Lanthanide(III) Bis(phthalocyaninato)-[60]Fullerene dyads: Synthesis, characterization, and photophysical properties

Article abstract of DOI:10.1002/chem.200902200

A novel series of doubledecker lanthanide(III) bis(phthalocyaninato)-C ₆₀ dyads [Ln^III(Pc)(Pc')]-C₆₀ (M = Sm, Eu, Lu; Pc = phthalocyanine) (1a-c) have been synthesized from unsymmetrically functionalized heteroleptic sandwich complexes [Ln^III(Pc)(Pc')] (Ln = Sm, Eu, Lu) 3a-c and fulleropyrrolidine carboxylic acid 2. The sandwich complexes 3a-c were obtained by means of a stepwise procedure from unsymmetrically substituted free-base phthalocyanine 5, which was first transformed into the monophthalocyaninato intermediate [Ln^III(acac) (Pc)] and further reacted with 1,2-dicyanobenzene in the presence of 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU). ¹H NMR spectra of the bis(phthalocyaninato) complexes 3a-c and dyads 1a-c were obtained by adding hydrazine hydrate to solutions of the complexes in [D₇]DMF, a treatment that converts the free radical double-deckers into the protonated species, that is, [Ln^III(Pc)(Pc')H] and [Ln^III(Pc)(Pc')H]- C₆₀. The electronic absorption spectra of 3a-c and 1a-c in THF exhibit typical transitions of free-radical sandwich complexes. In the case of dyads 1a-c, the spectra display the absorption bands of both constituents, but no evidence of ground-state interactions could be appreciated. When the UV/Vis spectra of 3a-c and 1a-c were recorded in DMF, typical features of the reduced forms were observed. Cyclic voltammetry studies for 3a-c and 1a-c were performed in THF The electrochemical behavior of dyads 1a-c is almost the exact sum of the behavior of the components, namely the double-decker [Ln^III(Pc) (Pc')] and the C₆₀ fullerene, thus confirming the lack of groundstate interactions between the electroactive units. Photophysical studies on dyads 1a-c indicate that only after irradiation at 387 nm, which excites both C ₆₀ and [Ln^III(Pc)(Pc')] components, a photoinduced electron transfer from the [Ln^III(Pc)(Pc')] to C₆₀ occurs.

Full text of DOI:10.1002/chem.200902200

DOI: 10.1002/chem.200902200
LanthanideACTHUNGTRENNUNG
Beatriz Ballesteros,[a] Gema de la Torre,*[a] Axel Shearer,[b] Anita Hausmann,[b]
M. ꢀngeles Herranz,[c] Dirk M. Guldi,*[b] and Tomꢁs Torres*[a]
Abstract: A novel series of double-
decker lanthanide(III) bis(phthalocya-
ninato)–C60 dyads [LnIII(Pc)
(Pc’)]–C60
complexes 3a–c and dyads 1a–c were
obtained by adding hydrazine hydrate
to solutions of the complexes in
[D7]DMF, a treatment that converts
the free radical double-deckers into the
protonated species, that is, [LnIII(Pc)-
preciated. When the UV/Vis spectra of
3a–c and 1a–c were recorded in DMF,
typical features of the reduced forms
were observed. Cyclic voltammetry
studies for 3a–c and 1a–c were per-
formed in THF. The electrochemical
behavior of dyads 1a–c is almost the
exact sum of the behavior of the com-
ponents, namely the double-decker
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
(M=Sm, Eu, Lu; Pc=phthalocyanine)
(1a–c) have been synthesized from un-
symmetrically functionalized heterolep-
tic sandwich complexes [LnIII(Pc)
N
(Pc’)H] and [LnIII(Pc)
ACHUTGTNERNNUG CAHUTGNTREN(NUGN Pc’)H]–C60. The
(Ln=Sm, Eu, Lu) 3a–c and fulleropyr-
rolidine carboxylic acid 2. The sand-
wich complexes 3a–c were obtained by
means of a stepwise procedure from
unsymmetrically substituted free-base
phthalocyanine 5, which was first trans-
formed into the monophthalocyaninato
electronic absorption spectra of 3a–c
and 1a–c in THF exhibit typical transi-
tions of free-radical sandwich com-
plexes. In the case of dyads 1a–c, the
spectra display the absorption bands of
both constituents, but no evidence of
ground-state interactions could be ap-
[LnIII(Pc)
ACTHUNGTRNEUNG(Pc’)] and the C60 fullerene,
thus confirming the lack of ground-
state interactions between the electro-
active units. Photophysical studies on
dyads 1a–c indicate that only after irra-
diation at 387 nm, which excites both
intermediate [LnIII
ACHTUNGTRENNUNG(acac)(Pc)] and fur-
ther reacted with 1,2-dicyanobenzene
in the presence of 1,8-diazabicyclo-
C60 and [LnIII(Pc)
photoinduced electron transfer from
the [LnIII(Pc)
(Pc’)] to C60 occurs.
ACHTUNGTREN(NUNG Pc’)] components, a
Keywords: fullerenes · lanthanides ·
phthalocyanines · sandwich com-
plexes
A
ACHTUNGTRENNUNG
spectra of the bis(phthalocyaninato)
Introduction
Phthalocyanines (Pcs)[1] are an important class of chromo-
phores that have fascinated scientists for many years due to
their applicability in different fields, such as nonlinear
optics,[2] organic solar cells,[3,4] and field-effect transistors.[5]
This range of applications arises from the ease of tuning spe-
cific properties through the introduction of substituents at
the aromatic ring and through the incorporation of up to 70
different metallic or metalloid elements into the central
cavity of the macrocyclic ligand (Pc2ꢀ). A large number of
metal ions, the ionic radii of which exceed what has been
called the “coordination space” of the dinegative quadriden-
tate phthalocyaninato ligand, cannot enter the central cavity
[a] Dr. B. Ballesteros, Dr. G. d. l. . Torre, Prof. T. Torres
Departamento de Quꢀmica Orgꢁnica
Universidad Autꢂnoma de Madrid
Cantoblanco, 28049, Madrid (Spain)
Fax : (+34)914-973-966
E-mail: tomas.torres@uam.es
[b] A. Shearer, A. Hausmann, Prof. D. M. Guldi
Department of Chemistry and Pharmacy &
Interdisciplinary Center for Molecular Materials
Friedrich-Alexander-Universitꢃt Erlangen-Nꢄrnberg
Egerlandstrasse 3, 91058 Erlangen (Germany)
of the Pc ring.[6] These metal ions (Ln3+, Sc3+, Y3+, Ce4+
etc.) prefer to have coordination numbers larger than six,
eight being the most common in lanthanide(III) phthalo-
cyaninato derivatives, thus displaying a sandwich-like struc-
ture. Lanthanide(III) bis(phthalocyaninato) complexes pos-
,
[c] Dr. M. ꢅ. Herranz
Departamento d Quꢀmica Orgꢁnica I
Facultad de Quꢀmica, Universidad Complutense
28040, Madrid (Spain)
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.200902200.
