A ditopic O4S2 macrocycle and its hard, soft, and hard/soft metal complexes exhibiting endo-, exo-, or endo/exocyclic coordination: Synthesis, crystal structures, NMR titration, and physical properties

Article abstract of DOI:10.1021/ic4030475

A 20-membered O₄S₂ macrocycle (L²) was synthesized as a ditopic ligating system toward hard and soft metal ions simultaneously. Five complexes (3-7) of L² with different structures and coordination modes, includ

Full text of DOI:10.1021/ic4030475

Article
pubs.acs.org/IC
A Ditopic O4S2 Macrocycle and Its Hard, Soft, and Hard/Soft Metal
Complexes Exhibiting Endo‑, Exo‑, or Endo/Exocyclic Coordination:
Synthesis, Crystal Structures, NMR Titration, and Physical Properties
Hyunsoo Ryu,† Ki-Min Park,† Mari Ikeda,‡ Yoichi Habata,§ and Shim Sung Lee*,†
†Department of Chemistry and Research Institute of Natural Science, Gyeongsang National University, Jinju 660-701, South 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: A 20-membered O4S2 macrocycle (L2) was synthesized as a ditopic ligating system toward hard and soft metal
ions simultaneously. Five complexes (3−7) of L2 with different structures and coordination modes, including discrete to infinite
forms, mono- to heteronuclear, and endo- to exo- and endo/exocoordination, were prepared and structurally characterized. First,
the reaction of L2 with Pb(ClO4)2·3H2O afforded a typical endocyclic mononuclear perchlorato complex [Pb(L2)(ClO4)2] (3) in
which one lead(II) is surrounded by the macrocycle adopting a “tight and bent” conformation. Meanwhile, the reaction with a
softer metal salt AgNO3 resulted in the formation of the dinuclear bis(macrocycle) complex [Ag2(L2)2(NO3)2] (4) in which two
exocyclic silver(I) ions are doubly linked by two nitrate ions. The treatment of L2 with CuI gave a mixture of the exocyclic
monomer complex [Cu(L2)I] (5) and the exocyclic dimer complex [(Cu2I2)(L2)2] (6), which were separated manually because
of their brick and rhomboid shapes of the crystals, respectively. Furthermore, the reaction of L2 with a mixture of CuI and NaI
afforded a photoluminescent heteronuclear complex [Na2(Cu6I8)(L2)2(CH3CN)4]n (7) in the endo/exocyclic coordination
mode. In this case, the endocyclic sodium(I) complex units are linked by the double-open cubanes-type cluster Cu6I8, yielding a
two-dimensional network. The structural and binding properties of the complex of L2 with silver(I) nitrate in solution were
monitored by the NMR titration. Photophysical and thermal properties for complex 7 were also investigated and discussed.
endocoordination.2,5,6 So, the exocoordination can also be used
INTRODUCTION
■
in crystal engineering as a versatile tool. For the stable host−
Because of the selective complexation through the central cavity
and the self-assembly toward the specific guest, macrocyclic
ligands have long been employed as a key species in
guest complexation of a given macrocycle, besides the choice of
metal cation, other controlling factors such as anion,3c,7
solvent,8 and coligand9 are important. Diverse types of
supramolecular coordination chemistry.1 Recently, much
supramolecular structures and coordination modes for the
progress in macrocyclic supramolecular chemistry has been
thiamacrocyclic complexes, including mono- to multinuclear,
made in regard to the heteronuclear and coordination network
systems.2 In other words, by selecting appropriate metal
species, counterions, clusters, as well as donor arrangement in
the macrocyclic host, the coordination mode and connectivity
discrete and infinite forms, as well as the endo- and exocyclic
systems have been introduced3−10 and reviewed.2
Recently, our group introduced the homo- and heteronuclear
polymeric networks linked with different types of CuI clusters
patterns of the resulting products can be rationally
controlled.2,3 For instance, a crown-type macrocycle forms
obtained from the assembly reaction of a ditopic O4S2
macrocycle L1 (Scheme 1b) with CuI in the absence and
stable complexes where the metal ion locates inside the cavity
(endocyclic coordination). However, a sulfur-containing macro-
presence of KI.11 In the former case, an emissive one-
dimensional (1D) species linked with the cubane CuI cluster
cycle (or thiamacrocycle) prefers an exocyclic coordination so
was isolated. In the latter case, however, the mixture of CuI and
often because of the propensity of sulfur atoms to orient toward
KI induced the endocoordination of L1 toward K+ and the
the outside the cavity.4
Synthetically, the exocoordination could be advantageous
because it often induces the formation of more exquisite
networks than could be possible to prepare through the
Received: December 12, 2013
Published: April 9, 2014
© 2014 American Chemical Society
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Preparation of Supramolecular Complexes with L2.
Five complexes (3−7) of L2 whose structures depend on the
coordination modes of L2 toward lead(II), silver(I), copper(I),
and sodium(I) salts were synthesized and structurally
characterized as depicted in Scheme 3. The resulting X-ray
crystal structures are shown in Figures 1−4, with X-ray data and
selected geometric parameters presented in Tables 1−6.
Scheme 1. (a) Concept of Ditopic Oxathia Macrocycles for
Endo/Exo-Coordination Modes and (b) O4S2 Macrocycle
Isomers L1 and L2
Endocyclic Monolead(II) Complex (3). The reaction of
L2 with Pb(ClO4)2·3H2O in acetonitrile/dichloromethane
yielded colorless crystalline product 3. The X-ray analysis
revealed that 3 is a 1:1 (metal-to-ligand) complex [Pb(L2)-
(ClO4)2]. The lead(II) is eight-coordinate in the macrocyclic
cavity, and the metal center is bound to all donor atoms of L2,
adopting a “tight and bent” conformation. The coordination
sphere of the metal center is completed by two O atoms from
the two monodentate perchlorate ions in both sides of the
macrocyclic plane. The coordination geometry can best be
described as a distorted hexagonal bipyramid with the O4S2
donors of L2 defining the hexagonal plane and the axial
positions occupied by two O atoms of two perchlorato ligands.
