Synthesis, characterization, and thermogravimetric studies of a phosphorus-containing dendron built from 1,5-diaminonaphthalene at the core

Article abstract of DOI:10.1080/00397911.2011.628773

A facile divergent synthesis of a phosphorus-containing dendron containing 1,5-diaminonaphthalene is described. The phosphorus-containing dendron, functionalized with a 1,5-diaminonaphthalene unit at the core and phenolic OH groups grafted at the periphery, has been accomplished in a versatile, simple fashion, using Schiff's condensation and nucleophilic substitution reactions with POCl₃, 3-hydroxy-benzaldehyde, 4-hydroxy-benzaldehyde, and 3-amino-phenol iteratively. The structures of intermediate dendrons were characterized by infrared, NMR (¹H, ¹³C, and ³¹P), liquid chromatography-mass spectrometry, and C, H, N analysis. The structure of the final dendron (6) was confirmed by infrared, NMR ( ¹H, ¹³C, and ³¹P), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and C, H, N analysis. The thermal stability and degradation of the resulting final dendron was checked by thermal gravitometric analysis/differential thermal analysis.

Full text of DOI:10.1080/00397911.2011.628773

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Synthesis, Characterization, and
Thermogravimetric Studies of a
Phosphorus-Containing Dendron Built
from 1,5-Diaminonaphthalene at the
Core
E. Dadapeer a , B. Satheesh Krishna a & C. Naga Raju a
a Department of Chemistry, Sri Venkateswara University, Tirupati,
India
Version of record first published: 21 Feb 2013.
To cite this article: E. Dadapeer , B. Satheesh Krishna & C. Naga Raju (2013): Synthesis,
Characterization, and Thermogravimetric Studies of a Phosphorus-Containing Dendron Built from
1,5-Diaminonaphthalene at the Core, Synthetic Communications: An International Journal for Rapid
Communication of Synthetic Organic Chemistry, 43:9, 1219-1228
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Synthetic Communications1, 43: 1219–1228, 2013
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2011.628773
SYNTHESIS, CHARACTERIZATION, AND
THERMOGRAVIMETRIC STUDIES OF A
PHOSPHORUS-CONTAINING DENDRON BUILT
FROM 1,5-DIAMINONAPHTHALENE AT THE CORE
E. Dadapeer, B. Satheesh Krishna, and C. Naga Raju
Department of Chemistry, Sri Venkateswara University, Tirupati, India
GRAPHICAL ABSTRACT
Abstract A facile divergent synthesis of a phosphorus-containing dendron containing 1,5-diami-
nonaphthalene is described. The phosphorus-containing dendron, functionalized with a 1,5-
diaminonaphthalene unit at the core and phenolic OH groups grafted at the periphery, has
been accomplished in a versatile, simple fashion, using Schiff’s condensation and nucleophilic
substitution reactions with POCl3, 3-hydroxy-benzaldehyde, 4-hydroxy-benzaldehyde, and
3-amino-phenol iteratively. The structures of intermediate dendrons were characterized by
infrared, NMR (1H, 13C, and 31P), liquid chromatography–mass spectrometry, and C, H, N
analysis. The structure of the final dendron (6) was confirmed by infrared, NMR (1H, 13C,
and 31P), matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, and
C, H, N analysis. The thermal stability and degradation of the resulting final dendron was
checked by thermal gravitometric analysis/differential thermal analysis.
Keywords 1,5-Diaminonaphthalene; facile divergent synthesis; phosphorus-containing
dendron; Schiff’s condensation; TGA=DTA analysis
Received July 18, 2011.
Address correspondence to C. Naga Raju, Department of Chemistry, Sri Venkateswara University,
Tirupati 517502, India. E-mail: rajuchamarthi10@gmail.com
1219

