Subphthalocyanines: Tuneable molecular scaffolds for intramolecular electron and energy transfer processes

Article abstract of DOI:10.1021/ja039883v

A series of four subphthalocyanine-C₆₀ fullerene dyads have been prepared through axial functionalization of the macrocycle with m-hydroxybenzaldehyde and a subsequent dipolar cycloaddition reaction. The subphthalocyanine moiety has been peripherally functionalized with substituents of different electronic character, namely fluorine or iodine atoms and ether or amino groups, thus reaching a control over its electron-donating properties. This is evidenced in cyclic voltammetry experiments by a progressive shift to lower potentials, by ca. 200 mV, of the first oxidation event of the SubPc unit in the dyads. As a consequence, the energy level of the SubPc ^.+-C₆₀^.- charge-transfer state may be tuned so as to compete with energy transfer deactivation pathways upon selective excitation of the SubPc component. For instance, excitation of those systems where the level of the radical pair lies high in energy triggers a sequence of exergonic photophysical events that comprise (i) nearly quantitative singlet-singlet energy transfer to the C₆₀ moiety, (ii) fullerene intersystem crossing, and (iii) triplet-triplet energy transfer back to the SubPc. On the contrary, the stabilization of the SubPc^.+-C ₆₀^.- radical pair state by increasing the polarity of the medium or by lowering the donor-acceptor redox gap causes charge transfer to dominate. In the case of 1c in benzonitrile, the thus formed radical pair has a lifetime of 0.65 ns and decays via the energetically lower lying triplet excited state. Further stabilization is achieved for dyad 1d, whose charge-transfer state would lie now below both triplets. The radical pair lifetime consequently increases in more than 2 orders of magnitude with respect to 1c and presents a significant stabilization in less polar solvents, revealing a low reorganization energy for this kind of SubPc-C₆₀ systems.

Full text of DOI:10.1021/ja039883v

Published on Web 05/01/2004
Subphthalocyanines: Tuneable Molecular Scaffolds for
Intramolecular Electron and Energy Transfer Processes
David Gonza´lez-Rodr´ıguez,† Toma´s Torres,*,† Dirk M. Guldi,*,‡ Jose´ Rivera,§,|
Maria AÄ ngeles Herranz,§ and Luis Echegoyen*,§
Contribution from the Departamento de Qu´ımica Orga´nica, Facultad de Ciencias,
UniVersidad Auto´noma de Madrid, E-28049 Madrid, Spain; the Radiation Laboratory,
UniVersity of Notre Dame, Indiana 46556; and the Department of Chemistry,
Clemson UniVersity, South Carolina 29634
Received December 1, 2003; E-mail: tomas.torres@uam.es; guldi.1@nd.edu; luis@clemson.edu
Abstract: A series of four subphthalocyanine-C60 fullerene dyads have been prepared through axial
functionalization of the macrocycle with m-hydroxybenzaldehyde and a subsequent dipolar cycloaddition
reaction. The subphthalocyanine moiety has been peripherally functionalized with substituents of different
electronic character, namely fluorine or iodine atoms and ether or amino groups, thus reaching a control
over its electron-donating properties. This is evidenced in cyclic voltammetry experiments by a progressive
shift to lower potentials, by ca. 200 mV, of the first oxidation event of the SubPc unit in the dyads. As a
consequence, the energy level of the SubPc•+-C60•- charge-transfer state may be tuned so as to compete
with energy transfer deactivation pathways upon selective excitation of the SubPc component. For instance,
excitation of those systems where the level of the radical pair lies high in energy triggers a sequence of
exergonic photophysical events that comprise (i) nearly quantitative singlet-singlet energy transfer to the
C60 moiety, (ii) fullerene intersystem crossing, and (iii) triplet-triplet energy transfer back to the SubPc. On
the contrary, the stabilization of the SubPc•+-C60•- radical pair state by increasing the polarity of the medium
or by lowering the donor-acceptor redox gap causes charge transfer to dominate. In the case of 1c in
benzonitrile, the thus formed radical pair has a lifetime of 0.65 ns and decays via the energetically lower
lying triplet excited state. Further stabilization is achieved for dyad 1d, whose charge-transfer state would
lie now below both triplets. The radical pair lifetime consequently increases in more than 2 orders of
magnitude with respect to 1c and presents a significant stabilization in less polar solvents, revealing a low
reorganization energy for this kind of SubPc-C60 systems.
Introduction
In such synthetic systems, C60 fullerenes have been widely
employed as the electron-acceptor unit, due to their unique re-
dox6 and structural7 properties. On the other hand, the prominent
ground-state absorption in the visible region of the spectrum of
π-conjugated macrocycles, such as porphyrins and phthalocya-
Conversion of solar energy into profitable chemical energy
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energy sources, chemical3 or electrical equivalents,4 or into
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† Universidad Auto´noma de Madrid.
‡ University of Notre Dame.
§ Clemson University.
| Current address: Department of Chemistry, Pontificial Catholic Uni-
versity, Ponce, Puerto Rico 00731. E-mail: jorivera@pucpr.edu
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J. AM. CHEM. SOC. 2004, 126, 6301-6313
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A R T I C L E S
Gonza´lez-Rodr´ıguez et al.
nines,8 together with their rich redox chemistry, provides both
excellent light-harvesting and electron-donor performances. In
render a C3-symmetrical cone-shaped structure14 that may give
rise to chirality when appropriately substituted.15
addition, porphyrin-9 or phthalocyanine-C60 arrays com-
Within the context of solar energy conversion, the strong
fluorophore features that SubPcs display in the visible are
promising means for efficient light harvesting. In particular,
intense Q-band transitions, in the 550-650 nm region, whose
extinction coefficients are on the order of ∼50.000 M-1 cm-1
clearly outscore those of porphyrins and metalloporhyrins. Their
high electronic excitation energy, exceeding 2.0 eV, is conceived
to power a strongly exergonic electron transfer, which subse-
quently intercedes the conversion between light and chemical/
electrical energy. Moreover, the rigid nonplanar SubPc core
affords small Stokes shifts and very low reorganizational
energies,19a which are both fundamental requisites for efficient
intramolecular electron/energy transfer reactions. In conclusion,
these characteristics render SubPcs a potential light-harvesting
synthon for the integration into novel donor-acceptor arrays.
Because of the versatile chemistry of SubPcs,11 their assembly
into multicomponent photo- and electroactive systems may be
performed via different routes involving peripheral20 or axial
functionalization.14c-e,21 The axial approach bears the two-fold
advantage that the macrocycle preserves its electronic charac-
teristics, since the substitution pattern on the benzene rings
remains unaltered, and that the preparation of unsymmetrically
substituted SubPcs, which would lead to specific dyads, is not
required. From our own experience, the exchange of the original
halogen atom with oxygen nucleophiles, particularly phenols,
is a very convenient method for increasing the solubility and
stability of these molecules and, at the same time, for introducing
diverse functional groups in the axial position of the ring.21b
We recently communicated the synthesis of SubPc-C60 dyads
in which the two components were linked through isomeric
ortho-, meta-, or para-substituted phenoxy spacers.22 In these
10
monly retain the characteristic low reorganization energies of
fullerenes and are therefore ideally suited for the high-yield
generation of long-lived charge-separated radical ion pairs.
Though these planar aromatic molecules have been the subject
of extensive research in this field, the potential of subphthalo-
cyanines (SubPcs),11 the singular lower analogues of phthalo-
cyanines, as active components in chemically/electronically
coupled systems is yet to be determined. Despite their early
discovery in 1972,12 the interest of the scientific community in
SubPcs actually arose in the 1990s, originally as synthetic
precursors of unsymmetrically substituted phthalocyanines,13 as
first described by Kobayashi and co-workers, and then in view
of their remarkable structural14,15 and physical properties.16-19
SubPcs are 14 π-electron aromatic macrocycles that comprise
three N-fused diiminoisoindole units and an axial ligand around
a tetracoordinated boron atom. Accordingly, these molecules
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(16) SubPcs have been considered as potential candidates in electrolithography
or printing technologies. (a) Reynolds, S. J.; Gairns, R. S.; Simpson, P. A.
(Zeneca Ltd.) PCT Int. Appl. WO 94,24,612, 1994 [Chem. Abstr. 1995,
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(17) For high-density optical recording applications of SubPcs, see: (a) Wang,
Y.; Gu, D.; Gan, F. Opt. Commun. 2000, 183, 445-450. (b) Wang, Y.;
Gu, D.; Gan, F. Phys. Status Solidi A 2001, 186, 71-77. (c) See also the
patents cited in ref 11.
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Lo´pez, F.; Sastre, A.; Torres, T.; Torruellas, W. E.; Stegeman, G. I. J.
Phys. Chem. 1995, 99, 14988-14991. (b) Sastre, A.; Torres, T.; D´ıaz-
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Zyss, J. J. Am. Chem. Soc. 1996, 118, 2746-2747. (c) Rojo, G.; Hierro,
A.; D´ıaz-Garc´ıa, M. A.; Agullo´-Lo´pez, F.; del Rey, B.; Sastre, A.; Torres,
T. Appl. Phys. Lett. 1997, 70, 1802-1804. (d) Rojo, G.; Agullo´-Lo´pez, F.;
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J. A.; Beggs, M.; Ensley, H. E.; Schmehl, R. H. J. Phys. Chem. A 1998,
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M and P, have been separated by chiral HPLC. (a) Claessens, C. G.; Torres,
T. Tetrahedron Lett. 2000, 41, 6361-6365. (b) Kobayashi, N.; Nonomura,
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Subphthalocyanines: Tuneable Molecular Scaffolds
A R T I C L E S
Figure 1. Structure and AM1-minimized model24 of SubPc-C60 dyads 1a-d, reference SubPcs 2a-d and fulleropyrrolidine 3.
Scheme 1. Synthesis of SubPc-C60 Dyads 1a-d
systems, we demonstrated a distance-dependent quenching of
the SubPc fluorescence by singlet-singlet energy transfer to
the fullerene unit. As one step further, we describe herein the
effect of the modulation of the electronic properties of the
macrocyclic moiety, while maintaining the same interchromo-
phoric distance, on the electrochemical and photophysical
properties of SubPc-C60 dyads (Figure 1). Thus, a m-disub-
stituted spacer was chosen as a compromise between the two
other extreme o- and p-topologies,22 and different peripheral
groups (i.e., fluorine or iodine atoms and unprecedented ether
or amino groups) were introduced in the SubPc core in order
to control the competition between energy and electron-transfer
phenomena to the fullerene.23
Results and Discussion
Synthesis. SubPcs 5a-c (Scheme 1) were synthesized by
condensation reaction of the corresponding phthalonitriles 4a-c
in the presence of boron trichloride, following a procedure
(23) (a) Guldi, D. M.; Luo, C.; Swartz, A.; Go´mez, R.; Segura, J. L.; Mart´ın,
N.; Christoph, B.; Serdar, S. N. J. Org. Chem. 2002, 67, 1141-1152. (b)
Guldi, D. M.; Swartz, A.; Luo, C.; Go´mez, R.; Segura, J. L.; Mart´ın, N. J.
