Synthesis and nonlinear optical, photophysical, and electrochemical properties of subphthalocyanines

Article abstract of DOI:10.1021/ja980508q

Novel boron(III) subphthalocyanines (SubPcs) soluble in organic solvents containing a variety of donor and acceptor substituent groups have been synthesized by boron trihalide-induced cyclotrimerization of adequately substituted derivatives of phthalonitr

Full text of DOI:10.1021/ja980508q

12808
J. Am. Chem. Soc. 1998, 120, 12808-12817
Synthesis and Nonlinear Optical, Photophysical, and Electrochemical
Properties of Subphthalocyanines
B. del Rey,† U. Keller,† T. Torres,*,† G. Rojo,‡ F. Agullo´-Lo´pez,*,‡ S. Nonell,*,§ C. Mart´ı,§
S. Brasselet, I. Ledoux, and J. Zyss*,
Contribution from the Departments of Organic Chemistry C-I and Physics of Materials C-IV, UniVersidad
Auto´noma de Madrid (UAM), Cantoblanco, Madrid-28049, Spain, Institut Qu´ımic de Sarria`, UniVersitat
Ramon Llull, Via Augusta 390, 08017-Barcelona, Spain, and Department d’Electronique Quantique et
Mole´culaire, France Telecom, CNET Paris-B, 196, AVenue Henri RaVera, 92225 Bagneux, France
ReceiVed February 16, 1998
Abstract: Novel boron(III) subphthalocyanines (SubPcs) soluble in organic solvents containing a variety of
donor and acceptor substituent groups have been synthesized by boron trihalide-induced cyclotrimerization of
adequately substituted derivatives of phthalonitrile in 1-chloronaphthalene. The choice of the substituents on
the 1,2-dicyanobenzene derivatives has been made taking into account the high reactivity of the Lewis acid
BCl3 toward many functional groups. Considering this limitation, we set out to synthesize phthalodinitriles
equipped with iodo, nitro, alkyl- or arylthio, alkyl- or arylsulfonyl groups that are sufficiently stable under the
required reaction conditions and also provide an easily accessible set of acceptor/donor substituents. The quadratic
and cubic hyperpolarizabilities of these compounds as well as their linear optical and electrochemical properties
have been measured by several techniques, including EFISH (at two wavelengths), HRS, and THG, steady-
state and time-resolved absorption and fluorescence, laser-induced optoacoustic calorimetry, time-resolved
near-infrared emission spectroscopy, and cyclic voltammetry. âHRS has been measured at 1.46 µm, where the
contamination from the multiphoton-induced fluorescence can be ruled out. âHRS reachs high values that markedly
depend on substitution. It shows a clear enhancement with the acceptor character of the substituents, the highest
values being obtained for the compounds bearing the strongest acceptor groups. They are comparable or even
superior to many efficient second-order compounds. A main outcome of these results is that an adequate
choice of the substituents offers a promising route for optimization of the quadratic response of the SubPcs.
This kind of compounds is less prone to aggregation than their expanded analogues, the phthalocyanines,
fluoresces with quantum yields ca. 0.25, lower than those typical for phthalocyanines, and has larger triplet
quantum yields. The triplet-state lifetime is in the 100-µs time range, long enough for efficient oxygen quenching.
Indeed, subphthalocyanines sensitize singlet molecular oxygen, O2(1∆g), with quantum yields ranging from
0.23 to 0.75. The ground-state oxidation potentials are similar to those of phthalocyanines, while the reduction
potentials are clearly more negative; i.e., they are more difficult to reduce. In contrast, electronically excited
subphthalocyanines are more easily oxidized than the corresponding phthalocyanines by ca. 500 mV which
results in lower photostability, especially in polar solvents.
Organic materials are increasingly considered as a real
effects emanate only from noncentrosymmetric molecules, and
their enhancement has mostly relied on push-pull systems.2
One particular promising route3 for both second- and third-
order NLO applications is provided by conjugated molecules
related to phthalocyanines (Pcs). These are well-known planar
compounds with excellent physicochemical properties, including
high aromaticity, associated with their 18 π-conjugated electron
system and very good thermal and chemical stability.4 With
regard to the third-order NLO response, high cubic hyperpo-
larizabilities γ have been recently measured, and good optical
alternative to inorganic compounds for nonlinear optical ap-
plications, such as parametric amplification and oscillation, and
all optical modulation and switching. Their main advantages
are high and ultrafast nonlinear optical (NLO) responses and
low dielectric constants as well as the possibility of tailoring
their physicochemical and NLO properties through molecular
engineering. The first step in obtaining efficient organic
materials is to design and synthesize molecules with high
nonresonant molecular hyperpolarizabilities.1 Whereas an electron-
delocalized organic system is the single prerequisite for achiev-
ing a third-order nonlinear response, second-order nonlinear
(2) Craig, G. S.; Cohen, R. E.; Silbey, R. R.; Pucceti, G.; Ledoux, I.;
Zyss, J. J. Am. Chem. Soc. 1993, 115, 860-871.
(3) (a) Nalwa, H. S.; Shirk, J. S. In Phthalocyanines: Properties and
Applications; Leznoff, C. C., Lever, A. B. P., Eds.; VCH: Weinheim, 1996;
Vol. 4, Chapter 3. (b) De la Torre, G.; Torres, T.; Agullo´-Lo´pez, F. AdV.
Mater. 1997, 9, 265-269. (c) de la Torre, G.; Va´zquez, P.; Agullo´-Lo´pez,
F.; Torres, T. J. Mater. Chem. 1998, 8, 1671-1683.
(4) (a)Phthalocyanines: Properties and Applications; Leznoff, C. C.,
Lever, A. B. P., Eds.; VCH: Weinheim, 1989, Vols. 1-4. (b) Hanack, M.;
Heckmann, H.; Polley, R. In Methods of Organic Chemistry (Houben-Weyl);
Schaumann, E., Eds.; Georg Thieme Verlag: Stuttgart, 1998; Vol. E 9d, p
717.
† Department of Organic Chemistry, UAM.
‡ Department of Physics of Materials, UAM.
§ IQS-Universitat Ramon Llull.
CNET.
(1) (a) Molecular Nonlinear Optics; Zyss, J., Ed.; Academic Press: New
York, 1993. (b) Nonlinear Optics of Organic Molecules and Polymers;
Nalwa, H. S., Miyata, S., Eds.; CRC Press: Boca Raton, FL 1997. (c)
Nonlinear Optics: Materials, Physics and DeVices; Zyss, J., Ed.; Academic
Press: Boston, 1993.
10.1021/ja980508q CCC: $15.00 © 1998 American Chemical Society
Published on Web 11/26/1998

Synthesis and Properties of Subphthalocyanines
J. Am. Chem. Soc., Vol. 120, No. 49, 1998 12809
published, despite their intense pink color and obvious fluo-
rescence. The ever-increasing use of Pcs as sensitizers in
photooxidation and photoinduced electron-transfer processes
suggests that SubPcs might be of interest for these applications.
In view of the nontrivial synthesis15 of the Subpcs, it is not
surprising that only very few examples of substituted derivatives
have been reported so far and studies on their nonlinear optical
properties are even more limited in number.12-14 Large third-
order susceptibilities, ø(3), have been measured12 on evaporated
thin films of unsubstituted SubPc 1 by third-harmonic generation
(THG). Moreover, high âHRS values have been inferred for
substituted compounds 2 and 3 from hyper-Rayleigh scattering
(HRS) experiments.13 On the other hand, the electric field-
induced second-harmonic (EFISH) generation yield from the
same substituted molecules was found to be very low and
comparable to that for the unsubstituted molecule 1. For this
reason, the good HRS results were attributed to a dominant
octupolar contribution3b,16 arising from the cone-shaped trigonal
geometry.8 The highest value of âHRS was measured for
derivative 3 bearing electron-attracting groups (-NO2), whereas
smaller values were obtained for unsubstituted SubPc 1 and a
derivative with electron-donating groups (tert-butyl), 2. Evapo-
rated and spin-coated films of 3 have been also studied by
SHG.14 This very promising behavior has prompted us to carry
out a detailed and systematic study of the NLO response of
SubPcs with special emphasis on elucidating the role of donor
and acceptor substituents. In the present paper, we report on
the synthesis of novel tri- and hexasubstituted Subpcs, the
characterization of their photophysical, photosensitizing, and
electrochemical properties, and a comparative study of the
nonlinear optical behavior of several of these compounds (3-
11 in Figure 1a). EFISH (at two frequencies), THG, and HRS
experiments have been performed in order to provide useful
data on the second- and third-order NLO responses. In addition,
we report that these SubPcs possess rich photophysical and
electrochemical properties that, combined with the unusual cone-
shaped geometry and the resulting lower tendency to aggregate,
make them interesting photosensitizers.
Figure 1. (a) Tri- and hexasubstituted subphthalocyanines 1-11. (b)
3-D structure of 1 as determined from X-ray analysis.
limiting capabilities have been achieved.3a This makes them
potentially useful for many third-order applications. On the other
hand, metallophthalocyanines are not, generally, suitable for
second-order applications because of their inversion symmetry.
