New coumarin-corrole and -porphyrin conjugate multifunctional probes for anionic or cationic interactions: Synthesis, spectroscopy, and solid supported studies

Article abstract of DOI:10.1016/j.tet.2013.07.022

Corroles and porphyrins are very promising probes to be used as materials for anion and metal ion detection. Here, we present the synthesis and characterization of two new corrole-coumarin derivatives 7-8 and some porphyrin-coumarin analogs 3-6. The sensing ability of the metalloconjugates was studied in the presence of spherical (F^-, Cl^-), linear (CN^-), and bulky anions (CH₃COO^-). The porphyrin free-base conjugates were studied with Na⁺, Ca ²⁺, Zn²⁺, Cd²⁺, Pb²⁺, Fe ²⁺, Ba²⁺, Cu²⁺, Ag⁺, and Hg ²⁺, showing a colorimetric effect (color change from purple to yellow) and an unprecedented selectivity for Hg²⁺. The insertion of coumarin moiety confers an unusual solubility of these conjugates in ethanol. One of the porphyrin free-base conjugate was fully studied in a mixture EtOH/H₂O (50:50) and showed a similar behavior with Hg²⁺. Under these conditions, the conjugate presented a higher association constant than in toluene and was able to detect and quantify a minimal amount of 0.6 ppm and 1.2 ppm of Hg²⁺, respectively. Having in mind the biological and environmental application of these conjugates, non-expensive solid supports, like agarose and natural cellulose polymers were developed. In the cellulose support material (filter paper) the colorimetric effect for Hg²⁺ reveals a similar behavior as in solution. In addition pH studies carried out with the same conjugate showed a green color at low pH and a yellow color at high pH values in solution and in solid supports.

Full text of DOI:10.1016/j.tet.2013.07.022

Tetrahedron xxx (2013) 1e10
Contents lists available at SciVerse ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
New coumarinecorrole and eporphyrin conjugate multifunctional
probes for anionic or cationic interactions: synthesis, spectroscopy,
and solid supported studies
,
c
,
y
d
a,
Carla I.M. Santos a, Elisabete Oliveira b , Jose C.J.M.D.S. Menezes y, Joana F.B. Barata a,
ꢀ
ꢀ
a
a
a,
*
M.Amparo F. Faustino , Vitor F. Ferreira , Jose A.S. Cavaleiro , M.Grac¸ a P.M.S. Neves
,
,
Carlos Lodeiro b
*
a Chemistry Department and QOPNA, University of Aveiro, 3810-193 Aveiro, Portugal
b BIOSCOPE Group, REQUIMTE-CQFB, Chemistry Department, Faculty of Science and Technology, University Nova of Lisbon, 2829-516 Monte de
Caparica, Portugal
c
ꢀ
Veterinary Science Department and CECAV, University of Tras-os-Montes and Alto Douro, 5001-801 Vila Real, Portugal
d
^
ꢀ
Instituto de Química, Departamento de Química Organica, Universidade Federal Fluminense, 24020-150 Niteroi-RJ, Brazil
a r t i c l e i n f o
a b s t r a c t
Article history:
Corroles and porphyrins are very promising probes to be used as materials for anion and metal ion
detection. Here, we present the synthesis and characterization of two new corroleecoumarin derivatives
7e8 and some porphyrinecoumarin analogs 3e6.
Received 14 May 2013
Received in revised form 2 July 2013
Accepted 8 July 2013
Available online xxx
The sensing ability of the metalloconjugates was studied in the presence of spherical (Fꢀ, Clꢀ), linear (CNꢀ),
and bulky anions (CH3COOꢀ). The porphyrin free-base conjugates were studied with Naþ, Ca2þ, Zn2þ, Cd2þ
,
Pb2þ, Fe2þ, Ba2þ, Cu2þ, Agþ, and Hg2þ, showing a colorimetric effect (color change from purple to yellow)
and an unprecedented selectivity for Hg2þ
Keywords:
Corroles
Porphyrins
Coumarins
Chemosensors
Mercury
.
The insertion of coumarin moiety confers an unusual solubility of these conjugates in ethanol. One of the
porphyrin free-base conjugate was fully studied in a mixture EtOH/H2O (50:50) and showed a similar
behavior with Hg2þ. Under these conditions, the conjugate presented a higher association constant than
in toluene and was able to detect and quantify a minimal amount of 0.6 ppm and 1.2 ppm of Hg2þ
,
Fluoride
Cyanide
Acetate ion
Agarose
Cellulose
respectively. Having in mind the biological and environmental application of these conjugates, non-
expensive solid supports, like agarose and natural cellulose polymers were developed. In the cellulose
support material (filter paper) the colorimetric effect for Hg2þ reveals a similar behavior as in solution.
In addition pH studies carried out with the same conjugate showed a green color at low pH and a yellow
color at high pH values in solution and in solid supports.
Ó 2013 Elsevier Ltd. All rights reserved.
1. Introduction
excellent method to develop ion-selective electrode and optical
sensor devices.8
Corroles and porphyrins are excellent candidates for a great
variety of sensing material applications. Chemosensors based on
these tetrapyrrolic macrocycles are being pursued as active mate-
rials owing to their large absorption coefficient and well tunable
fluorescence emission.1e6
In particular, optical sensors based on porphyrinic complexes of
Zn(II), Cd(II), and Hg(II) with amide functionality have shown
higher anion binding abilities in more competitive solvent medium
than those with metals like Fe(III), Co(III), Ni(II), and Cu(II).9 For
instance, a cage receptor based on tetra-triazole Zn(II) metal-
Porphyrin combined with other classes of molecules have been
used as fluorophores in the detection of heavy metals like Cd(II),
Pb(II), and Hg(II).7 Also, metalloporphyrins, depending on the metal
ion incorporated into the inner core of the complex, offer an
loporphyrin shows a naked-eye colorimetric response when
strongly bound to anions.10 Also, a Zn(II)eporphyrin bearing
naphthalimide or aza-crown ether-capped moieties created a fluo-
ride ion-triggered dual fluorescence molecular switch,11 or color
change in the presence of sodium cyanide.12
In the case of corroles, these macrocycles coordinate with a large
number of metals,13 and are very promising materials for optical
and sensing applications.14 Although a few number of free-base
corroles or their derivatives are being explored as selective
* Corresponding authors. Tel.: þ351 212948550; fax: þ351 212948300; e-mail
addresses: gneves@ua.pt (M.G.P.M.S. Neves), cle@fct.unl.pt (C. Lodeiro).
y
E. Oliveira and J. C. J. M. D. S. Menezes contributed equally to this work.
0040-4020/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tet.2013.07.022
Please cite this article in press as: Santos, C. I.M.; et al., Tetrahedron (2013), http://dx.doi.org/10.1016/j.tet.2013.07.022

2
C.I.M. Santos et al. / Tetrahedron xxx (2013) 1e10
sensors for Hg(II) ion,5,15 the Ga(III) complex is presently a selective
sensor for Fꢀ and CNꢀ ions,6 which empowers newer corrole de-
rivatives to be explored as sensors for anion selectivity.
