Synthesis,Structure And Properties Of Metal-Organic Frameworks Based On Dipyridine Diamide Ligands

Using mixed ligand strategy can alwayss generate MOFs with interesting architectures which in turn display interesting magnetic or luminescent properties.In this work,two bipyridine biamide ligands N,N'-bis-(3-pyridyl)isophthalamide(3-bpipa)and N,N'-bis-(3-pyridyl)terephthalamide(3-bptpa)were selected as main ligands,and different polycarboxylates[1,3,5-benzenetricarboxylic acid(1,3,5-H₃btc),5-hydroxyisophthalic acid(5-H₃hip),1,4-benzenedicarboxylic acid(1,4-H₂bdc)and 1,3-benzenedicarboxylic acid(1,3-H₂bdc)]have been used as auxiliary ligands to constructure coordination polymers with transition metal ions under hydrothermal conditions.Seven coordination polymers have been synthesized and structurally characterized by single-crystal X-ray diffraction analyses and IR spectra.The magnetic properties and fluorescent behaviors of some coordination polymers have been investigated.1.Using the 3-bpipa as main ligand and polycarboxylates as auxiliary ligands,five transition metals complexes with different structural features have been synthesized under hydrothermal conditions and structurally characterized.The influence of the 3-bpipa ligand,polycarboxylates auxiliary ligands and the central metals on the structures of complexes has been studied.[Co(3-bpipa)₂(1,3,5-Hbtc)]·2H₂O(1)[Ni(3-bpipa)(1,3-bdc)(H₂O)]·4H₂O(3)[Zn(3-bpipa)(1,3,5-Hbtc)]·2H₂O(5)[Cd(3-bpipa)(1,4-bdc)]·H₂O(6)[Cd(3-bpipa)₂(1,3,5-Hbtc)(H₂O)]·4H₂O(7)Single crystal X-ray diffraction analysis reveals that complexes 1?3 and 5-7 show different structures.Although complexes 3 and 7 show similar one-dimensional tubular structures,they are different from each other due to different polycarboxylates auxiliary ligands.Complexes 1 and 5 are also one-dimensional structures,1 is a one-dimensional tubular structure with double zigag chains and 5 is a one-dimensional wave-liked chains.Complex 6 is a rhombic framework.It is suggest that the coordination mode of organic polycarboxylates and main ligands play an important role in the construction of final frameworks.The magnetic properties and fluorescent behaviors of some coordination polymers have been investigated.Complex 7 emits MLCT fluorescence:?_em=460 nm;?_ex=330 nm.The magnetic interactions between Ni(II)ions in complex 3 were treated with molecular field approximation:z J?=-0.88cm^-1,g=2.09,R=6.5×10^-4.2.Using the 3-bptpa as main ligand,two complexes with different structural features have been hydrothermally synthesized and structurally characterized.[Co(3-bptpa)(1,3,5-Hbtc)]·H₂O(2)[Ni(3-bptpa)(5-Hhip)(H₂O)]·3.5H₂O(4)Complex 2 is connected by a one-dimensional ladder chain to generate a two-dimensional grid structure.Complex 4 is a two-dimensional network that is composed by one-dimensional[Ni-(3-bptpa)]_n and[Ni-(5-Hhip)]_n chain.It is suggest that the organic polycarboxylates play an important role in the construction of final frameworks.Furthermore,the magnetic properties of 2 and 4 have been investigated.The variable temperature magnetic susceptibility data of complex 2 at 16-300K were fitted by using the isotropic Co(II)single ion approximation of rotation-orbit coupling in octahedral field.The results are as follows:?=-100.4 cm^-1,A=1.0,z J?=-0.618 cm-1,R=1.62×10^-3.The magnetic interaction between Ni(II)ions in complex 4 was treated by molecular field approximate treatment.z J?=-1.04 cm^-1,g=2.21,R=4.6×10^-4.