Fluorenyl dendrimer porphyrins: synthesis and photophysical properties

Article abstract of DOI:10.1016/j.tet.2009.10.043

New symmetrical dendrimeric type super-porphyrin bearing sixteen fluorenyl donor groups sixteen fluorenylporphyrin SOFP (1) have been synthesized and characterized. Preliminary photophysical properties are reported; in comparison to the references first g

Full text of DOI:10.1016/j.tet.2009.10.043

Tetrahedron 65 (2009) 10693–10700
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Fluorenyl dendrimer porphyrins: synthesis and photophysical properties
,b,
Samuel Drouet a, Christine O. Paul-Roth a
*
a Groupe Inge´nierie Chimique & Mole´cules pour le Vivant, ICMV-SCR-UMR-CNRS 6226, Universite´ de Rennes I, 35042 Rennes Cedex, France
b Institut National des Sciences Applique´es-INSA de Rennes, France
a r t i c l e i n f o
a b s t r a c t
Article history:
New symmetrical dendrimeric type super-porphyrin bearing sixteen fluorenyl donor groups sixteen
fluorenylporphyrin SOFP (1) have been synthesized and characterized. Preliminary photophysical
properties are reported; in comparison to the references first generation dendrimer tetra-
fluorenylporphyrin TOFP (2) bearing four peripheral fluorenyl and second generation dendrimer octa-
fluorenylporphyrin OOFP (3) bearing eight peripheral fluorenyl, the luminescence properties are slightly
improved. It is found that the excitation energy transfer occurs from the sixteen fluorenyl units to the
porphyrin core, following what the porphyrin emits intense red light.
Received 8 September 2009
Received in revised form
8 October 2009
Accepted 12 October 2009
Available online 4 November 2009
Keywords:
Fluorescence
Porphyrins
Ó 2009 Elsevier Ltd. All rights reserved.
Fluorene
Light harvesting
Red emission
1. Introduction
family of relevant porphyrins was studied in collaboration with
Williams.13 Surprisingly, this porphyrin TFP exhibited a high quan-
There has been great interest in the synthesis of porphyrin sys-
tems because the peripheral substituent on the macrocyclic core can
modulate the physical properties at will. Consequently, they present
wide potential applications in different fields: such as, for instance,
light harvesting, Organic Light-Emitting Diodes (OLEDs) or switches.
Light harvesting can be optimized by attaching four energy donor
dendrons to the porphyrin skeleton, to obtain an antenna system
comprising a central porphyrin unit linked to four peripheral photon-
harvesting hydrocarbon moieties.1–3 Recently a series of star-shaped
tum yields (24%), demonstrating the good capacity of the fluorenyl
units to enhance quantum yields by increasing the radiative process.
By the fact that TFP exhibits good red chromaticity and enhanced
emission efficiency, it is interesting to incorporate this compound in
the fabrication of Organic Light-Emitting Diodes (OLEDs), this work is
actually in progress.14 In this view, very recently, a density functional
theory (DFT) study on photophysical properties of the complete
family of porphyrin bearing fluorenyl arms synthesized by Paul-Roth
was accomplished.15 This work, done by Ren et al., provides some
useful information for the charge carrier transport properties of high
efficiency red light-emitting material by theoretical investigations.
The aim of the present work was to exploit this capacity of the
fluorenyl arms to enhance further fluorescence. So the synthesis of
a super-porphyrin bearing sixteen peripheral fluorenyl groups is
proposed and compared to the references first generation molecule
bearing four units (TOFP) and second generation bearing eight units
(OFP). The target is to obtain highly luminescent soluble organic
compounds, by the design of porphyrin possessing fluorenyl arms
porphyrins bearing pendant linear oligofluorene arms have been
6
reported.4,5 Indeed, Frechet had demonstrated that the antenna ef-
´
fect was facilitated in dendritic architectures versus the correspond-
ing linear case and reported the synthesis of porphyrin systems with
modified fluorenyl units as light-harvesting two-photon absorbing
chromophores.7,8 The same year, for tuning the optical properties of
polymers, the synthesis of hyperbranched polymers containing por-
phyrin core possessing fluorenyl arms has also been reported.9
We have previously reported the synthesis of porphyrin pos-
sessing four fluorenyl arms directly connected at the meso-positions
(TFP compound 4) and demonstrated that the ruthenium(II) com-
plexes are efficient catalysts.10 More recently, we focused on the
photophysical properties of such porphyrins11,12 and a complete
´
using Frechet’s style dendritic strategy. In more details, in this paper,
we present systems in which a 5,10,15,20-tetraphenylporphyrin
(TPP) is linked, via ether bridges, to four, eight and sixteen fluorenyl
donor moieties, compounds 2, 3 and 1, respectively (Fig. 1), and in
a second part preliminary photophysical results are reported and
compared to previous data of these compounds in order to un-
derstand better the energy transfer between the fluorenyl units and
the macrocyclic core.
