Weak interactions direct crystal packings of arylated 1,3-butadienes

Article abstract of DOI:10.1016/j.molstruc.2014.02.033

Four novel aryl butadienes (substituted with R = Cl, OCH₃, NO₂ and H) were prepared and characterised by X-ray diffraction, IR, UV/Vis and NMR spectroscopies. A comparative analysis of crystal packings was aimed to determining influence of weak interactions: CHa?O and CHa?Cl hydrogen bonds, CHa?π interactions and dispersion interactions. Since no proton donors is present and since the molecules are sterically very similar, these weak interactions are responsible for wide variation in 3D packing and supramolecular motives.

Full text of DOI:10.1016/j.molstruc.2014.02.033

Journal of Molecular Structure 1065-1066 (2014) 43–51
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Weak interactions direct crystal packings of arylated 1,3-butadienes
a
b,
a
⇑
ˇ
´
Dragana Vuk , Krešimir Molcanov , Irena Škoric
a Department of Organic Chemistry, Faculty of Chemical Engineering and Technology, University of Zagreb, Maruli´cev Trg 19, 10000 Zagreb, Croatia
b
ˇ
Department for Physical Chemistry, Rudjer Boškovi´c Institute, Bijenicka 54, 10000 Zagreb, Croatia
h i g h l i g h t s
ꢀ
ꢀ
ꢀ
Four novel arylated 1,3-butadienes were prepared.
Isomers in solution were studied by NMR and UV/Vis spectroscopy.
Crystal packing of the compounds is directed by weak interactions, only.
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 2 January 2014
Received in revised form 5 February 2014
Accepted 13 February 2014
Available online 25 February 2014
Four novel aryl butadienes (substituted with R = Cl, OCH3, NO2 and H) were prepared and characterised
by X-ray diffraction, IR, UV/Vis and NMR spectroscopies. A comparative analysis of crystal packings was
aimed to determining influence of weak interactions: CAHꢁ ꢁ ꢁO and CAHꢁ ꢁ ꢁCl hydrogen bonds, CAHꢁ ꢁ ꢁ
p
interactions and dispersion interactions. Since no proton donors is present and since the molecules are
sterically very similar, these weak interactions are responsible for wide variation in 3D packing and
supramolecular motives.
Keywords:
Ó 2014 Elsevier B.V. All rights reserved.
1,3-Butadienes
Weak interactions
Crystal structure
Crystal engineering
NMR spectroscopy
Photochemistry
1. Introduction
nylon to modern drug design [11]. Under prolonged conjugated
system these derivatives also show a versatile photoreactivity
Crystal engineering using strong, directional intermolecular
interactions such as hydrogen bonds, dipolar interactions and ago-
stic interactions is very well-known [1–4]. Common supramolecu-
lar motives, called ‘supramolecular synthons’ and ‘tectons’, have
been recognised, and can be quite reliably used in design of molec-
ular crystals [5–8]. However, crystal packing of organic compounds
lacking strong proton donors and acceptors is less studied [9,10].
Such compounds are capable of forming only weak interactions,
which rarely, if ever, form commonly recognisable motives. There-
fore, a study of a series of closely related compounds lacking proton
donors and acceptors could be useful to find out factors influencing
their crystal packing. As a model system, we chose several aryl
substituted butadiene derivatives (compounds 1–4, Scheme 1).
1,3-Butadienes and their derivatives represent a class of well-
studied compounds. The interest in this kind of compounds has
spread from manufacture of synthetic rubber, latex paints, and
and formations of various photoproducts with remarkable electro-
chemical, optical, physical and biological properties [12–15]. Their
skeleton has also proved to be useful reactive intermediate in var-
ious stereoselective transformations making these derivatives
powerful building blocks in organic synthesis [16–19].
In continuation of our interest on intra- and intermolecular
photocycloaddition reactions of 1,3-butadiene derivatives,
molecule that combine the properties of both butadiene and
hexatriene systems [11–14], we extended synthesis to new aryl
butadienes 1–4 (substituted with R = H, Cl, OCH3 and NO2). In these
compounds, the butadiene groups in the position 1, 2, 3 and 4 are
not equivalent and might behave quite differently in the primary
process of photoisomerization. It was interesting to distinguish
the ethylenic moieties of the butadiene groups in the position 1,
2, 3 and 4 to be able to follow the path of the primary photoreac-
tion. Therefore, molecules of very similar structures can show
dramatically different photoinduced behaviour producing various
photoproducts intersting for further functionalization using simple
aproach with light as reagent.
