New and efficient arrays for photoinduced charge separation based on perylene bisimide and corroles

Article abstract of DOI:10.1002/chem.200700866

The bichromophoric systems C2-PI, C3-PI, and C3-PPI consisiting of corrole and perylene bisimide units and representing one of the rare cases of elaborate structures based on corrole, have been synthesized. Corroles C2 and C3 are, respectively, meso-substituted corroles with 2,6-dichlorophenyl and pentafluorophenyl substituents at the 5 and 15 positions. The three dyads were prepared by divergent strategy with the corrole-forming reaction as the last step of the sequence. C2-PI and C3-PI differ in the nature of the corroles, whereas C3-PI differs from C3-PPI in the presence of a further phenyl unit in the linker between photoactive units. The dyads display spectroscopic properties which are the superposition of the component spectra, indicating a very weak electronic coupling. Excitation of the corrole unit leads to charge separation with a rate which decreases from 2.4 × 10¹⁰, to 5.0 × 10⁹, and to 4.9 × 10⁷ s^-1 for C2-PI, C3-PI, and C3-PPI, respectively, where the reaction is characterized by a ΔG° > 0. Excitation of the perylene bisimide unit is followed by competing reactions of; 1) energy transfer to the corrole unit, which subsequently deactivates to the charge-separated state and; 2) electron transfer to directly form the charge-separated state. The ratio of electron-to-energy- transfer rates is 9;1 and 1;1 for C3-PI and C3-PPI, respectively. The yield of charge separation is essentially 100% for C2-PI and C3-PI, and approximately 50% (excitation of peryleneimide) or 15% (excitation of the corrole) for C3-PPI. The lifetime of the charge-separated state, observed for the first time in corrole-based structures, is 540 ps for C2-PI, 2.5 ns for C3-PI, and 24 ns for C3-PPI, respectively. This is in agreement with an inverted behavior, according to Marcus theory.

Full text of DOI:10.1002/chem.200700866

FULL PAPER
DOI: 10.1002/chem.200700866
New and Efficient Arrays for Photoinduced Charge Separation Based on
Perylene Bisimide and Corroles
Lucia Flamigni,*[a] Barbara Ventura,[a] Mariusz Tasior,[b] Thomas Becherer,[c]
Heinz Langhals,*[c] and Daniel T. Gryko*[b]
Abstract: The bichromophoric systems
C2-PI, C3-PI, and C3-PPI consisiting
of corrole and perylene bisimide units
and representing one of the rare cases
of elaborate structures based on cor-
role, have been synthesized. Corroles
C2 and C3 are, respectively, meso-sub-
stituted corroles with 2,6-dichlorophen-
yl and pentafluorophenyl substituents
at the 5 and 15 positions. The three
dyads were prepared by divergent
strategy with the corrole-forming reac-
tion as the last step of the sequence.
C2-PI and C3-PI differ in the nature of
the corroles, whereas C3-PI differs
from C3-PPI in the presence of a fur-
ther phenyl unit in the linker between
photoactive units. The dyads display
spectroscopic properties which are the
superposition of the component spec-
tra, indicating a very weak electronic
coupling. Excitation of the corrole unit
leads to charge separation with a rate
which decreases from 2.4”1010, to 5.0”
109, and to 4.9”107 sꢀ1 for C2-PI, C3-
PI, and C3-PPI, respectively, where the
reaction is characterized by a DG8>0.
Excitation of the perylene bisimide
unit is followed by competing reactions
of: 1) energy transfer to the corrole
unit, which subsequently deactivates to
the charge-separated state and; 2) elec-
tron transfer to directly form the
charge-separated state. The ratio of
electron-to-energy-transfer rates is 9:1
and 1:1 for C3-PI and C3-PPI, respec-
tively. The yield of charge separation is
essentially 100% for C2-PI and C3-PI,
and approximately 50% (excitation of
peryleneimide) or 15% (excitation of
the corrole) for C3-PPI. The lifetime
of the charge-separated state, observed
for the first time in corrole-based struc-
tures, is 540 ps for C2-PI, 2.5 ns for C3-
PI, and 24 ns for C3-PPI, respectively.
This is in agreement with an inverted
behavior, according to Marcus theory.
Keywords: charge separation · cor-
roles · electron transfer · photo-
chemistry · porphyrinoids
Introduction
or replicate the characteristics of already known dyes to be
used in the construction of functional molecular arrays and
materials is an important topic in synthetic and physical
chemistry nowadays. In the last decades the efforts to in-
crease the list of available chromophores adding new ones
with specific absorption, emission, redox, and excited-state
properties have produced a wide variety of compounds
which can be usefully employed in the engineering of smart
multicomponent structures able to perform light-driven ac-
tions.[1] The class of porphyrins has long been the most fre-
quently used in the construction of these arrays[2] and has re-
cently been extended with several new chromophores. Ex-
panded porphyrins,[3] porphyrin tapes,[4] phthalocyanines,[5]
subphthalocyanines,[6] chlorins,[7] porphyrins with an expand-
ed p-conjugated system[8] have proven to be viable alterna-
tives to simple porphyrins in the construction of photoactive
dyads or higher homologues.
Light-induced processes and properties are receiving in-
creasing interest regarding their potential use in several im-
portant fields. The search for new chromophores exhibiting
photo- and electroactive properties which can complement
[a]Dr. L. Flamigni, Dr. B. Ventura
Istituto ISOF-CNR, Via P. Gobetti 101, 40129 Bologna (Italy)
Fax : (+39)051-639-9844
E-mail: flamigni@isof.cnr.it
[b]M. Tasior, Dr. D. T. Gryko
Institute of Organic Chemistry of the Polish Academy of Sciences
Kasprzaka 44/52, 01–224 Warsaw (Poland)
Fax : (+48)22-632-6681
E-mail: daniel@icho.edu.pl
[c]T. Becherer, Prof. Dr. H. Langhals
Department of Chemistry, LMU University of Munich
Butenandtstrasse 13, 81377 Munich (Germany)
Fax : (+49)89-2180-77640
In this context, we have studied over the last few years
the photophysical properties of free-base corroles and their
potential use in the construction of assemblies with useful
E-mail: Langhals@lrz.uni-muenchen.de
Chem. Eur. J. 2008, 14, 169 – 183
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
169

photoinduced properties. This research can be regarded as
part of the more general and rapidly increasing interest in
corroles, their synthesis, reactivity, and applications.[9] Con-
cerning free base-corroles, we and others have shown that
these tetrapyrrolic species, especially when bearing electron-
withdrawing substituents, are photostable, display high lumi-
nescence, can sensitize singlet oxygen, have singlet and trip-
let excited states with well-characterized spectra and can be
easily oxidized and reduced.[10,11,12] Free-base corroles can
be connected to other units yielding photo- and thermally
stable dyads able to undergo interesting photoinduced pro-
cesses, such as energy[13,14,15] or electron transfer.[15] Herein
we address the formation of charge-separated states follow-
ing photoinduced electron transfer in new free-base corrole-
based dyads. To have efficient electron transfer and the pos-
sibility to unambiguously identify and study the charge-sepa-
rated states (CS) the corrole has been connected to a pery-
lene bisimide unit. The latter is a stronger electron acceptor
than the phenylene derivative and has similar electron affin-
ity to the naphthalene bisimide (E1/2 of the order of ꢀ0.5 V
versus SCE). It also has a well-characterized and extremely
phores is concerned we chose simple phenylmethylene and
biphenylmethylene groups which should guarantee a good
structural control and a sufficient electronic coupling to
allow intramolecular processes.
In light of the considerations above, the crucial part of
the synthesis of the dyads was the facile generation of the
pivotal perylene bisimide core, endowed with an aldehyde
functionality for further elaboration. Clearly, synthons for
such synthesis need to possess both primary amino and
formyl groups, but the formyl group needs to be present in a
protected form. Additionally, the perylene bisimide unit has
to show good solubility in common organic solvents,[21] pos-
sess a formyl group, and be robust. A few different ap-
proaches have been proposed towards producing perylene
bisimides with good solubility. The most common is to use
2,6-diisopropylphenylamine[19] or 2,5-di-tert-butylphenyla-
mine[22] as solubilizing moieties. After preliminary experi-
ments we decided to focus on less common, but more effi-
cient “swallow-tail” aliphatic amines introduced by Langh-
als.[23] We used monoimide-monoanhydride 4[24] as the cru-
cial building block which has to be combined with the unit
containing free amino and protected aldehyde units. Suita-
intense
spectrum
of
the
reduced
radical
(e
ꢁ100000mꢀ1 cmꢀ1) in the near-infrared (NIR) spectral
region and therefore is very useful in the characterization
and study of the CS state.[16–18]
ble building block 3 was synthesized in two steps
(Scheme 1) from 4-cyanobenzaldehyde (1).[25] Final conden-
sation performed in melted imidazole[26] in the presence of
zinc acetate afforded aldehyde 5 in 76% yield (Scheme 1).
A chromatographic purification of initially formed acetal
with silica[27] and ethanol proceeded with deprotection to
form the aldehyde 5 directly. Although it is well described
in the literature that mix-condensation of perylene bisanhy-
dride (6) with two different amines leads almost exclusively
to symmetrically substituted product,[21] we decided to try
this approach as a conceptually simpler alternative pathway.
Thus perylene-3,4,9,10-tetracarboxylic dianhydride 6, amine
7, and amine 8[15] (bearing a masked formyl group) were
heated in melted imidazole for 24 hours. After typical
workup, we were delighted to find that all three possible
products could be detected by using TLC. The column chro-
matography allowed us to separate the desired acetal from
PI0 and from the second symmetrical side product. Subse-
quent cleavage by using a DCM/TFA mixture afforded alde-
hyde 5 in 16% yield (after 2 steps).
Results and Discussion
Design and synthesis: Several issues merit particular consid-
eration when contemplating the synthesis of complex dyads
that contain corrole. Regarding synthetic efficiency, in anal-
ogy to porphyrins, two general strategies are possible. The
first starts with the synthesis of corrole followed by modifi-
cations of peripheral substituents. The second strategy starts
with the preparation of an elaborated aldehyde which will
then be used in the reaction that forms corrole. Given the
moderate stability of corroles it is desirable to perform as
few manipulations as possible. In this regard we decided to
follow the second route as in our previous endeavor.[15] It is
worth to mention that all dyads composed of perylene bisi-
mide and porphyrin moieties studied to date (with one ex-
ception)[19] were synthesized by the opposite approach (that
is, through joining both units).[7c,18i,19]
We decided to further build up our experience in the syn-
thesis of meso-substituted trans-A2B-corroles from dipyrro-
methanes and aldehydes.[20] This methodology allows the in-
troduction of the desired substituent at the 10 position of
the macrocycle core. The two remaining identical substitu-
ents at the positions 5 and 15 allow the control of other
properties of the system, such as, solubility, stability, and
redox properties. We envisaged the use of two different
types of substituents at these positions: The strongly elec-
tron-withdrawing pentafluorophenyl group and the sterically
hindered 2,6-dichlorophenyl group. This choice was induced
by the desire to achieve reasonable stability and solubility of
the dyads. As far as the linker connecting both chromo-
The synthesis of aldehyde 14 bearing the elongated biphe-
nylene unit took significantly longer although a similar
method was used. The crucial biphenyl linkage was created
through Suzuki coupling of 4-bromo-1-cyanobenzene (9)
and 4-formylboronic acid (10) (Scheme 2).[28] The following
protection with ethylene glycol and further reduction with
LAH afforded amine 13 in 19% overall yield. Subsequent
condensation with monoanhydride 4 afforded aldehyde 14
in 57% yield (Scheme 2). Both aldehydes were highly solu-
ble in CH2Cl2 which is the typical solvent of choice in the
synthesis of porphyrinoids.
Aldehydes 5 and 14 were subjected to conditions for the
synthesis of trans-A2B-corroles by using aldehydes and di-
pyrromethanes.[20] Poor solubility of perylene-aldehydes in
MeOH precluded the use of otherwise superior H2O/
170
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 169 – 183