AHCTUNGTRENNUNG
114
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Chem. Eur. J. 2010, 16, 114 – 125

FULL PAPER
sess intriguing and unique electronic and optical properties
that make them useful in materials science, because of their
possible applications in molecular electronics, molecular in-
formation storage, and nonlinear optics.[7] Rare-earth-metal
bisphthalocyanines are well explored electrochromic materi-
als, which are readily oxidized and reduced and exhibit sev-
eral colors.[8] The most familiar states are the “green” form,
a free-radical species in which one of the Pc rings possesses
17 electrons, and the “blue” form, obtained by one-electron
reduction. The blue form requires the presence of an “extra
hydrogen” to achieve charge neutrality, but its location is
unclear.[9]
The chemistry of sandwich-type complexes comprising
two identically functionalized Pc rings (homoleptic com-
plexes) has been studied for several decades.[10] In recent
years, heteroleptic rare-earth bis(phthalocyanines) com-
posed of two differently substituted Pc rings have been also
investigated, as well as other heteroleptic sandwich-type
complexes with different combination of tetrapyrrolic units
in a double- or triple-decker arrangement.[11,12]
other chromophore or electronic subunit in order to study
energy and electron transfer processes.[14]
Due to its extensive p-electron conjugation C60 has been
widely investigated for potential applications in different
fields.[15] C60 and its derivatives can reversibly accept up to
six electrons, because of their triply degenerate low-lying
LUMOs.[16] These features render C60 an ideal electron-ac-
ceptor molecule in donor–acceptor (D–A) systems designed
to mimic the photosynthetic reaction center.[17] In this
regard, we have previously described the preparation of
strongly coupled Pc–C60 dyads in which long-lived photoin-
duced charge-separated states are formed.[18] In these sys-
tems, phthalocyanines behave as the electron-donor partner.
LanthanideACTHNUGRTNEUNG(III) double-deckers show lower oxidation po-
tentials than mononuclear Pcs and, for this reason, they are
interesting candidates to be utilized as donor components in
D–A dyads or as active components in solar cells.[14,19] The
current work is expected to make a significant contribution
to this field of research. In this context, we describe in detail
the synthesis, and the electrochemical and photophysical
However, just a few examples of bis(phthalocyaninato)
complexes holding one unsymmetrically functionalized Pc
ring can be found in the literature.[13] The incorporation of
Pc cores bearing solubilizing moieties at three isoindole
units and one reactive group at the remaining position,
would allow the attachment of this type of complexes to
characterization of a set of three [LnIII(Pc)
ACTHNGUTERN(NUG Pc’)]–C60 com-
plexes (1a–c; Scheme 1) bearing different lanthanide ions.
To the best of our knowledge, these compounds represent
the first example of double-decker lanthanide
AHCTUNTGREGUN(NN phthalocyaninato)–C60 dyads.
ACHTUNGTRENN(UNG III) bis-
Scheme 1. Synthesis of [Ln(Pc)ACHTUNRGTENN(UG Pc’)] double-deckers 3a–c and the corresponding [Ln(Pc)ACHTUGNTREN(NGUN Pc’)]–C60 dyads 1a–c.
Chem. Eur. J. 2010, 16, 114 – 125
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115

D. M. Guldi, T. Torres, G. de la Torre et al.
Results and Discussion
(green forms) and the corresponding reduced protonated
complexes [LnIII(Pc)
ACTHUNTGRENNG(U Pc’)H]. In each case, purification of
Synthesis and spectroscopic characterization: The classical
method for the preparation of homoleptic sandwich com-
pounds involves the self-condensation of phthalonitriles in
the presence of metal salts.[20] Regarding heteroleptic rare-
earth bis(phthalocyaninato) compounds, two main synthetic
pathways have been reported thus far for the preparation of
this kind of complexes. The first method involves the reac-
tion of a rare-earth salt with two different lithium or metal-
the mixture was performed by repeated silica gel column
chromatography with chloroform as eluent. Oxidation of the
blue forms was observed when eluting along the column. As
a result, the corresponding radical species [LnIII(Pc)
ACHTUNGTRENNUNG
(3a–c) were isolated in about 20% yield. [LnIII(Pc)
ACHTUNGTRENNUNG
between the corresponding [LnIII(Pc)
ACTHNUTRGNE(UNG Pc’)] (3a–c) and 4-(1’-
octyl-3’,4’-fulleropyrrolidin-2’-yl)benzoic acid (2)[24] in the
presence of DMAP and DCC. A partial reduction of the
complexes was observed because of the presence of DMAP,
free phthalocyanines, H2/Li2(Pc) and H2/Li2ACTHNUTRGNEUNG
(Pc’).[21] Howev-
er, as expected, this reaction also produced the correspond-
ing homoleptic sandwich compounds, which can be separat-
ed only by repeated chromatographic procedures. To over-
come that drawback, an improved method, which involves
leading to a mixture of the radical dyads [LnIII(Pc)
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
the formation of intermediate mononuclear lanthanide
(III)
was carried out by exclusion size chromatography and re-
peated silica gel column chromatography, which ended in
the oxidation of the blue forms to the green ones. In this
way, radical dyads [LnIII(Pc)
in approximately 50% yield.
ACHTUNGTRNE(NUNG Pc’)]–C60 (1a–c) were obtained
In the present work, we have employed a similar stepwise
procedure for the preparation of heteroleptic sandwich com-
plexes 3a–c (Scheme 1), which are composed of one unsym-
metrically substituted Pc (holding six solubilizing p-tert-bu-
tylphenoxy moieties and one reactive hydroxymethylphenyl
one) and a “nacked” Pc ligand, using the corresponding
Compounds 3a–c and 1a–c gave satisfactory elemental
analysis data. Their sandwich nature was further unambigu-
ously confirmed by various spectroscopic methods. MALDI-
TOF spectra of all these double-deckers showed an isotopic
pattern in good agreement with the simulated spectrum.
This is exemplified in Figure 1, which depicts the theoretical
and experimental spectrum of dyad 1b. The IR spectra of
all the bis(phthalocyaninato) complexes (3a–c) and their
corresponding dyads (1a–c) showed an intense band at
lanthanideACHTUNGTRENNUNG AHCTUNGTERN(NUGN acac)3]·nH2O, Ln =
(III) acetylacetonate ([LnIII
Sm, Eu, Lu), phthalonitrile, and unsymmetrically substituted
metal-free phthalocyanine (H2Pc; 5)[23] as starting materials.
In a first step, [LnIII
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
and 5 at about 1708C in o-di-
chlorobenzene (o-DCB). The
formation of the mononuclear
complexes 4a–c was monitored
by UV/Vis experiments, in
which one can appreciate a de-
crease in the intensity of the
two bands of 5, centered at 706
and 672 nm, and the growing of
a new band centered at approx-
imately 685 nm. All three
lanthanideACHTUNGTRENNUNG(III) complexes were
fully formed in 1.5 h. After re-
moval of the solvents, the
mono
G
intermediates
were reacted, without further
purification, with dicyanoben-
zene in the presence of DBU in
o-DCB/1-pentanol at 1608C,
yielding the corresponding het-
eroleptic double-deckers 3a–c.