⇑
Corresponding author.
E-mail address: kmolcano@irb.hr (K. Molcanov).
ˇ
http://dx.doi.org/10.1016/j.molstruc.2014.02.033
0022-2860/Ó 2014 Elsevier B.V. All rights reserved.

44
D. Vuk et al. / Journal of Molecular Structure 1065-1066 (2014) 43–51
R
R
1)
OHC
CH2O
2)
NaOEt/EtOH
1
: R = Cl
2: R = OCH3
CH2P+Ph3Br-
CH2P+Ph3Br-
3
: R = NO2
1)
OHC
CHOCH3
NaOEt/EtOH
2)
4
trans,trans-
Scheme 1. Synthesis of butadiene derivatives 1–4 by Wittig reaction.
2. Results and discussion
1,0
1
2
3
4
2.1. Synthesis and spectroscopic characterisation
0,8
0,6
0,4
0,2
0,0
Butadiene derivatives 1–4 were prepared by Wittig reaction
from diphosphonium salt and the corresponding cinnamaldehydes
(Scheme 1). The products were obtained in good yields (65–78%) as
mixture of cis- and trans-isomers, which were separated by column
chromatography and completely characterised spectroscopically.
The syntheses were performed always from the corresponding
(E)-geometric isomers of the cinnamaldehyde, where the second
double bond (looking from the ortho-substitued central benzene
ring) in the products retain the (E)-configuration. Hence, the num-
ber of geometric isomers was reduced.
A
200
250
300
350
400
450
500
Fig. 1 display the normalised absorption spectra of trans-isomers
of 1–4 in ethanol. Band absorption maxima of all derivatives are
found in the range of 325–380 nm, and clearly show substituent
influence on absorption characteristic. Chloro and methoxy deriva-
tives 1–2 show a slight bathochromic shift (15–20 nm) compared to
the unsubstitued derivative 4. Nitro derivatives 3 results in signifi-
cant bathochromic shift (55 nm), compared to the absorption bands
of the previous componds 1, 2 and 4. This effect may be a
consequence of the more than doubled dipole moment of the
nitro derivatives in the excited state.
λ
/ nm
Fig. 1. Normalised absorption spectra of 1–4 in ethanol.
ethylenic protons in all examples appear between 6.61 and
7.13 ppm as doublet (HA, HD protons) or doublet of doublets (HB,
HC protons). The signals of HD protons are shifted to higher field
(6.61–6.70 ppm) in comparison to the HA protons (6.91–7.11).
Signals of HB and HC protons are widespread between 6.80–
7.13 ppm. The signals in all examples 1–3 are very similar and have
The 1H NMR spectra of the studied compounds 1–3 with the
emphasis on ethylenic protons are presented in Fig. 2. The
Cl
HA HC
HD
HA
HB
HC
HB HD
HB, HC
HA
OCH3
HA HC
HD
HB HD
Har
Har
NO2
HA HC
HB/HC
HA
HD
Har
HB/HC
HB HD
PPM
8.0
7.6
7.2
6.8
6.4
6.0
5.6
Fig. 2. 1H NMR spectra (CDCl3, 600 MHz) of 1–3.

D. Vuk et al. / Journal of Molecular Structure 1065-1066 (2014) 43–51
45
practically the same chemical shifts. Therefore it can be concluded
that the influence of substituents (Cl, OCH3, NO2) on ethylenic
moieties of compounds 1–3 is negligible.
2.2. Crystal structures
Molecular structures of compounds 1–4 are shown in Fig. 3.
Their geometries and conformations are similar, as can be seen in
an overlay (Fig. 4). Since the entire molecules comprise conjugated
bonds, they can be regarded as a single, delocalised,
p electron sys-
tem. The formally single CAC bonds in the butadienyl fragment
(bonds C4AC7, C8AC9 and C10AC11) are significantly shortened
(Table 1), indicating a considerable electron delocalisation.
