Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270102023041/dn1017sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270102023041/dn1017IIsup2.hkl | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270102023041/dn1017IIIsup3.hkl |
CCDC references: 195181; 195182
Commercially available (Aldrich) 3-iodo-1-nitrobenzene, (II), and 3-iodo-1,5-dinitro-benzene, (III), were heated in acetone until most of the solid had dissolved. Crystals suitable for X-ray diffraction analysis were obtained by slow cooling of solutions in what? containing a few drops of heptane. Please give details of major solvent for crystallization.
For compound (II), the Friedel pairs were not merged, owing to the determination of the absolute structure by refining the Flack parameter (Flack, 1983). The number of Friedel pairs measured was 625. For both compounds, H atoms were treated as riding, with C—H distances of 0.94%A. Is this added text OK?
For both compounds, data collection: SMART (Siemens, 1996); cell refinement: SAINT (Siemens, 1996); data reduction: SAINT; program(s) used to solve structure: SHELXTL (Siemens, 1996); program(s) used to refine structure: SHELXTL. Molecular graphics: SHELXTL for (II); SHELXTL and ORTEPIII (Farrugia, 1997) for (III). For both compounds, software used to prepare material for publication: SHELXTL.
C6H4INO2 | F(000) = 232 |
Mr = 249.00 | Dx = 2.284 Mg m−3 |
Monoclinic, P21 | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: P 2yb | Cell parameters from 102 reflections |
a = 5.977 (3) Å | θ = 5.0–17.0° |
b = 5.224 (3) Å | µ = 4.36 mm−1 |
c = 11.972 (6) Å | T = 213 K |
β = 104.383 (10)° | Needle, colourless |
V = 362.1 (3) Å3 | 0.3 × 0.1 × 0.1 mm |
Z = 2 |
Bruker SMART 1000 CCD area-detector diffractometer | 1797 independent reflections |
Radiation source: fine-focus sealed tube | 1584 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.037 |
ω scans | θmax = 30.0°, θmin = 3.5° |
Absorption correction: multi-scan [SADABS (Sheldrick, 1996; Blessing, 1995)] | h = −8→7 |
Tmin = 0.599, Tmax = 0.647 | k = −7→7 |
2423 measured reflections | l = −16→14 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.046 | H-atom parameters constrained |
wR(F2) = 0.112 | w = 1/[σ2(Fo2) + (0.0567P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.03 | (Δ/σ)max < 0.001 |
1797 reflections | Δρmax = 1.94 e Å−3 |
91 parameters | Δρmin = −1.11 e Å−3 |
1 restraint | Absolute structure: Flack (1983) and Bernardinelli & Flack (1985) |
Primary atom site location: structure-invariant direct methods | Absolute structure parameter: 0.09 (6) |
C6H4INO2 | V = 362.1 (3) Å3 |
Mr = 249.00 | Z = 2 |
Monoclinic, P21 | Mo Kα radiation |
a = 5.977 (3) Å | µ = 4.36 mm−1 |
b = 5.224 (3) Å | T = 213 K |
c = 11.972 (6) Å | 0.3 × 0.1 × 0.1 mm |
β = 104.383 (10)° |
