Biphenyl based non-symmetrical bent-core mesogens containing a chiral moiety and an olefinic end group

Article abstract of DOI:10.1080/15421406.2014.953746

New nonsymmetrical bent-core compounds consisting of a biphenyl-3,4'-diol central unit, a chiral terminal chain and an olefinic end group at the other terminus have been synthesized and characterized to study the influence of a chiral moiety, the length of terminal alkenyl chain, and the number of aromatic rings in the rod-like wings which are substituted at the 3- and 4-position of central biphenyl core on mesophase properties of bent-core mesogens. The liquid crystalline properties of the compounds were investigated by differential scanning calorimetry, optical polarizing microscopy, and electro-optic methods. Depending on the length of the olefinic chain and the number of aromatic rings in the rod-like wings, the bent-core compounds with a chiral moiety show B₁ type mesophase, polar smectic C phase (SmCP) or nonmesomorphic behavior.

Full text of DOI:10.1080/15421406.2014.953746

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Biphenyl Based Non-symmetrical Bent-
Core Mesogens Containing a Chiral
Moiety and an Olefinic End Group
Hale Ocaka & Belkiz Bilgin-Erana
a Department of Chemistry, Yildiz Technical University, Davutpaşa
Yerleşim Birimi, Esenler, Istanbul, Turkey
Published online: 11 Apr 2015.
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To cite this article: Hale Ocak & Belkiz Bilgin-Eran (2015) Biphenyl Based Non-symmetrical Bent-
Core Mesogens Containing a Chiral Moiety and an Olefinic End Group, Molecular Crystals and Liquid
Crystals, 609:1, 19-30, DOI: 10.1080/15421406.2014.953746
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Mol. Cryst. Liq. Cryst., Vol. 609: pp. 19–30, 2015
Copyright © Taylor & Francis Group, LLC
ISSN: 1542-1406 print/1563-5287 online
DOI: 10.1080/15421406.2014.953746
Biphenyl Based Non-symmetrical Bent-Core
Mesogens Containing a Chiral Moiety
and an Olefinic End Group
HALE OCAK∗ AND BELKIZ BILGIN-ERAN
Department of Chemistry, Yildiz Technical University, Davutpas¸a Yerles¸im
Birimi, Esenler, Istanbul, Turkey
New nonsymmetrical bent-core compounds consisting of a biphenyl-3,4ꢀ-diol central
unit, a chiral terminal chain and an olefinic end group at the other terminus have been
synthesized and characterized to study the influence of a chiral moiety, the length of
terminal alkenyl chain, and the number of aromatic rings in the rod-like wings which
are substituted at the 3- and 4-position of central biphenyl core on mesophase prop-
erties of bent-core mesogens. The liquid crystalline properties of the compounds were
investigated by differential scanning calorimetry, optical polarizing microscopy, and
electro-optic methods. Depending on the length of the olefinic chain and the num-
ber of aromatic rings in the rod-like wings, the bent-core compounds with a chiral
moiety show B1 type mesophase, polar smectic C phase (SmCP) or nonmesomorphic
behavior.
Keywords Bent-core mesogens; chiral moiety; liquid crystals; olefinic end group;
rod-like wings
1. Introduction
Bent-core molecules have attracted considerable attention as they can form polar switchable
(ferroelectric and antiferroelectric) smectic mesophases with a unique combination of layer
chirality and polarity [1]. Bent-core mesogens are formed by covalently linking two rod-
like segments to a central bent unit. A minor structural modification on these segments of
bent-core molecules can strongly alter the mesomorphic behavior or even leads to the loss
of the liquid crystalline properties. For example, the number of rings as well as the diversity
of the terminal alkyl chains in the rod-like wings plays a crucial role for the emergence of
polar-ordered mesophases [2].
Symmetrical bent-core molecules which are composed of a bent-core unit substitute
two identical linear rod-like mesogenic units generally exhibit higher transition tempera-
tures than nonsymmetrical bent-core molecules [3–5]. This means that the phase transition
temperatures can be lowered by introducing some nonsymmetry into the molecular struc-
ture [6, 7]. The nonsymmetry in the bent-core molecules can be provided by different
∗Address correspondence to Hale Ocak, Department of Chemistry, Yildiz Technical University,
Davutpas¸a Yerles¸im Birimi, TR-34220, Esenler, Istanbul, Turkey. E-mail: hocak@yildiz.edu.tr
Color versions of one or more of the figures in the article can be found online at
www.tandfonline.com/gmcl.
19

20
H. Ocak and B. Bilgin-Eran
rod-like wings at the two sides of the central core or arises from differences in the terminal
alkyl(oxy) chain length [8–10].
