Copper(ii) and cobalt(ii) complexes based on bis-benzimidazolyl ligand with 1,2-bis(2′-ethoxy)phenyl linker: Synthesis, crystal structure and conformations

Article abstract of DOI:10.1039/c3ce40957k

Seven Cu(ii) and Co(ii) complexes [Co(L)₂(H₂O) ₂]Cl₂ (1), [Cu(L)Cl₂]₂ (2), [Cu(L)(NO₃)₂]₂ (3), [Cu(L)(SO ₄)]₂ (4), [Co(L)(L_A

Full text of DOI:10.1039/c3ce40957k

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Copper(II) and cobalt(II) complexes based on
bis-benzimidazolyl ligand with 1,2-bis(2′-ethoxy)phenyl
linker: synthesis, crystal structure and conformations†
Cite this: CrystEngComm, 2014, 16,
1950
*
Qing-Xiang Liu, Yue Bi, Xiao-Jun Zhao, Zhi-Xiang Zhao, Jian-Hua Wang
and Xiu-Guang Wang
Seven Cu(II) and Co(II) complexes [Co(L)2(H2O)2]Cl2 (1), [Cu(L)Cl2]2 (2), [Cu(L)(NO3)2]2 (3), [Cu(L)(SO4)]2 (4),
[Co(L)(LA)]n (5), [Cu(L)(OAc)2] (6) and [Co(L)Cl2] (7) (L = 1,2-bis(2′-ethoxy)phenyl-bis(benzimidazole),
LA = terephthalate) have been prepared by means of self-assembly of Cu(II) or Co(II) salts with
bis-benzimidazolyl chelate ligand L and a 1,2-bis(2′-ethoxy)phenyl linker. These complexes are structurally
characterized by X-ray diffraction analyses. In complexes 1–4, two 15-membered macrometallocycles of
each molecule are linked together via sharing moieties (the sharing moieties: Co(II) atom for 1, two bridging
chlorine atoms for 2, two bridging nitrate groups for 3 and two bridging sulfate groups for 4) to afford a
dimer, in which each 15-membered macrometallocycle is constructed from one ligand L and one metal
atom (Co(II) for
1 and Cu(II) for 2–4). In complex 5, a 1D polymeric chain with 15-membered
macrometallocycles is formed via ligand L, terephthalate and a Co(II) atom. In complexes 6 and 7, each
molecule contains a 15-membered macrometallocycle formed by one ligand L and one metal atom (Cu(II)
for 6 and Co(II) for 7). In the crystal packings of 1–7, 2D supramolecular layers or 3D supramolecular frameworks
are formed via intermolecular weak interactions, including hydrogen bonds, π–π interactions and C–H⋯π
contacts. The conformations of the metal complexes based on ligand L are described. Additionally, the
fluorescence emission spectra of ligand L and the metal complexes 1–7, and the magnetic properties for
complexes 1–7 are reported.
Received 30th May 2013,
Accepted 28th November 2013
DOI: 10.1039/c3ce40957k
www.rsc.org/crystengcomm
with novel structures and interesting properties have been
reported.5 This type of ligand can coordinate with most transi-
Introduction
The rational design and synthesis of metal–organic frameworks
(MOFs) have received great research interest not only due
to their versatile intriguing architectures and topologies, but
also due to their potential applications in optics, magnetism,
porosity and biological modelling materials.1,2 The construc-
tion of molecular architectures depends mostly on the combi-
nation of several factors, such as the coordination geometry of
the metal ions, the nature of the organic ligands and counterions,
and the ratio between the metal salts and the ligands.3 Some
structures of MOFs may be predicted and controlled by the
use of organic ligands and the choice of metal salts.4 Among
the organic ligands, benzimidazole derivatives as ligands have
attracted much attention, and a large number of complexes
tion metals via the nitrogen atoms from the benzimidazole
rings because nitrogen donor atoms are a very common binding
site for metal ions.6,7 Additionally, some bis-benzimidazolyl
ligands have also been reported. In these ligands, a pair of
benzimidazole moieties are connected by a bridging linker,
such as aryl, picolyl, alkyl or ether chain.8 Some cyclic metal
complexes from these ligands have been prepared, and they
may have potential applications in organic reactions or mole-
cular recognition.9 As building blocks in constructing porous
complexes, some organic acids or diacids (like acetic acid and
terephthalic acid) along with bis-benzimidazole compounds as
mixed ligands can build up architectures of various sizes and
shapes. Our group has reported the coordination behavior of
bis-benzimidazolyl (or bis-imidazolyl) ligands bearing oligoether link-
ers or alkanyl linkers with metal ions, and some interesting coor-
dination architectures with variable cavities or channels have been
obtained.10 As a continuation, we report herein the preparation of
the ligand 1,2-bis(2′-ethoxy)phenyl-bis(benzimidazole) (L), as well as
the preparation, structures, fluorescence emission spectra and mag-
netic properties of its seven metal complexes [Co(L)2(H2O)2]Cl2 (1),
Tianjin Key Laboratory of Structure and Performance for Functional Molecules;
Key Laboratory of Inorganic-Organic Hybrid Functional Material Chemistry,
Ministry of Education; College of Chemistry, Tianjin Normal University,
Tianjin 300387, China. E-mail: tjnulqx@163.com
† Electronic supplementary information (ESI) available. CCDC 941767–941773.
For ESI and crystallographic data in CIF or other electronic format see DOI:
10.1039/c3ce40957k
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diffraction were grown by slowly evaporating their solvent at
room temperature. Complexes 1–7 are stable and can retain
their structural integrity at room temperature in solvent for
one month. The crystals of the complexes were left on the
bench for one week, and they still looked same. Moreover,
they still suit the needs of X-ray diffraction.
Scheme 1 The structures of the ligand (L) and terephthalic acid (H2LA).
Structures of complexes 1–7
In complexes 1–4 (Fig. 1(a)–4(a)), two 15-membered macro-
metallocycles of each molecule are linked together via sharing
moieties (the sharing moieties: Co(II) atom for 1, two bridging
chlorine atoms for 2, two bridging nitrate groups for 3 and two
bridging sulfate groups for 4) to afford a dimer, in which each
15-membered macrometallocycle is constructed from one metal
atom (Co(II) for 1 and Cu(II) for 2–4) and one bis-benzimidazolyl
chelate ligand L with a 1,2-bis(2′-ethoxy)phenyl linker. In the
dimers 2–4, an inversion center exists in each molecule. The
Cu⋯Cu separation is 3.404(0) Å for 2, 4.932(8) Å for 3 and
4.278(3) Å for 4, and these values show that weak Cu⋯Cu
interactions exist for 2, but there are no Cu⋯Cu interactions
for 3 and 4 (the van der Waals radii of Cu is 1.90 Å). In the same
ligand of 2–4, the dihedral angles between two benzimidazole
rings are 86.8(8)° for 2, 53.9(2)° for 3 and 81.2(3)° for 4, and the
dihedral angles between the benzene ring and two benzimidazole
rings are 85.6(2)° and 86.0(2)° for 2, 60.2(2)° and 73.4(2)° for 3,
and 58.7(1)°and 84.2(4)° for 4.
