Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S0108270111010109/bm3102sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270111010109/bm3102I-1sup2.hkl | |
Structure factor file (CIF format) https://doi.org/10.1107/S0108270111010109/bm3102I-2sup3.hkl |
CCDC references: 829711; 829712
For related literature, see: Bartholomew et al. (2000); Collas et al. (2011); Pham (2009); Schmidt (1971).
Benzene-1,2-diamine (2.6 g, 25 mmol) and 4-nitrobenzaldehyde (3.8 g, 50 mmol) were dissolved in ethanol (200 ml) and the resulting solution was boiled under reflux for 2 h. The resulting precipitate was filtered off, yielding a yellow–orange powder, part of which was recrystallized from acetonitrile to produce needles with a golden lustre (I-1). Slow evaporation of a CHCl3 solution yielded polymorph (I-2) as orange plates [m.p. (uncorrected) 512 (I-1) and 502 K (I-2)]. UV/vis (CH2Cl2) λmax = 391 nm (log ε = 4.45). 1H NMR (CDCl3, 400 MHz, TMS): δ 7.36 (s, 4H, H10 and H11), 8.10 (d, 4H, 3J = 8.8 Hz, H2 and H6), 8.35 (d, 3J = 8.8 Hz, H3 and H5), 8.62 (s, 2H, H7). 13C NMR (CDCl3, 100 MHz, TMS): δ 122.20 (C3 and C5), 124.09 (C10 and C11), 129.46 (C2 and C6), 141.53 (C1), 149.76 (C9), 149.76 (C4), 157.03 (C7).
In order to improve R statistics, the high-resolution data were truncated at a resolution of 0.8 Å; this value was chosen based on inspection of the analysis of variance section in the shelx.lst output file. H atoms were placed in calculated positions and refined as riding, with C—H distances of 0.93 Å and Uiso(H) values of 1.2Ueq(C).
For both compounds, data collection: APEX2 (Bruker, 2008); cell refinement: APEX2 (Bruker, 2008); data reduction: APEX2 (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 (Farrugia, 1997) and Mercury (Macrae et al., 2008); software used to prepare material for publication: WinGX (Farrugia, 1999) and PLATON (Spek, 2009).
C20H14N4O4 | Z = 1 |
Mr = 374.35 | F(000) = 194 |
Triclinic, P1 | Dx = 1.455 Mg m−3 |
Hall symbol: -P 1 | Mo Kα radiation, λ = 0.71073 Å |
a = 6.9357 (7) Å | Cell parameters from 1698 reflections |
b = 7.3036 (7) Å | θ = 2.4–31.6° |
c = 8.8768 (8) Å | µ = 0.11 mm−1 |
α = 73.295 (1)° | T = 173 K |
β = 82.707 (1)° | Plate, orange |
γ = 88.071 (1)° | 0.29 × 0.22 × 0.1 mm |
V = 427.20 (7) Å3 |
Bruker SMART APEX CCD diffractometer | 1731 independent reflections |
Radiation source: fine-focus sealed tube | 1496 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.018 |
ω scans | θmax = 26.4°, θmin = 2.4° |
Absorption correction: multi-scan (APEX2; Bruker, 2008) | h = −8→8 |
Tmin = 0.973, Tmax = 0.991 | k = −9→9 |
