Hexa-arm star shaped hydrazone derivatives from hexakis(4-formylphenoxy)- cyclotriphosphazene core

Article abstract of DOI:10.1016/j.molstruc.2011.07.020

A series of novel hexasubstituted cyclophosphazene hydrazones [N ₃P₃(OC₆H₄pCHNNHC(O)C ₆H₄pX)₆] (X = H, Br, Cl, F, OH, OCH ₃, CH₃, NO₂, NH₂) were prepared by a sixfold condensation reaction of [N₃P₃(OC ₆H₄pCHO)₆] with para-substituted benzoic hydrazides [NH₂NHC(O)C₆H₄pX] with excellent yields (91-98%). The structures of the compounds were confirmed by elemental analysis, FT-IR, ¹H, ¹³C, ³¹P, 2D-HSQC NMR and mass spectrometry (MALDI-TOF). All the synthesized cyclophosphazene hydrazones exhibit high thermal stability. The crystal structure of a homogeneously substituted hexakis(4-formylphenoxy)-cyclotriphosphazene was determined by X-ray diffraction analysis. The compound crystallizes in the monoclinic system, space group P2₁/n with a = 16.558(3) , b = 10.250(2) , c = 23.429(5) , α = γ = 90.00°, β = 90.461(4)°, V = 3976.5(14) ³ and Z = 4. The R value is 0.0823 for 4290 observed reflections. The conformations of the 4-formylphenoxy-groups are different at the three phosphorus atoms.

Full text of DOI:10.1016/j.molstruc.2011.07.020

Journal of Molecular Structure 1003 (2011) 52–61
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Hexa-arm star shaped hydrazone derivatives from
hexakis(4-formylphenoxy)-cyclotriphosphazene core
Basavaraj R. Patil a, Shrinath S. Machakanur a, Dayananda S. Badiger a, Rekha S. Hunoor a,
Kalagouda B. Gudasi a, , Munirathinam Nethaji b, S.W. Annie Bligh c
⇑
a Department of Chemistry, Karnatak University, Pavate Nagar, Dharwad, Karnataka 580 003, India
b Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore 560 012, India
c Institute for Health Research and Policy, London Metropolitan University, Holloway Road, London N7 8DB, UK
a r t i c l e i n f o
a b s t r a c t
Article history:
A
series of novel hexasubstituted cyclophosphazene hydrazones [N3P3(AOC6H4ApACH@NANHA
Received 1 March 2011
Received in revised form 8 July 2011
Accepted 9 July 2011
C(O)AC6H4ApAX)6] (X = H, Br, Cl, F, OH, OCH3, CH3, NO2, NH2) were prepared by a sixfold condensation
reaction of [N3P3(AOC6H4ApACHO)6] with para-substituted benzoic hydrazides [NH2ANHA
C(O)AC6H4ApAX] with excellent yields (91–98%). The structures of the compounds were confirmed by
elemental analysis, FT-IR, 1H, 13C, 31P, 2D-HSQC NMR and mass spectrometry (MALDI-TOF). All the
synthesized cyclophosphazene hydrazones exhibit high thermal stability. The crystal structure of a
homogeneously substituted hexakis(4-formylphenoxy)-cyclotriphosphazene was determined by X-ray
diffraction analysis. The compound crystallizes in the monoclinic system, space group P21/n with
a = 16.558(3) Å, b = 10.250(2) Å, c = 23.429(5) Å,
Z = 4. The R value is 0.0823 for 4290 observed reflections. The conformations of the 4-formylphenoxy-
groups are different at the three phosphorus atoms.
Available online 27 July 2011
Keywords:
Cyclophosphazene
Hexakis(4-formylphenoxy)-
cyclotriphosphazene
Crystal
a = c
= 90.00°, b = 90.461(4)°, V = 3976.5(14) Å3 and
Hydrazone
Hydrazide
Ó 2011 Elsevier B.V. All rights reserved.
1. Introduction
prototype system for the synthesis of polymer-bound chemother-
apeutic agents [12]. More recently, it has been used as a core for
Cyclophosphazenes containing alternate phosphorus and nitro-
gen atoms in their non-delocalized cyclic skeletons are an impor-
tant family of inorganic ring systems [1,2]. In the past few
decades a rich variety of cyclophosphazenes with interesting prop-
erties and applications are synthesized by easily replacing the
chlorine of the chlorocyclotriphosphazenes with various nucleo-
philes [3–5]. The properties of cyclophosphazenes depend on the
inorganic AP@NA skeleton as well as on the nature of the substit-
uents attached to the phosphorus atoms [6,7]. Reactivity of the
peripheral functionalities of the substituted cyclotriphosphazenes
make them versatile precursors to synthesize supermolecular li-
quid crystals [8] and a wide range of star-shaped polymers pos-
sessing unique structures and properties arising from three
dimensional compact shape [9,10]. The coordination chemistry of
cyclophosphazene-based ligands is quite exciting and several
structurally diverse metal complexes have been synthesized and
characterized [11].
the exploration of new dendritic structures [13–15]. Studies con-
cerning cyclophosphazenes bearing oxime groups [16] and Schiff
bases [17,18] prepared from HFPC are now well documented.
Although some examples of formation of hydrazones by the con-
densation of aldehydes with cyclophosphazene hydrazides have
been described [19], to our knowledge formation of hydrazones
by the reaction of aromatic hydrazides with HFPC has not been re-
ported and deserves further exploration.
Hydrazones containing an azometine (ANHN@CHA) group are
important synthons for several transformations and have gained
importance due to their broad spectrum of biological activities
[20,21]. Metal complexes of hydrazones have been found to have
therapeutic activity [22]. Hydrazone linkage provides a suitable
system for pH-dependent release of drugs from drug-conjugates
[23].
Here we present the synthesis of a series of cyclophosphazene
hydrazones by the condensation of HFPC with p-substituted ben-
zoic hydrazides. X-ray crystal structure of HFPC (1) was obtained
for its molecular dimensions. The symbiosis that exists between
cyclophosphazenes and the corresponding polymeric systems will
ensure that small molecule developments will be readily trans-
lated to the more complex macromolecules [24].
