Implementation of a Hamiliton-receptor-based hydrogen-bonding motif toward a new electron donor-acceptor prototype: Electron versus energy transfer

Article abstract of DOI:10.1021/ja075751g

A new modular concept for the self-assembly of electron donor-acceptor complexes is presented that ensures (i) fine-tuning the strength of the complexation, (ii) controlling the electronic coupling to impact electron and energy transfer processes, and (iii) high solubility of the corresponding hybrid architectures This task has been realized through developing a series of porphyrin-fullerene donor-acceptor systems held together by a Hamilton-receptor-based hydrogen-bonding motif. In this context, novel libraries of C₆₀ monoadducts (1) containing cyanuric acid side chains and of tetraphenylporphyrin derivatives (2) involving the complementary Hamilton-receptor unit were synthesized. The association constants of the corresponding 1:1 complexes (1·2) connected by six hydrogen bonds were determined complementary by NMR and fluorescence assays. Their strength, which was found to be in the range between 3.7 × 10³ and 7.9 × 10⁵ M^-1, depends on the nature of the spacers, namely, hexylene versus propylene chains. Finally transient absorption studies revealed photoinduced electron transfer from ZnP to C₆₀ in the corresponding 1·2 complexes, which generate radical ion pair states that are persistent well beyond the ns time scale. In the case of the analogous SnP complexes, energy instead of electron transfer was observed. This is due to the shift of oxidation potential caused by presence of Sn in the oxidation state of +4.

Full text of DOI:10.1021/ja075751g

Published on Web 12/06/2007
Implementation of a Hamiliton-Receptor-Based
Hydrogen-Bonding Motif toward a New Electron
Donor-Acceptor Prototype: Electron versus Energy Transfer
Florian Wessendorf,† Jan-Frederik Gnichwitz,† Ginka H. Sarova,‡ Kristine Hager,†
Uwe Hartnagel,† Dirk M. Guldi,*,‡ and Andreas Hirsch*,†
Contribution from the Institute of Organic Chemistry and Interdisciplinary Center for Molecular
Materials (ICMM), Friedrich-Alexander UniVersita¨t Erlangen-Nu¨rnberg, Henkestrasse 42, 91054
Erlangen, Germany, and Institute of Physical Chemistry and Interdisciplinary Center for
Molecular Materials (ICMM), Friedrich-Alexander UniVersita¨t Erlangen-Nu¨rnberg,
Egerlandstrasse 3, 91058 Erlangen, Germany
Received August 7, 2007; E-mail: dirk.guldi@chemie.uni-erlangen.de
Abstract: A new modular concept for the self-assembly of electron donor-acceptor complexes is presented
that ensures (i) fine-tuning the strength of the complexation, (ii) controlling the electronic coupling to impact
electron and energy transfer processes, and (iii) high solubility of the corresponding hybrid architectures.
This task has been realized through developing a series of porphyrin-fullerene donor-acceptor systems
held together by a Hamilton-receptor-based hydrogen-bonding motif. In this context, novel libraries of C60
monoadducts (1) containing cyanuric acid side chains and of tetraphenylporphyrin derivatives (2) involving
the complementary Hamilton-receptor unit were synthesized. The association constants of the corresponding
1:1 complexes (1‚2) connected by six hydrogen bonds were determined complementary by NMR and
fluorescence assays. Their strength, which was found to be in the range between 3.7 × 103 and 7.9 × 105
M-1, depends on the nature of the spacers, namely, hexylene versus propylene chains. Finally, transient
absorption studies revealed photoinduced electron transfer from ZnP to C60 in the corresponding 1‚2
complexes, which generate radical ion pair states that are persistent well beyond the ns time scale. In the
case of the analogous SnP complexes, energy instead of electron transfer was observed. This is due to
the shift of oxidation potential caused by presence of Sn in the oxidation state of +4.
molecular scale.2 Nature has long used these interactions to
create a formidable array of structures, where a great level of
Introduction
The transport of energy and electrons within nanoscale-
ordered materials is critical to the realization of systems for
artificial photosynthesis as well as engineering molecular
electronics and optoelectronics.1 Studying multifunctional fullerene
nanostructuresstheir design, synthesis, characterization, and
performancesmandates a careful control over composition,
interchromophore separation/angular relationship, overall dy-
namical and stimulus-induced reorganization, and electronic
coupling. The overall goal is to achieve control over both the
organization of the assemblies and their physical and chemical
properties (i.e., electronic structures, etc.) and, thereby, enhance
desired functionalities, through simple external parameters or
variables, with the intent of creating new tailored materials.
Among the tools exploitable for the creation of new assemblies
are organization principles, such as biomimetic methodologies,
that help regulate size, shape, and function down to the
control over the organization and an increased flexibility in
replacing individual building blocks have been realized.
Nanohybrid systems that combine the favorable features of,
for example, fullerenes and porphyrins as electron acceptors
and electron donors, respectively, have received considerably
interest.3 As a consequence, new materials with a wide range
of unique and spectacular physicochemical properties have
resulted in noteworthy advances in the areas of light-induced
electron-transfer chemistry and solar energy conversion. It is
mainly the small reorganization energy, which fullerenes exhibit
in electron-transfer reactions, that is accountable for a note-
worthy breakthrough.4 In particular, ultrafast charge separation
together with very slow charge recombination features lead to
unprecedented long-lived radical ion pair states formed in high
quantum yields. This aspect is crucial toward the use of solar
† Institute of Organic Chemistry and Interdisciplinary Center for Mo-
lecular Materials (ICMM).
(2) (a) McDermott, G.; Priece, S. M.; Freer, A. A.; Hawthornthwaite-Lawless,
A. M.; Papiz, M. Z.; Cogdell, R. J.; Isaaacs, N. W. Nature 1995, 374,
517-521. (b) Barber, J. Nature 1988, 333, 114-114. (c) Balzani, V., de
Cola, L., Eds. Supramololcular Chemistry; NATO ASI Series; Kluwer
Academic Publishers: Dordrech, The Netherlands, 1992. (d) Steed, J. W.;
Atwood, J. Supramol. Chem. Wiley: Chichester, U.K., 2000. (e) Balzani,
V.; Venturini, M.; Credi, A. Molecular DeVices and Machines; Wiley-
VCH: Weinheim, Germany, 2003. (f) Ozin, G. A.; Arsenault, A. C.
Nanochemistry; RSC Publishing: Cambridge, U.K., 2005.
‡ Institute of Physical Chemistry and Interdisciplinary Center for Mo-
lecular Materials (ICMM).
(1) For a recent status report, see: Adams, D. M.; Brus, L.; Chidsey, C. E. D.;
Creager, S.; Creutz, C.; Kagan, C. R.; Kamat, P. V.; Lieberman, M.;
Lindsay, S.; Marcus, R. A.; Metzger, R. M.; Michel-Beyerle, M. E.; Miller,
J. R.; Newton, M. D.; Rolison, D. R.; Sankey, O.; Schanze, K. S.; Yardley,
J.; Zhu, X. J. Phys. Chem. B 2003, 107, 6668.
9
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J. AM. CHEM. SOC. 2007, 129, 16057-16071
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Wessendorf et al.
energy conversion as a clean, abundant, and economical energy
source.
To this end, most electron donor-acceptor systems are based
on covalently linking, at least, two building blocks. Important
is that the bridges between the donor and acceptor govern the
donor-acceptor distance, spatial orientation, and flexibility.
Much less is, however, known about noncovalent fullerene
electron donor-acceptor nanohybrids and the function of the
intervening spacers.5 In a recent example, which was built on
noncovalent electrostatic interactions, where oppositely charged
fullerenes and porphyrins/cytochrome c interact tightly with each
other, sufficiently strong electronic couplings powered an
intrahybrid charge separation.6 This approach turned out to be
especially successful for constructing photovoltaic devices that
perform efficiently on the basis of photoinduced electron transfer
between the hierarchically ordered building blocks.7
There is little, if any, doubt that the most potent supramo-
lecular binding motif is, nevertheless, hydrogen bonding. Despite
its tremendous potential for the realization of highly directional
self-assembly, only a few examples of fullerene-porphyrin
donor-acceptor nanohybrids have been constructed in this way
so far.8
Figure 1. Schematic representation of the complementary hydrogen-
bonding motif of a cyanuric acid derivative and a Hamilton receptor.
association constants Kass. that range in apolar solvents (i.e.,
dichloromethane and toluene) between 103 and 106 M-1. Besides
dendritic achiral and chiral building blocks such as depsipeptide
dendrons, we have also tested chromophoric components to self-
assemble into novel dendrimeric architectures, namely, fullere-
neated cyanuric acid end-caps and Hamilton-receptor substituted
porphyrin cores. Important is that, in these architectures, the
fullerene and porphyrin building blocks were integrated sepa-
rately and just served as assembly determining building blocks
or as sensors for chirality transfer.
A significant set back is the poor solubility of the Hamilton-
receptor/cyanuric acid motif caused by inter- and intramolecular
aggregation,9 which is quite cumbersome for supramolecular
complexation experiments. To overcome this deficiency, we
have developed in the current work for the first time highly
soluble supramolecular porphyrin/fullerene dyads. Thereby the
association constants of these complexes could be determined
even in apolar solvents like toluene.
The strategy toward hydrogen-bonded electron donor-
acceptor nanohybrids developed in the current contribution is
sketched in Figure 2. In particular, fullerene 1 is a monoma-
lonate, where one branch carries a cyanuric acid moiety. The
corresponding linkers are either propylene or hexylene chains.
The second malonate branch, on the other hand, contains a
variety of dendritic termini that assist in guaranteeing high
solubility in solvents that do not compete with hydrogen bonding
(i.e., chloroform and dichloromethane). At the end of the
porphyrins (2), one of the four phenyl rings bears the Hamilton-
receptor connected via an amide spacer. To add diversity we
have pursuedsbesides free base porphyrin derivatives (i.e.,
H2P)sthe coordination of either tin or zinc as central metals.
Whereas the Zn derivatives (i.e., ZnP) involve a tetragonal
planar (NMR time scale) coordination motif, the Sn analogues
(i.e., SnP) exhibit an octahedral coordination pattern with two
additional axial ligands.
We have recently introduced the Hamilton-receptor9a/cyanuric
acid binding motif to self-assemble new dendrimer prototypes
(Figure 1).9b-e Importantly, the six-point hydrogen bonding leads
to comparatively strong bindings between hosts and guests with
(3) (a) Imahori, H.; Sakata, Y. AdV. Mater. 1997, 9, 537. (b) Prato, M. J. Mater.
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1999, 2445. (e) Diederich, F.; Gomez-Lopez, M. Chem. Soc. ReV. 1999,
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Bolskar, R. D. Chem. ReV. 2000, 100, 1075. (h) Gust, D.;. Moore, T. A.;
Moore, A. L. J. Photochem. Photobiol., B 2000, 58, 63. (i) Gust, D.; Moore,
T. A.; Moore, A. L. Acc. Chem. Res. 2001, 34, 40. (j) Guldi, D. M.; Martin,
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Photobiol., C 2003, 4, 51. (m) Nierengarten, J. F. Top. Curr. Chem. 2003,
228, 87. (n) El-Khouly, M. E.; Ito, O.; D’Souza, F. J. Photochem.
Photobiol., C 2004, 5, 79. (o) Guldi, D. M.; Zerbetto, F.; Georgakilas, V.;
Prato, M. Acc. Chem. Res. 2005, 38, 38. (p) Guldi, D. M.; Rahman, G. M.
A.; Ehli, C.; Sgobba, V. Chem. Soc. ReV. 2006, 35, 471. (q) Guldi, D. M.
Phys. Chem. Chem. Phys. 2007, 12, 1400.
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Y.; Fukuzumi, S. J. Am. Chem. Soc. 2001, 123, 6617. (b) Guldi, D. M.;
Imahori, H.; Tamaki, K.; Kashiwagi, Y.; Yamada, H.; Sakata, Y.; Fukuzumi,
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H.; Tamaki, K.; Sakata, Y. J. Am. Chem. Soc. 2000, 122, 6535.
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Seitz, W.; Guldi, D. M.; Sessler, J. L. Chem. Commun. 2007, 292. (b)
McClenaghan, N. D.; Grote, Z.; Darriet, K.; Zimine, M.; Williams, R. M.;
de Cola, L.; Bassani, D. M. Org. Lett. 2005, 7, 807. (c) Beckers, E. H.;
Schenning, A. P. H. J.; van Hal, P. A.; El-ghayoury, A.; Sanchez, L.;
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24, 749. (f). Hager, K.; Hartnagel, U.; Hirsch, A. Eur. J. Org. Chem. 2007,
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Results and Discussion
We have recently reported the syntheses of compounds 1e,f,
where a propylene spacer unit between the malonate and the
cyanuric acid moiety (n ) 1) was employed.1c To increase the
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N.; Hatzimarinaki, M.; Hirsch, A.; Prato, M.; Chem. Commun. 2004, 6,
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A.; Jux, N. J. Phys. Chem. B 2003, 107, 13273. (c) Hartnagel, U.; Balbinot,
D.; Jux, N.; Hirsch, A. Org. Biomol. Chem. 2006, 4, 1785.
