Novel bis(phenylselenoalkoxy)calix[4]arene molecular tweezer receptors as sensors for ion-selective electrodes

Article abstract of DOI:10.1039/b109238c

Four tweezer-like 25,27-dihydroxy-26,28-bis(phenylselenoalkoxy)-5,11,17,23-tetra-tert-butylcalix[4 ]arenes 5-8 were synthesized for the evaluation of their ion-selectivity in ion-selective electrodes (ISEs). For investigation of the influences of the coor

Full text of DOI:10.1039/b109238c

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Novel bis(phenylselenoalkoxy)calix[4]arene molecular tweezer
receptors as sensors for ion-selective electrodes
Xianshun Zeng,*a Xuebing Leng,a Langxing Chen,b Hao Sun,a,c Fengbo Xu,a Qingshan Li,a
Xiwen Heb and Zheng-Zhi Zhang*a
2
a State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071,
China
b Department of Chemistry, Nankai University, Tianjin 300071, China
c Department of Chemistry, Tianjin University, Tianjin 300072, China
Received (in Cambridge, UK) 12th October 2001, Accepted 6th February 2002
First published as an Advance Article on the web 21st February 2002
Four tweezer-like 25,27-dihydroxy-26,28-bis(phenylselenoalkoxy)-5,11,17,23-tetra-tert-butylcalix[4]arenes 5–8
were synthesized for the evaluation of their ion-selectivity in ion-selective electrodes (ISEs). For investigation of
the influences of the coordinate atoms on the ion-selectivity, 25,27-dihydroxy-26,28-bis(alkylthiaalkoxy)-5,11,17,23-
tetra-tert-butylcalix[4]arenes 9–11 were also prepared and characterized. On the other hand, 1,3-bis(phenylseleno)-
propane 12 was synthesized for comparison of the influences of coordinate patterns of different ionophores on the
ion-selectivity of ISEs. ISEs based on 5–12 as neutral ionophores were prepared, and their selectivity coefficients
pot
for Agϩ (log KAg,M) were investigated against alkali metal, alkaline-earth metal, lead, and ammonium ions and some
transition metal ions using the fixed interference method (FIM). These ISEs showed excellent Agϩ selectivity over
pot
most of the interfering cations examined, except for Hg2ϩ, which had relatively smaller interference (log KAg,Hg
Ϫ1.6).
≤
membrane electrodes based on these novel Agϩ-selective iono-
phores. Comparison of the ISE performances of ionophores 5–
8 with those of ionophores 9–11, together with the influences of
the tether length of the same type receptors on the ISE behavior
of 5–8, as well as the ISE behavior of 1,3-bis(phenylseleno)-
propane 12 will aid further understanding of the structure–
selectivity relationships and the influences of coordinate atom
types on the Agϩ-ISEs.
Introduction
Recently, research in the area of sensor development for metal
ion detection in chemical and biological applications has
received much attention. In particular, the application of host–
guest chemistry to sensor development has proved to be a very
valuable detection method. Numerous receptors including
crown ethers, cryptands, cyclodextrins and calixarenes have
been synthesized as molecular agents for the binding of all
kinds of cationic and anionic species.1,2 As for cationic sensors,
much work has focused on the main group metal ions.3–10 More
recently, the molecular design of sensors containing nitrogen,
sulfur or phosphorus donors with affinity for transition metal
ions has received considerable attention.11–15 In our previous
work, calix[4]arene-based tweezer-like receptors which are
made sensitive to Agϩ ion by incorporating nitrogen, sulfur or
phosphorus atoms in the lower rim of the calix[4]arene scaffold
were developed.16–20 We found that using calix[4]arene deriv-
atives containing sulfur or nitrogen atoms as ionophores in
ISEs gave a good Agϩ-selectivity against most interfering ions
such as alkali metal ions, alkaline-earth metal ions, lead ion and
transition metal ions. The interferences of Hg2ϩ towards these
electrodes are almost eliminated. We also found that the
nitrogen atom is a better donor than the sulfur atom or the
phosphorus () atom both in multipoint ionophores and in
tweezer-like two-point ionophores. These results prompted us
to investigate some novel ionophores containing other soft
donors such as selenium, and to compare their ion-selective
behavior with each other for further understanding of the
implications of the ion-selectivity mechanism in ionophore-
based ISEs.
Results and discussion
Syntheses
Diselenocalix[4]arenes 5–8 were synthesized in good yields by
reaction of the calix[4]arene dibromides 1–4 with the sodium
salt of selenophenol (Scheme 1). Thus, diphenyl diselenide was
treated with NaBH4 and NaOH in absolute ethanol. Then, the
preorganized tweezer-like calix[4]arene dibromides 1–4 were-
added to the prepared ethanol solution of sodium salt of selen-
ophenol and refluxed. The products were purified by column
chromatography. The yields of 5–8 are between 88% and 92%.
