Syntheses, structures and properties of nickel(II) and manganese(II) coordination polymers based on V-shaped bis-imidazole and aromatic carboxylate ligands

Article abstract of DOI:10.1016/j.poly.2016.05.019

Using V-shaped mixed ligands bis-imidazole and aromatic carboxylic acids, five new coordination polymers namely, {[Ni(B-im)(Br-a)Cl]·H₂O}_n (1), {[Ni(B-im)(I-a)(H₂O)₂]·0.5H₂O}_n (2), [Ni(B-im)(I-a)(H₂O)₂]_n (3), [Ni(B-im)(M-a)(H₂O)₂]_n (4) and {[Mn₂(B-im)₂(I-a)₂]·2H₂O}_n (5) [B-im = 1,1′-(5-methyl-1,3-phenylene)bis(1H-imidazole), Br-a = 5-bromonicotinic acid, I-a = isophthalic acid and M-a = 5-methylisophthalic acid] were solvothermally synthesized and fully characterized by IR spectra, element analyses, X-ray powder and single-crystal diffractions, and thermogravimetric analyses. Complexes 1 and 2 feature polymeric macrocyclic chain structures containing interesting nanotubular channels, which are constructed by bridging 30-membered macrocyclic [Ni₃(B-im)₃] subunits with Br-a ligands and by bridging folded 20-membered macrocyclic [Ni₂(B-im)₂] subunits with I-a ligands, respectively. Isomorphic complexes 3 and 4 represent double-chain structures containing folded 18-membered macrocyclic [Ni₂(B-im)(I-a)] subunits and [Ni₂(B-im)(M-a)] subunits, respectively. Complex 5 is a 2D porous coordination polymer containing novel chiral four-stranded Mn(II) chains consisting of two (B-im)-bridged aspiral chiral chains and two (I-a)-bridged heterochiral coaxial 2₁-helical chains. The results of thermal gravimetric analyses suggest that the dehydrated frameworks of 1-5 are stable up to 320 °C. Additionally, the magnetism of complexes 3 and 5 were also investigated.

