Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101021485/sk1529sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270101021485/sk1529Isup2.hkl |
CCDC reference: 182033
A sample of (I) was obtained from Bayer, and crystals suitable for single-crystal X-ray diffraction were grown from a solution in ethanol.
Compound (I) crystallized in the monoclinic system; space group P21/n was uniquely assigned from the systematic absences. H atoms were treated as riding, with C—H = 0.95 and N—H = 0.88 Å.
Data collection: KappaCCD Server Software (Nonius, 1997); cell refinement: DENZO-SMN (Otwinowski & Minor, 1997); data reduction: DENZO-SMN; program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLATON (Spek, 2001); software used to prepare material for publication: SHELXL97 and PRPKAPPA (Ferguson, 1999).
C7H4BrN3O2 | F(000) = 472 |
Mr = 242.04 | Dx = 1.949 Mg m−3 |
Monoclinic, P21/n | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2yn | Cell parameters from 1894 reflections |
a = 4.2494 (2) Å | θ = 3.1–27.5° |
b = 14.9094 (7) Å | µ = 4.95 mm−1 |
c = 13.0958 (7) Å | T = 150 K |
β = 96.138 (2)° | Needle, colourless |
V = 824.94 (7) Å3 | 0.25 × 0.07 × 0.04 mm |
Z = 4 |
Nonius KappaCCD diffractometer | 1894 independent reflections |
Radiation source: fine-focus sealed X-ray tube | 1413 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.067 |
ϕ scans, and ω scans with κ offsets | θmax = 27.5°, θmin = 3.1° |
Absorption correction: multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) | h = −5→5 |
Tmin = 0.647, Tmax = 0.820 | k = −19→19 |
6073 measured reflections | l = −16→16 |
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)] = 0.037 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.081 | H-atom parameters constrained |
S = 1.01 | w = 1/[σ2(Fo2) + (0.0309P)2] where P = (Fo2 + 2Fc2)/3 |
1894 reflections | (Δ/σ)max < 0.001 |
118 parameters | Δρmax = 0.54 e Å−3 |
0 restraints | Δρmin = −0.68 e Å−3 |
C7H4BrN3O2 | V = 824.94 (7) Å3 |
Mr = 242.04 | Z = 4 |
Monoclinic, P21/n | Mo Kα radiation |
a = 4.2494 (2) Å | µ = 4.95 mm−1 |
b = 14.9094 (7) Å | T = 150 K |
c = 13.0958 (7) Å | 0.25 × 0.07 × 0.04 mm |
β = 96.138 (2)° |
Nonius KappaCCD diffractometer | 1894 independent reflections |
Absorption correction: multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) | 1413 reflections with I > 2σ(I) |
Tmin = 0.647, Tmax = 0.820 | Rint = 0.067 |
6073 measured reflections |
R[F2 > 2σ(F2)] = 0.037 | 0 restraints |
wR(F2) = 0.081 | H-atom parameters constrained |
S = 1.01 | Δρmax = 0.54 e Å−3 |
1894 reflections | Δρmin = −0.68 e Å−3 |
118 parameters |
Experimental. The program DENZO-SMN (Otwinowski & Minor, 1997) uses a scaling algorithm [Fox, G. C. & Holmes, K. C. (1966). Acta Cryst. 20, 886–891] which effectively corrects for absorption effects. High-redundancy data were used in the scaling program, hence the `multi-scan' code word was used. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.6308 (6) | 0.3273 (2) | 0.3617 (2) | 0.0177 (7) | |
N1 | 0.8557 (6) | 0.31971 (18) | 0.44131 (19) | 0.0238 (6) | |
C2 | 0.5015 (6) | 0.2505 (2) | 0.3078 (2) | 0.0193 (7) | |
