Self-organization of adenine and thymine derivatives in thermotropic liquid crystal

Article abstract of DOI:10.1016/j.molstruc.2006.05.010

Self-organization of adenine and thymine derivatives was studied by comparison of IR spectra of these compounds in crystal, liquid crystal, and isotropic liquid states. The adenine derivative mainly formed weaker hydrogen-bonded assemblies in the liquid c

Full text of DOI:10.1016/j.molstruc.2006.05.010

Journal of Molecular Structure 827 (2007) 95–100
www.elsevier.com/locate/molstruc
Self-organization of adenine and thymine derivatives
in thermotropic liquid crystal
Toshio Itahara a,¤, Yukiko Yokogawa b
a Faculty of Engineering, Kagoshima University, Korimoto, Kagoshima 890-0065, Japan
b Faculty of Science, Kagoshima University, Korimoto, Kagoshima 890-0065, Japan
Received 5 September 2005; received in revised form 25 April 2006; accepted 10 May 2006
Available online 16 June 2006
Abstract
Self-organization of adenine and thymine derivatives was studied by comparison of IR spectra of these compounds in crystal, liquid
crystal, and isotropic liquid states. The adenine derivative mainly formed weaker hydrogen-bonded assemblies in the liquid crystal state,
compared with assemblies in crystal state. The thymine derivative existed as a component of a network of prolonged hydrogen bonds
interconnecting thymine rings in the liquid crystal state. The mixing of the adenine and thymine derivatives at a molar ratio of 1:1 resulted
in a formation of base pair between adenine and thymine rings. The structures of hydrogen-bonded assemblies in the liquid crystal state
were presumed on the basis of the temperature-dependent IR spectra.
© 2006 Elsevier B.V. All rights reserved.
Keywords: Temperature-dependent IR; Liquid crystal; Self-organization; Adenine; Thymine; 3-Methyluracil
1. Introduction
of temperature-dependent IR spectroscopy. Furthermore a
3-methyluracil derivative (3) was synthesized. IR spectra of
3 were compared with those of 2, because 3 cannot form a
hydrogen-bonded assembly as a result of the methylation
of NH at the 3-position (see Scheme 1).
Since the pioneering work of Kato and Frçcht [1] and
Lehn and co-workers [2], hydrogen-bonded liquid crystals
have been studied by several groups of workers [3]. The
presence of hydrogen bond in liquid crystal state has been
determined by IR spectroscopy [4] or the other methods.
On the other hand, it is well known that the nucleic bases
associate to form the hydrogen-bonded assemblies [5]. We
previously reported the liquid crystallinity of the adenine
derivative (1) and the thymine derivative (2) as a communi-
cation [6]. Although the temperature-dependent IR and
Raman spectra of the nucleic acid-related molecules are
known [7], the IR study of the nucleic base derivatives in
liquid crystal state has not been reported. It is expected that
the nucleic base derivatives can be ordered in liquid crystal
state, compared in isotropic liquid state. Therefore it
appeared of interest to investigate the self-organization of
the nucleic base derivatives in liquid crystal state by means
2. Experimental
2.1. General
The elemental analysis was performed in the Analytical
Center of Kyoto University. The 1H NMR spectrum
(400MHz) and 13C NMR spectrum (100 MHz) were
obtained with a JEOL GSX 400 spectrometer. The chemi-
cal shifts (ꢀ-values) were measured in parts per million
(ppm) down-Weld from tetramethylsilane as an internal ref-
erence. The IR spectra were recorded with a JASCO FT/
IR-420 spectrometer. The samples at various temperatures
were sandwiched between two KBr crystal plates with a
0.05 mm spacer. The sandwiched samples were held on a
hot stage (JASCO HC-500/H), equipped with a tempera-
ture controller (JASCO TC-1000). DiVerential scanning
*
Corresponding author. Tel./fax: +81 99 285 8208.
E-mail address: itahara@be.kagoshima-u.ac.jp (T. Itahara).