Because of the Pb1···O6 interaction [2.975(13) Å, dashed lines
in Figure 1], the O5−Pb1−O9 angle [147.8(4)°] is highly
distorted from the linearity, and the Pb1−O5 bond distance
[2.751(11) Å] is fairly elongated. Among the Pb−Oether bond
distances, the Pb1−O4 bond [2.930(8) Å] is longer than others
[2.674(9)−2.838(8) Å] due to its isolated location between
heterodonors. The Pb−S bond lengths [Pb1−S1 2.866(3),
Pb1−S2 2.936(3) Å] are within the normal range for this bond
type.14 The preference for the endocyclic mononuclear
complex formation may be associated with the intermediate
nature of the lead(II) between soft and hard acids.15
Exocyclic Silver(I) Nitrate Complex (4). Considering the
sulfur donors as a soft base, silver(I) nitrate was employed and
treated with L2 to yield the colorless complex 4 (Figure 2).
Unlike 3, complex 4 is a dinuclear bis(macrocycle) complex
with formula [Ag2(L2)2(NO3)2]. Further, the two crystallo-
graphically equivalent Ag atoms locate outside the macrocyclic
cavity in a bent conformation exhibiting an exocyclic
coordination mode. In the dimeric structure of 4, the two Ag
atoms are doubly linked by the two coordinating nitrate ions,
forming a Ag−(μ2-NO3)2−Ag square unit16 sandwiched by two
macrocycles. The Ag atom is five-coordinate, being bound by
OS2 donors from one L2, with the remaining three oxygen
donors between two benzo units uncoordinated. The
coordination sphere is completed by two monodentate nitrato
ligands bridging two Ag atoms. The Ag−S bond distances
[2.5147(5), 2.5235(5) Å] in 4 are typical, while the Ag1−O4
rearrangement of the ribbon-type CuI cluster in the exocyclic
mode.
As an extension of the above investigations, we focused our
attention not only on the new thiaphilic metal complex system
of thiamacrocycles but also on a hard/soft heteronuclear
complex species that would potentially influence the endo- and
exocyclic coordination modes as well as networking (Scheme
1a). In particular, we are interested in extending this area by
using a new ditopic O4S2 macrocycle L2, which is a regioisomer
of L1 (Scheme 1b). In the present study, we report the
synthesis of L2 as a potent ditopic ligand, its hard and soft metal
complexes, as well as a soft/hard heterometallic complex of it.
For example, following the formation of one endocyclic hard
metal complex and two soft metal exocyclic complexes, the
preparation and structural characterization of the endo/
exocyclic complex linked by CuI cluster adopting a double-
open cubane12 was proved possible.
RESULTS AND DISCUSSION
■
Synthesis of the O4S2 Macrocycle L2. Synthesis of the
target macrocycle L2 began with salicylaldehyde (Scheme 2).
Dichloride precursor 2 for the cyclization was prepared through
the chlorination of dialcohol 1, which obtained from the
reduction of dialdehyde.13 The macrocycle L2 was synthesized
from the coupling cyclization between dichloride 2 and 2-
mercaptoethyl ether in the presence of Cs2CO3 under high
dilution condition in a reasonable yield.
Scheme 2. Synthesis of L2
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Scheme 3. Complexes of L2 with Different Coordination Modes
structures.16a To the best of our knowledge, 4 is the first
characterized example of the discrete type, in which macro-
cycles are linked by such square unit.
Exocyclic Copper(I) Iodide Complexes (5 and 6).
Having obtained the lead(II) and silver(I) complexes of L2 in
the endo- and the exocoordination modes, respectively, we
have proceeded to the preparation of the complexes by
employing copper(I) iodide as an example of thiaphilic soft
metal species. As is well-known, the self-assembly of copper(I)
iodide with multidentate soft base ligands often leads to
discrete complexes and continuous ones because the copper(I)
halides are capable of adopting a variety of structural motifs
such as rhomboid dimer, cubane tetramer, hexagonal prism,
double cubanes, 1D chain, double-stranded stairs, and more
(Scheme 4).18 Such CuI clusters exhibit an unusual wealth of
stoichiometries and geometries because of the small energy
Figure 1. Endocyclic monolead(II) complex 3, [Pb(L2)(ClO4)2]: (a)
top view and (b) side view. Hydrogen atoms are omitted.
bond distance [2.7608(14) Å] is also within the normal
literature range for this bond type.17 The Ag···Ag separation in
4 is 3.986 Å. We have reported some coordination polymers of
thiamacrocycles linked by the Ag−(μ2-NO3)2−Ag square unit
adopting one-dimensional (1D) and two-dimensional (2D)
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Figure 2. Exocyclic silver(I) nitrate complex 4, [Ag2(L2)2(NO3)2]: (a) top view and (b) side view. Hydrogen atoms are omitted.
Figure 3. (a) Photomicroscope of a mixture of brick-shaped (5) and rhomboid-shaped (6) single crystals after the manual separation with a needle
under microscope, (b) PXRD data of 5, (top) as synthesized and (bottom) simulated, (c) PXRD data of 6, (top) as synthesized and (bottom)
simulated, (d) crystal structure of 5, [Cu(L2)I], and (e) crystal structure of 6, [(Cu2I2)(L2)2].
difference between the polymorphs, which are prepared
depending on synthetic conditions.