3748 measured reflections | l = −11→11 |
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)] = 0.042 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.106 | H-atom parameters constrained |
S = 1.08 | w = 1/[σ2(Fo2) + (0.0427P)2 + 0.1688P] where P = (Fo2 + 2Fc2)/3 |
1731 reflections | (Δ/σ)max < 0.001 |
127 parameters | Δρmax = 0.20 e Å−3 |
0 restraints | Δρmin = −0.22 e Å−3 |
C20H14N4O4 | γ = 88.071 (1)° |
Mr = 374.35 | V = 427.20 (7) Å3 |
Triclinic, P1 | Z = 1 |
a = 6.9357 (7) Å | Mo Kα radiation |
b = 7.3036 (7) Å | µ = 0.11 mm−1 |
c = 8.8768 (8) Å | T = 173 K |
α = 73.295 (1)° | 0.29 × 0.22 × 0.1 mm |
β = 82.707 (1)° |
Bruker SMART APEX CCD diffractometer | 1731 independent reflections |
Absorption correction: multi-scan (APEX2; Bruker, 2008) | 1496 reflections with I > 2σ(I) |
Tmin = 0.973, Tmax = 0.991 | Rint = 0.018 |
3748 measured reflections |
R[F2 > 2σ(F2)] = 0.042 | 0 restraints |
wR(F2) = 0.106 | H-atom parameters constrained |
S = 1.08 | Δρmax = 0.20 e Å−3 |
1731 reflections | Δρmin = −0.22 e Å−3 |
127 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. The high resolution data was truncated at a resolution of 0.8. |
x | y | z | Uiso*/Ueq | ||
C1 | 0.1930 (2) | 0.5579 (2) | 0.66288 (18) | 0.0178 (3) | |
C2 | 0.1905 (2) | 0.6598 (2) | 0.50347 (18) | 0.0194 (3) | |
H2 | 0.1518 | 0.7871 | 0.4763 | 0.023* | |
C3 | 0.2451 (2) | 0.5719 (2) | 0.38690 (18) | 0.0197 (3) | |
H3 | 0.2448 | 0.6388 | 0.2806 | 0.024* | |
C4 | 0.3006 (2) | 0.3814 (2) | 0.43101 (18) | 0.0189 (3) | |
C5 | 0.3016 (2) | 0.2756 (2) | 0.58687 (19) | 0.0203 (3) | |
H5 | 0.3369 | 0.1473 | 0.6132 | 0.024* | |
C6 | 0.2484 (2) | 0.3660 (2) | 0.70286 (19) | 0.0205 (3) | |
H6 | 0.2495 | 0.2981 | 0.8089 | 0.025* | |
C7 | 0.1418 (2) | 0.6508 (2) | 0.78899 (18) | 0.0192 (3) | |
H7 | 0.1684 | 0.5885 | 0.8913 | 0.023* | |
C9 | 0.0322 (2) | 0.9033 (2) | 0.88437 (17) | 0.0193 (3) | |
C10 | −0.1413 (2) | 1.0007 (2) | 0.90212 (18) | 0.0199 (3) | |
H10 | −0.2356 | 1.0023 | 0.8360 | 0.024* | |
C11 | 0.1744 (2) | 0.9046 (2) | 0.98217 (18) | 0.0201 (3) | |
H11 | 0.2916 | 0.8418 | 0.9697 | 0.024* | |
N1 | 0.36618 (18) | 0.29163 (19) | 0.30492 (16) | 0.0215 (3) | |
N2 | 0.06211 (18) | 0.81443 (18) | 0.76120 (15) | 0.0202 (3) | |
O1 | 0.41396 (17) | 0.12242 (16) | 0.34468 (15) | 0.0295 (3) | |
O2 | 0.37407 (18) | 0.38908 (17) | 0.16651 (13) | 0.0303 (3) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0133 (7) | 0.0190 (8) | 0.0217 (8) | −0.0004 (6) | −0.0007 (6) | −0.0076 (6) |
C2 | 0.0190 (8) | 0.0160 (7) | 0.0230 (8) | 0.0008 (6) | −0.0016 (6) | −0.0059 (6) |
