Binding and fluorescent sensing of dicarboxylates by a bis(calix[4]pyrrole) -substituted BODIPY dye

Article abstract of DOI:10.1002/ejoc.201201504

A bis(calix[4]pyrrole)-substituted BODIPY ditopic receptor 1 has been synthesised and characterised. The binding and sensing properties of 1 towards several aliphatic and aromatic dicarboxylates have been evaluated by using UV/Vis fluorescence and ¹H NMR spectroscopy. The receptor strongly binds linear α,ω-dicarboxylates of appropriate lengths (C9 and C10) by acting as a cleft. For all dicarboxylates, the binding event is detected by a bathochromic shift in the UV/Vis spectra of the receptor and by strong quenching of its fluorescence. The bis(calix[4]pyrrole)-substituted BODIPY ditopic receptor 1 shows high affinity towards linear α,ω- dicarboxylates of appropriate lengths. The binding event is detected by a bathochromic shift in the UV/Vis spectra of the receptor and by a strong quenching of its fluorescence. Copyright

Full text of DOI:10.1002/ejoc.201201504

Job/Unit: O21504
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Date: 29-01-13 16:31:53
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FULL PAPER
DOI: 10.1002/ejoc.201201504
Binding and Fluorescent Sensing of Dicarboxylates by a Bis(calix[4]pyrrole)-
Substituted BODIPY Dye
Raúl Gotor,[a,b] Ana M. Costero,*[a,b] Pablo Gaviña,[a,b] Salvador Gil,[a,b] and
Margarita Parra[a,b]
Keywords: Sensors / Fluorescent probes / Dyes/pigments
A bis(calix[4]pyrrole)-substituted BODIPY ditopic receptor 1
has been synthesised and characterised. The binding and
sensing properties of 1 towards several aliphatic and aro-
matic dicarboxylates have been evaluated by using UV/Vis
fluorescence and 1H NMR spectroscopy. The receptor
strongly binds linear α,ω-dicarboxylates of appropriate
lengths (C9 and C10) by acting as a cleft. For all dicarboxyl-
ates, the binding event is detected by a bathochromic shift
in the UV/Vis spectra of the receptor and by strong quench-
ing of its fluorescence.
Introduction
taching conjugated π-electron donor substituents to the
BODIPY core.[5] This strategy can be used in the construc-
tion of colorimetric or fluorescent chemosensors by using a
receptor with electron donating properties that are modu-
lated by coordination with the desired species.[6]
The development of neutral receptors for the recognition
and sensing of anions is a key research area in supramolec-
ular chemistry.[1] Among the different anions, dicarboxylate
anions are highly attractive targets because they play funda-
mental roles in many chemical and biochemical processes.[2]
Fluorescent and colorimetric chemosensors have received
special interest given their high sensitivity and easy detec-
tion methods. In general, these sensors are built by at-
taching a binding moiety to a fluorescent or chromogenic
signalling unit in such a way that anion complexation at the
binding site induces an observable change in the photophys-
ical properties of the signalling unit. Several receptors for
carboxylate and dicarboxylate anions have been reported,
most of which are based on neutral hydrogen-bond donors
such as amides, ureas and thioureas.[3] Calix[4]pyrroles are
another class of neutral receptor for anions that have been
used to design fluorescent chemosensors, although less at-
tention has been paid to them.[4] On the other hand, boron-
dipyrromethene (BODIPY) derivatives are an interesting
class of luminescent signalling units to be incorporated into
chemosensors. BODIPY-based dyes have undergone vast
development in recent years owing to their easy syntheses,
remarkable spectroscopic properties and high chemical- and
photostability. The simplest BODIPY absorbs and emits at
ca. 500 nm, but the absorbance (and the corresponding
fluorescence emission) can be redshifted by covalently at-
Quite recently, an 8-(p-bromophenyl)-substituted
BODIPY with two pending calix[4]pyrrole units was re-
ported by Shao,[7] and its binding and sensing properties
towards several organic and inorganic small anions (F–,
–
AcO–, H2PO4 and Cl–) have been studied by UV/Vis ab-
sorption and fluorescence emission. The calixpyrrole units
are connected to the BODIPY by a styrene linker, which
extends the π conjugation of the system. Upon anion coor-
dination, the intramolecular charge transfer (ICT) process
from the electron-rich calix[4]pyrrole to the electron-with-
drawing BODIPY core increases, which results in a redshift
of the absorption band and a quenching of fluorescence,
also attributed to an ICT process.
