Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101007053/sk1480sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270101007053/sk1480Iasup2.hkl | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270101007053/sk1480Ibsup3.hkl |
CCDC references: 170188; 170189
A solution of 4-nitroaniline (20 mmol) in methanol (40 cm3) was rapidly added to an aqueous solution of K[ICl2] (60 cm3, 0.67 mol dm-3) at room temperature (Larsen et al., 1956: Garden et al., 2001). The reaction mixture was stirred at room temperature for 2 h, and then filtered to remove the product. The product was washed with water, allowed to dry in air; after recrystallization from ethanol it had m. p. 385–387 K. NMR (CDCl3): δ(H) 4.84 (2H, br s, NH2), 6.66 (1H, d, J 9.2 Hz, H-6), 8.00 (1H, dd, J 2.4, 8.9 Hz, H-5), 8.51 (d, J 2.4 Hz, H-3); δ(C) 81.6 (C-2), 113.3(C-6), 126.7(C-5), 136.5 (C-3), 140.2 (C-4), 153.4(C-1). Crystals suitable for single-crystal X-ray diffraction were obtained from ethanol solution: samples of the two polymorphs were isolated manually at ambient temperatures.
Polymorph (I) is triclinic: space group P1 was chosen, and confirmed by the successful structure solution and refinement. Polymorph (Ib) is orthorhombic, and space group Pbca was uniquely assigned from the systematic absences. All H atoms were treated as riding atoms with N—H 0.86 or 0.88 Å and C—H 0.93 or 0.95 Å.
Molecules of 4-nitroanilines generally act as double donors of hydrogen bonds and as double acceptors, such that each molecule is linked to four other molecules by N—H···O hydrogen bonds. Thus, for example, the unsubstituted 4-nitroaniline itself [Cambridge Structural Database (CSD; Allen & Kennard, 1993) refcode NANILI02; Tonogaki et al., 1993)] forms sheets in the form of (4,4) nets (Batten & Robson, 1998) built from a single type of R44(22) ring (Bernstein et al., 1995). Similar (4,4) nets, albeit containing successively larger rings, are found in the structures of the extended 4-nitroaniline analogues 4-H2NC4H4-(C≡ C)n—C6H4NO2-4' (n = 0 - 3) [CSD refcodes KEFLEM (n = 0), KEFLOW (n = 1), KEFLUC (n = 2), KEFMAJ (n = 3); Graham et al., 1989)]. By contrast, 2-methyl-4-nitroaniline forms a continuous three-dimensional framework, in which each molecule is again linked to four other molecules (Ferguson et al., 2001).
Aromatic nitro groups also form robust supramolecular synthons with iodo-aromatics, as for example in 4-iodoaniline (CSD refcode ZONYIK; Thalladi et al., 1996) and 4-iodo-4'-nitrobiphenyl (CSD refcode RAYCID01; Masciocchi et al., 1998) as well as in the adducts of p-dinitrobenzene with p-diiodobenzene (CSD refcode YESZEB; Allen et al., 1994) and with 4-iodocinnamic acid (CSD refcode ZONYOQ; Thalladi et al., 1996). In all of these species, the shortest I···O distances are very much less than the sum of the van der Waals radii (3.50 Å; Bondi, 1964), while the associated C—I···O angles lie in the range 150–170°.
As part of a continuing study of supramolecular aggregation in substituted nitroanilines (Wardell et al., 2000; Cannon et al., 2001; Ferguson et al., 2001; Glidewell et al., 2001), we have now investigated the interplay of N—H···O hydrogen bonding and nitro···I interactions in 2-iodo-4-nitroaniline, C6H5IN2O2, where we have obtained two polymorphs, a triclinic form (I) in space group P1, and an orthorhombic form (Ib) in space group Pbca. Both forms have Z' = 1, and their crystal structures exhibit a combination of N—H···O hydrogen bonds, nitro···I interactions and aromatic π···π stacking interactions. \sch
In the triclinic polymorph (Ia) the planar molecules (Fig. 1a) are linked into chains by an uncommon synthon comprising pairs of N—H···O hydrogen bonds. The two N—H bonds in the molecule at (x, y, z) form hydrogen bonds (Table 1) with the two O atoms in the molecule at (x, 1 + y, -1 + z), so producing by translation a C(8)[R22(6)] chain of rings (Bernstein et al., 1995) running parallel to the [01–1] direction (Fig. 2). The N—H···O hydrogen bonding in (I) is thus wholly different from that normally found in 4-nitroanilines. In the R22(6) ring, the N—O···H angles are 111 and 110°, and the sum of the internal angles is 360° within experimental uncertainly, so that this ring is planar. The chain of rings can thus be regarded as a continuous sequence of planar hexagonal rings, in which the covalently-bonded aryl rings alternate with hydrogen-bonded rings of almost the same size. In this connection, Desiraju (1995) has already drawn attention to the importance of ring size and shape, as opposed to ring composition, as an important factor in crystal engineering and molecular recognition. There are two C(8)[R22(6)] chains of rings passing through each unit cell, related by the centres on inversion and thus running antiparallel to one another. A combination of nitro···I interactions and aromatic π···π stacking interactions links these chains into sheets, and it is convenient to consider these interactions in turn.