0022-2860/$ - see front matter © 2006 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2006.05.010

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T. Itahara, Y. Yokogawa / Journal of Molecular Structure 827 (2007) 95–100
NH2
N
N
N
N
O
COO
(CH2)12
Me
(1)
O
N
HN
O
(CH2)12
O
O
COO
(2)
O
N
Me
O
N
(CH2)12
COO
(3)
Scheme 1.
calorimetry (DSC) measurements were carried out with a
Shimadzu DSC-60. Microscopy observations were per-
formed under a Nikon Eclipse E600 POL equipped with a
hot stage (Tokai Hit ThermoPlate or Linkam LK-600PH).
form or a mixture of chloroform and methanol gave 1
(0.15 mmol), 2 (0.14 mmol), or 3 (0.17 mmol).
2.2.1. Cholesteryl p-[12-(adenin-9-yl)dodecyloxy]benzoate
(1)
2.2. Synthesis of adenine, thymine, and 3-methyluracil
derivatives
1H NMR (CDCl3) ꢀ 8.38 (s, 1H, A-2), 7.97 (d, 2H,
J D8.8Hz), 7.79 (s, 1H, A-8), 6.89 (d, 2H, J D8.8 Hz), 5.53 (s,
2H, Ade-NH2), 5.41 (d, 1H, J D3.6 Hz, Chol-6), 4.82 (m, 1H,
Chol-3), 4.19 (t, 2H, J D7.2 Hz), 4.00 (t, 2H, J D 6.4Hz), 2.45
(d, 2H, J D 7.6Hz, Chol-4), 1.06 (s, 3H, Chol-19 or 18), 0.92
(d, 3H, J D 6.4Hz, Chol-21), 0.87 (dd, 6H, J D6.4,
J D1.6 Hz, Chol-26,27), 0.69 (s, 3H, Chol-18 or 19) 2.10–
0.90 (m, 46H); 13C NMR (CDCl3) ꢀ 165.79, 162.81, 155.63,
152.94, 150.11, 140.36, 139.78, 131.50, 123.02, 122.64, 119.69,
113.96, 74.18, 68.17, 56.70, 56.16, 50.06, 43.95, 42.33, 39.76,
39.52, 38.31, 37.07, 36.66, 36.20, 35.80, 31.93, 31.89, 30.08,
29.48, 29.47, 29.45, 29.40, 29.33, 29.11, 29.04, 28.24, 28.01,
27.96, 26.66, 25.97, 24.29, 23.84, 22.82, 22.57, 21.06, 19.38,
18.73, 11.87. Found: C, 75.49; H, 9.45; N, 8.41. Calcd for
C51H77N5O3: C, 75.79; H, 9.60; N, 8.67.
A
solution of cholesteryl p-hydroxybenzoate [8]
(1 mmol) and 1,12-dibromododecane (1 mmol) in acetone
(150 ml) containing K2CO3 (1 mmol) was heated at reXux
temperature for 24 h under nitrogen atmosphere. The
reaction mixture was evaporated to give a residue, which
was chromatographed on silica gel. Elution by a mixture
of chloroform and hexane (2:1) gave cholesteryl p-(12-
bromododecyloxy)benzoate (0.56 mmol): mp 75–76 °C;
