Meso-indolo[3,2-6]carbazolyl-substitutedporphyrmoids: synthesis, characterization and effect of the number of indolocarbazole moieties on the photophysical properties

Article abstract of DOI:10.1002/ejoc.201000180

meso-Indolocarbazolylporphyrins endowed with a different number of indolocarbazole units have been synthesized via condensation of an appropriately substituted monoformylated 5,ll-dihydroindolo[3,2-b]carbazole precursor and mesityldipyrromethane. Under specific conditions, analogous meso- indolocarbazolylcorroles could also be prepared. The photophysical features of the novel luminescent free-base and Zn-porphyrin derivatives were investigated. The introduction of indolocarbazole substituents results in progressive bathochromic shifts of the porphyrin absorbance and fluorescence bands due to the rising energy of the a_2u orbital. The excitation energy is efficiently transferred from the mesoindolocarbazole units to the porphyrin macrocycle. An increased number of indolocarbazole moieties does not lead to porphyrin fluorescence quenching; on the contrary, a small increase of the fluorescence quantum yield is observed. The main route for excitation energy deactivation of all the studied porphyrins is intersystem S₁→ T₁ crossing, with the intersystem crossing quantum yield, as determined by the photosensitized formation of singlet molecular oxygen, being as high as about 70 % for the free-bases and more than 80 % for the Zn complexes. The intersystem crossing quantum yield seems to be barely affected by meso-indolocarbazole substitution. A noticeable part of the excitation energy was found to deactivate through radiationless internal S₁→S ₀ conversion.

Full text of DOI:10.1002/ejoc.201000180

FULL PAPER
DOI: 10.1002/ejoc.201000180
meso-Indolo[3,2-b]carbazolyl-Substituted Porphyrinoids: Synthesis,
Characterization and Effect of the Number of Indolocarbazole Moieties on the
Photophysical Properties
Wouter Maes,*[a,b] Thien H. Ngo,[a] Gu Rong,[a] Aleksander S. Starukhin,[c]
Mikalai M. Kruk,*[c] and Wim Dehaen*[a]
Keywords: Porphyrinoids / Nitrogen heterocycles / Photophysical properties / Luminescence / Molecular electronics / Exci-
tation energy deactivation
meso-Indolocarbazolylporphyrins endowed with a different
number of indolocarbazole units have been synthesized via
condensation of an appropriately substituted monoformyl-
ated 5,11-dihydroindolo[3,2-b]carbazole precursor and mesi-
tyldipyrromethane. Under specific conditions, analogous
meso-indolocarbazolylcorroles could also be prepared. The
photophysical features of the novel luminescent free-base
and Zn-porphyrin derivatives were investigated. The intro-
duction of indolocarbazole substituents results in progressive
bathochromic shifts of the porphyrin absorbance and fluores-
cence bands due to the rising energy of the a2u orbital. The
excitation energy is efficiently transferred from the meso-
indolocarbazole units to the porphyrin macrocycle. An in-
creased number of indolocarbazole moieties does not lead to
porphyrin fluorescence quenching; on the contrary, a small
increase of the fluorescence quantum yield is observed. The
main route for excitation energy deactivation of all the
studied porphyrins is intersystem S1ǞT1 crossing, with the
intersystem crossing quantum yield, as determined by the
photosensitized formation of singlet molecular oxygen, being
as high as about 70% for the free-bases and more than 80%
for the Zn complexes. The intersystem crossing quantum
yield seems to be barely affected by meso-indolocarbazole
substitution. A noticeable part of the excitation energy was
found to deactivate through radiationless internal S1ǞS0
conversion.
line) (e.g., triarylamines, carbazoles) and pentacene compo-
nents, have been applied as a new subclass of active (charge-
transport) materials for the construction of (opto)electronic
devices such as organic light-emitting diodes (LEDs),[2,3]
thin-film field-effect transistors (FETs),[3–5] and photovol-
taic cells (PCs).[5,6] The high current interest in indolocarba-
zoles as promising materials for high-performance organic
electronics can also be judged from the appreciable amount
of recent patents dealing with applications of these mole-
cules.[7]
Introduction
Indolocarbazoles, indole-carbazole ring-fused hetero-
cycles, have attracted considerable attention in recent years.
Among the five isomeric indolocarbazole ring systems, dif-
ferentiated by the position and orientation of the ring fu-
sion, indolo[3,2-b]carbazoles are actively being investigated,
both for their biological significance as well as their distinct
electrical and optical features.[1] Monomeric and (co)poly-
meric indolo[3,2-b]carbazole derivatives, electron-rich ex-
tended π structures related to well-established oligo(p-ani-
From a synthetic point of view, several pathways towards
indolo[3,2-b]carbazoles (ICZs) have been developed over
the years. Most of the reported methods, however, involve
multiple steps affording only slightly soluble, mostly sym-
metrical derivatives in rather low overall yields, hampering
straightforward elaboration to readily functionalized
[a] Molecular Design and Synthesis, Department of Chemistry,
Katholieke Universiteit Leuven,
Celestijnenlaan 200F, 3001 Leuven, Belgium
Fax: +32-16-327990
E-mail: wim.dehaen@chem.kuleuven.be
[b] Institute for Materials Research (IMO), Research Group Or-
ganic and (Bio)Polymeric Chemistry, Hasselt University, Uni- ICZs.[1] Within one of our groups, alternative protocols that
versitaire Campus,
allow a facile and rather general synthesis of various 6-
Agoralaan Building D, 3590 Diepenbeek, Belgium
monosubstituted and asymmetrically 6,12-disubstituted
5,11-dihydroindolo[3,2-b]carbazoles in moderate to good
yields (20–50%) have recently been established.[8] The en-
hanced solubility and stability towards oxidative degrada-
tion of the newly prepared ICZs enabled easy further struc-
tural modification of the indolocarbazole skeleton by nu-
merous pathways, e.g., N-alkylation and N-arylation,
Fax: +32-11-268399
E-mail: wouter.maes@uhasselt.be
[c] B. I. Stepanov Institute of Physics, National Academy of Sci-
ences,
68 Nezalezhnasci Ave., Minsk 220072, Belarus
Fax: +375-17-284-0679
E-mail: kruk@imaph.bas-net.by
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201000180.
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meso-Indolo[3,2-b]carbazolyl-Substituted Porphyrinoids
Ullmann coupling, regioselective bromination, formylation
and tert-butylation, azo-coupling and Suzuki cross-cou-
pling.
Since both indolo[3,2-b]carbazoles and porphyrins are
compounds with attractive properties for the design of elec-
tro-optical materials, novel systems combining both planar
aromatic chromophores into one single molecule are evi-
dently appealing targets.[9] In previous work, the Leuven
group has prepared porphyrins with appended hole-trans-
porting (oligo)carbazole dendrons and their photophysical
and redox behaviour were explored.[10] This study has now
been extended to the (indolocarbazole)–porphyrin conge-
ners. In this manuscript, we report the first synthetic proto-
cols towards both porphyrins and corroles with indolocar-
bazolyl moieties at the periphery in fair-to-good yields by
exploring different monoformylated ICZ starting products.
As a first step towards potential application of these novel
materials, their spectroscopic properties have been investi-
gated, with emphasis on the porphyrin moiety, to elucidate
how functionalization with ICZ fragments affects the pho-
tophysical properties of the porphyrin macrocycle.
Figure 1. Indolo[3,2-b]carbazole precursors 1–4.
may possibly be attributed to the limited solubility of ICZ
2 in dichloromethane. Even though a highly diluted solu-
tion was used (5.6 m), part of the aldehyde 2 still did not
dissolve. As a result, the ICZ-carbaldehyde was not equi-
molar to the dipyrromethane (DPM) in solution, favouring
the tetrapyrrane [2+1]-condensation product, which upon
oxidation furnished AB2-corrole 6. The reason for the very
slow conversion of the tetrapyrrolic precursor to the corre-
sponding corrole remains unclear at this stage.[13]
Results and Discussion
Synthetic Exploration
The synthesis of (indolocarbazole)–porphyrin conjugates
remains a challenging and to date unresolved task. To syn-
thesize porphyrins equipped with meso-indolo[3,2-b]-
carbazolyl moieties, suitable ICZ building blocks are re-
quired and effective macrocyclization conditions should be
pursued. Straightforward access to variously functionalized
ICZ derivatives has only recently been disclosed.[1c,8] Based
on previous work, 6-pentyl-5,11-dihydroindolo[3,2-b]carb-
azole (1) was chosen as the parent ICZ substrate of prefer-
ence for its high-yielding three-stage, one-pot synthesis
(47%), good solubility in common organic solvents and
simple conversion to the monoformylated ICZ derivative 2
(Figure 1). Indeed, 6-formyl-ICZ 2 was readily synthesized
by regioselective C-formylation of 1 under standard Vils-
meier conditions (POCl3, DMF; 50% yield).[8a,8c]
Scheme 1. Synthesis of ICZ-corrole conjugate 6.