C3 | 0.0194 (8) | 0.0198 (8) | 0.0191 (8) | −0.0003 (6) | −0.0014 (6) | −0.0047 (6) |
C4 | 0.0154 (7) | 0.0213 (8) | 0.0234 (8) | 0.0002 (6) | −0.0020 (6) | −0.0119 (6) |
C5 | 0.0183 (7) | 0.0169 (7) | 0.0268 (8) | 0.0031 (6) | −0.0043 (6) | −0.0075 (6) |
C6 | 0.0194 (8) | 0.0211 (8) | 0.0205 (8) | 0.0013 (6) | −0.0036 (6) | −0.0050 (6) |
C7 | 0.0195 (8) | 0.0199 (8) | 0.0176 (7) | −0.0011 (6) | −0.0016 (6) | −0.0046 (6) |
C9 | 0.0254 (8) | 0.0152 (7) | 0.0164 (7) | −0.0003 (6) | −0.0007 (6) | −0.0038 (6) |
C10 | 0.0250 (8) | 0.0176 (7) | 0.0170 (7) | 0.0019 (6) | −0.0054 (6) | −0.0040 (6) |
C11 | 0.0226 (8) | 0.0164 (7) | 0.0205 (8) | 0.0038 (6) | −0.0022 (6) | −0.0048 (6) |
N1 | 0.0182 (7) | 0.0245 (7) | 0.0254 (7) | 0.0005 (5) | −0.0031 (5) | −0.0128 (6) |
N2 | 0.0215 (7) | 0.0194 (7) | 0.0206 (7) | 0.0010 (5) | −0.0013 (5) | −0.0079 (5) |
O1 | 0.0340 (7) | 0.0258 (6) | 0.0354 (7) | 0.0132 (5) | −0.0115 (5) | −0.0179 (5) |
O2 | 0.0398 (7) | 0.0303 (7) | 0.0214 (6) | −0.0020 (5) | 0.0023 (5) | −0.0105 (5) |
C1—C6 | 1.397 (2) | C7—N2 | 1.2711 (19) |
C1—C2 | 1.399 (2) | C7—H7 | 0.9300 |
C1—C7 | 1.469 (2) | C9—C10 | 1.392 (2) |
C2—C3 | 1.376 (2) | C9—C11 | 1.396 (2) |
C2—H2 | 0.9300 | C9—N2 | 1.415 (2) |
C3—C4 | 1.388 (2) | C10—C11i | 1.387 (2) |
C3—H3 | 0.9300 | C10—H10 | 0.9300 |
C4—C5 | 1.378 (2) | C11—C10i | 1.387 (2) |
C4—N1 | 1.4704 (19) | C11—H11 | 0.9300 |
C5—C6 | 1.382 (2) | N1—O2 | 1.2256 (17) |
C5—H5 | 0.9300 | N1—O1 | 1.2300 (17) |
C6—H6 | 0.9300 | ||
C6—C1—C2 | 119.62 (14) | C1—C6—H6 | 119.6 |
C6—C1—C7 | 119.41 (14) | N2—C7—C1 | 121.39 (14) |
C2—C1—C7 | 120.96 (13) | N2—C7—H7 | 119.3 |
C3—C2—C1 | 120.05 (14) | C1—C7—H7 | 119.3 |
C3—C2—H2 | 120.0 | C10—C9—C11 | 119.42 (14) |
C1—C2—H2 | 120.0 | C10—C9—N2 | 118.31 (14) |
C2—C3—C4 | 118.73 (14) | C11—C9—N2 | 122.18 (14) |
C2—C3—H3 | 120.6 | C11i—C10—C9 | 120.37 (15) |
C4—C3—H3 | 120.6 | C11i—C10—H10 | 119.8 |
C5—C4—C3 | 122.83 (14) | C9—C10—H10 | 119.8 |
C5—C4—N1 | 119.05 (13) | C10i—C11—C9 | 120.20 (14) |
C3—C4—N1 | 118.10 (14) | C10i—C11—H11 | 119.9 |
C4—C5—C6 | 117.90 (14) | C9—C11—H11 | 119.9 |
C4—C5—H5 | 121.0 | O2—N1—O1 | 123.41 (13) |
C6—C5—H5 | 121.0 | O2—N1—C4 | 118.76 (13) |
C5—C6—C1 | 120.85 (14) | O1—N1—C4 | 117.82 (13) |
C5—C6—H6 | 119.6 | C7—N2—C9 | 118.55 (13) |
C6—C1—C2—C3 | −1.0 (2) | C11—C9—C10—C11i | −1.2 (2) |
C7—C1—C2—C3 | 177.85 (14) | N2—C9—C10—C11i | −177.87 (13) |
C1—C2—C3—C4 | 0.5 (2) | C10—C9—C11—C10i | 1.2 (2) |
C2—C3—C4—C5 | 0.7 (2) | N2—C9—C11—C10i | 177.73 (14) |
C2—C3—C4—N1 | −177.55 (13) | C5—C4—N1—O2 | −176.47 (14) |
