Synthesis,Structure And Properties Of Complexes Based On Azobenzene Tetracarboxylic Acid And Dipyridine Bisamide Ligands

A serials of metal-organic complexes based on the 3,3',5,5'-azobenzenetetracarboxylic acid(H₄ABTC),rigid and flexible bis-pyridyl-bis-amide Ligands were prepared under solvothermal condition by introducing transition metal ions,including Zn²⁺ and Cd²⁺,Co²⁺ and Ni²⁺ ions.The structures of the title complexes were characterized by single crystal x-ray diffraction(x-ray),IR,et al,and described in details.In addition,the solid-state fluorescence of the complexes,the fluorescence sensing behavior toward the cations,anions and antibiotics were also preliminarily discussed.1.Four metal-organic complexes 1-4 were synthesized under solvothermal condition using semi-rigid bi-pyridyl-bis-amide compounds,[N,N?-bis(3-pyridinecarboxamide)benzene](3-BPAM)and [N,N?-bis(4-pyridinecarboxamide)benzene](4-BPAM),as N-proton ligands in the presence of the H4 ABTC ligands,Cd(?)or Zn(?)ions.[Cd₄(DMF)₆(3-BPAM)(ABTC)₂]·H₂O(1)[Cd(DMF)(H₂O)(4-BPAM)_0.5(ABTC)_0.5]·3H₂O(2)[(CH₃)₂NH₂]₂[Cd₃(ABTC)₂]·3H₂O(3)[(CH₃)₂NH₂]₄[Zn₄(ABTC)₃](4)Complex 1 is a 3D interpenetrating framework structure.The ABTC ligands were arranged each other in the parallel manner,and coordinated with the Cd²⁺ to result in a 2D layer.The3-BPAM ligands acted as bridging ligands to connect these 2D layers into a 3D framework structure.Two such frameworks were interpenetrated each other to give a two-fold interpenetrating 3D framework of 1.Complex 2 has a 2D layer structure.The ABTC ligands provided the carboxyl groups to coordinate with Cd²⁺ ions to form a 1D circle-to-circle chain,which were connected by 4-BPAM ligands into the 2D layer structure of complex 2.In the structure of complexes 3 and 4,there were no the bi-pyridyl-bis-amide ligands.Complex 3 was a3 D framework structure based on ABTC ligands with the trinuclear Cd clusters as nodes,while complex 4 was also a 3D framework structure with the mononuclear Zn as nodes.Complexes 1and 3 showed better fluorescent sensing activities for Fe³⁺,MnO₄^- and nitrofurazone.2.Four metal-organic complexes 5-9 were synthesized under solvothermal condition by using (H₄ABTC),N,N?-bis(4-pyridinecarboxamide)-1,2-ethane(4-dpye)and N,N?-bis(4-pyridinecarboxamide)-1,4-butane(4-dpyb)as carboxylate and N-donor ligands,respectively,as well Cd²⁺ and Zn²⁺ as metal ions[Zn(4-dpyb)(ABTC)_0.5]·H₂O(5)[Cd(4-dpyb)(ABTC)_0.5]·H₂O(6)[Co(4-dpyb)(ABTC)_0.5]·H₂O(7)[Ni(4-dpyb)(ABTC)_0.5]·H₂O(8)[Cd(4-dpye)_0.5(ABTC)_0.5]·2H₂O(9)The structural analysis showed that the complex 5-8 were isostructural.In the structure,the ABTC ligands were arranged in a parallel manner,and linked into a 2D layer by metal ions.The4-dpyb ligand exhibited two kind of types A and B.Firstly,the 4-dpyb ligands in the type-A bridged these 2D layers into a 3D framework.Two such frameworks were interpenetrated each other to give a two-fold interpenetrating 3D framework.Then the 4-dpyb ligand in the type-A acted as a "lock" to hold the two frameworks together.Complex 9 was a 3D framework structure.The ABTC ligand used the carboxyl group to coordinate with Cd²⁺ ions to form a 1D circle-to-circle chain.The pyridyl groups of the 4-dpye coordinated with the Cd²⁺ ions from the chain to form a 2D layer.The novel structural feature was that the amide oxygen atoms of the4-dpye ligands coordinated with the Cd²⁺ ions from two adjacent layers to generate the 3D framework of complex 9.Complexes 5,6,8 and 9 showed better fluorescent sensing activities for Fe³⁺,MnO₄^- and nitrofurazone.