Porphyrins with four monodisperse oligocarbazole arms: Facile synthesis and photophysical properties

Article abstract of DOI:10.1021/jo702426r

(Chemical Equation Presented) A series of novel monodisperse, well-defined, star-shaped molecules T(OCAn)Ps (n = 2-6) with a central porphyrin core and four oligocarbazole arms are synthesized from the corresponding formyl-substituted oligocarbazoles via Adler reaction. The obtained star-shaped porphyrins are intrinsically two-dimensional nanosized molecules, and the diameter of compound T(OCA6)P is 7.4 nm, representing one of the largest known star-shaped conjugated systems. Their photophysical properties have been investigated by absorption and steady-state fluorescence spectroscopy, together with the corresponding monodisperse oligocarbazole aldehyde precursors. It is found that the light-harvesting capability of T(OCAn)Ps increases with the increasing length of the arms and reaches the maximum when n = 6. A selective excitation of the oligocarbazole arms leads to the typical emission from the porphyrin cores, indicating occurrence of photoinduced intramolecular energy transfer, and the energy transfer efficiency decreases from T(OCA2)P to T(OCA6)P owing to the Foerster energy-transfer process. Accordingly, the longest effective distance for Foerster energy transfer is estimated to be ca. 3 nm in our system. Such star-shaped porphyrins may find applications in photonic devices, with respect to their intense emission of red light. Notably, the monodisperse oligocarbazole aldehyde precursors give twisted intramolecular charge-transfer (TICT) excited states and luminescence in polar solvents with large Stokes shifts.

Full text of DOI:10.1021/jo702426r

Porphyrins with Four Monodisperse Oligocarbazole Arms: Facile
Synthesis and Photophysical Properties
Tinghua Xu, Ran Lu,* Xingliang Liu, Peng Chen, Xianping Qiu, and Yingying Zhao
State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin UniVersity,
Changchun 130012, People’s Republic of China
luran@mail.jlu.edu.cn
ReceiVed NoVember 12, 2007
A series of novel monodisperse, well-defined, star-shaped molecules T(OCAn)Ps (n ) 2-6) with a central
porphyrin core and four oligocarbazole arms are synthesized from the corresponding formyl-substituted
oligocarbazoles via Adler reaction. The obtained star-shaped porphyrins are intrinsically two-dimensional
nanosized molecules, and the diameter of compound T(OCA6)P is 7.4 nm, representing one of the largest
known star-shaped conjugated systems. Their photophysical properties have been investigated by absorption
and steady-state fluorescence spectroscopy, together with the corresponding monodisperse oligocarbazole
aldehyde precursors. It is found that the light-harvesting capability of T(OCAn)Ps increases with the
increasing length of the arms and reaches the maximum when n ) 6. A selective excitation of the
oligocarbazole arms leads to the typical emission from the porphyrin cores, indicating occurrence of
photoinduced intramolecular energy transfer, and the energy transfer efficiency decreases from T(OCA2)P
to T(OCA6)P owing to the Fo¨rster energy-transfer process. Accordingly, the longest effective distance
for Fo¨rster energy transfer is estimated to be ca. 3 nm in our system. Such star-shaped porphyrins may
find applications in photonic devices, with respect to their intense emission of red light. Notably, the
monodisperse oligocarbazole aldehyde precursors give twisted intramolecular charge-transfer (TICT)
excited states and luminescence in polar solvents with large Stokes shifts.
Introduction
tuning the electronic structures as well as the bandgaps of the
oligomers.2,7,8 Therefore, the monodisperse conjugated star-
shaped systems, on one hand, may become possible alternatives
to linear conjugated oligomers in optoelectronic applications.9
On the other hand, the communication between the conjugated
arms and core may result in some unique functionality.10
Because of the outstanding photophysical and redox properties
porphyrins have been recently widely used as building blocks
in the construction of π-conjugated molecules, possessing
potential applications in molecular electronics, photochemical
energy conversion and storage, switches, etc.6a,10,11 As reported
by Bo and co-workers, porphyrin was employed as the core to
Star-shaped molecules, in which linear arms are joined
together by a central core, have received much attention in the
past decade,1 specially the star-shaped architecture with con-
jugated moieties as the arms would exhibit novel electrical,
optical, and morphological properties, depending on the structure
of the central core. Nowadays, monodisperse linear π-conjugated
oligomers (MCOs) bearing well-defined and uniform structures
are of great interest in materials science,2 due to their potential
applications in organic light emitting diodes,3 field effect
transistors,4 photovoltaic cells,5 and molecular wires in the fields
of molecular electronics as well as in light-harvesting molecular
antenna-type architecture.6 Moreover, MCOs not only become
ideal models for understanding the structure-property relation-
ships of the corresponding conjugated polymers, but also favor
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10.1021/jo702426r CCC: $40.75 © 2008 American Chemical Society
Published on Web 01/30/2008
J. Org. Chem. 2008, 73, 1809-1817
1809

Xu et al.
SCHEME 1. Molecular Structures of T(OCAn)Ps 1-5
construct star-shaped oligofluorenes, in which the photoinduced
intramolecular energy transfer from oligofluorene arms to the
core could be intensified with increased conjugated length of
the oligofluorene arms.10c More recently, Meijer et al. introduced
oligo(p-phenylene vinylene) (OPV) into the porphyrin core, and
studied the energy and electron transfer in the π-conjugated
assemblies based on OPV-Zn porphyrin, OPV-H2 porphyrin,
and C60.10e,i Such model systems not only contribute to our
understanding of photosynthesis, but also provide an entry to
molecular electronics and molecular optics, which could enable
us to realize transport of information on a molecular level by
ultrafast energy- and electron-transfer processes, which highly
depend on the morphology of molecules.6a,12 Furthermore,
carbazoles are also alluring molecules on account of their special
photoelectric properties, for instance, the intense luminescence
favoring them to be used in OLEDs as blue emitters, and the
facile oxidation processes making them suitable as hole carri-
ers.13 In addition, carbazole can be readily functionalized at 3-,
6-, or 9-positions and covalently linked to other molecular
moieties,11h,14-15 which prompted us to prepare a series of
monodisperse oligocarbazoles linked via 3,9-positions (OCAns).15a
To the best of our knowledge, there is no report on the star-
shaped molecules with monodisperse oligocarbazoles as the
arms. Herein, we present the strategy toward novel nanosized
star-shaped porphyrins T(OCAn)Ps 1-5 incorporating OCAns
as arms (as shown in Scheme 1). In the case of compound 5,
its molecular diameter reaches 7.4 nm, representing one of the
largest known star-shaped conjugated systems. In addition, the
photophysical investigation reveals that efficient photoinduced
intramolecular energy transfer occurs from OCAns arms to the
porphyrin core, and the energy transfer efficiency decreases with
the increasing length of the oligocarbazole arms. The obtained
porphyrins can emit intense red light. So these functionalized
porphyrins may find applications in optical devices.
