Preparation and application of cholesteryl-benzo-15-crown-5/cholesteryl mixed liquid crystals

Article abstract of DOI:10.1002/jccs.200800085

Various mixed liquid crystals containing crown ether-cholesteryl liquid crystal, benzo-15-crown-5-COO-C₂₇H₄₅ (B15C5-COOCh), with various common cholesteric liquid crystals, e.g., cholesteryl chloride, cholesteryl benzoate and cholesteryl palmitate, were prepared and studied using polarizing microscopy and differential scanning calorimetry. Investigating the concentration effect of B15C5-COOCh in mixed liquid crystals revealed that the addition of B15C5-COOCh resulted in wider phase transition temperature ranges of these cholesteryl liquid crystals. The stability of these B15C5-COOCh/ cholesteryl mixed liquid crystals was studied using comprehensive graphic molecular modeling computer programs (Insight II and Discover) to calculate their molecular energy and stability energy. The effect of salts, e.g. Na ⁺, Co³⁺, Y³⁺ and La³⁺, on the transition temperature range of the mixed liquid crystals was also investigated. The crown ether cholesteric liquid crystal B15C5-COOCh was applied both as a surfactant and an ion transport carrier to transport metal ions through liquid membranes. Cholesteryl benzo-15-crown-5 exhibited distinctive characteristics of a surfactant and the critical micellar concentration (CMC) of the surfactant was investigated by the pyrene fluorescence probe method. Cholesteryl benzo-15-crown-5 was successfully applied as a good ion transport carrier (Ionophore) to transport various metal ions, e.g. Li⁺, Na ⁺, La³⁺, Fe³⁺ and Co³⁺, through organic liquid membranes. The transport ability of the cholesteryl benzo-15-crown-5 surfactant for these metal ions was in the order: Co ³⁺ ≥ Li⁺ > Fe³⁺ > Na⁺ > La³⁺.

Full text of DOI:10.1002/jccs.200800085

578
Journal of the Chinese Chemical Society, 2008, 55, 578-586
Preparation and Application of Cholesteryl-Benzo-15-Crown-5/Cholesteryl
Mixed Liquid Crystals
Ya-Chi Shena (
) and Jeng-Shong Shihb* (
)
aNan Jeon Institute of Technology, Yen-Shui, Tainan, Taiwan 737, Republic of China
bDepartment of Chemistry, National Taiwan Normal University, Taipei, Taiwan 116, Republic of China
Various mixed liquid crystals containing crown ether-cholesteryl liquid crystal, benzo-15-crown-5-
COO-C27H45 (B15C5-COOCh), with various common cholesteric liquid crystals, e.g., cholesteryl chlo-
ride, cholesteryl benzoate and cholesteryl palmitate, were prepared and studied using polarizing micros-
copy and differential scanning calorimetry. Investigating the concentration effect of B15C5-COOCh in
mixed liquid crystals revealed that the addition of B15C5-COOCh resulted in wider phase transition tem-
perature ranges of these cholesteryl liquid crystals. The stability of these B15C5-COOCh/cholesteryl
mixed liquid crystals was studied using comprehensive graphic molecular modeling computer programs
(Insight II and Discover) to calculate their molecular energy and stability energy. The effect of salts, e.g.
Na+, Co3+, Y3+ and La3+, on the transition temperature range of the mixed liquid crystals was also investi-
gated. The crown ether cholesteric liquid crystal B15C5-COOCh was applied both as a surfactant and an
ion transport carrier to transport metal ions through liquid membranes. Cholesteryl benzo-15-crown-5 ex-
hibited distinctive characteristics of a surfactant and the critical micellar concentration (CMC) of the
surfactant was investigated by the pyrene fluorescence probe method. Cholesteryl benzo-15-crown-5 was
successfully applied as a good ion transport carrier (Ionophore) to transport various metal ions, e.g. Li+,
Na+, La3+, Fe3+ and Co3+, through organic liquid membranes. The transport ability of the cholesteryl
benzo-15-crown-5 surfactant for these metal ions was in the order: Co3+ ³ Li+ > Fe3+ > Na+ > La3+.
Keywords: Liquid crystal; Crown ether liquid crystal; Surfactant; Ion transport carrier.