In the course of our research into chemical receptors and
sensors for dicarboxylate anions, we have independently
prepared a very closely related BODIPY-based bis(calix[4]-
pyrrole) ditopic receptor 1 and have extended this study
towards the recognition and sensing of aliphatic α,ω-dicarb-
oxylate and aromatic dicarboxylates of different chain
lengths. We reasoned that only those dicarboxylates with
appropriate lengths would form very stable 1:1 complexes
involving the simultaneous coordination of both calixpyr-
roles to both terminal carboxylate moieties. The enhance-
ment of the ICT process upon dicarboxylate coordination
should lead to changes in the UV/Vis spectra and in the
fluorescence properties of the receptor. Moreover, this bind-
ing process should also bring about the quenching of the
fluorescence emission of the dye either by photoinduced
electron transfer (PET) or ICT, similarly to that observed
[a] Centro de Reconocimiento Molecular y Desarrollo Tecnológico
(IDM), Unidad Mixta Universidad de Valencia-Universidad
Politécnica de Valencia,
46100 Burjassot (Valencia), Spain
Fax: +34-963543151
E-mail: ana.costero@uv.es
Homepage: http://idm.webs.upv.es/eng/index.php
[b] Departamento de Química Orgánica, Universidad de Valencia,
Dr. Moliner 50, 46100 Burjassot (Valencia), Spain
Supporting information for this article is available on the for other dye-substituted calixpyrroles.[4,6]
WWW under http://dx.doi.org/10.1002/ejoc.201201504.
Eur. J. Org. Chem. 0000, 0–0
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R. Gotor, A. M. Costero, P. Gaviña, S. Gil, M. Parra
FULL PAPER
Figure 1. The absorption (black) and emission (normalised, grey)
spectra of 1 in THF at room temperature. The excitation wave-
length used for the fluorescence spectrum was 672 nm.
The emission spectrum of 1 showed a strong lumines-
cence band at λem = 698 nm (λexc = 672 nm). The fluores-
cence quantum yield of a 10–5 m solution of 1 in THF was
calculated as øF = 0.38 with zinc phthalocyanine (øF = 0.30
in toluene/1% pyridine) as a standard.[10]
Compound 2 presented very similar spectroscopic fea-
tures with λabs = 589 nm (ε = 53470 cm–1 m–1) in THF solu-
tion and an emission band at λem = 615 nm. The batho-
chromic shifts of the optical transitions, as compared to
those of the parent BODIPY 3, were less pronounced than
for 1, which is in agreement with the presence of only one
pyrrole ring conjugated with the BODIPY unit.
Results and Discussion
Synthesis and Spectroscopic Properties of the Receptors
Bis(calix[4]pyrrole) receptor 1 was prepared in 33% yield
by a Knoevenagel condensation of tetramethyl BODIPY 3
with two equivalents of calix[4]pyrrole-β-carbaldehyde 4 in
the presence of piperidine and acetic acid (Scheme 1). For
comparison purposes, the monosubstituted BODIPY deriv-
ative 2 was also synthesised in 34% yield from the conden-
sation of 3 with only one equivalent of 4. In both syntheses,
different amounts of the mono- or the disubstituted
BODIPY derivatives were also isolated as byproducts.
Compounds 1 and 2 were fully characterised by 1H and 13
C
Anion-Binding and Sensing Studies
NMR spectroscopy and HRMS. The C2-symmetric struc-
ture of 1 was confirmed by the reduced number of signals
The recognition and sensing properties of ditopic recep-
tor 1 towards dicarboxylate anions in solution were tested
with several aliphatic α,ω-dicarboxylates of different chain
lengths (C2, C5 and C7–C12) and with three aromatic
naphthalene dicarboxylates (N1–N3), all as their tetrabu-
tylammonium (TBA) salts (Figure 2). The acetate anion (as
its TBA salt) was also tested as a model of simple aliphatic
carboxylate anions.
