Symmetric mesogenic twins derived from salicylaldimines

Article abstract of DOI:10.1016/j.tet.2013.03.087

The synthesis, characterization, and mesomorphic properties of a series of symmetric dimeric twins derived from mesogenic salicylaldimines 1a-e are reported. In order to understand the structure-property relations, the bridged spacer (m=5, 6, 7, 8, 9), an

Full text of DOI:10.1016/j.tet.2013.03.087

Tetrahedron 69 (2013) 4226e4235
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Tetrahedron
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Symmetric mesogenic twins derived from salicylaldimines
,
,
,b,
Hsiu-Ming Kuo a b, Chu-Hsuan I a b, Hwo-Shuenn Sheu c, Chung K. Lai a
*
a Department of Chemistry, National Central University, Chung-Li 32054, Taiwan, ROC
b Center for Nano Science Technology, UST, Chung-Li 32054, Taiwan, ROC
c National Synchrotron Radiation Research Centre, Hsinchu 30077, Taiwan, ROC
a r t i c l e i n f o
a b s t r a c t
Article history:
The synthesis, characterization, and mesomorphic properties of a series of symmetric dimeric twins
derived from mesogenic salicylaldimines 1aee are reported. In order to understand the structur-
eeproperty relations, the bridged spacer (m¼5, 6, 7, 8, 9), and alkoxy chains (n¼6, 8, 10, 12, 14) were
systematically varied. Except for 1a, all derivatives 1bee exhibited mesophases whose mesomorphic
properties strongly depended on the spacer parity and the alkoxy chains. Dimers 1a exhibited crystal or
SmX phases. Other dimers 1bee were truly mesogenic, giving enantiotropic SmC, SmA or/and N phases.
Oddeeven effect was observed on phase temperatures, and nematic phases were observed for de-
rivatives with odd spacer, and a value of d/l¼0.92 (1a; m¼5, n¼8)e0.84 (1c; m¼7, n¼14) was obtained by
powder X-ray diffraction data, therefore, a monolayer structure in mesophase was proposed.
Ó 2013 Elsevier Ltd. All rights reserved.
Received 22 January 2013
Received in revised form 10 March 2013
Accepted 22 March 2013
Available online 26 March 2013
1. Introduction
O
O
O
O
O
O
O
Mesogenic dimers, or so-called twins or bimesogens have
attracted scientific attention since the discovery of the first ex-
ample1 reported on 1927. All these dimeric structures2 generally
contained two non-identical Ia (unsymmetric) or identical Ib
(symmetric) core moieties linked or bridged by a flexible central
spacer. Then a sequence of rigid mesogen-flexible spacer-rigid
mesogen in a twin structure was therefore obtained. A variety of
flexible spacers, such as alkylene3 [e(CH2)ne] Ic, dioxyalkylene4
[eO(CH2)nOe] Id or ester5 [eCOO(CH2)nOOCe] Ib have been
incorporated to obtain such twins. Interestingly, an apparent
effect observed when replacing the alkyloxy chains in Ic by
alkylsulphanyl chains in Id on the formation of mesophases was
attributed to their molecular flexibilities6 known as the order:
ReOe<ReSe<ReCH2e. Sulfur atom was also considered as
more polarizable than oxygen atom. A few mesogenic examples
constructed by a siloxane core7 of varying length in the central
region was also studied. Such dimers have high conformational
flexibility in the central part of the molecule and also have
terminal groups with high spatial anisomery. The resulting
mesomorphic properties were significantly influenced by their
core structures, the spacer lengths, and the linker groups
as well.
Ia
Ib
X
O
X
X
S
O
X
Ic; X = O,
Id; X = O, S
An oddeeven effect,8 referred to the spacer parity-dependent
mesomorphic properties was observed due to their possibly exist-
ing conformations in this type of dimeric structures. The derivatives
with even spacers often possess higher phase transition tempera-
tures than those of the derivatives with the odd spacers, which were
attributed to their better structural linearity. In contrast, the mo-
lecular shapes of derivatives with odd spacers were likely less linear.
However, an unusual example9 of odd liquid crystalline dimers was
found to be linear. The single crystallographic data showed that the
odd dimer crystallizes adopting a molecular conformation in which
the two mesogenic groups are aligned with respect to each other, as
for the even dimer. Dimers were particularly interesting due to their
unique thermal behavior and structural features as model com-
pounds similar to the polymeric liquid crystals. Compared to the
conventional rod-like mesogens, the transitional properties pro-
duced by dimeric mesogens are in fact modified to a much larger
extent by changes in the length and parity10 of the alkyl chains. The
difference in phase behavior was mostly attributed to the
* Corresponding author. Tel.: þ886 03 4259207; fax: þ886 03 4277972; e-mail
address: cklai@cc.ncu.edu.tw (C.K. Lai).
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.03.087

H.-M. Kuo et al. / Tetrahedron 69 (2013) 4226e4235
4227
dependence of the molecular shape and/or geometry on the parity
of the central spacer when considered in the all-trans conformation.
In the all-trans conformations11 the two mesogenic cores are
arranged with an anti-parallel style, whereas in the all-cis confor-
mation they are slightly inclined with a bending angle to each other.
Most twin compounds formed layer smectic phases, in which
smectic intercalated, monolayer, and interdigitated phases were
commonly observed. Non-symmetric LC dimers usually exhibited
intercalated smectic phases, whereas, the symmetric LC dimers
formed monolayer smectic phases. In additions, a ferroelectric or
antiferroelectric phase was reported on some chiral twins.3a,12
Known examples of columnar twins13 were relatively limited;
a connection of two bent-core units linked with tetraethylene glycol
spacer resulted in a formation of columnar phases. Furthermore, an
were not mesogenic. In contrast, all other derivatives 1bee with
longer spacers (m¼6, 7, 8, 9) were truly mesogenic, giving nematic,
smectic or smectic C phases. A monolayer conformation in the SmC
phase was proposed based on XRD diffraction experiments.
RO
OR
N
N
O
O
O
O
O
m O
II; m = 3-11; n = 6-16; R = (CH2)nH
O
O
O
O
m
N
N
OH
HO
OR
RO
III; m = 1, 3; R = (CH2)nH
N
N
O
O
m
HO
O
OH
O
OCnH2n+1
H2n+1CnO
1a m = 5, n = 6, 8, 10, 12, 14
1b m = 6, n = 12
1c m = 7, n = 6, 8, 10, 12, 14
1d m = 8, n = 12
1e m = 9, n = 6, 8, 10, 12, 14
unconventional T-shaped non-symmetric dimeric LC14 was recently
reported, in which the spacer was proposed to adopt conformations
with two mesogenic units held more or less parallel.
2. Results and discussion
2.1. Synthesis and characterization
Among the reported LC dimers, examples of the rigid mesogens
were known, such as Schiff bases, stilbenes, aromatics, cholesterols,
and tolan moieties. Two symmetric twins incorporated with two
mesogenic heterocyclic benzoxazoles II15 or 1,3,4-oxadiazoles16 were
also reported. A series of dimeric twins derived from symmetric
heterocyclic benzoxazoles II exhibiting single smectic C phase were
reportedby this group. TheformationofSmC phases wasattributedto
theweakdipoleforceinducedbydonoreacceptor interaction(D/A).
A monolayer conformation was proposed based on the powder XRD
The synthetic procedures used to prepare compounds 1aee in
this work are given in Scheme 1. All compounds of 6-hydroxy-
naphthalene-2-carboxylic acid methyl ester, 6-alkoxy-naphtha-
lene-2-carboxylic acid methyl esters, and 6-alkoxy-naphthalene-2-
carboxylic acids 3 were similarly prepared according to literature.
The aldimine Schiff-base derivatives isolated as light yellow crystals
were obtained by condensation reactions of naphthalene-2-
carboxylic acid 4-formyl-3-hydroxyphenyl esters and alkyldi-
amines in refluxing absolute ethanol. The yields were ranged in
77e85%. All compounds were characterized by 1H NMR and 13C
NMR spectroscopy. For example, the 1H NMR spectroscopic data
(Table 1) of compounds 1aee showed one characteristic peak at
data. A value of entropy changes
in twin system due to oddeeven effects was found.