* Corresponding author. Tel.: þ33 02 23 23 63 72; fax: þ33 02 23 23 56 37.
E-mail addresses: christine.paul@univ-rennes1.fr, christine.paul@insa-rennes.fr
(C.O. Paul-Roth).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.10.043

10694
S. Drouet, C.O. Paul-Roth / Tetrahedron 65 (2009) 10693–10700
O
O
O
O
O
H C
2
O
O
CH
2
O
O
CH
O
2
O
H C
2
O
N
H
N
H
N
N
O
O
H C
2
CH
O
2
O
O
O
O
O
H C
2
O
H C
2
O
O
O
SOFP
Compound 1
CH2
CH2
CH2
O
O
O
CH2
O
CH2
O
CH2
N
N
H
O
N
H
N
H
N
H
N
N
N
O
O
H2C
H2C
O
O
H2C
O
H2C
O
H2C
H2C
TOFP
OOFP
Compound 3
Compound 2
N
H
N
N
H
N
N
H
H
N
N
N
TFP
TPP
Compound 4
Compound 5
OMe
OH
OMe
OH
MeO
HO
OMe
OH
N
N
H
H
N
N
H
H
N
N
N
N
MeO
HO
OMe
OH
MeO
HO
OMe
OH
OOMePP
Compound 6
OOHPP
Compound 7
Figure 1. Compounds 1, 2, 3, 4, 5, 6, and 7.

S. Drouet, C.O. Paul-Roth / Tetrahedron 65 (2009) 10693–10700
10695
OMe
OH
OMe
OH
OH
MeO
HO
N
H
OMe
N
H
OH
BBr
3
N
N
H
N
H
N
N
N
MeO
HO
OMe
CH2Cl2
MeO
OMe
HO
OH
OOHPP (7)
OOMePP (6)
Yield 93 %
D
OH
D
OH
OH
D
HO
N
H
D
N
OH
N
H
N
N
N
H
H
N
N
D
HO
D
K CO
2
3
18-crown-6
D
D
HO
OH
OOHPP (7)
THF
4 days,
SOFP (1)
Yield 33 %
O
Br
O
O
O
D =
O
10
Scheme 1. Synthesis of porphyrins 6, 7 and SOFP 1.
2. Results and discussion
2.1. Synthesis
porphyrin possessing eight anchoring points is synthesized as well
as the new dendron 10. In a second time, four of these dendrons are
connected to the mother porphyrin core.
In more details, the intermediate porphyrin 7 (OOHPP), was
obtained from the prepared methylated porphyrin analog, porphy-
rin 6 (OOMePP) by reaction with BBr3 as illustrated in Scheme 1.16
The synthetic strategy developed for the preparation of these
dendrimeric compounds is a Frechet’s style condensation. First the
PPh
CBr
3
4
NaBH
4
O
CH
2
C
CH
2
CH Cl
Br
EtOH
H
2
2
OH
r.t., 1 h
0°C, 1 h
8
Yield 55 %
Yield 96 %
OH
OH
K2CO3
O
O
HO
18-crow-6
HO
acetone (12h)
Br
9
8
Yield 71 %
O
O
PPh3
CBr4
HO
THF
Br
O
O
0°C, 1 h
10
9
Yield 80 %
Scheme 2. Synthesis of dendrons 9 and 10.

