Synthesis of V-Shaped liquid crystal benzoates

Article abstract of DOI:10.1134/S1070363215070051

V-Shaped mesogens, benzene-1,2-diylbis[4-(4-alkoxybenzoyloxy)benzoates], were synthesized and their mesomorphic behavior was studied. For the homolog with terminal heptyloxy group, enantiotropic nematic and monotropic smectic A phases were observed; the subsequent homologs formed exclusively enantiotropic smectic A phase. It was found that the isomeric ester of benzene-1,2-dicarboxylic acid with heptyloxy groups at the phenol fragments did not possess mesomorphism.

Full text of DOI:10.1134/S1070363215070051

ISSN 1070-3632, Russian Journal of General Chemistry, 2015, Vol. 85, No. 7, pp. 1606–1610. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © L.G. Derkach, N.S. Novikova, E. Górecka, E.D. Kilimenchuk, 2015, published in Zhurnal Obshchei Khimii, 2015, Vol. 85, No. 7,
pp. 1080–1084.
Synthesis of V-Shaped Liquid Crystal Benzoates
L. G. Derkacha, N. S. Novikovaa, E. Góreckab, and E. D. Kilimenchuka
a Bogatsky Physicochemical Institute of the National Academy of Sciences of Ukraine,
Lyustdorfskaya Doroga 86, Odessa, 65080 Ukraine
e-mail: nadyanovikova@rambler.ru
b University of Warsaw, Warsaw, Poland
Received February 26, 2015
Abstract—V-Shaped mesogens, benzene-1,2-diylbis[4-(4-alkoxybenzoyloxy)benzoates], were synthesized and
their mesomorphic behavior was studied. For the homolog with terminal heptyloxy group, enantiotropic
nematic and monotropic smectic A phases were observed; the subsequent homologs formed exclusively
enantiotropic smectic A phase. It was found that the isomeric ester of benzene-1,2-dicarboxylic acid with
heptyloxy groups at the phenol fragments did not possess mesomorphism.
Keywords: esters of 1,2-dihydroxybenzene and benzene-1,2-dicarboxylic acid, V-shaped mesogens
DOI: 10.1134/S1070363215070051
For the last 10 years the molecular design and
synthesis of new classes of liquid crystal compounds in
which anisotropic form of molecules varied from the
classical calamitic or discotic shape are of interest. The
bent-shaped molecules are classified by the following
categories: banana-shaped [1, 2], club-shaped [3, 4], λ-
[5, 6], W- [7, 8], and V(U)-shaped [9–11]. In the V
(U)-shaped compounds the lateral fragments occupied
the 1,2-positions of the central aromatic ring (Scheme 1).
3 and 4 of the benzene ring formed nematic, smectic A
and B phases [12]. The synthesis of V-shaped com-
pounds based on azobenzene III, which can form
nematic, smectic A, and crystal E phases, has been
described in [13]. 1,2-Benzene-1,2-diylbis[4-(4-ethoxy-
phenylazoxy)benzoate] IV is known to form nematic
phase [14].
Analysis of the published data showed that the
described compounds form mesophase in the high-
temperature range and are prone to oxidation.
Therefore for the investigation of the correlation
structure–mesomorphic properties we synthesized ben-
zene-1,2-diylbis[4-(4-alkoxybenzoyloxy)benzoates]
VIIa–VIIf containing exclusively ester groups as the
linkers (Scheme 2).
Mesomorphic behavior of esters I–IV based on
catechol and bearing azomethine (I, II) [12], azo- (III)
[13] and azoxy group (IV) [14] as a linker at the side
acidic fragment have been described. Benzene-1,2-
diylbis[4-(4-alkoxybenzylidenamino)benzoates] I, II
and their analogs bearing methyl group in the positions
Scheme 1.
O
OCnH2n+1
X
O
O
X
OCnH2n+1
O
I_IV
X = –N=CH– (I), –CH=N– (II), –N=N– (III), –N=N(O)– (IV); n= 1–16 (I, II), 4–10 (III), 2 (IV).
1606

1607
SYNTHESIS OF V-SHAPED LIQUID CRYSTAL BENZOATES
Scheme 2.
O
H2n+1CnO
O
O
OH
X
VIa_VIf
X
O
O
OH
OH
O
OCnH2n+1
3
2
1
4
5
O
O
10
9
DCC, DMAP
11
16
20
7
17
6
O
O
8
18
14
O
12
OCnH2n+1
13
15
X
19
VIIa_VIIf
n = 7 (a), 8 (b), 9 (c), 10 (d, f), 12 (e); Х = Н (а–e), Cl (f).
Scheme 3.
