Synthesis, photophysical and electrochemical properties and DSSC applications of triphenylamine chalcone dendrimers: Via click chemistry

Article abstract of DOI:10.1039/c7nj01059a

Fluorene-cored dendrimers containing a triphenylamine chalcone unit at the periphery have been synthesized by divergent methodology using a click chemistry approach, and their photophysical and electrochemical properties have been investigated. All of the dendrimers exhibited quasireversible oxidation reduction signals in cyclic voltammetry. All of the dendrimers were used as additives in dye-sensitized solar cells (DSSCs), and the higher generation dendrimers exhibited better power conversion efficiency than the lower generation dendrimers in solar energy harvesting systems.

Full text of DOI:10.1039/c7nj01059a

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The role of atropisomers on the photo-reactivity and fatigue of
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Synthesis, photophysical, electrochemical properties and DSSC application
of triphenylamine chalcone dendrimers via click chemistry
Devaraj Anandkumar,a Perumal Rajakumar,a* Shanmugam Ganesanb and
Pichai Maruthamuthuc
aDepartment of Organic Chemistry, University of Madras, Guindy Campus Chennai 600 025,
TamilNadu, India
bDepartment of Chemistry, SRM University, SRM Nagar, Kattankulathur, Chennaiꢀ603 203,
India
cDepartment of Energy, University of Madras, Guindy Campus, Chennai 600 025, India
Eꢀmail: perumalrajakumar@gmail.com; Tel: +91 044 2220 2814
Abstract
Fluoreneꢀcored dendrimer containing triphenylamine chalcone unit at the periphery
has been synthesized by divergent methodology using click chemistry approach and their
photophysical and electrochemical properties have been investigated. All the dendrimers
exhibited quasireversible oxidation reduction signals in cyclic voltammetry. All the
dendrimers are used as additives in dyeꢀsensitized solar cells (DSSCs) and the higherꢀ
generation dendrimer exhibit better power conversion efficiency than the lowerꢀgeneration
dendrimers in solar energy harvesting systems.
Keywords: Dendrimers, Fluorene, Triphenylamine, Click chemistry.
Introduction
Emitting organic compounds possessing extended πꢀconjugated system are of great
interest in recent years owing to their variety of applications in OLEDs,1 solidꢀstate lasers,2
sensors,3 fluorescence imaging,4 nonlinear optical materials,5 photophysical and in charge
transport devices. The energy demand increases worldwide but the fossil fuel reserves wear
out rapidly and hence there is an increase in pressure to use renewable energy sources to have
sustainable progress and development. Along these lines, Dyeꢀsensitized solar cells (DSSCs)
1

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have involved significant attention due to their low cost fabrication and high power
conversion efficiency (PCE) values. With the aim of increasing and improving renewable
energy sources, recently a large number of functional πꢀconjugated polymers,6 oligomers7
and dendrimers8 have been synthesized and used in DSSC and organic light emitting diodes
(OLEDs). DSSC fabricated using ruthenium complex9 first reported by Grätzel and
coworkers in 1991 had 11% power conversion efficiency. Recently,10 the record of high
conversion efficiency (η) of 13.0% has been achieved with Znꢀporphyrin complexꢀbased
DSSC. Dendrimers11 are highly branched macromolecules combining the merits of wellꢀ
defined structure with superior chemical purity and with excellent emissive property that
depend on the dendrimer generation. Dendrimers have attracted great attention in the past few
decades due to their variety of applications including optical data storage,12 solar cells13 and
medical applications.14
Triphenylamine (TPA) moiety possesses threeꢀdimensional propeller structure and its
derivatives have an important place in DSSC due to the electron donating property linked as a
sensitized dye with hole transporting ability. Extension of the dye linker stabilizes the charge
separation condition but delays electron donation.15 In photoelectric research TPA has been
reported as a good pꢀdoping unit and used as a holeꢀinjection moiety.16,17 Triphenylamine and
its derivatives have interesting properties in the development of photovoltaic devices as donor
moieties and hence they can be used as good antenna for the charge transfer and/or energy
transfer to the emitting center. TPAꢀbased starꢀshaped oligomeric and polymeric materials are
used as important organic semiconductors and as hole transporting materials in organic light
emitting diodes, solar cells, organic field effect transistors and in photorefractive
holography.18
Fluorene is a major component of fossil fuels and 9,9ꢀdialkylꢀsubstituted fluorene
derivatives often exhibit high fluorescence quantum yields, good solubility in organic
2

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solvents, with excellent thermoꢀ and photostability. Therefore, fluorenyl functionalized
materials have been extensively explored as active ingredients for electronic devices, such as
light emitting diodes, chargeꢀtransfer agents,19 field effect transistors20 and sensors.
Click chemistry is the most promising cycloaddition reaction in which copper (I) is
used as a catalyst for 1,3ꢀdipolar cycloaddition of terminal alkyne to azide developed by
Sharpless21a and Meldal.21b Click reaction21c is characterized by very high yields, mild and
simple reaction conditions and easy product isolations, with excellent chemoselective
affording reliable 1,4ꢀregiospecific 1,2,3ꢀtriazole even in the presence of a large variety of
other functional groups, which is a breakthrough in the synthesis of dendrimers22, 23 and
polymeric materials.24, 25
Recently, we have used dendrimers with pyrene,26 dimethyl isophthalate27 and
benzothiazole28 surface groups as additives to increase the openꢀcircuit voltage (Voc) in
DSSC. We report herein the synthesis of triphenylamine chalconeꢀbased triazole dendrimers
1–6 (Fig. 1) with their photophysical property and also their application to increase the
efficiency of DSSC when they are used as additives.
3

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N
N
N
N
C6H13 C6H13
N
N
O
O
O
O
N
N
G0
R
R
R
R
1 R = H
2 R = Br
N
N
C6H13
C6H13
N
N
R
R
N
N
O
O
O
O
O
O
N
N
N
N
N
N
N
N
N
N
N
N
N
N
R
R
O
O
O
O
R
R
N
N
G1
3 R = H
4 R = Br
R
R
O
O
R
R
N
N
N
C6H13
C6H13
N
N
N
N
O
N
O
O
O
N
N
N
N
N
N
N
N
N
N
N
R
R
R
N
N
O
N
O
R
N
N
N
N
N
N
N
N
N
N
O
O
O
O
N
N
N
N
R
N
N
O
O
R
N
N
N
N
N
O
N
N
O
N
O
O
O
O
O
O
N
N
R
R
R
R
R
R
N
N
G2
R
R
5 R = H
6 R = Br
Fig. 1 The molecular structure of triphenylchalcone dendrimers 1ꢀ6.
