Syntheses, characterizations, thermal and photophysical properties of cyclophosphazenes containing adamantane units

Article abstract of DOI:10.1016/j.ica.2013.01.028

In this study, phenoxy-adamantane substituted cyclophosphazene compounds (5-8) were synthesized in three steps. Firstly; adamantane derivatives (1 and 2) containing alkyne groups were prepared. Secondly; 2,2,4,4,6,6-hexzakis- (2′-azido-1′-ethoxy)-cyclotri

Full text of DOI:10.1016/j.ica.2013.01.028

Accepted Manuscript
Syntheses, characterizations, thermal and photophysical properties of cyclo‐
phosphazenes containing adamantane units
İlker Ün, Hanife İbişoğlu, Şule Şahin Ün, Bünyemin Çoşut, Adem Kılı ç
PII:
S0020-1693(13)00030-3
http://dx.doi.org/10.1016/j.ica.2013.01.028
ICA 15309
DOI:
Reference:
To appear in:
Inorganica Chimica Acta
Received Date:
Revised Date:
Accepted Date:
14 December 2012
28 January 2013
29 January 2013
Please cite this article as: İ. Ün, H. İbişoğlu, Ş. Ün, B. Çoşut, A. Kılı ç, Syntheses, characterizations, thermal and
photophysical properties of cyclophosphazenes containing adamantane units, Inorganica Chimica Acta (2013), doi:
http://dx.doi.org/10.1016/j.ica.2013.01.028
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1
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Syntheses, characterizations, thermal and photophysical properties of
cyclophosphazenes containing adamantane units
3
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7
İlker Ün a,b, Hanife İbişoğlu a,* , Şule Şahin Ün a, Bünyemin Çoşuta, Adem Kılıça
a Department of Chemistry, Gebze Institute of Technology, P.K:141 41400, Gebze/Kocaeli,
Turkey
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bTUBITAK-UME, Chemistry Group Laboratories P.O. Box 54, 41470 Gebze-Kocaeli, Turkey
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12 * Corresponding author. Address: Department of Chemistry, Gebze Institute of Technology,
13 PB.141 41400 Kocaeli, Turkey. Tel.: +90 262 6053087; fax: +90 262 6053101
14 E-mail address: ibisoglu@gyte.edu.tr.
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26

27 Abstract
28 In this study, phenoxy-adamantane substituted cyclophosphazene compounds (5-8) were
29 synthesized in three steps. Firstly; adamantane derivatives (1 and 2) containing alkyne groups
30 were prepared. Secondly; 2,2,4,4,6,6-hexzakis-(2’-azido-1’-ethoxy)-cyclotriphosphazatriene
31 (3) and 2,2,4,4,6,6,8,8-octakis-(2’-azido-1’-ethoxy)-cyclotetraphosphazatetraene (4) were
32
synthesized from the nucleophilic substitutions of 2-azido-1-ethanol with trimer (N3P3Cl6)
33 and tetramer (N4P4Cl8) in THF respectively. Thirdly; cyclophosphazenes containing
34 adamantane units (5-8) were obtained by the Cu (I) catalyzed click reactions of
35 cyclophosphazenes (3 and 4) with compounds 1 and 2. The structural investigations of newly
36 synthesized compounds 1-8 were evaluated by elemental analysis and FT-IR (ATR), mass
1
1
37 spectrometry, H, 13C, H-13C HSQC (for 6) and 31P NMR (for 3-8) spectroscopies.
38 Compound 1–8 were also reported for the first time. The thermal and photophysical properties
39 of 5-8 were investigated.
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41
42
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51
52 Keywords: Cyclophosphazene, Adamantane, Thermal stability, Fluorescence, NMR.

53 Introduction
54 Cyclic phosphazenes are an important class of inorganic heterocyclic rings containing an
55
[N=PX2] repeat unit [1, 2]. The inorganic phosphazenes have been well studied in both the
56 cyclic and linear form by several groups due to their diverse properties including catalytic
57 properties [3], electrical conductivity [4], liquid crystal [5] and biomedical activity [6].
58 Phosphazenes are attractive due to their higher thermal stability and flame retardancy
59 properties when compared with the organic homologues [7]. So, the physical and chemical
60 properties of cyclic phosphazenes can be tailored via the appropriate substituted groups on the
61 phosphorus atoms [8]. Owing to the excellent thermal stability and char yield performance,
62 the adamantyl substituted polymers have attracted interest for its potential application in
63 flame retardant [9-12]. However, there are limited examples of adamantyl substituted
64 cyclophosphazenes or polyphosphazenes [9, 13].
65
The field of luminescent materials is attracting interest because of their many
66 applications including emitting materials for organic light emitting diodes, light harvesting
67 materials for photocatalysis and fluorescent sensors for organic or inorganic analyzers [14].
68 Cyclic phosphazene based materials are suitable platform as luminescent materials because
69 they provide high thermal stability and the functional groups are projecting in 3 dimensions
70 thus producing a rigid spherical core from attach the dendrons interest. These rigid spheres
71 have been shown to promote amorphous properties that are known to be important for
72 electroluminescent devices [15, 16]. Recently there has been considerable interest in
73 fluorescent compounds based on cyclic phosphazene cores for use in OLEDs [16-19].
74
In phosphazene chemistry, there are some examples of adamantyl side group bearing
75 polyphosphazenes [9, 13a]. However, to the best of our knowledge, the synthesis of phenoxy-
76 adamantyl containing cyclic phosphazenes has not yet been reported. Hence, we report the
77 synthesis (Fig.1) and characterization of cyclic phophazenes bearing adamantyl groups (5-8)

