Polarization effect in luminescent mesogenic BF2 complexes derived from heterocyclic benzothiazoles

Article abstract of DOI:10.1016/j.molliq.2019.111660

Two series of benzo(thia)xazoles 1–2 and one series of boron difluoride complexes 2-BF₂ derived from benzothiazoles 2 were reported, and their mesomorphic and optical properties were investigated. The crystal and molecular structures of compound 2 and 2-BF₂ (all n = 8) were determined by means of X?ray structural analysis, and both crystallize in the triclinic P-1 and monoclinic P2₁/c. The geometry at boron center is perfectly tetrahedral, and the overall molecular shapes are considered as rod?shape. Both benzo(thia)xazoles 1 and 2 exhibited N or/and SmC phase, and boron complexes 2-BF₂ formed N or/and SmC phase. Benzothiazoles 2 showed a much wider temperature range of mesophase than those of benzoxazoles 1, which were attributed to the better polarization by sulfur atom incorporated. Boron complexes 2-BF₂ (n = 10, 12) emitted a yellow?to?green emission at λ_max = 569–571 nm in CH₂Cl₂. This is the first mesogenic BF₂ complexes derived from benzothiazoles.

Full text of DOI:10.1016/j.molliq.2019.111660

Journal Pre-proof
Polarization effect in luminescent mesogenic BF2 complexes
derived from heterocyclic benzothiazoles
Yuan-Chun Hsu, Chun-Yang Wang, Pei-Chi Hsiao, Yi-Hong Cai,
Gene-Hsiang Lee, Chung K. Lai
PII:
S0167-7322(19)32889-2
DOI:
https://doi.org/10.1016/j.molliq.2019.111660
MOLLIQ 111660
Reference:
To appear in:
Journal of Molecular Liquids
Received date:
Revised date:
Accepted date:
22 May 2019
24 August 2019
28 August 2019
Please cite this article as: Y.-C. Hsu, C.-Y. Wang, P.-C. Hsiao, et al., Polarization effect in
luminescent mesogenic BF2 complexes derived from heterocyclic benzothiazoles, Journal
of Molecular Liquids(2019), https://doi.org/10.1016/j.molliq.2019.111660
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Polarization effect in luminescent mesogenic BF2 complexes
derived from heterocyclic benzothiazoles
YuanChun Hsu a, ChunYang Wang a, PeiChi Hsiao a, Yi-Hong Cai a,
GeneHsiang Lee b, Chung K. Lai a*
a Department of Chemistry, National Central University, ChungLi 32001, Taiwan, ROC
b Instrumentation Center, National Taiwan University, Taipei 10660, Taiwan, ROC
ABSTRACT
Two series of benzo(thia)xazoles 1-2 and one series of boron difluoride complexes 2-BF2 derived
from benzothiazoles 2 were reported, and their mesomorphic and optical properties were
investigated. The crystal and molecular structures of compound 2 and 2-BF2 (all n = 8) were
determined by means of Xray structural analysis, and both crystallize in the triclinic P-1 and
monoclinic P21/c. The geometry at boron center is perfectly tetrahedral, and the overall molecular
shapes are considered as rodshape. Both benzo(thia)xazoles 1 and 2 exhibited N or/and SmC
phase, and boron complexes 2-BF2 formed N or/and SmC phase. Benzothiazoles 2 showed a much
wider temperature range of mesophase than those of benzoxazoles 1, which were attributed to the
better polarization by sulfur atom incorporated. Boron complexes 2-BF2 (n = 10, 12) emitted a
yellowtogreen emission at max = 569571 nm in CH2Cl2. This is the first mesogenic BF2
complexes derived from benzothiazoles.
* Corresponding author
E-mail address: cklai@cc.ncu.edu.tw
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1. Introduction
The research on boron difluoride (BF2) complexes [1-4] incorporating organic conjugated
backbones or motifs have extensively continuing during the past decades; many unique complexes
were prepared and investigated in a variety of applications. Lightemissive materials [5-7] were
among the most widely areas of molecular materials due to their unique, tunable and useful
absorption and emission properties. By designing appropriate chelating ligands, the molecular
structures of BF2 complexes could be modified or tuned for the optical properties. Boron difluoride
often coordinates oxygen or/and nitrogen atoms with chelating ligands and the resulting boron
complexes with a coordination number of four (CN = 4) and a tetrahedral geometry were often
obtained. On the other hand, among these known BF2 complexes, three coordination modes of [F2B-
O,O] [6-11], [F2B-O,N] [12-16] and [F2B-N,N] [17-21] were often generated. The common
chelating ligands incorporated to form BF2 complexes as the core structures included diketonates,
ketoiminates and diiminates. Many mesogenic momo-BF2 [22-25], mesogenic bis(BF2)2 [26-28] or
nonmesogenic tris(BF2)3 [29-30] complexes were consequently obtained. Boron diketonates were
not only investigated for liquid crystalline materials, but also to work as building blocks for
luminogenic nanomaterials. A typical emission band between max = 450-650 nm was often
observed. Furthermore, several boron diketonate complexes [31] exhibited a mechanofluouo-
chromic (MFC) behavior. In contrast, boron complexes of diiminates and benzothiazaxoles [32-34]
have been showed to be a potential candidate for use as aggregation-induced-emission (AIE) [35-39]
materials; diiminate derivatives were easily obtained by replacing a more electronegative nitrogen
atom from diketonates. Recently, the use of heterocyclic chelating ligands, such as pyrazoles [40-42]
and benzoxazoles [43] as building blocks has been widely applied in their structural modifications,
as well as their potential applications. A few luminescent di and trinuclear boron complexes
derived from iminopyrrolyl spacer ligands [44] were demonstrated in the use of OLEDs. The use of
benzothiazoles in the biological activities [45-46] has also been reviewed.
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We have been focusing on the study of the mesogenic materials containing BF2 moiety as core.
BF2 is often considered as a Lewis acid moiety; the coordination bonds with chelating oxygen
or/and nitrogen atoms enhance its overall molecular electron polarization or delocalization. Schiff
bases; such as salicylideneamines [47] or enaminoketones has been applied in this group in the
past to generate metallomesogenic materials. An interesting piezochromic luminescence behavior
[48-49] observed by benzothiazoleenamide boron difluoride complexes was reported. A few
interesting mesogenic materials [50-51] incorporating BF2 moiety (i.e. IIII) have been reported.
Our results showed that the imine C=N moiety was crucially important in inducing the
mesophases; it not only carries a dipole moment enhancing the overall molecular thermal stability,
but also increases molecular intermolecular attraction in their solid or/and LC states due to its better
core planarity of core sp2hybrid bonding.