Chirality is also known to have a major influence on the material properties of liq-
uid crystals. Molecular chirality can be incorporated into the bent-core molecules by
the introduction of asymmetric carbon centers at the chiral alkyl chains [11–16]. It
is remarkable that from some studies that molecular chirality has a pronounced effect
on determining the mesomorphism of bent-core molecules as in calamitic compounds
[17–19].
As reported in some studies [8], bent-core molecules with terminal double bonds may
show a lower transition temperatures than the similar compounds with the saturated terminal
alkyl tails. In addition, the olefin-terminated bent-core compounds having polymerisable
functional groups are promising materials for the preparation of oligomeric or polymeric
liquid crystal systems with unique polar properties [20–22].
Herein, the synthesis and characterization of nonsymmetrical bent-core compounds
consisting of a biphenyl-3,4ꢀ-diol central unit, a chiral terminal chain, and an olefinic end
group at the other terminus are reported. We have been specifically focused on studying the
influence of alkenyl chain length, molecular chirality, and the number of aromatic rings in
the rod-like wing groups on the mesomorphic properties of biphenyl-based nonsymmetric
bent-core compounds here.
2. Results and Discussion
2.1. Synthesis
The bent-core compounds 1–3 with a terminal double bond were synthesized as shown
in Scheme 1. First, the synthesis of 4ꢀ-Benzyloxybiphenyl-3-ol [23–26] was carried out
according to known procedures. Then, 4-[(S)-2-Methylbutoxy]benzoic acid [27] or 4-
[4-(S)-2-Methylbutoxybenzoyloxy]benzoic acid [17, 28, 29] were attached to the 4ꢀ-
Benzyloxybiphenyl-3-ol by esterification using dicyclohexylcarbodiimide (DCC) and 4-
dimethylaminopyridine (DMAP) as catalyst [30] to yield the benzylated intermediates Bz-A
and Bz-B [18], respectively. The chiral moiety of these benzoic acids were introduced by an
etherification reaction of ethyl 4-hydroxybenzoate with the (S)-2-Methylbutyltosylate which
was prepared from the commercially available chiral alcohol by tosylation [31]. After hy-
drolysis, 4-[(S)-2-Methylbutoxy]benzoic acid [27] was obtained. The DCC esterification of
the chiral benzoic acid with 4-hydroxybenzaldehyde, followed by oxidation using sodium
chlorite as oxidizing agent yields to the 4-[4-(S)-2-Methylbutoxybenzoyloxy]benzoic acid.
The spectroscopic data for 4-[4-(S)-2-Methylbutoxybenzoyloxy]benzoic acid are given in
Ocak et. al. [17].
As shown in Scheme 1, the hydrogenolytic deprotection [26] of the benzyl group of the
intermediates Bz-A and Bz-B [18] leads to 3ꢀ-[4-((S)-2-Methylbutoxy)benzoyloxy]biphenyl-
4-ol A and 3ꢀ-[4-((S)-2-Methylbutoxy)benzoyloxy]benzoyloxy]biphenyl-4-ol B [18], respec-
tively. In the final step, the esterification of deprotected intermediates A and B [18] with the
appropriate 4-[4-(alkenyloxy)benzoyloxy]benzoic acid C/n [8, 32] or 4-(alkenyloxy)benzoic
acid D/n [33, 34] by using dicyclohexylcarbodiimide (DCC) and 4-dimethylaminopyridine
(DMAP) as catalyst [30] in dichloromethane yield to the target compounds 1-3. The syn-
thesis of 4-[4-(alkenyloxy)benzoyloxy]benzoic acid C/n [8, 32] or 4-(alkenyloxy)benzoic
acid D/n [33, 34] which are attached to on the one sides of the biphenyl central unit were
carried out according to similar procedures described in ref. [35, 36]

Biphenyl Based Nonsymmetrical Bent-Core Mesogens
21
Scheme 1. Reagents and conditions: (i) cat. [Pd(PPh3)4], NaHCO3,H2O, glyme, reflux 9 h;23,24,25,26
(ii) DCC, DMAP, CH2Cl2, r.t.;30 (iii) H2, Pd/C, THF, 40◦C, 18 h26.
Due to the this fact that the stereogenic center of the chiral alcohol (S)-(-)-2-Methyl-
1-butanol was not touched throughout the synthesis as observed previously in our studies,
[17, 18, 37, 38] it can be assumed that the final products have approximately equal optical
purity as the starting material. Purification of final compounds 1-3 was carried out by column
chromatography on silica gel and crystallization from ethanol. The molecular structures
were characterized by spectroscopic methods (1H-NMR, 13C-NMR, and MS) and also by
elemental analysis. The spectroscopic and analytic data of the materials are consistent with
the proposed structures (see Experimental Details).
2.2. Liquid Crystalline Properties
The mesomorphic properties of the obtained compounds 1-3 were investigated by polarized
light optical microscopy (PM), differential scanning calorimetry (DSC), and one of them
by electro-optical studies. The transition temperatures, corresponding enthalpy values and
mesophase type observed for these compounds are summarized in Table 1.
