Synthesis of functionalized core-modified sapphyrins and covalently linked porphyrin-sapphyrin dyads

Article abstract of DOI:10.1016/j.tet.2011.11.030

We adopted simple synthetic strategy to synthesize mono-functionalized thiasapphyrins containing functionalized aryl group in the meso-position at thiophene side. The thiasapphyrin building block containing iodophenyl functional group was coupled with thr

Full text of DOI:10.1016/j.tet.2011.11.030

Tetrahedron 68 (2012) 1306e1314
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Synthesis of functionalized core-modified sapphyrins and covalently linked
porphyrinesapphyrin dyads
*
Rajeswara Rao Malakalapalli, Ravikanth Mangalampalli
Department of Chemistry, Indian Institute of Technology, Bombay, Powai, Mumbai 400 076, India
a r t i c l e i n f o
a b s t r a c t
Article history:
We adopted simple synthetic strategy to synthesize mono-functionalized thiasapphyrins containing
functionalized aryl group in the meso-position at thiophene side. The thiasapphyrin building block
containing iodophenyl functional group was coupled with three different porphyrin building blocks with
N4, N3S and N2S2 cores containing meso-ethynylphenyl functional group under mild Pd(0) coupling
conditions to synthesize three covalently linked diphenyl ethyne bridged porphyrinethiasapphyrin
dyads. The porphyrinethiasapphyrin dyads were characterized by mass, NMR, absorption, electro-
chemical and fluorescence techniques. The NMR, absorption and electrochemical studies indicated that
the two components in dyads interact weakly and retain their individual identities. The steady state
fluorescence studies indicated that the porphyrin fluorescence is reduced to a significant extent because
of energy and/or electron transfer to the thiasapphyrin unit. The protonation studies indicated that N4
porphyrin unit is more basic, whereas N3S and N2S2 porphyrin units are less basic compared to thia-
sapphyrin unit in respective dyads. We explored the potential of dyads as fluorescent anion sensors and
showed that two out of three dyads can be used as fluorescent anion sensors.
Received 12 September 2011
Received in revised form 6 November 2011
Accepted 10 November 2011
Available online 17 November 2011
Keywords:
Core-modified porphyrins
Thiasapphyrin building blocks
Anion sensor
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
conjugates are expected to undergo distinct multi-redox processes,
which may be interesting from multibit molecular based in-
Expanded porphyrins are synthetic analogues of the porphyrins
and differ from porphyrins by containing more than 18 electrons
formation storage point of view. Sessler and co-workers synthe-
sized non-covalently linked porphyrinesapphyrin conjugates and
demonstrated an efficient excitation energy transfer from por-
phyrin to sapphyrin.6a,b Inokuma and Osuka developed a simple
one-pot route for the synthesis of a series of meso-porphyrinyl
substituted expanded porphyrins.6c Chandrashekar and co-workers
p
in the conjugated pathway either due to an increased number of
heterocyclic rings or due to multiple meso carbon bridges.1 Recently
expanded porphyrins have attracted considerable attention be-
cause of their diverse applications. The expanded porphyrins ab-
sorb at longer wavelengths compared to porphyrins, hence these
systems could find use as sensitizers for photodynamic therapy.2
Since the expanded porphyrins have large central cavities, these
compounds show ability to coordinate large cations3 and anions
and in favourable cases, even transport anions.4 Recently, it was
found that the expanded porphyrins also show moderate to large
two photon absorption cross section values.5 The rich chemistry of
expanded porphyrins can be further fine tuned by linking them
with porphyrins either covalently or non-covalently.6 Porphyrin
subunits connected to expanded porphyrins would offer an op-
portunity to create interesting electronic interactions between two
macrocycles both in ground and excited states. Such interactions
may be tuned by appropriate cation or anion complexation at one
or both macrocycles. In addition, porphyrineexpanded porphyrin
synthesized mesoemeso linked core-modified 22
p smaragdyrins
and studied their unusual absorption properties.7 We recently re-
ported8 the synthesis of covalently linked porphyrinethiasap-
phyrin dyad I and porphyrineoxasmaragdyrin dyad II (Chart 1). We
used the concept of anion binding at the expanded porphyrin site in
its protonated form, which can be monitored by the following
changes observed in the fluorescence spectra of porphyrin unit.
Thus porphyrineexpanded porphyrin dyads can be used as fluo-
rescent sensors. We earlier showed that the porphyrinesapphyrin
dyad I cannot be used, whereas porphyrinesmaragdyrin dyad II
can be used as fluorescent sensor. This is because the smaragdyrin
unit in porphyrinesmaragdyrin dyad II is more basic and can accept
protons before the porphyrin unit, whereas in porphyr-
inesapphyrin dyad I, the porphyrin is more basic than the sap-
phyrin and gets protonated prior to sapphyrin unit. Although we
showed earlier that the porphyrinesmaragdyrin dyad II can be
used as potential fluorescent sensor, the disadvantage with this
system is that both porphyrin and smaragdyrin units are
* Corresponding author. E-mail address: ravikanth@chem.iitb.ac.in (R.
Mangalampalli).
0040-4020/$ e see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2011.11.030

R.R. Malakalapalli, R. Mangalampalli / Tetrahedron 68 (2012) 1306e1314
1307
2. Results and discussion
CH
H C
3
3
The sapphyrins with N2S3 core were prepared by 3þ2 conden-
sation ofbithiophene diol and16-thiatripyrraneunderstandard acid
catalyzed conditions.9 To synthesize the mono-functionalized N2S3
sapphyrin building blocks 1e4, one needs an access to the func-
tionalized unsymmetrical 16-thiatripyrranes 8e11 containing one
functional group. The functionalized unsymmetrical 16-
thiatripyrranes 8e11 were prepared from the respective un-
symmetrical thiophene diols 12e15, respectively. The un-
symmetrical thiophene diols 12e15 were prepared in two steps
starting with thiophene and the synthesis of these unsymmetrical
thiophene diols was reported.10 The functionalized 16-
thiatripyrranes 8e11 were prepared by treating 1 equiv of un-
symmetrical diols 12e15 with 40 equiv of pyrrole under argon at-
mosphere at room temperature for 30 min (Scheme 1). After
standard work, the crude compounds were purified by silica gel
column chromatography and afforded the pure functionalized 16-
thiatripyrranes 8e11 as orange oils in 70e80% yields. The func-
tionalized16-thiatripyrranes 8e11 wereconfirmedbymolecularion
peak in ES-MS mass spectra, clean 1H NMR and matching C,H,N,S
analysis. The other desired precursor, the symmetrical bithiophene
diol 16 was synthesized by following the literature procedure11 and
the spectral data was in agreement with the reported data.
CH
3
S
NH
N
S
N
H C
3
N HN
N
S
I
CH
CH
3
3
CH
3
CH
3
N
N
NH
N
N
H
O
H C
3
H
HN
NH
N
II
CH
3
CH
3
Chart 1.
