The title compound [systematic name: dimethyl 4,4'-(1,3,4-oxadiazole-2,5-diyl)diphenylenedicarboxylate], C18H14N2O5, crystallizes under similar conditions in two different orthorhombic crystalline forms. In both forms, the molecule consists of two equivalent parts. In form 1, these parts are related by a twofold axis of space group Pbcn, and in form 2, by a mirror plane of space group Cmc21. The O atom of the oxadiazole ring occupies a special position on the twofold axis and on the mirror plane in forms 1 and 2, respectively.
Supporting information
CCDC references: 152146; 152148
A mixture of terephthalic dimethylester (19.5 g) and hydrazine hydrate (5.57 g) was refluxed in methanol (500 ml) for 6 h. The resulting precipitate, viz. therephthalic acid monomethylester monohydrazide, was filtered, dried and refluxed twice in chloroform (100 ml). Therephthalic acid monomethylester monohydrazide (3 g) was stirred in absolute pyridine (50 ml) and therephthalic acid monomethylester chloride (3.07 g) in absolute THF was added dropwise. The reaction mixture was stirred for 6 h at room temperature and then poured in to a solution of water (600 ml) and HCl (50 ml, 37%). The pH value of the solution was corrected to 5, and the precipitated solid product, viz. di-(4-methoxycarbonylbenzol)-hydrazine, was filtered, washed several times with water and dried. Di-(4-methoxycarbonylbenzoyl)-hydrazine (4.8 g) was suspended in phosphoric acid chloride (50 ml) and some drops of DMF were added. The mixture was refluxed for 18 h and preciptated in ice water. The resulting 2,5-di-(4-methoxycarbonyl)-1,3,4-oxadiazole was recrystallized from DMF/ethanol (9:1) giving two different crystalline forms as mentioned above.
In the two crystalline forms of (I), the molecules consist of two equivalent parts, which are related by a twofold axis and by a mirror plane in forms 1 and 2, respectively. The O atoms of the oxadiazole rings occupy special positions. H atom positions were calculated geometrically and refined using a riding model.
Data collection: CAD-4 Software (Enraf–Nonius, 1977) for (I); CAD-4 (Enraf–Nonius, 1977) for (II). For both compounds, cell refinement: CAD-4; data reduction: MolEN (Fair, 1990); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL-NT (Sheldrick, 1999); software used to prepare material for publication: SHELXL97.
(I) dimethyl 4,4'-(1,3,4-oxadiazole-2,5-diyl)diphenylenedicarboxylate
top
Crystal data top
C18H14N2O5 | Dx = 1.432 Mg m−3 |
Mr = 338.31 | Mo Kα radiation, λ = 0.71069 Å |
Orthorhombic, Pbcn | Cell parameters from 25 reflections |
a = 4.735 (1) Å | θ = 12–20° |
b = 12.516 (2) Å | µ = 0.11 mm−1 |
c = 26.480 (3) Å | T = 293 K |
V = 1569.3 (5) Å3 | Needle, colourless |
Z = 4 | 0.42 × 0.13 × 0.11 mm |
F(000) = 704 | |
