Synthesis, characterization and comparative study of a series of fluorinated Schiff bases containing different orientation CHN spacers

Article abstract of DOI:10.1016/j.molstruc.2015.04.035

Investigation of the crystal structures of three pairs of multi-fluorinated compounds with bridge-flipped isomeric character, which on the molecular level differ only in the orientation of the bridging bond CHN connecting two larger parts of the molecule, offers a useful context for the examination and evaluation of supramolecular assembly in the case. The results show that the orientation of the bridging bond CHN determines the conformation of six organic molecules 1a-b, 2a-b and 3a-b, thus further influencing intermolecular weak interactions and final supramolecular arrangements. Accordingly, each molecule of six multi-fluorinated compounds as supramolecular building block unit, via strong intermolecular interactions, including interactions between fluorine atoms and aromatic ring hydrogen atoms, between fluorine atoms, and between hydroxyl groups and fluorine atoms, as well as interaromatic π?π stacking interactions etc., constructs a series of different and attractive crystal packings. These results demonstrate that by changing CHN orientation, we can obtain different hydrogen-bonded supramolecular structures through different interactions.

Full text of DOI:10.1016/j.molstruc.2015.04.035

Journal of Molecular Structure 1096 (2015) 21–28
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Synthesis, characterization and comparative study of a series
of fluorinated Schiff bases containing different
orientation ACH@NA spacers
b,
a
a
b
Wan Pang a,b, , Jing-Wei Zhao , Lei Zhao , Zhi-Kai Zhang , Shi-Zheng Zhu
⇑
⇑
a School of Chemical and Environmental Engineering, Shanghai Institute of Technology, 100 Haiquan Lu, Shanghai 201418, China
b Key Laboratory of Organofluorine Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 345 Lingling Lu, Shanghai 200032, China
h i g h l i g h t s
ꢀ
ꢀ
ꢀ
Three pairs of fluorinated Schiff bases isomers 1a–b, 2a–b and 3a–b were synthesized and characterized.
Their conformations are determined by different orientation ACH@NA spacers.
Each pair of isomers has different supramolecular stackings.
a r t i c l e i n f o
a b s t r a c t
Article history:
Investigation of the crystal structures of three pairs of multi-fluorinated compounds with bridge-flipped
isomeric character, which on the molecular level differ only in the orientation of the bridging bond
ACH@NA connecting two larger parts of the molecule, offers a useful context for the examination and
evaluation of supramolecular assembly in the case. The results show that the orientation of the bridging
bond ACH@NA determines the conformation of six organic molecules 1a–b, 2a–b and 3a–b, thus further
influencing intermolecular weak interactions and final supramolecular arrangements. Accordingly, each
molecule of six multi-fluorinated compounds as supramolecular building block unit, via strong inter-
molecular interactions, including interactions between fluorine atoms and aromatic ring hydrogen atoms,
Received 19 January 2015
Received in revised form 22 March 2015
Accepted 27 April 2015
Available online 6 May 2015
Keywords:
Synthesis and characterization
Fluorinated Schiff base
ACH@NA orientation
Supramolecular assemblies
between fluorine atoms, and between hydroxyl groups and fluorine atoms, as well as interaromatic
pꢁ ꢁ ꢁp
stacking interactions etc., constructs a series of different and attractive crystal packings. These results
demonstrate that by changing ACH@NA orientation, we can obtain different hydrogen-bonded
supramolecular structures through different interactions.
Ó 2015 Elsevier B.V. All rights reserved.
Introduction
packing arrangements largely arises from non-covalent interaction
between molecules, such as hydrogen bonding,
pꢁ ꢁ ꢁp stacking
Organic crystals have been attracting much attention for dec-
ades due to their superiority for understanding of intermolecular
interactions and potential applications in optoelectronics and
pharmaceutical products [1–2]. Detailed understanding of the elec-
tronic structure of the molecules and the specific intermolecular
interaction terms would enable us to engineer better molecular
structures and control their physic-chemical properties for tar-
geted applications [3–5]. The driving force for the molecular
interactions as well as van der Waals force. Most relevant of these
non-covalent interactions are stacking interactions and hydrogen
bonds, which have been subjects of extensive study in the last
two decades. In recent literature, due to the unique properties of
fluorinated compounds, substantial efforts have been put in by var-
ious researchers towards the understanding of interactions involv-
ing organic fluorine and the role they play in generating different
packing motifs which guides assembling of molecules in the crystal
lattice [3,6–9].
Schiff base is an interesting compound with a functional group
that contains a carbon–nitrogen double bond with the nitrogen
atom connected to an aryl or alkyl group. The chain on the nitrogen
makes the Schiff base a stable imine. They can form stable
⇑
Corresponding authors at: School of Chemical and Environmental Engineering,
Shanghai Institute of Technology, 100 Haiquan Lu, Shanghai 201418, China
(W. Pang). Tel.: +86 21 60877220, mobile: +86 13482389674.
E-mail addresses: pangwan@sit.edu.cn (W. Pang), zhaojingwei@sioc.ac.cn
(J.-W. Zhao).
http://dx.doi.org/10.1016/j.molstruc.2015.04.035
0022-2860/Ó 2015 Elsevier B.V. All rights reserved.

