Synthesis and functionalization of triply fused porphyrin dimers

Article abstract of DOI:10.1002/ejoc.201201622

Current applications of porphyrins in medicine and optics, such as photodynamic therapy or nonlinear absorption, increasingly require the use of far-red absorbing dyes. Modification of the porphyrin structure to accommodate these conditions can be achieved by extending the conjugation of the porphyrin π system, which causes a bathochromic shift in the absorption spectrum. Thus, conjugated porphyrin oligomers have found widespread use. However, past synthetic strategies have mainly targeted symmetric porphyrin dimers, trimers, and oligomers which limit the practical use of such chromophores. To further extend the absorption profile, a series of symmetric and unsymmetric dimeric and oligomeric porphyrin β-β, meso-meso, β′-β′ triply fused systems were synthesized by oxidative coupling methods. This required an analysis and optimization of the various synthetic strategies. These arrays exhibit a dramatic bathochromic shift into the near-infrared region and many display absorption at wavelengths greater than 1050 nm. Additionally, post-fusing chemical transformations, namely, organolithium, cycloaddition, and transition-metal-catalyzed reactions, at the meso and β positions enable the fine-tuning of such arrays to enhance the bathochromic shift and their potential optical applications. A library of symmetric and unsymmetric singly linked and triply fused porphyrin dimers are synthesized in moderate to very good yields. A variety of functional groups are tolerated. Numerous synthetic strategies, incorporating oxidative radical coupling and organolithium and palladium-catalyzed coupling methods, are utilized. Copyright

Full text of DOI:10.1002/ejoc.201201622

Job/Unit: O21622
/KAP1
Date: 18-04-13 15:48:36
Pages: 13
FULL PAPER
Porphyrinoids
A library of symmetric and unsymmetric
singly linked and triply fused porphyrin di-
mers are synthesized in moderate to very
good yields. A variety of functional groups
are tolerated. Numerous synthetic stra-
tegies, incorporating oxidative radical
coupling and organolithium and palla-
dium-catalyzed coupling methods, are util-
ized.
A. A. Ryan, M. O. Senge* .............. 1–13
Synthesis and Functionalization of Triply
Fused Porphyrin Dimers
Keywords: Porphyrinoids / Organolithium
reagents / C–C coupling / Cycloaddition /
Fused-ring systems
0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
1

Job/Unit: O21622
/KAP1
Date: 18-04-13 15:48:36
Pages: 13
A. A. Ryan, M. O. Senge
FULL PAPER
DOI: 10.1002/ejoc.201201622
Synthesis and Functionalization of Triply Fused Porphyrin Dimers
Aoife A. Ryan[a] and Mathias O. Senge*[a,b]
Keywords: Porphyrinoids / Organolithium reagents / C–C coupling / Cycloaddition / Fused-ring systems
Current applications of porphyrins in medicine and optics,
such as photodynamic therapy or nonlinear absorption, in-
creasingly require the use of far-red absorbing dyes. Modifi-
porphyrin β–β, meso–meso, βЈ–βЈ triply fused systems were
synthesized by oxidative coupling methods. This required an
analysis and optimization of the various synthetic strategies.
cation of the porphyrin structure to accommodate these con- These arrays exhibit a dramatic bathochromic shift into the
ditions can be achieved by extending the conjugation of the
porphyrin π system, which causes a bathochromic shift in the
absorption spectrum. Thus, conjugated porphyrin oligomers
have found widespread use. However, past synthetic strate-
gies have mainly targeted symmetric porphyrin dimers, tri-
mers, and oligomers which limit the practical use of such
chromophores. To further extend the absorption profile, a
series of symmetric and unsymmetric dimeric and oligomeric
near-infrared region and many display absorption at wave-
lengths greater than 1050 nm. Additionally, post-fusing
chemical transformations, namely, organolithium, cyclo-
addition, and transition-metal-catalyzed reactions, at the
meso and β positions enable the fine-tuning of such arrays to
enhance the bathochromic shift and their potential optical
applications.
so-called unsymmetric fused dimers[10] and post-modifica-
tions of fused arrays.[11] We envisaged the development of
new symmetric fused dimers and unsymmetric arrays and
their application to research fields such as nonlinear optics
(NLO),[12] organic light-emitting diodes (OLEDs),[13] and
two-photon absorption photodynamic therapy (2PA-
PDT).[14] The introduction of various substituents to the
porphyrin periphery[15] and subsequent post-fusing modifi-
cations enables the arrays to be fine-tuned for PDT by the
introduction of water-solubilizing groups[14a,16] and NLO
by the introduction of donor/acceptor groups to generate
push–pull systems.[17] Thus, synthetic strategies for the de-
velopment of such arrays will be described. Following the
synthesis by Susumu et al. in 1996 of meso–meso directly
linked porphyrins by a condensation reaction,[18] there have
been substantial developments in the synthesis of such ar-
rays. These include total synthesis,[19] Ulmann coupling,[20]
oxidative fusing of free-meso porphyrins with oxidants such
as silver salts (AgPF6),[5,21] 2,3-dichloro-5,6-dicyano-1,4-
benzoquinone (DDQ) and Sc(OTf)3,[22] and hypervalent
iodine [bis(trifluoroacetoxy)iodobenzene (PIFA)],[23] along
with electrochemical oxidation[24] and recently a method in-
volving the use of a manganese(IV)–oxo porphyrin as a cat-
alyst in a two-electron oxidation process.[25] A method de-
veloped by us[26] involves the oxidative dimerization of por-
phyrin anions, and a stepwise synthetic strategy involving
the activation of the porphyrin and subsequent Suzuki cou-
pling has been developed.[27] These meso–meso directly
linked porphyrin dimers are vital precursors for the synthe-
sis of triply fused bisporphyrins and, thus, can be used or
optimized to synthesize such arrays, depending on the sub-
stitution pattern on the periphery required (symmetric or
Introduction
Long-wavelength absorption of porphyrins is desired for
a wide range of applications[1] and there are many means
to achieve such a characteristic. These include the synthesis
of porphyrin arrays connected by conjugated linkers,[2] the
construction of perturbed porphyrinoid macrocycles
through various cycloaddition reactions,[3] and the con-
struction of fused or directly linked porphyrin arrays.[4] The
latter is favorable as triply linked porphyrin arrays result in
the extension of the absorption profile into the near-IR re-
gion. Pioneering methods developed by Sugiura et al.[5] and
Osuka and co-workers[6] can be adopted for the generation
of so-called triply fused porphyrin dimers and higher ar-
rays.[4a,7] A λmax value greater than 1050 nm may be
achieved for these covalently linked multiporphyrin arrays
and they can act as multichromophoric model systems for
the study of electron transfer in light-harvesting systems.
Although the Osuka group, amongst others,[4b,8] have ex-
tensively researched this area, their work primarily deals
with symmetric arrays and photophysical studies of such
porphyrins.[9] Only limited research has been performed on
[a] School of Chemistry, SFI Tetrapyrrole Laboratory, Trinity
Biomedical Sciences Institute, Trinity College Dublin,
152–160 Pearse St., Dublin 2, Ireland
[b] Medicinal Chemistry, Institute of Molecular Medicine, Trinity
Centre for Health Sciences, Trinity College Dublin,
St James’s Hospital, Dublin 8, Ireland
Fax: +353-1-896-8536
E-mail: sengem@tcd.ie
Homepage: http://www.tcd.ie/Chemistry/staff/people/mos/
main index.html
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201201622.
2
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O21622
/KAP1
Date: 18-04-13 15:48:36
Pages: 13
Triply Fused Porphyrin Dimers
unsymmetric). Similar to singly linked bisporphyrins, vari- sitions could be implemented. By using 0.8 equiv. of PIFA
ous synthetic strategies[7] have been developed for the gener- to avoid formation of the triply fused dimers, the bromo-
ation of triply fused porphyrins since their first synthesis by substituted symmetric dimers 4c[5]and 4d were synthesized
electrochemical oxidation by Osuka and co-workers.[6] One- in good-to-excellent yields of 58 and 86% from 2c[2a] and
electron chemical oxidation[28] of monomeric zinc(II) por- 2d, respectively (Table 1). The reaction mechanism involves
phyrins with free meso positions is the most attractive route the oxidative generation of a porphyrin cation radical,
for the synthesis of symmetric triply fused porphyrin di- which dimerizes to form the bisporphyrin product. Drawing
mers, and a variety of oxidants can be utilized. The most attention to the 3-methoxy substituent in 4d, we generated
efficient are Sc(OTf)3/DDQ and hypervalent iodine (PIFA), materials with this group owing to our interest in Foscan®
although other oxidants such as gold derivatives can be derivatives,[35] for which it is a useful precursor. The synthe-
used and give similar yields.[29] We primarily focused on the sis of dimers 4a and 4b with free meso positions in accept-
synthesis of new symmetric triply fused bisporphyrins and able yields from 2a[2a] and 2b[36] was unsuccessful. The de-
higher arrays by the above strategies and also the synthesis sired dimers were only synthesized in very low yields and
of unsymmetric fused dimers by similar principles. To fine- were identified by mass spectrometry and UV/Vis analysis
tune oligomeric porphyrins, post-fusing functionalizations of the reaction mixtures.
can be executed. These derivatizations enable fused dimers
to be more attractive candidates for practical applications.
Within our group, the focus is on PDT, NLO, and OLEDs
dation and organolithium reactions.
Table 1. Synthesis of directly linked bisporphyrins by PIFA oxi-
and, with these in mind, synthetic modifications of the pe-
ripheries of fused porphyrin dimers were undertaken. These
included activation reactions such as brominations and ni-
trations, which would enable, for example, the attachment
of sugars for PDT by Click chemistry[16b] or push–pull sub-
stituents for NLO.[30] Also, functionalization by cycload-
dition and organolithium reactions could be beneficial for
the enhancement of the bathochromic shift of the array.
Most previous post-modifications of fused arrays have dealt
with the pre-installation of activating substituents, whereas
we wanted to investigate the direct functionalizations of
these arrays and synthetic strategies to enable such.
Results and Discussion
Previously, we described the generation of directly linked
symmetric dimers in excellent yields by using organolithium
reagents, which can be used to introduce aryl and alky meso
substituents to the porphyrin periphery[31] and for the syn-
thesis of free-base meso–meso directly linked bisporphyrins
in good yields by radical dimerization.[26b,32]
Entry R1
R2
Product
Yield [%]
1
2
3
4
5
6
7
Ph
Ph
Ar
n-hexyl
Ph
Ph
Ph
n-butyl
Ph
H
H
Br
Br
3a[a]
3b[a]
3c[a]
4a[b]
4b[b]
4c[b]
4d[b]
68
59
74
n.d.[c]
n.d.