SOCl2
H15C7O
H15C7O
COCl
COOH
VIII
IX
HO
OH
O
H15C7O
Na2CO3
KOH
H2O,
OH
O
X
OC7H15
O
OH
O
3
O
2
1
4
5
O
O
OH
DCC, DMAP
7
O
6
16
19
O
17
18
14
O
15
20
OC7H15
XI
4-(4-Alkoxybenzoyloxy)benzoic acids VIa–VIe
were prepared according to the known procedure [15]
by acylation of 4-hydroxybenzaldehyde with the
chlorides of the corresponding 4-alkoxybenzoic acids
followed by oxidation of 4-(4-alkoxybenzoyloxy)-
benzaldehydes with the Jones reagent. 4-(4-De-
cyloxybenzoyloxy)-3-chlorobenzoic acid VIf was
prepared from 4-hydroxy-3-chlorobenzoic acid [16] by
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DERKACH et al.
Transition points (°C) of compounds VIIa–VIIf and XIa
of the lateral fragments connected with the central
aromatic ring by the carbonyl groups. Most probably,
the conformation of molecule at which the angle
between the lateral fragments 60°–70° cannot be
attained that is a necessary condition for the formation
of a mesophase by the V-shaped molecules. If the
mobility of the lateral fragments increases due to the
connection with the central aromatic ring through the
oxygen of an ester group or the oxygen of ether with
an aliphatic chain, such V-shaped structures can
exhibit mesomorphism [9–11].
Comp.
no.
R
Сr
●
SmA
N
(150.4) – 159.7
– 157.2
I
●
●
●
●
●
●
●
VIIa ОС7Н15
VIIb ОС8Н17
VIIc ОС9Н19
VIId ОС10Н21
VIIe ОС12Н25
VIIf OC10H21
151.1
154.1
136.9
122.5
121.8
56.6
●
●
●
●
●
– 159.3
●
– 160.3
●
– 165.9
●
●
The data of small angle X-ray scattering for
compounds VIIa–VIIe showed that the layer thickness
in mesomorphic state was twice less than the molecule
length; for example, for benzene-1, 2-diylbis[4-(4-
octyloxybenzoyloxy)benzoate] VIIb the molecule
length was 56.4 Å, and the layer thickness was 26.4 Å.
The increased length of the terminal alkoxy groups in
homologs VIId and VIIe caused an increase in the
layer thickness in smectic A phase up to 29.1 and
31.9 Å, respectively.
–
79.1
●
XI
ОС7Н15
–
– 143.2
●
a
(Сr) means crystal, (SmA) means smectic А, (N) means nematic,
(I) means isotropic phase.
acylation with 4-decyloxybenzoic acid chloride. The
reaction of acids VIa–VIf with 1,2-dihydroxybenzene
in the presence of N,N'-dicyclohexylcarbodiimide
(DCC) and 4-dimethylaminopyridine (DMAP) in
anhydrous chloroform provided the target compounds
VIIa–VIIf.
EXPERIMENTAL
1H NMR spectra for solutions in CDCl3 were
recorded on a Bruker AVANCE DRX 500 instrument
operating at 500 MHz; internal reference TMS. The
reaction progress and purity of the prepared com-
pounds were monitored by the means of TLC on
Sorbfil high effective aluminum UV plates in
chloroform–methanol (10 : 1); the spots development
was done with iodine vapor or under UV irradiation.
In addition, o-phthalic acid diester, bis[4-(4-heptyl-
oxybenzoyloxy)phenyl]benzene-1,2-dicarboxylate XI,
which is the isomer of benzene-1,2-diylbis[4-(4-
heptyloxybenzoyloxy)benzoate] VIIa, was synthesized
for the first time (Scheme 3).
The structure of compounds VIIa–VIIf, and XI
was established based on the data of 1H NMR
spectroscopy. Mesomorphic properties of the syn-
thesized compounds were investigated by polarization
microscopy (see the table).
Transition points were investigated by polarization
microscopy on a POLAM P-312 microscope. The
X-ray phase analysis was done in the light reflected
from free sample surface on a Bruker GAADS system.
Dielectric response was measured with the use of an
analyzer of complete resistance with the cell of 5 mm
thickness and gold electrodes.
As seen from the table, diesters VIIb–VIIe formed
enantiotropic smectic mesophase of A modification.
An increase in the terminal group length the caused
reduction of the transition point to liquid crystal state
and a weakly pronounced increase in the transition
point to isotropic liquid. Homolog VIIa formed enan-
tiotropic nematic phase and monotropic SmA phase.
Compounds V, VIa–VIf, and X were prepared by
the known methods [15–17].
