Structural and computational characterization of 4′,4′,6′,6′-tetrachloro-3-(2-methoxyethyl)-3H,4H-spiro-1,3,2-benzoxaza phosphinine-2,2′- [1,3,5,2,4,6] triazatriphosphinine

Article abstract of DOI:10.1016/j.molstruc.2016.03.085

In this study a new monospirocyclic phosphazene derivative, 4′,4′,6′,6′-tetrachloro-3-(2-methoxyethyl)-3H,4H-spiro [1,3,2-benzoxazaphosphinine-2,2′- [1,3,5,2,4,6] triazatriphosphinine] (SP1) was synthesized from the reaction of hexachlorocyclotriphosphaze

Full text of DOI:10.1016/j.molstruc.2016.03.085

Accepted Manuscript
Structural and Computational Characterization of 4',4',6',6'-tetrachloro-3-(2-
methoxyethyl)-3H,4H-spiro-1,3,2-benzoxaza phosphinine-2,2'- [1,3,5,2,4,6]
triazatriphosphinine
Muhammet Işıklan, Erdem Kamil Yıldırım, Murat Atiş, Ömer Sonkaya, Bünyemin
Çoşut
PII:
S0022-2860(16)30293-9
10.1016/j.molstruc.2016.03.085
MOLSTR 22396
DOI:
Reference:
To appear in: Journal of Molecular Structure
Received Date: 22 December 2015
Revised Date: 26 February 2016
Accepted Date: 25 March 2016
Please cite this article as: M. Işıklan, E.K. Yıldırım, M. Atiş, Ö. Sonkaya, B. Çoşut, Structural and
Computational Characterization of 4',4',6',6'-tetrachloro-3-(2-methoxyethyl)-3H,4H-spiro-1,3,2-
benzoxaza phosphinine-2,2'- [1,3,5,2,4,6] triazatriphosphinine, Journal of Molecular Structure (2016),
doi: 10.1016/j.molstruc.2016.03.085.
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ACCEPTED MANUSCRIPT
Graphical abstract
The synthesized new monospirocyclic phosphazene derivative, , 4',4',6',6'-tetrachloro-
3-(2-methoxyethyl)-3H,4H-spiro[1,3,2-benzoxazaphosphinine-2,2'-[1,3,5,2,4,6] triazatri
phosphinine] characterized by elemental analyses, X-ray, MS, FT-IR, NMR spectroscopy and
calculated by using B3LYP method with the standard 6-311++G(d,p) basis set; and also the
electrophilic and nucleophilic attack centers were predicted with the local softness values of
individual atoms.
HOMO
LUMO
Keywords: Cyclophosphazene, spirocyclophosphazene, DFT, NMR, Spectroscopy, Crystal
structure, Local softness.

ACCEPTED MANUSCRIPT
Structural and Computational Characterization of 4',4',6',6'-
tetrachloro-3-(2-methoxyethyl)-3H,4H-spiro-1,3,2-benzoxaza
phosphinine-2,2'-[1,3,5,2,4,6] triazatriphosphinine
Muhammet Işıklana, Erdem Kamil Yıldırım b, Murat Atişc,*, Ömer Sonkayad, Bünyemin
Çoşute
aDepartment of Chemistry, Faculty of Arts and Sciences, Kırıkkale University, 71450 -Kırıkkale, Turkey
bDepartment of Computer Engineering, Faculty of Engineering, Kırıkkale University, 71450 -Kırıkkale, Turkey
cErciyes University, Kayseri Vocational School, Electric and Energy Department, 38039 Melikgazi Kayseri,
Turkey
dAksaray University, Science and Technology Application and Research Center, 68100 Aksaray, Turkey
eDepartment of Chemistry, Faculty of Science, Gebze Technical University, Gebze, 41400-Kocaeli, Turkey
*Corresponding author. Tel.: +90 352 4374915 / 40714, Fax: +90 352 4375267 E-mail
address: atis@erciyes.edu.tr
Abstract
In this study a new monospirocyclic phosphazene derivative, 4',4',6',6'-tetrachloro-3-
(2-methoxyethyl)-3H,4H-spiro[1,3,2-benzoxazaphosphinine-2,2'-[1,3,5,2,4,6]
triazatriphosphinine]
(SP1)
was
synthesized
from
the
reaction
of
hexachlorocyclotriphosphazene (N3P3Cl6) with N/O donor-type, 2-{[(2-Metoxyethyl)
amino]methyl}phenol. The structural investigations of the compound were verified by
1
13
31
elemental analyses, MS, FTIR, H, C, P NMR spectroscopy and the single crystal X-ray
diffraction analysis. The structural and spectroscopic data of the molecule in the ground state
were calculated by using density functional method (DFT) using 6-311++G (d, p) basis set.
The complete assignments of all vibrational modes were performed on the basis of the total
energy distributions (TED). Isotropic chemical shifts (31P, 1H and 13C NMR) were calculated
using the gauge-invariant atomic orbital (GIAO) method. Theoretical calculations of bond
parameters, harmonic vibration frequencies and nuclear magnetic resonance are in good
agreement with experimental results. The electrophilic and nucleophilic attack centers in SP1
+
-
were predicted with the local softness values (sk , and sk ) of individual atoms and it is
confirmed that P atoms of the PCl2 groups are nucleophilic attack centers.

