Studies On Oligourea Ligands Bound To Anions And Incorporation With Halogen Bond And Metal Coordination Bond To Construct Self-assemblies

With the continuous exploration and extension of the field of chemistry,supramolecular chemistry began to emerge and became a hot favorite among contemporary scientists.In supramolecular self-assembly process,there are many non-covalent bond interaction forces,among which anion coordination and metal coordination have specific directionality and binding ability,which has become the focus of self-assembly research.In this paper,a series of oligourea ligands with different terminal substituent groups were designed and synthesized,the precursors were formed through the interaction with the preorganization of anions,and then combined the halogen bond or metal coordination bond to construct supramolecular assembles.The full paper is divided into four chapters,its main contents are as follows:The first chapter,supramolecular chemistry and supramolecular self-assembly are briefly introduced,and the research progress of spherical halogen anions(Cl^-,Br^-,I^-)and tetrahedral anions sulfate(SO₄^2-)in supramolecular inducing self-assembly by hydrogen bonds and halogen bonds are mainly discussed.And the construction of M₂L₄ and M₆L₁₂ assemblies in metal coordination chemistry are summarized.And expounded the purpose and significance of this paper.The second chapter,we designed and synthesized a nitro-substituted tetrakis(urea)ligand L¹,which can organize a dinuclear foldamer with the halide ions(Cl^-,Br^-,I^-).At this point,the anions are located at the two ends of the foldamer,in a semi-naked state,and can further participate in coordination.By changing the size of the counter cation(tetrabutylammonium cation to tetraethylammonium cation),the solvent molecule chloroform could enter into the system to coordinate with the halogen anion,successfully introducing a halogen bond,and six quaternary cocrystals were obtained by the both of hydrogen bond and halogen bond.When the counter cation was changed to the S-?-methylcholine,chloroform can form two halogen bonds with anions and connect two adjacent foldamers through halogen bonds.When increase the length of the halogen alkane is increased(1,2-dichloroethane)or the number of halogens is reduced(dibromomethane),the X???X^-(X represents the halogen atom)model halogen bond is absent.Therefore,the selection of halogen bond donor and the counter cation is crucial for halogen bond formation and the packing mode of the quaternary cocrystals.The third chapter,tris(urea)L² with the end of p-pyridine group as substituent was designed and synthesized,binding with chloride ion(Cl^-)and sulfate ion(SO₄^2-)formed a mononuclear crescent configuration.L² combined with chloride ion(Cl^-)in methanol and acetone solution obtained two isomerized crystal structures.L² connected with sulfate ion(SO₄^2-)received an anion nucleus crescent configuration.The crescent configuration can form a Pd₂L₄ supramolecular cage driven by palladium ion(Pd²⁺).In the presence of L²,1 eq.chloride ion(Cl^-)and 0.5 eq.palladium ion(Pd²⁺)can't obtain a lantern cage.Instead,a L²binding nitrate(NO₃^-)construction was discovered,this phenomenon may possibly because the chloride ion(Cl^-)can both bind to the ligand L² and coordinated with the metal palladium ion(Pd²⁺),the ligand L² binding with the chloride ion is not strongly enough to compete with palladium ion(Pd²⁺).Adding excess chloride ion or an equivalent amount of L² is used to combine with palladium chloride(Pd Cl₂),a square metallocycle[Cl₄Pd₂(L²)₂]can be gained.The fourth chapter,tetrakis(urea)L³ with the end of p-pyridine group as substituent was designed and synthesized,the self-assembly of the ligand with two anions and metal ion were discussed.First,the tetrakis(urea)L³ preorganized with chloride ion at a ratio of 1:2 to form a(TEA)₂[L³(Cl)₂]dinuclear foldamer.After folding,the spatial orientation of the two terminal pyridines is 71 degrees(close to 90 degrees).The tetrakis(urea)L³ binding with tetrahedral sulfate with a ratio of 1:1 constructed a(TEA)₂[L³SO₄]crescent structure.The two terminal pyridines of the ligand are close to each other with a spatial orientation of 43 degrees.The introduction of methanol solvent to assist complexes for crystal growth,we find two protonated complex(TEA)[HL³(Cl)₂]and(TEA)[HL³SO₄].For(TEA)[HL³(Cl)₂],the spatial orientation of the two terminal pyridines is 74 degrees,similar with(TEA)[HL³(Cl)₂].The Angle of the(TEA)[HL³SO₄]terminal pyridine toward into 6 degrees has great change compared with the(TEA)[HL³SO₄]43 degrees.This provides the inspiration for the study of transition metal ion self-assembly.Two different complexes,hexakarypalladium(II)Pd₆L₁₂cage and binuclear palladium(II)Pd₂L₄ lantern structure can be prepared by the combination of anion coordination and metal coordination.In the Pd₆L₁₂ cage,the terminal pyridine oriented 81 degrees,nearly 90 degrees.The mononuclear crescent configuration induced by sulfate is coordinated with metal ions to form an M₂L₄ lantern cage,and the pyridine orientation of the ligand ends tends to be parallel(6 degrees).¹H NMR,COSY,DOSY,ESI-MS and crystal structure can prove the existence of the two complexes in solid state and in solution.When no additional anions introduced into the system,palladium ions can still coordinate with the ligand to form a simple ML₂ configuration in the presence of the L³ ligand and palladium nitrate.