Highly Thermally and Chemically Stable Nickel(II) Coordination Polymers: Tentative Studies on Their Sorption, Catalysis, and Magnetism

Article abstract of DOI:10.1021/acs.cgd.8b01373

The five new Ni(II) coordination polymers (CPs) {[Ni(bitp)(bpe)_0.5(H₂O)₂]·0.5bpe}_n (1), {[Ni(bitp)(bpa)_0.5(H₂O)₂]·0.5bpa}_n (2), {[Ni(bitp)(4,4′-bpy)_0.5(H₂O)]·H₂O}_n (3), {[Ni_1.5(bitp)(Hbitp)(2,2′-bpy)(H₂O)]·3H₂O}_n (4), and [Ni(bitp)(bipyam)]_n (5), where H₂bitp = 2-(benzimidazol-1-yl)terephthalic acid, bpe = 1,2-bis(4-pyridyl)ethylene, bpa = 1,2-bis(4-pyridyl)ethylane, 4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine, and bipyam = 2,2′-bipyridylamine, were prepared under the same hydrothermal environments except for various N-donor ligands which can effectively regulate the structures of the complexes. For the bridging N-donor ligands bpe, bpa, and 4,4′-bpy, isostructural 1 and 2 feature three-dimensional (3D) layered-pillared frameworks with one-dimensional (1D) channels that house free bpe or bpa, while 3 is a wavelike two-dimensional (2D) stacked layer with similar 4,4′-bpy bridging auxiliary ligands. However, when terminal ligands 2,2′-bpy and bipyam are used, 2D 4 and 1D ladder chains 5 are obtained, respectively. Interestingly, 1-5 exhibit outstanding thermostability (up to 320 °C) and chemical stabilities (against boiling water, acids, bases, and organic solvents). Furthermore, on the basis of their highly thermal and chemical stability, tentative studies on the structures and properties (such as adsorption, catalysis, and magnetic properties) were undertaken. The gas sorption measurements show that 1 and 2 exhibit high adsorption selectivity of CO₂ over CH₄. The catalytic reactions demonstrate the role of catalysts 1-5 to synthesize 3,6-bis(pyridin-4-yl)-1,2,4,5-tetrazine. The magnetic analyses indicate that there exist a zero field splitting (ZFS) on the Ni(II) ions in 1-5.

Full text of DOI:10.1021/acs.cgd.8b01373

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Article
High Thermally and Chemically Stable Nickel(II) Coordination Polymers:
Tentative Studies on Their Sorption, Catalysis, and Magnetism
Hua Liu, Yi-Fan Kang, Yan-Ping Fan, Fu-Sheng Guo, Lang Liu, Jian-Li Li, Ping Liu, and Yao-Yu Wang
Cryst. Growth Des., Just Accepted Manuscript • DOI: 10.1021/acs.cgd.8b01373 • Publication Date (Web): 04 Dec 2018
Downloaded from http://pubs.acs.org on December 4, 2018
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High Thermally and Chemically Stable Nickel (II)
Coordination Polymers: Tentative Studies on Their
Sorption, Catalysis, and Magnetism
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§,†
§,‡
†
†
†
†
Hua Liu, Yi-Fan Kang, Yan-Ping Fan, Fu-Sheng Guo, Lang Liu, Jian-Li Li,
,
†
†
Ping Liu,* and Yao-Yu Wang
†Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of the
Ministry of Education, Shaanxi Key Laboratory of Physico–Inorganic Chemistry,
College of Chemistry & Materials Science, Northwest University, Xi'an 710127,
People’s Republic of China
‡College of Chemistry & Chemical Engineering, Shaanxi University of Science and
Technology, Xi'an 710021, People’s Republic of China
ABSTACT:
Five
new
Ni(II)
(1), {[Ni(bitp)(bpa) (H O) ]·0.5bpa}
n
coordination
polymers
(CPs),
{
[Ni(bitp)(bpe) (H O) ]·0.5bpe}
(2),
0
.5
2
2
n
0.5
2
2
{[Ni(bitp)(4,4'-bpy) (H O)]·H O} (3), {[Ni (bitp)(Hbitp)(2,2'-bpy)(H O)]·3H O}
n
0
.5
2
2
n
1.5
2
2
(
4) and [Ni(bitp)(bipyam)] (5), where H bitp = 2-(benzimidazol-1-yl)terephthalic
n 2
acid, bpe = 1,2-bis(4-pyridyl)ethylene, bpa = 1,2-bis(4-pyridyl)ethylane, 4,4'-bpy =
,4'-bipyridine, 2,2'-bpy = 2,2'-bipyridine and bipyam = 2,2'-bipyridylamine, were
4
prepared under the same hydrothermal environments except various N-donor
ligands which can effectively regulate the structure of complexes. For bridging
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N-donor ligands bpe (1), bpa (2) and 4,4'-bpy (3), isostructural 1−2 feature 3D
layered−pillared frameworks with one−dimensional (1D) channels that house free bpe
or bpa, while 3 is a wavelike 2D stacked layer with similar bridging auxiliary ligands
4,4'-bpy. But when terminal ligands 2,2'-bpy or bipyam used, 2D 4 and 1D ladder
chain 5 are obtained, respectively. Interestingly, 1−5 exhibit outstanding
thermostability (up to 320 °C) and chemical stabilities (against boiling water, acids,
bases and organic solvents). Furthermore, based on their high thermal and chemical
stability, tentative studies on the structure and property (such as adsorption, catalysis,
and magnetic properties) were undertaken. The gas sorption measurements show that
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and 2 exhibit highly adsorption selectivity of CO over CH . The catalytic reactions
2
4
demonstrate
the
catalysts
role
of
1−5
to
synthesize
3
,6-di(pyridine-4-yl)-1,2,4,5-tetrazine. The magnetic analysis indicates that there
presents a (ZFS) zero field splitting on the Ni (II) ions in 1−5.