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A. L.; Araki, Y.; Ito, O. Tetrahedron, 2005, 62, 1967. (b) Guldi, D. M.
Chem. Commun. 2000, 5, 321. (c) Sessler, J. S.; Wang, B.; Springs, S. L.;
Brown C. T. In CromprehensiVe Supramolecular Chemistry; Atwood, J.
L., Davies, J. E. D., MacNicol, D. D., Vo¨gtle, F., Eds.; Pergamon: New
York, 1996; Chapter 9. (d) Piotrowiak, P. Chem. Soc. ReV. 1999, 28, 143.
(8) (a) Sanchez, L.; Martin, N.; Guldi, D. M. Angew. Chem. 2005, 117, 5508;
Angew. Chem., Int. Ed. 2005, 44, 5374. (b) Sanchez, L.; Sierra, M.; Martin,
N.; Myles, A. J.; Dale, T. J.; Rebek, J., Jr.; Seitz, W.; Guldi, D. M. Angew.
Chem. 2006, 118, 4753; Angew. Chem., Int. Ed. 2006, 45, 4637.
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Hager, K.; Franz, A.; Hirsch, A. Chem.sEur. J. 2006, 12, 2663. (c) Hager,
K.; Hartnagel, U.; Hirsch, A. Eur. J. Org. Chem. 2007, 12, 1942. (d) Maurer,
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Int. Ed. 2005, 44, 1564.
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Electron versus Energy Transfer
A R T I C L E S
Figure 2. Schematic represention of the 1‚2 complexes between fullerene cyanurates and porphyrin-Hamilton receptors associated by 6-fold hydrogen
bonding.
flexibility and to facilitate the binding we introduce in this study
the syntheses of hexylene analogues. These were prepared by
following a modified synthetic procedure. For the syntheses of
the fullerene cyanurates 1 suitable malonate precursors were
prepared prior to the cyclopropanation of C6010 and subsequent
linkage of the cyanuric acid moiety. The sequence started from
1-bromohexane-6-ol, which was coupled with the monoacid 3
using standard ester coupling conditions (Scheme 1). The
resulting asymmetric malonate 4a was then treated with
trifluoroacetic acid (TFA) to provide acid 5. The latter serves
as anchor for the subsequent coupling of the corresponding
dendritic termini. The bromomalonates 4b-d were obtained by
modified Steglich conditions11 using dicyclohexylcarbodiimide
(DCC), 1-hydroxybenzotriazole (HOBT), and diaminopyridine
(DMAP) with yields up to 89% (Scheme 1).
For comparison we also synthesized the nondendric malonates
4e,f by simple treatment of methyl and ethyl malonyl chloride
with 1-bromohexane-6-ol (Scheme 2).
The fullerene monoadducts 6 were synthesized by standard
Bingel10 conditions (Scheme 3). In the case of chiral malonyl
system 6c and the malonates 6g,h clean cyclopropanation was
only successful by using iodine instead of CBr4 for the activation
of the central methylene group.
(11) (a) Ho¨fle, G.; Steglich, W. Synthesis 1972, 619. (b) Neiss, B.; Steglich,
(10) (a) Bingel, C. Chem. Ber. 1993, 126, 1957. (b) Camps, X.; Hirsch, A. J.
Chem. Soc., Perkin Trans. 1 1997, 1595.
W. Angew. Chem. 1978, 90, 556; Angew. Chem., Int. Ed. Engl. 1978, 17,
522.
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Scheme 1. Syntheses of the Dendromalonates 5a-da
Scheme 5. Synthesis of the Porphyrin Building Blocks 8 and 9ba
a Key: (i) DCC, HOBT, DMAP, CH2Cl2, 0 °C; (ii) TFA, CH2Cl2, RT;
(iii) dendrimer, DCC, HOBT, DMAP, CH2Cl2, 0 °C.
a Key: (i) BF3‚OEt2, DDQ, CH2Cl2, RT; (ii) (1) SnCl2, acetic acid, (2)
NaOH, ethanol, reflux.
Scheme 2. Syntheses of Malonates 4e,fa
For the synthesis of the Hamilton-receptor-substituted por-
phyrin 2a involving a very rigid spacer unit, amino derivative
712 was used as building block for the coupling with a suitable
tetraphenylporphyrin (TPP) derivative. For this purpose the
metal free methyl ester 8 containing three peripherical tert-butyl
substituents was chosen due to an increase in the overall
solubility. Conceptually, this TPP derivative can subsequently
be metalated and transformed into the free acid for further
coupling reactions.
a Key: (i) pyridine, CH2Cl2, 0 °C.
Scheme 3. Syntheses of the C60 Monoadducts 6a
a Key: (i) C60, I2, CBr4, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU),
toluene, RT.
Scheme 4. Synthesis of the Fullerene-Cyanuric Acid Derivatives
1a
The synthesis of 8 was carried out by a typical Lindsey
procedure13 using a 4:1:3 mixture of pyrrole, methyl 4-formyl-
benzoate, and 4-tert-butylbenzaldehyde as precursors for the
statistical condensation reaction (Scheme 5). Boron trifluoride
a Key: (i) cyanuric acid, DBU, DMF, 40 °C.
The final step in the synthesis of the target adducts 1 was a
SN2 substitution of the terminal bromine atom with cyanuric
acid (Scheme 4). Here, cyanuric acid was first deprotonated with
DBU to facilitate the substitution. The insertion of the cyanuric
acid had to be performed in the last reaction step due to the
low reactivity of the C60 monoadducts 6.
(12) Dirksen, A.; Hahn, U.; Schwanke, F.; Nieger, M.; Reek, J. N. H.; Vo¨gtle,
F.; De Cola, L. Chem.sEur. J. 2004, 10, 2036.
(13) (a) Littler, B. J.; Ciringh, Y.; Lindsey, J. S. J. Org. Chem. 1998, 64, 2864.
(b) Geier, R. G., III; Lindsey, J. S. J. Chem. Soc., Perkin Trans. 2001, 2,
677. (c) Lindsey, J. S.; Schreiman, I. C.; Hsu, H. C.; Kearney, P. C.;
Maguerettaz, A. M. J. Org. Chem. 1987, 52, 827. (d) Lindsey, J. S.; Wagner,
R. W. J. Org. Chem. 1989, 54, 828. (e) Lindsey, J. S.; MacCrum, K .A.;
Thyonas, J. S.; Chuang, Y.-Y. J. Org. Chem. 1994, 59, 579.
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A R T I C L E S
Scheme 7. Synthesis of the Porphyrin Derivative 11a
Scheme 6. Synthesis of the Hamilton-Receptor-Bearing Porphyrin
2aa
a Key: (i) 1-(3-(dimethylamino)propyl)-3-ethylcarbodiimide hydrochlo-
ride (EDC), HOBT, DMAP, CH2Cl2, 0 °C.
diethyl etherate was used as catalyst to promote the cyclization
reaction. For the final oxidation 2,3-dichloro-5,6-dicyano-1,4-
benzoquinone (DDQ) was used as oxidant. Due to the low
solubility of the corresponding deprotected free carboxylic acid,
we decided to metalate the porphyrin prior to the deprotection
(Scheme 5).
a Key: (i) BF3‚OEt2, DDQ, CH2Cl2, RT; (ii) formic acid, RT.
Tin(II) chloride was used for the metalation of 8, since when
complexed by a porphyrin, the most stable oxidation state of
+4 binds typically two anionic axial ligands. In such architec-
tures direct π-π-contacts between the fullerene and porphyrin
chromophores should not prevail. As a consequence electronic
interactions can only be accomplished through bonds involving
the H-bonding motif represented in Figure 1. After evaluation
of the literature precedents describing methods for the insertion
of tin into free base porphyrins,14 we decided to use the acetic
acid method, because the insertion is nearly quantitative and
the solvent can easily be removed by rotary evaporation. In this
regard, free base porphyrin 8 was dissolved in acetic acid in
the presence of SnCl2 and heated under reflux. During the
reaction Sn(II) was oxidized from the oxidation state of +2 to
+4. At the same time two chloride ligands bind in axial
positions. The subsequent deprotection was achieved by treat-
ment with NaOH. During this procedure the axial chloride
ligands were replaced by hydroxide to give the desired
compound 9b, which is sufficiently soluble in apolar solvents.
The protons of the hydroxo ligands appear as a broad singlet at
Indeed, no coupling was observed by using just 1 equiv of
coupling reagents. However, when 3 equiv of the coupling
reagent was used, the target compound 2a was obtained as the
major reaction product.
To introduce a more flexible spacer between the Hamilton
receptor and porphyrin part of 2 (Figure 2)sfor reasons of
comparisonswe decided to synthesize also the free base
porphyrin precursor 10. The synthesis of 10 was again carried
out using modified Lindsey conditions (Scheme 7). The
subsequent treatment of 10 with formic acid afforded porphyrin
11, which is very soluble in apolar solvents. In this case
metalation prior to the deprotection was not required.
Significantly, the subsequent coupling of 11 with the Hamil-
ton receptor 7 (Scheme 8) proceeded in higher yield (30%)
compared to that of 9b with 7 (18%). This is due to the fact
that the aliphatic carboxylate is more reactive than the aromatic
carboxlate involved in 9b.
The free base porphyrin 2b served as a versatile precursor
for the final metalation step. After treatment with SnCl2 and
Zn(OAc)2 the metalloporphyrins 2c,d were obtained in excellent
yields (Scheme 9).
1
-7.5 ppm in the HNMR spectrum of 9b recorded in CDCl3.
Since the protons of the hydroxo ligands are fairly acidic, we
expected that at least a 3-fold excess of HOBT has to be used
for the final Steglich coupling9 with Hamilton-receptor 7 to
obtain the target compound 2a where both hydroxo ligands are
replaced by two hydroxybenzotriazole molecules (Scheme 6).
The formation of the 1‚2 complexes was first investigated
1
by H NMR spectroscopy. In particular, the determination of
the association constant Kass. required a series of titration
experiments in CDCl3. The characteristic downfield shifts of
the NH1- and NH2-protons of the Hamilton-receptor moieties9b-e
in 2a were used to analyze the complex formation. Figure 3
depicts the corresponding shifts of the protons of 2a as a function
(14) (a) Buchler, J. W.; Puppe, L.; Rohbock, K.; Schneehage, H. H. Chem. Ber.
1973, 106, 2710. (b) Dorough, G. D.; Miller, J. R.; Huennekens, F. M. J.
Am. Chem. Soc. 1951, 73, 4315. (c) Rothemund, P.; Menotti, A. R. J. Am.
Chem. Soc. 1948, 70, 1808.
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Scheme 8. Synthesis of the Hamilton-Receptor-Bearing Porphyrin
2ba
a Key: (i) EDC, HOBT, DMAP, CH2Cl2, 0 °C.
Scheme 9. Syntheses of Hamilton-Receptor-Bearing Porphyrins
2c,da
Figure 3. Binding motif between 2a and 1a with indication of the NH
protons NH1, NH2, and NH3 and 1H NMR (300 MHz) spectra of 2a at 1.93
mM in CDCl3 with various equivalents of 1a.
a Key: (i) SnCl2, acetic acid, reflux; (ii) ZnOAc2, THF, reflux.
1
Figure 4. Job’s plot analysis of the H NMR (300 MHz) titration of 2a
with 1a in CDCl3.
of added fullerene derivative 1a. Additionally, the shifts of the
NH3-protons within the cyanuric acid moiety of 1a were
investigated. In a typical experiment, 0.5 mL of a 1.93 mM
solution of porphyrin derivative 2a was titrated with 100 µL of
regime) between bound and free cyanurate. On the basis of these
titration experiments, the association constants Kass. could be
determined with the help of the program Chem-Equili.15 In the
case of the complex 1a‚2a an association constant Kass of 1.79
× 104 M-1 was determined.
1
a 4.3 mM solution of fullerene derivative 1a. The H NMR
spectra were recorded approximately 3 min after mixing the
solutions. In each case, the spectrum remained unchanged after
30 min indicating a fast equilibrium formation.
Whereas the NH1- and NH2-protons undergo a shift to lower
fields, the NH3-protons of the cyanuric acid moieties at 13 ppm
are subject to an opposite effect. The corresponding signals
undergo a high-field shift during addition of the fullerene
cyanuric acid derivative 1a. Furthermore, they broaden and,
finally, they disappear. The reason for the disappearance in the
presence of an excess of 1a is a fast equilibrium (coalescence
In addition, a Job’s plot analysis of the titration data was
carried out (Figure 4). To this end, the chemical shift variation
of NH1 (∆(δ))was monitored as a function of the molar fraction
of the fullerene derivative Ì(1a) and the product of the mole
(15) (a) Solov’ev, V. P.; Vnuk, E. A.; Strakhova, N. N.; Reavsky, O. A.
VINITI: Moscow, 1991. (b) Solov’ev, V. P.; Baulin, V. E.; Strahova, N.
N.; Kazachenko, V. P.; Belsky, V. K.; Varnek, A. A.; Volkova, T. A.;
Wipff, G. J. Chem. Soc., Perkin Trans. 2 1998, 7, 1489.