Bruker SMART 1000 CCD area-detector diffractometer | 1797 independent reflections |
Absorption correction: multi-scan [SADABS (Sheldrick, 1996; Blessing, 1995)] | 1584 reflections with I > 2σ(I) |
Tmin = 0.599, Tmax = 0.647 | Rint = 0.037 |
2423 measured reflections |
R[F2 > 2σ(F2)] = 0.046 | H-atom parameters constrained |
wR(F2) = 0.112 | Δρmax = 1.94 e Å−3 |
S = 1.03 | Δρmin = −1.11 e Å−3 |
1797 reflections | Absolute structure: Flack (1983) and Bernardinelli & Flack (1985) |
91 parameters | Absolute structure parameter: 0.09 (6) |
1 restraint |
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. |
x | y | z | Uiso*/Ueq | ||
I1 | 0.25586 (6) | 0.50925 (17) | 0.05533 (3) | 0.03788 (17) | |
C1 | 0.5878 (8) | 0.011 (3) | 0.3332 (4) | 0.0229 (9) | |
C4 | 0.7230 (12) | 0.4138 (14) | 0.2194 (6) | 0.0275 (13) | |
H4A | 0.7681 | 0.5531 | 0.1804 | 0.033* | |
O1 | 0.3066 (9) | −0.2671 (11) | 0.3634 (5) | 0.0370 (12) | |
N1 | 0.5096 (10) | −0.2027 (11) | 0.3933 (5) | 0.0260 (12) | |
C2 | 0.4248 (10) | 0.1243 (13) | 0.2443 (6) | 0.0242 (12) | |
H2A | 0.2711 | 0.0665 | 0.2237 | 0.029* | |
O2 | 0.6537 (10) | −0.3080 (11) | 0.4727 (5) | 0.0384 (12) | |
C3 | 0.4958 (11) | 0.3234 (14) | 0.1879 (6) | 0.0255 (13) | |
C5 | 0.8808 (11) | 0.2949 (15) | 0.3091 (7) | 0.0307 (15) | |
H5A | 1.0344 | 0.3532 | 0.3301 | 0.037* | |
C6 | 0.8153 (11) | 0.0909 (14) | 0.3685 (7) | 0.0289 (15) | |
H6A | 0.9208 | 0.0110 | 0.4300 | 0.035* |
U11 | U22 | U33 | U12 | U13 | U23 | |
I1 | 0.0364 (2) | 0.0391 (2) | 0.0319 (2) | −0.0017 (3) | −0.00354 (15) | 0.0070 (3) |
C1 | 0.024 (2) | 0.019 (2) | 0.025 (2) | 0.005 (4) | 0.0057 (19) | 0.002 (4) |
C4 | 0.027 (3) | 0.030 (3) | 0.027 (3) | −0.006 (2) | 0.010 (3) | −0.002 (2) |
O1 | 0.033 (2) | 0.033 (3) | 0.044 (3) | −0.013 (2) | 0.008 (2) | 0.001 (2) |
N1 | 0.030 (3) | 0.020 (3) | 0.028 (3) | 0.001 (2) | 0.008 (2) | 0.000 (2) |
C2 | 0.020 (3) | 0.025 (3) | 0.027 (3) | −0.001 (2) | 0.003 (2) | −0.002 (2) |
O2 | 0.042 (3) | 0.031 (3) | 0.042 (3) | 0.005 (2) | 0.008 (3) | 0.009 (2) |
C3 | 0.020 (3) | 0.034 (4) | 0.021 (3) | 0.008 (2) | 0.004 (2) | −0.002 (2) |
C5 | 0.022 (3) | 0.031 (4) | 0.039 (4) | −0.007 (3) | 0.009 (3) | −0.005 (3) |
C6 | 0.024 (3) | 0.032 (4) | 0.031 (4) | −0.003 (2) | 0.007 (3) | −0.003 (2) |
I1—C3 | 2.095 (7) | O1—N1 | 1.224 (8) |
C1—C2 | 1.385 (10) | N1—O2 | 1.242 (8) |
C1—C6 | 1.385 (9) | C2—C3 | 1.364 (10) |
C1—N1 | 1.465 (12) | C2—H2A | 0.9400 |
C4—C5 | 1.388 (11) | C5—C6 | 1.390 (11) |
C4—C3 | 1.398 (9) | C5—H5A | 0.9400 |
C4—H4A | 0.9400 | C6—H6A | 0.9400 |
C2—C1—C6 | 123.7 (9) | C1—C2—H2A | 121.2 |
C2—C1—N1 | 117.0 (6) | C2—C3—C4 | 121.6 (6) |
C6—C1—N1 | 119.3 (6) | C2—C3—I1 | 119.4 (5) |
C5—C4—C3 | 119.1 (7) | C4—C3—I1 | 119.0 (5) |
C5—C4—H4A | 120.5 | C4—C5—C6 | 121.0 (6) |
C3—C4—H4A | 120.5 | C4—C5—H5A | 119.5 |
O1—N1—O2 | 123.4 (6) | C6—C5—H5A | 119.5 |