Depending on terminal chain length and the number of aromatic rings in the rod-like
wings which are attached of the 3ꢀ- or 4-position of biphenyl unit, bent-core compounds 1-3
show liquid crystalline mesophases such as SmCP and B1 or nonmesomorphic behavior
(see Table 1).
On cooling from the isotropic state, Compound 1a containing five aromatic rings
exhibit monotropic polar SmCP that can be detected by the typical Schlieren texture having
multiple brushes (see Fig. 1).
Figure 2 shows the current response of compound 1a under a triangular wave voltage.
When the sample was cooled under an applied field of 200 Vpp, two current peaks per half
period of the applied triangular voltage were detected at a temperature of 94.6◦C. No further
investigations such as direct current (DC) field were possible due to rapid crystallization
during experiment. Hence, the mesophase of compound 1a is assigned as a monotropic
SmCP phase without giving more detailed information about the type of switching (af/fe).

22
H. Ocak and B. Bilgin-Eran
Table 1. Mesophases, phase transition temperatures and transition enthalpies of the
olefins 1-3a
Compound
n
T/◦C [ꢀH/kJ mol-1]
1a
1b
2a
2b
3a
3bb
9
4
9
4
9
4
Cr1 85 [7.7] Cr2 116 [38.0] (SmCP 95 [5.3]) Iso
Cr 118 [32.8] Iso
Cr 103 [32.7] (B1 86 [13.7]) Iso
Cr 92 [19.5] Iso
Cr 143 [55.8] (B1 136 [14.5]) Iso
Cr 143 [22.3] B1 166 [11.1] Iso
aPerkin-Elmer DSC-7; heating/cooling rates 10 K min-1; enthalpy values are given in italics in
square parentheses; abbreviations: Cr = crystalline; B1 = rectangular columnar phase, SmCP =
polar smectic C phase and Iso = isotropic liquid phase; monotropic transitions are indicated by
parentheses.
bThe transition temperatures and mesomorphic properties of compound 3b have already been
reported in Ref. 18.
The SmCP phase obtained for bent-core compound 1a containing five aromatic rings shows
a high value of spontaneous polarization. Ps was calculated to ≈ 896 nC cm−2
.
When compared with compound 1a which exhibits SmCP phase, compound 1b with
a shorter terminal chain is nonmesomorphic. This must be related to the fact that the
shorter terminal chain of compound 1b containing only five aromatic rings in the bent-core
structure leads to relatively strong destabilization of the mesophase.
Compound 2a comprising a one aromatic ring in the olefine terminated rod-like wing
attached to the 4-position of biphenyl unit exhibit monotropic B1 mesophase. On cooling
from the isotropic liquid, a dendritic growth texture was observed which is a characteristic
of the B1 mesophase (see Fig. 1).
Compound 2b with shorter terminal chain behaves similar to compound 1b which has
the same terminal chain length. Increasing or decreasing in the number of the aromatic rings

Biphenyl Based Nonsymmetrical Bent-Core Mesogens
23
Figure 1. The textures obtained between crossed polarizers as observed during cooling just below
the isotropic phase: (a) SmCP phase at 88.8◦C and (b) B1 phase at 85.0◦C for the bent-core molecules
1a and 2a, respectively.
in the rod-like wings which are substituted at the 3- or 4-position of central biphenyl core
does not change the mesomorphic properties as we expected. This leads us to conclude that
the length of terminal chains plays a key role in the emergence of mesogenity for bent-core
compounds comprising five aromatic rings reported here.
Compounds 1 and 2 comprising five aromatic rings in the structure of bent-core
molecule have a lower melting point than compound 3 carrying two aromatic rings in each
rod-like wings. Compound 3a shows a monotropic B1 mesophase with a dendritic growth
texture (see Fig. 3) whereas compound 1a which have one aromatic ring in the chiral moiety
terminated rod-like wing attached to the 3-position of biphenyl central unit exhibits SmCP
phase.
Compound 3b which is previously reported in Ocak et al. [18] shows enatiotropic B1
mesophase. A comparison of the mesomorphic properties of the compound 3a and 3b shows
that thermal stability of B1 mesophase of compound 3b carrying a shorter alkenyl chain

24
H. Ocak and B. Bilgin-Eran
Figure 2. Switching current response on applying a triangular wave field (94.6◦C, 200 Vpp, 9 Hz, 5
kꢁ, 6 μm noncoated ITO cells) in the SmCP phase of compound 1a; (b) the texture observed under
the same conditions.
at terminus is greater than that of compound 3a. Nevertheless, the melting points of both
compounds are nearly the same. Compounds 3a and 3b also exhibits wider mesomorphic
temperature range in comparison with compounds 1 and 2 having a shorter wing at one of the
sides of the central biphenyl core. No polar switching could be observed for the mesophases
of neither compound 2a nor compounds 3a and 3b in the electro-optical studies, which is
also in line with B1 phases reported in refs. [2, 18, 39].
