Synthesis of novel phthalocyanine-tetrathiafulvalene hybrids; Intramolecular fluorescence quenching related to molecular geometry

Article abstract of DOI:10.1021/jo020340y

A number of silicon phthalocyanine bis-esters have been synthesized and characterized, with axial ligands containing one or more tetrathiafulvalene groups. Variations in the substitution positions around a central aromatic "hinge" within the ligands lead

Full text of DOI:10.1021/jo020340y

Syn th esis of Novel P h th a locya n in e-Tetr a th ia fu lva len e Hybr id s;
In tr a m olecu la r F lu or escen ce Qu en ch in g Rela ted to Molecu la r
Geom etr y
Christopher Farren, Christian A. Christensen, Simon FitzGerald, Martin R. Bryce,* and
Andrew Beeby*
Chemistry Department, University of Durham, South Road, Durham DH1 3LE, UK
m.r.bryce@durham.ac.uk; andrew.beeby@durham.ac.uk
Received May 17, 2002
A number of silicon phthalocyanine bis-esters have been synthesized and characterized, with axial
ligands containing one or more tetrathiafulvalene groups. Variations in the substitution positions
around a central aromatic “hinge” within the ligands lead to different molecular geometries, and
the fluorescence of the macrocyclic core is subsequently quenched to varying degrees by the electron-
rich tetrathiafulvalene moiety, the magnitude of this effect being dependent upon both the relative
separation of the two units and the flexibility of the linking group. Pc derivative 24, with a highly
flexible linker group, and pc derivative 28, with a dendritic axial ligand, have the intensity of the
macrocycle emission reduced by 99% and 96%, respectively, relative to a similar silicon pc reference
compound lacking the TTF moieties. Molecular modeling studies of a series of such hybrids allow
the degree of this fluorescence quenching to be related to the intramolecular spacing. Additionally,
the potential for rapid electrochemical switching of the phthalocyanine fluorescence by oxidation
of the appended tetrathiafulvalene units is explored.
In tr od u ction
macrocycles are not able to aggregate in solution and
have higher quantum yields and fluorescence lifetimes
than the more common zinc or aluminum pcs.1b Further-
more, pcs have long been known to undergo electron-
transfer reactions, both to14 and from15 their excited
states, and strong electron donors such as tetrathiaful-
valene (TTF) are able to quench the pc fluorescence by
intermolecular electron transfer.16 We have previously
described the synthesis of novel silicon pc bis-esters,17
and we have now extended this methodology to produce
new pc-TTF hybrids, which display intramolecular pho-
toinduced electron-transfer processes.
Phthalocyanines (pcs) and their macrocyclic analogues
continue to attract considerable attention, due in part
to their characteristic optical properties,1 and applica-
tions including medicinal therapeutic agents,2 photosen-
sitizers,3 photoconductors,4 catalysts,5 and nonlinear
optical devices6 have been demonstrated. Despite the fact
that many peripherally substituted pcs have been syn-
thesized, with equatorial groups including ferrocenes,7
crown ethers,8 dendrimers,9 solketal derivatives,10 sug-
ars,11 and biologically “active” nucleobases,12 there are
relatively few axially substituted silicon pcs.13 These
(1) Reviews: (a) Moser, F. H.; Thomas, A. L. Phthalocyanine
Compounds; Reinhold: New York, 1963. (b) Leznoff, C. C., Lever, A.
B. P., Eds. Phthalocyanines, Properties and Applications; VCH: New
York, 1989-1996; Vols. 1-4. (c) McKeown, N. B. Chem. Ind. 1999,
92.
(2) (a) Rosenthal, I. J . Photochem. Photobiol. 1991, 53, 859. (b)
Panday, P. K.; Herman, C. K. Chem. Ind. 1998, 739.
(3) (a) Nazeeruddin, M. K.; Humphry-Baker, R.; Gratzel, M.; Murrer,
B. A. Chem. Commun. 1998, 719. (b) Whitlock, J . B.; Panayotatos, P.;
Sharma, G. D.; Cox, M. D.; Sauer, R. R.; Bird, G. R. Opt. Eng. 1993,
32, 1921. (c) Wohrle, D.; Meissner, D. Adv. Mater. 1991, 3, 129.
(4) Ahuja, R. C.; Hauffe, K. Ber. Bunsen-Ges. Phys. Chem. 1980, 84,
68 and references therein.
Resu lts a n d Discu ssion
Syn th esis. In a previous article17 we have described
the synthesis of silicon phthalocyanine bis(4-tert-butyl)-
benzoate 2 via the condensation of silicon pc dichloride
(9) (a) Brewis, M.; Clarkson, G. J .; Holder, A. M.; McKeown, N. B.
Chem. Commun. 1998, 1979. (b) Ng, A. C. H.; Li, X.-Y.; Ng, D. K. P.
Macromolecules 1999, 32, 5292.
(10) Farren, C.; FitzGerald, S.; Beeby, A.; Bryce, M. R. Chem.
Commun. 2002, 572.
(5) (a) Parton, R. F.; Van Kelecom, I. F. J .; Bezoukhanova, M. J . A.;
J acobs, P. A. Nature 1994, 370, 541. (b) Lever, A. B. P.; Hempstead,
M. R.; Leznoff, C. C.; Liu, W.; Melnik, M.; Nevin, W. A.; Seymour, P.
Pure Appl. Chem. 1986, 58, 1467.
(6) Nalwa, H. S.; Shirk, J . S. In Phthalocyanines, Properties and
Applications; Leznoff, C. C., Lever, A. B. P., Eds.; VCH: New York,
1996; Vol. 4, pp 83-181 and references therein.
(7) Cook, M. J .; Cooke, G.; J afari-Fini, A. J . Chem. Soc., Chem.
Commun. 1995, 1715.
(11) Mallard, P.; Guerquin-Kern, J .-L.; Momenteau, M.; Gaspard,
S. J . Am. Chem. Soc. 1989, 111, 9125.
(12) Li, X.-Y.; Ng, D. K. P. Tetrahedron Lett. 2001, 42, 305.
(13) McKeown, N. B. J . Mater. Chem. 2000, 10, 1979.
(14) Daraio, M. E.; Volker, A.; Aramendia, P. F.; San Roman, E.
Langmuir 1996, 12, 2932.
(15) Darwent, J . R.; McCubbin, I.; Porter, G. J . Chem. Soc., Faraday
Trans. 2 1982, 78, 903.
(16) Wang, C.; Bryce, M. R.; Batsanov, A. S.; Stanley, C. F.; Beeby,
A.; Howard, J . A. K. J . Chem. Soc., Perkin Trans. 2 1997, 1671.
(17) Farren, C.; FitzGerald, S.; Bryce, M. R.; Beeby, A.; Batsanov,
A. S. J . Chem. Soc., Perkin Trans. 2 2002, 59.
(8) (a) Van Nostrum, C. F.; Picken, S. J .; Schouten, A. J .; Nolte, R.
J . M. J . Am. Chem. Soc. 1995, 117, 9957. (b) Van Nostrum, C. F.; Nolte,
R. J . M. Chem. Commun. 1996, 2385.
10.1021/jo020340y CCC: $22.00 © 2002 American Chemical Society
Published on Web 11/21/2002
9130
J . Org. Chem. 2002, 67, 9130-9139

Novel Phthalocyanine-Tetrathiafulvalene Hybrids
SCHEME 1
SCHEME 2
1 with the appropriate benzoic acid (Scheme 1). Due to
its high solubility in organic solvents, and its relative
stability in solution, 2 was used as a robust and reliable
reference compound for previous photochemical studies,
and this convention continues in the current work.
It is also known that (2-cyanoethyl)sulfanyl-substituted
TTF derivatives 3a -c can be used as nucleophilic build-
ing blocks,18 and following the protocol of Becher et al.19
we now demonstrate that deprotection of the hexyl-
substituted TTF derivative 3c18c with CsOH in DMF to
generate the trialkylsulfanyl thiolate, followed by nu-
cleophilic addition to methyl 4-bromomethylbenzoate
produces 4 (Scheme 2) in good yield. In the present work
our nomenclature uses a simple convention derived from
three variables: benzene substitution point, relative to
the benzoate group; number of atoms linking the two
π-systems; and functionality on the benzene ring. Hence
4 is referred to as the para-2-ester. 4 was then hydrolyzed
with sodium hydroxide in refluxing methanol/THF to give
the para-2-acid 5 in essentially quantitative yield, and
subsequent reaction with silicon pc dichloride 1 gave the
first pc-TTF hybrid, 6 (i.e. para-2-pc).
