3-Acetyl­anilinium bromide, nitrate and dihydrogen phosphate: hydrogen-bonding motifs in one, two and three dimensions

In the title compounds, namely 3-acetyl­anilinium bromide, C₈H₁₀NO⁺·Br⁻, (I), 3-acetyl­anilinium nitrate, C₈H₁₀NO⁺·NO₃⁻, (II), and 3-acetyl­anilinium dihydrogen phosphate, C₈H₁₀NO⁺·H₂PO₄⁻, (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...Br and N—H...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...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...O and O—H...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.

S1. Comment

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 pK_a 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.

Related literature

For related literature, see: Allen (2002); Allen et al. (1987); Bernstein et al. (1995); Cinčić & Kaitner (2008a, 2008b); Gould (1986); Haynes et al. (2005); Stahl & Wermuth (2002).

S2. Experimental

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.

S3. Refinement

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 U_iso(H) = 1.5U_eq(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 U_iso(H) = 1.5U_eq(O). Aromatic H atoms were placed in calculated positions and treated as riding on their parent C atoms [C—H = 0.93 Å and U_iso(H) = 1.2U_eq(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 U_iso(H) = 1.5U_eq(C).

Computing details

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).

Figures

	Fig. 1. The asymmetric unit of (I), showing the crystallographic numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. The asymmetric unit of (II), showing the crystallographic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii. Only one set of disordered methyl and ammonium H atoms is shown.
	Fig. 3. The asymmetric unit of (III), showing the crystallographic numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 4. A view of the one-dimensional hydrogen-bonded chain of (I), showing the aggregation of two hydrogen-bonding motifs, R^22(14) and R^24(8). Hydrogen bonds are drawn as dotted lines and C-bound H atoms have been omitted. Atoms marked with the suffixes a or b are at the symmetry positions (x - 1, y + 1, z - 1) and (-x - 1, 3 - y, -z), respectively.
	Fig. 5. A view of part of the crystal structure of (II), showing the aggregation of three hydrogen-bonding motifs, C^22(6), R^21(4) and R^46(14). Hydrogen bonds are drawn as dotted lines. Atoms marked with an ampersand (&) or a dollar sign ($) are at the symmetry positions (x, y + 1, z) and (1/2 - x, y + 3/2, z + 1/2), respectively. One set of disordered ammonium H atoms and C-bound H atoms have been omitted.
	Fig. 6. A view of the two-dimensional hydrogen-bonded network of (II), parallel to the (100) plane. Hydrogen bonds are drawn as dotted lines. One set of disordered ammonium H atoms and C-bound H atoms have been omitted.
	Fig. 7. A view of part of the crystal structure of (III), showing the aggregation of three hydrogen-bonding motifs, C(4), C^12(4) and R^33(10). Hydrogen bonds are drawn as dotted lines and C-bound H atoms have been omitted. Atoms marked with a hash (#) or an `at' symbol (@) are at the symmetry positions (x - 1, y, z) and (x - 2, y, z), respectively.
	Fig. 8. A view of part of the crystal structure of (III), showing a sheet parallel to (100). Hydrogen bonds are drawn as dotted lines and C-bound H atoms have been omitted. Atoms marked with the suffixes c or d are at the symmetry positions (1 - x, y - 1/2, 1/2 - z) and (-x, 1 - y, 1 - z), respectively.
	Fig. 9. Packing diagrams for compounds (I), (II) and (III), viewed along the c axes for (I) and (II) and the a axis for (III). The anions are shown as ball-and-stick models and C-bound H atoms have been omitted.

(I) 3-acetylanilinium bromide

Crystal data

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) Å^3

Data collection

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

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.018	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.049	w = 1/[σ^2(Fo^2) + (0.0269P)^2 + 0.1584P] where P = (Fo^2 + 2Fc^2)/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+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.094 (4)

Special details

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 (Ų)

	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 (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
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)

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)

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···O1^i	0.86 (3)	2.17 (3)	2.974 (2)	157 (2)
N1—H1A···Br1^ii	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

Crystal data

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) Å^3	Prism, colourless
Z = 4	0.31 × 0.26 × 0.13 mm

Data collection

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

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.042	H-atom parameters constrained
wR(F^2) = 0.129	w = 1/[σ^2(Fo^2) + (0.0669P)^2 + 0.2331P] where P = (Fo^2 + 2Fc^2)/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+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.029 (7)

Special details

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 (Ų)

	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 (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
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)

N1—O1	1.217 (2)	C2—H2	0.9300
N1—O2	1.2498 (15)	C3—C4	1.374 (3)
N1—O2^i	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—O2^i	121.39 (9)	C3—C4—H4	120.7
O2—N1—O2^i	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)

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···O2^i	0.89	2.12	2.979 (2)	163
N2—H2B···O2^ii	0.89	2.02	2.857 (2)	157
N2—H2C···O2^iii	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

Crystal data

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) Å^3	0.52 × 0.08 × 0.07 mm
Z = 4

Data collection

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

Refinement on F^2	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F^2 > 2σ(F^2)] = 0.047	H-atom parameters constrained
wR(F^2) = 0.150	w = 1/[σ^2(Fo^2) + (0.0746P)^2 + 0.5152P] where P = (Fo^2 + 2Fc^2)/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+0.001xFc^2λ^3/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.052 (7)

Special details

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 (Ų)

	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 (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
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)

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)

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···O1^i	0.96	1.76	2.707 (3)	168
N1—H1B···O2^ii	0.91	1.85	2.746 (3)	169
O3—H3A···O5^iii	0.82	1.86	2.665 (3)	165
O4—H4A···O1^iv	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.