M. Tian et al. / Journal of Molecular Structure 923 (2009) 39–44
41
pyridine (100 ml) containing DCC (3.4 g,16.5 mmol) and DMAP
3. Results and discussion
(0.25 g, 2.05 mmol). The reaction mixture was stirred for 20 h at
room temperature and filtrated. The filtrate was poured into water
and acidified with dilute hydrochloric acid. The crude product was
obtained by filtration and washed with water to neutral pH. The
white powder c2 was obtained by recrystallization from ethanol.
c0 Yield 89%. m.p. 123.0 °C. Elemental analysis calculated for
C151H152O31: C, 73.66; H, 6.18%. Found: C, 73.61; H, 6.21%.
IR (KBr, cmꢀ1): 2928–2856 (–CH2–); 1755, 1731, 1718 (C@O);
1601, 1501 (Ar–); 1288, 1192, 1162 (C–O–C).
3.1. Synthesis
The synthetic route for the mesogenic arms and the MALCs was
shown in Scheme 1. Their structural characterizations were in good
agreement with the prediction. The mesogenic units (b0, b1, b2)
were synthesized through the reaction of compounds a0, a1, a2
and sebacic acid chloride in THF and pyridine. IR spectra of b0,
b1, b2 showed characteristic bands at 3280–2558, 1747–1733,
1698, 1607 and 1509 attributed to carboxylic acid–OH, ester
C@O, carboxylic acid C@O and phenyl C@C stretching bands.
Whereas IR spectra of c0, c1, c2, d0, d1 and d2 did not show carbox-
ylic acid –OH stretching bands, the peak of the carboxylic acid C@O
stretching vibration disappeared as well. Analyzed with 1H NMR
spectra, c0–c2 showed multiple at 1.32, 1.26–3.95, 4.01–6.66 and
6.90–8.13 ppm corresponding to methyl, methylene, pyranose ring
and aromatic, respectively. This suggested that c0–c2 are the mix-
tures of alpha and beta isomers. d0–d2 showed multiple at 1.32,
1.26–3.95, 4.32–5.14 and 6.92–8.13 corresponding to methyl,
methylene, sorbitol chain and aromatic, respectively. The results
of FT-IR, Element analysis and 1H NMR spectroscopy indicated that
the target compounds c0–c2 and d0–d2 were obtained.
1H NMR (CDCl3, ppm): 1.29 (m, 80H, CH2), 1.58 (m, 40H, CH2),
2.23–2.60 (m, 40H, CH2), 4.01–5.61 [m, 12H, pyranose-H(except
H-1)], 5.73 (d,1H, H-1, J = 7.8 Hz), 6.66 (d, 1H, H-1, J = 3.6 Hz),
7.09–8.13 (m, 130H, Ar–H).
c1 Yield 92%. m.p. 116.0 °C. Elemental analysis calculated for
C156H162O36: C, 71.70; H, 6.21%. Found: C, 71.88; H, 6.13%.
IR (KBr, cmꢀ1): 2965–2852 (–CH3, –CH2–); 1751, 1735, 1715
(C@O); 1601, 1500 (Ar–); 1285, 1208, 1165 (C–O–C).
1H NMR (CDCl3, ppm): 1.28 (m, 80H, CH2), 1.58 (m, 40H, CH2),
2.23–2.61 (m, 40H, CH2), 3.78 (m, 30H, OCH3), 4.01–5.61 (m,
12H, pyranose-H (except H-1), 5.73(d, 1H, H-1, J = 7.8 Hz), 6.66
(d, 1H, H-1, J = 3.6 Hz), 6.95–8.06 (m, 120H, Ar–H).
c2 Yield 90%. m.p. 85 °C. Elemental analysis calculated for
C161H172O36: C, 72.09; H, 6.42%. Found: C, 71.90; H, 6.44%.
IR (KBr, cmꢀ1): 2963–2854 (–CH3, –CH2–); 1753, 1733, 1715
(C@O); 1601, 1497 (Ar–); 1281, 1203, 1169 (C–O–C).
3.2. Optical rotation
1H NMR (CDCl3, ppm): 1.29 (m, 80H, CH2), 1.32 (m, 30H, CH3),
1.56 (m, 40H, CH2), 2.22–2.60 (m, 40H, CH2), 3.95 (m, 20H,
OCH2), 4.01–5.61 (m, 12H, pyranose-H (except H-1), 5.73 (d, 1H,
H-1, J = 7.8 Hz), 6.66 (d, 1H, H-1, J = 3.6 Hz), 6.90–8.04 (m, 120H,
Ar–H).
