Synthesis and properties of hexakis-(β-carboxyethenylphenoxy)cyclotriphosphazene

Article abstract of DOI:10.1016/j.molstruc.2017.07.005

A new cyclotriphosphazene derivative (3) was prepared from the reaction of hexakis-(p-formilphenoxy)cyclotriphosphazene (2) with malonic acid. The structure of 3 was approved by spectroscopic techniques (FT-IR, ³¹P, ¹H, ¹³C NMR) and small-angle X-ray scattering method. The thermal behavior of compound 3 was investigated by thermogravimetric (TGA) analysis and differential scanning calorimetry (DSC). This compound was found to be stable up to about 300 °C. At 310 °C 3 was decarboxylated with simultaneous conversion of the multiple bonds and the formation of a highly cross-linked polymeric residue. By theoretical calculation a sphere diameter around a molecule 3 was installed. Whereby seems promising to use 3 as a nanoscale hybrid modifier various polymers, and for the synthesis of ion-exchange resins.

Full text of DOI:10.1016/j.molstruc.2017.07.005

Journal of Molecular Structure 1148 (2017) 1e6
Contents lists available at ScienceDirect
Journal of Molecular Structure
journal homepage: http://www.elsevier.com/locate/molstruc
Synthesis and properties of hexakis-(
cyclotriphosphazene
b-carboxyethenylphenoxy)
Evgeniy M. Chistyakov , Darya V. Panfilova *, Vyacheslav V. Kireev a,
a
a,
b
a
Vladimir V. Volkov , Michael F. Bobrov
D. I. Mendeleyev University of Chemical Technology of Russia, Miysskaya street, 9, 125047, Moscow, Russian Federation
a
b
Shubnikov Institute of Crystallography of Federal Scientific Research Centre “Crystallography and Photonics” of Russian Academy of Sciences, Russian
Federation
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 June 2017
Received in revised form
A
new cyclotriphosphazene derivative (3) was prepared from the reaction of hexakis-(p-for-
milphenoxy)cyclotriphosphazene (2) with malonic acid. The structure of 3 was approved by spec-
troscopic techniques (FT-IR, P, H, C NMR) and small-angle X-ray scattering method. The thermal
behavior of compound 3 was investigated by thermogravimetric (TGA) analysis and differential
scanning calorimetry (DSC). This compound was found to be stable up to about 300 C. At 310 C 3 was
decarboxylated with simultaneous conversion of the multiple bonds and the formation of a highly
cross-linked polymeric residue. By theoretical calculation a sphere diameter around a molecule 3 was
installed. Whereby seems promising to use 3 as a nanoscale hybrid modifier various polymers, and for
the synthesis of ion-exchange resins.
31
1
13
5
July 2017
Accepted 6 July 2017
Available online 12 July 2017
ꢀ
ꢀ
Keywords:
Phosphazene
Carboxylic derivates
Malonic acid
© 2017 Elsevier B.V. All rights reserved.
Cross-linked polymer
Nanoscale
Heat resistance
1. Introduction
ring [9], thus chemical modification inert to halogen-
phosphazenes group have been used. Disadvantage of these
Aryloxyphosphazene with side carboxy-groups are of
considerable scientific and practical interest due to their physical
and chemical properties. Supramolecular cylindrical polyamides
1], incombustible epoxy resins [2] and polyacids have been ob-
a
methods is occurring side reactions of other functional groups
during oxidation of the aldehyde group [10e12]. This method is
acceptable only for benzoic acids since the aliphatic chains will
undergo oxidation. Second method is the ester group hydrolysis. It
is also ineffective, since the reaction is accompanied by the
destruction of the phosphazene ring [13]. Another method is
adding anhydrides to hydroxyl- or amino-groups. This method is
rather difficult, as well as the reaction is not completely [9]. Thus,
the aim of the study was a new method for the synthesis of
phosphazenes carboxyl derivatives, which was devoid of the
above drawbacks. These compounds can be used as modifiers of
various polymer binders, in particular as additives to epoxy resins
to increase the fire-resistance and thermal stability of composi-
tions based on them.
[
tained based on it and could be applied as immunostimulatory
compounds and materials for microencapsulation of drugs [3,4].
Complex forming fluorescent water-soluble sopolymers have also
be obtained on the base of phosphazenes [5]. Industrial methods
for producing multi valent salt for water desalination by direct
osmosis have been investigated [6]. Dental surgery is one of a
prospective application of carboxyl derivatives derivatives [7,8]. It
is known, that phosphazenes containing free carboxy-groups
could't be obtained directly by reacting the appropriate phenol
or an aromatic amine with halogen-phosphazenes since the
carboxy-group is able to replace the halogen in the phosphazene
Herein, we reported synthesis, characterization and thermal
behavior
of
carboxyl
substituted-cyclotriphosphazene
compound (3).
*
Corresponding author.
E-mail address: dasha_panfilova@mail.ru (D.V. Panfilova).
http://dx.doi.org/10.1016/j.molstruc.2017.07.005
022-2860/© 2017 Elsevier B.V. All rights reserved.
0