C3—C4—C5—C6 | −1.4 (2) | C3—C4—N1—O2 | 1.9 (2) |
N1—C4—C5—C6 | 176.88 (13) | C5—C4—N1—O1 | 2.2 (2) |
C4—C5—C6—C1 | 0.8 (2) | C3—C4—N1—O1 | −179.51 (13) |
C2—C1—C6—C5 | 0.3 (2) | C1—C7—N2—C9 | −174.49 (13) |
C7—C1—C6—C5 | −178.54 (14) | C10—C9—N2—C7 | −139.76 (15) |
C6—C1—C7—N2 | −168.84 (14) | C11—C9—N2—C7 | 43.7 (2) |
C2—C1—C7—N2 | 12.3 (2) |
Symmetry code: (i) −x, −y+2, −z+2. |
C20H14N4O4 | F(000) = 388 |
Mr = 374.35 | Dx = 1.445 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 1008 reflections |
a = 6.567 (1) Å | θ = 3.2–23.5° |
b = 5.0227 (7) Å | µ = 0.10 mm−1 |
c = 26.723 (5) Å | T = 293 K |
β = 102.558 (4)° | Plate, orange |
V = 860.4 (2) Å3 | 0.55 × 0.37 × 0.07 mm |
Z = 2 |
Bruker SMART APEX CCD diffractometer | 1753 independent reflections |
Radiation source: fine-focus sealed tube | 1181 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.026 |
ω scans | θmax = 26.4°, θmin = 1.6° |
Absorption correction: multi-scan (APEX2; Bruker, 2008) | h = −8→7 |
Tmin = 0.955, Tmax = 0.993 | k = −6→6 |
4451 measured reflections | l = −31→33 |
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)] = 0.040 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.106 | H-atom parameters constrained |
S = 1.02 | w = 1/[σ2(Fo2) + (0.0467P)2 + 0.092P] where P = (Fo2 + 2Fc2)/3 |
1753 reflections | (Δ/σ)max < 0.001 |
127 parameters | Δρmax = 0.12 e Å−3 |
0 restraints | Δρmin = −0.18 e Å−3 |
C20H14N4O4 | V = 860.4 (2) Å3 |
Mr = 374.35 | Z = 2 |
Monoclinic, P21/c | Mo Kα radiation |
a = 6.567 (1) Å | µ = 0.10 mm−1 |
b = 5.0227 (7) Å | T = 293 K |
c = 26.723 (5) Å | 0.55 × 0.37 × 0.07 mm |
β = 102.558 (4)° |
Bruker SMART APEX CCD diffractometer | 1753 independent reflections |
Absorption correction: multi-scan (APEX2; Bruker, 2008) | 1181 reflections with I > 2σ(I) |
Tmin = 0.955, Tmax = 0.993 | Rint = 0.026 |
4451 measured reflections |
R[F2 > 2σ(F2)] = 0.040 | 0 restraints |
wR(F2) = 0.106 | H-atom parameters constrained |
S = 1.02 | Δρmax = 0.12 e Å−3 |
1753 reflections | Δρmin = −0.18 e Å−3 |
127 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 | ||
C1 | 0.0372 (2) | 1.1170 (3) | 0.37643 (6) | 0.0435 (4) | |
C2 | −0.1386 (2) | 1.1873 (4) | 0.39398 (7) | 0.0508 (4) | |
H2 | −0.1645 | 1.1065 | 0.4233 | 0.061* | |
C3 | −0.2753 (3) | 1.3746 (4) | 0.36876 (6) | 0.0501 (5) | |
H3 | −0.3942 | 1.4200 | 0.3805 | 0.060* | |
C4 | −0.2331 (2) | 1.4942 (3) | 0.32576 (6) | 0.0424 (4) | |
C5 | −0.0603 (3) | 1.4307 (4) | 0.30734 (6) | 0.0528 (5) | |
H5 | −0.0343 | 1.5142 | 0.2783 | 0.063* | |
C6 | 0.0740 (3) | 1.2408 (4) | 0.33280 (6) | 0.0529 (5) | |
