A sulfate-bridged CuII complex with 1-D helical-chain structure: Synthesis, structure and magnetic property

Article abstract of DOI:10.1016/j.inoche.2012.03.035

A new 1-D helical chain complex [Cu(H₂L)(SO₄)] ·CH₃OH (1) (H₂L = N,N-bis(3,5-dimethyl-2- hydroxybenzyl)-N-(2-pyridylmethyl)amine) was synthesized from the reaction of the tripodal tetradentate ligand H₂L with CuSO₄· 5H₂O under solvothermal conditions. Complex 1 was fully characterized by X-ray single crystal diffraction, elemental analysis and IR spectroscopy. X-ray analysis revealed that complex 1 displays a 1-D helical chain structure with the two adjacent metals being bridged by a sulfate ion. Each Cu ^II ion is penta-coordinated and exhibits a pseudo square pyramidal geometry. The low-temperature magnetic susceptibility measurement for the solid sample of 1 revealed the ferromagnetic Cu^IICu^II interactions.

Full text of DOI:10.1016/j.inoche.2012.03.035

Inorganic Chemistry Communications 21 (2012) 12–15
Contents lists available at SciVerse ScienceDirect
Inorganic Chemistry Communications
journal homepage: www.elsevier.com/locate/inoche
A sulfate-bridged CuII complex with 1-D helical-chain structure: Synthesis, structure
and magnetic property
Li-Juan Yang a, Tao Lei b, Wei Liu a, Wen-Qian Chen a, Miao-Shui Lin a, Lei Li a, Wu Li b, Yahong Li a,c,
⁎
a
Key Laboratory of Organic Synthesis of Jiangsu Province, College of Chemistry, Chemical Engineering and Materials Science, Soochow University, Suzhou 215123, China
CAS Key Laboratory of Salt Lake Resources and Chemistry, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China
b
c
State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A new 1-D helical chain complex [Cu(H2L)(SO4)]·CH3OH (1) (H2L=N,N-bis(3,5-dimethyl-2-hydroxybenzyl)-
N-(2-pyridylmethyl)amine) was synthesized from the reaction of the tripodal tetradentate ligand H2L with
CuSO4·5H2O under solvothermal conditions. Complex 1 was fully characterized by X-ray single crystal
diffraction, elemental analysis and IR spectroscopy. X-ray analysis revealed that complex 1 displays a 1-D helical
chain structure with the two adjacent metals being bridged by a sulfate ion. Each CuII ion is penta-coordinated
and exhibits a pseudo square pyramidal geometry. The low-temperature magnetic susceptibility measurement
for the solid sample of 1 revealed the ferromagnetic CuII⋯CuII interactions.
Received 21 February 2012
Accepted 23 March 2012
Available online 1 April 2012
Keywords:
Copper(II) complex
1-D helical chain
Solvothermal synthesis
Magnetic property
© 2012 Elsevier B.V. All rights reserved.
Recent years have witnessed an explosion of interest in the design
and synthesis of the high-nuclearity paramagnetic complexes [1].
The reasons for this are many, but the most important factors
are the search for models of metal-containing sites in biology [2]
and the relevance of these complexes to magnetic [3], optical [4],
electronic [5] and catalytic [6] materials. A synthetic challenge
involves discovering simple and efficient approaches to the incorpo-
ration of many metal ions in a small, single molecular entity. It is
found that the combination of two ligands will foster the formation of
high-nuclearity complexes [7].
We are interested in preparing high-nuclearity coordination
complexes by the combination of a tripodal tetradentate amine-bis
(phenolate) ligand H2L (H2L=N,N-bis(3,5-dimethyl-2-hydroxybenzyl)-
N-(2-pyridylmethyl)amine) with sulfate ions. There is a continuous
interest in the coordination chemistry of tetradentate amine-
bis(phenolate) ligand. The efforts of several research groups are
driven by a number of considerations. These include the develop-
ment of the structural models for mimicking the active site of
galactose oxidase [8], the application of metal ion/tetradentate
amine-bis(phenolate) systems as efficient catalysts for the poly-
merization of olefins and lactide [9], and the employment of the
tetradentate amine-bis(phenolate) ligands in the synthesis of
coordination complexes with interesting magnetic properties [10].
As a tetrahedral anion, sulfate can bind toward metal cations in
various ways [11], and the diverse coordination modes of sulfate anions
largely contribute to the formation of the high-nuclearity clusters. The
synthesis, structure and properties of a number of transition metal
sulfates have been reported in recent years [12]. To the best of our
knowledge, the synthesis of the 1-D chain CuII complexes supported by
both the tetradentate amine-bis(phenolate) ligands and sulfates has
never been reported. Herein, we report the synthesis of a 1-D helical
chain polymer [Cu(H2L)(SO4)]·CH3OH (1) via the reaction of the H2L
ligand with CuSO4·5H2O. The structural characterizations and the
magnetic properties of the complex were also presented.
Complex 1 was prepared under solvothermal conditions in CH3OH
(Scheme 1). Treatment of CuSO4·5H2O with H2L in a sealed Pyrex-tube
in CH3OH led to the formation of 1. Complex 1 was readily isolated as
green crystals with moderate yield.
The presence of \OH groups in 1 is manifested by a broad IR band
of medium intensity at 3420 cm−1. The band at 2930 cm−1 has been
ascribed to the νas(C\H) vibration. Several bands, which are assigned
as the stretching vibrations of the aromatic rings, appear in the
1612–1446 cm−1 range. The medium intensity band at 1156 cm−1
has been assigned to the ν(SO)sulfate mode.
The single crystal X-ray diffraction [13] determination reveals that
compound 1 is monoclinic and crystallizes in space group C2/c. The
asymmetric unit contains one CuII ion, one H2L ligand, one SO42− ion and
one solvate methanol molecule (Fig. 1). The CuII ion is five-coordinated.
The central metal ion displays a slightly distorted square-based
⁎
Corresponding author at: Key Laboratory of Organic Synthesis of Jiangsu Province,
College of Chemistry, Chemical Engineering and Materials Science, Soochow
University, Suzhou 215123, China. Fax: +86 512 65880089.
E-mail address: liyahong@suda.edu.cn (Y. Li).
1387-7003/$ – see front matter © 2012 Elsevier B.V. All rights reserved.
doi:10.1016/j.inoche.2012.03.035

