Synthesis of phenylethyne-linked porphyrin dyads

Article abstract of DOI:10.1016/j.tet.2004.01.003

Four new porphyrin dyads have been prepared for studies in artificial photosynthesis. The two porphyrins are joined at the meso positions via a phenylethyne linker and are present in zinc/zinc or zinc/free base metalation states. The porphyrin bearing the

Full text of DOI:10.1016/j.tet.2004.01.003

Tetrahedron 60 (2004) 2011–2023
Synthesis of phenylethyne-linked porphyrin dyads
*
Kin-ya Tomizaki, Andrey B. Lysenko, Masahiko Taniguchi and Jonathan S. Lindsey
Department of Chemistry, North Carolina State University, Raleigh, NC 27695-8204, USA
Received 8 December 2003; revised 6 January 2004; accepted 6 January 2004
Abstract—Four new porphyrin dyads have been prepared for studies in artificial photosynthesis. The two porphyrins are joined at the meso
positions via a phenylethyne linker and are present in zinc/zinc or zinc/free base metalation states. The porphyrin bearing the ethynyl unit
incorporates zero, one, or two pentafluorophenyl groups at non-linking meso positions for tuning the porphyrin redox potentials. The
synthetic approach entailed Pd-mediated coupling of porphyrin building blocks that bear a single ethynylphenyl or bromo/iodo substituent.
q 2004 Elsevier Ltd. All rights reserved.
1. Introduction
4,40-diphenylethyne,10 or 1,4-phenylene linker,11 respec-
tively (Chart 1). The mechanism of energy transfer was
found to be dominated by a through-bond contribution
(mediated by the linker) rather than a through-space
contribution (which would be independent of linker).12 To
investigate the effects of a slightly stronger coupling, we
considered the use of a linker that contains an ethynyl unit
attached directly to the porphyrin macrocycle.
Molecular architectures that incorporate multiple por-
phyrinic pigments can serve as prototype light-harvesting
antennas and charge-separation devices for studies in
artificial photosynthesis.1–8 In covalently linked archi-
tectures, the chief function of the linker is to anchor the
porphyrinic units in a defined location. In addition to this
mechanical role, the linker can interact electronically
with the porphyrin (altering redox potentials, absorption/
emission spectra, and excited-state lifetimes) and also
provide a conduit for electronic communication between
the porphyrins.
The study of ethynyl-porphyrins originated with the work
of Arnold, who synthesized a nickel(II)octaethylporphyrin
bearing an ethynyl group at the meso position.13 Further
work by the group of Hevesi14 and by Anderson15 led to
tetraalkynyl-substituted porphyrins. Ethynyl- or butadiynyl-
linked multiporphyrin arrays have been synthesized and
characterized by the groups of Arnold,16–22 Anderson,23–27
and Therien.28,29 The general features of alkynyl porphyrins
are as follows: (i) significantly red-shifted absorption
spectra, (ii) intensified Q-bands relative to the Soret
bands, and (iii) less negative reduction potentials.
In studies of multiporphyrin light-harvesting arrays, we
found that the use of aryl linkers with meso-substituted
porphyrins resulted in multiporphyrin arrays with visible
absorption spectra that were essentially unchanged from
those of benchmark reference porphyrins. However,
excited-state energy transfer between a zinc porphyrin and
a free base porphyrin occurred with high efficiency: the
rate was found to be (38 ps)21, (24 ps)21, or (3.5 ps)21 for
the porphyrin dyad joined by a 4,40-diphenylbutadiyne,9
Milgrom extended this work to porphyrins bearing aryl-
ethynyl substituents at the four meso positions.30–35 The
Chart 1.
Keywords: Porphyrin; Dipyrromethane; Ethyne; Phenylethyne; Energy transfer.
*
Corresponding author. Tel.: þ1-919-515-6406; fax: þ1-919-513-2830; e-mail address: jlindsey@ncsu.edu
0040–4020/$ - see front matter q 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2004.01.003

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K. Tomizaki et al. / Tetrahedron 60 (2004) 2011–2023
arylethynyl units enable incorporation of a variety of
substituents on the aryl unit for electronic modulation or
increased solubility of the porphyrin,30–44 and cause a
greater red shift and intensification of the Q bands versus
that of ethynyl groups alone. Indeed, the spectral pertur-
bation is so pronounced for meso-tetrakis(phenylethynyl)-
porphyrin versus meso-tetraphenylporphyrin that the former
afford green solutions, prompting Milgrom to term the
former ‘chlorphyrins’.30 Nakano et al. reported the synthesis
and energy-transfer properties of all-zinc porphyrin triads
wherein the linker was a phenylethynyl unit, or the central
porphyrin was substituted with two non-linking phenyl-
ethynyl groups.45 The phenylethynyl-substituted porphyrin
exhibits red-shifted spectral features and functions as the
low energy-trapping component in the light-harvesting
array. In general, in a phenylethyne-linked dyad composed
of identical porphyrin components, the ethyne-substituted
porphyrin is shifted to lower energy and serves as the
acceptor while the phenyl-substituted porphyrin is ener-
getically unperturbed and serves as the donor.
In this paper, we describe the synthesis of porphyrin dyads
where the porphyrins are joined by a phenylethyne linker
and the two porphyrins are in zinc/free base or zinc/zinc
metalation states (Chart 2). The dyads enable the role of the
phenylethyne linker in mediating excited-state energy
transfer to be probed, particularly by comparison with the
dyads described in Chart 1. In addition, we prepared a set of
dyads wherein one porphyrin contains one or two penta-
fluorophenyl groups at non-linking meso positions. The
pentafluorophenyl groups enable tuning of the energy
levels of the porphyrin, thereby opening the possibility of
employing the dyads as charge-separation units. For
comparison purposes, we have also prepared and
characterized a set of benchmark porphyrins containing
one or two meso-phenylethynyl groups. The electronic and
Chart 2.

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photochemical properties of the dyads and benchmarks are
reported elsewhere.46
2. Results and discussion
The synthetic route to the phenylethyne-linked porphyrin
dyads relies on three methods: (1) the rational synthesis
of porphyrin building blocks that bear distinct patterns of
substituents,47,48 including a single ethynylphenyl group or
one free meso position, (2) halogenation of the lone meso
position,49,50 and (3) Pd-mediated coupling of an ethynyl-
phenyl-porphyrin and a halo-porphyrin.51,52 This route
affords control over the metalation state and substituent
pattern in each porphyrin in the dyad. While each method is
well established, this approach to phenylethyne-linked
dyads composed of zinc and free base porphyrins has not
been investigated previously.
2.1. Synthesis of building blocks
The meso-halo-substituted porphyrin building blocks incor-
porate zero, one, or two pentafluorophenyl substituents to
systematically increase the oxidation potential of the
porphyrin. The porphyrins with zero or two pentafluoro-
phenyl groups are trans-AB2-porphyrins while those with
one pentafluorophenyl group are cis-AB2-porphyrins. The
Scheme 1.
Scheme 2.

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K. Tomizaki et al. / Tetrahedron 60 (2004) 2011–2023
Scheme 3.
synthesis of both types of porphyrins proceeds by
condensation of a dipyrromethane-dicarbinol and a dipyrro-
methane followed by oxidation.47
81% yield. Reduction of 6 with NaBH4 in dry THF/
methanol at room temperature gave the corresponding
dipyrromethane-dicarbinol, which was condensed with
5-phenyldipyrromethane (2b) in the presence of InCl3 in
CH2Cl2. Subsequent oxidation with DDQ and metalation
with Zn(OAc)2·2H2O afforded the pentafluorophenyl-
substituted porphyrin Zn3d in 18% yield (Scheme 2).
The synthesis of the trans-AB2-porphyrins begins with
known diacyldipyrromethanes. Thus, reduction of a diacyl-
dipyrromethane (1a–c)47,53 with NaBH4 in dry THF/
methanol at room temperature gave the corresponding
dipyrromethane-dicarbinol. Condensation of the latter with
dipyrromethane (2a) under new catalysis conditions54 that
employ a mild Lewis acid (InCl3 or Yb(OTf)3 in CH2Cl2 at
room temperature) followed by oxidation with DDQ
afforded the free base porphyrin. In one case, the free base
porphyrin was purified (Fb3a) while in others, the crude
product was treated with zinc acetate and the corresponding
zinc porphyrin was obtained (Zn3b and Zn3c) (Scheme 1).
It is noteworthy that earlier synthetic procedures were
developed for preparing the triphenylporphyrin Fb3a and
its zinc chelate Zn3a, including (1) mixed-aldehyde
condensation of benzaldehyde, paraformaldehyde, and
pyrrole,55 (2) reaction of 5,15-diphenylporphyrin with a
phenyl lithium reagent;56 and (3) Suzuki coupling of
phenylboronic acid and Zn(II)-5-bromo-10,20-diphenyl-
porphyrin.57
The availability of porphyrins with a single free meso
position facilitated preparation of the mono-halo-substituted
porphyrins. We prepared both meso-bromo and meso-iodo
porphyrins. Bromination was carried out with either zinc or
free base porphyrins (Fb3a, Zn3b–d) using NBS in CHCl3/
pyridine for 30 min at 0 8C,49 in each case affording the
mono-brominated porphyrin in high yield. The presence of
one or two pentafluorophenyl groups had no adverse effect
on the yield of halogenation. Iodination was carried out in
one case on a free base porphyrin (Fb3a) using [bis(tri-
fluoroacetoxy)iodo]benzene in CHCl3/pyridine for 1 h at
room temperature,50 affording Fb8a in 82% yield
(Scheme 3). Both procedures are straightforward and the
mono-halo-porphyrins are obtained without apparent forma-
tion of poly-halogenated products.
The mono-halo-porphyrins are stable to routine handling
and manipulation. The free base bromo-porphyrin Fb7a was
metalated with zinc acetate to give Zn7a in 89% yield. The
zinc iodo-porphyrin Zn8a, prepared by iodination of the
zinc porphyrin, also could be prepared by zincation of
the free base iodo-porphyrin Fb8a in 91% yield (Scheme 4).
The synthesis of the cis-AB2-porphyrin requires access to an
appropriate 1,9-diacyldipyrromethane, which was prepared
following the general procedures for the synthesis of
ABCD-porphyrins.47 Thus, dipyrromethane (2a)58,59 was
treated with S-2-pyridyl pentafluorobenzothioate (4)48 in the
presence of EtMgBr in THF, affording the 1-acyl-dipyrro-
methane 5 in 59% yield. The reaction of 5 with the more
potent acylating agent benzoyl chloride in the presence of
EtMgBr in toluene gave the 1,9-diacyldipyrromethane 6 in
2.2. Synthesis of phenylethyne-linked porphyrin dyads
We previously developed conditions for the Sonogashira

