Homo-and heteronuclear meso,meso-(E)-Ethene-1,2-diyl-Linked Diporphyrins: Preparation, X-ray crystal structure, electronic absorption and emission spectra and density functional theory calculations

Article abstract of DOI:10.1002/chem.201102995

Homo-and heteronuclear meso,meso-(E)-ethene-1,2-diyl-linked diporphyrins have been prepared by the Suzuki coupling of porphyrinylboronates and iodovinylporphyrins. Combinations comprising 5,10,15-triphenylporphyrin (TriPP) on both ends of the ethene-1,2-d

Full text of DOI:10.1002/chem.201102995

DOI: 10.1002/chem.201102995
Homo- and Heteronuclear meso,meso-(E)-Ethene-1,2-diyl-Linked
Diporphyrins: Preparation, X-ray Crystal Structure, Electronic Absorption
and Emission Spectra and Density Functional Theory Calculations
Oliver Locos,[a] Bruno Basˇic´,[a] John C. McMurtrie,[a] Paul Jensen,[b] and
Dennis P. Arnold*[a]
Abstract: Homo- and heteronuclear
meso,meso-(E)-ethene-1,2-diyl-linked
diporphyrins have been prepared by
the Suzuki coupling of porphyrinylbor-
onates and iodovinylporphyrins. Com-
binations comprising 5,10,15-triphenyl-
porphyrin (TriPP) on both ends of the
ethene-1,2-diyl bridge M210 (M2 =H2/
Ni, Ni2, Ni/Zn, H4, H2Zn, Zn2) and
5,15-bis(3,5-di-tert-butylphenyl)por-
complex Ni210, single crystal X-ray
structure determination. The crystal
structure shows ruffled distortions of
the porphyrin rings, typical of NiII por-
phyrins, and the (E)-C2H2 bridge
makes a dihedral angle of 508 with the
mean planes of the macrocycles. The
result is a stepped parallel arrangement
of the porphyrin rings. The dihedral
angles in the solid state reflect the in-
terplay of steric and electronic effects
of the bridge on interporphyrin com-
munication. The emission spectra in
particular, suggest energy transfer
across the bridge is fast in conforma-
tions in which the bridge is nearly co-
planar with the rings. Comparisons of
the fluorescence behaviour of H410 and
H2Ni10 show strong quenching of the
free base fluorescence when the com-
plex is excited at the lower energy
component of the Soret band, a feature
associated in the literature with more
planar conformations. TDDFT calcula-
tions on the gas-phase optimized geom-
etry of Ni210 reproduce the features of
the experimental electronic absorption
spectrum within 0.1 eV.
phyrinato-nickel(II) on one end and
H2, Ni, and ZnTriPP on the other
(M211), enable the first studies of this
class of compounds possessing intrinsic
polarity. The compounds were charac-
terized by electronic absorption and
Keywords: conjugation
·
density
functional calculations · electronic
spectra · porphyrinoids · Suzuki
coupling
1
steady state emission spectra, H NMR
spectra, and for the Ni2 bisACTHNUTRGNE(NUG TriPP)
Introduction
charge separation of the photosynthetic apparatus,[1a–f] and
ii) studies aimed at creating new arrays of porphyrinoids to
address fundamental questions relating to extended aromat-
ic systems.[1g–l] In the former category, covalently-linked oli-
goporphyrins with strong and controllable excited state elec-
tronic communication are most suitable.[2] In contrast, the
latter work is often aimed at inducing strong ground state
electronic communication, by connections using conjugating
or fused linkers, basically to generate fully delocalised super-
molecules. Examples of this type include the planar triply
linked porphyrin tapes of Osuka and co-workers,[3] and the
popular alkyne-linked dyads and higher arrays.[4] Recently,
there has been intense interest in the use of strongly conju-
gated, extended arrays of porphyrins in the burgeoning field
of organic materials for non-linear optics.[4d,l,m,5] It is there-
fore of considerable importance to understand the proper-
ties of the simplest bridges, in order to optimise the con-
struction of such synthetic oligoporphyrins.
The spectacular arrays of porphyrinoid macrocycles found
in natural light-harvesting systems and the arrangements of
pigments in photosynthetic reaction centres have inspired
the creation and investigation of a myriad of synthetic multi-
porphyrin constructs.[1] Numerous kinds of covalently at-
tached linkers have been employed in order to control the
degree of ground and/or excited state communication be-
tween the macrocycles. This work generally divides into i)
studies that are concerned with understanding and mimick-
ing the energy transduction mechanisms and photoinduced
ˇ ´
[a] Dr. O. Locos, Dr. B. Basic, Dr. J. C. McMurtrie, Prof. D. P. Arnold
School of Chemistry, Physics and Mechanical Engineering
Queensland University of Technology
G.P.O. Box 2434, Brisbane 4001 (Australia)
Fax : (+61)7-3864-2482
E-mail: d.arnold@qut.edu.au
Over the past decade, 5,15-diaryl- and 5,10,15-triarylpor-
phyrin starting materials[6] have become readily available,
and have been used almost exclusively in recent studies of
this type. Their convenient reactivity, versatility in substitu-
tion in the aryl groups, and applicability in palladium cata-
lysed coupling reactions have enabled synthesis and charac-
[b] Dr. P. Jensen
Crystal Structure Analysis Facility
School of Chemistry
University of Sydney, NSW 2006 (Australia)
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201102995.
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FULL PAPER
the synthesis, optical properties
and voltammetry of the dizinc
complex of (E)-1,2-bis[10,20-
bis(3,5-di-tert-butylphenyl)por-
phyrin-5-yl]ethene and the X-
ray crystal structure of the
dizinc complex of (E)-1,2-
bis[10,15,20-tris(3,5-di-tert-bu-
tylphenyl)porphyrin-5-yl]eth-
ene.[14] We prepared small
amounts of the dinickel(II)
complex of the former ligand
by the McMurry route in
1998,[15] but did not pursue this
project again until recently. Our
aim in the present work was to
develop a method that would
make the free bases accessible,
not just metal complexes, and
Scheme 1. Generic structures of meso,meso-, meso,b-(E)-ethenediyl- and azo-linked diporphyrins.
terization of very large multiporphyrin arrays.[3a] Of the vari-
ous potentially conjugating bridges that have been studied,
one that has been rather neglected in recent years is the
simple two-carbon ethene-1,2-diyl fragment. More than ten
years ago, there was a flurry of activity on this linker in oc-
taalkylporphyrin and particularly octaethylporphyrin (OEP)
dyads (A, Scheme 1). Ponomarev and collaborators discov-
ered a novel synthesis from the corresponding ethane-1,2-
diyl dyads,[7] while Smithꢁs group introduced the McMurry
coupling as a means of generating the linking double
bond.[8] Higuchi et al. have prepared extended systems with
three or four porphyrins involving both ethenediyl and buta-
diynediyl linkers.[9] The electronic absorption and emission
spectra and the electrochemistry of the OEP dyads suggest-
ed the presence of multiple conformations with differing ab-
sorption and emission characteristics.[10] In the solid state,
the favoured conformation has the alkene approximately or-
thogonal to the two porphyrin rings, which themselves are
related in a staircase manner, more or less parallel.[8,11]
Clearly, the flanking ethyl substituents contribute strongly to
the steric inhibition of full conjugation between the porphyr-
ins through the ethene orbitals. The (E)-ethenediyl OEP
dyads exhibit an unusual, extremely broad, low energy ab-
sorption band, as well as a characteristic band in the 500 nm
region.[7,10] It appears from the spectral studies that these
particular features are due to the more conjugated, near-
planar conformations.
The aforementioned diaryl- and triarylporphyrins afford
an opportunity to study this conformational problem and
the properties of this short linker in the absence of the
bulky ethyl substituents in the 3- and 7-positions adjacent to
the meso bridge. The synthesis of a (Z)-ethenediyl-linked di-
phenylporphyrin dyad by a Stille coupling was reported in
a patent in 1994,[12] but remarkably, until recently, there
were no reports of examples of (E)-ethenediyl-linked dyads
of this type (B, Scheme 1). An extended version, namely an
all-trans octatetraenediyl-linked dyad, was reported by Odo-
belꢁs group.[13] In 2005, Anderson and co-workers reported
specific combinations of the entities attached to the ethene
linker, that is, homo- or heterodiporphyrin, homo- or heter-
odimetallic, without relying on unselective metallations and
difficult separations. Odobel and co-workers reported the
only other example of a heterodimetallic “short-bridge”
conjugated diporphyrin in 2009, namely a ZnII/AuIII bis(triar-
ylporphyrin) linked by an ethyne bridge. This compound dis-
played remarkable non-linear optical properties as well as
very instructive electrochemical data.[16]
As we reported, the Heck-type alkenation of meso-vinyl-
porphyrins with meso-haloporphyrins failed to produce any
of the target meso,meso-ethenediyl-linked dyads, but instead
led to generally low yields of a new family of meso,b-ethene-
diyl-linked dyads (C, Scheme 1) via a novel meso-to-b Pd
migration process.[17] Herein we report our successful gener-
ation of a series of dyads of the desired meso,meso-linked
type, this time using the Suzuki coupling of meso-2-iodovi-
nylporphyrins[18] and meso-porphyrinylboronates. The mem-
bers of the series are compared in terms of their visible ab-
sorption and (in suitable cases) steady state fluorescence
spectra, and the X-ray crystal structure of the dinickel(II)
complex is also reported. The properties of the ethenediyl-
linked dyads are also compared with those of the analogous
azo-linked triphenylporphyrin dyads that we reported in
2007 (D, Scheme 1).[19] We recently prepared other azopor-
phyrins, including a tetraporphyrin linked by alternating azo
and butadiyndiyl bridges.[20] Furthermore, we report density
functional theory calculations of geometries, orbitals and ex-
cited states, and compare these with the experimental re-
sults. The hypothesis that was advanced for the OEP ethene-
diyl-linked dyads, namely the existence of a population com-
prising both strongly and weakly conjugated conformers, is
well supported by our results, although a broad, low-energy
absorption band is notably absent from the spectra of the
present series.