4-(4-Decyloxybenzoyloxy)-3-chlorobenzoic acid
1
An introduction of a chlorine atom in the aromatic
rings of the lateral acidic fragments caused virtually
two-fold reduction of the temperature of the phase
transitions for compound VIIf and the disappearance
of the ordered smectic phase compared to the unsub-
stituted analog VIIa. Compound XI did not show
mesomorphism probably due to the hampered rotation
(VIf). Yield 2.3 g (59%). Н NMR spectrum (DMSO-
d6), δ, ppm: 0.86 t (3Н, СН3, J 5.7 Hz), 1.15–1.52 m
(16Н, СН2), 1.68–1.85 m (2Н, СН2), 4.10 t (2Н,
OCH2, J 5.7 Hz), 7.14 d (2Н, ArOAlk, 3J 8.1 Hz), 7.60
3
d (1Н, ArCl, J 8.0 Hz), 7.99–8.00 dd (1Н, ArCl, J
4
8.0 Hz, J 0.8 Hz), 8.05–8.2 m (3Н, ArOAlk, ArCl),
13.42 br.s (1Н, СООН). Found, %: C 66.67; H 6.79;
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SYNTHESIS OF V-SHAPED LIQUID CRYSTAL BENZOATES
1
Cl 8.29. C24H29ClO5. Calculated, %: C 66.59; H 6.71;
Cl 8.21.
phous powder. Н NMR spectrum (CDСl3), δ, ppm:
0.91 t (6Н, СН3), 1.25–1.45 m (24Н, СН2), 1.45–1.55
m (4Н, ОСН2СН2СН2), 1.80–1.90 m (4Н, ОСН2СН2),
4.07 t (4Н, ОСН2, J 6.4 Hz) 6.98 d (4Н, Н17,19, J
8.6 Hz), 7.26–7.33 m (4Н, Н10,12), 7.37–7.47 m (4Н,
Н3,4,5,6), 8.10–8.20 m (8Н, Н9,13, 16,20). Found, %: C
74.59; H 7.03. C54H62O10. Calculated, %: C 74.48; H
7.13.
Benzene-1,2-diylbis[4-(4-alkoxybenzoyloxy)benz-
oates] (VIIa–VIIf) (general procedure). 4-(4-Alkoxy-
benzoyloxy)benzoic acid VIa–VIf (0.002 mol) and 4-
dimethylaminopyridine (0.0002 mol) were added to a
suspension of catechol (0.001 mol) in 30 mL of
anhydrous chloroform. The mixture was stirred at
room temperature for 10 min, then N,N'-dicyclohexyl-
carbodiimide (0.002 mol) was added. After 10 h, at
room temperature, the formed solid was filtered off
and washed with anhydrous chloroform (3 × 10 mL).
The filtrate was evaporated. The residue was ground
with cooled ethanol to form crystalline solid. The solid
was filtered off, dried, recrystallized from a mixture of
anhydrous benzene and ethanol (3 : 1), washed with
anhydrous alcohol, and dried.
Benzene-1,2-diylbis[4-(4-dodecyloxybenzoyloxy)-
benzoate] (VIIe). Yield 0.5 g (43.1%), white amor-
1
phous powder. Н NMR spectrum (CDСl3), δ, ppm:
0.91 t (6Н, СН3, J 6.6 Hz), 1.23–1.44 m (32Н, СН2),
1.45–1.55 m (4Н, ОСН2СН2СН2), 1.81–1.90 m (4Н,
ОСН2СН2), 4.07 t (4Н, ОСН2, J 6.6 Hz), 6.98 d (4Н,
Н17,19, J 8.8 Hz), 7.25–7.33 m (4Н, Н10,12), 7.36–7.47
m (4Н, Н3,4,5,6), 8.09–8.20 m (8Н, Н9,13, 16,20). Found,
%: C 75.29; H 7.48. C58H70O10. Calculated, %: C
75.16; H 7.56.
Benzene-1,2-diylbis[4-(4-heptyloxybenzoyloxy)-
benzoate] (VIIa). Yield 0.6 g (90.9%), white amor-
1
phous powder. Н NMR spectrum (CDСl3), δ, ppm:
Benzene-1,2-diylbis[4-(4-decyloxybenzoyloxy)-
0.91 t (6Н, СН3, J 6.9 Hz), 1.25–1.45 m (12Н, СН2),
1.45–1.55 m (4Н, ОСН2СН2СН2), 1.80–1.90 m (4Н,
ОСН2СН2), 4.07 t (4Н, ОСН2, J 6.6 Hz), 6.98 d (4Н,
Н17,19, J 8.6 Hz), 7.26–7.33 m (4Н, Н10,12), 7.37–7.47
m (4Н, Н3,4,5,6), 8.10–8.20 m (8Н, Н9,13,16,20). Found,
%: C 73.57; H 6.24. C48H50O10. Calculated, %: C
73.28; H 6.36.