58
From the 5,15-disubstituted porphyrins 1a[33] and 1b,[18]
the free-base dimers 3a,[26a] 3b,[26a] and 3c were obtained in
good yields of 59–74% (Table 1). The zinc(II) derivatives of
3a[21c] and 3c[8c] have previously been synthesized in similar
yields by DDQ and PIFA oxidation methods, but from tri-
substituted precursors. Additionally, hypervalent iodine rea-
gents such as PIFA can be applied for the synthesis of di-
rectly linked porphyrin arrays. PIFA contains a highly elec-
trophilic iodine center, which can promote diverse coupling
3-MeO-C6H4
86
[a] Reagents and conditions: i) R2Li, –78 to 0 °C, tetrahydrofuran
(THF), 1 h. ii) DDQ, 1 h. [b] Reagents and conditions: i) PIFA,
CH2Cl2, –78 °C. ii) room temp., 0.75 h. iii) NaBH4, MeOH. [c] n.d.
= not determined.
Owing to the inevitable formation of oligomerized prod-
reactions,[34] including the synthesis of directly meso–meso ucts, dimers 4a and 4b were not isolated and this method
linked bisporphyrins in excellent yields.[23b] Interestingly, was not feasible for the synthesis of bisporphyrins with un-
high yields were obtained with electronegative substituents substituted meso positions. Notably, this PIFA oxidation
such as trifluoroalkyl groups and, thus, bromo-substituted method can also be used for the synthesis of triply fused β–
monomers were chosen as starting materials, which enabled β, meso–meso, βЈ–βЈ linked bisporphyrins, by using an ex-
the generation of activated bisporphyrins. Likewise, 5,15- cess of PIFA oxidant.[8c] Moreover, for most cases in the
disubstituted porphyrins were employed for the synthesis of literature, bromo-substituted directly linked dimers were
bisporphyrins with two free meso positions, with the same synthesized by stepwise strategies[37] or by using other oxi-
objective in mind, as post-fusing modifications at these po- dants such as AgPF6 and I2.[5]
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
3

Job/Unit: O21622
/KAP1
Date: 18-04-13 15:48:36
Pages: 13
A. A. Ryan, M. O. Senge
FULL PAPER
To overcome the challenge of synthesizing directly linked synthesis, as they have a lower first oxidation potential and,
porphyrin dimers with free meso positions, a stepwise ap- therefore, are more easily oxidized than their Ni or Pd
proach, which culminates in a Suzuki–Miyaura coupling counterparts.[40] Similarly to that for singly linked arrays,
between a bromoporphyrin and borylated porphyrin to give the reaction mechanism involves oxidative double ring clo-
singly linked bisporphyrins, is necessary.[38] This strategy sure via a porphyrin cation radical,[7,41] which undergoes
was adopted to synthesize unsymmetric hexasubstituted di- radical cation coupling. Electron-withdrawing substituents
mers and dimers with free meso positions, which would en- on the porphyrin periphery can affect the yields for oxidat-
able “post-fusing” modifications. The Suzuki coupling of ive fusing,[29] although it was shown recently that an elec-
bromoporphyrins 5a–d with borylated porphyrins 6a–d[39] tron-deficient porphyrin tape can be synthesized in good
produced the desired dimers 7a–f in yields of 43–66% yields.[42] In spite of this, a series of symmetric dimers were
(Table 2). Although the yields for these Suzuki couplings synthesized and their yields were compared in relation to
were good, they were hindered by the competing homocou- their substituents (Table 3). Comparable yields were ob-
pling of the borylated porphyrins 6a and 6b to generate tained with both DDQ/Sc(OTf)3 and PIFA oxidants. The
dimers 8a[5] and 8b as side-products in yields of 18 and new triply fused bisporphyrins 10b–k were prepared from
22%, respectively. Such directly linked dimers were used in 5,10,15-trisubstituted zinc(II)porphyrin precursors 9a–
subsequent fusing reactions to form triply linked dimers
g
[5,15,32,43] in moderate-to-excellent yields of 42–73% by fol-
and also, in the cases of free-meso dimers 7c–d, in function- lowing the Osuka oxidation method, and this strategy can
alization reactions.
be applied for the synthesis of other fused arrays. For some
oxidations with DDQ/Sc(OTf)3, two products were ob-
served: the desired triply fused dimer and the directly linked
bisporphyrins 4e–g as side-products, and the yields of di-
mers 10c, 10f,[32] and 10g were thereby affected. Through
optimization of the conditions by increasing the reaction
temperature and increasing the reaction duration, the for-
Table 2. Synthesis of directly linked porphyrin dimers by Suzuki
coupling.
Table 3. Synthesis of triply fused symmetric dimers.
Entry R1
R2
n-hexyl Ph
Ph 4-Me-C6H4
3-MeO-C6H4 Ph
1-ethylpropyl Ph
3-MeO-C6H4 Ph
R3
R4 Product[a] Yield [%]
1
2
3
4
5
6
7
8
n-hexyl
Ph
H
H
H
H
H
7a
7b
7c
7d
7e
7f
52
76
56
63
61
69
18
20
Entry R1
R2
Product
Yield [%]
3-MeO-C6H4
4-Me-C6H4
4-Me-C6H4
1
2
3
4
5
6
7
8
Ph
Ph
10a[a]
67[8[c]
56
60, 23
73
Ar[c]
4-O2N-C6H4
10b[a]
3-MeO-C6H4 n-butyl
3-MeO-C6H4 3-MeO-C6H4
Ph
Ph
4-Me-C6H4
Ph
n-hexyl
Ph
10c, 4e[a]
10d[a]
Ph
Ph
Ph
Ph
H
3-MeO-C6H4 Ph
Ph
4-Me-C6H4
Ph
H
8a
8b
4-ethynyl-C6H4
10e[a]
67
4-Me-C6H4
n-hexyl
n-butyl
H
H
Br
10f, 4f[a]
10g, 4 g[a]
10h[b]
42, 30[32]
58, 29
n.d.[d]
n.d.
[a] Reagents and conditions: Pd(PPh3)4 (0.1–0.2 equiv.), Cs2CO3
(2.1 equiv.), toluene/N,N-dimethylformamide (3:1 v/v), 80 °C, 18–
24 h.
9
10
11
10i[b]
10j,[a,b] 4h
10k[a,b]
n.d.
15
We aspired to synthesize a variety of A3 and A2B sym-
metric bisporphyrins with a range of substituents, some of
which would permit follow-up chemistry to be performed.
The central metal ion is of great importance to the oxidative
3-MeO-C6H4 Br
[a] Reagents and conditions: DDQ (5 equiv.), Sc(OTf)3 (5 equiv.),
toluene, 50 °C, 3 h. [b] i) PIFA (2.5 equiv.), CH2Cl2, –78 °C to room
temp., 3 h. ii) NaBH4 (10 equiv.), MeOH, 0.5 h. [c] Ar = 3,5-di-
process and, thus, zinc porphyrins were employed for the tert-butyl-C6H3. [d] n.d.: not determined.
4
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O21622
/KAP1
Date: 18-04-13 15:48:36
Pages: 13
Triply Fused Porphyrin Dimers
mation of these side-products was minimized. For the di- tained. With the milder PIFA oxidant, oligomerization was
mers 10h and 10i with free meso positions and the bromo not minimized, and similar results were observed for dimers
dimers 10j and 10k, both the DDQ and PIFA method were 11c–d. For the hexasubstituted dimer 11e, this problem was
employed. Unfortunately, owing to the inherent polymeri- not encountered and it was obtained in a good yield of
zations of monomers 2a and 2b, dimers 10h and 10i were 56% following the oxidation of 7f with DDQ/Sc(OTf)3; this
not isolated, although their formation was indicated by indicates that the method can be applied to unsymmetric
their near-IR absorption profiles.
directly linked dimers.
All triply fused bisporphyrins exhibited characteristic H
1
As with their singly linked bisporphyrin counterparts,
this strategy is not attractive for the synthesis of free-meso NMR spectra, and the signals shifted drastically to higher
dimers. For 10k, the best results were acquired with PIFA fields upon fusing, owing to a decrease in aromaticity with
as oxidant, although the yields were much lower than those respect to their starting materials. As these arrays have ex-
for the alkyl and aryl-substituted dimers 10a–g. Previous tensive π-electron systems delocalized through the entire
syntheses of fused bromo dimers with these oxidants also molecule, a profound effect on the ring current of the array
gave poor results, and Anderson and co-workers reporting is observed.[45] With these bisporphyrins, the inner β pro-
only 9% yield for the synthesis of (3,5-di-tert-butyl)phenyl tons resonate as singlets at δ ≈ 7.0 ppm. This characteristic
derivative of 10j with DDQ.[44] This is because the electron- singlet was observed for all symmetric fused dimers 10a–
withdrawing nature of the bromo substituent raises the oxi- 10k and the unsymmetric dimer 11e. The resolution of
dation potential of the porphyrin and, thereby, reduces the peaks was dependent on the solubility of the array in
yields of such arrays. With DDQ, the singly directly linked CDCl3. In some cases, the use of [D5]pyridine in CDCl3
derivative of 10j (4h)[21c] was isolated in 10% yield, but the minimized aggregation and enabled the generation of
1
desired triply fused dimer was not obtained.
sharper and more distinguished peaks in H NMR spectra.
By adopting a synthetic strategy similar to that for the However, in spite of this, broad signals were still observed
symmetric arrays, directly linked unsymmetric bisporphyr- for the majority of fused arrays, possibly indicative of con-
ins were fused oxidatively by using DDQ/Sc(OTf)3 or PIFA formational equilibria in solution.
(Table 4). With dimers 7a–c, 7e, and 7f, attempts to synthe-
The extension of conjugation in triply fused porphyrin
size triply fused porphyrins had mixed results. For the free- arrays results in a significant bathochromic shift in the ab-
meso arrays, dimers 11b–d were not detected. Although all sorption profile; the energy gap between the highest occu-
crude samples exhibited typical triply fused near-infrared pied molecular orbital (HOMO) and the lowest unoccupied
absorption profiles, the desired dimers were not detected by molecular orbital (LUMO) is reduced, which causes a sizea-
mass spectrometry, and purification was not possible. ble shift into the near-infrared region.[46] There were signifi-
Again, there is preferential fusing at this “free-meso” side cant differences between the profile of the fused dimer 10g
of the directly linked bisporphyrin, which results in a mix- and those of its directly linked dimeric counterpart 4g and
ture of dimeric and tetrameric products. Owing to the poor monomer 9g (Figure 1). Monomer 9g exhibited a character-
solubility of these arrays, their isolation could not be istic metalated-porphyrin absorption profile with a λmax of
achieved by chromatographic methods. Trace quantities of 590 nm. Directly linked dimer 4g exhibited a splitting of the
n-hexyl-substituted dimer 11a were detected, but full char- Soret band owing to excitonic coupling between the por-
acterization was not achievable owing to the low yields ob- phyrin units and had a λmax of 566 nm. However, with triply
fused dimer 10g, a substantial shift was observed. There
was a broad splitting of the Soret band (at 414 and 576 nm),
again because of excitonic coupling between the porphyrin
Table 4. Synthesis of triply fused unsymmetric dimers.[a,b]
Entry R1
R2
n-hexyl Ph
Ph 4-Me-C6H4
R3
R4 Product Yield [%]
1
2
3
4
5
n-hexyl
Ph
3-MeO-C6H4 Ph
3-MeO-C6H4 Ph
H
H
H
H
11a
11b
11c
11d
Ͻ5
n.d.[c]
n.d.
n.d.
