Study On The Recognition Performance Of Salamo-type Fluorescent Sensors And Their Mixed-ligand Copper(Ⅱ)coordination Polymer

In the natural environment and biological fields,abnormal changes in the content of anions and amino acids can cause different degrees of environmental pollution and abnormal lesions in biological organisms.Due to the high sensitivity,convenience and low cost of fluorescent chemical sensors,fluorescent chemical sensors with different functions have been developed rapidly.The small molecule type temperature fluorescence sensor based on AIE characteristic was successfully developed here,which can also be used to respond to p H and enable continuous detection of Cu²⁺and S^2-in buffer solution with high water content;Based on this sensor structure,a bis（salamo）-type fluorescence sensor with ICT effect was synthesized,which can be suitable for continuous detection of Cu²⁺and cysteine.In addition,a metal-liganded polymer with Salamo-type mixed ligands was constructed,the interaction forces in its molecular structure were analyzed by combining the results of single-crystal X-ray diffraction and theoretical calculations,and its biological antibacterial properties were investigated.The main content is divided into the following four chapters.1.The development of fluorescence chemsensors and their common mechanisms of action are briefly introduced,the research advancement of multifunctional fluorometric sensors and salamo-type fluorometric sensors are listed,and the relevant research reports of mixed ligand-constructed metal complexes are summarized.2.A multifunctional half-salamo-type fluorescence sensor（HL¹）was developed.The sensor exhibits the rare AIE property in salamo-type compounds,based on which the fluorescence intensity of HL¹ in ethanol solution was found to vary with temperature and has excellent stability and recyclability.In addition,the fluorescence intensity of HL¹ gradually enhanced with the increase of p H,and showed favorable linear relationship between the fluorescence intensity and p H of the sensor in the range of p H 8-12,and the test results of fluorescence spectra are consistent with the naked-eye detection phenomenon.The response mechanism of HL¹ to p H was revealed by density functional theory（DFT）and time-containing density functional theory（TD-DFT）,and the results of ¹H NMR titration experiment further confirmed the rationality of the response mechanism.The fluorescence spectroscopy test results indicate that the sensor can also be applied to detect Cu²⁺in high water content systems,and the in situ generated Cu（Ⅱ）complex can be used for further detection of S^2-.Fluorescence titration and fluorescence anti-interference experiments revealed that the HL¹ has high sensitivity and selectivity for the continuous detection of Cu²⁺and S^2-.In addition,the sensor can be used in portable test strips and in real water samples for efficient detection of Cu²⁺and S^2-.3.A novel bis（salamo）-type fluorescent sensor（H₄L²）was developed by introducing fluorescent functional groups to the structure of HL¹,and a series of structural characterization was performed by elemental analysis,¹H NMR,high resolution mass spectrometry and infrared spectroscopy.The fluorescence spectroscopy tests showed that H₄L² has excellent luminescence property and can be used to identify Cu²⁺ions by fluorescence"off"in a buffered solution of DMSO/H₂O（v/v=9:1,p H=7.26）.The in situ generated complex H₄L²-Cu²⁺can be used in response to cysteine（Cys）by fluorescence"turn-on"in the same solvent system and exhibited good sensitivity,selectivity and fluorescence immunity.The lowest limit of detection（LOD）of this sensor for Cu²⁺and Cys was calculated according to the relevant equations to reach 191 n M and 211 n M,respectively.In addition,the fluorescence sensor H₄L² loaded onto medical swabs can achieve the detection of Cu²⁺,and the naked-eye detection results are consistent with the experimental test results.Finally,the mechanism of fluorescence switching action of H₄L² on Cu²⁺and Cys was reasonably explained based on high-resolution mass spectrometry studies and DFT-related theoretical calculations.4.A binuclear Cu（Ⅱ）coordination polymer[Cu₂（L¹）（L³）（NO₃）^-]_n·n CH₃OH（Cu（Ⅱ）-CP）based on different conformational salamo-type ligands was constructed.Single-crystal X-ray diffraction analysis showed that the asymmetric unit structure of one molecule of Cu（Ⅱ）-CP consists of two Cu（Ⅱ）atoms,deprotonated（L¹）^-and（L³）^2-ligand units,one coordinated NO₃^-anion and one molecule of crystalline methanol.The two Cu（Ⅱ）complex units are bridged by two oxygen atoms of NO₃^-anion to form the unique mixed-ligand Cu（Ⅱ）coordination polymer.In addition,both Cu（Ⅱ）atoms exhibit distorted octahedral geometries with each of the six surrounding coordination atoms.In the molecular structure of Cu（Ⅱ）-CP,two-dimensional supramolecular structure is formed through intermolecular hydrogen bonding interactions.The charge distribution and the distribution of weak interaction forces of the polymer monomer molecules were investigated by Mulliken charge distribution and electrostatic potential mapping.In addition,DFT,interaction region indicator（IRI）and bond level theory analyses further investigated the formation of the special structure and the frontline molecular orbital distribution characteristics of the polymer.In addition,the polymer showed excellent antibacterial activity against both E.coli and Bacillus subtilis.