1
present in the H and 13C NMR spectra.
Scheme 1. Synthesis of 1.
The spectroscopic properties of 1 and 2 in tetra-
hydrofuran (THF) were studied. Figure 1 depicts the ab-
sorption and normalised emission spectra of 1. The UV/Vis
spectrum of 1 shows an intense absorption band at λmax
=
Figure 2. The aliphatic and aromatic dicarboxylates used in this
study.
672 nm (ε = 1.09ϫ 105 cm–1 m–1) with a shoulder at 618 nm
that corresponds to the S0 Ǟ S1 (π–π*), (0–0) and (0–1)
transitions of the BODIPY chromophores and a weaker
The anion-binding ability of 1 in THF was evaluated by
broad band at around 350 nm that can be assigned to an UV/Vis titrations. Upon the addition of increasing concen-
S0 Ǟ S2 (π–π*) transition.[8] If we compare with the parent trations of the guest anions to a 10–5 m solution of receptor
BODIPY dye 3 (λabs = 500 nm in THF),[9] the absorption 1 in THF, the intensity of the main absorption band de-
band of 1 is redshifted by 172 nm. This can be attributed creased and it bathochromically shifted, most probably be-
to an increase in conjugation on grafting pyrrolvinyl moie- cause of an increase in the ICT process in the excited state.
ties at the 3,5 positions and to an intramolecular charge- For instance, in the titration of 1 with dicarboxylate C10
transfer contribution in the lower energy transition from (Figure 3) the intensity of the main peak at 672 nm grad-
the electron-rich conjugated pyrrole to the electron-with- ually diminished and a new peak corresponding to the host-
drawing BODIPY unit.[5b]
guest complex appeared at 704 nm. These changes in the
2
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Binding and Fluorescent Sensing of Dicarboxylates
UV/Vis spectra were accompanied by a slight change in the
This high association constant with C10 could be consis-
solution colour from green to greenish-blue, which was ob- tent with a cyclic 1:1 complex with both terminal carboxyl-
served by the naked eye.
ate groups of the guest dianion bound to both calixpyrrole
units of the receptor. It is quite likely that the length of this
dicarboxylate (ca. 11–12 Å in its extended conformation,
calculated by using molecular mechanics at the MM2 level)
would best fit the space between both calix[4]pyrroles. In
contrast, for shorter dicarboxylates, such as C2 or C5, their
small size would preclude or complicate the simultaneous
coordination of both calixpyrrole units to the guest.
Figure 5 shows the speciation diagrams of the LAx com-
plexes between 1 and different anions (C7, C10 and acetate)
as a function of anion concentration, calculated from the
titration curves by using the SPECFIT program.
Figure 3. UV/Vis titration of 1 in THF (1ϫ10–5 m) with increasing
amounts of C10 (0 to 5 equiv.).
The stoichiometries and the association constants of the
host–guest complexes of 1 with the different anions were
calculated from the titration curves by using the SPECFIT/
32 program.[11] The results are summarised in Table 1.
Table 1. Stoichiometries and binding constants (logβ) for receptor
1 with the TBA salts of dicarboxylate (and acetate) anions in THF
at 25 °C, calculated from UV/Vis titrations by using SPECFIT.