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Results and discussion
The synthesis of propargyloxy triphenylamine chalcone dendrons 10 and 11 was
achieved by controlled VilsmeierꢀHaack formylation of triphenyl amine to give 4ꢀformyl
triphenylamine 7, which was brominated using NBS in DMF at rt to give 4ꢀ(bis(4ꢀ
bromophenyl)amino)benzaldehyde 8 in good yield. ClaisenꢀSchmidt condensation of
triphenylamine aldehydes 7 and 8 with 1.0 equiv. of 4ꢀ(propargyloxy)acetophenone 9 using
ethanol as solvent and 10% sodium hydroxide as the base gave the corresponding
propargyloxy triphenylamine chalcones 10 and 11 in 83% and 84% yields respectively
(Scheme 1).
H3C
O
CHO
N
O
O
O
N
9
ii
X
X
7 X = H
8 X = Br
X
X
i
10 X = H
11 X = Br
Scheme 1
Reagents and conditions: (i) NBS, DMF, rt, 5h. (ii) aq.NaOH, EtOH, 80°C, 7 h, 10 (83%)
and 11 (84%).
1
In the H NMR spectrum, the alkyne dendron 10 displayed a triplet at δ 2.56 (J = 2.1
Hz) and a doublet at δ 4.76 (J = 1.8 Hz) for the acetylenic and propargyloxy protons and the
trans olefinic protons appeared at δ 7.40 (J = 15.6 Hz) and δ 7.76 (J = 15.6 Hz) respectively
in addition to the signals for the other aliphatic and aromatic protons. The 13C NMR spectrum
of 10 showed propargyl and carbonyl carbon at δ 55.9, 76.2, 77.9 and 188.8 respectively in
addition to the signals for the other aromatic carbons. In the mass spectrum (ESI) of the
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alkyne dendron 10, a peak appeared at m/z 430 (M+H)+ corresponding to the molecular ion.
The structure of the alkyne dendron 10 was further confirmed from elemental analysis.
Similarly, the structure of the alkyne dendron 11 was also confirmed from spectral and
analytical data.
The synthetic pathway leading to the chloro and the azidodendrimers 14, 16 and 15,
17 is shown in scheme 2. The divergent synthesis begins with the reaction of 1.0 equiv. of
2,7ꢀbis(azidomethyl)ꢀ9,9ꢀdihexylꢀ9Hꢀfluorene 13 with 2.1 equiv. of 1,3ꢀbis(chloromethyl)ꢀ5ꢀ
(propargyloxy)ꢀ benzene 12 under Cu(I) catalyzed click reaction conditions to give the chloro
dendrimer 14 in 93% yield, which on further treatment with NaN3 in DMF at 90 ºC afforded
1
the corresponding azido dendrimer 15 in 89% yield (Scheme 2). The H NMR spectrum of
the compound 15 displayed a singlet at δ 4.31 ppm for the azidomethyl protons and two
singlets at δ 5.20, 5.61 ppm for the Oꢀmethylene and Nꢀmethylene protons and a sharp singlet
at δ 7.53 ppm for the triazolyl proton in addition to the signals for the other aliphatic and
aromatic protons. The 13C NMR spectrum of the azido compound 15 displayed the
azidomethyl carbon at δ 54.4 ppm and two signals at δ 55.3, 62.2 ppm for the Nꢀmethylene
and Oꢀmethylene carbons respectively in addition to the signals for the other aliphatic and
aromatic carbons. The mass spectrum (ESIꢀMS) of the azidodendrimer 15 showed the
molecular ion peak at m/z 930 (M+1). Further the structure of the azidodendrimer 15 was also
confirmed from elemental analysis.
After synthesizing the firstꢀgeneration azido dendrimer, we focused our attention on
the synthesis of the secondꢀgeneration azido dendrimer. The reaction of 4.1 equiv. of 1,3ꢀ
bis(chloromethyl)ꢀ5ꢀ(propargyloxy)benzene 12 with 1.0 equiv. of the azidodendrimer 15
under Cu(I) catalyzed click reaction conditions gave the second generation chloro dendrimer
16 in 89% yield, which on further treatment with NaN3 in DMF at 90 °C afforded the
corresponding azido dendrimer 17 in 80% yield (Scheme 2).
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O
N
N
i
C6H13
+
C6H13
N
N
N3
N3
N
N
C6H13 C6H13
13
O
O
Cl
Cl
X
X
12 (2.1 equiv.)
X
X
14 X = Cl
15 X = N3
ii
i
12 (4.1 equiv.)
N
N
N
C6H13
C6H13
N
N
N
X
X
O
O
X
O
N
N
N
N
N
O
N
N
N
N
N
X
N
N
O
O
X
X
16 X = Cl
17 X = N3
X
X
ii
Scheme 2
Reagents and conditions: (i) CuSO4.5H2O (5 mol %), sodium ascorbate (10 mol %), H2O–
THF (1:3); rt, 12 h. 14 (93%), 16 (89%). (ii) 9 equiv. NaN3, DMF, 90 ºC, 3 h. 15 (89%), 17
(80%).
1
The H NMR spectrum of the compound 17 displayed a singlet at δ 4.31 ppm for the
azidomethyl protons and four singlets at δ 5.10, 5.21, 5.45 and 5.59 ppm for the different
types of Oꢀmethylene and Nꢀmethylene protons and a sharp singlet at δ 7.54 and 7.59 ppm for
the two different triazolyl protons in addition to the signals for the other aliphatic and
aromatic protons. The 13C NMR spectrum of the compound 17 displayed the azidomethyl
carbon at δ 54.4 ppm and four signals at δ 53.7, 55.3, 61.9 and 62.1 ppm for the four types of
Nꢀ methylene and Oꢀ methylene carbons respectively in addition to the signals for the other
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aliphatic and aromatic carbons. The mass spectrum (MALDIꢀTOF) of the azido dendrimer 17
showed the molecular ion peak at m/z 1921 [M + Na]+. Further the structure of azido
dendrimer 17 was also confirmed from elemental analysis.
The zeroth, first and second generation dendrimers 1 and 2 (G0), 3 and 4 (G1) and 5
and 6 (G2) could be achieved by ‘click’ chemistry approach using 2,7ꢀbis(azidomethyl)ꢀ9,9ꢀ
dihexylꢀ9Hꢀfluorene 13 as the core unit. The functionalization reaction of the zeroth, first and
second generation azidodendrimers 13, 15 and 17 with 2.1/4.1/8.1 equivalents of
propargyloxy triphenylamine chalcones 10 and 11 under Cu (I) catalyzed click reaction
conditions afforded the triphenylamine chalcone dendrimers 1, 2, 3, 4, 5 and 6 in 86%, 78%,
76%, 81%, 71% and 74% yields, respectively (Scheme 3).