In this work, two series of Schiff bases containing heterocyclic benzo(thio)xazoles 12 and one
series of complexes 2-BF2 derived from benzothiazoles 2 were described, and their mesomorphic
and optical properties were also investigated. Heterocyclic structures have been widely applied to
generate novel metal-free liquid crystalline materials [52]. The benzothiazoles 2 and their complexes
2-BF2 were particularly studied to understand the polarization effect on the formation of mesophase
in such molecular systems. In additions, the crystallographic data resolved from two single crystals
were used to correlate the formation of the mesomorphic behavior and their molecular structures.
2. Results and Discussions
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2.1 Synthesis and Characterization
The synthetic pathways to boron difluoride complexes 2-BF2 are summarized in Scheme 1. The
experimental preparations of compounds 2 were followed by our previous procedures. The
compounds 1 were obtained by the reactions of 6-alkoxybenzo [d]oxazol-2-amines and 4-alkoxy-2-
hydroxybenzaldehydes in refluxing absolute ethyl alcohol for 8 h. On the other hands, the
compounds 2, (E)-5-alkoxy-2-(((6-(dodecyloxy)benzo[d]thiazol-2-yl)imino)methyl)phenol were
obtained by the reaction of 6-alkoxybenzo[d] thiazol-2-amines and 4-alkoxy-2-hydroxy
benzaldehydes in refluxing absolute ethyl alcohol for 8 h. All compounds 1 and 2 were isolated as
light yellow solids. The final boron complexes 2-BF2 were obtained by the reactions of (E)-5-
alkoxy-2-(((6-alkoxybenzo[d]thiazol-2-yl)imino)methyl)phenols and boron trifluoride diethyl
etherate in refluxing in CH2Cl2 for 1.5 h. The complexes 2-BF2 isolated as orange powders were
purified by column chromatography eluting with CH2Cl2. These boron complexes are very air stable
and soluble in most organic solvents. However, the similar reactions of benzoxazoles 1 and boron
trifluoride diethyl etherate in refluxing in CH2Cl2 gave no BF2 complexes; a small amount of
starting materials were recovered. The 1H, 13C NMR and 19F NMR spectroscopy were used to
characterize all intermediates, and the elemental analysis and HRMS were used to confirm the purity
of the boron complexes. For example, the 1H NMR data in CDCl3, showed two characteristic peaks
assigned to phenolicH (COH) and methanimineH (CH=N), summarized in Table 1. On the 1H
NMR spectra, the original singlet assigned for phenolicOH of compounds 2 at  12.6312.64 were
all disappeared upon coordination to BF2 moiety. On the 19F NMR spectra, a doublet of doublets
appeared at δ 133.45 to 133.48 (i.e. 10BF, 0.2F) and  133.53to 133.55 (i.e. 11BF, 0.8F) was
observed for compounds 2-BF2. Elemental analysis and mass were also used to confirm the purity of
the boron complexes.
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Table 1
The characteristic 1H NMR peaksa assigned for compounds 1-2 and 2-BF2.
Compd.
1
2
2-BF2
OCH2
CH=N
COH (phenolic)
3.964.03 (m)
9.219.22 (s)
12.60 (s)
3.983.99 (t)
9.029.04 (br)
12.6312.64 (br)
4.00 (t), 4.054.06 (t)
9.359.36 (br)

a solution in CDCl3; unit () in ppm; s = singlet, t = triplet, m = multiplet and br = broad.
2.2 Single structure and molecular structures of (E)-5-(octyloxy)-2-(((6-(octyloxy)benzo[d]thia zol-
2-yl)imino)methyl)phenol 2 (n = 8) and boron complex of 7-(octyloxy)-3-(6-(octyloxy)benzo
[d]thiazol-2-yl)-2,2-difluoro-2H-benzo[e] [1,3,2]oxazaborinin-3-ium- 2-uide 2-BF2 (n = 8).
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In order to understand the correlation between the molecular structures and the formation of
mesophases, two single crystals of pale yellow compound 2 (n = 8) and its orange boron complex
2-BF2 (n = 8) were obtained and their single crystallographic data were investigated. Two crystals
suitable for X-ray diffraction analysis were slowly grown from THF at room temperature. Fig. 1
shows the molecular structures with the atomic numberings, and Table 2 lists the crystallographic
and structural refinement data for the two compounds. The crystal 2 crystallizes in triclinic space
group P-1, with a = 6.7094(3) Å, b =14.2811(7) Å, c = 16.1874(8) Å, and Z = 2, in contrast, the
crystal 2-BF2 crystallizes in monoclinic space group P21/c, with a = 16.5816(4) Å, b = 10.8598(3)
Å, c = 17.0697(4) Å, and Z = 4. The bond length of d = 1.294 Å for imine CH=N (i.e. atom
C1N1) in crystal 2 increased to d = 1.334 Å upon coordination to boron atom in crystal 2BF2 (see
Table 3). The four angles at tetrahedral boron atom in 2-BF2 were ranged from 108.9111.1,
slightly derived from perfect 109 (see Table 3). The overall structures of both crystals were
considered as rodlike shapes, and the molecular lengths were 33.03 Å (atom C22C30 in crystal 2)
and 33.02 Å (atom C22C30 in 2-BF2). The overall molecular structures in two crystals were quite
planar, and the dihedral angles derived from central plane (see Fig. 2) to neighboring rings were
10.05 (for 2) and 3.899 (for 2-BF2). The relatively small dihedral angles favored the formation
of mesophases.
Fig. 1 Two ORTEP drawings for two crystals 2 (n = 8, left) and 2-BF2 (n = 8, right) with the
numbering schemes, and thermal ellipsoids of nonhydrogen atoms are drawn at the 50%
probability level.
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Fig. 2 Two dihedral angles between the central boron and neighboring phenyl rings existed in
crystals 2 (n = 8, left) and 2-BF2 (n = 8, right). P1 and P2 are representative neighboring planes.
Table 2
Crystallographic data for two crystals 2 and 2-BF2.
Compds.