Hexakis(4-formylphenoxy)-cyclotriphosphazene (HFPC) (1)
possessing six reactive peripheral aldehyde groups is used as a
⇑
Corresponding author. Tel.: +91 836 2215286x28; fax: +91 836 2771275.
E-mail address: kbgudasi@gmail.com (K.B. Gudasi).
0022-2860/$ - see front matter Ó 2011 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2011.07.020

B.R. Patil et al. / Journal of Molecular Structure 1003 (2011) 52–61
53
Table 1
Table 2
Crystal data and structure refinement of HFPC (1).
Selected bond lengths (Å) of HFPC (1).
CCDC deposit no.
Crystal size
Color/shape
Empirical formula
Formula weight
Temperature (K)
Wavelength
Crystal system
Space group
678839
Bond
Å
Bond
Å
0.35 Â 0.32 Â 0.30 mm
P1AN1
P1AN3
P2AN1
P2AN2
P3AN2
P3AN3
1.568(3)
1.587(3)
1.571(3)
1.584(3)
1.578(3)
1.571(3)
P1AO1
P1AO2
P2AO3
P2AO4
P3AO5
P3AO6
1.580(2)
1.576(3)
1.569(3)
1.571(3)
1.588(3)
1.582(3)
Colorless/rectangular
C
42H30N3O12P3
861.60
293(2)
0.71073 Å
Monoclinic
P21/n
C1AO1
C8AO2
C15AO3
C22AO4
C29AO5
C36AO6
1.396(4)
1.399(4)
1.410(5)
1.389(4)
1.391(5)
1.404(5)
C7AO7
1.183(8)
1.257(7)
1.202(12)
1.190(6)
1.186(8)
1.179(8)
C14AO8
C21AO9
C28AO10
C35AO11
C42AO12
Cell dimensions
a = 16.558(3) Å
b = 10.250(2) Å
c = 23.429(5) Å
a
= 90.00°
b = 90.461(4)°
c
= 90.00°
Volume
3976.5(14) Å3
4
Z
Table 3
Selected bond angles (°) and torsion angles (°) of HFPC (1).
Density (calculated)
Absorption coefficient
F(000)
1.439 mg/m3
0.219 mmÀ1
1776
Bond angle
Degrees (°)
Torsion angle
Degrees (°)
h range for data collection
Reflections collected
Independent reflections
Refinement method
Data/restraints/parameters
Goodness-of-fit on F2
2.17–26.5°
8206
4290 [R(int) = 0.0241]
Full-matrix least-squares on F2
4290/5/541
P1AN1AP2
P2AN2AP3
P3AN3AP1
122.4(2)
122.4(2)
122.58(19)
N1AP1AN3AP3
N1AP2AN2AP3
N3AP3AN2AP2
6.2(3)
11.8(3)
À7.7(3)
À174.9(3)
À46.5(3)
70.9(3)
N1AP1AN3
N2AP2AN1
N3AP3AN2
117.47(16)
117.18(16)
116.92(17)
N1AP1AO1AC1
N3AP1AO1AC1
N1AP1AO2AC8
N3AP1AO2AC8
N1—P2—O3—C15
N2—P2—O3—C15
N1—P2—O4—C22
N2—P2—O4—C22
N2AP3AO5AC29
N3AP3AO5AC29
N2AP3AO6AC36
N3AP3AO6AC36
1.006
Final R indices [I > 2
R indices (all data)
r(I)]
R1 = 0.0823, wR2 = 0.2488
R1 = 0.1553, wR2 = 0.3177
0.069
À61.1(3)
O1AP1AO2
O3AP2AO4
O5AP3AO6
99.68(14)
98.68(14)
94.07(15)
68.8(4)
(D
(D
(D
/r)
max
q
q
)
)
0.661 e ÅÀ3
À62.5(4)
À172.1(3)
À42.9(4)
À62.6(3)
69.5(3)
67.8(3)
À63.4(3)
max
À0.417 e ÅÀ3
Bruker Smart Apex CCD
SADABS
min
Measurement
Program system
Structure determination
Refinement
P1AO1AC1
P1AO2AC8
P2AO3AC15
P2AO4AC22
P3AO5AC29
P3AO6AC36
128.0(3)
125.8(2)
125.6(3)
130.0(3)
122.1(3)
120.8(3)
SHELXS-97
SHELXL-97
O3AP2AN1AP1
O3AP2AN2AP3
O4AP2AN1AP1
O4AP2AN2AP3
O5AP3AN2AP2
O5AP3AN3AP1
O6AP3AN3AP1
O6AP3AN2AP2
À133.9(2)
140.1(2)
119.9(2)
À111.1(2)
121.0(2)
O7AC7AC4
106.3(7)
119.4(6)
111.7(10)
125.9(5)
114.1(8)
121.6(8)
2. Experimental
O8AC14AC11
O9AC21AC18
O10AC28AC25
O11AC35AC32
O12AC42AC39
2.1. Materials and measurements
À131.1(2)
126.0(2)
The 1H, 13C and 31P NMR spectra were recorded in DMSO-d6 sol-
vent on BRUKER AV-500 MHz High Resolution Multinuclear FT-
NMR Spectrometer at room temperature. The 1H and 13C NMR
chemical shifts were measured using SiMe4 as an internal standard
at d = 0 ppm. The 31P chemical shifts are reported in ppm relative to
85% H3PO4 at 0 ppm as an external standard. IR spectra were re-
corded in a KBr matrix using an Impact-410 Nicolet (USA) FT-IR
spectrometer in 4000–400 cmÀ1 range. Single crystal X-ray analy-
sis data was collected on a BRUKER SMART APEX CCD diffractom-
eter. The electronic spectra of the compounds were recorded in
HPLC grade DMSO solvent on a VARIAN CARY 50-BIO UV–visible
spectrophotometer in the region of 200–1000 nm. Elemental anal-
yses (C, H and N) were performed using Leco Model Truespec CHNS
Analyser. The MALDI-TOF mass spectrum was measured with a
À135.7(2)
compounds were routinely checked by thin-layer chromatography
(TLC) on aluminum-backed silica gel plates.