The mono-functionalized sapphyrins 1e4 were synthesized by
condensing bithiophene diol 16 with functionalized 16-
thiatripyrrane 8e11 under acid catalyzed conditions. Condensa-
tion of 1 equiv of symmetrical bithiophene diol 16 with 1 equiv of
appropriate unsymmetrical 16-thiatripyrrane 8e10 in CH2Cl2 in the
presence of 1 equiv of trifluoroacetic acid (TFA) at room tempera-
ture for 1 h under inert atmosphere followed by oxidation with
DDQ in open air for additional 1 h gave crude compound, which
contains the required mono-functionalized sapphyrin building
blocks 1e3 along with small amounts of other macrocycles formed
because of self condensation of diol and tripyrrane. The crude
compounds were subjected to silica gel column chromatographic
purification and the desired sapphyrin building blocks 1e3 moved
as second band were obtained as green solids in 10e20% yield. The
sapphyrin building block 4 was prepared by condensing 11 with 16
under Adler’s conditions.12 The sapphyrin building blocks 1e4 were
characterized by NMR, mass, absorption and C,H,N,S analysis. The
sapphyrin building blocks 1e4 exhibited molecular ion peak in ES-
MS mass spectra and the elemental analysis matched with the
expected composition confirmed the identity of the compounds. In
1H NMR, the compounds 1e4 exhibited similar NMR features like
5,10,15,20-tetratolyl-25,27,29-trithiasapphyrin9 17. However the
inverted thiophene ring protons, which appear as singlet at
fluorescent. The intense fluorescence band of smaragdyrin unit in
porphyrinesmaragdyrin dyad II is quenched completely on selec-
tive protonation of smaragdyrin unit, so that the addition of anion
that binds at the smaragdyrin site can be monitored by following
the changes in the porphyrin fluorescence. However, if experiment
is not carried out carefully, the fluorescence behaviour of the
smaragdyrin interferes in the use of this system as fluorescent
sensor, since the anion binding at the protonated smaragdyrin site
in dyad is associated with deprotonation mechanism. On the other
hand, in porphyrinethiasapphyrin dyad, the thiasapphyrin unit is
completely non-fluorescent in neutral and protonated form and
can be used as fluorescent sensor if thiasapphyrin unit gets pro-
tonated prior to the porphyrin unit. Thus, by replacing the por-
phyrin in porphyrinesapphyrin dyad I with a modified porphyrin
that is less basic would transform the porphyrinesapphyrin dyad
also as fluorescent sensor. Here, we report the synthesis of mono-
functionalized thiasapphyrin building blocks 1e4 and their use in
the synthesis of three porphyrinethiasapphyrin dyads 5e7 (Chart
2). Furthermore, based on fluorescence studies, we showed that
the dyads 6 and 7 can be used as fluorescent anion sensor, whereas
the dyad 5 cannot be used.
Chart 2.

1308
R.R. Malakalapalli, R. Mangalampalli / Tetrahedron 68 (2012) 1306e1314
Scheme 1. Synthesis of mono-functionalized sapphyrins 1e4.
CH3
wꢀ0.6 ppm in 17 due to symmetric substitution appeared as set of
unresolved AB quartet in 1e4 due to unsymmetric substitution
around thiophene ring. The absorption spectra of compounds 1e4
showed one strong soret at 512 nm and five Q-bands in
575e900 nm region and the peak maxima matched closely with
symmetrical sapphyrin 17.9
H3C
CH3
S
S
N
X
Y
N
N
+
N
H
H3C
S
The mono-functionalized sapphyrin building block 1 was used
further to synthesize three covalently linked porphyrinesapphyrin
dyads 5e7 using mild Pd(0) mediated coupling conditions as
shown in Scheme 2. The other desired mono-functionalized por-
phyrin building blocks, such as 5-(4-ethynylphenyl)-10,15,20-tri(p-
tolyl)porphyrin13 18, 5-(4-ethynylphenyl)-10,15,20-tri(p-tolyl)-21-
thiaporphyrin10 19 and 5-(4-ethynylphenyl)-10,15,20-tri(p-tolyl)-
21,23-dithiaporphyrin10 20 were synthesized by following the lit-
erature methods. The porphyrinesapphyrin dyads 5e7 were syn-
thesized by coupling14 1 equiv of sapphyrin building block 1 with
1 equiv of porphyrin building blocks 18, 19 and 20, respectively, in
the presence of Pd2(dba)3/AsPh3 in toluene/triethylamine at 50 ꢁC
for 12 h. The reaction progress was monitored by TLC analysis and
the reaction was stopped after complete disappearance of starting
precursors and with the appearance of new spot corresponds to the
expected dyad. The crude compounds were subjected to silica gel
column chromatography and afforded pure dyads 5e7 in 58e62%
yields. The coupling reactions worked efficiently and the isolated
dyads 5e7 were freely soluble in common organic solvents. The
dyads were confirmed by molecular ion peak in MALDI-TOF mass
spectra and clean 1H NMR spectra. A comparison of 1H NMR spectra
of N2S2 porphyrinesapphyrin dyad 7 along with its corresponding
monomeric precursors 1 and 20, over a selected region is presented
in Fig. 1. The resonances of dyads 5e7 were assigned on the basis of
the 1H NMR spectra observed for the constituted monomeric
building blocks. A close inspection of Fig. 1 indicates that the NMR
spectra of dyad 7 is just a combination of NMR spectra of consti-
tuted monomers with almost no change in the chemical shifts of
various protons compared to monomers indicating that the two
macrocycles in dyad 7 interact very weakly and retain their in-
dividual characteristic features. The dyads 5 and 6 also showed
I
CH3
1
CH3
X = Y = NH - 18
Pd2(dba)3,
AsPh3
19
X = NH, Y = S -
20
X = Y = S
-
Toluene: Et3N
CH3
CH3
S
N
Y
N
N
X
H3C
S
N
S
CH3
CH3
H3C
- 5
X = Y = NH
X = S, Y = NH
X = Y = S
6
-
-
7
Scheme 2. Synthesis of covalently linked porphyrinesapphyrin dyads 5e7.
similar 1H NMR characteristic features supporting the weak in-
teraction between the two macrocyclic units in dyads.
The absorption spectra of porphyrinesapphyrin dyads 5e7 and
their corresponding 1:1 mixture of monomers in toluene were
measured at room temperature and the data is presented in Table 1.
A comparison of absorption spectra of dyad 5 with 1:1 mixture of

R.R. Malakalapalli, R. Mangalampalli / Tetrahedron 68 (2012) 1306e1314
1309
Fig. 1. Comparison of 1H NMR spectra of dyad 7 along with corresponding monomers 1 and 20.