TABLE 1. P h otop h ysica l Da ta for p c-TTF Hybr id
System s
τf/nsa
dichloromethane
τ1 (yield) τ2 (yield)
6.7 (100%)c
2-methyltetrahydrofuran
τ1 (yield)
τ2 (yield)
Φfb
2
6
6.9 (100%)c
6.9 (100%)d
0.62 (100%)e
6.3 (93%)c 1.9 (7%)c 6.3 (94%)c
6.8 (98%)d
2.2 (6%)c 0.29 (47%)e
2.2 (2%)d
10 6.2 (91%)c 1.6 (9%)c 5.6 (86%)c
6.5 (95%)d
1.7 (14%)c 0.39 (63%)e
2.2 (5%)d
Pc-TTF hybrid 6 is typical of axially substituted silicon
14 6.4 (91%)c 1.8 (9%)c 6.3 (92%)c
6.5 (97%)d
2.8 (8%)c 0.45 (73%)e
2.1 (3%)d
1
pcs in that it gives characteristic H NMR data,17 the
extensive macrocyclic ring current inducing a large
upfield shift in the proton resonances of the proximal
ligand hydrogen atoms. The four protons on the benzene
ring in each of the two axial ligands thus give two distinct
doublets at δ 5.04 and 6.18 ppm, respectively, compared
to δ 7.41 and 8.05 ppm for the free benzoic acid 5, and
the pc equatorial hydrogen atoms give downfield-shifted
resonances as unresolved multiplets at δ 8.4 and 9.7 ppm.
Having determined that the TTF-containing axial
ligands in 6 reduce the pc fluorescence to under half that
of the reference compound 2 (Table 1, photophysics are
described in detail below), we synthesized pc-TTF hybrids
18 6.1 (96%)c 1.5 (4%)c 6.0 (88%)c
6.5 (92%)d
1.9 (12%)c 0.17 (27%)e
2.7 (8%)d
22 6.1 (92%)c 1.1 (8%)c 5.8 (95%)c
6.3 (93%)d
1.4 (5%)c 0.30 (48%)e
1.7 (7%)d
24
28
6.7 (93%)d
6.6 (92%)d
1.8 (7%)d 0.006 (1%)e
1.8 (8%)d 0.04 (6%)e
a
b
(0.1 ns, λex ) 635 nm, λem ) 690 nm. (5%, λex ) 612 nm,
λem ) 640-800 nm, 293 K, dichloromethane. c 293 K. 77 K.
fluorescence relative to reference compound 2.
%
d
e
with more flexible linking groups, to allow a greater
interaction between the two π-systems. Methyl 4-hy-
droxybenzoate was thus reacted with an excess of 1,4-
dibromobutane to give ester 7 (Scheme 3, n ) 1). TTF
derivative 3a 18 was deprotected and subsequently reacted
with 7 to give the para-6-ester 8, and base hydrolysis to
give the derived benzoic acid 9 followed by condensation
(18) (a) Lau, J .; Simonsen, O.; Becher, J . Synthesis 1995, 521. (b)
Simonsen, K. B.; Svenstrup, N.; Lau, J .; Simonsen, O.; Mørk, P.;
Kristensen, G. J .; Becher, J . Synthesis 1996, 407. (c) Christensen, C.
A.; Bryce, M. R.; Becher, J . Synthesis 2000, 1695.
(19) Simonsen, K. B.; Becher, J . Synlett 1997, 1211.
J . Org. Chem, Vol. 67, No. 26, 2002 9131

Farren et al.
SCHEME 3
SCHEME 4
SCHEME 5
with silicon pc dichloride 1 gave pc-TTF hybrid 10 (i.e.
para-6-pc). Similarly, methyl-4-hydroxybenzoate was
reacted with 1,10-dibromodecane (n ) 7), the TTF
derivative 3a was subsequently introduced, and hydroly-
sis and condensation gave the para-12-pc 14, with a 12
atom chain linking the two π-systems.
Bis-esters 10 and 14 were characterized in a manner
similar to 6, and fluorescence measurements indicated
that these two species displayed even less quenching of
the pc emission, with the degree of quenching reducing
with increasing linker group length. To more fully
investigate this phenomenon, we repeated the synthesis
using both 2- and 3-hydroxy-substituted methyl ben-
zoates and 1,4-dibromobutane as the linking groups
(Scheme 4). Thus were obtained pc bis-esters 18 and 22
(ortho-6-pc and meta-6-pc, respectively), and as the two
π-systems are forced into closer proximity the interaction
between them, and hence the quenching of the macro-
cycle emission, is increased.
All of the above pc-TTF hybrids have a benzoic acid
group as the link to the pc core, as such pc bis-esters have
been demonstrated to be chemically robust in both the
solid state and solution under ambient conditions.17
However, X-ray crystallography has shown that the
benzene ring in such esters is held rigidly orthogonal to
the plane of the macrocyclic core,17 and will thus impose
a certain minimum spacing between the pc and TTF
moieties in these compounds. We elected to synthesize a
more flexible ligand, and the typical synthetic pathway
was modified slightly. Silicon pc dichloride 1 was reacted
with 6-bromohexanoic acid to give a bis bromoalkyl
intermediate 23 (not shown) that was not characterized
but reacted directly with 3b to give hybrid 24 (Scheme
5). This compound showed dramatically reduced pc
emission under a range of conditions, and our naming
convention for this species is simply flex-pc.
Bis-ester 24, however, was less stable in solution than
the previous pc-TTF hybrids, presumably due to the
increased steric accessibility of the Si-O bonds, and an
alternative methodology was thus explored. To increase
the local TTF concentration around the macrocyclic core,
a TTF-containing dendritic species18c 25 (not shown) was
reacted with methyl 4-(bromomethyl)benzoate (as in
Scheme 2) to give ester 26. Hydrolysis to the acid 27 and
subsequent condensation gave the hybrid 28 (Scheme 6),
which was stable in solution and which also had a greatly
decreased macrocyclic emission intensity. Again, our
naming convention uses simply dendrimer-ester, den-
drimer-acid, and dendrimer-pc.
P h otop h ysics. We have previously reported17 the
photophysical properties of our reference compound 2, but
9132 J . Org. Chem., Vol. 67, No. 26, 2002

Novel Phthalocyanine-Tetrathiafulvalene Hybrids
SCHEME 6
groups consisting of 6 and 12 atoms, respectively) both
display reductions in fluorescence quenching relative to
6, with quantum yields of 0.39 and 0.45, respectively. It
is apparent that the increase in linker length across the
series 6 (2 atoms in a flexible unit), 10 (6 atoms), and 14
(12 atoms) has a direct effect upon the efficiency of
quenching by TTF. Molecular modeling confirms that the
increased flexibility in this series is more than offset by
the concomitant increase in pc-TTF separation distance
(Figure 1).
Fluorescence lifetimes for the three hybrids discussed
so far all display a second minor component; the fluo-
rescence decay of the reference compound 2 exhibits clear
single-exponential behavior, and the presence of the
quenching moiety in the pc-TTF hybrids seems to com-
plicate matters. It is interesting to note that the lifetimes
show no reduction in line with the reduced quantum
yields. Similar behavior was noted for a thiophene-
containing silicon phthalocyanine bis-ester,17 and it is
suggested that there are two possible states for these
compounds: an on state in which fluorescence is observed
with a normal lifetime and an off state in which fluores-
cence is rapidly and efficiently quenched, and for which
the lifetime is very short. With intermolecular emission
quenching, as displayed by reference compound 2 in the
presence of TTF, this phenomenon is not observed, and
fluorescence lifetime and quantum yield values decrease
proportionally as quencher concentration increases.
In a further attempt to increase the quenching of the
pc emission the ortho- and meta-substituted analogues
of 10 were synthesized as detailed above. Enhanced
quenching was observed for these two species, with 22
(meta) and 18 (ortho) possessing quantum yields of 0.30
and 0.17, respectively, the latter equivalent to 73%
quenching of the pc emission by the axial TTF groups.
Lifetimes were once again unperturbed by this quench-
ing. However, it was apparent that despite being able to
tune the degree of quenching by altering the ligand chain
length and substitution pattern, the extent of quenching
observed in the silicon pc bis-benzoate esters was far from
that obtained with the peripherally substituted zinc pcs.