However, a few unsymmetric substituted Pcs have been prepared
and their NLO properties studied, although very scarce informa-
tion is still available on their second-harmonic generation (SHG)
performance.3,5,6
Recently, a long-range research effort has been started on
intrinsically noncentrosymmetric Pc derivatives called subph-
thalocyanines (SubPcs), whose chemical structure is illustrated
in Figure 1a. Subphthalocyanines (SubPcs) are macrocycles
formed by three coupled isoindole moieties having a delocalized
14 π-electron system, whose synthesis was first reported in
1972.7 Unlike the related planar phthalocyanines, SubPcs have
a cone-shaped structure (Figure 1b), as established by X-ray
analysis,8 which does not prevent them from having an aromatic
nature.9 Twenty years later, SubPcs are again receiving con-
siderable attention as excellent building blocks for the synthesis
of unsymmetric phthalocyanines10,11 and as materials for
nonlinear optics.3b,12-14 Recently, their preparation and reactivity
have been reviewed.15 Interestingly, to the best of our knowl-
edge, no report on their photophysical properties has ever been
Results and Discussion
Synthesis and Spectroscopic Characterization. Following
a procedure initially reported by Meller and Ossko,7 the
synthesis of Subpcs is commonly carried out by boron trihalide-
induced cyclotrimerization of adequately substituted derivatives
of phthalonitrile in 1-chloronaphthalene. Accordingly, the choice
of the substituents on the 1,2-dicyanobenzene derivatives to be
(10) (a) Kobayashi, N.; Kondo, R.; Nakajima, S.; Osa, T. J. Am. Chem.
Soc. 1990, 112, 9640-9641. (b) Kasuga, K.; Idehara, T.; Handa, M.; Isa,
K. Inorg. Chim. Acta 1992, 196, 127-128. (c) Dabak, S.; Gu¨l, A.;
Bekaroglu, O¨ . Chem. Ber. 1994, 127, 2009-2012. (d) Bayir, Z. A.;
Hamuryudan, E.; Gu¨rek, A. G.; Bekaroglu, O. J. Porphyrins Phthalocya-
nines 1997, 1, 349-353. (e) Gu¨rek, A. G.; Bekaroglu, O. J. Porphyrins
Phthalocyanines 1997, 1, 67-76. (f) Weitemeyer, A.; Kliesch, H.; Wo¨hrle,
D. J. Org. Chem. 1995, 60, 4900-4904. (g) Kudrevich, S. V.; Gilbert, S.;
Van Lier, J. E. J. Org. Chem. 1996, 61, 5706-5707.
(5) (a) Liu, Y.; Xu, Y.; Zhu, D.; Wada, T.; Sasabe, H.; Liu, L.; Wang,
W.; Thin Solid Films 1994, 244, 943-946. (b) Liu, Y.; Xu, Y.; Zhu, D.;
Wada, T.; Sasabe, H.; Zhao, X.; Xie, X. J. Phys. Chem., 1995, 99, 6957-
6960. (c) Tian, M.; Wada, T.; Kimura-Suda, H.; Sasabe, H. J. Mater. Chem.
1997, 7, 861-863. (d) Liu, S.-G.; Liu, Y.-Q.; Xu, Y.; Zhu, D.-B.; Yu, A.-
Ch.; Zhao, X.-S. Langmuir 1998, 14, 690-695.
(6) (a) Sastre, A.; D´ıaz-Garc´ıa, M. A.; del Rey, B.; Dhenaut, C.; Zyss,
J.; Ledoux, I.; Agullo´-Lo´pez, F.; Torres, T. J. Phys. Chem. A 1997, 101,
9773-9777. (b) D´ıaz-Garc´ıa, M. A.; Agullo´-Lo´pez, F.; Sastre, A.; del Rey,
B.; Torres, T.; Dhenaut, C.; Ledoux, I.; Zyss, J. Mol. Cryst. Liq. Cryst. Sci.
Technol., Sect. B: Nonlinear Opt. 1996, 15, 251-254.
(11) (a) Sastre, A.; Torres, T.; Hanack, M. Tetrahedron Lett. 1995, 36,
8501-8504. (b) Sastre, A.; del Rey, B.; Torres, T. J. Org. Chem. 1996,
61, 8591-8597.
(12) D´ıaz-Garc´ıa, M. A.; Agullo´-Lo´pez, F.; Sastre, A.; Torres, T.;
Torruellas, W. E.; Stegeman, G. I. J. Phys. Chem. 1995, 99, 14988-14991.
(13) Sastre, A.; Torres, T.; D´ıaz-Garc´ıa, M. A.; Agullo-Lo´pez, F.;
Dhenaut, C.; Brasselet, S.; Ledoux, I.; Zyss, J. J. Am. Chem. Soc. 1996,
118, 2746-2747.
(7) Meller, A.; Ossko, A. Monatsh. Chem. 1972, 103, 150-155.
(8) (a) Kietaibl, H. Monatsh. Chem. 1974, 105, 405-418. (b) Rauschna-
bel, J.; Hanack, M. Tetrahedron Lett. 1995, 36, 1629-1632. (c) Kasuga,
K.; Idehara, T.; Handa, M.; Ueda, Y.; Fujiwara, T.; Isa, K. Bull. Chem.
Soc. Jpn. 1996, 69, 2559-2563.
(14) Rojo, G.; del Rey, B.; Agullo´-Lo´pez, F.; Torres, T. Appl. Phys. Lett.
1997, 1802-1804.
(15) Geyer, M.; Plenzig, F.; Rauschnabel, J.; Hanack, M.; del Rey, B.;
Sastre, A.; Torres, T. Synthesis 1996, 1139-1151.
(9) Kobayashi, N. J. Chem. Soc., Chem. Commun. 1991, 1203-1205.
(16) Zyss, J.; Ledoux, I. Chem. ReV. 1994, 94, 77-105.

12810 J. Am. Chem. Soc., Vol. 120, No. 49, 1998
del Rey et al.
Scheme 1. Synthesis of the Trisubstituted
Subphthalocyanines 6 and 7
Scheme 2. Synthesis of Hexasubstituted Subphthalocyanines
8 and 10
employed must take into account the high reactivity of the Lewis
acid BCl3 or BBr3 toward functional groups such as ether, alkyl,
etc. Considering this limitation, we set out to synthesize
phthalodinitriles equipped with iodo, nitro, alkyl- or arylthio,
alkyl- or arylsulfonyl groups that not only are expected to be
sufficiently stable under the required reaction conditions but
also provide an easily accessible set of acceptor/donor substit-
uents.
Scheme 3. Synthesis of Hexasubstituted Subphthalocyanines
9 and 11
Subphthalocyanines 1-4 have been previously described.15
Compound 6 was prepared from 4-nitrophthalonitrile17a (12) in
two steps (Scheme 1). Thus, treatment of 12 with octanethiol
and potassium carbonate in dimethyl sulfoxide (DMSO) as
solvent17b-d afforded the thioether 1317c,d in high yield. Com-
pound 13 was cyclotrimerized in the presence of boron
trichloride (BCl3) in 1-chloronaphthalene15 under argon to afford
6 in 27% yield as a sticky residue after purification by column
chromatography on alumina. On the other side, the preparation
of 7 was carried out from 13 by oxidation with m-chloroper-
benzoic acid (MCPBA) in dichloromethane to give 14 in good
yield, which was further reacted with BCl3. Compound 7 was
obtained in low yield (13%) after purification by solvent
extraction.
Compounds 6 and 7 are each mixtures of two constitutional
isomers with symmetries C1 and C3. The regioisomers could
not be separated by chromatography, but their presence was
clearly observed by 1H NMR. A 3:1 ratio of both isomers was
estimated from their 1H NMR spectra. This fact is in agreement
with previous results obtained by us for related compounds,11b
thus confirming that a nonregioselective statistical condensation
of the phthalonitrile subunits has taken place in the formation
of 6 and 7.
Compound 8 (Scheme 2) was prepared from 4,5-dichlo-
rophthalonitrile (15)18 in two steps. Treatment of 15 with
octanothiol and potassium carbonate using dimethylacetamide
(DMAC) as solvent afforded dithioether 16 in high yield. The
use of DMSO, usually employed in this kind of substitution
reaction,17b,18 is discouraged in this particular case since it is
known to effect readily the oxidative dimerization of thiols.19
Compound 16 was cyclotrimerized in the presence of boron
trichloride in the usual way.15 On the other hand, the preparation
of 10 (Scheme 2) was achieved from 16 by oxidation with
hydrogen peroxide in acetic acid to give 17, which was further
reacted with boron trichloride.
Subphthalocyanine 9 (Scheme 3) was prepared from di-
iodophthalonitrile (18)20 also in a two-step sequence. Compound
18 was treated with 4-methylthiophenol and potassium carbonate
in DMSO as solvent by modification of a known procedure18
to afford the thioether 19 in good yield. Compound 19 was then
reacted with BCl3 in the usual way15 to give 9. On the other
hand, the preparation of 11 was readily achieved from 19 by
oxidation with MCPBA to give 20, followed by cyclotrimer-
ization reaction of this in the presence of BCl3. Compounds 9
and 11 were obtained in 28 and 25% yield, respectively, the
first as a sticky residue. Moderate to low yields are typical in
the preparation of subphthalocyanines.15
Highly conjugated subphthalocyanine 521a was obtained by
a metal-mediated cross-coupling methodology.21b Thus, p-nitro-
ethynylbenzene21c (21) was reacted with triiodosubphthalocya-
nine 4 in the presence of bis[triphenylphosphine]palladium(II)
dichloride and copper(I) iodide in oxygen-free triethylamine at
room temperature, affording 5 in moderate yield (Scheme 4).