52
3-MeO-C6H4
4-Me-C6H4
Ph
Ph
3-MeO-C6H4 Ph 11e[a]
[a] Reagents and conditions: DDQ (1–5 equiv.), Sc(OTf)3 (1–
5 equiv.), toluene, 50 °C, 3 h. [b] Reagents and conditions: i) PIFA
(1–2.5 equiv.), CH2Cl2, –78 °C to room temp., 3 h. ii) NaBH4
(10 equiv.), MeOH, 0.5 h. [c] n.d.: not detected.
Figure 1. UV/Vis/NIR absorption spectra of monomer 9g (blue),
direct dimer 4g (green), and fused dimer 10g (pink) in tetra-
hydrofuran (R1 = 4-Me-C6H4, R2 = n-butyl).
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5

Job/Unit: O21622
/KAP1
Date: 18-04-13 15:48:36
Pages: 13
A. A. Ryan, M. O. Senge
FULL PAPER
units, and the λmax was well into the near-IR region at
1092 nm. Additionally, strong visible-region absorbances
were observed at 803 and 945 nm. A similar absorption pro-
file was observed for dimers 10a–k, and such characteristic
spectra provide a useful analytical tool for the formation of
the fused array. These absorption patterns were also ob-
served for the crude mixtures of free-meso dimers 10h–i and
their higher oligomers and demonstrated that fusing had
occurred.
An interesting effect was seen when a coordinating sol-
vent was employed for the UV/Vis/NIR analysis of fused
dimers. There have been many studies of solvent effects on
the absorption profiles of monomeric porphyrins. The spec-
tral shifts are generally attributed to displacement of the
metal ion, which distorts the macrocycle, or from a charge
transfer to the macrocycle from the coordinating solvent,
which increases the HOMO energy level and, thereby, re-
duces the energy gap.[47] As noted by Osuka and co-
workers,[36] the absorption is redshifted on addition of a
coordinating solvent. With dimers 10a and 10d, a signifi-
cant bathochromic shift of their profiles in CH2Cl2 was ob-
Figure 2. UV/Vis/NIR spectra of dimers 10a (blue) and 10d (green)
in (a) CH2Cl2 (solid line) and (b) CH2Cl2 with 2% TEA (dashed
line).
served when 2% triethylamine (TEA) was added (Figure 2). chromatography and some product was lost through con-
With dimer 10a, there was a redshift of 38 nm from 1067 tamination and co-elution with other fractions. Although
to 1105 nm, and with dimer 10d, this effect was less pro- copper-free Sonogashira conditions were used, the Glaser
nounced and a shift of 13 nm was observed.
homocoupled dimer was also detected in trace quantities
For the development of a new tetrameric porphyrin in- (Ͻ5%) and was most likely formed by a palladium-cata-
corporating a fused moiety and a conjugated linker, two lyzed homocoupling.[48b] This alkynyl dimer contains one
strategies were investigated. It was hoped that an alkynyl free meso position, whereby oxidative fusing can be per-
linker would enhance the optical properties of the array formed to generate the fused tetramer. The second strategy
owing to the increase in π conjugation. The first strategy involved the copper-free Sonogashira coupling[48b] of di-
involved the synthesis of alkynyl-linked dimer 13a in a yield rectly linked bromo bisporphyrin 4d with alkynyl porphyrin
of 43% by the copper-free Sonogashira coupling[48] of 12 to give the desired tetramer 13b in 27% yield (Scheme 1).
monobromo porphyrin 2d with alkynyl porphyrin 12 The yield of 13b was low owing to difficulties in separation
(Scheme 1).[49] This yield was moderate because of separa- and the formation of other oligomeric, namely trimeric and
tion difficulties; the desired dimer streaked during column dimeric, derivatives of 13b as side-products. Subsequent
Scheme 1. Synthesis of alkynyl dimer 13a and tetramer 13b by copper-free Sonogashira coupling. Reagents and conditions: (a) 12
(1 equiv.), 2d (1 equiv.), Pd2(dba)3 (0.1 equiv.), AsPh3 (2.1 equiv.), THF/TEA (3:1 v/v), 67 °C, 22 h. (b) 12 (2 equiv.), 4d (1 equiv.),
Pd2(dba)3 (0.15 equiv.), AsPh3 (2.1 equiv.), THF/TEA (3:1 v/v), 67 °C, 48 h.
6
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O21622
/KAP1
Date: 18-04-13 15:48:36
Pages: 13
Triply Fused Porphyrin Dimers
oxidation of dimer 13a and tetramer 13b to give the triply gated. Although high yielding for the introduction of meso
fused tetramer was executed by using both the DDQ/ substituents, the introduction of β substituents by organo-
Sc(OTf)3 and the PIFA methods. After many attempts, the lithium methods can be quite challenging and low yielding
desired tetramer was obtained from both strategies and and can result in the formation of chlorins, bacteriochlor-
with both oxidation methods in moderate yields, the highest ins, and porphodimethenes, depending on the reaction con-
of which was obtained with PIFA oxidation of dimer 13a. ditions and substrates.[50] By comparison with 5,10,15,20-
Here, there was less steric hindrance than with 13b and oxi- tetraphenylporphyrin (TPP), it was anticipated that the in-
dative fusing occurred at the free-meso side. Furthermore, troduction an n-butyl group at the β position of fused sym-
the dimer is more soluble in CH2Cl2 than tetramer 13b and metric dimer 10a would generate a fused porphyrin–chlorin
this affected the yield. Its formation was confirmed by hybrid. By using our previously developed method, whereby
HRMS (calculated for C148H88N16O4Zn4 [M + 2H]+ TPP was monobutylated at the β position in 17% yield, the
1
2408.4340; found 2408.4282) and UV/Vis analysis. The H fused dimer 10a was butylated under standard organo-
NMR spectra were difficult to assign because of overshad- lithium conditions.[23] Butylation was confirmed by HRMS
owing solvent peaks, although oxidative fusing of the cen- (calculated for C80H50N8Zn2 [M – 2H]+ 1250.2741; found
tral porphyrin units was evident as there were significant 1252.2770), and the other main component was unreacted
shift of the signals to higher fields. The characteristic singlet starting material 10a, separation from which was not pos-
at δ = 6.9 ppm is attributed to the inner β protons of the sible. The classic reduction of the porphyrin periphery to
central porphyrin units. This is substantially shifted from generate a chlorin species was also attempted with 10a. The
the resonances of the starting materials 13a and 13b, for diimide reduction of monomeric porphyrins to their respec-
which the β protons are observed at δ = 9–10.5 ppm. This tive chlorins and bacteriochlorins, developed by Whitlock
is the first example of an alkynyl-linked array incorporating et al.,[51] is widely known. Preliminary studies indicated that
a triply fused bisporphyrin moiety, and it exhibited unusual the reduction of 10a occurred efficiently, although isolation
photophysical characteristics. There was a considerable of the porphyrin–chlorin hybrid was not possible because
change in absorption, and the profiles of the products from of its instability.
the synthetic strategies (the oxidative fusing of tetramer 13b
Cycloaddition reactions of monomeric porphyrins gener-
and dimer 13a) were identical. The absorption profile of the ate perturbed macrocycles with enhanced photophysical
fused tetramer is significantly different to those of 13a and properties.[3a,52] To investigate the reactivity of the fused di-
13b (Figure 3).
mers, we decided to adopt the [3+2] annulation strategy de-
veloped by Osuka and co-workers.[3b] This involves a palla-
dium-catalyzed C–C bond forming reaction by carbopal-
ladation of a bromoporphyrin with internal alkynes.[53] The
product is a 7,8-dehydropurpurin that incorporates a fused
cyclopentadiene ring, which causes significant distortion of
the porphyrin macrocycle.
Tetrapyrroles with exocyclic five-membered rings have
biological significance, but in spite of this their synthetic
derivatives are not very common.[54] These species with per-
turbation of the macrocycle have interesting photophysical
properties and exhibit a bathochromic shift in their absorp-
tion profiles.[55] We sought to apply this chemistry to di-
meric porphyrins and to develop a new “fused-on-fused”
system, which we hoped would further enhance the proper-
ties of the triply fused array.[56] The initial strategy involved
the synthesis of a dehydropurpurin macrocycle with a free
meso position and subsequent fusing under standard oxi-
dative conditions, which we anticipated would yield the de-
Figure 3. UV/Vis/NIR spectra of dimer 13a (blue), tetramer 13b
(green), and fused tetramer (red) in ethyl acetate.
The Soret bands of oligomers 13a–b are split, similar to sired triply fused dimeric dehydropurpurin. To test the reac-
those of the alkynyl-linked dimers, and the maximum ab- tion conditions, the [3+2] annulation was performed with
sorption wavelengths are 696 and 700 nm for the dimer and bromoporphyrin 2e[57] and diphenylacetylene to form de-
tetramer, respectively. Upon fusing, a completely different hydropurpurin 14 in an excellent yield of 82%. Attempts to
profile was observed, specifically, a panchromatic spectrum triply fuse 14[3b] by employing standard oxidative condi-
with few distinguishable peaks. This could be attributed to tions with DDQ/Sc(OTf)3 were ineffective, and the main
aggregation effects of the fused tetramer, but it is clear there product isolated was the ring-opened adduct 15[3b]
is absorbance in the near-IR region. Despite the indistin- (Scheme 2). Unfortunately, as discovered by Osuka and co-
guishable peaks, the presence of a triply fused porphyrin workers, the zinc dehydropurpurins are unstable in solution
moiety was confirmed by the shift in absorption.
and on exposure to air and light. The cyclopentadiene ring
To further functionalize the β positions of the dimers, a opens to furnish 1,5-diketone 15, presumably from singlet
chlorin formation with organolithium reagents was investi- oxygen generation. The outer C–C double bond in the
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
7

Job/Unit: O21622
/KAP1
Date: 18-04-13 15:48:36
Pages: 13
A. A. Ryan, M. O. Senge
FULL PAPER
cyclopentadiene ring presumably undergoes a [2+2] cyclo-
Related studies on [3+2] cycloadditions require triply
addition with singlet oxygen generated in situ and forms fused bromo dimers. For this, the directly linked dimers 7c
a dioxetane intermediate, which decomposes to form the and 7d were brominated at their free meso position by using
diketone product[58] and, hence, does not survive these standard bromination conditions of N-bromosuccinimide
strong oxidative conditions.
