Synthesis and phase behavior of new isoflavone derivatives: Crystal structure of 7-hexyloxy-3-[4′-(3-methylbutyloxy)phenyl]-4H-1-benzopyran-4- one

Article abstract of DOI:10.1080/15421400801914723

This article describes the synthesis and mesomorophic behavior of a novel homologous series of 7-alkyloxy-3-[4'-(3-methylbutyloxyphenyl)-4H-1-benzopyran- 4-one. The title compounds were made up of central isoflavone core with branched and linear alkyloxy terminal chains at C-4' and C-7, respectively. The influences of linear alkyloxy terminal chain in different length of OR (where R=CnH2n+1; even number of n ranging from 4 to 18) were discussed. The thermal behavior especially the phase transition and respective enthalpy values of the compounds thus synthesized were analyzed using differential scanning calorimetry. The occurrence of mesophases under the polarized light has suggested the molecular orientation and arrangement of the title compounds. The molecular structure of compound 7-hexyloxy-3-[4'-(3methylbutyloxyphenyl)]-4H-1- benzopyran-4-one in crystal phase was confirmed by single-crystal X-ray diffraction of which the space group is P-1(#2) with the lattice parameters a=6.100(5) , b=11.704(10) , c=17.082(17) , =80.85(4), =85.56(4), =72.48(3), and V=1147.6(18) 3. The elongated alkyloxy terminal chains were found to be fully stretched in solid phase. All present compounds except the derivative with R=C4H9 were smectogenic.

Full text of DOI:10.1080/15421400801914723

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Synthesis and Phase
Behavior of New Isoflavone
Derivatives: Crystal Structure
of 7-Hexyloxy-3-[4′-(3-
methylbutyloxy)phenyl]-4H-1-
benzopyran-4-one
Guan-Yeow Yeap a , Wan-Sinn Yam a , Daisuke
Takeuchi b , Masaki Kakeya b & Kohtaro Osakada b
a Liquid Crystal Research Laboratory, School of
Chemical Sciences, Universiti Sains Malaysia ,
Penang, Malaysia
b Chemical Resources Laboratory, Tokyo Institute of
Technology , Yokohama, Japan
Published online: 22 Sep 2010.
To cite this article: Guan-Yeow Yeap , Wan-Sinn Yam , Daisuke Takeuchi , Masaki
Kakeya & Kohtaro Osakada (2008) Synthesis and Phase Behavior of New Isoflavone
Derivatives: Crystal Structure of 7-Hexyloxy-3-[4′-(3-methylbutyloxy)phenyl]-4H-1-
benzopyran-4-one, Molecular Crystals and Liquid Crystals, 482:1, 87-102, DOI:
10.1080/15421400801914723
To link to this article: http://dx.doi.org/10.1080/15421400801914723
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Mol. Cryst. Liq. Cryst., Vol. 482, pp. 87–102, 2008
Copyright # Taylor & Francis Group, LLC
ISSN: 1542-1406 print=1563-5287 online
DOI: 10.1080/15421400801914723
Synthesis and Phase Behavior of New Isoflavone
Derivatives: Crystal Structure of 7-Hexyloxy-3-[40-(3-
methylbutyloxy)phenyl]-4H-1-benzopyran-4-one
Guan-Yeow Yeap1, Wan-Sinn Yam1, Daisuke Takeuchi2,
Masaki Kakeya2, and Kohtaro Osakada2
1Liquid Crystal Research Laboratory, School of Chemical Sciences,
Universiti Sains Malaysia, Penang, Malaysia
2Chemical Resources Laboratory, Tokyo Institute of Technology,
Yokohama, Japan
This article describes the synthesis and mesomorophic behavior of a novel
homologous series of 7-alkyloxy-3-[40-(3-methylbutyloxyphenyl)-4H-1-benzopyran-
4-one. The title compounds were made up of central isoflavone core with branched
and linear alkyloxy terminal chains at C-40 and C-7, respectively. The influences of
linear alkyloxy terminal chain in different length of OR (where R¼CnH2nþ1; even
number of n ranging from 4 to 18) were discussed. The thermal behavior especially
the phase transition and respective enthalpy values of the compounds thus synthe-
sized were analyzed using differential scanning calorimetry. The occurrence of
mesophases under the polarized light has suggested the molecular orientation
and arrangement of the title compounds. The molecular structure of compound
7-hexyloxy-3-[40-(3methylbutyloxyphenyl)]-4H-1-benzopyran-4-one in crystal phase
was confirmed by single-crystal X-ray diffraction of which the space group is
˚
˚
P-1(#2) with the lattice parameters a ¼ 6.100(5) A, b ¼ 11.704(10) A,
ꢀ
ꢀ
ꢀ
˚
c ¼ 17.082(17) A, a ¼ 80.85(4) , b ¼ 85.56(4) , c ¼ 72.48(3) , and V ¼ 1147.6(18)
3
˚
A . The elongated alkyloxy terminal chains were found to be fully stretched in
solid phase. All present compounds except the derivative with R ¼ C4H9 were
smectogenic.
Keywords: 7-alkyloxy-3-[40-(3-methylbutyloxyphenyl)-4H-1-benzopyran-4-one; meso-
morphic behavior; single-crystal X-ray diffraction; smectogenic
Received April 25, 2007; accepted July 25, 2007.
Address correspondence to Guan-Yeow Yeap, Liquid Crystal Research Laboratory,
School of Chemical Sciences, University Sains Malaysia, Minden, Penang, 11800,
Malaysia. E-mail: gyyeap@usm.my or gyyeap_liqcryst_usm@yahoo.com
87

