Highly selective fluorescent sensors for Hg2+ and Ag+ based on bis-triazole-coupled polyoxyethylenes in MeOH solution

Article abstract of DOI:10.1002/ejoc.200900987

Fluorescent chemosensors 6-9, with variable length polyoxyethylenes between two triazolylmethyl ether units, have been synthesized under "click" conditions in which the bistriazoles and polyoxyethylenes were used as metal-ion binding sites and the pyrenes

Full text of DOI:10.1002/ejoc.200900987

FULL PAPER
DOI: 10.1002/ejoc.200900987
Highly Selective Fluorescent Sensors for Hg2+ and Ag+ Based on
Bis-triazole-Coupled Polyoxyethylenes in MeOH Solution
Hao-Chih Hung,[a] Chi-Wen Cheng,[a] Yu-Yun Wang,[a] Yu-Jen Chen,[a] and
Wen-Sheng Chung*[a]
Keywords: Sensors / Host-guest chemistry / Fluorescence / Fluorescent probes / Nitrogen heterocycles
Fluorescent chemosensors 6–9, with variable length polyoxy-
ethylenes between two triazolylmethyl ether units, have
been synthesized under “click” conditions in which the bis-
triazoles and polyoxyethylenes were used as metal-ion bind-
ing sites and the pyrenes as fluorophores. Of the 15 metal
ions screened, the fluorescence of chemosensors 6–9 in meth-
anol solution was found to be selectively quenched by only
quenched by only Hg2+. These results imply that the recogni-
tion of Hg2+ does not need the cooperation of two triazole
groups. Binding constants for the interactions of 6–9 with Ag+
increased as the chain length of the polyoxyethylene in-
creased. Finally, a very high selectivity of compound 9
towards Hg2+ in aqueous methanol solution was observed.
Hg2+ and Ag+. In contrast, the fluorescence of control com- (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
pound 10,
a
[(triazol-4-yl)methoxymethyl]pyrene, was
Germany, 2009)
formational change.[6] It has been reported that two pyrenyl
moieties connected by a series of polyoxyethylenes[6b] or di-
oxaoctanediamides[6f] show moderate-to-excellent selecti-
vity towards Ca2+ and Hg2+, respectively. Because triazole
is readily made by “click” chemistry[7] from an azide and
an alkyne,[6h,8,9c] it prompted us to explore the possibility
of combining two terminal pyrenes with bis-triazoles[6h,8,9c]
and polyoxyethylenes[6b,6c] for metal-ion screening studies.
We have previously reported the synthesis of a series of
1,n-bis-pyrenylmethoxymethyltriazoles linked by methylene
chains, which exhibit both monomer and excimer emission
quenching in the presence of Pb2+ and an enhanced mono-
mer but quenched excimer in the presence of Cd2+ and
Introduction
Fluorescent chemosensors that can selectively recognize
metal ions have attracted considerable attention in the fields
of supramolecular chemistry, biology, and medicinal chem-
istry.[1] An effective fluorescent chemosensor must convert
the cation recognition by an ionophore into an easily moni-
tored and highly sensitive light signal from the fluorophore.
Mercury ions are severe environmental pollutants, and sev-
eral diseases are known to be associated with mercury con-
tamination.[2] Silver ions also have adverse biological ef-
fects, and there are many reports of silver bioaccumulation
and toxicity.[3] Thus, the development of sensitive and selec-
tive chemosensors for Ag+ and Hg2+ in various media is of
considerable importance for environmental protection and
human health.[4] Zhang and co-workers reported that com-
pounds with two tetraphenylethylenes bearing adenine and
thymine moieties were fluorescence turn-on chemosensors
Zn2+ [6h]
The metal-ion selectivity in previous systems was
.
relatively poor (it responded to at least five metal ions in
CH3CN) and the fluorescence phenomena, despite being
significant, were quite complicated. Furthermore, the sol-
vent system is always a concern in the development of use-
ful metal ion sensors. We chose to replace the methylene
chain employed previously by polyoxyethylenes[6b,6c] be-
cause they may help the bis-triazole groups to coordinate
metal ions. Furthermore, they may also help to increase the
solubility of the bis-pyrenyl-triazole system in solvents
more polar than CH3CN.
for Ag+ and Hg2+ [5]
Lee and co-workers reported an
NS2O2-macrocycle-based fluoroionophore as a highly selec-
tive turn-on-type fluorescence chemosensor for Ag+ in
aqueous ethanol solution.[4e]
Pyrene is one of the most useful fluorogenic units be-
cause of its characteristic and sensitive emissions from both
the monomer and the excimer. Moreover, the ratio of its
monomer-to-excimer emission is a sensitive probe for con-
.
