Facile iterative synthesis, spectral characterization, electron microscopic study and thermogravimetric analysis of phosphorus dendron with bisphenol A at the focal point

Article abstract of DOI:10.1007/s13738-011-0063-2

A facile iterative synthesis of a phosphorus dendron with bisphenol A at the focal point by following the divergent procedure is described. The phosphorus dendron peripherally functionalized with phenolic OH group has been accomplished in a very versatile simple fashion, using the Schiff condensation and nucleophilic substitution reactions using P(S)Cl₃, P(O)Cl ₃, 3-hydroxybenzaldehyde and 3-aminopheno. The structures of intermediate dendrons were confirmed by IR, NMR (¹H, ¹³C and ³¹P), LC-Mass and C, H, N analysis. The structure of the final dendron (5) was confirmed by IR, NMR (¹H, ¹³C and ³¹P), MALDI-TOF-MS, and C, H, N analysis. The thermal stability of the resulting functionalized dendron has been checked by TGA/DTA analysis. The surface topography observed by scanning electronic microscopic study (SEM) gives the reminiscent of the dendritic structure. Iranian Chemical Society 2012.

Full text of DOI:10.1007/s13738-011-0063-2

J IRAN CHEM SOC (2012) 9:513–519
DOI 10.1007/s13738-011-0063-2
ORIGINAL PAPER
Facile iterative synthesis, spectral characterization, electron
microscopic study and thermogravimetric analysis of phosphorus
dendron with bisphenol A at the focal point
•
E. Dadapeer K. Reddi Mohan Naidu
•
C. Naga Raju
Received: 17 January 2011 / Accepted: 5 June 2011 / Published online: 5 January 2012
Ó Iranian Chemical Society 2012
Abstract A facile iterative synthesis of a phosphorus
dendron with bisphenol A at the focal point by following
the divergent procedure is described. The phosphorus
dendron peripherally functionalized with phenolic OH
group has been accomplished in a very versatile simple
fashion, using the Schiff condensation and nucleophilic
substitution reactions using P(S)Cl3, P(O)Cl3, 3-hydroxy-
benzaldehyde and 3-aminopheno. The structures of inter-
mediate dendrons were confirmed by IR, NMR (1H, 13C
and 31P), LC-Mass and C, H, N analysis. The structure of
the final dendron (5) was confirmed by IR, NMR (1H, 13C
and 31P), MALDI-TOF-MS, and C, H, N analysis. The
thermal stability of the resulting functionalized dendron
has been checked by TGA/DTA analysis. The surface
topography observed by scanning electronic microscopic
study (SEM) gives the reminiscent of the dendritic
structure.
But both the terms are typically encountered interchange-
ably [3]. The phosphorus-containing dendrimers have
many applications [4] in material science, biology and in
catalysis and make up an active subdivision [5]. In phos-
phorus-containing dendrimers and dendrons, the element
phosphorus makes the ease of synthesis; it helps in char-
acterization [6] and gives some special properties seldom
or never found for other dendrimers, such as high dipole
moment value due to the presence of thiophosphoryl
groups [7], as complexing agents [8] and hydrogels [9]. For
most applications of phosphorus-containing dendrimers
and dendrons the electron microscopic study and the
thermal stability appear as important properties. IR
and Raman Spectra of dendrimers are used mainly for
the analytical purposes [10] and matrix-assisted laser
desorption ionization time-of-flight mass spectrometry
(MALDI-TOF-MS) [11] is also used for analysing the high
molecular weight of the dendrimer.
Keywords Phosphorus dendron ꢀ Divergent procedure ꢀ
Bisphenol A ꢀ TGA/DTA analysis ꢀ SEM
In this paper, the iterative divergent synthesis is repo-
tred, characterization, scanning electron microscopic and
thermal properties of phosphorus-containing dendron hav-
ing bisphenol A at the core and phenolic OH groups at the
periphery.
Introduction
Synthesis of dendrimer has been fascinating for both aca-
demic and industrial chemists alike [1]. A dendrimer is
monodispersed macromolecule with a regular and three-
dimensional architecture containing three components like
core, branches and end groups [2]. A single chemically
reactive focal-point containing group is called a dendron.