INTRODUCTION
Coordination polymers (CPs) have aroused widespread concern with their diverse
interesting topologies as well as their intriguing potential applications such as gas
sorption and separation, heterogeneous catalysis and magnetism applications.1−7 Even
though CPs are promising porous materials in a variety of fields, in comparison with
other materials such as metal oxides, porous carbons, zeolites, silica, and
8
heteropolyanion salts, their limited thermal and chemical stability usually hamper
CP’s property applications in many fields.9,10 Therefore, the development of novel
and robust CPs under harsh conditions has motivated numerous investigations. As has
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been reported, the stability of CPs can be improved by enhancing the matching level
of coordination groups with metal ions.11−13 In other words, the complexes obtained
are more stable if the coordination groups and metal ions conform well to the rule of
acid-base hard-soft (HSAB) reaction. So one effective building strategy on stable CPs
is to combine multi−topic carboxylate ligands with parts of divalent transitional-metal
1
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2
+
2+
2+
2+ 14−18
(Zn , Co , Ni , and Cu ),
thereby possibly characterizing their
thermal/chemical stability as well as their properties. Now, though it is known that the
CP’s diverse properties are closely related to their structures and could be modulated
by tailoring their structures, it is still a challenge to design and prepare the CPs with
anticipated performance.19-21
The Ni(II) ion, as a nontoxic and abundant crustal element, has relatively larger
radius, mutable stereochemical activity, greater electronegativity, and a high
ligand−field stabilization energy (LFSE)22−24, making it possible to design and
prepare Ni(II)-CPs with rich topologies, high stabilities and multifarious
properties.25,26 For example, paramagnetic Ni(II) can be used to construct Ni(II)−CPs
with magnetic properties, and interestingly, the reported Ni(II)−CPs, as the rare
examples of ferromagnetic coupling via H-bonds, exhibit the weak ferromagnetic
coupling.27−29 In addition, the highly polar Ni(II)−CPs have been considered as a new
kind of CO separation and capture materials, ascribed to their high sorption affinity
2
and capacity by framework–adsorbate interactions.30−33 Not only that, it is also to be
observed that the coordinatively unsaturated Ni(II) is also able to function as Lewis
acid to catalyze organic reactions.34−36 For instance, Nickel triflates have been
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discovered as highly effective catalysts for the synthesis of 1,2,4,5-tetrazines. Thus,
explorations of the Ni(II)−CP’s structure and property are of crucial significance for
the development of advanced CPs−based materials.
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In this paper, we chose the 2-(benzimidazol-1-yl) terephthalic acid (H bitp) as the
2
main ligand to react with NiCl ·6H O and different auxiliary ligands under the same
2
2
hydrothermal conditions. The H bitp, as a kind of multicarboxylate ligands, possess
2
two carboxylic and one imidazol groups, which bound much more strongly with hard
Lewis acid Ni(II) and therefore probably generate CPs with improved stability and
more diverse structures.38,39 Five complexes, {[Ni(bitp)(bpe) (H O) ]·0.5bpe} (1),
0
.5
2
2
n
{
[Ni(bitp)(bpa) (H O) ]·0.5bpa} (2), {[Ni(bitp)(4,4'-bpy) (H O)]·H O} (3),
0.5 2 2 n 0.5 2 2 n
{[Ni (bitp)(Hbitp)(2,2'-bpy)(H O)]·3H O} (4) and [Ni(bitp)(bipyam)] (5), where
1
.5
2
2
n
n
bpe = 1,2-bis(4-pyridyl)ethylene, bpa = 1,2-bis(4-pyridyl)ethylane, 4,4'-bpy =
,4'-bipyridine, 2,2'-bpy = 2,2'-bipyridine and bipyam = 2,2'-dipyridylamine, were
4
obtained. In 1-5, we found that the addition of different kinds of auxiliary ligands
contribute to the framework, bridging ligands bpe/bpa/4,4'-bpy helping to extend the
framework into 3D or 2D structure while terminal ligands forming 2D or 1D structure
instead. 1/2 are bridged by bpe/bpa into 3D layered−pillared frameworks with 1D
channels housed by free bpe/bpa, while 3 exists in the form of 3D network shaped on
wavelike 2D layers through hydrogen bonding interactions. Moreover, when terminal
ligands are used to replace bridging ligands, 2D 4 and 1D ladder chain 5 are formed,
and further self−assembled through π···π interactions or hydrogen bonds to obtain
different 3D supramolecular frameworks. Notably, 1−5 exhibit enhanced
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thermostability up to 320 °C and chemical stability, which expand their practical
application. The gas adsorption properties of 1 and 2 were studied, which exhibits
high CO sorption heat and sorption selectivity for CO over CH . The catalytic
2
2
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results demonstrate the catalysts role of 1−5, and 2 is selected to synthesize
,6-di(pyridine-4-yl)-1,2,4,5-tetrazine as the target catalyst. The magnetic analysis of
3
1−5 indicates the presence of a (ZFS) zero field splitting on the Ni(II) ions.
EXPERIMENTAL SECTION
Materials and Methods. All synthetic reagents and solvents commercial
available were used directly. Elemental analyses (for carbon, hydrogen, and nitrogen)
were taken on a PerkinElmer 2400C elemental analyzer. The FT-IR spectra
−
1
(4000−400 cm ) were obtained on a Bruker EQUINOX−55 using KBr pellets. The
Powder X-ray diffraction (PXRD) data were tested on a Bruker D8 ADVANCE
X−ray powder diffractometer (Cu Kα, λ = 1.5418 Å) in the angular range of 5° ≤ 2θ
≤ 50°. The thermal stabilities were performed in a Netzsch TG209F3 apparatus. The
gas sorption isotherms of 1 and 2 were measured on a Micromeritics ASAP 2020 M
adsorption instrument. Magnetizability measurements were assessed on a Quantum
Design MPMS−XL−7 SQUID magnetometer.
{
[Ni(bitp)(bpe) (H O) ]·0.5bpe} (1). A mixture of H bitp (0.1 mmol, 28.2 mg),
0.5 2 2 n 2
NiCl ·6H O (0.1 mmol, 23.7 mg), bpe (0.1 mmol, 18.2 mg), NaOH (8 mg) and 10 mL
2
2
H O was placed in a Teflonlined stainless steel vessel (25 mL), heated to 150 °C for 3
2
o
−1
d. After it cooled to room temperature at a rate of 0.1 C min , dark−green block
crystals of 1 with 65% (based on H bitp) were collected. Anal. Calcd for
2
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1
1
1
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2
3
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3
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5
5
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−
1
C H N Ni O (1114.36 g mol ): C, 58.15; H, 3.95; N, 10.05%. Found: C, 58.67;
5
4
44
8
2
12
−
1
H, 3.89; N, 9.99%. IR (KBr, cm ): 3475 s, 2934 s, 1605 s, 1554 s, 1421 m, 1364 s,
1
240 m, 1010 w, 954 m, 906 w, 795 s, 747 w, 532 s.
0
1
2
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{[Ni(bitp)(bpa) (H O) ]·0.5bpa} (2). 2 is dark−green block crystal and gained
0.5
2
2
n
by similar synthetic operation with 1, except that bpe was changed as bpa (0.1 mmol,
18.4 mg). Yield: 67% (Based on H bitp ligand). Anal. Calcd for C H N Ni O
12
2
54 48
8
2
−
1
(
1118.39 g mol ): C, 57.94; H, 4.29; N, 10.01%. Found: C, 58.42; H, 4.33; N, 9.89%.