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Keywords: Cyclophosphazene, spirocyclophosphazene, DFT, NMR, Spectroscopy, Crystal
structure, Local softness.
1. Introduction
Phosphazenes are a class of inorganic molecules which may be in one of the three forms;
linear short chain molecules, cyclic and high molecular weight polymers. They all have
(-P=N-)n backbone and gave substitution reactions with nucleophiles. Phosphazenes have
many applications in the industry such as biomaterials [1-3], protective coatings [4], drug
delivery [5], lubricants [6], fire-resistant materials [7-10]. Cyclophospazenes especially have
attracted much attention because of their unusual structural characteristics [11].
Hexachlorocyclotriphosphazene, N3P3Cl6 is the most widely studied compound among the
family of phosphazenes. Reactions of N3P3Cl6 with bifunctional reagents lead to formation of
regioisomers; (i) spiro- (ii) ansa-, and (iii) bino-structures [12]. Spiro-cyclotriphosphazene
derivatives can form host-guest inclusion compounds with organic or inorganic molecules
[13-15].
The chemical reactivity of molecules depends on several factors. Coulombic
attractions, for example, can accelerate the rate of reactions. In reactions of a nucleophile
with an electrophile, the interaction between the HOMO (highest occupied molecular orbital)
with the LUMO (lowest unoccupied molecular orbital) of the nucleophile, contributes to the
attraction between the two reagents. The spatial distribution of HOMO and LUMO of the
reactants is expected to show whether or not the reaction is site specific. The gas phase
calculation results of the local softness, charge density, electric potential, and HOMO and
LUMO of an individual molecule give information on the reactivity of the molecule in an
actual reaction.
As indicated earlier these inorganic compounds are very important for synthetic
chemistry, material chemistry and have many application areas. Therefore it is important to
characterize such new compounds. Therefore the aim of this work is to report experimental
and theoretical information on a new spirocyclotriphosphazene derivative, SP1, and to gain
more understanding on the molecule by comparing theoretical and experimental data. The
structure of the compound was determined by elemental analyses, mass spectrometry (MS),
Fourier transform infrared spectrophotometry (FTIR), Raman spectrophotometry and 1H, 13C
and 31P NMR techniques. The solid state structure of the compound was established by X-ray
diffraction techniques. All the spectroscopic properties examined by the experimental

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techniques were also supported by the computed results. The electrophilic and nucleophilic
+
-
attack centers were predicted with the local softness values (sk , and sk ) of individual atoms.
2. Experimental
2.1. Materials
Hexachlorocyclotriphosphazene, N3P3Cl6 (Aldrich), was purified by fractional crystallization
from n-hexane. The reaction solvents (MeOH, THF and CHCl3) and triethylamine were
obtained from Merck (Germany) and were purified by standard methods [16]. Reaction of the
N3P3Cl6 with 2-{[(2-Metoxyethyl)amino]methyl}phenol was monitored using Thin Layer
Chromatography (TLC) which was performed on silica gel plates with 60F254 indicator
(Merck, Germany).
2.2. Physical measurements
The FTIR spectra were recorded on a BRUKER VERTEX70V FTIR spectrometer,
equipped with a diamond ATR device. The FT-Raman spectra were recorded on a BRUKER
Senterra spectrometer (532 nm laser). Elemental analyses were obtained using
1
13
31
ELEMENTAR vario microCUBE instrument. H, C, and P NMR spectra were recorded
on Bruker DPX FT-NMR (500 MHz) spectrometer (SiMe4 as internal and 85% H3PO4 as
external standards) which was equipped with a 5 mm PABBO BB inverse gradient probe.
Standard Bruker pulse programs1D WIN-NMR (release 6.0) and 2D WIN-NMR (release 6.1)
were used in the experiment. Mass spectra were recorded on a Shimatzu GC-MS QP 2010
Plus spectrometer equipped with a direct injection (DI) apparatus, using the electrospray
ionization (ESI) method (35Cl values were used for calculated masses).
2.3. Synthesis
2.3.1. Synthesis of 2-{[(2-Metoxyethyl)amino]methyl}phenol
Saliciylaldehyde (5.00 mL, 48.0 mmol) in dry methanol (100 mL) was introduced into
a 250 mL three-necked round-bottomed flask. 4.14 mL (48.0 mmol) of 2-methoxyethylamine
was added to the salicylaldehiyde solution by vigorous stirring. The mixture was refluxed for
1 h and after reaching to the room temperature sodium borohidride was partially added. The
reduction completed after 2 h. Then, the solvent evaporated in reduced pressure. The residue
was dissolved in water and extracted with 3x50 mL chloroform which was then evaporated
and the oily product was purified from n-hexane.