Experimental
Chemicals and apparatus
All the chemicals used were purchased from Sigma-
Aldrich Chemical Company and used without further
purification. All solvents (AR or extra pure grade) were
dried by standard methods. Thin layer chromatography was
performed on precoated plates with silica gel 60F254
(Merk). Column chromatography was performed on silica
E. Dadapeer ꢀ K. Reddi Mohan Naidu ꢀ C. Naga Raju (&)
Department of Chemistry, Sri Venkateswara University,
Tirupati 517 502, India
e-mail: rajuchamarthi10@gmail.com
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J IRAN CHEM SOC (2012) 9:513–519
gel (0.040–0.063 mm, Macherey–Nagel). IR spectra were
recorded on JASCO Japan FT/IR-5300 spectrometer at
University of Hyderabad using KBr optics.1H and 13C
NMR spectra were recorded on a Bruker A VIII 400 MHz
NMR spectrometer at Laila Impex, Vijayawada, operating
127.2, 119.6, 45.4, 30.8. 31P NMR (81 MHz, CDCl3): d
(ppm): 70.45. LC MS: m/z = 494 (M)?. Analysis:
C15H14Cl4O2P2S2, Calcd.: C, 36.46; H, 2.86%; found: C,
36.38; H, 2.91%.
1
at 400.13 MHz for H, 100.61 MHz for 13C NMR, data
Preparation of 2
were recorded in DMSO-d6 and chemical shifts were ref-
erenced to TMS (1H and 13C). 31P NMR spectra were
recorded on Bruker ACF Supercon 200 spectrometer
operating at 81 MHz at University of Hyderabad, Hyder-
abad. 31P NMR data were recorded in CDCl3 and chemical
shifts were referenced to 85% H3PO4. LC-mass spectra of
intermediate compounds 1, 2, 3, 4 were recorded on
LCMS-2010A Shimadzu, spectrometer at University of
Hyderabad, Hyderabad. MALDI mass spectrum of 5 and
dendron 6 were recorded using Applied Biosystems
MALDI-TOF Voyager depro spectrometer. The sample
was run using sinapic acid as the matrix with DMSO as the
solvent in dried-droplet preparation method, performed at
IIT-Madras, Chennai. TGA-DTA measurement was taken
using TA instrument, Waterloo, USA, performed at Sri
Krishnadevaraya University, Ananthapur, India. Scanning
electron microscopy (SEM) images were taken with a Carl
Zeiss, EVO MA15 Instrument. SEM operated at 20 kV,
performed at Department of Physics, S.V. University,
Tirupati, India. Elemental analyses were performed using
FLASH EA 1112 Thermo Finnigan instrument, France, at
University of Hyderabad, Hyderabad, India.
To a mixture of stirred solution of the filtrate 1 (0.005 mol)
and triethylamine (0.02 mol, 2.8 mL), a solution of
3-hydroxy-benzaldehyde (0.02 mol, 2.44 g) in 25 mL of dry
THF was added dropwise over a period of 20 min at -5 to
o
0 C. After stirring for 5 h at 40–45 °C, formation of 2 was
ascertained by TLC analysis run in a 2:3 mixture of ethyl
acetate and hexane and the average Rf value observed was
0.71. Triethylamine hydrochloride was removed by filtra-
tion. The solvent was evaporated under reduced pressure to
give crude product. It was purified by column chromatog-
raphy on silica gel (60–120 mesh, ethyl acetate:hexane, 1:4)
to afford the pure compound. The compound 2 thus obtained
was characterized by IR, NMR (1H, 13C and 31P), LC-mass
and C, H, N analysis and used for the next synthetic step.
Spectral data
Compound 2: Yield 80%, IR (KBr, cm-1): tmax: 1,693
(Ar–CHO), 1,167, 900 (P–O–Caromatic), 756 (P=S). 1H
NMR (400 MHz, DMSO-d6): d (ppm): 9.90 (4H, s, Ar–
CHO), 6.66–7.75 (24H, m, Ar–H), 1.54 (6 H, s, –CH3). 13
C
NMR (100 MHz, DMSO-d6): d (ppm): 193.0, 155.0, 147.3,
146.9, 137.6, 130.0, 127.1, 126.7, 121.8, 120.0, 114.8,
45.3, 30.7. 31P NMR (81 MHz, CDCl3): d (ppm): 69.09.
LC MS: m/z = 835 (M-1)?. Analysis: C43H34O12P2S2,
Calcd.: C, 61.72; H, 4.10%; found: C, 61.58; H, 4.19%.
