Donor-acceptor phthalocyanine nanoaggregates

Article abstract of DOI:10.1021/ja030038m

A novel donor-acceptor bisphthalocyanine (bis-Pc, 1) in which two different Pc units (Zn(II)-Pc and Ni(II)-Pc) are linked via vinylene spacers to the pseudopara positions of a central [2.2]paracyclophane moiety is described. The synthesis of 1 is achieved by two successive Heck reactions of pseudoparadivinyl[2.2]paracyclophane 9 with, sequentially, a zinc(II)- and a nickel(II)-iodophthalocyanine (4 and 5, respectively). The self-assembly ability of 1, which is the result of the complementary donor-acceptor character of its phthalocyanine units, has been assessed by a variety of techniques. It is revealed that 1 forms one-dimensional aggregates of nanometer-sized dimension, whereas equimolar mixtures of the donor and acceptor Pc subunits 2 and 3, although strongly interacting, do not give large arrays. The aggregates of 1 represent a novel type of supramolecular polymers based mainly upon donor-acceptor interactions.

Full text of DOI:10.1021/ja030038m

Published on Web 09/11/2003
Donor-Acceptor Phthalocyanine Nanoaggregates
†
†
‡
Andr e´ s de la Escosura, M. Victoria Mart ´ı nez-D ´ı az, Pall Thordarson,
‡
‡
,†
Alan E. Rowan, Roeland J. M. Nolte, and Tom a´ s Torres*
Contribution from the Departamento de Qu ´ı mica Org a´ nica, UniVersidad Aut o´ noma de Madrid,
Cantoblanco, 28049-Madrid, Spain, and the Department of Organic Chemistry, NSRIM Center,
UniVersity of Nijmegen, ToernooiVel, 6525 ED Nijmegen, The Netherlands
Received January 21, 2003; E-mail: tomas.torres@uam.es
Abstract: A novel donor-acceptor bisphthalocyanine (bis-Pc, 1) in which two different Pc units (Zn(II)-Pc
and Ni(II)-Pc) are linked via vinylene spacers to the pseudopara positions of a central [2.2]paracyclophane
moiety is described. The synthesis of 1 is achieved by two successive Heck reactions of pseudopara-
divinyl[2.2]paracyclophane 9 with, sequentially, a zinc(II)- and a nickel(II)-iodophthalocyanine (4 and 5,
respectively). The self-assembly ability of 1, which is the result of the complementary donor-acceptor
character of its phthalocyanine units, has been assessed by a variety of techniques. It is revealed that 1
forms one-dimensional aggregates of nanometer-sized dimension, whereas equimolar mixtures of the donor
and acceptor Pc subunits 2 and 3, although strongly interacting, do not give large arrays. The aggregates
of 1 represent a novel type of supramolecular polymers based mainly upon donor-acceptor interactions.
Introduction
chemistry and requires (i) the incorporation of functional
building blocks, (ii) a control of the supramolecular assembly
process, and (iii) a function or property derived from the specific
assembled architectures.
Self-assembly and self-organization are based on the mutual
noncovalent recognition of molecules containing specific struc-
tural information. This strategy, originating from the natural
1
The aromatic macrocycles phthalocyanines (Pcs)10 are one
of the best known synthetic porphyrin analogues. They are
highly versatile and stable chromophores with unique physico-
chemical properties that make them ideal building blocks in
the construction of molecular materials having special electronic
and optical properties. Interestingly, owing to their extended
flat hydrophobic aromatic surface, these macrocycles can interact
with each other by attractive π-π stacking interactions,11
leading to aggregation in solution. However, the formation of
long-range ordered Pc aggregates is not so easily realized and
requires additional structural features within the Pc ring such
world, has been elegantly applied using a wide variety of
recognition motifs for the construction of numerous supra-
2
3
4
molecular architectures such as infinite arrays, grids , cages,
5
6
7
tubes, liquid crystals, and monolayers. The construction of
8
9
precisely defined molecular materials and molecular machines
designed to perform specific functions such as chemical sensing,
electrical conductivity, mechanical movements, and so forth
represents the next step forward in the field of supramolecular
†
Universidad Aut o´ noma de Madrid.
University of Nijmegen.
‡
(
1) (a) Supramolecular Chemistry-Concepts and PerspectiVes; Lehn, J. M., Ed.;
VCH: Weinheim, 1995. (b) Philp, D.; Stoddart, J. F. Angew. Chem., Int.
Ed. Engl. 1996, 35, 1155. (c) Reichert, A.; Ringsdorf, H.; Schuhmacher,
P.; Baumeister, W.; Scheybani, T. Compr. Supramol. Chem. 1996, 9, 313.
12
as the presence of long flexible hydrocarbon side chains or/
13
and crowned phthalocyanines. While the former type of
(
d) Rebek, J. Chem. ReV. 1997, 97, 1647. (e) Gracias, D. H.; Tien, J.; Breen,
substituents promote a mesomorphic behavior, the crown ether
T. L, Hsu, C.; Whitesides, G. M. Science 2000, 289, 1170.
(
2) (a) Batten, S. R.; Robson, R. Angew. Chem., Int. Ed. 1998, 37, 1461. (b)
Glink, P. T.; Stoddart, J. F. Pure Appl. Chem. 1998, 70, 419. (c) Elemans,
J. A. A. W.; Rowan, A. E.; Nolte, R. J. M. J. Am. Chem. Soc. 2002, 124,
(10) (a) Phthalocyanines: Properties and Applications; Leznoff, C. C., Lever,
A. B. P., Eds.; VCH: Weinheim, 1989, 1993, 1996; Vols. 1-4. (b) Hanack,
M.; Heckmann, H.; Polley, R. In Methods in Organic Chemistry (Houben-
Weyl); Schaumann, E., Ed.; Thieme: Stuttgart, 1998; Vol. E 9d, p 717. (c)
de la Torre, G.; Nicolau, M.; Torres, T. In Phthalocyanines: Synthesis,
Supramolecular Organization and Physical Properties (Supramolecular
PhotosensitiVe and ElectroactiVe Materials); Nalwa, H. S., Ed.; Academic
Press: New York, 2001. (d) Rodr ´ı guez-Morgade, M. S.; de la Torre, G.;
Torres, T. In The Porphyrin Handbook; Kadish, K. M.; Smith, K. M.;
Guilard, R., Eds.; Academic Press: San Diego, 2003, Vol. 13.
(11) (a) Hunter, C. A.; Sanders, J. K. M. J. Am. Chem. Soc. 1990, 112, 5525.
(b) Meyer, E. A.; Castellano, R. K.; Diederich, F. Angew. Chem., Int. Ed.
2003, 42, 1210.
