Synthesis And Magnetic Properties Of The Complexes Based On Aromatic Heterocyclic Ligands

The rational design and construction of multifunctional metal organic coordination polymers is an interesting research field,which have attracted wide attention in China and abroad.This stems not only from their potential applications in optics,electricity and magnetism,but also from their intriguing structural topologies.In this paper,we analyze two types of organic ligands.The one is aromatic heterocyclic ligands that contain N,O-donor atoms,and the other is aromatic ligand that only contains O-donor atoms.They react with the transition and rare earth metal ions by hydro?solvo?thermal and conventional method,respectively,generating twelve new structures of complexes.The structures and their purities are characterized through the infrared spectrum analysis,X-ray single crystal diffraction,elemental analysis and X-ray powder diffraction.Besides,we study their thermogravimetric,solid fluorescence and magnetic properties.It mainly includes the following three aspects in this paper:1.Based on 4-?3,5-dicarboxylphenyl?-2,2?:6?,2?-terpyridine?H₂CPTPY?aromatic heterocyclic ligands reacting with transition metal cations,such as Mn???,Co???,Cu???,Zn???and Cd???in hydro?solvo?thermal reaction,generating five new complexes 1?5.The complexes 1 and 4 are 2D planar structures,the complexes 2 and 3 are0 D structures,and complex 5 is 3D network structure.The research showed that metal ions,solvents and pH value have certain effects on the structures of the coordination polymers.At the same time,the magnetic and solid fluorescence researches indicated that complex 1 had the weak ferromagnetic interactions,and complex 3 showed antiferromagnetic interactions;at room temperature,complexes 4 and 5 exhibited blue purple light under excitation at 380 nm.2.Based on 1,2-di?1H-benzimidazol-2-yl?ethane-1,2-diol?TDB?aromatic heterocyclic ligand reacting with the different Co???salts underhydrothermal conditions,we obtained 0D complexes 6?8 with the similar pentanuclear [Co5?H₂L?6]4+ clusters.In the process of these reactions,we found a novel in situ ethanol ligand 1,2-di?1H-benzimidazol-2-yl?ethanol by the intramolecular dehydration of TDB under high-temperature hydrothermal conditions.The structures are only different in independent of the anions,which indicates the different anions don't have much effect on their main structures.Besides,complexes 6?8 exhibit the similar antiferromagnetic interactions.3.Based on Di-p-toluoyl-D-tartaric acid?D-H₂DTTA?aromatic ligands reacting with rare earth cations sush as Tb???,Dy???and Ho???under solvent spun crystalline,we constructed four new polymers 9?12,in which complexes 9?11 are homogeneous with 1D chains,and complexe 12 is the Dy complex formed by the tartaric acid ligand produced by decomposition of D-H₂ DTTA.We found that rare earth metal cations coordinating with aromatic heterocyclic ligands contain only O-donor atoms was relatively easier than aromatic ligands including N,O-donor atoms.The magnetic investigation indicated that complexes9?11 showed antiferromagnetic interactions.The solid fluorescence research showed that complexes 9?11 exhibit broad fluorescent emission bands at 316?lex=280nm??317?lex=270nm?and 310nm?lex=280nm?.The observed blue-shift can be owed to the intra-ligand ?-?* transitions,and the weakened luminescence intensity can be attributed to the strong interactions between the deprotonated DTTA^2-ligands and the lanthanide centers;the complexes 9 and 10 exhibits the characteristic f-f transitions of Tb?III?and Dy?III?cations upon excitations at 280 and 270 nm.Four emission peaks at 488,536,581 and 618 nm are assigned to the transitions originating from ⁵D₄ to ⁷F_j?j=6,5,4,3?for Tb?III?cation.Two emission peaks at 478 and 572 nm are assigned to the ⁴F_9/2?6H_15/2 and ⁴F_9/2?⁶H_13/2.