Br2 | 0.64966 (7) | 0.13636 (2) | 0.35302 (2) | 0.02578 (14) | |
C3 | 0.2741 (7) | 0.2580 (2) | 0.2263 (2) | 0.0209 (7) | |
C4 | 0.1656 (7) | 0.3424 (2) | 0.1945 (2) | 0.0204 (7) | |
N4 | −0.0817 (6) | 0.35126 (18) | 0.1092 (2) | 0.0236 (6) | |
O41 | −0.1809 (5) | 0.28113 (16) | 0.06679 (17) | 0.0313 (6) | |
O42 | −0.1848 (5) | 0.42561 (16) | 0.08419 (17) | 0.0328 (6) | |
C5 | 0.2842 (7) | 0.4196 (2) | 0.2432 (2) | 0.0206 (7) | |
C6 | 0.5128 (6) | 0.4118 (2) | 0.3261 (2) | 0.0198 (7) | |
C61 | 0.6425 (6) | 0.4918 (2) | 0.3756 (2) | 0.0232 (7) | |
N61 | 0.7567 (7) | 0.55297 (19) | 0.4168 (2) | 0.0358 (7) | |
H11 | 0.9343 | 0.3681 | 0.4730 | 0.029* | |
H12 | 0.9247 | 0.2663 | 0.4618 | 0.029* | |
H3 | 0.1907 | 0.2059 | 0.1916 | 0.025* | |
H5 | 0.2097 | 0.4769 | 0.2201 | 0.025* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0186 (16) | 0.0153 (16) | 0.0193 (16) | −0.0011 (12) | 0.0023 (12) | −0.0006 (12) |
N1 | 0.0293 (14) | 0.0140 (14) | 0.0258 (15) | −0.0016 (11) | −0.0073 (11) | −0.0008 (11) |
C2 | 0.0224 (16) | 0.0136 (16) | 0.0218 (17) | −0.0022 (12) | 0.0019 (12) | −0.0043 (13) |
Br2 | 0.0325 (2) | 0.0148 (2) | 0.0284 (2) | 0.00081 (13) | −0.00392 (13) | −0.00073 (14) |
C3 | 0.0215 (15) | 0.0165 (17) | 0.0247 (18) | −0.0053 (13) | 0.0028 (12) | −0.0018 (13) |
C4 | 0.0199 (16) | 0.0228 (18) | 0.0179 (16) | −0.0021 (12) | −0.0012 (12) | −0.0020 (13) |
N4 | 0.0234 (14) | 0.0272 (17) | 0.0197 (14) | −0.0033 (12) | 0.0000 (11) | −0.0015 (13) |
O41 | 0.0366 (12) | 0.0274 (14) | 0.0270 (13) | −0.0080 (11) | −0.0092 (10) | −0.0040 (11) |
O42 | 0.0386 (13) | 0.0261 (14) | 0.0304 (13) | 0.0056 (11) | −0.0119 (10) | −0.0017 (11) |
C5 | 0.0216 (15) | 0.0171 (16) | 0.0230 (17) | −0.0004 (13) | 0.0012 (12) | −0.0029 (14) |
C6 | 0.0221 (16) | 0.0172 (17) | 0.0197 (16) | −0.0037 (13) | 0.0004 (12) | −0.0015 (13) |
C61 | 0.0252 (17) | 0.0201 (19) | 0.0220 (17) | 0.0014 (14) | −0.0083 (12) | 0.0038 (14) |
N61 | 0.0495 (18) | 0.0192 (16) | 0.0351 (17) | −0.0024 (13) | −0.0115 (14) | −0.0018 (14) |
C1—C2 | 1.424 (4) | C6—C61 | 1.439 (4) |
C2—C3 | 1.365 (4) | C61—N61 | 1.140 (4) |
C3—C4 | 1.388 (4) | N4—O41 | 1.236 (3) |
C4—C5 | 1.385 (4) | N4—O42 | 1.224 (3) |
C5—C6 | 1.382 (4) | N1—H11 | 0.8800 |
C6—C1 | 1.416 (4) | N1—H12 | 0.8800 |
C2—Br2 | 1.888 (3) | C3—H3 | 0.9500 |
C1—N1 | 1.342 (4) | C5—H5 | 0.9500 |
C4—N4 | 1.456 (4) | ||
N1—C1—C6 | 121.9 (3) | C5—C4—N4 | 118.4 (3) |
N1—C1—C2 | 121.5 (3) | C3—C4—N4 | 120.1 (3) |
C6—C1—C2 | 116.6 (3) | O42—N4—O41 | 123.4 (3) |
C1—N1—H11 | 120.0 | O42—N4—C4 | 119.7 (3) |
C1—N1—H12 | 120.0 | O41—N4—C4 | 116.8 (3) |
H11—N1—H12 | 120.0 | C6—C5—C4 | 118.9 (3) |
C3—C2—C1 | 121.7 (3) | C6—C5—H5 | 120.6 |
C3—C2—Br2 | 120.2 (2) | C4—C5—H5 | 120.6 |
C1—C2—Br2 | 118.1 (2) | C5—C6—C1 | 121.8 (3) |
C2—C3—C4 | 119.6 (3) | C5—C6—C61 | 119.2 (3) |
C2—C3—H3 | 120.2 | C1—C6—C61 | 119.0 (3) |
C4—C3—H3 | 120.2 | N61—C61—C6 | 176.9 (3) |
C5—C4—C3 | 121.5 (3) | ||
C3—C4—N4—O41 | −1.5 (4) | C5—C4—N4—O41 | 179.4 (3) |
C3—C4—N4—O42 | 177.2 (3) | C5—C4—N4—O42 | −1.9 (4) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H11···N61i | 0.88 | 2.19 | 3.019 (4) | 157 |