Analysis of the crystal structure of 1 shows that each Co(II)
is surrounded by four nitrogen donors from two bidentate
chelate ligands L and two oxygen donors from two water mole-
cules to afford an octahedral geometry (Fig. 1(a)). The axial
positions of the octahedron are occupied by N(1) and O(3A)
with axial distances of 2.144(3) Å and 2.171(3) Å, and with a
N(1)–Co(1)–O(3A) angle of 171.7(0)°. Four atoms, N(1A), N(4),
N(4A) and O(3), lie in the equatorial plane with a Co(1)–O(3)
bond distance of 2.171(3) Å and Co–N bond distances of
2.144(3)–2.169(3) Å. The N–Co–N and N–Co–O bond angles
are from 87.1(2)° to 171.3(8)° and from 84.8(7)° to 171.7(0)°,
respectively. The O(3)–Co(1)–O(3A) bond angle is 84.1(4)°.
These values are comparable with analogous values in other
Co(II) complexes.11 In the same ligand, the dihedral angles
between the benzene ring and two benzimidazole rings are
89.8(6)° and 78.6(6)°, respectively. Two benzene rings in two
ligands are approximately parallel with a dihedral angle of 4.4(5)°.
Four benzimidazole rings around the Co(II) center form dihedral
angles of 18.8(4)–60.6(8)°.
[Cu(L)Cl2]2 (2), [Cu(L)(NO3)2]2 (3), [Cu(L)(SO4)]2 (4), [Co(L)(LA)]n (5),
[Cu(L)(OAc)2] (6) and [Co(L)Cl2] (7) (LA = terephthalate). Addi-
tionally, the conformations of the metal complexes based on
ligand L are described (Scheme 1).
Results and discussion
Synthesis and characterization of ligand L and complexes 1–7
The ligand L was prepared as shown in Scheme 2. Catechol,
as a starting material, was reacted with 2-chloroethanol in
the presence of NaOH in an anhydrous ethanol solution
to afford 1,2-bis(1′-hydroxy-2′-ethoxy)benzene, and then
1,2-bis(1′-hydroxy-2′-ethoxy)benzene was reacted with thionyl
chloride in the presence of pyridine in a chloroform solu-
tion to form 1,2-bis(1′-chloro-2′-ethoxy)benzene. Lastly, the
1,2-bis(1′-chloro-2′-ethoxy)benzene was reacted with benzimidazole
in the presence of KOH and tetrabutyl ammonium bromide
(TBAB) in a CH3CN solution to afford the bidentate ligand
1,2-bis(2′-ethoxy)phenyl-bis(benzimidazole) (L). The ligand L is
soluble in common organic solvents (such as CH3OH, DMSO
and DMF), and therefore, crystallization of its complexes with
inorganic metal salts occurs readily.
Complex 1 was prepared via the reaction of ligand L with
CoCl2·2H2O in a Teflon-lined stainless steel container in a
mixed solvent of DMF–CH3OH–H2O at 110 °C. Complexes 2–4,
6 and 7 were prepared via the reaction of ligand L with metal
salts (CuCl2·2H2O for 2, Cu(NO3)2·3H2O for 3, CuSO4·5H2O for
4, Cu(OAc)2·H2O for 6 and CoCl2·2H2O for 7) in DMF–CH3OH.
Complex 5 was prepared via the reaction of ligand L and
terephthalic acid (H2LA) with Co(NO3)2·6H2O in the presence of
Et3N in DMF–CH3OH–H2O. Crystals of 1–7 suitable for X-ray
In complex 2 (Fig. 2(a)), each penta-coordinated Cu(II) center
adopts a distorted pentagonal dipyramidal geometry formed
by three chlorine donors and two nitrogen donors from two
benzimidazole rings. In the pentagonal dipyramid, the axial
positions are occupied by N(1) and Cl(1A) with axial distances
of 2.009(2) Å and 2.323(3) Å, and with a N(1)–Cu(1)–Cl(1A)
angle of 172.3(1)°. Three atoms, N(3), Cl(1) and Cl(2), lie in the
equatorial plane. The Cu–Cl bond distances are in the range
of 2.266(9)–2.650(7) Å, and the Cu(1)–N(1) bond distance is
2.009(2) Å. Among the four chlorine atoms of the molecule,
Scheme 2 Preparation of the dibenzimidazolyl chelate ligand L.
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Fig.
2
(a) Perspective view of
2
and anisotropic displacement
parameters depicting 50% probability. Selected bond lengths (Å) and
angles (°): Cu(1)–N(1) 2.009(2), Cu(1)–N(3) 1.999(2), Cu(1)–Cl(1) 2.650(7),
Cu(1)–Cl(2) 2.266(9); N(1)–Cu(1)–N(3) 86.8(7), N(3)–Cu(1)–Cl(2) 161.3(7),
Cl(1)–Cu(1)–Cl(2) 104.1(4), Cl(2)–Cu(1)–Cl(1A)i 91.9(1), Cu(1)–Cl(1)–Cu(1A)i
86.1(0), Cl(1)–Cu(1)–Cl(1A)i 93.9(0). Symmetry code: i = 2 − x, 1 − y, −z.
(b) 2D supramolecular layer of 2 formed via C–H⋯Cl hydrogen bonds.
(c) 3D supramolecular architecture of 2 formed via C–H⋯Cl hydrogen
bonds and C–H⋯π contacts. All the hydrogen atoms (except those
participating in the C–H⋯Cl hydrogen bonds for (b) and those
participating in the C–H⋯Cl hydrogen bonds and C–H⋯π contacts for
(c)) were omitted for clarity.
Fig. 1 (a) Perspective view of 1 and anisotropic displacement parameters
depicting 50% probability. Selected bond lengths (Å) and angles (°):
Co(1)–N(1) 2.144(3), Co(1)–N(4) 2.169(3), Co(1)–O(3)i 2.171(3); N(1)–Co(1)–N(4)
99.0(1), N(1)–Co(1)–N(4A)i 87.1(2), N(1)–Co(1)–N(1A)i 89.9(1), N(4)–Co(1)–N(4A)i
171.3(8), O(3)–Co(1)–O(3A)i 84.1(4), O(3)–Co(1)–N(1) 93.5(1), O(3)–Co(1)–N(4)
84.8(7), O(3)–Co(1)–N(1A)i 171.7(0). Symmetry code: i = 1 − x, y, 1.5 − z.
