Cation-Selective and Anion-Controlled Fluorogenic Behaviors of a Benzothiazole-Attached Macrocycle That Correlate with Structural Coordination Modes

Article abstract of DOI:10.1021/acs.inorgchem.6b00690

We report how the metal cation and its counteranions cooperate in the complexation-based macrocyclic chemosensor to monitor the target metal ion via the specific coordination modes. The benzothiazolyl group bearing NO₂S₂-macrocycle L

Full text of DOI:10.1021/acs.inorgchem.6b00690

Article
pubs.acs.org/IC
Cation-Selective and Anion-Controlled Fluorogenic Behaviors of a
Benzothiazole-Attached Macrocycle That Correlate with Structural
Coordination Modes
†
†,‡
†
†
†
†
Huiyeong Ju, Duk Jin Chang, Seulgi Kim, Hyunsoo Ryu, Eunji Lee, In-Hyeok Park,
†
§
,∥
,†
Jong Hwa Jung, Mari Ikeda, Yoichi Habata,* and Shim Sung Lee*
†
Department of Chemistry and Research Institute of Natural Science, Gyeongsang National University, Jinju 52828, S. Korea
Bongilcheon High School, Paju 10938, S. Korea
‡
§
Education Center, Faculty of Engineering, Chiba Institute of Technology, 2-1-1 Shibazono, Narashino, Chiba 275-0023, Japan
∥Department of Chemistry, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 261-0013, Japan
*
S Supporting Information
ABSTRACT: We report how the metal cation and its counteranions
cooperate in the complexation-based macrocyclic chemosensor to
monitor the target metal ion via the specific coordination modes. The
benzothiazolyl group bearing NO S -macrocycle L was synthesized, and
2
2
its mercury(II) selectivity (for perchlorate salt) as a dual-probe channel
UV−vis and fluorescence) chemosensor exhibiting the largest blue shift
and the fluorescence turn-off was observed. In the mercury(II) sensing
(
−
−
with different anions, except ClO4 and NO , no responses for
3
−
−
−
mercury(II) were observed with other anions such as Cl , Br , I ,
SCN , OAc , and SO . A crystallographic approach for the
−
−
2−
4
mononuclear mercury(II) perchlorate complex [Hg(L)(ClO ) ]·0.67CH Cl (1) and polymeric mercury(II) iodide complex
4
2
2
2
[
Hg(L)I ] (2) revealed that the observed anion-controlled mercury(II) sensing in the fluorescence mainly stems from the endo-
2 n
and exocoordination modes, depending on the anion coordinating ability, which induces either the Hg−N bond formation or
not. The detailed complexation process with mercury(II) perchlorate associated with the cation sensing was also monitored with
tert
the titration methods by UV−vis, fluorescence spectroscopy, and cold-spray ionization mass spectrometry.
1
0a
INTRODUCTION
anticancer and antimicrobial activities. In addition, benzo-
■
10
11
thiazole derivatives and their complexes have been studied
as excellent luminescent materials because of the heterocyclic
binding site, generating UV−vis and fluorescent signals as a
dual-channel probe.
Synthetic receptors for sensing toxic heavy metal ions have
been of widespread interest due to the environmental and
1
clinical importance. Thus, many efforts have been devoted to
design and construction of the photophysical chemosensors for
2
3
4
In this work, we propose a benzothiazole-attached NO S -
2
2
detecting mercury(II), lead(II), and cadmium(II). In the
5
macrocycle L and are currently working on its synthesis for the
detection of heavy metal ions. In particular, we have undertaken
a structure−function relationship as an extension of the anion
category of sensor molecules, dye-attached macrocycles
represent a promising research area, not only in terms of
their chromo- or fluorophoric function but also because of their
high selectivity for the metal ions of interest, including
mercury(II) and other heavy metal species. In particular,
some sulfur-containing mixed donor macrocycles have been
8
dependency on the mercury(II) sensing, with emphasis on the
fluorescence-modulation, because no examples of the fluo-
rescence sensor showing the cation-selective and anion-
controlled behaviors have been reported so far. Therefore, as
depicted in Chart 1, we assumed that the expected mercury(II)
selectivity might be controlled by its anions, and such
phenomena are strongly associated with the structures of the
respective complexes generated when the events occur.
To examine the proposed hypothesis, we decided to reveal
the molecular-level structures of the related species in the solid
state that exhibit the anion-controlled functions. We herein
6
proposed as excellent mercury(II) selective hosts.
