Novel quinoxalinophenanthrophenazine-based molecules as sensors for anions: synthesis and binding investigations

Article abstract of DOI:10.1016/j.tet.2010.02.075

The design and synthesis of two novel quinoxalinophenanthrophenazine-based anion sensors are reported. Binding studies of these sensors with an array of mono- and polyatomic anions using UV-vis, fluorescence, and NMR titrations have shown 1:1 and 1:2 sens

Full text of DOI:10.1016/j.tet.2010.02.075

Tetrahedron 66 (2010) 2944–2952
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Novel quinoxalinophenanthrophenazine-based molecules as sensors for anions:
synthesis and binding investigations
,
a,
*
Farah S. Raad a, Ala’a O. El-Ballouli a, Rasha M. Moustafa a, Mohammad H. Al-Sayah b , Bilal R. Kaafarani
*
a Department of Chemistry, American University of Beirut, Beirut 1107-2020, Lebanon
b Department of Biology and Chemistry, American University of Sharjah, Sharjah, United Arab Emirates
a r t i c l e i n f o
a b s t r a c t
Article history:
The design and synthesis of two novel quinoxalinophenanthrophenazine-based anion sensors are re-
ported. Binding studies of these sensors with an array of mono- and polyatomic anions using UV–vis,
fluorescence, and NMR titrations have shown 1:1 and 1:2 sensor-to-anion ratios. Binding constants were
calculated for anions, which exhibited high affinity for the sensors, including acetate, benzoate, cyanide,
and fluoride ions.
Received 5 November 2009
Received in revised form 30 January 2010
Accepted 22 February 2010
Available online 26 February 2010
Ó 2010 Elsevier Ltd. All rights reserved.
Keywords:
Quinoxalinophenanthrophenazine
Fluorescent sensors
Anion detection
Chemical sensors
Spectroscopic titrations
NMR titrations
1. Introduction
their consumption (e.g., oxalates) in high levels is hazardous for
people with kidney and intestinal disorders.16
The design of stable fluorescent chromophores is of great in-
terest due to their application in various fields of research including
photoconductors,1 light emitting diodes,2 and optical switches.3
Fluorophores with high quantum yields are perfect candidates for
applications in fluorescent sensors due to their innate high sensi-
tivity at low concentration, low cost, and ease of application as
a diagnostic tool.4,5 The design of new anion sensors is a growing
field due to the importance of detecting anions for medicinal, in-
dustrial, and environmental purposes.6–11 Among halide ions, for
instance, the fluoride ion is vital for prevention of dental caries and
treatment of osteoporosis,12,13 while chloride ion is a tracer of pol-
lution and its detection is essential to monitor intrusion of salt water
into drinking water supplies.14 Similarly, nitrate ion is usually
sensed to monitor environmental pollution from agriculture,14
while the highly toxic cyanide ion, which inhibits cellular respira-
tion and may kill mammals upon binding to a heme group in the
active site of cytochrome a3,5 is becoming a high-risk environmental
contaminant due to industrial release in areas such as gold-mining,
electroplating, herbicides, and resins.5,15 Furthermore, carboxylate
and dicarboxylate anions are naturally present in many foods and
Compared to cation sensing, anion recognition is more chal-
lenging and less explored due to the wide range of geometries and
conformations of anions, their significant charge delocalization, and
strong hydration.11,14,17 The design of fluorescent anion sensors re-
lies on various signaling mechanisms such as photo-induced elec-
tron transfer (PET),17,18 intramolecular charge transfer (ICT),18–20
metal-to-ligand charge transfer (MLCT),21 and/or excited state
intramolecular proton transfer (ESIPT).22 In a PET sensor, the non-
conjugated spacer between the ion receptor and the fluorophore
prevents n/
p and p/p ground state interactions between the
two components. However, anion binding to the receptor modu-
lates the excited state of the fluorophore causing PET quenching and
an increased reduction potential in the receptor.10,11,23 Nonetheless,
receptors that exhibit ICT reveal electronic transitions through
a ‘push–pull’ mechanism accompanied by changes in the dipole
moment of the fluorophore, depending on the electron donor/ac-
ceptor strengths.19,20 The binding of the electron-rich anion to ICT
receptor alters the electronics of the system leading to either
emission enhancement or quenching based on the electronics of
binding site. Finally, an ESIPT sensor allows proton transfer from
a H-bond donor, in the excited-state, to a H-bond acceptor resulting
in two excited species and two emission bands; wherein the red-
shifted band arises from an excited tautomer state.22 In some
cases, more than one signaling mechanism is recorded. For exam-
ple, Gunnlaugsson et al. reported a thiourea PET receptor, which
* Corresponding authors. Tel.: þ961 3 151451; fax: þ961 1 365217; e-mail
addresses: malsayah@aus.edu (M.H. Al-Sayah), bilal.kaafarani@aub.edu.lb (B.R.
