Dynamics of closure of zinc bis-porphyrin molecular tweezers with copper(II) ions and electron transfer

Article abstract of DOI:10.1002/chem.201101272

Zinc bis-porphyrin molecular tweezers composed of a N₄ spacer bound through pyridyl units to the meso position of porphyrins were synthesized, and the tweezers are closed by the coordination of a copper(II) ion inside the spacer ligand. The effect of the π-π interaction between the porphyrin rings in the closed conformation on the absorption spectra of multi-electron oxidized species and the reduction potentials were clarified by chemical and electrochemical oxidation of the closed form of the zinc bis-porphyrin molecular tweezers in comparison with the open form without copper(II) ion and the corresponding porphyrin monomer. The shifts in redox potentials and absorption spectrum of the porphyrin dication indicate a strong electronic interaction between the two oxidized porphyrins in the closed form, whereas there is little interaction between them in the neutral form. The dynamics of copper(II) ion coordination and subsequent electron transfer was examined by using a stopped-flow UV/Vis spectroscopic technique. It was confirmed that coordination of copper(II) occurs prior to electron-transfer oxidation of the closed form of the zinc bis-porphyrin molecular tweezers.

Full text of DOI:10.1002/chem.201101272

DOI: 10.1002/chem.201101272
Dynamics of Closure of Zinc Bis-Porphyrin Molecular Tweezers with
Copper(II) Ions and Electron Transfer
Benoit Habermeyer,[a] Atsuro Takai,[b, c] Claude P. Gros,[a] Maya El Ojaimi,[a, d]
Jean-Michel Barbe,*[a] and Shunichi Fukuzumi*[b, e]
Abstract: Zinc bis-porphyrin molecular
tweezers composed of a N4 spacer
bound through pyridyl units to the
meso position of porphyrins were syn-
thesized, and the tweezers are closed
by the coordination of a copper(II) ion
inside the spacer ligand. The effect of
the p–p interaction between the por-
phyrin rings in the closed conformation
on the absorption spectra of multi-elec-
tron oxidized species and the reduction
potentials were clarified by chemical
and electrochemical oxidation of the
closed form of the zinc bis-porphyrin
molecular tweezers in comparison with
the open form without copper(II) ion
and the corresponding porphyrin mo-
nomer. The shifts in redox potentials
and absorption spectrum of the por-
phyrin dication indicate a strong elec-
tronic interaction between the two oxi-
dized porphyrins in the closed form,
whereas there is little interaction be-
tween them in the neutral form. The
dynamics of copper(II) ion coordina-
tion and subsequent electron transfer
was examined by using a stopped-flow
UV/Vis spectroscopic technique. It was
confirmed that coordination of cop-
per(II) occurs prior to electron-transfer
oxidation of the closed form of the zinc
bis-porphyrin molecular tweezers.
Keywords: copper · electron trans-
fer · pi interactions · porphyrinoids ·
zinc
Introduction
Delocalization of p electrons between discrete p systems is
well known not only in porphyrin dimer radical cations but
also in aromatic dimer radical cations in general.[12–16] Such
delocalization of p electrons has recently been reported to
be finely controlled by anion binding in a supramolecular p
system based on a tetrathiafulvalene calix[4]pyrrole (an
electron donor) and a dicationic bis-imidazolium quinone
(an electron acceptor), wherein anion binding to the donor
promotes electron transfer by inducing a conformational
change that facilitates the p–p interaction in the p-dimer
radical cation.[17] In contrast to the anion binding, the cation
binding inhibits the p–p interaction to reverse the direction
of electron transfer.[17]
On the other hand, copper(I) ions have frequently been
utilized in the template synthesis of porphyrin catenanes
and rotaxanes in which the energy-transfer and electron-
transfer processes in the interlocked structures can be con-
trolled by the absence or presence of a copper(I) ion.[18,19]
Geometry control of the p–p interaction between p com-
pounds has also been made possible by metal-ion coordina-
tion.[20–22] Such a change in the p–p interaction is expected
to affect the redox properties of the p compounds. However,
the change in the redox properties associated with the ge-
ometry control of the p–p interaction between p compounds
by metal-ion coordination has yet to be studied. In addition,
there has been no report on the dynamics of metal-ion bind-
ing that induces the conformational change, although the dy-
namics of anion binding to diprotonated cyclo[8]pyrrole has
recently been reported.[23]
The crucial role of cofacial porphyrinoid dimers in the struc-
ture of the photosynthetic reaction center has stimulated ex-
tensive studies on mimics of this reaction center.[1–9] Strong
p–p interactions exist between the two macrocycles of the
special pair, in particular when it is oxidized to the radical
cation.[1,3] The electron-transfer properties of cofacial por-
phyrin dimers are known to be significantly enhanced due
to p-electron delocalization in the dimer radical cations.[10,11]
[a] B. Habermeyer, Dr. C. P. Gros, Dr. M. El Ojaimi, Dr. J.-M. Barbe
ICMUB, UMR CNRS 5260, Universitꢀ de Bourgogne
9 Avenue Alain Savary, BP 47870, 21078 Dijon CEDEX (France)
E-mail: Jean-Michel.Barbe@u-bourgogne.fr
[b] Dr. A. Takai, Prof. Dr. S. Fukuzumi
Department of Material and Life Science
Graduate School of Engineering, Osaka University and
ALCA, Japan Science and Technology Agency (JST)
2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan)
Fax : (+81)6-6879-7370
E-mail: fukuzumi@chem.eng.osaka-u.ac.jp
[c] Dr. A. Takai
Present Address: Organic Materials Group, Polymer Materials Unit
National Institute for Materials Science (NIMS)
1-2-1 Sengen, Tsukuba 305-0047 (Japan)
[d] Dr. M. El Ojaimi
Present Address: Department of Chemistry, University of Houston
Houston, Texas 77204 (USA)
[e] Prof. Dr. S. Fukuzumi
Department of Bioinspired Science
Ewha Womans University, Seoul 120-750 (Korea)
We report herein geometry control of p–p interaction be-
tween two p components by a metal ion which coordinates
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201101272.
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Chem. Eur. J. 2011, 17, 10670 – 10681

FULL PAPER
to the linker ligand of the two p components, and the dy-
namics of metal coordination followed by electron transfer.
We chose zinc bis-porphyrin molecular tweezers composed
of an N4 spacer bound through pyridyl units to the meso
position of porphyrins.[24] Closure of the tweezers from
the open form is made possible by the coordination of cop-
per(II) ion to the linker ligand, as shown in Scheme 1. In
the closed form, the enhanced p–p interaction between two
Results and Discussion
Synthesis of zinc bis-porphyrin molecular tweezers: Synthe-
ses of trans-AB2C boronated porphyrin 4 and dibrominated
spacer 7 are shown in Schemes 2 and 3, respectively. Several
methods have been reported for the synthesis of trans-AB2C
porphyrins. Statistical methods[25] are the most direct path-
way to obtain these derivatives, but purification by column
chromatography is often diffi-
cult and the yields are relatively
low. Combination of the meth-
ods of Woodward and MacDon-
ald and Markovac[26] with that
of Senge et al.[27] is a more ele-
gant alternative, despite the
fact that more synthetic steps
are required to access the final
derivative, which is formed by
condensation of 2 equivalents
of
dipyrromethane
with
2 equivalents of aldehyde in di-
chloromethane catalyzed by tri-
fluoroacetic acid. It is well-
known in the literature that
such a reaction usually leads to
some scrambling. As a conse-
quence, the purification steps
are often difficult and therefore
yields are low. For the synthesis
of 5,15-di-p-tolylporphyrin (1),
Scheme 1. Closure of a zinc bis-porphyrin tweezer from the open form by the coordination of copper(II) ion,
and structural change induced by electron-transfer oxidation.
porphyrins of the zinc bis-porphyrin is clearly recognized in
the oxidized states, as indicated by the shift in the absorp-
tion spectrum compared with the open form without cop-
per(II) ion. The changes in the oxidation potentials of the
bis-porphyrin on the coordina-
two strategies are possible: 1) reaction of 5-p-tolyldipyrro-
methane with formaldehyde and 2) condensation of 5-dihy-
drodipyrromethane with p-tolualdehyde. We explored only
the second strategy, for two reasons. Firstly 5-dihydrodipyr-
tion of a copper(II) ion to the
linker ligand were examined by
cyclic voltammetry in compari-
son with the porphyrin mono-
mer. The dynamics of the clo-
sure of the tweezers by coordi-
nation of the copper(II) ion to
the linker ligand and subse-
quent electron transfer from
copper(II) ion to the zinc por-
phyrin units in the closed form
have been examined for the
first time. This study provides
an excellent way not only to
control the geometry between
the porphyrin rings by coordi-
nation of copper(II) ion, but
also dynamics of the coordina-
tion of copper(II) ion and the
resulting electron transfer.
Scheme 2. Synthesis of boronated porphyrin 4. Conditions: i) TFA, CH2Cl2; ii) p-chloranil; iii) NEt3; iv) Zn-
(OAc)2·2H2O, NaOAc, CHCl3, MeOH; v) PhLi (2 m), THF, 08C; vi) H2O/THF; vii) DDQ; viii) NBS, py,
AHCTUNGTRENNUNG
CH2Cl2 08C; ix) acetone; x) pinacolborane, [PdACTHUNGTRNEUNG(PPh3)2Cl2] (3 mol%), NEt3, anhydrous DCE; xi) KCl/H2O
(30%).