Data collection top
Enraf–Nonius CAD-4 diffractometer | Rint = 0.000 |
Radiation source: fine-focus sealed tube | θmax = 25.0°, θmin = 3.1° |
Graphite monochromator | h = 0→5 |
2θ–ω scans | k = 0→14 |
1394 measured reflections | l = 0→31 |
1394 independent reflections | 3 standard reflections every 120 min |
1052 reflections with I > 2σ(I) | intensity decay: 0.5% |
Refinement top
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)] = 0.050 | H-atom parameters constrained |
wR(F2) = 0.164 | w = 1/[σ2(Fo2) + (0.1156P)2] where P = (Fo2 + 2Fc2)/3 |
S = 1.10 | (Δ/σ)max = 0.024 |
1394 reflections | Δρmax = 0.40 e Å−3 |
115 parameters | Δρmin = −0.39 e Å−3 |
30 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0065 (6) |
Crystal data top
C18H14N2O5 | V = 1569.3 (5) Å3 |
Mr = 338.31 | Z = 4 |
Orthorhombic, Pbcn | Mo Kα radiation |
a = 4.735 (1) Å | µ = 0.11 mm−1 |
b = 12.516 (2) Å | T = 293 K |
c = 26.480 (3) Å | 0.42 × 0.13 × 0.11 mm |
Data collection top
Enraf–Nonius CAD-4 diffractometer | Rint = 0.000 |
1394 measured reflections | 3 standard reflections every 120 min |
1394 independent reflections | intensity decay: 0.5% |
1052 reflections with I > 2σ(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.050 | 30 restraints |
wR(F2) = 0.164 | H-atom parameters constrained |
S = 1.10 | Δρmax = 0.40 e Å−3 |
1394 reflections | Δρmin = −0.39 e Å−3 |
115 parameters | |
Special details top
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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
O1 | 1.0000 | 0.36375 (14) | 0.2500 | 0.0362 (5) | |
O12 | −0.1000 (4) | 0.33040 (14) | 0.44691 (6) | 0.0588 (5) | |
O13 | 0.0266 (4) | 0.16457 (12) | 0.42257 (5) | 0.0512 (5) | |
N3 | 0.8955 (4) | 0.53195 (13) | 0.26846 (7) | 0.0453 (5) | |
C2 | 0.8406 (4) | 0.43110 (15) | 0.27771 (7) | 0.0372 (5) | |
C6 | 0.6358 (4) | 0.38895 (14) | 0.31382 (6) | 0.0324 (5) | |
C7 | 0.4895 (4) | 0.45633 (16) | 0.34545 (8) | 0.0417 (5) | |
H1 | 0.5228 | 0.5295 | 0.3439 | 0.050* | |
C8 | 0.2954 (5) | 0.41755 (17) | 0.37919 (8) | 0.0413 (5) | |
H2 | 0.1946 | 0.4646 | 0.3995 | 0.050* | |
C9 | 0.2484 (4) | 0.30767 (14) | 0.38315 (7) | 0.0381 (5) | |
C10 | 0.3999 (5) | 0.23987 (13) | 0.35125 (7) | 0.0391 (5) | |
H3 | 0.3702 | 0.1665 | 0.3534 | 0.047* | |
C11 | 0.5907 (4) | 0.27827 (15) | 0.31699 (6) | 0.0375 (5) | |
H4 | 0.6893 | 0.2317 | 0.2961 | 0.045* | |
C12 | 0.0387 (4) | 0.27178 (16) | 0.42063 (7) | 0.0396 (5) | |
C13 | −0.1667 (7) | 0.1217 (2) | 0.45906 (10) | 0.0653 (8) | |
H5 | −0.3006 | 0.0762 | 0.4424 | 0.078* | |
H6 | −0.2647 | 0.1792 | 0.4755 | 0.078* | |
H7 | −0.0640 | 0.0811 | 0.4837 | 0.078* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0496 (12) | 0.0218 (9) | 0.0371 (10) | 0.000 | 0.0055 (8) | 0.000 |