Am. Chem. Soc. 2002, 124, 10875-10886.
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A R T I C L E S
Gonza´lez-Rodr´ıguez et al.
recently reported by us.21b So far, the high tendency of boron
halides to cleave ether groups25 precluded the synthesis of ether-
substituted SubPcs from alkyloxyphthalonitriles.26 We found,
however, that the diphenyl ether moiety is stable enough to
survive a BCl3 cyclotrimerization and SubPc 5c could be
obtained in moderate yields (39%).
The axial chlorine atom in compounds 5a-c was efficiently
replaced with phenol derivatives heating a mixture of the
corresponding SubPc and an excess of phenol (for 2a-c) or
3-hydroxybenzaldehyde (for 6a-c) in toluene. The reaction rate
was found to be greatly dependent on the electronic nature of
both the macrocycle and the phenol, decreasing for SubPcs
bearing electron-withdrawing groups and for the formylphenol
(see Experimental Section). So, in these conditions, the reaction
between 5a and 3-hydroxybenzaldehyde proceeded very slowly
and the yield was improved using molten phenol as solvent.21b
With the aim of enhancing the donor ability of the macro-
cycle, the palladium-catalyzed cross-coupling methodology
between amines and aryl halides, mainly developed in the groups
of Buchwald and Hartwig,27 was tested on triiodoSubPcs 2b
and 6b. These reactions commonly employ a tert-butoxide base
that, in our case, produced the rapid decomposition of the
macrocycle. The substitution of this base by cesium carbonate,27b,28
however, allowed for the first time the synthesis of amino-
substituted SubPcs, which were obtained in excellent yields
(87% (2d) and 82% (6d)) considering that three C-N bonds
are being formed in one step. Despite this, any attempt to carry
out this amination reaction directly on dyad 1b was fruitless,
in all cases recovering the starting material.29
SubPc-C60 dyads 1a-d were prepared by a 1,3 dipolar
cycloaddition reaction between formyl-substituted SubPcs 6a-d
and C60 in the conditions described by Prato.30 Monoaddition
products were isolated in moderate yields (∼45%), and in all
cases, a small amount of bisadducts (∼8%) was also obtained.
Fulleropyrrolidine 3 was synthesized from 4-methoxybenz-
aldehyde following a similar procedure.31 In this instance, the
formation of multiple-addition compounds was more significant,
most probably due to the smaller steric effect of the aldehyde.
Dyads 1a-d are quite soluble in aromatic solvents (i.e., toluene,
o-dichlorobenzene, benzonitrile) and carbon disulfide. In contrast
to the starting SubPcs, they are sparingly soluble in other
common organic solvents (i.e., acetone, CH2Cl2, CHCl3). The
presence of diphenylamino groups in the macrocyclic benzene
rings increases notably the solubility of 1d with respect to the
other dyads.
Figure 2. Aromatic portion of the 1H NMR (300 MHz, CDCl3) spectra of
the C3 regioisomers of 2d and 1d. The presence of a 1:1 mixture of
diastereoisomers in 1d is reflected in the splitting of some of the signals.
1
All the compounds were purified and characterized by H
NMR, 13C NMR, UV-vis, FAB-MS or MALDI-TOF-MS, FT-
IR, and elemental analysis. In the case of SubPcs 5b, 2b and
2d, or dyads 1b and 1d, in which the macrocycle is trisubsti-
tuted, the corresponding C3 and C1 regioisomers could be
separated by column chromatography and were individually
characterized.32 For the dyads, each of these isomers is
constituted by a 1:1 mixture of diastereoisomers, since they
possess two chiral elements: the subphthalocyanine itself15 and
the asymmetric carbon atom in the pyrrolidine ring. This is
manifested by a clear splitting or broadening of some of the
NMR proton signals, as illustrated in Figure 2 for the C3 isomer
of dyad 1d. Unfortunately, we did not succeed in the chro-
1
matographic separation of these diastereoisomers. In H NMR
spectra (see Supporting Information), the effect of the aromatic
macrocycle ring-current on the proton signals of the peripheral
benzene rings, shifted downfield, and on those of the axial
phenoxy spacer, that experience a significant shift to higher
fields, should also be noted. In the latter case, the magnitude
of the shift essentially depends on the distance of the protons
to the core of the macrocycle and, to a lesser extent, on the
electronic density of the π-system, being slightly more pro-
nounced for the dodecafluoroSubPcs (series a).
Electrochemistry. The solution electrochemistry of SubPcs
2a-d and SubPc-C60 dyads 1a-d was investigated in THF
under high vacuum conditions (see Experimental Section for
details). The redox potentials obtained (vs ferrocene) are
summarized in Table 1.
(24) Structural modeling was performed using the Hyperchem 6.03 package
(Hypercube, Inc.) for Windows.
(25) (a) Gerrard, W.; Lappert, M. F. J. Chem. Soc. 1952, 1486-1490. (b)
McOmie, J. F.; Watts, M. L.; West, D. E. Tetrahedron. 1968, 24, 2289-
2292. (c) Bhatt, M. V.; Kulkarnyi, S. U. Synthesis 1983, 249-282.
(26) The condensation of a crown-ether phthalonitrile in the presence of BPh3
has been reported, but the macrocycle was isolated in a very low yield
(<0.5%); see ref 13i.
(27) (a) Hartwig, J. F. Angew. Chem., Int. Ed. 1998, 37, 2046-2067. (b) Wolfe,
J. P.; Wagaw, S.; Marcoux, J.-F.; Buchwald, S. L. Acc. Chem. Res. 1998,
31, 805-818. (c) Hartwig, J. F. Acc. Chem. Res. 1998, 31, 852-860. (d)
Yang, B. H.; Buchwald, S. L. J. Organomet. Chem. 1999, 576, 125-146.
(28) Wolfe, J. P.; Buchwald, S. L. Tetrahedron Lett. 1997, 38, 6359-6362.
(29) This fact is not surprising, since fullerenes are known to efficiently
coordinate Pd(0) species in a µ2-fashion. For a general review, see: Balch,
A. L.; Olmstead, M. M. Chem. ReV. 1998, 98, 2123-2165.
(30) (a) Maggini, M.; Scorrano, G.; Prato, M. J. Am. Chem. Soc. 1993, 115,
9798-9799. (b) Prato, M.; Maggini, M. Acc. Chem. Res. 1998, 31, 519-
526. (c) Tagmatarchis, N.; Prato, M. Synlett 2003, 6, 768-779.
(31) (a) Zhou, D. J.; Gan, L. B.; Tan, H. S.; Luo, C. P.; Huang, C. H. Chin.
Chem. Lett. 1995, 6, 1033-1036. (b) Jing, B.; Zhang, D.; Zhu, D.
Tetrahedron Lett. 2000, 41, 8559-8563.
SubPcs 2a-d exhibit several reduction peaks, with a revers-
ible first reductive process that involves one electron (Figure
3). SubPcs 2a, c, and d exhibit an additional reversible second
reduction wave followed by an irreversible multiple-electron
reduction wave (not shown for 2d). This irreversibility seems
to be due to chemical reactions following multiple-electron
reductions.22 An irreversible wave is generally observed between
+372 and +1057 mV in the oxidative scan that seems to involve
one electron. Additional waves are observed at +616 and +824
mV in the case of 2d, the latter corresponding to a three-electron
(32) The electrochemical and photophysical studies were performed, however,
on a 1:3 mixture of C3/C1 regioisomers, due to their almost identical physical
properties.
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6304 J. AM. CHEM. SOC. VOL. 126, NO. 20, 2004

Subphthalocyanines: Tuneable Molecular Scaffolds
A R T I C L E S
Table 1. Oxidation Peak Potentials and E1/2 Data (THF, in mV vs
Ferrocene) of SubPc-C60 Dyads 1a-d, SubPcs 2a-d, and
Fulleropyrrolidine 3
Table 2. Kinetic and Spectroscopic Features of Photoexcited and
One-Electron Oxidized SubPc References 2a-d in Toluene
feature
2a
2b
2c
2d
1
a
2
a
3
a
1
b
2
b
3
b
E pa,ox
E pa,ox
E pa,ox
E 1/2,red
E 1/2,red
-1690
E 1/2,red
absorption maximum, nm
fluorescence maximum, nm
fluorescence quantum yield
fluorescence lifetime, ns
phosphorescence
maximuma, nm
573
585
0.4
1.66
835
571
585
0.08
0.51
835
570
585
0.49
1.76
844
618
650
0.15
1.5
2a
2b
2c
2dc
1a
1b
1c
1dc
3
+1057
+821
+600
-1088
-1323
-1511
-2051
-2079
+374 +616 +824 (3e) -1579
>850
+1047
+779 +998
+645
-1053 (2e) -1554
-1004
-1032
-1675
-1511
-1347
singlet excited-state
660
650
675
730
-1528 (2e) -2220
-1532 (2e) -2162
maximum, nm
+372 +586 +840 (3e) -1017
-910
singlet excited-state lifetime,
ns
1.73
0.59
1.81
1.26
-1432
-2019
s-1
5.8 × 108 1.7 × 109 5.5 × 108 7.9 × 108
a Since these oxidative processes are irreversible, only anodic peak
potentials are reported. b Reversible reduction processes. Standard electrode
potentials are reported. c A gold electrode was used as the working electrode.
triplet excited-state
maximum, nm
460
28
460
32
480
36
550
40
triplet excited-state
lifetime, µs
radical cation maximumb,
nm
620
620
620
685
a In methylcyclohexane, 2-methyltetrahydrofuran, ethyliodide (2:1:1 v/v).
b In dichloromethane.
potentials follow the same trend. Remarkably, 2d is the most
easily oxidized subphthalocyanine reported thus far.11
Dyads 1a-d essentially retain the anodic electrochemical
pattern of both the parent [60]fullerene and SubPcs 2a-d
(Figure 3). However, the irreversible oxidation potentials are,
in general, shifted to less positive values when compared to
those of SubPcs 2a-d (Table 1).