D
S(SmC/I)/R¼2.00e6.50 associated
Both series of compounds II and III are considered as rod-like
twin mesogens. However, known examples derived from meso-
genic salicylaldimines17 III were relatively rare. Intramolecular or
intermolecular H-bonds induced in central core salicylaldimines
might play an important role in stabilizing the mesophases. Com-
pounds III are not heterocyclic and a mixed phase, as nematic,
smectic A, smectic C or smectic X phase was indeed observed in
compounds III, indication that a lateral interaction of side-by-side
molecules are also important.
In this work, we describe the synthesis, characterization, and
mesomorphic studies of a new series of symmetric dimers derived
from naphthalene substituted salicylaldimines bridged by a meth-
ylene as spacer group. These dimeric twins exhibited interesting
mesomorphic behavior. Derivatives 1a with shorter spacers (m¼5)
d
8.31e8.34 ppm, assigned to imineeH (eN]CH). The purity of
final compounds 1aee was also confirmed by elemental analysis.
2.2. Mesomorphic properties and thermal stability
The liquid crystalline behavior of compounds 1aee was char-
acterized and investigated by differential scanning calorimetry and
polarized optical microscope. The phase transitions and thermo-
dynamic data are summarized in Table 2. The formation of meso-
phases was dependent on the length of the spacer and the terminal
chains. All dimers 1a appended with a shorter spacer of C5-meth-
ylene exhibited crystal or/and highly ordered smectic X phases. For

4228
H.-M. Kuo et al. / Tetrahedron 69 (2013) 4226e4235
HO
HO
RO
a
b
COOH
COOCH3
COOCH3
c
RO
RO
d
O
COOH
O
3
2
OH
O
e
(CH2)m
N
O
N
O
O
OH
HO
O
RO
OR
1a-e; R = (CH2)nH
Scheme 1. Reagents and conditions. (a) H2SO4 (concd), refluxed in CH3OH, 24 h, 90%; (b) RBr (1.1 equiv), K2CO3 (2.0 equiv), KI, refluxing in dried CH3COCH3, 24 h, 78e88%; (c)
KOH, refluxed in C2H5OH/H2O (8/2), 24 h, 90e93%; (d) 2,4-dihydroxybenzaldehyde (1.0 equiv), DCC, DMAP, stirred in dried CH2Cl2, 24 h. 64e72%; (e) alkyldiamines (0.5 equiv),
refluxing in absolute C2H5OH, 24 h, 75e92%.
Table 1
Characteristic chemical peaksa on 1H and 13C NMR spectroscopes in compounds
Table 2
The transition temperatures and enthalpiesa of compounds 1aee
1aee and 2
Functional group
eCH]O in 2 (n¼12)
eCH]N in 1aee
128:9ð39:1Þ
110:4ð37:5Þ
1a; m¼5, n¼6
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
I
Cr
Spectroscope
1H NMR
121:7ð34:5Þ
102:4ð34:0Þ
133:3ð7:36Þ
8
Cr
9.87e9.88
195.50e195.52
8.31e8.34
165.06e165.38
SmX
SmX
SmX
SmX
SmC
13C NMR
131:4ð7:28Þ
146:0ð10:7Þ
112:6ð28:0Þ
a
Samples with a concentration of w1.0ꢁ10ꢂ3 M measured in CDCl3;
d in ppm.
10
Cr
Cr
Cr
Cr
91:0ð27:1Þ
108:8ð27:1Þ
143:1ð10:3Þ
150:8ð13:1Þ
12
the dimers 1bee bridged with a longer spacer of eC6e, eC7e,
eC8e, and eC9emethylene were truly liquid crystals, giving an
enantiotropic SmC, SmA or/and N phase. In these dimers, the spacer
has a significant influence on the thermal behavior. An oddeeven
effect on the melting and clearing temperatures was also observed.
For the dimer 1a appended with the shortest spacer (m¼5), the
derivative n¼6 was not mesogenic and all other four derivatives
n¼8,10,12,14 formed highly ordered smectic X phases. The melting
temperatures were ranged from 108.8e121.7 ꢀC. The clearing
temperatures were ranged from 128.9e153.7 ꢀC, which were in-
creased with carbon lengths. The temperature range of SmX phases
94:2ð27:4Þ
109:7ð24:7Þ
149:3ð12:9Þ
153:7ð9:15Þ
14
97:3ð24:5Þ
126:6ð39:5Þ
152:5ð9:17Þ
217:6ð22:3Þ
1b; m¼6, n¼12
98:2ð29:8Þ
210:6ð19:3Þ
125:2ð18:2Þ
130:9ð0:01Þ
169:2ð0:68Þ
1c; m¼7, n¼6
Cr
Cr
Cr
Cr
SmA
SmA
N
N
N
88:1ð19:2Þ
109:3ð12:4Þ
121:0ð0:09Þ
162:2ð0:88Þ
153:0ð1:00Þ
127:0
b
#
119:0
8
87:6ð12:8Þ
110:7ð12:0Þ
140:1ð0:58Þ
128:1ð1:64Þ
142:0
b
#
10
SmC
SmC
Cr
138:0
86:2ð14:3Þ
105:2ð23:3Þ
114:8ð2:63Þ
144:6ð9:45Þ
147:8ð1:65Þ
12
N
TSmX¼29.0 (n¼8)<52.1 (n¼10)<55.0 (n¼12)<55.2 ꢀC (n¼14).
86:0ð21:8Þ
138:0ð9:01Þ
99:4ð34:5Þ
142:5ð1:72Þ
is ca.
D
141:4ð15:7Þ
A texture of mosaic domains under optical microscope was obtained
when cooling from isotropic liquid (Fig. 1). The exact phase was not
attempted to identify. A highly ordered phase was confirmed by
variable temperature powder X-ray diffraction experiments.
On the other hands, all other derivatives 1bee formed enan-
tiotropic phases regardless of the alkoxy chain lengths. These de-
rivatives all exhibited nematic, smectic A, and/or smectic C phases,
as expected for the rod-like molecules. Two derivatives 1b with
even spacers (m¼6) and 1d (m¼8), and one derivative 1e with odd
spacer (m¼9) formed only monomorphism. Derivative 1b (n¼12)
have a highest clearing temperature at Tcl¼217.6 ꢀC, as well as
14
SmC
SmC
84:2ð34:7Þ
138:8ð14:6Þ
187:4ð13:5Þ
130:5ð46:5Þ
1d; m¼8, n¼12
Cr
Cr
Cr
Cr
Cr
Cr
104:9ð46:2Þ
133:9ð52:2Þ
182:8ð16:3Þ
152:8ð1:62Þ
1e; m¼9, n¼6
N
N
N
N
N
124:3ð51:8Þ
124:7ð43:0Þ
152:0ð1:54Þ
159:4ð1:15Þ
8
10
12
103:5ð40:9Þ
130:1ð52:6Þ
158:3ð1:05Þ
153:9ð1:23Þ
121:0ð52:5Þ
119:8ð29:6Þ
153:5ð1:41Þ
134:3ð1:27Þ
101:4ð28:0Þ
125:0ð33:0Þ
133:5ð1:15Þ
136:3ð1:21Þ
TSmC¼112.4 ꢀC
14
a widest temperature range of mesophases of
D
112:0ð32:2Þ
127:3ð1:19Þ
among all derivatives 1aee. The mesophase was identified as
smectic C phase based textures observed under optical microscope.
Derivatives 1c (n¼6, 8, 10, 12) formed polymorphism and de-
rivatives 1c (n¼14) formed monomorphism. Also, nematic phases
a
n¼Carbon lengths in the alkoxy groups. Cr¼Crystal, SmX¼smectic X,
SmC¼smectic C, SmA¼smectic A, and N¼nematic phases. Temperatures (ꢀC) and
enthalpies (kJ/mol) were obtained by DSC at a scan rate of 10.0 ꢀC/min.
b
Observed by polarizing optical microscope.