INTRODUCTION
Cholesteryl liquid crystals are very famous helical
In addition, cholesteryl derivatives always exhibit charac-
teristics of liquid crystals. Therefore, the crown ether cho-
lesteryl liquid crystal can be expected to show the charac-
teristics of a liquid crystal. Furthermore, a mixed liquid
crystal composed of two different cholesteryl liquid crys-
tals exhibits quite different optical sensitive properties and
transition temperature ranges compared with the com-
posed liquid crystals. In our previous study,16 a crown ether
cholesteryl liquid crystal, cholesteryl benzo-15-crown-5
(B15C5-COOCh), was synthesized. However, its transi-
tion temperature range (approx. 120-165 °C) means it is
not good enough to be used in optical display devices.
Therefore, in this study, various mixed crystals containing
a crown ether-cholesteryl liquid crystal with various com-
mon cholesteric liquid crystals, e.g., cholesteryl chloride,
cholesteryl benzoate and cholesteryl palmitate, were pre-
pared in order to obtain mixed liquid crystals with wider
transition temperature ranges. The crown ether-choles-
distortion liquid crystals1-4 and can be applied as highly op-
tical-sensitive ferro-liquid crystals (FLC)5-7 for optical dis-
play devices in microcomputers. The groups attaching to
cholesteryl (C27H45), such as benzyl (C6H5), ester (RCOO)
and chloride (Cl), can change the optical properties and the
transition temperature of the cholesteryl liquid crystals.
Crown ethers have a dual functionality, with a lipophilic
segment on the outer surface of the ring and a polar seg-
ment on the inner surface that can form stable complexes
with metal ions.8-13 Attaching a lipophilic long-chain alkyl
group to a crown ether can convert it into a surfactant,
which is capable of forming micelles in a manner analo-
gous to classical non-ionic surfactants.14-15 In other words,
cholesteryl-crown ether can be expected to show the char-
acteristics of a surfactant. It is well known that some sur-
factants of certain concentrations can form liquid crystals.
* Corresponding author. Fax: +886-2-2932-4249; E-mail: jsshih99@ms54.hinet.net

Cholesteryl-Benzo-15-Crown-5 Liquid Crystals
J. Chin. Chem. Soc., Vol. 55, No. 3, 2008 579
tery/cholestery mixed liquid crystals were studied using
polarizing microscopy with comprehensive graphic molec-
ular modeling computer programs (Insight II and Discover)
to calculate their molecular energy and stability energy. As
mentioned above, cholesteryl benzo-15-crown-5 can be
expected to be a crown ether surfactant. Thus, in this study,
the micellar formation of the crown ether surfactant was
investigated using the pyrene fluorescence probe and sur-
face tension methods. In addition, owing to their com-
plexing ability with alkali metal ions, crown ethers are also
expected to serve as ion transport carriers (Ionophores)
through biomoimetric membranes.17-19 The transport of al-
kali metal ions across a membrane plays an important role
in biology. Thus, in this study, the application of choles-
teryl benzo-15-crown-5 as an ion transport carrier (Iono-
phore) to transport various metal ions was also studied and
discussed.
chloro-carbonyl benzo-15-crown-5 (6.57 mol) and choles-
terol (6.57 mol) with pyridine (13 mmol) in benzene after
being refluxed for 24 h. The final product and the interme-
diates were identified by IR, NMR and mass spectra.
Liquid crystal study
The liquid crystal phases of various liquid crystals in-
cluding cholesteryl benzo-15-crown-5 and various mixed
crystals were observed using a polarizing microscope with
a heating device and the transition temperatures of various
liquid crystals were determined by differential scanning
calorimetry. The mixed liquid crystal was prepared by dis-
solving the mixture of two liquid crystals in dichlorometh-
ane by stirring and heating to remove the organic solvent.
Computer simulation for molecular structure and en-
ergy calculation
A commercial graphic molecular modeling program
Insight-II 2.10 was employed to draw the modeling struc-
tures of various liquid crystals including cholesteryl benzo-
15-crown-5 and some mixed liquid crystals. An energy an-
alytical program Discover 3.1 was also employed to calcu-
late the molecular energy and stability energy for these
pure liquid crystals and mixed liquid crystals.