In contrast, compound 24, without the rigid benzoate
ester linkage, shows a dramatic increase in quenching
relative to the previous compounds, and has a quantum
yield of <0.006 indicating >99% of the excited state is
quenched. That removal of the benzoate ester can result
in such a profound change in behavior emphasizes just
how rigid the benzoate ester group is in solution. Such
efficient quenching provided a suitable system with
which to investigate further the unusual two-state quench-
ing model. The possibility of there being distinct on and
off states for fluorescence led us to consider the effect of
temperature upon the equilibrium between these two
states. Cooling a solution of 24 (in 2-methyl-THF) to an
optically transparent glass at 77 K resulted in a 300-
fold increase in emission intensity,20 exhibiting a sharp
turn on below 125 K, coinciding with the glass point of
the solvent (Figure 2). As the solvent solidifies the flexible
ligand arm is frozen into its thermodynamically favored
for clarity they are summarized here. The bulky axial
ligands efficiently prevent aggregation in the concentra-
tion range 10-4-10-7 mol dm-3 and sharply defined
absorption and emission peaks are observed. As is typical
for silicon pcs, the lifetime and quantum yield are
increased with respect to the more commonly studied zinc
and aluminum pcs1b (Table 1).
The electron-rich TTF moiety is known to be an
efficient quencher of zinc pc emission by electron transfer,
in both intermolecular and intramolecular mechanisms,
the former with a rate constant of quenching kQ ≈ 1 ×
1010 dm3 mol-1 s-1 16
Similarly, we now show that 2
.
undergoes intermolecular quenching by TTF in dichlo-
romethane with a rate constant of kQ ) 1.6 × 1010 dm3
mol-1 s-1. This result is not unexpected, but is useful in
that it confirms that the presence of a central silicon atom
and axial ligands does not perturb this propensity for pc
fluorescence quenching by TTF.
The pc-TTF hybrid 6 shows a reduced quantum yield
relative to reference compound 2, equivalent to 53%
quenching of the macrocycle fluorescence by the TTF
electron donor. While this is a significant result, in
comparison with the g95.5% intramolecular quenching
exhibited by zinc pcs with four or eight peripheral TTF
subsituents16 the reduced efficiency of quenching in 6 was
rather surprising. However, the crystal structure of 2
clearly shows the molecular rigidity of the benzoate units,
which lie perpendicular to the plane of the macrocycle
ring,17 and the two atoms between the benzoate group
and the TTF unit in 6 will add only minimal flexibility.
Hence the reduced quenching in 6 is explained as being
a direct consequence of the TTF moiety being held at a
distance from the pc core. Compounds 10 and 14, with
added flexibility in the axial ligands (having linking
(20) As cooling results in the sharpening of both absorption and
emission spectra, and there is an increase in concentration as the
solvent contracts, emission spectra were corrected for changes in
absorption at the excitation point, and integrated emission spectra were
used to calculate the reported increases in emission intensity.
J . Org. Chem, Vol. 67, No. 26, 2002 9133

Farren et al.
F IGURE 1. Energetically minimized structures of compounds 6, 10, 14, and 28, modeled using CAChe.
room temperature, but was found to be 6.7 ns (plus a
minor second component) at 77 K, this being similar to
that of the reference 2.
The dendritic species, 28, despite the presence of the
benzoate linker, showed similar emission properties to
24, with a slightly larger quantum yield of 0.04 and
correspondingly reduced effect on cooling to 77 K. An
energy-minimized model of 28 is shown in Figure 1. The
greater flexibility of the dendritic arms may allow, in
dynamic solution, the outer TTF units to come into close
proximity to the phthalocyanine core, resulting in en-
hanced quenching. Additionally, the increased local TTF
concentration in 28 in comparison with 6, 10, and 14
would be expected to compound the quenching effect.
Electr och em istr y a n d Sp ectr oelectr och em istr y.
The electrochemistry of TTF is well-known,21,22 and
indeed cyclic voltametry of the para-2-pc compound 6
shows two clear and reversible one-electron TTF oxida-
tion waves (E1/2 ) 0.23 and 0.57 V, Figure 3). In addition,
however, 6 also shows three clear one-electron waves
from the pc core (one oxidation with E1/2 ) 0.78 V and
two reduction with E1/2 ) -0.98 V and Ered ) -1.36 V),
and the overall voltamogram is significantly cleaner than
the peripherally substituted pc-TTF hybrids we have
reported previously.16 In fact these species display almost
ideal behavior, reflecting the reduced intermolecular
interactions between the axially substituted pcs.
F IGURE 2. Temperature variation in emission of 24 in EPA
solution, λex ) 615 nm. (Arrows indicate spectral changes with
decreasing temperature.)
While TTF is an excellent electron donor, removal of
one or two electrons to form the radical cation or dication
species, respectively, imparts acceptor properties. The
TTF first oxidation potential lies well below that of the
pc core; hence it should be possible to selectively oxidize
the TTF, thereby preventing it (in its oxidized form) from
acting as an electron donor and quenching the pc emis-
sion. The result would be an electrochemically activated
fluorescence switch comprising the nonfluorescent pc-
TTF and fluorescent pc-TTF+• species. Reversible forma-
tion of the TTF radical cation and dication can be followed
spectroscopically,23 and with an optically transparent thin
configuration, and the dramatic increase in emission
indicates this to be with the TTF units held distant to
the pc macrocycle. Similar temperature dependence of
emission was observed for the other pc-TTF systems
previously described, with the exception of 10 and 14.
These two compounds show the least fluorescence quench-
ing at room temperature, and it is reasonable to suppose
that with the TTF moiety already far removed from the
pc core cooling has no further effect. The increase in
emission of the other species can be directly related to
their room-temperature quantum yields. Thus 24, with
the smallest quantum yield at 293 K, shows the largest
increase on cooling, while compounds 6, 22, and 18 show
more modest increases (1.5-, 2-, and 3-fold, respectively).
The fluorescence lifetime of 24 was not measurable at
(21) Hunig, S.; Kiesslich, G.; Quast, H.; Scheutzow, D. Liebigs Ann.
Chem. 1973, 310.
(22) Reviews: (a) Bryce, M. R. J . Mater. Chem. 2000, 10, 589. (b)
Segura, J . L.; Martin, N. Angew. Chem., Int. Ed. 2001, 40, 1372.
9134 J . Org. Chem., Vol. 67, No. 26, 2002

Novel Phthalocyanine-Tetrathiafulvalene Hybrids
F IGURE 3. Cyclic voltamogram of 6 in DCM (vs Ag/AgNO3, scan rate 20 mV/s, electrolyte ) 0.1 M Me4NBF4).
F IGURE 5. Absorbance changes from Pc f Pc•- (conditions
as above, degassed by freeze-thawing). (Arrows indicate
changes with increasing reduction potential.)
F IGURE 4. Absorbance changes from Pc f Pc•+ for
(electrolyte ) 0.1 M Me4NBF4) (Arrows indicate changes with
increasing oxidation potential.)
2
by new, broad absorption bands centered at 450 and 850
nm, which are assigned to the TTF+• species.23,26 The
selectivity of oxidation was indicated by the pc Q-bands,
which retained their shape and intensity throughout the
reversible electrochemical process (Figure 6). The B1/B2
envelope does show a reduction in absorption, but this
is due to removal of the overlapping TTF absorption (λmax
) 310 nm).
Emission spectra of the pc-TTF species were recorded
in the OTTLE cell, but despite our selective oxidation of
the TTF (as monitored by absorption spectroscopy) the
pc emission spectrum remained unchanged. In theory,
the observed quenching of the pc emission in the pc-TTF
hybrids occurs via a simple electron-transfer process,
from the TTF to the HOMO of the now excited pc*
(Figure 7). Calculations based on Rehm-Weller theory27
for electron transfer predict this to be a thermodynami-
cally feasible process, both inter- and intramolecularly,
and this is reflected in the observed and calculated rate
constants (Table 2).
layer electrochemistry (OTTLE) cell developed for ab-
sorption and emission spectroscopy, we first studied the
spectroelectrochemical behavior of the reference com-
pound 2.