2.2. Synthesis
2.2.1. Synthesis of Hexakis(4-formylphenoxy)-cyclotriphosphazene (1)
[N3P3(AOC6H4ApACHO)6]
The synthesis and main characteristics of the title compound
HFPC (1) were described earlier [12]. It was synthesized according
to modified method [9] and its single crystals suitable for X-ray dif-
fraction were obtained by slow evaporation of the ethylacetate
solution at room temperature. Yield: 90%, M.P. 141–142 °C dec.
Anal. Calc. for C42H30N3O12P3: C 58.55, H 3.51, N 4.88%. Found: C
58.59, H 3.61, N 4.66%. 1H NMR (DMSO-d6, ppm): 7.15 (d, 12H,
H2). 7.77 (d, 12H, H3), 9.92 (s, 6H, CHO),13C NMR (DMSO-d6,
ppm): 121.92 (C2), 132.35 (C3), 134.45 (C4), 154.47 (C1), 192.55
(CHO) ppm. 31P NMR (DMSO-d6, ppm): d 6.79 (s). IR (KBr, cmÀ1):
Voyager-DE STR spectrometer with
a-cyano-4-hydroxycinnamic
acid as a matrix. Thermogravimetric analysis (TGA) curves were re-
corded on Perkin Elmer TGA7 ANALYSER at a heating rate of 10 °C
per minute from room temperature to 800 °C under nitrogen atmo-
sphere. Melting points were determined in an open capillary on a
Gallenkamp melting point apparatus and are uncorrected.
All manipulations were carried out with standard high vacuum
or dry nitrogen atmosphere techniques. Hexachlorocyclotriphos-
phazene (Aldrich) was re-crystallized from dry hexane. Solvents
were purified by standard methods [25]. Tetrahydrofuran (Merck)
was distilled from sodium-benzophenone. Sodium hydride as 60%
dispersion in mineral oil (Loba) was used as received. All other
chemicals (sd fine chemicals, India) were used as received. All
3068
PAOAC).
m (w, CAHAr), 1704 (s, C@O) 1209, 1183 (s, P@N), 958 (s,
2.2.2. Synthesis of p-substituted benzoic hydrazides
Methyl benzoates were synthesized from their respective p-
substituted benzoic acids, using excess dry methanol in the

54
B.R. Patil et al. / Journal of Molecular Structure 1003 (2011) 52–61
Table 4
Physicochemical data for compounds 3a–i.
Compound
X
Formula
Yield (%)
M.P. (°C)
C%
H%
N%
Mass m/z (M+Na)+
k max (nm)
Obsd
Calcd
Obsd
Calcd
Obsd
Calcd
3a
3b
3c
3d
3e
3f
3g
3h
3i
H
Br
Cl
F
OH
OCH3
CH3
NO2
NH2
C
C
C
C
C
84H66N15O12P3
96.75
98.02
98.01
91.71
98.60
97.76
97.63
98.05
96.45
292–297
312–315
308–313
306–310
228–231
288–292
295–299
195–198
217–220
64.39
49.22
56.91
60.26
60.29
61.69
65.19
54.66
60.66
64.24
49.36
56.77
60.11
60.54
61.75
65.33
54.82
60.76
4.41
2.81
3.62
3.44
4.07
4.42
4.91
3.15
4.48
4.24
2.96
3.40
3.60
3.99
4.49
4.75
3.29
4.37
13.21
10.44
11.69
12.38
12.46
12.04
12.61
16.11
17.85
13.38
10.28
11.82
12.52
12.61
12.00
12.70
15.98
17.71
1593.3322
2059.7886
1796.0886
1701.275
1689.3286
1773.4981
1677.4917
1863.3178
1683.4203
308
305
310
304
310
307
306
275
309
84H60Br6N15O12P3
84H60Cl6N15O12P3
84H60F6N15O12P3
84H66N15O18P3
C90H78N15O18P3
C90H78N15O12P3
C84H60N21O24P3
C84H72N21O12P3
Table 5
Characteristic IR vibrations (in cmÀ1) of Compounds 3a–i.
Compound
m
(NAH)
m
(CAH)arom
m
(C@O)
m
(C@N)
m
(P@N)
m
(PAOAC)
Other
3a
3b
3c
3d
3e
3f
3g
3h
3i
3236
3236
3237
3239
N.O.
3236
3257
3247
3210
3062
3066
3067
3073
N.O.
3066
3074
3073
3069
1654
1654
1654
1654
1646
1652
1652
1661
1663
1604
1600
1600
1603
1606
1605
1607
1602
1608
1202–1173
1204–1178
1204–1178
1200–1168
1208–1166
1211–1179
1211–1182
1197–1169
1196–1177
955
959
958
957
956
957
957
952
960
–
–
–
–
m
–
–
–
m
(OH) 3425
(NH2) 3466, 3339
N.O.: not observed.
Table 6
1H NMR spectral data of 3a–i compounds in DMSO-d6.