A good fluorescent chemosensor must have a strong affinity and
selectivity for the analyte, no environmental interferences with the
fluorescence signal, and it must be photostable. It should also be
Recently we reported the hetero DielseAlder reaction of 2-
vinyl-5,10,15,20-tetraphenylporphyrinatozinc(II) 1a with o-qui-
none methides (o-QM) generated in situ from Knoevenagel re-
action of 4-hydroxycoumarin or 4-hydroxy-6-methylcoumarin
with paraformaldehyde that afforded, respectively, derivatives 3
and 4 (Scheme 1).30
O
5'
7'
O
8'
4'
a
b
R1
3'
10'
O
Ph
Ph
R
1'
1
N
N
N
N
N
N
N
o-QM
M
Ph
Ph
Zn
Ph
Ph
5
N
10 Ph
Ph
3 (88%) M = Zn; R1 = H
1a; R = CH=CH2
1b; R = H
4 (95%) M = Zn; R1 = CH3
5% TFA/
CHCl3
5 (97%) M = 2H; R1 = H
6 (92%) M = 2H; R1 = CH3
Scheme 1. Functionalization of 1a with coumarin units.30
easily accessible by organic reactions and be robust in nature. A
good strategy to develop new probes or chemosensors is the cou-
pling of two different molecules with well-established sensory
activities.
Coumarin derivatives have been utilized as sensors for
Hg(II),16e18 Fꢀ,19e23 and CNꢀ24,25 ions either in organic solvents or
aqueous mixtures at biological pH.
The inclusion of the coumarin nucleus in the porphyrin or cor-
role frameworks can enhance the fluorescence emission and fur-
nish better solubility in aqueous medium. It is reported that
coumarins transfer energy to the porphyrin molecule and increase
the fluorescence lifetimes.26,27 Similarly, corroles coumarin dyads
also have shown efficient energy transfer from the coumarin moi-
ety to corrole.28,29
Using this methodology we were able to functionalize
5,10,15,20-tetraphenylporphyrinatozinc(II) 1b at the -pyrrolic
position with coumarin units. Thus, using similar approach we
envisaged the design of corroles with coumarin moieties from the
recently developed gallium(III) complex of 3-vinyl-5,10,15-
tris(pentafluorophenyl)corrole 2.6
Following our interest, in the development of sensing mate-
rials,31 we synthesized the new corroleecoumarin derivatives 7
and 8 (Scheme 2). The photophysical characterizations of com-
pounds 3e6 and 7e8 were also carried out.
b
The sensing ability of the metalloconjugates towards the
spherical halide ions Fꢀ, Clꢀ, the linear anion CNꢀ, and the bulky
anion CH3COOꢀ was evaluated. Interaction studies of the porphy-
rins 5 and 6 with the metal ions Naþ, Ca2þ, Ba2þ, Fe2þ, Cd2þ, Cu2þ
,
OH
R1
HCHO
O
O
O
4'
5O'
3'
O
O
1
R1
7'
8'
1O'
N
N
N
Ga
Py N
N
N
N
Ga
Py N
5
O
C6F5
10'
C6F5
C6F5
C6F5
R1
Dioxane, Reflux
10
C6F5
C6F5
7 (92%) R1 = H
2
8 (87%) R1 = CH3
Scheme 2. Synthesis of corrole coumarin ligands 7 and 8.
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C.I.M. Santos et al. / Tetrahedron xxx (2013) 1e10
3
Pb2þ, Hg2þ, Zn2þ, Agþ were realized. Additionally, pH studies were
Table 1
Photophysical data of compounds 3e8 in toluene at 298 K
also performed with these two free-base porphyrins (5 and 6).
Considering the environmental monitoring of heavy metals7
and pH32 the potential of compound 5 was tested using non-
expensive natural solid supports, with simple fabrication and
handling towards Hg(II) and pH studies. The polymeric materials
selected were agarose33 used in gel electrophoresis, and cellulose.
Also, the use of these compounds for on-site Hg(II) detection, was
carried out by immersing a filter paper in the compound solution
and drying in air.
Compds.
lmax (nm):log ε
lem (nm)
Stoke’s
F
shift (nm)
3
4
5
426:5.23; 565:3.95; 599:3.21
426:5.28; 560:4.15; 599:3.31
421:5.32; 523:4.15; 557:3.85;
603:3.78; 652:3.56
599,646
599,646
652,719
47
47
67
0.02
0.01
0.02
6
420:5.38; 519:4.15; 560:3.86;
607:3.72; 652:3.40
652,713
61
0.02
7
8
427:5.51; 580:4.30; 601:3.81
426:5.53; 582:4.27; 601:3.76
602,650
602,651
48
49
0.06
0.09
2. Results and discussion
2.1. Synthesis
between 423 and 426 nm (due to the allowed transition from
S0/S2) and two weak Q bands (due to the transition from S0/S1)
at ca. 560e565 and 599 nm. The free-base derivatives 5 and 6 ex-
hibit the Soret band between 417 and 424 nm and four Q bands
centered between 519 and 654 nm. The absorption spectra of cor-
roles 7 and 8 present the Soret-type band between 426 and 430 nm
and two Q bands at ca. 580 and 603 nm except for compound 8 in
DMSO. In the case of compound 8 a bathochromic shift was visu-
alized with polarity increase, being the absorbance band centered
at ca. 582 nm (toluene)<585 nm (CH2Cl2)<587 nm (EtOH)<605 nm
(DMSO). This positive solvatochromic effect can be detected by
naked eye for compound 8, which shows different colors in dif-
ferent solvents (colorless; yellow and purpledFig. 1).
The synthetic strategy to obtain the new corroleecoumarin
conjugates 7 and 8 is shown in Scheme 2. The gallium(III) complex
of 3-vinyl-5,10,15-tris(pentafluorophenyl)corrole 2 was reacted
with the o-quinone methides, generated in situ from ca. 1.4 equiv of
4-hydroxycoumarins and 11 equiv of paraformaldehyde, under
reflux in 1,4-dioxane. The reaction of vinyl corrole 2 showed com-
plete consumption in 1 h (TLC) and after the workup and pre-
parative purification the adducts 7 (92% yield) and 8 (87% yield)
were isolated. The structures of these corroleecoumarin conjugates
were confirmed by NMR (1D and 2D), UVevis, and high resolution
mass spectrometry. In particular, from the analysis of 1H NMR
spectra of 7 (for numbering see Scheme 2) it was possible to assign,
the four multiplets between
protons of the dihydropyran ring and the double doublet at
to the H-20 proton (this feature is due to the non-equivalence of H-
30 protons). In the aromatic region, the multiplet at
7.19e7.24 was
assigned to the H-90 of coumarin nucleus, the ones at
7.38e7.42
and
7.66e7.68 to H-70 and H-80, respectively, and finally the
doublet at
7.84 to H-100. The beta substitution pattern of the
corrole nucleus was confirmed by the presence of the singlet at
9.40 due to H-2 proton resonance. The analysis of the 13C NMR
spectrum of 7 showed the signal at 163.2 and 75 assigned to the
d
2.65 and 3.02 to the H-30 and H-40
5.83
d
d
d
d
d
d
d
d
coumarin carbonyl (C50) and C20, respectively, which is in accor-
dance with the proposed structure; this shows that the addition
occurred selectively at the 3,4-position of the coumarin nucleus.30
In the 1H NMR spectrum of compound 8, the presence of the methyl
group on the coumarin moiety was confirmed by the appearance of
a singlet at
d 2.27.
