A Series of Compounds Based on [P2W18O62]6- and Transition Metal Mixed Organic Ligand Complexes with High Catalytic Properties for Styrene Epoxidation

Article abstract of DOI:10.1021/acs.inorgchem.8b01705

Seven compounds based on [P₂W₁₈O₆₂]^6- ({P₂W₁₈}) were successfully prepared and carefully characterized. [HC₅H₅N][Cu(2,2′-bpy)₂]₂[HP₂W<

Full text of DOI:10.1021/acs.inorgchem.8b01705

Article
Cite This: Inorg. Chem. XXXX, XXX, XXX−XXX
pubs.acs.org/IC
6
−
A Series of Compounds Based on [P W O ] and Transition Metal
2
18 62
Mixed Organic Ligand Complexes with High Catalytic Properties for
Styrene Epoxidation
†
,‡
Xiao Zhang,§ Xiao-Bing Cui,*,† and Ji-Qing Xu†
Ying Lu
̈
,
†College of Chemistry and State Key Laboratory of Inorganic Synthesis and Preparative Chemistry, Jilin University, Changchun, Jilin
1
30023, People’s Republic of China
‡
College of Chemistry, Tonghua Normal University, Tonghua, 134002, People’s Republic of China
§
MIIT Key Laboratory of Critical Materials Technology for New Energy Conversion and Storage, School of Chemistry and
Chemical Engineering, Harbin Institute of Technology, Harbin, People’s Republic of China
*
S Supporting Information
6−
ABSTRACT: Seven compounds based on [P W O ] ({P W }) were successfully prepared
2
18 62
2
18
and carefully characterized. [HC H N][Cu(2,2′-bpy) ] [HP W O ]·2H O (bpy = bipyridine)
5
5
2 2
2
18 62
2
2
+
(
[
1) is constructed from {P W } bridged by [Cu(2,2′-bpy) ] . [HC H N][Zn(2,2′-bpy) ] -
2
18
2
5
5
2 2
HP W O ]·4H O (1a) is isostructural and isomorphous with compound 1. [Cu (2,2′-
2
18 62
2
4
bpy) (nic) (OH) (H O)][H P W O ]·0.5H O (nic = nicotinic acid) (2) is formed by {P W }
3
3
2
2
3
2
18 62
2
2
18
and tetracopper transition metal mixed organic ligand complexes (TMMCs). [Cu (2,2′-
2
bpy) (C O )] [P W O ]·3H O (3) is made up of {P W } and bicopper TMMCs, [Cu (2,2′-
2
2
4
3
2
18 62
2
2
18
6
bpy) (OH) ][P W O ]·2H O (4) is built up from {P W }, and hexacopper complexes of 2,2′-
6
6
2
18 62
2
2
18
bpy and hydroxyls. [Cu(2,2′-bpy)(hnic) ][Cu (2,2′-bpy) (hnic) (H O) ][H P W O ] (hnic =
0
.5
3
3
2
2
2
3
2
18 62
hydroxyl nicotinic acid) (5a) contains two different TMMCs. In addition, compound 5a is the first
example of a compound that contains Cu−π interactions. [Cu (2,2′-bpy) (hnic)][H P W O ]·
2
2
4
2
18 62
2
+
xH O (x ≈ 50) (5b) is based on {P W } and [Cu (2,2′-bpy) (hnic)] . We discuss the
2
2
18
2
2
mechanisms for the formations of these compounds. All the catalytic performances of the
compounds for styrene epoxidation to styrene oxide are high.
INTRODUCTION
Scheme 1. Three Types of POM + TMMCs
■
Polyoxometalates (POMs), with diverse structures and
versatile properties, have attracted significant attention due
to their applications in analysis, nanotechnology, catalysis,
1
magnetism, biochemistry, and so on. Over the past few
decades, the chemistry of POM-based materials derived from
the combination of POMs and organic N-containing species or
metal complexes of organic N-containing species has
2
developed greatly.
On the basis of the analysis of literature reports, it is found
that POM-based compounds containing transition metal mixed
organic ligand complexes (TMMCs) are really scarce. Much
attention has been focused on the chemistry of metal
complexes of mixed organic ligands because they exhibit a
large number of structures and properties, and can be applied
in fields as photochemistry, magnetism, conducting materials,
more organic ligands composed of both organic N-containing
6
,4,7,8
ones and carboxylates.
Except for type B, several type A
and type C compounds were reported. POM + TMMC
hybrids of Wells−Dawson polyanions were scarcely reported.
To our knowledge, only several such compounds have been
3
biochemistry, optical materials, and catalysis. The introduc-
tion of TMMCs to POMs may generate compounds with
fascinating properties and interesting structures. According to
the three-category model to categorize POM + TMMC types
6d,e,8b
reported.
It will be attractive to explore the compounds of Wells-
Dawson POMs and TMMCs. In this paper, Cu was selected as
the metal of the TMMC because of its various coordination
4
proposed by our group, POM + TMMC compounds can be
classified into three types based on organic species (Scheme
1
): (a) type A includes TMMCs of two or more organic N-
5
containing ligands; (b) type B contains TMMCs of two or
more carboxylates; (c) type C comprises TMMCs of two or
Received: June 21, 2018
©
XXXX American Chemical Society
A
DOI: 10.1021/acs.inorgchem.8b01705
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
B
DOI: 10.1021/acs.inorgchem.8b01705
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
2
b,f,9
geometries and its close affinity for diverse organic ligands.
2
because it is a good chelating ligand for copper ions.
[Cu
4
(2,2′-bpy)
3
(nic)
3
(OH)
2
(H
2
O)][H
3
P
2
W
18
O
62]·0.5H
2
O (2). Com-
pound 2 was prepared using a procedure which is similar to that of 1,
except that nicotinic acid (123.00 mg,1.00 mmol) was used to replace
picolinic acid and Pr(NO ) ·6H O (443.00 mg, 1.00 mmol) was
added, and the pH was adjusted to 4 using 1.00 M NH ·H O solution.
Dark blue opacity block crystals were isolated with 53% yield (based
on W). Anal. calcd for C H Cu N O P W : W, 59.99; Cu, 4.61;
P, 1.12; C, 10.45; H, 0.81; N, 2.29%. Found: W, 59.73; Cu, 4.56; P,
1.01; C, 10.69; H, 0.91; N, 2.19%.
[Cu
procedure of 3 was similar to that of compound 1, except that
CuSO (499.00 mg, 2.00 mmol) replaced CuCl , oxalic acid (126.00
,2′-Bipyridine was chosen as the organic N-containing ligand
2b,10
3
3
2
Oxalic, picolinic, nicotinic, and isophthalic acids were selected
as the carboxylates. Fortunately, seven new hybrid compounds
3
2
based on {P W } were reported. [HC H N][Cu(2,2′-bpy) ] -
2
18
5
5
2 2
4
8
44
4
9
71.5
2
18
[
HP W O ]·2H O (1) exhibits a one-dimensional (1-D)
2 18 62 2
chain structure in which {P W } was linked by two [Cu(2,2′-
2
18
2
+
bpy) ] . [HC H N][Zn(2,2′-bpy) ] [HP W O ]·4H O
2
(2,2′-bpy) (C O )] [P W O62]·3H O (3). The synthesizing
2 2 4 3 2 18 2
2
5
5
2
2
2
18 62
2
(
1a) is isostructural and isomorphous with compound 1.
The difference between compounds 1 and 1a is that copper of
4
2
mg, 1.00 mmol) was used to replace picolinic acid, and the pH was
adjusted to 2.5 using 1.00 M HCl solution. Blue block crystals were
obtained in 42% yield (based on W). Anal. calcd for
C H Cu N O P W : W, 55.16; Cu, 6.35; P, 1.03; C, 13.21; H,
compound 1 was replaced by zinc in compound 1a. [Cu (2,2′-
4
bpy) (nic) (OH) (H O)][H P W O ]·0.5H O (2) shows a
3
3
2
2
3
2
18 62
2
1
-D chain structure formed by {P W } and tetracopper
2 18
6
6
54
6
12 77
2
18
TMMCs. [Cu (2,2′-bpy) (C O )] [P W O ]·3H O (3) is a
-D sinusoidal chain structure constructed from {P W } but
bicopper TMMCs. The structure of compound [Cu (2,2′-
bpy) (OH) ][P W O ]·2H O (4) is based on {P W }
2
2
2
4
3
2
18 62
2
0.91; N, 2.80%. Found: W, 54.93; Cu, 6.42; P, 1.10; C, 12.92; H, 0.71;
N, 2.69%.
[Cu
procedure that is similar to that of 3, except that isophthalic acid
66.00 mg, 1.00 mmol) replaced oxalic acid, and the pH was adjusted
to 3.5 using 1 M NH ·H O solution. Dark blue block crystals were
1
2 18
(2,2′-bpy)
(OH) ][P W O62]·2H O (4). 4 was prepared using a
6
6
6 6 2 18 2
6
6
2
18 62
2
2
18
1
linked by a hexacopper complex of 2,2′-bpy and hydroxyls.
3
2
[
[
Cu(2,2′-bpy)(hnic) ][Cu (2,2′-bpy) (hnic) (H O) ]-
0
.5
3
3
2
2
2
obtained with 47% yield (based on W). Anal. calcd for
C H Cu N O P W : W, 56.86; Cu, 6.55; P, 1.06; C, 12.38; H,
H P W O ] (5a) (2,2′-bpy = 2,2′-bipyridine) contains two
3
2
18 62
6
0
58
6
12 70
2
18
different TMMCs: the tetra-copper TMMC connects {P W }
2
18
1.00; N, 2.89%. Found: W, 56.59; Cu, 6.35; P, 0.96; C, 12.56; H, 1.04;
N, 2.93%.
to form a pseudo-1-D chain structure, whereas the tricopper
TMMC was supported by {P W }. [Cu (2,2′-bpy) (hnic)]-
H P W O ]·xH O (5b) is 1-D chain structure which is
generated from {P W } and bicopper [Cu (2,2′-
bpy) (hnic)] . We also discuss the mechanism for the
formation of these structures. The catalytic and photocatalytic
performances of all the hybrids were also carefully investigated.
2
18
2
2
Mixture of [Cu(2,2′-bpy)(hnic) ][Cu (2,2′-bpy) (hnic) (H O) ]-
0.5
3
3
2
2
2
[
5
H P W O ] (5a) [Cu2(2,2′-bpy)2(hnic)][H P W O ]·xH O (x ≈
[
3
2
18 62
4
2
18 62
2
4
2
18 62
2
0) (5b) and 1. The synthesizing procedure of the mixture is very
2
18
2
2
+
similar to that of compound 2, except that nicotinic acid (123.00 mg,
.00 mmol) replaced oxalic acid, and the pH was 2.5. A mixture of
three different types of crystals was obtained together with a total
weight of about 125.00 mg: the first was blue block crystals
2
1
(
(
(
compound 5a), the second was hyaline green block crystals
compound 1), and the third was opaque dark green block crystals
compound 5b). Unfortunately, the ratio of the three compounds is
EXPERIMENTAL SECTION
■
Materials and Methods. K [P W O ]·19H O was synthesized
6
2
18 62
2
hard to determine, for the three are similar to one another, so the
elemental analyses of these compounds were not carried out.