2 (n = 8)
2-BF2 (n = 8)
Empirical formula
Formula weight
Temperature (K)
Crystal system
Space group
C30H42N2O3S
510.72
150(2)
Triclinic
P-1
C30H41BF2N2O3S
558.52
200(2)
Monoclinic
P21/c
a (Å)
b (Å)
c (Å)
 (°)
6.7094(3)
14.2811(7)
16.1874(8)
115.115(2)
94.930(3)
94.839(3)
1386.59(11)
2
16.5816(4)
10.8598(3)
17.0697(4)
90
105.7016(12)
90
 (°)
 (°)
Volume (Å3)
Z
2959.09(13)
4
Density (calculated, Mg/m3)
Crystal size (mm3)
Theta range for data collection (°)
Reflections collected
Independent reflections
Final R1, wR2
1.223
1.254
0.50 x 0.20 x 0.15
1.40 to 27.50
18918
6295 [R(int) = 0.0466]
0.0449, 0.0983
0.359 x 0.247 x 0.027
4.881 to 71.998
16793
5783 [R(int) = 0.0340]
0.0572, 0.1460
Table 3
Selected bond lengths (Å) and angles (°) in crystals 2 and 2-BF2.
Crystal 2 (n = 8)
N1C1
1.294
1.392
0.840
115.92
121.44
S1C1
1.786
1.294
1.351
118.75
123.11
C1N2
N2C8
H1O1
O1C10
 C1N2C8
 N2C8C9
 S1C1N1
 S1C1N2
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Crystal 2-BF2 (n = 8)
N1C1
1.278
1.404
108.9
109.96
S1C1
1.751
1.334
107.6
111.1
C1N2
N2C8
 F1B1F2
 N2B1O1
 F1B1N2
 O1B1F2
As expected, a strong intramolecular Hbond was observed in crystal 2; a distance of  1.934 Å
(atom N2H1) was obtained, as shown Fig. 3. In contrast, quite a few weak intermolecular
Hbonds were observed in both crystals. A distance of  3.182 Å (atom S1H1) was obtained for
crystal 2, and a bond length ranged in d = 2.546 2.832 Å (Table 4) were obtained for crystal 2-BF2.
The intramolecular Hbonds kept the phenolic ring nearly coplanar to the benzo ring, and the better
planar structure was favorable for a better packing both in the solid or/and the liquid crystal state. In
contrast, other intermolecular interactions, such as σπ or ππ were also observed in two crystals. In
general, the CH or ππ interactions were much weaker than Hbonds. A distance ranged from d
= 2.88 3.224 Å were observed in both crystals (Table 5 and Fig. 4). These weak intermolecular
forces were very crucial on the induction and/or formation of mesophases in such heterocyclic
compounds. In crystal lattice, all alkoxy chains were not interdigitated between neighboring
molecules; all alkoxy chains were slightly interdigitated, giving a smaller layer distance both in N
and SmC phases upon heating to the mesophase temperatures (Fig. 5).
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Fig. 3 Hbond interactions observed in crystal 2 (n = 8, left) and 2-BF2 (n = 8, right).
Table 4
The Hbond interactions observed in crystals 2 and 2BF2.
Compds
Hbonds (DH…A) Distances (Å)
Angle DH…A (°)
Intramolecular Hbond
2 (n = 8)
N2H1O1
1.934
143.7
Intermolecular Hbond
2-BF2 (n = 8)
S1H1O1
C3H3F2
3.182
2.661
2.617
2.546
2.665
2.832
2.648
93.13
127.45
121.16
138.13
154.69
146.38
119.75
C11H11F2
C15H15AF1
C25H25AF2
C23H23BF2
C8H8F1
Table 5
Intermolecular interactionsa observed in crystals 2 and 2-BF2.
Compds
σπ or ππ
Distances (Å)
Angle (ringH…A) (°)
2 (n = 8)
2-BF2 (n = 8)
ringring
3.696
3.224
2.998
2.880

ringH28BC28
ringH26BC26
ringH23BC23
145.84
134.43
135.31
a: measured from the center of ring to the atom.
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Fig. 4 The  interactions observed in crystals 2 (n = 8, top) and 2-BF2 (n = 8, bottom)
Fig. 5 The layered structures observed in crystal 2 (n = 8, top) and 2-BF2 (n = 8, bottom).
2.3 Phase transitions, mesomorphic properties and thermal stability.
The thermal behavior of all compounds 12 and 2-BF2 was studied by polarized optical
microscopy and differential scanning calorimetry. The transition temperatures and enthalpies of the
compounds 1ac and 2-BF2 are summarized in Table 6. The results showed that all compounds 12
formed an enantiotropic mesomorphic behavior. For compounds 1, all melting temperatures were
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ranged from Tmp = 79.497.8 C, however, all clearing temperatures increased with the carbon
length of the alkoxy chains; Tcl = 93.1 (n = 8) < 97.1 (n = 10) < 97.6 (n = 12) < 97.7 (n = 14) < 99.9
C (n = 16), indicating that the van der Waals interaction played an important force in the LC states.
All benzoxazole 1 formed N or/and SmC phase; the two derivatives with shorter carbon length (n =
8, 10) formed N phases, and other three derivatives (n = 10, 12, 14, 16) exhibited SmC phase. This
is common behavior observed for the rodlike mesogens. Not surprised, the temperature range of
mesophases by compounds 1 decreased with carbon length; i.e. T = 25.6 (n = 8) > 21.6 (n = 10) >
14.3 (n = 12) > 9.1 (n = 14) > 4.3 C (n = 16) on cooling process. The enthalpy changed for the
transition of N  I phase and SmC  I phase was ranged from H = 1.391.43 KJ/mol and 6.67-
8.32 KJ/mol. However, the enthalpy for the transition of SmC  N phase for compound 1 (n = 10)
was often relatively small, i.e. 0.720.94 KJ/mol. The mesophases were then first characterized and
identified as N and SmC phases by POM; a Schlieren or focalconics texture was easily observed
under POM when cooled from their isotropic states.
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Table 6
The phase transitions and enthalpies[a] of compounds 1-2 and 2-BF2.