IR (CDCl3) ꢁ 1703, 1606, 1510, 1468, 1369, 1317, 1277,
1
1254, 1169, 1120, 1009 cm¡1; H NMR (CDCl3) ꢀ 7.98 (d,
2H, J D 8.8 Hz), 6.89 (d, 2H, J D 8.8 Hz), 5.42 (d, 1H,
J D 3.6 Hz, Chol-6), 4.82 (m, 1H, Chol-3), 4.00 (t, 2H,
J D 6.4 Hz), 3.41 (t, 2H, J D 6.4 Hz), 2.45 (d, 2H,
J D 7.6 Hz, Chol-4), 1.06 (s, 3H, Chol-19 or 18), 0.92 (d,
3H, J D 6.4 Hz, Chol-21), 0.87 (dd, 6H, J D 6.4 Hz,
J D 1.6 Hz, Chol-26,27), 0.69 (s, 3H, Chol-18 or 19) 2.10–
0.90 (m, 46H). Anal. Calcd for C46H73BrO3: C, 73.28; H,
9.76. Found: C, 73.22; H, 9.48.
A mixture of cholesteryl p-(12-bromododecyloxy)benzo-
ate (0.5 mmol) with adenine, thymine, or 3-methyluracil
(0.6mmol) in N,N-dimethylformamide (70ml) containing
K2CO3 (0.5mmol) was stirred at room temperature for 24 h
under nitrogen atmosphere. The reaction mixture was
evaporated to give a residue, which was chromatographed
on silica gel. By monitoring at 254 nm, elution by chloro-
2.2.2. Cholesteryl p-[12-(thymin-1-yl)dodecyloxy]benzoate
(2)
1H NMR (CDCl3) ꢀ 8.18 (s, 1H, T3-NH), 7.98 (d, 2H,
J D8.8 Hz), 6.97 (s, 1H, T6), 6.89 (d, 2H, J D 8.8 Hz), 5.42 (d,
1H, J D3.6 Hz), 4.84 (m, 1H), 4.00 (t, 2H, J D 6.4Hz), 3.68 (t,
2H, J D 6.8 Hz), 2.45 (d, 2H, J D 7.2Hz, Chol-4), 1.92 (d, 3H,
J D1.0 Hz, T5-Me), 1.06 (s, 3H, Chol-19 or 18), 0.92 (d, 3H,
J D6.4 Hz, Chol-21), 0.87 (dd, 6H, J D 6.4, J D1.6 Hz, Cho-
26,27), 0.69 (s, 3H, Chol-18 or 19) 2.10–0.90 (m, 46H); 13C
NMR (CDCl3) ꢀ 165.84, 164.09, 162.82, 150.73, 140.42,
139.80, 131.51, 123.04, 122.67, 113.98, 110.50, 74.21, 68.18,
56.72, 56.16, 50.08, 48.58, 42.34, 39.77, 39.53, 38.31, 37.08,

T. Itahara, Y. Yokogawa / Journal of Molecular Structure 827 (2007) 95–100
97
36.68, 36.20, 35.81, 31.95, 31.91, 29.50, 29.50, 29.49, 29.43,
29.34, 29.19, 29.11, 29.10, 28.24, 28.02, 27.97, 26.45, 25.98,
24.31, 23.85, 22.83, 22.57, 21.07, 19.40, 18.73, 12.33, 11.88.
Found: C, 76.60; H, 9.70; N, 3.44. Calcd for C51H78N2O5: C,
76.65; H, 9.84; N, 3.51.
vidual components, because 1 and 3 did not associate to
form an assembly.
The existence of hydrogen bonds of the nucleic base
derivatives was studied by comparison of IR spectra of
these compounds in the crystal, in the liquid crystal, and in
the isotropic liquid states. Fig. 1 shows the IR spectra of 1.
Four NH2 stretching bands were found at 3481 (non-H-
bond: non-hydrogen-bonded bands), 3403 (non-H-bond),
3327 (H-bond), and 3180cm¡1 (H-bond) in isotropic liquid
at 180°C. On the other hand, a smaller band at 3481 cm¡1
(non-H-bond) and larger bands at 3334 and 3178cm¡1 (H-
bond) were found in liquid crystal state at 160 °C. This sug-
gests that 1 mainly existed as a hydrogen-bonded form in
the liquid crystal. Furthermore NH2 scissoring vibrations
were observed at 1670cm¡1 in crystal at 20 °C, at 1651cm¡1
in liquid crystal at 160°C, and at 1628 cm¡1 in isotropic liq-
uid at 180 °C. In the classic IR study for 9-ethyladenine, the
band at 1675cm¡1 is assigned to the NH2 scissoring in the
spectrum of the solid and the band at 1629 cm¡1 is assigned
to that in the solution [9]. For reference the IR spectrum of
1 in CDCl3 at room temperature showed the band at
1630 cm¡1. These assignments are consistent with the data
reported in the recent study [10]. The scissoring vibrations
are expected to be higher in crystal because of stronger
hydrogen bond [9]. On the basis of these data, it can be pre-
sumed that 1 mainly formed weaker hydrogen-bonded
assemblies in the liquid crystal state, compared with assem-
blies in the crystal state. It is well known that rod-like mole-
cules or molecular aggregates tend to show a liquid
crystalline behavior. Therefore the hydrogen-bonded
assemblies in the liquid crystal state may be shown as (A)
and/or (B) as given in Scheme 2, although there are several
types of molecular assemblies for adenine itself [5,11].