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2.3.1. Synthesis of 4',4',6',6'-tetrachloro-3-(2-methoxyethyl)-3H,4H-spiro-1,3,2-benzoxaza
phosphinine-2,2'-[1,3,5,2,4,6] triazatriphosphinine
2.00 g (5.75 mmol) N3P3Cl6 was introduced into a 250 mL three-necked round-
bottomed flask and dissolved in 100 mL of dry THF. 5.00 mL (36.0 mmol) triethylamine was
added to the solution. One equivalent (1.04 g, 5.75 mmol) of 2-{[(2-
Metoxyethyl)amino]methyl}phenol was dissolved in 50 mL dry THF and placed in an
addition funnel. The 2{[(2-Metoxyethyl)amino]methyl}phenol solution was added dropwise
to the N3P3Cl6 solution and allowed to react for 24 h (Scheme 1). The precipitated
triethylamine hydrochloride was filtered off. The solvent was evaporated under vacuum and
the product was purified through a silica gel column with a mobile phase of toluene. The
product was then recrystallized from n-hexane to give colorless crystals. Yield: 1.1 g (42 %).
M.p.: 58 °C. ESI-MS: m/z: 455 [MH+]. Anal. Calcd. for C10H13N4 P3O2Cl4; C, 26.32; H, 2.87;
N, 10.25. Found; C, 26.09; H, 2.47; N, 10.54.
MeOH / NaBH4
MeOH
H N
CHO
R
+
CH=NR
CH2NHR
2
OH
OH
OH
Cl
Cl
Cl
Cl
P
P
N
N
P
N
N
N
THF / Et3N
+
Cl
Cl
Cl
Cl
CH2NH-R
O
Cl
P
P
P
N
OH
Cl
N
R
R = CH2CH2OCH3
Scheme 1 The synthesis pathways of the compound SP1
2.4. X-ray crystallographic analysis
Crystallographic data was collected on a Bruker APEX II QUAZAR diffractometer
using MoKα radiation (λ = 0.71073 Å). Absorption correction by multi-scan was applied to
all datasets [17]. Structures were solved by direct methods procedure in SHELXS-97 and

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refined by full-matrix least squares against F2 using SHELXL-97 [18]. All of the non-H
atoms were refined anisotropically. The H atom positions were calculated geometrically from
the parent atoms; a riding model was used during the refinement process and the Uiso (H)
values were constrained to be 1.2 Ueq (CH and CH2) and 1.5 Ueq (CH3). The general-purpose
crystallographic tool PLATON [19] and MERCURY [20] were used for the structure analysis.
Table 1
X-ray crystallographic data for SP1.
Empirical Formula
Formula weight
Temperature (K)
Crystal System
Space Group
C10H13Cl4N4O2P3
455.95
126(2)
monoclinic
P 2 1 /c
o
8.3355(7)
12.1759(10)
17.8708(16)
91.324(4)
1813.3(3)
4
1.670
0.928
920
a (A )
o
b (A )
o
c (A )
β
(°)
o
3
Volume (A
Z
)
Density (calc, g cm-3)
Absorption Coefficient (mm-1)
F(000)
Crystal size(mm)
0.39 x 0.41 x 0.60
27.56
2θmax (°)
Reflections collected
Independent reflections
Rint
29770
4170
0.0320
Parameter
209
0.0227
R [F2 >2
σ
(F2)]
wR (All data)
0.0634
1.061
0.499/ -0.403
Goodness-of-fit on F2 (S)
∆ρ max / min (eÅ-3)
2.5. Computational details
Density functional theory (DFT) calculations were performed at the
B3LYP/6-311++G (d,p) level of theory by using Gaussian 09 program [21]. Optimized

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structural parameters were used for calculations of vibrational wavenumbers, isotropic
chemical shifts and electronic transitions. The total energy distribution (TED) was calculated
1
by using the VEDA4 [22] program. H and 13C NMR chemical shifts calculations were
carried out in chloroform-d (CDCl3) solvent by using the gauge-invariant atomic orbital
(GIAO) method [23,24]. The GIAO method is one of the most common approaches for
calculating nuclear magnetic shielding tensors, and it allows the computation of the absolute
chemical shielding due to the electronic environment of the individual nuclei. Furthermore, it
is often more accurate than those calculated with other approaches for the same basis set size.
The chemical shifts were reported in ppm relative to gas-phase H3PO4 for 31P NMR and
tetramethylsilane (TMS) in the chloroform solvent for 1H and 13C NMR spectra.
3. Results and discussion
3.1. X-ray Structure of SP1
The molecular structure of SP1 has been established from single crystal X-ray
diffraction and the appropriate crystallographic data have been summarized in the Table 1.
Also, the optimized bond lengths, bond and dihedral angles calculated at the
B3LYP/6-311++G (d,p) level of theory are listed in Table 3 along with experimental data.
The molecular structure of SP1 is given in Fig. 1. Structural analysis of compound show that
the six-membered cyclotriphosphazene (P3N3) ring is slightly twisted planar conformation
with the maximum deviations from the plane of -0.0653 (5) Å [P1] (Fig. 2a). The 6-
membered spiro ring (P1/O1/C1/C6/C7/N4) is in twisted conformation (Fig. 2b). The plane
of the spiro ring is approximately perpendicular to the plane of the cyclotriphosphazene ring;
the angle between the planes is 87.60°.
Table 2
The selected bond lengths (Å), angles and torsion angles ( ͦ ) for compound SP1
Bond length XRD
Calc.
Bond Angle XRD
Calc.
Torsion Angle XRD
Calc.

