The crystal structure of the title compound, benzamide-2,3,4,5,6-pentafluorobenzoic acid (2/1), 2C
7H
7NO·C
7HF
5O
2, consists of centrosymmetric hexameric supermolecules composed of four amide and two carboxylic acid molecules connected
via O-H
O and N-H
O hydrogen bonds. No phenyl-perfluorophenyl
-
stacking interactions are observed in this cocrystal.
Supporting information
CCDC reference: 618647
Compound (I) was prepared from an eqimolar mixture of benzamide and pentafluorobenzoic acid (Aldrich) dissolved in an acetone/water (1:1 volume) mixture by slow evaporation of the solvent at room temperature. The first crystallization fraction consisted of (I) in the form of thin plates with a melting point of 361–363 K, whereas the second fraction was a mixture of crystals of (I) and pentafluorobenzoic acid.
All H atoms were located in electron-density difference maps. Positional and isotropic displacement parameters of H atoms from OH and NH2 groups were refined. Carbon-bonded H atoms were positioned with idealized geometry, with C—H = 0.96 Å, and refined isotropically using a riding model.
Data collection: CrysAlis CCD (Oxford Diffraction, 2000); cell refinement: CrysAlis CCD; data reduction: CrysAlis RED (Oxford Diffraction, 2000); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: Stereochemical Workstation Operation Manual (Siemens, 1989) and
Mercury (Version 1.4; Bruno et al., 2002); software used to prepare material for publication: SHELXL97.
benzamide–2,3,4,5,6-pentafluorobenzoic acid (2/1)
top
Crystal data top
2C7H7NO·C7HF5O2 | F(000) = 928 |
Mr = 454.35 | Dx = 1.546 Mg m−3 |
Monoclinic, P21/c | Melting point = 361–363 K |
Hall symbol: -p 2ybc | Mo Kα radiation, λ = 0.71073 Å |
a = 15.3195 (5) Å | Cell parameters from 5291 reflections |
b = 5.1799 (3) Å | θ = 3–25° |
c = 24.6053 (8) Å | µ = 0.14 mm−1 |
β = 90.784 (3)° | T = 130 K |
V = 1952.33 (14) Å3 | Prism, colourless |
Z = 4 | 0.58 × 0.23 × 0.20 mm |
Data collection top
Kuma KM-4-CCD κ geometry diffractometer | 2561 reflections with I > 2σ(I) |
Radiation source: fine-focus sealed tube | Rint = 0.040 |
Graphite monochromator | θmax = 25.0°, θmin = 2.1° |
ω scans | h = −18→18 |
19656 measured reflections | k = −3→6 |
3423 independent reflections | l = −29→29 |
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)] = 0.038 | Hydrogen site location: difference Fourier map |
wR(F2) = 0.092 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.00 | w = 1/[σ2(Fo2) + (0.0497P)2] where P = (Fo2 + 2Fc2)/3 |
3423 reflections | (Δ/σ)max = 0.001 |
