Luminescent mesogenic borondifluoride complexes with the Schiff bases containing salicylideneamines and β-enaminoketones core systems

Article abstract of DOI:10.1016/j.molliq.2018.03.047

Three new families of borondifluoride complexes 1a–c derived from salicylideneamines 2a and β-enaminoketonates 2b–c were reported, and their mesomorphic and optical properties were also investigated. One single crystal and molecular structure of nonmesogenic BF₂ complex 1c (n = 10) was resolved and the geometry of the central boron atom was tetrahedron. A larger dihedral angle of 81.3° between the two phenyl rings observed in crystal lattice was attributed to the lack of liquid crystallinity. Boron complexes 1a formed monotropic SmA phases, while boron complexes 1b exhibited enantiotropic SmC mesophases. The optical property of the boron complexes was dependent on their molecular structures, and they emitted a blue–to–green emission at λ_max = 476–541 nm in the solution and 488–550 nm in the solid state. This is the first group of mesogenic BF₂ complexes with the Schiff bases derived from respective salicylideneamines and β-enaminoketones.

Full text of DOI:10.1016/j.molliq.2018.03.047

Accepted Manuscript
Luminescent mesogenic borondifluoride complexes with the
Schiff bases containing salicylideneamines and β-enaminoketones
core systems
Zih-Yang Lei, Gene-Hsiang Lee, Chung K. Lai
PII:
DOI:
Reference:
S0167-7322(18)30080-1
doi:10.1016/j.molliq.2018.03.047
MOLLIQ 8821
To appear in:
Journal of Molecular Liquids
Received date:
Revised date:
Accepted date:
6 January 2018
10 March 2018
13 March 2018
Please cite this article as: Zih-Yang Lei, Gene-Hsiang Lee, Chung K. Lai , Luminescent
mesogenic borondifluoride complexes with the Schiff bases containing salicylideneamines
and β-enaminoketones core systems. The address for the corresponding author was
captured as affiliation for all authors. Please check if appropriate. Molliq(2018),
doi:10.1016/j.molliq.2018.03.047
This is a PDF file of an unedited manuscript that has been accepted for publication. As
a service to our customers we are providing this early version of the manuscript. The
manuscript will undergo copyediting, typesetting, and review of the resulting proof before
it is published in its final form. Please note that during the production process errors may
be discovered which could affect the content, and all legal disclaimers that apply to the
journal pertain.

ACCEPTED MANUSCRIPT
Luminescent Mesogenic Borondifluoride Complexes with the Schiff
bases Containing Salicylideneamines and β-Enaminoketones Core
Systems†
ZihYang Lei1, GeneHsiang Lee2, Chung K. Lai*1
1Department of Chemistry, National Central University, ChungLi 32011, Taiwan, ROC
2Instrumentation Center, National Taiwan University, Taipei 10660, Taiwan, ROC
*Corresponding auther e-mail: cklai@cc.ncu.edu.tw
Abstract: Three new families of borondifluoride complexes 1ac derived from salicylideneamines
2a and -enaminoketonates 2bc were reported, and their mesomorphic and optical properties were
also investigated. One single crystal and molecular structure of nonmesogenic BF2 complex 1c (n =
10) was resolved and the geometry of the central boron atom was tetrahedron. A larger dihedral
angle of 81.3 between the two phenyl rings observed in crystal lattice was attributed to the lack of
liquid crystallinity. Boron complexes 1a formed monotropic SmA phases, while boron complexes 1b
exhibited enantiotropic SmC mesophases. The optical property of the boron complexes was
dependent on their molecular structures, and they emitted a bluetogreen emission at max = 476
541 nm in the solution and 488550 nm in the solid state. This is the first group of mesogenic BF2
complexes with the Schiff bases derived from respective salicylideneamines and β-enaminoketones.
Keywords: smectic phases; borondifluoride; luminescent; salicylideneamines, enaminoketones
1

ACCEPTED MANUSCRIPT
1. Introduction
Borondifluoride (BF2) complexes have been intensively investigated to explore their applications as
potential materials used in diverse research fields during the past decades. Useful photophysical
properties such as fluorescence [111], fieldeffect transistors [12], OLED/laser dyes [13],
photosensitizers [14], solar cells [15] were obtained through structural modification. Three types of
coordination modes; [O, O] [1618], [N, O] [1922] and [N, N] [2326] were long known and
these BF2 complexes were often derived from a variety of chelating ligands, such as ,
–diketonates [2732], diketiminates [3334], formazanates [3539], and quinolineβketones
[40]. The BF2 complexes were generally prepared by the reactions of boron trifluoride with
appropriate ligands in the presence of weak bases (i.e. triethylamine). For the purpose of use in the
solidstate applications, the rigid –conjugated molecular structures could facilitate intense
luminescence, good thermal stability and high carrier mobility. A larger amount of fluorescent
materials was concentrated on structures with the BF2 moiety containing N, N’ or O, Nchelating
ligands. Among them, those with dipyrrin ligands, commonly known as BODIPYs [4144] were the
most popular studied systems. Boron has an oxidation state of three (OS = +3) and a coordination
number of three or four (CN = 3 or 4). The central geometry of boron atom was often found as a
tetrahedron.
A wellbalanced molecular interaction in preconstructed structures is crucially essential to the
formation of a specific arrangement in order to generate potential materials with cooperative
properties. This is particularly important in the design of mesogenic materials. Too strong or too
weak an interaction force often resulted in the formation of a solid or liquid state. However, such a
force balance seemed to be unpredictable and remained challenging. On the other hand, a systematic
study of the structure–property relationship in a particular system becomes necessary and effective.
Schiff bases, for example, salicylideneamines and enaminoketones were probably the most
studied among the most known mesogens due to their known chemistry and versatile structures. The
imine C=N moiety not only plays a role of linking group, but also carries a dipole moment, which
2

ACCEPTED MANUSCRIPT
can enhance the thermal stability of mesophases. In addition, a better core planarity of both
derivatives formed by intramolecular Hbonds also facilitated a more ordered or preferred
arrangement in mesogenic states. On the other hand, numerous metallomesogens with a variety of
novel structures or/and geometries derived from such two types of Schiff bases were also prepared
and their mesomorphic properties studied during the past decades. Almost every one of the first row
transition metals were know to form metallomesogens. Known examples of mesogenic BF2
complexes were relatively rare, and they were mostly derived from diketonate [4548],
triketonate [49], BODIPY [50], However, mesogenic BF2 complex from salicylaldimines and
enaminoketones has not been reported yet. Recently, the synthesis, mesomorphic and photophysical
properties of BF2 complexes of benzoxazoles I [51] and tetraketonates II [52] were reported by
this group. Single crystallographic analysis also demonstrated that the Hbonds and steric
interaction near to BF2 center was very sensitive to the formation of mesophases in such system. In
this work, the preparation, mesomorphic behavior and their optical properties of a few series of
mesogenic BF2 complex 1ab derived from Schiff bases, salicylaldimines 2a and
enaminoketones 2b were reported. To test the steric hindrance on the formation of the
mesomorphic behavior and their photophysical properties, complexes 1c with a methyl moiety
incorporated to the proximity of core center were also studied. This is the first mesogenic BF2
complexes derived from salicylaldimines and enaminoketones. The steric sensitivity by a
tetrahedral methyl group was also illustrated by its single crystallographic analysis.
2. Results and Discussion
2.1 Synthesis and Characterization
3

