КООРДИНАЦИОННАЯ ХИМИЯ, 2014, том 40, № 9, с. 569-574
УДК 541.49
SYNTHESIS AND STRUCTURES OF COPPER(II) AND CADMIUM(II) COMPOUNDS BASED ON PYRIDAZINE DERIVATIVE LIGANDS
© 2014 S. W. Li, Y. F. Wang, and J. S. Zhao*
Key Laboratory of Synthetic and Natural Functional Molecule Chemistry of Ministry of Education, Shaanxi Key Laboratory of Physico-Inorganic Chemistry, College of Chemistry & Material Science, Northwest University,
Xi'an, Shaanxi, 710069 P.R. China *E-mail: jszhao@nwu.edu.cn Received November 7, 2013
The two new compounds [Cu(HODA)2(H2O)2] • 3H2O (I) and [Cd(HODA)2(H2O)3] (II) (HODA = 6-oxo-1,6-dihydropyridazine-4-carboxylic acid) based on pyridazine derivation ligands have been synthesized and characterized by elemental analysis, infrared spectrum and X-ray single crystal diffraction. X-ray analysis shows that in compound I, Cu2+ ion is four-coordinated with a plane square geometry while Cu2+ ion in compound II is seven-coordinated with a distorted pentagonal bipyramid geometry. Both of the two units are all connected as 3D supramolecular structures by the intermolecular hydrogen bonds. Moreover, thermal gravimetric analysis of two compounds has been also investigated.
DOI: 10.7868/S0132344X14080052
INTRODUCTION
Nowadays, the design and construction of metal-organic materials have drawn enormous interests in modern inorganic chemistry, which not only due to their promising applications asfunctional materials in fields, including catalysis, gas adsorption, nonlinear optics, magnetism and luminescence but also their fascinating structural topologies [1—5]. It is well known that the resulting structures are mainly dependent upon several factors, such as the chemical nature of organic ligands and the coordination preference of metal ions and so on, while the match of mental centers with suitable ligands which is one of the most important factors [6]. Ligands containing nitrogen and carboxyl, which have been employed to construct many metal-organic frameworks (MOFs) with novel structures and properties, may play different roles [7—9]. Usually the further connection of the frameworks by nitrogen-containing ligands will devote to tuning the structures and properties of the final products, bringing about high dimensional coordination polymers, carboxyl ligands link metal ions into neutral 1D chains or 2D networks, as well as their versatile coordination conformations and strong coordination ability.
In the construction of MOFs, flexile pyrazine derivative ligands were well used for the construction of complexes due to their ready availability and strong coordination ability to transition metal ions. Meanwhile, the combination of N-donors and carboxyl-co-ordination groups in a promising metal organic ligand may raise a higher interest for structural evolution [10—12]. Inspired by the former considerations, we pushed our attention on exploring various MOFs
which can be formed via a mixed ligand system containing N-donors and carboxyl-co-ligand. In the present work, the rigid 6-oxo-1,6-dihydropyridazine-4-carboxylic acid (HODA) ligand has been employed as a building block, which based on the following considerations: (1) The nitrogen-donor ligands have been widely used as an auxiliary recent years, thus the introduction of them is an effective method on the structure of metal compounds owing to the fact that they can satisfy and even mediate the coordination needs of the metal centers and consequently generate more meaningful architectures [13, 14]. (2) The carboxyl-ligands have been intensely investigated, which can donate to the building of the structures with high dimensions. (3) Coordination polymers constructed from the combination of N-donor and carboxyl-ligands remain largely unexplored, therefore, the research of much work is still on the way, and is truely a good originality for the construction of novel topology and networks.
Considering the above-mentioned aspects, the two new compounds, [Cu(HODA)2(H2O)2] • 3H2O (I) and [Cd(HODA)2(H2O)3] (II), have been prepaered hydrothermal synthesis. They were well characterized by elemental analysis, infrared spectroscopy (IR) and X-ray single crystal diffraction. Thermo gravimetric analysis (TGA) of two compounds was also used to investigate.
EXPERIMENTAL
Materials and methods. HODA was purchased and used without further purification. All the other starting chemicals and solvents were of reagent grade and were
LI et al. (a)
N(1)
N(2)
O(5) (b) O(3^)
O(4)
O(1)
Fig. 1. Molecular structures of I (a) and II (b).
used as received. The FT-IR spectra were obtained from KBr pellets on a Bruker Vectorm 22 spectrometer in the 400—4000 cm-1 region. TGA was carried out on a Sta449c thermal analyzer from room temperature to 1000°C with a heating rate of 10°C min-1.
Synthesis of I and II. Compound I was synthesized by adding Cu(NO3)2 • 3H2O (0.06024 g, 0.25 mmol) to an ethanol solution in which contains HODA (0.07042 g, 0.5 mmol) and distilled water. Then it was put into a stainless-steel reactor with Teflon liner, heated to 150°C and kept at constant temperature for 72 h. After cooling to room temperature, green crystals of compound I were obtained. The yield was 55%.
For C^H^^Cu (I)
anal. calcd., %: C, 26.78; H, 4.020; N, 12.50. Found, %: C, 26.67; H, 4.000; N, 12.44.