Table 1
0.7
Absorption data of dyads 5e7 along with their 1:1 mixture of corresponding
monomers and protonated dyads 5$H22De7$H22D recorded in toluene
- - - - 1: 1 mixture of 1 and 18
0.6
0.5
0.4
0.3
0.2
0.1
0.0
Compound
Soret band
(nm) (log
l
Q-Bands l (nm) (log 3 )
5
3 )
1
512 (5.42)
625 (4.33), 683 (4.61),
782 (3.16), 884 (4.12)
630 (4.14), 651 (4.26),
682 (4.42), 781 (3.27),
882 (3.83)
1:1 of 1 and 18
422 (5.81), 513 (5.32)
1:1 of 1 and 19
1:1 of 1 and 20
5
432 (5.71), 513 (5.21)
439 (5.68), 513 (5.2)
422 (5.5), 513 (5.25)
622 (3.82), 682 (4.37),
781 (3.12), 883 (3.41)
630 (4.0), 692 (4.4),
781 (3.4), 880 (3.7)
626 (4.25), 651 (4.34),
682 (4.43), 781 (3.41),
882 (3.95)
400
500
600
700
800
900
Wavelength (nm)
6
432 (5.46), 513 (5.27)
439 (5.47), 513 (5.34)
445 (5.47), 513 (5.38)
432 (5.39), 525 (5.16)
439 (5.48), 523 (5.19)
622 (4.17), 682 (4.34),
781 (3.45), 883 (3.96)
630 (4.16), 685 (4.43),
781 (3.51), 880 (3.95)
669 (4.75), 782 (3.54),
883 (3.92)
674 (4.24), 790 (4.25),
840 (4.16)
638 (4.29), 698 (4.36),
792 (4.44), 838 (4.43)
Fig. 2. Comparison of absorption spectra of dyad 5 (d) and 1:1 (——) mixture of
monomers 1 and 18 and in toluene.
7
5$H22D
6$H22D
7$H22D
trifluoroacetic acid are shown in Fig. 3. The dyad 5 containing N4
porphyrin and thiasapphyrin units, on addition of TFA protonates
N4 porphyrin unit alone. This is reflected clearly in its Soret ab-
sorption band at 420 nm, which decreases in intensity with an
appearance of new band corresponding to diprotonated derivative
of N4 porphyrin unit at 440 nm. However, the band at 513 nm,
which corresponds to sapphyrin unit did not show any changes on
addition of TFA supporting that in dyad 5, the N4 porphyrin unit is
more basic and accepts protons before sapphyrin unit. This is in
agreement with our earlier observation for compound I.8 In-
terestingly, for dyads 6 and 7, the addition of TFA resulted in sig-
nificant spectral changes in 513 nm band without any change in the
Soret band of respective N3S and N2S2 porphyrin unit indicating
that the thiasapphyrin unit is more basic and accepts protons
compared to N3S and N2S2 porphyrin units in dyads 6 and 7, re-
spectively. Thus, the protonation studies clearly indicated that the
basicity of macrocycles follow the order: N4 porphyrin>N2S3
sapphyrin>N3S porphyrin>N2S2 porphyrin.
corresponding monomers 1 and 18 is shown in Fig. 2. As clear from
the Fig. 2 and the data in Table 1, the absorption spectra of dyads
5e7 were almost identical to those of their corresponding 1:1
mixture of monomers. For e.g., the dyad 6 showed absorption
bands at 432, 513, 622, 682, 781 and 883 nm corresponding to both
the macrocyclic units like its 1:1 mixture of monomers. However,
the extinction coefficients of absorption bands of dyad 6 are dif-
ferent from its corresponding 1:1 mixture of monomers indicating
that there is a weak interaction between the two components in
dyad 6.
Since both porphyrin and expanded porphyrin macrocycles can
accept protons, we carried out systematic protonation studies of
dyads 5e7 to understand which macrocycle is more basic in a giv-
en dyad. The protonation studies were carried out by titrating the
dyad with dilute trifluoroacetic acid and the changes were moni-
tored by absorption spectroscopy. The changes in the Soret ab-
sorption spectra of dyads 5e7 on increasing amounts of
The electrochemical properties of dyads 5e7 along with their
corresponding monomers were studied by cyclic voltammetry and
differential pulse voltammetry at a scan rate of 50 mV/s using
tetrabutylammonium perchlorate as the supporting electrolyte
(0.1 M) in CH2Cl2. The reduction waves of dyads 5 and 6 are shown

1310
R.R. Malakalapalli, R. Mangalampalli / Tetrahedron 68 (2012) 1306e1314
por
(a)
0.25
0.20
0.15
0.10
0.05
sap
400
500
600
Wavelength (nm)
Por
Fig. 4. The reduction waves of dyads 5 and 6 in dichloromethane containing 0.1 M
(b)
TBAP as supporting electrolyte recorded at 50 mV/s scan speed.
0.20
0.15
0.10
0.05
Table 2
Sap
Electrochemical redox data (V) of porphyrinethiasapphyrin dyads 1e7 and their
corresponding monomers recorded in dichloromethane containing 0.1 M TBAP as
supporting electrolyte using scan rate of 50 mV/s. E1/2 values reported are relative to
SCE
Compd
Oxidation E1/2/V vs SCE
Reduction E1/2/V vs SCE
H2TTP
STTPH
S2TTP
1
2
3
4
5
6
7
d
1.03
1.11
1.18
1.13
1.18
1.35
1.13
1.00
1.01
1.04
1.30
1.51
d
d
d
d
ꢀ1.23
ꢀ1.35
ꢀ1.23
d
ꢀ1.55
d
d
d
d
ꢀ1.03
d
d
d
d
d
0.89
0.90
1.01
0.86
0.78
d
1.38
1.49
1.63
1.43
1.35
1.28
1.35
1.65
1.74
1.83
1.70
1.43
1.55
1.56
ꢀ0.82
ꢀ0.61
ꢀ0.56
ꢀ0.68
ꢀ0.84
ꢀ0.80
ꢀ0.85
ꢀ1.06
ꢀ0.84
ꢀ0.69
ꢀ0.93
ꢀ1.09
ꢀ1.04
ꢀ1.10
ꢀ1.50
ꢀ1.31
ꢀ1.08
ꢀ1.42
ꢀ1.51
ꢀ1.49
ꢀ1.46
400
500
600
d
d
Wavelength (nm)
d
ꢀ1.18
ꢀ1.28
ꢀ1.25
Por
(c)
d
0.25
0.20
0.15
0.10
0.05
exclusively due to N4 porphyrin unit and ꢀ1.51 V was due to the
reduction of both the macrocycles of the dyad 5. Similarly, the
oxidations of the dyad 5 were also assigned based on the oxidation
potential data of its corresponding N4 porphyrin and sapphyrin
monomers. The other two dyads 6 and 7 also exhibited the redox
waves, which closely matched with the potentials of their consti-
tuted macrocycles. Thus, the electrochemical study of dyads 5e7
suggested that the two macrocycles in porphyrinesapphyrin dyads
retain their individual features.