The first attempt towards meso-indolocarbazolyl-substi-
tuted porphyrins involved a [2+2]-condensation of 6-form-
To verify our solubility hypothesis, a more soluble ICZ
yl-ICZ 2 and 5-mesityldipyrromethane (5),[11] in an equi- derivative,
5,11-diethyl-6-formyl-12-pentyl-5,11-dihydro-
molar ratio, under Lindsey conditions using boron trifluo- indolo[3,2-b]carbazole (3), was prepared by formylation of
ride–diethyl ether (0.5 equiv.) as a Lewis acid catalyst and the N,N-diethyl precursor, in turn easily accessible from 1
subsequent oxidation of the porphyrinogen with p- by N-alkylation with bromoethane (NaH, DMF, 70 °C;
chloranil.[12] Unfortunately, the targeted trans-A2B2-por- 83% yield), under similar Vilsmeier conditions in 71%
phyrin could not be obtained under these macrocyclization yield.[8a,8c] The synthesis of an ICZ-porphyrin conjugate
conditions (as analyzed by TLC and ESI-MS). Surprisingly, based on this novel aldehyde 3 was pursued under the afore-
when the crude reaction mixture, containing a considerable mentioned conditions, but again no porphyrinic material
amount of unreacted aldehyde 2, was left standing on the was obtained. In like fashion, a small amount of corrole
bench for a rather long time (ca. two months) open at the (ca. 3%) could be isolated when the crude reaction mixture
air, the formation of AB2-corrole 6 was observed (by TLC was allowed to stand open at the air for more than a month.
and ESI-MS), which was chromatographically purified and
At this stage, we argued that the reactivity of 6-formyl-
isolated in a modest 3% yield (Scheme 1). The formation ICZs towards reaction with a dipyrromethane might simply
of the contracted porphyrin analogue, meso-indolocarb- be too low (for electronical and, in particular, steric
azolylcorrole 6, rather than the expected A2B2-porphyrin reasons), impeding efficient (cyclo)condensation. Porphyrin
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syntheses starting from analogous sterically bulky aromatic
aldehydes, e.g., 9-anthrylaldehyde, are known to afford only
very low yields of porphyrin macrocycles under classical
Adler or Lindsey conditions.[14] Insertion of a phenyl ring
between the formyl group and the ICZ chromophore might
provide a solution to this problem. Hence, 6-(p-formyl-
phenyl)-12-pentyl-5,11-dihydroindolo[3,2-b]carbazole (4)[8a,8c]
(Figure 1) and its N,N-dimethylated analogue 9, both highly
soluble in dichloromethane, were prepared. N,N-Dimethyl-
ICZ 9 was synthesized via monobromination of 1 with an-
hydrous FeBr3, followed by N-methylation and subsequent
Suzuki cross-coupling with 4-formylbenzeneboronic acid
(Scheme 2).[8c]
Scheme 2. Synthesis of 6-(p-formylphenyl)-substituted ICZ 9.
Using the novel N-methylated ICZ-carbaldehyde 9, the
synthesis of ICZ-porphyrin conjugates finally succeeded
through cyclocondensation with 5-mesityldipyrromethane
(5), catalyzed by BF3·OEt2 (0.85 equiv.), and subsequent
oxidation with p-chloranil. However, not only the expected
Figure 2. meso-Indolo[3,2-b]carbazolyl-substituted porphyrins 10a/
b–13a/b.
trans-A2B2-porphyrin 11a, but a mixture of 4 different por- A4-porphyrin, neither for ICZ precursors 4 or 9. On metal-
phyrins 10a–13a was observed (Figure 2). After column lation of the free-base porphyrins 10a–13a with zinc(II)
chromatographic separation (silica), AB3-porphyrin 10a (A {using Zn(OAc)2 in chloroform}, Zn-porphyrins 10b–13b
= ICZ, B = mesityl) was obtained in 2.5% yield, a mixture were nearly quantitatively obtained (Figure 2).[17]
of both A2B2-porphyrin isomers 11a,12a (trans and cis,
Since corroles, contracted porphyrin congeners lacking
respectively) was obtained in 17% yield, and A3B-porphyrin one meso-carbon, are currently receiving steadily growing
13a was isolated in 7% yield. Traces of the symmetrical B4- interest due to their particular (catalytical, photophysical
porphyrin (tetramesitylporphyrin TMP) were also ob- and medicinal) properties,[18] a more usable, selective syn-
served, while no A4-porphyrin was detected.
thetic pathway towards meso-indolocarbazolylcorroles was
This mixture of ICZ-porphyrins can only be formed if pursued, based on the conditions previously optimized for
the oligopyrrolic nonaromatic porphyrin precursors are un- meso-pyrimidinylcorroles.[19] In a first attempt, 6-formyl-
dergoing (dynamic) fragmentation and recombination, a ICZ 2 and 5-mesityldipyrromethane (5) (2 equiv.) were con-
phenomenon referred to as scrambling.[15] The scrambling densed with a highly reduced amount of BF3·OEt2
observed for the combination of mesityldipyrromethane (0.086 equiv., 4.5 h at room temp.), favouring corrole for-
and ICZ 9 might be due to the rather low reactivity of the mation,[19] followed by oxidation with p-chloranil. Unfortu-
aldehyde and the high amount of borontrifluoride catalyst. nately, no AB2-corrole could be obtained from this ap-
When a smaller amount of BF3·OEt2 (0.425 equiv.) was proach. A similar reaction with 6-(p-formylphenyl)-ICZ 4
used, scrambling was still observed, but the ICZ-porphyrins (1 equiv. DPM, 1 equiv. BF3·OEt2, 4 h at room temp.) pro-
could be obtained in higher yields (6.5% AB3 10a, 29% vided only trace amounts of corrole and A2B2-porphyrin
trans-A2B2 or ABAB 11a, 6% cis-A2B2 or AABB 12a, 13% (as observed by ESI-MS). On the other hand, dropwise ad-
A3B 13a), the overall yield of porphyrinic material ex- dition of ICZ-carbaldehyde 9, activated by 0.043 equiv.
ceeding 50%. Separation of both A2B2-porphyrin isomers BF3·OEt2, to a solution of mesityldipyrromethane (5)
11a and 12a is not trivial, but could be realized by repeated (3 equiv.) in dichloromethane overnight, followed by further
and careful column chromatography. Direct condensation reaction for another 12 h and oxidation with p-chloranil,
with pyrrole under Lindsey conditions did not result in any afforded the desired AB2-corrole 14, albeit in only 1.5%
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meso-Indolo[3,2-b]carbazolyl-Substituted Porphyrinoids
yield (Scheme 3). On applying 6 equiv. of dipyrromethane 5 Characterization
and flash column chromatographic purification of the cor-
role, limiting oxidative degradation, the yield could be im-
proved to (a still modest) 5%.
All novel indolo[3,2-b]carbazoles and porphyrinoids were
1
fully characterized by H and 13C NMR spectroscopy,[20]
mass spectrometry (CI/ESI) and UV/Vis spectroscopy. Due
to hindered rotation, the meso-indolocarbazolyl moieties
may adopt different orientations with respect to the por-
phyrin plane and the other meso-substituents, and hence
different porphyrin (atrop)isomers may be formed de-
pending on the number of ICZ units, which is reflected in
1
1
their respective H NMR spectra. For example, in the H
NMR spectrum of free-base trans-A2B2-porphyrin 11a, for
which 2 isomers can be distinguished, several doublets (not
all well-resolved) were observed in the β-pyrrolic proton re-
gion (δ = 9.3–8.8 ppm), and multiple signals were observed
for the methyl groups of the meso-mesityl moieties (at
δ ≈ 2.7 and 2.0 ppm) (Figure 3). Variable-temperature
NMR studies allowed observation of the rotational barri-
ers. Coalescence of the o- and p-methyl signals was ob-
served at 50 °C, with a gradual sharpening of these signals
at higher temperatures (and a concurrent sharpening of the
pentyl signals), indicating facilitated rotation, while the
multiply coupled pattern for the β-pyrrolic protons simpli-
fied into two broad signals, both corresponding to 4 pro-
tons, at 100 °C (Figure 3). The NH resonance gradually
shifted to higher field upon raising the temperature (total
shift ca. 0.4 ppm in the range 278–373 K).[20]
Scheme 3. Synthesis of meso-indolo[3,2-b]carbazolyl-substituted
AB2-corrole 14.
