Synthesis and structure of hexa-p-acetamidophenoxycyclotriphosphazene

Article abstract of DOI:10.1134/S1070363212060047

Hexa-p-acetamidophenoxycyclotriphosphazene was synthesized and examined by the 31P and 1H NMR spectroscopy and XRD analysis. Original Russian Text.

Full text of DOI:10.1134/S1070363212060047

ISSN 1070-3632, Russian Journal of General Chemistry, 2012, Vol. 82, No. 6, pp. 1065–1068. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © E.M. Chistyakov, S.N. Filatov, V.V. Kireev, K.A. Lysenko, M.I. Buzin, V.P. Chuev, 2012, published in Zhurnal Obshchei Khimii,
2012, Vol. 82, No. 6, pp. 906–909.
Synthesis and Structure
of Hexa-p-acetamidophenoxycyclotriphosphazene
E. M. Chistyakova, S. N. Filatova, V. V. Kireeva,
K. A. Lysenkob, M. I. Buzinb, and V. P. Chuevc
a Mendeleev Russian Chemical-Technological University, Miusskaya pl. 9, Moscow, 125047 Russia
e-mail: kireev@muctr.ru
b Nesmeyanov Institute of Organoelemental Compounds, Moscow, Russia
c LLC “VladMiVa,” Belgorod, Russia
Received March 30, 2011
1
Abstract—Hexa-p-acetamidophenoxycyclotriphosphazene was synthesized and examined by the 31P and H
NMR spectroscopy and XRD analysis.
DOI: 10.1134/S1070363212060047
One of the important trends in chemistry is the study
of supramolecular structures organized on a nano-
level. Due to their structure and functionality as well as
the possibility to vary their properties by the chemical
modification, cyclophosphazenes, in particular hexachlo-
rocyclotriphosphazenes are an interesting object of both
theoretical and experimental supramolecular chemistry.
Starting from phosphazenes self-organizing structures
were obtained with a desired shape and geometry based
on electrostatic interactions, hydrogen or coordination
bonding [1–3]. Starting from cyclophosphazenes a
series of compounds capable of forming the clathrates
was also synthesized [4–7]. The formation of supra-
molecular ensembles in these clathrates occurs via the
immobilization of the small molecules in the lattices of
macromolecular compounds. The formed compounds
can be widely used, for example, in the manufacture of
matrices for polymerization reactions, to separate the
molecules in the preparation of compounds with
nonlinear optical activity, to purify drugs, to capture
and store toxic substances. The presence in the crystal
lattice of hexa-p-acetamidophenoxycyclotriphosphazene
of large cavities capable to form clathrate compounds
makes them promising for scientific and applied research.
The synthesis of hexa-p-acetamidophenoxycyclotri-
phosphazene (HCP) was performed by the phenolate
method as follows.
O
O
C2H5ONa
−C2H5OH
HO
CH3
NaO
C
CH3
NH
C
NH
O
C
HCP
−NaCl
N3P3
O
CH3
NH
6
HCP = Hexachlorocyclotriphosphazene.
During the reaction all the chlorine atoms in the tri-
phosphazene ring can be replaced with a minimal prob-
ability of side-reactions. The phenolates were obtained
in the reaction of phenol with sodium ethoxide.
1065

1066
CHISTYAKOV et al.
Fig. 1. General view of hexa-p-acetamidophenoxycyclotriphosphazene by the X-ray data.
Hexa-p-acetamidophenoxycyclotriphosphazene is a
tified directed along the crystallographic axis. During
the crystallization of hexa-p-acetamidophenoxy-
cyclotriphosphazene from THF these channels are able
to be filled with six solvent molecules (Fig. 2b).
crystalline substance. According to the XRD analysis,
the conformation of the phosphazene ring is a semi-
chair. The P1 and N2 atoms are out-of-plane by 0.22
and 0.14 Å (the standard deviation does not exceed
0.01 Å, Fig. 1). The main bond lengths and the bond
angles are given in Tables 1 and 2, respectively.
The TGA curve for the recrystallized sample of the
obtained phosphazene has a stepwise character (Fig. 3). In
the low-temperature range of 100–125°C the sample
mass loss is 7% due to the crystal solvate destruction
and THF removal. On recrystallization, a very stable
complex between the hexa-p-acetamidophenoxy-
Analysis of the crystal packing showed that the
molecules are bonded by the sufficiently strong
N–H···O bonds with the distance between the proton
donor and acceptor in the range of 2.732(3)–2.965(3) Å.
The molecules are cross-linked by these bonds into a
three-dimensional framework (Fig. 2a), where
sufficiently large channels 14×15 Å have been iden-
Table 2. Bond angles in the hexa-p-acetamidophenoxy-
cyclotriphosphazene molecule
Angle
ω, deg
Angle
ω, deg
N2P1O2
N2P1N1
O2P1N1
N2P1O1
O2P1O1
N1P1O1
P1АN2P1
106.56(18)
117.3(3)
112.3(2)
110.4(2)
99.25(17)
109.5(2)
122.1(4)
N1АP2N1
N1АP2O3
N1P2O3
N1P2O3А
O3P2O3А
P2N1P1
116.7(3)
Table 1. Bond lengths in the hexa-p-acetamidophenoxy-
cyclotriphosphazene molecule
110.35(17)
111.25(18)
110.35(17)
94.8(3)
Bond
Length, Å
Bond
Length, Å
P1–N2
P1–O2
P1–N1
1.577(3)
1.581(3)
1.580(5)
P1–O1
P2–N1
P2–O3
1.583(3)
1.577(4)
1.589(4)
122.6(2)
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 82 No. 6 2012

