Synthesis and Crystal Structure of a 1 D Chained Coordination Polymer Constructed from Ca 2 + and 2-[ ( E )-( 2-Furoylhydrazono ) methyl ] benzenesulfonate

A new Ca(II) coordination polymer, [{CaL2·(H2O)2·2H2O}]n (1) (L = 2-[(E)-(2furoylhydrazono)methyl]benzenesulfonate), has been obtained by one-pot method, and characterized by elemental analysis, IR spectrum, and X-ray single-crystal diffraction. The results showed that the Ca(II) coordination crystallizes in the orthorhombic space group with P21212, a = 16.355(3) Å, b = 17.478(4) Å, c = 5.4549(11) Å, α =β = γ = 90.00°, V = 1559.3(5) Å3, Z = 2, Mr = 698.69, Dc = 1.488 g/cm3, T = 293(2) K, F(000) = 724, μ(MoKa) = 0.408 mm−1, R = 0.0703 and wR = 0.1848. The Ca(II) ion is coordinated with four O atoms from two L ligands and two O atoms from two coordinated H2O molecules, and generates a distorted octahedral geometry. The 1D chained structure of Ca(II) coordination polymer is constructed from the bridging of SO3– groups. The 3D network structure is formed by the hydrogen bonds and π-π interaction between 1D chains.


Introduction
Coordination polymer materials have been demonstrated to have excellent properties and potential applications, such as catalysis, magnetics, optical materials, gas adsorption, antibacterial agents,

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antitumor drugs, and so on [1][2][3][4][5][6][7][8].In recent years, In order to study the novel structures and applications, many transition metal and rare earth metal coordination polymer materials have been prepared [9][10][11][12][13][14][15][16].However, the novel structures and applications of main metal coordination polymer materials have not been paid much attention relative to that of transition metal and rare earth metal coordination polymer materials [17].All the time, we have always been committed to the study of alkaline earth metal coordination polymer materials [18][19][20][21].In this paper, a new Ca(II) coordination polymer, 1), has been obtained and characterized by elemental analysis, IR, and X-ray single crystal diffraction analysis.

Elemental Analysis and IR Spectra
The result of elemental analysis shows that the asymmetric unit of Ca(II) coordination polymer is [CaL2•(H2O)2]•2H2O, indicating that the Ca(II) coordination polymer conforms to 1:2 metal-to-ligand stoichiometry.The IR spectrum of Ca(II) coordination polymer displays characteristic bands at 3228 cm −1 , 1651 cm −1 , 1230 cm −1 , and 1202 cm −1 , which can be assigned to ν (OH), ν (C=N) and ν (SO3 -) vibrations, respectively.The band at 3228 cm −1 shows that the Ca(II) coordination polymer contains water molecules.The band at 1651 cm −1 (ν (C=N)) shows that the C=N group do not coordinate to Ca(II) ion [22].The bands at 1230 cm −1 and 1202 cm −1 show that the O atoms of SO3 -group take part in coordination with Ca(II) ion [23].

Materials and Instrumentation
2-Formylbenzenesulfonic acid sodium, Ca(ClO4)2•4H2O, 2-furoic acid hydrazide and solvents were analytical grade and used without further purification.Elemental analysis for carbon, hydrogen, and nitrogen was performed on the Elementar Vario EL III elemental analyzer (Elementar Analysensysteme GmbH, Hanau, Germany).The Infrared spectrum (4000-400 cm −1 ) was recorded on a Nicolet AVATAR 360 FT-IR spectrophotometer (Nicolet Instrument Inc., Madison, WI, USA) using the KBr pellet.The crystal data collection was performed on a Bruker Smart CCD Area Detector (Bruker, Billerica, MA, USA).

Crystal Structure Determination
A single crystal with dimensions of 0.21 mm × 0.20 mm × 0.19 mm was selected for structural analysis on a Bruker Smart Apex CCD diffractometer with MoKα radiation and φ~ω scan mode at 293 (2) K.The structure was solved by direct methods using SHELXS-97 [24] program and refined on F 2 by full-matrix least-squares methods.All the non-hydrogen atoms were refined anisotropically.The H atoms of water were determined according to difference Fourier method and refined with a riding model.All the remaining H atoms were located theoretically and refined with a riding model.A total of 11112 reflection data were collected in the range of 3.41°-24.99°,and 2538 were observed with I > 2σ(I).The SHELXL-97 and Bruker SHELXTL program package [24] were used to refine structure, and the Mercury program [25] was used to draw molecular graphics.The final refinement shows R = 0.0703, and wR = 0.0.1848(w = 1/[δ 2 (Fo 2 ) + (0.905P) 2 + 2.5943P], P = (Fo 2 + 2Fc 2 )/3).Technical details of the data collection and refinement parameters for [{CaL2•(H2O)2•2H2O}]n are listed in Table 2.The selected bond lengths and bond angles are listed in Table 3.

Conclusions
In summary, a new Ca(II) coordination polymer, [{CaL2•(H2O)2•2H2O}]n (1) (L = 2-[(E)-(2furoylhydrazono)methyl]benzenesulfonate), has been obtained by one-pot method, and characterized by elemental analysis, IR spectrum and X-ray single-crystal diffraction.The results showed that the Ca(II) coordination polymer the Ca(II) ion is coordinated with four O atoms from two L ligands and two O atoms from two coordinated H2O molecules, and generates a distorted octahedral geometry.The 1D chained structure of Ca(II) coordination polymer is formed by the bridging of SO3 -groups.The 3D network structure is formed by the hydrogen bonds and π-π interaction between 1D chains.

Figure 1 .
Figure 1.The structure of ligand.

Figure 4 .
Figure 4. 3D network structure by the interaction of 1D chain.

Table 1 .
Hydrogen bonds data of 1.