The presence of molecular chirality for compounds 2 and 3 has clearly no effect on
the formation of B1 phases as previously reported bent-core compounds [18, 19, 37]. In
addition, the emergence of SmCP phase for compound 1a are more related to the structural

Biphenyl Based Nonsymmetrical Bent-Core Mesogens
25
Figure 3. The dendritic growth texture obtained between crossed polarizers as observed for the B1
phases of compound 3a at 130◦C.
modifications in this bent-core molecule such as the number of aromatic rings and terminal
chain length in the rod-like units attached to the 3ꢀ- and 4-positions of biphenyl unit than
the presence of a chiral terminal group according to the obtained mesomorphic properties
of the compounds with (S)-2-methylbutoxy group reported here.
3. Experimental Details
3.1. Characterization Methods
1
The characterization of the synthesized compounds are based on H-, 13C-NMR (Varian
Unity 500 and Varian Unity 400 spectrometers, in CDCl3 solutions, with tetramethylsilane
as internal standard), MS [AMD 402 (electron impact, 70 eV), and Thermo Finnigan LCQ
Advantage Max (electrospray ionization)]. Microanalysis was performed using a Leco
CHNS-932 elemental analyzer.
Transition temperatures were measured using a Mettler FP-82 HT hot stage and control
unit in conjunction with a Leica polarizing microscope. The associated enthalpies were
obtained from DSC-thermograms which were recorded on a Perkin-Elmer DSC-7, heating
and cooling rate: 10◦C min−1
.
Electro-optical investigation of compound 1a was carried out by using a commercially
available 6 μm noncoated indium tin oxide (ITO) cell (E.H.C. Japan) with a measuring
area of 1 cm2.
3.2. Synthesis and Analytical Data
Materials: (S)-(-)-2-Methyl-1-butanol (Fluka, 95.0%, [α]20 −6.3 0.5◦, c = 10 in EtOH),
D
was purchased commercially.
3.2.1. Synthesis of the 4ꢀ-Benzyloxy-3-[4-((S)-2-methylbutoxy)benzoyloxy]biphenyl Bz-
A and 4ꢀ-Benzyloxy-3-[4-((S)-2-methylbutoxy)benzoyloxy]benzoyloxy]biphenyl Bz-B. The

26
H. Ocak and B. Bilgin-Eran
synthesis of the 4ꢀ-Benzyloxy-3-[4-((S)-2-methylbutoxy)benzoyloxy]biphenyl Bz-A and
4ꢀ-Benzyloxy-3-[4-((S)-2-methylbutoxy)benzoyloxy]benzoyloxy]biphenyl Bz-B [18] was
carried out by the esterification of 4ꢀ-benzyloxybiphenyl-3-ol [23–26] with the 4-[(S)-
2-Methylbutoxy]benzoic acid27 or 4-[4-(S)-2-Methylbutoxybenzoyloxy]benzoic acid [17,
28, 29], respectively, according to known procedures. The crude products were purified by
column chromatography on silica gel, elution with dichloromethane and crystallized from
ethanol. The preparation procedures and spectroscopic data for compound Bz-B are given
in Ocak et al. [18].
4ꢀ-Benzyloxy-3-[4-((S)-2-methylbutoxy)benzoyloxy]biphenyl (C31H30O4; 466.57
g/mol)
1
Bz-A: Yield: 78%, white crystals; m.p.: 110◦C. H-NMR: δ (ppm) = 8.12 (d, J ≈
9.1 Hz; 2 Ar-H), 7.50 (d, J ≈ 8.9 Hz; 2 Ar-H), 7.45–7.41 (m, 4 Ar-H), 7.39–7.30 (m, 4
Ar-H), 7.12–7.09 (m, 1 Ar-H), 7.01 (d, J ≈ 8.9 Hz; 2 Ar-H), 6.95 (d, J ≈ 9.1 Hz; 2 Ar-H),
5.08 (s, 2H, OCH2Ph), 3.88, 3.80 (2dd, J ≈ 9.0 Hz and J ≈ 6.0 Hz each; 2H, OCH2, (chiral
alkyl chain)), 1.92–1.85 (m, 1H, CH), 1.60–1.19 (m, 2H, CH2), 1.02 (d, J ≈ 6.6 Hz; 3H,
CH3), 0.94 (t, J ≈ 7.5 Hz; 3H, CH3). 13C-NMR: δ (ppm) = 163.64 (CO), 158.56, 151.45,
142.34, 136.89, 133.06, 121.59 (Ar-C), 132.21, 129.56, 128.55, 128.20, 127.93, 127.42,
123.95, 120.06, 119.95, 115.20, 114.35 (Ar-CH), 73.22, 70.22 (OCH2), 34.79 (CH), 26.25
(CH2), 16.63, 11.42 (CH3). MS (EI): m/z (%) = 466 (16) [M+], 191 (100) [M+-C19H15O2],
121 (80) [C5H11], 91 (37) [C2H6].