The crystal structures of 5 and 6 are shown in Figure 3d,e,
respectively, and their selected geometric parameters are
presented in Tables 4 and 5. First, the crystal analysis confirms
that 5 is a half-sandwich type 1:1 (metal-to-ligand) complex
[Cu(L2)I]. The Cu(I) center in 5 is coordinated by OS2 donors
from L2 in a folded conformation, with the fourth coordination
site occupied by one iodo ligand. The coordination sphere of
the metal center is distorted tetrahedral, with the bond angles
ranging from 83.49(10)° for S1A−Cu1−O4 to 125.54(9)° for
S1−Cu1−S1A. The three oxygen donors (O1, O2, and O3)
between two benzo units remain uncoordinated.
As shown in Figure 3a, the reaction of L2 with copper(I)
iodide in acetonitrile afforded a mixture of two products, which
can be identified by naked eyes. In fact, the colorless crystalline
product shows two crystal shapes (or crystal habits): brick and
rhomboid (later compounds 5 and 6, respectively). As
mentioned, this seems to be the case for the product, which
contains a mixture of two species. No crystals except those with
either shape exist in the product. So it was possible to separate
these two types of crystals using a needle manually under the
microscope. As expected, the single-crystal X-ray analysis
revealed that the observed difference in the crystal habit
means different species. For example, the brick-shaped one (5)
and rhomboid-shaped one (6) crystallize with space groups
P21/m and P21/c, respectively (Figure 3). Also the agreement
between the powder X-ray diffraction (PXRD) patterns of each
manually separated product and the simulated patterns for the
corresponding single crystals indicates that two species are
effectively separated, showing the bulk purity (Figure 3b,c).
Meanwhile, 6 crystallized as a 2:2 complex [(Cu2I2)(L2)2],
with two macrocycles sandwiching an exodentate rhomboid
dimer cluster, Cu2I2 (see Scheme 4a). In 6, each Cu atom that
lies outside the macrocyclic cavity is also four-coordinate, being
bound to two S donors from one macrocycle and the two
bridging I atoms. Two Cu centers are then linked by two μ2-I
atoms, forming a rhomboid, with all O atoms of the macrocycle
remaining uncoordinated. The coordination geometry around
each Cu center is considerably distorted from regular
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Figure 4. Endo/exocyclic coordination polymer 7, [Na2(Cu6I8)(L2)2(CH3CN)4]n: (a) basic coordination unit, (b) coordination environment of
endocyclic Na1 atom showing a distorted pentagonal bipyramid geometry, (c) 2D brick-wall type network structure, and (d) double-open cubanes
unit Cu6I8.
Table 1. Crystallographic Data and Structure Refinement for Complexes 3−7
3
4
5
6
7
formula
C22H28Cl2O12PbS2
826.65
C44H54Ag2N2O14S4
1178.87
C22H28CuIO4S2
611.00
C44H56Cu2I2O8S4
1222.01
C26H34Cu3I4N2NaO4S2
1223.88
formula weight
temperature (K)
crystal system
space group
Z
173(2)
173(2)
173(2)
173(2)
173(2)
monoclinic
Pc
monoclinic
P21/c
monoclinic
P21/m
monoclinic
P21/c
monoclinic
P21/c
2
2
2
2
4
a (Å)
8.7113(3)
10.0389(3)
17.8182(5)
90
9.74720(10)
19.4245(3)
14.5507(2)
90
6.86320(10)
18.5960(3)
9.3849(2)
90
9.1904(6)
20.0371(14)
15.1204(9)
90
12.4226(6)
20.6183(9)
18.4739(6)
90
b (Å)
c (Å)
α (deg)
β (deg)
118.193(2)
90
118.4270(10)
90
97.2890(10)
90
120.884(4)
90
129.865(2)
90
γ (deg)
V (Å3)
1373.37(7)
1.999
2422.77(6)
1.616
1188.10(4)
1.708
2389.6(3)
1.698
3631.9(3)
2.238
Dx(g/cm3)
2θmax (deg)
R1, wR2 [I > 2σ(I)]
R1, wR2 [all data]
GOF
52
52
52
52
52
0.0478, 0.1301
0.0507, 0.1332
1.081
0.0233, 0.0547
0.0274, 0.0567
1.038
0.0498, 0.1261
0.0514, 0.1271
1.467
0.0203, 0.0558
0.0216, 0.0573
1.031
0.0219, 0.0448
0.0273, 0.0465
1.057
data/restraints/parameters
no. of reflection used [>2σ(I)]
structure determination
refinement
4205/2/352
4205 [Rint = 0.0561]
SHELXTL
full-matrix
4737/6/298
4737 [Rin = 0.0285]
SHELXTL
full-matrix
2426/18/142
2426 [Rint = 0.0246]
SHELXTL
full-matrix
4703/8/272
4703 [Rint = 0.0448]
SHELXTL
full-matrix
7135/0/381
7135 [Rint = 0.0355]
SHELXTL
full-matrix
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Table 2. Selected Bond Lengths (Å) and Bond Angles (deg)
for Complex 3
