Hydrogen bonding in the bromide salts of 4-amino­benzoic acid and 4-amino­acetophenone

In the title compounds, 4-carboxy­anilinium bromide, C₇H₈NO₂⁺·Br⁻, (I), and 4-acetyl­anilinium bromide, C₈H₁₀NO⁺·Br⁻, (II), each asymmetric unit contains a discrete cation with a protonated amino group and a halide anion. Both crystal structures are characterized by two-dimensional hydrogen-bonded networks. The ions in (I) are connected via N—H...Br, N—H...O and O—H...Br hydrogen bonds, with three characteristic graph-set motifs, viz. C(8), C₂¹(4) and R₃²(8). The centrosymmetric hydrogen-bonded R²₂(8) dimer motif characteristic of carboxylic acids is absent. The ions in (II) are connected via N—H...Br and N—H...O hydrogen bonds, with two characteristic graph-set motifs, viz. C(8) and R₄²(8). The significance of this study lies in its illustration of the differences between the supra­molecular aggregations in two similar compounds. The presence of the methyl group in (II) at the site corresponding to the hydroxyl group in (I) results in a significantly different hydrogen-bonding arrangement.

S1. Comment

The synthesis of salts provides pharmaceutical scientists with the opportunity to modify the physicochemical properties of active pharmaceutical ingredients (APIs) or potential drug substances. The salt form can influence the range of properties, such as aqueous solubility, melting point, hygroscopicity, dissolution rate and crystallinity (Gould, 1986; Bastin et al., 2000). The title compounds were originally investigated during salt screening of aromatic monoamines and represent a part of our research into intermolecular interactions in hydrogen-bonded ionic crystals of acid salts (Cinčić & Kaitner, 2007, 2008). 4-Aminobenzoic (PABA) acid is widely known as bacterial vitamin H and as one of the components of the vitamin B complex. It is also an important biological molecule, acting as an antagonist to the action of sulfanilamide drugs in competition for essential growth metabolites, as well as being an essential bacterial cofactor involved in the synthesis of folic acid (Woods, 1940; Brown et al., 1961). 4-Aminoacetophenone has been less extensively studied than PABA, but its derivatives have been widely studied. In the present study, we chose 4-aminoacetophenone as another compound containing both amino and carbonyl groups. The presence of the methyl group in (II) at the site corresponding to the hydroxyl group in (I) results in different crystal packing and hydrogen-bonding arrangements, as described below.

In the title compounds, 4-carboxyanilinium bromide, (I), and 4-acetylanilinium bromide, (II), the bond lengths and angles are all normal for their types (Allen et al., 1987). The asymmetric unit of (I) and (II) contains a halide anion and a discrete cation with a protonated amino group (Figs. 1 and 2). Compound (I) is isostructural with the analogous chloride salt (Colapietro et al., 1980). However, that study was concerned primarily with the detailed geometry of the aryl ring in the presence of two substituents with markedly different electron donor/acceptor properties, whereas the hydrogen bonding was discussed only rather briefly. Moreover, the precision of the present study is considerably higher, with a lower R index, despite a considerably higher ratio of data to parameters (15.8 versus 12.7) and with s.u.s on the ring bond angles ca 0.1 times those reported previously. Because of the difference in anionic radii, the volume of the unit cell in (I) is about 37 ų larger than that of the chloride salt. Compound (II) is not isostructural with that of the chloride analogue, which crystallizes as a monohydrate (Ersanlı et al., 2004).