2
3
9
8
H
H
H
H
5
P
H
O
N
P
N
O
C
X
10
9
P
N
NH
N
6
3
2
8
H
H
H
H
Compound
X
NH
H2
H3
H5
H8
H9
Other
(s, 6H)
(d, 12H)
(d, 12H)
(s, 6H)
(d, 12H)
(d, 12H)
3a
3b
3c
3d
3e
3f
3g
3h
3i
H
Br
Cl
F
OH
OCH3
CH3
NO2
NH2
11.93
11.85
11.85
11.87
11.71
11.74
11.78
12.10
11.88
7.11
7.04
7.05
7.06
7.02
7.03
7.04
7.13
7.04
7.68
7.60
7.60
7.63
7.59
7.60
7.60
7.69
7.61
8.58
8.47
8.47
8.49
8.51
8.51
8.51
8.55
8.53
7.94
7.76
7.84
7.94
7.82
7.87
7.79
8.09
7.72
7.51 (t)
7.66
7.48
7.29
6.82
6.96
7.24
8.26
6.98
C10H 7.62 (t, 6H)
–
–
–
AOH 10.14 (s, 6H)
C11H 3.81 (s, 18H)
C11H 2.36 (s, 18H)
–
ANH2 5.54 (s, 12H)
Chemical shifts (d) are reported in ppm; s, singlet; d, doublet; t, triplet.
presence of H2SO4. para-Substituted benzoic hydrazides (2a–i)
were prepared by reaction of the corresponding methyl benzoates
(10 mmol) with hydrazine hydrate 99% (50 mmol) in methanol
under reflux for 4–6 h. The excess solvent was removed under
vacuum and the residue was filtered under suction, washed with
water, and dried. The spectral and analytical data of benzoic
hydrazide (2a) [26], 4-bromobenzoic hydrazide (2b) [27], 4-chlo-
robenzoic hydrazide (2c) [28], 4-fluorobenzoic hydrazide (2d)
[26], 4-hydroxybenzoic hydrazide (2e) [29], 4-methoxybenzoic
hydrazide (2f) [30], 4-methylbenzoic hydrazide (2g) [28], 4-nitro-
benzoic hydrazide (2h) [28] and 4-aminobenzoic hydrazide (2i)
[28] are in good agreement with literature values.
2.2.3. Synthesis of cyclophopshazene hydrazone
[N3P3(AOC6H4ApACH@NANHAC(O)AC6H4ApAX)6]
{X = H
(3a); Br (3b); Cl (3c); F (3d); OH (3e); OCH3 (3f); CH3 (3g); NO2

B.R. Patil et al. / Journal of Molecular Structure 1003 (2011) 52–61
55
Table 7
13C NMR (decoupled) spectral data of the compounds 3a–i in DMSO-d6.
8
9
9
2
3
3
P
O
N
P
N
P
O
CH
5
X
7
1
6
10
4
N
NH
C6
N
8
2
6
Compound
X
C1
C2
C3
C4
C5
C7
C8
C9
C10
C11
3a
3b
3c
3d
3e
3f
3g
3h
3i
H
Br
Cl
F
OH
OCH3
CH3
NO2
NH2
151.19
151.16
151.18
150.65
151.06
151.06
151.10
151.32
151.08
121.38
121.38
121.37
120.81
121.33
121.34
121.35
121.40
121.38
129.07
130.11
129.95
130.26
130.19
130.02
130.77
129.60
130.06
129.16
131.82
132.68
131.56
132.37
132.3
132.24
131.90
132.33
147.56
147.81
147.8
146.98
146.71
146.96
147.28
148.55
147.53
163.70
162.66
162.53
163.02
163.4
162.43
163.52
161.80
162.68
133.68
132.67
132.31
129.51
124.09
125.67
129.35
139.17
123.57
128.10
128.85
132.07
128.87
115.33
115.46
114.06
129.05
123.84
115.24
132.21
126.00
137.04
165.00
161.22
163.13
142.22
149.52
152.32
–
–
–
–
129.17
129.18
128.6
129.01
129.04
128.11
129.31
128.41
–
55.82
21.49
–
–
3. Results and discussion
3.1. Synthesis of hexa-arm cyclophosphazene hydrazones
Table 8
31P NMR (decoupled) spectral data of
the compounds 3a–i.
The first reaction for the synthesis of the hexa-arm star shaped
hydrazones with different substitutions at para positions consists
of the grafting of six hydroxybenzaldehyde groups onto the cyclo-
triphosphazene core. The reaction of hexachlorocyclotriphospha-
zene with the sodium salt of 4-hydroxybenzaldehyde in THF
yielded hexakis(4-formylphenoxy)-cyclotriphosphazene. The sec-
ond step consists of the condensation of 6 equivalents of benzoic
hydrazide 2a–i with the aldehyde functions of HFPC (1) in THF
for 18–24 h at refluxing temperature and affords the correspond-
ing hexafunctionalized hydrazones 3a–i. The duration of the reac-
tion for the synthesis of 3e and 3h is comparatively more perhaps
due to the limited solubility of 4-hydroxybenzoic hydrazide and 4-
nitrobenzoic hydrazide in THF. All products were generally ob-
tained in high yields. General presentation of the reaction and
structures of the compounds are shown in Scheme 1.
Compound
ppm
3a
3b
3c
3d
3e
3f
3g
3h
3i
8.70
8.66
8.65
8.69
8.83
8.76
8.71
8.59
8.76
(3h); NH2 (3i)}. These compounds were prepared in a similar man-
ner. The following procedure is typical.
HFPC (1) (0.104 g, 0.12 mmol) was added to a solution of ben-
zoic hydrazide (0.109 g, 0.8 mmol) in tetrahydrofuran (75 mL)
and the reaction mixture was stirred under reflux for 18 h. The sol-
vent was removed by evaporation under reduced pressure. The res-
idue was filtered under suction and washed several times with hot
tetrahydrofuran. The resulting solid (3a) was dried in vacuo at
40 °C for 8 h.
The structure of HFPC (1) has been confirmed by single crystal
X-ray diffraction study. The synthesized cyclophosphazene hydra-
zone compounds were characterized by elemental analysis, FT-IR,
1H, 13C, 31P and 2D-HSQC NMR spectroscopy and MALDI-TOF mass
spectrometry.
The analytical and physicochemical data of compounds 3a–i are
summarized in Table 4. The diagnostic IR bands are summarized in
Table 5. Detailed assignment of 1H, 13C and 31P NMR resonances are
presented in Tables 6–8 respectively.
3.2. X-ray crystal structure HFPC (1)
The HFPC molecule comprises a cyclotriphosphazene core and
six 4-formylphenoxy groups. The X-ray crystallographic details
are given in Table 1. An ORTEP of 1 with thermal ellipsoids drawn
at 30% probability is shown in Fig. 1. It consists of a non-centro-
symmetric, non-planar cyclic trimeric phosphazene ring with each
phosphorus atom attached to two 4-formylphenoxy moieties.
