Synthesis of di-substituted calix[4]arene-based receptors for extraction of chromate and arsenate anions

Article abstract of DOI:10.1016/j.tet.2009.07.062

The article describes the synthesis of a family of novel calix[4]arene ionophores, 25,27-bis-(2-aminomethylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5a), 25,27-bis-(3-aminomethylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5b) and two chromogenic calix[4]arenes, 5,17-dinitro-25,27-bis-(2-aminomethylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5c), 5,17-dinitro-25,27-bis-(3-aminomethylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5d) bearing pyridinium units. In the synthesis, the upper and lower rims of p-tert-butylcalix[4]arene were modified in order to acquire binding sites for the recognition of arsenate and dichromate anions. It has been observed that protonated alkylammonium forms of the ionophores showed high affinity toward dichromate and arsenate anions.

Full text of DOI:10.1016/j.tet.2009.07.062

Tetrahedron 65 (2009) 7963–7968
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Synthesis of di-substituted calix[4]arene-based receptors for extraction
of chromate and arsenate anions
Mevl u¨ t Bayrakcı a b, S¸ eref Ertul , Mustafa Yilmaz a
,
a
,
*
a
Selçuk University, Department of Chemistry, Campus, 42031 Konya, Turkey
Ni g˘ de University, Department of Chemistry, Campus, 51100 Ni g˘ de, Turkey
b
a r t i c l e i n f o
a b s t r a c t
Article history:
The article describes the synthesis of a family of novel calix[4]arene ionophores, 25,27-bis-(2-amino-
methylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5a), 25,27-bis-(3-aminomethylpyridine-pro-
poxy)-26,28-dihydroxycalix[4]arene (5b) and two chromogenic calix[4]arenes, 5,17-dinitro-25,27-bis-(2-
aminomethylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5c), 5,17-dinitro-25,27-bis-(3-amino-
methylpyridine-propoxy)-26,28-dihydroxycalix[4]arene (5d) bearing pyridinium units. In the synthesis,
the upper and lower rims of p-tert-butylcalix[4]arene were modified in order to acquire binding sites for
the recognition of arsenate and dichromate anions. It has been observed that protonated alkylammo-
nium forms of the ionophores showed high affinity toward dichromate and arsenate anions.
Ó 2009 Elsevier Ltd. All rights reserved.
Received 7 February 2009
Received in revised form 8 June 2009
Accepted 23 July 2009
Available online 29 July 2009
Keywords:
Calixarene
Arsenate anion
Chromate anion
Proton-switchable
Liquid–liquid extraction
1
. Introduction
exist in several oxidation states, however, only the trivalent and
13
hexavalent forms are environmentally important. Chromium(III)
has been reported to be biologically essential to mammals as it
maintains effective glucose, lipid, and protein metabolisms. How-
Calixarenes are cyclic oligomers made of several phenolic units
bounded with methylene bridges and are regarded as the third
generation of host molecules because of their inclusion ability to
cations, anions, and neutral molecules.
easily functionalized both at the phenolic OH groups (lower rim)
and, after partial removal of tert-butyl groups, at the para positions
of the phenol rings (upper rim).
modified calixarenes exist in the cone conformation in which there
is a cavity suitable for reception of different ionic and neutral
species. Furthermore, the most significant feature of the chemistry
of these molecules is their ability to bind selectively alkali and al-
kaline earth cations. Chromate and arsenate anions are important
because of their high toxicity and because of their presence in soils
and waters.7 Arsenic is an omnipresent eco-toxin; the presence of
arsenic in water is a serious threat for more than 100 million people
2
ꢀ
ever, chromium(VI) can be toxic as it can diffuse as Cr
2
O
7
or
1
–3
ꢀ
Calix[4]arenes can be
HCr
2
O
7
through cell membranes and oxidize biological mole-
1
4
cules. Therefore, treatment of wastewater containing Cr(VI) prior
to discharge is essential. Solvent extraction is one of the most
commonly used treatment methods and employs a selective com-
plexant especially for ions in aqueous solution. Although there are
numerous examples of molecules that act as hosts and complexants
for cations, relatively fewer molecules have been reported as hosts
4
,5
The vast majority of these
6
15–18
for anions.
Thus, the development of efficient extractants for
anions has received considerable attention in recent years.
19
Compared to the number of reports on the binding of anions with
,8
20–24
calixarenes, reports on the binding of oxyanions are still limited.
From this point of view calixarene receptors bearing pyridinium
9
25,26
in the world. Humans are clearly sensitive to arsenic carcinogen-
esis; prolonged exposure to arsenic damages the central nervous
units are at the center of interest.