Crystallography. The data of compounds 1a and 2 were
measured on a Bruker D8 QUEST ECO diffractometer equipped
with a Mo Kα radiation (λ = 0.71073 Å) and the data of compounds
1
1
according to a published procedure and confirmed by IR analysis.
Infrared spectra were obtained on a PerkinElmer Spectrum One FTIR
spectra-photometer using KBr pellets. UV−vis spectra were analyzed
on a Shimadzu UV-3100 spectrophotometer. Powder X-ray diffraction
(
PXRD) patterns were recorded with a Scintag X1 powder
1
, 3, 4, 5a, and 5b were measured on an Agilent Technology
diffractometer system using Cu Kα radiation with a variable divergent
slit and a solid-state detector. The electrochemical measurements
were carried out on a CHI 660B electrochemical workstation.
SuperNova Eos Dual system with a Mo−Kα (λ = 0.71073 Å)
microfocus source and focusing multilayer mirror optics. The
structure solutions and full matrix least-squares refinements on F
were performed with SHELXS-2014/7 and SHELXL-2014/7
2
12
12
Synthetic Procedures. [HC H N][Cu(2,2′-bpy) ] [HP W O ]·
5
5
2 2
2
18 62
2
(
H O (1). The mixture of distilled water (20.00 mL), CuCl
2
2
using the WinGX program. Anisotropic parameters were refined to
the non-hydrogen atoms. Hydrogen atoms of organic ligands were
calculated in their ideal positions in all compounds, and the hydrogen
atoms attached to water molecules in all compounds were not located.
As for compound 3, Cu(1), Cu(3), O(41), N(3) 2,2′-bpy, and N(1)
342.00 mg, 2.00 mmol), picolinic acid (123.00 mg, 1.00 mmol),
and 2,2′-bpy (78.00 mg, 0.50 mmol) was stirred continuously for
about 1 h. After the addition of K [P W O ]·19H O (300.00 mg,
6
2
18 62
2
0
.06 mmol), the mixture was further stirred for 2 h, and the pH was
adjusted to 3 using 1.00 M HCl solution. The final suspension was
transferred in a Teflon-lined autoclave and allowed to react to 160 °C
for 3 days under autogenous pressure. After the autoclave was cooled
to room temperature, blue block crystals were obtained with 42%
−
nic are all statically disordered, and the site occupancy factors of
them are 0.5 except those of the N(3) pyridine ring of N(3) 2,2′-bpy.
Positions of C(12), C(13) and N(3) of N(3) 2,2′-bpy are occupied
by 1.0 C(12), 1.0 C(13) and 0.5 N(3) + 0.5 C(103), respectively. As
for compound 4, the two sets of three polar tungstens of {P W } are
statically disordered with occupancy factors of 0.5. As for compound
5a, the positions of Cu(4), Cu(5), the carbons and nitrogens of N(9),
N(11) 2,2′-bpy, and N(13) hnic are all disorderedly occupied with
occupancy factors of 0.5, too. CCDC number: 1587946 for 1,
1587947 for 1a, 1587948 for 2, 1587949 for 3, 1587950 for 4,
1587951 for 5a, and 1587952 for 5b. A summary of the
crystallographic data and refinements of all the compounds are
given in Table 1.
yield (based on W). Anal. calcd for C H Cu N O P W : W, 63.25;
4
5
43
2
9
64
2
18
2
18
Cu, 2.43; P, 1.18; C, 10.33; H, 0.83; N, 2.41%. Found: W, 63.12; Cu,
.66; P, 1.03; C, 9.96; H, 0.61; N, 2.14%.
2
2
−
[
HC H N][Zn(2,2′-bpy) ] [HP W O ]·4H O (1a). The mixture of
5
5
2 2
2
18 62
2
distilled water (20.00 mL), ZnCl (272.00 mg, 2.00 mmol), 2,6-
2
dipicolinic acid (160.00 mg, 1.00 mmol), and 2,2′-bpy (78.00 mg,
0
0
2
.50 mmol) was stirred for 1 h. K [P W O ]·19H O (300.00 mg,
6 2 18 62 2
.06 mmol) was then added. After the mixture was stirred for another
h, the pH became 1.5. The final suspension was transferred in a
Teflon-lined autoclave and heated to 165 °C for 3 days. The autoclave
was finally cooled to room temperature. Green block crystals were
obtained with 40% yield (based on W). Anal. calcd for
C H Zn N O P W : W, 62.77; Zn, 2.48; P, 1.18; C, 10.26; H,
Preparations of 1-, 1a-, 2-, 3-, 4-, and M5-CPEs. The 1-CPE
was fabricated as below: the mixture of Nujol (1 μL), graphite powder
(6 mg), and compound 1 (3 mg) were transferred in an agate mortar
and grounded homogeneously, then packed into a poly-
(tetrafluoroethylene) tube with a 1.5 mm inner diameter, and the
tube surface was carefully wiped with paper. In a similar manner, 1a-,
45
47
2
9
66
2
18
0
.90; N, 2.39%. Found: W, 62.11; Zn, 2.46; P, 1.13; C, 10.51; H, 0.80;
N, 2.33%.
C
DOI: 10.1021/acs.inorgchem.8b01705
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
2
-, 3-, 4-, and M5-CPEs were prepared with compounds 1a, 2, 3, 4,
compounds is directly introduced by using imidazole as the
starting material, but the pyridine in our compounds is
transformed via an in situ decarboxylation reaction.
and M5. CV measurements were carried out using a CHI 660b
electrochemical workstation. A three-electrode system was used with
Ag/AgCl as a reference electrode and Pt wire as a counter electrode.
CPEs were used as the working electrodes. CV measurements were
Crystal Structure of Compound 2. The asymmetric unit
2+
−
−
1
of compound 2 consists of four Cu , two nic , three halves of
,2′-bpy, and half a {P W }. As shown in Figure 2b, Cu(1) is
carried out in a 1 mol·L H SO solution.
2
4
2
2
18
RESULTS AND DISCUSSION
■
Crystal Structure of {P W }. The results of bond valence
2
18
sum calculations of tungstens of {P W } in compound 1 give
2
18
the average value 6.11, confirming that the tungstens are in the
1
3
+
6 oxidation state. The tungstens can be divided into two
types: six “polar” ones, grouped into two sets of three, and 12
equatorial” ones, grouped into two sets of six. Accordingly,
“
surface oxygens can be grouped into two kinds: polar and
equatorial ones.
Crystal Structure of Compounds 1 and 1a. The
asymmetric unit of compound 1 is composed of half a
2
+
[
Cu(2,2′-bpy) ] , a {P W }, a water molecule, and a
2
2
18
pyridine. Cu(1) is in an octahedral environment with four
,2′-bpy nitrogens and two oxygens from two {P W }. Two
2
2
18
Cu(1) serve as two bridges connecting {P W } to produce a
2
18
1
-D straight chain structure propagating along the [0 0 1]
direction. That is to say, {P W } was linked to one another in
2
18
a 1-D structure by the Cu(1)-complex double-bridge (Figure
14
1
). The pyridine, as the secondary organic species, does not
coordinate to any metal.
Figure 2. (a) Combined polyhedral and wire representation of the 1-
D chain formed by the pseudo-tetracopper TMMC and {P W } in
2
18
compound 2; (b) the triangle motif of the TMMC; (c) the horseshoe
motif of the TMMC. Some of the disordered atoms are half-
transparent. a: x, 1.5 − y, z.
Figure 1. Combined polyhedral and wire representation of the 1-D
chain in compound 1.
five-coordinated in a pyramidal geometry by O(40) from N(1)
−
nic , O(41) of a hydroxyl, O(35a, a: x, 1.5 − y, −1 + z)) from
Compounds 1 and 1a are isostructural and isomorphous.
The main difference between compounds 1 and 1a is that the
metal of the transition metal complex (TMC) is Zn in
compound 1a but Cu in compound 1. It should be noted that
the pyridine in compound 1 is transformed from the picolinic
acid via in situ decarboxylation. It has been reported that more
than 10 different in situ organic ligand formation reactions
a {P W } and N(1), N(2) from N(1) 2,2′-bpy. Cu(3) adopts
2
18
−
a pyramidal geometry with O(39) from N(1) nic , the same
hydroxyl oxygen O(41), O(38) of a coordinated water
molecule, O(37a) from another {P W }, and N(5) from
2
18
−
N(5) nic . Cu(2) displays a pyramidal geometry with two
−
O(42) from two N(5) nic and two N(4) from N(4) 2,2′-bpy
forming its square plane and O(2w) of a water molecule
located at its apical position, while Cu(4) exists in a pyramidal
geometry, of which the square plane comprises two N(6) from
15
were previously investigated. Hydrothermal decarboxylation
reactions has been observed several times in preparations of
15,16
−
coordination polymers.
In complete contrast to compound
N(6) 2,2′-bpy and two O(43) from two N(5) nic and the
1, the pyridine in compound 1a is transformed from 2,6-
apical position is occupied by O(10) from the same {P W }
2
18
dipicolinic acid via a more complex in situ reaction, for two
carboxyl groups were in situ eliminated to yield the pyridine.
To our knowledge, in situ decarboxylation with the elimination
of two carboxyl groups has never been reported before.