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P1-O1
P1-N1
P1-N3
P1-N4
P2- Cl2
P2-N1
P2-N2
P2-Cl1
P3- Cl3
P3-N3
P3-N2
P3-Cl4
C8-N4
C7- N4
C1- O1
C9- O2
C10- O2
1.5807(11) 1.6231
1.5966(12) 1.6153
1.6039(13) 1.6158
1.6305(12) 1.6494
O1-P1-N1
O1-P1-N3
N1-P1-N3
O1-P1-N4
N1-P1-N4
N3-P1-N4
N1-P2-N2
N1-P2-Cl1
N2-P2-Cl1
N1-P2-Cl2
N2-P2-Cl2
N3-P3-N2
N3-P3-Cl4
N3-P3-Cl3
P2-N2-P3
P2-N1-P1
P3-N3-P1
110.18(6) 111.52
105.68(7) 105.41
114.20(6) 114.09
103.59(5) 102.09
108.54(7) 108.74
114.06(7) 114.31
119.89(6) 118.48
108.44(5) 108.62
108.80(5) 108.73
110.19(5) 110.18
107.05(5) 108.41
119.27(6) 118.11
110.06(5) 108.94
110.63(5) 110.60
118.94(7) 120.86
122.95(8) 123.37
123.73(8) 123.93
N1-P2-N2-P3
3.63(12)
0.12
Cl1-P2-N2-P3 121.90(7)
Cl2-P2-N2-P3 129.96(7)
124.70
126.34
0.78
N3-P3-N2-P2
7.57(12)
2.0022(5)
2.0519
Cl4-P3-N2-P2 118.53(7)
Cl3-P3-N2-P2 133.77(7)
123.87
127.29
7.29
1.5661(12) 1.5879
1.5826(11) 1.5978
N2-P2-N1-P1
5.93(13)
1.9965(5)
2.0050(5)
2.0516
2.0514
Cl1-P2-N1-P1 131.63(8)
Cl2-P2-N1-P1 118.93(8)
131.93
118.31
106.76
12.52
141.42
5.44
1.5589(12) 1.5844
1.5870(11) 1.6007
O1-P1-N1-P2
N3-P1-N1-P2
N4-P1-N1-P2
N2-P3-N3-P1
O1-P1-N3-P3
N1-P1-N3-P3
N4-P1-N3-P3
108.10(9)
10.65(12)
139.12(9)
2.32(13)
1.9980(5)
2.0507
1.4717(17) 1.4688
1.4809(17) 1.4758
1.4014(15) 1.3910
1.4106(18) 1.4143
114.76(10) 111.07
6.51(13)
11.62
132.13(9)
137.65
1.417(2)
1.4162
N1-P1-O1-C1 107.62(12) 92.55

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Fig. 1 The molecular structure and atomic numbering scheme for SP1, with protons omitted
for clarity and ellipsoids shown at 50% probability.
For the cyclotriphosphazene rings, the P-N bond lengths and P-N-P bond angle are
within the expected ranges of the 1.54-1.63 Å, and 119-148° respectively, with the N-P-N
bond angles varying less than the P-N-P bond angles (116-120°) [25]. However, it was
observed that the P-N bond lengths of phosphorus atoms the spiro ring [P1 atom in structure,
in the range of 1.5966(12) Å - 1.6039(13) Å] are longer than those P-N bond lengths of
phosphorus atoms belonging to PCl2 groups [P2 and P3 atoms in structure, in the range of
1.5589(12) Å- 1.5870(11) Å] (Table 2). Similarly, there is a significant difference in the N-P-

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N and P-N-P bond angles between the bonds of phosphorus in the spiro ring and in the PCl2;
the N1-P1-N3 bond angles [114.20°] are smaller than N1-P2-N2 and N2-P3-N3 bond angles
[119.89° and 119.27°], while the P2-N1-P1and P3-N3-P1 bond angles [122.95° and 123.73°]
are larger than P2-N2-P3 bond angles [118.94°] (Table 2).
(a)
(b)
Fig. 2 The conformations of (a) the six-membered N/O spiro ring and (b) the phosphazene
ring in SP1. The substituents have been omitted for clarity.