27
In a previous study, we reported a di-substituted calix[4]arene
amide derivative bearing pyridinium units, which acted as a re-
ceptor for both dichromate anions and some selected cations, and
observed that pyridinium units were effective binding sites for
these ions. However, there are no articles showing the effect of
substituents on upper rim of calixarenes in literature. Thus, in this
study, we aimed to synthesized new calix[4]arene receptors bear-
ing pyridinium units on their lower rim and nitro substituents in-
stead of tert-butyl groups on their upper rim as mentioned in
system and results in diverse types of cancer in liver, lung, bladder,
and skin.1
0,11
Chromium and its compounds are widely used in
plating, leather tanning, dye, cement, and photographic industries,
producing large quantities of toxic pollutants.12 Chromium can
*
Corresponding author. Tel.: þ90 332 2232774; fax: þ90 332 2410520.
E-mail address: myilmaz42@yahoo.com (M. Yilmaz).
0
040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.07.062

7964
M. Bayrakcı et al. / Tetrahedron 65 (2009) 7963–7968
Scheme 1. Furthermore, their recognition abilities were in-
vestigated toward dichromate and arsenate anions by means of
liquid–liquid phase extraction processes.
2
was observed for the methylene bridge ArCH Ar protons at
3.49 ppm and 4.22 ppm (J¼13 Hz) for 5a, 3.45 ppm and 4.20 ppm
1
(J¼13.1 Hz) for 5c in the H NMR. The high field doublets at
3.49 ppm for 5a, and 3.45 ppm for 5c were assigned to the equa-
torial protons of methylene groups, whereas the low field signals at
.22 ppm for 5a, and 4.20 ppm for 5c were assigned to the axial
4
1
protons in the H NMR. However, some of the methylene protons
were overlapped in the case of 5b and 5d. Furthermore, the pyr-
idinium units on lower rim of calixarenes are characterized by the
i
OH OH OH HO
2
OH OH OH HO
1
presence of singlet peaks at 3.82, 4.10, 4.02, 4.12 ppm (NHCH Ar)
2
for 5a–d, respectively. Overlapping peaks in the range of 3.56–
ii
2
3.50 ppm (NH and ArCH Ar) for 5b and 5d and 2.44–2.30 ppm
2
NO NO2
(OCH CH CH and NH) for 5a and 5c were also observed. All other
2
2
2
data were in agreement with the proposed structures of 5a–d.
iii
2.2. Two-phase solvent extractions
O
OH OH
O
O
OH OH
O
2
.2.1. Arsenate anion. For a molecule to be effective as a host, it is
4
3
Br
Br
Br
Br
necessary that its structural features are compatible with those of
the guest anions. The arsenate (H
ꢀ
2ꢀ
4
) ions are dianions
2
AsO
4
/HAsO
where the periphery of the anions has oxide moieties. These oxides
are potential sites for hydrogen bonding to the host molecule.
A preliminary evaluation of the extraction efficiencies of 5a–d has
been carried out by solvent extraction of arsenate ions from water
into dichloromethane at different pH values. The results are sum-
marized in Table 1 and Figure 1.
iv
R
R
R
R
O
O
OH
OH
O
O
OH OH
Table 1
Percentage extraction of arsenate ion by extractants 5a and 5b at different pH
values
HN
NH
HN
NH
N
a,b
N
Compounds
pH
3.5
N
N
5c-d
5a-b
4.5
5.5
7.0
5
a R: H
5b R: H
5
5
a
b
32ꢂ1
5ꢂ1
50ꢂ1
24ꢂ1
22ꢂ1
10ꢂ1
2ꢂ1
3ꢂ1
5
c R: NO2
5d R: NO2
Scheme 1. Synthetic route of preparation of calix[4]arene derivatives. (i) AlCl
3
, phenol,
a
Averages and standard deviations calculated for data obtained from three in-
toluene, rt, 1 h; (ii) 1,3-dibromopropane, CH
3
CN, reflux, 48 h; (iii) HNO
3
(70%), glacial
ꢁ
dependent extraction experiments.
AcOH, 0 C, CH
2
Cl
2
, 2 h; (iv) 3-aminomethylpyridine and 2-aminomethylpyridine, THF,
b
arsenate]¼1ꢃ10ꢀ5 M;
Aqueous
phase,
[sodium
organic
phase,
NaI, reflux, 72 h.
[
ligand]¼1ꢃ10ꢀ M at 25 C, for 1 h.