Fig. 1. Solvatochromic effect of compound 8.
Similarly, the reaction of 2-vinyl-5,10,15,20-tetraphenylporphyri
natozinc(II) (1a) with the o-quinone methide, generated in situ
from 4-hydroxycoumarins and paraformaldehyde afforded the
porphyrinecoumarin conjugates 3 (88% yield) and 4 (95% yield).30
The decomplexation of porphyrinecoumarin conjugates 3 and 4 in
5% TFA/CHCl3 gave the corresponding free-bases 5 (97% yield) and 6
(92% yield). The structures of these coumarin conjugates were
confirmed by NMR, UVevis, and high resolution mass spectrome-
try. The NMR profile of the free-bases was similar to the metal-
loporphyrinic forms. The presence of the inner NeH of the
In order to characterize quantitatively this soluteesolvent in-
teraction the multiparametric fitting of KamleteTaft equation34
was realized by using of solvent parameters gathered in Table
SN2. Through this fitting a liner plot of nexp versus ncalcd was de-
termined for compound 8, being the fitted parameters
n0¼17,887 cmꢀ1, a¼ꢀ2274 cmꢀ1, b¼2156 cmꢀ1, and p¼ꢀ2283 cmꢀ1
with a correlation factor of 1. The negative value of p shows that the
contribution of dipolarity/polarizability decreases the stabilization
macrocycle at
d
ꢀ2.69 confirmed the success of the metal removal.
of the excited state in compound 8. The ground (mg) and excited (me
states dipole moments were estimated based on Kawski theory,35,36
whereas, a linear curve fitting of na nf and na nf as a function of
f(ε,n) and f(ε,n)þ2g(n). Values of mg¼0.42 D and me¼0.15 D were
determined, which indicate that in compound 8, the ground state is
slightly more polar than the excited state.
Fig. 2 shows the absorption (only Q band region), excitation, and
emission spectra, of compound 3 (Fig. 2A) as an example of met-
alloporphyrin series and of compound 7 (Fig. 2B) as an example of
the corrole series.
The perfect match between the absorption and excitation
spectra in Fig. 3, indicates the absence of any emissive impurity in
all cases.
)
2.2. Photophysical studies
ꢀ
þ
The photophysical characterization of compounds 3 to 8 were
performed in dichloromethane, DMSO, toluene, and ethanol solu-
tions at 298 K. Compound 5 was characterized in the solvents re-
ferred above and also in a mixture of ethanol/water (50:50). In
Table 1, the main photophysical data for all compounds in toluene
are reported and the results obtained in the other solvents are
presented in Supplementary data (Table SN1).
In toluene and in the other solvents, the absorption spectra of
the metalloporphyrin conjugates 3 and 4 showed the Soret band
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4
C.I.M. Santos et al. / Tetrahedron xxx (2013) 1e10
I
norm/a.u.
I
norm/a.u.
0.25
A
0.4
A
Abs
1
1
Emiss
Abs
Emiss
Exct
0.2
0.15
0.1
Exct
0.3
0.2
0.1
0
0.8
0.6
0.4
0.2
0
0.8
0.6
0.4
0.2
0
A
0.05
B
0
500
550
600
650
700
500
550
600
650
700
Wavelength/nm
Wavelength/nm
Fig. 2. Absorption, normalized emission and excitation spectra of porphyrin 3 (A) and corrole 7 (B) in toluene, ([3]¼[7]¼5.0ꢁ10ꢀ6 M, lexc (full line)3¼565 nm, lexc (full line)7¼580 nm
and lemiss
¼646 nm lemiss
¼650 nm).
(dotted line)7
(dotted line)3
Inorm/a.u.
I
norm/a.u.
I norm. /a.u.
I norm. /a.u.
1
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
0
1
0.8
0.6
0.4
0.2
646 nm
599 nm
0.8
0.6
0.4
0.2
0
602 nm
1.5
0
0 0.5 1 1.5 2 2.5 3 3.5
[Cl-]/[3]
0
0.5
1
2
[F-] / [7]
B
A
580 600 620 640 660 680 700
Wavelength/nm
600
650
700
750
800
Wavelength/nm
Fig. 3. Spectrofluorimetric titrations of compound 3 (A) and 7 (B) with the addition of Clꢀ and Fꢀ in toluene at room temperature. ([3]¼[7]¼1.0ꢁ10ꢀ5 M, lexc. ¼565 nm, lexc.
3
¼580 nm).
7
The fluorescence emission spectra of zinc porphyrins 3 and 4
obtained after excitation at ca. 560e565 nm, present two bands
centered at 599 and 646 nm that are characteristic of metal-
loporphyrins derivatives (see Table 1 and Table SN1). Otherwise,
the excitation of 5 and 6 at ca. 605 nm afforded two emission bands,
one centered at ca. 652 nm and the other between 713 and 719 nm.
In the case of corrole derivatives 7 and 8 the emission bands are
centered between 602 nm and 652 nm.
As can been seen in Table 1 and SN1, the excited state of
conjugates 3e7 are not affected by the dipole moment of the sol-
vent. The fluorescence quantum yields of porphyrin and corrole
derivatives were determined by the internal reference method with
respect to a solution of crystal violet in methanol as a standard
([ɸ]¼0.54) and the values are presented in Table 1 and Table SN1.
The fluorescence quantum yields of porphyrinic conjugates 3e6
(0.01<ɸ<0.03) are relatively lower than those obtained with the
corrole derivatives (0.04<ɸ<0.13), being the highest value de-
termined for compound 8 in an ethanolic solution. This behavior
can be due to the inherent differences of the tetrapyrrolic macro-
cycle.37 On the other hand, a better solubility conferred by the
coumarin unit to corrole may favor the decay of excited molecules
by fluorescence in ethanol.
of sensing material applications. These molecules are rather stable
compounds and their properties can be finely tuned by simple
modifications of their basic molecular structure. These macrocycles
offer a large variety of interaction mechanisms that can be exploi-
ted for chemical sensing. Hydrogen bonds, polarization, and po-
larity interactions are expected to take place between analyte
molecules and these tetrapyrrolic macrocycles.
For these reasons it was decided to study the potentialities of
these macrocycles in conjunction with coumarins in the signaling
of different anions and metals. The measurement of sensory activity
is generally undertaken in purely organic solvents or less efficiently
in aqueous mixtures. The combination of the corrole or porphyrin
macrocycles with coumarin moiety, conferred solubility to all
synthesized compounds in ethanol and in ethanol/water mixtures.
