Methodical Construction Of Terpyridinyl-Based 2D And 3D Giant Supramolecular Infrastructures

Supramolecular chemistry,first proposed by French scientist J.M.Lehn,is a multidisciplinary discipline with widely application in many fields and awarded the Nobel Prize in Chemistry in 1987 and 2016 respectively.Coordination driven supramolecular self-assembly is an important branch of supramolecular chemistry.Due to its unique mode of interaction,supramolecular self-assembly has attracted extensive attention from scientists in recent years.The construction of unique supramolecular structures through the precise design of metallo-organic ligands has become a research hotspot.Such supramolecular structures have attractive application prospects in catalysis,separation,biomedicine and energy.In this paper,two-dimensional and three-dimensional discrete supramolecular structures with strong self-recognition ability and selfclassification ability were designed and synthesized by constructing ligands with "mortise tenon" structure and adjusting the symmetry of ligand molecules.The main work of this paper is as follows:1)Three asymmetric metallo-organic ligands（MOL）L1,L2 and L3 were designed and synthesized through a step-wise strategy based on the strong coordination force and stable reactivities of Ru²⁺metal ions.The two ends of the three metal organic ligands have the characteristics of"mortise" and "tenon" respectively.After assembling each of the three ligands with metal ion Zn²⁺,the centrosymmetric pinwheel-shaped star trigon P1,pentagram P2,and hexagram P3 were obtained,and their structures were characterized by NMR,MS and TEM.And the effects of geometric orientation angles and geometric coordination sites on supramolecular self-assembly were discussed.To my knowledge,planar windmill supramolecules similar to P1,P2 and P3 are rarely reported in the field of supramolecular chemistry,the molecular weight of P3 is up to 56054 Da.2)Tripodal ligands L1,L2,L3 and L4 with " tenon " element and metalorganic ligands L5 and L6 with "mortise" element were designed and synthesized to explore the self-assembly behavior of mortise and mortise structure in the process of three-dimensional supramolecular self-assembly.Ligands L1 and L2 can be geometrically complementary with L5 in space,after mixing L1 and L2 assembled with L5,under the exist of Zn²⁺,generate double-cavity supramolecular cages S1 and S2,respectively.Use the same method,two double-cavity supramolecular cages S3 and S4 were obtained,after mixing L3 and L4 assembled with L6 under exist of Zn²⁺.The structures of supramolecules S1,S2,S3 and S4 were fully characterized by NMR and MS.We further investigate the dynamic ligand exchange behaviors between supramolecular cages S1-S4,meanwhile the host-guest interactions between S1-S4 and guest molecules were studied.3)In this work,a triphenylene-cored C3v symmetric hexapod terpyridine LA was synthesized,and then assembled with Zn²⁺ions to generate a pair of racemic chiral metallo-organic cages[Zn12L4]^-A and[Zn12L4]^-C.The structure of[Zn12L4]was unambiguously characterized by synchrotron Xray analysis and NMR,ESI-MS,TWIM-MS.There are two kinds of interaction forces in the crystal stacking of the metal-organic cage SA.One is the π-π stacking interaction between the supramolecules on triphenylene,the other is the interaction between the terpyridine unit and triphenylene.The crystal structure of the metal-organic cage SA presents a porous arrangement.In addition,a larger ligand LB was synthesized and assembled with Zn²⁺ions to generate a larger supramolecular cage SB,and the interaction between supramolecular cages and guest molecule were studied.4)By reducing the symmetry of ligand molecules,C₂-symmetric tetrapod ligand LA and hexapod ligand LB were designed and synthesized.The trimeric supramolecular SA was assembled by mixing the tetrapod ligand LA with the metal ion Zn²⁺,which presents a "bowl" structure.Based on ligand LA,ligand LB with four interposition terpyridines and two para-position terpyridines was designed and synthesized.After assembling with metal ion Zn²⁺,a "capsule" type supramolecular SB was obtained.The assembled supramolecules SA and SB were characterized by NMR and mass spectrometry.In addition,the fibrous stacking product of supramolecular SA was obtained in the process of crystal culture and the stacking morphology was characterized by SEM and TEM.