Sap
400
500
600
The steady state fluorescence measurements were carried out
on dyads 5e7 in toluene by using appropriate excitation wave-
length at which the corresponding porphyrin absorbs strongly. We
also studied the fluorescence properties of 1:1 mixture of their
corresponding monomers using the same concentrations. A com-
parison of fluorescence spectra of dyad 7 with its 1:1 mixture in
shown in Fig. 5 and the relevant photophysical data is tabulated is
Table 3. Upon excitation of 1:1 mixture at porphyrin Soret band, the
strong emission was observed from porphyrin with the quantum
yield matching with the appropriate porphyrin monomer. How-
ever, when dyads 5e7 were excited at the same excitation wave-
length, the weak emission was observed from porphyrin unit and
the quantum yields of porphyrin units in dyads 5e7 were quenched
by 90e95%. This indicates that the emission of porphyrin unit in
dyads was quenched because of either energy transfer or electron
transfer from porphyrin unit to thiasapphyrin unit. More studies
are required to understand the fluorescence quenching mechanism
of these dyads.
Wavelength (nm)
Fig. 3. Absorption spectra of compounds (a) 5, (b) 6 and (c) 7 (1
on increasing amounts of trifluoroacetic acid recorded in toluene. The acid concen-
trations used up to 440 M.
mM) in the soret region
m
in Fig. 4 and the redox data are presented in Table 2. In general, the
dyads exhibited three to four oxidations and reductions, which are
reversible or quasi-reversible (DEp¼60e120 mV) and in some
cases, irreversible. The redox waves of the dyads 5e7 were assigned
based on the redox chemistry of their corresponding porphyrin and
sapphyrin monomers. For example, the dyad 5 containing N4 por-
phyrin and thiasapphyrin units showed four reductions at ꢀ0.84,
ꢀ1.09, ꢀ1.18 and ꢀ1.51 V. The first two reduction waves at ꢀ0.84
and ꢀ1.09 V were assigned to the first and second reductions of the
thiasapphyrin unit on the basis of the fact that the potentials are
closer to thiasapphyrin monomer. The reduction at ꢀ1.18 V was

R.R. Malakalapalli, R. Mangalampalli / Tetrahedron 68 (2012) 1306e1314
1311
0.00126
0.00119
0.00112
0.00105
1000
800
600
400
200
0
120
90
60
0.00000
0.00006
0.00012
2-
[CO
3
]
650
700
750
800
30
Wavelength (nm)
Fig. 5. Comparison of steady-state emission spectra of dyad 7 (d) and 1:1 (——)
mixture of monomers 1 and 20.
650
700
750
800
Wavelength (nm)
0.00112
0.00104
0.00096
Table 3
160
Emission data of dyads 5e7 and monomers recorded in toluene
Compd
lex
d
F
% of quenching
H2TTP
STTP
S2TTP
5
6
7
420
430
435
420
430
435
d
0.110
0.016
0.007
0.003
0.001
0.0009
d
d
d
96
94
89
d
0.00088
120
d
0.00000
0.00007
0.00014
N4em
N3Sem
N2S2em
2-]
CO
3
[
80
2.1. Fluorescent anion sensor studies
40
The protonation studies clearly indicated that in dyad 5, the
porphyrin unit gets protonated prior to thiasapphyrin unit, but in
dyads 6 and 7, the thiasapphyrin unit gets protonated prior to N3S
and N2S2 porphyrin units, respectively. Thus, dyad 5 cannot be used
as fluorescent sensor, whereas dyads 6 and 7 can be used. Chan-
drashekar and co-workers showed15 earlier that the protonated
thiasapphyrin binds anions although less strongly compared to its
aza analogue and it binds strongly with carbonate anion compared
to other anions. Since the aim here is to show dyads as fluorescent
sensors by allowing the protonated thiasapphyrin unit of dyads to
bind anion and monitor the changes in the fluorescence intensity of
porphyrin fluorophore, we carried out the anion sensing experi-
ments with only carbonate anion. The experiments were done by
adding increasing amounts of K2CO3 to the protonated dyads 6$H22D
and 7$H22D in which the thiasapphyrin unit was selectively pro-
tonated and the fluorescence of the N3S porphyrin and N2S2 por-
phyrin, respectively, was monitored at their corresponding
emission maxima. The effect of adding increasing amounts of
K2CO3 on the fluorescence spectra of protonated dyads 6$H22D and
7$H22D are shown in Fig. 6. It is clear from Fig. 6 that the addition of
increasing amounts of carbonate anion resulted in a gradual en-
hancement of the intensity of the N3S porphyrin emission at
688 nm in protonated dyad 6$H22D and N2S2 porphyrin emission at
710 nm in protonated dyad in 7$H22D suggesting that the carbonate
anion was bound at the protonated thiasapphyrin site in both
dyads. The plot of quantum yield versus carbonate anion concen-
tration reaches a saturation and the quantum yield of N3S and N2S2
porphyrin unit at the saturation point are 0.0013 and 0.0011 in
protonated dyads 6$H22D and 7$H22D, respectively. The binding
constant calculated using BenesieHilderbrand equation for dyads 6
and 7 are 6.8ꢂ104 and 7.2ꢂ104, respectively, indicates that the
protonated thiasapphyrin unit in dyads can bind carbonate anion
effectively. This can be sensed by following the changes in the
680
720
760
800
Wavelength (nm)
Fig. 6. Fluorescence emission changes of dyads (a) 6$H22D
(
lex¼430 nm) and (b) 7$H22D
(
lex¼435 nm) upon the addition of potassium carbonate in toluene. The anion con-
centrations used up to 75 mM.
fluorescence spectra of N3S and N2S2 porphyrin units in respective
dyads. Thus dyads can act as potential fluorescent sensors.
3. Conclusions
In conclusion, we synthesized mono-functionalized thiasap-
phyrin building blocks containing functionalized aryl group in
meso-position at thiophene side using readily available precursors.
The sapphyrin building block containing meso-iodophenyl group
has been used to synthesize three covalently linked diphenyl eth-
yne bridged porphyrinesapphyrin dyads by coupling with appro-
priate ethynylphenyl containing porphyrin building blocks under
mild Pd(0) coupling conditions. The porphyrin units in dyads were
varied from N4 to N3S and N2S2 porphyrin and the dyads were
characterized by using various spectral and electrochemical stud-
ies. The protonation studies indicated that N4 porphyrin unit is
more basic, whereas N3S and N2S2 porphyrin units are less basic
than thiasapphyrin unit. These dyads have been tested for fluo-
rescent anion sensor applications. We anticipated that the pro-
tonated thiasapphyrin unit binds anion which can be monitored by
following changes in the fluorescence intensity of porphyrin unit.
Our studies indicated that two out of three covalently linked por-
phyrinesapphyrin dyads reported here can be used as fluorescent
anion sensors.

1312
R.R. Malakalapalli, R. Mangalampalli / Tetrahedron 68 (2012) 1306e1314
4. Experimental section
(90:10) to afford the desired functionalized 16-thiatripyrrane
8e11 as orange oil.