Absorption and Fluorescence Spectra
The UV/Vis absorption spectra of the ICZ-porphyrin
conjugates are composed of porphyrin bands, the intense
Soret band in the UV region and less intense Q-bands in
the visible range, and ICZ centered bands in the UV region,
the S0ǞS2 transition (vibronic progression) in the region
320–350 nm and the S0ǞS1 transition at higher wavelength
(ca. 400 nm) overlapped by the porphyrin Soret band (see
example in Figure 4).[21,22] The ground state interaction of
the porphyrin core and the ICZ substituents seems to be
rather weak.
When the excitation wavelength was chosen in the UV
range, where the ICZ moiety absorbs, no/hardly detectable
indolocarbazole emission signals, but strong porphyrin
emission was observed (see example in Figure 5). The emis-
sion of the porphyrin moiety upon UV excitation indicates
that light energy absorbed by the indolocarbazole units is
efficiently transferred to the porphyrin core. The fluores-
cence spectra of all the studied porphyrin–indolo[3,2-b]-
carbazole conjugates show the expected double porphyrin
S1ǞS0 emission bands, centered around 650 and 725 nm
for the free-base derivatives and around 600 and 650 nm for
the Zn complexes. Thus, the indolo[3,2-b]carbazole units
act as light-harvesting antennae for the porphyrin core.
A more detailed photophysical study of the meso-
indolo[3,2-b]carbazolylporphyrins was then undertaken,
with emphasis on the porphyrin chromophore, since the ex-
citation energy deactivation proceeds majorly via the por-
phyrin moiety. The progressive substitution with ICZ frag-
Figure 3. Detailed regions (β-pyrrolic protons at the top, methyl
groups of mesityl substituents at the bottom) of the 1H NMR spec-
trum (600 MHz) of trans-A2B2-porphyrin 11a in [D2]tetrachloro-
ethane, obtained at different temperatures (298 K down, 323 K
middle, 373 K up).[20]
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Figure 4. UV/Vis absorption spectra for ICZ-porphyrin conjugates
11a,b in CH2Cl2.
Figure 6. Absorption spectra of Zn-porphyrin complexes in tolu-
ene: Soret region (top) and visible region (bottom).
The fact to be stressed here is the change in the ratio of
the intensities of the pure electronic band and the vibronic
one in both absorption (A0,0/A1,0) and fluorescence (F0,0
/
F0,1) spectra. The A0,0/A1,0 ratio is directly proportional to
the ratio of the transition dipole moments of these transi-
tions. It is known that this ratio is proportional to the
square of the energy difference between the two one-elec-
Figure 5. Emission spectrum of ICZ-porphyrin conjugate 11a
measured upon excitation at 286 nm.
tron configurations for the porphyrin macrocycle: A0,0/A1,0
1
ments at the meso-positions of the porphyrin macrocycle ≈ [1E(a2u,eg) – E(a1u,eg)]2,[23] and it is often used as a mea-
leads to relatively small, but well detectable changes in the sure for the energy mismatch between the highest occupied
porphyrin absorption and fluorescence spectra (Figure 6 molecular orbitals (HOMOs) a2u and a1u (orbital notations
and Figure 7). The data obtained for both free-base and Zn are given for the D4h point symmetry group). It is well es-
complexes in toluene are listed in Table 1. Toluene has been tablished that addition of aryl substituents at the meso-posi-
used as a (noncoordinating) solvent to avoid any possible tions of a porphyrin macrocycle increases the energy of the
complications due to axial ligation.
a2u molecular orbital,[23] so the relationship 1E(a2u,eg)
Ͻ
The data in Table 1 show that the introduction of ICZ
1E(a1u,eg) holds. As a starting point for the analysis,
substituents results in progressive subtle bathochromic ZnTMP was selected, which can be considered as the parent
changes of the absorbance and fluorescence bands (see Fig- compound for molecules 10b, 11b and 13b. For ZnTMP, the
ures 6 and 7). The energy difference between the absorption value for the ratio A0,0/A1,0 is 0.09. Proceeding to com-
and fluorescence maxima remains practically the same pounds with an increasing number of ICZ substituents, the
(about 10 nm and 5.5–6.5 nm for the Zn and free-base de- ratio gradually increases up to 0.2 in the case of ZnA3B-
rivatives, respectively), indicating that there are no struc- porphyrin 13b (Table 1). This means that the ICZ substitu-
tural rearrangements (perturbations) in the excited singlet ents have an electron donation power which is higher than
state upon increase in the number of ICZ units. There are that of the mesityl substituents. As a result, the electronic
also no specific solute-solvent interactions since essentially density at the ICZ-substituted meso-carbon atoms in-
the same values have been measured for these compounds creases, leading to an increase in the energy of the a2u mo-
in dichloromethane (data are not shown).
lecular orbital of the porphyrin macrocycle and to a de-
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meso-Indolo[3,2-b]carbazolyl-Substituted Porphyrinoids
Figure 7. Fluorescence spectra of Zn complexes (top) and free-base
porphyrins (bottom) in toluene (λexc = 532 nm).
Figure 8. Configurational interaction dependencies for the studied
Zn-porphyrins.
Table 1. Spectral data for the studied porphyrin derivatives 10a/b–
13a/b in toluene.
Porphyrin
λ0,0abs /nm A0,0/A1,0 λ0,0fl /nm F0,0/F0,1
conclusion that the intensity changes are mainly due to the
rise of the a2u orbital is supported by the monotonic rela-
tionship between the A0,0/A1,0 ratio and the frequencies of
the 0,0-transition shifts measured relatively to the parent
ZnTMP molecule according to the predictions of the Gout-
erman four-orbital model (Figure 9).[23,25]
ZnAB3 10b
587.5
0.13
0.15
0.20
0.16
0.09
0.47
0.44
0.56
0.52
0.60
597.5
599.0
600.0
599.0
597.0
654.5
654.5
655.0
655.0
656.5
0.40
0.58
0.69
0.56
0.24
1.25
0.90
1.14
1.07
1.27
ZnABAB trans 11b 589.0
ZnA3B 13b
ZnTPP[a]
ZnTMP[b]
H2TPP
H2AB3 10a
H2ABAB trans 11a 649.0
590.0
588.5
586.0
648.0
649.0
H2AABB cis 12a
H2A3B 13a
650.0
650.0
[a] TPP: tetraphenylporphyrin. [b] TMP: tetramesitylporphyrin.
crease in the strength of the configurational interaction.[23]
Thus, as the mismatch between the a2u and a1u HOMOs
for these compounds increases, the maximum for the first
electronic transition undergoes a monotonic long wave-
length shift (this is also true for the Soret band, since EB –
EQ ≈ constant). The obtained dependencies on the number
of ICZ substituents for the Zn-porphyrins are depicted in
Figure 8. These dependencies indicate the character of the
changes in the configuration interaction upon substitution
with ICZ heterocycles.
Figure 9. Correlation between the A0,0/A1,0 ratio and the frequency
of the 0,0-transition.
As has been stated above, the increase in the energy gap
between the a2u and a1u HOMOs mainly leads to an in-
crease in the oscillator strength of the pure electronic band
As for the comparison of the disubstituted cis- (H2AABB
(the forbiddenness of the vibronic band has already been 12a) and trans-porphyrin (H2ABAB 11a), one can state that
removed with perturbation by vibronic coupling).[24] The symmetric trans-substitution effects the porphyrin macro-
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cycle electronic density slightly stronger. This conclusion is the quantum yield of the photosensitized formation of sing-
based on the differences found for the A0,0/A1,0 and F0,0 let molecular oxygen Φ∆. The obtained figures are listed in
F0,1 ratios: in the case of trans-substitution the shift of the Table 2. One can see that the intersystem crossing quantum
/
a2u orbital seems to be slightly higher.
yield for the Zn-porphyrins is barely affected by ICZ-substi-
tution. All the measured figures fall in the range
0.82Ϯ0.03, i.e. are the same within the limits of experimen-
tal error. At the same time, the kISC value slightly increases
upon going from unsubstituted ZnTMP to the ICZ-por-
phyrins with an increasing number of ICZ groups. The
trend observed for the free-base conjugates is the same: the
intersystem crossing quantum yield is barely affected by the
attachment of ICZ units at the meso-positions of the por-
phyrin macrocycle.