(b) 2D supramolecular architecture of 1 formed via π–π interactions and
C–H⋯π contacts. (c) 3D supramolecular architecture of 1 formed via
π–π interactions and C–H⋯π contacts. All the hydrogen atoms (except those
in two water molecules for (a) and those participating in the C–H⋯π
contacts for (b) and (c)) were omitted for clarity.
N(1)–Cu(1)–Cl(1), N(1)–Cu(1)–N(3), Cl(1)–Cu(1)–Cl(2) and
Cl(2)–Cu(1)–Cl(1A) bond angles are 161.3(7)°, 91.3(6)°, 86.8(7)°,
104.1(4)° and 91.9(1)°, respectively. These values are similar to those
of some known Cu(II) complexes.12 The dihedral angles between
the quadrangle Cu(1)–Cl(1)–Cu(1A)–Cl(1A) and two benzimidazole
rings from the same ligand are 16.7(6)° and 86.8(8)°, respectively.
two are bridging chlorine atoms (Cl(1) and Cl(1A)) and the
other two are terminal chlorine atoms (Cl(2) and Cl(2A)). Four
coplanar atoms Cu(1)–Cl(1)–Cu(1A)–Cl(1A) form a quadrangle,
and the Cl(1)–Cu(1)–Cl(1A) and Cu(1)–Cl(1)–Cu(1A) bond angles
are 93.9(0)° and 86.1(0)°, respectively. The N(3)–Cu(1)–Cl(2),
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Fig. 4 (a) Perspective view of 4 and anisotropic displacement parameters
depicting 50% probability. Selected bond lengths (Å) and angles (°):
Cu(1)–N(1) 1.964(5), Cu(1)–N(4) 1.962(6), Cu(1)–O(3) 1.979(5), Cu(1)–O(4)
2.009(5), Cu(1)–O(5A)i 2.232(6); N(1)–Cu(1)–N(4) 92.1(3), N(4)–Cu(1)–O(5A)i
90.4(3), O(3)–Cu(1)–N(4) 160.2(3). Symmetry code: i = −x, 1 − y, 1 − z.
(b) 2D supramolecular layer of 4 formed via π–π interactions and
C–H⋯π contacts. (c) 3D supramolecular layer of 4 formed via π–π
interactions, C–H⋯π contacts and C–H⋯O hydrogen bonds. All the
hydrogen atoms (except those participating in the C–H⋯π contacts
for (b) and those participating in the C–H⋯O hydrogen bonds and
C–H⋯π contacts for (c)) were omitted for clarity.
Fig. 3 (a) Perspective view of 3 and anisotropic displacement parameters
depicting 50% probability. Selected bond lengths (Å) and angles (°):
Cu(1)–N(1) 2.002(1), Cu(1)–N(4) 1.967(8), Cu(1)–O(3) 1.988(4), Cu(1)–O(6)
2.022(9), Cu(1)–O(8A)i 2.376(8); N(1)–Cu(1)–N(4) 94.0(6), N(1)–Cu(1)–O(3)
89.1(6), N(1)–Cu(1)–O(6) 169.2(4), N(1)–Cu(1)–O(8A)i 85.5(4), O(3)–Cu(1)–O(6)
92.6(9), O(3)–Cu(1)–O(8A)i 103.2(7), O(6)–Cu(1)–O(8A)i 83.7(2). Symmetry
code: i = 1 − x, 1 − y, 1 − z. (b) 2D supramolecular layer of 3 formed
via π–π interactions. (c) 3D supramolecular architecture of 3 formed via
π–π interactions and C–H⋯O hydrogen bonds. All the hydrogen atoms
(except those participating in the C–H⋯O hydrogen bonds for (c)) were
omitted for clarity.
In the two bridging nitrate groups, two oxygen atoms from
each nitrate group are connected to two different Cu(II) atoms,
respectively (the bond distances of Cu(1)–O(6) and Cu(1)–O(8A)
being 2.022(9) Å and 2.376(8) Å, respectively), and the third
oxygen atom is uncoordinated. In the two chelate nitrate groups,
two oxygen atoms from each nitrate group are chelated to one
Cu(II) atom (the bond distance of Cu(1)–O(3) is 1.988(4) Å),
and the third oxygen atom is uncoordinated. Two bridging
nitrate groups and two Cu(II) atoms form an eight-membered
ring, in which the two bridging nitrate groups are parallel. The
Cu(1)–N(1) and Cu(1)–N(4) bond distances are 2.002(1) Å and
1.967(8) Å, respectively. The N(1)–Cu(1)–N(4) bond angle is 94.0(6)°.
The N–Cu–O bond angles are in the range of 85.5(4)–169.2(4)°,
and the O–Cu–O bond angles are from 83.7(2)° to 103.2(7)°.
In complex 3, each Cu(II) atom is hexa-coordinated with four
oxygen donors from three nitrate groups and two nitrogen
donors from two benzimidazole rings to adopt a distorted
octahedral geometry. Interestingly, four nitrate groups in the
molecule are divided into two sets (one set being bridging
nitrate groups, and another set being chelate nitrate groups).
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These values are comparable with analogous values in complex
2 and other Cu(II) complexes.13
As shown in Fig. 4(a), the penta-coordinated Cu(II) atom of
complex 4 adopts a distorted pentagonal dipyramidal geometry
formed by three oxygen donors from two sulfate groups and
two nitrogen donors from two benzimidazole rings. The axial
positions of the pentagonal dipyramid are occupied by N(4)
and O(3) with axial distances of 1.962(6) Å and 1.979(5) Å, and
with a N(4)–Cu(1)–O(3) angle of 160.2(3)°. Three atoms, N(1),
O(4) and O(5A), lie in the equatorial plane. Among the four
oxygen atoms of each sulfate group, two oxygen atoms are
chelated to one Cu(II) atom, the third oxygen atom is bound to
another Cu(II) atom, and the fourth oxygen atom is uncoordinated.
Two sulfate groups and two Cu(II) atoms form an eight-membered
ring, in which the two planes of Cu(1)–O(3)–S(1)–O(4) and
Cu(1A)–O(3A)–S(1A)–O(4A) are parallel. The Cu(1)–N(1), Cu(1)–O(4)
and Cu(1)–O(5A) bond distances are 1.964(5) Å, 2.009(5) Å and
2.232(6) Å, respectively. The N(1)–Cu(1)–O(4), N(1)–Cu(1)–O(5A),
O(4)–Cu(1)–O(5A) and N(1)–Cu(1)–N(4) bond angles are 159.0(3)°,
96.0(3)°, 103.1(2)° and 92.1(3)°. These values are similar to
those of known Cu(II) complexes containing sulfate groups.14
Analysis of the crystal structure of 5 shows that a 1D poly-
meric chain is formed via ligand L, terephthalate LA and Co(II)
atoms (Fig. 5(a)). The hexa-coordinated Co(II) center adopts a
distorted octahedral geometry formed by four oxygen donors
from two terephthalates, and two nitrogen donors from two
benzimidazole rings. The axial positions of the octahedron are
occupied by N(1) and O(4) with axial distances of 2.085(2) Å and
2.261(2) Å. The axial position is distorted with an N(1)–Co(1)–O(4)
angle of 165.2(9)° and four atoms, N(4), O(3), O(5) and O(6),
lie in the equatorial plane. The Co–O distances are from 2.082(2) Å
to 2.256(2) Å, and the Co(1)–N(1) distance is 2.085(2) Å. The of
N(4)–Co(1)–O(3), O(3)–Co(1)–O(5) and N(1)–Co(1)–N(4) bond
angles are 107.4(8)°, 97.4(2)° and 94.3(9)°, respectively. These
values are similar to those of complex 1 and other known
Co(II) complexes.11 The neighboring Co⋯Co separation is
10.745(5) Å and the neighboring Co⋯Co⋯Co angle is 113.9(8)°.