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Results and Discussion
Syntheses of OCAn-CHO 6-10. The formyl-substituted
oligocarbazoles 6-10 have been synthesized via Ullmann
condensation reaction between p-iodobenzaldehyde and 3,9-
linked monodisperse oligocarbazoles 13, 15, 17, 19, and 21,
whose synthetic routes are shown in Scheme 2. 3-Iodo-9-
tosylcarbazole 11, as a key compound to prolong the length of
the oligocarbazoles, was prepared according to the literature.16
The Ullmann condensation reaction between compound 11 and
carbazole, which was catalyzed by Cu2O in N,N-dimethyl-
acetamide (DMAc) at 160 °C for 24 h, gave 12 in a yield of
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1810 J. Org. Chem., Vol. 73, No. 5, 2008

Porphyrins with Four Monodisperse Oligocarbazole Arms
SCHEME 2. Syntheses of Compounds 13, 15, 17, 19, and 21
83%.11h,14c-f,15 Compound 13 was readily obtained by cleaving
N-Ts bond of compound 12 in the mixture of THF/DMSO
(2/1, v/v), H2O, and KOH under reflux for 3-4 h in a high
yield of 95%. As reported, the reactivity of the N-H bond in
the carbazole under the Ullmann condensation reaction de-
creased with the increasing number of carbazole units in
OCAns.14c-f,15 Therefore, the Ullmann reactions between com-
pound 11 and dicarbazole 13 were carried out at higher
temperature (190 °C) for 24 h to afford compound 14 in a yield
of 80%, followed by the cleavage of N-Ts bond under the basic
environment to give compound 15. By using alternative Ullmann
condensation and basic hydrolysis reactions, compounds 17, 19,
and 21 were obtained in yields of ca. 69% for two steps.
Subsequently, the monodisperse oligocarbazole aldehydes
(OCAn-CHO) 6-10 could be easily synthesized from dicarba-
zole 13, tricarbazole 15, tetracarbazole 17, pentacarbazole 19,
and haxacarbazole 21 via Ullmann condensation reaction with
p-iodobenzaldehyde, and the synthetic routes were shown in
Scheme 3. We have previously found that the aldehyde group
could be partially oxidized by Cu2O at higher temperature under
the Ullmann condensation condition, for example, it was
oxidized completely over 190 °C for 24 h.15d However, we
succeeded in preparing the formyl-substituted oligocarbazoles
6-10 at lower temperature (165-170 °C) for 18 h in yields of
65-81%. As mentioned above, the Ullmann condensation
reactions between 3-iodo-9-tosylcarbazole and compounds 13,
15, 17, 19, and 21 were carried out at 190 °C for 24 h due to
the lower reactivity of oligocarbazoles. Concerned with the
higher reactivity of p-iodobenzaldehyde than 3-iodo-9-tosyl-
carbazole owing to the electron-pulling effect of the aldehyde
group, the reaction between p-iodobenzaldehyde and oligocar-
bazoles was carried out at lower temperature to avoid the
oxidation of the aldehydes.
Syntheses of T(OCAn)Ps (n ) 2-6). The syntheses of the
star-shaped porphyrins with monodisperse oligocarbazole arms
T(OCAn)Ps were shown in Scheme 4. The obtained aldehydes
6-10 were converted into the corresponding porphyrins T(O-
CAn)Ps 1-5 under the modified Adler-Longo reaction condi-
tion in xylene by using p-nitrobenzoic acid as the catalyst in
yields of 18%, 20%, 25%, 23%, and 26%, respectively.15b,17
The yields were higher than those of dendritic carbazole-based
porphyrins previously reported by our group15b because of the
less sterically hindered effect of the carbazole aldehydes 6-10
than that of the dendritic ones. The reaction time was prolonged
from 6 to 48 h for the preparation of compounds 1-5 due to
the decreased reactivity of formyl-substituted oligocarbazoles
with increasing number of carbazole units. For instance, the
formation of T(OCA2)P 1 from compounds 6 needed 6 h, while
T(OCA3)P 2 and T(OCA4)P 3 were obtained over 15 and 24
h, respectively. In the case of T(OCA5)P 4 and T(OCA6)P 5,
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J. Org. Chem, Vol. 73, No. 5, 2008 1811

Xu et al.
SCHEME 3. Syntheses of OCAn-CHO 6-10
SCHEME 4. Syntheses of T(OCAn)Ps 1-5
molecular weight from compound 1 to 5, and all the peaks were
symmetrical and monomodal with a polydispersity index of
1
1.03-1.08. The H NMR and the MALDI-TOF mass spectra
are given in the Supporting Information.
Photophysical Properties of OCAn-CHO 6-10. As shown
in Figure 2, the absorption spectra of OCAn-CHO 6-10 in
dichloromethane exhibit intense transitions in the UV region,
for instance, a broad absorption band appears at ca. 343 nm for
each compound, and other broad bands in the range of 250-
290 nm derive from the carbazole-centered transitions. Due to
the large torsion angle of the carbazole units, no significant
enlargement of the conjugation length of OCAn-CHO is
observed, which is in accordance with the slight red-shift with
increasing number of carbazole units. The molar extinction
coefficient at 294 nm increases linearly depending on the OCAn-
CHO length from dimer to hexamer, while no deviations from
the slope are observed in Figure S47 (Supporting Information)
(the absorption data are also listed in Table 1). It suggests that
in dilute solution (1 × 10-5 mol/L) neither intermolecular
aggregation (according with Beer’s law) nor intramolecular π-π
interactions between the conjugated arms happen.19 Besides the
carbazole-centered transitions, the absorption band between 300
and 400 nm may also be partly contributed to the charge-transfer
(CT) transitions because it is solvent dependent. Accordingly,
it exhibits a tail in CH2Cl2 and THF (probably due to the CT
contribution), and disappears in nonpolar solvent, notably, it
becomes structured in hexane (Figure S48, Supporting Informa-
tion). These absorption spectral behaviors are quite similar to
those of the dendritic carbazole aldehydes reported by Dehaen
et al.11h Since the oligocarbazoles as strong electron-donor
groups are decorated with an electron-acceptor unit (benzalde-
hyde) in compounds 6-10, the CT transitions could be observed
in polar solvents. As it is known that dendritic carbazole
aldehydes can give TICT excited state and luminescence in polar
even if the reaction time was prolonged to 48 h, a small quantity
of aldehyde precursors still remained. According to the previous
reports, the Adler condensation conditions are harsh and the
yields are low, but we obtained the functionalized porphyrins
in moderate yields in this application. We have also employed
the Lindsey reaction to prepare these star-shaped porphyrins,
but only traces of T(OCAn)Ps were obtained with use of
trifluoroacetic acid as the catalyst in CH2Cl2 in the dark,
followed by DDQ oxidation and Et3N neutralization.18
Notably, the obtained star-shaped porphyrins T(OCAn)Ps
1-5 bear no alkyl groups, but they are well soluble in common
organic solvents, such as chloroform, CH2Cl2, chlorobenzene,
toluene, xylene, mesitylene, and THF. The diameters of T(O-
CAn)Ps 1-5 are estimated from the optimized geometry (Cerius
2.0, Figures S49-S53) to be 3.4, 4.5, 5.4, 6.5, and 7.4 nm,
respectively, and 5 represents one of the largest known star-
shaped molecules. All the intermediates and final products were
purified by column chromatography on silica gel, and character-
1
ized by FT-IR, H NMR spectroscopy, C, H, and N elemental
analyses, and MALDI-TOF mass spectrometry. Meanwhile, the
purity of T(OCAn)Ps 1-5 was also confirmed by gel permeation
chromatography (GPC) with THF as eluent. As shown in Figure
1, the retention time decreased gradually with the increasing
(18) Lindsey, J. S.; Schreyman, L. C.; Hsu, H. C.; Kearney, P. C.;
Marguerettaz, A. M. J. Org. Chem. 1987, 52, 827-836.