Compds
Phase transitions and corresponding enthalpies (in parentheses) C (kJ/mol)
The second heating cycle
The second cooling cycle
1; n = 8
Cr 79.4 (31.0)  N 93.1 (1.39)  I
I 92.1 (1.39)  N 66.5 (32.1)  Cr
10
12
14
Cr 86.6 (30.4)  SmC 90.8 (0.72)  N 97.1 (1.48)  I
Cr 91.0 (50.2)  SmC 97.6 (6.67)  I
I 92.1 (1.39)  N 89.8 (0.94)  SmC 70.5 (32.3)  Cr
I 95.8 (7.57)  SmC 81.5 (54.1)  Cr
Cr 93.9 (56.7)  SmC 97.7 (8.32)  I
I 95.8 (7.64)  SmC 86.7 (53.5)  Cr
16
2; n = 8
10
Cr 97.8[b]  SmC 99.9 (76.5)[b]  I
I 97.5 (8.93)  SmC 93.2 (63.2)  Cr
Cr 78.4 (28.1)  SmC 125.9 (2.51) N 136.6 (2.37)  I
Cr 87.1 (0.37)  SmC 136.2 (9.64)  I
Cr 89.2 (7.28)  SmC 135.9 (8.61)  I
I 135.1 (2.64)  N 124.6 (2.25)  SmC 69.5 (27.7 )  Cr
I 133.4 (7.91)  SmC 71.4 (30.2)  Cr
12
I 133.1 (9.26)  SmC 76.0 (32.1)  Cr
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14
16
Cr 85.8 (42.3)  SmC 129.4 (12.4)  I
Cr 90.0 (47.2)  SmC 125.9 (13.5)  I
I 128.6 (10.7)  SmC 79.7 (42.2)  Cr
I 123.1 (11.6) SmC 81.5 (49.5)  Cr
2-BF2; n = 8 Cr 116.1 (41.5) SmC 133.4 (3.69) N 137.7 (2.83)  I
10 Cr 117.0 (20.0)  SmC 142.9 (8.97)  I
I 136.1 (2.97 )  N 131.1 (3.40) SmC 100.2 (16.5)  Cr
I 141.1 (8.42)  SmC 96.7 (23.7)  Cr
12 Cr 111.0 (29.0)  SmC 145.8 (11.5)  I
I 143.9 (11.0)  SmC 94.9 (32.3)  Cr
[a]: n = the carbon numbers of alkoxy chains; Cr = crystal, SmC = smectic C, N = nematic and I = isotropic phases.
[b]: observed from POM due to overlapping with clearing peak
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In contrast, all benzothiazoles 2 exhibited an improved mesomorphoric behavior over
benzoxazoles 1. Both compounds 1 and 2 are structurally similar, however, benzothiazole 2 has a
sulfur atom incorporated, larger in size than that of oxygen in benzoxazoles 1 (i.e. covalent radii
1.02 x 10-10 > 0.73 x 10-10 m). The difference in the clearing temperature might be attributed to the
molecular size or/and polarization effect. The clearing temperature of benzothiazoles 2 also
decreased with carbon length of alkoxy chains; i.e. Tcl = 136.6 (n = 8) > 136.2 (n = 10) > 135.9 (n =
12) > 129.4 (n = 14) > 125.4 C (n = 16), which were relatively higher than those of benzoxazoles 1
by an Tcl = 43.5 (n = 8) > 39.1 (n = 10) > 38.3 (n = 12) 31.7 (n = 14) > 26.0 C (n = 16). In
addition, the temperature range of mesophases also decreased with carbon length; i.e. Tmeso = 65.6
(n = 8) > 62.0 (n = 10) > 57.1 (n = 12) > 48.9 (n = 14) > 41.6 C (n = 16) C on the cooling process.
All benzoxazole 2 formed N or/and SmC phase; the derivatives with n = 8 formed N phases, and all
other derivatives (n = 10, 12, 14, 16) exhibited SmC phase. The mesophases were also characterized
and identified as N and SmC phases by POM; they showed identical textures as compounds 1; a
Schlieren and focalconic texture for N and SmC phases was observed when cooled from their
isotropic states (Fig. 6). The N or SmA phase, but not SmC phase showed homeotropic behavior
under polarized microscope. Also, the Schlieren textures observed by SmC phases gave only
singularities with four brushes while N phases showed extra singularities with two brushes. The
much wider temperature of mesophase by benzothiazoles 2 was probably attributed to the
polarization effect caused by sulfur atom incorporated.
In general, the overall geometries of the complexes are determined or controlled by both the
central metal and the organic moiety; a more bulky or steric core might reduce the preferred
molecular packing in the solid or LC states. This is particularly true in the design of the
metallomesogenic materials when metal was tetrahedral copper, cobalt or zinc ions. However, many
such tetrahedral metal complexes and borondifluoride in this work were demonstrated to be
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mesogens when ligands properly designed. Furthermore, the relatively smaller BF2 moiety might
provide a preferred dipole to induce the mesophases. Upon complexation to BF2 moiety, three
complexes 2-BF2 (n = 8, 10, 12) formed enantiotropic N or/and SmC phases. All clearing
temperatures were slightly higher than those of compounds 2 by an Tcl = 1.1 (n = 8) < 6.7 (n = 10)
< 10.9 C (n = 12). The results that a slightly increasing in the clearing temperatures and also
forming the mesophase were probably attributed to the relatively small steric effect caused by the
tetrahedral BF2 moiety. The temperature range of mesophases increased with carbon length; Tmeso
= 35.9 (n = 8) > 44.4 (n = 10) > 49.0 C C (n = 12) on the cooling process. The mesophase was
identified and characterized as N and SmC phases by POM and XRD experiments. The mesophases
were identified and characterized as SmC phase first based on POM. Bar graph showing the phase
behavior of compounds 1ac was shown in Fig. 7.
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Fig. 6 Optical textures observed. (a) N phase by 1 (n = 10) at 92.0 C; (b) SmC phase by 1 (n = 10)
at 87.0 C; (c) N phase by 2 (n = 8) at 130.0 C; (d) SmC phase by 2 (n = 8) at 125.0 C; (e) N phase
by 2-BF2 (n = 8) at 136.0 C and (f) SmC phase by 2-BF2 (n = 8) at 122.0 C. All temperatures were
taken on cooling process from their isotropic.
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Fig. 7 Bar graphs showing the phase behavior of compounds 1, 2 and 2-BF2.
2.4 Powder Xray diffractions
Variable-temperature powder XRD diffraction experiments were performed to confirm the
structures of the mesophases. Fig. 8 shows typical diffraction plots for one derivative 2 (n = 8) and
its boron complex 2-BF2 (n = 8). Both compounds formed similar mesomorphic behavior; SmC
phase at lower temperature and N phase at higher temperature due to their similar structures. For
compound 2 (n = 8) a strong diffraction with a dspacing of ca. d = 29.04 Å at 138 C and d = 27.13
Å at 125 C was obtained. A relatively broad and weak peak at 29.04 Å corresponded to N phase;
while a sharp and strong at 27.13 Å corresponded to the SmC phase (Table 8). In N phase the long
molecular axes of the individual molecules lie essentially parallel to one another. These dspacings
were slightly larger than those of value (i.e. 33.03 Å at 150 K) observed from crystallographic data.