22
W. Pang et al. / Journal of Molecular Structure 1096 (2015) 21–28
complexes with transition metals and tend to exhibit potent in the
fields of biochemistry [10–12], catalyst chemistry [13],
organometallic chemistry [14,15] and material chemistry [16–
18]. It has been found that the non-covalent interactions, such as
F
p
F
.
.
.
2
s
p
N
C
H
Nꢁ ꢁ ꢁH hydrogen bonds,
p p stacking have a significant influence
ꢁ ꢁ ꢁ
F
on the properties of the Schiff bases especially in the cases of fluo-
rine atoms. The small size of the fluoro-substituent enables its
incorporation into crystal structures without undue disruption,
and hence the crystal structures can still be exhibited. Moreover,
it is the combination of the small size and high polarity of F atom
which serves as proton acceptor can create strong intra/inter-
F
nearly coplanner in a series isomers
F
F
p
H
C
N
.
molecular actions in the form of CAHꢁ ꢁ ꢁF, Fꢁ ꢁ ꢁF, Fꢁ ꢁ ꢁ
p
, Fꢁ ꢁ ꢁ
p
F, and
.
.
F. All this weak interactions play an important role in gener-
F
p p
ꢁ ꢁ ꢁ
2
s
p
ating different packing motifs and related properties of fluorinated
F
compounds.
have 30-50 dihedral angles in b series isomers
In this paper, we report synthesis and crystal structures of four
new fluorinated Schiff base compounds (1a–b, 3a–b) as well as the
supramolecular chemistry of three pairs of multi-fluorinated Schiff
bases (1a–b, 2a–b, 3a–b) with different orientation of the bridging
bond ACH@NA/AN@CHA spacers in the solid state (Scheme 1).
Obviously, this is an excellent opportunity to elucidate the differ-
ence of supramolecular assembly in the orientation isomers,
though two crystal structures (2a–b) of six compounds (1a–b,
2a–b, 3a–b) have been reported [6]. To the best of our knowledge,
this firstly systematically investigate the supramolecular organiza-
tion in series of fluorinated Schiff base molecules with different
orientations of
Scheme 2. Difference in conformation between bridge-flipped isomeric fluorinated
benzylideneanilines from electron repulsion of electron-riched F atoms and lone-
pair in sp2 orbit of N atom.
namely the better coplanar in a series’ molecules makes them have
the better delocalization effect and become the rigid-rod-type con-
jugated chromophore molecules. However, reversing the orienta-
tion of bridging ACH@NA bond in molecules gives b series’
isomers without coplannarity from the electron repulsion between
the substituted electron-riched fluorine atoms and the lone-pairs
in nitrogen atoms (Scheme 2).
Results and discussion
General description of six crystal structures
Synthesis and general characterization of six compounds
All single crystals were obtained from EtOH or CH2Cl2 solution
after slow evaporation of the solvent at ambient conditions and
examined using single crystal X-ray diffraction method. It gave a
triclinic crystal lattice with a P-1 space group for 2a and 3a, mon-
oclinic crystal system with P21/c space group for 1b and 2b, an
orthorhombic crystal lattice with Pbca for 1a and with P212121
for 3b, respectively. All bond distances and angles of the molecules
are normal. Figs. 1–16 give the diagrams of all six compounds
including the intramolecular features of the CAHꢁ ꢁ ꢁF interaction
in six compounds, OAHꢁ ꢁ ꢁF and OAHꢁ ꢁ ꢁN in 3b as well as Fꢁ ꢁ ꢁF
Although two compounds 2a–b were once reported by Collas
et al. [6], their syntheses and characterization as well as structural
analyses are still C@N spacers. This opens the possibility to explore
the effect of fluorine atoms and C@N spacers in the Schiff base
molecular on formation of the crystal packing, and may be good
in industrial and pharmaceutical applications.
Briefly mentioned here and below for comparative study. Four
symmetrical Schiff base compounds 1a–b and 2a–b as well as
two unsymmetrical ones 3a–b (Scheme 1) were respectively syn-
thesized by the condensation of the corresponding aldehydes with
the corresponding benzene-1,4-diamines/aniline in EtOH/CH2Cl2,
in which a series’ isomers present dark yellow crystalline solid
and b series’ ones pale yellow crystalline solid, being in agreement
with their structures (see structural discussion section below),
interactions in 1a–b and
p p stacking in 2a–b, 3a–b [19–25].
ꢁ ꢁ ꢁ
Table 1 lists the relevant crystallographic and refinement data,
F
F
F
F
Fig. 1. Molecular structure of 1a with thermal ellipsoids at the 20% level. The atom-
numbering scheme is shown only for one-half of the molecule as the other half is
generated by (ꢂ1 ꢂ x, ꢂy, 1 ꢂ z).
N
C
C
N
C
N
N
C
F
F
F
F
1b
1a
F
F
F
F
F
F
F
F
F
C
C
N
F
F
N
F
F
N
C
C
N
F
F
F
F
F
HO
2a
F
F
F
F
F
F
3a
N
F
F
F
N
C
C
F
HO
2b
3b
Fig. 2. Molecular structure of 1b with thermal ellipsoids at the 25% level. The atom-
numbering scheme is shown only for one-half of the molecule as the other half is
generated by (2 ꢂ x, 2 ꢂ y, 1 ꢂ z).
Scheme 1. The chemical structures of six fluorinated Schiff base compounds.