Interval benzene rings from the terephthalate molecules in the
polymeric chain are parallel to each other, respectively. In each
flank of the polymeric chain, two benzimidazole rings from each
ligand and the corresponding benzimidazole rings of the other
ligands are parallel, respectively. In both flanks of the polymeric
chain, all the benzene rings from the diethoxyphenyl groups
are parallel to each other.
Fig. 5 (a) Perspective view of 5 and anisotropic displacement parameters
depicting 50% probability. Selected bond lengths (Å) and angles (°):
Co(1)–N(1) 2.085(2), Co(1)–N(4) 2.059(2), Co(1)–O(3) 2.082(2), Co(1)–O(4)
2.261(2); N(1)–Co(1)–N(4) 94.3(9), N(1)–Co(1)–O(4) 165.2(9), N(4)–Co(1)–O(3)
107.4(8), O(3)–Co(1)–O(5) 97.4(2), N(1)–Co(1)–O(5) 96.3(2). (b) 2D
supramolecular architecture of 5 formed via C–H⋯π contacts. (c) 3D
supramolecular architecture of 5 formed via C–H⋯O hydrogen bonds
and C–H⋯π contacts. All the hydrogen atoms (except those
participating in the C–H⋯π contacts for (b) and those participating in
the C–H⋯O hydrogen bonds and C–H⋯π contacts for (c)) were
omitted for clarity.
In complexes 6 and 7, each molecule contains one
15-membered macrometallocycle formed by one ligand L and
one metal atom (Cu(II) for 6 and Co(II) for 7), as shown in
Fig. 6(a) and 7(a). In the same ligand, the dihedral angles of
two benzimidazole rings are 87.3(7)° for 6 and 80.5(3)° for 7,
and the dihedral angles between the benzene ring and two
benzimidazole rings are 78.4(9)° and 84.1(4)° for 6, and 63.7(6)°
and 77.8(8)° for 7.
In complex 6, the coordination mode of the Cu(II) atom
is similar to the case of complex 3 in adopting a distorted
octahedral geometry. The difference is that the four oxygen
donors around the Cu(II) atom of 6 are from two acetate groups.
The axial positions of the octahedron are occupied by N(1)
and O(5) with axial distances of 1.989(4) Å and 1.975(4) Å, and
with a N(1)–Cu(1)–O(5) angle of 166.4(2)°. Four atoms, O(3), O(4),
O(6) and N(4), lie in the equatorial plane, and the Cu–O bond
distances are in the range of 1.978(4)–2.553(4) Å, and the
Cu(1)–N(4) bond distance is 1.984(5) Å. The N(1)–Cu(1)–N(4),
N(1)–Cu(1)–O(4), N(4)–Cu(1)–O(4) and O(4)–Cu(1)–O(5) bond
angles are 90.8(9)°, 91.7(5)°, 156.3(2)° and 90.3(2)°. These
values are comparable with those of complexes 2–4 and other
Cu(II) complexes.12–14
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Fig. 7 (a) Perspective view of 7 and anisotropic displacement parameters
depicting 50% probability. Selected bond lengths (Å) and angles (°):
Co(1)–N(1) 2.031(8), Co(1)–N(4) 2.018(1), Co(1)–Cl(1) 2.219(5), Co(1)–Cl(2)
2.210(9); N(1)–Co(1)–Cl(1) 117.2(7), N(1)–Co(1)–Cl(2) 106.7(0), N(1)–Co(1)–N(4)
99.0(3), N(4)–Co(1)–Cl(1) 107.5(1), N(4)–Co(1)–Cl(2) 112.7(3), Cl(1)–Co(1)–Cl(2)
112.9(1). (b) 2D supramolecular layer of 7 formed via two types of π–π
interactions and C–H⋯Cl hydrogen bonds. (c) 3D supramolecular
architecture of 7 via C–H⋯Cl hydrogen bonds, C–H⋯π contacts and
two types of π–π interactions. All the hydrogen atoms (except those
participating in the C–H⋯Cl hydrogen bonds for (b) and those
participating in the C–H⋯Cl hydrogen bonds and C–H⋯π contacts for
(c)) were omitted for clarity.
Fig. 6 (a) Perspective view of 6 and anisotropic displacement parameters
depicting 50% probability. Selected bond lengths (Å) and angles (°):
Cu(1)–N(1) 1.989(4), Cu(1)–N(4) 1.984(5), Cu(1)–O(4) 1.978(4), Cu(1)–O(5)
1.975(4); N(1)–Cu(1)–N(4) 90.8(9), N(1)–Cu(1)–O(4) 91.7(5), N(1)–Cu(1)–O(5)
166.4(2), N(4)–Cu(1)–O(4) 156.3(2), O(4)–Cu(1)–O(5) 90.3(2). (b) 2D
supramolecular layer of 6 formed via two types of π–π interactions.
(c) 3D supramolecular architecture of 6 formed via two types of π–π
interactions and C–H⋯π contacts. All the hydrogen atoms (except those
participating in the C–H⋯π contacts for (c)) were omitted for clarity.
The crystal packing of complexes 1–7
In the complex 7, the Co(II) atom is tetra-coordinated with
two nitrogen atoms from two benzimidazole rings and two
chlorine atoms to adopt a tetrahedral geometry. The Co–N bond
distances are from 2.018(1) Å to 2.031(8) Å, and the Co–Cl
bond distances are from 2.210(9) Å to 2.219(5) Å. The N–Co–Cl
bond angles are in the range of 106.7(0)–117.2(7)°. The
Cl(1)–Co(1)–Cl(2) and N(1)–Co(1)–N(4) bond angles are 112.9(1)°
and 99.0(3)°, respectively. These values are similar to those of
complexes 1, 5 and other Co(II) complexes.11
In the crystal packing of complex 1 (Fig. 1(b)), a 2D supramolecular
layer is formed via π–π interactions15 from the benzimidazole rings
and C–H⋯π contacts.16 In the C–H⋯π contacts, the hydrogen
atoms are from CH2 and the π systems are from the benzene
rings (the data of the π–π interactions and C–H⋯π contacts is
given in Table 1). Furthermore, the 2D supramolecular layers
are further extended into 3D supramolecular frameworks
through analogous C–H⋯π contacts (Fig. 1(c)).