Arrays for Photoinduced Charge Separation
FULL PAPER
Scheme 2. The synthesis of aldehyde 14.
Scheme 1. The synthesis of aldehyde 5.
dyads have different substituents around the corrole periph-
ery, 5,15-bis(2,6-dichlorophenyl)corrole moiety (C2), and a
5,15-bis(pentafluorophenyl)corrole moiety (C3) and the
latter dyads have different distances between the perylene
bisimide and the corrole component, having one or two
phenyl groups, respectively, between the imidic nitrogen and
the corrole meso position. The absorption spectra of the
components superimposed with the spectrum of the dyad
are reported in the three panels of Figure 1. Model C2 dis-
plays a splitting of the Soret band previously discussed[15]
and typical of corroles with a deviation from planarity of
the macrocycle induced by crowding of substituents and re-
ported for meso aryl groups bearing bulky ortho substitu-
ents.[12,11]
MeOH/HCl conditions.[29] Consequently, we condensed di-
pyrromethanes 15 and 16 with aldehyde 5 in CH2Cl2 in the
presence of TFA, under slightly more acidic conditions de-
scribed in original publications.[20c,d] Quenching of the reac-
tion with p-chloranil or DDQ resulted in the corresponding
dyads C2-PI and C3-PI in 14 and 15% yields, respectively
(Scheme 3). Analogous condensation of aldehyde 14 with di-
pyrromethane 16 furnished dyad C3-PPI in 11% yield.
Photophysical properties
Absorption spectroscopy: A spectroscopic and photophysi-
cal investigation was carried out on corrole component
models C2, C3, and on perylene bisimide model PI0, as well
as, on the three dyads C2-PI, C3-PI, C3-PPI. The first two
The dyads C2-PI, C3-PI, and C3-PPI display spectra
which are essentially the superimposed absorption spectra
of the component models, Figure 1. A very slight bathochro-
Chem. Eur. J. 2008, 14, 169 – 183
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
171

L. Flamigni, H. Langhals, D. T. Gryko et al.
mic shift (2–3 nm) in the absorption maximum of the dyads
with respect to the components can be noticed in C2-PI and
C3-PI, but it is completely absent in C3-PPI, where the in-
sertion of a further phenyl group electronically decouples
components even more. In all cases, the good additive prop-
erties of the spectra indicate a very weak electronic coupling
between the components and allow an approach based on a
localized description of the individual subunits in the subse-
quent discussion of the photoinduced-energy and electron-
transfer reactions.
dyads is possible at wavelength >560 nm, whereas major ex-
citation of the imide unit (about 85–90%) is possible on the
two major peaks of the PI unit at 490 and 527 nm.
Luminescence spectroscopy: The luminescence spectra of
model corroles C2 and C3 excited at 565 nm are reported in
Figure 2. The luminescence spectra of the dyads C2-PI, C3-
PI, C3-PPI selectively excited at the corrole units under the
same experimental conditions are also shown in Figure 2.
The fluorescence quantum yield of corroles is Ffl =0.06 and
0.14 for C2 and C3, respectively, whereas the fluorescence
of the corrole units in the dyads decreases in a different
From inspection of the spectra in Figure 1 one can see
that selective excitation of the corrole component in the
172
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 169 – 183

Arrays for Photoinduced Charge Separation
FULL PAPER
Scheme 3. The synthesis of dyads.
order: Ffl =0.0015, 0.0076, and 0.12 for C2-PI, C3-PI, and
C3-PPI, respectively. The quenching is quite strong in the
first two dyads, but it is only of the order of 15% in C3-PPI,
characterized by a larger distance between bisimide and cor-
role. The results of excitation at 490 nm, where the PI unit
is preferably excited (90% in C2-PI, 87% in C3-PI and C3-
PPI, respectively), are shown in Figure 3. This compares the
luminescence of the dyads with that of the models PI0, C2,
or C3 with concentrations adjusted to absorb the same
number of photons as those absorbed by the pertinent unit
in the dyad. The luminescence of PI0 is scaled by a factor of
100 to better visualize the less intense emissions from the
corroles and the dyads. The displayed results show that the
emission of the perylene bisimide unit is quenched to less
than 1% in all dyads, whereas the luminescence of corroles
is quenched to 20 and 25% in C2-PI and C3-PI, respectively
(less than upon selective excitation of the corrole unit), but
it is increased by a factor of approximately four in C3-PPI
(Figure 3). If one takes into account that at the excitation
wavelength the absorbance of the corrole unit in C3-PPI is
about 14% (see above) a quantitative sensitization of the
Figure 1. Absorbtion spectra of the model components and of the arrays
in toluene. a) C2 (b), PI0 (g), C2-PI (c); b) C3 (b), PI0
(g), C3-PI (c); c) C3 (b), PI0 (g), C3-PPI (c).
corrole unit by the bisimide component would increase the
corrole emission about seven times.
Time-resolved luminescence studies were performed by
using a picosecond time-resolved system after excitation at
532 nm and
a nanosecond-time-correlated single-photon
counting apparatus following excitation at 560 nm (selective
excitation of the corrole unit) and 465 nm (prevalent excita-
tion of the bisimide unit). Models C2, C3, and PI0 have life-
times of 1.7, 3.8, and 4 ns, respectively, in toluene, at room
temperature. Time-resolved spectra with picosecond resolu-
tion in the dyads C2-PI, C3-PI, and C3-PPI show the pres-
ence of the bisimide luminescence early on which decays
during the pulse and leaves the luminescence of the corrole
component. In all dyads the luminescence lifetime of the
Chem. Eur. J. 2008, 14, 169 – 183
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
173

L. Flamigni, H. Langhals, D. T. Gryko et al.
Figure 2. Room-temperature luminescence spectra in toluene of model
corroles and dyads excited at 565 nm. a) C2 (b) and C2-PI (c) A=
0.136; b) C3 (b), C3-PI (c), C3-PPI (g) A=0.133.
perylene bisimide unit is reduced to ꢂ10 ps (the time reso-
lution of the apparatus). The lifetime of the corrole unit is
decreased to 40 ps, 190 ps, and 3.2 ns in C2-PI, C3-PI, and
C3-PPI, respectively (Figure 4). These values represent
about 2, 5, and 85%, respectively, of the lifetimes of the per-
tinent model, and are fully consistent with the reduction in
luminescence quantum yield upon selective excitation of the
corrole unit at 565 nm discussed above and amounting to
2.5, 5.4, and 86% for C2-PI, C3-PI, and C3-PPI, respective-
ly (Table 1). It is therefore clear that after excitation of the
corrole unit in the dyad the excited state is depopulated by
a process with an efficiency decreasing in the order C2-PI>
C3-PI>C3-PPI, however, excitation of the bisimide under
certain conditions causes an increase of the population of
the excited state localized on corrole as verified by steady-
state luminescence results. Time-resolved luminescence
spectroscopy gives an “instant” picture rather than an “inte-
grated” picture and indicates that the luminescent excited
states of both imide and corrole undergo a decrease in life-
times, in most cases very important. To obtain more insight
on the mechanism of deactivation of the excited states, we
determined the excitation spectra of the corrole lumines-
cence at l=735 nm. The spectra, reported in Figure 5, show
that for all dyads excitation of perylene bisimide is effective
(the typical absorption peaks of PI0 appear at 490 and
527 nm) in producing corrole luminescence although with
different efficiencies, as the comparison with the normalized
absorption spectra shows. This indicates the occurrence of
Figure 3. Room-temperature luminescence spectra in toluene of models
and dyads excited at 490 nm. The luminescence of PI0 is divided by 100.
a) C2 (b), PI0 (g), C2-PI A=0.12 (c); b) C3 (b), PI0 (g),
C3-PI A=0.12 (c); c) C3 (b), PI0 (g), C3-PPI A=0.12 (c).
The absorbance of the solutions are arranged to provide the same num-
bers of photons absorbed by the reference model and the same unit in
the arrays.
an energy-transfer process from the bisimide excited state to
the corrole, however the absence of quantitative sensitiza-
tion of corrole luminescence in all dyads suggests the exis-
tence of other competitive processes which will be discussed
below.
Luminescence spectra and lifetimes of the models were
measured at 77 K in a glassy toluene matrix and are report-
ed in Table 1 along with the room-temperature lumines-
cence data. Model PI0 shows the same lifetime as at room
temperature, 4 ns, and a slight bathochromic shift. The cor-
roles display a slight increase in the lifetime and nearly iden-
174
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 169 – 183

Arrays for Photoinduced Charge Separation
FULL PAPER
Figure 4. Time evolution of the luminescence registered at 650 nm from
dyads in toluene after excitation with a laser pulse (35 ps, 532 nm, 1 mJ):
*
*
C2-PI (c), C3-PI ( ), and C3-PPI ( ).
tical band maxima. Concerning the dyads, though a quanti-
tative evaluation of emission quantum yields is prevented by
geometric factors (see Experimental Section for emission at
77 K), some qualitative considerations can be derived. PI lu-
minescence is nearly completely suppressed also at 77 K in
all dyads; the luminescence of the corrole unit is not
quenched or only slightly quenched in C3-PI and C3-PPI,
but it is absent in C2-PI (data not shown).
Transient absorption spectroscopy: Valuable information on
non-emitting intermediates formed during the deactivation
process can be gained by transient absorption techniques.
We performed transient absorbance experiments with pico-
second resolution upon excitation at 532 nm. At this wave-
length the perylene bisimide unit absorbs around 90% and
the corroles about 10% of the photons.
The end-of-pulse transient absorption spectra detected
with picosecond resolution of the models C2, C3, PI0, and
the dyads C2-PI and C3-PPI are reported in Figure 6. The
results for C3-PI show identical intensity and spectral shape
to those for C2-PI and are not shown. The absorbances of
the examined solutions have been arranged to provide the
same absorbance of the model solutions as that of the corre-
sponding unit in the array, in order to allow a direct compar-
Figure 5. Excitation spectra measured at 735 nm (c) and absorption
spectra normalized in the corrole Q-band region (b). a) C2-PI; b) C3-
PI; c) C3-PPI.
ison of the transient signals.
Table 1. Fluorescence data of dyads C2-PI, C3-PI, C3-PPI, and models in air-equilibrated toluene at 295 K,
and in rigid toluene glass at 77 K.
Models C2 and C3 display ab-
sorption spectra attributed to
the lowest singlet excited state
1C2 or 1C3 with negative fea-
tures at 655 nm, due to the
stimulated emission and posi-
295 K
lmax [nm]
77 K
lmax [nm]
[a]
[b]
[c]
State
Ffl
Ffl
Ffl
t[ns][d]
t[ns][d]
E[eV][e]
PI0
C2
C2-PI
1PI0
534, 574, 622
653, 710 (sh)
535, 576
652
656, 716 (sh)
535, 575
658, 728 (sh)
534, 574
657, 720 (sh)
0.92
0.06
4.0
1.7
543, 587, 638 4.0
2.28
1.90
2.28
1.90
1.90
2.28
1.90
2.28
1.89
1C2
652, 717
543, 587
653
2.5
C2-1PI
1C2-PI
1C3
0.0021
0.013
ꢂ10 ps
40 ps
3.8
ꢂ10 ps
190 ps
ꢂ10 ps
3.2
tive
absorbance
above
0.0015
750 nm.[10] The signal is, howev-
er, very weak under the experi-
mental conditions. Model PI0
displays negative signals around
575 and 625 nm, due to the
lowest energy bands of the
stimulated emission, and posi-
tive peaks at 690 and 855 nm,
C3
C3-PI
0.14
654, 718
543, 587
654, 720
543, 585
656, 718
5.2
C3-1PI
1C3-PI
0.0010
0.036
0.0023
0.54
0.0076
0.12
C3-PPI C3-1PPI
1C3-PPI
5.0
[a]Luminescence yields in air-equilibrated solutions, excitation at 490 nm for PI0 and at 560 nm for corroles.
[b]Luminescence yields upon selective excitation of corrole component at 565 nm. [c]Luminescence yields
upon excitation at 490 nm, absorption of the PI component in the dyads is about 90%. [d]Excitation at 465,
560, and 532 nm for PI0, corroles, and dyads, respectively. [e]Derived from the emission maxima at 77 K.
Chem. Eur. J. 2008, 14, 169 – 183
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
175