Their structures were confirmed by 1H NMR spectra. Two
doublets at nearly 4.23 and 3.28 ppm with the J values of about
13.0 Hz of the protons within the methylene bridges of the
Here we report the synthesis of a series of novel tweezer-like
receptor molecules 25,27-dihydroxy-26,28-bis(phenylseleno-
alkoxy)-5,11,17,23-tetra-tert-butylcalix[4]arenes 5–8 and 25,
27-dihydroxy-26,28-bis(alkylthiaalkoxy)-5,11,17,23-tetra-tert-
butylcalix[4]arenes 9–11 and their Agϩ selectivity behavior
monitored by electromotive force measurements of polymer
796
J. Chem. Soc., Perkin Trans. 2, 2002, 796–801
This journal is © The Royal Society of Chemistry 2002
DOI: 10.1039/b109238c

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Scheme 1
calix[4]aryl skeleton, the separation of the tert-butyl groups of
nearly 1.27 and 0.97 ppm and the separation of the phenyl
protons of nearly 7.02 and 6.80 ppm of the calix[4]aryl indi-
cated that compounds 5–8 were in a ‘pinched’ cone conform-
ation. The protons of the selenium atom-attached phenyls gave
two groups of complicated peaks at nearly 7.55 and 7.20 ppm.
Bis(alkylthiaalkoxy)calix[4]arenes 9–11 were synthesized by
the reaction of calix[4]arene dibromides 3 and 4 with pro-
panethiol and pentanethiol in the presence of NaH as a
base and purified by column chromatography. Their cone
conformation can be easily judged from the two doublets of
the protons within the methylene bridge of the calix[4]aryl
skeleton. 1,3-Bis(phenylseleno)propane 12 was obtained in
good yield by reaction of the sodium salt of selenophenol with
1,3-dibromopropane.
X-Ray crystallography of 6
The X-ray structure of calix[4]arene 6 was elucidated for
determination of the structure (Fig. 1a). As shown in Fig. 1a
and 1b, 6 is in a C2v symmetric cone conformation in the solid
state, with one molecule of CH2Cl2 embedded within the cavity
of four aromatic groups as a guest via a CH–π interaction.
Dichloromethane C(32) distances to the centroids of the four
aromatic rings (labeled X(1A), X(1B), X(1C), X(1D), respect-
ively) are 3.481, 3.481, 4.031 and 4.031 Å, respectively. The two
guest hydrogen atoms are opposite one another (see Fig. 1b).
The centroid ؒ ؒ ؒ H separation is 2.547 Å, with the centroid ؒ ؒ ؒ
H–C(32) angle of 164.4Њ. The two opposite arenes which bind
to guest H(32A) and H(32B) are with an interplanar angle of
38.2Њ. The other two aromatic rings are tilted away from the
cavity with an interplanar angle of 87.7Њ. The torsion angles of
O(2)–C(23)–C(24)–C(25) and C(23)–C(24)–C(25)–Se(1) are
Ϫ55.0Њ and Ϫ68.3Њ, respectively. In addition, the selenium
atoms (Se(1) and Se(2)) are disordered (only one position is
shown in Fig. 1).
Fig. 1 The structure of 6. a) Labeling of compound 6; b) Structure of
6ؒCH2Cl2.
pot
KAg,M) represents the preference of the ISE (or PVC membrane)
containing the bis(phenylselenoalkoxy) functionalized calix-
[4]arene for Agϩ over the other cations. Therefore, the co-
pot
I,M
efficient log K defines the ability of an ISE (or membrane) to
recognize different ions under the same conditions. The smaller
pot
I,M
the log K value, the greater the electrode preference for the
primary ion (Iϩ) over the interfering ion (Mϩ).