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E.M. Chistyakov et al. / Journal of Molecular Structure 1148 (2017) 1e6
Scheme 1. Chemical structure and synthetic pathway of 3.
2
. Experimental
recrystallized from petroleum ether. Mass spectra, 1H, 13C, solid
state C, P NMR and FT-IR spectra were recorded on a Bruker
Auto Flex II mass spectrometer, a Bruker AV-400 and an Magna-IR-
13
31
2.1. Materials and method
750 Nicolet FTIR spectrometer, respectively. Thermal analysis of the
4
-Hydroxybenzaldehyde, THF, pyridine, piperidine, malonic
compound was examined by thermogravimetric analysis (TGA) and
differential scanning calorimetry (DSC) using a Derivatograph_C
instrument (10 K/min) and a DSC-822e calorimeter (Mettler-
acid and the deuterated solvent (DMSO-d ) for NMR analysis were
purchased from Vecton. Hexachlorocyclotriphosphazene was
6
ꢀ
Toledo, Switzerland) (20 C/min), respectively. Theoretical calcu-
lation of molecule 3 was carried out based on compound “SIFKUFF”
structure from the Cambridge structural data base (CSD). Small-
angle X-ray scattering (SAXS) measurements were carried out on
a laboratory diffractometer “AMUR-K” at the Cu-K
a wavelength
l
¼ 0.154 nm.
2.2. Synthesis of hexachlorocyclotriphosphazene (1) and hexakis-
(p-formilphenoxy)cyclotriphosphazene (2)
Hexachlorocyclotriphosphazene (1) was synthesized and puri-
fied as defined by Sirotin et al. [14]. Compound 2 was obtained by
interaction 1 with p-hydroxybenzaldehyde sodium salt [15].
2.3. Synthesis of hexakis-(
b-carboxyethenylphenoxy)
cyclotriphosphazene (3)
In a round bottom flask equipped with magnetic stirrer were
dissolved compound 2 (2 g 0,002 mol) and malonic acid (2.1 g,
0
.02 mol) in dry pyridine (2,5 ml). Then one drop of piperidine
was added to the reaction mixture. Synthesis lasted for 10 h at
ꢀ
1
15 C. Then the product precipitated with aqueous solution of
2
hydrochloric acid (50 ml 36 wt% HCl in 100 ml H O). The
resulting precipitate was filtered off, washed with distilled water,
solid filtered and dried. Compound 3 was obtained as a white
solid. Yield: 2.4 g (93%). MALDI-MS: m/z calc.1113.17; found:
1
114.093 [MþH]þ. Acid number: 301 (calc.: 301). FT-IR (KBr)
n
max
ꢁ1
(cm ): 3021 and 3060 nAr-CH, 2928 nAliphatic-CH, 1692 nC]O, 1632
Fig. 1. 31P NMR spectrum of 3 (dimethylsulfoxide-d6).

E.M. Chistyakov et al. / Journal of Molecular Structure 1148 (2017) 1e6
3
n
C]C, 1179 and 1209
n
P]N, 956
n
PeOeC. 31P NMR (162 MHz, DMSO
: 6.47 (d,
H , ¼CHeCOO), 6.94 (d, 2 H, Ar-H ), 7.55 (d, H , AreCH¼), 7.61 (d,
168.01 ppm). The completeness of the condensation reaction and
the formation of carboxyl groups can also be judged from the
MALDI-TOF spectrum (Fig. 4), on which there is only one peak (m/
z ¼ 1114), completely corresponding to the molecular weight of
compound 3. The correspondence of a certain acid number to the
-
d6) d
d
p
: 9.49 (s). 1H NMR (400 MHz, DMSO -d6)
H
6
2
5
3
13
7
2
H, Ar-H ). C NMR (100.6 MHz, DMSO -d6)
d
C
¼ 168.01C
1
5
(
COOH), 151.30 Ar-C (PeOeC), 143.06C (Ar-CH]CH), 132.22
3
4
6
2
Ar-C , 130.11 Ar-C , 121.48C (Ar-CH]CH), 120.02 Ar-C .
theoretical
also
confirms
the
completeness
chemical
transformation.
The compound 3 was investigated by small-angle scattering
method (Table 1). The values of the interplanar distance and the
diameters of crystallinity were determined. The presence of
randomly spaced peaks suggests a three-dimensional ordering of
molecules. For systems quasicrystalline disorder parameter, usually
less than 0.10, found parameters indicate the presence of crystalline
areas in the investigated sample.
However, the melting point 3 could not be determined. On the
DSC curve of compound 3 (Fig. 5-a), as far as heating was con-
cerned, no endothermic effects were observed which should
correspond to the substance melting. Also, there were no thermal
capacity (glass-transition temperature) bounce specific of amor-
3
. Results and discussion
3.1. Synthesis and characterization
Suggested method for obtaining the carboxylic derivatives
based on the Knoevenagel reaction (Scheme 1).
This method allows to obtain phosphazenes containing as sub-
stituents at each phosphorus atom by two radical p-hydroxycin-
namic acid. In Ref. [16] describes the synthesis of similar
compounds, but this method is complicated and the main reaction
may be accompanied by the partial destruction of the phosphazene
cycle. 31P NMR spectra of 3 display the singlet (Fig. 1), which in-
phous substances. However, the curve has an exothermic peak at
dicates that during the reaction the phosphazene ring is completely
preserved.
ꢀ
ꢀ
3
10 C. TGA data (Fig. 5-b), shows that compound 3 is stable up to
In the 1H NMR spectra of compound 3 (Fig. 2), protons of the
310 C, after which a 20% loss of mass is observed on the curve.
Following the further heating, the substance is relatively stable
aldehyde groups [15] 10.14 ppm are disappeared. The C]C bonds
protons for the compound 3 were observed at 6.47 and 7.55 ppm.
The ratio of the protons integral height in the H NMR spectrum of
the compound 3 supports the proposed structure. The presence of
carboxyl groups in the compound is confirmed by the carbon NMR
spectrum (Fig. 3a), in which the corresponding signal is present at
ꢀ
and at 500 C the mass of the residue is about 60%.
1
It was suggested that the exothermic peak on the DSC curve and
ꢀ
the loss of 20% mass on the TGA curve at 310 C were due to
complete decarboxylation. This fact is consistent with the IR spectra
(Fig. 6): characteristic peak oscillations of carbonyl groups at
Fig. 2. 1H NMR spectrum of 3 (dimethylsulfoxide-d6).

