Synthesis And Fluorescence Sensing Properties Of Transition Metal Coordination Polymers Derived From Nitrogen Rich 3,5-Bis(1H-Benzo[D]Imidazol-1-yl)Pyridine

Coordination polymers are a new type of organic-inorganic hybrid materials with controllable structure and clear luminous position,which can be used in sensing and detection applications.The construction of coordination polymers is affected by many factors,such as ligands,metal ions,solvents,temperature and so on.It is of practical significance to reasonably select organic ligands,adopt appropriate methods to synthesize coordination polymers and explore the luminescent properties.Seven coordination polymers have been synthesized under the design of acid-base mixed ligands by using nitrogen-rich v-shaped semi-rigid 3,5-bis（1H-benzo[d]imidazol-1-yl）pyridine（BBIP）with good luminescent properties as the primary ligand and different auxiliary carboxylic acid ligands.Through structural characterization and performance testing,we found that some coordination polymers have high chemical stability and excellent luminescence properties,so the fluorescence sensing properties are studied.The main research contents are as follows:1.Four coordination polymers 1-4 were successfully prepared with Cd^Ⅱ/Zn^Ⅱby solvothermal method using three aromatic dicarboxylic acids as auxiliary ligands.Structural analysis shows that coordination polymers 1-4 have different structural dimensions（1 has a three-dimensional structure,2 and 3 have a two-dimensional structure,and 4（JXUST-30）has an one-dimensional double-chain structure）,which is related to the connection mode of acid-base ligands.When the ligand has more coordination sites and more complex coordination modes,it is easier to form high-dimensional structure.The fluorescence sensing experiments show that 1 has fluorescence quenching effect on Al³⁺/Cr³⁺,and the detection limits are 0.061μM and 0.070μM,respectively.4（JXUST-30）could be used as a multifunctional fluorescence turn-on sensor for detecting acetylacetone,glyoxal and salicylaldehyde with fast response time,high sensitivity and excellent cycle performance.In addition,we prepared portable fluorescent test strips,composite films and LED lamp beads based on 4（JXUST-30）,which provided the possibility for the practical application of fluorescence detection of small organic molecules.2.Three coordination polymers 5-7 were successfully prepared by adjusting the ratio of solvents and metal ions（Cd^Ⅱ/Zn^Ⅱ/Co^Ⅱ）under the hydrothermal condition with strong conjugated 2,6-naphthalenedioic acid as auxiliary ligand.The analysis of single crystal structure shows that 5-7 are 4-connected sql topologies with double interpenetrated structures,but due to the difference of the coordination number of central metals,there are two coordination modes of 2,6-naphthalenedioic acid in 5-7:chelating and monodentate coordination.Fluorescence sensing experiments show that 7 could be used as a multi-response fluorescence sensor to recognize acetylacetone and H₂PO₄^-by fluorescence enhancement effect and salicylaldehyde by fluorescence quenching effect,with detection limits of 0.103 m M,0.121μM and 0.606μM,respectively.