New topological 3D copper(ii) coordination networks: Catechol oxidation catalysis and solvent adsorption via porous properties

Article abstract of DOI:10.1039/c5ce00087d

The reaction of CuX₂ (X^- = ClO₄^- and BF₄^-) with a new 1,3,5-tris(isonicotinoyloxymethyl)benzene (L) ligand gives rise to 3D coordination networks, [Cu₃L₄(CH₃

Full text of DOI:10.1039/c5ce00087d

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New topological 3D copperIJII) coordination
networks: catechol oxidation catalysis and solvent
Cite this: DOI: 10.1039/c5ce00087d
adsorption via porous properties†
*
Doeon Kim, Byung Joo Kim, Tae Hwan Noh and Ok-Sang Jung
The reaction of CuX2 (X− = ClO4 and BF4−) with a new 1,3,5-trisIJisonicotinoyloxymethyl)benzene (L) ligand
−
gives rise to 3D coordination networks, ijCu3L4IJCH3CN)6]IJX)6, with a new topology of the Schlafli point
¨
symbol {4Ĵ82}4{42Ĵ82Ĵ102}2{84Ĵ122}. ijCu3L4IJCH3CN)6]IJClO4)6 and ijCu3L4IJCH3CN)6]IJBF4)6 networks have useful
oval-shaped pores of 11.2 × 11.2 × 24.8 Å3 and 11.1 × 11.1 × 24.4 Å3 dimensions, respectively. These porous
coordination networks act as good heterogeneous catalysts, oxidizing the catechols in the order 3,5-di-
tert-butylcatechol (3,5-DBuCat) > 4-tert-butylcatechol (4-BuCat) > 4-chlorocatechol (4-ClCat). The cata-
lytic effect of ijCu3L4IJCH3CN)6]IJBF4)6 is slightly higher than that of ijCu3L4IJCH3CN)6]IJClO4)6. The pores of the
3D networks reversibly adsorb the solvents in the order chloroform > tetrahydrofuran > acetone.
Received 14th January 2015,
Accepted 16th February 2015
DOI: 10.1039/c5ce00087d
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M–M bonds, electrostatic interactions, hydrogen bonds, and
π⋯π interactions.11–14 Recently, with some of the tridentate
Introduction
One issue in the field of coordination networks is the design
and construction of a new porous topology, preferably with
task-specific functions1,2 such as gas storage, adsorption,
sensing, separation, catalysis, nonlinear optics, biomedical
imaging, and drug delivery.3–10 For the purposes of practical
applications such as these, rational construction of unusual
topological coordination polymers with desirable pores via
manipulation of interchangeable components has been
attempted. Porous coordination networks have been synthe-
sized by suitable combination of the coordination geometry
of metal ions, bonding mode and flexibility of multidentate
donors, counteranions, metal-to-ligand ratio, temperature,
and reaction solvents, while often versatile molecular skele-
tons are serendipitously constructed owing to the unexpected
emergence of weak interactions such as van der Waals forces,
pyridyl donor ligands, exciting molecular structures, including
a variety of coordination modes, have been produced. These
successes are owed to tridentate ligands' flexibility in poten-
tial bridging capacity, flexible bite angles, and conformational
non-rigidity.15–22 However, production of new topological skel-
etons via the reaction of simple metal ions with the C3-sym-
metric tridentate ligand has proved challenging. In this con-
text, we report the synthesis of new topological 3D copperIJII)
−
coordination networks from the reaction of CuX2 (X− = ClO4
−
and BF4 ) with a new C3-symmetric tectonic ligand, 1,3,5-tris-
IJisonicotinoyloxymethyl)benzene (L). We additionally report
the achievement of significant heterogeneous catalytic effects
on catechol oxidation and molecular adsorption via porous
structures as well as surface properties. Some copperIJII) com-
plexes are known to play important roles in oxidation cataly-
sis chemistry, the Irving–Williams order of divalent metal
ions, coordination geometry, biological functionalities, and
Jahn–Teller distortion.23 Notably, some copperIJII) complexes
containing nitrogen-donor ligands have been developed as
alcohol-oxidation catalysts.24–26
Department of Chemistry, Pusan National University, Pusan 609-735, Republic of
Korea. E-mail: oksjung@pusan.ac.kr; Fax: +82 51 516 7421; Tel: +82 51 510 2591
† Electronic supplementary information (ESI) available: X-ray crystal structures