Chem. Eur. J. 2012, 18, 5574 – 5588
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D. P. Arnold et al.
Results and Discussion
The electrophilic partners for the proposed Suzuki reac-
tions, the meso-2-halovinylporphyrins, were prepared by two
routes, as shown in Schemes 4 and 5. The Takai iodoalkena-
tion[23] of the meso aldehydes Ni4 and Ni5 using iodoform
and chromium(II) chloride was used to prepare nickel
meso-2-iodovinylporphyrins Ni6 and Ni7 (Scheme 4).
Synthesis: A general synthesis of ethenediyl-linked dipor-
phyrins by the Suzuki coupling could potentially be ach-
ieved by two routes, shown retrosynthetically in Scheme 2,
namely i) a porphyrinylvinylboron reagent with a halopor-
phyrin or ii) a porphyrinylboron reagent with a halovinylpor-
phyrin. We briefly examined the former route but were
unable to prepare the desired boron reagents satisfactorily
and therefore turned to the second. As in our previous work
on the Heck coupling, we used two porphyrin building
blocks, namely 5,10,15-triphenylporphyrin (H2TriPP) and
5,15-bis(3,5-di-tert-butylphenyl)porphyrin (H2DAP). Using
the established method for the formation of meso-pinacol-
boronato porphyrins,[21] the bromoporphyrins H21, Ni1 and
Zn1 were converted using a ten-fold excess of pinacolborane
and [PdCl2ACHTUNGTRENNUNG(PPh3)2] as catalyst to the three required Suzuki
nucleophiles H22, Ni2 and Zn2 in yields of 72, 74 and 77%,
respectively (Scheme 3). Nickel complexes of boronatopor-
phyrins have only been reported recently.[22] The corre-
sponding debrominated porphyrins H23, Ni3 and Zn3 were
the only other products isolated. The only other point to
note is the wide variation in the time to consume the bromo
starting materials, which was one hour for Zn, 12 h for the
free base, and 18 h for the nickel complex.
Scheme 4. Preparation of iodovinyl nickel(II) porphyrins by the Takai re-
action.[23]
In the former case, although
the required product was
formed in >70% yield, several
unidentified impurities could
not be removed without severe
losses in recrystallisation. How-
ever, such samples were subse-
quently used successfully in the
Suzuki coupling. For Ni7, the
undesired Z isomer was also
formed, but likewise could not
be removed efficiently. We
Scheme 2. Retrosynthesis of meso,meso-ethenediyl-linked diporphyrin by the Suzuki coupling.
have previously shown that the
Takai reaction was not effective
for zinc porphyrins, although it
was satisfactory for the preparation of iodovinyl NiOEP,[23]
and the use of the chromium reagent precludes this method
for free bases. We therefore turned to our method for the
iodovinylporphyrins via the corresponding free base bromo-
vinyl species, which employs novel organopalladium deriva-
tives in situ (Scheme 5).[18]
We had previously prepared the meso-vinyl free base H28
by the Stille route for our Heck couplings,[17] and terminal
bromination using pyridinium tribromide in THF solution at
room temperature gave H29 in high yield. This reagent was
used many years ago to prepare a mixture of (E)- and (Z)-
2-bromovinyl NiOEP.[24] The bromine was exchanged with
iodine to yield H27 using our one-pot palladation–iodination
procedure reported elsewhere.[18] Metallation with NiII and
ZnII proceeded smoothly to give Ni7 and Zn7.[18] This route
to Ni7 is a slight improvement on the Takai version
Scheme 3. Preparation of the porphyrinylboronates.
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Homo- and Heteronuclear Diporphyrins
FULL PAPER
ing. By conducting the reaction
at 808C,
a moderate yield
(45%) of desired dyad Ni210
was isolated after two days. The
decomposition reactions of the
two starting materials were
likewise enhanced, and the de-
borylation product Ni3 was also
isolated. Changing the catalyst
to [Pd
(diphenylphosphino)ethane) or
[Pd(dppp)2] (dppp=1,3-bis(di-
ACHTUNGTNER(NNUG dppe)2] (dppe=1,2-bis-
AHCTUNGTRENNUNG
phenylphosphino)propane) in
both cases slightly improved
the yield of Ni210. Crystals suit-
able for X-ray single crystal
analysis were obtained from di-
Scheme 5. Preparation of iodovinylporphyrins by in situ palladation/iodination.[18]
chloromethane/methanol, and
the structure is reported below.
above,[23] in that the undesired Z isomer is avoided, and the
overall yield is comparable. With the required set of triphe-
nylporphyrin Suzuki partners assembled, and the diarylpor-
phyrin NiII complex Ni6 available, we then embarked on the
formation of the desired dyads, as shown in Scheme 6.
Our initial conditions were adapted from those used by
Osuka and co-workers in their synthesis of meso,meso di-
The latter catalyst was then used to couple Ni7 with H22
and Zn2, with isolated yields of H2Ni10 and NiZn10 of 30
and 26%, respectively. The order of yields found here for
the boronates, namely Ni>H2 >Zn, is the same as in our
Heck alkenation reactions with bromoporphyrins.[17] To
expand the suite of dyads to the heteroporphyrin type, cou-
pling of boronates 2 with the iodovinylDAP nickel complex
Ni6 was also performed under the same conditions, yielding
dyads H2Ni11 (34%), Ni211 (45%) and NiZn11 (28%), re-
spectively.
rectly linked dyads,[25] namely [Pd
ACHTNUTRGNEG(UN PPh3)4] as catalyst,
cesium carbonate as base, and DMF/toluene as solvent.
Cross-coupling between Ni7 and Ni2 was attempted at room
temperature but after four days no dyad formation was evi-
dent, and the two starting materials were slowly decompos-
When using the successful catalyst [Pd
ACHTUNGTERN(NUNG dppp)2], a major
side reaction was observed, namely the homocoupling of the
Scheme 6. Preparation of the ethenediyl-linked porphyrin dimers by the Suzuki coupling.
Chem. Eur. J. 2012, 18, 5574 – 5588
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5577

D. P. Arnold et al.
boronates H22 and Zn2, to give the meso,meso directly
linked dyads H412 and Zn212 (Scheme 6). These dyads were
unambiguously identified by the unique upfield shifts of the
porphyrin b-protons in their NMR spectra, analogous to the
known examples of Osuka.[26] This coupling was not ob-
served for the Ni analogue. Osuka and co-workers recently
reported
linked porphyrin dimers through the homocoupling of b-
borolanylporphyrins using Pd(OAc)2/dppp under aerobic
a convenient method for making b,b-directly
AHCTUNGTRENNUNG
conditions.[27] The mechanism of such an aerobic oxidative
coupling of arylboronic acids has been defined by Adamo
et al.[28] Thus the formation of some homocoupled product is
not unexpected under prolonged heating at 808C. Just why
the Ni complex should be immune is not clear at present,
but our results were reproducible. The series of TriPP dyads
was completed by coupling the appropriate iodovinyl and
boronate partners, leading to H410, H2Zn10 and Zn210, in
isolated yields of 49, 29, and 10%, respectively. In these
cases, however, reactions at 808C gave little or no target
dyads, but reactions at 408C proved to be successful. Fortu-
nately, in all cases in which the crude products contained
both the ethenediyl and directly linked dyads, the two were
separable by normal flash chromatography. The order of re-
activity of the porphyrin boronates is apparently H2 ꢀZn@
Ni; the free base and zinc derivatives are capable of reacting
close to room temperature while the nickel species requires
higher temperatures. Once palladium has inserted into the
iodovinylporphyrin, the reactivity of the organopalladiu-
m(II) intermediate apparently lies in the order Ni@H2 >
Zn; the nickel derivative is stable enough (or perhaps also
reactive enough) to participate well in the coupling with Ni2
whereas the free base and zinc derivatives are less effective.
We did not identify any breakdown products of the iodovin-
yl partners, although numerous minor side products were
observed.
It is interesting to compare the Suzuki coupling with
other techniques used to prepare meso,meso-(E)-ethenediyl-
linked diporphyrins. The present method gave us access to
a range of homo- and heterodinuclear dyads, as demonstrat-
ed by the use of two different porphyrins and three kinds of
central substitution. As the boronate can be attached to por-
phyrins irrespective of the presence or absence of a central
divalent metal, it may be more versatile than the CuI/CsF
promoted Stille coupling used by Anderson.[14] On the other
hand, the latter method gave significantly higher yields in
the cases of homodinuclear dizinc systems. In any case, the
concept of Suzuki coupling to form meso,meso-(E)-ethene-
diyl-linked homo- and heterodinuclear dyads was proved,
and sufficient material was obtained to enable us to com-
pare the electronic spectra among the members of the
series.
Figure 1. a) Ni2 porphyrin dimer Ni210, viewed perpendicular to the mean
planes of the porphyrin rings. b) “Side” view of the molecule illustrating
the extent to which the individual porphyrin rings are distorted from pla-
narity. The out-of-plane twist across the ethylene bridge is also evident.
The combination of these two factors leads to the loss of co-planarity of
the porphyrin rings, which, while parallel, are separated by 3.5 ꢂ.
from planarity. Maximum deviation from the mean plane of
the porphyrin (C20N4Ni) occurs for meso carbon atoms C5
(0.703 ꢂ), C10 (0.666 ꢂ), C15 (0.586 ꢂ) and C20 (0.561 ꢂ).