78 shown in Fig. 2 to investigate the thermal stability and fluorescence spectral properties of
79 these compounds. For this purpose, the fluorescence quantum yields and lifetimes of these
80 compounds have been investigated in dichloromethane.
81 Experimental
82 Materials
83 Hexachlorocyclotriphosphazene (trimer,) and octachlorocyclotetraphosphazane (tetramer),
84 which were obtained from Otsuka Chemical Co. Ltd., were purified by fractional
85 crystallization from n-hexane. The following chemicals were obtained from Merck; H2SO4
86 (98%), 2-aminopyridine (≥98%), n-hexane (>96%), tetrahydrofuran (THF) (≥99%),
87 dichloromethane (DCM) (≥99%), Na2SO4 (≥99.0%), K2CO3 (≥99%), N,N-
88 dimethylformamide (DMF) (≥99%), dimethyl sulfoxide (DMSO) (≥99%), phenol (≥99%),
89 ethanol (≥99.5%), NaOH (≥99%), diethylether (≥98%), Pd/C (%10). The following chemicals
90 were obtained from Aldrich; sodium azide (≥99.5%), 1-bromoadamantane (99%),
91 N,N,N′,N′′,N′′-pentamethyldiethylenetriamine (PMDTA) (99%). 2-bromoethanol (97%),
92 copper(I) bromide (98%), propargyl bromide (80% in toluene, stab. with MgO) were obtained
93 from Alfa-aesar and used as received. All solvents used in this work were purified by
94 conventional methods. THF was distilled over a sodium–potassium alloy under an argon
95 atmosphere. NaH (Merck, 60% dispersion in mineral oil) was removed by washing with dry
96 n-heptane followed by decantation. CDCl3 used for NMR spectroscopy was obtained from
97 Merck. 1, 8, 9-Anthracenetriol for the MALDI matrix was obtained from Fluka.
98 Measurements
99 UV/Vis spectra were recorded with a Shimadzu 2001 UV Pc spectrophotometer.
100 Fluorescence emission spectra were recorded on a Varian Eclipse spectrofluoremeter using 1
101 cm pathlength cuvettes at room temperature. Fluorescence quantum yields (ΦF) were
102 determined by the comparative method (Eq. 1) [20].

103
104
F . AStd . n 2
(1)
Φ
F
= Φ (Std)
F
F
Std . A . nS2td
105
106 where F and FStd are the areas under the fluorescence emission curves of the samples (5-8)
107 and the standard, respectively. A and AStd are the respective absorbance of the samples and
108 standard at the excitation wavelengths. The refractive indices of the solvents were employed
109 in calculating fluorescence quantum yields in different solvents. 2-aminopyridine (in 0.1 M
110 H2SO4) (ΦF = 0.60) [21] was employed as the standard. Both the samples and standard were
111 excited at the same wavelength. The concentrations of the solutions at the excitation
112 wavelengths were fixed at 1x10-5 mol.dm-3. Natural radiative (τ0) life times were determined
113 using PhotochemCAD program which uses the Strickler-Berg equation [22]. Thin layer
114 chromatography (TLC) was performed on Merck Silica gel plates (Merck 60, 0.25 mm
115 thickness) with F254 indicator. Column chromatography was performed on silica gel (Merck
116 60,0.063–0.200 mm; for 3 g crude mixture, 150 g silica gel was used in a column of 2 cm in
117 diameter and 120 cm in length). Elemental analyses were obtained using a Carlo Erba 1106
118 Instrument. IR spectra were recorded between 4000 and 650 cm-1 using a Perkin Elmer
119 Spectrum 100 FT-IR spectrometer with an attenuated total reflection (ATR) accessory
120 featuring a zinc selenide (ZnSe) crystal. The mass analyzer was a Bruker Daltonics
121 MicrOTOF mass spectrometer equipped with orthogonal electrospray ionization (ESI) source.
122 The instrument was operated in positive or negative ion mode using a range of m/z 50–3000.
123 Mass spectra were acquired in the linear mode with an average of 50 shots on a Bruker
124 Daltonics Microflex mass spectrometer (Bremen, Germany) equipped with a nitrogen UV-
125 Laser operating at 337nm.
126
1H, 13C and 31P NMR spectra were recorded on a Varian INOVA 500 MHz
1
127 spectrometer using TMS as an internal reference for H and 13C and 85% H3PO4 as an