Absorption spectra of phthalocyanine radical anions24
and cations25 are well-known, and both cationic and
anionic pc radicals display loss of Q-band absorption with
concomitant growth throughout the visible region. Refer-
ence compound 2 shows similar behavior, the radical
cationic species displays transitions which can be as-
signed to three distinct regions: the B1/B2 envelope (300-
450 nm), a π f π region (450-700 nm), and the Q-band
region (750-900 nm) (Figure 4). Similarly, the radical
anion shows new absorption bands at 410, 585, and 990
nm; the three regions described for the cation also apply
here, albeit with the Q-band region extended to even
lower energy, and the central area now assigned to π*
f π* transitions (Figure 5).24,25
For all the pc-TTF compounds it was possible to
achieve selective oxidation of the TTF group, apparent
Photoexcitation of the pc increases its acceptor strength
by an amount equal to the excitation energy (in this case
(23) Torrance, J . B.; Scott, B. A.; Welber, B.; Kaufman, F. B.; Seiden,
P. E. Phys. Rev. B 1979, 19, 731.
(24) Mack, J .; Stillman, M. J . J . Am. Chem. Soc. 1994, 116, 1292.
(25) Ough, E.; Gasyna, Z.; Stillman, M. J . Inorg. Chem. 1991, 30,
2301.
(26) Khodorkovsky, V.; Shapiro, L.; Krief, P.; Shames, A.; Mabon,
G.; Gorgues, A.; Giffard, M. Chem. Commun. 2001, 2736.
(27) Rehm, D.; Weller, A. Isr. J . Chem. 1970, 8, 1982.
J . Org. Chem, Vol. 67, No. 26, 2002 9135

Farren et al.
Con clu sion s
A range of pc-TTF hybrids have been synthesized and
characterized, the quenching of the pc emission by
electron transfer from the axially linked TTF groups has
been investigated, and the dependence of the quenching
efficiency on the pc-TTF separation has been demon-
strated. Variation of the axial ligand length and substitu-
tion position has resulted in pc-TTF hybrid systems with
quantum yields ranging from 0.45 to 0.006, i.e., between
73% and <1% relative to a structurally similar reference
compound 2 not containing the TTF moiety. The quench-
ing is observed to be highly temperature dependent, with
a sharp increase in emission at and below the glass point
of the solvent, this being a result of the axial ligands
being frozen into conformations where quenching is not
favorable.
Spectroelectrochemistry of the reference compound
shows absorption spectra for the pc radical anion and
cation which are similar to previously reported examples.
With the pc-TTF hybrid species, we have clearly dem-
onstrated the possibility of selective oxidation to form pc-
TTF+• compounds. Interestingly, such species undergo
fast electron transfer in the reverse direction to that of
the unoxidized pc-TTF hybrids, and we thus present a
facile method of reversing electron transfer within a
donor-acceptor system.
F IGURE 6. Spectroelectrochemistry of 28, E° ) 0.5 V.
(Arrows indicate spectral changes upon oxidation of the TTF
group.)
Exp er im en ta l Section
Syn th esis. All solvents were dried by standard methodolo-
gies prior to use and silicon pc dichloride (1) was used as
purchased (Fluka). While the “free” TTF-containing ligands
were fully characterizable, many of the final pc-TTF hybrids
did not give good mass spectra or elemental analysis but were
deemed pure by NMR (see Supporting Information.)
F IGURE 7. MO description of Pc emission quenching path-
ways.
P a r a -2-Ester (4). To a stirred solution of TTF derivative
3c18c (568 mg, 1.00 mmol) in dry degassed DMF (40 mL) was
added in one portion a solution of cesium hydroxide monohy-
drate (185 mg, 1.10 mmol) in dry degassed methanol (5 mL).
The color of the mixture changed from orange to dark red and
stirring was continued for 30 min. Methyl (4-bromomethyl)-
benzoate (252 mg, 1.10 mmol) was added as a solid in one
portion against a positive pressure of argon, causing the color
to change back to orange. The reaction mixture was stirred
for another 1 h before it was concentrated in vacuo. The
residue was purified by column chromatography (silica gel,
CH2Cl2-hexane 1:1 v/v) affording the para-2-ester 4 as an
1.81 eV) and hence electron transfer from TTF to pc*
proceeds readily and results in emisson quenching.
However, this increase in pc acceptor strength upon
excitation is accompanied by an equal increase in donor
strength, and thus pc* can readily donate electrons to
electron-deficient species. The TTF radical cation is just
such an electron-deficient species, and hence there
exists a new, reversed, electron-transfer path, from pc*
to TTF+•
.
1
Thus oxidation of TTF in the pc-TTF hybrids does not
result in an increase of fluorescence (reduction of quench-
ing), and the Rehm-Weller calculations concur, yielding
a quenching rate constant for this reverse process of 1.26
× 1010 dm3 mol-1 s-1. A similar phenomenon was reported
by other workers during the preparation of this paper.28
In their work enhanced fluorescence quenching of an-
thracene by TTF+• in comparison with neutral TTF was
observed, suggested to be due to increased binding
between the electron-rich anthracene and the TTF radical
cation. However, they do not discuss the nature of the
electron-transfer process causing the quenchingsalthough
it is likely that the excited-state anthracene is quenched
by the electron-deficient radical cation following a similar
reversed electron-transfer pathway to that shown in
Figure 7.
orange oil (649 mg, 98%). H NMR (200 MHz, CDCl3): δ 7.98
(2H, d, J ) 8.4 Hz), 7.37 (2H, d, J ) 8.4 Hz), 4.01 (2H, s), 3.91
(3H, s), 2.82 (4H, m), 2.21 (3H, br s), 1.63 (4H, m), 1.30 (12H,
m), 0.86 (6H, t, J ) 6.6 Hz). 13C NMR (100 MHz, CDCl3): δ
169.3, 143.0, 130.3, 128.9, 128.3, 51.9, 31.3, 31.2, 29.6, 28.0,
22.4, 19.0, 13.9. MS (EI+) m/z (%): 662 (100, [M]+) 378 (12),
149 (8), 121 (20). Anal. Calcd for C28H38O2S8: C, 50.68; H, 5.78.
Found: C, 50.85; H, 5.84.
P a r a -2-Acid (5). Compound 4 (623 mg, 0.94 mmol) was
dissolved in a mixture of dry tetrahydrofuran (15 mL) and dry
methanol (15 mL), and sodium hydroxide (1.00 g, 25.0 mmol)
was added as a solid in one portion. The reaction mixture was
refluxed for 3 h in which time the sodium hydroxide had
dissolved, whereupon it was concentrated under reduced
pressure. The residue was taken into a mixture of water (100
mL) and dichloromethane (100 mL), and dilute hydrochloric
acid (50 mL of a 0.5 M aqueous solution, 25.0 mmol) was added
with stirring, making the aqueous phase colorless and the
organic phase orange. The phases were separated and the
organic phase was washed with water, dried (MgSO4), and
concentrated in vacuo to give the para-2-acid 5 as an orange
(28) De Cremiers, H. A.; Clavier, G.; Ilhan, F.; Cooke, G.; Rotello,
V. M. Chem. Commun. 2001, 2232.
9136 J . Org. Chem., Vol. 67, No. 26, 2002

Novel Phthalocyanine-Tetrathiafulvalene Hybrids
TABLE 2. P c Em ission Qu en ch in g Ra te Con sta n t Ca lcu la tion s
acceptor
(EA/A /V)
donor
(ED /D/V)
a a
(nm)
∆G
∆G#
kQ(calcd)b
kQ(exptl) c
(kJ mol-1
)
(kJ mol-1
)
(dm3 mol-1 s-1
)
(dm3 mol-1 s-1
)
-
+
Pc (-0.69)
TTF (+0.59)
Pc (+1.04)
1
0.34
0.34
-66.4
-96.1
-176
1.47
1.03
0.57
1.14 × 1010
1.20 × 1010
1.26 × 1010
1.6 × 1010
TTF+• (+0.59)
a
Encounter distance: 1 nm for an intermolecular process, 0.34 nm for an intramolecular process (calculated via models generated in
CAChe). Rate constant for quenching of phthalocyanine emission by TTF obtained via Rehm-Weller calculations. c Obtained for 2 via
a Stern-Volmer plot.
b
glass (600 mg, 98%). Mp 91-92 °C. 1H NMR (400 MHz,
CDCl3): δ 8.05 (2H, d, J ) 8.0 Hz), 7.41 (2H, d, J ) 8.4 Hz),
4.02 (2H, s), 2.82 (4H, m), 2.23 (3H, s), 1.64 (4H, pent, J ) 6.8
Hz), 1.41 (4H, pent, J ) 6.8 Hz), 1.30 (8H, m), 0.89 (6H, t, J
) 6.4 Hz). 13C NMR (100 MHz, CDCl3): δ 171.5, 143.3, 130.5,
129.2, 128.3, 31.3, 31.3, 29.7, 28.2, 22.5, 19.1, 14.0. MS (EI+)
m/z (%): 648 (100, [M]+) 513 (83), 378 (17), 135 (45). Anal.