9
16062 J. AM. CHEM. SOC. VOL. 129, NO. 51, 2007

Electron versus Energy Transfer
A R T I C L E S
Figure 5. Schematic representation of the titrated compounds.
Figure 6. Changes in the Zn porphyrin 2d (1.9 × 10-6 M) electronic
absorption spectrum in toluene upon addition of increasing concentrations
of C60 derivative 1c ((0-2.8) × 10-6 M).
Figure 7. Fluorescence intensity of Zn porphyrin 2d (1.2 × 10-6 M) in
toluene upon addition of increasing amounts of C60 compound 1e ((0-7.1)
× 10-6 M).
fraction Ì[(fd)-1] and ∆(δ) was plotted as a function of Ì.
Well in line with the expectation, we found that the fitted curve
shows a maximum at 0.5 Ì(1a). Such a finding clearly confirms
the existence of a 1:1 stroichiometry.
We found in absorption experiments where Zn porphyrin 2d
and/or Sn porphyrin 2a solutions (i.e., CH2Cl2 or toluene) were
titrated (Figure 5) with variable concentrations of C60 derivative
1c (Figure 6), appreciable decreases in the intensity of both
Soret- and Q-bands. Moreover, two clear isosbestic pointssat
414 and 433 nmsevolve in the titration assays performed with,
for example, Zn porphyrin 2d and C60 derivative 1a, although
no overall shift was noted.16 Such a trend corroborates the NMR
experiments, which helped to attest a 1:1 ground state nano-
hybrid formation between 2a and/or 2c and 1a.
respectively, and plotted as a function of the fullerene concen-
tration. A nonlinear curve fitting according to eq 1 allowed
estimation of the association constants (Figure 7).
In eq 1, Io refers to the initial fluorescence intensity, co is
the total porphyrin concentration, cD is the total concentration
of the added fullerene, and Kass. is the association constant.
The obtained association constants are summarized in Tables 1
and 2.
First insights into electron donor-acceptor interactions were
derived from complementary fluorescence experiments. The
strong fluorescence of Zn porphyrin 2d (ΦF ) 4.0 × 10-2) and
Sn porphyrin 2a (ΦF ) 3.0 × 10-2), which were tested in the
absence and presence of variable concentrations of C60 deriva-
tives, gives rise to appreciable intrahybrid quenching, when the
fullerenes are present.
These dependencies were used to determine the association
constants for the formation of the fullerene-porphyrin nano-
hybrids. In particular, data were taken at the short-wavelength
emission maxima of Zn porphyrin 2d and Sn porphyrin 2a,
All values were estimated on the basis of a 1:1 nanohybrid
formation. As was expected, the association constant values
increase with decreasing solvent polarity and the substitution
of the hexylene alkyl spacer with a propylene spacer in 1e
strengthens the formation of the nanohybrid by a factor of
approximately 6.
The fluorescence decays for Zn porphyrin 2d and Sn
porphyrin 2a were well fitted with monoexponential fitting
functions, which gave lifetimes of 1.6 and 0.3 ns in toluene
and 1.3 and 0.3 ns in dichloromethane, respectively. However,
no fast decaying component, attributed to the complexed Zn
porphyrin or Sn porphyrin, was observed after addition of sev-
eral equivalents of fullerenes. Implicit is that Zn porphyrin 2d
and Sn porphyrin 2a singlet excited-state deactivation must be
faster than the time resolution of our apparatus (i.e., 100 ps).
(16) Likewise, a mixture of equimolar quantities of 2a and /or 2d and any of
the C60 derivatives shows an electronic absorption spectrum that differs
from the sum spectrum of the parent compounds, thus indicating notable
interactions between the donor and the acceptor moieties in the ground
state.
9
J. AM. CHEM. SOC. VOL. 129, NO. 51, 2007 16063

A R T I C L E S
Wessendorf et al.
Table 1. Association Constants (M-1) of the Titrated Assemblies
in CH2Cl2
porphyrin
fullerene
association constants
2a
1a
1b
1c
1d
1a
1b
1c
1d
1a
1b
1c
1d
1a
1b
1c
1d
1.76 × 104
2.82 × 104
2.81 × 103
3.68 × 103
2.72 × 104
7.48 × 104
7.67 × 104
5.16 × 104
4.42 × 104
5.34 × 104
7.21 × 104
3.63 × 104
2.93 × 104
1.70 × 104
2.54 × 104
6.54 × 104
2b
2c
2d
Table 2. Photophysical Parameters Obtained for the Studied
Assemblies
quenching
1
association constants, M-
efficiency,
1
porphyrin fullerene
toluene
CH2Cl2
%
kq, s-
τs, ns
2c
1e
1f
1c
1e
1f
9.2 × 104 2.2 × 104
67
27
71
87
75
7.80 × 109 0.35(0.08)
1.40 × 109 0.31(0.06)
1.55 × 109
1.9 × 104
2d
1.2 × 105
7.9 × 105 6.2 × 104
3.0 × 105 1.2 × 104
4.45 × 109 1.7(0.23)
1.94 × 109 1.3(0.02)
Intrahybrid electron donor-acceptor interactions were con-
firmed through time-resolved transient absorption measurements,
namely, following the photoexcitation of 2d or 2a and 2d‚1e
or 2a‚1e at 550 and 387 nm respectively in the corresponding
references and in the donor-acceptor nanohybrids.17
Figure 8. Top: Differential absorption spectra (visible and near-infrared)
obtained upon femtosecond flash photolysis (550 nm) of Zn porphyrin 2d
in nitrogen-saturated toluene with several time delays. Bottom: Time-
absorption profiles of the spectra shown above at 720 (gray spectrum) and
840 (black spetrum) nm, reflecting the formation and decay of the singlet
excited state.
Representative femtosecond time-resolved absorption spectra,
taken after a 150 fs laser pulse at 387 or 550 nm in a toluene
solution of the 2d reference, are displayed in Figure 8. The
differential spectrum recorded immediately after the laser pulse
is characterized by bleaching of the porphyrin Q-band absorp-
tions at 555 and 595 nm as well as broad absorption between
600 and 1100 nm. These spectral attributes are indicative of
the ZnP singlet excited state (ESinglet ) 2.00 eV), which decays
slowly (8.3 × 108 s-1) to the energetically lower lying triplet
excited state (ETriplet ) 1.53 eV) via intersystem crossing (ΦTriplet
) 0.88). The triplet excited-state features maxima at 475, 580,
625, and 845 nmswith the most important spectral characteristic
being the transient peak at 845 nm. Similar, although somewhat
faster (3.8 × 109 s-1), is the decay of the SnP singlet excited
state (ESinglet ) 1.98 eV) in 2a forming the corresponding triplet
manifold, for which we noted a characteristic marker at 500
nm; see Figure S1.
visible range around 630 nm grows in (Figure 9) accompanied
by another absorption in the near-infrared ranges1040 nm. On
the basis of a spectral comparison, we ascribe the former to the
Zn porphyrin π-radical cation (ZnP•+), while the latter band
belongs to the fullerene π-radical anion (C60•-).
In accordance with these results, we propose that charge
separation, from the ZnP singlet excited state to the electron-
accepting fullerene, creates the ZnP•+-C60 state, which is
•-
responsible for the fast deactivation of the photoexcited chro-
mophore. Analyzing the absorption time profiles, we derive a
rate constant of (4.3 × 109 s-1) for the intrahybrid charge
separation.
Contrary to the aforementioned ZnP/C60 donor-acceptor
hybrids, femtosecond photolysis (387 and 550 nm) of the SnP
moiety in 2a‚1e, for example, disclosed absorption features that
are solely assigned to the C60 singlet and triplet excited states
with characteristic features at 880 and 740 nm, respectively
(Figure 10). In fact, the absence of appreciable radical ion pair
absorptions led us to conclude that an unfavorably shifted
oxidation potential of about 1 Vswhen comparing ZnP with
SnP (1.44 V in dichloromethane versus SCE)sprecludes the
anticipated electron transfer.18 Instead, an exothermic energy
transfer process (i.e., 0.22 eV) is the main process of
Next, the transient absorption changes of 2d‚1e donor-
acceptor nanohybrids were recorded in toluene with several time
delays after the 550 nm femtosecond laser pulse and compared
with what we have noted for the ZnP reference. At early times
(i.e., 5-100 ps), these are practically identical with those of
the ZnP reference, disclosing strong bleaching at 550 nm.
However, at a delay time of 200 ps, a new transition in the
(17) Although the systems are not fully assembled under the conditions of the
experiment, photoexcitationsin particular at 550 nmsallowed us to follow
nevertheless the intrahybrid deactivation such as electron and energy
transfer.
9
16064 J. AM. CHEM. SOC. VOL. 129, NO. 51, 2007

Electron versus Energy Transfer
A R T I C L E S
Conclusions
We have investigated for the first time the self-assembly and
the photophysical properties of supramolecular fullerene-
porphyrin donor-acceptor nanohybrids connected via a Hamil-
ton-receptor based hydrogen bonding motif. In this light, we
have synthesized an entire modular set of new C60 monoadducts
1 carrying a cyanuric acid terminus within the malonate addend
connected via hexylene spacers. These new derivatives comple-
ment the structure of previously reported adducts bearing
propylene spacers. To overcome the overall poor solubility,
especially in solvents where no interference with the hydrogen
bonding is expected, we introduced as the second malonate
termini a variety of dendritic groups. The Hamilton-receptor
counterpart was coupled to a library of porphyrin derivatives
involving either tin or zinc as central metals leading to new
porphyrin building blocks 2. The corresponding association
constants were determined by NMR and fluorescence tritration
experiments. They were found to be in the range between
3.7 × 103 and 7.9 × 105 M-1. Interestingly, the association
constants decrease when hexylene instead of propylene spacers
are used.
In response to visible light irradiation, the corresponding 2d‚
1 complexes give rise to a fast charge separation evolving from
the photoexcited ZnP chromophores. Time-resolved fluorescence
and transient absorption measurements were employed to
corroborate this pathway. Most importantly, while the oxidized
zinc porphyrin π-radical cation (ZnP•+) was identified through
its fingerprint absorption in the 550-800 nm range, the signature
of the reduced the fullerene π-radical anion (C60•-) appeared at
1040 nm. In stark contrast, in the analogous SnP complexes
(2a‚1) energy transfer, instead of electron transfer, occurs from
the initially excited SnP excited state to C60. This is due to the
shifted oxidation potential when comparing ZnP and SnP.
Figure 9. Top: Differential absorption spectra (visible and near-infrared)
obtained upon femtosecond flash photolysis (550 nm) of Zn porphyrin 2d/
C60 compound 1e in nitrogen-saturated toluene with several time delays
(i.e., 0 ps, black spectrum, and 500 ps, brown spectrum). Bottom: Time-
absorption profile of the spectra shown above at 620 nm, reflecting the
formation of the radical ion pair state.
The most important and unprecedented finding is that
electronic communication between the porphyrin donor and
fullerene acceptor is even possible through a considerable
number of σ and hydrogen bonds. This is expected to open new
avenues for the inexpensive and efficient construction of new
prototypes of photovoltaic devices.
Experimental Section
General Remarks. Chemicals. C60 was obtained from Hoechst AG/
Aventis and separated from higher fullerenes by a plug filtration.19 All
chemicals were purchased by chemical suppliers and used without
further purification. All analytical reagent-grade solvents were purified
by distillation. Dry solvents were prepared using customary literature
procedures.20 Thin layer chromatography (TLC): Riedel-de Hae¨n silica
gel F254 and Merck silica gel 60 F254. Detection: UV lamp and iodine
chamber. Flash chromatography (FC): Merck silica gel 60 (230-400
mesh, 0.04-0.063 nm). Analytical high-performance liquid chroma-
tography (HPLC): Shimadzu LC-10 liquid chromatograph with Bus
modul CBM-10A, auto injector SIL-10A, two pumps LC-10AT, and
diode array detector. The HPLC-grade solvents were purchased from
Figure 10. Differential absorption spectra (visible and near-infrared)
obtained upon femtosecond flash photolysis (550 nm) of Sn porphyrin 2a/
C60 compound 1e in nitrogen-saturated toluene with several time delays
(i.e., 50 ps, black spectrum, and 3000 ps, brown spectrum), indicating the
formation of fullerene singlet and triplet excited state with transitions at
800 and 740 nm, respectively.
deactivation of the SnP singlet excited state (i.e., to C60)
followed by a rapid intersystem crossing to yield the fullerene
triplet excited state.
(19) (a) Reuther, U. Ph.D. Dissertation, University of Erlangen-Nu¨rnberg,
Germany, 2002. (b) Isaacs, L.; Wehrsig, A.; Diederich, F. HelV. Chim.
Acta 1993, 76, 1231-1250.
(20) Perrin, D. D.; Amarego, W. L. F. Purification of Laboratory Chemicals,
3rd ed.; Pergamon Press: Oxford, U.K., 1988.
(18) Ou, Z.; E, W.; Zhu, W.; Thordarson, P.; Sintic, P. J.; Crossley, M. J.; Kadish,
K. M. Inorg. Chem., published online Nov 10, 2007 http://dx.doi.org/
10.1021/ic7016165.