3
ꢁ
2
2
. Results and discussion
.1. Synthesis
As mentioned above, a set of new calix[4]arenes bearing pyri-
dine units on their lower rim and nitro groups instead of tert-butyl
groups on their upper rim were prepared. The binding properties of
calix[4]arene derivatives were explored toward dichromate and
arsenate anions. The synthesis of the new calix[4]arene derivatives
is given in Scheme 1. For the synthesis of calix[4]arenes and dinitro-
calix[4]arene based on pyridine units 5a–d, the parent compounds
(
1–3) and noncyclic compound (9) were prepared according to
5,28,29
published procedures.
All of the structures have been char-
acterized through 1H NMR, IR, and elemental analyses. Firstly,
p-tert-butylcalix[4]arene was dealkylated according to literature
procedure28 and then functionalized with 1,3-dibromopropane in
2 3
the presence of K CO to obtain the dibromocalix[4]arene com-
pound 3 by O-substitution on the lower rim of calix[4]arene in 1,3-
distal) position.2 The treatment of dibromocalix[4]arene with
9
(
HNO and CH COOH in dichloromethane gave the corresponding
3
3
Figure 1. Plots of extraction (E %) versus pH following the two-phase solvent extrac-
tion of arsenate with compounds 5a–d.
dinitro-substituted product on upper rim of the dibromocalix[4]-
arene compound 4. In the following step, these compounds 3 and 4
were treated with 2-aminomethylpyridine or 3-aminomethyl-
pyridine to synthesize corresponding dinitro-calix[4]arene and
calix[4]arene bearing pyridinium units 5a–d in the presence of
From the extraction data, 5a was found to be an effective
extractant for the phase transfer of arsenate anions at pH 4.5. From
Table 1 and Figure 1 it is clear that maximum extraction 50% for 5a
and 20% 5b occur at pH 4.5, which shows that best interaction
between the ligand 5a and the arsenate ions occurs at this pH. This
1
a catalytic amount of NaI in THF. H NMR data showed that com-
pounds 5a–d are in the cone conformation. A typical AX pattern

M. Bayrakcı et al. / Tetrahedron 65 (2009) 7963–7968
7965
O
OH OH
O
O
O
OH OH
O
O
OH OH
O
OH-
H+
H+
OH-
N H
O
O
H
O
HN
NH
H
N
NH
N
H
H
H
O
Cr
O
Cr
O
As
O
H
O
O
O
N
N
N
N
N
N
H
Scheme 2. The suggested complexation phenomena of arsenate and dichromate ion with 5b.
interaction is attributed to the hydrogen bonding and electrostatic
interaction between amino groups and the oxygens of arsenate
3
0
ions. The arsenate anion was not extracted by dinitro-calix[4]
arene 5c and 5d at pH 3.5–7.0 because of the solubilizing properties
31
of nitro-calix[4]arene in water. Among these compounds, calix-
arene derivatives 5a and 5b gave the best efficiency for the extraction
of arsenate ions in pH 4.5 medium. The proposed interaction for the
attraction between the arsenate and the ligand 5a is shown in
Scheme 2. As(V) speciation is affected by the solution pH through
3
2
the following equilibrium:
L
4
D
H AsO 4H AsO DH
pKa1 [ 2:3
pKa2 [ 6:8
pKa2 [ 11:6
(1)
(2)
(3)
3
4
2
H AsO4 4HAsO 24 LDH
L
D
2
HAsO 4AsO 34 LDH
2
4
L
D
From Eqs. 1–3, the As(V) species occurs mainly in the form of
ꢀ
ꢀ
H
H
1
2
AsO
AsO
4
2
4
in the pH range between 3 and 6, while a divalent anion
2
dominates at higher pH values (such as between pH 8 and
ꢀ
1). The monoanion (H
hydration than does the dianionic form HAsO
a smaller loss in hydration energy as H
2
AsO
4
) will have a smaller free energy of
Figure 2. Plots of extraction (E %) versus pH following the two-phase solvent extrac-
tion of dichromate with compounds 5a–d.
2
ꢀ
4
. As a result, there is
is transferred from the
ꢀ
2
AsO
4
aqueous phase into the dichloromethane phase. An additional ad-
pH. The percentage of dichromate ions extracted was 67% for 5a
and 72% for 5b when the pH of the aqueous solution was 1.5 and
they attained minimum level of 4% for 5a and 10% for 5b when the
pH of the aqueous solution was increased to 4.5. Calix[4]arene
derivatives 5a and 5b provide suitable binding sites for dichromate
anions at low pH due to containing protonable pyridyl and amine
moieties. Therefore, an anion-switchable complex is formed in the
two-phase extraction system (Scheme 2) because of the proton
transfer to the nitrogen atom of the alkyl chain in 5a and 5b.
