Studies On Synthesis Of New Molecular Tweezers Based On Glycoluril And Their Recognizing And Sensing Properties For Metal Ions

Selective recognition and sensing of metal ions via artifical receptors have attractrd increasing interest in the field of superamolecular chemistry due to significant importance and potential applications in the biological,environmental and medical filelds.The designs and synthesis of receptors is the key of metal ion recognition.Among the variety of artifical receptor models,a special class of receptors called molecular tweezer are currently attracting great interest.All these tweezer-type receptors not only have the cavities of inartifical receptors in structure,but also possess different sizes of clefts,different recognition sites,different rigidity and flexibility.They can provide a complementary microenvironment for specific substrate.Glycoluril is an important building block for supramolecular chemistry,and its derivatives have been used as the basis for molecular tweezers.Many molecular tweezers based on diphenyl glycoluril are efficient receptor for phenolic guests(e.g.resorcinol).On the other hand,much work can be done to expand the research filed about glycoluril-based molecular tweezers.In this dissertation,the efforts were focusd on design and synthesis of new fluorescent molecular tweezers derived from diphenyl glycoluril and diethoxycarbonyl glycoluril and their molecular recognition and sensing for metal ions. A series of important and creative results have been obtained.The research results were summarized below:1.Five novel molecular tweezers with hydrazide moiety as sidewalls were designed and synthesized,their structures and conformation was fully confirmed by single crystal X-ray diffraction. Among them,the chemosensory properties of two molecular tweezers derived from diethoxycarbonyl glycoluril for metal ions were studied by fluorescent spectroscope.It was found that they both exhibited selective recognition towards Fe³⁺among 13 metal ions investigated in DMF/CH₃OH(50:1, v/v)with fluorescence quenching,and formed 1:1 stoichiometry complex with Fe³⁺.Moreover,they showed different association constants with Fe³⁺because of the difference in their structures and conformations.2.Five novel asymmetrical molecular tweezers based on diethoxycarbonyl-and diphenyl glycoluril with different substituted groups of aromatic rings(H,OMe,Me,Br)and 1,2 -dihydro-indazol-3-one moiety as sidewalls were designed and synthesized.Among them,four compounds based on diethoxycarbonyl glycoluril were fully confirmed by X-ray crystallography,and their chemosensory properties for various metal ions were also investigated by fluorescent spectroscope.All of them showed the same selective recognition properties towards Fe³⁺with fluorescence quenching as that of the molecular tweezers with two 1,2-dihydro-indazol-3-one moiety sidewall.3.New molecular tweezers from diethoxycarbonyl glycoluril and phenyl- and benzyl amine appended different alkynes were synthesized.Among them,four aryl alkynes-appended molecular clips were used to study their recognition and sensing properties towards various metal ions.A interesting phenomenon was observated that this type of molecular clip also can selectively bind Fe³⁺ with fluorescence quenching,and formed 1:1 stoichiometry complex with Fe³⁺.4.A new type of fluorescent molecular tweezers from diethoxycarbonyl glycoluril and substituted 2,5-diphenyl furan were synthesized.It was found that they also exhibited selective recognition to Fe³⁺with fluorescence quenching over the other tested metals ions including alkali and alkaline earth metal cations.This experimental result shows that two polarized carbonyl groups oxygen atoms of glycolufil ring maybe an effective recognition position for Fe³⁺.