Excitation Energy Deactivation
Substitution at the meso-positions of a porphyrin with
ICZ heterocyclic fragments leads to changes in the photo-
physical properties of the porphyrin core. The photophysi-
cal properties measured for the free-base and Zn-por-
phyrins 10a/b–13a/b are listed in Table 2.
One other noteworthy point should be stressed. In both
cases (porphyrin free-bases and Zn complexes), the intersys-
tem crossing quantum yield ΦISC for the mono-ICZ-substi-
tuted porphyrin is slightly higher than for the other deriva-
tives. Maybe the reason for this small difference does arise
from the asymmetry of the electron density distribution in
the case of monosubstitution. However, these changes are
too small for an in-depth discussion.
Finally, a noticeable part of the excitation energy was
found to deactivate through internal radiationless S1ǞS0
conversion, as it was also found to be true for the parent
TMP compounds. The value of the internal conversion
quantum yield ΦIC is determined as 1-ΦISC-Φfl and, there-
fore, reflects the uncertainty of the ΦISC measurements. For
Table 2. Photophysical properties of the free-base and Zn-por-
phyrins 10a/b–13a/b.
Porphyrin τfl
/ns
Φfl
kfl
ΦISC
kISC
ΦIC
kIC
/107 s–1
/108 s–1
/107 s–1
10b
11b
13b
ZnTPP
ZnTMP
H2TPP
10a
11a
12a
2.13 0.037 1.74
1.98 0.039 1.97
1.43 0.041 2.97
1.75 0.033 1.89
2.33 0.032 1.37
12.2 0.090 0.74
0.85
0.79
0.83
0.90
0.83
0.68
0.71
0.67
0.68
0.68
4.0
4.0
5.8
5.1
3.6
0.56
–
–
–
–
0.11
0.17
0.13
0.07
0.14
0.23
0.20
0.24
0.23
0.23
5.2
8.5
9.1
4.3
5.6
0.19
–
–
–
–
–
–
–
–
0.092
0.093
0.093
0.095
–
–
–
–
13a
The differences in the photophysical parameters for the the Zn-porphyrins the internal conversion quantum yield
Zn complexes seem to result from changes in the electronic ΦIC varies as 0.14Ϯ0.03, and for the free-base porphyrins
structure of the porphyrin macrocycle induced by the at- as 0.22Ϯ0.02. The rate of the internal radiationless conver-
tachment of ICZ groups. Upon going from the parent un- sion kIC also slightly increases upon going from unsubsti-
substituted ZnTMP to the porphyrins with an increasing tuted ZnTMP to the porphyrins with more ICZ groups.
number of ICZ groups, some photophysical parameters
were found to alter. First of all, the fluorescence quantum
yield Φfl increases with an increase of the number of at-
tached meso-ICZ fragments. Fluorescence lifetime measure-
Conclusions
ments demonstrate that the decay also becomes faster with
In conclusion, novel indolo[3,2-b]carbazole–porphyrin
an increase of the number of ICZ groups. With these values conjugates with a different number of meso-indolocarbazo-
in hand, the rate kfl of the radiative deactivation of the low- lyl substituents have been prepared in fair-to-good yields
est singlet S1 state could be determined. Attachment of ICZ via scrambling condensation of a formylated indolo[3,2-b]-
groups leads to a more than twofold increase in kfl value: carbazole precursor and mesityldipyrromethane, taking ad-
from 1.37ϫ107 s–1 in the case of ZnTMP up to vantage of the broad functionalization scope of the parent
2.97ϫ107 s–1 for ZnA3B-porphyrin 13b. Thus, the forma- 6-pentyl-5,11-dihydroindolo[3,2-b]carbazole building block.
tion of highly ICZ-substituted compounds does not lead to Furthermore, analogous indolo[3,2-b]carbazole-corrole
fluorescence quenching; on the contrary, a small increase conjugates were also synthesized in modest yields. Detailed
of the fluorescence quantum yield is observed. The same spectroscopic studies on the free-base and Zn-porphyrins
noticeable trend was also found to be valid for the free-base have exposed small bathochromic shifts upon progressive
conjugates: the value of the fluorescence quantum yield Φfl substitution with ICZ fragments, both in the absorption
slightly increases from 0.092 for monosubstituted H2AB3- and fluorescence spectra, and this trend has a noteworthy
porphyrin 10a to 0.095 for trisubstituted H2A3B-porphyrin additive character. The introduction of ICZ substituents at
13a. However, one may notice this trend is weakly marked, the meso-positions of a porphyrin macrocycle leads to a
being within experimental error limits.
slight increase of the fluorescence quantum yield and a
The quantum yield for triplet state formation has been shortening of the fluorescence lifetime. The main route for
determined with the method of photosensitized formation the excitation energy deactivation is intersystem crossing
of singlet molecular oxygen. In case the probability of the with population of the lowest T1 triplet state. The intersys-
energy transfer from the porphyrin lowest triplet T1 state to tem crossing quantum yield ΦISC is about 0.8 and 0.7 for
–
the molecular oxygen ground state (3Σg ) is unit, the in- the Zn complexes and free-base compounds, respectively.
tersystem crossing S1ǞT1 quantum yield ΦISC is equal to The absence of radiationless internal conversion enhance-
2582
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 2576–2586

meso-Indolo[3,2-b]carbazolyl-Substituted Porphyrinoids
(s, 1 H, CHO), 8.51 (d, JH,H = 8.2 Hz, 1 H), 8.21 (d, JH,H = 8.2 Hz,
1 H), 7.71 (t, JH,H = 8.2 Hz, 2 H), 7.55 (t, JH,H = 7.3 Hz, 2 H),
7.34 (t, JH,H = 7.3 Hz, 1 H), 7.22 (t, JH,H = 7.3 Hz, 1 H), 4.70–4.50
(m, 4 H), 3.66 (br. s, 2 H), 1.88 (br. s, 2 H), 1.66 (br. s, 2 H), 1.50–
1.25 (m, 8 H), 0.94 (t, JH,H = 7.3 Hz, 3 H) ppm. 13C NMR
(75 MHz, [D6]DMSO, 25 °C, TMS): δ = 191.1 (CHO), 142.8, 142.6,
135.4, 133.1, 127.0, 126.9 (CH), 126.1 (CH), 124.7 (CH), 122.7,
122.5, 122.3 (CH), 122.0, 121.1, 119.9 (CH), 118.9 (CH), 113.6,
109.9 (CH), 109.6 (CH), 41.4 (CH2), 39.9 (CH2), 31.4 (CH2), 29.1
(CH2), 28.7 (CH2), 21.9 (CH2), 14.9 (CH3), 13.9 (CH3), 13.4 (CH3)
ppm.
ment upon progressive substitution with ICZ fragments is
likely to be an indication that no nonplanar macrocycle dis-
tortions are induced. There are no noticeable differences in
the photophysical properties of the trans- and cis-disubsti-
tuted free-base porphyrins. Further studies will be directed
towards thorough electrochemical characterization and the
prospective application of the novel materials in optoelec-
tronic devices, an area of ever growing technological and
scientific interest.
10-(12-Pentyl-5,11-dihydroindolo[3,2-b]carbazol-6-yl)-5,15-bis(2,4,6-
trimethylphenyl)corrole (6): Eluent CH2Cl2; yield 3%. MS (ESI)
Experimental Section
1
calcd. for C60H54N6: 858.4; found: m/z 859.6 [M + H]+. H NMR
General: NMR spectra were acquired on commercial instruments
(Bruker Avance 300 MHz, Bruker AMX 400 MHz or Bruker Av-
ance II+ 600 MHz) and chemical shifts (δ) are reported in parts
per million (ppm) referenced to tetramethylsilane or residual NMR
solvent signals.[26] Mass spectra were run using a HP5989A appara-
tus (CI and EI, 70 eV ionisation energy) with Apollo 300 data sys-
tem or a Thermo Finnigan LCQ Advantage apparatus (ESI). Exact
mass measurements were acquired on a Kratos MS50TC instru-
ment (performed in the EI mode at a resolution of 10000). Melting
points were determined using a Reichert Thermovar apparatus. For
column chromatography 70–230 mesh silica 60 (Merck) was used
as the stationary phase. Chemicals received from commercial
sources were used without further purification. Tetramesitylpor-
phyrin (TMP) was prepared according to a previously reported
procedure.[27] Zinc insertion in TMP was performed with
Zn(OAc)2 in CHCl3. UV/Vis spectra were taken on a Perkin–Elmer
Lambda 20 (KU Leuven) or a Varian CARY 500 Scan (Minsk)
spectrophotometer. The fluorescence measurements have been per-
formed in standard rectangular cells (1ϫ1 cm, Hellma) in air-
equilibrated solutions at 293Ϯ2 K. Deoxygenated solutions have
been used for the measurements of the fluorescence quantum yield.
