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In the title compounds, namely 3-acetylanilinium bromide, C
8H
10NO
+·Br
−, (I), 3-acetylanilinium nitrate, C
8H
10NO
+·NO
3−, (II), and 3-acetylanilinium dihydrogen phosphate, C
8H
10NO
+·H
2PO
4−, (III), each asymmetric unit contains a discrete cation, with a protonated amino group, and an anion. In the crystal structure of (I), the ions are connected
via N—H
![...](/logos/entities/ctdot_rmgif.gif)
Br and N—H
![...](/logos/entities/ctdot_rmgif.gif)
O hydrogen bonds into a chain of spiro-fused
R22(14) and
R24(8) rings. In compound (II), the non-H atoms of the cation all lie on a mirror plane in the space group
Pnma, while the nitrate ion lies across a mirror plane. The crystal structures of compounds (II) and (III) are characterized by hydrogen-bonded networks in two and three dimensions, respectively. The ions in (II) are connected
via N—H
![...](/logos/entities/ctdot_rmgif.gif)
O hydrogen bonds, with three characteristic graph-set motifs,
viz. C22(6),
R21(4) and
R46(14). The ions in (III) are connected
via N—H
![...](/logos/entities/ctdot_rmgif.gif)
O and O—H
![...](/logos/entities/ctdot_rmgif.gif)
O hydrogen bonds, with five characteristic graph-set motifs,
viz. D,
C(4),
C12(4),
R33(10) and
R44(12). The significance of this study lies in its illustration of the differences between the supramolecular aggregations in the bromide, nitrate and dihydrogen phosphate salts of a small organic molecule. The different geometry of the counter-ions and their different potential for hydrogen-bond formation result in markedly different hydrogen-bonding arrangements.
Supporting information
CCDC references: 707215; 707216; 707217
For the preparation of (I), 3-aminoacetophenone (100 mg, 0.74 mmol) was
dissolved in a hot mixture of ethanol and propan-2-ol (3 ml; 2:1
v/v). The resulting clear solution was added to aqueous
hydrobromic acid (2 ml, 2 M) and cooled to room temperature, and
colourless crystals were grown by slow evaporation.
For the preparation of (II), 3-aminoacetophenone (100 mg, 0.74 mmol) was
dissolved in hot ethanol (2 ml). The clear solution was added to aqueous
nitric acid (1 ml, 2 M) and cooled to room temperature, and colourless
crystals of (II) were grown by slow evaporation.
For the preparation of (III), 3-aminoacetophenone (100 mg, 0,74 mmol) was
dissolved in a hot mixture of ethanol and propan-2-ol (3 ml; 2:1
v/v). The clear solution was added to aqueous phosphoric acid (2 ml, 2 M) and cooled to room temperature, and colourless crystals of
(III) were grown by slow evaporation.
Crystals of (I), (II) and (III) were collected by vacuum filtration, washed
with cold acetone and dried in air. In a nitrogen atmosphere, (I), (II) and
(III) melt at 459, 425 and 447 K, respectively.
For (I) and (III), N-bound H atoms were located in difference Fourier maps. For
(I), the positions and isotropic displacement parameters of N-bound H atoms
were refined [N—H = 0.86 (3)–0.94 (3) Å]. The N-bound H atoms in (III) were
fixed in their as-found positions (N—H = 0.91–0.96 Å). The H atoms of the
methyl and ammonium groups in (II) display symmetry-induced disorder and were
each modelled using two sets of half-occupancy H atoms. The N—H distance and
C—N—H angles for N-bound H atoms were fixed, but the group was allowed to
rotate around the C—N bound, with N—H = 0.89 Å and Uiso(H) =
1.5Ueq(N). For (III), hydroxyl H atoms were placed in calculated
positions and treated as riding on their parent O atoms, with O—H = 0.82 Å
and Uiso(H) = 1.5Ueq(O). Aromatic H atoms were placed in
calculated positions and treated as riding on their parent C atoms [C—H =
0.93 Å and Uiso(H) = 1.2Ueq(C)]. For all compounds, the
C—H distances and C—C—H angles for the methyl H atoms were fixed, but
the group was allowed to rotate around the C—C bound, with C—H = 0.96 Å
and Uiso(H) = 1.5Ueq(C).
For all compounds, data collection: CrysAlis CCD (Oxford Diffraction, 2003); cell refinement: CrysAlis RED (Oxford Diffraction, 2003); data reduction: CrysAlis RED (Oxford Diffraction, 2003); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999), PARST97 (Nardelli, 1995), Mercury (Version 1.4; Macrae et al., 2006) and POVRay (Persistence of Vision Team, 2004).