In order to establish an effective role of the macrocyclic scaffold
of calixarenes (5a and 5b) in the anion binding, noncyclic mono-
meric analog (9) (Scheme 4) was synthesized. Because of the soluble
ꢀ
2ꢀ
4
is that for the former only one
vantage of H
2
AsO
4
over HAsO
sodium ion needs to be coextracted to maintain charge balance,
whereas for HAsO2
ꢀ
two sodium ions are extracted, with additional
4
3
2
loss of hydration energy.
2
ꢀ
ꢀ
2 7
O ) are
2
.2.2. Dichromate anion. The dichromate ions (Cr
2
O
7
/HCr
anions where the periphery of the anion has oxide moieties. It is
known that calix[4]arenes with a nitrogen functionality such as
pyridine, amino, and imino on their lower rim are efficient extrac-
tants for oxoanions.2
2–25
We have performed some preliminary
evaluations to investigate binding efficiencies of the extractants 5a
and 5b for Na Cr by using solvent extraction. The results showed
that Na Cr could be extracted from aqueous solution into
dichloromethane at different pH values. The results are summarized
in Table 2 and Figure 2. An aqueous solution of Na Cr shows no
ꢀ
2
2
O
7
properties of monomeric analog (9) in water at low pH, HCr O
2
7
2
2
O
7
anion was not extracted at low pH by the compound. In our previous
2
3,27
study,
to understand the chelating effect of both pyridine
2
2
O
7
fragments in the anion binding, noncyclic monomeric analog (8) of
macrocyclic ligands (7) (Scheme 3) was used. It was observed that
dichromate anion was only extracted in trace amounts. Based on the
extraction into an organic phase in the absence of the extractant.
The extraction data (Fig. 2) showed that the extractants 5a and
5
b are more effective for the extraction of dichromate anions at low
Table 2
Percentage extraction of dichromate by extractants 5a and 5b at different pH
a,b
values
Compounds
pH
.5
O
1
2.5
3.5
4.5
O
O
OH OH
O
O
OH OH
O
O
5
5
6
a
67ꢂ1
72ꢂ1
24.8
44ꢂ2
54ꢂ1
11.5
14ꢂ1
30ꢂ1
10.3
4ꢂ1
NH
NH
b
10ꢂ1
<1.0
O
O
O
O
NH
NH
c
HN
NH
HN
HN
O
O
N
N
a
Averages and standard deviations calculated for data obtained from three
independent extraction experiments.
6
N
8
b
dichromate]¼1ꢃ10ꢀ4 M;
Aqueous
phase,
[metal
organic
phase,
7
N
N
ꢀ
3
ꢁ
[
ligand]¼1ꢃ10 M at 25 C, for 1 h.
c
Scheme 3. Previously synthesized ligands 6, 7, and noncyclic analog 8.23,27
Ref. 27.

7966
M. Bayrakcı et al. / Tetrahedron 65 (2009) 7963–7968
DA ¼ ½Aꢄorg=½Aꢄaq
N
A
Consequently, a plot of log D versus log [L] leads to a straight line
with a slope that allows for the determination of the stoichiometry
of the extracted species, where [L] is defined as the analytical
concentration of the ligand in the organic phase. Figure 3 exhibits
the extraction into dichloromethane at different concentrations of
HN
O
5a and 5b with dichromate, respectively. A linear relationship be-
tween log D versus log [L] is observed with the slope of the line for
A
extraction of dichromate anion by ligands 5a and 5b is approxi-
mately equal to 1 (for ligands 5a and 5b at pH 1.5, respectively),
suggesting that these ligands 5a and 5b form 1:1 complexes with
the dichromate anion. However, it is well known that under more
9
2 2 7 2 2 7
acidic conditions Na Cr O is converted into H Cr O and after
Scheme 4. Noncyclic analog of new ligands 9.