128 external reference for 31P. Thermal properties of compounds were investigated on a Mettler
129 Toledo TGA/SDTA 851. Thermogravimetric analysis (TGA) was carried out at temperature
130 range from room temperature to 700°C at a heating rate of 10°C/min under a nitrogen gas
131 atmosphere, and the differential scanning calorimeter (DSC 821e) equipped with METTLER
132 TOLEDOSTAR e software at a heating rate of 10 °C min-1 under nitrogen flow (50 mL min-1).
133
Synthesis [23] and spectroscopic data for compounds 1 and 2 were given in
134 supplementary information.
135
2-azido-1-ethanol was prepared according to the literature [24]. Care was taken to
136 minimize the effect of possible explosions at all stages in the preparation and handling of the
137 azide samples [24], but no untoward occurrences were experienced during this work.
138 Synthesis of compound 3.
139 Hexachlorocyclotriphosphazene (1 g, 2.87 mmol) and 2-azido-1-ethanol (2 g, 23 mmol) were
140 dissolved in 40 mL of dry THF in a 100 mL three-necked round-bottomed flask under an
141 argon atmosphere. The reaction mixture was cooled in an ice-bath and NaH (1.15 g, 28.70
142 mmol) in 15 mL of dry THF was quickly added to a stirred solution under an argon
143 atmosphere. The reaction mixture was stirred for 24 h at room temperature and the reaction
144 followed on TLC silica gel plates using n-hexane:THF (3:2) as the mobile phase. The reaction
145 mixture was filtered to remove the sodium chloride formed and any other insoluble material.
146 The solvent was removed under reduced pressure and the resulting colorless oil was subjected
147 to column chromatography, using n-hexane:THF (3:2) as the mobile phase. 2,2,4,4,6,6-
148 hexzakis-(2’azido-1’-ethoxy)-cyclotriphosphazatriene (3) was obtained as a colorless oil (1.4
149 g, 2.15 mmol) in 75% yield. Anal. Calc. for C12H24N21O6P3; requires: C, 22.13; H, 3.71; N,
150 45.16%; M, 651.38 m/z. Found: C, 22.10; H, 3.70; N, 45.15%. MS (ESI) m/z (%):652.31
151 (100) [M+H]+. FT-IR (ATR, cm-1) 2949 (-CH str), 2093 (-N3), 1440, 1301, 1215 (P=N str),
152 1039, 963 (P-O-C str), 898, 749. 1H NMR (500 MHz, CDCl3, 25 °C, δ, ppm) 4.05 (m, 2H, -O-

153 CH2-) 3.40 (m, 2H, -CH2-N3). 13C NMR (125 MHz, CDCl3, 25 °C, δ, ppm) 65.13 (s, -O-CH2-
154 ), 50.69 (s, -CH2-N3).
155 Synthesis of compound 4.
156 The work-up procedure was similar to that of compound 3, using
157 octachlorocyclotetraphosphazene (1 g, 2.15 mmol), 2-azido-1-ethanol (1.69 g, 19.35 mmol)
158 NaH (0.78 g, 19.35 mmol). Compound 4, 2,2,4,4,6,6,8,8-octakis-(2’-azido-1’-ethoxy)-
159 cyclotetraphosphazatetraene, (colorless oil,1.3 g, 1.50 mmol) was obtained in 70% yield.
160 Anal. Calc. for C16H32N28O8P4; requires: C, 22.13; H, 3.71; N, 45.16%; M, 868.50 m/z.
161 Found: C, 22.12; H, 3.70; N, 45.15%. MS (ESI) m/z (%): 869.50 (100) [M+H]+. FT-IR
1
162 (ATR, cm-1) 2915 (-CH str), 2120 (-N3), 1220 (P=N str), 962 (P-O-C str). H NMR (500
°
13
163 MHz, CDCl3, 25 C, δ, ppm) 4.14 (m, 2H, -O-CH2-), 3.49 (m, 2H, -CH2-N3). C NMR (125
164 MHz, CDCl3, 25 °C, δ, ppm) 65.22 (s, -O-CH2-), 50.91 (s, -CH2-N3).
165 General method for synthesis of compounds 5–8
166 Azido cyclophosphazenes (3 or 4) and alkyne derivatives (1 or 2), copper (I) bromide and
167 PMDTA in dry DCM (20 mL) in a sealed tube was stirred for 48 h at room temperature under
168 an argon atmosphere. The reaction mixture was poured into water and then extracted with
169 DCM. The extract was washed with water and brine and dried over anhydrous Na2SO4. The
170 solvent was evaporated and the crude product was purified by column chromatography with
171 n-hexane:THF (3:2)
172 Synthesis of compound 5.
173 Compound 3 (0.20 g, 0.31 mmol), 1 (0.58 g, 2.17 mmol), copper (I) bromide (0.44 g, 3.10
174
mmol) and PMDTA (0.53 g, 3.10 mmol) were used. White powder, mp: 112.0 °C. Yield: 0.6 g,
175 0.26 mmol, 86%. Anal. Calc. for C126H156N21O12P3; requires: C, 67.27; H, 6.99; N, 13.08%;
176 M, 2249.64 m/z. Found: C, 67.25; H, 6.98; N, 13.06%. MS (MALDI ) m/z (%): 2250.37
177 (100) [M+H]+. FT-IR (ATR, cm -1) 3139 (Ar C-H), 2901, 2847 (-CH str), 1609 and