This fact also prompted us to perform pH sensing studies.
2.3.1. Anion sensing effects. The sensorial ability of metal-
locompounds 3, 4, 7, and 8 towards the spherical (Fꢀ, Clꢀ), linear
(CNꢀ), and bulky anions (CH3COOꢀ) was carried out by ligand ti-
trations with the addition of small amounts of the adequate anion
as tetrabutylammonium salt.
The titrations were followed by UVevis and fluorescence mea-
surements in toluene and the most significant data are gathered in
Table 2.
2.3. Spectrophotometric and spectrofluorimetric sensing
studies
Fluoride ion is added in drinking water and dental hygiene
products for the purpose of reducing the frequency of dental
caries. However, its ingestion in high or in low levels may result in
fluorosis, nephrotoxic changes, and urolithiasis in human.38 The
Corroles, porphyrins, and metalloporphyrins as it was already
referred are excellent multifunctional candidates for a great variety
Please cite this article in press as: Santos, C. I.M.; et al., Tetrahedron (2013), http://dx.doi.org/10.1016/j.tet.2013.07.022

C.I.M. Santos et al. / Tetrahedron xxx (2013) 1e10
5
Table 2
determined for compound 3 and 7, respectively. Similar in-
teractions were found for compounds 4 and 8.
Association constants of conjugates 3, 4, 7, and 8 in toluene
On the other hand, cyanide is one of the most poisonous and
toxic anions. It is a lethal anion for humans, as well as for aquatic
life.43 Most environmental cyanides are released by industries
involved in gold mining, electroplating, and metallurgy.44 Due to
its high toxicity, the highest allowable level of cyanide in
drinking water by the World Health Organization (WHO) is
Compound
Analyte (A)
Log Kass (A:L)
3
Clꢀ
5.43ꢂ0.03 (1:1)
6.57ꢂ0.01 (1:1)
4.87ꢂ0.02 (1:1)
5.40ꢂ0.03 (1:1)
6.53ꢂ0.01 (1:1)
4.85ꢂ0.02 (1:1)
5.28ꢂ0.01 (1:1)
6.11ꢂ0.01 (1:1)
4.32ꢂ0.01 (1:1)
5.04ꢂ0.01 (1:1)
6.08ꢂ0.01 (1:1)
4.11ꢂ0.01 (1:1)
CNꢀ
CH3COOꢀ
Clꢀ
4
7
8
CNꢀ
CH3COOꢀ
Fꢀ
1.9
m
M.45
The cyanide anion interacts with all metallocorroles and met-
CNꢀ
CH3COOꢀ
Fꢀ
alloporphyrins conjugates. The addition of CNꢀ to 3 promotes in
the absorption spectrum (Fig. SN1A) a small red-shift from 426 to
429 nm (Dl¼3 nm), accompanied by an increase of ca. 40% in the
band at 429 nm. An isosbestic point at 427 nm was also observed. A
similar behavior was observed in the case of Q-bands. Initially
there was a decrease in the intensity of the band centered at
550 nm, and an increase at 573 nm, with an isosbestic point at
560 nm. A new band appears at 600 nm (Fig. SN1B). Considering
the emission spectrum of 3 (Fig. 4A), the titration with CNꢀ was
responsible for a decrease of intensity of ca. 60% at 599 nm and also
at 646 nm (ca. 80%), followed by a red-shift from 599 to 605 nm
and from 646 to 656 nm. Similar spectral modifications were also
observed in compound 4.
CNꢀ
CH3COOꢀ
fluoride anion is known to be used in many industrial applications,
and in human diet, but, recently it has been accused for several
human pathologies (osteoporosis and poor dental health).39 The
EPA-recommended Fꢀ level in drinking water is 1 ppm, and over
2 ppm is considered a health-risk.40 The chloride ion has significant
role in biological, medical and environmental fields. The addition of
Clꢀ to chemosensors 3 and 4 was responsible for mild alterations in
their emission spectra. No spectral alterations were detected in
I
norm. /a.u.
1
I norm. /a.u.
I
/a.u.
I norm. /a.u.
1
0.8
1
0.8
0.6
0.4
0.2
0
1
599 nm
646 nm
601 nm
613 nm
0.8
0.6
0.4
0.2
0
0.8
0.6
0.4
0.2
0
0.6
0.4
0.2
0
0 0.5 1 1.5 2 2.5 3 3.5
[CN ] / [3]
0
0.5
1
1.5
2
[CN-]/[7]
B
A
580 600 620 640 660 680 700
Wavelength/nm
600
640
680
720
Wavelength/nm
Fig. 4. Spectrofluorimetric (A, B) titrations of compounds 3 and 7, in toluene, with the addition of CNꢀ in DMSO. The insets show the normalized emission intensity at 599 and
646 nm (A) and at 601 and 613 nm (B) ([3]¼[7]¼1.0ꢁ10ꢀ5 M, lexc. ¼565 nm, lexc. ¼580 nm, T¼278 K).
3
7
their absorption spectra, suggesting that their ground state is not
affected by the interaction with this spherical halide ion. Fig. 3A
shows the spectral changes, in the excited state, obtained for
compound 3 during the titration with Clꢀ. This addition leads to an
emission quenching of ca. 40% at 599 and of ca. 60% at 646 nm,
followed by a red-shift from 599 to 605 nm and from 646 to
656 nm. A similar spectral behavior was obtained for compound 4.
Considering the addition of Fꢀ to these two chromophores 3 and 4
no significant spectral changes were detected. In the case of corrole
conjugates 7 and 8 no spectral modifications were observed, in the
ground state, during the titrations with these anions and in the
excited state with Clꢀ. However, the titrations of these compounds
with Fꢀ were responsible for a quenching of ca. 40% at 602 nm.
Fig. 3B, shows the spectrofluorimetric titration of compound 7, in
toluene, in the presence of Fꢀ. Similar spectral changes were
detected for compound 8 with the addition of fluoride.
In the presence of CNꢀ, compounds 7 and 8, undergo strong
changes in the ground state. The addition of the anion produces
a decrease in the intensity of the initial bands centered at ca.
580 nm and 601 nm, with the concomitant appearance of two new
bands centered at 588 nm and 613 nm. Two isosbestic points were
detected at 586 nm and 607 nm (Fig. SN1C). Taking into account the
emission spectra (excited state), a quenching of ca. 40% at 601 nm
was observed (Fig. 4B) followed by a red-shift of 12 nm.
With respect to the association constants a value of Log
Kass.¼6.57ꢂ0.01 (1:1) and of Log Kass.¼6.11ꢂ0.01 (1:1) were de-
termined for compound 3 and 7, respectively (Table 2).
Compounds 3, 4, and 7, 8 were titrated with the acetate anion
(CH3COOꢀ), and spectral changes in the ground and excited state
were observed, in both macrocycles. In compound 3, like in 4, a red-
shift in the absorption spectra from 426 nm to 430 nm, as well as,
an emission quenching of ca. 80% at 599 nm and 646 nm, was
observed, with the addition of 1 equiv of the anion (see Fig. SN2).