The overall shape of the UV-visible spectra of subphthalo-
cyanines is similar to that of the metallophthalocyanines, and
so dominated by two intense bands: the Q-band around 560
nm (in the unsubstituted compound 1) and the Soret (B)
transition in the UV region of the spectrum around 300 nm.
(Figure 2). The bands are blue-shifted compared to those of
metallophthalocyanines owing to the smaller conjugated system
(14 vs 18 π electrons) and have lower absorption coefficients.
The position of the Q-band in SubPcs can be clearly red-
shifted (bathochromic shift) with regard to the unsubstituted
derivative by introducing electron-donor substituents (2, 6, 8,
(17) (a) Young, J. G.; Onyebuagu, W. J. Org. Chem. 1990, 55, 2155-
2159. (b) Gu¨rol, I.; Ahsen, V.; Bekaroglu, O¨ . J. Chem. Soc., Dalton Trans.
1994, 497-500. (c) Okada, S.; Masaki, A.; Nakanishi, H.; Suda, Y.;
Shigehara, K.; Yamada, A. Proc. SPIE-Int. Soc. Opt. Eng. 1990, 1337
(Nonlinear Opt. Prop. Org. Mater. 3), 105-113. (d) Taniguchi, M.;
Narizuka, T.; Tomita, H. Jpn. Kokai Tokkyo Koho JP 08,269,004, 1996.
(18) Wo¨hrle, D.; Eskes, M.; Shigehara, K.; Yamada, A. Synthesis 1993,
194-196.
(20) Terekov, D. S.; Nolan, K. J. M.; McArthur, C. R.; Leznoff, C. C.
J. Org. Chem. 1996, 61, 4-3040.
(21) (a) del Rey, B.; Torres, T. Tetrahedron Lett. 1997, 38, 5351-5354.
(b) Grosshenny, V.; Romero, F. M.; Ziessel, R. J. Org. Chem. 1997, 62,
1491-1494. (c) Takahashi, S.; Kuroyama, Y.; Sonogashira, K.; Hagihara,
N. Synthesis 1980, 627-630.
(19) (a) Epstein, W. W.; Sweat F. W. Chem. ReV. 1967, 67, 247-251.
(b) Johnson, C. R.; Sharp, J. C. Q. Rep. Sulfur Chem. 1969, 4, 2-10. (c)
Yiannios, C. N.; Karabinos J. V. J. Org. Chem. 1963, 28, 3246-3259.

Synthesis and Properties of Subphthalocyanines
J. Am. Chem. Soc., Vol. 120, No. 49, 1998 12811
Figure 2. UV-vis absorption spectrum of subphthalocyanines 4, 5, 7, and 8 in chloroform solution (2.5 × 10-5, 1.7 × 10-5, 7.4 × 10-6, and 2
× 10-5 M, respectively).
Table 1. Experimental Data Obtained from EFISH, THG, and
HRS Experiments for Compounds 4-11a
Scheme 4. Synthesis of Trisubstituted Subphthalocyanine 5
γTHG
âHRS
γ
EFISH (10-34 esu)
compd (nm) (D) 1.9 µm 1.34 µm
λmax
µ0
(10-34 esu), (10-30 esu),
1.34 µm
1.46 µm
3
4
5
6
7
8
9
10
11
586
573
590 10.1
584
570
603 15
607 4.8
5.5
5.3
-8.5
-7.3
-6
16
4.3
7
9.7
22.3
13
13.6
80
-13
-5.8
-14
144.3
164.5
38
76.5
168.5
40
64.3
260
211.5
6.7
7.6
-3.7
-6.6
-3
-23.4
-18
-106
-70
-8
579 14.8 -15
587
-27
8.6 -13.4
130
-1.6
a The λmax corresponding to the Q-band transition and the measured
ground-state dipole moment are also included.
and 9). The same effect, but less important, takes place by
introduction of electron-acceptor substituents in the SubPc (3,
4, 5, 7, 10, and 11). The hexasubstituted SubPcs show larger
red shifts (up to 40 nm for 9) than the trisubstituted ones,
probably reflecting a geometrical distortion of the outer benzo
rings. Figure 2 shows the UV-visible absorption spectra in
chloroform solution of SubPcs 4, 5, 7, and 8 as representative
examples of the compounds studied in this paper. The curious
observation that bathochromic shifts of the Q-band are found
for both donor and acceptor substituents may indicate a
distortion of the SubPc geometry. This behavior is well
advantage for applications as photosenzitizers, as aggregation
invariably results in the deterioration of the photophysical
properties.
All the compounds were characterized by NMR, IR, MS-
FAB or MS-EI, UV-visible, and elemental analysis (see
Experimental Section).
Nonlinear Optical Properties. The data for all investigated
molecules obtained by the various NLO techniques are sum-
marized in Table 1, together with the values for the permanent
dipole moments (µ0). It appears that most molecules are
moderately polar, whereas 5, 8, and 10 are more strongly polar
(µ0 g 10 D).
Let us first discuss the EFISH data taken at two fundamental
wavelengths: 1.9 and 1.34 µm. γEFISH values at 1.9 µm are
negative and do not show large differences among the various
molecules. On the other hand, for 1.34 µm, the EFISH
hyperpolarizability becomes positive, and measured values
become strongly dependent on the particular compound. They
are quite high for the molecules having acceptor substituents
and reach a very remarkable value for 10 and particularly for
SubPc 11. On the other hand, molecules having donor substit-
uents (6, 8, and 9) show rather small γEFISH values. These are
in the same range as those reported for some unsymmetrically
substituted Pcs.6
documented for related porphyrins and phthalocyanines.4,22
A
new transition between the Soret and the Q-bands appears in
the UV-visible spectrum of compounds bearing thioether
groups. This band appears at 413 nm for 8. Similar absorptions
are also observed for 6 and 9 (not represented in Figure 2).
Unlike phthalocyanines, SubPcs remain monomeric in CHCl3
solutions, even at concentrations of 1 mM; i.e., they have a
remarkably lower tendency toward aggregation. This is a
consequence of the nonplanar geometry and is of great
(22) (a) Sparks, L. D.; Medforth, C. J.; Park, M.-S.; Chamberlain, J. R.;
Ondrias, M. R.; Senge, M. O.; Smith, K. M.; Shelnutt, J. A. J. Am. Chem.
Soc. 1993, 115, 581-592 and references therein. (b) Drain, C. M.; Kirmaier,
C.; Medforth, C. J.; Nurco, D. J.; Smith, K. M.; Holten, D. J. Phys. Chem.
1996, 100, 11984-11993.

12812 J. Am. Chem. Soc., Vol. 120, No. 49, 1998
del Rey et al.
All the above γEFISH data include an electronic γe (-2ω: 0,
ω, ω) contribution, together with an orientational term propor-
tional to µ•â ) µ0âz, where â is the vector part of the âij tensor
and âz its projection on µ. To separate this orientational
contribution and calculate âz, the electronic component γe should
be known or considered negligible. This last possibility does
not appear reasonable in view of the comparable values obtained
for γEFISH and γTHG (see Table 1), to be discussed below.
Let us now comment on the HRS results obtained at λ )
1.46 µm, where the possible spurious multiphoton-induced
luminescence can be ruled out. The âHRS values are also strongly
dependent on the donor/acceptor character of the substituents
and show the same trend as that previously described for γEFISH
at λ ) 1.34 nm. The highest values (∼2 × 10-28 esu) are
reached for the molecules containing the electron acceptor
groups (3, 4, 7, 10, and 11), whereas much lower values are
measured for the case of electron-donor groups (6, 8, and 9). It
is even remarkable that these lower values correspond to more
resonant conditions than those for acceptor groups, due to the
clear red shift of the Q-band associated with the donor groups.
Note that the value, now measured at 1.46 µm, for 3 is
remarkably lower than that previously reported at 1.34 µm.13
This is possibly due to residual fluorescence contamination at
the latter wavelength that could not be avoided in our previous
setup.
As a summary, one can state that the â values measured for
SubPcs are reasonally high in comparison to those reported for
most organic compounds23 and clearly superior to those available
for related unsymmetrically substituted porphyrins.24b However,
we should mention that very high HRS values have been
obtained recently for some push-pull arylethynyl porphyrins,24c
suggesting further optimization possibilities for SubPcs.