Two very similar compounds (Himi) [{M(2,2′-bpy) } -
involving Cu(3). Obviously, Cu(1) and Cu(3) are joined by
the hydroxyl O(41) and the bis-monodentate coordination
−
bridging N(1) nic , Cu(2) and Cu(4) are respectively linked
−
by N(5) and N(5a) nic with a bis-monodentate coordination
mode, while Cu(2), Cu(3), and Cu(4) are joined by N(5) nic−
2
2 2
(
P W O )]·H O (M = Mn and Cu) have been reported by
using a tri-monodentate coordination mode. Alternatively,
2
18 62
2
17
−
Zhou et al. recently. The main difference between our
compounds and Zhou’s compounds is that the isolated organic
moieties in our compounds are pyridine but imidazole in
Zhou’s compounds. More importantly, the imidazole in Zhou’s
N(5) nic serving as a μ -bridge joins Cu(2), Cu(3), and
3
−
Cu(4), N(5a) and N(1) nic as μ -bridges connect Cu(2),
2
Cu(4), and Cu(1), Cu(3), respectively. Therefore, a tetra-
copper TMMC was formed. For Cu(1), Cu(3), O(41), N(3)
D
DOI: 10.1021/acs.inorgchem.8b01705
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
−
2−
2
,2′-bpy, and N(1) nic are all disordered, the TMMC is thus
respectively through copper-two-ox -oxygens and copper-
two-2,2′-bpy-nitrogens of Cu(2) and Cu(3) TMMCs are in
the range of 37.452° and 38.105°, whereas the corresponding
dihedral angle of the Cu(1) TMMC is 21.822°. The dihedral
angle in the Cu(1) TMMC is obviously smaller, indicating the
weak steric hindrance between the Cu(1) TMMC and
a pseudo-tetracopper one. It is interesting to see that the
TMMC shows a horseshoe shape (Figure 2c). If we do not
omit the disordered atoms, the TMMC exhibits a triangle
shape (Figure 2b). In addition, the two chelating 2,2′-bpy of
Cu(2) and Cu(4) are arranged parallel with the plane to plane
distance and dihedral angles of ca. 3.9 Å and 12.1°, indicating
the existence of the weak π···π interaction between the two,
which can lead to an increase of the stability of the TMMC.
One {P W } using its two terminal oxygens interacts with
{P
Cu(1) TMMC serves as the bridge linking {P
knowledge, compound 3 is the first extended structure of
W
18}. Perhaps this is the main reason why only the
2
W
2
18}. To our
2−
{P W18} and TMMC of ox .
2
18
2
2
+
[
Cu (2,2′-bpy) (ox)] , which was first synthesized by
Cu(3) and Cu(4) of TMMC with Cu−O bond lengths of
2
2
Gutierrez-Zorrilla, bridges Keggin POMs in extended structur-
́
2
.22(1)−2.287(9) Å, while Cu(1) of TMMC further interacts
6
a,b
es. The first difference between Gutierrez-Zorrilla’s
́
compounds and compound 3 is that the size of {P W } is
obviously bigger than that of the Keggin POM in Gutier
Zorrilla’s compounds; the second is that there are two
additional different TMMCs supported by {P W } in
with a terminal oxygen from another {P W } with the Cu−O
2
18
bond length of 2.303(8) Å, meaning that TMMC acts as a
bridge joining {P W } to give rise to a 1-D straight chain
2
18
́
rez-
2
18
structure (Figure 2a). To our knowledge, such a complicated
structure containing POMs and TMMCs was not reported
previously.
Crystal Structure of Compound 3. There are three Cu ,
three 2,2′-bpy, three halves of ox , two water molecules, and
half a {P W } in the asymmetric unit of compound 3. Cu(1)
is six-coordinated in an octahedral geometry by two 2,2′-bpy
nitrogens, two oxygens from ox , and two oxygens from two
P W }. Two Cu(1) are linked by the bis-bidentate
coordination ox to form the Cu(1) TMMC which bridges
adjacent {P W } to generate a zigzag chain structure along the
0 1 0] direction. In contrast, both Cu(2) and Cu(3) are five-
coordinated in a pyramidal geometry by two 2,2′-bpy
nitrogens, two oxygens from ox , and one oxygen from
P W }. Two Cu(2) and Cu(3) are respectively joined by one
ox using a bis-bidentate coordination mode to form Cu(2)
and Cu(3) TMMCs, both of which are supported by one
2
18
compound 3, but Gutierrez-Zorrilla’s compounds contain
́
2+
2
+
only [Cu (2,2′-bpy) (ox)] bridges. In 2007, Xu and Liu
2
2
2
−
prepared two compounds which were similar to Gutierrez-
́
Zorrilla’s compounds but based on Anderson POMs with a
2
18
18
smaller size. Very recently, we also reported a bicapped
Keggin Mo−V cluster with the intermediate size linked by the
2−
19
identical TMMC. The difference between our recently
reported compound and compound 3 is that, except for the
TMMC linker, there are two different dissociated TMCs in our
recently reported compound, but there are two different
supported TMMCs in compound 3. The analogous TMMC of
cobalt and phen has been prepared by us recently, too, but the
cobalt analogue did not serve as the bridge, and the involved
{
2
18
2
−
2
18
[
2
−
{
2
18
20
2
−
POM was arsenic−vanadium cluster.
Both compounds 1 and 2 are examples of {P W } with its
2
18
polar terminal oxygens interacting with copper complexes. The
reason can be concluded as follows: (1) more negative charges
are distributed on the surface of the polar area of {P W },
{
P W } via Cu−O contacts to give rise to a POM supported
complex. In conclusion, compound 3 is built on {P W }
2
18
2
18
2
18
connected by Cu(1) TMMC via axial Cu···O−W bounds,
indicating that the polar oxygens are more nucleophilic and
easy to bind to metals. (2) Another reason is that TMMC has
two or more organic ligands and metals, indicating that the size
of TMMC is big and the steric hindrance between any two
TMMCs is strong. Therefore, the polar oxygens are more
suitable for two TMMCs to coordinate to so the two TMMCs
can be positioned farther away from each other. That is the
reason why 1-D chain structures were formed in compounds 1,
leading to a {[P W ][Cu (2,2′-bpy) (C O )]} 1-D zigzag
2
18
2
2
2
4
n
chain. Two additional TMMCs (Cu(2) and Cu(3) ones) are
also connected to each {P W }, ensuring the electroneutrality
2
18
of compound 3 (Figure 3).
What makes Cu(1) TMMC different from Cu(2) and
Cu(3) TMMCs? Detailed analysis of the two kinds of TMMCs
is shown below: the dihedral angles between the two planes
1
a, and 2. (3) The M−M distance of TMMC and the O −O
t 2 18
t
t
(
O : terminal orygen) distance of {P W } can fit into each
other or not. As for TMMCs of compound 2, Cu(1)−Cu(3)
distance is 3.42 Å, and Cu(3)−Cu(4) distance is 7.29 Å. O −
t
O distances between any two polar oxygens are 5.53−5.54 Å.
t
Therefore, Cu(1)−Cu(3) cannot, but Cu(3)−Cu(4) can
simultaneously interact with two polar O . As for compound
t
3
, Cu(1) TMMC interacts with two polar O , while Cu(2) and
t
Cu(3) TMMCs interact with two equatorial O . M−M
t
distances of all the three TMMCs are 5.09−5.16 Å. O −O
t
t
distances between any two polar O are 5.53−5.54 Å, whereas
t
O −O distances between any two equatorial O can be
t
t
t
grouped into two sets: one is in the range of 4.82−4.85 Å, and
the other is in the 5.48−5.52 Å range. Clearly, O −O distances
t
t
between two polar O and one set equatorial O are
t
t
comparable, and thus all these involved pairs of O can show
t
interactions with the coppers of TMMCs simultaneously. (4)
Sometimes, the above-mentioned speculations cannot fully
explain the bonds of some structures; for example, the
Figure 3. Combined polyhedral and wire representation of the 1-D
chain in compound 3.
equatorial O has the priority over the polar ones to coordinate
t
E
DOI: 10.1021/acs.inorgchem.8b01705
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
to the metal of TMMC in some structures. The reason is that,
by Wang et al. Wang’s complex is a bicopper hydroxyl
7d
with the priority of the equatorial O , there will be more Cu−O
cluster. Obviously, Wang’s compound and compound 4 are
significantly different. Compound 4 here is the first structure
constructed from POMs and high-nuclear copper (>2)
hydroxyl 2,2′-bpy complexes.
t
interactions formed between TMMCs and {P W } in those
2
18
structures, and consequently, more Cu−O interactions will
significantly increase the stability of the crystals. As for
compound 3, only the Cu(2) TMMC interacts with a pair of
Crystal Structure of Compounds 5a and 5b. The
polar O , but the Cu(1) and Cu(3) TMMCs interact with two
2+
t
asymmetric unit of compound 5a is composed of five Cu , five
pairs of equatorial O . If the Cu(3) TMMC was supported by
2−
2−
t
2
{
,2′-bpy, three hnic (hnic = hydroxyl nicotinic acid), a
two polar O , there would be strong steric hindrance between
t
P W } and three coordination water molecules. Cu(1)
2
18
the Cu(3) and Cu(1) TMMCs, so the Cu(1) TMMC cannot
presents an octahedral geometry with O(103), O(104) from
be coordinated by the equatorial O , and then the Cu(1)
t
2−
N(5) hnic , O(1w), O(2w) of water molecules and N(1),
TMMC will be dissociated. If the Cu(1) TMMC bridges two
pairs of polar O from two adjacent {P W }, there will be a
N(2) form N(1) 2,2′-bpy. Cu(2) is in a pyramidal environ-
t
2
18
2−
ment with O(105) of N(5) hnic hydroxyl, O(104) from
dimer of {P W } joined by the Cu(1) TMMC with two
2
18
2−
2−
N(5) hnic , O(101) from N(6) hnic and N(3), N(4) from
Cu(2) TMMCs supported by each {P W }, and the Cu(3)
2
18
N(3) 2,2′-bpy. Cu(3) is five-coordinated by O(100) and
TMMC will be dissociated. Comparing the structure of
compound 3 and the two kinds of speculations, we can see
that there are more Cu−O interactions in compound 3, and
consequently, the structure of compound 3 is more reasonable.
Crystal Structure of Compound 4. The asymmetric unit
2−
O(101) from N(6) hnic , O(26a, a: 1 + x, −1 + y, z) from
2
−
{P W } and N(7), N(8) from N(7) 2,2′-bpy. N(5) hnic in a
2
18
bis-bidentate coordination mode respectively chelates Cu(1)
2−
and Cu(2), while N(6) hnic adopting the bidentate and
monodentate coordination mode coordinates to Cu(2) and
Cu(3) (Figure 5c). Thus, Cu(1), Cu(2), and Cu(3) were
2
+
of compound 4 is comprised of half a {P W }, three Cu ,
2
18
2
+
three 2,2′-bpy, and three hydroxyl atoms. The three Cu
adopt almost the same pyramidal geometry. Cu(1) is five-
2−
linked by N(5) and N(6) hnic to form a tricopper TMMC,
coordinated by a terminal oxygen from {P W }, two hydroxyl
2
18
which interacts with {P W } via a Cu−O contact with the
2
18
oxygens, and two 2,2′-bpy nitrogens, while Cu(2) and Cu(3)
Cu−O bond length of 2.50(1) Å, generating a {P W }
2
18
are respectively bonded to three hydroxyl oxygens and two
2−
−
supported complex. Hnic is transformed from the nic via in
situ hydroxylation, which is first reported by our group
2
,2′-bpy nitrogens. As shown in Figure 4, Cu(1) shares two
Figure 4. Combined polyhedral and wire representation of {P W }
2
18
and hexacopper TMC in compound 4. a: −x, 1 − y, 1 − z.
hydroxyls and one hydroxyl with Cu(2) and Cu(3),
respectively, Cu(2) respectively shares two hydroxyls and
one hydroxyl with Cu(3) and Cu(3a), while Cu(3) and
Cu(3a) are further linked by sharing two hydroxyls. Therefore,
two Cu(1), two Cu(2), and two Cu(3) complexes are join to
form a novel hexacopper unit. The plane-to-plane distances of
adjacent 2,2′-bpy are in the range of 3.5−3.7 Å, and the
corresponding dihedral angles are in the range of 1.014−
1
3.969°, indicating that π···π interactions exist between any
two of the 2,2′-bpy ligands. The apical position of Cu(1)
pyramid is occupied by a terminal oxygen from {P W } with a
2
18
strong Cu−O covalent interaction (Cu−O bond: 2.28(3) Å),
indicating that the hexacopper cluster acts as a bridge linking
adjacent {P W } to produce a straight chain structure (Figure
2
18
4
).