L. Flamigni, H. Langhals, D. T. Gryko et al.
Figure 6. End-of-pulse absorption spectra of C2 (b) A=0.05, C3 (d)
*
*
A=0.05, PI0 (g) A=0.43, C3-PI A=0.6 ( ), C3-PPI A=0.6 ( ), C2-
PI A=0.6 is superimposable on that of C3-PI and not shown. The ab-
sorbance of the solutions has been adjusted to provide the same light ab-
sorbance by the unit in the model and in the dyad.
1
assigned to the singlet excited state PI0. The decay of the
spectra in the time window of the experiment (0–3.3 ns) is
low, but compatible with a lifetime of 4 ns, confirming the
assignment to the lowest singlet excited state. The spectra in
the dyads are characterized by very strong features with
maxima at 710, 800, and 960 nm identical for the three
dyads, but in C3-PPI the intensity of the signal is only half
that in C2-PI and C3-PI. Since these bands are not present
in the component units and they appear very quickly, we
have to assign them to the product of an intramolecular pro-
cess. According to previous spectroelectrochemical charac-
terization, they can be assigned to the perylene bisimide
anion.[16,17] To explain this, we assume that intramolecular
transfer of an electron takes place leading to the formation
of a charge-separated state (CS) with the hole localized on
the corrole unit and the electron on the PI unit.[18] The time
evolution of the bands assigned to CS is different for the dif-
ferent dyads. In Figure 7 the time-resolved spectra taken at
710 nm with delays of 165 ps for C2-PI and C3-PI are
shown. The CS time evolution is characterized for both
dyads by an immediate (during the laser pulse) formation
and by a slower rise with lifetimes of 40 and 190 ps for C2-
PI and C3-PI, respectively. This slower rise accounts for
20% of the total band intensity for C3-PI and for a value of
the order of 30–50% for C2-PI, a more precise estimate is
precluded by the timescale of the determination, which is
close to the instrumental resolution. The formation is fol-
lowed by an exponential decay to the baseline of the CS
bands which is fitted by a single exponential with a lifetime
of 540 ps for C2-PI and 2.5 ns for C3-PI. For C3-PPI the sit-
uation is different, there is essentially no decay of the CS
bands in the time window explored by the picosecond ex-
periment, about 3.5 ns, and a nanosecond flash-photolysis
experiment was performed in order to detect the decay of
the CS bands. Figure 8 shows the spectrum for air-purged
solutions of C3-PPI in toluene at the end of the pulse and
after the interfering emission signal coming from the pery-
lene imide excited state. It displays the anion bands at 710
and 800 nm and decays exponentially with a lifetime of
Figure 7. Time evolution of the transient spectra in toluene after excita-
tion at 532 nm (3.3 mJ) taken with delays of 165 ps. In the insets, the
time evolution of the absorbance at 710 nm and the biexponential fitting
are shown. a) C2-PI, A=0.6; b) C3-PI, A=0.6.
Figure 8. Time evolution of the transient spectrum of C3-PPI in toluene,
A=1.24, after excitation with a nanosecond laser at 532 nm (3.5 mJ),
*
*
spectra at 20 ns after the pulse ( ) and at 120 ns after the pulse ( ). In
the inset, the time evolution of the absorbance at 710 nm and the expo-
nential fitting are shown.
24 ns. The time resolution of this experiment, approximately
10 ns, did not allow the detection of the presence of a part
that rises in the CS spectrum, similarly to what was detected
for the other dyads C2-PI and C3-PI.
Photoinduced processes: To discuss the photoinduced pro-
cesses occurring in the dyads it is convenient to introduce
176
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 169 – 183

Arrays for Photoinduced Charge Separation
FULL PAPER
Scheme 4. Energy level diagrams and main reaction paths following excitation of C2-PI, C3-PI, and C3-PPI.
the energy level diagram showing the energy of the excited
states and of the states originating from possible intramolec-
ular reactions, such as the CS derived from the transfer of
an electron from one component to the other (Scheme 4).
The excited-state energy levels are derived from the lumi-
nescence maxima at 77 K shown in Table 1 and the CS
energy levels are derived from the energy necessary to
reduce the acceptor and oxidize the donor after correction
for the different solvents used in the photophysical experi-
ments and in the electrochemical determinations. Electro-
chemical data are available from the literature, the phenyl-
substituted compound corresponding to PI0 reduces at
ꢀ0.92 V versus Fc+/Fc in acetonitrile[16] which is converted
to ꢀ0.52 V versus SCE.[30]
state luminescence data, see above. The only feasible pro-
cess for quenching of the corrole unit is process 1 (see
Scheme 4), electron transfer from excited corrole to the per-
ylene bisimide to form the CS states C2+-PIꢀ, C3+-PIꢀ, and
C3+-PPIꢀ. However, whereas the DG8 is positive (DG8=
+0.07 eV) for C3-PPI, it is slightly negative (DG8=
ꢀ0.05 eV) for C3-PI, and even more negative for C2-PI
(DG8=ꢀ0.19 eV). This allows a very fast reaction for C2-PI
and a still efficient process in C3-PI, but a very slow reac-
tion in C3-PPI, where the electron-transfer process is
slowed down with respect to the similar C3-PI both by the
unfavorable thermodynamics and by the increased distance
between photoactive units. The reaction rates k1 of this elec-
tron transfer can be calculated from the experimental life-
times by the equation k=1/tꢀ1/t0, where t and t0 represent
the lifetimes of the excited state in the model and in the
dyad, respectively (Table 1). The calculated rates are k1 =
2.4”1010, 5”109, and 4.9”107 sꢀ1 for C2-PI, C3-PI, and C3-
PPI, respectively, unable in the latter to compete successful-
ly with the intrinsic deactivation of corrole, k=1/t0 =2.6”
108 sꢀ1.
Corroles are known to display irreversible oxidation at
potentials which depend on the substitution pattern.[12] The
one-electron oxidation is followed by fast chemical reactions
which shift peak potentials to less positive values, thus oxi-
dation peak potentials should be considered as lower limits
of the thermodynamic oxidation potentials. For the present
corroles, oxidation in benzonitrile occurs at +0.72 V versus
SCE for C2, and at +0.86 V versus SCE for C3.[15] Given
the very weak coupling of the components in the dyads (see
spectroscopic data), we can reasonably assume that the
above oxidation and reduction values are retained by the
components in the dyads.
When nearly selective excitation of the perylene bisimide
1
unit at 490 nm is performed, a strong quenching of the PI
unit is detected, as well as a quenching of the corrole lumi-
nescence, except in the case of C3-PPI, where a sensitization
of the luminescence of corrole is noted (Figure 3). This is in-
dicative of an energy-transfer process from the PI unit to
the corrole unit in the dyads, step 2, as confirmed by the ex-
citation spectra, see Figure 5. Clearly the sensitized excited
After corrections,[31,32] CS state levels in toluene are calcu-
lated at about 1.71, 1.85, and 1.96 eV for C2-PI, C3-PI, and
C3-PPI, respectively; these figures should be considered as
approximate values. It should be noticed that for all dyads
the CS state involving the transfer of an electron from the
bisimide to the corrole has higher energy than the excited
states of the system, and will not be considered here.[33]
Selective excitation of the lowest singlet excited state of
corrole units in the dyads, which was performed by using
steady-state experiments at l=565 nm, indicates a very high
quenching for the corrole luminescence except for C3-PPI,
where quenching is only of the order of 15% (Table 1 and
Figure 2). Time-resolved experiments agree with the steady-
1
1
1
states C2-PI, C3-PI, and C3-PPI undergo electron transfer
as discussed above, resulting in a further strong quenching
for the former two cases, whereas 1C3-PPI which is only
weakly quenched by electron transfer, appears sensitized.
The luminescence lifetime of the PI unit in all dyads is re-
duced from 4 ns in the model to ꢂ10 ps, indicating a very ef-
ficient quenching, with a rate ꢃ1011 sꢀ1. The excited state lo-
calized on the perylene bisimide C2-1PI, C3-1PI, and
C3-1PPI can deactivate, in addition to step 2, through an
electron transfer from ground-state corrole to yield the
Chem. Eur. J. 2008, 14, 169 – 183
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
177