Deoxygenation was achieved by bubbling argon through the solu-
tion during 20 min just before the measurements. The fluorescence
and fluorescence excitation spectra have been measured with the
use of a spectrofluorometer SFL-1211 (Solar, Belarus). The fluores-
cence decay kinetics have been measured with the use of a photon
counting system FLA-900 (Edinburgh Instruments, UK). The fluo-
rescence quantum yield (Φfl) and singlet oxygen photosensitization
quantum yield (Φ∆) have been determined using the standard sam-
ple method, with free-base 5,10,15,20-tetraphenylporphyrin
(H2TPP) and Zn-5,10,15,20-tetraphenylporphyrin (ZnTPP) as
(400 MHz, CDCl3, 25 °C, TMS): δ = 8.89 (d, JH,H = 4.0 Hz, 2 H,
Hβ), 8.40–8.17 (m, 9 H, 6ϫ Hβ), 7.42 (d, JH,H = 8.0 Hz, 2 H), 7.30–
7.18 (m, 5 H), 7.05–6.97 (m, 2 H), 3.76 (br. t, JH,H = 8.0 Hz, 2 H,
CH2), 2.55 (s, 6 H, CH3-Mes), 2.27–2.18 (m, 2 H, CH2), 2.00 (s, 6
H, CH3-Mes), 1.85 (s, 6 H, CH3-Mes), 1.84–1.75 (m, 2 H, CH2),
1.64–1.54 (m, 2 H, CH2), 1.05 (t, JH,H = 7.4 Hz, 3 H, CH3-pent)
ppm. UV/Vis (CH2Cl2): λmax (logε) = 277 (4.582), 318 (sh, 4.411),
331 (4.504), 411 (4.800), 566 (3.970), 601 (3.812), 631 (3.615) nm.
6-Bromo-5,11-dimethyl-12-pentyl-5,11-dihydroindolo[3,2-b]carb-
azole (8): To a flame-dried, N2-flushed round-bottomed flask con-
taining a solution of monobrominated ICZ 7[8c] (0.5 g, 1.2 mmol)
in dry THF (20 mL), cooled to 0 °C, NaH (0.5 g, 12 mmol) was
portionwise added. After the addition of CH3I (0.38 mL, 6 mmol,
5 equiv.), the mixture was warmed slowly to room temp. and then
heated at 60 °C overnight under a N2 atmosphere. The reaction
mixture was subsequently cooled down to room temp., distilled
water (20 mL) was added and the solution was extracted with
CH2Cl2 (3ϫ30 mL). The organic extracts were combined, washed
with brine, dried with MgSO4 and concentrated in vacuo. The
crude residue was purified by flash column chromatography (silica,
eluent CH2Cl2/heptane, 4:6) to yield ICZ 8 (0.43 g, 80 %) as a
slightly yellow solid, and immediately used further on in the prepa-
ration of ICZ precursor 9.
6-(p-Formylphenyl)-5,11-dimethyl-12-pentyl-5,11-dihydroindolo[3,2-b]-
carbazole (9): ICZ 9 was prepared according to the Suzuki protocol
described for the analogous non-N-methylated monobrominated
ICZ using 6-bromo-5,11-dimethyl-12-pentyl-5,11-dihy-
droindolo[3,2-b]carbazole (8) (0.100 g, 0.23 mmol), 4-formylphen-
ylboronic acid (0.052 g, 0.35 mmol), K2CO3 (0.080 g, 0.58 mmol)
and Pd(PPh3)4 (1.3 mg, 1.2 µmol).[8c] Column chromatographic pu-
rification (silica, eluent CH2Cl2/heptane, 4:6) afforded ICZ 9
(0.070 g, 55%) as a yellow solid; m.p. 277–278 °C. HRMS (EI):
calcd. for C32H30N2O: 458.2358; found: m/z 458.2354. 1H NMR
(300 MHz, CDCl3, 25 °C, TMS): δ = 10.22 (s, 1 H, CHO), 8.24 (d,
standard samples (Φ0 = 0.09, Φ0 = 0.68 and Φ0 = 0.033, Φ0
=
fl
∆
fl
∆
0.90, respectively).
5,11-Diethyl-6-formyl-12-pentyl-5,11-dihydroindolo[3,2-b]carbazole
(3): ICZ 3 was prepared according to the procedure described for
the non-N-alkylated 6-formyl-ICZ analogue 2.[8c] To a solution of
5,11-diethyl-6-pentyl-5,11-dihydroindolo[3,2-b]carbazole (0.6 g,
1.6 mmol) in 1,2-dichloroethane (10 mL) at room temp., DMF
(0.15 mL, 1.9 mmol, 1.2 equiv.) was added, and subsequently
POCl3 (0.17 mL, 1.9 mmol, 1.2 equiv.) was added dropwise under
a N2 atmosphere. The mixture was stirred for 10 min and then
heated at reflux temperature overnight under a N2 atmosphere. The
resulting mixture was cooled down to room temp., poured into ice
water and extracted with ethyl acetate. The organic extracts were
combined, washed with brine, dried with Na2SO4 and concentrated
in vacuo. The crude residue was purified by column chromatog-
raphy (silica, eluent ethyl acetate/heptane, 2:8) to afford ICZ 3
(0.46 g, 71 %) as a yellow solid; m.p. 73–75 °C. MS (CI): 411
JH,H = 8.2 Hz, 1 H), 8.09 (d, JH,H = 7.3 Hz, 2 H), 7.76 (d, JH,H
=
8.2 Hz, 2 H), 7.48 (t, JH,H = 7.3 Hz, 1 H), 7.39–7.21 (m, 4 H), 6.84–
6.77 (m, 1 H), 6.52 (d, JH,H = 7.3 Hz, 1 H), 4.19 (s, 3 H, NCH3),
3.78 (br. t, JH,H = 8.4 Hz, 2 H), 3.26 (s, 3 H, NCH3), 2.06 (br. s, 2
H), 1.77–1.63 (m, 2 H), 1.58–1.46 (m, 2 H), 1.02 (t, JH,H = 7.3 Hz,
3 H, CH3-pent) ppm. 13C NMR (75 MHz, CDCl3, 25 °C, TMS): δ
= 192.2 (CHO), 146.2, 143.9, 143.4, 136.0, 134.5, 134.0, 132.2
(CH), 130.1 (CH), 125.7 (CH), 125.5 (CH), 122.8 (CH), 122.7,
122.6, 122.3, 122.1, 122.0 (CH), 120.4, 118.7 (CH), 118.2 (CH),
115.0, 108.44/108.38 (CH), 33.6 (CH3), 32.7 (CH3), 32.5 (CH2),
30.9 (CH2), 29.2 (CH2), 22.8 (CH2), 14.4 (CH3) ppm. UV/Vis
(CH2Cl2): λmax (logε) = 265 (4.734), 285 (4.924), 321 (4.490), 336
(4.684), 418 (3.984) nm.
[MH+]. HRMS (EI): calcd. for C28H30N2O: 410.2358; found: m/z Synthesis of meso-Indolo[3,2-b]carbazolylporphyrins 10a–13a: To
410.2350. 1H NMR (300 MHz, [D6]DMSO, 25 °C, TMS): δ = 11.24 CH2Cl2 (50 mL), purged with Ar for 15 min (while stirring vigor-
Eur. J. Org. Chem. 2010, 2576–2586
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2583

W. Maes, M. M. Kruk, W. Dehaen et al.
FULL PAPER
ously), mesityldipyrromethane (5) (87 mg, 0.33 mmol) and 5,11-di-
9.16 (m, 1.5 H, Hβ), 9.13 (s, 0.5 H, Hβ), 9.01 (d, JH,H = 4.5 Hz, 0.5
methyl-6-(p-formylphenyl)-12-pentyl-5,11-dihydroindolo[3,2-b]carb- H, Hβ), 8.98 (d, JH,H = 4.5 Hz, 0.5 H, Hβ), 8.88 (d, JH,H = 4.3 Hz,
azole (9) (150 mg, 0.33 mmol, 1 equiv.) were added, immediately 1 H, Hβ), 8.83 (d, JH,H = 4.5 Hz, 1 H, Hβ), 8.78 (s, 2 H, Hβ), 8.53–
followed by the addition of BF3·OEt2 (175 µL, 0.14 mmol,
0.425 equiv.), and the solution was stirred at room temp. for 1 h
(under an Ar atmosphere and protected from light). p-Chloranil
(81 mg, 0.33 mmol, 1 equiv.) was subsequently added and the mix-
ture was heated at reflux for 1 h. The solvent was removed in vacuo
and the crude porphyrin mixture was separated in its components
10a–13a by column chromatography (silica, eluent CH2Cl2/petro-
leum ether, 1:1).