There is a very short intermolecular I···O contact [I···O2i 3.266 (5) Å, C—I···O2i 154.5 (2)°, I···O2i—N4i 154.1 (4)°; symmetry code i = (-1 + x, 1 + y, -1 + z)], which serves to link parallel chains of the same polarity into two-dimensional sheets parallel to (011), in which the R22(6) rings described above alternate with larger rings (Fig. 2). If the graph-set notation generally employed for hydrogen-bonded motifs is extended to other directed but non-covalent interactions (Starbuck et al., 1999), these larger rings may be described as being of R44(20) type. The shortest intermolecular I···O distance involving the other O atom [I···O1ii 3.494 (5) Å; symmetry code ii = (-x, 2 - y, 1 - z)] is not significantly shorter than the sum of the van der Waals radii, and is thus not regarded as structurally significant. Two (011) sheets pass through each unit cell, and these sheets are themselves linked into pairs by aromatic π···π stacking interactions. Molecules at (x, y, z) and (1 - x, 2 - y, 1 - z) are linked by a π···π interaction: the interplanar spacing is 3.451 (3) Å and the centroid offset is 0.747 (3) Å.
In the orthorhombic polymorph (Ib) (Fig. 1 b), the dihedral angles between the aryl ring and the C—NO2 plane is 11.1 (5)°. The hydrogen bonding differs from that in (I) in that the molecules of (Ib) act as single donors and as single acceptors of hydrogen bonds, so that simple C(8) chains are formed, rather than chains of rings, as in (I), or the sheets commonly found in 4-nitroanilines and their analogues. Amino N1 at (x, y, z) acts as hydrogen-bond donor to O1 at (1 - x, -1/2 + y, 1/2 - z), while N1 at (1 - x, -1/2 + y, 1/2 - z) in turn acts as donor to O1 at (x, -1 + y, z): hence a C(8) spiral is generated around the 21 screw axis along (1/2, y, 1/4) (Fig. 3). Four such chains run through each unit cell, one around each of the 21 axes parallel to [010]: two lie in the domain 0.30 < x < 0.70, and the other two lie in the domain 0.80 < x < 1.20.
Within each of these domains, the chains are linked into sheets by nitro···I interactions, having I····O1iii 3.153 (7) Å, C—I···O1iii 171.5 (3)°, I···O1iii—N4iii 112.6 (5) [symmetry code: (iii) x, 3/2 - y, 1/2 + z)] and propagation of this interaction generates sheets parallel to (100) built from alternating R24(12) and R44(28) rings (Fig. 3). As in the triclinic polymorph, only one O forms I···O contacts shorter than the sum of the van der Waals radii. There are two (100) sheets passing through each unit cell, and each sheet is linked to its two immediate neighbours by aromatic π···π stacking interactions (Fig. 4), so generating a continuous three-dimensional structure. The aryl ring at (x, y, z) is a component of the (100) sheet in the domain 0.30 < x < 0.70; this ring forms π···π interactions with the rings at (1/2 + x, y, 1/2 - z) and (-1/2 + x, y, 1/2 - z) which are components of the sheets in the domains 0.80 < x < 1.20 and -0.20 < x < 0.20 respectively. These rings are not all parallel by symmetry, but the interplanar angles are only ca 2.0°, with interplanar spacings of ca 3.56 Å and centroid offsets of ca 1.21 Å.
The C—I distances in (Ia) and (Ib) are 2.098 (5) Å and 2.087 (8) Å: the other bond lengths and angles show no unexpected features.