88
G.-Y. Yeap et al.
INTRODUCTION
The mesogenicity of several isoflavone derivatives with classical
calamitic structure containing one or two terminal chains have exten-
sively been studied in recent years [1–4]. The introduction of hetero-
cyclic rings within the central core and the linking groups between
the middle and the terminal fragments have claimed to be responsible
for the liquid crystalline behavior of classical calamitic mesogens
leading to various mesomorphism. The relationship between the
difference in phase behavior of this type of compounds and their
molecular structure has recently been reported in our laboratory of
which the anisotropic properties of the molecules were dependent on
their polarizability values which in turn corresponded with the occur-
rence of intermolecular interaction within the mesomorphic region [5].
In this article, we report the synthesis and mesomorphic properties of
other newly derived isoflavones 7-alkyloxy-3-[40-(3-methylbutyloxy-
phenyl)-4H-1-benzopyran-4-one. A crystal structure of 7-hexyloxy-
3-[40-(3-methyl-butyloxyphenyl)]-4H-1-benzopyran-4-one was confirmed
along with Fourier transformed infrared (FTIR) and high resolution
nuclear magnetic resonance (1H and 13C NMR) spectroscopy.
The phase behavior and texture observation were investigated using
differential scanning calorimetry (DSC) and polarizing optical micro-
scope (POM). The synthetic routes towards the formation of the
intermediates and title compounds were shown in Scheme 1.
EXPERIMENTAL
4-Hydroxyphenylacetic acid, 1-bromo-3-methylbutane (Acros), resorci-
nol (Aldrich), methanesulfonyl chloride, boron trifluoride, potassium
carbonate, 1-bromobutane, 1-bromohexane, 1-bromooctane, 1-bromo-
decane, 1-bromododecane, 1-bromotetradecane, 1-bromohexadecane
and 1-bromooctadecane (Merck) were used directly without further
purification.
Thin-layer chromatography analyses were performed using
aluminium-backed silica-gel plates (Merck 60 F254) and were exam-
ined under UV light. Column chromatography was performed under
gravity using Merck 60-mesh silica gel.
Microanalyses for all the final compounds 4–11 were carried out on
2400 LS Series CHNS=O analyzer.
The FTIR data were recorded using a Perkin Elmer 2000-FTIR spec-
trophotometer in the frequency range 4000-400 cmꢁ1 with samples pre-
pared in KBr pellets. The bands associated with the stretching
=
=
vibrations of aliphatic C-H, C O pyranone and C C in compounds

Synthesis and Phase Behavior of New Isoflavone Derivatives
89
SCHEME 1 Synthetic route towards the formation of intermediates (2, 3) and
title compounds 4–11. Reagents and conditions: (i) BF3=Et2O heat at 70–75ꢀC
for 4h; (ii) N2 atmosphere, DMF, BF3=Et2O heat at 55ꢀC for 1 h; MeSO2Cl heat
=
for 1.5 h; (iii) RBr (R CnH2nþ1 and n are even numbers ranging from 4 to 18);
K2CO3=acetone; reflux overnight.
4–11 were observed in their respective FTIR spectra (nCꢁH
¼
2850–2957 cmꢁ1, nC O ¼ 1631–1633 cmꢁ1, and nC ¼ 1256–1258 cmꢁ1).
=
BC
NMR (1H and 13C) analyses were performed by a Bruker 400 MHz
ultrashield spectrometer. Deuterated chloroform (CDCl3) and
dimethylsulphoxide (DMSO-d6) were used as solvents and TMS as
internal standard. The NMR spectra for all members of the homo-
logous series exhibit similar trend in 1H-1H splitting and
chemical shifts. Aromatic protons are observed within the chemical
shift (d) range of 6.82–8.23 ppm whereas the triplets observed at
d ¼ 4.04–4.06 ppm and 4.00–4.03 ppm for the compounds 4–11 can be

90
G.-Y. Yeap et al.
ascribed to the OCH2 attached to C-7 and C-40 at the respective ether
linkages. The signals due to the methylene and methine protons in the
branched alkyloxy chain at C-40 were overlapped within d ¼ 1.80–
1.91 ppm. The resonances in relation to two methyl protons in the
branched alkyloxy chain appear as doublet within d ¼ 0.97–0.99.
Multiplets and triplets within the d ¼ 1.26–1.80 ppm and 0.88–0.96 ppm
can be attributed to the presence of methylene and methyl protons
of the linear alkyloxy terminal chain attached to C-7. Inspection
from the 13C NMR spectra shows the peaks at d ¼ 175.89–176.29 ppm
=
owing to the presence of pyranone C O. The presence of peaks at
66.45–69.15 ppm indicates the presence of ether groups.
The phase transition temperatures and enthalpy values were
measured by Seiko DSC6200R differential scanning calorimetry at
heating and cooling rate of 5ꢀC minꢁ1 and ꢁ5ꢀC minꢁ1, respectively.
The textures of the mesophases were studied using a Carl Zeiss polar-
izing microscope attached with a Linkam LTS350 hot stage and
temperature controller. The samples studied by optical microscopy
were prepared in thin film sandwiched between glass slide and cover.
The thermal behavior was studied via the enthalpy values expressed
in kJ molꢁ1
.
The molecular simulation using the ACD=Chemsketch Version 4.5
has been carried out in order to acquire the information with respect
to the molecular conformation and geometry. The refinement on the
conformation can be achieved through the geometrical optimization
or energy minimization upon the molecule prior to obtain the polariz-
ability of each compound.
X-Ray Crystal Structure Analysis for Compound 5
A colorless prism crystal of C26H32O having approximate dimensions
of 0.17 ꢂ 0.15 ꢂ 0.10 m was mounted on a glass fiber. All measurement
were carried out on a Crystal Clear (Rigaku) Saturn CCD area detec-
˚
tor with graphite monochromated Mo-Ka radiation, (k ¼ 0.71070 A)
with the aid of CrystalStructure and related software [6,7] to a
maximum 2h value of 54.8ꢀ. Cell constants and an orientation matrix
for data collection corresponded to a primitive triclinic cell. Data were
collected at a temperature of ꢁ160 ꢃ 1ꢀC. A total of 720 oscillation
images were collected. A sweep of data was done using x scans from
ꢁ110.0 to 70.0ꢀ in 0.5ꢀ step, at v ¼ 45.0ꢀ and / ¼ 0.0ꢀ. The exposure
rate was 100.0 [sec=ꢀ]. The detector swing angle was ꢁ20.07ꢀ. A second
sweep was performed using x scans from ꢁ110.0 to 70.0ꢀ in 0.5ꢀ step,
at v ¼ 45.0ꢀ and 90.0ꢀ with the same exposure rate and detector swing
angle. Readout was performed in the 0.547 mm pixel mode.

