Tetraanthra[2,3-b,g,l,q]porphyrin

Full text of DOI:10.1134/S0012500808090036

ISSN 0012-5008, Doklady Chemistry, 2008, Vol. 422, Part 1, pp. 212–215. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © S.E. Aleshchenkov, A.V. Cheprakov, I.P. Beletskaya, 2008, published in Doklady Akademii Nauk, 2008, Vol. 422, No. 2, pp. 189–192.
CHEMISTRY
Tetraanthra[2,3-b,g,l,q]porphyrin
S. E. Aleshchenkov, A. V. Cheprakov, and Academician I. P. Beletskaya
Received March 17, 2008
DOI: 10.1134/S0012500808090036
Porphyrins with extended π systems (containing third ring via cycloaddition with the use of butadiene
annelated aromatic systems) are of great interest as pos- resulting in situ from sulfolene (Fig. 2).
sible photosensitizers for photodynamic therapy [1],
By means of the procedure previously developed for
sensors [2], working materials for optoelectronic
similar 1,4-dihydronaphthalene [6], 1,4-dihydroan-
devices, and light-harvesting complexes in the long-
thracene 4 was converted through allyl sulfone 5 into
wavelength visible and near infrared (NIR) regions [3,
the tert-butoxycarbonyl derivative of dihydroisoindole
4
]. Recently, we developed a general and versatile syn-
6
, using the sulfonyl modification of the Barton–Zard
thetic approach to functionalized tetrabenzoporphyrins
TBPs) and tetranaphthoporphyrins (TNPs) using
,7-dihydroisoindole (1) or 4,9-dihydrobenzo[f]isoin-
reaction [9]. It should be noted that vinyl sulfones in the
described method undergo the Barton–Zard reaction
because the first stage of the reaction is a conjugated
addition of the isocyanoacetate anion to the double
bond of vinyl sulfone. We have shown, however, that
allyl sulfones can be involved into the Barton–Zard
reaction by the addition of 5% excess of potassium tert-
butoxide to the reaction mixture because vinyl and allyl
sulfones undergo interconversion in the presence of a
catalytic amount of a strong base. This modification was
found to be extremely convenient because, in the prepa-
ration of unsaturated sulfones via chlorosulphenylation–
oxidation–elimination [10], as shown previously [6], the
double bond migrates quantitatively to the conjugated
position to form allyl sulfones similar to 5.
(
4
dole (2) and their derivatives substituted at the anne-
lated rings (Fig. 1) as universal synthons (the dihy-
droisoindole method) [5, 6]. TBPs and TNPs with a dif-
ferent degree of substitution obtained by the
dihydroisoindole method and their metal complexes
show long-wavelength absorption bands in the range up
to 750 nm. A number of science and technology appli-
cations require a further shift of the long-wavelength
absorption bands of porphyrin chromophores to the
NIR region. To solve this task, in this work, we extend
the dihydroisoindole method to previously unknown
tetraaryltetraanthraporphyrins (tetraanthraporphyrin is
denoted for convenience as TAP).
The hydrolysis and decarboxylation of ester 6 were
The sole publication on the tetraanthraporphyrin carried out under mild conditions by treatment with tri-
system in the literature deals with the synthesis of a Zn fluoroacetic acid, and the resultant dihydronaph-
complex of triarylTAP [7] by the high-temperature thoisoindole without purification was subjected to con-
template condensation of sodium p-phenylphenylace- densation with aromatic aldehyde by the standard pro-
tate and anthracene-2,3-dicarboximide. Severe uncon- cedure of tetraarylporphyrin synthesis.
trolled reaction conditions (temperature above 350°C)
It is interesting to note that the aromatization of por-
of this process caused a random distribution of meso
phyrinogens was not accompanied by the simultaneous
substituents, a very poor yield, and a low stability of the
aromatization of the partially hydrogenated six-mem-
product.
bered rings of the isoindole system when the reaction
mixture was treated with dichlorodicyanobenzo-
Our approach developed for the use of the dihy-
quinone (DDQ) to form TBP and TNP from corre-
droisoindole method in the synthesis of TAP requires
sponding dihydroisoindoles 1 or 2 [5, 6]. Complete aro-
the following benzo-annelated dihydroisoindole: previ-
matization in these cases should be carried out by the
ously unknown 4,11-dihydronaphtho[2,3-f]isoindole 3.
treatment with additional amounts of DDQ, sometimes
This compound was obtained starting from known
with solvent replacement and at elevated temperature.
1
,4-dihydroanthracene 4 [8], prepared from the adduct
On the contrary, it was shown in this work that the aro-
matization of similar intermediate porphyrin 7 pro-
ceeds so fast that the formation of target TAP 8 lasts for
of dehydrobenzene and furan by the formation of the
3
0 min after the addition of the aromatization reagent
Chemistry Department, Moscow State University, Moscow,
119899 Russia
(Fig. 3) and neither the intermediate porphyrin nor
other incompletely aromatized compounds are detected
2
12