The long axes of the molecules in SmC phase are tilted with respect to the planes of the layers. The
optical character is positive biaxial. The much smaller d-spacing indicated that the molecules were
tilted or/and the terminal alkoxy chains were to some extent interdigitated in SmC phase.
Furthermore, a very broad and weak peak at 4.53  4.63 Å was observed, and this peak was assigned
to the molten alkoxy chains. In contrast, for the compound 2-BF2 (n = 8), a similar XRD plots were
observed. a strong diffraction with a dspacing of ca. d = 24.87 Å at 135 C and d = 24.12 Å at 114
C was obtained. These peaks corresponded to N and SmC phase. Also a very broad and weak peak
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at 4.50  4.55 Å was observed, and this peak was assigned to the molten alkoxy chains. A schematic
representation of molecular organization proposed in SmA phase by compounds 2 and 2BF2 is
shown in Fig. 9 and Fig. 10.
(a)
(b)
(c)
(d)
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Fig. 8 The powder Xray diffraction plots. (a) Compound 2 (n = 8) at 138 C; (b) compound 2
(n = 8) at 125 C; (c) compound 2-BF2 (n = 8) at 135 C and (d) compound 2-BF2 (n = 8) at 114 C.
Table 7
The powder Xray diffraction data for compounds 1-2 and 2-BF2.
Compds.
Mesophase/temp.a
dSpacing/Å
MLb
Index
halo
1 (n = 8)
N phase at 100 C
29.67 (29.67)
4.53 (br)
33.09
1 (n = 10)
1 (n = 12)
1 (n = 14)
N phase at 95 C
32.83 (32.83)
4.50 (br)
35.34 (35.34)
4.52 (br)
37.80 (37.80)
19.06 (18.90)
4.48 (br)
38.11
43.05
48.37
halo
001
halo
001
002
halo
SmC phase at 105 C
SmC phase at 106 C
2 (n = 8)
N phase at 138 C
29.04 (29.04)
4.63 (br)
halo
001
halo
001
halo
001
002
halo
001
002
halo
001
002
halo
SmC phase at 125 C
SmC phase at 130 C
SmC phase at 100 C
27.13 (27.13)
4.53 (br)
30.54 (30.54)
4.51 (br)
34.11 (34.11)
17.11 (17.06)
4.53 (br)
37.64 (37.64)
19.06 (18.82)
4.63 (br)
33.03
38.31
43.27
2 (n = 10)
2 (n = 12)
2 (n = 14)
SmC phase at 125 C
SmC phase at 135 C
N phase at 135 C
48.24
53.21

2 (n = 16)
39.92 (39.92)
19.93 (19.96)
4.59 (br)
2-BF2 (n = 8)
24.87 (24.87)
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4.55 (br)
24.12 (24.12)
4.50 (br)
halo
001
halo
SmC phase at 114 C
a: Sample was heated above the clearing temperature and the diffraction data recorded on
cooling process.
b: Molecular lengths were calculated by MM2 model.
Fig. 9. The molecular arrangements proposed for compound 2 (n = 8) in Cr, N and SmC phases. The
molecular length of 33.03 Å obtained from crystallographic data was correlated with the d-spacing
of 29.04 Å in N phase and the d-spacing of 27.13 Å in SmC phase.
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Fig. 10. The molecular arrangements proposed for boron complex 2-BF2 (n = 8) in Cr, N and SmC
phases. The molecular length of 33.03 Å obtained from crystallographic data was correlated with the
d-spacing of 24.87 Å in N phase and the d-spacing of 24.12 Å in SmC phase.
2.5 Optical properties
Photophysical behavior of few representative compounds 12 and 2-BF2 (all n = 10, 12)
dissolved in CH2Cl2 solution at room temperature are presented in Fig. 11. The max peaks of
UVvis absorptions and PL spectra for these compounds were listed in Table 8. Both UVvis
absorptions and PL emission spectra were insensitive to the carbon number of terminal alkoxy
chains. The PL spectra were excited at 393 (for 1), 394 (for 2) and 420 nm (for 2-BF2). On the
UVvis spectra, a strong broad absorption peak at 393394 nm was observed for compounds 1 and
2, which were attributed to * transitions arising from heterocyclic ring. The two UV spectra
profiles for complexes 1 and 2 were almost identical due to their similar structures. For the HBO and
HBT, an absorption at 320 and 332 nm, and an emission peak at 500 and 530 nm (see Table 8) was
observed; the large Stocks shift was attributed to the ESIPT. In contrast, the absorption max peaks of
complexes 2BF2 (n = 10, 12) were slightly redshifted to 420 nm; a redshift of max = 2627 nm
from those of chelating ligands 1-2 might be caused by an intramolecular electron delocalization,
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leading to an extendedconjugation skeleton.
On the other hand, the PL spectra for complexes 2-BF2 were also similar in emission peak profiles;
showing one broad peak located at max = 569571 nm. A Stokes shift of  = 6.26.3 /103 cm-1,
similar to those of free ligands 1-2 ( = 6.2 /103 cm-1) was obtained for boron complexes. These
two boron complexes 2-BF2 showed a redshift emission when compared to all other similar boron
complexes listed in the Table 8. This might be due to their longer molecular conjugation length.
These boron complexes adopted a typical DπA structure, in which terminal alkoxyphenyl group
acted as the electron donor (D) and the borondifluoride moiety was as the acceptor (A).
Furthermore, the PL data indicated that the photoluminescent emissions of boron difluoride
complexes were quite sensitive to the molecular structures; i.e. λmax = 571 (2-BF2; n = 12) > 541
(III; X = H) > 491 (III; X = Me) > 476 (II) > 433 (HBT-BF2) > 408 (HBO-BF2) > 368 nm (I). Part
of the wavelength shift in PL emissions was attributed to the conjugation length. The max of PL
emissions were slightly redshifted to 598 and 602 nm for two boron complexes (2-BF2, n = 10, 12).
However, the overall molecular planarity also played an important factor from our previous xray
crystallographic analysis of few boron difluoride complexes. A higher fluorescence quantum yield
(ΦF = 0.440.47) of boron complexes than those of free ligands (ΦF = 0.0270.045) determined with
anthracene (ΦF = 0.27 in hexane solution) as a reference dye was obtained for all three BF2
complexes.
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Fig. 11 UVvis absorbance (top) and emission spectra in the CH2Cl2 solution (bottom) of the
compounds 1-2 (n = 10, 12) and 2-BF2 (n = 10, 12) at room temperature.