Anion (A)
LA complex
LA2 complex
C2
4.4Ϯ0.5
4.7Ϯ0.3
5.1Ϯ0.1
5.9Ϯ0.3
7.1Ϯ0.2
7.7Ϯ0.3
6.7Ϯ0.1
6.5Ϯ0.1
7.1Ϯ0.6
6.6Ϯ0.2
6.8Ϯ0.5
5.8Ϯ0.3
9.4Ϯ0.4
C5
10.5Ϯ0.1
10.7Ϯ0.1
11.8Ϯ0.4
13.1Ϯ0.2
13.9Ϯ0.4
12.8Ϯ0.1
12.8Ϯ0.1
12.4Ϯ0.6
12.1Ϯ0.2
11.8Ϯ0.5
11.1Ϯ0.2
C7
C8
C9
C10
C11
C12
N1
N2
N3
AcO–
When the association constants for the 1:1 complexes of
1 with the aliphatic dicarboxylates (C2–C12) were plotted
vs. the number of methylene groups in the chain (n), the Ka
values remarkably increased as chain length extended (see
Figure 4). This plot reached a maximum for the sebacic di-
anion, C10 (n = 8, logKa = 7.7), and then slowly decreased
again as the size of the dicarboxylate further enlarged.
Figure 5. Speciation distribution diagrams for the UV/Vis titrations
of 1 with (top) C7; (middle) C10 and (bottom) AcO–.
In all cases, 1:2 (receptor/carboxylate) binding stoichio-
metries dominated at high anion concentrations. However,
in the presence of 1 equiv. of the anion, the 1:1 complex was
by far the dominant species in solution for C10, whereas for
C7 or acetate anion, mixtures of 1:1 and 1:2 complexes and
free receptor were observed.
Furthermore, the relatively high values of the association
constants obtained for the 1:1 complexes between 1 and
the naphthalene dicarboxylate anions, as compared to those
obtained with aliphatic dicarboxylate anions of similar
Figure 4. Association constants (logK) for the 1:1 complexes be-
tween 1 and several aliphatic α,ω-dicarboxylates.
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R. Gotor, A. M. Costero, P. Gaviña, S. Gil, M. Parra
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lengths (C5–C8), could be due to the rigidity of the guest periment. Thus, the shifts were bigger for the sebacic di-
and to some additional stabilising effect involving the aro- anion (C10) than for acetate carboxylate (see Figure 6 for
matic rings. For instance, the logβ value of the 1:1 complex acetate and sebacic anions). For instance, the NH signals
between 1 and N3 (6.8) was two orders of magnitude higher were shifted by ca. 3 and 0.3 ppm when 1 equiv. of anion
than that of the 1:1 complex between 1 and C5 (4.7), even (C10 or AcO–) was added. The addition of 2 equiv. of acet-
though both dianions presented similar intercarboxylate ate caused a similar shift of the NH proton signals (up to
distances (ca. 5.3 Å).
0.7 ppm), whereas 4 equiv. of sebacic dicarboxylate (C10)
For comparison, we decided to use UV/Vis spectroscopy were required to reach a 4 ppm shift for the NH proton
to also study the binding properties of receptor 2, which signals. A less intense but similar behaviour was observed
has only one calix[4]pyrrole unit, towards two representa- for the shift in the olefinic and β-pyrrolic protons (shifts of
tive aliphatic dicarboxylates, C5 and C10. As observed for 0.02 ppm for 1 equiv. of acetate and ca. 0.2 ppm for 1 equiv.
receptor 1, the addition of the dicarboxylate to a THF solu- of sebacic anion). These data are consistent with the forma-
tion of 2 induced a redshift of the absorption band of ca. tion of a strong 1:1 complex in the case of the sebacic
18 nm and a change in the solution colour from bright pink anion.
to purple-blue. The association constant values (logKa) ob-
Very interesting results were obtained from the fluores-
tained for both 1:1 complexes in THF were similar cence measurements of receptor 1 in THF in the presence
(5.60Ϯ0.11 for C5 and 5.08Ϯ0.05 for C10). These values of increasing amounts of TBA dicarboxylate. The emission
are in the range of those obtained for the 1:1 complexes spectra of 1 in the presence of excess guest anions showed
between 1 and the shortest dicarboxylates (and also with significant changes. In all cases, the fluorescence emission
acetate), and are two orders of magnitude lower than the maxima shifted bathochromically upon the binding of the
association constant values of the complexes between 1 and carboxylate guest to the calixpyrrole receptor and its inten-
C9 or C10. This fact once again supports the cyclic struc- sity dramatically decreased at the same time. This strong
ture of the 1:1 complex between 1 and the longer dicarb- quenching of fluorescence upon coordination to the anions
oxylates and involves the simultaneous coordination of is in agreement with a PET process involving the coordi-
both terminal carboxylate moieties to both calixpyrrole nated pyrrole rings, as previously reported for other calix-
units.