1220
E. DADAPEER, B. S. KRISHNA, AND C. N. RAJU
INTRODUCTION
Dendrimers are highly branched monodispersed compounds having a
three-dimensional structure of dendritic wedges (dendrons) that proceed from one
center, called the core or focal point.[1] These molecules have a variety of applica-
tions from biology to material science based on their size, topography, molecular
weight, and properties.[2] The dendritic molecules having one function located at
the focal point and several other functions on the surface are called dendrons. Sev-
eral dendrons can be associated with their core by reaction with a multifunctional
core, depending on the function.[3] The specially designed dendrimers can be
obtained using dendrons.[4] In phosphorus-containing dendrimers and dendrons,
the element phosphorus characterizes each step of the synthesis.[5] In the buildup
of phosphorus-containing dendron, we use aldehyde, P-Cl, -NH2, and -OH groups
because they offer a wide range of possibilities for grafting other functions on the
surface of the intermediate compounds.[6] In the preparation of the dendrimer or
dendron, the most reactive site is the core function and the -NH2 group is preferred
because it can form versatile a Schiff’s base with an aldehyde. In a dendrimer or den-
dron the most reactive sites are the terminal groups. The dendrimers and dendrons
generally constitute three components, namely an interior core, repeating branching
units, and functional terminal groups attached to the outermost branching units. The
dendritic architectures are sometimes found in the biological world, such as branches
and roots of plants.[7] These natural dendritic architectures are similar to the artificial
dendrimers and dendrons.[8] To understand the properties and applications imparted
by dendrimers, it is highly desirable to study their structure by well-defined NMR,[9]
infrared (IR),[10] matrix-assisted laser desorptionionization time-of-flight mass spec-
trometry (MALDI-TOF-MS)[11] (for analyzing the high molecular weight), thermal
analysis, and scanning electron microscopy. The presence of phosphorus in a
dendrimer or in a dendron confers fascinating properties.[12]
In view of many potential applications for dendrimers,[13] in this article, we
report the facile iterative divergent synthesis of phosphorus-containing dendrons,
built from 1,5-diaminonaphthalene at the core and phenolic OH groups at the per-
iphery. The characterization, scanning electron microscopic, and thermogravimetric
properties of the phosphorus dendron are also studied.
RESULTS AND DISCUSSION
Scheme 1 shows the synthetic strategy for assembling a facile phosphorus-
dendron framework. 1,5-Diaminonaphthalene was used in the preparation of
dendron based on its solubility and commercial availability, previously naphthalene
was used in the preparation of a dendrimer.[14]
Compound 1 was synthesized by a Schiff’s condensation reaction of 1 molar
equivalent of 1,5-diaminonaphthalene with 2 equivalents of 3-hydroxy-benzaldehyde
with stirring for 4 h in refluxing dry EtOH. In the second step, compound 1 was
treated with 2 equivalents of POCl3 in dry tetrahydrofuran (THF) in the presence
of triethylamine at 5 to 40 ꢀC with stirring for 4 h to form compound 2. After
filtration, compound 2 was reacted with 4 equivalents of 3-hydroxy-benzaldehyde
in dry THF in presence of triethylamine at 40–45 ꢀC with stirring for 5 h to obtain

PHOSPHORUS-CONTAINING DENDRON
1221
Scheme 1. Synthesis of dendron 6.

1222
E. DADAPEER, B. S. KRISHNA, AND C. N. RAJU
compound 3. Compound 3 was treated with 4 equivalents of 3-amino phenol with
stirring for 6 h in refluxing dry EtOH to afford compound 4. In the next step, com-
pound 4 was then reacted with 4 equivalents of POCl3 in dry THF in the presence of
triethylamine at 5 to 50 ꢀC with stirring for 6 h to form compound 5. After filtration,
compound 5 was treated with 8 equivalents of hydroquinone in dry THF in the pres-
ence of triethylamine at 10 to 50 ꢀC with stirring for 6 h to get compound 6. As the
size of the dendron increases, the reaction is sluggish and the yield is poor. To
improve the yield of 6 the temperature is maintained at 45–50 ꢀC and stirring for
a longer period. The synthesis of the dendron 6 was accomplished by adopting a
facile iterative divergent method as shown in Scheme 1. The overall yield of the final
dendrimer 6 was 55%. All the intermediate compounds 1, 2, 3, 4 and 5 were charac-
terized by IR, NMR (1H, 13C and 31P), liquid chromatography–mass spectrometry
(LC-MS) data, and C, H, N analysis. The data are given in the experimental section.
The synthetic and analytical data of the dendron 6 are is also presented in the experi-
=
mental section. The dendron 6 exhibited absorption bands for –OH, P O, and
ꢁ1
=
CH N in the regions 3381, 1233, 1240 and 1627, and 1643 cm
respectively.
In the
P-O-C(aromatic) gave two absorptions in the regions 933 and 1160 cmꢁ1 [15]
1H NMR spectra (400 MHz) of 6, the aromatic protons gave multiplets in the region
d 6.63–7.57, the -OH protons resonated at d 10.41 as singlets, and the imine CH
.
=
protons (CH N) gave two singlets at d 8.09 and 8.35, indicating two different envir-
onments. 13C NMR spectrum was recorded for compound 6 and the data are given
in the experimental section. The aromatic carbons resonated in the region
108.7–160.5 ppm. Two -CH¼N carbon signals were observed at d 157.6 and 158.3
(see Fig. 1 for notation for 13C). The compound 6 showed two 31P NMR signals,
Figure 1. Notation for 13C NMR of dendron 6.