Results and Discussions
[a] Department of Applied Chemistry, National Chiao Tung Uni-
versity,
The synthetic pathways for chemosensors 6–9, control
compound 10, and 11[6h] are summarized in Scheme 1. The
polyoxyethylene diazides 1–4 were first prepared by treating
the corresponding di-O-tosyl-polyoxyethylenes with sodium
Hsinchu 30050, Taiwan, Republic of China,
Fax: +886-3-5723764
E-mail: wschung@cc.nctu.edu.tw
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.200900987.
6360
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 6360–6366

Highly Selective Fluorescent Sensors for Hg2+ and Ag+
azide. The subsequent reaction of 1-(propagyloxymethyl)- periments were carried out for 6–9 and revealed a 1:1 com-
pyrene (5)[6h] with the corresponding polyoxyethylene di- plex for each of them with Hg2+ and Ag+ in MeOH. By
azides 1–4 under click conditions afforded the target mole- using Stern–Volmer plots, the association constants of 6–9
cules 6–9 in 45–77% yields, with the triazoles and polyoxy- with Hg2+ were calculated to be 9.9ϫ104, 1.5ϫ105,
ethylenes designed to function as metal-ion binding sites 6.6ϫ104, and 6.1ϫ104 –1, respectively.[10]
and the pyrenes as reporting fluorophores.[6,9] The forma-
The control compound 10, bearing a triazolylmethoxy-
tion of triazoles 6–9 was monitored by 1H NMR spec- methylpyrene, showed selective quenching of the monomer
troscopy by the appearance of a new singlet arising from emissions of pyrene at λem = 375 and 395 nm upon addition
the triazole proton at around δ = 7.4–7.7 ppm.[6h,9]
of Hg2+ (Figure 2). Under these conditions, compound 10
did not show any excimer emission from the pyrenyl group.
This result implies that in MeOH the recognition of Hg2+
by 10 does not need the cooperation of two triazole groups;
alternatively, the fluorescence of two pyrenyl groups may be
quenched by the bound Hg2+
.
Figure 3 shows the gradual change in the fluorescence
spectra of 9 upon addition of Ag+ and the corresponding
Job plot. By using Stern–Volmer plots, the binding con-
stants of 6–9 with Ag+ in MeOH were calculated to be
7.1ϫ103, 1.4ϫ104, 3.3ϫ104, and 4.3ϫ104 –1, respec-
tively.[10] Note that the binding constants of 6–9 with Ag+
increase as the polyoxyethylene chain increases. The encour-
aging results obtained with these chemosensors in MeOH
led us to explore their metal-ion selectivities in aqueous sol-
vent. When a mixture of H2O/MeOH (9:1, v/v) was used as
the solvent system, 9 showed monomer emission at λem
=
375 and 395 nm and excimer emission at λem = 490 nm. We
found that in aqueous methanol solution, 9 still showed the
same selectivity towards Hg2+ and Ag+: Both monomer and
excimer emissions were quenched upon complexation (Fig-
ure 4, a). From a Stern–Volmer plot, the association con-
stant of 9 with Hg2+ in a mixture of H2O/MeOH (v/v, 9:1)
was calculated to be 8.8ϫ103 –1.[10] In sharp contrast,
when the fluorescence quenching experiments of 6–9 were
carried out in MeCN, poor selectivity for metal ions was
found, that is, they showed various fluorescence-sensing be-
havior towards Cu2+, Hg2+, Cr3+, Cd2+, Zn2+, and Pb2+
(Table S2 and Figure S14 of the Supporting Information).
Part b of Figure 4 shows that the monomer and excimer
emissions of the pyrene groups in chemosensor 9 were
quenched by Cu2+, Hg2+, Cr3+, and Pb2+; whereas en-
hanced monomer but quenched excimer emissions were ob-
Scheme 1. Synthesis of chemosensors 6–9, control compound 10,
and 11.[6h]
When excited at 312 nm, compounds 6–9 (10 µ in served for Ca2+, Cd2+, and Zn2+
MeOH) showed strong intramolecular excimer emissions at
.