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S. Fukuzumi, J.-M. Barbe et al.
was added to the reaction mix-
ture to facilitate the oxidative
addition step. Boronated por-
phyrin 4 was added slowly over
10 h to avoid side reactions
such as formation of meso–
meso porphyrin dimer 8. Be-
cause we observed some insta-
bility of spacer 7 in solution,
the reaction was carried out
with only 1 equivalent of boro-
nated porphyrin 4 and 1 equiva-
lent of spacer 7, contrary to the
stoichiometry of the reaction.
Scheme 3. Synthesis of spacer 7. Conditions: i) NaBH4, MeOH; ii) H2O; iii) SOCl2, toluene; iv) K2CO3, MeCN.
romethane is much more resistant to acidolysis than 5-p-tol-
yldipyrromethane. Therefore, less scrambling is expected.
Secondly, synthesis of 5-dihydrodipyrromethane is a high-
yield reaction.[28] This strategy allowed us to obtain the de-
sired porphyrin 1 in 49% yield on the gram scale without
any scrambling (Scheme 2).
Despite this instability of spacer 7, tweezers bis-Zn 9 could
be obtained in 20–40% yield. It was characterized by
1H NMR, 13C NMR, and UV/Vis spectroscopy, and ESI/
TOF HRMS (Figures S1–S3, Supporting Information). The
1H NMR spectra of compounds 1 to 7 are given in the Sup-
porting Information (Figures S4–S10).
Afterwards, a third aryl group was selectively introduced
at one of the two meso positions of 1 by addition of phenyl-
lithium at 08C,[27] affording 2 in 70% yield. The last unsub-
stituted meso position of 2 was then brominated by classical
reaction with recrystallized N-bromosuccinimide at room
temperature in 72% yield.[29]
Copper(II) was coordinated inside the spacer of bis-Zn 9
by addition of copper(II) acetate monohydrate or copper(II)
triflate. The reaction of bis-Zn 9 with copper(II) acetate
monohydrate in CHCl3/MeOH (1/1), followed by the purifi-
cation on silica gel and recrystallization, led to bis-Zn/Cu
This reaction was further im-
proved (90% yield) by decreas-
ing the reaction temperature to
08C in the presence of a base.
Bromoporphyrin
3 was then
quantitatively transformed into
4 by addition of pinacolborane,
catalyzed by palladium(II) in
anhydrous 1,2-dichloroethane
(DCE) in the presence of trie-
thylamine
as
base
(Scheme 2).[30,31]
Dibromo spacer 7 was ob-
tained in high yield according
to the reaction pathway in
Scheme 3. Key derivative 6 was
synthesized by stepwise reduc-
tion and chlorination of com-
mercially available methyl 5-
bromopyridine-2-carboxylate.
The Suzuki–Miyaura cou-
pling reaction between 4 and 7
is shown in Scheme 4.[30] To per-
form the coupling reaction be-
tween boronated porphyrin 4
and dibrominated spacer 7,
[{PdClACHTUNGTRENNUNG
(h3-C3H5)}2] was chosen
as precatalyst with PPh3 as
ligand in a toluene/DMF (5/3).
Cesium(I) carbonate was used
Scheme 4. Synthesis of molecular tweezers
9
and 10. Conditions: {[PdCl
(OAc)2·H2O, CHCl3/MeOH.
(h3-C3H5)]2} (10 mol%), PPh3
ACHTUNGTRENNUNG
as a base, while sodium iodide (4 equiv), Cs2CO3, NaI, toluene/DMF (5:3); ii) Cu
ACHTUNGTRENNUNG
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Zinc Bis-Porphyrin Molecular Tweezers
FULL PAPER
10, which was isolated in 65% yield (Scheme 4). Formation
of bis-Zn/Cu 10 was proved by the HRMS (ESI/TOF) spec-
trum, which exhibited an ionic pattern at 1599.4124 Da cor-
responding to [Mꢀ2OAc]+ (4 ppm deviation with respect to
calculated mass; Figure S11, Supporting Information).
An EPR spectrum of bis-Zn/Cu 10 in frozen medium
(77 K) is shown in Figure S12 of the Supporting Informa-
tion. This spectrum exhibits typical EPR signals due to the
copper(II) ion. The EPR parameters (g? <gk =2.173, Ak =
218 G) indicate that the copper(II) ion of bis-Zn/Cu 10 is
coordinated to the spacer with a slightly distorted square-
planar geometry.[32]
The UV/Vis spectra of zinc(II) tetra-p-tolylporphyrin
(TpTP)Zn, bis-Zn 9, and bis-Zn/Cu 10 are compared in
Figure 1. The same absorption maxima are observed for ref-
Figure 2. Optimized structures of a) bis-Zn 9 and b) bis-Zn/Cu 10 calcu-
lated by DFT (B3LYP/LanL2DZ level). Protons are not shown for clari-
ty.
Figure 1. Comparison of a) whole absorption spectra and b) Q bands of
(TpTP)Zn (g), bis-Zn 9 (a), and bis-Zn/Cu 10 (c) in CH2Cl2 at
298 K.
erence monomer (TpTP)Zn and bis-Zn 9.[33] This indicates
that the two porphyrin units of bis-Zn 9 behave separately
without any interaction. In contrast, the absorption bands of
bis-Zn/Cu 10 are slightly redshifted. Although the interac-
tion between the two porphyrins of bis-Zn/Cu 10 may be
weak in the neutral form due to the steric hindrance of the
tolyl groups at the meso positions,[10] the redshifted absorp-
tion bands of bis-Zn/Cu 10 indicate a conformational
change.[34]
The optimized structures of bis-Zn 9 and bis-Zn/Cu 10
calculated by DFT are shown in Figure 2. In bis-Zn 9, the
spacer is linear and the porphyrins are far from each
other.[35] After insertion of copper(II), the molecular tweez-
ers undergo a structural rearrangement which brings the two
porphyrins close to each other. The orientation between the
two chromophores is not strictly cofacial but slightly slipped,
in agreement with the weak bathochromic shift observed by
UV/Vis spectroscopy[34] and X-ray crystal structures of relat-
ed compounds.[36]
Figure 3. CV of the oxidation part of a) (TpTP)Zn (0.5 mm), b) bis-Zn 9
(1.0 mm), and c) bis-Zn/Cu 10 (1.0 mm) in PhCN containing 0.1m
nBu4NPF6.
These one-electron processes are attributed to (TpTP)Zn/ACHTUNG-
Electrochemical studies: To confirm the structural reorgani-
zation and the interactions between the porphyrin units on
metalation, the electrochemical behavior of (TpTP)Zn, bis-
Zn 9, and bis-Zn/Cu 10 were investigated. The cyclic vol-
tammogram (CV) of (TpTP)Zn (Figure 3) exhibits two re-
versible redox waves at 0.35 and 0.75 V (vs. Ag/AgNO3).
[(TpTP)Zn]·+ and [(TpTP)Zn]·+ [(TpTP)Zn]2+ redox cou-
TRENNUG /ACHTUNGTRENNGUN
ples, respectively. Two reversible redox waves were also ob-
served for bis-Zn 9, and the oxidation potentials (0.42 and
0.78 V) are higher than those of (TpTP)Zn due to the influ-
ence of the pyridyl group, which is a more electron with-
drawing group than a tolyl substituent. Judging from the cur-
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S. Fukuzumi, J.-M. Barbe et al.
Table 1. Half-wave and peak potentials* (V vs. Ag/AgNO3) of the redox
center in (TpTP)Zn, bis-Zn 9, and bis-Zn/Cu 10 in PhCN containing
0.1m nBu4NPF6 at 298 K.
rent intensity of each redox process of bis-Zn 9 as compared
with that of (TpTP)Zn, each reversible redox wave corre-
sponds to a two-electron process for bis-Zn 9, that is, there
is no interaction between two zinc porphyrin moieties in the
open form (bis-Zn 9).
Eox
Ered
Por·+/Por2+ Por/Por·+ CuII/CuI Spacer Por/Por·ꢀ
A
0.75
0.78
0.35
0.42
0.41
–
–
–
–
In contrast to the open form (bis-Zn 9), the CV and differ-
ential pulse voltammogram (DPV) of the closed form (bis-
Zn/Cu 10) shows three oxidation waves (Figure 3c and Fig-
ure S13, Supporting Information).[37] The initial oxidation of
bis-Zn/Cu 10 at 0.41 V is a two-electron process, similar to
that of bis-Zn 9, while the third and fourth oxidation pro-
cesses of bis-Zn/Cu 10 are split into two redox waves.[38]
Such splittings clearly indicate that the two porphyrin rings
interact in the oxidized states.[5b,10,20a,d,39] The fourth oxida-
tion potential of bis-Zn/Cu 10 is considerably shifted in the
positive direction because of the electrostatic repulsion be-
tween doubly charged porphyrin rings in the closed form of
ꢀ1.17
ꢀ1.49*
bis-Zn/Cu 10 0.67, 1.03
ꢀ0.74*
ꢀ1.10
ꢀ1.60*
The existence of interactions in the oxidized states is
shown by spectrophotometric titration of bis-Zn/Cu 10 by a
one-electron oxidant such as [Ru
pyridine).[40] The reduction potential Ered([Ru
(bpy)3]2+) is 1.25 V (vs. SCE) in PhCN containing 0.1m
nBu4NPF6. Figure S18 (Supporting Information) shows the
spectral changes of (TpTP)Zn on addition of [Ru
(bpy)3]3+
in PhCN. When 1 equivalent of [Ru
(bpy)3]3+ was added, the
ACHUTGTNRNENUG(bpy)3]ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
[bis-Zn/Cu]4+
.
