Pseudohalides of boron subphthalocyanine

Article abstract of DOI:10.1021/jo202365x

The synthesis and study of a series of pseudohalides of boron subphthalocyanine (BsubPc) are reported. Each pseudohalide has been compared to the more common chloride and bromide of BsubPc, and we have found that most react slower under standard phenoxyla

Full text of DOI:10.1021/jo202365x

Note
pubs.acs.org/joc
Pseudohalides of Boron Subphthalocyanine
Andrew S. Paton,† Graham E. Morse,† David Castelino,† and Timothy P. Bender*,†,‡
†Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College Street, Toronto,
Ontario, M5S 3E5, Canada
‡Department of Chemistry, University of Toronto, 80 St. George Street, Toronto, Ontario, M5S 3H6, Canada
S
* Supporting Information
ABSTRACT: The synthesis and study of a series of pseudohalides
of boron subphthalocyanine (BsubPc) are reported. Each
pseudohalide has been compared to the more common chloride
and bromide of BsubPc, and we have found that most react slower
under standard phenoxylation and hydrolysis conditions. Three
pseudohalides (TsO-BsubPc, MsO-BsubPc, and BsO-BsubPc) do
not hydrolyze at all even after prolonged periods of time in the
presence of water. Single crystals of TsO-, MsO-, and ClsO-BsubPc
were obtained, and their structures were unambiguously deter-
mined.
oron subphthalocyanine (BsubPc, Scheme 1) is a unique,
ring-reduced member of the common phthalocyanine
used as leaving groups in basic chemistry, modern uses for
pseudohalides (such as mesylates and tosylates) include their
use as leaving groups in Heck and Suzuki cross-coupling
reactions.12 Concurrent with our study, Guilleme et al.
published a method for the generation of triflate-BsubPc
(TfO-BsubPc). This intermediate was generated in situ using
silver triflate or trimethylsilyl triflate to effect the abstraction of
chloride from Cl-BsubPc and form TfO-BsubPc.13 They further
showed that TfO-BsubPc could react at a high rate with oxygen,
nitrogen, and carbon-based nucleophiles in order to produce
new BsubPc derivatives. TfO-BsubPc could not be isolated
because of its high reactivity with water.
In this note, we report the synthesis and isolation of a series
of five sulfonic-acid-based pseudohalides of BsubPc. Their
structures were unambiguously confirmed using either
spectroscopic or crystallographic methods or both. We
compare the rates of reaction of the pseudohalides under
phenoxylation and hydrolysis conditions and compare them to
Cl-BsubPc and Br-BsubPc. We draw a conclusion on their
suitability to replace Cl-BsubPc and Br-BsubPc as standard
precursor compounds. We also compared the electrochemical
and optical properties of the pseudohalides using cyclic
voltammetry, absorption spectroscopy, and fluorescence spec-
troscopy against Cl-BsubPc, should someone consider them as
replacements for Cl-BsubPc in organic electronic devices.
Typically, the synthesis of sulfonic-acid-based pseudohalides
involves the reaction of the corresponding sulfonic acid
chloride (RS(O)2Cl) or anhydride (RS(O)2O
S(O)2R) with a hydroxy group. While this approach was
the most obvious first method to obtain a pseudohalide BsubPc
B
family of compounds. Its aromatic, three-membered hetero-
cyclic ring is nonplanar and bowl-shaped. BsubPcs typically
have a maximum absorption in the visible region of the
electromagnetic spectrum around 565 nm. There has been
recent interest in incorporating BsubPc derivatives into organic
electronic devices, particularly into organic light-emitting
diodes1 and organic photovoltaics.2 Common BsubPc deriva-
tives in use contain an axial halogen (commonly chloride) or
those in which the halogen has been displaced by a nucleophile
(most commonly oxygen-based such as phenol). The latter are
of particular interest, as we have previously shown that
variations in the axial phenoxy fragment can provide new
solid-state arrangements.3−5 The most commonly used
precursor to phenoxylated BsubPcs is Cl-BsubPc.6,7 We have
noticed that the conversion from Cl-BsubPc to phenoxylated
derivatives can be exceedingly slow;3 others have shown that
alkynyl derivatives produced through reaction of a Grignard
reagent with Cl-BsubPc react with some speed.2e,8 While the
synthesis of Br-BsubPc is known,9,10 it is difficult to produce
with high purity, and we have noticed that it is hydrolytically
sensitive, which may contribute to the limited literature
surrounding its use as a precursor compound.11
In order to expand the number of BsubPc precursors, we
have been interested in the synthesis and study of the
pseudohalides of BsubPc. The aim for our study was to
determine if there was a pseudohalide of BsubPc that could be
easily isolated and was more reactive than Cl-BsubPc but less
reactive (and thus more hydrolytically stable) than Br-BsubPc.
