(E)-4-[2-(3,4,5-Trimethoxyphenyl)-ethenyl]nitrobenzene and its 'bridgeflipped' analogues

Article abstract of DOI:10.1107/S0108270111030952

The solid-state structures of three push-pull acceptor-π-donor (A-π-D) systems differing only in the nature of the π-spacer have been determined. (E)-1-Nitro-4-[2-(3,4,5-trimethoxyphenyl)ethenyl]benzene, C ₁₇H₁₇NO₅, (I), and its 'bridgeflipped' imine analogues, (E)-3,4,5-trimethoxyN-(4-nitrobenzylidene)aniline, C ₁₆H₁₆N₂O₅, (II), and (E)-4-nitro-N-(3,4,5-trimeth-oxy-benzyl-idene)aniline, C₁₆H ₁₆N₂O₅, (III), display different kinds of supramolecular networks, viz. corrugated planes, a herringbone pattern and a layered structure, respectively, all with zero overall dipole moments. Only (III) crystallizes in a noncentrosymmetric space group (P2₁2 12 ₁) and is, therefore, a potential material for second-harmonic generation (SHG).

Full text of DOI:10.1107/S0108270111030952

organic compounds
Acta Crystallographica Section C
Crystal Structure
Communications
Push–pull acceptor-ꢀ-donor (A-ꢀ-D) systems are of parti-
cular interest in this context because of their superior charge-
transfer-related nonlinear electrical and optical properties,
such as the electro-optic effect (EO) and second-harmonic
generation (SHG). Unfortunately, the large molecular dipoles
associated with such push–pull systems usually lead to
centrosymmetric organization of the molecules in the crystal
structure, annihilating bulk second-order optical effects such
as SHG. It has been suggested that whether or not an asym-
metric dipolar BA crystallizes centrosymmetrically is largely
dependent on the molecular planarity, which may be directly
ISSN 0108-2701
(E)-4-[2-(3,4,5-Trimethoxyphenyl)-
ethenyl]nitrobenzene and its ‘bridge-
flipped’ analogues
Alain Collas and Frank Blockhuys*
Department of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610
Antwerp, Belgium
Correspondence e-mail: frank.blockhuys@ua.ac.be
Received 5 July 2011
Accepted 1 August 2011
Online 17 August 2011
The solid-state structures of three push–pull acceptor-ꢀ-donor
(A-ꢀ-D) systems differing only in the nature of the ꢀ-spacer
have been determined. (E)-1-Nitro-4-[2-(3,4,5-trimethoxy-
phenyl)ethenyl]benzene, C17H17NO5, (I), and its ‘bridge-
flipped’ imine analogues, (E)-3,4,5-trimethoxy-N-(4-nitro-
benzylidene)aniline, C16H16N2O5, (II), and (E)-4-nitro-N-
(3,4,5-trimethoxybenzylidene)aniline, C16H16N2O5, (III), dis-
play different kinds of supramolecular networks, viz. corru-
gated planes, a herringbone pattern and a layered structure,
respectively, all with zero overall dipole moments. Only (III)
crystallizes in a noncentrosymmetric space group (P212121)
and is, therefore, a potential material for second-harmonic
generation (SHG).