In (I), the ions are connected into a two-dimensional hydrogen-bonded network parallel to the (010) plane via N—H···Br, N—H···O and O—H···Br hydrogen bonds. There are no centrosymmetric hydrogen-bonded dimers between the carboxylic acid groups of adjacent 4-carboxyanilinium cations, which is a characteristic feature found in most salts of 3- and 4-aminobenzoic acid (Cambridge Structural Database, Version?; Allen, 2002). The carbonyl O atom participates in hydrogen bonding with another neighbouring cation through an N—H···O hydrogen bond. This interaction links the glide-plane related cations into zigzag chains which run parallel to the [001] direction and which can be described by a graph-set motif of C(8) (Bernstein et al., 1995) (Fig. 3). The carboxylic H atom participates in hydrogen bonding with a neighbouring anion through an O—H···Br hydrogen bond. All ammonium group 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 three hydrogen bonds. 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 a graph-set motif of C₂¹(4). The noncentrosymetric hydrogen-bonded rings formed by adjacent 4-carboxyanilinium cations and one halide anion can be described by the graph-set motif R₃²(8). The aggregation of ring and chain motifs results in a two-dimensional hydrogen-bonded sheet-like structure overall (Fig. 3). Adjacent sheets are stacked in the [010] direction to give a three-dimensional framework, where the interplanar distance between the aromatic rings of each sheet is ca 3.38 Å. The interplanar distance between aromatic rings of each sheet in the isostructural chloride salt is, unexpectedly, almost the same at ca 3.33 Å, and adjacent sheets are further linked with interlayer N—H···Cl interaction.

Because of the different functional group on atom C7 of (I) and (II), the supramolecular structure of (II), as expected, differs from that of (I). Fig. 4 clearly compares the packing arrangement of both compounds. The ions of (II) are connected into a two-dimensional hydrogen-bonded network, this time parallel to the (102) plane, via N—H···Br and N—H···O hydrogen bonds (Table 2). As in (I), all ammonium group 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. Also as in (I), the carbonyl O atom participates in hydrogen bonding with another neighbouring cation through an N—H···O hydrogen bond. This interaction links the glide-plane related cations into zigzag chains which run parallel to the [001] direction and which can be described by a graph-set motif of C(8) (Fig. 5). The centrosymmetric hydrogen-bonded rings formed by adjacent cations in the chains can be described by the graph-set motif R₄²(8). The aggregation of ring and chain motifs in (II) also leads to a two-dimensional hydrogen-bonded sheet-like structure (Fig. 5). Adjacent sheets are stacked in the [102] direction to give a three-dimensional framework, where weak interlayer C—H···Br interactions are present [C6···Br1(x + 1, y, z) = 3.854 (3) Å and C8···Br1(x + 1, -y + 1/2, z - 1/2) = 3.809 (4) Å]. No intermolecular π–π interactions are evident in either crystal structure. The shortest centroid-to-centroid distances in (I) and (II) are ca 4.06 and 3.86 Å, respectively.

Related literature

For related literature, see: Allen (2002); Allen et al. (1987); Bastin et al. (2000); Bernstein et al. (1995); Brown et al. (1961); Cinčić & Kaitner (2007, 2008); Colapietro et al. (1980); Ersanlı, Odabaşoğlu, Albayrak, Büyükgüngör & Erdönmez (2004); Gould (1986); Woods (1940).

S2. Experimental

For the preparation of (I), 3-aminobenzoic acid (100 mg, 0,73 mmol) was dissolved in hot ethanol (2 ml). The clear solution was added to aqueous hydrobromic acid (2 ml, 2 M) and cooled to room temperature. Colourless crystals of (I) were grown by slow evaporation.

For the preparation of (II), 4-aminoacetophenone (100 mg, 0.74 mmol) was dissolved in hot mixture of ethanol and propan-2-ol (3 ml; 2:1 v/v). The clear solution was added to hydrobromic acid (1 ml, 2 M) and cooled to room temperature. Colourless crystals of (II) were grown by slow evaporation.

Crystals of (I) and (II) were collected by vacuum filtration, washed with cold acetone and dried in air. In a nitrogen atmosphere, (I) and (II) melt at 524 K and 472 K, respectively.