9
J. AM. CHEM. SOC. VOL. 129, NO. 51, 2007 16065

A R T I C L E S
Wessendorf et al.
SDS or Acros Organics. Analytical column: Nucleosil 5 µm, 200 × 4
mm, Macherey-Nagel, Du¨ren, Germany. Preparative high-performance
liquid chromatography (HPLC): Shimadzu Class LC 10 with Bus
module CBM-10A, auto injector SIL-10A, two pumps LC-8A, UV
detector SPD-10A, and fraction collector FRC-10A. Solvents were
purified by distillation prior to use. UV/vis spectroscopy: Shimadzu
UV-3102 PC UV/vis/NIR scanning spectrophotometer; absorption
maxima λmax given in nm. Mass spectrometry: Micromass Zabspec,
FAB (LSIMS) mode, matrix 3-nitrobenzyl alcohol. NMR spectros-
copy: JEOL JNM EX 400, JEOL JNM GX 400, and Bruker Avance
300. The chemical shifts are given in ppm relative to TMS. The
resonance multiplicities are indicated as s (singlet), d (doublet), t
(triplet), q (quartet), quin (quintet), and m (multiplet); nonresolved and
broad resonances as br. Elemental analysis (C, H, N): succeeded by
combustion and gas chromatographical analysis with an EA 1110 CHNS
analyzer (CE Instruments). Fluorescence spectroscopy: Flouromax3
Jobin Yvon Horiba, Horiba Jobin Yvon GmbH, Mu¨nchen, Germany.
1729, 1710, 2864, 2941. Anal. Calcd for C13H21O6Br (Mr ) 352.25):
C, 44.21; H, 5.99. Found: C, 44.47; H, 6.13.
3-((3,5-Bis(benzyloxy)carbonyl)propyl 6-Bromohexyl Malonate
(4b). A 224 mg (0.635 mmol) amount of 5 was added to a solution of
78 mg (0.635 mmol) of DMAP and 94 mg (0.699 mmol) of 1-HOBT
in 50 mL of dry CH2Cl2. After cooling of the reaction mixture to 0 °C,
180 mg (0.873 mmol) of DCC was added. The reaction mixture was
stirred for 30 min until a white precipitate (DCU) attended. To this
suspension 254 mg (0.794 mmol) of (3,5-bis(benzyloxy)phenyl)-
methanol was added. The suspension was stirred overnight allowing it
to reach room temperature. DCU was filtered off, and the solvent was
removed under reduced pressure. The remainder was dissolved in cool
(-16 °C) EtOAc, and the mixture was then filtered to separate the
raw product and DCU. After distillation of the solvent the remainder
was purified by flash chromatography (500 mL SiO2, 3:1 hexane/
EtOAc). A 294 mg (0.448 mmol, 71%) amount of a colorless high
viscous oil was obtained. 1H NMR (CDCl3, 400 MHz, RT) [δ (ppm)]:
1.33 (m, 2H), 1.43 (m, 2H), 1.62 (m, 2H), 1.82 (m, 2H), 1.98 (m, 2H),
Photophysics. Femtosecond transient absorption studies were per-
formed with 387 nm laser pulses (1 kHz, 150 fs pulse width) from an
amplified Ti:sapphire laser system (Clark-MXR, Inc.). Fluorescence
lifetimes were measured with a laser strope fluorescence lifetime
spectrometer (Photon Technology International) with 337 nm laser
pulses from a nitrogen laser fiber-coupled to a lens-based T-formal
sample compartment equipped with a stroboscopic detector. Details of
the laser strobe systems are described on the manufacture’s web site.
Emission spectra were recorded by using a FluoroMax-3 (Horiba Co.).
The experiments were performed at 20 °C.
3
3
2.44 (t, J ) 7.40 Hz, 2H), 3.34 (s, 2H), 3.37 (t, J ) 7.10 Hz, 2H),
3
3
4.11 (t, J ) 6.87 Hz, 2H), 4.18 (t, J ) 6.32 Hz, 2H), 5.01 (s, 2H),
5.03 (s, 4H), 6.56 (s, 2H), 7.39 (m, 10H). 13C NMR (CDCl3, 100.5
MHz, RT) [δ (ppm)]: 23.84, 24.98, 27.68, 28.26, 30.57, 32.53, 33.68,
41.48, 64.40, 65.34, 66.22, 70.11, 101.71, 107.08, 128.04, 128.44,
128.61, 136.67, 138.08, 160.09, 166.50, 172.43. MS (FAB, NBA): m/z
655, [M]+. FT-IR (diamond, RT) [ν˜ (cm-1)]: 699, 737, 834, 880, 911,
1027, 1058, 1150, 1216, 1266, 1293, 1324, 1378, 1413, 1451, 1498,
1451, 1498, 1729, 2864, 2937.
3-(tert-Butoxycarbonyl)propyl 6-Bromohexyl Malonate (4a). A
solution of 600 mg (2.45 mmol) of 3, 299 mg (2.45 mmol) of DMAP,
and 364 mg (2.7 mmol) of 1-HOBT in 50 mL of dry CH2Cl2 was cooled
to 0 °C using an ice bath. Under inert atmosphere, 695 mg (3.37 mmol)
of DCC was added and the mixture was stirred at 0 °C for 30 min.
Then 551 mg (3.05 mmol) of 6-bromohexane-1-ol was added to the
reaction mixture. After another 1 h of stirring at 0 °C, the mixture was
allowed to reach room temperature. The reaction progress was
controlled using TLC (3:1 hexane/EtOAc). N,N′-Dicyclohexylurea
(DCU) was filtered off after 17 h of stirring, and the solvent was
evaporated. The remainder was dissolved in cooled (-16 °C) EtOAc
and was then filtered to separate the raw product and DCU. After
distillation of the solvent the remainder was purified by flash chroma-
tography (500 mL SiO2, 3:1 hexane/EtOAc). A 754 mg (1.84 mmol,
Newkome First G-(carbonyl)propyl 6-Bromohexyl Malonate (4c).
To a solution of 78 mg (0.637 mmol) of DMAP and 95 mg (0.701
mmol) of 1-HOBT in 50 mL of dry CH2Cl2 was added 225 mg (0.637
mmol) of 5. After the reaction mixture was cooled to 0 °C, 181 mg
(0.876 mmol) of DCC was added and the mixture was stirred for 30
min until a white precipitate (DCU) attended. To this suspension was
added 334 mg (0.796 mmol) of di-tert-butyl 4-(2-tert-butoxycarbonyl)-
ethyl)-4-aminoheptanedioate, and the mixture was stirred overnight
allowing it to reach room temperature. DCU was filtered off, and the
solvent was distilled. After the yellowish remainder was dissolved in
cool (-16 °C) EtOAc and the remaining DCU was separated from the
solution, the solvent was removed in vacuum. The remaining yellow
oil was purified using flash chromatography (400 mL of SiO2, 2:1
hexane/EtOAc). A 268 mg (0.355 mmol, 56%) amount of a colorless
1
1
75%) amount of a yellow, highly viscous oil was obtained. H NMR
high viscous oil was obtained. H NMR (CDCl3, 400 MHz, RT) [δ
[CDCl3, 400 MHz, RT (room temperature)] [δ (ppm)]: 1.37 (m, 2H),
(ppm)]: 1.33 (m, 2H), 1.41 (s, 27H), 1.44 (m, 2H), 1.61 (m, 2H), 1.85
3
3
1.41 (s, 9H), 1.43 (m, 2H), 1.63 (m, 2H), 1.84 (m, 2H), 1.90 (m, 2H),
(m, 2H), 1.94 (m, 8H), 2.17 (t, J ) 7.81 Hz, 2H), 2.19 (t, J ) 7.32
3
3
3
3
2.27 (t, J ) 7.10 Hz, 2H), 3.34 (s, 2H), 3.37 (t, J ) 7.10 Hz, 2H),
4.11 (t, 3J ) 6.60 Hz, 2H), 4.14 (t, 3J ) 6.60 Hz, 2H). 13C NMR (CDCl3,
100.5 MHz, RT) [δ (ppm)]: 23.96, 24.95, 27.65, 28.03, 28.23, 31.74,
32.50, 33.60, 41.48, 64.52, 65.34, 80.48, 166.48, 171.93. MS (FAB,
NBA): m/z 408, [M]+. FT-IR (diamond, RT) [ν˜ (cm-1)]: 753, 845,
1034, 1096, 1146, 1212, 1254, 1328, 1366, 1393, 1459, 1729, 2864,
2937, 2976. Anal. Calcd for C17H29O6Br (Mr ) 408.11): C, 49.88; H,
7.14. Found: C, 49.62; H, 7.29.
Hz, 6H), 3.37 (s, 2H), 4.13 (t, J ) 6.59 Hz, 2H), 4.16 (t, J ) 6.23
Hz, 2H), 6.56 (broad s, 1H). 13C NMR (CDCl3, 100.5 MHz, RT) [δ
(ppm)]: 24.66, 24.99, 27.71, 28.05, 28.27, 29.79, 32.29, 32.54, 33.65,
41.47, 57.45, 64.50, 65.54, 80.63, 166.47, 166.91, 171.21, 172.85. MS
(FAB, NBA): m/z 752, [M]+. FT-IR (diamond, RT) [ν˜ (cm-1)]: 757,
849, 953, 1031, 1104, 1146, 1216, 1254, 1316, 1366, 1393, 1420, 1459,
1536, 1660, 1679, 1725, 2937, 2980.
(R,R)-1,2-Bis((benzyloxy)carbonyl)-2-oxyethylbenzoate 6-Bromo-
hexyl Malonate (4d). After preparation of a solution of 104 mg (0.85
mmol) of DMAP and 126 mg (0.94 mmol) of 1-HOBT in 50 mL of
dry CH2Cl2, 300 mg (0.85 mmol) of 5 was added. After cooling of the
reaction mixture to 0 °C, DCC (241 mg (1.17 mmol)) was added. The
mixture was stirred for 30 min before 462 mg (1.06 mg) of (R,R)-1,2-
bis(benzyloxy)carbonyl)-2-hydroxethyl benzoate was added. The sus-
pension was stirred overnight reaching room temperature. After filtration
the remaining solution was concentrate in vacuum. After the appearance
of DCU, cool (-16 °C) ethyl acetate was given to the suspension to
separate DCU from the main product. Ethyl acetate was removed in
vacuum, and the remainder must be purified by flash chromatography
(400 mL SiO2, 95:5 CH2Cl2/EtOAc). A 580 mg (0.75 mmol, 89%)
4-(2-((6-Bromohexyloxy)carbonyl)acetoyloxy)butanoic Acid (5).
To a solution of 222 mg (0.542 mmol) of 4a in CH2Cl2 was added 4
mL of TFA. This solution was stirred for 2 h. The solvent was distilled,
and the remaining yellow oil was dissolved in CH2Cl2 again. After
removal of the solvent, 5 was obtained as a yellow high viscous oil
1
(190 mg (0.538 mmol, 99%)). H NMR (CDCl3, 400 MHz, RT) [δ
(ppm)]: 1.35 (m, 2H), 1.44 (m, 2H),1.64 (m, 2H),1.83 (m, 2H), 1.97
3
3
(m, 2H), 2.43 (t, J ) 7.42 Hz, 2H), 3.35 (s, 2H), 3.36 (t, J ) 7.10
3
3
Hz, 2H), 4.12 (t, J ) 6.55 Hz, 2H), 4.19 (t, J ) 6.32 Hz, 2H), 9.65
(broad s, 1H). 13C NMR (CDCl3, 100.5 MHz, RT) [δ (ppm)]: 23.62,
24.96, 27.66, 28.24, 30.25, 32.51, 33.65, 41.47, 64.26, 65.46, 166.48,
166.54, 177.97. MS (FAB, NBA): m/z 352, [M]+. FT-IR (diamond,
RT) [ν˜ (cm-1)]: 884, 965,1031, 1096, 1150, 1266, 1332, 1393, 1413,
1
amount of white crystals was obtained. H NMR (CDCl3, 400 MHz,
9
16066 J. AM. CHEM. SOC. VOL. 129, NO. 51, 2007

Electron versus Energy Transfer
A R T I C L E S
RT) [δ (ppm)]: 1.36 (m, 2H), 1.43 (m, 2H), 1.64 (m, 2H), 7.93 (m,
2H), 1.87 (m, 2H), 7.38 (m, 2H), 2.36 (m, 2H), 2.41 (m, 2H), 3.36 (s,
2H), 3.37 (t, 3J ) 6.00 Hz, 2H), 4.12 (t, 3J ) 6.60 Hz, 4H), 5.13 (d, 2J
143.86, 144.61, 144.67, 144.88, 145.10, 145.17, 145.20, 145.26, 163.58,
171.14. MS (FAB, NBA): m/z 1128, [M]+. FT-IR (diamond, RT) [ν˜
(cm-1)]: 760, 799, 956, 1056, 1205, 1231, 1395, 1725, 2850, 2935.
UV/vis (CH2Cl2) [λ (nm)]: 254, 325, 425.5.