O12 | 0.0689 (11) | 0.0528 (9) | 0.0546 (10) | 0.0066 (8) | 0.0044 (8) | −0.0098 (8) |
O13 | 0.0694 (11) | 0.0398 (9) | 0.0443 (9) | −0.0056 (7) | 0.0114 (7) | −0.0015 (7) |
N3 | 0.0536 (11) | 0.0274 (8) | 0.0549 (11) | 0.0016 (7) | 0.0055 (9) | −0.0005 (7) |
C2 | 0.0451 (9) | 0.0306 (9) | 0.0358 (9) | 0.0019 (7) | −0.0059 (8) | −0.0022 (7) |
C6 | 0.0375 (9) | 0.0302 (9) | 0.0296 (9) | 0.0005 (7) | −0.0013 (7) | −0.0064 (6) |
C7 | 0.0546 (13) | 0.0273 (9) | 0.0433 (10) | −0.0002 (8) | −0.0022 (8) | −0.0052 (8) |
C8 | 0.0489 (11) | 0.0360 (10) | 0.0391 (10) | 0.0087 (9) | −0.0007 (7) | −0.0100 (8) |
C9 | 0.0487 (11) | 0.0214 (9) | 0.0444 (11) | −0.0044 (7) | −0.0062 (8) | −0.0027 (7) |
C10 | 0.0551 (13) | 0.0207 (8) | 0.0415 (10) | −0.0006 (8) | −0.0030 (8) | −0.0067 (7) |
C11 | 0.0498 (12) | 0.0280 (9) | 0.0347 (10) | −0.0009 (8) | 0.0005 (7) | −0.0018 (7) |
C12 | 0.0432 (10) | 0.0389 (10) | 0.0366 (10) | −0.0057 (8) | −0.0054 (7) | −0.0050 (8) |
C13 | 0.0781 (17) | 0.0577 (15) | 0.0601 (16) | −0.0132 (13) | 0.0098 (14) | 0.0054 (12) |
Geometric parameters (Å, º) top
O1—C2i | 1.349 (2) | C7—H1 | 0.9300 |
O1—C2 | 1.349 (2) | C8—C9 | 1.397 (3) |
O12—C12 | 1.206 (3) | C8—H2 | 0.9300 |
O13—C12 | 1.344 (2) | C9—C10 | 1.396 (3) |
O13—C13 | 1.435 (3) | C9—C12 | 1.474 (3) |
N3—C2 | 1.312 (3) | C10—C11 | 1.368 (3) |
N3—N3i | 1.391 (4) | C10—H3 | 0.9300 |
C2—C6 | 1.460 (3) | C11—H4 | 0.9300 |
C6—C7 | 1.376 (3) | C13—H5 | 0.9600 |
C6—C11 | 1.404 (2) | C13—H6 | 0.9600 |
C7—C8 | 1.370 (3) | C13—H7 | 0.9600 |
| | | |
C2i—O1—C2 | 102.6 (2) | C8—C9—C12 | 117.25 (18) |
C12—O13—C13 | 115.21 (18) | C11—C10—C9 | 121.82 (17) |
C2—N3—N3i | 105.79 (12) | C11—C10—H3 | 119.1 |
N3—C2—O1 | 112.89 (18) | C9—C10—H3 | 119.1 |
N3—C2—C6 | 126.98 (18) | C10—C11—C6 | 119.13 (18) |
O1—C2—C6 | 120.13 (17) | C10—C11—H4 | 120.4 |
C7—C6—C11 | 119.45 (18) | C6—C11—H4 | 120.4 |
C7—C6—C2 | 120.77 (17) | O12—C12—O13 | 124.2 (2) |
C11—C6—C2 | 119.78 (17) | O12—C12—C9 | 124.76 (19) |
C8—C7—C6 | 121.16 (18) | O13—C12—C9 | 111.01 (17) |
C8—C7—H1 | 119.4 | O13—C13—H5 | 109.5 |
C6—C7—H1 | 119.4 | O13—C13—H6 | 109.5 |
C7—C8—C9 | 120.30 (19) | H5—C13—H6 | 109.5 |
C7—C8—H2 | 119.8 | O13—C13—H7 | 109.5 |
C9—C8—H2 | 119.8 | H5—C13—H7 | 109.5 |
C10—C9—C8 | 118.11 (19) | H6—C13—H7 | 109.5 |
C10—C9—C12 | 124.64 (18) | | |
Symmetry code: (i) −x+2, y, −z+1/2. |
(II) dimethyl 4,4'-(1,3,4-oxadiazole-2,5-diyl)diphenylenedicarboxylate
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Crystal data top
C18H14N2O5 | Dx = 1.456 Mg m−3 |
Mr = 338.31 | Mo Kα radiation, λ = 0.71069 Å |
Orthorhombic, Cmc21 | Cell parameters from 25 reflections |
a = 36.708 (4) Å | θ = 12–21° |
b = 6.974 (1) Å | µ = 0.11 mm−1 |
c = 6.030 (1) Å | T = 293 K |
V = 1543.7 (4) Å3 | Needle, colourless |
Z = 4 | 0.39 × 0.11 × 0.10 mm |
F(000) = 704 | |