ACCEPTED MANUSCRIPT
The synthetic pathways to borondifluoride complexes 1ac are summarized in Scheme 1. The
experimental preparations of compounds 2 were followed by our previous procedures. These Schiff
base derivatives were characterized by 1H and 13C NMR spectroscopy. Schiff bases can potentially
exist possibly in several different keto–enol tautomeric forms [5354]. The 1H NMR data in CDCl3,
showed three characteristic peaks assigned to olefinic methineH (CH=C), imineH (CH=N) and
amineH (CNH), summarized in Table 1. For example, boron complexes 1 were prepared by the
reactions of ligands 2ac and 5.0 equivalents of boron trifluoride diethyl etherate in refluxing
CH2Cl2 for 24 h under nitrogen atmosphere. The triethylamine was added as a base. Solvents such as
THF or CH3OH were not used in this synthetic work; these two solvents tended to destabilize or
decompose the final borondifluoride complexes for an unknown reason. Boron complexes 1 were
isolated as yellow powders. These boron complexes are very air stable and soluble in most organic
solvents. All boron complexes 1 were characterized by 1H NMR, 13C NMR and 19F NMR
spectroscopy. On the 1H NMR spectra, the original singlet assigned for phenolicOH of compounds
2a at  13.8913.91, amineNH of compounds 2b at 12.0812.09 and enolOH of compound 2c at
12.8012.81 were all disappeared upon coordination to BF2 moiety. On the 19F NMR spectra, a
doublet of doublets appeared at δ 135.40  135.44 (1a), δ 133.33  133.35 (1b) and δ 135.64
(1c) was observed. Elemental analysis and mass spectrometry were also used to confirm the purity
of the metal complexes.
4

ACCEPTED MANUSCRIPT
Table 1. The characteristic chemical peaksa on 1H NMR spectroscopes for compounds 12.
Compd.
2a
2b
2c
1a
1b
1c
CH=C
=CHNH
CH=N


8.48

5.91
5.80




8.19

6.18
7.79

6.08


7.377.38b


CH3C=N
2.03

2.03
5

ACCEPTED MANUSCRIPT
CNH


12.0812.09b









COH (enol)
12.8012.81b



COH (phenolic) 13.8913.91b
a samples measured in CDCl3. Unit () in ppm.
b a range of chemical shifts represented value observed by different derivatives with alkoxy chain.
2.2 Single structure and molecular structures of BF2 complex of (1Z,3E)-1-(4-(decyloxy)
phenyl)-3-((4-(decyloxy)phenyl)imino)but-1-en-1-ol 1c (n = 10)
A single crystal of the nonmesogenic complex 1c (n = 10) suitable for crystallographic analysis was
obtained by slow vaporization from CH2Cl2 at room temperature and their structures resolved.
Figure 1 shows its molecular structure with the atomic numbering scheme. Table 2 lists its
crystallographic and structural refinement data for the crystal. It crystallizes in an orthorhombic
space group Pbca with a Z = 8. The crystallographic data confirmed the expected coordination mode
of [O, N]BF2. The coordination geometry at core boron in crystal 1c can be described as tetrahedral
and the four angles around boron atom were in the range of ca. 108.12110.89, which were near to
109 for a perfect tetrahedron. The molecule was considered as linearshaped and the molecular
length was ca. 38.28 Å (C26C36 atom), shown in Figure 1. The two lengths for BF bonds were
approximately equal; i.e. B1F1 = 1.3756(17) Å and B1F2 = 1.3849(18) Å. On the other hand, the
lengths of BO and BN bonds were ranged in 1.4707 Å and 1.5559 Å. The overall molecule was in
fact not flat; a dihedral angle of 10.12 and 71.28 between the central boron plane and the left and
right phenyl rings was observed for the crystal (Figure 1). This large dihedral angle of 71.28 was
caused by the neighboring tetraherdal methyl group (C10). The length of N1C1 bond (i.e. = 1.3224
Å) was slightly longer than that of imineC=N bonds (i.e. 1.301 Å) typically found in uncoordinated
ligands, consistent with its lesser characteristic double bond. Some selected bond angles and bond
lengths are listed in Table 3.
6

ACCEPTED MANUSCRIPT
38.28 Å
Figure 1. Top plot: an ORTEP drawing for single crystal 1c (n = 10) with the numbering schemes,
and thermal ellipsoids of nonhydrogen atoms are drawn at the 50% probability level. Bottom plot:
The two dihedral angles of the crystal 1c (n = 10) between the central boron and neighboring phenyl
rings.
Table 2. Crystallographic data for single crystals 1c (n = 10).
Compds.
1c (n = 10)
Empirical formul
C36H54BF2NO3
597.61
Formula weight
Temperature (K)
200(2)
Crystal system
Orthorhombic
Pbca
Space group
a(Å)
15.8088(4)
7.0692(2)
62.3539(14)
90
b(Å)
c(Å)
α(o)
β(o)
90
γ(o)
90
Volume (Å3)
6968.4(3)
8
Z
Density (calculated, Mg/m3)
Crystal size (mm3)
Theta range for data collection (o)
Reflections collected
Independent reflections
Final R1, wR2
1.139 Mg/m
3
0.396 x 0.148 x 0.075
2.835 to 69.996
31221
6584 [R(int) = 0.0167]
0.0464, 0.2162
7

ACCEPTED MANUSCRIPT
Table 3. Selected bond lengths [Å] and angles [°] in crystal 1c (n = 10).
Bond distances
O(1)C(3)
B(1)O(1)
B(1)F(1)
1.3196(16)
1.4707(17)
1.3756(17)
N(1)C(3)
B(1)N(1)
B(1)F(2)
1.3224(17)
1.5559(17)
1.3849(18)
Bond angles
C(3)O(1)B(1)
O(1)B(1)F(1)
N(1)B(1)F(1)
O(1)B(1)N(1)
122.32(11)
108.12(11)
110.89(10)
109.63(10)
C(1)N(1)B(1)
O(1)B(1)F(2)
N(1)B(1)F(2)
120.49(10)
109.49(11)
108.32(11)
Not suprisingly, two weak intramolecular Hbonds were observed in the crystal lattice (shown in
Figure 2) and the distances were measured as ca. 2.422 Å (O1H9) and 2.860 Å (F1H12). In
addition, a few intermolecular Hbonds formed between OH and FH atom were also observed,
and the bond lengths were ranged in 2.2832.751 Å (Figure 3). Often this type of Hbonds might be
favorable in molecular arrangements. Not as expected [5558], the alkoxy chains were not
interdigated in a very complicated style of headtohead arrangements. These intermolecular FH
interactions were found to be crucial, faciliating molecules to better align in a style of headtohead
arrangements required for the formation of mesophases. In contrast, when viewed from the top, four
intermolecular σπ interactions existing between above and below layers were existent in crystal
lattices. These interaction were relatively weak and the distances were ranged in 3.0133.099 Å
(Figure 4 and Table 5).
Figure 2. Intramolecular Hbond interactions observed in 1c (n = 10)
8

ACCEPTED MANUSCRIPT
Figure 3. Intermolecular Hbond interactions observed in crystal 1c (n = 10).
Table 4. Hbonds observed in crystal 1c (n = 10)
Compds
No. of Hbonds
(CHO or F)
Bond distance/Å
Angles/
Intramolecular
Hbond
1
1
H9O1 = 2.422
H12F1 = 2.860
∠C9H9O1 = 99.56
∠C7H7F1 = 96.17
Intermolecular
Hbond
2
2
1
2
2
2
2
1
H8F2 = 2.283
H10CF1 = 2.599
H6O2 = 2.614
H10CO1 = 2.645
H17AF2 = 2.728
H17BF2 = 2.734
H17BF1 = 2.750
H13O3 = 2.751
∠C8H8F2 = 174.134
∠C10H10CF1 = 143.929
∠C6H6O2 = 141.964
∠C10H10CO1 = 132.304
∠C17H17AF2 = 108.760
∠C17H17BF2 = 108.348
∠C17H17BF1 = 156.964
∠C13H13O3 = 155.604
Figure 4. Intermolecular σπ interactions observed in crystal 1c (n = 10)
9