K. Tomizaki et al. / Tetrahedron 60 (2004) 2011–2023
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typically afford the desired diphenylethyne-linked por-
phyrin array in ,60% yield in addition to a sizable quantity
of high molecular weight material (HMWM). The purifi-
cation protocol entails removal of palladium reagents by
silica-pad filtration, separation of the target array and
HMWM by gravity-flow size exclusion chromatography
(SEC), and final silica-gel chromatography to remove
residual impurities (including those introduced from the
SEC column).
The coupling of ethynylphenyl-porphyrin Zn951 and iodo-
porphyrin Zn8a under the standard conditions (0.38 mM
Pd2(dba)3 and 3.0 mM P(o-tol)3 in toluene/TEA (5:1) at
40 8C with 2.5 mM of each porphyrin) afforded Dyad-1 in
56% yield accompanied by HMWM as judged by analytical
SEC. Several modifications to the reaction conditions were
investigated with yields estimated by analytical SEC.
Reaction under continuous sonication, replacement of P(o-
tol)3 with AsPh3, or an increased concentration of the
porphyrin building blocks (10 mM) each gave Dyad-1 in
lower yield (,40–45%). On the other hand, reaction with a
decreased concentration of the porphyrin building blocks
(1.25 or 0.63 mM) gave Dyad-1 in 60 or 65%. Alterna-
tively, addition of samples of Zn9 in four portions at 20 min
intervals to the reaction mixture gave Dyad-1 in 65% yield.
On the basis of these results, the dyad-forming reactions
were performed under Pd-coupling conditions with equi-
molar quantities of the two porphyrins at 0.63 mM.
Scheme 4.
coupling of an ethynylphenyl-porphyrin and an iodophenyl-
porphyrin to give the diphenylethyne-linked porphyrin
dyad.51,52 The key features of the reaction conditions
developed for this Pd-mediated coupling reaction were (1)
the use of equimolar quantities of the two porphyrins, (2) the
reaction in dilute solution, typically 2.5 mM for each
porphyrin, (3) the use of low temperatures (e.g., 35 8C),
and (4) the absence of copper, which can readily metalate
free base porphyrins. We also extended this method to
include bromoaryl-porphyrins.60 The coupling reactions
Scheme 5.

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K. Tomizaki et al. / Tetrahedron 60 (2004) 2011–2023
The dilute-solution Pd-coupling conditions were applied to
prepare Dyad-1 as shown in Scheme 5. The same coupling
conditions were employed with bromo-porphyrins to give
Dyads-2–4, although the temperature was increased from
40 to 50 8C due to the use of a meso-bromo-porphyrin in
place of a meso-iodo-porphyrin. After chromatographic
workup (three column procedure: silica, SEC, silica),
Dyads-1–4 were obtained in 41–62% yield. The dyads
were stable to routine handling.
2.3. Synthesis of benchmark porphyrins
For comparison purposes, a series of porphyrins was
prepared wherein each porphyrin contains one phenyl-
ethynyl group. Thus, the coupling reaction of phenylacetyl-
ene and a bromo-porphyrin (Zn7b–d) was performed under
a slight modification to the standard conditions for
bromoaryl-porphyrins [Pd2(dba)3 and P(o-tol)3 in toluene/
TEA (5:1) at 50 8C];60 the modification entailed (1) initial
reaction of 2.5 mM porphyrin and 10 mM phenylacetylene,
and (2) later addition of an equal quantity of phenylacetyl-
ene. After chromatographic workup, phenylethynyl-substi-
tuted porphyrins Zn10b–d were obtained in 52–74% yield
(Scheme 6).
Scheme 7.
Scheme 6.
Treatment of Zn11 with NBS afforded dibromo-porphyrin
Zn12a in 82% yield. Zn12a is a known compound but the
synthetic procedure has not been described.61
2.4. Synthesis of bis(phenylethynyl)porphyrins
Porphyrins bearing two phenylethynyl groups in a trans-
configuration at the meso positions were prepared following
a general procedure for the synthesis of trans-A2B2-por-
phyrins (Scheme 7).48 Reduction of 1-acyldipyrromethane 5
with NaBH4 in dry THF/methanol at room temperature
afforded the corresponding dipyrromethane-monocarbinol,
which underwent self-condensation in CH2Cl2 containing
InCl3. Subsequent oxidation with DDQ and metalation
with zinc acetate afforded porphyrin Zn11 in 16% yield.
Porphyrins Zn12a and Zn12b49 were each coupled with
excess phenylacetylene in the presence of Pd2(dba)3 and
P(o-tol)3 in THF/TEA (5:1) at 40 8C. The solvent THF was
employed owing to the limited solubility of the dibromo-
porphyrins in toluene (Scheme 8). Upon chromatographic
workup, Zn13a and Zn13b were obtained in 53 and 43%
yields, respectively.

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4. Experimental
4.1. General
1H (400 or 300 MHz) and 13C (100 or 75 MHz) NMR
spectra were recorded in CDCl3 or THF-d8. Mass spectra of
porphyrins were obtained by high-resolution fast atom
bombardment (FAB-MS), by laser desorption mass spec-
trometry (LD-MS) with neat samples,63 and/or by matrix
assisted laser desorption mass spectrometry (MALDI-MS).
Absorption and emission spectra were collected in toluene
unless noted otherwise. Elemental analyses were performed
by Atlantic Microlab, Inc. Melting points are uncorrected.
Silica gel (Baker 40 mm average particle size) was used for
column chromatography. Preparative SEC was performed
using BioRad Bio-Beads SX-1 (200–400 mesh) beads.
Analytical SEC was performed using an HP 1100 Series
˚
Liquid Chromatograph (column size¼300 mm, 1000 A;
flow rate¼0.800 mL/min; solvent¼THF; quantitation at
420 and 450 nm; reference at 680 nm; oven tempera-
ture¼25 8C).64 All Pd-mediated reactions were performed
using a Schlenk line. The conditions for Sonogashira
reactions with porphyrins use tris(dibenzylideneacetone)di-
palladium(0) (Pd2(dba)3) and the ligand P(o-tol)3 in the
absence of any copper reagents.51,52 Palladium insertion and
transmetalation have not been observed with these con-
ditions. Toluene and triethylamine (TEA) were freshly
distilled from CaH2 and sparged of oxygen prior to use.
Chloroform contained 0.8% ethanol as a stabilizer.
Scheme 8.
2.5. Characterization
Each porphyrin was characterized by absorption spectro-
1
scopy, laser-desorption mass spectrometry, FAB-MS, H
NMR spectroscopy, and 13C NMR spectroscopy. Each dyad
was examined for purity by analytical SEC and character-
ized by absorption spectroscopy, fluorescence spectroscopy,
laser-desorption mass spectrometry, FAB-MS, 1H NMR
spectroscopy, and 13C NMR spectroscopy (except for
Dyad-2). It is noteworthy that the 13C NMR spectra showed
chemical shifts typical of porphyrins bearing four identical
meso substituents,62 with multiple resonances consistent
with the expected pattern of substituents about the porphyrin
perimeter. In the case of zinc porphyrins, characteristic
signals of the a-,b-, and meso-carbons were easily observed.
The signals of the pyrrole a-carbons were observed at
149–153 ppm, while the pyrrole b-carbons gave signals at
130–134 ppm. The chemical shifts of the meso-carbons
depend on the adjacent substituents: meso-H (106 ppm),
meso-aryl (120 ppm), meso-Br (103–104 ppm), meso-I
(77 ppm), and meso-ethyne (100 ppm). In phenylethyne-
substituted porphyrins, characteristic signals (93 and
96 ppm) of the ethyne moiety were observed.
4.2. Non-commercial compounds
Compounds 1a,53 1b,47 1c,53 2a,58,59 2b,59 4,48 Zn9,51 and
Zn12b49 were prepared according to the literature.
4.3. Pd-coupling conditions
The standard Pd-coupling conditions51,52,60 for use with
metalloporphyrins and free base porphyrins were modified
slightly for the reactions performed herein. The following
dilute-solution coupling method was identified for use with
an ethynylphenyl-porphyrin and a meso-iodo-porphyrin:
[ethynylphenyl-porphyrin]¼[iodo-porphyrin]¼0.63 mM,
[Pd2(dba)3]¼0.38 mM, [P(o-tol)3]¼3.0 mM in toluene/TEA
(5:1) at 40 8C. The dyad-forming reactions with a bromo-
porphyrin were performed at 50 8C. The reaction of
phenylacetylene and a bromo-porphyrin was carried out in
a similar manner but with 2.5 mM porphyrin and a 5 or
6-fold molar excess of phenylacetylene (with accompanying
Pd-coupling reagents) added in two batches.
3. Conclusions
The synthetic route employed herein relies on the rational
synthesis of porphyrin building blocks followed by joining
of an ethynylphenyl-porphyrin and a bromo/iodo-porphyrin
in a Pd-mediated coupling reaction. The resulting phenyl-
ethyne-linked dyads contain porphyrins with defined
metalation states and substitution patterns. The phenyl-
ethynyl group perturbs the optical and electronic properties
of the attached porphyrin. In multiporphyrin arrays, the
phenylethyne linker provides a conduit for excited-state
energy transfer. The availability of rational synthetic routes
to phenylethyne-linked porphyrins enables the phenylethy-
nyl motif to be employed where appropriate in artificial
photosynthetic systems.
4.4. Porphyrin building blocks
4.4.1. 5,10,15-Tris(4-methylphenyl)porphyrin (Fb3a).
Following a standard procedure,47,54a solution of diacyldi-
pyrromethane 1a (1.00 g, 2.12 mmol) in dry THF/methanol
(50 mL, 10:1) was treated with NaBH4 (1.59 g, 42.4 mmol)
at room temperature for 55 min. The reaction was quenched
with aqueous NH4Cl. The mixture was extracted with
CH2Cl2. The combined extracts were washed with water,
dried (Na2SO4), and concentrated to dryness. The resulting
dipyrromethane-dicarbinol and dipyrromethane 2a (310 mg,
2.12 mmol) were dissolved in CH2Cl2 (848 mL) and treated