These lanthanideACHTUNGTRENNUNG(III) bis(ph-
thalocyaninato) complexes are
obtained as a mixture of the
free-radical
Figure 1. Top: partial MALDI-TOF mass spectrum of 1b, showing the isotopic distribution of the molecular
[LnIII(Pc)
ACTHNGUTERN(UNG Pc’)] ion. Bottom: corresponding simulated pattern.
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Sandwich Complexes
FULL PAPER
1318–1325 cmꢀ1 (Figure S5 and S8 in the Supporting Infor-
mation), which shifts to higher wavenumbers along with the
lanthanide contraction, and is a marker band for the Pc p
radical,[25] as it is also manifested in the UV/Vis spectra (see
below).
induces broadening of the signals, but still the typical pat-
tern of resonances can be distinguised.
Ground-state electronic absorption spectra: Electronic ab-
sorption spectra of compounds 1a–c and 3a–c were record-
ed in CHCl3 (Figure 3 and S2 in the Supporting Informa-
tion). The spectra of the neutral double-deckers complexes
1H NMR spectra: Because of the presence of the unpaired
electron, NMR data for all the single-hole lanthanide
N
ACHTNGURTENNUG CAHTUNGTRNE(NUNG Pc’)]–C60
[LnIII(Pc)(Pc’)] (3a–c) and their dyads [LnIII(Pc)
bis(phthalocyaninato) complexes are difficult to obtain.
However, upon addition of hydrazine hydrate as reducing
agent, well-resolved H NMR spectra (Figure S1 and S6 in
(1a–c) exhibit typical features of single-hole bis(phthalo-
1
the Supporting Information) could be recorded for the re-
duced blue forms of all the heteroleptic double-deckers 1a–
c
and 3a–c (i.e., [LnIII(Pc2ꢀ)(Pc’2ꢀ)H] and [LnIII(Pc2ꢀ)-
ACHTUNGTREUNNGN ACHTUNGTRENNUNG ACTHNUGTRENNGUN
ACHTUNGTRENNUNG
(Pc’2ꢀ)H]–C60), as both macrocyclic ligands become diamag-
netic anions. The use of [D7]DMF as deuterated solvent was
necessary to completely reduce the radical forms of 3a–c
and 1a–c, as well as the addition of one drop of CCl4 to
1
fully dissolve all the complexes. Figure 2 shows the H NMR
spectra of the reduced forms of 3b and 1b in the region
from 12 to 2 ppm. As a general rule, the a protons of the
unsubstituted Pc ring resonate at lower field followed by the
a’ protons of the substituted Pc ring. The b and b’ protons
appear at higher field. In particular, the europium
ACHTUNGTRENN(UNG III) de-
rivatives [EuIII(Pc)(Pc’)H] and [EuIII(Pc)
G
ACHTUNGTRENNUNG
down-field shifts for all the resonances with respect to the
SmIII and LuIII derivatives. The presence of C60 in all re-
Figure 3. Electronic absorption spectra of 1a–c complexes in CHCl3.
duced forms (i.e., [LnIII(Pc)
ACHTNUTRGNEGNU(Pc’)H]–C60) of complexes 1a–c
AHCTUNGTRENNUNG
a
Soret band at 320-326 nm with
a shoulder at the lower-energy
side, involving a couple of elec-
tronic transitions dealing with
the third occupied HOMO and
the first LUMO. It is worth
noting that similar splitting of
the Soret band had been previ-
ously observed for other homo-
and heteroleptic bis(phthalo-
cyaninato) rare-earth complex-
es.[8e,22b,26] The
AHCTUNGTERUNNNG Q bands for
these compounds appear in the
670–680 nm range (with two vi-
brational shoulders at 588–590
and 603–615 nm) resulting from
the transitions from the first
semi-occupied molecular orbital
(SOMO) to the second LUMO
and from the second fully occu-
pied HOMO to the first
LUMO.[27] In addition, the two
weak p-radical bands at about
460–490 nm and 913–922 nm
can be attributed to the elec-
tronic transitions involving the
Figure 2. 1H NMR spectra of [EuIII(Pc)(Pc’)H] (reduced form of 3b) and [EuIII(Pc)
ACTHNUTRGENNUG CAHTUNGTRNE(NUGN Pc’)H]–C60 (reduced form
of 1b) in [D7]DMF/CCl4/N2H4.
Chem. Eur. J. 2010, 16, 114 – 125
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117

D. M. Guldi, T. Torres, G. de la Torre et al.
SOMO. With exception of the p-radical band at abour
915 nm, the absorption wavelengths of all the other bands
experiment hypsochromic shifts when the ionic radii of the
lanthanide cations decrease (from Sm to Lu), because the
interaction between the two rings becomes stronger. The
spectra of dyads 1a–c is a linear superimposition of the ab-
sorption of the individual components; that is, the
lanthanideACHTUNGTRENNUNG(III) bis(phthalocyaninato) unit and the fullerene
one, thus indicating the lack of ground-state interactions be-
tween the subunits.
When the UV/Vis spectra of 3a–c and 1a–c were record-
ed in DMF, a progressive formation of the anionic blue
forms was observed (Figure S3 in the Supporting Informa-
tion). The absorption spectra of the protonated species
[LnIII(Pc)
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
Gd).[30] The spectra show medium-to-high intense Soret
bands at 340 nm, and split Q bands in the 620–700 nm
region; this splitting is more prominent for the heavier lan-
thanides (from Sm to Lu). In the case of the protonated
[LnIII(Pc)
ACHTUNGTRENNUNG(Pc’)H]–C60 dyads, the absorption spectra are also
a superimposition of the features of both constituents.
Ground-state electrochemistry: The solution electrochemis-
try of dyads 1a–c was studied using cyclic voltammetry
(CV) and Osteryoung square wave voltammetry (OSWV).
The results obtained for 1a–c were compared with those of
Figure 4. CVs of bis(phthalocyaninato) complexes 3a–c, dyads 1a–c, and
reference compound 6 in THF at room temperature.
the model lanthanideACTHNUTRGNEUNG(III) bis(phthalocyaninato) complexes
3a–c and the fulleropyrrolidine compound 6. For compara-
tive purposes, 6 was synthesized through an esterification re-
action between 2 and 4-tert-butylphenylmethanol (see Ex-
perimental Section). The CV results are presented in
Figure 4 and the potential data collected in Table 1.
these conditions. As in many other series of double-deckers,
the redox potentials of 3a–c depend on the ionic radius of
the metal center.[8g,11,12c] As shown in Table 1, the half-wave
potentials of the oxidation and the first reduction processes,
both of which involve the SOMO orbital, shift slightly in the
negative direction as the metal center decreases.