(I) 3-acetylanilinium bromide
top
Crystal data top
C8H10NO+·Br− | Z = 2 |
Mr = 216.08 | F(000) = 216 |
Triclinic, P1 | Dx = 1.694 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 5.0530 (4) Å | Cell parameters from 5234 reflections |
b = 9.4145 (9) Å | θ = 5–32° |
c = 9.5169 (9) Å | µ = 4.79 mm−1 |
α = 75.239 (8)° | T = 295 K |
β = 89.253 (9)° | Prism, colourless |
γ = 75.757 (10)° | 0.47 × 0.36 × 0.10 mm |
V = 423.74 (7) Å3 | |
Data collection top
Oxford Diffraction Xcalibur CCD diffractometer | 1809 independent reflections |
Radiation source: fine-focus sealed tube | 1668 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.011 |
ω scans | θmax = 27.0°, θmin = 4.2° |
Absorption correction: analytical (Alcock, 1970) | h = −6→6 |
Tmin = 0.155, Tmax = 0.631 | k = −12→12 |
5468 measured reflections | l = −12→12 |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.018 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.049 | w = 1/[σ2(Fo2) + (0.0269P)2 + 0.1584P] where P = (Fo2 + 2Fc2)/3 |
S = 1.12 | (Δ/σ)max = 0.001 |
1809 reflections | Δρmax = 0.33 e Å−3 |
114 parameters | Δρmin = −0.40 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.094 (4) |
Crystal data top
C8H10NO+·Br− | γ = 75.757 (10)° |
Mr = 216.08 | V = 423.74 (7) Å3 |
Triclinic, P1 | Z = 2 |
a = 5.0530 (4) Å | Mo Kα radiation |
b = 9.4145 (9) Å | µ = 4.79 mm−1 |
c = 9.5169 (9) Å | T = 295 K |
α = 75.239 (8)° | 0.47 × 0.36 × 0.10 mm |
β = 89.253 (9)° | |
Data collection top
Oxford Diffraction Xcalibur CCD diffractometer | 1809 independent reflections |
Absorption correction: analytical (Alcock, 1970) | 1668 reflections with I > 2σ(I) |
Tmin = 0.155, Tmax = 0.631 | Rint = 0.011 |
5468 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.018 | 0 restraints |
wR(F2) = 0.049 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.12 | Δρmax = 0.33 e Å−3 |
1809 reflections | Δρmin = −0.40 e Å−3 |
114 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 | |
H1A | 0.084 (5) | 0.909 (3) | 0.698 (3) | 0.049 (6)* | |
H1C | 0.349 (5) | 0.812 (3) | 0.764 (3) | 0.046 (6)* | |
H1B | 0.308 (5) | 0.852 (3) | 0.610 (3) | 0.050 (6)* | |
Br1 | 0.34300 (3) | 0.906927 (19) | 0.346035 (17) | 0.03578 (9) | |
O1 | 0.4280 (3) | 0.28602 (16) | 1.02641 (15) | 0.0454 (3) | |
N1 | 0.2260 (3) | 0.82336 (17) | 0.69825 (17) | 0.0311 (3) | |
C1 | 0.1253 (3) | 0.43018 (18) | 0.82662 (17) | 0.0270 (3) | |
C2 | 0.2270 (3) | 0.55732 (18) | 0.81775 (17) | 0.0276 (3) | |
H2 | 0.3646 | 0.5535 | 0.8836 | 0.033* | |
C3 | 0.1212 (3) | 0.68851 (18) | 0.71044 (17) | 0.0268 (3) | |
C4 | −0.0842 (3) | 0.6972 (2) | 0.61118 (18) | 0.0315 (3) | |
H4 | −0.1528 | 0.7863 | 0.5390 | 0.038* | |
C5 | −0.1852 (4) | 0.5718 (2) | 0.62093 (19) | 0.0345 (4) | |
H5 | −0.3239 | 0.5769 | 0.5551 | 0.041* | |
C6 | −0.0824 (4) | 0.4378 (2) | 0.72788 (19) | 0.0323 (3) | |
H6 | −0.1518 | 0.3538 | 0.7335 | 0.039* | |
C7 | 0.2458 (3) | 0.28805 (19) | 0.94281 (17) | 0.0291 (3) | |
C8 | 0.1405 (4) | 0.1514 (2) | 0.9535 (2) | 0.0399 (4) | |
H8A | 0.2265 | 0.0727 | 1.0371 | 0.060* | |
H8B | 0.1809 | 0.1164 | 0.8673 | 0.060* | |
H8C | −0.0538 | 0.1769 | 0.9627 | 0.060* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
Br1 | 0.03690 (12) | 0.03572 (12) | 0.02944 (12) | −0.00475 (7) | −0.00523 (7) | −0.00294 (7) |
O1 | 0.0527 (8) | 0.0350 (7) | 0.0431 (7) | −0.0169 (6) | −0.0230 (6) | 0.0061 (6) |
N1 | 0.0324 (7) | 0.0259 (7) | 0.0309 (7) | −0.0080 (6) | −0.0048 (6) | 0.0007 (6) |
C1 | 0.0277 (7) | 0.0266 (8) | 0.0245 (7) | −0.0068 (6) | 0.0001 (6) | −0.0029 (6) |
C2 | 0.0273 (7) | 0.0288 (8) | 0.0247 (7) | −0.0077 (6) | −0.0045 (6) | −0.0024 (6) |
C3 | 0.0269 (7) | 0.0261 (8) | 0.0253 (7) | −0.0069 (6) | 0.0014 (6) | −0.0026 (6) |