TETRAANTHRA[2,3-b,g,l,q]PORPHYRIN
213
TAP
TNP
TBP
TNP
⇒
⇒
NH
1
2
TBP
R
R
R
R
N
H
NH
N
N
H
N
TAP
⇒
NH
3
Fig. 1. Porphyrins with extended π systems and their synthetic precursors.
a
b
c
SO Ph
2
4
5 (75%)
COOBu-t
(65%)
N
N
H
H
6
3 (95%)
Fig. 2. Synthesis of 4,11-dihydronaphtho[2,3-f]isoindole at ambient temperature: (a) (1) PhSCl, CH Cl , 30 min; (2) Oxone,
2
2
MeOH–H O, 5 h; (3) DBU, CH Cl , 30 min; (b) CNCH CO Bu-t, t-BuOK, THF, 12 h; (c) CF COOH, 30 min.
2
2
2
2
2
3
when the reaction mixtures are analyzed by MALDI–
TOF mass spectroscopy.
Figure 4 shows electronic absorption spectra. As
compared with similar TNP, the effect of the additional
ring appears as a strong shift of the long-wavelength
absorption bands; the most intense Q band is shifted by
The target tetraanthraporphyrin was isolated from
the reaction mixture by flash chromatography and crys-
1
00 nm (832 nm for TAP and 732 nm for TNP). The
tallization in 32% yield. Similarly to tetraarylTNP, TAP short-wavelength B bands are very close (508 nm for
8
strongly tends to form aggregates in solutions, which TAP and 500 nm for TNP); therefore, the distance
leads to broadening of absorption bands, its solubility between the Q and B bands in TAP is considerably
in common organic solvents being substantially higher larger. The presence of a wide free range between the
1
long-wavelength and short-wavelength bands (trans-
parency window) is very important for up-conversion
systems [3] because it allows one to allocate absorption
bands of emitting molecules within this region.
than that of similar TNP [6]. The H NMR spectrum of
the obtained porphyrin is very similar to the spectrum
of the corresponding TNP: the close values of chemical
shifts for the analogous groups of protons obviously
result from the similar distribution of magnetic anisot-
ropy cones of the aromatic ring system, which, in turn, mophores with an extended π system is the relative
indicates the resemblance of the structures of these two intensity of Q and B bands in the spectrum: the data
Another important characteristic of porphyrin chro-
series.
obtained indicate that the relative intensity of the long-
DOKLADY CHEMISTRY Vol. 422 Part 1 2008

