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The title compound, C7H8N2O2, is monoclinic (space group P21/n) at 295 (2) K with Z' = 2. The two types of mol­ecule form independent C(7) chains, and the structure is related to that of the low-temperature triclinic polymorph, where Z' = 4 in P\overline 1, by a simple displacive transformation.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270101012185/gg1075sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S0108270101012185/gg1075Isup2.hkl
Contains datablock I

CCDC reference: 174842

Comment top

When crystallized from ethanol, 4-methyl-3-nitro-aniline, (I), is triclinic P1 at 150 (2) K with Z' = 4 (Cannon et al., 2001). Of the four independent molecules, two form individual chains built from N—H···O hydrogen bonds, while the other two types combine to form molecular ladders. At ambient temperatures, however, this material is monoclinic P21/n with Z' = 2. The unit-cell dimensions and the atomic coordinates indicate that the low-temperature triclinic and the ambient-temperature monoclinic polymorphs are related by a simple displacive phase-transformation.

The molecular dimensions of the two independent molecules in the monoclinic polymorph (Fig. 1) are very similar (Table 1) and the C—C bond lengths show a significant deviation of the aryl rings from regular hexagons; this feature was observed also in the triclinic polymorph. The two molecules do, however, differ markedly in the twist of the nitro groups out of the plane of the adjacent rings (Table 1); this difference alone precludes the possibility of any further symmetry.

Each molecule acts as a single donor and as a single acceptor in N—H···O hydrogen bonds (Table 2); thus, half of the N—H bonds and half of the O atoms do not participate in the hydrogen bonding, so that the sole motif of supramolecular aggregation is the formation of C(7) chains (Bernstein et al., 1995). Molecules of type 1 and 2, containing atoms N11 and N21, respectively, each act as hydrogen-bond donors to another molecule of the same type, so generating by translation two distinct chains, both running parallel to the [100] direction and each containing just one type of molecule (Fig. 2). Four chains of each type run through each unit cell, but there are no hydrogen bonds of either N—H···O type or C—H···O type between adjacent chains, nor are there any aromatic ππ-stacking interactions.

The unit-cell dimensions of the triclinic and monoclinic polymorphs of (I) are very similar and the triclinic unit cell can be derived from the present monoclinic cell by means of the transformation (010, 100, 001). Subject to this transformation and an origin shift, the atomic coordinates of the two forms indicate that triclinic molecules of types 1 and 2 (Cannon et al., 2001) map into the monoclinic type 2 molecules at (x, y, z) and (1/2 - x, 1/2 + y, 1/2 - z), respectively, while triclinic molecules 3 and 4 map into the monoclinic type 1 molecules at (-x, -y, -z) and (-1/2 + x, 1/2 - y, 1/2 + z), respectively. It is noteworthy that the conformations of the various molecules, as judged by the C—C—N—O torsion angles (Table 1) and particularly by the dihedral angles between the aryl rings and the C—NO2 groups, faithfully follow this mapping. Thus, in the triclinic polymorph, molecules 1 and 2 have nitro-group twists of 31.91 (8) and 28.99 (8)°, respectively, comparable with the 32.5 (2)° twist in monoclinic type 2 molecules, while triclinic type 3 and 4 molecules have nitro-group twists of 7.91 (8) and 3.92 (8)°, respectively, compared with a twist of 7.5 (2)° in monoclinic type 1 molecules. These observations all point to a simple displacive phase transformation between the triclinic and monoclinic polymorphs.

Experimental top

A sample of compound (I) was obtained from Aldrich. Crystals suitable for single-crystal X-ray diffraction were grown from a solution in ethanol. The same phase was obtained by recrystallization from CH2Cl2.

Refinement top

Compound (I) crystallized in the monoclinic system; space group P21/n was uniquely assigned from the systematic absences. H atoms were treated as riding atoms with C—H distances of 0.93 (aromatic) or 0.96 Å (methyl), and an N—H distance of 0.86 Å. The crystal quality was not high and, as expected, only ca 50% of the reflections were labelled `observed' at ambient temperature.

Computing details top

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 (Sheldrick, 1997) and PRPKAPPA (Ferguson, 1999).

