84
D.-S. Yao et al. / Journal of Molecular Structure 881 (2008) 83–89
crystal phases were studied through polarized optical
microscopy (POM) and were conformed by using X-ray
diffraction method. The influence of the length of the mes-
ogenic units on phase behavior of the star-shaped com-
pounds were discussed.
decanedioic acid monocholesterol ester 2d, the same
method was adopted. The synthesis of 2b was given as an
example. Adipyl chloride (18.2 g, 0.10 mol) obtained from
hexanedioic acid reacting with excess thionyl chloride was
dissolved in 50 ml THF, cholesterol (7.6 g, 0.02 mol) in
50 ml THF with the presence of 5 ml pyridine was added
2
. Experimental procedures
dropwise with stirring, the reaction mixture was refluxed
for 10 h in a dry atmosphere. After cooling to room tem-
perature, the mixture was poured into 200 ml cold water
and acidified with 6 N hydrochloric acid. The precipitate
was isolated by filtration and dried in a vacuum oven.
Recrystallization from ethanol gave white crystals of 2b.
Yield 58%.
2
.1. Materials
Cholesterol was purchased from Henan Xiayi Medical
Co. 1,3,5-trihydroxybenzene, succinic anhydride, hexa-
nedioic acid, octanedioic acid and decanedioic acid were
purchased from Beijing Chemical Company (China) and
used without any further purification. All solvents and
reagents were purified by standard methods.
2.3.2. Tri[x-alkyl diacid monocholesterol ester]
phloroglucinol ester (4a–4d)
All star-shaped liquid crystals (4a–4d) were prepared by
the same synthetic method. First, x-alkyl diacid monocho-
lesterol ester 2a–2d (0.033 mol) was reacted at 65 ꢁC with
50 ml thionyl chloride containing a few drops of N,N-dim-
ethylfomamide (DMF) for 3 h, and then the excess thionyl
chloride was removed under reduced pressure to give the
corresponding acid chloride 3. The acid chloride obtained
was dissolved in 20 ml dry THF, followed by adding
1,3,5-trihydroxybenzene (0.01 mol) in 20 ml pyridine. The
reaction mixture was refluxed for 12 h in a dry atmosphere.
After cooling to room temperature, the mixture was
poured into 150 ml cold water and acidified with 6 N
hydrochloric acid. The crude product obtained was col-
lected by filtration, and was purified by recrystallization
from acetone to yield white crystals 4a–4d (65–76%).
4a Yield 65%. m.p. 150–151 ꢁC. Anal. calcd for
C H O : C, 77.65; H, 9.80%. Found: C, 77.47; H,
2
.2. Measurements
The element analyses were carried out by using a Ele-
mentar Vario EL III (Elementar, Germany). FT-IR spectra
were measured on a Perkin-Elmer spectrum One (B) spec-
trometer (Perkin-Elmer, Foster City, CA). H NMR spec-
tra (300 MHz) were obtained with a Varian Gemini 300
spectrometer (Varian Associates, Palo Alto, CA). Optical
rotations were obtained on a Perkin-Elmer 341 polarime-
ter. Phase transition temperatures and thermodynamic
parameters were determined by using a Netzsch DSC 204
1
(
Netzsch, Germany) equipped with a liquid nitrogen cool-
ing system. The heating and cooling rates were 10 ꢁC/min.
A Leica DMRX (Leica, Germany) POM equipped with a
Linkam THMSE-600 (Linkam, England) hot stage was
used to observe phase transition temperatures and analyze
LC properties for the mesogenic units and star-shaped
liquid crystals through observation of optical textures.
XRD measurements were performed with a nickel-filtered
9
9
150 12
ꢀ
1
9.71%. IR (KBr, cm ): 2950, 2869 (ACH , ACH A);
3
2
1768, 1735 (C@O); 1606, 1506 (ArA); 1272, 1135
1
(CAOAC). H NMR (CDCl , ppm): 0.64–2.10 (m, 129H,
3
Cu-K (k = 0.1542 nm) radiation with a DMAX-3A Riga-
cholesteryl-H), 2.55 (m, 12H, AOCCH A), 3.95–4.08 (m,
a
2
ku (Rigaku, Japan) powder diffractometer.
3H, OCH< in cholesteryl), 5.23–5.35 (m, 3H, @CHA in
cholesteryl), 7.03 (s, 3H, ArAH).
2
.3. Synthesis
4b Yield 72%. m.p. 126–128 ꢁC. Anal. calcd for
C105H162O : C, 78.07; H, 10.04%. Found: C, 78.23; H,
12
ꢀ
1
The synthetic routes of the mesogenic units containing
9.88%. IR (KBr, cm ): 2945, 2866 (ACH , ACH A);
3
2
monocholesterol ester (2a–2d) and star-shaped liquid crys-
tals (4a–4d) were shown in Scheme 1.
1762, 1731 (C@O); 1608, 1510 (ArA); 1280, 1142
1
(CAOAC). H NMR (CDCl , ppm): 0.63–2.07 (m, 141H,
3
cholesteryl-H and AOCCH (CH ) A), 2.46 (m, 12H,
2
2 2
2
.3.1. x-Alkyl diacid monocholesterol ester (2a–2d)
AOCCH A), 3.92–4.06 (m, 3H, AOCH< in cholesteryl),
2
Butanedioic acid monocholesterol ester 2a was prepared
by an esterification of cholesterol (3.8 g, 0.01 mol) with
butanedioic anhydride (1.0 g, 0.01 mol) in 20 ml THF using
5.38–5.50 (m, 3H, @CHA in cholesteryl), 6.95 (s, 3H,
ArAH).
4c Yield 76%. m.p. 108–110 ꢁC. Anal. calcd for
2
ml pyridine as catalyst. The mixture was refluxed for 18 h
C111H174O : C, 78.45; H, 10.25%. Found: C, 77.97; H,
12
ꢀ
1
in a dry atmosphere. Cooled to room temperature, the
reaction solution was poured into 100 ml cold water. The
precipitate was isolated by filtration, washed with hot
water, then recrystallized from ethanol to yield white crys-
tals (74%).
10.59%. IR (KBr, cm ): 2948, 2864 (ACH , ACH A);
3
2
1766, 1732 (C@O); 1605, 1502 (ArA); 1275, 1140
1
(CAOAC). H NMR (CDCl , ppm): 0.60–2.04 (m, 153H,
3
cholesteryl-H and AOCCH (CH ) A), 2.42 (m, 12H,
2
2 2
AOCCH A), 3.96–4.04 (m, 3H, AOCH< in cholesteryl),
2
For the synthesis of hexanedioic acid monocholesterol
ester 2b, octanedioic acid monocholesterol ester 2c and
5.36–5.46 (m, 3H, @CA in cholesteryl), 7.02 (s, 3H,
ArAH).