178 1511(C=C str), 1450, 1229 (P=N str), 1040 (C-O-C str), 963 (P-O-C str), 805. 1H NMR (500
179 MHz, CDCl3, 25 °C, δ, ppm) 7.71 (s, 1H, Hc), 7.26 (d, J = 8.8 Hz, 2H, Hh), 6.91 (d, J = 8.8 Hz,
180 2H, Hg), 5.10 (s, 2H, He), 4.44 (t, J = 4.8 Hz, 2H, Ha), 4.01 (br, s, 2H, Hb), 2.07 (br, s, 3H, Hl),
181 1.85 (d, J = 2.3 Hz, 6H, Hk), 1.74 (dd, J = 28.0, 12.1 Hz, 6H, Hm). 13C NMR (125 MHz,
182 CDCl3, 25 °C, δ, ppm) 156.20 (s, Cf), 144.68 (s, Cd), 144.30 (s, Ci), 126.19 (s, Ch), 124.50 (s,
183 Cc), 114.39 (s, Cg), 64.45 (s, Cb), 61.95 (s, Ce), 50.15 (s, Ca), 43.54 (s, Ck), 36.94 (s, Cm),
184 35.79 (s, Cj), 29.14 (s, Cl).
185
186
187 Synthesis of compound 6.
188
189
Compound 4 (0.20 g, 0.23 mmol, 1 (0.55 g, 2.07 mmol), copper (I) bromide (0.40 g, 2.76 mmol)
and PMDTA (0.48 g, 2.76 mmol) were used. White powder, mp: 114.5 °C. Yield: 0.57 g, 0.19
190 mmol, 81.7%. Anal. Calc. for C168H208N28O16P4; requires C, 67.27; H, 6.99; N, 13.08%; M,
191 2999.52 m/z. Found: C, 67.24; H, 6.96; N, 13.05%. MS (MALDI ) m/z (%):3000.80
-1
192 m/z[M+H]+. FT-IR (ATR, cm ) 3139 (Ar C-H str), 2901, 2847 (-CH str), 1609 and 1511
193 (C=C str), 1450, 1317, 1241 (P=N str), 1041(C-O-C str), 954 (P-O-C str), 805. 1H NMR (500
°
194 MHz, CDCl3, 25 C, , ppm) 7.70 (s, 1H, Hc), 7.24 (d, J = 8.7 Hz, 2H, Hh), 6.89 (d, J = 8.7
195 Hz, 2H, Hg), 5.07 (s, 2H, He), 4.39 (t, J = 4.8 Hz, 2H, Ha), 3.97 (br, s, 2H, Hb), 2.06 (br, s, 3H,
13
196 Hl), 1.84 (d, J = 2.1 Hz, 6H, Hk), 1.74 (dd, J = 29.0, 12.0 Hz, 6H, Hm). C NMR (125 MHz,
°
197 CDCl3, 25 C, , ppm) 156.20 (s, Cf), 144.68 (s, Cd), 144.23 (s, Ci), 126.19 (s, Ch), 124.46 (s,
198 Cc), 114.39 (s, Cg), 64.63 (s, Cb), 61.93 (s, Ce), 50.29 (s, Ca), 43.54 (s, Ck), 36.94 (s, Cm), 35.78
199 (s, Cj), 29.14 (s, Cl).