For related literature, see: Allen & Kennard (1993); Allen et al. (1994); Batten & Robson (1998); Bernstein et al. (1995); Bondi (1964); Cannon et al. (2001); Desiraju (1995); Ferguson et al. (2001); Garden et al. (2001); Glidewell et al. (2001); Graham et al. (1989); Larsen et al. (1956); Masciocchi et al. (1998); Starbuck et al. (1999); Thalladi et al. (1996); Tonogaki et al. (1993); Wardell et al. (2000).
Data collection: Kappa-CCD Server Software (Nonius, 1997) for (Ia); SMART (Bruker, 1999) for (Ib). Cell refinement: DENZO-SMN (Otwinowski & Minor, 1997) for (Ia); SAINT (Bruker, 1999) for (Ib). Data reduction: DENZO-SMN for (Ia); SAINT for (Ib). For both compounds, 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).
C6H5IN2O2 | Z = 2 |
Mr = 264.02 | F(000) = 248 |
Triclinic, P1 | Dx = 2.278 Mg m−3 |
a = 7.1647 (4) Å | Mo Kα radiation, λ = 0.71073 Å |
b = 7.9572 (4) Å | Cell parameters from 1728 reflections |
c = 8.0489 (5) Å | θ = 3.1–27.5° |
α = 67.905 (3)° | µ = 4.11 mm−1 |
β = 86.956 (3)° | T = 150 K |
γ = 65.744 (2)° | Needle, yellow |
V = 384.84 (4) Å3 | 0.28 × 0.08 × 0.03 mm |
Kappa-CCD diffractometer | 1728 independent reflections |
Radiation source: fine-focus sealed X-ray tube | 1556 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.047 |
φ scans, and ω scans with κ offsets | θmax = 27.5°, θmin = 3.1° |
Absorption correction: multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) | h = −9→9 |
Tmin = 0.393, Tmax = 0.887 | k = −10→10 |
4602 measured reflections | l = −10→9 |
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)] = 0.046 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.120 | H-atom parameters constrained |
S = 1.09 | w = 1/[σ2(Fo2) + (0.0662P)2 + 1.2313P] where P = (Fo2 + 2Fc2)/3 |
1728 reflections | (Δ/σ)max < 0.001 |
100 parameters | Δρmax = 2.77 (0.96 Å from I2) e Å−3 |
0 restraints | Δρmin = −2.14 (0.83 Å from I2) e Å−3 |
C6H5IN2O2 | γ = 65.744 (2)° |
Mr = 264.02 | V = 384.84 (4) Å3 |
Triclinic, P1 | Z = 2 |
a = 7.1647 (4) Å | Mo Kα radiation |
b = 7.9572 (4) Å | µ = 4.11 mm−1 |
c = 8.0489 (5) Å | T = 150 K |
α = 67.905 (3)° | 0.28 × 0.08 × 0.03 mm |
β = 86.956 (3)° |
Kappa-CCD diffractometer | 1728 independent reflections |
Absorption correction: multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) | 1556 reflections with I > 2σ(I) |
Tmin = 0.393, Tmax = 0.887 | Rint = 0.047 |
4602 measured reflections |
R[F2 > 2σ(F2)] = 0.046 | 0 restraints |
wR(F2) = 0.120 | H-atom parameters constrained |
S = 1.09 | Δρmax = 2.77 (0.96 Å from I2) e Å−3 |
1728 reflections | Δρmin = −2.14 (0.83 Å from I2) e Å−3 |
100 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. No transmission coefficients are available from the program (only scale factors for each frame). The scale factors in the experimental table are calculated from the 'size' command in the SHELXL97 input file. |
x | y | z | Uiso*/Ueq | ||
N1 | 0.5600 (9) | 1.1211 (8) | 0.1092 (7) | 0.0313 (11) | |
C1 | 0.5549 (9) | 0.9692 (8) | 0.2561 (7) | 0.0235 (11) | |