ACHTUNGTRENNUNG
Reduction of bis-Zn 9 and bis-Zn/Cu 10 was also exam-
ined under the same conditions (Figure 4). Bis-Zn 9 under-
goes two irreversible reductions at ꢀ1.17 and ꢀ1.49 V. The
first peak can be assigned to reduction of the spacer unit,
spectrum displayed two broad absorption bands located at
lmax =612 and 847 nm, which are typically assigned to the
radical cation [(TpTP)Zn]·+.[41] On addition of a further
(bpy)3]3+ dication [(TpTP)Zn]2+ is
equivalent of [RuACHTUNGTRNENUG ,
formed and the absorption
band at lmax =612 nm disap-
pears, while the absorption
band increases in intensity and
shifts to 858 nm.
The same conditions were
employed for titration of bis-
Zn/Cu 10 (Figure 5). After ad-
dition of 1 equivalent of [Ru-
AHCTUNGTERNNUNG =
(bpy)3]3+, the Q band at lmax
555 nm decreases while a broad
absorption band appears
around 617 nm. A new band,
characteristic of radical
cation, also exists at lmax
a
=
877 nm. When 2 equivalents of
oxidant are added, the Q bands
completely disappear. This
clearly indicates formation of
Figure 4. CV and DPV of the reduction part of a) bis-Zn 9 (1.0 mm) and b) bis-Zn/Cu 10 (1.0 mm) in PhCN
containing 0.1m nBu4NPF6.
bis(radical
cation)
[bis-Zn/
Cu]2+. Thus, absorption bands
because reference compound N,N-bis(pyridin-2-ylmethyl)-
propane-1,3-diamine exhibits a similar irreversible cathodic
wave at ꢀ1.10 V (Figure S15, Supporting Information). The
second peak is attributed to reduction of each porphyrin
macrocycle leading to the bis-radical dianion [bis-Zn]2ꢀ
.
Similarly, two reduction processes for bis-Zn/Cu 10 at ꢀ1.10
and ꢀ1.60 V are assigned to reduction of the spacer unit and
porphyrin rings, respectively. Another irreversible peak at
ꢀ0.74 V corresponds to the CuII/CuI process. All electro-
chemical data of (TpTP)Zn, bis-Zn 9 and bis-Zn/Cu 10 are
summarized in Table 1. The electrochemical measurements
for a series of porphyrins in PhCN/MeCN (1/1) containing
0.1m NaOTf are also shown in Figure S16 of the Supporting
Information.
Figure 5. Spectrophotometric titration of bis-Zn/Cu 10 (1.0ꢂ10ꢀ5 m) by
[Ru
(bpy)3]3+ (c: bis-Zn/Cu, g: [bis-Zn/Cu]·+, a: [bis-Zn/Cu]2+
ACHTUNGTERNNUNG ,
b: [bis-Zn/Cu]3+, c: [bis-Zn/Cu]4+) in PhCN at 298 K.
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Zinc Bis-Porphyrin Molecular Tweezers
FULL PAPER
at lmax =615 and 878 nm increase by a factor of two
(bpy)3]3+
(Figure 5). After addition of 3 equivalents of [RuCAHTUNGTERNUNGN ,
the band at 615 nm partially decreases, while that at 878 nm
increases in intensity and shifts to 883 nm. The resulting
spectrum is assigned to trication [bis-Zn/Cu]3+. The fully
oxidized species [bis-Zn/Cu]4+ is finally obtained by adding
4 equivalents of [Ru
883 nm increases again in intensity and shifts to 885 nm.
ACHTUNGTRENNUNG =
(bpy)3]3+. The absorption band at lmax
Comparing UV/Vis spectra of fully oxidized species [bis-
Zn]4+ and [bis-Zn/Cu]4+ (Figure 6) clearly indicates a red-
shift of the absorption bands of [bis-Zn/Cu]4+ due to elec-
tronic interaction between the two porphyrin units in bis-
Zn/Cu 10. Such an electronic interaction was detected in the
oxidized state only for bis-Zn/Cu 10, in agreement with the
conformational change from the open form of bis-Zn 9 to
the closed form of bis-Zn/Cu 10.
Figure 7. a) UV/Vis spectral titration of bis-Zn 9 (2.2ꢂ10ꢀ5 m) by Cu-
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
Figure 8. EPR spectra of Cu
ACHTUNGRTEN(NUNG OTf)2 (a) and bis-Zn 9 in the presence of
1 equiv of Cu(OTf)2 (c) in CH2Cl2/MeOH (1/1) at 298 K.
AHCTUNGTRENNUNG
Figure 6. a) Comparison of UV/Vis spectra of [(TpTP)Zn]·+ (a), [bis-
Zn]2+ (g), and [bis-Zn/Cu]2+ (c) in PhCN (1ꢂ10ꢀ5 m) at 298 K.
b) Comparison of UV/Vis spectra of [(TpTP)Zn]2+ (a), [bis-Zn]4+
(g), and [bis-Zn/Cu]4+ (c) under the same conditions as a).
are shown in Figure 9a and b. A decrease in intensity and
redshift of Q bands at 550 and 598 nm along with increase
in intensity at 450 nm due to copper(II) inside the spacer
are observed. The same experiments were performed with
Dynamics of copper(II) coordination and electron transfer:
Spectral titration of bis-Zn 9 by copper(II) triflate (Cu-
different amounts of CuACTHNUTRGNE(UGN OTf)2 (Figure 9c), and each decay
A
of the absorbance at 598 nm obeys pseudo-first-order kinet-
ics. From the plot of the observed pseudo-first-order rate
constant kobs versus [CuACHTUNTRGNEUNG(OTf)2], the rate constant of coordi-
per(II) ion is coordinated to the spacer unit stoichiometri-
cally. Coordination of the copper(II) ion to the N-donor
unit of bis-Zn 9 is evidenced by the EPR spectrum, which is
clearly different from that of Cu
Figure 8. A decrease in the isotropic g value (g0 =2.124 for
bis-Zn/Cu and g0 =2.207 for Cu(OTf)2) and an increase in
the isotropic hyperfine coupling due to copper(II) ion (A0 =
87 G for bis-Zn/Cu and A0 =38 G for Cu(OTf)2) observed in
nation of CuACHTNUTRGNEG(UN OTf)2 to bis-Zn in a CH2Cl2/MeOH (1/1) at
298 K was determined to be kcoord. =4.0ꢂ104 mꢀ1 sꢀ1.
In PhCN/MeCN (1/1), electron transfer from bis-Zn 9 to
Cu
ACHTUNGRTEN(NGNU OTf)2 occurs following coordination of copper(II) in bis-
Zn 9 (Scheme 5), because the reduction potential of Cu-
ACHTUNGRTEN(NGNU OTf)2 (Supporting Information Figure S19: peak potential
Figure 8 are known to result from the stronger equatorial
ligand field caused by coordination of copper(II) ion to the
N donors of the spacer unit.[42]
at 0.52 V for CuII/CuI vs. Ag/AgNO3 in PhCN/MeCN) is
high enough to oxidize bis-Zn 9 and bis-Zn/Cu 10 to dicat-
ionic species in PhCN/MeCN.[43–45] Figure 10 shows spectral
Kinetic studies were performed by using a stopped-flow
UV/Vis spectroscopic technique. Transient absorption spec-
tra after addition of 10 equivalents of CuACTHNURTGNENG(U OTf)2 to bis-Zn 9
titration of bis-Zn 9 by CuACTHUNGTERNU(NG OTf)2 in PhCN/MeCN (1/1). Nei-
ther a decrease in absorbance at 558 nm due to neutral por-
phyrin nor an increase in absorbance at 620 nm due to por-
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S. Fukuzumi, J.-M. Barbe et al.
Scheme 5. Electron transfer from (TpTP)Zn to Cu
dination of copper(II) to bis-Zn 9 followed by electron transfer from bis-
Zn/Cu to Cu(OTf)2 (right).
ACHTUNGRTEN(NUGN OTf)2 (left), and coor-
AHCTUNGTRENNUNG
Figure 9. a) UV/Vis spectral changes on adding 10 equiv of CuACTHNUTRGNEUNG(OTf)2 to
bis-Zn 9 (3.5ꢂ10ꢀ5 m) in CH2Cl2/MeOH (1/1); inset: expanded view of
the absorbance at ꢁ600 nm. b) Absorbance changes at 450 and 598 nm.
c) Decay of DAbs. at 598 nm for different CuACTHNUTRGENUG(N OTf)2 concentrations;
inset: plot of kobs vs. [CuACHTUNGTRENNUNG(OTf)2].
phyrin radical cation was observed before addition of
1 equivalent of Cu(OTf)2 (Figure 10c). Further addition of
Cu(OTf)2 resulted in electron-transfer oxidation of bis-Zn/
Cu 10. The spectrum obtained after addition of 3 equiva-
lents of Cu
(OTf)2 agrees with the spectrum of [bis-Zn/Cu]2+
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
(Figure 5). This result indicates that 1:1 stoichiometric coor-
dination between bis-Zn 9 and copper(II) ion occurs prior
to electron transfer. In sharp contrast, only the electron-
transfer oxidation of the porphyrin ring takes place in case
Figure 10. UV/Vis spectral changes of bis-Zn 9 (3.0ꢂ10ꢀ5 m) on addition
of Cu(OTf)2. a) 0 to 1 equiv, b) 1 to 3 equiv in PhCN/MeCN (1/1) at
298 K. c) Absorbance (Abs.) changes at 558 and 620 nm.
AHCTUNGTRENNUNG
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Chem. Eur. J. 2011, 17, 10670 – 10681

Zinc Bis-Porphyrin Molecular Tweezers
FULL PAPER
of (TpTP)Zn on addition of Cu
ing Information). Stoichiometric oxidation of (TpTP)Zn
with 1 equivalent of Cu
(OTf)2 affords (TpTP)Zn·+.