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K. Tomizaki et al. / Tetrahedron 60 (2004) 2011–2023
with InCl3 (60 mg, 0.32 mmol) at room temperature for
20 min. DDQ (1.44 g, 6.36 mmol) was added and the
mixture was stirred at room temperature for 1 h. The
reaction mixture was neutralized with TEA and concen-
trated to dryness. Chromatography [silica, CH2Cl2/hexanes
(2:1)] afforded a purple solid (177 mg, 14%): 1H NMR
(CDCl3) d 22.97 (s, 2H), 2.70–2.75 (br s, 9H), 7.56 (d,
J¼7.6 Hz, 2H), 8.11 (d, J¼7.6 Hz, 2H), 7.60 (d, J¼7.6 Hz,
4H), 8.14 (d, J¼7.6 Hz, 4H), 8.89–8.95 (m, 4H), 9.05 (d,
J¼4.4 Hz, 2H), 9.33 (d, J¼4.4 Hz, 2H), 10.20 (s, 1H); 13C
NMR (THF-d8) d 20.77 (two peaks have overlapped),
104.68, 119.60, 120.54, 127.33, 127.62, 130.2–130.5
(broadening due to NH tautomerism), 131.0–131.6 (broad-
ening due to NH tautomerism), 134.43, 134.66, 137.46 (two
peaks have overlapped), 139.22, 140.07, 145.2–145.6
(broadening due to NH tautomerism); LD-MS obsd 580.4;
FAB-MS obsd 580.2635, calcd 580.2627 (C41H32N4); labs
414, 509, 544, 585, 641 nm.
8.20–8.23 (m, 2H), 8.93 (d, J¼5.1 Hz, 2H), 9.05–9.08
(m, 4H), 9.52 (d, J¼5.1 Hz, 2H), 10.36 (s, 1H); 13C NMR
(THF-d8) d 101.63, 106.47, 117.6–118.1 (m), 122.19,
126.48, 127.65, 129.90, 130.68, 133.04, 133.22, 134.61,
135.9–136.3 (m), 139.2–139.6 (m), 143.22, 143.4–143.8
(m), 145.1–145.5 (m), 147.3–147.6 (m), 148.3–148.7 (m),
149.46, 149.68, 150.49, 150.97; MALDI-MS (dithranol)
obsd 776.60 [Mþ]; FAB-MS obsd 780.0391, calcd 780.0350
(C38H14F10N4Zn); labs 416, 542, 576 nm; lem (lex¼
540 nm) 583, 637 nm.
4.4.4.
1-(Pentafluorobenzoyl)dipyrromethane
(5).
Following a standard procedure,48 a solution of dipyrro-
methane 2a (731 mg, 5.00 mmol) in THF (5.0 mL) was
treated with EtMgBr (12.5 mL, 12.5 mmol, 1.0 M solution
in THF) under argon at 278 8C for 10 min. A solution of 4
(1.53 g, 5.00 mmol) in THF (5.0 mL) was added over 1 min.
The reaction mixture was stirred at 278 8C for 10 min, then
at room temperature for 30 min. Standard workup and
chromatography [silica, CH2Cl2/ethyl acetate (98:2)]
afforded a colorless solid (826 mg, 59%): mp 125–
4.4.2. Zn(II)-5,10,15-triphenylporphyrin (Zn3b). Follow-
ing a standard procedure47,54 a solution of 1b (300 mg,
0.700 mmol) in dry THF/methanol [30 mL (10:1)] was
treated with NaBH4 (526 mg, 14.0 mmol) at room tempera-
ture for 40 min. The resulting dipyrromethane-dicarbinol
and 2a (102 mg, 0.700 mmol) were dissolved in CH2Cl2
(280 mL) and treated with Yb(OTf)3 (555 mg, 0.896 mmol)
at room temperature for 20 min. DDQ (477 mg, 2.10 mmol)
was added and the mixture was stirred at room temperature
for 1 h. After standard workup, chromatography [silica,
CH2Cl2/hexanes (2:1)] afforded the free base porphyrin.
The resulting porphyrin was treated with Zn(OAc)2·2H2O
(154 mg, 0.700 mmol) in CHCl3 (10 mL) and methanol
(3 mL) at room temperature for 15 h. Standard workup,
chromatography [silica, CHCl3/hexanes (2:1)], and tritura-
tion (hexanes) afforded a purple solid (49 mg, 12%):
1H NMR (CDCl3) d 7.72–7.80 (m, 9H), 8.21–8.25
(m, 6H), 8.97 (d, J¼4.4 Hz, 2H), 8.99 (d, J¼5.1 Hz, 2H),
9.09 (d, J¼4.4 Hz, 2H), 9.39 (d, J¼4.4 Hz, 2H), 10.24
(s, 1H); 13C NMR (THF-d8) d 105.43, 120.10, 120.96,
126.32, 126.43, 127.29 (two peaks have overlapped), 131.27,
131.39, 131.49, 132.01, 134.59, 134.71, 143.72, 143.92,
149.78, 150.10, 150.18, 150.23; LD-MS obsd 598.56 [Mþ];
FAB-MS obsd 600.1307, calcd 600.1292 (C38H24N4Zn); labs
418, 543 nm; lem (lex¼540 nm) 590, 637 nm.
1
127 8C; H NMR (CDCl3) d 4.06 (s, 2H), 6.04–6.07 (m,
1H), 6.11–6.14 (m, 1H), 6.18–6.20 (m, 1H), 6.66–6.68 (m,
1H), 6.69–6.72 (m, 1H), 8.80 (s, 1H), 11.02 (s, 1H); 13C
NMR (CDCl3) d 26.8, 107.2, 108.7, 111.9, 118.1, 125.0,
126.8, 131.0, 136.1–136.3 (m), 139.2–139.7 (m), 140.6–
140.9 (m), 142.2–142.5 (m), 143.9–144.3 (m), 144.5,
145.5–145.8 (m), 172.0; FAB-MS obsd 340.0632, calcd
340.0635 (C16H9F5N2O). Anal. Calcd: C, 56.48; H, 2.67; N,
8.23. Found: C, 56.44; H, 2.71; N, 8.22.
4.4.5. 1-Benzoyl-9-pentafluorophenyldipyrromethane
(6). Following a standard procedure,48 a solution of 5
(830 mg, 2.44 mmol) in toluene (5 mL) was treated with
EtMgBr (4.88 mL, 4.88 mmol, 1.0 M solution in THF) at
room temperature under argon. After 5 min, a solution of
benzoyl chloride (343 mg, 2.44 mmol) in toluene (5 mL)
was added and the mixture was stirred at room temperature
for 10 min. A subsequent addition of EtMgBr (2.44 mL,
2.44 mmol, 1.0 M solution in THF) and a solution of
benzoyl chloride (343 mg, 2.44 mmol) in toluene (5 mL)
was performed. Standard workup, chromatography [silica,
CH2Cl2/ethyl acetate (97:3!95:5)], and precipitation
(CH2Cl2/hexanes) afforded colorless crystals (882 mg,
1
81%): mp 166–168 8C; H NMR (THF-d8) d 4.15 (s, 2H),
4.4.3. Zn(II)-5,15-bis(pentafluorophenyl)-10-phenylpor-
phyrin (Zn3c). Following a standard procedure,47,54
5.50–5.51 (m, 1H), 6.05–6.11 (m, 1H), 6.62–6.67 (m, 1H),
6.74–6.75 (m, 1H), 7.42–7.54 (m, 3H), 7.84–7.86 (m, 2H),
11.34 (s, 1H), 11.69 (s, 1H); 13C NMR (THF-d8) d 27.2,
110.3, 111.4, 120.2, 122.9, 129.0, 129.7, 132.2, 132.5,
136.8–137.2 (m), 137.4, 140.1–140.5 (m), 141.0–141.4
(m), 142.0, 143.1–143.3 (m), 144.5–144.6 (m), 146.3–
146.6 (m), 171.4, 184.2; FAB-MS obsd 444.0892, calcd
444.0897 (C23H13F5N2O2). Anal. Calcd: C, 62.17; H, 2.95;
N, 6.30. Found: C, 60.36; H, 2.96; N, 6.04.
a
solution of 1c (750 mg, 1.23 mmol) in dry THF/methanol
[40 mL (10:1)] was treated with NaBH4 (924 mg,
24.6 mmol, 20 M equiv.) at room temperature for 40 min.
The resulting dipyrromethane-dicarbinol and 2a (180 mg,
1.23 mmol) were dissolved in CH2Cl2 (492 mL) and treated
with InCl3 (35.0 mg, 0.157 mmol) at room temperature for
30 min. DDQ (838 mg, 3.69 mmol) was added and the
mixture was stirred at room temperature for 1 h. After
standard workup, chromatography [silica CH2Cl2/hexanes
(3:1)] afforded the free base porphyrin. The resulting
porphyrin was treated with Zn(OAc)2·2H2O (360 mg,
1.64 mmol) in CHCl3 (40 mL) and methanol (10 mL) at
room temperature for 4 h. Standard workup, chroma-
tography [silica, CHCl3/hexanes (2:1) then CHCl3/hexanes
(3:2)], and trituration (hexanes) afforded a purple solid
4.4.6. Zn(II)-5-pentafluorophenyl-10,15-diphenylpor-
phyrin (Zn3d). Following a standard procedure,47,54
a
solution of 6 (420 mg, 0.945 mmol) in dry THF/methanol
[25 mL (10:1)] was treated with NaBH4 (712 mg,
18.9 mmol, 20 M equiv.) at room temperature for 30 min.
The resulting dipyrromethane-dicarbinol and 2b (210 mg,
0.945 mmol) were dissolved in CH2Cl2 (378 mL) and
treated with InCl3 (26.0 mg, 0.118 mmol, 0.32 mM) at
1
(132 mg, 14%): H NMR (CDCl3) d 7.77–7.82 (m, 3H),