−1
IR (KBr, cm ): 3475 s, 2960 s, 1615 s, 1562 s, 1421 m, 1364 s, 1240 m, 1004 m, 910
m, 795 s, 747 w, 532 s.
{
[Ni(bitp)(4,4'−bpy) (H O)]·H O} (3). 3 is green block crystal and gained by
0.5 2 2 n
similar synthetic operation with 1 except that bpe was changed as 4,4'−bpy (0.1
mmol, 15.7 mg). Yield: 35% (Based on H bitp ligand). Anal. Calcd for C H N NiO
6
2
20 16
3
−1
(
453.05 g mol ): C, 52.97; H, 3.53; N, 9.27%. Found: C, 53.40; H, 3.65; N, 9.33%.
−
1
IR (KBr, cm ): 3312 s, 1613 m, 1577 m, 1545 s, 1511 s, 1417 m, 1391 s, 1240 m,
1
012 w, 815 m, 739 m, 635 m.
{[Ni (bitp)(Hbitp)(2,2'−bpy)(H O)]·3H O} (4). 4 is green block crystal and
1.5
2
2
n
gained by similar synthetic operation with 1 except that bpe was changed as 2,2'−bpy
0.1 mmol, 15.7 g). Yield: 66% (Based on H bitp ligand). Anal. Calcd for
(
2
−
1
C H N Ni O (1755.52 g mol ): C, 54.73; H, 3.76; N, 9.57%. Found: C, 54.95; H,
8
0
66 12
3
24
−
1
3
.62; N, 9.66%. IR (KBr, cm ): 3381 s, 1705 m, 1605 s, 1511 w, 1468 m, 1372 s,
1240 m, 1022 w, 910 m, 764 s, 515 w.
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[Ni(bitp)(bipyam)] (5). 5 is green block crystal and gained by similar synthetic
n
operation with 1 except that bpe was changed as bipyam (0.1 mmol, 17.1 g). Yield:
−1
6
3% (Based on H bitp ligand). Anal. Calcd for C H N NiO (510.14 g mol ): C,
2 25 17 5 4
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
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4
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5
5
5
5
5
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2
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2
3
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5
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8
9
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2
3
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7
8
9
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2
3
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9
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2
3
4
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9
0
−
1
58.80; H, 3.33; N, 13.72%. Found: C, 59.43; H, 3.23; N, 13.53%. IR (KBr, cm ):
3
242 m, 1655 m, 1570 s, 1538 w, 1485 s, 1432 m, 1400 w, 1236 s, 1150 m, 1012 m,
823 w, 755 s.
Single-Crystal Structure Analysis. The X−ray diffraction data were collected
at 293(2) K using a Bruker SMART APEX II CCD diffractometer equipped with
Mo−Kα (λ = 0.71073 Å) radiation. The structures of 1−5 were solved and refined by
full−matrix least−squares procedure based on F2.40,41 All the non−hydrogen atoms
were located with anisotropic displacement parameters. And all hydrogen atoms
except for water molecules were located and fixed in idealized positions. The crystal
data, selected bond distances and angles for for 1−5 are presented in Table S1 and
Table S2. CCDC: 1810869-1810873 for 1−5.
RESULTS AND DISCUSSION
Crystal Structures of {[Ni(bitp)(bpe) (H O) ]·0.5bpe}
(1) and
[Ni(bitp)(bpa) (H O) ]·0.5bpa} (2). The complexes 1 and 2 are isostructural
0.5
2
2
n
{
0.5
2
2
n
and isomorphous with similar auxiliary ligand (bpe for 1, bpa for 2) and only 1 with
detailed discussion. X-ray diffraction data displays that 1 is 3D layered−pillared
structure with 1D channels housed by free bpe and belongs to the triclinic space group
P−1. The asymmetry unit of 1 contains one Ni(II) ion (a half Ni1 and a half Ni2), one
2
−
bitp , a half coordinated bpe, a half bpe guest and two coordinated water (Figure 1a).
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Both the Ni1 and Ni2 centers are hexa−connected. The Ni1 is surrounded by four
2
−
oxygen atoms from two bitp ligands, two coordinated water molecules (O1W) as
2−
well as two nitrogen atoms from two bitp ligands, presenting a distorted octahedral
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coordination environment. Compared with Ni1, Ni2 bonds to two nitrogen atoms
2
−
from two bpe ligands, four oxygen atoms from two bitp ligands and two coordinated
water molecules (O2W). The distance of water molecules between the adjacent layers
(
O1W···O1W, 15.015 Å) is within the length of the bpe ligand (N −N = 9.358 Å),
bpe bpe
compared to the distance of O2W···O2W (16.174 Å). Thus, O1W, bonded with Ni1,
is used to stabilize free bpe reside in the quadrangle channels by forming strong
hydrogen bonds (O1W−H1WB···N4, 2.852(2) Å). O2W, bonded with Ni2, is used to
stabilize whole framework by forming strong hydrogen bonds with the coordinated
water molecules (O2W−H2WB···O1W, 2.842(3) Å) and monodentate coordinated
carboxylic oxygens (O2W−H2WA···O4, 2.609(9) Å). All coordinated water
molecules point into the channel where the free bpe is resided, which certainly crowd
the channels of 1. The distance of Ni−O and Ni−N bond is within the reported
distance.42−44 All carboxyl groups of the H bitp ligand adopt one coordination mode:
2
1
0
2−
μ −η :η (Table 1). The Ni1 centers are coordinated by bitp ligands to form a 1D
1
loop chain along b axis with the Ni1···Ni1 distance being 10.656 Å, the adjacent
chains are further joined via Ni2−O bonds to obtain a 2D parallel layer along the bc
crystal face (Figure 1b). Finally, the bridging bpe ligands serve as pillars connecting
the adjacent layers together to result in a 3D network with 1D channels in which the
free bpe are housed by forming strong hydrogen bonds with the coordinated water
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molecules (O1W−H1WB···N4). The bpe molecules act both as the secondary ligands
as well as the guest molecules. The steric hindrance of free bpe/bpa works markedly
for absence of solvent molecules in the cavity. (Figure 1c). The topological expression
is a (3, 4, 4) −connected framework where the complex symbol is
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
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1
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2
3
4
5
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8
9
0
2
2
2
2
4
(
4.8 ) (4 .8 .10 )(8.10 .12), by denoting both Ni1(II) and Ni2(II) ion as
2
2
−
four−connected nodes and bitp as a three−connected nodes (Figure 1d).