With respect to the interaction of compound 7 and 8 with acetate
a similar behavior to the one observed for cyanide was found (see
Fig. SN3). An association constant of Log Kass.¼4.87ꢂ0.02 and of Log
Kass.¼4.32ꢂ0.01, with a stoichiometry of one ligand per anion was
determined for compounds 3 and 7, respectively. Similar in-
teractions were found for compounds 4 and 8.
The association constants for the interaction of Fꢀ and Clꢀ with
the different ligands were determined using the HypSpec41 pro-
gram and are summarized in Table 2.
Looking at Table 2, for the anions chloride and fluoride a stoi-
chiometry of one ligand per anion was postulated, and was con-
firmed by Job’s plot method (SI).42 Thus, a value of Log Kass.
¼5.43ꢂ0.03 (1:1); and of Log Kꢀass. ¼5.28ꢂ0.01 (1:1), were
ꢀ
Cl
F
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6
C.I.M. Santos et al. / Tetrahedron xxx (2013) 1e10
It is to be noted that the sensing ability of porphyrin precursor
1b was also evaluated for all the anions and under the experimental
conditions used, no changes in the ground and excited states were
observed (see Fig SN4). These results are in accordance with
literature.9
Additionally, the detection (LOD) and quantification (LOQ) limits
for the anions studied were determined and the values gathered in
Table 3 show that the lowest values for LOD (0.09 and 0.10 ppm)
and LOQ (0.18 and 0.19) were obtained for compound 3 and 4, re-
spectively, with the addition of chloride anion.
Table 3
Detection (LOD) and quantification (LOQ) limits of conjugates 3, 4, 7, and 8 in toluene
Compound
Analyte (A)
LOD (ppm)
LOQ (ppm)
3
Clꢀ
0.09
0.13
0.20
0.10
0.13
0.21
0.52
0.18
0.40
0.50
0.19
0.41
0.18
0.27
0.40
0.19
0.27
0.42
0.87
0.27
0.60
0.85
0.28
0.62
CNꢀ
CH3COOꢀ
Clꢀ
4
7
8
CNꢀ
CH3COOꢀ
Fꢀ
CNꢀ
CH3COOꢀ
Fꢀ
CNꢀ
CH3COOꢀ
2.3.2. Metal sensing effects. The sensorial ability of compounds 5
and 6 towards the metal ions Naþ, Ca2þ, Zn2þ, Cd2þ, Pb2þ, Fe2þ, Ba2þ
,
Cu2þ, Agþ, and Hg2þ was investigated by the titration of the ligands,
dissolved in toluene, with small amounts of the adequate metal salt
dissolved in acetonitrile. These experiments were followed by UV/
vis and fluorescence emission spectroscopy. It is worth to refer that,
mercury ions are environmentally toxic ions and are responsible for
pollution and adverse effects to human health.46
Fig. 5. Spectrophotometric (A and B) and spectrofluorimetric (C) titration of com-
pound 5 with the addition of Hg2þ in toluene. The inset represents the absorption (A,
B) at 421 nm, 434 nm for (A) and 520 nm for (B); and represents the emission intensity
(C) at 654 and 714 nm, as function of [Hg2þ]/[5]. ([5]¼1ꢁ10ꢀ5 M, lexc¼592 nm,
T¼298 K).
In these conditions, only the Hg(II) cation caused significant
changes in the ground and excited states of porphyrins 5 and 6. No
changes were detected upon addition of the other metal ions to the
derivatives 5 and 6. Fig. 5A, B and C shows the alterations observed
in the absorption and emission spectra of compound 5 with the
increasing addition of Hg2þ, in toluene.
I norm. /a.u.
I norm. /a.u.
1.2
In the absorption spectra, the addition of Hg2þ to 5 results in
a decrease in the band at 421 nm and an increase at 434 nm. A
colorimetric effect was observed (a change of color from purple to
yellow), which allows a naked-eye detection of Hg2þ (see Fig. 5A).
In the emission spectra a quenching in the emission intensity at
654 nm was visualized (Fig. 5C). The association constant was de-
1.2
5
654 nm
654 nm
a
b
1
c
d
e
f
g
0.9
0.6
0.3
0
0.8
0.6
0.4
0.2
0
termined by HypSpec program and the value of Log Kass.
2þ
¼5.51ꢂ0.01, was obtained with a stoichiometry of one ligands
Hg
d
g
a
e
f
c
5h
h
per one metal ion.
b
Compound 5 was also titrated with Hg2þ in a mixture of EtOH/
H2O (50:50), and in the emission spectra (see Fig. SN5B) a similar
behavior, to the one found in toluene was detected. In the ground
state a slight decrease in the absorbance at 421 nm was observed
(see Fig. SN5A). A higher association constant for Hg2þ was ob-
tained for EtOH/H2O with respect to toluene, yielding a value of Log
Kass.¼7.13ꢂ0.01. At 654 nm the detection (LOD) and quantification
(LOQ) limits were of 1.05ꢂ0.11 and 1.31ꢂ0.40, respectively. Thus,
the minimal amount of Hg2þ detectable in an aqueous solution
(EtOH/H2O/50:50) by compound 5 was 0.6 ppm and the minimal
amount quantified was 1.2 ppm.
[5] vs [Mn+]
Fig. 6. Black bar: normalized relative emission intensity of compound 5 upon the
addition of 2 equiv of a (Naþ), b (Ca2þ), c (Zn2þ), d (Cd2þ), e (Pb2þ), f (Fe2þ), g (Agþ) and
h (Hg2þ). Red bar: normalized emission intensity of 5 with Hg2þ upon addition of
100 equiv of the metal ions a to g. ([5]¼1ꢁ10ꢀ5 M, lexc¼603 nm).
2.3.3. Solid supports and pH studies. Several pH studies with
compound 5 were carried out in mixtures of ethanol/water (50:50).
Fig. SN6 shows the absorption spectra of compound 5 at different
pH’s. Compound 5 behaves as a colorimetric sensor with the change
in pH. Increasing the pH, compound 5 change its color from green
(low pH) to yellow (high pH) (see Fig. 7A). This behavior is typical
of meso-tetraarylporphyrins like 5,10,15,20-tetraphenylporphyrin
In competitive studies with compound 5 in toluene a higher
affinity and an unprecedented selectivity for Hg2þ metal was seen
(Fig. 6), where a normalized emission intensity towards the addi-
tion of 2 equiv of metal ions studied is showed. A similar conduct
was observed during the titrations with compound 6.
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C.I.M. Santos et al. / Tetrahedron xxx (2013) 1e10
7
This emission quenching in solid state was monitored using a fiber
optic system and the results are presented in Fig. 8A.