L. Flamigni, H. Langhals, D. T. Gryko et al.
charge-separated states C2+-PIꢀ, C3+-PIꢀ, and C3+-PPIꢀ,
step 3 (see Scheme 4). Both reactions are characterized by a
strong driving force, DG8=ꢀ0.4 eV for 2 and ꢀ0.57 eV<
DG8<ꢀ0.32 eV depending on the dyad, for process 3.
ment upon excitation at 490 nm, which corresponds to an ef-
ficiency of energy-transfer step 2 of around 50% (Figure 3).
Therefore, for C3-PPI, k3 is equal to k2 which represents a
noticeable increase of k2 with respect to C3-PI, for which
k3 =9k2. This remarkable change in the relative value of the
two rates seems to be due more to the change in the ther-
modynamic parameters of step 3, with a net decrease in
driving force of the order of 0.11 eV from C3-PI to C3-PPI,
rather than to the increase in distance between the donor
and the acceptor, which would affect both energy- and elec-
tron-transfer rates. We will try to make a quantitative evalu-
ation of such effects on each process below. Energy-transfer
rates calculated according to a Fçrster mechanism are con-
sistent with the experimental ones,[35,36] therefore, a dipole–
dipole interaction mechanism is considered sufficient to ex-
plain the process, without requiring the contribution of an
exchange mechanism (Dexter). However, the latter was
found to be necessary to explain the high energy-transfer
rates in several porphyrinic donor–acceptor systems con-
nected by highly conjugated bridges.[37] With a Fçrster
model we would expect a 1/R6DA dependence of the energy-
transfer rate and consequently an increase in distance R
from 13.5 Š for C3-PI to 17.7 Š for C3-PPI would lead to a
fivefold reduction in k2. Concerning the bridge-mediated
electron transfer, it has recently been pointed out that the
key parameter electronic coupling has a donor-bridge (and
acceptor-bridge) energy gap dependence in addition to the
most obvious donor–acceptor distance dependence.[38] This
can cause a more complex formulation of electron-transfer
rate than in terms of bridge type and length, that is, k=
Charge separation can be produced both by step 3 and
step 1, with different mechanisms. When the PI unit is excit-
ed, a reductive quenching of its excited state will occur, that
is, the electron will move from the HOMO localized on the
donor corrole to the HOMO localized on the perylene bisi-
mide. When the corrole is excited, an electron will move
from the LUMO localized on the donor to the LUMO on
the perylene bisimide acceptor. Steps 3 and 1 can be distin-
guished by their kinetics; in the former case, the rate is very
fast and formation occurs within the laser pulse whereas the
latter process is characterized by slower rates coincident
with the decay of corrole luminescence in the dyads, 2.4”
1010, 5”109, and 4.9”107 sꢀ1 for C2-PI, C3-PI, and C3-PPI,
respectively. In agreement, two steps can be identified in the
formation of the CS spectrum, as discussed in the section on
transient absorbance, a fast step occurring during the pulse
and a slower one with rates of 2.4”1010 and 5”109 sꢀ1 for
C2-PI and C3-PI, respectively. For C3-PPI the timescale of
the formation is too slow for the picosecond experiment and
too fast for the nanosecond experiment and cannot be re-
solved (Figure 7). It should be noted that the CS spectrum
(lmax =710, 800, and 960 nm) is essentially identical to that
of the reduced perylene bisimide radical and no contribution
can be detected from the corrole-oxidized radical. This is
not surprising given the rather low molar absorption coeffi-
cient expected for the corrole cation, of the order of 104 sim-
ilar to parent tetrapyrrole cations,[34] whereas the remarka-
bly high molar absorption coefficient of the PIꢀ radical, of
the order of 100000, can account for this observation.[16,17]
An estimate of the relative values of k1 and k2 can be at-
tempted if one takes into account that the slower formation
of CS ascribable to step 1 accounts for 20% of the total in
C3-PI and that by excitation at 532 nm approximately 10%
of the corrole excited state is formed directly by the absorp-
tion of light, a contribution of about 10% can be ascribed to
sensitization of this state by the excited state of perylene bi-
simide (step 2). From this value an approximate estimate of
the efficiency of the energy-transfer step 2 of about 10%
can be derived for C3-PI, and k3 =9k2 is calculated, indicat-
ing a minor contribution of energy-transfer step 2 with re-
spect to electron-transfer step 3. A similar evaluation for
C2-PI is difficult because of the uncertainty in the determi-
nation of the pre-exponential coefficient, see above.
A0exp
A
bridge. Though not accurate, for the present purposes the
simpler exponential dependence with distance can be used
with a damping factor b=0.4 Šꢀ1, previously derived for
electron-transfer processes between porphyrinic units con-
nected by poly(phenylene) bridges.[39] Within this model, the
increase in distance from C3-PI to C3-PPI would lead to an
approximately fivefold decrease in rate, which is the same
ratio found for the energy-transfer attenuation. Therefore,
in the context of this simplified interpretation, a distance in-
crease would affect both energy and electron transfer to the
same extent and the reason for the decrease in electron-
transfer efficiency from the excited state localized on PI
seems to be ascribable to the change in thermodynamic pa-
rameters of the reactions. On the other hand the electron-
transfer reaction from the excited state localized on corrole
1C3-PPI, which has a positive DG8, becomes very slow and
noncompetitive with the intrinsic deactivation of the lumi-
nescence, in fact, the efficiency of electron transfer is only
15%.
Concerning the yield of the electron-transfer reaction, as-
suming a similar molar absorption coefficient for the CS of
the different dyads, that is, C2+-PIꢀ, C3+-PIꢀ, and C3+-
PPIꢀ, CS yield in C3-PPI is about half that determined for
the corresponding C3-PI. For the C3-PI a CS yield of about
100% can be assumed because nearly all photons eventually
generate C3+-PIꢀ (see Scheme 4) and consequently for C3-
PPI a CS yield of about 50% can be calculated. This is in
good agreement with the sensitization of corrole lumines-
cence by a factor of four detected in the steady-state experi-
Once CS has been formed through the steps discussed
above, it recombines to the ground state without leaving any
residual species, as verified by the absence of residual ab-
sorbance in the spectra. The recombination rates of the CS
states are rather different and depend both on the thermo-
dynamics of the process and on the distance of the reduced
acceptor and oxidized donor which can favor a better cou-
178
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 169 – 183

Arrays for Photoinduced Charge Separation
FULL PAPER
pling and faster recombination. The lifetime of the CS state
increases from 540 ps for a recombination DG8 of about
ꢀ1.71 eV in C2-PI to 2.5 ns for a DG8 of about ꢀ1.85 eV in
C3-PI and to a lifetime of 24 ns for a DG8 of approximately
ꢀ1.96 eV in C3-PPI; the reaction is very likely placed in the
Marcus inverted region and, as such, its rate decreases by in-
creasing the driving force.[40] In addition, for the latter two
cases where a tenfold increase is registered, the parameter
of the distance has, as discussed above, an important effect.
The lifetimes of charge-separated states in the system cor-
role/perylene bisimide are not very different from those re-
ported for other tetrapyrrole/perylene bisimide dyads, rang-
ing from hundreds of picoseconds to a few tens of nanosec-
onds (just one case reports a lifetime of one hundred pico-
seconds for a noncovalently linked array[5c]) depending on
parameters like solvent, bond type, position of the connect-
ing bridge, thermodynamics.[18a–k] However the 24 ns lifetime
measured for the CS state in C3-PPI is one of the longest in
covalently connected dyads, which is remarkable if one con-
siders the relatively short center-to-center distance between
the reacting units, less than 18 Š.
(light-to-electrical energy) and artificial photosynthetic
(light-to-chemical energy) applications.
Experimental Section
Synthesis: All chemicals were used as received unless otherwise noted.
Reagent-grade solvents (CH2Cl2, hexanes, cyclohexane) were distilled
prior to use. All reported 1H NMR and 13C NMR spectra were recorded
on Bruker AM 500 MHz or Varian 400 MHz spectrometer. Chemical
shifts (d [ppm]) were determined with TMS as the internal reference.
UV/Vis spectra were recorded in toluene (Cary). Chromatography was
performed on silica (silica gel 60, 200–400 mesh), or dry column vacuum
chromatography (DCVC)[41] was performed on preparative thin-layer-
chromatography silica (Merck 107747). Mass spectra were obtained by
using EI, field desorption (FD) or electrospray MS (ESI-MS). The fol-
lowing compounds were synthesized according to the literature proce-
dures: 4,[24] 7,[42] 8,[15] 11,[28] 15,[43] 16,[43] PI0,[44] C2,[15] and C3.[20d] The
purity of all new corroles was established based on 1H NMR spectra and
elemental analysis.
4-(1,1-Dimethoxymethyl)benzonitrile (2): 4-Cyanobenzaldehyde (1,
4.85 g 37 mmol), trimethylorthoformiate (12.0 mL, 110 mmol), anhydrous
methanol (150 mL), and 6n HCl (7 drops) were heated at 408C for 3 h,
stirred at room temperature for 12 h, treated with saturated aqueous
Na2CO3 (10 mL), extracted three times with isohexane (20 mL each),
dried (MgSO4), evaporated in vacuo, and distilled in vacuo. Yield 5.09 g
(78%) colorless liquid, b.p. 128–1308C/18 mbar. Other physicochemical
properties agree with published data.[25a]
Conclusion
4-(1,1-Dimethoxymethyl)benzylamine (4): 4-(1,1-Dimethoxymethyl)ben-
zonitrile (2, 4.00 g, 22.6 mmol) in anhydrous diethyl ether (15 mL) was
added dropwise to a suspension of lithium aluminum hydride (1.72 g,
45.2 mmol) in anhydrous diethyl ether (50 mL, 08C, Ar atmosphere)
within 10 min, allowed to come to room temperature, stirred for 12 h,
cooled (ice), treated dropwise with 20% aqueous NaOH with cooling
(12 mL), and extracted three times with ether (50 mL each). The com-
bined organic phases were dried (MgSO4), filtered, and evaporated in
vacuo. Yield 2.37 g (58%) yellowish oil, n2D0 =1.528; 1H NMR (300 MHz,
CDCl3, 258C): d=1.55 (s, 2H; NH2), 3.31 (s, 6H; 2”CH3), 3.86 (s, 2H;
CH2), 5.37 (s, 1H; CH), 7.30 (d, 3J=8.2 Hz, 2H; CHarom.), 7.41 (d, 3J=
8.1 Hz, 2H; CHarom.); 13C NMR (75 MHz, CDCl3, 258C): d=50.4, 56.8,
107.3, 131.1, 140.9, 147.7 ppm; IR (ATR): n˜ =3375.9 (w), 2989.8 (w),
2935.2 (m), 2828.6 (m), 1615.4 (w), 1511.7 (w), 1443.5 (w), 1414.7 (w),
1350.6 (m), 1303.1 (w), 1213.5 (m), 1191.8 (m), 1097.9 (s), 1047.1 (vs),
1019.6 (w), 979.7 (m), 908.8 (w), 806.1 (m), 770.6 (w), 658.2 cmꢀ1 (w); MS
(DEI+/70 eV): m/z (%): 181 (5) [M+], 150 (100) [M+ꢀCH3O], 134 (17)
[M+ꢀC2H7O], 120 (17) [M+ꢀC2H5O2], 118 (24) [M+ꢀC2H9NO], 106 (6)
[M+ꢀC3H7O2], 91 (10) [M+ꢀC3H8NO2], 77 (7) [M+ꢀC4H10NO2], 75 (9)
[C3H7O2]; HRMS (C10H15NO2): m/z: calcd: 181.110; found: 181.110; ele-
mental analysis calcd (%) for C10H15NO2 (181.2): C 66.30, H 8.34, N 7.73;
found: C 66.42, H 8.54, N 7.82.
We proved that complex corrole dyads can be synthesized in
an elegant way from respective perylene bisimide-aldehydes.
Moreover it was shown that asymmetrically N-substituted
perylene bisimides can be synthesized by mix-condensation
in a moderate yield when the two employed amines display
similar reactivity.
Upon illumination in an extended wavelength range (380–
680 nm) the studied dyads can convert the light energy
stored in their excited states into chemical energy, yielding
charge-separated states with an electron localized on the
perylene bisimide unit and a hole localized on the corrole
component. The yield of charge separation changes from
nearly 100% to about 50% for excitation of the perylene bi-
simide unit (100 and 15% for excitation of the corrole unit)
and the lifetime of the charge-separated state varies from
0.54 to 24 ns. The relatively long lifetimes of the CS state
compared to the close spacing of the counterparts (center-
to-center distance of 13.5 Š for C2-PI or C3-PI and 17.7 Š
for C3-PPI) render these arrays promising with respect to a
possible utilization of the stored energy, eventually after fur-
ther elaboration of the dyads into more complex structures.
These systems represent important progress in photoactive
multicomponent structures: 1) they contain a new, easily
available tetrapyrrolic chromophore with good photochemi-
cal properties; 2) they have clearly overcome the previously
reported instability of free-base corroles; 3) the properties
reported here can favorably compare with those of the most
frequently used porphyrin-based arrays, as shown by the
lifetimes and yields of the CS states.
4-[9-(1-Hexylheptyl)-1,3,8,10-tetraoxo-3,8,9,10-tetrahydro-1H-
anthra[2,1,9-def;6,5,10-d’e’f’]diisoquinoline-2-ylmethyl]benzaldehyde (5):
Method A. 9-(1-Hexylheptyl)-2-benzopyrano[6’,5’,4’:10,5,6]anthra[2,1,9-
def]isoquinoline-1,3,8,10-tetraone (4, 860 mg, 1.50 mmol), imidazole
(17.0 g), and a microspatula quantity of zinc acetate (Zn(OAc)2·2H2O)
A
were homogenized, heated under argon at 1408C, treated with 4-(1,1-di-
methoxymethyl)benzylamine (3, 460 mg, 2.55 mmol), heated at 1408C for
2 h with stirring, allowed to cool, treated with ethanol (50 mL), precipi-
tated with aqueous 2m HCl (150 mL), collected by vacuum filtration,
thoroughly washed with distilled water, dried in air at 1108C for 16 h,
and purified and deprotected with column separation (silica gel, chloro-
form/ethanol 40:1). Compound 5 was obtained after an orange-colored
forerun as an intensely red-to-orange band and was dissolved in a small
amount of chloroform and precipitated with acetonitrile. Yield 785 mg
(76%). Method B. A dispersion of perylene-3,4,9,10-tetracarboxylic bi-
sanhydride (6, 1.96 g, 5 mmol), 1-hexylheptylamine (7, 1.095 g, 6 mmol)
and acetal 8 (1.215 g, 6 mmol) in imidazole (40 g) was heated at 1608C,
This confirms that free-base corroles are valuable compo-
nents in the construction of artificial arrays for light energy
conversion and open new possibilities for photovoltaic
Chem. Eur. J. 2008, 14, 169 – 183
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
179