With regard to the cubic hyperpolarizability data, γTHG, the
values obtained are negative and markedly lower than those
reported for symmetric phthalocyanines25 but quite comparable
to those for some unsymmetric Pcs.6 This could indicate a
decrease in the π-conjugation related to the smaller aromaticity
of SubPcs in comparison to Pcs. On the other hand, they show
a rather opposite trend with the substituents from that found
for the quadratic polarizability â. In fact, the highest γTHG values
are obtained for those compounds, 6, 8, and 9, containing donor
substituent groups. This behavior may be due to the large red
shift of the Q optical absorption band that should increase the
resonant behavior at 2ω. Moreover, these compounds show an
additional band at ca. 400 nm that is strongly resonant at the
third-harmonic frecuency and so should also contribute to the
enhancement.
Figure 3. Absorption and fluorescence spectrum of SubPc 1 in
benzene.
nines, e.g., ΦF ) 0.58 for AlPcCl.26 Clearly, nonradiative
deactivation channels, i.e., internal conversion and intersystem
crossing, are more efficient for SubPcs. The 10-fold decrease
for SubPc 4 is readily explained on the basis of the highly
efficient intersystem crossing characteristic of heavy-atom-
substituted aromatic compounds.27 The lifetimes of the excited
singlet states, τS, measured by the single-photon-counting
technique, are ca. 3 ns for all compounds but 4, again about
half the value for phthalocyanines (see Table 2).
Intersystem crossing to the triplet state occurs in high yield,
as demonstrated by transient absorption experiments. Thus,
transients are observed throughout the visible spectrum that are
identified as triplet states owing to their lifetime sensitivity to
oxygen and the concomitant production of singlet oxygen, O2-
(1∆g) (see below). Figure 4 shows the triplet-minus-singlet
absorption spectrum of 2 with a maximum at 460 nm and a
minimum at 560 nm, corresponding to the S0-to-S1 absorption
maximum. The transients decay following first-order kinetics,
with lifetimes, τT, ranging from 82 µs for 1 to 157 µs for 9 in
argon-saturated solutions. Compound 4 shows a shorter lifetime,
which can be rationalized again in terms of heavy-atom induced
intersystem crossing T1-S0. For all compounds, the decay rate
constants increase linearly with oxygen concentration, which
allows the derivation of the bimolecular quenching rate con-
O2
stants, kq , through the Stern-Volmer treatment. The values
observed are typical for aromatic hydrocarbons.28
Failing to observe any phosphorescence even in 1-iodopro-
pane at 77 K, the energy level of the triplet state, ET, was
estimated using the correlation described by Dreeskamp et al.29
between the rate constant of fluorescence quenching by 1-io-
dopropane, kqIpr, and the energy gap between the first excited
singlet state and the nearest lower triplet state (Figure 5). This
correlation was originally used for aromatic hydrocarbons but
has been recently used for tetrapyrrolic compounds as well.30
While the values obtained are, in principle, upper limits for ET,
the triplet quantum yield values, ΦT, calculated from the product
ΦTET by LIOAC, are consistent with the singlet oxygen
quantum yield data (see below and Table 2). The singlet-to-
triplet energy gap (30-40 kJ mol-1) is significantly smaller than
Photophysical and Electrochemical Properties. Figure 3
shows the normalized absorption and fluorescence spectra of 1
in benzene. The intersection of both curves was taken as the
energy contents of the first excited singlet state, ES. The small
Stokes shift suggests minor geometry differences between the
ground and excited states.
Subphthalocyanines are fluorescent, with quantum yields, ΦF,
ca. 0.25, about half the value observed for related phthalocya-
(23) Kanis, D. R.; Ratner, M. A.; Marks, T. J. Chem. ReV. 1994, 94,
195-242.
(24) (a) Sen, A.; Ray, P. C.; Das, P. K.; Krishnan, V. J. Phys. Chem.
1996, 100, 19611-19613. (b) LeCours, S. M.; Guan, H. W.; DiMagno, S.
G.; Wang, C. H.; Therien, M. J. J. Am. Chem. Soc. 1996, 118, 1497-
1503.
(25) (a) D´ıaz-Garc´ıa, M. A.; Agullo´-Lo´pez, F.; Hutchings, M. G.; Gordon,
P. F.; Kajzar, F. Mol. Cryst. Liq. Cryst. Sci. Technol., Sect. B: Nonlinear
Opt. 1995, 14, 169-174. (b) D´ıaz-Garc´ıa, M. A.; Ledoux, I.; Duro, J. A.;
Torres, T.; Agullo´-Lo´pez, F.; Zyss, J. J. Phys. Chem. 1994, 98, 8761-
8764.
(26) Darwent, J. R.; Douglas, P.; Harriman, A.; Porter, G.; Richoux, M.
C. Coord. Chem. ReV. 1982, 44, 83-126.
(27) Turro, N. J. Modern Molecular Photochemistry; University Science
Books: Mill Valley, CA, 1991; pp 121-130.
(28) Murov, S. L.; Carmichael, I.; Hug, G. L. Handbook of Photochem-
istry; Marcel Dekker: New York, 1993; pp 223-259.
(29) Dreeskamp, H.; Koch, E.; Zander, M. Ber. Bunsen.-Ges. Phys. Chem.
1974, 78, 1328-1334.
(30) Grewer, C.; Schermann, G.; Schmidt, R.; Vo¨lcker, A.; Brauer, H.
D.; Meier, A.; Montforts, F. P. J. Photochem. Photobiol. B: Biol. 1991,
11, 285-293.

Synthesis and Properties of Subphthalocyanines
J. Am. Chem. Soc., Vol. 120, No. 49, 1998 12813
Table 2. Summary of Photophysical (in Benzene) and Electrochemical (in CH2Cl2) Properties of the SubPcs Studieda
1
2
3
4
6
7
9
11
591
4.6
200
0.23
2.9
AlPcCl
λ
max/nm
564
4.8
209
0.25
3.3
30
175
0.62
570
4.7
209
0.16
2.8
13
166
0.55
127
460
586
4.5
203
0.20
3.2
572
4.7
208
0.013
<0.5
20
169
0.77
56
440
586
4.7
202
0.25
2.8
49
173
0.62
130
460
573
4.5
207
0.18
3.1
11
162
0.25
144
460
606
4.9
195
0.24
2.9
40
164
0.69
157
480
680b
5.1b
log(ꢀS/M-1 cm-1
ES/kJ‚mol-1
ΦF
)
174b
0.58b
6.8b
τs (Ar)/ns
kqIPr/107 M-1 s-1
ET/kJ‚mol-1
ΦT
8.0
8.9
154
0.49
109
470
1.38
152
0.42
132
480
1.43
116b
0.4b
τT (Ar)/µs
82
450
1.32
500b
490c
2.66c
λ
max(T-S)/nm
∆ꢀT-S/104 M-1 cm-1
1.19
1.13
1.35
1.21
1.10
kq /10 M-1 s-1
FD
1.79
0.61
3.3
0.88
0.47
15
0.98
-1.11
-0.74
0.61
1.33
0.46
36
1.34
-0.57
-0.26
1.03
1.15
0.74
20
1.13
-0.92
-0.62
0.83
1.46
0.61
4
0.95
-1.09
-0.84
0.70
0.95
0.23
9.5
1.18
0.64
3.3
1.17
0.30
41
1.29
-0.78
-0.28
0.79
O
9
2
0.36d
kqS/107 M-1 s-1
E
1/2(S+/S)/Ve
1.04
1.27
1.02
0.96b
-0.66b
-0.24b
0.56b
E1/2(S/S-)/Ve
-1.05
-0.77
0.76
-0.70
-0.41
0.98
-0.97
-0.68
0.73
E1/2(S+/3S*)/Ve,f
E1/2(3S*/S-)/Ve,g
a Data for AlPcCl are given for comparison. See text for the use of abbreviations. b Reference 26. c Reference 44. d For several sulfonic acid
derivatives, ref 35. e Versus the AgCl/Ag electrode. f Calculated as E1/2(S+/S) - ET/F, where F is the Faraday constant. g Calculated as E1/2(S/S-)
+ ET/F.
the energy stored in the long-lived triplet state, ΦTET, plus the
energy lost by fluorescence, ΦFEF, where EF is the average
fluorescence energy calculated over the entire emission spec-
trum. Using the above-determined values for ET, ΦF, and EF,
values for ΦT (lower limit) could be readily calculated (see Table
2). The rate constants for intersystem crossing, calculated as
kisc ) ΦT/τs, decrease smoothly as the singlet-to-triplet energy
gap increases and are more than 3-fold larger than that for
chloroaluminumphthalocyanine, as anticipated. Internal conver-
sion is also more effective than that for phthalocyanines,
probably reflecting a lower degree of rigidity of the SubPcs.
The SubPcs are excellent photosensitizers and produce singlet
Figure 4. Triplet-minus-singlet absorption spectrum of 2 in argon-
saturated benzene. Inset: Transient absorption at 460 nm. λexc ) 337
nm.
oxygen, O2(1∆g), in large quantities, as measured by the O2-
(1∆g) phosphorescence at 1270 nm.34 Singlet oxygen production
occurs by exothermic energy transfer from the highly populated,
long-lived triplet state, as shown by the triplet quenching
experiments above. The quantum yields, Φ∆, agree with the
ΦT values derived from LIOAC, thus supporting the ET values
determined by the fluorescence method of Dreeskamp et al.