of L, ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN, and ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN,
schematic representation showing the linkage of the subunits, UV/vis
spectra and the plot showing the oxidative catalytic yields of catechols using
ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN, a mixture of CuIJClO4)2 and L, and
only CuIJClO4)2 as catalysts, the plot showing the catalytic oxidation yield of
catechols using the copperIJII) complexes in a 2 : 1 [catalyst] : [catechol] ratio,
UV/vis spectra showing the oxidation of 3,5-DBuCat using CuCl2 and CuO,
IR spectra of ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN before and after
catechol oxidation catalysis of 3,5-DBuCat, TGA/DSC curves of the copperIJII)
complexes, 1H NMR spectra of the acetonitrile-desolvated species and
solvent-reincorporated samples. CCDC 1043333, 1043334, and 1043335 for L,
ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN, and ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN,
respectively. For ESI and crystallographic data in CIF or other electronic format
see DOI: 10.1039/c5ce00087d
Experimental
Materials and measurements
All chemicals including copperIJII) perchlorate and copperIJII)
tetrafluoroborate were purchased from Aldrich, and were
used without further purification. Elemental microanalyses
(C, H, N) were performed on crystalline samples at Pusan
Center, KBSI, using a Vario-EL III. Thermal analyses were car-
ried out under a dinitrogen atmosphere at a scan rate of
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10 °C min−1 using a Labsys TG-DSC 1600. Infrared spectra were
pellet, cm−1): 3585 (br), 1731 (s), 1619 (w), 1564 (w), 1504 (w),
1452 (w), 1423 (m), 1375 (w), 1330 (m), 1282(s), 1230 (w),
obtained on a Nicolet 380 FT-IR spectrophotometer with sam-
1
−
ples prepared as KBr pellets or Nujol. H (300 MHz) and 13C
1124 (s), 1083 (s), 1060 (s), 1031 (s, BF4 ), 858 (m), 763 (w),
(75 MHz) NMR spectra were recorded on a Varian Mercury
Plus 300. The absorption spectra were recorded on a UV-vis
spectrophotometer S-3150. Inductively coupled plasma
atomic emission spectroscopy (ICP-AES) was performed by
using a JY HORIVA spectrometer (ACTIVA) at Pusan Center,
KBSI.
700 (w), 520 (w).
Catalysis
3,5-Di-tert-butylcatechol (3,5-DBuCat), 4-tert-butylcatechol
(4-BuCat), and 4-chlorocatechol (4-ClCat) were employed as
oxidation catalysis substrates. Catalysis using the present
products was carried out relative to the simple salts, CuX2
Synthesis of 1,3,5-trisIJisonicotinoyloxymethyl)benzene (L)
(X− = Cl−, ClO4 , BF4 ) and CuO:27 each catalyst was treated
with the respective substrate in a 1 : 1 mole ratio in 20 mL of
chloroform at 40 °C under aerobic conditions. The cataly-
sis was monitored with reference to the increase in absor-
bance at 404, 388, and 396 nm for each oxidized species,
−
−
A chloroform solution of the mixture of triethylamine (5.1 mL,
35 mmol) and pyridine (0.2 mL, 2.5 mmol) was slowly
added into a stirred mixture of isonicotinoyl chloride hydro-
chloride (2.93 g, 16.5 mmol) and 1,3,5-benzenetrimethanol
(0.84 g, 5.0 mmol) in chloroform (180 mL) at 60 °C. The reac-
tion mixture was refluxed for 12 h. The resulting solution was
washed with water several times. The chloroform layer was
dried over anhydrous magnesium sulfate and filtered. Evapo-
ration of chloroform gave a white solid product in 91% yield
(2.20 g). The white crude product was recrystallized from a
mixture of acetone and water, and was obtained as a
dihydrate crystalline product suitable for single crystal X-ray
diffraction measurement. Mp 73 °C. Found: C, 62.49; H, 4.84;
N, 8.11. Calc. for C27H21N3O6Ĵ2H2O: C, 62.42; H, 4.85; N,
8.09%. IR (KBr pellet, cm−1): 3430 (br), 1724 (s), 1612 (w),
1596 (w), 1562 (w), 1450 (w), 1407 (m), 1369 (w), 1326 (m),
1278 (s), 1216 (s), 1168 (w), 1126 (m), 1116 (m), 1064 (w), 993
(w), 871 (w), 850 (w), 755 (m), 725 (w), 705 (m), 682 (w), 667
(w). δH (300 MHz, CDCl3, ppm): 8.79 (d, J = 4.5 Hz, 6H), 7.86
(d, J = 4.5 Hz, 6H), 7.53 (s, 3H), 5.44 (s, 6H). δC NMR (75
MHz, CDCl3, ppm): 164.63, 150.43, 136.79, 136.43, 128.06,
122.67, 66.58.