[4]pyrrole-based fluorescent anion sensors, and the emission
To gain a better insight into the complexation event and maxima shift can be attributed to a change in the donor–
the structures of the complexes between 1 and some of the acceptor electronic properties of the molecule (an increase
1
dicarboxylates, NMR studies were undertaken. In the H in the ICT process as a result of the charge donation from
NMR titration experiments, the expected low-field shift of the carboxylate moieties). Figure 7 depicts an example of
the NH signals was observed as complexation occurred the fluorescence quenching of 1 (10–5 m in THF) in the pres-
(Figure 6). In addition, a shielding effect was noted on both ence of increasing amounts of C10 (the interaction between
the olefinic (Hc) and the β-pyrrolic (He) protons at δ = 7.1 1 and C10 is depicted in Figure 8). Upon the addition of
and 6.4 ppm, respectively. This is consistent with a higher 1 equiv. of C10, the intensity of the fluorescence emission
electron donation from the pyrrolic system to the BODIPY was quenched by ca. 80%, and this emission almost disap-
moiety.
peared (Ͻ 5%) in the presence of 1.8 equiv. of the anion.
Figure 7. The fluorescence emission spectra of 1 (10–5 m in THF;
λexc = 672 nm) in the presence of increasing amounts of C10 (0 to
5 equiv.).
The deconvolution of the emission spectra of 1 perfectly
fitted to two Gaussian bands centred at 697 and 730 nm
(Figure 9, top). These bands have been formerly assigned in
related BODIPY compounds to a locally excited state (LE)
Figure 6. 1H NMR spectra (selected regions) of (a) 1, (b) 1 +
1 equiv. of AcO–, (c) 1 + 2 equiv. of AcO–, (d) 1 + 1 equiv. of C10
and (e) 1 + 4 equiv. of C10.
In addition, clear differences in the 1H NMR spectra and a weakly emissive charge-transfer state (CT), respec-
were seen depending on the anion used in the titration ex- tively, which leads to a dual emission of the dye in polar
4
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Binding and Fluorescent Sensing of Dicarboxylates
Experimental Section
Materials and Methods: 1,3,5,7-Tetramethyl-8-phenylboron-dipyr-
romethene (BODIPY), 3[9] and meso-octamethylcalix[4]pyrrole
(OMCP)[12] were prepared according to the procedures described
in the literature. meso-Octamethylcalix[4]pyrrole-β-carbaldehyde
(4) was prepared by the direct formylation of OMCP with the
Vilsmeyer reagent.[13] The tetrabutylammonium (TBA) salts of the
different dicarboxylates were prepared by the addition of two
equivalents of TBA hydroxide to the corresponding dicarboxylic
acid in THF, followed by evaporation of the solvent. All TBA salts
were stored in a vacuum oven for at least 24 h prior to use. All
other reagents were commercially available and were used as re-
ceived. THF was distilled from Na/benzophenone prior to use. All
synthetic reactions were performed under an argon atmosphere and
by using standard techniques. Column chromatography was per-
formed with either silica gel 60 (230–400 mesh) or alumina (neutral,
70–290 mesh). 1H and 13C NMR spectra were recorded with a
Bruker DRX-500 spectrometer; the deuterated solvent signal was
used as the lock signal and the residual solvent signal was used
as the internal reference. High-resolution mass spectra (EI) were
recorded in the positive ion mode with a Shimadzu QP5050A in-
strument. Absorption spectra were recorded with a Shimadzu UV-
2101PC spectrophotometer with a 1 cm path length quartz cuvette.
Fluorescence spectra were recorded with a Varian Cary Eclipse
fluorescence spectrophotometer.