200
201
202 Synthesis of compound 7.
203 Compound 3 (0.2 g, 0.31 mmol), 2 (0.78 g, 2.17 mmol), copper (I) bromide (0.44 g, 3.10
°
204 mmol mmol) and PMDTA (0.53 g, 3.10 mmol) were used. White powder, mp: 123.3 C.
205 Yield: 0.53 g, 0.2 mmol, 61.13%. Anal. Calc. for C162H186N27O12P3; requires: C, 67.27; H,
206 6.99; N, 13.08%; M, 2796.30 m/z. Found: C, 67.25; H, 6.98; N, 13.06%. MS (MALDI ) m/z
-1
207 (%):2797.40 (100) [M+H]+. FT-IR (ATR, cm ) 3132 (N-H str), 3038 (Ar C-H str), 2901,
208 2847 (-CH str), 1501 and 1449 (C=C str), 1229 (P=N str), 1084, 1039 (C-O-C str), 958 (P-O-
209 C str), 874, 750. 1H NMR (500 MHz, CDCl3, 25 °C, δ, ppm) 7.61 (s, 1H, Hc), 7.23 (d, J = 7.9
210 Hz, 2H, Hm), 6.85 (m, 4H, Hl, Hi), 6.74 (m, 2H, Hh), 4.59 (br, s, 2H, He), 4.38 (br, s, 2H, Ha),
211 4.09 (br, s, 1H, Hf), 3.94 (s, 2H, Hb), 2.06 (br, s, 3H, Hr), 1.86 (br, s, 6H, Hp), 1.74 (dd, J =
212 26.2, 11.8 Hz, 6H, Hs). 13C NMR (125 MHz, CDCl3, 25 °C, δ, ppm) 156.01 (s, Ck), 149.75 (s,
213 Cd), 148.54 (s, Cj), 145.93 (s, Cn), 144.33 (s, Cg), 126.20 (s, Cc), 121.22 (s, Cm), 120.62 (s, Ci),
214 117.41 (s, Cl), 114.32 (s, Ch), 64.57 (s, Cb), 50.20 (s, Ca), 47.35 (s, Ce), 43.53 (s, Cp), 36.95 (s,
215 Cs), 35.91 (s, Co), 29.15 (s, Cr).
216
217 Synthesis of compound 8.
218
219
Compound 4 (0.2 g, 0.23 mmol), 2 (0.74 g, 2.07 mmol), copper (I) bromide 0.40 g, 2.76
mmol) and PMDTA (0.48 g, 2.76) were used. White powder, mp: 130.8 °C.Yield: 0.46 g, 0.13
220 mmol, 53.68%. Anal. Calc. for C216H248N36O16P4; requires: C, 69.58; H, 6.70; N, 13.52%; M,
221 3728.40 m/z. Found: C, 69.56; H, 6.70; N, 13.50%. MS (MALDI ) m/z (%):3729.30 (100)

-1
222 [M+H]+. FT-IR (ATR, cm ) 3132 (N-H str), 3041 (Ar C-H str), 2901 and 2847 (-CH str),
223 1501 and 1450(C=C str), 1231(P=N str), 1084, 1042 (C-O-C str), 954 (P-O-C str), 874, 750.
°
224 1H NMR (500 MHz, CDCl3, 25 C, δ, ppm) δ 7.58 (s, 1H, Hc), 7.23 (d, J = 7.7 Hz, 2H, Hm),
225 6.82 (m, 4H, Hl, Hi), 6.61 (m, 2H, Hh ), 4.57 (br, s, 2H, He), 4.35 (br, s, 2H, Ha), 4.11 (br, s,
226 1H, Hf), 3.88 (s, 2H, Hb), 2.05 (br, s, 3H, Hr), 1.84 (br, s, 6H, Hp), 1.73 (dd, J = 27.0, 11.9 Hz,
227 6H, Hs). 13C NMR (125 MHz, CDCl3, 25 °C, δ, ppm) 156.54 (s, Ck), 149.77 (s, Cd), 148.52 (s,
228 Cj), 145.95 (s, Cn), 144.34 (s, Cg), 126.21 (s, Cc), 121.21 (s, Cm), 120.60 (s, Ci), 117.44 (s, Cl),
229 114.29 (s, Ch), 64.72 (s, Cb), 50.36 (s, Ca), 43.53 (s, Ce), 40.33 (s, Cp), 36.95 (s, Cs), 35.91 (s,
230 Co), 29.15 (s, Cr).
231
232
233 Results and discussion
234 Syntheses and characterizations of compounds
235 First of all, adamantane derivatives containing alkyne groups (1 and 2) were synthesized for
236 using in the click reactions. Then, 2-azido-1-ethanol was prepared from the reaction of 2-
237 bromoethanol with sodium azide according to the literature [24]. Cyclophospazene derivatives
238 with azido groups (3 and 4) were synthesized from the reactions of 2-azido-1-ethanol with
239 trimer and tetramer, respectively. Further, end-group modifications of azide functional cyclic
240 phosphazenes (3 and 4) were achieved quantitatively via the Cu(I) catalyzed click reaction
241 between azide functional groups and compound 1- 2 in the final step (Fig.1 ).
242
The structures of the compound 1-8 (Figs.1-2) were fully characterized by
243 spectroscopic techniques. The elemental analysis and FT-IR (ATR), 1H and 13C NMR results
244 for each new compound were provided as part of the analytical data in the synthesis section.