Table 6. Selected Bond Lengths (Å) and Bond Angles (deg)
for Complex 7
Pb1−S1
Pb1−O1
Pb1−O3
Pb1−O5
2.866(3)
2.810(8)
2.838(8)
2.751(11)
82.09(9)
126.15(19)
92.5(2)
Pb1−S2
Pb1−O2
Pb1−O4
Pb1−O9
2.936(3)
2.674(9)
2.930(8)
2.495(10)
71.26(18)
147.11(19)
75.2(3)
Cu1−S1
Cu1−I3
Cu2−S2B
Cu2−I2
Cu3−I2
Cu3−I3A
Na1−S2
Na1−O2
Na1−O4
2.337(1)
2.706(1)
2.325(1)
2.640(1)
2.643(1)
2.638(1)
2.883(1)
2.374(2)
2.373(2)
2.396(4)
111.6(1)
108.6(1)
114.5(2)
105.2(1)
105.3(1)
111.1(2)
107.1(2)
112.3(2)
114.1(2)
83.1(1)
Cu1−I1
Cu1−I4
Cu2−I1
Cu2−I4
Cu3−I3
Cu3−I4
Na1−O1
Na1−O3
Na1−N1
2.615(1)
2.636(1)
2.666(1)
2.689(1)
2.669(1)
2.738(1)
2.837(3)
2.953(3)
2.416(3)
S1−Pb1−S2
S1−Pb1−O2
S1−Pb1−O5
S2−Pb1−O1
S2−Pb1−O3
S2−Pb1−O9
O1−Pb1−O3
O1−Pb1−O9
O2−Pb1−O5
O3−Pb1−O5
O5−Pb1−O9
S1−Pb1−O1
S1−Pb1−O3
S1−Pb1−O9
S2−Pb1−O2
S2−Pb1−O5
O1−Pb1−O2
O1−Pb1−O5
O2−Pb1−O3
O2−Pb1−O9
O3−Pb1−O9
147.87(19)
72.04(18)
80.8(3)
127.2(2)
127.6(3)
62.2(2)
Na1−N2
123.8(2)
75.4(3)
72.4(3)
S1−Cu1−I1
S1−Cu1−I4
I1−Cu1−I4
S2B−Cu2−I1
S2B−Cu2−I4
I1−Cu2−I4
I2−Cu3−I3
I3−Cu3−I4
I3A−Cu3-I2
S2−Na1- N1
O1−Na1−O2
O2−Na1−O3
S1−Cu1−I3
I1−Cu1−I3
I3−Cu1−I4
S2B−Cu2−I2
I1−Cu2−I2
I2−Cu2−I4
I2−Cu3−I4
I3A−Cu3−I4
I3A−Cu3−I3
S2−Na1−O3
O1−Na1−N1
O4−Na1−N2
100.0(1)
106.8(2)
114.5(2)
107.1(1)
112.5(2)
114.8(2)
113.1(2)
99.1(2)
61.8(2)
97.7(3)
68.5(3)
119.3(3)
147.8(4)
80.8(3)
Table 3. Selected Bond Lengths (Å) and Bond Angles (deg)
for Complex 4
111.0(2)
71.2(1)
Ag1−S1
Ag1−O4
Ag1−O5A
S1−Ag1−S2
S1−Ag1−O5
S2−Ag1−O4
S2−Ag1−O5A
O4−Ag1−O5A
2.5235(5)
2.7608(14)
2.3900(14)
125.411(17)
112.61(4)
72.54(3)
Ag1−S2
Ag1−O5
2.5147(5)
2.5161(14)
62.3(1)
82.3(1)
64.0(1)
161.0(1)
S1−Ag1−O4
S1−Ag1−O5A
S2−Ag1−O5
O4−Ag1−O5
O5−Ag1−O5A
73.86(3)
104.69(4)
93.23(4)
165.05(4)
71.34(5)
Endo/Exocyclic Heteronuclear Na(I)/Cu(I) Network
Complex (7). As proposed in Scheme 1, we also examined
the ditopic behaviors of L2, employing the mixture of hard and
soft metal iodides to isolate the heterometallic complexes with
an endo/exocyclic coordination. Among the mixed system of
the metal salts, when a mixture of NaI and CuI was used in the
reactions of L2, colorless crystalline product 7 suitable for X-ray
analysis was obtained.
129.42(4)
121.14(4)
Table 4. Selected Bond Lengths (Å) and Bond Angles (deg)
for Complex 5
Cu1−S1
Cu1−O4
S1−Cu1−S1A
S1A−Cu1−O4
S1A−Cu1−I1
2.2677(17)
2.356(7)
Cu1−S1A
Cu1−I1
S1−Cu1−O4
S1−Cu1−I1
O4−Cu1−I1
2.2677(17)
2.5199(9)
83.49(10)
116.74(4)
114.83(19)
X-ray analysis revealed that 7 is a 2D network complex
[Na2(Cu6I8)(L2)2(CH3CN)4]n involving heterometallic Na(I)/
Cu(I) ions, in which the two different metal ions are positioned
inside and outside the cavity (Figure 4). The purity of the bulk
product 7 was also confirmed by comparing the simulated
PXRD patterns from the single-crystal data with those from the
bulk sample (Figure 5). The gross 2D architecture for 7 can be
considered as an infinite brick-wall pattern (Scheme 3 and
Figure 4c). And the asymmetric unit for 7 contains one L2, one
Na atom, two acetonitrile molecules, three Cu atoms, and four I
atoms. The single brick unit for 7 contains four asymmetric
units, with each macrocycle being linked by a Cu6I8 unit.
The Na atom in the macrocyclic cavity is seven-coordinate,
with the coordination to four O atoms and one S atom from L2
in a twisted arrangement (Figure 4a). The remaining two sites
are occupied by two acetonitrile molecules in one side of the
macrocyclic plane. The sodium(I) coordination in 7 can be
described as a distorted pentagonal bipyramidal geometry,
where O1, O2, O3, S2, and N1 atoms form the pentagonal
plane, while N2 and O4 atoms occupy the axial positions [N2−
Na1−O4 161.0(1)°] (Figure 4b). The bite angles between two
adjacent donors on the pentagonal plane vary from 62.3(1) to
83.1(1)°. Some of the Na−O bonds [Na1−O1 2.837(3), Na1−
O3 2.953(3) Å] show elongated lengths because of the larger
macrocyclic cavity size for the sodium(I) complexation. Other
Na−O bond distances [2.373(2)−2.396(4) Å] are typical. The
Na1−S2 length [2.883(1) Å] is shorter than the sum of the van
der Waals radii (2.30 + 1.80 Å),19 suggesting that the S atom is
a weaker donor for the endocyclic coordination of sodium(I).