C2 | 0.3716 (9) | 0.9557 (8) | 0.3118 (7) | 0.0236 (11) | |
I2 | 0.08930 (6) | 1.17350 (5) | 0.15765 (5) | 0.03361 (19) | |
C3 | 0.3701 (9) | 0.8046 (8) | 0.4684 (8) | 0.0244 (11) | |
C4 | 0.5571 (9) | 0.6618 (8) | 0.5699 (7) | 0.0223 (11) | |
O1 | 0.3910 (7) | 0.5031 (6) | 0.7809 (6) | 0.0339 (10) | |
O2 | 0.7239 (7) | 0.3786 (6) | 0.8240 (6) | 0.0350 (10) | |
N4 | 0.5571 (8) | 0.5051 (7) | 0.7357 (6) | 0.0253 (10) | |
C5 | 0.7436 (9) | 0.6646 (8) | 0.5181 (7) | 0.0237 (11) | |
C6 | 0.7417 (9) | 0.8177 (8) | 0.3609 (8) | 0.0259 (11) | |
H11 | 0.4444 | 1.2177 | 0.0434 | 0.038* | |
H12 | 0.6790 | 1.1237 | 0.0790 | 0.038* | |
H3 | 0.2441 | 0.7986 | 0.5057 | 0.029* | |
H5 | 0.8699 | 0.5637 | 0.5889 | 0.028* | |
H6 | 0.8686 | 0.8208 | 0.3229 | 0.031* |
U11 | U22 | U33 | U12 | U13 | U23 | |
N1 | 0.044 (3) | 0.026 (2) | 0.025 (2) | −0.020 (2) | 0.003 (2) | −0.004 (2) |
C1 | 0.036 (3) | 0.018 (2) | 0.016 (2) | −0.011 (2) | 0.002 (2) | −0.006 (2) |
C2 | 0.028 (3) | 0.014 (2) | 0.022 (3) | −0.004 (2) | −0.003 (2) | −0.004 (2) |
I2 | 0.0321 (3) | 0.0226 (2) | 0.0316 (3) | −0.00509 (18) | −0.00796 (17) | −0.00137 (18) |
C3 | 0.027 (3) | 0.018 (2) | 0.023 (3) | −0.005 (2) | −0.001 (2) | −0.007 (2) |
C4 | 0.035 (3) | 0.015 (2) | 0.012 (2) | −0.009 (2) | 0.002 (2) | −0.0015 (19) |
O1 | 0.034 (2) | 0.025 (2) | 0.031 (2) | −0.0097 (18) | 0.0073 (18) | −0.0022 (18) |
O2 | 0.034 (2) | 0.024 (2) | 0.028 (2) | −0.0086 (18) | −0.0084 (18) | 0.0064 (17) |
N4 | 0.033 (3) | 0.018 (2) | 0.020 (2) | −0.010 (2) | 0.0020 (19) | −0.0043 (19) |
C5 | 0.024 (3) | 0.020 (2) | 0.022 (3) | −0.005 (2) | −0.001 (2) | −0.008 (2) |
C6 | 0.026 (3) | 0.021 (3) | 0.030 (3) | −0.011 (2) | 0.005 (2) | −0.008 (2) |
N1—C1 | 1.348 (7) | C3—H3 | 0.9500 |
N1—H11 | 0.8800 | C4—C5 | 1.385 (8) |
N1—H12 | 0.8800 | C4—N4 | 1.444 (7) |
C1—C2 | 1.399 (8) | O1—N4 | 1.230 (7) |
C1—C6 | 1.409 (8) | O2—N4 | 1.229 (6) |
C2—C3 | 1.380 (8) | C5—C6 | 1.384 (8) |
C2—I2 | 2.098 (5) | C5—H5 | 0.9500 |
C3—C4 | 1.386 (8) | C6—H6 | 0.9500 |
C1—N1—H11 | 120.0 | C5—C4—C3 | 122.3 (5) |
C1—N1—H12 | 120.0 | C5—C4—N4 | 119.0 (5) |
H11—N1—H12 | 120.0 | C3—C4—N4 | 118.7 (5) |
N1—C1—C2 | 123.0 (5) | O2—N4—O1 | 123.2 (5) |
N1—C1—C6 | 119.0 (5) | O2—N4—C4 | 118.1 (5) |
C2—C1—C6 | 118.0 (5) | O1—N4—C4 | 118.7 (5) |
C3—C2—C1 | 121.8 (5) | C6—C5—C4 | 118.5 (5) |
C3—C2—I2 | 118.6 (4) | C6—C5—H5 | 120.7 |
C1—C2—I2 | 119.6 (4) | C4—C5—H5 | 120.7 |
C2—C3—C4 | 118.3 (5) | C5—C6—C1 | 121.1 (5) |
C2—C3—H3 | 120.9 | C5—C6—H6 | 119.4 |
C4—C3—H3 | 120.9 | C1—C6—H6 | 119.4 |
C3—C4—N4—O1 | 0.3 (8) | C3—C4—N4—O2 | 179.6 (6) |
C5—C4—N4—O1 | −179.9 (6) | C5—C4—N4—O2 | −0.6 (8) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H11···O1i | 0.88 | 2.35 | 2.994 (7) | 130 |
N1—H12···O2i | 0.88 | 2.40 | 3.000 (8) | 126 |
Symmetry code: (i) x, y+1, z−1. |
C6H5IN2O2 | Dx = 2.265 Mg m−3 |
Mr = 264.02 | Mo Kα radiation, λ = 0.71073 Å |
Orthorhombic, Pbca | Cell parameters from 2339 reflections |
a = 7.4215 (5) Å | θ = 2.5–31.1° |