4
E.M. Chistyakov et al. / Journal of Molecular Structure 1148 (2017) 1e6
Fig. 3. 13C NMR spectrum (dimethylsulfoxide-d ) of 3 (a) and solid state 13С NMR spectrum 3 heated at 320 ꢀC during 10 min (b).
6

E.M. Chistyakov et al. / Journal of Molecular Structure 1148 (2017) 1e6
5
Fig. 4. MALDI TOF-MS spectrum of compound 3.
Table 1
The small-angle scattering method, the long range order (L), the Bragg spacing (D)
and the degree of disorder interplanar distances ( =D)
D
Peak numbers
L, Å
D, Å
D=D
1
2
3
4
5
345
293
400
1053
379
19.6
11.4
8.4
7.9
7.2
0.076
0.063
0.046
0.028
0.044
ꢀ
Fig. 6. IR spectrum starting (a) and heated at 320 C for 10 min (b) compound 3.
ꢁ
1
692 cm 1 is completely absent after heating.
about new types of nuclei.
In addition, in IR spectrum the heated sample bandwidth os-
cillations of double bonds disappears (1632 cm ) and a peak ap-
pears at 525 cm , corresponding deformation and pendular
oscillations of CeH, typical for polystyrene chains. The formation of
ꢁ1
As a result of the theoretical calculation, in a molecule found 3
non-covalent interactions, leading to the formation various
pseudo-cycles between the atoms of one substituent at the phos-
phorus atom and between two geminal substituents (Fig. 7).
Solubility 3 only in highly polar aprotic solvents, amines and
alkalies concentrated solutions may also indicate a large amount of
intermolecular hydrogen bonds.
ꢁ
1
carbon-chain polymer structures is also confirmed by the solid-
state 13C spectrum (Fig. 3b). There is no signal of the carbon atom
of the carbonyl group (168.01 ppm) in the spectrum, but there are
signals of carbon atoms of the aromatic ring (149.42, 140.10, 128.94
and 120.58 ppm) and the hydrocarbon polymer chain in the
4e44 ppm region. All other peaks are lateral rotation lines from
signals of different carbon atoms and do not carry information
By theoretical calculation a sphere diameter around a molecule
3
was installed. It is 1.8 nm, whereby seems promising to use 3 as
3
a nanoscale hybrid modifier various polymers [17,18], for synthesis
metallated complexes derivatives of the cyclophosphazene [19]
and
promising
candidate
materials
for
biomedical
applications [20].
4. Conclusion
As a result of the study, a new method for the synthesis of
31
phosphazenes carboxyl derivatives was developed. By means of
P
NMR spectroscopy, it was found that during the synthesis of hex-
akis-( -carboxyethenylphenoxy)cyclotriphosphazene (3) no
b
destruction of the phosphazene ring was not observed. The com-
plete conversion of formyl groups to acrylic groups was confirmed
1
by H NMR spectroscopy. It was determined that compound 3 was
ꢀ
thermally stable to 310 C, after which it had complete decarbox-
ylation. As a result of theoretical calculation the size of a molecule 3
equal to 1.8 nm was estimated and a large number of intermolec-
ular non-covalent bonds was confirmed. The resulting compound
can be used as a modifier of various polymer binders, dental ma-
terials and epoxy resins.
Fig. 5. DSC (a) and TGA (b) curves compound 3.

6
E.M. Chistyakov et al. / Journal of Molecular Structure 1148 (2017) 1e6
Fig. 7. A fragment of molecular structure 3, a dotted line indicated by non-covalently bonded atoms (R e oxy-coumaric radicals).
Acknowledgment
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