125.54(9)
83.49(10)
116.74(4)
Table 5. Selected Bond Lengths (Å) and Bond Angles (deg)
for Complex 6
Cu1−S1
Cu1−I1
S1−Cu1−S2
S1−Cu1−I1A
S2−Cu1−I1A
2.3247(6)
Cu1−S2
Cu1−I1A
S1−Cu1−I1
S2−Cu1−I1
I1−Cu1−I1A
2.3234(5)
2.5871(3)
106.562(16)
91.377(15)
115.465(9)
2.7377(3)
121.977(19)
102.416(16)
118.766(15)
tetrahedral, with the bond angles ranging from 91.377(15)° for
S2−Cu1−I1 to 121.977(19)° for S2−Cu1−S1. The Cu···Cu
distance (2.846 Å) in 6 is slightly longer than the sum of the
van der Waals radii (2.80 Å).19 Several dimeric copper(I) halide
complexes of thiamacrocycles with similar structures have been
previously reported by us.20
The overall conformational difference between 5 and 6 in the
exocoordination mode originates mainly from the monomer
and the dimer arrangement. Accordingly, the coordination
environment of each copper(I) center in both compounds is
more or less different. For example, the Cu1−O4 [2.356(7) Å]
in 5 is consistent with typical strong coordination to the copper
center; however, the Cu1···O4 [2.997(2) Å] in 6 shows fairly
elongated distance due to the two Cu1−I bond formation for
the dimerization.
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Scheme 4. Representation of Some CuI Clusters
Physical Properties of the Complexes. Since the
photoluminescence behaviors of copper(I) halide clusters for
such thiamacrocyclic complexes is highly dependent on their
structures,18,23 the photoluminescence spectra of the above
products were measured in the solid state. As mentioned above,
two cases of the compounds involving the double-open cubanes
Cu6I8 have been reported.12 However, note that no photo-
luminescence properties of those complexes have been reported
so far, in contrast to the cubane tetramer Cu4I4 complexes
showing the well-explored photoluminescence behaviors.20a,b,24
Upon excitation at 365 nm, however, complex 7 in the solid
state exhibits a weak yellow-green emission with a maximum at
418 nm dominated by a high-energy band (HE, Figure 6). The
Figure 5. PXRD patterns for complex 7: (top) as synthesized and
(bottom) simulated from the single-crystal X-ray data.
Notably, the S1 atom coordinates not to the Na(I) center
[Na1···S1 4.370(2) Å] but to the Cu1 atom [Cu1−S1 2.337(1)
Å] in an exocoordination mode to form a 2D network. In 7,
there are three crystallographically independent Cu atoms
(Cu1, Cu2, and Cu3) linked by four I atoms, forming a double-
open cubanes cluster Cu6I8 that acts as a planar four-connecting
node (see Scheme 4e and Figure 4d). The Cu6I8 motif, in
which two open-cubane21 Cu3I4 units are doubly linked via
Cu−I bonds, is constructed from six Cu, four μ2-I, and four μ3-I
atoms. Thus, the double-open cubane motif can be regarded as
the deformation of the normal double cubanes22 clusters by
removing three Cu−I bonds located at the same corner (the
dashed lines in Scheme 4e) of each cubane tetramer. Each
Cu6I8 unit is connected by four macrocyclic ligands in a trans
conformation, generating a brick-wall type 2D (4,4) layer with a
single brick containing four macrocycles and four Cu6I8 clusters
with a dimension of ca. 20 × 30 Å2. Until now only two
compounds with the double-open cubanes-type Cu6I8 cluster
have been reported by Sheldrick12a and our group.12b Thus, to
our knowledge, 7 is the third example. Consequently,
sodium(I) iodide induces not only the endocyclic cation
complexation of the macrocycle but also the formation of the
negatively charged double-open cubanes-type copper(I) iodide
cluster, which generates the 2D network structure via the
exocyclic coordination.
Figure 6. Solid-state photoluminescence spectrum of complex 7 at
room temperature (excitation at 365 nm).
absolute quantum yield for 7 in the solid state at 365 nm in
room temperature was determined to be Φ = 0.01. The
emission of 7 presented may be assigned to a triplet halide-to-
ligand charge transfer (XLCT) excited state.25 In the cubane
tetramer Cu4I4 complex, the emissions observed around 550
nm at room temperature are dominated by the low-energy band
(LE: XMCT/CC) while, at low temperature, the emissions
around 420 nm are dominated by a high energy one (HE:
XLCT).25 As expected, 5 and 6 show no photoluminescence in
the solid state.
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Figure 7. (a) 1H NMR spectra of L2 following the stepwise addition of AgNO3 in CD3CN and (b) their titration curves for each proton in L2. [L2] =
7.61 × 10−3 M, [AgNO3] = (0−1.39) × 10−2 M.
Thermogravimetric analysis (TGA) performed on 7 shows a
weight loss of 6.48% at around 180 °C, corresponding to the
loss of coordinated acetonitrile molecules (expected value
6.71%) (Figure S1 in the Supporting Information). The IR
spectrum of 7 obtained after heating to 190 °C also confirms
the removal of acetonitrile by the disappearance of the
absorption peak at 2268 cm−1 (νCN). Because single
crystallinity was not retained during the removal process of
the coordinated acetonitrile by heating, further structural
studies were not available.
contribution of the S donors to the coordination. From these
results, the silver(I) ion is mainly stabilized by the −S−O−S−
donor set in the flexible segment and the contribution from the
−O−O−O− segment is negligible, similar to the result
suggested in the solid state.
CONCLUSION
■
The new O4S2-donor macrocycle L2 was proposed as a ditopic
ligating system toward the hard and soft metal ions
simultaneously. The macrocycle L2 was synthesized and used
to prepare its endocyclic lead(II) complex together with
exocyclic silver(I) nitrate and copper(I) iodide complexes.