The potentials for the remaining three reduction processes
are insensitive to the ionic size of the lanthanideACTHNUTRGNE(UNG III) center,
suggesting that the energy level of the LUMO does not
change significantly with the metal center. According to the
orbital scheme depicted in Figure 5, DE01=2 (potential differ-
ence between the first oxidation and the first reduction pro-
cess), represents the energy of putting a second electron in
the SOMO of the neutral double-decker radical 3a–c or re-
moving one of the two electrons from the HOMO of the
corresponding reduced double-decker species [LnIII(Pc)-
AHCTUNGTRENNUNG
(Pc’)]ꢀ. For all the compounds DE10=2 spans a very narrow
Within the electrochemical window of THF, all the
double-decker compounds 3a–c undergo one quasi-reversi-
ble one-electron oxidation and up to four quasi-reversible
one-electron reductions (Figure 5 and Figure S11 in the Sup-
porting Information). All these redox processes can be at-
tributed to the successive removal or addition of electrons
from/or to the ligand-based orbitals, as the trivalent
range (i.e., 0.47–0.49 V), which correlates well with previous
reported results for bis(phthalocyaninato) complexes.[8g,12c]
Furthermore, the potential difference between the first
and second reduction processes for compounds 3a–c corre-
sponds to the potential difference between the first oxida-
tion and the first reduction of [LnIII(Pc)
(Pc’)]ꢀ, DE
00
1=2
(Table 1). The values range from 1.12 V (3c) to 1.23 V (3b)
and 1.25 V (3a), diminishing gradually with the decrease of
lanthanide
ACHTUNGTRENNUNG
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Sandwich Complexes
FULL PAPER
Table 1. Electrochemical data [mV vs. Fc/Fc+] for bis(phthalocyaninato) complexes 3a–c, dyads 1a–c, and reference compound 6 in THF.
[a]
[a]
E11=2,red
[b]
[a,b]
[a]
E41=2,red
[b]
[a]
[c]
00 [d]
DE
1=2
E11=2,ox
E21=2,red
E31=2,red
E51=2,red
E61=2,red
DE01=2
6
ꢀ1008
ꢀ1020
ꢀ955
ꢀ1574
ꢀ1506
ꢀ1558
ꢀ1506
ꢀ1529
ꢀ1493
ꢀ1531
ꢀ2187
ꢀ2306
ꢀ2226
ꢀ2211
3a
1a
3b
1b
3c
1c
+206
+184
+192
+203
+114
+114
ꢀ261
ꢀ296
ꢀ278
ꢀ288
ꢀ371
ꢀ395
ꢀ1914
ꢀ1932
ꢀ1910
ꢀ1914
ꢀ1901
ꢀ1921
ꢀ2371
ꢀ2388
ꢀ2352
ꢀ2390
ꢀ2261
ꢀ2410
0.47
0.48
0.47
0.49
0.49
0.51
1.25
0.72
1.23
0.67
1.12
0.61
ꢀ1007
[a] Bis(phthalocyaninato)-complex-based redox process. [b] C60-based reduction. [c] DE01=2 in V, is the energy required to put a second electron in the
SOMO of the neutral double-decker radical [LnIII(Pc)
G
[LnIII(Pc)
ACHTUNGTRENNUNG
00
1=2
HOMO–LUMO gap of the reduced double-decker species [LnIII(Pc)
N
N
.
tion waves correspond again to reductions on the double-
decker moiety, whereas the fith reduction is C60-based.
The potential difference between the first oxidation pro-
cess and the first reduction process for dyads 1a–c (DE01=2) is
almost independent of the ionic radius of the metal center,
although the values are slightly larger than those of model
systems 3a–c. It is also worth mentioning that the potential
Figure 5. Frontier orbitals and first one-electron redox processes of
[LnIII(Pc)
(Pc’)] compounds.
difference between the first reduction of the [LnIII(Pc)
ACHTUNGTRENNUNG(Pc’)]
ACHTUNGTRENNUNG
moiety and the first reduction of the C60 addend corresponds
to the electrochemical molecular band gap, which ranges
from 0.61 to 0.72 V across the series, gradually diminishing
the lanthanide
G
with the decrease of lanthanideACHTNGUTERN(UNG III) radius.
effect and indicates the enhanced p–p interactions in the
double-deckers with smaller lanthanides compared with that
connected by larger lanthanides. As the first reduction step
and second reduction step of 3a–c (or the first oxidation
and first reduction of the corresponding reduced forms
Photophysics: The photophysical section focuses exclusively
on the excited state interactions between the two electroac-
tive moieties in 1a–c (i.e., [LnIII(Pc)
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
[LnIII(Pc)
G
complexes, but not the corresponding reduced forms.
spectively, of the molecules, the energy difference between
these two redox processes corresponds to their electrochem-
ical molecular band gap.
The cyclic voltammograms of dyads 1a–c are similar to
those of 3a–c. All dyads are electrochemically active in both
anodic and cathodic directions and the electrochemistry of
the three species is almost the exact sum of the behavior of
the independent components: the double-decker [LnIII(Pc)-
Considering the dominant absorptions of the [LnIII(Pc)-
AHCTUNGTREG(NNUN Pc’)] derivatives 3a–c all throughout the visible region, we
focused on their fluorescence features upon 330, 335, and
675 nm excitation. A fluorescence pattern evolves that is a
mirror image to the ground-state absorptions, with maxima
in the visible at around 690 nm that resembles that of struc-
turally simpler metallated phthalocyanines (i.e., ZnIIPc,
etc.). Figure 6 illustrates the sharp fluorescence maxima that
were recorded for 3c and 3a at 695 nm, while in the case of
3b the maxima are seen to split into a set of two, at 687 and
705 nm. The overall trend resembles, nevertheless, that seen
in the absorption characteristics. Despite the apparent simi-
larity between mononuclear metallated phthalocyanines (i.e,
ZnIIPc), on one hand, and 3a–c, on the other hand, the over-
all quantum yields differ largely (0.3 versus 0.004). In refer-
ence to the long wavelength absorption (i.e., 900–950 nm),
no emission was discernable. When turning to the corre-
ACHTUNGTRENNUNG(Pc’)] and the C60 portions. Thus, in the anodic direction,
1a–c show one double-decker-based one-electron quasi-re-
versible oxidation wave. In the cathodic direction, between
0 and ꢀ2.5 V, dyads 1a–c show six quasi-reversible reduc-
tion waves that can be easily assigned either to the C60 or
the double-decker [LnIII(Pc)
ACTHNUTRGNE(NUG Pc’)] moieties when compared
to those of 3a–c and 6. The first reduction wave corresponds
in all dyads to the first reduction of the double-decker, and,
as in reference systems 3a–c, the potentials shift to negative
values when decreasing the ionic radii of the metal center.