H.-M. Kuo et al. / Tetrahedron 69 (2013) 4226e4235
4229
Fig. 1. Optical textures observed. (a) Top left: SmX phase by 1a (m¼5, n¼8) at 121 ꢀC; (b) top right: N phase by 1c (m¼7, n¼8) at 139 ꢀC; (c) central left: N phase by 1e (m¼9, n¼6) at
151 ꢀC; (d) central right: N phase by 1e (m¼9, n¼12) at 132 ꢀC; (e) bottom left: N phase at by 1c (m¼7, n¼6) at 150 ꢀC; (f) bottom right: SmC phase by 1c (m¼7, n¼12) at 110 ꢀC.
were observed for all derivatives with an odd spacer 1c (except for
n¼14) and 1e (m¼9), whereas smectic C phases were obtained for
other derivatives 1b (m¼6) and 1d (m¼8) with an even spacer. The
difference on the formation of phases was correlated with the
conformations displayed by oddeeven spacers, which was also
observed in other similar mesogenic twins. For the compounds 1c
(m¼7; n¼6, 8, 10, 12, 14) the clearing temperatures were decreased
with the carbon numbers of the terminal alkyl chains, i.e., Tcl¼169.2
(n¼6)>141.4 ꢀC (n¼14), however, the melting temperatures
remained at 125.2 ꢀC (n¼10)e99.4 ꢀC (n¼14). The mesophase
identified by microscope. The phases were identified as nematic,
smectic A and smectic C phases, and typical textures described as
focal-conic or Schlieren domains (Fig. 1) were easily observed un-
der optical polarized microscope when cooling from their isotropic
liquids. A texture appeared as focal-conic characterized for SmA
phases was also confirmed by its homeotropic domain, which were
not observed in SmC phases. A relatively smaller enthalpy of
D
H¼0.58e1.72 kJ/mol on cooling process for compounds 1c for the
transition of I/N phase and an enthalpy of
H¼0.09e1.82 kJ/mol
for the transition of N/SmA phases were obtained. In contrast,
a larger enthalpy of
H¼1.64e9.45 kJ/mol for the transition of
SmC/N phases was obtained for all derivatives 1c. A large en-
thalpy of
H¼15.7 kJ/mol was also obtained for 1c (n¼14).
D
temperatures were ranged;
D
TM¼51.8 (n¼10)e74.1 (n¼6) ꢀC on
D
cooling process. Two derivatives 1c with shorter carbon lengths
(n¼6, 8) exhibited nematic phases at higher temperature and
smectic A phases at lower temperatures, whereas two other de-
rivatives with longer carbon lengths (n¼10, 12) exhibited nematic
phases at higher temperature and smectic C phases at lower tem-
peratures. The derivative 1c with longest carbon lengths (n¼14)
formed only smectic C phases. The dependence of phase with car-
bon lengths was probably attributed to an enhanced dispersive
interaction or van der Waals between the terminal alkoxy chains as
carbon lengths increases. The mesophases were characterized and
D
Derivative 1d (m¼8, n¼12) formed smectic C phase with
a temperature range of
D
TSmC¼77.9 ꢀC. The temperature range of
mesophase was relatively wider than those of other derivatives 1c
(D
T¼56.5 ꢀC) and 1e (
D
T¼32.1 ꢀC) with a carbon length n¼12.
When spacer was elongated to an odd m¼9, nematic phases were
solely observed. All clearing temperatures were ranged in Tcl¼134.3
(n¼12)e159.4 (n¼8) ꢀC. Compared to all other three derivatives
1bed, the temperature range of mesophases was apparently

4230
H.-M. Kuo et al. / Tetrahedron 69 (2013) 4226e4235
reduced to ca.
D
TN¼10.3 (n¼14)e34.8 ꢀC (n¼6). The melting tem-
The relationship plot between the melting temperatures,
clearing temperatures, and the temperature range for all twins
1aee was given in Fig. 4. For detail comparison, the dependence of
melting and clearing temperatures on the spacer lengths (m¼5, 6, 7,
8, 9) in compounds 1aee (all with carbon length n¼12 in the ter-
minal alkoxy groups) was given in Fig. 5. Both derivatives with even
spacer cleared at higher temperatures, i.e., Tcl¼217.6 ꢀC (m¼6,
n¼12) and 187.4 ꢀC (m¼8, n¼12) than those of derivatives with odd
spacer (m¼7, 9), i.e., Tcl¼147.8 ꢀC (m¼7, n¼12) and 134.3 ꢀC (m¼9,
n¼12). Derivatives 1b, d with even spacers (m¼6, 8) formed
smectic phase, whereas derivatives 1c, e with odd spacers (m¼7, 9)
exhibited nematic and smectic C phase. The derivative 1b (n¼12)
have a highest clearing temperature at Tcl¼217.6 ꢀC and a widest
peratures were slightly higher than those of derivatives 1ced,
whereas, the clearing temperatures remained at Tcl¼159.4 (n¼8)e
136.3 ꢀC (n¼14). The thermal stability of compounds 1aed (all
n¼12) was also characterized by thermogravimetric analyses (TGA),
as shown in Fig. 2. Two compounds showed excellent thermal
stability above their clearing temperature. For example, the de-
composition temperatures for a 5% weight loss for 1a (m¼5, n¼12),
1b (m¼6, n¼12), 1c (m¼7, n¼12), and 1d (m¼8, n¼12) were ob-
tained at Td¼346.0 ꢀC, 337.0 ꢀC, 342.0 ꢀC, and 339.0 ꢀC.
1a; m = 5, n = 12
100
1b; m = 6, n = 12
temperature range of
D
TSmC¼112.4 ꢀC among all twins 1aee. When
1c; m = 7, n = 12
1d; m = 8, n = 12
80
60
40
20
100
200
300
400
500
600
700
Temperature(oC)
Fig. 2. The TGA thermographs of compounds 1aed.
2.3. Oddeeven effect
The difference on the formation of phases in these twins 1aee
was attributed to the conformations displayed by oddeeven
spacers, which was also observed in other similar mesogenic twins.
Molecules or twins with an even spacer displayed a more linear
shaped or conformation, often giving smectic C phases (Fig. 3). It has
been known that spacers with even parity have more conformers,
which allowed parallel arrangements between cores, whereas odd
spacers possess more conformers, which often resulted in bent
configuration. The oddeeven effect on the phase temperatures;
both melting and clearing temperatures was also examined.
Fig. 4. Bar graphs showing the phase behavior of compounds 1aee. All temperatures
were taken from heating process.
Fig. 3. Schematic ball-and-stick representation of the all-trans conformations. Top:
bent-shaped by an odd-1a (m¼5) and bottom: linear-shaped by an even membered
dimer 1b (m¼6).
Fig. 5. Dependence of melting and clearing temperatures on the spacer lengths (m¼5,
6, 7, 8, 9) in compounds 1aee (all with carbon length n¼12 in the terminal alkoxy
groups). All temperatures were taken from cooling process.

H.-M. Kuo et al. / Tetrahedron 69 (2013) 4226e4235
4231
Table 3
compounds with even carbon spacer and molecules were consid-
A summary of powder XRD diffraction peaks of compounds 1a and 1c
ered in all-trans conformations, the overall molecules were more
likely linear, resulting in a better packing in mesophases. Therefore,
their clearing temperatures were often much higher than those of
compounds with odd carbon spacer, in which all molecules were
considered as more bent-shaped.
Compds
Mesophases Molecular
d-Spacing
obs. (calcd)
Miller Aspect
indices ratio d/l
ꢀ
length (A)
1a (m¼5, n¼8) SmX
1c (m¼7, n¼14) SmC
54.0
49.51 (49.5) 001
0.92
35.02 (35.02) 100
24.71 (24.75) 001
17.51 (17.51) 200
2.4. Variableetemperature X-ray diffraction data
67.6
56.68 (56.68) 001
28.41 (28.34) 002
0.84
Three molecular organizations proposed in such twins were
known; monolayers, interdigitated layers, and intercalated layers,
as shown in Fig. 6. Symmetric twins adopt monolayers or in-
terdigitated layers, whereas unsymmetric twins favor intercalated
layers. The powder X-ray diffraction experiments of two de-
rivatives 1a (m¼5, n¼8) and 1c (m¼7, n¼14) were performed to
confirm the layer structures. The X-ray diffraction data were
summarized in Table 3. Derivative 1a (m¼5, n¼8) gave a more
ordered diffraction pattern; two strong and two weaker diffraction
3. Conclusions
A new series of mesogenic twins with different spacer lengths
(m¼5, 6, 7, 8, 9) was prepared and studied. These dimeric twins
were constructed by mesogenic salicylaldimines linked with ter-
minal naphthalene as core. The two naphthalene moieties in-
corporated might enhance pep interaction between smectic layers.