Data collection top
Enraf-Nonius CAD-4 diffractometer | Rint = 0.000 |
Radiation source: fine-focus sealed tube | θmax = 25.0°, θmin = 2.2° |
Graphite monochromator | h = 0→43 |
2θ–ω scans | k = 0→8 |
1377 measured reflections | l = −7→7 |
1377 independent reflections | 3 standard reflections every 120 min |
1058 reflections with I > \2s(I) | intensity decay: 0.3% |
Refinement top
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)] = 0.034 | H-atom parameters constrained |
wR(F2) = 0.089 | w = 1/[σ2(Fo2) + (0.0379P)2] where P = (Fo2 + 2Fc2)/3 |
S = 0.98 | (Δ/σ)max = 0.017 |
1377 reflections | Δρmax = 0.25 e Å−3 |
116 parameters | Δρmin = −0.16 e Å−3 |
31 restraints | Extinction correction: SHELXL97, Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0059 (6) |
Crystal data top
C18H14N2O5 | V = 1543.7 (4) Å3 |
Mr = 338.31 | Z = 4 |
Orthorhombic, Cmc21 | Mo Kα radiation |
a = 36.708 (4) Å | µ = 0.11 mm−1 |
b = 6.974 (1) Å | T = 293 K |
c = 6.030 (1) Å | 0.39 × 0.11 × 0.10 mm |
Data collection top
Enraf-Nonius CAD-4 diffractometer | Rint = 0.000 |
1377 measured reflections | 3 standard reflections every 120 min |
1377 independent reflections | intensity decay: 0.3% |
1058 reflections with I > \2s(I) | |
Refinement top
R[F2 > 2σ(F2)] = 0.034 | 31 restraints |
wR(F2) = 0.089 | H-atom parameters constrained |
S = 0.98 | Δρmax = 0.25 e Å−3 |
1377 reflections | Δρmin = −0.16 e Å−3 |
116 parameters | |
Special details top
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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
O1 | 0.0000 | 0.2528 (4) | 0.0020 (4) | 0.0350 (7) | |
O12 | 0.20010 (6) | 0.2069 (4) | −0.0760 (5) | 0.0630 (9) | |
O13 | 0.17827 (5) | 0.3043 (4) | −0.3968 (3) | 0.0520 (8) | |
N3 | 0.01894 (8) | 0.1836 (4) | 0.3356 (5) | 0.0525 (7) | |
C2 | 0.02934 (7) | 0.2248 (4) | 0.1368 (4) | 0.0356 (7) | |
C6 | 0.06595 (7) | 0.2393 (5) | 0.0478 (5) | 0.0350 (6) | |
C7 | 0.09463 (8) | 0.1797 (5) | 0.1843 (6) | 0.0380 (7) | |
H7 | 0.0901 | 0.1333 | 0.3263 | 0.049* | |
C8 | 0.12983 (8) | 0.1913 (4) | 0.1035 (4) | 0.0382 (7) | |
H8 | 0.1493 | 0.1535 | 0.1924 | 0.050* | |
C9 | 0.13627 (7) | 0.2584 (5) | −0.1077 (5) | 0.0331 (6) | |
C10 | 0.10806 (7) | 0.3159 (4) | −0.2411 (6) | 0.0367 (7) | |
H10 | 0.1127 | 0.3616 | −0.3831 | 0.048* | |
C11 | 0.07235 (8) | 0.3056 (4) | −0.1635 (5) | 0.0347 (7) | |
H11 | 0.0531 | 0.3431 | −0.2536 | 0.045* | |
C12 | 0.17562 (7) | 0.2568 (5) | −0.1847 (5) | 0.0399 (8) | |
C13 | 0.21456 (10) | 0.2924 (5) | −0.4880 (8) | 0.0610 (10) | |
H131 | 0.2141 | 0.3305 | −0.6410 | 0.079* | |
H132 | 0.2232 | 0.1629 | −0.4768 | 0.079* | |
H133 | 0.2305 | 0.3760 | −0.4068 | 0.079* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0364 (15) | 0.0407 (14) | 0.0280 (16) | 0.000 | 0.000 | −0.0014 (14) |
