Synthesis Of Bis-schiff Base And Acylhydrazone Receptors And Their Anion Recognition Properties

Supramolecular chemistry as a dynamic and rapidly developing field, its interdisciplinary nature has caused the chemist, physicist, crystallization, inorganic solid chemist wide attention. Nowadays, ion recognition has become an important research content of supramolecular chemistry. How to design and synthesis of anion recognition receptors with high sensitivity and selectivity have promoted domestic and foreign experts enthusiasm for the study of this field. However, when compared to neutral molecules and metal cations, non covalent anion coordination chemistry development is relatively slow, so need to be enriched and developed quickly.This paper take these factors in mind, has been designed and synthesised bis-schiff base and acylhydrazone. Furthermore, the corresponding research of fluorescence spectrum and UV-vis spectrum recognition performance was also investigated. The concrete research content mainly includes four chapters:Chapter 1: This chapter introduces the nature of the host-guest interaction for anion recognition. We summarized some related literature in recent years, expounds the research progress and the latest development of anion recognition. Mainly including?analyzes? from the following several aspects:?1? the principle and the significance for anion recognition;?2? anion structure characteristics and the main design concept;?3? the application of stimulus — response type fluorescent switch in ion recognition;?4? The research progress of anion recognition based on schiff base;?5? The research progress of anion recognition based on acylhydrazone.Chapter 2: Synthesis and fluoride anion recognition properties of Bis-Schiff base chemosensor based on 2-hydroxy-1-naphthaldehyde.With phenolic hydroxyl and imide as binding sites and hydroxynaphthalene group as the fluorophore, fluorescence sensor TY was synthesized and designed. The receptor can detection of fluoride anion with absorption spectrum and fluorescence spectrum. Upon the addition of F^- to the sensor of TY into a DMSO solution, as the phenolic hydroxyl group has a certain acid and the deprotonation of the hydroxyl group accured when exposed to alkali ions, this can broke the rigid plane structure of sensor TY, as a result the fluorescence quenching. Other alkaline anions?Ac O^- ?H₂PO₄^-? hardly disturbing the recognition process. It is interesting to note that Ca²⁺and F^- can form a stable compound Ca F₂ and then release free H⁺, therefore the sensor back to its initial state and fluorescence change by showing “ON” behavior.For this reason, the system of TY-F^- for cation Ca²⁺ implements “ON^-OFF^-ON” type fluorescent identification. The continuous recognition of F^- and Ca²⁺ could be repeated several times with little fluorescence efficiency loss. This kind of fluorescent switch can be utilised to build molecular IMP logic gate, show a good application value.Chapter 3: Synthesis and cyanide recognition properties of salicylaldehyde hydrazone based on naphthaleneA fluorescent cyanide sensor LY with highly selective and sensitive over other competitive anions in the aqueous solution was designed. The sensor is bearing of isophthalic dihydrazide and hydroxynaphthaldehyde forms a bidentate acyl hydrazone compounds. Sensor LY have?-CONHN=C-? and-OH as binding sites, which enable detection of CN^- in aqueous system. As carbonyl and aromatic ring have the function of electrophilic, which makes amide and hydroxyl protons show the weak acid and then alkaline ion will deprotonation of the hydroxyl and amide groups. Moreover, the nitrogen anion from acyl hydrazone functional groups provide a lone pairs of electrons for donation and then produce of P-? conjugate effect, which makes the acyl hydrazone compounds more stable and not easy to hydrolysis. As a result, sensor LY in DMSO^-H2O?6:4, v/v? have high selective recognition for CN^-, other basic anion?Ac O^-?F^-?H₂PO₄^-? in aqueous solution with high salvation energies and negligible interference will occur in the detection. The addition of CN^- ions destroyed the intramolecular hydrogen bonds, and deprotonation of the hydroxyl group. In the deprotonated species containing N^- and O^- ions produce of P-? conjugate effect with aromatic rings. This process promoted the intramolecular charge transfer?ICT? and then the fluorescence enhanced drastically act as “Turn-On” behavior. The deprotonation of amide hydrogen and naphthyl OH proton enhanced negative charge density, then developed bathochromic shift with naked eye detection in the absorption.Chapter 4: Synthesis and recognition properties of a reversible dual-channel chemosensor for fluoride anion based on salicylaldehyde derivantIn this chapter we designed and synthesized receptor YT with dimethylbenzidine as the substrate. We have investigated the recognition ability of receptor YT in DMSO with ten kinds of anion through the naked eye detection and fluorescence spectrum recognition. Receptor YT has a symmetry plane structure, in addition, the hydroxyl groups and the imine nitrogen atoms formed intramolecular hydrogen bond at either end. The addition of F^- destroyed the intramolecular hydrogen bonding, thus suppresses the intramolecular photoinduced electron transfer?PET?, the formation of two phenol oxygen atom promoted the intramolecular charge transfer?ICT? process,in turn the fluorescence performance for “ON” state. It is noteworthy that the addition of Ca²⁺ can help the fluorescence intensity back to its initial state, so we using the Fand Ca²⁺ as the inputs signal, while the emission intensity at 552nm?I = 552? acts as the output to build an INHIBIT logic devices at the molecular level. Therefore,receptpr YT as a new selective colorimetric and fluorescent chemosensor can be used for the detection of fluoride anion conveniently and quickly, which show an excellent application value.