(12) (a) Schutte, W. J.; Sluyters-Rehbach, M.; Sluyters, J. H. J. Phys. Chem.
1993, 97, 6069. (b) Engel, M. K.; Bassoul, P.; Bosio, L.; Lehmann, J.;
Hanack, M.; Simon, J. Liq. Cryst. 1993, 15, 709. (c) van Nostrum, C. F.;
Bosman, A. W.; Gelinck, G. H.; Schouten, P. G.; Warman, J. M.; Kentgens,
A. P. M.; Meijerink, A.; Picken, S. J.; Devillers, M. A. C.; Sohling, U.;
Schouten, A.-J.; Nolte, R. J. M. Chem.sEur. J. 1995, 1, 171. (d) Duro, J.
A.; de la Torre, G.; Barber a´ , J.; Serrano, J. L.; Torres, T. Chem. Mater.
1996, 8, 1061.
1
532.
(
(
(
(
3) Semenov, A.; Spatz, J. P.; Moller, M.; Lehn, J.-M.; Sell, B.; Schubert, D.;
Weidl, C. H.; Schubert, U. S. Angew. Chem., Int. Ed. 1999, 38, 2547.
4) Ikeda, A.; Ayabe, M.; Shinkai, S.; Sakamoto, S.; Yamaguchi, K. Org. Lett.
2
000, 2, 3707.
5) Bong, D. T.; Clark, T. D.; Granja, J. R.; Ghadiri, M. R. Angew. Chem.,
Int. Ed. 2001, 40, 988.
6) Metallomesogens. Synthesis, Properties and Applications; Serrano, J. L.,
Ed.; VCH: Weinheim, 1996.
(
7) Kumar, A.; Biebuyck, H. A.; Whitesides, G. M. Langmuir 1994, 10, 1498.
8) (a) van Nostrum, C. F.; Nolte, R. J. M. Chem. Commun. 1996, 2385. (b)
Service, R. F. Science 1998, 279, 1135. (c) Bjornholm, T.; Hassenkam,
T.; Reitzel, N. J. Mater. Chem. 1999, 9, 1975. (d) Tully, D. C.; Frechet, J.
M. J. Chem. Commun. 2001, 1229.
(
(
9) (a) Pease, A. R.; Jeppesen, J. O.; Stoddart, J. F.; Luo, Y.; Collier, C. P.;
Heath, J. R. Acc. Chem. Res. 2001, 34, 433. (b) Ballardini, R.; Balzani,
V.; Credi, A.; Gandolfi, M. T.; Venturi, M. Acc. Chem. Res. 2001, 34,
4
45. (c) Collin, J.-P.; Dietrich-Buchecker, C.; Gavi n˜ a, P.; J ´ı menez-Molero,
M. C.; Sauvage, J. P. Acc. Chem. Res. 2001, 34, 477.
1
2300 J. AM. CHEM. SOC. 2003, 125, 12300-12308
9
10.1021/ja030038m CCC: $25.00 © 2003 American Chemical Society

Donor−Acceptor Phthalocyanine Nanoaggregates
A R T I C L E S
Figure 1. Computer generated model of the proposed phthalocyanine aggregate formed by self-association of 1.
moieties help to form columnar aggregates in the presence of
metal salts due to complexation of the cation by the crown ether
subunits. Alternative molecular recognition motifs have also
been used such as hydrogen-bonding14 and metal-ligand15
interactions to self-assemble phthalocyanine molecules forming
either discrete supramolecular structures or infinite ill-defined
aggregates.
In spite of the extensive research in the field of phthalocyanine
assemblies, there are very few examples of supramolecular
phthalocyanine heterodimers to be found in the literature. One
such system is based on the recognition between the comple-
mentary peripheral substituents of a symmetrically substituted
(pCp) moiety. We have introduced short alkyl chains in the
peripheral alkoxy and alkylsulfonyl substituents, namely butoxy
and propylsulfonyl, respectively, in order to minimize the for-
mation of columnar assemblies driven by van der Waals inter-
actions between the peripheral alkyl chains. The aggregation
behavior of compound 1 in comparison with that of a 1:1 molar
mixture of monophthalocyanines 2 and 3 is described as well
as the aggregate architectures formed by the self-assemby of 1.
2
0
Results and Discussion
Synthesis and Characterization. Scheme 2 shows the
convergent strategy used to synthesize compound 1, which
involves first the preparation of the iodophthalocyanine precur-
1
8-crown-8-metallophthalocyanine and a tetra(alkylammonium)
16
21
22
derivative. In an alternative approach, noncovalent porphyrin
heterodimers have been constructed using electrostatic interac-
tions between macrocycles with opposite-charged substituents.
However, to our knowledge, donor-acceptor interactions have
never been explored in phthalocyanine systems and may
constitute a new way of constructing functional supramolecular
architectures based on these units.19
sors 4 and 5 (Scheme 1) with different donor/acceptor
character, by statistical crossover condensation of 4-iodophthalo-
17
23
24
nitrile (6) and 4,5-dibutoxyphthalonitrile (7) or 4,5-dipropyl-
18
22
sulfonylphthalonitrile (8), respectively. The two differently
substituted phthalocyanine fragments were connected to the
pseudopara-divinyl[2.2]paracyclophane 9 by two successive
Heck reactions.
Phthalocyanine 4 was prepared by heating a 1:3 mixture of
phthalonitriles 6 and 7 in the presence of Zn(OAc)2 in N,N-
dimethylaminoethanol (DMAE). The electron-deficient phthalo-
cyanine 5 was prepared in a similar way from phthalonitriles 6
and 8 using NiCl2 and a mixture of o-dichlorobenzene and DMF
as solvents in order to avoid nucleophilic attack to the sulfone
groups. The desired macrocycles were isolated from the
statistical mixture of phthalocyanines by column chromatogra-
phy on silica gel.
In this paper, we describe the first Pc supramolecular
assembly (see Figure 1) driven by strong donor-acceptor
interactions between Zn(II)- and Ni(II)-phthalocyanine rings
possessing at the periphery alkoxy and alkylsulfonyl substituents,
respectively.
We report here on the synthesis of the bisphthalocyanine
system 1 (Chart 1) which consists of two Pc units, one of them
electron-deficient and the other one electron-rich, conjugated
to the pseudopara positions of a central [2.2]paracyclophane
2
5
The [2.2]paracyclophane 9 was prepared in good yield in two
steps which involve the bromination of commercially available
(
(
(
13) (a) Sielcken, O. E.; van Tilborg, M. M.; Roks, M. F. M.; Hendriks, R.;
Drenth, W.; Nolte, R. J. M. J. Am. Chem. Soc. 1987, 109, 4261. (b) van
Nostrum, C. F.; Picken, S. J.; Nolte, R. J. M. Angew. Chem., Int. Ed. Engl.
