| In this paper,a type of pyridine amide ligand[N,N'-bis(pyridin-3-ylmethyl)-terephthalamide]is designed and synthesized as the main ligand,three carboxylic acids with different position of substituents[terephthalic acid(1,4-H2BDC),isophthalic acid(1,3-H2BDC),phthalic acid(1,2-H2BDC)]are used as auxiliary ligands,self-assembled with different transition metal ions,twelve coordination polymers{[Zn(L)(1,4-BDC)]·H2O(1),[Zn(L)(1,3-BDC)]·H2O(2),[Zn(L)(1,2-BDC)](3),[Cd(L)0.5(1,2-BDC)(H2O)](4),[Cu2(L)2(1,4-BDC)2(H2O)2]·H2O(5),[Cu(L)(1,3-BDC)]·(H2O)3(6),[Cu(L)(1,2-BDC)](7),[Co(L)(1,4-BDC)(H2O)2](8),[Co2(L)2(1,3-BDC)2](9),[Co(L)(1,2-BDC)](10),[Ni(L)(1,4-BDC)(H2O)2](11)and[Ni(L)(1,3-BDC)(H2O)]·H2O(12)}were successfully obtained.The new complexes were structurally characterized using single-crystal X-ray diffraction analyses,powder X-ray diffraction(PXRD)and IR spectra.1 and 2 are both 2D structures with 63 and44 topology,3 shows a 4-connected 3D framework,and 4 features a 1D structure with single/double alternate linkers.5,6 and 7 are all Cu-based 3D complexes.8 and 11 are isomorphic,which show 2D parallelogram structures.9 and 10 belong to the 3D Co-based metal-organic frameworks.12 is a 2D quadrilateral structure.In order to systematically study the fluorescence sensing properties of the coordination polymers,the previously reported complex[Cd3(L)2(1,4-BDC)3]·4H2O(1a)was also studied.Fluorescence sensing experiments show that 1–4 and 1a show multi-functional fluorescent responses towards metal ion(Fe3+),anions(CrO42–,Cr2O72–)and pesticide(2,6-DC-4-NA)and have good stability in a wide range of p H values.It has high fluorescence quenching efficiency and KSV value,good selectivity,sensitivity,cyclability and low detection limit.In addition,the mechanism of fluorescence quenching is explored.Owing to the weak solid-state fluorescence properties,5–12 cannot be used as fluorescence sensing materials.The results show that the metal ions in the complexes have a significant influence on the final properties of the complex materials. |
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