319 parameters | Δρmax = 0.16 e Å−3 |
0 restraints | Δρmin = −0.21 e Å−3 |
Crystal data top
2C7H7NO·C7HF5O2 | V = 1952.33 (14) Å3 |
Mr = 454.35 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 15.3195 (5) Å | µ = 0.14 mm−1 |
b = 5.1799 (3) Å | T = 130 K |
c = 24.6053 (8) Å | 0.58 × 0.23 × 0.20 mm |
β = 90.784 (3)° | |
Data collection top
Kuma KM-4-CCD κ geometry diffractometer | 2561 reflections with I > 2σ(I) |
19656 measured reflections | Rint = 0.040 |
3423 independent reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.038 | 0 restraints |
wR(F2) = 0.092 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.00 | Δρmax = 0.16 e Å−3 |
3423 reflections | Δρmin = −0.21 e Å−3 |
319 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 | |
O1 | 0.38044 (8) | 0.5139 (3) | 0.39226 (5) | 0.0288 (3) | |
H1O | 0.3698 (16) | 0.378 (5) | 0.4199 (11) | 0.076 (9)* | |
O2 | 0.24639 (8) | 0.6662 (2) | 0.40844 (5) | 0.0296 (3) | |
C1 | 0.33106 (12) | 0.8640 (3) | 0.33997 (7) | 0.0230 (4) | |
C2 | 0.26394 (12) | 0.9338 (4) | 0.30436 (8) | 0.0267 (4) | |
C3 | 0.27441 (13) | 1.1189 (4) | 0.26499 (8) | 0.0316 (5) | |
C4 | 0.35315 (14) | 1.2434 (4) | 0.26044 (8) | 0.0308 (5) | |
C5 | 0.42136 (12) | 1.1791 (4) | 0.29461 (8) | 0.0292 (5) | |
C6 | 0.41046 (12) | 0.9889 (4) | 0.33302 (8) | 0.0260 (4) | |
C7 | 0.31553 (12) | 0.6692 (3) | 0.38426 (7) | 0.0234 (4) | |
F2 | 0.18631 (7) | 0.8129 (2) | 0.30621 (5) | 0.0391 (3) | |
F3 | 0.20838 (8) | 1.1759 (2) | 0.23032 (5) | 0.0482 (4) | |
F4 | 0.36292 (8) | 1.4287 (2) | 0.22279 (5) | 0.0463 (3) | |
F5 | 0.49748 (7) | 1.3055 (2) | 0.29072 (5) | 0.0420 (3) | |
F6 | 0.47881 (7) | 0.9363 (2) | 0.36586 (5) | 0.0360 (3) | |
O1A | 0.37070 (8) | 0.1534 (2) | 0.45781 (5) | 0.0277 (3) | |
N1A | 0.23748 (10) | 0.2524 (3) | 0.48880 (7) | 0.0251 (4) | |
H1AB | 0.1964 (13) | 0.238 (4) | 0.5120 (8) | 0.033 (6)* | |
H1AA | 0.2336 (11) | 0.383 (4) | 0.4654 (8) | 0.023 (5)* | |
C1A | 0.31857 (11) | −0.1015 (3) | 0.53055 (7) | 0.0223 (4) | |
C2A | 0.39700 (12) | −0.2353 (4) | 0.53341 (8) | 0.0289 (5) | |
H2AA | 0.4435 | −0.1911 | 0.5094 | 0.041 (6)* | |
C3A | 0.40848 (13) | −0.4324 (4) | 0.57087 (8) | 0.0328 (5) | |
H3AA | 0.4628 | −0.5245 | 0.5727 | 0.034 (5)* | |
C4A | 0.34168 (13) | −0.4967 (4) | 0.60573 (8) | 0.0333 (5) | |
H4AA | 0.3500 | −0.6321 | 0.6319 | 0.031 (5)* | |
C5A | 0.26314 (14) | −0.3661 (4) | 0.60282 (8) | 0.0343 (5) | |
H5AA | 0.2167 | −0.4119 | 0.6268 | 0.047 (6)* | |
C6A | 0.25119 (13) | −0.1689 (4) | 0.56534 (8) | 0.0296 (5) | |
H6AA | 0.1965 | −0.0787 | 0.5633 | 0.034 (5)* | |