C4 | 0.0299 (8) | 0.0318 (8) | 0.0259 (8) | −0.0029 (7) | −0.0054 (6) | 0.0002 (6) |
C5 | 0.0313 (8) | 0.0385 (9) | 0.0311 (8) | −0.0075 (7) | −0.0100 (7) | −0.0054 (7) |
C6 | 0.0328 (8) | 0.0325 (9) | 0.0325 (8) | −0.0118 (7) | −0.0034 (7) | −0.0064 (7) |
C7 | 0.0307 (8) | 0.0270 (8) | 0.0273 (7) | −0.0079 (6) | −0.0010 (6) | −0.0021 (6) |
C8 | 0.0480 (10) | 0.0312 (9) | 0.0392 (9) | −0.0169 (8) | −0.0068 (8) | 0.0006 (7) |
Geometric parameters (Å, º) top
O1—C7 | 1.218 (2) | C3—C4 | 1.386 (2) |
N1—C3 | 1.470 (2) | C4—C5 | 1.380 (3) |
N1—H1A | 0.94 (3) | C4—H4 | 0.9300 |
N1—H1C | 0.86 (3) | C5—C6 | 1.391 (2) |
N1—H1B | 0.94 (3) | C5—H5 | 0.9300 |
C1—C6 | 1.394 (2) | C6—H6 | 0.9300 |
C1—C2 | 1.398 (2) | C7—C8 | 1.489 (2) |
C1—C7 | 1.499 (2) | C8—H8A | 0.9600 |
C2—C3 | 1.379 (2) | C8—H8B | 0.9600 |
C2—H2 | 0.9300 | C8—H8C | 0.9600 |
| | | |
C3—N1—H1A | 111.1 (15) | C3—C4—H4 | 120.5 |
C3—N1—H1C | 113.8 (17) | C4—C5—C6 | 120.84 (15) |
H1A—N1—H1C | 110 (2) | C4—C5—H5 | 119.6 |
C3—N1—H1B | 112.9 (15) | C6—C5—H5 | 119.6 |
H1A—N1—H1B | 104 (2) | C5—C6—C1 | 119.59 (16) |
H1C—N1—H1B | 105 (2) | C5—C6—H6 | 120.2 |
C6—C1—C2 | 119.75 (15) | C1—C6—H6 | 120.2 |
C6—C1—C7 | 121.74 (15) | O1—C7—C8 | 121.19 (15) |
C2—C1—C7 | 118.51 (14) | O1—C7—C1 | 119.62 (15) |
C3—C2—C1 | 119.35 (14) | C8—C7—C1 | 119.19 (15) |
C3—C2—H2 | 120.3 | C7—C8—H8A | 109.5 |
C1—C2—H2 | 120.3 | C7—C8—H8B | 109.5 |
C2—C3—C4 | 121.43 (15) | H8A—C8—H8B | 109.5 |
C2—C3—N1 | 120.36 (14) | C7—C8—H8C | 109.5 |
C4—C3—N1 | 118.21 (14) | H8A—C8—H8C | 109.5 |
C5—C4—C3 | 119.05 (15) | H8B—C8—H8C | 109.5 |
C5—C4—H4 | 120.5 | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1B···Br1 | 0.94 (3) | 2.45 (3) | 3.322 (2) | 156 (2) |
N1—H1C···O1i | 0.86 (3) | 2.17 (3) | 2.974 (2) | 157 (2) |
N1—H1A···Br1ii | 0.94 (3) | 2.38 (2) | 3.284 (1) | 163 (2) |
Symmetry codes: (i) −x+1, −y+1, −z+2; (ii) −x, −y+2, −z+1. |
(II) 3-acetylanilinium nitrate
top
Crystal data top
C8H10NO+·NO3− | F(000) = 416 |
Mr = 198.18 | Dx = 1.437 Mg m−3 |
Orthorhombic, Pnma | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ac 2n | Cell parameters from 3490 reflections |
a = 16.7754 (4) Å | θ = 4–25° |
b = 6.6044 (2) Å | µ = 0.12 mm−1 |
c = 8.2683 (2) Å | T = 295 K |
V = 916.06 (4) Å3 | Prism, colourless |
Z = 4 | 0.31 × 0.26 × 0.13 mm |
Data collection top
Oxford Diffraction Xcalibur CCD diffractometer | 1086 independent reflections |
Radiation source: fine-focus sealed tube | 824 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.020 |
ω scans | θmax = 27.0°, θmin = 3.9° |
Absorption correction: analytical (Alcock, 1970) | h = −21→21 |
Tmin = 0.968, Tmax = 0.987 | k = −8→8 |
9987 measured reflections | l = −10→10 |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.042 | H-atom parameters constrained |
wR(F2) = 0.129 | w = 1/[σ2(Fo2) + (0.0669P)2 + 0.2331P] where P = (Fo2 + 2Fc2)/3 |
S = 1.12 | (Δ/σ)max < 0.001 |
1086 reflections | Δρmax = 0.22 e Å−3 |
85 parameters | Δρmin = −0.16 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.029 (7) |
Crystal data top
C8H10NO+·NO3− | V = 916.06 (4) Å3 |
Mr = 198.18 | Z = 4 |
Orthorhombic, Pnma | Mo Kα radiation |
a = 16.7754 (4) Å | µ = 0.12 mm−1 |
b = 6.6044 (2) Å | T = 295 K |
c = 8.2683 (2) Å | 0.31 × 0.26 × 0.13 mm |
Data collection top
Oxford Diffraction Xcalibur CCD diffractometer | 1086 independent reflections |
Absorption correction: analytical (Alcock, 1970) | 824 reflections with I > 2σ(I) |
Tmin = 0.968, Tmax = 0.987 | Rint = 0.020 |
9987 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.042 | 0 restraints |
wR(F2) = 0.129 | H-atom parameters constrained |
S = 1.12 | Δρmax = 0.22 e Å−3 |
