Syntheses, structures, and properties of two new Co(II) coordination frameworks based on R-isophthalate (R =-CH3 or-OCH3) and two flexible bis(imidazol) coligands

Article abstract of DOI:10.1080/15533174.2012.751418

Two new coordination polymers, {[Co(CH₃-ip)(1,4-bib)]· 2H₂O}_n (1) and {[Co(CH₃O-ip)(1,6-bih)]} _n (2) (CH₃-H₂ip = 5-methylisophthalic acid, CH₃O-H₂ip = 5-methoxyisophthalic acid, 1,4-bib = 1, 4-bis(imidazol-1-yl)butane, 1,6-bih = 1,6-bis(imidazol-1-yl)hexane), have been obtained under hydrothermal conditions. Complexes 1 and 2 were determined by single-crystal X-ray diffraction analysis and further characterized by elemental analysis and IR spectroscopy. Complex 1 shows a two-dimensional (2D) corrugated layer containing left and right-handed helical chains. Compound 2 exhibits a 2-fold parallel interpenetrated 2D → 2D net. Furthermore, thermogravimetric properties of 1 and 2 were also investigated. Supplemental materials are available for this article. Go to the publisher's online edition of Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry to view the supplemental file.

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Syntheses, Structures, and Properties of Two
New Co(II) Coordination Frameworks Based on R-
Isophthalate (R = –CH3 or –OCH3) and Two Flexible
Bis(imidazol) Coligands
Xin-Hong Chang a , Xiao-Jie Wu a & Na Chai a
a College of Chemistry and Chemical Engineering , Luoyang Normal University , Luoyang , P.
R. China
Published online: 02 May 2013.
To cite this article: Xin-Hong Chang , Xiao-Jie Wu & Na Chai (2013) Syntheses, Structures, and Properties of Two New Co(II)
Coordination Frameworks Based on R-Isophthalate (R = –CH3 or –OCH3) and Two Flexible Bis(imidazol) Coligands, Synthesis and
Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:8, 952-956, DOI: 10.1080/15533174.2012.751418
To link to this article: http://dx.doi.org/10.1080/15533174.2012.751418
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Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry, 43:952–956, 2013
Copyright ꢀ Taylor & Francis Group, LLC
C
ISSN: 1553-3174 print / 1553-3182 online
DOI: 10.1080/15533174.2012.751418
Syntheses, Structures, and Properties of Two New
Co(II) Coordination Frameworks Based on R-Isophthalate
(R = –CH3 or –OCH3) and Two Flexible Bis(imidazol)
Coligands
Xin-Hong Chang, Xiao-Jie Wu, and Na Chai
College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang, P. R. China
to metal salt ratio, template, metal ion, pH value, and coun-
teranion.[12–17] In the assembly process of MOFs, the rational
choice and reasonable use of the characteristic ligand are very
important in the construction of the desired MOFs.
Two new coordination polymers, {[Co(CH3-ip)(1,4-bib)]·
2H2O}n (1) and {[Co(CH3O-ip)(1,6-bih)]}n (2) (CH3-H2ip = 5-
methylisophthalic acid, CH3O-H2ip = 5-methoxyisophthalic acid,
1,4-bib = 1, 4-bis(imidazol-1-yl)butane, 1,6-bih = 1,6-bis(imidazol-
1-yl)hexane), have been obtained under hydrothermal conditions.
Complexes 1and 2were determined by single-crystal X-ray diffrac-
tion analysis and further characterized by elemental analysis and
IR spectroscopy. Complex 1 shows a two-dimensional (2D) corru-
gated layer containing left and right-handed helical chains. Com-
pound 2 exhibits a 2-fold parallel interpenetrated 2D → 2D net.
Furthermore, thermogravimetric properties of 1 and 2 were also
investigated.
Aromatic polycarboxylates have been to date the most popu-
lar choice of connecting ligands for the construction of divalent
metal coordination polymers, wherein the geometric disposition
of the carboxylate ligands and their numerous possible binding
modes play a crucial role in structure direction, in tandem
with coordination geometry preferences.[18–21] In this context,
5-methylisophthalate (CH3-ip) and 5-methoxyisophthalate
(CH3O-ip) can bridge metal cations while providing the struc-
tural integrity and required charge balance for formation of a
stable neutral crystalline framework. Diverse structural topolo-
gies are observed in these systems, depending on the coordina-
tion environment preferences at the metal ions, the geometric
orientation of the carboxylate groups on the aromatic ring, and
the inclusion of any dipodal nitrogen-base tethering ligands.
Recently we have successfully obtained a series of coordi-
nation polymers with the CH3O-H2ip and CH3-H2ip ligands, as
well as bis(imidazole)-type coligands.[22–24] With the aim of fur-
ther understanding the coordination chemistry of these ligands
and preparing new materials with interesting structural motifs
and physical properties. We report herein the binding of CH3-
H2ip, CH3O-H2ip ligands, and bis(imidazole)-type coligands to
Co(II) centers to afford two different 2D structures.
Supplemental materials are available for this article. Go to the
publisher’s online edition of Synthesis and Reactivity in Inorganic,
Metal-Organic, and Nano-Metal Chemistry to view the supplemen-
tal file.
Keywords 5-methylisophthalic acid, 5-methoxyisophthalic acid,
1, 4-bis(imidazol-1-yl)butane, 1, 6-bis(imidazol-1-yl)
hexane, Co(II) complexes, crystal structures
INTRODUCTION
In the field of crystal engineering, the design and synthesis
of metal-organic frameworks (MOFs) have attracted upsurging
research interest not only on their intriguing structural diversity
but also on their potential applications in molecular adsorp-
tion, separation processes, gas storage, ion exchange, catalysis,
sensor technology, and so on.[1–11] All aspects of this research
hotspot have been deeply discussed by some recent reviews,
which show that the diverse structures of such materials are al-
ways dependent on many factors, such as substituent and num-
ber of coordination sites provided by organic ligands, ligand
EXPERIMENTAL
Materials and Physical Measurements
All commercially available solvents and chemicals were
of analytical grade. Elemental analyses for carbon, hydrogen,
and nitrogen atoms were performed on a Vario EL III el-
emental analyzer (Elementar, Germany). The infrared spec-
tra (4000–400 cm−1) were recorded by using KBr pellet
on an AvatarTM 360 E.S.P. IR spectrometer (Madison, WI,
USA). The crystal was determined on a Bruker SMARTAPEX
IICCD diffractometer (Madison, WI, USA) equipped with a
graphitemonochromatized MoKα radiation (λ = 0.71073 Å).
Received 27 August 2012; accepted 16 November 2012.
This work was supported financially by a key scientific and techno-
logical project of Henan Provincial Department of Science and Tech-
nology (No. 112102310640).
Address correspondence to Xin-Hong Chang, College of Chem-
istry and Chemical Engineering, Luoyang Normal University, Luoyang
471022, P. R. China. E-mail: fromchang@yahoo.com.cn
952