(NBS) and chloroform to yield dimers 16a and 16b in excel-
lent yields of 76 and 91%, respectively (Scheme 3). These
bromoporphyrins were oxidized with PIFA or DDQ/
Sc(OTf)3 to form the triply fused dimers 17a and 17b in
approximate yields of 25–30%. Preliminary results for the
[3+2] cycloaddition reaction of these dimers indicate the
formation of the desired cyclo adducts in low yields, al-
though further investigations are necessary.
Conclusions
A library of symmetric directly singly and triply linked
dimers were synthesized in moderate-to-good yields by oxi-
dative fusing and tolerate a wide range of functionalities on
the porphyrin periphery. In most cases, attempts to triply
fuse monomers and dimers with one or two free meso posi-
tions were unsuccessful owing to the inevitable formation
of oligomerized products. Although there was limited suc-
cess with alkyl-substituted dimers, this route is not viable as
the yields were low. A series of unsymmetric directly linked
dimers were synthesized in good yields by a stepwise strat-
egy. However, the oxidative double ring closing of free-meso
dimers was unsuccessful. As a result, a change in strategy
was needed for post-functionalization of triply fused arrays.
All triply linked dimers isolated exhibited a substantial ba-
thochromic shift in their absorption profile into the near-
infrared region, which makes these arrays potential candi-
dates for optical applications such as PDT and NLO. There
are considerable possibilities for the development of a li-
brary of unsymmetrically fused dimers, the properties of
which could be fine-tuned for optical applications. The
fused tetramer synthesized is the first example of a fused
array incorporating alkynyl-linked porphyrins, and other
linkages could also be explored. Numerous strategies
towards the functionalization of porphyrin arrays were in-
vestigated. The reactivity of directly linked dimers reflects
that of monomeric porphyrins, and brominations and cy-
cloadditions were achievable in high yields. For fused ar-
rays, the reactivity is somewhat diminished owing to the
poor solubility of the arrays. However, these investigations
showed that fused dimers can be functionalized directly
through organolithium reactions and indirectly through
palladium-catalyzed coupling reactions with pre-installed
activators such as bromine. Such post-fusing modifications
demonstrate the ability to fine-tune the arrays for optical
applications, as the bathochromic shift can be enhanced,
and, although further investigations are necessary, prelimi-
nary studies are promising. Further research into the di-
imide reduction reaction is necessary, and this would pro-
vide a straightforward route to chlorin-fused dimers. With
more solubilizing substituents, the reactivity of the bromo
dimers should improve. It could also be possible to generate
fused dimers with free meso positions by debromination
Scheme 2. Synthesis of dehydropurpurin 14 and 1,5-diketone 15.
Reagents and conditions: (a) diphenylacetylene, Pd2(dba)3,
(o-Tol)3P, toluene, N,N-dicyclohexylamine, 120 °C, 24 h. (b) DDQ,
Sc(OTf)3, toluene, room temp., 3 h.
Scheme 3. Oxidative fusing of bromo dimers 16a and 16b to give
fused dimers 17a and 17b. Reagents and conditions: (a): i) PIFA
(2.5 equiv.), CH2Cl2, –78 °C to room temp., 3 h. ii) NaBH4
(10 equiv.), MeOH, 0.5 h. (b) DDQ, Sc(OTf)3, toluene, 50 °C, 3 h.
8
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O21622
/KAP1
Date: 18-04-13 15:48:36
Pages: 13
Triply Fused Porphyrin Dimers
Bis[5,10,20-bis(4-methoxyphenyl)porphyrin-13,15,17-triylato]zinc-
(II) (10d): Compound 10d was synthesized according to the general
procedure above from 9d (40 mg, 0.058 mmol), DDQ (66 mg,
0.289 mmol), and Sc(OTf)3 (142 mg, 0.289 mmol) in dry toluene
(40 mL) heated at 50 °C for 4.5 h. THF (8 mL) was added, and the
mixture was stirred for a further 0.8 h at room temperature. The
reaction mixture was filtered through a short plug of silica gel with
CH2Cl2 as eluent to give one fraction, which was discarded as no
fused product was detected by UV/Vis/NIR analysis. With CH2Cl2/
THF (1:1, v/v) as eluent, a second (main) fraction containing 10d
was isolated. The solvents were removed in vacuo and 10d was
isolated as a dark purple solid (33 mg, 0.024 mmol, 83%), m.p. Ͼ
300 °C. 1H NMR (400 MHz, CDCl3/[D5]pyridine, 10:1): δ = 3.88
(s, 12 H, OCH3), 3.94 (s, 6 H, OCH3), 7.01 (s, 4 H, Hβ), 7.02 (d,
methods, and the reactivity of such could be probed by
using organolithium methods.
Experimental Section
General Procedure for the Oxidative Coupling of 5,10,15-Trisub-
stituted Porphyrins with DDQ/Sc(OTf)3: A 100 mL Schlenk tube
was charged with metalloporphyrin (1 equiv.) dissolved in dry tolu-
ene. The solution was degassed by three freeze–pump–thaw cycles.
DDQ (5 equiv.) and Sc(OTf)3 (5 equiv.) were added, and the reac-
tion was heated to 50 °C under argon for 3–18 h. THF was added
and the reaction was stirred at room temperature for a further 1 h.
The reaction mixture was then passed through a short plug of alu-
mina or silica gel with CH2Cl2 and then THF as eluents. The sol-
vent was removed in vacuo, and the residue was purified by column
chromatography on silica gel to yield the desired triply fused dimer.
3
3JH,H = 8.3 Hz, 6 H, C6H4-H), 7.09 (dd, JH,H = 8.3, 2.4 Hz, 4 H,
C6H4-H), 7.27 (m, 2 H, C6H4-H), 7.29 (m, 2 H, C6H4-H), 7.40 (t,
3
3JH,H = 7.8 Hz, 6 H, C6H4-H), 7.51 (d, JH,H = 4.6 Hz, 4 H, Hβ),
3
3
7.56 (d, JH,H = 4.6 Hz, 4 H, Hβ), 7.63 (d, JH,H = 8.3 Hz, 4 H,
C6H4-H) ppm. 13C NMR (150 MHz, CDCl3/[D5]pyridine, 10:1): δ
= 55.4, 112.3, 112.9, 118.8, 124.1, 124.8, 126.1, 126.5, 127.3, 130.3,
130.7, 133.8, 134.2, 135.9, 142.9, 152.8, 153.1, 154.4, 157.8,
158.9 ppm. UV/Vis (EtOAc): λmax (logε) = 420 (4.91), 471 (4.52),
562 (4.86), 584 (4.82), 820 (4.62), 952 (4.00), 1092 (4.23) nm.
HRMS (MALDI): calcd. for C82H54N8O6Zn2 [M]+ 1374.2749;
found 1374.2723.
Bis[5,15-Bis(3,5-di-tert-butylphenyl)-20-(4-nitrophenyl)porphyrin-
13,15,17-triylato]zinc(II) (10b): Compound 10 b was synthesized ac-
cording to the general procedure above from [5,15-bis(3,5-di-tert-
butylphenyl)-10-(4-nitrophenyl)porphyrinatozinc(II)] (9b, 20 mg,
0.023 mmol), DDQ (26 mg, 0.115 mmol), and Sc(OTf)3 (57 mg,
0.115 mmol) in dry toluene (20 mL) heated at 50 °C for 3 h. THF
(5 mL) was added, and the reaction mixture was stirred for a fur-
ther 1 h at room temperature. The reaction mixture was filtered
through a short plug of alumina with CH2Cl2 and then CH2Cl2/
THF (1:1, v/v) as eluent to give an intense purple fraction. The
solvents were removed, and the residue was filtered through a sec-
ond plug of alumina with CH2Cl2 as eluent. The solvents were
removed in vacuo and 10b was isolated as a dark solid (13 mg,
Bis[5-(4-ethynylphenyl)-10,20-diphenylporphyrin-13,15,17-triylato]-
zinc(II) (10e): Bisporphyrin 10e was synthesized by following the
general procedure above from 9e (60 mg, 0.109 mmol), DDQ
(113 mg, 0.498 mmol), and Sc(OTf)3 (245 mg, 0.498 mmol) in dry
toluene (60 mL) heated at 50 °C for 3.5 h. THF (15 mL) was added,
and the reaction was stirred for a further 1 h at room temperature.
The reaction mixture was filtered through a short plug of alumina
with CH2Cl2/THF (1:1, v/v) as eluent. The solvents were removed,
and 10e was isolated as a dark solid (48 mg, 0.040 mmol, 79%),
1
0.007 mmol, 64%), m.p. Ͼ 300 °C. H NMR (400 MHz, CDCl3):
3
δ = 1.48 (s, 72 H, tert-butyl-H), 7.37 (s, 4 H, Hβ), 7.61 (d, JH,H
=
3
4.5 Hz, 4 H, Hβ), 7.67 (m, 12 H, Ar-H), 7.75 (d, JH,H = 4.6 Hz, 4
3
3
1
H, Hβ), 8.00 (d, JH,H = 8.2 Hz, 4 H, C6H4-H), 8.48 (d, JH,H
=
m.p. Ͼ 300 °C. H NMR (600 MHz, CDCl3/[D5]pyridine, 10:1): δ
8.2 Hz, 4 H, C6H4-H) ppm. 13C NMR (150 MHz, CDCl3): δ =
30.8, 106.2, 107.5, 120.9, 122.2, 124.2, 127.7, 128.1, 130.1, 131.9,
133.4, 135.9, 139.5, 147.3, 147.8, 151.6, 153.5, 153.9, 154.1 ppm.
UV/Vis (THF): λmax (logε) = 423 (5.12), 566 (5.17), 886 (4.00), 967
( 4. 3 3 ), 1 1 10 (4 . 6 3) n m. H R MS ( M A LD I ) : c al c d . fo r
C108H104N10O4Zn2 [M]+ 1732.6825; found 1732.6816.
= 3.22 (s, 2 H, CϵCH), 6.98 (s, 4 H, Hβ), 7.50 (m, 20 H, Ph-H),
3
7.66 (d, JH,H = 8.0 Hz, 8 H, Hβ), 7.71 (m, 8 H, Hβ) ppm. 13C
NMR (150 MHz, CDCl3/[D5]pyridine, 10:1): δ = 77.7, 83.7, 126.4,
126.5, 127.0, 130.6, 132.9, 135.9, 139.4 ppm. UV/Vis (CH2Cl2):
λmax (logε) = 421 (5.01), 563 (4.85), 586 (4.85), 671 (4.83), 968
(4.01), 1096 (4.27) nm. HRMS (MALDI): calcd. for C80H42N8Zn2
[M]+ 1242.2115; found 1242.2145.