The second reduction process in 1a–c corresponds in all
cases to the first reduction of the C60 core. The obtained re-
duction potentials (between ꢀ955 and ꢀ1020 mV) are typi-
cal of fullerene mono-adducts.[18] The third reduction wave
is a two-electron process, which involves the second reduc-
tion of the C60 core and the second reduction of the double-
sponding electron donor–acceptor [LnIII(Pc)
ACTHNUGTRNE(UNG Pc’)]–C60 conju-
gates 1a–c, it is remarkable that the Pc-centered fluores-
cence reveals negligible impacts. At the very best, the fluo-
rescence of the [LuIII(Pc)
ACTHNUTRGNE(NUG Pc’)] moiety in 1c seems to be af-
fected, relative to what is seen in 3c. Moreover, it is inter-
esting to note the lack of the characteristic C60-centered
fluorescence features, which could have originated from
direct excitation of the C60 moiety (i.e., 330 and 335 nm ex-
decker [LnIII(Pc)
ACHTUNGTRENNUNG(Pc’)] moiety. The fourth and sixth reduc-
Chem. Eur. J. 2010, 16, 114 – 125
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119

D. M. Guldi, T. Torres, G. de la Torre et al.
Figure 6. Steady-state fluorescence spectra of double-deckers—upper
part: 3a (solid line), 3b (dashed line), 3c (dotted line)—and the corre-
sponding dyads—lower part: 1a (solid line), 1b (dashed line), 1c (dotted
line) in toluene at 335 nm excitation.
Figure 7. Upper part: differential absorption spectra (visible and near-in-
frared) obtained upon femtosecond flash photolysis (665 nm) of 3a in ni-
trogen-saturated toluene with time delays of 1 ps (filled circles) and 50 ps
(crosses) at room temperature. Lower part: time-absorption profiles of
the spectra shown above at 460, 560, and 690 nm, monitoring the excited-
state formation and deactivation.
citation) or through energy transfer from the photoexcited
[LnIII(Pc)
ACHTUNGTRENNUNG(Pc’)] center (i.e., 675 nm excitation). Time-re-
solved measurements of 3a–c and donor–acceptor dyads
1a–c failed to provide any meaningful insight into the radia-
tive deactivation of the photoexcited lanthanideACTHNUTRGNE(UNG III) double-
deckers and their corresponding C60 conjugates. A possible
rationale implies a rapid deactivation - less than the time
resolution of our experimental set up of 200 ps, which is in
line with the low fluorescence quantum yields.
trinsically unstable and gives intersystem crossing with a
lifetime of 3.5 ps to the corresponding quartet excited state.
Spectroscopic features of the latter excited state include, in
all cases, maxima that are shifted relative to those of the
doublet excited state, namely at 520, 620, 695 and 1020 nm.
Figure 7 documents that the quartet excited state features
are also short lived, with an underlying lifetime of 16 ps.
The photoreactivity of 3a–c is somewhat changed when
using 387 nm excitation—compare Figures 7 and 8. In partic-
ular, new transients with maxima at 550 and 840, and
minima at 705 nm develop simultaneously with the decay of
the quartet excited state in all cases. Notable is an overall
reminiscence with features that are linked to the one-elec-
tron oxidized forms of mononuclear H2Pc, ZnIIPc, RuIIPc,
etc. In other words, excitation into the Soret-band region of
complexes 3a–c seems to trigger a photochemical reaction
like that seen for MgIIPc.[31]
Next, we turned to femtosecond transient absorption
measurements to conduct excitation experiments at 387 or
665 nm, which photoexcite the [LnIII(Pc)
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
clusively (i.e., 665 nm). First, we performed the experiments
on the sandwich complexes 3a–c. In accordance with the
ground-state features, transient minima, in the form of
bleach, occur at 460, 600, 675, and 900 nm, while transient
maxima appear at 555, 630, 705, and 955 nm (see Figure 7)
for compounds 3a,b. In the case of 3c, a slight difference is
discernable, with minima and maxima that were found at
460, 573, 597 and 620, 698, 915, 960 nm, respectively. Taking
the open-shell character of 3a–c into consideration, their
doublet ground state is instantaneously transformed (<
0.5 ps) into the doublet excited state. The doublet excited
In the corresponding [LnIII(Pc)
ACTHNUGTRNEUGN(Pc’)]–C60 dyads 1a–c, exci-
tation at 665 nm leads to the same sequence of rapid excited
state deactivation, that is, doublet-to-quartet intersystem
crossing (i.e., 3.5 ps) and ground state recovery (i.e., 16 ps),
that is seen with sandwich complexes 3a–c. An example
state of these lanthanideACTHNUGRTENUNG(III) double-deckers is, however, in-
120
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Chem. Eur. J. 2010, 16, 114 – 125

Sandwich Complexes
FULL PAPER
Figure 8. Upper part: differential absorption spectra (visible and near-in-
frared) obtained upon femtosecond flash photolysis (387 nm) of 3a in ni-
trogen-saturated toluene with time delays of 1 ps (filled circles) and 50 ps
(crosses) at room temperature. Lower part: time-absorption profiles of
the spectra shown above at 630, 665, and 690 nm monitoring the excited-
state formation and deactivation.
Figure 9. Upper part: differential absorption spectra (visible and near-in-
frared) obtained upon femtosecond flash photolysis (387 nm) of 1b in ni-
trogen-saturated toluene with a time delay of 50 ps at room temperature.
Lower part: time-absorption profiles of the spectra shown above at 545,
665, and 690 nm monitoring the excited-state formation and deactivation.
(i.e., 1a) is given in Figure S12 in the Supporting Informa-
tion. Implicit is that the selective excitation of the [LnIII(Pc)-
electron reduced C60 at 1010 nm. On the other hand, oxida-
(Pc’)] moieties in dyads 1a–c is an insufficient means to
tion of the [LnIII(Pc)
ACTHNGUTERNNU(G Pc’)] component in conjugates 1a–c is
power a charge transfer reaction, although being thermody-
namically feasible. It is mainly the short lifetimes of the ex-
implied by the new maxima at 515 nm and 760 nm and con-
firmed by electrochemical and radiolytical assays—see
Figure 10. No notable decay is seen for the newly formed
cited states of the [LnIII(Pc)
ACTHNUTRGNE(NUG Pc’)] double-decker compo-
nents that bring about alternative deactivation mechanisms.
The latter argument led us to focus on the excitation of
C60 in the [LnIII(Pc)
ACTHNUTRGEN(UNG Pc’)]–C60 conjugates 1a–c. Notable is
the singlet excited state lifetime of C60 (i.e., 1.4 ns). There-
fore, we turned to 387 nm excitation, which excites, never-
theless, both C60 and [LnIII(Pc)
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
in the spectra of 1a–c. In Figure 9 (i.e., dyad 1b) the
minima are seen at 460, 600, 675, and 900 nm, while at 555,
630, 705, and 955 nm new maxima develop. In addition, a
broad transition around 880 nm, which correlates with the
singlet excited state of C60, seems to be superimposed to the
aforementioned [LnIII(Pc)
ACHTUNGTRENNUNG
the disappearance of [LnIII(Pc)
AHCTUNGTRENNUNG
at about 20 to 30 ps, the charge-separated state features
start to evolve, namely, the fingerprint absorption of one-
Figure 10. Spectroelectrochemical oxidation of 1b in nitrogen-saturated
toluene at an applied potential of +0.6 V.