1086 reflections | Δρmin = −0.16 e Å−3 |
85 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) |
N1 | 0.24693 (11) | 0.2500 | 0.1370 (2) | 0.0517 (5) | |
O1 | 0.26880 (14) | 0.2500 | −0.0034 (2) | 0.0873 (7) | |
O2 | 0.23509 (8) | 0.08846 (19) | 0.21195 (15) | 0.0700 (4) | |
O3 | 0.04075 (11) | 0.2500 | 1.05502 (18) | 0.0662 (5) | |
N2 | 0.20049 (11) | 0.2500 | 0.5409 (2) | 0.0522 (5) | |
H2A | 0.2075 | 0.2725 | 0.4357 | 0.078* | 0.50 |
H2B | 0.2213 | 0.1305 | 0.5670 | 0.078* | 0.50 |
H2C | 0.2245 | 0.3471 | 0.5974 | 0.078* | 0.50 |
C1 | 0.01183 (12) | 0.2500 | 0.7771 (2) | 0.0434 (5) | |
C2 | 0.09282 (12) | 0.2500 | 0.7382 (2) | 0.0438 (5) | |
H2 | 0.1312 | 0.2500 | 0.8194 | 0.053* | |
C3 | 0.11501 (12) | 0.2500 | 0.5780 (2) | 0.0447 (5) | |
C4 | 0.06002 (15) | 0.2500 | 0.4548 (2) | 0.0509 (5) | |
H4 | 0.0764 | 0.2500 | 0.3473 | 0.061* | |
C5 | −0.01974 (14) | 0.2500 | 0.4938 (3) | 0.0555 (6) | |
H5 | −0.0577 | 0.2500 | 0.4118 | 0.067* | |
C6 | −0.04419 (13) | 0.2500 | 0.6538 (3) | 0.0498 (5) | |
H6 | −0.0983 | 0.2500 | 0.6786 | 0.060* | |
C7 | −0.01066 (13) | 0.2500 | 0.9518 (3) | 0.0496 (5) | |
C8 | −0.09734 (15) | 0.2500 | 0.9969 (3) | 0.0676 (7) | |
H8A | −0.1252 | 0.1522 | 0.9322 | 0.101* | 0.50 |
H8B | −0.1194 | 0.3820 | 0.9781 | 0.101* | 0.50 |
H8C | −0.1028 | 0.2158 | 1.1092 | 0.101* | 0.50 |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
N1 | 0.0516 (10) | 0.0543 (11) | 0.0492 (10) | 0.000 | 0.0000 (8) | 0.000 |
O1 | 0.0968 (15) | 0.1110 (18) | 0.0543 (11) | 0.000 | 0.0234 (10) | 0.000 |
O2 | 0.0943 (10) | 0.0477 (7) | 0.0679 (8) | 0.0028 (6) | 0.0075 (6) | 0.0030 (6) |
O3 | 0.0651 (10) | 0.0921 (13) | 0.0415 (8) | 0.000 | −0.0032 (7) | 0.000 |
N2 | 0.0568 (10) | 0.0526 (10) | 0.0471 (9) | 0.000 | 0.0057 (8) | 0.000 |
C1 | 0.0486 (11) | 0.0388 (9) | 0.0429 (10) | 0.000 | −0.0031 (8) | 0.000 |
C2 | 0.0467 (10) | 0.0464 (10) | 0.0384 (9) | 0.000 | −0.0067 (8) | 0.000 |
C3 | 0.0525 (11) | 0.0384 (9) | 0.0430 (10) | 0.000 | 0.0008 (8) | 0.000 |
C4 | 0.0701 (14) | 0.0443 (10) | 0.0383 (10) | 0.000 | −0.0052 (9) | 0.000 |
C5 | 0.0644 (14) | 0.0525 (12) | 0.0496 (11) | 0.000 | −0.0194 (10) | 0.000 |
C6 | 0.0482 (11) | 0.0475 (11) | 0.0538 (12) | 0.000 | −0.0100 (9) | 0.000 |
C7 | 0.0530 (12) | 0.0476 (11) | 0.0480 (11) | 0.000 | −0.0001 (9) | 0.000 |
C8 | 0.0571 (13) | 0.0794 (17) | 0.0663 (15) | 0.000 | 0.0131 (12) | 0.000 |
Geometric parameters (Å, º) top
N1—O1 | 1.217 (2) | C2—H2 | 0.9300 |
N1—O2 | 1.2498 (15) | C3—C4 | 1.374 (3) |
N1—O2i | 1.2498 (15) | C4—C5 | 1.376 (4) |
O3—C7 | 1.214 (3) | C4—H4 | 0.9300 |
N2—C3 | 1.466 (3) | C5—C6 | 1.385 (3) |
N2—H2A | 0.8900 | C5—H5 | 0.9300 |
N2—H2B | 0.8900 | C6—H6 | 0.9300 |
N2—H2C | 0.8900 | C7—C8 | 1.501 (3) |
C1—C6 | 1.386 (3) | C8—H8A | 0.9600 |
C1—C2 | 1.396 (3) | C8—H8B | 0.9600 |
C1—C7 | 1.493 (3) | C8—H8C | 0.9600 |
C2—C3 | 1.376 (3) | | |
| | | |
O1—N1—O2 | 121.39 (9) | C3—C4—C5 | 118.6 (2) |
O1—N1—O2i | 121.39 (9) | C3—C4—H4 | 120.7 |
O2—N1—O2i | 117.21 (18) | C5—C4—H4 | 120.7 |
C3—N2—H2A | 109.5 | C4—C5—C6 | 120.8 (2) |
C3—N2—H2B | 109.5 | C4—C5—H5 | 119.6 |
H2A—N2—H2B | 109.5 | C6—C5—H5 | 119.6 |
C3—N2—H2C | 109.5 | C5—C6—C1 | 120.1 (2) |
H2A—N2—H2C | 109.5 | C5—C6—H6 | 120.0 |
H2B—N2—H2C | 109.5 | C1—C6—H6 | 120.0 |
C6—C1—C2 | 119.38 (19) | O3—C7—C1 | 120.1 (2) |
C6—C1—C7 | 122.68 (19) | O3—C7—C8 | 120.9 (2) |
C2—C1—C7 | 117.95 (18) | C1—C7—C8 | 119.0 (2) |
C3—C2—C1 | 119.00 (18) | C7—C8—H8A | 109.5 |
C3—C2—H2 | 120.5 | C7—C8—H8B | 109.5 |
C1—C2—H2 | 120.5 | H8A—C8—H8B | 109.5 |
C4—C3—C2 | 122.1 (2) | C7—C8—H8C | 109.5 |
C4—C3—N2 | 120.11 (18) | H8A—C8—H8C | 109.5 |
C2—C3—N2 | 117.76 (18) | H8B—C8—H8C | 109.5 |