Stopped-flow UV/Vis spectroscopy was used under the
same conditions to compare the rate constants of copper(II)
coordination to bis-Zn 9 and electron-transfer oxidation of
bis-Zn/Cu. The absorption spectrum of bis-Zn 9 changes im-
(OTf)2 (Figure S20, Support-
ent conditions. The pseudo-first-order rate constant kobs in-
creases linearly with increasing concentration of CuACHTUNGTRENNUNG(OTf)2
G
to give an electron-transfer rate constant of ket =5.3ꢂ
104 mꢀ1 sꢀ1 (Figure 11c).
Similar experiments were performed for (TpTP)Zn in the
presence of an excess of CuACTHNUTRGNE(UNG OTf)2 (Figure S22, Supporting
Information). The ket value for (TpTP)Zn was determined
to be 6.8ꢂ104 mꢀ1 sꢀ1. The slightly faster electron-transfer ox-
idation of (TpTP)Zn is in accordance with the lower oxida-
tion potential of (TpTP)Zn than that of bis-Zn/Cu (Table 1).
mediately after addition of 1 equivalent of CuACTHNUGTRENUNG(OTf)2 due to
copper(II) coordination (Figure S21, Supporting Informa-
tion). From the time profile of the spectral change at
598 nm, the coordination rate constant is estimated to be
greater than 107 mꢀ1 sꢀ1 in PhCN/MeCN. Once a copper(II)
ion is coordinated to bis-Zn 9 to form bis-Zn/Cu, two-elec-
tron oxidation of bis-Zn/Cu occurs on the millisecond time-
scale (Figure 11). The rise and decay at 620 and 558 nm, re-
spectively, obey pseudo-first-order kinetics under the pres-
Conclusion
Zinc bis-porphyrin molecular tweezers bis-Zn 9 was ob-
tained by multistep synthesis in high yield. Coordination of
a copper(II) ion inside the bridge of the molecular tweezers
induced a conformational change of the tweezers from an
open to a closed form. The two-electron oxidation potentials
of zinc porphyrin radical cations of bis-Zn 9 are split into
two one-electron oxidation potentials in the closed form of
the tweezers with coordinated copper(II) ion due to elec-
tronic communication between porphyrins in the two-elec-
tron-oxidized state. The rate constant of coordination of Cu-
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
occurred with a rate constant of 5.3ꢂ104 mꢀ1 sꢀ1 to afford
zinc porphyrin radical cations, which interact with each
other in the closed form of the tweezers. Such dynamics of
metal-ion coordination and electron transfer which induce
conformational changes of complexes provide a new basis
for the design of metal complexes whose electronic structure
and electron-transfer properties are well controlled by
metal-ion coordination.
Experimental Section
Chemicals and reagents: Silica gel (Merck; 70–120 mm) and alumina
(Merck; aluminum oxide 90 standardized) were used for column chroma-
tography. Analytical thin layer chromatography was performed on Merck
60 F254 silica gel (precoated sheets, 0.2 mm thick). Reactions were moni-
tored by thin-layer chromatography, UV/Vis spectroscopy, and MALDI/
TOF mass spectrometry. [RuIII
(PF6)3 was prepared from [RuII-
ACHUTGTNRNENUG(bpy)3]ACHTUNGTRENNUGN
AHCTUNGTRENNUNG
Erba) and CHCl3 for synthesis and dichloromethane, spectroscopic-grade
MeCN (Nacalai Tesque), and 2-MeTHF (Tokyo Chemical Industry Co.)
for analysis, were obtained commercially and used without further purifi-
cation. Benzonitrile was purchased from Wako Pure Chemical Industries
and distilled with P2O5 under reduced pressure.[47] THF (Acros) and tolu-
ene (Aldrich) for reactions were of reagent grade and dried and distilled
from sodium/benzophenone under nitrogen immediately before use.
Methyl-5-bromopyridine-2-carboxylate is commercially available and was
used as received. Zinc(II) tetra-p-tolylporphyrin[48] and 5-dihydrodipyrro-
methane[28] were synthesized as already described.
Figure 11. a) UV/Vis spectral changes of bis-Zn/Cu 10 (2.8ꢂ10ꢀ5 m) on
addition of Cu
rise and decay at 558 and 620 nm. b) Increase in Abs. at 620 nm for dif-
ferent Cu(OTf)2 concentrations. c) Plot of kobs vs. [Cu(OTf)2].
ACHTUNGTRENNUNG
(OTf)2 (6.0ꢂ10ꢀ4 m) in a PhCN/MeCN (1:1) mixture; inset:
Physicochemical characterization of compounds: 1H NMR and 13C NMR
spectra for synthesized compounds were recorded on a Bruker DRX-300
A
U
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10677

S. Fukuzumi, J.-M. Barbe et al.
AVANCE spectrometer and a Bruker DRX-600 AVANCE II spectrome-
ter, respectively, at the Plateforme dꢃAnalyse Chimique et de Synthꢄse
Molꢀculaire de lꢃUniversitꢀ de Bourgogne (PACSMUB). Chemical shifts
for 1H NMR spectra are expressed in parts per million (ppm) relative to
chloroform (7.26 ppm) or [D5]pyridine (7.22, 7.58, and 8.74 ppm). Chemi-
cal shifts for 13C NMR spectra are expressed in ppm relative to
[D5]pyridine (123.87, 135.91, and 150.35 ppm). The mass spectra were ob-
tained on a Bruker Daltonics Ultraflex II spectrometer at PACSMUB in
the MALDI/TOF reflectron mode with dithranol as matrix. High-resolu-
tion mass spectra (HRMS) were recorded on a Bruker Daltonics Ultra-
flex II with polyethylene glycol ion series as internal calibrant or on a
Bruker Micro-ToF Q instrument in ESI mode. GC-MS analysis was car-
ried out on a Thermo Trace GC-Ultra-DSQII instrument in EI ionization
mode (Thermo TR-5MS nonpolar column, 0.25 mm diameterꢂ30 m
length). Microanalyses were performed on a CHNS/O Analysis Thermo
Electron Flash EA 1112 Series.
tion of phenyllithium (2m, 0.54 mL, 1.08 mmol). After 15 min of stirring
at 08C and 15 min of stirring at RT, water/THF (10%, 10 mL) was care-
fully added. The reaction mixture was stirred for 10 min at RT and 2,3-di-
chloro-5,6-dicyano-p-benzoquinone (DDQ; 164.2 mg, 0.72 mmol) was
added. After 1 h, the reaction mixture was filtered over alumina gel
(CH2Cl2) and column chromatography over alumina gel (heptane/CH2Cl2
1
3/1) gave 2 (79.2 mg, 70%). H NMR (300 MHz, CDCl3): d=2.73 (s, 6H;
3
3
CH3), 7.57 (d, J=7.7 Hz, 4H; Hm-tolyl), 7.74 (d, J=7.6 Hz, 2H; Hm-phenyl),
7.75 (dd, 3J1 =3J2 =7.6 Hz, 1H; Hp-phenyl), 8.09 (d, 3J=7.7 Hz, 4H; Ho-tolyl),
8.21 (dd, 3J1 =7.6 Hz, 3J2 =1.6 Hz, 2H; Ho-phenyl), 8.95 (d, 3J=4.5 Hz, 2H;
3
3
H
b-pyrr.), 9.00 (d, J=4.5 Hz, 2H; Hb-pyrr.), 9.01 (d, J=4.5 Hz, 2H; Hb-pyrr.),
9.21 (d, 3J=4.5 Hz, 2H;
Hb-pyrr.), 9.99 ppm (s, 1H; Hmeso); UV/Vis
(CH2Cl2): lmax (10ꢀ3 e)=415 (471), 544 (18.7), 581 nm (2.7mꢀ1 cmꢀ1); MS
(MALDI/TOF): m/z calcd for C40H29N4Zn+: 629.17; found: 628.90
[M+H]+.
Zinc(II) 5,15-p-tolyl-10-phenyl-20-bromoporphyrin (3): Zinc(II) 5,15-p-
Photophysical measurements: UV/Vis/NIR spectra were recorded on a
Varian Cary 1 spectrophotometer, a Shimadzu UV-3100PC spectrometer,
or a Hewlett Packard 8453 diode-array spectrophotometer. Kinetic meas-
urements were performed by using a UNISOKU RSP-601 stopped-flow
spectrophotometer with an MOS-type high-sensitivity photodiode array.