b = 12.6755 (9) Å | µ = 4.08 mm−1 |
c = 16.4638 (11) Å | T = 296 K |
V = 1548.77 (18) Å3 | Plate, yellow |
Z = 8 | 0.20 × 0.20 × 0.03 mm |
F(000) = 992 |
Bruker SMART 1000 CCD detector diffractometer | 2339 independent reflections |
Radiation source: fine-focus sealed X-ray tube | 1109 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.089 |
φ–ω scans | θmax = 31.1°, θmin = 2.5° |
Absorption correction: multi-scan (SADABS; Bruker, 1997) | h = −10→10 |
Tmin = 0.495, Tmax = 0.887 | k = −17→14 |
12391 measured reflections | l = −22→23 |
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)] = 0.063 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.180 | H-atom parameters constrained |
S = 0.96 | w = 1/[σ2(Fo2) + (0.0943P)2] where P = (Fo2 + 2Fc2)/3 |
2339 reflections | (Δ/σ)max = 0.001 |
100 parameters | Δρmax = 2.20 (0.91 Å from I2) e Å−3 |
0 restraints | Δρmin = −1.21 (0.90 Å from I2) e Å−3 |
C6H5IN2O2 | V = 1548.77 (18) Å3 |
Mr = 264.02 | Z = 8 |
Orthorhombic, Pbca | Mo Kα radiation |
a = 7.4215 (5) Å | µ = 4.08 mm−1 |
b = 12.6755 (9) Å | T = 296 K |
c = 16.4638 (11) Å | 0.20 × 0.20 × 0.03 mm |
Bruker SMART 1000 CCD detector diffractometer | 2339 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 1997) | 1109 reflections with I > 2σ(I) |
Tmin = 0.495, Tmax = 0.887 | Rint = 0.089 |
12391 measured reflections |
R[F2 > 2σ(F2)] = 0.063 | 0 restraints |
wR(F2) = 0.180 | H-atom parameters constrained |
S = 0.96 | Δρmax = 2.20 (0.91 Å from I2) e Å−3 |
2339 reflections | Δρmin = −1.21 (0.90 Å from I2) e Å−3 |
100 parameters |
x | y | z | Uiso*/Ueq | ||
C1 | 0.5827 (11) | 0.4747 (7) | 0.3056 (5) | 0.0464 (19) | |
N1 | 0.5512 (11) | 0.4240 (6) | 0.3743 (5) | 0.062 (2) | |
C2 | 0.6364 (10) | 0.5828 (7) | 0.3030 (4) | 0.0427 (19) | |
I2 | 0.66772 (8) | 0.66835 (5) | 0.41043 (3) | 0.0531 (3) | |
C3 | 0.6636 (11) | 0.6331 (6) | 0.2307 (5) | 0.0426 (17) | |
C4 | 0.6401 (11) | 0.5789 (7) | 0.1593 (5) | 0.0438 (19) | |
N4 | 0.6642 (10) | 0.6332 (7) | 0.0834 (4) | 0.0529 (18) | |
O1 | 0.6825 (10) | 0.7298 (6) | 0.0850 (4) | 0.0669 (19) | |
O2 | 0.6703 (9) | 0.5836 (6) | 0.0201 (4) | 0.075 (2) | |
C5 | 0.5885 (12) | 0.4739 (8) | 0.1586 (6) | 0.056 (2) | |
C6 | 0.5595 (11) | 0.4233 (7) | 0.2307 (6) | 0.050 (2) | |
H11 | 0.5164 | 0.3593 | 0.3734 | 0.075* | |
H12 | 0.5655 | 0.4557 | 0.4201 | 0.075* | |
H3 | 0.6979 | 0.7036 | 0.2299 | 0.051* | |
H5 | 0.5737 | 0.4383 | 0.1096 | 0.067* | |
H6 | 0.5234 | 0.3530 | 0.2302 | 0.060* |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.039 (5) | 0.049 (5) | 0.052 (4) | 0.002 (4) | −0.003 (4) | 0.005 (4) |
N1 | 0.057 (5) | 0.067 (5) | 0.062 (4) | −0.007 (4) | −0.010 (4) | 0.025 (4) |
C2 | 0.027 (4) | 0.062 (5) | 0.039 (4) | 0.009 (3) | −0.003 (3) | −0.003 (4) |
I2 | 0.0436 (3) | 0.0690 (5) | 0.0468 (3) | 0.0027 (3) | 0.0007 (3) | −0.0096 (3) |
C3 | 0.031 (4) | 0.046 (4) | 0.051 (4) | 0.000 (4) | 0.001 (4) | 0.001 (3) |
C4 | 0.031 (4) | 0.057 (5) | 0.043 (4) | 0.008 (4) | −0.001 (3) | −0.003 (4) |