H6 | 0.1915 | 1.1944 | 0.3206 | 0.063* | |
C7 | 0.1888 (3) | 0.9248 (3) | 0.40361 (6) | 0.0485 (4) | |
H7 | 0.3038 | 0.8836 | 0.3900 | 0.058* | |
C9 | 0.3384 (2) | 0.6540 (3) | 0.47115 (6) | 0.0403 (4) | |
C10 | 0.2953 (2) | 0.4366 (3) | 0.49885 (6) | 0.0467 (4) | |
H10 | 0.1574 | 0.3930 | 0.4985 | 0.056* | |
C11 | 0.5467 (2) | 0.7157 (3) | 0.47324 (6) | 0.0470 (4) | |
H11 | 0.5794 | 0.8628 | 0.4554 | 0.056* | |
N1 | −0.3757 (2) | 1.7008 (3) | 0.29970 (5) | 0.0503 (4) | |
N2 | 0.17115 (19) | 0.8119 (3) | 0.44468 (5) | 0.0455 (4) | |
O1 | −0.3319 (2) | 1.8127 (3) | 0.26298 (5) | 0.0696 (4) | |
O2 | −0.5305 (2) | 1.7529 (3) | 0.31623 (5) | 0.0688 (4) |
U11 | U22 | U33 | U12 | U13 | U23 | |
C1 | 0.0441 (9) | 0.0464 (10) | 0.0393 (8) | 0.0038 (8) | 0.0080 (7) | −0.0024 (8) |
C2 | 0.0479 (10) | 0.0577 (11) | 0.0498 (10) | 0.0031 (9) | 0.0176 (8) | 0.0108 (9) |
C3 | 0.0446 (9) | 0.0559 (11) | 0.0525 (10) | 0.0050 (8) | 0.0166 (8) | 0.0030 (9) |
C4 | 0.0455 (9) | 0.0420 (9) | 0.0375 (8) | 0.0028 (8) | 0.0045 (7) | −0.0018 (8) |
C5 | 0.0585 (11) | 0.0627 (12) | 0.0399 (9) | 0.0081 (9) | 0.0166 (8) | 0.0062 (9) |
C6 | 0.0502 (10) | 0.0677 (12) | 0.0442 (9) | 0.0149 (9) | 0.0180 (7) | 0.0037 (9) |
C7 | 0.0474 (9) | 0.0548 (11) | 0.0439 (9) | 0.0076 (8) | 0.0112 (7) | −0.0027 (9) |
C9 | 0.0400 (8) | 0.0414 (9) | 0.0402 (8) | 0.0049 (7) | 0.0101 (7) | −0.0019 (8) |
C10 | 0.0374 (8) | 0.0488 (10) | 0.0556 (10) | −0.0002 (8) | 0.0141 (7) | 0.0030 (9) |
C11 | 0.0454 (9) | 0.0453 (10) | 0.0522 (10) | −0.0005 (8) | 0.0145 (7) | 0.0093 (8) |
N1 | 0.0562 (9) | 0.0478 (9) | 0.0452 (8) | 0.0068 (7) | 0.0071 (7) | −0.0044 (7) |
N2 | 0.0419 (7) | 0.0451 (8) | 0.0487 (8) | 0.0037 (6) | 0.0083 (6) | 0.0025 (7) |
O1 | 0.0782 (9) | 0.0681 (9) | 0.0631 (8) | 0.0133 (8) | 0.0170 (7) | 0.0207 (8) |
O2 | 0.0664 (8) | 0.0756 (10) | 0.0667 (8) | 0.0288 (7) | 0.0195 (7) | 0.0009 (7) |
C1—C2 | 1.383 (2) | C7—N2 | 1.263 (2) |
C1—C6 | 1.388 (2) | C7—H7 | 0.9300 |
C1—C7 | 1.461 (2) | C9—C10 | 1.383 (2) |
C2—C3 | 1.372 (2) | C9—C11 | 1.392 (2) |
C2—H2 | 0.9300 | C9—N2 | 1.414 (2) |
C3—C4 | 1.377 (2) | C10—C11i | 1.371 (2) |
C3—H3 | 0.9300 | C10—H10 | 0.9300 |
C4—C5 | 1.369 (2) | C11—C10i | 1.371 (2) |
C4—N1 | 1.469 (2) | C11—H11 | 0.9300 |
C5—C6 | 1.375 (2) | N1—O1 | 1.2186 (18) |
C5—H5 | 0.9300 | N1—O2 | 1.2215 (18) |
C6—H6 | 0.9300 | ||
C2—C1—C6 | 118.76 (15) | C1—C6—H6 | 119.5 |
C2—C1—C7 | 121.91 (15) | N2—C7—C1 | 123.17 (15) |
C6—C1—C7 | 119.28 (15) | N2—C7—H7 | 118.4 |
C3—C2—C1 | 120.93 (16) | C1—C7—H7 | 118.4 |
C3—C2—H2 | 119.5 | C10—C9—C11 | 117.92 (15) |