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Table 1 Distances (Å) of the π–π interactions, and distances (Å) and angles (°) of the C–H⋯π contacts for 1–7
π–π
C–H⋯π
H⋯π
Complex
Face-to-face
Center-to-center
C–H⋯π
1
2
3
4
5
6
3.419(5) (benzimidazole)
—
3.527(2) (benzimidazole)
3.472(6) (benzimidazole)
—
3.351(8) (benzimidazole)
3.637(8) (benzene)
3.483(3) (benzimidazole)
3.552(2) (benzene)
3.837(1) (benzimidazole)
—
3.861(2) (benzimidazole)
3.640(6) (benzimidazole)
—
3.617(1) (benzimidazole)
3.861(3) (benzene)
3.848(1) (benzimidazole)
3.817(1) (benzene)
2.635(2)
2.497(2)
—
2.567(5)
2.647(1)
3.157(3)
148.3(2)
151.7(6)
—
136.7(8)
145.7(2)
116.4(4)
7
2.687(1)
153.7(1)
Analysis of the crystal packing of 2 shows that a 2D supra-
molecular layer is formed via intermolecular C–H⋯Cl hydrogen
bonds,17 as shown in Fig. 2(b) (the data of the hydrogen bonds
is given in Table 2). In the hydrogen bonds, the hydrogen
atoms are from the benzene rings. Additionally, the 2D supra-
molecular layers are further extended into 3D supramolecular
frameworks through C–H⋯π contacts (Fig. 2(c), Table 1). In the
C–H⋯π contacts, the hydrogen atoms are from the benzimidazole
rings and the π systems are from the benzene rings.
In the crystal packing of 3 (Fig. 3(b)), a 2D supramolecule
layer is formed through π–π interactions from intermolecular
benzimidazole rings (Table 1). The 2D supramolecular layers
are further extended into 3D supramolecular frameworks
through C–H⋯O hydrogen bonds,18 as shown in Fig. 3(c)
(Table 2). In the hydrogen bonds, the hydrogen atoms are
from the benzimidazole rings and the oxygen atoms are from
nitrate groups.
In the crystal packing of 4 (Fig. 4(b)), a 2D supramolecule
layer is formed through π–π interactions from intermolecular
benzimidazole rings and C–H⋯π contacts. In the C–H⋯π
contacts, the hydrogen atoms are from CH2 and the π systems
are from the benzimidazole rings. The 2D supramolecular
layers are further extended into 3D supramolecular frameworks
through C–H⋯O hydrogen bonds, as shown in Fig. 4(c). In
the hydrogen bonds, the hydrogen atoms are from CH2 and
the oxygen atoms are from sulfate groups.
hydrogen bonds, as shown in Fig. 5(c). In the hydrogen bonds,
the hydrogen atoms are from CH2 and the oxygen atoms are
from terephthalate groups.
In the crystal packing of 6 (Fig. 6(b)), a 2D supramolecular
layer is formed via two types of π–π interactions, one is from
intermolecular benzimidazole rings and another is from inter-
molecular benzene rings. The 2D supramolecular layers are
further extended into 3D supramolecular frameworks via C–H⋯π
contacts (Fig. 6(c)). In the C–H⋯π contacts, the hydrogen
atoms are from acetate groups and the π systems are from
benzene rings.
In the crystal packing of 7, a 2D supramolecular layer is
formed via C–H⋯Cl hydrogen bonds and two types of π–π
interactions (Fig. 7(b)). In the two types of π–π interactions,
one is from intermolecular benzimidazole rings and another
is from intermolecular benzene rings. In the hydrogen bonds,
the hydrogen atoms are from the benzimidazole rings. The
2D supramolecular layers are further extended into 3D supra-
molecular frameworks via C–H⋯π contacts (Fig. 7(c)). In the
C–H⋯π contacts, the hydrogen atoms are from CH2 and the
π systems are from benzimidazole rings.
The conformations of the complexes formed via L
and metal salts
The metal complexes formed via L and metal salts contain
mainly four types of conformations (Scheme 3), namely: (1) the
macrometallocycle (I) formed by one ligand L and one metal
atom (like complexes 6 and 7); (2) the macrometallocycle
dimer (II and III), in which two macrometallocycle monomers
are connected together by different bridging linkers (such as
complex 1 using one Co(II) atom as a bridge, complex 2 using
two chlorine atoms as bridges, complex 3 using two nitrate groups
as bridges and complex 4 using two sulfate groups as bridges);
(3) the 1D polymeric chain (IV) formed by a macrometallocycle
monomer and organic diacids (like complex 5), in which the
ligand L is arranged on both sides of the polymeric chain due
to the steric hindrance between the macrometallocycles. These
conformations have similarity, namely, they contain the similar
macrometallocycle formed by one ligand L and one metal atom.
This indicates that the bis-benzimidazolyl chelate ligand L
bearing a 1,2-bis(2′-ethoxy)phenyl linker and metal ions easily
forms a chelate macrometallocycle due to the particular steric
In the crystal packing of 5 (Fig. 5(b)), a 2D supramolecular
layer is formed by C–H⋯π contacts. In the C–H⋯π contacts,
the hydrogen atoms are from CH2 and the π systems are from
the benzene rings. The 2D supramolecular layers are further
extended into 3D supramolecular frameworks via C–H⋯O
Table 2 H-bonding geometry (Å, °) for 2–5 and 7
D–H⋯A
D–H
H⋯A
D⋯A
D–H⋯A
2
3
4
5
7
C(15)–H(15)⋯Cl(2)ii
C(21)–H(21)⋯O(4)ii
C(8)–H(8B)⋯O(6)ii
C(17)–H(17B)⋯O(5)i
C(7)–H(7)⋯Cl(2)i
0.92(8)
0.92(9)
0.97(0)
0.97(0)
0.92(9)
2.864(8)
2.640(1)
2.567(5)
3.202(6)
2.730(5)
3.685(8)
3.511(4)
3.339(5)
3.899(1)
3.539(9)
148.1(2)
156.3(1)
136.7(8)
130.2(5)
146.0(1)
Symmetry code: ii = x, −1 + y, z for 2; ii = 1 + x, −1 + y, 1 + z for 3;
ii = −1 + x, −1 + y, −1 + z for 4; i = x, −1 + y, 1 + z for 5; i = x,
1 + y, 1 + z for 7.