O12 | 0.0435 (15) | 0.0786 (19) | 0.0670 (18) | 0.0056 (14) | −0.0077 (14) | 0.0044 (14) |
O13 | 0.0432 (15) | 0.0585 (16) | 0.0541 (16) | −0.0035 (10) | 0.0007 (11) | 0.0014 (12) |
N3 | 0.0430 (14) | 0.0658 (17) | 0.0488 (17) | 0.0060 (14) | 0.0010 (13) | −0.0017 (15) |
C2 | 0.0267 (15) | 0.0444 (16) | 0.0357 (17) | 0.0008 (13) | −0.0035 (11) | −0.0022 (14) |
C6 | 0.0333 (13) | 0.0384 (13) | 0.0332 (14) | −0.0022 (10) | −0.0019 (12) | −0.0020 (14) |
C7 | 0.0388 (16) | 0.0383 (15) | 0.0368 (19) | −0.0014 (12) | −0.0009 (12) | 0.0011 (13) |
C8 | 0.0385 (16) | 0.0389 (18) | 0.0372 (18) | 0.0056 (13) | −0.0044 (13) | 0.0038 (12) |
C9 | 0.0286 (15) | 0.0339 (12) | 0.0369 (16) | 0.0023 (11) | −0.0019 (12) | −0.0012 (14) |
C10 | 0.0343 (15) | 0.0397 (14) | 0.0362 (16) | −0.0028 (13) | −0.0017 (13) | 0.0068 (14) |
C11 | 0.0339 (16) | 0.0371 (14) | 0.0332 (17) | 0.0002 (13) | −0.0007 (12) | 0.0034 (12) |
C12 | 0.0339 (18) | 0.0405 (19) | 0.0454 (18) | −0.0011 (12) | 0.0089 (13) | −0.0014 (17) |
C13 | 0.060 (2) | 0.061 (2) | 0.062 (3) | 0.0019 (14) | 0.016 (2) | −0.004 (2) |
Geometric parameters (Å, º) top
O1—C2 | 1.363 (3) | C7—H7 | 0.9300 |
O1—C2i | 1.363 (3) | C8—C9 | 1.377 (4) |
O12—C12 | 1.165 (4) | C8—H8 | 0.9300 |
O13—C12 | 1.325 (4) | C9—C10 | 1.371 (4) |
O13—C13 | 1.444 (4) | C9—C12 | 1.517 (4) |
N3—C2 | 1.290 (4) | C10—C11 | 1.394 (4) |
N3—N3i | 1.391 (6) | C10—H10 | 0.9300 |
C2—C6 | 1.451 (4) | C11—H11 | 0.9300 |
C6—C11 | 1.375 (4) | C13—H131 | 0.9600 |
C6—C7 | 1.400 (4) | C13—H132 | 0.9600 |
C7—C8 | 1.383 (4) | C13—H133 | 0.9600 |
| | | |
C2—O1—C2i | 104.4 (3) | C8—C9—C12 | 116.4 (3) |
C12—O13—C13 | 114.9 (3) | C9—C10—C11 | 119.9 (3) |
C2—N3—N3i | 107.19 (19) | C9—C10—H10 | 120.1 |
N3—C2—O1 | 110.6 (3) | C11—C10—H10 | 120.1 |
N3—C2—C6 | 129.3 (3) | C6—C11—C10 | 119.3 (3) |
O1—C2—C6 | 120.1 (2) | C6—C11—H11 | 120.4 |
C11—C6—C7 | 121.1 (3) | C10—C11—H11 | 120.4 |
C11—C6—C2 | 121.6 (2) | O12—C12—O13 | 124.1 (3) |
C7—C6—C2 | 117.3 (3) | O12—C12—C9 | 124.4 (3) |
C8—C7—C6 | 118.6 (3) | O13—C12—C9 | 111.3 (3) |
C8—C7—H7 | 120.7 | O13—C13—H131 | 109.5 |
C6—C7—H7 | 120.7 | O13—C13—H132 | 109.5 |
C9—C8—C7 | 120.4 (3) | H131—C13—H132 | 109.5 |
C9—C8—H8 | 119.8 | O13—C13—H133 | 109.5 |
C7—C8—H8 | 119.8 | H131—C13—H133 | 109.5 |
C10—C9—C8 | 120.8 (3) | H132—C13—H133 | 109.5 |
C10—C9—C12 | 122.8 (3) | | |
Symmetry code: (i) −x, y, z. |
Experimental details
| (I) | (II) |
Crystal data |
Chemical formula | C18H14N2O5 | C18H14N2O5 |
Mr | 338.31 | 338.31 |
Crystal system, space group | Orthorhombic, Pbcn | Orthorhombic, Cmc21 |
Temperature (K) | 293 | 293 |
a, b, c (Å) | 4.735 (1), 12.516 (2), 26.480 (3) | 36.708 (4), 6.974 (1), 6.030 (1) |
V (Å3) | 1569.3 (5) | 1543.7 (4) |
Z | 4 | 4 |
Radiation type | Mo Kα | Mo Kα |
µ (mm−1) | 0.11 | 0.11 |