K. Tomizaki et al. / Tetrahedron 60 (2004) 2011–2023
2019
room temperature for 30 min. DDQ (645 mg, 2.84 mmol)
was added and the mixture was stirred at room temperature
for 1 h. After standard workup, chromatography [silica
CH2Cl2/hexanes (3:1)] afforded the free base porphyrin. The
resulting porphyrin was treated with Zn(OAc)2·2H2O
(170 mg, 0.780 mmol) in CH2Cl2 (20 mL) and methanol
(5.0 mL) at room temperature for 16 h. Standard
workup, chromatography [silica, CH2Cl2/hexanes (2:1)],
and trituration (hexanes) afforded a purple solid (120 mg,
and pyridine (41 mL) at 0 8C for 30 min. Standard workup,
chromatography [silica, CHCl3/hexanes (2:1)!(3:1)], and
trituration (hexanes) afforded a purple solid (116 mg, 96%):
1H NMR (CDCl3) d 7.74–7.82 (m, 3H), 8.16–8.19 (m, 2H),
8.84 (d, J¼5.1 Hz, 2H), 8.95 (d, J¼4.4 Hz, 2H), 8.99 (d,
J¼5.1 Hz, 2H), 9.86 (d, J¼5.1 Hz, 2H); 13C NMR (THF-d8)
d 103.00, 104.62, 117.4–117.7 (m), 122.63, 126.62, 127.81,
130.53, 131.39, 133.50, 133.93, 134.52, 135.9–136.5 (m),
139.2–139.7 (m), 140.4–140.7 (m), 142.77, 143.6–144.1
(m), 144.9–145.7 (m), 148.1–148.6 (m), 149.95, 150.00,
150.40, 151.53;- MALDI-MS (dithranol) obsd 855.46 [Mþ];
FAB-MS obsd 857.9459, calcd 857.9455 (C38H13BrF10N4-
Zn); labs 425, 552 nm.
1
18%): H NMR (CDCl3) d 7.74–7.83 (m, 6H), 8.20–8.22
(m, 4H), 8.90–8.91 (m, 1H), 8.96–8.98 (m, 2H), 9.00–9.02
(m, 1H), 9.06 (d, J¼4.4 Hz, 1H), 9.35 (d, J¼4.4 Hz, 1H),
9.48 (d, J¼5.1 Hz, 1H), 10.25 (s, 1H); 13C NMR (THF-d8) d
99.82, 106.06, 118.1–118.4 (m), 121.68, 121.98, 126.42,
126.48, 127.59 (two peaks have overlapped), 129.38,
130.13, 131.57, 131.68, 131.80, 132.66, 132.99, 133.07,
134.59, 134.70, 136.3–136.9 (m), 138.8–139.4 (m), 140.4–
140.8 (m), 143.0–143.4 (m), 143.41, 143.56, 145.4–146.0
(m), 147.8–148.4 (m), 149.56, 149.78, 149.90, 150.06,
150.17, 150.31, 150.43, 150.66; MALDI-MS (dithranol)
obsd 692.87 [Mþ], 679.76 [(M2F)þ]; FAB-MS obsd
690.0850, calcd 690.0821 (C38H19F5N4Zn); labs 417,
543 nm; lem (lex¼540 nm) 585, 636 nm.
4.4.10. Zinc(II)-5-bromo-20-pentafluorophenyl-10,15-
diphenylporphyrin (Zn7d). Following a standard pro-
cedure,49 a solution of Zn3d (100 mg, 0.145 mmol) in
CHCl3 (30 mL) was treated with NBS (26 mg, 0.15 mmol)
and pyridine (42 mL) at 0 8C for 30 min. Standard workup,
chromatography [silica, CHCl3/hexanes (3:1)], and tritura-
1
tion (hexanes) afforded a purple solid (102 mg, 91%): H
NMR (CDCl3) d 7.74–7.78 (m, 6H), 8.17–8.18 (m, 4H),
8.81–8.82 (m, 1H), 8.90–8.93 (m, 3H), 8.98–9.01 (m, 2H),
9.76 (d, J¼4.4 Hz, 1H), 9.85 (d, J¼4.4 Hz, 1H); 13C NMR
(THF-d8) d 101.15, 104.23, 117.6–118.1 (m), 122.26,
123.39, 126.56, 126.59, 127.67, 127.72, 130.02, 130.95,
132.05, 132.42, 132.46, 133.24, 133.41, 133.85, 134.52,
134.66, 136.3–136.9 (m), 138.8–139.4 (m), 140.5–141.1
(m), 143.08, 143.1–143.6 (m), 143.12, 145.4–146.0 (m),
147.8–148.4 (m), 149.92, 150.12, 150.18 (two peaks have
overlapped), 150.51, 150.61, 150.91, 151.32; MALDI-MS
(dithranol) obsd 770.67 [Mþ], 753.64 [(M2F)þ], 694.55
[(M2Br)þ]; FAB-MS obsd 767.9951, calcd 767.9926
(C38H18BrF5N4Zn); labs 426, 553, 594 nm.
4.4.7. 5-Bromo-10,15,20-tris(4-methylphenyl)porphyrin
(Fb7a). Following a standard procedure,49 a solution of
Fb3a (581 mg, 1.00 mmol) in CHCl3 (250 mL) was treated
with NBS (178 mg, 1.00 mmol) and pyridine (1.0 mL) at
0 8C for 15 min. Acetone (20 mL) was added. The reaction
mixture was concentrated to dryness. Chromatography
[silica, CHCl3/hexanes (3:1)] and recrystallization
(CHCl3/methanol) afforded a purple solid (645 mg, 98%):
1H NMR (CDCl3) d 22.72 (s, 2H), 2.70–2.74 (br s, 9H),
7.54–7.60 (m, 6H), 8.05–8.11 (m, 6H), 8.80–8.83 (m, 4H),
8.93 (d, J¼4.8 Hz, 2H), 9.67 (d, J¼4.8 Hz, 2H); 13C NMR
(THF-d8) d 20.76 (two peaks have overlapped), 102.09,
121.01, 121.30, 127.57 (two peaks have overlapped),
134.38, 134.54, 137.70, 137.74, 139.15, 139.26, resonances
from the a- and b-carbons of the porphyrin were not
observed due to NH tautomerism; LD-MS obsd 659.3;
FAB-MS obsd 658.1749, calcd 658.1732 (C41H31BrN4);
labs 423, 486, 520, 554, 597, 655 nm.
4.4.11. 5-Iodo-10,15,20-tris(4-methylphenyl)porphyrin
(Fb8a). Following a standard procedure,50 a solution of
porphyrin Fb3a (871 mg, 1.50 mmol) and I2 (267 mg,
1.05 mmol) in CHCl3 (210 mL) was treated with a solution
of [bis(trifluoroacetoxy)iodo]benzene (478 mg, 1.20 mmol)
and pyridine (1.3 mL) in CHCl3 (30 mL). The mixture was
stirred for 1 h at room temperature. The reaction mixture
was diluted with CH2Cl2, washed with aqueous Na2S2O3,
and dried (Na2SO4). The solution was concentrated to
,100 mL, then 30 mL of hexanes was added. The resulting
purple precipitate was filtered, washed (CH2Cl2, hexanes)
and dried to give a purple powder (618 mg). The filtrate was
concentrated and chromatographed [silica, warm toluene/
hexanes (7:3)] affording an additional amount of the title
4.4.8. Zn(II)-5-bromo-10,15,20-triphenylporphyrin
(Zn7b). Following a standard procedure,49 a solution of
Zn3b (44 mg, 73 mmol) in CHCl3 (15 mL) was treated with
NBS (13 mg, 73 mmol) and pyridine (21 mL) at 0 8C for
30 min. Standard workup, chromatography [silica, CHCl3/
hexanes (2:1)], and trituration (hexanes) afforded a purple
1
1
solid (38.0 mg, 77%): H NMR (CDCl3) d 7.77–7.78 (m,
compound (253 mg). The total yield is 871 mg (82%): H
9H), 8.11–8.27 (m, 6H), 8.85–8.92 (m, 4H), 8.98–8.99 (m,
2H), 9.68–9.80 (m, 2H); 13C NMR (THF-d8) d 103.54,
121.45, 121.63, 126.48, 126.59, 127.47, 127.50, 131.828,
121.832, 132.26, 132.74, 134.46, 134.62, 143.33, 143.41,
149.68, 150.55, 150.62, 150.69; LD-MS obsd 678.45 [Mþ];
FAB-MS obsd 678.0397, calcd 678.0398 (C38H23BrN4Zn);
labs 426, 555 nm. Zn7b is a known compound but the
synthetic procedure has not been described.61
NMR (CDCl3) d 22.70 (s, 2H), 2.69–2.74 (br s, 9H), 7.53–
7.59 (m, 6H), 8.04–8.09 (m, 6H), 8.78–8.83 (m, 4H), 8.89
(d, J¼4.8 Hz, 2H), 9.67 (d, J¼4.8 Hz, 2H); 13C NMR
(THF-d8) d 20.77 (two peaks have overlapped), 77.92,
121.04, 121.45, 127.53, 127.59, 134.41, 134.53, 137.72
(two peaks have overlapped), 139.71, 139.28, resonances
from the a-and b-carbons of the porphyrin were not
observed due to NH tautomerism; LD-MS obsd 706.9;
FAB-MS obsd 706.1613, calcd 706.1593 (C41H31IN4); labs
424, 520, 557, 598, 656 nm.
4.4.9. Zn(II)-5-bromo-10,20-bis(pentafluorophenyl)-15-
phenylporphyrin (Zn7c). Following a standard pro-
cedure,49 a solution of Zn3c (110 mg, 0.141 mmol) in
CHCl3 (30 mL) was treated with NBS (25 mg, 0.14 mmol)
4.4.12. Zn(II)-5-bromo-10,15,20-tris(4-methylphenyl)-
porphyrin (Zn7a).
A solution of porphyrin Fb7a