W. Pang et al. / Journal of Molecular Structure 1096 (2015) 21–28
23
Fig. 3. The 1-D tape-like structure with width of 12.5 Å in 1a in ac plane assembled
by hydrogen bonding CAHꢁ ꢁ ꢁF interactions.
Fig. 8. The 2-D crystal packing in 2a constructed by hydrogen bonding CAHꢁ ꢁ ꢁF
(light orange dotted line) and Fꢁ ꢁ ꢁF (violet dotted line) interactions. (a) viewed
down the c-axis, (b) viewed in ac plane. (For interpretation of the references to color
in this figure legend, the reader is referred to the web version of this article.)
Fig. 4. The 2-D layer-like structure in 1a with the thickness 12.5 Å viewed down the
c-axis, constructed by hydrogen bonding CAHꢁ ꢁ ꢁF (green dotted line), CAHꢁ ꢁ ꢁN
(blue dotted line) and
pꢁ ꢁ ꢁp stacking(red dotted line) interactions. (For interpre-
tation of the references to color in this figure legend, the reader is referred to the
web version of this article.)
Fig. 5. The 2-D layer-like structure in 1b with the thickness 19 Å viewed down the
b-axis, constructed by hydrogen bonds CAHꢁ ꢁ ꢁF (light orange dotted line) and Fꢁ ꢁ ꢁF
contact (violet dotted line) and
interpretation of the references to color in this figure legend, the reader is referred
to the web version of this article.)
pꢁ ꢁ ꢁp interactions (turquoise dotted line). (For
Fig. 9. The 2-D crystal packing in 2b constructed by hydrogen bonding CAHꢁ ꢁ ꢁF
(light orange dotted line) and Fꢁ ꢁ ꢁF (violet dotted line) interactions. (a) viewed
down the a-axis, (b) viewed down b-axis. (For interpretation of the references to
color in this figure legend, the reader is referred to the web version of this article.)
Fig. 6. Molecular structure of 2a with thermal ellipsoids at the 30% level. The atom-
numbering scheme is shown only for one-half of the molecule as the other half is
generated by (3 ꢂ x, 2 ꢂ y, 1 ꢂ z).
All the compounds have been examined with respect to the
propensity of generating supramolecular packing motifs particu-
larly involving Fꢁ ꢁ ꢁF, OAHꢁ ꢁ ꢁF, and CAHꢁ ꢁ ꢁF intermolecular
interactions.
Description of the crystal structures 1a and 1b
Fig. 7. Molecular structure of 2b with thermal ellipsoids at the 30% level. The atom-
numbering scheme is shown only for one-half of the molecule as the other half is
generated by (2 ꢂ x, 1 ꢂ y, ꢂz).
The crystal structures of 1a–b are shown in Figs. 1 and 2,
respectively. From the Figs. 1 and 2, their asymmetric units contain
one half of the organic molecules, and the other half related by cen-
trosymmetric operation (ꢂ1 ꢂ x, ꢂy, 1 ꢂ z) for 1a and (2 ꢂ x, 2 ꢂ y,
1 ꢂ z) for 1b. Compared with 1a and 1b, it is found that their
while Table 2 lists all intra- and intermolecular hydrogen bonds,
short contacts (Fꢁ ꢁ ꢁF) and
pꢁ ꢁ ꢁp stacking interactions, respectively.

24
W. Pang et al. / Journal of Molecular Structure 1096 (2015) 21–28
Fig. 14. The 3-D crystal packing of 3a viewed down the a-axis, constructed by
hydrogen bonding C(O)AHꢁ ꢁ ꢁF (light orange dotted line), OAHꢁ ꢁ ꢁN (turguoise
Fig. 10. The 3-D crystal packing of 2b viewed down the b-axis, constructed by
hydrogen bonding CAHꢁ ꢁ ꢁF (light orange dotted line) and Fꢁ ꢁ ꢁF (violet dotted line)
interactions. (For interpretation of the references to color in this figure legend, the
reader is referred to the web version of this article.)
dotted line), halogen bonding Oꢁ ꢁ ꢁF (violet dotted line) and
pꢁ ꢁ ꢁp packing (pink
dotted line) interactions. (For interpretation of the references to color in this figure
legend, the reader is referred to the web version of this article.)
Fig. 11. Molecular structure of 3a with thermal ellipsoids at the 30% level.
Fig. 12. Molecular structure of 3b with thermal ellipsoids at the 30% level.
Fig. 15. The 1-D supramolecular tape-like structure in 3b assembled by hydrogen
bonding C(O)AHꢁ ꢁ ꢁF (light orange dotted line) and OAHꢁ ꢁ ꢁN (sea green dotted line)
interactions viewed in (a) ac plane (b) bc plane. (For interpretation of the references
to color in this figure legend, the reader is referred to the web version of this
article.)
Fig. 13. The 2-D structure in 3a in ac plane assembled by hydrogen bonding
C(O)AHꢁ ꢁ ꢁF (light orange dotted line) and OAHꢁ ꢁ ꢁN (turguoise dotted line). (For
interpretation of the references to color in this figure legend, the reader is referred
to the web version of this article.)