3. Conclusions
New corroleecoumarin derivatives 7 and 8, and the porphyr-
inecoumarin conjugates 3e6 were successfully obtained and fully
characterized. The compounds were photophysically characterized
in dichloromethane, DMSO, toluene, and ethanol. Compound 8 is
slightly more polar in the ground state (mg¼0.42 D) than in the
excited state (me¼0.15 D), showing a positive solvatochromic effect,
while the other conjugates were practically not affected by the
solvent. A strong color change from purple to yellow (colorimetric
effect) and an unprecedented selectivity for Hg2þ was detected for
compound 5 in EtOH/H2O (50:50); the association constant in
Fig. 7. A. Color change (from green to yellow) at different pH, of compound 5 in EtOH/
H2O (50:50). B. Agarose gel doped with compound 5 exposed at different pH (from pH
0.8e12).
EtOH/H2O (50:50) was higher than in toluene (Log Kass.
EtOH/
¼7.13ꢂ0.01; Log Kass.
¼5.51ꢂ0.01). In addition, com-
water
toluene
pound 5 was able to detect and quantify the minimal amount of
0.6 ppm and 1.2 ppm of Hg2þ in aqueous solution (EtOH/H2O,
50:50).
(the free-base of 1b),47 but the great advantage of conjugate 5 is its
high solubility in polar solvent, such as ethanol and water, which
allows its use in non-expensive solid supports. The green color at
very low pH, according with literature,48 is due to the formation of
dicationic species, confirmed by the appearance of a band at
650 nm, in the absorption spectra (Fig. SN6). During the pH ex-
periments with compound 5, two low-cost polymers, agarose and
cellulose, were tested (see Fig. 7B and SN7). Thus, an agarose and
a natural cellulose polymer (carboxymethylcellulose sodium salt)
doped with compound 5 were exposed to different pH’s (from 0.8
to 12). The same color changes (green at low pH to yellow at higher
pH) were observed in solution EtOH/H2O (50:50) when the com-
pound 5 was doped in the agarose and cellulose polymers. The
emission of both polymers at different pH’s was also recorded in
solid state, using a fiber optic system connected to the Horiba Jobin-
Yvon Fluoromax 4. As can be seen in Fig. SN8 with the pH, the
emission intensity of the polymers doped with 5 was practically not
affected. From these results compound 5 can be considered as
a colorimetric pH probe, which can be applied in low cost materials,
such as agarose and cellulose. It is worthwhile to mention that
under the same conditions (EtOH/H2O) the free-base of 1b showed
limited solubility.
The naked eye sensorial ability of the colorimetric effect of 5 for
Hg2þ was successfully applied in a solid support material, a cellu-
lose paper (filter paper).
The sensorial ability of conjugate 5 for Hg2þ was maintained
when applied in cellulose paper allowing naked eye detection.
Moreover, pH studies carried out with conjugate 5 showed
a green color at low pH and a yellow color at high pH values in
solution and solid supports.
4. Experimental section
4.1. Chemicals
NaCH3SO3, Ca(CH3SO3)2, Ba(CH3SO3)2, Cd(CH3SO3)2, Cu(BF4)2$
6H2O, Pb(BF4)2$6H2O, Hg(CH3SO3)2, Zn(CH3SO3)2, Fe(CH3SO3)2
AgCH3SO3, (CH3CH2CH2CH2)4NF, (CH3CH2CH2CH2)4NCl, (CH3CH2
CH2CH2)4N(CN), (CH3CH2CH2CH2)4N(CH3CO2) salts, paraformalde
hyde, methanesulfonic acid (CH3SO3H), carboxymethylcellulose so-
dium salt, agarose, 4-hydroxycoumarin, and 4-hydroxy-6-methyl
coumarin were purchased from SigmaeAldrich. All these chem-
icals were used without further purification. The solvents were ob-
tained from Panreac and Riedel-de Haen and used as received or
distilled and dried using standard procedures.
In order to explore the colorimetric properties of compound 5
and its application in solid support materials, cellulose paper, in
this case filter paper, containing compound 5 was exposed to dif-
ferent amounts of mercury(II) metal ion. As can be seen in Fig. 8, the
cellulose paper with 5 was purple and showed a strong red emis-
sion under a UV lamp lexc¼365 nm. After the addition of Hg2þ
metal ion, the color of the cellulose paper changes from purple to
yellow, and under the UV lamp the strong red emission disappears.
4.2. Physical measurements
HRMS were carried out at the University of Vigo (CACTI), Spain.
1H and 13C NMR spectra were recorded on Bruker Avance 500 (at
I norm. /a.u.
0.5 equiv. Hg2+
1
0.8
0.6
0.4
0.2
0
5 + 4 equiv. Hg2+
5
4 equiv. Hg2+
A
λ
UV lamp exc. = 365 nm
640
680
720
760
800
Wavelength/nm
Fig. 8. Spectrofluorimetric titration of compound 5 in a cellulose paper with the addition of 0e4 equiv of the metal ions Hg2þ in water, lexc.¼592 nm.
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8
C.I.M. Santos et al. / Tetrahedron xxx (2013) 1e10
500 and 125 MHz, respectively) and 300 (at 300 and 75 MHz, re-
spectively) spectrometers. 19F NMR spectra were also obtained on
a Bruker Avance 300 at 282 MHz. CDCl3 and pyridine-d5 were used
as solvents with tetramethylsilane (TMS) as the internal reference;
compounds were purified by preparative TLC using hexane/ethyl
acetate/pyridine (150:50:1) system.
4.4.1.1. Compound 3. {2-(5-Oxo-2,3,4,5-tetrahydro-2H-pyrano
[3,2-c]chromen-2-yl)-5,10,15,20-tetraphenylporphyrinato}zin-
the chemical shifts are expressed in
d (parts per million) with the
coupling constants (J) in Hertz (Hz). Unequivocal 1H assignments
were made using 2D COSY experiments (mixing time of 800 ms),
while 13C assignments were made on the basis of 2D HSQC and
HMBC experiments (delay for long-range J CeH couplings was
optimized for 7 Hz). Preparative thin-layer chromatography (TLC)
was carried out on 20ꢁ20 cm glass plates coated with silica gel
(0.5 mm thick). Analytical TLC was carried out on precoated sheets
with silica gel (Merck 60, 0.2 mm thick).