C7A | 0.30918 (11) | 0.1113 (3) | 0.49024 (7) | 0.0227 (4) | |
O1B | 0.07544 (8) | 0.3153 (2) | 0.54375 (5) | 0.0283 (3) | |
N1B | −0.07015 (11) | 0.2670 (3) | 0.53585 (8) | 0.0283 (4) | |
H1BA | −0.1179 (13) | 0.215 (4) | 0.5510 (8) | 0.030 (6)* | |
H1BB | −0.0719 (13) | 0.387 (4) | 0.5107 (9) | 0.039 (6)* | |
C1B | 0.00768 (11) | 0.0300 (3) | 0.60598 (7) | 0.0222 (4) | |
C2B | 0.07598 (12) | 0.0416 (4) | 0.64358 (8) | 0.0272 (5) | |
H2BA | 0.1205 | 0.1706 | 0.6399 | 0.030 (5)* | |
C3B | 0.08042 (14) | −0.1310 (4) | 0.68632 (8) | 0.0327 (5) | |
H3BA | 0.1279 | −0.1212 | 0.7121 | 0.038 (6)* | |
C4B | 0.01664 (14) | −0.3183 (4) | 0.69203 (8) | 0.0353 (5) | |
H4BA | 0.0199 | −0.4386 | 0.7217 | 0.033 (5)* | |
C5B | −0.05170 (14) | −0.3313 (4) | 0.65502 (9) | 0.0367 (5) | |
H5BA | −0.0959 | −0.4610 | 0.6589 | 0.039 (6)* | |
C6B | −0.05676 (12) | −0.1584 (4) | 0.61229 (8) | 0.0299 (5) | |
H6BA | −0.1047 | −0.1677 | 0.5869 | 0.040 (6)* | |
C7B | 0.00658 (12) | 0.2153 (3) | 0.55979 (7) | 0.0233 (4) | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0260 (7) | 0.0284 (8) | 0.0323 (8) | 0.0051 (6) | 0.0060 (6) | 0.0063 (7) |
O2 | 0.0223 (7) | 0.0349 (8) | 0.0319 (8) | 0.0022 (6) | 0.0053 (6) | 0.0062 (6) |
C1 | 0.0268 (10) | 0.0224 (10) | 0.0199 (10) | 0.0004 (8) | 0.0032 (8) | −0.0029 (8) |
C2 | 0.0264 (11) | 0.0269 (11) | 0.0269 (11) | −0.0043 (9) | 0.0015 (8) | −0.0012 (9) |
C3 | 0.0394 (12) | 0.0319 (12) | 0.0234 (11) | 0.0023 (10) | −0.0054 (9) | 0.0005 (9) |
C4 | 0.0479 (13) | 0.0228 (11) | 0.0218 (11) | −0.0008 (9) | 0.0080 (9) | 0.0030 (9) |
C5 | 0.0310 (11) | 0.0284 (11) | 0.0285 (11) | −0.0042 (9) | 0.0105 (9) | −0.0016 (9) |
C6 | 0.0257 (10) | 0.0277 (11) | 0.0246 (10) | 0.0038 (9) | 0.0040 (8) | −0.0020 (9) |
C7 | 0.0231 (10) | 0.0236 (10) | 0.0235 (10) | −0.0015 (9) | −0.0003 (8) | −0.0031 (8) |
F2 | 0.0324 (7) | 0.0461 (7) | 0.0384 (7) | −0.0120 (6) | −0.0093 (5) | 0.0086 (6) |
F3 | 0.0526 (8) | 0.0530 (8) | 0.0384 (7) | −0.0034 (7) | −0.0159 (6) | 0.0141 (6) |
F4 | 0.0665 (9) | 0.0375 (7) | 0.0349 (7) | −0.0070 (6) | 0.0049 (6) | 0.0125 (6) |
F5 | 0.0366 (7) | 0.0423 (7) | 0.0473 (8) | −0.0109 (6) | 0.0113 (6) | 0.0071 (6) |
F6 | 0.0240 (6) | 0.0427 (7) | 0.0413 (7) | −0.0024 (5) | 0.0002 (5) | 0.0070 (6) |
O1A | 0.0237 (7) | 0.0295 (8) | 0.0301 (8) | 0.0026 (6) | 0.0073 (6) | 0.0044 (6) |
N1A | 0.0228 (9) | 0.0268 (10) | 0.0260 (9) | 0.0031 (8) | 0.0047 (8) | 0.0058 (8) |
C1A | 0.0210 (10) | 0.0227 (10) | 0.0232 (10) | −0.0016 (8) | −0.0003 (8) | −0.0022 (8) |
C2A | 0.0225 (10) | 0.0291 (11) | 0.0351 (12) | −0.0026 (9) | 0.0001 (9) | 0.0034 (9) |