Fig. 16. The 3-D crystal packing of 3b viewed down the a-axis, constructed by
hydrogen bonding C(O)AHꢁ ꢁ ꢁF (light orange dotted line) and OAHꢁ ꢁ ꢁN (sea green
dotted line) interactions. (For interpretation of the references to color in this figure
legend, the reader is referred to the web version of this article.)
conformations are significantly different and the dihedral angles
between the plane of the phenyl ring and the fluorinated benzene
ring are nearly coplanar with values of 8.8(2)° in 1a (Fig. 1), while
50.9° in 1b and obviously three benzene rings in the molecule 1b
are not in the same plane (Fig. 2 and Scheme 2).
Fig. 3 shows each 1a molecule is linked with two neighboring
molecules through the intermolecular CAHꢁ ꢁ ꢁF hydrogen bonds
(Table 2), forming highly ordered 1D tapes, and then through
hydrogen bond CAHꢁ ꢁ ꢁN as well as the face-to-face
pꢁ ꢁ ꢁp stacking
between the core fluoro-substituted rings and the terminal ben-
zene rings with the centroid-to-centroid distance of 3.871 and
3.865 Å, 2-D layer-like supramolecular structure is assembled with
the thickness of 12.5 Å (Figs. 3 and 4). However, two terminal

W. Pang et al. / Journal of Molecular Structure 1096 (2015) 21–28
25
benzene rings in 1b twist out of the plane defined by the bridge
ACH@NA bonds and the core fluoro-substituted benzene ring with
the dihedral angle of 51°, so that the fluorinate atoms in core ben-
zene rings tend to form multiple supramolecular interactions with
the adjacent molecules involving hydrogen bonds CAHꢁ ꢁ ꢁF and
Fꢁ ꢁ ꢁF contact (Table 2), finally resulting in 2-D supramolecular
sheet with the thickness of 19 Å as shown in Fig. 5. At the same
layer, involving CAHꢁ ꢁ ꢁF/Fꢁ ꢁ ꢁF, but also in the different layers,
involving Fꢁ ꢁ ꢁF contacts. By virtue of these weak interactions, 3-D
supramolecular network is constructed as shown in Fig. 10.
Crystal structure of compound 3a and 3b
From above discussion, in isomeric pairs 1a–b and 2a–b with
symmetric character, the orientation of the ACH@NA linkage in
the molecules significantly affects the molecular conformation in
the solid state, and further affects weak intermolecular interac-
tions/contacts and packing arrangements. If the isomeric pair is
unsymmetry, such as 3a–b, in the solid state molecular conforma-
tion, intermolecular interactions/contacts and packing arrange-
ments change or not?
Figs. 11 and 12 show the molecular structures of 3a and 3b,
respectively. The same as the isomeric pairs 1a–b and 2a–b, if
the nitrogen atom in the bridging ACH@NA linkage does not
directly connect the fluoro-substituted benzene ring, whole mole-
cule is coplanar with the dihedral angle of 3.3(2)° between two
aromatic rings (for 3a in Fig. 11). However, if the nitrogen atom
directly links one, the molecule shows a larger twist with the dihe-
dral angle of 50.7(2)° between two aromatic rings (for 3b in
Fig. 12). Apparently in the case orientation of the bridging group
ACH@NA do also play a very important role in controlling the con-
formation of the unsymmetrical molecules 3a and 3b as the sym-
metrical molecules 1a–b and 2a–b.
time, intermolecular
lizes the supramolecular network (Fig. 5).
p p stacking interaction also further stabi-
ꢁ ꢁ ꢁ
Description of the crystal structures 2a and 2b
In going from the fluoro-substituted core benzene rings iso-
meric pair 1a–b to the fluoro-substituted terminal benzene ring
isomeric pair 2a–b, the increased number and changed position
of the fluorine atoms lead to a new kind of intermolecular contacts
in the fluoro-substituted terminal benzene ring isomeric pair 2a
and 2b once reported [6]. The molecular structure of 2a is similar
to that of 1a, namely all aromatic rings in the molecule are nearly
coplanar with the dihedral angles of 4.0(1)° between the plane of
core phenyl ring and the terminal fluorinated benzene ring
(Fig. 6), while 35.9(2)° in 2b and obviously three benzene rings
in the molecule 2b are not in the same plane as in 1b (Fig. 7 and
Scheme 2).
Generally speaking, differences between the isomers with
respect to their molecular conformations tend to differentiate their
solid-state intermolecular interactions and molecular packing
arrangements. A comparison of molecular packing structures
found in the fluoro-substituted terminal benzene rings isomeric
pair 2a and 2b is shown in Figs. 8–10. In 2a, due to the presence
of the fluorine atoms in terminal benzene rings of the planar mole-
cules, the inter- or intramolecular CAHꢁ ꢁ ꢁF interactions along with
Fꢁ ꢁ ꢁF contacts form strictly flat 2-D layers (Fig. 8 and Table 2).
While in 2b, the terminal fluoro-substituted benzene rings twist
out of the plane defined by the bridge ACH@NA bonds and the
core benzene ring with the dihedral angle of 36°, so that the fluo-
rinate atoms in terminal benzene rings tend to form supramolecu-
lar interactions with the adjacent molecules not only in the same
Views of the packing are shown in Figs. 13 and 14 for 3a and
Figs. 15 and 16 for 3b, relevant distances and angles are given in
Table 2. The hydroxyl group in benzene ring might well produce
intramolecular hydrogen bonds OAHꢁ ꢁ ꢁF(N) in 3a and OAHꢁ ꢁ ꢁF
and OAHꢁ ꢁ ꢁN interactions in 3b, associating with intermolecular
hydrogen bonding C(O)AHꢁ ꢁ ꢁF(N) interactions [26], 2-D
supramolecular layers (for 3a) and 3-D tape-like structures (for
3b) are respectively assembled as shown in Figs. 13, 15 and 16.