Figures top
[Figure 1] Fig. 1. The two independent molecules in (I) showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 30% probability level.
[Figure 2] Fig. 2. Part of the crystal structure of (I), showing the two independent C(7) chains. For the sake of clarity, H atoms bonded to C atoms have been omitted. Atoms marked with an asterisk (*) or hash (#) are at the symmetry positions (1 + x, y, z) and (-1 + x, y, z), respectively.
4-Methyl-3-nitroaniline top
Crystal data top
C7H8N2O2F(000) = 640
Mr = 152.16Dx = 1.363 Mg m3
Monoclinic, P21/nMo Kα radiation, λ = 0.71073 Å
a = 8.2473 (7) ÅCell parameters from 3128 reflections
b = 7.5676 (7) Åθ = 3.2–27.5°
c = 23.7798 (16) ŵ = 0.10 mm1
β = 91.717 (5)°T = 295 K
V = 1483.5 (2) Å3Plate, orange
Z = 80.36 × 0.18 × 0.08 mm
Data collection top
Kappa-CCD
diffractometer
3128 independent reflections
Radiation source: fine-focus sealed X-ray tube1517 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.105
ϕ scans, and ω scans with κ offsetsθmax = 27.5°, θmin = 3.2°
Absorption correction: multi-scan
(DENZO-SMN; Otwinowski & Minor, 1997)
h = 1010
Tmin = 0.951, Tmax = 0.985k = 99
11137 measured reflectionsl = 3028
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.061Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.204H-atom parameters constrained
S = 1.01 w = 1/[σ2(Fo2) + (0.1003P)2]
where P = (Fo2 + 2Fc2)/3
3128 reflections(Δ/σ)max = 0.002
201 parametersΔρmax = 0.15 e Å3
0 restraintsΔρmin = 0.13 e Å3
Crystal data top
C7H8N2O2V = 1483.5 (2) Å3
Mr = 152.16Z = 8
Monoclinic, P21/nMo Kα radiation
a = 8.2473 (7) ŵ = 0.10 mm1
b = 7.5676 (7) ÅT = 295 K
c = 23.7798 (16) Å0.36 × 0.18 × 0.08 mm
β = 91.717 (5)°
Data collection top
Kappa-CCD
diffractometer
3128 independent reflections
Absorption correction: multi-scan
(DENZO-SMN; Otwinowski & Minor, 1997)
1517 reflections with I > 2σ(I)
Tmin = 0.951, Tmax = 0.985Rint = 0.105
11137 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0610 restraints
wR(F2) = 0.204H-atom parameters constrained
S = 1.01Δρmax = 0.15 e Å3
3128 reflectionsΔρmin = 0.13 e Å3
201 parameters
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C110.7363 (3)0.1807 (4)0.02890 (10)0.0718 (7)
N110.8565 (4)0.2392 (5)0.00532 (13)0.1207 (12)
C120.5764 (3)0.2283 (4)0.01893 (9)0.0683 (7)
C130.4595 (3)0.1742 (3)0.05494 (10)0.0663 (6)
N130.2933 (3)0.2317 (4)0.04011 (11)0.0855 (7)
O110.1829 (4)0.1746 (7)0.06640 (19)0.1696 (16)
O120.2714 (3)0.3355 (4)0.00279 (10)0.1187 (9)
C140.4913 (3)0.0696 (3)0.10266 (10)0.0695 (7)
C170.3714 (5)0.0100 (5)0.14474 (14)0.0988 (10)
C150.6533 (4)0.0225 (4)0.11058 (10)0.0717 (7)
C160.7720 (3)0.0732 (4)0.07528 (10)0.0713 (7)
C210.6440 (3)0.0732 (3)0.35279 (9)0.0629 (6)
N210.5306 (3)0.0434 (4)0.39292 (9)0.0874 (7)
C220.8069 (3)0.0431 (3)0.36392 (9)0.0601 (6)
C230.9181 (3)0.0699 (3)0.32240 (9)0.0586 (6)
N231.0872 (3)0.0316 (3)0.33856 (10)0.0749 (6)
O211.1323 (3)0.0552 (3)0.38727 (9)0.0985 (8)
O221.1771 (3)0.0229 (5)0.30290 (11)0.1264 (10)
C240.8766 (3)0.1309 (3)0.26819 (9)0.0618 (6)
C270.9930 (4)0.1617 (4)0.22176 (11)0.0860 (8)
C250.7130 (3)0.1659 (4)0.25962 (9)0.0695 (7)
C260.5993 (3)0.1387 (4)0.29952 (10)0.0712 (7)
H11A0.83270.30660.03350.145*
H11B0.95560.20840.00140.145*
H120.54800.29720.01220.082*
H17A0.42750.04860.17540.148*
H17B0.29550.07030.12710.148*
H17C0.31430.11060.15870.148*
H150.68220.04710.14150.086*
H160.87810.03570.08220.086*
H21A0.56070.00530.42570.105*
H21B0.42960.06280.38530.105*
H220.84190.00480.39940.072*
H27A1.08240.23200.23570.129*
H27B0.93840.22260.19130.129*
H27C1.03270.05030.20870.129*
H250.67840.21040.22480.083*