10696
S. Drouet, C.O. Paul-Roth / Tetrahedron 65 (2009) 10693–10700
The 2-hydroxyl-methyl-fluorene was obtained by reduction of
commercial fluorene-2-carboxaldehyde and the corresponding al-
cohol was then brominated with carbon tetrabromide to obtain 2-
bromomethyl-fluorene 8. The detailed synthesis of these building
blocks was described earlier.17 First the alcoholic form of the den-
dron 9 was obtained by condensation from the previous prepared
bromide 8 and from commercial 5-hydroxymethyl-benzen-1,3-diol
in acetone using potassium carbonate as a base in presence of 18-
crown-6 (Scheme 2). Finally, the intermediate dendron 9 was
obtained pure as a white solid after purification in 71% yield. The
alcohol 9 was then brominated with carbon tetrabromide inTHFand
the desired brominated dendron 10 was obtained pure as a white
solid after flash chromatography in 80% yield.
The target super-porphyrin 1 (Fig. 1), containing 16 absorbing
donor chromophores in a multivalent dendritic configuration was
eventually synthesized from the prepared bromide dendron 10
(10 equiv) and OOHPP 7 (1 equiv) in dry THF using potassium
carbonate as a base in presence of 18-crown-6 (Scheme 2). The
fixation of all 16 donor chromophores in compound 1 was con-
firmed by matrix-assisted laser desorption ionization time-of-flight
mass spectrometry (MALDI-TOF MS) as well as by NMR. Compound
1 is soluble in most organic solvents but can be purified by pre-
cipitation and is well-behaved on silica gel chromatography. The
desired porphyrin 1 was thus obtained as a brown-violet solid
(33%).
notice that the absorption in the UV of the fluorenyl groups at
270 nm is as strong as the Soret band.
Figure 3 shows the absorption spectra of 1, 6, and 10. The ab-
sorption spectrum of 1 shows the characteristic peaks at 280 and
300 nm of compound 10 in addition to the porphyrin Soret band at
423 nm and less intense Q-bands, the first of which appear at
513 nm for compound 6. Obviously, the dendrons and the por-
phyrin core retain their individual characteristics. These consider-
ations indicate that this molecular pentad 1, in which the porphyrin
acceptor is linked, via spacers, to four donor dendrons, forms
a suitable choice for exploiting the antennae effect between pe-
ripheral units and the central core. Effectively, for this effect, it is
better to have a multicomponent structure in which the donors and
acceptors retain their individual characteristics. Elsewhere for
a realistic description of the photosynthetic antenna function,
a porphyrin-based model system should exhibit high local con-
centrations of the light-harvesting chromophores.
1,4
1,2
Br
Donor Chromophore 10
1
MeO OMe
MeO
MeO
OMe
OMe
0,8
0,6
0,4
0,2
0
Molecular structure of the target system (1)
In the conditions used, the non-substituted fluorenyl arm is
stable, but note that alkyl chains have often been introduced on the
position-9 of the fluorenyl units by other researchers to increase
their solubility. This is presently not necessary for compound 1.5
MeO OMe
Acceptor Chromophore 6
2.2. Photophysical properties
225
325
425
525
625
725
2.2.1. Electronic spectra. The UV–visible spectra of 1, 2, and 3 ex-
hibit an intense Soret band with a maximum absorption similar
around 423 nm (Fig. 2). This band is slightly red shifted compared
to 417 nm for TPP (5), but not as much as for TFP (4) (426 nm).
This tendency in red shifting is observed as well for the Q-bands.
Wavelength (nm)
Figure 3. Absorption spectra of 6 (red), 10 (blue), and 1 (green) in chloroform at room
temperature. The spectrum of 10 is normalized to the spectrum of 1 at 300 nm, while
the height of the Soret band at 420 nm in the spectrum of 6 is normalized to the height
of the Soret band of 1.
The
p–
p absorption in the UV range is clearly apparent, due to the
*
presence of fluorene. For compound 2, the four fluorene arms ab-
sorb in the UV range with a maximum absorption peak at 272 nm,
while for compound 3 possessing eight arms the absorption is
stronger with a maximum at 263 nm. These units were absorbing at
270 nm for new compound 1. For the super-porphyrin 1, we can
2.2.2. Emission spectroscopy. The emission spectrum of compound
1, after excitation in the Soret band reveals a strong red fluorescence
with a peak maximum at 656 nm and a big shoulder at 721 nm
(Fig. 4). For comparison, the emission spectrum of compound 2 is
1,1
1
0,9
0,8
0,7
0,6
0,5
0,4
0,3
0,2
0,1
0
240
340
440
540
640
740
240
340
440
540
640
740
Wavelength (nm)
Wavelength (nm)
Figure 4. Photoluminescence spectra of free ligands 1 (plain green), 2 (plain red) and 3
(plain blue) in CH2Cl2 solution (w1.0ꢁ10ꢂ6 M), at 25 ꢀC, the emission spectra were cut
above 800 nm. Excitation spectra of compounds 1 (dashed green), 2 (dashed red) and 3
(dashed blue) at 660 nm.