Three of the six 4-formylphenoxy substituents are on one side of
the cyclophosphazene ring while the other three substituents are
located on another side (Fig. 1). Selected bond distances are sum-
marized in Table 2. A list of significant bond angles and torsion an-
gles are given in Table 3.
The compound 1 crystallizes in P21/n space group with z = 4.
The six-membered phosphazene ring is slightly non-planar with
a total puckering parameter of QT = 0.1104(2) Å. The conformation
of the P3N3 ring is that of a twisted-boat with q2 = 0.1071(2) Å,
q3 = À0.0269(2) Å, U2 = À28.06(1)° and h2 = 104.08(1)°. Of the
other molecules whose structures have been studied, the chloro
2.2.4. X-ray crystallography
A single crystal having dimensions of 0.35 Â 0.32 Â 0.30 mm
was chosen for X-ray diffraction studies. The data were collected
on a ‘BRUKER SMART APEX CCD’ diffractometer using graphite-
monochromatized Mo
Ka radiation (k = 0.71073 Å); the scan
modes were in the range 2.17–26.5°. The absorption correction
was applied by the use of SADABS. The structure of the compound
was solved by direct methods and refined by full-matrix least-
squares techniques on F2 by using SHELXS-97 [31]. All of the
non-H atoms were refined anisotropically. The positions of hydro-
gen atoms were found in a difference Fourier map and refined with
isotropic thermal parameters. Details of the data collection and
structure refinement are given in Table 1.

56
B.R. Patil et al. / Journal of Molecular Structure 1003 (2011) 52–61
O
H
O
H
O
O
H
Cl
P
Cl
P
THF, NaH
Reflux
N
P
N
P
O
N
N
P
O
O
O
HO
CHO
Cl
Cl
+
P
O
N
Cl
N
H
O
Cl
H
O
X
O
H
1
O
O
NH2
HN
HN
N
N
HN
O
H
X
X
H
O
P
H
H
O
N
P
N
N
O
N
P
THF
X
N
O
O
O
N
Reflux
O
N
H
2a-i
H
O
H
X
N
X
NH
N
H
a
b
c
d
e
f
h
i
2, 3
g
NH
O
OCH3 CH3 NO2 NH2
X =
H
Br Cl
F
OH
O
X
3a-i
Scheme 1. Synthetic pathway and chemical structure for cyclophosphazene hydrazones 3a–i.
derivative [N3P3(Cl)6] has slightly non-planar rings in the chair
conformation [32] and phenoxy derivative [N3P3(AOC6H5)6] has
slightly folded ring with approximate C2 symmetry [33]. The devi-
ations from planarity have been ascribed to intra- and inter-molec-
ular steric effect [32,33].
The 4-formylphenoxy groups of the HFPC molecule show signif-
icant deviations from a symmetrical arrangement. The most nota-
ble of these distortions is the inequivalence of the orientation of
the two 4-formylphenoxy groups bonded to each P atom. Fig. 2
shows orientations of these groups relative to the OAPAO planes.
The arrangements are in fact different at the three phosphorus
atoms, so that the molecule deviates from the threefold symmetry,
at least, in the crystalline state.
The bond angles (Table 3) at phosphorus and nitrogen also
show significant variations from threefold symmetry. The NAPAN
angles in the ring are significantly smaller than the PANAP angles.
The N3AP3AN2 angle, 116.92(17)° is smaller than the NAPAN an-
gles at Pl and P2. The PANAP angles at N1, N2 and N3 are nearly
equal. The most significant feature is that the O5AP3AO6 angle,
94.07(15)° is smaller than the OAPAO angles at Pl and P2. The
OAPAN and PAOAC angles vary over several degrees, and these
values are probably influenced by the orientation of the 4-formyl-
phenoxy groups.
CACAC bond angles of the phenyl ring are in the range
117.8(4)–122.7(4)° which is characteristic of the sp2-hybridized
carbons. OACAC and OACAH angles around the carbonyl carbon
of the aldehyde group are in the range 106.3(7)–125.9(5)° and
117.1–126.8° respectively. As the OACAC angle of the carbonyl
carbon increases the OACAH angle decreases. Crystal packing
forces may explain this variation.
Fig. 1. ORTEP plot of HFPC (1) with the thermal ellipsoids drawn at the 30%
probability level. Hydrogen atoms of the phenyl rings are omitted for clarity.
The PAN distances range from 1.568(3) to 1.587(3) Å, with a
mean value of 1.576(3) Å which is essentially equal to the mean

B.R. Patil et al. / Journal of Molecular Structure 1003 (2011) 52–61
57
Fig. 2. Views along the OAPAO planes, showing arrangement of the p-formylphenoxy groups.
PAN distances of 1.575(2) in N3P3(AOC6H4)6 molecule [33] and
3.3. IR spectral studies
1.578(3) in N3P3(AOC6H4AoAOCH3ApACHO)6 molecule [34]. The
PAO bonds are in the range 1.569(3)–1.588(3) Å, with a mean dis-
tance of 1.577(3) Å are 0.13 Å shorter than the single-bond dis-
The diagnostic IR bands are summarized in Table 5. The alde-
hyde carbonyl groups of the core (1) which were observed at
1704 cmÀ1 disappeared following hydrazone formation, accompa-
nied by the appearance of C@N stretching frequencies in the 1600–
1608 cmÀ1 region. A broad band at 3236–3257 cmÀ1 is due to NAH
stretching frequency of the amide (ANHAC@O) moiety. In case of
3e amide band was merged with OAH stretching frequency. A
strong band at 1646–1663 cmÀ1 is ascribed to the amide carbonyl
(ANHAC@O) stretching frequencies. A medium intensity absorp-
tion band at 3062–3074 cmÀ1 is attributed to the stretching vibra-
tions of the aromatic CAH groups. The P@N stretching vibrations,
which are observed between 1166 and 1211 cmÀ1 as sharp bands
are characteristic of cyclophosphazenes. Furthermore, these cyclo-
phosphazene derivatives show another important infrared band in
the 952–960 cmÀ1 region attributed to PAOAR stretching. Thus,
the IR spectral data results provide strong evidences for the forma-
tion of the cyclotriphosphazene hydrazones.
tance [35], suggesting considerable exocyclic
p-bonding. The
distances of CAO bonds between the first carbon atom of each phe-
nyl ring and the O atom attached to the P atom of the cyclophos-
phazene ring range from 1.389(4) to 1.410(5) Å and are higher
than the value of 1.354(2) Å for the corresponding CAO bond in
4-hydroxybenzaldehyde [36]. It indicates that the conjugation of
oxygen with the aromatic ring is decreased due to p-bond charac-
ter of the OAP bonds.