Due to the steric repulsions, the molecules are not perfectly pla-
nar, but slightly bent: average deviations from molecular mean
plane are 0.156, 0.178, 0.118 and 0.061 Å for compounds 1, 2, 3
and 4, respectively. The most twisted molecule, 2, has a dihedral
angle between two phenyl ring planes of 19.1°. In the other three
molecules, it is much smaller, 2.2°, 5.4° and 6.1°, respectively.
Little steric differences and absence of strong intermolecular
interactions would imply similar crystal packings. However, this
is not the case for the studied compounds. Crystal packings differ
radically and the differences can be ascribed mostly to the weak
intermolecular interactions: CAHꢁ ꢁ ꢁO and CAHꢁ ꢁ ꢁCl hydrogen
bonds (in 1, 2 and 3), CAHꢁ ꢁ ꢁ
p (in 1 and 2) [10,20] interactions
and dispersion interactions.
In 1 there is a single, very elongated, CAHꢁ ꢁ ꢁCl hydrogen bond
(Table 2), which generates chains extending in the direction
[001] (Fig. 5a). CAHꢁ ꢁ ꢁ
p interactions [10,20] (Table 3) generate
chains parallel to [100]. In these interactions, aromatic ring acts
as a proton donor, while the butadienyl moiety is an acceptor;
therefore they resemble T-shaped ‘‘
Overall, a 2D motive is generated (Fig. 5b).
p p’’ interactions [10,20,21].
ꢁ ꢁ ꢁ
Hydrogen bonding is most pronounced in 3 due to the presence
of a strong acceptor, the nitro group. Therefore, three symmetry-
independent hydrogen bonds can be recognised (Table 2, Fig. 6a).
A pair of bonds C3AH3ꢁ ꢁ ꢁO1 and C7AH7ꢁ ꢁ ꢁO1 link the molecules
ꢀ
into zig–zag chains parallel to [110] and ½110ꢂ (Fig. 6b) while
the third one forms chains in the direction [101] (Fig. 6c), therefore
generating a 3D network. This motive is analogous to the isolated
[001] chain in 1 (Fig. 5a).
In 2 a single, weak, proton acceptor is present – the ether oxy-
gen. Therefore, a single CAHꢁ ꢁ ꢁO hydrogen bond exists (Table 2),
which links the molecules into chais running in the direction
[010] (Fig. 7a). There are also CAHꢁ ꢁ ꢁ
p interactions (Table 3,
Fig. 7b) linking the chains into layers parallel to (001) (Fig. 7c).
Only dispersion interactions are present between the layers.
Unlike other structures, packing of the unsubstituted hydrocar-
bon 4 appears to be directed by dispersion interactions, only. The
closest intermolecular contacts are by some 0.1 Å longer than the
sum of van der Waals radii, and the resulting crystal packing
displays a herringbone-like pattern (Fig. 8), in agreement with
Kitaigorodskii’s principle of close packing.
Fig. 3. Molecular structures of compounds 1–4. Displacement ellipsoids are drawn
for the probability of 50% and hydrogen atoms are shown as spheres of arbitrary
radii.
3. Conclusions
– parallel, offset [21] and ’’T-shaped’’, which can also be recognised
as CAHꢁ ꢁ ꢁ
p
interaction [10,20]. It is still an open question which
interactions do not
Crystal packings of four closely related aryl substituted butadi-
ene derivatives were studied. Since no strong proton donor is pres-
ent, the molecules are held together by weak intermolecular
one is more stable [21,22]. However, CAHꢁ ꢁ ꢁ
p
necessarily involve aromatic rings, but any C@C double bond or a
conjugated system may act as a proton acceptor. We have identi-
fied and described several such examples in crystal packings of 1
and 2 and it is interesting to note the apparent competition be-
interactions: CAHꢁ ꢁ ꢁO and CAHꢁ ꢁ ꢁCl hydrogen bonds, CAHꢁ ꢁ ꢁ
p
interactions and dispersion interactions. While all compounds
comprise two aromatic rings, no stacking of rings was observed.
tween CAHꢁ ꢁ ꢁ
There is yet another interesting observation: compounds 1–3,
which involve CAHꢁ ꢁ ꢁO and CAHꢁ ꢁ ꢁCl hydrogen bonds, CAHꢁ ꢁ ꢁ
interactions crystallise in acentric space groups (Table 4), while 4
p
interactions [10,20] and ’’
p
ꢁ ꢁ ꢁ
p stacking’’.