2
2
) 11.55 Hz, 4Η), 5.82 (d, J ) 2.20 Hz, 1H), 5.91 (d, J ) 2.10 Hz,
1H), 7.30 (m, 4H), 7.40 (m, 4H), 7.42 (m, 2H), 7.57 (m, 1H). 13C NMR
(CDCl3, 100.5 MHz, RT) [δ (ppm)]: 23.60, 24.97, 27.68, 28.26, 29.87,
32.53, 33.66, 41.45, 64.11, 65.43, 67.62, 70.96, 71.14, 128.39, 128.44,
128.48, 128.62, 130.07, 133.65, 134.46, 134.84, 164.99, 165.49, 166.45,
166.50, 171.32. MS (FAB, NBA): m/z 771, [M]+. FT-IR (diamond,
RT) [ν˜ (cm-1)]: 714, 803, 826, 849, 907, 949, 1027, 1069, 1096, 1131,
1193, 1258, 1332, 1382, 1455, 1602, 1729, 2957.
Monoadduct 6b. C60 (474 mg (0.659 mmol)) was dissolved in 150
mL of toluene under exclusion of light and air during 45 min. Then
137 mg (0.384 mmol) of CBr4 and 240 mg (0.366 mmol) of 4b were
added before 111 mg (109 µL (0.732 mmol)) of DBU, dissolved in
toluene, was added dropwise during 1 h. After 2 h of stirring at room
temperature and under exclusion of air and light, the reaction mixture
was concentrated and then purified by flash chromatography (350 mL
of SiO2, toluene f 9:1 toluene/EtOAc). The obtained red solid was
dissolved in a small amount of CH2Cl2 and then precipitated by adding
n-pentane. After centrifugation, decantation, and drying, 250 mg (0.182
mmol, 48%) of brown solid was obtained. 1H NMR (CDCl3, 400 MHz,
RT) [δ (ppm)]: 1.46 (m, 2H), 1.47 (m, 2H), 1.53 (m, 2H), 1.81 (m,
6-Bromohexyl Methyl Malonate (4e). A solution of 300 mg (1.66
mmol) of 6-bromohexane-1-ol in 35 mL of dry CH2Cl2 was prepared,
and 134 µL (1.66 mmol) of pyridine was added before the reaction
mixture was cooled to 0 °C. During 1.5 h, a solution of 178 µL (1.66
mmol) of methyl malonyl chloride in 20 mL of dry CH2Cl2 was added
dropwise. After stirring of the solution overnight (0 °C f RT), the
organic layer was washed three times with 80 mL of water and dried
over MgSO4. The solvent was distilled in vacuum, and the yellow
remainder was purified using flash chromatography (350 mL of SiO2,
3:1 hexane/EtOAc). A 400 mg (1.42 mmol, 86%) amount of a viscous
3
3
2H), 2.17 (m, 2H), 2.58 (t, J ) 7.42 Hz, 2H), 3.37 (t, J ) 6.87 Hz,
3
3
2H), 4.47 (t, J ) 6.60 Hz, 2H), 4.54 (t, J ) 6.32 Hz, 2H), 5.04 (s,
2H), 5.06 (s, 2H), 6.57 (s, 3H), 7.38 (m, 10H). 13C NMR (CDCl3, 100.5
MHz, RT) [δ (ppm)]: 23.98, 24.98, 25.16, 28.40, 30.55, 32.57, 33.65,
52.17, 66.15, 66.39, 67.24, 70.12, 71.49, 101.74, 107.16, 127.54, 128.06,
128.61, 136.64, 137.97, 138.82, 139.05, 140.93, 140.96, 141.81, 142.16,
142.95, 143.07, 143.83, 143.86, 144.59, 144.67, 144.87, 145.03, 145.08,
145.12, 145.17, 145.21, 145.24, 160.10, 163.52, 172.23. MS (FAB,
NBA): m/z ) 1374 [M]+. FT-IR (diamond, RT) [ν˜ (cm-1)]: 676, 710,
760, 780, 830, 926, 1150, 1204, 1231, 1737. UV/vis (CH2Cl2) [λ (nm)]:
223, 230.5, 258, 326, 426.5.
1
oil was obtained. H NMR (CDCl3, 400 MHz, RT) [δ (ppm)]: 1.36
(m, 2H), 1.45 (m, 2H), 1.65 (m, 2H), 1.84 (m, 2H), 3.36 (s, 2H), 3.39
3
3
(t, J ) 6.71 Hz, 2H), 3.73 (s, 3H), 4.13 (t, J ) 6.59 Hz, 2H). 13C
NMR (CDCl3, 100.5 MHz, RT) [δ (ppm)]: 24.97, 27.68, 28.25, 32.54,
33.63, 41.35, 52.49, 65.40, 166.53, 167.00. MS (FAB, NBA): m/z 281,
[M]+. FT-IR (diamond, RT) [ν˜ (cm-1)]: 687, 730, 849, 1023, 1146,
1200, 1270, 1336, 1390, 1413, 1436, 1733, 2864, 2941.
Monoadduct 6c. During 45 min, 426 mg (0.591 mmol) of C60 was
dissolved in 250 mL of toluene under exclusion of light and air. Then
115 mg (0.245 mmol) of CBr4 and 248 mg (0.329 mmol) of 4c were
added before 100 mg (98 µL (0.658 mmol)) of DBU, dissolved in
toluene, was added dropwise during 2.5 h. After 1.5 h of stirring at
room temperature and under exclusion of light and air, the reaction
mixture was concentrated and purified by flash chromatography (350
mL of SiO2, toluene f 9:1 toluene/EtOAc). The obtained red brown
solid was dissolved in a small amount of CH2Cl2 and then precipitated
using n-pentane. After centrifugation, decantation, and drying, 203 mg
6-Bromohexyl Ethyl Malonate (4f). To a solution of 300 mg (1.66
mmol) of 6-bromohexane-1-ol in 35 mL of dry CH2Cl2 was added 134
µL (1.66 mmol) of pyridine before the reaction mixture was cooled to
0 °C. Then a solution of 235 µL (1.82 mmol) of ethyl malonyl chloride
in 20 mL of dry CH2Cl2 was dropped into the reaction mixture during
1.5 h. The solution was stirred overnight (0 °C f RT), and the organic
layer was washed three times with 100 mL water and dried over MgSO4.
After distillation of the solvent in vacuum, the yellow residue was
purified using flash chromatography (350 mL of SiO2, 3:1 hexane/
EtOAc). A 440 mg (1.49 mmol, 90%) amount of of a viscous oil was
1
(0.138 mmol, 42%) of a brown powder appeared. H NMR (CDCl3,
1
3
obtained. H NMR (CDCl3, 400 MHz, RT) [δ (ppm)]: 1.26 (t, J )
400 MHz, RT) [δ (ppm)]: 1.38 (m, 2H), 1.42 (s, 27H), 1.50 (m, 2H),
7.15 Hz, 3H), 1.37 (m, 2H), 1.45 (m, 2H), 1.65 (m, 2H), 1.84 (m, 2H),
1.57 (m, 2H), 1.86 (m, 2H), 1.95 (m, 2H), 1.97 (m, 6H), 2.21 (t, 3J )
3
3
3
3
3.35 (s, 2H), 3.39 (t, J ) 6.87 Hz, 2H), 4.13 (t, J ) 6.60 Hz, 2H),
7.82 Hz, 2H), 2.29 (t, J ) 7.69 Hz, 6H), 3.40 (t, J ) 6.71 Hz, 2H),
4.18 (q, J ) 7.15 Hz, 2H). 13C NMR (CDCl3, 100.5 MHz, RT) [δ
4.49 (t, J ) 6.47 Hz, 2H), 4.52 (t, J ) 6.34 Hz, 2H), 6.02 (broad s,
1H). 13C NMR (CDCl3, 100.5 MHz, RT) [δ (ppm)]: 24.62, 25.21,
27.70, 28.08, 28.42, 29.84, 30.02, 32.58, 33.70, 52.24, 57.55, 66.57,
67.30, 71.53, 80.73, 138.95, 138.98, 140.96, 140.99, 141.85, 141.87,
142.16, 143.00, 143.02, 143.11, 143.89, 144.65, 144.69, 144.90, 145.12,
145.19, 145.26, 145.28, 163.54, 163.77, 172.84, 170.78. MS (FAB,
NBA): m/z 1465, [M]+. FT-IR (diamond, RT) [ν˜ (cm-1)]: 706, 726,
787, 849, 876, 931, 950, 992, 1011, 1054, 1100, 1150, 1231, 1293,
1366, 1390, 1428, 1455, 1529, 1679, 1702, 1725. UV/vis (CH2Cl2) [λ
(nm)]: 258, 325.5, 425.5.
3
3
3
(ppm)]: 14.07, 24.99, 27.70, 28.28, 32.56, 33.62, 41.65, 61.50, 65.33,
166.57, 166.65. MS (FAB, NBA): m/z 295, [M]+. FT-IR (diamond,
RT) [ν˜ (cm-1)]: 683, 730, 849, 992, 1031, 1146, 1185, 1224, 1266,
1332, 1370, 1390, 1413, 1463, 1729, 2864, 2941.
Monoadduct 6a. Under inert conditions 474 mg (0.659 mmol) of
C60 was dissolved in 200 mL of toluene and the solution was stirred
for 45 min at room temperature and exclusion of light. After C60 had
dissolved, 127 mg (0.384 mmol) of CBr4 and 150 mg (0.366 mmol) of
4a were added. A solution of 113 µL (0.732 mmol) of DBU in toluene
was added dropwise during a period of 1 h. After stirring of the solution
for another 1 h at room temperature and exclusion of light, the reaction
mixture was concentrated and surplus C60 was removed using flash
chromatography (500 mL of SiO2, 100% toluene). 8 was achieved by
flash chromatography (500 mL SiO2, 100% toluene) as bordeaux oil.
The oil was dissolved in a small amount of CH2Cl2 and precipitated
using fresh distilled n-pentane. The brownish crystals (194 mg, 0.172
Monoadduct 6d. C60 (542 mg (0.752 mmol)) was dissolved in 300
mL of toluene during 45 min before 105 mg (0.414 mmol) of I2 and
290 mg (0.376 mmol) of 4d were added under inert atmosphere and
exclusion of light. A solution of DBU [62 µL (0.414 mmol)] in toluene
was added dropwise over a period of 0.5 h. Afterward the reaction
mixture was stirred for 2.5 h. The product was extracted by flash
chromatography (300 mL SiO2, toluene f 95:5 toluene/EtOAc). The
appearing dark red solid was dissolved in a small amount of CH2Cl2
and precipitated with n-pentane. After centrifugation, decantation, and
drying, 270 mg (0.184 mmol, 48%) of black powder appeared. 1H NMR
(CDCl3, 400 MHz, RT) [δ (ppm)]: 1.27 (m, 2H), 1.54 (m, 2H), 1.81
(m, 2H), 2.07 (m, 2H), 2.37 (m, 2H), 2.49 (t, 3J ) 7.14 Hz, 2H), 3.35
1
mmol, 47%) were removed using a centrifuge. H NMR (CDCl3, 400
MHz, RT) [δ (ppm)]: 0.86 (m, 2H), 1.43 (m, 2H), 1.45 (s, 9H), 1.46
(m, 2H), 1.84 (m, 2H), 2.11 (m, 2H), 2.41 (t, 3J ) 7.10 Hz, 2H), 3.40
3
3
3
(t, J ) 7.10 Hz, 2H), 4.49 (t, J ) 6.60 Hz, 2H), 4.51 (t, J ) 6.60
Hz, 2H). 13C NMR (CDCl3, 100.5 MHz, RT) [δ (ppm)]: 24.10, 25.19,
27.69, 28.14, 28.40, 31.68, 33.65, 52.14, 64.52, 66.34, 67.20, 71.50,
80.75, 138.97, 140.96, 141.85, 141.88, 142.18, 142.98, 143.00, 143.06,
3
3
2
(t, J ) 6.60 Hz, 2H), 4.12 (t, J ) 6.32 Hz, 4H), 5.14 (d, J ) 3.42
Hz, 2H), 5.27 (d, 2J ) 3.54 Hz, 2H), 5.86 (d, 2J ) 2.20 Hz, 1H), 5.92
9
J. AM. CHEM. SOC. VOL. 129, NO. 51, 2007 16067

A R T I C L E S
Wessendorf et al.
(d, 2J ) 2.10 Hz, 1H), 7.10 (m, 4H), 7.33 (m, 4H), 7.18 (m, 2H), 7.41
(m, 2H), 7.56 (m,1H), 7.92 (m, 2H). 13C NMR (CDCl3, 100.5 MHz,
RT) [δ (ppm)]: 23.78, 25.15, 27.66, 28.41, 29.88, 32.57, 33.68, 52.14,
65.92, 67.29, 67.80, 67.97, 71.04, 71.14, 71.50, 128.33, 128.38, 128.51,
128.67, 130.05, 133.69, 134.86, 134.84, 138.98, 140.96, 140.99, 141.84,
141.89, 142.19, 143.00, 143.07, 143.27, 143.41, 142.88, 144.06, 144.63,
144.68, 144.90, 145.09, 145.14, 145.20, 145.26, 145.49, 145.85, 146.57,
146.70, 146.98, 163.49, 164.98, 165.11, 165.48, 171.11. MS (FAB,
NBA): m/z 1488, [M]+. FT-IR (diamond, RT) [ν˜ (cm-1)]: 732, 799,
899, 926, 972, 1015, 1054, 1092, 1131, 1204, 1231, 1702, 1733. UV/
vis (CH2Cl2) [λ (nm)]: 217, 228.5, 258.5, 327, 425.5.