related to the molecular rigidity mentioned above; more
planar molecules have a greater possibility of crystallizing in a
noncentrosymmetric space group (Zhang, 2002). To verify
Zhang’s correlation, a search of the Cambridge Structural
Database (CSD, Version 5.32, with update of February 2011;
Allen, 2002) was conducted for all stilbenes and BAs having
no ortho substituents. Indeed, since ortho substituents can
easily give rise to steric hindrance or intramolecular hydrogen
bonding, a correlation involving the planarity of the systems
would be biased. Erroneous, cocrystal, polymeric, ionic,
powder and organometallic structures, and symmetric struc-
tures with Z0 = 0.5, were also excluded. On the other hand,
heterocyclic rings with the heteroatom in the 3-, 4- or 5-
position were allowed. For the stilbenes, only E configurations
[ꢁ(C1—C7—C8—C9) = 180ꢀ15ꢁ] were considered. The
distribution of torsion angles in the resulting structures is
given in Fig. 1. As can be seen from these polar histograms, the
stilbenes are all quasiplanar (Fig. 1a). The majority of the BAs,
on the other hand, display conformations with torsion angles
within the ꢀ45ꢁ range (Fig. 1b). 64 of the 169 stilbenes and 44
of the 178 BAs found belong to noncentrosymmetric space
groups. 53 stilbenes and 81 BAs are donor–acceptor (DA)
systems. 17 and 19 of these, respectively, belong to noncen-
Comment
For several years now, the liquid-crystal-forming properties of
N-benzylideneaniline (BA) and its derivatives have been
studied in great detail (Kitamura et al., 1986; Ajeetha &
Pisipati, 2006; Fakruddin et al., 2009); their rod-like shape is
the basis of a number of unique properties which lead to
calamitic liquid crystals that may find application in custo-
mizable electro-optical switches. The aromatic moieties in BAs
have been described as the main recognition points of the
mesogens used in the organization of the liquid-crystalline
superstructure (Neuvonen et al., 2006). Extended alkyl or
alkoxy chains are substituted onto these aromatic fragments to
introduce the necessary flexibility into the molecular structure,
and this flexibility is further enhanced by the imine spacers
present in the BA. It is the subtle equilibrium between the
rigid rod-like structure and the presence of flexible groups that
determines the physical properties of the liquid-crystalline
phase. Since the solid-state structures of these materials can
not be studied in the liquid-crystalline phase, the extended
side chains must be replaced by shorter ones, such as methoxy
groups, in order to investigate the intermolecular interactions
involving the mesogen.
o364 # 2011 International Union of Crystallography
doi:10.1107/S0108270111030952
Acta Cryst. (2011). C67, o364–o369

organic compounds
available, so that a direct comparison of the effect of the
spacer on the supramolecular structure is impossible. In order
to make just such a comparison, the stilbene (E)-1-nitro-4-[2-
(3,4,5-trimethoxyphenyl)ethenyl]benzene, (I), and its two
‘bridge-flipped’ (Ojala et al., 2009) imine derivatives, (E)-3,4,5-
trimethoxy-N-(4-nitrobenzylidene)aniline, (II), and (E)-4-
nitro-N-(3,4,5-trimethoxybenzylidene)aniline, (III) (Fig. 2),
were prepared and structurally characterized.
Compounds (I) and (II) crystallize in the centrosymmetric
space group P21/c, while (III) crystallizes in the chiral space
group P212121. Compound (I) is quasiplanar, while the imine
derivatives (II) and (III) display the typical 40ꢁ twist around
the C—N bond which is also found in the calculated gas-phase
Figure 1
Polar histograms illustrating the distribution of (a) torsion angles ꢁ(C2—
C1—C7—C8) in stilbenes, (b) torsion angles ꢁ(C2—C1—N2—C8) in BAs
and (c) torsion angles of donor–acceptor BAs in noncentrosymmetric
space groups; see Comment for details.
trosymmetric space groups. As can be seen from Fig. 1(c)
though, the torsion angles of these 19 BAs (or 23 structures,
with the addition of four polymorphs) are quite well distrib-
uted over the entire ꢀ45ꢁ range. Based on these results, the
suggested correlation seems unlikely.
It is interesting to note that usually just one of the structures
of the three possible stilbene/BA derivatives (i.e. with
—CH CH—, —CH N— or —N CH— as spacer) is
Figure 2
The molecular structures of (I), (II) and (III), showing the atom-
numbering scheme. In each case, the nitro-substituted ring is labelled A.
Displacement ellipsoids are drawn at the 50% probability level. H atoms
are represented by spheres of arbitrary radii and bear the same number as
the C atom to which they are attached.
ꢂ
Acta Cryst. (2011). C67, o364–o369
Collas and Blockhuys
C17H17NO5 and two isomers of C16H16N2O5 o365

organic compounds
Figure 3
(a) The corrugated planes in the structure of (I), held together by (b) ꢀ–ꢀ, (c) OCH3ꢄ ꢄ ꢄꢀ and (d) C—Hꢄ ꢄ ꢄO interactions (all interactions are shown as
dashed lines). Symmetry codes are as in Table 2.
structures, as evidenced by the values of ꢁ(C1—N2) for (II)
and ꢁ(N2—C9) for (III) in Table 1.
The quasiplanar molecules of (I) (Fig. 3a) form pairs, in
a mutual weak hydrogen bond involving atom H6 and an O
atom of the nitro group (Fig. 4b and entry 1 in Table 3).