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Scheme 3 The conformations of the metal complexes formed by the dibenzimidazolyl chelate ligand L and metal salts.
structure of ligand L. The difference in these conformations
is that diverse linking manners exist (like I–IV) between
macrometallocycles owing to the influence of different metal
ions and counter-ions. On the whole, the conformations of
the metal complexes based on the dibenzimidazolyl chelate
ligand L are related mainly to the structure of the ligand,
metal ions, counter-ions, and solvent, as well as the steric
hindrance around the metal centers.
which may be attributed to intraligand n–π* and π–π* transitions.19
Complexes 1–7 exhibit similar fluorescence emission bands at
the corresponding regions of the ligand, but the fluorescence
emission of these complexes is almost quenched in comparison
with that of the ligand, which should result from the metal
perturbing intraligand processes.20
Magnetic studies for complexes 1–7
The variable-temperature magnetic susceptibilities for com-
plexes 1–7 were measured on polycrystalline samples between 2 K
to 300 K at 1000 Oe. In Co(II) complexes 1, 5 and 7 (Fig. S1, S5
and S7 in the ESI†), the χmT values are 1.64 cm3 K mol−1 for 1,
3.14 cm3 K mol−1 for 5 and 2.49 cm3 K mol−1 for 7 at 300 K. The
value of 1 is slightly smaller and the values of 5 and 7 are
Fluorescence emission spectra of ligand L and complexes 1–7
As indicated in Fig. 8, the fluorescence emission spectra of
ligand L and complexes 1–7 in acetonitrile at room temperature
are obtained upon excitation at 271 nm. The ligand L shows
strong triple emission bands in the range of 295–310 nm,
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may be ascribed to ν(N–O) modes from a nitrate group. The
absorption peaks at 1132 cm−1 for 4 are attributed to the
stretching vibrations of S–O from a sulfate group. Strong bands
for the carbonyl group from carboxyl groups were observed at
1668 cm−1 for 5 and 1596 cm−1 for 6.
Powder X-ray diffraction of complexes 1–7
In order to establish their crystalline phase purity, powder X-ray
diffraction (PXRD) experiments were carried out on complexes
1–7. As shown in the PXRD patterns (Fig. S8–S14, ESI†), the
excellent agreement between the experimental PXRD patterns
of the bulk samples 1–7 and the patterns simulated from the
single-crystal data of 1–7 proved the crystalline phase purity of
the corresponding complexes 1–7.
Fig. 8 Emission spectra of L (—), 1 (— —), 2 (· · ·), 3 (— -), 4 (-··), 5 (–),
6 (··) and 7 (⋯) at room temperature in a CH3CN (5.0 × 10−5 M) solution.
Thermogravimetric analyses for complexes 1–7
larger than the expected value (χmT = 1.87 cm3 K mol−1) for
high spin Co2+ ions with octahedral coordination geometry
(S = 3/2 and g = 2.0), and these values are in accordance with
the well-documented orbital contribution of the octahedral
Co2+ ion. Upon cooling, the χmT values continuously decrease
to reach 0.92 cm3 K mol−1 for 1, 1.58 cm3 K mol−1 for 5 and
1.32 cm3 K mol−1 for 7 at 2 K due to the spin–orbital couplings
of the Co2+ ions and/or antiferromagnetic interactions between
adjacent spin centers.
In binuclear Cu(II) complexes 2–4 (Fig. S2–S4, ESI†), the
χmT values are 0.53 cm3 K mol−1 for 2, 1.13 cm3 K mol−1 for 3
and 1.05 cm3 K mol−1 for 4 at 300 K. The value of 2 is slightly
smaller and the values of 3 and 4 are larger than the expected
value (χmT = 0.75 cm3 K mol−1) for two isolated Cu2+ ions (S = 1/2
and g = 2.0). Upon cooling, the χmT values continuously decrease
to reach 0.39 cm3 K mol−1 for 2, 0.45 cm3 K mol−1 for 3 and
0.48 cm3 K mol−1 for 4 at 2 K, suggesting an antiferromagnetic
coupling within the binuclear Cu2+ units.
To examine the thermal stability of 1–7, thermogravimetric ana-
lyses for crystal samples 1–7 were performed under a simulated
air atmosphere with a heating rate of 20 °C min−1 from ambient
temperature up to 800 °C. As shown in Fig. S15 and S21 in the
ESI,† the TG curves of 1 and 6 reveal that the complexes start to
decompose from ambient temperature to 56.7 °C for 1 and to
64.4 °C for 6, representing the loss of approximately 0.25 equiv.
of water molecules for 1 and 1.75 equiv. of water molecules
for 6 (calcd: 0.93%, found: 0.92% for 1; calcd: 4.97%, found:
4.94% for 6). These two compounds then experience weight
losses of 41.2% from 359.8 °C to 469.3 °C for 1 and 56.55% from
187.5 °C to 390.6 °C for 6, which are attributed to the thermal
decomposition of the organic components, and does not stop
until heating ends at 800 °C. The TG analyses for 2, 4 and 7
(Fig. S16, S18 and S21, ESI†) indicate that these compounds
have high thermal stability and exhibit similar thermal behavior.
These compounds are still stable up to 329.8 °C for 2, 254.2 °C
for 4 and 344.6 °C for 7, and they experience almost one-step
weight loss of 56.27% from 329.8 °C to 464.9 °C for 2, 65.08%
from 254.2 °C to 433.8 °C for 4 and 47.42% from 344.6 °C to
472.5 °C for 7. These weight losses are attributed to the thermal
decomposition of the organic components, and do not stop
until heating ends at 800 °C. The TG curve of 3 (Fig. S17, ESI†)
reveals a weight loss of 1 equiv. of DMF (calcd: 11.09%, found:
11.25%) from 230.6 °C to 254.3 °C, and the complex experi-
ences a weight loss of 32.21% from 266.2 °C to 470.9 °C. This
weight loss is attributed to the thermal decomposition of the
organic components, and does not stop until heating ends at
800 °C. The TG curve of 5 (Fig. S19, ESI†) reveals that a weight
loss of 19.39% (calcd: 19.04%) from 104.3 °C to 258.6 °C
corresponds to the loss of 2 equiv. of DMF, and then the com-
pound experiences multiple steps of thermal decomposition
of the organic components from 420.6 °C to 800 °C.
The χmT of mononuclear Cu(II) complex 6 (Fig. S6, ESI†)
is 0.78 cm3 K mol−1 at 300 K. The value is slightly larger than the
expected value (χmT = 0.37 cm3 K mol−1) for a single Cu2+ ion
(S = 1/2 and g = 2.0). Upon cooling, the χmT value continuously
decreases to reach 0.05 cm3 K mol−1 at 2 K, suggesting an anti-
ferromagnetic coupling within the mononuclear Cu2+ unit.