3.2.2. Synthesis of the 3ꢀ-[4-((S)-2-Methylbutoxy)benzoyloxy]biphenyl-4-ol A and 3ꢀ-[4-
((S)-2-Methylbutoxy)benzoyloxy]benzoyloxy]biphenyl-4-ol B. The deprotection of the ben-
zyl group of the Bz-A and Bz-B to obtain 3ꢀ-[4-((S)-2-Methylbutoxy)benzoyloxy]biphenyl-
4-ol A and 3ꢀ-[4-((S)-2-Methylbutoxy)benzoyloxy]benzoyloxy]biphenyl-4-ol B [18] was
carried out under catalytic hydrogenation conditions (H2, Pd/C in THF) according to pro-
cedures described in ref.26 The compounds were purified by column chromatography on
silica gel using dichloromethane as eluent.
The preparation procedures and spectroscopic data for compound B are given in Ocak
et al. [18].
3ꢀ-[4-((S)-2-Methylbutoxy)benzoyloxy]biphenyl-4-ol (C24H24O4; 376.45 g mol−1
)
A: Yield: 47%, yellowish crystals; m.p.: 99◦C. H-NMR: δ (ppm) = 8.14 (d, J ≈
8.7 Hz; 2 Ar-H), 7.45–7.39 (m, 4 Ar-H), 7.37–7.35 (m, 1 Ar-H), 7.13–7.10 (m, 1 Ar-H),
6.96 (d, J ≈ 8.7 Hz; 2 Ar-H), 6.86 (d, J ≈ 8.3 Hz; 2 Ar-H), 3.89, 3.81 (2dd, J ≈ 8.9 Hz
and J ≈ 6.2 Hz each; 2H, OCH2, (chiral alkyl chain)), 1.93–1.85 (m, 1H, CH), 1.60–1.20
(m, 2H, CH2), 1.03 (d, J ≈ 6.6 Hz; 3H, CH3), 0.95 (t, J ≈ 7.3 Hz; 3H, CH3). 13C-NMR: δ
(ppm) = 163.74 (s; CO), 155.46, 151.43, 142.39, 132.90, 121.46 (Ar-C), 132.26, 129.62,
128.41, 123.99, 120.07, 119.93, 115.65, 114.33 (Ar-CH), 73.10 (OCH2), 34.62 (CH), 26.06
(CH2), 16.46, 11.26 (CH3). MS (EI): m/z (%) = 376 (36) [M+], 191 (100) [M+-C12H9O2],
121 (77) [C5H11].
1
3.2.3. Synthesis of the Olefins 1-3. Compounds 1-3 with a terminal double bond
were obtained by esterification of 3ꢀ-[4-((S)-2-Methylbutoxy)benzoyloxy]biphenyl-4-
ol A (2 mmol) or 3ꢀ-[4-((S)-2-Methylbutoxy)benzoyloxy]benzoyloxy]biphenyl-4-ol B
with the appropriate 4-[4-(alkenyloxy)benzoyloxy]benzoic acid C/n (2 mmol) or 4-
(alkenyloxy)benzoic acid D/n (2 mmol), using 2.3 mmol of dicyclohexylcarbodiimide
(DCC) as condensation agent and DMAP (0.4 mmol) as catalyst in 20 ml of dry
dichloromethane [30]. The reaction mixture was stirred at room temperature under an argon
atmosphere for 24 h. The precipitate was filtered, the solvent was evaporated. The crude

Biphenyl Based Nonsymmetrical Bent-Core Mesogens
27
products were purified by column chromatography on silica gel using dichloromethane as
eluent and recrystallized from ethanol. The spectroscopic data for compound 3b are given
in Ocak et al. [18].