7
́
Martinez-Man
́
̃
ez and co-workers have introduced a
phenoxazinone-attached azaoxathia-macrocyclic mercury(II)
chemosensor that can be used in the parts per billion level
by using either absorption or emission spectroscopy. With the
similar parent host, our group has reported several N-azo-
coupled chromogenic macrocycles whose mercury(II) selectiv-
8
,9
ity is controlled by anions. However, benzothiazole is an
important bicyclic ring system with multiple applications in the
biological and luminescent materials. For example, it is known
to exhibit a wide range of biological properties including
Received: March 19, 2016
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.6b00690
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Chart 1. Anion-Controlled Cation Selectivity of Fluorescent
Macrocycle L via Endo- or Exocoordination
Figure 1. Crystal structure of L. Displacement ellipsoids were drawn at
3
0% probability level, and H atoms were omitted for clarity.
1
73.2° and S2−C−C−N1−160.6°), indicating a propensity for
each linkage to adopt an anti−anti conformation.
Photophysical Properties of L. The macrocyclic chemo-
sensor L exhibits an intense absorption and fluorescence
properties in solution state. As shown in Figure 2a, L presents
the absorption and emission spectra in acetonitrile, showing an
absorption maximum at 358 nm (pale yellow, ε = 57 100
max
−1
−1
M
cm ) and a strong emission band centered at 416 nm as a
characteristic emission band for the benzothiazole unit. The
13
report the synthesis of the N-benzothiazolyl group attached
NO S -macrocycle L and an in-depth study demonstrating the
anion-controlled mercury(II) sensing both in the UV−vis and
fluorescence channels. This is the first systematic study of the
anion effect on the fluorescence on−off behaviors via
structure−function relationship based on the single-crystal X-
ray analysis.
2
2
absolute quantum yield for L in acetonitrile was determined to
be Φ = 0.83 (5.0 × 10 M at 365 nm). As shown in Figure 2b,
the single crystals of L exhibit a broad band with weak blue
−4
emission maxima at 425 and 450 nm (λ = 365 nm) arising
ex
7
,14
from the intramolecular charge transfer.
Selectivity for Metal Ions. The metal-sensing abilities of L
+
2+
2+
2+
were examined with several metal ions (Ag , Hg , Co , Ni ,
RESULTS AND DISCUSSION
2+
2+
2+
■
Zn , Cd , and Pb ) by UV−vis and fluorescence spectros-
copy in acetonitrile with respect to the cation-induced spectral
changes. Considering the solubility and the influences of
counteranions, which are described in the latter part, metal
perchlorates were used. Addition of mercury(II) (5.0 equiv) to
the solution of L provided noticeable changes in the absorption
(Figure 3a) and emission (Figure 3b) spectra. In the UV−vis
experiments, for instance, the mercury(II) induced the largest
Synthesis of Chemosensor L. Three-step reactions
involving the coupling cyclization led to the synthesis of the
target macrocycle L (Scheme 1). The key macrocyclic
precursor 3 was prepared by the coupling cyclization between
dichloride 4 and corresponding dithiol as described pre-
1
2
viously. The target macrocycle L was obtained from the
reaction of 3 with 2-aminobenzenthiol in 40% yield.
−1
Crystal Structure of L. The structure of L was also
characterized in the solid state by single-crystal X-ray
crystallography (Figure 1 and Table S1). Colorless single
crystals of L were prepared by slow evaporation of its
dichloromethane solution. In the crystal structure, the macro-
cycle unit adopts a slightly twisted conformation in which two
oxygen donors are oriented in an endodentate fashion with a
gauche arrangement, while two sulfur donors are positioned
exodentate with respect to the ring cavity. The S1···S2 distance
is 7.56 Å, and the macrocyclic ring is flattened with the two
torsion angles between S and N donors (S1−C−C−N1−
blue shift from 358 nm (27 933 cm ) to 308 nm (32 468
−
1
−1
cm ) [Δλ = 50 nm (4535 cm )] with the decrease of
max
absorption intensity, changing its solution color from pale
yellow to colorless.
In the fluorescence study, L is also highly selective for
mercury(II) leading to a drastic change from bright (on) to
dark (off) in the emission intensity centered at 416 nm (Figure
3b), while no significant fluorescence spectral changes were
observed upon addition of the other metal ions. These
observed results in the both ways are quite different from
those obtained with other mercury(II) sensor molecules that
Scheme 1. Synthesis of L
B
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Figure 2. (a) Absorption and fluorescence spectra of L in acetonitrile ([L] = 1.5 × 10−5 M) and (b) solid-state photoluminescence spectrum of L.
Figure 3. (a) UV−vis and (b) fluorescence spectra of L in the presence of metal perchlorates (5.0 equiv) in acetonitrile ([L] = 1.5 × 10−5 M).