Full text of DOI:10.1016/j.poly.2016.05.019

Accepted Manuscript
Syntheses, Structures and Properties of Nickel(II) and Manganese(II) Coordi-
nation Polymers Based on V-shaped Bis-imidazole and Aromatic Carboxylate
Ligands
Lu-Lu Lv, Li-Jun Zhang, Hong Zhao, Ben-Lai Wu
PII:
S0277-5387(16)30162-0
DOI:
http://dx.doi.org/10.1016/j.poly.2016.05.019
POLY 11993
Reference:
Polyhedron
To appear in:
Received Date:
Accepted Date:
17 March 2016
9 May 2016
Please cite this article as: L-L. Lv, L-J. Zhang, H. Zhao, B-L. Wu, Syntheses, Structures and Properties of Nickel(II)
and Manganese(II) Coordination Polymers Based on V-shaped Bis-imidazole and Aromatic Carboxylate Ligands,
Polyhedron (2016), doi: http://dx.doi.org/10.1016/j.poly.2016.05.019
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Syntheses, Structures and Properties of Nickel(II) and Manganese(II)
Coordination Polymers Based on V-shaped Bis-imidazole and
Aromatic Carboxylate Ligands
Lu-Lu Lv a, Li-Jun Zhang b, Hong Zhao a, Ben-Lai Wu a,*
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aCollege of Chemistry and Molecular Engineering, Zhengzhou University, Zhengzhou
450052, P. R. China
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bHenan Vocational College of Applied Technology, Zhengzhou 450042, P. R. China
*Corresponding author Tel.: +86 0371 67763675.
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E-mail address: wbl@zzu.edu.cn (B.Wu)
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ABSTRACT
Using V-shaped mixed ligands bis-imidazole and aromatic carboxylic acids, five new
coordination
polymers
namely,
(2),
{[Ni(B-im)(Br-a)Cl]·H2O}n
[Ni(B-im)(I-a)(H2O)2]n
(1),
(3),
=
{[Ni(B-im)(I-a)(H2O)2]·0.5H2O}n
[Ni(B-im)(M-a)(H2O)2]n (4) and {[Mn2(B-im)2(I-a)2]·2H2O}n (5) [B-im
1,1'-(5-methyl-1,3-phenylene)bis(1H-imidazole), Br-a = 5-bromonicotinic acid, I-a =
isophthalic acid and M-a = 5-methylisophthalic acid] were solvothermally synthesized
and fully characterized by IR spectra, element analyses, X-ray powder and
single-crystal diffractions, and thermogravimetric analyses. Complexes 1 and 2
feature polymeric macrocyclic chain structures containing interesting nanotubular
channels, which are constructed by bridging 30-membered macrocyclic [Ni3(B-im)3]
subunits with Br-a ligands and by bridging folded 20-membered macrocyclic
[Ni2(B-im)2] subunits with I-a ligands, respectively. Isomorphic complexes 3 and 4
represent double-chain structures containing folded 18-membered macrocyclic
[Ni2(B-im)(I-a)] subunits and [Ni2(B-im)(M-a)] subunits, respectively. Complex 5 is a
2D porous coordination polymer containing novel chiral four-stranded Mn(II) chains
consisting of two (B-im)-bridged aspiral chiral chains and two (I-a)-bridged
heterochiral coaxial 21-helical chains. The results of thermal gravimetric analyses
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suggest that the dehydrated frameworks of 1−5 are stable up to 320 °C. Additionally,
the magnetism of complexes 3 and 5 were also investigated.
Keywords: Coordination polymer; Crystal structure; V-shaped mixed ligand system;
Metal-organic nanotube; Magnetism
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1. Introduction
Over the last several decades there has been much interest in the area of crystal
engineering of metal-organic frameworks (MOFs) in view of their potential
applications in adsorption [1], photochemical area [2], catalysis [3], and magnetism [4]
as well as their variety of intriguing architectures [5]. As is known to all, the structures
of coordination polymers determine their properties, which has stimulated extensive
study upon the internal structure-function relationship [6]. To get novel structures with
unique performances, much effort has been devoted to controlling the assembled
motifs via selecting suitable organic ligands, metal ions, and building blocks [7–12].
The N-containing heterocyclic ligands are studied most frequently not only due to their
strong coordination ability of nitrogen atoms with most transition metal ions by
coordination bonds, but also due to their rigid skeleton structures and abundant
recognition sites for further assembling into higher-dimensional multifunctional
supramolecular frameworks through hydrogen bonds, π···π stacking and Van der
Waals' force [13, 14]. Besides, ligands including polycarboxylic groups possess strong
coordination ability and diverse coordination models, which makes them being a kind
of popular multifunctional ligands [15].
Although the N-containing heterocyclic ligands and aromatic carboxylic acid
ligands have been studied a lot, systematic investigation upon the collaborative effect
of a mixed ligand system including V-shaped bis-imidazole and aromatic carboxylate
ligands in the fabrication of novel MOFs has been reported a little [16]. In this context,
a V-shaped molecule 1,1'-(5-methyl-1,3-phenylene)bis(1H-imidazole) (B-im) was
choicely selected as the main ligand. The main ligand B-im is a typical angular ditopic
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linker featuring a semi-rigid skeleton with two extrorse bites, and thereby may have a
trend to bridge metal ions into macrocycles or helixes. And meanwhile, V-shaped
aromatic carboxylic acids such as 5-bromonicotinic acid (Br-a), isophthalic acid (I-a)
and 5-methylisophthalic acid (M-a) which have different symmetric structures and
functional groups (see Scheme 1) were introduced as the auxiliary ligands. Through
solvothermal reactions of nickel(II) and manganese(II) salts with above mentioned
V-shaped ligands, respectively, five new MOFs, namely, {[Ni(B-im)(Br-a)Cl]·H2O}n
(1),
{[Ni(B-im)(I-a)(H2O)2]·0.5H2O}n
(2),
[Ni(B-im)(I-a)(H2O)2]n
(3),
[Ni(B-im)(M-a)(H2O)2]n (4) and {[Mn2(B-im)2(I-a)2]·2H2O}n (5) were obtained and
fully characterized by IR spectra, element analyses, X-ray powder and single-crystal
diffractions, and thermogravimetric analyses. Additionally, the magnetic properties for
crystalline compounds 3 and 5 were also investigated.
2. Experimental section
2.1. General information and materials
All chemicals purchased were of reagent grades or better and used without further
purification. Element analyses were performed with a Carlo-Erba 1106 elemental
analyzer. IR spectra (KBr pellets) were recorded on a Nicolet NEXUS 470 FT–IR
spectrophotometer from 400 to 4000 cm−1. Thermal analysis curves were scanned
under air on a STA 409 PC thermal analyzer. The powered X-ray diffraction (PXRD)
patterns of the samples were recorded by a RIGAKU-DMAX2500 X-ray
diffractometer with Cu-Kα radiation. The temperature-dependent magnetic
measurements were determined on a Quantum Design SQUID-XL7 magnetometer.
Diamagnetic corrections were made using Pascal’s constants.
2.2. Syntheses
2.2.1. Synthesis of {[Ni(B-im)(Br-a)Cl]·H2O}n (1)
A mixture of B-im (0.05 mmol, 0.0112 g), Br-a (0.05 mmol, 0.0101 g), NiCl2·6H2O
(0.05 mmol, 0.0119 g), NaOH (0.05 mmol, 0.002 g), CH3OH (4 mL) and H2O (4 mL)
was stirred at room temperature for half an hour, and then sealed into a 25 mL
Teflon-lined stainless autoclave. The autoclave was heated in an oven at 80 °C for 3 d
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and then gradually cooled to room temperature. Green prismatic crystals of 1 were
collected, washed with ethanol, and dried naturally. Yield: 58% (based on Ni).
Selected IR (KBr, cm–1): 3450 (s), 3136 (m), 1608 (s), 1549 (m), 1510 (m), 1441 (m),
1390 (s), 1283 (m), 1127 (m), 1070 (m), 752 (m), 657 (m). Anal. Calcd. for
C19H17BrClN5O3Ni (%): C, 42.46; H, 3.19; N, 13.03. Found (%): C, 42.80; H, 3.18; N,
13.13.
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2.2.2. Synthesis of {[Ni(B-im)(I-a)(H2O)2]·0.5H2O}n (2)
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A procedure identical to that for 1 was followed to prepare green needle crystals 2,
except that Br-a (0.05 mmol, 0.0101 g) and NaOH (0.05 mmol, 0.002 g) were