The CAC bond distances of the phenyl ring are in the normal
range of 1.354(7)–1.406(6) Å which is characteristic of the delocal-
ized phenyl rings. The CAO bonds of the aldehyde group exhibits a
typical double-bond character with bond distance ranging from
1.179(8) to 1.257(7) Å. The CAC bonds between the carbon of the
aldehyde group and the carbon atom of phenyl ring are in the
range 1.463(7)–1.646(8) Å. Most of the shorter contacts involve
the 4-formylphenoxy groups.
There are no significant differences among chemically equivalent
bond lengths. The angular deviations from threefold symmetry are
probably a result of steric interactions among the bulky 4-formyl-
phenoxy-groups. The observed molecular geometry is probably
adopted to optimize both intra- and inter-molecular steric
interactions.
3.4. NMR investigations
l
The H, 13C and 31P NMR spectra were obtained in dimethyl
sulfoxide-d6. According to the NMR spectral data, all the cyclophos-
phazene hydrazone (3a–i) molecules appear to have symmetric
structures in the solution. The 2D-Heteronuclear Single Quantum

58
B.R. Patil et al. / Journal of Molecular Structure 1003 (2011) 52–61
9.0
8.5
8.0
7.5
7.0
6.5
Chemical Shift (ppm)
12
11
10
9
8
7
6
5
4
3
2
1
Chemical Shift (ppm)
Fig. 3. 1H NMR spectrum of 3f in DMSO-d6 (expansion of the aromatic region is shown in the box inset).
and H10) protons. The six para-hydroxy (AOH) protons of 3e
resonate as a singlet in the downfield region 10.14 ppm. In case
of 3f and 3g a singlet at 3.81 ppm and 2.36 ppm accounts for
eighteen protons of p-methoxy (AOCH3) and p-methyl (ACH3)
groups respectively.
A
representative 1H NMR spectrum of
compound 3f is displayed in Fig. 3.
3.4.2. 13C NMR spectral studies
13C NMR analysis agreed with the 1H NMR analysis in demon-
strating the architecture of the star shaped hydrazones. In the
13C NMR spectrum of compound 1, the aldehyde carbon atoms
are observed at 192.55, at the lowest downfield position of the
carbon atoms. None of the 13C NMR spectra of compounds 3a–i
exhibited any signal that could be attributed to unreacted alde-
hyde functions. 13C NMR spectra of hydrazones showed resonance
in the range 146.71–148.55 ppm due to the carbons (C5) of the
azomethine (HC@NAN) functions. 2D-HSQC NMR confirms that
the signal observed in 161.8–163.7 ppm region is devoid of directly
attached hydrogen and is assigned to amide carbonyl C6.
Fig. 4. The 13C NMR spectra of 3f in DMSO-d6.
Coherence (HSQC) NMR study was undertaken to correlate chemical
shifts of directly bound 1H and 13C nuclei and a representative
spectrum of compound 3f is displayed in Fig. 5. Detailed assignment
of 1H and 13C NMR resonances presented in Tables 6 and 7
respectively was made based on the 2D-HSQC NMR analysis.
From 2D HSQC NMR spectrum it is clear that the 13C peaks of
3a–i at d values 150.65–151.32 and 129.16–132.68 ppm are due
to carbons which do not bear directly attached hydrogen and are
assigned to C1 and C4 respectively. The resonances arising from
C1 carbons are shifted upfield by 3.15–3.82 ppm compared to the
corresponding signal at 154.47 ppm in 1. The signals of C2 and C3
were observed in the range 120.81–121.40 and 129.07–130.77
ppm respectively. The resonances of these inner aromatic ring
carbons remain almost unperturbed by the influence of the para-
substituents at the periphery of the hydrazone arm.
3.4.1. 1H NMR studies
1H NMR spectrum of 1 showed a singlet peak at 9.92 ppm for
aldehyde protons in addition to the two doublet peaks at 7.15
and 7.77 ppm for the aromatic ring protons. The absence of the
aldehydic proton resonance and the appearance of azomethine
(AHC@NANA) protons in the range 8.47–8.58 ppm integrating
for six protons along with hydrazide (ACOANHAN@C) protons as
a broad singlet peak accounting for six protons in the downfield
region 11.71–12.10 ppm confirms the formation of hydrazones
compounds 3a–i. The resonances due to 48 aromatic (H2, H3, H8
and H9) protons appear in the range 6.82–8.26 ppm as four
doublets for the new compounds except for 3a which exhibited
two triplets and three doublets accounting for 54 (H2, H3, H8, H9
C7 and C9 do not have directly attached protons hence does not
exhibit contours in 2D HSQC NMR spectrum and the resonances of
these carbons are influenced by the substituent at C10 carbon.