Pseudo-first-order rate constants were determined by least-squares curve
fits.
tolyl-10-phenylporphyrin
2 (140.3 mg, 0.223 mmol) was dissolved in
CH2Cl2 (220 mL) and cooled to 08C. After adding two drops of pyridine
and recrystallized N-bromosuccinimide (43.8 mg, 0.246 mmol), reaction
mixture was stirred for 30 min at 08C. Then, reaction was quenched by
acetone (11 mL). The organic layer was washed three times with distilled
water, dried over magnesium sulfate, and the solvent evaporated. The
crude product was purified by column chromatography over silica gel
1
(CH2Cl2), affording the porphyrin 3 (142.1 mg, 90%). The H NMR spec-
trum of free base 3’ was measured after demetalation of 3. H NMR of 3’
Electrochemical measurements: Cyclic voltammetry (CV) and differen-
tial pulse voltammetry (DPV) were carried out with a BAS 100W electro-
chemical analyzer in a deaerated solvent containing 0.10m nBu4NPF6 as a
supporting electrolyte at 298 K. A conventional three-electrode cell was
used with a platinum working electrode and a platinum wire as countere-
lectrode. The redox potentials were measured with respect to the Ag/
AgNO3 (1.0ꢂ10ꢀ2 m) reference electrode. The oxidation potential of fer-
rocene as external standard is 0.06 V in PhCN.
1
(300 MHz, CDCl3): d=ꢀ2.74 (s, 2H; NH), 2.71 (s, 6H; CH3), 7.55 (d,
3J=7.7 Hz, 4H; Hm-tolyl), 7.73 (d, J=7.6 Hz, 2H; Hm-phenyl), 7.74 (dd, J1 =
3
3
3J2 =7.6 Hz, 1H; Hp-phenyl), 8.06 (d, J=7.7 Hz, 4H; Ho-tolyl), 8.18 (dd, J1 =
3
3
7.6 Hz, 4J2 =1.6 Hz, 2H; Ho-phenyl), 8.78 (d, 3J=4.5 Hz, 2H; Hb-pyrr.), 9.82
3
3
(d, J=4.5 Hz, 2H; Hb-pyrr.), 8.91 (d, J=4.5 Hz, 2H; Hb-pyrr.), 9.64 ppm (d,
3J=4.5 Hz, 2H; Hb-pyrr.); UV/Vis (CH2Cl2): lmax (10ꢀ3 e)=423 (446), 555
(16.7), 597 nm (5.6mꢀ1 cmꢀ1); MS (MALDI/TOF): m/z calcd for
C40H28BrN4Zn+: 707.08; found: 706.86 [M+H]+.
EPR measurements: The EPR spectra were measured with a JEOL X-
band spectrometer (JES-RE1XE). The EPR spectra were recorded
under nonsaturating microwave power. The magnitude of the modulation
was chosen to optimize the resolution and the signal-to-noise ratio of the
observed spectra. The g values were calibrated with an Mn2+ marker.
PhCN solutions were deaerated by argon purging for 10 min prior to use.
Zinc(II) 5,15-di-p-tolyl-10-phenyl-20-[4’,4’,5’,5’-tetramethyl-(1’,2’,3’dioxa-
borolan-2’-yl)]porphyrin (4): Under nitrogen atmosphere, triethylamine
(0.32 mL, 2.30 mmol), trans-[PdCl2ACHTNUTRGENNUG(PPh3)] (3.8 mg, 0.005 mmol), pinacol-
borane (0.21 mL, 1.45 mmol), and 3 (124.1 mg, 0.18 mmol) were dissolved
in 1,2-dichloroethane (20 mL) dried over molecular sieves. After 1 h at
reflux, the reaction mixture was cooled to RT. The reaction was
quenched by adding an aqueous solution of KCl (30%, 7 mL) and the
product extracted with CH2Cl2 (100 mL). The organic layer was washed
three times with distilled water, dried over magnesium sulfate, and the
solvent evaporated. The crude product was purified by column chroma-
tography over silica gel (CH2Cl2/heptane 1/1), affording porphyrin 4
(131.9 mg, 99%). 1H NMR (300 MHz, CDCl3): d=1.85 (s, 12H; CH3),
Theoretical calculations: DFT calculations were performed on a 32-pro-
cessor QuantumCube. Geometry optimizations were carried out with the
Becke 3LYP functional and LanL2DZ basis set in Gaussian 09, revisio-
n A.02.[49] The graphics were drawn with the Gauss View software pro-
gram (version 5.0) developed by Semichem.
5,15-Di-p-tolylporphyrin (1): p-Tolualdehyde (1 mL, 8.45 mmol) and tri-
fluoroacetic acid (0.40 mL, 5.38 mmol) were added to a solution of 5-di-
hydrodipyrromethane (1.25 g, 8.55 mmol) in degassed CH2Cl2 (1.5 L).
Under nitrogen atmosphere, the solution was stirred for 3 h at RT in the
dark. After adding tetrachloro-p-benzoquinone (TCQ; 3.15 g,
12.81 mmol), the reaction mixture was stirred for three more hours. Trie-
thylamine (3 mL) was added and the reaction mixture was filtered
through alumina gel. Compound 1 was eluted with CH2Cl2 and recrystal-
lized from CH2Cl2/MeOH (1.00 g, 49%). 1H NMR (300 MHz, CDCl3):
d=ꢀ3.11 (s, 2H; NH), 2.72 (s, 6H; CH3), 7.61 (d, 3J=7.7 Hz, 4H; Hm-
tolyl), 8.15 (d, 3J=7.7 Hz, 4H; Ho-tolyl), 9.09 (d, 3J=4.5 Hz, 4H; Hb-pyrr.),
3
3
2.71 (s, 6H; PhCH3), 7.55 (d, J=7.7 Hz, 4H; Hm-tolyl), 7.73 (d, J=7.6 Hz,
2H; Hm-phenyl), 7.74 (dd, 3J1 =3J2 =7.6 Hz, 1H; Hp-phenyl), 8.10 (d, 3J=
7.7 Hz, 4H; Ho-tolyl), 8.20 (dd, 3J1 =7.6 Hz, 4J2 =1.6 Hz, 2H; Ho-phenyl), 8.94
3
3
(d, J=4.5 Hz, 2H; Hb-pyrr.), 9.82 (d, 3J=4.5 Hz, 2H; Hb-pyrr.), 9.10 (d, J=
4.5 Hz, 2H;
H Hb-pyrr.); UV/Vis
b-pyrr.), 9.90 ppm (d, 3J=4.5 Hz, 2H;
(CH2Cl2): lmax (10ꢀ3 e)=418 (366), 548 (13.1), 584 nm (1.4mꢀ1 cmꢀ1); MS
(MALDI/TOF): m/z calcd for C40H40BN4O2Zn+: 755.25; found: 755.22
[M+H]+.
2-Bromo-2-hydroxymethylpyridine (5):[50] A solution of ethyl 5-bromo-
pyridine-2-carboxylate (1.00 g, 4.63 mmol) in MeOH (20 mL) was cooled
to 08C. Sodium borohydride (0.92 g, 24.33 mmol) was added portionwise.
After 4 h of stirring at RT, the solvent was evaporated. Then, distilled
water was added and the product extracted with CH2Cl2. The organic
layer was washed two times with distilled water, dried over magnesium
sulfate and the solvent evaporated to afford 5 (0.58 g, 67%) without any
purification. 1H NMR (300 MHz, CDCl3): d=4.74 (s, 2H; CH2OH), 4.89
(s, 1H; OH), 7.21 (d, 3J=8.2 Hz, 1H; H3), 7.83 (dd, 3J1 =8.2 Hz, 4J2 =
1.5 Hz, 1H; H4), 8.63 ppm (d, 4J=1.5 Hz, 1H; H6); GC-MS (EI, 70 eV):
m/z calcd for C6H6BrNO+: 187.0; found: 187.0 (8) [M]+; m/z calcd for
C5H4BrN+: 157.0; found: 157.0 (15) [MꢀCH2OH]+.
9.37 (d, 3J=4.5 Hz, 4H;
Hb-pyrr.), 10.29 ppm (s, 2H; Hmeso); UV/Vis
(CH2Cl2): lmax (10ꢀ3 e)=407 (321), 503 (15.1), 538 (6.0), 577 (5.5), 631 nm
(2.4mꢀ1 cmꢀ1); MS (MALDI/TOF): m/z calcd for C34H27N4+: 491.22;
found: 490.86 [M+H]+.
Zinc(II) 5,15-di-p-tolyl-10-phenylporphyrin (2): 5,15-p-Tolylporphyrin 1
(89.8 mg, 0.18 mmol) was dissolved in CHCl3 (100 mL), and a solution of
zinc(II) acetate dihydrate (80.4 mg, 0.37 mmol) and anhydrous sodium
acetate (61.0 mg, 0.74 mmol) in MeOH (100 mL) was added. After 2 h at
reflux, the reaction mixture was cooled to RT. The organic layer was
washed three times with a solution of water saturated in sodium bicar-
bonate, dried over magnesium sulfate, and the solvent evaporated. The
crude product was purified by column chromatography over silica gel
(CH2Cl2), affording the metalated porphyrin (100.4 mg, 0.18 mmol). This
was then dissolved in distilled and degassed THF (55 mL). Under argon,
the reaction mixture was cooled to 08C before adding dropwise a solu-
2-Chloromethyl-5-bromopyridine (6):[51] Compound 5 (1.61 g, 8.56 mmol)
was dissolved in toluene (40 mL). Thionyl chloride (1.9 mL, 26.19 mmol)
was added dropwise. After 3 h of stirring at RT, the reaction mixture was
10678
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Chem. Eur. J. 2011, 17, 10670 – 10681

Zinc Bis-Porphyrin Molecular Tweezers
FULL PAPER
quenched by addition of an aqueous solution saturated with sodium bi-
carbonate. The crude product was extracted three times with CH2Cl2.