replaced by I-a (0.05 mmol, 0.0084 g) and NaOH (0.1 mmol, 0.004 g), respectively.
For 2, Yield: 62% (based on Ni). Selected IR (KBr, cm–1): 3442 (s), 3130 (m), 1609 (s),
1509 (s), 1367 (s), 1242 (m), 1110 (m), 1075 (m), 742 (m), 709 (m), 654 (m), 423 (m).
Anal. Calcd. for C21H21N4O6.5Ni (%): C, 51.25; H, 4.30; N, 11.39. Found (%): C,
51.47; H, 4.27; N, 11.31.
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2.2.3. Synthesis of [Ni(B-im)(I-a)(H2O)2]n (3)
A mixture of B-im (0.05 mmol, 0.0112 g), I-a (0.05 mmol, 0.0084 g), NiSO4·6H2O
(0.05 mmol, 0.0131 g), NaOH (0.1 mmol, 0.004 g), CH3OH (1 mL) and H2O (7 mL)
was stirred at room temperature for half an hour, and then sealed into a 25 mL
Teflon-lined stainless autoclave. The autoclave was heated in an oven at 120 °C for 4
d and then gradually cooled to room temperature. Green rod-shaped crystals 3 were
collected, washed with ethanol, and dried naturally. Yield: 78% (based on Ni).
Selected IR (KBr, cm–1): 3455 (m), 3139 (w), 1609 (s), 1509 (s), 1367 (s), 1287 (m),
1247 (m), 1111 (m), 1074 (m), 938 (m), 828 (m), 744 (s), 708 (s), 653 (m), 427 (m).
Calcd. for C21H20N4O6Ni (%): C, 52.21; H, 4.17; N, 11.60. Found (%): C, 51.98; H,
4.15; N, 11.69.
2.2.4. Synthesis of [Ni(B-im)(M-a)(H2O)2]n (4)
A procedure identical to that for 2 was followed to prepare green needle crystals 4,
except that I-a (0.05 mmol, 0.0084 g) was replaced by M-a (0.05 mmol, 0.009 g). For
4, Yield: 43% (based on Ni). Selected IR (KBr, cm–1): 3462 (m), 3147 (m), 3130 (m),
1612 (s), 1539 (s), 1500 (s), 1434 (m), 1363 (s), 1283 (m), 1247 (m), 1108 (m), 1067
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(m), 935 (m), 857 (m), 836 (m), 750 (m), 717 (s), 654 (m). Calcd. for C22H22N4O6Ni
(%): C, 53.21; H, 4.46; N, 11.27. Found (%): C, 53.52; H, 4.58; N, 11.32.
2.2.5. Synthesis of {[Mn2(B-im)2(I-a)2]·2H2O}n (5)
A mixture of B-im (0.05 mmol, 0.0112 g), I-a (0.05 mmol, 0.0084 g), MnCl2 (0.05
mmol, 0.0099 g), NaOH (0.1 mmol, 0.004 g), CH3CN (3 mL) and H2O (5 mL) was
stirred at room temperature for half an hour, and then sealed into a 25 mL Teflon-lined
stainless autoclave. The autoclave was heated in an oven at 110 °C for 4 d and then
gradually cooled to room temperature. Pale yellow block crystals 5 were collected,
washed with CH3CN, and dried naturally. Yield: 63% (based on Mn). Selected IR
(KBr, cm–1): 3423 (s), 3138 (w), 1604 (s), 1545 (s), 1505 (s), 1385 (s), 1239 (m), 1112
(m), 1067 (m), 1025 (m), 933 (m), 815 (m), 755 (s), 710 (m), 651 (m). Calcd. for
C42H36N8O10Mn2(%): C, 54.67; H, 3.93; N, 12.14. Found (%): C, 54.39; H, 3.86; N,
12.09.
2.3. X-ray structure determination
Crystallographic data were collected on an Oxford Xcalibur Gemini diffractometer
with an Eos detector at 293(3) K using Cu Kα radiation (λ = 1.5418 Å) except for 3
using Mo Kα radiation (λ = 0.71073 Å). Raw data collection and reduction were done
using CrysAlisPro software. Empirical absorption correction using spherical
harmonics, implemented in SCALE3 ABSPACK scaling algorithm. Structures were
solved by direct methods and refined by full-matrix least-squares on F2 using
SHELXTL [17]. The non-hydrogen atoms were refined with anisotropic thermal
parameters. The carbon H atoms were included in geometric positions and given
thermal parameters setting to 1.2 × Ueq of the attached atoms. Lattice water H atoms
in 5 were not added owing to their disorder. The other water H atoms in those
compounds were located from different maps and their positions were fixed during
the refinement such that they remained in chemically meaningful positions. Crystal
data are summarized in detail in Table 1 while the selected bond lengths and bond
angles are listed in Table 2.
3. Results and discussion
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3.1. Syntheses and IR spectra
Compounds 1‒5 were solvothermally prepared at a lower temperature range of
80–120 °C using mixed solvents of H2O and CH3OH for 1‒4 and mixed solvents of
H2O and CH3CN for 5. The total solvent volume in all the reactions was controlled in
8 mL while the ratios of two mixed solvents were carefully adjusted to fit the initial
syntheses of the exhibited compounds perfectly. In all the reactions the equivalent
amount of NaOH was added for the full deprotonation of the aromatic carboxylic
acids used.
In the IR spectra of 1–5, the broad absorptions around 3420–3462 cm–1 are ascribed
to O–H stretching vibration of water molecule, and the weaker absorptions around
3136–3156 cm–1 are characteristic stretching vibration of C–H in aromatic rings.
There is no strong absorption peak around 1700 cm−1 for the –COOH stretch,
implying that the carboxylic groups in all the compounds are completely deprotonated.
Characteristic bands of carboxylates for asymmetric stretches [νas(COO–)] are at 1608
cm−1 for 1, 1609 cm−1 for 2 and 3, 1612 cm−1 for 4, and 1545 and 1604 cm−1 for 5.
Characteristic bands of carboxylates for symmetric stretches [νs(COO–)] appear at
1390 cm−1 for 1, 1367 cm−1 for 2 and 3, 1363 cm−1 for 4, and 1365 cm−1 for 5. The
obviously different values of ∆ν = νas(COO–) − νas(COO–) suggest the different
coordination environment of the carboxylates in 1–5 [18]. Notably, the values of ∆ν
for 2–4 are similar and lager (in a range from 242 to 249 cm−1), suggesting a
unidentate coordination mode of carboxylates in each complex. As for 5, the splitting
of νas(COO–) indicates the different coordination environment of carboxylates. In
conclusion, the IR data are good agreement with the X-ray analyses.
3.2. Crystal Structures
Compound 1 crystallizes in the hexagonal P63mc space group with a Flack
parameter of 0.03(3). The asymmetrical unit of 1 consists of one-half Ni, one-half
B-im, one-half Br-a, one-half Cl−, and one-half free water molecule. As shown in Fig.
1, the central Ni atom adopts a distorted octahedral geometry ligated by one terminal
Cl atom, two O atoms from the chelating carboxyl group of one Br-a ligand and three
nitrogen atoms from two B-im ligands and another Br-a ligand (The Ni−Cl bond is
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2.356(2) Å while the Ni−N and Ni−O bonds range from 2.084(3) to 2.225(4) Å).
In 1, three V-shaped B-im ligands bridge three Ni nodes into a 30-membered
macrocyclic [Ni3(B-im)3] subunit (SBU). In the SBU, the three Ni nodes are coplanar
and uniformly separated by 9.7025(9) Å. Owing to the obvious distortion of the
methylbenzene groups in the B-im ligands from the Ni3 plane, the SBU looks like a
plate where three free water molecules are located through complicated C−H···O and
O−H···Cl hydrogen-bonding interactions (C9···O3 = 3.447(7) Å, O3···Cl1 = 3.305(3)
Å; see Fig. 2a). Intriguingly, three Br-a ligands pillared adjacent SBUs through
carboxyl O atoms chelating the Ni centers in one SBU and pyridyl N atoms
coordinating the Ni centers in the other, and thereby forming a novel 1D polymeric
metal-organic nanotube 1 with the diameter of the opening being about 12 Å (see Fig.
2b). In the nanotube the distance between the adjacent Ni3 planes of [Ni3(B-im)3]
SBUs separated by pillars Br-a is 7.739(1) Å. The nanotube has C3v symmetry, and
extends along c-axis. In comparison with the limited 1D polymeric metal-organic
nanotubes being reported so far, the 1D nanotubular structure with the higher
symmetry in 1 is particularly rare [19]. In 1 those 1D nanotubes array parallelly, and
every nanotube interdigitates with three adjacent nanotubes through the mutual
insertion of B-im ligands into the tubular cavities (see Fig. S1). Clearly, this deep
insertion of B-im ligands reduces the effective free volume of the nanotubes.
Complex 2 crystallizes in the orthorhombic Imcm space group, and its
asymmetrical unit consists of one-half Ni, one-half B-im, one-half I-a, two one-half
coordinated water molecules, and a quarter of lattice water molecule. The Ni atom is