RT) [δ (ppm)]: 24.13, 25.45, 26.03, 27.61, 28.15, 28.34, 31.78, 41.74,
52.21, 66.41, 67.24, 71.55, 80.96, 138.98 140.95, 141.86, 141.98,
142.19, 142.98, 143.01, 143.07, 143.86, 144.60, 144.67, 144.88, 145.14,
145.18, 145.26, 147.34, 148.81, 163.57, 172.11. MS (FAB, NBA): m/z
1175, [M]+. FT-IR (diamond, RT) [ν˜ (cm-1)]: 760, 799, 856, 923,
982, 1009, 1143, 1231, 1352, 1388, 1420, 1553, 1688, 1725. UV/vis
(CH2Cl2) [λ (nm)]: 257, 326.5, 425.
Monoadduct 1b. Cyanuric acid (147 mg (1.136 mmol)) was
dissolved in 40 mL of dry DMF under inert atmosphere before 9 µL
(0.057 mmol) of DBU was added. After heating of the solution to 40
°C, 78 mg (0.057 mmol) of 6b was added to the mixture. After being
stirred for 5 h under inert atmosphere and exclusion of light, the mixture
was quenched by adding 100 mL of H2O and the product was extracted
with 100 mL of CH2Cl2. The organic layer was washed three times
with 100 mL of H2O, dried over MgSO4, and purified by flash
chromatography (250 mL of SiO2, 1:1 CH2Cl2/EtOAc). The obtained
red brown solid was dissolved in a small amount of CH2Cl2 and
precipitated by adding n-pentane. After centrifugation, decantation, and
drying, 15 mg (0.011 mmol, 19%) of a brown powder could be isolated.
1H NMR (CDCl3, 400 MHz, RT) [δ (ppm)]: 1.39 (m, 2H), 1.48 (m,
2H), 1.55 (m, 2H), 1.81 (m, 2H), 2.17 (m, 2H), 2.56 (t, 3J ) 7.15 Hz,
2H), 3.80 (t, 3J ) 7.42 Hz, 2H), 4.46 (t, 3J ) 6.60 Hz, 2H), 4.54 (t, 3J
) 6.32 Hz, 2H), 5.00 (s, 2H), 5.06 (s, 4H), 6.57 (s, 1H), 6.58 (s, 2H),
7.38 ((m(, 10H), 8.16 (s, 2H). 13C NMR (CDCl3, 100.5 MHz, RT) [δ
(ppm)]: 23.96, 25.43, 26.01, 28.32, 30.61, 34.85, 41.74, 52.16, 66.21,
66.44, 67.24, 70.25, 71.50, 101.74, 107.19, 127.56, 128.06, 128.61,
136.64, 137.99, 136.64, 137.99, 138.79, 139.10, 140.93, 141.83, 142.16,
142.96, 143.85, 144.61, 144.88, 145.04, 145.12, 145.17, 145.23, 146.67,
148.49, 160.07, 163.57, 165.58, 172.52. MS (FAB, NBA): m/z 1422,
[M]+. FT-IR (diamond, RT) [ν˜ (cm-1)]: 672, 688, 733, 795, 834, 880,
907, 942, 961, 1004, 1054, 1089, 1146, 1173, 1208, 1227, 1320, 1347,
1386, 1428, 1455, 1540, 1559, 1602, 1702, 1725, 1961, 1980, 2007,
2034, 2081, 2131, 2169, 2189, 2243, 2277, 2853, 2922, 2941. UV/vis
(CH2Cl2) [λ (nm)]: 220.5, 232, 255, 328.5, 425.
Monoadduct 6e. A solution of 1.024 g (1.423 mmol) of C60 in 350
mL of toluene was prepared under inert atmosphere and exclusion of
light. I2 (199 mg (0.782 mmol)) and 4e (200 mg (0.711 mmol)) were
added to the solution before 138 µL (0.924 mmol) of DBU in toluene
was carefully dropped into the solution during 2.5 h. After stirring of
the solution for 2 h, the product was isolated using flash chromatography
(350 mL of SiO2, 2:1 toluene/hexane). The appeared dark brown solid
was dissolved in a minimal amount of CH2Cl2 and precipitated with
n-pentane. After centrifugation, decantation, and drying, 413 mg (0.413
1
mmol, 58%) of a brown powder was isolated. H NMR (CDCl3, 400
MHz, RT) [δ (ppm)]: 1.50 (m, 2H), 1.51 (m, 2H), 1.53 (m, 2H), 1.85
3
3
(m, 2H), 3.40 (t, J ) 6.71 Hz, 2H), 4.08 (s, 3H), 4.49 (t, J ) 6.47
Hz, 2H). 13C NMR (CDCl3, 100.5 MHz, RT) [δ (ppm)]: 25.18, 27.69,
28.39, 32.59, 33.65, 52.08, 54.02, 67.19, 71.48, 138.86, 139.12, 140.96,
141.87, 141.92, 142.19, 142.97, 143.01, 143.09, 143.88, 144.63, 144.69,
144.89, 145.08, 145.11, 145.14, 145.19, 145.27, 163.59, 164.11. MS
(FAB, NBA): m/z 998, [M]+. FT-IR (diamond, RT) [ν˜ (cm-1)]: 703,
726, 795, 876, 930, 1000, 1038, 1058, 1112, 1185, 1208, 1231, 1428,
1640, 1671, 1698, 1741. UV/vis (CH2Cl2) [λ (nm)]: 255, 326.5,
425.5.
Monoadduct 6f. After preparation of a solution of 1.073 g (1.49
mmol) of C60 in 300 mL of toluene, 208 mg (0.82 mmol) of I2 and 220
mg (0.745 mmol) of 4f were added under inert atmosphere and
exclusion of light. DBU (144 µL (0.97 mmol) in toluene was carefully
dropped to the solution during 2 h. After stirring of the solution for
another 2 h, the product was extracted using flash chromatography (350
mL of SiO2, 2:1 toluene/hexane). The occurring brown solid was
dissolved in a tiny amount of CH2Cl2 and precipitated with n-pentane.
After centrifugation, decantation, and drying, 290 mg (0.286 mmol,
38%) of a brown powder could be isolated. 1H NMR (CDCl3, 400 MHz,
Monoadduct 1c. Cyanuric acid (145 mg (1.12 mmol)) was dissolved
in 35 mL of dry DMF before 8.5 µL (0.056 mmol) of DBU was added
under inertatmosphere. After heating of the solution to 40 °C, 83 mg
(0.056 mmol) of 6c was added. The reaction mixture was stirred for 6
h under inert atmosphere and exclusion of light. The reaction temper-
ature was 40 °C. When no change in progress was noticed, the reaction
mixture was quenched by 100 mL of H2O and the organic compounds
were extracted with 100 mL of CH2Cl2. After washing of the organic
layer three times with 100 mL of H2O, it was dried over MgSO4. The
product could by isolated by flash chromatography (120 mL of SiO2,
2:1 CH2Cl2/EtOAc). The occurring dark red solid was dissolved in a
minimum amount of CH2Cl2 and precipitated by adding n-pentane. After
centrifugation, decantation, and drying, 12 mg (0.008 mmol, 14%) of
a brown powder appeared. 1H NMR (CDCl3, 400 MHz, RT) [δ (ppm)]:
1.38 (m, 2H), 1.41 (s, 27H), 1.50 (m, 2H), 1.54 (m, 2H), 1.65 (m,
3
RT) [δ (ppm)]: 1.47 (t, J ) 6.97 Hz, 3H), 1.49 (m, 2H), 1.50 (m,
3
2H), 1.53 (m, 2H), 1.85 (m, 2H), 3.40 (t, J ) 6.60 Hz, 2H), 4.54 (t,
3J ) 7.15 Hz, 2H), 4.56 (q, 3J ) 7.15 Hz, 2H). 13C NMR (CDCl3, 400
MHz, RT) [δ (ppm)]: 14.30, 25.21, 27.73, 28.43, 32.60, 33.63, 52.26,
63.45, 67.15, 71.60, 138.90, 139.10, 140.96, 141.91, 142.21, 143.01,
143.09, 143.88, 144.62, 144.68, 144.88, 145.14, 145.18, 145.26, 143.35,
163.57, 163.67. MS (FAB, NBA): m/z 1014, [M]+. FT-IR (diamond,
RT) [ν˜ (cm-1)]: 695, 791, 938, 1004, 1058, 1112, 1177, 1231, 1266,
1428, 1737. UV/vis (CH2Cl2) [λ (nm)]: 256, 327, 426.
3
2H), 1. 99 (m, 2H), 2.19 (m, 6H), 2.21 (t, J ) 7.32 Hz, 2H), 2.33 (t,
Monoadduct 1a. Cyanuric acid (183 mg (1.42 mmol)) was dissolved
in 25 mL of dry DMF before 11 µL (0.071 mmol) of DBU was added
and the reaction mixture was heated to 40 °C. Under inert atmosphere
and exclusion of light, 80 mg (0.071 mmol) of 6a was added. The
solution was stirred for 6 h under these conditions before 100 mL of
H2O was added and the organic compounds were extracted with CH2-
Cl2. After washing of the organic layer three times with 100 mL of
H2O and drying over MgSO4, the product could be isolated by flash
chromatography (250 mL of SiO2, 1:1 CH2Cl2/EtOAc). The appearing
dark solid was dissolved in a minimum amount of CH2Cl2 and
precipitated by adding n-pentane. After centrifugation, decantation, and
3
3
3J ) 7.08 Hz, 6H), 3.85 (t, J ) 7.32 Hz, 2H), 4.49 (t, J ) 6.00 Hz,
3
2H), 4.50 (t, J ) 6.47 Hz, 2H), 6.18 (broad s, 1H), 9.16 (broad s,
2H). 13C NMR (CDCl3, 100.5 MHz, RT) [δ (ppm)]: 24.73, 25.98,
27.58, 28.08, 28.32, 29.90, 30.08, 33.27, 41.57, 52.12, 57.60, 66.71,
67.13, 71.54, 80.98, 138.78, 139.29, 140.93, 140.96, 141.86, 141.92,
142.19, 143.01, 143.07, 143.88, 144.62, 144.67, 144.88, 145.07, 145.11,
145.17, 145.26, 147.37, 149.13, 163.58, 163.66, 171.34, 173.19. MS
(FAB, NBA): m/z 1518, [M]+. FT-IR (diamond, RT) [ν˜ (cm-1)]: 705,
751, 746, 845, 961, 1031, 1069, 1116, 1154, 1189, 1258, 1285, 1305,
1390, 1463, 1536, 1613, 1687, 1729, 1768. UV/vis (CH2Cl2) [λ (nm)]:
254.5, 326.5, 426.
1
drying, 15 mg (0.013 mmol, 18%) of a brown powder appeared. H
Monoadduct 1d. Cyanuric acid (121 mg (0.94 mmol)) was dissolved
in 40 mL of dry DMF before 7.2 mg (0.047 mmol) of DBU was added,
and the reaction mixture was heated to 40 °C. Under inert atmosphere
and exclusion of light, 70 mg (0.046 mmol) of 6d was added. The
NMR (CDCl3, 400 MHz, RT) [δ (ppm)]: 1.42 (m, 2H), 1.43 (m, 2H),
3
1.45 (s, 9H), 1.63 (m, 2H), 1.84 (m, 2H), 2.11 (m, 2H), 2.41 (t, J )
3
3
7.42 Hz, 2H), 3.83 (t, J ) 7.42 Hz, 2H), 4.49 (t, J ) 6.60 Hz, 2H),
4.51 (t, 3J ) 6.60 Hz, 2H), 8.79 (s, 2H). 13C NMR (CDCl3, 100.5 MHz,
9
16068 J. AM. CHEM. SOC. VOL. 129, NO. 51, 2007

Electron versus Energy Transfer
A R T I C L E S
solution was stirred for 4.5 h under the same conditions and was
quenched by adding 100 mL of H2O afterward. To extract the organic
compounds, 100 mL of CH2Cl2 was added. The organic layer was
washed three times with 100 mL of H2O and dried over MgSO4. The
product could be isolated by flash chromatography (150 mL SiO2, 3:1
CH2Cl2/EtoAC). The occurring dark red solid was dissolved in a small
amount of CH2Cl2 and precipitated with n-pentane. After centrifugation,
decantation, and drying, 10 mg (0.007 mmol, 14%) of a dark brown
142.98, 143.78, 144.03, 144.51, 144.59, 144.78, 145.08, 145.12, 145.15,
145.21, 145.31, 147.84, 149.42, 163.46, 163.55. MS (FAB, NBA): m/z
1062, [M]+. FT-IR (diamond, RT) [ν˜ (cm-1)]: 772, 791, 861, 926,
969, 1011, 1061, 1116, 1189, 1235, 1270, 1289, 1386, 1432, 1467,
1741. UV/vis (CH2Cl2/THF) [λ (nm)]: 254, 327, 426.
5-(p-Carboxymethyphenyl)-10,15,20-(p-tert-butyltriphenyl)por-
phyrin (8). A solution of 6.8 mL of pyrrole (0.10 mol), 12.6 mL of
4-tert-butylbenzaldehyde (0.075 mol), 4.10 g of methyl 4-formylben-
zoate (0.025 mol), 20 mL of ethanol, and 100 mg of tetraphenylphos-
phonium chloride in 2.5 L of dichloromethane was stirred for 30 min.