(19) Cho, S.; Li, W.-S.; Yoon, M,-C.; Ahn, T. K.; Jiang, D.-L.; Kim, J.;
Aida, T.; Kim, D. Chem.-Eur. J. 2006, 12, 7576-7584.
1812 J. Org. Chem., Vol. 73, No. 5, 2008

Porphyrins with Four Monodisperse Oligocarbazole Arms
FIGURE 1. GPC elution traces of 1-5 with THF as eluent.
FIGURE 3. Room temperature emission spectra of the OCAn-CHO
6-10 in CH2Cl2 (1 × 10-5 mol/L).
FIGURE 2. Absorption spectra of OCAn-CHO 6-10 in CH2Cl2 (1
× 10-5 mol/L).
FIGURE 4. Room temperature normalized emission spectra of OCA2-
CHO 6 in solvents with different polarities.
TABLE 1. Absorption and Fluorescent Emission Data in CH2Cl2
for OCAn-CHO 6-10
λem
Stokes
(nm) shift (nm)
max
compd
λabsmax (nm) (ꢀ, M-1 cm-1
)
6
7
8
9
10
261 (45400), 294 (30500), 344 (19300)
263 (61300), 294 (47800), 344 (21800)
264 (83400), 294 (69200), 345 (26500)
265 (104300), 294 (89000), 344 (31700)
267 (125000), 294 (109200), 345 (35800)
525
524
523
523
524
181
180
178
179
179
solvents,11h so TICT emission of OCAn-CHO 6-10 could be
expected, which is further proposed by the following evidence:
(i) the large Stoke’s shift (Table 1), which rules out a singlet
π-π* emission, and (ii) the broad shape of the emission spectra
(Figure 3). In particular, the solvent dependence of the emission
can also support the large polar character of the emitting excited
state, which is in good agreement with the TICT assignment.
Taking compound 6 as an example, as shown in Figure 4 we
observe significant red-shift of the emission band from 385 nm
in hexane to 550 nm in DMSO with increasing the solvent
polarity. The emission spectrum becomes structured in hexane,
similar to that of the carbazole-centered compound, so it is
deemed that the excited state contributive to the emission in
hexane is the LE (locally excited) one. It is well-known that
the TICT state is very unlikely in nonpolar solvent, where it
can hardly be stabilized.11h,20 To demonstrate the large confor-
mational change (as in the TICT formation) on the excited state
surface prior to the emission, we present the plotting of the
FIGURE 5. Lippert-Mataga plot: fluorescence emission maximum
energy of OCA2-CHO 6 as a function of solvent polarity.
emission maximum energy as a function of the Lippert solvent
polarity in Figure 5.21 In such “Lippert-Mataga” plots,11h,22 the
slope can be used to evaluate the variation in dipole moment
upon excitation, and the break in the linear relationship indicates
the presence of two different excited states. Accordingly, the
deviation of the emission maximum energy in hexane from the
linear relationship followed by the emission energy in other
solvents can further support that in compounds 6-10 the LE
state is responsible for the emission in nonpolar solvents and
the TICT state is contributable to the emission in polar solvents.
(20) (a) Jones, G., II; Jackson, W. R.; Choi, C.; Bergmark, W. R. J.
Phys. Chem. 1985, 89, 294-300. (b) Nad, S.; Pal, H. J. Phys. Chem. A
2001, 105, 1097-1106.
(21) Reichardt, C. Chem. ReV. 1994, 94, 2319-2358.
(22) Mataga, N.; Kubota, T. Molecular Interactions and Electronic
Spectra; Dekker: New York, 1970.
J. Org. Chem, Vol. 73, No. 5, 2008 1813

Xu et al.
FIGURE 7. Emission spectra of T(OCAn)Ps 1-5 in THF (1 × 10-6
mol/L, λex ) 294 nm).
FIGURE 6. Normalized UV/vis absorption spectra of 1-5 in THF.
TABLE 2. Photophysical Data for TPP and T(OCAn)Ps 1-5 in
THF
recorded at 294 nm, and the ΦET values for T(OCAn)Ps 1-5
are found to be 100%, 100%, 95%, 90%, and 76%, respectively
(Table 2).23 The effective number of carbazoles which can
transfer the light-harvesting energy to the porphyrin core in each
oligocarbazole arm of compounds 1-5 is calculated as 2.0, 3.0,
3.8, 4.5, and 4.6 (the value is obtained from the multiplication
between the number of carbazoles in each arm and ΦET),
respectively. The observation that the energy-transfer efficiency
decreases with the increasing length of carbazole arms can be
explained by the Fo¨rster mechanism of energy transfer, and the
distance between the donor and the acceptor plays an important
role in the energy transfer. Generally, the Fo¨rster energy transfer
may occur when the distance between energy donor and acceptor
is in the range of 10-100 Å, and such resonance energy transfer
depends on 1/R6, where R is the distance of the donor-acceptor
separation.12 As the size of star-shaped molecules increases, two
competing factors, including the increasing number of carbazole
units and the distance between the core and the end-groups,
become prevalent. In another words, the enlargement of the
molecular length allows for higher light-harvesting due to more
light-collecting sites; however, to some extent, it is expected
that R will become too large to sustain the energy transfer
efficiency. It is thus necessary to reach a balance between the
light-harvesting capacity of OCAns arms and the energy transfer
efficiency to the core. The distances between the outermost
carbazole and the center of the porphyrin core are obtained by
Cerius 2.0 to be 1.5, 2.0, 2.4, 3.0, and 3.5 nm, respectively
(Figures S49-S53).24 As demonstrated in the context, it is
estimated that the longest distance for Fo¨ster energy transfer is
ca. 3 nm in T(OCAn)Ps 1-5. The emission spectra of T(OCAn)-
Ps 1-5 reveal that these star-shaped molecules can emit intense
red light (Figure 7), and the fluorescence quantum yields (ΦF)
of 1-5 in THF are determined by using TPP (ΦF ) 0.11) as
the standard. The ΦF values of 1-5 are in the range of 0.145-
0.173 (Table 2), higher than that of TPP. Since the light energy
absorbed by OCAns arms can be transferred to the porphyrin
core, the emission intensity (λex ) 294 nm) of the porphyrin
core is correlated to the effective carbazole number in energy
transfer and the ΦF of the star-shaped molecules. The relative
emission intensity for 1-5 is estimated as 1:1.4:1.8:2.1:1.9,
which is the ratio of the values from the effective carbazole
λabsmax (nm)
λemmax (nm)a
ΦETb (%)
ΦF
c
compd
TPP
T(OCA2)P
T(OCA3)P
T(OCA4)P
T(OCA5)P
T(OCA6)P
416
651, 717
655, 720
655, 722
656, 721
655, 720
654, 721
0.110
0.173
0.170
0.167
0.157
0.145
294, 343, 423
294, 343, 423
294, 344, 423
294, 344, 423
294, 345, 423
100
100
95
90
76
a Excited at 294 nm. b Energy transfer efficiency (ΦET) was calculated
by comparing the absorption with the excitation spectra of star-shaped
porphyrins by monitoring the emission of the porphyrin core (655 nm).
c The fluorescence quantum yields were determined against TPP in THF
(ΦF ) 0.110, λex ) 423 nm) as the standard.