Figure 2. UV–visible absorption spectra for compounds 1 (green), 2 (red) and 3 (blue),
in CH2Cl2 at 25 ꢀC (w2.0ꢁ10ꢂ6 M for 1 and normalized to the same absorbance for 2
and 3).

S. Drouet, C.O. Paul-Roth / Tetrahedron 65 (2009) 10693–10700
10697
also reported, after excitation in the Soret band, a strong red emis-
sion at 663 nm and a weaker shoulder at 728 nm are observed
(Fig. 4). Concerning, compound 3, after excitation in the Soret band,
a strong red emission at 656 nm and a stronger shoulder at 721 nm
are observed. The emission profile for compounds 1 and 3 are quite
similar. The emission for compound 2 possessing only four fluorenyl
groups in the para position, is slightly red shifted.
indices of solvents is in this case not necessary]. The quantum yield
was calculated from the following equation:
2
Fs
FTPP
ð
Þ
ð
Þ
ð
¼
ꢁ Fs=FTPP ꢁ ATPP=As ꢁ nTPP=ns
Þ
In the above expression, Fs is the fluorescent quantum yield of
the new compound, F is the integration of the emission intensities,
n is the index of refraction of the solution, and A is the absorbance
of the solution at the exciting wavelength. The subscripts TPP and s
denote the reference (TPP) and unknown samples, respectively.22
Values of quantum yields of free ligands 1, 2, 3, 4, and 5 are
reported in Table 1. All measurements were obtained under an
argon atmosphere to limit photo-oxidative degradation (Table 1).
Compounds 1, 2 and 3 present a luminescence quantum yield (14,
10 and 13%, respectively), which is similar to that of the reference
compound 5 (12%). Further photophysical investigations will be
undertaken to rationalize these results.18
2.2.3. Energy transfer. The emission spectra of compound 1 show
that the fluorenyl donors transfer energy with high efficiency to the
porphyrin acceptor (Fig. 5). Excitation of 1 at 300 nm results mainly
in the red emission of porphyrins with a maximum at 656 nm. It is
noteworthy that the blue fluorenyl emission is almost completely
quenched, and emission is seen predominantly from the porphyrin.
Compound 1 shows nice red emission when excited at 300 nm or
423 nm. Efficiency of energy transfer in this complex process will
be studied in details.18
Table 1
Photophysical properties of the fluorenyl porphyrins 1, 2, and 3 in dilute CH2Cl2
solution at 298 K, and of 4 and 5, under the same conditions for comparison
423 nm
300 nm
Porphyrin
SOFP (1)
TOFP (2)
OOFP (3)
TFP (4)
TPP (5)
lmax/nma
Soret band
lem/nm
423
423
423
426
417
656, 721
0.14
663, 728
0.10
656, 721
0.13
663, 730
0.24
653, 721
0.12
b
Ff
a
Wavelengths of the absorption maxima in the Soret or B band region (400–
450 nm range).
b
Fluorescence quantum yields in degassed solution, using TPP in toluene as
standard, following excitation into the Soret bands.
Molecular structure of the target system
(1)
3. Conclusions
In summary, we have synthesized and characterized a new super-
porphyrin 1 bearing 16 fluorenyl pendant arms at the meso-positions.