Copper mixed-ligand complexes of hydroxyl and 2,2′-bpy
2
1
have been intensively studied. and the biggest cluster
reported was just {Cu (OH) },
21i,j
which is identical to the
6
6
copper hydroxyl cluster in compound 4. The biggest difference
of the reported compounds and compound 4 is that the copper
hydroxyl cluster here is not discrete but acts as an inorganic
ligand rigidly linked to {P W }. A compound constructed
Figure 5. (a) Combined ellipsoid (50% probability), polyhedron, and
wire representation of the 1-D chain in compound 5; Combined
ellipsoid (50% probability) and wire representation of pseudo-
tetracopper TMMCs (b) and the tricopper (c) in compound 5. a: 2 −
x, 1 − y, −z.
2
18
from complexes of hydroxyl and Keggin POMs was reported
F
DOI: 10.1021/acs.inorgchem.8b01705
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
4
recently. In addition, the bis-bidentate coordination mode of
interacts with four polar O atoms from four {P W }, for the
t
2
18
2−
4
N(5) hnic was not reported previously.
four {P W } each have already supported a tricopper TMMC.
2 18
Except for the tricopper TMMC, there is a pseudo-
tetracopper TMMC (Figure 5b). Cu(4) is seven-coordinated
by two 2,2′-bpy nitrogens, two carboxylic oxygens from N(13a,
That is to say, the two sides of each {P W } will be one
2 18
pseudo-tetracopper TMMC and one tricopper TMMC,
respectively. So, no 1-D extended structure mentioned above
will be formed, and also not so many Cu−O contacts will be
formed too. As mentioned above, more Cu−O contacts will
increase the stability of the crystal structure. Therefore, the
tetracopper TMMC has to be coordinated by equatorial Ot.
We have focused on the preparations and characterizations
of POM-TMMCs recently. A series of POM-based hybrids of
2−
a: 2 − x, 1 − y, −z) hnic , one terminal oxygen form a
{
P W }, one heterocyclic nitrogen and carbon from N(13)
2 18
2
−
hnic . The short Cu−N (2.06(8) Å) and Cu−C (2.11(9) Å)
distances between the Cu(4) and N(13) pyridine ring of
2
−
N(13) hnic indicate that there is a special cation−π
interaction between Cu(4) and the N(13) pyridine ring with
Cu−N−C and Cu−C−N angles of 74.5° and 66.7°. The
4
,8
TMMCs have been synthesized by us. To our knowledge,
POM-based hybrids based on two TMMCs like compound 5a
have never been reported before.
coordination mode can be regarded as η . Cu(5) displays a
2
square pyramidal geometry with two 2,2′-bpy nitrogens, one
2−
carboxylic oxygen, and the hydroxyl oxygen from N(13) hnic
Compound 5b with compound 5a was synthesized together.
The structure of compound 5b is much simpler than that of
compound 5a. In compound 5b, there is only one TMMC
and a terminal oxygen from another {P W }. Cu(5) and
2
18
Cu(4a, a: 2 − x, 1 − y, −z) are linked by the bis-bidentate
2−
2+
2−
coordination N(13) hnic , while Cu(4) is linked to the N(13)
[Cu (2,2′-bpy) (hnic)] , which consists of a hnic , two
2
2
2−
hnic via the special Cu-π interaction. Therefore, two Cu(4)
coppers, and two 2,2′-bpy. Cu(1) is six-coordinated in an
2
−
and two Cu(5) are joined by two N(13) hnic to form a
octahedral geometry by the hydroxyl oxygen O(65) and one
2−
tetracopper TMMC. For Cu(4), Cu(5), N(9), N(11) 2,2′-bpy,
carboxylic oxygen of N(5) hnic , two oxygens from two
2−
and N(13) hnic are all disorderedly occupied, and the
TMMC here is a pseudo-tetracopper TMMC.
{P W }, and two nitrogens from a 2,2′-bpy. Cu(2) is five-
2
18
2
−
coordinated by the other carboxylic oxygen of N(5) hnic ,
Some complexes of Ag−π and Au−π interactions were
two oxygens from two {P W }, and two nitrogens from a 2,2′-
2
18
22,23
2−
reported and studied.
Theoretical study about Cu−π
bpy, adopting a pyramidal geometry. N(5) hnic adopts a
monodentate and bidentate coordination mode to connect the
two coppers in the TMMC. Both coppers show covalent
interactions with the same two {P W }, indicating that the
+
24
interactions of Cu has been reported too. However, to our
knowledge, still no complexes of Cu−π interactions have been
reported up to now. Compound 5a is the first example of
complexes containing Cu−π interactions. The existing of
cation−π interaction or not is important in a number of
2
18
two coppers serve as bridges linking {P W } in a 1-D chain
2
18
structure (Figure 6).
25
supramolecular systems. And recently, it has been proposed
that the interaction of Cu−π plays a significant role in the
26
aromatic cross-coupling reaction. Therefore, one needs to
know more about the Cu−π interaction. Compound 5a here
provides a remarkable example.
Both Cu(4) and Cu(5) have strong Cu−O covalent
interactions with equatorial O from {P W } (Cu−O
t
2
18
distances: 2.41(2)−2.55(3) Å). That is to say, each pseudo-
tetracopper TMMC is linked to four {P W }, while each
2
18
{
P W } is connected to two pseudo-tetracopper TMMCs.
2 18
Thus, {P W } and pseudo-tetracopper TMMCs are con-
2
18
nected to form a pseudo-1-D double chain structure. To our
knowledge, such an interesting compound was not reported
previously (Figure 5a).
Cu(2)−Cu(3) and Cu(1)−Cu(3) distances of the tricopper
TMMC are 5.39 and 7.02 Å, indicating that both Cu(2)−
Cu(3) and Cu(1)−Cu(3) can be coordinated simultaneously
by two O . But there is only one copper of the tricopper
t
TMMC coordinated by a polar O , and the reason is that the
t
steric hindrance between the tricopper TMMC and {P W }
2
18
cannot let any two of its coppers to be coordinated by two Ot
simultaneously. The Cu(4)−Cu(5) distance of the pseudo-
tetracopper TMMC is 5.59 Å, but Cu(4)−Cu(5) were not
Figure 6. Combined ellipsoid (50% probability), polyhedron, and
wire representation of the TMMC and {P W } in compound 5b.
coordinated by any two O simultaneously, too, also for the
t
2
18
strong steric hindrance between the pseudo-tetracopper
TMMC and {P W } .
2
18
The tricopper TMMC was supported by {P W } using one
It is interesting to discuss the interactions between the
2
18
of its polar O . There is a question: why the pseudo-
TMMC and the its two adjacent {P W }. The involved Cu−
t
2
18
tetracopper TMMC interacts with {P W } via equatorial O
O contacts of Cu(2) (1.99(3) and 2.37(3) Å) in TMMC are
much stronger than those of Cu(1) (2.5282(1) and 2.7190(1)
Å), indicating that the driving force that causes the formation
of compound 5b is Cu−O interactions between Cu(2) and the
two equatorial O atoms from two neighboring {P W }. It
2
18
t
atoms but not polar ones. As shown in Figure 5, the pseudo-
tetracopper TMMC can interact with four equatorial O atoms
t
from four {P W } (all the metals of the TMMC show
2
18
interactions with {P W }). If the pseudo-tetracopper TMMC
2
18
t
2
18
G
DOI: 10.1021/acs.inorgchem.8b01705
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
should be noted that the two corresponding {P W } also
2-, 3-, 4-, and M5-CPEs) between −650 and +50 mV were
2
18
sandwich Cu(1) in TMMC via one polar and one equatorial
O atoms from the two {P W }, respectively (Figure S1). The
recorded in Figure S5. Three pairs of redox couple peaks with
E1/2 = (Epa + E )/2 of −571, −342, −101 mV, −590, −365,
t
2
18
pc
Cu−O contacts of Cu(1) are weaker but also important for the
−128 mV, −585, −356, −115 mV, −567, −345, −106 mV,
−572, −349, −120 mV and −578, −354, −102 mV,
respectively, were observed in the CVs of 1, 1a, 2−4, and
M5- CPEs. All the CVs are similar, confirming the same
polyanions in them. The peaks can be associated with one two-
electron processes and two consecutive one-electron processes
structure. If one of the two equatorial O around Cu(2) were
t
substituted by one polar O from one of the two {P W }, there
t
2
18
will be no chance for Cu(1) to interact with any O of the same
t
{
P W }, because the two {P W } O atoms coordinating to
2 18 2 18 t
Cu(2) are located in cis-positions. Thus, Cu(2) interacting
28
with two equatorial O can make the interactions between
of {P W }.
t
2 18
29
Cu(1) and the two {P W } possible and consequently
POM materials may be photocatalysts to decolorize dyes.
2
18
increase the number of Cu−O contacts.