Synthesis and Phase Behavior of New Isoflavone Derivatives
91
Of the 6347 reflections that were collected, 3982 were unique
(Rint ¼ 0.036); equivalent reflections were merged. Data were collected
and processed using Crystal Clear (Rigaku). The linear absorption
coefficient, l, for Mo-Ka radiation is 0.781 cmꢁ1. An empirical absorp-
tion correction was applied which resulted in transmission factors
from 0.739 to 0.992. The data were collected for Lorentz and polariza-
tion effects. The structure was solved by direct methods [8] and
expanded using Fourier techniques [9]. The nonhydrogen atoms were
refined anisotropically. Hydrogen atoms were refined using the riding
model. The final cycle of full-matrix least-squares refinement on F2
was based on 1916 observed reflections and 303 variable parameters
and converged (largest parameter shifts was 0 times its esd) with
unweighted and weighted agreement factors of R1 ¼ 0.0823 and
wR2 ¼ 0.2121. The standard deviation of an observation of unit
weight was 1.00. A Sheldrick weighting scheme was used. Plots of
2
RwðjFoj ꢁ jFcjÞ versus jFoj, reflection order in data collection, sin
h=k, and various classes of indices showed no unusual trends. The
maximum and minimum peaks on the final difference Fourier map
corresponded to 0.51 and ꢁ0.31 eAꢁ3, respectively.
˚
Neutral atom scattering factors were taken from Cromer and Waber
[10]. Anomalous dispersion effects were included in Fcalc [11]; the
values for Df 0 and Df 00 were those of Creagh and McAuley [12]. The
values for the mass attenuation coefficients are those of Creagh and
Hubbell [13].
Synthesis
The synthesis of the intermediates 1–3 and the ultimate compounds
4–11 were carried out using the experimental procedure described in
Scheme 1.
Synthesis of 4-(3-Methylbutyloxy)phenylacetic Acid, 1
To a cold solution containing 10.0 g of 4-hydroxybenzoic acid
in 25.0 ml of methanol, 7.4 g of potassium hydroxide in 25.0 ml of
methanol was added. The ice bath was then removed and 10.1 g of
1-bromo-3-methylbutane was added and the reaction mixture was
heated under reflux for 18 h. The solvent was subsequently removed
and the mixture was neutralized with 10% of aqueous hydrochloric
acid. The solid was filtered off, washed thoroughly with water and
recrystallized from methanol. Yield: 75%. IR (KBr)=cmꢁ1 2957,
=
=
2933, 2868 (CH2 aliphatic), 1695 (C O), 1616 (C C aromatic), and
1246 (C-O).

92
G.-Y. Yeap et al.
Synthesis of 1-(2,4-Dihydroxyphenyl)-2-[40-(3-
methylbutyloxyphenyl)]-ethanone, 2
A mixture containing 9.0 g of 4-(3-methylbutyloxy)phenylacetic acid
and 4.5 g of resorsinol in 82.0 ml BF3 ꢄ Et2O was heated for 4 h at
70–75ꢀC under nitrogen atmosphere. The resulting mixture was later
poured into an ice-water bath whereupon the precipitate formed. The
oil was separated, air dried, and purified using chloroform. Yield:
70%. IR (KBr)=cmꢁ1 3126 (OH), 2957, 2873 (CH2 aliphatic), 1625
=
=
(C O), 1611 (C C aromatic), and 1249 (C-O).
Synthesis of 7-Hydroxy-3-[40-(3-methylbutyloxyphenyl)]-4H-1-
benzopyran-4-one, 3
Seven grams of compound 2 in dry DMF was treated cautiously
with 4-equivalence of BF3 ꢄ Et2O. To this mixture, 3-equivalence of
MeSO2Cl was added at 50ꢀC. The mixture was further heated under
nitrogen atmosphere for 1.5 h at 75–80ꢀC. Subsequently, the mixture
was poured with rapid stirring into ice-water bath whereupon the
solid formed. The product was purified via recrystallization from
chloroform. Yield: 45%. IR (KBr)=cmꢁ1 3206 (OH), 1628 (C O), 1610
=
1
=
(C C aromatic) and 1246 (C-O). H-NMR (DMSO-d6) d=ppm 12.79 (s,
7-OH), 9.58 (s, 40-OH), 6.72–8.27 (8H, Ar-H), 4.04–4.06 (2H,
d, OCH2), 1.83–1.89 (3H, m, OCH2CH2CH(CH3)CH3), 0.99 (6H, d,
13
=
OCH2CH2CH(CH3)CH3). C-NMR (DMSO-d6) d=ppm 176.32 (C O),
163.93 (OH attached to C-7), 159.52–100.89 (C aromatic), aliphatic
chains: 66.59 (C-O), 37.83 (OCH2CH2CH(CH3)CH3), 31.70 (CH2CH2O)
and 22.69 (OCH2CH2CH(CH3)CH3)
Synthesis of 7-Alkyloxy-3-[40-(3-methylbutyloxyphenyl)]-4H-1-
benzopyran-4-one, 4–11
To a mixture containing 0.3 g of compound 3 in acetone, 2.5 equiv-
alence of potassium carbonate and 1.2 equivalence of the correspond-
ing 1-bromoalkane were added. The mixture was heated under reflux
for 12 h. The solvent was removed and the crude product was purified
using column chromatography with chloroform:ethyl acetate (9:1) as
eluent. The analytical data for compounds 4–11 are shown as follows.
Compound 4: Yield: 33%. Elemental analysis found: C, 82.94;
H, 8.57%. Calculated: C, 82.90; H, 8.58%. IR (KBr)=cmꢁ1 2957,
=
=
2923, 2856 (CH2 aliphatic), 1633 (C O), 1606 (C C aromatic), 1257
1
(CO). H-NMR (CDCl3) d=ppm 6.83–8.21 (8H, H-Ar), 4.04–4.06 (2H,
t, OCH2 attached to C-7), 4.01–4.03 (2H, t, OCH2 attached to C-40),
1.84–1.91 (3H, m, OCH2CH2CH(CH3)CH3), 1.69–1.76 (2H, m,
CH2-CH2O), 1.40–1.58 (2H, m, OCH2CH2CH2CH3), 0.98 (6H, d,