Ribbons are then generated by a weak C—Hꢄ ꢄ ꢄO hydrogen
bond between the methoxy groups in the 4- and 5-positions
(Fig. 4b and entry 2 in Table 3). Simultaneously, atom H41B
engages in a C—Hꢄ ꢄ ꢄꢀ contact with the ꢀ-system of the
methoxy-substituted aniline fragment (entry 3 in Table 3, not
shown in Fig. 4). Perpendicular to these ribbons, another
OCH3ꢄ ꢄ ꢄꢀ contact is initiated by the methoxy group in the
3-position, which is made possible by the twist of the aniline
ring (entry 4 in Table 3, not shown in Fig. 4). In the third
direction, a C—Hꢄ ꢄ ꢄO interaction (entry 5 in Table 3) and an
OCH3ꢄ ꢄ ꢄꢀ interaction (entry 6 in Table 3) stabilize the struc-
ture further (not shown in Fig. 4). Both the imine N atom and
the relatively acidic H8 atom remain unused in this structure.
Compound (III), which crystallizes in the chiral space group
P212121, does not form these antiparallel assemblies. It is
remarkable that a hydrogen bond involving imine atom N2 as
acceptor generates a ribbon of molecules in the bc plane
(Fig. 5b and entry 1 in Table 4). These ribbons are further
expanded into a plane of molecules by an additional hydrogen
bond (Fig. 5b and entry 2 in Table 4). In the direction
perpendicular to the plane, the [100] direction, atom O2 of the
nitro group contacts the ꢀ-systems of the aniline rings in the
planes above (Fig. 5a and entry 3 in Table 4) and below the
molecule (entry 4 in Table 4, not shown in Fig. 5). Thus, the
layered structure (Fig. 5c) is stabilized in all three directions,
but as a result of this particular stacking, the molecular dipoles
add up to zero, in keeping with the observed space group
symmetry.
which the two molecules are held together by dipolar forces
i
and ꢀꢂ+–ꢀꢂꢃ interactions, with CgAꢄ ꢄ ꢄCgB = 3.936 (4) A
˚
[CgA and CgB are the centroids of the nitro-substituted (A)
and trimethoxy-substituted (B) benzene rings, respectively;
symmetry code: (i) ꢃx, ꢃy + 1, ꢃz], ꢃ = 2.20 (14)ꢁ and ꢄ =
30.07ꢁ, where ꢃ is defined as the dihedral angle between the
least-squares (LS) planes through rings A and B, and ꢄ as the
angle between the CgAꢄ ꢄ ꢄCgB vector and the normal to the
LS plane through ring B (Fig. 3b). This two-by-two arrange-
ment leads to layers in which the distance between the mol-
˚
ecules is less than 4.2 A – the photochemical criterion
(Schmidt, 1971) – and, as a consequence, this crystal structure
should be photosensitive, but this was not observed during the
manipulation of the compound. These nonpolar pairs are
further stabilized on both sides by weak hydrogen bonds
involving the O atom of the nitro group (Fig. 3d and entry 1 in
Table 2) and an O atom of a methoxy group (Fig. 3d and entry
2 in Table 2), which gives a structure formed of planes two
molecules thick. These planes are then fused together by
reciprocal OCH3ꢄ ꢄ ꢄꢀ contacts (Fig. 3c and entry 3 in Table 2).
The overall result is a supramolecular structure of corrugated
planes (Fig. 3a).
The crystal structure of (II) is also based on pairs of mol-
ecules in which their large individual dipoles are cancelled. As
a result, ꢀ–ꢀ stacking can be easily recognized [CgAꢄ ꢄ ꢄCgAv =
ꢁ
ꢁ
˚
3.993 (1) A, ꢃ= 0.0 and ꢄ = 25.79 ; symmetry code: (v) ꢃx + 1,
ꢃy + 2, ꢃz + 1] (Fig. 4). These dimers are further stabilized by
ꢂ
o366 Collas and Blockhuys
C17H17NO5 and two isomers of C16H16N2O5
Acta Cryst. (2011). C67, o364–o369

organic compounds
Figure 4
(a) The herringbone pattern in the structure of (II), viewed along the a axis and (b) the various other intermolecular contacts (dashed lines). Symmetry
codes are as in Table 3.
