Synthesis of oligo(p-phenylene)-linked dyads containing free base, zinc(II) or thallium(III) porphyrins for studies in artificial photosynthesis

Article abstract of DOI:10.1016/j.tet.2010.05.059

A series of (p-phenylene)_n-linked meso-mesityl-substituted porphyrin dyads (n=2-4) was prepared via Suzuki coupling of zinc(II) and free base porphyrin building blocks. The resulting zinc(II)/free base porphyrin dyads were demetalated. The series of free base porphyrin dimers (n=1-4), four other por- phyrin dimers (with p-phenylene, diphenylethyne or diphenylbutadiyne linkers; and aryl or tridec-7-yl meso substituents), and several benchmark monomers were converted to the thallium(III)chloride complexes under mild conditions. The collection of eight Tl(III)Cl/Tl(III)Cl dimers is designed for studies of ground-state hole-transfer processes and comparison with the excited-state energy- and hole-transfer processes of the corresponding Zn(II)/free base dyads. Altogether, 18 new porphyrin arrays and benchmark monomers have been prepared.

Full text of DOI:10.1016/j.tet.2010.05.059

Tetrahedron 66 (2010) 5549e5565
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of oligo(p-phenylene)-linked dyads containing free base, zinc(II)
or thallium(III) porphyrins for studies in artificial photosynthesis
*
Masahiko Taniguchi, Jonathan S. Lindsey
Department of Chemistry, North Carolina State University, Box 8204, Raleigh, NC 27695-8204, USA
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 13 April 2010
Received in revised form 13 May 2010
Accepted 14 May 2010
Available online 17 June 2010
A series of (p-phenylene)n-linked meso-mesityl-substituted porphyrin dyads (n¼2e4) was prepared via
Suzuki coupling of zinc(II) and free base porphyrin building blocks. The resulting zinc(II)/free base
porphyrin dyads were demetalated. The series of free base porphyrin dimers (n¼1e4), four other por-
phyrin dimers (with p-phenylene, diphenylethyne or diphenylbutadiyne linkers; and aryl or tridec-7-yl
meso substituents), and several benchmark monomers were converted to the thallium(III)chloride
complexes under mild conditions. The collection of eight Tl(III)Cl/Tl(III)Cl dimers is designed for studies
of ground-state hole-transfer processes and comparison with the excited-state energy- and hole-transfer
processes of the corresponding Zn(II)/free base dyads. Altogether, 18 new porphyrin arrays and bench-
mark monomers have been prepared.
Keywords:
Artificial photosynthesis
Porphyrin
Building block
Array
Ó 2010 Elsevier Ltd. All rights reserved.
Electron transfer
Energy transfer
Hole transfer
Thallium
Zinc
Free base
Suzuki
Sonogashira
1. Introduction
parameter under investigation, such as distance, orientation,
energetics, frontier-orbital composition, excited-state lifetime,
One of the key objectives in artificial photosynthesis is to gain
a deep understanding of the physical principles that underlie light-
harvesting and energy-transduction processes. The processes of
interest include excited-state energy-transfer (as occurs in the
photosynthetic antenna complexes), excited-state electron-trans-
fer (as occurs in the reaction center), and subsequent ground-state
hole- and electron-transfer reactions that give rise to a spatially
separated hole and electron of sufficient lifetime for ultimate
storage of energy in the form of chemical fuels.
Studies to examine electronic communication among interact-
ing constituents have focused on multiporphyrin arrays wherein
the porphyrins serve as surrogates for the naturally occurring
(bacterio)chlorophylls, and the linker that joins the porphyrins
provides for architectural control in lieu of a protein matrix. A vast
number of synthetic arrays have been prepared to date.1e14 Still,
there remains a need for arrays with systematic variation of the
p-framework (e.g., hydroporphyrin vs porphyrin), etc. Our goal was
to create a set of arrays to enable direct comparison of processes of
(1) excited-state energy transfer in neutral complexes, (2) excited-
state hole transfer in singly oxidized complexes, and (3) ground-
state hole-transfer in singly oxidized complexes, all as a function of
increasing linker length between two interacting porphyrins. The
collective studies were aimed to deepen our understanding of
electronic communication between the porphyrins, largely medi-
ated by the intervening linker that supports such processes.
To achieve this goal we sought a specific set of compounds
wherein two porphyrins of distinct or identical metalation states
were joined at the meso-positions via a relatively rigid linker of
defined distance (Chart 1). The metalation states included zinc(II)/
free base (‘ZnFb’) for excited-state energy-transfer and hole-
transfer studies, and thallium(III)/thallium(III) (‘TlTl’) for ground-
state hole-transfer studies. Diverse ZnFb porphyrin dyads have
been prepared with linkers of a range of lengths,6 but to our
knowledge, no Tl(III)-containing porphyrin arrays of any type have
heretofore been prepared. For our studies, the primary linker of
choice was an oligo(p-phenylene) unit to achieve a high degree of
* Corresponding author. Tel.: þ1 9195156406; fax: þ1 9195132830; e-mail
address: jlindsey@ncsu.edu (J.S. Lindsey).
0040-4020/$ e see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.05.059

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M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
molecular rigidity and substantial increments of distance (phenyld
quaterphenyl) within a given molecular composition. Two other
linkers (diphenylethyne, diphenylbutadiyne) were employed for
comparison with the large body of available data concerning
multiporphyrin arrays of these types.7
2. Routes to oligo(p-phenylene)-linked porphyrin dyads
Synthetic oligo(p-phenylene)-linked porphyrin dyads have been
prepared via a wide variety of chemistries. The various approaches
can be assessed on the basis of (i) whether the route provides rational
accessto(symmetric)dimersor(unsymmetric)dyads,and(ii)atwhat
stage in the synthesis the porphyrin macrocycle is constructed. In this
regard, the oligo(p-phenylene) linker can be pre-installed on an
acyclic precursor to the porphyrin followed by a cyclization reaction
to create the porphyrin macrocycle, or intact porphyrin building
blocks can be joined via Suzuki coupling to form the oligo(p-phe-
nylene) linker. The Suzuki coupling can entail a single joining (mono-
coupling) to create dyads or a double joining (bis-coupling) to create
dimers. In general, any route to dyads can be employed to access
dimers. Representative routes are displayed in Table 1.
Synthesis of a biphenyl-linked porphyrin dimer was first
reported by McLendon and co-workers, via condensation of a 4,40-
biphenyl-linked bis(dipyrromethane) and a 1,9-diformyldipyrro-
methane followed by oxidation (entry 1).17,18 Extension of this
method with a 4,400-terphenyl- or 4,4000-quaterphenyl-linked bis
(dipyrromethane) afforded terphenyl- or quaterphenyl-linked
porphyrin dimers.19 Alternatively, the reaction of biphenyl-4,40-
dicarboxaldehyde, a dipyrromethane and an aldehyde gave a sym-
metric biphenyl-linked porphyrin dimer (entry 2).20e22 Similar
reaction of terephthalaldehyde, benzaldehyde, and pyrrole affor-
ded the p-phenylene-linked dimer (entry 3).23,24 This reaction is
statistical in that multiple porphyrin products can form, and is
undirected in that no control is provided over the individual
metalation state of each porphyrin.
R15
R15
N
N
N
N
R10
R10
M1
R5
meso-substituents
M2
linker
N
N
N
N
R5
linkers
R5 = R10 = R15
n
n = 1-4
R5 = R10 = R15
R5 = R15
10 = mesityl
;
R
metals
M1 = Zn; M2 = H,H
R5 = R10 = R15
M1 = M2 = H,H
The Suzuki coupling reaction enables CeC bond formation to
create the oligo(p-phenylene) linkers, which gives strategic flexibil-
ity in the preparation of oligo(p-phenylene)-linked porphyrin arrays.
Biphenyl- and terphenyl-linked porphyrin dimers were prepared by
Suzuki coupling of a halophenylporphyrin and a linker bearing a bis
(boronic acid) unit (entry 4).25,26 Similar Suzuki coupling was
employed with a meso-substituted dioxaborolanylporphyrin and
a dihalo-substituted phenylene linker (entry 5).27 Both examples
provide rational access to dimers yet were undirected with respect to
the metalation states and substituents of the respective porphyrins.
The synthesis of dyads requires a directed route wherein the two
porphyrins are created sequentially, or two porphyrin building
blocks are joined in an unsymmetric fashion. The condensation of
a porphyrin bearing a p-biphenylcarboxaldehyde unit with a dipyr-
romethane and an aldehyde gave the biphenyl-linked porphyrin
dyad (entry 6).28,29 This approach was statistical in that a porphyrin
triad and a porphyrin monomer also could form. We reported the
Suzuki mono-coupling of a dioxaborolanylphenylporphyrin and
a meso-haloporphyrin; although the synthesis was rational and
entailed a directed coupling, the product was a p-phenylene-linked
porphyrin dimer rather than a dyad given that both porphyrins
contained the same substituents and were free base species (entry
7).30 Nocera and co-workers recently reported the Suzuki mono-
coupling of a dioxaborolanylbiphenylporphyrin and a meso-halo-
porphyrin to give a biphenyl-linked porphyrin dyad (entry 7).31
Following these approaches, porphyrin dyads bearing linkers as
long as the quaterphenyl unit have been reported so far.18
M1 = M2 = Tl(III)Cl
Chart 1.
Key molecular design issues in addition to the linker included
the following: (i) pattern of substitution of the non-linking sub-
stituents, (ii) electronic features of the non-linking substituents,
and (iii) solubilizing features of the non-linking substituents.7
Porphyrins bearing electron-releasing aryl groups (e.g., phenyl) or
alkyl groups located at the meso-positions typically exhibit the a2u
HOMO (vs a1u HOMO with
b-alkyl or meso-pentafluorophenyl-
substituted porphyrins). The a2u orbital is desired owing to the
large electron density at the meso-position, the site where the oligo
(p-phenylene) linker is positioned. Accordingly, a bulky, electron-
rich group was located at each of the non-linking meso-positions to
achieve the desired frontier-orbital composition and a high degree
of solubilization in organic solvents.
In this paper we report the synthesis of 18 new porphyrin arrays
and benchmark compounds. The primary targets included the
arrays containing two porphyrins linked by oligo-p-phenylene
units (spanning phenyldquaterphenyl), mesityl groups at the non-
linking meso sites, and several distinct metalation states (FbFb,
ZnFb, and TlTl). Four TlTl dimers equipped with various non-linking
substituents (mesityl, 3,5-di-tert-butylphenyl, tridec-7-yl) and
linkers (p-phenylene, diphenylethyne, diphenylbutadiyne) also
were prepared. Of this latter set, three of the constructs were
previously known as the FbFb species and were subjected here to
metalation, whereas the swallowtail-substituted diphenylethyne-
linked FbFb dimer was prepared herein from the corresponding
building blocks. Altogether, three new ZnFb porphyrin dyads, three
new FbFb porphyrin dimers, eight new TlTl porphyrin dimers, and
four thallium-containing porphyrin monomers are described
herein. The photochemical features of the ZnFb porphyrin dyads
were recently described,15,16 whereas the ground-state hole-
transfer properties of the TlTl porphyrin dimers will be described
elsewhere.
The reaction of a porphyrin bearing a dipyrromethane with
a
dipyrromethane/dicarbinol (or vice versa) afforded the
corresponding p-phenylene-linked porphyrin dyad (entry 8).32 The
porphyrin-forming conditions were sufficiently mild to accom-
modate metalation states such as Zn/Fb, Mg/Fb, and Zn/Mg.
Porphyrin dyads in distinct metalation states (e.g., ZnFb) in prin-
ciple can be prepared by statistical metalation or demetalation of
porphyrin dimers. In practice, however, separation of zinc/zinc,
zinc/free base, and free base/free base arrays typically entails
elaborate chromatography.