The 1H NMR spectrum of the dendrimer (G0) 2 showed a set of four proton singlets at
δ 5.26 and 5.62 for the Oꢀmethylene and Nꢀmethylene protons and a sharp singlet at δ 7.55
ppm for the triazolyl proton in addition to the signals for the other aliphatic and aromatic
protons. The 13C NMR spectrum of the dendrimer 2 showed signals at δ 55.4 and 62.1 for the
Oꢀmethylene and Nꢀmethylene carbons and the carbonyl carbon appeared at δ 188.6 in
addition to the signals for the other aliphatic and aromatic carbons. The mass spectrum
(MALDIꢀTOF) of the compound 2 showed the molecular ion peak at m/z 1642 [M + Na]+.
Further, the structure of the compound 2 was also confirmed from elemental analysis.
Similarly, the structure of the zeroth, first and second generation dendrimers 1, 3, 4, 5 and 6
was also confirmed from spectral and analytical data.
The symmetrical structures of 1ꢀ6 and their extensive spectral studies viz NMR,
MALDIꢀTOF MS, and size exclusion chromatography (SEC) led to an unambiguous
structural determination. The formation of triazole chalcone 2, 3 and 6 was evidenced by the
appearance of newly formed triazolyl protons at δ 7.55, 7.60 and 7.60 ppm, respectively,
from the corresponding 1H NMR spectrum.
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O
O
17 (0.13 equiv.)
13 (0.5 equiv.)
5 & 6
1 & 2
i
i
N
R
R
10 R = H
11 R = Br
i
15 (0.25 equiv.)
3 & 4
Scheme 3
Reagents and conditions: (i) CuSO4.5H2O (5 mol %), sodium ascorbate (10 mol %), THF:
H2O (3:1), rt, 12 h, 1 (86%), 2 (78%), 3 (76%), 4 (81%), 5 (71%), 6 (74%).
UVꢀvis absorption studies
The UVꢀVis absorption spectra of the dendrimers 1ꢀ6 recorded in CH2Cl2 (1 x 10ꢀ6 M)
are presented in Fig. 2 and the λmax values are summarized in Table 1. In the absorption
spectra, dendrimers 1ꢀ6 exhibited two absorption bands at 308 and 408 nm which
corresponds to π–π*and n–π* transitions due to the presence of triphenylamine and fluorene
units. The dendrimers 1, 3 and 5 shows a small red shift of 14 nm compared to the
dendrimers 2, 4 and 6, due to the presence of electron withdrawing bromine atom. Molar
extinction coefficient of the dendrimers 1ꢀ6 increases significantly with increase in the
dendrimer generation. As the number of triphenylamine units increases from zeroth
generation to second generation, the absorption intensity also increases which indicates that
the amount of light absorbed by the dendritic antenna increases from lower generation to
higher generation which is otherwise known as valence effect in dendrimer chemistry.29
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Fig. 2 UV absorption spectra of dendrimers 1ꢀ6 in CH2Cl2 (1 x 10ꢀ6 M).
Emission studies
Fluorescence spectra of the dendrimers 1ꢀ6 were recorded with fluorescence
spectrophotometer using CH2Cl2 as solvent and the fluorescence parameters are presented in
the Table 1. As shown in Fig. 3, upon excitation at 420 nm, the dendrimers 1ꢀ6 show a strong
emission band in the range of 608–665 nm. The emission intensity of the dendrimers 1ꢀ6
gradually increases with increase in the dendritic generation due to the higher number of
triphenylamine moieties in periphery. The dendrimers 1, 3 and 5 exhibited strong red shift
compared to the dendrimers 2, 4 and 6. Due to the presence of electronegative bromine, the
second generation dendrimer 6 shows blue shift of 38 nm compared to the dendrimer 5
.
Fig. 3 Fluorescence spectra (λexc = 420nm) of dendrimers 1ꢀ6 in CH2Cl2 (1 x 10ꢀ6 M) at room
temperature.
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Table 1 Photophysical studies of dendrimers 1ꢀ6 (rt, in CH2Cl2).
max
ԑmax (M−1
cm−1 × 106)
3.8, 3.3
λem
Stokes shift
cmꢀ1
Dendrimers λabmax (nm)
Φf
(nm)
308, 420
309, 406
299, 416
309, 406
301, 422
308, 408
657
608
654
621
665
627
8589
0.14
0.12
0.11
0.10
0.10
0.08
1
2
3
4
5
6
3.0, 2.2
8184
4.3, 4.1
8747
3.9, 2.9
8528
5.2, 4.6
8659
4.0, 3.5
8561
The fluorescence quantum yields Φf of dendrimers 1–6 has been measured in ethanol
using coumarin 153 as the standard. The fluorescence quantum yields of 1, 2, 3, 4, 5 and 6 lie
in the range of 0.14ꢀ0.08 and the compound 6 shows the lowest fluorescence quantum yield
of 0.08 (Table 1).
The solvatochromism study was carried out for all the dendrimers in different solvents
to evaluate the effect of solvent polarity on the optical properties of the molecules. The
absorption and emission spectra of 1ꢀ6 were recorded in solvents of different polarity such as
1,4ꢀdioxane (Diox), chloroform (CHCl3), tetrahydrofuran (THF), dichloromethane (DCM)
and N,Nꢀdimethylformamide (DMF). The absorption and emission data observed in selected
solvents are listed in Table 2. The dendrimers 1ꢀ6 showed small changes in absorption on
varying the polarity of the solvent used for the measurement (SI Fig.1 & 2 and table 1).
However, the dendrimers 5 and 6 (Figure 5) showed prominent positive solvatochromism in
the emission spectra only. The dendrimers 5 and 6 exhibit strong emission band in the range
of 621–667 nm in dichloromethane, chloroform, 1,4ꢀdioxane and N,Nꢀdimethylformamide,
whereas in tetrahydrofuran the peak were observed at lower emission wavelength of 533 and
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534 nm and the corresponding photographic images of fluorescent solutions are inserted in
Fig. 5.
Figure 4 Absorption spectra of a) 5 and b) 6 recorded in selected solvents of different
polarity.
Figure 5 Emission spectra of a) 5 and b) 6 recorded in selected solvents of different polarity.
However, in solvents such as dichloromethane, chloroform, 1,4ꢀdioxane and N,Nꢀ
dimethylformamide the emission peak shifted to the red compared with that of the solvent
tetrahydrofuran as shown in Fig. 5. Similarly, the Stokes shift is more in polar solvents for
the dendrimers 5 and 6 which has more number of triphenylamine moieties at the surface. As
they show greater polarization than ground states, excited states will be stabilized in polar
solvents. Evidence for this are larger Stokes’ sifts and longer emission wavelengths. It is
reasonable to assume that the fluorene unit acts as a strong πꢀacceptor in the excited state.
