Preparation And Fluorescence Sensing Properties Of Transition Metal Coordination Polymers Based On 3,5-Bis(benzimidazol-1-yl)pyridine

Due to the novel and various topological structures and excellent luminescent properties,luminescent coordination polymers have been regarded as a class of promising fluorescent materials in the field of chemistry and materials science,which have attracted extensive attention from chemists and materials scientists.In this thesis,V-shaped semi-rigid3,5-bis(benzimidazol-1-yl)pyridine(BBIP)and different aromatic carboxylic acids were chosen as the primary and auxiliary ligands,respectively,and fourteen novel transition metal coordination polymers have been synthesized under solvothermal conditions and structurally characterized by X-ray single-crystal diffraction,IR,X-ray powder diffraction and so on.Moreover,the thermal stability,chemical stability and fluorescence sensing properties of some coordination polymers were investigated.The main contents are summarized as follows:1.By using four Y-shaped aromatic carboxylic acids with different substituents as auxiliary ligands and diverse transition metal ions,five transition metal coordination polymers with novel structures have been successfully constructed and structurally characterized.Topological analysis shows that coordination polymers 1 and 3 could be simplified as two-dimensional 4-connected sql topology,and coordination polymer 2 displays a rare3-connected KIa topology.The fluorescence experiments indicate that coordination polymer 5could be considered as a good multi-responsive sensing material for detecting Fe³⁺,MnO₄^-,Cr₂O₇^2-,salicylaldehyde and ethylenediamine via the fluorescence quenching effect with the detection limits of 0.53,0.98,3.6,0.42 and 5.3 ppm,respectively.2.With the auxiliary ligands of three different conjugated aromatic carboxylic acids and different transition metal ions,four transition metal coordination polymers with novel structures have been successfully prepared and structurally characterized.Topological analysis indicates that coordination polymer 6 could be simplified as 4-connected sql topology,coordination polymer 7 could be simplified as 3-connected fes topology,and coordination polymer 8 shows three-dimensional(3,5)-connected gra topology.The fluorescence experiments show that coordination polymer 7 could selectively and sensitively recognize Al³⁺and Ga³⁺through fluorescence enhancement effect along with a relatively large red shift.The detection limits for Al³⁺and Ga³⁺are 0.17 and 0.69 ppm,respectively.Interestingly,the sensing process for both Al³⁺and Ga³⁺could be directly observed with naked eyes under 365 nm UV lamp.More imporantly,coordination polymer 7 is the second case of metal-organic framework based fluorescent sensor toward Ga³⁺.3.Based on the auxiliary ligands of four aromatic carboxylic acids with different spacer groups as and different transition metal ions,five transition metal coordination polymers have been successfully synthesized and structurally characterized.Topological analysis shows that coordination polymers 10-14 could be simplified as 4-connected sql topology.The fluorescence experiments indicate that coordination polymers 10 and 12 could selectively recognize MnO₄^-through fluorescence quenching effect,and the detection limits of 0.30 and1.22 ppm,respectively.Coordination polymer 11 could selectively recognize Fe³⁺,Cr₂O₇^2-and acetylacetone through fluorescence quenching effect,and the detection limits of 0.14,1.33 and 6.53 ppm.Notably,coordination polymer 11 is the second case of metal-organic framework based fluorescent sensor for Fe³⁺,Cr₂O₇^2-and acetylacetone,simultaneously.