−5
Figure 4. (a) UV−vis and (b) fluorescence titrations of L ([L] = 1.5 × 10 M) with mercury(II) perchlorate (0−3.0 equiv) in acetonitrile. (insets)
Titration curves.
have usually been affected by silver(I) and other heavy metal
ions.
UV−vis and Fluorescence Titrations. In an attempt to
probe the origins of the above photophysical changes related to
the mercury(II) selectivity, the characteristics of the mercury-
complex that has no spectral difference with the free L. In the
region 2 (between 0.5 and 2.0 equiv), the ligand peak gradually
decreased, whereas the absorption for the complexed species
gradually increased showing an isosbestic point at 335 nm until
1.0 equiv. After this no more free ligand peak exists, and the
complex peak shifts toward shorter wavelength (308 nm), most
likely indicating the formation of a 1:1 species and its gradual
conversion to a 2:1 species. In the region 3 (after 2.0 equiv),
the absorption at 308 nm corresponding to the complexed
species shows no significant changes, indicating the stable
formation of the 2:1 species, and no other species with higher
stoichiometry are formed.
1
5
(II) complexes were investigated. Since L has multiple binding
sites, its mercury(II) complexes could exist in different
stoichiometric combinations in solution. So, the interaction of
L with mercury(II) perchlorate in acetonitrile was examined by
means of UV−vis and fluorescence titrations.
According to the UV−vis titration in Figure 4a, there are
three distinct regions of the titration curve. In the region 1 (up
to 0.5 equiv), the absorption at 358 nm shows no significant
changes, suggesting the formation of a 1:2 (metal-to-ligand)
As shown in Figure 4b, the fluorescence titration of L with
mercury(II) perchlorate demonstrates the cation-induced
C
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quenching behaviors, and the unusual shape of the titration
curve also suggests the coexistence of more than one
complexed species in solution. Upon addition of mercury(II),
the peak intensity at 416 nm shows no significant changes until
The Equilibria of the Hg2+ Complexation. As observed
from the experiments by UV−vis, fluorescence spectroscopy,
and CSI mass spectrometry, the complexation equilibria
between mercury(II) and L could not be described using one
or two species binding model. Therefore, the fitting of the UV−
vis titration data to determine the stability constants of the
mercury(II) complexation was performed with HyperSpec
software by employing the multiple binding model including
1:2, 1:1, and 2:1 ratios (Figure 6a), and a good fit of the data
was obtained (Figure 6b). In the distribution curves for the
0
.5 equiv. In the range of 0.5−2.0 equiv, the fluorescence
intensity of L gradually decreases without peak shift. Above the
.0 equiv, no longer emissions were observed, indicating the
2
17
formation of the nonemissive product. The observed
fluorescence titration curve also reflects the stepwise equilibria
involving the complexed species with 1:2, 1:1, and 2:1
stoichiometries.
complexation equilibria shown in Figure 6a, the HgL content
2
Comparative Cold-Spray Ionization Mass Spectrome-
is predominant around 0.5 equiv of mercury(II). Around 1.0
equiv, similar amounts of the three complexed species coexist,
and when the mercury(II) is in excess, the data are consistent
try. Cold-spray ionization (CSI) mass spectrometry is effective
16
for detection of the labile supramolecules in solution. So the
CSI mass experiments were performed by varying the
mercury(II) content (0−2.5 equiv) in the presence of L, and
the formation of the complexes with different stoichiometries
were confirmed (Figure 5). The mass spectrum of the free
with the formation of a Hg L species, presumably involving two
2
mercury(II) binding to one L. As listed in Table 1, the fitting
yields the log K values of 7.21 ± 0.03 (log K ), 13.14 ± 0.06
11
(log K ), and 14.06 ± 0.03 (log K ) between L and Hg(II).
12
21
The proposed complexation process for these Hg L, HgL, and
2
HgL species together with the stepwise log K values between
2
two species are given in Scheme 2.
Anion Effect on the Mercury(II) Sensing. While
investigating the metal-sensing and the related complexation
equilibria for L discussed above, a spectral dependence on the
anion employed was observed. In this work, we found that the
observed mercury(II) selectivity of L as the UV−vis probe was
effective in ClO4− or NO3− anion system: for instance, the blue
−
1
−1
shift from 358 nm (27 933 cm ) to 308 nm (32 468 cm )
−1
[
Δλ = 50 nm (4535 cm )] for perchlorate ion or to 320 nm
max
−1 −1
(
31 250 cm ) [Δλ = 30 nm (3317 cm )] for nitrate ion
max
were observed (Figure 7a). However, no significant spectral
changes were observed for the other anions. In the fluorescence
study for the anion effect on the mercury(II) sensing, addition
of mercury(II) perchlorate or nitrate to the solution of L
displays the cation binding interaction with L, leading to the
drastic fluorescence quenching (Figure 7b). However, the
−
addition of mercury(II) salts with the other anions such as Cl ,
−
−
−
−
2−
Br , I , OAc , SCN , or SO
shows no responses to the
4
mercury(II), leading to almost no spectral change. Con-
sequently, no anions gave a meaningful quenching except
ClO4 or NO3− in the fluorescence experiments.