Through analyzing the crystal structure of 1 and 2, it could be known that the
distances of layer−to−layer (11.729 Å) and Ni2···Ni2 separated by the bpe (13.508 Å)
in 1 are a bit larger than that in 2(11.675 Å and 13.504 Å), which could be ascribed to
the difference in length of bpe/bpa (9.358 Å/9.214 Å). Furthermore, 1 and 2 also with
2
2
different pore dimensions (10.361 × 11.729 Å for 1, 10.305 × 11.675 Å for 2,
included vander Waals radius). The diverse dihedral angles between benzene ring
and benzimidazole moiety (ca. 87.4° for 1 and 85.5° for 2) give rise to the difference
for Ni1···Ni1 nonbonding separations (10.608(3) Å for 2).
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2
2
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1
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1
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3
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1
2
3
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5
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9
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1
2
3
4
5
6
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8
9
0
Figure 1. (a) Coordinated environment of the Ni (II) in 1. Symmetry codes: A = − x+
1, − y + 2, − z + 1; B = x, y + 1, z; C =− x + 1, − y + 1, − z + 1; D = − x + 1, − y, − z;
E = − x + 2, − y + 1, − z. (b) The 2D layer of 1 shown down the bc plane. (c) The 3D
framework displaying the connectivity between the layers by the bpe ligand. (d)
Hydrogen bond diagram between free bpe and coordination water. (e) Schematic
representation of the four−connected 3D topology network for 1.
Crystal Structures of {[Ni(bitp)(4,4'-bpy) (H O)]·H O} (3). 3 exists as a
0.5
2
2
n
3
D network stacked by 2D layers through hydrogen bonding interactions and falls
within the C2/c space group. As seen in Figure 2a, the asymmetric unit is composed
2
−
of one Ni (II) ion, one bitp ligand, a half 4,4'-bpy linker lying at an inversion centre,
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one coordinated water molecule and one lattice water molecule. Each Ni atom is
six-coordinated by four carboxylate O atoms from two bitp2− ligands and two
2−
coordinated water as well as two imidazole N atoms from one bitp ligand and one
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
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4
4
4
5
5
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5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
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9
0
4,4'-bpy, to construct a distorted octahedral environment (Figure 2a). The Ni−O and
Ni−N bond lengths are in the range 2.070(2)−2.080(2) Å and 2.075(2)−2.165(2) Å,
respectively, which are within the reported distance values.42−44 Each bitp links to
2−
2
+
three Ni ions to obtain a 1D chain with the dihedral angles between benzene ring
and benzimidazole moiety are ca. 67.18°, in which two carboxyl groups adopt
0
1
1
1
μ −η :η and μ −η :η coordination mode (Table 1). Adjacent chains are linked by
1
1
4
,4'-bpy to obtain 2D wavelike layers along the ab plane (Figure 2c). Moreover, the
coordinated water oxygen atom (O5) is linked with a carboxylate oxygen atom (O3)
through the hydrogen bond (O5−H5A···O3 = 2.714(3) Å) to connect the adjacent 2D
layers, further forming a 3D framework (Figure 2b).
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1
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2
2
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Figure 2. (a) Coordinated environment of Ni (II) ions in 3. Symmetry codes: A = x −
0
.5, − y + 0.5, z − 0.5; B = − x + 0.5, − y + 0.5, – z + 1; C = − x + 0.5, − y+ 1.5, − z+
1. (b) The 3D network built on hydrogen bonding interactions. (c) The 2D layer of 3
shown down the ab plane. (d) View of the 1D chain in 3.
Crystal Structures of {[Ni (bitp)(Hbitp)(2,2'−bpy)(H O)]·3H O} (4). 4
1.5
2
2
n
falls within the triclinic space group P−1, showing a 2D network. And each
asymmetric unit contains one and a half crystallographically independent Ni(II) ions
-
(
one half of Ni1 and one Ni2), one bitp2− ligand, one Hbitp ligand, one 2,2'-bpy
ligand, one coordinated water molecule and three lattice water molecules (Figure 3a).
2
−
Ni1 is surrounded by four carboxylate O atoms from two bitp and two coordinated
−
water molecules as well as two imidazole N atoms from two Hbitp ligands to take on
a distorted octahedral coordination environment. Ni2 shows a distorted quadrangle
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2
−
pyramid geometry and connects with two carboxylate O atoms from one bitp and
-
2−
one Hbitp and three N atoms from one 2,2'-bpy and one bitp imidazole. All Ni−O
and Ni−N bond lengths within the range of Ni-MOFs.42−44 Different from 1−3, the
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
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9
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2
−
−
H bitp in 4 takes two deprotonation modes: bitp and Hbitp . The former connects to
2
2
+
three Ni ions in which the carboxyl groups are fully deprotonated, its dihedral angle
between the benzimidazole and benzene ring is ca. 76.04° and the latter links two Ni2+
ions in which the carboxyl groups are partly deprotonated with the angle is ca. 54.21°
2+
2−
(
Table 1). Four Ni ions (2Ni1 + 2Ni2) are first connected by two bitp and two
−
Hbitp to give a [Ni (bitp) ] square, further extended into a 1D chain. Furthermore,
4
4
2
−
adjacent chains are connected via Ni2−N (from bitp ) bonds to form a 2D layer
(Figure 3b). The 3D network is constructed by 2D layers through weak π···π stacking
interaction between the parallel pyridine rings, with centroid distance, vertical
distance, and angle of 3.739(2) Å, 3.568(4) Å and 17.39(5)° (Figure 3c and 3d).
Moreover, coordination water, carboxyl and guest water molecules housed at pores
produce multiform H−bonds each other.
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Figure 3. (a) Coordinated environment of Ni (II) ions in 4. Symmetry codes: A = − x
+ 1, − y + 2, − z + 1; B = x, y + 1, z; C =− x + 1, − y + 1, − z+ 1; D = x + 1, y, z. (b)
Schematic view of the 2D structure of 4 along c axis. (c) The 3D network of 4. (d)
The schematic view of weak π···π stacking interactions between the parallel pyridine
rings.
Crystal Structures of [Ni(bitp)(bipyam)] (5). 5 forms the triclinic space
n
2
−
group P−1. The asymmetric unit contains one Ni(II) ion, one bitp ligand and one
bipyam ligand. As Figure 4a shown, Ni(II) ion displays a distorted octahedral
2
−
coordination geometry definited by three oxygen atoms from two bitp ligands and
three nitrogen atoms from one bipyam ligand and one bitp2− ligands. The average
bond distances of Ni−O (2.085(4)−2.159(4) Å) and Ni−N (2.011(4)−2.181(4) Å) are
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within the reported distance values.42−44 Ni (II) ions are connected by μ −η :η
0
1
1
1
1
carboxyl groups and μ −η :η carboxyl groups, giving a 1D ladder chain. And the
1
dihedral angle between the benzimidazole and benzene ring is ca. 71.86°.