The result would be a precursor that could be produced in
significant quantities and used over time without concerns of
hydrolysis on storage. While pseudohalides have long been
Received: December 6, 2011
Published: February 8, 2012
© 2012 American Chemical Society
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Note
a
Scheme 1. Synthesis of Pseudohalides of BsubPc (3a−e) via Two Different Pathways
a
Conditions: (i) water, pyridine, reflux. (ii) RS(O)2OS(O)2R, pyridine, toluene, reflux. (iii) (py+)(RS(O)2O−), toluene, reflux and
subsequent phenoxylation to phenoxy-BsubPc 4. ((iii) path 2: phenol, chlorobenzene, 100 °C.) and hydrolysis back to HO-BsubPc 2. (iv) DMSO,
pyridine, water, 60 °C.
(path i in Scheme 1), it was unclear whether the hydroxyl group
of HO-BsubPc would react as a “normal” hydroxyl group. After
synthesizing hydroxy-BsubPc (HO-BsubPc) using the method
of Potz,10 it was mixed with p-toluene sulfonic acid chloride
(TsCl) in toluene with pyridine and heated to reflux.
Surprisingly, we observed complete transformation of HO-
BsubPc to Cl-BsubPc (confirmed by HPLC retention time to a
genuine standard). We hypothesized that the liberated chloride
anion reacted with TsO-BsubPc produced in situ to form Cl-
BsubPc. The same result was obtained if the reaction was
conducted in chlorobenzene. Next, we tried to use the sulfonic
acid anhydride in place of the chloride. Following the same
procedure, conversion to TsO-BsubPc (3a, Scheme 1) was
observed without the formation of Cl-BsubPc (Scheme 1, path
i). The product was purified by simple removal of the reaction
solvent under vacuum followed by rinsing with methanol until
pure. This route was also successful in producing MsO-BsubPc
(3b, Scheme 1). In these two cases, the purity and composition
of the final compounds was confirmed using chromatography,
spectroscopy (including HRMS), and crystallography (Figures
S23−S25, Supporting Information). Single crystals were grown
through vapor diffusion of heptane into a benzene solution of
TsO-BsubPc and of pentane into a dichloromethane solution of
MsO-BsubPc. In the case of MsO-BsubPc, two different crystal
types were obtained: rhomboids and needles (Figure S27,
Supporting Information). Although both are solvates, the
rhomboid structure contains two MsO-BsubPc molecules and
one dichloromethane molecule in the asymmetric unit (Figure
S24), whereas the needle solvate incorporated disordered
solvent into its structure (which has been removed from the
atomic displacement plot shown in Figure S25, Supporting
Information). A more detailed discussion of the solid state
arrangement of these derivatives is given in the Supporting
Information accompanying this article.
Given our observation that chloride could displace/exchange
with tosylate in the presence of pyridine, we began to consider
whether halides and pseudohalides could be interchanged by
treatment of a common precursor (Br-BsubPc) with a
pyridinium salt of the respective pseudohalide ((py+)(R
S(O)2O−)). Indeed, we found this to be the case (Scheme
1, path ii). Briefly, Br-BsubPc was dissolved in toluene, and 2.2
equiv of the pyridinium salt of the pseudohalide was added.
Under stirring and a positive pressure of argon, the solution was
heated to reflux until complete conversion was observed by
HPLC analysis (<8 h). The solvent was then removed under
vacuum, and the solid was rinsed with methanol until pure.