Synthesis and Phase Behavior of New Isoflavone Derivatives
93
OCH2CH2CH(CH3)CH3), 0.94–0.96 (3H, t, OCH2CH2(CH2)7CH3).
13
=
C-NMR (CDCl3) d=ppm 176.24 (C O), 163.58–100.76 (C aromatic),
69.15 (OCH2 attached to C-7), 66.96 (OCH2 attached to C-40), 37.89
(OCH2CH2CH(CH3)CH3),
23.68–32.06
(OCH2CH2CH2CH3,
OCH2CH2CH(CH3)CH3), 22.62 (OCH2CH2CH(CH3)CH3), 14.10 (CH3).
Compound 5: Yield: 36%. Elemental analysis found: C, 83.12; H,
8.97%. Calculated: C, 83.32; H, 8.98%. IR (KBr)=cmꢁ1 2954, 2922,
=
=
2854 (CH2 aliphatic), 1632 (C O), 1607 (C C aromatic), 1257 (CO).
1H-NMR (CDCl3) d=ppm 6.85–8.23 (8H, H-Ar), 4.06–4.09 (2H, t,
OCH2 attached to C-7)), 4.03–4.06 (2H, t, OCH2 attached to C-40),
1.82–1.90 (3H, m, OCH2CH2CH(CH3)CH3), 1.69–1.74 (2H, m,
CH2-CH2O), 1.36–1.56 (6H, m, OCH2CH2(CH2)3CH3), 0.99 (6H, d,
OCH2CH2CH(CH3)CH3), 0.93–0.96 (3H, t, OCH2CH2(CH2)7CH3).
13
=
C-NMR (CDCl3) d=ppm 176.25 (C O), 163.93-100.68 (C aromatic),
69.13 (OCH2 attached to C-7), 66.82 (OCH2 attached to C-40), 38.08
(OCH2CH2CH(CH3)CH3),
23.28–32.30
(OCH2CH2(CH2)3CH3,
OCH2CH2CH(CH3)CH3), 22.68 (OCH2CH2CH(CH3)CH3), 14.51 (CH3).
Compound 6: Yield: 42%. Elemental analysis found: C, 83.28; H,
9.32%. Calculated: C, 83.11; H, 9.30%. IR (KBr)=cmꢁ1 2956, 2923,
=
=
2854 (CH2 aliphatic), 1632 (C O), 1607 (C C aromatic), 1256 (CO).
1H-NMR (CDCl3) d=ppm 6.83–8.21 (8H, H-Ar), 4.04–4.06 (2H, t,
OCH2 attached to C-7), 4.01–4.03 (2H, t, OCH2 attached to C-40),
1.80–1.89 (3H, m, OCH2CH2CH(CH3)CH3), 1.67–1.72 (2H, m,
CH2ꢁCH2O), 1.30–1.50 (10H, m, OCH2CH2(CH2)5CH3), 0.97 (6H, d,
OCH2CH2CH(CH3)CH3), 0.88–0.91 (3H, t, OCH2CH2(CH2)5CH3).
13
=
C-NMR (CDCl3) d=ppm 175.94 (C O), 163.55-100.56 (C aromatic),
68.73 (OCH2 attached to C-7), 66.45 (OCH2 attached to C-40), 37.99
(OCH2CH2CH(CH3)CH3),
22.66–31.80
(OCH2CH2(CH2)5CH3,
OCH2CH2CH(CH3)CH3), 22.60 (OCH2CH2CH(CH3)CH3), 14.10 (CH3).
Compound 7: Yield: 45%. Elemental analysis found: C, 83.43; H,
9.63%. Calculated: C, 83.32; H, 9.61%. IR (KBr)=cmꢁ1 2957, 2922,
=
=
2852 (CH2 aliphatic), 1631 (C O), 1607 (C C aromatic), 1257 (CO).
1H-NMR (CDCl3) d=ppm 6.83–8.21 (8H, H-Ar), 4.04–4.06 (2H, t,
OCH2 attached to C-7), 4.01–4.03 (2H, t, OCH2 attached to C-40),
1.80–1.87 (3H, m, OCH2CH2CH(CH3)CH3), 1.67–1.72 (2H, m, CH2-
CH2O), 1.28–1.50 (14H, m, OCH2CH2(CH2)7CH3), 0.97 (6H, d
OCH2CH2CH(CH3)CH3), 0.87–0.90 (3H, t, OCH2CH2(CH2)7CH3).
13
=
C-NMR (CDCl3) d=ppm 176.29 (C O), 163.93-100.95 (C aromatic),
69.16 (OCH2 attached to C-7), 66.83 (OCH2 attached to C-40), 38.38
(OCH2CH2CH(CH3)CH3),
23.08–32.29
(OCH2CH2(CH2)7CH3,
OCH2CH2CH(CH3)CH3), 22.99 (OCH2CH2CH(CH3)CH3), 14.51 (CH3).
Compound 8: Yield: 40%. Elemental analysis found: C, 83.55; H,
9.90%. Calculated: C, 83.58; H, 9.89%. IR (KBr)=cmꢁ1 2957, 2922,