Calcd for C27H36O2S8: C, 49.96; H, 5.59. Found: C, 49.87; H,
5.61.
P a r a -2-P c (6). Para-2-acid 5 (300 mg, 0.48 mmol) and
silicon phthalocyanine dichloride 1 (100 mg, 0.16 mmol) were
stirred together in di(methoxyethyl) ether (5 mL) at 160 °C
for 6 h. Quenching of the reaction mixture in water (50 mL)
and filtration of the resulting precipitate gave para-2-Pc 6 as
a dark blue-green solid (134 mg, 46%) after column chroma-
tography (silica gel, CH2Cl2). Mp >250 °C. 1H NMR (400 MHz,
CDCl3): δ 9.71 (4H, m), 8.39 (4H, m), 6.18 (2H, d, J ) 8.4 Hz),
5.04 (2H, d, J ) 8.4 Hz), 3.32 (2H, s), 2.79 (2H, t, J ) 7.6 Hz),
2.71 (2H, t, J ) 7.6 Hz), 1.65 (3H, s), 1.56-1.25 (16H, m), 0.90
(3H, t, J ) 7.6 Hz), 0.84 (3H, t, J ) 7.6 Hz). 13C NMR (100
MHz, CDCl3): δ 158.9, 150.2, 139.8, 135.5, 132.9, 131.4, 129.5,
127.8, 127.7, 127.4, 127.3, 124.1, 123.1, 110.8, 109.0, 39.6, 36.3,
36.2, 31.3, 31.2, 29.7, 29.6, 28.2, 28.1, 22.6, 22.5, 18.4, 14.1,
14.0. (NMR in Supporting Information.)
Meth yl 4-(4′-Br om obu toxy)ben zoa te (7). Methyl 4-hy-
droxybenzoate (1.00 g, 6.57 mmol), 1,4-dibromobutane (4.26
g, 19.72 mmol), and potassium carbonate (9.08 g, 65.70 mmol)
were stirred in dry, degassed DMF (30 mL) for 24 h. The
solvent was removed in vacuo and the residue taken up in
CH2Cl2 and filtered. The filtrate was concentrated in vacuo
and dried (MgSO4), giving methyl 4-(4′-bromobutoxy)benzoate
(7) as a white solid (1.55 g, 82%) after column chromatography
(silica gel, CH2Cl2). Mp 42-43 °C. 1H NMR (400 MHz,
CDCl3): δ 7.97 (2H, d, J ) 8.8 Hz), 6.89 (2H, d, J ) 8.8 Hz),
4.04 (2H, t, J ) 6.0 Hz), 3.88 (3H, s), 3.49 (2H, t, J ) 6.4 Hz),
2.07 (2H, m), 1.97 (2H, m). 13C NMR (100 MHz, CDCl3): δ
166.8, 162.56, 131.6, 122.6, 114.0, 67.0, 51.9, 33.3, 29.3, 27.7.
MS (EI+) m/z (%): 286/288 (25, [M]+), 255/257 (10), 152 (25),
135/137 (94), 121 (100), 55 (93). Anal. Calcd for C12H15BrO3:
C, 50.19; H, 5.27. Found: C, 50.04; H, 5.26.
) 9.0 Hz), 6.67 (2H, d, J ) 8.8 Hz), 3.81 (2H, t, J ) 6.0 Hz),
2.65 (2H, t, J ) 7.2 Hz), 2.17 (9H, br s), 1.72 (2H, pent, J )
7.6 Hz), 1.59 (2H, pent, J ) 7.6 Hz). 13C NMR (100 MHz,
CDCl3): δ 168.36, 162.40, 131.44, 130.08, 127.04, 124.52,
122.23, 113.59, 110.21, 67.01, 35.32, 27.26, 25.82, 18.48, 18.40.
MS (EI+) m/z (%): 566 (100, [M]+), 373 (23), 238 (32), 151 (24),
121 (29), 91 (33). Anal. Calcd for C20H22O3S8: C, 42.37; H, 3.91.
Found: C, 42.73; H, 3.92. HRMS: C20H22O3S8 requires [M]+,
565.9334. Found: [M]+, 565.9330. Difference: 0.8 ppm.
P a r a -6-P c (10). Para-6-acid 9 (280 mg, 0.49 mmol) and
silicon phthalocyanine dichloride 1 (100 mg, 0.16 mmol) were
reacted as above to give the para-6-Pc 10 as a dark blue-green
solid (102 mg, 38%) after column chromatography over silica
gel (eluent: CH2Cl2). Mp >250 °C; 1H NMR (400 MHz, CDCl3)
δ 9.70 (4H, m), 8.38 (4H, m), 5.83 (2H, d, J ) 8.4 Hz), 5.06
(2H, d, J ) 8.4 Hz), 3.30 (2H, t, J ) 7.6 Hz), 2.82 (2H, t, J )
7.2 Hz), 2.41 (3H, s), 2.38 (6H, s), 1.32 (4H, m). 13C NMR (100
MHz, CDCl3): δ 159.2, 150.1, 136.2, 133.4, 132.3, 130.7, 129.8,
127.2, 127.2, 126.1, 123.8, 122.5, 112.6, 110.9, 110.3, 66.2, 36.1,
30.6, 30.5, 29.5, 28.5, 19.1. Anal. Calcd for C72H58N8O6S16Si:
C, 51.71; H, 3.50; N, 12.96. Found: C, 51.48; H, 3.41, 12.82.
Met h yl 4-(10-Br om od ecyloxy)ben zoa t e (11). Methyl
4-hydroxybenzoate (2.00 g, 13.15 mmol), 1,10-dibromodecane
(11.83 g, 39.44 mmol), and potassium carbonate (18.17 g,
131.45 mmol) were reacted as before to give methyl 4-(10′-
bromodecoxy)benzoate (11) as a white solid (4.19 g, 86%) after
column chromatography (silica gel, CH2Cl2). Mp 64-65 °C. 1H
NMR (400 MHz, CDCl3): δ 7.97 (2H, d, J ) 9.2 Hz), 6.90 (2H,
d, J ) 9.2 Hz), 4.00 (2H, t, J ) 6.4 Hz), 3.88 (3H, s), 3.41 (2H,
t, J ) 6.8 Hz), 1.82 (4H, m), 1.38 (12H, m). 13C NMR (100 MHz,
CDCl3): δ 166.9, 162.9, 131.5, 122.3, 114.0, 68.1, 51.8, 34.1,
32.8, 29.4, 29.3, 29.3, 29.1, 28.7, 28.1, 25.9. MS (EI+) m/z (%):
370/372 (30, [M]+), 339/341 (4), 152 (100), 121 (69). Anal. Calcd
for C18H27BrO3: C, 58.22; H, 7.33. Found: C, 57.96; H, 7.42.
P a r a -12-Ester (12). Compound 3a 18 (524 mg, 1.22 mmol),
cesium hydroxide monohydrate (226 mg, 1.30 mmol), and
methyl 4-(10′-bromodecoxy)benzoate (11, 336 mg, 1.17 mmol)
were reacted as before, but again alkylation took 16 h.
Purification by column chromatography (silica gel, CH2Cl2-
hexane 2:1 v/v until excess alkylation reagent was off the
column, then CH2Cl2) afforded the para-12-ester 12 as a yellow
solid (802 mg, 98%). Mp 74-75 °C. 1H NMR (400 MHz,
CDCl3): δ 7.97 (2H, d, J ) 8.4 Hz), 6.90 (2H, d, J ) 8.4 Hz),
4.00 (2H, t, J ) 6.4 Hz), 3.88 (3H, s), 2.81 (2H, t, J ) 6.4 Hz),
2.42 (9H, br s), 1.79 (2H, pent, J ) 6.8 Hz), 1.63 (2H, pent, J
) 6.8 Hz), 1.45-1.30 (12H, m). 13C NMR (100 MHz, CDCl3):
δ 166.9, 162.9, 132.5, 129.3, 127.5, 127.4, 126.0, 122.3, 114.0,
68.1, 51.8, 36.3, 29.7, 29.4, 29.4, 29.3, 29.1, 29.0, 28.4, 26.0,
19.2, 19.2. MS (EI+) m/z (%): 664 (100, [M]+), 373 (9), 238 (15),
152 (12), 121 (25). Anal. Calcd for C27H36O3S8: C, 48.76; H,
5.46. Found: C, 48.99; H, 5.54.
P a r a -6-Ester (8). Compound 3a 18 (500 mg, 1.17 mmol),
cesium hydroxide monohydrate (216 mg, 1.29 mmol), and
methyl 4-(4′-bromobutoxy)benzoate (7, 336 mg, 1.17 mmol)
were reacted as before, but in this case alkylation took 16 h.