8.46 (m, 4 H), 8.36 (d, JH,H = 7.8 Hz, 2 H), 8.09–7.98 (m, 4 H),
7.63–7.47 (m, 8 H), 7.39–7.26 (m, 8 H), 7.20 (t, JH,H = 7.0 Hz, 2
H), 4.34 (s, 3 H, NCH3), 4.33 (s, 3 H, NCH3), 3.97–3.82 (m, 10 H,
CH2/NCH3), 2.69–2.64 (m, 6 H, CH3-Mes), 2.35–2.05 (br. s, 4 H,
CH2), 1.96–1.90 (m, 12 H, CH3-Mes), 1.81 (q, JH,H = 7.3 Hz, 4 H,
CH2), 1.61 (s, JH,H = 7.3 Hz, 4 H, CH2), 1.07 (t, JH,H = 7.3 Hz, 6
H, CH3-pent), –2.44 (br. s, 2 H, NH) ppm. 13C NMR (100 MHz,
CDCl3, 25 °C, TMS): δ = 144.21/144.18, 143.6, 142.2, 139.6, 138.9,
138.4, 138.01/137.98, 135.1 (CH), 135.0 (CH), 134.8, 134.7, 132–
130 (br., CHβ), 129.7 (CH), 127.99/127.95 (CH), 125.8 (CH), 125.5
(CH), 123.5, 123.2, 122.9 (CH), 122.7 (CH), 122.6 (CH), 122.4,
120.0, 119.5, 118.67/118.63 (CH), 118.3 (CH), 116.4, 108.56/108.48
(CH), 33.7 (CH3-N), 32.7 (CH3-N), 32.7 (CH2), 31.1 (CH2), 29.4
(CH2), 22.9 (CH2), 21.9/21.7 (CH3-Mes), 14.4 (CH3) ppm. UV/Vis
(toluene): λmax (logε) = 422.0 (5.591), 515.5 (4.243), 549.5 (3.924),
593.0 (3.705), 650.0 (3.565) nm.
5-[4-(5,11-Dimethyl-12-pentyl-5,11-dihydroindolo[3,2-b]carbazol-6-
yl)phenyl]-10,15,20-tris(2,4,6-trimethylphenyl)porphyrin (10a): Yield
6.5% (8 mg). MS (ESI): calcd. for C78H72N6: 1092.6; found: m/z
1
1093.6 [M + H]+. H NMR (400 MHz, CDCl3, 25 °C, TMS): δ =
9.15 (d, JH,H = 4.8 Hz, 1 H, Hβ), 8.93 (d, JH,H = 4.8 Hz, 1 H, Hβ),
8.84 (d, JH,H = 4.8 Hz, 1 H, Hβ), 8.79 (d, JH,H = 4.5 Hz, 1 H, Hβ),
8.69–8.63 (m, 4 H, Hβ), 8.44 (d, JH,H = 8.0 Hz, 2 H), 8.35 (d, JH,H
= 7.8 Hz, 1 H), 7.99 (d, JH,H = 7.8 Hz, 2 H), 7.60–7.47 (m, 4 H),
7.35–7.27 (m, 8 H), 7.19 (td, JH,H = 7.2, 1.5 Hz, 1 H), 4.31 (s, 3 H, 5,10,15-Tris[4-(5,11-dimethyl-12-pentyl-5,11-dihydroindolo[3,2-b]carb-
NCH3), 3.91 (br. t, JH,H = 8.6 Hz, 2 H, CH2), 3.83 (s, 3 H, NCH3), azol-6-yl)phenyl]-20-(2,4,6-trimethylphenyl)porphyrin (13a): Yield
2.66–2.62 (m, 9 H, CH3-Mes), 2.30–2.05 (br. s, 2 H, CH2), 1.91– 13% (24 mg). MS (ESI): calcd. for C122H108N10: 1712.9; found: m/z
1
1.86 (m, 18 H, CH3-Mes), 1.78 (q, JH,H = 7.3 Hz, 2 H, CH2), 1.60 1714.8 [M + H]+. H NMR (300 MHz, CDCl3, 25 °C, TMS): δ =
(s, JH,H = 7.3 Hz, 2 H, CH2), 1.06 (t, JH,H = 7.3 Hz, 3 H, CH3-
9.43–9.34 (m, 2 H, Hβ), 9.27–9.14 (m, 3 H, Hβ), 9.08–9.00 (m, 1
pent), –2.46 (br. s, 2 H, NH) ppm. 13C NMR (100 MHz, CDCl3, H, Hβ), 8.95 (d, JH,H = 4.6 Hz, 1 H, Hβ), 8.90 (d, JH,H = 4.6 Hz,
25 °C, TMS): δ = 144.2, 143.6, 142.1, 139.6, 138.8, 138.5, 138.3, 1 H, Hβ), 8.58–8.48 (m, 6 H), 8.36 (d, JH,H = 7.3 Hz, 3 H), 8.11–
137.9, 134.9 (CH), 134.8, 134.7, 132–130 (br., CHβ), 129.6 (CH), 7.99 (m, 6 H), 7.63–7.46 (m, 12 H), 7.41–7.18 (m, 11 H), 4.33 (s, 9
127.97/127.93 (CH), 125.8 (CH), 125.4 (CH), 123.5, 123.2, 122.9 H, NCH3), 3.98–3.80 (m, 15 H, CH2/NCH3), 2.69 (br. s, 3 H, CH3-
(CH), 122.7 (CH), 122.4, 120.0, 119.0, 118.7 (CH), 118.3 (CH),
118.0, 116.4, 108.54/108.47 (CH), 33.7 (CH3-N), 32.9 (CH3-N), 32.7
Mes), 2.35–2.00 (br. s, 6 H, CH2), 1.97 (br. s, 6 H, CH3-Mes), 1.81
(q, JH,H = 7.3 Hz, 6 H, CH2), 1.60 (s, JH,H = 7.3 Hz, 6 H, CH2),
(CH2), 31.1 (CH2), 29.4 (CH2), 22.9 (CH2), 21.91/21.88/21.6 (CH3- 1.07 (t, JH,H = 7.3 Hz, 9 H, CH3-pent), –2.43 (br. s, 2 H, NH) ppm.
Mes), 14.4 (CH3) ppm. UV/Vis (toluene): λmax (log ε) = 420.5 13C NMR (75 MHz, CDCl3, 25 °C, TMS): δ = 144.2, 143.6, 142.2,
(5.665), 515.0 (4.321), 547.5 (3.912), 593.0 (3.768), 650.0 (3.560) nm. 142.0, 139.6, 139.0, 138.4, 138.1, 135.2 (CH), 135.1 (CH), 134.8,
134.6, 132.5–130 (br., CHβ), 129.8 (CH), 128.0 (CH), 125.9 (CH),
5,15-Bis[4-(5,11-dimethyl-12-pentyl-5,11-dihydroindolo[3,2-b]carb-
azol-6-yl)phenyl]-10,20-bis(2,4,6-trimethylphenyl)porphyrin (11a):
125.8 (CH), 125.5 (CH), 123.5, 123.2, 122.9 (CH), 122.7 (CH),
122.4, 120.1, 119.8, 119.1, 118.7 (CH), 118.3 (CH), 116.4, 108.6
(CH), 108.5 (CH), 33.7 (CH3-N), 33.1 (CH3-N), 32.9 (CH3-N), 32.7
(CH2), 31.1 (CH2), 29.4 (CH2), 22.8 (CH2), 21.9/21.7 (CH3-Mes),
Yield 29% (67 mg). MS (ESI): calcd. for C100H90N8: 1402.7; found:
1
m/z 1403.6 [M + H]+. H NMR (400 MHz, CDCl3, 25 °C, TMS):
δ = 9.21 (d, JH,H = 4.5 Hz, 2 H, Hβ), 9.00 (d, JH,H = 4.5 Hz, 2 H,
14.3 (CH3) ppm. UV/Vis (toluene) λmax (log ε) = 423.0 (5.656),
Hβ), 8.92 (d, JH,H = 4.6 Hz, 2 H, Hβ), 8.86 (d, JH,H = 4.5 Hz, 2 H,
516.5 (4.306), 551.0 (4.030), 593.5 (3.768), 649.0 (3.686) nm.