Fig. 2 shows the IR spectra of 2. Two NH stretching
bands of 2 were found at 3413 (non-H-bond) and 3205cm¡1
(H-bond) in isotropic liquid state at 200°C, suggesting that
2 existed in both non-hydrogen-bonded and hydrogen-
bonded forms at 200°C. However the non-hydrogen-
2.2.3. Cholesteryl p-[12-(3-methyluracil-1-yl)
dodecyloxy]benzoate (3)
1H NMR (CDCl3) ꢀ 7.97 (d, 2H, J D8.0Hz), 7.11 (d, 1H,
J D7.6 Hz, U6), 6.89 (d, 2H, J D8.0 Hz), 5.73 (d, 1H,
J D7.6 Hz, U5), 5.41 (d, 1H, J D3.6 Hz), 4.81 (m, 1H), 4.00
(t, 2H, J D 6.4Hz), 3.73 (t, 2H, J D 6.8Hz), 3.34 (s, 3H, U3-
Me), 2.45 (d, 2H, J D 7.2Hz, Chol-4), 1.06 (s, 3H, Chol-19 or
18), 0.92 (d, 3H, J D 6.4 Hz, Chol-21), 0.87 (dd, 6H, J D 6.4,
J D1.6 Hz, Cho-26,27), 0.69 (s, 3H, Chol-18 or 19) 2.10–0.90
(m, 46H); 13C NMR (CDCl3) ꢀ 165.74, 163.29, 162.76,
151.56, 142.05, 139.73, 131.45, 122.98, 122.61, 113.92, 101.25,
74.15, 68.12, 56.66, 56.11, 50.01, 49.90, 42.28, 39.71, 39.48,
38.26, 37.02, 36.62, 36.15, 35.75, 31.89, 31.85, 29.45, 29.44,
29.44 29.37, 29.28, 29.11, 29.06, 28.98, 28.19, 27.96, 27.91,
27.72, 26.42, 25.92, 24.25, 23.79, 22.77, 22.52, 21.01, 19.34,
18.69, 11.82. Anal. Calcd for C51H78N2O5: C, 76.65; H, 9.84;
N, 3.51. Found: C, 76.35; H, 9.77; N, 3.50.
3. Results and discussion
The thermal mesomorphic phases of the nucleic base
derivatives and their mixtures were analyzed by diVerential
scanning calorimetry (DSC) and polarizing microscopy.
The polarizing microscopy observation showed the chole-
steric liquid crystallinity of 1, 2, and 3. The thermodynamic
data are summarized in Table 1. Equimolecular amounts of
1 and 2 were dissolved in chloroform and the solvent was
allowed to evaporate slowly, leaving a white solid behind.
The clearing point of the mixture of 1 and 2 was 190°C,
and those of 1 and 2 alone were 168 and 185 °C, respec-
tively. Therefore the mixing of 1 and 2 resulted in a stabil-
ization of the liquid crystalline phase. This may be caused
by a formation of base-paired assembly between 1 and 2.