ꢀ
2ꢀ
ionization in an aqueous solution it exists in the HCr
2
O
7
/Cr
2
O
7
ꢀ
2ꢀ
results, it has been concluded that calix[4]arene unit plays an im-
portant role in confirming the cooperative participation of the
functional groups. From the extraction data in Table 2, calix[4]arene
bearing amide-pyridinium units 6 (Scheme 3) exhibited lower ex-
tractability (24.8%) than the calix[4]arene derivative bearing amine-
pyridinium units (5a and 5b). This reflects the fact that calix[4]arene
amine binding sites more strongly complex with dichromate in low
form. At more strongly acidic conditions HCr O and Cr O dimers
2
7
2
7
6
þ
become the dominant Cr form and pKa1 and pKa2 values of these
equations are 0.74 and 6.49, respectively. It is clear that the ligands
ꢀ
5a and 5b form complexes mostly with HCr O ions. This has
2
7
allowed us to consider that this simultaneous extraction of 1:1
complexes occurs according to the following equilibria:
a
pH medium. The pK of protonated nitrogen of secondary amine
groups is around 10–11, the protonated form of calix[4]arene de-
rivatives (5a and 5b) is expected to be present in significant con-
a
centration in aqueous solution (generally the pK of protonated
3
3
pyridine is around 5.25). However, it was also observed that the
replacement of tert-butyl groups in calix[4]arene by nitro groups
ꢀ
affects the extraction ability. HCr
2
O
7
ions were not extracted by the
dinitro-calix[4]arenes 5c and 5d due to their solubilization in wa-
31
ter. Among these compounds, calixarene derivatives 5a and 5b
ꢀ
therefore present the best efficiency for the extraction of HCr
2
O
7
/
2
ꢀ
Cr
formed in the two-phase extraction system. Upon addition of NaOH
to the aqueous layer, the deprotonated calixarene in CH Cl is no
and the dianion then
2
O
7
ions in a low pH medium. An anion-switchable complex is
2
2
2
ꢀ
longer an effective host molecule for Cr O
2 7
migrates back into the aqueous layer in a reversible process as
shown in Scheme 2. This situation results from the proton transfer
to the nitrogen atom of the alkyl chain in compounds 5a and 5b. In
aqueous solutions having a lower pH the dichromate will be pri-
ꢀ
marily in its protonated form HCr
2
O
7
. This monoanion will have
a smaller free energy of hydration compared to dianionic form
Figure 3. log D versus log [L] for the extraction of dichromate and its anions by the
ligands 5a and 5b from an aqueous phase into dichloromethane at 25 C and pH 1.5.
2
ꢀ
. As a result, there is a smaller loss in hydration energy as
Cr
HCr
methane phase. An additional advantage of HCr
that for the former, only one sodium ion needs to be coextracted to
2
O
7
ꢁ
ꢀ
2 7
O is transferred from the aqueous phase into the dichloro-
ꢀ
2ꢀ
7
is
2
O
7
over Cr
2
O
ꢀ
þꢁ
ꢀ
ꢁ
Kex
þ
ꢀ
2
ꢀ
LH
þHCr Oꢀ ! LH ; HCr O
(7)
maintain charge balance, whereas for Cr
2
O
7
two sodium ions are
2
7aq
2
7
org
org
3
4
extracted, with additional loss of hydration energy. All data have
been analyzed using the classical slope analysis method. Assum-
ing that the extraction of an anion A by the receptor LH is
according to following equilibrium:
2
3
According to these assumptions, the extraction constant has been
calculated from the experimental data with similar Kex values using
Eq. 6. Calculations of these constant values lead to
log Kex¼2.24ꢂ0.2 for 5a and log Kex¼4.23ꢂ0.2 for 5b. Figure 4
shows UV–vis spectra of 5c and 5d in dichloromethane.
While compounds 5c–d could not be used in the recognition
studies of dichromate anions because of the increased solubility of
compounds 5c–d in water at low pH, examination of the spectra
showed broad absorption bands at 331 and 332 nm suggesting that
compounds 5c and 5d could potentially be used as a sensor for
anions.
nꢀ
nþ
ꢀ
nþꢁ
hꢀ nþꢁ
i
n LH
orgþnA na qꢀ
!
