Syntheses And Electrochemical Sensing Properties Of Coordination Polymers Of Benzimidazole Carboxylic Acid

Coordination polymers（CPs）with periodic network structures constructed by metal ions/clusters and organic ligands through coordination interactions,which show enormous variety of impressive structures and significant potentials in many fields.On the other hand,non-enzymatic electrochemical sensors possess many remarkable advantages,such as high sensitivity,low detection limit,fast detection,portable equipment,simple operation and so on.In this thesis,the benzimidazole carboxylic acid ligands with multiple coordination sites were designed and synthesized through the aldehydramine condensation reactions,which were employed to self-assemble with metal ions(Co²⁺,Ni²⁺)by solvothermal methods to produce three CPs,the crystal structures and chemical compositions of three CPs were characterized by single-crystal X-ray diffraction and other methods.Moreover,three CPs were modified on carbon paste electrodes（CPE）and their electrochemical properties were studied.The details are as follows:1.The condensation reaction of 4-（1H-1,2,4-triazol-1-yl）benzaldehyde and3,4-diaminobenzoic acid to produce the organic ligand 2-（4-（1H-1,2,4-triazol-1-yl）phenyl）-1H-benzo[d]imidazole-5-carboxylic acid（H₂tpbimc）,which was solvothermally reacted with Co²⁺ion to give a isolated CP,{[Co（Htpbimc）₂（H₂O）₄]·H₂O}_n（1）.Single-crystal structural analysis showed that CP 1 belonged to the monoclinic ctystal system with the space group C2/c.In the asymmetrical skeleton of CP 1,there were one six-coordinated octahedral Co²⁺ion,two Htpbimc^-ligands,four coordinated water molecules and one lattice water molecule.Adjacent structural units were formed a three-dimensional（3D）supramolecular framework through hydrogen bonds.CP 1 was modified CPE to construct a non-enzymatic hydrogen peroxide（H₂O₂）electrochemical sensor（CPE 1）,which exhibited excellent electrocatalytic activity towards H₂O₂in the 0.1 mol·L^-1Na OH solution.Under the optimal experimental conditions and the linear range was 0.05–0.35 mmol·L^-1,the limit of detection（LOD）was 1.03μmol·L^-1.Moreover,it performed excellent stability,repeatability and anti-interference.2.When4-（1H-1,2,4-triazol-1-yl）benzaldehydewassubstitutedfor2-pyridinecarboxaldehyde,the organic ligand 2-（2′-pyridyl）-benzimidazole-6-carboxylic（H₂pybimc）was synthesized under similar conditions,and then reacted with Ni²⁺ion under the solvothermal conditions to present a 2D layer structure,{[Ni（Hpybimc）（NO₃）（H₂O）]}_n（2）.Structural analysis revealled that CP 2 crystallized in the monoclinic ctystal system with the space group C2/c,which consisted of one six-coordinated octahedral Ni²⁺ion,one Hpybimc^-ligand,one NO₃^-and one coordinated water molecule in the asymmetrical unit.Adjacent Ni²⁺ions were bridged by Hpybimc^-ligands to present a 2D layer,which further stacked to give a supramolecular structure.In addition,its spatial structure can be simplified to a 3-node‘fes’type topology.CP 2 was modified CPE to construct a non-enzymatic ascorbic acid（AA）electrochemical sensor（CPE 2）,which displayed excellent electrocatalytic activity towards AA in the 0.1 mol·L^-1Na H₂PO₄-Na₂HPO₄（p H=6.6）buffer solution.Under the optimal experimental conditions and the linear range was 5×10^-4–7.3 mmol·L^-1,the LOD was as low as 0.85μmol·L^-1,and it has satisfactory stability,repeatability,and anti-interference.In addition,it was successfully applied to the detection in real samples with recoveries of 96.8–102.4%.3.When introduced 1,4-benzenedicarboxylic acid（1,4-H₂bdc）into the reaction system of H₂pybimc ligand and Ni²⁺ion,a 2D network with mixed ligands was harvested by solvothermal method,{[Ni（Hpybimc）（bdc）_0.5（H₂O）]}_n（3）.Single-crystal structural analysis indicated that CP 3 belonged to the monoclinic ctystal system with the space group P2₁/n,which consisted of one six-coordinated octahedral Ni²⁺ion,one Hpybimc^-ligand,0.5 bdc^2-and one coordinated water molecule in the asymmetrical sketelon.CP 3 modified CPE to construct a non-enzymatic nitrite（NO₂^-）electrochemical sensor（CPE 3）,which revealled excellent electrocatalytic activity towards NO₂^-in the 0.1 mol·L^-1Na H₂PO₄-Na₂HPO₄（p H=6.7）buffer solution.Under the optimal experimental conditions and the linear range is 0.01–10.0 mmol·L^-1,the LOD was 0.66μmol·L^-1,and it has good stability,reproducibility and anti-interference.