Hβ), 8.49 (d, JH,H = 8.0 Hz, 4 H), 8.35 (d, JH,H = 7.8 Hz, 2 H),
8.00 (d, JH,H = 7.3 Hz, 4 H), 7.60–7.45 (m, 8 H), 7.38–7.29 (m, 8 Zinc(II) Metallation: Zn(OAc)2·2H2O (5 equiv.) was added to a
H), 7.19 (t, JH,H = 7.2 Hz, 2 H), 4.30 (s, 6 H, NCH3), 3.90 (br. t, solution of the free-base porphyrin 10a–13a (10 mg, 1 equiv.) in
JH,H = 7.3 Hz, 4 H, CH2), 3.83 (s, 6 H, NCH3), 2.70–2.65 (m, 6 H,
CHCl3 (5 mL) and the mixture was stirred overnight at room temp.
CH3-Mes), 2.30–2.00 (br. s, 4 H, CH2), 1.97–1.92 (m, 12 H, CH3- (gradual colour change from purple to pink-purple). The metalla-
Mes), 1.78 (q, JH,H = 7.3 Hz, 4 H, CH2), 1.60 (s, JH,H = 7.3 Hz, 4 tion progress was monitored by UV/Vis spectroscopy. The solution
H, CH2), 1.06 (t, JH,H = 7.2 Hz, 6 H, CH3-pent), –2.43 (br. s, 2 H, was diluted with CHCl3 and washed with saturated NaHCO3 (aq)
NH) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = 144.1, and water. The organic layer was dried with MgSO4 and filtered.
143.6, 141.9, 140.9, 139.6, 138.8, 138.5, 138.0, 134.9 (CH), 134.7,
The respective ZnII-porphyrins 10b–13b were obtained as pink-red-
134.6, 132–130 (br., CHβ), 129.7 (CH), 128.0 (CH), 125.7 (CH), dish solids (in a nearly quantitative yield) after flash column
125.4 (CH), 123.4, 123.2, 122.94 (CH), 122.88, 122.6 (CH), 122.3, chromatography (silica, eluent CH2Cl2/petroleum ether, 1:1, Rf
120.0, 119.2, 118.8, 118.6 (CH), 118.3 (CH), 116.4, 108.53/108.44 ≈ 0.05 lower than the corresponding free-base analogue).
(CH), 33.7 (CH3-N), 32.9 (CH3-N), 32.7 (CH2), 31.1 (CH2), 29.4
{5-[4-(5,11-Dimethyl-12-pentyl-5,11-dihydroindolo[3,2-b]carbazol-6-
yl)phenyl]-10,15,20-tris(2,4,6-trimethylphenyl)porphyrinato}zinc(II)
(CH2), 22.9 (CH2), 21.9/21.7 (CH3-Mes), 14.4 (CH3) ppm. UV/Vis
(CH2Cl2): λmax (logε) = 286 (5.073), 321 (4.719), 336 (5.021), 420
(5.638), 516 (4.292), 550 (3.941), 591 (3.750), 647 (3.634) nm. UV/
Vis (toluene): λmax (log ε) = 422.0 (5.615), 515.5 (4.288), 549.5
(10b): MS (ESI): calcd. for C78H70N6Zn: 1154.5; found: m/z 1155.7
1
[M + H]+, 1187.6 [M + Na]+. H NMR (400 MHz, CDCl3, 25 °C,
TMS): δ = 9.24 (d, JH,H = 4.5 Hz, 1 H, Hβ), 9.02 (d, JH,H = 4.5 Hz,
1 H, Hβ), 8.92 (d, JH,H = 4.6 Hz, 1 H, Hβ), 8.86 (d, JH,H = 4.5 Hz,
(3.995), 593.0 (3.735), 649.0 (3.589) nm.
5,10-Bis[4-(5,11-dimethyl-12-pentyl-5,11-dihydroindolo[3,2-b]carb-
azol-6-yl)phenyl]-15,20-bis(2,4,6-trimethylphenyl)porphyrin (12a):
Yield 6% (14 mg). MS (ESI): calcd. for C100H90N8: 1402.7; found:
1 H, Hβ), 8.77–8.70 (m, 4 H, Hβ), 8.46 (d, JH,H = 8.0 Hz, 2 H),
8.35 (d, JH,H = 8.1 Hz, 1 H), 7.98 (d, JH,H = 7.3 Hz, 2 H), 7.60–
7.47 (m, 4 H), 7.36–7.27 (m, 8 H), 7.19 (t, JH,H = 7.2 Hz, 1 H),
4.32 (s, 3 H, NCH3), 3.91 (br. t, JH,H = 8.2 Hz, 2 H, CH2), 3.85 (s,
3 H, NCH3), 2.68–2.61 (m, 9 H, CH3-Mes), 2.35–2.05 (br. s, 2 H,
1
m/z 1403.8 [M + H]+. H NMR (400 MHz, CDCl3, 25 °C, TMS):
δ = 9.36 (s, 0.5 H, Hβ), 9.33 (d, JH,H = 4.5 Hz, 0.5 H, Hβ), 9.21–
2584
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 2576–2586

meso-Indolo[3,2-b]carbazolyl-Substituted Porphyrinoids
CH2), 1.93–1.86 (m, 18 H, CH3-Mes), 1.81 (q, JH,H = 7.3 Hz, 2 H, CH2Cl2 (150 mL), purged with Ar for 10 min, a solution of p-for-
CH2), 1.60 (s, JH,H = 7.3 Hz, 2 H, CH2), 1.06 (t, JH,H = 7.3 Hz, 3
mylphenyl-ICZ 9 (50 mg, 109 µmol, 1 equiv.) in CH2Cl2 (50 mL),
H, CH3-pent) ppm. 13C NMR (100 MHz, CDCl3, 25 °C, TMS): δ = activated with BF3·OEt2 (5.7 µL 10% solution in CH2Cl2,
150.15/150.10/150.0/149.96/149.91 (Cα), 144.2, 143.6, 142.9, 139.50/
139.47, 139.23/139.21, 139.1, 138.4, 137.62/137.58, 134.83 (CH),
134.83/134.79/134.65, 132.1/131.9/131.37/131.33/131.31/131.0/130.9
(CHβ), 129.4 (CH), 127.84/127.80 (CH), 125.7 (CH), 125.4 (CH),
123.5, 123.2, 122.9 (CH), 122.7 (CH), 122.3, 119.92/119.86, 119.17/
4.5 µmol, 0.043 equiv.), was added dropwise at room temp. over-
night, under an Ar atmosphere and protected from light, and the
resulting solution was stirred for another 12 h at room temp. p-
Chloranil (80 mg, 325 µmol, 3 equiv.) was subsequently added and
the mixture was heated at reflux for 1 h. The solvent was removed
119.14, 118.9, 118.6 (CH), 118.2 (CH), 116.6, 108.50/108.45 (CH), in vacuo and the AB2-corrole was obtained as a purple solid (5 mg,
33.7 (CH3-N), 32.9 (CH3-N), 32.7 (CH2), 31.1 (CH2), 29.4 (CH2), 5%) after flash column chromatographic purification (silica, eluent
22.9 (CH2), 21.93/21.87/21.85/21.63 (CH3-Mes), 14.4 (CH3) ppm.
CH2Cl2/petroleum ether, 1:1). MS (ESI): calcd. for C68H62N6:
UV/Vis (toluene) λmax (logε) = 423.0 (5.684), 550.0 (4.342), 587.5 962.5; found: m/z 964.1 [M + H]+. 1H NMR (400 MHz, CDCl3,
(3.456) nm.
25 °C, TMS): δ = 8.91 (d, JH,H = 3.3 Hz, 2 H, Hβ), 8.81 (d, JH,H
= 4.8 Hz, 1 H, Hβ), 8.65–8.61 (m, 2 H, Hβ), 8.59 (d, JH,H = 4.8 Hz,
1 H, Hβ), 8.40–8.32 (m, 5 H), 7.95 (d, JH,H = 7.6 Hz, 2 H), 7.58–
7.45 (m, 4 H), 7.34–7.09 (m, 7 H), 4.30 (s, 3 H, NCH3), 3.90 (br.
t, JH,H = 8.2 Hz, 2 H, CH2), 3.81 (s, 3 H, NCH3), 2.62 (s, 6 H,
CH3-Mes), 2.40–2.00 (br. s, 2 H, CH2), 1.97 (s, 6 H, CH3-Mes),
1.96 (s, 6 H, CH3-Mes), 1.83–1.74 (m, 2 H, CH2), 1.62–1.55 (m, 2
H, CH2), 1.06 (t, JH,H = 7.3 Hz, 3 H, CH3-pent) ppm. UV/Vis
(CH2Cl2): λmax (logε) = 286 (4.798), 321 (4.495), 336 (4.703), 408
(4.925), 427 (4.909), 567 (4.099), 604 (3.947), 636 (3.715) nm.