Then 6.3 mL of boron trifluoride etherate (0.049 mol) was added
changing the color of the solution to purple red. The mixture was stirred
for at least 35 min and no longer than 40 min. Next, 16.69 g of 2,3-
dichloro-5,6-dicyano-1,4-benzoquinone (0.075 mol) was added under
atmospheric conditions. The reaction mixture was stirred for 15 h. The
solvent was removed under evaporation and filtered over silica in
dichloromethane. The residue was purified with column chromatography
with dichloromethane as eluent. The product was obtained by crystal-
1
powder appeared. H NMR (CDCl3, 400 MHz, RT) [δ (ppm)]: 1.23
(m, 2H), 1.58 (m, 2H), 1.82 (m, 2H), 2.19 (m, 2H), 2.35 (m, 2H), 2.48
3
3
3
(t, J ) 6.84 Hz, 2H), 3.80 (t, J ) 7.69 Hz, 2H), 4.47 (t, J ) 6.23
Hz, 2H), 4.48 (t, 3J ) 6.47 Hz, 2H), 5.16 (d, 2J ) 8.18 Hz, 4Η), 5.87
(d, 2J ) 2.90 Hz, 1H), 5.93 (d, 2J ) 2.80 Hz, 1H), 7.08 (m, 4H), 7.17
(m, 2H), 7.34 (m, 4H), 7.40 (m, 2H), 7.56 (m, 1H), 7.91 (m, 2H), 8.35
(s, 2H). 13C NMR (CDCl3, 100.5 MHz, RT) [δ (ppm)]: 23.65, 24.16,
26.03, 27.59, 29.88, 33.68, 41.72, 52.14, 66.95, 67.88, 67.98, 68.07,
71.15, 71.52, 71.60, 128.33, 128.37, 128.49, 128.67, 130.07, 133.71,
134.41, 134.82, 138.90, 138.99, 139.10, 140.95, 141.89, 142.19, 142.54,
142.98, 143.01, 143.88, 144.62, 144.68, 144.90, 145.09, 145.18, 145.26,
146.40, 146.79, 148.55, 150.06, 164.99, 164.63, 165.11, 165.66, 171.27.
MS (FAB, NBA): m/z 1536, [M]+. FT-IR (diamond, RT) [ν˜ (cm-1)]:
710, 741, 869, 907, 965, 1004, 1027, 1069, 1116, 1189, 1270, 1332,
1382, 1436, 1498, 1602, 1691, 1745. UV/vis (CH2Cl2) [λ (nm)]: 256.5,
324, 426.5.
1
lization in pentane (2.5 g, 12%). H NMR (CDCl3, 400 MHz, RT) [δ
(ppm)]: -2.59 (s, 2H), 1.66 (s, 18H), 1.67 (s, 9H), 4.16 (s, 3H), 7.79
(d, 3J ) 8.3 Hz, 4H), 7.80 (d, 3J ) 8.3 Hz, 2H), 8.20 (d, 3J ) 8.3 Hz,
3
3
3
4H), 8.22 (d, J ) 8.3 Hz, 2H), 8.41 (d, J ) 8.3 Hz, 2H), 8.51 (d, J
3
3
) 8.3 Hz, 2H), 8.88 (d, J ) 4.9 Hz, 2H), 8.98 (s, 4H), 9.01 (d, J )
4.9 Hz, 2H). 13C NMR (CDCl3, 100.5 MHz, RT) [δ (ppm)]: 31.61,
34.81, 52.33, 118.24, 120.56, 120.84, 123.67, 127.94, 129.52, 131.14,
134.52, 134.72, 139.14, 139.21, 147.35, 150.63, 167.48. FT-IR
(diamond, RT) [ν˜ (cm-1)]: 710, 733, 799, 965, 1108, 1189, 1220, 1270,
1351, 1397, 1475, 1606, 1725, 2868, 2903, 2957, 3316. UV/vis (CH2-
Cl2) [λmax, nm (log ꢀ)]: 418 (5.69), 516 (4.67), 553 (4.43), 592 (4.19),
647 nm (4.15). Anal. Calcd for C58H56N4O2‚H2O (Mr ) 859.11): C,
81.09; H, 6.80; N, 6.52. Found: C, 81.49; H, 6.88; N, 6.36.
Monoadduct 1e. Cyanuric acid (336 mg (2.6 mmol)) was dissolved
in 40 mL of dry DMF before 20 mg (0.13 mmol) of DBU was added,
and the solution was heated to 40 °C. Under inert atmosphere and
exclusion of light, 130 mg (0.13 mmol) of 6e was added. To increase
the solubility, 5 mL of dry CH2Cl2 was added. The reaction mixture
was stirred for 5 h under these conditions. Then 100 mL of H2O was
added and the organic compounds were extracted with 100 mL of CH2-
Cl2. The organic layer was washed three times with 100 mL of H2O
and dried over MgSO4. The product could be isolated by flash
chromatography (100 mL of SiO2, CH2Cl2). The appearing black solid
was dissolved in a small amount of CH2Cl2/THF and precipitated by
adding n-pentane. After centrifugation, decantation, and drying, 14 mg
[5-(p-Carboxymethyphenyl)-10,15,20-(p-tert-butyltriphenyl)por-
phyrinato]tin(IV) (9a). To a solution of 1 g of 8 (1.1 mmol) in 500
mL of acetic acid was added 2.6 g of SnCl2 (10 mmol), and the mixture
was heated to reflux over a period of 15 h. The complete insertion of
the tin was observed with TLC. The reaction was nearly quantitative.
The solvent was removed on a rotary evaporator. The residue was
purified with column chromatography with a mixture of dichlo-
romethane/ethyl acetate (4:1) as eluent. The solution was concentrated
on a rotary evaporator and washed three times with 10% hydrochloric
acid to obtain the dichloro complex. The product was obtained by
1
(0.013 mmol, 10%) of a brown powder attended. H NMR (CDCl3/
THF-d8, 400 MHz, RT) [δ (ppm)]: 1.37 (m, 2H), 1.47 (m, 2H), 1.62
3
(m, 2H), 1.82 (m, 2H), 3.79 (t, J ) 7.42 Hz, 2H), 4.04 (s, 3H), 4.45
(t, 3J ) 6.32 Hz, 2H), 9.95 (s, 2H). 13C NMR (CDCl3/THFd8, 400 MHz,
RT) [δ (ppm)]: 26.18, 27.71, 28.34, 30.73, 41.36, 52.06, 53.93, 67.27,
71.46, 138.82, 139.04, 140.89, 141.80, 141.84, 142.12, 142.92, 142.98,
143.80, 144.53, 144.61, 144.80, 145.03, 145.11, 145.18, 145.24, 147.89,
149.39, 163.47, 164.01. MS (FAB, NBA): m/z 1048, [M]+. FT-IR
(diamond, RT) [ν˜ (cm-1)]: 710, 737, 764, 795, 857, 938, 907, 999,
1061, 1116, 1185, 1235, 1266, 1397, 1428, 1463, 1559, 1594, 1687,
1741. UV/vis (CH2Cl2/THF) [λ (nm)]: 251.5, 325.5, 426.
1
crystallization in pentane (1.1 g, 98%). H NMR (CDCl3, 400 MHz,
RT) [δ (ppm)]: 1.67 (s, 27H), 4.16 (s, 3H), 7.86 (d, 3J ) 8,3 Hz, 4H),
8.28 (d, 3J ) 8.3 Hz, 4H), 8.46 (d, 3J ) 8.3 Hz, 2H), 8.55 (d, 3J ) 8.3
Hz, 2H), 9.16 (d, 3J ) 4.9 Hz, 2H), 9.28 (s, 4H), 9.31 (d, 3J ) 4.9 Hz,
2H). 13C NMR (CDCl3, 100.5 MHz, RT) [δ (ppm)]: 31.60, 34.97,
52.49, 119.24, 121.67, 121.93, 124.10, 128.30, 130.39, 131.92, 132.87,
132.96, 133.21, 134.89, 134.98, 137.58, 145.51, 145.69, 146.52, 146.61,
146.77, 151.63, 167.23. FT-IR (diamond, RT) [ν˜ (cm-1)]: 741, 764,
799, 1073, 1011, 1108, 1208, 1239, 1274, 1363, 1397, 1463, 1610,
1725, 2926, 2957. UV/vis (CH2Cl2) [λmax, nm (log ꢀ)]: 323 (4.37),
408 (4.65), 429 (5.66), 562 (4.34), 604 nm (4.31). Anal. Calcd for
C58H54Cl2N4O2Sn‚H2O‚CH2Cl2‚CH3COOH (Mr ) 1193.83): C, 61.37;
H, 6.75; N, 4.69. Found: C, 61.30; H, 6.46; N, 4.42.
Monoadduct 1f. To a solution of 271 mg (2.1 mmol) of cyanuric
acid in 40 mL of dry DMF was added 16 mg (0.105 mmol) of DBU.
After heating the solution to 40 °C, 106 mg (0.105 mmol) of 6f was
added under inert atmosphere and exclusion of light. To increase the
solubility, 5 mL of dry CH2Cl2 was added. After the solution was stirred
for 6 h under these conditions, 100 mL of H2O was added and the
organic compounds were extracted with 100 mL of CH2Cl2. The organic
layer was washed three times with 100 mL of H2O and dried over
MgSO4. The product could be isolated by flash chromatography (100
mL of SiO2, CH2Cl2). The occurring dark brown solid was dissolved
in a small amount of CH2Cl2/THF and precipitated by adding n-pentane.
After centrifugation, decantation, and drying, 11 mg (0.01 mmol, 10%)
of a brown powder appeared. 1H NMR (CDCl3/THF-d8, 400 MHz, RT)
{(5-Amido-N,N′-bis[6-(3,3-dimethylbutyrylamino)pyridin-2-yl]-
isophthalamidophenyl)-10,15,20-(p-tert-butyltriphenyl)porphyrinato}-
tin(IV) (2a). To a solution of 1 g of 9a (0.97 mmol) in 300 mL of
ethanol was added an excess of sodium hydroxide, and the mixture
was heated to reflux over a period of 8 h to get the free carboxylic
acid 9b. The completion of the reaction was monitored via TLC. The
solvent was removed on a rotary evaporator, and the residue was
dissolved in dichloromethane. The solution was washed three times
with citric acid to protonate the carboxylic acid. The organic phase
was dried with MgSO4 and the solvent was removed on a rotary
evaporator. The deprotection of the methyl ester is quantitative. The
3
[δ (ppm)]: 1.24 (m, 2H), 1.37 (m, 2H), 1.43 (t, J ) 7.08 Hz, 3H),
3
3
1.61 (m, 2H), 2.04 (m, 2H), 3.76 (t, J ) 7.57 Hz, 2H), 4.43 (t, J )
7.20 Hz, 2H), 4.51 (t, J ) 7.00 Hz, 2H), 10.02 (s,2H). 13C NMR
3
(CDCl3/THF-d8, 100.5 MHz, RT) [δ (ppm)]: 14.17, 25.51, 26.21, 27.70,
28.37, 41.33, 52.21, 63.35, 67.62, 71.55, 140.84, 141.81, 142.12, 142.91,
9
J. AM. CHEM. SOC. VOL. 129, NO. 51, 2007 16069

A R T I C L E S
Wessendorf et al.
deprotected tin porphyrin was dissolved in 200 mL of dichloromethane
at 0 °C. A 560 mg amount of EDC (2.91 mmol), 400 mg of HOBT
(2.91 mmol), and 355 mg of DMAP (2.91 mmol) were added, and the
solution was stirred for 1 h at 0 °C. After that period, 600 mg of
5-amino-N,N′-bis[6-(3,3-dimethylbutyrylamino)pyridine-2-yl]isoph-
thalamide (7) (1.1 mmol) was added to the solution and the mixture
was stirred at RT for 48 h. The solvent was removed on a rotary
evaporator, and the residue was purified by column chromatography
on silica gel with a mixture of dichloromethane/ethyl acetate (3:1) as
eluent. The product was obtained by crystallization in pentane. The
yield was 300 mg (18%). 1H NMR (THF-d8, 400 MHz, RT) [δ (ppm)]:
1.09 (s, 18H), 1.66 (s, 27H), 2.26 (s, 4H), 3.41 (d, 3J ) 8.3 Hz, 2H),
The product was obtained by crystallization in pentane. The yield was
460 mg (30%). 1H NMR (CDCl3, 400 MHz, RT) [δ (ppm)]: -2.69 (s,
2H), 1.18 (s, 18H), 1.57 (s, 18H), 1.62 (s, 9H), 2.45 (s, 4H), 5.01 (s,
3
3
3
2H), 7.37 (d, J ) 8.5 Hz, 2H), 7.67 (d, J ) 8.5 Hz, 2H), 7.74 (d, J
3
3
) 8.5 Hz, 2H), 8.00 (t, J ) 8.0 Hz, 2H), 8.08 (d, J ) 8.5 Hz, 2H),
8.14 (d, 3J ) 7.3 Hz, 2H), 8.20 (d, 3J ) 7.3 Hz, 2H), 8.65 (s, 1H), 8.68
(s, 2H), 8.82 (d, J ) 4.6 Hz), 8.90 (m, 10H), 9.39 (s, 1H). 13C NMR
3
(CDCl3, 100.5 MHz, RT) [δ (ppm)]: 29.78, 31.40, 31.54, 31.58, 34.73,
34.78, 50.95, 68.43, 109.64, 110.70, 113.15, 118.58, 119.73, 120.34,
120.47, 122.31, 123.57, 131.37, 134.47, 135.47, 135.97, 138.24, 139.09,
139.16, 149.06, 150.30, 150.50, 156.54, 163.77, 167.91, 171.68. FT-
IR (diamond, RT) [ν˜ (cm-1)]: 729, 799, 965, 984, 1235, 1297, 1444,
1505, 1586, 1675, 2868, 2926, 2957, 3312. UV/vis (CH2Cl2) [λmax, nm
(log ꢀ)]: 301 (4.32), 400 (4.52), 419 (5.30), 517 (3.90), 553 (3.68),
593 (3.42), 648 (3.48). Anal. Calcd for C88H91N11O6‚ethyl acetate (Mr
) 1486.84): C, 74.32; H, 6.71; N, 10.36. Found: C, 74.04; H, 7.08;
N, 10.03.