It may be clear from the above that (I) and (II) aggregate as
dimers, cancelling out the net dipole in each case and
constructing centrosymmetric corrugated layered and
herringbone networks, respectively. ꢀ–ꢀ stacking involving the
nitro-substituted A rings occurs in the solid-state structures of
(I) and (II) as a consequence of the contribution of dipolar
forces (see Table 1 for the calculated dipole moments). The
methoxy groups are engaged in almost equal numbers of
Figure 5
(a) The NOꢄ ꢄ ꢄꢀ contacts, (b) the interactions within the layers and (c) the layered structure of (III), viewed along b (all interactions are shown as dashed
lines). Symmetry codes are as in Table 4.
ꢂ
Acta Cryst. (2011). C67, o364–o369
Collas and Blockhuys
C17H17NO5 and two isomers of C16H16N2O5 o367

organic compounds
Compound (I)
OCH3ꢄ ꢄ ꢄꢀ and C—Hꢄ ꢄ ꢄO interactions. Surprisingly,
compound (III) possesses the largest dipole but displays a
noncentrosymmetric network based on weak hydrogen bonds
involving the imine N atom. The chiral network is essential for
displaying nonlinear responses based on the second-order
nonlinear electrical susceptibility (ꢅ(2)).
Crystal data
3
˚
V = 1564.6 (13) A
Z = 4
C17H17NO5
Mr = 315.32
Monoclinic, P21=c
Mo Kꢃ radiation
ꢇ = 0.10 mmꢃ1
T = 293 K
0.42 ꢅ 0.39 ꢅ 0.39 mm
˚
a = 10.459 (2) A
˚
b = 12.88 (1) A
˚
c = 14.021 (4) A
ꢆ = 124.069 (15)ꢁ
Experimental
Data collection
All reagents and solvents were obtained from ACROS and used as
received. All NMR spectra were recorded on a Bruker Avance II
Enraf–Nonius CAD-4
diffractometer
5901 measured reflections
2867 independent reflections
1500 reflections with I > 2ꢈ(I)
Rint = 0.043
3 standard reflections every 60 min
intensity decay: none
spectrometer at frequencies of 400 MHz for 1H and 100 MHz for 13
C
in CDCl3 with tetramethylsilane (TMS) as internal standard;
chemical shifts ꢂ are given in p.p.m. and coupling constants J in Hz.
Melting points were obtained with an open capillary electrothermal
melting-point apparatus and are uncorrected.
Refinement
R[F2 > 2ꢈ(F2)] = 0.045
wR(F2) = 0.135
S = 1.00
211 parameters
H-atom parameteꢃrs3 constrained
(E)-1-Nitro-4-[2-(3,4,5-trimethoxyphenyl)ethenyl]benzene, (I), was
prepared by adding LiOH (0.7 g, 0.03 mol) to a stirred solution of
(4-nitrobenzyl)triphenylphosphonium chloride (13.1 g, 0.03 mol)
and 3,4,5-trimethoxybenzaldehyde (6.0 g, 0.03 mol) in propan-2-ol
(110 ml). The resulting suspension was refluxed for 18 h. After
cooling to room temperature, water (100 ml) was added, and since no
precipitate was formed the solution was extracted with diethyl ether
(3 ꢅ 50 ml). The organic layer was separated off and evaporated to
dryness. Isomerization of the crude product in p-xylene (50 ml) with a
catalytic amount of I2 yielded 2.4 g (0.007 mol, 23%) of long yellow
needles of (I). Characterization: m.p. 466 K; 1H NMR: ꢂ 3.89 (s, 3H,
4-OCH3), 3.93 (s, 6H, 3-OCH3 and 5-OCH3), 6.78 (s, 2H, H2 and H6),
7.03 (d, 3J = 16.1, 1H, H7), 7.19 (d, 3J = 16.1, 1H, H8), 7.61 (d, 3J = 8.2,
˚
Áꢉmax = 0.35 e A
Áꢉmin = ꢃ0.14 e A
ꢃ3
˚
2867 reflections
Compound (II)
Crystal data
3
˚
V = 1517.0 (6) A
Z = 4
C16H16N2O5
Mr = 316.31
Monoclinic, P21=c
Mo Kꢃ radiation
ꢇ = 0.10 mmꢃ1
T = 293 K
0.3 ꢅ 0.3 ꢅ 0.3 mm
˚
a = 7.512 (2) A
˚
b = 7.895 (1) A
˚
c = 26.441 (6) A
3
2H, H11 and H13), 8.20 (d, J = 8.2, 2H, H10 and H14); 13C NMR:
ꢆ = 104.667 (19)ꢁ
ꢂ 56.22 (3-OCH3 and 5-OCH3), 60.98 (4-OCH3), 104.32 (C2 and C6),
124.15 (C10 and C14), 125.69 (C8), 126.74 (C7), 131.86 (C11 and
C13), 133.31 (C1), 139.13 (C4), 143.82 (C12), 146.73 (C9), 153.56 (C3
and C5). Crystals used in the diffraction experiment were grown by
slow cooling of an ethyl acetate–hexane (1:1 v/v) solution.