M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
5551
Table 1
Routes to oligo(p-phenylene)-linked porphyrin dimers and dyads
Entry
Reactants
Joining Reaction
nb
Type
Architecture
Dimer
References
OHC
H
H
NH
NH
HN
HN
HN
HN
+
Porphyrin
formation
Rational,
undirected
1
2e4
17e19
20e22
n
OHC
n = 2-4
HN
HN
Porphyrin
formation
Statistical,
undirected
+
+
aldehyde
OHC
CHO
2
2
Dimer
n
n = 2
Porphyrin
formation
Statistical,
undirected
+
+
aldehyde
3
OHC
M
CHO
1
3
Dimer
Dimer
23,24
25,26
N
H
N
N
Suzuki bis-
coupling
Rational,
undirected
4a
(HO)2B
B(OH)2
X
+
N
N
j
j = 1
O
O
N
N
Suzuki bis-
coupling
Rational,
undirected
5a
2,3
2,3
Dimer
Dyad
27
B
+
X
X
M
M
N
N
n = 2, 3
n
HN
HN
N
N
+
Porphyrin
formation
Statistical,
directed
CHO
+ aldehyde
6a
28,29
N
N
n
n = 2, 3
O
O
N
N
N
M1
B
n = 1, 2
N
n
Suzuki mono-
coupling
Rational,
directed
7a
1,2
Dyad
30,31
N
N
X
M2
+
N
N
R2
R1
H
HN
HN
N
NH
NH
N
+
M
Porphyrin
formation
Rational,
directed
8a
1
Dyad
32
N
N
R2
R1
R1 = H, R2 = CH(OH)Ar or R1 = CH(OH)Ar, R2 = H
a
Substituents on the porphyrin macrocycle are not shown for clarity.
Number of p-phenylene units in the oligo(p-phenylene) linker.
b
3. Results and discussion
To minimize the number of reaction steps, meso-phenyl and
meso-biphenyl-substituted porphyrins were prepared, instead of
meso-halo or meso-pinacolatoboron-substituted porphyrins, which
require additional steps for halogenation and introduction of the
pinacolatoboron unit. The choice of mesityl groups at the non-
linking positions to impart solubility requires use of mixed-alde-
hyde condensations to prepare the A3B-porphyrin building blocks,
because trimesitylporphyrins cannot yet be prepared in a rational
3.1. Synthesis of oligo(p-phenylene)-linked porphyrin dyads
and dimers
To achieve a rational, directed synthesis of oligo(p-phenylene)-
linked porphyrin dyads, we chose the Suzuki mono-coupling of a
zinc porphyrin and a free base porphyrin, as in entry 7 of Table 1.

5552
M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
N
N
I
Zn
N
N
Zn1-I
Bis(pinacolato)diboron
78%
Pd(dppf)Cl2, KOAc, DMF
100 °C, Schlenk, 60 h
O
O
N
N
B
Zn
N
N
Zn1-B
N
HN
N
I
NH
34%
Fb1-I
Pd(dppf)Cl2, KOAc
Toluene/DMF/H2O
100 °C, Schlenk, 16 h
N
N
N
HN
N
Zn
N
NH
N
ZnFbΦ
2
Scheme 1.
manner.33 Thus, all trimesityl-substituted porphyrin building
blocks were synthesized via statistical condensations34 of pyrrole,
mesitaldehyde, and a second aldehyde in the presence of BF3$O
(Et)2/ethanol cocatalysis.35
preparative-scale size-exclusion chromatography (SEC) to separate
the target array from monomers and higher-molecular weight
materials (e.g., oligomers); and (3) silica to remove materials de-
rived from the SEC column.36 In some cases here, the first silica
column was omitted. Thus, treatment of the crude mixture in this
manner afforded biphenyl-linked porphyrin dyad ZnFbF2 in 34%
yield.
The synthesis of the biphenyl-substituted porphyrin building
blocks requires access to bifunctionalized biphenyl units. Thus,
monoformylation of 4,40-dibromobiphenyl with n-BuLi and DMF
following a known procedure37 gave aldehyde I-Br (Scheme 2).
Pd-mediated reaction of I-Br and bis(pinacolato)diboron gave known
aldehyde I-B.38 A mixed condensation was performed of 2.5 mM
of biphenylcarboxaldehyde I-Br or I-B, 7.5 mM of mesitaldehyde,
and 10 mM of pyrrole. The reaction was carried out in CHCl3
(containing 0.8% ethanol)35 in the presence of 3 mM BF3$O(Et)2
The synthesis of biphenyl-linked porphyrin dyad ZnFbF2 is
outlined in Scheme 1. Pd-mediated coupling of known36 iodo-
phenyl-substituted zinc porphyrin Zn1-I with bis(pinacolato)
diboron gave meso-dioxaborolanylphenylporphyrin Zn1-B in 78%
yield. Suzuki coupling of Zn1-B and known34 iodophenyl-
substituted free base porphyrin Fb1-I was carried out in toluene/
DMF/water containing 1,10-bis(diphenylphosphino)ferrocene-
palladium(II)dichloride dichloromethane adduct and potassium
acetate. In general, the purification of multiporphyrin arrays formed
upon Pd-mediated coupling is typically best achieved via a multi-
column chromatographic sequence: (1) silica chromatography to
remove palladium species and other polar materials; (2)

M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
5553
Oligo(p-phenylene)-linked free base porphyrin dimers were
prepared via demetalation of zinc-free base dyads containing the
biphenyl, terphenyl, or quaterphenyl linker to give porphyrin
dimers FbFbF2, FbFbF3, or FbFbF4, respectively (Scheme 4). The
R
I-Br R = Br
I-B R =
O
O
+
+
p-phenylene-linked porphyrin dimer FbFb
prepared by mixed condensation of mesitaldehyde, pyrrole, and
terephthalaldehyde, and ZnFb was prepared therefrom by sta-
F was previously
B
N
H
CHO
F
(7.5 mM)
(10 mM)
tistical metalation.24 The excited-state processes for ZnFb
F in the
CHO
respective neutral24 and oxidized15 form have been characterized.
(2.5 mM)
(1) BF3·O(Et)2 (3 mM), CHCl3, rt, 1 h
(2) DDQ (7.5 mM), rt, 1 h
3.2. Synthesis of a swallowtail-substituted porphyrin dimer
The Sonogashira coupling of swallowtail-substituted porphyrin
building blocks was employed to prepare the corresponding diphe-
nylethyne-linked swallowtail porphyrin dimer. The swallowtail
substituents have previously beenemployed to impart highsolubility
to porphyrins and multiporphyrin arrays in organic solvents.39,40
Thus, the known free base swallowtail porphyrins39 bearing ethynyl
(Fb4-E) and iodo (Fb4-I) groups were coupled under copper-free,
palladium-mediated coupling conditions41,42 to afford the dipheny-
lethyne-linked dimer FbFb-SW-PEP in 48% yield (Scheme 5).
N
HN
R
NH
N
3.3. Synthesis of thallium(III) complexes of porphyrins
Fb2-Br R = Br
Fb2-B R =
13%
8%
3.3.1. Prior metalation conditions. The first report concerning the
synthesisofathalliumporphyrinapparentlywasduetoFischer, while
the modern era began with the work of Smith.43 Smith prepared
thallium(III) chelates of 2,3,7,8,12,13,17,18-octaethylporphyrin, meso-
tetraphenylporphyrin, and several derivatives of naturally occurring
porphyrins; subsequent characterization methods included absorp-
tion, IR, and 1H NMR spectroscopy.43 He also reported 13C NMR
spectra of selected thallium(III) porphyrins.44 Thallium(III) porphy-
rins are class II metalloporphyrins, which characteristically resist
demetalation except under quite acidic conditions (conc. H2SO4 at
room temperature),45 although reducing agents that give the Tl(I)
species enable milder demetalation.43 The traditional methods for
thallium(III) chelation include treating the free base porphyrin with
a thallium salt in refluxing pyridine or refluxing DMF;45 however,
Smith employed Tl(O2CCF3)3 in a solvent mixture (THF and CH2Cl2)
that was warmed slightly or at room temperature.43 This extensive
prior work provided the foundation for the following studies con-
cerning the metalation of various porphyrin dimers.
O
O
B
(Fb2-Br only)
73% Zn(OAc)2·2H2O, CH2Cl2
rt, 2 h
N
N
Zn
Br
N
N
Zn2-Br
Scheme 2.
3.3.2. Metalation conditions for diverse synthetic porphyrins. The
studies of ground-state hole transfer in the TlTl dimers require the
presence of identical counterions at the two metal centers, and are
best performed with chloride counterions. The reaction of a free
base porphyrin and TlCl3$(H2O)4 in DMF under reflux affords
the thallium(III) complex wherein the apical ligand typically is
chloride.46 Alternatively, a thallium(III) complex wherein the apical
ligand is acetate or trifluoroacetate can be subjected to exchange to
form the chlorothallium(III) complex.47e52 The reaction of free base
meso-tetramesitylporphyrin (Fb-TMP) with TlCl3$(H2O)4 in DMF at
150 ꢀC for 2 h afforded the thallium complex Tl-TMP bearing
chloride as the apical ligand. However, thallium metalation of
swallowtail porphyrin dimer FbFb-SW-PEP with TlCl3$(H2O)4 in
DMF at 150 ꢀC resulted in decomposition within 30 min. Thus,
reactions under milder conditions were explored.
We found that the reaction of free base porphyrins with
a methanolic solution of TlCl3$(H2O)4 in CH2Cl2 at room tempera-
ture proceeds smoothly; the reaction mixture quickly turns (within
1 min) from purple to green. The formation of the thallium por-
phyrin can be readily monitored by absorption spectroscopy (vide
infra) and by TLC, which imply that >90% of the free base porphyrin
is converted to the corresponding thallium porphyrin within 1 h.
These room temperature conditions for thallium metalation are
for 1 h, followed by oxidation with DDQ to form the mixture of
porphyrins. Chromatography of the crude reaction mixture
readily gave the desired A3B-porphyrin Fb2-Br or Fb2-B in 13
or 8% yield, respectively, which is comparable to the typical
yield of A3B-porphyrins via mixed-aldehyde condensations
(10e14%).34 Treatment of Fb2-Br with Zn(OAc)2$2H2O in CH2Cl2
at room temperature gave Zn2-Br in 73% yield. For comparison,
an analogous meso-biphenyl-substituted porphyrin was prepared
by two Suzuki coupling procedures: (1) chemoselective Suzuki
mono-coupling of a meso-(dioxaborolanylphenyl)porphyrin and
4-iodo-1-chlorobenzene, (2) Suzuki bis-coupling of the resulting
meso-(p-chlorobiphenyl)porphyrin and bis(pinacolato)diboron.31
Terphenyl- and quaterphenyl-linked porphyrin dyads were
synthesized via Suzuki coupling of the corresponding building
blocks in a manner similar to that employed in the synthesis
of ZnFbF2 (Scheme 3). Suzuki coupling of dioxaboro-
lanylphenylporphyrin Zn1-B and bromobiphenylporphyrin Fb2-Br
gave terphenyl-linked porphyrin dyad ZnFbF3 in 58% yield,
whereas bromobiphenylporphyrin Zn2-Br and dioxaboro-
lanylbiphenylporphyrin Fb2-B gave quaterphenyl-linked porphyrin
dyad ZnFbF4 in 63% yield. These reactions were carried out at
a scale that gave dyads in quantities of up to 50 mg.

