Construction And Properties Study Of Novel Functional[2] Catenanes System

As one of the classical mechanically interlocked molecules（MIMs）,[2]catenanes are novel topological structures with two interlocking macrocyclic componets held together by mechanical bonds.Chemists have paid more and more attention to the synthesis,characterizations,properties,and potential applications of[2]catenanes owing to their unique topology structure and controllable dynamic features,which make them privileged platforms for wide applications in molecular motors,liquid crystals,catalysis and soft materials etc.In particular,the topologically chiral[2]catenanes that composed of two“oriented”macrocyclic components have attracted widespread attention because of its stable absolute configuration and diverse conformational expression.However,due to the difficulties in synthesis and chiral resolution,the progress of the development and applications of topologically chiral[2]catenanes is quite slow.Therefore,the efficient synthesis of topologically chiral[2]catenanes and the further study of their chiral properties remain attractive scientific problems that need to be solved.In this thesis,a series of[2]catenanes have been successfully developed as functionalization platforms to deal with the key problems of[2]catenanes including the efficient synthesis,post-modification and precise regulation of chirality expression and transfer.The structure-property relationship between the conformation and chirality expression of[2]catenanes was systematically studied,and the expression,transfer and amplification of topological chirality at the molecular level were revealed.Therefore,the research contents of this thesis are of great significance for the synthesis and chiral properties of topologically chiral MIMs.Specifically,it is mainly composed of the following five parts:Chapter I:the research in the synthetic strategies and applications of[2]catenanes are systematically summarized firstly,including the recent progress in topological chiral[2]catenanes.Secondly,the research progress of oligo[n]catenanes is summarized.Finally,the synthetic methodologies and potential applications of poly[n]catenanes are briefly introduced.Chapter II:Novel sulfonamide[2]catenanes were successfully prepared through a hydrogen bond self-templation approach.The catenated skeletons were confirmed by traveling-wave ion-mobility spectrometry（TWIMS）combined with gradient tandem mass spectroscopy（g MS²）.Moreover,two pyrene units were further introduced into the[2]catenane through the alkylation reaction of the sulfonamide moieties,resulting in the successful synthesis of a novel pyrene-functionalized[2]catenane which displayed a switchable fluorescence output triggered by sodium cations and cryptands.Chapter III:Using the[2]catenane skeletons developed in chapter II,the key[2]catenane building block with growth sites is synthesized by unsymmetric post-modification.We realized the first successful preparation of catenanes-branched dendrimers,in which the individual[2]catenane units serve as the branches of dendrimer skeleton,up to the third generation.In particular,the third-generation catenane-branched dendrimer with twenty-one[2]catenane moieties might be the most complicated discrete high-order MIMs comprised of[2]catenane units.Furthermore,the controllable encapsulation/release of protonated dopamine by the resultant catenane-branched dendrimer was successfully realized through the regulation of its host-guest interactions with the oligoethylene glycol moieties within the[2]catenane branches.Chapter IV:Aiming at the construction of novel circularly polarized luminescence（CPL）switches with multiple switchable emission states and high dissymmetry factors(g_lum),topologically chiral[2]catenanes were employed as the key platform to construct a novel multistate CPL switching system.Taking advantage of the precise co-conformation regulations of the resultant pyrene-functionalized[2]catenanes under different external stimuli,reversible transformations between three emission states with different CPL performances,i.e.the initial“closed”form with a|g_lum|value of 0.012,the“open”form with an almost complete turn-off of CPL emission,and the“protonated”form with a boosted|g_lum|value of 0.022,were successfully realized.This study demonstrates the successful construction of not only the first topological chirality-based CPL switch,but also a novel bidirectional CPL switch.Finally,the mechanism of CPL switching was studied in detail through computational simulations.Chapter V:To gain more in-depth understanding of the induction,transfer,and switching of topological chirality,poly[2]catenanes with polyacetylenes（PAs）as the main chain and topologically chiral[2]catenanes as the side-chain pendants were designed and synthesized for the first time.The CD investigations revealed that PAs adopt preferred-handed helical conformations depending on the topologically chiral[2]catenanes.Furthermore,the precise regulations of the transfer from the topological chirality to the helical chirality were achieved by switching either the co-conformation of side-chain pendants or the main chain pitch lengths.It is worth noting that the preferred-handed helix and the stimuli-response properties of the resultant poly[2]catenanes were almost not disturbed by an additional point chirality unit within the[2]catenane skeleton.