Construction And Performance Study Of Supramolecular Assembly Based On Spiral Cucurbit Rin

Supramolecular chemistry is the study of supramolecular systems with specific structures and functions concluded between two or more chemical species through weak intermolecular force interactions.Unlike traditional polymers based on covalent bonds,supramolecular polymers are composed of non-covalent bonds between monomers,which exhibit the structure and properties of polymers.The action based on non-covalent bonds endows supramolecular polymers with special properties such as stimulus responsiveness,self-healing properties,molecule-specific recognition,and structure-controlled regulation.Supramolecular macrocycles as important building blocks in supramolecular chemistry,are the driving force for the development and progress of supramolecular chemistry,where supramolecular assemblies based on cucurbit[n]urils constructions have been applied in fields such as life sciences and materials science.As one of the important members of the cucurbit[n]urils family,twisted cucurbit[n]urils with their natural double cavity structure and unique host-guest recognition are the best choice for constructing supramolecular polymer systems.However,the functional applications of constructing supramolecular assemblies based on twisted cucurbit[n]urils are under-researched.Through the implementation of this research work,the functions of constructing supramolecular materials based on twisted cucurbit[n]urils are gradually being applied in the fields of biomedicine and chemical sensing.Fluorescent functional materials have important applications in frontier scientific fields such as biofluorescent probes,cell imaging,information encryption and anti-counterfeiting,and analytical assays.However,traditional fluorescent molecules with luminescent conjugate groups in the aggregated state can cause fluorescence aggregation bursting Aggregation-caused quenching（ACQ）due toπ-πstacking,which greatly limits its development and application.Fortunately,the aggregation-induced emission（AIE）phenomenon of AIE molecules has opened a new path for fluorescent molecules,and the AIE luminescence mechanism is attributed to the Restriction of intramolecular motions（RIM）.In short,the intra-molecular motions of AIE molecules in the aggregated state are restricted due to the large energy barrier,thus blocking the non-radiative leap mode and exhibiting fluorescence enhancement,which brings new opportunities for functional fluorescent materials and targeted imaging.Based on the above background,in this thesis,a series of AIE molecular derivatives with different functional structures are designed&synthesized based on the host-guest chemistry of twisted cucurbit[n]urils combined with AIE fluorescence enhancement technology,and supramolecular polymers with different topologies and fluorescence enhancement properties are constructed by the host-guest interaction of the double cavity structure of twisted cucurbit[n]urils.They are used in cell imaging,artificial light-harvesting systems,analytical assays,and environmental pollutant adsorption and removal.The research work in this thesis is important for the functionalized application of constructing supramolecular assemblies based on twisted cucurbit[n]urils,which brings new design ideas for twisted cucurbit[n]urils-based in tunable smart supramolecular fluorescent materials.This dissertation is divided into seven main sections including the following:（1）In part Ⅰ,the experimental methods and reaction conditions were improved rationally and effectively,resulting in higher yields and shorter isolation cycles of tQ[13-15].The fluorescence emission phenomenon of tQ[14]was reported for the first time and revealed that it is a new CTE macrocyclic compound.The luminescence properties and mechanism of tQ[14]in formic acid solution were systematically investigated.The luminescence mechanism of tQ[14]is mainly attributed to the outer wall-induced effect of tQ[14]itself.During the formation of cluster aggregation,the C=O（πelectrons）on the carbonyl port of tQ[14]can aggregate with each other through n-π*interactions,while the carbonyl oxygen overlaps with the methyl and methylene on the outer wall of tQ[14]through hydrogen bonding,forming a spatial conjugation effect of unconventional emission,thus having unique CTE effect.Finally,tQ[14]can be used directly as a fluorescent probe for the detection of Fe³⁺with a limit detection value as low as 1.71×10^-5 M.（2）In part Ⅱ,guest molecules with three functional groups（bipyridyl,alkyl chain,and naphthyl）were designed and synthesized to construct linearly controllable supramolecular polymers with two macrocyclic compounds（tQ[14]and Q[8]）by self-sorting.The naphthyl part of BNB is arranged in the cavity of Q[8]byπ-πstacking,and the alkyl part of BNB enters into the two cavities of tQ[14].TQ[14]and Q[8]act as a"molecular handcuff"to connect the BNB molecules,and the three are assembled as supramolecular polymers.In addition,the addition of AH with a stronger binding ability to Q[8]can drive the BNB molecules out of the Q[8]cavity and achieve effective depolymerization of the supramolecular polymer.