Figure 8. Simplified model of the interaction between 1 and C10
that leads to fluorescence quenching.
solvents such as THF.[9] After complexation, the LE state
can deactivate through both a nonradiative PET process
and an internal system crossing to the CT state. This
suggestion is in agreement with the observed behaviour, in
which the LE band decreased and the CT state became the
principal radiative relaxation pathway (Figure 9, bottom).
Compound 1: BODIPY derivative 3 (65 mg, 0.2 mmol) and the form-
ylcalixpyrrole derivative 4 (209 mg, 0.46 mmol) were dissolved in
toluene (30 mL) in a two-neck round-bottomed flask connected to
a Dean–Stark apparatus. Acetic acid (0.7 mL), piperidine (0.8 mL)
and a small amount of molecular sieves (3 Å) were added to the
solution, and the mixture was heated to reflux under Ar for 2 h.
At this time, TLC of the mixture showed the consumption of the
starting aldehyde. The reaction mixture was allowed to reach room
temperature, and the solvent was evaporated. The residue was dis-
solved in ethyl acetate, washed with 10% aq. NaHCO3 and then
dried with MgSO4. The solvent was evaporated, and the crude
product was purified by column chromatography on alumina (95:5
hexane/AcOEt as the eluent) to yield 1 (79 mg, 33%) as a turquoise
solid. 1H NMR (500 MHz, CD2Cl2): δ = 7.63 (d, J = 15.9 Hz, 2
H), 7.55–7.46 (m, 3 H), 7.39–7.32 (m, 2 H), 7.28 (s, 2 H), 7.22 (d,
J = 15.9 Hz, 2 H), 6.95 (s, 2 H), 6.90 (s, 2 H), 6.54 (s, 2 H), 6.40
(d, J = 2.9 Hz, 2 H), 5.96–5.93 (m, 4 H), 5.92 (t, J = 2.9 Hz, 4 H),
5.87 (t, J = 3.0 Hz, 2 H), 5.82 (t, J = 3.0 Hz, 2 H), 1.69 (s, 12 H),
Figure 9. Fit of the LE and CT band of the emission spectra of 1
(top) and 1 + 1 equiv. of C10 (bottom) in THF.
1.52 (s, 12 H), 1.51 (s, 12 H), 1.50 (s, 12 H), 1.44 (s, 6 H) ppm. 13
C
NMR (126 MHz, CD2Cl2): δ = 153.0, 141.3, 139.3, 138.9, 138.5,
138.2, 138.1, 137.60, 137.58, 137.4, 136.6, 135.45, 132.6, 131.9,
130.85, 128.9, 128.8, 128.7, 117.5, 116.95, 114.7, 103.6, 103.5,
102.85, 102.75, 102.5, 101.86, 37.4, 35.15, 35.1, 35.0, 29.5, 28.95,
28.41, 28.36, 14.25 ppm. HRMS (EI): calcd. for C77H88N10F2B [M
+ H]+ 1201.7249; found 1201.7235.
Conclusions
A ditopic receptor (1) consisting of a BODIPY dye elec-
tronically connected through an ethylenic bridge to two ca- Compound 2: A solution of BODIPY 3 (429 mg, 1.3 mmol) and
the formylcalixpyrrole derivative 4 (400 mg, 0.88 mmol) in toluene
(30 mL) was placed into a two-neck round-bottomed flask con-
nected to a Dean–Stark apparatus. Piperidine (2.8 mL), a catalytic
amount of p-toluenesulfonic acid and a few 3 Å molecular sieves
were added to the mixture, which was then heated to reflux under
argon for 2 h. The mixture was then allowed to reach room tem-
perature. It was then filtered, and the solvent was evaporated. The
residue was dissolved in ethyl acetate, washed with 10% NH4Cl
and dried with MgSO4. The crude product was purified by column
chromatography on silica gel (previously neutralised with Et3N)
with hexane/ethyl acetate (95:5 to 85:15) as the eluent to afford 2
lix[4]pyrrole coordinating units is able to bind aliphatic and
aromatic dicarboxylates of different chain lengths. This co-
ordination event is reflected by changes in the UV/Vis spec-
tra and by a strong quenching of the emission fluorescence
of the dye. The ditopic receptor shows a high affinity for
those α,ω-aliphatic dicarboxylates with 7 or 8 methylene
groups in the chain (C9 and C10), most probably because
of the formation of a cyclic 1:1 complex involving the simul-
taneous coordination of both carboxylate groups of the
guest to both calixpyrrole units of the host.