On the other hand, the clearing point of a mixture of 1 and
3 at a molar ratio of 1:1 was lower than those of the indi-
Table 1
Thermal behavior of the nucleic base derivatives
Compounds
Phase behaviora (°C)
Heating
Cooling
1
2
3
C
C
C
C
C
152
162
153b
138
136
N¤
N¤
N¤
N¤
N¤
168
185
170c
190
160
I
I
I
I
I
162
180
160
180
154
N¤
N¤
N¤
N¤
N¤
143
113
141
70
C
C
C
G
G
1+2 (1:1)d
1+3 (1:1)d
a
132
Fig. 1. IR spectra of 1 in crystal, in liquid crystal, and in isotropic liquid
states. C (crystal at room temperature, 20 °C): 3311, 3149, 2929, 2852,
1709, 1670, 1606, 1574, 1510, 1468, 1417 cm¡1. LC (liquid crystal at 160 °C
upon heating): 3481, 3334, 3178, 2931, 2852, 1709, 1651, 1601, 1574, 1508,
1468, 1414 cm¡1. I (isotropic liquid at 180 °C upon heating): 3481, 3403,
3327, 3180, 2929, 2856, 1712, 1628, 1603, 1576, 1508, 1466, 1414 cm¡1. For
reference in (CDCl3) at room temperature: 3519, 3408, 2935, 2856, 1701,
The thermal mesomorphic phases were determined by polarizing
microscopy and diVerential scanning calorimetry upon heating and cool-
ing at a rate of 5 °C. C, crystal; N¤, cholesteric liquid crystal; I, isotropic
liquid; G, glass solid.
b
ꢀH D 28.6 kJ/mol.
c
ꢀH D 1.1 kJ/mol.
d
1630, 1604, 1580, 1510, 1469, 1414 cm¡1
.
A molar ratio.

98
T. Itahara, Y. Yokogawa / Journal of Molecular Structure 827 (2007) 95–100
H
O
N
N
N
H
H
N
O
N
O
CO
(CH2)12
N
OC
N
O
(CH2)12
N
N
N
A
H
N
H
N
O
N
H
OC
O
N
(CH2)12
O
N
O
CO
N
(CH2)12
N
H
N
N
H
N
B
Scheme 2.
Fig. 2. IR spectra of 2 in crystal, in liquid crystal, and in isotropic liquid states. C (crystal at 30 °C upon heating): 3155, 3062, 2931, 2852, 1707, 1682, 1651,
1608, 1510, 1468, 1429 cm¡1. LC (liquid crystal at 170 °C upon heating): 3180, 3059, 2933, 2854, 1701, 1673, 1604, 1508, 1464, 1417 cm¡1. I (isotropic liquid
at 200 °C upon heating): 3413, 3205, 3062, 2929, 2856, 1712(broad), 1603, 1508, 1464, 1419 cm¡1. For reference, in (CDCl3) at room temperature: 3392,
3170, 3035, 2931, 2856, 1700, 1682, 1606, 1510, 1468 cm¡1
.
bonded NH stretching vibration was little found in liquid
crystal state at 170°C and in crystal state at 30 °C. This sug-
gests that 2 primarily existed as a hydrogen-bonded form in
not only the crystal state but also the liquid crystal state.
Interestingly three bands of the carbonyl stretching at 1707
(cholesteryl benzoate), 1682 (thymine at 2-position), and
1651cm¡1 (thymine at 4-position) in the crystal state were
replaced by two bands at 1701 (cholesteryl benzoate) and
1673cm¡1 (thymine at 2- and 4-positions) in the liquid crys-
tal state. For reference the IR spectrum of 2 in CDCl3 at
room temperature showed the bands at 1700 (cholesteryl
benzoate) and 1682cm¡1 (thymine at 2- and 4-positions, a
broad band). From a consideration of the IR data, it can be
concluded that 2 existed in a network of prolonged hydro-
gen bonds interconnecting thymine rings in the liquid crystal
state. Therefore we picture the structure as (C) in Scheme 3
that has the bifurcated system of hydrogen bonds [12].
