Synthesis Of Ligands Of Flexible Chain Biurea And Tetraurea And Self-assembly Of Anions

Anion coordination chemistry,as an important branch of supramolecular chemistry research,has received extensive attention in recent years.In this paper,the synthesis of flexible chain biurea,tetraurea and tetrazolium ligand bridged by m-xylylene and its self-assembly behavior with tetrahedral oxyanion?phosphate?are introduced in detail.The full text is divided into three chapters,the first chapter introduces the origin and development of supramolecular chemistry and anion coordination chemistry,and analyzes the current research situation of anion receptors,supramolecular self-assembly based on crown ether and cryptand,as well as the main purpose and significance of the topic.The second chapter and the third chapter are the main contents of this paper,and the results are summarized as follows:1.Due to the high similarity between the anion self-assembly and the cation self-assembly,we draw on the structural characteristics of 2,2'-bipyridine,design the backbone of the o-phenylenediurea ligand,and introduce the flexible ether oxygen chain at the end obtained biurea ligand L¹,by interacting with PO₄^3-and alkali metal cations,we expect to obtain a triple helix structure of the ion pair double recognition site.Finally,a 3:1 single crystal structure of[L₃¹?PO₄?₁]?TMA?₃ was obtained,in which a total of 12 NH and 6groups of urea formed a saturated 12-coordinate hydrogen bond,indicating there is a very high degree of matching between the two.Through the nuclear magnetic titration,the nuclear magnetic test of the complex and the high-resolution mass spectrometry,it is proved that L¹ and?TMA?₃PO₄ are assembled into a 3:1 structure.At the same time,L¹and?TBA?₃PO₄ self-assembly are also tried,through nuclear magnetic titration and complex nuclear magnetic testing as well as high-resolution mass spectrometry test can prove that the assembly mode of L¹ and phosphate is still 3:1,which shows that the interaction of phosphate with different cations and don't affect L¹ and phosphates self-assembly;we also obtained a single crystal structure of[L₃¹?PO₄?₁]?TMA?₃+NaPF₆,but in this structure,no occlusion of cations at the ether oxygen chain was observed,It may be that the terminal ether oxygen chain is too flexible,and this structure is inconsistent with the stretching direction of the single crystal structure ether oxygen chain of[L₃¹?PO₄?₁]?TMA?₃.2.We noticed that in the previous work of our group,diphenylmethylene and ethyl as a bridging group of tetraurea ligands could construct a regular triple helix structure.Here we introduce a flexible bridging group to give the tetraurea ligand L²,we expect that L² can interact with PO₄^3-and alkali metal cations to achieve the configuration of the pseudo-cryptand and can sandwich the behavior of the cation.Finally,a 2:1 crystal structure of[L₂²?PO₄?₁]?TMA?₃+KPF₆ was obtained,and no occlusion phenomenon was observed at the ether oxygen chain,but the two ether oxygen chains contained water,we guess that may be caused by the ethereal oxygen chain being too flexible.The phosphate in the complex is coordinated with 11 NH of the two urea groups of the two ligands,and the other hydrogen bond is the water molecule from the ether oxygen chain.By testing the nuclear magnetic properties of L² and phosphates of different cations,we found only the?TMA?₃PO₄ formed a single complex,other cationic solutions may have multiple coordination structures or configurations,so we guess that the assembly of L² and phosphate will be affected by the cations.In order to investigate the configuration in which L² and PO₄^3-did not form pseudo-cryptand,due to the flexibility of the ether oxygen chain,we changed the flexible ether oxygen chain bridging group to rigid meta-xylylene to obtain tetraurea ligand L³,finally obtained two monomeric structures of[L₃³?PO₄?₂]?TMA?₆,[L₃³?PO₄?₂][K?18-C-6?]₆,respectively,[L₃³?PO₄?₂]?TMA?₆ cavity encloses a TMA⁺,[L₃³?PO₄?₂][K?18-C-6?]₆ has no entrapment in the cavity,thus causing the crystal structure that the distance between P and P is different.At the same time,it can be further explained that the rigidity and flexibility of the linker are crucial for forming a 3:2 assembly.