26
[2.2]paracyclophane using the Reich and Cram conditions and
a subsequent Stille reaction in hot toluene using vinyltributyltin
as nucleophile and Pd(PPh3)4 as catalyst (Scheme 2). [2.2]Para-
cyclophane 9 was further reacted with phthalocyanine 4 in the
1
994, 33, 2173. (a) van Nostrum, C. F.; Picken, S. J.; Schouten, A.-J.;
Nolte, R. J. M. J. Am. Chem. Soc. 1995, 117, 9957.
14) (a) Duro, J. A.; de la Torre, G.; Torres, T. Tetrahedron Lett. 1995, 36,
8
079. (b) L u¨ tzen, A.; Starnes, S. D.; Rudkevich, D. M.; Rebek, J.
Tetrahedron Lett. 2000, 41, 3777. (c) Mart ´ı nez-D ´ı az, M. V.; Rodr ´ı guez-
Morgade, M. S.; Feiters, M. C.; van Kan, P. J. M.; Nolte, R. J. M.; Stoddart,
J. F.; Torres, T. Org. Lett. 2000, 2, 1057.
+
-
presence of Pd(OAc)2, Et3N, and Bu4N Br yielding 56% of
15) (a) Hanack, M. Hirsch, A.; Lehmann, H. Angew. Chem., Int. Ed. Engl.
(20) It is well-known that phthalocyanines containing long alkoxy chains are
prompt to form aggregates (see: Mausurel, D.; Sirlin, C.; Simon, J. New
J. Chem. 1987, 11, 4559). This tendency is reduced by using shorter chains.
The choice of a given peripheral lipophilic substituent implies playing with
the chain length for reaching enough solubility and low aggregation.
(21) Garc ´ı a-Frutos, E. Ph.D. Thesis, Universidad Aut o´ noma de Madrid, 2002.
(22) Maya, E. M.; Garc ´ı a, C.; Garc ´ı a-Frutos, E. M.; V a´ zquez, P.; Torres, T. J.
Org. Chem. 2000, 65, 2733.
1
990, 29, 1467. (b) Kobayashi, N.; Muranaka, A.; Nemykin, V. N.
Tetrahedron Lett. 2001, 42, 913.
(
16) Nikolaitchik, A. V.; Rodgers, M. A. J. J. Phys. Chem. A 1999, 103, 7597.
17) (a) Lipskier, J. F.; Tran-Thi, T. H. Inorg. Chem. 1993, 32, 722. (b) Lauceri,
R.; Raudino, A.; Scolaro, L. M.; Micalli, N.; Purrello, R. J. Am. Chem.
Soc. 2002, 124, 894.
(
(18) Hunter, C. A.; Lawson, K. R.; Perkins, J.; Urch, C. J. J. Chem. Soc., Perkin
Trans. 2 2001, 651.
(23) Marcuccio, S. M.; Svirskaya, P. I.; Greenberg, S.; Lever, A. B. P.; Leznoff,
C. C.; Tomer, K. B. Can. J. Chem. 1985, 63, 3057.
(
19) For recent papers of our group on bisphthalocyanines and related systems,
see: (a) de la Torre, G.; Gouloumis, A.; V a´ zquez, P.; Torres, T. Angew.
Chem., Int. Ed. 2001, 40, 2895. (b) Claessens, C. G.; Torres, T. Angew.
Chem., Int. Ed. 2002, 41, 2561. (c) Claessens, C. G.; Gonz a´ lez-Rodr ´ı guez,
D.; Torres, T. Chem. ReV. 2002, 102, 835. (d) Claessens C. G.; Torres, T.
J. Am. Chem. Soc. 2002, 124, 14522.
(24) (a) W o¨ hrle, D.; Schmidt, V. S. J. Chem. Soc., Dalton Trans. 1988, 549.
(b) Kobayashi, N.; Opallo, M.; Osa, T. Heterocycles 1990, 30, 389.
(25) de la Torre, G.; Mart ´ı nez-D ´ı az, M. V.; Ashton, P. R.; Torres, T. J. Org.
Chem. 1998, 63, 8888.
(26) Reich, H. J.; Cram, D. J. J. Am. Chem. Soc. 1969, 91, 3527.
J. AM. CHEM. SOC.
9
VOL. 125, NO. 40, 2003 12301

A R T I C L E S
de la Escosura et al.
Chart 1
Scheme 1. Synthesis of Iodophthalocyanine Precursors 4 and 5
by Statistical Condensation
methodology (Scheme 2). Thus, a Heck reaction between the
monovinyl[2.2]paracyclophane 11 and the iodophthalocyanine
4
or 5 in the appropriate conditions (depending on the
substituents at the periphery, OC4H9 or SO2C3H7) afforded
compounds 2 and 3, respectively, in good yields.
All the compounds were characterized by mass spectrometry
and UV-vis spectroscopy and, when it was possible, by NMR
1
spectroscopy. The H NMR spectra of phthalocyanine deriva-
tives 3 and 5 bearing sulfone groups showed well-resolved sets
of resonances. The high-resolution found in these spectra is
indicative of a low degree of aggregation in solution, that has
to be attributed to the high polarity of the sulfonyl groups
25
surrounding the Pc core. The aromatic phthalocyanine protons
for the isoindole units bearing sulfone groups appear as six
singlets in the range of δ 9.8 to 10.2 ppm (see Supporting
Information). The alkoxy substituted phthalocyanines are, in
1
general, more prone to aggregation, which results in H NMR
spectra with broadened signals, as was observed for compound
1
4
. In contrast, the H NMR spectra in CDCl3 of hexabutoxy-
phthalocyanines 2 and 10, in which a paracyclophane subunit
has been attached, showed resolved sets of resonances assigned
to the Pc ring protons in the range of 7.5 to 8.5 ppm (see
Supporting Information) which indicates that the presence of
such a bulky substituent has significantly reduced the macro-
cycle aggregation in solution.
1
The H NMR spectrum in CDCl3 of bisphthalocyanine 1
showed the typical broadened resonances of phthalocyanine
aggregates (see Supporting Information). As this phenomenon
is not observed with compounds 2 and 10, these results suggest
that inter- or intramolecular interactions are occurring between
the differently substituted, donor and acceptor, phthalocyanine
units. For this reason, monophthalocyanines 2 and 3 have been
prepared, to more closely study the inter- or intramolecular
nature of these interactions.
derivative 10. The second phthalocyanine unit was introduced
by an additional Heck reaction using milder conditions, namely
i
Pd(MeCN)2Cl2 and a less nucleophilic base such as Et2 PrN.