4.1. General
4.3.1. 5-(p-Iodophenyl),10-tolyl-16-thia-15,17-dihydrotripyrrane
(8). Yield 71%; [Found: C, 60.83; H, 4.08; N, 5.12; S, 6.11. C27H23IN2S
requires C, 60.68; H, 4.34; N, 5.24; S, 6.00%]; Rf (pet. ether/8% ethyl
The 1H and 13C NMR (
d in ppm) spectra were recorded using
Varian VXR 400 spectrometer. TMS was used as an internal
reference for recording 1H (residual proton; 7.26) and 13C (
d
d
77.0)
acetate) 0.60; IR (neat): v¼3440, 3256, 3090, 2860,1497,1436,1068,
~
NMR spectra in CDCl3. The ES-MS mass spectra were recorded
with a Q-Tof micro mass spectrometer. MALDI-TOF mass spectra
were obtained from Axima-CFR manufactured by Kratos analyti-
cals. Absorption and steady state fluorescence spectra were ob-
tained with PerkineElmer Lambda-35 and Lambda-55
instruments, respectively. Cyclic voltammetric (CV) and differential
pulse voltammetric (DPV) studies were carried out with BAS elec-
trochemical system utilizing the three electrode configuration
consisting of a glassy carbon (working electrode), platinum wire
(auxiliary electrode) and saturated calomel (reference electrode)
electrodes. The experiments were done in dry dichloromethane
using 0.1 M tetrabutylammonium perchlorate as supporting elec-
trolyte. Microanalyses were performed on a Thermo Finnigan
(FLASH EA 1112) microanalyzer. THF and chloroform were dried
over sodium benzophenone ketyl and distilled prior to use.
BF3$Et2O, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) and
N,N,N0,N-tetramethylethylenediamine (TMEDA), were used as ob-
tained. All other chemicals used for the synthesis were reagent
grade unless otherwise specified. Column chromatography was
performed on silica (60e120 mesh).
818, 746 cmꢀ1 1H NMR (400 MHz, CDCl3,
; d in ppm): 2.32 (s, 3H;
tol), 5.46 (s, 1H; eCH), 5.48 (s, 1H; eCH), 5.87e5.91(m, 2H; pyrrole),
6.12e6.13 (m, 2H; pyrrole), 6.57 (d, 1H, 3J¼3.6 Hz; thiophene), 6.61
(d, 1H, 3J¼3.6 Hz; thiophene), 6.66e6.67 (m, 2H; pyrrole), 6.96 (d,
2H, 3J (H, H)¼8.2 Hz; Ar), 7.12 (s, 4H; Ar), 7.60 (d, 2H, 3J (H, H)¼
8.2 Hz; Ar), 7.89 (br s, 2H; eNH); 13C NMR (75 MHz, CDCl3): 21.2,
45.6, 45.7, 107.5, 107.8, 108.2, 108.3, 108.4, 117.3, 117.6, 125.3, 125.6,
128.3, 129.4, 130.5, 132.4, 133.2, 136.8, 137.7, 139.7, 142.6, 145.0,
146.6; ES-MS: (C27H23IN2S) 534.8 [Mþ].
4.3.2. 5-(p-Bromophenyl),10-tolyl-16-thia-15,17-dihydrotripyrrane
(9). Yield 80%; [Found: C, 66.71; H, 4.78; N, 5.63; S, 6.40.
C27H23BrN2S requires C, 66.53; H, 4.76; N, 5.75; S, 6.58%]; Rf (pet.
~
ether/8% ethyl acetate) 0.62; IR (neat): v¼3444, 3260, 3090, 2853,
1502, 1436, 1050, 810, 750 cmꢀ1 1H NMR (400 MHz, CDCl3,
; d in
ppm): 2.32 (s, 3H; tol), 5.56 (s, 1H; eCH), 5.57 (s, 1H; eCH),
5.86e5.90 (m, 2H; pyrrole), 6.12e6.13 (m, 2H; pyrrole), 6.57 (d,
1H, 3J (H, H)¼3.6 Hz; thiophene), 6.61 (d, 1H, 3J (H, H)¼3.6 Hz;
thiophene), 6.67e6.68 (m, 2H; pyrrole), 7.08e7.09 (m, 6H; Ar),
7.40 (d, 2H, 3J (H, H)¼7.9Hz; Ar), 7.88 (br s, 2H; eNH); 13C NMR
(75 MHz, CDCl3,
d in ppm): 21.1, 45.5, 45.7, 107.5, 107.8, 108.4,
108.5, 117.3, 117.6, 121.0, 125.4, 125.6, 128.3, 129.4, 130.2, 131.7,
132.5, 133.2, 136.8, 139.7, 141.8, 145.0, 146.7; ES-MS: (C27H23BrN2S)
487.1 [Mþ].
4.2. Fluorescence studies
Stock solutions of K2CO3 (10 mM) was prepared in methanol
containing minimum amount of water and stock solution of 6 and
7 (1 mM) was prepared in toluene. The stock solutions of dyads 6
4.3.3. 5-(p-Nitrophenyl),10-tolyl-16-thia-15,17-dihydrotripyrrane
(10). Yield 75%; [Found: C, 71.11; H, 4.90; N, 9.21; S, 7.12.
C27H23N3O2S requires C, 71.50; H, 5.11; N, 9.29; S, 7.07%]; Rf (pet.
and 7 were diluted to 1
mM with toluene and used dilute tri-
fluoroacetic acid to generate selectively protonated dyads 6$H22D
and 7$H22D. Titration experiments were performed by placing
~
ether/10% ethyl acetate) 0.50; IR (neat): v¼3440, 3232, 3070, 2862,
1460, 1050, 808, 740 cmꢀ1 1H NMR (400 MHz, CDCl3,
; d in ppm):
2.5 mL of solution 6$H22D and 7$H22D (1
mM) in a quartz cuvette of
2.33 (s, 3H; tol), 5.53 (s, 1H; eCH), 5.65 (s, 1H; eCH), 5.85e5.86 (m,
1H; pyrrole), 5.92e5.93 (m, 1H; pyrrole), 6.13e6.14 (m, 2H; pyr-
role), 6.60 (d, 1H, 3J (H, H)¼3.6 Hz; thiophene), 6.65 (d, 1H, 3J (H,
H)¼3.6 Hz; thiophene), 6.68e6.69 (m, 1H; pyrrole), 6.71e6.72 (m,
1H; pyrrole), 7.12e7.13 (m, 4H; Ar), 7.38 (d, 2H, 3J (H, H)¼8.5 Hz; Ar),
7.87 (br s, 1H; eNH), 7.98 (br s, 1H; eNH), 8.15 (d, 2H, 3J (H, H)¼
1 cm path length, and various amounts of K2CO3 was added in-
crementally by means of a micro-pipette. Excitation was provided
at 430 nm and 435 nm for dyads 6$H22D and 7$H22D, respectively,
and emission was collected from 600 to 800 nm. The association
constant of the anion complex formed in the solution has been
estimated using the standard BenesieHildebrand equation, viz.,
8.5 Hz; Ar); 13C NMR (75 MHz, CDCl3,
d in ppm): 21.2, 45.8, 45.8,
107.6, 108.2, 108.4, 108.8, 117.4, 118.0, 123.9, 125.6, 126.0, 128.3,
129.4, 129.5, 131.4, 133.1, 137.0, 139.5, 143.7, 147.0, 147.4, 150.2; ES-
MS: (C27H23N302S) 453.9 [Mþ].