Crystal size (mm) | 0.42 × 0.13 × 0.11 | 0.39 × 0.11 × 0.10 |
|
Data collection |
Diffractometer | Enraf–Nonius CAD-4 diffractometer | Enraf-Nonius CAD-4 diffractometer |
Absorption correction | – | – |
No. of measured, independent and observed reflections | 1394, 1394, 1052 [I > 2σ(I)] | 1377, 1377, 1058 [I > \2s(I)] |
Rint | 0.000 | 0.000 |
(sin θ/λ)max (Å−1) | 0.596 | 0.596 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.050, 0.164, 1.10 | 0.034, 0.089, 0.98 |
No. of reflections | 1394 | 1377 |
No. of parameters | 115 | 116 |
No. of restraints | 30 | 31 |
H-atom treatment | H-atom parameters constrained | H-atom parameters constrained |
Δρmax, Δρmin (e Å−3) | 0.40, −0.39 | 0.25, −0.16 |
Compounds containing a 1,3,4-oxadiazole ring as a basic building block are known as scintillator materials or as biologically active agents. Modifications of their chemical structures open up possibilities for new technical applications, for instance, as potential electroluminiscent materials or as active sensor materials. In addition, their optical properties should be taken into account, such as their potential for non-linear processes. In particular, polymers of 1,3,4-oxadiazoles show interesting properties, including high thermal resistivity, good environmental stability, doping possibility or mechanical toughness. The molecule in form 1 of the title compound, (I), is nearly planar. The dihedral angle between the central 1,3,4-oxadiazol ring and the phenyl ring is 4.64 (9)o. The angle between the phenyl ring and the methoxycarbonyl group is 3.93 (9)°. The corresponding angles in form 2 are 8.86 (9) and 7.58 (8)°, respectively. However, in contrast to the molecule of form 1, the molecule of form 2 adopts a slightly bent shape. As shown in Fig. 2 (top), the molecules in form 1 build up a herring-bone structure, with stacks extended along the x direction. Within the stacks, there are strong π–π interactions between adjacent molecular planes related by ao translation. The first plane formed by all of the non-H atoms of the molecule is defined by the equation 3.3409x − 0.0y + 18.7644z = 8.0320, with an r.m.s. deviation of 0.0547 Å. The equation of the corresponding translated plane is 3.3409x − 0.0y + 18.7644z = 11.3730. The distance between the two planes is 3.341 (3) Å. The molecular packing of form 2 is shown in Fig. 2 (bottom). The packing is unlike that of form 1 in that no stacking interactions are found in form 2, as there are no molecules arranged parallel to one another. The angle between the planes of two neighbouring molecules related by a c-glide plane is 23.19 (3)°. The equations of the correponding planes are 0.0x + 6.8316y + 1.2121z = 1.604 and 0.0x − 6.8316y + 1.2121z = 2.2101. The r.m.s. deviation above each? plane is 0.1689 Å.