3ꢀ-[4-((S)-2-Methylbutoxy)benzoyloxy]-4-{4-[4-(10-undecenyloxy)benzoyloxy] ben-
zoyloxy}biphenyl (C49H52O8; 768.95 g/mol)
1a: Yield: 0.87 g (57%) of white crystals. 1H-NMR: δ (ppm) = 8.28 (d; J ≈ 8.7 Hz; 2
Ar-H), 8.15 (d; J ≈ 8.9 Hz; 2 Ar-H), 8.14 (d; J ≈ 8.9 Hz; 2 Ar-H), 7.64 (d; J ≈ 8.5 Hz; 2
Ar-H), 7.48-7.47 (m; 2 Ar-H), 7.42 (broad s; 1 Ar-H), 7.36 (d; J ≈ 8.7 Hz; 2 Ar-H), 7.29
(d; J ≈ 8.5 Hz; 2 Ar-H), 7.21-7.18 (m, 1 Ar-H), 6.97 (d; J ≈ 8.9 Hz; 4 Ar-H), 5.85-5.75
(m; 1H, CH2 = CH), 5.00-4.91 (m; 2H, CH2 = CH), 4.04 (t; J ≈ 6.4 Hz; 2H, OCH2), 3.90,
3.82 (2dd, J ≈ 9.1 Hz and J ≈ 6.0 Hz each; 2H, OCH2, (chiral alkyl chain), 2.06-2.00 (m;
2H, CH2 = CH-CH2), 1.94-1.87 (m; 1H, CH), 1.86-1.77 (m, 2H, CH2), 1.63-1.24 (m; 7
CH2), 1.03 (d; J ≈ 6.6 Hz; 3H, CH3), 0.96 (t; J ≈ 7.5 Hz; 3H, CH3). 13C-NMR: δ (ppm)
= 164.83, 164.35, 164.20 (CO), 163.76, 163.69, 155.30, 151.50, 150.57, 141.92, 138.10,
126.84, 121.52, 121.01 (Ar-C), 132.38, 132.26, 131.79, 129.72, 128.28, 124.41, 122.08,
122.01, 120.72, 120.55, 114.45, 114.37 (Ar-CH), 139.12 (CH2 = CH), 114.13 (CH2 =
CH), 73.22, 68.49 (OCH2), 34.80 (CH), 33.92, 29.83, 29.62, 29.54, 29.47, 29.24, 29.07,
26.26, 26.12 (CH2), 16.65, 11.45 (CH3). MS (EI): m/z (%) = 768 (1) [M+], 393 (4) [M+-
C24H23O4], 273 (45) [C7H4O2], 191 (69) [M+-C37H37O6], 121 (100) [C5H11]. C49H52O8
(768.95); Anal. Calc.: C, 76.53; H, 6.81. Found: C, 76.23; H, 6.67%.
3ꢀ-[4-((S)-2-Methylbutoxy)benzoyloxy]-4-{4-[4-(5-hexenyloxy)benzoyloxy] benzoy-
loxy}biphenyl (C44H42O8; 698.81 g/mol)
1b: Yield: 0.77 g (55%) of white crystals. 1H-NMR: δ (ppm) = 8.28 (d; J ≈ 8.7 Hz; 2
Ar-H), 8.14 (d; J ≈ 8.9 Hz; 2 Ar-H), 8.13 (d; J ≈ 8.9 Hz; 2 Ar-H), 7.64 (d; J ≈ 8.7 Hz; 2
Ar-H), 7.48-7.47 (m; 2 Ar-H), 7.42 (broad s; 1 Ar-H), 7.36 (d; J ≈ 8.7 Hz; 2 Ar-H), 7.28
(d; J ≈ 8.7 Hz; 2 Ar-H), 7.20-7.17 (m, 1 Ar-H), 6.97 (d; J ≈ 8.9 Hz; 4 Ar-H), 5.87-5.77
(m; 1H, CH2 = CH), 5.06-4.97 (m; 2H, CH2 = CH), 4.05 (t; J ≈ 6.4 Hz; 2H, OCH2), 3.90,
3.82 (2dd, J ≈ 9.1 Hz and J ≈ 6.0 Hz each; 2H, OCH2, (chiral alkyl chain)), 2.16-2.11 (m;
2H, CH2 = CH-CH2), 1.92-1.87 (m; 1H, CH), 1.86-1.80 (m, 2H, CH2), 1.62-1.24 (m; 2
CH2), 1.03 (d; J ≈ 6.6 Hz; 3H, CH3), 0.96 (t; J ≈ 7.5 Hz; 3H, CH3). 13C-NMR: δ (ppm)
= 164.84, 164.35, 164.19 (CO), 163.77, 163.68, 155.37, 151.49, 150.56, 141.92, 138.10,
126.85, 121.51, 121.07 (Ar-C), 132.39, 132.25, 131.79, 129.72, 128.28, 124.41, 122.07,
122.00, 120.72, 120.55, 114.90, 114.43 (Ar-CH), 138.26 (CH2 = CH), 114.37 (CH2 =
CH), 73.22, 68.25 (OCH2), 34.80 (CH), 33.49, 28.67, 26.26, 25.41 (CH2), 16.65, 11.45
(CH3). MS (EI): m/z (%) = 698 (1) [M+], 203 (59) [M+-C31H27O6], 191 (58) [C32H27O6],
121 (100) [C5H11]. C44H42O8 (698.81); Anal. Calc.: C, 75.62; H, 6.06. Found: C, 75.60;
H, 6.05%.