Symmetry code: (i) x, −y+1/2, z. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H2A···O2 | 0.89 | 2.26 | 2.979 (2) | 137 |
N2—H2A···O2i | 0.89 | 2.12 | 2.979 (2) | 163 |
N2—H2B···O2ii | 0.89 | 2.02 | 2.857 (2) | 157 |
N2—H2C···O2iii | 0.89 | 1.97 | 2.857 (2) | 172 |
Symmetry codes: (i) x, −y+1/2, z; (ii) −x+1/2, −y, z+1/2; (iii) −x+1/2, y+1/2, z+1/2. |
(III) 3-acetylanilinium dihydrogen phosphate
top
Crystal data top
C8H10NO+·H2O4P− | F(000) = 488 |
Mr = 233.16 | Dx = 1.480 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 2888 reflections |
a = 4.6733 (2) Å | θ = 4–25° |
b = 10.5962 (4) Å | µ = 0.26 mm−1 |
c = 21.1801 (9) Å | T = 295 K |
β = 93.631 (3)° | Prism, colourless |
V = 1046.72 (7) Å3 | 0.52 × 0.08 × 0.07 mm |
Z = 4 | |
Data collection top
Oxford Diffraction Xcalibur CCD diffractometer | 2270 independent reflections |
Radiation source: fine-focus sealed tube | 1593 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.028 |
ω scans | θmax = 27.0°, θmin = 3.9° |
Absorption correction: analytical (Alcock, 1970) | h = −5→5 |
Tmin = 0.879, Tmax = 0.986 | k = −13→12 |
10065 measured reflections | l = −26→27 |
Refinement top
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.047 | H-atom parameters constrained |
wR(F2) = 0.150 | w = 1/[σ2(Fo2) + (0.0746P)2 + 0.5152P] where P = (Fo2 + 2Fc2)/3 |
S = 1.16 | (Δ/σ)max < 0.001 |
2270 reflections | Δρmax = 0.48 e Å−3 |
141 parameters | Δρmin = −0.38 e Å−3 |
0 restraints | Extinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.052 (7) |
Crystal data top
C8H10NO+·H2O4P− | V = 1046.72 (7) Å3 |
Mr = 233.16 | Z = 4 |
Monoclinic, P21/c | Mo Kα radiation |
a = 4.6733 (2) Å | µ = 0.26 mm−1 |
b = 10.5962 (4) Å | T = 295 K |
c = 21.1801 (9) Å | 0.52 × 0.08 × 0.07 mm |
β = 93.631 (3)° | |
Data collection top
Oxford Diffraction Xcalibur CCD diffractometer | 2270 independent reflections |
Absorption correction: analytical (Alcock, 1970) | 1593 reflections with I > 2σ(I) |
Tmin = 0.879, Tmax = 0.986 | Rint = 0.028 |
10065 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.047 | 0 restraints |
wR(F2) = 0.150 | H-atom parameters constrained |
S = 1.16 | Δρmax = 0.48 e Å−3 |
2270 reflections | Δρmin = −0.38 e Å−3 |
141 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 | |
P1 | 0.31660 (12) | 0.38250 (6) | 0.39549 (3) | 0.0375 (2) | |
O1 | 0.0660 (4) | 0.35625 (18) | 0.43449 (8) | 0.0472 (5) | |
O2 | 0.4202 (4) | 0.51558 (16) | 0.39925 (9) | 0.0446 (5) | |
O3 | 0.2065 (5) | 0.3485 (2) | 0.32609 (10) | 0.0704 (7) | |
H3A | 0.3376 | 0.3569 | 0.3025 | 0.106* | |
O4 | 0.5555 (4) | 0.2874 (2) | 0.41515 (16) | 0.0859 (9) | |
H4A | 0.6870 | 0.2945 | 0.3916 | 0.129* | |
O5 | 0.4268 (5) | 0.8522 (2) | 0.26528 (10) | 0.0615 (6) | |
N1 | −0.0857 (4) | 0.64195 (18) | 0.43749 (10) | 0.0376 (5) | |
C1 | 0.1007 (5) | 0.9169 (2) | 0.33820 (12) | 0.0409 (6) | |
C2 | 0.0868 (5) | 0.7941 (2) | 0.36229 (11) | 0.0367 (5) | |
H2 | 0.1865 | 0.7290 | 0.3440 | 0.044* | |
C3 | −0.0746 (5) | 0.7700 (2) | 0.41299 (11) | 0.0349 (5) | |
C4 | −0.2223 (6) | 0.8655 (2) | 0.44158 (13) | 0.0469 (6) | |
H4 | −0.3301 | 0.8484 | 0.4760 | 0.056* | |
C5 | −0.2061 (7) | 0.9869 (3) | 0.41791 (15) | 0.0554 (7) | |
H5 | −0.3041 | 1.0518 | 0.4368 | 0.067* | |
C6 | −0.0469 (6) | 1.0132 (2) | 0.36680 (13) | 0.0486 (6) | |
H6 | −0.0382 | 1.0952 | 0.3515 | 0.058* | |
C7 | 0.2794 (6) | 0.9376 (3) | 0.28374 (12) | 0.0478 (6) | |
C8 | 0.2801 (10) | 1.0632 (3) | 0.25226 (18) | 0.0808 (12) | |
H8A | 0.3806 | 1.0573 | 0.2142 | 0.121* | |
H8B | 0.3739 | 1.1236 | 0.2803 | 0.121* | |
H8C | 0.0862 | 1.0895 | 0.2420 | 0.121* | |
H1A | −0.1047 | 0.6389 | 0.4825 | 0.062 (9)* | |