Table 8
Absorption and PL emission dataa of compounds 1-2 and 2-BF2.
b
Compds.
Abs/nm
em/nm
Stokes shift
( / 103 cm-1)
ΦF
HBOc,d
HBO-BF2
HBTc
HBT-BF2
I
II
III (X = H)
III (X = Me)
1 (n = 10)
1 (n = 12)
2 (n = 10)
2 (n = 12)
2-BF2 (n = 10)
2-BF2 (n = 12)
320
344
332
364
351
368
393
360
393 (26800)
393 (29300)
394 (34900)
394 (35700)
420 (27600)
420 (27700)
500
408
530
433
368
476
541
491
520
521
519
520
569/598e
571/602e
11.5
4.6
11.2
4.4
1.3
6.2
6.9
7.4
6.2
6.2
6.2
6.2
6.2
6.3
0.02
0.20
0.006
0.23




0.027
0.030
0.045
0.043
0.445
0.473
a: samples were measured in CH2Cl2 solution (10-5 M) at rt. The samples were excited at 393 nm
for 1, 394 nm for 2 and 420 nm for 2-BF2.
b: the standard is anthracene (ΦF = 0.27 in hexane solution).
c: HBO and HBT is 2-(2'-hydroxyphenyl)benzoxazole and 2-(2-hydroxyphenyl)benzothiazole.
d: see ref.: R. Daengngern, N. Kungwan, J. of Lumi, 167 (2015) 132-139.
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e: max for powder sample.
3. Conclusions
Two series of benzo(thia)xazoles 1-2 and one series of borondifluoride complexes 2-BF2 derived
from benzothiazoles 2 were reported, and their mesomorphic and optical properties were
investigated. The correlation between the crystal and molecular structures of compounds 2 and 2-
BF2 (all n = 8) and the formation of mesophase in such system was demonstrated. Boron complexes
2-BF2 formed N or/and SmC phase. Boron complexes 2-BF2 emitted a yellowtogreen emission at

max = 569571 nm in CH2Cl2, redshifted by 5052 nm from benzothiazoles 2. The better
polarization inherent from sulfur atom incorporated was attributed to the improved mesomorphic
and luminescent behavior. To our best knowledge, this is the first mesogenic BF2 complexes derived
from benzothiazoles.
4. Experimental
4.1 Techniques
All chemicals and solvents were reagent grade from Aldrich Chemical Co., and solvents were
dried by standard techniques. 1H and 13C NMR spectra were measured on a Bruker DRS500. 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 analyses were performed on a Heraeus CHNRapid elemental analyzer. The powder
diffraction data were collected from the Wiggle A beam line of the National Synchrotron Radiation
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Research Center (NSRRC) with a wavelength of 1.3223 Å. The powder samples were charged in
Lindeman capillary tubes (80 mm long x 0.01 mm thick) purchased from Charles Supper Co. with
an inner diameter of 1.0 mm.
4.2 materials
The compounds of 3-alkoxyphenols, 5-alkoxy-2-nitrophenols, 2-amino-5-alkoxy phenols, 4-
alkoxy-2-hydroxybenzaldehydes, 1-alkoxy-4-nitrobenzenes, 4-alkoxybenzeneamines, 5-alkoxy-2-
nitro phenols and 4-alkoxy-2-hydroxybenzaldehydes were similarly prepared by literature's
procedures.
4.2 6-(Dodecyloxy)benzo[d]oxazol-2-amine 3 (n = 12)
A solution of 2-amino-5-(dodecyloxy)phenol (2.00 g, 6.82 mmol) dissolved in 100 mL methanol
was added cyanogen bromide (5.49 g, 51.83 mmol). The solution was stirred at room temperature
for 4 days, and then a saturated NaHCO3 solution was slowly added to quench the reaction. The
mixture was concentrated by rotary evaporation and the mixture was extracted twice with 50 mL of
ethyl acetate/H2O (1/2). Organic layers were collected and dried over MgSO4. The solution was
concentrated under vacuum, and the products isolated as yellow solids were purified by column
chromatography eluting with ethyl acetate/hexane (4/1). Yield 70%. 1H NMR (300 MHz ,
d6DMSO): δ 0.85 (t, 3H, CH3, J = 6.30 Hz), 1.241.40 (m, 18H, CH2), 1.631.72 (m, 2H,
CH2), 3.91 (t, 2H, OCH2, J = 6.30 Hz), 6.67 (dd, 1H, ArH, 3J = 8.41 Hz, 4J = 2.40 Hz), 6.98 (d,
1H, ArH, J = 2.40 Hz), 7.05 (d, 1H, ArH, J = 8.41 Hz), 7.13 (s, 2H, ArNH2). 13C NMR (75
MHz, d6DMSO) δ 13.95, 22.12, 25.57, 28.75, 28.81, 29.04, 31.33, 68.24, 96.25, 110.23, 114.96,
136.92, 148.45, 153.56, 162.13.
4.3 (E)-5-(Dodecyloxy)-2-(((6-(dodecyloxy)benzo[d]oxazol-2-yl)imino)methyl)phenol 1 (n = 12)
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A solution of 6-(dodecyloxy)benzo[d]oxazol-2-amine (0.50 g, 1.57 mmol) dissolved in 40 mL
absolute ethyl alcohol was added 4-(dodecyloxy)-2-hydroxybenzaldehyde (0.48 g, 1.57 mmol). The
solution was refluxed for 8 h. The solution was cooled to room temperature, and the yellow solids
were filtered and collected. The products isolated as yellow powder were obtained by
recrystallization from THF/MeOH. Yield 78%; mp 81.5 C. 1H NMR (300 MHz, CDCl3): δ 0.86 (t,
6H, CH3, J = 6.30 Hz), 1.251.46 (m, 36H, CH2), 1.761.82 (m, 4H, CH2), 3.964.02 (m, 4H,
OCH2), 6.496.54 (m, 2H, ArH), 6.90 (dd, 1H, ArH, 3J = 8.71, 4J = 2.40 Hz), 7.00 (d, 1H,
ArH, J = 2.40 Hz), 7.34 (d, 1H, ArH, J = 8.41 Hz), 7.51 (d, 1H, ArH, J = 8.71 Hz), 9.22 (s, 1H,
CH=N), 12.60 (s, 1H, ArOH). 13C NMR (75 MHz , CDCl3): δ 14.05, 22.64, 25.90, 26.02, 28.94,
29.21, 29.30, 29.35, 29.54, 29.60, 31.88, 68.57, 68.91, 96.11, 101.51, 109.21, 112.47, 113.22,
119.49, 135.36, 135.52, 150.55, 157.56, 161.55, 164.94, 165.82, 167.33. MS (HRFAB, m/z): calcd
for [M+H]+: 606.4400. Found: 606.4389. Calcd for C38H58N2O4: C, 75.21; H, 9.69; N, 4.62; Found:
C, 74.82; H, 9.69; N, 4.55.