On the reduction scan, the waves can be assigned to the C60
or to the subphthalocyanine core. The first reversible reduction
1
waves are assigned in all the cases to the C60 core. For 1a (E 1/2,
red ) -1053 mV), this wave corresponds to a two-electron
process, since it overlays with the first reduction of the
subphthalocyanine moiety. In 1b, the reduction of both frag-
ments is clearly distinguished, but this is not the case for dyads
1c and 1d, where again, the second reduction wave is a two-
electron process, which involves the second reduction of the
C60 core and the first reduction of the oxo- or amino-SubPcs
1
(E 1/2,
) -1528 and -1532 mV, respectively). Dyad 1b
red
seems to be the easiest to reduce in the series (by ca. 15 mV),
but electrochemically, no ground-state interactions between both
electroactive units are observed in these dyads.
Photophysics. Because of the diverse oxidation potentials
that the newly synthesized SubPc moieties exhibit (vide supra),
we tested donor-acceptor dyads 1a-d by means of various
photolytic techniques (i.e., steady-state and time-resolved) and
compared their transient behavior with the excited-state proper-
ties featured by the adequate references, that is, SubPcs 2a-d,
which are summarized in Table 2, and fullerene 3.
SubPc References 2a-d. Despite the different substituents,
placed on the periphery of the SubPc core, 2a-c reveal nearly
superimposable singlet ground-state transitions. Soret-band like
absorptions are typically seen at 330 nm, while the energetically
lower lying Q-bands appear at 570 nm (Figure 4). This leads
to the conclusion that the SubPc substituent has little impact
on the S0fS2 and S0fS1 energy gaps. The only exception is
2d, whose transitions are considerably red-shifted (i.e., Q-band
maximum at 618 nm) bringing about marked changes in color
from the typical intense magenta (2a-b) to green (2d). SubPcs
2c and 2d present an additional broad band around 450 nm,
which is attributed to n-π* transitions.
Figure 3. Cyclic voltammograms of SubPcs 2a-d and dyads 1a-d in
THF and 0.1 M TBAPF6 as supporting electrolyte.
process due to the oxidation of the diphenylamino groups in
the SubPc.33 After a full anodic scan, strong adsorption occurred
in the working electrode, especially evident for amino-
substituted compounds, which seems to be the cause of this
irreversibility.
The nature of the peripheral substituents on the macrocycle
modify strongly the reduction and oxidation potentials of the
subphthalocyanines. The redox potentials follow the trend one
would anticipate from the substitution pattern, the amino
derivative 2d being the easiest to oxidize (E1pa,ox ) +374 mV),
followed by the oxo derivative 2c (E1
) +600 mV) and
pa,ox
finally the SubPcs featuring iodo and fluoro substituents 2a and
2b (E1pa,ox ) +821 and +1057 mV, respectively). The reduction
(33) Liu, S.-G.; Shu, L.; Rivera, J.; Liu, H.; Raimundo J.-M.; Roncali, J.;
Gorgues, A.; Echegoyen, L. J. Org. Chem. 1999, 64, 4884-4886.
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A R T I C L E S
Gonza´lez-Rodr´ıguez et al.
Figure 4. UV-vis spectra of SubPcs 2a (pink), 2b (blue), 2c (red), and
2d (green) in CHCl3.
The substitution pattern that the reference SubPcs bear,
including heavy atom providing iodine, on the other hand, exerts
notable effects on the fluorescing features (i.e., λmax ) 585 nm).
For example, diverse fluorescence quantum yields of the SubPc
emission were detected in room-temperature experiments, which
are as low as 0.08 (2b) but reach up to 0.49 (2c). From the 585
nm fluorescence maxima, we derive singlet excited state energies
of 2.1 eV. It is important to note that these values are
substantially and slightly higher than those seen for phthalo-
cyanines (∼1.7 eV) and porphyrins (∼2.0 eV), respectively.8
The fluorescence lifetimes, another radiative property, paralleled
the aforementioned fluorescence quantum yields. Hereby a good
correlation was established between these two radiative param-
eters; that is, higher quantum yields coincide always with longer
lifetimes. Again 2d is different, with a rather low singlet excited-
state energy of 1.9 eV.
Since we are concerned with determining the excited-state
energy levels of these novel chromophores, we complemented
the emission assay with phosphorescence measurements in the
reference SubPcs 2a-d. These inherently weak features, with
room-temperature quantum yields well below our ∼ 10-6
detection limit, necessitated working at low temperature (i.e.,
frozen glass matrix) and with the help of ethyliodide, a classical
heavy atom provider. As a result, the fluorescent SubPc singlet
excited state, emitting around 585 nm, was qualitatively
abolished. Instead, a new emitting transition, located in the near-
infrared region (i.e., 835 nm -2b), was registered. We ascribe
the latter to the phosphorescent triplet state (see Figure S1 in
Supporting Information). Based on these maxima, we derive
triplet energies of 1.45 eV, in accordance with previous studies
that set an upper limit for this energy level of 1.7 eV.18e
Considering singlet-triplet energy gaps of ca. 0.65 eV in
subphthalocyanines, we notice an evident trend towards larger
gaps relative to phthalocyanines (0.2 eV) and porphyrins (0.5
eV). For 2d, the phosphorescence lies outside of our detection
limit, which shifts its triplet energy below 1.45 eV.
Figure 5. Differential absorption spectra obtained (a) upon picosecond flash
photolysis (532 nm) and (b) upon nanosecond flash photolysis (532 nm) of
∼1.0 × 10-5 M solutions of SubPc 2b in nitrogen saturated toluene with
a time delay of 25 ps and 50 ns, respectively.
in the blue region, similar to the features shown in Figure 5b.
Particularly important are the nearly identical time constants
of the decay (2a: 5.8 × 108 s-1) and growth (2a: 4.5 × 108
s-1) processes, which leads consequently to the conclusion that
a spin-forbidden intersystem crossing (ISC) to the energetically
lower-lying triplet excited-state prevails. It is worthwhile to
underline that the kinetics of ISC reveal a strong resemblance
with the fluorescence dynamics.
An additional test in support of the ISC hypothesis required
examining the triplet absorption characteristics in nanosecond
experiments, for example, following 10 ns pulses at 532 nm.
In this context, probing similar solutions in nanosecond experi-
ments allowed the confirmation of the picosecond experiments.
In fact, the triplet-triplet maxima were, as shown in Figure
5b, in perfect accord with the spectral features observed at the
end of the picosecond time scale.
In addition to characterizing the ground and excited states of
SubPcs 2a-d, we examined the differential absorption changes
of their oxidized states as well. More specifically, we subjected
solutions of approximately 5.0 × 10-5 M of 2a-d to pulse
radiolytic oxidation in oxygenated dichloromethane. In short,
these pulse radiolysis conditions lead to the instantaneous
formation of the solvent radical cations (i.e., [CH2Cl2]•+) and
In terms of nonfluorescing singlet-singlet transitions, all the
singlet excited states display, besides their strong bleaching in
the Q-band region, characteristic features in the far visible. For
example, following a 18 ps laser pulse, photoexcitation of 2a-d
led to the instantaneous formation of sharp maxima in the 620-
750 nm region; see Figure 5a. Typically, these transients are
short-lived with decay dynamics that obey to a monoexponential
rate law, yielding rates on the order of 109 s-1. While the
absorption changes in the near-infrared are governed by the
disappearance of the singlet-singlet absorption, simultaneous
formation of new maxima, typically around 450 nm, were noted
•
the associated peroxyl radicals (i.e., OOCH2Cl/•OOCHCl2).34
Both are known to initiate the selective one-electron oxidation
of macrocyclic systems, including porphyrins, phthalocyanines,
and so forth. In this light, we ascribe the differential absorption
changes to the one-electron oxidized π-radical cation (see Figure
S2 in Supporting Information). Important attributes are, besides
(34) Shank, N. E.; Dorfman, L. M. J. Chem. Phys. 1970, 52, 4441-4447.
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6306 J. AM. CHEM. SOC. VOL. 126, NO. 20, 2004

Subphthalocyanines: Tuneable Molecular Scaffolds
A R T I C L E S
Table 3. Photophysical Parameters of SubPc-C60 Dyads 1a-d
feature
solvent
1a
1b
1c
1d
fluorescence maximum, nm
toluene
toluene
ODCB
bzcn
toluene
ODCB
bzcn
toluene
ODCB
bzcn
588
592
588
655
fluorescence quantum yield (SubPc)
1.2 × 10-3
1.1 × 10-3
1.4 × 10-3
5.0 × 10-4
4.5 × 10-4
4.4 × 10-4
<0.1
9.6 × 10-4
1.0 × 10-3
9.6 × 10-4
4.8 × 10-4
4.7 × 10-4
3.9 × 10-4
<0.1
3.1 × 10-3
2.8 × 10-3
2.9 × 10-3
4.9 × 10-4
4.7 × 10-4
1.3 × 10-5
<0.1
1.1 × 10-3
7.8 × 10-4
5.1 × 10-4
<10-4
fluorescence quantum yield (C60)
fluorescence lifetime (SubPc), ns
fluorescence lifetime (C60), ns
0.25
0.22
0.2
toluene
ODCB
bzcn
1.44
1.39
1.42
1.17
1.26
1.21
1.27
1.24
0.14
0.52
0.28
0.16
singlet excited-state lifetime (SubPc)
toluene
0.05 ns
2.0 × 1010 s-1
b
0.041 ns
2.4 × 1010 s-1
b
0.04 ns
2.5 × 1010 s-1
b
0.25 ns
4.0 × 10-9 s-1
0.20 ns
5.0 × 10-9 s-1
0.16 ns
6.25 × 10-9 s-1
a
THF
bzcn
0.031 ns
3.2 × 1010 s-1
1.25
singlet excited-state lifetime (C60), ns
toluene
THF
bzcn
toluene
ODCB
bzcn
1.39
1.30
1.35
0.48
0.43
0.43
1.25
1.29
1.21
0.43
0.43
0.40
0.2
triplet excited-state quantum yield (SubPc)
0.45
0.42
radical pair state
0.1
a Masked by the strong SubPc features. b Not stable.
the transient bleaching of the Q-bands around 560 nm, a new
broad transition, which centers around 620 nm.