Kaafarani).
0040-4020/$ – see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2010.02.075

F.S. Raad et al. / Tetrahedron 66 (2010) 2944–2952
2945
exhibited ICT due to the presence of a large dipole moment in the
naphthalimide fluorophore.18 Such a ‘push–pull’ chromophore
usually undergoes dramatic color changes upon H-bonding or
sensors have been reported earlier, there is still a need to develop
highly selective and sensitive anion sensors the binding effective-
ness of which to the analyte can be monitored easily.
proton-transfer to anions producing
a
colorimetric sensing
Recently, we have reported a crown-ether-based molecule as
a fluorescent sensor for metal ions.31 The molecule consisted of
a tetrasubstituted quinoxalinophenanthrophenazine (TQPP) fluo-
rescent core derivatized with crown ether groups as binding ligands
for alkaline and alkali earth metals. In this report, we introduce two
new molecules (1 and 2) based on the fluorescent core of TQPP but
derivatized with sulfonamide groups, which act as binding sites for
anions. The function of these molecules as sensors is based on the
hydrogen-bonding ability of the N–H bonds of the sulfonamide
groups to anions. This binding leads to alteration of the electronic
density on the sensor’s aromatic system producing significant
changes in its absorption and emission profiles. These changes in
the photophysical properties of the molecules are associated with
the concentration and the type of the introduced anion.
probe.18,24
Several fluorescent anion sensors, which range from highly se-
lective to broad-range detectors, have been reported.15,25 These
sensors are neutral receptors with selective anion recognition el-
ements based on H-bonding, which exhibit high binding strength
and selectivity.26,27 In many examples, the binding motif consists of
N–H fragments of amides, ureas, thioureas, or pyrroles that can
bind to anions in a reversible manner to allow continuous moni-
toring.10,11 For instance, dipyrrolylquinoxalines (DPQ) exhibited
a relatively large binding constant toward fluoride ions through
a combination of electronic and conformational changes upon H-
bonding between the two pyrrole NH groups and the anion.12,28,29
Further modification of the DPQ systems with electron-
withdrawing groups at the pyrrole or quinoxaline subunits led to
enhanced anion binding due to the increased acidity of the N–H
protons.30 Another reported example of sensors for cyanide ions
was based on dipyrrole carboxamide moiety as a recognition site.15
The sensor exhibited selective green fluorescence with more than
ten-fold enhancement in its emission in the presence of cyanide
anions in comparison to the other anions studied. Although many
2. Results and discussion
The synthesis of sensors 1 and 2 is illustrated in Scheme 1. The
intermediates 2,7-di-tert-butyldiketopyrene (5) and 2,7-di-tert-
butyltetraketopyrene (6) were prepared by the catalytic oxidation
of di-tert-butylpyrene (4) using ruthenium(III) chloride and sodium
O
O
O
O
O
O
a
b
or
3
4
5
6
NH2
O2N
O2N
NHTs
NHTs
H2N
H2N
NHTs
NHTs
NHTs
c
d
e
NH2
NHTs
7
8
9
10
Ts =Tosylate
H5 H6
H4
H2
H3
H
O
N
S
O
N
H1
f
CH3
+
5
10
N
NHTs
H7
H8
1
H12 H13
H11
H10
H
O
S
O
TsHN
TsHN
N
N
N
N
CH3
H14
f
+
6
10
N
NHTs
H15
2
Scheme 1. Synthesis of sensors 1 and 2. (a) t-BuCl, AlCl3; (b) RuCl3$xH2O, NaIO4, CH2Cl2, MeCN, H2O; (c) p-toluenesulphonyl chloride, pyridine; (d) HNO3, acetic acid; (e) H2 (40 psi),
Pd/C, ethanol; (f) acetic acid/ethanol.