six-coordinated by two nitrogen atoms (N1 and N1A) from two B-im, two oxygen
atoms (O1 and O1A) from two I-a, and two oxygen atoms (O3 and O4) from two
coordinated water molecules, and thus forming a slightly distorted octahedron
geometry with N1, N1A, O1 and O1A in the equatorial plane and O3 and O4 at axial
positions (Fig. 3a). A mirror plane m containing the O3 and O4 divides the
coordination geometry into two equivalent parts. The Ni−N and Ni−O bonds range
from 2.085(2) to 2.118(3) Å.
In 2, two B-im ligands link two Ni ions into a folded 20-membered macrocyclic
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[Ni2(B-im)2] SBU which is also halved by the mirror plane m containing the O3 and
O4 (Fig. 3b). Each SBU is bonded by four I-a ligands, and those SBUs are further
interconnected by the I-a ligands through the monodentate bridging of their two
carboxyl groups forming a zigzag polymeric chain in which all the SBUs cap the up
and down vertices of the zigzag (Fig. 4a). In particular, the chain structure of 2
consists of another kind of greater 36-membered macrocycle [Ni4(B-im)2(I-a)2]
formed by two I-a ligands bridging two macrocyclic [Ni2(B-im)2] SBUs. In the
resulting 36-membered macrocycle [Ni4(B-im)2(I-a)2] the four Ni centers are
completely coplanar and form a rectangle with the length and width being 10.979 and
9.025 Å, respectively, and the dihedral angle between the two adjacent Ni4 planes
being 115.68° (Fig. 4a). Interestingly, when viewed along the a-axis, the chain
exhibits an oval or quadrangular pore which extends along the chain so that the chain
can be thought as a metal-organic polymeric nanotube (Fig. 4b). Indeed, the nanotube
2 is irregular in comparison with the nanotube 1. The dimensions of the nanotube
approximate to the sizes of the rectangle of the Ni4.
In 2, every coordination water molecule O3 forms three intrachain hydrogen bonds:
As a donor hydrogen-bonding two the uncoordinated carboxyl O2 (O3···O2 = 2.654(2)
Å), as an acceptor capturing the lattice water molecule O5 in the larger oval pore
[Ni4(B-im)2(I-a)2] (O5···O3 = 2.947(4) Å). Additionally, every coordination water
molecule O4 forms two interchain hydrogen bonds with the coordinated carboxyl O1
(O4···O1D = 2.741(3) Å, D = x,–y+1/2,–z+3/2), through which extends those
nanotubes into a 3D supramolecular architecture (Fig. 5). Notably, those zigzag
polymeric chains interdigitate along b-axis with their 20-membered macrocyclic
[Ni2(B-im)2] SBUs inserting into adjacent nanotubes, in which there are obviously
interchain π···π interactions between benzene rings of B-im (centroid-to-centroid
distance = 3.771(2) Å, Fig. S2). Such stacking sharply reduces the effective free
volume of the nanotubes.
As adjusted the reaction conditions of 2, i.e., changing the ratio of water and
methanol and the reaction temperature from 1:1 and 80 °C to 1:7 and 120 °C, or
followed the same reaction procedure for 2 only using M-a instead of I-a, isomorphic
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complexes 3 and 4 were obtained, respectively. For terseness only the structure of 4 is
discussed in detail. The coordination environment around Ni in 3 is given in Fig. S3.
Complex 4 crystallized in the orthorhombic Pnma space group. The asymmetric
unit of 4 contains one-half Ni, one-half B-im ligand, one-half M-a ligand and one
coordinated water molecule. The six-coordinated Ni atom located at an inversion
center i is in a slightly distorted octahedron geometry ligated by two nitrogen atoms
(N1 and N1A) from two B-im and two oxygen atoms (O1 and O1A) from two Ma2– in
the equatorial plane, and by two oxygen atoms (O3 and O3A) from two terminal
water molecules at axial positions (Fig. 6). The Ni−N bonds are 2.076(2) Å while
Ni−O bonds cover a range of 2.074(1)–2.121(1) Å. In 4 two Ni ions are bonded by a
B-im bridge and a M-a bridge to form another folded 18-membered macrocyclic
[Ni(B-im)(M-a)] SBU which is halved by a mirror plane m perpendicular to the
straight line connecting the two Ni atoms. Those SBUs are further interconnected
through sharing common metal nodes, and thereby resulting in the 1D
double-stranded chain architecture in 4 (Fig. 6). Every chain further interacts with
adjacent chains through π···π interactions between the benzene rings of B-im from
adjacent chains (centroid-to-centroid distance = 3.681(2) Å) and C−H···π interactions
occurring from the methyls of M-a and B-im to the benzene rings of the M-a ligands
in adjacent chains (C-to-centroid distances being 3.456(4) and 3.407(3) Å,
respectively), and in this way to produce a 3D supramolecular framework in 4 (Fig.
S4).
Complex 5 crystallizes in the orthorhombic Pna21 space group with a Flack
parameter of 0.484(8). The asymmetrical unit of 5 consists of two Mn, two B-im, two
I-a and two free water molecules. In 5, the two crystallographically independent Mn1
and Mn2 centers adopt five-coordinated patterns, and are located in distorted trigonal
bipyramid geometries with three carboxyl O atoms from two different I-a forming the
equatorial plane and two N atoms occupying the vertex positions (Fig. 7). The Mn−N
and Mn−O bonds cover a normal range from 2.034(5)–2.263(5) Å [20].
Complex 5 features a 2D porous coordination polymer containing novel chiral
four-stranded Mn(II) chains consisting of two (B-im)-bridged aspiral chiral chains and
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two (I-a)-bridged heterochiral coaxial 21-helical chains (Fig. 8). In 5, deprotonated I-a
ligands have two coordination modes: One half as bis-monodentate bridges like those
found in 2 and 3, and the other half as four-connected bridges in a µ4-kO:kO′:kO′′:kO′′′
coordination mode. Every four-connected I-a uses its every carboxyl group bridging
the crystallographically independent Mn1 and Mn2, and in this way it results in a
double-stranded chain structure containing two (I-a)-bridged heterochiral coaxial
21-helical chains [namely, −(Mn1)−(I-a)−(Mn1)− and −(Mn2)−(I-a)−(Mn2)− helixes]
along c-axis with the 21 helical pitches being 19.1087(3) Å (Fig. 8a). Along the
double-stranded chain structure, the crystallographically independent Mn1 and Mn2
are also linked by B-im ligands into two almost parallel (B-im)-bridged aspiral chiral
chains, and thereby forming the novel chiral four-stranded Mn(II) chain (Fig. 8a).
Those four-stranded Mn(II) chains are further connected by the bis-monodentate
bridges I-a to form the 2D polymer 5. In crystal structure, those 2D layers pack up
along b-axis through the interdigitation of B-im between adjacent layers (Fig. S5).
3.3. Thermogravimetric analysis (TGA) and Powder X-ray diffraction (PXRD)
To evaluate the thermal stability of compounds 1−5, their thermal gravimetric
analyses were carried out under air atmosphere with a heating rate of 10 °C min−1 and
the results are given in Fig. S6. For complex 1, the dehydration process occurred from
room temperature to 167 °C with a weight loss of 2.61% corresponding to the
removal of the lattice water molecules (calcd 3.35%), and then a successive mass loss
occurred from 362 to 700 °C, indicating the complete decomposition of the compound.
As for the resulting residue of 14.67%, it is presumed to be NiO (calcd 13.90%). For 2,
the slow dehydration process occurred from room temperature to 232 °C with a
weight loss of 8.28% corresponding to the release of the lattice and coordinated water
molecules (calcd 9.15%), and then a successive sharp mass loss followed up to 350 °C.
The remaining residue of 16.00% is considered to be NiO (calcd 15.18%). Below
100 °C the isostructural compounds 3 and 4 are stable. The dehydration processes
occurred at 124−224 °C for 3 with a weight loss of 7.32 (calcd 7.46%) and at
107−159°C for 4 with a weight loss of 6.35 (calcd7.25%). The dehydrated
frameworks of 3 and 4 are stable up to 354°C and 392 °C, respectively. For compound
10