Resonances in the range 128.10–129.31 ppm are attributed to C8
carbons. The C10 carbons show large variation in their resonances
depending upon the inductive and mesomeric effect of the substi-
tuent attached. In case of 3a, carbons (C10) bonded to hydrogen

B.R. Patil et al. / Journal of Molecular Structure 1003 (2011) 52–61
59
Fig. 5. 2D-HSQC-NMR spectra of 3f in DMSO-d6 (expanded form of the aromatic region is shown in the box inset).
symmetrically substituted phosphorus atoms in the cyclophospha-
zene ring. A deshielding effect of 1.8–2.04 ppm was detected in 31
P
NMR when moving from aldehyde groups (d 31P = 6.79 ppm) to
hydrazone groups. The para-substituents on the peripheral phenyl
group are presumably too far from the cyclophosphazene center to
influence the 31P NMR shift to a larger extent. In the 31P NMR spec-
trum of 3f given as an example at Fig. 6, singlet appears at
8.76 ppm.
3.5. Electronic absorption
The electronic absorption spectra of 3a–i in DMSO solvent were
recorded at room temperature and the absorption band maxima
assignments are listed in Table 1. Cyclotriphosphazene ring
themselves do not absorb in near UV region. The UV–vis spectra
of the hydrazone cyclphosphazene derivatives 3a–i exhibit a band
100
80
60
40
20
0
-20
-40
-60
-80
-100
Chemical Shift (ppm)
in the range 304–310 nm which can be attributed to p?
pà transi-
Fig. 6. 31P NMR spectra of 3f in DMSO-d6.
tions according to absorption of similar molecules [18].
3.6. Mass spectrometry
show resonances at 132.21 while in 3g they are attached to methyl
group and resonates at 142.22 ppm. The signals due to the C10
attached to bromine (3b), chlorine (3c) and fluorine (3d) show
downfield shift with increasing electronegativity of halogen substi-
tutions and were observed at 126.00, 137.04 and 165.00 ppm
respectively. The resonances arising from C10 attached to the
hydroxy (3e), methoxy (3f) nitro (3h) and amino (3i) groups are
observed at 161.22, 163.13, 149.52 and 152.32 ppm respectively.
A representative 13C NMR spectrum of 3f is given at Fig. 4.
The complete reaction of all peripheral aldehyde groups of 1
and the single molecular nature of the hydrazone trimers 3a–i
was also checked by MALDI-TOF mass spectrometry, which
confirmed the expected chemical structures with m/z values corre-
sponding to (M+Na)+ ion (Table 1). MALDI-TOF mass spectrometry
of 3f is given as an example at Fig. 7.
3.7. Thermal decomposition studies
3.4.3. 31P NMR spectral studies
The high thermal stability of organophosphazenes is well-
known [37] and has made these inorganic scaffolds good candidates
for the preparation of thermally stable materials. The newly synthe-
sized cyclophosphazene hydrazones are stable up to a temperature
The 1H-decoupled 31P NMR data of the cyclophosphazenes are
given in Table 8. The 31P NMR spectra of cyclophosphazene
compounds 3a–i bearing the six hydrazone arms exhibited a
unique sharp singlet in the range 8.59–8.83 ppm indicating the
close to 310 °C as measured by TGA at a heating rate of 10 °C minÀ1
.

60
B.R. Patil et al. / Journal of Molecular Structure 1003 (2011) 52–61
Voyager Spec #1[BP = 135.0, 46246]
135.0761
205.1408
100
90
80
70
60
50
40
30
20
10
0
4.6E+4
297.1685
172.0723
146.0895
234.0351
271.1269
167.0975
227.1076
294.1114
230.2588
152.0874 282.1588
113.0974
164.0924
441.0341
1773.4981
71.9910
91.0634
86.1056
95.0695
285.1476
242.2948
650.0597
553.2224
461.1318
367.1584
193.5891
861.1015
309.1403
0
2501.0
49.0
539.4
1029.8
1520.2
2010.6
Mass (m/z)
Fig. 7. MALDI-TOF mass spectrum of 3f, m/z value 1773.4981 corresponds to (M+Na)+ ion.
could be readily elaborated to the hexafunctionalized hydrazones
by condensation with the benzoic hydrazides. Formation of the
hydrazone moieties was corroborated by the absence of signals
due to aldehyde groups and presence of hydrazone moieties in
1H, 13C and 2D-HSQC NMR as well as in IR spectroscopy. The con-
stitutions and the structural homogeneities of the hexa-arm star
shaped hydrazones were ascertained by 31P NMR spectrum. MAL-
DI-TOF mass spectrometry and microanalysis also confirmed the
expected chemical structures. These cyclophosphazene hydra-
zones exhibit high thermal stability, as deduced from the thermo-
gravimetric curves.
The compounds 3a–i have been identified as fully substituted
symmetric trimers and are important as synthetic and structural
models for the reactions and molecular structure of the analogous
high-polymeric phosphazenes [24]. Efforts on the synthesis and
characterization of corresponding linear macromolecules and
other cyclophosphazene hydrazones are in progress and will be re-
ported in future communications.
Fig. 8. TGA thermogram of 3f.
Thermal decomposition of 3a–i proceeds in two stages. The first
stage loss in the temperature range of 329–345 °C is related to
the volatilization of organic components arising from the periphe-
ral phenyl groups. The second stage loss at higher temperature
range of 489–528 °C is associated with the decomposition of the
intermediate product. The final decomposition product (40–45%)
at 800 °C is a pyrolitic residue [38]. A representative TGA thermo-
gram of compound 3f is displayed in Fig. 8.
Supplementary material
CCDC 678839 contains full crystallographic data for HFPC (1)
molecule. Copies of this information may be obtained free of
charge from the Cambridge Crystallographic Data Centre via
www.ccdc.cam.ac.uk/data_request/cif. or from the Cambridge
Crystallographic Data Centre (CCDC), 12 Union Road, Cambridge
CB2 1EZ, UK; fax:+44 1223 336033; email: deposit@ccdc.
cam.ac.uk.