PHOSPHORUS-CONTAINING DENDRON
1223
indicating two different types of phosphorus atoms. The intermediate compounds 2,
3, 4, and 5 gave phosphorus-31 resonance signals at d ꢁ30.45, ꢁ32.09, ꢁ28.54 and
ꢁ22.48, and ꢁ31.88 respectively.[16] The mass spectral properties of the dendron 6
was studied by MALDI-TOF mass spectrometry. The mass obtained from the
MALDI measurements corresponds closely to the calculated value. The molecular
decomposition of the dendron 6 was investigated by both thermogravimetric analysis
(TGA) and differential thermal analysis (DTA).
TGA-DTA ANALYSIS
TGA-DTA measures both heat flow and weight changes in a material as a
function of temperature in a controlled air atmosphere. An overlay of TGA-DTA
plots for the test compound 6 up to 700 ꢀC in an air atmosphere is shown in
Figs. 2 and 3. The decomposition of the final dendron 6 was followed by TGA.
Figure 2. TGA of dendron 6.
Figure 3. DTA of dendron 6.

1224
E. DADAPEER, B. S. KRISHNA, AND C. N. RAJU
The compound is stable up to 90 ꢀC. An initial decomposition starts in the range of
90–110 ꢀC with a corresponding weight loss of approximately 3%. This is attributed
to the loss of water molecules. Then the compound is stable up to 200 ꢀC. Again the
decomposition starts in the range 200–300 ꢀC with a corresponding weight loss of
approximately 43–44%. Then the compound is stable in the range of 300–450 ꢀC,
and immediately starts to decompose in between 450 and 550 ꢀC with approximate
weight loss of 18–20%. The total loss of the compound is around 65% of the total
mass of the material. Similarly, DTA was also used on dendron 6 to detect the
changes in the sample, either exothermic or endothermic. The DTA profile (Fig. 3)
shows that the endotherm peak at 100 ꢀC corresponds to the loss of water and
exotherms at 250 and 490 ꢀC correspond to the loss of most of the dendritic wedges
of the dendron 6.
EXPERIMENTAL
All the chemicals used were purchased from Sigma-Aldrich Chemical
Company and used without further purification. All solvents (analytic reagent or
extrapure grade) were dried by standard methods. Thin-layer chromatography
(TLC) was performed on precoated plates with silica gel 60 F254(Merk). Column
chromatography was performed on silica gel (60–120 mesh), and ethyl acetate–hex-
ane was used as eluent. IR spectra were recorded on JASCO Japan FT=IR-5300
1
spectrometer at the University of Hyderabad using KBr optics. H and 13C NMR
spectra were recorded on a Bruker A VIII 400 MHz NMR spectrometer at Laila
1
Impex, Vizayawada (operating at 400 MHz for H and 100 MHz for 13C NMR).
Data were recorded in dimethylsulfoxide (DMSO-d6) and chemical shifts were refer-
enced to tetramethylsilane (TMS) (1H and 13C). 31P NMR spectra were recorded on
Bruker ACF Supercon 200 spectrometer operating at 81 MHz at the University of
Hyderabad, Hyderabad. 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, and 5 were recorded on a LCMS-2010A Shimadzu spectrometer at the University
of Hyderabad, Hyderabad. The MALDI mass spectrum of dendron 6 was recorded
using an Applied Biosystems Voyager DE-PRO MALDI-TOF spectrometer. The
sample was run using sinapic acid as the matrix with DMSO as the solvent in the
dried-droplet preparation method, performed at the Indian Institute of Technology,
Madras, Chennai. TGA-DTA measurement was taken using a TA instrument,
Waterloo, USA, performed at Sri Krishnadevaraya University, Ananthapur, India.
Elemental analyses were performed using a FLASH EA 1112 Thermo Finnigan
instrument (France) at the University of Hyderabad, Hyderabad, India.
Synthesis of 1
A solution of 3-hydroxybenzaldehyde (0.01 mol, 1.22 g) in 20 mL of dry EtOH
was added at room temperature to a stirred solution of 1,5-diaminonaphthalene
(0.005 mol, 0.79 g) in 20 mL of dry EtOH. After stirring for 4 h at reflux temperature,
formation of the compound 1 was ascertained by TLC analysis run in a 1:4 mixture
of ethyl acetate and hexane, and the average Rf value observed was 0.75. The solvent
was evaporated under reduced pressure to give the crude product. It was purified by