As can be seen from Table 1, all polymer membranes contain-
pot
ing calix[4]arenes 5–8 as ionophores gave excellent log KAg,M
)
values (≤ Ϫ3.4) against most of the interfering cations exam-
ined (i.e., Naϩ, Kϩ, NH4ϩ, Ca2ϩ, Mg2ϩ, Ni2ϩ, Zn2ϩ, Cu2ϩ, Cd2ϩ
and Pb2ϩ), except for Hg2ϩ which gave a relatively smaller inter-
ference. It is interesting to note that, despite the different tether
length incorporated between phenylseleno and calix[4]aryl,
5–8-based ISEs exhibited the same characteristic ion selectivity
tendencies which resemble each other. Although the bis-
(alkylthiaalkoxy) functionalized calix[4]arenes 9–11-based ISEs
Ion selectivity
The Agϩ selectivities of phenylselenoalkoxy functionalized
calix[4]arenes 5–8 were evaluated by the potentiometric selectiv-
pot
ity coefficients (log KAg,M). For comparison, alkylthiaalkoxy
pot
functionalized calix[4]arenes 9–11 and 1,3-bis(phenylseleno)-
propane 12 were examined under the same conditions. The
polymer membrane was composed of PVC as the matrix,
dibutyl phthalate (DBP) as the membrane solvent, and a
bis(phenylselenoalkoxy) functionalized calix[4]arene as the
ionophore. The membranes also contained 75 mol% of potas-
sium tetrakis(p-chlorophenyl)borate (KTClPB) relative to the
ionophore for the purpose of reducing membrane resistance
and suppressing permeation of counteranions in the aqueous
phase into the membrane phase. The potentiometric selec-
tivity coefficients for Agϩ, determined by the fixed interference
method, are illustrated in Table 1. The selectivity coefficient (log
also gave the same ion selectivity tendencies, the log KAg,M
values are usually higher by one order of magnitude than
those of the 5–8-based ISEs for the same cation. The selectivity
coefficients of 1,3-bis(phenylseleno)propane 12-based ISEs
are similar to those of 9–11-based ISEs. Therefore, the per-
formance of 5–8-based ISEs is superior to that displayed by
traditional Ag2S-based electrode or 9–12-based ISEs and is
satisfactory as Agϩ-ISE. The fact that polymer membranes con-
pot
I,M
taining ionophores 5–8 gave excellent log K values (≤ Ϫ3.4)
against Naϩ, Kϩ, NH4ϩ, Ca2ϩ, Mg2ϩ, Ni2ϩ, Cu2ϩ, Zn2ϩ, Cd2ϩ
and Pb2ϩ means that 5–8-based ISEs possess high Agϩ selectiv-
ities and only weakly respond to the above interfering ions. The
J. Chem. Soc., Perkin Trans. 2, 2002, 796–801
797

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pot
Table 1 Selectivity coefficients (log KAg,M) of the electrodes based on ionophores 5–12a
pot
log KAg,M
Ion
5
6
7
8
9
10
11
12
Agϩ
Naϩ
Kϩ
0
0
0
0
0
0
0
0
Ϫ4.2
Ϫ4.2
Ϫ4.4
Ϫ5.0
Ϫ5.0
Ϫ5.2
Ϫ5.2
Ϫ5.0
Ϫ5.0
Ϫ5.4
Ϫ1.7
Ϫ4.2
Ϫ4.1
Ϫ4.3
Ϫ5.2
Ϫ5.2
Ϫ5.3
Ϫ5.3
Ϫ5.1
Ϫ5.0
Ϫ4.9
Ϫ1.8
Ϫ3.2
Ϫ3.7
Ϫ4.1
Ϫ5.0
Ϫ4.9
Ϫ5.1
Ϫ4.8
Ϫ5.0
Ϫ5.2
Ϫ5.0
Ϫ1.7
Ϫ3.5
Ϫ3.4
Ϫ3.5
Ϫ4.6
Ϫ4.7
Ϫ4.6
Ϫ4.6
Ϫ4.5
Ϫ4.9
Ϫ4.1
Ϫ1.6
Ϫ2.9
Ϫ2.9
Ϫ4.5
Ϫ4.3
Ϫ4.4
Ϫ4.4
Ϫ4.3
Ϫ4.4
Ϫ4.3
Ϫ4.5
Ϫ1.2
Ϫ3.1
Ϫ3.1
Ϫ4.0
Ϫ4.5
Ϫ4.3
Ϫ4.3
Ϫ4.0
Ϫ4.1
Ϫ4.3
Ϫ4.4
Ϫ1.4
Ϫ3.0
Ϫ3.4
Ϫ3.4
Ϫ3.3
Ϫ4.0
Ϫ3.9
Ϫ3.6
Ϫ3.4
Ϫ3.9
Ϫ3.9
Ϫ1.8
Ϫ3.5
Ϫ3.2
Ϫ3.4
Ϫ4.1
Ϫ4.6
Ϫ4.5
Ϫ4.4
Ϫ4.3
Ϫ4.5
Ϫ4.2
Ϫ2.2
ϩ
NH4
Ca2ϩ
Mg2ϩ
Ni2ϩ
Cu2ϩ
Zn2ϩ
Cd2ϩ
Pb2ϩ
Hg2ϩ
pot
a Note: Selectivity coefficients (log KAg,M) of the electrodes based on ionophores 5–12 are mean data of two measurements using FIM.
