Synthesis,Structures,Luminescence And Magnetism Of The Complexes Based On Aromatic Tricarboxylic Acid Ligands

The construction of multifunctional metal organic complexes with novel structures and various properties has always been one of the key research areas for researchers in China and abroad.In this paper,we chose two ligands characterized by rigidity and flexibility respectively.They are aromatic ligands that only contain O-donor atoms.The react with the transition and rare earth metal ions by hydro(solvent)thermal method,generate twelve new complexes.The structures and their purities are characterized through the infrared spectra,X-ray single crystal diffraction,elemental analysis and X-ray powder diffraction.The thermal stability,optical and magnetic properties are studied.It mainly includes the following three aspects in this paper:1.Based on 3,4',5-biphenyl tricarboxylic acid(H3BPT)ligands five new complexes 1?5 with rare earth metal ions,such as Ce3+,Pr3+,Nd3+,Sm3+ and Tb3+ in hydro(solvo)thermal reaction are generated.The complexes 1?4 are isostructural,and they are binuclear and three-dimensional structures.Whereas complex 5 is a tetranuclear and three-dimensional structure.H3BPT ligands are completely dehydrogenized and coordinate with metal ions.The coordination modes in complexes 1?4 are ?5-?1:?1:?1:?1:?1:?2:?1 and ?4-?1:?1:?1:?1:?1 in complex 5.The research shows the regulating effects of metal ions on the structures of these complexes.Complexes 1?5 exhibit the antiferromagnetic interactions,which may be related to the larger bond angles of M-O-M in the complexes.The solid fluorescence spectra show that the ligand has the strongest emission peak at 397 nm under the excitation of 280 nm,and the emission peak of complexes 1?4 are blue shift compared to the ligand,at the same time the fluorescence is significantly enhanced.It is shown that after the formation of the complex the rigidity of the structure is stronger than that of the ligand.The complex 5 exhibits the characteristic f-f transitions of Tb3+ ion upon excitations at 335 nm.The ligand can sensitize the erbium ion.Four emission peaks at 620,589,543,and 489 nm are assigned to the transitions originating from 5D4 to 7Fn(n = 3,4,5,6)for Tb3+ion.The emission peak at 543 nm is assigned to the 5D4 to 7F5.2.Based on 1,3,5-tris(4-carboxyphenoxy)benzene(H3TCPB)ligands four new complexes 6-9 with rare earth metal ions,such as La3+,Ce3+,Pr3+and Nd3+ in hydro(solvo)thermal reaction are constructed.The complexes 6?9 are iso structural 3D network structures.All of the carboxyl groups of H3TCPB are completely dehydrogenated and coordinate with metal ions.The coordination mode is ?6-?1:?1:?1:?2:?1.The complexes 6?9 exhibit the antiferromagnetic interactions,which may be related to the larger bond angles of M-O-M in the complexes.Although the complexes 7?9 generally show antiferromagnetic properties,the magnetic interactions are different in each temperature range.Complexes 7 and 8 exhibit weak ferromagnetism at the certain temperature ranges,while complex 9 exhibits antiferromagnetic interaction at full temperature range.In terms of fluorescence intensity,complexes 7 and 9 are stronger than the ligand,but complex 8 is the weakest.It can be seen that even for isostructural complexes with light rare-earth ions,the properties of the complexes can be significantly different due to the different types of metal ions.3.Based on 1,3,5-tris(4-carboxyphenoxy)benzene(H3TCPB)ligands complexes 10-12 with transition metal Cd2+ and nitrogen-containing ligand 1,4-bisimidazole(1,4-bib)benzene are synthesized by hydro(solvo)thermal reaction.The complex 10 has a one-dimensional structure,in which the carboxyl groups of H3TCPB are partly dehydrogenated.The coordination mode is ?2-?1:?1:?1:?1.The synthesis condition of complex 11 is similar to that of 10 except that the reaction temperature is increased.Complex 11 is a 3D network structure.Complex 12 is a two-dimensional structure,which is obtained by adding the auxiliary ligand 1,4-bib under the same reaction temperature of 11,and the auxiliary ligand participates in the coordination.All of the carboxyl groups of H3TCPB are dehydrogenated and coordinate with metal ions.The coordination modes are ?6-?2:?1:?1:?1:?1 and?6-?1:?1:?1:?2:?2:?1 in 11 and 12 respectively.It can be found that elevated temperatures and the addition of ancillary ligands can affect the dehydrogenation capacity of the primary ligand.The fluorescence intensity of complex 12 is stronger than that of the ligand and complexes 10 and 11.Thermal stability of complex 12 is higher than that of complexes 10 and 11.It can be seen that different reaction temperatures and the participation of ancillary ligands can lead to great differences in the structures and properties of complexes.