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Table 2 Absorption and emission data for compounds 5 and 6 recorded in different solvents.
max
max
Polarity
index
3.1
λab
ԑmax (L M−1
cm−1 × 106)
0.4550
λem
Stokes
shift (cmꢀ1)
8704
Compound Solvent
(nm)
422
405
425
411
414
(nm)
667
533
663
635
635
DCM
THF
4.0
4.1
4.8
6.4
0.4827
0.4951
0.5350
0.5031
5929
8446
8608
8407
CHCl3
Dioxane
DMF
5
6
DCM
THF
CHCl3
Dioxane
DMF
3.1
4.0
4.1
4.8
6.4
409
401
412
402
405
0.3506
0.5258
0.5404
0.6507
0.5172
621
534
641
625
634
8321
6211
8671
8902
8893
Electrochemical properties
The redox behaviour of dendrimers 1ꢀ6 was studied by cyclic voltammetry (CV) in
CH2Cl2 (1 x 10ꢀ3 M) at room temperature at the scan rate at 50 mV sꢀ1 with 0.1 M
tetrabutylammonium perchlorate as the supporting electrolyte and Ag/AgCl electrode as the
reference electrode and Pt wire counter electrode. All the compounds exhibit electrochemical
response and the cyclic voltammogram of the dendrimers 1ꢀ6 are shown in Fig. 6, with redox
potentials listed in Table 3. Oxidation and reduction potential for all the dendrimers appeared
in the potential range of ꢀ2.0 to +2.0 V. The reversible oxidation potentials for the dendrimers
1, 2, 3, 4, 5 and 6 were obtained at 1.18 V, 1.24 V, 1.20 V, 1.36 V, 1.33 V and 1.49 V,
respectively, and the reversible reduction peaks were observed at 0.83 V, 0.87 V, 0.74 V,
0.92 V, 0.80 V and 0.84 V, respectively. All the dendrimers exhibit the quasiꢀreversible
behavior in cyclic voltammogram responsible to the strong electron donating triphenylamine
moiety. More importantly, both oxidation and reduction peaks occur at the positive potential
regions, revealing that these dendrimers easily lose the electron from the triphenylamine
units. Further, the oxidation potential increase with increase in the dendrimer generation in
the following order 1 (1.18 V), 3 (1.20 V), 2 (1.24 V), 5 (1.33 V), 4 (1.36 V), and 6 (1.49 V).
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The second generation dendrimers 5 and 6 exhibited a facile oxidation at the higher positive
potential attributed to the removal of electron from the triphenylamine units. The cathodic
peak potential is shifted from lower to higher generation dendrimers due to the presence of
more number of triphenylamine units at the periphery, which increases the electron density in
the dendrimeric system.
Fig. 6 Cyclic voltammogram of dendrimers 1ꢀ6 in CH2Cl2 (1 x 10ꢀ3 mol Lꢀ1), scanned at 50
mV sꢀ1
Table 3 Electrochemical parameters of dendrimers 1ꢀ6 in CH2Cl2 (1 x 10ꢀ3 mol Lꢀ1).
Dendrimers
Epc(V)
1.18
1.24
1.20
1.36
1.33
1.49
Epa(V)
0.83
0.87
0.74
0.92
0.80
0.84
E1/2= (Epc + Epa)/2
∆Ep= Epc ꢀ Epa
0.35
1.005
1.055
0.97
1
2
3
4
5
6
0.37
0.46
1.14
0.44
1.065
1.165
0.53
0.65
Dyeꢀsensitized solar cell studies
Various nitrogen based organic molecules such as aminopyridine, pyrimidine,
pyrrolidinopyridine, pyrrolidinoethylpyridine have been used as additives to increase Voc
which ultimately increases the solar energy harvesting efficiency (ƞ) of the DSSCs. In an
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attempt to examine the effect of dendrimers as additive in solar cell performance, studies
were carried out to observe the nature of the electrolytic solution in enhancing the
performance of DSSC. The efficiency of a dyeꢀsensitized solar cell is related to the various
components of DSSC such as TiO2, dye, iodide/triiodide concentration and Pt surface.
ꢀ
Among these, the redox electrolyte system (Iꢀ/I3 ) occupies an important role in the power
conversion efficiency of a DSSC. The redox couples without organic additives show a
decreased openꢀcircuit voltage (Voc) and shortꢀcircuit current (Jsc). After adding the
dendrimers as additive the sublimation of iodine is decreased which in turn increases the Voc
and Jsc and improve the efficiency (ƞ). Hence, nitrogen containing compounds form stable
ꢀ
molecular complexes with the (Iꢀ/I3 ) electrolyte system and drastically alter the Voc due to the
electron donating property of the lone pair of electrons on the nitrogen atom. In the present
investigation, we have synthesized a new series of 1,2,3ꢀtriazole based electron rich
triphenylamine chalcone dendrimers 1ꢀ6 and employed them as additives for DSSCs. The
tested dendrimers significantly affect the performance of the dyeꢀsensitized solar cell as
shown in Fig. 7.
Fig. 7 Current–voltage curves of DSSCs with dendrimer additives 1ꢀ6. The experiments were
conducted under simulated solar light at 70 mW cmꢀ2.
On passing from zerothꢀgeneration dendrimers to secondꢀgeneration dendrimers, Voc,
Jsc and current also increase due to the presence of increasing number of triazole and
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triphenylamine units. The higher generation dendrimers 5 and 6 shows greater efficiency in
harvesting the solar energy than the lower generation dendrimers 1, 2, 3 and 4 when used as
additive in DSSC. The photovoltaic performance data of the shortꢀcircuit current (Jsc), the
openꢀcircuit voltage (Voc), the fill factor and the electric energy efficiency (ƞ) are summarized
in Table 4.
Table 4 The photovoltaic properties of the dendrimers 1ꢀ6 in the electrolyte system (Iꢀ/I3 )
ꢀ
under illumination of 70 mW cmꢀ2 at AM 1.5.
Electrolyte system
N3 dye TiO2/KI/I2/1/Pt
N3 dye TiO2/KI/I2/2/Pt
N3 dye TiO2/KI/I2/3/Pt
N3 dye TiO2/KI/I2/4/Pt
N3 dye TiO2/KI/I2/5/Pt
N3 dye TiO2/KI/I2/6/Pt
Jsc/mA cmꢀ2
6.3
Voc/mV
790
Fill factor
0.52
η (%)
3.7
5.7
755
0.50
3.0
9.7
840
0.51
5.9
7.8
825
0.50
4.6
13.1
11.4
870
0.53
8.6
860
0.51
7.1
In conclusion using click chemistry approach, the dendrimers with
triphenylaminochalcone group have been synthesized in good yields. Photophysical studies
reveal that the presence of more triazolyl and triphenylamine units increases the light
absorbing capacity of the dendritic antenna and hence higher generation dendrimers show
greater light absorbing ability than the lower generation dendrimers and in electrochemical
studies the cathodic potential also increases as the dendrimer generation increases. Further,
from DSSC studies as the dendritic generation increases the power conversion efficiency (η)
also increases due to the increased number of triazole and triphenylamine units. Dendrimers 5
and 6 exhibit better power conversion efficiency (η) of 8.6 and 7.1%, respectively, when used
as additives in DSSC than the control (N3 dye/KI/I2) as well as when other
triphenylaminochalcone dendrimers are used as additives.