strong Hg2ϩ interference in some ionophore-based ISEs12,21,22
and traditional Ag2S-based ISEs23 is largely eliminated in the
present ISEs (log KAg,Hg ≤ Ϫ1.6 for the present ISEs). A possible
explanation is that those ions with high hydration energies,
such as Naϩ, Kϩ, NH4ϩ, Ca2ϩ, Mg2ϩ, Pb2ϩ and most divalent
transition metal ions, cannot strongly interact with selenium
donors in the ionophores, while less heavily hydrated soft Agϩ
complexes are usually in a trans-conformation.25 Thus, 12 might
adopt some complicated coordination patterns with guest
cations compared with ionophores 5–8 in a two-coordinate
trans-conformation. Therefore, the selectivity for silver ion is
relatively lower than that of any one of the 5–8-based ISEs. The
pot
pot
log KAg,M values of the interfering Naϩ, Kϩ, NH4ϩ, Ca2ϩ, Mg2ϩ
and Pb2ϩ, as well as most of the transition metal ions, are larger
than those of any one of the 5–8-based ISEs. As can be seen
from Table 1, the compound 12-based ISE gave the weakest
Hg2ϩ interference towards Agϩ of all the 5–12-based ISEs. It is
known that free Hg2ϩ only exists in a strongly acidic medium
(pH < 2). When the medium pH > 2, Hg2ϩ usually exists in the
form of Hg(OH)ϩ. The oxygen atoms on the lower rim of
the calix scaffold in the ionophores 5–11 will more or less assist
the ligation of Hg(OH)ϩ via O–H ؒ ؒ ؒ O hydrogen bonds. Our
previous studies have demonstrated the strongest examples of
the oxygen atoms close to the soft bonding donors giving rise to
a relatively strong Hg2ϩ interference towards Agϩ. Because
there are no hard donors in the ionophore 12, 12-based ISEs
give the weakest interference of Hg2ϩ towards Agϩ of all the
5–12-based ISEs.
coordinates to soft selenium donors selectively. The fact that
pot
I,M
polymer membranes containing 9–11 gave greater log K
values against most interfering ions than any one of the 5–8-
based ISEs means that 9–11-based ISEs possess lower Agϩ
selectivity than any one of the 5–8-based ISEs. This can be
tentatively rationalized as follows. The two selenium atoms
in the ionophores 5–8 are softer than the two sulfur atoms in
the ionophores 9–11. Compared with sulfur donors, the hard
cations with high hydration energies cannot interact strongly
with the selenium donors. Thus, the softer selenium donors
benefit the coordination with silver ion selectively in the
membrane phase. On the other hand, the neighboring phenyl
of ionophores 5–8 may act as a π-donor to assist the ligation
of silver ion via so called cation–π interactions.24 Although it
is not exact to use the solid state of ionophores to explain the
complicated ISE behavior in the liquid membrane phase, the
solid state conformation of the ionophore may assist further
understanding of the mechanisms of the ionophore-based
ISEs; at least we can predict the tendencies of the ISE
behavior from the solid state structure of the ionophores. As
can be seen from Fig. 1, the two phenyls take an opposite
orientation along the phenyl–selenium axis in the solid state.
This conformation may favor the cation–π coordination
patterns in the spatial orientation.
Besides the differences in the ion-selectivities, there are some
other differences in the performances of 5–12-based ISEs. The
response characteristics of silver ISEs such as response slope,
linear range and response time are summarized in Table 2. As
can be seen from Table 2, the Nernstian slopes of 5–8-based
ISEs are between 54.2 1.5 and 57.2 1.8 mV decadeϪ1 to the
activity of Agϩ in the activity range 5 × 10Ϫ6–1 × 10Ϫ1.4
M
AgNO3. The relevant values of 9–11-based ISEs are between
51.7 1.8 and 52.4 1.8 mV decadeϪ1 to the activity of Agϩ in
the activity range 5 × 10Ϫ6–1 × 10Ϫ2 M AgNO3. The Nernstian
slope of 5–8-based ISEs is remarkably higher than that of
9–11-based ISEs. The linear response range of 5–8-based ISEs
is larger by one order of magnitude than that of 9–11-based
ISEs. The response time of 5–12-based ISEs is within 15 s. One
possible explanation is that sulfur donors give relatively strong
binding of silver ion compared with that of a selenium donor.
The stronger binding of silver ion by a sulfur donor might
interfere in the rapid ion exchange at the interface of membrane
electrodes. On the other hand, the Nernstian slopes of the pres-
ent tweezer-like ionophores 5–8-based ISEs are better than
those of diphenyl selenide, dibenzyl selenide or benzyl phenyl
selenide based ISEs reported by Katsu and co-workers.26 The
ion-selectivity and the Nernstian slopes are also better than
those of our previously reported phosphorus and pyridyl
functionalized tweezer-like calix[4]arenes.16
pot
As shown in Table 1, the log KAg,M values gradually increased
for the interfering Naϩ, Kϩ, NH4ϩ, Ca2ϩ, Mg2ϩ and Pb2ϩ, as
well as most of the transition metal ions examined with the
tether length increased between the selenium atom and calix-
[4]aryl for the same type of ionophores 5–8. There are two
possible explanations for this ion-selectivity tendency. The first
one is that the coordinate adjustable abilities decrease for the
two donor groups with the increase of the tether length between
the selenium atom and the calix scaffold. The second one is that
the ionophores gradually exhibit the signs of ditopic receptors
with the increase of the tether length, namely, the four oxygen
atoms on the lower rim of calix[4]arene act as a hard donor
centre and the two phenylseleno groups act as a soft coordinate
centre. The hard donor centre has an affinity for high hydrate
ions, and the soft donor centre has an affinity for silver ion
selectively.