The displacement of these atoms from the mean plane of
the ring occurs such that C5 and C15 project on one side of
the mean plane of the porphyrin while C10 and C15 project
on the other. This distortion is referred to in the literature
as “ruffled”[29] and has been observed by us[19,30] and
others[8,11] in a range of Ni porphyrins and porphyrin dimers.
ꢁ
The dihedral angle between the mean plane of the C C=
ꢁ
C C ethenediyl bridge and the mean planes of the porphy-
rin rings is 508. A similar out-of-plane twist is observed in
Andersonꢁs Zn2 dimer (458)[14] and is due to the close prox-
imity of the ethenediyl CH group (C21) to the nearby b-CH
group (C3’) of the porphyrin, with the twist alleviating some
intramolecular steric interference. As noted by Anderson
and co-workers, the only other reported structures of (E)-
ethene-1,2-diyl diporphyrins are those derived from NiOEP,
for which a chloroform solvate (dihedral angle 748) and
a toluene solvate (898) are known.[8,11] By contrast, the anal-
ogous azo-linked Ni2 porphyrin dimer, which does not con-
tain H atoms on the bridge, displays considerably less out-
of-plane twist (378).[19,30] Presumably, this is due to reduced
intramolecular steric strain.
X-ray crystal structure of the dinickel complex Ni210: The
porphyrin dimer Ni210 has crystallographic inversion sym-
metry (Figure 1; ORTEP depiction with all non-hydrogen
atoms labelled is shown in Figure S1, Supporting Informa-
tion). The porphyrin rings display considerable distortion
The mean (C20N4Ni) planes of the porphyrin rings are ex-
actly parallel (as must be the case given the Ci point symme-
try of the molecule in the structure). The mean planes are
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Homo- and Heteronuclear Diporphyrins
FULL PAPER
not co-planar but are displaced by 3.5 ꢂ. The displacement
of the mean planes of the porphyrin rings is a consequence
of the out-of-plane twist of the ethylene bridge and the ruf-
fled structure of the porphyrin. The degree of separation in
this structure is relatively large but reasonable for a Ni2
dimer. By comparison, the separation of the mean planes of
the porphyrin rings in the Ni2 azo-linked analogue is slightly
less at 3.2 ꢂ due to the reduced out-of-plane twist of the
bridge and much less in the Zn2 ethenediyl-linked dimer
(distance between planes 1.5 ꢂ)[14] due to the lower degree
of porphyrin “ruffle” in that molecule.
Electronic absorption spectra: In order to detect “interpor-
phyrin electronic interaction”, the easiest and most obvious
tool is the visible absorption spectrum. Of course, there are
many subtleties that fall under this umbrella term, and other
techniques such as fluorescence lifetimes, voltammetry, spec-
troelectrochemistry and molecular orbital calculations are
all applicable. The discussion can centre on ground state or
excited state interactions, and can be treated by several ap-
proaches. In this work, we have examined our suite of
dimers by the basic techniques of absorption and steady
state emission spectroscopy. Our goals here are empirical
comparisons among the dyads that we now have at our dis-
posal. The relevant features of the UV-visible spectra of the
meso,meso (10 and 11) and previously reported[17] meso,b
(13) ethenediyl-linked dyads are collected in Table 1.
Figure 2. Electronic absorption spectra of model monomer meso-phenyle-
thenylNiTriPP (a), and dimers meso,meso’-Ni210 (c) and meso,b-
Ni213[16] (g) (in CH2Cl2).
a result of the smaller coefficients of the interacting orbitals
on the b carbons.[17] The Soret bands of meso,b dyads are
similar to those of the sterically-congested OEP ethenediyl-
linked dyads and triads.[7,9–10] However, unlike the OEP
series, the meso,b dyads do not possess a weak, very broad
transition in the near-infrared between 800 and 1100 nm.
The absence of this band may suggest the associated transi-
tion is due to physical properties in octaethylporphyrins that
are not present in meso-arylporphyrins. However, while the
B1 shoulder to the Soret band for the meso,b dyads is gener-
ally less red-shifted than the corresponding shoulder in the
OEP species, the HOMO–LUMO transition for the former
is considerably more red-shifted. Therefore, the presence of
a similar broad, structureless transition beyond 1100 nm is
possible. This is outside the range of our instrument and
until studies are performed using longer wavelengths, no de-
The first comparison to be made is between alkenyl mo-
noporphyrins and the dyads, for which we have both meso,-
meso and meso,b examples. To set the scene for this discus-
sion, the electronic absorption spectra for a typical ethenyl
monomer (meso-phenylethenylNiTriPP),[17]
a meso,meso
(Ni210) and a meso,b (Ni213)[17] ethenediyl-linked porphyrin
dyad are shown in Figure 2.The absorption spectra of the
meso,b ethenediyl-linked dyads H2Ni13–NiZn13 exhibit
a shoulder, B1, on the red edge of a broadened Soret band,
B, as well as an intensified and red-shifted HOMO–LUMO
(Q) transition. We have concluded that porphyrins linked by
a meso,b ethenediyl bridge are weakly conjugated, as
Table 1. Selected features of the UV-visible absorption and steady state fluorescence spectra of ethenediyl-linked porphyrin dyads (in CH2Cl2).
Dyad
(meso,meso)
B [nm]
B [cmꢁ1
]
B1 [nm]
B1 [cmꢁ1
]
D
(BꢁB1) [cmꢁ1
]
Q [nm]
lem [nm]
Ff[a]
H2Ni10
Ni210
NiZn10
H410
419
410
415
421
417
424
423
415
423
23865
24390
24095
23755
23980
23585
23640
24095
23640
469
471
468
468
468
469
466
466
465
21320
21230
21370
21370
21370
21320
21460
21460
21505
2545
3160
2725
2385
2610
2265
2180
2635
2135
677
632
626
680
673
633
675
625
625
649, 710
0.005
n.m.
n.m.[b]
626, 658sh
657, 720
0.005
0.030
0.025[d]
0.018
0.003
n.m.
H2Zn10[c]
Zn210[d]
H2Ni11
Ni211
597, 664, 723
620 sh, 657, 760
659, 720
n.m.[b]
617, 660
NiZn11
0.001
ACHTUNGTRENNUNG(meso,b)
H2Ni13
Ni213
NiZn13
425
422
425
23530
23695
23530
448
458
447
22320
21835
22370
1210
1860
1160
673
619
620
656, 716
n.m.[b]
ca. 670
0.002
n.m.
<0.001[d]
[a] Calculated by comparison with H2TPP (Ff =0.11). [b] Fluorescence of dinickel dyads not measured. [c] Shoulder at 23255 cmꢁ1 (loge 5.17). [d] By
comparison with ZnTPP (Ff =0.033). [e] Shoulder at 23255 cmꢁ1 (loge 5.33).
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D. P. Arnold et al.
finitive conclusion can be drawn about this band being an
intrinsic property of OEPs or being a consequence of a par-
ticular conformation of an ethenediyl-linked dyad.
As exemplified in Figure 2, and similar to Andersonꢁs
ethenediyl-linked dyad,[14] the dyads 10 (and 11, not shown)
possess considerably red-shifted and intensified Q bands as
well as a clear splitting of the Soret band due to the stronger
interaction between porphyrins linked in the meso-position
by an ethenediyl bridge. The HOMO–LUMO transition for
the meso,meso linked dyads is red-shifted compared with
porphyrin monomers with extended conjugation and the
meso,b ethenediyl-linked dyads. The combination of the
diaryl- with the triarylporphyrin results apparently in a small-
er degree of inter-porphyrin interaction than in the meso,-
meso linked dyads, as Ni210 experiences a greater splitting
and red-shift than Ni211 (Table 1). The NMR spectrum sug-
gests that the two porphyrins in the dyad Ni211 are very sim-
ilar electronically, as a single NMR peak is observed for the
two intrinsically inequivalent ethenediyl protons. It seems
likely therefore that the porphyrin/alkene/porphyrin dihe-
dral angles in Ni211 and Ni210 will be similar. Therefore, the
electronic spectra appear to be very sensitive to quite subtle
differences in the porphyrin and/or dyad symmetries.
Also of note in Table 1 are the differences between Ni210,
H410 and Zn210. The extent of splitting in the Soret band
follows the trend Ni > 2H > Zn. This splitting is conceiva-
bly related to the dihedral angles between the planes of the
porphyrins or perhaps, more importantly, between the
planes of the alkene and each porphyrin. The conjugation
between the two chromophores of a homo-metal dyad may
be inferred as increasing in the order Zn < 2H < Ni. In
other conjugated dyads studied by our group, such as the
butadiyne-linked OEP series, several measurements sup-
ported the same order.[4a–c] However, in a way this can be
deceptive, as another significant point is the well-document-
ed non-planarity of Ni porphyrins versus the free base and
zinc complexes, as seen in the X-ray crystal structure dis-
cussed above. This argument can be reduced in simple terms
to: “conjugation between aromatic systems is reduced when
the systems are most aromatic”, that is, strongly aromatic
systems prefer to remain “insulated”. Proton chemical shifts
of peripheral protons of Ni porphyrins always lie upfield of
those of free base and Zn porphyrins, supporting the propo-
sition that the former are “less aromatic”. So this putative
“electronic” effect of Ni may be due really to the small size
of the NiII ion and the out-of-plane distortion of the rings.
Once the heterobimetallic dyads are considered, there are
several factors that may conflict in influencing porphyrin–
porphyrin interaction. To illustrate the degree of difference
among these examples, Figure 3 shows the spectra of the
series H410, H2Ni10, and H2Zn10. Considering the complete
bis(triphenylporphyrin) dyad series 10, the extent of splitting
in the Soret band decreases in the order Ni–Ni > Ni–Zn >
2H–Zn ꢀ 2H–Ni > 2H–2H > Zn–Zn. Central substituents
of different electronegativity should create a donor–acceptor
(“push–pull”) situation, resulting in a contraction of the
HOMO–LUMO gap and perhaps allowing greater interac-
Figure 3. Electronic absorption spectra of H410 (c), H2Ni10 (g) and
H2Zn10 (a) (in CH2Cl2).
tion. However, the effects of the central substituents upon
macrocycle planarity and the porphyrin-alkene-porphyrin
dihedral angles will affect the degree of conjugation, which
may result in unpredictable trends. Further discussion of the
details of this order is not justified, until other data such as
electrode potentials and more crystal structures are pub-
lished.