EXPERIMENTAL
Synthesis of cholesteryl benzo-15-crown-5
Cholesteryl benzo-15-crown-5 (B15C5-COOC27H45)
was prepared as shown in Fig. 1. The intermediate benzo-15-
crown-5 (B15C5) was prepared, as reported by Pederson,8
through the reaction between ortho-catechol (0.4 mol) and
1,11-dichloro-3,6,9-trioxaundecane (0.4 mol) in butanol
(600 mL) mixed with NaOH (37.0 g) aqueous solution (40
mL) after being refluxed for 30 hr. The intermediates,
namely 4¢-acetyl-benzo-15-crown-5,4¢-carboxyl-benzo-
15-crown-5 and 4¢-chloro-carbonyl benzo-15-crown-5
were synthesized as described by Stott,20 Wada21 and
Haines,22 respectively. The final solid product B15C5-
COOC27H45 was obtained from the reaction between 4¢-
Critical micellar concentration (CMC) measurements
In this study, cholesteryl benzo-15-crown-5 was found
to exhibit distinctive characteristics of a surfactant. The
pyrene fluorescence probe method was employed to mea-
sure the CMC of cholesteryl benzo-15-crown-5 in aqueous
solutions. In the pyrene fluorescence method, an alter-
ation intensity ratio (I1/I3) of pyrene fluorescence bands I
(373 nm) and III (383 nm) occurs upon formation of mi-
celles.23-26 The CMC of cholesteryl benzo-15-crown-5
surfactant was measured at various aqueous concentrations
with 3 ´ 10-7 M pyrene added. The plot of I1/I3 against log
[surfactant] shows a significant change in slope of the
curve in which concentrations are denoted as CMC of cho-
lesteryl benzo-15-crown-5.
Ion transport through liquid membranes
Fig. 2 shows the experimental setup of the ion trans-
port of various metal ions through organic liquid mem-
branes. Aqueous solution (0.1 M, 20 mL) containing metal
salts (MXn) and pure water (20 mL) were prepared as
source solution and target solution, respectively, and cho-
lesteryl benzo-15-crown-5 (10-3 M) in dichloromethane
(30 mL) was prepared as the liquid membrane. Metal (Mn+)
ions in the source solution were transported through the
surfactant liquid membrane into the target solution and
Fig. 1. Scheme for the synthesis of cholesteryl benzo-
15-crown-5 (B15C5COOC27H45).

580 J. Chin. Chem. Soc., Vol. 55, No. 3, 2008
Shen and Shih
Fig. 2. Ion transport apparatus with cholesteryl benzo- 15-crown-5 (B15C5COOC27H45) liquid membrane.
were then detected by a conductivity detector.
Apparatus
In addition, the transition temperature range (49.9-172.4
°C) of the B15C5-COOCh/Ch-Cl mixed liquid crystal
seems to be greater than that of the single liquid crystal
B15C5-COOCh (122-166 °C) or Ch-Cl (62-97 °C) as shown
in Fig. 3. Similarly, other mixed liquid crystals, e.g., cho-
lesteryl benzoate (Ch-Bz)/B15C5-COOCh, also showed
liquid crystal characteristics (Fig. 4) and greater transition
temperature ranges than single liquid crystals, e.g., Ch-Bz
or B15C5-COOCh.
JASCO FTIR-5300 Fourier transform infra-red (FTIR)
and JEOL EX400 Fourier transform NMR and JEOL JMS-
DI300 mass spectrometers were employed to identify the
final product, cholesteryl benzo-15-crown-5, and its inter-
mediates. An OLYMPUS BH-2 polarizing microscope was
also employed to observe the liquid crystal phases and a
DSC-50I differential scanning calorimeter was utilized to
determine the transition temperatures of various liquid crys-
tals. A JASCO-FP 770 spectro-fluorometer and a KYOWA
CBVP-A3 surface-tense meter were employed for deter-
mining the CMC of cholesteryl benzo-15-crown-5. A DCM-
3 conductivity detector was employed to measure the
amount of metal ions passing through the liquid membrane
in the ion transport study.
Furthermore, it was found that the transition tempera-
ture range of the mixed liquid crystal seemed to depend on
the ratio (w/w) of the composed liquid crystals. For exam-
ple, the transition temperature range of B15C5-COOCh/
Ch-Cl mixed liquid crystals can be significantly changed
with different ratios (w/w) of B15C5-COOCh/Ch-Cl by
cooling or heating processes as shown in Fig. 5. The opti-
Reagents
Cholesteryl chloride, cholesteryl benzoate and cho-
lesteryl palmite were obtained from Janessen Co., while
cholesterol was purchased from Fluka Co. All other chemi-
cals used were of analytical grade.
RESULTS AND DISCUSSION
The liquid crystal characteristics and phase transition
temperatures of various mixed crystals containing cho-
lesteryl benzo-15-crown-5 (B15C5-COOC27H45, B15C5-
COOCh) or crown ether B15C5-COOH with various com-
mon cholesteric liquid crystals, e.g., cholesteryl chloride
(C27H45Cl, Ch-Cl), cholesteryl benzoate (Ch-Bz) and cho-
lesteryl palmitate (Ch-PA), were investigated using differ-
ential scanning calorimetry (DSC) by cooling and heating
processes. As shown in Fig. 3, these mixed crystals of
B15C5-COOCh and common cholesteric liquid crystals,
e.g., cholesteryl chloride (Ch-Cl), still show the character-
istics of the liquid crystals and have transition temperatures
of the liquid crystals by either cooling or heating processes.