94
G.-Y. Yeap et al.
=
=
2851 (CH2 aliphatic), 1631 (C O), 1607 (C C aromatic), 1256 (CO).
1H-NMR (CDCl3) d=ppm 6.83–8.21 (8H, H-Ar), 4.04–4.06 (2H, t,
OCH2 attached to C-7), 4.01–4.03 (2H, t, OCH2 attached to C-40),
1.82–1.85 (3H, m, OCH2CH2CH(CH3)CH3), 1.68–1.72 (2H, m, CH2-
CH2O), 1.27–1.48 (18H, m, OCH2CH2(CH2)9CH3), 0.97 (6H, d,
OCH2CH2CH(CH3)CH3), 0.86–0.90 (3H, t, OCH2CH2(CH2)9CH3).
13
=
C-NMR (CDCl3) d=ppm 175.89 (C O), 163.57-100.63 (C aromatic),
68.76 (OCH2 attached to C-7), 66.50 (OCH2 attached to C-40), 38.03
(OCH2CH2CH(CH3)CH3),
22.70–31.93
(OCH2CH2(CH2)9CH3,
OCH2CH2CH(CH3)CH3), 22.60 (OCH2CH2CH(CH3)CH3), 14.11 (CH3).
Compound 9: Yield: 48%. Elemental analysis found: C, 83.67; H,
10.14%. Calculated: C, 83.63; H, 10.13%. IR (KBr)=cmꢁ1 2956, 2920,
=
=
2850, (CH2 aliphatic), 1631 (C O), 1607 (C C aromatic), 1258 (CO).
1H-NMR (CDCl3) d=ppm 6.83–8.21 (8H, H-Ar), 4.04–4.06 (2H, t,
OCH2 attached to C-7), 4.01–4.03 (2H, t, OCH2 attached to C-40),
1.82–1.87 (3H, m, OCH2CH2CH(CH3)CH3), 1.67–1.80 (2H, m,
CH2ꢁCH2O), 1.26–1.50 (22H, m, OCH2CH2(CH2)11CH3), 0.97 (6H, d,
OCH2CH2CH(CH3)CH3), 0.86–0.90 (3H, t, OCH2CH2(CH2)11CH3).
13
=
C-NMR (CDCl3) d=ppm 176.27 (C O), 163.92-100.94 (C aromatic),
69.11 (OCH2 attached to C-7), 66.82 (OCH2 attached to C-40), 38.37
(OCH2CH2CH(CH3)CH3),
23.08–32.31
(OCH2CH2(CH2)11CH3,
OCH2CH2CH(CH3)CH3), 22.98 (OCH2CH2CH(CH3)CH3), 14.50 (CH3).
Compound 10: Yield: 42%. Elemental analysis found: C, 83.77; H,
10.36%. Calculated: C, 83.73; H, 10.38%. IR (KBr)=cmꢁ1 2957, 2921,
=
=
2850 (CH2 aliphatic), 1631 (C O), 1607 (C C aromatic), 1256 (CO).
1H-NMR (CDCl3) d=ppm 6.83–8.21 (8H, H-Ar), 4.04–4.06 (2H, t,
OCH2 attached to C-7), 4.00–4.03 (2H, t, OCH2 attached to C-40),
1.82–1.89 (3H, m, OCH2CH2CH(CH3)CH3), 1.69–1.72 (2H, m,
CH2ꢁCH2O), 1.26–1.52 (26H, m, OCH2CH2(CH2)13CH3), 0.97 (6H, d,
OCH2CH2CH(CH3)CH3), 0.82–0.88 (3H, t, OCH2CH2(CH2)13CH3).
13
=
C-NMR (CDCl3) d=ppm 175.89 (C O), 163.54-100.56 (C aromatic),
68.73 (OCH2 attached to C-7), 66.45 (OCH2 attached to C-40), 37.99
(OCH2CH2CH(CH3)CH3),
22.70–31.94
(OCH2CH2(CH2)13CH3,
OCH2CH2CH(CH3)CH3), 22.60 (OCH2CH2CH(CH3)CH3), 14.13 (CH3).
Compound 11: Yield: 43%. Elemental analysis found: C, 83.86; H,
10.56%. Calculated: C, 83.84; H, 10.54%. IR (KBr)=cmꢁ1 2954, 2922,
=
=
2854, (CH2 aliphatic), 1631 (C O), 1607 (C C aromatic), 1257 (CO).
1H-NMR (CDCl3) d=ppm 6.82–8.21 (8H, H-Ar), 4.04–4.06 (2H, t,
OCH2 attached to C-7), 4.00–4.03 (2H, t, OCH2 attached to C-40),
1.82–1.88 (3H, m, OCH2CH2CH(CH3)CH3), 1.67–1.80 (2H, m,
CH2-CH2O), 1.26–1.51 (30H, m, OCH2CH2(CH2)15CH3), 0.97 (6H, d,
OCH2CH2CH(CH3)CH3), 0.86–0.90 (3H, t, OCH2CH2(CH2)15CH3).
13
=
C-NMR (CDCl3) d ppm 175.89 (C O), 163.54-100.56 (C aromatic),