5554
M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
O
N
N
N
HN
N
B
+
Br
Zn
N
NH
N
O
Zn1-B
Fb2-Br
Pd(dppf)Cl2, KOAc
Toluene/DMF/H2O
100 °C, Schlenk, 16 h
58%
ZnFbΦ
n = 3
3
N
N
N
HN
N
Zn
N
NH
N
n
ZnFbΦ
n = 4
4
Pd(dppf)Cl2, KOAc
63% Toluene/DMF/H2O
100 °C, Schlenk, 16 h
O
N
N
N
HN
N
Br
+
B
Zn
N
NH
N
O
Zn2-Br
Fb2-B
Scheme 3.
mild and quite attractive in affording conversion of 90% or greater;
however, the reaction is typically not fully complete. Achieving high
purity is essential for photochemical studies.
Thallium porphyrin Tl3-OH (prepared from known53 Fb3-OH)
bears a hydroxymethyl group for surface attachment.
The thallium(III) complexes of the porphyrin dimers that were
prepared herein are shown in Chart 3. The dimers wherein the linker
varies in length and composition include the oligo-(p-phenylene)-
linked architectures as well as those containing the diphenylethyne
(TlTl-PEP) and diphenylbutadiyne (TlTl-PEEP) linkers. The latter
arrays were obtained by metalation of the known free base archi-
tectures (FbFb-PEP,54 FbFb-PEEP41). To study the effect of meso
We found the full conversion to the thallium chelate could not be
achieved despite (1) prolonged reaction time (up to 72 h), (2) use of
a large excess of TlCl3$(H2O)4 (up to 200 equiv), and (3) use of higher
temperature (e.g., in THF at reflux; in DMF at 150 ꢀC). As a result,
purification of the thallium complex from the unreacted free base
porphyrin (up to 5%) is required. Whereas the thallium porphyrin
monomers can be readily purified by chromatography (silica or
neutral alumina) to remove the unreacted free base porphyrin, pu-
rification of the TlTl porphyrin dimer from a trace amount of the Tl/
Fb porphyrin dyad and starting material required extensive chro-
matography. Alternatively, the thallium porphyrin species (mono-
mers and dimers) could be recrystallized upon diffusion of methanol
(or hexanes) into a chloroform solution of the mixture of porphyrins.
Application of such chromatographic or crystallization methods
afforded the requisite purity in each case.
substituents, known30 p-phenylene-linked dimer FbFb-Ar-
the new diphenylethyne-linked swallowtail dimer FbFb-SW-PEP
were converted to the corresponding thallium complexes TlTl-Ar-
F and
F
and TlTl-SW-PEP. All thallium porphyrins described herein were
analyzed by fluorescence emission and excitation spectroscopy to
verify that the samples were devoid of free base porphyrins. MALDI-
MS analysis of the thallium porphyrins typically exhibited two
dominant peaks in the positive ion spectrum including the molecule
ion and a daughter ion formed upon loss of chloride.
The reaction conditions applied for thallium metalation and the
yields obtained are summarized in Table 2. The thallium(III) por-
phyrin monomers that were prepared herein are illustrated in
Chart 2. The thallium porphyrins Tl1-E and Tl4-E were prepared
(by metalation of the free base species Fb1-E and Fb4-E) as
benchmark compounds for comparison with the analogous dimers.
3.4. Characterization of synthetic porphyrins and arrays
All porphyrin monomers, dimers (FbFb, TlTl), and dyads (ZnFb)
1
were characterized by H NMR spectroscopy, absorption spectros-
copy, emission spectroscopy, laser-desorption mass spectrometry

M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
5555
CHO
+
+
N
H
CHO
CHO
(7.5 mM)
(10 mM)
(1.25 mM)
(1) BF3·O(Et)2 (3 mM), CHCl3, rt, 1 h
(2) DDQ (7.5 mM), rt, 1 h
1%
FbFbΦ n = 1
N
N
HN
N
HN
N
NH
NH
n
FbFbΦ
FbFbΦ3 n = 4
n = 2
n = 3
FbFbΦ2
4
70-95%
TFA, CH2Cl2
N
N
N
N
HN
N
Zn
N
NH
n
ZnFbΦ
ZnFbΦ3 n = 4
n = 2
n = 3
ZnFbΦ2
4
Scheme 4.
(low resolution), electrospray mass spectrometry (high resolution),
and analytical SEC (vide infra). The characterization of the arrays by
13C NMR spectroscopy proved difficult owing to very low solubility
for the FbFb dimers, complexity of the spectra for the ZnFb dyads
(composed of two distinct A3B-porphyrins), and strong Tl-C
couplings in the TlTl dimers. The NMR spectral features of the
porphyrin monomers, dimers, and dyads are described below.
distinct from that of the monomer upon analytical SEC, consistent
with the dimer architecture.
3.4.2. NMR spectra of thallium porphyrins. To our knowledge, the
only thallium complexes of meso-substituted porphyrins that have
been characterized by 1H NMR and 13C NMR spectroscopy are sym-
metric A4-porphyrins (i.e., bearing four identical meso-sub-
stituents).52,56e61 The 1H and 13C NMR spectra obtained herein of
a thallium complex of an A4-porphyrin, namely Tl-TMP, are very
similar to those previously reported for thallium complexes of A4-
porphyrins. Due to the strong thallium-proton and thallium-carbon
couplings, thefollowingcharacteristic patternswereobserved:(1) 1H
3.4.1. Size-exclusion chromatography. Analytical size-exclusion
chromatography (SEC) has served as an effective means of estab-
lishing the purity of diverse covalently linked multiporphyrin
arrays.36,41,42,55 A very attractive feature of SEC is that because the
mode of separation relies on differences in molecular size rather
than adsorption, essentially all of the material injected into the
column elutes from the column. Each of the new purified oligo
(p-phenylene)-linked arrays was examined by analytical SEC with
visible-region absorption spectroscopic detection. Each compound
gave a single peak, as expected, upon SEC analysis (Fig. 1). The
retention time for an array with a given linker was essentially
constant regardless of metalation state (Table 3). Moreover, the
retention time decreased by w0.4 min per additional p-phenylene
unit regardless of metalation state. Accordingly, the existence of
a single peak for each array is indicative of sample purity. The data
listed in Table 3 are for the arrays with increasing number of
p-phenylene units. The swallowtail dimer also gave a single peak
NMR spectra; (a) the b
-protons show strong 4J couplings (62.4 Hz)
with thallium, (b) the o-/o0-methyl and m-/m0-H in the mesityl group
are differentiated due to the presence of the axial ligand. (2) 13C NMR
spectra; (a) the magnitude of the coupling constants between carbon
and thallium decreases in the following order: meso-porphyrin car-
bon (3J,146 Hz)> -porphyrin carbon (3J,116 Hz)>>o-mesityl carbon
b
(4J, 26 Hz)>m-mesityl carbon (5J, 19 Hz)¼
a
-porphyrin carbon (2J,
19 Hz), (b) in addition to the Tl-C coupling, the o-/o0- and m-/m0-
mesityl carbons are differentiated due to the presence of the axial
ligand; thus, the o-mesityl carbon affords a doublet of doublets
pattern.
The effects of thallium on the 13C NMR spectra are best
illustrated by comparison of the 13C NMR spectra in the series of

5556
M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
N
N
HN
N
HN
N
+
H
I
NH
NH
Fb4-E
Fb4-I
Pd2(dba)3, P(o-tol)3
Toluene/triethylamine (5:1)
40 °C, Schlenk, 4.5 h
48%
N
N
HN
N
HN
N
NH
NH
FbFb-SW-PEP
Scheme 5.
meso-tetramesitylporphyrin species including the free base
(Fb-TMP), zinc chelate (Zn-TMP),62 and chlorothallium derivative
(Tl-TMP). The spectra are displayed in Figure 2. Each of the por-
phyrins is of the A4-type, and in each case all of the observed signals
protons. Out of four sets of inequivalent b-porphyrin protons (total
8H), two sets of
b-porphyrin protons adjacent to two mesityl
groups (4H) are overlapped and appear as a doublet [4J(TleH)¼
62.0 Hz] (note that 3J(HeH) are not observed). Each of the
are readily assignable. Note that the signal for the porphyrin
carbon of Fb-TMP is missing (owing in part to NH tautomerization)
under the spectroscopic conditions employed.
The NMR spectra of thallium A3B-porphyrins are more compli-
cated due to the decreased symmetry (vs the A4-porphyrins) of the
porphyrin macrocycle. For instance, the 1H NMR spectrum of A3B-
a
-
remaining two sets of b-porphyrin protons (4H) appears as a dou-
blet of doublets [4J(TleH)¼62.8 Hz, 3J(HeH)¼4.7 Hz] and [4J
(TleH)¼64.5 Hz, 3J(HeH)¼4.7 Hz]. The 1H NMR spectra of thallium
porphyrin dimers are essentially the superposition of the spectra of
the constituent thallium A3B-porphyrins.
The 13C NMR spectra of thallium-containing A3B-porphyrins and
TlTl dimers (which contain two identical A3B-porphyrins) show
typical patterns for coupling between carbon and thallium as seen
for A4-porphyrins. However, the assignment and interpretation of
the resonances are complicated due to the decreased symmetry of
the porphyrin macrocycle and the strong thallium/carbon coupling,
whereas the signal-to-noise is limited owing to available quantity
of the sample. Representative 13C NMR spectra of one Tl-porphyrin
monomer and five TlTl dimers are shown in Figure 3. 13C NMR
spectra of seven such compounds are provided without assign-
ments as Supplementary data.
porphyrin Tl1-E exhibits four sets of inequivalent
b-porphyrin
Table 2
Synthesis of thallium(III) complexes of porphyrins and porphyrin dimers
Free base
porphyrin
Thallium
chelate
Solvent
Temp
(ꢀC)
Time
(h)
Yield
(%)
Fb-TMP
Fb1-E
Fb3-OH
Fb4-E
Tl-TMP
Tl1-E
Tl3-OH
Tl4-E
DMF
150
rt
rt
rt
150
rt
rt
rt
rt
rt
2
75
90
78
63
75
80
83
84
78
71
66
76
CH2Cl2/CH3OH
CH2Cl2/CH3OH
CH2Cl2/CH3OH
DMF
CH2Cl2/CH3OH
CH2Cl2/CH3OH
CH2Cl2/CH3OH
CH2Cl2/CH3OH
CH2Cl2/CH3OH
CHCl3/CH3OH
CH2Cl2/CH3OH
0.5
48
2
2
2
2
14
2
16
1.5
2
FbFb-Ar-
F
TlTl-Ar-
F
FbFb-
F
TlTl-F
3.4.3. Absorption spectra of thallium(III) porphyrins. The absorption
spectra of the thallium(III) porphyrins are summarized in Table 4.
Representative spectra of thallium(III) complexes of porphyrin di-
FbFb-F2
FbFb-F3
FbFb-F4
FbFb-PEP
FbFb-PEEP
FbFb-SW-PEP
TlTl-F2
TlTl-F3
TlTl-F4
TlTl-PEP
TlTl-PEEP
TlTl-SW-PEP
mers and the corresponding free base porphyrins (FbFbF4, TlTl-F4
FbFb , and TlTl- ) are displayed in Figure 4. The absorption
spectra of thallium(III) porphyrins show patterns typical for
,
60
rt
F
F