However, the nature of the interaction commonly called ‘‘
stacking’’ is ambiguous at best [21–23]. Two arrangements of
p p
ꢁ ꢁ ꢁ
p
planar rings are usually considered to be energetically favourable

46
D. Vuk et al. / Journal of Molecular Structure 1065-1066 (2014) 43–51
Nd:YAG laser operating at 355 nm with firing rate 200 Hz in the
positive (H+) or negative (Hꢃ) ion reflector mode. Silica gel
(0.063–0.2 mm) was used for chromatographic purifications.
Thin-layer chromatography (TLC) was performed silica gel 60
F254 plates. Solvents were purified by distillation. Para-methoxy-
cinnamaldehyde, para-nitro-cinnamaldehyde, para-chloro-cinna-
maldehyde and acetaldehyde were obtained from a commercial
source, b,b-o-xylyl(ditriphenylphosphonium) dibromide was
prepared from o-xylyldibromide and triphenylphosphine in
dimethylformamide.
4.2. General method for the synthesis of 1–3
Compounds 1–3 were prepared by Wittig reaction from o-xylyl-
enebis(triphenylphosphonium bromide) and the corresponding
aldehydes, para-methoxy-cinnamaldehyde and para-nitro-cinna-
maldehyde. To a stirred solution of the triphenylphosphonium salt
(0.001 mol) and the corresponding aldehyde (0.011 mol) in abso-
lute ethanol (200 mL), a solution of sodium ethoxide (0.253 g,
0.011 mol in 15 mL of absolute ethanol) was added dropwise. Stir-
ring was continued under a stream of nitrogen for 1 h at RT. Under
the stream of dry nitrogen gaseous formaldehyde (obtained by
decomposition of paraformaldehyde taken in excess, 1.5 g) was
introduced and the next quantity of sodium ethoxide (0.253 g,
0.011 mol in 15 mL of absolute ethanol) was added dropwise.
The reaction was completed within 3–4 h (usually was left to stand
overnight). After removal of the solvent, the residue was worked
up with water and toluene. The toluene extracts were dried (anhy-
drous MgSO4) and concentrated. The crude reaction mixture was
purified and the isomers of products 1 (78%), 2 (69%) and 3 (65%)
were separated by repeated column chromatography on silica gel
using petroleum ether as the eluent. The first fractions yielded
cis-and the last fractions trans-isomers. The 1-(p-chlorophenyl)-
4-(o-styrenyl)-1,3-butadiene (1) is described in Ref. [9]. The data
of the new compounds 2 and 3 are given below.
Fig. 4. Least-squares overlay of molecules 1 (light gray), 2 (black) 3 (dark gray) and
4 (white). For on-line colour version: 1 (green), 2 (black) 3 (red) and 4 (light blue).
(For interpretation of the references to colour in this figure legend, the reader is
referred to the web version of this article.)
Table 1
Selected bond lengths (Å).
1
2
3
4
C4AC7
C7AC8
C8AC9
C9AC10
C10AC11
1.460(3)
1.335(3)
1.444(3)
1.341(3)
1.466(2)
1.461(3)
1.333(2)
1.441(3)
1.328(2)
1.466(2)
1.459(3)
1.334(3)
1.441(3)
1.332(3)
1.459(3)
1.456(2)
1.330(3)
1.436(2)
1.321(3)
1.463(2)
crystallises in a centric space group. This may be a result of the
molecular geometry (4 is slightly different from other three, see
Fig. 4), but intermolecular interactions may also play a role. How-
ever, presently we can not give a definite answer.
Therefore, crystal packings of new compounds 1–4 (substituted
with R = Cl, OCH3, NO2 and H), that combine the properties of both
butadiene and hexatriene systems, depend on a subtle interplay of
weak interactions and steric effects. Based on the information
about the packing it is possible to propose and distinguish which
ethylenic moieties of the butadiene and/or vinyl and propenyl
groups could be involved in the primary photoreaction what is
important for the discussion of the reaction mechanisms.