In our previous studies,[6h] the bis-triazolylmethoxymeth-
around λmax = 478 nm and weak monomer emission bands ylpyrenes linked by methylene chains showed dual-mode re-
at around 376 and 395 nm.[6] The changes in the fluores- cognition of transition-metal ions in CH3CN; see Figure 5a
cence intensities of 6–9 (10 µ) in the presence of 10 equiv. for the titration results for compound 11. However, when
of 15 metal perchlorate salts (Li+, Na+, K+, Mg2+, Ca2+
,
we repeated the metal-ion screening experiments using
Ba2+, Cr3+, Mn2+, Ni2+, Cu2+, Zn2+, Ag+, Cd2+, Hg2+, and MeOH/MeCN (97.5:2.5, v/v) as solvent,[11] compound 11
Pb2+) were studied and the results are summarized in Fig- showed selective fluorescence quenching only towards Hg2+
ure 1 and Table S1 of the Supporting Information. Figure 1 (Figure 5, b). Based on these results, we believed that in
shows the changes in the fluorescence spectra of 6–9 (10 µ MeOH solution the bis-triazole groups are not effective co-
in MeOH) upon addition of 10 equiv. of metal ions. Note ordination sites of Ag+ ions; Ag+ ions were further stabi-
that there is a gradual increase in fluorescence quenching lized by coordination with the polyoxyethylene ethers. Thus,
towards Ag+ as the chain length of the polyoxyethylenes in the polyoxyethylene chains in 6–9 not only serve as a spacer
compounds 6–9 increases. In the presence of Hg2+ and Ag+, for linking the bis-triazoles but also serve as binding sites
the fluorescence spectra of 6–9 showed not only a quenched for Ag+. Furthermore, the longer chain lengths of the poly-
monomer, but also a quenched excimer due to conforma- oxyethylenes allow more flexible conformational change to
tional distortion of the polyoxyethylene chains. Job plot ex- achieve a better binding for the Ag+ ions.
Eur. J. Org. Chem. 2009, 6360–6366
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
6361

H.-C. Hung, C.-W. Cheng, Y.-Y. Wang, Y.-J. Chen, W.-S. Chung
FULL PAPER
Figure 1. Fluorescence changes for the hosts (a) 6, (b) 7, (c) 8, and (d) 9 (10 µ in MeOH) upon the addition of 15 metal ions (10 equiv.,
λex = 312 nm, 298 K).
strongly shifted upfield (∆δ = –0.42, –0.33, and –0.79 ppm,
respectively). These results imply that complexation of 9
with Hg2+ induces a large conformational change that
causes these protons to be shielded by pyrene rings. The
protons of the polyoxyethylenes also showed some chemical
shift changes, which suggests that the polyoxyethylene moi-
eties are also involved in the coordination with Hg2+
.
Figure 7 shows the stacked plots of the 1H NMR spectra
of 9 (5 m) in the absence and presence of 1 equiv. of Ag+
at 25 °C. Upon complexation with 1 equiv. of Ag+, only the
protons Hb showed a significant upfield shift (∆δ =
–0.30 ppm); the oxyethylene protons (Hd–Hf, Hh, and Hi)
did not show much change. For more detailed titration
plots of 9 (5 m) in the absence and presence of various
amounts of Ag+, see Figure S14 of the Supporting Infor-
mation. Despite the nonsystematic changes in the chemical
shifts of these protons, the observations suggest that both
the polyoxyethylenes and the bis-triazoles try to reorient
themselves to coordinate the Ag+. It is expected that the
coordination of 9 with Ag+ should be very close to the tri-
azole and oxygen atoms of the ether groups that distort the
original conformation.
Figure 2. Fluorescence changes for the control compound 10
(10 µ in MeOH) upon addition of 15 metal ions (10 equiv., λex
=
312 nm, 298 K).
To obtain structural information and conformational
change in the complexes formed between 9 and Hg2+ (and
Ag+), we carried out 1H NMR titration experiments in
CD3CN/CD3OD (1:4, v/v) solution. Figure 6 shows the
The results of the fluorescence quenching suggest that
1
stacked plots of the H NMR spectra of 9 (5 m) in the the pyrene units behave as PET donors and the metal-ion-
1
absence and presence of 1 equiv. of Hg2+ at 25 °C. The H bound triazole groups behave as electron acceptors.[6h,12] As
NMR spectra of 9 (5 m) with various amounts of Hg2+ the chain length of the polyoxyethylene increases, the bind-
are shown in Figure S13 of the Supporting Information. ing ability of chemosensors 6–9 towards Ag+ increases.