298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
5, the dehydration process occurred at 57–147 °C with a weight loss of 4.18%
corresponding to the removal of the lattice water molecules (calcd 3.90%), and then a
successive mass loss occurred from 320 to 520 °C, indicating the complete
decomposition of the dehydrated framework of 5. As for the resulting residue of
19.50%, it is presumed to be MnO2 (calcd18.84%).
Apart from the thermal stability, the phase purity of the prepared crystal materials
1−5 were determined by powered X-ray diffraction (PXRD) measurements, and the
experimental and simulated PXRD patterns of those compounds are shown in Figs.
S7−S11. The calculated PXRD patterns from the single-crystal X-ray diffraction data
are in agreement with the observed ones, indicating the phase purity of those
synthesized crystalline products. The differences in intensity may be due to the
preferred orientation of the powder samples.
3.3. Magnetic Properties
Compounds based on carboxylate-bridged paramagnetic metal ions usually display
interesting magnetism [21], and thus the temperature-dependent magnetic
susceptibilities (χM) of polycrystalline samples 3 and 5 were measured at a field of
1000 G in the temperature range of 2–300 K, respectively. The corresponding graphs
of χM vs T and χMT vs T are shown in Figs. 9−10. For 3, the χMT of 1.29 cm3 mol−1 K
per Ni(II) at room temperature is higher than the expected spin-only value of 1.00cm3
mol−1 K per Ni(II) (S =1, g = 2), revealing a significant orbital contribution which
always causes zero-field splitting. The linear decrease of the χMT, from room
temperature dawn to ca 50 K, is strange and seems to be the signature of a TIP
contribution. Upon cooling, the χMT values gradually decrease to 1.23 cm3 mol−1 K at
22 K. As the temperature is lowered the χMT values slightly increase to 1.24 cm3
mol−1 K at 9 K, and then abruptly decrease to 1.11 cm3 mol−1 K at 2 K. By eliminating
the TIP contribution, the data rather suggest a ferromagnetic coupling of the Ni(II)
ions. The magnetic behavior of 3 can be explained by large zero-field splitting, as
well as a weak ferromagnetic interaction under the molecular field approximation.
The best fit of eqn. (1) to the data was achieved with g = 2.14, D/k = 6.74 K, θ = 0.82,
TIP = 121 × 10−5 and R = 1.1 × 10−6 (R = ∑(χobsd-χcacld)2/∑χobsd2).
11