(1Z,3E)-1-(p-Methoxyphenyl)-4-(o-styrenyl)-1,3-butadiene
(cis-2): 32%; Rf 0.28 (petroleum ether/dichloromethane = 8:2);
colourless oil; UV (96% EtOH) kmax (log
e) 323 (4.73), 235
(4.56); 1H NMR (CDCl3, 600 MHz) d 7.56 (d, J = 9.0 Hz, 1H), 7.31
(d, J = 8.9 Hz, 1H), 7.28 (d, J = 8.7 Hz, 2H), 7.25 – 7.29 (m, 2H),
6.92 (dd, J = 17.4; 11.0 Hz, 1H), 6.90 (dd, J = 15.6; 11.1 Hz, 1H),
6.82 (d, J = 8.7 Hz, 2H), 6.63 (d, J = 15.6 Hz, 1H), 6.55 (d,
J = 11.2 Hz, 1H), 4.46 (t, J = 11.1 Hz, 1H), 5.68 (dd, J = 17.4;
1.1 Hz, 1H), 5.28 (dd, J = 11.0; 1.1 Hz, 1H), 3.79 (s, 3H, AOCH3);
13C NMR (CDCl3, 150 MHz, ppm) d 158.9 (s), 136.0 (s), 135.4 (s),
134.7 (d), 133.6 (d), 130.9 (d), 129.7 (d), 129.6 (s), 127.6 (d),
127.5 (d), 127.3 (2d), 126.8 (2d), 125.2 (d), 123.0 (d), 115.0 (t),
4. Experimental section
4.1. Physical measurements
The 1H spectra were recorded on a spectrometer at 600 MHz.
The 13C NMR spectra were registered at 150 MHz. All NMR spectra
were measured in CDCl3 using tetramethylsilane as reference. The
assignment of the signals is based on 2D-CH correlation and 2D-
HH-COSY experiments. UV spectra were measured on a UV/Vis
Cary 50 spectrophotometer. IR spectra were recorded on a FTIR-
ATR (film). Irradiation experiments were preformed in a quartz
vessel in toluene solution in a photochemical reactor equipped
with 3000 Å lamps. All irradiation experiments were carried out
in deaerated solutions by bubbling a stream of argon prior to irra-
diation. Melting points were obtained using microscope equipped
apparatus and are uncorrected. HRMS analysis were carried out
on a mass spectrometer (MALDI TOF/TOF analyzer), equipped with
113.6 (d), 54.8 (q); IR
772.
mmax. 3005, 1604, 1510, 1250, 1174, 1035,
(1E,3E)-1-(p-Methoxyphenyl)-4-(o-styrenyl)-1,3-butadiene
(trans-2): 37%; Rf 0.25 (petroleum ether/dichloromethane = 8:2);
colourless crystals; mp 114–116 °C; UV (96% EtOH) kmax (log e)
344 (4.32); 1H NMR (CDCl3, 600 MHz) d 7.51 (d, J = 7.5 Hz, 1H),
7.44 (d, J = 7.5 Hz, 1H), 7.38 (d, J = 8.6 Hz, 2H), 7.24 (dt, J = 7.5;
0.9 Hz, 1H), 7.21 (dt, J = 7.5; 0.9 Hz, 1H), 7.07 (dd, J = 17.4;
11.0 Hz, 1H), 6.91 (d, J = 14.7 Hz, 1H), 6.88 (d, J = 8.6 Hz, 2H), 6.80
– 6.88 (m, 2H), 6.63 (d, J = 14.7 Hz, 1H), 5.62 (dd, J = 17.4; 1.1 Hz,

D. Vuk et al. / Journal of Molecular Structure 1065-1066 (2014) 43–51
47
Table 2
Geometric parameters of hydrogen bonds.
DAH (Å)
Hꢁ ꢁ ꢁA (Å)
Dꢁ ꢁ ꢁA (Å)
DAHꢁ ꢁ ꢁA (°)
Symm. op. on A
2
C17AH17ꢁ ꢁ ꢁO1
0.93
2.56
3.422(2)
154
1 ꢃ x, 1/2 + y, 3/2 ꢃ z
3
C3AH3ꢁ ꢁ ꢁO1
C7AH7ꢁ ꢁ ꢁO1
C18AH18Aꢁ ꢁ ꢁO2
0.93
0.93
0.93
2.59
2.63
2.72
3.443(3)
3.488(3)
3.645(4)
152
154
174
ꢃ1 + x, ꢃ1 + y, z
ꢃ1 + x, ꢃ1 + y, z
1/2 + x, 1 ꢃ y, 1/2 + z
Fig. 5. Crystal packing of 1: (a) chain parallel to [001] generated by CAHꢁ ꢁ ꢁCl hydrogen bondis, (b) chain parallel to [100] generated by CAHꢁ ꢁ ꢁ
p interactions.