Bis[5-Butyl-10,20-bis(3-methoxyphenyl)porphyrin-13,15,17-triylato]-
zinc(II) (10c):[59] Compound 10c was synthesized from 9c (20 mg,
0.031 mmol), DDQ (35 mg, 0.156 mmol), and Sc(OTf)3 (77 mg,
0.156 mmol) in dry toluene (20 mL) heated at 50 °C for 3 h, accord-
ing to the general procedure above. THF (6 mL) was added, and
the reaction was stirred for a further 1 h at room temperature. The
reaction mixture was filtered through a short plug of alumina with
CH2Cl2 as eluent to give side-product 4e and with CH2Cl2/THF
(1:1, v/v) as eluent to give a fraction containing dimer 10c. The
solvents were removed in vacuo, and the residue was subjected to
column chromatography with CH2Cl2 as eluent to give two frac-
tions, the first of which was side-product 4e, and the second was
the desired dimer 10c. The solvents were removed, and 10c was
isolated as a dark solid (14 mg, 0.011 mmol, 70%), m.p. Ͼ 300 °C.
1H NMR (400 MHz, CDCl3/[D5]pyridine, 10:1): δ = 0.82 (m, 6 H,
Bis[5-butyl-10,20-bis(4-methylphenyl)porphyrin-13,15,17-triylato]-
zinc(II) (10g): Compound 10g was synthesized according to the
general procedure above from 9g (30 mg, 0.049 mmol), DDQ
(56 mg, 0.246 mmol), and Sc(OTf)3 (121 mg, 0.246 mmol) in dry
toluene (30 mL) heated at 50 °C for 3.5 h. THF (7 mL) was added,
and the reaction was stirred for a further 0.5 h at room tempera-
ture. The reaction mixture was filtered through a short plug of
alumina with CH2Cl2 as eluent to give side-product 4g and with
THF as eluent to give a second fraction containing dimer 10g. The
solvents were removed in vacuo, and the residue was subjected to
column chromatography (silica gel, CH2Cl2/n-hexane, 9:1 + 1%
TEA) to give 10g as the main fraction. The solvents were removed,
and 10g was isolated as a dark purple solid (16 mg, 0.013 mmol,
54%), m.p. Ͼ 300 °C. 1H NMR (400 MHz, CDCl3/[D5]pyridine,
3
CH3), 1.46 (m, 4 H, CH2), 1.95 (m, 4 H, CH2), 3.78 (s, 12 H, 10:1): δ = 0.97 (t, JH,H = 7.8 Hz, 6 H, CH3), 1.47 (m, 4 H, CH2),
OCH3), 5.17 (m, 4 H, CH2), 6.99 (m, 6 H, Hβ/C6H4-H), 7.14 (m, 2.04 (m, 4 H, CH2), 2.57 (s, 12 H, tolyl-CH3), 3.89 (m, 4 H, CH2),
3
8 H, C6H4-H), 7.32 (m, 4 H, C6H4-H), 7.53 (m, 8 H, Hβ), 8.15 (m,
2 H, C6H4-H) ppm. UV/Vis (THF): λmax (logε) = 422 (5.20), 459
(4.89), 559 (4.95), 949 (4.14), 1092 (4.41), 1094 (4.41) nm. HRMS
(MALDI): calcd. for C76H58N8O4Zn2 [M]+ 1274.3164; found
1274.3123.
7.01 (s, 4 H, Hβ), 7.32 (d, JH,H = 7.2 Hz, 8 H, C6H4-H), 7.59 (m,
4 H, C6H4-H), 7.59 (m, 4 H, Hβ), 8.21 (d, 3JH,H = 4.3 Hz, 4 H, Hβ)
ppm. 13C NMR (150 MHz, CDCl3/ [D5]pyridine, 10:1): δ = 14.0,
20.9, 22.7, 35.0, 40.7, 117.5, 122.3, 126.8, 127.5, 135.7, 139.9, 148.4,
154.9 ppm. UV/Vis (THF): λmax (logε) = 414 (4.99), 443 (4.70), 576
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
9

Job/Unit: O21622
/KAP1
Date: 18-04-13 15:48:36
Pages: 13
A. A. Ryan, M. O. Senge
FULL PAPER
(4.89), 945 (4.16), 1092 (4.22) nm. HRMS (MALDI): calcd. for
C76H58N8Zn2 [M]+ 1210.3367; found 1210.3375.
linked dimer 7a (20 mg, 0.019 mmol), DDQ (22 mg, 0.096 mmol),
and Sc(OTf)3 (47 mg, 0.096 mmol) in dry toluene (20 mL) heated
at 50 °C for 3 h. THF (6 mL) was added, and the reaction was
stirred for a further 1 h at room temperature. The reaction mixture
was filtered through a short plug of alumina with CH2Cl2/THF
(1:1, v/v) as eluent. The solvents were removed, and the residue was
subjected to column chromatography (CH2Cl2/n-hexane, 5:1, v/v)
to give three fractions, the first of which was unreacted starting
material 7a (3 mg, 14%), the second contained 11a, and the third
contained oligomerized product. The solvents were removed, and
11a was isolated as a dark solid (3 mg, 0.002 mmol, 15%). UV/Vis
(THF): λmax (logε) = 416 (4.97), 578 (4.70), 672 (4.56), 987 (3.87),
1106 (4.09) nm. HRMS (MALDI): calcd. for C70H62N8Zn2 [M]+
1142.3680; found 1142.3625.
Bis[5-bromo-10,20-bis(3-methoxyphenyl)porphyrin-13,15,17-triyl-
ato]zinc(II) (10k):[59] Compound 10k was synthesized from [5-
bromo-10,20-(3-methoxyphenyl)porphyrinato]zinc(II) 2d (60 mg,
0.091 mmol) dissolved in dry CH2Cl2 (60 mL) in a 100 mL Schlenk
tube. The solution was degassed and cooled to –78 °C. PIFA
(32 mg, 0.075 mmol) was added at –78 °C, and the reaction mixture
was warmed to room temp. and then stirred at this temperature for
2 h. NaBH4 (12 mg, 0.305 mmol) in MeOH (5 mL) was added, and
the reaction was stirred for a further 45 min. The reaction mixture
was added to H2O (100 mL), and the organic layer was extracted
with CH2Cl2/THF (1:1, v/v). The organic layer was washed with
NaHCO3 (2 ϫ 50 mL) and H2O (30 mL) and then dried with
Na2SO4, which was then removed by filtration. The solvents were
removed in vacuo, and the dark residue was redissolved and filtered
through a short plug of silica with CHCl3/THF (1:1, v/v) as eluent
to give a green fraction. The solvents were removed in vacuo, and
the residue was recrystallized from CH2Cl2/n-hexane to give a dark
purple solid (3 mg, 0.002 mmol, 14%), m.p. Ͼ 300 °C. 1H NMR
(400 MHz, CDCl3): δ = 3.93 (s, 12 H, OCH3), 7.04 (s, 4 H, Hβ),
7.16 (m, 4 H, C6H4-H), 7.70 (m, 6 H, C6H4-H), 7.73 (m, 10 H,
C6H4-H/Hβ), 8.45 (m, 2 H, Hβ), 8.61 (m, 2 H, Hβ) ppm. UV/Vis
(CH2Cl2/THF, 1:1, v/v): λmax (logε) = 425 (5.01), 459 (4.66), 566
(4.68), 871 (3.98), 1110 (4.17) nm. HRMS (MALDI): calcd. for
C68H40Br2N8O4Zn2 [M]+ 1318.0122; found 1318.0150.
{5-[5Ј-Phenyl-10Ј,20Ј-bis(3-methoxyphenyl)porphyrin-13Ј,15Ј,17Ј-tri-
ylato]-10,15,20-triphenylporphyrinato}zinc(II) (11e): Fused dimer
11e was synthesized from dimer 7f (40 mg, 0.032 mmol), DDQ
(36 mg, 0.158 mmol), and Sc(OTf)3 (78 mg, 0.158 mmol) in toluene
(50 mL). The reaction was heated to 50 °C and stirred at this tem-
perature for 3 h. THF (8 mL) was added, and the reaction was
stirred for a further 1 h at room temperature. The reaction mixture
was filtered through a plug of alumina with CH2Cl2 and then
CH2Cl2/THF (1:1, v/v) as eluent. The solvents were removed in
vacuo to give a dark residue, which was redissolved in CH2Cl2 and
subjected to column chromatography (n-hexane/ethyl acetate, 6:1,
v/v) to give two fractions. The first yielded unreacted starting mate-
rial 7f (6 mg, 15%), and the second contained the desired fused
dimer 11e. The solvents were removed in vacuo to yield a dark
solid (21 mg, 0.017 mmol, 52 %), m.p. Ͼ 300 °C. 1H NMR
(400 MHz, CDCl3/[D5]pyridine, 20:1): δ = 3.93 (s, 6 H, OCH3),
7.03 (m, 4 H, Hβ), 7.13 (m, 4 H, C6H4-H), 7.23 (m, 2 H, C6H4-H),
7.43 (m, 2 H, C6H4-H), 7.49–7.62 (m, 20 H, Ph-H/ Hβ), 7.70–7.83
(m, 8 H, Ph-H/Hβ) ppm. 13C NMR (100 MHz, CDCl3/[D5]pyr-
idine, 20:1): δ = 55.4, 112.9, 126.5, 126.9, 127.3, 128.8, 130.6, 130.9,
157.8 ppm. UV/Vis (CH2Cl2): λmax (logε) = 422 (5.15), 455 (4.11),
556 (4.53), 579 (4.50), 917 (3.66), 1039 (3.90) nm. HRMS
(MALDI): calcd. for C78H46N8O2Zn2 [M]+ 1254.2327; found
1254.2286.
Bis[(5-n-butyl)-10,20-bis(3-methoxyphenyl)porphyrin-15-ylato]zinc-
(II) (4e): Compound 4e was isolated as a side-product from the
synthesis of 10c. The reaction mixture was filtered through a short
plug of alumina with CH2Cl2 as eluent to give a fraction containing
4e. The solvents were removed in vacuo to yield a red-purple solid
(4 mg, 0.003 mmol, 19%), m.p. Ͼ 300 °C; Rf = 0.53 (CH2Cl2/n-
hexane = 2:1, v/v). 1H NMR (400 MHz, CDCl3): δ = 0.89–0.93 (m,
6 H, CH3), 1.19 (m, 4 H, CH2), 1.93 (m, 4 H, CH2), 3.93 (s, 12 H,
OCH3), 5.19 (t, 3JH,H = 7.6 Hz, 4 H, CH2), 7.25 (d, 3JH,H = 8.6 Hz,
3
4 H, C6H4-H), 7.57 (t, JH,H = 7.7 Hz, 4 H, C6H4-H), 7.82 (m, 8
3
H, C6H4-H), 8.08 (m, 4 H, Hβ), 8.67 (m, 4 H, Hβ), 9.12 (d, JH,H
3
= 4.8 Hz, 4 H, Hβ) 9.71 (d, JH,H = 4.8 Hz, 4 H, Hβ) ppm. 13C
{5-[(10Ј,20Ј-Bis(3-methoxyphenyl)porphyrinato-5-yl)zinc(II)]ethynyl-
10,15,20-triphenylporphyrinato}zinc(II) (13a): This procedure was
adapted from a method by Lindsey et al.[45] Alkynyl porphyrin 12
(56 mg, 0. 089 mmol), bromoporphyrin 2d (60 mg, 0.089 mmol),
AsPh3 (57 mg, 0.185 mmol), and tris(dibenzylideneacetone)dipalla-
dium(0) [Pd2(dba)3, 8 mg, 0.008 mmol) were added to a 100 mL
Schlenk tube and dried under high vacuum. The flask was purged
with argon, and dry THF (12 mL) and TEA (4 mL) were added.