ꢀ
peaks, appeared at a d-spacing of 49.51 (49.5), 35.02 and 24.71 A
All the derivatives 1a with shorter spacers (m¼5) were not meso-
genic. On the other hand, all other derivatives 1bee with longer
spacers (m¼6, 7, 8, 9) formed nematic, smectic A or smectic C
phases. The temperatures were relatively narrow in all derivatives.
An oddeeven effect both on the melting and isotropization tem-
peratures was observed. A monolayer structure in this type of di-
meric twin liquid crystals was proposed.
were observed, as shown Fig. 7. This diffraction pattern was typ-
ically characteristic of layer structures observed for a more highly
ordered SmX phases. The exact mesophase was not attempted to
identify. In contrast, 1c (m¼7, n¼14) displayed a diffraction pattern
ꢀ
ꢀ
with one strong peak at 56.68 A and one very weak at 28.41 A, and
these two diffraction peaks at lower angle were assigned as Mill
indices 001 and 002. This diffraction pattern was typically char-
acteristic of layer structures observed for SmC phases. A very
ꢀ
broad and very weak peak at 4.44e4.61 A was also observed, and
4. Experimental
4.1. General
this peak was assigned to the molten alkoxyl chains. The d-spacing
ꢀ
ꢀ
of two compounds; 49.51 A and 56.68 A was well correlated with
ꢀ
ꢀ
the calculated molecular lengths of 54.0 A and 67.6 A. Two
structures in such layer mesophases were proposed for symmetric
twins; intercalated and non-intercalated (or monolayer). In in-
tercalated phase the d-spacing value was approximately equal to
a half of molecular length dw(1/2)L whereas d-spacing was equal
to molecular length d¼L in non-intercalated structure. In-
terdigitated layer structures were ruled out in this system. In
many mesogenic twin systems, most dimeric molecules exhibiting
smectic phases adopted intercalated arrangements. In contrast,
the dimeric molecules 1cee will form monolayer arrangement
when d/l¼w1.0. A value of d/l¼0.92 (1a; m¼5, n¼8)e0.84 (1c;
m¼7, n¼14) was obtained. Therefore, a monolayer structure18 in
mesophase was proposed.
All chemicals and solvents were reagent grades from Aldrich
Chemical Co. Solvents used were dried by standard technique. 1H
and 13C NMR spectra were measured on a Bruker DRS-200. DSC
thermographs were carried out on a Mettler DSC 822 and calibrated
with a pure indium sample. All phase transitions are determined by
a scan rate of 10.0 ꢀC/min. Optical polarized microscopy was carried
out on Zeiss Axioplan 2 equipped with a hot stage system of Mettler
FP90/FP82HT. Elemental analysis for carbon, hydrogen, and nitro-
gen were conducted at Instrumentation Center, National Taiwan
University on a Heraeus CHNeO-Rapid elemental analyzer. The
powder diffraction data were collected from the Wiggler-A
beamline of the National Synchrotron Radiation Research Center
Fig. 6. The monolayer arrangements in SmC phases proposed for compounds 1d (m¼8) with an aspect ratio of d/L w1.0. The terminal alkoxyl chains are not interdigitated.

4232
H.-M. Kuo et al. / Tetrahedron 69 (2013) 4226e4235
0.025 mol), K2CO3 (6.83 g, 0.049 mol), and KI was gently refluxed in
70000
60000
50000
40000
30000
20000
10000
0
dried for 24 h under nitrogen atmosphere. The solution was con-
centrated and extracted with 100 mL of CH2Cl2/H2O (1/1). The or-
ganic layers were collected and dried over anhydrous NaSO4. The
products isolated as white solids were obtained after re-
crystallization from CH3COCH3/H2O. Yield 88%. 1H NMR (500 MHz,
CDCl3):
d
0.85e0.88 (t, 3H, eCH3, J¼6.6 Hz), 1.29e1.50 (m, 18H,
eCH2),1.83e1.85 (m, 2H, eCH2), 4.08e4.11 (t, 2H, eOCH2, J¼6.5 Hz),
7.14 (s, 1H, AreH), 7.18e7.20 (d, 1H, AreH, J¼8.9 Hz), 7.73e7.75 (d,
1H, AreH, J¼8.6 Hz), 7.83e7.85 (d, 1H, AreH, J¼8.9 Hz), 8.04e8.06
(d, 1H, AreH, J¼8.8 Hz), 8.59 (s, 1H, AreH). 13C NMR (125 MHz,
CDCl3):
d 13.91, 22.55, 26.05, 29.15, 29.28, 29.35, 31.75, 68.30,
106.72, 119.97, 121.29, 124.16, 126.05, 126.85, 127.85, 130.95, 131.80,
137.75, 159.51.
0
5
10
15
20
25
30
4.2.3. 6-(Dodecyloxy)naphthalene-2-carboxylic acid 3 (n¼12). White
solids, yield 93%. 1H NMR (500 MHz, CDCl3):
d 0.87 (t, 3H, eCH3,
2 Theta
J¼6.69 Hz), 1.26e1.50 (m, 18H, eCH2), 1.78e1.84 (m, 2H, eCH2), 4.09
(t, 2H, eOCH2, J¼6.53 Hz), 7.13 (s, 1H, AreH), 7.16 (d, 1H, AreH,
J¼11.34 Hz), 7.70 (d, 1H, AreH, J¼8.64 Hz), 7.81 (d, 1H, AreH,
J¼8.97 Hz), 7.99 (d, 1H, AreH, J¼10.12 Hz), 8.49 (s, 1H, AreH). 13C
35000
30000
25000
20000
15000
10000
5000
0
NMR (125 MHz, CDCl3):
d 13.92, 22.58, 26.05, 28.84, 29.17, 29.25,
29.32, 29.47, 29.52, 29.57, 31.85, 68.26,106.68,119.76,125.66,125.88,
126.64, 127.92, 130.65, 130.74, 137.21, 159.11, 166.90.
4.2.4. 6-Dodecyloxynaphthalene-2-carboxylic acid 4-formyl-3-hydro
xyphenyl ester 2 (n¼12). The solution of 6-dodecyloxynaphthalene-
2-carboxylic acid (2.00 g, 6.0 mmol), 4-dimethyl aminopyridine
(DMAP; 0.89 g, 7 mmol), and 2,4-dihydroxybenzoaldehyde (0.84 g,
0.006 mol) was stirred at ice bath temperature for 30 min. The so-
lution was warmed up to room temperature. The solution was then
added N,N0-dicyclohexylcarbodiimide (DCC; 1.51 g, 7.0 mmol), and
stirred at room temperature for 24 h. The insoluble solids were fil-
tered off. The solution was concentrated to give off-white solids and
the residue was purified by column chromatography (silica gel,
hexane/CH2Cl2; 1/1). White solids were obtained after re-
crystallization from CH2Cl2/CH3OH. Yield 72%. 1H NMR (500 MHz,
0
5
10
15
20
25
30
2 Theta
Fig. 7. Variable temperature powder X-ray diffraction plots of compounds. Top plot:
SmX phase by 1a (m¼5, n¼8) at 120 ꢀC (top plot) and bottom: SmC phase by 1c (m¼7,
n¼14) at 120 ꢀC (bottom plot).
CDCl3):
d
0.86e0.90 (t, 3H, eCH3, J¼6.7 Hz), 1.27e1.56 (m, 18H,
eCH2), 1.83e1.86 (m, 2H, eOCH2), 4.08e4.10 (t, 2H, eOCH2,
J¼6.5 Hz), 6.91 (s, 1H, AreH), 6.93e6.96 (d, 1H, AreH, J¼8.4 Hz), 7.15
(s, 1H, AreH), 7.20e7.22 (d, 1H, AreH, J¼8.9 Hz), 7.60e7.62 (d, 1H,
AreH, J¼8.4 Hz), 7.77e7.79 (d, 1H, AreH, J¼8.6 Hz), 7.85e7.87 (d, 1H,
AreH, J¼8.9 Hz), 8.08e8.10 (d, 1H, AreH, J¼8.6 Hz), 8.65 (s, 1H,
AreH), 9.88 (s, 1H, eCHO), 11.25 (s, 1H, AreOH). 13C NMR (125 MHz,
CDCl3): 14.11, 22.67, 26.10, 29.15, 29.25, 29.37, 31.83, 68.28, 106.48,
110.94, 114.18, 118.68, 120.33, 123.51, 126.00, 127.16, 127.75, 131.04,
132.06, 134.98, 137.86, 157.93, 159.70, 163.25, 164.48, 195.50.
