Studies Of Cucurbituril-Based Supramolecular Orthogonal Assemblies Using Host-Guest/Coordination Interactions

Supramolecular chemistry focuses on the construction of complex,functionally diverse supramolecular assemblies with a highly ordered arrangement of component units.As research grows,it is imperative to construct more complex supramolecular assemblies and to expand the scope of supramolecular chemistry.Complex assemblies can be constructed in a variety of ways,generally by changing the structure,composition,and order of the component monomers.The use of different noncovalent interactions in the orthogonal construction of supramolecular assemblies is one of the most advantageous and important strategies and tools.Complex orthogonal supramolecular assemblies are produced by designing and synthesizing compounds with specific noncovalent interaction sites and using orthogonal assembly strategies to link two or more noncovalent interactions.Since the interactions of orthogonal assemblies do not interfere with each other,orthogonal supramolecular assemblies with different functions and structures can be prepared by increasing or adjusting the type or direction of noncovalent interactions,thus avoiding complex synthesis.As the orthogonal assembly is an effective means of constructing complex assemblies,it is essential to study the process of orthogonal assembly in-depth and to acquire basic experience in regulating the process,as well as to summarize the universal assembly law and use it to prepare complex orthogonal assemblies purposefully.At the same time,it is also important to explore the potential applications of orthogonal assemblies and to promote their practical application.In this paper,cucurbit[n]uril（Q[n]or CB[n]for short）was chosen as an important component and source of host-guest interaction for the construction of orthogonal assemblies.The cucurbituril cavities are very rigid and can specifically recognize cavity-matched neutral and positively charged molecules,and exhibit excellent properties and unique attractions.The coordination interaction are also used to construct orthogonal assemblies,which not only possess molecular recognition specificity,sensitive environmental responsiveness,and high orientation but are also capable of coordinating various geometrical configurations and possessing strong and tunable binding capabilities.This thesis,therefore,focuses on the construction,properties,and applications of cucurbit[n]uril-based orthogonal assemblies:In the first part,a melamine Schiff base derivative（TBT）was designed and synthesized using melamine as the molecular center.Three separate assemblies were constructed by exploiting the differences in cucurbituril cavity sizes.It was confirmed by ¹H NMR and UV-vis titration experiments that the TMe Q[6]-TBT assemblies were driven by cucurbituril outer-surface interactions,and the Q[7]-TBT and Q[8]-TBT assemblies were formed by host-guest interactions.Among the three assemblies mentioned above,the Q[7]-TBT assembly possesses a clearer model of interaction and was therefore chosen as one of the building blocks for the orthogonal assemblies,and the final supramolecular orthogonal assemblies were constructed with Ag⁺.The Q[7]-TBT-Ag⁺orthogonal assembly was also hypothesized to be formed by the secondary assembly of Ag⁺with the carboxyl group of TBT through coordination interaction.The Q[7]-TBT-Ag⁺orthogonal assembly was linked by Ag⁺and achieved the upgrade from simple complex to complex assembly,which provides ideas for the construction of subsequent orthogonal assemblies.In the second part,1,3,6,8-tetra（4-pyridyl）pyrene was used as the molecular center to design and synthesize pyrene derivatives（TPYP）.¹H NMR,fluorescence,and UV-vis spectroscopy were used to verify the host-guest interaction of the TPYP-t Q[14],which shows that t Q[14]combined with the pyridinium and alkyl chains of TPYP and extended into the TPYP-t Q[14].It was postulated that the assembly possessed some characteristics of a supramolecular polymer and exhibited a loose external morphology under SEM.Subsequent metal selecting experiment revealed that the TPYP-t Q[14]specifically recognized Ni²⁺.Utilizing IR spectroscopy,etc.,it was hypothesized that Ni²⁺undergoes metal coordination with the third carbonyl port at the angle of t Q[14]and constructs the TPYP-t Q[14]-Ni²⁺orthogonal assemblies.This study makes full use of the third port of t Q[14]to achieve the preparation of complex assemblies and the modulation of the structure and morphology of the assemblies,providing a new method for the construction of orthogonal assemblies by t Q[14].In the third part,a potential biological dye Cy5PQ with NIR emission was synthesized by using Cyanine 5 as the molecular center and a bipyridine as the host-guest interaction active group.Q[8]was selected as the host by fluorescence spectroscopy experiments.By IR,UV-vis spectroscopy,and SEM experiments,it was verified that Q[8]interacts with the bipyridine moiety of Cy5PQ in a host-guest interaction to form a cross-linked Q[8]-Cy5PQ assembly.Subsequently,UV-vis spectroscopy was used as the primary means to select Cu²⁺as the secondary assembled metal.The IR spectroscopy experiments revealed that Cu²⁺produced metal-πinteractions and metal coordination interactions with the long-chain double bonds of the Cy5PQ and the Q[8]-ported carbonyl groups,respectively,and further assemble into Q[8]-Cy5PQ-Cu²⁺supramolecular orthogonal assemblies with a spherical external morphology.In the fourth part,the conjugated molecule was used as the molecular center and the carboxyl chain was used as the coordination interaction active site to synthesize the fluorescent molecule OPVCOOH.¹H NMR,fluorescence spectroscopy,mass spectrometry,and DLS were used to trace and characterize the formation of the Q[10]-OPVCOOH assembly.It was shown that Q[10]could generate a supramolecular rotaxane structure with a host-guest interaction ratio of 3:2 by shuttling back and forth on the J-dimer of OPVCOOH.The Q[10]-OPVCOOH-Fe²⁺orthogonal assemblies were constructed by selecting Fe²⁺as an important component of the secondary assembly.The metal coordination interaction of Fe²⁺with the carboxyl group of the Q[10]-OPVCOOH assembly was further verified by ¹H NMR titration experiments,etc.to inhibit the rotamer structure of the assembly.In addition,the orthogonal assemblies exhibit broad fluorescence emission with an emission spectrum covering 439～700 nm,and thus near-white light emission in an aqueous solution can be achieved by adjusting the metal concentration with the chromaticity coordinates of（0.28,0.33）.Finally,the polymer compound polyvinyl alcohol was used to increase the adhesion of the orthogonal assemblies,which were prepared as coating materials for near-white LED lamps.The work exploits the unique luminescent properties of the Q[10]-OPVCOOH-Fe²⁺orthogonal assemblies for the facile preparation of near-white LED lamps without lanthanide doping,providing ideas for the practical application of cucurbituril-based orthogonal assemblies.In the fifth part,a terpyridine derivative（TPDPB）was designed and synthesized using p-phenylene vinylene as the molecular center and terpyridine as the recognition site for the main guest.The Q[10]-TPDPB supramolecular assemblies were prepared using the specific recognition of Q[10]with the terpyridine moiety,and the assembly process was accompanied by fluorescence-enhanced red-shift.It was verified that Q[10]-induced charge transfer interaction between TPDPBs was the main cause of the fluorescence change.The Q[10]-TPDPB assemblies were found to have a certain recognition ability for Lu³⁺in lanthanide,which could effectively induce metal-ligand inter-charge transfer interaction through metal coordination interaction,thus constructing the Q[10]-TPDPB-Lu³⁺orthogonal assemblies.Due to the presence of multiple charge transfer interactions in this orthogonal assembly,further studies by fluorescence and UV-vis spectroscopy revealed that the orthogonal assembly can be applied to the recognition and classification of some common anions.This work,on the one hand,provides a new option for the specific guest of the Q[10],and on the other hand,provides a reference for the extension of the application of cucurbituril-based orthogonal assemblies.