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From the experimental data, P-N bonds of phosphazene ring are in the range of 1.56-1.60 Å.
As seen from the Table 2, calculated P-N bond lengths are in excellent agreement with the
XRD data within 0.01-0.02 Å. Since in the literature, the PN single and double bonds are
generally reported in the ranges of 1.628–1.691 Å and 1.571–1.604 Å respectively [26], it is
possible to say that some of the PN bonds in the phosphazene ring are double bond character.
The stretching of PN bonds of phosphazene ring is due to the addition of aromatic ring and
aliphatic chain. However close inspection of PN bond lengths reveals that individual
experimental and calculated PN bond lengths of this molecule are in good agreement.
Similarly, calculated PCl bond lengths of the phosphazene ring in the molecule is in excellent
agreement with the experimental PCl bond lengths. The calculated average PCl bond length
is 2.051 Å while the experimental PCl bond length of hexachlorocyclotriphosphazene is
1.993 Å. As seen, addition of benzene ring and aliphatic chain cannot alter the P-Cl bond
length which may be stabilized by the heavy Cl atom. Experimental and calculated bond
angles are in excellent agreement and PNP bond angles are larger than NPN bond angles.
However there are discrepancies between the experimental and calculated torsion angles and
this discrepancy is about 3 to 15 degrees. This may be due to that the theoretical calculations
are performed for an isolated molecule in the gas phase, while experimental results are from a
similar molecule in the solid state.
3.2. Vibrational Analysis
Vibrational frequencies, calculated in the gas phase at the same level of theory as
optimization, and probability assignments with TED are presented only for IR and Raman
active vibrational frequencies in Table 3. It is well known that DFT overestimates the
harmonic frequencies relative to the experimental values. This is due to the electron
correlation effects, basis set deficiencies, and harmonicity. Therefore calculated harmonic
frequencies are scaled down to improve the consistency with experiment. For that matter,
wave numbers between 4000-1700 cm-1 and lower that 1700 cm-1 are multiplied by 0.958 and
0.983 respectively [26]. As seen from Table 3, no imaginary frequencies were observed, so
that the optimized structure was accepted as minimum on the potential energy surface. There
are 26 IR and Raman active vibrational frequencies. For the both, experimental and
theoretical IR data, main peaks are concentrated between 466 cm-1 and 1217 cm-1. Also some
small peaks are located between 2815 cm-1 and 2987 cm-1 and they are attributed to the C-H
stretching vibrations from the aliphatic chain. In this group, the peak at 2987 cm-1 originates
from C-H stretching vibrations of methyl, and none of the methylene contributes to this

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vibration. The stretching vibration of C-H from -NCH2- produces the peak at 2926 cm-1 to
which there is no contribution from the other methylene and methyl groups. The next two
peaks at 2873 and 2815 cm-1 mainly originates from the C-H stretching vibrations of –
CH2CH3 but the other methylene and methyl also make small contribution to these vibrations.
In the experimental IR spectrum the second small peak group is located between 1618 cm-1
and 1309 cm-1. In this region, peaks at 1618 cm-1 and 1587 cm-1 represents the C-C stretching
vibrations of the benzene ring while the peak at 1490 cm-1 represents the mixture of aromatic
C-C stretching vibrations and aliphatic H-C-H in plane bending vibrations. The peak at 1457
cm-1 is due to only the methyl group H-C-H in plane bending vibrations. In this group, the
peak is located at 1382 cm-1 is mainly due to H-C-H in plane bending vibration where carbon
atom bridges the aliphatic chain and benzene ring.
Table 3
Comparison of the theoretical and experimental vibrational spectra and proposal assignmentsa
Raman Exp.
2982
SRaman
TED (≥10%)
υCH(94)
υCH(97)
υCH(84)
υCH(97)
υCH(86)
υCH(83)
υCC(50)
υCC(47)
υCC(11)+βHCH(35)
βHCH(73)
βHCH(31)+ τHCCC(22)
βHCC,HCO(42)+ τHCCC(13)
υNC(11)+βHCO,HCN(45)
υCC, PN(32)
βHCH(11)+τHCOC(59)
υPN(46)
υPN(47)+βNPN(11)
τHCOC(32)
υOC(78)
υPN(24)
υOC(62)
IR Exp.
2987
2926
2873
2851
2852
2815
1618
1587
1490
1457
1382
1261
1245
1217
IR Calc.
2987
2917
2888
2855
2852
2836
1623
1599
1493
1451
1383
1265
1246
1204
1200
1179
1173
1147
1126
1099
959
IR Int.
28.034
25.076
31.813
35.271
77.406
46.021
12.982
23.298
68.116
0.770
24.469
17.205
32.430
461.369
42.833
958.885
1056.808
31.693
187.114
56.819
20.334
10.308
24.631
273.972
80.328
19.517
1.582
148.36
102.09
86.44
214.65
198.3
43.26
23.47
33.29
1.29
5.06
5.08
3.81
9.57
44.86
1.39
10.18
1193.54
4.11
5.96
4.63
6.57
0.7
2868
2844
1618
1588
1451
1200
1183
1171
1150
1118
1099
962
867
752
506
466
1154
965
856
858
747
496
465
409
333
υHC(72)
βCCC(13)+τHCCC(10)
υClP(42)
τCCCC(12)
τCCCC(41)
5.8
2.48
4.91
3.6
469
413
332
2.65
βNPO(10)
a IRint – IR intensity (Kmmol-1), SRaman - Raman Activity, υ-stretching; β-in-plane-bending; γ-out-of-plane
bending; τ-torsion. TED≥10% is shown.