S3. Refinement

For (I), all N– and O-bound H atoms, and for (II), all N-bound H atoms, were located in difference Fourier maps. For both compounds, the positions and isotropic displacement parameters of the N-bound H atoms were refined, giving a range of N—H distances of 0.81 (4)–0.90 (4) Å. The hydroxyl H atom in (I) was fixed at the position found from the difference map, giving O—H = 0.78 Å. H atoms bonded to C atoms were treated as riding, with C—H = 0.93 Å (aromatic) or 0.96 Å (methyl), and with U_iso(H) = kU_eq(C), where k = 1.5 for methyl H and 1.2 for aromatic H.

Computing details

For both 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 POV-RAY (Persistence of Vision Team, 2004).

Figures

	Fig. 1. The asymetric unit of (I), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 2. The asymmetric unit of (II), showing the atom-numbering scheme. Displacement ellipsoids are drawn at the 30% probability level and H atoms are shown as small spheres of arbitrary radii.
	Fig. 3. A view of the two-dimensional hydrogen-bonded network of (I) parallel to the (010) plane, showing the aggregation of three hydrogen-bonding motifs, C(8), C2^1(4) and R3^2(8). Hydrogen bonds are drawn as dotted lines and C-bound H atoms have been omitted. Atoms marked with an ampersand (&), an `at' sign (@), a hash symbol (#) or a dollar sign ($) are at the symmetry positions (2 + x, y, z), (1 + x, y, z), (x, 3/2 - y, 1/2 + z), (2 + x, 3/2 - y, 1/2 + z), respectively.
	Fig. 4. Packing diagrams of (I) (left) and (II) (right), viewed along the c and b axis, respectively.
	Fig. 5. A view of the two-dimensional hydrogen-bonded network of (II) parallel to the (102) plane, showing the aggregation of three hydrogen-bonding motifs, C(8) and R4^2(8). Hydrogen bonds are drawn as dotted lines and aromatic C-bound H atoms have been omitted. Atoms marked with the suffixes a, b, c and d are at the symmetry positions (1 - x, 1 - y, 1 - z), (1 - x, -y, 1 - z), (2 - x, y - 1/2, 3/2 - z) and (-x, y - 1/2, 1/2 - z), respectively.

(I) 4-carboxyanilinium bromide

Crystal data

C7H8NO2^+·Br^−	F(000) = 432
Mr = 218.05	Dx = 1.768 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 4235 reflections
a = 5.8209 (9) Å	θ = 4–35°
b = 8.5101 (11) Å	µ = 4.97 mm^−1
c = 16.648 (3) Å	T = 295 K
β = 96.660 (13)°	Prism, colourless
V = 819.1 (2) Å^3	0.50 × 0.11 × 0.11 mm
Z = 4

Data collection

Oxford Diffraction Xcalibur CCD diffractometer	1787 independent reflections
Radiation source: fine-focus sealed tube	1573 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.023
ω scans	θmax = 27.0°, θmin = 4.1°
Absorption correction: analytical (Alcock, 1970)	h = −7→7
Tmin = 0.294, Tmax = 0.619	k = −10→10
7029 measured reflections	l = −21→21

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.030	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.093	H atoms treated by a mixture of independent and constrained refinement
S = 1.16	w = 1/[σ^2(Fo^2) + (0.0516P)^2 + 0.4207P] where P = (Fo^2 + 2Fc^2)/3
1787 reflections	(Δ/σ)max < 0.001
113 parameters	Δρmax = 0.61 e Å^−3
0 restraints	Δρmin = −0.60 e Å^−3