Upon complexation with 1 equiv. of Hg2+, the 5-triazole Based on the H NMR titration results and fluorescence
1
proton Hc and the methylene protons Hb and Hd were changes, we propose that Hg2+ and Ag+ are bound between
6362
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 6360–6366

Highly Selective Fluorescent Sensors for Hg2+ and Ag+
Figure 3. (a) Changes in the fluorescence spectra (λex = 312 nm) of 9 (10 µ in MeOH) upon addition of various amounts of Ag+ and
(b) job plot for 9 with Ag+ at 298 K.
Figure 4. Fluorescence changes for compound 9 (10 µ) upon addition of 15 metal ions (10 equiv.) in (a) H2O/MeOH (9:1, v/v; λex
333 nm, 298 K) and (b) MeCN solution (λex = 312 nm, 298 K).
=
Figure 5. Fluorescence changes for compound 11 (10 µ) upon addition of 15 metal ions (10 equiv.) in (a) MeCN and (b) MeOH/MeCN
(97.5:2.5, v/v) solution (λex = 312 nm, 298 K).
the 3-N atoms of the bis-triazoles, the pyrenylmethyl ether (monitored at 376 nm) in 9 exhibited two stepwise changes:
groups, and the polyoxyethylene bridge of 9 (Scheme 2), It reached a maximum above pH 9, entered a plateau region
which distorts the original conformation and thus in the range pH 6–8, and reached a minimum below pH 3
quenches both the monomer and excimer emissions of the (see Figure S16 of the Supporting Information). Two sets
pyrenes.
of experiments were then carried out on 9 at pH 4 and 9.
Because metal ions can be detected by molecule 9 The fluorescence responses of 9 towards Hg2+ were less sen-
through fluorescence in a 10% aqueous methanol solution, sitive than that at pH 7. Thus, the fluorescent chemosensor
we further tested its fluorescence response as a function of 9 in H2O/MeOH (9:1, v/v) works well only under neutral
pH. The fluorescence intensity of the pyrene monomer conditions.
Eur. J. Org. Chem. 2009, 6360–6366
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
6363

H.-C. Hung, C.-W. Cheng, Y.-Y. Wang, Y.-J. Chen, W.-S. Chung
FULL PAPER
Scheme 2. Possible binding modes of 9 with Hg2+ and Ag+ in
MeOH.
creased. Finally, the very high selectivity of compound 9
towards Hg2+ in aqueous methanol solution shows that the
readily synthesized [(triazol-4-yl)methoxymethyl]pyrene
system is a potential fluorogenic sensor for the environmen-
tal or biological detection of Hg2+ ions.
1
Figure 6. The H NMR titration spectra of (a) 9 (5 m) and (b) 9
in the presence of 1 equiv. of Hg2+ in CD3CN/CD3OD (1:4, v/v):
x and @ represent solvent signals.
Experimental Section
General: All reported yields are isolated yields. Flash column
chromatography was performed by using silica gel (70–230 mesh).
Melting points were determined with a Yanaco MP500D apparatus
1
and are uncorrected. H NMR spectra were recorded at 300 MHz
with the solvent peak (usually CDCl3) as the internal standard and
13C NMR spectra were recorded at 75.4 MHz. Mass spectra were
recorded in the FAB mode with m-nitrobenzyl alcohol (NBA) as
the matrix. UV/Vis spectra were recorded with a HP-8453 spectro-
photometer, fluorescence spectra were measured with an Aminoco
Bowman Series-2-type spectrofluorimeter, and solvents were of
HPLC grades.