C1—C2—H2 | 119.5 | C10—C9—N2 | 118.92 (14) |
C2—C3—C4 | 118.66 (16) | C11—C9—N2 | 123.05 (15) |
C2—C3—H3 | 120.7 | C11i—C10—C9 | 120.84 (15) |
C4—C3—H3 | 120.7 | C11i—C10—H10 | 119.6 |
C5—C4—C3 | 122.12 (16) | C9—C10—H10 | 119.6 |
C5—C4—N1 | 119.16 (15) | C10i—C11—C9 | 121.24 (15) |
C3—C4—N1 | 118.70 (15) | C10i—C11—H11 | 119.4 |
C4—C5—C6 | 118.44 (16) | C9—C11—H11 | 119.4 |
C4—C5—H5 | 120.8 | O1—N1—O2 | 123.61 (15) |
C6—C5—H5 | 120.8 | O1—N1—C4 | 118.02 (14) |
C5—C6—C1 | 121.08 (16) | O2—N1—C4 | 118.37 (15) |
C5—C6—H6 | 119.5 | C7—N2—C9 | 118.59 (14) |
C6—C1—C2—C3 | 0.4 (3) | C11—C9—C10—C11i | −1.1 (3) |
C7—C1—C2—C3 | 177.88 (16) | N2—C9—C10—C11i | −177.37 (15) |
C1—C2—C3—C4 | −0.7 (3) | C10—C9—C11—C10i | 1.1 (3) |
C2—C3—C4—C5 | 0.4 (3) | N2—C9—C11—C10i | 177.21 (15) |
C2—C3—C4—N1 | −178.05 (14) | C5—C4—N1—O1 | −1.5 (2) |
C3—C4—C5—C6 | 0.2 (3) | C3—C4—N1—O1 | 177.00 (15) |
N1—C4—C5—C6 | 178.67 (15) | C5—C4—N1—O2 | 179.13 (16) |
C4—C5—C6—C1 | −0.6 (3) | C3—C4—N1—O2 | −2.4 (2) |
C2—C1—C6—C5 | 0.3 (3) | C1—C7—N2—C9 | −172.48 (15) |
C7—C1—C6—C5 | −177.30 (16) | C10—C9—N2—C7 | −148.67 (16) |
C2—C1—C7—N2 | −0.5 (3) | C11—C9—N2—C7 | 35.2 (2) |
C6—C1—C7—N2 | 177.02 (16) |
Symmetry code: (i) −x+1, −y+1, −z+1. |
Experimental details
(I-1) | (I-2) | |
Crystal data | ||
Chemical formula | C20H14N4O4 | C20H14N4O4 |
Mr | 374.35 | 374.35 |
Crystal system, space group | Triclinic, P1 | Monoclinic, P21/c |
Temperature (K) | 173 | 293 |
a, b, c (Å) | 6.9357 (7), 7.3036 (7), 8.8768 (8) | 6.567 (1), 5.0227 (7), 26.723 (5) |
α, β, γ (°) | 73.295 (1), 82.707 (1), 88.071 (1) | 90, 102.558 (4), 90 |
V (Å3) | 427.20 (7) | 860.4 (2) |
Z | 1 | 2 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.11 | 0.10 |
Crystal size (mm) | 0.29 × 0.22 × 0.1 | 0.55 × 0.37 × 0.07 |
Data collection | ||
Diffractometer | Bruker SMART APEX CCD diffractometer | Bruker SMART APEX CCD diffractometer |
Absorption correction | Multi-scan (APEX2; Bruker, 2008) | Multi-scan (APEX2; Bruker, 2008) |
Tmin, Tmax | 0.973, 0.991 | 0.955, 0.993 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3748, 1731, 1496 | 4451, 1753, 1181 |
Rint | 0.018 | 0.026 |
(sin θ/λ)max (Å−1) | 0.625 | 0.625 |
Refinement | ||
R[F2 > 2σ(F2)], wR(F2), S | 0.042, 0.106, 1.08 | 0.040, 0.106, 1.02 |
No. of reflections | 1731 | 1753 |
No. of parameters | 127 | 127 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.20, −0.22 | 0.12, −0.18 |
Computer programs: APEX2 (Bruker, 2008), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 (Farrugia, 1997) and Mercury (Macrae et al., 2008), WinGX (Farrugia, 1999) and PLATON (Spek, 2009).