The organic layer was dried over magnesium sulfate and the solvent
evaporated to give 6 (1.48 g, 84%) without any purification. 1H NMR
(10ꢀ3 e)=422 (639), 551 (26.2), 606 nm (6.8mꢀ1 cmꢀ1); MS (MALDI/
+
TOF): m/z calcd for C97H76CuN12Zn2
: 1599.42; found: 1599.40
[Mꢀ2OAc]+; HR-MS (ESI/TOF) m/z calcd for C97H76CuN12Zn2
1599.4189; found: 1599.4124 [Mꢀ2OAc]+.
:
+
3
(300 MHz, CDCl3): d=4.67 (s, 2H; CH2Cl), 7.43 (d, J=8.2 Hz, 1H; H3),
3
4
7.90 (dd, J1 =8.2 Hz, J2 =2.2 Hz, 1H; H4), 8.64 ppm (d, 4J=2.2 Hz, 1H;
H6); GC-MS (EI, 70 eV): m/z calcd for C6H5ClBrN+: 204.9; found: 204.9
(38) [M]+; m/z calcd for C6H5BrN+: 170.0; found: 169.9 (60) [MꢀCl]+.
N,N’-Bis[(5-bromopyrid-2-yl)methyl]-N,N’-dimethylpropane-1,3-diamine
(7): Potassium carbonate (3.6 g, 26.05 mmol) was introduced into a three-
neck round-bottom flask. After three vacuum/argon cycles, 6 (1.34 g,
6.49 mmol) and N,N’-dimethylpropane-1,3-diamine (0.47 mL, 3.24 mmol)
dissolved in acetonitrile (90 mL) were added. After three days of stirring
at RT, the crude product was extracted with CH2Cl2. The organic layer
was washed three times with distilled water, dried over magnesium sul-
fate, and the solvent evaporated at 408C to obtain 7 (1.42 g, 99%) with-
out any purification. 1H NMR (300 MHz, CDCl3): d=1.65 (qt, 3J=
7.0 Hz, 2H; CH2CH2CH2), 2.15 (s, 6H; CH3), 2.37 (t, 3J=7.0 Hz, 4H;
CH2CH2CH2), 3.50 (s, 4H; CH2Py), 7.21 (d, 3J=8.2 Hz, 2H; H3), 7.67
Acknowledgements
We are grateful to Dr. Kei Ohkubo (Osaka University) for his valuable
cooperation in theoretical studies. The Ministry of Research, the Burgun-
dy Council, and the “Centre National de Recherche Scientifique”
(CNRS; UMR 5260) are acknowledged for funding this research. B.H.
acknowledges a Ph.D. support grant from the CNRS and the Burgundy
Council. A.T. appreciates financial support from JSPS fellowship for
young scientists. B.H. and A.T. also appreciate support of an internship
from the Global COE program “Global Education and Research Center
for Bio-Environmental Chemistry” of Osaka University (S.F.). Grants-in-
Aid (no. 20108010) from the Ministry of Education, Culture, Sports, Sci-
ence and Technology, Japan and KOSEF/MEST through WCU project
(R31-2008-000-10010-0) of Korea are also acknowledged for funding.
3
4
4
(dd, J1 =8.2 Hz, J2 =2.2 Hz, 2H; H4), 8.50 ppm (d, J=2.2 Hz, 2H; H6);
MS: compound 7 could not be characterized by mass spectrometry due
to its instability.
N,N’-Bis[({5-
methyl]-N,N’-dimethylpropane-1,3-diamine (9): Sodium iodide (0.24 g,
1.60 mmol), cesium(I) carbonate (1.61 g, 4,94 mmol), [{PdCl
(h3-C3H5)}2]
(57.3 mg, 0.16 mmol), and triphenylphosphine (169.9 mg, 0.65 mmol)
were introduced into three-neck round-bottom flask. After three
A
5,15-p-tolyl-10-phenylporphyrin]}pyrid-2-yl)-
AHCTUNGTRENNUNG
[1] a) The Reaction Center of Photosynthetic Bacteria (Ed.: M. E.
Michel-Beyerle), Springer, Berlin, 1996; b) The Photosynthetic Reac-
tion Center (Eds.: J. Deisenhofer, J. R. Norris), Academic Press, San
Diego, 1993; c) P. Heathcote, P. K. Fyfe, M. R. Jones, Trends Bio-
chem. Sci. 2002, 27, 79; d) A. Remy, K. Gerwert, Nat. Struct. Biol.
2003, 10, 637.
[2] a) S. G. Boxer, Annu. Rev. Biophys. Biophys. Chem. 1990, 19, 267;
b) G. T. Babcock, Proc. Natl. Acad. Sci. USA 1999, 96, 12971;
c) H. B. Gray, J. R. Winkler, Biochim. Biophys. Acta Bioenerg. 2010,
1797, 1563.
[3] a) A. Amunts, O. Drory, N. Nelson, Nature 2007, 447, 58; b) B. Loll,
J. Kern, W. Saenger, A. Zouni, J. Biesiadka, Nature 2005, 438, 1040;
c) A. A. Pascal, Z. Liu, K. Broess, B. van Oort, H. van Amerongen,
C. Wang, P. Horton, B. Robert, W. Chang, A. Ruban, Nature 2005,
436, 134; d) K. N. Ferreira, T. M. Iverson, K. Maghlaoui, J. Barber,
S. Iwata, Science 2004, 303, 1831; e) Z. Liu, H. Yan, K. Wang, T.
Kuang, J. Zhang, L. Gui, X. An, W. Chang, Nature 2004, 428, 287.
[4] a) D. Gust, T. A. Moore, A. L. Moore, Acc. Chem. Res. 2009, 42,
1890; b) N. Aratani, D. Kim, A. Osuka, Acc. Chem. Res. 2009, 42,
1922.
[5] a) M. Tanaka, K. Ohkubo, C. P. Gros, R. Guilard, S. Fukuzumi, J.
Am. Chem. Soc. 2006, 128, 14625; b) A. Takai, M. Chkounda, A. Eg-
genspiller, C. P. Gros, M. Lachkar, J.-M. Barbe, S. Fukuzumi, J. Am.
Chem. Soc. 2010, 132, 4477; c) S. Fukuzumi, Org. Biomol. Chem.
2003, 1, 609; d) S. Fukuzumi, Bull. Chem. Soc. Jpn. 2006, 79, 177;
e) S. Fukuzumi, Phys. Chem. Chem. Phys. 2008, 10, 2283; f) S. Fuku-
zumi, T. Kojima, J. Mater. Chem. 2008, 18, 1427; g) S. Fukuzumi, T.
Honda, K. Ohkubo, T. Kojima, Dalton Trans. 2009, 3880.
a
vacuum/argon cycles, DMF (90 mL) dried over molecular sieves and dis-
tilled toluene (150 mL) containing 7 (0.73 g, 1.65 mmol) were added. The
reaction mixture was heated at 808C for 12 h before addition of 4 (1.21 g,
1.60 mmol) in distilled toluene (50 mL). The reaction mixture was then
heated to reflux for a further 12 h at 808C. After cooling to RT, the or-
ganic layer was washed three times with an aqueous solution saturated
with sodium bicarbonate, dried over magnesium sulfate, and the solvent
evaporated. The crude product was purified by column chromatography
over silica gel neutralized by adding triethylamine (eluent: CH2Cl2 then
CH2Cl2/EtOH/NH3 (25% in water) 80/20/1) to obtain 9 (634.3 mg, 52%).
1H NMR (300 MHz, [D5]pyridine): d=2.04 (qt, 3J=7.0 Hz, 2H;
CH2CH2CH2), 2.40 (s, 12H; PhCH3), 2.51 (s, 6H; NCH3), 2.84 (t, 3J=
7.0 Hz, 4H; CH2CH2CH2), 4.18 (s, 4H; CH2Py), 7.33 (d, 3J=7.7 Hz, 8H;
3
3
H
H
m-tolyl), 7.64 (d, J=5.2 Hz, 4H; Hm-phenyl), 7.65 (dd, J1 =3J2 =5.2 Hz, 2H;
p-phenyl), 8.04 (d, J=7.7 Hz, 2H; H3), 8.11 (dd, J1 =3J2 =5.4 Hz, 8H; Ho-
3
3
tolyl), 8.27 (dd, 3J1 =5.4 Hz, 4J2 =1.5 Hz, 4H; Ho-phenyl), 8.64 (dd, 3J1 =
8.2 Hz, 4J2 =2.2 Hz, 2H; H4), 9.04 (d, 3J=4.5 Hz, 4H; Hb-pyrr.), 9.08 (d,
3J=4.5 Hz, 8H; Hb-pyrr.), 9.10 (d, 3J=4.5 Hz, 4H; Hb-pyrr.), 9.64 ppm (d,
4J=2.2 Hz, 2H; H6); 13C DEPT-135 NMR (150 MHz, [D5]pyridine): d=
22.0 (4 PhCH3), 26.5 (CH2CH2CH2), 43.1–43.5 (2NCH3), 56.1–56.4
(CH2CH2CH2), 64.2–65.0 (2CH2Py), 117.7 (2Cmeso), 119.7 (2Cmeso), 121.8
(2CHpy), 122.2 (4Cmeso), 127.5 (6CHphenyl), 128.3 (8CHtolyl), 132.3–133.4
(16CHꢅ-pyrr.), 135.6 (8CHtolyl +4CHphenyl), 137.8 (4Ctolyl), 138.3 (2Cphenyl),
139.7 (2CHpy), 141.4 (4Ctolyl), 144.4 (2Cpy), 151.2–151.6 (16Cpyrr.), 154.0
(2CHpy), 160.1 ppm (2Cpy); UV/Vis (CH2Cl2): lmax (10ꢀ3 e)=421 (655),
551 (22.4), 603 nm (8.7mꢀ1 cmꢀ1); MS (MALDI/TOF): m/z calcd for
C97H77N12Zn2+: 1537.50; found: 1537.40 [M+H]+; HRMS (ESI/TOF):
m/z calcd for C97H77N12Zn2+: 1537.4972; found: 1537.4814 [M+H]+; ele-
mental analysis calcd (%) for C97H76N12Zn2·CH2Cl2·2EtOH·2NH3:
C 69.94, H 5.52, N 11.19; found: C 69.93, H 5.75, N 11.13.