ꢀ
(NSRRC) with the wavelength of 1.3263 A. Diffraction patterns were
recorded in
q/2q
geometry with step scans normally 0.02ꢀ in
2
q
¼1e10ꢀ stepꢂ1 sꢂ1 and 0.05ꢀ in 2
q
¼10e25ꢀ stepꢂ1 sꢂ1 and a gas
flow heater was used to control the temperature. The powder
samples were charged in Lindemann capillary tubes (80 mm long
and 0.01 mm thick) from Charles Supper Co. with an inner diameter
of 1.0 mm.
4.2.5. N,N-(1,5-Pentylene)-bis(4-dodecyloxynaphthalenelidenimine)
1a (m¼5, n¼12). The solution of 6-dodecyloxynaphthalene-2-
carboxylic acid 3-hydroxy-4-(2-methoxy-ethyl)-phenyl ester
(0.50 g, 0.94 mmol) dissolved in 10.0 mL of absolute ethanol was
added a few drops of CH3COOH and 1,5-diaminopentane (0.047 g,
0.46 mmol). The solution was refluxed for 24 h. The yellow solids
were collected. The products isolated as yellow solids were ob-
tained by recrystallization from CH2Cl2/hexane. Yield 88%. 1H NMR
4.2. Synthetic preparation of compounds 1aee
4.2.1. 6-Hydroxy-naphthalene-2-carboxylic acid methyl ester. The
solution of 6-hydroxy-2-naphthaoic acid (10.0 g, 0.053 mol) dis-
solved in CH3OH was slowly added 2.0 mL of concentrated H2SO4
and the solution was refluxed for 24 h. The solution was cooled to
room temperature, and the solids as light brown solids were col-
lected. The solids were purified by recrystallization from methanol.
(500 MHz, CDCl3):
d
0.87 (t, 6H, eCH3, J¼6.72 Hz), 1.25e1.27 (m,
Yield 90%. 1H NMR (500 MHz, CDCl3):
d
3.95 (s, 3H, eOCH3), 5.74 (s,
36H, eCH2), 1.46e1.51 (m, 4H, eCH2), 1.78e1.86 (m, 8H, eCH2), 3.61
(t, 4H, eCH2NCH, J¼6.57 Hz), 4.09 (t, 4H, eOCH2, J¼6.48 Hz), 6.76 (s,
2H, AreH), 6.85 (s, 2H, AreH), 7.14 (s, 2H, AreH), 7.20 (s, 2H, AreH),
7.27 (d, 2H, AreH, J¼8.4 Hz), 7.75 (d, 2H, AreH, J¼8.6 Hz), 7.84 (d,
2H, AreH, J¼8.9 Hz), 8.09 (d, 2H, AreH, J¼8.6 Hz), 8.10 (d, 2H, AreH,
J¼8.6 Hz), 8.33 (s, 2H, eNCH), 8.65 (s, 2H, AreH). 13C NMR
1H, AreOH), 7.15 (d, 2H, AreH, J¼7.62 Hz), 7.67 (d, 1H, AreH,
J¼8.58 Hz), 7.83 (d, 1H, AreH, J¼9.69 Hz), 7.98 (d, 1H, AreH,
J¼8.72 Hz), 8.51 (s, 1H, AreH). 13C NMR (125 MHz, CDCl3):
d 50.0,
109.3,118.5,125.3,125.9,126.5,127.9,130.7,131.2,136.4,155.6,167.0.
4.2.2. 6-Dodecyloxynaphthalene-2-carboxylic acid methyl ester
(n¼12). The mixture of 6-hydroxy-naphthalene-2-carboxylic acid
methyl ester (5.0 g, 0.025 mol), 1-bromododecane (6.16 g,
(125 MHz, CDCl3): d 14.13, 22.70, 24.67, 26.10, 29.17, 29.36, 29.41,
29.60, 29.62, 29.65, 29.68, 30.47, 31.93, 58.89, 68.24, 106.44, 110.65,
112.30, 116.64, 120.15, 124.12, 126.11, 127.00, 127.78, 131.00, 131.82,

H.-M. Kuo et al. / Tetrahedron 69 (2013) 4226e4235
4233
132.12, 137.66, 154.23, 159.48, 163.41, 164.11, 165.05. Anal. Calcd for
C65H82N2O8: C, 76.59; H, 8.11. Found C, 76.54; H, 8.22.
CDCl3):
d
0.89 (t, 6H, eCH3, J¼6.62 Hz), 1.27e1.39 (m, 36H, eCH2),
1.46e1.53 (m, 8H, eCH2),1.73e1.75 (m, 4H, eCH2),1.84e1.88 (m, 4H,
eCH2CH2), 3.61 (t, 4H, eCH2eN]CH, J¼6.57 Hz), 4.11 (t, 4H, eOCH2,
J¼6.51 Hz), 6.77 (d, 2H, AreH), 6.79 (s, 2H, AreH), 7.17 (s, 2H, AreH),
7.21 (d, 2H, AreH, J¼2.39 Hz), 7.22 (d, 2H, AreH, J¼8.39 Hz), 7.28 (d,
2H, AreH, J¼8.39 Hz), 7.78 (d, 2H, AreH, J¼8.65 Hz), 7.87 (d, 2H,
AreH, J¼8.65 Hz), 8.12 (d, 2H, AreH, J¼1.54 Hz), 8.34 (s, 2H, eN]
4.2.6. N,N-(1,5-Pentylene)-bis(4-hexyloxynaphthalenelidenimine) 1a
(m¼5, n¼6). Light yellow solids, yield 77%. 1H NMR (500 MHz,
CDCl3):
d
0.93 (t, 6H, eCH3, J¼6.72 Hz), 1.37e1.40 (m, 12H, eCH2),
1.51e1.53 (m, 4H, eCH2), 1.75e1.79 (m, 4H, eCH2), 1.84e1.90 (m,
8H, eCH2CH2), 3.62 (t, 4H, eCH2N]CH, J¼6.57 Hz), 4.11 (t, 4H,
eOCH2, J¼6.54 Hz), 6.79 (d, 2H, AreH), 6.86 (s, 2H, AreH), 7.16 (s,
2H, AreH), 7.22 (d, 2H, AreH, J¼8.66 Hz), 7.28 (d, 2H, AreH,
J¼8.39 Hz), 7.77 (d, 2H, AreH, J¼8.66 Hz), 7.86 (d, 2H, AreH,
J¼8.98 Hz), 8.12 (d, 2H, AreH, J¼7.30 Hz), 8.34 (s, 2H, eN]CH), 8.67
CH), 8.68 (s, 2H, AreH) 13C NMR (125 MHz, CDCl3):
d 14.45, 23.02,
26.42, 27.12, 29.49, 29.68, 29.73, 29.92, 29.94, 29.97, 30.00, 30.97,
32.25, 59.16, 68.57, 106.79, 110.99, 112.54, 116.97, 120.48, 124.47,
128.12, 131.33, 132.14, 132.42, 137.99, 154.57, 159.81, 163.91, 164.31,
165.37. Anal. Calcd for C66H84N2O8: C, 76.71; H, 8.19. Found C, 76.88;
H, 8.21.
(s, 2H, AreH). 13C NMR (125 MHz, CDCl3):
d 14.13, 22.95, 24.98,
26.10, 29.46, 30.79, 31.92, 59.19, 68.56, 106.78, 110.97, 112.61, 116.97,
120.47, 124.46, 126.44, 127.34, 128.11, 131.33, 132.14, 132.44, 137.99,
154.56,159.81, 163.74,164.44,165.36. Anal. Calcd for C53H58N2O8: C,
74.80; H, 6.87. Found C, 74.31; H, 6.87.