2020
K. Tomizaki et al. / Tetrahedron 60 (2004) 2011–2023
(594 mg, 0.900 mmol) in THF (60 mL) was treated with
Zn(OAc)2·2H2O (988 mg, 4.50 mmol). The mixture was
heated (,50 8C) for a few minutes and then stirred at room
temperature for 11 h. Standard workup, chromatography
[silica, CHCl3/hexanes (3:2)] and recrystallization (hexanes/
140.62, 143.91, 149.74, 149.78, 149.86, 149.88, 150.04,
150.16, 150.80, 152.47; MALDI-MS (dithranol) obsd
1465.84 [Mþ]; FAB-MS obsd 1466.4607, calcd 1466.4619
(C96H74N8Zn2); labs 442, 445, 553, 618 nm; lem
(lex¼550 nm) 627, 681 nm.
1
CH2Cl2) afforded a purple solid (582 mg, 89%): H NMR
(CDCl3) d 2.67 (s, 3H), 2.70 (s, 6H), 7.52–7.60 (m, 6H),
8.00–8.08 (m, 6H), 8.78–8.82 (m, 4H), 8.91 (d, J¼4.8 Hz,
2H), 9.68 (d, J¼4.8 Hz, 2H); 13C NMR (THF-d8) d 20.78,
20.80, a resonance from the C–Br carbon was not observed,
119.88, 120.03, 127.02, 127.07, 128.44, 131.11, 131.28,
131.80, 134.44, 134.47, 136.73, 136.77, 140.97, 141.07,
149.86, 149.96, 150.23, 150.42; LD-MS obsd 723.8; FAB-
MS obsd 720.0901, calcd 720.0867 (C41H29BrN4Zn); labs
427, 555, 595 nm.
4.5.2. Dyad-2. A mixture of Zn9 (25 mg, 30 mmol), Fb7a
(20 mg, 30 mmol), Pd2(dba)3 (17 mg, 18 mmol), and
P(o-tol)3 (44 mg, 0.14 mmol) in toluene/TEA [48 mL
(5:1)] was stirred at 50 8C for 1.5 h under argon. Standard
workup, preparative SEC (THF), chromatography [silica,
CHCl3/hexanes (2:1)], and trituration (THF/hexanes)
1
afforded a purple solid (19 mg, 47%): H NMR (CDCl3) d
22.23 (s, 2H), 1.86–1.89 (m, 18H), 2.63–2.65 (m, 9H),
2.71 (s, 3H), 2.73 (s, 6H), 7.28–7.30 (m, 6H), 7.56 (d,
J¼7.3 Hz, 2H), 7.60 (d, J¼8.1 Hz, 4H), 8.08 (d, J¼8.1 Hz,
2H), 8.13 (d, J¼8.1 Hz, 4H), 8.40 (d, J¼8.1 Hz, 2H), 8.45
(d, J¼8.1 Hz, 2H), 8.72–8.73 (m, 4H), 8.80–8.81 (m, 4H),
8.83 (d, J¼4.4 Hz, 2H), 9.01–9.04 (m, 4H), 9.93 (d, J¼
5.1 Hz, 2H); MALDI-MS (dithranol) obsd 1409.27
[(MþH)þ]; FAB-MS obsd 1404.5476, calcd 1404.5484
(C96H76N8Zn); labs 422, 439, 550, 578, 672 nm; lem
(lex¼550 nm) 675, 747 nm.
4.4.13. Zn(II)-5-iodo-10,15,20-tris(4-methylphenyl)por-
phyrin (Zn8a). A solution of Fb8a (353 mg, 0.500 mmol)
in THF (60 mL) was treated with Zn(OAc)2·2H2O (1.10 g,
5.00 mmol). The mixture was heated (,50 8C) for a few
minutes and then stirred at room temperature for 8 h.
Standard workup, chromatography [silica, CHCl3/hexanes
(1:1)], and recrystallization (hexanes/CH2Cl2) afforded a
purple solid (349 mg, 91%): 1H NMR (CDCl3) d 2.67–2.70
(br s, 9H), 7.53–7.59 (m, 6H), 8.01–8.06 (m, 6H), 8.76–
8.80 (m, 4H), 8.86–8.91 (m, 2H), 9.72 (d, J¼4.4 Hz, 2H);
13C NMR (THF-d8) d 20.79, 20.80, 79.54, 121.51, 121.92,
127.16 (two peaks have overlapped), 131.16, 131.70,
131.83, 132.98, 134.55 (two peaks have overlapped),
137.07, 137.10, 140.47, 140.56, 150.70 (two peaks have
overlapped), 151.29, 152.13; LD-MS obsd 770.5; FAB-MS
obsd 768.0760, calcd 768.0728 (C41H29IN4Zn); labs 429,
519, 556, 596 nm.
4.5.3. Dyad-3. A mixture of Zn9 (20 mg, 24 mmol), Zn7c
(21 mg, 24 mmol), Pd2(dba)3 (13 mg, 14 mmol), and
P(o-tol)3 (35 mg, 0.11 mmol) in toluene/TEA [38 mL
(5:1)] was stirred at 50 8C for 1.5 h under argon. Standard
workup, preparative SEC (THF), chromatography [silica,
CHCl3/hexanes (2:1!3:1)], and trituration (hexanes)
1
afforded a purple solid (24 mg, 62%): H NMR (CDCl3) d
1.87–1.89 (m, 18H), 2.63–2.66 (m, 9H), 7.28–7.29 (m,
2H), 7.30–7.32 (m, 4H), 7.75–7.82 (m, 3H), 8.21 (d,
J¼7.3 Hz, 2H), 8.42 (d, J¼7.3 Hz, 2H), 8.47 (d, J¼8.1 Hz,
2H), 8.73–8.75 (m, 4H), 8.84–8.86 (m, 4H), 9.00 (d,
J¼5.1 Hz, 2H), 9.03–9.05 (m, 4H), 10.12 (d, J¼4.4 Hz,
2H); 13C NMR (THF-d8) d 20.83 (two peaks have
overlapped), 21.30, 21.35, 93.37, 96.74, 100.86, 103.43,
117.5–117.8 (m), 118.25, 118.38, 119.14, 123.25, 123.58,
126.62, 127.71, 127.74, 127.82, 129.70, 130.08, 130.20,
130.52, 130.63, 131.09, 131.70, 132.30, 133.32, 134.52,
135.11, 136.4–137.0 (m), 137.32 (two peaks have over-
lapped), 139.0–139.6 (m), 139.14 (two peaks have
overlapped), 139.84, 139.94, 140.5–141.0 (m), 142.85,
143.1–143.6 (m), 144.42, 145.3–145.9 (m), 147.8–148.4
(m), 149.46, 149.77, 149.78, 149.82, 149.87, 149.89,
150.88, 153.13; MALDI-MS (dithranol) obsd 1604.77
[Mþ]; FAB-MS obsd 1604.3187, calcd 1604.3208
(C93H58F10N8Zn2); labs 422, 445, 553, 607 nm; lem
(lex¼550 nm) 616, 678 nm.
4.5. Porphyrin dyads
4.5.1. Dyad-1. Samples of Zn9 (11 mg, 13 mmol), Zn8a
(10 mg, 13 mmol), Pd2(dba)3 (7.1 mg, 7.7 mmol), and
P(o-tol)3 (19 mg, 62 mmol) were placed into a 100 mL
Schlenk flask which was then pump-purged three times with
argon. Toluene/TEA [20.6 mL (5:1)] was added, and the
reaction mixture was stirred at 40 8C for 1.5 h. The reaction
mixture was concentrated to dryness. The resulting residue
was passed through a pad of silica (CHCl3). The eluant was
concentrated and then further purified by preparative SEC
(THF) and adsorption chromatography [silica, CHCl3/
hexanes (2:1)]. The desired fraction was concentrated to
dryness and then triturated with methanol. Filtration
afforded the title compound as a purple solid (7.3 mg,
41%): 1H NMR (CDCl3) d 1.86–1.88 (m, 18H), 2.63–2.64
(m, 9H), 2.72 (s, 3H), 2.74 (s, 6H), 7.29 (s, 2H), 7.30 (s, 4H),
7.56 (d, J¼8.1 Hz, 2H), 7.60 (d, J¼8.1 Hz, 4H), 8.09 (d,
J¼8.1 Hz, 2H), 8.14 (d, J¼8.1 Hz, 4H), 8.41–8.46 (m, 4H),
8.71–8.74 (m, 4H), 8.84 (d, J¼5.1 Hz, 2H), 8.90–8.93 (m,
4H), 9.05 (d, J¼4.4 Hz, 2H), 9.12 (d, J¼4.4 Hz, 2H), 10.03
(d, J¼4.4 Hz, 2H); 13C NMR (THF-d8) d 20.80 (two peaks
have overlapped), 20.82 (two peaks have overlapped),
21.27, 21.33, 94.40, 95.89, 99.10, 118.18, 118.33, 119.31,
121.89, 122.78, 123.78, 127.15, 127.22, 127.71 (two peaks
have overlapped), 129.50, 130.16, 130.43, 130.46, 130.57,
131.32, 131.66, 131.75, 132.44, 132.47, 134.37, 134.54,
135.03 (two peaks have overlapped), 137.08, 137.30, 139.14
(two peaks have overlapped), 139.85, 139.95, 140.52,
4.5.4. Dyad-4. A mixture of Zn9 (12 mg, 15 mmol), Zn7d
(12 mg, 15 mmol), Pd2(dba)3 (9.0 mg, 9.0 mmol), and
P(o-tol)3 (22 mg, 0.072 mmol) in toluene/TEA [24 mL
(5:1)] was stirred at 50 8C for 1.5 h under argon. Standard
workup, preparative SEC (THF), and chromatography
[silica, CHCl3/hexanes (2:1)] afforded a purple solid
1
(11 mg, 48%): H NMR (CDCl3) d 1.86–1.89 (m, 18H),
2.62–2.65 (m, 9H), 7.29–7.30 (m, 6H), 7.74–7.83 (m, 6H),
8.19–8.22 (m, 2H), 8.24–8.26 (m, 2H), 8.41–8.47 (m, 4H),
8.71–8.74 (m, 4H), 8.81–8.85 (m, 3H), 8.89–8.93 (m, 2H),
8.99 (d, J¼4.4 Hz, 1H), 9.02 (d, J¼5.1 Hz, 1H), 9.04 (d,
J¼5.1 Hz, 2H), 9.12 (d, J¼4.4 Hz, 1H), 10.05 (d, J¼4.4 Hz,