This method proved successful to use the pyridinium salts of p-
toluene, methane, benzene, p-chlorobenzene, and m-nitro-
benzene sulfonic acid to produce TsO-BsubPc, MsO-BsubPc,
BsO-BsubPc, ClsO-BsubPc, and NsO-BsubPc, respectively
(compounds 3a−e, Scheme 1). Where the pyridinium salt
was not commercially available, we made it beforehand by
neutralization of the corresponding acid with pyridine. In each
case, the composition and purity of the final compounds was
confirmed using a combination of spectroscopy, and in the case
of ClsO-BsubPc, crystallography. Synthetic path ii negates the
need to hydrolyze Br-BsubPc to HO-BsubPc and to produce
the sulfonic acid anhydride while providing yields upward of
90% in all cases. We also attempted the synthesis of TfO-
BsubPc using this method, starting with pyridinium triflate and
Br-BsubPc. Similar to the observations of Guilleme et al.,13 we
were unable to isolate the TfO-BsubPc product, presumably
because of its high sensitivity to water; we saw rapid conversion
into a mixture of HO-BsubPc and μ-oxo(BsubPc)2 (the μ-oxo
dimer is easily identified based on its unique UV−vis
specrtum14) by HPLC analysis (in each case confirmed against
a genuine sample).
Next, we performed a series of experiments to compare the
conversion over time of each pseudohalide to phenoxy-BsubPc
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and to HO-BsubPc. The phenoxylation reaction was performed
under conditions that we have previously established (5 equiv
phenol, chlorobenzene), albeit at slightly reduced temperature
(100 °C) to facilitate long reaction times without loss of
solvent.3 For hydrolysis, each pseudohalide BsubPc was heated
at 60 °C in a mixture of pyridine, water, and DMSO. The
conversion to product was monitored by HPLC (retention
times compared against know standards), and the conversion
percentage was calculated as a function of time (as the
integrated area of the product peak divided by the sum of the
area of the starting material and product peaks in a 2d
chromatogram extracted from a PDA 3d chromatogram at 560
nm).
frequent sampling. It is perhaps then not surprising to see some
variability, given the accepted mechanism for these substitution
reactions is SN1 in nature11a and thus highly dependent on
concentration of the pseudohalide/halide of BsubPc. It should
also be noted that we make no attempt to sequester the halo
acid or sulfonic acid produced as a byproduct of these
reactions,15 The other pseudohalide derivatives ClsO-BsubPc
(3d), BsO-BsubPc (3c), MsO-BsubPc (3b), and TsO-BsubPc
(3a) achieved 50, 32, 25, and 17% conversion to phenoxy-
BsubPc after 24 h, respectively. In each case, complete
conversion could not be achieved in a reasonable amount of
time. By best fitting a line through the initial data points of
Figure 1a (for a magnified view, see Figure S28, Supporting
Information) and examining the slope, we can quantify the
relative reactivities for the series Br-BsubPc, NsO-BsubPc,
ClsO-BsubPc, Cl-BsubPc, BsO-BsubPc, MsO-BsubPc, and
TsO-BsubPc as follows: ∼200, 19, 4, 4, 1.2, 0.7, and 0.5% h−1,
respectively. We did not see any evidence of the formation of
normal phthalocyanines by ring expansion under the conditions
studied.
Figure 1a shows the conversion of the pseudohalides (3a−e)
and halides (Cl-BsubPc and Br-BsubPc) to phenoxy-BsubPc (4,
In comparing the hydrolysis rates of the pseudohalide
BsubPcs, the compounds that were more reactive during
phenoxylation were also more susceptible to hydrolysis. As
shown in Figure 1b, Br-BsubPc converted to HO-BsubPc after
a period of only 2 h, while Cl-BsubPc took >40 h. NsO-BsubPc
showed the highest hydrolysis rate of the pseudohalides,
becoming fully hydrolyzed after only 7 h. The next most
reactive pseudohalide (ClsO-BsubPc) showed faster hydrolysis
than Cl-BsubPc (100% converted to HO-BsubPc after 24 h),
even though under phenoxylation conditions it had a nearly
identical rate to Cl-BsubPc. The other three pseudohalides,
BsO-BsubPc, MsO-BsubPc, and TsO-BsubPc showed no
hydrolysis under the conditions tested. By examining the initial
slope of the data in Figure 1b, we can also quantify the relative
hydrolysis rate for the series Br-BsubPc, NsO-BsubPc, ClsO-
BsubPc, Cl-BsubPc, BsO-BsubPc, MsO-BsubPc, and TsO-
BsubPc as follows: ∼50, 18, 5.6, 1.7, 0, 0, and 0% h−1,
respectively.