Synthesis and Phase Behavior of New Isoflavone Derivatives
95
68.73 (OCH2 attached to C-7), 66.45 (OCH2 attached to C-40), 37.99
(OCH2CH2CH(CH3)CH3), 22.70–31.94 (OCH2CH2(CH2)15CH3,
OCH2CH2CH(CH3)CH3), 22.60 (OCH2CH2CH(CH3)CH3), 14.12 (CH3).
RESULTS AND DISCUSSION
Thermal Behavior and Texture Observation
for Compounds 4–11
The phase transition temperatures and their respective enthalpy
values obtained from DSC measurement are collated in Table 1. The
DSC thermogram for compound 4 exhibits only one transition tem-
perature during heating and cooling processes. This observation indi-
cates the absence of liquid crystalline properties in compound 4 in
similar manner to a main chain polymer containing banana-shaped
mesogens and dodecyl spacers [14]. The clearing temperature for
compound 4 is also found to be highest among the members within
this series. This phenomenon can be ascribed to the presence of inter-
molecular attraction force among short-chain molecules leading to a
restricted thermal motion [14,15].
Whilst compounds 5 and 6 are monotropic, the compounds 7–11
exhibit enantiotropic behaviors. Through heating process we can
TABLE 1 Transition Temperatures and Enthalpies
for 7-Alkyloxy-3-[40-(3-Methyl-Butyloxyphenyl)]-4H-
1-Benzopyran-4-ones
Transition temperatures=ꢀC (Enthalpy
Compound
changes=kJmolꢁ1) – Heating Cooling
4
5
Cr 148.0 (25.00) I
I 130.4 (23.29) Cr
Cr 152.2 (39.20 ) I
I 139.6 (5.49) SmA 135.5 (34.75) Cr
Cr 147.1 (21.41) I
6
I 142.0(7.21) SmA 132.0 (35.39) Cr
Cr 133.6 (33.25) SmA 141.0 (7.84) I
I 139.2 (8.17) SmA 107.4 (33.98) Cr
Cr 136.2 (40.42) SmA 139.4 (8.04) I
I 137.9 (9.09) SmA 117.3 (43.49) Cr
Cr 129.1 (38.0) SmA 136.6 (7.96) I
I 134.8 (8.13) SmA 99.4 (38.36) Cr
Cr 125.9 (42.35) SmA 133.5 (8.47) I
I 131.7 (8.56) SmA 94.1 (44.35) Cr
Cr 123.7 (40.92) SmA 129.2 (7.88) I
I 127.7 (7.90) SmA 93.8 (45.84) Cr
7
8
9
10
11

96
G.-Y. Yeap et al.
observe a gradual decrease in clearing temperature (Tc) when we
ascend from compounds 7 to 11 (Table 1). This observation agrees with
the previously reported homologous series N,N’-bis(3-methoxy-4-
alkyloxybenzylidene)-1,4-phenylenediamin in which the homolog with
the longest terminal chains was nonlinear leading to lower clearing
temperature [16]. The phenomenon can also be explained in terms of
dilution effect of the flexible chains as reported for a series of laterally
branched azobenzenes [17]. This phenomenon indicates that the depen-
dence of the molecular anisotropy upon the molecular length and hence
the polarizability as reported for Schiff base esters [18] is not applicable
for the present compounds 5–11. This has been well reflected by
the polarizability values of the compounds 5–11 in which the values
for 5 [(50.01 ꢃ 0.5) ꢂ 10ꢁ24 cmꢁ3] < 6 [(53.69 ꢃ 0.5) ꢂ 10ꢁ24 cmꢁ3] < 7
[(57.36 ꢃ 0.5) ꢂ 10ꢁ24 cmꢁ3] < 8
[(64.70 ꢃ 0.5) ꢂ 10ꢁ24 cmꢁ3] < 10
[(61.03 ꢃ 0.5) ꢂ 10ꢁ24 cmꢁ3] < 9
[(68.37 ꢃ 0.5) ꢂ 10ꢁ24 cmꢁ3] < 11
[(72.04 ꢃ 0.5) ꢂ 10ꢁ24 cmꢁ3] in spite of the clearing temperatures
change in the reverse order (Tc for 5 > 6 > 7 > 8 > 9 > 10 > 11).
The clearing temperatures for all the compounds 5–11 in this hom-
ologous series are generally high (>110.0ꢀC) and this observation can
be due to the increased polarity of the endocyclic O atom in the central
core which enhances the anisotropy properties. However, the thermal
mesomorphic range was small (<10ꢀC) which can be rationalized in
FIGURE 1 Optical photomicrograph of compound 11 exhibiting focal-conic
texture (SmA) at 129.2ꢀC.

Synthesis and Phase Behavior of New Isoflavone Derivatives
97
TABLE 2 Crystal Structure Summary for Compound 5
Empirical Formula
Formula Weight
Crystal Color, Habit
Crystal Dimensions
Crystal System
Lattice Type
C26O4H32
408.54
Colorless, prism
0.17 ꢂ 0.15 ꢂ 0.10 mm
Triclinic
Primitive
Detector Position
Pixel Size
Lattice Parameters
45.32 mm
0.137 mm
˚
a ¼ 6.100(5) A
˚
˚
b ¼ 11.704(10) A
c ¼ 17.082(17) A
a ¼ 80.85(4)ꢀ
b ¼ 85.56(4)ꢀ
c ¼ 72.48(3)ꢀ
3
˚
V ¼ 1147.6(18) A
Space Group
Z value
Dcalc
P-1 (#2)
2
1.182 g=cm3
440.00
F000
l(MoKa)
Detector
Goniometer
Radiation
0.781 cmꢁ1
Rigaku Saturn
Rigaku AFC10
˚
MoKa (k ¼ 0.71070 A)
Graphite monochromated
70 mm ꢂ 70 mm
Detector Aperture
Data Images
2hmax
720 exposures
54.8ꢀ
No. of Reflections Measured
Total: 6347
Unique: 3982 (Rint ¼ 0.036)
Lorentz-polarization absorption
(trans. factors: 0.739–0.992)
Direct Methods
Corrections
Structure Solution
Refinement
Function Minimized
Least Squares Weights
2hmax Cutoff
Full-matrix least-squares on F2
2
R wðF2o ꢁ F2c Þ
1=[0.0066Fo2 þ 0.9600r(Fo2)]=(4Fo
)
2
54.8ꢀ
Anomalous Dispersion
No. Observations (I > 2.00r(I))
No. Variables
All nonhydrogen atoms
1916
303
Reflection=Parameter Ratio
Residuals: R1 (I > 2.00r(I))
Residuals: wR2 (I > 2.00r(I))
Goodness of Fit Indicator
Max Shift=Error in Final Cycle
Maximum Peak in Final Diff. Map
Minimum Peak in Final Diff. Map
6.32
0.0823
0.2121
1.000
0.000 ꢁ
3
˚
0.51 e =ꢁA
3
˚
ꢁ0.31 e =A

