Construction And Properties Of Crystalline Supramolecular Macrocycles And Organic Framework Materials

Supramolecular chemistry is the study of molecular aggregates based on non-covalent interactions.Supramolecular macrocycles are an important research part of supramolecular chemistry.Pillar[n]arenes,as the fifth generation of cyclic hosts after crown ethers,cyclodextrins,calixarenes and cucurbiturils,have been widely studied and developed in liquid host–guest chemistry and solid-phase functional materials,and have made great progress in catalysis,mechanical interlocking structures,supramolecular self-assembly and adsorption-separation.Dative boron-nitrogen（BN）bonds are a new class of Lewis acid-based coordination bonds.The wide availability of substrates and good crystallinity of products have attracted people’s research interest.Novel supramolecular macrocycles and framework materials based on dative BN bonds have been paid much attention due to their unique topologies and potential application prospects.This dissertation is focused on pillar[n]arenes in host–guest recognition in solution phase and the application in adsorption and separation in solid phase,as well as novel crystalline macrocycles and organic framework materials based on dative BN bonds with exquisite structures,functions and performances in adsorption and separation,including the following four parts:In the first part,we constructed novel pseudorotaxanes based on a pillar[4]arene[1]quinone and 1,10-dibromodecane.X-ray single crystal diffraction analysis showed that an alkane molecule threaded into cavities of two pillar[4]arene[1]quinone molecules,forming a[3]pseudorotaxane in the solid state.However,¹H NMR experiments revealed that the pillar[4]arene[1]quinone encapsulated the guest molecule with 1:1 stoichiometry to form a[2]pseudorotaxane in solution,with the complexation constant K_a of 20.0（±2.5）M^-1.The reason might be that the interactions between the host and guest were weak and there was a complexation competition with solvent molecules.Furthermore,the addition of guest molecules did not change the maximum UV-vis absorption wavelength of host molecules.The bromine atoms at the ends of the guest molecule provided convenience for the further capping of pseudorotaxanes to construct rotaxanes,which broadened the potential applications of pillararene derivatives in the fabrication of sophisticated supramolecular architectures and functional supramolecular systems.In the second part,we investigated the separation of monosubstituted aromatic heterocyclic compound,2-chloropyridine（2-CP）and 3-chloropyridine（3-CP）,using nonporous adaptive crystals of perethylated pillar[5]arene（Et P5）,perethylated pillar[6]arene（Et P6）,perbromoethylated pillar[5]arene（Br P5）and perbromoethylated pillar[6]arene（Br P6）.We compared the differences in adsorption and selectivity of these pillararene crystals with different cavity sizes and substituents.Et P5 and Br P5 have smaller sorption capacities than Et P6 and Br P6 due to their smaller cavities.Nevertheless,only Br P6 can separate 2-CP from the 2-CP/3-CP mixture vapours.Single crystal X-ray diffraction indicated the more stable crystal structure and stronger host–guest interactions in（2-CP）₂@Br P6 vs.（3-CP）₂@Br P6.Combined with the PXRD results,it was speculated that the reason why other pillararenes showed no obvious selectivity resulted from the formation of similar spatial structures and host-guest interactions after uptaking of different guest molecules.The excellent selectivity of Br P6 exhibited potentiality for industrial applications.Besides,this material did not degrade its performance in separation after multiple cycles.It should be noted that this is the first application of nonporous adaptive crystals（NACs）in separating aromatic heterocyclic isomers.In the future,it is believed that NACs can make a difference in the separation of other important isomers and product mixtures.In the third part,we constructed three macrocycles based on dative BN bonds,which could be synthesized in one step by the[2+2]coordination form with 1,4-bis（benzodioxaborole）benzene and bidentate pyridine ligands of different lengths.According to the characteristic functional groups of ligands,the three macrocycles,named BNC1,BNC2 and BNC3,had different sizes and properties,respectively.The solvent p-xylene kept the stability of BNC1.In addition,a two-dimensional supramolecular polymer formed by intermolecular hydrogen bonding between BNC1and p-xylene molecules.The formation of BNC2 was not highly dependent on the solvent,thus it could be activated by solvent exchange and had the ability to adsorb carbon dioxide.This was the first porous crystalline macrocyclic materials based on dative BN bonds,which was expected to be applied in the field of adsorption and separation.BNC3 crystals with azobenzene units did not show obvious color change in UV light at 365 nm for 24 hours,indicating that the dative BN bonds had a certain stabilizing effect on the configuration of trans-4,4-azobispyridine.In the fourth part of the work,based on dative BN bonds,we fabricated a 3D crystalline porous organic framework（DOF 1）by virtue of mortise-and-tenon structure using three simple building blocks:TPPE,1,4-phenylenediboronic acid and4,5-dichlorocatechol.Single crystal X-ray diffraction analysis showed that adjacent TPPE molecules with an 87°dihedral angle provided two adjacent pyridine arms connected by dative BN bonds to form diamond-shaped spiral channels in 2D networks.Dichlorobenzene units were evenly distributed on the upper and lower surfaces of the 2D network to form mortise-and-tenon nodes,and adjacent layers were interlocked through mortise-and-tenon joints.At the same time,π···πstacking interactions between layers stabilized this unique structure,thus forming a fascinating3D network topology.On the one hand,the presence of the mortise-and-tenon structure endowed DOF 1 crystal with stronger mechanical properties.On the other hand,the tenon and mortise structure enabled DOF 1 to effectively avoid the occurrence of interpenetration,which is widely observed in organic crystal frameworks,thus allowing the original channels of the 2D network to be preserved.In addition,DOF 1 crystals could be applied in the separation of benzene and cyclohexane.Through the mortise-and-tenon strategy,we opened up a new way for the synthesis of 3D crystalline organic frameworks,and provided a new example for the construction of crystalline organic frameworks with complex topologies.