LH
n; A
nꢀ
(4)
(5)
(6)
n
org
The extraction constant Kex is then defined by:
hꢀꢀ
ꢁ
ꢁi
nþ
nꢀ
LH
n; A
n
org
K
ex
¼
h
i
h
i
n
n
nꢀ
nþ
LH
A
aq
org
Eq. 5 can be re-written as:
3. Conclusion
h
nþi
log DA ¼ log Kex þ n log LH
In conclusion, the synthesis and ion extraction abilities of
calix[4]arene and dinitro-calix[4]arene based on pyridinium units
receptors 5a–d were studied. The spectroscopic data indicated that
the new compounds are in the cone conformation. The dichromate
org
where D
the anion A in both phases:
A
is defined as the ratio of the analytical concentration of
nꢀ

M. Bayrakcı et al. / Tetrahedron 65 (2009) 7963–7968
7967
procedure.35 The dinitro-calix[4]arene (4) and final products (5a–
d) were synthesized according to the following procedures:
4
.2.1. 5,17-Dinitro-25,27-bis-(bromopropoxy)-26,28-dihydroxy-
calix[4]arene (4). 25,27-Bis-(bromopropoxy)-26,28-dihydroxycalix[4]
arene (3) (3.3 mmol) and acetic acid (118 mmol) in 60 mL CH
2
Cl
2
was
ꢁ
added to solution of 65% HNO
3
(168 mmol) at 0 C in ice bath, and
then stirred for half an hour. Then, water (50 mL) was added. The
organic layer was separated and washed with water (3ꢃ50 mL), dried
under sodium sulfate, filtered, and evaporated under reduced pres-
sure. The crude product was recrystallized from CH
Yield 55%, pale yellow solid, mp 323–325 C with decomposition. H
2
Cl
2
and MeOH.
ꢁ
1
NMR (CDCl
ArH), 6.9 (t, 2H, J¼8 Hz, ArH), 4.30–4.27 (d, 4H, J¼13.5 Hz, ArCH
.20–4.18 (t, J¼5 Hz, 4H, OCH ), 3.96 (t, 4H, J¼7 Hz, CH Br), 3.57–3.54
d, 4H, J¼14 Hz, ArCH Ar), 2.59–2.56 (t, J¼6 Hz, 4H, CH CH CH ); IR
) 2900, 2860 (C–H), 1600 (CN), 1555, 1525, 1480 (C]C), 810 (C–Br).
Anal. Calcd C34 . C, 53.99; H, 4.26; N, 3.70%. Found: C,
3
):
d
9.07 (s, 2H, OH), 8.05 (s, 4H, ArH), 7.0 (d, 2H, J¼7 Hz,
2
Ar),
4
2
2
(
2
2
2
2
(n
2 2 8
H32Br N O
53.93; H, 4.31; N, 3.73%.
Figure 4. The UV–vis spectrum of compounds 5c and 5d.
4.2.2. General procedure for the synthesis of ligands. 25,27-Bis-
and arsenate anion studies showed that compounds 5a and 5b
(bromopropoxy)-26,28-dihydroxycalix[4]arene (3) and 5,17-di-
nitro-25,27-bis-(bromopropoxy)-26,28-dihydroxycalix[4]arene
compounds (4) (0.6 mmol) were refluxed in THF (30 mL) in the
presence of catalytic amount of NaI for 1 h. To this mixture, excess
of suitable pyridine compounds 3-aminomethylpyridine and
2-aminomethylpyridine (1.4 mmol) were added dropwise and then
refluxed for 72 h. After filtration, the solution was evaporated to
dryness. The residue was washed with water. Then, the product
ꢀ
ꢀ
4
anions. The va-
were effective extractants for HCr
2
O
7
and H
2
AsO
riety of hydrogen bonding sites that occur in these calix[4]arene
derivatives may be of considerable importance for the future design
of novel calix[4]arene-based receptors, carriers, or supramolecular
structures. The calix[4]arene and dinitro-calix[4]arene based on
pyridinium units receptors could be proved to find remarkable
applications in the design of chemical sensors, in anion-binding
processes, especially phase-transfer catalyses and solid-state
sensors.
was recrystallized from CH
2 2
Cl and MeOH.
4
.2.3. 25,27-Bis-(2-aminomethylpyridine-propoxy)-26,28-dihydroxy-
ꢁ
calix[4]arene (5a). Yield 35%, dark yellow solid, mp 111–112 C with
decomposition. H NMR (CDCl
4
4
. Experimental
1
3
):
d
8.65(d, J¼8.0 Hz, 2H, Py-H), 8.30(t,
J¼7.9 Hz, 2H, Py-H), 8.02 (t, 2H, J¼7.9 Hz, Py-H), 7.35 (d, 2H, J¼7.7 Hz,
.1. General
Py-H), 7.25 (s, 2H, OH), 7.05 (d, J¼8 Hz, 4H, ArH), 6.96 (d, J¼8.1 Hz, 4H,
ArH), 6.79–6.75 (m, 4H, ArH), 4.22–4.20 (d, 4H, J¼13.1 Hz, ArCH
2
Ar),
Ar), 3.49–3.46 (d, 4H,
Ar), 3.38–3.36 (t, J¼8 Hz, 4H, NHCH ), 2.30 (br m, 6H,
and NH); IR ( ) 3185 (NH), 2900, 2875 (C–H),1610 (CN),
555, 1510, 1485 (C]C). Anal. Calcd C46 . C, 76.64; H, 6.70; N,
All of the reagents used in this study were obtained from Merck
or Fluka and used without further purification. Dry THF was dis-
tilled from the ketyl prepared from sodium and benzophenone.