（3）In part Ⅲ,an anthracene derivative with AIE effect was designed and synthesized as a guest molecule（APy）,and two macrocycles（tQ[15]and Q[10]）were selected as the host molecules.tQ[15]and Q[10]were constructed with APy as a linear supramolecular polymer with AIE-enhanced fluorescence through the host-guest interaction and used as an energy donor.Subsequently,a dye molecule（RB）was selected as an energy acceptor,and an efficient artificial light-harvesting system（ALHS）was constructed in an aqueous solution by the FRET mechanism.Finally,the ALHSs were applied to the bioimaging of Hela cells and were able to show good staining and recognition of cell morphology in the red channel.（4）In part Ⅳ,tQ[14],ADPy,NiR,and RB were selected to construct two artificial light-harvesting systems with efficient energy transfer in an aqueous solution using a supramolecular self-assembly strategy.Among them,tQ[14]and ADPy were aggregated to form spherical supramolecular nanoparticles through host-guest interaction,which exhibited strong fluorescence-enhancing phenomena and could serve as excellent energy donors.Two fluorescent dyes（NiR and RB）were selected as energy acceptors and loaded into spherical supramolecular nanoparticles to construct two light-harvesting systems in an aqueous environment,which not only showed long fluorescence lifetimes and high fluorescence quantum yields but also showed high antenna effects and energy transfer efficiency.It is worth highlighting that the ADPy@tQ[14]-NiR assembly shows a high antenna effect（52.4）and excellent energy transfer efficiency（72.4%）,similar to natural light-harvesting systems.（5）In part Ⅴ,inspired by the multi-level energy transfer in plant photosynthesis in nature.An imidazole derivative（DIm）with blue light emission was designed and synthesized,and it was successfully constructed with tQ[14],ESY,and NiR relying on non-covalent bonding to construct an efficient artificial light-harvesting system with two-step energy transfer in the aqueous phase.The linear supramolecular polymer（DIm@tQ[14]）constructed by the self-assembly of DIm and tQ[14]has an excellent aggregation-induced emission effect,which was used as an ideal energy donor for this study.Subsequently,the acceptor（ESY）was loaded into the supramolecular polymer to achieve a primary energy transfer from DIm@tQ[14]to ESY.Next,NiR was selected as the second energy acceptor,and an artificial light-harvesting system（DIm@tQ[14]-ESY-NiR）with efficient multi-stage energy transfer was successfully constructed with two steps of sequential energy efficiency of 42.67%and 91.47%,respectively.In addition,the construction process involves the emission behavior of fluorescence in the350 nm-750 nm band range with changes in fluorescence color（cyan-yellow-green-orange-red）.Finally,the molar ratio of donor/acceptor can be controlled to achieve bright white light emission,and these ALHSs can be applied to white LED materials to achieve white light emission from LED lamp.（6）In part Ⅵ,a supramolecular reticulated polymer（TPAP-Mb@tQ[14]]）with AIE effect was constructed based on tQ[14].The polymer was constructed by the supramolecular assembly of the butyl and methylpyridine parts of the three branchings"arms"of the guest molecule（TPAP-Mb）with two cavities of tQ[14],which triggered aggregation-induced yellow light emission by the Ri R mechanism.TPAP-Mb@tQ[14]could detect the residual Fe（CN）₆^3-in an aqueous solution with high sensitivity.Fe（CN）₆^3-with a detection limit of 1.64×10^-7 M.More importantly,TPAP-Mb@tQ[14]exhibited an efficient removal of Fe（CN）₆^3-with a removal rate of 97.38%.Finally,the rare and precious macrocyclic tQ[14]could be recovered after high-speed centrifugation in acetone/chloroform mixed solution medium with 68.3%recovery.（7）In part Ⅶ,Fe³⁺is a trace element in human cells,and its concentration directly affects human life activities.The present work is based on tQ[14]and TPE-4P to construct supramolecular reticulated polymers with the yellow fluorescence emission.Among them,the host-guest interaction between tQ[14]and the methyl pyridine part of TPE-4P leads to the rotation restriction of the benzene ring within TPE-4P to induce an intramolecular rotation restriction mechanism to further trigger the AIE effect.TPE-4P@tQ[14]has good biocompatibility and low physiological toxicity and can show excellent imaging effects in the cytoplasm of Hela cells.Meanwhile,it can sensitively and specifically identify Fe³⁺in an aqueous solution with a detection limit of 1.46×10^-6 M.Finally,TPE-4P@tQ[14]was successfully applied to detect the abnormal presence of Fe³⁺ions in Hela cells,enabling a fluorescence response to different concentrations of Fe³⁺in cells under confocal microscopy,which can be used to discriminate normal cells from iron-overloaded abnormal cells.