Photophysical Properties of T(OCAn)Ps 1-5. The photo-
physical data for T(OCAn)Ps 1-5 are listed in Table 2. Figure
6 shows the absorption spectra of compounds 1-5 in THF; we
observe several absorption bands in visible region, including
four Q-bands in the range of 500-700 nm (consistent with the
free-base porphyrin), together with the Soret band at 423 nm,
and others in the UV region (250-350 nm) due to the carbazole
units. With the increasing length of the arms in these star-shaped
molecules, the absorbance of carbazole units is clearly propor-
tional to their increased number in each molecule, which
indirectly reflects the structural flawlessness or perfection of
the as-synthesized star-shaped porphyrins. Meanwhile, neither
distinct spectral shift nor spectral broadening of the absorption
bands for carbazole units as well as the porphyrin core is
observed. Thus, it provides an opportunity to study the intramo-
lecular energy transfer properties by selectively exciting the
oligocarbazole arms, whose emission band overlaps the absorp-
tion band of the porphyrin core. As shown in Figure 7, on
excitation at 294 nm, T(OCAn)Ps 1-5 give strong emission
bands at ca. 655 and 720 nm attributable to the emission of
porphyrin cores, and weak emissions at ca. 430 nm to the
OCAns. Since the porphyrin cannot emit red light under
excitation at 294 nm, we conclude that intramolecular energy
transfer from oligocarbazole units to porphyrin cores (energy
trap) occurs. The light-harvesting ability is improved from 1 to
5 on account of multiplying the number of carbazole units
(energy-collecting sites) and reaches the maximum when n )
6, whereas the emission intensity of T(OCAn)Ps 1-5 is
enhanced with the increasing length of OCAns arms except for
compound 5. The lower emission intensity of compound 5 than
4 might depend on its lower efficiency of energy transfer and
lower fluorescence quantum yield, which will be discussed
below. The energy transfer efficiency (ΦET) can be estimated
by comparing the UV/vis spectrum with the excitation spectrum
(23) (a) Stryer, L.; Haugland, R. P. Proc. Natl. Acad. Sci. U.S.A. 1967,
58, 719-726. (b) Devadoss, C.; Bharathi, P.; Moore, J. S. J. Am. Chem.
Soc. 1996, 118, 9635-9644. (c) Jiang, D.-L.; Aida, T. J. Am, Chem. Soc.
1998, 120, 10895-10901.
(24) Rappe´, A. K.; Casewit, C. J.; Colwell, K. S.; Goddard, W. A., III;
Skiff, W. M. J. Am. Chem. Soc. 1992, 114, 10024-10035.
1814 J. Org. Chem., Vol. 73, No. 5, 2008

Porphyrins with Four Monodisperse Oligocarbazole Arms
mL of H2O and the mixture was stirred for 20 min. The crude
product was collected by filtration and purified by chromatography
(silica gel, petroleum ether) to give 3.2 g (81%) of a light-yellow
solid, mp 142.0-144.0 °C. IR (KBr, cm-1): a strong peak at 1692.8
number multiplying ΦF. That is in agreement with the observa-
tion of why the emission intensity of compound 5 is lower than
that of compound 4.
1
cm-1 is the νs of a CdO moiety. H NMR (500 MHz, CDCl3) δ
Conclusions
10.19 (s, 1 H, -CHO), 8.33 (s, 1 H), 8.24-8.21 (dd, J ) 5.5, 4.5
Hz, 4 H), 8.15 (d, J ) 8.0 Hz, 1 H), 7.92 (d, J ) 8.0 Hz, 2 H),
7.72 (d, J ) 9.0 Hz, 1 H), 7.62-7.59 (t, 2 H), 7.55-7.52 (t, 1 H),
7.47-7.38 (m, 5 H), 7.35-7.32 (t, 2 H) (see Figures S5 and S6,
Supporting Information). MALDI-TOF: calcd 436.5, found 437.1
(see Figure S7, Supporting Information). Anal. Calcd for
C31H20N2O: C 85.30, H 4.62, N 6.42. Found: C 85.45, H 4.69, N
6.32.
We have designed and synthesized five soluble monodisperse
star-shaped molecules with a porphyrin central core function-
alized with oligocarbazole arms T(OCAn)Ps 1-5. The diameter
of compound 5 is 7.4 nm, to the best of our knowledge, which
represents one of the largest known conjugated star-shaped
systems. The present synthetic strategy provides a useful method
for the preparation of porphyrins with various functional arms.
Because the emission band of monodisperse oligocarbazoles
overlaps the absorption of the porphyrin, efficient photoinduced
intramolecular energy transfer occurs from oligocarbazole arms
to the porphyrin core. The energy transfer efficiency decreases
with increasing length of the OCAns arms, although the light-
harvesting ability of T(OCAn)Ps increases with increasing
number of carbazole units (the light-harvesting ability reaches
a maximum when n ) 6), due to Fo¨rster energy-transfer
mechanism. We estimate the longest distance for Fo¨rster energy
transfer is ca. 3 nm in such systems. Meanwhile, the obtained
star-shaped porphyrins could emit intense red light with high
fluorescence quantum yields, so they might be good candidates
for photonic devices.
3-(3-(9H-Carbazol-9-yl)-9H-carbazol-9-yl)-9-tosyl-9H-carba-
zole (14). By following the synthetic procedure for compound 12,
and using compound 13 (7.0 g, 21.1 mmol), 3-iodo-9-tosylcarbazole
11 (10.5 g, 23.5 mmol), Cu2O (6.0 g, 42.0 mmol) ,and DMAc (30
mL) as reagents, and adopting the Ullmann reaction condition at
190 °C in oil bath for 24 h, 11.0 g (80%) of compound 14 was
obtained after recrystallization from EtOH:THF (1:1, v/v) as a white
1
solid, mp 183.0-185.0 °C. H NMR (500 MHz, CDCl3) δ 8.60
(d, J ) 9.0 Hz, 1 H), 8.41 (d, J ) 8.0 Hz, 1 H), 8.31 (s, 1 H),
8.20-8.13 (m, 4 H), 7.95 (d, J ) 7.5 Hz, 1 H), 7.84 (d, J ) 8.0
Hz, 2 H), 7.76-7.74 (m, 1 H), 7.62-7.55 (m, 3 H), 7.50-7.41
(m, 7 H), 7.35-7.29 (m, 3 H), 7.22 (d, J ) 8.5 Hz, 2 H), 2.34 (s,
3 H, -CH3) (See Figures S8 and S9, Supporting Information). Anal.
Calcd for C43H29N3O2S: C 79.24, H 4.48, N 6.45. Found: C 79.14,
H 4.53, N 6.44.