Chem. Eur. J. 2010, 16, 114 – 125
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121

D. M. Guldi, T. Torres, G. de la Torre et al.
ment. Melting points were determined in a Bꢄchi 504392-S equipment
and are uncorrected. IR spectra were recorded on a Bruker Vector 22
spectrophotometer using KBr disks. MALDI-TOF-MS spectra were de-
termined on a BRUKER REFLEX III instrument equipped with a nitro-
gen laser operating at 337 nm. NMR spectra were recorded with a
Bruker AC-300 instrument. UV/vis spectra were recorded with a Hew-
lett–Packard 8453 instrument.
charge separated state on the timescale of the femtosecond
experiments, that is, 3 ns, which suggests an upper limit for
lifetime of >3 ns in toluene.
Conclusions
Electrochemistry: Electrochemical measurements were performed at
room temperature in a potentiostate/galvanostate Autolab PGSTAT30.
Measurements were carried out in a home-built one-compartment cell
with a three-electrode configuration, containing 0.1m tetrabutylammoni-
um hexafluorophosphate (TBAPF6) as supporting electrolyte. A glassy
carbon (GCE) was used as the working electrode, a platinum wire as the
counter electrode and, a Ag/AgNO3 non-aqueous electrode was used as
reference. Prior to each voltammetric measurement the cell was degassed
under an argon atmosphere for about 20 min. The solvent, THF, was
freshly distilled from Na. The electrochemical measurements were per-
formed by using a concentration of approximately 0.2 mm of the corre-
sponding compound, and ferrocene was added as an internal reference.
We have prepared a series of novel lanthanide
(phthalocyaninato)–C60 complexes 1a–c. The synthetic strat-
egy towards 1a–c consisted in the preparation of heterolep-
tic lanthanide(III) bis(phthalocyaninatos) 3a–c, which have
ACHTUNGTRENN(UNG III) bis-
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
one unsubstituted Pc ring and another one unsymmetrically
functionalized with six solubilizing moieties and one reactive
position (i.e., a primary alcohol). Therefore, the esterifica-
tion reaction of these unsymmetric double-deckers with a
carboxylic acid containing fullerene derivative (2) affords
[LnIII(Pc)
ACHTUNGTRENNUNG(Pc’)]–C60 conjugates 1a–c in reasonable yields.
Photophysics: Steady-state emission spectra were recorded on a Fluoro-
Max 3 fluorometer (vis detection) and on a Fluorolog spectrometer
(NIR detection). Both spectrometers were built by HORIBA JobinYvon.
The measurements were carried out at room temperature. Femtosecond
transient absorption studies were performed with 665 nm and 387 nm
laser pulses (1 kHz, 150 fs pulse width) from an amplified Ti:Sapphire
laser system (Clark-MXR, Inc.), the laser energy was 200 nJ.
The solution electrochemistry for all these dyads shows one
double-decker-based oxidation process and six reduction
ones, which are centered either on the C60 or on the
[LnIII(Pc)
[LnIII(Pc)
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
wave corresponds to the first reduction of the double-decker
component, that is, putting a second electron in its SOMO.
As a consequence, the electrochemical molecular band gap
Pulse radiolysis: Pulse radiolysis experiments were performed by using
50 ns pulses of 15 MeV electrons from a linear electron accelerator
Cꢀ,
(LINAC). Dosimetry was based on the oxidation of SCNꢀ to (SCN)2
which in aqueous, N2O-saturated solution takes place with Gꢁ6 (G de-
notes the number of species per 100 eV, or the approximate mm concen-
tration per 10 J absorbed energy). The radical concentration generated
per pulse was varied between (1–3)ꢈ10ꢀ6 m.
for these [LnIII(Pc)
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
Spectroelectrochemistry: All the experiments were performed with a
home-built cell and a three-electrode setup: a light-transparent platinum
gauze as working electrode, a platinum wire as counter electrode, and a
silver wire as quasi reference electrode. Potentials were applied and
monitored with an EG&G Princeton Applied Research potentiostat
(model 263 A). The spectra were recorded with a UV/Vis/NIR-spectrom-
eter Cary 5000 (VARIAN). The pathlength of the cell was determined to
2.3 mm. The results are finally shown as differential spectra, that is, the
difference between a spectrum with and without an applied potential.
ACHTUNGTRENNUNG
is, the second reduction process in 1a–c. In light of their
electron donor–acceptor character and the thermodynamic
feasibility for the formation of the charge-separated state,
we probed 1a–c in their free-radical forms in a series of
steady-state and time-resolved photophysical assays. Photo-
excitation of C60 (387 nm) in 1a–c leads to a rapid (i.e.,
ꢁ30 ps) and long-lived (i.e., beyond our time resolution of
3 ns) charge transfer. In contrast, the short-lived nature of
Standard procedure for the synthesis of [LnIII(Pc)
ACHTUNGTREN(NUGN Pc’)] (Ln=Sm, Eu,
Lu) (3a–c): A mixture of 5,[23] DBU and [Ln
AHCTUNGTRENNUNG
heated at 1708C for 1.5 h under a slow stream of argon. The resulting
green solution was cooled to room temperature, and the volatiles were
removed under reduced pressure. The residue was washed with hexane
the [LnIII(Pc)
ACHTUNGTRENNUNG(Pc’)] excited states fails to trigger analogous
charge-transfer reactions. This result stands, however, in
stark contrast to the photophysical behavior of related self-
assembled ZnPc binuclear derivatives that are non-covalent-
ly linked to a C60 moiety; in this system, it is only the ZnPc
triplet excited state that triggers a photoinduced charge
transfer.[32]
to give intermediates [LnIII
ACTHUNRTGNE(GNU acac)(Pc)] 4a–c, which were then reacted
with 1,2-dicyanobenzene and DBU in o-DCB/1-pentanol (1:1) for 3.5 h
at 1608C. The resulting blue solution was cooled to room temperature,
and reduced to dryness. The blue solid was washed with hexane, poured
onto a silica gel column and eluted with chloroform. Repeated chroma-
tography followed by recrystallization from MeOH afforded pure
[LnIII(Pc)
[SmIII(Pc)
[Sm(acac)3]·nH2O (34 mg, 0.07 mmol) in o-DCB (4 mL) gave [Sm-
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
Experimental Section
(acac)(Pc)] (4a), which was reacted with 1,2-dicyanobenzene (34 mg,
0.26 mmol) and DBU (1 drop) in o-DCB/1-pentanol (1:1) (6 mL) to yield
33 mg of
[D7]DMF/CCl4/N2H4): d=8.5–8.4 (m, 8H; H-a), 8.3–8.2 (m, 8H; H-a’),
8.04 (d, J=8.3 Hz, 1H; H-b’), 7.9–7.7 (m, 24H; H-b, H-phenyl), 7.5–7.3
(m, 12H; H-phenyl, H-AA’BB’), 4.94 (s, 2H; CH2OH), 1.6–1.5 ppm (m,
a
green solid (23%). M.p. >3008C; 1H NMR (300 MHz,
General methods: Chemicals were purchased from commercial suppliers
and used without further purification. 4-(1’-octyl-3’,4’-fulleropyrrolidin-2’-
yl)benzoic acid[24] and 2,3,9,10,16,17-hexa-(p-tert-butylphenoxy)-23-(p-hy-
droxymethyl)phenyl-phthalocyanine[23] were prepared using described
procedures. Column chromatography was carried out on silica gel
(Merck, Kieselgel 60, 230–400 mesh, 60 ꢇ), and TLC, on aluminium
sheets precoated with silica gel 60 F254 (E. Merck). Size exclusion chro-
matography was carried out on Bio-Beads S-X1 (200–400 mesh). Ele-
mental analyses were performed with a Perkin–Elmer 2400 CHN equip-
54H;
CACHTNGUETRNNU(G CH3)3); MS (MALDI, dithranol): m/z: 2167–2177; UV/Vis
(CHCl3): lmax (log e)=913 (3.5), 681 (5.4), 613 (4.8), 489 (4.6), 326 nm
(5.3); FT-IR (KBr) : n˜ =2959, 2904, 2866, 1598, 1507, 1486, 1444, 1392,
1363, 1318, 1292, 1265, 1216, 1178, 1113, 1094, 1061, 1038, 1023, 1014,
883, 830, 813, 779, 755, 731 cmꢀ1
.