H260.49090.16400.29110.085*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C110.0582 (16)0.0864 (18)0.0708 (14)0.0048 (13)0.0011 (10)0.0005 (11)
N110.0735 (19)0.176 (3)0.1136 (19)0.0034 (19)0.0154 (14)0.0478 (19)
C120.0623 (16)0.0749 (16)0.0671 (13)0.0019 (12)0.0089 (10)0.0024 (10)
C130.0550 (14)0.0624 (14)0.0810 (14)0.0011 (11)0.0075 (10)0.0090 (10)
N130.0580 (15)0.0864 (17)0.1112 (17)0.0025 (12)0.0121 (12)0.0093 (13)
O110.0513 (16)0.192 (4)0.266 (4)0.0012 (18)0.0152 (19)0.091 (3)
O120.0852 (17)0.153 (2)0.1165 (17)0.0308 (16)0.0253 (12)0.0201 (15)
C140.0701 (17)0.0589 (14)0.0796 (15)0.0008 (12)0.0062 (11)0.0056 (10)
C170.098 (3)0.092 (2)0.109 (2)0.0017 (19)0.0340 (17)0.0098 (16)
C150.0768 (19)0.0673 (15)0.0708 (14)0.0067 (12)0.0015 (11)0.0048 (10)
C160.0565 (15)0.0779 (16)0.0792 (15)0.0090 (12)0.0045 (11)0.0002 (11)
C210.0527 (14)0.0694 (15)0.0666 (13)0.0009 (11)0.0012 (9)0.0056 (10)
N210.0549 (14)0.126 (2)0.0811 (14)0.0001 (13)0.0065 (10)0.0016 (11)
C220.0506 (13)0.0678 (14)0.0617 (12)0.0002 (10)0.0033 (9)0.0028 (9)
C230.0471 (12)0.0585 (12)0.0701 (13)0.0000 (10)0.0013 (9)0.0010 (9)
N230.0513 (13)0.0806 (15)0.0929 (15)0.0007 (10)0.0032 (11)0.0125 (10)
O210.0611 (13)0.132 (2)0.1012 (14)0.0076 (12)0.0230 (10)0.0174 (11)
O220.0718 (17)0.182 (3)0.1263 (18)0.0433 (17)0.0202 (13)0.0067 (16)
C240.0659 (16)0.0559 (13)0.0636 (12)0.0003 (11)0.0038 (9)0.0010 (9)
C270.093 (2)0.0890 (19)0.0770 (16)0.0054 (16)0.0202 (13)0.0101 (12)
C250.0707 (17)0.0734 (15)0.0637 (13)0.0039 (12)0.0100 (11)0.0060 (10)
C260.0545 (15)0.0789 (17)0.0793 (15)0.0086 (12)0.0123 (11)0.0037 (11)
Geometric parameters (Å, º) top
C11—C121.381 (4)C21—C221.380 (4)
C12—C131.371 (4)C22—C231.383 (4)
C13—C141.402 (4)C23—C241.402 (3)
C14—C151.390 (4)C24—C251.384 (4)
C15—C161.364 (4)C25—C261.370 (4)
C16—C111.395 (4)C26—C211.399 (3)
C11—N111.374 (4)C21—N211.374 (4)
C13—N131.471 (4)C23—N231.465 (3)
N13—O111.201 (4)N23—O211.219 (3)
N13—O121.195 (4)N23—O221.215 (3)
C14—C171.497 (4)C24—C271.503 (4)
N11—H11A0.8600N21—H21A0.8600
N11—H11B0.8600N21—H21B0.8600
C12—H120.9300C22—H220.9300
C15—H150.9300C25—H250.9300
C16—H160.9300C26—H260.9300
C17—H17A0.9600C27—H27A0.9600
C17—H17B0.9600C27—H27B0.9600
C17—H17C0.9600C27—H27C0.9600
N11—C11—C12121.1 (3)N21—C21—C22121.2 (2)
N11—C11—C16121.1 (3)N21—C21—C26121.4 (2)
C12—C11—C16117.8 (2)C22—C21—C26117.4 (2)
C11—N11—H11A120.0C21—N21—H21A120.0
C11—N11—H11B120.0C21—N21—H21B120.0
H11A—N11—H11B120.0H21A—N21—H21B120.0
C13—C12—C11120.0 (2)C21—C22—C23120.1 (2)
C13—C12—H12120.0C21—C22—H22119.9
C11—C12—H12120.0C23—C22—H22119.9
C12—C13—C14123.8 (2)C22—C23—C24123.8 (2)
C12—C13—N13115.4 (2)C22—C23—N23115.50 (19)
C14—C13—N13120.8 (2)C24—C23—N23120.7 (2)
O12—N13—O11121.6 (3)O21—N23—O22122.5 (3)
O12—N13—C13119.5 (3)O22—N23—C23118.7 (2)
O11—N13—C13119.0 (3)O21—N23—C23118.8 (2)
C15—C14—C13114.2 (2)C25—C24—C23114.1 (2)
C15—C14—C17118.9 (2)C25—C24—C27120.2 (2)
C13—C14—C17126.8 (3)C23—C24—C27125.6 (2)
C14—C17—H17A109.5C24—C27—H27A109.5
C14—C17—H17B109.5C24—C27—H27B109.5
H17A—C17—H17B109.5H27A—C27—H27B109.5
C14—C17—H17C109.5C24—C27—H27C109.5
H17A—C17—H17C109.5H27A—C27—H27C109.5
H17B—C17—H17C109.5H27B—C27—H27C109.5
C16—C15—C14123.3 (2)C26—C25—C24123.6 (2)
C16—C15—H15118.3C26—C25—H25118.2
C14—C15—H15118.3C24—C25—H25118.2
C15—C16—C11120.8 (3)C25—C26—C21120.9 (2)
C15—C16—H16119.6C25—C26—H26119.6
C11—C16—H16119.6C21—C26—H26119.6
C12—C13—N13—O11172.5 (4)C22—C23—N23—O2131.5 (3)
C12—C13—N13—O128.4 (4)C22—C23—N23—O22148.3 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N11—H11B···O11i0.862.413.181 (5)150
N21—H21B···O21ii0.862.453.285 (4)163
Symmetry codes: (i) x+1, y, z; (ii) x1, y, z.