2
14
ALESHCHENKOV et al.
X
X
XC H CHO,
6
4
BF3 · Et O,
2
NH
N
N
NH
N
N
CH Cl
2
2
3
X
X
X
X
HN NH
HN NH
X
7
X
8
X = COOMe
Fig. 3. Synthesis of tetrakis(p-methoxycarbonylphenyl)tetraanthra[2,3-b,g,l,q]porphyrin.
wavelength B band builds up when passing from TBP 20 min even under a scattered artificial lighting
to TNP and further to TAP, i.e., on extending the conju- (according to electronic absorption spectra). Let us note
gated system. This effect is even more pronounced for for comparison that similar solutions of TBP and TNP
metal complexes. The metalation of TAP increases the are stable under these conditions and display porphyrin
intensity and decreases the width of the bands, the spec- decomposition only when exposed to direct sunlight for
a long time. Therefore, all manipulations with TAP
solutions should be carried out in the dark and under an
inert gas atmosphere. TAP crystals are quite stable.
trum of the Zn complex shows a slight hypsochromic
shift of the Q bands and no marked effect on the posi-
tion of the B band, whereas all bands for the Pd com-
plex are shifted to the short-wavelength region by 20–
Thus, we developed for the first time a convenient
0 nm. These trends are quite similar to those observed synthetic approach to previously unknown tetraaryltet-
3
for TNP. An interesting property of TAP is the raanthra[2,3-b,g,l,q]porphyrins. TAP shows intense
extremely high sensitivity to photooxidation: TAP narrow absorption bands in the long-wavelength spec-
completely decomposes in a dilute solution within tral region, the shift of the Q bands being maximal
among all known porphyrins with an extended π sys-
tem. This affords a maximal transparency window
A
.0
B band
between the absorption bands. The unique photophysi-
cal properties of this system provide the possibility to
use it in up-conversion systems and other optical appli-
cations in the near infrared region.
2
1
1
0
Q band
.5
.0
.5
EXPERIMENTAL
2
Chemicals and solvents were purified by standard
procedures. Electronic absorption spectra were
recorded on a PerkinElmer Lambda 40 spectrophotom-
eter; LDI–TOF mass spectra were obtained on a Bruker
Daltonics Alphaflex II mass spectrometer without use
of template. NMR spectra were recorded on a Bruker
Avance 400 spectrometer.
1
Synthesis of tetrakis(p-methoxycarbonylphe-
nyl)tetraanthra[2,3-b,g,l,q]porphyrin
8.
Dihy-
4
00
500
600
700
800
900
λ, nm
droisoindole 3 (0.24 g, 1.1 mmol) dissolved in freshly
distilled CH Cl (150 mL) was placed into a flask pro-
2
2
tected from light and equipped with an inert gas inlet
and magnetic stirrer, p-methoxycarbonylbenzaldehyde
Fig. 4. Electronic absorption spectra of tetranaphthopor-
phyrin 8 (1) and its zinc complex (2) in toluene.
DOKLADY CHEMISTRY Vol. 422 Part 1 2008

TETRAANTHRA[2,3-b,g,l,q]PORPHYRIN
215
(0.2 g, 1.2 mmol) was added. Then, BF3 · Et O salts (toluene, CF COOH): 544, 800, 914; Zn complex
2 3
(
0.03 mL) was added, the mixture was stirred at ambi- (toluene–pyridine): 510 (4.68), 732 (3.66), 810 (4.54);
ent temperature for 1 h, a solution of dichlorodicy- Pd complex (toluene): 470, 704, 790.
anobenzoquinone (0.38 g) in 1 mL of toluene was
added, and the mixture was stirred for 12 h at ambient
ACKNOWLEDGMENTS
temperature. The resultant dark solution was washed
with a 10% aqueous solution of Na SO (2 × 100 mL), a
This work was supported by the Russian Foundation
2
3
1
0% aqueous solution of Na CO (50 mL), and a satu- for Basic Research (project no. 07–03–01121).
2 3
rated solution of NaCl, and dried with Na SO . The sol-
2
4
vent was removed in a vacuum, the residue was purified
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DOKLADY CHEMISTRY Vol. 422 Part 1 2008