3,5-DBuBQ, 4-BuBQ, and 4-ClBQ (BQ
respectively, as a function of time.28
= benzoquinone),
Crystal structure determination
All of the X-ray data were collected on a Bruker SMART auto-
matic diffractometer with graphite-monochromated Mo Kα
radiation (λ = 0.71073 Å) and a CCD detector at −25 °C.
Thirty-six frames of two-dimensional diffraction images were
collected and processed to obtain the cell parameters and ori-
entation matrix. The data were corrected for Lorentz and
polarization effects. Absorption effects were corrected by the
multi-scan method (SADABS).29 The structures were solved by
the direct method (SHELXS 97) and refined by full-matrix
least squares techniques (SHELXL 97).30 The non-hydrogen
atoms were refined anisotropically, and the hydrogen atoms
were placed in calculated positions and refined using a riding
model. Structure refinement of all of the compounds for the
disordered electron density, using the SQUEEZE routine31 in
PLATON, led to better refinement (see the ESI† for details).
The final formulae ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN
and ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN were determined
by combined elemental and thermal analyses and 1H NMR
spectroscopic measurement. The crystal parameters and pro-
cedural information corresponding to the data collection and
structure refinement are listed in Table 1.
Synthesis of ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN
An acetonitrile solution (12 mL) of CuIJClO4)2Ĵ6H2O (22 mg,
0.06 mmol) was slowly diffused into a dichloromethane solu-
tion (8 mL) of L (39 mg, 0.08 mmol). Blue crystals of
ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN formed at the inter-
face and were obtained in 7 days in 81% yield (57 mg).
Mp 237 °C (dec.). Found: C, 44.10; H, 4.20; N, 9.38. Calc.
for C132H158N24O67Cl6Cu3: C, 44.58; H, 4.48; N, 9.45%.
IR (KBr pellet, cm−1): 3552 (br), 1731 (s), 1619 (w), 1564
(w), 1504 (w), 1454 (w), 1423 (m), 1373 (w), 1330 (w), 1282
Results and discussion
Synthetic aspects
−
(s), 1230 (w), 1122 (s), 1087 (s, ClO4 ), 1060 (m), 862 (w),
The new ligand, 1,3,5-trisIJisonicotinoyloxymethyl)benzene
(L), was synthesized in a high yield by the reaction of 1,3,5-
benzene-trimethanol with isonicotinoyl chloride in chloro-
form in the presence of an excess amount of triethylamine
and pyridine. Recrystallization of the crude product from a
mixture of acetone and water afforded colorless single crys-
tals suitable for X-ray diffraction measurement. Self-assembly
763 (w), 698 (w), 622 (w).