SYNTHESIS AND STRUCTURE
1067
(a)
(b)
Fig. 2. Fragment of the crystal packing of hexa-p-acetamidophenoxycyclotriphosphazene: (а) N–H···O hydrogen bonding and (b) a
solvate with THF molecules.
cyclophosphazene and the solvent in an equimolar
ratio is formed. The product formed after the solvent
removal is thermally stable up to 325°C.
the sample remains amorphous. The DSC curve
(Fig. 4, curve 2) contains only a change in a heat
capacity of the sample at the glass transition point. The
DSC termogram of reheating the hexa-p-acetamido-
phenoxycyclotriphosphazene (Fig. 4, curve 3) contains
a heat capacity jump at the devitrification of the
amorphous phase (Tv 113°C) and successive exo- and
endothermal effects corresponding to the formation
and melting of the crystal phase. On re-heating the
heats of the cold crystallization and melting of hexa-p-
acetamidophenoxycyclotriphosphazene are similar and
equal to 54.5 J g–1. The melting point (the maximum
endothermic peak at 257°C) is slightly lower than that
observed during the first heating of the sample. Thus,
the crystallization from the melt in a DSC experiment
leads to the formation of more defective crystalline
phase than during the crystallization from solution.
Some thermal effects appear on the DSC curve of
the recrystallized sample of hexa-p-acetamido-
phenoxycyclophosphazene at the first heating (Fig. 4,
curve 1). The first, endothermic, effect at 99°C (ΔH
6.31 J g–1) corresponds to the removal of the solvent
molecules. The second, exothermic, effect occurs in
the temperature range of 120–170°C and is associated
with the recrystallization of the fragments of the
cyclotriphosphazene crystal lattice broken in the
solvent removing process (ΔH 7.18 J g–1). Finally, the
third, endothermic, peak with a maximum at 260°C
corresponds to the crystalline phase melting (ΔH
80.6 J g–1). On cooling with a rate of 20 deg min–1
Tv
T, °C
Fig. 4. DSC curve of hexa-p-acetamidophenoxycyclo-
triphosphazene at the first (1), the second (3) heating and
cooling (2). The heating/cooling rate is 20 deg min–1 in
argon atmosphere.
T, °C
Fig. 3. TGA curve of hexa-p-acetamidophenoxycyclo-
triphosphazene at heating in air with a rate of 10 deg min–1.
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1068
CHISTYAKOV et al.
stirrer and reflux condenser was placed 7.9 g
EXPERIMENTAL
(0.06 mol) of p-acetamidophenol and 30 ml of
ethanol. After the complete dissolution of p-acetamido-
phenol a solution of sodium ethoxide [prepared by
dissolving 1.15 g (0.05 mol) of sodium in 20 ml of
ethanol] was added with stirring. The reaction was carried
out over 10 min, after which ethanol was distilled off
on a vacuum rotary evaporator. The resulting
phenolate was dried in a vacuum to the constant mass.
4-Acetamidophenol (paracetamol, 98%, Acros),
sodium metal (pure, Reachim, Czechia), phosphorus
pentachloride (98%, Acros), ammonium chloride (of
chemical grade, Laverna), petroleum ether 40–70
(LLC “Khimvest”), 2-methoxyethyl ether (99%, Acros),
pyridine (of analytical grade, LLC “Khimvest”) were
used without further purification. Benzene (of
analytical grade, “Khimmed”) was dried over calcium
chloride and distilled. Tetrahydrofuran and dioxane
(BASF) were kept over alkali, then dried and distilled
over metallic sodium. Ethyl alcohol (96.5%, Glavspirt)
was dried over aluminum amalgam and distilled.
Into a 3-neck flask equipped with a stirrer and
reflux condenser were placed 10.38 g (0.06 mol) of
paracetamol phenolate and 40 ml of 2-methoxyethyl
ether. In parallel, a solution of 2.61 g (0.0075 mol) of
hexachlorotriphosphazene in 20 ml of 2-methoxyethyl
ether was prepared, which was poured into the reaction
flask with stirring. The reaction was performed over 9 h
in a boiling solvent, and then the reaction mixture was
filtered. The resulting solution was evaporated on a
vacuum rotary evaporator. The product was purified by
the recrystallization from THF. Yield 60%, mp 260°C.
1H NMR [200 MHz, (CD3)2SO], δ, ppm: 1.98 s (CH3),
6.74 d (HmAr), 7.37 d (HoAr), 9.88 s (NH). 31P NMR
spectrum [81.0 MHz, (CD3)2SO]: δP 10.43 ppm.
1
The 31P and H NMR spectra were registered on a
Bruker CXP-200 spectrometer in a DMSO-d6 solution.
The X-ray diffraction analysis was performed on a
SMART APEX II CCD diffractometer (MoKα-
irradiation, graphite monochromator, ω-scanning). The
structure was solved by the direct methods and refined
by a full-matrix anisotropic approximation F2hkl.
The thermogravimetric study (TGA) was performed
on a Derivatograph-C instrument (MOM, Hungary) for
the sample of ~10 mg in air at a heating rate of
10 deg min–1.
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The differential scanning calorimetry (DSC) was
performed on a DSC-822e calorimeter (Mettler-
Toledo, Switzerland) for the sample of ~10 mg at a
rate of heating/cooling of 20 deg min–1 in an argon
atmosphere. The transition temperatures were determined
by the minimum/maximum peak position on the DSC-
termogram.
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Synthesis of hexa-p-acetamidophenoxycyclo-tri-
phosphazene. Into a 3-neck flask equipped with a
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 82 No. 6 2012