−
Crystallographic Study on the Mercury(II) Complexes.
As mentioned above, the observed anion-controlled behaviors
in both probes (UV−vis and fluorescence) are assumed to be
associated with the structures of the respective complexes
generated in the corresponding solution state. Previously, we
reported the anion-controlled endo/exocyclic coordination
behaviors of the silver(I) complexes with S O -macrocycle in
Figure 5. CSI-mass spectra of L (5.0 × 10−4 M) in the presence of
different mole ratios of mercury(II) perchlorate in acetonitrile: (a) 0,
(
b) 0.5, (c) 1.0, (d) 1.5, (e) 2.0, and (f) 2.5 equiv.
2
3
18
the solid state.
ligand L shows the presence of some univalent monomer and
dimer ligand species due to the protonation or interactions with
the abundant alkali metal ions (Figure 5a). The mass spectra of
L with 0.5 equiv (Figure 5b) and 1.0 equiv (Figure 5c) of
mercury(II) were dominated by peaks for the 1:1 complexes
To gain further insight for the complexation-based and
anion-controlled mercury(II)-sensing fluorescence, we thus
decided to reveal the crystal structures of the related complex
species because no anion-controlled cation-sensing fluorescence
system has been reported so far. On complexation of L with
mercury(II) salts, it was possible to isolate a perchlorate
complex 1 and an iodo complex 2 from the nonemissive and
emissive solutions, respectively, as single crystals suitable for X-
ray analysis.
2+
+
+
(
Hg /L) such as [HgL(CH CN)(OH)] , [HgL(ClO )] , and
3
4
+
[
HgL(CH CN)(H O)(ClO )] . Additions of 1.5 to 2.5 equiv
3 2 4
of mercury(II) led to a new set of peaks in accord with the
2
+
formation of the 2:1 species such as [Hg L(ClO )(OH)] and
2
4
+
[
Hg L(ClO ) (OH)] (Figure 5d−f). Once again, this
observation suggests that L forms 1:2 (HgL ), 1:1 (HgL),
The X-ray analysis revealed that the perchlorate complex 1 is
2
4 2
a mononuclear species with the formula of [Hg(L)(ClO ) ]·
2
4 2
and 2:1 (Hg L) complexes and that these species coexist with
0.67CH Cl (Figure 8 and Table S2). In the asymmetric unit of
2
2
2
different composition depending on the mole ratios (Figure
1, three crystallographically different mononuclear species exist,
6a).
but their structures and coordination environments are not
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Figure 6. Fitting of UV−vis titration data to determine the stability constants of the mercury(II)-L complexation with HyperSpec software by
employing the multiple binding model including 1:2, 1:1, and 2:1 ratios: (a) species distribution diagram for L and its mercury(II) complexes as a
2+
function of the mole ratio (Hg /L) and (b) HyperSpec output (□: experimental points, solid line: theoretical fit).
Table 1. Stability Constants for the Complexations of L with
Mercury(II) Perchlorate in Acetonitrile
significantly different (Figures S1 and S2). Above all, each
Hg(II) atom in 1 resides inside the macrocyclic cavity to form a
:1 (metal-to-ligand) stoichiometric complex. For example, the
a
1
reactions
products
stability constants
PL switching
endocyclic Hg1 atom in 1 is seven-coordinate being bound to
all donors from the macrocycle in a bent conformation
adopting a “tight” conformation. The coordination sphere is
completed by two perchlorate O atoms (O3 and O9). The
coordination geometry can be best described as a distorted
pentagonal bipyramid (Figure 8b). The Hg1−S bond distances
[Hg1−S1 2.423(2), Hg1−S2 2.422(2) Å] in 1 are typical.
Hg2+ + 2 L
Hg2+ + L
Hg2+ + L
13.14 ± 0.06
7.21 ± 0.03
14.06 ± 0.03
on
HgL2
log K12
log K11
log K21
HgL
weak
2
Hg2L
off
a
17
UV−vis titration method at 25 °C using the HyperSpec software.