General procedure for synthesis of dendron 6
Preparation of 1
A solution of P(S)Cl3 (0.01 mol, 1.01 mL) in 20 mL of dry
THF was added dropwise over a period of 20 min to a mix-
ture of stirred solution of 2,20-bis(4-hydroxyphenyl)propane
(0.005 mol, 1.14 g) in 25 mL of dry THF and triethylamine
(0.01 mol, 1.38 mL) at -5 to 5 °C. After stirring for 4 h at
35–40 °C, formation of the compound 1 was ascertained by
TLC analysis run in a 1:9 mixture of ethyl acetate and hexane
and the average Rf value observed was 0.80. Triethylamine
hydrochloride was removed by filtration. The compound 1
thus obtained was characterized by IR, NMR (1H, 13C and
31P), LC-mass and C, H, N analysis and used for the next
synthetic step without further purification.
Preparation of 3
To a stirred solution of 2 (0.005 mol) in 25 mL of dry
EtOH, a solution of 3-aminophenol (0.02 mol, 2.18 g) in
25 mL of dry EtOH, was added at room temperature. After
stirring for 5 h at reflux temperature, formation of 3 was
ascertained by TLC analysis run in a 1:1 mixture of ethyl
acetate and hexane and the average Rf value observed was
0.65. The solvent was evaporated under reduced pressure to
give crude product. It was purified by column chromatog-
raphy on silica gel (60–120 mesh, ethyl acetate:hexane,
2:8) to afford the pure compound. The imine thus obtained
was characterized by IR, NMR (1H, 13C and 31P), LC-mass
and C, H, N analysis and used for the next synthetic step.
Spectral data
Compound 1: Yield 90%, IR (KBr, cm-1): tmax: 1,172,
926 (P–O–Caromatic), 733 (P=S). 1H NMR (400 MHz,
DMSO-d6): d (ppm): 6.96–6.98 (4H, d, Ar–H, J = 8 Hz),
6.93–6.95 (4H, d, Ar–H, J = 8 Hz), 1.73 (6H, s, –CH3).
13C NMR (100 MHz, DMSO-d6): d (ppm): 147.5, 147.1,
Spectral data
Compound 3: Yield 70%, IR (KBr, cm-1): tmax: 3,378
(Ar–OH), 1,614 (CH=N), 1,167, 968 (P–O–Caromatic), 790
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515
(P=S). 1H NMR (400 MHz, DMSO-d6): d (ppm): 8.79 (4H,
s, Ar–OH), 8.51 (4H, s, –CH=N), 6.80–7.55 (40H, m,
Ar–H), 1.56 (6 H, s, –CH3). 13C NMR (100 MHz, DMSO-
d6): d (ppm): 158.1, 156.7, 154.9, 147.1, 139.4, 130.5,
127.2, 122.0, 120.1, 129.3, 115.9, 114.6, 113.9, 110.8,
45.3, 30.8. 31P NMR (81 MHz, CDCl3): d (ppm):
64.54 ppm. LC MS: m/z = 1,202 (M ? 1)?. Analysis:
C67H54N4O10P2S2, Calcd.: C, 66.99; H, 4.53; N, 4.66%;
found: C, 66. 85; H, 4.48; N, 4.55%.
reduced pressure to get crude product. It was purified by
column chromatography on silica gel (60–120 mesh,
ethylacetate: hexane, 3:2) to afford the pure compound.
The compound thus obtained was characterized by 1H,
13C and 31P NMR, MALDI-TOF–MS, and C, H, N
analysis.
Spectral data
Compound 5: Yield 58%, IR (KBr, cm-1): tmax: 1,620
(CH=N), 1,234 (P=O), 1,172, 975 (P–O–Caromatic), 806
Preparation of 4
1
(P=S). H NMR (400 MHz, DMSO-d6): d (ppm): 10.45
To a stirred solution of 3 (0.005 mol) and triethylamine
(0.02 mol, 2.8 mL) in 30 mL of dry THF, a solution of
P(O)Cl3 (0.02 mol, 1.86 mL) in 25 mL of dry THF was
added dropwise over a period of 20 min at -5 to 0 °C.
After stirring for 5 h at 40–45 °C, formation of 4 was
ascertained by TLC analysis run in a 3:7 mixture of ethyl
acetate and hexane, and the average Rf value observed was
0.60. Triethylamine hydrochloride was removed by filtra-
tion. The solvent was evaporated under reduced pressure to
get crude product. It was purified by column chromatog-
raphy on silica gel (60–120 mesh, ethyl acetate:hexane,
3:7) to afford the pure compound. The compound 4 thus
obtained was characterized by IR, NMR (1H, 13C and 31P),
LC-mass and C, H, N analyses and used for the next syn-
thetic step.
