Synthesis And Properties Of Coordination Ploymers Based On 'Multi-arm' Flexible Thiopyridine Ligands

Flexible thioether pyridine ligands,a kind of ligand with thioether bonds and pyridine functional groups,not only have the characteristics of strong coordination ability of pyridine ligands,but also have the characteristics of rich conformation of flexible ligands.Therefore,researches on the structure and applications of coordination polymers synthesized by flexible thioether pyridine ligands have attracted people's attention.This paper mainly adopts the mixed ligands strategy,uses multi-arm(‘double-arm',‘three-arm'and‘four-arm')flexible thioether pyridine ligand as the main ligand,and uses V-shaped or linear rigid carboxylate acid ligand as an auxiliary ligand to constructed coordination polymers.By changing synthesis method and experimental conditions,ten coordination polymers were constructed and characterized.The main contents of this paper are as follows:1.Based on the‘double-arm'flexible ligand,bpb(1,2-bis((pyridin-4-ylthio)methyl)benzene),we used the mixed ligand strategy,selected V-shaped structure of auxiliary ligands and transition metal ions to assemble six coordination polymers 1-6:{[Co(bpb)(tbip)]_n·H₂O}_n(1);{[Co(bpb)(mip)]}_n(2);{[Mn(bpb)(mip)]}_n(3);{[Co(bpb)(5-eip)]}_n(4);{[Co(bpb)(5-pip)]·H₂O}_n(5);{[Co(bpb)(5-nip)]·H₂O}_n(6)(H₂tbip=5-tert-butyl-1,3-benzenedicarboxylic acid;H₂mip=5-methoxyisophthalicacid;H₂eip=5-ethoxyisophthalicacid;H₂pip=5-propoxyisophthalic acid;H₂nip=5-nitroisophthalic acid)under hydrothermal conditions.Single crystal diffraction shows that 1-6 are all one-dimensional chain structures with binuclear metal ion clusters as structural elements.In addition,IR(infrared spectra),TGA(themogravimetric analysis)and PXRD(powder X-ray diffraction)were performed.The Hirshfeld surface analysis method was used to compare the effects of different substituents on the weak interaction forces between molecules in 1-6.Magnetic analysis shows that the Co(II)ions of 1,2,4,5 and 6 have similar antiferromagnetic coupling interactions,while the antiferromagnetic coupling interaction between Mn(II)ions of 3 differs from the other five complexes due to the different spin states of the ions.2.By selecting the‘three-arm'flexible thioether pyridine ligand(1,3,5-tris(4-pyridylsulfanylmethyl)-2,4,6-trimethyl benzene),we have obtained the crystalline product{[Cd(tptb)₂(H₂O)₂]·2NO₃}_n(7)with a two-dimensional layered structure under normal temperature volatilization conditions;by adding the rigid linear ligand,H₄DOBDC(2,5-dihydroxyphthalic acid),we have obtained a three-dimensional triple interpenetration framework material,{[Cd(tptb)(H₂DOBDC)(H₂O)]·DMF}_n(8,DMF=N,N-dimethylformamide)with a complex structure than 7,more stable than 7,and a luminescence performance better than 7 in suspension.Hirshfeld surface analysis method was used to compare the weak interaction force between 7 and 8 molecules after adding H₄DOBDC.We also performed IR,TGA and PXRD related characterization and fluorescence tests on these two coordination polymers.Fluorescence test results show that 7 can not only selectively identify and detect Fe³⁺,Cr O₄^2-and Cr₂O₇^2-ions in DMA solution,but also selectively identify and detect Cr O₄^2-ions at p H 13.0.In addition,the fluorescence quenching mechanism was studied.3.Based on the‘four-arm'flexible thioether pyridine ligand,tpb(1,2,4,5-tetra(4-pyridylsulfanylmethyl)benzene),we have successfully constructed a coordination polymer,{Cu(tpb)₄(H₂O)}_n(9)with the two-dimensional layered structure of the‘windmill'structural unit,and a two-dimensional framework material,{[Zn(tpb)(tbip)]·0.5H₂O}_n(10)constructed with the 8-like structural unit under hydrothermal conditions.Hirshfeld surface analysis method was used to compare the difference of the intermolecular interaction force between 9 and 10.And PXRD characterization,thermogravimetric analysis,and solid-state fluorescence spectroscopy analysis was carried out.