C3A | 0.0265 (11) | 0.0297 (11) | 0.0418 (13) | 0.0022 (9) | −0.0074 (9) | 0.0050 (10) |
C4A | 0.0437 (13) | 0.0274 (11) | 0.0286 (12) | −0.0012 (10) | −0.0062 (10) | 0.0071 (10) |
C5A | 0.0399 (13) | 0.0331 (12) | 0.0302 (12) | −0.0026 (10) | 0.0089 (10) | 0.0048 (10) |
C6A | 0.0292 (11) | 0.0301 (11) | 0.0296 (11) | 0.0042 (9) | 0.0040 (9) | 0.0029 (9) |
C7A | 0.0203 (10) | 0.0247 (10) | 0.0231 (10) | −0.0014 (8) | −0.0003 (8) | −0.0031 (8) |
O1B | 0.0200 (7) | 0.0329 (8) | 0.0320 (8) | 0.0007 (6) | 0.0041 (6) | 0.0073 (6) |
N1B | 0.0206 (9) | 0.0319 (10) | 0.0326 (10) | −0.0019 (8) | 0.0019 (8) | 0.0077 (8) |
C1B | 0.0215 (10) | 0.0209 (10) | 0.0242 (10) | 0.0019 (8) | 0.0050 (8) | −0.0013 (8) |
C2B | 0.0266 (10) | 0.0291 (11) | 0.0259 (11) | −0.0009 (9) | 0.0049 (8) | −0.0003 (9) |
C3B | 0.0387 (12) | 0.0341 (12) | 0.0252 (11) | 0.0036 (10) | −0.0014 (9) | 0.0002 (9) |
C4B | 0.0494 (14) | 0.0278 (12) | 0.0290 (11) | 0.0049 (10) | 0.0104 (10) | 0.0049 (10) |
C5B | 0.0382 (12) | 0.0293 (12) | 0.0430 (13) | −0.0071 (10) | 0.0095 (10) | 0.0037 (11) |
C6B | 0.0272 (11) | 0.0278 (11) | 0.0347 (12) | −0.0022 (9) | 0.0010 (9) | −0.0004 (9) |
C7B | 0.0223 (10) | 0.0231 (10) | 0.0247 (10) | 0.0021 (8) | 0.0039 (8) | −0.0023 (8) |
Geometric parameters (Å, º) top
O1—C7 | 1.292 (2) | C3A—C4A | 1.385 (3) |
O1—H1O | 0.99 (3) | C3A—H3AA | 0.9600 |
O2—C7 | 1.222 (2) | C4A—C5A | 1.381 (3) |
C1—C2 | 1.389 (3) | C4A—H4AA | 0.9601 |
C1—C6 | 1.390 (3) | C5A—C6A | 1.387 (3) |
C1—C7 | 1.507 (3) | C5A—H5AA | 0.9600 |
C2—F2 | 1.345 (2) | C6A—H6AA | 0.9600 |
C2—C3 | 1.374 (3) | O1B—C7B | 1.244 (2) |
C3—F3 | 1.347 (2) | N1B—C7B | 1.335 (2) |
C3—C4 | 1.374 (3) | N1B—H1BA | 0.87 (2) |
C4—F4 | 1.344 (2) | N1B—H1BB | 0.88 (2) |
C4—C5 | 1.373 (3) | C1B—C2B | 1.388 (3) |
C5—F5 | 1.342 (2) | C1B—C6B | 1.398 (3) |
C5—C6 | 1.377 (3) | C1B—C7B | 1.488 (3) |
C6—F6 | 1.342 (2) | C2B—C3B | 1.381 (3) |
O1A—C7A | 1.262 (2) | C2B—H2BA | 0.9600 |
N1A—C7A | 1.320 (2) | C3B—C4B | 1.385 (3) |
N1A—H1AB | 0.86 (2) | C3B—H3BA | 0.9601 |
N1A—H1AA | 0.89 (2) | C4B—C5B | 1.380 (3) |
C1A—C2A | 1.388 (2) | C4B—H4BA | 0.9600 |
C1A—C6A | 1.394 (3) | C5B—C6B | 1.382 (3) |
C1A—C7A | 1.488 (3) | C5B—H5BA | 0.9600 |
C2A—C3A | 1.385 (3) | C6B—H6BA | 0.9601 |
C2A—H2AA | 0.9599 | | |
| | | |
C7—O1—H1O | 114.4 (14) | C5A—C4A—H4AA | 120.0 |
C2—C1—C6 | 116.28 (17) | C3A—C4A—H4AA | 120.0 |
C2—C1—C7 | 120.48 (16) | C4A—C5A—C6A | 120.15 (19) |
C6—C1—C7 | 123.21 (16) | C4A—C5A—H5AA | 119.9 |
F2—C2—C3 | 117.41 (17) | C6A—C5A—H5AA | 119.9 |