PHOSPHORUS-CONTAINING DENDRON
1225
column chromatography. Yield: 85%. Anal. calcd. for C24H18N2O2: C, 78.67; H,
4.95; N, 7.65%. Found: C, 78.01; H, 4.89; N, 7.55%. IR (KBr, cmꢁ1): 3385 (Ar-OH),
1
=
1620 (CH N); H NMR (400 MHz, DMSO-d6, d=ppm): 6.72–7.57 (14 H, m, Ar-H),
8.64 (2H, s, Ar-OH), 9.92 (2H, s, –CH N); 13C (100 MHz, DMSO-d6,d=ppm): 149.5
(C0 ), 116.6 (C0 ), 127.5 (C0 ), 125.6 (C0 ), 130.2 (C0 =C0 ), 157.0 (C1 ), 114.7 (C1 ),
=
1
2
3
4
5
6
1
2
3
4
5
6
=
137.7 (C1 ), 122.1 (C1 ), 130.1 (C1 ), 119.7 (C1 ), 157.9 (CH N). LC MS: m=z 367
(M þ 1)þ.
Synthesis of 2
A solution of POCl3 (0.01 mol, 0.93 mL) in 20 mL of dry THF was added
dropwise to a mixture of stirred solution of 1 and triethylamine (0.01 mol,
1.38 mL) in 25 mL of dry THF over a period of 20 min at ꢁ5 to 0 ꢀC. After stirring
for 5 h at 40–45 ꢀC, formation of 2 was ascertained by TLC analysis run in a 1:4
mixture of ethyl acetate and hexane, and the average Rf value observed was 0.72.
Triethylamine hydrochloride was removed by filtration. The solvent was evaporated
under reduced pressure to give crude product. It was purified by column chromato-
graphy. Yield: 82%. Anal. calcd. for C24H16Cl4N2O4P2: C, 48.03; H, 2.69; N, 4.67.
Found: C, 47.91; H, 2.53; N, 4.65. IR (KBr, cmꢁ1): 1221(P O), 953, 1158 (P-O-
=
1
=
C
aromatic), 1615 (CH N). H (400 MHz, DMSO-d6, d=ppm): 7.16–7.44 (14 H, m,
Ar-H), 9.94 (2H, s, –CH N). 13C (100 MHz, DMSO-d6, d=ppm): 150.1
(C0 ), 116.8 (C0 ), 127.9 (C0 ), 126.6 (C0 ), 130.3 (C0 =C0 ), 152.8 (C1 ), 115.5
=
3
1
2
4
5
6
1
(C1 ), 138.1 (C1 ), 122.0 (C1 ), 131.1 (C1 ), 121.7 (C1 ), 158.2 (CH N). 31P NMR
2
3
4
5
6
=
(81 MHz, CDCl3d=ppm): ꢁ30.45 ppm. LC MS: m=z 600 (M)þ..
Synthesis of 3
A solution of 3-hydroxy-benzaldehyde (0.02 mol, 2.44 g) in 25 mL of dry THF was
added dropwise to a mixture of stirred solution of 2 and triethylamine (0.02 mol,
2.76 mL) in 25mL of dry THF over a period of 20 min at 0 ꢀC. After stirring for 5 h
at 40–45 ꢀC, formation of 3 was ascertained by TLC analysis run in a 3:7 mixture of
ethyl acetate and hexane, and the average Rf value observed was 0.70. Triethylamine
hydrochloride was removed by filtration. The solvent was evaporated under reduced
pressure to get the crude product. It was purified by column chromatography. Yield:
75%. Anal. calcd. for C52H36N2O12P2: C, 66.25; H, 3.85; N, 2.97. Found: C, 66.48;
H, 3.82; N, 2.93. IR (KBr, cmꢁ1): 1690 (Ar-CHO), 1230 (P O), 940, 1165 (P-O-Caro-
=
1
=
matic), 1622 (CH N). H (400 MHz, DMSO-d6. d=ppm): 7.02–7.57 (30H, m, Ar-H),
8.62 (2H, s, –CH N), 9.90 (4H, s, Ar-CHO). 13C (100 MHz, DMSO-d6. d= ppm):
151.1 (C0 ), 115.7 (C0 ), 128.6 (C0 ), 127.6 (C0 ), 130.5 (C0 =C0 ), 150.8 (C1 ), 115.8
=
1
2
3
4
5
6
1
2
3
4
5
6
1
(C1 ), 138.6 (C1 ), 121.5 (C1 ), 131.3 (C1 ), 121.9 (C1 ), 153.7 (C2 ), 113.5 (C2 ), 140.3
2
(C2 ), 124.0 (C2 ), 130.6 (C2 ), 126.4 (C2 ), 159.1 (CH N),192.9 (Ar-CHO). 31P NMR
3
4
5
6
=
(81MHz, CDCl3,d=ppm): -32.09 ppm. LC MS: m=z 944 (M þ 1)þ.
Synthesis of 4
A solution of 3-aminophenol (0.02 mol, 2.18 g) in 20 mL of dry EtOH was
added to a stirred solution of 3 in 25 mL of dry EtOH at room temperature. After