Glucose and sorbitol were optically active in water solution in
the light of a Na-lamp at k = 589 nm. The specific rotation (SROT)
of glucose was +52.85° (c = 0.8 g/L), and the SROT of sorbitol was
ꢀ32.5° (c = 0.8 g/L). The MALCs (in THF, c = 0.8 g/L) exhibited opti-
cal active, too. It is obvious that the chiral cores played an impor-
tant role to the optical active of the MALCs. However, the SROTs of
the MALCs showed contrary handedness to the corresponding chi-
ral cores. Generally, solvent, temperature, chain length and substi-
tuent play an important effect on handedness of the cholesteric
liquid crystals [51,52]. In present study, the results suggest that
the long mesogenic arms play an important effect on the change
of the behavior of SROTs for MALCs compared with the chiral cores.
The SROTs of c0, c1, c2, d0, d1 and d2 were ꢀ2.01, ꢀ3.92, ꢀ10.61,
+6.3, +12.39 and +16.80, respectively. These data were showed in
Table 1. For the MALCs c0–c2 (or d1–d2), which have the same
cores but different mesogenic units, the absolute value of SROT in-
creased with the increase of terminal chain length in the meso-
genic units. It indicates that the longer the terminal chain is, the
more freedom the chain structure has and the higher the SROT va-
lue is.
2.3.4. Hexa {8-[4-(4-R-benzoyloxy)biphenyl-40-yloxycarbonyl]
pelargonic acid} sorbitol ester (d0–d2)
d0–d2 were prepared by the same synthetic method. The syn-
thesis of d2 was given as an example. The anhydrous sorbitol
(0.546 g, 3 mmol) solution in dry pyridine (20 ml) was added drop-
wise into the solution of b2 (9.32 g, 18.0 mmol), DCC (3.71 g,
18 mmol) and DMAP (0.366 g, 3 mmol) in dry pyridine (100 ml).
The reaction mixture was stirred for 20 h at room temperature
and filtrated. The filtrate was poured into water and acidified with
dilute hydrochloric acid. The crude product was obtained by filtra-
tion and washed with water to neutral pH. The white powder d2
was obtained by recrystallization from ethanol.
d0 Yield 92%. m.p. 111–112 °C. Elemental analysis calculated for
C180H182O36: C, 72.02; H, 6.24%. Found: C, 71.89; H, 6.31%.
IR (KBr, cmꢀ1): 2928–2847 (–CH2–); 1755, 1731, 1718 (C@O);
1601, 1501, (Ar–); 1278, 1198, 1156 (C–O–C).
3.3. Thermal analysis
1H NMR (CDCl3, ppm): 1.26 (m, 48H, CH2), 1.59 (m, 24H, CH2),
2.29 (m, 24H, CH2), 4.32–5.14 (m, 8H, sorbitol-H), 6.95–8.13 (m,
78H, Ar–H).
The thermal properties and phase behavior of b0–b2, c0–c2, and
d0–d2 were investigated with DSC. Their phase-transition temper-
atures and corresponding enthalpy changes, obtained on the first
heating and cooling cycle, were summarized in Table 1, and the
representative DSC curves were presented in Fig. 1.
The mesogenic units b0, b1 and b2 exhibited liquid crystalline
properties on heating and cooling cycle. They showed a melting
transition at 118.2, 132.0 and 161.0 °C, a clearing transition at
d1 Yield 89%. m.p. 104–106 °C. Elemental analysis calculated for
C186H194O42: C, 72.05; H, 6.26%. Found: C, 72.20; H, 6.11%.
IR (KBr, cmꢀ1): 2965–2845 (–CH3, –CH2–); 1753, 1735, 1715
(C@O); 1601, 1500, (Ar–); 1285, 1195, 1165 (C–O–C).
1H NMR (CDCl3, ppm): 1.28 (m, 48H, CH2), 1.55 (m, 24H, CH2),
2.22 (m, 24H, CH2), 3.75 (m, 18H, OCH3), 4.32–5.14 (m, 8H, sorbi-
tol-H), 6.92–8.03 (m, 72H, Ar–H).
d2 Yield 92%. m.p. 80–82 °C. Elemental analysis calculated for
C192H206O42: C, 72.41; H, 6.47%. Found: C, 72.17; H, 6.51%.
IR (KBr, cmꢀ1): 2965–2843 (–CH3, –CH2–); 1758, 1735, 1711
(C@O); 1610, 1510, (Ar–); 1270, 1208, 1113 (C–O–C).
1H NMR (CDCl3, ppm): 1.29 (m, 48H, CH2), 1.37 (m, 18H, CH3),
1.61 (m, 24H, CH2), 2.24 (m, 24H, CH2), 3.90 (m, 12H, OCH2),
4.32–5.14 (m, 8H, sorbitol-H), 6.92–8.01 (m, 72H, Ar–H).
201.5, 244.5 and 222.0 °C, the mesogenic region (
83.3, 112.5 and 61.0 °C on heating cycle. While on cooling cycle,
the mesogenic region
DT1) about
(DT2) was 32.7, 92.3 and 43.8 °C,
respectively.
DSC curves of c0–c2 and d0–d2, obtained on first heating and
cooling cycle, showed two endothermic or exothermic peaks,
which represented a melting and a LC-isotropic phase transition
or crystal and isotropic-LC phase transition, respectively.