H1B | −0.2426 | 0.6012 | 0.4196 | 0.055 (8)* | |
H1C | 0.0819 | 0.5936 | 0.4291 | 0.071 (10)* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
P1 | 0.0311 (4) | 0.0328 (4) | 0.0497 (4) | 0.0005 (2) | 0.0113 (3) | −0.0020 (2) |
O1 | 0.0353 (9) | 0.0613 (12) | 0.0461 (10) | −0.0039 (8) | 0.0107 (7) | 0.0022 (8) |
O2 | 0.0416 (9) | 0.0326 (9) | 0.0604 (11) | 0.0003 (7) | 0.0094 (8) | −0.0029 (8) |
O3 | 0.0700 (14) | 0.0896 (17) | 0.0540 (12) | −0.0261 (12) | 0.0246 (10) | −0.0291 (11) |
O4 | 0.0363 (11) | 0.0384 (11) | 0.184 (3) | 0.0059 (8) | 0.0116 (13) | 0.0212 (14) |
O5 | 0.0748 (14) | 0.0554 (12) | 0.0579 (12) | 0.0120 (10) | 0.0317 (11) | 0.0095 (9) |
N1 | 0.0391 (11) | 0.0314 (10) | 0.0433 (11) | −0.0023 (8) | 0.0101 (8) | −0.0001 (8) |
C1 | 0.0446 (13) | 0.0353 (12) | 0.0431 (13) | −0.0010 (10) | 0.0051 (10) | 0.0007 (10) |
C2 | 0.0383 (12) | 0.0323 (12) | 0.0398 (12) | 0.0019 (9) | 0.0055 (9) | −0.0012 (9) |
C3 | 0.0353 (11) | 0.0296 (11) | 0.0398 (12) | −0.0002 (9) | 0.0023 (9) | −0.0015 (9) |
C4 | 0.0519 (14) | 0.0392 (14) | 0.0515 (15) | 0.0034 (11) | 0.0185 (12) | −0.0043 (11) |
C5 | 0.0697 (18) | 0.0346 (14) | 0.0642 (18) | 0.0098 (12) | 0.0213 (14) | −0.0044 (12) |
C6 | 0.0638 (16) | 0.0311 (13) | 0.0512 (15) | 0.0051 (11) | 0.0073 (12) | 0.0018 (11) |
C7 | 0.0596 (16) | 0.0421 (14) | 0.0422 (13) | −0.0018 (12) | 0.0087 (12) | 0.0033 (11) |
C8 | 0.126 (3) | 0.0463 (19) | 0.074 (2) | 0.0061 (19) | 0.044 (2) | 0.0170 (16) |
Geometric parameters (Å, º) top
P1—O2 | 1.4915 (18) | C1—C7 | 1.483 (4) |
P1—O1 | 1.5011 (17) | C2—C3 | 1.375 (3) |
P1—O4 | 1.542 (2) | C2—H2 | 0.9300 |
P1—O3 | 1.568 (2) | C3—C4 | 1.386 (3) |
O3—H3A | 0.8200 | C4—C5 | 1.384 (4) |
O4—H4A | 0.8200 | C4—H4 | 0.9300 |
O5—C7 | 1.217 (3) | C5—C6 | 1.380 (4) |
N1—C3 | 1.455 (3) | C5—H5 | 0.9300 |
N1—H1A | 0.964 | C6—H6 | 0.9300 |
N1—H1B | 0.912 | C7—C8 | 1.488 (4) |
N1—H1C | 0.962 | C8—H8A | 0.9600 |
C1—C6 | 1.392 (3) | C8—H8B | 0.9600 |
C1—C2 | 1.400 (3) | C8—H8C | 0.9600 |
| | | |
O2—P1—O1 | 114.06 (11) | C2—C3—N1 | 119.07 (19) |
O2—P1—O4 | 112.13 (12) | C4—C3—N1 | 119.7 (2) |
O1—P1—O4 | 107.88 (13) | C5—C4—C3 | 118.7 (2) |
O2—P1—O3 | 110.70 (12) | C5—C4—H4 | 120.6 |
O1—P1—O3 | 104.60 (11) | C3—C4—H4 | 120.6 |
O4—P1—O3 | 106.98 (16) | C6—C5—C4 | 121.0 (2) |
P1—O3—H3A | 109.5 | C6—C5—H5 | 119.5 |
P1—O4—H4A | 109.5 | C4—C5—H5 | 119.5 |
C3—N1—H1A | 113.07 | C5—C6—C1 | 120.0 (2) |
C3—N1—H1B | 109.84 | C5—C6—H6 | 120.0 |
H1A—N1—H1B | 105.86 | C1—C6—H6 | 120.0 |
C3—N1—H1C | 112.50 | O5—C7—C1 | 119.8 (2) |
H1A—N1—H1C | 107.0 | O5—C7—C8 | 120.3 (3) |
H1B—N1—H1C | 108.28 | C1—C7—C8 | 119.9 (3) |
C6—C1—C2 | 119.1 (2) | C7—C8—H8A | 109.5 |
C6—C1—C7 | 123.3 (2) | C7—C8—H8B | 109.5 |
C2—C1—C7 | 117.6 (2) | H8A—C8—H8B | 109.5 |
C3—C2—C1 | 119.8 (2) | C7—C8—H8C | 109.5 |
C3—C2—H2 | 120.1 | H8A—C8—H8C | 109.5 |
C1—C2—H2 | 120.1 | H8B—C8—H8C | 109.5 |
C2—C3—C4 | 121.2 (2) | | |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1C···O2 | 0.96 | 1.93 | 2.878 (3) | 170 |
N1—H1A···O1i | 0.96 | 1.76 | 2.707 (3) | 168 |
N1—H1B···O2ii | 0.91 | 1.85 | 2.746 (3) | 169 |
O3—H3A···O5iii | 0.82 | 1.86 | 2.665 (3) | 165 |
O4—H4A···O1iv | 0.82 | 2.05 | 2.504 (3) | 115 |
Symmetry codes: (i) −x, −y+1, −z+1; (ii) x−1, y, z; (iii) −x+1, y−1/2, −z+1/2; (iv) x+1, y, z. |
Experimental details
| (I) | (II) | (III) |
Crystal data |
Chemical formula | C8H10NO+·Br− | C8H10NO+·NO3− | C8H10NO+·H2O4P− |
Mr | 216.08 | 198.18 | 233.16 |
Crystal system, space group | Triclinic, P1 | Orthorhombic, Pnma | Monoclinic, P21/c |
Temperature (K) | 295 | 295 | 295 |
a, b, c (Å) | 5.0530 (4), 9.4145 (9), 9.5169 (9) | 16.7754 (4), 6.6044 (2), 8.2683 (2) | 4.6733 (2), 10.5962 (4), 21.1801 (9) |