N4 | 0.036 (4) | 0.079 (6) | 0.044 (4) | 0.000 (4) | 0.005 (3) | 0.005 (4) |
O1 | 0.076 (5) | 0.069 (5) | 0.056 (4) | 0.002 (4) | 0.008 (3) | 0.014 (3) |
O2 | 0.076 (5) | 0.107 (6) | 0.043 (3) | −0.001 (4) | 0.011 (3) | −0.012 (4) |
C5 | 0.047 (5) | 0.063 (6) | 0.058 (5) | −0.002 (4) | −0.004 (4) | −0.014 (4) |
C6 | 0.041 (5) | 0.043 (5) | 0.067 (5) | −0.003 (4) | −0.006 (4) | 0.003 (4) |
C1—N1 | 1.323 (10) | C3—H3 | 0.9300 |
C1—C6 | 1.404 (11) | C4—C5 | 1.384 (12) |
C1—C2 | 1.428 (12) | C4—N4 | 1.439 (10) |
N1—H11 | 0.8600 | N4—O2 | 1.218 (9) |
N1—H12 | 0.8600 | N4—O1 | 1.231 (12) |
C2—C3 | 1.365 (11) | C5—C6 | 1.368 (12) |
C2—I2 | 2.087 (8) | C5—H5 | 0.9300 |
C3—C4 | 1.373 (11) | C6—H6 | 0.9300 |
N1—C1—C6 | 120.2 (8) | C3—C4—C5 | 121.6 (8) |
N1—C1—C2 | 122.7 (8) | C3—C4—N4 | 119.3 (8) |
C6—C1—C2 | 117.0 (7) | C5—C4—N4 | 119.1 (8) |
C1—N1—H11 | 120.0 | O2—N4—O1 | 121.9 (7) |
C1—N1—H12 | 120.0 | O2—N4—C4 | 120.0 (9) |
H11—N1—H12 | 120.0 | O1—N4—C4 | 118.1 (7) |
C3—C2—C1 | 121.0 (7) | C6—C5—C4 | 119.1 (8) |
C3—C2—I2 | 118.7 (6) | C6—C5—H5 | 120.4 |
C1—C2—I2 | 120.3 (6) | C4—C5—H5 | 120.4 |
C2—C3—C4 | 119.6 (8) | C5—C6—C1 | 121.7 (8) |
C2—C3—H3 | 120.2 | C5—C6—H6 | 119.2 |
C4—C3—H3 | 120.2 | C1—C6—H6 | 119.2 |
C3—C4—N4—O1 | −9.2 (12) | C3—C4—N4—O2 | 169.1 (8) |
C5—C4—N4—O1 | 169.0 (8) | C5—C4—N4—O2 | −12.7 (12) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H11···O1i | 0.86 | 2.31 | 3.085 (11) | 150 |
Symmetry code: (i) −x+1, y−1/2, −z+1/2. |
Experimental details
(Ia) | (Ib) | |
Crystal data | ||
Chemical formula | C6H5IN2O2 | C6H5IN2O2 |
Mr | 264.02 | 264.02 |
Crystal system, space group | Triclinic, P1 | Orthorhombic, Pbca |
Temperature (K) | 150 | 296 |
a, b, c (Å) | 7.1647 (4), 7.9572 (4), 8.0489 (5) | 7.4215 (5), 12.6755 (9), 16.4638 (11) |
α, β, γ (°) | 67.905 (3), 86.956 (3), 65.744 (2) | 90, 90, 90 |
V (Å3) | 384.84 (4) | 1548.77 (18) |
Z | 2 | 8 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 4.11 | 4.08 |
Crystal size (mm) | 0.28 × 0.08 × 0.03 | 0.20 × 0.20 × 0.03 |
Data collection | ||
Diffractometer | Kappa-CCD | Bruker SMART 1000 CCD detector |
Absorption correction | Multi-scan (DENZO-SMN; Otwinowski & Minor, 1997) | Multi-scan (SADABS; Bruker, 1997) |
Tmin, Tmax | 0.393, 0.887 | 0.495, 0.887 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 4602, 1728, 1556 | 12391, 2339, 1109 |
Rint | 0.047 | 0.089 |
(sin θ/λ)max (Å−1) | 0.649 | 0.728 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.046, 0.120, 1.09 | 0.063, 0.180, 0.96 |
No. of reflections | 1728 | 2339 |
No. of parameters | 100 | 100 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 2.77 (0.96 Å from I2), −2.14 (0.83 Å from I2) | 2.20 (0.91 Å from I2), −1.21 (0.90 Å from I2) |
Computer programs: Kappa-CCD Server Software (Nonius, 1997), SMART (Bruker, 1999), DENZO-SMN (Otwinowski & Minor, 1997), SAINT (Bruker, 1999), DENZO-SMN, SAINT, SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), PLATON (Spek, 2001), SHELXL97 and PRPKAPPA (Ferguson, 1999).