The two monophthalocyanine-[2.2]paracyclophane systems
2
and 3 were prepared by means of the same synthetic
12302 J. AM. CHEM. SOC.
9
VOL. 125, NO. 40, 2003

Donor−Acceptor Phthalocyanine Nanoaggregates
A R T I C L E S
Scheme 2. Synthesis of Bis- and Monophthalocyanine-[2.2]Paracyclophanes 1, 2, and 3
The same conclusions concerning the aggregation properties
of the molecules were also obtained using UV-vis spectroscopy.
The shape and location of the so-called Q-band is known to be
a sensitive probe in determining the aggregation properties of
cyanine units of the molecule. The CT band can be more clearly
observed by subtracting the UV-vis spectra of monophthalo-
cyanines 2 and 3 from the spectrum of 1 (see Figure S2 in the
Supporting Information). The subtracted spectrum also shows
the characteristic aggregation band at 638 nm due to the cofacial
aggregation of phthalocyanines.
2
7
these macrocycles. The UV-vis spectra of compounds 1, 2,
and 3 in CHCl3 are shown in Figure 2. Compound 2 exhibits
an intense Q-band absorption centered at 692 nm, typical of
monomeric metallophthalocyanines.10 The intrinsic lack of
symmetry of compound 3 is also reflected in its UV-vis
spectrum, showing a split Q-band. Interestingly, a new broad
blue shifted absorption centered at ca. 639 nm is observed in
the spectrum of compound 1, indicative of cofacial aggregation.
Additionally, the UV-vis spectrum of compound 1 reveals a
broad low intensity band at around 740 nm assignable to a
charge-transfer (CT) band28 which is a consequence of the
electronic coupling between the donor and acceptor phthalo-
Aggregation Studies. Prior to any binding analyses, UV-
1
vis and H NMR dilution studies were carried out with the
monomers 2 and 3 in order to evaluate the contribution of the
self-association processes. No significant changes in the absorp-
tion spectra of these compounds in CHCl3 were detected in the
-
6
-4
range of 5 × 10 to 1 × 10 molar concentration. These
results indicate that aggregation of these [2.2]paracyclophane-
phthalocyanines is not significant in this range of concentration
in contrast with the usual behavior of peripherally alkoxy
1
2a
substituted phthalocyanines. To evaluate more precisely the
Figure 2. Electronic absorption spectra in CHCl3 of 1 (7.5 × 10-6 M, plain line), 2 (8.1 × 10-6 M, dashed line), and 3 (6.9 × 10-6 M, solid line).
J. AM. CHEM. SOC.
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VOL. 125, NO. 40, 2003 12303

A R T I C L E S
de la Escosura et al.
Table 1. Association Constants (M-1) and Free Energy of
Formation (kJ/mol) at 298 K
solvent
K
a
−∆G°
4
a,b
2
3
2
1
1
1
CHCl3
CHCl3
CHCl3
toluene
CHCl3
DMF
1 × 10
a
1175
17.5 ( 1
42 ( 4
54 ( 10
34 ( 2
28 ( 2
7
9
c
c
6
•3
2 × 10
3 × 10
c
c
1.1 × 10
4
9.2 × 10
a
Determined by 1H NMR. b Upper estimated value. c Determined by
UV-vis spectroscopy.
Figure 3. Schematic representation of some of the possible conformations
of a noncovalent dimer of 3: parts a and b represent cofacial conformations,
and part c represents a staggered conformation.
Figure 4. Electronic absorption spectra in CHCl3 of 1 (solid line, 7.5 ×
-
6
-6
10
M) and an equimolar mixture of 2 and 3 (dotted line, 4 × 10 M).
-
6
-4
Inset: concentration dependence (from 1 × 10 to 1 × 10 M) of the
electronic spectrum of 1 in chloroform solution.
1
self-association constants, H NMR studies in the range of 1 ×
-
4
-3
1
0
to 1 × 10 M concentrations were carried out. In these
studies, a 1:1 homodimer complex was assumed as the only
type of association event occurring in solution. Several aromatic
signals of compounds 2 and 3 were monitored as a function of
concentration, and quantitative analysis of the data was ac-
complished using a custom written global29 nonlinear regression
analysis program within the Matlab 5.3 package30 (see Sup-
porting Information). The 1:1 self-dimerization of compound 3
The UV-vis spectrum of an equimolar mixture of donor and
acceptor phthalocyanines 2 and 3 in CHCl3 showed remarkably
similar features to those seen for compound 1 (see Figure 4),
namely the appearance of a blue shifted maximum absorption
centered at 639 nm and a low intensity charge transfer band at
around 740 nm, thus confirming the intermolecular nature of
this CT band. This result indicates that, in addition to the
hydrophobic effect, which is known to induce phthalocyanines
to form aggregates in solution, the two Pc halves of compound
-
1
was found to be Kdimer ) 1175 M in CHCl3 (Table 1). In the
case of compound 2, the spectra throughout the H NMR binding
1
study were too broad to obtain any accurate result. However,
the upper limit of the value of the dimerization constant of this
compound can tentatively be estimated to be in the order of
1
may be considered as donor and acceptor subunits that interact
with each other mainly in an intermolecular fashion.
UV-vis spectroscopy was found to be an ideal technique31
for studying the interaction between 2 and 3. The concentration
of compound 2 was kept constant at 1.5 µM in CHCl3, to which
was added increasing concentrations of the monophthalo-
cyanine-cyclophane 3. The heterodimer 2‚3/monomer 3 ratio
was monitored as a function of the concentration of 3 by plotting
the absorption ratio at 639 and 705 nm [A(639)/A(705)] versus
concentration of monomer 3 (Figure 5). These two maxima were
chosen since they are characteristic absorptions of the dimeric
and the monomeric species, respectively. Upon aggregation, a
decrease in the intensity of the maxima at 705 nm (assigned to
the monomeric phthalocyanine 3) and concomitant increase of
the maxima at 639 nm (assigned to the heterodimer formed
4
-1
12a
1
0 M considering the results reported in the literature and
the particular structural features of 2, namely, the presence of
both a very bulky substituent (the paracyclophane) and short
alkoxy chains.
Upon dilution, both the chemical shifts and the number of
peaks changed, in particular in the aromatic region of the spectra.
-
5
The spectrum of the most diluted sample (8.25 × 10 M)
showed the expected three singlets for compound 3. Upon
increasing the concentration, the aromatic resonances shifted
to higher field and doubled in number (from 3 to 6 resonances).
This doubling might be a consequence of the formation of a
noncovalent dimer with low symmetry, as the one depicted
schematically in Figure 3c, in which the macrocycles have
adopted a staggered geometry that accounts for the observed
breaking of symmetry.