ACCEPTED MANUSCRIPT
Table 5. Intermolecular σπ interactionsa observed in crystal 1c (n = 10)
Compds
No. of
Bond distance/Å
Angles/
σπ
1c
2
1
1
ringH16 = 3.019
ringH5 = 3.013
ringH12 = 3.099
∠ringH16C16 = 161.4
∠ringH5C5 = 139.8
∠ringH16C16 = 152.5
a: measured from the center of ring to the atom.
2.3 Phase transitions, mesomorphic properties and thermal stability
The thermal behavior of compounds 1ac was studied by polarized optical microscopy (POM) and
differential scanning calorimetry (DSC). The transition temperatures and enthalpies of the
compounds 1ac are listed in Table 6. Compounds 2a and 2b (n = 12) formed enantiotropic
properties. Compound 2b has a higher melting and clearing temperature than those of compound 2a;
i.e. Tmp = 99.2 > 83.9 C and Tcl = 180.1 > 124.9 C. As expected, compound 2b (n = 12) has a
wider temperature range of SmC phase than that of compound 2a (n = 12), TSmC = 83.5 > 42.9 C
on cooling process. The mesophase was characterized and identified as SmC phases by POM; a
focalconics texture was observed under POM when cooled from their isotropic states. Not
surprisingly, compound 2c (n = 12) was not mesogenic and a transition of crystaltoisotropic at Tcl
= 119.9 C was solely observed. Bulkier or steric groups incorporated or bonded closer to core
center, such as methyl would not be favorable for molecules to pack in the solid or liquid crystal
state [5962]. The much weaker intermolecular interaction inherent in compound 2c (n = 12) was
also consistent with its lower clearing temperature than that of compound 2b; Tcl = 119.9 < 180.1 C
on heating process. Upon complexation to BF2 moiety, all clearing temperatures of borondifluoride
complexes 1ac decreased slightly than those of compounds 2ac by Tcl = 3.8 (1a, n = 12) < 18.6
(1c, n = 12) < 21.3 C (1b, n = 12). This lowering in clearing temperatures was probably attributed
to the steric effect cause by the tetrahedral BF2 moiety complexed to the core center.
10

ACCEPTED MANUSCRIPT
Four complexes 1a (n = 8, 10, 12, 14) formed mesogenic behavior, whereas the other two
derivatives (n = 6, 16) were not mesogenic. A transition temperature of crystaltoisotropic (Cr 
Icl) at Tcl = 121.2 C and Tcl = 120.8 C was observed for complexes 1a n = 6 and n = 16,
respectively. All other four derivatives 1a (n = 8, 10, 12, 14) were monotropic mesogens.
Monotropic was a kinetically unstable state, in which mesomorphic behavior was only observed
during the cooling process. The DSC data showed that the clearing temperatures of four derivatives
11

ACCEPTED MANUSCRIPT
n = 8, 10, 12, 14 remained in the range of Tcl = 119.6 (n = 8)  123.2 C (n = 10). The insensitivity of
the clearing temperature indicated that the van der Waals interaction induced by alkoxy chains was
not crucial force in forming mesogens. The mesophase was then further characterized by POM; a
typical focalconics texture observed for SmA phases was observed under POM when cooled from
their isotropic states (see Figure 5). The textures were also accompanied by slightly homeotropic
behavior, which was commonly observed for SmA phases. The temperature range of the SmA phases
was very short; i.e. TSmA = 0.8 (n = 8)7.3 C (n = 10) on cooling process. The kinetically unstable
SmA phase observed in this system might be due to a poor aspect ratio formed by salicylideneamine.
On the other hand, all complexes 1b showed an improved mesomorphic behavior. All complexes
1b (n = 8, 10, 12, 14, 16) exhibited an enantiotropic mesomorphic behavior and the better
mesomorphic behavior was probably attributed to a better rod or linearshaped molecule by
enaminoketonate 2b than that of salicylideneamine 2a. In addition, enaminoketonate 2b has a
better or longer conjugation length compared to salicylideneamine 2a. The melting temperature of
complexes 1b increased with carbon length of alkoxy chains; Tmp = 79.4 (n = 10)  98.4 C (n = 16)
on the heating process, whereas, all clearing temperatures slightly decreased with carbon length; Tcl
= 161.0 (n = 10)  153.0 C (n = 16). On the other hand, the temperature range of mesophases
decreased with carbon length; Tmeso = 95.4 (n = 8) > 82.4 (n = 12) > 58.1 C C (n = 16) on the
cooling process. The mesophases were identified and characterized as SmC phase first based on
POM. When a thinner sample was heated on the hot stage, a typical schlieren texture for SmC phase
was observed when cooled from its isotropic state under POM. However, a focalconics texture was
observed for a thicker sample [63]. The optical textures were also differentiated with that of SmA
phases by homeotropic test. Also, for SmC phases with schlieren domains, only singularities with
four brushes were observed and N phases may also show extra singularities with two brushes. A
wider temperature range of mesophases observed in complexes 1b over complexes 1a might be
probably attributed to their better or more appropriate aspect ratios, required for the formation or/and
induction of the mesophases. Elongation of the rigid molecular core resulted in broadening of the
12

ACCEPTED MANUSCRIPT
mesophases.
Figure 5. Optical textures observed. (A) SmC phase by 2a (n = 12) at 120.0 C; (B) SmC phase by
2b (n = 12) at 175.0 C; (C) SmA phase by 1a (n = 10) at 110.0 C; (D) SmC phase by 1b (n = 10) at
140.0 C; (E) SmC phase by 1b (n = 14) at 155.0 C and (F) SmA phase by 1c (n = 12) at 86.0 C.
All temperatures were taken upon cooling from isotropic phase.
In order to understand the steric effect on the formation of mesophases, three complexes 1c (n =
10, 12, 14) with a bulkier methyl moiety incorporated to the terminal end of enaminoketonate was
prepared. Interestingly, only one complexes 1c (n = 12) showed monotropic mesomorphic behavior.
All other two complexes 1c were not mesogenic, and a transition temperature of crystaltoisotropic
13

ACCEPTED MANUSCRIPT
state at Tcl = 95.9 and 106.4 C was observed for n = 10 and 14, respectively. Surprisingly, a very
short temperature range of TSmA = 0.50 C was observed for the derivative n = 12. The exothermic
peak was not observed on the DSC thermograph, and the temperature was obtained by POM
observation. The mesophases was identified as SmA phase by optical texture. The steric effect by
methyl group was also observed in our previous bimetallomesogens derived from
enaminoketonate [61, 6465]. The central geometry of novel metallomesogens, such as copper or
palladium ions derived from enaminoketonates were often square planar, which were favorable
on the formation of the mesophases. A tetrahedral methyl group could expand their layer structures;
therefore increasing the interlayer distances, and destroying the mesophase. All clearing
temperatures of complexes 1c were much lower than those of complexes 1b by Tcl = 65.1 (n = 10)
> 57.5 (n = 12) > 50.8 C (n = 14), appearing that the much weaker interaction in complexes 1c
might not be strong to induce the mesophases. Both BF2 and CH3 moieties, considered as a relatively
tetrahedral geometry would slightly twist the layer packing in the crystal or/and liquid crystalline
states. However, the smaller BF2 moiety might provide a preferred dipole to induce the mesophases.
Bar chart showing the phase behavior of compounds 1ac was shown in Figure 6.
Figure 6. Bar chart showing the phase behavior of compounds 1-2.
The thermal stability of three complexes 1ac (all n = 12) was also performed by
14

ACCEPTED MANUSCRIPT
thermogravimetric analyses (TGA) under nitrogen atmosphere, shown in Figure 7. All three
compounds showed good thermal stability at temperature Tdec = 316.2 (1a) < 325.3 (1b) < 340.7 C
(1c). The decomposition temperature was defined at a temperature with a weight loss of 5% and the
thermal decomposition was not probably related to sublimation or/and evaporation. The
decomposition might be due to the fragmentation of boron difluoride or imine moieties. The
decomposition temperatures for a 5% weight loss were listed in Table 7.
100
1a (n = 12)
1b (n = 12)
80
60
40
20
0
1c (n = 12)
0
100
200
300
400
500
600
Temperature (0C)
Figure 7. The TGA thermograms of compounds 1ac (all n = 12).
Table 7. The decomposition temperaturea of compounds 1ac by TGA analysis
Compd.
Tdec (C)
1a (n = 12)
1b (n = 12)
1c (n = 12)
316.2
325.3
340.7
a: Temperatures taken with a 5% weight loss.
2.4 Powder Xray diffractions
Variabletemperature powder XRD experiments were performed to confirm the structure of the
mesophases of two BF2 complexes 1a (n = 10) and 1b (n = 12) on the cooling process. Complexes 1
were all rodshaped molecules; they exhibited monotropic SmA or enantiotropic SmC phases. For
example, for complex 1a (n = 10) at 108.0 C a diffraction pattern with one strong peak at 29.51 Å
15