Fullerene Reference 3. The well-known excited-state proper-
ties of fullerene reference 3, that is, a fulleropyrrolidine, shall
be discussed in brief, since they emerge as important reference
points for the interpretation of the features seen in dyads 1a-
d.9g In contrast to SubPcs 2a-d, the fullerene emission is rather
weak with a quantum yield of 6 × 10-4, despite the comparable
fluorescence lifetime of ca. 1.5 ns. The singlet excited state,
displaying a distinctive singlet-singlet transition around 880
nm, undergoes a quantitative intersystem crossing with a rate
of 5 × 108 s-1. The ISC process yields the long-lived triplet
manifold, for which maxima are noted at 360 and 700 nm,
followed by a low-energy shoulder at 800 nm.
Figure 6. Fluorescence spectra of SubPc 2b (dashed line) and dyad 1b
(solid line) in toluene with matching absorption at the 570 nm excitation
Dyads 1a-d. The electronic absorption spectra of the
SubPc-C60 ensembles display common features of each subunit
(see Supporting Information). The presence of the fullero-
pyrrolidine fragment is evidenced by the higher absorption
between 250 and 350 nm and in the weak typical band around
430 nm, whereas the macrocyclic unit dominates the red part
of the spectrum, its Q-band suffering a small bathochromic shift
in the dyads.
First, quantitative information on intramolecular deactivation
of, for instance, the photoexcited subphthalocyanine chro-
mophore (i.e., excitation at 570 nm) was lent from fluorescence
experiments, steady-state and time-resolved. Importantly, when
the SubPc fluorescence in dyads 1a-d is compared with that
in references 2a-d, a strong decrease in intensity is noted
(Figure 6). While we determined quantum yields for 2a-d on
the order of 0.5, in 1a-d representative values are typically on
the order of (7.5 ( 2.5) × 10-4; see Table 3. The difference in
fluorescing quenching between the individual solvents is
marginally small, suggesting intramolecular processes that
proceed with nearly activationless kinetics.
wavelength; O.D.570
toluene (solid line), o-dichlorobenzene (dashed line), and benzonitrile (dotted
line).
) 0.5. Inset: Fluorescence spectra of dyad 1b in
nm
quantum yields, we can approximate the deactivation rates,
which correspond to intramolecular events of 1010 s-1
Although, at the chosen 570 nm excitation wavelength, the
fullerene absorption (ꢀ570
irrelevant role, relative to the strong absorption of the sub-
phthalocyanine (ꢀ570
parallel with the reduced SubPc fluorescence, the typical
fullerene fluorescence at lower energies, as shown in Figure 6.
In particular, in most solvents and most compounds, the 720
nm fingerprint is seen. The determination of the fullerene
fluorescence quantum yield, employing 3 as a standard with
matching absorption at the excitation wavelength, afforded
values that are ∼5 × 10-4. Since these Φ-values nearly approach
that measured for 3, namely, 6.0 × 10-4, this process appears
to be nearly quantitative. Because of the dominant absorp-
tion of the SubPc moiety at the 570 nm excitation wave-
length, we gather a highly efficient transduction of singlet
excited-state energy from the photoexcited subphthalocyanine
to the fullerene.22
.
≈ 2.000 M-1 cm-1) plays an
nm
≈ 50.000 M-1 cm-1), we noticed,
nm
Likewise with the fluorescence quantum yields, the SubPc
fluorescence lifetimes are noticeably shorter in 1a-d relative
to what was seen in 2a-d. Considering both lifetimes and
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J. AM. CHEM. SOC. VOL. 126, NO. 20, 2004 6307

A R T I C L E S
Gonza´lez-Rodr´ıguez et al.
Figure 8. Time-absorption profiles at 650 nm (solid line) and 880 nm
(dashed line) of dyad 1b in nitrogen saturated toluene; the intensity of the
solid line is decreased by a factor of 2. The baseline drift in the time window
prior to the laser pulse is due to scattering.
Figure 7. Excitation spectra (normalized to exhibit matching signals around
570 nm) of SubPc 2b (dashed line) and dyad 1b (solid line) in toluene
monitoring the SubPc emission around 600 nm and the fullerene emission
at 720 nm, respectively.
Since the energy transfer process is thermodynamically
feasible, we probed excitation spectra of the fullerene emission.
In line with our energy transfer hypothesis, the excitation
spectrum resembles the ground-state spectrum of the SubPc and
the excitation spectrum of the SubPc fluorescence; an illustration
is given in Figure 7, displaying the spectra of 2b and dyad 1b.
In conclusion, the fluorescence assay prompts for dyads 1a-c
to a rapid and nearly quantitative transfer of singlet-excited-
state energy from the subphthalocyanine (2.1 eV) to the fullerene
moiety (1.76 eV).
Exceptions from this trend are dyad 1c in benzonitrile and
dyad 1d in all the solvents studied. In the earlier case, no
fullerene emission was seen at all. In the latter case, the red-
shifted SubPc fluorescence extends into the region of the
fullerene fluorescence, which, in turn, renders a quantitative and
exact quantum yield determination rather difficult. But in
comparing the fluorescence ratio at 560 versus 720 (i.e.,
fluorescence maxima of the SubPc and fullerene core) in
reference 2d and dyad 1d, we can estimate an upper fluorescence
quantum yield (Φ < 1.0 × 10-4) for the fullerene moiety.
Interestingly, the SubPc moiety in dyad 1d is the best electron
donor among those investigated. Thus, we postulate at this point
that here an intramolecular electron-transfer process may occur;
more details will follow below.
As far as the time-resolved fluorescence decay measurements
are concerned, only the fullerene contributions were seen at
∼715 nm with fluorescence lifetimes (∼1.5 ns) that are, in dyads
1a-c, virtually indistinguishable from those measured for 3.
In other words, once formed, the fullerene singlet excited state
decays via the ordinary ISC process. In 1d, on the other hand,
the fullerene fluorescence is much shorter lived, indicating that
it decays via a rapid intramolecular electron transfer; see below.
Please note that detection of the subphthalocyanine fluorescence
was hampered by the instrumental time resolution (<100 ps)
for all but 1d.
Figure 9. Differential absorption spectra obtained upon picosecond flash
photolysis (532 nm) of ∼1.0 × 10-5 M solutions of dyad 1b in nitrogen
saturated toluene (a) 50 ps and (b) 2500 ps, showing the fullerene singlet
and SubPc triplet excited-state features.
lifetimes, as they were determined from an average of first-
order fits of the time-absorption profiles at various wavelengths,
are listed in Table 3. An example of the SubPc decay at 650
nm is given in Figure 8. Spectroscopically, the transient
absorption changes, taken after the completion of the decay,
bear no resemblance with the SubPc triplet excited state (vide
supra). In particular, the new transients reveal broad maxima
at 880 nm, which match those of the C60 singlet-singlet
features. Figure 9 illustrates the spectral differences of the two
spectra, namely, that of the C60 singlet and that of the SubPc
triplet for the dyad (i.e., 1b). An important kinetic aspect is
that the SubPc singlet excited state lifetimes match quantitatively
those values derived in the fluorescence experiments. This
In time-resolved transient absorption measurements, an
instantaneous grow-in of a 650 nm absorption results from the
532 nm laser irradiation. The similarity of this transition with
those noted for the SubPc singlet excited-state features in 2a-d
(see Figure 5a) affirms the successful SubPc excitation in the
dyads, 1a-d. Instead of seeing, however, the slow ISC dynamics
that 2a-d exhibit (∼108 s-1), the SubPc singlet-singlet
absorptions decay when C60 is present (i.e., 1a-c) with ultrafast
dynamics of (2 ( 1) × 1010 s-1. The singlet excited-state
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Subphthalocyanines: Tuneable Molecular Scaffolds
A R T I C L E S
confirms, spectroscopically and kinetically, the transduction of
singlet excited state from the SubPc (2.1 eV) to the C60 moiety
(1.76 eV).
In reference 3, and also in other C60 derivatives, the
deactivation of the singlet excited state is dominated by ISC
(5.0 × 108 s-1) to the energetically lower lying triplet. In this
regard, it is important to note that, in 1a-c, the 880 nm
transition decays with kinetics that are hardly faster (∼8.0 ×
108 s-1) than the inherent ISC dynamics; see Figure 8.
Interestingly, we did not find the characteristic C60 triplet
features, including a strong triplet-triplet transition at 700 nm
with an extinction coefficient of ∼15.000 M-1 cm-1 at the end
of the C60 singlet deactivation/ISC. On the contrary, a maximum
around 620 nm and a minimum at 570 nm were concluded.
Earlier we established that such features are reliable attributes
of the SubPc triplet excited state. Please note the excellent
agreement of the 500-950 nm region in Figures 9b and 5b,
showing the SubPc triplet spectra in 1b and 2b, respectively.
From this we infer that the C60 triplet (1.5 eV), once formed,
undergoes a thermodynamically allowed transfer of triplet
energy to the SubPc triplet (1.45 eV). Nearly, similar kinetics
at the 570-nm minimum, which allowed us to follow the
generation of the SubPc triplet, further furnishes the following
kinetic assignment: the rate-determining step in the SubPc triplet
formation is the C60 intersystem crossing.
Figure 10. Differential absorption spectrum obtained upon nanosecond
flash photolysis (532 nm) of ∼1.0 × 10-5 M solutions of dyad 1d in nitrogen
saturated benzonitrile with a time delay of 50 ns, showing the radical pair
features.
The only component seen in the complementary nanosecond
experiments was that of the SubPc triplet (λmax ) 460, 620 nm,
λmin ) 570 nm), similar to what is shown in Figure 5b. In
addition, high SubPc triplet quantum yields in 1a-c, as
determined in a variety of solvents, further confirm the cascade
of singlet-singlet and triplet-triplet energy transfer processes,
transducing the excitation energy back and forth between the
two moieties.
Figure 11. Differential absorption spectrum obtained upon picosecond flash
photolysis (532 nm) of ∼1.0 × 10-5 M solutions of dyad 1c in nitrogen
saturated benzonitrile with a time delay of 50 ps, showing the radical pair
features.
Quite different is the situation for 1d. While the excited state
of 2d is essentially stable on the picosecond time scale and
recovers to the triplet state, the SubPc singlet excited state related
features transform in 1d within 300 ps into a broad absorbing
species. The rate constant of (4.5 ( 0.5) × 109 s-1 is somewhat
slower than what is noted for 1a-c. Again, the kinetics are
matching those registered in the fluorescence experiments. The
transient product of the rapid singlet deactivation shows maxima
at 685 nm, which match those of the one-electron oxidized
SubPc radical cations (SubPc•+), and 1000 nm, which resembles
that of the one-electron reduced C60 radical anions (C60•-).