Synthesis of ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN
An acetonitrile solution (12 mL) of CuIJBF4)2ĴnH2O (14 mg,
0.06 mmol) was slowly diffused into a dichloromethane
solution (8 mL) of L (39 mg, 0.08 mmol). Blue crystals of
ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN formed at the interface
and were obtained in 7 days in 76% yield (51 mg). Mp 227 °C
(dec.). Found: C, 45.90; H, 4.40; N, 9.40. Calc. for
−
−
of acetonitrile solution of CuX2 (X− = ClO4 and BF4 ) with
dichloromethane solution of L produced blue parallel-pipe-
shaped single crystals consisting of 3D coordination poly-
mers and ijCu3L4IJCH3CN)6]IJX)6 composition in high yields, as
C130H149N23O40B6F24Cu3: C, 46.12; H, 4.44; N, 9.52%. IR (KBr
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Table 1 Crystal refinement parameters for L, ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN, and ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN
L·2H2O
ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN
ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN
Formula*
Mw*
Crystal system
Space group
a (Å)
b (Å)
c (Å)
α (°)
β (°)
C27H25N3O8
519.50
C120H102N18O48Cl6Cu3
2967.52
Monoclinic
C2/c
41.190(1)
20.6334(4)
27.0979(8)
90
129.772(3)
90
17700.8(8)
1.114
C120H102N18O24Cu3
2370.82
Orthorhombic
Ibam
20.6958(5)
27.2441(9)
31.2425(7)
90
Triclinic
¯
P1
7.4117(4)
12.1658(6)
14.2115(7)
85.918(3)
77.087(3)
77.944(3)
1221.1(1)
1.413
90
90
γ (°)
V (Å3)
17615.7(8)
0.894
4
σ (Mg m−3)*
Z
2
4
μ (mm−1
)
0.106
0.519
0.411
Rint
0.0384
0.0756
0.1735
Data/parameters
Completeness (%)
GoF on F2
5054/343
99.9 (θ = 26.50°)
1.024
0.0454
0.1167
17 337/879
99.6 (θ = 26.00°)
0.951
0.0942
0.2965
8843/461
100.0 (θ = 26.00°)
0.851
0.0864
0.2720
a
R1
b
wR2
P
P
P
P
a
b
2
R1
=
‖Fo| − |Fc‖/ |Fo|. wR2 = IJ ijwIJFo − Fc2)2]/ ijwIJFo2)2])1/2. *The solvent molecules (in both cases) and anions (in the case of
ijCu3IJL)4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN) of the copperIJII) complexes are missing from the formula. Due to extensive disorder, they could not
be located.
shown in Scheme 1. The copperIJII) networks' formation of 3 : 4
composition products was attributed to the intrinsic prop-
erties of the C3-symmetric tectonic L and copperIJII) ions. That
is, the assembly reaction was initially conducted in a 1 : 1
copperIJII) ion : L mole ratio, but the product formation was
not significantly affected by the change in the reactants' mole
ratio and concentration, indicating that the 3 : 4 composition
products were thermodynamically stable. Crystalline solid
products (except for solvate molecules, which evaporate on
crystal surfaces) are stable under aerobic conditions, and are
insoluble in water and common organic solvents such as ace-
tone, benzene, chloroform, ethyl acetate, and tetrahydrofu-
ran, but are dissociated in strong polar solvents such as ace-
tonitrile, dimethyl sulfoxide, and N,N-dimethylformamide.
Thus, it was found that the combined effects of the stable
tridentate ligand and the appropriate copperIJII) geometry,
along with the coordinating capacity of solvate acetonitrile,
might be a significant driving force behind the formation of
the unusual 3D network species. The compositions and struc-
tures were confirmed by elemental analyses, IR, thermal anal-
ysis, and X-ray single crystallography. The characteristic
strong IR bands at 1087 and 1031 cm−1 were found to corre-
−
−
spond to ClO4 and BF4 , respectively.
Crystal structures
The new L was fully characterized by X-ray single crystallogra-
phy. The crystal structure of L·2H2O is depicted in Fig. S1
(ESI†). The dihedral angles between the central benzyl plane
and each pyridyl moiety were determined to be 11.80(6),
18.99(7), and 27.70IJ4)°. There are intermolecular π⋯π inter-
actions between the adjacent central benzyl groups (3.58(2) Å
and 0.00IJ5)° for the distance and dihedral angle, respectively)
and the pyridyl groups (3.58(2) Å and 0.00IJ8)° for the
Scheme
1
Procedure for synthesis of 3D copperIJII) networks,
−
ijCu3L4IJCH3CN)6]IJClO4)6 (X− = ClO4 and BF4−). The gray balls represent
the coordinating acetonitrile molecules.
distance
and
dihedral
angle,
respectively).