The photophysical properties are compared to the references first
generation dendrimer bearing four units and second generation
bearing eight units. These porphyrins emit essentially red light after
selective UV or visible irradiation. In case of UV irradiation, these
systems comprising a central porphyrin like TPP linked to peripheral
photon-harvesting fluorene moieties have been shown to act as ef-
ficient antennae. Due to the flexibility of molecular design, dendritic
architectures allow site-specific positioning of multiple chromo-
phore units in three-dimensional space; we have found that a large,
spherical third-generation dendrimer porphyrin, upon exposure to
UV light, shows high energy transfer efficiency from the peripheral
aromatic fluorenyl units to the porphyrin core. These results suggest
that a judicious choice of meso-aryl dendrons can allow the proper-
ties of porphyrins to be optimized for OLEDs, both in terms of effi-
ciency and color tuning. Based on our recent results of anodic
electropolymerization of monomers 4,10 523, and 6,24,25 we now ex-
pect to obtain a polymeric 3D network composed of spherical
chromophores after connections of the 16 fluorenyl pendant arms.
This should allow growing a dendrimer-polymeric 3D structure from
such macrocycles, possessing several connecting points for each
monomer. This family of compounds constitutes therefore an in-
teresting building block to access new red emissive organic materials.
300
350
400
450
500
550
600
650
700
750
800
Wavelength (nm)
Figure 5. Fluorescence spectra of 1 in chloroform at room temperature under single
photon excitation conditions. A near complete quenching of the donor emission is
observed upon excitation of 1 at 300 nm (blue), resulting in a significant porphyrin
emission from 1, compared to direct emission of 1 at 423 nm (red).
The excitation spectrum of compound 1 around 660 nm reveals
that the strong emission from the Soret state is populated when the
fluorenyl band is excited. This indicates that excitation over all the
200–650 nm region leads to the population of the fluorescent ex-
cited states of the porphyrin, as the fluorene absorption becomes
apparent under such excitation conditions. For comparison, the
corresponding excitation spectra of compounds 1, 2, and 3 are
shown in Figure 4, and we can see a nicely regular enhancement in
the UV region due to the fluorenyl arms.
Thus for these compounds 1, 2, and 3, the luminescence can be
modulated in a large range of excitation wavelengths from UV to
red, to finally obtain the desired red emission.
4. Experimental
4.1. General
2.2.4. Fluorescence quantum yields. The fluorescence quantum
yields of these compounds were next determined by comparing
with a calibration standard of compound 5 (TPP) in degassed tol-
uene solution presenting a fluorescence quantum yield of 0.12,19
preferentially to a benzene solution with a fluorescence quantum
yield of 0.13.20 [In this latter case, different refractive indices of the
solvents used in the standard and sample must be corrected.21 In
consequence the correction made for the difference in refractive
All reactions were performed under argon and were magneti-
cally stirred. Solvents were distilled from appropriate drying agent
prior to use, CH2Cl2 from CaH2, CHCl3 from P2O5 and all other sol-
vents were HPLC grade. Commercially available reagents were used
without further purification unless otherwise stated. 1H NMR and

10698
S. Drouet, C.O. Paul-Roth / Tetrahedron 65 (2009) 10693–10700
H
6'
C
H
6'
5'
H
7'
C
5'
C
7'
H
4'
C
5''
C
8'
C
C
9'
4'
8''
C
H
O
4''
8'
H
3'
C
3'
H
C
B'
C
D'
C
9''
H
9'
C
B'
H
E'
C
E'
C
2'
H
C
9''
1'
H
H1
C
A'
C
D'
H
C
B'
1'
O
C
H
H'1
HO
H
H2
H
H'2
Compound 9
H
6'
H
C
7'
6'
H
5'
C
C
7'
5'
H
4'
C
8'
C
5''
H
C
8'
8''
C
C
4'
4''
1'
O
C
9'
H
H
C
C
H
9'
3'
3'
9''
H
B'
C
D'
C
H
B'
9''
E'
C
C
C
2'
E'
H
H1
C
A'
H
C
1'
D'
C
B'
O
C
H
H'1
Br
H
H2
H
H'2
Compound 10
H
6'
H
C
6'
5'
H
7'
C
5'
C
7'
H
4'
C
5''
C
8'
C
4'
C
C
1'
8''
4''
O
H
8'
H
E'
3'
C
3'
H
C
C
9'
B'
C
D'
9''
H
9'
C
B'
H
C
E'
C
2'
C
H
9''
H
H1
C
A'
C
D'
H
C
1'
B'
O
C
H
H'1
O
H
H2
H
H'2
O
H
H
3
2
H
B
H
E
C
D
C
C
C
C
C
B
A
E
2
3
C
C
C
1
4
D
D
C
C
C
C
20
19
5
B
N
H
O
C
H
B
6
C
C
C
C
18
17
7
8
N
N
O
C
C
C
16
9
H
N
C
10
15
D
C
C
11
D
14
C
C
12
13
Compound 1
Figure 6. Hydrogen and carbon atom-labeling for dendrons 9, 10 and for the porphyrin 1.