Collectively, these features confirm the successful generation
of SubPc•+-C60•-, for which we determined an energy level
of approximately 1.4 eV.
Similarly, in dyad 1c we found the SubPc•+-C60 radical
•-
pair (see Figure 11) as the metastable photoproduct, but only
in benzonitrile! From the electrochemical experiments we
approximate an SubPc•+-C60•- energy level of ca. 1.65 eV. In
line with the fact that the radical pair state is higher than the
two triplets, namely, fullerene (1.5 eV) and subphthalocyanine
(1.46 eV), we notice at time delays of 2 ns and more only the
SubPc triplet features. The triplet grow-in is, however, kineti-
cally linked to the decay of the charge-separated ion pair
absorption (SubPc•+-C60•-). They follow similar kinetics with
a τ of about 0.65 ns. This would signify that the charge-separated
state in benzonitrile decays via the energetically lower lying
triplet excited state (1.46 eV) with small -∆GCR to regenerate
the ground state, rather than a direct recombination to the latter.
The SubPc•+-C60•- transients for 1d are stable up to the time
scale of 100 ns (Figure 10). To examine the charge-recombina-
tion dynamics, the spectral fingerprints of C60•- (1000 nm) and
that of SubPc•+ (685 nm) are useful probes. Important is the
fact that the decays of both probes resemble each other and
give rise to unimolecular recovery kinetics of the singlet ground
state. Relative to the radical pair lifetimes of 145 ns (i.e., in
THF) and 101 ns (i.e., ODCB), benzonitrile discloses a further
destabilizing trend. In particular, 72 ns is in line with our
Summary and Conclusions
In this article, we have introduced subphthalocyanines as
novel and promising light-harvesting and/or donor units for
artificial photosynthetic systems. For this task, we prepared a
series of four SubPc-C60 dyads, in which the rational func-
tionalization of the macrocycle by groups of different electronic
character provides the means to control the interplay between
energy and charge transfer processes. Key to this objective was
the development of synthetic routes to SubPcs featuring electron-
donating substituents, such as ether or amino groups, which were
successfully introduced by condensation of suitable phthalo-
•-
previous observation on ZnP•+/C60 radical pairs,9 which
implies charge-recombination deep in the inverted region, since
-∆GCR becomes gradually less negative in the THF < ODCB
< benzonitrile order.
9
J. AM. CHEM. SOC. VOL. 126, NO. 20, 2004 6309

A R T I C L E S
Gonza´lez-Rodr´ıguez et al.
electrode configuration, containing 0.1 M tetrabutylammonium hexa-
fluorophosphate (TBAPF6) as the supporting electrolyte, which was
recrystallized twice from ethanol and dried under vacuum. A glassy
carbon or gold electrode (3 or 1.5 mm φ, respectively) was used as the
working electrode, and a platinum mesh and a silver wire, separated
from the solution by a Vycor tip, were employed as the counter and
the reference electrodes, respectively. Prior to each voltammetric
measurement, the cell was degassed and pumped to 10-6 mmHg. The
solvent, THF (5 mL), which had also been degassed and pumped to
the same pressure, was then vapor-transferred into the cell, directly
from Na/K. The electrochemical measurements were performed using
a concentration of approximately 0.5 mM of the corresponding
compound, and ferrocene was added as an internal reference.
Photophysics. Picosecond laser flash photolysis experiments were
carried out with 532-nm laser pulses from a mode-locked, Q-switched
Quantel YG-501 DP Nd:YAG laser system (18 ps pulse width, 2-3
mJ/pulse). Nanosecond Laser Flash Photolysis experiments were
performed with laser pulses from a Quanta-Ray CDR Nd:YAG system
(532 nm, 6 ns pulse width) in a front face excitation geometry.
Fluorescence lifetimes were measured with a Laser Strobe 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,
http://www.pti-nj.com. Emission spectra were recorded with an SLM
8100 spectrofluorometer. The experiments were performed at room
temperature. Each spectrum represents an average of at least five
individual scans, and appropriate corrections were applied whenever
necessary. Pulse radiolysis experiments were performed by utilizing
50-ns pulses of 8 MeV electrons from a model TB-8/16-1S Electron
Linear Accelerator. Details on such equipment, in general, and the data
analysis have been described elsewhere.36
nitrile precursors or by a palladium-catalyzed amination reaction,
respectively. The fullerene fragment was attached via the axial
position of the macrocycle, which represents a simple and
efficient approach to SubPc-based dyads.
The detailed electrochemical and photophysical characteriza-
tion of the reference SubPc and C60 compounds furnished the
comprehension and rationalization of the different mechanistic
scenarios, energy and electron-transfer deactivation of the
photoexcited SubPcs, occurring in the dyads upon initial light
irradiation. Cyclic voltammetry experiments revealed the first
oxidation process of the macrocycle to gradually shift to lower
potentials (by ca. 200 nm) in the series a > b > c > d, whereas
the first C60-based reduction process remained virtually un-
affected. As a consequence, the energy level of the SubPc•+-
C60•- charge-separation states are tuned so as to compete with
energy transfer deactivation pathways. More specifically, the
selective excitation of the SubPc unit in dyads 1a and 1b, or in
dyad 1c in a nonpolar environment, gives rise to a sequence of
exergonic photophysical events that involve (i) nearly quantita-
tive singlet-singlet energy transfer to the C60 moiety, (ii)
fullerene centered intersystem crossing, and (iii) triplet-triplet
energy transfer back to the SubPc. In fact, the energy level of
the overall product, the SubPc triplet excited state, has been
for the first time ascertained from phosphorescence measure-
ments around 1.45 eV, just below the fullerene triplet state. On
the contrary, the stabilization of the SubPc•+-C60•- radical pair
state in more polar media or by lowering the redox gap causes
charge transfer to dominate. In the case of 1c in benzonitrile,
the thus formed radical pair has a lifetime of 0.65 ns and decays
via the energetically lower lying triplet excited state. Further
stabilization is achieved for dyad 1d, whose charge-transfer state
would lie now below both triplets. The radical pair lifetime
consequently increases in more than 2 orders of magnitude with
respect to 1c and presents a significant stabilization in less polar
solvents, a clear attribute of the inverted region of the Marcus
parabola.
Dibenzo[b,e][1,4]dioxine-2,3-dicarbonitrile (4c): In a 100-mL
round-bottomed flask, equipped with a magnetic stirrer and rubber seal,
4,5-dichlorophthalonitrile (2.4 g, 12.2 mmol), dry K2CO3 (5.0 g, 36.2
mmol), and dry dimethylacetamide (30 mL) were placed. Then, catechol
(1.34 g, 12.2 mmol) was added. The resulting mixture was stirred under
argon at room temperature for 16 h and at 50 °C during 3 h. After that
time, it was poured into 100 mL of cold water, and the precipitate
formed was collected by filtration and subjected to column chroma-
tography on silica gel using a 1:1 mixture of CH2Cl2/hexane. In this
way, 3.2 g (89%) of compound 4c were isolated as a white solid. Mp:
In conclusion, we have proven that subphthalocyanines are
synthetically and electronically versatile molecular units for the
construction of multicomponent photoactive systems. Future
research will be aimed at determining the electron-accepting
ability of these chromophores in specifically designed dyads.
1
138-139 °C. H NMR (300 MHz, CDCl3): δ ) 7.19 (s, 2H), 7.05-
6.85 ppm (AA’BB’, 4H). 13C NMR (75.5 MHz, CDCl3): δ ) 146.0,
140.3, 125.6, 121.4, 116.8, 114.6, 111.6 ppm. MS (EI): m/z ) 234
[M]+ (100%). FT-IR (KBr): ν ) 3078, 2988 (CsH), 2236 (CtN),
1616, 1503, 1284, 1242 (CsO), 869, 747 cm-1. Anal. Calcd for
C14H6N2O2: C, 71.80; H, 2.58; N, 11.96. Found: C, 71.78; H, 2.59;
N, 11.93.
Experimental Section
General Methods. Melting points (mp) were determined in a Bu¨chi
504392-S equipment and are uncorrected. UV/vis spectra were recorded
with a Hewlett-Packard 8453 instrument. IR spectra were recorded on
a Bruker Vector 22 spectrophotometer. LSI-MS and HRMS spectra
were determined on a VG AutoSpec apparatus, and MALDI-TOF-MS
spectra were obtained from a BRUKER REFLEX III instrument
equipped with a nitrogen laser operating at 337 nm. NMR spectra were
recorded with a BRUKER AC-300 instrument. Elemental analyses were
performed with a Perkin-Elmer 2400 CHN equipment. Column
chromatography was carried out on silica gel Merck-60 (230-400 mesh,
60 Å), and TLC, on aluminum sheets precoated with silica gel 60 F254
(E. Merck). Chemicals were purchased from commercial suppliers and
used without further purification. Phthalonitrile 4b was prepared
following a reported procedure.35
Standard Procedure for the Synthesis of SubPcs 5a-c: In a 25-
mL two-necked round-bottomed flask, equipped with a condenser,
magnetic stirrer, and rubber seal, BCl3 (5 mL, 1M solution in p-xylene)
was added to the corrresponding dry phthalonitrile (5 mmol) under
argon atmosphere. The reaction mixture was then stirred under vigorous
reflux for 20 min, allowed to reach room temperature, and flushed with
argon. The dark purple reaction slurry was dissolved in toluene/THF
(10:1) and passed through a short silica plug. The solvent was removed
by vacuum distillation, and the resulting dark solid was subjected to
column chromatography on silica gel using a 3:1 mixture of hexane/
ethyl acetate (5a and 5c) or toluene (5b) as eluent. Compounds 5a-c
were further purified by recrystallization from CH2Cl2/hexane (5a and
5b) or methanol/water (5c) mixtures. The characterization of SubPc
5a14f and the C3 and C1 regioisomers of SubPc 5b15a has been recently
reported.
Electrochemistry. Electrochemical measurements were performed
at room temperature in a home-built one-compartment cell with a three-
(35) Marcuccio, M. S.; Polina, I.; Greenberg, S.; Lever, A. B. P.; Leznoff, C.
(36) Hug, G. L.; Wang, Y.; Scho¨neich, C.; Jiang, P.-Y.; Fessenden, R. W. Radiat.
Phys. Chem. 1999, 54, 559.
C.; Tomer, B. Can. J. Chem. 1985, 63, 3057-3069.