4. Conclusion
Acknowledgements
A new general synthesis of the hexa-arm star shaped molecules
bearing hydrazone functions is reported. Hexakis(4-formylphen-
oxy)-cyclotriphosphazene (1), a trimer which possesses six aldehy-
dic functions on the side substituents was used as starting
material. X-ray crystal analysis of the HFCP (1) was undertaken
in order to determine the influences of the steric and electronic
factors of the 4-formylphenoxy groups on the trimeric phospha-
zene ring system. The reactive terminal aldehyde groups in HFCP
The authors thank the NMR Research Center, Indian Institute of
Science, Bangalore, for NMR facility. Fellowship for B.R. Patil and
S.S. Machakanur by the University Grants Commission under Re-
search Fellowship in Sciences for Meritorious Students (UGC-
RFSMS) is gratefully acknowledged. K.B. Gudasi is thankful to the
Association of Commonwealth Universities, for Commonwealth
fellowship.

B.R. Patil et al. / Journal of Molecular Structure 1003 (2011) 52–61
61
[19] V. Chandrasekhar, P. Thilagar, V. Krishnan, J.F. Bickley, A. Steiner, Cryst. Growth
Des. 7 (2007) 668–675.
References
[20] S. Rollas, S.G. Küçükgüzel, Molecules 12 (2007) 1910–1939.
[21] B. Narasimhan, P. Kumar, D. Sharma, Acta Pharmaceut. Sci. 52 (2010) 169–180.
[22] A.M. Stadler, J. Harrowfield, Inorg. Chim. Acta 362 (2009) 4298–4314 (and the
references therein).
[23] K. Ulbrich, V. Subr, Adv. Drug Deliv. Rev. 56 (2004) 1023–1050.
[24] H.R. Allcock, Acc. Chem. Res. 12 (1979) 351–358.
[25] W.L.F. Armarego, D.D. Perrin, Purification of Laboratory Chemicals, fourth ed.,
Elsevier, 1996.
[1] H.R. Allcock, Phosp., Sulfur, Silicon Relat. Elem. 179 (2004) 661–671.
[2] H.R. Allcock, Polymer 21 (1980) 673–683.
[3] C.W. Allen, Coord. Chem. Rev. 130 (1994) 137–173.
[4] R. De Jaeger, M. Gleria (Eds.), Applicative Aspects of Cyclophosphazenes, Nova
Science Publishers, Inc., New York, 2004.
[5] H.R. Allcock, Chemistry and Applications of Polyphosphazenes, Wiley, New
York, 2003 (Chapter 3).
[6] C.W. Allen, Chem. Rev. 91 (1991) 119–135.
[7] H.R. Allcock, M.S. Connolly, J.T. Sisko, S. Al-Shali, Macromolecules 21 (1988)
323–334.
[8] J. Jiménez, A. Laguna, A.M. Molter, J.L. Serrano, J. Barberá, L. Oriol, Chem. Eur. J.
17 (2011) 1029–1039.
[9] J.Y. Chang, H.J. Ji, M.J. Han, S.B. Rhee, S. Cheong, M. Yoon, Macromolecules 27
(1994) 1376–1380.
[10] Y.J. Cui, X.M. Ma, X.Z. Tang, Y.P. Luo, Eur. Polym. J. 40 (2004) 299–305.
[11] V. Chandrasekhar, P. Thilagar, B.M. Pandian, Coord. Chem. Rev. 251 (2007)
1045–1074.
[12] H.R. Allcock, P.E. Austin, Macromolecules 14 (1981) 1616–1622.
[13] N. Launay, A.M. Caminade, J.P. Majoral, J. Organomet. Chem. 529 (1997) 51–
58.
[14] J.P. Majoral, A.M. Caminade, in: Fritz Vögtle (Ed.), Dendrimers, Topics in
Current Chemistry, vol. 197, Springer-Verlag, Heidelberg, 1998, pp. 79–124.
[15] V. Maraval, R. Laurent, P. Marchand, A.M. Caminade, J.P. Majoral, J. Organomet.
Chem. 690 (2005) 2458–2471.
[16] E. Cil, M. Arslan, A.O. Gorgulu, Polyhedron 25 (2006) 3526–3532.
[17] F. Aslan, Z. Demirpence, R. Tatsiz, H. Turkmen, A.I. Ozturk, M. Arslan, Z. Anorg,
Allg. Chem. 634 (2008) 1140–1144.
[26] K.K. Bedia, O. Elçin, U. Seda, K. Fatma, S. Nathaly, R. Sevim, A. Dimoglo, Eur. J.
Med. Chem. 41 (2006) 1253–1261.
[27] C.L. Zhao, W. Huang, Central Eur. J. Chem. 5 (2007) 303–315.
[28] P. Kumar, B. Narasimhan, D. Sharma, Arkivoc xiii (2008) 159–178.
[29] I. Angurell, C.O. Turrin, R. Laurent, V. Maraval, P. Servin, O. Rossell, M. Seco,
A.M. Caminade, J.P. Majoral, J. Organomet. Chem. 692 (2007) 1928–1939.
[30] N. Dodoff, K. Grancharov, N. Spassovska, J. Inorg. Biochem. 60 (1995) 257–266.
[31] G.M. Sheldrick, SHELXS97 and SHEXL97, Program for Crystal Structure
Solution and Refinement, University of Göttingen, Germany, 1997.
[32] G.J. Bullen, J. Chem. Soc. A (1971) 1450–1453.
[33] W.C. Marsh, J. Trotter, J. Chem. Soc. A (1971) 169–173.
[34] Y. Tümer, H. Bati, N. Çalisßkan, Ç. Yüksektepe, O. Büyükgüngör, Z. Anorg. Allg.
Chem. 634 (2008) 597–599.
[35] D.W.J. Cruickshank, J. Chem. Soc. (1961) 5486–5504.
[36] J.P. Jasinski, R.J. Butcher, B. Narayana, M.T. Swamy, H.S. Yathirajan, Acta Cryst.
E64 (2008) o187.
[37] R. De Jaeger, M. Gleria, Prog. Polym. Sci. 23 (1998) 179–276 (and references
therein).
[38] H.R. Allcock, G.S. McDonnell, G.H. Riding, I. Manners, Chem. Mater. 2 (1990)
425–432.
[18] M. Odabasoglu, G. Turgut, H. Karaer, Phosp. Sulfur Silicon 152 (1999) 9–25.