Table 3
Geometric parameters of the CAHꢁ ꢁ ꢁ
p
interactions.
Hꢁ ꢁ ꢁCga (Å)
CAHꢁ ꢁ ꢁCga (°)
Cꢁ ꢁ ꢁCga (Å)
Symm. operation on Cga
1
C2AH2ꢁ ꢁ ꢁC17AC18
C6AH6ꢁ ꢁ ꢁC7AC8AC9
C13AH13ꢁ ꢁ ꢁC8AC9AC10
3.17
2.97
3.08
142
163
161
3.953
3.872
3.969
1/2 ꢃ x, 1/2 + y, ꢃ1/2 + z
1/2 + x, 1/2 ꢃ y, z
ꢃ1/2 + x, 3/2 ꢃ y, z
2
C3AH3ꢁ ꢁ ꢁC10AC11
2.72
2.82
165
153
3.630
3.715
ꢃx, ꢃ1/2 + y, 3/2 ꢃ z
1 + x, y, z
C19AH19Cꢁ ꢁ ꢁC4AC7
a
Cg is the centre of gravity of the proton acceptor moiety.

48
D. Vuk et al. / Journal of Molecular Structure 1065-1066 (2014) 43–51
ꢀ
Fig. 6. Hydrogen bonding 3: (a) three symmetry-inequivalent hydrogen bonds form (b) chains parallel to [110] and ½110ꢂ and (c) zig–zag chains parallel to [101]. Symmetry
operators: (i) ꢃ1 +x, ꢃ1 +y, z; (ii) 1/2 + x, 1 ꢃ y, 1/2 + z.
1H), 5.35 (dd, J = 11.0; 1.1 Hz, 1H), 3.82 (s, 3H, AOCH3); 13C NMR
(CDCl3, 150 MHz) d 158.9 (s), 135.7 (s), 135.1 (s), 134.5 (d), 132.1
(d), 131.2 (d), 129.7 (s), 128.6 (d), 127.3 (d), 127.1 (2d), 127.0 (d),
126.9 (2d), 126.2 (d), 125.3 (d), 115.9 (t), 113.7 (d), 54.8 (q); IR

D. Vuk et al. / Journal of Molecular Structure 1065-1066 (2014) 43–51
49
mmax. 2962, 1599, 1508, 1252þ, 991, 748; HRMS (TOF ES+) m/z for
C
19H18O: Mþ
262.1352; Mfound 262.1347 (for a mixture of iso-
calcd:
mers 2).
(1Z,3E)-1-(p-Nitrophenyl)-4-(o-styrenyl)-1,3-butadiene (cis-
3): 20%; Rf 0.58 (petroleum ether/dichloromethane = 1:1); col-
ourless crystals; mp 96–98 °C; UV (96% EtOH) kmax (log
e)
368 (4.35), 287 (4.04), 246 (4.25); 1H NMR (CDCl3, 600 MHz)
d 8.12 (d, J = 8.8 Hz, 2H), 7.58 (d, J = 7.3 Hz, 1H), 7.26 – 7.35
(m, 3H), 7.14 (ddd, J = 15.7; 11.2; 0.7 Hz, 1H), 6.88 (dd,
J = 17.5; 11.0 Hz, 1H), 6.79 (d, J = 11.2 Hz, 1H), 6.70 (d,
J = 15.7 Hz, 1H), 6.52 (t, J = 11.2 Hz, 1H), 5.70 (dd, J = 17.5;
0.8 Hz, 1H); 5.30 (d, J = 11.0 Hz, 1H); 13C NMR (CDCl3,
150 MHz) d 143.4 (s), 143.3 (s), 136.2 (s), 134.6 (s), 132.1 (d),
131.3 (d), 129.8 (d), 129.6 (d), 129.5 (d), 127.5 (d), 126.3
(2d), 126.1 (d), 125.5 (d), 123.6 (d), 123.5 (d), 115.5 (t); IR mmax.