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Acknowledgements
The authors thank UGC, New Delhi, for financial assistance under UPE Phase II
programme and DSTꢀFIST for providing NMR facility to the department. The authors also
thank. DST Fast Track, New Delhi for carrying out solar cells studies.
Experimental section
General information
All chemicals and solvents were purchased commercially and used as such without
further purification. All melting points were determined using a Toshniwal melting point
apparatus by open capillary tube method and are uncorrected. Column chromatography was
performed on silica gel (ACME, 100ꢀ200 mesh). TLC was performed either on glass plates
coated with silica gelꢀG (ACME) of about 0.25 mm thickness and visualized with iodine. 1H
13
NMR and C NMR spectra were recorded on Bruker 300 MHz instruments. Chemical shifts
are given in parts per million, and J values are in hertz. UVꢀVis absorption spectra were
measured with a Perkin–Elmer Lambda 35 UVꢀvis spectrometer. Elemental analyses were
carried out using a PerkinꢀElmer CHNS 2400 instrument. Matrixꢀassisted laser desorption
ionization timeꢀofꢀflight mass spectrometry (MALDIꢀTOF MS) was performed with a 2,5ꢀ
dihydroxy benzoic acid (DHB) matrix.
General procedure for chalcone dendrons (Procedure A):
To a solution of 4ꢀ(propargyloxy)acetophenone and 4ꢀformyl triphenylamine/ 4ꢀ
(bis(4ꢀbromophenyl)amino)benzaldehyde in ethanol (10 mL) added 10% NaOH (5 mL) and the
reaction mixture was stirred at 80°C for 8 h after which the reaction mixture was acidified with
1N HCl (1 mL) and evaporated to dryness. The residue obtained was extracted with ethyl
acetate (3x 100 mL) washed with water (3x 100 mL), brine (100 mL) and then dried over
Na2SO4. Evaporation of the organic layer gave the residue, which was purified by column
chromatography using hexane:CHCl3 (3:2) as an eluent.
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General procedure for azidation of dendritic chloride (Procedure B):
To the solution of corresponding dendritic chloride (1 mmol) in dry DMF (20 mL),
sodium azide (1.5 mmol) was added and stirred at 75 ºC for 12 h. The reaction mixture was
allowed to cool to room temperature. It was then poured into iceꢀcold water (30 mL) and
extracted with CHCl3 (3 × 100 mL). The organic layer was washed with water (100 mL) and
saturated NaCl solution (3 × 100 mL), dried over Na2SO4. Solvent was evaporated under
reduced pressure to afford the crude product, which was purified by column chromatography
(SiO2), using the eluent as mentioned under each compound.
General procedure for Cu (I)ꢀcatalyzed azide−alkyne cycloaddition (Procedure C):
A mixture of polypropargylated compound (1.0 equiv per azide functionalization) and
azido compound (1.2 equiv), CuSO4·5H2O (0.3 equiv), and sodium Lꢀascorbate (0.3 equiv)
was stirred at room temperature for 18 h in a 3:1 mixture of THF/water. After confirming the
completion of reaction by TLC, chloroform (100 mL) was added to the reaction mixture and
the organic layer was washed with water (50 mL), and brine (50 mL), dried over Na2SO4 and
evaporated to obtain the crude product, which was then purified by column chromatography
(SiO2), using the eluent as mentioned under each compound.
Synthesis of propargyloxy triphenylamine chalcone 10:
Following the general procedure A, the alkyne dendron 10 was obtained as yellow
colored solid from 4ꢀ(propargyloxy)acetophenone 9 (0.35 g, 2.01 mmol) and 4ꢀformyl
triphenylamine 7 (0.5 g, 1.83 mmol) and then by eluting from the column with
CHCl3:Hexane (3:1). Yield: 0.65g, 83%; M.p.: 108°C; 1H NMR: (300 MHz, CDCl3): δH 2.56
(t, 1H, J = 2.1 Hz); 4.76 (d, 2H, J = 1.8 Hz); 7.01ꢀ7.15 (m, 10H); 7.27ꢀ7.32 (m, 4H); 7.40 (d,
1H, J = 15.6 Hz); 7.48 (d, 2H, J = 8.4 Hz); 7.76 (d, 1H, J = 15.6 Hz); 8.03 (d, 2H, J = 8.7
Hz). 13C NMR: (75 MHz, CDCl3): δC 55.9, 76.2, 77.9, 114.7, 119.2, 121.7, 124.1, 125.4,
128.0, 129.5, 129.7, 130.6, 132.3, 144.1, 146.9, 150.1, 161.0, 188.8. MS (ESI): m/z = 430 [M
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+ 1]. Anal. Calcd. For C30 H23 N O2: C, 83.89; H, 5.40; N, 3.26. Found: C, 83.75; H, 5.33; N,
3.37.
Synthesis of propargyloxy triphenylamine chalcone 11:
Following the general procedure A, the dendron 11 was obtained as yellow colored
solid from the 4ꢀ(propargyloxy)acetophenone 9 (0.5 g, 2.76 mmol) and 4ꢀ(bis(4ꢀ
bromophenyl)amino)benzaldehyde 8 (0.5 g, 1.31 mmol) and then by eluting from the column
with CHCl3:Hexane (3:1). Yield: 0.65g, 84%; M.p.: 120°C; 1H NMR: (300 MHz, CDCl3): δH
2.57 (t, 1H, J = 2.4 Hz); 4.78 (d, 2H, J = 2.4 Hz); 6.98ꢀ7.08 (m, 9H); 7.39ꢀ7.41 (m, 4H); 7.51
(d, 2H, J = 8.7 Hz); 7.75 (d, 1H, J = 15.6 Hz); 8.04 (d, 2H, J = 8.7 Hz). 13C NMR: (75 MHz,
CDCl3): δC 55.9, 76.2, 77.8, 114.7, 116.9, 120.0, 122.6, 126.5, 129.8, 130.6, 132.1, 132.7,
133.0, 143.6, 145.7, 149.0, 161.1, 188.7. MS (ESI): m/z = 588 [M + 1]. Anal. Calcd. For C30
H21 Br2 N O2: C, 61.35; H, 3.60; N, 2.38. Found: C, 61.47; H, 3.43; N, 2.27.