1226
E. DADAPEER, B. S. KRISHNA, AND C. N. RAJU
stirring for 5 h at reflux temperature, formation of the compound 4 was ascertained
by TLC analysis run in a 2:3 mixture of ethyl acetate and hexane, and the average Rf
value observed was 0.65. The solvent was evaporated under reduced pressure to
obtain the crude product. It was purified by column chromatography. Yield: 65%.
Anal. calcd. for C76H56N6O12P2: C, 69.83; H, 4.32; N, 6.43. Found: C, 69.88; H,
4.31; N, 6.39. IR (KBr, cmꢁ1): 3375 (Ar-OH), 1242 (P O), 938, 1173 (P-O-Caromatic),
=
1
=
1622, 1628 (CH N). H (400 MHz, DMSO-d6. d=ppm): 6.64–7.54 (46 H, m, Ar-H),
8.58, 8.63 (6H, s, –CH N), 9.75 (4H, s, Ar-OH). 13C (100 MHz, DMSO-d6, d=ppm):
149.9 (C0 ), 115.0 (C0 ), 127.1 (C0 ), 128.1 (C0 ), 129.8 (C0 =C0 ), 151.2 (C1 ), 114.8
=
2
1
3
4
5
6
1
2
3
4
5
6
(C1 ), 139.1 (C1 ), 122.0 (C1 ), 130.7 (C1 ), 122.9 (C1 ), 154.5 (C2 ), 114.1 (C2 ), 141.1
1
2
3
(C2 ), 125.1 (C2 ), 130.9(C2 ), 127.3 (C2 ), 160.5 (C3 ), 110.8 (C3 ), 155.3 (C3 ),
4
5
6
1
2
3
116.22 (C3 ), 132.9 (C3 ), 114.0 (C3 ), 159.1, 160.8 (CH N). 31P NMR (81 MHz,
4
5
6
=
CDCl3, d= ppm):ꢁ28.54 ppm. LC MS: m=z 1308 (M þ 1)þ.
Synthesis of 5
A solution of POCl3 (0.02 mol, 1.86 mL) in 30 mL of dry THF was added
dropwise to a stirred solution of 4 and triethylamine (0.02 mol, 2.76 mL mL) in
30 mL of dry THF, 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 0.55. Triethylamine
hydrochloride was removed by filtration. The solvent was evaporated under reduced
pressure to get the crude product. It was purified by column chromatography. Yield:
58%. Anal. calcd. for C76H52N6O14P6: C, 51.43; H, 2.95; N, 4.74. Found: C, 51.47;
H, 2.91; N, 4.71. IR (KBr, cmꢁ1): 1228, 1242 (P O), 933, 1160 (P-O-Caromatic), 1618,
=
1
=
1635 (CH N). H (400 MHz, DMSO-d6. d=ppm): 7.09–7.41 (46 H, m, Ar-H), 8.91,
9.90 (6H, s, –CH N). 13C (100 MHz, DMSO-d6, d=ppm): 150.7 (C0 ), 116.1(C0 ),
127.4 (C0 ), 128.6 (C0 ), 130.1 (C0 =C0 ), 152.2 (C1 ), 115.2 (C1 ), 140.2 (C1 ),
1
2
=
3
4
5
6
1
2
3
4
121.8 (C1 ), 129.8 (C1 ), 123.4 (C1 ), 155.1 (C2 ), 115.9 (C2 ), 142.5 (C2 ), 126.0
5
6
1
2
3
4
5
6
1
2
3
4
(C2 ), 131.5(C2 ), 126.9 (C2 ), 161.5 (C3 ), 109.7 (C3 ), 156.0 (C3 ), 116.5 (C3 ),
5
6
133.4(C3 ), 113.9 (C3 ), 160.9, 162.4 (CH N). 31P NMR (81 MHz, CDCl3, d=
=
ppm): ꢁ22.48, ꢁ31.88 ppm. LC MS: m=z 1776 (M þ 1)þ.
Synthesis of 6
A solution of hydroquinone (0.04 mol, 4.40 g) in 35 mL of dry THF was added
dropwise to a stirred solution of 5 and triethylamine (0.04 mol, 5.52 mL mL) in
35 mL of dry THF over a period of 20 min at ꢁ5 to 0 ꢀC. After stirring for 5 h at
45–50 ꢀC, formation of 6 was ascertained by TLC analysis run in a 4:1 mixture of
ethyl acetate and hexane, and the average Rf value observed was 0.50. Triethylamine
hydrochloride was removed by filtration. The solvent was evaporated under reduced
pressure to get the crude product. It was purified by column chromatography. Yield:
55%. Anal. calcd. for C124H92N6O32P6: C, 63.00; H, 3.92; N, 3.56. Found: C, 63.12;
H, 3.90; N, 3.61. IR (KBr, cmꢁ1): 3381 (Ar-OH), 1233, 1240 (P O), 925, 1172 (P-O-
=
1
=
C
aromatic), 1627, 1643 (CH N). H (400 MHz, DMSO-d6. d=ppm): 6.63–7.57 (78 H,
m, Ar-H), 8.09, 8.35 (6H, s, –CH N), 10.41 (8H, s, Ar-OH). 13C (100 MHz, DMSO-
=
1
2
3
4
5
6
d6. d=ppm): 151.2 (C0 ), 115.9 (C0 ), 128.2 (C0 ), 129.2 (C0 ), 131.1 (C0 =C0 ), 151.8