F2—C2—C1 | 120.31 (16) | C5A—C6A—C1A | 120.04 (18) |
C3—C2—C1 | 122.23 (17) | C5A—C6A—H6AA | 120.0 |
F3—C3—C2 | 120.37 (18) | C1A—C6A—H6AA | 120.0 |
F3—C3—C4 | 119.88 (18) | O1A—C7A—N1A | 121.03 (17) |
C2—C3—C4 | 119.75 (18) | O1A—C7A—C1A | 118.90 (16) |
F4—C4—C5 | 120.29 (18) | N1A—C7A—C1A | 120.07 (16) |
F4—C4—C3 | 119.85 (18) | C7B—N1B—H1BA | 119.5 (13) |
C5—C4—C3 | 119.85 (18) | C7B—N1B—H1BB | 118.1 (13) |
F5—C5—C4 | 119.52 (17) | H1BA—N1B—H1BB | 120.2 (19) |
F5—C5—C6 | 120.78 (18) | C2B—C1B—C6B | 118.88 (18) |
C4—C5—C6 | 119.70 (18) | C2B—C1B—C7B | 118.79 (16) |
F6—C6—C5 | 117.24 (17) | C6B—C1B—C7B | 122.31 (17) |
F6—C6—C1 | 120.55 (17) | C3B—C2B—C1B | 120.54 (18) |
C5—C6—C1 | 122.13 (18) | C3B—C2B—H2BA | 119.7 |
O2—C7—O1 | 126.04 (17) | C1B—C2B—H2BA | 119.8 |
O2—C7—C1 | 120.48 (16) | C2B—C3B—C4B | 120.20 (19) |
O1—C7—C1 | 113.47 (16) | C2B—C3B—H3BA | 119.9 |
C7A—N1A—H1AB | 123.4 (13) | C4B—C3B—H3BA | 119.9 |
C7A—N1A—H1AA | 119.1 (12) | C5B—C4B—C3B | 119.8 (2) |
H1AB—N1A—H1AA | 117.0 (18) | C5B—C4B—H4BA | 120.1 |
C2A—C1A—C6A | 119.44 (17) | C3B—C4B—H4BA | 120.1 |
C2A—C1A—C7A | 118.63 (16) | C4B—C5B—C6B | 120.29 (19) |
C6A—C1A—C7A | 121.93 (16) | C4B—C5B—H5BA | 119.9 |
C3A—C2A—C1A | 120.24 (18) | C6B—C5B—H5BA | 119.8 |
C3A—C2A—H2AA | 119.9 | C5B—C6B—C1B | 120.29 (19) |
C1A—C2A—H2AA | 119.9 | C5B—C6B—H6BA | 119.8 |
C4A—C3A—C2A | 120.08 (19) | C1B—C6B—H6BA | 119.9 |
C4A—C3A—H3AA | 120.0 | O1B—C7B—N1B | 121.46 (18) |
C2A—C3A—H3AA | 120.0 | O1B—C7B—C1B | 120.67 (16) |
C5A—C4A—C3A | 120.04 (19) | N1B—C7B—C1B | 117.86 (17) |
| | | |
O1—C7—C1—C2 | 141.33 (17) | O1A—C7A—C1A—C6A | −176.03 (17) |
O1—C7—C1—C6 | −40.6 (2) | O1B—C7B—C1B—C2B | 24.3 (3) |
O1A—C7A—C1A—C2A | 4.1 (3) | O1B—C7B—C1B—C6B | −154.49 (18) |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1O···O1A | 0.99 (3) | 1.49 (3) | 2.4733 (18) | 169 (2) |
N1A—H1AB···O1B | 0.86 (2) | 2.06 (2) | 2.862 (2) | 154.9 (18) |
N1A—H1AA···O2 | 0.89 (2) | 2.04 (2) | 2.920 (2) | 170.1 (16) |
N1B—H1BA···O2i | 0.87 (2) | 2.30 (2) | 3.064 (2) | 146.6 (17) |
N1B—H1BB···O1Bi | 0.88 (2) | 2.04 (2) | 2.919 (2) | 176.0 (19) |
C5B—H5BA···F2ii | 0.96 | 2.45 | 3.382 (2) | 163 |
C3A—H3AA···O1iii | 0.96 | 2.54 | 3.373 (2) | 145 |
Symmetry codes: (i) −x, −y+1, −z+1; (ii) −x, −y, −z+1; (iii) −x+1, −y, −z+1. |
Experimental details
Crystal data |
Chemical formula | 2C7H7NO·C7HF5O2 |
Mr | 454.35 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 130 |
a, b, c (Å) | 15.3195 (5), 5.1799 (3), 24.6053 (8) |
β (°) | 90.784 (3) |
V (Å3) | 1952.33 (14) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.14 |