ACCEPTED MANUSCRIPT
and another very weak peak at 14.82 Å was observed (Figure 8 and Table 8). These two diffraction
peaks at lower angle assigned as 001 and 002 was typically characteristics of layer structures
observed for SmA phase. In SmA phase, the rodlike molecules were all lined up parallel to one
another. They were arranged in layers with a thickness about equal to the length of the molecules, in
which the long axes was directed perpendicular to the layer planes. Within the layers, the centers of
molecular gravity of the molecules were randomly ordered. Thus, SmA possess the onedimensional
pseudo longrange positional order and within the layers molecules showed a relatively high
mobility. In contrast, boron complex 1b (n = 12) gave a much larger dspacing of 33.01 and 16.51 Å
at 150 C, which were assigned as 001 and 002. A broad halo peak appeared at 4.63 and 4.67 Å was
also observed for both compounds. This broad and diffused peak often occurred at 4.10–4.70 Å (i.e.
dhalo) corresponded to liquidlike correlations between alkoxy chains. In SmC phase the molecules
were also arranged in layers, whereas the long axes of the molecules were tilted to the layers planes.
A summary of diffraction data was listed in Table 8. A schematic representation of molecular
organization proposed in SmA and SmC phase by complexes 1ab is shown in Figure 9.
20000
d001 = 33.01
10000
dhalo = 4.67
d002 = 16.51
0
0
10
20
30
2 Theta
16

ACCEPTED MANUSCRIPT
10000
5000
0
d001 = 29.51
d002 = 14.82
dhalo = 4.63
0
10
20
30
2 Theta
Figure 8. The powder Xray diffraction plots; complex 1a (n = 10) at 108 C (top plot) and 1b (n =
12) at 150 C (bottom plot).
Table 8. The powder Xray diffraction data for complexes 1a and 1b.
Compds.
Mesophase/temp.a
dSpacing/Å (calcd.)
Index
1a (n = 10)
SmA phase at 108 C
29.51 (29.51)
14.82 (14.76)
4.63 (br)
33.01 (33.01)
16.51 (16.51)
4.67 (br)
001
002
halo
001
002
halo
1b (n = 12)
SmC phase at 150 C
a: Sample was heated above and the diffraction data recorded on cooling process.
17

ACCEPTED MANUSCRIPT
Figure 9. A schematic representation of molecular organization proposed in SmA phase (top) by
compounds 1a (n = 10) and in SmC phase (bottom) by compounds 1b (n = 12).
2.5 Optical properties
The UV/PL behavior of borondifluoride complexes with N, Ocoordination modes appears to be the
most studied among the class of conjugated ligands. These complexes adopt a typical DA
structure with the alkoxyphenyl group as the electron donor (D) and the borondifluoride moiety as
the acceptor (A). Photophysical data of three complexes 1ac (all n = 12) performed in CH2Cl2
solution and in the powder state at room temperature are presented in Figure 10. The max peaks of
UVvis absorptions and PL spectra for compounds 1ac were listed in Table 9. Both UVvis
absorptions and PL spectra were not sensitive to the carbon number of terminal alkoxy chains
appended to the benzene. The PL spectra were excited at 360 (1c), 368 (1a) and 393 nm (1b).
On UVvis spectrum, a strong absorption peak at 368 nm and a weak shoulder at 294 nm were
observed for complex 1a, which were attributed to * and n transitions arising from chelating
ring. The two UV spectra profiles for complexes 1bc were quite similar; a very strong absorption
max peaks located at ca. 393 and 360 nm and a weaker shoulder peak occurred at ca. 321 and 274
nm. These peaks were also ascribed to * and n transitions arising from chelating ring. A
weaker shoulder occurred at ca. 333 nm was observed for complex 1a. These absorption max peaks
of complexes 1b were slightly redshifted by a max = 3347 nm when compared to those of
complexes 1c.
18

ACCEPTED MANUSCRIPT
On the other hand, the three PL spectra for complexes 1ac were quite similar in emission peak
profiles; showing one broad peak located at max = 476541 nm in the solution and max = 488550
nm in the solid state. A Stokes shift of max = 108148 nm was obtained for complexes 1ac.
Complex 1bc showed a redshift emission compared to complex 1a by max = 1565 nm in
solution and max = 1762 nm in solid state, which might be due to their longer molecular
conjugation length. However, the emission in complex 1c (i.e. 491 nm) in solution showed a
blueshift than in complex 1b (i.e. 541 nm); the LUMO orbital in complex 1c was elevated in
energy by electron donation, causing the band gap larger. As expected, all BF2 complexes also
showed redshifted emissions in the solid state with respect to the corresponding emissions in the
solution by ca. max = 914 nm, which might be attributed to the increasing intermolecular
interactions. Furthermore, the emission peaks in the solid state were found to be slightly broader
than those in the solution and this might be attributed to its selfquenching of fluorescence at higher
concentration and/or the  the stacking in the solid state. Furthermore, the PL data indicated that
the photoluminescent emissions of boron difluoride complexes [5152] were quite sensitive to the
molecular structures; i.e. max = 541 (1b) > 538 (II) > 491 (1c) > 476 (1a) > 399 nm (I). The
compound 1b emitted light at  = 541 nm-1, which was very close to that of compound II (X = Y =
H; n = 8) emitted at  = 538 cm-1, but much lower than that of compound I (n = 12) at  = 399 cm-1.
All three compounds were quite distinct in molecular structures and part of the shift in PL emissions
was probably due to the conjugation length of the core group [63]. In contrast, the more bulkier CH3
moiety for complex 1c exhibited a slightly larger redshift [19, 3334, 41] in the solid state by
max = 14 nm than in the solution for complex 1b by max = 9.0 nm. A very low fluorescence
quantum yield, determined with anthracene (ΦF = 0.27 in hexane solution) as a reference dye was
obtained for all three BF2 complexes
19

ACCEPTED MANUSCRIPT
1a (n = 12)
1b (n = 12)
1c (n = 12)
1.00
0.75
0.50
0.25
0.00
200 250 300 350 400 450 500 550 600
Wavelength (nm)
1a (n = 12)
1b (n = 12)
1c (n = 12)
1.00
0.75
0.50
0.25
0.00
400
450
500
550
600
650
700
Wavelength (nm)
1a (n = 12) solid
1b (n = 12) solid
1c (n = 12) solid
1.0
0.8
0.6
0.4
0.2
0.0
450
500
550
600
650
700
750
800
Wavelength (nm)
Figure 10. The normalized UVvis absorbance (top), emission spectra in the CH2Cl2 solution
(middle) and emission spectra in the solid state (bottom) of the compounds 1ac (n = 12) at room
temperature.
20

ACCEPTED MANUSCRIPT
Table 9. Absorption and PL emission dataa of compounds 1 (all n = 12) and III.
b
Compds.
Absorption (ε x10-4, M-1cm-1)/λ
Emission/
Emission/
ΦF
(sol’n) λmax
(powder) λmax
1a
1b
1c
Id
294 (1.9), 333c (2.8), 368 (4.6)
321 (0.6), 393 (4.1)
274 (0.4), 360 (3.9)
351, 368
476
541
491
399
538
488
< 0.1
< 0.1
< 0.1