3022, 1509, 1336, 979, 768.
(1E,3E)-1-(p-Nitrophenyl)-4-(o-styrenyl)-1,3-butadiene
(trans-3): 45%; Rf 0.58 (petroleum ether/dichloromethane = 1 : 1);
colourless crystals; mp 127–129 °C; UV (96% EtOH) kmax (log
(4.52), 295 (4.13), 245 (4.18), 224 (4.18); 1H NMR (CDCl3, 600 MHz)
8.19 (d, J = 8.8 Hz, 2H), 7.55 (d, J = 8.8 Hz, 2H),
e) 379
d
7.52 – 7.55 (m, 1H), 7.45 – 7.48 (m, 1H), 7.26 – 7.30 (m, 2H),
7.13 (dd, J = 15.5; 10.6 Hz, 1H), 7.11 (d, J = 15.5 Hz, 1H), 7.06 (dd,
J = 17.4; 11.0 Hz, 1H), 6.87 (dd, J = 15.5; 10.6 Hz, 1H), 6.70 (d,
J = 15.5 Hz, 1H), 5.64 (dd, J = 17.4; 1.0 Hz, 1H), 5.39 (dd, J = 11.0;
1.0 Hz, 1H); 13C NMR (CDCl3, 150 MHz) d 146.6 (s), 143.9 (s),
136.8 (s), 134.7 (d), 134.0 (d), 133.6 (d), 130.3 (d), 130.3 (d),
128.3 (d), 127.9 (d), 126.9 (d), 126.7 (2d), 126.0 (d), 124.2 (2d),
117.2 (t); IR mmax. 3020, 1508, 1334, þ983, 770; HRMS (TOF ES+)
m/z for C18H15NO2: Mþcalcd: 277.1097; Mfound 277.1106 (for a mixture
of isomers 3).
4.3. General method for the synthesis of 4
Compound 4 was prepared by Wittig reaction from o-xylylene-
bis(triphenylphosphonium bromide) and the cinnamaldehyde. To
a stirred solution of the triphenylphosphonium salt (0.001 mol)
and the cinnamaldehyde (0.011 mol) in absolute ethanol (200 mL),
a solution of sodium ethoxide (0.253 g, 0.011 mol in 15 mL of abso-
lute ethanol) was added dropwise. Stirring was continued under a
stream of nitrogen for 1 h at RT, when was 1.1 eq of acetaldehyde
(0.011 mol) introduced and the next quantity of sodium ethoxide
(0.253 g, 0.011 mol in 15 mL of absolute ethanol) was added drop-
wise. The reaction was completed within 3–4 h (usually was left to
stand overnight). After removal of the solvent, the residue was
worked up with water and toluene. The toluene extracts were dried
(anhydrous MgSO4), concentrated and the crude reaction mixture
was purified. After repeated column chromatography on silica gel
using petroleum ether as the eluent only the trans,trans-isomer of
4 was isolated and completely characterised.
Fig. 7. Crystal packing of 2: (a) Hydrogen bonding chains extending in the direction
interactions, (c) layers parallel to (001) are generated by
(1E,3E)-1-{o-[(E)-1-Propenyl]phenyl}-4-phenyl-1,3-butadi-
ene (trans,trans-4): 30%; Rf 0.88 (petroleum ether/dichlorometh-
ane = 1:1); colourless oil; UV (96% EtOH) kmax (log e) 334 (4.58),
[101], (b) CAHꢁ ꢁ ꢁ
p
hydrogen bonds and CAHꢁ ꢁ ꢁp interactions. Symmetry operator (i) 1 ꢃ x, 1/2 + y,
3/2 ꢃ z.

50
D. Vuk et al. / Journal of Molecular Structure 1065-1066 (2014) 43–51
Fig. 8. Crystal packing of 4.
Table 4
Crystallographic, data collection and structure refinement details.