TWO NEW CO(II) COORDINATION FRAMEWORKS
953
TABLE 1
Crystallographic data for 1 and 2
Thermogravimetric analyses were measured on a STA449C in-
tegration thermal analyzer (Netzsch, Germany).
Empirical formula C19 H24 Co N4 O6 C21 H24 Co N4 O5
Synthesis of {[Co(CH3-ip)(1,4-bib)]·2H2O}n (1)
Formula weight
Temperature (K)
Crystal system
Space group
463.35
296(2)
Monoclinic
P2(1)/n
471.37
296(2)
Triclinic
¯
P1
Complex 1 was prepared under the hydrothermal conditions.
A mixture of CH3-H2ip (17.7 mg, 0.1 mmol), 1,4-bib (19.0 mg,
0.1 mmol), and Co(OAc)2·4H2O (24.9 mg, 0.1 mmol) in dis-
tilled water (8 mL) were placed in a Teflon-lined stainless steel
vessel, heated to 120◦C for three days, and then cooled to room
temperature over 48 h. Red block crystals of 1 were collected
by filtration, washed with water, and dried in air. Yield: 47%
based on Co. IR (KBr, cm−1): 3408 m, 3130 s, 1617 s, 1558 m,
1443 m, 1339 s, 1241 s, 1103 s, 1000 m, 950 s, 831 m, 795 m,
775 s, 729 s. Anal. Calcd. (%) for C19H24CoN4O6: C, 49.25; H,
5.22; N, 12.09. Found (%): C, 48.72; H, 5.04; N, 12.32.
Unit cell dimensions
a = 7.6441(7) Å
a = 9.830(2) Å
b = 18.1243(17) Å b = 10.117(2) Å
c = 16.7284(16) Å c = 11.463(3) Å
α = 94.147(2)◦
β = 93.5890(10)◦ β = 101.236(2)◦
γ = 105.715(2)◦
Volume, Z
2313.1(4), 4
1066.9(4), 2
1.467
Calculated density 1.331
Synthesis of {[Co(CH3O-ip)(1,6-bih)]}n (2)
(Mg/m3)
2 was synthesized in the similar way as that described for
1, except that CH3-H2ip and 1,4-bib were replaced by CH3O-
H2ip (19.2 mg, 0.1 mmol) and 1,6-bih (22.1 mg, 0.1 mmol),
respectively. Yield: 42% based on Co. IR (KBr, cm−1): 3111 s,
2926 m, 1624 s, 1583 m, 1543 m, 1455 s, 1369 s, 1319 s, 1262 s,
1110 s, 1049 s, 943 s, 916 s, 830 s, 788 s m, 720 s. Anal. Calcd.
(%) for C21H24CoN4O5: C, 53.51; H, 5.13; N, 11.89. Found
(%): C, 53.65; H, 5.04; N, 11.75.
F(000)
964
490
Crystal size (mm3) 0.41 × 0.35 × 0.25 0.25 × 0.21 × 0.19
θ range for data
collection (◦)
Reflections
collected
2.25 ∼ 25.50
2.53 ∼ 25.50
17180
8068
Independent
reflections
Final R indices
[I > 2σ(I)]
R indices (all data) R1 = 0.0994,
wR2 = 0.2089
4304
3914
(Rint = 0.0737)
R1 = 0.0663,
wR2 = 0.1915
(Rint = 0.0286)
R1 = 0.0453,
wR2 = 0.1244
R1 = 0.0517,
wR2 = 0.1311
Crystallographic Data Collection and Structures
Determination
Single-crystal X-ray diffraction analysis of the complex
was carried out on a Bruker SMART APEX II CCD diffrac-
tometer (Madison, WI, USA) equipped with a graphite-
monochromatized MoKα radiation (λ = 0.71073 Å) by using
the φ/ω scan technique at room temperature. The structure was
solved by direct methods with SHELXS-97.[25] The hydrogen
atoms were assigned with common isotropic displacement fac-
tors and included in the final refinement by use of geometrical
restrains. The final agreement factor values are R1 = 0.0663,
wR2 = 0.1915 for 1 and R1 = 0.0453, wR2 = 0.1244 for 2,
respectively. Table 1 shows crystallographic crystal data of the
complexes 1 and 2. Moreover, selected bond lengths and angles
are listed in Tables 2 and 3.
forming a distorted CoN2O2 tetrahedron. Co-O bond lengths are
1.969(3) (Co1-O2) and 1.990(3) Å (Co1-O3A), and Co-N bond
distances are 2.006(4) (Co1-N3) and 2.020(4) Å (Co1-N1B).
Both the two carboxylic groups of each CH3-ip ligand adopt
the same μ1-η1:η0 coordination modes to bridge adjacent Co(II)
ions to give a wavelike 1D chain (Figure 1), which are further
linked together through additional Co-N bonds by 1,4-bip lig-
ands to form a 2D corrugated layer (Figure 1). In the 2D layer,
the 1,4-bip ligand links neighboring Co(II) ions to form a left-
and right-handed helical chain (Figure 1), the opposite chirality
helical chains arrange alternately along the c-axis.
RESULTS AND DISCUSSION
Crystal Structure Description
{[Co(CH3-ip)(1,4-bib)]·2H2O}n, (1)
{[Co(CH3O-ip)(1,6-bih)]}n (2)
Single-crystal X-ray diffraction measurement reveals that
Single-crystal X-ray diffraction measurement reveals that
¯
complex 1 crystallizes in the monoclinic system with P21/n complex 2 crystallizes in the triclinic system with P1 space
space group. The asymmetric unit consists of one Co(II) ion, group. There are one Co(II) ion, one CH3O-ip anion and one
one CH3-ip, one 1,4-bip ligand, as well as two lattice water 1,6-bih ligand in the asymmetric unit of 2. As illustrated in Fig-
molecules. As shown in Figure 1, each Co(II) center is sur- ure 2, the Co(II) ion adopts a tetrahedral coordination geometry,
rounded by two nitrogen atoms (N1B and N3, Symmetry codes: coordinating to two carboxylic O atoms from two CH3O-ip an-
(B) –x – 1/2, y + 1/2, –z + 3/2) from two different 1,4-bip ions (Co(1)-O(1) = 1.9931(19) and Co(1)-O(4)A = 1.9807(18)
ligands, and two carboxylic oxygen atoms (O2 and O3A, Sym- Å) and two N atoms from two 1,6-bih ligands (Co(1)-N(1) =
metry codes: (A) x – 1/2, –y + 5/2, z – 1/2) from two CH3-ip, 2.010(2) and Co(1)-N(3) = 2.028(2) Å).