[6] a) S. Faure, C. Stern, R. Guilard, P. D. Harvey, J. Am. Chem. Soc.
2004, 126, 1253; b) M. A. Filatov, R. Guilard, P. D. Harvey, Org.
Lett. 2010, 12, 196; c) P. D. Harvey, C. Stern, C. P. Gros, R. Guilard,
Coord. Chem. Rev. 2007, 251, 401; d) P. D. Harvey, N. Proulx, G.
Martin, M. Drouin, D. J. Nurco, K. M. Smith, F. Bolze, C. P. Gros, R.
Guilard, Inorg. Chem. 2001, 40, 4134.
N,N’-Bis[({5-
G
5,15-p-tolyl-10-phenylporphyrin]}-pyrid-2-yl)-
methyl]-N,N’-dimethylpropane-1,3-diamine copper(II) (10): A solution of
MeOH (5 mL) containing copper(II) acetate monohydrate (31.1 mg,
0.156 mmol) was added to a solution of 9 (53.0 mg, 0.034 mmol) in
CH2Cl2 (10 mL). The reaction mixture was stirred for 5 min at RT. Then
the crude product was extracted with CH2Cl2 and the organic layer
washed three times with distilled water, dried over magnesium sulfate,
and the solvent evaporated. Purification by column chromatography over
silica gel neutralized by adding triethylamine (eluent: CH2Cl2 then
CH2Cl2/EtOH/NH3 (25% in water) 80/20/1) and recrystallization from
CH2Cl2/MeOH yielded 10 (38.6 mg, 65%);.UV/Vis (CH2Cl2): lmax
[7] a) D. Sun, F. S. Tham, C. A. Reed, L. Chaker, P. D. Boyd, J. Am.
Chem. Soc. 2002, 124, 6604; b) L. Flamigni, M. R. Johnston, L. Giri-
babu, Chem. Eur. J. 2002, 8, 3938; c) R. Rein, M. Gross, N. Solladiꢀ,
Chem. Commun. 2004, 1992; d) L. Flamigni, A. M. Talarico, B. Ven-
tura, R. Rein, N. Solladiꢀ, Chem. Eur. J. 2006, 12, 701.
[8] a) F. DꢃSouza, O. Ito, Coord. Chem. Rev. 2005, 249, 1410; b) F.
DꢃSouza, R. Chitta, S. Gadde, L. M. Rogers, P. A. Karr, M. E. Zan-
dler, A. S. Sandanayaka, Y. Araki, O. Ito, Chem. Eur. J. 2007, 13,
916; c) R. Chitta, F. DꢃSouza, J. Mater. Chem. 2008, 18, 1440; d) F.
DꢃSouza, E. Maligaspe, K. Ohkubo, M. E. Zandler, N. K. Subbaiyan,
Chem. Eur. J. 2011, 17, 10670 – 10681
ꢁ 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
10679

S. Fukuzumi, J.-M. Barbe et al.
S. Fukuzumi, J. Am. Chem. Soc. 2009, 131, 8787; e) F. DꢃSouza, O.
Ito, Chem. Commun. 2009, 4913.
[9] a) D. M. Guldi, Chem. Soc. Rev. 2002, 31, 22; b) D. M. Guldi,
G. M. A. Rahman, F. Zerbetto, M. Prato, Acc. Chem. Res. 2005, 38,
871; c) D. M. Guldi, Pure Appl. Chem. 2003, 75, 1069.
[10] A. Takai, C. P. Gros, J.-M. Barbe, R. Guilard, S. Fukuzumi, Chem.
Eur. J. 2009, 15, 3110.
[11] A. Takai, C. P. Gros, J.-M. Barbe, S. Fukuzumi, Phys. Chem. Chem.
Phys. 2010, 12, 12160.
[22] a) C. Zhong, M. Zhao, C. Stern, A. G. M. Barrett, B. M. Hoffman,
Inorg. Chem. 2005, 44, 8272; b) T. Kojima, N. Hirasa, D. Noguchi, T.
Ishizuka, S. Miyazaki, Y. Shiota, K. Yoshizawa, S. Fukuzumi, Inorg.
Chem. 2010, 49, 3737.
[23] E. Karnas, S. K. Kim, K. A. Johnson, J. L. Sessler, K. Ohkubo, S. Fu-
kuzumi, J. Am. Chem. Soc. 2010, 132, 16617.
[24] M. El Ojaimi, B. Habermeyer, C. P. Gros, J.-M. Barbe, J. Porphyrins
Phthalocyanines 2010, 14, 469.
[25] a) R. G. Little, J. Heterocycl. Chem. 1981, 18, 129; b) R. G. Little,
J. A. Anton, P. A. Loach, J. A. Ibers, J. Heterocycl. Chem. 1975, 12,
343.
[26] a) A. Markovac, S. F. MacDonald, Can. J. Chem. 1965, 43, 3364;
b) R. B. Woodward, Angew. Chem. 1960, 72, 651.
[27] a) M. O. Senge, X. Feng, J. Chem. Soc. Perkin Trans. 1 2000, 3615;
b) M. O. Senge, Y. M. Shaker, M. Pintea, C. Ryppa, S. S. Hatscher,
A. Ryan, Y. Sergeeva, Eur. J. Org. Chem. 2010, 237.
[28] J. K. Laha, S. Dhanalekshmi, M. Taniguchi, A. Ambroise, J. S. Lind-
sey, Org. Process Res. Dev. 2003, 7, 799.
[29] L. L. Chng, C. J. Chang, D. G. Nocera, J. Org. Chem. 2003, 68, 4075.
[30] a) A. G. Hyslop, M. A. Kellett, P. M. Iovine, M. J. Therien, J. Am.
Chem. Soc. 1998, 120, 12676; b) N. Miyaura, A. Suzuki, Chem. Rev.
1995, 95, 2457.
[31] M. Murata, S. Watanabe, Y. Masuda, J. Org. Chem. 1997, 62, 6458.
[32] a) A. Bencini, I. Bertini, D. Gatteschi, A. Scozzafava, Inorg. Chem.
1978, 17, 3194; b) H. Ohtsu, Y. Shimazaki, A. Odani, O. Yamauchi,
W. Mori, S. Itoh, S. Fukuzumi, J. Am. Chem. Soc. 2000, 122, 5733;
c) S. Goubert-Renaudin, M. Etienne, S. Brandes, M. Meyer, F.
Denat, B. Lebeau, A. Walcarius, Langmuir 2009, 25, 9804.
[33] The same absorption maxima are also observed for mono-pyridyl-
substituted porphyrins. This indicates that a single pyridyl group
scarcely affects the electronic structure of porphyrins.[24]
[34] The open form of bis-Zn 9 (Figure 2a) was always obtained as the
optimized structure even when the calculation started from the
closed structure. The heat of formation for the open form of bis-Zn
9 is more negative by 40 kcal than that of the closed form, according
to single-point energy calculation.
[12] a) I. C. Lewis, L. S. Singer, J. Chem. Phys. 1965, 43, 2712; b) T. Bally,
K. Roth, R. Straub, J. Am. Chem. Soc. 1988, 110, 1639; c) H. Yokoi,
A. Hatta, K. Ishiguro, Y. Sawaki, J. Am. Chem. Soc. 1998, 120,
12728; d) T. Tachikawa, S. Tojo, M. Fujitsuka, T. Majima, Langmuir
2004, 20, 4327; e) T. N. Das, J. Phys. Chem. A 2009, 113, 6489.
[13] a) E. C. Lim, Res. Chem. Intermed. 2002, 28, 779; b) B. K. Mishra,
V. K. Bajpai, V. Ramanathan, S. R. Gadre, N. Sathyamurthy, Mol.
Phys. 2008, 106, 1557; c) R. Montero, A. Longarte, R. Martꢆnez,
M. N. Sꢇnchez Rayo, F. CastaÇo, Chem. Phys. Lett. 2009, 468, 134;
d) I. A. Shkrob, M. C. Sauer, Jr., A. D. Liu, R. A. Crowell, A. D. Tri-
funac, J. Phys. Chem. A 1998, 102, 4976.
[14] a) D. Small, V. Zaitsev, Y. Jung, S. V. Rosokha, M. Head-Gordon,
J. K. Kochi, J. Am. Chem. Soc. 2004, 126, 13850; b) J. K. Kochi, R.
Rathore, P. L. Magueres, J. Org. Chem. 2000, 65, 6826; c) V. Gane-
san, S. V. Rosokha, J. K. Kochi, J. Am. Chem. Soc. 2003, 125, 2559;
d) J.-M. Lꢈ, S. V. Rosokha, J. K. Kochi, J. Am. Chem. Soc. 2003, 125,
12161.