Purification by column chromatography (silica gel, CH2Cl2)
afforded the para-6-ester 8 as a red oil, which solidified to an
1
orange solid upon standing (634 mg, 93%). Mp 88-89 °C. H
NMR (400 MHz, CDCl3): δ 7.99 (2H, d, J ) 9.0 Hz), 6.91 (2H,
d, J ) 9.0 Hz), 4.05 (2H, t, J ) 6.0 Hz), 3.90 (3H, s), 2.91 (2H,
t, J ) 7.0 Hz), 2.43 (9H, br s), 1.97 (2H, pent, J ) 7.0 Hz),
1.85 (2H, pent, J ) 7.0 Hz). 13C NMR (100 MHz, CDCl3): δ
166.79, 162.60, 131.54, 130.29, 127.40, 124.91, 122.47, 113.99,
110.74, 67.34, 51.83, 35.83, 27.76, 26.23, 19.19, 19.16. MS (EI+)
m/z (%): 580 (100, [M]+), 373 (21), 238 (24), 165 (23), 121 (49),
91 (38). Anal. Calcd for C21H24O3S8: C, 43.42; H, 4.16. Found:
C, 43.63; H, 4.19.
P a r a -12-Acid (13). Compound 12 (670 mg, 1.01 mmol) was
treated with sodium hydroxide (1.00 g, 25.0 mmol) as before
and subsequently neutralized using dilute hydrochloric acid
to give the para-12-acid 13 as a bright yellow powder (622 mg,
95%). Mp 120-121 °C. 1H NMR (400 MHz, CDCl3): δ 8.07
(2H, d, J ) 9.0 Hz), 6.94 (2H, d, J ) 9.0 Hz), 4.04 (2H, t, J )
6.5 Hz), 2.83 (2H, t, J ) 7.5 Hz), 2.44 (9H, br s), 1.82 (2H,
pent, J ) 7.5 Hz), 1.65 (2H, pent, J ) 7.5 Hz), 1.48-1.32 (12H,
m). 13C NMR (100 MHz, CDCl3): δ 171.6, 163.6, 132.3, 129.3,
127.5, 127.4, 126.0, 121.3, 114.2, 68.2, 36.3, 29.7, 29.4, 29.4,
P a r a -6-Acid (9). Compound 8 (484 mg, 0.833 mmol) was
treated with sodium hydroxide (1.00 g, 25.0 mmol) as before
and subsequently neutralized using dilute hydrochloric acid
to give the para-6-acid 9 as an orange solid (462 mg, 98%).
Mp 139-140 °C. 1H NMR (400 MHz, CDCl3): δ 7.71 (2H, d, J
J . Org. Chem, Vol. 67, No. 26, 2002 9137

Farren et al.
29.3, 29.1, 29.0, 28.4, 26.0, 19.2, 19.2. MS (EI+) m/z (%): 650
(100, [M]+), 388 (19), 308 (13), 238 (27), 138 (71), 121 (43). Anal.
Calcd for C26H34O3S8: C, 47.96; H, 5.26. Found: C, 48.77; H,
5.38. HRMS: C26H34O3S8 requires [M]+, 650.0274. Found:
[M]+, 650.0259. Difference: 2.3 ppm.
P a r a -12-P c (14). Para-12-acid 13 (250 mg, 0.38 mmol) and
silicon phthalocyanine dichloride 1 (100 mg, 0.16 mmol) were
reacted as before to give para-12-Pc 14 as a dark blue-green
solid (127 mg, 43%) after column chromatography (silica gel,
CH2Cl2). Mp >250 °C. 1H NMR (400 MHz, CDCl3): δ 9.70 (4H,
m), 8.37 (4H, m), 5.69 (2H, d, J ) 8.8 Hz), 5.04 (2H, d, J ) 8.8
Hz), 3.34 (2H, t, J ) 6.8 Hz), 2.73 (2H, t, J ) 7.2 Hz), 2.39
(3H, s), 2.38 (3H, s), 2.36 (3H, s), 1.05-1.56 (16H, m). 13C NMR
(100 MHz, CDCl3): δ 161.0, 150.2, 135.6, 132.2, 131.2, 129.3,
129.2, 127.4, 127.4, 126.0, 124.0, 122.6, 112.4, 111.2, 110.3,
67.2, 36.2, 29.7, 29.6-28.3 (m), 25.6, 19.2. (NMR in Supporting
Information.)
Meth yl 2-(4′-Br om obu toxy)ben zoa te (15). Methyl 2-hy-
droxybenzoate (910 mg, 5.95 mmol), 1,4-dibromobutane (5.14
g, 23.80 mmol), and potassium carbonate (8.22 g, 59.47 mmol)
were reacted as before to give methyl 2-(4′-bromobutoxy)-
benzoate (15) as a colorless oil (1.22 g, 71%) after column
chromatography (silica gel, CH2Cl2). 1H NMR (400 MHz,
CDCl3): δ 7.77 (1H, d d, J ) 7.6, 2.0 Hz), 7.43 (1H, t m, J )
7.8 Hz), 6.94 (2H, t, J ) 7.6 Hz), 4.05 (2H, t, J ) 6.0 Hz), 3.87
(3H, s), 3.51 (2H, t, J ) 6.4 Hz), 2.11 (2H, m), 1.97 (2H, m).
13C NMR (100 MHz, CDCl3): δ 166.7, 158.2, 133.3, 131.6,
120.2, 120.2, 113.0, 67.6, 51.9, 33.6, 29.3, 27.6. MS (EI+) m/z
(%): 286/288 (5, [M]+), 255/257 (3), 135/137 (31), 120 (100), 92
(49), 55 (86). Anal. Calcd for C12H15BrO3: C, 50.19; H, 5.27.
Found: C, 49.97; H, 5.34.
solid (88 mg, 29%) after column chromatography (silica gel,
CH2Cl2). Mp >250 °C. 1H NMR (400 MHz, CDCl3): δ 9.69 (4H,
m), 8.37 (4H, m), 6.45 (1H, t, J ) 8.5 Hz), 5.74 (3H, m), 3.23
(2H, t, J ) 8.0 Hz), 2.94 (2H, t, J ) 7.0 Hz), 2.79 (3H, s), 2.72
(4H, m), 1.74 (2H, pent, J ) 8.0 Hz), 1.66 (2H, pent, J ) 7.5
Hz), 1.38 (12H, m), 0.92 (6H, t, J ) 7.2 Hz). 13C NMR (100
MHz, CDCl3); δ 158.6, 157.0, 150.0, 133.9, 131.6, 131.5, 130.0,
128.9, 127.0, 124.9, 123.8, 119.9, 117.3, 110.8, 109.4, 65.9, 35.8,
35.4, 30.8, 30.5, 29.3, 27.3, 26.6, 22.0, 19.0, 14.1. (NMR in
Supporting Information.)
Meth yl 3-(4′-Br om obu toxy)ben zoa te (19). Methyl 3-hy-
droxybenzoate (0.91 g, 5.95 mmol), 1,4-dibromobutane (5.14
g, 23.80 mmol), and potassium carbonate (8.22 g, 59.47 mmol)
were reacted as before to give methyl 3-(4′-bromobutoxy)-
benzoate (19) as a colorless oil (1.28 g, 75%) after column
chromatography (silica gel, CH2Cl2). 1H NMR (400 MHz,
CDCl3): δ 7.61 (1H, d m, J ) 7.6 Hz), 7.53 (1H, t, J ) 2.4 Hz),
7.32 (1H, t, J ) 8.0 Hz), 7.07 (1H, d d m, J ) 8.0, 2.4 Hz), 4.02
(2H, t, J ) 6.0 Hz), 3.90 (3H, s), 3.48 (2H, t, J ) 6.4 Hz), 2.06
(2H, m), 1.94 (2H, m). 13C NMR (100 MHz, CDCl3): δ 166.8,
158.7, 131.3, 123.3, 121.9, 119.8, 114.5, 66.9, 52.1, 33.3, 29.3,
27.7. MS (EI+) m/z (%): 286/288 (17, [M]+), 255/257 (11), 152
(37), 135/137 (98), 121 (100), 55 (86). Anal. Calcd for C12H15
BrO3: C, 50.19; H, 5.27. Found: C, 49.94; H, 5.23.