245 31P NMR data for compound 3-8 were summarized in Table 1. General presentation of the
246 reactions was shown in Fig.1 and structures of the compound 5-8 were shown in Fig. 2.
247
The FT-IR spectra of 5-8 showed characteristic stretching bands at around 3040–3060
248 cm-1 (νC–H, aryl), 1215 -1241 cm-1 (νP=N) and 3132 cm-1 (νN–H) and 954-963 cm-1 (νP-O) as
249 expected [19,25]. As an example, steps of formation of compound 6 were investigated by FT-
250 IR (ATR) spectra (Figs.3a-d). It was observed that the O-H stretching of 4-(1-
251 adamantyl)phenol at 3206 cm-1 (Fig. 3a) disappeared after converted to alkyne derivative (1)
252 [(-CªCH) stretching at 3305 cm-1 (Fig.3b)]. N3 streching of 4 was seen at 2093 cm-1 (Fig.
253 3c). The (-CªCH) and N3 stretching bands were disappeared after formation of compound 6
254 (Fig. 3d).
255
The MS spectrum of 1-8 provided definitive characterization and the results were
256 given in the experimental section. The mass spectrum of compound 6 as an example was
257 given in Fig. 4. The peak at 3000.803 Da representing the protonated molecular ion provided
258 for definitive characterization. In addition mass spectra of other compounds also compatible
259 with the calculated data.
260
The proton decoupled 31P NMR spectra of all derivatives were observed as A3 (for
261 trimeric compounds) and A4 (for tetrameric compounds) spin systems due to equivalent
262 phosphorus nucleus of the cyclic phosphazene rings. The cyclotriphosphazenes (3, 5, and 7)
263
showed singlet peak between at δ=16.85-17.39 ppm in high field compare with trimer,
264 whereas cyclotetraphosphazenes (4, 6 and 8) showed a signal between at δ= (-0.93)-(-1.45)
265 ppm in low field compare with tetramer (Table 1).
266
The expected carbon signals were assigned from the 13C NMR spectra of all the
267 phosphazenes. The average δ- shift values of OCH2-, adamantyl and aromatic carbons were
268 observed at around ≅ 50.20 ppm, ≈ 29.15-43.50 ppm and ≈ 111.39-156.54 ppm, respectively.
1
269 As an example, the H-13C HSQC spectrum of 6 was illustrated in Fig. 5. This spectrum

270 correlated chemical shifts of protons directly bound to carbon atoms. Therefore, all carbon
271 signals of 6 were verified and also confirmed the structure of compound 6.
1
1
272
Afterwards, the H NMR spectra of the compounds were evaluated. In general, H
273 NMR spectra of the compounds 5-8 were similar. As expected, the average δ- shift values of
274 OCH2-, adamantyl, aromatic and -CH-(triazole group) hydrogens were observed at around ≅
275 4.05, ≈ 1.7-2.1, ≈ 6.9-7.3, ≈7.7 ppm, respectively. NH- proton was also seen as broad about
276 = 4.09-4.11 ppm for compounds 7 and 8.
277 Thermal Properties
278 The glass transition temperatures (Tg) of all compounds were clearly detected by DSC from
279 25 to 150°C with a heating rate of 10°C/min under nitrogen flow. The Tg of all new
280 phosphazene compounds (5-8) represented in Table 1 and the DSC thermograms are given in
281 supplementary information in Figure S1.
282
Phosphazenes are attractive compounds because they not only have a wide range of
283 thermal stability, but also can provide improved flame retardant properties when compared
284 with the organic homologues [19, 25, 26]. Owing to the excellent thermal stability and char
285 yield, the adamantane substituted polyphosphazene have attracted interest for their potential
286 application in flame retardants [9, 13]. TGA was utilized to evaluate the thermal stability of
287 the cyclophosphazenes containing adamantane units in terms of onset decomposition
288 temperatures (Td). The decomposition temperatures were recorded at a heating rate of 10
289 °C/min and Td-values were collected (Table 1). According to the TGA thermograms of
°
290 compound 5-8 (Fig.6), the Td-values of adamantane derivatives ranged from 282 to 293 C
291 indicated fairly high thermal stabilities. The Td-values of adamantane based
292 cyclophosphazenes increased with increasing rigid phenyl groups. Therefore, adamantane
293 based cyclophosphazenes could be useful candidates for flame retardant additives to organic
294 polymers [9, 13]. As a result, the high char yields and Td’s of phosphazene compounds (5-8)