Scheme 2. Proposed Complexation Process of L and Related
Fluorescence Behaviors
Those of Hg1−O
bonds [Hg1−O1 2.660(6), Hg1−O2
ether
19
2
.580(6) Å] are also within the normal literature range. And
two monodentate perchlorate ions show different Hg1−
O
bond strengths [Hg1−O3 2.593(6), Hg1−O9
perchlorate
3.161(6) Å]. Notably, the Hg−N bond distance [Hg1−N1
2.671(6) Å] in 1 falls into the longer end of the normal range
tert
20
(
2.02−2.74 Å). The preferred endocyclic coordination of the
complex 1 is mainly due to the relatively weak coordination
affinity of ClO4− toward the metal center. From this result, it is
found that the Hg−N bond formation by the endocoordi-
tert
nation reflects the mercury(II) sensing via the fluorescent
quenching in the presence of ClO4− as shown in Figure 7b. The
details for the structure−function relationship for the anion-
controlled mercury(II) sensing from the crystal structures with
different anions are discussed in the later part.
On reaction with HgI , L forms a pale yellow crystalline
2
product 2. Unlike the endocyclic mononuclear perchlorato
2
+
−5
Figure 7. Hg -induced (a) UV−vis and (b) fluorescence spectral changes of L by varying anions in acetonitrile ([L] = 1.5 × 10 M; added
mercury(II) salt, 5.0 equiv).
E
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Figure 8. Crystal structure of the mercury(II) perchlorate complex [Hg(L)(ClO ) ]·0.67CH Cl (1): (a) an endocyclic mononuclear structure
4
2
2
2
showing an Hg1−N1 bond [2.671(6) Å] and (b) a distorted octahedral coordination environment of Hg1 atom. Noncoordinated solvent molecule
is omitted. Displacement ellipsoids were drawn at 30% probability level, and H atoms were omitted for clarity.
Figure 9. Crystal structure of the mercury(II) iodide complex [Hg(L)I ] (2): (a) basic coordination unit showing the Hg atom bound from outside
2
n
the macrocyclic cavity (exocoordination mode) and no interaction between Hg atom and Ntert donor (Hg1···N1 5.38 Å) and (b) 1D polymeric chain
structure of 2. Displacement ellipsoids were drawn at 30% probability level, and H atoms were omitted for clarity.
complex 1, this iodo complex 2 adopts a one-dimensional (1D)
polymeric arrangement with the formula of [Hg(L)I ] (Figure
complex 1, the iodo complex 2 shows a 1D chain polymeric
structure via the exocoordination. The preferred exocyclic
2
n
−
9
and Table S3). Asymmetric unit of 2 contains one
structure in 2 is mainly due to the strong coordination of I ion,
mercury(II) atom and two iodide ions. Notably, the Hg1
atom in 2 is outside the macrocyclic cavity in a tetrahedral
arrangement and links macrocycles via Hg−S bonds [Hg1−S1
which inhibits the metal ion from locating inside the cavity.
Instead the exocoordination mode induces the bond formation
of the S1−Hg1−S2A linkage between two adjacent macrocycles
2.780(1), Hg1−S2A 2.802(1) Å] forming an “L-Hg-L-Hg”
outside the cavity, leaving the N atom, which regulates the
tert
zigzag 1D pattern. The exocyclic Hg1 atom in 2 is four-
coordinate, being bound by two S donors from different
macrocycles, and the coordination sites are completed by two
terminal iodide atoms. Accordingly, the distance between
exocyclic Hg1 atom and N1 atom in 2 is 5.38 Å, which means
no interaction and much longer than that of the endocyclic
Hg1−N1 distance [2.671(6) Å] in 1. Unlike 1, the preferred
exocyclic coordination in the iodo complex 2 is mainly due to
the stronger affinity of the iodide ion with soft base nature
toward the soft mercury(II) center. Clearly, this situation
appears in the solution state as shown in Figure 7 where the
inactive mercury(II) sensing in the presence of iodide ion and
other anions with the stronger coordination affinity occurs.
Role of Anions in the Mercury(II) Fluorescence
Sensing and the Structure−Function Relationship. As
mentioned, the perchlorato complex 1 is an endocyclic species
in which the central Hg atom is seven-coordinate, being bound
to all five donors in the macrocycle including the regular Hg−
fluorescence uncoordinated (Hg1···Ntert 5.38 Å). This result
could be the evidence for the no fluorescence change from free
L upon addition of the mercury(II) salts shown in Figure 7b
and Scheme 3. The comparison of the coordination modes
between the endotype in 1 and the exotype in 2 supports the
understanding of the anion-controlled cation-sensing system by
showing the structure−function relation.
In the back-titration experiments, the evidence for the
proposed anion-controlled cation sensing was also observed.