-
Meta -6-Ester (20). Compound 3b (540 mg, 1.00 mmol) was
deprotected using sodium methoxide as above (2.20 mL, 1.10
mmol of a 0.5 M solution in methanol) and alkylated using
compound 19 (0.316 g, 1.10 mmol) over 16 h. Purification by
column chromatography (silica gel, CH2Cl2) afforded the meta-
6-ester 20 as an orange oil that solidified upon standing (671
1
mg, 97%). Mp 54-55 °C. H NMR (400 MHz, CDCl3): δ 7.64
(1H, d m, J ) 7.5 Hz), 7.56 (1H, m), 7.35 (1H, t, J ) 7.5 Hz),
7.10 (1H, d d m, J ) 8.0, 3.0 Hz), 4.05 (2H, t, J ) 6.0 Hz), 3.93
(3H, s), 2.92 (2H, t, J ) 7.0 Hz), 2.82 (4H, m), 2.44 (3H, s),
1.97 (2H, pent, J ) 7.5 Hz), 1.86 (2H, pent, J ) 7.5 Hz), 1.64
(4H, m), 1.36 (8H, m), 0.91 (6H, t, J ) 7.5 Hz). 13C NMR (100
MHz, CDCl3): δ 166.9, 158.8, 131.4, 130.2, 129.4, 127.7, 125.0,
122.0, 120.0, 114.5, 109.9, 67.4, 52.2, 36.2, 35.9, 30.6, 30.6, 29.4,
29.4, 27.9, 26.3, 22.2, 19.2, 14.0. MS (EI+) m/z (%): 692 (100,
[M]+), 590 (5), 485 (5), 350 (7), 207 (11), 165 (14), 121 (20).
Anal. Calcd for C29H40O3S8: C, 50.25; H, 5.82. Found: C, 50.04;
H, 5.83.
Meta -6-Acid (21). Compound 20 (485 mg, 0.700 mmol) was
treated with sodium hydroxide (1.00 g, 25.0 mmol) as before
and subsequently neutralized using dilute hydrochloric acid
to give the meta-6-acid 21 as an orange oil which solidified
upon standing (438 mg, 92%). Mp 91-92 °C. 1H NMR (400
MHz, CDCl3): δ 7.64 (1H, d, J ) 7.8 Hz), 7.54 (1H, br s), 7.30
(1H, t, J ) 8.0 Hz), 7.08 (1H, d, J ) 7.8 Hz), 3.95 (2H, m),
2.82 (6H, m), 2.44 (3H, s), 1.88 (4H, m), 1.64 (4H, m), 1.35
(8H, m), 0.91 (6H, t, J ) 5.6 Hz). 13C NMR (100 MHz, CDCl3):
δ 158.8, 130.2, 129.4, 127.7, 125.0, 122.6, 120.4, 114.9, 111.0,
109.6, 67.4, 36.2, 35.9, 30.6, 30.6, 29.4, 29.4, 27.9, 26.3, 22.2,
19.2, 14.0. MS (EI+) m/z (%): 678 (100, [M]+), 485 (7), 454 (10),
350 (11), 193 (14), 138 (20), 121 (29). Anal. Calcd for
Or th o-6-Ester (16). To a solution of 3b (synthesized in a
manner analogous to 3a ) (540 mg, 1.00 mmol) in dry degassed
DMF (40 mL) was added a solution of sodium methoxide (2.20
mL, 1.1 mmol of a 0.5 M solution in methanol) in one portion.
The color of the mixture changed from orange to dark red and
stirring was continued for 30 min. Compound 15 (316 mg, 1.10
mmol) was dissolved in dry degassed DMF (5 mL) and added
to the reaction in one portion, causing the color to change back
to orange. The reaction mixture was stirred for 16 h before it
was concentrated in vacuo. The residue was purified by column
chromatography (silica gel, CH2Cl2) affording the ortho-6-ester
1
16 as a sticky orange oil (674 mg, 97%). H NMR (400 MHz,
CDCl3): δ 7.78 (1H, d m, J ) 7.8 Hz), 7.44 (1H, t m, J ) 7.8
Hz), 6.97 (2H, m), 4.06 (2H, t, J ) 5.8 Hz), 3.88 (3H, s), 2.92
(2H, t, J ) 7.2 Hz), 2.80 (4H, t, J ) 7.2 Hz), 2.41 (3H, s), 1.95
(4H, m), 1.63 (4H, m), 1.36 (8H, m), 0.89 (6H, t, J ) 6.8 Hz).
13C NMR (100 MHz, CDCl3): δ 166.8, 158.3, 133.4, 131.7,
129.9, 127.8, 125.3, 120.2, 113.1, 111.0, 109.6, 68.1, 52.0, 36.2,
35.9, 30.6, 29.4, 29.4, 27.8, 26.3, 22.2, 19.2, 14.0. MS (EI+) m/z
(%): 692 (100, [M]+), 590 (5), 485 (5), 350 (7), 121 (13). Anal.
Calcd for C29H40O3S8: C, 50.25; H, 5.82. Found: C, 50.20; H,
5.81.
Or th o-6-Acid (17). Compound 16 (549 mg, 0.792 mmol)
was treated with sodium hydroxide (1.00 g, 25.0 mmol) as
before and subsequently neutralized using dilute hydrochloric
acid to give the ortho-6-acid 17 as a sticky orange oil (535 mg,
99%). 1H NMR (400 MHz, CDCl3): δ 8.18 (1H, d d, J ) 7.8,
4J HH ) 1.8 Hz), 7.55 (1H, t m, J ) 8.4 Hz), 7.14 (1H, t, J ) 7.8
Hz), 7.05 (1H, d, J ) 8.4 Hz), 4.28 (2H, t, J ) 6.4 Hz), 2.89
(2H, t, J ) 6.8 Hz), 2.80 (4H, t, J ) 6.8 Hz), 2.43 (3H, s), 2.10
(2H, pent, J ) 7.6 Hz), 1.84 (2H, pent, J ) 7.2 Hz), 1.63 (4H,
m), 1.34 (8H, m), 0.89 (6H, t, J ) 6.4 Hz). 13C NMR (100 MHz,
CDCl3): δ 165.2, 157.3, 135.0, 133.8, 131.2, 125.9, 122.3, 117.7,
112.5, 69.5, 36.2, 30.6, 30.6, 29.4, 27.6, 25.8, 22.2, 19.1, 14.0.
MS (EI+) m/z (%): 678 (46, [M]+), 556 (28), 500 (29), 338 (15),
138 (47), 120 (100). Anal. Calcd for C28H38O3S8: C, 49.52; H,
5.64. Found: C, 49.15; H, 5.57. HRMS: C28H38O3S8 requires
[M]+, 678.0587. Found: [M]+, 678.0592. Difference: 0.8 ppm.
C
28H38O3S8: C, 49.52; H, 5.64. Found: C, 49.26; H, 5.63.
Meta -6-P c (22). Meta-6-acid 21 (280 mg, 0.49 mmol) and
silicon phthalocyanine dichloride 1 (100 mg, 0.16 mmol) were
reacted as before to give the meta-6-pc 22 as a dark blue-green
solid (106 mg, 35%) after column chromatography (silica gel,
CH2Cl2). Mp >250 °C. 1H NMR (400 MHz, CDCl3): δ 9.71 (4H,
m), 8.39 (4H, m), 6.14 (2H, m), 4.85 (1H, m), 4.34 (1H, s), 4.23
(2H, t, J ) 6.4 Hz), 2.76 (6H, m), 2.34 (3H, s), 1.55 (4H, m),
1.35 (12H, m), 0.88 (6H, m). 13C NMR (100 MHz, CDCl3): δ
159.0, 157.1, 150.2, 135.5, 131.7, 131.5, 130.0, 128.8, 127.7,
127.7, 125.1, 124.1, 119.9, 119.0, 110.9, 110.8, 66.1, 36.2, 35.7,
30.6, 30.6, 29.4, 29.4, 27.4, 26.0, 22.1, 19.1, 13.9. (NMR in
Supporting Information.)
F lex-P c (24). Silicon pc dichloride 1 (200 mg, 0.32 mmol)
was reacted with 6-bromohexanoic acid (250 mg, 1.28 mmol)
as above to give the derived bis-bromoalkyl substituted pc 23.