S. Drouet, C.O. Paul-Roth / Tetrahedron 65 (2009) 10693–10700
10699
13C NMR in CDCl3 were recorded using Bruker 200 DPX, 300 DPX
and 500 DPX spectrometers. The chemical shifts are referenced to
internal TMS. The assignments were performed by 2D NMR ex-
periments: COSY (Correlation Spectroscopy), HMBC (Heteronuclear
Multiple Bond Correlation) and HMQC (Heteronuclear Multiple
Quantum Coherence). UV spectra were recorded on UVIKON XL
from Biotek instruments. PL emission was recorded on a Photon
Technology International (PTI) apparatus coupled on an 814
Photomultiplier Detection System, Lamp Power Supply 220B and
MD-5020. Pyrrole and 2-fluorenecarboxaldehyde were purchased
from Aldrich and were used as received. References TFP¼tetra-
fluorenylporphyrin, TPP¼tetraphenylporphyrin. The hydrogen and
carbon atom-labeling scheme for the porphyrin ligand 1 as well as
for dendron 9 and 10 are shown in Figure 6.
porphyrin, 7 (74 mg, 0.09 mmol), K2CO3 (219 mg, 1.59 mmol) and
18-crown-6 (26 mg, 0.01 mmol), were dissolved in 20 mL of dry THF
and stirred under argon at reflux for four days. Then the reaction
mixture was cooled to room temperature and evaporated to dryness.
The crude product was partitioned between water (200 mL) and
dichloromethane (200 mL), the aqueous layer was extracted with
dichloromethane (200 mL), and the combined extracts were dried by
MgSO4 and evaporated to dryness. Purification by flash chromatog-
raphy eluting with 4:6 pentane/dichloromethane gave the super-
porphyrin 1, as a violet powder (150 mg, yield 33%).
1H NMR (assignments aided by COSY) (CDCl3):
d
8.85 (s, 8H,
3
3
0
pyrrole), 7.55 (d, JHH¼7.4 Hz, 16H, H5 ), 7.49 (d, JHH¼7.8 Hz, 16H,
4
0
0
H4 ), 7.45 (d, JHH¼2.2 Hz, 8H, HB), 7.35 (s, 16H, H1 ), 7.34 (d,
3
3
0
0
JHH¼7.4 Hz, 16H, H8 ), 7.22 (t, JHH¼6.7 Hz, 16H, H6 ), 7.16
3
3
0
0
(t, JHH¼7.3 Hz, 16H, H7 ), 7.15, (d, JHH¼7.1 Hz, 16H, H3 ), 7.04 (t,
4
4
4
0
4.2. Synthesis of the arms
JHH¼2.1 Hz, 4H, HE), 6.70 (d, JHH¼2.1 Hz, 16H, HB ), 6.59 (t,
0
0
0
JHH¼2.1 Hz, 8H, HE ), 5.07 (s, 16H, HH1–H1 ), 4.92 (s, 32H, HH2–H2 ),
0
00
4.2.1. Synthesis of 2-bromomethyl-fluorene (8) from 2-hydroxyl-
3.66 (s, 32H, H9 –9 ), ꢂ2.72 (br s, 2H, NH).
methyl-fluorene was described earlier17
.
1H NMR (200 MHz, CDCl3):
13C NMR (CDCl3):
d
160.30 (CD ), 157.91 (CD), 143.54 (C9 ),
0
00
3
3
00
00
7.81 (d, JHH¼8.0 Hz, 1H), 7.75 (d, JHH¼7.7 Hz, 1H), 7.59 (d,
143.32 (C4 ), 143.00 (br s, C1–4–6–9–11–14–16–19), 141.50 (C8 ),
3
3
3JHH¼8.8 Hz, 2H), 7.43 (d, JHH¼7.9 Hz, 1H), 7.38 (d, JHH¼8.0 Hz,
141.19 (C5 ), 135.13 (C2 ), 131.00 (br s, C2–3–7–8–12–13–17–18),
00
0
0
0
0
0
0
1H), 7.37 (s, 1H), 4.61 (s, 2H, CH2–Br), 3.94 (s, 2H, CH2fluorene).