X-ray
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crystallographic characterization revealed that the skele-
lateral CuIJ2)⋯CuIJ2) distances are 12.783(6); 24.342(7) Å and
12.788(2); 24.288(2) Å, respectively. As shown in Fig. S3 (ESI†),
the unit cages are connected through Cu(2) in the crystallo-
graphic bc-direction, and are linked through Cu(1) to form
1D linked cages running perpendicular to the bc-plane. The
pore dimensions were determined to be 11.2 × 11.2 × 24.8 Å3
and 11.1 × 11.1 × 24.4 Å3 for ijCu3L4IJCH3CN)6]IJClO4)6 and
ijCu3L4IJCH3CN)6]IJBF4)6, respectively. The porous volume is
filled with solvent molecules and counteranions for the cat-
ionic skeleton (Fig. 2).
tons
of
ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN
and
ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN are, as depicted
in Fig. 1, 3D coordination frameworks. Their relevant
bond lengths and angles are listed in Table 2. For
ijCuL4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN, there are two crystal-
lographically independent copperIJII) ions, two L, three coordi-
nating CH3CN molecules, and three perchlorate counteranions
in an asymmetric unit, as indicated in Fig. S2 (ESI†). Each L
connects three copperIJII) ions to produce the 3D network. The
coordinating environment of the copperIJII) ions is a typical
octahedral geometry with four N-donors from four L (Cu–N =
2.02IJ3)–2.03IJ3) Å) in a basal plane and with two N-donors from
two coordinating CH3CN molecules (Cu–N = 2.47IJ4)–2.61IJ4) Å)
in the axial position. The axial Cu–N bond elongation seems
to come from the typical Jahn–Teller distortion of a d9-CuIJII)
system.32 In order to simplify the structural representation
of the present copperIJII) complexes, a topological analysis
was performed. As shown in Fig. 1, L can be defined as a
3-connected node, and two copperIJII) centers act as
4-connected nodes, resulting in a 3D coordination network
of a new trinodal 3,4,4-connected net topology with the
Catalytic oxidation of catechols
Both of the 3D copperIJII) networks were subjected to
catecholase-mimetics to determine their catalytic activity in
the oxidation of catechols to the corresponding
o-benzoquinones. In order to elucidate the substituent effects
of substrates on the catalytic activity, 3,5-di-tert-butylcatechol
(3,5-DBuCat), 4-tert-butylcatechol (4-BuCat), and 4-chloro-
catechol (4-ClCat) have been employed as catalytic reaction
substrates, because their low potentials allow for their
smooth oxidation without side reactions,34 and also because
their oxidized o-benzoquinone species have been very useful
ligands for non-innocent intramolecular electron transfer
molecular systems35,36 that exhibit a λmax absorption band
around 390–400 nm.28 Thus, in the present study, their
catalytic activities, including reaction rates, listed in Table 3,
were easily determined according to the increase in absor-
bance of the oxidized o-benzoquinone species as a function
of time. To this end, each catalyst was treated with the
respective catechol substrate in a 1 : 1 molar ratio in 20 mL
of chloroform at 40 °C under aerobic conditions. For
ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN, the oxidations of
3,5-DBuCat, 4-BuCat, and 4-ClCat were completed within 8,
12, and 15 h, respectively (Fig. S4, ESI†). The respective
turnover frequencies (TOFs) for 3,5-DBCat, 4-BuCat, and
4-ClCat were determined to be 0.125, 0.083, and 0.067 h−1.
That is, the catalytic rates were in the order 3,5-DBuCat >
4-BuCat > 4-ClCat, which indicated that the reaction rate was
dependent on the electron-donating ability of the catechol
substituents.37,38 By comparison, the catalytic reactions using
ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN were completed within
4, 6, and 12 h, respectively (Fig. 3 and S5, ESI†), and the corre-
sponding TOFs were 0.25, 0.167, and 0.083 h−1, respectively,
indicating that ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN is more
effective than ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN. Such a
fact can be explained by the tetrafluoroborate anion's superior
lipophilicity relative to the perchlorate anion in chloroform.