Data collection
Enraf–Nonius CAD-4
diffractometer
5826 measured reflections
2803 independent reflections
2023 reflections with I > 2ꢈ(I)
Rint = 0.052
3 standard reflections every 60 min
intensity decay: 4%
(E)-3,4,5-Trimethoxy-N-(4-nitrobenzylidene)aniline, (II), was
prepared by dissolving 3,4,5-trimethoxyaniline (1.8 g, 0.01 mol) and
4-nitrobenzaldehyde (1.5 g, 0.01 mol) in ethanol (100 ml) and stirring
the solution overnight. The orange precipitate which formed was
filtered off, yielding 3.0 g (9.5 mmol, 95%) of (II). Characterization:
m.p. 430 K; 1H NMR: ꢂ 3.88 (s, 3H, 4-OCH3), 3.92 (s, 6H,
3-OCH3 and 5-OCH3), 6.56 (s, 2H, H2 and H6), 8.07 (d, 3J = 8.8, 2H,
H10 and H14), 8.32 (d, 3J = 8.8, 2H, H11 and H13), 8.57 (s, 1H, H8);
13C NMR: ꢂ 56.23 (3-OCH3 and 5-OCH3), 61.02 (4-OCH3), 98.60 (C2
and C6), 124.03 (C11 and C13), 129.31 (C10 and C14), 137.58 (C4),
141.53 (C9), 146.63 (C1), 149.31 (C12), 153.86 (C3 and C5), 156.40
(C8). Crystals used in the diffraction experiment were grown by slow
evaporation from a CH2Cl2 solution.
Table 1
Selected geometric data for (I), (II) and (III); calculated (DFT) and
experimental (XRD) torsion angles in degrees (ꢁ), and calculated dipole
moments ꢇ in Debye.
Compound
(I)
Parameter
XRD
DFT
ꢇ
C2—C1—C7—C8
C1—C7—C8—C9
C7—C8—C9—C10
C2—C1—N2—C8
C1—N2—C8—C9
N2—C8—C9—C10
C2—C1—C7—N2
C1—C7—N2—C9
C7—N2—C9—C10
ꢃ11.0 (5)
178.7 (3)
ꢃ172.1 (3)
ꢃ38.4 (2)
179.4 (1)
ꢃ11.5 (2)
4.1 (4)
176.2
0.3
4.2
31.6
177.4
1.4
1.4
176.4
42.5
5.48
4.59
6.15
(II)
(E)-4-Nitro-N-(3,4,5-trimethoxybenzylidene)aniline, (III), was pre-
pared by refluxing 3,4,5-trimethoxybenzaldehyde (3.0 g, 0.015 mol)
and 4-nitroaniline (2.1 g, 0.015 mol) in methanol (100 ml) for 3 h. The
resulting yellow precipitate was collected by filtration and recrys-
tallized from acetonitrile, yielding 3.5 g (11 mmol, 75%) of (III).
Crystals from this batch were used in the crystallographic experiment.
Characterization: m.p. 428 K; 1H NMR: ꢂ 3.94 (s, 3H, 4-OCH3), 3.95
(s, 6H, 3-OCH3 and 5-OCH3), 7.18 (s, 2H, H2 and H6), 7.23 (dd, 3J =
(III)
177.8 (2)
ꢃ39.5 (4)
Table 2
Weak hydrogen bonds in (I) (A, ).
ꢁ
˚
4
8.9, 4J = 1.9, 2H, H10 and H14), 8.25 (dd, 3J = 8.9, J = 1.9, 2H, H11
Entry
D
H
A
Hꢄ ꢄ ꢄA
Dꢄ ꢄ ꢄA
D—Hꢄ ꢄ ꢄA
and H13), 8.32 (s, 1H, H7); 13C NMR: ꢂ 56.33 (3-OCH3 and 5-OCH3),
61.03 (4-OCH3), 106.44 (C2 and C6), 121.29 (C10 and C14), 125.04
(C11 and C13), 130.81 (C1), 142.01 (C4), 145.45 (C12), 153.65 (C3 and
C5), 157.87 (C9), 162.08 (C7).