O1—N1—C1 | 118.6 (5) | C1—C6—C5 | 117.1 (7) |
O2—N1—C1 | 117.9 (5) | C1—C6—H6A | 121.4 |
C3—C2—C1 | 117.5 (7) | C5—C6—H6A | 121.4 |
C3—C2—H2A | 121.2 |
C6H3IN2O4 | F(000) = 1104 |
Mr = 294.00 | Dx = 2.309 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 53 reflections |
a = 13.842 (9) Å | θ = 3.4–17.6° |
b = 8.164 (5) Å | µ = 3.77 mm−1 |
c = 15.288 (9) Å | T = 213 K |
β = 101.766 (12)° | Needle, colourless |
V = 1691.2 (18) Å3 | 0.4 × 0.2 × 0.2 mm |
Z = 8 |
Bruker SMART 1000 CCD area-detector diffractometer | 2404 independent reflections |
Radiation source: fine-focus sealed tube | 1927 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.042 |
ω scans | θmax = 30.0°, θmin = 2.9° |
Absorption correction: multi-scan [SADABS (Sheldrick, 1996; Blessing, 1995)] | h = −19→19 |
Tmin = 0.421, Tmax = 0.470 | k = −11→8 |
6318 measured reflections | l = −21→21 |
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) = 0.084 | H-atom parameters constrained |
S = 1.07 | w = 1/[σ2(Fo2) + (0.0103P)2 + 2.3695P] where P = (Fo2 + 2Fc2)/3 |
2404 reflections | (Δ/σ)max < 0.001 |
118 parameters | Δρmax = 0.93 e Å−3 |
0 restraints | Δρmin = −0.99 e Å−3 |
C6H3IN2O4 | V = 1691.2 (18) Å3 |
Mr = 294.00 | Z = 8 |
Monoclinic, C2/c | Mo Kα radiation |
a = 13.842 (9) Å | µ = 3.77 mm−1 |
b = 8.164 (5) Å | T = 213 K |
c = 15.288 (9) Å | 0.4 × 0.2 × 0.2 mm |
β = 101.766 (12)° |
Bruker SMART 1000 CCD area-detector diffractometer | 2404 independent reflections |
Absorption correction: multi-scan [SADABS (Sheldrick, 1996; Blessing, 1995)] | 1927 reflections with I > 2σ(I) |
Tmin = 0.421, Tmax = 0.470 | Rint = 0.042 |
6318 measured reflections |
R[F2 > 2σ(F2)] = 0.037 | 0 restraints |
wR(F2) = 0.084 | H-atom parameters constrained |
S = 1.07 | Δρmax = 0.93 e Å−3 |
2404 reflections | Δρmin = −0.99 e Å−3 |
118 parameters |
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. |
x | y | z | Uiso*/Ueq | ||
I1 | 0.100566 (19) | 0.80925 (3) | 0.380331 (14) | 0.03627 (11) | |
O1 | 0.1019 (3) | 0.6800 (4) | 0.80264 (19) | 0.0559 (9) | |
C1 | 0.1186 (3) | 0.6743 (4) | 0.6559 (2) | 0.0287 (7) | |
C2 | 0.1089 (3) | 0.7634 (4) | 0.5773 (2) | 0.0270 (7) | |
H2A | 0.0980 | 0.8771 | 0.5763 | 0.032* | |
C3 | 0.1158 (3) | 0.6784 (4) | 0.5002 (2) | 0.0259 (7) | |
N1 | 0.1096 (3) | 0.7627 (5) | 0.7376 (2) | 0.0435 (9) | |
C6 | 0.1357 (3) | 0.5090 (5) | 0.6610 (2) | 0.0304 (8) | |
H6A | 0.1422 | 0.4513 | 0.7151 | 0.036* | |
O3 | 0.1861 (3) | 0.1901 (4) | 0.6581 (3) | 0.0648 (11) | |
C4 | 0.1326 (3) | 0.5120 (5) | 0.5017 (2) | 0.0295 (7) | |
H4A | 0.1370 | 0.4547 | 0.4493 | 0.035* | |
O2 | 0.1094 (4) | 0.9105 (5) | 0.7352 (2) | 0.0717 (12) | |
N2 | 0.1617 (3) | 0.2547 (5) | 0.5853 (3) | 0.0412 (8) | |
C5 | 0.1427 (3) | 0.4324 (4) | 0.5828 (2) | 0.0294 (7) | |
O4 | 0.1494 (4) | 0.1813 (4) | 0.5149 (3) | 0.0734 (13) |
U11 | U22 | U33 | U12 | U13 | U23 | |