Fig. 3 shows the IR spectra of 3. The carbonyl stretching
bands of 3 were found at 1711 (cholesteryl benzoate) and
1668 cm¡1 (thymine at 2- and 4-positions) in crystal state at
25°C, at 1711 and 1670cm¡1 in liquid crystal state at 160°C,
and at 1712 and 1672cm¡1 in isotropic liquid state at 180°C.
The carbonyl stretching bands were little shifted by the
increase in temperature. As we would expect, this suggests
that 3 cannot form a hydrogen-bonded assembly. As a
result, the spectra in the crystal, in the liquid crystal, and in
the isotropic liquid states were similar to one another.
Fig. 4 shows the IR spectra of a mixture of 1 and 2 at a
molar ratio of 1:1. The NH2 and NH stretching bands of
the mixture were found at 3332 (H-bond: hydrogen-bonded
bands) and 3186 cm¡1 (H-bond) in crystal state at 25 °C, at
3481 (non-H-bond, a small band), 3327 (H-bond) and
3195 cm¡1 (H-bond) in liquid crystal state at 160 °C, and at
3483 (non-H-bond), 3404 (non-H-bond), 3332 (H-bond)

T. Itahara, Y. Yokogawa / Journal of Molecular Structure 827 (2007) 95–100
99
Me
O
N
O
(CH2)12
Me
O
CO
O
H
O
N
O
N
N
OC
O (CH2)12
H
O
Me
N
O
O
H
(CH2)12
O
CO
O
O
N
N
OC
O
O (CH2)12
H
N
O
Me
C
Scheme 3.
Fig. 3. IR spectra of 3 in crystal, in liquid crystal, and in isotropic liquid
states. C (crystal at 25 °C upon heating): 2929, 2854, 1711, 1668, 1606,
1510, 1463, 1412, 1383 cm¡1. LC (liquid crystal at 160 °C upon heating):
2930, 2855, 1711, 1670, 1604, 1508, 1462, 1412, 1381 cm¡1. I (isotropic liq-
uid at 180 °C upon heating): 2931, 2856, 1712, 1672, 1603, 1508, 1458,
Fig. 4. IR spectra of a mixture of 1 and 2 at a molar ratio of 1:1 in crystal,
in liquid crystal, and in isotropic liquid states. C (crystal at 25 °C upon
heating): 3332, 3186, 2931, 2852, 1711 (broad), 1672, 1606, 1510, 1442,
1416, 1365, 1317 cm¡1. LC (liquid crystal at 160 °C upon heating): 3481,
3327, 3195, 2929, 2854, 1714(broad), 1660 (sh), 1605, 1508, 1441, 1417,
1363, 1317 cm¡1. I (isotropic liquid at 195 °C upon heating): 3483, 3404,
3332, 3195, 2931, 2856, 1712(broad), 1635, 1603, 1508, 1441, 1416, 1358,
1414, 1379 cm¡1
.
1315 cm¡1
.
and 3195 cm¡1 (H-bond) in isotropic liquid state at 195 °C.
The hydrogen-bonded bands of the mixture were similar in
the crystal, in the liquid crystal, and in the isotropic liquid
states. It is known that a mixture of adenine and thymine
exists as the base-paired form in the solid state [13]. There-
fore it can be assumed that 1 and 2 were primarily associ-
ated to form a base pair between adenine and thymine rings
not only in the solid state but also in the liquid crystal and
isotropic liquid states. We were not able to analyze the car-
bonyl stretching bands because of broad spectra, but NH2
scissoring vibrations were observed at 1672 cm¡1 in the
crystal state, at ca. 1660 cm¡1 (a shoulder-band) in the liq-
uid crystal state, and at 1635 cm¡1 in the isotropic liquid
state. Although there are several types of base pairs
between adenine and thymine rings [5,11], the hydrogen-
bonded assemblies in the liquid crystal state may be shown
as (D) and/or (E) in Scheme 4.