2946
F.S. Raad et al. / Tetrahedron 66 (2010) 2944–2952
meta periodate.32 The reaction of 1,2-phenylenediamine (7) with
p-toluenesulfonyl chloride afforded 1,2-bis(p-methylphenylsul-
fonamido)benzene (8),33 which upon nitration with nitric acid in
sulfuric acid produced 1,2-bis(p-methylphenylsulfonamido)-4,5-
dinitrobenzene (9).34 The reduction of 9 led to 1,2-bis(p-methyl-
phenylsulfonamido)-4,5-diaminobenzene (10).35 Condensation of
5 and 10 afforded 1 whereas the condensation of 6 and 10 yielded 2.
The binding efficacy of sensors 1 and 2 to anions was explored
using absorption, emission, and NMR spectroscopies where spec-
tral changes of the sensors were recorded as anion solutions were
introduced at increasing concentrations. Typically, the UV–vis
spectrum of 1 exhibited characteristic peaks at 280 nm, 355 nm,
and 450 nm (Fig. 1). The addition of anions to 1 led to a decrease in
the absorbance at 280 nm and to an enhanced absorbance at
355 nm and 450 nm concomitant with a bathochromic shift of peak
maximum to 470 nm combined with three isosbestic points at
300 nm, 330 nm, and 430 nm. This behavior indicates strong
binding interaction between the sensor and the anion. Figure 1
illustrates the changes observed on the absorption spectra of 1
(5.0 mM in 1:1 CH2Cl2/CH3CN) upon titrating it with a solution of
tetrabutylammonium cyanide (TBACN) (1.0 mM in 1:1 CH2Cl2/
CH3CN). Similar spectral changes were observed for the interaction
of 1 with acetate, benzoate, and fluoride anions while insignificant
changes were observed for chloride, bromide, iodide, nitrate, and
perchlorate anions.
The change in the absorbance of 1 at 470 nm upon titrating
with different anions (Fig. 2) indicated 2–3 times enhancement in
the absorbance as one equivalent of the anion was added. When
more anion solution was introduced, the change in the absor-
bance became insignificant. This indicates that sensor had
reached a saturation level as it binds to its anion guest through
1:1 binding stoichiometry. This was also suggested by Job’s plot
(Fig. 1), which indicated maximum absorbance at 0.5 mol frac-
tion. Therefore, the binding isotherms of 1 to acetate, benzoate,
cyanide, and fluoride anions were well-fitted to 1:1 binding
model with the association constant values presented in Table 1.
The binding constants of the other anions were too low to fit the
model.
Figure 1. UV–vis spectra (left) of 1 upon titration with solutions of TBACN and Jobs’ Plot (right).
Figure 2. The change in the absorbance of 1 (5.0 mM) at 470 nm upon titration with different anion solutions (1.0 mM) in 1:1 CH2Cl2/CH3CN. The solid lines represent the generated
fit-curves from the data sets.

F.S. Raad et al. / Tetrahedron 66 (2010) 2944–2952
2947
Table 1
Binding constants of sensors 1 and 2 to the corresponding anionsa
Sensor
Anion
1
2
log K
log K1
log K2
AcOꢀ
BzOꢀ
CNꢀ
Fꢀ
5.2 (5.9)b
5.3 (5.5)
6.1 (5.6)
4.4 (4.9)
3.8
3.0
3.5
4.7
4.5
4.0
3.2
4.2
a
See Supplementary data for more details on Ka calculations.
The values in brackets were calculated from changes in absorbance at 470 nm.
b
Similar, but more pronounced, changes were observed in the
absorption spectrum of 2 (5.0 mM in 1:1 CH2Cl2/CH3CN) upon
titrating with TBA solutions (2.0 mM) of acetate, benzoate, cyanide,
or fluoride anions. Sensor 2 (Fig. 3) exhibited characteristic peaks at
284 nm, 340 nm, 408 nm, and 433 nm in CH2Cl2/CH3CN (1:1). The
addition of fluoride anion resulted in decrease in the absorption of
2 at 284 nm, 408 nm, and 433 nm with enhancements of the peaks
at 303 nm, 340 nm, and 470 nm implying very strong binding of the
anion to the sensor. Besides, several isosbestic points appeared on
the spectra at 294 nm, 382 nm, and 440 nm indicating a clean
transfer from the free sensor state to the bound form with the
anion. Similar behavior was observed upon titrating with solutions
of acetate, benzoate, and cyanide anions.