1,8-Bis[4-(pyren-1-ylmethoxymethyl)-1H-1,2,3-triazole-1-yl]-3,6-di-
oxaoctane (6): A mixture of 1-[(prop-2-ynyloxy)methyl]pyrene
(0.27 g, 1.0 mmol), 1,8-diazido-3,6-dioxaoctane (0.1 g, 0.5 mmol),
and CuI (about 5 mg, 0.02 mmol) in THF and water (9:1, v/v,
30 mL) was stirred vigorously at 70 °C for 18 h. The mixture was
extracted thrice (5 mLϫ3) with chloroform. The chloroform layer
was dried with MgSO4 and the solvent was removed under reduced
pressure. The residue obtained was purified through a silica gel
column eluting with ethyl acetate/MeOH (30:1, v/v) to give 0.28 g
(77 %) of 6. Yellow oil; Rf = 0.325 (EtOAc/MeOH = 10:1). 1H
NMR (CDCl3, 300 MHz): δ = 8.26 (d, J = 9.2 Hz, 2 H, CHpyrene),
8.14–7.94 (m, 16 H, CHpyrene), 7.45 (s, 2 H, CH5-triazole), 5.22 (s, 4
H, CpyreneCH2O), 4.73 (s, 4 H, OCH2C4-triazole), 4.20 (t, J = 4.5 Hz,
4 H, N1-triazoleCH2C), 3.52 (t, J = 4.5 Hz, 4 H, CCH2O), 3.29 (s, 4
H, OCH2CH2O) ppm. 13C NMR (CDCl3, 75.4 MHz): δ = 144.8
(Cq), 131.3 (Cq), 131.1 (Cq), 130.8 (Cq), 130.6 (Cq), 129.3 (Cq),
127.7 (CH), 127.4 (CH), 127.3 (CH), 127.2 (CH), 125.9 (CH), 125.2
(CH), 125.2 (CH), 124.7 (Cq), 124.5 (Cq), 124.4 (CH), 123.7 (CH),
123.3 (CH), 71.0 (CH2), 70.0 (CH2), 69.0 (CH2), 63.7 (CH2), 49.9
(CH2) ppm. HRMS (FAB): calcd. for C46H40N6O4 [M]+ 740.3111;
found 740.3116.
1
Figure 7. H NMR titration of (a) 9 (5 m) and (b) 9 in the pres-
ence of 1 equiv. of Ag+ in CD3CN/CD3OD (1:4, v/v): x and @
represent solvent signals.
Conclusions
A series of new fluoroionophores 6–9 with bis-triazoles
and polyoxyethylenes as cationic binding sites and pyrenes
as the reporting units have been synthesized. In MeOH
solution, of the 15 metal ions screened, chemosensors 6–9
responded selectively to Hg2+ and Ag+. Under similar con-
ditions, the control compound 10, a [(triazol-4-yl)meth-
oxymethyl]pyrene, showed selective fluorescence quenching
only towards Hg2+. These results imply that the recognition
of Hg2+ does not need the cooperation of two triazole
groups. Note that the binding constants of 6–9 towards Ag+
1,11-Bis[4-(pyren-1-ylmethoxymethyl)-1H-1,2,3-triazole-1-yl]-3,6,9-
trioxaundecane (7): A mixture of 1-[(prop-2-ynyloxy)methyl]pyrene
(0.27 g, 1.0 mmol), 1,11-diazido-3,6,9-trioxaundecane (0.12 g,
increased as the chain length of the polyoxyethylenes in- 0.50 mmol), and CuI (about 5 mg, 0.02 mmol) in THF and water
6364
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 6360–6366

Highly Selective Fluorescent Sensors for Hg2+ and Ag+
(9:1, v/v, 30 mL) was stirred vigorously at 70 °C for 18 h. The mix-
ture was extracted thrice (5 mLϫ3) with chloroform. The chloro-
form layer was dried with MgSO4 and the solvent was removed
under reduced pressure. The residue obtained was purified through
a silica gel column eluting with ethyl acetate/MeOH (30:1, v/v) to
percentage fluorescence changes for hosts 6–9 in CH3OH upon ad-
dition of various metal ions at 298 K (Table S1), fluorescence ti-
tration spectra for 6–9 with various amounts of Hg2+ and Ag+ in
CH3OH solution (Figures S9–S12), 1H NMR titrations of 6–9 in
the presence of various amounts of metal ions Hg2+ and Ag+ (Fig-
ures S13 and S14), percentage fluorescence changes for hosts 6–9
give 0.18 g (47%) of 7. Yellow oil; Rf = 0.18 (EtOAc/MeOH =
1
10:1). H NMR (CDCl3, 300 MHz): δ = 8.29 (d, J = 9.2 Hz, 2 H, (10 µ in CH3CN) upon addition of various metal ions (Table S2),
CHpyrene), 8.16–7.95 (m, 16 H, CHpyrene), 7.57 (s, 2 H, CH5-triazole), and fluorescence changes for hosts 6–9 upon addition of 15 metal
5.25 (s, 4 H, CpyreneCH2O), 4.76 (s, 4 H, OCH2C4-triazole), 4.32 (t, J ions (Figure S15).