That is, it helps with the substrate diffusion into the 3D
porous network of the crystal surface in chloroform media.
When the amount of catalyst was increased twice, the catalytic
rates increased significantly (Fig. S6, ESI†). Additionally, inter-
esting results were obtained in control experiments by
2
2
2
2
4
2 33
¨
Schlafli point symbol {4Ĵ8 }4{4 Ĵ8 Ĵ10 }2{8 Ĵ12 }. This 3D
network basically consists of oval-shaped cages, in which
two Cu(1) are positioned on the top and bottom facets, and
four Cu(2) are set in the apex (Fig. S1 and S2, ESI†). The
intracage CuIJ1)⋯CuIJ1) distances are 15.8336(7)
Å and
15.6213(4) Å for ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN and
ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN, respectively, and their
Fig. 1 Topological representation of ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN:
(a) ball-and-stick diagram of 3-connected
L
with schematic
employing the simple mixtures of CuX2 (X− = ClO4 and BF4 )
and L in a 3 : 4 mole ratio. As depicted in Fig. 3 and S3
(ESI†), the catalytic oxidations using the simple mixtures
−
−
connectivity to three neighboring copperIJII) ions, (b) schematic
drawing of the subunit, and (c) 3-D coordinating framework with a
new Schlafli point symbol of {4Ĵ82}4{42Ĵ82Ĵ102}2{84Ĵ122}.
¨
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Table 2 Selected bond lengths (Å) and angles (°) for ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN and ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CNa
Paper
ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN
ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN
CuIJ1)–NIJ1)
CuIJ1)–NIJ4)
2.03(2)
2.03(2)
2.50(4)
2.02(3)
2.02(3)
2.03(3)
2.02(3)
2.61(4)
2.47(4)
175.5(1)
91.7(9)
94.6(1)
176.1(1)
91.1(1)
89.0(1)
178.7(1)
175.5(1)
178.2(1)
CuIJ1)–NIJ2)
CuIJ1)–NIJ6)
CuIJ2)–NIJ1)
CuIJ2)–NIJ3)#6
CuIJ2)–NIJ4)
CuIJ2)–NIJ5)
2.054(4)
2.354(7)
2.035(6)
2.000(6)
2.341(7)
2.374(8)
CuIJ1)–NIJ7)
CuIJ2)–NIJ2)#1
CuIJ2)–NIJ3)#2
CuIJ2)–NIJ5)#3
CuIJ2)–NIJ6)
CuIJ2)–NIJ8)
CuIJ2)–NIJ9)
NIJ1)–CuIJ1)–NIJ4)
NIJ1)–CuIJ1)–NIJ1)#4
NIJ1)–CuIJ1)–NIJ7)
NIJ7)–CuIJ1)–NIJ7)#5
NIJ2)#1–CuIJ1)–NIJ6)
NIJ3)#2–CuIJ1)–NIJ6)
NIJ5)#3–CuIJ1)–NIJ6)
NIJ2)#1–CuIJ1)–NIJ3)#2
NIJ8)–CuIJ2)–NIJ9)
NIJ2)–CuIJ1)–NIJ2)#7
NIJ2)–CuIJ1)–NIJ2)#8
NIJ2)–CuIJ1)–NIJ2)#9
NIJ2)#7–CuIJ1)–NIJ2)#8
NIJ6)–CuIJ1)–NIJ6)#8
NIJ1)–CuIJ2)–NIJ1)#10
NIJ1)–CuIJ2)–NIJ3)#6
NIJ1)#10–CuIJ2)–NIJ3)#11
NIJ4)–CuIJ2)–NIJ5)
91.4(3)
88.8(3)
175.1(3)
175.1(1)
180.0
90.4(3)
179.3(3)
179.3(3)
179.3(4)
a
Symmetry codes: #1 −x + 1/2, −y + 3/2, −z + 1, #2 x, −y + 1, z − 1/2, #3 −x + 1/2, y − 1/2, −z + 1/2, #4 −x + 1, y, −z + 3/2, #5 −x + 1, y, −z + 3/2, #6
x − 1/2, −y + 1/2, −z, #7 −x − 2, y, −z + 1/2, #8 x, −y, −z + 1/2, #9 −x − 2, −y, z, #10 x, y, −z, #11 x − 1/2, −y + 1/2, z.