N1—H12···O41ii | 0.88 | 2.17 | 2.854 (3) | 134 |
Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) x+3/2, −y+1/2, z+1/2. |
Experimental details
Crystal data | |
Chemical formula | C7H4BrN3O2 |
Mr | 242.04 |
Crystal system, space group | Monoclinic, P21/n |
Temperature (K) | 150 |
a, b, c (Å) | 4.2494 (2), 14.9094 (7), 13.0958 (7) |
β (°) | 96.138 (2) |
V (Å3) | 824.94 (7) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 4.95 |
Crystal size (mm) | 0.25 × 0.07 × 0.04 |
Data collection | |
Diffractometer | Nonius KappaCCD diffractometer |
Absorption correction | Multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) |
Tmin, Tmax | 0.647, 0.820 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 6073, 1894, 1413 |
Rint | 0.067 |
(sin θ/λ)max (Å−1) | 0.649 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.037, 0.081, 1.01 |
No. of reflections | 1894 |
No. of parameters | 118 |
H-atom treatment | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.54, −0.68 |
Computer programs: KappaCCD Server Software (Nonius, 1997), DENZO-SMN (Otwinowski & Minor, 1997), DENZO-SMN, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 2001), SHELXL97 and PRPKAPPA (Ferguson, 1999).
C1—C2 | 1.424 (4) | C1—N1 | 1.342 (4) |
C2—C3 | 1.365 (4) | C4—N4 | 1.456 (4) |
C3—C4 | 1.388 (4) | C6—C61 | 1.439 (4) |
C4—C5 | 1.385 (4) | C61—N61 | 1.140 (4) |
C5—C6 | 1.382 (4) | N4—O41 | 1.236 (3) |
C6—C1 | 1.416 (4) | N4—O42 | 1.224 (3) |
C2—Br2 | 1.888 (3) | ||
C3—C4—N4—O41 | −1.5 (4) | C5—C4—N4—O42 | −1.9 (4) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H11···N61i | 0.88 | 2.19 | 3.019 (4) | 157 |
N1—H12···O41ii | 0.88 | 2.17 | 2.854 (3) | 134 |
Symmetry codes: (i) −x+2, −y+1, −z+1; (ii) x+3/2, −y+1/2, z+1/2. |
We have recently reported the striking differences which are induced in the hydrogen-bonding schemes in nitroanilines by the introduction of simple substituents elsewhere in the aryl ring (Cannon et al., 2001; Ferguson et al., 2001; Garden et al., 2001; McWilliam et al., 2001; Zakaria et al., 2001). As part of this study, we have reported the structures of two polymorphs of 2-iodo-4-nitroaniline, where the I···NO2 interactions provide an effective alternative to hard and soft hydrogen bonds as determinants of supramolecular aggregation (McWilliam et al., 2001).
Seeking to introduce an additional hydrogen-bond acceptor as a potential alternative to the nitro group O atoms, we have now investigated the structure of 2-bromo-6-cyano-4-nitroaniline, (I), where the cyano group is potentially an effective acceptor of hydrogen bonds, as demonstrated by the structures of the isomeric cyanoanilines (Merlino & Sartori, 1982; Heine et al., 1994; Laine et al., 1996). \sch
In compound (I) (Fig. 1), the amino group acts as a double donor of hydrogen bonds. The cyano atom N61 acts as a single acceptor, as does one of the nitro O atoms O41, but atom O42 does not participate in the hydrogen bonding. These two hydrogen bonds (Table 2) link the molecules into sheets, within which each molecule is directly connected to three others.