Fig. 3. Thermal analysis curve of differential scanning
calorimetry (DSC) for B15C5COOC27H45/
C27H45Cl mixed liquid crystal (LC).

Cholesteryl-Benzo-15-Crown-5 Liquid Crystals
J. Chin. Chem. Soc., Vol. 55, No. 3, 2008 581
mum ratio of B15C5-COOCh/Ch-Cl = 4 for obtaining the
largest transition temperature range of the mixed liquid
crystal was found. The plot of maximum and minimum
transition temperature range against the ratio (w/w) of
B15C5-COOCh/Ch-Cl reveals that the lowest minimum
transition temperature at B15C5-COOCh/Ch-Cl = 4 is
around 25 °C as shown in Fig. 6. In other words, the mixed
liquid crystal with the ratio of B15C5-COOCh/Ch-Cl =
4.0 can be a liquid crystal at room temperature (25 °C)
while B15C5-COOCh or Ch-Cl is a solid at room temper-
ature. Even with the addition of common crown ether
B15C5COOH which did not show the liquid crystal char-
acteristics, the transition temperature range of cholesteryl
liquid crystals, e.g., C27H45Cl (Ch-Cl) can be changed as
shown in Fig. 7. B15C5COOH/Ch-Cl mixed crystal also
showed liquid crystal characteristics and greater transi-
tion temperature ranges (40-170 °C) than those of the
components, Ch-Cl (62-97 °C) and B15C5COOH (mp.
170 °C). Similarly, the transition temperature range of
B15C5COOH/Ch-Cl mixed crystal also varied with the
changes in weight ratio of B15C5COOH/Ch-Cl as shown
in Fig. 7.
ing computer programs (Insight II and Discover) were em-
ployed to calculate their molecular energy and stability en-
ergy. The molecular modeling graphs of composed mono-
molecular liquid crystals (e.g. B15C5-COOCh) and mixed
liquid crystals (e.g. B15C5-COOCh/Ch-Cl) in the lowest
average molecular energy states can be obtained with the
Insight II program as shown in Figs. 8 and 9, respectively.
According to these molecular modeling graphs, two B15C5-
COOCh molecules (Fig. 8) seem to overlap with each other
while there is no overlap between B15C5-COOCh and
Ch-Cl molecules (Fig. 9). This reveals that the B15C5-
COOCh/Ch-Cl mixed liquid crystal is more stable than the
The greater transition temperature range of mixed
cholesteryl liquid crystals than that of composed liquid
crystals seems to indicate that mixed crystals are more sta-
ble than composed liquid crystals. In order to study the sta-
bility of mixed and composed mono-molecular cholesteryl
liquid crystals, comprehensive graphic molecular model-
Fig. 5. Weight ratio effect of B15C5COOC27H45/
C27H45Cl on the transfer temperature range of
the mixed liquid crystal by (a) cooling and (b)
heating processes (Ch = C27H45).
Fig. 4. DSC
thermal
analysis
curve
for
B15C5COOC27H45/Ch-Ben mixed liquid crys-
tal (Ch-Bz = Cholesteryl benzoate).

582 J. Chin. Chem. Soc., Vol. 55, No. 3, 2008
Shen and Shih
mono-B15C5-COOCh molecular liquid crystal. Further-
more, the addition of Ch-Cl molecules may reduce the at-
traction between two B15C5-COOCh molecules, causing
these molecules to be in array and increasing the stability of
the liquid crystal.
The stability of these liquid crystals can be estimated
from their molecular energies. The average molecular ener-
gies of various cholestery mixed and mono-molecular liq-
uid crystals were calculated using the Discover program
and are shown in Table 1. As can be seen, the average mo-
lecular energy of the B15C5-COOCh/Ch-Cl mixed liquid
crystal (170 Kcal/mole) is lower than that of the B15C5-
COOCh mono-molecular liquid crystal (305 Kcal/mole),
indicating that the B15C5-COOCh/Ch-Cl mixed liquid
crystal is more stable than the B15C5-COOCh mono-mo-
lecular liquid crystal, which may result in a greater transi-
tion temperature range of B15C5-COOCh/Ch-Cl than of
B15C5-COOCh. The stability energy (Eb) of a mixed liquid
Fig. 6. Cooling phase diagram of B15C5COOC27H45/
C27H45Cl mixed liquid crystal (A) Maximum
temperature and (B) Minimum temperature for
liquid crystal phase (Ch = C27H45).