Polymorph (I-1) | Polymorph (I-2) | MUBTEJ | REGBEK | |
C2—C1—C7—N2/C8 | 12.3 (2) | -0.5 (3) | 9.5 (2) | -5.1 (4) |
C1—C7—N2/C8—C9 | -174.49 (13) | -172.48 (15) | 179.9 (1) | -178.4 (2) |
C11—C9—N2/C8—C7 | 43.7 (2) | 35.2 (2) | -177.6 (1) | -175.8 (2) |
Entry | D | X | A | Distance | Angle |
1 | C5 | H5 | O1i | 2.55 | 153 |
2 | Cg(A) | Cg(A)ii | 3.5212 (9) | 15.64 | |
3 | Cg(A) | Cg(A)iii | 3.5981 (9) | 24.53 | |
4 | C10 | H10 | O1ii | 2.52 | 155 |
5 | C6 | H6 | Cg(B)iv | 2.83 | 129 |
Entry | D | X | A | Distance | Angle |
1 | N1 | O1 | N1i | 2.982 (2) | 121.20 (11) |
2 | N1 | O1 | Cg(A)ii | 3.5301 (17) | 86.14 (10) |
3 | N1 | O2 | Cg(A)ii | 3.9359 (18) | 67.91 (9) |
4 | C6 | H6 | O1iii | 2.66 | 135 |
5 | C7 | H7 | O2iv | 2.54 | 152 |
Entry | D | X | A | Distance | Angle |
1 | Cg(A) | Cg(B)i | 3.8933 (11) | 29.52 | |
2 | C5 | H5 | Cg(A)ii | 2.764 (15) | 160.2 (13) |
3 | C6 | H6 | O1iii | 2.659 (15) | 146.0 (11) |
4 | C7 | H7 | O1iii | 2.419 (15) | 161.8 (12) |
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Oligomers of poly(p-phenylenevinylene) (PPV) and its isoelectronic counterpart poly(1,4-phenylenemethylidynenitrilo-1,4-phenylenenitrilomethylidyne) (PPI) constitute an interesting class of organic semiconductors, mainly because of the fact that these materials display useful opto-electronic properties. Using oligomers instead of polymers has proved to be a worthwhile endeavour, as the former are far more straightforward to produce, characterize and process than the latter (Müllen & Wegner, 1998). Also, such low-molecular-weight compounds can be subtly tailored to enhance the molecular properties desired for a specific application, by substituting them with functional groups such as electron donors and/or acceptors, thereby making optimal use of their potential as new materials for a variety of applications. However, since these materials are often used in the solid state, it is of equal importance to gain insight into their solid-state structures to correlate their structural characteristics with the experimentally determined opto-electronic properties of interest. In this paper, we present two conformational polymorphs of (E,E)-N,N'-bis(4-nitrobenzylidene)benzene-1,4-diamine, (I), a nitro-substituted PPI oligomer.