550, 584c
505


IIe
285, 459, 482c
a: measured in CH2Cl2 solution (10-5 M) at room temperature. The samples were excited at 368 (for
1a, n = 12), 393 (for 1b, n = 12) and 360 (for 1c, n = 12). The unit in wavelength is nm.
b: the standard is anthracene (ΦF = 0.27 in hexane solution).
d: shoulder peak.
d: data for the compound I (R = C12H25).
e: data for the compound II (X = Y = H; R = C8H17).
3. Conclusion
A systematic investigation on the relationship between molecular structure, mesomorphic behavior
and fluorescence was studied in this work. Three new series of BF2 complexes 1ac derived from
substituted Schiff bases salicylideneamine and -enaminoketonates were reported, and their
mesomorphic and optical properties were investigated. Single crystallographic structure of 1c (n =
10) were resolved and a larger twisted angle caused by methyl group observed in the unit cell was
probably resulted in the lack of mesophases in such system. Complexes 1a formed monotropic SmA
phases and 1b exhibited enantiotropic SmC phases. However, only one complexes 1c (n = 12)
formed a very short temperature of SmA phases. BF2 complexes 1ac (n = 12) possess a
bluetogreen emission in solution and in solid state at room temperature. The luminescent emission
showed a strong dependence with conjugation and/or bulkier methyl moiety incorporated. To our
best knowledge, this is the first example of mesogenic BF2 complexes derived from Schiff bases of
salicylideneamines and enaminoketones.
21

ACCEPTED MANUSCRIPT
4. Experimental Section
Techniques
All chemicals and solvents were reagent grade from Aldrich Chemical Co., and solvents were dried
1
by standard techniques. H 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
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.
Materials
The compounds of 4-alkoxy-nitrobenzenes, 4-alkoxy-2-hydroxybenzaldehydes, (Z)-3-(4-alkoxy
phenyl)-3-hydroxyacrylaldehydes and (Z)-4-(4-alkoxyphenyl)-4-hydroxybut-3-en-2-ones were
similarly prepared by literature’s procedures [54].
Synthesis of (Z)-3-(4-(dodecyloxy)phenyl)-3-hydroxyacrylaldehyde (n = 12)
A solution of 1-(4-(dodecyloxy) phenyl)ethanone (4.0 g, 0.01 mol) dissolved in 100 mL ethyl
formate added sodium methoxide (2.13 g, 3.0 mmol). The solution was stirred at room temperature
for 24 h. The yellow solids were filtered and collected. The products isolated as yellow powder were
obtained by recrystallization from CH2Cl2/MeOH. Yield 74%.1H NMR(500 MHz, CDCl3): δ 0.86 (t,
3H, CH3, J = 6.92 Hz), 1.231.79 (m, 20H, CH2), 4.00 (t, 2H, OCH2, J = 6.6 Hz), 6.13 (d, 1H,
CH, J = 4.4 Hz), 6.92 (d, 2H, ArH, J = 8.95 Hz ), 7.86 (d, 2H, ArH, J = 8.8 Hz), 8.11 (d, 1H,
CH, J = 4.4 Hz), 15.41 (s, 1H, OH); 13C NMR (125 MHz, CDCl3) δ 14.10, 22.68, 25.97, 29.09,
29.34, 29.54, 29.57, 29.62, 31.90, 68.32, 97.69, 114.48, 114.54, 127.46, 129.59, 130.83, 163.22,
176.52, 188.17.
Synthesis of (E)-5-(dodecyloxy)-2-(((4-(dodecyloxy)phenyl)imino)methyl)phenol 2a (n = 12)
22

ACCEPTED MANUSCRIPT
A solution of 4-(dodecyloxy)aniline (1.00 g, 3.6 mmol) dissolved in 80 mL THF/ethanol (3/5) was
added 4-(dodecyloxy)-2-hydroxybenzaldehyde (1.04 g, 3.6 mmol) and drops of acetic acid. The
solution was refluxed for 24 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 CH2Cl2/MeOH. Yield 79%; mp 83.2 C. 1H NMR (500 MHz, CDCl3): δ 0.86
(t, 6H, CH3, J = 6.8 Hz), 1.241.50 (m, 36H, CH2),1.741.80 (m, 4H, OCH2CH2), 3.933.98 (m,
4H, OCH2), 6.436.46 (m, 2H, ArH), 6.90 (d, 2H, ArH, J = 8.9 Hz), 7.187.23 (m, 3H, ArH),
8.48 (s, 1H, N=CH), 13.91 (s, 1H, OH). 13C NMR (125 MHz, CDCl3): δ 14.09, 22.67, 25.99, 26.03,
29.09, 29.27, 29.34, 29.39, 29.58, 29.63, 31.91, 68.22, 68.37, 101.61, 107.38, 113.11, 115.18,
121.94, 133.08, 141.24, 157.99, 159.45, 163.24, 163.76. MS (HRFAB, m/z): calcd for [M+H]+:
566.4568. Found: 566.4544.
Synthesis of (E)-5-(hexyloxy)-2-(((4-(hexyloxy)phenyl)imino)methyl)phenol 2a (n = 6)
1
Light yellow powder; mp 71.6 C. H NMR (500 MHz, CDCl3): δ 0.89 (t, 6H, CH3, J = 6.9 Hz),
1.281.50 (m, 12H, CH2), 1.77 (m, 4H, OCH2CH2), 3.903.99 (m, 4H, OCH2), 6.436.48 (m,
4H, ArH), 6.90 (d, 2H, ArH), 7.187.23 (m, 3H, ArH), 8.48 (s, 1H, N=CH), 13.89 (s, 1H,
OH). 13C NMR (125 MHz, CDCl3): δ 14.03, 22.60, 25.68, 25.72, 29.07, 29.25, 29.34, 31.56, 31.60,
68.22, 68.36, 101.60, 107.38, 113.11, 115.18, 121.96, 133.10, 141.24, 158.00, 159.46, 163.24,
163.75. MS (HRFAB, m/z): calcd for [M+H]+: 398.2690. Found: 398.2670.
Synthesis of (E)-5-(octyloxy)-2-(((4-(octyloxy)phenyl)imino)methyl)phenol 2a (n = 8)
1
Light yellow powder; mp 69.7 C. H NMR (500 MHz, CDCl3): δ 0.86 (t, 6H, CH3, J = 6.9 Hz),
1.201.50 (m, 20H, CH2), 1.731.81 (m, 4H, OCH2CH2), 3.933.99 (m, 4H, OCH2), 6.436.47
(m, 2H, ArH), 6.90 (d, 2H, ArH, J = 8.9 Hz), 7.187.23 (m, 3H, ArH), 8.48 (s, 1H, N=CH),
13.91 (s, 1H, OH). 13C NMR (125 MHz, CDCl3): δ 14.09, 22.65, 26.00, 26.05, 29.10, 29.23, 29.29,
29.33, 29.36, 31.81, 68.23, 68.37, 101.61, 107.38, 113.11, 115.19, 121.95, 133.10, 141.24, 158.00,
159.46, 163.25, 163.76. MS (HRFAB, m/z): calcd for [M+H]+: 454.3316. Found: 454.3286.
Synthesis of (E)-5-(decyloxy)-2-(((4-(decyloxy)phenyl)imino)methyl)phenol 2a (n = 10)
23