4.2.11. N,N-(1,7-Heptylene)-bis(4-hexyloxynaphthalenelidenimine)
1c (m¼7, n¼6). Light yellow solids, yield 74%. 1H NMR (500 MHz,
CDCl3):
d
0.94 (t, 6H, eCH3, J¼6.52 Hz), 1.37e1.40 (m, 15H, eCH2),
1.41e1.53 (m, 4H, eCH2), 1.70e1.71 (m, 4H, eCH2), 1.83e1.89 (m,
4H, eCH2CH2), 3.58 (t, 4H, eCH2eN]CH, J¼6.52 Hz), 4.10 (t, 4H,
eOCH2, J¼6.42 Hz), 6.77 (d, 2H, AreH), 6.88 (s, 2H, AreH), 7.16 (s,
2H, AreH), 7.21 (d, 2H, AreH, J¼2.40 Hz), 7.22 (d, 2H, AreH,
J¼6.62 Hz), 7.27 (d, 2H, AreH, J¼8.40 Hz), 7.77 (d, 2H, AreH,
J¼8.66 Hz), 7.86 (d, 2H, AreH, J¼8.98 Hz), 8.12 (d, 2H, AreH,
J¼1.52 Hz), 8.31 (s, 2H, eN]CH), 8.68 (s, 2H, AreH). 13C NMR
4.2.7. N,N-(1,5-Pentylene)-bis(4-octyloxynaphthalenelidenimine) 1a
(m¼5, n¼8). Light yellow solids, yield 79%. 1H NMR (500 MHz,
CDCl3):
d
0.89 (t, 6H, eCH3, J¼6.16 Hz), 1.29e1.37 (m, 16H,
eCH2CH3), 1.47e1.51 (m, 6H, eOCH2CH2), 1.74e1.77 (m, 4H, eCH2),
1.83e1.86 (m, 4H, eCH2), 3.60 (t, 4H, eCH2eN]CH, J¼6.44 Hz),
4.08 (t, 4H, eOCH2, J¼6.48 Hz), 6.76 (d, 2H, AreH), 6.77 (s, 2H,
AreH), 7.14 (s, 2H, AreH), 7.18 (d, 2H, AreH, J¼8.66 Hz), 7.20 (d, 2H,
AreH, J¼8.39 Hz), 7.26 (d, 2H, AreH, J¼8.66 Hz), 7.75 (d, 2H, AreH,
J¼8.98 Hz), 8.11 (d, 2H, AreH, J¼7.30 Hz), 8.32 (s, 2H, eN]CH), 8.65
(125 MHz, CDCl3):
d 14.33, 22.88, 26.04, 27.29, 29.26, 29.40, 30.96,
31.86, 59.13, 68.49, 106.73, 110.94, 112.41, 116.40, 120.41, 124.41,
126.36, 127.28, 128.05, 131.25, 132.05, 132.36, 137.93, 154.52, 159.75,
163.97, 164.17, 165.26. Anal. Calcd for C55H62N2O8: C, 75.14; H, 7.11.
Found C, 75.76; H, 6.92.
(s, 2H, AreH) 13C NMR (125 MHz, CDCl3):
d 14.15, 22.70, 24.67,
26.12, 29.19, 29.28, 29.40, 30.48, 31.85, 58.88, 68.24, 106.44, 110.65,
112.29, 116.65, 120.16, 124.12, 126.12, 127.02, 128.78, 131.00, 131.82,
132.14, 137.66, 154.23, 159.23, 159.48, 163.42, 164.12, 165.04. Anal.
Calcd for C57H66N2O8: C, 75.47; H, 7.33. Found C, 75.35; H, 7.38.
4.2.12. N,N-(1,7-Heptylene)-bis(4-octyloxynaphthalenelidenimine)
1c (m¼7, n¼8). Light yellow solids, yield 83%. 1H NMR (500 MHz,
CDCl3):
d
0.88 (t, 6H, eCH3, J¼6.58 Hz), 1.37e1.39 (m, 20H, eCH2),
4.2.8. N,N-(1,5-Pentylene)-bis(4-decanoxynaphthalenelidenimine)
1.40e1.51 (m, 4H, eCH2), 1.69e1.83 (m, 4H, eCH2), 1.85e1.87 (m,
4H, eCH2), 3.58 (t, 4H, eCH2eN]CH, J¼6.67 Hz), 4.09 (t, 4H,
eOCH2, J¼6.51 Hz), 6.74 (d, 2H, AreH), 6.84 (s, 2H, AreH), 7.14 (s,
2H, AreH), 7.21 (d, 2H, AreH, J¼2.39 Hz), 7.22 (d, 2H, AreH,
J¼6.62 Hz), 7.27 (d, 2H, AreH, J¼8.39 Hz), 7.76 (d, 2H, AreH,
J¼8.67 Hz), 7.85 (d, 2H, AreH, J¼8.99 Hz), 8.11 ( d, 2H, AreH,
J¼1.52 Hz), 8.31 (s, 2H, eN]CH), 8.66 (s, 2H, AreH). 13C NMR
1a (m¼5, n¼10). Light yellow solids, yield 77%. 1H NMR (500 MHz,
CDCl3):
d
0.89 (t, 6H, eCH3, J¼6.21 Hz), 1.29e1.38 (m, 20H, eCH2),
1.48e1.53 (m, 6H, eOCH2), 1.76e1.79 (m, 4H, eCH2CH2), 1.85e1.88
(m, 4H, eCH2), 3.62 (t, 4H, eCH2eN]CH, J¼6.52 Hz), 4.11 (t, 4H,
eOCH2, J¼6.49 Hz), 6.77 (d, 2H, AreH), 6.79 (s, 2H, AreH), 7.16 (s,
2H, AreH), 7.21 (d, 2H, AreH, J¼8.66 Hz), 7.22 (d, 2H, AreH,
J¼8.39 Hz), 7.28 (d, 2H, AreH, J¼8.66 Hz), 7.77 (d, 2H, AreH,
J¼8.98 Hz), 8.13 (d, 2H, AreH, J¼7.30 Hz), 8.34 (s, 2H, eN]CH), 8.67
(125 MHz, CDCl3):
d 14.15, 22.70, 26.12, 27.05, 29.02, 29.18, 29.28,
29.39, 30.71, 31.85, 58.95, 68.24, 106.42, 110.71, 112.19, 116.64,
120.17, 124.12, 126.14, 127.02, 127.78, 131.02, 132.09, 137.66, 154.22,
159.48, 163.68, 163.89, 165.07. Anal. Calcd for C59H70N2O8: C, 75.77;
H, 7.54. Found C, 75.96; H, 7.72.
(s, 2H, AreH). 13C NMR (125 MHz, CDCl3):
d 14.45, 23.02, 24.99,
26.43, 29.50, 29.66, 29.74, 29.90, 29.92, 30.79, 32.24, 59.20, 68.56,
106.77, 110.97, 112.61, 116.96, 120.47, 124.45, 126.44, 127.34, 128.11,
131.33, 132.14, 132.44, 137.98, 154.56, 159.80, 163.75, 164.44, 165.37.
Anal. Calcd for C61H74N2O8: C, 76.06; H, 7.74. Found C, 75.92; H, 7.83.
4.2.13. N,N-(1,7-Heptylene)-bis(4-decanoxynaphthalenelidenimine)
1c (m¼7, n¼10). Light yellow solids, yield 81%. 1H NMR (500 MHz,
4.2.9. N,N-(1,5-Pentylene)-bis(4-tetradecanoxynaphthalenelidenimine)
CDCl3):
d
0.87 (t, 6H, eCH3, J¼6.34 Hz), 1.34e1.39 (m, 24H, eCH2),
1a (m¼5, n¼14). Light yellow solids, yield 74%. 1H NMR (500 MHz,
1.46e1.51 (m, 4H, eCH2), 1.69e1.82 (m, 4H, eCH2), 1.85e1.87 (m,
4H, eCH2), 3.58 (t, 4H, eCH2eN]CH, J¼6.53 Hz), 4.08 (t, 4H,
eOCH2, J¼6.45 Hz), 6.74 (d, 2H, AreH), 6.84 (s, 2H, AreH), 7.15 (s,
2H, AreH), 7.21 (d, 2H, AreH, J¼2.39 Hz), 7.26 (d, 2H, AreH,
J¼6.39 Hz), 7.76 (d, 2H, AreH, J¼8.77 Hz), 7.85 (d, 2H, AreH,
J¼8.97 Hz), 8.10 (d, 2H, AreH, J¼8.50 Hz), 8.31 (s, 2H, eN]CH), 8.66
CDCl3):
d
0.88 (t, 6H, eCH3, J¼6.52 Hz), 1.27e1.39 (m, 44H, eCH2),
1.48e1.51 (m, 6H, eCH2), 1.76e1.79 (m, 4H, eCH2), 1.85e1.88 (m,
4H, eCH2CH2), 3.62 (t, 4H, eCH2eN]CH, J¼6.40 Hz), 4.11 (t, 4H,
eOCH2, J¼6.48 Hz), 6.77 (d, 2H, AreH), 6.79 (s, 2H, AreH), 7.16 (s,
2H, AreH), 7.21 (d, 2H, AreH, J¼8.66 Hz), 7.22 (d, 2H, AreH,
J¼8.39 Hz), 7.28 (d, 2H, AreH, J¼2.39 Hz), 7.77 (d, 2H, AreH,
J¼8.98 Hz), 8.13 (d, 2H, AreH, J¼7.30 Hz), 8.34 (s, 2H, eN]CH),
(s, 2H, AreH). 13C NMR (125 MHz, CDCl3):
d 14.16, 22.71, 26.12,
27.05, 29.02, 29.18, 29.36, 29.43, 30.60, 29.62, 31.71, 31.93, 58.94,
68.23, 106.42, 110.71, 112.19, 116.64, 120.17, 124.12, 126.13, 127.02,
127.78, 131.02, 131.83, 132.10, 137.66, 154.23, 159.48, 163.69, 163.90,
165.07. Anal. Calcd for C63H78N2O8: C, 76.33; H, 7.93. Found C, 76.58;
H, 8.19.