SubPcs show slightly larger Φ∆ values than the related phtha-
locyanines,35 which make them interesting candidates for use
in photosensitization processes, especially in situations where
absorption in the red part of the spectrum is not required. SubPcs
quench singlet oxygen with rate constants kqS ranging from 3.3
× 107 M-1 s-1 for 1 to 4.1 × 108 M-1 s-1 for 11 in benzene.
The rate constants are, in general, higher than those observed
for related macrocycles and increase with the ring oxidation
potential, in contrast with the trend observed for related
compounds.36 This probably reflects specific substituent con-
tributions that may offset the charge-transfer-mediated ring
contribution to the quenching.
Figure 5. Stern-Volmer plot for 2 fluorescence quenching by
1-iodopropane in benzene. Inset: Dreeskamp plot of the quenching
rate constant vs the singlet-triplet energy gap. Data from ref 29.
that of the phthalocyanines (50-70 kJ mol-1).26 Consistent with
this, the intersystem crossing rate constants and quantum yields
are larger.31
The quantum yield from triplet production, ΦT, was deter-
mined by laser-induced optoacoustic calorimetry (LIOAC).32,33
The difference between the pulsed-laser energy absorbed and
the heat released within the first microsecond was ascribed to
There is a report in the literature discussing photostability of
SubPcs in solution.8c While SubPcs are, in general, less stable
than the parent Pcs, decomposition is important only in polar
solvents, stability being much more pronounced in apolar
solvents. Indeed, we could not notice any decomposition along
our photochemistry experiments in benzene.
(34) Mart´ı, C.; Ju¨rgens, O.; Cuenca, O.; Casals, M.; Nonell, S. J.
Photochem. Photobiol. A: Chem. 1996, 97, 11-18.
(35) Wilkinson, F.; Helman, W. P.; Ross, A. B. J. Phys. Chem. Ref.
Data 1993, 22, 113-262.
(36) Tanielian, C.; Wolff, C. Photochem. Photobiol. 1988, 78, 277-
280.
(31) Klessinger, M.; Michl, J. Excited States and Photochemistry of
Organic Complexes; VCH Publishers: Weinheim, 1995; pp 252-260.
(32) Nonell, S.; Aramend´ıa, P. F.; Heihoff, K.; Martin-Negri, R.;
Braslavsky, S. E. J. Phys. Chem. 1990, 94, 5879-5883.
(33) Braslavsky, S. E.; Heibel, G. E. Chem. ReV. 1992, 92, 1381-1410.

12814 J. Am. Chem. Soc., Vol. 120, No. 49, 1998
del Rey et al.
1
ment. H NMR and 13C NMR spectra were recorded with a Bruker
AC-200 spectrometer (200 and 50 MHz, respectively).
1,2-Dicyano-4-octylthiobenzene (13).17c,d A mixture of 4-nitro-
phthalonitrile (12)17a (10 g, 57.8 mmol) and octanethiol (8.4 g, 57.8
mmol) in DMSO (39 mL) was stirred at room temperature for 10 min.
Then, dry potassium carbonate (8 g, 58 mmol) was added in small
portions during 2 h. The mixture was vigorously stirred under argon
atmosphere for 16 h. Water (50 mL) was added, and the product was
extracted with CH2Cl2 (2 × 50 mL). The organic phase was washed
with water (3 × 50 mL) and with a 5% solution of sodium carbonate
(1 × 50 mL) and dried over sodium sulfate. The solvent was removed
under reduced pressure, and the residue was chromatographed (SiO2,
CH2Cl2/hexane 4:1) to afford 13 g (83%) of 13.
Mp: 32-35 °C. 1H NMR (200 MHz, CDCl3): δ 0.88 (t, 3H), 1.7-
1.2 (m, 12H), 3.0 (t, 2H), 7.4 (d, 1H), 7.5 (dd, 1H), 7.6 (d, 1H) ppm.
13C NMR (50 MHz, CDCl3): δ 147.5, 132.8, 129.9, 129.7, 116.1, 115.5,
115.1, 110.5, 31.8, 31.7, 29.0, 28.9, 28.7, 28.1, 22.5, 14.0 ppm. EI-
MS: m/z 272 [M+, 100]. IR (KBr): ν 721, 2228 cm-1. Anal. Calcd
for C16H20N2S: C, 70.54; H, 7.40; N, 10.28; S, 11.77. Found: C, 70.21;
H, 7.35; N, 10.0: S, 11.97.
Figure 6. (A) Laser-energy dependence of the zero-time O2(1∆g) 1270-
nm phosphorescence intensity in air-saturated benzene sensitized by 2
(open symbols) and PN (closed symbols) as a function of the solution
absorbance. Inset: Typical transient luminescence signal for 2. (B)
Slopes of the energy plots as a function of the sample absorption. The
ratio of slopes yields the ratio of Φ∆s for sample and reference.
1,2-Dicyano-4-octylsulfonylbenzene (14). To a solution of 1,2-
dicyano-4-octylthiobenzene (13) (4 g, 14.7 mmol) in dry CH2Cl2 (17
mL) cooled at 0 °C was slowly added m-chloroperbenzoic acid (12.7
g, 73.5 mmol) in CH2Cl2 (300 mL). The mixture was warmed to room
temperature and vigorously stirred at this temperature overnight (12
h). A saturated sodium sulfite solution was then added, and the organic
phase was extracted with CH2Cl2 (3 × 50 mL) and dried over sodium
sulfate. The solvent was removed under reduced pressure, and the solid
was recrystallized from toluene/heptane (1:3) to give 3.3 g (74%) of
14 as a white solid.
Mp: 70-72 °C. 1H NMR (200 MHz, CDCl3): δ 0.9 (m, 3H), 1.1-
1.9 (m, 12H), 3.1 (m, 2H), 8.10 (d, 1H), 8.30 (d, 1H), 8.35 (dd, 1H)
ppm. 13C NMR (50 MHz, CDCl3): δ 144.3, 134.6, 133.0, 132.5, 120.3,
117.3, 114.1, 114.0, 56.0, 31.6, 28.9, 28.2, 22.5, 22.4, 13.9 ppm. EI-
MS: m/z 304 [M+]. IR (KBr): ν 1113, 1137, 2239 cm-1. Anal. Calcd
for C16H20N2O2S: C, 63.13; H, 6.62; N, 9.20; S, 10.53. Found: C,
63.16; H, 6.49; N, 9.29; S, 10.78.
Figure 7. Cyclic voltammogram of 3 (50 mM) in N2-saturated 0.1 M
TBAP CH2Cl2. Scan rate: 100 mV s-1
.
The first oxidative and reductive half-wave potential of the
SubPcs, E1/2(S+/S) and E1/2(S/S-), have been measured by cyclic
voltammetry in dichloromethane containing tetrabutylammo-
nium perchlorate (0.1 mol‚dm-3). A voltammogram for 3 is
shown in Figure 7. The oxidation and reduction potentials follow
the trend one would anticipate from the substitution pattern,
the nitro derivative 3 being the easiest to reduce by ca. 500
mV relative to 1, followed by the sulfonyl derivatives 11 and 7
(by 350 and 270 mV, respectively). The oxidation potentials
follow the same trend (see Table 2). While some degree of
irreversibility is apparent in the voltammograms, our results for
1 (1.04 and -1.05 V vs AgCl/Ag, respectively) are in excellent
agreement with those reported for a 1 analogue having a bromine
atom in the axial position instead of chlorine (1.03 and -1.06
V, respectively).8c The oxidation potential is close to that of
AlPcCl (0.96 V), while the reduction one is clearly more
negative (-1.05 for SubPc 1 vs -0.66 V for AlPcCl);26 i.e.,
SubPcs are, in general, more difficult to reduce. There are no
data available for analogues to SubPcs 2-11. For photoinduced
electron-transfer processes, the relevant potentials are those of
the excited states. Table 2 lists the oxidation and reduction
potentials for the longer-lived triplet state, calculated adding
(for reduction) or subtracting (for oxidation) the triplet energy
contents ET to the ground-state potentials.26 The electronically
excited subphthalocyanines are more easily oxidized than the
phthalocyanines (by ca. 500 mV). This is consistent with the
observation that SubPcs decompose under light in polar
solvents,8c while Pcs are notorious for their stability.
1,2-Dicyano-4,5-bis(octylthio)benzene (16). 4,5-Dichloro-1,2-di-
cyanobenzene18 (15) (2.4 g, 12.2 mmol), dry K2CO3 (5.0 g, 36.2 mmol),
and 30 mL of dimethylacetamide (DMAC) were placed in a 100-mL
round-bottom flask, equipped with a magnetic stirrer, rubber seal, and
globe. After a stream of argon had been passed through the slurry in
order to remove oxygen, 4.7 mL of 1-octanethiol (3.9 g, 26.8 mmol)
was added through a syringe, and the resulting mixture was stirred at
90 °C during 6 h. The reaction was poured into 100 mL of cold water,
and the separated precipitate was collected and crystallized from cold
ethanol (150 mL) to yield 4.0 g (79%) of 1,2-dicyano-4,5-bis(octylthio)-
benzene (16) as white needles.