Furthermore, these 1D chains are linked by the hydrogen bonding interactions to
obtain a 2D layer (N4−H4···O3 2.865 Å) (Figure 4b) and 3D supramolecular
framework (C17−H17···O3 3.460 Å) (Figure 4c).
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
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3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 4. (a) Coordinated environment of Ni (II) ions in 5. Symmetry codes: A = − x
+
1 , − y + 1, − z + 1; B = − x, − y + 1, – z + 1. (b) The 2D layer of 5. (c) The 3D
network of 5.
Table 1. The coordination modes of H bitp in complexes 1−5.
2
Complexes
1
2
3
4
5
Coordination
modes
Dihedral
angles
87.4 ° 85.5°
67.18°
54.21°
76.04°
71.86°
Structural Comparison of Complexes 1−5 and the Influencing Factors.
As summarized in the Table 1, The H bitp ligand and auxiliary ligands lead to the
2
structural diversities. The H bitp ligand exhibits three different coordination modes,
2
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and coordinates with two or three Ni (II) ions by using the benzimidazole N atom and
monodentate/chelating carboxyl groups. In addition, the dihedral angles between the
benzimidazole and benzene ring show a correlation with coordination modes. It is
obvious that the dihedral angles wherein the carboxylic groups uncoordinate with the
metal atom or adopt a chelating mode in 3−5 are smaller than that in 1 and 2 in which
the carboxylic groups coordinate in a monodentate mode. Therefore, distinct dihedral
angles contribute to the different framework. And auxiliary ligands in 1−5 contribute
to the structural extension. Bridging ligands bpa/bpa in 1/2 extend the 2D wavelayer
into 3D network while the bridging 4,4'-bpy in 3 connect the 1D zigzag chains into
0
1
2
3
4
5
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2
D layers. In 4 and 5, terminal 2,2'-bpy( for 4) and bipyam (for 5) ligands occupy the
huge space around the Ni(II), further preventing the extension of the framework to
form 2D and 1D complexes, respectively.Thus, bridging ligands help to extend the
framework into 3D or 2D structure while terminal ligands form 2D or 1D structure
instead.
By comparing the deprotonation of H bitp ligands in 1−5, it is obvious that the
2
H bitp ligands are fully deprotonated in 1, 2, 3, and 5, while in 4 it is partly
2
deprotonated or fully deprotonated. 1−3 are prepared under the same experimental
condition with various straight line N−donor ligands (bpe, bpa, 4,4'-bpy for 1, 2 and 3,
respectively) which result in some differences on their frameworks due to the
2
−
conformation of the bitp ligand and nature of auxiliary ligands. There are two Ni (II)
ions in 1 and 2 asymmetric unit compared to the mononuclear structure of 3. In 1 and
2
, both carboxylic groups adopt monodentate coordination mode, while in 3, a
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carboxylic group exist in two forms: monodentate coordination mode and bidentate
chelating mode. It occupies a coordination site, hindering the extension of the
framework and inducing a 2D layer. Moreover, because of the flexibility of the bitp2−
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
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4
4
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4
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5
5
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0
1
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7
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0
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0
ligand, the dihedral angles between the benzimidazole and benzene ring is ca. 87.4°
for 1 and 85.5° for 2 compared with the dihedral angle of 67.18° in 3. The bpe and
bpa are more flexible spacer−shaped ligand whereas 4,4'-dpy is a rigid bridging
ligand. Similarly, 4 and 5 also form different structures.
Thermal and Chemical Stability. The PXRD patterns of complexes 1−5 were
determined and shown in Figure S1. the experimental PXRD patterns were in good
match with the simulated, which conformed the phase pureness of the samples. It is
considerable for the chemical stability of CPs in organic solvents, acid, base and
moisture/water,45,46 which is quite important in many fields. However, as most CPs
are unstable in acids and bases or even in moist air, the chemical stability of CPs are
always an obstacle for their application. It is worth mentioning that the chemical
stability of 1−5 are determined by immersing samples in dichloromethane, methanol,
N, N-dimethylformamide, N-methyl-2-pyrrolidone, ether, acetonitrile, ethanediol,
alcohol or water at least for 7 days. The PXRD indicate that the crystal frameworks
of 1−5 can remain their completeness (Figure S2). The difference in diffraction
intensity between the experimental and simulated PXRD is mainly ascribed to
nonrandom orientation of crystallites. The slight peak shift could be due to the
solvent effect. 47 As shown in Figure S3, 1−5 can well maintain their crystallinity
when immersed in the boiling water, boiling methanol, which reveal quite high
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resistance toward these treatments. Furthermore, this is also true for crystals of 1−5
upon immersed in acidic or basic aqueous solutions with the pH range of 3−12 for at
least 7 days, and the PXRD confirmed that the high chemical stability of 1−5.
0
1
2
3
4
5
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0
Although some reported CPs with high stability, such as PCN−225, NO −tagged
2
UiO−66 and pyrazole−based Ni(II)−CPs,48−50 seldom porous CPs have been reported
to maintain the integrities in the acidic and basic aqueous solutions in such broad pH
range.
Careful analyses of five Ni (II)−CPs in this work, the high chemical stability could
be attributed to the following factors: first, the carboxylic group as a hard Lewis base,
imidazol group as a boundary base which bound much more strongly with hard Lewis
acid Ni(II) and thus conform to the HSAB reaction rule. Second, the rigid bitp2−
ligand, uniform and dense assembly structure also contributes a lot to its stability.
Last, the open channels in 1 and 2 are largely occupied by guest molecules and
coordinated water molecules, which essentially provide a solvophilic condition for
capturing polar organic solvents and water molecules, thereby effectively preventing
their attacks on inorganic nodes. 51,52
The TGA data were performed in a flowing of N environment during 30−800 °C.
2
As shown in Figure 5, 1−5 are thermally stable up to 320 °C. The sample lose weight
of 6.89% (for 1) and 6.78% (for 2) in the temperature range of 115−142 °C (for 1) and
3
5−125 °C(for 2), corresponding to the release of two coordinated water molecules
(6.46% for 1, and 6.43% for 2), and then a half of free bpe/bpa ligand start to break
down until 358 °C or 280 °C with the loss of 16.25% for 1 (calcd. 16.33%) and
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16.44% for 2 (calcd. 16.45%), respectively. And accompanying with the
decomposition of the framework. The result shows that 1 is more stable than 2, which
is possible ascribed to that the bpe is a rigid N-donor while bpa is a flexible one.