= 5.0 Hz, 4 H, N1-triazoleCH2C), 3.57 (t, J = 5.0 Hz, 4 H, CCH2O),
3.28 (br. s, 8 H, OCH2CH2O) ppm. 13C NMR (CDCl3, 75.4 MHz):
δ = 144.7 (Cq), 131.3 (Cq), 131.1 (Cq), 130.9 (Cq), 130.7 (Cq), 129.4
Acknowledgments
(Cq), 127.7 (CH), 127.5 (CH), 127.3 (CH), 127.2 (CH), 125.9 (CH),
We thank the National Science Council (NSC), Taiwan and the
125.2 (CH), 125.2 (CH), 124.8 (Cq), 124.6 (Cq), 124.4 (CH), 123.8
MOE ATU Program of the Ministry of Education, Taiwan, Repub-
lic of China for financial support.
(CH), 123.4 (CH), 71.0 (CH2), 70.2 (CH2), 70.1 (CH2), 69.0 (CH2),
63.6 (CH2), 50.1 (CH2) ppm. HRMS (FAB): calcd. for C48H44N6O5
[M]+ 784.3373; found 784.3380.
[1] a) A. P. de Silva, H. Q. N. Gunaratne, T. Gunnlaugsson,
1,14-Bis[4-(pyren-1-ylmethoxymethyl)-1H-1,2,3-triazole-1-yl]-
3,6,9,12-tetraoxatetradecane (8): A mixture of 1-[(prop-2-ynyloxy)-
methyl]pyrene (0.380 g, 1.42 mmol), 1,14-diazido-3,6,9,12-tetra-
oxatetradecane (0.20 g, 0.71 mmol), and CuI (about 5 mg,
A. J. M. Huxley, C. P. McCoy, J. T. Rademacher, T. E. Rice,
Chem. Rev. 1997, 97, 1515–1566; b) J.-P. Desvergne, A. W.
Czarnik in Chemosensors of Ion and Molecular Recognition,
Kluwer, Dordrecht, 1997; c) B. Valeur, I. Leray, Coord. Chem.
0.02 mmol) in THF and water (9:1, v/v, 30 mL) was stirred vigor-
ously at 70 °C for 18 h. The mixture was extracted thrice (5 mLϫ3)
with chloroform. The chloroform layer was dried with MgSO4 and
the solvent was removed under reduced pressure. The residue ob-
tained was purified through a silica gel column eluting with ethyl
acetate/MeOH (30:1, v/v) to give 0.26 g (45%) of 8. Yellow oil; Rf
= 0.2 (EtOAc/MeOH = 10:1). 1H NMR (CDCl3, 300 MHz): δ =
8.29 (d, J = 9.2 Hz, 2 H, CHpyrene), 8.15–7.94 (m, 16 H, CHpyrene),
7.65 (s, 2 H, CH5-triazole), 5.26 (s, 4 H, CpyreneCH2O), 4.78 (s, 4 H,
OCH2C4-triazole), 4.39 (t, J = 5.0 Hz, 4 H, N1-triazoleCH2C), 3.67 (t,
J = 5.0 Hz, 4 H, CCH2O), 3.38–3.30 (m, 12 H, OCH2CH2-
OCH2) ppm. 13C NMR (CDCl3, 75.4 MHz): δ = 144.8 (Cq), 131.2
(Cq), 131.1 (Cq), 130.9 (Cq), 130.7 (Cq), 129.3 (Cq), 127.7 (CH),
127.4 (CH), 127.3 (CH), 127.1 (CH), 125.9 (CH), 125.2 (CH), 125.2
(CH), 124.8 (Cq), 124.5 (Cq), 124.4 (CH), 123.9 (CH), 123.3 (CH),
70.9 (CH2), 70.2 (CH2), 70.2 (CH2), 70.1 (CH2), 69.1 (CH2), 63.6
(CH2), 50.1 (CH2) ppm. HRMS (FAB): calcd. for C50H48N6O6
[M]+ 828.3635; found 828.3615.