For example, after mercury(II) perchlorate was added (0−3
equiv) to L, then iodide (0−3 equiv, as tetramethylammonium
salt) was titrated. Because of the solubility problem of
tetramethylammonium iodide, a mixture of methanol/acetoni-
trile (1:1) was used as a solvent. In this case, the decreased
absorption for free L (360 nm) by mercury(II) perchlorate
sharply increased, and finally its absorption intensity was
recovered by excess amount of the titrated iodide ion (Figure
S3). In the fluorescence (Figure S4), similar to the UV−vis
results, the mercury(II) perchlorate-induced quenching (430
nm) was recovered by excess amount of the titrated iodide ion.
The observed back-titration results also reflect the anion-
N
bond. The coordination environment in 1 is completed by
tert
two perchlorate O atoms via the weak Hg−O bond. In marked
contrast to the endocoordination mode in the perchlorato
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Scheme 3. Anion-Controlled Mercury(II)-Fluorosensor (L)
via Endo- or Exocoordination
result can also be explained by the covalent character of the
bonds between mercury(II) and some nucleophilic anions
−
(
halides including I ) that show higher affinity to the metal
center. The present study corresponds to the first systematic
work on the relationship between the structure and the
fluorescence change for the macrocyclic receptor.
EXPERIMENTAL SECTION
■
General. All chemicals and solvents employed in the syntheses
were of reagent grade and were used without further purification. Mass
spectra were obtained on a Thermo Scientific LCQ Fleet
spectrometer. CSI mass spectra were measured on a JEOL AccuTOF
(JMS-T100CS) mass spectrometer with ESI ion source. NMR spectra
were recorded on a Bruker DRX 300 spectrometer. FT-IR spectra
were measured with a ThermoFisher Scientific Nicolet iS 10 FT-IR
spectrometer. The elemental analysis was performed on a Thermo-
Fisher Scientific Flash 2000 elemental analyzer. Caution! Perchlorate
salts of metal complexes are potentially explosive and should be handled
with great care.
Synthesis and Characterization of L. The mixed ethanol (96%)
solution (200 mL) of 3 (2.3 g, 6.47 mmol), 2-aminobenzenethiol (1.1
g, 8.79 mmol), and a drop of acetic acid was refluxed with stirring for
controlled cation-sensing behaviors. In addition, the titrations
of L in the presence of iodide (5 equiv, as tetramethylammo-
nium salt) were also performed both in absorption and
emission modes (Figures S5 and S6). The titrated mercury(II)
perchlorate to the solution of L containing an excess amount (5
equiv) of iodide ion showed no absorption decrease or
fluorescence quenching. Once again, these results suggest that
the iodide acts as a strong coordinating anion, which inhibits
the endocyclic coordination of the mercury(II) with the
macrocycle L.
1
2 h. After the reaction, the mixture was first concentrated, and 250
mL of water was added. The solution was extracted with CH Cl . The
2
2
extract was dried over NaSO , and solvent was evaporated in vacuo.
4
The residue was purified with recrystallization using n-hexane, which
led to the isolation of L as a crystalline product in a 40% yield. mp 127
°
C. IR (KBr pellet): 2882, 1605, 1527, 1477, 1426, 1353, 1281, 1183,
−
1
1
129, 1102, 1075, 821, 763, and 732 cm . Anal. Calcd for
C H N O S : C, 59.97; H, 6.13; N, 6.08; S, 20.88. Found: C,
2
3
28
2
2 3
1
59.73; H, 6.12; N, 6.05; S, 20.84%. H NMR (300 MHz, CDCl
Figure S7a, Supporting Information): 7.98 (d, J = 8.3 Hz, 1H, Ar),
, δ, see
3
7
8
.94 (d, J = 8.9 Hz, 2H, Ar), 7.84 (d, J = 7.9 Hz, 1H, Ar), 7.43 (dd, J =
.3 Hz, 1H, Ar), 7.30 (dd, J = 7.1 Hz, 1H, Ar), 6.69 (d, J = 8.9 Hz, 2H,
Consequently, it was found that the Hg−N
bond
tert
formation is controlled by the anions that push the metal ion
inside the cavity to allow the bond formation when the anion
coordinating ability is weaker. Oppositely, the anions with the
stronger coordinating ability tend to pull out the metal ion
outside the cavity to inhibit the Hg−Ntert bond formation.
