The Synthesis And Study On Carboxyl-bridged Cu-Lanthanide Heteronuclear Complexes

Studies of heteronuclear metal complexes started at the end of the 1960s due to an interest in the physicochemical properties arising from the presence of dissimilar metal ions in close proximity. Researches on bridged 3d—4f heteronuclear complexes have significant values,which have potential applications, such as gas storage, gas/vapor separation, catalysis, luminescence, and drug delivery. Molecular materials are systems that may be considered as built of discrete molecules, the so-called "building blocks". This structural feature creates great opportunities for the modeling of electrical, magnetic and optical properties of materials through the selection of appropriate constituent molecules. At the same time, it is crucial to design new processes that would make it possible to control the directional arrangement of molecules in the space.We have been synthesized and characterized the structure of the carboxy bridged Cu—lanthanide heteronuclear complexes,having following results.(1)①[CuGdL5Py(H2O)]n and③[CeCu2L'4LPy2(NO3)2(H2O)]n are all 1D coordination polymers, they have similar structure. X—ray diffraction analysis reavealed that complexe①was crystallized in trigonal space group P1 as complexe③was crystallized in monoclinic space group P21. In the crystal of [CuGdL5Py(H2O)]n, the Cu(Ⅱ) ion has four-coordinate square planar geometry with one nitrogen atom from pyridine, three oxygen atom from methacrylate. Gd(Ⅲ) ion has eights-coordinate square antiprism (D4d) geometry with seven oxygen atom from methacrylate, one oxygen atom from a aqua molecule. A Cu(Ⅱ) ion and a Gd(Ⅲ) ion obtain the formation of tetra-nuclear unit (Cu Gd Gd Cu or Gd Cu Cu Gd) with inversion operation. These units are linked together resulting in the formation of a 1D coordination polymer. This complexe [CeCu2L'4LPy2(NO3)2(H2O)]n consists of trinuclear Cu2Ce unit, each unit include two Cu(Ⅱ) ion,one Ce (Ⅲ) ion and four isobutyrate ion, two nitrate ion, one methacrylate ion, two pyridine as well as one aqua molecule. Among these ligands, isobutyrate ion and nitrate ion serve as bridging ligand with different pattern of coordination. two isobutyrate ligand bidentate bridged Cu(Ⅱ) ion and Ce (Ⅲ) ion. Besides bidentate bridged Cu(Ⅱ) ion and Ce (Ⅲ) ion, the other two isobutyrate ligand alsoμ2-O bridged two Cu(Ⅱ) ion, this means one carboxylate oxygen atom linked two Cu(Ⅱ) ion all together. As a result, isobutyrate ion linked all metal ion form 1D chain structure. Complexe②CuGdL5Py(HL)(H2O) belongs to discrere dinuclear structure, which is completely different from complexe①[CuGdL5Py(H2O)]n. Cu(Ⅱ) ion has five-coordinate square pyramid geometry with one nitrogen atom from pyridine, three oxygen atom from methacrylate bridging ligands and one oxygen atom from neutral methacrylic molecule. Gd(Ⅲ) ion has eight-coordinate distorted square antiprism (D4d) geometry with four oxygen atom from two methacrylate chelating ligands, three oxygen atom from three methacrylate bridging ligands and one oxygen atom from one aqua molecule.(2) The results suggested that{Cu-Gd} heteronuclear complexe①[CuGdL5Py(H2O)]n and②CuGdL5Py(HL)(H2O) have different magnetic property result from different molecular geometries. Temperature dependent magnetic susceptibilities of complexes①,②were measured in 10000 Oe (DC) (1 Oe=4π×10-3 H) from low temperature to room temperature. The Plots of 1/xM vs T were well fit for the Curie—Weiss Law. Because the interaction among paramagnetic ion at room temperature can be neglected, the Curie values of two complexes is similar. As they have different magnetic property at low temperature, the Weiss values (0) were-1.25K,0.137 K for①,②respectively from the plots of 1/xM vs T. That reavealed:that complexe①[CuGdL5Py(H2O)]n exhibited antiferromagnetic interaction as complexes②CuGdL5Py(HL)(H2O) exhibited ferromagnetic interaction. Especially at low temperature, the antiferromagnetic interaction between Cu···Cu was more strong even overtaken the ferromagnetic interaction between Cu···Gd. At low temperature, intermolecular antiferromagnetic interaction in complexes①and②was strong, reavealed obvious antiferromagnetic interaction.