954
X.-H. CHANG ET AL.
TABLE 2
Selected bond lengths (Å) and bond angles (◦) for 1
Bond
(Å)
Bond
(Å)
Co(1)-O(2)
Co(1)-N(3)
1.969(3)
2.006(4)
Co(1)-O(3)#1
Co(1)-N(1)#2
1.990(3)
2.020(4)
Angle
(◦)
Angle
(◦)
O(2)-Co(1)-O(3)#1
O(3)#1-Co(1)-N(3)
O(3)#1-Co(1)-N(1)#2
107.96(15)
124.27(15)
107.28(15)
O(2)-Co(1)-N(3)
O(2)-Co(1)-N(1)#2
N(3)-Co(1)-N(1)#2
107.17(15)
96.86(15)
109.85(16)
Symmetry code used to generate equivalent atoms: #1: x – 1/2, –y + 5/2, z – 1/2; #2: –x – 1/2, y + 1/2, –z + 3/2.
TABLE 3
Selected bond lengths (Å) and bond angles (◦) for 2
Bond
(Å)
Bond
(Å)
Co(1)-O(4)#1
Co(1)-N(1)
1.9807(18)
2.010(2)
Co(1)-O(1)
Co(1)-N(3)
1.9931(19)
2.028(2)
Angle
(◦)
Angle
(◦)
O(4)#1-Co(1)-O(1)
O(1)-Co(1)-N(1)
O(1)-Co(1)-N(3)
97.72(8)
113.99(9)
110.85(9)
O(4)#1-Co(1)-N(1)
O(4)#1-Co(1)-N(3)
N(1)-Co(1)-N(3)
101.57(9)
115.96(9)
115.25(10)
Symmetry code used to generate equivalent atoms: #1: x, y + 1, z.
FIG. 1. (a) Coordination environment of Co(II) ion in 1. The hydrogen atoms are omitted for clarity. Symmetry codes: A: x – 1/2, –y + 5/2, z – 1/2; B: –x – 1/2,
y + 1/2, –z + 3/2. (b) The 1D chain constructed by CH3-ip anions and Co(II) atoms along the c-axis. (c) 2D layer of 1. (d) View of left- and right-handed helical
chains. The CH3-ip groups are omitted for clarity.