I1 | 0.04522 (17) | 0.04186 (17) | 0.02156 (12) | −0.00267 (12) | 0.00645 (10) | 0.00836 (9) |
O1 | 0.070 (2) | 0.077 (3) | 0.0245 (13) | 0.0093 (19) | 0.0184 (14) | 0.0080 (13) |
C1 | 0.0337 (18) | 0.035 (2) | 0.0190 (14) | −0.0019 (16) | 0.0084 (13) | −0.0003 (12) |
C2 | 0.0361 (19) | 0.0202 (16) | 0.0265 (15) | −0.0005 (15) | 0.0110 (14) | 0.0029 (12) |
C3 | 0.0287 (16) | 0.0291 (18) | 0.0202 (14) | −0.0019 (15) | 0.0057 (12) | 0.0030 (12) |
N1 | 0.060 (2) | 0.052 (2) | 0.0208 (14) | 0.001 (2) | 0.0134 (15) | −0.0031 (14) |
C6 | 0.0321 (18) | 0.0319 (19) | 0.0276 (16) | −0.0008 (16) | 0.0069 (14) | 0.0098 (13) |
O3 | 0.083 (3) | 0.0376 (19) | 0.070 (2) | 0.0053 (19) | 0.006 (2) | 0.0210 (15) |
C4 | 0.0335 (18) | 0.0285 (18) | 0.0272 (16) | −0.0010 (16) | 0.0078 (13) | −0.0034 (13) |
O2 | 0.133 (4) | 0.044 (2) | 0.0466 (18) | −0.009 (2) | 0.040 (2) | −0.0178 (15) |
N2 | 0.0399 (19) | 0.0253 (16) | 0.058 (2) | 0.0007 (16) | 0.0086 (16) | 0.0019 (16) |
C5 | 0.0307 (17) | 0.0238 (17) | 0.0325 (17) | −0.0018 (16) | 0.0038 (13) | 0.0058 (13) |
O4 | 0.118 (4) | 0.0310 (18) | 0.069 (3) | 0.008 (2) | 0.014 (2) | −0.0094 (15) |
I1—C3 | 2.094 (3) | N1—O2 | 1.207 (6) |
O1—N1 | 1.225 (5) | C6—C5 | 1.370 (5) |
C1—C6 | 1.370 (5) | C6—H6A | 0.9400 |
C1—C2 | 1.388 (5) | O3—N2 | 1.215 (5) |
C1—N1 | 1.470 (5) | C4—C5 | 1.383 (5) |
C2—C3 | 1.388 (5) | C4—H4A | 0.9400 |
C2—H2A | 0.9400 | N2—O4 | 1.213 (5) |
C3—C4 | 1.377 (5) | N2—C5 | 1.473 (5) |
C6—C1—C2 | 123.5 (3) | C1—C6—C5 | 116.2 (3) |
C6—C1—N1 | 118.6 (3) | C1—C6—H6A | 121.9 |
C2—C1—N1 | 117.9 (3) | C5—C6—H6A | 121.9 |
C1—C2—C3 | 117.5 (3) | C3—C4—C5 | 117.7 (3) |
C1—C2—H2A | 121.3 | C3—C4—H4A | 121.2 |
C3—C2—H2A | 121.3 | C5—C4—H4A | 121.2 |
C4—C3—C2 | 121.3 (3) | O4—N2—O3 | 124.1 (4) |
C4—C3—I1 | 120.3 (2) | O4—N2—C5 | 118.1 (4) |
C2—C3—I1 | 118.4 (3) | O3—N2—C5 | 117.7 (4) |
O2—N1—O1 | 125.1 (4) | C6—C5—C4 | 123.8 (3) |
O2—N1—C1 | 117.8 (3) | C6—C5—N2 | 118.1 (3) |
O1—N1—C1 | 117.1 (4) | C4—C5—N2 | 118.1 (3) |
Experimental details
(II) | (III) | |
Crystal data | ||
Chemical formula | C6H4INO2 | C6H3IN2O4 |
Mr | 249.00 | 294.00 |
Crystal system, space group | Monoclinic, P21 | Monoclinic, C2/c |
Temperature (K) | 213 | 213 |
a, b, c (Å) | 5.977 (3), 5.224 (3), 11.972 (6) | 13.842 (9), 8.164 (5), 15.288 (9) |
β (°) | 104.383 (10) | 101.766 (12) |
V (Å3) | 362.1 (3) | 1691.2 (18) |
Z | 2 | 8 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 4.36 | 3.77 |
Crystal size (mm) | 0.3 × 0.1 × 0.1 | 0.4 × 0.2 × 0.2 |
Data collection | ||
Diffractometer | Bruker SMART 1000 CCD area-detector diffractometer | Bruker SMART 1000 CCD area-detector diffractometer |
Absorption correction | Multi-scan [SADABS (Sheldrick, 1996; Blessing, 1995)] | Multi-scan [SADABS (Sheldrick, 1996; Blessing, 1995)] |