And then through
p p packing interactions from two adjacent
ꢁ ꢁ ꢁ
reversed arranging aromatic rings with centroid-to-centroid dis-
tance of 3.677 Å, 3-D supramolecular network in 3a is further con-
structed as indicated in Fig. 14, respectively.
Table 1
Crystal data and structure refinement of 1a–b and 3a–b.
1a
1b
3a
3b
Chemical formula
M
Crystal system
Space group
a/Å
b/Å
c/Å
C
20H12F4N2
C20H12F4N2
356.32
Monoclinic
P21/c
16.353(3)
4.1114(7)
11.984(2)
90
100.583(3)
90
792.1(2)
2
C13H7F4NO
269.20
Triclinic
P-1
6.3852(13)
7.3876(15)
12.161(2)
73.210(3)
89.281(4)
84.066(4)
546.16(18)
2
C13H7F4NO
269.20
Orthorhombic
P212121
5.9626(19)
7.682(3)
24.303(8)
90
90
90
1113.2(6)
4
356.32
Orthorhombic
Pbca
10.630(3)
7.692(2)
20.262(5)
90
90
90
1656.8(8)
4
a
/°
b/°
c
/°
V/Å3
Z
T/K
293(2)
728
1.429
293(2)
364
1.494
293(2)
272
1.637
0.151
293(2)
544
1.606
F(000)
Dcalcd/g cmꢂ3
l
/mmꢂ1
0.117
0.122
0.148
k/Å
Rint
0.71073
0.1865
7528/0/118
1.068
0.0527
0.0792
0.71073
0.0302
3930/0/118
1.056
0.0386
0.1105
0.71073
0.1861
2812/0/174
0.991
0.0694
0.1807
0.71073
0.0775
5708/0/172
1.027
0.0581
0.1263
Data/restraints/param
GOF
R1 [I = 2
r
(I)]a
(I)]b
wR2 [I = 2
r
a
R1
wR2 = [
=
R
||Fo| ꢂ |Fc||/|Fo|.
b
R
w(F2o ꢂ F2c)2/
R r
w(F2o)2]1/2, where w = 1/[ 2(Fo2) + (aP)2 + bP]. P = (Fo2 + 2F2c)/3.

26
W. Pang et al. / Journal of Molecular Structure 1096 (2015) 21–28
Table 2
bridging ACH@NA bond in molecules gives three corresponding
b series’ isomers without co-plannarity stemming from the steric
effect between the substituted fluorine atoms and the lone-pairs
in nitrogen atoms with the corresponding dihedral angles of
50.9° in 1b, 35.9° in 2b, and 50.7(2)° in 3b, respectively.
Obviously, the results show that in the solid state the orientation
of the bridging ACH@NA linkage connecting two larger parts of
the organic molecule would significantly affect the organic molec-
ular conformation. Differences of molecular conformations
between the isomers can tune weak intermolecular interactions/-
contacts, and further tend to differentiate their solid-state molecu-
lar packing arrangements. Because series a molecules have the
almost co-planar structures and easily form intra-layer weak inter-
actions, resulting in assembly of 2-D supramolecular structures as
1a, 2a and 3a. Apparently, it is very easy to understand that series
Distances (Å) and angles (°) of hydrogen bonds and Fꢁ ꢁ ꢁF contacts as well as
interaromatic
pꢁ ꢁ ꢁp
packing for compounds 1–3a.
d(Hꢁ ꢁ ꢁA)
DAHꢁ ꢁ ꢁA/Fꢁ ꢁ ꢁF
1a
d(Dꢁ ꢁ ꢁA)
\DAHꢁ ꢁ ꢁA
C(5)AH(5)ꢁ ꢁ ꢁF(1)#5
C(4)AH(4)ꢁ ꢁ ꢁF(1)#5
C(4)AH(4)ꢁ ꢁ ꢁF(1)#5
C(7)AH(7)ꢁ ꢁ ꢁN(1)#5
pCg1ꢁ ꢁ ꢁpCg2
2.605(2)
2.826(2)
2.636(3)
2.660(3)
3.269(3)
3.374(3)
3.678(3)
3.398(3)
3.865
128.7(3)
118.8(3)
173.7(3)
136.8(3)
pCg2ꢁ ꢁ ꢁpCg1
1b
3.87
C(7)AH(7)ꢁ ꢁ ꢁF(1)
C(7)AH(7)ꢁ ꢁ ꢁF(2)#6
C(5)AH(5)ꢁ ꢁ ꢁF(2)#6
F(1)ꢁ ꢁ ꢁF(1)#6
pCg1ꢁ ꢁ ꢁpCg2
2.527(2)
2.733(2)
2.795(3)
2.860(3)
3.573(3)
3.135(3)
2.810(3)
3.982
109.2(3)
150.7(2)
108.8(3)
b
molecules with non-coplanarity is easier to form 3-D
2a
supramolecular networks as 2b and 3b with an exception of 1b
(having 2D).