The solution was degassed by three freeze–pump–thaw cycles. The
flask was sealed, and the reaction mixture was heated to 67 °C.
After 22 h, the solvents were removed, and the residue was redis-
solved in CH2Cl2 and filtered through a plug of silica with CH2Cl2
as eluent. The solvents were removed, and the residue was sub-
jected to column chromatography (silica, n-hexane/ethyl acetate,
4:1, v/v) to give four fractions. The first fraction contained mono-
mer 12 (8 mg, 14%), and fractions two and three contained mix-
tures of undesired oligomers. The fourth fraction contained the de-
sired dimer 13a. The solvents were removed in vacuo to give a dark
green solid 13a (46 mg, 0.038 mmol, 43%), m.p. Ͼ 300 °C; Rf =
0.35 (n-hexane/EtOAc, 3:2, v/v). 1H NMR (400 MHz, CDCl3/[D5]-
NMR (150 MHz, CDCl3): δ = 14.0, 22.5, 31.8, 41.0, 55.3, 109.9,
112.6, 119.6, 120.9, 127.9, 128.9, 131.7, 133.5, 142.5, 149.2, 154.9,
157.6 ppm. UV/Vis (CH2Cl2): λmax (logε) = 424 (5.35), 457 (5.27),
568 (4.59) nm. HRMS (MALDI): calcd. for C76H62N8O4Zn2 [M]+
1278.3477; found 1278.3438.
Bis[(5-n-butyl)-10,20-bis(4-methylphenyl)porphyrin-15-ylato]zinc(II)
(4g): Compound 4g was synthesized as a side-product of 10g and
was isolated as the first fraction from filtration through a plug of
alumina with CH2Cl2 as eluent. The solvents were removed in
vacuo to give a red-purple solid 4g (8 mg, 0.007 mmol, 27%) M.p.
Ͼ 300 °C; Rf = 0.45 (CH2Cl2/n-hexane = 3:2, v/v). 1H NMR
(400 MHz, CDCl3): δ = 0.90 (m, 6 H, CH3), 1.19 (m, 4 H, CH2),
3
1.92 (m, 4 H, CH2), 2.64 (s, 12 H, tolyl-CH3), 5.17 (t, JH,H
=
3
8.2 Hz, 4 H, CH2), 7.50 (d, JH,H = 7.8 Hz, 8 H, C6H4-H), 8.07 (d,
3JH,H = 4.9 Hz, 4 H, Hβ), 8.12 (d, JH,H = 7.8 Hz, 8 H, C6H4-H),
3
3
3
8.65 (d, JH,H = 8.7 Hz, 4 H, Hβ), 9.10 (d, JH,H = 4.7 Hz, 4 H,
Hβ), 9.68 (d, JH,H = 4.7 Hz, 4 H, Hβ) ppm. 13C NMR (150 MHz,
3
CDCl3): δ = 14.2, 21.3, 23.7, 35.6, 41.1, 118.7, 121.2, 122.1, 127.0,
128.8, 131.7, 131.9, 133.4, 134.1, 136.8, 139.7, 149.4, 149.9, 150.1,
154.9 ppm. UV/Vis (CH2Cl2): λmax (logε) = 423 (5.54), 456 (5.45),
566 (4.80) nm. HRMS (MALDI): calcd. for C76H62N8Zn2 [M]+
1214.3680; found 1214.3663.
3
pyridine, 20:1): δ = 4.07 (s, 6 H, OCH3), 7.38 (dd, JH,H = 7.3,
2.4 Hz, 2 H, C6H4-H), 7.78 (m, 11 H, Ph/C6H4-H), 7.89 (m, 2 H,
C6H4-H), 8.23 (m, 6 H, Ph-H), 8.30 (m, 2 H, C6H4-H), 9.01 (d,
3
[5,10,20-Trihexyl-15-(10Ј,20Ј-diphenylporphyrin-5Ј-yl)-13,15,17-tri-
ylato]zinc(II) (11a): Bisporphyrin 11a was synthesized from directly
3JH,H = 4.6 Hz, 2 H, Hβ), 9.04 (d, JH,H = 4.4 Hz, 2 H, Hβ), 9.11
3
3
(d, JH,H = 4.5 Hz, 2 H, Hβ), 9.21 (d, JH,H = 4.5 Hz, 2 H, Hβ),
10
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O21622
/KAP1
Date: 18-04-13 15:48:36
Pages: 13
Triply Fused Porphyrin Dimers
3
3
9.30 (d, JH,H = 4.4 Hz, 2 H, Hβ), 9.96 (d, JH,H = 4.6 Hz, 2 H,
pound 16b was synthesized from dimer 7d (30 mg, 0.026 mmol)
and NBS (5 mg, 0.026 mmol) dissolved in CHCl3 (40 mL) at 0 °C.
Hβ), 10.11 (s, 1 H, Hmeso), 10.46 (d, 3JH,H = 4.6 Hz, 2 H, Hβ), 10.49
(d, JH,H = 4.6 Hz, 2 H, Hβ) ppm. 13C NMR (100 MHz, CDCl3/ Pyridine (0.1 mL) was added, and the reaction mixture was stirred
3
[D5]pyridine, 20:1): δ = 55.6, 100.7, 107.2, 113.1, 120.1, 120.8, at this temperature for 3 h. The solvents were removed in vacuo,
121.1, 122.0, 122.1, 122.4, 126.3, 126.4, 127.3, 127.4, 128.0, 130.6,
131.5, 131.6, 131.8, 132.0, 132.2, 132.7, 132.8, 133.1, 134.4, 134.5,
134.6, 143.0, 143.2, 143.3, 144.5, 149.6, 149.7, 149.8, 150.0, 150.4,
150.7, 152.6, 153.0 153.5, 157.9 ppm. UV/Vis (CH2Cl2): λmax (logε)
and the residue was redissolved in CH2Cl2 and filtered through a
plug of silica with CH2Cl2 as eluent. The solvents were removed in
vacuo to give a purple solid 16b (29 mg, 0.024 mmol, 91%), m.p.
Ͼ 300 °C; Rf = 0.48 (CH2Cl2/n-hexane = 1:1, v/v). 1H NMR
3
= 452 (5.06), 481 (5.22), 568 (4.08), 696 (4.64) nm. HRMS (400 MHz, CDCl3): δ = 0.99 (t, JH,H = 7.1 Hz, 12 H, CH3), 2.66
(MALDI): calcd. for C74H46N8O2Zn2 [M]+ 1206.2327; found
1206.2341.
(s, 6 H, tolyl-H), 2.80 (m, 8 H, CH2), 5.05 (m, 1 H, CH), 5.16 (m,
3
1 H, CH), 7.51 (d, JH,H = 7.6 Hz, 4 H, C6H4-H), 7.83 (m, 3 H,
Ph-H), 8.08 (m, 4 H, Ph-H/Hβ), 8.13 (d, 3JH,H = 7.6 Hz, 4 H, C6H4-
Bis(5-{[10Ј,20Ј-bis(3-methoxyphenyl)porphyrinato-15Ј-
yl]zinc(II)}ethynyl-10,15,20-triphenylporphyrin-15Ј-ylato)zinc(II)
(13b): Alkynyl porphyrin 12 (65 mg, 0.104 mmol), bromoporphyrin
dimer 4d (66 mg, 0.049 mmol), AsPh3 (32 mg, 0.104 mmol), and
Pd2(dba)3 (7 mg, 0.007 mmol) were added to a Schlenk tube and
dried under high vacuum. The flask was purged with argon, and
dry THF (10 mL) and TEA (1 mL) were added. The solution was
degassed by three freeze–pump–thaw cycles. The flask was sealed,
and the reaction mixture was heated to 67 °C. After 48 h, the sol-
vents were removed, and the residue was redissolved in CH2Cl2 and
filtered through a plug of silica with CH2Cl2/ethyl acetate (9:1,
v/v) as eluent. The solvents were removed, and the residue was
subjected to column chromatography (silica, n-hexane/ethyl acetate,
6:1, v/v) to give four fractions. The first three fractions contained
undesired dimeric and trimeric products, and the fourth fraction
contained the desired tetramer 13b. The solvents were removed in
vacuo to give dark green solid 13b (34 mg, 0.011 mmol, 27%), m.p.
Ͼ 300 °C; Rf = 0.27 (hexane/ethyl acetate = 3:2, v/v). 1H NMR
(600 MHz, CDCl3): δ = 3.93 (m, 12 H, OCH3), 7.26 (m, 4 H, C6H4-
H), 7.62 (m, 4 H, C6H4-H), 7.84 (m, 22 H, Ph/C6H4-H), 8.19 (m,
4 H, Hβ) 8.26 (d, 3JH,H = 6.4 Hz, 8 H, C6H4-H), 8.32 (m, 8 H, Ph-
3
H), 8.32 (m, 2 H, Hβ), 8.66 (d, JH,H = 4.6 Hz, 2 H, Hβ), 9.04 (m,
3
2 H, Hβ), 9.10 (d, JH,H = 4.5 Hz, 2 H, Hβ), 9.41 (m, 2 H, Hβ),
3
9.77 (m, 2 H, Hβ), 9.87–9.88 (d, JH,H = 4.5 Hz, 2 H, Hβ) ppm.
13C NMR (100 MHz, CDCl3): δ = 14.4, 21.5, 22.7, 29.7, 34.8, 50.5,
105.0, 113.5, 121.1, 122.5, 124.9, 126.4, 127.2, 127.4, 130.1, 132.1,
132.8, 133.1, 134.2, 134.3, 137.2, 139.6, 143.5, 143.6, 149.6, 150.3,
151.2, 155.3 ppm. UV/Vis (CH2Cl2): λmax (logε) = 414 (5.32), 450
(5.27), 554 (4.54) nm. HRMS (MALDI): calcd. for C70H57N8Zn2Br
[M]+ 1216.2472; found 1216.2509.