M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
5557
architectures containing two porphyrins joined via a covalent
linker, yet there remains a need for systematically designed sets of
dyads and dimers to address key mechanistic questions. One set of
architectures prepared herein includes two meso-substituted por-
phyrins joined via an oligo(p-phenylene) linker, mesityl groups at
the non-linking meso positions, and three different combinations of
metalation states. The metalation states include Zn(II)/free base for
study of excited-state energy-transfer and hole-transfer processes;
Tl(III)/Tl(III) for study of ground-state hole-transfer processes; and
free base/free base as synthetic intermediates. The oligo(p-phe-
nylene) linker, while examined previously in a variety of arrays but
not in the systematic set of porphyrin dyads as prepared herein,
enables a range of porphyrin/porphyrin distances of separation to
be accessed while limiting changes in other molecular parameters.
Several arrays with diphenylethyne or diphenylbutadiyne linkers
also were prepared.
Cl
Tl
N
N
N
N
Tl-TMP
Cl
Tl
N
N
H
N
N
There are at least three key distinctions between the oligo
(p-phenylene) linkers and the linkers containing one or more eth-
yne units (i.e., diphenylethyne or diphenylbutadiyne). First, the
latter are more flexible than the former. The greater flexibility is
expected on first principles, is predicted by calculations, and has
been established by NMR spectroscopy of analogous multiporphyrin
arrays.63 The greater flexibility stems from the sp-hybridization of
the ethyne carbon atoms versus the sp2-hybridization of the carbon
atoms in the aryl units. In other words, the diphenylethyne and
diphenylbutadiyne linkers are more prone to bending (at the ethyne
carbons) than are the oligo(p-phenylene) linkers. Second, the
ethyne-containing linkers have a lower energy barrier to rotation
about the linker axis versus oligo(p-phenylene) linkers owing to the
cylindrical symmetry of the ethyne bond. Third, the ethyne-
containing linkers generally have smaller HOMO/LUMO gaps than
those of the oligo(p-phenylene) linkers (although the HOMO/LUMO
gaps of the quaterphenyl and diphenylethyne linkers are compa-
rable).16 Accordingly, arrays of nominally identical distances of
separation of the porphyrin centers may exhibit different rates of
key processes (excited-state energy transfer and hole transfer;
ground-state hole transfer) owing to the distinct physical properties
of the two classes of linkers.
Tl1-E
Cl
Tl
N
N
CH2OH
N
N
Tl3-OH
Cl
Tl
N
N
H
N
N
5. Experimental
Tl4-E
5.1. General methods
1H NMR spectra (300 MHz) and 13C NMR spectra (75 MHz) were
collected in CDCl3 or toluene-d8. Absorption and fluorescence
spectra were collected in CH2Cl2 at room temperature unless noted
otherwise. Laser-desorption mass spectra of porphyrins were
obtained via matrix-assisted laser desorption ionization mass
spectrometry (MALDI-MS) using a matrix of 1,4-bis(5-phenyl-
oxazol-2-yl)benzene.64 Electrospray ionization mass spectrometry
(ESIMS) data are reported for the molecule ion or protonated
molecule ion. Analytical-scale size-exclusion chromatography
(SEC) and preparative-scale SEC (BioeBeads SX-1, toluene) were
carried out as described previously.36,42,55 Analytical-scale SEC was
performed using three columns (100 Å, 500 Å, and 1000 Å; Polymer
Laboratories, PLgel GPC) in series eluting with THF at a flow rate of
0.8 mL/min. Neutral alumina (activity grade I) was obtained from
commercial suppliers and used as received.
Chart 2.
metalloporphyrins.43 Thallium complexation causes
a
batho-
chromic shift of the B band (w16 nm), and the Q bands appear at
around 568 and 608 nm. The absorption spectra of thallium(III)
complexes of porphyrin monomers prepared herein (Tl-TMP, Tl1-E,
and Tl3-OH) are essentially the same as previously reported for the
thallium(III) complexes of meso-tetraarylporphyrins.48,49,52 The
absorption spectra of the thallium(III) complexes of porphyrin
dyads dimers containing biphenyl, terphenyl, quaterphenyl,
diphenylethyne, and diphenylbutadiyne linkers are similar to those
of the corresponding thallium(III) complexes of the porphyrin
monomers. On the other hand, the p-phenylene-linked dyad shows
a split B band owing to strong electronic coupling between the two
porphyrins (Fig. 3).
5.2. Solvents
CHCl3 contained 0.8% ethanol. Toluene, DMF, and triethylamine
for the Pd-mediated coupling reactions (Suzuki or Sonogashira
couplings) were used as obtained from commercial sources with-
out further purification. The solvent mixture of toluene/DMF/water
(for Suzuki coupling) or toluene/triethylamine mixture (for
4. Outlook
Extensive studies in artificial photosynthesis spanning more
than 30 years have yielded a very large collection of molecular

5558
M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
Cl
Tl
Cl
Tl
N
N
N
N
N
N
N
N
n
n = 1
n = 2
n = 3
n = 4
TlTl-Φ
TlTl-Φ
TlTl-Φ2
TlTl-Φ3
4
Cl
Tl
Cl
N
N
N
N
Tl
N
N
N
N
n
n = 1
n = 2
TlTl-PEP
TlTl-PEEP
t-Bu
t-Bu
Cl
Tl
Cl
Tl
t-Bu
t-Bu
N
N
N
N
N
N
N
N
t-Bu
t-Bu
TlTl-Ar-Φ
t-Bu
t-Bu
Cl
Tl
Cl
Tl
N
N
N
N
N
N
N
N
TlTl-SW-PEP
Chart 3.
Sonogashira coupling) was freeze/pump/thawed three times under
argon prior to use. The Pd-mediated coupling reactions were car-
ried out under anaerobic conditions with the use of standard
Schlenk-line techniques.
tetramesitylporphyrin (Zn-TMP),62 5,10,15-trimesityl-20-(4-iodo-
phenyl)porphyrin (Fb1-I),34 zinc(II)-20-(4-iodophenyl)-5,10,15-tri-
mesitylporphyrin
(Zn1-I),36
5-(4-ethynylphenyl)-10,15,20-
trimesitylporphyrin (Fb1-E),34 5-[4-(hydroxymethyl)phenyl]-
10,15,20-tri-p-tolylporphyrin (Fb3-OH),53 5-(4-ethynylphenyl)-
10,15,20-tris(tridec-7-yl)porphyrin (Fb4-E),39 and 5-(4-iodo-
phenyl)-10,15,20-tris(tridec-7-yl)porphyrin (Fb4-I)39 and the por-
phyrin dimers 1,4-bis(5,10,15-trimesitylporphin-20-yl)benzene
5.3. Non-commercial compounds
The biphenyl building blocks 40-bromobiphenyl-4-carbox-
aldehyde (I-Br)37 and 40-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan
-2-yl)biphenyl-4-carboxaldehyde (I-B)38 the porphyrins meso-
(FbFb
butylphenyl)-10-mesitylporphin-20-yl]benzene (FbFb-Ar-
pound 12 in Ref. 30),30 1,2-bis[4-(5,10,15-trimesitylporphin-20-yl)
F
; compound Fb2F in Ref. 24),24 1,4-bis[5,15-(3,5-di-tert-
; com-
F
tetramesitylporphyrin
(Fb-TMP),35
zinc(II)-meso-