C(9)AH(9)ꢁ ꢁ ꢁF(1)
C(10)AH(10)ꢁ ꢁ ꢁF(1)
C(10#1)AH(10#1)ꢁ ꢁ ꢁF(2)
C(7#1)AH(7#1)ꢁ ꢁ ꢁF(2)
F(3)ꢁ ꢁ ꢁF(3)#2
2.562(2)
2.692(2)
2.723(2)
2.757(3)
3.205(3)
3.266(2)
3.466(3)
3.554(3)
2.969(3)
2.900(3)
126.7(2)
120.6(2)
172.3(2)
162.3(2)
Meanwhile, the substituted-position of fluorine atoms in the
organic molecules also plays an important role in constructing dif-
ferent topological 2D/3D supramolecular networks in present sys-
tem. Closely compared with two pairs of isomers 1a–b and 2a–b,
the substituted fluorine atoms in 1a and 1b only lie in core ben-
F(2)ꢁ ꢁ ꢁF(5)#1
2b
C(7)AH(7)ꢁ ꢁ ꢁF(1)
C(7)AH(7)ꢁ ꢁ ꢁF(5)#2
C(9)AH(9)ꢁ ꢁ ꢁF(5)#2
F(2)ꢁ ꢁ ꢁF(3)#3
F(3)ꢁ ꢁ ꢁF(2)#3
F(4)ꢁ ꢁ ꢁF(1)#4
2.399(2)
2.536(2)
2.851(2)
2.871(3)
3.426(3)
3.575(3)
2.859(3)
2.859(3)
2.843(3)
111.3(3)
159.9(3)
147.1(3)
zene ring, it is found that formation of intermolecular
p p stack-
ꢁ ꢁ ꢁ
ing interactions is more easily than Fꢁ ꢁ ꢁF contact in the case.
Obviously, this work may provide a potential route for construct-
ing high-dimensional supramolecular framework architectures
with different topologies and properties by changing the orienta-
tion of bridging ACH@NA bond and the fluoro-substituted posi-
tions in organic molecules.
3a
O(1)AH(1)ꢁ ꢁ ꢁN(1)
O(1)AH(1)ꢁ ꢁ ꢁF(1)
C(2)#7AH(2)#7ꢁ ꢁ ꢁF(1)
C(11)AH(11)ꢁ ꢁ ꢁF(2)#7
C(3)#8AH(3)#8ꢁ ꢁ ꢁF(2)
C(4)#8AH(4)#8ꢁ ꢁ ꢁF(2)
C(4)#9AH(4)#9ꢁ ꢁ ꢁF(3)
C(5)#9AH(5)#9ꢁ ꢁ ꢁF(3)
C(5)AH(5)ꢁ ꢁ ꢁF(4)#8
C(7)AH(7)ꢁ ꢁ ꢁF(4)#8
C(11)AH(11)ꢁ ꢁ ꢁF(3)#9
pCg1ꢁ ꢁ ꢁpCg2
1.949(3)
2.769(3)
2.874(3)
2.843(3)
2.823(2)
2.855(2)
2.866(2)
2.866(2)
2.818(2)
2.844(2)
2.567(2)
2.621(3)
3.626(3)
3.609(3)
3.274(3)
3.486(3)
3.449(3)
3.452(4)
3.451(4)
3.596(3)
3.594(4)
3.490(3)
3.677(4)
135.8(2)
158.2(2)
126.9(2)
115.2(2)
120.4(2)
122.8(3)
122.2(3)
122.1(3)
157.8(3)
152.6(3)
172.1(3)
Experimental
Instrumentation
NMR spectra were recorded in CDCl3 on 300 MHz spectrometer
(Bruke AM300) or Varian VXR) with TMS as internal standard. IR
spectra were carried on a Perkin-Elmer 983 spectrophotometer.
Lower resolution mass spectrums were obtained from a Finnigan
GC–MS 4021 instrument using the electron impact ionization tech-
nique (70 eV).
3b
O(1)AH(1)ꢁ ꢁ ꢁN(1)
O(1)AH(1)ꢁ ꢁ ꢁF(1)#10
C(3)AH(3)ꢁ ꢁ ꢁF(3)#11
C(7)AH(7)ꢁ ꢁ ꢁF(1)#12
C(5)AH(4)ꢁ ꢁ ꢁF(4)#12
C(5)AH(5)ꢁ ꢁ ꢁF(2)#12
C(11)#12AH(11)#12ꢁ ꢁ ꢁF(3)
C(11)AH(11)ꢁ ꢁ ꢁF(3)#13
pCg1ꢁ ꢁ ꢁpCg2
1.905(2)
2.866(2)
2.774(2)
2.549(2)
2.804(2)
2.820(2)
2.514(2)
2.514(2)
2.628(3)
3.242(3)
3.515(3)
2.896(3)
3.383(3)
3.402(3)
3.196(3)
3.196(3)
3.755
146.4(2)
110.1(2)
137.5(3)
112.5(2)
121.4(2)
121.6(2)
130.3(2)
130.3(2)
Materials
The compounds terephthalaldehyde, aniline, 2,3,5,6-tetrafluoro
benzene-1,4-diamine, benzaldehyde, 2,3,4,5,6-pentafluorobenzal
pCg2ꢁ ꢁ ꢁpCg1
3.821
dehyde,
fluoroaniline, thionyl chloride, terephthalic aldehyde, poly-
fluorobenzaldehyde, 2-aminophenol, salicylic aldehyde,
2,3,4,5,6-pentafluorobenzaldehyde,
2,3,4,5,6-penta-
a
Symmetry transformation used to generate equivalent atoms: #1 2 ꢂ x, 3 ꢂ y,
1 ꢂ z; #2 x, y + 1, z; #3 ꢂ1 ꢂ x, 0.5 + y, 1.5 ꢂ z; #4 1.5 + x, 0.5 ꢂ y, ꢂ0.5 + z; #5
ꢂ1 + x, y, z; #6 ꢂ1 + x, y, ꢂ1 + z; #7 x, y, 1 + z; #8 ꢂ2 + x, 1 + y, z; #9 1 ꢂ x, 1 ꢂ y,
1 ꢂ z; #10 ꢂ0.5 + x, 1.5 ꢂ y, 2 ꢂ z; #11 ꢂ1.5 + x, 1.5 ꢂ y, 2 ꢂ z; #12 ꢂ0.5 + x, 1.5 ꢂ y,
2 ꢂ z; #13 ꢂ2 + x, y, z. Cg1 and Cg2 respectively denote the centroids of benzene
and fluoro-substituted benzene rings in the six compounds 1a–b, 2a–b and 3a–b.