1
I ꢀ I0
1
1
Â
Ã
¼
þ
ðI1 ꢀ I0ÞKa Aꢀ
I1 ꢀ I0
where I0 is the intensity of 6$H22D or 7$H22D before addition of an-
ion, I is the intensity in the presence of Aꢀ, I1 is intensity upon
saturation with Aꢀ and Ka is the association constant of the complex
formed.
4.3.4. 5-(p-Hydroxyphenyl),10-tolyl-16-thia-15,17-dihydrotripyrrane
(11). Yield 69%; [Found: C, 76.41; H, 5.88; N, 6.43; S, 7.21.
C27H24N2OS requires C, 76.38; H, 5.70; N, 6.60; S, 7.55%]; Rf (pet.
~
ether/16% ethyl acetate) 0.48; IR (neat): v¼3403, 3260, 3058, 2850,
1486,1436,1050, 810, 750, 690 cmꢀ1; 1H NMR (400 MHz, CDCl3,
d in
4.3. Synthesis of functionalized 16-thiatripyrranes (8e11)
ppm): 2.31 (s, 3H; tol), 5.46 (s, 1H; eCH), 5.49 (s, 1H; eCH),
5.89e5.90 (m, 2H; pyrrole), 6.12e6.13 (m, 2H; pyrrole), 6.58e6.59
(m, 2H; thiophene), 6.64e6.65 (m, 2H; pyrrole), 6.72 (d, 2H, 3J (H,
H)¼8.2; Ar), 7.10e7.05 (m, 6H; Ar), 7.87 (br s, 2H; eNH); 13C NMR
A
mixture of corresponding unsymmetrical diol 12e15
(2.3 mmol) and pyrrole (92 mmol) in 250 mL round bottom flask
was degassed with nitrogen for 10 min under stirring at room
temperature. The reaction was initiated by adding BF3$Et2O
(0.23 mmol) and the reaction mixture was stirred for 30 min. The
reaction mixture was diluted with dichloromethane (100 mL) and
washed thoroughly with 0.1 M NaOH followed by brine solution.
The organic layer was separated and dried over anhydrous
Na2SO4. The solvent was removed under reduced pressure and
the resulted viscous dark yellow liquid was purified by silica
column chromatography using petroleum ether/ethyl acetate
(75 MHz, CDCl3, d in ppm): 21.2, 45.3, 45.7, 107.5, 108.3, 115.5, 117.3,
117.8, 125.2, 125.3, 128.4, 129.4, 129.7, 133.4, 133.5, 135.1, 136.8,
139.8, 146.2, 146.3, 154.7; ES-MS: (C27H24N2OS) 425.2 [Mþ1]þ.
4.4. Synthesis of mono-functionalized thiasapphyrin building
blocks (1e3)
Samples of symmetrical bithiophene diol 16 (0.49 mmol) and
16-thiatripyrrane 8e10 (0.49 mmol) in dry dichloromethane

R.R. Malakalapalli, R. Mangalampalli / Tetrahedron 68 (2012) 1306e1314
1313
(200 mL) were stirred under nitrogen atmosphere for 15 min at
room temperature. Trifluoroacetic acid (0.49 mmol) was added to
initiate the condensation and the reaction mixture was stirred at
room temperature for 1 h. DDQ (0.49 mmol) was then added and
the reaction mixture was stirred in air for additional 1 h. After re-
moving the solvent, the crude compound was subjected to silica gel
column chromatography and the desired N2S3 sapphyrin 1e3 was
eluted with petroleum ether/dichloromethane (50:50). The solvent
was removed under vacuo to afford 1e3 as a green colour solid.
77.63; H, 4.60; N, 3.55; S, 12.19%]; Rf (pet. ether/60% dichloro-
methane) 0.46; 1H NMR (400 MHz, CDCl3,
d
in ppm): ꢀ0.88 (br s,
2H;
b
-thiophene), 2.73 (s, 9H; tol), 7.12 (d, 2H, 3J (H, H)¼7.6 Hz; Ar),
7.58 (d, 2H, 3J (H, H)¼8.0 Hz; Ar), 7.66 (d, 4H, 3J (H, H)¼8.0 Hz; Ar),
8.18e8.21 (m, 8H; Ar), 8.50 (d, 1H, 3J (H, H)¼4.3 Hz;
b-pyrrole), 8.54
(d, 1H, 3J (H, H)¼3.9 Hz;
b-pyrrole), 8.66e8.67 (m, 2H; b-pyrrole),
9.78 (d, 2H, 3J (H, H)¼4.2 Hz;
b
-bithiophene),10.20 (d, 2H, 3J (H, H)¼
4.6 Hz; b
-bithiophene); ES-MS: (C51H36N2OS3) 789.0 [M]þ; UVevis
(in toluene, lmax/nm,
3
/molꢀ1 dm3 cmꢀ1) (log
): 513 (5.5), 624 (4.4),
3
683 (4.7), 782 (3.2), 877 (4.1).
4.4.1. 10-(p-Iodophenyl),5,15,20-tritolyl-25,27,29-trithiasapphyrin
(1). Yield 14%; mp >300 ꢁC; [Found: C, 67.81; H, 4.14; N, 3.43; S,
10.32. C51H35IN2S3 requires C, 68.14; H, 3.92; N, 3.12; S, 10.70%]; Rf
(pet. ether/40% dichloromethane) 0.58; 1H NMR (400 MHz, CDCl3,
4.5. Covalently linked diphenyl ethyne bridged
porphyrinethiasapphyrin dyads (5e7)
d
in ppm): ꢀ0.69 (m, 2H;
b
-thiophene), 2.73 (s, 9H; tol), 7.60 (d, 2H,
Samples of 10-(4-iodophenyl),5,15,20-tritolyl-25,27,29-trithia-
sapphyrin 1 (0.011 mmol) and appropriate mono-functionalized
ethynylphenyl porphyrin building block 18e20 (0.011 mmol)
were dissolved in dry toluene/triethylamine (5:1, 30 mL) in a 50 mL
round bottomed flask. The flask was fitted with a reflux condenser,
gas inlet and gas outlet tubes for nitrogen purging. The reaction
vessel was placed in an oil bath preheated to 50 ꢁC. After purging
nitrogen for 15 min, AsPh3 (0.013 mmol) followed by Pd2(dba)3
(0.0016 mmol) were added to this solution and the reaction mix-
ture was stirred under nitrogen at 50 ꢁC for 12 h. TLC analysis of the
reaction mixture showed the disappearance of spots corresponding
to starting materials and the appearance of a new spot corre-
sponding to the required dyad. After removal of the solvent, the
crude compound was purified by silica gel column chromatography
using petroleum ether/dichloromethane (40:60) as eluent to afford
the desired dyad 5e7 as brown solid.