98
G.-Y. Yeap et al.
term of a reduced compatibility in geometry of the branched methyl
group in the terminal chain at C-40 which is unfavorable for the non-
tilting lamellar packing of molecules that give rise to the formation
of smectic A phase. The textures observed under the POM at the initial
heating and cooling processes can be substantiated through compari-
son with those analogous compounds reported in the literature [19].
The smectic A phase observed for compounds 5–11 can be clearly
assigned by the formation of batonnets that coalesce to form a focal
conic fan-shape texture characteristic of smectic A phase as depicted
by a representative compound 11 (Fig. 1).
TABLE 3 Atomic Coordinates and Biso=Beq. The General Temperature Factor
2
2
2
Expression: exp[ꢁ2p2 (aꢅ U11h2 þ bꢅ U22k2 þ cꢅ U33l2 þ 2aꢅbꢅU12hk þ 2aꢅcꢅU13hl
þ 2bꢅcꢅU23kl)]
Atom
x
y
z
Beq
O1
O2
O3
O4
C1
C2
C3
C4
C5
C6
C7
C8
0.6237(6)
0.0514(6)
0.2763(6)
0.5135(6)
0.5613(9)
0.3761(8)
0.2266(9)
0.2943(8)
0.1717(9)
0.2455(9)
0.4512(9)
0.5736(9)
0.4942(9)
0.3391(8)
0.5299(9)
0.5040(9)
0.2832(9)
0.0907(9)
0.1206(9)
0.7369(9)
0.7690(10)
1.0120(10)
1.0620(10)
1.2992(12)
1.3517(15)
0.0559(9)
0.0955(10)
ꢁ0.1031(10)
ꢁ0.0406(11)
ꢁ0.3217(11)
0.1899(3)
0.2640(3)
0.7362(3)
ꢁ0.1875(3)
0.2903(4)
0.3206(4)
0.2425(5)
0.1339(4)
0.0480(4)
ꢁ0.0570(5)
ꢁ0.0792(5)
0.0046(4)
0.1092(4)
0.4308(4)
0.4562(5)
0.5584(4)
0.6391(4)
0.6155(4)
0.5110(4)
ꢁ0.2247(4)
ꢁ0.3485(5)
ꢁ0.3957(5)
ꢁ0.5216(5)
ꢁ0.5630(5)
ꢁ0.6879(7)
0.8284(5)
0.9220(5)
1.0379(5)
1.1240(5)
1.0116(6)
0.5806(2)
0.4465(2)
0.2451(2)
0.7040(2)
0.5246(3)
0.4777(3)
0.4873(3)
0.5470(3)
0.5612(3)
0.6131(3)
0.6538(3)
0.6430(3)
0.5896(3)
0.4167(3)
0.3727(3)
0.3173(3)
0.3019(3)
0.3439(3)
0.4008(3)
0.7380(3)
0.7870(3)
0.8221(3)
0.8706(3)
0.9067(3)
0.9549(5)
0.2307(3)
0.1636(3)
0.1504(3)
0.0811(3)
0.1321(4)
2.22(8)
2.49(9)
2.79(9)
2.64(9)
2.08(12)
1.76(11)
2.08(12)
1.76(11)
2.06(12)
2.35(13)
2.03(12)
2.04(12)
2.03(12)
2.00(12)
2.30(12)
2.05(12)
2.05(11)
2.11(12)
2.02(12)
2.53(13)
2.58(13)
3.31(15)
3.25(14)
3.98(17)
6.7(2)
C9
C10
C11
C12
C13
C14
C15
C16
C17
C18
C19
C20
C21
C22
C23
C24
C25
C26
2.64(13)
2.86(14)
2.82(13)
3.36(15)
3.92(17)