Excess hexanoic acid was removed by washing with hexane,
Or th o-6-P c (18). Ortho-6-acid 17 (280 mg, 0.49 mmol) and
silicon phthalocyanine dichloride 1 (100 mg, 0.16 mmol) were
reacted as before to give ortho-6-Pc 18 as a dark blue-green
9138 J . Org. Chem., Vol. 67, No. 26, 2002

Novel Phthalocyanine-Tetrathiafulvalene Hybrids
and the resulting blue solid was not purified but reacted with
an excess of TTF derivative 3b (517 mg, 0.96 mmol) as above
to give the flex-pc 24 as a dark blue-green solid (56 mg, 10%)
after column chromatography (silica gel, CH2Cl2). Mp >250
fonated aluminum pc in water (Φf ) 0.40) using the method
of Williams et al.30
F lu or escen ce Lifetim es Acqu isition . The technique of
time correlated single photon counting31 was used to record
fluorescence lifetimes of the phthalocyanine. All solutions
under study were prepared with a concentration such that the
maximum absorbance at the Q-band absorption was no greater
than 0.05, to eliminate the effects of reabsorption.29 The
excitation source consists of a pulsed 635 nm diode laser (IBH
NanoLED Model-02) providing output pulses of <200 ps at a
repetition rate of 1 MHz. The fluorescence emission was
collected at 90° to the excitation source, and the emission
wavelength selected using a monochromator (J obin Yvon Triax
190). The fluorescence was detected using a photomultiplier
tube (IBH Model TBX-04) linked to a time-to-amplitude
converter (Ortec 567) and multichannel analyzer (E. G. & G.
Trump Card and Maestro for Windows v.5.10). The instrument
response function (IRF) of the apparatus was measured using
a dilute suspension of milk powder in water as a scattering
medium giving an IRF with a duration of 450 ps full-width at
half-maximum (fwhm). The time per channel was typically
∼50 ps, giving a full range of ∼50 ns over the 1024 point data
set. All fluorescence decays were recorded to a minimum of
10 000 counts in the peak channel of the pulse height analyzer.
The data were transferred to a computer and analyzed by
using the standard method of iterative reconvolution and
nonlinear least-squares fitting in a Microsoft Excel spread-
sheet.31 The quality of calculated fits was judged using
statistical parameters including the Durbin-Watson param-
eter, reduced ø2, random residuals, and autocorrelated residu-
als.
1
°C dec. H NMR (400 MHz, CDCl3): δ 9.71 (4H, m), 8.40 (4H,
m), 2.79 (4H, m), 2.26 (3H, s), 2.09 (2H, t, J ) 7.2 Hz), 1.62
(4H, m), 1.35 (8H, m), 0.85 (6H), 0.46 (2H, m), -0.62 (4H, m),
-0.90 (2H, m). 13C NMR (100 MHz, CDCl3): δ 166.9, 150.0,
135.4, 131.4, 129.1, 129.0, 128.0, 126.1, 124.0, 110.8, 110.2,
38.2-13.9 (m). (NMR in Supporting Information.)
Den d r im er -Ester (26). The TTF-dendron 2518c (1.192 g,
0.865 mmol) was deprotected using cesium hydroxide mono-
hydrate (0.174 g, 1.04 mmol) as before and alkylated using
methyl 4-bromomethylbenzoate (229 mg, 1.00 mmol). Purifica-
tion by column chromatography (silica gel, CH2Cl2-EtOAc 98:2
v/v) afforded the dendrimer-ester 26 as a dark orange syrup
(1.194 g, 94%). 1H NMR (400 MHz, CDCl3): δ 7.98 (2H, d, J )
8.4 Hz), 7.38 (2H, d, J ) 8.4 Hz), 4.01 (2H, s), 3.91 (3H, s),
3.69 (16H, m), 3.01 (8H, q, J ) 4.8 Hz), 2.42 (18H, br s), 2.23
(3H, s). 13C NMR (100 MHz, CDCl3): δ 129.9, 129.1, 124.4,
109.7, 70.5, 70.1, 52.2, 35.5, 19.2. MS (ES+) m/z: 1472-1477
([M]+), 1493-1498 ([M + Na]+), 1509-1513 ([M + K]+). Anal.
Calcd for C46H54O6S24: C, 37.27; H, 3.70. Found: C, 37.48; H,
4.08.
Den d r im er -Acid (27). Dendron 26 (1.140 g, 0.774 mmol)
was treated with sodium hydroxide (1.00 g, 25.0 mmol) as
above and subsequently neutralized using dilute hydrochloric
acid to give the dendrimer-acid 27 as a dark red toffee (1.107
g, 98%). 1H NMR (400 MHz, CDCl3) δ 8.02 (2H, d, J ) 8.2
Hz), 7.39 (2H, d, J ) 8.2 Hz), 4.02 (2H, s), 3.73 (16H, m), 3.02
(8H, m), 2.43 (18H, br s), 2.27 (3H, s). 13C NMR (100 MHz,
CDCl3): δ 168.8, 142.7, 134.7, 130.9, 130.3, 129.4, 128.3, 127.4,
70.5-70.1 (m), 35.4, 35.3, 19.2, 19.2. MS (ES+) m/z: 1456-
1460 ([M]+), 1480-1486 ([M + Na]+), 1495-1499 ([M + K]+).
Sp ectr oelectr och em istr y. Spectroelectrochemical studies
were performed using an optically transparent thin layer
electrode (OTTLE) cell, comprising a 1 mm path length quartz
cuvette, platinum mesh as the working electrode, and plati-
num wire reference and counter electrodes, as described
elsewhere.32 Absorption studies were achieved by passing the
probe beam through the working electrode (and solution of
interest). For fluorescence the cell was held at 45° to the
excitation beam which was focused into the center of the cell.
The emission was collected from the opposite side of the cell.
Anal. Calcd for C45H52O6S24
37.47; H, 3.89.
: C, 37.06; H, 3.59. Found: C,
Den d r im er -p c (28). Dendron 27 (597 mg, 0.41 mmol) and
silicon phthalocyanine dichloride 1 (100 mg, 0.16 mmol) were
reacted as above to give the dendrimer-pc 28 as a dark blue-
green solid (183 mg, 33%) after column chromatography (silica
gel, CH2Cl2). Mp >250 °C dec; 1H NMR (400 MHz, CDCl3): δ
9.71 (4H, m), 8.40 (4H, m), 6.18 (2H, d, J ) 8.4 Hz), 5.05 (2H,
d, J ) 8.4 Hz), 3.63 (16H, m), 3.56 (2H, br s), 2.99 (8H, m),
2.38 (18H, br s), 2.17 (3H, s). (NMR in Supporting Informa-
tion.)
Molecu la r Mod elin g. The computer program CAChe
(v.5.02, Oxford Molecular, Ltd.) was used to perform structural
optimization of the structures of the phthalocyanine com-
pounds. The MM3 algorithm was used for the MOPAC
structural optimizations, using the standard procedure for
energy minimization.
Ackn owledgm en t. We gratefully acknowledge fund-
ing for C.F. and S.F. from the E.P.S.R.C. and funding
for C.A.C. from the Danish Research Agency.
Su p p or t in g In for m a t ion Ava ila b le: 1H and 13C NMR
spectra of compounds 6, 14, 18, 22, and 24 and the 1H NMR
spectrum of 28. This material is available free of charge via
the Internet at http://pubs.acs.org.
Stea d y-Sta te Sp ectr oscop y. Background corrected UV-
visible absorption spectra were recorded on an ATI Unicam
UV/VIS UV2 spectrometer. Emission spectra were recorded
on a Perkin-Elmer LS-50B luminescence spectrometer and
were corrected for the spectral response of the machines.
Fluorescence spectra were recorded under conditions carefully
chosen to avoid the effects of reabsorption as described by
Dhami et al.29 Fluorescence quantum yields were recorded
relative to Cresyl Violet in methanol (Φf ) 0.54), and disul-
J O020340Y
(29) Dhami, S.; de Mello, A. J .; Rumbles, G.; Bishop, S. M.; Phillips,
D.; Beeby, A. Photochem. Photobiol. 1995, 61, 341.
(30) Williams, A. T. R.; Winfield, S. A.; Miller, J . N. Analyst 1983,
108, 1067.
(31) O’Connor, D. V.; Phillips, D. Time Correlated Single Photon
Counting; Academic Press: London, UK, 1984.
(32) Huff, C. M.; Heath, G. A. Inorg. Chem. 1991, 30, 2528.
J . Org. Chem, Vol. 67, No. 26, 2002 9139