(8H, s, Ar–CHO), 9.91 (4H, s, –CH=N), 7.14–7.35 (72H,
m, Ar–H), 1.70 (6 H, s, –CH3). 13C NMR (100 MHz,
DMSO-d6): d (ppm): 193.0, 158.1, 157.4, 155.3, 154.1,
150.5, 148.0, 145.9, 140.3, 139.1, 131.5, 130.8, 127.8,
127.4, 123.1, 120.8, 118.3, 115.9, 115.1, 114.8, 114.3,
109.6, 29.5, 45.3. 31P NMR (81 MHz, CDCl3): d (ppm):
–22.84, 63.10. MALDI MS: m/z = 2,355 (M ? 1)?;
Analysis: C123H90N4O30P6S2, Calcd.: C, 62.76; H, 3.85; N,
2.38%; found: C, 62.88; H, 3.81; N, 2.45%.
Preparation of 6
To a stirred solution of 5 (0.005 mol) in 25 mL of dry
EtOH, a solution of 3-aminophenol (0.04 mol, 4.36 g) in
25 mL of dry EtOH was added at room temperature. After
stirring for 7 h at reflux temperature, formation of 6 was
ascertained by TLC analysis run in a 3:2 mixture of ethyl
acetate and hexane, and the average Rf value observed was
0.50. The solvent was evaporated under reduced pressure to
give crude product. It was purified by column chromatog-
raphy on silica gel (60–120 mesh, ethyl acetate:hexane,
1:1) to afford the pure compound. The imine thus obtained
was characterized by IR, NMR (1H, 13C and 31P), MALDI-
MS and C, H, N analyses.
Spectral data
Compound 4: Yield 65%, IR (KBr, cm-1): tmax: 1,612
(CH=N), 1,253 (P=O), 1,172, 970 (P–O–Caromatic), 806
1
(P=S). H (400 MHz, DMSO-d6): d (ppm): 9.91 (4H, s,
–CH=N), 6.50–7.85 (40H, m, Ar–H), 1.72 (6 H, s, –CH3).
13C (100 MHz, DMSO-d6): d (ppm): 159.4, 156.7, 156.3,
153.1, 147.5, 146.1, 138.4, 128.2, 131.1, 130.9, 122.7,
121.9, 119.2, 115.4, 115.0, 114.5, 110.5, 45.0, 30.5. 31P
NMR (81 MHz, CDCl3): d (ppm): -10.37, 67.10. LC MS:
m/z = 1,670 (M ? 1)?. Analysis: C67H50Cl8N4O14P6S2,
Calcd.: C, 48.22; H, 3.02; N, 3.36%; found: C, 48.05; H,
3.12; N, 3.45%.
Spectral data
Compound 6: Yield 58%, IR (KBr, cm-1): tmax: 3,392
(Ar–OH), 1,614 (CH=N), 1,219 (P=O), 1,167, 976 (P–O–
1
C
aromatic), 790 (P=S). H NMR (400 MHz, DMSO-d6): d
Preparation of 5
(ppm): 10.60 (8H, s, Ar–OH), 9.93, 9.85 (12H, s, –CH=N),
6.02–7.30 (104H, m, Ar–H), 1.82 (6 H, s, –CH3). 13C NMR
(100 MHz, DMSO-d6): d (ppm): 160.3, 158.1, 158.0,
156.1, 155.5, 155.3, 149.5, 148.8, 146.2, 140.3, 139.0,
132.1, 132.5, 131.7, 128.1, 127.1, 122.8, 122.1, 119.8,
119.0, 116.7, 116.4, 116.1, 115.9, 115.0, 114.8, 111.2,
110.1, 45.3, 30.8. 31P NMR (81 MHz, CDCl3): d (ppm):
62.50, -39.18. MALDI MS: m/z = 3,084 (M ? 1)?.
Analysis: C171H130N12O30P6S2, Calcd.: C, 66.62; H, 4.25;
N, 5.45%; found: C, 66.71; H, 4.21; N, 5.38%.