Synthesis and Phase Behavior of New Isoflavone Derivatives
99
ꢀ
ꢀ
˚
TABLE 4 Selected Bond Lengths (A), angles ( ), and Torsion Angles ( ) for
compound 5
O(1)-C(1)
O(2)-C(3)
O(3)-C(22)
O(4)-C(16)
C(2)-C(3)
C(3)-C(4)
C(4)-C(9)
C(6)-C(7)
C(8)-C(9)
C(10)-C(15)
C(12)-C(13)
C(14)-C(15)
C(20)-C(21)
C(24)-C(25)
1.369(6)
1.260(7)
1.458(6)
1.438(7)
1.458(8)
1.470(6)
1.399(7)
1.416(8)
1.386(6)
1.397(6)
1.409(6)
1.411(7)
1.515(10)
1.530(8)
O(1)-C(9)
O(3)-C(13)
O(4)-C(7)
C(1)-C(2)
C(2)-C(10)
C(4)-C(5)
1.387(7)
1.364(6)
1.379(6)
1.361(7)
1.494(6)
1.406(8)
1.372(7)
1.384(9)
1.418(8)
1.379(7)
1.404(8)
1.519(7)
1.522(7)
1.520(10)
C(5)-C(6)
C(7)-C(8)
C(10)-C(11)
C(11)-C(12)
C(13)-C(14)
C(16)-C(17)
C(23)-C(24)
C(24)-C(26)
C(1)-O(1)-C(9)
C(7)-O(4)-C(16)
C(1)-C(2)-C(3)
C(3)-C(2)-C(10)
O(2)-C(3)-C(4)
C(3)-C(4)-C(5)
C(5)-C(4)-C(9)
C(5)-C(6)-C(7)
O(4)-C(7)-C(8)
C(7)-C(8)-C(9)
118.4(4)
C(13)-O(3)-C(22)
O(1)-C(1)-C(2)
C(1)-C(2)-C(10)
O(2)-C(3)-C(2)
C(2)-C(3)-C(4)
C(3)-C(4)-C(9)
C(4)-C(5)-C(6)
O(4)-C(7)-C(6)
C(6)-C(7)-C(8)
O(1)-C(9)-C(4)
118.2(4)
117.9(4)
118.8(4)
122.8(4)
121.1(5)
122.6(5)
117.1(4)
118.9(5)
124.3(4)
118.5(5)
116.3(5)
119.7(4)
118.0(4)
120.0(5)
125.1(4)
119.6(4)
107.8(5)
113.7(5)
112.8(6)
114.9(4)
111.1(5)
125.3(5)
118.4(5)
122.9(4)
116.0(4)
120.3(5)
122.0(5)
114.9(5)
120.8(4)
121.1(4)
122.6(5)
122.3(4)
121.6(4)
115.3(4)
119.6(4)
121.1(5)
110.1(5)
112.1(5)
107.1(4)
109.4(4)
109.3(5)
O(1)-C(9)-C(8)
C(4)-C(9)-C(8)
C(2)-C(10)-C(11)
C(11)-C(10)-C(15)
C(11)-C(12)-C(13)
O(3)-C(13)-C(14)
C(13)-C(14)-C(15)
O(4)-C(16)-C(17)
C(17)-C(18)-C(19)
C(19)-C(20)-C(21)
C(22)-C(23)-C(24)
C(23)-C(24)-C(26)
C(2)-C(10)-C(15)
C(10)-C(11)-C(12)
O(3)-C(13)-C(12)
C(12)-C(13)-C(14)
C(10)-C(15)-C(14)
C(16)-C(17)-C(18)
C(18)-C(19)-C(20)
O(3)-C(22)-C(23)
C(23)-C(24)-C(25)
C(25)-C(24)-C(26)
C(1)-O(1)C(9)-C(8)
175.5(4)
5.2(8)
179.8(4)
41.9(8)
177.5(4)
4.5(7)
C(9)-O(1)-C(1)-C(2)
C(16)-O(4)-C(7)-C(6)
C(1)-C(2)-C(10)-C(11)
C(10)-C(2)-C(3)-C(4)
C(3)-C(4)-C(5)-C(6)
O(4)-C(7)-C(8)-C(9)
O(3)-C(13)-C(14)-C(15)
2.2(7)
170.7(4)
40.3(7)
176.7(4)
175.4(5)
178.9(4)
179.4(5)
C(22)-O(3)-C(13)-C(14)
C(1)-C(2)-C(3)-O(2)
C(3)-C(2)-C(10)-C(15)
O(2)-C(3)-C(4)-C(9)
C(3)-C(4)-C(9)-O(1)
C(2)-C(10)-C(15)-C(14)
O(4)-C(16)-C(17)-C(18)
178.9(5)
177.5(4)

100
G.-Y. Yeap et al.
FIGURE 2 Crystal structure with atomic numbering scheme for compound 5.
Crystal Structure Determination on Compound 5
Crystal data of compound 5 are summarized in Table 2. Whilst the
atomic coordinates and Biso=Beq are shown in Table 3, the selected
bond lengths, angles, and torsion angles are given in Table 4. The mol-
ecular structure with the atom-numbering scheme and packing of
compound 5 are shown in Figures 2 and 3, respectively. It can be
observed from Fig. 2 that the two phenyl rings (C1-C2-C3-C4-C9-O
and C4-C5-C6-C7-C8-C9-O) are almost coplanar with a dihedral angle
of 3.67ꢀ. The ring C11-C12-C13-C14-C15-C16 is twisted from the mean
plane of fused-ring C1-C2-C3-C4-C9-O by 41.9(8)ꢀ. It can also be
inferred from Table 4 that the endocyclic O1 atom is out-of-plane with
a deviation of 2.2(7)ꢀ from the mean plane. In addition, the elongated
alkyloxy chain (from C16 to C21) attached to another fused-ring C4-
C5-C6-C7-C8-C9 via ether linkage is colinear with zig-zagconforma-
tion made up of methylene moiety. In general, the bond lengths and
angles associated with the central core are in good agreement with
those values observed in licoricone monobromoacetate [20]. However,
the torsion angle (C3-C2-C10-C15) and bond length (C(2)-C(10)) as
found in the present compound are less than those observed in licori-
cone monobromoacetate [20]. This observation can be attributed to the
FIGURE 3 Molecular packing of compound 5 along b axis.

Synthesis and Phase Behavior of New Isoflavone Derivatives
101
steric hindrance due to the bulky bromoacetate group at the position
similar to C(15) in the present compound 5. The crystal structure
(Fig. 3) shows that the molecules lie antiparallel to each other with
the molecules arranged in layers and stacked along b axis. The prob-
able reason contributing to the layered structure in crystal 5 is the
cohesive force resulting from dipolar or van der Waals interaction
between the molecules which resemble that appeared in monomeric
and dimeric imines [15, 16].
Supplementary Material
Crystallographic data for the crystal structure 5 reported in the
present report have been deposited at Cambridge Crystallographic
Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK (CCDC
649408). The data including the structure factors are available from
the corresponding author.
ACKNOWLEDGMENT
The main author (G-Y. Yeap) would like to thank Universiti Sains
Malaysia and the Malaysian Government especially the Ministry of
Science, Technology, and Innovation (MOSTI) for the eScience grant
no. 305=PKIMIA=613315 and USM Short-Term grant no. 304=
PKIMIA=638006. The authors are also grateful to the staff from the
Universiti Sains Malaysia for giving indirect support to make this
project a success.
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