Rhodamine B (RhB) is selected as model pollutant to evaluate
the photocatalytic activity of photocatalysts. The performances
of compounds 1, 1a, 2−4, and M5 for degrading RhB have
been investigated with the process: catalyst (5 mg) was added
Syntheses and Discussion. All compounds were prepared
hydrothermally at 160 °C except that compound 1a was
obtained at 165 °C. According to the experiments, the
combination of different Cu salts, different carboxylates and
−
5
−1
in RhB solution (100 mL, 3.0 × 10 mol·L ), and the
suspension was stirred magnetically for 30 min in the dark and
then were placed about 4−5 cm under the irradiation of a 500
W Hg lamp. The stirring rate was 790−800 rpm. At 60 min
intervals, 4 mL of samples was taken out, centrifuged, and then
analyzed by UV−vis spectroscopy. The RhB photodegradation
without catalyst was carried out for comparison, and 30.1% of
RhB was decolorized after 360 min (Figure S6). Changes in
the C /C plot of RhB solutions versus reaction time are
2
,2′-bpy resulted in different products. The pH has a
significant influence on the preparations. The pH was adjusted
in the range of 2.5−4 for all compounds. When the pH was out
of the range, only unidentified precipitates were obtained. The
molar ratio of {P W }/2,2′-bpy/carboxylate/metal is also very
2
18
important for the preparations of these hybrids. We found that
the molar ratio of about 3:25:50:100 is optimal for these
compounds. In the synthesis of compound 2, Pr(NO ) was
3
3
t
0
used as a starting material; unfortunately, Pr was not
incorporated into compound 2. Although Pr is absent in the
product, Pr(NO ) is necessary for the formation of compound
displayed in Figure S7. The absorption peaks of all compounds
decreased more rapidly upon irradiation, indicating that these
catalysts exhibit photocatalytic properties. Though compound
1 and 1a are isostructural and isomorphous, the degradation
efficiency of compound 1a (69.41%) is much higher than that
of compound 1 (56.57%). Compound M5 contains com-
pounds 1, 5a, and 5b, the RhB degradation of M5 (58.12%) is
very similar to the degradation of 1. Of the compounds, and
compound 1a exhibits the best photocatalytic activity with the
RhB degradation of 69.41%. Compound 3 based on TMMC of
3
3
2
. One or more starting materials that were not incorporated
into the final products were often observed in hydrothermal
2
7
preparations. In summary, the pH, reaction temperature,
selection, and molar ratio of raw materials are key factors for
the preparations of these compound.
CHARACTERIZATION OF THE COMPOUNDS
■
2
−
As shown in Figure S2, four peaks at 1094, 961, 901, and 790
2,2′-bpy and ox exhibits the lowest degradation efficiency,
−
1
cm were observed in the IR spectra of 1, ascribed to ν(P−
which is only 34.59%.
O ), ν(W−O ), ν(W−O −W), and ν(W−O −W), respec-
Repeated photocatalytic experiments of compound 1 were
carried out to evaluate its stability and reusability because its
amount is enough. With the dose of 1 increased up to 50 mg,
the conversion increased from 56.57% to 89.83%. After each
cycle of photocatalytic degradation, 1 was separated, washed
with water, dried, and reused directly. The degradation rates of
compound 1 and the recovered 1 after three cycles decreased
from 89.83% to 85.60%, indicating the good reusability of
compound 1 (Figure S8). The XRD and IR analysis (Figure
S9) of the recovered samples further demonstrated the stability
of 1.
c
t
b
c
−
1
tively. The bands of 1618−1188 cm are assigned to 2,2′-bpy
in 1. IR spectra of compounds 1a, 2−4, and the mixture of
compounds 5a, 5b, and 1 (the mixture of compounds 5a, 5b,
and 1 = compounds M5) exhibit four similar characteristic
peaks at 1093, 960, 902, 790 cm , 1093, 950, 906, 793 cm ,
092, 955, 906, 814 cm , 1091, 954, 910, 790 cm , and 1089,
−
1
−1
−
1
−1
1
9
−
1
54, 914, 793 cm , respectively, indicating the same POMs in
all these compounds.
The phase purity of compounds 1, 1a, and 2−4 has been
confirmed by the XRD analysis (Figure S3). The electronic
spectra (UV−vis) of compounds 1, 1a, and 2−4 and M5 are
presented in Figure S4. There are two peaks and a shoulder
peak at 258, 287, and 315 nm in the UV−vis spectrum of 1,
associated with O → W charge transfer of {P W } and n →
The epoxidation of alkenes is a significant reaction because
epoxides are rather important intermediates for organic
3
0
synthesis. POMs have been paid more attention as a
31
significant family of catalysts in the epoxidation. Our group
2
18
π* transitions of 2,2′-bpy. UV−vis spectra of compounds 1a,
also used some POM-based compounds as catalysts for styrene
5g,20
2
3
3
−4, and M5 present similar peaks at 256, 283, 304 nm, 256,
02, 313 nm, 257, 302, 313 nm, 257, 302, 313 nm and 256,
02, 313 nm, also due to their {P W } and organic ligands,
epoxidation, and some display higher catalytic activities.
The styrene epoxidation using aqueous tertbutyl hydro-
peroxide (TBHP) with catalysts 1, 1a, 2−4, and M5 was
performed. The catalytic reactions were performed based on
the following procedure. An acetonitrile (2 mL) solution of
styrene (0.114 mL, 1 mmol) as the substrate, 2 mg catalyst
(compounds 1, 1a, 2−4, and M5) were mixed to a 10 mL two-
neck flask where one neck was equipped with a reflux
condenser. The mixture was continuously stirred and then
heated to 80 °C. After the addition of 2 mmol TBHP to start
the reaction, the products of the reaction were identified and
2
18
respectively. The peaks due to 2,2′-bpy of compounds 1 and
1
a are centered at 287 and 283 nm, whereas the corresponding
peaks of compounds 2−4 and M5 were centered at 302 nm.
The red shift of the peaks in the spectra of compounds 2−4
and M5 may be attributed to the relatively complex
coordination environments in compounds 2−4 and M5.
The cyclic voltammograms (CVs) of the carbon-paste
electrodes (CPEs) modified with 1, 1a, 2−4 and M5 (1a-,
H
DOI: 10.1021/acs.inorgchem.8b01705
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
a
quantified by gas chromatography (Shimadzu, GC-8A)
equipped with an HP-5 capillary column and a flame detector.
The result of the styrene epoxidation experiment without
catalyst showed that the styrene conversion is about zero after
Table 3. Recyclability and Reusability of Compound 3
product selectivity (%)
catalysts
styrene conversion (%)
So
Bza
others
8
h. The results obtained in the styrene oxidation with various
first
second
third
95.93
95.72
94.86
86.06
76.18
88.55
13.94
15.00
9.21
0
8.82
2.24
catalysts is shown in Table 2. Though compound 1a displays
a
a
Table 2. Catalytic Activity and Product Distribution
So: styrene oxide, Bza: benzaldehyde, others: including benzoic acid,
phenylacetaldehyde.
product selectivity (%)
catalysts
styrene conversion (%)
So
Bza
others
recyclability of 3. The IR and X-ray analysies of the catalyst
after three reaction cycles have been further recorded (Figure
S10), suggesting that the catalyst has an excellent stability
during the styrene selective oxidation reactions. Though
compound 3 is stable during the catalytic reaction and only
a few of compound 3 were leached into the solution, there is a
significant activity in the supernatant after the suspension of
compound 3 is used (after a catalytic run, filter to remove the
insoluble catalyst, and repeat the reaction by adding fresh
oxidant and substrate to the previously used supernatant
MeCN solution. The conversion of styrene is 57.5%, and the
selectivity is 79.9%). Therefore, the leached compound 3
argues for the homogeneous nature of the catalytic
epoxidation.
no catalyst
∼0
compound 1
compound 1a
compound 2
compound 3
compound 4
compounds M5
compound 6
compound 7
K P W
93.75
16.38
85.05
92.54
91.33
91.96
78.4
84.28
32.63
65.53
82.98
70.00
76.15
67.2
15.72
67.37
33.41
11.25
30.00
16.17
30.30
30.80
89.10
0
0
1.05
5.77
0
7.68
2.4
0.0
0.1
54.0
22.5
69.2
10.8
6
2
18
a
So: styrene oxide, Bza: benzaldehyde, others: including benzoic acid,
phenylacetaldehyde. K P W K [P W O ]·19H O
6
2
18
6
2
18 62
2
To further investigate the catalytic mechanism of these
compounds, we used the same procedure except that
the highest photocatalytic degradation efficiency, compound
a shows the lowest activity for styrene oxidation with a
conversion of 16.38% and a selectivity of 32.63%. 1 displays
1
K [P W O ]·19H O was not added in the mixture to prepare
6
2
18 62
2
the TMMC compound of compound 3, and finally after the
autoclave was cooled to room temperature and blue solid
crystals of 8 were obtained. Unfortunately, these crystals of 8
were not suitable for single crystal analysis. Then we used these
crystals of 8 as the catalyst for styrene epoxidation. From the
comparison of the catalytic properties of these crystals of 8, the
the best catalytic activity with the conversion and selectivity of
9
3.75% and 84.28%. Compounds 2, 3, 4, and M5 also show
better catalytic conversions of 85.05, 92.54, 91.33, 91.96% and
selectivities of 65.53, 83.98, 70.00, and 76.15%, respectively.
Compared with the catalytic result of K [P W O ]·19H O,
all the compounds of copper in this article were excellent
catalysts for the styrene selective oxidation.
6
2
18 62
2
10b
mixture of the crystals of 8 and K [P W O ]·19H O, and
6
2
18 62
2
compound 3 (Table 4), we can conclude that compound 8 is
Although compound 1 and 1a are isostructural and
isomorphous, the catalytic activities of the two have a
significant difference, which is mainly attributed to the
distinction of the transition metals. It is still elusive why
these compounds of copper are good catalysts. Very recently,
we synthesized two compounds based on {P W } and copper
Table 4. Comparison of Compound 8, Mixture of 8 and
a
K P W18 and Compound 3
6 2
product selectivity (%)
2
18
styrene
TMCs [Cu(phen) ][Cu(phen)(H O) ][Cu(phen) (H O)]-
2
2
3
2
2
catalysts
(0.4 mg)
conversion (%)
So
Bza
Others
[
[
(
P W O ]·8H O (6) (phen = 1,10-phenanthroline) and
2 18 62 2
8
61.2
67.4
47.4
57.8
43.3
37.1
9.3
5.1
Cu(2,2′-bpy)(H O) ] [Cu(2,2′-bpy) ][P W O ]·3.5H O
2
2
2
2
2
18 62
2
1
0b
8 (0.4 mg) + K P W
6 2 18
7).
Compound 1 of the five compounds of copper is
(
1.6 mg)
similar to the two reported compounds, but the catalytic
performance of compound 1 is significantly higher than those
of compounds 6−7. The first difference between compound 1
and compounds 6−7 is that the copper TMCs in compound 1
and the two reported compounds is different. The second and
the most important difference between 1 and compounds 6−7
is that compound 1 is a 1-D extended structure, but the two
are discrete. It should be noted that all the compounds here are
compound 3
92.54
82.98
11.25
5.77
a
So: styrene oxide, Bza: benzaldehyde, others: including benzoic acid,
phenylacetaldehyde. K P W K [P W O ]·19H O.
6
2
18
6
2
18 62
2
very important for the epoxidation of styrene, and the final
product of compound 3 is also very important for the catalytic
process. The simple mixture of 8 and K [P W O62]·19H O
only slightly increased the conversion, but compound 3
significantly increased the conversion of styrene. The
comparison of these catalytic results further verified that the
structure of the multicomponent catalyst significantly
6 2 18 2
1
-D extended structures. Is the 1-D extended structure the
main reason for the high performances of compounds 1−4 and
M5? We think we still need more different catalysts and
catalytic results to demonstrate it.