Figure 4. Relative change in the absorbance of 2 (5.0
of different anion solutions in 1:1 CH2Cl2/CH3CN.
m
M) at 470 nm upon introduction
indication of the stabilization of the charged-transfer emission
state of the sensor by the anion. Figure 5 shows the changes in the
emission of 1 upon titrating with acetate and cyanide anions. The
other anions (chloride, bromide, iodide, nitrate, and perchlorate)
had little effect on the emission of 1.
Figure 3. UV–vis spectra (left) for 2 upon titration with solutions of TBAF and Job’s plot (right).
The relative change in the absorbance of 2 at 470 nm upon
titrating with different anions (Fig. 4) indicated 6–10 times en-
hancement in the absorbance at 470 nm upon the addition of more
than two equivalents of the anion. Absorbance increased as the
anions were added until about three equivalents of the anion had
been added but as more anion solution was introduced, the change
in the absorbance became insignificant. This indicated that the
sensor binding had reached a saturation level of 2 as it binds to its
anion guest through 1:2 binding stoichiometry. Job’s plot (Fig. 3)
supported this conclusion as it indicates maximum absorbance at
a mole fraction of 0.67 of the anion. Such behavior was specifically
noticed with acetate, benzoate, cyanide, and fluoride anions while
other anions showed insignificant effect on the absorbance of 2.
The binding of anions to 1 and 2 resulted in dramatic changes in
emission spectra of each sensor. Sensor 1 exhibited an emission
maximum at 500 nm upon excitation at 350 nm in CH2Cl2/CH3CN
(1:1) solution. However, titrating sensor 1 with acetate, benzoate,
cyanide, or fluoride anions led to enhancement of the sensor’s
emission with a bathochromic shift of the peak to 550 nm. This is an
The relative change in the emission of 1 at 550 nm is shown as
a function of the mole ratio of the sensor to the anion in Figure 6.
The emission of 1 at 550 nm increased quickly as anion solution
was titrated in until it reached a constant value after one equivalent
of the anion (acetate, benzoate, and cyanide) had been added. The
fluoride anion required the addition of more than three equiva-
lences of anion until it reached constant emission intensity. Besides,
it was noticed that the highest response was for cyanide anion with
about three times enhancement in emission followed by acetate,
benzoate, and fluoride anions, respectively. This may be attributed
to the higher charge density and basicity of the cyanide anion as
compared to that of stabilized carboxylate and fluoride anions.10
The emission spectrum of 2 was significantly different from that
of 1 due to the symmetrical structure of the chromophore. In the
absence of anions, sensor 2 exhibited emission maximum at
450 nm with a shoulder emission at 470 nm (Fig. 7) upon excitation
at 350 nm. As anion (acetate, benzoate, cyanide, or fluoride) solu-
tion was titrated in, the emission at 450 nm decreased until it
reached its minimum after one equivalent of the anion had been

2948
F.S. Raad et al. / Tetrahedron 66 (2010) 2944–2952
Figure 5. Emission spectra of 1 (5.0
mM) upon addition of TBAOAc (left) and TBACN (right) solutions (1.0 mM) in 1:1 CH2Cl2/CH3CN.
Figure 6. Relative change in the emission of 1 (5.0 mM) at 550 nm upon titration with different anion solutions (1.0 mM) in 1:1 CH2Cl2/CH3CN.
Figure 7. Emission spectra of 2 (5.0 mM) upon addition of TBAF (left) and TBAOAc (right) solutions (2.0 mM) in 1:1 CH2Cl2/CH3CN.

F.S. Raad et al. / Tetrahedron 66 (2010) 2944–2952
2949
added, Figure 8. As the anion amount increased above two equiv-
alents of 2, a new emission peak started to appear at 550 nm,
Figure 7. This peak continued to increase until it reached its max-
imum at four equivalents of the anion, Figure 8. Comparing the
effect of each anion on the emission at 450 nm and 550 nm clearly
indicates that sensor 2 had higher affinity for acetate, benzoate,
cyanide, and fluoride anions (vide infra).
signals of the aromatic protons are shown as the concentration of
the fluoride anion was increased. The signals of H2, H4, and H6
shifted upfield from 8.272 ppm, 7.991 ppm, and 7.247 ppm to
8.173 ppm, 7.956 ppm, 7.109 ppm, respectively. This was attributed
to the increase of the electronic density of the aromatic system
upon hydrogen bonding between the N–H protons and the anion
(through-bond effect). Meanwhile, the signal of H5 shifted down-
Figure 8. Relative change in the emission of 2 (5.0 mM) at 450 nm (top) and 550 nm (bottom) upon titration with different anion solutions (2.0 mM) in 1:1 CH2Cl2/CH3CN.