c(II).30 88%, 1H NMR (CDCl3, 500 MHz): 2.25e2.29 (m, 2H, H-30
d
and H-40), 2.61e2.67 (m, 2H, H-30 and H-40), 5.04 (d, 1H, J¼8.5 Hz,
H-20), 7.19 (ddd, 1H, J¼8.1, 7.2, 1.0 Hz, H-90), 7.34 (dd, 1H, J¼8.5,
1.0 Hz, H-70), 7.40e7.45 (m, 1H, Hp-Ph), 7.49 (ddd, 1H, J¼8.5, 7.2,
1.4 Hz, H-80), 7.71e7.81 (m, 12H, Hm,p-Ph, H-100), 8.16e8.23 (m, 8H,
Ho-Ph), 8.75 (d, 1H, J¼4.6 Hz, H-
b
), 8.90 (d, 1H, J¼4.6 Hz, H-
b
), 8.94
(s, 2H, H-12 and H-13), 8.95 (d, 1H, J¼4.6 Hz, H-
b), 8.97 (d, 1H,
J¼4.6 Hz, H-
b
), 9.15 (d, 1H, J¼0.5 Hz, H-3); 13C NMR (CDCl3,
125 MHz):
d
20.9 (C-40), 30.03 (C-30), 75.9 (C-20), 101.2(C-40a), 115.9
4.3. Photophysical measurements
(C-100a), 116.5(C-70), 120.5, 121.1, 121.3, 121.6, 122.5 (C-100), 123.7 (C-
90); 126.4, 126.5, 126.6, 126.7, 127.6, 127.7, 128.5 (C-m,p); 131.2 (C-
Absorption spectra were recorded on JASCO V-650 spectro-
photometer and fluorescence emissions were performed on
a Spectrofluorimeter HORIBA-JOBIN-YVON Fluoromax 4. The line-
arity of the fluorescence emission versus concentration was
checked in the concentration range used (10ꢀ4 to 10ꢀ6 M). A cor-
rection for the absorbed light was performed when necessary. The
spectroscopic characterizations and titrations were performed us-
ing stock solutions of the studied compounds (ca.10ꢀ3 M), prepared
by dissolving the appropriate amount of porphyrin/corrole de-
rivatives in toluene, dichloromethane, ethanol or DMSO in a 10 mL
volumetric flask. The studied solutions were prepared by appro-
priate dilution of the stock solutions up to 10ꢀ5 to 10ꢀ6 M. Titrations
of the ligands 3e8 were carried out by the addition of microliter
amounts of standard solutions of cations in acetonitrile and anions
in DMSO or toluene, respectively. All the measurements were
performed at 298 K. Fluorescence quantum yields were measured
using a solution of cresyl violet perchlorate in absolute ethanol as
a standard ([ɸ] 0.54),18 and were corrected for different refraction
indexes of solvents. Fluorescence spectra of the doped solid sup-
ports were recorded using a fiber optic system connected to
a Horiba Jobin-Yvon Fluoromax 4 spectrofluorimeter, exciting at
80); 131.7, 132.3, 132.35, 132.6 (C-
b); 133.4, 133.5, 134.37, 134.4,
134.42, 134.47, 134.5 (C-o); 142.3, 142.4, 142.5, 142.7, 143.5 (C-1),
145.6, 147.8, 150.2, 150.4, 150.5, 150.6, 150.9, 152.4 (C-60a), 160.7
(C-100b), 163.4 (C-50); HRMS-ESI-TOF m/z calcd for C56H37N4O3 Zn
[MþH]þ 877.2152, found 877.2116.
4.4.1.2. Compound 4. {2-(9-Methyl-5-oxo-2,3,4,5-tetrahydro-
2H-pyrano[3,2-c]chromen-2-yl)-5,10,15,20-
tetraphenylporphyrinato}zinc(II). 95%, 1H NMR (CDCl3, 500 MHz):
d
2.17e2.31 (m, 2H, H-30 and H-40), 2.33 (s, 3H, CH3), 2.61e2.68 (m,
2H, H-30 and H-40), 5.06 (d, 1H, J¼10.4 Hz, H-20), 7.24 (d, 1H,
J¼8.4 Hz, H-70), 7.31 (dd, 1H, J¼8.4, 1.7 Hz, H-80), 7.44e7.45 (m, 1H,
Hm,p-Ph), 7.49 (d,1H, J¼1.7 Hz, H-100), 7.71e7.79 (m,11H, Hm,p-Ph),
8.15e8.28 (m, 8H, Ho-Ph), 8.76 (d, 1H, J¼4.7 Hz, H-
b), 8.90 (d, 1H,
J¼4.7 Hz, H-
b
), 8.94 (s, 2H, H-12 and H-13), 8.96 (d, 1H, J¼4.7 Hz, H-
b
), 8.97 (d, 1H, J¼4.7 Hz, H-
b
), 9.15 (s, 1H, H-3); 13C NMR (CDCl3,
125 MHz): d
20.9 (AreCH3), 21.0 (C-40), 30.2 (C-30), 76.0 (C-20), 101.1
(C-40a), 115.6 (C-100a), 116.3 (C-70), 120.5, 121.05, 121.3, 121.6, 122.2
(C-100), 126.4, 126.5, 126.6, 126.8, 127.6, 127.66, 128.6 (C-m,p); 131.7,
132.2, 132.3, 132.4, 132.5, 132.6 (C-80 and all C-
b); 133.37, 133.4,
133.6, 134.37, 134.41, 134.44, 134.6 (C-o); 142.2, 142.5, 142.8, 143.6,
appropriate
l
(nm) for the solid supports. The limit of detection
145.5, 147.8, 150.2, 150.4, 150.5, 150.6, 150.7, 150.8, 160.7 (C-100b),
163.6 (C-50); HRMS-ESI-TOF m/z calcd for C57H38N4O3Zn [M]þ
ꢃ
(LOD) and the limit of quantification (LOQ) for the analytes were
performed, having in mind their use for real ions detection and
analytical applications. For these measurements, ten different
analyses for the selected receptor were performed in order to ob-
tain the LOQ. The LOD was obtained by applying the formula:
ydl¼yblankþ3std where ydl¼signal detection limit and std¼standard
deviation.
890.2230, found 890.2236.