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H11···O1i | 0.88 | 2.35 | 2.994 (7) | 130 |
N1—H12···O2i | 0.88 | 2.40 | 3.000 (8) | 126 |
Symmetry code: (i) x, y+1, z−1. |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H11···O1i | 0.86 | 2.31 | 3.085 (11) | 150 |
Symmetry code: (i) −x+1, y−1/2, −z+1/2. |
Molecules of 4-nitroanilines generally act as double donors of hydrogen bonds and as double acceptors, such that each molecule is linked to four other molecules by N—H···O hydrogen bonds. Thus, for example, the unsubstituted 4-nitroaniline itself [Cambridge Structural Database (CSD; Allen & Kennard, 1993) refcode NANILI02; Tonogaki et al., 1993)] forms sheets in the form of (4,4) nets (Batten & Robson, 1998) built from a single type of R44(22) ring (Bernstein et al., 1995). Similar (4,4) nets, albeit containing successively larger rings, are found in the structures of the extended 4-nitroaniline analogues 4-H2NC4H4-(C≡ C)n—C6H4NO2-4' (n = 0 - 3) [CSD refcodes KEFLEM (n = 0), KEFLOW (n = 1), KEFLUC (n = 2), KEFMAJ (n = 3); Graham et al., 1989)]. By contrast, 2-methyl-4-nitroaniline forms a continuous three-dimensional framework, in which each molecule is again linked to four other molecules (Ferguson et al., 2001).
Aromatic nitro groups also form robust supramolecular synthons with iodo-aromatics, as for example in 4-iodoaniline (CSD refcode ZONYIK; Thalladi et al., 1996) and 4-iodo-4'-nitrobiphenyl (CSD refcode RAYCID01; Masciocchi et al., 1998) as well as in the adducts of p-dinitrobenzene with p-diiodobenzene (CSD refcode YESZEB; Allen et al., 1994) and with 4-iodocinnamic acid (CSD refcode ZONYOQ; Thalladi et al., 1996). In all of these species, the shortest I···O distances are very much less than the sum of the van der Waals radii (3.50 Å; Bondi, 1964), while the associated C—I···O angles lie in the range 150–170°.
As part of a continuing study of supramolecular aggregation in substituted nitroanilines (Wardell et al., 2000; Cannon et al., 2001; Ferguson et al., 2001; Glidewell et al., 2001), we have now investigated the interplay of N—H···O hydrogen bonding and nitro···I interactions in 2-iodo-4-nitroaniline, C6H5IN2O2, where we have obtained two polymorphs, a triclinic form (I) in space group P1, and an orthorhombic form (Ib) in space group Pbca. Both forms have Z' = 1, and their crystal structures exhibit a combination of N—H···O hydrogen bonds, nitro···I interactions and aromatic π···π stacking interactions. \sch
In the triclinic polymorph (Ia) the planar molecules (Fig. 1a) are linked into chains by an uncommon synthon comprising pairs of N—H···O hydrogen bonds. The two N—H bonds in the molecule at (x, y, z) form hydrogen bonds (Table 1) with the two O atoms in the molecule at (x, 1 + y, -1 + z), so producing by translation a C(8)[R22(6)] chain of rings (Bernstein et al., 1995) running parallel to the [01–1] direction (Fig. 2). The N—H···O hydrogen bonding in (I) is thus wholly different from that normally found in 4-nitroanilines. In the R22(6) ring, the N—O···H angles are 111 and 110°, and the sum of the internal angles is 360° within experimental uncertainly, so that this ring is planar. The chain of rings can thus be regarded as a continuous sequence of planar hexagonal rings, in which the covalently-bonded aryl rings alternate with hydrogen-bonded rings of almost the same size. In this connection, Desiraju (1995) has already drawn attention to the importance of ring size and shape, as opposed to ring composition, as an important factor in crystal engineering and molecular recognition. There are two C(8)[R22(6)] chains of rings passing through each unit cell, related by the centres on inversion and thus running antiparallel to one another. A combination of nitro···I interactions and aromatic π···π stacking interactions links these chains into sheets, and it is convenient to consider these interactions in turn.