were negligible (less than 10%) until 24 h, but were signifi-
cant after 24 h. This result indicated that the catalytic reac-
tion proceeded after the formation of the copperIJII) frame-
that the structures including the surface properties of the
present 3D porous materials play an important role in the
catalysis. Crucially, the cages and their windows are suffi-
ciently large to allow the catechol substrates' access. The cat-
alytic mechanism of the present copperIJII) systems appears to
be the same as that of other copperIJII)-based complexes,
which involves complexation of the catechol to a vacant site
on the copperIJII) center, oxidation of the catechol by molecu-
lar oxygen, and subsequent release of the product.21,39,40
These porous catalytic systems are not much more effective
than that of dinuclear copperIJII) complexes for mimicking
naturally occurring enzymes through four-electron reduction
of molecular oxygen to water.41–43 Since the two 3D copperIJII)
networks were not dissociated in chloroform during catalysis,
the recyclability of the heterogeneous catalytic systems was
tested. An 80 mg sample of each 3D copperIJII) network was
−
−
works. When simple salts, CuX2 (X− = Cl−, ClO4 , and BF4 ),
were used as catalysts (Fig. S7, ESI†), the catalytic effects
(3–12%) were of course very low compared with those of the
present 3D network catalytic systems. Such a fact suggests
employed as
a catalyst, and the catalytic oxidation of
3,5-DBuCat (5 mg) in 20 mL of chloroform was carried out
for 3 h at 40 °C. Upon completion of the oxidation, the
Table 3 Catalytic yields for catechol oxidationc
Entry
Catalyst
Catechols
Yield (%)
a
a
a
b
b
b
1
2
3
4
5
6
7
8
9
3,5-DBuCat
4-BuCat
4-CuCat
3,5-DBuCat
4-BuCat
4-CuCat
3,5-DBuCat
3,5-DBuCat
3,5-DBuCat
98
93
41
100
100
89
9
CuIJClO4)2
CuIJBF4)2
CuO
7
3
a
ijCu L IJCH CN) ]IJClO ) Ĵ19H OĴ6CH CN. b ijCu L IJCH CN) ]IJBF ) Ĵ16H OĴ5CH CN.
Fig.
2 Side (a) and top (b) views showing the unit cage of
3 4
3
6
46
2
3
3 4
3
6
46
2
3
c
ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN. The counteranions and
coordinating acetonitrile molecules were omitted for clarity.
The [catalyst] : [catechol] ratio was 1 : 1. The catalytic reaction time
and temperature were 6 h and 40 °C, respectively.
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copperIJII) catalysts and the four-time-recycled catalysts were
shown to be identical (Fig. S8, ESI†).
Thermal behavior and solvent adsorption
Thermogravimetric analysis (TGA) and differential scanning calo-
rimetry (DSC) overlays of the 3D copperIJII) networks demonstrated
that the skeletons of ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN
and ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN had drastically
collapsed at 237 and 227 °C, respectively (Fig. 5 and S9,
ESI†). Prior to this thermal decomposition, both the
coordinating and solvate acetonitrile molecules evaporated
in the 30–95 and 30–105 °C range, respectively
IJ[Cu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN:
calcd.
13.9%,
found 9.4%; ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN: calcd.
13.3%, found 13.0%). However, the solvate water mole-
cules were safely nestled in the 3D framework, as confirmed
Fig. 3 Plot showing catalytic yields of 3,5-DBuCat (triangle), 4-BuCat
(circle), and 4-ClCat (squares) using ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN
(blue lines), a mixture of CuIJBF4)2 and L in a 3 : 4 ratio (red line), and
only CuIJBF4)2 (green line) as catalysts. The [catalyst] : [catechol] ratio
was 1 : 1 in CHCl3 at 40 °C. Inset: UV/vis spectra showing the oxidation
of 3,5-DBuCat to 3,5-DBuBQ using ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN
as a heterogeneous catalyst.