Although the diseleno compound 12 can provide two
coordination positions for guest ions, unlike the ionophores
5–8, it cannot provide a trans-coordinating geometric con-
figuration for silver ion. It is known that two-coordinate silver
Conclusions
Tweezer-like receptor molecules 25,27-dihydroxy-26,28-bis-
(phenylselenoalkoxy)-5,11,17,23-tetra-tert-butylcalix[4]arenes
798
J. Chem. Soc., Perkin Trans. 2, 2002, 796–801

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Table 2 The response characteristics of silver ISEs based on 5–12
Ionophore
5
6
7
8
9
10
11
12
Slopea/mV decadeϪ1
Linear range/M
Response time/s
54.9 1.4
10Ϫ6–10Ϫ1.4
<10
54.2 1.5
10Ϫ6–10Ϫ1.4
<10
57.2 1.8
10Ϫ6–10Ϫ1.4
<10
56.5 1.6
10Ϫ6–10Ϫ1.4
<10
52.0 1.6
10Ϫ5.3–10Ϫ2
<15
52.4 1.8
10Ϫ5.3–10Ϫ2
<15
51.7 1.8
10Ϫ5.3–10Ϫ2
<15
56.4 1.5
10Ϫ6–10Ϫ2
<10
a Note: the slopes are calculated within their linear range and are mean data of four electrodes (standard deviations given at 95% confidence level) for
each ionophore.
5–8 have been synthesized as sensors for Agϩ-selective elec-
trodes. 25,27-Dihydroxy-26,28-bis(alkylthiaalkoxy)-5,11,17,23-
tetra-tert-butylcalix[4]arenes 9–11 and 1,3-bis(phenylseleno)-
propane 12 were also prepared for the comparison of the ISEs’
performances with 5–8-based ISEs. The polymer membranes
ArCH2Ar), 1.26(s, 18H, t-Bu-H), 0.93(s, 18H, tBu-H). FABϩ-
MS m/z 1016.1 (Mϩ, Calcd, 1016.4). Calcd. for C60H72O4Se2: C,
70.99; H, 7.15. Found: C, 70.91; H, 7.15%.
25,27-Dihydroxy-26,28-bis(phenylselenopropoxy)-5,11,17,23-
tetra-tert-butylcalix[4]arene (6). Reaction of 2 (1 mmol) with
diphenyl diselenide (2 mmol) according to the general pro-
cedure A gave 6 in 91% yield; mp 133–134 ЊC. 1H NMR: 7.82(s,
2H, OH), 7.62(m, 4H, Se-phenyl-H), 7.20(m, 6H, Se-phenyl-H),
7.03(s, 4H, Ar-H), 6.84(s, 4H, Ar-H), 4.23(d, 4H, J = 13.2 Hz,
ArCH2Ar), 4.07(t, 4H, J = 5.3 Hz, OCH2CH2), 3.36(t, 4H,
J = 6.6 Hz, SeCH2CH2), 3.30(d, 4H, J = 13.2 Hz, ArCH2Ar),
2.27(m, 4H, SeCH2CH2CH2), 1.26(s, 18H, t-Bu-H), 0.99(s, 18H,
t-Bu-H). FABϩ-MS m/z 1044.5 (Mϩ, Calcd, 1044.4). Calcd. for
C62H76O4Se2: C, 71.38; H, 7.34. Found: C, 71.21; H, 7.48%.
pot
containing 5–8 gave good selectivity for Agϩ (logKAg,M ≤ Ϫ3.4)
against most of the interfering cations examined (i.e., Naϩ, Kϩ,
NH4ϩ, Mg2ϩ, Ca2ϩ, Ni2ϩ, Cu2ϩ, Zn2ϩ, Cd2ϩ and Pb2ϩ), except
for Hg2ϩ. Ionophores 5–8-based ISEs gave the best selectivity
and sensitivity towards Agϩ against interfering cations of the
eight investigated ionophore based ISEs. The performance of
the present ISEs is superior to that displayed by the traditional
Ag2S-based electrode.
Experimental
1H NMR spectra were recorded on a Bruker AC-P200 spec-
trometer at 200 MHz in CDCl3 solution. Tetramethylsilane
was used as an internal standard. Elemental analyses were
performed on a Perkin-Elmer 2400C instrument. FAB-MS
spectra were obtained on a VG ZAB-HS spectrometer. All
solvents were purified by standard procedures. Poly(vinyl
chloride) (PVC) and potassium tetrakis(4-chlorophenylborate)
(KTClPB) were purchased from Fluka (Buchs, Switzerland).