Fig. 7. Cooling phase diagram of B15C5COOH/
C27H45Cl mixed liquid crystal (A) Maximum
temperature and (B) Minimum temperature for
liquid crystal phase (Ch = C27H45).
Fig. 8. Computer simulating molecular modeling for
mono-molecular
B15C5COOC27H45/
B15C5COOC27H45 liquid crystal.

Cholesteryl-Benzo-15-Crown-5 Liquid Crystals
J. Chin. Chem. Soc., Vol. 55, No. 3, 2008 583
Table 1. Molecular energy and stability energy of crown ether/cholesteryl mixed liquid
crystals
Liquid crystal (LC)
Homo-LC
Molecular energy Stability energy Eb
Compounda
(Kcal/mole)
(Kcal/mole)b
B15C5Ch/B15C5Ch
ChCl/ChCl
ChBZ/ChBz
ChPA/ChPA
B15C5COOH/B15C5COOH
B15C5Ch/ChCl
B15C5Ch/ChBz
B15C5COOH/ChCl
B15C5COOH/ChBz
B15C5COOH/ChPA
305 (Eo)
96 (Eo)
--
--
--
--
--
170 (Eo)
176 (Eo)
136 (Eo)
Mixed-LC
170 (EAB
224 (EAB
86 (EAB
161 (EAB
147 (EAB
)
)
)
)
)
31.0
16.5
47.0
12.0
06.0
a B15C5Ch: Benzo-15-crown-5-COOC27H45; ChCl: Cholesteryl chloride; ChBz: Cholesteryl
benzoate; ChPA: Cholesteryl palmitate.
b Stability energy (Eb) = 1/2 (EoA + EoB) – EAB
crystal AB can be estimated using the molecular energies
of components A, B and the mixed crystal AB as follows:
Stability (Eb) = 1/2 (EoA + Eo ) – EAB
(1)
B
where Eo , EoB and EAB are molecular energies of compo-
A
nents A, B and the mixed liquid crystal AB, respectively.
As shown in Table 1, mixed crown ether/cholesterol
chloride (ChCl) liquid crystals, B15C5Ch/ChCl and
B15C5COOH/ChCl, are more stable with much larger sta-
bility energies (31.0 and 47.0 Kcal/mole) than other mixed
liquid crystals, e.g., B15C5Ch/ChBz and B15C5COOH
/ChPA. This may be attributed to the greater steric effects
of benzyl of ChBz and palmitate of ChPA than those of
chloride of ChCl, which causes instability of B15C5Ch/
ChBz and B15C5COOH/ChPA mixed liquid crystals.
Since the crown ether B15C5 in the B15C5COOCh/
ChCl mixed liquid crystal can be expected to form stable
complexes with various metal ions,8 the effect of metal
ions on the stability and transfer temperature range of the
B15C5COOCh/ChCl mixed liquid crystal was also inves-
tigated in this study. As shown in Fig. 10, the presence of
La(NO3)3 with different mole ratios of La/LC (liquid crys-
tal) in B15C5COOCh/ChCl mixed liquid crystal led to its
loss of liquid crystal characteristics. This may be attrib-
uted to the formation of La(III)/B15C5COOCh complex,
which results in large repulsion between two La(III)/
B15C5COOCh molecules, thus destroying the liquid crys-
tal structure and causing the mixed liquid crystal to lose its
liquid crystal characteristics. Similar effects of NaCl,
Fig. 9. Computer simulating molecular modeling for
hetero-molecular B15C5COOC27H45/C27H45Cl
mixed liquid crystal.

584 J. Chin. Chem. Soc., Vol. 55, No. 3, 2008
Shen and Shih
Co(NO3)3 and Y(NO3)3 on the loss of the liquid crystal
characteristics of the B15C5COOCh/ChCl mixed liquid
crystal were also found as shown in Fig. 11.
As mentioned above, cholesteryl-crown ether is ex-
pected to show the characteristics of a surfactant. In this
study, the fluorescence probe of pyrene was applied as a
sensitive tool to study the formation of micelles and deter-
mine the critical micellar concentration (CMC) of cho-
lesteryl-crown ether B15C5COOCh. The CMC value of
B15C5COOCh as a surfactant in aqueous solution was ob-
tained by measuring pyrene fluorescence and plotting the
I1/I3 intensity ratio against B15C5COOCh concentration
where the slope of the curve changes dramatically, as
shown in Fig. 12. The CMC value can be estimated as the
B15C5COOCh concentration at the inflection point N in
Fig. 12 and is approximately 8 ´ 10-4 M in H2O as obtained
by the pyrene fluorescence probe method. This seems to in-
dicate that the cholesteryl-crown ether B15C5COOCh can
be considered as a surfactant as expected.