Steady state fluorescence: The fluorescence properties of
trans-stilbenes (1,2-diarylethenes) have been studied exten-
sively and the trends noted in their emission spectra serve as
a useful basis for comparison with the bis(porphyrinyl)-
ethenes.[31] Partial conjugation between simple aryl groups
across an ethenediyl bridge results in an increase in fluores-
cence intensity and Stokes shift relative to biphenyls. Modi-
fication of electron distribution due to the presence of
either donor or acceptor substituents alone results in red-
shifts and lower quantum yields. However, conjugative inter-
action between such unlike substituents in the same mole-
cule increases the intensity. Steric inhibition of inter-aryl
conjugation causes larger Stokes shifts, but can markedly de-
crease quantum yields. With these points in mind, we have
recorded the steady state emission of all those new dyads in
which at least one of the macrocycles is a free base or ZnII
complex, initially using the wavelength of the highest-energy
component of the Soret band for excitation. The data are in-
cluded in Table 1. NiII porphyrins are usually non-emissive,
due to spin-orbit quenching by the d8 metal ion. Mononu-
clear free base and ZnII porphyrins without heavy atom sub-
stituents usually emit fluorescence with quantum yields be-
tween 0.03 and 0.15 and Stokes shifts <1000 cmꢁ1. The
steady state fluorescence properties of the series of mononu-
clear alkenyl-substituted free base porphyrins and their zinc
complexes that we prepared by Heck coupling have been re-
corded and their features fit into this typical pattern.[31] Thus
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Homo- and Heteronuclear Diporphyrins
FULL PAPER
the more unusual data in Table 1 represent the influence of
dinuclearity and the ethenediyl bridge.
from the more electron-rich macrocycle to the more elec-
tron-deficient one.[35] However, without the detailed infor-
mation afforded by transient absorption spectra and excited
state lifetimes, we cannot speculate more about the relative
contributions of through-space and through-bridge mecha-
nisms for this transfer. Because all of our examples of
meso,b linked dyads contain nickel, discerning a difference
between meso,b and meso,meso linkages is difficult due to
the inherently weak fluorescence.
One striking observation from Figure 4 and the data in
Table 1 is that the emission envelopes are not mirror images
of the absorption spectra. The fluorescence component at
highest energy has an anti-Stokes shift from the S1 ! S0 ab-
sorption band. Therefore, it is likely that excitation is ac-
companied by changes in geometry.[36] Considering the
“normal” Stokes shifts observed in alkenyl-substituted mon-
omers, the behaviour of the dyads may be attributed to the
existence of a distribution of conformations that are more
or less conjugated. Accordingly, a change in geometry after
excitation can lead to the apparent anti-Stokes shifts, or the
emission envelope is simply the superposition of the compo-
nents derived from the various ground state geometries, as
expected for any molecule with several conformations that
individually have rather different absorption/emission prop-
erties. To investigate this aspect further, we measured both
the emission spectra of H410, H2Zn10, Zn210, and H2Ni10 at
different excitation wavelengths, and the excitation spectra
contributing to particular maxima in the emission spectra.
To illustrate the results, the data for Zn210, H410 and
H2Ni10 are displayed in Figures 5, 6 and 7, respectively.
In Figure 4, the emission spectra of the series H410,
H2Zn10, and Zn210 are shown, together with those of
H2Ni10. There have been very few studies of the fluores-
cence spectra of analogous dyads containing NiII porphyrins,
and as far as we know, the saturated ethane-1,2-diyl bridge
is the only type that has been investigated.[32] Not surprising-
ly, all the ethenediyl-linked dyads have lower quantum
yields than their mononuclear analogues. The NiII-contain-
ing dyads have very low quantum yields, indeed less than
1%, as expected. As the concentrations of all the dyads
were maintained at about 10ꢁ7 m, most likely this quenching
is not intermolecular. Such
a dramatic intramolecular
quenching provides strong evidence of energy transfer
across the bridge, complementing the data on ground state
interactions from the absorption spectra, although as the
emission properties of no other Ni-containing dyads have
been studied, we cannot actually attribute the quenching
specifically to the ethenediyl linker per se. The emission
spectra of H410, H2Zn10, and Zn210 show remarkable red-
shifts of the main fluorescence band when the dyad contains
only free base or Zn porphyrins. For comparison, the dizinc
dyad studied by Anderson and co-workers gave a quantum
yield of 4.1% and a fluorescence maximum at 765 nm (in
benzene + 1% pyridine).[14] In aromatic dyads,[33] including
porphyrin dyads,[34] linked by an alkene-containing bridge,
a large Stokes shift has been observed, which was attributed
to a change in conformation of the dyad as a result of the
electronic excitation.
Comparing the fluorescence spectra of H410, H2Zn10, and
Zn210 in Figure 4, it is clear that the emission of the hetero-
nuclear dyad exhibits features of both its homonuclear ana-
logues, but the elements associated with the free base
appear to dominate. The spectrum of H2Ni10 is also a strong-
ly attenuated version of H410. In heterobimetallic porphyrin
oligomers linked by diarylethynediyl units, Lindsey and co-
workers attributed the resulting features to energy transfer
Figure 5. Steady state fluorescence spectra of Zn210 excited at different
wavelengths: 420 nm (c), 472 nm (b) and 523 nm (g), and excita-
tion spectra monitored at the 621 nm emission band (a) at the 657 nm
emission band (d) and at the 760 nm emission band (c).
For Zn210, the major emission band peaking at 760 nm
arises from excitation at both major components of the
Soret envelope, namely at 420 and 472 nm, but the shorter
wavelength fluorescence band at 657 nm arises selectively
by excitation at the higher energy Soret component. The ex-
citation spectra likewise show that the emission band at
657 nm results from a conformation that has the characteris-
tics of a monoporphyrin, that is, a Soret band with just the
Figure 4. Steady state fluorescence spectra of H410 (c), H2Zn10 (a),
Zn210 (g) and H2Ni10 (d), excited at the maximum of the highest
energy component of the respective Soret envelopes.
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D. P. Arnold et al.
than those from excitation at either 416 or 521 nm. The exci-
tation spectra confirm that the residual fluorescence of
H2Ni10 is largely due to absorption at these wavelengths.
Although the relative intensities between the Soret and Q
bands in the excitation spectra are distorted from those of
ground state absorption spectra, they resemble the absorp-
tion profile of a monoporphyrin. This striking result is clear
evidence that the nickel moiety quenches the excited state
of the dyad most efficiently when the two porphyrins are
conjugated across the ethenediyl bridge, that is, from confor-
mations that possess the signature 469 nm band.
Density functional theory calculations of geometries: The
calculation of electronic structures and the application of
density-functional theory to the time-dependent domain
have been studied for conjugated porphyrin dyads, especial-
ly those containing alkynyl bridges.[4c,37] Sundstrçm and co-
workers have used semi-empirical equilibrium geometry cal-
culations to investigate the possibility of different conforma-
tions of ethenediyl-linked octaethylporphyrin dimers contri-
buting differently to their electronic spectra.[10a] Johnson
et al. also calculated van der Waals forces for b-ethenediyl-
linked chlorins to determine similar properties,[38] but there
has been little theoretical investigation into the electronic
structure and nature of the singlet excited states of ethene-
diyl-linked porphyrin dyads. The calculations reported in
this section extend the theoretical investigation on ethenedi-
yl-linked dyads. Emphasis will be placed upon the physical
properties of these dyads that can be explained qualitatively
by the modelling results.
Figure 6. Steady state fluorescence spectra of H410 excited at different
wavelengths: 419 nm (c), 468 nm (a) and 520 nm (g), and excita-
tion spectra monitored at the 657 nm emission band (c) and at the
720 nm emission band (d).
All geometry, electronic structure and time-dependent
calculations were performed as restricted closed-shell calcu-
lations using the DFT model with B3LYP exchange-correla-
tion functionals and a 6-31G basis set. Although the 6-
31G(d) basis set is much more desirable as it allows a better
account of the bonding interaction between atoms, the phe-
nomenal increase in the number of degrees of freedom re-
sulting from this basis set for a porphyrin dyad, which con-
tains a very large number of atoms, makes the calculation
extremely difficult.[1g] As discussed above, the absorption
and emission spectra of ethenediyl-linked porphyrin dyads
are explainable by hypothesising different conformations of
the dyads, in equilibrium, in solution; each conformation
has a different degree of conjugation and so gives rise to
slightly different absorption and emission spectra that over-
lap with the spectra of other conformations.
To investigate the suite of possible conformations, equilib-
rium geometry calculations were performed on the di-nickel
triphenylporphyrin dyad, Ni210, from four different initial
geometries. The first starting geometry was generated from
a calculation at the semi-empirical level using the PM3
method.[39] This geometry was then manipulated by rotation
of the two porphyrins about their bond with the alkene. The
rotations consisted of placing both porphyrins in plane with
the alkene (08, 08), one porphyrin in plane and one orthogo-
nal to the alkene (08, 908) and placing both porphyrins or-
thogonal to the alkene (908, 908) to generate the second,
Figure 7. Steady state fluorescence spectra of H2Ni10 excited at different
wavelengths: 416 nm (c), 469 nm (g) and 521 nm (a), and excita-
tion spectra monitored at 649 nm emission band (c) and at 710 nm
emission band (d).
higher energy component. The emission band at 760 nm,
however, results also from the red-shifted Soret component,
suggesting the lower energy fluorescence band results from
a more planar, more conjugated conformation. Turning to
H410 (Figure 6), the same number of emission bands is ob-
served at each excitation frequency, but the relative intensi-
ties among these differ, with excitation at the 468 nm Soret
component selectively enhancing the long wavelength emis-
sion band at 720 nm. Thus the conclusions from both are
similar.