8.67 (s, 2H, AreH). 13C NMR (125 MHz, CDCl3):
d 14.46, 23.03,
24.99, 26.43, 29.51, 29.70, 29.74, 29.93, 29.95, 30.03, 30.80, 32.27,
59.21, 68.56, 106.79, 110.98, 112.62, 116.97, 120.48, 124.47, 127.34,
128.12, 131.33, 132.14, 132.44, 137.99, 154.57, 159.82, 163.75,
164.44, 165.37. Anal. Calcd for C69H90N2O8: C, 77.06; H, 8.43.
Found C, 77.56; H, 8.45.
4.2.14. N,N-(1,7-Heptylene)-bis(4-dodecyloxynaphthalenelidenimine)
1c (m¼7, n¼12). Light yellow solids, yield 71%. 1H NMR (500 MHz,
4.2.10. N,N-(1,5-Hextylene)-bis(4-dodecyloxynaphthalenelidenimine)
CDCl3):
d
0.87 (t, 6H, eCH3, J¼6.43 Hz), 1.36e1.38 (m, 36H, eCH2),
1b (m¼6, n¼12). Light yellow solids, yield 84%. 1H NMR (500 MHz,
1.46e1.53 (m, 4H, eCH2),1.69e1.82 (m, 4H, eCH2),1.85e1.89 (m, 4H,

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H.-M. Kuo et al. / Tetrahedron 69 (2013) 4226e4235
eCH2), 3.60 (t, 4H, eCH2eN]CH, J¼6.37 Hz), 4.10 (t, 4H, eOCH2,
J¼6.43 Hz), 6.75 (d, 2H, AreH), 6.86 (s, 2H, AreH), 7.17 (s, 2H, AreH),
7.22 (d, 2H, AreH, J¼1.93 Hz), 7.30 (d, 2H, AreH, J¼6.39 Hz), 7.78 (d,
2H, AreH, J¼8.67 Hz), 7.87 (d, 2H, AreH, J¼8.97 Hz), 8.12 (d, 2H,
AreH, J¼8.55 Hz), 8.33 (s, 2H, eN]CH), 8.67 (s, 2H, AreH). 13C NMR
(s, 2H, AreH). 13C NMR (125 MHz, CDCl3):
d 14.44, 22.99, 26.42,
27.39, 29.49, 29.51, 29.58, 31.08, 32.15, 59.22, 68.55, 106.77, 111.03,
112.45, 116.94, 120.48, 124.46, 126.44, 127.33, 128.11, 131.33, 132.14,
132.38, 137.98, 154.57, 159.80, 164.13, 165.37. Anal. Calcd for
C61H74N2O8: C, 76.06; H, 7.74. Found C, 75.93; H, 7.89.
(125 MHz, CDCl3):
d 14.46, 23.03, 26.43, 27.36, 29.33, 29.50, 29.69,
29.74, 29.93, 29.95, 29.98, 30.00, 31.02, 32.26, 59.24, 68.56, 106.77,
111.02, 112.50, 116.95, 120.48, 124.46, 126.45, 127.34, 128.11, 131.33,
132.14, 132.40, 137.99, 154.57, 159.81, 164.02, 164.22, 165.37. Anal.
Calcd for C67H86N2O8: C, 76.33; H, 7.93. Found C, 76.58; H, 8.19.
4.2.19. N,N-(1,9-Nontylene)-bis(4-decanoxynaphthalenelidenimine)
1e (m¼9, n¼10). Light yellow solids, yield 78%. 1H NMR (500 MHz,
CDCl3):
d
0.87 (t, 6H, eCH3, J¼6.53 Hz), 1.27e1.37 (m, 36H, eCH2),
1.46e1.51 (m, 4H, eOCH2), 1.67e1.70 (m, 4H, eCH2), 1.82e1.86 (m,
4H, eCH2), 3.57 (t, 4H, eCH2eN]CH, J¼6.64 Hz), 4.09 (t, 4H,
eOCH2, J¼6.52 Hz), 6.73 (d, 2H, AreH), 6.83 (s, 2H, AreH), 7.15 (s,
2H, AreH), 7.20 (d, 2H, AreH, J¼6.73 Hz), 7.26 (d, 2H, AreH,
J¼8.41 Hz), 7.77 (d, 2H, AreH, J¼8.65 Hz), 7.85 (d, 2H, AreH,
J¼8.99 Hz), 8.11 (d, 2H, AreH, J¼8.49 Hz), 8.31 (s, 2H, eN]CH), 8.66
4.2.15. N,N-(1,7-Heptylene)-bis(4-tetradecanoxynaphthalenelidenimine)
1c (m¼7, n¼14). Light yellow solids, yield 82%. 1H NMR (500 MHz,
CDCl3):
d
0.86 (t, 6H, eCH3, J¼6.65 Hz), 1.36e1.39 (m, 44H, eCH2),
1.46e1.52 (m, 4H, eCH2), 1.69e1.70 (m, 4H, eCH2), 1.83e1.88 (m, 4H,
eCH2), 3.58 (t, 4H, eCH2eN]CH, J¼6.59 Hz), 4.09 (t, 4H, eOCH2,
J¼6.50 Hz), 6.74 (d, 2H, AreH), 6.83 (s, 2H, AreH), 7.17 (s, 2H, AreH),
7.20 (d, 2H, AreH, J¼2.22 Hz), 7.27 (d, 2H, AreH, J¼8.39 Hz), 7.76 (d,
2H, AreH, J¼8.68 Hz), 7.85 (d, 2H, AreH, J¼8.99 Hz), 8.09 (d, 2H, AreH,
J¼1.35 Hz), 8.31 (s, 2H, eN]CH), 8.66 (s, 2H, AreH). 13C NMR
(s, 2H, AreH). 13C NMR (125 MHz, CDCl3):
d 14.15, 22.70, 26.11,
27.08, 29.17, 29.21, 29.35, 29.38, 29.42, 29.59, 30.77, 31.92, 58.94,
68.24, 106.43, 110.72, 112.14, 116.64, 120.17, 124.13, 126.13, 127.02,
127.78, 131.02, 131.83, 132.06, 137.66, 154.23, 159.48, 163.77, 163.82,
165.06. Anal. Calcd for C65H82N2O8: C, 76.59; H, 8.11. Found C, 76.48;
H, 8.09.
(125 MHz, CDCl3): d 14.16, 23.72, 26.11, 27.05, 29.02, 29.17, 29.39, 29.43,
29.61, 29.64, 29.69, 29.71, 30.71, 31.95, 58.97, 68.23, 106.41, 110.70,
112.20, 116.64, 120.17, 124.12, 126.14, 127.02, 127.78, 131.02, 131.83,
132.09, 137.66, 154.21, 159.48, 163.66, 163.89, 165.07. Anal. Calcd for
C71H94N2O8: C, 77.28; H, 8.59. Found C, 77.30; H, 8.77.
