Synthesis, Anion Recognition And Crystal Structure Of Tweezer Acyl-thiourea Derivatives

Molecular recognition is the process that host molecular binding with guest molecular selectively and produce some special function,which includes the recognition of neutral molecules,cations and anions.Design,synthesis and investigation of kinds of novel different anion receptors has recently grown into a subject of great interest in supramolecular chemistry because they has been gradually known as played important roles in biology,pharmacy,catalysis and environmental science.Systems employing amide and thiourea moieties have been proven especially efficient and extensively used as the anion-binding site in the hydrogen bonding receptor in constructing anion receptors for the merit that hydrogen bonds is great selected and directed non-covalence intermolecular force.In view of above,the tweezer shape receptor with rigid or flexible spacer which contained thioureido-NH protons are very efficient,extensive and significative strategy in this topic.Here we report the design synthesis,characterization,anion recognition nature and crystal structure of two series acyl-thiourea Based tweezer receptors.In detail,this thesis contains three major segments as shown below.The first chapter gives a brief review of the thesis.Which contain the following topics:supramoleclar chemistry,molecular recognition,structural characters of anions, historical overview of synthetic anion receptor chemistry,the development of thiourea based anion receptors especially these have tweezer structure.Chapter 2:A series of 3,3'-di(4-substitued)-1,1'-isophthaloylbis(thiourea)were designed as novel neutral,tweezer anion receptors and synthesized under ultrasonic radiation in high yeild.The single crystal structure of compounds 4c(R=p-OC₂H₅) and 4d(R=p-Cl)show shat a solvent DMF molecule was captured by the host which show as a molecular tweezer by intermolecular hydrogen bonding in addition with the exists of symbol N-H…O intramolecular hydrogen bonding of acyl-thiourea. It also show that compound 4d self-assembled as a supramolecular system for the presence of intermolecular hydrogen bonding N-H...Cl andΠ-Πinteractions between phenyl groups.Their application as anion receptors have been examined by UV-vis and ¹H-NMR spectroscopy,it presented that they had a high selectivity for F^-compared with other halides.The host and guest formed a 1:1 stoichiometry complex through hydrogen bonding interactions in the first step,which then following a process of deprotonation in presence of an excess of F^- in the sovent of DMF.Chapter 3:A series of bis(2,2'-substituted-benzoyl thioureaphenyl)glycol ether were designed as novel neutral anion receptors and synthesized under ultrasonic radiation.The binding properties of 4 of these which are non-substituted and o-,m-, p-NO₂ substituted,with F^-,Cl^-,Br^-,I^-,CH₃COO^-,HSO₄^-,NO₃^-,H₂PO₄^- in DMSO were examined by UV-Vis and ¹H NMR spectroscopy methods.The results showed that these tweezer receptors with flexible spacer had a better selectivity for F^- and CH₃COO^-,H₂PO₄^-,but no evident binding with other anions.Moreover,5d(R= p-NO₂)form a color change from colorless to yellow in the process,then maybe a potential anion sensor.¹H NMR spectroscopy conformed that the host and guest formed a 1:1 stoichiometry complex through hydrogen bonding interactions in the first step,which then following a process of deprotonation in presence of an excess of anions.The single crystal structure of compound 5a(R=H)show shat this kinds of compounds are not good at anion recognition for its tendency to adapt a centrosymmetric conformation.