1
Mp: 62 °C. H NMR (200 MHz, CDCl3): δ 0.89 (t, 6H), 1.1-1.6
(bm, 20H), 1.6-1.8 (m, 4H), 3.0 (m, 4H), 7.40 ppm (s, 2H). 13C NMR
(CDCl3, 50 MHz): δ 14.0, 22.5, 28.0, 28.8, 29.0, 31.7, 32.7, 111.0,
115.6, 128.1, 144.2 ppm. MS (EI): m/z 416 [M+, 100]. IR (KBr): ν
1114, 1226, 1348, 1460, 1562, 2229, 2852, 2923, 2957, 3077 cm-1
.
Anal. Calcd for C24H36N2S2: C, 69.18; H, 8.71; N, 6.72; S, 13.39.
Found: C, 69.12; H, 8.41; N, 6.53; S, 13.76.
1,2-Dicyano-4,5-bis(octylsulfonyl)benzene (17). 1,2-Dicyano-4,5-
bis(octylthio) benzene (16) (1.2 g, 2.91 mmol) was dissolved in 35
mL of acetic acid at 90 °C. To the stirred solution was added a total of
15 mL of 33% H2O2 in 1-mL portions in the course of 4 h. The resulting
turbid mixture was allowed to cool to room temperature and stirred
overnight, and the white precipitate was collected by filtration,
subsequently washed several times with water, and crystallized from
ethanol (50 mL) to give 1.17 g (84%) of pure 1,2-dicyano-4,5-bis-
(octylsulfonyl)benzene (17) as a white powder.
1
Mp: 75 °C. H NMR (200 MHz, CDCl3): δ 0.89 (t, 6H), 1.1-1.5
(bs, 20H), 1.6-1.9 (m, 4H), 3.7 (m, 4H), 8.69 ppm (s, 2H). 13C NMR
(CDCl3, 50 MHz): δ 14.0, 22.3, 22.5, 28.1, 31.6, 57.1, 113.1, 121.1,
137.4, 144.4 ppm. MS (EI): m/z 480 [M+, 100]. IR (KBr): ν 1123,
1155, 1315, 1343, 1470, 2238, 2854, 2920, 2949, 3105 cm-1. Anal.
Calcd for C24H36N2O4S2: C, 59.97; H, 7.55; N, 5.83; S, 13.34. Found:
C, 59.98; H, 7.23; N, 5.63; S, 13.75.
Experimental Section
The UV-visible and infrared measurements were carried out
respectively on Perkin-Elmer model Lambda 6 and Bruker IFS66V
instruments. MS spectra were determined on a VG AutoSpec instru-

Synthesis and Properties of Subphthalocyanines
J. Am. Chem. Soc., Vol. 120, No. 49, 1998 12815
1,2-Dicyano-4,5-p-tolylthiobenzene (19). A mixture of 4,5-di-
iodophthalonitrile (18)20 (195 mg, 1 mmol), p-thiocresol (744 mg, 6
mmol), and (2.36 g, 32 mmol) of potassium carbonate in dry DMSO
(2 mL) was heated at 90 °C for 30 min. The mixture was then cooled,
ice was added carefully, and a yellow solid precipitated out. It was
filtered, dried, and then purified by column chromatography (SiO2,
hexane/CH2Cl2, 3:10) to give 301 mg (81%) of 19.
solid was washed with cold methanol and filtered to yield 140 mg (13%)
of 7 as a violet powder.
1
Mp: >250 °C. H NMR (200 MHz, acetone-d6): δ 0.8 (m, 9H),
1.0-2.5 (m, 36H), 3.5 (m 6H), 8.5 (m, 3H), 9.2 (m, 3H), 9.4 (m, 3H)
ppm. FAB-MS (3-NOBA): m/z 958 [M+], 959 [M + H+]. UV/vis
(CHCl3): λmax (log ꢀ/dm3 mol-1 cm-1) 570 (4.5), 523 (sh), 307 nm
(4.6). IR (KBr): ν 970, 1140, 1302, 1734, 2855, 2925 cm-1. Anal. Calcd
for C48H60N6O6S3BCl: C, 60.10; H, 6.30; N, 8.76; S, 10.01. Found:
C, 60.34; H, 6.41; N, 9.01; S, 10.37.
Mp: 195-197 °C. 1H NMR (200 MHz, CDCl3): δ 2.4 (s, 3H), 6.9
(s, 1H), 7.3 and 7.4 (AA′BB′ system, 4H) ppm. 13C NMR (50 MHz,
CDCl3): δ 21.3, 111.1, 115.4, 124.5, 129.2, 131.3, 135.3, 141.2, 144.3
Chloro[2,3,9,10,16,17-hexaoctylthiosubphthalocyaninato]boron-
(III) (8). Four milliliters of dry 1-chloronaphthalene was saturated at
0 °C with a slow stream of gaseous BCl3. Three milliliters of this
solution was rapidly transferred to a flask cooled in an ice bath and
containing 1,2-dicyano-4,5-bis(octylthio)benzene (16) (450 mg, 1.08
mmol) under argon atmosphere. While stirring, the reaction mixture
was allowed to warm to room temperature and subsequently kept at
60 °C for 40 min. For a nonaqueous work up, the reaction mixture
was diluted with 30 mL of cold hexane and the black precipitate formed
finely divided in the mixed solvents by sonication. The suspension
obtained was freed from 1-chloronaphthalene by suction filtration
through a layer of silica gel (5 cm) and repeated addition of hexane
followed by elution of the subphthalocyanine with CH2Cl2. Removal
of CH2Cl2 and of remaining traces of 1-chloronaphthalene was
completed under high vacuum at 80 °C to give 120 mg (26%) of
hexaoctylthiosubphthalocyanine (8) as a dark green sticky oil.
1H NMR (200 MHz, CDCl3): δ 0.86 (t, 18H), 1.4 (bm, 48H), 1.6
(m, 12H), 1.9 (m, 12H), 3.1 (m, 12H), 8.57 (s, 6H) ppm. 13C NMR
(CDCl3, 50 MHz): δ 7.5, 23.1, 23.5, 28.7, 29.3, 32.4, 33.3, 33.7, 119.6,
128.3, 140.9, 149.1 ppm. FAB-MS (3-NOBA): m/z 1295 [M + H]+.
UV/vis (CHCl3): λmax (log ꢀ/dm3 mol-1 cm-1) 603 (4.9), 557 (4.4),
413 (4.5), 387 (4.5) 304 (4.8) nm. IR (KBr): ν 785, 978, 1081, 1419,
1435, 1461, 1596, 2852, 2924, 2954 cm-1. Anal. Calcd for C72H108N6S6-
BCl: C, 66.71; H, 8.40; N, 6.48; S, 14.84. Found: C, 66.48; H, 8.08;
N, 6.12; S, 14.80.
Chloro[2,3,9,10,16,17-hexa-p-tolylthiosubphthalocyaninato]boron-
(III) (9). Dried 1,2-dicyano-4,5-p-tolylthiobenzene (19, 400 mg, 1.07
mmol) was suspended in 1-chloronaphthalene (0.5 mL) under argon.
Then BCl3 (0.1 mL, 1.07 mmol, previously condensed at -78 °C) was
added through a cannula with the help of a slightly positive argon
pressure. The mixture was stirred for 10 min at room temperature and
then was heated at 120 °C for 20 min. After cooling, the black
precipitate was purified by column chromatography on Al2O3 in two
steps (hexane, hexane/CH2Cl2, 1:1) to give 116 mg (28%) of 9 as a
sticky violet compound.
1H NMR (200 MHz, CDCl3): δ 2.45 (s, 18H), 7.4 and 7.2 (AA′BB′
system, 12H), 8.37 (s, 6H) ppm. 13C NMR (50 MHz, CDCl3): δ 21.2,
122.9, 129.5, 130.7, 133.2, 139.3, 141.5, 149.1 ppm. FAB-MS
(3-NOBA): m/z 1162 [M+], 1163 [M + H+]. UV/vis (CHCl3): λmax
(log ꢀ/dm3 mol-1 cm-1) 607 (4.9), 550 (sh), 389 (4.3), 293 nm (4.6).
IR (KBr): ν 975, 788, 809, 1413, 2850, 2918 cm-1. Anal. Calcd for
C56H48N6S6BCl: C, 64.45; H, 4.64; N, 8.05; S, 18.43. Found: C, 64.82;
H, 4.81; N, 7.82; S, 17.92.
Chloro[2,3,9,10,16,17-hexaoctylsulfonylsubphthalocyaninato]boron-
(III) (10). Three milliliters of dry 1-chloronaphthalene was saturated
at 0 °C with a slow stream of gaseous BCl3. Three milliliters of this
solution was rapidly transferred to the flask containing 1,2-dicyano-
4,5-bis(octylsulfonyl)benzene (17) (203 mg, 0.42 mmol) under argon
atmosphere at 0 °C. The stirred reaction mixture was allowed to warm
to room temperature and subsequently kept at 70 °C for 2 h. For
workup, the reaction mixture was diluted with 30 mL of cold hexane
and the black precipitate formed finely divided in the mixed solvents
by sonication. This suspension was freed from 1-chloronaphthalene by
suction filtration through a layer of silica gel (5 cm) and repeated
addition of hexane followed by elution of the subphthalocyanine with
CH2Cl2. Removal of CH2Cl2 and of remaining traces of 1-chloronaph-
thalene was completed under high vacuum at 80 °C to give 23 mg
(11%) of hexaoctylsulfonylsubphthalocyanine (10) as a violet solid.
