O7—C13—N3 | 121.3 (2) |
C3—C2—C1 | 120.4 (3) | O7—C13—C14 | 120.1 (2) |
C3—C2—H2 | 119.8 | N3—C13—C14 | 118.6 (2) |
C1—C2—H2 | 119.8 | C13—C14—H14A | 109.5 |
C2—C3—C4 | 119.7 (2) | C13—C14—H14B | 109.5 |
C2—C3—H3 | 120.1 | H14A—C14—H14B | 109.5 |
C4—C3—H3 | 120.1 | C13—C14—H14C | 109.5 |
C3—C4—C5 | 120.9 (3) | H14A—C14—H14C | 109.5 |
C3—C4—N1 | 120.1 (2) | H14B—C14—H14C | 109.5 |
C5—C4—N1 | 119.0 (3) | O8—C15—N4 | 121.3 (2) |
C6—C5—C4 | 119.4 (3) | O8—C15—C16 | 120.1 (2) |
C6—C5—H5 | 120.3 | N4—C15—C16 | 118.5 (2) |
C4—C5—H5 | 120.3 | C15—C16—H16A | 109.5 |
C5—C6—C1 | 121.1 (2) | C15—C16—H16B | 109.5 |
C5—C6—H6 | 119.4 | H16A—C16—H16B | 109.5 |
C1—C6—H6 | 119.4 | C15—C16—H16C | 109.5 |
O4—C7—C8 | 118.5 (2) | H16A—C16—H16C | 109.5 |
O4—C7—C12 | 122.6 (3) | H16B—C16—H16C | 109.5 |
C8—C7—C12 | 118.9 (2) | O3—N1—O2 | 121.7 (2) |
C9—C8—C7 | 120.8 (2) | O3—N1—C4 | 119.3 (2) |
C9—C8—H8 | 119.6 | O2—N1—C4 | 119.0 (2) |
C7—C8—H8 | 119.6 | O6—N2—O5 | 122.2 (2) |
C8—C9—C10 | 119.4 (2) | O6—N2—C10 | 119.7 (2) |
C8—C9—H9 | 120.3 | O5—N2—C10 | 118.1 (2) |
C10—C9—H9 | 120.3 | C13—N3—H3A | 120.0 |
C11—C10—C9 | 120.9 (2) | C13—N3—H3B | 120.0 |
C11—C10—N2 | 120.5 (2) | H3A—N3—H3B | 120.0 |
C9—C10—N2 | 118.6 (2) | C15—N4—H4A | 120.0 |
C12—C11—C10 | 120.0 (2) | C15—N4—H4B | 120.0 |
C12—C11—H11 | 120.0 | H4A—N4—H4B | 120.0 |
C10—C11—H11 | 120.0 | C1—O1—H1 | 109.5 |
C11—C12—C7 | 120.0 (3) | C7—O4—H4 | 109.5 |
O1—C1—C2—C3 | 178.5 (3) | C8—C9—C10—N2 | −177.6 (2) |
C6—C1—C2—C3 | −1.2 (4) | C9—C10—C11—C12 | 0.0 (4) |
C1—C2—C3—C4 | 0.7 (4) | N2—C10—C11—C12 | 178.2 (2) |
C2—C3—C4—C5 | 0.6 (4) | C10—C11—C12—C7 | −0.8 (4) |
C2—C3—C4—N1 | −179.2 (2) | O4—C7—C12—C11 | −179.7 (2) |
C3—C4—C5—C6 | −1.2 (4) | C8—C7—C12—C11 | 1.0 (4) |
N1—C4—C5—C6 | 178.5 (2) | C3—C4—N1—O3 | −176.3 (2) |
C4—C5—C6—C1 | 0.7 (4) | C5—C4—N1—O3 | 3.9 (4) |
O1—C1—C6—C5 | −179.2 (2) | C3—C4—N1—O2 | 3.7 (4) |
C2—C1—C6—C5 | 0.5 (4) | C5—C4—N1—O2 | −176.0 (2) |
O4—C7—C8—C9 | −179.7 (2) | C11—C10—N2—O6 | 179.5 (2) |
C12—C7—C8—C9 | −0.4 (4) | C9—C10—N2—O6 | −2.3 (4) |
C7—C8—C9—C10 | −0.4 (4) | C11—C10—N2—O5 | −2.0 (4) |
C8—C9—C10—C11 | 0.6 (4) | C9—C10—N2—O5 | 176.3 (2) |
D—H···A | D—H | H···A | D···A | D—H···A |
N3—H3A···O8 | 0.88 | 2.05 | 2.927 (3) | 172 |
N3—H3B···O2i | 0.88 | 2.21 | 3.036 (3) | 156 |
N4—H4A···O7 | 0.88 | 2.11 | 2.976 (3) | 170 |
N4—H4B···O5ii | 0.88 | 2.29 | 3.129 (3) | 161 |
O1—H1···O7 | 0.84 | 1.77 | 2.613 (3) | 176 |
O4—H4···O8 | 0.84 | 1.79 | 2.624 (3) | 176 |