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After this second group of peaks, a very crowded region starts at 1261 cm-1 and ends roughly
at 1062 cm-1 in which the most intense peaks are located. In this region, majority of peaks are
due to the vibrations from aliphatic chain, benzene ring or both. The most intense
experimental peak is located at 1171 cm-1, but DFT calculations underestimate the peak
intensity which may be due to that the solid phase of the molecule is used in the experiments
while calculations were carried in the gas phase. This peak is attributed to PN stretching and
NPN in plane bending vibrations of phosphazene ring. The experimental peaks at 1118 cm-1
and 962 cm-1 are due to asymmetric and symmetric CO stretching vibrations respectively,
where oxygen atom connects the methylene and methyl groups. The peak at 867cm-1 stands
from aromatic CH out of plane bending vibrations. In plane bending vibrations of aromatic
CCC and torsion vibrations of aromatic HCCC produce the peak at 752 cm-1. ClP stretching
vibration of phosphazene ring results in the peak at 505 cm-1. CCCC torsion vibration of
aromatic ring occurs at 466 cm-1, and 413 cm-1. After these two peaks, another small peak
appears at 332 cm-1, which is due to in plane bending vibration of NPO. As expected, small
peaks at between 300-50 cm-1 are due to wagging vibrations.
3.3. HOMO-LUMO Analysis
In order to obtain more information about the energy levels of the SP1, we also calculated
HOMO (highest occupied molecular orbital)-LUMO (lowest unoccupied molecular orbital)
energy levels (Fig.3) and the results of HOMO–LUMO analysis were presented in Table 4.
These calculations were performed at the TD-DFT/B3LYP/6-311++G (d, p) level of theory.
HOMO and LUMO are important for many physical and chemical properties such as
electrical, optical properties and chemical reactions [28, 29]. HOMO-LUMO energy gap also
determines the bioactivity and chemical activity of a molecule. Large energy gap makes it
difficult to excite an electron from the HOMO to the LUMO level. Figure 3 shows the charge
density of HOMO and LUMO levels. For the HOMO level charge is mainly concentrated
around the benzene ring and the oxygen atom which connects the benzene and phosphazene
rings while the charge distribution of the HOMO level of N3P3Cl6 mainly localized on
nitrogen and chlorine atoms [30]. The electron attraction of benzene ring and oxygen atom in
the SP1, is larger than that of nitrogen and chlorine atoms, so that electrons are concentrated
on benzene ring, oxygen, and nitrogen atoms of the spiro-ring after the substitution. In the

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case of LUMO for the N3P3Cl6, charge is distributed on all atoms in the molecule while for
the LUMO of the title molecule charge distribution is mainly concentrated on both PCl2
groups. Therefore nucleophilic substitutions can take place from the phosphorus of PCl2
groups. The HOMO-LUMO gap energy of the title molecule is 4.975 eV which is lower than
that of N3P3Cl6 (5.745 eV) [30]. HOMO energy of the molecule is -7.059 eV, and most of the
contributions to this orbital comes from P(1s), N(4py) of phosphazene ring, O(2px) (connects
the phosphazene and benzene ring), and C(4px,4py) of benzene ring. The energy of LUMO
level is -2.084 eV, and almost all charge density concentrated around the phosphazene ring.
Therefore contribution to this orbital is mainly from phosphazene ring. This shows that of the
excitation of an electron from HOMO to LUMO would cause very big charge transfer from
benzene and spiro-ring to the phosphazene ring. The charge distribution of HOMO level
allows determining possible sites for interaction with nucleophiles. Sites with less charge
concentration are possible coordination points, and since most of the charge density
concentrated around the benzene ring in this molecule, phosphazene ring should be
considered as a coordination point. The molecules with high HOMO energy tend to react
more easily with the electrophiles. On the other hand, for the interaction with nucleophiles, a
molecule with low LUMO energy is essential. LUMO energy of the title molecule (-2.084 eV)
is higher than that of the N3P3Cl6 (-2.810 eV) [30], therefore title molecule is less reactive
with the nucleophiles.
Hardness is the measure of resistance towards the change in the electron distribution of a
molecule [31] and calculated as;
Hardness value for the SP1 is 2.4875 eV which is lower than that of N3P3Cl6 (2.8725 eV). As
a result of that, it is possible to state that SP1 is softer than the N3P3Cl6.