IR spectra analyses for complexes 1–7
Complexes 1–7 have similar infrared spectra because their
ligands are the same. In each case, the absorption peaks
around 1619–1615 cm−1 may result from ν(CN) modes of
imidazole rings. The peaks in the 1258–1200 cm−1 region
originate from νs(C–C) or νs(C–N) modes of benzimidazole
rings. The absorption peaks at around 2946–2859 cm−1 can
be assigned to ν(C–H) modes. The peaks in the region of
1596–1560 cm−1 may be ascribed to C–H bending vibrations
and are due to the asymmetric and symmetric modes of the
benzimidazole ring. The broad peaks at 3440 cm−1 for 1 are
attributed to the stretching vibrations of O–H due to the presence
of water molecules. The absorption peaks at 1673 cm−1 for 3
Conclusion
In summary, seven metal complexes 1–7 have been prepared
and characterized. In complexes 1–4, two 15-membered macro-
metallocycles are linked together through sharing moieties
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(the sharing moieties: Co(II) atom for 1, two bridging chlorine
atoms for 2, two bridging nitrate groups for 3, two bridging
sulfate groups for 4) to form a dimer, in which each
15-membered macrometallocycle is constructed from one
bis-benzimidazolyl chelate ligand L and one metal atom
(Co(II) for 1, and Cu(II) for 2–4). In complex 5, a 1D polymeric
chain with 15-membered macrometallocycles is formed via
ligand L, terephthalate (LA) and a Co(II) atom, in which the
15-membered macrometallocycles lie on two sides of the 1D
polymeric chain. In complexes 6 and 7, each 15-membered
macrometallocycle is formed by one ligand L and one metal
atom (Cu(II) for 6 and Co(II) for 7). In the crystal packings
of 1–7, 2D supramolecular layers and 3D supramolecular
frameworks are formed via intermolecular weak interactions,
including hydrogen bonds, π–π interactions and C–H⋯π contacts.
The resultant structures of the complexes will provide valuable
experimental data for crystal engineering and supramolecular
chemistry. Further studies on new metal complexes from
ligand L and analogous ligands are under way.
1,2-bis(1′-hydroxy-2′-ethoxy)benzene as a white powder. Yield:
25.769 g (65%).
The thionyl chloride (12.004 g, 101 mmol) was added drop-
wise to a chloroform solution (100 mL) of 1,2-bis(1′-hydroxy-
2′-ethoxy)benzene (4.000 g, 20 mmol) and pyridine (7.982 g,
101 mmol) at room temperature for 1 h. Then, the solution
was stirred continually for 12 h at 70 °C. The mixture was
cooled and washed with water (3× 100 mL). The organic layer was
dried over anhydrous MgSO4. After removing the chloroform,
1,2-bis(1′-chloro-2′-ethoxy)benzene was obtained as a pale yellow oil.
Yield: 2.755 g (58%).
A CH3CN solution (100 mL) of benzimidazole (1.252 g,
10.6 mmol), KOH (0.676 g, 12.1 mmol) and tetrabutyl ammo-
nium bromide (TBAB) (0.155 g, 0.5 mmol) was stirred for
2 h under refluxing. Then, a CH3CN solution (10 mL) of
1,2-bis(1′-chloro-2′-ethoxy)benzene (2.000 g, 4.8 mmol) was
dropped into the above solution, and the mixture was stirred
continually for 48 h at 80 °C to give a white precipitate. The pre-
cipitate was filtered and washed with water (3× 100 mL) to afford
a white powder of 1,2-bis(2′-ethoxy)phenyl-bis(benzimidazole) (L).
Yield: 1.689 g (88%). mp: 166–168 °C. Anal. calcd for C24H22N4O2:
C, 72.34; H, 5.56; N, 14.06. Found: C, 72.48; H, 5.73; N, 14.32.
1H NMR (400 MHz, DMSO-d6): δ 4.24 (t, J = 5.0 Hz, 4H, CH2),
4.58 (t, J = 5.0 Hz, 4H, CH2), 6.81–6.84 (m, 2H, PhH), 6.86–6.89
(m, 2H, PhH), 7.19–7.27 (m, 4H, PhH), 7.67 (t, J = 6.4 Hz, 4H, PhH),
8.26 (s, 2H, 2-bimiH) (bimi = benzimidazole). IR (KBr, cm−1):
3066m, 3033w, 2929w, 2876w, 2370m, 1619m, 1586m, 1503vs,
1457s, 1378m, 1353m, 1258vs, 1200s, 1142s, 1042s, 910m, 756vs.
Experimental section
Materials and methods
All the reagents for the synthesis and analyses were of analytical
grade and used without further purification. Melting points
were determined with a Boetius Block apparatus. 1H NMR
spectra were recorded on a Varian Mercury Vx 400 spectro-
meter at 400 MHz. Chemical shifts, δ, are reported in ppm
relative to the internal standard, TMS for 1H NMR, and J values
are given in Hz. The elemental analyses of all compounds were
obtained from the recrystallised powder compounds, and mea-
sured using a Perkin-Elmer 2400C elemental analyzer. IR spectra
(KBr) were taken on an Bruker Equinox 55 spectrometer. The
luminescent spectra were conducted on a Cary Eclipse fluores-
cence spectrophotometer. The X-ray powder diffractometry (XRPD)
study was performed on a PANalytical X-Pert Pro diffractometer
with Cu–Kα radiation. The thermogravimetric analysis (TGA) was
performed with a NETZSCH STA 449C instrument. Magnetic
susceptibility was measured by a Quantum Design MPMS super-
conducting quantum interference device (SQUID).
Synthesis of [Co(L)2(H2O)2]Cl2 (1)
A reaction mixture of L (0.050 g, 0.1 mmol) and CoCl2·2H2O
(0.036 g, 0.3 mmol) in DMF (5 mL), CH3OH (5 mL) and H2O
(5 mL) was sealed in a 20 mL Teflon-lined stainless steel con-
tainer and heated at 110 °C for 7 days. After cooling to room
temperature, pink block crystals of 1 were collected by filtra-
tion and washed with water and ethanol. Yield: 0.040 g (66%)
(based on L). mp: 110–112°C. Anal. calcd for C48H48Cl2CoN8O6:
C, 59.88; H, 5.03; N, 11.64. Found: C, 59.64; H, 5.24; N, 11.43.
IR (KBr, cm−1): 3440m, 3100m, 3058w, 2938w, 2884w, 2353w,
2336w, 1619m, 1594m, 1515s, 1506s, 1385m, 1253s, 1226m,
1214m, 918m, 763m, 747s.