Different from 1 and 2, 3 and 4 exhibit a weight reduction of 8.27% and 8.23% in the
range of 116-252 °C and 30−165 °C, assigning to the decrease of the coordinated and
free water molecules (calcd. 7.95% and 8.21%). Then it is a platform until 320 °C,
and the structure begins to topple down. There is no solvent molecule in 5, therefore,
the TG curve exhibits platform before 380 °C, showing high thermal stability, and
then followed by the framework’s fall down.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 5. TGA curves of complexes 1−5.
IR Spectra. As shown in Figure S6, complexes 1−5 have similar infrared spectra,
2
−
and present characteristic absorption band of the bitp and auxiliary ligands. The IR
−
1
−1
spectra of 1−5 with major absorption peaks at 1550−1625 cm and 1350−1450 cm
could be attributed to the asymmetric and symmetric stretching vibrations of
carboxylic groups, representing the presence of the coordinated −COO group.53,54 The
−
1
broad absorption bands at 2900−3475 cm of 1−4 are in line with the asymmetric
vibration of ν , indicating the existence of H O molecules. The weak peak at 3424
OH
2
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2
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5
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7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
−
1
55
−1
cm in 5 could be ascribed to the moisture in the air. The separation of 241 cm (for
−
1
−1
−1
1
), 251 cm (for 2) and 233 cm (for 4) between these two bands [νas(COO ) −
−1
56,57
νs(COO )] is typical of monodentate coordination of carboxylate group.
Δν = 186
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
−
1
−1
cm for 3 and 170 cm for 5 are assigned to the stretching modes of the chelating
−
1
carboxylate. For 4, the existence of the medium peak at 1705 cm attributable to the
C=O vibration of the −COOH group conforms the partial deprotonation of the
dicarboxylic ligand.58,59 Furthermore, the sharp absorption bands at 1543−1545 and
−1
1
445−1460 cm correspond to the characteristic absorption of the C=C and C=N in
the benzimidazole. Absorption region at 600−1300 cm−1 stemming from N−donor
ligands viz. bpa, bpe, bpy and bipyam are similar to those observed for N ligands.60
Gas Sorption Properties. The excellent thermal and chemical stability of
complexes 1 and 2 encourage us to evaluate its porosity. The samples of 1 and 2 was
activated by heating 1 and 2 at 200 °C for 5 h under a high vacuum. PXRD patterns
still closely matched the simulated patterns of 1 and 2, indicating that the samples
after activated retained the intact host frameworks of 1 and 2.
Figure 6. CO and CH adsorption isotherms for 1 (a) and 2 (b) for CH and CO at
2
4
4
2
298 K and 273K.
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1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
Figure 7. Pressure-dependent selectivities of 1 (a) and 2 (b) over CH calculated by
4
the IAST method.
3
−1
Complexes 1 and 2 exhibit very small N uptake (25 cm g at 101.325 kPa) at 77
2
K. This could be ascribed to structural shrinkage arising from the free bpe/bpa ligands
6
1
in 1D channel after desolvation, which leads to the blocked diffusion. At 273 and
3
−1
2
98 K, 1 and 2 are almost nonadsorptive for CH (18.2 and 7.8 cm g for 1, 11.9 and
4
3
−1
3
−1
7.7 cm g for 2) but moderate of CO is captured (58.1 and 40.1 cm g for 1, 39.4
2
3
−1
and 33.8 cm g for 2) (Figure 6), demonstrating their vital gas adsorption selectivity
of CO over CH and N . During separation, the selectivity of different components in
2
4
2
the mixture is a key factor for the adsorbents, and the selectivity for CO capture was
2
calculated by ideal adsorbed solution theory (IAST).62,63 For CO /CH mixtures with
2
4
general feed compositions of land fill gas (CO /CH = 50/50), the CO /CH
4
2
4
2
selectivities calculated at 1 atm were 29.3 for 1 and 11.0 for 2, respectively (Figure 7).
The notable selectivity for CO over N and CH highlight the potential of 1 and 2
2
2
4
for CO capture after postcombustion and in gas separation processes.
2
According to the adsorption isotherms of CO at 273K and 298K, the adsorption
2
affinity of 1 and 2 for CO could be assessed by the adsorption isotherms(Q )
2
st
−
1
calculated by the adsorption data. (Figure S11). The Q is 35.3 kJ mol for 1 and
st
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1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
−
1
22.8 kJ mol for 2 at zero loading, implying that the possible strong framework−CO
2
interactions might exist, thereby resulting in the apparent selectivity for CO . The Q
2
st
for 1 remains essentially unchanged with the increase of pressure, the Q for 2 slowly
st
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
−
1
decreased remaining up to 8.4 kJ mol at maximum loading. The key factors for high
Q over CO in 1 and 2 as follows: first, CO could be directly extracted by the
st
2
2
uncoordinated N atoms in bpe/bpa through dipole−quadrupole interactions with a
larger quadrupole moment and a higher polarizability value (29.1 × 10−25 cm ) over
−3
−25
−3
−25
−3
CH (25.9 × 10 cm ) and N (17.4 × 10 cm ). Second, the steric hindrance of
4
2
free bpe/bpa crowds the pores of 1 to some degree, strengthening the network−CO2
interactions. Moreover, CO molecules are tightly bound together in small channels,
2
6
4
resulting in CO −CO interactions and providing appropriate contributions to Q .
2
2
st
Catalysis Properties. Based on our particular interest on the synthesis and
application potential of tetrazines and inspiring by their synthetic routes using Lewis
3
7
acids Ni(II)/Zn(II) triflates as catalysts, we try to look for a new effective catalyst,
especially the Ni(II)-MOFs catalyst, to easily prepare tetrazines from nitriles and
hydrazine hydrate, for anhydrous hydrazine is limited commercial availability in
China due to safety concerns. Here in, our first tentative studies are reported.
To explore the catalytic effect of 1−5, the catalytic experiment of 4-cyanopyridine
with hydrazine hydrate for the synthesis of 3,6-di(pyridine-4-yl)-1,2,4,5-tetrazine was
performed. The reaction was conducted by mixing 4-cyanopyridine (1 mmol),
hydrazine hydrate (5 mmol), and the nickel catalysts (2.5 mol%) in ethanol at 78 °C
and stirring the mixture for 24 h. (Table 2, entry 1−6). Remarkably, in the absence of
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catalyst, the products could not be obtained. And it was found that the yields of
tetrazine catalyzed by complex 1−5 are not good (about 15%). For optimizing the
reaction conditions, we therefore selected 2 as the target catalyst. Concentration of the
catalysts and different solvents were screened. When the same reaction was
performed in ethanol at 78 °C at the catalyst 2 loading of 0.5, 1, 1.5, 2 and 2.5
(mol%), the catalyst 2 (0.5 mol%) show superior activity (Table 2, entry 7−11).