126.68 (C7 ), 126.65 (C6 ), 126.28 (C3 ), 124.94 (C8 ), 124.26 (C1 ),
0
0
0
119.86 (C5 ), 119.76 (C4 ), 115.36 (CB), 106.45 (CB ), 102.42 (CE),
0
4.2.2. Synthesis of alcool 9. To a solution of the commercial 5-
hydroxymethyl-benzen-1,3-diol (0.98 g, 7.02 mmol) and 2-bromo-
methyl-fluorene 8 (4.00 g,15.44 mmol) in 20 mL of dry acetone was
added K2CO3 (3.87 g, 28.0 mmol) and 18-crown-6 (1.85 g,
7.02 mmol). This solution is stirred under argon at reflux during
12 h. The reaction mixture was cooled at room temperature, filtered
and evaporated to dryness. The crude product was partitioned
between water and CH2Cl2, and the organic phase was dried over
MgSO4 and evaporated to dryness. The residue was purified by
column chromatography on silica gel (CH2Cl2) to yield 2.47 g of
102.41 (C5–10–15–20), 101.86 (CE ), 70.38 (CH1), 70.31 (CH2), 36.67
0
(C9 ).
Anal. Calcd for C324H238N4O24$3CHCl3: C, 79.67; H, 4.93; N, 1.14.
Found: C, 79.50; H, 5.36; N, 0.29. MALDI-TOF MS calcd for
C324H238N4O24
:
4572.4645 [MH]þ, found 4575.9907 [MH]þ,
4398.4219 [MHꢂfluorenyl]þ, 4220.0283 [MHꢂ2fluorenyl]þ,
4039.8440 [MHꢂ3fluorenyl]þ. UV–vis (CH2Cl2): lmax/nm (10ꢂ3
e)
270 (421, fluorene), 304 (194, fluorene), 423 (433, Soret band), 517
(17, Q1), 552 (6, Q2), 590 (5, Q3), 647 (3, Q4).
a white solid (71%).
Acknowledgements
3
1H NMR (200 MHz, CDCl3):
d
7.81 (d, JHH¼7.5 Hz, 4H, H4 –5 ),
0
0
3
0
0
0
7.64 (s, 2H, H1 ), 7.57 (d, JHH¼7.1 Hz, 2H, H8 ), 7.46–7.26 (m, 6H, H3 –
The authors are grateful to S. Sinbandhit (CRMPO), G. Simon-
neaux and P. Le Maux (ICMV-UMR 6226) for their technical assis-
tance and helpful discussions.
0
0
0
0
0
6 –7 ), 6.69 (br s, 2H, HB ) 6.63 (br s, 1H, HE ), 5.15 (s, 4H, H2–2 ), 4.68
(d, 3JHH¼3.7 Hz, 2H, H1–1 ), 3.95 (s, 4H, H9 –9 ).
0
0
00
4.2.3. Synthesis of final dendron 10. To a THF solution (100 mL) of
alcohol 9 (1.60 g, 3.22 mmol) was added carbon tetrabromide
(1.28 g, 38.7 mmol) followed by the portion-wise addition of tri-
phenylphosphine (1.01 g, 38.7 mmol). The mixture was stirred at
0 ꢀC for 1 h, and 2 h at room temperature. The crude product was
partitioned between water (to neutralize CBr4) and CH2Cl2 then the
organic phase was dried over MgSO4 and evaporated to dryness.
The residue was purified by column chromatography on silica gel
References and notes
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(5:1 pentane/CH2Cl2) to give 1.44 g (80%) of 10 as a white solid.
3
1H NMR (200 MHz, CDCl3):
d
7.81 (d, JHH¼7.5 Hz, 4H, H4 –5 ),
0
0
3
0
0
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0
0
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0
0
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compound 10 (500 mg, 0.90 mmol), tetrakis (3,5-dihydroxyphenyl)-

10700
S. Drouet, C.O. Paul-Roth / Tetrahedron 65 (2009) 10693–10700
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