9
6310 J. AM. CHEM. SOC. VOL. 126, NO. 20, 2004

Subphthalocyanines: Tuneable Molecular Scaffolds
A R T I C L E S
Chloro-[2,3,9,10,16,17-tri(benzo[1,4]dioxine)subphthalocyaninato]-
boron (III) (5c). Compound 5c was obtained as a red solid: 0.49 g
(39%). Mp > 250 °C. 1H NMR (300 MHz, CDCl3): δ ) 8.23 (s, 6H),
7.05-6.9 ppm (AA′BB′, 12H). 13C NMR (75.5 MHz, CDCl3): δ )
149.1, 145.0, 141.5, 127.4, 124.5, 116.6, 109.2 ppm. MS (FAB,
m-NBA): m/z ) 749 [M]+, 714 [M - Cl]+. HRMS calcd for
C42H18N6O6BCl: 748.1069; found, 748.1106. UV-vis (CHCl3): λmax
(log ꢀ) ) 574 (4.6), 532 (sh), 408 (3.9), 292 nm (4.5). FT-IR (KBr):
ν ) 1565, 1490, 1284, 1133, 956 (B-Cl), 870, 742 cm-1. Anal. Calcd
for C42H18N6O6BCl: C, 67.36; H, 2.42; N, 11.22. Found: C, 67.40;
H, 2.35; N, 11.30.
3-Formylphenoxy-[2,9,16(17)-triiodosubphthalocyaninato]-
boron (III) (6b; 1:3 Mixture of C3 and C1 Isomers). Compound 6b
1
was obtained as a pink solid: 0.32 g (73%). Mp > 250 °C. H NMR
(300 MHz, CDCl3): δ ) 9.59 (s, 1H), 9.15-9.0 (m, 3H), 8.5-8.35
(m, 3H), 8.2-8.0 (m, 3H), 7.15 (d, Jo ) 7.6 Hz, 1H), 6.93 (dd, Jo )
Jo′ ) 7.6 Hz, 1H), 5.91 (s (br), 1H), 5.61 ppm (dd, Jo′ ) 7.6 Hz, Jm
)
1.2 Hz, 1H). 13C NMR (75.5 MHz, CDCl3): δ ) 191.5, 153.0, 151.5,
151.3, 151.1, 150.3, 150.2, 150.1, 149.9, 138.8, 137.3, 132.0, 129.7,
131.5, 131.4, 129.7, 125.2, 123.5, 123.4, 119.6, 96.4 ppm. MS (FAB,
m-NBA): m/z ) 894 [M]+, 773 [M - axial group]+. HRMS calcd for
C31H14N6O2BI3: 893.8405; found, 893.8431. UV-vis (CHCl3): λmax
(log ꢀ) ) 571 (4.6), 530 (sh), 326 (4.0), 273 nm (4.3). FT-IR (KBr):
ν ) 1694 (CdO), 1598, 1546, 1460, 1436, 1382, 1308, 1266, 1222,
1173, 1141, 1044 (BsO), 968, 816, 777, 752, 701 cm-1. Anal. Calcd
for C31H14N6O2BI3: C, 41.65; H, 1.58; N, 9.40. Found: C, 41.51; H,
1.65; N, 9.41.
Standard Procedure for the Synthesis of SubPcs 2a-c and 6b-
c: In a 25-mL round-bottomed flask, equipped with a condenser and a
magnetic stirrer, the corresponding phenol (2.5 mmol) and the SubPc
(0.5 mmol) were refluxed in toluene (2 mL) for 40 h (2a), 16 h (2b),
4h (2c), 40 h (6b), or 9 h (6c), depending in each case on the reactivity
of the starting SubPc and phenol. The reaction mixture was cooled to
room temperature, the solvent was evaporated, and the resulting residue
was washed with a 4:1 mixture of methanol/water. The dark magenta
solid was then subjected to column chromatography on silica gel using
toluene (2a-c) or mixtures of toluene/THF (30:1 for 6b or 20:1 for
6c). The C3 and C1 regioisomers of 2b were separated during
chromatography, and their individual characterization data are listed
below following their elution order. Compounds 2a-c and 6b-c were
further purified by recrystallization from CH2Cl2/hexane mixtures. The
characterization of SubPcs 2a14f and 6a21b has been recently reported.
Phenoxy-[2,9,16-triiodosubphthalocyaninato]boron (III) (2b; C3
Isomer). Compound 2b (C3) was obtained as a magenta solid: 80 mg
3-Formylphenoxy-[2,3,9,10,16,17-tri(benzo[1,4]dioxine)sub-
phthalocyaninato]boron (III) (6c). Compound 6c was obtained as a
red solid: 0.27 g (65%). Mp > 250 °C. 1H NMR (300 MHz, CDCl3):
δ ) 9.62 (s, 1H), 8.16 (s, 6H), 7.1-6.7 (m, 14H), 5.92 (s (br), 1H),
5.62 ppm (dd, Jo ) 8.2 Hz, Jm ) 1.6 Hz, 1H). 13C NMR (75.5 MHz,
CDCl3): δ ) 191.7, 151.9, 150.4, 144.8, 141.4, 137.2, 129.5, 127.2,
125.6, 125.4, 122.7, 120.1, 116.5, 109.0 ppm. MS (FAB, m-NBA):
m/z ) 835 [M]+, 713 [M - axial group]+. HRMS calcd. for
C49H23N6O8B: 834.1670; found, 834.1663. UV-vis (CHCl3): λmax (log
ꢀ) ) 572 (4.6), 533 (sh), 403 (3.9), 288 nm (4.5). FT-IR (KBr): ν )
1698 (CdO), 1636, 1567, 1494, 1465, 1386, 1305, 1283, 1240, 1169,
1132, 1102, 1042 (BsO), 864, 829, 749 cm-1. Anal. Calcd for
C49H23N6O8B: C, 70.52; H, 2.58; N, 10.07. Found: C, 70.36; H, 2.70;
N, 10.02.
1
(20%). Mp > 250 °C. H NMR (300 MHz, CDCl3): δ ) 9.16 (d, Jm
) 1.4 Hz, 3H), 8.50 (d, Jo ) 8.2 Hz, 3H), 8.17 (dd, Jo ) 8.2 Hz, Jm
) 1.4 Hz, 3H), 6.76 (dd, Jo ) 8.2 Hz, Jo′ ) 7.1 Hz, 2H), 6.64 (t, Jo′
)
Standard Procedure for the Synthesis of SubPcs 2d and 6d: An
oven-dried 25-mL flask was charged with finely ground Cs2CO3 (294
mg, 0.9 mmol), Pd2(dba)3 (8 mg, 0.009 mmol), BINAP (5.6 mg, 0.009
mmol), diphenylamine (152 mg, 0.9 mmol), and the corresponding
SubPc (2b or 6b (1:3 mixture of C3/C1 regioisomers); 0.1 mmol). The
flask was then purged with argon, and dry toluene (10 mL) was added
through a syringe. The mixture was heated to reflux under argon
atmosphere with continuous stirring for 8 h in both cases. The solution
was cooled to room temperature, diluted with toluene (20 mL), filtered,
and concentrated to ca. 2-3 mL. The crude product was then purified
by flash chromatography on silica gel using a mixture of hexane/THF
(4:1 for 2d and 3:1 for 6d) as eluent. The C3 and C1 regioisomers of
2d were separated during chromatography, and their individual
characterization data are listed below following their elution order. The
resulting deep green solids could be further purified by precipitation
from cold hexane.
7.1 Hz, 1H), 5.36 ppm (d, Jo ) 8.2 Hz, 2H). 13C NMR (75.5 MHz,
CDCl3): δ ) 152.1, 151.3, 150.1, 138.8, 132.2, 129.8, 131.4, 129.0,
123.5, 121.8, 119.0, 96.2 ppm. MS (FAB, m-NBA): m/z ) 866 [M]+,
773 [M - axial group]+. UV-vis (CHCl3): λmax (log ꢀ) ) 573 (4.5),
558 (sh), 530 (sh), 340 (4.0), 317 (4.1), 277 nm (4.2). FT-IR (KBr):
ν ) 1599, 1439, 1177, 1056 (B-O), 820, 757, 705 cm-1. Anal. Calcd
for C30H14N6OBI3: C, 41.61; H, 1.63; N, 9.70. Found: C, 41.46; H,
1.77; N, 9.54.
Phenoxy-[2,9,17-triiodosubphthalocyaninato]boron (III) (2b; C1
Isomer). Compound 2b (C1) was obtained as a magenta solid: 0.28 g
1
(66%). Mp > 250 °C. H NMR (300 MHz, CDCl3): δ ) 9.15-9.1
(m, 3H), 8.55-8.45 (m, 3H), 8.2-8.1 (m, 3H), 6.77 (dd, Jo ) Jo′
)
7.6 Hz, 2H), 6.64 (t, Jo′ ) 7.6 Hz, 1H), 5.38 ppm (d, Jo ) 7.6 Hz, 2H).
13C NMR (75.5 MHz, CDCl3): δ ) 152.1, 151.5, 151.3, 151.1, 150.3,
150.2, 150.0, 138.7, 132.3, 132.2, 132.1, 129.9, 129.7, 131.4, 129.0,
123.52, 123.46, 121.8, 119.0, 96.2 ppm. MS (FAB, m-NBA): m/z )
866 [M]+, 773 [M - axial group]+. HRMS calcd for C30H14N6OBI3:
865.8456; found, 865.8451. UV-vis (CHCl3): λmax (log ꢀ) ) 573 (4.6),
558 (sh), 532 (sh), 342 (sh), 317 (4.2), 276 nm (4.3). FT-IR (KBr): ν
Phenoxy-[2,9,16-tri(diphenylamino)subphthalocyaninato]-
boron(III) (2d; C3 Isomer). Compound 2d (C3) was obtained as a
green solid: 20 mg (20%). Mp > 250 °C. 1H NMR (300 MHz,
CDCl3): δ ) 8.52 (d, Jo ) 8.8 Hz, 3H), 8.37 (d, Jm ) 2.0 Hz, 3H),
7.51 (dd, Jo ) 8.8 Hz, Jm ) 2.0 Hz, 3H), 7.32 (dd, Jo ) Jo′ ) 7.6 Hz,
12H), 7.19 (d, Jo ) 7.6 Hz, 12H), 7.13 (t, Jo′ ) 7.6 Hz, 6H), 6.77 (dd,
Jo ) Jo′ ) 7.6 Hz, 2H), 6.60 (t, Jo′ ) 7.6 Hz, 1H), 5.42 ppm (d, Jo )
7.6 Hz, 2H). 13C NMR (75.5 MHz, CDCl3): δ ) 151.0, 150.7, 150.0,
147.3, 132.8, 129.7, 128.8, 125.3, 124.5, 124.3, 124.1, 122.7, 121.0,
118.7, 114.4 ppm. MS (FAB, m-NBA): m/z ) 989 [M]+. UV-vis
(CHCl3): λmax (log ꢀ) ) 622 (4.6), 556 (sh), 437 (4.2), 400 (sh), 311
nm (4.6). FT-IR (KBr): ν ) 3067, 3010 (C-H), 1592, 1488, 1474,
1326 (C-N), 1272, 1191, 1137, 1056 (B-O), 751, 697 cm-1. Anal.