3
2
between 2 and 3) are observed. The formation of higher
aggregates (n ) 3, 4, etc.) has been neglected, taking into
account the low concentration used. The dimerization constant
Having previously analyzed the tendency of monomeric
phthalocyanines 2 and 3 to self-associate, we have carried out
further binding studies to determine the heteroassociation
constants of the differently substituted phthalocyanine units
present in 1, 2 and 3.
2
9,30
in CHCl3 calculated
(see Supporting Information) from the
1
(
31) To determine the exact association constants, H NMR binding studies in
3
CDCl were performed in which the concentration of 3 was held constant
at 1 mM in the presence of increasing concentrations of 2. Unfortunately,
1
the H NMR signals were not sufficiently resolved at relatively low
concentrations to obtain any accurate data from this experiment.
(
(
(
(
27) Schutte, W. J.; Sluyters-Rehbach, M.; Sluyters, J. H. J. Phy. Chem. 1993,
7, 6069.
28) Guldi, D. M.; Gouloumis, A.; V a´ zquez, P.; Torres, T. Chem. Commun.
002, 2056.
29) Beechem, J. M. In Methods in Enzymology; Brand, L., Johnson, M. L.,
Eds.; Academic Press: San Diego, 1992; Vol. 210, pp 37-54.
30) Matlab, version 5.3.0.620a (R11); The Mathworks, Inc.: Natick, MA, 1999.
(32) However, it is necessary to point out that both the absorption spectra of
monomeric phthalocyanines 2 and 3 and the heterodimer 2‚3 appear in the
same spectral region, and therefore, it is very difficult to obtain clean spectra
for each species. Most probably, a small contribution of the other species
to the selected maxima absorption (mainly the one at 639 nm) cannot be
discarded, obviously contributing to the experimental small error of this
analysis.
9
2
12304 J. AM. CHEM. SOC.
9
VOL. 125, NO. 40, 2003

Donor−Acceptor Phthalocyanine Nanoaggregates
A R T I C L E S
The aggregation of the bisphthalocyanine-[2.2]paracyclophane
was found also to be temperature dependent. The heat of
1
association (W) can be estimated by UV-vis spectroscopy by
plotting the ratio of absorbances of the aggregate (639 nm) and
the monomer (692 nm) versus the temperature for four different
concentrations of 1 in toluene (see Supporting Information). The
aggregation number is related to this absorbance ratio; that is,
at a fixed ratio the weight fraction of the monomer, m1, is
constant. For a constant m1, the following relationship holds
3
4
for linear aggregates of uniform structure:
W ) R[∆ ln c/∆(1/T)]
where W(∆H) is the heat of association, R is the gas constant,
∆
ln c is the difference between two Pc concentrations, and
∆
(1/T) is related to the temperature difference that has to be
Figure 5. Ratio of the absorbances at 639 and 705 nm plotted versus the
concentration of monomer 3 in chloroform.
applied to maintain a constant m1. The temperature (T) values
at which the absorbance ratio equals 0.8 were obtained by
intrapolation of the data points at each concentration c and
plotted as ln c versus 1/T (see Supporting Information). A
straight line was obtained from which a value of W ) -30 kJ
mol was determined. In combination with ∆G measure-
ments obtained by binding studies, the entropy of association
can be calculated as ∆S ≈ 80 J K mol . This tentatively
suggests that desolvation of the monomer 1 is an important
factor in driving the self-association of this compound in
7
-1
UV-vis studies is Kdimer ) 2 × 10 M (Table 1). This large
dimerization value certainly demonstrates the strong preference
for the qualitative formation of a heterodimer by intermolecular
interactions of the donor and acceptor phthalocyanines 2 and
-1
3
.
-
1
-1
The aggregation of bisphthalocyanine 1 was also studied by
UV-vis spectroscopy. Dilution experiments carried out in
solvents with different dielectric constants (namely toluene,
-
6
35
CHCl3 and DMF) in the range of concentration 1 × 10 to 1
toluene.
-
4
×
10 M showed a clear concentration dependency. The
Higher values of heats of associations (-125 kJ/mol) have
been reported for liquid-crystalline phthalocyanines, which form
larger linear aggregates in a chloroform solution, as a conse-
quence of additional van der Waals interactions between the
peripheral substituents. However, in our system, we have tried
to minimize the contribution of the peripheral substituents to
the aggregation, and therefore, the heat of association comes
primarily from the donor-acceptor interactions between dif-
ferent types of Pc macrocycles.
Electron Microscopy Studies. Considering the complexation
studies mentioned above, we believed the interaction between
the different phthalocyanine units of compound 1 could result
in the formation of a large phthalocyanine array (see Figure 1
and Figure 6a). To investigate the formation of these aggregates,
several samples of different concentration in hot n-butanol were
studied by transmission electron microscopy (TEM). n-Butanol
was chosen as the solvent for technical reasons, among others,
its high boiling point. The formation of large aggregates was
not observed in the low concentration samples. However, as
the concentration of 1 reached approximately 1 mM, aggregates
became visible (Figure 7). A unique feature of these aggregates
is that they are very monodisperse in both shape and size (typical
different absorption spectra of compound 1 in CHCl3 are shown
in the inset of Figure 4. As the concentration is increased, a
decrease in the absorption maxima at 692 nm (corresponding
to the monomer) and an increase of the absorption at 639 nm
due to the aggregate are observed. The data from these dilution
13a
2
9,30
studies were fitted
(see Supporting Information) to a 1:1
dimerization binding model, assuming no higher aggregates, to
6
give Kdimer ) 1.1 × 10 in CHCl3 (Table 1). This value is an
-
1
order of magnitude (ca. 8 kJ mol ) lower than that observed
for the heterodimerization of 2 and 3. This suggests that 1 cannot
assemble to form a perfectly cofacial “double dimer” (Figure
6
b) (due to the cyclophane step that forces the phthalocyanine
units to offset) and rather prefers to assemble into an “elongated
dimer” (Figure 6a) in which only two phthalocyanines interact,
with the possibility of further aggregation in one dimension.
Possible staggered conformations cannot be ruled out from the
latter assembly.
The donor-acceptor nature of the dimerization is highlighted
by the sensitivity to the solvent polarity. The influence of the
solvent polarity in the association constant can also give valuable
information about the nature of the interactions controlling the
complexation.33 In general, complexes involving nonpolar
interactions are stabilized by polar solvents and complexes
involving polar interactions (electrostatics) are more stable in
nonpolar solvents. A higher association constant was measured
2
dimensions 290 × 90 nm ). In contrast and as expected, no
aggregates were detected when using an equimolar mixture of
phthalocyanines 2 and 3. Indeed, the presence of the bulky
paracyclophane unit prevents the formation of large phthalo-
cyanine nanoaggregates.