Experimental details

Crystal data
Chemical formulaC7H8N2O2
Mr152.16
Crystal system, space groupMonoclinic, P21/n
Temperature (K)295
a, b, c (Å)8.2473 (7), 7.5676 (7), 23.7798 (16)
β (°) 91.717 (5)
V3)1483.5 (2)
Z8
Radiation typeMo Kα
µ (mm1)0.10
Crystal size (mm)0.36 × 0.18 × 0.08
Data collection
DiffractometerKappa-CCD
diffractometer
Absorption correctionMulti-scan
(DENZO-SMN; Otwinowski & Minor, 1997)
Tmin, Tmax0.951, 0.985
No. of measured, independent and
observed [I > 2σ(I)] reflections
11137, 3128, 1517
Rint0.105
(sin θ/λ)max1)0.650
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.061, 0.204, 1.01
No. of reflections3128
No. of parameters201
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.15, 0.13

Computer programs: KappaCCD Server Software (Nonius, 1997), DENZO-SMN (Otwinowski & Minor, 1997), DENZO-SMN, SHELXS97 (Sheldrick, 1997), PLATON (Spek, 2001), SHELXL97 (Sheldrick, 1997) and PRPKAPPA (Ferguson, 1999).

Selected geometric parameters (Å, º) top
C11—C121.381 (4)C21—C221.380 (4)
C12—C131.371 (4)C22—C231.383 (4)
C13—C141.402 (4)C23—C241.402 (3)
C14—C151.390 (4)C24—C251.384 (4)
C15—C161.364 (4)C25—C261.370 (4)
C16—C111.395 (4)C26—C211.399 (3)
C11—N111.374 (4)C21—N211.374 (4)
C13—N131.471 (4)C23—N231.465 (3)
N13—O111.201 (4)N23—O211.219 (3)
N13—O121.195 (4)N23—O221.215 (3)
C14—C171.497 (4)C24—C271.503 (4)
C12—C13—N13—O11172.5 (4)C22—C23—N23—O2131.5 (3)
C12—C13—N13—O128.4 (4)C22—C23—N23—O22148.3 (3)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N11—H11B···O11i0.862.413.181 (5)150
N21—H21B···O21ii0.862.453.285 (4)163
Symmetry codes: (i) x+1, y, z; (ii) x1, y, z.
 

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