L. Flamigni, H. Langhals, D. T. Gryko et al.
for 24 h. The resulting mixture was diluted with water (20 mL) and 2m
HCl (140 mL) and allowed to sediment for 24 h. The precipitate was col-
lected by vacuum filtration, washed with water, dried, and purified by
column chromatography (silica, CH2Cl2, then CH2Cl2/acetone 98:2). The
second fluorescent fraction was evaporated (mixture of acetal/aldehyde
9:1 based on NMR spectrscopy), the residue was dissolved in CH2Cl2/
TFA/H2O mixture (40:10:1, 51 mL), and stirred for 16 h. Saturated
NaHCO3 was carefully added and the organic phase was separated,
washed with water, dried with Na2SO4, and evaporated. The pure alde-
hyde was obtained after refluxing with MeOH and filtration, red crystals,
540 mg, 16% after 2 steps. M.p.=>2508C; Rf (silica gel, CHCl3/EtOH
40:1)=0.29; 1H NMR (600 MHz, CDCl3, 258C): d=0.82 (t, 3J=7.0 Hz,
6H; 2”CH3), 1.28 (m, 16H; CH2), 1.87 (m, 2H; a-CH2), 2.23 (m, 2H; a-
CH2), 5.18 (m, 1H; a-CH), 5.48 (s, 2H; NCH2), 7.70 (d, 3J=8.2 Hz, 2H;
CHarom.), 7.85 (d, 3J=8.3 Hz, 2H; CHarom.), 8.68 (m, 8H; CHarom.),
9.98 ppm (s, 1H; CHO); 13C NMR (125 MHz, CDCl3): d=13.7, 22.3,
26.7, 28.9, 31.5, 32.1, 43.2, 54.6, 122.4, 122.5, 122.9, 126.0, 129.0, 129.1,
129.2, 129.7, 131.2, 134.6, 135.5, 143.5, 162.9, 191.5 ppm; IR (ATR): n˜ =
2953.8 (m), 2923.0 (s), 2855.3 (m), 1697.4 (s), 1646.4 (vs), 1610.0 (m),
1593.4 (s), 1577.3 (m), 1506.9 (w), 1436.2 (m), 1403.9 (m), 1378.2 (w),
1336.1 (s), 1301.7 (w), 1249.8 (m), 1212.4 (w), 1199.7 (w), 1168.2 (m),
1125.2 (w), 1106.0 (w), 987.0 (w), 849.6 (w), 823.9 (w), 808.9 (m), 774.3
(w), 742.6 (m), 723.1 (w), 631.4 cmꢀ1 (w); UV/Vis (CHCl3): lmax (e)=
459.1 (18600), 491.0 (51400), 527.4 nm (85800); fluorescence (CHCl3):
lmax (I)=534.5 (1.00), 578.0 nm (0.50), fluorescence quantum yield
(CHCl3, lexc =491 nm, E491nm =0.0212 cmꢀ1, reference: 2,9-bis-(1-hexyl-
heptyl)anthra[2,1,9-def;6,5,10-d’e’f’]diisoquinoline-1,3,8,10-tetraone with
F=1.00): 1.00; MS (DEI+/70 eV): m/z (%): 690 (33) [M+], 508 (100)
[M+ꢀC13H26], 374 (14), [M+ꢀC21H35O2], 346 (19) [M+ꢀC22H34NO2] , 44
(15) [CH2NO]; HRMS: m/z: calcd: C45H42N2O5: 690.309; found: 690.308;
elemental analysis calcd (%) for C45H42N2O5: C 78.24, H 6.13, N 4.06;
found: C 77.98, H 6.01, N 4.05.
dehyde (14): 9-(1-Hexylheptyl)-2-benzopyrano[6’,5’,4’:10,5,6]anthra[2,1,9-
def]isoquinoline-1,3,8,10-tetraone (4, 400 mg, 0.697 mmol), 4’-(1,3-dioxo-
lan-2-yl)biphenyl-4-methanamine (13, 350 mg, 1.37 mmol)), imidazole
(10.0 g), and a microspatula quantity of zinc acetate (Zn(OAc)2·2H2O)
A
were allowed to react under argon as was described for 5 and the product
was purified and deprotected by column separation (silica gel, chloro-
form/ethanol 40:1). The intensely reddish-orange main fraction was col-
lected after an orange forerun and was evaporated, dissolved in the mini-
mum amount of chloroform, and precipitated with acetonitrile. Bright
light-red solid; yield 440 mg (57%); m.p. >2508C, Rf (silica gel, CHCl3/
EtOH 40:1)=0.28; 1H NMR (600 MHz, CDCl3, 258C, TMS): d=0.82 (t,
3J
(H;H)=7.0 Hz, 6H; 2”CH3), 1.18–1.38 (m, 16H; 8”CH2), 1.83–1.91
G
(m, 2H; b-CH2), 2.21–2.29 (m, 2H; b-CH2), 5.15–5.22 (m, 1H; a-CH),
5.46 (s, 2H; NCH2), 7.58–7.61 (m, 2H; CHaryl), 7.67–7.72 (m, 4H; CHaryl),
7.91–7.94 (m, 2H; CHaryl), 8.59–8.71 (m, 8H; CHperylene), 10.0 ppm (s, 1H;
CHO); 13C NMR (150 MHz, CDCl3, 258C, TMS): d=14.3, 22.8, 27.2,
29.4, 32.0, 32.6, 43.7, 55.1, 123.2, 123.5, 126.6, 126.8, 127.7, 127.8, 129.7,
129.8, 129.9, 130.5, 132.0, 135.3, 135.4, 137.7, 139.3, 147.0, 163.7,
192.1 ppm; IR (ATR): n˜ =2952.5 (m), 2924.0 (s), 2854.9 (m),1691.9 (s),
1650.2 (vs), 1592.6 (s), 1577.7 (m), 1506.5 (w), 1456.1 (w), 1434.7 (w),
1403.6 (m), 1378.0 (w), 1332.6 (s), 1247.0 (m), 1214.8 (w), 1169.3 (m),
1125.8 (w), 1106.2 (w), 1003.6 (w), 987.8 (w), 849.6 (w), 808.2 (m), 782.0
(w), 748.8 (w), 740.3 (w), 606.5 cmꢀ1 (w); UV/Vis (CHCl3): lmax (e Erel.)=
459.2 (0.22), 490.4 (0.60), 527.0 nm (1.00); fluorescence (CHCl3): lmax
(Irel.)=535.2 (1.00), 576.5 nm (0.50); fluorescence quantum yield (CHCl3,
lexc =490 nm, E490 nm =0.0132 cmꢀ1, reference: 2,9-bis-(1-hexylheptyl)an-
thra[2,1,9-def;6,5,10-d’e’f’]diisoquinoline-1,3,8,10-tetraone with F=1.00):
1.00; MS (DEI+/70 eV): m/z (%): 766 (21) [M+], 584 (100) [M+
ꢀC13H26], 346 (55) [M+ꢀC28H38NO2], 195 (14) [C14H11O]; HRMS
(C53H50N2O6): m/z: calcd: 766.340; found: 766.339.
10-[(4-[9-(1-Hexylheptyl)-1,3,8,10-tetraoxo-3,8,9,10-tetrahydro-1H-
anthra[2,1,9-def;6,5,10-d’e’f’]diisoquinoline-2-ylmethyl]phenyl)]-5,15-
bis(2,6-dichlorophenyl)corrole (C2-PI): 2,6-Dichlorophenyldipyrrome-
thane 15 (232 mg, 0.8 mmol) and aldehyde 5 (276 mg, 0.4 mmol) were
dissolved in CH2Cl2 (6 mL). TFA (12 mL, 0.16 mmol) was added and mix-
ture was stirred at RT for 20 min. Et3N (22 mL, 0.16 mmol) was added
followed by p-chloranil (296 mg, 1.2 mmol) and stirring was continued
for 16 h. The reaction mixture was concentrated and was purified by
chromatography (DCVC, silica, CH2Cl2). After evaporation, the residue
was dissolved in THF and loaded on an SEC column (THF). The corrole
fraction was collected, evaporated, refluxed with MeOH, and filtered to
afford 70 mg (14%) of corrole C2-PI. Rf =0.5 (silica, CH2Cl2); 1H NMR
(500 MHz, CDCl3) d=ꢀ3–ꢀ1 (sbr, 3H; NH), 0.84 (t, J=6.2 Hz, 6H; 2”
CH3), 1.20–1.40 (m, 16H; alkyl), 1.85–1.95 (m, 2H; alkyl), 2.22–2.32 (m,
2H; alkyl), 5.15–5.25 (m, 1H; CH), 5.62 (s, 2H; CH2), 7.60 (t, J=8 Hz,
2H; C6H3Cl2), 7.72 (d, J=8 Hz, 4H; C6H3Cl2), 8.09, 8.25 (AA’BB’, J=
6.5 Hz, 2”2H; C6H4), 8.28–8.70 (m, 14H; 8H; C20H8 +6H; b-H),
8.97 ppm (d, J=4 Hz, 2H; b-H); labs (toluene, e)=413 (113), 428 (104),
459 (22.2), 492 (51.7), 528 (85.3), 561 (18.5), 611 (11.5), 640 nm (6.6 ”
10ꢀ3); ESI-LR obsd: 1246.3 [M++H]; elemental analysis calcd (%) for
C75H58Cl4N6O4: C 72.12, H 4.68, N 6.73; found: C 72.24, H 4.87, N 6.58;
4’-(1,3-Dioxolan-2-yl)biphenyl-4-carbonitrile (12): 4’-Formylbiphenyl-4-
carbonitrile (11, 1.45 g, 7.00 mmol) and ethylene glycol (1.74 g,
28.0 mmol) in toluene (50 mL) was allowed to react analogously to 2 and
was crystallized from hexane/ethanol 5:1. Yield 610 mg (35%) colorless
1
crystalline solid, m.p. 170–1718C; H NMR (200 MHz, CDCl3, 258C): d=
4.02–4.21 (m, 4H; 2”CH2O), 5.87 (s, 1H; CH), 7.60–7.76 ppm (m, 8H;
CHarom.); 13C NMR (150 MHz, CDCl3, 258C): d=65.6, 103.5, 111.4, 119.1,
127.4, 127.5, 128.0, 132.8, 138.7, 140.3, 145.5 ppm; IR (ATR): n˜ =3409.2
(w), 3070.0 (w), 2956.2 (m), 2884.5 (s), 2364.8 (w), 2225.5 (vs), 1930.0
(w), 1808.3 (w), 1699.7 (w), 1607.0 (s), 1555.9 (w), 1495.9 (m), 1481.2 (w),
1432.2 (m), 1401.8 (s), 1386.3 (s), 1312.4 (w), 1286.4 (w), 1227.2 (w),
1212.0 (w), 1184.5 (w), 1137.2 (w), 1117.2 (w), 1073.1 (s), 1021.8 (m),
1005.9 (w), 971.7 (m), 942.1 (m), 860.5 (w), 817.4 (vs), 720.2 (w), 689.9
(w), 648.7 cmꢀ1 (w); MS (DEI+/70 eV): m/z (%): 251 (69) [M+], 250
(100) [M+ꢀH], 206 (35) [M+ꢀC2H5O], 190 (21) [M+ꢀC2H5O2], 179 (72)
[M+ꢀC3H4O2], 151 (17) [M+ꢀC4H6NO2], 73 (14) [C3H5O2]; HRMS
(C16H13NO2): m/z: calcd: 251.095; found: 251.095.
4’-(1,3-Dioxolan-2-yl)biphenyl-4-methanamine (13): 4’-(1,3-Dioxolan-2-
yl)-biphenyl-4-carbonitrile (12, 600 mg, 2.39 mmol) in THF (10 mL) and
lithium aluminum hydride (181 mg, 4.78 mmol) in THF (10 mL) were al-
lowed to react analogously to (1,1-dimethoxymethyl)benzylamine (3).
Brown crystalline solid, yield 375 mg (62%); m.p 120–1238C; 1H NMR
(200 MHz, [D6]DMSO, 258C): d=3.75 (s, 2H; CH2), 3.92–4.12 (m, 4H;
2”CH2O), 5.77 (s, 1H; CH), 7.39–7.69 ppm (m, 8H; CHarom.); 13C NMR
(100 MHz, [D6]DMSO, 258C, TMS): d=45.9, 65.5, 103.3, 127.0, 127.1,
127.8, 128.3, 137.7, 138.4, 141.6, 144.2 ppm; IR (ATR): n˜ =3380.3 (m),
3029.3 (w), 2953.7 (m), 2887.5 (s), 1915.2 (w), 1613.6 (w), 1562.6 (w),
1498.1 (m), 1432.5 (m), 1403.6 (m), 1382.7 (m), 1346.3 (w), 1310.3 (w),
1277.7 (w), 1205.8 (m), 1183.7 (w), 1114.2 (w), 1074.0 (vs), 1017.0 (m),
1003.6 (w), 964.8 (m), 939.1 (s), 877.8 (w), 838.2 (m), 798.0 (vs),
697.2 cmꢀ1 (w); MS (DEI+/70 eV): m/z (%): 255 (100) [M+], 210 (14)
[M+ꢀC2H5O], 196 (6) [M+ꢀC2H3O2], 182 (42) [M+ꢀC3H5O2], 166 (40)
[M+ꢀC3H7NO2], 152 (15) [M+ꢀC4H9NO2], 106 (18) [M+ꢀC9H9O2] , 73
(25) [C3H5O2]; HRMS (C16H17NO2): m/z: calcd: 255.126; found: 255.126.
10-[(4-[9-(1-Hexylheptyl)-1,3,8,10-tetraoxo-3,8,9,10-tetrahydro-1H-
anthra[2,1,9-def;6,5,10-d’e’f’]diisoquinoline-2-ylmethyl]phenyl)]-5,15-bis-
(pentafluorophenyl)corrole (C3-PI): Pentafluorophenyldipyrromethane
(16) (250 mg, 0.8 mmol) and aldehyde 5 (276 mg, 0.4 mmol) were dis-
solved in CH2Cl2 (6 mL). TFA (12 mL, 1.6 mmol) was added, and the mix-
ture was stirred at room temperature. After 20 min Et3N (22 mL,
0.16 mmol) was added followed by CH2Cl2 (14 mL). DDQ (590 mg,
2.6 mmol) was dissolved in toluene/CH2Cl2 (1:3, 20 mL) and both mix-
tures were added simultaneously to vigorously stirred CH2Cl2 (20 mL).
After 15 min the reaction mixture was concentrated and was purified by
chromatography (DCVC, silica, CH2Cl2). After evaporation, the residue
was dissolved in THF and loaded on an SEC column (THF). The corrole
fraction was collected, evaporated, refluxed with MeOH, and collected
by vacuum filtration to afford 76 mg (15%) of corrole C3-PI. Rf (silica,
CH2Cl2)=0.43; 1H NMR (500 MHz, CDCl3): d=(ꢀ3)–(ꢀ1) (sbr, 3H;
NH), 0.83 (t, J=7 Hz, 6H; 2”CH3), 1.20–1.40 (m, 16H; alkyl), 1.85–1.95
(m, 2H; alkyl), 2.22–2.32 (m, 2H; alkyl), 5.10–5.20 (m, 1H; CH), 5.50
(sbr, 2H; CH2), 8.09, 8.25 (AA’BB’, J=6.5 Hz, 2”2H; C6H4), 8.28–8.70
4’-[9-(1-Hexylheptyl)-1,3,8,10-tetraoxo-3,8,9,10-tetrahydro-1H-
anthra[2,1,9-def;6,5,10-d’e’f’]diisoquinoline-2-ylmethyl]biphenyl-4-carbal-
180
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 169 – 183