Dibutyl phthalate (DBP) was obtained from Shanghai
Chemical Reagent Corporation (Shanghai, China). The silver
nitrate (guaranteed reagent) and analytical reagent grade
nitrates of sodium, potassium, ammonium, calcium, mag-
nesium, cadmium, copper, nickel, zinc, lead and mercury were
supplied by Tianjin Chemical Reagent Factory. All solutions
were prepared with distilled deionized water. Compounds 1–4
were prepared according to the literature procedures.27
25,27-Dihydroxy-26,28-bis(phenylselenobutoxy)-5,11,17,23-
tetra-tert-butylcalix[4]arene (7). Reaction of 3 (1 mmol) with
diphenyl diselenide (2 mmol) according to the general pro-
1
cedure A gave 7 in 86% yield; mp 98–99 ЊC. H NMR: 7.72(s,
2H, OH), 7.47(m, 4H, Se-phenyl-H), 7.18(m, 6H, phenyl-H),
7.03(s, 4H, Ar-H), 6.81(s, 4H, Ar-H), 4.23(d, 4H, J = 12.7 Hz,
ArCH2Ar), 3.95(t, 4H, J = 4.8 Hz, OCH2CH2), 3.28(d, 4H,
J = 12.7 Hz, ArCH2Ar), 3.08(t, 4H, J = 5.3 Hz, SeCH2CH2),
2.10(m, 8H, CH2CH2), 1.28(s, 18H, t-Bu-H), 0.97(s, 18H,
t-Bu-H). FABϩ-MS m/z 1072.1 (Mϩ, Calcd, 1072.4). Calcd. for
C64H80O4Se2: C, 71.76; H, 7.53. Found: C, 71.68; H, 7.29%.
25,27-Dihydroxy-26,28-bis(phenylselenohexoxy)-5,11,17,23-
tetra-tert-butylcalix[4]arene (8). Reaction of 4 (1 mmol) with
diphenyl diselenide (2 mmol) according to the general pro-
cedure A gave 8 in 91% yield; mp 99–100 ЊC. 1H NMR: 7.67(s,
2H, OH), 7.48(m, 4H, Se-phenyl-H), 7.19(m, 6H, Se-phenyl-H),
7.02(s, 4H, Ar-H), 6.80(s, 4H, Ar-H), 4.24(d, 4H, J = 12.8 Hz,
ArCH2Ar), 3.92(t, 4H, J = 6.8 Hz, OCH2CH2), 3.27(d, 4H,
J = 12.8 Hz, ArCH2Ar), 2.98(t, 4H, J = 7.1 Hz, SeCH2CH2),
1.98, 1.82, 1.55(m, 16H, –(CH2)4–), 1.31(s, 18H, t-Bu-H), 0.97(s,
18H, t-Bu-H). FABϩ-MS m/z 1127.6 ([M Ϫ 1]ϩ, Calcd, 1128.5).
Calcd. for C68H88O4Se2: C, 72.45; H, 7.87. Found: C, 72.61; H,
7.88%.
General procedure A for the preparation of
diselenocalix[4]arenes 5–8
Diphenyl diselenide (624 mg, 2 mmol), NaOH (240 mg, 6
mmol) and NaBH4 (228 mg, 6 mmol) were added to a 250 mL
flask. After the system was charged with nitrogen, anhydrous
ethanol (30 mL) was added to the stirred mixture. After the
mixture was refluxed for 1 h, a solution of calix[4]arene
dibromide (1 mmol) in 60 mL THF was added to the yellowish
transparent solution. After the addition was completed, the
system was refluxed for another 6 h. Then, the solvent was
removed under reduced pressure. The solid residue was dis-
solved in CH2Cl2 (50 mL) and washed with water (100 mL × 2).
After the organic phase had been dried with anhydrous sodium
sulfate, the filtered solution was condensed to dryness. The
yellowish solid was purified by column chromatography
(petroleum ether : CHCl3 = 1 : 3) and then recrystallized from
CH2Cl2 and methanol.
General procedure B for the preparation of dithiacalix[4]arenes
9–11
Calix[4]arene dibromide (1 mmol) was added to a 100 mL
round-bottomed flask, together with anhydrous potassium
carbonate (276 mg, 2 mmol), and thiol (0.5 mL) in THF
(60 mL). After the system had been charged with nitrogen, the
mixture was refluxed until the disappearance of calix[4]arene
dibromide, monitored by TLC. Then, the solvent was removed
under reduced pressure. The residue was dissolved in CH2Cl2
(50 mL) and washed with water (50 mL × 3). The organic phase
was separated and dried with anhydrous sodium sulfate. After
the filtered solution had been condensed to dryness, the yellow-
ish residue was purified by column chromatography (petroleum
ether : CH2Cl2, 1 : 2).