We can then examine whether we have achieved our goal of
having a precursor BsubPc, which is more reactive than Cl-
BsubPc while possessing better hydrolytic stability than Br-
BsubPc. NsO-BsubPc fits the criteria with a rate of
phenoxylation that is 4−5 times that of Cl-BsubPc while
simultaneously having a hydrolysis rate that is approximately
half that of Br-BsubPc. However, and perhaps more interesting,
we have obtained several pseudohalides that do not hydrolyze
even on prolonged contact with water. Given that Cl-BsubPc
has been applied in organic electronic derivatives, it would be of
interest to compare the basic photophysical and electronic
properties of the hydrolytically stable pseudohalides (and for
that matter, all the pseudohalides) to that of Cl-BsubPc, as the
application of a hydrolytically stable alternative to Cl-BsubPc in
an organic electronic device may be desirable.1,2
Cyclic voltammetry was first used to examine the electro-
chemical properties of the pseudohalides (dichloromethane
solution; tetrabutylammonium perchlorate electrolyte; deca-
methylferrocene as an internal reference16). In general, the
pseudohalide BsubPcs possessed irreversible oxidation and
reduction events, and thus, we are only able to comment on
their respective peak potentials which ranged from a low of
1.237 V for ClsO-BsubPc to a high of 1.316 V for MsO-BsubPc
(Table S22, Supporting Information). The reduction peak
potentials ranged from a low of −0.975 V for ClsO-BsubPc to a
Figure 1. Reactions of Br-BsubPc, Cl-BsubPc, and the pseudohalides
(3a−e) under (a) phenoxylation at 100 °C to give phenoxy-BsubPc
(4) and (b) hydrolysis at 60 °C to give HO-BsubPc (2).
Scheme 1). The rate of reaction of Cl-BsubPc and Br-BsubPc
(1) was as expected, with Br-BsubPc being the more reactive
and achieving 100% conversion in about 1 h, whereas Cl-
BsubPc reached 56% conversion in 24 h. In general,
pseudohalides 3a−e were slower to react than both of the
halides with two exceptions. ClsO-BsubPc (3d) reacted at
approximately the same rate as Cl-BsubPc and NsO-BsubPc
(3e), which reacted faster, reaching ∼77% conversion after 24
h. Complete conversion of Cl-BsubPc took well in excess of
150 h, whereas it took approximately 140 h to achieve complete
conversion of NsO-BsubPc (Figure S28, Supporting Informa-
tion). We have noted some variability in the rate of conversion,
and we have represented this as error bars on the conversion
percentage. While we take precautions to minimize the loss of
solvent over such prolonged reaction times, we cannot
absolutely ensure a constant solvent volume, especially with
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Note
this salt is hygroscopic, although in our study it was used before water
absorption. Yield 7.2 g (95%): mp = 127−132 °C, lit. 125−130 °C.20
Pyridinium 4-Chlorobenzenesulfonate. Compound has been
previously reported, but the report does not contain detailed
characterization.21 Similar to pyridinium benzenesulfonate, except 4-
chlorobenzene sulfonic acid (5.05 g, 0.026 mol) was used. The result
was a white powder, pyridinium 4-chlorobenzenesulfonate. Indications
are that this salt is hygroscopic, although in our study it was used
high of −1.051 V for MsO-BsubPc. For comparison, Cl-BsubPc
shows a reduction peak potential in a similar range of −1.050 V,
while the oxidation peak potential is much lower at 0.981 V,
and each oxidation and reduction events are also irreversible
(Table S22, Supporting Information).