Several solvents were also screened for this reaction, and ethanol was seen to be the
best under above-selected reaction conditions (Table 2, entry 12−17). Thus, our
optimized conditions as follows: complex 2 as the catalyst (0.5 mol%) and ethanol as
the solvent, reaction temperature at 78°C. The characterization data for the
3,6-di(pyridine-4-yl)-1,2,4,5-tetrazine are given in the Supporting Information.
Though it was found that the yield of tetrazine catalyzed by complex 1−5 are not good
and similar to the other reported,65−67 the results showed the catalysts role of 1−5. This
tentative study not only provides the possibility that MOFs can catalyze the synthesis
of tetrazine, but also lays a foundation for our further exploration and even hopeful
discovery of efficient MOFs as the catalysts to prepare tetrazine.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
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1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
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4
4
4
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5
5
6
Table 2. Optimization of reaction condition a
NH NH •H O
2
2
2
N N
N N
catalyst
N
CN
N
N
solution T (°C)
b
Entry
Catalyst (mol %)
none
Solution
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
EtOH
Time (h)
24
T (°C)
78
Yield (%)
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
CP1
24
78
16
18
15
14
14
18
19
24
26
26
9
CP2
24
78
CP3
24
78
CP4
24
78
CP5
24
78
CP2 (2.5%)
CP2 (2%)
CP2 (1.5%)
CP2 (1%)
CP2 (0.5%)
CP2
24
78
24
78
24
78
1
0
24
78
11
24
78
1
1
2
3
2
H O
24
Reflux
Reflux
Reflux
Reflux
Reflux
Reflux
CP2
MeOH
24
15
26
17
18
24
14
CP2
EtOH
Toluene
24
1
1
5
6
CP2
24
CP2
DMF
24
17
CP2
Chlorobenzene
24
a
Reaction conditions: 4-cyanopyridine (1 mmol), N H ·H O (5 mmol), catalyst
2
4
2
b
(0.005mmol), solvent (5 mL), 78°C (oil bath) for 24 h. Isolated yield.
Magnetism. The static magnetic moments of polycrystalline sample of 1−5 were
characterized in the temperature range of 2 to 300 K at 1000 Oe. As shown in Figure
S12, complexes 1−5 possess similar curve trends. χ T values are stable at around 20
m
K, after which it then drops sharply to a minimum value at 2.0 K. The decrease at low
temperatures indicates the presence of a (ZFS) zero field splitting on the Ni(II) ions
and/or a weak antiferromagnetic interactions between Ni(II) ions. The susceptibility
3
-1
data obey the Curie−Weiss law with C = 1.23(1) cm K mol , θ = -0.58(1) K for 1, C
3
−1
3
-1
=
1.22(1) cm K mol , θ = -0.88(1) K for 2, C = 1.19(1) cm K mol , θ = -0.50(1) K
3
-1
3
-1
for 3, C = 1.31(1) cm K mol , θ = -1.41(1) K for 4, and C = 1.25(1) cm K mol , θ =
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-1.07(1) K for 5, respectively. Owing to that the Ni(II) ions are well isolated in the
structures, the coupling between Ni(II) ions are neglectable, the magnetic
68
susceptibility measurements were fitted using the program Phi. As described by the
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
2
spin Hamiltonian, Ĥ = DŜ + gμ Ŝ H, where D is the axial ZFS parameter, S is the
z
B z
spin of Ni(II), g is the Lande factor, μ is the Bohr magneton and H is the magnetic
B
−
1
−1
field. The best fitting give D = 6.3(2) cm , and g = 2.21(1) for 1, D = 6.1(2) cm ,
−
1
−1
and g = 2.18(1) for 2, D = 5.2(1) cm , and g = 2.17(1) for 3, D = 9.0(3) cm , and g =
−1
2
.28(1) for 4, and D = 5.3(1) cm , and g = 2.22(1) for 5.
CONCLUSIONS
In summary, under the same experimental environments except various N−donor
ligands, we have successfully synthesized five novel Ni−CPs, ranging from 1D ladder
chains, 2D layers to 3D layered-Pillared structure, suggesting that the coordination
modes of H bitp ligand, structure of N−donor ligand contribute to the final structures.
2
1−5 exhibit enhanced thermostability up to 320 °C and chemical stabilities against
common organic solvents, boiling water, acids and bases relative to most CPs, which
expands their practical application. Furthermore, gas sorption measurements for 1 and
2
display a high absorption selectivity of CO over CH . The catalytic results
2 4
demonstrate that 1−5 can be used as catalysts to synthesize
3,6-di(pyridine-4-yl)-1,2,4,5-tetrazine. The tentative studies put forward the
possibility that coordination polymers as catalysts to prepare tetrazines. The magnetic
analysis of 1−5 indicates the presence of a (ZFS) zero field splitting on the Ni(II)
ions.
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1
1
1
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2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
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4
4
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4
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5
5
5
5
5
5
5
6
ASSOCIATED CONTENT
Supporting Information. Crystallographic data, PXRD patterns, IR spectra,
sorption patterns, magnetic curves and additional synthetic procedure. This material is
available free of charge on the ACS Publications website.
AUTHOR INFORMATION
0
1
2
3
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5
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Corresponding Author
*
(P. Liu): liuping@nwu.edu.cn.
Author Contributions
§H. L. and Y.-F. K. contributed equally.
ACKNOWLEDGMENT
This work was supported by the NSF of China (No. 21673173, 21572177,
1371142, 21531007 and 21501142), the NSF of Shaanxi Province of China (No.
2
2016JZ004 and 2015JZ003), and the Xi'an City Science and Technology Project (No.
2
017085CG/RC048(XBDX004)).
REFERENCES
(1) Zhang, F. M.; Sheng, J. L.; Yang, Z. D.; Sun, X. J.; Tang, H. L.; Lu, M.; Dong,
H.; Shen, F. Cui.; Liu, J.; Lan, Y. Q. Rational Design of MOF/COF Hybrid
Materials for Photocatalytic H Evolution in the Presence of Sacrificial Electron
2
Donors. Angew. Chem. Int. Ed. 2018, 57, 12106-12110.