32
influenced their catalytic properties.
3
was chosen to investigate its stability and recyclability, for
the amount of 3 is sufficient (Table 3). The experimental
conditions were the same, except that the dose of compound 3
was increased to 10 mg. With the dose increased, the
conversion increased to 95.93%, and the selectivity was also
higher. The styrene conversion is reduced from 95.93% to
CONCLUSIONS
■
Seven new compounds of Wells-Dawson POMs were
synthesized and characterized. All the compounds had a 1-D
chain structure. Compounds 1 and 1a are isomorphous and
isostructural with each other, and both exhibit a 1-D chain
9
4.86% after three cycles (Table 3), showing the good
I
DOI: 10.1021/acs.inorgchem.8b01705
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
structure. It is well-known that both Cu and Zn are amphoteric
cations, which are, we think, the reason why compounds 1 and
G.; Gouzerh, G.; Izzet, G. Functionalization and post-functionaliza-
tion: a step towards polyoxometalate-based materials. Chem. Soc. Rev.
2
012, 41, 7605. (f) Wang, S. S.; Yang, G. Y. Recent Advances in
Polyoxometalate-Catalyzed Reactions. Chem. Rev. 2015, 115, 4893−
962. (g) Clemente-Juan, J. M.; Coronado, E.; Gaita-Arino, A.
1
a are isomorphous and isostructural. Compound 2 is based
on a tetracopper TMMC, while compound 3 is based on a
bicopper TMMC. Compound 4 is the first compound that is
based on POM and hexacopper TMMC of 2,2′-bpy and
hydroxyls. Compound 5a is the first compound that contains
4
̃
Magnetic polyoxometalates: from molecular magnetism to molecular
spintronics and quantum computing. Chem. Soc. Rev. 2012, 41, 7464.
(h) Du, D. Y.; Qin, J. S.; Li, S. L.; Su, Z. M.; Lan, Y. Q. Recent
Cu···π interactions. Compound 5b is formed by {P W } and
2
18
advances in porous polyoxometalate-based metal-organic framework
materials. Chem. Soc. Rev. 2014, 43, 4615.
2+
[
Cu (2,2′-bpy) (hnic)] . We not only present several novel
2
2
compounds with unprecedented structures, we but also studied
the catalytic properties of these novel compounds, and all of
them exhibit high catalytic performances for styrene epox-
idation.
(2) (a) Hill, C. L. Introduction: Polyoxometalates Multicomponent
Molecular Vehicles To Probe Fundamental Issues and Practical
Problems. Chem. Rev. 1998, 98, 1. (b) Hagrman, P. J.; Hagrman, D.;
Zubieta, J. Organic-inorganic hybrid materials: From “simple”
coordination polymers to organodiamine-templated molybdenum
oxides. Angew. Chem., Int. Ed. 1999, 38, 2638. (c) Miras, H. N.;
Yan, J.; Long, D. L.; Cronin, L. Engineering polyoxometalates with
emergent properties. Chem. Soc. Rev. 2012, 41, 7403. (d) Du, D. Y.;
Yan, L. K.; Su, Z. M.; Li, S. L.; Lan, Y. Q.; Wang, E. B. Chiral
polyoxometalate-based materials: From design syntheses to functional
applications. Coord. Chem. Rev. 2013, 257, 702. (e) Miras, H. N.; Vila-
Nadal, L.; Cronin, L. Polyoxometalate based open-frameworks
ASSOCIATED CONTENT
Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.inorg-
chem.8b01705.
■
*
S
The coordination environments of Cu(1) and Cu(2) in
compound 5b. IR spectra of compounds. XRD patterns.
UV-vis spectra. Cyclic voltammograms. UV-vis absorp-
tion spectra of the RhB solutions degraded with
(POM-OFs). Chem. Soc. Rev. 2014, 43, 5679. (f) Zubieta, J.,
Applications of hydrothermal synthesis to solid state coordination
chemistry. In Comprehensive Coordination Chemistry II; McCleverty, J.
A.; Meyer, T. J., Eds.; Elsevier Science, 2003; p 697. (g) Zhao, J. W.;
Li, Y. Z.; Chen, L. J.; Yang, G. Y. Research progress on
polyoxometalate-based transition-metal-rare-earth heterometallic de-
rived materials: synthetic strategies, structural overview and functional
applications. Chem. Commun. 2016, 52, 4418. (h) Monakhov, K. Y.;
compounds. Changes in the C /C0 plots of RhB
t
solutions versus reaction time. The reproducibility of
compound 1 for photodegradation of RhB for three
cycles. X-ray powder diffraction patterns and IR spectra
of compound 1 after each cycle of the photodegradation
of RhB. X-ray powder diffraction patterns and IR spectra
of compound 3 after three cycles of epoxidation of
styrene to styrene oxide (PDF)
Bensch, W.; Kogerler, P. Semimetal-functionalised polyoxovanadates.
̈
Chem. Soc. Rev. 2015, 44, 8443. (i) Jin, L.; Zhu, Z. K.; Wu, Y. L.; Li, X.
X.; Qi, Y. j.; Zheng, S. T. Record High-Nuclearity Polyoxoniobates:
Discrete Nanoclusters {Nb-114}, {Nb-81}, and {Nb-52}, and
Extended Frameworks Based on {Cu3Nb78} and {Cu4Nb78}.
Angew. Chem., Int. Ed. 2017, 56, 16288. (j) Li, Z.; Li, X. X.; Yang,
Y.; Cai, Z. W.; Zheng, S. T. Four-Shell Polyoxometalates Featuring
High-Nuclearity Ln(26) Clusters: Structural Transformations of
Nanoclusters into Frameworks Triggered by Transition-Metal Ions.
Angew. Chem., Int. Ed. 2017, 56, 2664. (k) Song, Y. F.; Tsunashima, R.
Recent advances on polyoxometalate-based molecular and composite
materials. Chem. Soc. Rev. 2012, 41, 7384.
Accession Codes
CCDC 1587946−1587952 contain the supplementary crys-
tallographic data for this paper. These data can be obtained
free of charge via www.ccdc.cam.ac.uk/data_request/cif, or by
emailing data_request@ccdc.cam.ac.uk, or by contacting The
Cambridge Crystallographic Data Centre, 12 Union Road,
Cambridge CB2 1EZ, UK; fax: +44 1223 336033.
(3) (a) Panish, R. A.; Chintala, S. R.; Fox, J. M. A Mixed-Ligand
Chiral Rhodium(II) Catalyst Enables the Enantioselective Total
Synthesis of PiperarborenineB. Angew. Chem., Int. Ed. 2016, 55, 4983.
AUTHOR INFORMATION
■
Corresponding Author
(b) Domínguez-Martín, A.; Brandi-Blanco, M. D.; Matilla-Hernan
A.; Bakkali, H. E.; Nurchi, V. M.; Gonzalez-Perez, J. M.; Castineiras,
A.; Niclos-Gutierrez, J. Unravelling the versatile metal binding modes
́
dez,
*E-mail: cuixb@mail.jlu.edu.cn.
́
́
̃
́
́
ORCID
of adenine: Looking at the molecular recognition patterns of deaza-
and aza-adenines in mixed ligand metal complexes. Coord. Chem. Rev.
013, 257, 2814. (c) Szacilowski, K.; Macyk, W.; Stochel, G.; Stasicka,
Xiao Zhang: 0000-0002-3036-7001
Xiao-Bing Cui: 0000-0002-5254-7935
2
Notes
Z.; Sostero, S.; Traverso, O. Ligand and medium controlled
photochemistry of iron and ruthenium mixed-ligand complexes:
prospecting for versatile systems. Coord. Chem. Rev. 2000, 208, 277.
The authors declare no competing financial interest.
(
d) Deplano, P.; Pilia, L.; Espa, D.; Mercuri, M. L.; Serpe, A. Square-
ACKNOWLEDGMENTS
This manuscript was supported by National Science
Foundation of China (No. 21003056).
■
planar d(8) metal mixed-ligand dithiolene complexes as second order
nonlinear optical chromophores: Structure/property relationship.
Coord. Chem. Rev. 2010, 254, 1434.
(
4) Zhao, D. C.; Hu, Y. Y.; Ding, H.; Guo, H. Y.; Cui, X. B.; Zhang,
REFERENCES
X.; Huo, Q. S.; Xu, J. Q. Polyoxometalate-based organic-inorganic
hybrid compounds containing transition metal mixed-organic-ligand
complexes of N-containing and pyridinecarboxylate ligands. Dalton
Trans. 2015, 44, 8971.
(5) (a) Yuan, L.; Qin, C.; Wang, X. L.; Wang, E. B.; Chang, S. Two
Extended Organic-inorganic Assemblies Based on Polyoxometalates
and Copper Coordination Polymers with Mixed 4,4 ′-Bipyridine and
2,2 ′-Bipyridine Ligands. Eur. J. Inorg. Chem. 2008, 2008, 4936.
(b) Lisnard, L.; Dolbecq, A.; Mialane, P.; Marrot, J.; Codjovi, E.;
■
(
1) (a) Pope, M. T. Heteropoly and Isopoly Oxometalates; Springer:
Berlin, 1983. (b) Pope, M. T.; Mu
̈
ller, A. Polyoxometalates: From
Platonic Solids to Anti-Retro Viral Activity; Kluwer: Dordrecht: The
Netherlands, 1994. (c) Long, D. L.; Tsunashima, R.; Cronin, L.
Polyoxometalates: Building Blocks for Functional Nanoscale Systems.
Angew. Chem., Int. Ed. 2010, 49, 1736. (d) Dolbecq, A.; Dumas, E.;
Mayer, C. R.; Mialane, P. Hybrid Organic-Inorganic Polyoxometalate
Compounds: From Structural Diversity to Applications. Chem. Rev.
2010, 110, 6009. (e) Proust, A.; Matt, B.; Villanneau, R.; Guillemot,
Sec
́
heresse, F. Molecular and multidimensional polyoxotungstates
J
DOI: 10.1021/acs.inorgchem.8b01705
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
functionalized by {Cu(bpy)}(2+) groups. Dalton Trans. 2005, 24,
(9) Santini, C.; Pellei, M.; Gandin, V.; Porchia, M.; Tisato, F.;
Marzano, C. Advances in Copper Complexes as Anticancer Agents.
Chem. Rev. 2014, 114, 815.
(10) (a) Smith, T. M.; Perkins, K.; Symester, D.; Freund, S. R.;
Vargas, J.; Spinu, L.; Zubieta, J. Solid state coordination chemistry of
oxomolybdenum-organodiphosphonate materials: consequences of
introducing xylyldiphosphonate components. CrystEngComm 2014,
3
913. (c) Jin, H.; Qi, Y. F.; Wang, E. B.; Li, Y. G.; Qin, C.; Wang, X.