The first polymorph, (I-1), crystallizes in the triclinic space group P1 with one molecule per unit cell lying across a crystallographic inversion centre. Its central ring (B) is twisted out of the plane defined by the peripheral nitro-substituted aromatic ring (A) by 56.99 (7)° (Fig. 1); this is further illustrated by the torsion angles presented in Table 1. These twisted conformations are well known within this class of compounds and originate from electronic effects rather than from steric hindrance (Collas et al., 2011). The supramolecular structure of (I-1) is based on extended chains of molecules, generated by a mutual weak hydrogen bond involving the relatively acidic aromatic H5 atom and an O atom from the nitro group in the 4-position (Fig. 2 and Table 2, entry 1). π–π stacks of nitro-substituted rings extend along the direction of the a axis (Fig. 2 and Table 2, entries 2 and 3). Within these stacks, an additional weak hydrogen bond involving H10 of the central ring (C10—H10···O1) operates in the same direction (Fig. 2 and Table 2, entry 4). Finally, a mutual weak hydrogen bond, linking H6 to the π-system of the central ring, holds the stacks together (Fig. 3 and Table 2, entry 5). It is interesting to note that the most acidic H atom, H7, is not involved in the crystal packing.
The second polymorph, (I-2), crystallizes in the monoclinic space group P21/c with two molecules per unit cell lying across crystallographic inversion centres. In its structure one can also easily see that the central ring is twisted out of the plane of the peripheral one (Fig. 1), but to a lesser extent than for (I-1): the angle between the two planes through rings A and B is 36.29 (8)°. As can be seen from Table 1, the torsion angle τ(C11—C9—N2—C7) is the largest contributor to the twists in both structures. The crystal packing of (I-2) is quite different from that of (I-1), as contacts between the nitro groups dominate the supramolecular structure. A `T'-shaped contact between the partially positively charged N atom and the partially negatively charged O atom of the nitro groups results in a herringbone pattern (Fig. 4 and Table 3, entry 1). This type of stacking is reinforced by mutual N—O···π interactions (Fig. 4 and Table 3, entries 2 and 3). Further stacking of the molecules is achieved by two additional weak C—H···O hydrogen bonds involving H6 and H7 (Fig. 5 and Table 3, entries 4 and 5).
The distyrylbenzene (DSB) analogue of the title compounds, namely (E,E)-1,4-bis[2-(4-nitrophenyl)ethenyl]benzene, (II), originally reported by Pham [Pham, 2009; Cambridge Structural Database (CSD; Allen, 2002) refcode MUBTEJ], is quasi-planar with a dihedral angle of 11.86 (7)° between the planes through the peripheral and central rings. The previously reported dimethylformamide (DMF) solvate (Bartholomew et al., 2000; CSD refcode REGBEK) has a dihedral angle of only 2.29 (10)°, but as the solvent molecules interfere in the inter-oligomer contacts, we will only consider the crystal packing of MUBTEJ (Fig. 6). Here, π–π stacking is present but, unlike in the structure of (I-1), it occurs between the two different rings A and B (Table 4, entry 1), which leads to a photoreactive structure that may undergo a topochemical polymerization. Indeed, the distance between the vinyl spacers is 3.95 Å, which is smaller than the experimentally determined limit of 4.2 Å (Schmidt, 1971). Perpendicular to these photoreactive stacks, molecules are connected through three weak hydrogen bonds (Table 4, entries 2, 3 and 4): one in which an aromatic H atom, H5, contacts the π-system of ring A and two in which one of the O atoms of the nitro group, O2, acts as an acceptor for aromatic H atoms H6 and H7.
Thus, the three structures show completely different packing schemes. While in the structure of polymorph (I-1), the central ring B acts as an acceptor for an aromatic H atom, H6, and as a hydrogen-bond donor to a nitro group (C10—H10···O1, Table 2, entry 4), this ring does not take part in the crystal packing of (I-2). Beside the fact that (I-2) and (II) share the same space group, they also share two active sites on their carbon backbone: in both structures, atoms H6 and H7 are engaged in weak hydrogen bonds with the O atoms of the nitro groups. However, in the latter only one O atom is available, while in the former both O atoms are used as acceptor sites. The presence of the N atom in (I), which results in a twist of the central ring, precludes the possibility of closer stacking and, as a result, a photosensitive supramolecular structure based on π–π, as seen in (II), cannot be formed.