2Ng2β 2 2kT / D − 2kT exp
(
1 + 2exp − D/ kT
− D/ kT
)
/ D + exp(− D/ kT
)


328
(1)
xM
=
+ TIP



(
)
3k(T −θ )

329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
For 5, the χMT of 4.32 cm3 mol−1 K per Mn(II) at room temperature is similar to the
expected spin-only value of 4.38 cm3 mol−1 K per Mn(II) (S =5/2, g = 2). Upon
cooling, the χMT values decrease slowly from 300 to 25K, and quickly decrease to the
minimum 1.86 cm3 mol−1 K at 2 K. This phenomenon is typical for antiferromagnetic
interactions. Besides, the 1/χM vs T plot follows the Curie–Weiss law with a negative
Weiss constant (θ = −2.38 K; Fig. S12), indicating weakly antiferromagnetic
interactions between Mn(II) ions.
3. Conclusion
In summary, we have solvothermally synthesized five new nickel(II) and
manganese(II) MOFs with the mixed V-shaped ligands bis-imidazole and aromatic
carboxylates. In particular, the assemblies of transition metal nickel(II) with the mixed
V-shaped B-im and Br-a or I-a contribute to the formation of novel metal-organic
polymeric nanotubes owing to the interestingly sorted-recognition and hierarchical
assembly between nickel(II) ions and the V-shaped ligands bis-imidazole B-im and
carboxylates Br-a or I-a through coordination interactions. In addition, the structure
architectures of those MOFs are obviously influenced by reaction conditions, and
especially by the auxiliary aromatic carboxylates ligands used. The results of thermal
gravimetric analyses suggest that the dehydrated frameworks of 1−5 are stable up to
320 °C.
Appendix A. Supplementary material
CCDC 1465489−1465493 contains the supplementary crystallographic data for 1–5,
respectively.
These
data
can be obtained
or
free of
from the
charge
via
http://www.ccdc.cam.ac.uk/conts/retrieving.html,
Cambridge
Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: +44
1223-336-033; or e-mail: deposit@ccdc.cam.ac.uk. Other supporting information
contains Figs. S1−S12.
12

357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
Acknowledgements
We gratefully acknowledge financial support from the National Natural Science
Foundation of China (21271157), and the Foundation and Research in Cutting-Edge
Technologies in the Project of Henan Province (122300410092).
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14

417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
Captions for the Scheme and Figures:
Scheme 1. Schematic representation of the selected V-shaped bis-imidazole and aromatic
carboxylic acid ligands.
Fig. 1. Coordination environment of Ni(II) atom in 1. Symmetry codes: A = x, x−y, z; B = 1−y, x−y,
z, C = x, y, z+1; E = 1−y, 1−x, z.
Fig. 2. (a) 30-membered macrocyclic [Ni3(B-im)3] SBU in 1, showing the intricate interactions
between the SBU and the captured water molecule. (b) View of the 1D polymeric metal-organic
nanotube 1.
Fig. 3. (a) Coordination environment of Ni(II) atom in 2. (b) View of 20-membered macrocyclic
[Ni2(B-im)2] SBU in 2. Symmetry codes: A = −x+3/2, y, z.
Fig. 4. (a) 1D zigzag polymeric chain with the macrocyclic [Ni2(B-im)2] SBUs capping the up and
down vertices, showing greater 36-membered macrocycle [Ni4(B-im)2(I-a)2] formed by two I-a
ligands bridging two macrocyclic [[Ni2(B-im)2] SBUs. (b) View of the nanotube extending along
a-axis in 2.
Fig. 5. View of 3D supramolecular network in 2 formed by interchain hydrogen bonds, with the
coordinated and lattice water molecules O3 and O5 being omitted for clarity.
Fig. 6. View of double-strand chain in 4 with hydrogen atoms being omitted for clarity, showing
the coordination environment of Ni(II) and 18-membered macrocyclic [Ni2(B-im)(M-a)] SBU.
Symmetry codes: A = 2−x, 1−y, 1−z; B = x, 3/2−y, z, C = 2−x, y−1/2, 1−z.
Fig. 7. Coordination environment of Mn(II) in 5. Symmetry codes: A = x−1, y, z.
Fig. 8. (a) View of novel chiral four-stranded Mn(II) chain consisting of two (B-im)-bridged
aspiral chiral chains and two (I-a)-bridged heterochiral coaxial 21-helical chains. (b) 2D porous
polymeric structure in 5.
−)
Fig. 9. χM (■) and χMT (○) vs T with the theoretical fit ( for 3.
Fig. 10. χM (■) and χMT (○) vs T for 5.
15

