Two polymorphic forms of 2,5-bis-(4-methoxycarbonylphenyl)-1,3,4-oxadiazole

Article abstract of DOI:10.1107/S0108270103021413

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

Full text of DOI:10.1107/S0108270103021413

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
ISSN 0108-2701
Two polymorphic forms of 2,5-bis-
(
4-methoxycarbonylphenyl)-1,3,4-
Figure 1
The molecular structure of (I), showing 50% probability displacement
oxadiazole
ellipsoids (SHELXTL; Sheldrick, 1999). H-atom labels have been
1
a
b
b
omitted for clarity. [Symmetry code, for form 1: (i) 2 � x, y, � z; for
G uÈ nter Reck, * Ingo Orgzall, Burkhard Schulz and
2
form 2: (i) � x, y, z.]
b
Birgit Dietzel
a
Bundesanstalt f uÈ r Materialforschung und -pr uÈ fung, Richard-Willst aÈ tter-Straûe 11,
the angle between a phenyl ring and its methoxycarbonyl
ꢀ
b
D-12489 Berlin, Germany, and Universit aÈ t Potsdam, Am Neuen Palais 10,
group is 3.93 (9) . The corresponding angles in form 2 are
ꢀ
D-14469 Potsdam, Germany
8
.86 (9) and 7.58 (8) , respectively. However, in contrast to the
Correspondence e-mail: guenter.reck@bam.de
molecule of form 1, the molecule of form 2 adopts a slightly
bent shape. As shown in Fig. 2, the molecules in form 1 build
up a herring-bone structure, with stacks extending along the a
direction. Within the stacks, there are strong ꢀ±ꢀ interactions
Received 18 September 2003
Accepted 29 September 2003
Online 22 October 2003
between adjacent molecular planes related by a translations.
o
0
The title compound [systematic name: dimethyl 4,4 -(1,3,4-
oxadiazole-2,5-diyl)diphenylenedicarboxylate], C H N O ,
The ®rst plane formed by all of the non-H atoms of the mol-
ecule is de®ned by the equation 3.3409x � 0.0y + 18.7644z =
1
8
14
2
5
Ê
8.0320, with an r.m.s. deviation of 0.0547 A. The equation of
crystallizes under similar conditions in two different ortho-
rhombic 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
the corresponding translated plane is 3.3409x � 0.0y +
18.7644z = 11.3730. The distance between the two planes is
Ê
3.341 (3) A. The molecular packing of form 2 is shown in Fig. 2.
plane of space group Cmc2 . The O atom of the oxadiazole
1
ring occupies a special position on the twofold axis and on the
mirror plane in forms 1 and 2, respectively.
Comment
Compounds containing a 1,3,4-oxadiazole ring as a basic
building block are known as scintillator materials and as
biologically active agents. Modi®cations of the chemical
structures of these compounds open up possibilities for new
technical applications, for instance, as potential electro-
luminiscent materials or as active sensor materials. In addition,
the optical properties of these compounds should be taken
into account, such as their potential for non-linear processes.
In particular, polymers of 1,3,4-oxadiazoles exhibit interesting
properties, including high thermal resistivity, good environ-
mental stability, doping potential and mechanical toughness.
The title compound, (I), crystallizes in two different
orthorhombic crystalline forms (Fig. 1). The molecule of form
1 is nearly planar; the dihedral angle between the central 1,3,4-
ꢀ
oxadiazole ring and each of the phenyl rings is 4.64 (9) , and
Figure 2
The molecular packing in form 1 (top) and form 2 (bottom).
o634 # 2003 International Union of Crystallography
DOI: 10.1107/S0108270103021413
Acta Cryst. (2003). C59, o634±o635