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
Br1	0.91216 (5)	0.36393 (3)	0.273722 (18)	0.04142 (14)
O1	0.8162 (4)	0.9638 (3)	0.59961 (14)	0.0487 (5)
O2	0.5421 (5)	0.8338 (4)	0.65491 (16)	0.0637 (7)
N1	0.4156 (5)	0.5442 (4)	0.29843 (18)	0.0408 (6)
C1	0.5832 (5)	0.7887 (3)	0.51721 (17)	0.0329 (6)
C2	0.7277 (5)	0.7977 (4)	0.45628 (19)	0.0396 (6)
H2	0.8626	0.8571	0.4641	0.048*
C3	0.6705 (5)	0.7182 (4)	0.38407 (17)	0.0381 (6)
H3	0.7672	0.7229	0.3434	0.046*
C4	0.4690 (5)	0.6323 (3)	0.37328 (17)	0.0310 (6)
C5	0.3199 (5)	0.6246 (3)	0.43172 (18)	0.0353 (6)
H5	0.1825	0.5683	0.4226	0.042*
C6	0.3786 (5)	0.7027 (4)	0.50459 (18)	0.0360 (6)
H6	0.2810	0.6975	0.5450	0.043*
C7	0.6431 (5)	0.8644 (3)	0.59718 (19)	0.0380 (7)
H1	0.8573	1.0030	0.6412	0.069 (14)*
H1A	0.516 (8)	0.482 (6)	0.288 (3)	0.071 (14)*
H1B	0.427 (7)	0.599 (5)	0.258 (3)	0.061 (13)*
H1C	0.295 (7)	0.495 (5)	0.296 (2)	0.056 (11)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0356 (2)	0.0423 (2)	0.0462 (2)	−0.00311 (11)	0.00399 (13)	0.00186 (12)
O1	0.0578 (13)	0.0521 (13)	0.0356 (12)	−0.0177 (11)	0.0035 (10)	−0.0018 (10)
O2	0.0573 (15)	0.0934 (19)	0.0434 (14)	−0.0268 (14)	0.0186 (12)	−0.0170 (13)
N1	0.0372 (14)	0.0485 (16)	0.0381 (14)	−0.0037 (13)	0.0098 (11)	−0.0014 (12)
C1	0.0339 (13)	0.0331 (13)	0.0323 (14)	0.0031 (11)	0.0069 (10)	0.0039 (11)
C2	0.0322 (14)	0.0409 (16)	0.0464 (17)	−0.0068 (12)	0.0077 (12)	0.0008 (13)
C3	0.0376 (14)	0.0494 (17)	0.0296 (14)	−0.0055 (12)	0.0137 (11)	0.0021 (12)
C4	0.0327 (13)	0.0347 (14)	0.0257 (13)	0.0022 (10)	0.0042 (10)	0.0038 (10)
C5	0.0276 (13)	0.0403 (15)	0.0387 (16)	−0.0030 (10)	0.0073 (11)	0.0052 (11)
C6	0.0318 (13)	0.0427 (15)	0.0344 (14)	0.0007 (11)	0.0083 (10)	0.0030 (12)
C7	0.0356 (15)	0.0416 (16)	0.0369 (16)	0.0012 (11)	0.0041 (12)	0.0005 (12)

Geometric parameters (Å, º)

O1—C7	1.312 (4)	C1—C7	1.484 (4)
O1—H1	0.781	C2—C3	1.386 (4)
O2—C7	1.212 (4)	C2—H2	0.9300
N1—C4	1.456 (4)	C3—C4	1.376 (4)
N1—H1A	0.82 (5)	C3—H3	0.9300
N1—H1B	0.83 (5)	C4—C5	1.378 (4)
N1—H1C	0.81 (4)	C5—C6	1.390 (4)
C1—C2	1.393 (4)	C5—H5	0.9300
C1—C6	1.393 (4)	C6—H6	0.9300
C7—O1—H1	117.2	C4—C3—H3	120.4
C4—N1—H1A	115 (3)	C2—C3—H3	120.4
C4—N1—H1B	112 (3)	C3—C4—C5	122.0 (3)
H1A—N1—H1B	94 (4)	C3—C4—N1	118.6 (3)
C4—N1—H1C	113 (3)	C5—C4—N1	119.3 (3)
H1A—N1—H1C	107 (4)	C4—C5—C6	118.8 (3)
H1B—N1—H1C	114 (4)	C4—C5—H5	120.6
C2—C1—C6	119.8 (3)	C6—C5—H5	120.6
C2—C1—C7	122.1 (3)	C5—C6—C1	120.1 (3)
C6—C1—C7	118.1 (3)	C5—C6—H6	119.9
C3—C2—C1	120.0 (3)	C1—C6—H6	119.9
C3—C2—H2	120.0	O2—C7—O1	123.8 (3)
C1—C2—H2	120.0	O2—C7—C1	122.2 (3)
C4—C3—C2	119.2 (3)	O1—C7—C1	114.0 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1A···Br1	0.84 (6)	2.55 (5)	3.343 (3)	159 (5)
O1—H1···Br1^i	0.78	2.47	3.238 (2)	170
N1—H1B···O2^ii	0.83 (5)	1.99 (5)	2.781 (4)	158 (5)
N1—H1C···Br1^iii	0.81 (4)	2.48 (4)	3.291 (3)	173 (4)