M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
5559
Table 3
Analytical SEC retention times of porphyrin dimers and dyadsa
Compound
Retention time (min)
ZnFbF2
ZnFbF3
ZnFbF4
26.41
26.04
25.72
FbFb
F
26.92
26.49
26.14
25.82
FbFbF2
FbFbF3
FbFbF4
TlTl
F
26.86
26.46
26.10
25.76
TlTlF2
TlTlF3
TlTlF4
a
Data were obtained upon chromatography with three columns (100 Å, 500 Å,
and 1000 Å) in series and a flow rate of 0.8 mL/min (THF). The void volume corre-
sponded to w2.8 min.
trimesitylporphyrin (Zn1-I, 93.0 mg, 100
diboron (76.2 mg, 300
mol), 1,10-bis(diphenylphosphino)ferro-
cene-palladium(II)dichloride dichloromethane adduct [Pd(dppf)
Cl2] (4.9 mg, 6.0 mol), and potassium acetate (88.3 mg,
mmol), bis(pinacolato)
m
m
0.900 mmol) were weighed into a 25-mL Schlenk flask, which was
then pump-purged three times with argon. DMF (10 mL, bubbled
through argon for 1 h) was added and the reaction mixture was
stirred at 100 ꢀC for 60 h. Standard workup including chromatog-
raphy [silica, hexanes/CH2Cl2/triethylamine (66:33:1)] gave a purple
solid (74.1 mg, 78%): 1H NMR (CDCl3)
d 1.50 (s,12H),1.84 (s,12H),1.85
(s, 6H), 2.63 (s, 6Hþ3H), 7.27 (s, 6H), 8.14e8.27 (m, 4H), 8.67e8.72
(m, 4H), 8.74 (d, J¼4.7 Hz, 2H), 8.84 (d, J¼4.7 Hz, 2H); MALDI-MS
obsd 928.9; ESI-HRMS obsd 929.3924 (MþH)þ corresponds to
928.3851 (M), calcd 928.3866 (C59H57BN4O2Zn); labs (relative in-
tensity) 423 (1.00), 550 (0.05) nm; lem
(
lex¼423 nm) 599, 648 nm.
5.4.2. 5,10,15-Trimesityl-20-[40-(4,4,5,5-tetramethyl-1,3,2-dioxaboro-
lan-2-yl)biphen-4-yl]porphyrin (Fb2-B). Following a standard pro-
cedure for the synthesis of A3B-porphyrins via mixed
condensations,34,35 a solution of 40-(4,4,5,5-tetramethyl-1,3,2-dioxa-
borolan-2-yl)biphenyl-4-carboxaldehyde (I-B, 462 mg, 1.50 mmol,
2.5 mM), mesitaldehyde (667 mg, 4.50 mmol, 7.5 mM), and pyrrole
(403 mg, 6.00 mmol, 10 mM) in chloroform (600 mL) was treated
withBF3$O(Et)2 (222 mL,1.80 mmol, 3.0 mM)atroom temperaturefor
1 h. After the addition of DDQ (1.02 g, 4.50 mmol), the reaction mix-
ture was stirred at room temperature for 1 h, whereupon triethyl-
amine (0.5 mL) was added. The reaction mixture was concentrated to
dryness. The residue was chromatographed [silica, CH2Cl2] to give
a mixture of porphyrins. The crude porphyrin mixture was subjected
to further chromatography [silica, hexanes/CH2Cl2 (2:1)]; the second
fraction gave the title compound as a purple solid (115 mg, 8%): 1H
NMR (CDCl3)
d
ꢁ2.57 to ꢁ2.52 (br, 2H),1.42 (s,12H),1.85 (s, 6Hþ12H),
2.62 (s, 3Hþ6H), 7.28 (s, 6H), 7.94 (d, J¼8.1 Hz, 2H), 8.00 (d, J¼8.1 Hz,
2H), 8.04 (d, J¼8.1 Hz, 2H), 8.27 (d, J¼8.1 Hz, 2H), 8.60e8.66 (m, 4H),
8.69 (d, J¼4.7 Hz, 2H), 8.85 (d, J¼4.7 Hz, 2H); MALDI-MS obsd 942.4
[based on the most abundant (100%) signal]; ESI-HRMS obsd
942.5142, calcd 942.5153 [(MþH)þ, M¼C65H63BN4O2, based on the
smallest isotopic (10B) signal]; labs (relative intensity) 421 (1.00), 516
Figure 1. Analytical SEC traces of the three series of oligo(p-phenylene)-linked por-
phyrin dimers and dyads.
(0.05), 549 (0.02), 592 (0.01) nm; lem
(
lex¼421 nm) 653, 723 nm.
phenyl]ethyne (FbFb-PEP; compound Fb2U in Ref. 54),54 and 1,4-bis
[4-(5,10,15-trimesitylporphin-20-yl)phenyl]buta-1,3-diyne (FbFb-
PEEP; compound 5 in Ref. 41)41 were prepared following literature
procedures.
5.4.3. 20-[40-Bromobiphen-4-yl]-5,10,15-trimesitylporphyrin (Fb2-
Br). Following a standard procedure for the synthesis of A3B-
porphyrins via mixed-aldehyde condensations,34,35 a solution of
40-bromobiphenyl-4-carboxaldehyde (I-Br, 653 mg, 2.50 mmol,
2.5 mM), mesitaldehyde (1.11 g, 7.50 mmol, 7.5 mM), and pyrrole
(671 mg, 10.0 mmol, 10 mM) in chloroform (1 L) was treated with
5.4. Synthesis of porphyrin building blocks
BF3$O(Et)2 (370 mL, 3.00 mmol, 3.0 mM) at room temperature for
5.4.1. Zinc(II)
5,10,15-trimesityl-20-[4-(4,4,5,5-tetramethyl-1,3,2-
1 h. After the addition of DDQ (1.70 g, 7.50 mmol), the reaction
mixture was stirred at room temperature for 1 h, whereupon
dioxaborolan-2-yl) phenyl]porphyrin (Zn1-B). Following a standard
procedure,31 samples of zinc(II)-20-(4-iodophenyl)-5,10,15-

5560
M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
triethylamine (0.5 mL) was added. The reaction mixture was
concentrated to dryness. The residue was chromatographed
[silica, CH2Cl2] to give a mixture of porphyrins. The crude por-
phyrin mixture was subjected to further chromatography [silica,
hexanes/CH2Cl2 (2:1)]; the second fraction gave the title com-
7.71 (d, J¼8.5 Hz, 2H), 7.79 (d, J¼8.5 Hz, 2H), 7.93 (d, J¼8.5 Hz,
2H), 8.27 (d, J¼8.5 Hz, 2H), 8.61e8.65 (m, 4H), 8.69 (d, J¼4.7 Hz,
2H), 8.83 (d, J¼4.7 Hz, 2H); MALDI-MS obsd 895.1; ESI-HRMS
obsd 895.3374 (MþH)þ corresponds to 894.3301 (M), calcd
894.3297 (C59H51BrN4); labs (relative intensity) 421 (1.00),
pound as a purple solid (287 mg, 13%): 1H NMR (CDCl3)
d
ꢁ2.58 to
516 (0.04), 548 (0.02), 593 (0.01) nm; lem
(
lex¼421 nm) 653,
ꢁ2.53 (br, 2H), 1.85 (s, 6Hþ12H), 2.62 (s, 3Hþ6H), 7.28 (s, 6H),
724 nm.
5.4.4. Zinc(II) 20-(40-bromobiphenyl-4-yl)-5,10,15-trimesitylporphyrin
(Zn2-Br). A solution of Fb2-Br (89.6 mg, 100 mol) in CH2Cl2
m
(20 mL) was treated with a solution of Zn(OAc)2$2H2O (439 mg,
2.00 mmol) in methanol (2 mL), and the reaction mixture was
stirred at room temperature for 2 h. Standard workup including
chromatography [silica, hexanes/CH2Cl2 (2:1)] gave a purple solid
(69.8 mg, 73%): 1H NMR (CDCl3)
d
1.84 (s, 6Hþ12H), 2.63 (s,
3Hþ6H), 7.27 (s, 6H), 7.71 (d, J¼8.5 Hz, 2H), 7.80 (d, J¼8.5 Hz, 2H),
7.93 (d, J¼8.1 Hz, 2H), 8.29 (d, J¼8.1 Hz, 2H), 8.68e8.73 (m, 4H), 8.77
(d, J¼4.7 Hz, 2H), 8.91 (d, J¼4.7 Hz, 2H); MALDI-MS obsd 957.1; ESI-
HRMS obsd 956.2427 (M)þ corresponds to 956.2432 (M), calcd
956.2432 (C59H49BrN4Zn); labs (relative intensity) 423 (1.00), 550
(0.04) nm; lem
(lex¼423 nm) 597, 647 nm.
5.5. Synthesis of ZnFb porphyrin dyads
5.5.1. 4-(Zinc(II) 5,10,15-trimesitylporphin-20-yl)-40-(5,10,15-trimes-
itylporphin-20-yl)-biphenyl (ZnFbF2). Following a standard pro-
cedure for Suzuki coupling of porphyrins,31 samples of Zn1-B
(46.5 mg, 50.0
mmol), 5,10,15-trimesityl-20-(4-iodophenyl)porphy-
rin (Fb1-I, 43.3 mg, 50.0
m
mol), Pd(dppf)Cl2 (12.2 mg, 15.0 mol),
m
and potassium acetate (73.6 mg, 0.750 mmol) were weighed into
a 25-mL Schlenk flask, which was then pump-purged three times
with argon. Toluene/DMF/H2O (10:5:1, 10 mL, freeze/pump/thawed
three times under argon) was added, and the reaction mixture was
stirred at 100 ꢀC for 16 h. Toluene (25 mL) and H2O (25 mL) were
added to the reaction mixture. The organic phase was extracted,
dried (Na2SO4), and filtered. The filtrate was concentrated to dry-
ness. The residue was purified by preparative SEC followed by ad-
sorption chromatography [the crude compound was dissolved in
a minimal amount of toluene, loaded on silica, and eluted with
hexanes/CH2Cl2/triethylamine (66:33:1)] to give a purple solid
(26.5 mg, 34%): 1H NMR (toluene-d8)
d
ꢁ1.78 to ꢁ1.73 (br, 2H), 1.87
(s, 6H), 1.99 (s, 6Hþ12H), 2.06 (s, 12H), 2.47 (s, 3H), 2.51 (s, 3Hþ6H),
2.53 (s, 6H), 7.15 (s, 2H), 7.20 (s, 2Hþ4H), 7.25 (s, 4H), 8.01e8.10 (m,
4H), 8.22 (d, J¼8.1 Hz, 2H), 8.39 (d, J¼8.1 Hz, 2H), 8.74e8.81 (m, 4H),
8.88 (d, J¼4.7 Hz, 2H), 8.89e8.93 (m, 4H), 8.99 (d, J¼4.7 Hz, 2H), 9.06
(d, J¼4.7 Hz, 2H), 9.18 (d, J¼4.7 Hz, 2H); MALDI-MS obsd 1541.0; ESI-
HRMS obsd 1541.6844 (MþH)þ corresponds to 1540.6771 (M), calcd
1540.6736 (C106H92N8Zn); labs (relative intensity) 426 (1.00), 516
(0.03), 550 (0.04), 592 (0.01) nm; lem
(lex¼426 nm) 653, 724 nm.
5.5.2. 4-(Zinc(II)
5,10,15-trimesitylporphin-20-yl)-400-(5,10,15-tri-
mesitylporphin-20-yl)terphenyl (ZnFbF3). Following the general
procedure described in the Section 5.5.1, samples of Zn1-B
(46.5 mg, 50.0
(12.2 mg, 15.0
mmol), Fb2-Br (44.8 mg, 50.0 mmol), Pd(dppf)Cl2
m
mol), and potassium acetate (73.6 mg, 0.750 mmol)
were treated in toluene/DMF/H2O (10:5:1, 10 mL) at 100 ꢀC for 16 h.
Standard workup including chromatography [preparative SEC, tol-
uene; silica, hexanes/CH2Cl2/triethylamine (66:33:1)] gave a purple
solid (47.0 mg, 58%): 1H NMR (toluene-d8)
d
ꢁ1.80 to ꢁ1.76 (br, 2H),
1.86 (s, 6H), 1.98 (s, 12H), 1.99 (s, 6H), 2.06 (s, 12H), 2.47 (s, 3H), 2.51
(s, 3Hþ6H), 2.54 (s, 6H), 7.14 (s, 2H), 7.20 (s, 2Hþ4H), 7.25 (s, 4H),
7.89e8.02 (m, 8H), 8.18 (d, J¼8.1 Hz, 2H), 8.35 (d, J¼8.1 Hz, 2H),
8.73e8.80 (m, 4H), 8.85 (d, J¼4.7 Hz, 2H), 8.82e8.93 (m, 4H), 8.96
(d, J¼4.7 Hz, 2H), 9.00 (d, J¼4.7 Hz, 2H), 9.12 (d, J¼4.7 Hz, 2H);
MALDI-MS obsd 1617.4; ESI-HRMS obsd 1617.7122 (MþH)þ corre-
sponds to 1616.7049 (M), calcd 1616.7049 (C112H96N8Zn); labs
Figure 2. 13C NMR spectra of Fb-TMP (in toluene-d8), Zn-TMP (in toluene-d8), and,
Tl-TMP (in CDCl3). The atom labeling of the meso-tetramesitylporphyrin (M¼H, H; Zn;
or ClTl) macrocycle is shown at top.