4
.15 (t, J¼5 Hz, 4H, OCH
J¼13 Hz, ArCH
OCH CH CH n
2 2
), 4.02 (s, 4H, NHCH
2
2
2
2
2
Acetonitrile was dried from calcium hydride and stored under N
over molecular sieves (4 Å). CH Cl was distilled from CaCl $MeOH
2
1
48 4 4
H N O
2
2
2
7
.77%. Found: C, 76.65; H, 6.73; N, 7.73%.
over Mg and stored over molecular sieves. Anions were used as
their sodium salts. Thin layer chromatography (TLC) was performed
using silica gel on glass TLC plates (silica gel H, type 60, Merck).
Generally solvents were dried by storing them over molecular
sieves (Aldrich; 4 Å, 8–12 mesh). All aqueous solutions were pre-
pared with deionized water that had been passed through a Milli-
pore Milli-Q Plus water purification system. Melting points were
4.2.4. 25,27-Bis-(3-aminomethylpyridine-propoxy)-26,28-dihydroxy-
ꢁ
calix[4]arene (5b). Yield 38%, pale yellow solid, mp 138–140 C
with decomposition. H NMR (CDCl ): d 8.69 (br s, 2H, Py-H), 8.60
3
1
(
d, 2H, Py-H), 8.27 (t, J¼6.5 Hz, 2H, Py-H), 7.95 (d, J¼7.9 Hz, 2H, Py-
H), 7.40 (s, 2H, OH), 7.21–7.19 (d, J¼8 Hz, 4H, ArH), 6.96–6.94 (d,
J¼7.9 Hz, 4H, ArH), 6.80 (m, 4H, ArH), 4.27–4.20 (overlapped, 8H,
1
determined on a Gallenkamp apparatus. H NMR spectra were
OCH
2
and ArCH
2
Ar), 4.13 (br s, 4H, NHCH
2
Ar), 3.55–3.50 (over-
),
) 3185 (NH), 2900,
875 (C–H), 1610 (CN), 1555, 1510, 1485 (C]C). Anal. Calcd
. C, 76.64; H, 6.70; N, 7.77%. Found: C, 76.55; H, 6.77; N,
obtained using a Varian 400 MHz spectrometer operating at
lapped, 6H, NH and ArCH
2
Ar), 3.12–3.08 (t, 4H, J¼7.5 Hz, NHCH
CH and NH); IR (
2
4
00 MHz. IR spectra were recorded on a Perkin–Elmer 1605 FTIR
2
2
C
.30–2.26 (m, 4H, CH
2
CH
2
2
n
spectrometer as KBr pellets. UV–visible spectra were obtained on
Jenway 6105 and Shimadzu 160 A UV–visible recording spectro-
photometers. Atomic absorption spectra were obtained on ContrAA
46
48 4 4
H N O
7.80%.
3
00 (Analytikjeno). Elemental analyses were performed using
a Leco CHNS-932 analyzer. An Orion 410Aþ pH meter was used for
4
2
.2.5. 5,17-Dinitro-25,27-bis-(2-aminomethylpyridine-propoxy)-
the pH measurements.
6,28-dihydroxycalix[4]arene (5c). Yield 40%, dark yellow solid, mp
ꢁ
1
180–182 C with decomposition. H NMR (CDCl ): d 8.70 (d,
3
4
.2. Synthesis
,11,17,23-Tetra-tert-butyl-25,26,27,28-tetrahydroxycalix[4]
J¼7.9 Hz, 2H, Py-H), 8.35 (t, J¼7.9 Hz, 2H, Py-H), 8.00 (t, 2H,
J¼8.1 Hz, Py-H), 7.38 (d, 2H, J¼7.7 Hz, Py-H), 7.22 (s, 2H, OH), 7.12 (d,
J¼7.9 Hz, 4H, ArH), 6.95 (d, J¼8.0 Hz, 4H, ArH), 6.81 (m, 4H, ArH),
5
arene (1), 25,26,27,28-tetrahydroxycalix[4]arene (2), and 25,27-
bis-(bromopropoxy)-26,28-dihydroxycalix[4]arene compounds (3)
were synthesized according to literature procedures.