organic compounds
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
Form 2 of (I)
Crystal data
C
18
14
H N
O
2 5
Mo Kꢁ radiation
Cell parameters from 25
re¯ections
r
M = 338.31
Orthorhombic, Cmc21
ꢀ
plane is 23.19 (3) . The equations of the corresponding planes
are 0.0x + 6.8316y + 1.2121z = 1.604 and 0.0x � 6.8316y +
Ê
a = 36.708 (4) A
b = 6.9740 (10) A
ꢀ
ꢂ = 12±21
Ê
Ê
� 1
ꢃ = 0.11 mm
T = 293 (2) K
1
0
.2121z = 2.2101. The r.m.s. deviation about each plane is
Ê
.1689 A.
c = 6.0300 (10) A
Ê
V = 1543.7 (4) A
3
Needle, colourless
0.39 Â 0.11 Â 0.10 mm
Z = 4
�
3
D
x
= 1.456 Mg m
Experimental
Data collection
A mixture of dimethyl terephthalate (19.5 g) and hydrazine hydrate
(5.57 g) was re¯uxed in methanol (500 ml) for 6 h. The resulting
Enraf±Nonius CAD-4
diffractometer
2ꢂ±! scans
h = 0 ! 43
k = 0 ! 8
precipitate, viz. methyl terephthalate monohydrazide, was ®ltered
off, dried and re¯uxed twice in chloroform (100 ml). The terephtha-
late monohydrazide (3 g) was stirred in absolute pyridine (50 ml),
and methyl terephthalate chloride (3.07 g) in absolute tetra-
hydrofuran was added dropwise. The reaction mixture was stirred for
l = � 7 ! 7
1
1
1
ꢂ
377 measured re¯ections
377 independent re¯ections
058 re¯ections with I > 2ꢄ(I)
3 standard re¯ections
frequency: 120 min
intensity decay: 0.3%
ꢀ
max = 25.0
Re®nement
6
h at room temperature and then poured into a solution of water
600 ml) and HCl (50 ml, 37%). The pH of the solution was corrected
2
2
2
2
(
Re®nement on F
2
w = 1/[ꢄ (F
where P = (F + 2F )/3
) + (0.0379P) ]
o
2
2
2
R[F > 2ꢄ(F )] = 0.034
wR(F ) = 0.089
S = 0.98
to 5, and the precipitated solid product, viz. bis(4-methoxy-
carbonylbenzoyl)hydrazine, was ®ltered off, washed several times
with water and dried. Bis(4-methoxycarbonylbenzoyl)hydrazine
o
c
2
(Á/ꢄ)max = 0.017
Áꢅmax = 0.25 e A
Ê
� 3
Ê
� 3
1377 re¯ections
116 parameters
H-atom parameters constrained
Áꢅmin = � 0.16 e A
(4.8 g) was suspended in phosphoric acid chloride (50 ml) and a few
Extinction correction: SHELXL97
Extinction coef®cient: 0.0059 (6)
drops of dimethylformamide (DMF) were added. The mixture was
re¯uxed for 18 h and the product was precipitated in ice water. The
title compound 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 re®ned using a riding model.
Form 1 of (I)
Crystal data
For both forms of (I), data collection: CAD-4 Software (Enraf±
Nonius, 1977); cell re®nement: CAD-4 Software; data reduction:
MolEN (Fair, 1990); program(s) used to solve structure: SHELXS97
(Sheldrick, 1990); program(s) used to re®ne structure: SHELXL97
C
18
H
14
N
2
O
5
Mo Kꢁ radiation
Cell parameters from 25
re¯ections
r
M = 338.31
Orthorhombic, Pbcn
Ê
a = 4.7350 (10) A
b = 12.516 (2) A
c = 26.480 (3) A
Ê
V = 1569.3 (5) A
Z = 4
D
ꢀ
ꢂ = 12±20
ꢃ = 0.11 mm
T = 293 (2) K
Ê
Ê
� 1
(Sheldrick, 1997); molecular graphics: SHELXTL-NT (Sheldrick,
3
1999); software used to prepare material for publication:
SHELXL97.
Needle, colourless
0.42 Â 0.13 Â 0.11 mm
�
3
x
= 1.432 Mg m
The authors cordially thank Mrs G. Bannier for technical
assistance.
Data collection
Enraf±Nonius CAD-4
diffractometer
h = 0 ! 5
k = 0 ! 14
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: NA1617). Services for accessing these data are
described at the back of the journal.
2
1
1
1
ꢂ
ꢂ±! scans
l = 0 ! 31
394 measured re¯ections
394 independent re¯ections
052 re¯ections with I > 2ꢄ(I)
3 standard re¯ections
frequency: 120 min
intensity decay: 0.5%
ꢀ
max = 25.0
References
Re®nement
Enraf±Nonius (1977). CAD-4 Software. Enraf±Nonius, Delft, The Nether-
lands.
Fair, C. K. (1990). MolEN. Enraf±Nonius, Delft, The Netherlands.
Flack, H. D. (1983). Acta Cryst. A39, 876±881.
Sheldrick, G. M. (1990). Acta Cryst. A46, 467±473.
Sheldrick, G. M. (1997). SHELXL97. University of G oÈ ttingen, Germany.
Sheldrick, G. M. (1999). SHELXTL-NT. Version 5.10. Bruker AXS Inc.,
Madison, Wisconsin, USA.
2
2
2
2
Re®nement on F
2
w = 1/[ꢄ (F ) + (0.1156P) ]
o
2
2
2
R[F > 2ꢄ(F )] = 0.050
wR(F ) = 0.164
S = 1.10
where P = (Fo + 2F )/3
(Á/ꢄ)max = 0.024
Áꢅmax = 0.40 e A
c
2
Ê
� 3
Ê
� 3
1
1
394 re¯ections
15 parameters
Áꢅmin = � 0.39 e A
Extinction correction: SHELXL97
Extinction coef®cient: 0.0065 (6)
H-atom parameters constrained
ꢁ
Acta Cryst. (2003). C59, o634±o635
G uÈ nter Reck et al.
C H
18 14
N O
2 5
o635