9-(9H-Carbazol-3-yl)-3-(9H-carbazol-9-yl)-9H-carbazole (15).
By following the synthetic procedure for compound 13, and using
compound 14 (9.0 g, 13.8 mmol), KOH (10.0 g, 0.179 mol), THF
(40 mL), DMSO (20 mL), and H2O (5 mL) as solvents, 6.5 g (95%)
of compound 15 was obtained after chromatography (silica gel,
petroleum ether/ethyl acetate ) 3:1, v/v) as a white solid, mp
Experimental Section
9-(9-Tosyl-9H-carbazol-3-yl)-9H-carbazole (12). Carbazole (5.0
g, 0.03 mol), 3-iodo-9-tosylcarbazole 11 (11.0 g, 0.025 mol), Cu2O
(7.0 g, 0.049 mol), and DMAc (25 mL) were added sequentially
into a seal-tube under nitrogen atmosphere and heated to 160 °C
in an oil bath for 20 h. Then the mixture was cooled to room
temperature and filtrated. The filtrate was poured into 500 mL of
H2O and the mixture was stirred for 20 min. The crude product
was collected by filtration and recrystallized from EtOH:THF (1:
1, v/v) to give 10.0 g (83%) of a white solid, mp 173.0-175.0 °C.
1H NMR (500 MHz, CDCl3) δ 8.54 (d, J ) 8.5 Hz, 1 H), 8.40 (d,
J ) 8.5 Hz, 1 H), 8.18 (d, J ) 7.5 Hz, 2 H), 8.09 (s, 1 H), 7.89 (d,
J ) 7.5 Hz, 1 H), 7.82 (d, J ) 7.5 Hz, 2 H), 7.67 (d, J ) 9.0 Hz,
1 H), 7.58-7.55 (t, 1 H), 7.39 (m, 5 H), 7.32-7.29 (t, 2 H), 7.21
(d, J ) 9.0 Hz, 2 H), 2.34 (3 H, s, -CH3) (see Figures S1 and S2,
Supporting Information). Anal. Calcd for C31H22N2O2S: C 76.52,
H 4.56, N 5.76. Found: C 76.44, H 4.58, N 5.90.
1
193.0-195.0 °C. H NMR (500 MHz, CDCl3) δ 8.31 (s, 3 H),
8.19 (d, J ) 7.0 Hz, 2 H), 8.15 (d, J ) 7.5 Hz, 1 H), 8.10 (d, J )
6.5 Hz, 1 H), 7.70-7.68 (d, J ) 6.5 Hz, 1 H), 7.65-7.63 (d, J )
7.0 Hz, 1 H), 7.54-7.42 (m, 10 H), 7.30 (s, 4 H) (see Figure S10,
Supporting Information). MALDI-TOF: calcd 497.6, found 497.8
(see Figure S11, Supporting Information). Anal. Calcd for
C36H23N3: C 86.90, H 4.66, N 8.44. Found: C 86.81, H 4.70, N
8.26.
4-(3-(3-(9H-Carbazol-9-yl)-9H-carbazol-9-yl)-9H-carbazol-9-
yl)benzaldehyde (7). By following the synthetic procedure for
compound 6, and using compound 15 (2.0 g, 4.0 mmol), 4-iodo-
benzaldehyde (1.4 g, 6.0 mmol), Cu2O (1.2 g, 8.3 mmol), and
DMAc (8 mL) as reagents, 1.8 g (74%) of compound 7 was
obtained after chromatography (silica gel, petroleum ether/ethyl
acetate ) 3:1, v/v) as a light-yellow solid, mp 195.0-197.0 °C.
IR (KBr, cm-1): a strong peak at 1699.9 cm-1 is the νs of a CdO
9-(9H-Carbazol-3-yl)-9H-carbazole (13). Compound 12 (9.5
g, 0.02 mol) was dissolved in THF (40 mL), DMSO (20 mL), and
H2O (6 mL), then KOH (12.0 g, 0.214 mol) was added. The mixture
was refluxed for 4 h (monitored by TLC). Then THF was
completely removed from the mixture by distillation. Then the
residuals were cooled to room temperature, neutralized by HCl,
and poured into 400 mL of water to give a white solid. The crude
product was purified on silica gel with petroleum ether/ethyl acetate
(3:1, v/v) as eluent to afford 6.2 g (95%) of a white solid, mp:
1
moiety. H NMR (500 MHz, CDCl3) δ 10.17 (s, 1 H, -CHO),
8.39 (s, 1 H), 8.33 (m, 1 H), 8.23-8.15 (m, 6 H), 7.91 (d, J ) 8.5
Hz, 2 H), 7.50 (d, J ) 9.0 Hz, 1 H), 7.68-7.66 (d, J ) 8.5 Hz, 1
H), 7.59-7.52 (m, 4 H), 7.49-7.45 (m, 2 H), 7.43-7.38 (m, 5 H),
7.35-7.29 (m, 3 H) (see Figures S12 and S13, Supporting
Information). MALDI-TOF: calcd 601.7, found 602.0 (see Figure
S14, Supporting Information). Anal. Calcd for C43H27N3O: C 85.83,
H 4.52, N 6.98. Found: C 85.80, H 4.57, N 7.01.
1
210.0-211.0 °C. H NMR (500 MHz, CDCl3) δ 8.25 (s, 1 H),
8.22-8.18 (m, 3 H), 8.05 (d, J ) 6.5 Hz, 1 H), 7.62 (s, 1 H),
7.56-7.49 (m, 3 H), 7.40 (m, 4 H), 7.29 (m, 3 H) (see Figure S3,
Supporting Information). MALDI-TOF: calcd 332.4, found 331.3
(see Figure S4, Supporting Information). Anal. Calcd for
C24H16N2: C 86.72, H 4.85, N 8.43. Found: C 86.75, H 4.67, N
8.49.
3-(3-(3-(9H-Carbazol-9-yl)-9H-carbazol-9-yl)-9H-carbazol-9-
yl)-9-tosyl-9H-carbazole (16). By following the synthetic procedure
for compound 12, using compound 15 (10.0 g, 0.02 mol), 3-iodo-
9-tosylcarbazole 11 (10.0 g, 0.022 mol), Cu2O (6.0 g, 0.042 mol),
and DMAc (30 mL) as reagents, and adopting the Ullmann reaction
condition at 190 °C in an oil bath for 24 h, 12.0 g (73%) of
compound 16 was obtained after recrystallization from EtOH:THF
4-(3-(9H-Carbazol-9-yl)-9H-carbazol-9-yl)benzaldehyde (6).