ACCEPTED MANUSCRIPT
1
Light yellow powder; mp 77.1 C. H NMR (500 MHz, CDCl3): δ 0.86 (t, 6H, CH3, J = 6.9 Hz),
1.201.50 (m, 28H, CH2), 1.731.82 (m, 4H, OCH2CH2), 3.923.99 (m, 4H, OCH2), 6.416.44
(m, 2H, ArH), 6.90 (d, 2H, ArH, J = 8.8 Hz), 7.187.23 (m, 3H, ArH), 8.48 (s, 1H, N=CH),
13.90 (s, 1H, OH). 13C NMR (125 MHz, CDCl3): δ 14.11, 22.68, 26.00, 26.04, 29.10, 29.29, 29.31,
29.37, 29.40, 29.56, 31.90, 68.22, 68.37, 101.60, 107.39, 113.10, 115.18, 121.95, 133.10, 141.22,
157.99, 159.46, 163.24, 163.77. MS (HRFAB, m/z): calcd for [M+H]+: 510.3942. Found: 510.3903.
Synthesis of (E)-5-(tetradecyloxy)-2-(((4-(tetradecyloxy)phenyl)imino)methyl)phenol 2a (n = 14)
1
Light yellow powder; mp 91.7 C. H NMR (500 MHz, CDCl3): δ 0.86 (t, 6H, CH3, J = 6.8 Hz),
1.231.48 (m, 44H, CH2), 1.731.81 (m, 4H, OCH2CH2), 3.933.99 (m, 4H, OCH2), 6.426.48
(m, 2H, ArH), 6.90 (d, 2H, ArH, J = 8.8 Hz), 7.187.23 (m, 3H, ArH), 8.48 (s, 1H, N=CH),
13.89 (s, 1H, OH). 13C NMR (125 MHz, CDCl3): δ 14.12, 22.69, 26.00, 26.04, 29.10, 29.28, 29.36,
29.60, 29.66, 31.93, 68.22, 68.37, 101.60, 107.39, 113.10, 115.18, 121.95, 133.09, 141.22, 157.99,
159.45, 163.24, 163.77. MS (HRFAB, m/z): calcd for M+: 621.5121. Found: 621.5121.
Synthesis of (E)-5-(hexadecyloxy)-2-(((4-(hexadecyloxy)phenyl)imino)methyl)phenol 2a (n = 16)
1
Light yellow powder; mp 93.9 C. H NMR (500 MHz, CDCl3): δ 0.86 (t, 6H, CH3, J = 6.7 Hz),
1.181.48 (m, 52H, CH2), 1.731.81 (m, 4H, OCH2CH2), 3.923.99 (m, 4H, OCH2), 6.426.47
(m, 2H, ArH), 6.90 (d, 2H, ArH, J = 8.8 Hz), 7.187.23 (m, 3H, ArH), 8.48 (s, 1H, N=CH),
13.90 (s, 1H, OH). 13C NMR (125 MHz, CDCl3): δ 14.10, 22.69, 26.00, 26.04, 29.10, 29.28, 29.36,
29.59, 29.69, 31.93, 68.22, 68.37, 101.61, 107.39, 113.11, 115.18, 121.95, 133.09, 141.22, 158.00,
159.45, 163.25, 163.77. MS (HRFAB, m/z): calcd for [M+H]+: 678.5820. Found: 678.5791.
Synthesis of (Z)-1-(4-(dodecyloxy)phenyl)-3-((4-(dodecyloxy)phenyl)amino)prop-2-en-1-one
2b (n = 12)
A solution of 4-(dodecyloxy)aniline (0.60 g, 2.2 mmol) dissolved in 80 mL THF/ethanol (3/5) was
slowly added (Z)-3-(4-(dodecyloxy)phenyl)-3-hydroxyacrylaldehyde (0.73 g, 2.2 mmol) and drops
of acetic acid. The solution was gently refluxed for 24 h. The solution was cooled to room
temperature, and the yellow solids were filtered and collected. The products isolated as yellow
1
powder were obtained by recrystallization from CH2Cl2/MeOH. Yield 72%, mp 99.2 C. H NMR
24

ACCEPTED MANUSCRIPT
(300 MHz, CDCl3): δ 0.86 (t, 6H, CH3, J = 6.8 Hz), 1.181.48 (m, 36H, CH2), 1.691.84 (m, 4H,
OCH2CH2), 3.91 (t, 2H, OCH2, J = 6.6 Hz), 3.99 (t, 2H, OCH2, J = 6.6 Hz), 5.91 (d, 1H,
C=CHC=O, J = 7.9 Hz), 6.86 (d, 2H, ArH, J = 8.9 Hz), 6.90 (d, 2H, ArH, J = 8.9 Hz), 7.00 (d,
2H, ArH, J = 9.0 Hz), 7.38 (dd, 1H, C=CHN, J = 12.3, 7.77 Hz), 7.88 (d, 2H, ArH, J = 8.9 Hz),
12.09 (d, 1H, C=CNH, J = 12.5 Hz). 13C NMR (125 MHz, CDCl3): δ 14.11, 22.69, 26.02, 29.19,
29.30, 29.37, 29.59, 29.69, 31.93, 68.17, 68.47, 92.56, 114.11, 115.65, 117.73, 129.18, 131.89,
133.87, 142.14, 145.23, 189.69. MS (HRFAB, m/z): calcd for [M+H]+: 59.4724. Found: 592.4700.
Synthesis of (Z)-1-(4-(octyloxy)phenyl)-3-((4-(octyloxy)phenyl)amino)prop-2-en-1-one 2b (n = 8)
1
Yellow powder, mp 109.7 C. H NMR (500 MHz, CDCl3): δ 0.87 (t, 6H, CH3, J = 6.5 Hz),
1.211.48 (m, 20H, CH2), 1.711.82 (m, 4H, OCH2CH2), 3.91 (t, 2H, OCH2, J = 6.6 Hz), 3.99 (t,
2H, OCH2, J = 6.6 Hz), 5.91 (d, 1H, C=CHC=O, J = 7.7 Hz), 6.86 (d, 2H, ArH, J = 8.7 Hz),
6.90 (d, 2H, ArH, J = 9.0 Hz), 7.00 (d, 2H, ArH, J = 8.8 Hz), 7.38 (dd, 1H, C=CHN, J = 12.3,
13
7.7 Hz), 7.88 (d, 2H, ArH, J = 8.7 Hz), 12.08 (d, 1H, C=CNH, J = 12.3 Hz). C NMR (125
MHz, CDCl3): δ 14.10, 22.66, 26.03, 29.19, 29.24, 29.30, 29.35, 31.81, 68.17, 68.47, 92.56, 114.11,
115.65, 117.73, 129.19, 131.88, 133.86, 142.14, 145.23, 155.77, 161.97, 189.69. MS (HRFAB, m/z):
calcd for [M+H]+: 480.3472. Found: 480.3454.
Synthesis of (Z)-1-(4-(decyloxy)phenyl)-3-((4-(decyloxy)phenyl)amino)prop-2-en-1-one 2b (n = 10)
1
Yellow powder; mp 102.8 C. H NMR (300 MHz, CDCl3): δ 0.86 (t, 6H, CH3, J = 6.3 Hz),
1.201.50 (m, 28H, CH2), 1.681.84 (m, 4H, OCH2CH2), 3.91 (t, 2H, OCH2, J = 6.5 Hz), 3.99 (t,
2H, OCH2, J = 6.5 Hz), 5.91 (d, 1H, C=CHC=O, J = 7.8 Hz), 6.86 (d, 2H, ArH, J = 8.9 Hz),
6.90 (d, 2H, ArH, J = 8.9 Hz), 7.00 (d, 2H, ArH, J = 9.0 Hz), 7.37 (dd, 1H, C=CHN, J = 12.3,
13
7.8 Hz), 7.88 (d, 2H, ArH, J = 8.9 Hz), 12.08 (d, 1H, C=CNH, J = 12.5 Hz). C NMR (125
MHz, CDCl3): δ 14.10, 22.67, 26.03, 29.18, 29.30, 29.56, 31.89, 68.17, 68.47, 92.56, 114.11, 115.66,
117.74, 129.18, 131.89, 133.87, 145.23, 155.78, 161.98, 189.69. MS (HRFAB, m/z): calcd for
[M+H]+: 536.4098. Found: 536.4060.
Synthesis of (Z)-1-(4-(tetradecyloxy)phenyl)-3-((4-(tetradecyloxy)phenyl)amino)prop-2-en-1-one
2b (n = 14)
25