25,27-Dihydroxy-26,28-bis(phenylselenoethoxy)-5,11,17,23-
tetra-tert-butylcalix[4]arene (5). Reaction of 1 (1 mmol) with
diphenyl diselenide (2 mmol) according to the general pro-
cedure A gave 5 in 92% yield; mp 105–106 ЊC. 1H NMR:
7.58(m, 4H, Se-phenyl-H), 7.23(m, 6H, Se-phenyl-H), 7.16(s,
2H, OH), 7.02(s, 4H, Ar-H), 6.75(s, 4H, Ar-H), 4.25(d, 4H,
J = 13.7 Hz, ArCH2Ar), 4.17(t, 4H, J = 6.8 Hz, OCH2CH2),
3.44(t, 4H, J = 6.8 Hz, SeCH2CH2), 3.26(d, 4H, J = 13.7 Hz,
25,27-Dihydroxy-26,28-bis(propylthiabutoxy)-5,11,17,23-
tetra-tert-butylcalix[4]arene (9). Reaction of 3 (1 mmol) with
propanethiol (0.5 mL) according to the general procedure B
J. Chem. Soc., Perkin Trans. 2, 2002, 796–801
799

View Article Online
gave 11 in 93% yield; mp 104–106 ЊC. 1H NMR: 7.80(s,
2H, OH), 7.02(s, 4H, Ar-H), 6.81(s, 4H, Ar-H), 4.25(d, 4H,
J = 12.8 Hz, ArCH2Ar), 3.98(t, 4H, J = 6.4 Hz, OCH2), 3.29(d,
4H, J = 12.8 Hz, ArCH2Ar), 2.67(t, 4H, J = 6.4 Hz, CH2),
2.52(t, 4H, J = 7.2 Hz, –CH2), 2.04, 2.00(m, 8H, CH2), 1.61(m,
4H, CH2), 1.26(s, 18H, t-Bu-H), 0.97(s, 18H, t-Bu-H), 0.96(t,
6H, J = 7.3 Hz, SCH2CH2CH3). FABϩ-MS m/z 908.2 (Mϩ,
Calcd, 908.6). Calcd. for C58H84O4S2ؒ0.75CH2Cl2: C, 72.51; H,
8.86. Found: C, 72.81; H, 9.01%.
Table 3 Crystal data and refinement parameters
Data
6
Formula
Formula wt/g molϪ1
T /K
Wavelength/Å
Crystal system
Space group
a/Å
b/Å
c/Å
α/deg
C62H76O4Se2ؒCH2Cl2
1128.07
293(2)
0.71073
Monoclinic
C2/c
21.4021(18)
12.7375(11)
21.3752(18)
90
25,27-Dihydroxy-26,28-bis(propylthiahexoxy)-5,11,17,23-
tetra-tert-butylcalix[4]arene (10). Reaction of 4 (1 mmol) with
propanethiol (0.5 mL) according to the general procedure
B gave 10 in 87% yield. 1H NMR: 7.82(s, 2H, OH), 7.01(s, 4H,
Ar-H), 6.80(s, 4H, Ar-H), 4.26(d, 4H, J = 13.0 Hz, ArCH2Ar),
3.98(t, 4H, J = 6.8 Hz, OCH2), 3.29(d, 4H, J = 13.0 Hz,
ArCH2Ar), 2.48, 1.95(m, 24H, CH2), 1.60(m, 4H, CH2), 1.25(s,
18H, t-Bu-H), 0.97(s, 18H, t-Bu-H), 0.84(t, 6H, J = 7.3 Hz,
–CH3). FABϩ-MS m/z 964.9 (Mϩ, Calcd, 964.6). Calcd. for
C62H92O4S2: C, 77.13; H, 9.60. Found: C, 77.25; H, 9.49%.
β/deg
90.207(2)
90
5827.0(9)
4
1.286
2360
γ/deg
V/Å3
Z
Dc/Mg mϪ3
F (000)
Crystal size/mm
µ (Mo Kα)/mmϪ1
θ range/deg
Reflns collected
Independent reflns
Rint
Restraints
Parameters
GOOF
0.3 × 0.2 × 0.15
1.406
1.86 to 25.03
11775
5140
0.0210
0
330
1.050
25,27-Dihydroxy-26,28-bis(pentylthiahexoxy)-5,11,17,23-
tetra-tert-butylcalix[4]arene (11). Reaction of 4 (1 mmol) with
n-pentanethiol (0.7 mL) according to the general procedure
B gave 11 as a sticky oil in 88% yield. 1H NMR: 7.84 (s,
2H, OH), 7.03 (s, 4H, Ar-H), 6.82 (s, 4H, Ar-H), 4.27 (d, 4H,
J = 12.9 Hz, ArCH2Ar), 3.97 (t, 4H, J = 6.8 Hz, OCH2), 3.29
(d, 4H, J = 12.9 Hz, ArCH2Ar), 2.58 (m, 8H, CH2), 2.01, 1.65,
1.57, 1.37 (m, 28H, CH2), 1.27 (s, 18H, t-Bu-H), 0.96 (s, 18H,
t-Bu-H), 0.87 (t, 6H, J = 7.2 Hz, –CH3). FABϩ-MS m/z 1020.4
(Mϩ, Calcd, 1020.7). Calcd. for C66H100O4S2: C, 77.59; H, 9.87.
Found: C, 77.56; H, 9.59%.
R1
wR2
0.0543
0.1597
of saturated Hg/Hg2Cl2 electrode with 3 M KNO3 as bridge
electrolyte.