Compound 13 (3.0 g, 9.0 mmol), 4-iodobenzaldehyde (2.7 g, 12.0
mmol), Cu2O (2.5 g, 17.0 mmol), and DMAc (12 mL) were added
sequentially into a seal-tube under nitrogen atmosphere and heated
to 165 °C in an oil bath for 18 h. Then the mixture was cooled to
room temperature and filtrated. The filtrate was poured into 300
1
(3:2, v/v) as a white solid, mp 215.0-217.0 °C. H NMR (500
MHz, CDCl3) δ 8.62 (d, J ) 8.5 Hz, 1 H), 8.43-8.40 (t, 2 H),
8.32 (s, 1 H), 8.20-8.15 (m, 5 H), 7.95 (d, J ) 7.5 Hz, 1 H), 7.85
(d, J ) 8.0 Hz, 2 H), 7.78-7.76 (d, J ) 9.0 Hz, 1 H), 7.62-7.54
J. Org. Chem, Vol. 73, No. 5, 2008 1815

Xu et al.
(m, 5 H), 7.51-7.42 (m, 9 H), 7.38-7.28 (m, 4 H), 7.23 (d, J )
8.0 Hz, 2 H), 2.35 (s, 3 H, -CH3) (see Figures S15 and S16,
Supporting Information). Anal. Calcd for C55H36N4O2S: C 80.86,
H 4.44, N 6.86. Found: C 80.81, H 4.51, N 6.65.
bath for 18 h, 2.2 g (65%) of compound 9 was obtained after
chromatography (silica gel, petroleum ether/CH2Cl2 ) 4:1, v/v) as
a light-yellow solid, mp >250 °C. IR (KBr, cm-1): a strong peak
1
at 1702.0 cm-1 is the νs of a CdO moiety. H NMR (500 MHz,
CDCl3) δ 10.18 (s, 1 H, -CHO), 8.42 (d, J ) 9.5 Hz, 3 H), 8.33
(s, 1 H), 8.23-8.15 (m, 8 H), 7.92 (d, J ) 7.5 Hz, 2 H), 7.77 (d,
J ) 8.0 Hz, 1 H), 7.70-7.59 (m, 7 H), 7.56-7.50 (m, 8 H), 7.43-
7.31 (m, 10 H) (see Figures S26 and S27, Supporting Information).
MALDI-TOF: calcd 932.1, found 932.1 (see Figure S28, Support-
ing Information). Anal. Calcd for C67H41N5O: C 86.34, H 4.43, N
7.51. Found: C 86.60, H 4.48, N 7.32.
3-(3-(9H-Carbazol-9-yl)-9H-carbazol-9-yl)-9H-(9H-carbazol-
3-yl)-9H-carbazole (17). By following the synthetic procedure
for compound 13, and using compound 16 (13.0 g, 0.016 mol),
KOH (10.0 g, 0.179 mol), THF (60 mL), DMSO (30 mL), and
H2O (7 mL) as reagents, 10.0 g (95%) of compound 17 was
obtained after chromatography (silica gel, petroleum ether/ethyl
1
acetate ) 3:1, v/v) as a white solid, mp >250 °C. H NMR (500
MHz, CDCl3) δ 8.40 (s, 1 H), 8.32 (s, 3 H), 8.20-8.15 (m, 4 H),
8.11 (d, J ) 7.0 Hz, 1 H), 7.70 (d, J ) 7.5 Hz, 1 H), 7.66-7.60
(m, 4 H), 7.56-7.47 (m, 7 H), 7.43 (s, 4 H), 7.37-7.30 (m, 5 H)
(see Figure S17, Supporting Information). MALDI-TOF: calcd
662.8, found 661.5 (see Figure S18, Supporting Information). Anal.
Calcd for C48H30N4: C 86.98, H 4.56, N 8.45. Found: C 87.02, H
4.54, N 8.42.
3-(3-(3-(3-(9H-Carbazol-9-yl)-9H-carbazol-9-yl)-9H-carbazol-
9-yl)-9H-carbazol-9-yl)-9-(9-tosyl-9H-carbazol-6-yl)-9H-carba-
zole (20). By following the synthetic procedure for compound 12,
using compound 19 (9.5 g, 11.5 mmol), 3-iodo-9-tosylcarbazole
11 (6.8 g, 15.2 mmol), Cu2O (3.5 g, 24.3 mmol), and DMAc (30
mL) as reagents, and adopting the Ullmann reaction condition at
190 °C in an oil bath for 24 h, 10.0 g (76%) of compound 20 was
obtained after recrystallization from EtOH:THF (3:2, v/v) as a white
4-(3-(3-(3-(9H-Carbazol-9-yl)-9H-carbazol-9-yl)-9H-carbazol-
9-yl)-9H-carbazol-9-yl)benzaldehyde (8). By following the syn-
thetic procedure for compound 6, using compound 17 (2.0 g, 3.0
mmol), 4-iodobenzaldehyde (1.2 g, 5.2 mmol), Cu2O (1.0 g, 7.0
mmol), and DMAc (8 mL) as reagents, and adopting the Ullmann
reaction condition at 170 °C in an oil bath for 18 h, 1.8 g (78%) of
compound 8 was obtained after chromatography (silica gel,
petroleum ether/CH2Cl2 ) 4:1, v/v) as a light-yellow solid, mp
>250 °C. IR (KBr, cm-1): a strong peak at 1701.5 cm-1 is the νs
1
solid, mp >250 °C. H NMR (500 MHz, CDCl3) δ 8.62 (d, J )
8.5 Hz, 1 H), 8.42 (s, 4 H), 8.33 (s, 1 H), 8.20-8.15 (m, 7 H),
7.96 (d, J ) 7.5 Hz, 1 H), 7.86 (d, J ) 7.5 Hz, 2 H), 7.77 (d, J )
8.0 Hz, 1 H), 7.70-7.58 (m, 8 H), 7.56-7.43 (m, 14 H), 7.37-
7.30 (m, 6 H), 7.24-7.20 (m, 2 H), 2.35 (s, 3 H, -CH3) (see Figures
S29 and S30, Supporting Information). Anal. Calcd for
C79H50N6O2S: C 82.70, H 4.39, N 7.32. Found: C 82.63, H 4.56,
N 7.48.
1
of a CdO moiety. H NMR (500 MHz, CDCl3) δ 10.17 (s, 1 H,
3-(3-(3-(3-(9H-Carbazol-9-yl)-9H-carbazol-9-yl)-9H-carbazol-
9-yl)-9H-carbazol-9-yl)-9-(9H-carbazol-6-yl)-9H-carbazole (21).
By following the synthetic procedure for compound 13, and using
compound 20 (7.0 g, 6.1 mmol), KOH (6.0 g, 0.11 mol), THF (30
mL), DMSO (15 mL), and H2O (5 mL) as reagents, 5.5 g (91%)
of compound 21 was obtained after chromatography (silica gel,
petroleum ether/ethyl acetate ) 3:1, v/v) as a white solid, mp
-CHO), 8.41 (d, J ) 6.5 Hz, 2 H), 8.33 (s, 1 H), 8.23-8.15 (m,
7 H), 7.91 (d, J ) 8.0 Hz, 2 H), 7.76 (d, J ) 8.5 Hz, 1 H), 7.70-
7.68 (d, J ) 8.5 Hz, 1 H), 7.63-7.48 (m, 10 H), 7.43-7.28 (m, 9
H) (see Figures S19 and S20, Supporting Information). MALDI-
TOF: calcd 766.9, found 767.1 (see Figure S21, Supporting
Information). Anal. Calcd for C55H34N4O: C 86.14, H 4.47, N 7.31.