The transport of metal ions, e.g. Na+ and Fe3+ ions,
across a membrane plays an important role in biology. The
effect of the cholesteryl-crown ether B15C5COOCh as an
ionophore to carry various metal ions through an organic
(dichloromethane) liquid membrane was investigated in
this study. Amechanism for the transport of metal ions, e.g.
Na+, with B15C5COOCh was proposed as shown in Fig.
13. The Na+ ion in the source aqueous layer first forms a
complex with B15C5COOCh and is transported through
the organic (CH2Cl2) liquid membrane into the target aque-
ous layer. The transport concentrations of Na+ and Fe3+
ions in the target layer as a function of time were measured
Fig. 10. Effect of La(NO3)3 added on the transfer tem-
perature range of B15C5COOCh/C27H45Cl
(mole ratio 1:1) mixed liquid crystal (LC) by
cooling process. (Mole ratio: 1: La3+
/
/
/
/
B15C5COOCh-ChCl
B15C5COOCh-ChCl
B15C5COOCh-ChCl
=
=
=
0; 2: La3+
1; 3: La3+
2; 4: La3+
B15C5COOCh-ChCl = 3).
Fig. 11. Effect of various salts on the transfer tempera-
ture range of B15C5COOC27H45/C27H45Cl
mixed liquid crystal by cooling process. (1:
No salt, 2: NaCl, 3: Co(NO3)3, 4: Y(NO3)3, 5:
La(NO3)3; Mole ratio: Salt/B15C5COOC27H45/
C27H45Cl = 1:1:1).
Fig. 12. Determination of critical micellar concentra-
tion (CMC) of B15C5COOC27H45 in aqueous
solutions using pyrene fluorescence probe
method (Ch = C27H45).

Cholesteryl-Benzo-15-Crown-5 Liquid Crystals
J. Chin. Chem. Soc., Vol. 55, No. 3, 2008 585
using a conductivity detector. As shown in Fig. 14, the
transport concentrations for both Na+ and Fe3+ ions ap-
peared to reach equilibrium after 200 min. and the equilib-
rium transport concentration of Fe3+ ion was obviously
greater than that of Na+ ion. The cavity of crown ether
15C5 of B15C5COOCh calculated using the Insight II
graphic molecular modeling computer program was ap-
proximately 1.54 Å. However, the diameter of Na+ ion
(approx. 1.9 Å)27 is obviously too large for the cavity of
B15C5COOCh (1.54 Å), which is relatively difficult to
complex with B15C5COOCh. On the other hand, although
the diameter of Fe3+ ion (approx. 1.25 Å) is slightly smaller
than the cavity of B15C5COOCh (1.54 Å), the Fe3+ ion can
still be inserted into the cavity of B15C5COOCh and forms
Fe3+ B15C5COOCh complex, resulting in the transport of
Fe3+ ions through the liquid membrane more easily than
that of Na+ ions. The transport of other metal ions, e.g. Li+,
Co3+ and La3+, through the liquid membrane was also in-
vestigated. As shown in Fig. 15, the transport concentra-
tion of these metal ions seems to be inversely proportional
to the diameter of these metal ions. The diameter (approx.
1.5 Å) of Li+ ion obviously fits the cavity of B15C5COOCh
(1.54 Å) quite well and Li+ ion can be expected to form
stronger complex with B15C5COOCh than both Na+ and
La3+, which are too big for the cavity of B15C5COOCh.
However, Co3+ ions show greater transport concentration
than Li+ ions, which may be attributed to the larger charge/
size of Co3+ than that of Li+, resulting in stronger absorp-
tion of Co3+ ions into the cavity of B15C5COOCh and
greater transport concentration of Co3+ ions through the
liquid membrane. This result seems to indicate that both
size and charge affect the association and dissociation of
metal ions with liquid membranes.
CONCLUSION
In conclusion, the mixed liquid crystals composed of
B15C5COOCh and common cholesteryl liquid crystals,
Fig. 14. Ion transport of (a) Na+ and (b) Fe3+ through
the B15C5COOC27H45/dichloromethane liq-
uid membrane (C.E. = B15C5COOC27H45).