4.4.1.3. Compound 7. {3-(5-Oxo-2,3,4,5-tetrahydro-2H-pyrano
[3,2-c]chromen-2-yl)-5,10,15-tris(pentafluorophenyl)corrolato}
gallium(III). 92%, 1H NMR (CDCl3, a few drops of pyridine-d5,
500 MHz):
d 2.65e2.72, 2.75e2.81, 2.85e2.89, 2.98e3.02 (4m, 4H,
H-30 and H-40), 2.97e3.04 (m, 2H, H-30 and H-40), 5.83 (dd, 1H,
J¼9.7, 1.8 Hz, H-20), 7.22 (dt, 1H, J¼7.8, 1.0 Hz H-90), 7.40 (dd, 1H,
J¼8.4, 0.6 Hz, H-70), 7.66e7.68 (m, 1H, H-80), 7.84 (dd, J¼7.8 Hz, H-
4.4. Synthesis of organic ligands
The precursors 2-vinyl-5,10,15,20-tetraphenylporphyrinatozinc
(II) 1a and gallium(III) complex of 3-vinyl-5,10,15-tris(pentafluoro
phenyl)corrole 2 were synthesized according to the procedures
described within the literature.6,30
100), 8.63e8.64 (m, 2H, H-
b
), 8.72 (d, 1H, J¼4.5 Hz, H-
b
), 8.83 (d, 1H,
), 9.25 (d, 1H, J¼4.0 Hz, H-
18), 9.40 (s, 1H, H-2); 13C NMR (CDCl3, a few drops of pyridine-d5,
125 MHz):
22.6 (C-40), 29.3 (C-30), 75.0 (C-20), 101.1, 115.4, 116.4 (C-
70), 116.5 (C-2), 118.0 (C-18), 122.5 (C-100), 124.2 (C-90), 124.4 (C-
),
124.5 (C-b), 125.6 (C-17), 127.6 (C-b), 128.3 (C-b), 131.5, 131.7, 131.8,
J¼4.0 Hz, H-17), 8.87 (d, 1H, J¼4.5 Hz, H-
b
d
b
4.4.1. General procedure for preparing 3, 4, 7, and 8. In a round-
bottom flask, equipped with a magnetic stirring bar, a solution of
131.9, 132.0, 133.4 (C-80), 135.7, 137.0, 137.4, 140.8, 141.4, 143.7, 147.6,
4-hydroxycoumarin (5.7 mg, 35.5
marin (6.2 mg; 35.5 mol), 1,4-dioxane (5 mL), paraformalde
hyde (8.5 mg, 284 mol), and porphyrin 1a (25 mg, 35.5 mol)/
corrole 2 (25 mg, 25.8 mol) was heated at reflux until consump-
mmol)/4-hydroxy-6-methylcou
152.3, 160.4 (C-100b), 163.2 (C-50); 19F NMR (CDCl3, a few drops of
m
pyridine-d5, 282 MHz):
d
ꢀ161.3 to ꢀ161.4 (m, 6F, Fortho), ꢀ177.2 to
m
m
ꢀ177.5 (m, 3F, Fpara), ꢀ185.7 to ꢀ186.2 (m, 6F, Fmeta); HRMS-ESI-
49H16F15N4O3Ga [M]þ 1062.3830, found
ꢃ
m
TOF m/z calcd for
C
tion of the starting porphyrin 1a/corrole 2 (1 h). 1,4-Dioxane was
then removed under reduced pressure, chloroform (50 mL) was
added to the residue and the mixture was washed with saturated
aqueous sodium bicarbonate (2ꢁ20 mL). The organic phase was
concentrated under vacuum and the porphyrin residue was puri-
fied by column chromatography on silica gel and subsequently by
preparative TLC using chloroform as the eluent. The corrole
1062.3617.
4.4.1.4. Compound 8. {3-(9-Methyl-5-oxo-2,3,4,5-tetrahydro-
2H-pyrano[3,2-c]chromen-2-yl)-5,10,15-tris(pentafluorophenyl)
corrolato}gallium(III). 87%, 1H NMR (CDCl3, a few drops of pyridine-
d5, 300 MHz):
d
2.27 (s, 3H, CH3), 2.63e3.06 (m, 4H, H-30 and H-40),
5.82e5.91 (m, 1H, H-20), 7.21e7.37 (m, 2H, H-70 and H-80), 7.63 (d,
Please cite this article in press as: Santos, C. I.M.; et al., Tetrahedron (2013), http://dx.doi.org/10.1016/j.tet.2013.07.022

C.I.M. Santos et al. / Tetrahedron xxx (2013) 1e10
9
1H, J¼1.8 Hz, H-90), 8.59e8.93 (m, 5H, H-
b
), 9.20e9.28 (m, 1H, H-
b
),
SFRH/BPD/72557/2010 and SFRH/BPD/63237/2009, respectively.
J.C.J.M.D.S.M also thanks QOPNA for a research grant.
9.35e9.42 (m, 1H, H-b d 20.8 (AreCH3),
). 13C NMR (75 MHz, CDCl3)
22.7 (C-40), 29.4 (C-30), 74.9 (C-20), 101.0, 115.1, 116.2, 116.3, 118.1,
123.7, 124.4, 125.6, 127.2, 127.8, 128.1, 128.6, 129.7, 132.6, 133.5,
Supplementary data
133.6, 133.7, 136.0, 137.3, 140.9, 141.4, 143.2, 150.6, 160.5, 163.6. 19
F
NMR (CDCl3, a few drops of pyridine-d5, 282 MHz):
d
ꢀ159.1 to
Photophysical data of compounds 3e8 in other solvents stud-
ied. Spectroscopic polarity parameters, physical properties and
polarity functions of employed solvents. Detection (LOD) and
quantification (LOQ) limits of compounds 3, 4, 7 and 8 in toluene.
Titrations of compounds 3 and 7 with cyanide and acetate. Nor-
malized emission of 1b with chloride, fluoride, cyanide and ace-
tate. Titration of compound 5 with Hg2þ in EtOH/H2O(50:50),
absorption spectra of 5 at different pH’s. Image of a cellulose
polymer with 5 at pH 1, 7 and 12. Emission spectra of 5 in agarose
gel and cellulose polymer at different pH’s are available. The 1D
and 2D NMR and HRMS spectra for compounds 3e8 are also
provided. Supplementary data related to this article can be found
at http://dx.doi.org/10.1016/j.tet.2013.07.022.
ꢀ159.2 (dd, 1F, J¼25.0, 7.2 Hz, Fortho), ꢀ161.0 to ꢀ161.2 (dd, 1F,
J¼25.4, 9.0 Hz, Fortho), ꢀ161.4 to ꢀ161.5 (m, 4F, Fortho), ꢀ174.9 (t,
1F, J¼21.2 Hz, Fpara), ꢀ176.8 (t, F, J¼21.0 Hz, Fpara), ꢀ177.0 (t, 1F,
J¼21.0 Hz, Fpara), ꢀ184.1 to ꢀ184.3 (m, 1F, Fmeta), ꢀ185.0 to ꢀ185.2
(m, 1F, Fmeta), ꢀ185.5 to ꢀ186.0 (m, 4F, Fmeta); HRMS-ESI-TOF m/z
calcd for C50H18F15N4O3Ga [M]þꢃ 1076.0412, found 1076.0362.
4.4.2. General procedure for porphyrin decomplexation. Zneporphyrins
3 and 4 (8.98 mmol) were treated with a mixture of 5% TFA in chlo-
roform (1 mL). The reaction mixture was stirred at room temperature
for 30 min and then neutralized with a saturated solution of NaHCO3.
The aqueous phase was extracted with chloroform, and the organic
phase was dried over Na2SO4 and evaporated under vacuum to dry-
ness. The resulting residue was purified by preparative TLC using
chloroform as eluent.
References and notes
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d
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Authors are grateful to Xunta de Galicia (Spain) through project
10CSA383009PR and Scientific PROTEOMASS Association (Portu-
~
^
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cia e a Tecnologia (FCT, Portugal), European Union, QREN, FEDER
and COMPETE for funding the QOPNA research unit (project PEst-C/
QUI/UI0062/2011) and the Portuguese National NMR Network, also
supported by funds from FCT. C.S., E.O. and J.B. thanks also FCT for
their doctoral and post-doctoral grants, SFRH/BD/64155/2009,
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Please cite this article in press as: Santos, C. I.M.; et al., Tetrahedron (2013), http://dx.doi.org/10.1016/j.tet.2013.07.022