Arrays for Photoinduced Charge Separation
FULL PAPER
(m, 14H; 8H; C20H8 and 6H; b-H), 8.93 ppm (d, J=4 Hz, 2H; b-H); labs
(toluene, e)=421 (124), 460 (25.5), 492 (57.7), 529 (94.4), 563 (19.6), 616
(11.6), 643 nm (8.8 ”10ꢀ3); ESI-LR obsd 1290.5 [M++H]; elemental
analysis calcd (%) for C75H52F10N6O4·H2O: C 68.98, H 4.27, N 6.35;
found: C 68.95, H 4.08, N 6.48.
by applying standard iterative procedures. More details can be found
elsewhere.[48] Nanosecond-laser flash-photolysis experiments were per-
formed by using a system based on a Nd:YAG laser (JK Lasers, 532 nm,
3.5 mJ, 18 ns pulse) by using a right-angle analysis on the excited sample,
previously described.[49]
10-[4’-[9-(1-Hexylheptyl)-1,3,8,10-tetraoxo-3,8,9,10-tetrahydro-1H-
Experimental uncertainties were estimated to be within 10% for lifetime
determination, 15% for quantum yields, 20% for molar absorption coef-
ficients, and 3 nm for emission and absorption peaks. The temperature of
operation was 295 K except otherwise stated. Molecular dimensions were
estimated after MM2 minimization by CS Chem3D Ultra 6.0 software.[50]
Computation of the integral overlap and of the rate for the energy-trans-
fer processes according to the Fçrster mechanism were performed with
the use of Matlab 5.2.[51]
anthra[2,1,9-def;6,5,10-d’e’f’]diisoquinoline-2-ylmethyl]biphenyl-4-]-5,15-
bis(pentafluorophenyl)corrole (C3-PPI): Pentafluorophenyldipyrrome-
thane (16) (125 mg, 0.4 mmol) and aldehyde 14 (153 mg, 0.2 mmol) were
dissolved in CH2Cl2 (6 mL). TFA (6 mL, 0.8 mmol) was added, and the
mixture was stirred at room temperature. After 40 min, Et3N (44 mL,
0.16 mmol) was added, followed by CH2Cl2 (306 mL). The reaction was
quenched by addition of DDQ (118 mg, 0.52 mmol), dissolved in toluene
(1 mL), and stirring was continued for 20 min. The reaction mixture was
concentrated and was purified by chromatography (DCVC, silica,
CH2Cl2). After evaporation, the residue was dissolved in THF and loaded
onto an SEC column (THF). The corrole fraction was collected, evapo-
rated, refluxed with MeOH, and filtered to afford 30 mg (11%) of cor-
role C3-PPI. Rf =0.6 (silica, CH2Cl2); 1H NMR (500 MHz, CDCl3): d=
(ꢀ3)–(ꢀ1) (sbr, 3H; NH), 0.84 (t, J=7 Hz, 6H; 2”CH3), 1.20–1.40 (m,
16H; alkyl), 1.86–1.96 (m, 2H; alkyl), 2.22–2.32 (m, 2H; alkyl), 5.15–5.25
(m, 1H; CH), 5.34 (sbr, 2H; CH2), 7.72, 8.86 (AA’BB’, J=6.5 Hz, 2”
2H; C6H4), 7.90, 8.10 (AA’BB’, J=6.5 Hz, 2”2H; C6H4), 8.15–8.70 (m,
14H; 8H; C20H8 and 6H; b-H), 8.94 ppm (sbr, 2H; b-H); labs (toluene,
e)=422 (121), 491 (53.4), 528 (88.6), 564 (18.2), 617 (10.8), 643 nm (7.9 ”
Acknowledgements
We thank CNR of Italy (PM.P04.010 MACOL), Ministero dell’Istruzione,
dell’Università e della Ricerca of Italy (FIRB, RBNE019H9K), Polish
Ministry of Research and Higher Education, the Deutsche Forschungsge-
meinschaft and the Fonds der Chemischen Industrie for financial sup-
port.
10ꢀ3); FD-LR obsd. 1366.4 [M +]; elemental analysis calcd (%) for
C
[1]a) G. Kodis, Y. Terazono, P. A. Liddell, J. Andreasson, V. Garg, M.
Hambourger, T. A. Moore, A. L. Moore, D. Gust, J. Am. Chem. Soc.
2006, 128, 1818–1827; b) E. H. A. Beckers, Z. Chen, S. C. J. Mesk-
ers, P. Jonkheijm, A. P. H. J. Schenning, X.-Q. Li, P. Osswald, F.
Wꢁrthner, R. Janssen, J. Phys. Chem. B 2006, 110, 16967–16978;
c) J. Segura, N. Martin, D. M. Guldi, Chem. Soc. Rev. 2005, 34, 31–
47; d) S. Chakraborty, T. J. Wadas, H. Hester, R. Schmehl, R. Eisen-
berg, Inorg. Chem. 2005, 44, 6865–6878; e) M. H. Huynh, D. M.
Dattelbaum, T. J. Meyer, Coord. Chem. Rev. 2005, 249, 457–483;
f) L. Flamigni, E. Baranoff, J.-P. Collin, J.-P. Sauvage, Chem. Eur. J.
2006, 12, 6592–6606; g) M. Borgstrçm, N. Shaikh, O. Johansson,
M. F. Anderlund, S. Styring, B. Škermark, A. Magnuson, L. Ham-
marstrçm, J. Am. Chem. Soc. 2005, 127, 17504–17515; h) F. Giac-
alone, J. Segura, N. Martin, J. Ramey, D. M. Guldi, Chem. Eur. J.
2005, 11, 4819–4834; i) J. Daub, R. Engl, J. Kurzawa, S. E. Miller, S.
Schneider, A. Stockmann, M. R. Wasielewski, J. Phys. Chem. A
2001, 105, 5655–5665; j) Y. Chen, M. E. El-Khouly, X.-D. Zhuang,
N. He, Y. Araki, Y. Lin, O. Ito, Chem. Eur. J. 2007, 13, 1709–1714;
k) R. Ziessel, G. Ulrich, A. Harriman, New J. Chem. 2007, 31, 496–
501; l) M. R. Wasielewski, J. Org. Chem. 2006, 71, 5051–5066.
[2]a) D. Gust, T. A. Moore, A. L. Moore, Acc. Chem. Res. 2001, 34,
40–48; b) M. R. Wasielewski, Chem. Rev. 1992, 92, 435–461; c) L.
Flamigni, V. Heitz, J.-P. Sauvage, Struct. Bonding (Berlin) 2006, 121,
217–261; d) K. Saito, Y. Kashiwagi, K. Ohkubo, S. Fukuzumi, J. Por-
phyrins Phthalocyanines 2006, 10, 1380–1391.
C81H56F10N6O4: C 71.15, H 4.13, N 6.15; found: C 71.02, H 3.88, N 5.96.
Spectroscopy and photophysics: Spectrophotometric grade toluene at
295 K and at 77 K was used without further purification. Standard 10-mm
fluorescence cells were used at 295 K, whereas for experiments at 77 K,
we used capillary tubes in a home-made quartz Dewar filled with liquid
nitrogen. Due to these geometrical conditions at 77 K the absolute quan-
tum yield could not be determined with confidence, only qualitative in-
formation could be derived. If not otherwise specified, solutions were air-
equilibrated. Air-free solutions were bubbled for 10 min with a stream of
argon in home-modified 10-mm fluorescence cells.
A Perkin–Elmer
Lambda 9 UV/Vis and a Spex Fluorolog II spectrofluorimeter were used
to acquire absorption and emission spectra. Reported luminescence spec-
tra were uncorrected unless otherwise specified. Emission quantum
yields were determined after correction for the photomultiplier response,
with reference to an air-equilibrated toluene solution of PI0 in dichloro-
methane with a Ffl =0.99,[45] or to TPP with a Ffl =0.11,[46] for corroles.
Luminescence lifetimes in the nanosecond range were obtained with an
IBH single-photon counting apparatus with excitation at 465 or 560 nm
from pulsed-diode sources (resolution 0.3 ns). For determination of emis-
sion lifetimes in the picosecond range an apparatus based on a Nd:YAG
laser (35 ps pulse duration, 532 nm, 1.5 mJ) and a Streak Camera with
overall resolution of 10 ps was used.[47] Transient absorbance in the pico-
second range made use of a pump and probe system based on a Nd:YAG
laser (Continuum PY62/10, 35 ps pulse). The second harmonic (532 nm)
at a frequency of 10 Hz and an energy of about 3.5 mJ/pulse was used to
excite the samples the absorbance of which at the excitation wavelength
was approximately 0.6. The residual 1064 nm light (about 40 mJ) was fo-
cused on a stirred 10-cm cell containing a mixture of D2O/D3PO4 to pro-
duce a white-light continuum which was used as analyzing light. A com-
puter-controlled optical delay stage (Ealing) on the path of the excitation
beam provided a delay between excitation and analysis. The analyzing
light was split in two parts probing irradiated and unirradiated portions
of the sample, respectively, and crossed the sample cell in a nearly collin-
ear geometry with respect to the excitation beam. The transmitted
[3]Z. S. Yoon, J. H. Kwon, M.-C. Yoon, M. K. Koh, S. B. Noh, J. L.
Sessler, J. T. Lee, D. Seidel, A. Aguilar, S. Shimizu, M. Suzuki, A.
Osuka, D. Kim, J. Am. Chem. Soc. 2006, 128, 14128–14134.
[4]a) N. Mataga, S. Taniguchi, H. Chosrowjan, A. Osuka, N. Yoshida,
Photochem. Photobiol. Sci. 2003, 2, 493–500; b) I. W. Hwang, T.
Kamada, T. K. Ahn, D. M. Ko, T. Nakamura, A. Tsuda, A. Osuka,
D. Kim, J. Am. Chem. Soc. 2004, 126, 16187–16198; c) K. Ogawa, Y.
Kobuke, J. Photochem. Photobiol. C 2006, 7, 1–16; d) H. L. Ander-
son, Chem. Commun. 1999, 2323–2330; e) T. V. Duncan, K.
Susumu, L. E. Sinks, M. J. Therien, J. Am. Chem. Soc. 2006, 128,
9000–9001.
probes were fed through optical fibers into
a spectrograph (Spec-
trapro 275, Acton) and were detected in two separate regions of a CCD
detector (Princeton Instruments). The control units for the delay line, for
the spectrograph and for the CCD detector were driven by customized
software (Eurins) which also allowed spectral acquisition at increasing
time delays between the pump and the probe. Typically, 200 to 500 laser
shots were collected and averaged to obtain a single spectrum at a specif-
ic time delay. Kinetic analyses were made by selecting the absorbance
values of successive time-resolved spectra at the selected wavelength and
[5]a) X. Li, L. E. Sinks, B. Rybtchinski, M. R. Wasielewski, J. Am.
Chem. Soc. 2004, 126, 10810–10811; b) D. M. Guldi, I. Zilbermann,
A. Gouloumis, P. Vazquez, T. Torres, J. Phys. Chem. B 2004, 108,
18485–18494; c) M. S. Rodriguez-Morgade, T. Torres, C. Atienza-
Castellanos, D. M. Guldi, J. Am. Chem. Soc. 2006, 128, 15145–
15154.
[6]a) D. Gonzalez-Rodriguez, T. Torres, D. M. Guldi, J. Rivera, M. A.
Herranz, L. Echegoyen, J. Am. Chem. Soc. 2004, 126, 6301–6313;
Chem. Eur. J. 2008, 14, 169 – 183
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
181