Interestingly, the latter one contains a mixture of one monomer
and one dimer complexes, which can be separated manually
because of their different shapes of the crystals. The ditopic
ligand L2 also enabled us to prepare an emissive heteronuclear
complex comprising a 2D polymeric network in which the
endocyclic heteronuclear [Na(I)/Cu(I)] complex units are
linked with double-open cubanes-type copper(I) iodide cluster
to form a brick-wall type structure. From these results, it is
concluded that by employing the preferred exocyclic coordina-
tion mode based on the thiaphilicity of soft metals, in
association with the endocoordination of the hard metal ions,
it is possible to construct the endo/exocyclic heteronuclear
network species displaying a considerable degree of sophisti-
cation.
1H NMR Study of the Ag(I) Complexation. To obtain
1
information on the complexation behavior in solution, the H
NMR titration was carried out. For the titrations of L2 with Na+
or other alkali metal ions, the cation-induced spectral changes
were negligible, suggesting very weak interactions due to the
existence of two soft sulfur donors in L2. When the metal
species was changed to silver(I) nitrate in the titration
experiment, it was possible to obtain the meaningful complex-
ation-induced chemical shifts for the ligand exhibiting a typical
slow-exchange system (Figure 7).
For the free L2, the signals of the aromatic protons (Ha−d
)
and the methylene protons (H1−5) are well-identified (Figure
7a). The cation-induced chemical shift changes (Δδ) were
measured on the variation of the mole ratio (Ag+/L2, 0−2.2
equiv) (Figure 7b). The titration curves show that all the
methylene proton signals except H5 shifted downfield and
exhibit no more shifts above a mole ratio (Ag+/L2) of 1.0,
indicating a 1:1 stoichiometry for the complexation.
The magnitudes of the cation-induced shifts follow the
sequence H5 ≫ H4 > H2, H3 > H1. The largest shift (toward
upfield) for H5 adjacent to the O donor between two S donors
shows the key contribution of this O donor to the coordination
is, to some extent, exceptional because the observed chemical
shifts for H1 and H2 adjacent to other three O donors are much
smaller than that for the former one. The second largest shift
(toward downfield) for H4 adjacent to the S donor shows the
EXPERIMENTAL SECTION
■
General. All chemicals and solvents used in the syntheses were of
reagent grade and were used without further purification. The
electrospray ionization (ESI) mass spectra were obtained on a
Thermo Scientific LCQ Fleet spectrometer. The high resolution mass
spectra (HRMS) were obtained on a JEOL JMS-700 spectrometer.
NMR spectra were recorded on a Bruker 300 spectrometer (300
MHz). The Fourier tranform infrared (FT-IR) spectra were measured
with a Nicolet iS10 spectrometer. The elemental analysis was carried
out on a LECO CHNS-932 elemental analyzer. The absolute quantum
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yield was measured with a Hamamatsu Quantaurus-QY C11347−11
absolute photoluminescence quantum yields measurement system.
Synthesis of Compound 1. To a warm ethanolic solution (100 mL)
of dialdehyde (3.0 g, 9.54 mmol) was added NaBH4 (1.15 g, 30.54
mmol) slowly, and then half of the solvent volume was reduced by
boiling the reaction mixture. After this mixture was cooled to room
temperature, water (400 mL) was added to precipitate the colorless
solid product. IR (KBr, pellet): 3384, 3274 (br, O−H), 2935, 2882 (m,
aliphatic C−H), 1603, 1591 (m, aromatic CC), 1492, 1453 (s,
aromatic CC), 1286 (m), 1239 (s), 1124(m), 1047 (s, C−O),
932(w), 755 (s) cm−1. 1H NMR (300 MHz, CDCl3, δ): 6.85−7.27 (m,
8H, aromatic), 4.62 (s, 4H, ArCH2), 4.21 (t, 4H, ArOCH2), 3.99 (t,
2H, ArCH2OH), 3.89 (t, 4H, ArOCH2CH2). 13C{1H} NMR (75
MHz, CDCl3) 156.9, 130.2, 129.6, 129.0, 121.3, 112.2, 69.8, 67.8, 61.8.
HRMS (fast atom bombardment (FAB)): Calcd for C18H23O5 ([M +
H]+): 319.1545, Found: 319.1553.
CD3CN, δ): 7.46−7.04 (m, 8H, aromatic), 4.52 (t, 4H, ArOCH2),
4.26 (t, 4H, ArOCH2CH2), 4.50 (s, 4H, ArCH2), 3.81 (t, 4H,
OCH2CH2S), 3.24 (t, 4H, OCH2CH2S). Mass spectrum m/z (ESI):
726.9 [Pb(L2)(ClO4)]+.
Caution! The perchlorate-containing complexes are potentially explosive
and should be handled with great care.
Preparation of [Ag2(L2)2(NO3)2] (4). AgNO3 (8.1 mg, 0.048
mmol) in methanol was added to a solution of L2 (20.0 mg, 0.048
mmol) in dichloromethane (1 mL). Slow evaporation of the solution
afforded a white precipitate. The precipitate was filtered off, washed
with methanol and diethyl ether, and dried. Vapor diffusion of diethyl
ether into DMF solution afforded a colorless crystalline product 4
suitable for X-ray analysis. mp 159−160 °C. IR (KBr, pellet): 3072,
3019 (m, aromatic C−H), 2923, 2868, 2838 (m, aliphatic C−H),
1598, 1584 (m, aromatic CC), 1493, 1452 (m, aromatic CC),
−
1401 (s, NO3 ), 1283, 1251 (s, allyl C−S), 1133−1103 (s, C−O),
1057 (m, C−O), 1018 (m), 936 (w), 768 (m), 745 (m) cm−1. Anal.