447
448
449
Table 1
Crystal date and structure refinement for complexes 1−5.
Compounds
Formula
T / K
1
2
3
4
5
C19H17BrClN5NiO3 C21H21N4NO6.5
C21H20N4NiO6 C21H20N4NiO6 C42H36Mn2N8O10
293(2) 293(2) 293(2)
Orthorhombic Orthorhombic Orthorhombic
293(2)
Hexagonal
P63mc
21.9372(4)
21.9372(4)
7.7390(1)
90
293(2)
Orthorhombic
Imcm
Crystal system
Space group
a / Å
Pnma
6.7623(2)
17.4552(6)
17.3632(7)
90
Pnma
6.8518(2)
17.3501(5)
17.4764(5)
90
Pna21
14.4770(2)
15.4690(3)
19.1087(3)
90
18.5892(4)
8.8087(2)
27.4440(7)
90
b / Å
c / Å
α / °
β / °
90
90
90
90
90
γ / °
120
90
90
90
90
V / Å3
3225.36(9)
6
4493.9(2)
8
2049.5(1)
4
2077.6(1)
4
4279.3(1)
4
Z
Dc / g cm‒3
GOF
1.660
1.455
1.566
1.589
1.432
1.146
1.067
1.020
1.096
1.061
R1
0.0374
0.0950
0.0483
0.1389
0.0346
0.0792
0.0355
0.0904
0.0548
0.1449
wR2 (I>2σ (I))
Largest
diff. 0.563
1.120
0.260
0.325
1.162
peak and hole
−0.341
−0.294
−0.348
−0.394
−0.354
450
451
452
453
454
455
456
16

457
458
Table 2
Selected bond distances (Å) and angles (°) for complexes 1−5.
1
Ni1−N2
2.084(3)
2.102(4)
175.7(2)
88.1(1)
90.0(1)
61.6(1)
99.7(1)
Ni1−N2A
2.084(3)
2.225(4)
89.0(1)
88.1(1)
90.0(1)
92.05(9)
167.6(1)
Ni1−N1
Ni1−Cl1
2.086(5)
2.356(2)
89.0(1)
Ni1−O1C
Ni1−O2C
−Ni1−N1
N2
N2A−Ni1−N2
N2A−Ni1−O1C
N2A−Ni1−O2C
O1C−Ni1−O2C
N1−Ni1−Cl1
N2A−Ni1−N1
−Ni1−O
N2
1C
N1−Ni1−O1C 92.7(2)
N1−Ni1−O2C 154.3(2)
N2−Ni1−O2C
N2A−Ni1−Cl1
O1C−Ni1−Cl1
N2−Ni1−Cl1
92.1(1)
O2C−Ni1−Cl1 106.0(1)
2
Ni1−O1
2.085(2)
2.087(2)
89.3(1)
Ni1−O1A
Ni1−O4
2.085(2)
2.088(3)
177.34(9)
177.34(9)
86.64(8)
91.28(8)
91.30(8)
Ni1−N1
Ni1−O3
2.087(2)
2.118(3)
Ni1−N1A
O1−Ni1−O1A
O1−Ni1−N1A
O1−Ni1−O4
N1A−Ni1−O4
N1−Ni1−O3
O1−Ni1−N1
O1A−Ni1−N1 91.31(8)
N1−Ni1−N1A 88.0(1)
91.31(8)
86.64(8)
90.80(9)
91.30(8)
O1A−Ni1−N1A
O1A−Ni1−O4
O1−Ni1−O3
N1A−Ni1−O3
3
N1−Ni1−O4
90.80(9)
O1A−Ni1−O3 91.28(7)
O4−Ni1−O3
177.1(1)
Ni1−N1A
2.067(2)
2.086(2)
180.0
Ni1−N1
2.067(2)
2.121(2)
90.76(7)
90.76(7)
90.00(7)
90.01(7)
92.41(6)
Ni1−O3
2.086(2)
2.121(2)
89.24(7)
Ni1−O3A
Ni1−O1
Ni1−O1A
N1−Ni1−O3
N1A−Ni1−N1
N1A−Ni1−O3A
N1A−Ni1−O1
O3A−NA−O1
O3−Ni1−O1A
N1A−Ni1−O3
N1−Ni1−O3A
N1−Ni1−O1
N1A−Ni1−O1A
O3A−Ni1−O1A
4
89.24(7)
89.99(7)
87.59(6)
87.59(6)
O3−Ni1−O3A 180.0
O3−Ni1−O1
92.41(6)
N1−Ni1−O1A 89.99(7)
O1−Ni1−O1A 180.0
Ni1−O3A
Ni1−N1A
2.074(2)
2.076(2)
Ni1−O3
2.074(2)
2.121(1)
Ni1−N1
Ni1−O1
2.076(2)
2.121(1)
Ni1−O1A
17