The fluorescence quantum efficiencies (ϕPL) of the
pseudohalide BsubPcs were measured using a standard
procedure.1b,17 The ϕPL of Cl-BsubPc and Br-BsubPc were
also measured for comparison (Table S22, Supporting
Information). It was found that the ϕPL of all of the
pseudohalides were all approximately 0.4: the highest was
0.42 (TsO-BsubPc), and the lowest was 0.36 (NsO-BsubPc).
We also found that the ϕPL of Br-BsubPc was low at 0.18 and
that the ϕPL of Cl-BsubPc was rather high at 0.77. Thus, the
pseudohalides had neither an unusually low nor an unusually
high ϕPL.
In summary, a series of sulfonic-acid-based pseudohalide
BsubPcs were synthesized and characterized. A comparison has
been made between their rates of reaction (phenoxylation and
hydrolysis) relative to the reference compounds Cl-BsubPc and
Br-BsubPc. On the basis of their relative conversions, we have
identified one pseudohalide, NsO-BsubPc, to be both more
reactive than Cl-BsubPc and more hydrolytically stable than Br-
BsubPc; however, its rate of reaction falls off considerably at
high conversion, thus potentially limiting its usefulness. Three
of the other pseudohalides TsO-BsubPc, MsO-BsubPc, and
BsO-BsubPc were shown to have very good hydrolytic stability
(we did not observe hydrolysis under the conditions studied).
Their resistance to hydrolysis while maintaining a electro-
chemical and photophysical properties typical of BsubPcs
suggests that the hydrolytically stable pseudohalides might be
suitable for application and study in organic electronic devices.
We have also highlighted in the Supporting Information
accompanying this article the solid state arrangements of TsO-
BsubPc and ClsO-BsubPc, which showed enhanced π-stacking
compared to Cl-BsubPc, an attractive feature for an organic
electronic material.
1
before water absorption. Yield 6.31 g (89%): mp = 137−139 °C; H
NMR (400 MHz, CDCl3, Me4Si) δ 7.32−7.35 (2H, m), 7.84−7.87
(2H, m), 8.00 (2H, t, J = 7.2 Hz), 8.46 (1H, tt, J = 7.9, 1.5 Hz), 9.02
(2H, dd, J = 6.5, 1.5 Hz); 13C NMR (400 MHz, DMSO) δ 127.2,
127.5, 127.7, 133.0, 142.2, 146.4, 147.1.
4-Toluenesulfonate-boronsubphthalocyanine (TsO-BsubPc,
3a). Path 1. HO-BsubPc (0.071 g, 0.00017 mol) and 4-tolu-
enesulfonic anhydride (0.300 g, 0.00092 mol) were dissolved in
toluene (5 mL) and pyridine (3 mL). The mixture was stirred
under argon and heated at reflux for 60 min. Reaction was
determined complete via HPLC by the absence of HO-BsubPc.
The solvent was removed using rotary evaporation, and the solid
was rinsed with methanol until pure to give a pink powder, TsO-
1
BsubPc. Yield 0.051 g (51%): H NMR (400 MHz; CDCl3;
Me4Si) δ 2.23 (3H, s), 6.83−6.89 (4H, m), 7.93−7.95 (6H, m),
8.84−8.86 (6H, m); 13C NMR (400 MHz, CDCl3, Me4Si) δ 21.5,
96.9, 122.5, 126.2, 129.1, 130.2, 131.1, 143.1, 150.9; 11B NMR
(400 MHz; CDCl3; BF3·OEt2) δ −15.19 (s); λabs,max(toluene) 566
nm; λPL,max(toluene) 573 nm; HRMS (EI) Calcd. for
[C31H19BN6O3S] ([M]+) m/z 566.1332, found 566.1332.