[15] a) W. R. Scheidt, B. S. Cheng, K. J. Haller, A. Mislankar, A. D. Rae,
K. V. Reddy, H. S. Song, R. D. Orosz, C. A. Reed, F. Cukiernik, J. C.
Marchon, J. Am. Chem. Soc. 1993, 115, 1181; b) W. R. Scheidt, K. E.
Brancato-Buentello, H. S. Song, K. V. Reddy, B. S. Cheng, Inorg.
Chem. 1996, 35, 7500; c) K. E. Brancato-Buentello, S. J. Kang, W. R.
Scheidt, J. Am. Chem. Soc. 1997, 119, 2839; d) K. E. Brancato-Buen-
tello, W. R. Scheidt, Angew. Chem. 1997, 109, 1608; Angew. Chem.
Int. Ed. Engl. 1997, 36, 1456; e) W. R. Scheidt, J. Biol. Inorg. Chem.
2001, 6, 727.
[16] a) S. Fukuzumi, R. Hanazaki, H. Kotani, K. Ohkubo, J. Am. Chem.
Soc. 2010, 132, 11002; b) S. Fukuzumi, H. Kotani, K. Ohkubo, Phys.
Chem. Chem. Phys. 2008, 10, 5159.
[17] J. S. Park, E. Karnas, K. Ohkubo, P. Chen, K. M. Kadish, S. Fukuzu-
mi, C. W. Bielawski, T. W. Hudnall, V. M. Lynch, J. L. Sessler, Sci-
ence 2010, 329, 1324.
[35] A. Satake, Y. Kobuke, Org. Biomol. Chem. 2007, 5, 1679.
[36] T. Pandiyan, H. J. Guadalupe, J. Cruz, S. Bernes, V. M. Ugalde-Sal-
vdivar, I. Gonzalez, Eur. J. Inorg. Chem. 2008, 3274.
[37] The peak-to-peak separations of redox waves for bis-Zn/Cu 10 in
Figure 3c are 110, 130, and 120 mV. These values are slightly larger
than those of ferrocene and (TpTP)Zn (80 mV). Nevertheless, the
cyclic voltammograms clearly exhibit three pairs of redox waves.
[38] The current intensity at 1.03 V seems larger than that of the third
oxidation process of the porphyrin units at 0.67 V, because one-elec-
tron oxidation of the CuII-coordinated spacer (1.04 V) overlaps, as
shown in Figure S14a and S14b of the Supporting Information. Simi-
larly, the broadened redox wave of bis-Zn 9 at around 0.68 V is due
to overlap of the oxidation process of the pristine spacer unit (Fig-
ure S14c, Supporting Information).
[39] a) R. Guilard, J.-M. Barbe, C. Stern, K. M. Kadish in The Porphyrin
Handbook, Vol. 18 (Eds.: K. M. Kadish, K. M. Smith, R. Guilard),
Academic Press, San Diego, 2003, p. 303; b) Y. Le Mest, M. LꢃHer,
N. H. Hendricks, K. Kim, J. P. Collman, Inorg. Chem. 1992, 31, 835;
c) D. A. Shultz, H. Lee, R. K. Kumar, K. P. Gwaltney, J. Org. Chem.
1999, 64, 9124; d) G. Pognon, C. Boudon, K. J. Schenk, M. Bonin, B.
Bach, J. Weiss, J. Am. Chem. Soc. 2006, 128, 3488.
[18] a) C. Dietrich-Buchecker, J.-P. Sauvage, Chem. Rev. 1987, 87, 795;
b) D. B. Amabilino, J. F. Stoddart, Chem. Rev. 1995, 95, 2725; c) J.-C.
Chambron, J.-P. Collin, J.-O. Dalbavie, C. O. Dietrich-Buchecker, V.
Heitz, F. Odobel, N. Solladiꢀ, J.-P. Sauvage, Coord. Chem. Rev. 1998,
178, 1299; d) J.-P. Sauvage, Acc. Chem. Res. 1998, 31, 611; e) L. Fla-
migni, V. Heitz, J.-P. Sauvage, Struct. Bonding (Berlin) 2006, 121,
217; f) M. D. Lankshear, P. D. Beer, Acc. Chem. Res. 2007, 40, 657;
g) J. A. Faiz, V. Heitz, J.-P. Sauvage, Chem. Soc. Rev. 2009, 38, 422;
h) J.-P. Sauvage, J.-P. Collin, S. Durot, J. Frey, V. Heitz, A. Sour, C.
Tock, C. R. Chim. 2010, 13, 315.
[19] a) M. Andersson, M. Linke, J. C. Chambron, J. Davidsson, V. Heitz,
L. Hammarstrçm, J.-P. Sauvage, J. Am. Chem. Soc. 2002, 124, 4347;
b) M. Beyler, V. Heitz, J.-P. Sauvage, J. Am. Chem. Soc. 2010, 132,
4409; c) J.-P. Collin, F. Durola, J. Frey, V. Heitz, F. Reviriego, J.-P.
Sauvage, Y. Trolez, K. Rissanen, J. Am. Chem. Soc. 2010, 132, 6840.
[20] a) Y. Tomohiro, A. Satake, Y. Kobuke, J. Org. Chem. 2001, 66, 8442;
b) S. Richeter, C. Jeandon, J.-P. Gisselbrecht, R. Graff, R. Ruppert,
H. J. Callot, Inorg. Chem. 2004, 43, 251; c) Y. J. Li, X. F. Li, Y. L. Li,
H. B. Liu, S. Wang, H. Y. Gan, J. B. Li, N. Wang, X. R. He, D. B.
Zhu, Angew. Chem. 2006, 118, 3721; Angew. Chem. Int. Ed. 2006,
45, 3639; d) J.-M. Barbe, B. Habermeyer, T. Khoury, C. P. Gros, P.
Richard, P. Chen, K. M. Kadish, Inorg. Chem. 2010, 49, 8929;
e) K. F. Cheng, C. M. Drain, K. Grohmann, Inorg. Chem. 2003, 42,
2075.
[40] Spectroelectrochemistry was also performed on bis-Zn 9 in PhCN
containing 0.1m nBu4NPF6 as supporting electrolyte. The UV/Vis/
NIR spectral changes are shown in Figure S17 of the Supporting In-
formation.
[41] a) J. Fajer, D. C. Borg, A. Forman, D. Dolphin, R. H. Felton, J. Am.
Chem. Soc. 1970, 92, 3451; b) J. H. Fuhrhop, P. Wasser, D. Riesner,
D. Mauzerall, J. Am. Chem. Soc. 1972, 94, 7996.
ˇ
ˇ
ˇ
[42] R. Sipos, T. Szabꢉ-Plꢇnka, A. Rockenbauer, N. V. Nagy, J. Sima, M.
Melnꢆk, I. Nagypꢇl, J. Phys. Chem. A 2008, 112, 10280.
[21] a) S. Yamaguchi, H. Shinokubo, A. Osuka, J. Am. Chem. Soc. 2010,
132, 9992; b) J. X. Song, N. Aratani, J. H. Heo, D. Kim, H. Shinoku-
bo, A. Osuka, J. Am. Chem. Soc. 2010, 132, 11868.
[43] The oxidation potential of the porphyrin is more positively shifted
in CH2Cl2/MeOH due to destabilization of the oxidized states of the
10680
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Chem. Eur. J. 2011, 17, 10670 – 10681

Zinc Bis-Porphyrin Molecular Tweezers
FULL PAPER
porphyrin in nonpolar solvent, such as CH2Cl2, which also hamper
electron transfer from porphyrin to CuACTHNUGTRENUNG(OTf)2.
[44] PhCN/MeCN (1/1) was used because of the solubility of CuACTHNUTRGNEUNG(OTf)2
J. A. Montgomery, Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J.
Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, R. Kobayashi, J.
Normand, K. Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar,
J. Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox,
J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E.
Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W.
Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A.
Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, ꢊ.
Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski, D. J. Fox, Gaussian,
Inc., Wallingford CT, 2009.
and bis-Zn 9.
[45] The copper(I) ion that is formed after electron transfer from por-
phyrin to copper may be immediately consumed by dioxygen in a
cuvette.
[46] R. E. DeSimone, R. S. Drago, J. Am. Chem. Soc. 1970, 92, 2343.
[47] W. L. F. Armarego, C. L. L. Chai, Purification of Laboratory Chemi-
cals, 5th ed., Butterworth-Heinemann, Oxford, 2003.
[48] A. D. Adler, F. R. Longo, J. D. Finarelli, J. Goldmacher, J. Assour,
L. Korsakoff, J. Org. Chem. 1967, 32, 476.
[50] M. W. Carson, M. W. Giese, M. J. Coghlan, Org. Lett. 2008, 10, 2701.
[51] G. Roelfes, V. Vrajmasu, K. Chen, R. Y. N. Ho, J. U. Rohde, C. Zon-
dervan, R. M. la Crois, E. P. Schudde, M. Lutz, A. L. Spek, R. Hage,
B. L. Feringa, E. Mꢈnck, L. Que Jr. , Inorg. Chem. 2003, 42, 2639.
[49] Gaussian 09, Revision A.02, M. J. Frisch, G. W. Trucks, H. B. Schle-
gel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V.
Barone, B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X.
Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Son-
nenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven,
Received: April 26, 2011
Published online: August 11, 2011
Chem. Eur. J. 2011, 17, 10670 – 10681
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10681