ACCEPTED MANUSCRIPT
1
Yellow powder; mp 103.9 C. H NMR (300 MHz, CDCl3): δ 0.86 (t, 6H, CH3, J = 6.2 Hz),
1.201.50 (m, 44H, CH2), 1.681.84 (m, 4H, OCH2CH2), 3.91 (t, 2H, OCH2, J = 6.5 Hz), 3.99 (t,
2H, OCH2, J = 6.5 Hz), 5.91 (d, 1H, C=CHC=O, J = 7.8 Hz), 6.86 (d, 2H, ArH, J = 9.0 Hz),
6.90 (d, 2H, ArH, J = 9.1 Hz), 7.00 (d, 2H, ArH, J = 9.0 Hz), 7.37 (dd, 1H, C=CHN, J = 12.3,
7.8 Hz), 7.88 (d, 2H, ArH, J = 8.8 Hz), 12.08 (d, 1H, C=CNH, J = 12.6 Hz). 13C NMR (125
MHz, CDCl3): δ 14.11, 22.69, 26.03, 29.18, 29.30, 29.36, 29.59, 29.66, 31.92, 68.17, 68.48, 92.56,
114.11, 115.66, 117.74, 129.18, 131.90, 133.88, 145.23, 155.77, 161.98, 189.69. MS (HRFAB, m/z):
calcd for[M+H]+: 648.5350. Found: 648.5291.
Synthesis of (Z)-1-(4-(hexadecyloxy)phenyl)-3-((4-(hexadecyloxy)phenyl)amino)prop-2-en-1-one
2b (n = 16)
1
Yellow powder; mp 108.4 C. H NMR (300 MHz, CDCl3): δ 0.86 (t, 6H, CH3, J = 6.4 Hz),
1.221.48 (m, 52H, CH2), 1.691.83 (m, 4H, OCH2CH2), 3.91 (t, 2H, OCH2, J = 6.5 Hz), 3.99 (t,
2H, OCH2, J = 6.6 Hz), 5.91 (d, 1H, C=CHC=O, J = 7.8 Hz), 6.85 (d, 2H, ArH, J = 8.9 Hz),
6.90 (d, 2H, ArH, J = 8.9 Hz), 7.00 (d, 2H, ArH, J = 9.0 Hz), 7.37 (dd, 1H, C=CHN, J = 12.3,
13
7.8 Hz), 7.88 (d, 2H, ArH, J = 8.9 Hz), 12.09 (d, 1H, C=CNH, J = 12.5 Hz). C NMR (125
MHz, CDCl3): δ 14.11, 22.70, 26.02, 29.19, 29.30, 29.37, 29.59, 29.69, 29.93, 31.93, 42.61, 68.17,
68.47, 92.56, 114.11, 115.65, 117.73, 129.18, 131.89, 133.87, 142.23, 145.23, 189.69. MS (HRFAB,
m/z): calcd for [M+H]+: 704.5982. Found: 704.5976.
Synthesis of (1Z,3E)-1-(4-(dodecyloxy)phenyl)-3-((4-(dodecyloxy)phenyl)imino)but-1-en-1-ol
2c (n = 12)
A solution of 4-(dodecyloxy)aniline (0.60 g, 2.2 mmol) dissolved in 80 mL THF/ethanol (3/5) was
added (Z)-4-(4-(dodecyloxy)phenyl)-4-hydroxybut-3-en-2-one (0.76 g, 2.2 mmol) and drops of
acetic acid. The solution was refluxed for 24 h. The solution was cooled to room temperature, and
off-white solids were filtered and collected. The products isolated as white powder were obtained by
recrystallization from CH2Cl2/MeOH. Yield 63%; mp 117.9 C. 1H NMR (500 MHz, CDCl3): δ 0.86
(t, 6H, CH3, J = 6.7 Hz), 1.221.48 (m, 36H, CH2), 1.721.81 (m, 4H, OCH2CH2), 2.03 (s, 3H,
CCH3), 3.93 (t, 2H, OCH2, J = 6.6 Hz), 3.98 (t, 2H, OCH2, J = 6.6 Hz), 5.80 (S, 1H,
26

ACCEPTED MANUSCRIPT
C=CHC=O), 6.85 (d, 2H, ArH, J = 8.8 Hz), 6.89 (d, 2H, ArH, J = 8.9 Hz), 7.06 (d, 2H, ArH, J
= 8.8 Hz), 7.86 (d, 2H, ArH, J = 8.9 Hz), 12.80 (s, 1H, COH). 13C NMR (125 MHz, CDCl3): δ
14.11, 20.27, 22.68, 26.04, 29.22, 29.27, 29.34, 29.39, 29.59, 29.63, 29.65, 31.92, 68.11, 68.32,
92.99, 113.98, 114.86, 126.54, 128.86, 131.49, 132.58, 157.33, 161.49, 162.34, 187.67. MS
(HRFAB, m/z): calcd for [M+H]+: 606.4881. Found: 606.4831.
Synthesis of (1Z,3E)-1-(4-(decyloxy)phenyl)-3-((4-(decyloxy)phenyl)imino)but-1-en-1-ol 2c (n = 10).
1
White powder, mp 118.3 C. H NMR (500 MHz, CDCl3): δ 0.86 (t, 6H, CH3, J = 6.6 Hz),
1.201.48 (m, 28H, CH2), 1.721.81 (m, 4H, OCH2CH2), 2.03 (s, 3H, CCH3), 3.93 (t, 2H,
OCH2, J = 6.6 Hz), 3.98 (t, 2H, OCH2, J = 6.6 Hz), 5.80 (S, 1H, C=CHC=O), 6.85 (d, 2H,
ArH, J = 8.8 Hz), 6.89 (d, 2H, ArH, J = 8.9 Hz), 7.06 (d, 2H, ArH, J = 8.8 Hz), 7.86 (d, 2H,
ArH, J = 8.7 Hz), 12.81 (s, 1H, COH). 13C NMR (125 MHz, CDCl3): δ 14.10, 20.27, 22.68,
26.04, 29.22, 29.28, 29.32, 29.39, 29.56, 31.90, 68.11, 68.31, 92.99, 113.98, 114.86, 126.53, 128.86,
131.49, 132.58, 157.33, 161.49, 162.34, 187.66. MS (HRFAB, m/z): calcd for [M+H]+: 550.4255.
Found: 550.4215.
Synthesis of (1Z,3E)-1-(4-(tetradecyloxy)phenyl)-3-((4-(tetradecyloxy)phenyl)imino)but-1-en-1-ol
2c (n = 14)
1
White powder; mp 117.6 C. H NMR (500 MHz, CDCl3): δ 0.86 (t, 6H, CH3, J = 6.7 Hz),
1.201.49 (m, 44H, CH2), 1.711.81 (m, 4H, OCH2CH2), 2.03 (s, 3H, CCH3), 3.93 (t, 2H,
OCH2, J = 6.6 Hz), 3.98 (t, 2H, OCH2, J = 6.6 Hz), 5.80 (S, 1H, C=CHC=O), 6.85 (d, 2H,
ArH, J = 8.8 Hz), 6.89 (d, 2H, ArH, J = 8.8 Hz), 7.06 (d, 2H, ArH, J = 8.8 Hz), 7.86 (d, 2H,
13
ArH, J = 8.7 Hz), 12.81 (s, 1H, COH). C NMR (125 MHz, CDCl3): δ 14.11, 20.27, 22.69,
26.04, 29.22, 29.28, 29.36, 29.39, 29.59, 29.66, 29.65, 31.93, 68.11, 68.32, 92.99, 113.98, 114.86,
126.54, 128.86, 131.49, 132.58, 157.33, 161.49, 162.34, 187.67. MS (HRFAB, m/z): calcd for
[M+H]+: 662.5507. Found: 662.5452.
Synthesis of BF2 complex of (E)-5-(dodecyloxy)-2-(((4-(dodecyloxy)phenyl)imino)methyl)phenol
la (n = 12)
A solution of (E)-5-(dodecyloxy)-2-((4-(dodecyloxy)phenylimino)methyl)phenol (0.40 g, 0.7 mmol)
27