4.4 (E)-5-(Octyloxy)-2-((6-(octyloxy)benzo[d]oxazol-2-ylimino)methyl)phenol 1 (n = 8)
Yellow powder; yield 78%; mp 66.5 C. 1H NMR (300 MHz , CDCl3): δ 0.87 (t, 6H, CH3, J =
6.00 Hz), 1.271.46 (m, 20H, CH2), 1.741.82 (m, 4H, CH2), 3.964.02 (m, 4H, OCH2,),
6.496.54 (m, 2H, ArH), 6.90 (dd, 1H, ArH, 3J = 8.71, 4J = 2.40 Hz), 7.00 (d, 1H, ArH, J = 2.40
Hz), 7.34 (d, 1H, ArH, J = 8.41 Hz), 7.51 (d, 1H, ArH, J = 8.71 Hz), 9.22 (s, 1H, CH=N), 12.60
(s, 1H, ArOH). 13C NMR (75 MHz , CDCl3): δ 14.07, 22.64, 25.94, 26.06, 28.97, 29.24, 29.36,
31.80, 68.61, 68.94, 96.14, 101.55, 109.25, 112.51, 113.26, 119.53, 135.39, 135.56, 150.59, 157.59,
161.58, 164.97, 165.86, 167.37. MS (HRFAB, m/z): calcd for [M+H]+: 494.3100. Found: 494.3140.
Calcd for C30H42N2O4: C, 72.84; H, 8.53; N, 5.58; Found: C, 72.45; H, 8.53; N, 5.58.
4.5 (E)-5-(Decyloxy)-2-((6-(decyloxy)benzo[d]oxazol-2-ylimino)methyl)phenol 1 (n= 10)
Yellow powder; yield 82%; mp 70.6 C. 1H NMR (300 MHz , CDCl3): δ 0.86 (t, 6H, CH3, J =
6.30 Hz), 1.261.46 (m, 28H, CH2), 1.761.82 (m, 4H, CH2), 3.964.02 (m, 4H, OCH2),
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6.496.54 (m, 2H, ArH), 6.90 (dd, 1H, ArH, 3J = 8.71, 4J = 2.40 Hz), 7.00 (d, 1H, ArH, J = 2.10
Hz), 7.44 (d, 1H, ArH, J = 8.71 Hz), 7.51 (d, 1H, ArH, J = 8.71 Hz), 9.21 (s, 1H, CH=N), 12.60
(s, 1H, ArOH). 13C NMR (75 MHz , CDCl3): δ 14.07, 22.66, 25.93, 26.04, 28.96, 29.23, 29.29,
29.38, 29.53, 31.88, 68.60, 68.93, 96.13, 101.54, 109.23, 112.50, 113.25, 119.51, 135.38, 135.55,
150.58, 157.58, 161.57, 164.96, 165.85, 167.36. MS (HRFAB, m/z): calcd for [M+H]+: 550.3800.
Found: 550.3763. Calcd for C34H50N2O4: C, 74.14; H, 9.15; N, 5.08; Found: C, 73.96; H, 9.221; N,
5.01.
4.6 (E)-5-(Tetradecyloxy)-2-((6-(tetradecyloxy)benzo[d]oxazol-2-ylimino)methyl)phenol 1 (n = 14)
Yellow powder; yield 81%; mp 86.7 C. 1H NMR (300 MHz , CDCl3): δ 0.86 (t, 6H, CH3, J =
6.60 Hz), 1.251.46 (m, 44H, CH2), 1.771.81 (m, 4H, CH2), 3.964.03 (m, 4H, OCH2),
6.496.54 (m, 2H, ArH), 6.91 (dd, 1H, ArH, 3J = 8.71, 4J = 2.40 Hz), 7.01 (d, 1H, ArH, J = 2.40
Hz), 7.34 (d, 1H, ArH, J = 8.71 Hz), 7.51 (d, 1H, ArH, J = 8.71 Hz), 9.22 (s, 1H, CH=N), 12.60
(s, 1H, ArOH). 13C NMR (75 MHz , CDCl3): δ 14.09, 22.68, 25.94, 26.05, 28.97, 29.25, 29.34,
29.58, 29.66, 31.92, 68.61, 68.95, 96.16, 101.56, 109.25, 112.52, 113.27, 119.53, 135.40, 135.56,
150.59, 157.60, 161.60, 164.98, 165.87, 167.38. MS (HRFAB, m/z): calcd for [M+H]+: 662.5000.
Found: 662.5024. Calcd for C42H66N2O4: C, 76.09; H, 10.03; N, 4.23; Found: C, 75.90; H, 9.99; N,
4.21.
4.7 (E)-5-(Hexadecyloxy)-2-((6-(hexadecyloxy)benzo[d]oxazol-2-ylimino)methyl)phenol 1 (n = 16)
Yellow powder; yield 82%; mp 89.6 C. 1H NMR (300 MHz , CDCl3): δ 0.86 (t, 6H, CH3, J =
6.30 Hz), 1.241.46 (m, 52H, CH2), 1.761.82 (m, 4H, CH2), 3.964.03 (m, 4H, OCH2),
6.496.54 (m, 2H, ArH), 6.90 (dd, 1H, ArH, 3J = 8.71, 4J = 2.40 Hz), 7.01 (d, 1H, ArH, J = 2.40
Hz), 7.34 (d, 1H, ArH, J = 8.41 Hz), 7.51 (d, 1H, ArH, J = 8.71 Hz), 9.22 (s, 1H, CH=N), 12.60
(s, 1H, ArOH). 13C NMR (75 MHz , CDCl3): δ 14.10, 2.68, 25.95, 26.04, 28.92, 29.00, 29.35,
29.58, 29.68, 30.33, 31.92, 68.53, 68.75, 101.09, 101.50, 105.23, 108.78, 108.96, 112.35, 116.15,
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123.27, 135.20, 157.16, 164.47, 165.14, 165.37, 167.15. MS (HRFAB, m/z): calcd for [M+H]+:
718.5600. Found: 718.5653. Calcd for C46H74N2O4: C, 76.83; H, 10.37; N, 3.90; Found: C, 76.77; H,
10.20; N, 3.89.