Synthesis of 1,2-bis(2′-ethoxy)phenyl-bis(benzimidazole) (L)
Synthesis of [Cu(L)Cl2]2 (2)
An anhydrous ethanol (300 mL) solution of catechol (22.000 g,
200 mmol) and sodium hydroxide (16.000 g, 400 mmol)
was stirred for 2 h at 50 °C. Then, 2-chloroethanol (48.312 g,
600 mmol) was added dropwise into above solution, and stirred
continually for 12 h under refluxing. After the reaction
was stopped, the solvent was removed under vacuum, and
50 mL of water was added. The mixture was extracted with
ethyl acetate (3× 100 mL) and the extracting solution was
dried over anhydrous MgSO4. After removing ethyl acetate,
the crude product was obtained, and the crude product
was recrystallized with ethyl acetate–ethyl ether to give
An N,N-dimethylformamide (DMF) solution (5 mL) containing
L (0.050 g, 0.1 mmol) was added to a methanol solution (15 mL)
of CuCl2·2H2O (0.044 g, 0.3 mmol). The reaction mixture was
stirred for 1 h at 40 °C. The filtrate was allowed to evaporate
slowly under ambient conditions, and green crystals suitable
for X-ray analysis were obtained by slow evaporation of the
solvents within seven days. Yield: 0.038 g (57%) (based on L).
mp: 230–232°C. Anal. calcd for C24H22Cl2CuN4O2: C, 54.09; H, 4.16;
N, 10.51. Found: C, 54.21; H, 4.32; N, 10.42. IR (KBr, cm−1):
2968m, 2781m, 2360m, 2341m, 1666s, 1616s, 1507m, 1457m,
1438m, 1397vs, 1256m, 1105m, 918w, 753s.
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Synthesis of [Cu(L)(NO3)2]2 (3)
obtained by slow evaporation of the solvents within seven days.
Yield: 0.041 g (62%) (based on L). mp: 260–261°C. Anal. calcd
for C24H22Cl2CoN4O2: C, 54.56; H, 4.20; N, 10.61%. Found:
C, 54.31; H, 4.43; N, 10.78%. IR (KBr, cm−1): 3062w, 2935w,
2881w, 2359m, 2340m, 1615w, 1593w, 1558w, 1516vs, 1506vs,
1479m, 1465s, 1385m, 1296m, 1253vs, 1214s, 1129s, 1049s,
922m, 748vs.
This complex was prepared in a manner analogous to that
of 2, only with Cu(NO3)2·3H2O (0.072 g, 0.3 mmol) instead of
CoCl2·2H2O, and blue crystals suitable for X-ray analysis were
obtained by slow evaporation of the solvents within seven
days. Yield: 0.055 g (67%) (based on L). mp: 140–142°C. Anal.
calcd for C24H22CuN6O8: C, 49.19; H, 3.78; N, 14.34%. Found:
C, 49.20; H, 3.43; N, 14.48%. IR (KBr, cm−1): 3095m, 2946w,
2859w, 2365m, 1673s, 1619m, 1594m, 1503s, 1465s, 1382vs,
1295s, 1250s, 1208s, 1125s, 1088m, 1051m, 1005m, 922w, 744s.
X-ray data collection and structure determinations
X-ray single-crystal diffraction data for complexes 1–7 were
collected using a Bruker Apex II CCD diffractometer at 296(2)
K with Mo–Kα radiation (λ = 0.71073 M) by the ω scan mode.
There was no evidence of crystal decay during the data collection
in all cases. Semi-empirical absorption corrections were applied
using SADABS and the SAINT program was used for the inte-
gration of the diffraction profiles.21 All the structures were
solved by direct methods using the SHELXS program of the
SHELXTL package and refined with SHELXL22 by the full-matrix
least-squares methods with anisotropic thermal parameters
for all non-hydrogen atoms on F2. Hydrogen atoms bonded to
C atoms were placed geometrically and presumably solvent
H atoms were first located in difference Fourier maps and
then fixed in the calculated sites. Further details of the crystal-
lographic data and structural analysis are listed in Tables S1
and S2 in the ESI† and were generated using Crystal-Maker.23
Synthesis of [Cu(L)(SO4)]2 (4)
This complex was prepared in a manner analogous to that of
2, only with CuSO4·5H2O (0.103 g, 0.3 mmol) instead of
CoCl2·2H2O, and blue crystals suitable for X-ray analysis were
obtained by slow evaporation of the solvents within seven
days. Yield: 0.043 g (61%) (based on L). mp: >320°C. Anal.
calcd for C24H22CuN4O6S: C, 51.65; H, 3.97; N, 10.04%.
Found: C, 51.77; H, 3.81; N, 10.32%. IR (KBr, cm−1): 3112w,
2934w, 2929w, 2876w, 2359m, 2340m, 1615w, 1590w, 1520m,
1506m, 1253m, 1222m, 1132s, 1052m, 986m, 946w, 747m.
Synthesis of [Co(L)(LA)]n (5)
An N,N-dimethylformamide (DMF) solution (5 mL) of terephthalic
acid (H2LA) (0.046 g, 0.3 mmol) was added to a methanol solution
(10 mL) of L (0.050 g, 0.1 mmol). After ca. 3 min of vigorous
mixing, an aqueous solution (5 mL) of Co(NO3)2·6H2O (0.073 g,
0.3 mmol) was added and the pH value of the solution was
adjusted to approximated 7 by triethylamine. The reaction
mixture was stirred for 1 h at ca. 40 °C. The filtrate was
allowed to evaporate slowly under ambient conditions, and
purple crystals suitable for X-ray analysis were obtained within
seven days. Yield: 0.066 g (69%) (based on L). mp: >320 °C.
Anal. calcd for C32H26CoN4O6: C, 61.84; H, 4.22; N, 9.02%.
Found: C, 61.55; H, 4.36; N, 9.41%. IR (KBr, cm−1): 3058w,
2938w, 2880w, 2357w, 2328w, 1668vs, 1616m, 1560s, 1506s,
1465m, 1388s, 1295m, 1254s, 1214m, 1128m, 1087m, 1049m,
910w, 746s.
Acknowledgements
This work was financially supported by the National Natural
Science Foundation of China (No. 21172172) and Tianjin Natural
Science Foundation (No. 11JCZDJC22000).
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Synthesis of [Cu(L)(OAc)2] (6)
This complex was prepared in a manner analogous to that of
2, only with Cu(OAc)2·H2O (0.060 g, 0.3 mmol) instead of
CoCl2·2H2O, and blue crystals suitable for X-ray analysis were
obtained by slow evaporation of the solvents within seven
days. Yield: 0.052 g (64%) (based on L). mp: 140–142°C. Anal.
calcd for C28H27CuN4O6: C, 58.07; H, 4.70; N, 9.68%. Found:
C, 58.34; H, 4.52; N, 9.82%. IR (KBr, cm−1): 3431m, 3108w,
2921w, 2880w, 2361m, 1698w, 1596s, 1506s, 1394s, 1333m,
1250m, 1208m, 1125m, 1047m, 910w, 744m.
Synthesis of [Co(L)Cl2] (7)
This complex was prepared in a manner analogous to that
of 2, only with CoCl2·2H2O (0.036 g, 0.3 mmol) instead of
CoCl2·2H2O, and blue crystals suitable for X-ray analysis were
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