Synthesis of 2,7ꢀbis(azidomethyl)ꢀ9,9ꢀdihexylꢀ9Hꢀfluorene 13:
Following the general procedure B, 2,7ꢀbis(azidomethyl)ꢀ9,9ꢀdihexylꢀ9Hꢀfluorene 13
was obtained as colorless oil from 2,7ꢀbis(bromomethyl)ꢀ9,9ꢀdihexylꢀ9Hꢀfluorene (5.3 g,
10.2 mmol) and sodium azide (2.0 g, 25.4 mmol) and then by eluting from the column with
hexane. Yield: 4.0g, 89%; 1H NMR(300 MHz, CDCl3): δH 0.60 (br s, 4H); 0.76 (t, 6H, J = 6.6
Hz); 1.04ꢀ1.12 (m, 12H); 1.94 (m, 4H); 4.41 (s, 2H); 7.35ꢀ7.37 (m, 6H); 7.63 (d, 2H, J = 8.1
Hz). 13C NMR: (75 MHz, CDCl3) δc 14.0, 22.5, 23.6, 23.7, 29.6, 31.4, 40.1, 55.2, 120.1,
128.0, 136.9, 140.8, 151.8. MS (ESI): m/z = 445 [M + 1]. Anal. Calcd. For C27 H36 N6: C,
72.94; H, 8.16; N, 18.90. Found: C, 72.82; H, 8.28; N, 18.75.
First generation chlorodendrimer 14:
Following the general procedure C, the chlorodendrimer 14 was obtained as white
solid from 2,7ꢀbis(azidomethyl)ꢀ9,9ꢀdihexylꢀ9Hꢀfluorene 13 (0.7 g, 1.58 mmol) and 1,3ꢀ
bis(chloromethyl)ꢀ5ꢀ(propargyloxy)ꢀ benzene 12 (0.79 g, 3.47 mmol) and then by eluting
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1
from the column with CHCl3: MeOH (19:1). Yield: 1.30g, 93%; M.p.: 118 °C; H NMR:
(300 MHz, CDCl3): δH 0.54 (br s, 4H); 0.73 (t, 6H, J = 6.6 Hz); 1.01ꢀ1.08 (m, 12H); 1.88ꢀ
1.93 (m, 4H); 4.52 (s, 8H); 5.19 (s, 4H); 5.62 (s, 4H); 6.95 (s, 4H); 7.01 (s, 2H); 7.23 (s, 1H);
13
7.26 (s, 3H); 7.54 (s, 2H); 7.69 (d, 2H, J = 7.5 Hz). C NMR: (75 MHz, CDCl3): δC 14.0,
22.5, 23.8, 29.5, 31.4, 40.0, 45.7, 54.6, 55.4, 62.2, 114.9, 120.6, 121.4, 122.5, 122.8, 127.2,
133.5, 139.5, 140.9, 144.1, 152.0, 158.7. MS (ESI): m/z = 904 [M + 1]. Anal. Calcd. For C49
H56 Cl4 N6 O2: C, 65.19; H, 6.25; N, 9.31. Found: C, 65.35; H, 6.33; N, 9.17.
First generation azidodendrimer 15:
Following the general procedure B, reaction of the first generation chlorodendrimer
14 (1.2 g, 1.33 mmol, 1.0 equiv.) with NaN3 (0.52 g, 7.97 mmol, 6.0 equiv.) gave the
azidodendrimer 15 as white solid after eluting from the column with CHCl3: MeOH (19:1).
1
Yield: 1.10g, 89%; M. P.: 140 ºC; H NMR: (300 MHz, CDCl3): δH 0.55 (br s, 4H); 0.73 (t,
6H, J = 6.6 Hz); 1.01ꢀ1.08 (m, 12H); 1.88ꢀ1.93 (m, 4H); 4.31 (s, 8H); 5.20 (s, 4H); 5.61 (s,
4H); 6.87 (s, 3H); 6.89 (s, 3H); 7.23 (s, 1H); 7.26 (s, 3H); 7.53 (s, 2H); 7.68 (d, 2H, J = 7.5
Hz). 13C NMR: (75 MHz, CDCl3): δC 13.9, 22.4, 23.8, 29.4, 31.4, 40.0, 54.4, 54.6, 55.3, 62.2,
114.3, 120.5, 120.6, 122.5, 122.8, 127.9, 133.6, 137.7, 140.9, 144.1, 152.0, 158.9. MS (ESI):
m/z = 930 [M + 1]. Anal. Calcd. For C49 H56 N18 O2: C, 63.34; H, 6.08; N, 27.14. Found: C,
63.45; H, 6.23; N, 27.27.
Second generation chlorodendrimer 16:
Following the general procedure C, reaction of 1,3ꢀbis(chloromethyl)ꢀ5ꢀ
propargyloxybenzene 12 (0.52g, 2.26 mmol, 6.2 equiv.) with the azidodendrimer 15 (0.5g,
0.54 mmol, 1.0 equiv.) gave the chlorodendrimer 16 as white solid after eluting from the
1
column with CHCl3: MeOH (19:1). Yield: 0.88g, 89%; M. P.: 141 ºC; H NMR: (300 MHz,
CDCl3): δH 0.53 (br s, 4H); 0.70 (t, 6H, J = 6.6 Hz); 0.98ꢀ1.05 (m, 12H); 1.87ꢀ1.92 (m, 4H);
4.50 (s, 16H); 5.08 (s, 4H); 5.18 (s, 8H); 5.44 (s, 8H); 5.58 (s, 4H); 6.77 (s, 2H); 6.84 (s, 4H);
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6.95 (s, 11H); 6.99 (s, 4H); 7.04 (s, 1H); 7.22 (d, 2H, J = 7.8 Hz); 7.55 (s, 2H); 7.60 (s, 2H);
13
7.66 (d, 2H, J = 7.8 Hz). C NMR: (75 MHz, CDCl3): δC 14.0, 22.4, 23.7, 29.4, 31.4, 39.9,
45.7, 53.7, 54.6, 55.3, 56.0, 61.9, 62.1, 76.0, 78.1, 114.7, 115.0, 115.1, 120.1, 120.6, 121.4,
121.7, 122.9, 122.9, 123.0, 127.2, 133.5, 137.1, 139.4, 139.5, 140.9, 143.4, 144.2, 152.0,
158.0, 158.6, 159.2. MS (MALDIꢀTOF): m/z = 1868 [M + Na]+. Anal. Calcd. For C93 H96 Cl8
N18 O6: C, 60.53; H, 5.24; N, 13.66. Found: C, 60.39; H, 5.37; N, 13.57.