9
-1
for compound 1 in toluene (Kdimer ) 3 × 10 M , ∆G ) -54
-
1
kJ mol ). This trend is in line with the idea that polar
interactions play an important role in the complex formation
between the two phthalocyanine surfaces, one with acceptor and
the other one with donor character.
Phthalocyanines 2 and 3, in the presence of 1, could
eventually act as stoppers of an infinite array made of compound
1 units, preventing the growth of the aggregate. The effect of
the addition of these monophthalocyanines on the aggregates
(
33) (a) Breault, G. A.; Hunter, C. A.; Mayers, P. C. J. Am. Chem. Soc. 1998,
(34) O¨ lschl a¨ ger, H. J. Colloid Interface Sci. 1969, 31, 503.
(35) For an example of desolvation effects in self-assembly, see: Taylor, P.
N.; Anderson, H. L. J. Am. Chem. Soc. 1999, 121, 11538.
1
20, 3402. (b) Cubberley, M. S.; Iverson, B. L. J. Am. Chem. Soc. 2001,
23, 7560.
1
J. AM. CHEM. SOC.
9
VOL. 125, NO. 40, 2003 12305

A R T I C L E S
de la Escosura et al.
Figure 6. Schemetic representation of the type of aggregates that bisphthalocyanine 1 could form by donor-acceptor interactions: (a) one-dimensional
aggregates or (b) columnar aggregates.
Figure 7. (a,b) Transmission electron micrographs of 1. Samples were prepared from hot n-butanol solutions (1 × 10-3 M).
Figure 8. Size distribution diagrams of lengths and widths of aggregates formed by (a) bisphthalocyanine 1 and (b) a 2:1:1 mixture of 1, 2, and 3 (each
diagram contains around 150 data points).
size of the bisphthalocyanine 1 was investigated also by means
of TEM in different samples in which the bisPc/monoPcs ratio
was changed. Using a 2:1:1 mixture of 1, 2, and 3, well-defined
aggregates were observed with the same shape as those obtained
with compound 1. Figure 8 presents the size distribution diagram
of lengths and widths of the aggregates formed by (a) pure
bisphthalocyanine 1 and (b) the 2:1:1 mixture of 1, 2, and 3.
They both show similar lengths, widths, and size dispersities
of the structures. This result indicates that the size of the
bisphthalocyanine 1 aggregates is not dramatically modified by
12306 J. AM. CHEM. SOC.
9
VOL. 125, NO. 40, 2003

Donor−Acceptor Phthalocyanine Nanoaggregates
A R T I C L E S
addition of monophthalocyanines 2 and 3, probably due to the
higher tendency of these molecules to form discrete dimers
rather than to be incorporated within the phthalocyanine
aggregate.
CH
m, 24H, CH
H), 2957, 2920, (CH), 1605 (CdC), 1279 (ArOsC), 1097, 1048, 743
2
), 3.5 (br. s, 1H, pCpsCH
2
), 3.2 (m, 6H, pCpsCH
2
), 2.1-1.8 (2
×
2
), 1.2 ppm (m, 18H, CH
3
); IR (KBr) ν ) 3442 (ArCs
-1
cm ; UV/vis (CHCl
3
) λmax (log ꢀ) ) 291 (4.68), 355 (4.95), 622 (4.4),
+
6
92 nm (5.14); MS (FAB) m/z ) 1240.5 [M + H ], 1137.4 [M -
+
8 7 80 8 6
H ] . Calculated for C74H N O Zn (1242.87): C, 71.45; H, 6.44;
C
Conclusions
N, 9.01. Found: C, 44; H, 6.27; N, 9.11.
In conclusion, heteroassociation between electron-rich Zn(II)-
hexabutoxyphthalocyanines and electron-deficient Ni(II)hexa-
Hexa(propylsulfonyl)phthalocyaninatonickel(II)-[2.2]paracyclo-
phane (3). A solution of hexa(propylsulfonyl)iodophthalocyaninato-
nickel(ΙΙ) (5)22 (50 mg, 0.037 mmol), 4-vinyl[2.2]paracyclophane (11)
(alkylsulfonyl)phthalocyanines has been observed for the first
i
time. Donor-acceptor interactions have been shown to be the
main driving force for the association of bisphthalocyanine 1,
which forms one-dimensional nanoaggregates through inter-
molecular interactions between its complementary, donor and
acceptor, Pc fragments. We believe that this novel recognition
motif and the formation of these novel π-π supramolecular
polymers represent a useful tool to control the organization of
phthalocyanines into functional supramolecular systems.
(9.6 mg, 0.040 mmol), Et
2
PrN (0.1 mL), tetra-n-butylammonium
bromide (11.2 mg, 0.040 mmol), and Pd(CH
3
CN) Cl (0.6 mg, 0.0035
2
2
mmol) in anhydrous DMF (3 mL) was heated at 80 °C for 12 h under
an argon atmosphere. The solvent was evaporated, and the solid residue
was triturated with methanol, filtered, and purified by column chro-
matography (SiO
blue solid. Mp >250 °C; H NMR (200 MHz, CDCl
10.1-9.8 (six s, 6H, arom. Pc), 9.0 (m, 2H, arom. Pc), 8.41 (d, J )
.8 Hz, 1H, arom. Pc), 7.61 and 7.33 (AB system, J ) 15.6 Hz, 2H,
vinyl), 6.91 (s, 1H, arom. pCp), 6.77 (d, 1H, arom. pCp), 6.6 (m, 5H,
arom. pCp), 4.1 (m, 12H, SO CH ), 3.7 (m,1H, pCpsCH ), 3.3-3.0
(m, 7H, pCpsCH ), 2.2 (m, 12H, CH ), 1.2 ppm (m, 18H, CH ); IR
2
, CHCl
3
1
/Et
2
O 30:1) to yield 3 (20 mg, 37%) as a
3
, 25 °C, TMS) δ
)
7
Experimental Section
2
2
2
Melting points were determined on a B u¨ chi apparatus and are
uncorrected. Infrared spectra were recorded on a Bruker (FT-IR)
2
2
3
(KBr) νj ) 3452 (ArCsH), 2967, 2933 (CH), 1604 (CdC), 1295, 1145,
1
-1
spectrophotometer. The H NMR spectra were recorded on a Bruker
3
1086 cm ; UV/vis (CHCl ) λmax (log ꢀ) ) 267 (4.63), 300 (4.66), 347
AC-200 (200 MHz) and AC-300 (300 MHz). UV/vis spectra were
recorded on a Perkin-Elmer 8453 spectrophotometer. The mass spectra
were determined on a VG AutoSpec spectrometer. Elemental analyses
were performed on a Perkin-Elmer 2400 CHN elemental analyzer.