α, β, γ (°) | 75.239 (8), 89.253 (9), 75.757 (10) | 90, 90, 90 | 90, 93.631 (3), 90 |
V (Å3) | 423.74 (7) | 916.06 (4) | 1046.72 (7) |
Z | 2 | 4 | 4 |
Radiation type | Mo Kα | Mo Kα | Mo Kα |
µ (mm−1) | 4.79 | 0.12 | 0.26 |
Crystal size (mm) | 0.47 × 0.36 × 0.10 | 0.31 × 0.26 × 0.13 | 0.52 × 0.08 × 0.07 |
|
Data collection |
Diffractometer | Oxford Diffraction Xcalibur CCD diffractometer | Oxford Diffraction Xcalibur CCD diffractometer | Oxford Diffraction Xcalibur CCD diffractometer |
Absorption correction | Analytical (Alcock, 1970) | Analytical (Alcock, 1970) | Analytical (Alcock, 1970) |
Tmin, Tmax | 0.155, 0.631 | 0.968, 0.987 | 0.879, 0.986 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 5468, 1809, 1668 | 9987, 1086, 824 | 10065, 2270, 1593 |
Rint | 0.011 | 0.020 | 0.028 |
(sin θ/λ)max (Å−1) | 0.639 | 0.639 | 0.639 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.018, 0.049, 1.12 | 0.042, 0.129, 1.12 | 0.047, 0.150, 1.16 |
No. of reflections | 1809 | 1086 | 2270 |
No. of parameters | 114 | 85 | 141 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.33, −0.40 | 0.22, −0.16 | 0.48, −0.38 |
Hydrogen-bond geometry (Å, º) for (I) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1B···Br1 | 0.94 (3) | 2.45 (3) | 3.322 (2) | 156 (2) |
N1—H1C···O1i | 0.86 (3) | 2.17 (3) | 2.974 (2) | 157 (2) |
N1—H1A···Br1ii | 0.94 (3) | 2.38 (2) | 3.284 (1) | 163 (2) |
Symmetry codes: (i) −x+1, −y+1, −z+2; (ii) −x, −y+2, −z+1. |
Hydrogen-bond geometry (Å, º) for (II) top
D—H···A | D—H | H···A | D···A | D—H···A |
N2—H2A···O2 | 0.89 | 2.26 | 2.979 (2) | 137 |
N2—H2A···O2i | 0.89 | 2.12 | 2.979 (2) | 163 |
N2—H2B···O2ii | 0.89 | 2.02 | 2.857 (2) | 157 |
N2—H2C···O2iii | 0.89 | 1.97 | 2.857 (2) | 172 |
Symmetry codes: (i) x, −y+1/2, z; (ii) −x+1/2, −y, z+1/2; (iii) −x+1/2, y+1/2, z+1/2. |
Hydrogen-bond geometry (Å, º) for (III) top
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1C···O2 | 0.96 | 1.93 | 2.878 (3) | 170 |
N1—H1A···O1i | 0.96 | 1.76 | 2.707 (3) | 168 |
N1—H1B···O2ii | 0.91 | 1.85 | 2.746 (3) | 169 |
O3—H3A···O5iii | 0.82 | 1.86 | 2.665 (3) | 165 |
O4—H4A···O1iv | 0.82 | 2.05 | 2.504 (3) | 115 |
Symmetry codes: (i) −x, −y+1, −z+1; (ii) x−1, y, z; (iii) −x+1, y−1/2, −z+1/2; (iv) x+1, y, z. |
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The formation of multi-component ionic crystals, or salts, is of fundamental importance to the development of most active pharmaceutical ingredients (APIs), where the approach is used for both purification and physical property optimization. There is a wide range of acids and bases, with a range of pKa values, solubilities, molecular weights, geometry and other properties, used for salt formation to increase or decrease solubility, to improve stability or toxicity and to reduce hygroscopicity of APIs (Gould 1986; Stahl & Wermuth 2002). The ten most frequently occurring counterions of salts of small organic molecules in the Cambridge Structural Database (CSD, Version 5.25; Allen 2002), in order of decreasing occurrence, are chloride, bromide, nitrate, ammonium, sulfate, tosylate, dihydrogen phosphate, tartrate, ethylenediamine (di-ion) and maleate (mono-ion) (Haynes et al., 2005). Most of these counterions are in the pharmaceutical `Top Ten' list. The aim of this study lies in its illustration of the differences between the supramolecular aggregations in the bromide, nitrate and dihydrogen phosphate salts of a small organic molecule. The different geometry of the counterions and their different potential for hydrogen-bond formation result in markedly different hydrogen-bonding arrangements of the ions in the crystal structures.