Symmetry codes: (i) x, −y+3/2, z+1/2; (ii) x, −y+3/2, z−1/2; (iii) x−1, y, z.

(II) 4-acetylanilinium bromide

Crystal data

C8H10NO^+·Br^−	F(000) = 432
Mr = 216.08	Dx = 1.624 Mg m^−3
Monoclinic, P21/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybc	Cell parameters from 4979 reflections
a = 7.4423 (8) Å	θ = 4–35°
b = 15.4529 (10) Å	µ = 4.60 mm^−1
c = 7.6833 (14) Å	T = 295 K
β = 90.828 (8)°	Prism, colourless
V = 883.5 (2) Å^3	0.41 × 0.10 × 0.09 mm
Z = 4

Data collection

Oxford Diffraction Xcalibur CCD diffractometer	1904 independent reflections
Radiation source: fine-focus sealed tube	1710 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.061
ω scans	θmax = 27.0°, θmin = 3.8°
Absorption correction: analytical (Alcock, 1970)	h = −9→9
Tmin = 0.347, Tmax = 0.701	k = −19→19
12753 measured reflections	l = −9→9

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)] = 0.039	H atoms treated by a mixture of independent and constrained refinement
wR(F^2) = 0.127	w = 1/[σ^2(Fo^2) + (0.0713P)^2 + 0.1936P] where P = (Fo^2 + 2Fc^2)/3
S = 1.23	(Δ/σ)max = 0.001
1904 reflections	Δρmax = 0.78 e Å^−3
114 parameters	Δρmin = −0.62 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: 0.030 (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
Br1	0.35133 (5)	0.46073 (2)	0.74958 (5)	0.0546 (2)
O1	1.2667 (3)	0.21261 (17)	0.7039 (4)	0.0620 (7)
N1	0.5238 (4)	0.35630 (19)	0.4274 (4)	0.0416 (6)
C1	0.9728 (4)	0.21606 (19)	0.6006 (4)	0.0351 (6)
C2	0.8226 (4)	0.17181 (19)	0.5394 (4)	0.0384 (6)
H2	0.8217	0.1116	0.5381	0.046*
C3	0.6745 (4)	0.2174 (2)	0.4803 (4)	0.0379 (6)
H3	0.5736	0.1884	0.4377	0.045*
C4	0.6780 (3)	0.30638 (19)	0.4853 (4)	0.0338 (6)
C5	0.8255 (4)	0.3516 (2)	0.5460 (4)	0.0399 (7)
H5	0.8253	0.4118	0.5481	0.048*
C6	0.9723 (4)	0.30590 (19)	0.6032 (4)	0.0379 (6)
H6	1.0732	0.3354	0.6444	0.045*
C7	1.1350 (4)	0.1704 (2)	0.6668 (4)	0.0405 (7)
C8	1.1337 (5)	0.0745 (2)	0.6896 (6)	0.0545 (8)
H8A	1.1552	0.0471	0.5797	0.082*
H8B	1.0189	0.0567	0.7322	0.082*
H8C	1.2262	0.0581	0.7716	0.082*
H1A	0.552 (5)	0.402 (3)	0.365 (5)	0.045 (10)*
H1B	0.463 (5)	0.373 (3)	0.515 (6)	0.059 (12)*
H1C	0.452 (5)	0.324 (3)	0.358 (5)	0.055 (11)*