K. Tomizaki et al. / Tetrahedron 60 (2004) 2011–2023
2021
1H), 10.13 (d, J¼5.1 Hz, 1H); 13C NMR (THF-d8) d 20.82
(two peaks have overlapped), 21.28, 21.33, 93.79, 96.40,
100.21, the meso-carbon adjacent to the pentafluorophenyl
group was not observed, 118.20, 118.35, 119.20, 123.23,
123.46, 123.64, 126.55, 126.57, 127.66 (two peaks have
overlapped), 127.72 (two peaks have overlapped), 129.52,
129.60, 129.52, 129.60, 130.17, 130.48, 130.59 (two peaks
have overlapped), 131.71, 131.93, 132.14 (two peaks have
overlapped), 132.94, 133.16, 134.47, 134.63, 135.07 (two
peaks have overlapped), 137.30 (two peaks have over-
lapped), 139.14 (two peaks have overlapped), 139.84,
139.94, 143.13, 143.15, 144.20, 149.75, 149.78, 149.84,
149.87, 150.59, 152.75, resonances from some of the
a-carbons of the porphyrin were not observed clearly, and
resonances from the carbons of the pentafluorophenyl group
were not observed; MALDI-MS (dithranol) obsd 1518.39
[Mþ]; FAB-MS obsd 1514.3712, calcd 1514.3679
(C93H63F5N8Zn2); labs 422, 446, 553, 611 nm; lem (lex¼
550 nm) 618, 675 nm.
(m), 142.81, 143.0–143.5 (m), 145.2–145.8 (m), 147.8–
148.3 (m), 149.37, 149.81, 150.82, 152.96; MALDI-MS
(dithranol) obsd 793.71 [(MþH)þ], 775.58 [(M2F)þ];
FAB-MS obsd 790.1099, calcd 790.1134 (C46H23F5N4Zn);
labs 442, 567, 606 nm; lem (lex¼560 nm) 612, 671 nm.
4.6.3. Zn(II)-5,15-bis(pentafluorophenyl)-10-phenyl-20-
(phenylethynyl)porphyrin (Zn10d). A mixture of Zn7d
(40 mg, 46 mmol), phenylacetylene (25 mL, 0.23 mmol),
Pd2(dba)3 (6.4 mg, 7.0 mmol), and P(o-tol)3 (17 mg,
55 mmol) in toluene/TEA [18 mL (5:1)] was stirred at
50 8C under argon. After 5 h, phenylacetylene (25 mL,
0.23 mmol), Pd2(dba)3 (6.4 mg, 7.0 mmol), and P(o-tol)3
(17 mg, 55 mmol) were added. After 18 h, the reaction
mixture was concentrated to dryness. Chromatography
[silica, CH2Cl2/hexanes (3:2)] and trituration (hexanes)
afforded a purple solid (30 mg, 74%): 1H NMR (THF-d8) d
7.50–7.54 (m, 1H), 7.57–7.62 (m, 2H), 7.72–7.79 (m, 3H),
8.08 (d, J¼6.6 Hz, 2H), 8.16–8.19 (m, 2H), 8.85 (d, J¼
5.1 Hz, 2H), 8.88 (d, J¼5.1 Hz, 2H), 9.03 (d, J¼5.1 Hz,
2H), 9.88 (d, J¼4.4 Hz, 2H); 13C NMR (THF-d8) d 92.79,
95.95, 100.05, 101.58, 117.9–118.1 (m), 123.17, 123.55,
124.54, 126.53, 126.55, 127.65 (two peaks have over-
lapped), 128.48, 128.81, 129.49, 130.47, 130.62, 131.61,
131.84, 131.89, 131.99, 132.82, 133.12, 134.45, 134.59,
136.5–137.0 (m), 138.8–139.3 (m), 140.3–140.8 (m),
143.10, 143.13, 143.2–143.4 (m), 145.4–1445.8 (m),
147.8–148.4 (m), 149.47, 149.84, 149.90, 150.22, 150.53,
150.58, 152.67, 152.69; MALDI-MS (dithranol) obsd
882.07 [Mþ]; FAB-MS obsd 880.0638, calcd 880.0663
(C46H18F10N4Zn); labs 443, 566, 602 nm; lem (lex¼
565 nm) 616, 674 nm.
4.6. Benchmark phenylethynyl-porphyrins
4.6.1. Zn(II)-5-(phenylethynyl)-10,15,20-triphenylpor-
phyrin (Zn10b). A mixture of Zn7b (30 mg, 44 mmol),
phenylacetylene (24 mL, 0.22 mmol), Pd2(dba)3 (6.1 mg,
6.7 mmol), and P(o-tol)3 (16 mg, 53 mmol) in toluene/TEA
[18 mL (5:1)] was stirred at 50 8C under argon. After 6 h,
phenylacetylene (24 mL, 0.22 mmol), Pd2(dba)3 (6.1 mg,
6.7 mmol), and P(o-tol)3 (16 mg, 53 mmol) were added.
After 14 h, the reaction mixture was concentrated to
dryness. Chromatography [silica, CH2Cl2/hexanes (3:2)]
and trituration (hexanes) afforded a blue-purple solid
1
(16 mg, 52%): H NMR (CDCl3) d 7.46–7.51 (m, 1H),
7.54–7.59 (m, 2H), 7.70–7.82 (m, 9H), 8.03 (d, J¼7.3 Hz,
2H), 8.17–8.22 (m, 6H), 8.86–8.87 (m, 4H), 9.01 (d,
J¼4.4 Hz, 2H), 9.84 (d, J¼4.4 Hz, 2H); 13C NMR (THF-d8)
d 92.95, 96.48, 100.49, 122.27, 122.99, 124.45, 126.82,
126.88, 127.86 (two peaks have overlapped), 128.65,
128.91, 131.15, 131.85, 132.16, 132.46, 133.13, 134.52,
134.64, 142.66, 142.77, 150.12, 150.27, 150.77, 152.53;
LD-MS obsd 700.15 [Mþ]; FAB-MS obsd 700.1610, calcd
700.1605 (C46H28N4Zn); labs 440, 567, 611 nm; lem (lex¼
560 nm) 618, 673 nm.
4.6.4. Zn(II)-5,15-bis(pentafluorophenyl)porphyrin
(Zn11). Following a standard procedure,48,54 a solution of
5 (681 mg, 2.00 mmol) in dry THF/methanol [66 mL,
(10:1)] was treated with NaBH4 (1.50 g, 40.0 mmol) at
room temperature for 40 min. The resulting dipyrro-
methane-monocarbinol was dissolved in CH2Cl2 (400 mL)
and treated with InCl3 (28 mg, 0.13 mmol, 0.32 mM) at
room temperature for 30 min. DDQ (681 mg, 3.00 mmol)
was added and the mixture was stirred at room temperature
for 1 h. Standard workup and chromatography [silica,
CH2Cl2/hexanes (3:1)] afforded a mixture of free base
porphyrin and chlorin. The mixture was dissolved in toluene
(100 mL) and reoxidized with DDQ (681 mg, 3.00 mmol)
under reflux for 1 h. The reaction mixture was cooled,
diluted with hexanes (100 mL), and filtered. The resulting
porphyrin was treated with Zn(OAc)2·2H2O (3.29 g,
15.0 mmol) in CHCl3 (800 mL) and methanol (30 mL) at
room temperature for 3 days. Standard workup and
trituration (methanol) afforded a purple solid (114 mg,
16%): 1H NMR (THF-d8) d 9.12 (d, J¼4.4 Hz, 4H), 9.52 (d,
J¼4.4 Hz, 4H), 10.39 (s, 2H); 13C NMR (THF-d8) d 100.08,
106.75, 130.52, 133.13, 149.50, 150.45, resonances from
the C–F carbons of the pentafluorophenyl group were not
observed; MALDI-MS (dithranol) obsd 704.23 [Mþ],
686.20 [(M2F)þ]; FAB-MS obsd 704.0049, calcd
704.0037 (C32H10F10N4Zn); labs (THF) 409, 541, 575 nm;
lem (lex¼540 nm, THF) 581, 633 nm.
4.6.2. Zn(II)-5-pentafluorophenyl-10,15-diphenyl-20-
(phenylethynyl)porphyrin (Zn10c). A mixture of Zn7c
(20 mg, 26 mmol), phenylacetylene (14 mL, 0.13 mmol),
Pd2(dba)3 (3.7 mg, 4.0 mmol), and P(o-tol)3 (9.9 mg,
32 mmol) in toluene/TEA [10.4 mL (5:1)] was stirred at
50 8C under argon. After 5 h, phenylacetylene (14 mL,
0.13 mmol), Pd2(dba)3 (3.7 mg, 4.0 mmol), and P(o-tol)3
(9.9 mg, 32 mmol) were added. After 15 h, the reaction
mixture was concentrated to dryness. Chromatography
[silica, CH2Cl2/hexanes (3:2)] and trituration (hexanes)
1
afforded a purple solid (15 mg, 73%): H NMR (CDCl3) d
7.49–7.58 (m, 3H), 7.72–7.81 (m, 6H), 8.00–8.03 (m, 2H),
8.16–8.22 (m, 4H), 8.79 (d, J¼5.1 Hz, 1H), 8.86–8.89 (m,
2H), 8.93 (d, J¼4.4 Hz, 1H), 8.96 (d, J¼5.1 Hz, 1H), 9.02
(d, J¼4.4 Hz, 1H), 9.83 (d, J¼5.1 Hz, 1H), 9.92 (d, J¼
4.4 Hz, 1H); 13C NMR (THF-d8) d 92.35, 96.26, 100.68,
103.33, 117.5–117.8 (m), 123.52, 124.33, 126.59, 127.79,
128.67, 128.85, 130.03, 130.95, 131.69, 132.13, 133.28,
134.48, 136.5–137.1 (m), 138.8–139.4 (m), 140.6–1401.1
4.6.5. Zn(II)-5,15-dibromo-10,20-bis(pentafluorophe-
nyl)porphyrin (Zn12a). Following a standard procedure,49