122
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Chem. Eur. J. 2010, 16, 114 – 125

Sandwich Complexes
FULL PAPER
A
E
MS (MALDI, dithranol): m/z: 3171–3179 [M]+, 2453 [MꢀC60]+; UV/Vis
(CHCl3): lmax (log e)=921 (3.0), 668 (5.4), 603 (4.6), 463 (4.5), 321 nm
(5.3); FT-IR (KBr) : n˜ =3423, 2952, 2922, 2853, 2361, 1713, 1597, 1506,
1443, 1394, 1362, 1322, 1291, 1263, 1215, 1173, 1112, 1095, 1025, 1013,
ACHTUNGTRENNUNG
(acac)(Pc)] (4b), which was reacted with 1,2-dicyanobenzene (34 mg,
0.26 mmol) and DBU (1 drop) in o-DCB/1-pentanol (1:1) (6 mL) to yield
30 mg of
883, 827, 814, 756, 732 cmꢀ1
.
[D7]DMF/CCl4/N2H4): d=11.4 (s, 8H; H-a), 11.32 (s, 1H; H-a’), 11.09 (s,
1H; H-a’), 11.00 (s, 1H; H-a’), 10.99 (s, 1H; H-a’), 10.96 (d, J=7.8 Hz,
1H; H-a’), 10.88 (s, 1H; H-a’), 10.83 (s, 1H; H-a’), 10.75 (s, 1H; H-a’),
9.46 (d, J=7.8, 1H; H-b’), 9.3–9.2 (m, 8H; H-b), 8.8–8.4 (m, 28H; H-
phenyl, H-AA’BB’), 5.34 (s, 2H; CH2OH), 1.6–1.5 ppm (m, 54H; C-
Benzoic acid, 4[(1’-octyl-3’,4’-fulleropyrrolidin-2’-yl]-[4’’-(1’’’,1’’’-dimethyl-
phenyl)] methyl ester (6):
mixture of compound 2[16] (70 mg,
A
0.07 mmol), DCC (14 mg, 0.07 mmol), and DMAP (9 mg, 0.07 mmol) was
reacted in dry THF (5 mL) at 08C for 20 min. Then, 4-tert-butyl-benzyl
alcohol (12 mg, 0.07 mmol) was added and the mixture was stirred for
2 days at room temperature. After that, the solvent was removed under
reduced pressure, toluene (10 mL) was added and the mixture was filtrat-
ed. The residue was purified by column chromatography on silica gel
using dichloromethane as eluent. Recrystallization from MeOH yielded
42 mg (52%) of pure 6 as a brown solid. M.p. >2508C; 1H NMR
(300 MHz, CDCl3): d=8.12 (d, J=7.9 Hz, 2H; H-Ar), 7.9 (brs, 2H; H-
Ar), 7.40 (s, 4H; H-Ar), 5.32 (s, 2H; CH2-Ar), 5.13 (d, J=9.3 Hz, 1H;
CH2-pyrr), 5.11 (s, 1H; CH-pyrr), 4.16 (d, J=9.4 Hz, 1H; CH2-pyrr), 3.1–
3.0 (m, 1H; CH2N), 2.6–2.5 (m, 1H; CH2N), 1.9–1.8 (m, 2H; CH2CH3),
1.4–1.3 (m, 10H; CH2), 1.42 (s, 9H; C(CH)3)3), 0.9–0.8 ppm (m, 3H;
CH3); 13C NMR (300 MHz, CDCl3): d=166.5 (CO), 156.5, 154.3, 153.3,
153.0, 151.6, 147.5, 146.7, 146.6, 146.5, 146.4, 146.3, 146.2, 146.1, 146.0,
145.9, 145.7, 145.6, 145.5, 145.4, 145.3, 144.9, 144.8, 144.6, 144.5, 143.3,
143.2, 143.1, 142.9, 142.8, 142.7, 142.5, 142.4, 142.3, 142.2, 142.1, 142.0,
141.9, 141.7, 140.4, 140.1, 139.7, 137.2, 136.7, 136.1, 135.8, 133.1, 130.4,
130.2, 129.6, 128.5, 125.7, 82.3 (OCH2), 69.2 (NCHC6H4), 67.1 (CH2N),
ACHTUNGTRENNUNG(CH3)3); MS (MALDI, dithranol): m/z: 2171–2177; UV/Vis (CHCl3): lmax
(log e)=915 (3.5), 679 (5.4), 612 (4.8), 486 (4.6), 326 nm (5.3); FT-IR
(KBr) : n˜ =2958, 2360, 2341, 1598, 1507, 1486, 1444, 1392, 1362, 1318,
1291, 1264, 1215, 1176, 1113, 1093, 1034, 1023, 1013, 922, 883, 829,
779 cmꢀ1
[LuIII(Pc)
[Ln(acac)3]·nH2O (31 mg, 0.09 mmol) in o-DCB (4 mL) gave [Lu-
.