Crystal size (mm) | 0.58 × 0.23 × 0.20 |
|
Data collection |
Diffractometer | Kuma KM-4-CCD κ geometry diffractometer |
Absorption correction | – |
No. of measured, independent and observed [I > 2σ(I)] reflections | 19656, 3423, 2561 |
Rint | 0.040 |
(sin θ/λ)max (Å−1) | 0.595 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.038, 0.092, 1.00 |
No. of reflections | 3423 |
No. of parameters | 319 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.16, −0.21 |
Selected geometric parameters (Å, º) topO1—C7 | 1.292 (2) | C1A—C7A | 1.488 (3) |
O2—C7 | 1.222 (2) | O1B—C7B | 1.244 (2) |
C1—C7 | 1.507 (3) | N1B—C7B | 1.335 (2) |
O1A—C7A | 1.262 (2) | C1B—C7B | 1.488 (3) |
N1A—C7A | 1.320 (2) | | |
| | | |
O1A—C7A—N1A | 121.03 (17) | O1B—C7B—N1B | 121.46 (18) |
| | | |
O1—C7—C1—C6 | −40.6 (2) | O1B—C7B—C1B—C2B | 24.3 (3) |
O1A—C7A—C1A—C2A | 4.1 (3) | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1O···O1A | 0.99 (3) | 1.49 (3) | 2.4733 (18) | 169 (2) |
N1A—H1AB···O1B | 0.86 (2) | 2.06 (2) | 2.862 (2) | 154.9 (18) |
N1A—H1AA···O2 | 0.89 (2) | 2.04 (2) | 2.920 (2) | 170.1 (16) |
N1B—H1BA···O2i | 0.87 (2) | 2.30 (2) | 3.064 (2) | 146.6 (17) |
N1B—H1BB···O1Bi | 0.88 (2) | 2.04 (2) | 2.919 (2) | 176.0 (19) |
C5B—H5BA···F2ii | 0.96 | 2.45 | 3.382 (2) | 163 |
C3A—H3AA···O1iii | 0.96 | 2.54 | 3.373 (2) | 145 |
Symmetry codes: (i) −x, −y+1, −z+1; (ii) −x, −y, −z+1; (iii) −x+1, −y, −z+1. |
Aryl–perfluoroaryl stacking interactions have attracted increasing attention in crystal engineering (Reichenbächer et al., 2005) and have become a powerful tool in rational supramolecular synthesis (Coates et al., 1997; Collings et al., 2002; Shu et al., 2006; Watt et al., 2004; Xu et al., 2006). Recently, we have shown that, when used in cooperation with hydrogen bonding, these specific intermolecular interactions can be employed to control an aggregation mode of carboxylic acid dimers (Gdaniec et al., 2003). Shortly thereafter Reddy et al. (2004) reported that phenyl–perfluorophenyl stacking interactions play an important role in the cocrystallization process of benzamide with pentafluorobenzamide, or benzamide with pentafluorobenzoic acid. In the latter case, the 1:1 adduct was obtained from an equimolar mixture of the acid and the amide, dissolved in ethyl acetate/hexane. The crystal consisted of acid–amide heterodimers arranged into centrosymmetric pairs via phenyl–perfluorophenyl stacking interactions. At that time we were also examining cocrystallization of benzamides or benzoic acids with