Amino atom N1 in the molecule at (x, y, z) acts as a hydrogen-bond donor, via H11, to cyano N61 at (2 - x, 1 - y, 1 - z), thereby generating a dimer unit centred at (1, 1/2, 1/2) and containing a centrosymmetric R22(12) ring. Atom N1 at (x, y, z) also acts as a donor, this time via H12, to nitro O41 at (3/2 + x, 1/2 - y, 1/2 + z), which is part of the dimeric unit centred at (5/2, 0, 1). Propagation of these two hydrogen bonds thus generates a sheet, parallel to (103), built from alternating R22(12) and R66(36) rings arranged in a checkerboard fashion (Fig. 2). Three of these sheets are required to define the structure fully, but since the sheets are virtually planar, there is no possibility of any interweaving. If the individual molecules are regarded as the nodes of the resulting net, then this net is of the (6,3) type (Batten & Robson, 1998), while if the R22(12) dimers are taken as the nodes, then the net is of the (4,4) type. There are no aromatic π···π stacking interactions, or other direction-specific interactions, between adjacent sheets, so that the supramolecular structure is strictly two-dimensional.
Although the nitro atom O42 plays no role in the hydrogen bonding, it does participate in a fairly short intermolecular Br···O contact. Atom Br2 in the molecule at (x, y, z) makes a short contact with O42 in the molecule at (1/2 - x, y - 1/2, 1/2 - z), part of the dimer unit centred at (-1/2, 0, 0) (Fig. 2), and there are thus centrosymmetrically related pairs of such interactions within each of the R66(36) rings. The Br2···O42i distance is 3.247 (2) Å and the C2—Br2···O42i angle is 163.0 (2)° [symmetry code: (i) 1/2 - x, y - 1/2, 1/2 - z]. However, this Br···O distance is comparable with the shortest intermolecular I···O distances in 2-iodo-4-nitroaniline, 3.266 (5) Å in the triclinic polymorph and 3.153 (7) Å in the orthorhombic polymorph (McWilliam et al., 2001), and hence this contact is more likely to be an adventitious consequence of the ring structure generated by the hydrogen bonds than to be structurally significant in itself. There are no short Br···Br contacts nor any C—H···O hydrogen bonds in the structure.
It is of interest to compare the hydrogen-bonding pattern in (I) arising from the cyano and amino groups acting as the acceptors, with those in the isomers of cyanoaniline itself. In 2-cyanoaniline, where the original report (Laine et al., 1996) gave no analysis of the supramolecular structure, the amino group acts as a double donor of hydrogen bonds and the cyano N acts as a double acceptor, and the molecules are thereby linked into deeply puckered sheets of alternating R42(8) and R44(24) rings (Fig. 3). Within these sheets, no dimer motif can be identified analogous to that in (I). By contrast, 3-cyanoaniline (Merlino & Sartori, 1982) forms a three-dimensional framework structure in which both N atoms act as acceptors in N—H···N hydrogen bonds. 4-Cyanoaniline crystallizes in both monoclinic (Merlino & Sartori, 1982) and orthorhombic (Heine et al., 1994) polymorphs, at ambient and reduced temperatures, respectively, and in both forms the supramolecular aggregation takes the form of simple C(8) chains, generated by a glide plane in P21/c and a screw axis in P212121, respectively. In both these polymorphs, only one N—H bond of the amino group is engaged in the hydrogen bonding.
The bond distances in (I) (Table 1) provide some evidence for a contribution to the overall electronic structure from the canonical forms (Ia) and (Ib). In particular, the C—NH2 and C—NO2 bonds are both short for their types (Allen et al., 1987). The C2—C3 bond is the shortest of the ring bonds, and C1—C2 and C6—C1 are the longest. For 4-cyanoaniline, (II), and a range of methylated derivatives (Heine et al., 1994), the quinonoid form (IIa), analogous to (Ib), was found to be significant.