Path 2. Br-BsubPc (1.002 g, 0.00211 mol) and pyridinium p-
toluenesulfonate (1.063 g, 0.00425 mol) were dissolved in toluene (50
mL) and heated under argon while stirring. The reaction was
maintained at reflux until it was determined complete via HPLC
(about 6 h). The solvent was removed using rotary evaporation, and
the solid was rinsed with methanol until pure and dried in air to give a
pink powder with a golden sheen, TsO-BsubPc. Yield 0.905 g (76%).
Characterization equivalent to product obtained above using path 1.
Methylsulfonate-boronsubphthalocyanine (MsO-BsubPc,
3b). Path 1. HO-BsubPc (0.071 g, 0.00017 mol) and methyl-
sulfonic anhydride (0.300 g, 0.00092 mol) were dissolved in
toluene (5 mL) and pyridine (3 mL). The mixture was stirred
under argon and heated at reflux for 60 min. Reaction was
determined complete via HPLC by the absence of HO-BsubPc.
The solvent was removed using rotary evaporation, and the
solid was rinsed with methanol until pure to give a pink
EXPERIMENTAL SECTION
■
1
powder, MsO-BsubPc. Yield 0.051 g (51%): H NMR (400
Materials and Methods. Toluene, methanol, chlorobenzene, 1,2-
dichlorobenzene, pyridine, HPLC-grade acetonitrile, triflic acid, 4-
toluenesulfonic anhydride, 4-toluenesulfonyl chloride, pyridinium 4-
toluenesulfonate, methylsulfonic anhydride, methylsulfonyl chloride,
methylsulfonic acid, 4-chlorobenzenesulfonic acid, benzenesulfonic
acid, and pyridinium 3-nitrobenzenesulfonate were purchased from
normal suppliers and used as received. For general methods of
phenoxylation and hydrolysis, please see the Supporting Information
(ESI) accompanying this article. Cl-BsubPc,3,7 Br-BsubPc,10 and HO-
BsubPc10 were synthesized according to the reported procedures.
Pyridinium trifluoromethylsulfonate was synthesized according to the
reported procedure.18 The remaining pyridinium salts were prepared
as follows.
MHz; CDCl3; Me4Si) δ 1.91 (3H, s), 7.95−7.97 (6H, m), 8.90−
8.92 (6H, m); 13C NMR (400 MHz, CDCl3, Me4Si) δ 38.8,
122.7, 130.4, 131.2, 151.3; 11B NMR (400 MHz; CDCl3; BF3·
OEt2) δ −15.00 (s); λabs,max(toluene) 566 nm; λPL,max(toluene) 572
nm; HRMS (EI) Calcd. for [C25H15BN6O3S] ([M]+) m/z
490.1031, found 490.1019.
Path 2. Br-BsubPc (1.115 g, 0.00235 mol) and pyridinium
methylsulfonate (1.205 g, 0.00688 mol) were dissolved in toluene
(50 mL) and heated under argon while stirring. The reaction was
maintained at reflux until it was determined complete via HPLC
(about 6 h). The solvent was removed under rotary evaporation, and
the solid was rinsed with methanol until pure and dried in air to give a
pink powder with a golden sheen, MsO-BsubPc. Yield 0.750 g (65%).
Characterization equivalent to product obtained above using path 1.
Benzenesulfonate-boronsubphthalocyanine (BsO-BsubPc,
3c). Br-BsubPc (0.195 g, 0.00041 mol) and pyridinium methylsulfo-
nate (0.244 g, 0.00103 mol) were dissolved in toluene (15 mL) and
heated under argon while stirring. The reaction was maintained at
reflux until it was determined complete via HPLC (about 6 h). The
solvent was removed using rotary evaporation, and the solid was rinsed
with methanol until pure and dried in air to give a pink powder with a
golden sheen, BsO-BsubPc. Yield 0.126 g (56%): 1H NMR (400
MHz; CDCl3; Me4Si) δ 6.96 (2H, d, J = 8.4 Hz), 7.09 (2H, t, J = 7.9
Hz), 7.28 (1H, t, J = 7.4 Hz), 7.93−7.95 (6H, m), 8.84−8.86 (6H, m);
13C NMR (400 MHz, CDCl3, Me4Si) δ 122.5, 126.1, 128.5, 130.4,
Pyridinium Methylsulfonate. A modification of a reported
procedure:19 Pyridine (2.95 g, 0.037 mol) was dissolved in toluene and
slowly neutralized with methylsulfonic acid (3.58 g, 0.037 mol). The
precipitate was filtered, and the resulting solid was dried under
vacuum, leaving a white solid product, pyridinium methylsulfonate.