Symmetry codes: (i) x, −y+3/2, z+1/2; (ii) x, −y+1/2, z−1/2. |
Experimental details
Crystal data | |
Chemical formula | C6H5NO3·C2H5NO |
Mr | 198.18 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 100 |
a, b, c (Å) | 20.370 (3), 3.7506 (6), 24.070 (3) |
β (°) | 94.873 (3) |
V (Å3) | 1832.3 (5) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 0.12 |
Crystal size (mm) | 0.5 × 0.4 × 0.1 |
Data collection | |
Diffractometer | Bruker SMART APEX diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 8627, 3239, 2683 |
Rint | 0.142 |
(sin θ/λ)max (Å−1) | 0.595 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.070, 0.185, 1.08 |
No. of reflections | 3239 |
No. of parameters | 257 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.40, −0.28 |
Computer programs: SMART (Bruker, 1988), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), SHELXTL (Bruker, 1988).
D—H···A | D—H | H···A | D···A | D—H···A |
N3—H3A···O8 | 0.88 | 2.05 | 2.927 (3) | 171.9 |
N3—H3B···O2i | 0.88 | 2.21 | 3.036 (3) | 155.9 |
N4—H4A···O7 | 0.88 | 2.11 | 2.976 (3) | 170.3 |
N4—H4B···O5ii | 0.88 | 2.29 | 3.129 (3) | 160.7 |
O1—H1···O7 | 0.84 | 1.77 | 2.613 (3) | 176.3 |
O4—H4···O8 | 0.84 | 1.79 | 2.624 (3) | 175.7 |
Symmetry codes: (i) x, −y+3/2, z+1/2; (ii) x, −y+1/2, z−1/2. |
Type of Hydrogen bond | a | b | c | d | e | f |
a | D | |||||
b | - | D | ||||
c | - | - | D | |||
d | - | - | R22(8) | D | ||
e | - | C22(12) | - | - | D | |
f | C22(12) | - | - | - | - | D |
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We report here the structure and graph-set analysis of the congruent 1:1 molar compound 4-nitrophenol–acetamide (1:1), (III) (m.p. 370 K), which forms eutectics with each of its two components, viz 4-nitrophenol, (I), and acetamide, (II) (Dzhelomanova et al., 1956). This molar compound crystallizes with Z' = 2 (Fig. 1) and retains some of the hydrogen-bond patterns observed in the crystal structure of the single components (Etter & MacDonald, 1990; Etter, 1990; Bernstein et al., 1995).
4-Nitrophenol, (I), has a relatively high melting point (386 K) and crystallizes in two polymorphs (Coppens & Schimdt, 1965a,b; Kulkarni et al., 1998; Wójcik & Mossakowska, 2006). The crystal structures are characterized by hydrogen bonding between hydroxyl and nitro groups of adjacent molecules, forming endless continuous chains which are described as C(8), creating a herring-bone pattern (Coppens & Schimdt, 1965a,b; Wójcik & Mossakowska, 2006).