Synthesis of Compound 2. To a stirred suspension of compound 1
(2.00 g, 6.3 mmol) in dichloromethane (100 mL) was added thionyl
chloride (2.99 g, 25 mmol) dropwise. The reaction mixture was
maintained for 4 h. Ethanol (95%, 5 mL) was added carefully, and the
reaction mixture stirred at room temperature for a further 2 h. The
solvent was evaporated to yield a light yellow oil. Water (100 mL) was
added, and the mixture was extracted with dichloromethane (3 × 100
mL). The organic phase was dried over anhydrous sodium sulfate and
filtered, and the solvent was removed to yield a yellow oil 2 (2.18 g) in
98% yield. IR (KBr, pellet): 3082, 3037 (m, aromatic C−H), 2924,
2885 (m, aliphatic C−H), 1603, 1588 (m, aromatic CC), 1495,
1450 (s, aromatic CC), 1262, 1249 (s, CH2−Cl), 1132−1047 (m,
C−O), 959 (m), 828 (m), 753 (s, C−Cl), 659 (m) cm−1. HRMS (EI)
Calc. for C44H56Ag2N2O14S4: C, 44.75; H, 4.78; N, 2.37; S, 10.86.
1
Found: C, 44.83; H, 4.75; N, 2.38; S, 10.84%. H NMR (300 MHz,
CD3CN, δ): 7.34−6.91 (m, 8H, aromatic), 4.24 (t, 4H, ArOCH2),
3.98 (t, 4H, ArOCH2CH2), 3.91 (s, 4H, ArCH2), 3.33 (t, 4H,
OCH2CH2S), 2.76 (t, 4H, OCH2CH2S). Mass spectrum m/z (ESI):
529.12 [Ag(L)]+.
Preparation of [Cu(L2)I] (5) and [(Cu2I2)(L2)2] (6). CuI (4.6 mg,
0.024 mmol) and L2 (10.0 mg, 0.024 mmol) were dissolved in
acetonitrile. Slow evaporation of the solution afforded a mixture of
colorless rhomboid- and brick-shaped single crystals. Under the
microscope, the products were separated manually. The bulk purity for
each part was confirmed by PXRD and identified through single-crystal
X-ray analysis. The rhomboid-shaped crystals were [Cu(L2)I] (5), and
the brick-shaped crystals were [(Cu2I2)(L2)2] (6).
1
Calcd for C18H20Cl2O3 (M+): 354.0789. Found: 354.0794. H NMR
(300 MHz, CDCl3, δ): 6.80−7.28 (m, 8H, aromatic), 4.61 (s, 4H,
ArCH2), 4.08 (t, 4H, ArOCH2), 3.86 (t, 4H, ArOCH2CH2). 13C{1H}
NMR (75 MHz, CDCl3) 156.8, 130.7, 130.2, 126.3, 121.1, 112.3, 70.0,
68.4, 41.8.
For 5, mp 158−159 °C. IR (KBr, pellet): 3065, 3021 (m, aromatic
C−H), 2935, 2885, 2872 (m, aliphatic C−H), 1599, 1586 (m,
aromatic CC), 1492, 1449 (s, aromatic CC), 1252 (s, allyl C−S),
1136−1105 (s, C−O), 1049 (m), 1015(m), 944 (m), 753 (s) cm−1.
Anal. Calcd for C22H28I1Cu1O4S2: C, 43.25; H, 4.62; S, 10.49. Found:
C, 43.06; H, 4.58; S, 10.72%. 1H NMR (300 MHz, CD3CN, δ): 7.35−
6.93 (m, 8H, aromatic), 4.18 (t, 4H, ArOCH2), 3.97 (t, 4H,
ArOCH2CH2), 3.89 (s, 4H, ArCH2), 3.65 (t, 4H, OCH2CH2S), 2.67
(t, 4H, OCH2CH2S). Mass spectrum m/z (ESI): 483.12 [CuL2]+.
For 6, mp 155−156 °C. IR (KBr, pellet): 3067, 3019 (m, aromatic
C−H), 2923, 2907, 2864 (m, aliphatic C−H), 1598, 1586 (m,
aromatic CC), 1490, 1449 (s, aromatic CC), 1249 (s, allyl C−S),
1133, 1106 (s, C−O), 1049 (m), 1019 (m), 940 (m), 751 (s) cm−1.
Anal. Calcd for C44H56I2Cu2O8S4: C, 43.25; H, 4.62; S, 10.49. Found:
C, 43.05; H, 4.61; S, 10.74%. 1H NMR (300 MHz, CD3CN, δ): 7.35−
6.93 (m, 8H, aromatic), 4.18 (t, 4H, ArOCH2), 3.97 (t, 4H,
ArOCH2CH2), 3.88 (s, 4H, ArCH2), 3.64 (t, 4H, OCH2CH2S), 2.67
(t, 4H, OCH2CH2S).
Synthesis of L2. Cesium carbonate (2.57 g, 7.88 mmol) was
dissolved in dimethylformamide (DMF) (1500 mL) in a 3 L round-
bottom flask. 2-Mercaptoethyl ether (0.78 g, 5.63 mmol) and
dichloride 2 (2.00 g, 5.63 mmol) were dissolved in DMF (100 mL)
and placed in a 50 mL glass syringe. The contents of the syringe were
added dropwise at a regular rate (0.6 mL h−1) into the Cs2CO3−DMF
solution under a nitrogen atmosphere with the aid of a micro-
processor-controlled syringe pump at 55−60 °C over 50 h. The
mixture was allowed to stand for a further 10 h. After it was cooled to
room temperature, the reaction mixture was filtered, and the solvent
was evaporated. Water (100 mL) was added, and the mixture was
extracted with dichloromethane. The organic phase was dried over
anhydrous sodium sulfate and filtered, and the solvent was removed to
give a yellow oil. Flash column chromatography (SiO2, n-hexane/ethyl
acetate 8:2) afforded the final product L2 as a colorless solid in 43%
yield. For L2, mp 88−90 °C. IR (KBr, pellet): 3063, 3021 (m, aromatic
C−H), 2922, 2862 (m, aliphatic C−H), 1598, 1588 (m, aromatic C
C), 1494, 1450 (s, aromatic CC), 1250 (s, allyl C−S), 1127−1049
(s, C−O), 950 (m), 761 (m), 752 (m) cm−1. Anal. Calcd for
C22H28O4S2: C, 62.83; H, 6.71; S, 15.25. Found: C, 63.07; H, 6.64; S,
15.18%. 1H NMR (300 MHz, CDCl3, δ): 6.85−7.35 (m, 8H,
aromatic), 4.19 (t, 4H, ArOCH2), 4.01 (t, 4H, ArOCH2CH2), 3.85 (s,
4H, ArCH2), 3.60 (t, 4H, OCH2CH2S), 2.65 (t, 4H, OCH2CH2S).