Second generation azidodendrimer 17:
Following the general procedure B, reaction of the second generation
chlorodendrimer 16 (1.0 g, 0.54 mmol, 1.0 equiv.) with NaN3 (0.35g, 5.42 mmol, 10.0 equiv.)
gave the azidodendrimer 17 as colorless gel after eluting from the column with CHCl3:
MeOH (19:1). Yield: 0.80g, 80%; M. P.: 135 ºC; 1H NMR: (300 MHz, CDCl3): δH 0.53 (br s,
4H); 0.71 (t, 6H, J = 6.6 Hz); 0.99ꢀ1.08 (m, 12H); 1.87ꢀ1.93 (m, 4H); 4.31 (s, 16H); 5.10 (s,
4H); 5.21 (s, 8H); 5.45 (s, 8H); 5.59 (s, 4H); 6.79 (s, 2H); 6.86 (s, 6H); 6.90 (s, 12H); 7.22 (d,
13
2H, J = 7.8 Hz); 7.54 (s, 2H); 7.59 (s, 4H); 7.67 (d, 2H, J = 7.8 Hz). C NMR: (75 MHz,
CDCl3): δC 14.0, 22.4, 23.7, 29.4, 29.7, 31.4, 39.9, 53.7, 54.4, 54.6, 55.3, 61.9, 62.1, 77.3,
114.3, 114.7, 120.1, 120.6, 120.6, 122.9, 122.9, 123.0, 127.2, 133.5, 137.1, 137.7, 140.9,
143.4, 144.3, 152.0, 158.8, 159.2. MS (MALDIꢀTOF): m/z = 1921 [M + Na]+. Anal. Calcd.
For C93 H96 N42 O6: C, 58.85; H, 5.10; N, 30.99. Found: C, 58.97; H, 5.27; N, 30.77.
Synthesis of G0 dendrimer 1:
Following the general procedure C, the dendrimer 1 was obtained as yellow colored
solid from 2,7ꢀbis(azidomethyl)ꢀ9,9ꢀdihexylꢀ9Hꢀfluorene 13 (0.15 g, 0.34 mmol) and (E)ꢀ3ꢀ
(4ꢀ(diphenylamino)phenyl)ꢀ1ꢀ(4ꢀ(propꢀ2ꢀynyloxy)phenyl)propꢀ2ꢀenꢀ1ꢀone 10 (0.33 g, 0.71
mmol) and after eluting from the column with CHCl3ꢀMeOH (19:1). Yield: 0.38g, 86%;
M.p.: 96°C; 1H NMR: (300 MHz, CDCl3): δH 0.52 (br s, 4H); 0.73 (t, 6H, J = 6.6 Hz); 0.98ꢀ
1.08 (m, 12H); 1.86ꢀ1.92 (m, 4H); 5.26 (s, 4H); 5.61 (s, 4H); 7.04ꢀ7.15 (m, 18H); 7.22ꢀ7.32
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(m, 16H); 7.38 (d, 2H, J = 15.6 Hz); 7.48 (d, 2H, J = 8.4 Hz); 7.54 (s, 2H); 7.67ꢀ7.78 (m,
4H); 8.00 (d, 4H, J = 9 Hz). 13C NMR: (75 MHz, CDCl3): δC 14.0, 22.4, 23.8, 29.5, 29.7,
31.4, 40.0, 54.6, 55.4, 62.2, 114.5, 119.1, 120.6, 121.7, 122.4, 122.5, 122.8, 124.1, 125.0,
125.1, 125.4, 127.2, 128.0, 129.4, 129.5, 129.6, 130.7, 132.0, 133.5, 140.9, 144.0, 146.9,
147.1, 150.1, 152.0, 161.7, 188.7. MS (MALDIꢀTOF): m/z = 1326 [M + Na]+. Anal. Calcd.
For C87 H82 N8 O4: C, 80.16; H, 6.34; N, 8.60. Found: C, 80.37; H, 6.27; N, 8.77.
Synthesis of G0 dendrimer 2:
Following the general procedure C, the dendrimer 2 was obtained as yellow colored
solid from 2,7ꢀbis(azidomethyl)ꢀ9,9ꢀdihexylꢀ9Hꢀfluorene 13 (0.1 g, 0.22 mmol) and (E)ꢀ3ꢀ
(4ꢀ(bis(4ꢀbromophenyl)amino)phenyl)ꢀ1ꢀ(4ꢀ(propꢀ2ꢀynyloxy)phenyl)propꢀ2ꢀenꢀ1ꢀone
11
(0.29 g, 0.49 mmol) and after eluting from the column with CHCl3ꢀMeOH (19:1). Yield:
1
0.28g, 78%; M.p.: 108°C; H NMR: (300 MHz, CDCl3): δH 0.53 (br s, 4H); 0.73 (t, 6H, J =
6.6 Hz); 1.00ꢀ1.06 (m, 12H); 1.87ꢀ1.92 (m, 4H); 5.26 (s, 4H); 5.62 (s, 4H); 7.00ꢀ7.06 (m,
18H); 7.23ꢀ7.26 (m, 2H); 7.38ꢀ7.43 (m, 10H); 7.50 (d, 4H, J = 8.4 Hz); 7.55 (s, 2H); 7.67ꢀ
7.77 (m, 4H); 8.01 (d, 4H, J = 8.7 Hz). 13C NMR: (75 MHz, CDCl3): δC 14.0, 22.5, 23.8,
29.5, 29.7, 31.4, 40.0, 54.6, 55.4, 62.1, 114.6, 116.9, 119.9, 120.6, 122.6, 122.8, 126.5, 127.2,
129.3, 129.8, 130.7, 131.8, 132.7, 133.5, 141.0, 143.5, 143.9, 145.7, 149.0, 152.0, 161.8,
188.6. MS (MALDIꢀTOF): m/z = 1642 [M + Na]+. Anal. Calcd. For C87 H78 Br4 N8 O4: C,
64.53; H, 4.86; N, 6.92. Found: C, 64.35; H, 4.97; N, 6.79.
Synthesis of G1 dendrimer 3:
Following the general procedure C, the dendrimer 3 was obtained as yellow colored
solid from the azidodendrimer 15 (0.1 g, 0.11 mmol) and (E)ꢀ3ꢀ(4ꢀ(diphenylamino) phenyl)ꢀ
1ꢀ(4ꢀ(propꢀ2ꢀynyloxy) phenyl) propꢀ2ꢀenꢀ1ꢀone 10 (0.19 g, 0.45 mmol) and after eluting from
the column with CHCl3ꢀMeOH (19:1). Yield: 0.19g, 76%; M.p.: 138°C; 1H NMR: (300 MHz,
CDCl3): δH 0.52 (br s, 4H); 0.68 (t, 6H, J = 6.3 Hz); 0.97ꢀ1.05 (m, 12H); 1.87 (br s, 4H); 5.07
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(s, 4H); 5.24 (s, 8H); 5.44 (s, 8H); 5.44 (s, 8H); 5.58 (s, 4H); 6.75 (s, 2H); 6.84 (s, 4H); 7.00ꢀ
7.14 (m, 36H); 7.21 (d, 4H, J = 7.8 Hz); 7.26ꢀ7.40 (m, 16H); 7.47 (d, 8H, J = 8.7 Hz); 7.54
(s, 2H); 7.60 (s, 4H); 7.65 (d, 2H, J = 7.5 Hz); 7.74 (d, 4H, J = 15.6 Hz); 7.98 (d, 8H, J = 8.7
Hz). 13C NMR: (75 MHz, CDCl3): δC 14.0, 22.4, 23.8, 29.4, 29.7, 31.4, 53.7, 62.1, 114.6,
114.7, 119.1, 119.9, 120.6, 121.6, 122.9, 122.9, 123.0, 124.1, 125.4, 127.2, 128.0, 129.4,
129.5, 129.7, 130.7, 132.0, 133.5, 137.1, 140.9, 143.4, 144.0, 144.1, 146.9, 147.1, 150.1,
152.0, 159.5, 161.7, 188.7. MS (MALDIꢀTOF): m/z = 2670 [M + Na]+. Anal. Calcd. For C169
H148 N22 O10: C, 76.68; H, 5.64; N, 11.64. Found: C, 76.57; H, 5.77; N, 11.57.