M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
5561
Figure 3. 13C NMR spectra of Tl-3OH, TlTl-Ar-
F
, TlTl-PEP, TlTl-F2, TlTl-F3, and TlTl-F4, (in CDCl3), typically the result of data acquisition over the course of 12e18 h.
(relative intensity) 425 (1.00), 516 (0.02), 550 (0.04), 592 (0.01) nm;
lem
lex¼425 nm) 653, 724 nm.
were treated in toluene/DMF/H2O (10:5:1, 10 mL) at 100 ꢀC for 16 h.
Standard workup including chromatography [preparative SEC, tol-
uene; silica, hexanes/CH2Cl2/triethylamine (66:33:1)] gave a purple
(
5.5.3. 4-(Zinc(II)
5,10,15-trimesitylporphin-20-yl)-400-(5,10,15-tri-
mesitylporphin-20-yl)quaterphenyl (ZnFbF4). Following the gen-
eral procedure described in the Section 5.5.1, samples of Zn2-Br
solid (53.5 mg, 63%): 1H NMR (toluene-d8)
d
ꢁ1.80 to ꢁ1.76 (br, 2H),
1.86 (s, 6H), 1.98 (s, 6Hþ12H), 2.05 (s, 12H), 2.47 (s, 3H), 2.50 (s,
3Hþ6H), 2.53 (s, 6H), 7.15 (s, 2H), 7.20 (s, 2Hþ4H), 7.24 (s, 4H),
7.78e7.99 (m, 12H), 8.16 (d, J¼8.1 Hz, 2H), 8.34 (d, J¼8.1 Hz, 2H),
8.74e8.80 (m, 4H), 8.84 (d, J¼4.7 Hz, 2H), 8.88e8.92 (m, 4H), 8.95
(48.0 mg, 50.0
mmol), Fb2-B (47.0 mg, 50.0
mmol), Pd(dppf)Cl2
(12.2 mg, 15.0
mmol), and potassium acetate (73.6 mg, 0.750 mmol)
Table 4
Absorption spectral properties of free base and thallium porphyrinsa
Compound
B Band
Q Band
TMP
Tl-TMP
Tl1-E
418 (100)
434 (100)
437 (100)
419 (100)
435 (100)
421 (100)
435 (100)
419 (87), 427 (100)
435 (88), 443 (100)
418 (82), 427 (100)
433 (81), 443 (100)
423 (100)
439 (100)
421 (100)
437 (100)
421 (100)
437 (100)
424 (100)
439 (100)
426 (100)
440 (100)
424 (100)
440 (100)
514 (4.3)
547 (1.2)
567 (3.9)
569 (4.2)
552 (2.0)
569 (4.0)
557 (2.6)
575 (3.4)
554 (3.9)
569 (6.4)
551 (3.3)
568 (639)
550 (2.6)
568 (5.7)
550 (2.1)
568 (4.9)
549 (2.1)
568 (4.4)
551 (2.5)
568 (5.4)
558 (3.6)
575 (4.9)
550 (2.6)
570 (5.4)
590 (1.2)
606 (1.7)
609 (3.2)
590 (1.2)
608 (3.0)
600 (1.3)
615 (3.0)
592 (2.3)
610 (5.0)
592 (2.3)
609 (3.8)
591 (1.8)
608 (3.2)
592 (1.5)
608 (2.7)
593 (1.5)
608 (2.4)
592 (1.7)
608 (3.0)
600 (1.6)
615 (4.7)
593 (1.7)
610 (3.2)
647 (0.8)
529 (sh, 0.8)
529 (sh, 1.3)
516 (3.9)
528 (sh, 1.3)
521 (4.1)
533 (sh, 0.8)
518 (6.5)
530 (sh, 1.5)
516 (7.4)
528 (sh, 1.3)
516 (5.9)
528 (sh, 1.1)
516 (5.1)
528 (sh, 1.2)
516 (5.0)
528 (sh, 0.9)
516 (5.4)
Fb3-OH
Tl3-OH
Fb4-E
Tl4-E
FbFb-Ar-
TlTl-Ar-
FbFb-
TlTl-
FbFb-F2
TlTl-F2
FbFb-F3
TlTl-F3
FbFb-F4
TlTl-F4
FbFb-PEP
TlTl-PEP
FbFb-SW-PEP
TlTl-SW-PEP
FbFb-PEEP
TlTl-PEEP
647 (1.0)
656 (1.7)
648 (2.0)
648 (1.7)
647 (1.3)
647 (1.1)
647 (1.0)
647 (1.2)
656 (2.2)
647 (1.3)
F
F
F
F
527 (sh, 1.0)
522 (5.2)
532 (sh, 1.0)
515 (5.6)
530 (sh, 1.0)
a
At room temperature in dichloromethane. The numbers shown in parentheses are relative intensities in %.

5562
M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
Figure 4. Absorption spectra of thallium(III)porphyrins in CH2Cl2 at room temperature. Panel 1: FbFb-F4 (dashed line), TlTl-F4 (solid line). Panel 2: FbFb-
F (dashed line), TlTl-F
(solid line).
(d, J¼4.7 Hz, 2H), 8.99 (d, J¼4.7 Hz, 2H), 9.12 (d, J¼4.7 Hz, 2H);
MALDI-MS obsd 1693.7; ESI-HRMS obsd 1693.7475 (MþH)þ cor-
responds to 1962.7402 (M), calcd 1692.7362 (C118H100N8Zn); labs
(relative intensity) 427 (1.00), 515 (0.03), 556 (0.04), 596 (0.02) nm;
intensity) 421 (1.00), 516 (0.05), 549 (0.02), 593 (0.01), 647 (0.01)
nm; lem
lex¼421 nm) 652, 720 nm.
(
5.6.4. 1,2-Bis[4-[5,10,15-tris(tridec-7-yl)porphin-20-yl]phenyl]ethyne
(FbFb-SW-PEP). Following a copper-free procedure for Sonogashira
couplingofporphyrins,41,42 samples of5-(4-ethynylphenyl)-10,15,20-
lem
(lex¼423 nm) 653, 723 nm.
tris(tridec-7-yl)porphyrin (Fb4-E, 14.4 mg, 15.0
phenyl)-10,15,20-tris(tridec-7-yl)porphyrin (Fb4-I,
15.0 mol), Pd(dba)3 (2.1 mg, 2.3 mol), and P(o-tol)3 (5.5 mg,
18 mol) were weighed into a 10-mL Schlenk flask, which was then
pump-purged three times with argon. Toluene/triethylamine (5:1,
6 mL, freeze/pump/thawed three times under argon) was added, and
the reaction mixture was stirred at 40 ꢀC for 4.5 h (whereupon ana-
lyticalSEC showedthe completion of the reaction). The crude mixture
was concentrated to dryness, and passed through silica [silica, hex-
anes/CH2Cl2 (5:1)] to remove palladiums species and monomeric
porphyrins. The residue was purified by preparative SEC followed by
adsorption chromatography [silica, hexanes/CH2Cl2 (5:1)] to give
m
mol), 5-(4-iodo-
5.6. Synthesis of FbFb porphyrin dimers
15.9 mg,
m
m
5.6.1. 4,40-Bis(5,10,15-trimesitylporphin-20-yl)biphenyl (FbFbF2). A
m
solution of ZnFbF2 (23.1 mg, 15.0
treated with TFA (110 L, 1.50 mmol) for 2 h. Standard workup in-
cluding chromatography [silica, hexanes/CH2Cl2 (2:1)] gave a pur-
ple solid (21.2 mg, 95%): 1H NMR (toluene-d8)
mmol) in CH2Cl2 (3 mL) was
m
d
ꢁ1.83 to ꢁ1.77 (br,
4H),1.82 (s,12H),1.94 (s, 24H), 2.42 (s, 6H), 2.46 (s,12H), 7.10 (s, 4H),
7.16 (s, 8H), 7.96 (AA0BB0, 4H), 8.17 (AA0BB0, 4H), 8.71 (d, J¼4.8 Hz,
4H), 8.74 (d, J¼4.8 Hz, 4H), 8.83 (d, J¼4.8 Hz, 4H), 9.00 (d, J¼4.8 Hz,
4H); MALDI-MS obsd 1476.5; ESI-HRMS obsd 1479.7665 (MþH)þ
corresponds to 1478.7592 (M), calcd 1478.7601 (C106H94N8); labs
(relative intensity) 423 (1.00), 516 (0.06), 550 (0.03), 591 (0.02), 647
a purple solid (13.6 mg, 48%): 1H NMR (CDCl3)
d
ꢁ2.48 to ꢁ2.40 (br,
4H), 0.69e0.80 (m, 36H), 1.03e1.44 (m, 96H), 2.68e2.82 (m, 12H),
2.87e3.01 (m, 12H), 5.08e5.24 (m, 6H), 8.07 (AA0BB0, 2H), 8.25
(AA0BB0, 2H), 8.80e8.91 (m, 4H), 9.44e9.78(m,12H);MALDI-MSobsd
1885.8; ESI-HRMS obsd 1888.5165(MþH)þ corresponds to 1887.5092
(M), calcd 1887.5113 (C132H109N8); labs (relative intensity) 426 (100),
522 (5.2), 558 (3.6), 600 (1.6), 656 (2.2) nm.
(0.01) nm; lem
(lex¼423 nm) 651, 721 nm.
5.6.2. 4,400-Bis(5,10,15-trimesitylporphin-20-yl)terphenyl
(FbFbF3). A solution of ZnFbF3 (32.4 mg, 20.0 mol) in CH2Cl2
m
(4 mL) was treated with TFA (0.15 mL, 2.0 mmol) for 2 h. Standard
workup including chromatography [silica, hexanes/CH2Cl2 (1:1)]
gave a purple solid (24.0 mg, 77%): 1H NMR (CDCl3)
d
ꢁ2.54 to
5.7. Synthesis of chlorothallium(III) porphyrins
ꢁ2.48 (br, 4H), 1.88 (s, 12Hþ24H), 2.63 (s, 6H), 2.64 (s, 12H), 7.28 (s,
4H), 7.30 (s, 8H), 8.12 (AA0BB0, 4H), 8.14e8.18 (m, 4H), 8.35 (AA0BB0,
4H), 8.62e8.68 (m, 8H), 8.73 (d, J¼4.8 Hz, 4H), 8.92 (d, J¼4.8 Hz,
4H); MALDI-MS obsd 1552.7; ESI-HRMS obsd 1555.7948 (MþH)þ
corresponds to 1554.7855 (M), calcd 1554.7914 (C112H98N8); labs
(relative intensity) 421 (1.00), 516 (0.05), 550 (0.02), 592 (0.02),
CAUTION: Thallium is a toxic substance, is accumulated through
the skin and mucous membranes, and should be handled with
appropriate care.65
5.7.1. Chloro(tetramesitylporphinato)thallium(III) (Tl-TMP). A solu-
tion of meso-tetramesitylporphyrin (Fb-TMP, 23.5 mg, 30.0 mmol)
647 (0.01) nm; lem
(
lex¼421 nm) 652, 721 nm.
5.6.3. 4,4000-Bis(5,10,15-trimesitylporphin-20-yl)quaterphenyl
(FbFbF4). A solution of ZnFbF4 (33.9 mg, 20.0 mol) in CH2Cl2
in DMF (3 mL) was treated with TlCl3$(H2O)4 (93 mg, 0.30 mmol) at
150 ꢀC for 2 h. The reaction mixture was concentrated to dryness
under reduced pressure. The resulting residue was dissolved in
CH2Cl2 (30 mL) and washed with saturated aqueous NaCl. The
organic layer was separated, dried (Na2SO4), filtered, and concen-
trated to dryness under reduced pressure. The resulting solid was
chromatographed [silica, hexanes/CH2Cl2 (2:1)] to give a greenish
m
(4 mL) was treated with TFA (0.15 mL, 2.0 mmol) for 2 h. Standard
workup including chromatography [silica, hexanes/toluene (1:1)]
gave a purple solid (22.8 mg, 70%): 1H NMR (toluene-d8)
d
ꢁ1.81 to
ꢁ1.75 (br, 4H), 1.86 (s, 12H), 1.97 (s, 24H), 2.47 (s, 6H), 2.50 (s, 12H),
7.15 (s, 4H), 7.20 (s, 8H), 7.80 (AA0BB0, 4H), 7.87 (AA0BB0, 4H), 7.90
(AA0BB0, 4H), 8.16 (AA0BB0, 4H), 8.75 (d, J¼4.8 Hz, 4H), 8.78 (d,
J¼4.8 Hz, 4H), 8.84 (d, J¼4.8 Hz, 4H), 8.98 (d, J¼4.8 Hz, 4H); MALDI-
MS obsd 1628.4; ESI-HRMS obsd 1631.8279 (MþH)þ corresponds to
1630.8206 (M), calcd 1630.8227 (C118H102N8); labs (relative
purple solid (23.1 mg, 75%): 1H NMR (CDCl3)
d 1.74 (s, 12H), 1.97 (s,
12H), 2.63 (s, 12H), 7.23e7.28 (m, 4H), 7.29e7.34 (m, 4H), 8.82 [d, 4J
(TleH)¼62.4 Hz, 8H]; 13C NMR (CDCl3)
d
21.8, 21.9, 22,2, 120.3 [3J
(TleC)¼146 Hz, Cmeso], 128.0 and 128.2 (C-3), 132.0 [3J(TleC)¼