13C{1H} NMR (75 MHz, CDCl3) 156.5, 130.7, 128.3, 127.7, 121.3,
111.8, 70.7, 70.3, 68.3, 31.0, 30.0. Mass spectrum m/z (ESI): 420.6
[C22H28O4S2]+.
Preparation of [Na2(Cu6I8)(L2)2(CH3CN)4]n (7). A dichloro-
methane (1 mL) solution of L2 (15.0 mg, 0.036 mmol) was allowed
to diffuse slowly into an acetonitrile (1 mL) solution of CuI (27.2 mg,
0.144 mmol) and NaI (10.7 mg, 0.072 mmol) in a capillary tube (i.d. 5
mm). Slow evaporation of the solution afforded a colorless crystalline
product 7 suitable for X-ray analysis. mp 164−165 °C. IR (KBr,
pellet): 2923, 2907, 2864 (m, aliphatic C−H), 2268 (w, CN−), 1598,
1586 (m, aromatic CC), 1490, 1449 (m, aromatic CC), 1288
(w), 1238 (s, allyl C−S), 1092−1033 (s, C−O), 951 (m), 978 (m),
771 (m), 755 (m) cm−1. Anal. Calcd for C52H68N4O8S4Na2Cu6O8: C,
25.51; H, 2.80; N, 2.29; S, 5.24. Found: C, 25.49; H, 2.77; N, 2.20; S,
5.12%.
X-ray Crystallographic Analysis. All data were collected on a
Bruker SMART APEX2 ULTRA diffractometer equipped with
graphite monochromated Mo Kα radiation generated by a rotating
anode. Data collection, data reduction, and semiempirical absorption
correction were carried out using the software package APEX2.26 All of
the calculations for the structure determination were carried out using
the SHELXTL package.27 All hydrogen atoms were placed in idealized
positions and refined isotropically in a riding manner along with their
Preparation of [Pb(L2)(ClO4)2] (3). Pb(ClO4)2·3H2O (16.4 mg,
0.036 mmol) in acetonitrile was added to a solution of L2 (15.0 mg,
0.036 mmol) in dichloromethane (1 mL). Slow evaporation of the
solution afforded an orange crystalline product 3 suitable for X-ray
analysis. IR (KBr, pellet): 3070, 3028 (m, aromatic C−H), 2932, 2883
(m, aliphatic C−H), 1602, 1587 (m, aromatic CC), 1495, 1452 (m,
aromatic CC), 1233 (m, allyl C−S), 1130−1103 (s, C−O), 1091 (s,
−
ClO4 ), 1035 (s, C−O), 929 (m), 914 (m), 762(m), 627 (m), 619
(m) cm−1. Anal. Calcd for C22H28O12S2Pb1Cl2: C, 31.96; H, 3.41; S,
7.76. Found: C, 32.05; H, 3.33 S, 8.07%. 1H NMR (300 MHz,
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respective parent atoms. Relevant crystal data collection and
refinement data for the crystal structures are summarized in Table 1.
(9) (a) Park, K.-M.; Seo, J.; Moon, S.-H.; Lee, S. S. Cryst. Growth Des.
2010, 10, 4148. (b) Kim, K.; Park, S.; Park, K.-M.; Lee, S. S. Cryst.
Growth Des. 2011, 11, 4059. (c) Ju, H.; Lee, S. S. Cryst. Growth Des.
2012, 12, 4972.
ASSOCIATED CONTENT
* Supporting Information
■
(10) (a) Blake, A. G.; Schroder, M. Adv. Inorg. Chem. 1990, 35, 1.
̈
S
(b) Loeb, S. J.; Shimizu, G. K. H. Inorg. Chem. 1993, 32, 1001.
(c) Sultana, K. F.; Lee, S. Y.; Lee, J. Y.; Park, K.-M.; Lee, S. S. Bull.
Korean Chem. Soc. 2008, 29, 241. (d) Yoon, I.; Seo, J.; Lee, J.-E.; Park,
K.-M.; Kim, J. S.; Lah, M. S.; Lee, S. S. Inorg. Chem. 2006, 45, 3487.
(e) Lee, S. Y.; Seo, J.; Yoon, I.; Kim, C.-S.; Choi, K. S.; Kim, J. S.; Lee,
S. S. Eur. J. Inorg. Chem. 2006, 3525.
TGA data for 7. Crystallographic data in CIF format. This
material is available free of charge via the Internet at http://
pubs.acs.org. CCDC 965568 (3), 989559 (4), 965569 (5),
965570 (6), and 965571 (7) contain the supplementary
crystallographic data for this Paper. These data can be obtained
free of charge from The Cambridge Crystallographic Data
Center via www.ccdc.cam.ac.uk/data_request/cif.
(11) Jin, Y.; Kim, H. J.; Lee, J. Y.; Lee, S. Y.; Shim, W. J.; Hong, S. H.;
Lee, S. S. Inorg. Chem. 2010, 49, 10241.
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Inorg. Chem. 2009, 48, 8934.
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AUTHOR INFORMATION
Corresponding Author
*E-mail: sslee@gnu.ac.kr.
■
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
This work was supported by NRF (BRL-2012R1A4A1027750
and 2013R1A2A2A01067771).
■
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