p-toluenesulfonic acid and 2,3,5,6-tetrafluoroaniline, as well as sol-
vents dichloro methane, ethanol and toluene were used as
supplied.
(N,N0E,N,N0E)-N,N0-(perfluoro-1,4-phenylene)bis(methan-1-yl-1-
ylidene)dibenzenamine (1a)
Conclusion
In summary, three isomeric pairs 1a–b, 2a–b and 3a–b are
structurally analyzed by the pairwise comparison of
bridge-flipped isomers. When the carbon atom of the bridging
ACH@NA linkage is directly connected to multi-fluorinated aryl
rings, three a series’ compounds 1a, 2a, and 3a are given, in which
the phenyl ring and the fluorinated benzene ring are nearly copla-
nar with dihedral angles of 8.8(2)° in 1a, 4.0(1)°in 2a, and 3.3(2)° in
3a, respectively. However simply reversing the orientation of
A
mixture of 206 mg (1.0 mmol) terephthalaldehyde and
205 mg (2.2 mmol) aniline was stirred at 120 °C for 16 h. Then
extracted by dichloro methane, the crude product was obtained.
It was purified by column chromatogram to give product. Yield
67%. 1H NMR (300 Hz, CDCl3): d 8.52 (s, 2H, ACH@), 7.44–7.23
(m, 10H, A2C6H5A). 19F NMR: d ꢂ143.1 (s, 4F). FT-IR (KBr, cmꢂ1):
2918 (w), 1603 (vs), 1521 (vs), 1498 (vs), 1485 (s), 1417 (s),
1379 (s), 1313 (s), 1157 (s), 1141 (s), 1011 (vs), 967 (vs), 947

W. Pang et al. / Journal of Molecular Structure 1096 (2015) 21–28
27
(vs), 848 (vs), 581 (w). ESI–MS: m/z 357 ([M+1]+, 62%), 356 ([M]+,
(E)-2-((2,3,5,6-tetrafluorophenylimino)methyl)phenol (3b)
88%).
A
50 mL flask was filled with 20 mL of toluene,
122 mg(1.0 mmol) of salicylic aldehyde, 1.7 mg (0.01 mmol) of
p-toluenensulfonic acid and 165 mg (1.0 mmol) of
(N1E,N4E)-N1,N4-dibenzylidene-2,3,5,6-tetrafluorobenzene-1,4-
diamine (1b)
2,3,5,6-tetrafluoroaniline. The mixture was heated with reflux for
20 h, then solution was cooled to ambient temperature, filtered
and the solvent was removed in vacuum resulting deep yellow
oil. The residue was purified by column chromatography using sil-
ica gel to give the product. Yield 66%. 1H NMR (300 Hz, CDCl3): d
12.25 (s, 1H, AOH), 8.83 (s, 1H, ACH@), 7.47–7.39 (m, 2H,
A2C6H4(OH)), 7.21–7.12 (m, 1H, C6F4H), 7.07–6.99 (m, 2H,
A2C6H4(OH)). 19F NMR: d ꢂ139.3 (m, 2F), ꢂ152.5 (m, 2F). FT-IR
(KBr, cmꢂ1): 3322 (m, br), 2927 (w), 1660 (s), 1611 (s), 1523 (vs),
1496 (vs), 1483 (vs), 1421 (s), 1394 (s), 1312 (s), 1153 (s), 1139
(s), 1010 (vs), 957 (vs), 922 (m), 835 (s), 570 (w). ESI–MS: m/z
270 ([M+1]+, 47%), 269 ([M]+, 91%).
A
mixture of 180 mg (1.0 mmol) 2,3,5,6-tetrafluorobenze
ne-1,4-diamine and 212 mg (2.0 mmol) benzaldehyde in ethanol
(20 mL) was refluxed for 2 h. After cooling, the organic crystals
were collected by filtration and washed with cold ethanol. Yield
63%. 1H NMR (300 Hz, CDCl3): d 8.48 (s, 2H, ACH@), 7.65–7.30
(m, 10H, A2C6H5A). 19F NMR: d ꢂ151.5 (s, 4F). FT-IR (KBr, cmꢂ1):
2933 (w), 1612 (vs), 1516 (vs), 1495 (s), 1479 (vs), 1422 (s),
1368 (s), 1319 (s), 1161 (m), 1137 (vs), 1008 (s), 971 (vs), 943
(vs), 855 (vs), 575 (w). ESI–MS: m/z 357 ([M+1]+, 56%), 356
([M]+, 93%).