A
ACHTUNGTRENNUNG
(Pc’)] (3c) :H2Pc 5[23] (120 mg, 0.08 mmol), DBU (1 drop), and
ACHTUNGTRENNUNG
(acac)(Pc)] (4c), which was reacted with 1,2-dicyanobenzene (41 mg,
0.32 mmol) and DBU (1 drop) in o-DCB/1-pentanol (1:1) (6 mL) to yield
33 mg of
a
green solid (19%). M.p. >3008C; 1H NMR (300 MHz,
[D7]DMF/CCl4/N2H4): d=9.4–9.3 (m, 6H; H-a), 9.19 (s, 1H; H-a’), 9.1–
9.0 (m, 2H; H-a), 8.97 (d, J=7.9 Hz, 1H; H-a’), 8.75 (s, 1H; H-a’), 8.74
(s, 1H; H-a’), 8.7–8.6 (m, 4H; H-a’), 8.4–8.2 (m, 8H; H-b), 8.04 (d, J=
7.9 Hz, 1H; H-b’), 8.0–7.9 (m, 16H; H-phenyl), 7.8–7.7 (m, 12H; H-
phenyl, H-AA’BB’), 5.04 (s, 1H; CH2OH), 1.8–1.6 ppm (m, 54H; C-
ACHTUNGTRENNUNG(CH3)3); MS (MALDI, dithranol): m/z: 2194–2200; UV/Vis (CHCl3): lmax
53.4 (NCH2CH2), 34.8 (CACHTUNTGRENN(UG CH3)3), 32.1 (CH2CH2CH3), 31.5 (CACHTUNGTRENNUNG(CH3)3),
(log e)=922 (3.2), 668 (5.5), 603 (4.7), 463 (4.6), 322 nm (5.3); FT-IR
(KBr) : n˜ =2956, 2865, 1718, 1644, 1604, 1507, 1480, 1446, 1393, 1363,
1319, 1290, 1263, 1214, 1175, 1110, 1078, 1038, 1023, 1013, 882, 827, 752,
29.8 (CH2), 29.5 (CH2), 28.5 (CH2CH2N), 27.7 (CH2CH2CH2N), 22.9
(CH3CH2), 14.4 ppm (CH3CH2); MS (MALDI, dithranol): m/z: 1142
[M+H]+; HRMS (MALDI, dithranol): m/z: calcd for C88H39NO2:
1141.2981; found: 1141.2961; UV/Vis (CHCl3): lmax (log e)=431 (2.6),
331 (sh) (4.5), 257 nm (5.1); FT-IR (KBr) : n˜ =2950, 2920, 2851, 1719,
730 cmꢀ1
.
Standard procedure for the synthesis of [LnIII(Pc)
ACHTNUTRGNE(UNG Pc’)]–C60 (Ln=Sm,
Eu, Lu) (1a–c): A mixture of 2,[24] DMAP, and DCC in dry THF was re-
acted at 08C for 20 min. Then, the corresponding lanthanide bis(phthalo-
cyaninato) 3a–c was added, and the mixture was stirred for two days at
room temperature. After that, the solvent was removed under reduced
pressure, hexane was added and the mixture was filtrated. The residue
was first purified by size exclusion chromatography (THF) and then by
column chromatography on silica gel using chloroform as eluent. Repeat-
ed chromatography followed by recrystallization from MeOH afforded
1609, 1459, 1422, 1370, 1267, 1171, 1097, 1017, 818, 765, 710 cmꢀ1
.
Acknowledgements
pure [LnIII(Pc)
[SmIII(Pc)
(Pc’)]-C60 ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
Funding from MEC (CTQ2008-00418/BQU, CONSOLIDER-INGENIO
2010 CDS2007-00010 NANOCIENCIA MOLECULAR), ESF-MEC
(MAT2006-28180-E, SOHYDS), COST Action D35, and CAM (S-0505/
PPQ/000225) is acknowledged. This work was also supported by the
Deutsche Forschungsgemeinschaft through SFB583, DFG (GU 517/4-1),
FCI, and the Office of Basic Energy Sciences of the U.S. Department of
Energy.
A
U
(6 mg, 0.03 mmol), DCC (30 mg, 0.03 mmol), and 3a (60 mg, 0.03 mmol)
in THF (10 mL) yielded 48 mg of a green solid (52%). M.p. >3008C;
1H NMR (300 MHz, [D7]DMF/CCl4/N2H4): d=8.6–8.4 (m, 8H; H-a),
8.3–8.2 (m, 8H; H-a’), 8.0–7.8 (m, 25H; H-b, H-bꢉ, H-phenyl), 7.5–7.3
(m, 12H; H-phenyl, H-AA’BB’), 1.7–1.4 ppm (m, 54H; C(CH)3)3); MS
(MALDI, dithranol): m/z: 3144–3156, 2430 [MꢀC60]+; UV/Vis (CHCl3):
lmax (log e)=914 (3.0), 681 (5.0), 615 (4.5), 489 (4.3), 326 nm (5.1); FT-IR
(KBr) : n˜ =3423, 2960, 2926, 2865, 1713, 1607, 1508, 1481, 1448, 1394,
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1364, 1319, 1263, 1217, 1176, 1091, 1023, 883, 804, 731 cmꢀ1
[EuIII(Pc) (1b) : Compound 2[24] (30 mg, 0.03 mmol), DMAP
(Pc’)]-C60
.
A
R
ACHTUNGTRENNUNG
(6 mg, 0.03 mmol), DCC (30 mg, 0.03 mmol), and 3b (60 mg, 0.03 mmol)
in THF (10 mL) yielded 48 mg of a green solid (48%). M.p. >3008C;
1H NMR (300 MHz, [D7]DMF/CCl4/N2H4): d=11.5 (s, 8H; H-a), 11.0–
10.7 (m, 8H; H-a’), 9.5 (d, J=7.8 Hz, 1H; H-b’), 9.3 (s, 8H; H-b), 8.8–8.4
(m, 28H; H-phenyl, H-AA’BB’), 1.5–1.3 ppm (m, 54H; C(CH)3)3); MS
(MALDI, dithranol): m/z: 3148–3156, 2431 [MꢀC60]+; UV/Vis (CHCl3):
lmax (log e)=914 (3.4), 679 (5.0), 612 (4.4), 485 (4.2), 326 nm (5.0); FT-IR
(KBr) : n˜ =3443, 2952, 2921, 2851, 1713, 1596, 1506, 1485, 1441, 1392,
1361, 1318, 1263, 1216, 1173, 1112, 1092, 1038, 1013, 881, 828, 754,
729 cmꢀ1
[LuIII(Pc) (1c) : Compound 2[24] (20 mg, 0.02 mmol), DMAP
ACHTUNGTRENNUNG(Pc’)]-C60 ACHTUNGTRENNUNG
.
N
(3 mg, 0.02 mmol), DCC (6 mg, 0.02 mmol), and 3c (39 mg, 0.02 mmol)
in THF (10 mL) yielded 32 mg of a green solid (52%). M.p. >3008C;
1H NMR (300 MHz, [D7]DMF/CCl4/N2H4): d=9.4–9.3 (m, 6H; H-a), 9.2
(s, 1H; H-a’), 9.1 (s, 2H; H-a), 9.0 (s, 1H; H-a’), 8.8–8.6 (m, 6H; H-a’),
8.5–8.2 (m, 9H; H-b, H-b’), 8.1–7.9 (m, 24H; H-phenyl), 7.8–7.6 (m, 4H;
H-AA’BB’), 6.0–5.3 (m, 3H; H-pyrrol), 1.8–1.5 ppm (m, 54H; C(CH)3)3);
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124
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Received: August 6, 2009
Published online: December 8, 2009
Chem. Eur. J. 2010, 16, 114 – 125
ꢆ 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
125