Yield 6.20 g (95%): mp = 185−189 °C, lit. 185 °C.19
Pyridinium Benzenesulfonate. Benzenesulfonic acid (5.06 g,
0.032 mol) was dissolved in toluene and stirred until well mixed. Then
pyridine was slowly added in high excess. After neutralization had
occurred, the toluene and excess pyridine were removed through
rotary evaporation, leaving the respective pyridinium salt as an off-
white/tan powder, pyridinium benzenesulfonate. Indications are that
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Note
131.1, 132.3, 151.0 (only 7 13C resonances observed due to low
solubility); 11B NMR (400 MHz; CDCl3; BF3·OEt2) δ −15.13 (s);
λabs,max(toluene) 566 nm; λPL,max(toluene) 573 nm; HRMS (EI) Calcd.
for [C30H17BN6O3S] ([M]+) m/z 552.1176, found 552.1177.
AUTHOR INFORMATION
Corresponding Author
*E-mail: tim.bender@utoronto.ca.
■
4-Chlorobenzenesulfonate-boronsubphthalocyanine (ClsO-
BsubPc, 3d). Br-BsubPc (0.209 g, 0.00044 mol) and pyridinium
methylsulfonate (0.263 g, 0.00097 mol) were dissolved in toluene (15
mL) and heated under argon while stirring. The reaction was
maintained at reflux until it was determined complete via HPLC
(about 6 h). The solvent was removed using rotary evaporation, and
the solid was rinsed with methanol until pure and dried in air to give a
pink powder with a golden sheen, ClsO-sBsubPc. Yield 0.160 g
Notes
The authors declare no competing financial interest.
REFERENCES
■
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1
(62%): H NMR (400 MHz; CDCl3; Me4Si) δ 6.89 (2H, d, J = 8.8
Hz), 7.06 (2H, d, J = 8.8 Hz), 7.94−7.96 (6H, m), 8.85−8.88 (6H,
m); 13C NMR (400 MHz, CDCl3, Me4Si) δ 122.6, 127.6, 128.8, 130.5,
131.1, 136.8, 150.9; 11B NMR (400 MHz; CDCl3; BF3·OEt2) δ −15.47
(s); λabs,max(toluene) 567 nm; λPL,max(toluene) 574 nm; HRMS (EI)
Calcd. for [C30H16BN6O3SCl] ([M]+) m/z 586.0786, found 586.0804.
3-Nitrobenzenesulfonate-boronsubphthalocyanine (NsO-
BsubPc, 3e). Br-BsubPc (0.106 g, 0.00022 mol) and pyridinium
methylsulfonate (0.160 g, 0.00057 mol) were dissolved in toluene (15
mL) and heated under argon while stirring. The reaction was
maintained at reflux until it was determined complete via HPLC
(about 6 h). The solvent was removed using rotary evaporation, and
the solid was rinsed with methanol until pure and dried in air to give a
pink powder with a golden sheen, NsO-BsubPc. Yield 0.088 g (66%):
1H NMR (400 MHz; CDCl3; Me4Si) δ 7.28 (1H, dt, J = 8.0, 1.4 Hz),
7.38 (1H, t, J = 8.0 Hz), 7.82 (1H, s), 7.95−7.97 (6H, m), 8.15−8.18
(1H, m), 8.85−8.87 (6H, m); 13C NMR (400 MHz, CDCl3, Me4Si) δ
122.7, 130.7, 150.9 (only 3 13C resonances detectable due to low
solubility); 11B NMR (400 MHz; CDCl3; BF3·OEt2) δ −15.04 (s);
λabs,max(toluene) 568 nm; λPL,max(toluene) 575 nm; HRMS (EI) Calcd.
for [C30H16BN7O5S] ([M]+) m/z 597.1027, found 597.1046.