4.20–4.18 (d, 4H, J¼13.1 Hz, ArCH
2
Ar), 4.15–4.13 (t, J¼5 Hz, 4H,
Ar),
CH
n) 3200 (NH), 2910, 2875 (C–H), 1625 (CN), 1555, 1500
OCH
3.35–3.32 (t, J¼8.1 Hz, 4H, NHCH
and NH); IR (
2
), 3.82 (s, 4H, NHCH
2
Ar), 3.45–3.42 (d, 4H, J¼13 Hz, ArCH
2
5
,28,29
Com-
2
), 2.44–2.40 (m, 6H, CH CH
2
2
2
pound was synthesized through modified literature
4
a

7968
M. Bayrakcı et al. / Tetrahedron 65 (2009) 7963–7968
(
C¼C). Anal. Calcd C46
H
46
N
6
O
8
. C, 68.13; H, 5.72; N, 10.36%. Found:
References and notes
C, 68.03; H, 5.68; N, 10.31%.
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Asymmetry 2008, 19, 2020–2025.
. Memon, S.; Roundhill, D. M.; Yilmaz, M. Collect. Czech. Chem. Commun. 2004, 69,
1231–1250.
4
2
.2.6. 5,17-Dinitro-25,27-bis-(3-aminomethylpyridine-propoxy)-
2
6,28-dihydroxycalix[4]arene (5d). Yield 44%, pale yellow solid, mp
ꢁ
1
3. Demirtas, H. N.; Bozkurt, S.; Durmaz, M.; Yilmaz, M.; Sirit, A. Tetrahedron 2009,
5, 3014–3018.
180–182 C with decomposition. H NMR (CDCl ): d 8.70 (br s, 2H,
3
6
Py-H), 8.55 (d, 2H, Py-H), 8.20 (t, J¼6.5 Hz, 2H, Py-H), 8.0 (d,
4
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6
.96–6.94 (d, J¼8 Hz, 4H, ArH), 6.84 (m, 4H, ArH), 4.30–4.25
5
(
overlapped, 8H, OCH
2
and ArCH
.51 (overlapped, 6H, NH and ArCH
), 2.32–2.25 (m, 4H, CH CH
800 (C–H), 1610 (CN), 1510, 1500, 1485 (C]C). Anal. Calcd
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2
Ar), 4.1 (br s, 4H, NHCH
Ar), 3.15–3.12 (t, 4H, J¼7.5 Hz,
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C
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2
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7
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46 46
N
6
O
8
8
10.40%.
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1
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4
.3. Liquid–liquid extraction studies
The dichromate anion and arsenate extraction experiments of
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1
1
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calix[4]arene derivatives bearing pyridine units 5a–d were studied
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3
6
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Cr
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7
or Na
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HAsO
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$7H
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O solution at a concentra-
$7H O), a few drops of
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ꢀ
4
ꢀ5
tion of 1ꢃ10 M (1ꢃ10 for Na
2
HAsO
4
2
19. Hamdi, A.; Nam, K. C.; Ryu, B. J.; Kim, J. S.; Vicens, J. Tetrahedron Lett. 2004, 45,
0
.01 M KOH/HCl solution in order to obtain the desired pH at
ꢀ
3
4689–4692.
equilibrium and 10 mL of 1ꢃ10 M calixarene ligand in CH
2 2
Cl .
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ꢁ
66, 1342–1349.
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by atomic absorption spectrometer. Blank experiments showed
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the following expression:
2
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2
2
2
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1
03, 3782–3792.
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18–623.
2
3
Extraction% [ ðA LA=A Þ3100
0
0
6
0. Memon, S.; Akceylan, E.; Sap, B.; Tabakci, M.; Roundhill, D. M.; Yilmaz, M.
J. Polym. Environ. 2003, 11, 67–74.
0
where A and A are the initial and final concentrations of the di-
chromate and arsenate ion before and after the extraction,
respectively.
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3
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a
Prediction for Organic Acids and
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Acknowledgements
34. Memon, S.; Yilmaz, A.; Roundhill, D. M.; Yilmaz, M. J. Macromol. Sci., Part A
2004, 41, 433–447.
The authors gratefully would like to thank The Scientific and
Technological Research Council of Turkey (TUBITAK Grant No.
3
5. Kelderman, E.; Derhaeg, L.; Heesink, G. J. T.; Verboom, W.; Engbersen, J. F. J.; van Hulst,
N. F.; Persoons, A.; Reinhoudt, D. N. Angew. Chem., Int. Ed. Engl. 1992, 31, 1075–1077.
107T873) and S.U. Research Foundation (BAP) for financial
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37. Delig o¨ z, H.; Yilmaz, M. Solvent Extr. Ion Exch. 1995, 13, 19–26.
support.