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LUMO+1
E=-1.241
LUMO
(First excited
state)
E=-2.084
∆E=-4.975
∆E=-6.164
HOMO
(Groundstate)
E=-7.059
HOMO-1
E=-7.406
Fig. 3 The atomic orbital compositions of the frontier molecular orbital of SP1 (eV)
Electronic chemical potential is defined [32] as the characteristic of electronegativity of
molecules and calculated as;

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According to our calculations electronegativity of SP1 and N3P3Cl6 are 4.5715 eV and 5.6825
eV respectively. Therefore N3P3Cl6 is more electronegative compared to the SP1.
Table 4
Calculated energy values, Electronegativity (χ), Chemical Potential (ꢀ), Global Hardness (η),
Global Softness (S), Global Electrophilicity Index (ω), Dipole moment, (µ) and in its ground
state with singlet symmetry at DFT method in the gas phase.
TD-DFT/B3LYP/6-311++G (d, p)
Energy
HOMO
LUMO
εH - εL
GAS
-7.059 (eV)
-2.084 (eV)
-4.975(eV)
-4.5715
Electronegativity (χ)
Chemical Potential (ꢀ)
Global Hardness (η)
Global Softness (S)
Global Electrophilicity Index (ω)
Dipole moment, µ
Symmetry
4.5715
2.4875
0.2010 (eV-1)
4.2007 (eV)
5.720 (D)
C1
Local reactivity of a molecule is investigated by means of Fukui functions, which provide a
way of distinguishing each part of a molecule according to their chemical behavior. Therefore
an atom in a molecule with a maximum Fukui function (ƒ+) should represent the nucleophilic
site. Similarly electrophilicity of a site is determined by the ƒ- . Calculated Fukui functions of
this study are given in Table 5. As seen, P1, P2 and P3 atoms have ƒ+ values 0.0237, 0.0699
and 0.0675 respectively. Since the P2, and P3 atoms have the largest ƒ+ values, they may be
considered as nucleophilic attack centers for the SP1.
Another way of evaluating the electrophilic and nucleophilic attack centers in a molecule is to
+
-
consider local softness values (sk , and sk ) of individual atoms. In order to reduce the effects
+
-
of basis set and correlation effects on the calculated sk , and sk values, Roy et al. [33]
+
-
proposed an alternative way. They suggested the site having the highest sk /sk is the most
-
+
probable site to be attacked by a nucleophile, and the site having the highest sk /sk ratio is the
+
-
most probable site to be attacked by an electrophile. Therefore we calculated the sk /sk , and
-
+
+
-
sk /sk ratios for the P1, P2, and P3 atoms. The sk /sk ratios for the P1, and P2 atoms are 2.0

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-
+
while for P3 atom it is 4.7. Similarly, the sk /sk ratios for the P1, and P2 atoms are 0.5 while
for P3 atom it is 0.21. As a result, it is possible to conclude that P2, and P3 atoms are
nucleophilic attack centers. These results are also consistent with the Fukui function results
mentioned above.
Table 5
+
-
+
-
Fukui functions (fk , fk ) and Local softness (sk , SK , eV-1) for selected atomic sites of SP1.
+
-
+
-
+
-
-
+
Atom
P1
P2
fk
fk
sk
sk
sk / sk
sk / sk
0.0237
0.0699
0.0675
0.0191
0.0158
0.0200
0.0056
0.0016
0.0016
0.0119
0.0148
0.0150
0.0336
0.0185
0.0281
0.0335
0.0055
0.041
0.0048
0.014
0.014
0.0038
0.0032
0.0040
0.0011
0.00030
0.00030
0.0024
0.0030
0.0030
0.0067
0.0037
0.0056
0.0067
0.0080
0.008
2.0
4.7
4.7
0.57
0.87
0.71
0.16
0.027
0.037
0.50
0.21
0.21
1.8
1.2
1.4
6.1
37
P3
N1
N2
N3
N4
O1
O2
27
3.4. NMR
The experimental and calculated 31P, 13C and 1H NMR data of the SP1 were given in Table 6.
The 31P NMR data of the title molecule refer to the spiro structure. The spin system is
interpreted as AX2 which causes one triplet and one doublet. These results are in accordance
with the two kinds of P atoms present in the cyclophosphazene ring. The chemical shift
values are 5.23 ppm for spiro (P1) group, and 23.73 ppm for PCl2 (P2, 3) groups. The coupling
2
constant Jpp is 56.9 Hz. As seen, there are three 31P chemical shift values (49.65, 48.45, and
1.74) observed from the calculation. Despite the difference in the experimental and calculated
chemical shift values, these peaks can be attributed as environmentally different two
phosphorous sites present in the molecule. The peaks at the 49.65 and 48.45 ppm are from
PCl2 groups while the peak at 1.74 ppm is from P (spiro).
1
In the SP1 13C and H NMR signals are assigned on the basis of chemical shifts,
multiplicities and coupling constants (related data is given in section 2.3). The expected
13
carbon signals are assigned from the C NMR spectra of the SP1. The experimental carbon
signals of aromatic ring are in the range of 118.69 ppm-149.94 ppm whereas calculated
carbon NMR signals are in the range of 124.59 ppm-160.80 ppm. The experimental carbon
NMR signals of aliphatic group are in the range of 48.11-71.74 ppm while the calculated