L.; Chang, S. A novel copper(I) halide framework templated by
organic-inorganic hybrid polyoxometalate chains formed in situ: A
new route for the design and synthesis of porous frameworks. Eur. J.
Inorg. Chem. 2006, 2006, 4541. (d) Jin, H.; Qi, Y. F.; Wang, E. B.; Li,
Y. G.; Wang, X. L.; Qin, C.; Chang, S. Molecular and multidimen-
sional organic-inorganic hybrids based on polyoxometalates and
copper coordination polymer with mixed 4,4 ′-bipyridine and 2,2
16, 191. (b) Lu, Y.; Xiao, L. N.; Hao, X. R.; Cui, X. B.; Xu, J. Q. A
̈
series of organic-inorganic hybrid compounds formed by
[P2W18O62](6-) and several types of transition metal complexes.
Dalton Trans. 2017, 46, 14393.
′
-bipyridine ligands. Cryst. Growth Des. 2006, 6, 2693. (e) Fu, H.; Li,
Y. G.; Lu, Y.; Chen, W. L.; Wu, Q.; Meng, J. X.; Wang, X. L.; Zhang,
Z. M.; Wang, E. B. Polyoxometalate-Based Metal-Organic Frame-
works Assembled under the Ionothermal Conditions. Cryst. Growth
Des. 2011, 11, 458. (f) Wang, L. M.; Wang, Y.; Fan, Y.; Xiao, L. N.;
Hu, Y. Y.; Gao, Z. M.; Zheng, D. F.; Cui, X. B.; Xu, J. Q. The design,
syntheses and characterization of a series of hybrids based on
polyoxometalates and metal complexes. CrystEngComm 2014, 16, 430.
(
11) Contant, R. In Inorganic Syntheses; John Wiley: New York,
990; Vol. 27, p 104.
12) Sheldrick, G. M. A short history of SHELX. Acta Crystallogr.,
Sect. A: Found. Crystallogr. 2008, 64, 112.
13) Brown, I. D. In Structure and Bonding in Crystals; O’Keefe, M.,
Navrotsky, A., Eds.; Academic Press: New York, 1981; Vol. 2, pp 1−
0.
14) (a) Shi, S. Y.; Zou, Y. C.; Cui, X. B.; Xu, J. N.; Wang, Y.; Wang,
1
(
(
3
(
(
g) Guo, H. Y.; Li, Z. F.; Zhang, X.; Fu, L. W.; Hu, Y. Y.; Guo, L. L.;
Cui, X. B.; Huo, Q. S.; Xu, J. Q. New self-assembly hybrid compounds
based on arsenic-vanadium clusters and transition metal mixed-
organic-ligand complexes. CrystEngComm 2016, 18, 566.
G. W.; Yang, G. D.; Xu, J. Q.; Wang, T. G.; Gao, Z. M. 0D and 1D
dimensional structures based on the combination of polyoxometa-
lates, transition metal coordination complexes and organic amines.
CrystEngComm 2010, 12, 2122. (b) Xiao, L. N.; Wang, L. M.; Shan, X.
N.; Guo, H. Y.; Fu, L. W.; Hu, Y. Y.; Cui, X. B.; Li, K. C.; Xu, J. Q.
Secondary organic moiety templated organic-inorganic polyoxometa-
late-based frameworks. CrystEngComm 2015, 17, 1336.
(
6) (a) Reinoso, S.; Vitoria, P.; Lezama, L.; Luque, A.; Gutierrez-
́
Zorrilla, J. M. A novel organic-inorganic hybrid based on a dinuclear
copper complex supported on a keggin polyoxometalate. Inorg. Chem.
2003, 42, 3709. (b) Reinoso, S.; Vitoria, P.; Gutierrez-Zorrilla, J. M.;
́
Lezama, L.; San Felices, L. S.; Beitia, J. I. Inorganic-metalorganic
hybrids based on copper(II)-monosubstituted Keggin polyanions and
dinuclear copper(II)-oxalate complexes. Synthesis, X-ray structural
characterization, and magnetic properties. Inorg. Chem. 2005, 44,
(
15) Zhang, X. M. Hydro(solvo)thermal in situ ligand syntheses.
Coord. Chem. Rev. 2005, 249, 1201.
16) Hou, J. J.; Xu, X.; Jiang, N.; Wu, Y. Q.; Zhang, X. M. Selective
(
adsorption in two porous triazolate-oxalate-bridged antiferromagnetic
metal-azolate frameworks obtained via in situ decarboxylation of 3-
amino-1,2,4-triazole-5-carboxylic acid. J. Solid State Chem. 2015, 223,
9
731. (c) Reinoso, S.; Vitoria, P.; Felices, L.; Lezama, L.; Gutierrez-
́
Zorrilla, J. M. Analysis of weak interactions in the crystal packing of
inorganic metalorganic hybrids based on keggin polyoxometalates and
dinuclear copper(II)-acetate complexes. Inorg. Chem. 2006, 45, 108.
7
(
3.
17) Yu, K.; Yu, Y.; Jiang, B. D.; Zhou, B. B. Assembly of organic−
(
d) Zhao, X. Y.; Liang, D. D.; Liu, S. X.; Sun, C. Y.; Cao, R. G.; Gao,
inorganic hybrid supramolecular materials based on {P2W18O62}62
C. Y.; Ren, Y. H.; Su, Z. M. Two Dawson-templated three-
dimensional metal-organic frameworks based on oxalate-bridged
binuclear cobalt(II)/nickel(II) SBUs and bpy linkers. Inorg. Chem.
anion and Cu(II)/Mn(II) complex. CrystEngComm 2013, 15, 5156.
(18) Cao, R. G.; Liu, S. X.; Xie, L. H.; Pan, Y. B.; Cao, J. F.; Ren, Y.
H.; Xu, L. Organic-inorganic hybrids constructed of anderson-type
polyoxoanions and oxalato-bridged dinuclear copper complexes. Inorg.
Chem. 2007, 46, 3541.
2008, 47, 7133. (e) Yang, Y.; Liu, S. X.; Li, C. C.; Li, S. J.; Ren, G. J.;
Wei, F.; Tang, Q. A metal-organic framework based on Wells-Dawson
polyoxometalates [As2W18O62](6-) template. Inorg. Chem. Commun.
(19) Xiao, L. N.; Zhao, C. X.; Shi, X. M.; Zhang, H.; Wu, W.; Cui, X.
2012, 17, 54. (f) Han, Q. X.; Ma, P. T.; Zhao, J. W.; Wang, J. P.; Niu,
B. Three new compounds based on similar molybdenum-vanadium
clusters and several types of copper complexes. CrystEngComm 2018,
J. Y. A novel 1D tungstoarsenate with mixed organic ligands
assembled by hexa-Cu sandwiched Keggin units and dinuclear
copper-oxalate complexes. Inorg. Chem. Commun. 2011, 14, 767.
2
(
0, 969.
20) Guo, H. Y.; Zhang, X.; Cui, X. B.; Huo, Q. S.; Xu, J. Q.
(
7) (a) Lu, C. Z.; Wu, C. D.; Zhuang, H. H.; Huang, J. S. Three
Structural influences of arsenic-vanadium clusters and transition metal
complexes on final structures of arsenic-vanadium-based hybrids.
CrystEngComm 2016, 18, 5130.
polymeric frameworks constructed from discrete molybdenum oxide
anions and 4,4 ′-bpy-bridged linear polymeric copper cations. Chem.
Mater. 2002, 14, 2649. (b) Zhang, S. W.; Li, Y. X.; Liu, Y.; Cao, R. G.;
Sun, C. Y.; Ji, H. M.; Liu, S. X. Synthesis and characterization of B-
type Anderson polyoxoanions supported copper complexes with
mixed ligands. J. Mol. Struct. 2009, 920, 284. (c) Wang, X. L.; Hu, H.
L.; Tian, A. X. Cryst. Growth Des. 2010, 10, 4786. (d) Wang, X. L.;
Gao, Q.; Liu, G. C.; Lin, H. Y.; Tian, A. X.; Li, J. Self-assembly of a 2D
helical coordination polymer from Keggin-type polyoxoanion and
metal-organic fragment by in situ ligand transformation. Inorg. Chem.
Commun. 2011, 14, 745. (e) Qu, Z. K.; Yu, K.; Zhao, Z. F.; Su, Z. H.;
Sha, J. Q.; Wang, C. M.; Zhou, B. B. An organic-inorganic hybrid
semiconductor material based on Lindqvist polyoxomolybdate and a
tetra-nuclear copper complex containing two different ligands. Dalton
Trans. 2014, 43, 6744.
(21) (a) Toofan, M.; Boushehri, A.; Mazhar-Ul-Haque, M. Crystal
and molecular structure of di-μ-hydroxo-bis[bipyridylcopper(II)]
diperchlorate. J. Chem. Soc., Dalton Trans. 1976, 217. (b) Zheng, Y.
Q.; Lin, J. L. Crystal structures of [Cu-2(bpy)(2)(H2O)(OH)
(
2)(SO4)] center dot 4H(2)O and [Cu(bpy)(H2O)(2)]SO4 with
bpy = 2,2 ′-bipyridine. Z. Anorg. Allg. Chem. 2003, 629, 1622.
c) Hammond, R. P.; Cavaluzzi, M.; Haushalter, R. C.; Zubieta, J. A.
(
Investigations of the copper bromide-2,2 ′-dipyridyl system: Hydro-
thermal synthesis and structural characterization of molecular
Cu3Br4(C10H8N2)(2), one-dimensional CuBr2(C10H8N2), and
two-dimensional [Cu-2(OH)(2)(C10H8N2)(2)][Cu4Br6]. Inorg.
Chem. 1999, 38, 1288. (d) Doyle, R. P.; Julve, M.; Lloret, F.;
Nieuwenhuyzen, M.; Kruger, P. E. Hydrogen-bond tuning of
ferromagnetic interactions: synthesis, structure and magnetic proper-
ties of polynuclear copper(II) complexes incorporating p-block oxo-
anions. Dalton Trans. 2006, 2081. (e) Sletten, J.; Sorensen, A.; Julve,
M.; Journaux, Y. A tetranuclear hydroxo-bridged copper(II) cluster of
the cubane type. Preparation and structural and magnetic character-
ization of tetrakis[(2,2′-bipyridyl)hydroxocopper(II)] hexafluoro-
phosphate. Inorg. Chem. 1990, 29, 5054. (f) Castro, I.; Faus, J.;
Julve, M.; Bois, C.; Real, J. A.; Lloret, F. Synthesis, crystal structure
(
8) (a) Hu, Y. Y.; Xiao-Zhang, X.; Zhao, D. C.; Guo, H. Y.; Fu, L.