4.2.20. N,N-(1,9-Nontylene)-bis(4-dodecyloxynaphthalenelidenimine)
1e (m¼9, n¼12). Light yellow solids, yield 83%. 1H NMR (500 MHz,
CDCl3):
d
0.87 (t, 6H, eCH3, J¼6.73 Hz), 1.25e1.37 (m, 46H, eCH2),
1.46e1.51 (m, 4H, eCH2),1.67e1.70 (m, 4H, eCH2),1.83e1.86 (m, 4H,
eCH2), 3.57 (t, 4H, eCH2eN]CH, J¼6.62 Hz), 4.08 (t, 4H, eOCH2,
J¼6.52 Hz), 6.74 (d, 2H, AreH), 6.84 (s, 2H, AreH), 7.15 (s, 2H, AreH),
7.20 (d, 2H, AreH, J¼8.53 Hz), 7.26 (d, 2H, AreH, J¼8.41 Hz), 7.76 (d,
2H, AreH, J¼8.64 Hz), 7.85 (d, 2H, AreH, J¼8.99 Hz), 8.10 (d, 2H,
AreH, J¼7.07 Hz), 8.31 (s, 2H, eN]CH), 8.66 (s, 2H, AreH). 13C NMR
4.2.16. N,N-(1,8-Octylene)-bis(4-dodecyloxynaphthalenelidenimine)
1d (m¼8, n¼12). Light yellow solids, yield 82%. 1H NMR (500 MHz,
CDCl3):
d
0.89 (t, 6H, eCH3, J¼6.31 Hz), 1.37e1.39 (m, 44H, eCH2),
1.49e1.53 (m, 4H, eCH2), 1.68e1.72 (m, 4H, eCH2CH2), 1.84e1.88
(m, 4H, eCH2), 3.59 (t, 4H, eCH2eN]CH, J¼6.67 Hz), 4.11 (t, 4H,
eOCH2, J¼6.51 Hz), 6.76 (d, 2H, AreH), 6.86 (s, 2H, AreH), 7.17 (s,
2H, AreH), 7.22 (d, 2H, AreH, J¼6.80 Hz), 7.28 (d, 2H, AreH,
J¼8.40 Hz), 7.78 (d, 2H, AreH, J¼8.66 Hz), 7.87 (d, 2H, AreH,
J¼8.97 Hz), 8.12 (d, 2H, AreH, J¼8.69 Hz), 8.33 (s, 2H, eN]CH), 8.68
(125 MHz, CDCl3):
d 14.17, 22.73, 26.12, 27.09, 29.18, 29.22, 29.39,
29.44, 29.62, 29.64, 29.67, 29.70, 30.77, 31.95, 58.95, 68.23, 106.41,
110.72, 112.15, 116.63, 120.18, 124.11, 126.14, 127.02, 127.77, 131.02,
131.83, 132.07, 137.66, 154.22, 159.48, 163.78, 163.82, 165.08. Anal.
Calcd for C69H90N2O8: C, 77.06; H, 8.43. Found C, 76.93; H, 8.73.
(s, 2H, AreH). 13C NMR (125 MHz, CDCl3):
d 14.45, 23.03, 26.42,
27.37, 29.50, 29.69, 29.73, 29.92, 29.94, 29.98, 30.00, 31.06, 32.25,
59.23, 68.56, 106.79, 111.03, 112.47, 116.96, 120.48, 124.47, 126.44,
127.34, 128.12, 131.33, 131.83, 132.14, 132.38, 137.99, 154.58, 159.81,
164.08, 164.17, 165.38. Anal. Calcd for C68H88N2O8: C, 76.95; H, 8.36.
Found C, 76.78; H, 8.38.
4.2.21. N,N-(1,9-Nontylene)-bis(4-tetradecanoxynaphthalenelidenimine)
1e (m¼9, n¼14). Light yellow solids, yield 81%. 1H NMR (500 MHz,
CDCl3):
d
0.86 (t, 6H, eCH3, J¼6.45 Hz), 1.25e1.37 (m, 60H, eCH2),
1.49e1.52 (m, 4H, eCH2), 1.67e1.70 (m, 4H, eCH2), 1.82e1.87 (m, 4H,
eCH2), 3.57 (t, 4H, eCH2eN]CH, J¼6.43 Hz), 4.08 (t, 4H, eOCH2,
J¼6.36 Hz), 6.74 (d, 2H, AreH), 6.84 (s, 2H, AreH), 7.15 (s, 2H, AreH),
7.20 (d, 2H, AreH, J¼8.53 Hz), 7.26 (d, 2H, AreH, J¼8.36 Hz), 7.76 (d,
2H, AreH, J¼8.63 Hz), 7.85 (d, 2H, AreH, J¼8.93 Hz), 8.10 (d, 2H, AreH,
J¼8.47 Hz), 8.30 (s, 2H, eN]CH), 8.66 (s, 2H, AreH). 13C NMR
4.2.17. N,N-(1,9-Nontylene)-bis(4-hexyloxynaphthalenelidenimine)
1e (m¼9, n¼6). Light yellow solids, yield 79%. 1H NMR (500 MHz,
CDCl3):
d
0.93 (t, 6H, eCH3, J¼6.69 Hz), 1.34e1.39 (m, 20H, eCH2),
1.49e1.53 (m, 4H, eCH2), 1.69e1.72 (m, 4H, eCH2), 1.85e1.88 (m,
4H, eCH2), 3.59 (t, 4H, eCH2eN]CH, J¼6.66 Hz), 4.10 (t, 4H,
eOCH2, J¼6.49 Hz), 6.76 (d, 2H, AreH), 6.86 (s, 2H, AreH), 7.16 (s,
2H, AreH), 7.19 (d, 2H, AreH, J¼6.80 Hz), 7.28 (d, 2H, AreH,
J¼8.38 Hz), 7.78 (d, 2H, AreH, J¼8.64 Hz), 7.87 (d, 2H, AreH,
J¼8.84 Hz), 8.12 (d, 2H, AreH, J¼8.61 Hz), 8.32 (s, 2H, eN]CH), 8.68
(125 MHz, CDCl3): d 14.16, 22.73, 26.11, 27.09, 29.18, 29.22, 29.40, 29.43,
29.62, 29.64, 29.70, 29.72, 30.77, 31.95, 58.95, 68.23, 106.41, 110.72,
112.15, 116.64, 120.17, 124.12, 126.14, 127.02, 127.78, 131.02, 131.83,
132.07, 137.67, 154.22, 159.48, 163.78, 163.82, 165.07. Anal. Calcd for
C73H98N2O8: C, 77.48; H, 8.73. Found C, 77.44; H, 8.42.
(s, 2H, AreH). 13C NMR (125 MHz, CDCl3):
d 14.37, 22.94, 26.10,
27.38, 29.45, 29.51, 29.68, 31.07, 31.91, 59.22, 68.54, 106.76, 111.03,
112.44, 116.94, 120.47, 124.45, 126.44, 127.33, 128.10, 131.32, 132.13,
132.38, 137.98, 154.56, 159.79, 164.13, 164.13, 165.36. Anal. Calcd for
C57H66N2O8: C, 75.47; H, 7.33. Found C, 75.48; H, 7.38.
Acknowledgements
We thank the National Science Council of Taiwan, ROC for
funding (NSC 100-2113-M-008-002-MY2) in generous support of
this work.
4.2.18. N,N-(1,9-Nontylene)-bis(4-octyloxynaphthalenelidenimine)
1e (m¼9, n¼8). Light yellow solids, yield 81%. 1H NMR (500 MHz,
References and notes
CDCl3):
d
0.90 (t, 6H, eCH3, J¼6.53 Hz), 1.31e1.39 (m, 28H, eCH2),
1.48e1.53 (m, 4H, eCH2), 1.69e1.72 (m, 4H, eCH2), 1.85e1.88 (m,
4H, eCH2), 3.59 (t, 4H, eCH2eN]CH, J¼6.69 Hz), 4.10 (t, 4H,
eOCH2, J¼6.51 Hz), 6.76 (d, 2H, AreH), 6.78 (s, 2H, AreH), 7.17 (s,
2H, AreH), 7.21 (d, 2H, AreH, J¼6.93 Hz), 7.28 (d, 2H, AreH,
J¼8.41 Hz), 7.78 (d, 2H, AreH, J¼8.67 Hz), 7.87 (d, 2H, AreH,
J¼8.99 Hz), 8.12 (d, 2H, AreH, J¼7.08 Hz), 8.32 (s, 2H, eN]CH), 8.68
€
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