3ꢀ-{4-[4-((S)-2-Methylbutoxy)benzoyloxy]benzoyloxy}-4-[4-(10-undecenyloxy)ben-
zoyloxy] biphenyl (C49H52O8; 768.95 g/mol)
2a: Yield: 0.71 g (46%) of white crystals. 1H-NMR: δ (ppm) = 8.29 (d; J ≈ 8.7 Hz; 2
Ar-H), 8.14 (d; J ≈ 8.7 Hz; 4 Ar-H), 7.63 (d; J ≈ 8.5 Hz; 2 Ar-H), 7.49-7.48 (m; 2 Ar-H),
7.44 (broad s; 1 Ar-H), 7.37 (d; J ≈ 8.7 Hz; 2 Ar-H), 7.27 (d; J ≈ 8.5 Hz; 2 Ar-H), 7.21-7.18
(m, 1 Ar-H), 6.98 (d; J ≈ 8.7 Hz; 2 Ar-H), 6.96 (d; J ≈ 8.7 Hz; 2 Ar-H), 5.79-5.75 (m;
1H, CH2 = CH), 5.00-4.90 (m; 2H, CH2 = CH), 4.03 (t; J ≈ 6.6 Hz; 2H, OCH2), 3.90,
3.83 (2dd, J ≈ 9.0 Hz and J ≈ 5.8 Hz each; 2H, OCH2, (chiral alkyl chain)), 2.04-2.00 (m;
2H, CH2 = CH-CH2), 1.91-1.88 (m; 1H, CH), 1.83-1.79 (m, 2H, CH2), 1.60-1.24 (m; 7
CH2), 1.04 (d; J ≈ 6.6 Hz; 3H, CH3), 0.96 (t; J ≈ 7.5 Hz; 3H, CH3). 13C-NMR: δ (ppm)
= 164.84, 164.41, 164.26 (CO), 163.96, 163.55, 155.41, 151.32, 150.85, 142.15, 137.73,
126.87, 121.50, 120.97 (Ar-C), 132.37, 132.27, 131.79, 129.79, 128.20, 124.64, 122.14,

28
H. Ocak and B. Bilgin-Eran
122.08, 120.51, 120.40, 114.45, 114.32 (Ar-CH), 139.14 (CH2 = CH), 114.10 (CH2 = CH),
73.20, 68.36 (OCH2), 34.69 (CH), 33.81, 29.51, 29.43, 29.36, 29.13, 28.96, 26.14, 26.01
(CH2), 16.52, 11.32 (CH3). MS (EI): m/z (%) = 768 (10) [M+], 273 (100) [M+-C31H27O6],
191 (31) [M+-C37H37O6], 121 (71) [C5H11]. C49H52O8 (768.95); Anal. Calc.: C, 76.54; H,
6.81. Found: C, 76.44; H, 6.64%.
3ꢀ-{4-[4-((S)-2-Methylbutoxy)benzoyloxy]benzoyloxy}-4-[4-(5-hexenyloxy)benzoy-
loxy] biphenyl (C44H42O8; 698.81 g/mol)
2b: Yield: 1.05 g (75%) of white crystals. 1H-NMR: δ (ppm) = 8.30 (d; J ≈ 8.7 Hz; 2
Ar-H), 8.16 (d; J ≈ 8.5 Hz; 4 Ar-H), 7.65 (d; J ≈ 8.6 Hz; 2 Ar-H), 7.51-7.50 (m; 2 Ar-H),
7.45 (broad s; 1 Ar-H), 7.38 (d; J ≈ 8.7 Hz; 2 Ar-H), 7.29 (d; J ≈ 8.6 Hz; 2 Ar-H), 7.23-7.21
(m, 1 Ar-H), 6.99 (d; J ≈ 8.5 Hz; 2 Ar-H), 6.97 (d; J ≈ 8.5 Hz; 2 Ar-H), 5.84-5.81 (m;
1H, CH2 = CH), 5.07-4.98 (m; 2H, CH2 = CH), 4.06 (t; J ≈ 6.4 Hz; 2H, OCH2), 3.92,
3.84 (2dd, J ≈ 9.1 Hz and J ≈ 6.0 Hz each; 2H, OCH2, (chiral alkyl chain)), 2.17-2.13 (m;
2H, CH2 = CH-CH2), 1.93-1.88 (m; 1H, CH), 1.86-1.82 (m, 2H, CH2), 1.63-1.25 (m; 2
CH2), 1.05 (d; J ≈ 6.8 Hz; 3H, CH3), 0.97 (t; J ≈ 7.5 Hz; 3H, CH3). 13C-NMR: δ (ppm)
= 164.78, 164.37, 164.22 (CO), 163.92, 163.45, 155.39, 151.30, 150.82, 142.13, 137.73,
126.88, 121.58, 120.98 (Ar-C), 132.37, 132.28, 131.78, 129.79, 128.21, 124.64, 122.14,
122.09, 120.52, 120.40, 114.88, 114.47 (Ar-CH), 138.29 (CH2 = CH), 114.33 (CH2 = CH),
73.27, 68.20 (OCH2), 34.80 (CH), 33.50, 28.69, 26.26, 25.42 (CH2), 16.64, 11.45 (CH3).