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K. M., Eds.; Academic: San Diego, CA, 2003; Vol. 18, pp
63–250.
a solution of Zn11 (100 mg, 0.142 mmol) in CHCl3 (30 mL)
was treated with NBS (50 mg, 0.28 mmol) and pyridine
(0.1 mL) at 0 8C for 30 min. Standard workup, chroma-
tography [silica, THF/hexanes (3:17)], and trituration
(methanol) afforded a purple solid (101 mg, 82%): 1H
NMR (THF-d8) d 9.00 (d, J¼5.1 Hz, 4H), 9.75 (d, J¼
5.1 Hz, 4H); 13C NMR (THF-d8) d 103.69, 105.33, 116.8–
117.5 (m), 131.85, 134.32, 136.3–136.9 (m), 138.8–139.4
(m), 140.7–141.3 (m), 143.2–143.7 (m), 145.3–145.9 (m),
147.7–148.4 (m), 150.31, 150.98; MALDI-MS (dithranol)
obsd 862.16 [Mþ], 844.27 [(M2F)þ], 782.45 [(M2Br)þ];
FAB-MS obsd 859.8242, calcd 859.8247 (C32H8Br2F10N4Zn);
2. Burrell, A. K.; Officer, D. L.; Plieger, P. G.; Reid, D. C. W.
Chem. Rev. 2001, 101, 2751–2796.
3. Aratani, N.; Osuka, A. Macromol. Rapid Commun. 2001, 22,
725–740.
4. (a) Gust, D.; Moore, T. A.; Moore, A. L. Acc. Chem. Res.
2001, 34, 40–48. (b) Gust, D.; Moore, T. A.; Moore, A. L.
Acc. Chem. Res. 1993, 26, 198–205. (c) Gust, D.; Moore, T. A.
Top. Curr. Chem. 1991, 159, 103–151.
5. Tamiaki, H. Coord. Chem. Rev. 1996, 148, 183–197.
6. (a) Wasielewski, M. R. Chem. Rev. 1992, 92, 435–461.
(b) Wasielewski, M. R. In Chlorophylls. Scheer, H., Ed.; CRC:
Boca Raton, FL, USA, 1991; pp 269–286.
l
abs (THF) 427, 562, 608 nm.
7. Gribkova, S. E.; Evstigneeva, R. P.; Luzgina, V. N. Russ.
Chem. Rev. 1993, 62, 963–979.
4.6.6. Zn(II)-5,15-bis(pentafluorophenyl)-10,20-bis-
(phenylethynyl)porphyrin (Zn13a). A mixture of Zn12a
(90 mg, 0.10 mmol), phenylacetylene (69 mL, 0.62 mmol),
Pd2(dba)3 (29 mg, 32 mmol), and P(o-tol)3 (76 mg,
0.13 mmol) in THF/TEA [42 mL (5:1)] was stirred at
40 8C under argon. After 4 h, phenylacetylene (69 mL,
0.22 mmol), Pd2(dba)3 (29 mg, 32 mmol), and P(o-tol)3
(76 mg, 0.13 mmol) were added. After 18 h, the mixture
was concentrated to dryness. Chromatography [silica, THF/
hexanes (3:17)] and trituration [CHCl3/hexanes (1:1), then
8. Boxer, S. G. Biochim. Biophys. Acta 1983, 726, 265–292.
9. Youngblood, W. J.; Gryko, D. T.; Lammi, R. K.; Bocian, D. F.;
Holten, D.; Lindsey, J. S. J. Org. Chem. 2002, 67, 2111–2117.
10. Hsiao, J.-S.; Krueger, B. P.; Wagner, R. W.; Johnson, T. E.;
Delaney, J. K.; Mauzerall, D. C.; Fleming, G. R.; Lindsey,
J. S.; Bocian, D. F.; Donohoe, J. Am. Chem. Soc. 1996, 118,
11181–11193.
11. Yang, S. I.; Lammi, R. K.; Seth, J.; Riggs, J. A.; Arai, T.; Kim,
D.; Bocian, D. F.; Holten, D.; Lindsey, J. S. J. Phys. Chem. B
1998, 102, 9426–9436.
1
methanol] afforded a blue-purple solid (50 mg, 53%): H
NMR (THF-d8) d 7.63–7.68 (m, 2H), 7.71–7.75 (m, 4H),
8.19–8.22 (m, 4H), 9.10 (d, J¼5.1 Hz, 4H), 9.95 (d, J¼
5.1 Hz, 4H); 13C NMR (THF-d8) d 92.24, 96.86, 102.26,
104.27, 117.1–117.9 (m), 124.14, 128.83, 128.86, 130.92,
131.73, 132.27, 136.4–137.0 (m), 138.9–139.5 (m), 140.6–
141.2 (m), 143.1–143.7 (m), 145.3–145.9 (m), 147.7–
148.3 (m), 149.55, 152.76; MALDI-MS (dithranol) obsd
904.35 [Mþ], 885.40 [(M2F)þ]; FAB-MS obsd 904.0646,
calcd 904.0663 (C48H18F10N4Zn); labs 454, 585, 627 nm;
lem (lex¼585 nm) 633, 697 nm.
12. Holten, D.; Bocian, D. F.; Lindsey, J. S. Acc. Chem. Res. 2002,
35, 57–69.
13. Arnold, D. P.; Johnson, A. W.; Mahendran, M. J. Chem. Soc.,
Perkin Trans. 1 1978, 366–370.
14. Proess, G.; Pankert, D.; Hevesi, L. Tetrahedron Lett. 1992, 33,
269–272.
15. Anderson, H. L. Tetrahedron Lett. 1992, 33, 1101–1104.
16. Arnold, D. P.; Nitschinsk, L. J. Tetrahedron 1992, 48,
8781–8792.
17. Arnold, D. P.; Heath, G. A. J. Am. Chem. Soc. 1993, 115,
12197–12198.
4.6.7. Zn(II)-5,15-diphenyl-10,20-bis(phenylethynyl)por-
phyrin (Zn13b).
A
mixture of Zn12b (100 mg,
18. Arnold, D. P.; James, D. A.; Kennard, C. H. L.; Smith, G.
J. Chem. Soc., Chem. Commun. 1994, 2131–2132.
19. Arnold, D. P.; Heath, G. A.; James, D. A. New J. Chem. 1998,
12, 1377–1387.
0.146 mmol), phenylacetylene (96 mL, 0.88 mmol),
Pd2(dba)3 (40 mg, 44 mmol), and P(o-tol)3 (107 mg,
350 mmol) in THF/TEA [58 mL (5:1)] was stirred at
40 8C under argon. After 6 h, phenylacetylene (96 mL,
0.88 mmol), Pd2(dba)3 (40 mg, 44 mmol), and P(o-tol)3
(107 mg, 350 mmol) were added. After 17 h, the mixture
was concentrated to dryness. Chromatography [silica, THF/
hexanes (3:17), then CH2Cl2/hexanes (2:1)] and trituration
(hexanes) afforded a blue-purple solid (46 mg, 43%).
Analytical data were identical to those described in the
literature for the synthesis using copper as a cocatalyst.37
20. Arnold, D. P.; Heath, G. A.; James, D. A. J. Porphyrins
Phthalocyanines 1999, 3, 5–31.
21. Arnold, D. P. Synlett 2000, 296–305.
22. Arnold, D. P.; Hartnell, R. D. Tetrahedron 2001, 57,
1335–1345.
23. Taylor, P. N.; Huuskonen, J.; Rumbles, G.; Aplin, R. T.;
Williams, E.; Anderson, H. L. Chem. Commun. 1998,
909–910.
24. Anderson, H. L. Chem. Commun. 1999, 2323–2330.
25. Wilson, G. S.; Anderson, H. L. Chem. Commun. 1999,
1539–1540.
Acknowledgements
26. Taylor, P. N.; Anderson, H. L. J. Am. Chem. Soc. 1999, 121,
11538–11545.
This research was supported by a grant from the NSF (CHE-
9988142). Mass spectra were obtained at the Mass
Spectrometry Laboratory for Biotechnology at North
Carolina State University. Partial funding for the Facility
was obtained from the North Carolina Biotechnology
Center and the NSF.
27. Piet, J. J.; Taylor, P. N.; Anderson, H. L.; Osuka, A.; Warman,
J. M. J. Am. Chem. Soc. 2000, 122, 1749–1757.
28. Lin, V. S.-Y.; DiMagno, S. G.; Therien, M. J. Science 1994,
264, 1105–1111.
29. Shediac, R.; Gray, M. H. B.; Uyeda, H. T.; Johnson, R. C.;
Hupp, J. T.; Angiolillo, P. J.; Therien, M. J. J. Am. Chem. Soc.
2000, 122, 7017–7033.
References and notes
30. Milgrom, L. R.; Yahioglu, G. Tetrahedron Lett. 1995, 36,
9061–9064.
1. Harvey, P. D. The porphyrin handbook; Kadish, K. M., Smith,