295 make them a good flame retardant in theory [27] and the adamantane based cyclophosphazene
296 derivatives exhibit excellent thermal properties. In order to see what happened after heating
297 (up to 200°C), the emission spectra of compound 5-8 was measured under the same
298 conditions. The spectrum of compound 5 as an example was exhibited in Fig. S2. However,
299 no changes were observed. According to this result of compounds 5-8, they remain stable
300 until the decomposition temperatures.
301 Absorption and Fluorescence Properties
302 The absorption and the fluorescence spectra of compound 5-8 were measured in
303 dichloromethane with dilute solutions of 1x10-5 mol.dm-3 upon excited 260 nm. Absorption
304 bands were observed at 275 and 280 nm for compounds 5 and 6, 250 and 310 nm for
305 compounds 7 and 8 (Fig. 7). Fluorescence spectra in dichloromethane were depicted in Fig. 8.
306 The increase of maximum fluorescence emissions for compounds 6 vs. 5 and 8 vs. 7 could be
307 explained with the increasing substitution degree of cyclophosphazene core as expected [19,
308 25, 28]. Fluorescence emission peaks were observed at around 300 nm for compounds 5 and
309 6 in DCM. The most interesting observations from emission studies of compounds 7 and 8 are
310 two bands at 287 and 357 nm (Fig. 8). In order to get more information on the observed
311 additional band, the emission spectrum of compound 2 was measured under the same
312 conditions (1x10-1 mol.dm-3, 1x10-3 mol.dm-3 and 1x10-5 mol.dm-3 in CH2Cl2, λexc:260 nm)
313 (Fig. 9). The emission spectrum of 2 in dichloromethane (1x10-5 mol.dm-3) showed only one
314 band at 287 nm. As can be seen in Fig. 9, an obvious enhancement of the excimer emission
315 occurred when the concentration of 2 increased up to 1x10-1 mol.dm-3, whilst the
316 accompanying monomer emission decreased. It was notable that the formation of the excimer
317 emission in 2 was caused by an intermolecular excimer. Therefore, we could clearly say that
318 the appearance of the 357 nm band in compounds 7 and 8 was originated from the formation
319 of intramolecular interactions as reported in the earlier study [29]. These studies suggested

320 that intramolecular π-π interactions were stronger in compounds 7 and 8 than those in
321 compounds 5 and 6. Meanwhile, these results indicated strong hydrogen bonds (N-H…N)
322 between (triazole)-aminodiphenyl ether moieties in compounds 7 and 8. The fluorescence
323 quantum yields (ΦF) were determined by the standard method using 1x10-5 M 2-
324 aminopyridine in a 0.1 M H2SO4 solution as the standard for compound 5-8. The refractive
325 indexes of the solvents were taken into account in the measurements. The fluorescence
326 quantum yields (ΦF) of phosphazene derivatives increased with respect to the increment of the
327 side groups and their values were 0.11 for 5, 0.14 for 6, 0.18 for 7 and 0.20 for 8. The
328 tetrameric phosphazene compounds 6 and 8 showed higher fluorescence quantum yields than
329 the trimeric core phosphazene compounds 5 and 7. Fluorescence lifetimes (τF) of compound
330 5-8 were calculated using the Strickler-Berg equation [22]. The τF values were 0.27 ns for 5,
331 0.28 ns for 6, 0.52 ns for 7 and 0.45 ns for 8 in DCM. The comparison between the
332 cyclophosphazenes (5-8), the compounds 7 and 8 showed longer τF values than the
333 compounds 5 and 6 in DCM. The rate constants for fluorescence (kF) and radiative lifetime
334 (τ0) were also measured for synthesized phosphazene compounds in this study. The kF values
335 were 4.21x108 for 5, 5.09x108 for 6, 3.42x108 for 7 and 4.45x108 for 8 and τ0 values were
336 1.74 ns for 5, 1.96 ns for 6, 2.91 ns for 7 and 2.24 ns for 8 in DCM.
337 Conclusion
338 In this study, the cyclophosphazenes containing phenoxy-adamantane derivatives (5-8) were
339 synthesized successfully in good yields through three-steps. The structures of all the starting
340 compounds (1-4) and final products (5-8) were characterized by standard spectroscopic
341 techniques and were reported for the first time. The thermal stability and fluorescence spectral
342 properties of cyclic phosphazene compounds (5-8) were investigated. According to thermal
343 analyses of adamantane substituted cyclophosphazene derivatives (5-8), it was found that
344 compounds 7 and 8 had high thermal stabilities and char yields when compared to 5 and 6.