M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
5563
116 Hz, Cb], 138.0 [4J(TleC)¼26 Hz, C-1], 138.3 (C-4), 139.0, and
140.6 [5J(TleC)¼19 Hz, C-2], 149.8 [2J(TleC)¼19 Hz, Ca]; MALDI-MS
obsd 1020.5; ESI-HRMS obsd 1021.3688 (MþH)þ corresponds to
1021.3615 (M), calcd 1020.3624 (C56H52ClN4Tl); labs (relative in-
tensity) 434 (100), 529 (sh, 0.8) 567 (3.9), 606 (1.7) nm. Alterna-
CH2Cl2 (13.5 mL) was treated with a solution of TlCl3$(H2O)4
(233 mg, 0.750 mmol) in methanol (1.5 mL) at room temperature
for 2 h. Standard workup including chromatography [silica, hex-
anes/CH2Cl2 (1:1)] gave a greenish purple solid (22.5 mg, 80%): 1
H
NMR (CDCl3)
d 1.81 (s, 6H), 1.83 (s, 12H), 1.98 (s, 6H), 2.03 (s, 12H),
tively, a solution of Fb-TMP (157 mg, 300
m
mol) in CH2Cl2 (36 mL)
2.65 (s, 6H), 2.68 (s, 12H), 7.28e7.31 (m, 2H), 7.31e7.36 (m, 2Hþ4H),
7.36e7.40 (m, 4H), 8.51 (s, 1H), 8.57 (d, J¼8.4 Hz, 1H), 8.81 (d,
J¼8.4 Hz, 1H, overlapped), 8.88 (s, 1H), 8.90 [d, 4J(TleH)¼62.0 Hz,
4Hþ4H], 9.08 [dd, 4J(TleH)¼62.9 Hz, 3J(HeH)¼4.4 Hz, 4H], 9.42
[dd, 4J(TleH)¼64.5 Hz, 3J(HeH)¼4.4 Hz, 4H]; MALDI-MS obsd
1879.0; ESI-HRMS obsd 1879.5902 (MþH)þ corresponds to
1878.5829 (M), calcd 1878.5840 (C100H86Cl2N8Tl2); labs (relative
intensity) 433 (81), 443 (100), 528 (sh, 1.3), 568 (6.9), 609 (3.8) nm.
was treated with a solution of TlCl3$(H2O)4 (1.55 g, 5.00 mmol) in
methanol (4 mL) at room temperature for 14 h. Standard workup
and recrystallization (diffusion of hexanes into a chloroform solu-
tion of the mixture of porphyrins) gave a greenish purple solid
(135 mg, 66%). Characterization data (LD-MS, 1H NMR, UVevis)
were identical as described above.
5.7.2. Chloro[5-(4-ethynylphenyl)-10,15,20-trimesitylporphinato]
5.8.2. 4,40-Bis(chlorothallium(III) 5,10,15-trimesitylporphinato-20-yl)
biphenyl (TlTl-F2). A solution of FbFb-F2 (14.8 mg, 10.0 mmol) in
thallium(III) (Tl1-E). A solution of 5-(4-ethynylphenyl)-10,15,20-
trimesitylporphyrin (Fb1-E, 11.5 mg, 15.0 mmol) in CH2Cl2 (2.25 mL)
was treated with a solution of TlCl3$(H2O)4 (93 mg, 0.30 mmol) in
methanol (0.75 mL) at room temperature for 30 min. Standard
workup including chromatography [silica, hexanes/CH2Cl2 (2:1),
then hexanes/CH2Cl2 (1:1)] gave a greenish purple solid (13.6 mg,
CH2Cl2 (20 mL) was treated with a solution of TlCl3$(H2O)4 (155 mg,
0.500 mmol) in methanol (2 mL) at room temperature for 2 h.
Standard workup including chromatography [silica, hexanes/
CH2Cl2 (1:2)] gave a greenish purple solid (16.1 mg, 83%): 1H NMR
90%): 1H NMR (CDCl3)
d 1.74 (s, 6H), 1.76 (s, 3H), 1.93 (s, 3H), 1.95 (s,
(CDCl3)
d
1.79 (s, 6Hþ12H), 1.97 (s, 6H), 2.00 (s, 12H), 2.64 (s, 6H),
6H), 2.64 (s, 3Hþ6H), 3.33 (s, 1H), 7.24e7.29 (m, 1Hþ2H), 7.29e7.34
(m, 1Hþ2H), 7.87 (AA0BB0, 1H), 7.95 (AA0BB0, 1H), 8.05 (AA0BB0, 1H),
8.38 (AA0BB0, 1H), 8.85 [d, 4J(TleH)¼62.0 Hz, 2Hþ2H], 8.89 [dd, 4J
(TleH)¼62.8 Hz, 3J(HeH)¼4.7 Hz, 2H], 8.94 [dd, 4J(TleH)¼64.5 Hz,
3J(HeH)¼4.7 Hz, 2H]; MALDI-MS obsd 1002.4; ESI-HRMS obsd
1003.3209 (MþH)þ corresponds to 1002.3136 (M), calcd 1002.3155
(C55H46ClN4Tl); labs (relative intensity) 437 (100), 529 (sh, 1.3), 569
(4.2), 609 (3.2) nm.
2.66 (s,12H), 7.26e7.32 (m, 2Hþ4H), 7.32e7.38 (m, 2Hþ4H), 8.33 (s,
2Hþ2H), 8.41 (d, J¼8.1 Hz, 2H), 8.65 (d, J¼8.1 Hz, 2H), 8.88 [d, 4J
(TleH)¼61.6 Hz, 4Hþ4H], 8.96 [dd, 4J(TleH)¼63.4 Hz, 3J(HeH)¼
4.4 Hz, 4H], 9.17 [dd, 4J(TleH)¼65.4 Hz, 3J(HeH)¼4.4 Hz, 4H];
MALDI-MS obsd 1955.3; ESI-HRMS obsd 1955.6167 (MþH)þ cor-
responds to 1954.6094 (M), calcd 1954.6153 (C106H90Cl2N8Tl2); labs
(relative intensity) 439 (100), 528 (sh, 1.1), 568 (5.7), 608 (3.2) nm.
5.8.3. 4,400-Bis(chlorothallium(III) 5,10,15-trimesitylporphinato-20-
yl)terphenyl (TlTl-F3). A solution of FbFb-F3 (15.6 mg, 10.0 mmol)
5.7.3. Chloro[5-[4-(hydroxymethyl)phenyl]-10,15,20-tri-p-tolylpor-
phinato]thallium(III) (Tl3-OH). A solution of 5-[4-(hydroxymethyl)
in CH2Cl2 (9 mL) was treated with a solution of TlCl3$(H2O)4
(155 mg, 0.500 mmol) in methanol (1 mL) at room temperature for
14 h. Standard workup including chromatography [silica, hexanes/
CH2Cl2 (2:3), then hexanes/CH2Cl2 (1:2)] gave a greenish purple
phenyl]-10,15,20-tri-p-tolylporphyrin
(Fb3-OH,
27.5 mg,
40.0 mol) in CH2Cl2 (6 mL) was treated with a solution of
m
TlCl3$(H2O)4 (0.25 g, 0.80 mmol) in methanol (2 mL) at room
temperature for 48 h. Standard workup including chromatography
(silica, CH2Cl2) gave a greenish purple solid (28.7 mg, 78%): 1H NMR
solid (17.0 mg, 84%): 1H NMR (CDCl3)
d
1.78 (s, 6Hþ12H), 1.96 (s,
6H), 1.99 (s, 12H), 2.65 (s, 6Hþ12H), 7.26e7.39 (m, 12H), 8.12 (d,
J¼8.1 Hz, 2H), 8.17 (s, 2Hþ2H), 8.17e8.27 (m,12H), 8.57 (d, J¼8.1 Hz,
2H), 8.87 [d, 4J(TleH)¼61.2 Hz, 4Hþ4H], 8.94 [dd, 4J(TleH)¼
63.2 Hz, 3J(HeH)¼4.8 Hz, 4H], 9.12 [dd, 4J(TleH)¼64.9 Hz, 3J
(HeH)¼4.8 Hz, 4H]; MALDI-MS obsd 2030.5; ESI-HRMS obsd
2031.6491 (MþH)þ corresponds to 2030.6418 (M), calcd 2030.6466
(C112H94Cl2N8Tl2); labs (relative intensity) 437 (100), 528 (sh, 1.2),
568 (4.9), 608 (2.7) nm.
(CDCl3)
d
2.01 (t, J¼6.0 Hz, 1H), 2.71 (s, 3Hþs, 6H), 5.07 (d, J¼6.0 Hz,
2H), 7.54 (AA0BB0, 1Hþ2H), 7.61 (AA0BB0, 1Hþ2H), 7.75 (AA0BB0, 1H),
7.79 (AA0BB0, 1H), 8.00 (AA0BB0, 1Hþ2H), 8.12 (AA0BB0, 1H), 8.24
(AA0BB0, 1Hþ2H), 8.36 (AA0BB0, 1H), 9.02 [dd, 4J(TleH)¼65.0 Hz, 3J
(HeH)¼4.7 Hz, 2H], 9.07 [d, 4J(TleH)¼65.0 Hz, 2Hþ2H], 9.08 [dd, 4J
(TleH)¼64.5 Hz, 3J(HeH)¼4.7 Hz, 2H]; MALDI-MS obsd 924.3,
calcd 924.2 (C48H36ClN4OTl); ESI-HRMS obsd 887.2600, calcd
887.2607 [(MꢁCl)þ, M¼C48H36N4OTl]; labs (relative intensity) 435
(100), 528 (sh, 2.3), 569 (4.0), 608 (3.0) nm.
5.8.4. 4,4000-Bis(chlorothallium(III) 5,10,15-trimesitylporphinato-20-
yl)quaterphenyl (TlTl-F4). A solution of FbFb-F4 (16.3 mg,
10.0 mmol) in CH2Cl2 (9 mL) was treated with a solution of
5.7.4. Chloro[5-(4-ethynylphenyl)-10,15,20-tris(tridec-7-yl)porphi-
nato]thallium(III) (Tl4-E). A solution of Fb4-E (5.7 mg, 6.0 mmol) in
CH2Cl2 (2 mL) was treated with a solution of TlCl3$(H2O)4 (93 mg,
0.30 mmol) in methanol (0.5 mL) at room temperature for 2 h.
Standard workup including chromatography [silica, hexanes/
CH2Cl2 (5:1)] gave a greenish purple solid (4.6 mg, 63%): 1H NMR
TlCl3$(H2O)4 (155 mg, 0.500 mmol) in methanol (1 mL) at room
temperature for 2 h. Standard workup including chromatography
[silica, hexanes/CH2Cl2 (2:1), then hexanes/CH2Cl2 (1:1)] gave
a greenish purple solid (16.4 mg, 78%): 1H NMR (CDCl3)
d 1.77 (s,
12H), 1.78 (s, 6H), 1.96 (s, 6H), 1.99 (s, 12H), 2.65 (s, 6Hþ12H),
7.26e7.31 (m, 2Hþ4H), 7.31e7.37 (m, 2Hþ4H), 8.00 (d, J¼8.1 Hz,
4H), 8.07 (d, J¼8.1 Hz, 2H, overlapped), 8.11 (d, J¼8.1 Hz, 4H), 8.16 (d,
J¼8.1 Hz, 2H), 8.21 (d, J¼8.1 Hz, 2H), 8.54 (d, J¼8.1 Hz, 2H), 8.86 [d, 4J
(TleH)¼61.6 Hz, 4Hþ4H], 8.93 [dd, 4J(TleH)¼63.4 Hz, 3J(HeH)¼
4.8 Hz, 4H], 9.10 [dd, 4J(TleH)¼64.7 Hz, 3J(HeH)¼4.8 Hz, 4H];
MALDI-MS obsd 2106.5; ESI-HRMS obsd 2107.6809 (MþH)þ corre-
sponds to 2106.6736 (M), calcd 2106.6779 (C118H98Cl2N8Tl2); labs
(relative intensity) 437 (100), 528 (sh, 0.9), 568 (4.4), 608 (2.4) nm.
(CDCl3)
d 0.60e0.80 (m, 18H), 0.98e1.45 (m, 48H), 2.68e3.12 (m,
12H), 3.34 (s, 1H), 5.20e5.41 (m, 3H), 7.80e7.90 (m, 1H), 7.91e8.07
(m, 2H), 8.30e8.42 (m, 1H), 8.95 [d, 4J(TleH)¼63.2 Hz, 2H],
9.53e10.08 (m, 6H); MALDI-MS obsd 1193.7; ESI-HRMS obsd
1195.6973 (MþH)þ corresponds to 1194.6900 (M), calcd 1194.6911
(C67H94ClN4Tl); labs (relative intensity) 435 (100), 533 (sh, 0.8), 573
(3.4), 615 (3.0) nm.
5.8. Metalation of FbFb porphyrin dimers to give the bis
(thallium) complexes
5.8.5. 1,4-Bis[chlorothallium(III)
10-trimesitylporphinato-20-yl]benzene (TlTl-Ar-
FbFb-Ar- (16.8 mg, 10.0 mol) in DMF (2 mL) was treated with
TlCl3$(H2O)4 (155 mg, 0.500 mmol) at 150 ꢀC for 2 h. Standard
5,15-bis(3,5-di-tert-butylphenyl)-
F). A solution of
5.8.1. 1,4-Bis(chlorothallium(III) 5,10,15-trimesitylporphinato-20-yl)
benzene (TlTl-F). A solution of FbFb-F (21.0 mg, 15.0 mmol) in
F
m

