Design,Synthesis And Binding Ability Of Cyanides Chemosensor Based On Potential Intramolecular Br···H Hydrogen Bonding

Cyanide ions play an extremely important role in many fields such as life sciences,medicine,environmental monitoring and industrial process.The release of hypertoxic cyanide derivatives into the environment can cause huge damage to living organisms and the environment.Therefore,developing an effective method for detecting cyanide ions is greatly imperative.The development of chemosensors for the sensing of cyanides by colorimetric or fluorescent response has attracted great attention because of its remarkable merits,such as high selectivity,high sensitivity,simplicity,low cost,which makes the research of developing novel sensing mechanism,involving reversible and well water-operating cyanide receptors become a promising research hotspot.In this paper,inspired by the previous research of our group,based on 1,8-naphthylimide fluorophore skeleton,two series of FRET-based and ESIPT-based cyanide ion fluorescent receptors have been designed and synthesized by constructing intramolecular Br···H hydrogen bond fragments.The binding ability of these probes for cyanides sensing was confirmed by UV-vis,fluorescence spectra,¹H NMR titration,mass spectrometry and the application of probes in test paper,solid color changes and cell fluorescence imaging also have been investigated.In the second chapter,based on 3-bromo-4-pyridineacetonitrile-1,8-naphthalimide fluorophore skeleton followed by introducing of a coumarin fluorophore to naphthalimide skeleton,a cyanide fluorescent probe 4-Br based on FRET mechanism featuring a potential the intramolecular CH...Br hydrogen bond was further successfully designed and synthesized.When treatment with cyanides,the results indicated that a new absorption band at 685 nm was developed in the UV-vis absorption spectrum and the red-shift in fluorescent spectrum can reach 65 nm.At the same time,the 4-Br showed obvious color change?yellow to green?and fluorescence responses?blue to green?to CN^-.Importantly,it is suitable for fluorescence imaging of cyanides in living cell.In the third chapter,based on 4-hydrazone-pyridine group as binding motif,a4-hydrazone-pyridine-1,8-naphthalimide receptor 4a-E was constructed with a intramolecular NH...N hydrogen bond.Meanwhile,the Br was also introduced into C³,C⁵ position of the1,8-naphthalimide skeleton to give the control probes 4b-E and 4c-Z,respectively.Analysis by UV-vis,fluorescence spectroscopy,NMR titration experiments,the mechanism indicated that NH group of hydrazone can be used as a potential hydrogen bond donor to form intramolecular hydrogen bonds with pyridine N atom.Upon photo-triggered or cyanide-induced,ESIPT occurs by transferring NH proton to pyridine N atom followed by formation of a tautomer emission form?T?.Interestingly,a potential intramolecular NH···Br hydrogen bonding in the control probes 4b-E and 4c-Z might be compete with the anion-induced intermolecular NH...A^-hydrogen bonding,which results in the dramatical suppression of ESIPT.Furthermore,probe 4a-E showed high selectivity and reversibility for CN^-sensing in mixed solvents?THF/H₂O=1:1,v/v?and solid test papers.More importantly,it exhibits great potential application for cyanides detection of cyanide-containing food materials and excellent performance in real-word water samples.