Study On The Interaction And Properties Of Chromones And Cucurbit[n]uril

Chromone compounds are a type of natural oxygen-containing heterocyclic compounds widely existing in plants.Because of their special chemical structure,they can be used as colorimetric and fluorescent probes for the effective detection of metal ions in aqueous solutions.Chromone natural compounds also have a variety of biological activities such as anti-inflammatory,antibacterial,antiviral and anticancer activities.Due to their poor water solubility,the further clinical applications of these compounds are limited.Cucurbit[n]uril(Q[n]s)is a type of macrocyclic synthetic compound with a bipolar negative potential carbonyl port and a nearly neutral hydrophobic cavity.It can not only contain guest molecules and ions in its cavity,but also coordinate with guest molecules and metal cations through the carbonyl oxygen atom of the port to form supramolecular compound,thus forming a unique host-guest chemistry and coordination chemistry based on the cucurbit[n]uril.In this paper,cucurbit[7]uril(Q[7])and cucurbit[8]uril(Q[8])were selected as the host,chromone(CMO)and 2-(2-phenylethyl)chromone(PCM)as the guest.The host-guest interactions and their mechanism of action of chromones-cucurbit[n]uril in neutral aqueous solution was studied,investigate the use of chromone-cucurbit[n]uril inclusion compound as a fluorescent probe to detect metal cations in aqueous solution,and as ligand to trigger the luminescence of lanthanides in aqueous solution.At the same time,the effects of cucurbit[n]uril on the water solubility,stability and in vitro release pathway of 2-(2-phenylethyl)chromone were investigated,which provided a theoretical basis for the comprehensive development and utilization of chromones compounds.The main research contents and conclusions are as follows:?:The interaction between CMO and Q[7],Q[8],as well as the interaction between PCM and Q[7],were investigated by UV-Vis absorption spectrum,isothermal titration calorimeter,mass spectrometry and ¹H NMR.The results show that CMO can interact with Q[7]or Q[8]to form a host guest inclusion complex with an inclusion ratio of 1:1.The inclusion mode is that the whole CMO molecule enters into the cavity of cucurbit[n]uril,and the binding constants are 3.54×10⁵ L·mol^–1 and 3.39×10⁵ L·mol^-1,respectively.CMO@Q[7](1:1,L)was used as fluorescent probe to detect common metal cations in neutral aqueous solution.The results show that L can selectively recognize Zn²⁺and Cd²⁺,and can be used as a fluorescent probe with high selectivity for the detection of Zn²⁺and Cd²⁺in water.There is a good linear relationship between the fluorescence intensity of L and the concentrations of Zn²⁺and Cd²⁺in the range of0-3.00×10^-5 mol·L^-1,and the detection limits are 2.03×10^-6 and 1.89×10^-6 mol·L^-1,respectively.X-ray crystal structure shows that Zn²⁺and Cd²⁺have different coordination modes with L.The interaction ratio of L to Zn²⁺is 2:1,and that of L to Cd²⁺is 1:1.However,both metal ions coordinate with the carbonyl oxygen on CMO and Q[7],and the lone pair electrons on CMO transfer to metal ions,which prevents the photoinduced electron transfer(PET)process of CMO and leads to the enhancement of CMO fluorescence.L can coordinate with Eu³⁺,Tb³⁺,Dy³⁺and Sm³⁺to form four2:2 complexes;L@Eu³⁺,L@Tb³⁺,L@Dy³⁺as well as L@Sm³⁺.The four lanthanide ions have strong fluorescence intensity and long lifetime.The formation of these complexes can not only trigger the luminescence of lanthanide,but also produce a specific fluorescence reaction to antibiotics in aqueous solution,which can realize the selective recognition of lincomycin hydrochloride in aqueous solution.The detection limits were 1.20×10^-8,5.75×10^–9,1.26×10^–8 and 2.28×10^–8 mol·L^-1,respectively.It provides a new idea for the application of cucurbit[n]uril host-guest chemistry.?:PCM interacts with Q[7]to form a 1:1 host guest inclusion complex with a binding constant of 2.93×10⁸ L·mol^-1.The inclusion mode is that the phenylethyl enters the cavity of Q[7]and the chromone part of the PCM molecule is located at the port of Q[7].The effects of Q[7]on the water solubility,stability and cumulative release of PCM were investigated by UV-Vis absorption spectra.The results show that Q[7]has solubilization effect on PCM.When the concentration of Q[7]is 1.00×10^-3 mol·L^-1,the solubility of PCM increases by 7.45 times.In the artificial gastric juice(p H=1.2)and the artificial intestinal juice(p H=6.8),PCM and PCM@Q[7]are very stable,indicating that Q[7]does not affect the stability of PCM.The cumulative release of PCM@Q[7]in artificial gastric juice and artificial intestinal juice was higher than that of PCM,increased by 3.92 times and 3.49 times,respectively,and almost reached a stable level after 7h.