1
2
3
C14
C7
C31
H14
H7
H31B
O2ii
2.69
2.57
2.83
3.526 (4)
3.447 (3)
3.718 (5)
151
158
154
O4iii
CgBiv
Symmetry codes: (ii) x, ꢃy + 21, z ꢃ 21; (iii) x, ꢃy + 23, z + 12; (iv) x + 1, ꢃy + 1, ꢃz.
ꢂ
o368 Collas and Blockhuys
C17H17NO5 and two isomers of C16H16N2O5
Acta Cryst. (2011). C67, o364–o369

organic compounds
Table 3
Weak hydrogen bonds in (II) (A, ).
the unit-cell coordinate system. The polar histograms were generated
using the VISTA program in the CSD suite.
ꢁ
˚
All H atoms were treated as riding using SHELXL97 (Sheldrick,
˚
2008) defaults at 293 (1) K, with C—H = 0.93 A and Uiso(H) =
˚
1.2Ueq(C) for aromatic H atoms, and C—H = 0.96 A and Uiso(H) =
Entry
D
H
A
Hꢄ ꢄ ꢄA
Dꢄ ꢄ ꢄA
D—Hꢄ ꢄ ꢄA
1
2
3
4
5
6
C6
H6
O2v
O5vi
2.54
2.50
2.96
2.78
2.71
2.94
3.423 (2)
3.450 (3)
3.626 (3)
3.463 (3)
3.542 (3)
3.631 (3)
160
168
128
129
145
130
C41
C41
C31
C31
C51
H41C
H41B
H31A
H31B
H51B
1.5Ueq(C) for methyl H atoms. The displacement parameters of atoms
C7 and C8 in (I) seem to suggest disorder typical of ethenylic spacers
in stilbene-type systems (see Vande Velde et al., 2011), but attempts
to refine a disordered model did not lead to satisfactory results.
However, since only a small fraction of misoriented fragments is
present, the quality of the nondisordered model was found to be
sufficient, even though this leads to slightly larger displacement
ellipsoids for the mentioned atoms. For (III), Friedel pairs were
collected independently but were merged (MERG 3 command in
SHELXL97) for the final refinement. In the absence of a heavy atom
[Z > 14 (Si)], and with the use of Mo radiation, anomalous scattering
could not be used to determine an absolute structure and thus it was
chosen arbitrarily.
CgBvii
CgBviii
O1ix
CgAx
Symmetry codes: (v) ꢃx + 1, ꢃy + 2, ꢃz + 1; (vi) ꢃx + 3, y + 12, ꢃz + 23; (vii) ꢃx + 3, y ꢃ ,
1
2
ꢃz + 23; (viii) ꢃx + 2, y + 12, ꢃz + 23; (ix) x + 1, ꢃy + 23, z + 21; (x) x + 1, y ꢃ 1, z.
Table 4
Short contacts in (III) (A, ).
ꢁ
˚
Entry
D
X
A
Xꢄ ꢄ ꢄA
Dꢄ ꢄ ꢄA
D—Xꢄ ꢄ ꢄA
1
2
3
4
C41
C6
N1
N1
H41B
H6
O2
N2xi
2.66
2.58
3.610 (4)
3.912 (4)
3.537 (4)
3.450 (4)
3.587 (4)
4.578 (4)
153
156
79.1 (2)
115.7 (2)
O1xii
CgBxiii
CgBxiv
For all compounds, data collection: CAD-4 EXPRESS (Enraf–
Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction:
XCAD4 (Harms & Wocadlo, 1996); program(s) used to solve struc-
ture: SHELXS97 (Sheldrick, 2008); program(s) used to refine struc-
ture: 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).
O2
Symmetry codes: (xi) ꢃx, 12 + y, 21 ꢃ z; (xii) ꢃx, 21 + y, ꢃ ꢃ z; (xiii) ꢃ + x, 12 ꢃ y, ꢃz; (xiv)
1
2
1
2
1
2
+ x, 12 ꢃ y, ꢃz.