The dyad H2Ni10 exhibits unique emission and excitation
spectra in comparison with the other three (Figure 7). The
emission intensity from excitation at 469 nm, is much less
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Homo- and Heteronuclear Diporphyrins
FULL PAPER
third and fourth starting geometries respectively. The results
of the DFT equilibrium geometry calculations on these start-
ing geometries are listed in Table 2, in terms of the angle be-
tween the mean planes of the porphyrins, a, and the angles
between the mean plane of each porphyrin and the plane of
the alkene, b and g.
Table 2. Angles between the mean planes of the porphyrins (a) and be-
tween each porphyrin and the plane of the alkene (b and g) of the mini-
mized structures from various starting geometries of the dyad Ni210.
Ni210 Starting geometry
a [8]
b [8]
g [8]
PM3 optimised
08, 08
08, 908
89.94
68.75
81.14
72.03
44.34
40.05
40.58
36.01
46.10
47.51
40.56
36.02
908, 908
The equilibrium geometry calculations on all four starting
geometries produce slightly different conformations, which
differ as much as 108 with respect to the plane of the por-
phyrins and the plane of the alkene, and 218 in the angle be-
tween the planes of the porphyrins. The convergence criteri-
on for the root-mean-square displacement in the elements
of the density matrix was set to be less than 0.0012 on two
successive self-consistent field iterations, which was the de-
fault setting for the software. Geometry calculations per-
formed previously on ethenediyl-linked OEPs found two
conformations from two different starting geometries; one
conformation held both porphyrins completely orthogonal
to the alkene (“P-type”), while the two macrocycles were
almost in plane with the alkene in the second conformation
(“U-type”).[10a] While our molecular mechanics (MM) calcu-
lations produce different conformations from those found in
previous work, this work complements the results found by
Sundstrçm and co-workers[10a] and supports the plausibility
of different conformers with similar energies contributing to
the absorption and emission spectra of ethenediyl-linked
dyads.
Density functional theory calculations of molecular orbitals
of Ni210: Discussions of the electronic structures of conju-
gated porphyrin dyads are often concentrated on the eight
frontier orbitals that are derived from interactions of the
four “Gouterman orbitals” of each porphyrin across the p-
conjugating bridge.[4a–e,37d] For these dyads, the labels of each
frontier orbital are assigned on the basis of the molecule
lying in the xy plane with the x axis along the 15,5,5’,15’ po-
sitions of the porphyrins (the porphyrins being substituted
in the 5,5’ positions by the alkene). As most conformations
of the dyads used for electronic structure calculations pos-
sess only C1 symmetry, no symmetry labels can be assigned
to the frontier orbitals. Instead, each orbital has been la-
belled x or y depending on its origin. The orbitals labelled
x are ultimately derived from the a2u and egx orbitals of
a D4h metalloporphyrin, while the orbitals labelled y are de-
rived from the a1u and egy orbitals. These orbitals for the
“parallel” conformation of Ni210 are shown in Figure 8.
Figure 8. Eight frontier molecular orbitals calculated by DFT for Ni210.
Both the HOMO-1 and LUMO display in-phase orbital
interactions that span the carbons on the alkene and the ad-
jacent meso carbons, while the HOMO and LUMO+3 dis-
play out-of-phase orbital interactions in this region. All of
the x orbitals show substantial electron density on the
alkene, which shows the integral role of this bridge, in these
particular conformations, in the electronic structure of the
dyad. For meso,meso linked dyads, the y orbitals possess
nodes at the meso-carbons, so as a result these non-interact-
ing orbitals do not possess coefficients on the alkene. In
comparison to the four orbitals of the Gouterman model,
the x (a2u-derived) orbitals are elevated in respect to y (a1u-
derived) orbitals, which is expected due to the overlap of
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5583

D. P. Arnold et al.
the alkene p-orbitals with the porphyrin orbitals. Interest-
ingly, the results of electronic structural calculations on the
ethynediyl-linked dyads by Therien and co-workers placed
the out-of-phase x orbital, but not the in-phase orbital,
above the y orbitals,[37b] whereas calculations of the butadiy-
nediyl-linked dyad by Wilson and Arnold gave comparable
results to those for the ethenediyl-linked dyad Ni210.[4c] The
more recent calculations of Ohira and Brꢃdas for alkyne-
bridged diporphyrins at the 6-31G** level placed the two y
levels as HOMO-3 and HOMO-2, and the two y* levels as
LUMO+2 and LUMO+3,[37d] so slightly different theoreti-
cal methods do not agree on the exact placement of the por-
phyrin-localised pairs with respect to the x, x* sets.
Kyrychenko and Albinsson have used the orbital splitting
in the lowest excited singlet state as a measure of the exci-
tonic coupling within arylethylenediyl-linked porphyrin
dimers.[40] The relationship is such that the greater the split-
ting between the excited states, the greater the excitonic
coupling. As the orbitals in the excited-state that represent
interaction between the porphyrins will be involved in exci-
tonic coupling, the difference in energies between the x1*
and x2* states should be a qualitative measure of the split-
ting in the lowest excited singlet state for the ethenediyl-
linked porphyrin dyads. This splitting is represented graphi-
cally in Figure 9. In our earlier DFT studies, we were
uniquely able to address this gap in a dyad by considering
the reduced and oxidised states of the butadiyndiyl dyads.[4c]
The spectrum of the monoanion has one electron in the or-
bital labelled x1*, thus allowing a transition x1* ! x2*, which
can be observed in the electronic spectrum (under spectroe-
lectrochemical conditions at low temperature).[4b,41]
the near-infrared or infrared as was observed for the ethene-
diyl-linked OEP dimers.
While these calculations produced an extensive amount of
data, Table 3 shows a selection of the excited states which
yield an oscillator strength, f, ꢂ0.01, for optical transitions
of wavelength ꢂ385 nm for the conformation of Ni210 that
was optimised semi-empirically. The full list of excited states
for Ni210 is available in the Supporting Information. Table 3
reveals that the first excited state has contributions from
three y ! y* transitions and the classical x2 ! x1* HOMO–
LUMO transition. Beyond the first excited state, the
number of transitions leading to each excitation becomes
too large to relate simply to the orbitals, but it is evident
that each excited state with an oscillator strength ꢂ0.01 is
largely comprised of transitions involving the eight frontier
orbitals. The remainder of the transitions results mostly
from lower-lying orbitals to either the frontier or slightly
higher anti-bonding orbitals.
The first Soret band in the experimental data (410 nm)
corresponds to the 33rd excited state, and the second Soret
band (471 nm) with the 22nd excited state, according to
their large oscillator strengths. Interestingly, while these ex-
cited states over-estimate the energies of these transitions
(396 and 468 nm, respectively), the difference between the
predicted and real energies is only of the order of 0.1 eV.
For the HOMO–LUMO transition, the difference between
the predicted and real data is less than 0.01 eV. A compari-
son between the experimental absorption data and excited
state transition energies for Ni210 are shown in Figure 10.
The general absorption profile of the dyad is clearly evident
in the time-dependent data. Interestingly, of the 100 excited
states, the majority of the absorption spectrum may be char-
acterised largely by about 10 of these states.
For Ni210, Figure 10 shows that the two conformations
used for the excited state calculations produce the same
transitions but these differ slightly in energy and oscillator
strength. Interestingly, in comparing the two conformations,
the more planar dyad (optimised from the 0, 908 starting ge-
ometry) has a more red-shifted HOMO–LUMO transition,
but slightly blue-shifted Soret bands. For the more planar
geometry, the red-shifted Soret band also possesses larger
oscillator strength relative to its blue-shifted Soret partner
whereas the less planar dyad has a higher oscillator strength
for its blue-shifted Soret band. This comparison shows quali-
tatively that different conformations are accentuated in dif-
ferent parts of the absorption profile, with the more planar
dyad having a more prominent role in the red-shifted Soret
band, and the less planar dyad having a more prominent
role in the blue-shifted Soret band. This hypothesis is sup-
ported nicely by the excitation spectra shown in Figures 5–7,
as the first fluorescence band arises from conformations of
the dyad where there is less conjugation. In the absorption
spectra of ethenediyl-linked OEP dyads, a weak, structure-
less band was observed between 800 and 1100 nm.[7c,10a] It
was speculated above that while this band was not observed
in the visible-near-IR region for the dyads in this study, it
may still exist but lies beyond the spectral region which was
Figure 9. Calculated eight-orbital manifold showing the splitting in the
lowest excited singlet state.