Acetamide, (II), is also high melting (353 K) for such a simple compound and its structure is characterized by multiple N—H···O(C) bonds. This small molecule crystallizes in two forms. The more common one is the orthorhombic, which contains two molecules in the asymmetric unit (Hamilton, 1965; Jeffrey et al., 1980; Ottersen, 1975) and a more unusual rhombohedral with only one molecule in the asymmetric unit (Denne & Small, 1971; Senti & Harker, 1940). These two forms establish different hydrogen-bond patterns. The motifs in its orthorhombic form are described as C(4)C(4)DD and in the rhombohedral as C(4)C(4), reflecting the endless chains formed at the first level graph set in both forms (Bernstein et al., 1995). At the second level graph set, both forms generate ring patterns, viz. R22(8) in the orthorhombic form and R63(12) in the rhombohedral (Bernstein et al.,1995). In the orthorhombic form, the ring pattern is created through two N—H···O(C) hydrogen bonds between the two molecules present in the asymmetric unit (Bernstein et al.,1995). In the rhombohedral form, the ring is created through N—H···O(C) hydrogen bonds amongst four neighbouring acetamide molecules (Bernstein et al., 1995).
In the complex, (III), the four independent molecules present in the asymmetric unit establish six different hydrogen bonds (Fig, 1 and Table 1). These bonds have been labelled a–f to help in the assignment of the patterns formed (Etter & MacDonald, 1990; Etter, 1990; Bernstein et al., 1995). Surprisingly, although complex (III) forms six different hydrogen bonds, it only creates finite D patterns (Table 2). The D motifs, which are present in the orthorhombic form of acetamide, are retained in complex (III). In this case, bonds c and d generate identical D motifs to those observed in acetamide (Table 2). The other N—H···O(C) bond in acetamide (II) generates the C(4) motif. In complex (III) this C(4) motif is not retained because atoms H4B and H3B are hydrogen bonded, respectively, to O5ii and O2i, thereby establishing two new D motifs (e and f; Fig. 1).
In 4-nitrophenol, (I), a single chain is formed through O—H···O(N) hydrogen bonding between the hydroxyl H atom of one molecule and a nitro O atom of a neighbouring molecule. This pattern is not retained in the crystal structure of complex (III), in which the hydroxyl H1 and H4 atoms establish new O—H···O(C) hydrogen bonds to amide atoms O7 and O8, thereby creating two D patterns (a and b; Table 2 and Fig. 2). Thus, at the first level graph set, compound (III) is described as N1=DDDDDD, reflecting the large number of molecules present in the unit cell.
At the second level of the graph set, more of the patterns generated in (III) are ones retained from structures seen in the individual components (I) and (II). In the orthorhombic form of the single amide component (II), dimers are formed from two N—H···O(C) bonds. This feature is retained in complex (III) and dimers are formed through bonds c and d (Fig. 1 and Table 2). Thus, the R22(8) ring pattern observed in complex (III) is identical to that observed in the isolated amide (II). The C(4) chains formed through N—H···O(C) hydrogen bonds between pairs of molecules in (II) (Bernstein et al., 1995) are not retained in complex (III). In the latter, the amide H atoms, which are not involved in dimer formation, instead establish hydrogen bonds with nitrophenol to create a chain of alternating (I) and (II) units. Two C22(12) chains are created by the pair a/f and another by the pair b/e (Fig. 2). The chains are symmetrically different and run parallel to each other along the c axis. These chains form a wave-type structure that is held together through dimers of acetamide forming a pleated sheet (Fig. 2). They are identical to the `flat' features observed in the structures of the pure components (I) and (II), but in complex (III) the chains adopt the pleated sheet form (Fig. 2). No other patterns are present at this level, therefore, the overall second level graph set for compound (III) is described as N2 = R22(8)C22(12)C22(12), reflecting the rings and chains observed at this level.
The structures of the pure components (I) and (II) do not have any higher level graph sets of hydrogen-bond patterns but their complex (III) does. This pattern is formed by combining bonds a, c, b, e, d and f or a, d, b, e, c and f (Fig. 2), which combinations describe two C55(22) chains. These chains include the acetamide dimers and are better described as a chain of rings. Thus, the hydrogen-bond patterns at the sixth level graph set for complex (III) are described as N6=C55(22)[R22(8)]. No other patterns were observed at higher level graph sets for complex (III).