(N1E,N4E)-N1,N4-bis(perfluorobenzylidene)-benzene-1,4-diamine
(2a)
X-ray crystal structure determinations
A mixture of 392 mg (2.0 mmol) 2,3,4,5,6-pentafluorobenzalde
hyde and 108 mg (1.0 mmol) 2,3,4,5,6-pentafluorobenzaldehyde
in ethanol (20 mL) was refluxed for 2 h. After cooling, the orange
crystals were collected by filtration and washed with cold ethanol.
Yield 45%. 1H NMR (300 Hz, CDCl3): d 8.62 (s, 2H, ACH@), 7.32 (s,
4H, AC6H4A). 19F NMR: d 20.1 (m, 4F), 12.5 (t, 2F), 0.4 (m, 4F).
FT-IR (KBr, cmꢂ1): 2923 (w), 1919 (w), 1652 (m), 1604 (s), 1522
(vs), 1493 (vs), 1482 (vs), 1415 (s), 1380 (s), 1311 (s), 1153 (s),
1138 (s), 1010 (vs), 965 (vs), 951 (vs), 845 (vs), 727 (w), 661 (m),
577 (w). ESI–MS: m/z 465 ([M+1]+, 58%), 464 ([M]+, 95%).
Data collections were performed at 293 K on a Bruker Smart
Apex II diffractometer with graphite-monochromated Mo Ka radi-
ation (k = 0.71073 Å) for 1a–b and 3a–b. Absorption corrections
were applied by using the multi-scan program SADABS [27].
Structural solutions and full-matrix least-square refinements
based on F2 were performed with the SHELXS-97 [28] and
SHELXL-97 [29] program packages, respectively. All the
non-hydrogen atoms were refined anisotropically. The hydrogen
atoms were placed at calculated positions and included in the
refinement in the riding model approximation. The organic hydro-
gen atoms were generated geometrically (CAH = 0.93 or 0.96 Å)
and refined with isotropic temperature factors. Details of the crys-
tal parameters, data collections and refinement for four new com-
plexes are summarized in Table 1. Hydrogen-bonding data of six
complexes 1a–b, 2a–b, 3a–b are listed in Table 2. CCDC 741404,
812960, 741403, 741402, 635189 and 635190 are for 1a–b, 2a–b,
3a–b, respectively.
(N,N0E,N,N0E)-N,N0-(1,4-phenylenebis-(methan-1-yl-1-
ylidene))bis(2,3,4,5,6-pentafluorobenzenamine) (2b)
366 mg (2.0 mmol) 2,3,4,5,6-pentafluoroaniline was added to
thionyl chloride (20 mL) contained in 50 mL three-necked round
bottom flask provide with a reflux condenser protected by a cal-
cium chloride drying tube and maintained under nitrogen. The
mixture was stirred and heated to reflux for 8 h. Then solution
was cooled and the solvent removed in vacuo. The residue was dis-
solved in CH2Cl2 (20 mL), 134 mg (1.0 mmol) terephthalic alde-
hyde (1.34 g, 10 mmol) was then added and the mixture was
stirred at room temperature for overnight. After evaporated in
vacuo, the crude product was recrystallized from ethanol and
yielded product. Yield 50%. 1H NMR (300 Hz, CDCl3): d 8.56 (s,
2H, ACH@), 7.85 (s, 4H, AC6H4A). 19F NMR: d 8.9 (m, 4F), 2.1 (t,
2F), ꢂ0.8 (m, 4F). FT-IR (KBr, cmꢂ1): 2928 (w), 1918 (w), 1651
(m), 1604 (s), 1523 (vs), 1493 (vs), 1481 (vs), 1416 (s), 1380 (s),
1311 (s), 1153 (s), 1138 (s), 1010 (vs), 965 (vs), 951 (vs), 845
(vs), 727 (w), 661 (m), 577 (w), 537(w). ESI–MS: m/z 465
([M+1]+, 49%), 464 ([M]+, 97%).
Acknowledgements
This work was financially supported by the Shanghai Municipal
Natural Science Foundation (Grant No. 12ZR450200) and the
National Natural Science Foundation of China (NNSFC) (Nos.
21102163). The authors would like to thank Prof. Y. P. Cai at
South China Normal University for technical assistance.
Appendix A. Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.molstruc.2015.04.
035.
(E)-2-(2,3,5,6-tetrafluorobenzylideneamino)-phenol (3a)
References
A solution of 178 mg (1.0 mmol) polyfluorobenzaldehyde and
109 mg (1.0 mmol) 2-aminophenol in CH2Cl2 over anhydrous
MgSO4 was left at room temperature for 24 h. The solution was fil-
tered and the solvent was removed by rotary evaporation affording
the product. Yield 79%. 1H NMR (300 Hz, CDCl3): d 8.88 (s, 2H,
ACH@), 7.44 (d, 1H, C6H4), 7.36 (d, 1H, AC6H4A), 7.30–7.24 (m,
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958 (vs), 922 (m), 835 (s), 571 (w). ESI–MS: m/z 270 ([M + 1]+,
42%), 269 ([M]+, 83%).
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