1
by the relavant IR and H NMR spectra. As depicted in Fig. 5,
the vCN band at 2251 cm−1 (in a Nujol mull) disappeared
˜
after the sample was evacuated at 80 °C for 1 day, whereas
the vOH band in the 3300–3600 cm−1 range was retained.
˜
catalyst was simply filtered off and reused for the next cataly-
sis. As plotted in Fig. 4, the catalytic activity in both cases
gradually declined over the course of four consecutive reac-
tions. The heterogeneity of the catalytic reactions was evalu-
ated by inductively coupled plasma atomic emission spectro-
scopy (ICP-AES) analysis of the post-catalysis supernatant.
As expected, copperIJII) cations were scarce in both cases
(not detected for ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN; 0.01
ppm for ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN), indicating
that the 3D coordinating framework was robust during the
catalytic reactions. Also, the IR spectra of the as-synthesized
Fig.
partial
of
5 IR (Nujol mull) spectra (top), TGA curves (bottom), and
1H
ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN
NMR
IJMe2SO-d6)
spectra
(inset
(red),
in
bottom)
acetonitrile-
Fig. 4 Recycling test of ijCu3L4IJCH3CN)6]IJClO4)6Ĵ19H2OĴ6CH3CN (top)
and ijCu3L4IJCH3CN)6]IJBF4)6Ĵ16H2OĴ5CH3CN (bottom) catalysts for
oxidation of 3,5-DBuCat.
desolvated ijCu3L4]IJClO4)6Ĵ19H2O (blue), and acetone-adsorbed
ijCu3L4]IJClO4)6Ĵ19H2OĴ7Me2CO (green). The daggers denote the vibra-
tional frequency corresponding to the sp3 hydrocarbon of Nujol.
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In order to determine the adsorption ability of versatile
organic solvent molecules, the acetonitrile-free species,
ijCu3L4]IJClO4)6Ĵ19H2O, was immersed in chloroform, tetrahy-
drofuran (THF), and acetone. Thus, the incorporated solvent
molecules could be checked by 1H NMR in Me2SO-d6 even
though the 3D coordination skeletons were dissociated in
Me2SO-d6. Within 24 h, solvent adsorption was accomplished
(Fig. S10, ESI†) yielding ijCu3L4]IJClO4)6Ĵ19H2OĴ12CHCl3,
ijCu3L4]IJClO4)6Ĵ19H2OĴ13THF, and ijCu3L4]IJClO4)6Ĵ19H2OĴ7Me2CO,
respectively. The IR spectra corresponding to the species'
skeleton remained virtually unchanged, suggesting that the
3D coordination network is retained after solvent adsorption
(Fig. 5). The same experiment employing the acetonitrile-free
species ijCu3L4]IJBF4)6Ĵ16H2O produced ijCu3L4]IJBF4)6Ĵ16H2OĴ7CHCl3,
ijCu3L4]IJBF4)6Ĵ16H2OĴ8THF, and ijCu3L4]IJBF4)6Ĵ16H2OĴ4acetone,
respectively (Fig. 5 and S11, ESI†). Further, the acetonitrile-
desolvated species ijCu3L4]IJClO4)6Ĵ19H2O and ijCu3L4]IJBF4)6Ĵ16H2O
were immersed in a mixture of chloroform, tetrahydrofuran,
and acetone IJv/v/v = 1 : 1 : 1) for 1 day, resulting in the incor-
poration of chloroform, tetrahydrofuran, and acetone in
5 : 2 : 1 and 3 : 2 : 1 ratios, respectively (Fig. S12, ESI†). This
might be ascribed to the polarity of the solvent molecules
rather than the coordinating ability or size effects.
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−
−
Reactions of CuX2 (X− = ClO4 and BF4 ) with a new 1,3,5-tris-
IJisonicotinoyloxymethyl)benzene (L) ligand give rise to
unusual 3D, ijCu3L4IJCH3CN)6]IJX)6 coordination networks,
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new topology of the Schlafli point symbol
with
a
{4Ĵ82}4{42Ĵ82Ĵ102}2{84Ĵ122}. The 3D network basically has oval-
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