ACCEPTED MANUSCRIPT
dissolved in 40 mL CH2Cl2 was slowly added triethylamine (0.21 g, 2.1 mmol) and boron trifluoride
diethyl etherate (0.43 mL, 3.5 mmol) under nitrogen atmosphere. The mixture was gently refluxed
for 24 h. The solution was concentrated and the products isolated as yellow powder were obtained
1
by recrystallization from CH2Cl2/hexane. Yield 33%; mp 97.7 C. H NMR (500 MHz, CDCl3): δ
0.86 (t, 6H, CH3, J = 6.7 Hz), 1.221.47 (m, 36H, CH2),1.731.83 (m, 4H, OCH2CH2), 3.96 (t,
2H, OCH2, J = 6.5 Hz), 4.02 (t, 2H, OCH2, J = 6.6 Hz), 6.536.58 (m, 2H, ArH), 6.93 (d, 2H,
ArH, J = 8.9 Hz), 7.32 (d, 1H, ArH, J = 8.5 Hz), 7.42 (d, 1H, ArH, J = 8.9 Hz), 8.19 (s, 1H,
13
N=CH). C NMR (125 MHz, CDCl3): δ 14.11, 22.69, 25.91, 26.00, 28.85, 29.17, 29.30, 29.34,
29.53, 29.57, 29.63, 31.92, 68.45, 68.89, 102.09, 104.68, 109.99, 115.24, 124.49, 133.10, 135.51,
19
159.47, 160.20, 162.43, 168.48. F NMR (282.41 MHz, CDCl3): δ 135.44 (dd, JFF = 29.58, J =
13.51 Hz). Anal. Calcd for C37H58BF2NO3: C, 72.42; H, 9.53; N, 2.28. Found C, 72.26; H, 9.52; N,
2.20. MS (HRFAB, m/z): calcd for M+: 613.4478. Found: 613.4478.
Synthesis of BF2 complex of (E)-5-(hexyloxy)-2-(((4-(hexyloxy)phenyl)imino)methyl)phenol
la (n = 6)
1
Yellow powder; mp 121.2 C. H NMR (500 MHz, CDCl3): δ 0.89 (t, 6H, CH3, J = 6.7 Hz),
1.291.49 (m, 12H, CH2), 1.731.83 (m, 4H, OCH2CH2), 3.96 (t, 2H, OCH2, J = 6.6 Hz), 4.02 (t,
2H, OCH2, J = 6.5 Hz), 6.536.57 (m, 2H, ArH), 6.93 (d, 2H, ArH, J = 9.0 Hz), 7.32 (d, 1H,
13
ArH, J = 8.4 Hz), 7.42 (d, 1H, ArH, J = 8.8 Hz), 8.19 (s, 1H, N=CH). C NMR (125 MHz,
CDCl3): δ 14.00, 22.55, 22.59, 25.57, 25.67, 28.82, 29.13, 31.48, 31.55, 68.43, 68.88, 102.08,
19
110.00, 111.07, 115.23, 124.48, 133.14, 135.50, 159.46, 160.23, 162.40, 168.48. F NMR (282.41
MHz, CDCl3): δ 135.40 (dd, JFF = 30.15, J = 13.66 Hz). Anal. Calcd for C25H34BF2NO3: C, 67.42;
H, 7.70; N, 3.15. Found C, 67.06; H, 7.73; N, 3.18. MS (HRFAB, m/z): calcd for M+: 445.2600.
Found: 445.2592.
Synthesis of BF2 complex of (E)-5-(octyloxy)-2-(((4-(octyloxy)phenyl)imino)methyl)phenol la (n = 8)
1
Yellow powder; mp 119.5 C. H NMR (300 MHz, CDCl3): δ 0.87 (t, 6H, CH3, J = 6.7 Hz),
1.221.48 (m, 20H, CH2), 1.721.85 (m, 4H, OCH2CH2), 3.96 (t, 2H, OCH2, J = 6.5 Hz), 4.02 (t,
28

ACCEPTED MANUSCRIPT
2H, OCH2, J = 6.5 Hz), 6.536.58 (m, 2H, ArH), 6.93 (d, 2H, ArH, J = 9.0 Hz), 7.32 (d, 1H,
13
ArH, J = 9.2 Hz), 7.43 (d, 1H, ArH, J = 8.9 Hz), 8.19 (s, 1H, N=CH). C NMR (125 MHz,
CDCl3): δ 14.08, 22.64, 25.90, 26.00, 28.85, 29.17, 29.22, 29.25, 29.32, 31.78, 31.80, 68.44, 68.89,
19
102.08, 110.00, 111.08, 115.24, 124.48, 133.12, 135.52, 159.47, 160.21, 162.42, 168.48. F NMR
(282.41 MHz, CDCl3): δ 135.42 (dd, JFF = 29.61, J = 13.29 Hz). Anal. Calcd for C29H42BF2NO3:
C, 69.46; H, 8.44; N, 2.79. Found C, 69.36; H, 8.45; N, 2.78. MS (HRFAB, m/z): calcd for M+:
501.3226. Found: 501.3227.
Synthesis of BF2 complex of (E)-5-(decyloxy)-2-(((4-(decyloxy)phenyl)imino)methyl)phenol
la (n = 10)
1
Yellow powder; mp 119.3 C. H NMR (500 MHz, CDCl3): δ 0.86 (t, 6H, CH3, J = 6.7 Hz),
1.181.48 (m, 28H, CH2),1.731.83 (m, 4H, OCH2CH2), 3.96 (t, 2H, OCH2, J = 6.6 Hz), 4.02 (t,
2H, OCH2, J = 6.6 Hz), 6.536.58 (m, 2H, ArH), 6.93 (d, 2H, ArH, J = 8.9 Hz), 7.32 (d, 1H,
13
ArH, J = 8.4 Hz), 7.42 (d, 1H, ArH, J = 8.9 Hz), 8.19 (s, 1H, N=CH). C NMR (125 MHz,
CDCl3): δ 14.10, 22.67, 25.90, 26.00, 28.85, 29.16, 29.30, 29.36, 29.53, 31.89, 31.80, 68.45, 68.89,
19
102.10, 109.99, 111.09, 115.24, 124.49, 133.10, 135.52, 159.47, 160.21, 162.43, 168.48. F NMR
(282.41 MHz, CDCl3): δ 135.42 (dd, JFF = 29.333, J = 12.41 Hz). Anal. Calcd for C33H50BF2NO3:
C, 71.09; H, 9.04; N, 2.51. Found C, 70.97; H, 9.09; N, 2.52. MS (HRFAB, m/z): calcd for [M+H]+:
558.3925. Found: 558.3927.
Synthesis of BF2 complex of (E)-5-(tetradecyloxy)-2-(((4-(tetradecyloxy)phenyl)imino)methyl)phenol
la (n = 14)
1
Yellow powder; mp 120.4 C. H NMR (500 MHz, CDCl3): δ 0.86 (t, 6H, CH3, J = 6.7 Hz),
1.221.48 (m, 44H, CH2), 1.731.83 (m, 4H, OCH2CH2), 3.96 (t, 2H, OCH2, J = 6.6 Hz), 4.02 (t,
2H, OCH2, J = 6.5 Hz), 6.536.58 (m, 2H, ArH), 6.93 (d, 2H, ArH, J = 9.0 Hz), 7.32 (d, 1H,
13
ArH, J = 8.6 Hz), 7.42 (d, 1H, ArH, J = 8.9 Hz), 8.19 (s, 1H, N=CH). C NMR (125 MHz,
CDCl3): δ 14.10, 22.69, 25.91, 26.00, 28.86, 29.17, 29.30, 29.36, 29.53, 29.57, 29.66, 31.92, 68.45,
19
68.89, 102.10, 109.98, 111.10, 115.24, 124.49, 133.09, 135.52, 159.47, 160.20, 162.44, 168.49. F
NMR (282.41 MHz, CDCl3): δ 135.43 (dd, JFF = 30.46, J = 14.16 Hz). Anal. Calcd for
29