W.; Guo, L. L.; Cui, X. B.; Huo, Q. S.; Xu, J. Q. Tuning the structures
based on polyoxometalates from 1-D to 2-D by using different
secondary organic ligands. Dalton Trans. 2015, 44, 14830. (b) Hu, Y.
Y.; Zhang, T.-T.; Cui, X. B.; Huo, Q. S.; Xu, J. Q.; Zhang, X.; Zhao,
D.-C. New organic-inorganic hybrid compounds constructed from
polyoxometalates and transition metal mixed-organic-ligand com-
plexes. Dalton Trans. 2016, 45, 2562.
K
DOI: 10.1021/acs.inorgchem.8b01705
Inorg. Chem. XXXX, XXX, XXX−XXX

Inorganic Chemistry
Article
and magnetic properties of di-μ-hydroxo-bis[(2,2′-bipyridine)-
(27) Hagrman, P. J.; Zubieta, J. Solid-state coordination chemistry:
Influences of {M(terpyridyl)} (M = Ni(III), Cu(II), Ni(II)} subunits
on molybdenum oxide structures. Inorg. Chem. 2000, 39, 3252.
(28) (a) Zhang, J.; Bhatt, A. I.; Bond, A. M.; Wedd, A. G.; Scott, J.
L.; Strauss, C. R. Voltammetric studies of polyoxometalate micro-
particles in contact with the reactive distillable ionic liquid
DIMCARB. Electrochem. Commun. 2005, 7, 1283. (b) Bernardini,
G.; Wedd, A. G.; Bond, A. M. Reactivity of one-, two-, three- and four-
electron reduced forms of alpha-[P2W18O62](6-) generated by
controlled potential electrolysis in water. Inorg. Chim. Acta 2011, 374,
(
trifluoromethanesulfonato-O)-copper(II)]. J. Chem. Soc., Dalton
Trans. 1992, 47. (g) van Albada, G. A.; Mutikainen, I.; Roubeau,
O.; Turpeinen, U.; Reedijk, J. , Ferromagnetic trinuclear carbonato-
bridged and tetranuclear hydroxo-bridged Cu(II) compounds with 4,4
′
-dimethyl-2,2 ′-bipyridine as ligand. X-ray structure, spectroscopy
and magnetism. Inorg. Chim. Acta 2002, 331, 208. (h) Haddad, M. S.;
Wilson, S. R.; Hodgson, D. J.; Hendrickson, D. N. Magnetic exchange
interactions in binuclear copper(II) complexes with only a single
hydroxo bridge: the x-ray structure of.mu.-hydroxo-tetrakis(2,2′-
bipyridine)dicopper(II) perchlorate. J. Am. Chem. Soc. 1981, 103,
3
(
27.
29) (a) Wang, X. L.; Zhao, D.; Tian, A. X.; Ying, J. Three 3D silver-
3
84. (i) Li, X.; Cheng, S. Y.; Lin, J. L.; Li, Z. F.; Zheng, Y. Q. Di-,
bis(triazole) metal-organic frameworks stabilized by high-connected
Wells-Dawson polyoxometallates. Dalton Trans. 2014, 43, 5211.
Tetra-, Hexanuclear Hydroxy-Bridged Copper(II) Cluster Com-
pounds: Syntheses, Structures and Properties (vol 8, pg 2860,
(
b) Li, X. R.; Xue, H. G.; Pang, H. Facile synthesis and shape
2
008). Cryst. Growth Des. 2008, 8, 2853. (j) Zheng, Y. Q.; Cheng, D.
evolution of well-defined phosphotungstic acid potassium nanocryst-
Y.; Liu, B. B.; Huang, W. X. , New Cu(II) complexes based on the
hydroxo-bridged dinuclear [Cu(OH)(2)Cu] units: step-like di- and
trimerizations of [Cu(OH)(2)Cu] units. Dalton Trans. 2011, 40, 277.
als as a highly efficient visible-light-driven photocatalyst. Nanoscale
2
(
017, 9, 216.
30) (a) Bregante, D. T.; Flaherty, D. W. Periodic Trends in Olefin
(
k) Diwan, K.; Singh, B.; Singh, S. K.; Drew, M. G. B.; Singh, N. ,
Epoxidation over Group IV and V Framework-Substituted Zeolite
Catalysts: A Kinetic and Spectroscopic Study. J. Am. Chem. Soc. 2017,
139, 6888. (b) Theodorou, A.; Kokotos, C. G. Green Organocatalytic
Synthesis of Indolines and Pyrrolidines from Alkenes. Adv. Synth.
Catal. 2017, 359, 1577. (c) Talsi, E. P.; Rybalova, T. V.; Bryliakov, K.
P. Ti-salalen mediated asymmetric epoxidation of olefins with H2O2:
Effect of ligand on the catalytic performance, and insight into the
oxidation mechanism. J. Mol. Catal. A: Chem. 2016, 421, 131.
(31) (a) Mizuno, N.; Misono, M. Heterogeneous Catalysis. Chem.
Rev. 1998, 98, 199. (b) Song, X. J.; Zhu, W. C.; Li, K. G.; Wang, J.;
Niu, H. L.; Gao, H. C.; Gao, W. X.; Zhang, W. X.; Yu, J. H.; Jia, M. J.
Epoxidation of olefins with oxygen/isobutyraldehyde over transition-
metal-substituted phosphomolybdic acid on SBA-15. Catal. Today
Facile in situ copper(II) mediated C-S bond activation transforming
dithiocarbimate to carbamate and thiocarbamate generating Cu(II)
and Cu(I) complexes. Dalton Trans. 2012, 41, 367.
(
22) (a) Xiao, L. N.; Song, X. J.; Fu, L. W.; Hu, Y. Y.; Guo, H. Y.;
Cui, X. B.; Jia, M. J.; Zhang, X.; Xu, J. N.; Xu, J. Q. Two novel
structures based on an organic ligand with two different coordination
modes. RSC Adv. 2015, 5, 46790. (b) Kang, H. C.; Hanson, A. W.;
Eaton, B.; Boekelheide, V. [26](1,2,4,5)Cyclophane (deltaphane) and
related compounds. Simultaneous.pi.-electron interaction among
three benzene rings. J. Am. Chem. Soc. 1985, 107, 1979. (c) Xu, W.;
Puddephatt, R. J.; Muir, K. W.; Torabi, A. A. Silver Ion Inclusion by
Calix[4]arene Ethers. Organometallics 1994, 13, 3054. (d) Wang, Q.
M.; Mak, T. C. W. A novel organometallic columnar complex
containing endohedral silver(I)-ethynediyl binding and exterior silver
2
016, 259, 59. (c) Song, X. J.; Zhu, W. C.; Yan, Y.; Gao, H. C.; Gao,
W. X.; Zhang, W. X.; Jia, M. J. Triphenylamine-based porous organic
polymers: Synthesis and application for supporting phosphomolyb-
date to fabricate efficient olefin oxidation catalysts. Microporous
Mesoporous Mater. 2017, 242, 9.
(
I)-aromatic interaction. Chem. Commun. 2002, 2682. (e) Schmidbaur,
H.; Bublak, W.; Huber, B.; Reber, G.; Muller, G. Coordination-
̈
Polymeric Paracyclophane Complexes of Copper and Silver. Angew.
Chem., Int. Ed. Engl. 1986, 25, 1089.
(32) Gao, H. C.; Yan, Y.; Xu, X. H.; Yu, J. H.; Niu, H. L.; Gao, W.
X.; Zhang, W. X.; Jia, M. J. Catalytic epoxidation of olefin over
supramolecular compounds of molybdenum oxide clusters and a
copper complex. Chin. J. Cata. 2015, 36, 1811.
(
23) (a) Xu, F. B.; Li, Q. S.; Zhang, Z. Z.; Wu, L.-Z.; Leng, X.-Z.; Li,
Z.-C.; Zeng, X.-S.; Chow, Y. L. Formation of group 11 metal(I)-arene
complexes: Bonding mode and molecule-responsive spectral varia-
tions. Organometallics 2003, 22, 633. (b) Li, Q. S.; Wan, C. Q.; Zhang,
Z. Z.; Zou, R.-Y.; Xu, F.-B.; Song, H.-B.; Wan, X.-J. Gold(I) eta(2)-
arene complexes. Inorg. Chem. 2006, 45, 1888. (c) Herrero-Gom
E.; Echavarren, A. M.; Nieto-Oberhuber, C.; Lopez, S.; Benet-
Buchholz, A. M. Cationic eta(1)/eta(2)-gold(I) complexes of simple
arenes. Angew. Chem., Int. Ed. 2006, 45, 5455. (d) Perez-Galan, P.;
Delpont, N.; Herrero-Gomez, E.; Maseras, F.; Echavarren, A. M.
́
ez,
́
́
́
́
Metal-Arene Interactions in Dialkylbiarylphosphane Complexes of
Copper, Silver, and Gold. Chem. - Eur. J. 2010, 16, 5324.
(
24) Zhang, S. L.; Liu, L.; Fu, Y.; Guo, Q. X. Cation-pi interactions
of Cu+. J. Mol. Struct.: THEOCHEM 2005, 757, 37.
25) (a) Solomon, E. I.; Chen, P.; Metz, M.; Lee, S. K.; Palmer, A. E.
(
Oxygen binding, activation, and reduction to water by copper
proteins. Angew. Chem., Int. Ed. 2001, 40, 4570. (b) Rorabacher, D. B.
Electron transfer by copper centers. Chem. Rev. 2004, 104, 651.
(
26) (a) Ley, S. V.; Thomas, A. W. Modern synthetic methods for
copper-mediated C(aryl)-O, C(aryl)N, and C(aryl)-S bond for-
mation. Angew. Chem., Int. Ed. 2003, 42, 5400. (b) Ma, D.; Zhang, Y.;
Yao, J.; Wu, S.; Tao, F. Accelerating Effect Induced by the Structure
of α-Amino Acid in the Copper-Catalyzed Coupling Reaction of Aryl
Halides with α-Amino Acids. Synthesis of Benzolactam-V8. J. Am.
Chem. Soc. 1998, 120, 12459. (c) Zhu, W.; Ma, D. Synthesis of aryl
azides and vinyl azides via proline-promoted CuI-catalyzed coupling
reactions. Chem. Commun. 2004, 888. (d) Zhu, W.; Ma, D. W.
Synthesis of aryl sulfones via L-proline-promoted CuI-catalyzed
coupling reaction of aryl halides with sulfinic acid salts. J. Org. Chem.
2005, 70, 2696.
L
DOI: 10.1021/acs.inorgchem.8b01705
Inorg. Chem. XXXX, XXX, XXX−XXX