TWO NEW CO(II) COORDINATION FRAMEWORKS
955
FIG. 2. (a) Coordination environment of Co(II) ion in 2. The hydrogen atoms are omitted for clarity. Symmetry codes: A: x, y + 1, z. (b) The 1D chain constructed
by CH3O-ip anions and Co(II) atoms along the b-axis. (c) 2D layer of 2. (d) A schematic view of the 2-fold interpenetrating in 2.
FIG. 3. TGA plots of (a) 1 and (b) 2.
Similar to 1, the two carboxylate groups of CH3O-ip in 2 begins to decompose. 2 shows no weight loss at low tempera-
also exhibit the same μ1–η1:η0 coordination modes, linking ture because it has no solvent molecules in the framework. The
the Co(II) centers together to form a 1D polymeric chain compound degrades at about 269◦C.
(Figure 2), which are further extended by exo-bidentate 1,6-bih
spacers to produce a 2D (4,4) corrugated layer (Figure 2). Then
a pair of identical 2D single nets is interlocked with each other
CONCLUSIONS
Assembly of Co(II) salt with 5-methylisophthalic acid (CH3-
H2ip), 5-methoxyisophthalic acid (CH3O-H2ip) and two ratio-
to form a 2-fold parallel interpenetrated 2D → 2D architecture
(Figure 2).
nally selected bidentate N-donor ligands, results in the formation
of two coordination polymers with a 2D layer structure contain-
Thermogravimetric Analysis
ing left and right-handed helical chains (1), a 2-fold parallel in-
terpenetrating 2D → 2D network (2). The successful isolation of
the two new complexes not only further enriches the coordina-
tion chemistry of these ligands, but also illustrates that both the
dicarboxylate ligands and the flexibility of the bis(imidazole)
ligands play an important role in governing the final structures
of 1 and 2. Further studies based on these ligands are underway
in our laboratory and will be reported in due course.
The thermal behavior of 1 and 2 were examined by TGA in
Figure 3. The experiment were performed on samples consisting
of numerous single crystals of 1 and 2 under N2 atmosphere with
a heating rate of 10◦C min−1. For 1, the first weight loss is ob-
served from 70 to 115◦C corresponding to the release of the free
water molecules (calcd. 7.8%, exp. 7.6%). No further weight
loss was observed until 391◦C at which point the compound

956
X.-H. CHANG ET AL.
13. Yamada, T.; Iwakiri, S.; Hara, T.; Kanaizuka, K.; Kurmoo, M.; Kitagawa,
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