Time-dependent density functional theory calculations for
ethenediyl-linked porphyrin dyad Ni210: Calculations for the
lowest 100 excited states of ethenediyl-linked porphyrin
dyad Ni210 in the gas phase were carried out in the time-de-
pendent domain. For this di-nickel dyad, excited state calcu-
lations were performed for two conformations, the mini-
mized structure resulting from the PM3 minimization, and
that resulting from the (0,908) starting geometry (see
above). The large number of excited states was generated in
order to calculate a theoretical absorption spectrum for
each dyad so as to add support to the orbital and MM calcu-
lations performed already. The TD calculations were also
performed to see if an excited state would be predicted in
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Homo- and Heteronuclear Diporphyrins
FULL PAPER
Table 3. TDDFT calculated excitation energies, one-electron transitions and oscillator strengths for selected
optical transitions of Ni210 in the gas phase (l ꢂ385 nm, f ꢂ0.05, % contribution ꢂ10%).
positions, the di-zinc triarylpor-
phyrin dyad synthesised by An-
dersonꢁs group, has a dihedral
angle between the porphyrins
and the alkene of 458.[14] How-
ever, it is notable that all crystal
structures of trans-ethenediyl-
linked porphyrin dyads show
both porphyrins twisting in op-
posite directions with respect to
the alkene, resulting in the por-
phyrin planes being almost par-
allel with each other.[8,11,14] Pre-
liminary calculations of the
equilibrium geometry of meso,
meso ethenediyl-linked dyad
Zn210 predict the twist of the
alkene from the plane of the
macrocycle remarkably well
(42.98),[31] but the two porphyr-
ins are twisted in the same
sense from the alkene, resulting
in a near-orthogonal disposition
of the porphyrin planes. The
major difference between the
Excited state
Orbital composition [%]
Excitation
Oscillator
strength f
[eV]
[nm]
[cmꢁ1
ACHTUNGTERNNUNG ]
1
12
HOMO (x2)
HOMO-2 (y2)
HOMO-1 (x1)
HOMO (x2)
HOMO-5
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
!
LUMO (x1*)
LUMO (x1*)
LUMO+2 (y2*)
LUMO+2 (y2*)
LUMO (x1*)
82
34
20
20
28
15
11
11
10
13
31
12
34
29
10
26
27
40
39
18
21
1.97
2.53
629
490
15894
20399
0.84
0.05
13
2.56
484
20647
0.05
HOMO-3 (y1)
HOMO-1 (x1)
HOMO (x2)
HOMO-3 (y1)
HOMO-2 (y2)
HOMO-1 (x1)
HOMO-2 (y2)
HOMO-2 (y2)
HOMO-1 (x1)
HOMO-3 (y1)
HOMO-3 (y1)
HOMO-1 (x1)
HOMO-1 (x1)
HOMO-3 (y1)
HOMO-7
LUMO (x1*)
LUMO+1 (y1*)
LUMO+1 (y1*)
LUMO+2 (y2*)
LUMO+1 (y1*)
LUMO+3 (x2*)
LUMO (x1*)
LUMO+3 (x2*)
LUMO+2 (y2*)
LUMO (x1*)
LUMO+3 (x2*)
LUMO+1 (y1*)
LUMO+3 (x2*)
LUMO+3 (x2*)
LUMO+3 (x2*)
LUMO+3 (x2*)
22
23
26
2.69
2.75
2.78
460
451
445
21731
22184
22461
0.60
0.05
0.09
33
34
3.15
3.21
393
387
25430
25866
1.02
0.74
HOMO-2 (y2)
calculated and crystal conformations may be crystal packing
forces, which result in the alignment of the two porphyrins
in the Anderson dyad.[14] The inter-porphyrin angle is ex-
pected, intuitively, to be less relevant to the absorption and
emission properties of ethenediyl-linked porphyrin dyads,
than the angle between the porphyrins and the alkene.
Conclusion
We have prepared a variety of homo- and heterodiporphyr-
in, and homo- and heterodimetallic porphyrins linked by
a meso,meso-(E)-ethene-1,2-diyl bridge, using the Suzuki
coupling of porphyrinyl boronates and iodovinyl porphyrins.
This complements the Stille-coupling strategy of Anderson
and co-workers for homonuclear analogues. Through crystal
structure determination, electronic absorption and steady
state emission studies, and theoretical geometry and spectral
calculations, we have characterized the series thoroughly.
The overall conclusions from this study are that the ethene-
diyl-linked dyads exist in solution in a family of conforma-
tions that differ in the extent of conjugation across the
bridge, due to differing dihedral angles between the porphy-
rin and alkene planes. The fluorescence band at highest
energy, with a “monoporphyrin” excitation signature, results
from less planar conformations, while the lower energy
emission components result from conformations with small-
er dihedral angles. Anderson and co-workers likewise attrib-
uted the large Stokes shift, the broad absorption bands and
the low fluorescence quantum yield in their analogue of
Zn210 (compared to the ethynediyl-linked dyad), to the ef-
fects of populations with different torsional angles.[14] Wasie-
Figure 10. Experimental absorption spectrum (—) and predicted line
spectra from TDDFT calculations of the excited states of the conforma-
tions generated by geometry optimizations of Ni210 with two starting ge-
ometries (see text).
observed. It is therefore significant then that no such transi-
tion was predicted by the TDDFT calculations. As a result,
it is suggested that this band results from a dynamic process
unique to the OEP ethenediyl-linked dyads that cannot be
accounted for in gas-phase calculations of static structures.
In the crystal structures of meso,meso ethenediyl-linked
OEP dyads reported previously, the dihedral angle between
the porphyrin and the alkene is almost 908.[8,11] The only ex-
ample of a meso,meso ethenediyl-linked dyad with free b-
Chem. Eur. J. 2012, 18, 5574 – 5588
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
5585

D. P. Arnold et al.
sired product Ni210, which was recrystallised from CHCl3/methanol
lewski and co-workers concluded from temperature- and
solvent-dependence studies that two major conformations
give rise to the emission of a b,b ethenediyl-linked methyl-
pyrochlorophyllide a dyad, and that the two conformations
are related by a “bicycling” rotation of the single bonds be-
tween the alkene and the macrocycle.[36] Similar experiments
would be valuable in the current situation, but are beyond
the scope of the current work. Electronic structure calcula-
tions show that the meso,meso linked dyads have substantial
porphyrin interaction across the x bonding and anti-bonding
orbitals with a high electron density located on the alkene.
This highlights the importance of this bridge in the electron-
ic structures of these dyads.
1
3
(13.5 mg, 55%). H NMR (400 MHz, CDCl3, 258C, TMS): d=9.61 (d, J-
(H,H)=5.2 Hz, 2H, b-H), 9.01 (s, 2H, alkene-H), 8.88 (d, 3J
(H,H)=
5.2 Hz, 2H, b-H), 8.69 (d, 3J(H,H)=5.2 Hz, 2H, b-H), 8.67 (d, 3J-
AHCTUNGERTG(NNUN H,H)5.2 Hz, 2H, b-H), 8.01 (m, 12H, o-Ph-H), 7.68 ppm (m, 18H, m, p-
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
Ph-H); UV/Vis (DCM): lmax (loge)=410 (5.32), 471 (5.35), 538 (4.60),
632 nm (4.59); MS (LDI+): m/z: calcd for C78H48N8Ni2: 1212.27 [M+];
found: 1214.49.
5-[(10,15,20-Triphenyl)porphyrinatozinc(II)-5-yl]-[(10,15,20-triphenyl)-
porphyrinato-zinc(II)] (Zn212) and (E)-1-[10,15,20-triphenylporphyrina-
tonickel(II)-5-yl]-2-[10,15,20-triphenyl-5-ylporphyrinatozinc(II)-5-yl]e-
thene (NiZn10): Produced from Ni7 (14.9 mg) and Zn2 (14.8 mg) by the
general method at 808C. The product was purified by column chromatog-
raphy using CH2Cl2/n-hexane 40:60. The first minor band comprised
a mixture of unidentified porphyrins. The second band contained Zn3
while the third band contained the directly linked dyad Zn212. The
fourth band corresponded to the desired product NiZn10, which was re-
crystallised using CHCl3 (1% pyridine)/methanol (7.7 mg, 32%). Zn212:
1H NMR (400 MHz, CDCl3, 258C, TMS): d=8.91 (d, 3J
4H, b-H), 8.89 (d, 3J(H,H)=4.9 Hz, 4H, b-H), 8.49 (d, 3J
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
Experimental Section
R
4H, b-H), 8.26 (m, 4H, o-Ph-H), 8.18 (m, 8H, o-Ph-H), 7.81 (d, 3J
4.9 Hz, 4H, b-H), 7.75 (m, 6H, m, p-Ph-H), 7.62 ppm (m, 12H, m, p-Ph-
H); UV/Vis (DCM): lmax (loge) = 420 (5.32), 458 (5.29), 564 (4.60),
606 nm (3.81).
General procedure for Suzuki coupling for porphyrin dyads: Iodoethenyl-
porphyrin (0.02 mmol), borolanylporphyrin (0.02 mmol), bisACTHNUTRGENNG[U bisCAHTUNGTRENN(UGN 1,3-(di-
phenylphosphino)propane]palladium(0) (3.7 mg, 0.004 mmol, 20 mol%),
and Cs2CO3 (7.8 mg, 0.024 mmol) were added to a Schlenk tube and
dried under vacuum. The vacuum was released under argon to allow the
addition of dry DMF (0.75 mL), and dry toluene (1.5 mL). The mixture
was degassed via three freeze-pump-thaw cycles before the vessel was
purged with argon again. The Schlenk flask was sealed and the reaction
mixture was allowed to stir for 2 d. The progress of the reactions was
monitored by TLC using CH2Cl2/n-hexane 50:50 for free base porphyrin
and CHCl3/n-hexane (50:50) for metallated porphyrins. After 2 d, TLC
showed the complete consumption of borolanylporphyrin, so the mixture
was diluted with toluene (10 mL) and washed with water (10 mL x 2).
The organic layer was collected, dried and the residue was subjected to
column chromatography.