{5-[5Ј-Bromo-10Ј,20Ј-bis(3-methoxyphenyl)porphyrin-13Ј,15Ј,17Ј-yl-
ato]-10,20-bis(3-methoxyphenyl)-15-phenylporphyrinato}zinc(II)
(17a):[59,60] Compound 17a was synthesized from bromo dimer 16a
(20 mg, 0.038 mmol) and PIFA (35 mg, 0.094 mmol) dissolved in
CH2Cl2 (60 mL) in a 250 mL Schlenk tube. The reaction was stirred
at room temperature for 3 h. NaBH4 (7 mg, 0.190 mmol) in MeOH
(5 mL) was added, and the reaction was stirred for a further 1 h
at room temperature. The reaction mixture was poured into H2O
(50 mL) and was then extracted with CH2Cl2. The organic layer
was washed with NaHCO3 (2ϫ 50 mL) and H2O (50 mL), dried
with Na2SO4, and filtered. The solvents were removed to give a
dark green residue, which was redissolved in CH2Cl2 and filtered
through a short plug of alumina. The solvents were removed in
vacuo to yield a dark green solid 17a (22 mg, 0.011 mmol, 44%),
3
H), 8.73 (m, 4 H, Hβ), 8.95 (d, JH,H = 6.5 Hz, 8 H, Hβ), 9.24 (d,
3
3JH,H = 4.1 Hz, 4 H, Hβ), 9.28 (m, 4 H, Hβ), 10.55 (d, JH,H
=
4.3 Hz, 8 H, Hβ) ppm. 13C NMR (150 MHz, CDCl3): δ = 55.4,
55.5, 101.0, 102.4, 113.6, 120.3, 122.5, 123.0, 126.7, 126.8, 127.4,
127.6, 127.7, 131.0, 132.1, 132.3, 133.2, 133.4, 134.2, 134.3, 134.5,
142.5, 142.6, 143.6, 150.1, 150.3, 150.4, 150.7, 152.9, 153.0, 155.0,
157.9 ppm. UV/Vis (CH2Cl2): λmax (logε) = 411 (5.31), 498 (5.54),
564 (4.61), 700 (5.07) nm. HRMS (MALDI): calcd. for
C148H90N16O4Zn4 [M]+ 2410.4497; found 2410.4441.
1
m.p. Ͼ 300 °C. H NMR (600 MHz, CDCl3/[D5]pyridine, 10:1): δ
3
= 3.86–3.93 (m, 12 H, OCH3), 6.55 (d, JH,H = 4.3 Hz, 2 H, Hβ),
3
6.95 (m, 2 H, aryl-H), 7.04 (m, 4 H, C6H4-H), 7.12 (d, JH,H
=
4.3 Hz, 2 H, Hβ), 7.16 (m, 4 H, C6H4-H), 7.35 (m, 2 H, aryl-H),
3
7.45 (m, 4 H, aryl-H), 7.64 (d, JH,H = 4.3 Hz, 2 H, Hβ), 7.75 (m,
3
4 H, C6H4-H), 8.44 (d, JH,H = 4.3 Hz, 2 H, Hβ), 9.09–9.11 (d,
3
3JH,H = 4.7 Hz, 4 H, Hβ), 9.68–9.69 (d, JH,H = 4.7 Hz, 4 H, Hβ)
{5-[5Ј-Bromo-10Ј,20Ј-bis(3-methoxyphenyl)porphyrin-15Ј-ylato]-
10,20-bis(3-methoxy)-15-phenylporphyrinato}zinc(II) (16a):[60]
Bromo bisporphyrin 16a was produced from dimer 7c (150 mg,
0.120 mmol) and NBS (32 mg, 0.180 mmol) dissolved in CHCl3
(50 mL) in a 100 mL round-bottomed flask at 0 °C. Pyridine
(0.1 mL) was added, and the reaction was stirred at this tempera-
ture for 3 h. The solvents were removed in vacuo, and the residue
was redissolved in CH2Cl2 and filtered through a plug of silica with
CH2Cl2 as eluent. The solvents were removed in vacuo to give a
dark solid 16a (120 mg, 0.091 mmol, 76%), m.p. Ͼ 300 °C; Rf =
0.54 (CH2Cl2). 1H NMR (400 MHz, CDCl3): δ = 3.92 (s, 6 H,
OCH3), 3.94 (s, 6 H, OCH3), 7.23 (m, 4 H, C6H4-H), 7.56 (m, 4
H, C6H4-H), 7.80 (m, 11 H, Ph/C6H4-H), 8.03 (m, 4 H, Hβ), 8.12
ppm. UV/Vis (THF): λmax (logε) = 423 (5.10), 562 (4.64), 1037
(3.94) nm.
{5-[5Ј-Bromo-10Ј,20Ј-bis(4-methylphenyl)porphyrin-13Ј,15Ј,17Ј-yl-
ato]-10,20-bis(1-ethylpropyl)-15-phenylporphyrinato}zinc(II) (17b):[59]
Compound 17b was synthesized from bromo dimer 16b (20 mg,
0.016 mmol), DDQ (19 mg, 0.082 mmol), and Sc(OTf)3 (40 mg,
0.082 mmol) dissolved in toluene (25 mL) in a 100 mL Schlenk
tube. The reaction mixture was heated to 50 °C and stirred at this
temperature for 3 h. THF (8 mL) was added, and the reaction mix-
ture was stirred for a further 0.5 h at room temperature. The reac-
tion mixture was filtered through a short plug of alumina with
CH2Cl2 as eluent to give a fraction that contained starting material
16b and with CH2Cl2/THF (1:1, v/v) as eluent to give fused dimer
17b. The solvents were removed in vacuo to give a dark green solid
3
(d, JH,H = 5.3 Hz, 2 H, Ph-H), 8.64 (m, 2 H, Hβ), 8.68 (m, 2 H,
3
3
Hβ), 9.04 (q, JH,H = 12.1 Hz, 4 H, Hβ), 9.08 (d, JH,H = 4.7 Hz, 2
H, Hβ), 9.85 (d, JH,H = 4.7 Hz, 2 H, Hβ) ppm. 13C NMR
3
17b (12 mg, 0.010 mmol, 65%), m.p.
Ͼ
300 °C. 1H NMR
(100 MHz, CDCl3): δ = 55.4, 113.3, 120.2, 120.3, 121.6, 122.6,
126.6, 127.2, 127.5, 131.8, 132.8, 133.7, 134.1, 134.5, 143.0, 143.4,
143.9, 144.1, 149.9, 150.2, 150.5, 150.9, 155.3, 157.7 ppm. UV/Vis
(CH2Cl2): λmax (logε) = 418 (5.21), 450 (5.17), 558 (4.55) nm.
(400 MHz, CDCl3): δ = 0.92 (m, 12 H, CH3), 2.31 (m, 8 H, CH2),
2.53 (s, 6 H, tolyl-CH3), 5.44 (m, 2 H, CH2), 6.84 (m, 2 H, Hβ),
7.16 (m, 2 H, Hβ), 7.39–7.87 (m, 21 H, Ph-H/Hβ) ppm. UV/Vis
(THF): λmax (logε) = 422 (5.18), 565 (5.04), 965 (4.32) nm. HRMS
(MALDI): calcd. for C70H53N8Zn2Br [M]+ 1212.2159; found
1212.2200.
{5-[5Ј-Bromo-10Ј,20Ј-bis(4-methylphenyl)porphyrin-15Ј-ylato]-
10,20-bis(1-ethylpropyl)-15-phenylporphyrinato}zinc(II) (16b): Com-
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
11

Job/Unit: O21622
/KAP1
Date: 18-04-13 15:48:36
Pages: 13
A. A. Ryan, M. O. Senge
FULL PAPER
Locos, C. C. Heindl, A. Corral, M. O. Senge, E. M. Scanlan,
Eur. J. Org. Chem. 2010, 1026–1028.
E. G. A. Notaras, M. Fazekas, J. J. Doyle, W. J. Blau, M. O.
Senge, Chem. Commun. 2007, 2166–2168.
K. Susumu, T. Shimidzu, K. Tanaka, H. Segawa, Tetrahedron
Lett. 1996, 37, 8399–8402.
Supporting Information (see footnote on the first page of this arti-
cle): General methods including experimental procedures, charac-
terization data, and 1H and 13C NMR spectra. The 1D and 2D
NMR spectra of compounds 10d, 10e, 11e, and 13a are provided.
[17]
[18]
[19]
R. T. Holmes, J. J. Lin, R. G. Khoury, C. P. Jones, K. M. Smith,
Chem. Commun. 1997, 819–820.
Acknowledgments
[20]
[21]
X.-Q. Lu, Y. Guo, Q.-Y. Chen, Synlett 2011, 77–80.
a) A. Osuka, H. Shimidzu, Angew. Chem. 1997, 109, 93; Angew.
Chem. Int. Ed. Engl. 1997, 36, 135–137; b) N. Aratani, A.
Osuka, Y. H. Kim, D. H. Jeong, D. Kim, Angew. Chem. 2000,
112, 1517; Angew. Chem. Int. Ed. 2000, 39, 1458–1462; c) N.
Yoshida, H. Shimidzu, A. Osuka, Chem. Lett. 1998, 55–56.
M. Kamo, A. Tsuda, Y. Nakamura, N. Aratani, K. Furukawa,
T. Kato, A. Osuka, Org. Lett. 2003, 5, 2079–2082.
a) L.-M. Jin, J.-J. Yin, L. Chen, C.-C. Guo, Q.-Y. Chen, Synlett
2005, 2893–2898; b) L.-M. Jin, L. Chen, J.-J. Yin, C.-C. Guo,
Q.-Y. Chen, Eur. J. Org. Chem. 2005, 3994–4001.
a) T. Ogawa, Y. Nishimoto, N. Ono, N. Yoshida, A. Osukua,
Chem. Commun. 1998, 337–338; b) T. Ogawa, Y. Nishimoto,
N. Yoshida, N. Ono, A. Osuka, Angew. Chem. 1999, 111, 140;
Angew. Chem. Int. Ed. 1999, 38, 176–179.
This work was supported by a grant from the Science Foundation
Ireland (SFI) (P.I. 09/IN.1/B2650).
[1] R. K. Pandey, G. Zheng, in: The Porphyrin Handbook, vol. 6
(Eds.: K. M. Kadish, K. M. Smith, R. Guilard), Academic
Press, San Diego, 2000, pp. 157–230.
[2] a) V. Lin, S. DiMagno, M. Therien, Science 1994, 264, 1105–
1111; b) H. L. Anderson, Inorg. Chem. 1994, 33, 972–981.
[3] a) D.-M. Shen, C. Liu, Q.-Y. Chen, Chem. Commun. 2005,
4982–4984; b) A. K. Sahoo, S. Mori, H. Shinokubo, A. Osuka,
Angew. Chem. 2006, 118, 8140; Angew. Chem. Int. Ed. 2006,
45, 7972–7975.
[4] a) A. Tsuda, A. Nakano, H. Furuta, H. Yamochi, A. Osuka,
Angew. Chem. 2000, 112, 572; Angew. Chem. Int. Ed. 2000, 39,
558–561; b) N. K. S. Davis, A. L. Thompson, H. L. Anderson,
Org. Lett. 2010, 12, 2124–2127.
[5] K.-i. Sugiura, T. Matsumoto, S. Ohkouchi, Y. Naitoh, T. Ka-
wai, Y. Takai, K. Ushiroda, Y. Sakata, Chem. Commun. 1999,
1957–1958.