4.8 6-(Dodecyloxy)benzo[d]thiazol-2-amine 4 (n = 12)
The 2-amino-6-substituted benzothiazoles were prepared by mixing 4-(dodecyloxy)benzenamine
(10.00 g, 36.04 mmol) and potassium thiocyanate (7.01 g, 72.08 mmol) in 50 ml of 96% acetic acid.
To this was added drop wise, with stirring, a solution of Br2 (1.86 mL, 36.04 mmol) in 25 ml of
glacial acetic acid. After all the bromine solution was added, the mixture was stirred for another 24 h
at room temperature, and NH4OH solution was slowly added to quench the reaction. The mixture
was concentrated by rotary evaporation and the mixture was extracted twice with 80 mL ethyl
acetate/H2O (1/2). Organic layers were collected and dried over MgSO4. The solution was
concentrated under vacuum, and the products isolated as yellow solids were purified by column
chromatography eluting with ethyl acetate/hexane (4/1). Yield 40%. 1H NMR (300 MHz,
d6DMSO): δ 0.85 (t, 3H, CH3, J = 5.70 Hz), 1.241.39 (m, 18H, CH2), 1.641.70 (m, 2H,
CH2), 3.91 (t, 2H, OCH2, J = 6.30 Hz), 6.78 (dd, 1H, ArH, 3J = 8.71, 4J = 2.40 Hz), 7.187.22
(m, 3H, ArH, ArNH2), 7.26 (d, 1H, ArH, J = 2.40 Hz). 13C NMR (75 MHz, d6DMSO): δ 13.92,
22.09, 25.52, 28.71, 28.76, 29.00, 31.29, 67.96, 106.18, 113.35, 117.99, 131.84, 146.75, 153.61,
164.65.
4.9 (E)-5-(Dodecyloxy)-2-(((6-(dodecyloxy)benzo[d]thiazol-2-yl)imino)methyl)phenol 2 (n = 12)
A solution of 6-(dodecyloxy)benzo[d]thiazol-2-amine (0.50 g, 1.49 mmol) dissolved in 30 mL
absolute ethyl alcohol added 4-(dodecyloxy)-2-hydroxybenzaldehyde (0.46 g, 1.49 mmol). The
solution was refluxed for 8 h. The solution was cooled to room temperature, and the yellow solids
were filtered and collected. The products isolated as yellow powder were obtained by
recrystallization from THF/MeOH. Yield 80%; mp 89.2 C. 1H NMR (300 MHz , CDCl3): δ 0.86 (t,
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6H, CH3, J = 6.30 Hz), 1.251.46 (m, 36H, CH2), 1.751.82 (m, 4H, CH2), 3.99 (t, 4H, OCH2,
J = 6.60 Hz), 6.496.53 (m, 2H, ArH), 7.04 (dd, 1H, ArH, 3J = 8.71, 4J = 2.40 Hz), 7.25 (d, 1H,
ArH, J = 2.40 Hz), 7.33 (d, 1H, ArH, J = 8.71 Hz), 7.79 (d, 1H, ArH, J = 9.01 Hz), 9.04 (s, 1H,
CH=N), 12.63 (s, 1H, ArOH). 13C NMR (75 MHz , CDCl3): δ 14.12, 22.70, 25.95, 26.05, 28.99,
29.25, 29.35, 29.60, 29.65, 31.92, 68.53, 68.72, 101.47, 105.18, 108.97, 110.57, 112.31, 116.14,
123.26, 135.21, 135.48, 157.13, 164.45, 165.14, 165.35, 167.14. MS (HRFAB, m/z): calcd for
[M+H]+: 622.4200. Found: 622.4166. Calcd for C38H58N2O3S: C, 73.27; H, 9.38; N, 4.50; S, 5.15;
Found: C, 73.15; H, 9.49; N, 4.44; S, 5.20.
4.10 (E)-5-(Octyloxy)-2-(((6-(octyloxy)benzo[d]thiazol-2-yl)imino)methyl)phenol 2 (n = 8)
Yellow powder; yield 82%; mp 78.4 C. 1H NMR (300 MHz , CDCl3): δ 0.87 (t, 6H, CH3, J =
6.90 Hz), 1.271.45 (m, 20H, CH2), 1.731.84 (m, 4H, CH2), 3.98 (t, 4H, OCH2, J = 6.60 Hz),
6.486.52 (m, 2H, ArH), 7.03 (dd, 1H, ArH, 3J = 8.71, 4J = 2.40 Hz), 7.33 (d, 1H, ArH, J = 8.71
Hz), 7.78 (d, 1H, ArH, J = 8.71 Hz), 9.02 (s, 1H, CH=N), 12.63 (s, 1H, ArOH). 13C NMR (75
MHz, CDCl3): δ 14.12, 22.68, 25.97, 26.07, 29.01, 29.26, 29.31, 29.37, 31.73, 68.53, 68.71, 101.46,
105.16, 108.96, 112.31, 116.14, 123.26, 135.21, 135.47, 145.78, 157.13, 164.45, 165.13, 165.35,
167.13. MS (HRFAB, m/z): calcd for [M+H]+: 510.2900. Found: 510.2919. Calcd for C30H42N2O3S:
C, 70.55; H, 8.29; N, 5.48; S, 6.28; Found: C, 70.49; H, 8.28; N, 5.49; S, 6.36.
4.11 (E)-5-(Decyloxy)-2-(((6-(decyloxy)benzo[d]thiazol-2-yl)imino)methyl)phenol 2 (n = 10)
Yellow powder; yield 81%; mp 87.1 C. 1H NMR (300 MHz , CDCl3): δ 0.86 (t, 6H, CH3, J =
6.90 Hz), 1.251.45 (m, 28H, CH2), 1.731.82 (m, 4H, CH2), 3.98 (t, 4H, OCH2, J = 6.60 Hz),
6.486.52 (m, 2H, ArH), 7.03 (dd, 1H, ArH, 3J = 9.01, 4J = 2.40 Hz), 7.33 (d, 1H, ArH, J = 8.41
Hz), 7.78 (d, 1H, ArH, J = 9.01 Hz), 9.02 (s, 1H, CH=N), 12.63 (s, 1H, ArOH). 13C NMR (75
MHz , CDCl3): δ 14.15, 22.70, 25.96, 26.06, 29.00, 29.26, 29.34, 29.41, 29.57, 31.91, 68.53, 68.70,
101.45, 105.14, 108.98, 112.30, 116.15, 123.26, 135.22, 135.47, 145.76, 157.13, 164.44, 165.14,
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