Tmin, Tmax | 0.599, 0.647 | 0.421, 0.470 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 2423, 1797, 1584 | 6318, 2404, 1927 |
Rint | 0.037 | 0.042 |
(sin θ/λ)max (Å−1) | 0.703 | 0.704 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.046, 0.112, 1.03 | 0.037, 0.084, 1.07 |
No. of reflections | 1797 | 2404 |
No. of parameters | 91 | 118 |
No. of restraints | 1 | 0 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 1.94, −1.11 | 0.93, −0.99 |
Absolute structure | Flack (1983) and Bernardinelli & Flack (1985) | ? |
Absolute structure parameter | 0.09 (6) | ? |
Computer programs: SMART (Siemens, 1996), SAINT (Siemens, 1996), SAINT, SHELXTL (Siemens, 1996), SHELXTL and ORTEPIII (Farrugia, 1997).
I1—C3 | 2.095 (7) | O1—N1 | 1.224 (8) |
C1—N1 | 1.465 (12) | N1—O2 | 1.242 (8) |
C2—C1—N1 | 117.0 (6) | O2—N1—C1 | 117.9 (5) |
C6—C1—N1 | 119.3 (6) | C2—C3—I1 | 119.4 (5) |
O1—N1—O2 | 123.4 (6) | C4—C3—I1 | 119.0 (5) |
O1—N1—C1 | 118.6 (5) |
I1—C3 | 2.094 (3) | O3—N2 | 1.215 (5) |
O1—N1 | 1.225 (5) | N2—O4 | 1.213 (5) |
C1—N1 | 1.470 (5) | N2—C5 | 1.473 (5) |
N1—O2 | 1.207 (6) | ||
C6—C1—N1 | 118.6 (3) | O1—N1—C1 | 117.1 (4) |
C2—C1—N1 | 117.9 (3) | O4—N2—O3 | 124.1 (4) |
C4—C3—I1 | 120.3 (2) | O4—N2—C5 | 118.1 (4) |
C2—C3—I1 | 118.4 (3) | O3—N2—C5 | 117.7 (4) |
O2—N1—O1 | 125.1 (4) | C6—C5—N2 | 118.1 (3) |
O2—N1—C1 | 117.8 (3) | C4—C5—N2 | 118.1 (3) |
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In this communication, we report the crystal structures of two iodo-substituted nitrobenzenes. A comparison with related iodo-substituted nitrobenzenes shows that the different possibilities of I···NO2 interactions depend on the substitution pattern of the nitro and iodo groups on the benzene ring. Recently, Desiraju et al. (1993) observed that halogen atoms, presumably due to their polarizabilities, may form symmetrical (P) and unsymmetrical (Q, R) recognition motifs with nitro groups; Scheme 1 illustrates these types of iodo···nitro intermolecular interactions. Add Scheme 1 tag.
In the structures of 4-iodonitrobenzene, (I) (Thalladi et al., 1996), and the 1:1 complex of 1,4-dinitrobenzene and 1,4-diiodobenzene (Allen et al., 1994), there are linear ribbon patterns linked exclusively via symmetrical iodo···nitro motifs (P). These motifs are formed from two convergent polarization-induced I···O interactions. As part of a continuing study of intermolecular interactions in such compounds, we have investigated compounds containing 3-iodonitrobenzene substitution patterns and have determined the crystal structures of 3-iodo-1-nitrobenzene, (II), and 3-iodo-1,5-dinitro-benzene, (III). \sch
A search of the Spring 2002 release of the Cambridge Structural Database (CSD: Allen, 2002) for structures containing 3-iodonitrobenzene substitution patterns revealed only a few compounds containing additional groups on the aromatic system.