Calcd for C66H44N9OB: C, 80.08; H, 4.48; N, 12.73. Found: C, 79.93;
H, 4.61; N, 12.80.
) 1523, 1428, 1252, 1171, 1063 (B-O), 1036, 807, 753, 699 cm-1
Anal. Calcd for C30H14N6OBI3: C, 41.61; H, 1.63; N, 9.70. Found: C,
41.55; H, 1.67; N, 9.72.
.
Phenoxy-[2,3,9,10,16,17-tri(benzo[1,4]dioxine)subphthalocyaninato]-
boron (III) (2c). Compound 2c was obtained as a red solid: 0.32 g
(79%). Mp > 250 °C. 1H NMR (300 MHz, CDCl3): δ ) 8.18 (s, 6H),
7.05-6.8 (AA′BB′, 12H), 6.78 (dd, Jo ) 7.6 Hz, Jo′ ) 8.2 Hz, 2H),
6.64 (t, Jo′ ) 8.2 Hz, 1H), 5.39 ppm (d, Jo ) 7.6 Hz, 2H). 13C NMR
(75.5 MHz, CDCl3): δ (ppm) ) 152.0, 150.4, 144.7, 141.5, 128.9,
127.3, 124.3, 121.5, 119.1, 116.5, 109.0 ppm. MS (FAB, m-NBA):
m/z ) 806 [M]+, 713 [M - axial group]+. HRMS calcd for
C48H23N6O7B: 806.1721; found, 806.1700. UV-vis (CHCl3): λmax (log
ꢀ) ) 571 (4.7), 555 (sh), 532 (sh), 401 (4.0), 287 nm (4.7). FT-IR
(KBr): ν ) 1636, 1568, 1495, 1465, 1389, 1285, 1243, 1133, 1037
(B-O), 866, 810, 747, 704 cm-1. Anal. Calcd for C48H23N6O7B: C,
71.48; H, 2.87; N, 10.42. Found: C, 71.39; H, 2.97; N, 10.40.
Phenoxy-[2,9,17-tri(diphenylamino)subphthalocyaninato]-
boron(III) (2d; C1 Isomer). Compound 2d (C3) was obtained as a
green solid: 66 mg (67%). Mp > 250 °C. 1H NMR (300 MHz,
CDCl3): δ ) 8.58 (d, Jo ) 8.8 Hz, 1H), 8.57 (d, Jo ) 8.8 Hz, 1H),
8.50 (d, Jo ) 8.8 Hz, 1H), 8.37 (d, Jm ) 1.8 Hz, 1H), 8.32 (d, Jm ) 1.8
9
J. AM. CHEM. SOC. VOL. 126, NO. 20, 2004 6311

A R T I C L E S
Gonza´lez-Rodr´ıguez et al.
Hz, 1H), 8.31 (d, Jm ) 1.8 Hz, 1H), 7.6-7.45 (m, 3H), 7.4-7.0 (m,
30H), 6.78 (dd, Jo ) Jo′ ) 7.6 Hz, 2H), 6.61 (t, Jo′ ) 7.6 Hz, 1H), 5.43
(d, Jo ) 7.6 Hz, 2H). 13C NMR (75.5 MHz, CDCl3): δ ) 151.5, 150.3,
150.1, 149.8, 149.6, 149.4, 147.33, 147.28, 133.2, 133.0, 132.7, 129.7,
129.65, 129.59, 128.8, 125.4, 125.3, 125.2, 124.6, 124.5, 124.3, 124.2,
124.1, 124.0, 122.9, 122.8, 122.7, 121.0, 118.8, 114.6, 114.5, 114.3
ppm. MS (FAB, m-NBA): m/z ) 989 [M]+, 896 [M - axial group]+.
HRMS calcd. for C66H45N9OB: 990.3840; found, 990.3897. UV-vis
(CHCl3): λmax (log ꢀ) ) 620 (4.6), 554 (sh), 473 (4.2), 428 (4.2), 305
nm (4.7). FT-IR (KBr): ν ) 3065, 3010 (C-H), 1601, 1480, 1328
(C-N), 1277, 1183, 1061 (B-O), 830, 751, 697 cm-1. Anal. Calcd
for C66H44N9OB: C, 80.08; H, 4.48; N, 12.73. Found: C, 80.02; H,
4.57; N, 12.75.
(1:5)): δ ) 9.2-9.1 (m, 3H), 8.6-8.4 (m, 3H), 8.25-8.05 (m, 3H),
7.1-6.8 (m, 1H), 6.8-6.7 (m, 1H), 5.85-5.6 (m, 1H), 5.4-5.25 (m,
1H), 4.95-4.8 (m, 1H), 4.55-4.4 (m, 1H), 4.08 (d, 2J ) 9.2 Hz, 1H),
2.57 ppm (s, 3H). MS (MALDI-TOF, dithranol): m/z ) 1641-1646
[M + H]+. UV-vis (CHCl3): λmax (log ꢀ) ) 573 (4.5), 524 (sh), 432,
322 (4.4), 260 nm (4.8). FT-IR (KBr): ν ) 2965, 2922, 1628, 1451,
1346, 1275, 1059 cm-1 (B-O). Anal. Calcd for C93H19N7OBI3: C,
68.04; H, 1.17; N, 5.97. Found: C, 67.81; H, 1.22; N, 6.03.
3-(1-Methyl-3,4-[60]fulleropyrrolidin-2-yl)phenoxy-[2,9,17-tri-
iodosubphthalocyaninato]boron (III) (1b; C1 Isomer; 1:1 Mixture
of Diastereoisomers). Compound 1b (C1) was obtained as a dark red
1
solid: 51 mg (35%). Mp > 250 °C. H NMR (300 MHz, CDCl3/CS2
(1:5)): δ ) 9.2-9.0 (m, 3H), 8.6-8.4 (m, 3H), 8.25-8.1 (m, 3H),
7.1-6.8 (m, 1H), 6.8-6.7 (m, 1H), 5.85-5.6 (m, 1H), 5.4-5.25 (m,
1H), 4.95-4.8 (m, 1H), 4.55-4.45 (m, 1H), 4.10 (d, 2J ) 9.4 Hz, 1H),
2.57 ppm (s, 3H). 13C NMR (75.5 MHz, CDCl3/CS2 (1:5)): δ ) 153.3,
152.7, 152.50, 152.49, 151.9, 151.3, 151.2, 151.15, 151.10, 151.05,
150.2, 150.1, 150.0, 149.9, 149.1, 146.6, 146.5, 145.7, 145.6, 145.52,
145.46, 145.39, 145.32, 145.2, 145.14, 145.11, 144.85, 144.81, 144.7,
144.54, 144.51, 144.0, 143.7, 143.6, 142.4, 142.3, 141.9, 141.72, 141.69,
141.6, 141.5, 141.42, 141.36, 141.32, 141.2, 141.1, 140.9, 140.83,
140.79, 139.5, 139.2, 137.6, 136.0, 135.1, 138.5, 132.0, 131.63, 131.58,
129.6, 128.6, 123.4, 123.3, 122.0, 118.6, 109.0, 97.0, 96.8, 82.4, 69.5,
68.4, 39.5 ppm. MS (MALDI-TOF, dithranol): m/z ) 1641-1646 [M
+ H]+. UV-vis (CHCl3): λmax (log ꢀ) ) 573 (4.5), 522 (sh), 431, 322
(4.4), 260 nm (4.8). FT-IR (KBr): ν ) 2964, 2920, 1628, 1449, 1345,
1280, 1059 cm-1 (B-O). Anal. Calcd for C93H19N7OBI3: C, 68.04;
H, 1.17; N, 5.97. Found: C, 67.90; H, 1.24; N, 6.08.
3-Formylphenoxy-[2,9,16(17)-tri(diphenylamino)subphthalo-
cyaninato]boron(III) (6d; 1:3 Mixture of C3 and C1 Isomers).
Compound 6d was obtained as a green solid: 83 mg (82%). Mp >
1
250 °C. H NMR (300 MHz, CDCl3): δ ) 9.62 (s, 1H), 8.6-8.5 (m,
3H), 8.45-8.25 (m, 3H), 7.6-7.45 (m, 3H), 7.4-7.0 (m, 31H), 6.94
(dd, Jo ) Jo′ ) 7.6 Hz, 1H), 5.99 (s (br), 1H), 5.64 ppm (d, Jo′ ) 7.6
Hz, 1H). 13C NMR (75.5 MHz, CDCl3): δ ) 191.9, 153.8, 152.3, 151.5,
150.9, 150.6, 150.4, 150.2, 150.1, 150.0, 149.9, 147.3, 147.22, 147.17,
137.2, 133.1, 132.9, 132.6, 129.7, 129.5, 125.4, 125.3, 125.2, 125.1,
124.3, 124.2, 124.1, 122.9, 122.8, 122.7, 122.4, 120.6, 114.4, 114.3,
114.2, 114.1. MS (FAB, m-NBA): m/z ) 1018 [M + H]+. HRMS
calcd for C67H45N9O2B: 1018.3789; found, 1018.3768. UV-vis
(CHCl3): λmax (log ꢀ) ) 624 (4.6), 580 (sh), 428 (4.3), 301 (4.8) nm.
FT-IR (KBr): ν ) 1697 (CdO), 1614 (CdN), 1490, 1260, 1194, 1150,
1041 (BsO), 756, 702 cm-1. Anal. Calcd for C67H44N9O2B: C, 79.05;
H, 4.36; N, 12.38; C, 78.98; H, 4.41; N, 12.34.
3-(1-Methyl-3,4-[60]fulleropyrrolidin-2-yl)phenoxy-[2,3,9,10,
16,17-tri(benzo[1,4]dioxine)subphthalocyaninato]boron(III) (1c).
