| Pyrazole ligands , as a series multifunctional organic ligands, show more varoius self-assembly capability comparison with monodentate ligands, and colud bind transition-metal or rare eath to form diatomic or polyatomic complexes, which is used to study relationship bettwen the structure, properties and magnetic exchange mechanism. After the pyrazol-bridged complexes and their structure were summarized, a new ligand, 3,5-bis[N-(2-hydroxy-3-metho- xybenzoic)-carbamoyl] pyrazole(H3L), was synthesized and was characterized by IR spectrum, elemental analysis, HNMR.Four complexes NH4[Ln(OVA)4] (Ln = Pr, Nd, Gd, Ho, OVA = 2-hydroxy-3-methoxy- benzoate) were synthesized by reacting ovanillinc with LnCl3-6H2O (Ln=Pr, Nd, Gd, Ho) in water, and were characterized by IR, TG-DSC, elemental analysis and X-ray diffraction. Complexes NH4 [Ln(OVA)4](Ln=Pr, Nd, Gd) are allomers and are all Orthorhombic with Space group Pnna. With the atomic number increases, the cell parameters a, b, c and the Ln...Ln distance decrease. They are consistent with lanthanide contraction regularity. The Ln3+ ion displayed as a distorted square anti-prismatic configuration, each pair of metal atoms was bridged by four carboxylate ions, where all carboxylate ions act as Z,Z-type bidentate to form a 1-D carboxylate-bridged metal chains parallel to the a axis of the crystal.NH4[Ho(OVA)4] is orthorhombic crystal system, Ccc2 space group. There are two types of carboxylate in structure: chelating-type bidentates, Z,Z-type bridging bidentate. The displays as a dodecahedral octa-coordination configuration and Ho3+...Ho3+ is connected by two Z,Z-type bidentates to form a 1 -D carboxylate-bridged coordination polymers, which parallel to the c axis of the crystal. All the Ho3+ are in one line, and channels are formed along the a axis direction.Three new complexes [Zn(OVA)2·2H2O], [Ni(H2O)6](OVA)2·2H2O and [Co(H2O)6](OV-A)2·2H2O were synthesized and were characterized by TG-DSC and X-ray diffraction. [Zn(OVA)2·2H2O] is monoclinic with C2/c space group. Each zinc (II) is coordinated by two oxygen atoms from two waters and two oxygen atoms from two OVA- to form a distorted tetrahedron geometry. Two carboxyl groups 8in the complex act as mono-dentate coordination. [Ni(H2O)6](OVA)2·2H2O and [Co(H2O)6](OVA)2·2H2O are both triclinic with P-1 space group. The metal center coordinated with six waters diaplays as a distorted octa-coordination configuration. The carboxyl groups did't coordinated with metal center and they connected by hydrogen bonds to form 3-D networks. |
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