To a stirred solution of 4 (0.005 mol) and triethylamine
(0.04 mol, 5.6 mL) in 30 mL of dry THF, a solution of
3-hydroxy-benzaldehyde (0.04 mol, 4.88 g) in 25 mL of
dry THF, was added dropwise over a period of 20 min at
-5 to 0 °C. After stirring for 5 h at 40–45 °C, formation
of 5 was ascertained by TLC analysis run in a 7:3 mixture
of ethyl acetate and hexane and the average Rf value
observed was 0.57. Triethylamine hydrochloride was
removed by filtration. The solvent was evaporated under
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Results and discussion
Compound 1, was prepared by a condensation reaction
of one molar equivalent of 2,20-bis(4-hydroxyphenyl)
propane with two equivalents of P(S)Cl3 in the presence of
triethylamine (base) at -5 to 5 °C in dry THF with stirring
for 4 h. After filtration, in the second step, comound 1 was
treated with four equivalents of 3-hydroxy-benzaldehyde in
dry THF in presence of triethylamine at 40–45 °C with
stirring for 5 h to form compound 2. After filtration,
compound 2 was treated with four equivalents of 3-amino
phenol with stirring for 5 h in refluxing dry EtOH to afford
The synthetic strategy for assembling facile phosphorus
dendron framework is shown in Scheme 1. Bisphenol A
(BPA, 2,20-bis(4-hydroxyphenyl)propane) was used as a
core and dendrons were built around it, based on its solu-
bility, commercial availability and previously reported its
use as a monomer for the production of polycarbonate, a
stabilizing material for a polymer (Polyvinyl chloride,
PVC) [12].
Scheme 1 Synthesis of
dendron 6
2 P(S)Cl3
CH3
S
P
CH3
S
P
Cl
Cl
THF
Cl
Cl
O
C
O
HO
C
OH
2 Et3N
CH3
CH3
-5 to 5 oC
1
CHO
CHO
OH
4
S
P
CH3
C
S
O
CHO
O
P
O
O
O
O
THF
CH3
4 Et3N
40 - 45 oC
CHO
CHO
2
OH
HO
N
HC
N
CH
OH
CH3
C
S
S
4
O
O
O
P
O
O
P
O
NH2
CH3
3
EtOH
refux
HC
N
N
CH
OH
HO
Cl
O
Cl
Cl
O
O
P
P
Cl
O
N
HC
N
CH
4 P(O)Cl3
THF
S
P
S
P
CH3
C
O
O
O
O
O
O
CH3
2 Et3N
-5 to 0 °C
HC
N
4
N
CH
O
Cl
O
P
Cl
Cl
O
Cl
P
O
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517
Scheme 1 continued
CHO
CHO
O
O
O
P
O
O
O
P
O
O
N
HC
N
CH
CH
OH
CHO
CHO
8
S
P
CH3
C
CH3
S
P
CHO
O
O
O
O
O
O
CHO
CHO
5
THF
HC
N
N
8 Et3N
O
O
O
40- 45 oC
P
O
O
P
O
O
O
CHO
CHO
OH
8
NH2
EtOH
refux
HO
OH
N
HC
O
N
CH
O
P
O
O
P
O
O
O
O
OH
HC
HC
N
N
HC
N
CH
HO
N
N
CH
CH3
C
S
P
S
O
O
O
O
O P
O
CH3
N
N
HC
OH
6
CH
N
CH
HO
O
P
O
O
O
O
O
O
P
O
N
HC
OH
CH
N
HO
compound 3. The compound 3 was reacted with four
equivalents of POCl3 in presence of triethylamine at -5 to
0 °C in dry THF with stirring for 5 h to obtain the com-
pound 4. After filtration, the compound 4 was then treated
with eight equivalents of 3-hydroxy-benzaldehyde in dry
THF in presence of triethylamine at 40–45 °C with stirring
for 5 h to form compound 5. Triethylamine hydrochloride
was removed by filtration; compound 5 was treated with 8
equivalents of 3-aminophenol with stirring for 6 h in re-
fluxing dry EtOH to get compound 6. As the size of the
dendron increases, the reaction is sluggish and the yield is
low. To improve the yield of 6 the temperature is
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Scanning electronic microscopic study
maintained at 45–50 °C and continued stirring for longer
period. The synthesis of the dendron 6 was accomplished by
adopting an iterative divergent approach as shown in
Scheme 1. The overall yield of the final dendrimer 6 was
60%. The formation of all the intermediate compounds 1, 2,
3, 4 and 5 were characterized by IR, NMR (1H, 13C and 31P),
LC–MS data and C, H, N analyses. Their data are given in
the experimental part. The synthetic and analytical data of
the dendrimer 6 is also presented in the experimental part.