{5,15-Bis[4-(5,11-dimethyl-12-pentyl-5,11-dihydroindolo[3,2-b]carb-
azol-6-yl)phenyl]-10,20-bis(2,4,6-trimethylphenyl)porphyrinato}zinc(II)
(11b): MS (ESI): calcd. for C100H88N8Zn: 1464.6; found: m/z
1466.4 [M + H]+. H NMR (300 MHz, CDCl3, 25 °C, TMS): δ =
1
9.30 (d, JH,H = 4.6 Hz, 2 H, Hβ), 9.09 (d, JH,H = 4.6 Hz, 2 H, Hβ),
8.99 (d, JH,H = 4.6 Hz, 2 H, Hβ), 8.94 (d, JH,H = 4.6 Hz, 2 H, Hβ),
8.51 (d, JH,H = 8.2 Hz, 4 H), 8.35 (d, JH,H = 8.2 Hz, 2 H), 8.01 (d,
JH,H = 7.3 Hz, 4 H), 7.62–7.47 (m, 8 H), 7.38–7.29 (m, 8 H), 7.20
(t, JH,H = 7.3 Hz, 4 H), 4.32 (s, 6 H, NCH3), 3.92 (br. t, 4 H, CH2),
3.86 (s, 6 H, NCH3), 2.71–2.63 (m, 6 H, CH3-Mes), 2.35–2.00 (br. s,
4 H, CH2), 1.97–1.89 (m, 12 H, CH3-Mes), 1.78 (q, JH,H = 7.3 Hz, 4
H, CH2), 1.60 (s, JH,H = 7.3 Hz, 4 H, CH2), 1.07 (t, JH,H = 7.3 Hz,
6 H, CH3-pent) ppm. 13C NMR (75 MHz, CDCl3, 25 °C, TMS): δ
= 150.4/150.3/150.2 (Cα), 144.1, 143.6, 142.7, 139.5, 139.1, 138.5,
137.7, 134.9 (CH), 134.8, 134.6, 132.4 (CHβ), 132.3 (CHβ), 131.3
(CHβ), 131.2 (CHβ), 129.5 (CH), 127.9 (CH), 125.7 (CH), 125.4
(CH), 123.5, 123.2, 122.9 (CH), 122.7 (CH), 122.3, 120.2, 119.9,
119.8, 118.6 (CH), 118.3 (CH), 116.5, 108.51/108.44 (CH), 33.7
(CH3-N), 32.9 (CH3-N), 32.7 (CH2), 31.1 (CH2), 29.4 (CH2), 22.9
(CH2), 21.9/21.7 (CH3-Mes), 14.4 (CH3) ppm. UV/Vis (CH2Cl2):
λmax (logε) = 286 (5.060), 321 (4.695), 336 (4.909), 423 (5.590), 512
(3.483), 549 (4.253), 588 (3.507) nm. UV/Vis (toluene) λmax (logε)
= 425.0 (5.643), 550.0 (4.328), 589.0 (3.504) nm.
Supporting Information (see also footnote on the first page of this
article): 1H and 13C NMR spectra for ICZ precursor 9 and the
novel porphyrinoids, additional data on the VT NMR studies and
UV/Vis absorption spectra of a few ICZ precursors and meso-
indolocarbazolylcorroles 6 and 14.
Acknowledgments
We thank the Research Foundation Flanders (FWO Vlaanderen)
for financial support and for a postdoctoral fellowship to W. M.,
and the Katholieke Universiteit Leuven and the Ministerie voor
Wetenschapsbeleid for continuing financial support. T. H. N. is
grateful to the IWT (Institute for the Promotion of Innovation
through Science and Technology in Flanders) for a doctoral fellow-
ship. M. M. K. and A. S. S. thank the Foundation for Fundamental
Research of the Republic of Belarus for partial financial support.
{5,10,15-Tris[4-(5,11-dimethyl-12-pentyl-5,11-dihydroindolo[3,2-b]carb-
azol-6-yl)phenyl]-20-(2,4,6-trimethylphenyl)porphyrinato}zinc(II)
(13b): MS (ESI): calcd. for C122H106N10Zn: 1774.8; found: m/z
1777.5 [M + H]+, 888.0 [M + 2H]2+. H NMR (300 MHz, CDCl3,
1
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(br. s, 9 H, NCH3), 3.98–3.83 (m, 15 H, CH2/NCH3), 2.73–2.67 (m,
3 H, CH3-Mes), 2.35–2.05 (br. s, 6 H, CH2), 2.00–1.94 (m, 6 H,
CH3-Mes), 1.86–1.74 (m, 6 H, CH2), 1.67–1.54 (m, 6 H, CH2), 1.08
(t, JH,H = 7.3 Hz, 9 H, CH3-pent) ppm. 13C NMR (75 MHz,
CDCl3, 25 °C, TMS): δ = 150.54/150.45/150.3/150.2 (Cα), 144.2,
143.6, 143.4, 142.7, 139.5, 139.1, 138.6, 138.5, 137.8, 135.1 (CH),
134.9 (CH), 134.8, 134.6, 132.7–131.3 (m, CHβ), 129.6 (CH), 128.0
(CH), 127.9 (CH), 125.8 (CH), 125.4 (CH), 123.5, 123.2, 122.9
(CH), 122.7 (CH), 122.3, 120.8, 120.1, 118.6 (CH), 118.3 (CH),
116.5, 108.53/108.47 (CH), 108.2 (CH), 33.7 (CH3-N), 33.1 (CH3-
N), 32.9 (CH3-N), 32.7 (CH2), 31.1 (CH2), 29.4 (CH2), 22.9 (CH2),
22.0/21.7 (CH3-Mes), 14.5 (CH3) ppm. UV/Vis (toluene) λmax
(logε) = 426.5 (5.656), 551.5 (4.322), 590.0 (3.623) nm.
10-[4-(5,11-Dimethyl-12-pentyl-5,11-dihydroindolo[3,2-b]carbazol-6-
yl)phenyl]-5,15-bis(2,4,6-trimethylphenyl)corrole (14): To a solution
of mesityldipyrromethane (5) (172 mg, 651 µmol, 6 equiv.) in
Eur. J. Org. Chem. 2010, 2576–2586
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2585

W. Maes, M. M. Kruk, W. Dehaen et al.
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A. M. Marguerettaz, J. Org. Chem. 1987, 52, 827–836; b) J. S.
Lindsey, R. W. Wagner, J. Org. Chem. 1989, 54, 828–836.
[13] Formation of a corrole as a side product in porphyrin synthesis
has been observed before: E. Rose, A. Kossanyi, M. Quel-
quejeu, M. Soleilhavoup, F. Duwavran, N. Bernard, A. Lecas,
J. Am. Chem. Soc. 1996, 118, 1567–1568.
[14] A. Tohara, M. Sato, J. Porphyrins Phthalocyanines 2007, 11,
513–518, and references therein.
[15] The applied conditions were taken from previous work within
our group on analogous (likewise rather nonbasic) meso-pyrim-
idinylporphyrinoids (ref.[16]), for which no scrambling was ob-
served under these conditions (BF3·OEt2 catalysis). Selective
synthesis of trans-A2B2-porphyrin 11a could be pursued under
optimized Lindsey “minimal scrambling” conditions: B. J. Lit-
tler, Y. Ciringh, J. S. Lindsey, J. Org. Chem. 1999, 64, 2864–
2872. At this stage, however, the observed scrambling was con-
[25] M. Meot-Ner, A. D. Adler, J. Am. Chem. Soc. 1975, 97, 5107–
5111.
[26] H. E. Gottlieb, V. Kotlyar, A. Nudelman, J. Org. Chem. 1997,
62, 7512–7515.
[27] P. Kalimuthu, S. A. John, Anal. Chim. Acta 2008, 627, 247–
253.
Received: February 10, 2010
Published Online: March 23, 2010
2586
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Eur. J. Org. Chem. 2010, 2576–2586