O3A−Ni1−O3
O3A−Ni1−N1A
O3A−Ni1−O1A
N1A−Ni1−O1A
N1−Ni1−O1
180.0
O3A−Ni1−N1
O3−Ni1−N1A
O3−Ni1−O1A
O3A−Ni1−O1
N1A−Ni1−O1
89.06(7)
89.06(7)
88.46(6)
88.46(6)
90.54(7)
O3−Ni1−N1
90.94(7)
90.94(7)
91.54(6)
89.46(7)
89.46(7)
N1−Ni1−N1A 180.0
N1−Ni1−O1A 90.54(7)
O3−Ni1−O1
91.54(6)
O1A−Ni1−O1 180.0
5
Mn1−O8A
Mn1−N1
2.034(5)
2.240(5)
2.196(4)
2.221(5)
Mn1−O4B
Mn1−N5
2.100(4)
2.263(5)
2.203(5)
Mn1−O1
Mn2−O5
Mn2−O2
2.186(4)
2.181(5)
2.204(5)
Mn2−O3B
Mn2−N4B
Mn2−N8C
O8A−Mn1−O4B 118.8(3)
O8A−Mn1−O1
O4B−Mn1−N1
O4B−Mn1−N5
O5−Mn2−O3B
O5−Mn2−O2
109.6(3)
85.0(2)
89.9(2)
141.3(2)
96.7(2)
87.9(2)
85.8(2)
O4B−Mn1−O1 131.3(2)
O8A−Mn1−N1
O8A−Mn1−N5
N1−Mn1−N5
95.1(2)
85.3(2)
174.4(2)
O1−Mn1−N1
O1−Mn1−N5
85.6(2)
99.5(2)
O5−Mn2−N8C 89.3(2)
O3C−Mn2−O2 120.9(2)
O3B−Mn2−N4B 86.3(2)
O3B−Mn2−N8C 100.7(2)
N8C−Mn2−O2 86.9(2)
N8C−Mn2−N4B 171.8(2)
O5−Mn2−N4B
O2−Mn2−N4B
Symmetry codes: A = x, x−y, z; B = 1−y, x−y, z, C = x, y, z+1; E = 1−y, 1−x, z for 1. A = −x+3/2, y, z
for 2. A = 2−x, 1−y, 1−z for 3. A = 2−x, 1−y, 1−z for 4. A = x−1, y, z; B = 1−x, 1−y, z−1/2, C = 1−x,
1−y, z+1/2 for 5.
459
460
461
462
463
464
Scheme 1. Schematic representation of the selected V-shaped bis-imidazole and aromatic
carboxylic acid ligands.
18

465
466
467
468
469
470
471
472
473
474
Fig. 1. Coordination environment of Ni(II) atom in 1. Symmetry codes: A = x, x−y, z; B = 1−y, x−y,
z, C = x, y, z+1; E = 1−y, 1−x, z.
a
b
475
476
477
478
479
480
Fig. 2. (a) 30-membered macrocyclic [Ni3(B-im)3] SBU in 1, showing the intricate interactions
between the SBU and the captured water molecule. (b) View of the 1D polymeric metal-organic
nanotube 1.
19

481
a
b
482
483
484
485
486
Fig. 3. (a) Coordination environment of Ni(II) atom in 2. (b) View of 20-membered macrocyclic
[Ni2(B-im)2] SBU in 2. Symmetry codes: A = −x+3/2, y, z.
487
488
Fig. 4. (a) 1D zigzag polymeric chain with the macrocyclic [Ni2(B-im)2] SBUs capping the up and
down vertices, showing greater 36-membered macrocycle [Ni4(B-im)2(I-a)2] formed by two I-a
ligands bridging two macrocyclic [[Ni2(B-im)2] SBUs. (b) View of the nanotube extending along
a-axis in 2.
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Fig. 5. View of 3D supramolecular network in 2 formed by interchain hydrogen bonds, with the
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coordinated and lattice water molecules O3 and O5 being omitted for clarity.
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Fig. 6. View of double-strand chain in 4 with hydrogen atoms being omitted for clarity, showing
the coordination environment of Ni(II) and 18-membered macrocyclic [Ni2(B-im)(M-a)] SBU.
Symmetry codes: A = 2−x, 1−y, 1−z; B = x, 3/2−y, z, C = 2−x, y−1/2, 1−z.
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Fig. 7. Coordination environment of Mn(II) in 5. Symmetry codes: A = x−1, y, z.
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b
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Fig. 8. (a) View of novel chiral four-stranded Mn(II) chain consisting of two (B-im)-bridged
aspiral chiral chains and two (I-a)-bridged heterochiral coaxial 21-helical chains. (b) 2D porous
polymeric structure in 5. Symmetry codes: B = 1−x, 1−y, z−1/2; C = 1−x, 1−y, z+1/2; D = x, y, z−1;
E = 1−x, 1−y, z−3/2.
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Fig. 9. χM (■) and χMT (○) vs T with the theoretical fit (─) for 3.
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Fig. 10. χM (■) and χMT (○) vs T for 5.
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Table of Contents Graphic
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Synopsis
Syntheses, Structures and Properties of Nickel(II) and Manganese(II)
Coordination Polymers Based on V-shaped Bis-imidazole and
Aromatic Carboxylate Ligands
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Lu-Lu Lv a, Li-Jun Zhangb, Hong Zhao a, Ben-Lai Wu a,*
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A serial of Ni(II) and Mn(II) coordination polymers based on V-shaped mixed ligands
bis-imidazole and aromatic carboxylic acids were solvothermally synthesized and
fully characterized. Intriguingly, sorted-recognition and hierarchical assembly
between Ni(II) and mixed ligands result in novel nanotubes.
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Research Highlights
> Ni(II) and Mn(II) MOFs based on V-shaped mixed ligands are synthesized.
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> Sorted-recognition and hierarchical assembly between Ni(II) and mixed ligands result in novel
nanotubes.
> Those MOFs are obviously influenced by auxiliary V-shaped carboxylates ligands.
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