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values are in the range of 50.02-73.42 ppm. As seen the discrepancies between the
experimental and calculated chemical shifts are less for aliphatic groups comparing to the
aromatic groups.
The 1H NMR spectra of the compound were evaluated. The benzylic (H7) protons give rise to
doublets (3JPH = 15.2 Hz), indicating that these protons are equivalent. The H8 protons give
3
rise to a multiplets (3JPH= 14 Hz, JHH= 5.4 Hz). The H9 protons give rise to triplets (3JHH=
5.4 Hz), and H10 protons give rise to a singlet. Calculated chemical shifts for H8A and H8B
protons are 3.30, and 2.93 ppm respectively. However experimental value for the both
protons is 3.28 ppm. A similar discrepancy between the experimental and calculated chemical
shifts is also observed for H7, H9, and H10 protons. The reason for these discrepancies may
be, taking the atomic positions as static during the calculations, therefore considering the
same protons in the different chemical environments.
Table 6 The predicted and experimental (in CDCl3 ) 31P-, 13C- and 1H NMR data (δ in ppm, J
in Hz) for SP1 (isotropic chemical shifts with respect to TMS and 85 % H3PO4)a.
Atom B3LYP Exp.
Atom B3LYP Exp.
P1
P2
P3
C1
C2
C3
C4
1.74
5.23 (t, 2JPNP= 56.9)
23.73 (d, 2JPNP= 56.9)
23.73 (d, 2JPNP= 56.9)
H2
7.40
7.58
7.38
7.31
3.68
4.79
3.30
7.09
49.65
48.45
H3
7.25
H4
7.08
160.80 149.94 (d, 2JPC= 8.5)
124.59 118.69 (d, 3JPC= 8.3 )
135.94 128.90 (s)
H5
7.06
H7A
H7B
H8A
4.40 (d, 2H, 3JPH= 15.2)
4.40
131.05 124.27 (s)
3.28 (dt, 2H, 3JPH= 14.0
3JHH= 5.4)
C5
132.73 126.49 (s)
H8B
2.93
3.28 (dt, 2H, 3JPH= 14.0
3JHH= 5.4)
C6
C7
C8
C9
C10
134.59 124.46 (d, 3JPC= 7.2)
H9A
H9B
3.33
3.18
3.59 (t, 3JHH= 5.4)
3.59 (t, 3JHH= 5.4)
3.36 (s)
54.21
50.02
73.42
61.60
49.87 (d, 2JPC= 2.6)
48.11(d, 2JPC= 4.9)
71.74 (d, 2JPC= 3.5)
59.07 (s)
H10A 3.32
H10B 3.83
H10C 3.30
3.36 (s)
3.36 (s)
a s= singlet, d= doublet, t= triplet, dt= doublet of triplets.

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4. Conclusion
The combination of the experimental methods with the quantum chemical DFT computations
provides detailed information about the structure of the technologically important materials.
By using atomic positions obtained from the experimental X-ray data, structure of the
molecule was optimized at the B3LYP/6-311++G (d,p) level of theory. After that, theoretical
IR and Raman spectra were calculated from the optimized geometry at the same level of
theory. These theoretical spectra were compared with the experimental ones, and found that
they are in agreement. Furthermore we also did peak assignments according to the results of
1
detailed frequency analysis. We also calculated the H, 13C and 31P NMR spectra and
compared them with the experimental results. It seems that there are some discrepancies
between both data, which may be due to that the calculations, were performed in the gas
phase, while experiments performed in the solid state. Our HOMO-LUMO calculations show
that charge distribution of the HOMO and LUMO levels for the title molecule are
concentrated around the benzene, spiro rings and phosphazene ring respectively. In addition
calculated HOMO-LUMO gap energy of the title molecule is lower than that of N3P3Cl6. This
indicates that the title molecule is less reactive than N3P3Cl6, which is also in agreement with
the experimental results. Fukui functions (ƒ+ and ƒ-) and local softness (sk , and sk ) values of
+
-
individual atoms showed that the nucleophilic centers for the title molecule are PCl2 groups.
Appendix A. Supplementary data
The CCDC number of 1438282 contains the supplementary crystallographic data (CIF) for
this compound. These data can be obtained free of charge from the Director, CCDC, 12
Union Road, Cambridge CB2 1EZ, UK (Fax: +44-1223-336-033; e-mail: deposit@ccdc.cam.
ac.uk or http://www.ccdc.cam.ac.uk).
Acknowledgement
The authors gratefully acknowledge the financial support from the “Kırıkkale University,
Scientific Research Projects Coordination Unit” (grant No. 2012/14).

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Highlights
•
•
•
The investigated molecule is a new material which is synthesized by our group.
The FT-IR, 13C, 1H and 31P NMR and X-ray were used for characterization.
The B3LYP method with the standard 6-311++G(d,p) basis set was used for
calculations.
•
•
The Fukui functions, local softness and chemical potentials were calculated.
The energy distributions of vibrational modes were presented.