345 The absorption and the fluorescence spectra of 5-8 were measured in DCM. It could be
346 suggested that both intramolecular non-covalent π-π interactions and strong hydrogen bonds
347 (N-H…N) between (triazole)-aminodiphenyl ether moieties resulted the higher fluorescence
348 behavior of 7 and 8 when compared to 5 and 6. Thus, it could be concluded that compound 5-
349 8 might be suitable candidates for flame retardant additives to polymers or light emitting
350 electroluminescent devices in some industrial applications.
351 Acknowledgment
352 The authors would like to thank the Scientific and Technical Research Council of Turkey for
353 financial support (Grant 209T131).
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403
404
405
406
407
408
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410
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416
417
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419 Table 1. 31P NMR parameters and thermal properties of cyclophosphazenes
Compound
Td (°C)a
Yb(%)
31 P{H} NMR
shifts (ppm)c
DSC(°C)
Trimer
-
-
-
19.9
Tetramer
-
-
-
-5.4
3
4
5
6
7
8
-
-
-
-
-
-
17.39
-1.45
16.85
-0.93
16.94
-1.10
112.0
114.5
123.3
130.8
282
288
286
293
24.95
22.02
27.52
28.83
420 a The temperature for which the weight loss is 5%.
421 b Char yields at 700°C.
422
423
c 202.38 MHz 31P NMR chemical shifts (ppm) in CDCl3
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438

439 Captions for figures
440 Fig. 1. The reaction pathway for the phosphazene derivatives.
441 Fig.2. Structures of 5-8.
442 Fig.3. FT –IR (ATR) spectra of (a) 4-(1-adamantyl) phenol, (b) 1, (c) 4, (d) 6
443 Fig.4. Positive ion and linear mode MALDI TOF-MS spectrum of 6 was obtained in 1,8,9-
444 anthracenetriol (20 mg/mL THF) MALDI matrix using nitrogen laser accumulating 50 laser
445 shots.
446 Fig.5. The 1H-13C HSQC spectrum of compound 6.
447 Fig.6. TGA curves of compounds 5-8 from 25 to 700 ºC at a heating rate of 10°C/min under
448 N2 flow of 50 mL/min.
449 Fig. 7. The absorption spectra of 5- 8 in dichloromethane. Concentration: 1x10-5 mol.dm-3.
450 Fig.8. The fluorescence emission spectra of 5-8 in dichloromethane. Concentration: 1x10-5
451 mol.dm-3. Excitation wavelength: 260 nm.
452 Fig. 9. The fluorescence emission spectra of 2 in dichloromethane. λexc: 260 nm.
453

3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
454
455
456 Fig.1. The reaction pathway for the phosphazene derivatives

457
R
R
N
R
R
N
N
N
N
N
N
N
N
N
N
N
N
N
R
N
N
R
N
O
P
N
O
P
O
N
N
R
R
O
O
R
O
P
N
N
N
N
N
N
N
N
O
P
N
O
N
N
N
O
O
O
N
P
P
P
O
O
N
N
N
O
N
N
N
N
R
R
N
N
N
R
N
N
N
N
N
N
R
R
R
O
O
CH2
H
N
R
CH2
458
459
460
461
462
463
464
465
Fig.2. Structures of 5-8.

466
467
468
Fig. 3. FT –IR (ATR) spectra of (a) 4-(1-adamantyl) phenol, (b) 1, (c) 4, (d) 6.
469
470
471
472
473
474
475
476
477
478

479
480 Fig.4. Positive ion and linear mode MALDI TOF-MS spectrum of 6 was obtained in 1,8,9-
481 anthracenetriol (20 mg/mL THF) MALDI matrix using nitrogen laser accumulating 50 laser
482 shots.
483
484
485
486
487
488
489
490
491
492
493
494
495

496
497
Fig.5. The 1H-13C HSQC spectrum of compound 6.
498
499
500
501
502
503
504
505
506
507

508
509 Fig. 6. TGA curves of compounds 5-8 from 25 to 700 ºC at a heating rate of 10°C/min under
510 N2 flow of 50 mL/min.
511
512
513
514
515
516

517
518 Fig. 7. The absorption spectra of 5- 8 in dichloromethane. Concentration: 1x10-5 mol.dm-3.
519
520
521
522
523
524
525
526

527
528 Fig. 8. The fluorescence emission spectra of 5-8 in dichloromethane. Concentration: 1x10-5
529 mol.dm-3. Excitation wavelength: 260 nm.
530
531
532
533
534
535
536
537
538

539
540 Fig. 9. The fluorescence emission spectra of 2 in dichloromethane. λexc: 260 nm.

541
542 Syntheses,
characterizations,
thermal
and
photophysical
properties
of
543 cyclophosphazenes containing adamantane units
544
545 İlker Ün, Hanife İbişoğlu, Şule Şahin Ün , Bünyemin Çoşut, Adem Kılıç
546
547 In this work was shown that synthesis and characterization of cyclophosphazenes containing
548 adamantane derivatives. The thermal stabilities and fluorescence spectral properties of these
549 compounds have been investigated in CH2Cl2 solution.
550
551
552