3
NiZn10: 1H NMR (400 MHz, CDCl3, 258C, TMS): d=9.84 (d, J (H,H)=
3
4.9 Hz, 2H, b-H, NiTriPP), 9.79 (d, J
A
9.54 (d, 3J
1H, 1-alkene-H), 8.99 (d, 3J
3J
(H,H)=15.2 Hz, 1H, 2-alkene-H), 9.47 (d, 3J
ACHUTGTNRENNUG CAHTUNGTRENNUNG
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
(d, JACTHNUTRGNENGU ACHUTTGNREN(NUGN H,H)=4.9 Hz, 2H b-
(H,H)=4.9 Hz, 2H, b-H, NiTriPP), 8.69 (d, 3J
3
H, NiTriPP), 8.22 (m, 6H, o-Ph-H, ZnTriPP), 8.04 (m, 6H, o-Ph-H, Ni-
TriPP), 7.70 ppm (m, 18H, m, p-Ph-H, ZnTriPP, NiTriPP); UV-Vis
(DCM): lmax (loge)=415 (5.33), 468 (5.19), 549 (4.18), 626 nm (4.13); MS
(ESI+): m/z: calcd for C78H48N8NiZn: 1218.2647 [M+]; found: 1218.2637.
(E)-1,2-Bis(10,15,20-triphenylporphyrin-5-yl)ethene (H410): Produced
from H27 (13.8 mg) and H22 (13.3 mg) by the general method at 408C.
The product was purified by column chromatography using CH2Cl2/n-
hexane 30:70. The first minor band contained an unidentified mixture of
porphyrins. The second band contained H23 and the third band contained
the directly linked dyad H412. The fourth band corresponded to the de-
sired product H410, which was recrystallised using CHCl3/methanol
(10.8 mg, 49%). 1H NMR (400 MHz, CDCl3, 258C, TMS): d=9.96 (s,
5-[(10,15,20-Triphenyl)porphyrin-5-yl]-[(10,15,20-triphenyl)porphyrin]
(H412) and (E)-1-(10,15,20-triphenylporphyrin-5-yl)-2-[10,15,20-triphenyl-
porphyrinatonickel(II)-5-yl]ethene (H2Ni10): Produced from Ni7
(14.9 mg) and H22 (13.3 mg) by the general method at 808C. CH2Cl2/n-
hexane 30:70 was used as eluent for the column. The first minor band
contained an unidentified green compound. The second band contained
H23 while the third band contained the directly linked dyad H412. The
fourth band corresponded to the desired product H2Ni10, which was re-
crystallised from CH2Cl2/methanol (6.9 mg, 30%). H412: 1H NMR
2H, alkene-H), 9.93 (d, 3J(H,H)=5.2 Hz, 4H, b-H), 9.01 (d, 3J
ACTHNUTRGENNUG ACHTUNGTRENNUNG(H,H)=
4.9 Hz, 4H, b-H), 8.84 (s, 8H, b-H), 8.26 (m, 12H, o-Ph-H), 7.78 (m,
18H, m, p-Ph-H), ꢁ2.26 ppm (br s, 4H, N-H); UV/Vis (DCM): lmax
(loge)=421 (5.21), 468 (4.86), 519 (4.28), 596 (4.27), 680 nm (4.08);
HRMS (LSIMS+) m/z: calcd for C78H53N8 +H+: 1101.4365 [M+H+];
found: 1101.4393).
(400 MHz, CDCl3, 258C, TMS): d=8.93 (d, 3J
8.90 (d, 3J(H,H)=4.9 Hz, 4H, b-H), 8.59 (d, 3J
8.29 (m, 4H, o-Ph-H), 8.22 (m, 8H, o-Ph-H), 8.08 (d, 3J
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
4H, b-H), 7.78 (m, 6H, m, p-Ph-H), 7.67 (m, 12H, m, p-Ph-H),
ꢁ2.21 ppm (brs, 4H, N-H); UV/Vis (DCM): lmax (loge)=414 (5.42), 450
(5.45), 524 (4.77), 560sh (4.26), 594 (4.32), 652 nm (4.02); HRMS (ESI+):
m/z: calcd for C76H50N8 +H+: 1075.4232 [M+H+]; found: 1075.4237.
(E)-1-[10,15,20-Triphenylporphyrinatozinc(II)-5-yl]-2-(10,15,20-triphenyl-
porphyrin-5-yl)-ethene (H2Zn10): Produced from H27 (13.8 mg) and Zn2
(14.8 mg) by the general method at 408C. The product was purified by
column chromatography using CH2Cl2/n-hexane 50:50. The first minor
band contained an unidentified mixture of porphyrins. The second band
contained Zn3 and the third band contained the directly linked dyad
Zn212 (9.1 mg). The fourth band corresponded to the desired product
H2Zn10, which was recrystallised using CHCl3(1% pyridine)/methanol
H2Ni10: 1H NMR (400 MHz, CDCl3, 258C, TMS): d=9.83 (d,3J
ACHTUNGTRENNUNG
4.9 Hz, 2H, b-H, NiTriPP), 9.76 (d, 3J
9.61 (d, 3J
ACHTUNGTRENNUNG
N
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
ACHTUNGTRENNUNG
1
3
(7.2 mg, 31%). H NMR (400 MHz, CDCl3, 258C, TMS): d=10.08 (d, J-
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
2H, b-H, NiTriPP), 8.26 (m, 6H, o-Ph-H, H2TriPP), 8.06 (m, 6H, o-Ph-H,
NiTriPP), 7.79 (m, 9H, m, p-Ph-H, H2TriPP), 7.72 (m, 9H, m, p-Ph-H,
NiTriPP), ꢁ2.30 ppm (brs, 2H, N-H, H2TriPP); UV/Vis (DCM): lmax
(loge)=419 (5.26), 469 (5.27), 521 (4.55), 560 (4.48), 606 (4.57), 677 nm
(4.46); HRMS (ESI+): m/z: calcd for C78H50N8Ni+H+: 1157.3590
[M+H+]; found: 1157.3570.
3
3
alkene-H), 9.97 (d, J (H,H)=15.3 Hz, 1H, alkene-H), 9.97 (d, JACHTUNGTRENNUNG
4.7 Hz, 2H, b-H, H2TriPP), 9.14 (d, JACTHUNGTRENNNUG
9.02 (d, JACTHUNGTRENNNUG
8.85 (s, 4H, b-H, ZnTriPP), 8.26 (m, 12H, o-Ph-H, H2TriPP, ZnTriPP),
7.78 (m, 18H, p-Ph-H, H2TriPP, ZnTriPP), ꢁ2.26 ppm (brs, 2H, N-H,
H2TriPP); UV/Vis (DCM): lmax (loge)=417 (5.21), 468 (4.82), 518 (4.16),
560 (4.17), 608 (4.18), 673 nm (3.97); HRMS (ESI+) m/z: calcd for
C78H51N8Zn+H+: 1163.3518 [M+H+]; found: 1163.3528.
3
3
(E)-1,2-Bis[10,15,20-triphenylporphyrinatonickel(II)-5-yl]ethene (Ni210):
Produced from Ni7 (14.9 mg) and Ni2 (14.7 mg) by the general method
at 808C. CHCl3/n-hexane 30:70 was used as the eluent for the column.
The first minor band contained an unidentified green compound. The
second band contained Ni3 while the third band corresponded to the de-
(E)-1,2-Bis[10,15,20-triphenylporphyrinatozinc(II)-5-yl]ethene (Zn210):
Produced from Zn7 (14.9 mg) and Zn2 (14.8 mg) by the general method
5586
www.chemeurj.org
ꢀ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2012, 18, 5574 – 5588

Homo- and Heteronuclear Diporphyrins
FULL PAPER
at 408C. CHCl3/n-hexane (30:70) was used as the eluent for the column.
The first band contained Zn3, the second band corresponded to directly
linked dimer Zn212 and the third band contained the desired product
Zn210, which was recrystallised using CHCl3(1% pyridine)/methanol
calcd for C88H75N8NiZn: 1366.4838 [M+]; found: 1366.4851. Third and
fourth bands were collected, containing Zn3 and Zn212, respectively.
1
3
(2.5 mg, 10%). H NMR (400 MHz, CDCl3, 258C, TMS): d=10.01 (d, J-
3
(H,H)5.2 Hz, 4H, b-H), 9.97 (s, 2H, alkene-H), 9.01 (d, J
E
Acknowledgements
3
3
4H, b-H), 8.85 (d, JACHTUNGTRENNUNG(H,H)=5.2 Hz, 4H, b-H), 8.83 (d, J (H,H)=5.2 Hz,
4H b-H), 8.24 (m, 8H, o-Ph-H), 8.21 (m, 4H, o-Ph-H), 7.72 ppm (m,
18H, m, p-Ph-H); UV/Vis (DCM): lmax (loge)=424 (5.35), 469 (5.19),
555 (4.55), 633 nm (4.48); MS (ESI+): m/z: calcd for C78H48N8Zn2:
1226.2585 [M+]; found: 1224.2461.
We thank the Queensland University of Technology for Post-Graduate
Scholarships for O.L. and B.B. We thank Dr. Llew Rintoul and Dr. Greg
Wilson for advice regarding DFT calculations and Jocelyn Bouzaid for
HRMS measurements.
(E)-1-[10,20-Bis(3,5-di-tert-butylphenyl)porphyrinatonickel(II)-5-yl]-2-
(10,15,20-triphenylporphyrin-5-yl)ethene (H2Ni11): Produced from Ni6
(17.9 mg) and H22 (13.3 mg) by the general method at 808C. CH2Cl2/n-
hexane 50:50 was used as the eluent for the column. The first minor band
contained an unidentified green compound. The second band contained
the desired product H2Ni11, which was recrystallised using CH2Cl2/meth-
anol (8.9 mg, 34%). 1H NMR (400 MHz, CDCl3, 258C, TMS): d=9.85
[1] a) T. S. Balaban, Acc. Chem. Res. 2005, 38, 612–623; b) M. R. Wa-
sielewski, J. Org. Chem. 2006, 71, 5051–5066; c) S. Fukuzumi, Bull.
Chem. Soc. Jpn. 2006, 79, 177–195; d) M. S. Choi, T. Yamazaki, I.
Yamazaki, T. Aida, Angew. Chem. 2004, 116, 152–160; Angew.