Compound 1c was obtained as a purple solid: 65 mg (46%). Mp >
Standard Procedure for the Synthesis of SubPc-C60 Dyads 1a-
d: A dry toluene solution (50 mL) of C60 fullerene (70 mg, 0.1 mmol),
N-methylglycine (25 mg, 0.27 mmol), and the corresponding (formyl-
phenoxy)SubPc 6a-d (0.09 mmol) was heated to reflux under argon
atmosphere for 20 h. The solution was then cooled to room temperature
and concentrated under vacuum until ca. 10 mL. The resulting mixture
was poured onto a silica gel column and eluted with the corresponding
solvent mixture to separate the monoaddition products from the
bisadducts and unreacted fullerene. The C3 and C1 regioisomers of 1b
and 1d were separated during chromatography, and their individual
characterization data are listed below following their elution order.
Further purification of the monoadducts was achieved by thoroughly
washing the solid products with acetone, methanol, and hexane.
3-(1-Methyl-3,4-[60]fulleropyrrolidin-2-yl)phenoxy-[1,2,3,4,8,9,
10,11,15,16,17,18-dodecafluorosubphthalocyaninato]boron(III) (1a).
Compound 1a was obtained as a purple solid: 58 mg (44%). Mp >
250 °C. 1H NMR (300 MHz, CDCl3/CS2 (1:5)): δ ) 7.1-6.9 (m, 1H),
6.81 (dd, Jo ) Jo′ ) 7.6 Hz, 1H), 5.9-5.7 (m, 1H), 5.34 (d (br), Jo )
7.6 Hz, 1H), 4.94 (d (br), 2J ) 9.4 Hz, 1H), 4.56 (s (br), 1H), 4.16 (d,
2J ) 9.4 Hz, 1H), 2.73 nm (s, 3H). 13C NMR (75.5 MHz, CDCl3/CS2
(1:5)): δ ) 155.5, 153.2, 153.1, 152.5, 152.4, 151.6, 151.1, 148.0,
146.8, 146.0, 145.9, 145.7, 145.62, 145.57, 145.2, 145.1, 145.0, 144.9,
144.8, 144.7, 144.5, 144.3, 144.2, 144.0, 143.9, 143.8, 143.6, 142.7,
142.6, 142.3, 142.2, 142.1, 141.73, 141.67, 141.51, 141.46, 141.4, 141.3,
141.2, 141.1, 141.0, 140.81, 140.76, 140.7, 140.61, 140.59, 140.56,
140.4, 140.3, 140.1, 139.9, 139.8, 139.7, 139.5, 139.3, 138.8, 138.6,
138.2, 135.8, 135.5, 135.31, 135.26, 152.5, 148.0, 138.8, 128.8, 122.9,
118.1, 115-0-114.4, 110.1, 82.2, 69.5, 68.4, 39.5 ppm. MS (MALDI-
TOF, dithranol): m/z ) 1478-1483 [M + H]+. UV-vis (CHCl3): λmax
(log ꢀ) ) 573 (4.6), 529 (sh), 430, 316 (4.5), 260 nm (4.8). FT-IR
1
250 °C. H NMR (300 MHz, CDCl3/CS2 (1:5)): δ ) 8.08 (s, 6H),
7.0-6.8 (m, 13H), 6.73 (dd, Jo ) 7.6 Hz, Jo′ ) 7.6 Hz, 1H), 5.8-5.6
(m, 1H), 5.32 (d (br), Jo ) 7.1 Hz, 1H), 4.87 (d (br), 2J ) 9.4 Hz, 1H),
2
4.49 (s (br), 1H), 4.09 (d, J ) 9.4 Hz, 1H), 2.61 ppm (s, 3H). 13C
NMR (75.5 MHz, CDCl3/CS2 (1:5)): δ ) 155.4, 153.4, 152.8, 152.7,
152.5, 150.0, 146.6, 146.5, 146.1, 145.8, 145.6, 145.5, 145.4, 145.3,
145.2, 145.0, 144.8, 144.7, 144.5, 144.4, 144.3, 144.0, 143.9, 143.6,
143.5, 142.3, 142.2, 141.9, 141.8, 141.7, 141.5, 141.4, 141.3, 141.1,
141.0, 140.9, 139.4, 139.2, 138.8, 137.3, 136.1, 136.0, 135.2, 135.1,
128.7, 127.0, 124.1, 121.8, 118.6, 116.3, 109.0, 108.9, 82.4, 69.5, 68.3,
39.4 ppm. MS (MALDI-TOF, dithranol): m/z ) 1580-1586 [M +
H]+. UV-vis (CHCl3): λmax (log ꢀ) ) 573 (4.6), 529 (sh), 430, 256
nm (5.0). FT-IR (KBr): ν ) 1621, 1450, 1345, 1280, 1187, 1065 cm-1
(B-O). Anal. Calcd for C111H28N7O7B: C, 84.26; H, 1.78; N, 6.20.
Found: C, 84.11; H, 1.83; N, 6.17.
3-(1-Methyl-3,4-[60]fulleropyrrolidin-2-yl)phenoxy-[2,9,16-tri-
(diphenylamino)subphthalocyaninato]boron(III) (1d; C3 Isomer; 1:1
Mixture of Diastereoisomers). Compound 1d (C3) was obtained as a
1
dark red solid: 19 mg (12%). Mp > 250 °C. H NMR (300 MHz,
CDCl3): δ ) 8.49, 8.47 (2xd, Jo ) 8.6 Hz, 3H), 8.4-8.3 (m, 3H),
7.5-7.4 (m, 3H), 7.4-7.0 (m, 31H), 6.8-6.65 (m, 1H), 5.8-5.7 (m,
1H), 5.45-5.25 (m, 1H), 4.9-4.7 (m, 1H), 4.45 (s (br), 1H), 4.06,
4.04 (2xd, 2J ) 9.2 Hz, 1H), 2.56, 2.50 ppm (2xs, 3H). MS (MALDI-
TOF, dithranol): m/z ) 1763-1768 [M + H]+. UV-vis (CHCl3): λmax
(log ꢀ) ) 626 (4.6), 584 (sh), 433 (4.2), 308 (4.9), 258 nm (5.0). FT-
IR (KBr): ν ) 2949, 2917, 1595, 1480, 1455, 1277, 1185, 1050 (B-
O), 751, 700 cm-1. Anal. Calcd for C129H49N10OB: C, 87.75; H, 2.80;
N, 7.93. Found: C, 87.49; H, 2.82; N, 7.88.
(KBr): ν ) 1462, 1395, 1273, 1139, 1044 (B-O), 869, 743 cm-1
.
3-(1-Methyl-3,4-[60]fulleropyrrolidin-2-yl)phenoxy-[2,9,17-tri-
(diphenylamino)subphthalocyaninato]boron(III) (1d; C1 Isomer; 1:1
Mixture of Diastereoisomers). Compound 1d (C1) was obtained as a
Anal. Calcd for C93H10N7OF12B: C, 75.48; H, 0.68; N, 6.63; C, 75.26;
H, 0.71; N, 6.57.
1
3-(1-Methyl-3,4-[60]fulleropyrrolidin-2-yl)phenoxy-[2,9,16-triiodo-
subphthalocyaninato]boron (III) (1b; C3 Isomer; 1:1 Mixture of
Diastereoisomers). Compound 1b (C3) was obtained as a dark red
dark red solid: 52 mg (33%). Mp > 250 °C. H NMR (300 MHz,
CDCl3): δ ) 8.55-8.4 (m, 3H), 8.4-8.25 (m, 3H), 7.5-7.35 (m, 3H),
7.35-7.05 (m, 31H), 6.75-6.6 (m, 1H), 5.95-5.55 (m, 1H), 5.45-
1
2
solid: 17 mg (12%). Mp > 250 °C. H NMR (300 MHz, CDCl3/CS2
5.2 (m, 1H), 4.9-4.65 (m, 1H), 4.40 (s (br), 1H), 4.00 (d (br), J )
9
6312 J. AM. CHEM. SOC. VOL. 126, NO. 20, 2004

Subphthalocyanines: Tuneable Molecular Scaffolds
A R T I C L E S
9.2 Hz, 1H), 2.52, 2.50 ppm (2xs, 3H). 13C NMR (75.5 MHz, CDCl3):
δ ) 155.8, 155.7, 153.4, 153.3, 153.2, 151.9, 151.8, 151.1, 151.0, 150.2,
150.0, 149.7, 149.6, 149.4, 149.33, 149.27, 148.7, 148.5, 147.3, 147.2,
147.1, 146.3, 146.1, 146.0, 145.6, 145.5, 145.3, 145.2, 145.0, 144.9,
144.8, 144.73, 144.68, 144.5, 144.4, 144.0, 143.8, 143.2, 142.3, 142.0,
141.6, 141.4, 141.34, 141.29, 141.17, 141.0, 140.9, 140.6, 139.3, 139.2,
139.0, 138.9, 137.6, 136.2, 136.1, 135.1, 135.0, 133.6, 133.4, 133.0,
129.8, 129.7, 128.7, 125.6, 125.4, 125.3, 124.7, 124.6, 124.4, 124.2,
124.1, 123.2, 123.1, 123.0, 122.0, 115.7, 114.5, 114.4, 114.3, 111.8,
82.8, 69.5, 68.5, 39.7 ppm. MS (MALDI-TOF, dithranol): m/z )
1763-1768 [M + H]+. UV-vis (CHCl3): λmax (log ꢀ) ) 626 (4.6),
566 (sh), 432 (4.2), 308 (5.0), 258 nm (5.2). FT-IR (KBr): ν ) 1594,
1449, 1273, 1179, 1098, 1044 (B-O), 805, 751, 697 cm-1. Anal. Calcd
for C129H49N10OB: C, 87.75; H, 2.80; N, 7.93. Found: C, 87.56; H,
2.85; N, 7.90.
European Union through grants BQU2002-04697, 07N/0030/
2002, and HPRN-CT-2000-0127, respectively (T.T.). This work
was also partially supported by the U.S. National Science
Foundation, grant CHE-0135786 (L.E.), and the Office of
Basic Energy Sciences of the U.S. Department of Energy (D.G.).
This is document 4524 from the Notre Dame Radiation
Laboratory.
Supporting Information Available: Phosphorescence emis-
sion spectrum, differential absorption spectrum of the SubPc
radical cation,1H NMR, 13C NMR and UV-vis spectra of dyads
1a-d, reference compounds 2a-d and 3 and SubPcs 6a-d and
complete assignment of NMR signals. This material is available
free of charge via the Internet at http://pubs.acs.org.
Acknowledgment. The authors are grateful for the financial
support of the CICYT (Spain), Comunidad de Madrid and the
JA039883V
9
J. AM. CHEM. SOC. VOL. 126, NO. 20, 2004 6313