Compound
1
2
3
4
Empirical formula
C
18H15Cl
C19H18
262.33
O
C18H15NO2
277.31
C19H17
245.33
Formula wt. (g molꢃ1
)
266.75
Crystal dimensions (mm)
Space group
a (Å)
b (Å)
c (Å)
0.20 ꢄ 0.15 ꢄ 0.10
P n a 21
13.7153(4)
4.0083(1)
25.5354(6)
90
0.14 ꢄ 0.12 ꢄ 0.10
P 21 21 21
6.7023(2)
8.4739(3)
26.5374(7)
90
0.16 ꢄ 0.14 ꢄ 0.11
0.14 ꢄ 0.10 ꢄ 0.07
P n
P 21/a
3.9700(1)
6.9998(3)
25.6681(8)
90
14.0608(8)
5.3605(4)
20.0356(12)
90
a
(°)
b (°)
90
90
90
90
91.062(3)
90
98.614(5)
90
c
(°)
Z
4
4
2
4
V (Å3)
1403.81(6)
1.262
2.242
1507.18(8)
1.156
0.537
713.17(4)
1.291
0.676
1493.11(17)
1.091
0.461
Dcalc (g cmꢃ3
l
)
(mmꢃ1
)
H
T (K)
range (°)
3.46–75.61
293(2)
3.33–75.76
293(2)
3.44–75.16
293(2)
4.46–75.88
293(2)
Radiation wavelength
Diffractometer type
Range of h, k, l
1.54179 (Cu K
Xcalibur Nova
ꢃ17 < h < 15;
ꢃ4 < k < 5;
ꢃ30 < l < 31
3852
a
)
1.54179 (Cu K
Xcalibur Nova
ꢃ8 < h < 8;
ꢃ10 < k < 10;
ꢃ33 < l < 24
4680
a
)
1.54179 (Cu K
Xcalibur Nova
ꢃ4 < h < 2;
ꢃ8 < k < 7;
ꢃ31 < l < 32
2742
a
)
1.54179 (Cu K
Xcalibur Nova
ꢃ17 < h < 12;
ꢃ6 < k < 6;
ꢃ21 < l < 23
7527
a)
Reflections collected
Independent reflections
Observed reflections
2187
2086
2715
2441
1871
1716
3066
2163
(I P 2r)
Absorption correction
Rint
Multi-scan
0.0192
Multi-scan
0.0182
Multi-scan
0.0189
Multi-scan
0.0229
R (F)
0.0319
0.0859
0.0381
0.1068
0.0366
0.1021
0.0551
0.2001
Rw (F2)
Goodness of fit
H atom treatment
No. of parameters
No. of restraints
1.058
Constrained
172
1.058
Constrained
181
1.034
Constrained
190
1.041
Constrained
172
1
0
2
0
D
qmax
,
D
qmin (eÅꢃ3
)
0.148; ꢃ0.148
0.113; ꢃ0.092
0.106; ꢃ0.112
0.161; ꢃ0.155

D. Vuk et al. / Journal of Molecular Structure 1065-1066 (2014) 43–51
51
326 (4.58), 266 (4.07), 233 (4.09); 1H NMR (CDCl3; 300 MHz) d 7.51
(d, J = 9.0 Hz, 1H), 7.45 (d, J = 7.4 Hz, 1H), 7.37 (d, J = 9.0 Hz, 1H),
7.32 (t, J = 7.4 Hz, 1H), 7.18–7.25 (m, 3H), 7.02 (dd, J = 15.6;
10.4 Hz, 1H), 6.98 (d, J = 15.6 Hz, 1H), 6.84 (dd, J = 15.6; 10.4 Hz,
1H), 6.72 (dd, J = 15.5; 1.7 Hz, 1H), 6.67 (d, J = 15.6, 1H), 6.09 (dd,
J = 15.5; 6.6 Hz, 1H), 1.94 (dd, J = 6.6, 1.7 Hz, 3H, ACH3); 13C NMR
(CDCl3; 75 MHz) d 137.4 (s), 136.6 (s), 134.8 (s), 132.7 (d), 130.8
(d), 130.6 (d), 129.6 (d), 128.8 (d), 128.7 (2d), 128.6 (d), 127.6
(d), 127.5 (d), 127.0 (d), 126.8 (d), 126.4 (2d), 125.7 (d), 18.9 (q);
supplementary crystallographic data for this paper. Supplementary
data associated with this article can be found, in the online version,
at http://dx.doi.org/10.1016/j.molstruc.2014.02.033.
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19H18: Mþ
calcd:
4.4. Crystallography
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