Rev. 2000, 205, 3–40; d) A. W. Czarnik (Ed.) in Fluorescent
Chemosensors for Ion and Molecule Recognition, American
Chemical Society, Washington, DC, 1993; e) B. Valeur, in: Mo-
lecular Fluorescence: Principles and Applications, Wiley-VCH,
Weinheim, 2002.
[2] a) H. H. Harris, I. Pickering, G. N. George, Science 2003, 301,
1203–1203; b) I. Onyido, A. R. Norris, E. Buncel, Chem. Rev.
2004, 104, 5911–5929.
[3] a) H. T. Ratte, Environ. Toxicol. Chem. 1999, 18, 89–108; b)
H. Q. Peng, B. W. Brooks, R. Chan, O. Chyan, T. W. L. Point,
Chemosphere 2002, 46, 1141–1146; c) M. R. Ganjali, P. Nor-
ouzi, T. Alizadeh, M. Adib, J. Braz. Chem. Soc. 2006, 17, 1217–
1222; d) X. B. Zhang, Z. X. Han, Z. H. Fang, G. L. Shen, R. Q.
Yu, Anal. Chim. Acta 2006, 562, 210–215.
[4] a) R.-H. Yang, W.-H. Chan, A. W. M. Lee, P.-F. Xia, H.-K.
Zhang, K. Li, J. Am. Chem. Soc. 2003, 125, 2884–2885; b) A.
Coskun, E. U. Akkaya, J. Am. Chem. Soc. 2005, 127, 10464–
10465; c) L. Liu, D. Zhang, X. Zhang, J. Xiang, D. Zhu, Org.
Lett. 2008, 10, 2271–2274; d) M. Nolan, S. J. Lippard, Chem.
Rev. 2008, 108, 3443–3480; e) C.-S. Park, J.-Y. Lee, E.-J. Kung,
J.-E. Lee, S.-S. Lee, Tetrahedron Lett. 2009, 50, 671–675; f)
K. M. K. Swamy, H.-N. Kim, J.-H. Soh, Y. Kim, S.-J. Kim, J.
Yoon, Chem. Commun. 2009, 1234–1236; g) J. Kang, M. Choi,
J. Y. Kwon, E. Y. Lee, J. Yoon, J. Org. Chem. 2002, 67, 4384.
[5] L. Liu, G. Zhang, J. Xiang, D. Zhang, D. Zhu, Org. Lett. 2008,
10, 4581–4584.
[6] a) . F. M. Winnik, Chem. Rev. 1993, 93, 587–614; b) . Y. Suzuki,
T. Morozumi, H. Nakamura, M. Shimomura, T. Hayashita,
R. A. Bartsh, J. Phys. Chem. B 1998, 102, 7910–7917; c) J.-S.
Yang, C.-S. Lin, C.-Y. Hwang, Org. Lett. 2001, 3, 889–892; d)
J.-S. Kim, K.-H. Noh, S.-H. Lee, S.-K. Kim, S.-K. Kim, J.
Yoon, J. Org. Chem. 2003, 68, 597–600; e) H. Yuasa, N. Miya-
gawa, T. Izumi, M. Nakatani, M. Izumi, H. Hashimoto, Org.
Lett. 2004, 6, 1489–1492; f) Y. Shiraishi, Y. Tokitoh, T. Hirai,
Org. Lett. 2006, 8, 3841–3844; g) J. S. Kim, M. G. Choi, K. C.
Song, K. T. No, S. Ahn, S.-K. Chang, Org. Lett. 2007, 9, 1129–
1132; h) H.-C. Hung, C.-W. Cheng, I.-T. Ho, W.-S. Chung, Tet-
rahedron Lett. 2009, 50, 302–305.