Fig. 13. Scheme for Na+ ion transport through the
B15C5COOC27H45/dichloromethane liquid
membrane.

586 J. Chin. Chem. Soc., Vol. 55, No. 3, 2008
Shen and Shih
REFERENCES
1. de Gennas, P. G. The Physics of Liquid Crystal; Oxford
Univ.: London, 1974.
2. Gray, G. W.; Winsor, P. A. Liquid Crystal and Plastic Crys-
tals; Ellis Horwood: New York, 1974.
3. Leder, L. B. J. Chem. Phys. 1971, 55, 2649.
4. Park, J. W.; Labes, M. M. Mol. Cryst. Liq. Cryst. 1975, 31,
355.
5. Shinkai, S. Chem. Soc. Chem.Commun. 1991, 339.
6. Adams, J. E.; Hass, W. E. L.; Wysocki, J. J. Phys. Cryst. Liq.
Cryst. 1977, 42, 15.
7. Musubuchi, S.; Akahane, T.; Kakuo, K.; Tako, T. Mol.
Cryst. Liq. Cryst. Liq. Cryst. 1977, 38, 265.
8. Pedersen, C. J. J. Am. Chem. Soc. 1967, 89, 7017.
9. Dietrich, B.; Lehn, J. M.; Sauvage, J. P. Tetrahedron Lett.
1969, 34, 2885.
10. Kelthoff, I. M. Anal. Chem. 1979, 51, 1R.
11. Christensen, J. J. Progress in Macrocyclic Chemistry;
Wiley-Interscience: New York, 1979.
12. Shih, J. S. J. Chin. Chem. Soc. 1992, 39, 551.
13. Mario, Y.; Promauro, E.; Gratzel, M.; Pelizzetti, E.; Tundo,
P. J. Collid. Interface Sci. 1979, 69, 341.
Fig. 15. Effect of metal ion diameter on ion transports
of various metal ions through the
B15C5COOC27H45/dichloromethane liquid
membrane.
14. Kuo, P. L.; Ikoda, I.; Okahara, M. Tenside Deterg 1982, 19,
4.
15. Chou, F. F.; Shih, J. S. J. Chin. Chem. Soc. 2002, 49, 599.
16. Lee, J. L.; Shen, Y. C.; Shih, J. S. J. Chin. Chem. Soc. 2003,
50, 861.
e.g. cholesteryl chloride and cholesteryl benzoate exhib-
ited wider phase transition temperature ranges than those
of common cholesteryl liquids. Some B15C5COOCh/
cholesteryl mixed liquid crystals showed the transition
temperature at room temperature. The Insight II/Discover
graphic molecular modeling computer programs were suc-
cessfully employed to calculate the average molecular en-
ergy and explain the stability of mixed liquid crystals.
Crown ether cholesteryl liquid crystal B15C5COOCh also
showed the characteristics of a surfactant in forming mi-
celles in water. Furthermore, B15C5COOCh also served as
a good ion transport carrier to transport metal ions through
the organic liquid membrane.
17. Choy, E. M.; Evans, D. F.; Cussler, E. L. J. Am. Chem. Soc.
1974, 96, 7085.
18. Yoshida, S.; Hayano, S. J. Am. Chem. Soc. 1986, 108, 3903.
19. Hwang, W. Y.; Shih, J. S. J. Chin. Chem. Soc. 2000, 47,
1215.
20. Stott, P. E.; Bradshaw, J. S. J. Org. Chem. 1980, 45, 4716.
21. Wada, F.; Kikukawa, K.; Shinkai, S.; Maysuda, T. J. Org.
Chem. 1990, 55, 541.
22. Haines, A. H.; Hodgkisson, I.; Smith, C. J. J. Chem. Soc.,
Perkin Trans. 1983, 1, 311.
23. Kalyanasundaram, K.; Gratzel, M.; Thomas, J. K. J. Am.
Chem. Soc. 1975, 97, 3915.
24. Kalyanasundaram, K.; Thomas, J. K. J. Am. Chem. Soc.
1977, 99, 2039.
25. Jane, Y. S.; Shih, J. S. J. Chin. Chem.Soc. 1994, 41, 159.
26. Hwang, W. Y.; Shih, J. S. J. Chin. Chem. Soc. 2000, 47,
1215.
ACKNOWLEDGEMENT
The authors would like to express their appreciation
to the National Science Council of the Republic of China in
Taiwan for the financial support of this study.
27. Cotton, F. A.; Wilkinson, F. R. Advanced Inorganic Chemis-
try, 4th ed.; Wiley: New York, 1980; p 14.