NMR titrations of 1 and 2 further supported the trend of anion
binding as observed in photophysical studies. The chemical shifts of
the N–H protons of the sulfonamide groups, which are associated
with the binding process did not appear in the proton NMR spec-
trum, even before anion was added, probably due to chemical ex-
change with the solvent. Thus, the chemical shifts of the CdH
neighboring protons were monitored as aliquots of anion solution
were added into solution of the sensors in CDCl3 (1) and DMSO-d6
(2). Figure 9 shows partial proton NMR spectra of 1 where the
field from 7.738 ppm to 7.837 ppm due to through-space effect of
the anion bound at close proximity to these protons. With respect
to H3, there was hardly any effect on the chemical shift of the signal
corresponding to these protons.
The change in the chemical shift of the neighboring protons
to the binding site was also used to calculate the binding constants
of the sensor to the anions. The chemical shift of H4 decreased upon
the addition of the anions and it reached a constant value once one
equivalent of the anion had been added indicating strong binding

2950
F.S. Raad et al. / Tetrahedron 66 (2010) 2944–2952
Figure 9. Partial 1H NMR spectra of 1 (1.0 mM) upon titrating with TBAF solution (10 mM) in CDCl3.
with 1:1 stoichiometry. For example, the addition of TBAOAc
solution to a solution of 1 in CDCl3, Figure 10, caused to the shift of
the signal of H4 from 7.991 ppm to 7.956 ppm. Job’s plot of this
titration, based on the change in the chemical shift, indicated 1:1
binding stoichiometry and the isotherm fitted to 1:1 binding model
with Ka of 1.75ꢁ105 Mꢀ1. The values of the binding constants cal-
culated through NMR titrations for all anion were in good agree-
ment with the values obtained through absorbance studies, Table 1.
electronic density of the aromatic ring through bond-effect. Mean-
while, the through-space electrostatic effect was insignificant due to
the high dielectric constantof DMSO leading to an upfield shift of H12
instead of a downfield shift (as was noticed for H5 of sensor 1). The
shifts of these signals were minimal after the addition of two
equivalents of the anion which implied 1:2 binding stoichiometry of
2 to the anion. Besides, the observed broadness in the signals of H11
and H13 can be attributed to the slow conformational changes that
Figure 10. Change in the chemical shift of H4 of 1 (1.0 mM) upon titrating with TBAOAc solution (10 mM) in CDCl3 and Job’s plot (inset) for the binding.
NMR titrations of 2 were conducted in DMSO-d6 solvent due to
the low solubility of 2 in CDCl3 at 1 mM concentration. Figure 11
exhibits partial proton NMR spectra of 2 that include the signals
corresponding to the aromatic protons H10, H11, H12, and H13, at in-
creasing concentrations of acetate anion. The signals of H11, H12, and
H13 shifted upfield from 7.941 ppm, 7.803 ppm, and 7.411 ppm to
7.714 ppm, 7.763 ppm, and 7.286 ppm, respectively, as acetate anions
were added. These changes were in accordance with the increase of
need to take place around the sulfonamide group to accommodate
the anion. The signals regained their sharpness once the sensor was
saturated with the anion (>2 equiv). Finally, the binding constants of
2 were calculated (Table 1) by fitting the changes in the chemical
shift of H11 to a 1:2 binding model using non-linear least square
regression methods (see Supplementary data).
On the other hand, the signal of H10 exhibited an interesting
behavior over the course of the titration, Figure 12. As the anion was

F.S. Raad et al. / Tetrahedron 66 (2010) 2944–2952
2951
Figure 11. Partial 1H NMR spectra of 2 (1.0 mM) upon titrating with TBAOAc solution (10 mM) in DMSO-d6.
