Studies On Spectra And Properties Of Planar Pyridine Fluorescent Molecules

In the field of supramolecular chemistry and material science,efficient luminescent materials with tunable,multi-color emission based on the principle of aggregation-induced emission（AIE）are well-prepared owing to their wide-ranging applications in biological imaging and sensing,anti-counterfeiting,light emitting diodes,molecular switches and logic gates etc.In this context,three series of pyridine-based fluorescent molecules were synthesized,and their host-guest interactions and ions recognition properties were studied.The following tasks were mainly completed:1.Five pyridinium guests with alkyl chains of different lengths have been synthesized with tris（4-bromo）aniline and 4-pyridineboronic acid as main raw materials.The host-guest interactions between Q[7]/Q[8]and five guests were studied by spectroscopy and morphology characterization.Studies show that Q[7]with all guests can form a 1:3 supramolecular self-assembly mode（guest/Q[7]）in neutral water,and Q[8]can form two self-assembly modes:2:1 and 2:3（guest/Q[8]）.The guests form aggregates with different morphologies due to their structural difference properties.When Q[8]was added,both of the aggregation and morphology of guests were changed.In addition,the enhanced fluorescent emission can be attributed to the better planarity of guests after the host-guest interactions in aqueous solution.2.Three pyridinium guests with alkyl chains of different lengths have been synthesized with tris（4-bromo）aniline and 4-（4-pyridinium）phenylboronic acid as main raw materials.The host-guest interactions between Q[8]and the guests were analyzed by NMR,UV-vis,and fluorescence spectroscopy and morphology.Studies show that all guests can form aggregates with different morphologies due to the self-assembly of the guests in aqueous solution.When Q[8]was added to the guest solution,a novel dimer with molar ratio 2:3（guest/Q[8]）was formed.Meanwhile,the enhanced red-shift fluorescent emission ascribed to the better planarity of the dimer guests after the host-guest interactions in aqueous solution.3.A water-soluble terpyridine-based cationic fluorescent probe（SP-TPy）with p H-dependent amphiphilicity and AIE properties has been synthesized using4-bromobenzaldehyde,2-acetylpyridine,4-pyridineethylene and bromohexanoic acid as main raw materials.Research shows that the fluorescent probe has the ability of self-assembly and disassembly in aqueous media.In neutral water（p H 7.4）,a moderate sensing response to Hg²⁺ions was given by the self-assembly of SP-TPy.However,in acidic aqueous media（p H 2.0）,the monomer of SP-TPy not only appeared to be highly selective and sensitive for Hg²⁺ions,but also displayed highly efficient removal of Hg²⁺ions from solution by rapid precipitation,which was attributed to the coordination-triggered reassembly of SP-TPy.The removal efficiency of SP-TPy for Hg²⁺was found to be over 99%.Further study indicated that the precipitates were composed of various polyhedral porous frameworks,a property that was further used to adsorb H₂S gas to form Hg S complexes with higher uptake capacities.Besides,SP-TPy can be efficiently regenerated and recycled using a simple treatment with acidic water after adsorption of the H₂S gas.