Found: C 86.22, H 4.40, N 7.36.
1
>250 °C. H NMR (500 MHz, CDCl3) δ 8.43 (s, 3 H), 8.33 (s, 3
H), 8.2-8.15 (m, 6 H), 8.12 (m, 1 H), 7.70 (m, 1 H), 7.66-7.60
(m, 8 H), 7.55-7.47 (m, 11 H), 7.43 (s, 4 H), 7.31-7.26 (m, 7 H)
(see Figure S31, Supporting Information). MALDI-TOF: calcd
993.2, found 993.4 (see Figure S32, Supporting Information). Anal.
Calcd for C72H44N6: C 87.07, H 4.47, N 8.46. Found: C 87.03, H
4.45, N 8.35.
3-(3-(3-(3-(9H-Carbazol-9-yl)-9H-carbazol-9-yl)-9H-carbazol-
9-yl)-9H-carbazol-9-yl)-9-tosyl-9H-carbazole (18). By following
the synthetic procedure for compound 12, using compound 17 (8.0
g, 0.012mol), 3-iodo-9-tosylcarbazole 11 (6.5 g, 0.015 mol), Cu2O
(3.5 g, 0.024 mol), and DMAc (20 mL) as reagents, and adopting
the Ullmann reaction condition at 190 °C in an oil bath for 24 h,
9.0 g (76%) of compound 18 was obtained after recrystallization
from EtOH:THF (3:2, v/v) as a white solid, mp >250 °C. 1H NMR
(500 MHz, CDCl3) δ 8.63 (d, J ) 8.0 Hz, 1 H), 8.42 (d, J ) 7.0
Hz, 3 H), 8.33 (s, 1 H), 8.20-8.15 (m, 6 H), 7.96 (d, J ) 8.0 Hz,
1 H), 7.86 (d, J ) 7.5 Hz, 2 H), 7.78 (d, J ) 8.5 Hz, 1 H), 7.64-
7.55 (m, 7 H), 7.50-7.43 (m, 11 H), 7.37-7.30 (m, 5 H), 7.24 (d,
J ) 7.5 Hz, 2 H), 2.35 (s, 3 H, -CH3) (see Figures S22 and S23,
Supporting Information). Anal. Calcd for C67H43N5O2S: C 81.93,
H 4.41, N 7.13. Found: C 81.95, H 4.39, N 7.23.
4-(3-(3-(3-(3-(3-(9H-Carbazol-9-yl)-9H-carbazol-9-yl)-9H-car-
bazol-9-yl)-9H-carbazol-9-yl)-9H-carbazol-9-yl)-9H-carbazol-9-
yl)benzaldehyde (10). By following the synthetic procedure for
compound 6, using compound 21 (4.0 g, 4.0 mmol), 4-iodoben-
zaldehyde (1.8 g, 7.8 mmol), Cu2O (1.5 g, 0.01 mol), and DMAc
(15 mL) as reagents, and adopting the Ullmann reaction condition
at 170 °C in an oil bath for 18 h, 3.1 g (70%) of compound 10 was
obtained after chromatography (silica gel, petroleum ether/CH2Cl2
) 4:1, v/v) as a light-yellow solid, mp >250 °C. IR (KBr, cm-1):
a strong peak at 1701.0 cm-1 is the νs of a CdO moiety. 1H NMR
(500 MHz, CDCl3) δ 10.18 (s, 1 H, -CHO), 8.42 (d, J ) 10.5 Hz,
4 H), 8.32 (s, 1 H), 8.23-8.14 (m, 9 H), 7.91 (d, J ) 7.5 Hz, 2H),
7.76 (d, J ) 8.5 Hz, 1 H), 7.70-7.58 (m, 9 H), 7.56-7.49 (m, 10
H), 7.43-7.29 (m, 11 H) (see Figures S33 and S34, Supporting
Information). MALDI-TOF: calcd 1097.3, found 1097.0 (see Figure
S35, Supporting Information). Anal. Calcd for C79H48N6O: C 86.47,
H 4.41, N 7.66. Found: C 86.41, H 4.23, N 7.59.
9-(9-(9-(9H-Carbazol-3-yl)-9H-carbazol-3-yl)-9H-carbazol-3-
yl)-3-(9H-carbazol-9-yl)-9H-carbazole (19). By following the
synthetic procedure for compound 13, and using compound 18 (8.5
g, 8.7 mmol), KOH (5.0 g, 89.2 mmol), THF (40 mL), DMSO (20
mL), and H2O (6 mL) as reagents, 6.5 g (90%) of compound 19
was obtained after chromatography (silica gel, petroleum ether/
1
ethyl acetate ) 3:1, v/v) as a white solid, mp >250 °C. H NMR
(500 MHz, CDCl3) δ 8.41 (s, 2 H), 8.32 (s, 2 H), 8.29 (s, 1 H),
8.20-8.09 (m, 6 H), 7.68-7.60 (m, 7 H), 7.55-7.43 (m, 13 H),
7.35-7.30 (m, 6 H) (see Figure S24, Supporting Information).
MALDI-TOF: calcd 827.3, found 826.6 (see Figure S25, Support-
ing Information). Anal. Calcd for C60H37N5: C 87.04, H 4.50, N
8.46. Found: C 87.10, H 4.57, N 8.60.
T(OCA2)P (1). Compound 6 (0.8 g, 1.8 mmol) and p-
nitrobenzoic acid (0.16 g, 0.1 mmol) were dissolved in xylene (40
mL). The mixture was heated to reflux, a solution of pyrrole (0.13
mL, 1.9 mmol) in xylene (5 mL) was slowly added, and the system
was stirred for another 6 h. Xylene (30 mL) was distilled from the
mixture, then MeOH (70 mL) was added. The crude product was
collected by filtration and purified through a short pad of silica gel
with CH2Cl2 as eluent to afford the crude porphyrin. Further
chromatography (silica gel, petroleum ether/CH2Cl2 ) 4:3, v/v) gave
4-(3-(3-(3-(3-(9H-Carbazol-9-yl)-9H-carbazol-9-yl)-9H-carba-
zol-9-yl)-9H-carbazol-9-yl)-9H-carbazol-9-yl)benzaldehyde (9).
By following the synthetic procedure for compound 6, using
compound 19 (3.0 g, 3.6 mmol), 4-iodobenzaldehyde (1.2 g, 5.2
mmol), Cu2O (1.0 g, 6.9 mmol), and DMAc (8 mL) as reagents,
and adopting the Ullmann reaction condition at 170 °C in an oil
1
the product as a purple solid (160 mg, 18%), mp >250 °C. H
NMR (500 MHz, CDCl3) δ 9.22 (s, 6 H), 9.01 (d, J ) 8.5 Hz,1
1816 J. Org. Chem., Vol. 73, No. 5, 2008

Porphyrins with Four Monodisperse Oligocarbazole Arms
H), 8.88 (s, 1 H), 8.64 (d, J ) 8.0 Hz, 6 H), 8.45 (s, 4 H), 8.30-
8.24 (m, 12 H), 8.20-8.17 (d, J ) 8.0 Hz, 8 H), 8.10-8.08 (d,
J ) 8.5 Hz, 4 H), 7.97-7.95 (d, J ) 8.5 Hz, 4 H), 7.78-7.76 (d,
J ) 10.0 Hz, 4 H), 7.71-7.68 (m, 4 H), 7.54-7.49 (m, 20 H),
7.38-7.35 (m, 10 H), -2.50 (s, 2 H, -NH) (see Figure S36,
Supporting Information). MALDI-TOF: calcd 1936.3, found 1936.9
(see Figure S37, Supporting Information). Anal. Calcd for
xylene (5 mL) was added, and the system was stirred for 24 h.