Figure 12. The change in the chemical shift of H10 of sensor 2 (1.0 mM) upon titrating it with TBAOAc solution (10 mM) in DMSO-d6.
added, the signal of H10 shifted downfield due to the electrostatic
(through-space) effect of the increased electronic density on the
neighboring N-atom of the TQPP system. When the added acetate
became more than one equivalent, the signal started to shift back
upfield where it stopped after two equivalents had been added. This
implies that as the second binding site of the sensor became en-
gaged in binding the anion, the increased electronic density
through-bond effect overcame the electrostatic effect of the
neighboring N-atom of TQPP shifting the signal upfield.
fluorescent sensors for several anions. Sensors 1 and 2 have
exhibited high affinity to acetate, benzoate, cyanide, and fluoride
ions reflected through the changes in the absorption and emission
spectra of the sensors upon the addition of the ions at different
concentrations. These changes can be attributed to the alterations of
the electronic density of the chromophore and, hence the ‘push–
pull’ mechanism upon anion binding. Meanwhile, deprotonation of
the sensors by the anions was considered unlikely at such anion-to-
sensor ratios. This conclusion is supported by the lack of significant
color change or dramatic shifts in absorbance spectra of the sensors
upon addition of anions. Also, NMR titrations supported these
finding and the mode of binding of these sensors through the sul-
fonamide groups. For example, if deprotonation was taking place,
a triplet signal would have been observed in the NMR spectrum at
3. Conclusion
In summary, two quinoxalinophenanthrophenazine-based
molecules have been synthesized and were shown to be effective

2952
F.S. Raad et al. / Tetrahedron 66 (2010) 2944–2952
16 ppm (corresponding to H2Fꢀ) upon titrating the sensors with the
fluoride anion.18 Finally, the low acidity of sulfonamide (pKa¼16 in
DMSO)36,37 as compared to acetic acid (pKa¼12 in DMSO) and
benzoic acid (pKa¼11 in DMSO) makes deprotonation of the sensors
by the acetate or the benzoate anions unfeasible even if 10 M
equivalents of the anion were present.
chemical shifts of the aromatic protons were recorded. The col-
lected data was analyzed using a non-linear least square regression
program to fit the data to a theoretical model of a 1:1 for sensor 1
and 1:2 for sensor 2 (see Supplementary data).
Acknowledgements
4. Experimental
This work was supported by the University Research Board
(URB) of the American University of Beirut, American University of
Sharjah (grant # FRG08-01), the Royal Society of Chemistry, and by
the Petroleum Research Foundation of the American Chemical So-
ciety (grant #: 47343-B10). The authors are grateful for this
support.
4.1. General
Chemicals and solvents were purchased from Acros. Standard
grade silica gel (60 Å, 32–63 mm) and silica gel plates (200 mm) were
purchased from Sorbent Technologies. Reactions that required an-
hydrous conditions were carried out under argon in oven-dried
glassware. A Bruker spectrometer was used to record the NMR
spectra. CDCl3 and DMSO-d6 were the solvents for NMR measure-
ments and chemical shifts relative to TMS at 0.00 ppm are reported
Supplementary data
Absorption titration spectra of the sensors, calculations of
binding constants, and the curve fit of NMR data are provided in the
Supplementary data. Supplementary data associated with this ar-
ticle can be found, in the online version, at doi:10.1016/
j.tet.2010.02.075.
in parts per million (ppm) on the
d scale. Elemental analyses were
performed at Atlantic Microlab Inc., Norcross, GA.
4.1.1. Sensor 1. 2,7-Di-tert-butyldiketopyrene (5)32 (230 mg,
0.67 mmol)
and
1,2-bis(p-methylphenylsulfonamido)-4,5-di-
References and notes
aminobenzene (10)35 (300 mg, 0.67 mmol) were refluxed in
a mixture of (1:1) ethanol/acetic acid (60 mL) for 24 h. The reaction
mixture was filtered and washed with cold ethanol to yield a fluo-
rescent green solid of 1 (385 mg, 77%), mp >300 ꢂC. 1H NMR
1. Kitamura, N.; Inoue, T.; Tazuke, S. Chem. Phys. Lett. 1982, 89, 329–332.
2. Tao, Y.; Wang, Q.; Yang, C.; Wang, Q.; Zhang, Z.; Zou, T.; Qin, J.; Ma, D. Angew.
Chem., Int. Ed. 2008, 47, 8104–8107.