K. Tomizaki et al. / Tetrahedron 60 (2004) 2011–2023
2023
31. Milgrom, L. R.; Yahioglu, G. Tetrahedron Lett. 1996, 37,
4069–4072.
48. Rao, P. D.; Littler, B. J.; Geier, III., G. R.; Lindsey, J. S. J. Org.
Chem. 2000, 65, 1084–1092.
32. Milgrom, L. R.; Rees, R. D.; Yahioglu, G. Tetrahedron Lett.
1997, 38, 4905–4908.
49. DiMagno, S. G.; Lin, V. S.-Y.; Therien, M. J. J. Org. Chem.
1993, 58, 5983–5993.
33. Milgrom, L. R.; Yahioglu, G.; Bruce, D. W.; Morrone, S.;
Henari, F. Z.; Blau, W. J. Adv. Mater. 1997, 9, 313–316.
34. Henari, F. Z.; Blau, W. J.; Milgrom, L. R.; Yahioglu, G.;
Phillips, D.; Lacey, J. A. Chem. Phys. Lett. 1997, 267,
229–233.
50. (a) Boyle, R. W.; Johnson, C. K.; Dolphin, D. J. Chem. Soc.,
Chem. Commun. 1995, 527–528. (b) Shanmugathasan, S.;
Johnson, C. K.; Edwards, C.; Matthews, E. K.; Dolphin, D.;
Boyle, R. W. J. Porphyrins Phthalocyanines 2000, 4,
228–232.
35. Lacey, J. A.; Phillips, D.; Milgrom, L. R.; Yahioglu, G.; Rees,
R. D. Photochem. Photobiol. 1998, 67, 97–100.
36. Anderson, H. L.; Wylie, A. P.; Prout, K. J. Chem. Soc., Perkin
Trans. 1 1998, 1607–1611.
51. Wagner, R. W.; Johnson, T. E.; Li, F.; Lindsey, J. S. J. Org.
Chem. 1995, 60, 5266–5273.
52. Wagner, R. W.; Ciringh, Y.; Clausen, C.; Lindsey, J. S. Chem.
Mater. 1999, 11, 2974–2983.
37. LeCours, S. M.; DiMagno, S. G.; Therien, M. J. J. Am. Chem.
Soc. 1996, 118, 11854–11864.
53. Gryko, D.; Lindsey, J. S. J. Org. Chem. 2000, 65, 2249–2252.
54. Geier, III., G. R.; Callinan, J. B.; Rao, P. D.; Lindsey, J. S.
J. Porphyrins Phthalocyanines 2001, 5, 810–823.
55. Wojaczynski, J.; Latos-Grazynski, L.; Chmielewski, P. J.; Van
Calcar, P.; Balch, A. L. Inorg. Chem. 1999, 38, 3040–3050.
56. (a) Senge, M.; Feng, X. Tetrahedron Lett. 1999, 40,
4165–4168. (b) Senge, M. O.; Feng, X. J. Chem. Soc., Perkin
Trans. 1 2000, 3615–3621.
38. LeCours, S. M.; Guan, H.-W.; DiMagno, S. G.; Wang, C. H.;
Therien, M. J. J. Am. Chem. Soc. 1996, 118, 1497–1503.
39. LeCours, S. M.; Philips, C. M.; de Paula, J. C.; Therien, M. J.
J. Am. Chem. Soc. 1997, 119, 12578–12589.
40. (a) Shultz, D. A.; Gwaltney, K. P.; Lee, H. J. Org. Chem. 1998,
63, 769–774. (b) Shultz, D. A.; Gwaltney, K. P.; Lee, H.
J. Org. Chem. 1998, 63, 4034–4038.
57. Yoshida, N.; Shimidzu, H.; Osuka, A. Chem. Lett. 1998,
55–56.
41. Jiang, B.; Yang, S.-W.; Barbini, D. C.; Jones, Jr. W. E. Chem.
Commun. 1998, 213–214.
58. Wang, Q. M.; Bruce, D. W. Synlett 1995, 1267–1268.
59. Laha, J. K.; Dhanalekshmi, S.; Taniguchi, M.; Ambroise, A.;
Lindsey, J. S. Org. Process Res. Dev. 2003, 7, 799–812.
60. Loewe, R. S.; Lammi, R. K.; Diers, J. R.; Kirmaier, C.; Bocian,
D. F.; Holten, D.; Lindsey, J. S. J. Mater. Chem. 2002, 12,
1530–1552.
42. Screen, T. E. O.; Lawton, K. B.; Wilson, G. S.; Dolney, N.;
Ispasoiu, R.; Goodson, III., T.; Martin, S. J.; Bradley, D. D. C.;
Anderson, H. L. J. Mater. Chem. 2001, 11, 312–320.
43. Plater, M. J.; Aiken, S.; Bourhill, G. Tetrahedron 2002, 58,
2415–2422.
44. Plater, M. J.; Aiken, S.; Bourhill, G. Tetrahedron 2002, 58,
2405–2413.
61. Therien, M. J.; DiMagno, S. G. WO 9404614..
62. Medforth, C. J. The porphyrin handbook, Kadish, K. M.,
Smith, K. M., Guilard, R., Eds.; Academic: San Diego, CA,
2000; Vol. 5, pp 1–80.
45. Nakano, A.; Yasuda, Y.; Yamazaki, T.; Akimoto, S.;
Yamazaki, I.; Miyasaka, H.; Itaya, A.; Murakami, M.;
Osuka, A. J. Phys. Chem. A 2001, 105, 4822–4833.
46. Hindin, E.; Kirmaier, C.; Diers, J. R.; Tomizaki, K.-Y.;
Taniguchi, M.; Lindsey, J. S.; Bocian, D. F.; Holten, D. J. Phys.
Chem. Submitted.
63. Fenyo, D.; Chait, B. T.; Johnson, T. E.; Lindsey, J. S.
J. Porphyrins Phthalocyanines 1997, 1, 93–99.
64. del Rosario Benites, M.; Johnson, T. E.; Weghorn, S.; Yu, L.;
Rao, P. D.; Diers, J. R.; Yang, S. I.; Kirmaier, C.; Bocian, D. F.;
Holten, D.; Lindsey, J. S. J. Mater. Chem. 2002, 12, 65–80.
47. Rao, P. D.; Dhanalekshmi, S.; Littler, B. J.; Lindsey, J. S.
J. Org. Chem. 2000, 65, 7323–7344.