L. Flamigni, H. Langhals, D. T. Gryko et al.
b) D. Gonzalez-Rodriguez, C. G. Claessens, T. Torres, S. G. Liu, L.
Echegoyen, N. Vila, S. Nonell, Chem. Eur. J. 2005, 11, 3881–3893.
[7]a) V. Huber, M. Katterle, M. Lysetska, F. Wꢁrthner, Angew. Chem.
Int. Ed. 2005, 117, 3208–3212; Angew. Chem. Int. Ed. 2005, 44,
3147–3151; b) S. Sasaki, T. Mizoguchi, H. Tamiaki, Tetrahedron
2005, 61, 8041–8048; c) R. F. Kelley, M. J. Tauber, M. R. Wasielew-
ski, J. Am. Chem. Soc. 2006, 128, 4779–4791; d) C. Rçger, M. G.
Mꢁller, M. Lysetska, Y. Miloslavina, A. R. Holzwarth, F. Wꢁrthner,
J. Am. Chem. Soc. 2006, 128, 6542–6543; e) T. S. Balaban, Acc.
Chem. Res. 2005, 38, 612–623.
Hofkens, J. Phys. Chem. C 2007, 111, 4861–4870; d) R. F. Kelley,
W. S. Shin, B. Rybtchinski, L. E. Sinks, M. R. Wasielewski, J. Am.
Chem. Soc. 2007, 129, 3173–3181; e) M. P. OꢅNeil, M. P. Niemczyk,
W. A. Svec, D. Gosztola, G. L. Gaines III, M. R. Wasielewski, Sci-
ence 1992, 257, 63–65; f) S. I. Yang, S. Prathapan, M. A. Miller, J.
Seth, D. F. Bocian, J. S. Lindsey, D. Holten, J. Phys. Chem. B 2001,
105, 8249–8258; g) A. Prodi, C. Chiorboli, F. Scandola, E. Iengo, E.
Alessio, R. Dobrawa, F. Wꢁrthner, J. Am. Chem. Soc. 2005, 127,
1454–1462; h) C. Kirmaier, E. Hindin, J. K. Schwartz, I. V. Sazano-
vich, J. R. Diers, K. Muthukumaran, M. Taniguchi, D. F. Bocian, J. S.
Lindsey, D. Holten, J. Phys. Chem. B 2003, 107, 3443–3454; i) S.
Prathapan, S. I. Yang, J. Seth, M. A. Miller, D. F. Bocian, D. Holten,
J. S. Lindsey, J. Phys. Chem. B 2001, 105, 8237–8248; j) S. Xiao,
M. E. El-Khouly, Y. Li, Z. Gan, H. Liu, L. Jiang, Y. Araki, O. Ito,
D. Zhu, J. Phys. Chem. B 2005, 109, 3658–3667; k) M. J. Arhens,
R. F. Kelley, Z. E. X. Dance, M. R. Wasielewski, Phys. Chem. Chem.
Phys. 2007, 9, 1469–1478; l) W. E. Ford, H. Hiratsuka, P. V. Kamat,
J. Phys. Chem. 1989, 93, 6692–6696; m) H. Langhals, U. Ritter, Per-
sistent Perylene Bisimide Radical Anions as NIR Dyes, DE
102006011269.5, March 10, 2006; n) H. Langhals, W. Jona, Chem.
Eur. J. 1998, 4, 2110–2116; o) H. Langhals, S. Saulich, Chem. Eur. J.
2002, 8, 5630–5643.
[8]a) M. J. Crossley, P. J. Sintic, R. Walton, J. R. Reimers, Org. Biomol.
Chem. 2003, 1, 2777–2787; b) L. Flamigni, M. R. Johnston, L. Giri-
babu, Chem. Eur. J. 2002, 8, 3938–3947.
[9]a) R. Paolesse in The Porphyrin Handbook, Vol. 2 (Eds.: K. M.
Kadish, K. M. Smith, R. Guilard), Academic Press, New York, 2000,
pp. 201–232; b) S. Nardis, D. Monti, R. Paolesse, Mini-Rev. Org.
Chem. 2005, 2, 355–372; c) D. T. Gryko, J. P. Fox, D. P. Goldberg, J.
Porphyrins Phthalocyanines, 2004, 8, 1091–1105; d) 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), Elsevier Sci-
ence, Boston, 2003, pp. 303–349; e) Z. Gross, N. Galili, I. Saltsman,
Angew. Chem. Int. Ed. 1999, 111, 1530–1533; Angew. Chem. Int.
Ed. 1999, 38, 1427–1429; f) R. Paolesse, S. Nardis, F. Sagone, R. G.
Khoury, J. Org. Chem. 2001, 66, 550–556; g) B. Ramdhanie, C. L.
Stern, D. P. Goldberg, J. Am. Chem. Soc. 2001, 123, 9447–9448;
h) J.-M. Barbe, G. Canard, S. Brandꢂs, R. Guilard, Angew. Chem.
2005, 117, 3163–3166; Angew. Chem. Int. Ed. 2005, 44, 3103–3106;
i) K. M. Kadish, J. Shao, Z. Ou, L. Frꢃmond, R. Zhan, F. Burdet, J.-
M. Barbe, C. P. Gros, R. Guilard, Inorg. Chem. 2005, 44, 6744–6754;
j) R. Goldschmidt, I. Goldberg, Y. Balazs, Z. Gross, J. Porphyrins
Phthalocyanines 2006, 10, 76–86; k) M. Brçring, F. Brꢃgier, E. C.
Tejero, C. Hell, M. C. Holthausen, Angew. Chem. 2007, 119, 449–
452; Angew. Chem. Int. Ed. 2007, 46, 445–448; l) I. Aviv, Z. Gross,
Chem. Commun. 2007, 1987–1999; m) J. Poulin, C. Stern, R. Gui-
lard, P. D. Harvey, Photochem. Photobiol. 2006, 82, 171–176; n) R.
Paolesse, F. Sagone, A. Macagnano, T. Boschi, L. Prodi, M. Montal-
ti, N. Zaccheroni, F. Bolletta, K. M. Smith, J. Porphyrins Phthalocya-
nines 1999, 3, 364–370; o) J. Sankar, H. Rath, V. Prabhuraja, S. Go-
kulnath, T. K. Chandrashekar, C. S. Purohit, S. Verma, Chem. Eur. J.
2007, 13, 105–114; p) R. Kumar, R. Misra, V. PrabhuRaja, T. K.
Chandrashekar, Chem. Eur. J. 2005, 11, 5695–5707; q) S. Hiroto, K.
Furukawa, H. Shinokubo, A. Osuka, J. Am. Chem. Soc. 2006, 128,
12380–12381; r) C. P. Gros, J.-M. Barbe, E. Espinoza, R. Guillard,
Angew. Chem. 2006, 118, 5770–5773; Angew. Chem. Int. Ed. 2006,
45, 5642–5645; s) I. Aviv, Z. Gross, Chem. Commun. 2007, 1987–
1999.
[19]F. Graser, (BASF AG), DE 3049215, July 15, 1982; [Chem. Abstr.
1982, 97, 129114].
[20]a) D. T. Gryko, K. Jadach, J. Org. Chem. 2001, 66, 4267–4275;
b) D. T. Gryko, K. E. Piechota, J. Porphyrins Phthalocyanines 2002,
6, 81–97; c) D. T. Gryko, B. Koszarna, Org. Biomol. Chem. 2003, 1,
350–357; d) D. T. Gryko, B. Koszarna, Synthesis 2004, 2205–2209;
[21]a) H. Langhals, Helv. Chim. Acta 2005, 88, 1309–1343; b) H. Lang-
hals, Heterocycles 1995, 40, 477–500.
[22]a) H. Langhals, DE 3016764, April 30, 1980; [Chem. Abstr. 1982, 96,
P70417x]; b) H. Langhals, Nachr. Chem. Tech. Lab. 1980, 28, 716–
718; [Chem. Abstr. 1981, 95, R9816q].
[23]a) S. Demmig, H. Langhals, Chem. Ber. 1988, 121, 225–230; b) H.
Langhals, S. Demmig, T. Potrawa, J. Prakt. Chem. 1991, 333, 733–
748.
[24]H. Kaiser, J. Lindner, H. Langhals, Chem. Ber. 1991, 124, 529–535.
[25]a) P. D. R. Rose, A. Williams, J. Chem. Soc. Perkin Trans. 2 2002,
1589–1595; b) O. Ouari, F. Chalier, R. Bonaly, B. Pucci, P. Tordo, J.
Chem. Soc. Perkin Trans. 2 1998, 2299–2307.
[26]H. Langhals, Chem. Ber. 1985, 118, 4641–4645.
[27]The use of silica from Acros resulted in a complete deprotection
whereas partial deprotection was observed with silica from Merck.
[28]M. A. Ismail, A. Batista-Parra, M. Adalgisa, Y. Miao, W. D. Wilson,
T. Wenzler, R. Brun, D. W. Boykin, Bioorg. Med. Chem. 2005, 13,
6718–6726.
[10]B. Ventura, A. Degli Esposti, B. Koszarna, D. T. Gryko, L. Flamigni,
New J. Chem. 2005, 29, 1559–1566.
[11]a) T. Ding, E. A. Alemꢄn, D. A. Mordarelli, C. J. Ziegler, J. Phys.
Chem. A 2005, 109, 7411–7417; b) R. Paolesse, A. Marini, S. Nardis,
A. Froiio, F. Mandoj, D. J. Nurco, L. Prodi, M. Montalti, K. M.
Smith, J. Porphyrins Phthalocyanines 2003, 7, 25–36.
[12]J. Shen, J. Shao, Z. Ou, W. E. B. Koszarna, D. T. Gryko, K. M.
Kadish, Inorg. Chem. 2006, 45, 2251–2265.
[13]L. Flamigni, B. Ventura, M. Tasior, D. T. Gryko, Inorg. Chim. Acta
2007, 360, 803–813.
[14]C. P. Gros, F. Brisach, A. Meristoudi, E. Espinosa, R. Guillard, P. D.
Harvey, Inorg. Chem. 2007, 46, 125–135.
[15]M. Tasior, D. T. Gryko, M. Cembor, J. S. Jaworski, B. Ventura, L.
Flamigni, New J. Chem. 2007, 31, 247–259.
[16]J. Salbeck, H. Kumkely, H. Langhals, R. W. Saalfrank, J. Daub,
Chimia 1989, 43, 6–9.
[17]T. Kircher, H. G. Lçhmannsrçber, Phys. Chem. Chem. Phys. 1999, 1,
3987–3992.
[29]B. Koszarna, D. T. Gryko, J. Org. Chem. 2006, 71, 3707–3717.
[30]N. G. Connelly, W. E. Geiger, Chem. Rev. 1996, 96, 877–910.
[31]A. Weller, Z. Phys. Chem. (Muenchen Ger.) 1982, 133, 93–98.
[32]The common correction used to determine the CS state energy level
in an apolar solvent from the values of the redox potentials in a
polar solvent takes into account the Coulombic interaction term and
the ion solvation energy based on the Born dielectric continuum
model according to Weller (ref. [31]). The energy of the charge-sep-
arated states relative to the ground state, DGCS, can thus be calculat-
ed by the following equation: DGCS =EoxꢀEredꢀ(14.32/RDAeS)+
14.32(1/2rD+1/2rA)(1/eSꢀ1/eP) For the formation of the charge-sepa-
rated state involving the transfer of an electron from the corrole to
the perylene bisimide, Eox and Ered are the first oxidation potential
of the corrole and the first reduction potential of perylene bisimide,
respectively, which are +0.72 V versus SCE for C2, +0.86 V versus
SCE for C3, and ꢀ0.54 V versus SCE for PI0, eS =2.4 is the dielec-
tric constant of toluene, eP =31.2 is an average of the dielectric con-
stant of benzonitrile and acetonitrile. RDA, the center-to-center
[18]a) B. Rybtchinski, L. E. Sinks, M. R. Wasielewski, J. Am. Chem. Soc.
2004, 126, 12268–12269; b) L. Flamigni, B. Ventura, C.-C. You, C.
Hippius, F. Wꢁrthner, J. Phys. Chem. C 2007, 111, 622–630; c) C.
Flors, I. Oesterling, T. Schnitzler, E. Fron, G. Schweitzer, M. Sliwa,
A. Herrmann, M. van der Auweraer, F. C. de Schryver, K. Mullen, J.
donor–acceptor distance is 13.5 Š for C2-PI and C3-PI, and 17.7 Š
for C3-PPI, and the perylene bisimide and corrole radii are taken
rA =rD =6 Š.
[33]The oxidation potential of PI0 in acetonitrile is of the order of
+1.6 V versus SCE and the reduction potential of corroles C2 and
182
www.chemeurj.org
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2008, 14, 169 – 183