3. Cuisdo, J.; Deniz, E.; Raymo, F. M. Eur. J. Org. Chem. 2009, 2031–2045.
4. Aldakov, D.; Palacios, M. A.; Anzenbacher, P., Jr. Chem. Mater. 2005,17, 5238–5241.
5. Lee, K.-S.; Kim, H.-J.; Kim, G.-H.; Shin, I.; Hong, J.-I. Org. Lett. 2008, 10, 49–51.
6. Gale, P. A. Coord. Chem. Rev. 2001, 213, 79–128.
7. Sessler, J. L.; Davis, J. M. Acc. Chem. Res. 2001, 34, 989–997.
8. de Silva, A. P.; Gunaratne, H. Q. N.; Gunnlaugsson, T.; Huxley, A. J. M.; McCoy, C.
P.; Rademacher, J. T.; Rice, T. E. Chem. Rev. 1997, 97, 1515–1566.
9. Beer, P. D.; Gale, P. A. Angew. Chem., Int. Ed. 2001, 40, 486–516.
10. Amendola, V.; Esteban-Gomez, D.; Fabbrizzi, L.; Licchelli, M. Acc. Chem. Res.
2006, 39, 343–353.
(300 MHz, DMSO-d6):
d
9.40 (2H, d, J¼1.8 Hz), 8.46 (2H, d,
J¼2.1 Hz), 8.16 (2H, s), 7.94 (2H, s), 7.79 (4H, d, J¼8.4 Hz), 7.39 (4H, d,
J¼8.4 Hz), 2.35 (6H, s), 1.60 (18H, s). 13C NMR (75 MHz, CDCl3):
d
149.8, 144.6, 144.3, 140.4, 135.0, 132.2, 131.1, 129.9, 128.5, 127.7,
126.2, 124.3, 124.2, 121.7, 35.52, 21.61. Anal. Calcd for C44H42N4O4S2:
C, 70.00; H, 5.61; N, 7.42. Found: C, 69.90; H, 5.50; N, 7.30.
4.1.2. Sensor 2. 2,7-Di-tert-butyltetraketopyrene (6)32 (150 mg,
0.40 mmol) and 1,2-bis(p-methylphenylsulfonamido)-4,5-dia-
minobenzene (10)35 (360 mg, 0.81 mmol) were refluxed in a mixture
of(1:1)ethanol/acetic acid(60 mL)underargonfor24 h. Thereaction
mixture was filtered and washed with cold ethanol to yield a yellow
solid, whichwastrituratedusinghot tolueneviaSoxhletextractionto
yield 2 (330 mg, 70%), mp >300 ꢂC. 1H NMR (300 MHz, DMSO-d6):
11. Gunnlaugsson, T.; Glynn, M.; Tocci, G. M.; Kruger, P. E.; Pfeffer, F. M. Coord. Chem.
Rev. 2006, 250, 3094–3117.
12. Black, C. B.; Andrioletti, B.; Try, A. C.; Ruiperez, C.; Sessler, J. L. J. Am. Chem. Soc.
1999, 121, 10438–10439.
13. Kleerekoper, M. Endocrinol. Metab. Clin. North Am. 1998, 27, 441–452.
14. Davis, F.; Collyer, S. D.; Higson, S. P. J. Top. Curr. Chem. 2005, 255, 97–124.
15. Chen, C.-L.; Chen, Y.-H.; Chen, C.-Y.; Sun, S.-S. Org. Lett. 2006, 8, 5053–5056.
16. Morozumi, M.; Hossain, R. Z.; Yamakawa, K.-i.; Hokama, S.; Nishijima, S.;
Oshiro, Y.; Uchida, A.; Sugaya, K.; Ogawa, Y. Urol. Res. 2006, 34, 168–172.
17. Gunnlaugsson, T.; Davis, A. P.; O’Brien, J. E.; Glynn, M. Org. Biomol. Chem. 2005,
3, 48–56.
18. Gunnlaugsson, T.; Kruger, P. E.; Lee, T. C.; Parkesh, R.; Pfeffer, F. M.; Hussey, G. M.
Tetrahedron Lett. 2003, 44, 6575–6578.
19. Bernard, V. Molecular Fluorescence: Principles and Applications; Wiley-VCH:
Weinheim, Germany, 2001.