IR (KBr; v, cm-1): 3025, 1760, 1600, 1320, 950, 725, 710.
Compound II was prepared following the same synthetic procedure as that for compound I, except that Cd(NO3)2 • 4H2O was used instead of Cu(NO3)2 • 3H2O. Light yellow crystals of compound II were obtained. The yield was 63%.
For C10H12N4O9Cd (II)
anal. calcd., %: C, 27.13; H, 2.713; N, 12.67. Found, %: C, 27.02; H, 2.702; N, 12.61.
IR (KBr; v, cm-1): 3160, 1754, 1610, 1335, 955, 725,715.
X-ray crystallography. Single-crystal X-ray diffraction measurements were performed on Brucker Smart Apexccd diffractometer with a graphite-monochro-mated Mo^a radiation at 296(2) K. Absorption corrections were applied to the date using SADABS program. The hydrogen atoms were assigned with common isotropic displacement factors and included in the final refinement by use of geometrical restrains, while the non-hydrogen atoms were treated with common anisotropic displacement factors and included in the final refinement with geometrical restrains. The structures were solved by direct methods and refined on F2 by full-matrix least-squares using the SHELXL program. The details of the crystal parameters, data collections and refinements for compounds I and II are summarized in Table 1, selected bond distances and angles are listed in Table 2.
RESULTS AND DISCUSSION
The single-crystal X-ray diffraction analysis reveals that compound I is a 3D supramolecular polymer. It contains one Cu2+ ion, two HODA ligands, two coordinated water molecules and three lattice water molecules, in which the Cu2+ ion is four-coordination. The molecular structure of the compound I is shown in Fig. 1a. The plane is occupied by two carboxylic oxygen atoms (O(3), O(3A)) from two different HODA ligands and two other oxygen atoms (O(5), O(5A))
SYNTHESIS AND STRUCTURES OF COPPER(II) AND CADMIUM(II) 571
Table 1. Crystallographic data and structural refinement details of complexes I and II
Parameter Value
I II
Color/shape Green/block Light yellow/block
Formula weight 449.82 444.64
Wavelength, A 0.71073 0.71073
Crystal system Triclinic Orthorhombic
Space group PI Fdd2
Unit cell dimensions:
a, A 6.2777(8) 12.8227(13)
b, A 6.9141(9) 36.088(4)
c, A 10.7504(14) 6.1875(6)
a, deg 72.986(2)
ß, deg 77.784(2)
Y, deg 73.604(2)
Z; V, A3 1; 423.80(9) 8; 2863.3(5)
Pcalcd mg/m3 1.763 2.063
Absorption coefficient, mm-1 1.363 1.585
/(000) 231 1760
9 Range for data collection, deg 2.00-26.05 3.37-26.77
Reflections collected 2296 3903
Independent reflection (Rint) 1627 (0.0142) 1456 (0.0239)
Refinement method Full-matrix least-squares on F 2
Data/restraints/parameters 1627/6/133 1456/1/127
Goodness-of-fit on F2 1.122 1.079
Final R indices (I> 2o(I)) R1 = 0.0348, wR2 = 0.1126 R1 = 0.0239, wR2 = 0.0635
R indices (all data) R1 = 0.0391, wR2 = 0.1398 R1 = 0.0253, wR2 = 0.0644
Largest diff. peak and hole, e/A3 0.316 and -0.593 0.290 and -0.272
from coordinated water molecules. The length of the Cu(1)—O(3) bond is 1.933(2) Á and that of Cu(1)-O(5) is 1.984(2) Á, which form a plane square structure. As the Table 2 shows, the bond angle of O(3)Cu(1)O(5) do not significantly deviate from orthogonal, ranging from 87.6(10)° to 92.4(10)°.
In compound I, there are three kinds of the intermolecular H-bonds interactions. As shown in Fig. 2a, one kind of hydrogen bonds of N-H-O type has been observed between the hydrogen atoms from the lattice water molecules and the nitrogen atoms from the HODA ligands (2.823 Á for N(2).-O(2)). The second kind of hydrogen bonds existing between the lattice water molecules and the coordinated water molecules has been found (2.727 Á for O(5).-O(2) and 2.796 Á for O(6)...O(2)). The third kind of hydrogen bonds is between the coordinated water molecules and the oxygen atoms from the HODA ligands, in which the
O(6)...O(5) bond is relatively longer (3.190 Á) (Table 3). Thus the units of I are linked as a 3D su-pramolecular structure by the intermolecular H-bonds.
In compound II (Fig. 1b), Cd(II) atom is seven-coordinated in a distorted pentagonal bipyramid geometry, in which the equatorial sites are occupied by five oxygen atoms (O(1), O(L4), O(2), O(2A), and O(4)). The four in five oxygen atoms mentioned are from two HODA ligands, while the last one is from the coordinated water molecule. The bond lengths range from 2.234(5) to 2.431(3) Á. The axial site is formed by the two coordinated water molecules (O(3), O(3A)), while the length of those bonds are all 2.349(3) Á. In compound II, the bond angles of OCdO do not significantly deviate from orthogonal (Table 2).
As shown in Fig. 2b, hy
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