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7
8
9
(2) Guo, L.; Wang, M.; Cao, D. P. A Novel Zr-MOF as Fluorescence Turn-On
Probe for Real-Time Detecting H S Gas and Fingerprint Identification. Small. 2018,
2
1
4, 1703822.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
(3) Chen, C. H.; Wang, X. S.; Li, L.; Huang, Y. B.; Cao, R. Highly selective sensing
of Fe3+ by an anionic metal–organic framework containing uncoordinated nitrogen
and carboxylate oxygen sites. Dalton Trans. 2018, 47, 3452–3458.
(4) Huang, R. W.; Dong, X. Y.; Yan, B. J.; Du, X. S.; Wei, D. H.; Zang, S. Q.; Mak,
T. Tandem Silver Cluster Isomerism and Mixed Linkers to Modulate the
Photoluminescence of Cluster-Assembled Materials. Angew. Chem. Int. Ed. 2018, 57,
8
560-8566.
(5) Zheng, T.; Yang, Z. X.; Gui, D. X.; Liu, Z. Y.; Wang, X. X.; Dai, X.; Liu, S. T.;
Zhang, L. J.; Gao, Y.; Chen, L. H.; Sheng, D. P.; Wang, Y. L.; Wu, J. D.; Wang, J. Q.;
Zhou, R. H.; Chai, Z. F.; Albrecht-Schmitt, T. E.; Wang, S. A. Overcoming the
crystallization and designability issues in the ultrastable zirconium phosphonate
framework system. Nat. Commun. 2017, 8, 15369.
(6) Liao, P. Q.; Zhou, D. D.; Zhu, A. X.; L. Jiang; Lin, R. B.; Zhang, J. P.; Chen, X.
M. Strong and Dynamic CO Sorption in a Flexible Porous Framework Possessing
2
Guest Chelating Claws. J. Am. Chem. Soc. 2012, 134, 17380.
(7) Song, T. Q.; Dong, J.; Yang, A. F.; Che, X. J.; Gao, H. L.; Cui, J. Z.; Zhao, B.
Wheel-like Ln18 Cluster Organic Frameworks for Magnetic Refrigeration and
Conversion of CO . Inorg. Chem. 2018, 57, 3144-3150.
2
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1
2
3
4
5
6
7
8
9
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
3
3
3
3
3
3
3
3
3
3
4
4
4
4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
5
5
6
(8) Barton, T. J.; Bull, L. M.; Klemperer, W. G.; Loy, D. A.; McEnaney, B.; Misono,
M.; Monson, P. A.; Pez, G.; Scherer, G. W.; Vartuli, J. C.; Yaghi, O. M. Tailored
Porous Materials. Chem. Mater. 1999, 11, 2633.
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
5
6
7
8
9
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1
2
3
4
5
6
7
8
9
0
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2
3
4
5
6
7
8
9
0
(9) Canivet, J.; Fateeva, A.; Guo, Y. M.; Coasne, B.; Farrusseng, D. Water
adsorption in MOFs: fundamentals and applications. Chem. Soc. Rev. 2014, 43, 5594–
5617.
(10) Burtch, N. C.; Jasuja, H.; Walton, K. S. Water Stability and Adsorption in
Metal–Organic Frameworks. Chem. Rev. 2014, 114, 10575–10612.
(11) Montoro, C.; Linares, F.; Procopio, E. Q.; Senkovska, I.; Kaskel, S.; Galli, S.;
Masciocchi, N.; Barea, E.; Navarro, J. A. Capture of Nerve Agents and Mustard Gas
Analogues by Hydrophobic Robust MOF-5 Type Metal–Organic Frameworks. J. Am.
Chem. Soc. 2011, 133, 11888−11891.
(12) Cavka, J. H.; Jakobsen, S.; Olsbye, U.; Guillou, N.; Lamberti, C.; Bordiga, S.;
Lillerud, K. P. A New Zirconium Inorganic Building Brick Forming Metal Organic
Frameworks with Exceptional Stability. J. Am. Chem. Soc. 2008, 130, 13850−13851.
(13) Wang, K.; Lv, X. L.; Feng, D.; Li, J.; Chen, S.; Sun, J.; Song, L.; Xie, Y.; Li, J.
R.; Zhou, H. C. Pyrazolate-Based Porphyrinic Metal–Organic Framework with
Extraordinary Base-Resistance. J. Am. Chem. Soc. 2016, 138, 914−919.
ACS Paragon Plus Environment

Page 29 of 39
Crystal Growth & Design
1
2
3
4
5
6
7
8
9
(14) Chen, H.; Liu, P. X.; Xu, N.; Meng, X.; Wang, H. N.; Zhou, Z. Y. A visible
light-driven photocatalyst of a stable metal–organic framework based on Cu Cl
4
clusters and TIPE spacers. Dalton Trans. 2016, 45, 13477.
1
1
1
1
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
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0
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2
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7
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9
0
(15) Cui, J. H.; Li, Y. Z.; Guo, Z. J.; Zheng, H. G. A porous metal–organic
framework based on Zn O clusters: chemical stability, gas adsorption properties and
6
2
solvatochromic behavior. Chem. Commun. 2013, 49, 555.
(16) Galli, S.; Maspero, A.; Giacobbe, C.; Palmisano, G.; Nardo, L.; Comotti, A.;
Bassanetti, I.; Sozzanic, P.; Masciocchia, N. When long bis(pyrazolates) meet late
transition metals: structure, stability and adsorption of metal–organic frameworks
featuring large parallel channels. J. Mater. Chem. A. 2014, 2, 12208.
(17) Huang, N.; Wang, K.; Drake, H.; Cai, P.; Pang, J.; Li, J.; Che, S.; Huang, L.;
Wang, Q.; Zhou, H. C. Tailor-Made Pyrazolide-Based Metal−Organic Frameworks
for Selective Catalysis. J. Am. Chem. Soc. 2018, 140, 6383−6390.
(18) Wang, M.; Liu, X. B.; Qi, D. D.; Xu, Y. W.; Zhang, L. L.; Liu, X. Q.; Jiang,
J. Z.; Dai, F. N.; Xiao, X.; Sun, D. F. A Zn Metal–Organic Framework with High
Stability and Sorption Selectivity for CO . Inorg. Chem. 2015, 54, 10587−10592.
2
(19) Li, Y. X.; Yang, Z. X.; Wang, Y. L.; Bai, Z. L.; Zheng, T.; Dai, X.; Liu, S. T.;
Gui, D. X.; Liu, W.; Chen, M.; Chen, L. H.; Wu, J. D; Zhu, L. Y.; Zhou, R. H.; Chai,
Z. F.; Albrecht-Schmitt, T. E.; Wang, S. A. A mesoporous cationic thorium-organic
framework that rapidly traps anionic persistent organic pollutants. Nat. Commun.
2
017, 8, 1354.
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