1H NMR (200 MHz, CDCl3): δ 0.83 (t, 18H), 1.1-1.9 (bm, 72H),
3.8 (bm, 12H), 9.87 ppm (s, 6H). 13C NMR (CDCl3, 50 MHz): δ 14.0,
22.5, 22.6, 28.2, 28.9, 31.6, 57.2, 128.9, 132.6, 141.7, 150.5 ppm. FAB-
MS (3-NOBA): m/z 1487 [M + H]+. UV/vis (CHCl3) λmax (log ꢀ/dm3
ppm. EI-MS: m/z 372 [M+, 100]. IR (KBr): ν 760, 2226, 2919 cm-1
.
Anal. Calcd for C22H16N2S2: C, 70.94; H, 4.33; N, 7.52; S, 17.21.
Found: C, 71.01; H, 4.44; N, 7.49; S, 17.46.
1,2-Dicyano-4,5-p-tolylsulfonylbenzene (20). To a solution of 1,2-
dicyano-4,5-p-tolylthiobenzene (19) (400 mg, 1.07 mmol) in dry CH2-
Cl2 (10 mL) cooled at 0 °C was slowly added m-chloroperbenzoic acid
(1.84 g, 10.7 mmol) in dry CH2Cl2 (120 mL). The mixture was then
warmed to room temperature and vigorously stirred for 2 days. Saturated
sodium sulfite solution was then added, the product was extracted with
CH2Cl2 (3 × 50 mL), and the organic phase was dried over sodium
sulfate. The solvent was removed to yield 461 mg (99%) of 20 as a
white solid.
1
Mp: 223-225 °C. H NMR (200 MHz, CDCl3): δ 2.45 (s, 3H),
7.3 and 7.9 (AA′BB′ system, 4H), 8.78 (s, 1H) ppm. 13C NMR (50
MHz, CDCl3): δ 21.7, 113.2, 120.5, 129.0, 129.9, 136.2, 137.1, 145.9,
146.2 ppm. FAB-MS (3-NOBA): m/z 437 [M + H+]. IR (KBr): ν
810, 921, 1082, 1159, 2250, 3090 cm-1
. Anal. Calcd for
C22H16N2S2O4: C, 60.54; H, 3.70; N, 6.42; S, 14.67. Found: C, 60.24;
H, 3.74; N, 6.19; S, 14.26.
Chloro[2,9,16(2,9,17)-tri-p-nitrophenylethynylsubphthalocyaninato]-
boron(III) (Regioisomers Mixture) (5). A mixture of triiodosubph-
thalocyanine (4) (808 mg, 1 mmol), p-nitroethynylbenzene (21)21c (529
mg, 3.6 mmol), bis[triphenylphosphine]palladium(II) dichloride (21 mg,
0.03 mmol), and copper(I) iodide (3 mg, 0.015 mmol) in 10 mL of
triethylamine was stirred for 1.5 h at room temperature under argon
atmosphere. For working up, water was added, the mixture was
extracted with CH2Cl2 (3 × 50 mL), and the extracts were dried over
Na2SO4. The solvent was removed, and the residue was purified by
flash column chromatography (SiO2) using CH2Cl2 as eluent, to yield
251 mg (29%) of tri-p-nitrophenylethynyl subphthalocyanine (5)
(regioisomer mixture) as a violet powder.
1
Mp: >200 °C. H NMR (200 MHz, CDCl3): δ 8.1 (m, 1H), 8.3
and 7.8 (AA′BB′ system, 4H), 8.9 (m, 1H), 9.1 ppm (m, 1H). FAB-
MS (3-NOBA): m/z 865 [M + H]+. UV/vis (CHCl3): λmax (log ꢀ/dm3
mol-1 cm-1) 590 (4.6), 540 (sh), 355 (4.5), 285 (4.6) nm. IR (KBr): ν
2210, 1592, 1331, 1185, 854 cm-1. Anal. Calcd for C48H21N9O6BCl:
C, 66.58; H, 2.45; N, 14.57. Found: C, 66.20; H, 2.64; N, 14.17.
Chloro[2,9,16(2,9,17)-trioctylthiosubphthalocyaninato]boron-
(III) (Regioisomers Mixture) (6). Dried 4-octylthiophthalonitrile (13)
(460 mg, 1.79 mmol) was suspended in 1-chloronaphthalene (0.5 mL)
under argon. Then BCl3 (0.15 mL, 1.79 mmol, previously condensed
at -78 °C) was added through a cannula with the help of a slightly
positive argon pressure. The mixture was stirred for 10 min at room
temperature and then heated at 80 °C for 15 min. After cooling, the
black precipitate was washed with hexane; the solid was filtered and
chromatographed (Al2O3, hexane/CH2Cl2, 1:1) to give 138 mg (27%)
of 6 as a sticky violet compound.
1H NMR (200 MHz, CDCl3): δ 0.8 (m, 9H), 1.7-1.2 (m, 36H),
3.1 (m, 6H), 7.7 (d, 3H), 8.6 (m, 6H) ppm. FAB-MS (3-NOBA): m/z
862 [M+], 863 [M + H+]. UV/vis (CHCl3): λmax (log ꢀ/dm3 mol-1
cm-1) 584 (4.7), 540 (sh), 361 (4.2), 289 nm (4.6). IR (KBr): ν 968,
1730, 2952, 3853 cm-1. Anal. Calcd for C48H60N6S3BCl: C, 66.76; H,
7.00; N, 9.73; S, 11.14. Found: C, 67.12; H, 7.40; N, 9.37; S, 10.69.
Chloro[2,9,16(2,9,17)-trioctylsufonylsubphthalocyaninato]boron-
(III) (Regioisomers Mixture) (7). BCl3 (0.28 mL, 3.28 mmol),
previously condensed at -78 °C, was added to a solution of 1,2-
dicyano-4-octylsulfonylbenzene (14) (1 g, 3.28 mmol) in 1-chloronaph-
thalene (1 mL). The mixture was stirred at room temperature for 10
min and then was heated at 150 °C for 15 min. After cooling, the blue
precipitate was washed with hexane and extracted with diethyl ether
using a Soxhlet extractor for 2 h. The solvent was removed, and the

12816 J. Am. Chem. Soc., Vol. 120, No. 49, 1998
del Rey et al.
mol-1 cm-1): 684 (3.5), 579 (4.8), 532 (sh), 296 (4.7) 241 (4.8) nm.
IR (KBr): ν 803, 979, 1103, 1314, 1466, 1615, 1784, 2855, 2926, 2954
cm-1. Anal. Calcd for C72H108N6S6O12BCl: C, 58.11; H, 7.31; N, 5.65;
S, 12.92. Found: C, 58.30; H, 7.14; N, 5.34; S, 12.73.
to a grating monochromator. Cyclic voltammograms were recorded
using a three-electrode potentiostat, CAEM Instrumentation PGA 1210.
Fluorescence quantum yields were determined by comparing the area
under the corrected spectra recorded for optically matched ((0.001
AU) solutions of the SubPcs in benzene and CVP in methanol (Φf )
0.54),39 exciting at 530 nm. Linearity in absorbance in the range 0.010-
0.030 was carefully checked. The intensities were corrected for
refraction index differences between methanol and benzene. No
difference could be observed between air- and argon-saturated samples.
Rate constants of fluorescence quenching by 1-iodopropane were
determined by measuring the fluorescence intensity for several quencher
concentrations. The absorbances of the SubPcs at the excitation
wavelength were always smaller than 0.020. Singlet-state lifetimes were
measured by the single-photon-counting technique in nitrogen-saturated
benzene. Monoexponential decay kinetics were observed throughout.
The triplet-minus-singlet absorption coefficients were determined
by transient absorption spectroscopy using the comparative method of
Bensasson et al.40 with benzophenone in benzene as reference (ΦT∆ꢀT-S
) 7220 M-1 cm-1 at 525 nm).41 The ΦT∆ꢀT-S values obtained were
combined with the ΦT values determined by LIOAC to render the
absorption coefficients. The methods used to determine ΦT by LIOAC
and Φ∆ by TRPD are variations of the comparative method of
Bensasson et al., described in detail elsewhere.34 For LIOAC, 2-hy-
droxybenzophenone was used for calibration purposes, while for TRPD,
phenalenone was the reference compound (Φ∆ ) 0.95).34,42,43
Chloro[2,3,9,10,16,17-hexa-p-tolylsulfonylsubphthalocyaninato]-
boron(III) (11). A solution of dry 1,2-dicyano-4,5-p-tolylsulfonylben-
zene (20, 500 mg, 1.14 mmol) in anhydrous 1-chloronaphthalene (0.5
mL) was magnetically stirred at room temperature under argon
atmosphere. Then 0.1 mL (1.14 mmol) of boron trichloride (previously
condensed at -78 °C) was added through a cannula. The mixture was
stirred at room temperature for 10 min. The reaction mixture was then
heated at 140 °C during 30 min. After the mixture was cooled at room
temperature, the solvent was removed by repeatedly washing with
n-hexane. The residue was placed in the thimble of a Soxhlet extractor
and extracted with chloroform. After the solvent was evaporated, the
residue was washed with cold diethyl ether to yield 128 mg (25%) of
subphthalocyanine 11 as a blue powder.