Received December 28, 2007.

586 J. Chin. Chem. Soc., Vol. 55, No. 3, 2008
Shen and Shih
REFERENCES
1. de Gennas, P. G. The Physics of Liquid Crystal; Oxford
Univ.: London, 1974.
2. Gray, G. W.; Winsor, P. A. Liquid Crystal and Plastic Crys-
tals; Ellis Horwood: New York, 1974.
3. Leder, L. B. J. Chem. Phys. 1971, 55, 2649.
4. Park, J. W.; Labes, M. M. Mol. Cryst. Liq. Cryst. 1975, 31,
355.
5. Shinkai, S. Chem. Soc. Chem.Commun. 1991, 339.
6. Adams, J. E.; Hass, W. E. L.; Wysocki, J. J. Phys. Cryst. Liq.
Cryst. 1977, 42, 15.
7. Musubuchi, S.; Akahane, T.; Kakuo, K.; Tako, T. Mol.
Cryst. Liq. Cryst. Liq. Cryst. 1977, 38, 265.
8. Pedersen, C. J. J. Am. Chem. Soc. 1967, 89, 7017.
9. Dietrich, B.; Lehn, J. M.; Sauvage, J. P. Tetrahedron Lett.
1969, 34, 2885.
10. Kelthoff, I. M. Anal. Chem. 1979, 51, 1R.
11. Christensen, J. J. Progress in Macrocyclic Chemistry;
Wiley-Interscience: New York, 1979.
12. Shih, J. S. J. Chin. Chem. Soc. 1992, 39, 551.
13. Mario, Y.; Promauro, E.; Gratzel, M.; Pelizzetti, E.; Tundo,
P. J. Collid. Interface Sci. 1979, 69, 341.
Fig. 15. Effect of metal ion diameter on ion transports
of various metal ions through the
B15C5COOC27H45/dichloromethane liquid
membrane.
14. Kuo, P. L.; Ikoda, I.; Okahara, M. Tenside Deterg 1982, 19,
4.
15. Chou, F. F.; Shih, J. S. J. Chin. Chem. Soc. 2002, 49, 599.
16. Lee, J. L.; Shen, Y. C.; Shih, J. S. J. Chin. Chem. Soc. 2003,
50, 861.
e.g. cholesteryl chloride and cholesteryl benzoate exhib-
ited wider phase transition temperature ranges than those
of common cholesteryl liquids. Some B15C5COOCh/
cholesteryl mixed liquid crystals showed the transition
temperature at room temperature. The Insight II/Discover
graphic molecular modeling computer programs were suc-
cessfully employed to calculate the average molecular en-
ergy and explain the stability of mixed liquid crystals.
Crown ether cholesteryl liquid crystal B15C5COOCh also
showed the characteristics of a surfactant in forming mi-
celles in water. Furthermore, B15C5COOCh also served as
a good ion transport carrier to transport metal ions through
the organic liquid membrane.
17. Choy, E. M.; Evans, D. F.; Cussler, E. L. J. Am. Chem. Soc.
1974, 96, 7085.
18. Yoshida, S.; Hayano, S. J. Am. Chem. Soc. 1986, 108, 3903.
19. Hwang, W. Y.; Shih, J. S. J. Chin. Chem. Soc. 2000, 47,
1215.
20. Stott, P. E.; Bradshaw, J. S. J. Org. Chem. 1980, 45, 4716.
21. Wada, F.; Kikukawa, K.; Shinkai, S.; Maysuda, T. J. Org.
Chem. 1990, 55, 541.
22. Haines, A. H.; Hodgkisson, I.; Smith, C. J. J. Chem. Soc.,
Perkin Trans. 1983, 1, 311.
23. Kalyanasundaram, K.; Gratzel, M.; Thomas, J. K. J. Am.
Chem. Soc. 1975, 97, 3915.
24. Kalyanasundaram, K.; Thomas, J. K. J. Am. Chem. Soc.
1977, 99, 2039.
25. Jane, Y. S.; Shih, J. S. J. Chin. Chem.Soc. 1994, 41, 159.
26. Hwang, W. Y.; Shih, J. S. J. Chin. Chem. Soc. 2000, 47,
1215.
ACKNOWLEDGEMENT
The authors would like to express their appreciation
to the National Science Council of the Republic of China in
Taiwan for the financial support of this study.
27. Cotton, F. A.; Wilkinson, F. R. Advanced Inorganic Chemis-
try, 4th ed.; Wiley: New York, 1980; p 14.
Received December 28, 2007.