5564
M. Taniguchi, J.S. Lindsey / Tetrahedron 66 (2010) 5549e5565
workup including chromatography [neutral alumina activity I,
hexanes/CH2Cl2 (2:1)] gave a greenish purple solid (16.2 mg, 75%):
obtained at the Mass Spectrometry Laboratory for Biotechnology at
North Carolina State University, or the University of California
Riverside High Resolution Mass Spectrometry Facility. Partial
funding for the former facility was obtained from the North Caro-
lina Biotechnology Center and the National Science Foundation.
1H NMR (CDCl3)
d 1.57 (s, 36H), 1.62 (s, 36H), 1.83 (s, 6H), 2.00 (s,
6H), 2.66 (s, 6H), 7.29e7.32 (m, 2H), 7.33e7.38 (m, 2H), 7.88 (t,
J¼1.8 Hz, 4H), 8.08e8.12 (m, 4H), 8.29e8.34 (m, 4H), 8.53 (s, 1H),
8.58 (d, J¼8.1 Hz, 1H), 8.79 (d, J¼8.1 Hz, 1H), 8.86 (s, 1H, over-
lapped), 8.97 [dd, 4J(TleH)¼62.5 Hz, 3J(HeH)¼4.8 Hz, 4H], 9.13 [dd,
4J(TleH)¼64.9 Hz, 3J(HeH)¼4.8 Hz, 4H], 9.29 [dd, 4J(TleH)¼
65.9 Hz, 3J(HeH)¼4.8 Hz, 4H], 9.50 [dd, 4J(TleH)¼63.2 Hz, 3J
(HeH)¼4.8 Hz, 4H]; MALDI-MS obsd 2159.0; ESI-HRMS obsd
2159.8979 (MþH)þ corresponds to 2158.8906 (M), calcd 2158.8970
(C120H126Cl2N8Tl2); labs (relative intensity) 435 (88), 443 (100), 530
(sh, 1.5), 569 (6.4), 610 (5.0) nm.
Supplementary data
13C NMR spectra of eight compounds are provided, including
seven thallium-containing porphyrin monomers and dimers.
Supplementary data associated with this article can be found in
the online version at doi:10.1016/j.tet.2010.05.059.
References and notes
5.8.6. 1,2-Bis[chlorothallium(III) 4-(5,10,15-trimesitylporphinato-20-
yl)phenyl]ethyne (TlTl-PEP). A solution of FbFb-PEP (15.0 mg,
10.0 mmol) in CH2Cl2 (4.5 mL) was treated with a solution of
TlCl3$(H2O)4 (155 mg, 0.500 mmol) in methanol (0.5 mL) at room
temperature for 16 h. Standard workup including chromatography
[neutral alumina activity I, hexanes/CH2Cl2 (2:1), then hexanes/
CH2Cl2 (1:2)] gave a greenish purple solid (14.1 mg, 71%): 1H NMR
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(CDCl3) d 1.77 (s, 12H), 1.78 (s, 6H), 1.95 (s, 6H), 1.98 (s, 12H), 2.64 (s,
6H), 2.65 (s, 12H), 7.26e7.31 (m, 2Hþ4H), 7.31e7.37 (m, 6H), 8.06
(AA0BB0, 2H), 8.15 (AA0BB0, 2H), 8.18 (AA0BB0, 2H), 8.50 (AA0BB0, 2H),
8.87 [d, 4J(TleH)¼61.6 Hz, 4Hþ4H], 8.95 [dd, 4J(TleH)¼63.1 Hz, 3J
(HeH)¼4.8 Hz, 4H], 9.06 [dd, 4J(TleH)¼64.9 Hz, 3J(HeH)¼4.8 Hz,
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nm.
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a solution of TlCl3$(H2O)4 (93 mg, 0.30 mmol) in methanol (1 mL) at
room temperature for 2 h. Standard workup including chroma-
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gave a greenish purple solid (10.8 mg, 76%): 1H NMR (CDCl3)
d
0.61e0.81 (m, 36H), 1.01e1.47 (m, 96H), 2.72e3.14 (m, 24H),
5.26e5.46 (m, 6H), 8.03e8.22 (m, 6H), 8.45e8.58 (m, 2H), 9.09 [d, 4J
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(100), 532 (sh, 1.0), 575 (4.9), 615 (4.7) nm.
5.8.8. 1,4-Bis[chlorothallium(III) 4-(5,10,15-trimesitylporphinato-20-
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(15.3 mg, 10.0 mmol) in CHCl3 (1.5 mL) was treated with a solution
of TlCl3$(H2O)4 (62 mg, 0.20 mmol) in methanol (0.5 mL) under
reflux for 1.5 h. Standard workup including chromatography [silica,
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d 1.76 (s, 12H), 1.77 (s,
ꢀ
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6H), 1.95 (s, 6H), 1.97 (s, 12H), 2.64 (s, 6H), 2.65 (s, 12H), 7.25e7.31
(m, 2Hþ4H), 7.31e7.36 (m, 2Hþ4H), 7.99 (AA0BB0, 2H), 8.07 (AA0BB0,
2H), 8.12 (AA0BB0, 2H), 8.46 (AA0BB0, 2H), 8.85 [d, 4J(TleH)¼61.5 Hz,
4Hþ4H], 8.92 [dd, 4J(TleH)¼63.3 Hz, 3J(HeH)¼4.7 Hz, 4H], 9.00
[dd, 4J(TleH)¼65.0 Hz, 3J(HeH)¼4.7 Hz, 4H]; MALDI-MS obsd
2001.1; ESI-HRMS obsd 2003.6203 (MþH)þ corresponds to
2002.6130 (M), calcd 2002.6153 (C110H90Cl2N8Tl2); labs (relative
intensity) 440 (100), 530 (sh, 1.0), 570 (5.4), 610 (3.2) nm.
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Acknowledgements
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