Phenoxylation of Various Boron Subphthalocyanines.
BsubPc precursor (0.075 g) was dissolved in chlorobenzene (10
mL), and the respective phenol (5 equiv) was then added. The
reaction mixture was continuously stirred and heated to 100 °C under
argon gas. The temperature was maintained for a period of 120 h,
during which samples were extracted from the homogeneous reaction
mixture at periodic time intervals. These samples were analyzed by
HPLC in order to determine conversion percentage. The percent
conversion from reactant (BsubPc) to product (phenoxy-BsubPc)
versus time was determined from the HPLC data as the percentage of
the integrated product peak of the total area of the integrated product
and reactant peaks extracted at 560 nm.
(2) (a) Gommans, H.; Cheyns, D.; Aernouts, T.; Birotto, C.;
Poortmans, J.; Heremans, P. Adv. Funct. Mater. 2007, 17, 2653.
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P; Medina, A.; Claessens, C. G.; Torres, T. Adv. Funct. Mater. 2009, 19,
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Mark, G.; Schuchmann, H. P.; von Sonntag, C.; MacDonald, J. G.;
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A.; Homburg, H. Z. Anorg. Allg. Chem. 2000, 626, 588.
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Hydrolysis of Various Boron Subphthalocyanines. BsubPc
precursor (0.1 g) was dissolved in DMSO (12.0 mL) and pyridine (0.4
mL) and stirred in a closed container for a few minutes. Distilled water
(0.8 mL) was then added, and the reaction mixture was heated to a
temperature of 60 °C under normal atmosphere while stirring. The
temperature was maintained for a period of 28 h, during which
samples were taken and analyzed by HPLC as described above. The
percent conversion from reactant (BsubPc) to hydrolysis product
(HO-BsubPc) versus time was determined from the HPLC data
similar to above.
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ASSOCIATED CONTENT
■
S
* Supporting Information
(15) The presence of base (to sequester the produced HX) shows
little effect on conversion and in many cases is known to degrade the
General procedures for phenoxylation and hydrolysis; 1H NMR
spectra of all newly synthesized pyridinium salts and
compounds 3a−3e; cyclic voltammograms of compounds
3a−3e; absorption and fluorescence spectra of compounds
3a−3e; X-ray crystallographic data, thermal ellipsoid plots, and
CIF files for all crystal structures; a discussion of crystal
packing; and longer time-scale phenoxylation data. This
material is available free of charge via the Internet at http://
pubs.acs.org.
BsubPc; see: (a) Gonzal
́
ez-Rodríguez, D.; Torres, T. Eur. J. Org. Chem.
2009, 1871−1879. (b) Weitemeyer, A.; Kliesch, H.; Wohrle, D. J. Org.
̈
Chem. 1995, 60, 4900−4904.
(16) Noviandri, I.; Brown, K. N.; Fleming, D. S.; Gulyas, P. T.; Lay,
P. A.; Masters, A. F.; Phillips, L. J. Phys. Chem. B 1999, 103, 6713−
6722.
́
(17) Gonzalez-Rodríguez, D.; Torres, T.; Guldi, D. M.; Rivera, J.;
Herranz, M. A. A.; Echegoyen, L. J. Am. Chem. Soc. 2004, 126, 6301−
6313.
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The Journal of Organic Chemistry
Note
(18) Marwitz, A. J. V.; Jenkins, J. T.; Zakharov, L. N.; Liu, S.-Y.
Angew. Chem., Int. Ed. 2010, 49, 7444−7447.
(19) Looker, J. H.; Krieger, A. L.; Kennard, K. C. J. Org. Chem. 1954,
1741−1748.
(20) Field, L. J. Am. Chem. Soc. 1952, 74, 394−398.
(21) Although pyridinium 4-chlorobenzenesulfonate has been used in
the literature, no characterization was reported. See: Enomoto, T.;
Iino, M.; Matsuda, M.; Tokura, N. Bull. Chem. Soc. Jpn. 1971, 44,
3140−3143.
2536
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