Transmission electron microscopy was carried out with a Philips
TEM 201 instrument. Small drops of the samples in hot n-butanol, at
concentrations of approximately 10 , 10 , and 10 , were placed on
carbon-coated grids. The material was allowed to adsorb for 1 min,
and then the grids were blotted dry by touching the edges with filter
paper. Finally, the structures were visualized by TEM.
(4.79), 615 (4.37), 677 (4.96), 705 nm (4.81); MS (FAB) m/z ) 1439
+
[M + H ]. Calculated for C68
68 8 6
H N S O12Ni (1440.38): C, 56.65; H,
4.72; N, 7.78; S, 13.37. Found: C, 56.59; H, 4.44; N, 7.83; S 13.31.
4,12-Divinyl[2.2]paracyclophane (9). A mixture of 4,12-dibromo-
[2.2]-paracyclophane26 (80 mg, 0.22 mmol) and [Pd(PPh
3 4
) ] (24 mg,
0.021 mmol) in toluene (20 mL) was stirred under argon. Then tributyl-
(vinyl)tin (0.27 mL, 0.88 mmol) was added. The reaction mixture was
-
5
-4
-3
heated at 100 °C for 48 h. After removal of the solvent, CH
added and the organic layer was washed with water, dried (Na
2
Cl
2
was
SO ),
2
4
and filtered. The solvent was removed in vacuo, and the residue was
purified by column chromatography using hexane/ether 150:1 as eluent.
Compound 9 was obtained as a white solid (43 mg, 75%). Mp 164 °C;
Bisphthalocyaninato-[2.2]paracyclophane (1). A solution of hexa-
(
0
butoxy)phthalocyaninatozinc(ΙΙ)-[2.2]paracyclophane (10) (40 mg,
22
1
13
.032 mmol), hexa(propylsulfonyl)iodophthalocyanatonickel(ΙΙ) (5)
H and C NMR (CDCl
3
) are in agreement with those reported in ref
i
-1
(45 mg, 0.034 mmol), Et
2
PrN (0.1 mL), tetra-n-butylammonium
36; IR (KBr) νj ) 3092-3010, 2934-2851, 1622, 1588, 980, 770 cm
MS m/z (%) ) 260 (30) [M ], 131 (55), 130 (61), 129 (100), 128
;
+
bromide (12.6 mg, 0.039 mmol), and Pd(CH
3
CN) Cl (0.5 mg, 0.0030
2
2
mmol) in 5 mL of anhydrous DMF was heated at 80 °C for 12 h under
argon atmosphere. After the solution cooled to room temperature, the
solvent was evaporated and the residue was triturated with methanol,
(37), 115 (60). Calculated for C20
Found: C, 92.07; H, 7.68.
H20 (260.16): C, 92.25; H, 7.75.
Hexa(butoxy)phthalocyaninatozinc(II)-vinyl[2.2]paracyclo-
filtered, and finally purified by column chromatography (SiO
ethyl acetate/acetone 30:1:1) to afford 1 (27 mg, 34%) as a green solid;
2
, CHCl
3
/
phane (10). A solution of hexa(butoxy)iodophthalocyaninatozinc(ΙΙ)
(4) (52 mg, 0.045 mmol), 4,12-divinyl[2.2]paracyclophane (9) (11.9
21
mp > 250 °C; IR (KBr) ν ) 3442 (ArCsH), 2958, 2920 (CH), 1605
mg, 0.045 mmol), K CO (32 mg, 0.23 mmol), tetra-n-butylammonium
2
3
-
1
(CdC), 1263 (ArOsC), 1145, 1097, 1046 cm ; UV/vis (CHCl
3
) λmax
bromide (14.4 mg, 0.045 mmol), LiCl (2 mg, 0.047 mmol), and
palladium(ΙΙ) acetate (1.1 mg, 0.0045 mmol) in 4 mL of anhydrous
DMF was heated at 100 °C for 8 h. After the reaction mixture cooled
to room temperature, the solvent was removed under reduced pressure.
(
log ꢀ) ) 298 (4.99), 347 (5.05), 639 (5.02), 679 nm (5.15); MALDI-
+
TOF MS m/z ) 2471 [M ]. Calculated for C126
132 16 6
H N S O18NiZn
(
2474.96): C, 61.20; H, 5.33; N, 9.05; S, 7.78. Found: C, 61.01; H,
.29; N, 9.04; S, 7.68.
Hexa(butoxy)phthalocyaninatozinc(II)-[2.2]paracyclophane (2).
A solution of hexa(butoxy)iodophthalocyaninatozinc(ΙΙ) (4)21 (60 mg,
.053 mmol), 4-vinyl[2.2]-paracyclophane (11) (15 mg, 0.064 mmol),
CO (37 mg, 0.27 mmol), tetra-n-butylammonium bromide (17 mg,
.053 mmol), LiCl (2 mg, 0.047 mmol), and palladium(ΙΙ) acetate (1.3
mg, 0.0053 mol) in 3 mL of anhydrous DMF was heated at 100 °C for
h. After the reaction mixture cooled to room temperature, the solvent
was removed under reduced pressure. CH Cl was added, and the
organic layer was washed several times with water, dried (Na SO ),
5
CH
2
Cl
2
was added, and the organic layer was washed several times
SO ), filtered, and evaporated. The crude was
with water, dried (Na
2
4
purified by chromatography on silica gel with hexane/dioxane (4:1) as
0
eluent. The product was obtained as a green solid: 20 mg (56%); mp
1
K
2
3
> 250 °C; H NMR (CDCl
3
, 300 MHz, 25 °C, TMS) δ 8.5 ) (br. s,
0
2H, arom. Pc), 8.3 (br. s, 2H, arom. Pc), 7.8-7.7 (m, 5H, arom. Pc),
7.50 (d, J ) 15.8 Hz, 1H, vinyl), 7.19 (d, J ) 15.8 Hz, 1H, vinyl),
6.98 (s, 1H, arom. pCp), 6.94 (dd, J ) 17.4, 10.9 Hz, 1H, vinyl Hgem),
6.8 (m, 3H, arom. pCp), 6.68 (s, 1H, arom. pCp), 6.50 (dd, J ) 7.3,
4.9 Hz, 1H, arom. pCp), 5.64 (d, J ) 17.4 Hz, 1H, vinyl Htrans), 5.39
8
2
2
2
4
filtered, and evaporated. The crude was purified by column chroma-
tography on silica gel with hexane/dioxane (4:1) as eluent. The product
was obtained as a green solid: 39 mg (60%); mp >250 °C; H NMR
(d, J ) 10.9 Hz, 1H, vinyl Hcis), 4.2-3.9 (2 × m, 12 H, OCH
2
), 3.8
), 3.1 (m, 6H, pCpsCH ),
); IR (KBr) νj )
(m, 1H, pCpsCH
2
), 3.6 (m, 1H, pCpsCH
2
2
1
2.0-1.7 (2 × m, 24H, CH
2
), 1.2 ppm (m, 18H, CH
3
3442 (ArCsH), 2957, 2920, (CH), 1605 (CdC), 1279 (ArOsC), 1097,
3
(300 MHz, CDCl , 25 °C, TMS) δ ) 8.5 (br s, 2H, arom. Pc), 8.4 (br
-1
s, 2H, arom. Pc), 7.8-7.6 (m, 5H, arom. Pc), 7.5 (m, 1H; vinyl), 7.3
1048, 743 cm ; UV/vis (CHCl
(36) Alay, A. A.; Hopf, H.; Ernst, L. Eur. J. Org. Chem. 2000, 3021.