EMF Measurements
All EMF (electromotive force) measurements were made at
25 0.1 ЊC, using a pH/mV meter. Sample solutions were mag-
netically stirred and kept in a thermostated water bath. The
EMF values were corrected by subtracting the liquid-junction
potential between the external reference electrode and the
sample solution in the high Agϩ concentration. The com-
position of the electrochemical cell is given as AgؒAgCl|0.01 M
AgNO3|PVC membrane |sample solution |3 M KNO3 |saturated
KCl|Hg2Cl2ؒHg.
1,3-Bis(phenylseleno)propane (12). Diphenyl diselenide
(512 mg, 1.6 mmol), NaOH (192 mg, 4.8 mmol) and NaBH4
(182 mg, 4.8 mmol) were added to a 250 mL flask. After the
system had been charged with nitrogen, anhydrous ethanol
(30 mL) was added to the stirred mixture. After the mixture
had been refluxed for 1 h, a solution of 1,3-dibromopropane
(212 µL, ca. 1.52 mmol) in 60 mL THF was added dropwise to
the yellowish transparent solution. After the addition was
completed, the system was refluxed for another 6 h. Then, the
solvent was removed under reduced pressure. The oily resi-
due was dissolved in CH2Cl2 (50 mL) and washed with water
(50 mL × 2). After the organic phase had been dried with
anhydrous sodium sulfate, the filtered solution was condensed
to dryness. The yellowish oil was purified by column chrom-
atography (petroleum ether : CHCl3 = 3 : 1). 15 was obtained as
a yellowish oil (0.323 g) in 60% yield. 1H NMR: 7.45–7.41
(m, 4H), 7.23–7.20 (m, 6H), 2.97 (t, 4H, J = 7.2 Hz), 2.02
(m, 2H, J = 7.2 Hz). FABϩ-MS m/z 355.7 (Mϩ, Calcd, 355.9).
Calcd. for C15H16Se2: C, 58.86; H, 4.55. Found: C, 59.41; H,
4.21%.
Selectivity coefficients
pot
The potentiometric selectivity coefficients KAg,M determined
here are defined in the Nicolsky–Eisenman equation (eqn. (1)).
(1)
E represents the experimentally observed potential, R the
gas constant, T the thermodynamic temperature in K, F
the Faraday constant, aAg the Agϩ activity, aM the activity of
the foreign cation, and ZM the charge of the foreign cation.
The selectivity coefficients were determined by the fixed inter-
ference method (FIM).28 According to this method, the
Membrane electrode preparation
A typical procedure for membrane preparation is as follows.
Poly(vinyl chloride) (PVC) (132 mg, 33%), dibutyl phthalate
(DBP) (264 mg, 65–66%), benzothiazolyl functionalized calix-
[4]arene (4 mg, 1%) and potassium tetrakis(p-chlorophenyl)-
borate (KTClPB) (75 mol% relative to the ionophore) were
dissolved in 5 mL of THF. This solution was then poured into a
flat-bottomed petri dish of 32 mm inner diameter and 50 mm
height. Gradual evaporation of the solvent at room temper-
ature gave a transparent, flexible membrane of about 0.3 mm in
thickness. A disk of 7 mm in diameter was cut from the PVC
membrane and incorporated into a PVC tube tip with 5% THF
solution. After injection of 0.01 M aqueous solution of AgNO3
as the internal solution, the electrode was conditioned by soak-
ing in 0.01 M aqueous solution of AgNO3 for 24 h before
measurements. The reference electrode is a double junction type
pot
potentiometric selectivity coefficients, KAg,M, can be evaluated
from the potential measurements on solutions containing a
fixed concentration of the interfering ions (Mnϩ) and varying
amounts of Agϩ ion concentration by using eqn. (2)
(2)
pot
The resulting log KAg,M values are summarized in Table 1.
Crystallographic structural determination
Crystals of 6 suitable for X-ray crystallography were grown by
slow evaporation from the CH2Cl2–MeOH solution of 6. X-ray
800
J. Chem. Soc., Perkin Trans. 2, 2002, 796–801

View Article Online
12 K. M. O’Conner, G. Svehla, S. J. Harris and M. A. McKervey,
crystallographic data were obtained on a Bruker SMART 1000
instrument. Structures were solved with the SHELXS-97 soft-
ware. Crystal, data collection, and refinement parameters are
given in Table 3.29
Anal. Proc., 1993, 30, 137.
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Cobben, R. J. M. Egberink, J. G. Bomer, P. Bergveld, W. Verboom
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Acknowledgements
The National Natural Science Foundation of China and the
Foundation of Nankai University supported this work.
16 X. Zeng, L. Weng, L. Chen, X. Leng, H. Ju, X. He and Z. Z. Zhang,
J. Chem. Soc., Perkin Trans. 2, 2001, 545.
17 X. Zeng, L. Weng, L. Chen, X. Leng, Z. Z. Zhang and X. He,
Tetrahedron Lett., 2000, 41, 4917.
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