Chem. Int. Ed. 2004, 43, 150–158; e) S. Fukuzumi, in Handbook of
Porphyrin Science Vol. 10 (Eds.: K. M. Kadish, K. M. Smith, R. Gui-
lard), World Scientific, Singapore, 2010, pp. 183–243; f) P. D.
Harvey, C. Stern, R. Guilard, in Handbook of Porphyrin Science
Vol. 11 (Eds.: K. M. Kadish, K. M. Smith, R. Guilard), World Scien-
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Hough, M. J. Crossley, N. S. Hush, J. R. Reimers, J. Am. Chem. Soc.
2002, 124, 9299–9309; h) Y. Nakamura, N. Aratani, H. Shinokubo,
A. Takagi, T. Kawai, T. Matsumoto, Z. S. Yoon, D. Y. Kim, T. K.
Ahn, D. Kim, A. Muranaka, N. Kobayashi, A. Osuka, J. Am. Chem.
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shi, K. Tanaka, J. Mater. Chem. 2001, 11, 2262–2270; j) K. Tagami,
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Matsuzaki, A. Nogami, A. Tsuda, A. Osuka, K. Tanaka, J. Phys.
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book of Porphyrin Science Vol. 1 (Eds.: K. M. Kadish, K. M. Smith,
R. Guilard), World Scientific, Singapore, 2010, pp. 1–132.
(d, 3J(H,H)=4.9 Hz, 2H, b-H, NiDAP), 9.76 (d, 3J
ACHTUNGTRENNUNG ACHTUNTGREN(NUGN H,H)=4.9 Hz, 2H b-
H, H2TriPP), 9.74 (s, 1H, meso-H, NiDAP), 9.64 (d, 3J
N
3
3
1H, 2-alkene-H), 9.45 (d, J
U
A
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
NiDAP), 7.76 (m, 11H, m, p-Ph-H, H2TriPP, p-Ar-H, NiDAP), 1.50 (s,
36H, tBu-H, NiDAP), ꢁ2.34 ppm (brs, 2H, N-H, H2TriPP); UV/Vis
(DCM): lmax (loge)=423 (5.38), 466 (5.33), 523 (4.56), 562 (4.45), 606
(4.56), 675 nm (4.42); MS (ESI+) m/z: calcd for C88H79N8Ni: 1304.5703
[M+]; found: 1305.5643. Third and fourth bands were collected, contain-
ing H23 and H412, respectively.
(E)-1-[Bis(3,5-di-tert-butylphenyl)porphyrinatonickel(II)-5-yl]-2-
[10,15,20-triphenylporphyrinatonickel(II)-5-yl]ethene (Ni211): Produced
from Ni6 (17.9 mg) and Ni2 (14.7 mg) by the general method at 808C.
CHCl3/n-hexane (50:50) was used as the eluent for the column. The first
minor band contained an unidentified green compound. The second band
contained the desired product Ni211, which was recrystallised using
CHCl3/methanol (12.2 mg, 45%). 1H NMR (400 MHz, CDCl3, 258C,
[2] D. Holten, D. F. Bocian, J. S. Lindsey, Acc. Chem. Res. 2002, 35, 57–
69.
[3] a) T. Ikeda, J. M. Lintuluoto, N. Aratani, Z. S. Yoon, D. Kim, A.
Osuka, Eur. J. Org. Chem. 2006, 3193–3204; b) A. K. Sahoo, Y. Na-
kamura, N. Aratani, K. S. Kim, S. B. Noh, H. Shinokubo, D. Kim, A.
Osuka, Org. Lett. 2006, 8, 4141–4144; c) Y. Nakamura, N. Aratani,
K. Furukawa, A. Osuka, Tetrahedron 2008, 64, 11433–11439; d) Y.
Nakamura, S. Y. Jang, T. Tanaka, N. Aratani, J. M. Lim, K. S. Kim,
D. Kim, A. Osuka, Chem. Eur. J. 2008, 14, 8279–8289.
[4] a) D. P. Arnold, G. A. Heath, D. A. James, New J. Chem. 1998, 22,
1377–1387; b) D. P. Arnold, G. A. Heath, D. A. James, J. Porphyrins
Phthalocyanines 1999, 3, 5–31; c) G. J. Wilson, D. P. Arnold, J. Phys.
TMS): d=9.70 (s, 1H, meso-H, NiDAP), 9.65 (d, 3J
b-H, NiDAP), 9.63 (d, 3J (H,H)=4.9 Hz, 2H, b-H, NiTriPP), 9.08 (d, 3J-
(H,H)=4.9 Hz, 2H, b-H, NiDAP), 9.07 (s, 2H, alkene-H), 8.Ni3 (d, 3J-
(H,H)=4.9 Hz, 2H, b-H, NiDAP), 8.88 (d, 3J
(H,H)=4.9 Hz, 2H, b-H,
ACHTUNGTREN(NGNU H,H)=4.9 Hz, 2H,
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
3
3
NiDAP), 8.87 (d, JACHTUNGTRENNUNG(H,H)=4.9 Hz, 2H, b-H, NiTriPP), 8.69 (d, JACHTNUGTRENNUNG
4.9 Hz, 2H, b-H, NiTriPP), 8.67 (d, 3J
ACHTUNGTRENNUNG
8.01 (m, 6H, o-Ph-H, NiTriPP), 7.90 (d, 4J
(H,H)=1.7 Hz, 4H, o-Ar-H,
(H,H)=1.7, 2H, p-Ar-H, NiDAP), 7.68 (m, 9H, m, p-
4
Chem.
A 2005, 109, 6104–6113; d) H. L. Anderson, Chem.
NiDAP), 7.74 (d, J
G
Commun. 1999, 2323–2330; e) J. J. Piet, P. N. Taylor, B. R. Wegewijs,
H. L. Anderson, A. Osuka, J. M. Warman, J. Phys. Chem. B 2001,
105, 97–104; f) A. Karotki, M. Drobizhev, Y. Dzenis, P. N. Taylor,
H. L. Anderson, A. Rebane, Phys. Chem. Chem. Phys. 2004, 6, 7–
10; g) M. Drobizhev, Y. Stepanenko, Y. Dzenis, A. Karotki, A.
Rebane, P. N. Taylor, H. L. Anderson, J. Am. Chem. Soc. 2004, 126,
15352–15353; h) T. V. Duncan, S. P. Wu, M. J. Therien, J. Am.
Chem. Soc. 2006, 128, 10423–10435; i) K. Susumu, P. R. Frail, P. J.
Angiolillo, M. J. Therien, J. Am. Chem. Soc. 2006, 128, 8380–8381;
j) K. Ogawa, H. Hasegawa, Y. Inaba, Y. Kobuke, H. Inouye, Y. Ka-
nemitsu, E. Kohno, T. Hirano, S.-i. Ogura, I. Okura, J. Med. Chem.
2006, 49, 2276–2283; k) T.-H. Huang, Y.-J. Chen, S.-S. Lo, W.-N.
Yen, C.-L. Mai, M.-C. Kuo, C.-Y. Yeh, Dalton Trans. 2006, 2207–
2213; l) M. Hoffmann, C. J. Wilson, B. Odell, H. L. Anderson,
Angew. Chem. 2007, 119, 3183–3186; Angew. Chem. Int. Ed. 2007,
46, 3122–3125; m) M. Hoffmann, J. Kornbratt, M.-H. Chang, L. M.
Herz, B. Albinsson, H. L. Anderson, Angew. Chem. 2008, 120,
5071–5074; Angew. Chem. Int. Ed. 2008, 47, 4993–4996.
Ph-H, H2TriPP), 1.50 ppm (s, 36H, tBu-H, NiDAP); UV-Vis (DCM): lmax
(loge)=415 (5.30), 466 (5.33), 533 (4.59), 625 (4.53) nm; MS (LDI+)
m/z: calcd for C88H76N8Ni2: 1360.5 [M+]; found: 1361.5.
(E)-1-[10,20-Bis(3,5-di-tert-butylphenyl)porphyrinatonickel(II)-5-yl]-2-
[10,15,20-triphenylporphyrinatozinc(II)-5-yl]ethene (NiZn11): Produced
from Ni6 (17.9 mg) and Zn2 (14.8 mg) by the general method at 808C.
The product was purified by column chromatography using CHCl3/n-
hexane (50:50). The first minor band contained an unidentified mixture
of porphyrins. The second band contained the desired product NiZn11,
which was recrystallised using CHCl3(1% pyridine)/methanol (7.7 mg,
28%). 1H NMR (400 MHz, CDCl3, 258C, TMS): d=9.87 (d, 3J
5.1 Hz, 2H, b-H, NiDAP), 9.80 (d, 3J
(H,H)=4.9 Hz, 2H, b-H, ZnTriPP),
9.70 (s, 1H, meso-H, NiDAP), 9.58 (d, 3J
(H,H)=15.2 Hz, 1H, 2-alkene-
H), 9.51 (d, 3J(H,H)=15.2 Hz, 1H, 1-alkene-H), 9.09 (d, 3J
(H,H)=
4.9 Hz, 2H, b-H, NiDAP), 8.98 (d, 3J
(H,H)=5.1 Hz, 2H, b-H, NiDAP),
8.97 (d, 3J(H,H)=4.6 Hz, 2H, b-H, ZnTriPP), 8.89 (d, 3J
(H,H)=4.9 Hz,
ACHTUNGTRNE(NUNG H,H)=
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
A
ACHTUNGTRENNUNG
2H, b-H, NiDAP), 8.82 (br s, 4H, b-H, ZnTriPP), 8.21 (m, 6H, o-Ph-H,
4
ZnTriPP), 8.17 (m, 2H, o-Ph-H, ZnTriPP), 7.92 (d, J
N
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Received: September 23, 2011
Published online: March 27, 2012
5588
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Chem. Eur. J. 2012, 18, 5574 – 5588