3J (H, H)¼7.0 Hz; Ar), 7.66 (d, 4H, 3J (H, H)¼7.8 Hz; Ar), 8.09e8.10 (m,
4H; Ar), 8.12e8.13 (m, 4H; Ar), 8.25 (d, 2H, 3J (H, H)¼7.8 Hz; Ar),
8.50 (d, 1H, 3J (H, H)¼4.3 Hz;
b
-pyrrole), 8.54 (d, 1H, 3J (H, H)¼
4.3 Hz; b-pyrrole), 8.66e8.67 (m, 2H; b
-pyrrole), 8.78 (d, 2H, 3J (H,
H)¼4.5 Hz;
b
-bithiophene), 10.21 (d, 2H, 3J (H, H)¼4.5 Hz;
b-
bithiophene); ES-MS: (C51H35IN2S3) 899.8 [Mþ1]þ; UVevis (in
toluene, lmax/nm,
3
/molꢀ1 dm3 cmꢀ1) (log
): 512 (5.4), 625 (4.3),
3
683 (4.6), 782 (3.1), 884 (4.1).
4.4.2. 10-(p-Bromophenyl),5,15,20-tritolyl-25,27,29-trithiasapphyrin
(2). Yield 20%; mp >300 ꢁC; [Found: C, 70.61; H, 4.24; N, 3.26; S,
11.02. C51H35BrN2S3 requires C, 71.90; H, 4.14; N, 3.29; S, 11.29%]; Rf
(pet. ether/40% dichloromethane) 0.60; 1H NMR (400 MHz, CDCl3,
d
inppm): ꢀ0.68 (m, 2H;
b
-thiophene), 2.72 (s, 9H; Tol), 7.60 (d, 2H, 3J
(H, H)¼7.9 Hz; Ar), 7.67 (d, 4H, 3J (H, H)¼7.6 Hz; Ar), 7.90 (d, 2H, 3J (H,
H)¼8.2 Hz; Ar), 8.20e8.28 (m, 8H; Ar), 8.49 (d, 1H, 3J (H, H)¼4.3 Hz;
b
2H;
-pyrrole), 8.54 (d, 1H, 3J (H, H)¼4.3 Hz;
b
-pyrrole), 8.66e8.67 (m,
-bithiophene), 10.22
4.5.1. Compound 5. Yield 62%; mp >300 ꢁC; [Found: C, 83.16; H,
4.52; N, 5.40; S, 6.96. C100H70N6S3 requires C, 82.73; H, 4.86; N, 5.79;
S, 6.63%]; Rf (pet. ether/60% dichloromethane) 0.48; 1H NMR
b
-pyrrole), 9.79 (d, 2H, 3J (H, H)¼4.6 Hz;
b
(d, 2H, 3J (H, H)¼4.6 Hz;
b-bithiophene); ES-MS: (C51H35BrN2S3)
851.0 [M]þ; UVevis (in toluene, lmax/nm,
3
/molꢀ1 dm3 cmꢀ1) (log
3 ):
(400 MHz, CDCl3,
d
in ppm): ꢀ2.75 (s, 2H; eNH), ꢀ0.65 (d, 2H, 3J (H,
512 (5.4), 624 (4.3), 682 (4.6), 782 (3.2), 884 (4.1).
H)¼4.1 Hz;
b-thiophene), 2.71 (s, 18H; tol), 7.50e7.73 (m, 16H; Ar),
8.07e8.46 (m, 16H; Ar), 8.60 (d, 1H, 3J (H, H)¼4.5 Hz;
b-pyrrole),
4.4.3. 10-(p-Nitrophenyl),5,15,20-tritolyl-25,27,29-trithiasapphyrin
(3). Yield 13%; mp >300 ꢁC, [Found: C, 74.93; H, 4.12; N, 5.11; S,11.96.
C51H35N3O2S3 requires C, 74.88; H, 4.31; N, 5.14; S, 11.76%]; Rf (pet.
8.62 (d, 1H, 3J (H, H)¼4.5 Hz;
b
-pyrrole), 8.64 (d, 1H, 3J (H, H)¼
4.5 Hz;
b
-pyrrole), 8.70 (d, 1H, 3J (H, H)¼4.5 Hz;
b-pyrrole),
8.80e8.94 (m, 8H;
b
-pyrrole), 9.81 (d, 2H, 3J (H, H)¼4.0 Hz;
b-
ether/50% dichloromethane) 0.45; 1H NMR (400 MHz, CDCl3,
d
in
bithiophene), 10.20 (d, 2H, 3J (H, H)¼4.5 Hz;
b-bithiophene);
ppm): ꢀ0.51 (d, 1H, 3J (H, H)¼5.1 Hz;
b
-thiophene), ꢀ0.45 (d, 1H, 3J
MALDI-TOF mass (C100H70N6S3): 1451.7 [Mþ1]þ; UVevis (in tolu-
(H, H)¼5.1 Hz;
b
-thiophene), 2.73 (s, 9H; tol), 7. 59 (d, 2H, 3J (H, H)¼
ene, lmax/nm,
3
/molꢀ1 dm3 cmꢀ1) (log
): 422 (5.5), 513 (5.4), 593
3
7.6 Hz; Ar), 7.68 (d, 4H, 3J (H, H)¼7.6 Hz; Ar), 8.18e8.24 (m, 8H; Ar),
(4.2), 626 (4.1), 651 (4.2), 682 (4.5), 781 (3.5), 882 (4.0).
8.40 (d, 1H, 3J (H, H)¼4.3 Hz;
b-pyrrole), 8.50e8.51 (m, 2H; Ar),
8.61e8.67 (m, 3H;
b
-pyrrole), 9.74e9.96 (dd, 2H, 3J (H, H)¼4.6 Hz, 4J
4.5.2. Compound 6. Yield 58%; mp >300 ꢁC; [Found: C, 81.46; H,
4.63; N, 4.92; S, 8.96. C100H69N5S4 requires C, 81.77; H, 4.73; N, 4.77;
S, 8.73%]; Rf (pet. ether/60% dichloromethane) 0.46; 1H NMR
(H, H)¼2.4 Hz;
b
-bithiophene),10.15e10.16 (dd, 2H, 3J (H, H)¼4.6 Hz;
4J (H, H)¼2.4 Hz;
b-bithiophene); ES-MS: (C51H35N3O2S3) 818.8
[M]þ; UVevis (in toluene, lmax/nm,
3
/molꢀ1 dm3 cmꢀ1) (log
3 ): 513
(400 MHz, CDCl3,
d
in ppm): ꢀ2.65 (s, 1H; eNH), ꢀ0.67 (d, 2H, 3J (H,
(5.5), 624 (4.4), 683 (4.7), 782 (3.2), 877 (4.1).