20. Wen, Z.-C.; Jiang, Y.-B. Tetrahedron 2004, 60, 11109–11115.
21. Atkinson, P.; Bretonniere, Y.; Parker, D. Chem. Commun. 2004, 438–439.
22. Li, Z.; Chen, Y. H.; Jiang, Y. B. Sci. China, Ser. B: Chem. 2009, 52, 786–792.
23. de Silva, A. P.; Nimal, H. Q.; Gunaratne, N.; Gunnlaugsson, T.; McCoy, C. P.; Max-
well, P. R. S.; Rademacher, J. T.; Rice, T. E. Pure Appl. Chem. 1996, 68, 1443–1448.
24. Gunnlaugsson, T.; Ali, H. D. P.; Glynn, M.; Kruger, P. E.; Hussey, G. M.; Pfeffer, F.
M.; dos Santos, C. M. G.; Tierney, J. J. Fluoresc. 2005, 15, 287–299.
25. Chung, S.-Y.; Nam, S.-W.; Lim, J.; Park, S.; Yoon, J. Chem. Commun. 2009, 2866–
2868.
26. Wei, L.-H.; He, Y.-B.; Wu, J.-L.; Wu, X.-J.; Meng, L.-Z.; Yang, X. Supramol. Chem.
2004, 16, 561–567.
27. Kato, R.; Nishizawa, S.; Hayashita, T.; Teramae, N. Tetrahedron Lett. 2001, 42,
5053–5056.
28. Anzenbacher, P., Jr.; Palacios, M. A.; Jursikova, K.; Marquez, M. Org. Lett. 2005, 7,
5027–5030.
29. Jose, D. A.; Kumar, D. K.; Ganguly, B.; Das, A. Org. Lett. 2004, 6, 3445–3448.
30. Ghosh, T.; Maiya, B. G.; Wong, M. W. J. Phys. Chem. A 2004, 108, 11249–11259.
31. Jradi, F. M.; Al-Sayah, M. H.; Kaafarani, B. R. Tetrahedron Lett. 2008, 49, 238–242.
32. Hu, J.; Zhang, D.; Harris, F. W. J. Org. Chem. 2005, 70, 707–708.
33. Elderfield, R. C.; Meyer, V. B. J. Am. Chem. Soc. 1954, 76, 1887–1891.
34. Cheeseman, G. W. H. J. Chem. Soc. 1962, 1170–1176.
35. Kleineweischede, A.; Mattay, J. Eur. J. Org. Chem. 2006, 947–957.
36. Bordwell, F. G. Acc. Chem. Res. 1988, 21, 456–463.
37. Fu, Y.; Liu, L.; Li, R.-Q.; Liu, R.; Guo, Q.-X. J. Am. Chem. Soc. 2004, 126, 814–822.
d
9.51 (4H, s), 7.93 (4H, s), 7.78 (4H, d, J¼6.9 Hz), 7.38 (4H, d, J¼7.2 Hz),
2.35 (12H, s), 1.60 (18H, s). 13C NMR (75 MHz, DMSO-d6):
d
150.6,
143.9, 141.7, 139.3, 136.6, 133.5, 129.9, 128.7, 126.9, 124.5, 123.5, 118.7,
35.3, 31.4, 20.9. Anal. Calcd for C64H58N8O8S4: C, 64.30; H, 4.89; N,
9.37. Found: C, 64.06; H, 4.91; N, 9.12.
4.1.3. Spectroscopic titration. A solution of the sensor (5 mM, 2 mL)
in CH2Cl2/CH3CN (1:1) placed into a 1ꢁ1 cm cuvette was titrated
with a solution of the anion (1.0 mM or 2.0 mM, CH2Cl2/CH3CN
(1:1)) that contained the sensor (5 mM). Aliquot amounts of the
anion solution were added to the cuvette via a syringe until a total
of six or more equivalents of the anion had been added (the number
of additions was around 20 with an increase in the amount of anion
solution added). The UV–vis spectrum and emission spectrum
(lex¼350 nm) were scanned after each addition.
4.1.4. 1H NMR titration. A solution of the sensor (1 mM, 600
mL) in
CDCl3 (1) or DMSO-d6 (2) placed in an NMR tube was titrated with
a solution of the anion (10 mM). Aliquot amounts of the anion so-
lution were added to the NMR tube via a syringe until a total of ten
equivalents of the anion were added (the number of additions was
around 17 with an increase in the amount of anion solution added).
A
1H NMR spectrum was recorded after each addition and the