J. AM. CHEM. SOC. VOL. 125, NO. 40, 2003 12307
3
) λmax (log ꢀ) ) 276 (4.79), 356 (4.92),
(
(
m, 1H, vinyl), 6.9 (m, 1H, arom. pCp), 6.8 (s, 1H, arom. pCp), 6.6
m, 5H, arom. pCp), 4.3-3.9 (2 × m, 12H, OCH ), 3.8 (m, 1H, pCps
2
9

A R T I C L E S
de la Escosura et al.
+
global29 nonlinear regression analysis program within the Matlab 5.330
package (see also Supporting Information).
6
-
20 (4.26), 692 nm (4.94); MS (FAB) m/z ) 1266.6 [M ], 1136.3 [M
+
10 82 8 6
C H10] . Calculated for C76H N O Zn (1268.52): C, 71.89; H, 6.46;
N, 8.83. Found: C, 71.88; H, 6.44; N, 8.62.
UV/vis Titration of Donor and Acceptor Phthalocyanines (2 and
). A stock 1.5 µM solution of compound 2 was prepared in chloroform
4
-Vinyl[2.2]paracyclophane (11). To a stirred solution of 4-bromo-
3
37
[
2.2]-paracyclophane (100 mg, 0.35 mmol) and [Pd(PPh
3 4
) ] (18 mg,
and then used as solvent for the preparation of a stock 69.5 µM solution
of 3. This procedure ensures a constant concentration of 2 throughout
the titration. The titration was performed by adding the required volumes
of the solution of the acceptor phthalocyanine 3 to 2 mL of the donor
phthalocyanine 2 solution. The Q-band absorptions were monitored as
a function of the concentration of 3, and the data were analyzed by a
0
.018 mmol) in toluene (20 mL), tributyl(vinyl)tin (0.20 mL, 1.05
mmol) was added. The mixture was heated at 100 °C for 24 h. After
removal of the solvent under reduced pressure, dichloromethane was
added and the solution was washed with water and dried (Na
the solvent was evaporated. The residue was purified by column
chromatography (SiO , CH Cl /hexane 1:1) to give 11 (71 mg, 87%)
as a white solid. Mp 70 °C; H NMR (CDCl , 300 MHz, 25 °C, TMS)
δ ) 6.81 (dd, J ) 17.8, 11.3 Hz, 1H, vinyl Hgem), 6.73 (d, J ) 7.7 Hz,
H, arom.), 6.6-6.4 (m, 6H, arom. H), 5.55 (d, J ) 17.8 Hz, 1H, vinyl
trans), 5.29 (d, J ) 11.3 Hz, 1H, vinyl Hcis), 3.5 (m, 1H, pCp-CH ),
, 300 MHz, 25
C, TMS) δ ) 139.3, 137.2, 135.1, 134.7, 133, 131.9, 131.8, 130.1,
2 4
SO );
2
2
2
29
custom written global nonlinear regression analysis program within
1
3
30
the Matlab 5.3 package (see also Supporting Information).
UV/vis Dilution Studies of Bisphthalocyanine 1. Stock solutions
of compound 1 in different solvents (chloroform, DMF, and toluene)
were prepared in a volumetric flask (2 mL). More diluted solutions
were prepared in 2 mL volumetric flasks by diluting the required
amounts of the stocks. This procedure was repeated for the three
different solvents giving in each case a total of eight concentrations.
The Q-band absorptions were monitored as a function of the concentra-
1
H
2
1
3
3
2 3
.2-2.8 ppm (m, 7H, pCp-CH ); C NMR (CDCl
°
1
29.5, 114.2, 35.4, 35.2, 34.6, 33.6 ppm; IR (KBr) νj ) 3090-3009,
-
1
2
927-2851, 1621, 1590, 989, 906 cm ; MS (EI) m/z (%) ) 234.1
+
+
+
8 8
H ] . Calculated
(24) [M ], 129.1 (100) [M - C
8
H
8
] , 105.1 (34) [C
29
tion of 1, and the data were analyzed a custom written global nonlinear
regression analysis program within the Matlab 5.330 package (see also
Supporting Information).
for C18
H18 (234.34): C, 92.17; H, 7.68. Found: C, 92.01; H, 7.59.
1
H NMR Dilution Studies of Phthalocyanines 2 and 3. Stock
chloroform solutions of compounds 2 and 3 (1.11 mM and 2.64 mM,
respectively) were prepared in volumetric flasks (2 mL). For each
compound, an aliquot of the stock solution (1 mL) was transferred to
a dry vial using a syringe and diluted with chloroform (1 mL). This
solution was then used as the stock in the preparation of a third dilution.
This procedure was repeated to give a total of five different concentra-
tions. An aliquot of each concentration (0.5 mL) was then transferred
to a dry NMR sample tube. The NMR spectra were referenced to TMS,
and the aromatic signals were recorded as a function of the concentration
Supporting Information Available: Details on calculations
1
of binding constants, H NMR spectra of compounds 1, 2, and
3
, figures showing the temperature dependence of association
for compound 1, and the UV-vis spectrum of bisphthalocyanine
1 obtained upon subtracting the absorption spectra of the
reference molecules 2 and 3 showing both the aggregation and
CT bands. This material is available free of charge via the
Internet at http://pubs.acs.org.
(T ) 298 K). The dilution data were analyzed using a custom written
(37) Cram, D. J.; Day, A. C. J. Org. Chem. 1966, 31, 1227.
JA030038M
12308 J. AM. CHEM. SOC.
9
VOL. 125, NO. 40, 2003