PHOSPHORUS-CONTAINING DENDRON
1227
1
(C1 ), 115.6 (C1 ), 140.9 (C1 ), 121.9 (C1 ), 130.3 (C1 ), 122.6 (C1 ), 156.3 (C2 ), 116.7
2
3
4
5
6
1
2
3
4
5
6
1
2
(C2 ), 143.1 (C2 ), 125.5 (C2 ), 130.7 (C2 ), 127.1 (C2 ), 160.5 (C3 ), 108.7 (C3 ), 155.1
3
4
5
6
1
2
6
(C3 ), 117.1 (C3 ), 134.1(C3 ), 114.6 (C3 ), 143.5 (C4 ), 117.7 (C4 =C4 ), 116.5 (C4 =
3
C4 ), 150.5 (C4 ), 157.6, 158.3 (CH N). 31P NMR (81 MHz, CDCl3, d=ppm): ꢁ
5
4
=
41.44, ꢁ39.13 ppm. MALDI-TOF-MS: m=z 2364 (M)þ (calcd. 2363.9).
CONCLUSION
Facile iterative divergent synthesis of a novel phosphorus dendron 6 was
accomplished. The Schiff’s base (imine) formation reactions were performed in dry
ethanol and substitution reactions were perfomed in dry THF in presence of triethy-
lamine. The thermal stability and changes in weight in relation to change in tempera-
ture and the heat of the dendron 6 were established by TGA-DTA analysis.
ACKNOWLEDGMENT
The authors thank Human Resource Development Group, Council of Scien-
tific and Industrial Research, New Delhi, India, for sanctioning a major research
project [No. 01(2309)=09=EMR-II].
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New York, 2002.
2. Newkome, G. R.; Moorefield, C. N.; Vogtle, F. Dendrimers and Dendrons: Concepts,
Synthesis, Applications; VCH: Weinheim, 2001.
3. Zimmerman, S. C.; Zeng, F.; Reichert, D. E. C.; Kolotuchin, S. V. Self-assembling
dendrimers. Science 1996, 271, 1095–1098.
4. Maraval, V.; Laurent, R.; Donnadieu, B.; Mauzac, M.; Caminade, A. M.; Majoral, J. P.
Rapid synthesis of phosphorus-containing dendrimers with controlled molecular architec-
tures: First example of surface-block, layer-block, and segment-block dendrimers issued
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