H)¼4.7 Hz;
b-thiophene), 2.70 (s, 18H; tol), 7.53e7.69 (m, 12H; Ar),
8.06e8.08 (m, 8H; Ar), 8.14 (d, 2H, 3J (H, H)¼7.6 Hz; Ar), 8.22e8.33
4.4.4. 10-(p-Hydroxyphenyl)-5,15,20-tritolyl-25,27,29-
trithiasapphyrin (4). Samples of diol 16 (0.49 mmol) and 16-
thiatripyrrane 11 (0.49 mmol) were dissolved in 100 mL pro-
pionic acid and refluxed for 3 h. The propionic acid was removed
under vacuum and resultant black solid was washed with hot water
several times and dried in an oven at 100 ꢁC. The crude black solid
was passed through the silica gel column using dichloromethane
and methanol as solvent mixture to remove nonporphyrinic im-
purities. The TLC analysis of the compound after filtration column
showed spot corresponds to desired compound 11 along with other
functionalized macrocycles. The compound was subjected to sec-
ond silica gel column chromatography using dichloromethane/
methanol (98:2) as eluent and afforded the desired hydroxyl
functionalized sapphyrin 4 as green solid (10% yield); mp >300 ꢁC;
[Found: C, 77.46; H, 4.52; N, 3.40; S, 11.96. C51H35N3O2S3 requires C,
(m, 8H; Ar), 8.43 (d, 2H, 3J (H, H)¼7.6 Hz; Ar), 8.56 (d, 1H, 3J (H, H)¼
4.3 Hz;
b
-pyrrole), 8.59 (d, 1H, 3J (H, H)¼4.3 Hz;
b-pyrrole), 8.61 (d,
1H, 3J (H, H)¼4.5 Hz;
b
-pyrrole), 8.66 (d, 1H, 3J (H, H)¼4.5 Hz;
b-
pyrrole), 8.69e8.72 (m, 4H;
b-pyrrole), 8.95 (s, 2H; b-pyrrole),
9.76e9.80 (m, 4H;
H)¼3.7 Hz; -bithiophene); MALDI-TOF mass (C100H69N5S4):
1468.8 [M]þ; UVevis (in toluene, lmax/nm, /molꢀ1 dm3 cmꢀ1
(log ): 432 (5.4), 513 (5.2) 622 (4.1), 682 (4.3), 781 (3.4), 883 (3.9).
b
-thiopheneþ
b
-bithiophene), 10.20 (d, 2H, 3J (H,
b
3
)
3
4.5.3. Compound 7. Yield 58%; mp >300 ꢁC; [Found: C, 81.06; H,
4.63; N, 3.62; S, 10.56. C100H68N4S5 requires C, 80.83; H, 4.61; N,
3.77; S, 10.79%]; Rf (pet. ether/40% dichloromethane) 0.44; 1H NMR
(400 MHz, CDCl3,
d
in ppm): ꢀ0.65 (d, 2H, 3J (H, H)¼4.0 Hz;
b-
thiophene), 2.73 (s, 18H; tol), 7.50e7.77 (m, 16H; Ar), 8.07e8.40 (m,
16H; Ar), 8.60 (d, 1H, 3J (H, H)¼3.9 Hz;
b
-pyrrole), 8.65 (d, 1H, 3J (H,

1314
R.R. Malakalapalli, R. Mangalampalli / Tetrahedron 68 (2012) 1306e1314
Mirsaidov, U.; Markert, J. T. Inorg. Chem. 2005, 44, 2125e2127; (e) Mori, S.;
Osuka, A. J. Am. Chem. Soc. 2005, 127, 8030e8031; (f) Weghorn, S. J.; Sessler,
J. L.; Lynch, V.; Baumann, T. F.; Sibert, J. W. Inorg. Chem. 1996, 35,
1089e1090.
H)¼3.9 Hz;
b
-pyrrole), 8.68 (d, 1H, 3J (H, H)¼3.9 Hz;
b
-pyrrole), 8.71
b-pyrrole), 8.75e8.77 (m, 4H; b-pyrrole),
(d, 1H, 3J (H, H)¼3.9 Hz;
9.70e9.80 (m, 6H;
b
-thiopheneþ
b
-bithiophene), 10.20 (d, 2H, 3J (H,
4. (a) Sessler, J. L.; Davis, J. M. Acc. Chem. Res. 2001, 34, 989e997; (b) Sessler, J. L.;
Andrievsky, A.; Genge, J. W. Adv. Supramol. Chem. 1997, 4, 97e142; (c) Sessler,
J. L.; Sansom, P. I.; Andrievsky, A.; Kral, V. In Supramolecular Chemistry of An-
ions; Bianchi, A., James, K. B., Espana, E. G., Eds.; Wiley-VCH: New York, NY,
1997; pp 355e419; (d) Shionoya, M.; Furuta, H.; Lynch, V.; Harriman, A.;
Sessler, J. L. J. Am. Chem. Soc. 1992, 114, 5714e5722; (e) Sessler, J. L.; Hoehner,
M. C.; Gebauer, A.; Andrievsky, A.; Lynch, V. J. Org. Chem. 1997, 62, 9251e9260;
H)¼4.1 Hz;
1485.9 [M]þ; UVevis (in toluene, lmax/nm,
(log ): 439 (5.4), 513 (5.3) 630 (4.1), 685 (4.4), 781 (3.5), 880 (3.9).
b
-bithiophene); MALDI-TOF mass (C100H68N4S5):
3
/molꢀ1 dm3 cmꢀ1
)
3
Acknowledgements
ꢀ
(f) Sessler, J. L.; Andrievsky, A.; Kral, V.; Lynch, V. J. Am. Chem. Soc. 1997, 119,
This work was supported by a grant from Board of Research in
Nuclear Sciences, Department of Atomic Energy, Govt. of India and
M.R.R. thanks CSIR for fellowship.
ꢀ
9385e9392; (g) Kral, V.; Sessler, J. L.; Furuta, H. J. Am. Chem. Soc. 1992, 114,
8705e8707; (h) Furuta, H.; Cyr, M. J.; Sessler, J. L. J. Am. Chem. Soc. 1991, 113,
6677e6678.
5. (a) Yoon, Z. S.; Cho, D.-G.; Kim, K. S.; Sessler, J. L.; Kim, D. J. Am. Chem. Soc. 2008,
130, 6930e6931; (b) Yoon, Z. S.; Kwon, J. H.; Yoon, M.-C.; Koh, M. K.; Noh, S. B.;
Sessler, J. L.; Lee, J. T.; Seidel, D.; Aguilar, A.; Shimizu, S.; Suzuki, M.; Osuka, A.;
Kim, D. J. Am. Chem. Soc. 2006, 128, 14128e14134; (c) Rath, H.; Sankar, J.;
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Supplementary data
The complete spectroscopic data for all new compounds and
anion binding studies. Supplementary data associated with this
article can be found, in the online version, at doi:10.1016/
j.tet.2011.11.030.
ꢀ
6. (a) Springs, S. L.; Gosztola, D.; Wasielewski, M. R.; Kral, V.; Andrievsky, A.;
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Sessler, J. S. J. Am. Chem. Soc. 1999, 121, 2281e2289; (b) Kral, V.; Springs, S. L.;
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Org. Lett. 2004, 6, 3663e3666; (d) Tanaka, T.; Aratani, N.; Lim, J. M.; Kim, K. S.;
Kim, D.; Osuka, A. Chem. Sci. 2011, 2, 1414e1418.
7. Misra, R.; Kumar, R.; Chandrashekar, T. K.; Suresh, C. H. Chem. Commun. 2006,
4584e4586.
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