L.-J. Yang et al. / Inorganic Chemistry Communications 21 (2012) 12–15
13
H
S
N
O
O
O
N
S
N
O
O
OH
Cu
O
O
H
CH3OH,T,P
O
O
S
H
O
O
N
CuSO4
+
5H2O
O
O
N
N
Cu
H
O
S
O
O
O
O
N
Cu
O
O
OH
H
O
N
O
H
Scheme 1. Synthesis of complex 1.
pyramidal geometry with τ=0.013 [14], composed of two
nitrogen atoms (N1, N2), one oxygen atom (O2) from one H2L ligand
(Cu–N1=2.015(3)Å, Cu–N2=1.976(3)Å and Cu–O2=2.001(3)Å)
and one oxygen atom (O6) from the SO42− ion (Cu–O6=1.949(2)Å)
in the equatorial plane, the other one oxygen atom of another SO42− ion
is at the axial position (Cu–O3=2.302(3)Å).
The most remarkable structural feature of 1 is that it exhibits a 1-D
single helical chain structure (Fig. 2a–d). The helical chain is made up
of metal centers, SO42− ions and the H2L ligands. The adjacent CuII ions
are linked by two oxygen atoms of a SO42− ion (η1:η1: μ2 or 2.1100
coordination mode [15]), giving rise to an infinite helical chain
[\Cu(H2L)\O\S(O2)\O]n along the b axis.
tripodal tetradentate amine-bis(phenolate) ligands are combined to
give a 1-D helical chain structure.
Magnetic property studies on polynuclear metal complexes are of
continuing interest for coordination chemists since they can provide
understanding of fundamental factors governing their magnetic
properties. The dc magnetic property for 1 was measured in the
temperature range of 2–300 K at the applied magnetic field of
1000 Oe. The obtained data are shown in Fig. 3 in the χMT vs. T and
χ
M vs. T forms.
The χMT value is 0.343 cm3 mol−1 K per CuII ion at 300 K, which is
close to the expected value for one magnetically isolated CuII ion
(0.375 cm3 mol−1 K for g=2.0, S=1/2). The χMT product increases
continuously to a maximum of 0.47 cm3 mol−1 K at 4 K before dropping
to 0.45 cm3 mol−1 K at 2 K, suggesting dominating ferromagnetic
interactions. The temperature dependence of the reciprocal susceptibil-
ity (χM−1) above 2 K obeys the Curie–Weiss law χM=C/(T−θ) with
Curie constant C=0.34 cm3 mol−1 K and Weiss constant θ=+5.79 K,
thus indicating a ferromagnetic behavior in complex 1.
Complex
1 joins a small family of coordination complexes
employing sulfates as ligands [12]. To the best of our knowledge, 1
is also the first CuII coordination polymer in which SO42− ions and the
In summary, under solvothermal conditions one 1-D helical chain
CuII complex [Cu(H2L)(SO4)]n·CH3OH (1) was synthesized and
characterized by X-ray single crystal diffraction, IR spectroscopy,
and elemental analysis. The weak ferromagnetic CuII⋯CuII interactions
were determined. As a tripodal tetradentate amine-bis(phenolate)
ligand supported 1-D helical chain, complex 1 has potential utility in
biologic systems, nonlinear optical materials and catalysis. The in-
depth researches to produce more interesting coordination polymers
by adding alternative tripodal amine-bis(phenolate) ligands and
other transition metal ions are under investigation in our lab. Our
studies, already well advanced, will be reported in due course.
Acknowledgments
The authors appreciate the financial support of the Hundreds of
Talents Program (2005012) of CAS, Natural Science Foundation of
China (20872105), “Qinglan Project” of Jiangsu Province (Bu109805),
Open Project of Key Laboratory for Magnetism and Magnetic
Materials of the Ministry of Education of Lanzhou University
(LZUMMM2010003) and a project funded by the Priority Academic
Program Development of Jiangsu Higher Education Institution.
Appendix A. Supplementary data
CCDC 821012 for 1 contains the supplementary crystallographic
data for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre via http://www.ccdc.cam.ac.
uk/data_request/cif. Supplementary data associated with this article
can be found in the online version, at doi:10.1016/j.inoche.2012.03.035.
Fig. 1. Coordination environment of CuII atom in 1. All the H atoms and the solvate
molecule are omitted for clarity.

14
L.-J. Yang et al. / Inorganic Chemistry Communications 21 (2012) 12–15
Fig. 2. (A) The 1-D helical chain of 1 viewed down the c-axis. (B) The 1-D sulfate-bridged chain of 1 viewed down the c-axis. (C) Space filling view of the 1-D helical chain of 1.
(D) Polyhedron view of the 1-D helical chain of 1.
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