MS (EI): m/z (%) = 698 (1) [M+], 203 (91) [M+-C31H27O6], 191 (38) [M+-C32H27O6],
121 (100) [C5H11]. C44H42O8 (698.81); Anal. Calc.: C, 75.62; H, 6.05. Found: C, 75.37;
H, 6.00%.
3ꢀ-{4-[4-((S)-2-Methylbutoxy)benzoyloxy]benzoyloxy}-4-{4-[4-(10-undecenyloxy)
benzoyloxy]benzoyloxy}biphenyl (C56H56O10; 889.05 g mol−1
)
3a: Yield: 1.17 g (66%) of white crystals. 1H-NMR: δ (ppm) = 8.29 (d; J ≈ 8.7 Hz; 2
Ar-H), 8.28 (d; J ≈ 8.7 Hz; 2 Ar-H), 8.14 (d; J ≈ 8.9 Hz; 4 Ar-H), 7.65 (d; J ≈ 8.7 Hz; 2
Ar-H), 7.51-7.50 (m; 2 Ar-H), 7.44 (broad s; 1 Ar-H), 7.37 (d; J ≈ 8.7 Hz; 2 Ar-H), 7.36
(d; J ≈ 8.7 Hz; 2 Ar-H), 7.30 (d; J ≈ 8.7 Hz; 2 Ar-H), 7.22-7.19 (m, 1 Ar-H), 6.98 (d; J ≈
8.9 Hz; 2 Ar-H), 6.97 (d; J ≈ 8.9 Hz; 2 Ar-H), 5.84-5.77 (m; 1H, CH2 = CH), 5.00-4.91
(m; 2H, CH2 = CH), 4.04 (t; J ≈ 6.6 Hz; 2H, OCH2), 3.91, 3.83 (2dd, J ≈ 9.1 Hz and
J ≈ 6.0 Hz each; 2H, OCH2, (chiral alkyl chain)), 2.06-2.00 (m; 2H, CH2 = CH-CH2),
1.93-1.88 (m; 1H, CH), 1.85-1.78 (m, 2H, CH2), 1.62-1.24 (m; 7 CH2), 1.04 (d; J ≈ 6.9 Hz;
3H, CH3), 0.96 (t; J ≈ 7.3 Hz; 3H, CH3). 13C-NMR: δ (ppm) = 164.42, 164.34, 164.31,
164.20 (CO), 163.92, 163.75, 155.42, 151.33, 150.63, 142.06, 137.98, 126.87, 126.83,
121.02, 120.99 (Ar-C), 132.39, 131.80, 129.83, 128.30, 124.67, 122.09, 122.05, 120.58,
120.42, 114.46, 114.45 (Ar-CH), 139.09 (CH2 = CH), 114.12 (CH2 = CH), 73.20, 68.42
(OCH2), 34.69 (CH), 33.81, 30.98, 29.51, 29.43, 29.36, 29.13, 28.96, 26.14, 26.01 (CH2),
16.52, 11.32 (CH3). MS (EI): m/z (%) = 889 (1) [M+], 393 (5) [M+-C31H27O6], 273 (45)
[M+-C7H4O2], 191 (74) [M+-C44H41O8], 121 (100) [C5H11]. C56H56O10 (889.05); Anal.
Calc.: C, 75.65; H, 6.35. Found: C, 75.35; H, 6.14%.
4. Conclusions
We have synthesized and characterized new nonsymmetrical bent-core compounds consist-
ing of a biphenyl-3,4ꢀ-diol central unit, a chiral terminal chain and an olefinic end group at
the other terminus to study structure—mesogenic property relations of bent-core molecules
combining molecular chirality with superstructural chirality. The thermal stability and
mesophase type of the non-symmetrical bent-core molecules are significantly influenced
by varying the structure of rod-like wings at the two sides of the 3ꢀ- or 4-position of biphenyl

Biphenyl Based Nonsymmetrical Bent-Core Mesogens
29
central core. Depending on the length of the olefinic chain and the number of aromatic rings
in the rod-like wings, the studied compounds exhibit liquid crystalline mesophases such as
SmCP and B1 or nonmesomorphic behavior. For one of the five-ring compounds with the
chiral moiety at the shorter wing of the bent structure, the SmCP was observed. Decreasing
the terminal alkenyl chain length of bent-core compounds comprising five aromatic rings
leads to nonmesomorphism. The broader mesomorphic ranges were exclusively obtained
for biphenyl based bent-core compounds with the longer wings. From the obtained data, we
also conclude that the molecular chirality has no effect on the mesophases of the molecules
reported here.
Funding
The work has been supported by the Scientific and Technological Research Council of
Turkey (TUBITAK) under Project Number: 107T395.
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