Ar), 3.82 (t, J = 5.1 Hz, 4H, SCH CH N), 3.71 (t, J = 8.1 Hz, 4H,
2
2
OCH CH S), 3.65 (s, 4H, OCH CH O), 2.93 (t, J = 8.1 Hz, 4H,
2
2
2
2
13
OCH CH S), 2.77 (t, J = 5.1 Hz, 4H, SCH CH N). C NMR (75
2
2
2
2
MHz, CDCl ) 168.5, 154.4, 149.1, 134.6, 129.2, 126.0, 124.2, 122.3,
3
121.6, 121.4, 111.6, 74.3, 70.7, 51.9, 31.3, 29.5. CSI-mass spectrum m/
+
z: 461.08064 [L+H] .
CONCLUSION
The proposed benzothiazolyl group bearing NO S -macrocycle
L showed the mercury(II) selectivity as a dual-probe channel
Preparation of 1, [Hg(L)(ClO ) ]·0.67CH Cl . Mercury(II)
■
4 2
2
2
perchlorate hydrate (11.0 mg, 0.022 mmol) in acetone (2 mL) was
2
2
added to a solution of L (10.0 mg, 0.022 mmol) in dichloromethane
(2 mL). The solution was stirred at room temperature. A fine powder,
(
UV−vis and fluorescence) chemosensor, but its sensing
which precipitated from the solution, was filtered off. Slow evaporation
of the solution afforded a pale yellow crystalline product 1 suitable for
X-ray analysis. For the elemental analysis and melting point
measurement, the sample was dried under vacuum (70 °C, 12 h).
mp 162 °C. IR (KBr pellet): 2989, 2946, 2875, 1605, 1480, 1457,
1437, 1412, 1314, 1172, 1116, 1037, 1022, 917, 762, 727, and 621
− −
behaviors work only in the presence of ClO or NO . To
4
3
understand the observed anion-controlled mercury(II)-sensing,
especially in the fluorescence, we assumed that it requires the
structural information in the solid state. This approach enabled
us to isolate the single crystals from the corresponding
solutions of the mixtures of L and mercury(II) salts with
different anions. In the crystal structures, the perchlorato
complex 1 and the iodo complex 2 showed very distinct
structures mainly due to the coordination modes, specifically,
the endocoordinated complex 1 with the discrete form and the
exocoordinated complex 2 with the continuous form. The
observed solid structures clearly support the structure−function
hypothesis because the anion-controlled fluorescence phenom-
−1
cm . Anal. Calcd for C H N O S HgCl : C, 32.12; H, 3.28; N,
23 28
2
10
3
2
3
.26; S, 11.18 Found: C, 32.10; H, 3.25; N, 3.05; S, 11.53%.
Preparation of 2, [Hg(L)I ] . Mercury(II) iodide (9.9 mg, 0.022
2
n
mmol) in acetone (2 mL) was added to a solution of L (10.0 mg,
.022 mmol) in chloroform (2 mL). The solution was stirred at room
0
temperature. Slow evaporation of the solution afforded a pale yellow
crystalline product 2 suitable for X-ray analysis. mp 164 °C. IR (KBr
pellet): 2888, 2855, 1604, 1557, 1526, 1477, 1427, 1390, 1342, 1232,
−1
1191, 1099, 1004, 963, 816, 754, and 724 cm . Anal. Calcd for
C H28HgI N O S : C, 30.19; H, 3.08; N, 3.06; S, 10.51 Found: C,
23 2 2 2 3
ena mainly stem from the complexation via either the Hg−N
tert
3
0.02; H, 3.02; N, 2.84; S, 10.63%.
Crystallographic Structure Determinations. All data were
bond formation or not. In another word, the less coordinating
−
ClO4 allows the mercury(II) engage the Ntert lone pair and
collected on a Bruker Smart Apex2 Ultra diffractometer equipped with
graphite monochromated Mo Kα radiation (λ = 0.710 73 Å) generated
by a rotating anode. Data collection, data reduction, and semiempirical
absorption correction were performed using the software package
thereby results in the direct Hg−N bonding in the endocyclic
tert
fashion, leading the fluorescence quenching (from ON to
−
OFF), while the stronger coordinating I , which participates in
2
1
the coordination sphere, induces the metal ion outside the
cavity showing no influence to the fluorescence change because
of no interaction between mercury(II) and Ntert atom. This
APEX2. All of the calculations for the structure determination were
2
2
performed using the SHELXTL package. Relevant crystal data
collection and refinement data for the crystal structures are
G
DOI: 10.1021/acs.inorgchem.6b00690
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
summarized in Table S1. CCDC reference numbers 1457993 (L),
(5) (a) Dix, J. P.; Vo
Vo
B.; Martínez-Man
2001, 40, 2640. (d) Aragoni, M. C.; Arca, M.; Demartin, F.;
Devillanova, F. A.; Isaia, F.; Garau, A.; Lippolis, V.; Jalali, F.; Papke, U.;
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̈
gtle, F. Chem. Ber. 1980, 113, 457. (b) Dix, J. P.;
1
457994 (1), and 1457995 (2).