benzoates] (VIIf). Yield 0.67 g (43.1%), white amor-
phous powder. Н NMR spectrum (CDСl3), δ, ppm:
1
0.91 t (6Н, СН3, J 6.8 Hz), 1.25–1.45 m (24Н, СН2),
1.45–1.55 m (4Н, ОСН2СН2СН2), 1.80–1.90 m (4Н,
ОСН2СН2), 4.07 t (4Н, ОСН2, J 6.4 Hz) 6.98 d (4Н,
Н17,19, J 8.6 Hz), 7.26–7.33 m (4Н, Н10,12), 7.37–7.47
m (4Н, Н3,4,5,6), 8.10–8.20 m (8Н, Н9,13, 16,20). Found,
%: C 68.89; H 6.33. C54H60Cl2O10. Calculated, %: C
69,01; H 6.39.
Benzene-1,2-diylbis[4-(4-octyloxybenzoyloxy)-
benzoate] (VIIb). Yield 1.6 g (78.6%), white amor-
1
phous powder. Н NMR spectrum (CDСl3), δ, ppm:
Bis[4-(4-heptyloxybenzoyloxy)phenyl]benzene-
1,2-dicarboxylate (XI). A mixture of 4-hydroxy-phenyl-
4-heptyloxybenzoate X (0.83 g, 2.5 mmol), o-phthalic
acid (0.21 g, 1.25 mmol), 4-dimethylamino-pyridine
(0.0305 g, 0.25 mmol), and 20 mL of anhyd-rous
chloroform was stirred for 10 min followed by addition
of N,N'-dicyclohexylcarbodiimide (0.515 g, 2.5 mmol).
The reaction mixture was stirred for 20 h, at room
temperature, the formed precipitate was filtered off and
washed with anhydrous chloroform. The filtrate was
evaporated; the residue was recrystallized from ethanol.
Yield 0.8 g (81.6%), white amorphous powder, mp
0.92 t (6Н, СН3, J 6.1 Hz), 1.26–1.44 m (16Н, СН2),
1.45–1.56 m (4Н, ОСН2СН2СН2), 1.80–1.90 m (4Н,
ОСН2СН2), 4.07 t (4Н, ОСН2, J 6.1 Hz), 6.98 d (4Н,
Н17,19, J 8.6 Hz), 7.25–7.33 m (4Н, Н10,12), 7.37–7.47
m (4Н, Н3,4,5,6), 8.21–8.07 m (8Н, Н9,13, 16,20). Found,
%: C 73.79; H 6.71. C50H54O10. Calculated, %: C 73.71;
H 6.63.
Benzene-1,2-diylbis[4-(4-nonyloxybenzoyloxy)-
benzoates] (VIIc). Yield 0.45 g (81.8%), white amor-
1
phous powder. Н NMR spectrum (CDСl3), δ, ppm:
0.93 t (6Н, СН3, J 6.6 Hz), 1.30–1.45 m (20Н, СН2),
1.45–1.55 m (4Н, ОСН2СН2СН2), 1.81–1.90 m (4Н,
ОСН2СН2), 4.07 t (4Н, ОСН2, J 6.6 Hz), 6.98 d (4Н,
Н17,19, J 8.8 Hz), 7.26–7.33 m (4Н, Н10,12), 7.37–7.47
m (4Н, Н3,4,5,6), 8.12–8.17 m (8Н, Н9,13, 16,20). Found,
%: C 69.79; H 7.8. C52H58O10. Calculated, %: C 74.11;
H 6.89.
1
142.3°С. Н NMR spectrum (CDCl3), δ, ppm: 0.90 t
(6Н, СН3, J 6.6 Hz), 1.25–1.43 m (12Н, СН2), 1.43–
1.53 m (4Н, ОСН2СН2СН2), 1.75–1.87 m (4Н,
ОСН2СН2), 4.04 t (4Н, ОСН2, J 6.6 Hz), 6.98 m (4Н,
Н17,19), 7.22–7.33 m (8Н, Н10,12,9,13), 7.37–7.47 m (4Н,
Н
3,4,5,6), 7.70–7.75 m (2Н, Н4,5), 7.98–8.04 m (2Н,
Н3,6) 8.10–8.20 m (4Н, Н16,20). Found, %: C 73.14; H
Benzene-1,2-diylbis[4-(4-decyloxybenzoyloxy)-
benzoate] (VIId). Yield 0.6 g (69%), white amor-
6.58. C48H50O10. Calculated, %: C 73.28; H 6.36.
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DERKACH et al.
vol. 13, p. 2880. DOI: 10.1039/b304964g.
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