The dendrimer 6 exhibited absorption bands for –OH,
P=O, P=S and CH=N in the regions 3,392, 1,219, 790
and 1,614 cm-1, respectively. P–O–C(aromatic) gave two
absorptions in the regions 976 and 1,172 cm-1,respectively
[13]. In the 1H NMR spectra (400 MHz) of 6, the aromatic
protons gave multiplets in the region d 6.02–7.30, the –OH
protons resonated at d 10.60 as singlets and the imine CH
protons (CH=N) gave two singlets at d 9.93, 9.85 indicating
two different environments. The –CH3 protons gave singlet
at d 1.82. 13C NMR spectrum was recorded for compound 6
and the data are given in the experimental part. The aro-
matic carbons resonated in the region 110.1–158.0 ppm. –
CH=N Carbon signal was observed at d 160.3. The com-
pounds 4, 5 and 6 showed two 31P NMR signals indicating
two different types of phosphorus atoms. The intermediate
compounds 1, 2, 3, 4 and 5 gave phosphorus-31 resonance
signals at d 70.45, 69.09, 64.54, (–10.37, 67.10) and
(–22.84, 63.10) respectively. The mass spectral properties
of the dendrons 5 and 6 were studied by matrix assisted laser
desorption/ionisation (MALDI-TOF) mass spectrometry.
As expected, the mass obtained from the MALDI mea-
surements corresponds closely to the calculated value. The
surface topography of the dendron 6 was studied by scan-
ning electron microscopy (SEM), while the molecular
decomposition of the dendron 6 was investigated by both
thermo gravimetric analysis (TGA) and differential thermal
analysis (DTA).
SEM image depicts deeper insight of the surface structure
of the dendron 6. With increasing the size, it was clear that
the overall surface morphology of the material tended to
assume a nanoscale size particle shape at a line width of
20 lm. From Fig. 1, the nanoscale sized morphology of the
resultant dendron 6 was observed.
TGA-DTA analysis
Simultaneous TGA-DTA measures both heat flow and
weight changes (TGA) in a material as a function of tem-
perature in a controlled air atmosphere was recorded. An
overlay of TGA-DTA plots for the test compound 6 up to
700 °C in air atmosphere is shown in Figs. 2, 3. The
decomposition of the final compound 6 was followed by
TGA. A typical trace can be seen in Fig. 2. An initial
decomposition starts between the range 90–100 °C with a
Fig. 2 TGA of 6
Fig. 1 SEM picture of the dendron 6
Fig. 3 DTA of 6
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J IRAN CHEM SOC (2012) 9:513–519
519
corresponding weight loss of approximately 3–4%. This is
attributed to the loss of water molecules. Then the com-
pound is stable up to 190 °C. Again the decomposition
starts between the range 190–355 °C with a corresponding
weight loss of approximately 18–20%. Then dendron is
again decomposed in between the temperature range
360–400 °C. Then the compound is kept stable in between
the temperature range of 400–500 °C. Then immediately
starts the decomposition between the range 500–550 °C.
The total account for loss of the compound is around 50%
of the total mass of the molecule. Similarly, differential
thermal analysis (DTA), is also tested on 6 to detect the
changes in the sample, either exothermic or endothermic.
The DTA profile (Fig. 3) shows the endotherm peaks at
95 °C which corresponds to the loss of water and exo-
therms at 285, 380, 525 °C, corresponds to the loss of most
of the the dendritic wedges of the dendron 6.
change in temperature and the heat of the dendron 6 were
established by TGA-DTA analysis.
Acknowledgments The authors thank HRDG, CSIR, New Delhi,
India, for sanctioning a major Research project [01(2309)/09/EMR-II].
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Conclusion
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13. L.C. Thomas, Interpretation of Infrared Spectra of Organo-
phosphorus Compounds (Heydon and Sons, London, 1974)
Facile iterative synthesis of a novel phosphorus dendron 6
was accomplished by divergent method. The Schiff’s
condensation reactions were performed in dry ethanol and
substitution reactions were performed in dry tetrahydrofu-
ran in the presence of triethylamine. The surface topogra-
phy of the dendron 6 was observed by SEM image. It
reveals a nano-sized molecule with a diameter of 20 lm.
The thermal stability and changes in weight in relation to
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