Fig. 5 shows the IR spectra of a mixture of 1 and 3 at a
molar ratio of 1:1. The NH2 stretching bands of 1 were
found at 3327 (H-bond) and 3153 cm¡1 (H-bond) in crystal
state at 21 °C, while the bands were found at 3481 (non-H-
bond), 3400 (non-H-bond), 3331 (H-bond) and 3182cm¡1
O
O
(CH2)12
O
CO
N
H
N
N
N
O
N
O
OC
N
O
(CH2)12
Me
D
N
H
H
H
N
N
H
Me
O
N
O
N
H
N
N
OC
O
(CH2)12
N
(CH2)12
O
CO
O
O
E
Scheme 4.

100
T. Itahara, Y. Yokogawa / Journal of Molecular Structure 827 (2007) 95–100
Therefore, it is conceivable that the nucleic base derivatives
form rod-like assemblies in the liquid crystal state. From a
consideration of the present IR data, it seems most reason-
able to conclude that the self-organization of the nucleic
base derivatives results in a formation of a network of pro-
longed hydrogen bonds interconnecting the nucleic bases in
liquid crystal state, and as a result, the order of the rod-like
assemblies is kept dynamically.
References
[1] T. Kato, J.M.J. Frçcht, J. Am. Chem. Soc. 111 (1989) 8533.
[2] M.-J. Brienne, J. Gabard, J.-M. Lehn, I. Stibor, J. Chem. Soc. Chem.
Commun. (1989) 1868.
[3] (a) ReviewsT. Kato, N. Mizoshita, K. Kanie, Macromol. Rapid Com-
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(b) C.M. Paleos, D. Tsiourvas, Liq. Cryst. 28 (2001) 1127.
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(2000) 85;
Fig. 5. IR spectra of a mixture of 1 and 3 at a molar ratio of 1:1 in crystal,
in liquid crystal, and in isotropic liquid states. C (crystal at room tempera-
ture, 21 °C): 3327, 3153, 2929, 2852, 1711, 1664, 1655(sh), 1606, 1583,
1510, 1466, 1416, 1383, 1367, 1354, 1317 cm¡1. LC (liquid crystal at 150 °C
upon heating): 3481, 3400, 3331, 3182, 2931, 2854, 1713, 1670, 1630, 1603,
1583(sh), 1508, 1462, 1414, 1379, 1352, 1317 cm¡1. I (isotropic liquid at
190 °C upon heating): 3481, 3398, 3342, 3188, 2929, 2858, 1714, 1670,
1628, 1603, 1583(sh), 1508, 1462, 1412, 1377, 1352, 1317 cm¡1
.
(b) M. Parra, J. Alderete, C. Zuniga, V. Jimenez, P. Hidalgo, Liq.
Cryst. 30 (2003) 297;
(c) A. Schaz, E. Valaityte, G. Lattermann, Liq. Cryst. 31 (2004) 1311;
(d) Y. Wu, S. Jiang, Y. Ozaki, Spectrochim. Acta A 60 (2004) 1931,
and references therein.
(H-bond) in liquid crystal state at 150 °C, and at 3481 (non-
H-bond), 3398 (non-H-bond), 3342 (H-bond) and
3188cm¡1 (H-bond) in isotropic liquid state at 190 °C. In
comparison with Fig. 4, the NH2 stretching bands in Fig. 5
were remarkably dependent on the increase in temperature,
because 1 and 3 did not associate to form an assembly. This
presents further evidence in support of the base pairing
between 1 and 2 in Fig. 4.
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4. Conclusion
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Although the literature contains a lot of references to the
self-organization of nucleic base derivatives [5], we report
for the Wrst time the self-organization of adenine and thy-
mine derivatives in thermotropic liquid crystal on the basis
of the temperature-dependent IR spectra. The adenine
derivative, the thymine derivative, and the mixture of ade-
nine and thymine derivatives in a molar ratio of 1:1 primar-
ily existed as hydrogen-bonded assemblies in liquid crystal
state. It is well known that rod-like molecules or molecular
aggregates tend to show a liquid crystalline behavior.
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