Arrays for Photoinduced Charge Separation
FULL PAPER
C3 are of the order of ꢀ0.75 V and ꢀ0.65 V versus SCE, respective-
ly, in benzonitrile (M. Cembor, J. S. Jaworski, private communica-
tion), which would leave the CS energy level at about 1.7 eV after
correction for the polarity of the solvent.
E. Ronnow, T. Ljungdahl, J. Martensson, B. Albinsson, J. Phys.
Chem. A 2006, 110, 310–318.
[38]a) M. P. Eng, B. Albinsson, Angew. Chem. 2006, 118, 5754–5757;
Angew. Chem. Int. Ed. 2006, 45, 5626–5629; b) J. Wiberg, L. J. Guo,
K. Pettersson, D. Nilsson, T. Ljungdahl, J. Martensson, B. Albinsson,
J. Am. Chem. Soc. 2007, 129, 155–163.
[34]J. Fajer, D. C. Borg, A. Forman, D. Dolphin, R. H. Felton, J. Am.
Chem. Soc. 1970, 92, 3451–3459.
[35]Th. Fçrster, Discuss. Faraday Soc. 1959, 27, 7–17.
[39]A. Helms, D. Heiler, G. McLendon, J. Am. Chem. Soc. 1992, 114,
6227–6238.
[36]The Fçrster rates keFn were calculated by means of Equation (1)[35]
[40]R. A. Marcus, Angew. Chem. 1993, 105, 1161–1172; Angew. Chem.
Int. Ed. Engl. 1993, 32, 1111–1121.
8:8ꢄ10ꢀ25 k2
kFen
=
FJF
(1)
n4tR6DA
[41]D. S. Pedersen, C. Rosenbohm, Synthesis 2001, 2431–2434.
[42]M. W. Holman, R. Liu, D. M. Adams, J. Am. Chem. Soc. 2003, 125,
12649–12654.
[43]a) C.-H. Lee, J. S. Lindsey, Tetrahedron 1994, 50, 11427–11440;
b) J. K. Laha, S. Dhanalekshmi, M. Taniguchi, A. Ambroise, J. S.
Lindsey, Org. Process Res. Dev. 2003, 7, 799–812.
[44]R. Kumar, A. K. Chakraborti, Tetrahedron Lett. 2005, 46, 8319–
8323.
in which F and t are the emission quantum yield (0.92) and the life-
time (4 ns) of the donor PI, RDA is the donor–acceptor center-to-
center distance (13.5 Š for C2-PI and C3-PI, and 17.7 Š for C3-
PPI), n is the refractive index of toluene and JF is the overlap inte-
gral. k2, the orientation factor, can be simplified to the statistical
value, 2/3. JF, the Fçrster overlap integral, is calculated from the
overlap between the luminescence spectrum of the donor PI0, F(n˜)
(cmꢀ1 units), and the absorption spectrum e(n˜) of the acceptors C2
and C3 (cmꢀ1 units), according to the Equation (2) (ref. [35])
[45]H. Langhals, J. Karolin, L. B.-Š. Johansson, J. Chem. Soc. Faraday
Trans. 1998, 94, 2919–2922.
[46]P. G. Seybold, M. Gouterman, J. Mol. Spectrosc. 1969, 31, 1–13.
[47]L. Flamigni, J. Phys. Chem. 1993, 97, 9566–9571.
[48]L. Flamigni, N. Armaroli, F. Barigelletti, V. Balzani, J.-P. Collin, J.-
O. Dalbavie, V. Heitz, J.-P. Sauvage, J. Phys. Chem. B 1997, 101,
5936–5943.
[49]a) L. Flamigni, J. Phys Chem. 1992, 96, 3331–3337; b) L. Flamigni,
J. Chem. Soc. Faraday I, 1994, 90, 2331–2336.
[50]CS Chem3D Ultra CambridgeSoft. Com, Cambridge MA, USA,
2000.
R
4
~
~
~
~
dn
FRðnÞeðnÞ=n
JF =
(2)
~
~
FðnÞdn
From the experimental emission and absorption spectra an overlap
integral JF =1.1”10ꢀ13 cm3 mꢀ1 is calculated for dyad C2-PI and a
JF =1.3”10ꢀ13 cm3 mꢀ1 is derived for C3-PI and C3-PPI. A rate of
energy transfer keFn =5.0”1011 sꢀ1, 5.8”1011 sꢀ1, and 9.9”1010 sꢀ1 cal-
culated for the dyads C2-PI, C3-PI, and C3-PPI, respectively. These
rates are in agreement with the experimental results.
[51]Matlab 5.2., The MathWorks Inc., Natik, MA 01760, USA, 1998.
[37]a) H. S. Cho, D. H. Jeong, M. C. Yoon, Y. H. Kim, Y. R. Kim, D.
Kim, S. C. Jeoung, S. K. Kim, N. Aratani, H. Shinmori, A. Osuka, J.
Phys. Chem. A 2001, 105, 4200–4210; b) S. I. Yang, J. Seth, T. Bala-
subramanian, D. Kim, J. S. Lindsey, D. Holten, D. F. Bocian, J. Am.
Chem. Soc. 1999, 121, 4008–4018; c) K. Pettersson, A. Kyrychenko,
Received: June 6, 2007
Published online: October 9, 2007
Chem. Eur. J. 2008, 14, 169 – 183
ꢀ 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
183