1
Mp: >250 °C. H NMR (200 MHz, CDCl3): δ 2.4 (s, 18H), 7.3
and 7.9 (AA′XX′ system, 24H), 8.9 (s, 6H) ppm. FAB-MS (3-
NOBA): m/z 1354 [M+], 1355 [M + H+]. UV/vis (CHCl3): λmax (log
ꢀ/dm3 mol-1 cm-1): 655 (3.8), 586 (4.6), 533 (sh), 313 nm (4.4). IR
(KBr): ν 809, 1093, 1157, 1594, 2851, 2921 cm-1. Anal. Calcd for
C56H48N6S6O12BCl: C, 48.19; H, 3.47; N, 6.02; S, 13.72. Found: C,
48.52; H, 3.21; N, 6.42; S, 14.01.
NLO Experimental Section. The permanent dipole moments in the
ground state were experimentally obtained from capacitance measure-
ments in chloroform solutions by a classical Guggenheim method.37
Cyclic voltammograms were recorded in the dark in a 10-mL cell.
Dichloromethane solutions containing 0.1 M TBAP were purged with
nitrogen for 20 min prior to the experiment. A cylindrical glassy carbon,
a platinum wire, and a Ag/AgCl electrode were used as the working
electrode, counter electrode, and reference electrode, respectively. The
EFISH experiments have been performed in chloroform solutions,
as a function of the concentration at two fundamental wavelengths,
1.907 and 1.34 µm. The shorter wavelength is directly emitted by a
Q-switched Nd:YAG laser, whereas the longer one is obtained by
Raman shifting the 1.064-µm emission of another Q-switched Nd:YAG
laser in a high-pressure hydrogen cell (60 bar). A liquid cell with thick
windows in the wedge configuration38 was used to obtain a Maker
fringes pattern. The incident beam was synchronized with a dc field
applied to the solution in order to break its centrosymmetry.
scan speed was set to 100 mV‚s-1
.
Summary and Conclusions
Novel boron(III) subphthalocyanines (SubPcs) soluble in
organic solvents containing a variety of donor and acceptor
substituent groups have been synthesized by boron trihalide-
induced cyclotrimerization of adequately substituted derivatives
of phthalonitrile in 1-chloronaphthalene. For this purpose, we
set out to synthesize phthalodinitriles equipped with iodo, nitro,
alkyl- or arylthio, alkyl- or arylsulfonyl groups that are
sufficiently stable under the required reaction conditions and
also provide an easily accessible set of acceptor/donor substit-
uents.
Their quadratic and cubic hyperpolarizabilities have been
measured by EFISH (at two wavelengths), HRS, and THG to
have a detailed assessment of their NLO response. âHRS has
been measured at 1.46 µm, where contamination from the
multiphoton-induced fluorescence can be ruled out. âHRS reaches
high values that markedly depend on substitution. It shows a
clear enhancement with the acceptor character of the substitu-
ents, the highest values being obtained for the strongest acceptor
groups (10 and 11). They are comparable or even superior to
many efficient second-order compounds. Much lower â values
are obtained for the donor-substituted molecules, although the
measurements are performed under more resonant conditions.
A main outcome of these results is that an adequate choice of
the substituents offers a promising route for optimization of the
HRS experiments were performed by measuring the intensity of the
second-order scattered light on focusing an intense laser beam on the
solution. The measurements were carried out at 1.46 µm to avoid the
absorption bands at the harmonic signal and a possible multiphoton-
induced fluorescence. In fact, the emitted light was spectrally analyzed
to rule out this spurious contribution.
The experimental setup for the THG experiment at 1.34 µm is the
same as the one used in EFISH experiments, but in this case without
an external electric field.
No indications of any molecular degradation during the realization
of the NLO experiments were observed.
Photophysical and Electrochemical Methods. Phenalenone (PN),
2-hydroxybenzophenone (2HBP), cresyl violet perchlorate (CVP), and
propyl iodide were purchased from Aldrich. Tetrabutylammonium
perchlorate (TBAP) was from Fluka. All were used as received.
Spectroscopic grade benzene, methanol, and dichloromethane were from
SDS. Dichloromethane was dried and columnated with basic alumina
prior to use.
Absorption spectra were measured with a Varian Cary 4E spectro-
photometer, periodically calibrated with a holmium oxide filter
(Hellma). Fluorescence spectra were registered with a Shimadzu RF540.
Fluorescence lifetimes were measured using an Edinburgh FL900 time-
correlated single-photon-counting spectrometer. The laser setups for
time-resolved O2(1∆g) near-IR phosphorescence detection (TPRD) and
laser-induced optoacoustic calorimetry (LIOAC) have been described
in detail elsewhere.34 The system is based on a 5-ns pulsed nitrogen
laser for excitation at 337 nm and uses a NorthCoast EO-817P
germanium detector for TRPD and a 1-MHz piezoelectric ceramic
transducer for LIOAC. The system has been expanded to accommodate
a UV-vis transient absorption detection line, based on a 75-W Xe
lamp and a red-sensitive Hammamatsu R928 photomultiplier coupled
(39) Magde, D.; Brannon, J. H.; Cremers, T. L.; Olmsted, J., III. J. Phys.
Chem. 1979, 83, 696-699.
(40) Bensasson, R. V.; Goldsmith, C. R.; Land, E. J.; Truscott, T. G.
Photochem. Photobiol. 1978, 28, 277-281.
(41) Carmichael, I.; Hug, G. L. J. Phys. Chem. Ref. Data 1986, 15,
1-250.
(42) Oliveros, E.; Murasecco, P. S.; Saghafi, T. A.; Braun, A. M.; Hansen,
H. J. HelV. Chim. Acta 1991, 74, 79-90.
(43) Schmidt, R.; Tanielian, C.; Dunsbach, R.; Wolff, C. J. Photochem.
Photobiol. A: Chem. 1994, 79, 11-17.
(37) Guggenheim, E. A. Trans. Faraday Soc. 1949, 45, 714-723.
(38) Kajzar, F.; Messier, J. ReV. Sci. Instrum. 1987, 58, 2081-2363.
(44) Ohno, T.; Kato, S.; Yamada, A.; Tanno, T. J. J. Phys. Chem. 1983,
87, 775-781.

Synthesis and Properties of Subphthalocyanines
J. Am. Chem. Soc., Vol. 120, No. 49, 1998 12817
quadratic response of the SubPcs and confirms the high potential
of these compounds for NLO applications. The cubic hyper-
polarizabilities γTHG show an opposite trend with substitution
to that of â, possibly due to frequency dispersion effects.
However, a quantitative analysis has not been possible due to
the strong resonance with the B band.
The photophysical and electrochemical properties of this
series of compounds have been determined and compared to
those of their expanded analogues, the phthalocyanines. The
compounds are strongly fluorescent, exhibit large intersystem-
crossing quantum yields, sensitize the production of singlet
oxygen with high efficiency, and are better photoreducing agents
than phthalocyanines. These properties, combined with a
remarkably lower tendency to aggregate owing to their cone-
shaped geometry, make them candidates worthy of further
studies for use in photosensitization and photoinduced electron-
transfer processes.
the EC through Grant ERBCHRX-CT94-0558. We are indebted
to Professors M. Mosquera and F. R. Prieto (University of
Santiago de Compostela, Spain) for the fluorescence lifetime
measurements and to Dr. R. W. Redmond (Wellman Labora-
tories of Photomedicine, Boston, MA) for technical advice with
the transient absorption experiments. U.K. gratefully acknowl-
edges financial support granted by the scientific committee of
the NATO through the DAAD. C.M. thanks the Spanish
Ministerio de Educacio´n y Cultura, and B.R. thanks the
Fundacio´n Caja de Madrid for predoctoral fellowships.
Supporting Information Available: 13C NMR assignment
for 8, 9, 10, 13, 14, 19, and 20; absorption and fluorescence
spectra of SubPcs 2, 3, 4, 6, 7, 9, and 11; Stern-Volmer plots
for 1, 2, 4, 6, 7, 9, and 11; determination of ΦTET by LIOAS;
cyclic voltammograms of 1, 2, 4, 6, 7, 9, and 11; triplet-minus-
singlet absorption spectra of 1, 3, 4, 6, 7, 9, and 11; and
determination of FD by TRPD for 1, 3, 4, 6, 7, 9, and 11 (40
pages, print/PDF). See any current masthead page for ordering
information and Web access instructions.
Acknowledgment. This work was supported by CICYT
(Spain), the Generalitat de Catalunya, and the Comunidad
Auto´noma de Madrid through Grants MAT96/0654, TIC 96-
0668 QFN94-4613-C02-1, and 06T/017/96 respectively, and by
JA980508Q