Construction Of Several Macrocyclic Arene-Based Supramolecular Systems For Detection And Separation

The discovery of molecular machines is a major breakthrough and milestone in the history of supramolecular chemistry and organic chemistry.Molecular machines conduct the strategy of modular composition and operation to realize specific functions including energy conversion,rotation,expansion and contraction,loading,and transportation,which makes a big step forward to further recognize the living system.Synthetic macrocyclic arenes as an indispensable element in the construction of molecular machines have attracted much attention in recent years.The design,synthesis,functionalization,and application of new macrocyclic host molecules are important and challenging topics in the field of supramolecular chemistry.Many macrocyclic arenes possess adaptive cavity,unique molecular recognition ability,and versatile modification,providing great advantages to explore and develop their extensive applications.For instance,many smart stimuli-responsive supramolecular polymers are fabricated on the basis of non-covalent interactions between functionalized macrocycles and guests.Besides,several supramolecular macrocycles are utilized as building blocks to construct conjugated polymers with organic molecules through covalent bonds.Therefore,many representative supramolecular systems have been widely applied in smart luminescent materials,gel materials,photothermal therapy,sensing and detection,adsorption and separation,etc.Pillar[n]arenes(n=5-15),as a new class of supramolecular macrocyclic arenes,have become star supramolecular molecules after crown ethers,cyclodextrins,calixarenes,and cucurbiturils due to their excellent binding properties,modification ease,and unique cavities.With the rapid development of pillararenes,many pillararene homologues with outstanding properties have been designed,synthesized,and intensively investigated for constructing supramolecular systems.My research mainly focuses on the design and synthesis of pillararene homologues and the exploitation of their supramolecular systems.In this dissertation,the design and synthesis of new macrocycles and their wide applications in detection and separation are mainly demonstrated in the following four aspects.In the first part,a homologue of pillararene,namely[2]biphenyl-extended pillar[6]arene(Bp P6)was used as the starting material,and the side arm of Bp P6 was modified by selective functionalization for obtaining the thymine(T)-modified Bp P6(DTBp P6,H).Taking advantage of the electron-rich and size-matched cavity of H,we designed and synthesized a tetraphenylethylene-bridged bis(quaternary ammonium)guest(DQTPE,G),which could self-assemble in solution by host-guest interaction to result in linear supramolecular polymers.Upon adding Hg²⁺into the abovementioned linear polymer,the thymine moieties on the side arm of H interacted with mercury ions intensely through T-Hg²⁺-T bonds.Meanwhile,the direction of T-Hg²⁺-T interaction was almost perpendicular to the direction of the host-guest interaction in G?H,thereby constructing a novel three-dimensional supramolecular polymer.The three-dimensional skeleton restricted the rotation of G to exhibit strong fluorescence,for detecting and removing mercury ions simultaneously directed by supramolecular assembly-induced emission enhancement(SAIEE).In summary,we have developed Bp P6 for the detection and separation of mercury ions in aqueous solution through the SAIEE mechanism,expanding the promising application of SAIEE and stimulating new thinking for environmental remediation.In the second part,inspired by the thymine-functionalized Bp P6,we decided to investigate a per-functionalized derivative of Bp P6 and prepared a per-triflate modified Bp P6(Bp P6-OTf).According to the crystal analysis of Bp P6-OTf,we found that-OTf groups occupied the cavity and significantly narrowed the size,which was conducive to the adsorption of size-matched gas molecules.Then,we carried out the Sonogashira-Hagihara cross-coupling reaction between Bp P6-OTf and 1,4-diethynylbenzene/4,4'-diethynylbiphenyl to obtain two conjugated macrocycle polymers(CMP-1 and CMP-2)with different crosslinking degree.The gas-sorption experiments showed that the CMP-2 based on Bp P6-OTf and 4,4'-diethynylbiphenyl possessed the highest selectivity for CO₂ adsorption at room temperature.The two materials introduced Bp P6into porous organic polymer and expanded applications of CMPs in gas adsorption and separation,especially in the field of peak carbon dioxide emissions and carbon neutrality,paving the way for designing novel functionalized porous materials.With the in-depth study of CMPs,in the third part,we prepared leaning tower[6]arene(LT6)as a new building block,in order to develop applications of CMPs in more fields.The per-triflate functionalized LT6(LT6-OTf)was designed and synthesized in a high yield.Interestingly,the LT6-OTf exhibited a highly titled conformation,and the staggered parallel packing modes were beneficial to generate more channels in addition to its own cavity,making the materials fabricated from LT6-OTf more favorable to capture iodine.The LT6-OTf was reacted with 1,4-diethynylbenzene/4,4'-diethynylbiphenyl through Sonogashira-Hagihara cross-coupling reaction for preparing CMP-3 and CMP-4.Taking advantage of numerous porous channels and aromatic rings of the CMPs,we carried out iodine-sorption experiments and the results showed that the CMP-4 constructed from LT6-OTf and 4,4'-diethynylbiphenyl possessed larger iodine capacity.The introduction of LT6-OTf provided a broad application prospect for CMPs in iodine capture.In the fourth part,inspired by the synthetic strategy of Bp P6 and LT6,we prepared the intermediate first and then conducted the macrocyclic reaction to successfully obtain a novel supramolecular macrocycle,namely new pillar[8]arene(NP8).The single crystal structure showed that NP8 was in a chair-shaped conformation,and the packing modes of NP8 presented an interesting"standing man"form,which distinctly provided evidence for traditional pillar[8]arene maintaining the pillar-shaped conformation and rigid structure.We also designed and synthesized a series of NP8functionalized derivatives,and developed a water-soluble CNP8 for selective recognition of L-cysteine among 20 natural amino acids.In conclusion,the newly designed NP8 with advantages of particular conformation,multiple sites for post-modification,and unique host-guest recognition ability is promising to be applied in energy storage,crystal engineering,and environmental remediation in the near future.