1,17-Bis[4-(pyren-1-ylmethoxymethyl)-1H-1,2,3-triazole-1-yl]-
3,6,9,12,15-pentaoxaheptadecane (9): A mixture of 1-[(prop-2-ynyl-
oxy)methyl]pyrene (0.27 g, 1.0 mmol), 1,17-diazido-3,6,9,12,15-
pentaoxaheptadecane (0.17 g, 0.50 mmol), and CuI (about 5 mg,
0.02 mmol) in THF and water (9:1, v/v, 30 mL) was stirred vigor-
ously at 70 °C for 18 h. The mixture was extracted thrice (5 mLϫ3)
with chloroform. The chloroform layer was dried with MgSO4 and
the solvent was removed under reduced pressure. The residue ob-
tained was purified through a silica gel column eluting with ethyl
acetate/MeOH (30:1, v/v) to give 0.23 g (52%) of 9. Yellow oil; Rf
1
= 0.25 (EtOAc/MeOH = 10:1). H NMR (CDCl3, 300 MHz): δ =
8.30 (d, J = 9.2 Hz, 2 H, CHpyrene), 8.16–7.94 (m, 16 H, CHpyrene),
7.69 (s, 2 H, CH5-triazole), 5.27 (s, 4 H, CpyreneCH2O), 4.79 (s, 4 H,
OCH2C4-triazole), 4.43 (t, J = 5.0 Hz, 4 H, N1-triazoleCH2C), 3.72 (t,
J = 5.0 Hz, 4 H, CCH2O), 3.42–3.37 (m, 16 H, OCH2CH2OCH2-
CH2O) ppm. 13C NMR (CDCl3, 75.4 MHz): δ = 144.8 (Cq), 131.2
(Cq), 131.1 (Cq), 130.9 (Cq), 130.6 (Cq), 129.3 (Cq), 127.6 (CH),
127.3 (CH), 127.3 (CH), 127.1 (CH), 125.8 (CH), 125.1 (CH), 124.7
(Cq), 124.5 (Cq), 124.4 (CH), 123.9 (CH), 123.3 (CH), 70.8 (CH2),
70.3 (CH2), 70.2 (CH2), 70.2 (CH2), 70.1 (CH2), 69.2 (CH2), 63.6
(CH2), 50.1 (CH2) ppm. HRMS (FAB): calcd. for C52H52N6O7
[M]+ 872.3898; found 872.3889.
[7] a) H. C. Kolb, M. G. Finn, K. B. Sharpless, Angew. Chem. Int.
Ed. 2001, 40, 2004–2021; b) V. V. Rostovtsev, L. G. Green, V. V.
Fokin, K. B. Sharpless, Angew. Chem. Int. Ed. 2002, 41, 2596–
2599; c) L. Zhang, X. Chen, P. Xue, H. H. Y. Sun, I. D. Wil-
liams, K. B. Sharpless, J. Am. Chem. Soc. 2005, 127, 15998–
15999.
[8] For the coordination potential of triazoles, see: a) T. L. Mindt,
H. Struthers, L. Brans, T. Anguelov, C. Schweinsberg, V. Maes,
D. Tourwé, R. Schibli, J. Am. Chem. Soc. 2006, 128, 15096–
Supporting Information (see also the footnote on the first page of
this article): 1H and 13C NMR spectra for 6–9 (Figures S1–S8),
Eur. J. Org. Chem. 2009, 6360–6366
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
6365

H.-C. Hung, C.-W. Cheng, Y.-Y. Wang, Y.-J. Chen, W.-S. Chung
FULL PAPER
15097; b) S. Huang, R. J. Clark, L. Zhu, Org. Lett. 2007, 9,
4999–5002, and references cited therein.
[11]
As a result of the poor solubility of previous series of com-
pounds in pure MeOH, a small amount of CH3CN was needed
for their complete dissolution. Thus, metal-ion screening ex-
periments were carried out in MeOH/CH3CN (97.5:2.5, v/v).
[12] S.-M. Park, M.-H. Kim, J.-I. Choe, K.-T. No, S.-K. Chang, J.
Org. Chem. 2007, 72, 3550–3553.
[9] a) Y.-J. Shiao, P.-C. Chiang, A. Senthilvelan, M.-T. Tsai, G.-H.
Lee, W.-S. Chung, Tetrahedron Lett. 2006, 47, 8383–8386; b)
A. Senthilvelan, M.-T. Tsai, K.-C. Chang, W.-S. Chung, Tetra-
hedron Lett. 2006, 47, 9077–9081; c) K.-C. Chang, I.-H. Su, A.
Senthilvelan, W.-S. Chung, Org. Lett. 2007, 9, 3363–3366.
[10] The fluorescence titration results are shown in the Supporting
Information.
Received: August 31, 2009
Published Online: November 11, 2009
6366
www.eurjoc.org
© 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2009, 6360–6366