̈
gtle, F. Chem. Ber. 1981, 114, 638. (c) Sancenon
́
, F.; Descalzo, A.
́
̃
ez, R.; Miranda, M. A.; Soto, J. Angew. Chem., Int. Ed.
ASSOCIATED CONTENT
■
* Supporting Information
S
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.6b00690.
6
623. (e) Nishiyabu, R.; Palacios, M. A.; Dehaen, W.; Anzenbacher, P.,
Jr. J. Am. Chem. Soc. 2006, 128, 11496. (f) Kim, J. S.; Shon, O. J.; Lee,
J. K.; Lee, S. H.; Kim, J. Y.; Park, K.-M.; Lee, S. S. J. Org. Chem. 2002,
6
7, 1372. (g) Lee, H.; Lee, S. S. Org. Lett. 2009, 11, 1393. (h) Seo, J.;
Crystal data, geometric parameters, crystal structures,
and titration data. (PDF)
X-ray crystallographic information. (CIF)
Park, S.; Lee, S. S.; Fainerman-Melnikova, M.; Lindoy, L. F. Inorg.
Chem. 2009, 48, 2770.
(
6) (a) Kursunlu, A. N.; Deveci, P.; Guler, E. J. Lumin. 2013, 136,
4
30. (b) Yoon, S.; Albers, A. E.; Wong, A. P.; Chang, C. J. J. Am. Chem.
AUTHOR INFORMATION
Soc. 2005, 127, 16030. (c) Atilgan, S.; Kutuk, I.; Ozdemir, T.
Tetrahedron Lett. 2010, 51, 892. (d) Shiraishi, Y.; Sumiya, S.; Kohno,
Y.; Hirai, T. J. Org. Chem. 2008, 73, 8571.
■
Corresponding Authors
E-mail: habata@chem.sci.toho-u.ac.jp. (Y.H.)
E-mail: sslee@gnu.ac.kr. (S.S.L.)
*
́
̃
(7) Descalzo, A. B.; Martínez-Manez, R.; Radeglia, R.; Rurack, K.;
*
Soto, J. J. Am. Chem. Soc. 2003, 125, 3418.
Notes
(8) Lee, S. J.; Jung, J. H.; Seo, J.; Yoon, I.; Park, K.-M.; Lindoy, L. F.;
Lee, S. S. Org. Lett. 2006, 8, 1641.
The authors declare no competing financial interest.
(
(
9) Lee, H.; Lee, S. S. Org. Lett. 2009, 11, 1393.
10) (a) Ali, R.; Siddiqui, N. J. Chem. 2013, 2013, 1. (b) Gabr, M. T.;
ACKNOWLEDGMENTS
■
2
El-Gohary, N. S.; El-Bendary, E. R.; El-Kerdawy, M. M.; Ni, N.;
Shaaban, M. I. Chin. Chem. Lett. 2015, 26, 1522. (c) Gogoi, A.;
Samanta, S.; Das, G. Sens. Actuators, B 2014, 202, 788. (d) Ghosh, K.;
Kar, D. J. Inclusion Phenom. Macrocyclic Chem. 2013, 77, 67.
(11) (a) Aich, K.; Goswami, S.; Das, S.; Mukhopadhyay, C. D.; Quah,
C. K.; Fun, H.-K. Inorg. Chem. 2015, 54, 7309. (b) Gromov, S.;
Dmitrieva, P. S. N.; Vedernikov, A. I.; Kurchavov, N. A.; Kuz’mina, L.
G.; Sazonov, S. K.; Strelenko, Y. A.; Alfimov, M. V.; Howard, J. A. K.;
Ushakov, E. N. J. Org. Chem. 2013, 78, 9834. (c) Mei, Q.; Hua, Q.;
Tong, B.; Shi, Y.; Chen, C.; Huang, W. Tetrahedron 2015, 71, 9366.
This work was supported from NRF (2012R1A4A1027750 and
013R1A2A2A01067771), S. Korea, the Gyeongsang National
University Fund for Professors on Sabbatical Leave (2014), and
the Strategic Research Foundation at Private Universities
(
2012−2016) from the Ministry of Education, Culture, Sports,
Science and Technology of Japan.
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DOI: 10.1021/acs.inorgchem.6b00690
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Inorganic Chemistry
Article
(
21) Bruker. APEX2 Version 2009.1−0 Data Collection and Processing
Software; Bruker AXS Inc: Madison, WI, 2008.
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I
DOI: 10.1021/acs.inorgchem.6b00690
Inorg. Chem. XXXX, XXX, XXX−XXX