Refinement
R[F2 > 2ꢈ(F2)] = 0.036
wR(F2) = 0.104
S = 1.05
211 parameters
H-atom parameteꢃrs3 constrained
˚
Áꢉmax = 0.14 e A
AC thanks the Institute for the Promotion of Innovation by
Science and Technology in Flanders (IWT) for his predoctoral
grants. Financial support by FWO–Vlaanderen under grant
No. G.0129.05 and by the University of Antwerp under grant
No. GOA-2404 is gratefully acknowledged.
ꢃ3
˚
2803 reflections
Áꢉmin = ꢃ0.18 e A
Compound (III)
Crystal data
3
˚
V = 1519.4 (8) A
Z = 4
C16H16N2O5
Mr = 316.31
Orthorhombic, P212121
Supplementary data for this paper are available from the IUCr electronic
archives (Reference: FA3256). Services for accessing these data are
described at the back of the journal.
Mo Kꢃ radiation
ꢇ = 0.10 mmꢃ1
T = 293 K
0.4 ꢅ 0.4 ꢅ 0.3 mm
˚
a = 7.215 (3) A
˚
b = 14.429 (2) A
˚
c = 14.595 (5) A
References
Ajeetha, N. & Pisipati, V. G. K. M. (2006). Mol. Cryst. Liq. Cryst. 457, 3–25.
Allen, F. H. (2002). Acta Cryst. B58, 380–388.
Data collection
Enraf–Nonius CAD-4
diffractometer
1358 reflections with I > 2ꢈ(I)
Rint = 0.057
Enraf–Nonius (1994). CAD-4 EXPRESS. Enraf–Nonius, Delft, The Nether-
lands.
4683 measured reflections
1618 independent reflections
3 standard reflections every 60 min
intensity decay: 10%
Fakruddin, K., Kumar, R. J., Prasad, P. V. D. & Pisipati, V. G. K. M. (2009). Mol.
Cryst. Liq. Cryst. 511, 1616–1627.
Farrugia, L. J. (1997). J. Appl. Cryst. 30, 565.
Farrugia, L. J. (1999). J. Appl. Cryst. 32, 837–838.
Frisch, M. J., et al. (2009). GAUSSIAN09. Revision A.02. Gaussian Inc.,
Pittsburgh, Pennsylvania, USA.
Harms, K. & Wocadlo, S. (1996). XCAD4. University of Marburg, Germany.
Kitamura, T., Mukoh, A., Isogai, M., Inukai, T., Furukawa, K. & Terashima, K.
(1986). Mol. Cryst. Liq. Cryst. 136, 167–173.
Refinement
R[F2 > 2ꢈ(F2)] = 0.052
wR(F2) = 0.141
S = 1.07
212 parameters
H-atom parameteꢃrs3 constrained
˚
Áꢉmax = 0.30 e A
ꢃ3
˚
1618 reflections
Áꢉmin = ꢃ0.21 e A
Macrae, C. F., Bruno, I. J., Chisholm, J. A., Edgington, P. R., McCabe, P.,
Pidcock, E., Rodriguez-Monge, L., Taylor, R., van de Streek, J. & Wood,
P. A. (2008). J. Appl. Cryst. 41, 466–470.
Neuvonen, H., Neuvonen, K. & Fulop, F. (2006). J. Org. Chem. 71, 3141–
3148.
Ojala, W. H., Lystad, K. M., Deal, T. L., Engelbretson, J. E., Spude, J. M.,
Balidemaj, B. & Ojala, C. R. (2009). Cryst. Growth Des. 9, 964–970.
Schmidt, G. M. J. (1971). Pure Appl. Chem. 27, 647–678.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112–122.
Spek, A. L. (2009). Acta Cryst. D65, 148–155.
Vande Velde, C. M. L., Collas, A., De Borger, R. & Blockhuys, F. (2011).
Chem. Eur. J. 17, 912–919.
Zhang, D.-C. (2002). Acta Cryst. C58, o351–o352.
The molecular structures of isolated molecules of (I), (II) and (III)
were optimized at the DFT/B3LYP/6-31G* level of theory using the
GAUSSIAN09 program package (Frisch et al., 2009); the functional
and basis set were used as they are implemented in the program.
Frequency calculations were performed to ascertain that the resulting
structures are minima on the potential-energy surface (PES). Mol-
ecular dipoles of the four molecules in the unit cell of (III) were
calculated in their solid-state geometries at the same level of theory.
The resulting vectors were then transformed from the Cartesian to
ꢂ
Acta Cryst. (2011). C67, o364–o369
Collas and Blockhuys
C17H17NO5 and two isomers of C16H16N2O5 o369