[22]
[23]
[24]
[25]
[26]
A. Takai, B. Habermeyer, S. Fukuzumi, Chem. Commun. 2011,
47, 6804–6806.
a) M. O. Senge, X. Feng, Tetrahedron Lett. 1999, 40, 4165–
4168; b) M. O. Senge, X. Feng, J. Chem. Soc. Perkin Trans. 1
2000, 3615–3621.
a) N. Miyaura, K. Yamada, A. Suzuki, Tetrahedron Lett. 1979,
20, 3437–3440; b) N. Miyaura, T. Yanagi, A. Suzuki, Synth.
Commun. 1981, 11, 513–519.
[6] A. Tsuda, H. Furuta, A. Osuka, Angew. Chem. 2000, 112, 2649;
[27]
Angew. Chem. Int. Ed. 2000, 39, 2549–2552.
[7] A. Tsuda, A. Osuka, Science 2001, 293, 79–82.
[8] a) K. J. McEwan, P. A. Fleitz, J. E. Rogers, J. E. Slagle, D. G.
McLean, H. Akdas, M. Katterle, I. M. Blake, H. L. Anderson,
Adv. Mater. 2004, 16, 1933–1935; b) F. Cheng, S. Zhang, A.
Adronov, L. Echegoyen, F. Diederich, Chem. Eur. J. 2006, 12,
6062–6070; c) Q. Ouyang, Y.-Z. Zhu, C.-H. Zhang, K.-Q. Yan,
Y.-C. Li, J.-Y. Zheng, Org. Lett. 2009, 11, 5266–5269; d)
N. K. S. Davis, A. L. Thompson, H. L. Anderson, J. Am.
Chem. Soc. 2011, 133, 30–31; e) V. V. Diev, K. Hanson, J. D.
Zimmerman, S. R. Forrest, M. E. Thompson, Angew. Chem.
2010, 122, 5655; Angew. Chem. Int. Ed. 2010, 49, 5523–5526;
f) V. V. Diev, C. W. Schlenker, K. Hanson, Q. Zhong, J. D. Zim-
merman, S. R. Forrest, M. E. Thompson, J. Org. Chem. 2011,
77, 143–159.
[28]
[29]
J. H. Fuhrhop, D. Mauzerall, J. Am. Chem. Soc. 1969, 91,
4174–4181.
A. K. Sahoo, Y. Nakamura, N. Aratani, K. S. Kim, S. B. Noh,
H. Shinokubo, D. Kim, A. Osuka, Org. Lett. 2006, 8, 4141–
4144.
M. Fazekas, M. Pintea, M. O. Senge, M. Zawadzka, Tetrahe-
dron Lett. 2008, 49, 2236–2239.
M. O. Senge, Acc. Chem. Res. 2005, 38, 733–743.
M. O. Senge, M. Pintea, A. Ryan, Z. Naturforsch. B 2011, 66,
553–558.
C. Bruckner, J. J. Posakony, C. K. Johnson, R. W. Boyle, B. R.
James, D. Dolphin, J. Porphyrins Phthalocyanines 1998, 2, 455–
465.
a) T. Dohi, M. Ito, K. Morimoto, M. Iwata, Y. Kita, Angew.
Chem. 2008, 120, 1321; Angew. Chem. Int. Ed. 2008, 47, 1301–
1304; b) T. Wirth, Angew. Chem. 2005, 117, 3722; Angew.
Chem. Int. Ed. 2005, 44, 3656–3665.
M. O. Senge, J. C. Brandt, Photochem. Photobiol. 2011, 87,
1240–1296.
S. Hiroto, A. Osuka, J. Org. Chem. 2005, 70, 4054–4058.
R. W. Wagner, J. Seth, S. I. Yang, D. Kim, D. F. Bocian, D.
Holten, J. S. Lindsey, J. Org. Chem. 1998, 63, 5042–5049.
N. Aratani, A. Osuka, Org. Lett. 2001, 3, 4213–4216.
a) A. G. Hyslop, M. A. Kellett, P. M. Iovine, M. J. Therien, J.
Am. Chem. Soc. 1998, 120, 12676–12677; b) E. M. Finnigan,
R. Rein, N. Solladié, K. Dahms, D. C. G. Götz, G. Bringmann,
M. O. Senge, Tetrahedron 2011, 67, 1126–1134; c) S. Punidha,
N. Agarwal, I. Gupta, M. Ravikanth, Eur. J. Org. Chem. 2007,
1168–1175.
R. H. Felton, H. Linschitz, J. Am. Chem. Soc. 1966, 88, 1113–
1116.
N. Aratani, A. Osuka, Chem. Rec. 2003, 3, 225–234.
H. Mori, T. Tanaka, N. Aratani, B. S. Lee, P. Kim, D. Kim, A.
Osuka, Chem. Asian J. 2012, 7, 1811–1816.
[30]
[31]
[32]
[33]
[34]
[9] H. S. Cho, D. H. Jeong, S. Cho, D. Kim, Y. Matsuzaki, K.
Tanaka, A. Tsuda, A. Osuka, J. Am. Chem. Soc. 2002, 124,
14642–14654.
[10] T. Sakurai, K. Shi, H. Sato, K. Tashiro, A. Osuka, A. Saeki,
S. Seki, S. Tagawa, S. Sasaki, H. Masunaga, K. Osaka, M.
Takata, T. Aida, J. Am. Chem. Soc. 2008, 130, 13812–13813.
[11] a) T. Tanaka, Y. Nakamura, A. Osuka, Chem. Eur. J. 2008, 14,
204–211; b) J. Chen, N. Aratani, H. Shinokubo, A. Osuka,
Chem. Asian J. 2009, 4, 1126–1133.
[12] M. O. Senge, M. Fazekas, E. G. A. Notaras, W. J. Blau, M. Za-
wadzka, O. B. Locos, E. M. Ni Mhuircheartaigh, Adv. Mater.
2007, 19, 2737–2774.
[13] a) A. C. Grimsdale, K. Leok Chan, R. E. Martin, P. G. Jokisz,
A. B. Holmes, Chem. Rev. 2009, 109, 897–1091; b) C. Borek,
K. Hanson, P. I. Djurovich, M. E. Thompson, K. Aznavour,
R. Bau, Y. Sun, S. R. Forrest, J. Brooks, L. Michalski, J.
Brown, Angew. Chem. 2007, 119, 1127; Angew. Chem. Int. Ed.
2007, 46, 1109–1112.
[35]
[36]
[37]
[38]
[39]
[40]
[14] a) M. Balaz, H. A. Collins, E. Dahlstedt, H. L. Anderson, Org.
Biomol. Chem. 2009, 7, 874–888; b) K. Ogawa, Y. Kobuke,
Anti-Cancer Agents Med. Chem. 2008, 8, 269–279; c) K.
Ogawa, Y. Kobuke, Org. Biomol. Chem. 2009, 7, 2241–2246.
[15] M. O. Senge, Y. M. Shaker, M. Pintea, C. Ryppa, S. S.
Hatscher, A. Ryan, Y. Sergeeva, Eur. J. Org. Chem. 2010, 237–
258.
[41]
[42]
[43]
[44]
L. He, Y.-Z. Zhu, J.-Y. Zheng, Y.-F. Ma, Y.-S. Chen, J. Pho-
tochem. Photobiol. A: Chem. 2010, 216, 15–23.
I. M. Blake, A. Krivokapic, M. Katterle, H. L. Anderson,
Chem. Commun. 2002, 1662–1663.
[16] a) V. Sol, V. Chaleix, Y. Champavier, R. Granet, Y. M. Huang,
P. Krausz, Bioorg. Med. Chem. 2006, 14, 7745–7760; b) O. B.
12
www.eurjoc.org
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O21622
/KAP1
Date: 18-04-13 15:48:36
Pages: 13
Triply Fused Porphyrin Dimers
[45]
[46]
[54] C. Bauder, R. Ocampo, H. J. Callot, Tetrahedron 1992, 48,
5135–5150.
[55] M. O. Senge, Chem. Commun. 2006, 243–256.
[56] A. Nakano, N. Aratani, H. Furuta, A. Osuka, Chem. Commun.
2001, 1920–1921.
[57] R. Shediac, M. H. B. Gray, H. T. Uyeda, R. C. Johnson, J. T.
Hupp, P. J. Angiolillo, M. J. Therien, J. Am. Chem. Soc. 2000,
122, 7017–7033.
[58] a) A. A. Frimer, Chem. Rev. 1979, 79, 359–387; b) P. D. Bart-
lett, A. P. Schaap, J. Am. Chem. Soc. 1970, 92, 3223–3225; c)
S. Mazur, C. S. Foote, J. Am. Chem. Soc. 1970, 92, 3225–3226.
[59] The attainment of carbon spectra was not as straightforward,
and for dimers 10c, 10k, 17a, and 17b the addition of [D5]-
pyridine had a negative effect on the 13C NMR spectra as this
solvent overshadows the spectrum. Therefore, for these dimers,
carbon assignments were impossible to achieve.
[60] HRMS was attained but the m/z value was approximately 0.9
higher than the exact mass. This could be attributed to a solu-
bility issue of the dimer.
J. S. Lindsey, S. Prathapan, T. E. Johnson, R. W. Wagner, Tetra-
hedron 1994, 50, 8941–8968.
N. Aratani, A. Osuka, H. S. Cho, D. Kim, J. Photochem. Pho-
tobiol. C: Photochem. Rev. 2002, 3, 25–52.
[47]
[48]
P. Bhyrappa, P. Bhavana, Chem. Phys. Lett. 2001, 342, 39–44.
a) K. Sonogashira, Y. Tohda, N. Hagihara, Tetrahedron Lett.
1975, 16, 4467–4470; b) R. W. Wagner, T. E. Johnson, F. Li,
J. S. Lindsey, J. Org. Chem. 1995, 60, 5266–5273.
[49] O. B. Locos, K. Dahms, M. O. Senge, Tetrahedron Lett. 2009,
50, 2566–2569.
[50] a) B. Krattinger, H. J. Callot, Eur. J. Org. Chem. 1999, 1857–
1867; b) N. N. Sergeeva, Y. M. Shaker, E. M. Finnigan, T.
McCabe, M. O. Senge, Tetrahedron 2007, 63, 12454–12464.
[51] a) H. W. Whitlock Jr., R. Hanauer, M. Y. Oester, B. K. Bower,
J. Am. Chem. Soc. 1969, 91, 7485–7489; b) M. O. Senge, W. W.
Kalisch, S. Runge, Tetrahedron 1998, 54, 3781–3798.
[52] H. Shinokubo, A. Osuka, Chem. Commun. 2009, 1011–1021.
[53] a) G. Wu, A. L. Rheingold, S. J. Geib, R. F. Heck, Organome-
tallics 1987, 6, 1941–1946; b) R. C. Larock, M. J. Doty, Q.
Tian, J. M. Zenner, J. Org. Chem. 1997, 62, 7536–7537.
Received: December 2, 2012
Published Online: ᭿
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
13