3
3
3
6.39 (dd, J ) 8.0 Hz, 2H), 6.65 (dd, J ) 8.0 Hz, 2H), 7.04 (d, J )
3
3
8.3 Hz, 2H), 7.78 (dd, J ) 8.0 Hz, 2H), 7.91 (d, J ) 8.3 Hz, 6H),
3
3
8.08 (d, J ) 8.0 Hz, 2H), 8.13 (m, 8H), 8.28 (d, J ) 8.3 Hz, 2H),
8.33 (s, 1H), 8.46 (d, 3J ) 8.3 Hz, 2H), 8.86 (s, 2H), 9.07 (d, 3J ) 4.9
Hz, 2H), 9.16 (m, 6H), 9.21 (s, 2H), 9.63 (s, 2H), 10.29 (s, 1H). 13C
NMR (THF-d8, 100.5 MHz, RT) [δ (ppm)]: 29.98, 31.61, 31.83, 35.54,
50.66, 107.17, 110.00, 110.34, 118.67, 121.34, 122.30, 123.21, 123.28,
123.44, 124.28, 124.84, 124.91, 127.08, 133.23, 133.99, 134.04, 134.29,
135.60, 135.80, 136.87, 138.60, 140.67, 141.41, 144.95, 147.95, 148.47,
148.63, 151.33, 151.87, 152.32, 165.49, 166.69, 171.01. FT-IR
(diamond, RT) [ν˜ (cm-1)]: 741, 799, 1011, 1031, 1108, 1239, 1393,
1447, 1513, 1586, 1679, 2868, 2907, 2957, 3312. UV/vis (CH2Cl2)
[λmax, nm (log ꢀ)]: 305 (4.33), 406 (4.34), 427 (5.43), 560 (4.01), 601
(3.92). Anal. Calcd for C99H95N17O7Sn‚2CDCl3 (Mr ) 1994.4): C,
60.82; H, 5.00; N, 11.75. Found: C, 60.36; H, 5.19; N, 11.64.
[5-(3,5-Bis[6-(3,3-dimethylbutyrylamino)pyridin-2-yl]isophthala-
mideamidoacetatophenoxy)-10,15,20-(p-tert-butyltriphenyl)porphy-
rinato]tin(IV) (2c). A 200 mg amount of 2b (0.15 mmol) was dissolved
in 100 mL of acetic acid. A 500 mg amount of SnCl2 (1.8 mmol) was
added to this solution, and the mixture was heated to reflux over a
period of 15 h. The complete insertion of the tin was observed with
TLC. The reaction was nearly quantitive. The solvent was removed on
a rotary evaporator. The residue was purified with column chroma-
tography with a mixture of dichloromethane/methanol (9:1) as eluent.
The solution was concentrated on a rotary evaporator, and the product
was obtained by crystallization in pentane. The yield was 231 mg (97%).
1H NMR (THF-d8, 400 MHz, RT) [δ (ppm)]: 1.08 (s, 18H), 1.63 (s,
27H), 2.25 (s, 4H), 4.62 (s, 2H), 7.39 (d, 3J ) 8.5 Hz, 2H), 7.75 (t, 3J
5-(p-tert-Butylacetatophenoxy)-10,15,20-(p-tert-butyltriphenyl)-
porphyrin (10). A solution of 6.8 mL of pyrrole (0.10 mol), 12.56
mL of 4-tert-butylbenzaldehyde (0.075 mol), 5.90 g of tert-butyl 2-(4-
formyl-phenoxy)acetate (0.025 mol), 20 mL of ethanol, and 100 mg
of tetraphenylphosphonium chloride in 2.5 L of dichloromethane was
stirred for 30 min. Then 6.3 mL of boron trifluoride etherate (0.049
mol) was added changing the color of the solution to purple red. The
mixture was stirred for at least 35 min and no longer than 40 min.
Then 16.69 g of 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (0.075 mol)
was added under open air conditions. The reaction mixture was stirred
for 15 h. The solvent was removed under evaporation and filtered over
silica in dichloromethane. The residue was purified with column
chromatography with dichloromethane as eluent. The product was
obtained by crystallization in pentane. The yield was 2.7 g (11.8%).
1H NMR (CDCl3 ,400 MHz, RT) [δ (ppm)]: -2.65 (s, 2H), 1.66 (m,
3
3
) 8.0 Hz, 2H), 7.89 (d, J ) 8.3 Hz, 6H), 8.03 (d, J ) 7.8 Hz, 2H),
8.08 (d, 3J ) 7.8 Hz, 2H), 8.22 (d, 3J ) 8.3 Hz, 6H), 8.25 (d, 3J ) 8.5
Hz, 2H), 8.41 (s, 1H), 9.12 (m, 10H), 9.37 (s, 2H), 9.50 (s, 2H), 9.67
(s, 1H). 13C NMR (THF-d8, 100.5 MHz, RT) [δ (ppm)]: 30.00, 31.63,
31.87, 35.83, 50.67, 68.15, 109.98, 110.34, 111.89, 122.20, 122.31,
122.49, 124.66, 131.62, 133.03, 135.55, 136.54, 136.80, 139.31, 140.67,
147.78, 151.37, 151.96, 152.18, 154.07, 159.41, 165.37, 167.98, 171.00.
FT-IR (diamond, RT) [ν˜ (cm-1)]: 718, 799, 1011, 1031, 1235, 1297,
1363, 1397, 1447, 1505, 1586, 2864, 2961. UV/vis (CH2Cl2) [λmax, nm
(log ꢀ)]: 305 (4.25), 406 (4.19), 427 (5.33), 560 (3.91), 601 nm (3.83).
[5-(3,5-Bis[6-(3,3-dimethylbutyrylamino)pyridin-2-yl]isophthala-
mideamidoacetatophenoxy)-10,15,20-(p-tert-butyl-triphenyl)porphy-
rinato]zinc (2d). A 400 mg amount of 2b (0.29 mmol) was dissolved
in THF, and 160 mg of zinc acetate (0.86 mmol) was added. The
mixture was heated to reflux over a period of 4 h. The metal insertion
was nearly quantitative. The solvent was removed on a rotary
evaporator, and the residue was purified with column chromatography
on silica gel with a mixture of dichloromethane/ethyl acetate (3:1) as
eluent. Final crystallization in pentane gave a purple red solid in good
3
3
36H), 4.86 (s, 2H), 7.33 (d, J ) 8.3 Hz), 7.79 (d, J ) 8.1 Hz), 8.20
(m, 8H), 8.94 (m, 8H). 13C NMR (CDCl3,100.5 MHz, RT) [δ (ppm)]:
28.11, 31.63, 34.83, 66.02, 82.56, 112.92, 119.42, 120.25, 123.64,
131.04, 134.54, 134.58, 135.64, 135.68, 139.28, 150.53, 157.68, 168.3.
FT-IR (diamond, RT) [ν˜ (cm-1)]: 729, 799, 965, 1235, 1297, 1444,
1505, 1586, 1675, 2868, 2926, 2957, 3312. UV/vis (CH2Cl2) [λmax, nm
(log ꢀ)]: 418 (5.69), 516 (4.22), 552 (3.99), 591 (3.59), 648 (3.69).
Anal. Calcd for C62H64N4O3‚CH2Cl2 (Mr ) 998.13): C, 75.81; H, 6.66;
N, 5.61. Found: C, 75.63; H, 6.64; N, 5.47.
1
yield (410 mg, 98%). H NMR (THF-d8, 400 MHz, RT) [δ (ppm)]:
5-(3,5-Bis[6-(3,3-dimethylbutyrylamino)pyridin-2-yl]isophthala-
mideamidoacetatophenoxy)-10,15,20-(p-tert-butyltriphenyl)porphy-
rin (2b). A solution of 1 g of 10 (1.1 mmol) and 200 mL of formic
acid was stirred for 4 h to obtain the deprotected acid 11. The completed
reaction was observed via TLC. After that period the solvent was
removed on a rotary evaporator and the product was dried on an oil
pump. The dried product was dissolved in dichloromethane at 0 °C. A
210 mg amount of EDC (1.1 mmol), 150 mg of HOBT (1.1 mmol),
and 135 mg of DMAP (1.1 mmol) were added, and the solution was
stirred for 1 h at 0 °C. After that period, 600 mg of 5-amino-N,N′-bis-
[6-(3,3-dimethylbutyrylamino)pyridin-2-yl]isophthalamide (7) (1.1 mmol)
was added to the solution and the mixture was stirred at room
temperature for 48 h. The solvent was removed on a rotary evaporator,
and the residue was purified with column chromatography on silica
gel with a mixture of dichloromethane/ethyl acetate (3:1) as eluent.
3
1.10 (s, 18H), 1.62 (s, 27H), 2.28 (s, 4H), 5.03 (s, 2H), 7.50 (d, J )
3
3
8.5 Hz, 2H), 7.75 (dd, J ) 8.0 Hz, 2H), 7.80 (d, J ) 8.3 Hz, 6H),
8.04 (d, 3J ) 7.8 Hz, 2H), 8.08 (d, 3J ) 7.8 Hz, 2H), 8.14 (d, 3J ) 8.3
Hz, 6H), 8.19 (d, 3J ) 8.5 Hz, 2H), 8.31 (s, 1H), 8.71 (d, 3J ) 1.5 Hz,
2H), 8.87 (m, 8H), 9.29 (s, 2H), 9.66 (s, 2H), 10.01 (s, 1H). 13C NMR
(THF-d8, 100.5 MHz, RT) [δ (ppm)]: 30.01, 31.66, 31.94, 35.41, 50.70,
68.99, 109.98, 110.33, 113.72, 120.71, 121.50, 122.75, 122.87, 124.13,
131.39, 132.25, 135.37, 136.49, 136.93, 138.12, 140.4, 140.68, 141.64,
150.83, 151.16, 151.42, 151.97, 158.63, 165.46, 168.24, 171.04. FT-
IR (diamond, RT) [ν˜ (cm-1)]: 718, 795, 995, 1069, 1227, 1297, 1444,
1505, 1583, 1675, 2868, 2903, 2953, 3277, 3397. UV/vis (CH2Cl2)
[λmax, nm (log ꢀ)]: 303 (4.34), 399 (4.16), 421 (5.19), 549 (3.85), 593
(3.50). Anal. Calcd for C88H89N11O6Zn‚0.66CH2Cl2 (Mr ) 1518): C,
70.12; H, 6.00; N, 10.14. Found: C, 70.60; H, 5.91; N, 9.76.
9
16070 J. AM. CHEM. SOC. VOL. 129, NO. 51, 2007

Electron versus Energy Transfer
A R T I C L E S
Acknowledgment. We thank the Deutsche Forschungsge-
meinschaft (SFB 583: Redoxaktive Metallkomplexe-Reaktivi-
ta¨tssteuerung durch molekulare Architekturen) for financial
support. We dedicate this article to Klaus-Dieter Asmus on the
occasion of his 70th birthday.
flash photolysis (387 nm) of Sn porphyrin and time-absorption
profile, reflecting the formation and decay of the singlet excited
state. This material is available free of charge via the Internet
at http://pubs.acs.org.
Supporting Information Available: Differential absorption
JA075751G
spectra (visible and near-infrared) obtained upon femtosecond
9
J. AM. CHEM. SOC. VOL. 129, NO. 51, 2007 16071