Synthesis of G1 dendrimer 4:
Following the general procedure C, the dendrimer 4 was obtained as yellow colored
solid from the azidodendrimer 15 (0.1 g, 0.11 mmol) and (E)ꢀ3ꢀ(4ꢀ(bis(4ꢀ
bromophenyl)amino)phenyl)ꢀ1ꢀ(4ꢀ(propꢀ2ꢀynyloxy)phenyl)propꢀ2ꢀenꢀ1ꢀone 11 (0.1 g, 0.45
mmol) and after eluting from the column with CHCl3ꢀMeOH (19:1). Yield: 0.25g, 81%;
M.p.: 138°C; 1H NMR: (300 MHz, CDCl3): δH 0.54 (br s, 4H); 0.70 (t, 6H, J = 6.3 Hz);
0.98ꢀ1.05 (m, 12H); 1.88 (br s, 4H); 5.09 (s, 4H); 5.26 (s, 8H); 5.46 (s, 8H); 5.60 (s, 4H);
5.58 (s, 4H); 6.77 (s, 2H); 6.86 (s, 4H); 6.98ꢀ7.06 (m, 32H); 7.23 (d, 2H, J = 7.8 Hz); 7.39ꢀ
7.44 (m, 20H); 7.51 (d, 8H, J = 8.4 Hz); 7.54 (d, 4H, J = 10.2 Hz); 7.62 (s, 2H); 7.74 (d, 4H,
J = 15.3 Hz); 8.00 (d, 8H, J = 8.7 Hz). 13C NMR: (75 MHz, CDCl3): δC 14.0, 22.4, 23.8, 31.4,
39.9, 53.7, 69.1, 62.1, 114.6, 114.7, 116.9, 119.9, 120.6, 122.6, 122.9, 123.0, 123.1, 126.5,
127.2, 129.4, 129.8, 130.7, 131.8, 132.7, 133.5, 137.1, 140.9, 143.4, 143.6, 144.0, 145.7,
149.0, 152.0, 159.2, 161.8, 188.5. MS (MALDIꢀTOF): m/z = 3301 [M + Na]+. Anal. Calcd.
For C169 H140 Br8 N22 O10: C, 61.92; H, 4.30; N, 9.40. Found: C, 61.79; H, 4.47; N, 9.57.
Synthesis of G2 dendrimer 5:
Following the general procedure C, the dendrimer 5 was obtained as yellow colored
solid from the azidodendrimer 17 (0.15 g, 0.08 mmol) and (E)ꢀ3ꢀ(4ꢀ(diphenylamino) phenyl)ꢀ
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1ꢀ(4ꢀ(propꢀ2ꢀynyloxy) phenyl) propꢀ2ꢀenꢀ1ꢀone 10 (0.29 g, 0.67 mmol) and after eluting from
the column with CHCl3ꢀMeOH (19:1). Yield: 0.30g, 71%; M.p.: 122°C; 1H NMR: (300 MHz,
CDCl3): δH 0.50 (br s, 4H); 0.64 (t, 6H, J = 6 Hz); 0.86ꢀ0.92 (m, 12H); 1.85 (br s, 4H); 4.95
(s, 4H); 5.00 (s, 8H); 5.16 (s, 16H); 5.36 (s, 24H); 5.55 (s, 4H); 6.71ꢀ6.77 (m, 20H); 6.88ꢀ
7.73 (m, 166H); 7.98 (d, 12H, J = 8.7 Hz). 13C NMR: (75 MHz, CDCl3): δC 14.0, 22.4, 22.7,
29.3, 29.4, 31.3, 31.9, 53.6, 61.9, 114.5, 118.9, 121.5, 122.3, 123.6, 123.7, 124.1, 125.1,
125.4, 127.9, 128.4, 129.2, 129.4, 129.5, 129.7, 130.6, 130.6, 131.9, 137.1, 143.8, 144.0,
146.8, 147.0, 150.1, 158.9, 161.7, 188.6. MS (MALDIꢀTOF): m/z = 5357 [M + Na]+. Anal.
Calcd. For C333 H280 N50 O22: C, 74.98; H, 5.29; N, 13.13. Found: C, 74.87; H, 5.17; N,
13.27.
Synthesis of G2 dendrimer 6:
Following the general procedure C, the dendrimer 6 was obtained as yellow colored
solid from the azidodendrimer 17 (0.1 g, 0.05 mmol) and (E)ꢀ3ꢀ(4ꢀ(bis(4ꢀ
bromophenyl)amino)phenyl)ꢀ1ꢀ(4ꢀ(propꢀ2ꢀynyloxy)phenyl)propꢀ2ꢀenꢀ1ꢀone 11 (0.26 g, 0.45
mmol) and after eluting from the column with CHCl3ꢀMeOH (19:1). Yield: 0.25g, 74%;
M.p.: 158°C; 1H NMR: (300 MHz, CDCl3): δH 0.51 (br s, 4H); 0.64 (t, 6H, J = 5.7 Hz); 0.93ꢀ
1.00 (m, 12H); 1.87 (br s, 4H); 4.96 (s, 4H); 5.00 (s, 8H); 5.16 (s, 16H); 5.37 (s, 24H); 5.57
(s, 4H); 6.72ꢀ7.79 (m, 166H); 7.93 (d, 16H, J = 8.1 Hz). 13C NMR: (75 MHz, CDCl3): δC
14.0, 22.4, 29.4, 29.7, 31.3, 53.5, 61.9, 114.5, 114.6, 116.9, 119.8, 120.0, 122.5, 123.5, 124.1,
124.8, 125.4, 126.5, 129.1, 129.5, 129.7, 129.8, 130.6, 130.7, 131.7, 132.3, 132.4, 132.6,
137.1, 143.4, 143.5, 145.6, 146.7, 148.9, 158.9, 161.7, 188.4. MS (MALDIꢀTOF): m/z =
6619 [M + Na]+. Anal. Calcd. For C333 H264 Br16 N50 O22: C, 60.63; H, 4.03; N, 10.62. Found:
C, 60.81; H, 4.17; N, 10.50.
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