pentafluorobenzamide, and cocrystallization of benzamide with pentafluorobenzoic acid using an acetone/water mixture as a solvent. The outcome of these experiments was rather poor, showing that the structure-directing role of the phenyl–pentafluorophenyl synthon in cocrystallization of aromatic amides, or aromatic amides with aromatic acids, was significantly limited when compared with that found in cocrystallization of aromatic acids. The only cocrystals isolated from these experiments were the benzamide pentafluorobenzamide (1/1) adduct reported by Reddy et al. (2004) and a new form of pentafluorobenzoic acid benzamide cocrystal with a 1:2 stoichiometry, (I). The melting point of (I) (361–363 K) was slightly higher than that reported for the 1:1 adduct (359 K).
The asymmetric unit of (I) (Fig. 1) comprises two amide molecules and one molecule of the carboxylic acid. The molecules are assembled via hydrogen bonds into centrosymmetric hexameric supermolecules consisting of the amide homodimer A and two amide–acid heterodimers B (see scheme and Fig. 1). The amide molecule forming the dimer B is essentially planar and coplanar with the carboxylic group. The very strong O—H···O hydrogen bond (Table 2) within the heterodimer strongly influences the geometry of the amide group. The C═O and C—N bond lengths for amide molecule B, not involved in strong hydrogen bonding, are 1.244 (2) and 1.335 (2) Å, respectively, whereas in molecule A the corresponding bond lengths are 1.292 (2) and 1.320 (2) Å.
Interestingly, it is quite unusual for the two motifs, A and B, to co-exist in one crystal structure. Our search of the Cambridge Structural Database (CSD; Version 5.27 plus January 1 update; Allen & Motherwell, 2002) did not reveal any crystal structure with a similar carboxylic acid–primary amide aggregation mode. Only in two structures [CSD refcodes MIHWUV (Ito et al., 2000) and XAXQAO (Hosomi et al., 2000)], among 51 crystal structures containing the heterodimeric hydrogen-bond motif A, do hydrogen bonds generate both types of ring motif; however, their arrangement in those structures is different from that in (I).
In contrast with the 1:1 adduct, no phenyl–perfluorophenyl stacking interactions are observed in (I) (Fig. 2). The shortest distances between the phenyl ring centroids of 5.1799 (3) Å correspond to the contacts between molecules related by the unit translation along the y axis. The hexameric assemblies interact via weak C—H···F and C—H···O hydrogen bonds (Table 2). All intermolecular F···F contacts exceed 2.90 Å.