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.0577 (3)	0.0429 (3)	0.0634 (3)	0.00159 (13)	0.00520 (19)	−0.00488 (14)
O1	0.0441 (13)	0.0483 (14)	0.093 (2)	−0.0009 (10)	−0.0285 (13)	0.0057 (13)
N1	0.0346 (13)	0.0409 (15)	0.0490 (15)	0.0039 (11)	−0.0097 (12)	−0.0025 (13)
C1	0.0335 (13)	0.0377 (14)	0.0341 (14)	−0.0006 (11)	−0.0018 (11)	0.0013 (11)
C2	0.0380 (14)	0.0314 (14)	0.0456 (16)	−0.0030 (11)	−0.0032 (12)	−0.0031 (12)
C3	0.0313 (13)	0.0405 (15)	0.0418 (15)	−0.0073 (11)	−0.0037 (11)	−0.0024 (12)
C4	0.0283 (12)	0.0377 (14)	0.0351 (13)	0.0008 (10)	−0.0051 (10)	−0.0024 (11)
C5	0.0391 (14)	0.0313 (14)	0.0490 (17)	−0.0024 (11)	−0.0082 (12)	−0.0021 (12)
C6	0.0328 (13)	0.0373 (15)	0.0434 (15)	−0.0065 (11)	−0.0084 (11)	−0.0028 (12)
C7	0.0383 (15)	0.0420 (16)	0.0410 (16)	0.0034 (12)	−0.0037 (12)	0.0027 (13)
C8	0.0456 (18)	0.0416 (18)	0.076 (2)	0.0084 (14)	−0.0038 (16)	0.0028 (18)

Geometric parameters (Å, º)

O1—C7	1.208 (4)	C3—C4	1.376 (4)
N1—C4	1.448 (4)	C3—H3	0.9300
N1—H1A	0.88 (4)	C4—C5	1.377 (4)
N1—H1B	0.86 (4)	C5—C6	1.369 (4)
N1—H1C	0.90 (4)	C5—H5	0.9300
C1—C2	1.387 (4)	C6—H6	0.9300
C1—C6	1.388 (4)	C7—C8	1.492 (5)
C1—C7	1.482 (4)	C8—H8A	0.9600
C2—C3	1.380 (4)	C8—H8B	0.9600
C2—H2	0.9300	C8—H8C	0.9600
C4—N1—H1A	114 (2)	C5—C4—N1	117.2 (3)
C4—N1—H1B	110 (3)	C6—C5—C4	118.4 (3)
H1A—N1—H1B	108 (3)	C6—C5—H5	120.8
C4—N1—H1C	110 (2)	C4—C5—H5	120.8
H1A—N1—H1C	106 (3)	C5—C6—C1	120.9 (3)
H1B—N1—H1C	109 (4)	C5—C6—H6	119.5
C2—C1—C6	119.7 (3)	C1—C6—H6	119.5
C2—C1—C7	122.0 (3)	O1—C7—C1	118.6 (3)
C6—C1—C7	118.3 (3)	O1—C7—C8	121.0 (3)
C3—C2—C1	119.7 (3)	C1—C7—C8	120.4 (3)
C3—C2—H2	120.1	C7—C8—H8A	109.5
C1—C2—H2	120.1	C7—C8—H8B	109.5
C4—C3—C2	119.1 (3)	H8A—C8—H8B	109.5
C4—C3—H3	120.5	C7—C8—H8C	109.5
C2—C3—H3	120.5	H8A—C8—H8C	109.5
C3—C4—C5	122.2 (3)	H8B—C8—H8C	109.5
C3—C4—N1	120.6 (3)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
N1—H1B···Br1	0.86 (4)	2.41 (4)	3.236 (3)	162 (4)
N1—H1A···Br1^i	0.88 (4)	2.41 (4)	3.278 (3)	168 (3)
N1—H1C···O1^ii	0.90 (4)	1.89 (4)	2.766 (4)	163 (4)

Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) x−1, −y+1/2, z−1/2.