The title compounds, 3-acetylanilinium bromide, (I), 3-acetylanilinium nitrate, (II) and 3-acetylanilinium dihydrogen phosphate, (III), were originally investigated during salt screening of aromatic monoamines and represent part of our research into hydrogen-bonded ionic crystals of acid salts (Cinčić & Kaitner 2008a,b). 3-Aminoacetophenone has been much less studied than similar organic molecules, such as 3- and 4-aminobenzoic acid or 4-aminoacetophenone. There are no entries in the CSD for any 3-acetylanilinium salt.
In compounds (I)–(III), the bond lengths and angles are all normal for their types (Allen et al., 1987). The asymmetric unit of each compound contains an anion and a discrete cation with a protonated amino group (Figs. 1–3).
In (I), the ions are connected via N—H···Br and N—H···O hydrogen bonds (Table 1) into one-dimensional hydrogen-bonded chains which run parallel to the [111] direction. All ammonium H atoms are involved in hydrogen bonds with two different Br- ions and with the carbonyl O atom of a neighbouring cation, while each anion accepts two hydrogen bonds. The centrosymmetric hydrogen-bonded rings formed by adjacent 3-acetylanilinium cations and two Br- anions can be described by the graph-set motif R24(8) (Bernstein et al., 1995). The carbonyl O atom participates in hydrogen-bonding with a neighbouring cation through an N—H···O hydrogen bond. This interaction links cations into another centrosymmetric hydrogen-bonded ring which can be described by the graph-set motif R22(14). The aggregation of two ring motifs results in an overall one-dimensional hydrogen-bonded chain structure along the [111] direction (Fig. 4).
The supramolecular structure of (II) differs markedly from that of (I). Atoms C7, C8 and O3 are coplanar with the phenyl ring and, together with atoms N1 and O1, lie on a mirror plane of symmetry where the two O atoms of the anion are crystallographically equivalent. The H atoms of the methyl and ammonium groups display symmetry-induced disorder over two sets of positions. The ions are connected via N—H···O hydrogen bonds (Table 2) into a two-dimensional hydrogen-bonded network parallel to the (100) plane. As in (I), all ammonium H atoms are involved in hydrogen bonds, but this time with three different NO3- ions, while each anion accepts four hydrogen bonds. Only two O atoms of the anion are involved in strong hydrogen bonds, while the third does not participate in any strong interaction. The anions and cations are connected via a three-centred hydrogen bond into a ring which can be described by the graph-set motif R21(4) (Fig. 5). Another ammonium–anion interaction links the anions and cations in an alternating fashion into extended chains along the [010] direction which can be described by the graph-set motif C22(6) (Fig. 5). There are no centrosymmetric hydrogen-bonded dimers of adjacent 3-acetylanilinium cations, as in (I). Also, the carbonyl O atom does not participate in any strong intermolecular interaction. The noncentrosymmetric hydrogen-bonded ring formed by three adjacent 3-acetylanilinium cations and three nitrate anions can be described by the graph-set motif R46(14) (Fig. 5). The aggregation of ring and chain motifs results in an overall two-dimensional hydrogen-bonded sheet-like structure (Fig. 6). Adjacent sheets are stacked in the [100] direction to give a three-dimensional framework, where the interplanar distance between the aromatic rings of each sheet is ca 3.30 Å.
In (III), the ions are connected into a three-dimensional hydrogen-bonded network via N—H···O and O—H···O hydrogen bonds (Table 3). All ammonium H atoms are involved in hydrogen bonds with three H2PO4- ions, while each anion accepts six hydrogen bonds. Similar to (II), the two ammonium–anion interactions link the anions and cations in an alternating fashion into extended chains along the [100] direction which can be described by the graph-set motif C12(4) (Fig. 7). The anions themselves are linked via an O—H···O interaction into chains, also along the [100] direction, which can be described by the graph-set motif C(4). The combination of these two chain motifs generates noncentrosymmetric fused rings which can be described by the graph-set motif R33(10) (Fig. 7). The centrosymmetric hydrogen-bonded ring formed by two adjacent 3-acetylanilinium cations and two H2PO4- anions can be described by the graph-set motif R44(12) (Fig. 8). The carbonyl O atom of the cation participates in a finite hydrogen-bonding motif, D, with a neighbouring anion through an O—H···O hydrogen bond. The combination of this finite motif and the R44(12) motif generates a sheet parallel to (100) (Fig. 8). The aggregation of all these ring and chain motifs results in an overall three-dimensional hydrogen-bonded framework.
Fig. 9 clearly compares the packing arrangements of (I)–(III). The crystal packings of all three compounds are characterized by layers of 3-acetylanilinium cations which are embedded between ionic layers of anions, forming an alternating hydrocarbon–ionic layer structure. No intermolecular π–π interactions are evident in the hydrocarbon layer in any crystal structure. The shortest centroid-to-centroid distances between adjacent cations in (I), (II) and (III) are ca 4.65, 4.00 and 4.67 Å, respectively.