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as a deep blue solid (225 mg, 34%). The disubstituted BODIPY 1
(80 mg, 4%) was also recovered from the column. 1H NMR
(CD2Cl2, 500 MHz): δ = 7.70 (d, J = 15.7 Hz, 1 H), 7.57–7.52 (m,
3 H), 7.40–7.36 (m, 2 H), 7.31 (s, 1 H), 7.29 (s, 1 H), 7.20 (dd, J =
15.9 and 1.9 Hz, 1 H), 7.02 (s, 1 H), 6.95 (s, 1 H), 6.60 (s, 1 H),
6.39 (d, J = 2.9 Hz, 1 H), 6.04 (s, 1 H), 6.01–5.95 (m, 4 H), 5.91
(t, J = 3.0 Hz, 1 H), 5.87 (t, J = 3.0 Hz, 1 H), 2.58 (s, 3 H), 1.72
(s, 6 H), 1.57 (s, 6 H), 1.56 (s, 6 H), 1.55 (s, 6 H), 1.48 (s, 3 H),
1.44 (s, 3 H) ppm. 13C NMR (126 MHz, CD2Cl2): δ = 155.26,
152.42, 143.26, 140.83, 139.38, 139.07, 138.92, 138.67, 138.63,
138.27, 137.50, 137.47, 137.44, 135.21, 132.93, 132.31, 130.97,
129.01, 128.77, 128.43, 120.25, 117.42, 117.32, 114.12, 103.68,
103.66, 103.52, 102.83, 102.78, 102.47, 101.85, 37.45, 35.15, 35.08,
35.01, 30.57, 29.50, 28.95, 28.41, 28.35, 14.38, 14.27, 13.94 ppm.
HRMS (EI): calcd. for C48H54N6F2B [M + H]+ 763.4466; found
763.4439.
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UV/Vis and Fluorescence Titrations: UV/Vis and fluorescence ti-
trations were performed by adding anion aliquots [A/L (mol/mol):
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and 5.0] to the sensor solution (1ϫ10–5 m in THF). The volume
changes did not exceed 10%. The absorbance values were cor-
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stoichiometries with the Specfit computer program.
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Supporting Information (see footnote on the first page of this arti-
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emission quenching profiles for 1 in the presence of increasing
amounts of C7, N1 and acetate.
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Acknowledgments
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Received: November 9, 2012
Financial support from the Spanish Government (project
MAT2009-14564-C04-02) and from Generalitat Valenciana (project
PROMETEO/2009/095) is gratefully acknowledged. R. G. is grate-
ful to the Spanish Ministry of Education for an FPU grant. SCSIE
(Universidad de Valencia) is gratefully acknowledged for all of the
equipment employed.
Published Online: ᭿
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Eur. J. Org. Chem. 0000, 0–0

Job/Unit: O21504
/KAP1
Date: 29-01-13 16:31:53
Pages: 7
Binding and Fluorescent Sensing of Dicarboxylates
Fluorescent Probes
The bis(calix[4]pyrrole)-substituted BOD-
IPY ditopic receptor 1 shows high affinity
towards linear α,ω-dicarboxylates of ap-
propriate lengths. The binding event is de-
tected by a bathochromic shift in the UV/
Vis spectra of the receptor and by a strong
quenching of its fluorescence.
R. Gotor, A. M. Costero,* P. Gaviña,
S. Gil, M. Parra ............................... 1–7
Binding and Fluorescent Sensing of Di-
carboxylates by a Bis(calix[4]pyrrole)-Sub-
stituted BODIPY Dye
Keywords: Sensors / Fluorescent probes /
Dyes/pigments
Eur. J. Org. Chem. 0000, 0–0
© 0000 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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