The molecular structure of (II) is shown in Fig. 1a, with the associated distances and angles of special interest given in Table 1. The C—I [2.095 (7) Å] and N—O [1.224 (8) and 1.242 (8) Å] distances are in good agreement with values reported for (I) [C—I 2.097 (5), and N—O 1.2242 (6) and 1.232 (6) Å; Thalladi et al., 1996]. The planar molecules are linked into zigzag chains by I···Ii interactions of 3.990 (7) Å [Fig. 1 b; symmetry code: (i) −x, 1/2 + y, −z]. A similar pattern of I···I zigzag chains has also been observed for 1,2-diiodo-4-nitro-5-(n-butylamino)benzene (Senskey et al., 1995). The overall network is formed using additional NO2···NO2 interactions, with O2N1···O2iiNO 2.928 (12) Å [symmetry code: (ii) 1 − x, 1/2 + y, 1 − z]. These distances are within the acceptable limits described in the literature for 1,2,4-trinitrobenzene (Laerdahl et al., 1998). In contrast with the crystal structures of (I) and related compounds, the lack of iodo···nitro interactions in (II) is surprising.
In an attempt to engineer a two-dimensional network with high symmetric P motifs, we looked to iodo-substituted nitrobenzene with additional nitro groups on the ring and determined the structure of 3-iodo-1,5-dinitrobenzene, (III). The molecular structure of (III) is shown in Fig. 2a, with the associated dimensions given in Table 2. The C—I and N—O distances are in good agreement with the determined structures of (I) and (II). Neither NO2 group is exactly coplanar with the benzene ring. The angles between the least-squares planes of the nitro groups and the benzene ring are 13 and 21°. The crystal packing of (II) can be described as a periodical arrangement of two nearly parallel sheets of molecules (Fig. 2 b), and two such sheets are linked by NO2···NO2 interactions, with N1iii···O1iv 2.944 (7) Å [symmetry codes: (iii) 1/2 + x, 1/2 − y, 1/2 + z; (iv) 1/2 − x, 1/2 − y, −z]. Each sheet forms I···NO2 interactions, with I1v···O2iii 3.206 (3) Å [symmetry code: (v) 1/2 + x, 1/2 + y, z], which conforms to the R type of motif, with only one of the two nitro O atoms in contact with an I atom. The presence of one iodo and two nitro groups is still not sufficient to engineer crystal packings containing symmetrical P motifs as building blocks.
In contrast, the higher-substituted compound 2-iodo-1,3,5-trinitrobenzene, (IV) (Weiss et al., 1999), forms planes using I···NO2 P motifs and these planes are linked by NO2···NO2 interactions. The P motifs are generated by the nitro and iodo groups arranged in the para position. A comparison of selected N—O–, N—C– and C—I bond lengths and angles of compounds (I)-(IV) shows no significant differences to explain the presence of different intermolecular interactions.
We have compared these structures with related iodo-substituted nitrobenzenes containing additional substituents, such as I (Garden et al., 2002), NH2 (McWilliams et al., 2001), NHR (Senskey et al., 1995) and OH (Garden et al., 2002). In these crystal packings, we only observed the I···NO2 interactions of the type P motif if the nitro and iodo groups were arranged in the para position. Fundamental organic chemistry suggests that there is a reactivity difference between meta- and para-substituted benzene rings. These differences are based on electronic arguments.
In this case, however, additional substitution in the ortho or meta position has no effect; it is only those complexes with I in the para position which display the P-type motif of crystal packing. Allen et al. (1997) combined a CSD search and an ab initio orbital study of the geometrical parameters of halogen···nitro supramolecular synthons. These indicated that halogen···nitro interactions increase in strength in the order Cl > Br > I, and that the frequency of formation of higher symmetrical motifs increases in the same order. To understand if there is a relationship between the role of substitution pattern on the benzene ring backbone and different types of intermolecular interactions, we will investigate other supramolecular synthons in the future.