There is a very short intermolecular I···O contact [I···O2i 3.266 (5) Å, C—I···O2i 154.5 (2)°, I···O2i—N4i 154.1 (4)°; symmetry code i = (-1 + x, 1 + y, -1 + z)], which serves to link parallel chains of the same polarity into two-dimensional sheets parallel to (011), in which the R22(6) rings described above alternate with larger rings (Fig. 2). If the graph-set notation generally employed for hydrogen-bonded motifs is extended to other directed but non-covalent interactions (Starbuck et al., 1999), these larger rings may be described as being of R44(20) type. The shortest intermolecular I···O distance involving the other O atom [I···O1ii 3.494 (5) Å; symmetry code ii = (-x, 2 - y, 1 - z)] is not significantly shorter than the sum of the van der Waals radii, and is thus not regarded as structurally significant. Two (011) sheets pass through each unit cell, and these sheets are themselves linked into pairs by aromatic π···π stacking interactions. Molecules at (x, y, z) and (1 - x, 2 - y, 1 - z) are linked by a π···π interaction: the interplanar spacing is 3.451 (3) Å and the centroid offset is 0.747 (3) Å.
In the orthorhombic polymorph (Ib) (Fig. 1 b), the dihedral angles between the aryl ring and the C—NO2 plane is 11.1 (5)°. The hydrogen bonding differs from that in (I) in that the molecules of (Ib) act as single donors and as single acceptors of hydrogen bonds, so that simple C(8) chains are formed, rather than chains of rings, as in (I), or the sheets commonly found in 4-nitroanilines and their analogues. Amino N1 at (x, y, z) acts as hydrogen-bond donor to O1 at (1 - x, -1/2 + y, 1/2 - z), while N1 at (1 - x, -1/2 + y, 1/2 - z) in turn acts as donor to O1 at (x, -1 + y, z): hence a C(8) spiral is generated around the 21 screw axis along (1/2, y, 1/4) (Fig. 3). Four such chains run through each unit cell, one around each of the 21 axes parallel to [010]: two lie in the domain 0.30 < x < 0.70, and the other two lie in the domain 0.80 < x < 1.20.
Within each of these domains, the chains are linked into sheets by nitro···I interactions, having I····O1iii 3.153 (7) Å, C—I···O1iii 171.5 (3)°, I···O1iii—N4iii 112.6 (5) [symmetry code: (iii) x, 3/2 - y, 1/2 + z)] and propagation of this interaction generates sheets parallel to (100) built from alternating R24(12) and R44(28) rings (Fig. 3). As in the triclinic polymorph, only one O forms I···O contacts shorter than the sum of the van der Waals radii. There are two (100) sheets passing through each unit cell, and each sheet is linked to its two immediate neighbours by aromatic π···π stacking interactions (Fig. 4), so generating a continuous three-dimensional structure. The aryl ring at (x, y, z) is a component of the (100) sheet in the domain 0.30 < x < 0.70; this ring forms π···π interactions with the rings at (1/2 + x, y, 1/2 - z) and (-1/2 + x, y, 1/2 - z) which are components of the sheets in the domains 0.80 < x < 1.20 and -0.20 < x < 0.20 respectively. These rings are not all parallel by symmetry, but the interplanar angles are only ca 2.0°, with interplanar spacings of ca 3.56 Å and centroid offsets of ca 1.21 Å.
The C—I distances in (Ia) and (Ib) are 2.098 (5) Å and 2.087 (8) Å: the other bond lengths and angles show no unexpected features.