Xylene (40 mL) was distilled from the mixture, then MeOH (70
mL) was added. The crude product was collected by filtration and
purified through a short pad of silica gel with CH2Cl2 as eluent to
afford the crude porphyrin. Further chromatography (silica gel,
petroleum ether/CH2Cl2 ) 2:3, v/v) gave the product as a purple
1
solid (270 mg, 23%), mp >250 °C. H NMR (500 MHz, CDCl3)
C
140H86N12: C 86.84, H 4.48, N 8.68. Found: C 86.90, H 4.52, N
8.39.
T(OCA3)P (2). Following a procedure for the preparation of
δ 9.21 (s, 4 H), 9.01 (d, 2 H), 8.88 (s, 2 H), 8.65 (d, J ) 7.0 Hz,
6 H), 8.53 (s, 4 H), 8.45-8.40 (m, 10 H), 8.32 (s, 8 H), 8.25-8.12
(m, 30 H), 7.96 (d, J ) 8.0 Hz, 4 H), 7.84 (d, J ) 8.0 Hz, 4 H),
7.75-7.28 (m, 94 H), -2.51 (s, 2 H, -NH) (see Figure S42,
Supporting Information). MALDI-TOF: calcd 3915.4, found 3915.9
(see Figure S43, Supporting Information). Anal. Calcd for
compound 1, compound 7 (1.0 g, 1.7 mmol), p-nitrobenzoic acid
(0.15 g, 0.9 mmol), pyrrole (0.13 mL, 1.9 mmol), and xylene (35
mL) were refluxed for 15 h to give the crude porphyrin, which
was purified by column chromatography (silica gel, petroleum ether/
CH2Cl2 ) 1:1 v/v) to afford compound 2 as a purple solid (220
mg, 20%), mp >250 °C. 1H NMR (500 MHz, CDCl3) δ 9.24 (s, 6
H), 9.03 (d, 1 H), 8.90 (s, 1 H), 8.67 (d, J ) 8.0 Hz, 6 H), 8.54 (s,
4 H), 8.39 (s, 4 H), 8.33 (d, J ) 7.5 Hz, 4 H), 8.24-8.20 (m, 18
H), 8.14 (d, J ) 9.0 Hz, 4 H), 7.98 (d, J ) 8.5 Hz, 4 H), 7.85 (d,
J ) 8.5 Hz, 4 H), 7.71 (d, J ) 8.5 Hz, 8 H), 7.63-7.28 (m, 48 H),
-2.49 (s, 2 H, -NH) (see Figure S38, Supporting Information).
MALDI-TOF: calcd 2597.0, found 2597.1 (see Figure S39,
Supporting Information). Anal. Calcd for C188H114N16: C 86.95,
H 4.42, N 8.63. Found: C 86.87, H 4.43, N 8.56.
T(OCA4)P (3). Following a procedure for the preparation of
compound 2, compound 8 (0.93 g, 1.2 mmol), p-nitrobenzoic acid
(0.13 g, 0.8 mmol), pyrrole (0.1 mL, 1.4 mmol), and xylene (35
mL) were refluxed for 24 h to give the crude porphyrin, which
was purified by column chromatography (silica gel, petroleum ether/
CH2Cl2 ) 1:1 v/v) to afford compound 3 as a purple solid (250
mg, 25%), mp >250 °C. 1H NMR (500 MHz, CDCl3) δ 9.21 (s, 4
H), 9.02 (s, 2 H), 8.88 (s, 2 H), 8.65 (d, J ) 7.5 Hz, 4 H), 8.53 (s,
4 H), 8.44 (s, 6 H), 8.33 (m, 8H), 8.26-8.12 (m, 24 H), 8.03-
7.95 (m, 4 H), 7.84 (m, 4 H), 7.73-7.29 (m, 78 H), -2.51 (s, 2 H,
-NH) (see Figure S40, Supporting Information). MALDI-TOF:
calcd 3257.8, found 3256.7 (see Figure S41, Supporting Informa-
tion). Anal. Calcd for C236H142N20: C 87.01, H 4.39, N 8.60.
Found: C 86.96, H 4.35, N 8.67.
C
284H170N24: C 87.05, H 4.37, N 8.58. Found: C 87.11, H 4.29, N
8.62.
T(OCA6)P (5). By following a procedure for the preparation of
compound 4, and using compound 10 (1.5 g, 1.4 mmol), p-
nitrobenzoic acid (0.15 g, 0.9 mmol), pyrrole (0.15 mL, 2.1 mmol),
and xylene (60 mL) as reagents, 410 mg (26%) of compound 5
was obtained after chromatography (silica gel, petroleum ether/
CH2Cl2 ) 1:4, v/v) as a purple solid, mp >250 °C. 1H NMR (500
MHz, CDCl3) δ 9.21-9.17 (d, 4 H), 9.00 (s, 2 H), 8.88 (s, 2 H),
8.45-8.40 (m, 14 H), 8.32 (s, 8 H), 8.26-8.10 (m, 34 H), 8.03-
7.95 (m, 4 H), 7.84 (s, 4 H), 7.74-7.29 (m, 116 H), -2.51 (s, 2 H,
-NH). (see Figure S44, Supporting Information). MALDI-TOF:
calcd 4575.6, found 4576.8 (see Figure S45, Supporting Informa-
tion). Anal. Calcd for C332H198N28: C 87.08, H 4.36, N 8.56.
Found: C 87.23, H 4.40, N 8.76.
Acknowledgment. This work is financially supported by the
National Natural Science Foundation of China (NNSFC, No.
20574027) and the Program for New Century Excellent Talents
in University (NCET).
Supporting Information Available: 1H NMR spectra of 1-10
and 12-21, MALDI-TOF mass spectra of 1-10, 13, 15, 17, 19,
and 21, GPC spectra of 1-5, UV/vis spectra of 6 recorded in
different solvents, plotting between the molar extinction coefficient
at 294 nm and the number of carbazoles in 6-10, and Universal
1.02 force field optimized geometry for 1-5. This material is
available free of charge via the Internet at http://pubs.acs.org.
T(OCA5)P (4). Compound 9 (1.1 g, 1.2 mmol) and p-nitro-
benzoic acid (0.13 g, 0.8 mmol) were dissolved in xylene (50 mL).
The mixture was heated to reflux, a solution of pyrrole (0.10 mL,
1.4 mmol) in xylene (5 mL) was slowly added, and the system
was stirred for another 24 h. Then pyrrole (0.05 mL, 0.7 mmol) in
JO702426R
J. Org. Chem, Vol. 73, No. 5, 2008 1817